US3412721A

US3412721A - Composite casting

Info

Publication number: US3412721A
Application number: US534563A
Authority: US
Inventors: Earl A Thompson
Original assignee: EARL A THOMPSON Manufacturing CO
Current assignee: EARL A THOMPSON Manufacturing CO
Priority date: 1966-03-02
Filing date: 1966-03-02
Publication date: 1968-11-26
Anticipated expiration: 1985-11-26

Description

Nov. 26, 1968 E. A. THOMPSON 3,412,721

COMPOS ITE CASTING Original Filed April 2, ,1962 8 Sheets-Sheet 1 SOL 24%?! 2 98 .96 {5; 84

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Nov. 26, 1968 E. A. THOMPSON COMPOSITE CASTING Original Filed April 2, 1962 8 Sheets-Sheet 2 iii 1 1 r 1 1 1 11 1 1 1/ 1/ 1, 1 l 1 I 1 mmvrox:

EA PL A. THOMPSON Q AGENT Nov. 26, 1968 E. A. THOMPSON 3, ,72

COMPOSITE CASTING Original Filed April 2, 1962 8 Sheets-Sheet 5 INVENTOR: EARL A. THOMPSON AGENT Nov. 26, 1968 E. A. THOMPSON 3,

COMPOSITE CASTING Original Filed April 2, 1962 s Sheefs-Sheet 4 INV EN TOR.

4 AGENT EARL A. THOMPSON Nov. '26, 1968 E. A. THOMPSON 3,412,721

COMPOS ITE CASTING Original Filed April 2, 1962 8 Sheets-Sheet 5 'lili: HI 'Illl" I I I I" I umlglll INVENTOR. EARL A. THOMPSON AGENT Nov. 26, 1968 E. A. THOMPSON 3,412,721

COMPOSITE CASTING 8 Sheets-Sheet 6 Original Filed April 2, 1962 AGENT Nov. 26, 1968 E. A. THOMPSON 35412,?21

COMPOSITE CASTING Original Filed April 2, 1962 8 Sheets-Sheet 7 INVENTOR: EARL A. THOMPSON AGENT Nov. 26, 1968 E. A. THOMPSON 3,412,721

COMPOS ITE CASTING Original Filed April 2, 1962 8 Sheets-Sheet 8 l l I Percent Carbon Attorny United States Patent 3,412,721 COMPOSITE CASTING Earl A. Thompson, Bloomfield Hills, Mich., assignor to Earl A. Thompson Manufacturing Co., a corporation of Michigan Continuation of application Ser. No. 184,476, Apr. 2, 1962. This application Mar. 2, 1966, Ser. No. 534,563 19 Claims. (Cl. 12390) This application is a continuation of my application Ser. No. 184,476 filed Apr. 2, 1962, now abandoned.

This invention relates to casting and to cast articles, and more particularly to the art of casting composite metal articles in production quantities which articles have a juncture zone Where different metals merge in a metallurgical blend.

It has long been known that, with certain fusible metals, when one is poured in the molten state into a mold and then another is poured into the mold before the first hardens, the result is a mixing of the two metals throughout a substantial zone providing a strong union. See for example the US. patent to Wilmington 82,466, Sept. 22, 1868. Likewise, it has long been appreciated, as in the US. patents to Foster 95,577, Oct. 5, 1869, Totten 399,295, Mar. 12, 1889, Krepps 2,710,997, June 21, 1955, that certain articles are most desirably formed so that different parts are composed of different metals having particular life, wearing, texture, machining, weight, heatresisting, corrosion-resisting, flexing and other service or cost characteristics especially suited to the demands made on those parts in the articles intended use. Such an article, for example, as a valve tappet or a hydraulic valve lifter body is preferably formed with one portion embodying qualities of machinability while an adjoining portion is of an extremely wear resistant metal. Such articles are illustrative only of the type of article which may be produced by this invention, and reference thereto should in no way be construed to limit the basic invention.

Certain problems, however, have until this invention confronted workers in the art in their attempts to mass produce small articles such as tappets in the form of composite castings. First, there has been no practical solution to the problem of metering precise amounts of a high melting point metal into a mold. The difficulty of designing valves of suitable refractory material to function repeatedly at elevated temperatures to accurately measure quantities of less than one cubic inch can be better appreciated when it is realized that some moving parts of the valve are preferably bathed with an inert gas to prevent oxidation and the like.

The problems of measuring accurately the quantities of the successive metals poured, and of keeping each ingredient from getting into the part of the casting where it should not be are particularly difficult to solve in the case of tappets or hydraulic valve lifters for internal combustion engines. Not only is the quantity of each metal to be poured very small, but the volume in the tappet to which that metal must be precisely confined, makes it difiicult, although the metals may be measured accurately, to control the distribution of the metals precisely while insuring an adequate bond or joint between the two. With an article such as a tappet, the portions requiring a certain metal must be composed exclusively of that metal, and

3,412,721 Patented Nov. 26, 1968 "ice any intermixing of another metal from an adjoining portion will cause early failure of the article under use and other undesirable results. Such an excess mixing of the metals is often caused by pouring the second while the first is in an entirely liquid state allowing the two to swirl and mix throughout substantially the entire mold or at least large portions of it. Conversely if the second metal is poured after the first is frozen there will be no satisfactory fused junction of the dissimilar metal pieces and the article will rupture as a result of load or shock during use.

Furthermore the joint itself is necessarily of small area, while the stresses put on the joint in service are severe and of high frequency.

Furthermore, mass production of similar articles by conventional methods utilizing a plurality of forms in a single mold is not economically desirable because of the waste inherent in the long runners, sprues, and other connectors by means of which the castings are poured.

Accordingly, it is one object of the present invention to provide improved apparatus for individually pouring composite metal castings following a method which insures an improved article and uniform quality in article after article.

Another object of this invention is to provide a method of forming a single integral casting having parts of different physical characteristics (due to different metallurgical ingredients) which insures a metallurgical confluence of dissimilar metals throughout a controlled zone only.

More particularly it is an object of this invention to provide an improved multi-metal casting by pouring one molten metal into a mold containing a dilferent molten metal, after forming a temporary barrier on the first molten metal against which the second metal is poured. This is to control the desired mixing of the two molten metals, and to maintain separated molten masses of the individual metals. The different metals are mixed throughout a controlled layer when the barrier is melted by the second molten metal, and the mixing is controlled and confined to a narrow zone. In this zone the two metals form an intimate bond when the two molten metals are cooled and solidified at the same time.

Another object is to provide an improved casting (especially where the juncture zone is subjected to stresses in shear) in which the juncture zone has qualities produced by the simultaneous solidifying of two different metals kept separated in the molten state by a controlled layer of a mixture of the two metals.

More particularly it is an object of the invention to provide an improved composite metal product such as a valve tappet or similar article which is a single integral casting of dissimilar metals autogenously bonded or united in a zone or by a layer which is a carefully controlled blend of such metals progressing from the composition of one metal to the composition of the other metal. Autogenously bonded means that the joint is formed of the two fused metals alone without the addition of other substances.

A further object of the invention is to provide fully automatic apparatus, including a mechanico-hydraulic motivator of the type having a rotary cam which controls a liquid column motion transfer device, for metering successive quantities of separate molten metals to a plurality of identical molds presented seriatim.

A further object of the invention is to provide an improved arrangement for use with molten metals to meter precise amounts thereof and in which the operative portions are exposed to inert gases .to prevent oxidation of the metals.

Further objects and advantages of the present invention will be apparent from the following detailed description, with reference to the accompanying drawings in which like reference characters refer to the same parts throughout the several views, and in which:

FIGURE 1 is a view in schematic fashion showing the general arrangement for supplying molten metal to suecessively presented molds;

FIGURE 2 is a view showing an arrangement for measuring and delivering a predetermined amount of molten metal from a crucible to a mold;

FIGURE 3 is a view showing a shiftable member successively presenting the mold and core arrangements of this invention to different pouring stations;

FIGURE 4 is a plan view with parts broken away showing the general scheme of the transfer arm loading means for the fresh molds;

FIGURE 5 is a sectional elevational view of the mechanism for swinging and elevating a transfer arm;

FIGURE 6 is a sectional view on line 66 of FIG- URE 5 showing the fluid motor for swinging a transfer arm;

FIGURE 7 is a plan view showing the general scheme of the transfer arm unloading means for the filled molds;

FIGURE 8 is a fragmentary view showing a corner of the mold and core arrangement in sectional elevation with a first amount of one molten metal poured therein;

FIGURE 9 is a view similar to FIGURE 8 showing the recently poured metal after a desired predetermined time lapse;

FIGURE 10 is a view similar to FIGURE 8 with a second amount of another molten metal poured into the mold into contact with the first poured metal;

FIGURE 11 is a view on the same scale as FIGURES 8, 9 and 10 showing a product obtained by the steps of this invention;

FIGURE 12 is a perspective view of a valve lifter blank formed according to this invention with portions broken away to indicate the cross sectional configuration of the article;

FIGURE 13 is a photomicrograph depicting as Example I the juncture of dissimilar metals in a product cast in accordance with this invention;

FIGURE 14 is a photomicrograph depicting as EX- ample II the juncture of dissimilar metals in a product cast in accordance with this invention;

FIGURE 15 is a photomicrograph depicting as Example III the juncture of dissimilar metals in a product cast in accordance with this invention;

FIGURE 16 is a photomicrograph depicting as Example IV the juncture of dissimilar metals in a product cast in accordance with this invention;

FIGURE 17 is a photomicrograph depicting as EX- ample V the juncture of dissimilar metals in a product cast in accordance with this invention; and

FIGURE 18 is a constitution diagram.

Referring generally to FIGURE 1, a mold 10 for molten metal is automatically loaded into a bracket 12 secured to a shiftable table or other indexing member 14, and then moved beneath a container, a pot or pouring crucible 16 of molten metal. When the mold is beneath the pouring crucible 16, a valve or metering arrangement 18 measures and delivers a small predetermined amount of molten metal to the mold. The valve 18 and the shiftable member 14 are both operated in timed sequence by a mechanico-hydraulic motivator unit 20 of the rotary cam powered and controlled liquid column type. An additional supply of molten metal is maintained in a reserve or holding container 22 from which it is metered to the pouring crucible 16 by a valving arrangement 24 whenever the amount of molten metal in the pouring container 16 falls to a predetermined minimum. Sensing means responsive to the amount of molten metal in the pot 16 is connected to operate the valve 24. The various elements which thus comprise the apparatus of this invention will separately be described in detail.

The means for measuring and delivering a predetermined amount of molten metal from the pouring container 16 to a mold 16 is best visualized by reference to FIGURE 2. Such a device may comprise, for example only, an induction heating coil 26 spirally and concentrically surrounding the container 16 and separated therefrom by a centering and insulating layer of packed casting sand 28, and powered by a suitable source of electric current, not shown.

The container 16 and heating arrangement 26 may be supported upon suitable slabs 30 of refractory or ceramic material located upon a bed 32 of stronger material supported at its edges by suitable angled frame members 34. Snugly mounted in aligned holes through the container bottom and the various layers of supporting material is a pouring spout or conduit 36 of refractory material having its lower end 38 positioned immediately above the mold path, and its upper end terminating in a semispherical, dished valve seat 40 located well above the bottom of the container 16 and fully within the heating range of the coil 26.

A generally tubular, rotary valve body member 18 is centered and received at its lower end in the spherical seat 40 and is held there with a force adequate to exclude molten metal from the joint. The pouring opening 36 is eccentric in the seat 40 which latter also contains another eccentric port 42 which communicates at its outer end with the molten metal in container 16 at a fixed depth, as indicated by dashed lines in FIG. 2. Metal pouring port means comprising a pair of diametrically opposed and angled channels 44 in the bottom end of the valve body member 18 can be aligned selectively to connect a chamber 46 either to the metal inlet port 42 or the metal outlet port 36 in the seat as the valve body member is oscillated about its longitudinal axis. The channels 44 communicate at their inner extremities with the lower chamber 46 which, together with an upper chamber 48 and a narrow interconnecting capillary passage 50 formed by enlarged wall portions of the body, constitute a metal measuring cavity.

The lower chamber portion 46 of the metal measuring cavity is adapted to contain a predetermined amount of molten metal and the upper chamber portion 48 of the cavity is adapted to contain a predetermined volume of inert gas. Such gas may be admitted to the upper end of the cavity through a connection 52 in a manner later to be described. The entire valve body member 18 is made of suitable refractory material and is appropriately journalled to be oscillated so that when the lower port means 44 is in communication with the metal in the container 16 by means of the inlet port 42, the chamber 46 is cut 0H from the discharge port 36 and metal will fill the measuring cavity to a predetermined height, preferably within the range of the narrow interconnecting channel 50. When the metal pouring port means 44 is in communication with the pouring spout 36, on the other hand, the inlet port 42 is closed and the molten metal in the cavity will be delivered to the mold.

For oscillating the valve member 18, there is an arm 56 secured by a series of bolts 54 to the upper portion of the valve body member. Angular to and fro shifting of the arm is accomplished by the rod 58 of a piston 60 shiftable to and fro in a cylinder 62 constituting a double acting fluid motor having support, not shown, on the framework 34. The motor operates the valve to connect the lower port means with the desired opening in the spherical seat 40. If desired, the upper chamber 48 of the metal measuring cavity may be volumetrically increased by the addition of an auxiliary tank unit 64 (see FIGURE 1) mounted above the valve member to contain an increased amount of gas for a purpose that will later become apparent. An atmosphere sealing cover 66 of suitable refractory material for the pouring container 16 may contain an opening 68 for the tubular valve body member as well as an opening 70 for a conduit 72 of refractory material for the addition of more molten metal to the container 16; likewise, another opening 74 may be provided for the admission of .a desired gaseous atmosphere, such as nitrogen, through a conductor 76 from a suitable source A to inhibit the formation of slag and other undesirable oxidation products on the surface of the molten metal in the pot 16.

To maintain a predetermined depth of molten metal in the pouring container .16 and thus provide a relatively constant head of metal above the inlet 42, a sensing arrangement is provided by this invention which intermittently admits additional metal to the container from the storage or holding pot 22. Referring again to FIGURE 1, the holding crucible 22 is periodically charged with molten metal from a batch type melting furnace, not shown, and is also provided with suitable heating means 78 such as an induction coil, and is mounted on refractory material 80 rigidly supported on a fixed base or pedestal 82. Through a lid 84 of the holding crucible the valve member 24 extends which is somewhat similar to the metal measuring and delivering means 18 in the pouring crucible. However, the tubular valve body member 24 for the holding crucible contains only a central bore 86 for gas connecting with an angled outlet port means 88 to direct gas to a transfer conduit or pouring opening 90 in the pipe 72. A diameteral groove 92 across the lower spherical end of the valve member 24 serves to interconnect the pouring spout 90 with an inlet port 94 when the valve rod member is in the proper angular position. When the gas duct 88 is in communication with the spout 90, the groove 92 is out of communication with the inlet 94 so that no metal flows to the spout 90. The valve body member 24 is journalled to be angularly moved to and fro by an .arm 96 similar to the arm 56 of the valve arrangement for the pouring container. However, in this case, the arm 96 may be shifted back and forth by a solenoid motor 98 which is spring urged to its rest position connecting the gas port 88 with the pouring spout 90.

Operation of the solenoid 98 is controlled by sensing means responsive to the amount of metal in the pouring container 16. This container supported on its framework 34 may be pivotally mounted about a fixed fulcrum 100 for generally up and down movement closely limited by fixed abutments 102. An adjustable counter-weight 104 on the structure 34 may be adjusted to effect a balanced position when a desired amount of molten metal is contained within the pot 16. An abutment or trip member 106 also integral with the pivotally mounted container brace arrangement is adapted to close a limit switch LS1 when the weight of metal in the container 16 reaches a predetermined minimum. Similarly, the normally closed contacts of a limit switch LS2 are positioned to be opened by the abutment member 106 when the weight of metal in the container 16 reaches a preset maximum. (The electrical symbols for the limit switches are superimposed in FIG. 1 on the mechanical representations of the limit switches for purposes of clarity.)

Suitable electric circuitry, deriving its power from input lines L1 and L2, energizes the solenoid 98 when the limit switch LS1 contacts are closed by the abutment 106 when the minimum quantity of metal is in the crucible 16; such circuitry holds the solenoid 98 energized until the contacts of the limit switch LS2 are opened by the trip 106 when the maximum amount of metal is in the crucible 116. Such circuitry may comprise a holding circuit of conventional variety utilizing a solenoid closed spring-opened relay 108 to complete and hold the circuit to the solenoid 98 upon closing of the contact at LS1,

and to interrupt the circuit to the solenoid 98 only upon breaking the contacts at LS2, as can be understood.

This invention further contemplates the use of a pressurized inert gas in connection with the operation of the valving arrangements 18 and 24. Such a gas may preferably be an inert gas, such as argon gas, under relatively high pressure in a bottle container or other source 110, the outflow pressure of which may be determined by a visual indicator 112 upon settin of an outflow regulating valve 114. The pressurized gas utilized by the upper valving arrangement 24 is first controlled by a flow regulating valve 116, including a visual flow rate reading device 118, to admit a predetermined amount of gas to a cooling tank 120. The tank may have cooling coils, not shown, in or around it to maintain the fixed volume at a constant temperature, preferably near or below normal room temperature, and thus constitute a source of inert gas at an accurately regulated pressure. From the cooling tank 120, the gas is allowed to flow to the valving arrangement 24 only when needed under control of a solenoid opened, spring-closed two position valve 122 in a connecting line 124 flexibly secured to the upper end of the oscillating valve rod. When the valve 122 is down in the normal spring-urged rest position, the condition shown in the uppermost (cross-hatched) rectangle is established, that is the valve is closed. When the valve is up in the solenoid actuated open position,

. the connections shown in the lowermost rectangle are solenoid 98. When the solenoid 98 is energized to turn the valve 24 to flow metal from the storage container 22 to the pouring crucible 16 through the end groove 92, then the switch LS3 is closed to energize the solenoid opening the gas valve 122 to permit flow of gas from the cooling tank 120 to the central passage 86 in the valve rod 24 from which further flow is prevented by the spherical valve seat 86 closing the duct 88.

Gas for the valvin arrangement 18 is also obtained from the pressurized source 110 and also utilizes a flow regulating valve 126, including a visual reading device 128, prior to admitting gas to another cooling tank similar to tank 120. From the cooling tank 130, the gas flows to a two position, double acting fluid-operated valve 132 and then through a line 134 flexibly secured to the upper portion of the valving arrangement 18. When the valve 132 is in its nomal rest position, the condition shown in the uppermost (cross-hatched) rectangle is established, that is, the valve is closed and when the valve is held open by fluid in line 234, the connections shown in the lowermost rectangle are established. Fluid motor operation of the gas valve 132 by conduit 234 is controlled by the mechanico-hydraulic motivator 20 in timed sequence with operation of the valve rod operating motor 62 as well as with shifting motion of the mold carrying member 14 as will be explained.

The shiftable support or table member 14 upon which a plurality of molds 10 are supported is preferably shifted with an intermittent motion most desirably of the stepby-step type including a dead stop between shifts. This may be accomplished either by a rotary indexing table, a series of adjacent tables moved in a generally horizontal endless rectangular path, or a plurality of support members secured to an endless type chain following a generally vertical oval path, as can be understood. Whatever the path followed by the molds 10, the shiftable member 14 may be driven relative to its fixed supporting member 136 by means of a lash-free double acting fluid motor 138 which may operate any suitable ratchet to power any suitable step-by-step drive mechanism 140 connected to the table 14.

On the shiftable member 14, the molds 10 are supported against relative horizontal movement by cylindrical sockets 142 in the low brackets or holders 12, and against a vertical downward movement by narrow annular shoulders 144 formed by bores 146 in the shiftable member 14 centrally of each socket 142. Each identical mold and core arrangement may comprise a plurality of interfitting forms preferably of the blown shell mold variety defining the shape of the article to be a cast. When, for instance, a blank for a valve lifter body or tappet is to be cast, the mold and core arrangement may utilize a cup-shaped bottom member 150, a tubular shaped intermediate member 152, an upper end closure member 153 including a depending concentric core 154, and a plug member 156 to close the upper end of the depending core if the core is hollow. These various interfitting members may be formed of suitably bonded sand and individually assembled by automatic equipment before being automatically loaded into the sockets on the shiftable member 14. The mold and core members when assembled define the generally cup-shaped configuration of the valve lifter body blank or tappet including the variously stepped diameter portions of the tubular wall or body portion as well as a filling hole 153 connecting with an upper pocket 160 for extra metal needed to make up for shrinkage of the cooling casting. While the mold for casting articles individually shown in the drawings forms only a single article, it will be understood that such a mold may be utilized which forms several such articles by clustering the forms equi-distant about a central pouring sprue with gates leading to each cup-shaped form, and providing a suitably enlarged bracket on the shiftable member.

Each molten metal pouring station may include both the pouring and holding containers diagrammatically illustrated in FIGURE 1. This invention utilizes a plurality of such stations, two of which are indicated in FIGURE 3. The stations may be similar except for the type, temperature and amount of metal which is to be metered to the mold, and similar parts bear similar reference characters with the addition of a prime mark. Thus, each mold moves from left to right in FIGURE 3 on the shiftable member 14, stopping first beneath the spout 38 for the first metal to be poured and then beneath the spout 38 for the next metal to be poured.

See FIGS. 4 to 7. For loading and unloading the molds 10 to and from the holders 12 on the shiftable member 14, a pair of transfer arms may be provided, one at a first station ahead of the plurality of pouring stations and one at a final station following the series of pouring stations. The loading means 174 at the first station is illustrated in FIGURE 4; the unloading means 176 at the final station is illustrated in FIGURE 7. Both means may comprise horizontally swinging transfer arms with a gripper at the outer end and an elevating mechanism at the pivot, and they may be identical in structure differing only in operational timing of moving parts-thus detailed description of one will sufiice to disclose the structure of both.

As can be seen in FIGURES 46, such a transfer arm may comprise a generally horizontally extending swinging body member 178 fixed at one end on a vertical pivot shaft 180 which is journalled in and axially shiftable through suitable bearings 181 in the machine base. Pinion teeth 182 integral with the pivot shaft are engaged by the teeth of a shiftable rack 183. A pair of U-cup sealed piston faces 184 on either end of the rack 183 reciprocate in aligned cylinders 185 to shift the rack to and fro between adjustable limit stops 186. Pressurized fluid admitted through a connection 187 swings the arm away from the index member 14, and pulsator fluid admitted through a connection 188 swings the arm in the opposite direction toward the index member 14, as can be understood.

The lower end of the arm pivot shaft 180 has a swivel connection 189 with the upper end of the rod 190 of a piston 191 vertically reciprocable in a cylinder 192 in the machine base. Pressurized fluid admitted to the cylinder 192 through a connection 193 biases the shaft downwardly on the machine base, and hydraulic medium admitted through a connection 194 elevates the shaft 180 and consequently lifts the arm 178 bodily upward a predetermined distance. It will be noted that the pinion teeth 182 are axially elongated so as to retain their meshing engagement with the rack 183 as the arm is raised and lowered.

On the outer end of such a transfer arm, a pair of gripper jaws 195 are shiftable in opposition to one another along the arm axis. They shift in unison by means of a common double rack and central pinion assembly 196 housed in the arm itself. Double piston-cylinder arrangement 197 in the arm serves to close the jaws when controlled by hydraulic pressure through a connection 198, and open the jaws when subjected to superior hydraulic pressure through a connection 199.

The transfer arms may be operated by the mechanicohydraulic motivator (explained in detail below) in the following fashion. First, the jaws of the loading arm 174 close to grip a fresh shell mold 10 at a supply statiton continuously replenished with fresh molds by suitable means such as an endless belt. Then the loading arm is raised to lift the mold clear of guide rails at the supply station so that it may swing clockwise (FIGURE 4) to position the gripped mold over the socket 142 of a holder 12 presented at the loading station. Lowering of the arm and subsequent opening of the jaws serves to deposit the mold on the index member, which may begin its next indexing movement prior to the arm swinging counterclockwise back to the mold supply station.

The unloading arm 176 (FIGURE 7) may move through a somewhat different cycle. As a filled mold is indexed by the member 14 to the unloading station, the jaws of the unloading arm close to grip the mold, crunching through any loose sand if necessary and engaging the cooling casting. Then the arm will raise bodily, lifting the casting clear of the fixture 12 free to swing counterclockwise to a position above a shaker screen. At this point, the jaws may open and allow the workpiece to drop to the screen which will vibrate it away toward a gate removal operation, freeing the casting of loose sand as it goes. The unloading arm may then be lowered as it is returned in a clockwise direction to receive the next filled shell mold. Thus, the loading and unloading means, while identical in structure, follow different programs to render the composite casting apparatus of this invention entirely automatic and well suited to modern high volume mass production requirements.

For operating the gas cycle valve 132 and the tube oscillating fluid motor 62 for each of the pouring stations, the loading and unloading means, and the drive motor 138 for the mold shifting member, a mechanico-hydraulic motivator is provided, as shown schematically in FIG. 1. Briefly, such a unit 20 ordinarily comprises a main camshaft 210 having a plurality of rotary cams 212 keyed thereon, each cam having a contour (not specifically shown) having suitable rise and fall ramps to produce a desired motion of a roller type cam follower 216 during each complete revolution or cycle of the cam. The camshaft 210 may derive its rotary motion from a worm wheel secured thereon and driven by a worm gear on a cross shaft 222 in a transmission unit 226 driven by a motor 224. The transmission may be of the plural speed variety to impart rapid rotary motion to the camshaft 210 during one portion of its revolution, and the slower rotary motion through the remaining portion of its revolution, as desired; suitable means controlled by the camshaft 210 itself may be utilized to shift the transmission 226 from high to low speed, and vice-versa.

Each cam follower 216 is journalled in the end of the rod 228 of a pulsator piston Z30 reciprocable within a fixed cylinder 232. The cam, cam follower, piston linked to the cam follower, and the fixed cylinder form a pulse transmitter of the expansible chamber type. Interconnecting each fluid motor, such as the motor 138 which comprises an expansible chamber type receiver, with each 9 transmitter for the purpose of transferring motion between the cams and the motors, is a liquid column 234. The liquid columns may comprise any suitable hydraulic medium confined by either rigid conduits or flexible piping. They conduct to-and-fro motion between the transmitters and the corresponding receivers.

The head B of each pulsator unit may also include a combined replenishing and relief valve which may be referred to as a balancing valve, and serves to balance the volume of liquid in each of the cam operated liquid column sections. Each balancing valve contains a replenishing check valve 236 and a spring closed relief valve 238. All the replenishing and relief valves are connected to a common oil reservoir 240 formed, for instance, in the housing for the mechanico-hydraulic drive unit. The reservoir 240 is preferably subjected to a low, superatmospheric pressure by a body of compressed air or other pressure maintaining arrangement. Check valves 236 allow flow from the reservoir 240 to the liquid columns, while relief valves 238 allow flow oppositely when the pressure exceeds a certain value.

In order to insure proper synchronization of the driving and driven elements of each pulsator section, it is desirable to provide slightly more fluid displacement in the driving or transmitting elements 230, 232, than is present in their respective fluid motors at the opposite end of the liquid column line. Thus, at the end of each advancing stroke of a transmitter piston 230, a small amount of fluid will be discharged to the reservoir 240 through a relief valve 238. This amount, plus any amount lost through leakage, will be returned to the liquid column at the end of the return stroke by the operation of the replenishing valve 236.

In FIGURES 1 and 4-7, there are shown several circles marked RO connected to the end of the hydraulically operated valve and the other fluid motors opposite the liquid column connections. These symbols designate the return oil connections by means of which a pulsator system may be hydraulically biased so as to maintain the follower in close contact with the cam as the falling portion of the cam contour recedes from the fo -lower. This bias is maintained by a high pressure accumulator or oil reservoir, not shown, which may be provided with a manifold whereby all of the R connections are joined together and to. the high pressure reservoir. The showing of separate return oil connections is indicative of any suitable type of biasing pressure source, whether it be a single accumulator or multiplicity thereof.

The left-handmost pulsator section in the upper bank thereof operates, by means of its liquid column 234, the cycle gas valve 132 for admitting a fixed volume of gas to the valve body member 18. The middle pulsator section of the upper bank of pul'sators operates, by means of its liquid column 234, the fluid motor 62 for cyclicly rotating the valve body member 18 in timed relation to the presentation of a fresh mold beneath the pouring pot 16. The right-handmost transmitter in the upper bank operates, by means of its liquid column 234, the fluid motor 138 for driving the shiftable mold carrying member 14. The lefthandmost transmitter in the lower ban-k may connect by means of its liquid column 234 with the connection 199 of the fluid motor means 197 for operating the gripper jaws on the transfer arm. The middle pulsator section of the lower bank may connect with the motor cylinder 192 at 194 for raising the transfer arm. Finally, the right-handmost pulsator may connect at 188 with the motor cylinder 185 for swinging the transfer arm. It will be understood that additional similar transmitter units are provided on the camshaft 210. to operate the fluid motors for valves similar to the ones 132 nd 18 at the other pouring station as well as to operate the three fluid motors of the other transfer arm 176 for unloading filled molds in timed sequence with theirpresentation by the index mold support 14.

The small finished article formed by the mold and core 10 arrangement 10, such as a valve lifter or tappet, may best be visualized with reference to FIGURE 12. Such a product maycornprise a cup-like body 162 approximately two inches in overall length having a generally tubular wall portion 164 including a thin part 164a and a thick part 1641) which latter is closed by a disk-shaped end closure member or bottom 166. The bottom 166 forms with the thick part 16% the usual, known pocket 167. The bottom face 168 of the tappet body is adapted to follow a rotary cam in an automotive engine or other such machine, and is preferably of an extremely wear resistant material. An annular inner surface 170 extending around the inner periphery of the body skirt or wall portion 164 begins at a point 172 intermediate the ends of the product and extends from that point a certain distance axially toward the upper end. It is adapted to receive a slidable plunger with a predetermined leakage fit when in ultimate operation; consequently, such a surface 170 is preferably formed of readily machineable material so that it can later be finished by an internal grinding or similar step to the precise dimensions required in the finished product. Other thicker and thinner wall portions evident from the cutaway portion of FIGURE 12 are'provided for other operational requirements of the tappet.

It will be obvious, then, that the first 'wear resistant molten material must be poured into the mold and core arrangement to a height above the line marked 174 in FIGURE 11 but not higher than the point 172 where the accurately finished surface 170 begins. Such a range is marked in FIGURE 11 by a dimension arrow 176. Preferably the height to which the first metal is poured lies between the top and bottom of the spring pocket, in the thick walled part of the tubular portion, as indicated in FIG. 9. Then, the next poured readily machineable type of molten material is admitted to the mold directly on top of the first poured after a surface barrier has formed, and it is allowed to fill more than the cavity which forms the cup 162 in the mold to complete the pouring of the article.

I have discovered that by carefully controlling the mixing of the two molten metals, not only is each metal confined to the intended part of the final casting, but a greatly improved bond or joint between the two metals is formed.

I control the joint or bond by forming on the top, exposed surface of the first metal a non-liquid barrier which prevents flow of metal through itself. This barrier may be a solidified or frozen skin or film or layer of the first metal on top of the molten remainder of the first metal. Or it may be a screen of interlaced or connected solid crysta s with interstitial liquid. Whatever its nature, it prevents the second metal, when poured onto the first, from flowing through the barrier. The barrier, by preventing the second metal from flowing through it, prevents flowing, swirling and mixing of the first and second metals into each other. There is then a temporary barrier of solid first metal between two masses of molten metal. The temperature and mass of the second metal are such that the molten second metal then melts the barrier. As the barrier melts the two metals mix in the space occupied by the barrier, but neither metal occupies any significant amount of space in that part of the mold assigned to the other metal. This mixing is continued to a thin layer or zone and produces a bond which I have found to be different from, and stronger than, bonds produced by any method heretofore known.

The skin or barrier may be formed by carefully controlling the cooling of the first metal. The cooling will be understood by referring to FIG. 18; which is part of a typical constitution diagram showing the liquidus and solidus lines for a representative iron-carbon alloy of'the type I may use in carrying out my invention. In FIG. 18 ordinates represent temperatures F, and abscissae represent percentages of carbon in an iron alloy. The upper or broken line is the liquidus or locus of liquidus temperatures. At temperatures above this line all of the alloy is liquid, whatever percentage of carbon it may contain.

The lower or unbroken line is the solidus. At temperatures below this line all of the alloy is solid, regardless of its percentage of carbon. At temperatures and percentages of carbon between the solidus and liquidus, the alloy is partly liquid and partly solid, that is solid particles are forming in a liquid.

I form the barrier on the surface of the first liquid by reducing the temperature of the surface to about the solidus. The temperature of the metal below the surface is maintained well above the solidus, so that the metal beneath the barrier remains molten, that is predominantly liquid. A screen type barrier may form when the tentperature is near, but above the solidus, or if the metal cools slightly below the solidus a frozen skin or film type barrier will form on its surface. Either form of barrier will carry out my invention as long as it prevents the second molten metal from flowing through it and is subsequently remelted. When the second metal is poured, this melts the barrier sufiiciently to establish a single mass of molten metal which has ditferent properties in different parts of the mold.

Referring in particular to FIGURES 8, 9 and 10, the critical nature of the time element in relation to the metal temperatures can best be appreciated. In FIGURE 8, the lower corner of a mold and core arrangement is illustrated in longitudinal sectional view as it appears immediately after a metered amount of a first molten metal is poured therein. The metal fills the mold in a liquid state to a certain point and begins to cool, and then freezes relatively quickly depending upon its pouring temperature and the cross-sectional area of the casting. As indicated in FIGURE 9 by cross-hatching of the metal in the mold, the cooling takes place first at the outer layers of the quantity of metal, the layers in contact with the relatively cold sand. Metal holders such as the brackets 12 adjacent the sand molds serve to impart an additional chill to the metal and cause a quicker freezing of the adjacent outer layers of metal.

If the first metal is entirely molten when the next molten metal is poured into the mold, an undesirable contamination of the lower portions of the casting will result from turbulence and inter-mixing of the two molten metals. For instance, the second amount of metal entering the mold from a certain height under the force of gravity will penetrate beneath the surface of the first poured metal and mix therewith throughout an undesirably large zone. On the other hand, if the first poured metal has solidified, no satisfactory blending and joining of the two metals will take place. Such a joint will be unacceptable for many uses, particularly where the joint is subject to thermal stresses in shear such as valve lifter components.

As the casting cools, or as the finished tappet changes temperature in use, it is known that the thick disk shaped end 166 may change dimension radially at a different rate than the tubular shell 164. This may be due to differences in coefiicients of thermal expansion of the two materials, or to differences in the mass or thickness of the two portions, or to both. Such changes in radial dimension, if different, produce radial stresses in the tappet, which appear as stresses in shear in the juncture zone shown in FIGS. 11 and 12.

The desired composite casting for valve lifter bodies and the like includes a substantial but clearly defined zone of blending of the two adjacent metals anywhere within the axial distance 176. This is preferably an annular zone as shown in FIG. 12 between two tubular portions joined end to end. To obtain such a zone of blending, the second poured metal must be introduced to the mold when a barrier of necessary strength or thickness has formed on the upper portion of the first poured metal, and at a temperature high enough to remelt the barrier without first being cooled itself below the solidus.

The barrier must be strong enough to break the fall of the second poured metal to prevent complete mixing throughout the entire lower portion of the casting, yet

12 mus-t be thin enough to be remelted by contact with the second poured molten metal so that the two masses of molten metal of different characteristics may blend in the liquid state throughout the substantial, controlled zone. Furthermore, the molten core of the first poured metal behind the skin aids the second metal, which may settle quickly to a quiescent or non-turbulent state, to remelt the intervening surface skin. Finally, with the separating barrier dissolved or melted, slight motion of the second metal as it moves to feed the shrinking metal prevents voids in the first metal. It is important that the time between the introduction of successive amounts of different molten metals to a single mold must be accurately controlled and is affected by their pouring temperatures to produce a composite article of a given cross-sectional size in production quantities having the desired joint characteristics.

For instance, in FIGURES 13 through 17 there is illustrated, by means of photomicrographs, the metallurgical structures of five exemplary composite castings. Each of the castings was sectioned, polished and nitol etched preparatory to photographing at approximately one hundred times original size. The photographs clearly show the zones of confluence or blending between dissimilar metals.

Example I in FIGURE 13 shows a composite casting produced by first pouring a approximately 2700 degrees Fahrenheit, and allowing it to settle by gravity to fill the lower portion of a mold, a molten iron-carbon compound of the gray iron variety having the following approximate analysis:

Carbon 2.70 Silicon 1.64 Manganese .65 Chromium .03 Sulphur .04 Molybdenum .02 Nickel .03 Phosphorous .10 Vanadium .02

Balance iron.

The mold was an invested shell mold at room temperature forming a cylindrical cavity of an inch in diameter and about 4 inches long, providing a circular horizontal cross sectional configuration of about .11 square inches. Two (2) seconds after pouring the first amount of molten metal, an amount of molten iron-carbon compound identified as 1095 nonresulfurized carbon steel at approximately 2800 degrees was introduced to the mold in direct contact with the previously cast iron to complete the casting process. After air cooling in the mold, the casting was normalized for about one-half hour at 1600 degrees, then reheated to 1550 degrees and oil quenched.

The photomicrograph shows in the lower portion the normal structure of a mottled to gray iron. Bright carbides, unconnected and uniformly distributed in random array, are clearly visible, some of which had started to decompose from a temperature increase and deposit dark temper carbon nodules in the solid iron. In the upper portion is the fine grained structure, probably martensitic with some scattered carbides, of normalized and hardened 1095 steel.

In the mid-portion of the picture, a dark, heavy concentration of carbon diffusing temper carbon deposits upwardly in decreasing abundance across the zone between the iron and steel is clearly demarked by the light zone of decarburization caused by the high carbon of the cast irOn diffusing rapidly to the steel and leaving a zone of depleted carbon. Below and to the right of this line of demarcation, the iron and steel intermingled in the liquid state as is evidenced, for instance, by the carbides in the steel.

Example II in FIGURE 14 shows a composite casting produced by first pouring at approximately 2750 degrees, and allowing it to settle by gravity to fill the lower portion of a mold, a molten iron-carbon compound of the alloy iron variety having the following approximate analysis:

Carbon 2.8-3.4. Silicon 2.0-2.4. Manganese .7- .9. Chromium .91.25. Sulphur .1 max. Molybdenum .4- .7. Nickel .4- .7. Phosphorous .2 max.

Balance Iron.

The mold was a blown shell mold at room temperature forming a generally cup-shaped cavity the walls of which had a .875 inch outer diameter and a .46 inch inner diameter providing an annular horizontal cross sectional configuration of about .445 square inch. Eight (8) seconds after pouring the first amount of molten metal, an amount of molten iron-carbon compound identified as 1144 openhearth resulfurized carbon steel at 2970 degrees was introduced to the mold in direct contact with the previously cast alloy iron to complete the casting process. After air cooling in the mold, the casting was normalized for about one-half hour at 1600 degrees, then reheated to 1550 degrees and oil quenched.

The photomicrograph shows in the lower portion the normal white structure of alloy iron created by the presence of small, separated cementite particles. In the upper portion is the structure of a fine grained steel with no effect of the alloy iron. Because of the heat treatment, the structure is predictably martensite with fine pearlite at the grain boundaries, especially near the top.

In the mid-portion of the picture, the sharp line of demarcation indicates where carbon and other combining ingredients from below the line in the alloy iron difiused upwardly with decreasing abundance into the steel, leaving no carbides visible in the light carbon depleted zone immediately below the line. Evidence of metallurgical blending exists below the line down to where the characteristic cementite configuration of alloy iron is manifested, and above the line up to where the characteristic fine grained steel containing fine pearlite, which would not form with the presence of excess alloys from the lower iron, is manifested.

Example III in FIGURE 15 shows a composite casting produced by first pouring, at approximately 2700 degrees, into the bottom of a cylindrical mold similar to the mold in Example I a molten iron-carbon compound of the alloy iron variety having an analysis similar to the alloy iron of Example II. Six and one-half (6 /2) seconds after pouring the first amount of molten metal, an amount of molten iron-carbon compound at about the same temperature was introduced which was of the gray iron variety having the following approximate analysis:

Balance Iron.

The completed composite casting was air cooled in the mold and the photomicrograph taken prior to any normalizing or heat treating operations to illustrate the appearance of such an article as cast.

The photomicrograph shows in the lower portion that the alloy iron cast essentially as white iron due to the small cross section of the casting and the resultant rapid cooling rate, cementite being evident. In the upper portion is the normal composition of gray iron, with some ferrite formed around the usual type A and type B graphite.

In the mid-portion of the picture, the intermingling or blending of the two metals forms a thorough bond. Some type D graphite and some pearlite is evident; some of the eutectic carbides have decomposed to graphite.

The gray iron shows in addition the diffusion of alloys and carbon into it, evidencing the mutually penetrating nature of such a metallurgical blend.

Example IV in FIGURE 16 and Exatmple V in FIG- URE 17 show composite castings produced under similar conditions with the single exception of the length of time between the first and second pours. In both, the first metal was an iron-carbon compound, poured at approximately 2710 degrees, of the alloy iron variety having an analysis similar to the alloy iron of Examples II and III; the molds were identical to the cup-shaped tappet body mold used to produce the casting of Example II; the second poured metal was an iron-carbon compound, poured at approximately 2720 degrees, of the gray iron variety having an analysis similar to the gray iron of Example III. Both castings were air cooled in their respective molds, normalized for about one-half hour at 1600 degrees, then reheated to 1550 degrees and oil quenched.

As to the difference in time lapse between pours, in Example IV of FIGURE 16' twelve (12) seconds was allowed to elapse; whereas, there was a period of only seven (7) seconds in Example V of FIGURE 17.

Both photomicrographs show in the lower one-fourth to one-third portion the normal structure of hardened alloy iron. White, uniformly distributed, unconnected crystals of eutectic cementite are surrounded by a largely martensitic matrix. Stabilizing carbide forming alloys such as molybdenum and chromium resisted most decomposition of these carbides during reheating; however, some small portion of the cementite has decomposed to form temper carbon up near the junction with the gray iron. Because of the small cross-section and consequent relatively rapid freezing rate, some flake type D graphite is apparent.

In the upper portion, both photomicrographs show the normal structure of machineable gray iron distinguished by a virtual absence of carbides due to the high silicon content and a general lack of alloy influence. In Example IV this pure zone extends from the top about one-fourth of the way down the left-hand side, and one-half way down the right-hand side, of FIGURE 16, leaving a relatively narrow zone of comingling or blending because of the longer cooling time between the first and second pours. In Example V this pure gray iron zone is visible only along the upper edge and upper left-hand corner of FIGURE 17, leaving a relatively wide zone of blending because of the shorter cooling time between successive pours of dissimilar metals.

In the mid-portion of both pictures, the lower portion of the juncture zone begins where the free cementite of the alloy iron is randomly distributed from its lower regular pattern. Above this, flake graphite formed in the liquid state of the gray iron is mixed with decreasing cementite of the alloy iron; this is a graduated dispersion of one iron into the other, the upper portion of this zone of confluence merging smoothly with the gray iron characteristics, and the lower portion exhibiting an increasing amount of cementite particles eventually forming into their traditional alloy iron orientation. Thus, Examples IV and V illustrate the manner in which the range of the blending zone between two metals may be controlled, other factors being equal, by the time lapse between successive pours of molten metals into a common mold.

The five examples of composite cast articles illustrate different results obtainable with the method and apparatus of this invention. In each, however, the first and second poured metals are separated by the blending zone, which leaves the separated zones of metal essentially unmodified. Each separated zone retains its as-cast characteristics without invasion or influence of the other metal. It will be noted that if the cross-section of the casting, the analysis and pouring temperatures of the two metals, and the time lapse between pours are not controlled in accordance with the principles and teachings 15 of this invention, such a controlled zone of blending would not be produced.

For instance, the extent of the blend zone in Examples I and II is roughly of the same range or length between the upper and lower metals in their undisturbed state, but the time lapses (2 seconds as against 8 seconds) is quite different. However, control was exercised to obtain similar blend depths by providing a difference of about 170 in the pouring temperatures of the steels, as well as a variance in the size and shape of the mold. While the first poured iron in Example II cooled for 8 seconds to form a relatively thick surfiace skin, the hotter steel was able to effect a more significant remelting thereof to give a desired range to the conflux.

Similarly, the size and shape of the mold and the pouring temperatures were identical in Examples IV and V, but the time lapse alone controlled the extent of confluence, as noted above. Yet in each of the five examples, the identity of the upper and lower iron-carbon compounds has been preserved, a result which would not have been obtained if the time limit were too short, the casting too large, the metals too hot, or the like, which would have allowed uncontrolled intermixing over an undesirably large range and perhaps throughout the entire mold.

It will be clear that many other combinations of casting materials, cross sections of the casting, molds, pouring temperatures, time lapses and the like may be employed in the practice of this invention depending upon the characteristics desired in the finished product. Consequently, these illustrations are to be construed as illustrative only of several possible products, and not in an exclusive or limiting sense.

In operation, fresh shell molds 10 are cast, assembled and then continually fed by the belt conveyor to the supply station where the loading arm 174 transfers them to the brackets 12 on the shiftable member 14. The table 14 presents the molds successively beneath the plurality of molten

metal pouring containers

16 and 16. As an individual mold is shifted beneath the container 16, the arrangement 18 measures and delivers a predetermined amount of a desired molten metal to the lower portion of the concentric mold and core arrangement 10 to form the lower cam contacting portion of the valve tappet body blank. Then, the member 14 is shifted to present the same mold beneath the container 16 whereupon the arrangement 18' measures and delivers a second predetermined amount of a different desired molten metal to the mold in contact with the first poured to fill the mold up to the excess metal pocket 160 to complete the cast composite article. The amount of time between the first and second pourings of metal to the individual mold is governed by the spacing of the pouring stations and by the speed with which the member 14 shifts the mold between the two stations. The valving arrangements 18 and 18' at each pouring station, as well as the tables shifting motion, are regulated in an accurately timed sequence controlled and powered by the rotary cams of the mechanico-hydraulic motivator 20. This insures that an exact amount of time elapses between the first and second pourings of molten metal to each individual mold as it is presented beneath the plurality of pouring stations. Such power and control arrangement together with controllable heating means 26- renders this invention applicable to casting identical composite articles in production quantities. As the castings cool and the bonding medium burns off the sand in the molds, the table may shift the bracket 12 to the ejecting station where the castings are removed by the unloading arm 176 and placed on the shaker screen to remove loose sand.

The means for measuring and delivering a predetermined amount of molten metal from the various pouring containers to the molds are operated by the fluid motor 62 and the fluid operated valve 132. When a valve rod 18 is in the delivering positoin indicated in FIGURE 2, molten metal from the container cannot enter the measuring cavity 46 from the relatively constantly pressurized supply in the crucible. When the valve member 18 is turned about its longitudinal axis by the motor 62, however, the lower port means 44 disconnects from the pouring spout 36 and connects with the metal inlet port 42 in the container. As the valve rod is so shifted, the inert gas metering valve 132 is opened by the timed influence of its control cam in the mechanico-hydraulic motivator to admit a predetermined volume of gas from the cooling tank to the upper gas chamber 48 of the metal measuring cavity. As metal and gas enter the metal measuring cavity from below and above, respectively, a balance between the two is attained dependent upon the pressure of both the gas in the cavity and the metal near the inlet opening 42 in the seat to regulate the amount of metal that enters the measuring cavity. The depth of molten metal in the container 16 is maintained between high and low depth limits covering a small range to insure a generally constant pressure of molten metal at the inlet port means 42; this pressure is a combination of atmospheric pressure on the surface of the metal, the weight of the column of metal, or head, above the port 42, plus any increase attributable to the nitrogen or other atmosphere admitted from the source A through the pipe 76.

The fixed volume of inert gas admitted to the upper portion of the measuring cavity while metal is flowing in at the lower portion will immediately begin to expand as it flows downwardy in contact with the hot cavity walls of the tubular valve arrangement 18. The quickly heating gas creates an increasing counterpressure on the metal admitted to the lower portion of the measuring cavity, and tends to gradually push the level of the metal in the cavity downward. For instance, molten metal may initially fill the measuring cavity to a point near the top of the narrow connecting passage 50. However, as the gas pressure in the upper chamber 48 increases due to the heating effect of the proximity of molten metal at elevated temperatures, the level of metal in the cavity recedes in the narrow zone 50. Since this all takes place in a matter of a second or less, and since the head of molten metal effective on the inlet port 42 is generally constant, and since the volume of gas admitted to the upper chamber 48 of the metal measuring cavity is the same every cycle as a result of the temperature controlled tank 130, it will be evident that oscillation of the valve member 18 about its longitudinal axis at a present time interval will effectively determine the amount of metal retained in the metal measuring cavity when the lower port means 44 is disconnected from the inlet port 42, Such a timed control for isolating the metal measuring cavity from the supply of molten metal in the container can very effectively be established by the cam timed power and control of the mechanico-hydraulic motivator 20.

As the valve 18 is turned with the metal measuring cavity containing the desired predetermined amount of molten metal, the lower molten metal port means 44 will connect with the pouring spout 36. By this time, the gas in the upper chamber 48 of the metal measuring cavity is heated to the point where it exerts a downward pressure on the molten metal via the restrictive passage 50- greater than the atmospheric pressure present at the exterior of the container 16 (that is, in the pouring spout 36). Consequently, the molten metal in the measuring cavity will be forced downwardly and out the bottom of the pouring spout 36 and into the mold 10. At this point, the initially regulated volume of inert gas will have expanded down through the

passages

50, 46, 44 and 36 to fill a volume allowing its pressure to recede to slightly above atmospheric. Some gas will thus escape out the bottom of the pouring spout 36 to establish atmospheric equilibrium, and this gas, being heavier than the surrounding air, will sink into the mold 10 following the shot of metal, covering the upper surface of the metal and 1 7 thus impede the formation of oxidation scum on the mctal's surface. The gas that escapes from the metal measuring cavity each cycle is equal to the amount introduced to the upper portion of the cavity at the beginning of the cycle, Thus, the small amount of cool gas that is admitted every cycle is lost on every cycle; however, this amount is small in terms of cool gas which is then economically expanded by the heat of the molten metal to a volume which fills the entire empty metal measuring cavity, pouring spout and shell mold after the metal has been delivered to the mold, and bathcs the various surfaces with which molten metal comes into contact with the inert gas to prevent oxidation and formation of undesirable by-products thereof.

As successive amounts of molten metal are metered from the container 16 by operation of the arrangement 18 cycle after cycle, the level of the molten metal in the container 16 will reach the predetermined minimum and the limit switch LS1 will be tripped by the abutment 106. This, through the electric circuitry and solenoid 98, operates the valve arrangcmcnt 24 to rotate it about its longitudinal axis so that the end groove 92 connects the inlet port 94 with the pouring spout 90 of the upper or holding container 22. Metal may holding container 22 to the lower crucible 16 until the lower crucible contains an amount which will cause breaking of electrical contact at LS2. While metal is flowing from the upper to the lower container, LS3 is closed by the position of the solenoid 98 and gas from the cooling tank 120 is admitted to the central bore 86 of the upper valve arrangement 24. When the valve 24 is returned to its inoperative position to stop metal flow, the valve 122 also shuts off gas flow. The'lower port 88 then allows the expanding gas in the bore 86 to flow downwardly under its increasing pressure and force all metal out of the pouring spout 90 and into the lower crucible 16. Aside from bathing all the metal contacting parts of the upper valve and its pouring spout 72 with an inert gas to prevent oxidation, the gas pressure also insures that no metal remains in the spout 90 where it might cool between the

pots

16 and 22 and cause clogging or other maifu'nctioning.

Thus, an improvement in composite casting has been disclosed which provides a simple, efficient, and-dependable means of metering precise amounts of different molten metals to a single mold at precise time intervals to obtain a uniformity in the finished product. The cast article has existed as a single, unitary, integral unassembled entity from the time it solidified from the molten state and became a recognizable solid article. Moreover, this casting is not a homogeneous structure because it is composed of distinct zones of differing materials which nevertheless are autogenously united or bonded they are formed in the ultimate article as indicated by the-photo micrographs. Such a casting has advantages over similar appearing'articles which are formed of"pre-existin'g"'por tions which are welded, brazed, fused or otherwise I bonded together. Such other articles which are the result of a later uniting of pre-formed bodies are more costly to manufacture in production quantities. Each portion must first be created individually, and then another operation must be performed to unite fusing or otherwise uniting of dissimilar metal pieces is at best a difficult task, and other different qualities of the metals involved. Often, if a joint can be obtained at all, it is not as satisfactory as the metallurgical blending obtained by this invention.

The metallurgical blending, as exemplified by the photomicrographs of ferrous metal composite castings, provides a. zone or bonding layer of iron-carbon compound comprising alloy a considerable range. It is like neither of the metals originally introduced to the mold which it-scparates, but constitutes a different metal having qualities at one side of the layer like one of the metals, and qualities at the the portions. But thedepending upon the melting point then run by gravity from the characteristics of a changing nature over i molten-interior of the body a non-liquid barrier which other side of the layer like the other metal, with a gradual or-progrcssivc change of such qualities across the thickness of the layer. There may be both an intcrmingling of entire islands of one metal into the body of the other metal, as well as a diffusion of constituents of one metal into the body of the other metal. While an intermingled amount of one metal may transform or effect qualities of the other metal, if at all, only around the borders of the displaced quantity, the diffused elements of one may change or modify the qualities of the other throughout the migration zone to varying extents depending upon the type and concentration of the diffused constituent. Other characteristics, such as temper carbon, are formed in the solid or frozen metal by reheating, a reheating which may occur as the second shot of metal is introduced to the mold, while characteristics such as flake graphite are formed in the liquid phase of the metal prior to hardening. Cementite particles in the first poured metal, too, may be decomposed to some extent in the area reheated by the second poured metal, a reaction controllable in part by the presence of carbide forming alloys. it will be obvious, too, that different analyses of the separate metals employed will produce different responses to heating and quenching, without.additional-wprevious carbu jzjng, so that the alloy make-up may be varied tobtain hardenability characteristics as desired. Depending upon the requirements, then, of the finished product, articles may be produced according to this invention having a zone of blended metals entirely different from the joint area produced by known processes of fusing together pieces of dissimilar metal.

The method for obtaining such a product makes use of a precise time lapse between the introduction of the successive amounts of metal to a mold to obtain only a desired amount of barrier on the first metal so that the second metal at a given temperature will rcmelt such barrier portions upon contact before the second metal itself freezes. Such a control step in the method insures similar articles time after time in mass production quantitles.

The disclosed apparatus by means of which the method of this invention is practiced provides for relative motion between the mold and the pouring stations at a predetermined rate. The spacings of the pouring stations from one another and the rate of relative motion between them and a mold insure: proper performance of the method, and the mechanico-hydraulic motivator combines therewith to comprise apparatus suitable to modern industrial use.

The difficult problem of metering predetermined small amounts of molten metals at elevated temperatures from a supply of such metal has been overcome to insure satisf factory composito casting by utilizing the inherent qualitics of an inert gas and a molten metal at given temperatures, volumes and pressures whereby, if the temperature requirements are satisfactorily maintained, the volume defining apparatus will-inherently function properly to measure and-deliver, by the operation of predictable pressures, predetermined amounts of molten metal to a mold;

While'the above described embodiment constitutes a preferred mode of carrying out this invention, many other forms might be adopted within the scope of the actual invention, whichis variously claimed as:

1. A method of controlling the bond between two different metals in a composite cup-shaped lappet body having a generally tubular wall portion closed at one end .comprising introducing a quantity of one molten metal into a mold, allowing the metal to form a first body of molten metal filling the mold part way up the wall, cooling the metal in the mold to form over the prevents the flow of molten metal therethrough, then introducing a quantity of another molten metal onto the barrier tolfill the mold and increase the height of the wall while melting the barrier so that th molten metals willmutually blend constituents of one into the other throughout the space occupied by the barrier to form an annular junction zone of a substantial axial extent that ends short of both the bottom and the top of the mold leaving separate zones of each molten metal-as introduced separated by the junction zone, one of the separate zones being an annular one at the upper portion of the wall and the other being a predominantly disk-like one across the bottom of the cup-shaped tappet body, and cooling the zones to unite autogenously the two metals as they solidify.

2. A method of controlling the bond between two different metals in a composite tappet body having a generally tubular wall portion closed at one end comprising providing a mold defining the generally cup-shaped configuration of the tappet body, introducing to the mold a quantity of a first molten metal including iron-carbon compound containing carbide forming alloys in amounts sufficient to produce a hard cementite structure upon freezing, collecting the quantity of said first molten metal in the closed end of the mold, forming on the exposed surface of said first molten metal a non-liquid barrier which prevents the fiow of molten metal therethrough, then filling the rest of the same mold with a quantity of a second metal including molten iron-carbon compound characterized by an absence of carbide forming alloys in amounts which would producea hard cementite structure upon freezing, the temperature of pouring of the second metal and the quantity of the second metal poured being such as to melt the barrier to produce a blending to the two metals in the space occupied by'the barrier to provide an autogenous union therebetween upon freezing.

3. A tappet body comprising a ferrous metal casting including two metals autogenously united to form a wall portion and a bottom face adapted to follow a rotary cam, part of the wall portion being composed of a gray iron containing silicon in amounts sufficient to produce graphitization of some combined carbon to the extent that the amount of hard, brittle carbides is insignificant, the bottom cam following face being composed of a hardenable alloy iron containing carbide forming elements in amounts sufficient to produce a uniformly distributed cementite structure with little free graphite, the gray iron being autogenously united to the hardenable alloy iron by a transitional iron-carbon metal having the properties of a metal which has been formed by the process of forming from the molten hardenablealloy iron on the surface thereof a non-liquid barrier which prevents the flow of molten metal therethrough, pouring the gray iron while molten onto the barrier so that there is a non-liquid barrier between a mass of molten hardenable alloy iron and a mass of molten gray iron, melting the barrier to form a single mass of molten metal, mixing the gray iron and hardenable alloy iron in the space occupied by the barrier and cooling saidsingle mass of molten metal.

4. A tappet body comprising a ferrous metal casting" including two metals autogenously united to form a generally tubular wall portion and a bottom closing one end thereof and forming therewith a generally cup-like body the bottom face of which is adapted tofollow a rotary cam, the entire ferrous metal casting being hardenable to a substantial extentby heating and subsequent fiuid medium quenching, part of the tubular wall portion of the cup-like body having a metallurgical analysis having one response to such heating and quenching, and the bottom cam following face of the cup-like bodyvhaving a metallurgical analysis .having a materially different response to such heating and quenching.

5. A tappet body comprising a ferrous metal composite casting including two metals autogenously united to form a generally tubular wall portion including an annular inner surface intermediate its ends and a bottom closing one end of the tubular wall portion andforming therewith a generally cup-like body the bottom face of which is adapted to follow a rotary cam, part of the tubular wall portion of the body including the annular inner surface being composed of an iron-carbon compound characterized by a relatively low content of carbide forming alloys and a minimal amount of hard, brittle carbides, the bottom cam following face being composed of a wearresistant hardenable alloy iron characterized by a generally m'artensitic matrix having substantially uniformly distributed unconnected carbides and a minor amount of free graphite, and the part between the annular inner surface on the wall portion and the cam following face including a transformation zone characterized by a decomposition of some carbides into temper carbon as well as a graduated diminishing of carbide particles and an increase in flake graphite going away from the bottom of the body.

6. A cast body of a tappet for an internal combustion engine comprising in combination a tubular portion having a thin walled part and a thick walled part and a cam follower closing one end of the thick-walled part, the tubular portion being cast of a first metal having a first combination of properties and the cam follower being cast of a second metal having a second combination of properties, the cam follower and thick walled part of the tubular portion being autogenously united by a cast bond of a third metal which has a progressive blend of properties from the first combination of properties to the second combination of properties.

7. A body of a tappet' for an internal combustion engine comprising in combination an integral structure including a tubular portion and a cam follower portion closing one end of the tubular portion, the tubular portion being' cast of a first metal having a first combination of properties and the cam follower being cast of a second metal having a second combination of properties, the cam follower and tubular portion being autogenously united by a cast bond of a third metal which has a progressive blend of properties from the first combination of properties to the second combination of properties.

8. A cast tappet body for an internal combustion engine comprising an integral structure including three co-axial parts, namely. a thin walled part of a tubular portion, a

. first thick walled part of the same tubular portion joined end-to-cnd to the thin walled part and a cam follower joined to the thick walled part, the tubular portion being cast of a first metal having first properties, and the cam follower being cast of a second metal having second and different properties, the cam follower including a second thick walled tubular part and a member integrally cast with, and closing the second thick-walled tubular part, the two thick-walled tubular parts being autogenously united by a cast bond of a third metal derived from the first and second metals and which includes a progressive blend of properties from the first properties to the second properties.

9. A composite east article comprising a first part of one metal, a second part of another metal and a juncture zone autogenously connecting first and second parts, the juncture zone being composed of metal having the properties of a juncture zone which has been formed by partly filling a mold with first molten metal having first properties, then cooling the exposed surface of the first metal to a temperature about the solidus of the first metal while maintaining mQlten metal below the surface so that there is nowon the surface of molten first metal a non-liquid barrier which prevents the flow of molten metal therethrough, then pouring onto the barrier second molten metal having second and different properties so that there is now a nonliquid barrier between two bodies of molten metal, then melting the barrier to form a single mass of molten metal haying portions of different properties while mixing the a two molten metals in the space occupied by the'barrier and then solidifying said single body of molten metal.

10. A cast article comprising first and second parts composed of firstand second ferrous metals respectively,

both metals being hardenable to a substantial extent by heating and subsequent quenching, the first metal having a metallurgical analysis having one response to such heating and quenching, and the second metal having a metallurgical analysis having a materially different response to such heating and quenching, said first and second parts being autogenously connected but separated in space by a juncture zone composed of metal having the properties of a juncture zone which has been formed by partly filling a mold with the first molten metal, then cooling the exposed surface of the first metal to a temperature about the solidus for the first metal while maintaining molten metal below the surface so that there is now on the surface of molten first metal a non-liquid barrier which prevents the flow of molten metal therethrough, then pouring second molten metal onto the barrier so that there is now a non-liquid barrier between two bodies of molten metal, then melting the barrier to form a single mass of molten metal having portions of different properties, while mixing the two molten metals in the space occupied by the barrier and then solidifying said single body of molten metal.

11. A method of controlling the bonding zone between two different metals in a composite casting having portions composed of different metals autogenously united, which includes providing a first source of first molten metal having first properties and a second source of second molten metal having second and different properties spaced from the first source, placing a mold for the casting at the first source, partly filling the mold with a predetermined quantity of first molten metal, then moving the mold and the sources relative to each other to place the mold at the second source, the movement being at such rate that in the time from pouring of the first metal to the placing of the mold at the second source the exposed surface of the first metal is cooled to about the solidus for the first metal while maintaining molten metal below the surface so that there is now on the surface of the molten first metal a non-liquid barrier which prevents the flow of molten metal therethrough, then pouring onto the barrier second molten metal from the second source so that there is now a non-liquid barrier between two bodies of molten metal, then melting the barrier to form a single mass of molten metal having portions of different properties while mixing the two molten metals in the space occupied by the barrier and then solidifying said single body of molten metal.

12. The method of controlling the bonding zone between two different metals in a composite casting having portions composed of different metals autogenously united which includes partly filling a mold with first molten metal having first properties, then cooling the exposed surface of the first metal to about the solidus for the first metal while maintaining molten metal below the surface so that there is now on the surface of molten first metal a nonliquid barrier which prevents the flow of molten metal therethrough, then pouring onto the barrier second molten metal having second and different properties so that there is now a non-liquid barrier between two bodies of molten metal, then melting the barrier to form a single mass of molten metal having portions of different properties while mixing the two molten metals in the space occupied by-the barrier and solidifying said single body of molten metal.

13. The method as defined in claim 12 in which pouring temperature and mass of the second metal are of such values as to raise the temperature of the barrier to about the liquidus.

14. The method as defined in claim 12 in which the first metal is an iron-carbon mixture containing carbide forming ingredients in an amount sufficient to provide a hard cementite type structure upon freezing, and the second metal is an iron-carbon mixture characterized by an absence of carbide forming ingredients in amounts which would produce a hard cementite structure upon freezing.

15. The method of making a casting having portions composed of different metals autogenously united which includes partly filling :a mold with a first molten metal having the first properties, introducing into the mold a non-oxidizing gas under pressure, forming on the exposed surface of the molten metal a non-liquid barrier which prevents the flow of liquid metal therethrough, pouring on the barrier a second molten metal having second and different properties to form the remainder of the casting,

- melting the barrier to form a single mass of molten metal having one portion of the first properties and another portion of the second properties and cooling the mass of molten metal to solidify it into a single integral casting having portions of different properties autogenously united.

16. The method of making a casting having portions composed of different metals autogenously united which includes partly filling a chamber with a predetermined quantity of molten metal having first properties, filling the remainder of the chamber with a predetermined quantity of inert gas under pressure, ejecting the molten metal and gas into a mold to fill the mold partly with molten metal :and partly with inert gas, forming on the exposed surface of the molten metal a non-liquid barrier which prevents the flow of molten metal therethrough, pouring a second molten metal having second and different properties on the barrier to form the remainder of the casting, melting the barrier to form a single mass of molten metal having one portion of the first properties and :another portion of the second properties and cooling the mass of molten metal to solidify it into a single integral casting having portions of different properties autogenously united.

17. The method of making a casting having portions composed of different metals autogenously united which includes partly filling a chamber with :a first molten metal having first properties and filling the chamber with inert gas under pressure, discharging the molten metal and gas into a mold, forming on the exposed surface of the molten metal a non-liquid barrier which prevents the flow of liquid metal thenethrough, pouring onto the barrier a second molten metal having second and different properties to form the remainder of the casting and expell the gas therefrom, melting the barrier to form a single mass of molten metal having one portion of the first properties and another portion of the second properties and cooling the mass of molten metal to solidify it into a single integral casting having portions of different properties autogenously united.

18. In a method of making a unitary casting having metals of different properties united by an annular joint in which significant thermal stresses in the joint are in shear, the improvement which consists in pouring a first molten metal having first properties into a mold to occupy a part only of the mold, temporarily forming on the exposed surface of the molten metal a non-liquid barrier which prevents the flow of molten metal therethrough, pouring a second molten metal having second and different properties on the barrier to form the remainder of the casting, melting the barrier to form a single mass of molten metal having portions of different characteristics and cooling the mass of molten metal to solidify it into a single integral casting having portions of different properties autogenously united by a layer subject to thermal stress in shear, which layer is composed of metal having a progressive blend of the first and second properties.

19. A body of a tappet for an internal combustion engine comprising in combination an integral structure including a tubular portion and a cam follower portion closing one end of the tubular portion, the tubular portion being cast of a first ferrous metal having a first combination of properties :and the cam follower being cast of a second ferrous metal having a second combination of properties, the cam follower and tubular portion being cast to form an autogenously bonded integral body.

(References on following page) UNITED 23 References Cited STATES PATENTS Wilks 22-205 Campbell 22-205 -Mer1e 22-201 X Bush 22-201 Wilcox 123-90 Fahrenwald 148-3 Fahrenwald 148-3 X WENDELL E. BURNS, Primary Examiner. I

Claims

7. A BODY OF A TAPPET FOR AN INTERNAL COMBUSTION ENGINE COMPRISING IN COMBINATION AN INTEGRAL STRUCTURE INCLUDING A TABULAR PORTION AND A CAM FOLLOWER PORTION CLOSING ONE END OF THE TUBULAR PORTION, THE TUBULAR PORTION BEING CAST OF A FIRST METAL HAVING A FIRST COMBINATION OF PROPERTIES AND THE CAM FOLLOWER BEING CAST OF A SECOND METAL HAVING A SECOND COMBINATION OF PROPERTIES, THE CAM FOLLOWER ANT TUBULAR PORTION BEING AUTOGENOUSLY UNITED BY A CAST BOND OF A THIRD METAL WHICH HAS A PROGRESSIVE BLEND OF PROPERTIES FROM THE FIRST COMBINATION OF PROPERTIES TO THE SECOND COMIBINATION OF PROPERTIES.
9. A COMPOSITE CAST ARTICLE COMPRISING A FIRST PART OF ONE METAL, A SECOND PART OF ANOTHER METAL AND A JUNCTURE ZONE AUTOGENOUSLY CONNECTING FIRST AND SECOND PARTS, THE JUNCTURE ZONE BEING COMPOSED OF METAL HAVING THE PROPERTIES OF A JUNCTURE ZONE WHICH HAS BEEN FORMED BY PARTLY FILLING A MOLD WITH FIRST MOLTEN METAL HAVING FIRST PROPERTIES, THEM COOLING THE EXPOSED SURFACE OF THE FIRST METAL TO A TEMPERATURE ABOUT THE SOLIDUS OF THE FIRST METAL WHILE MAINTAINING MOLTEN METAL BELOW THE SURFACE SO THAT THERE IS NOW ON THE SURFACE OF MOLTEN FIRST METAL A NON-LIQUID BARRIER WHICH PREVENTS THE FLOW OF MOLTEN METAL THERETHROUGH, THEN POURING ONTO THE BARRIER SECOND MOLTEN METAL HAVING SECOND AND DIFFERENT PROPERTIES SO THAT THERE IS NOW A NONLIQUID BARRIER BETWEEN TWO BODIES OF MOLTEN METAL, THEN MELTING THE BARRIER TO FORM A SINGLE MASS OF MOLTEN METAL HAVING A PORTIONS OF DIFFERENT PROPERTIES WHILE MIXING THE TWO MOLTEN METALS IN THE SPACE OCCUPIED BY THE BARRIER AND THEN SOLIDIFYING SAID SINGLE BODY OF MOLTEN METAL.
12. THE METHOD OF CONTROLLING THE BONDING ZONE BETWEEN TWO DIFFERENT METALS IN A COMPOSITE CASTING HAVING PORTIONS COMPOSED OF DIFFERENT METALS AUTOGENOUSLY UNITED WHICH INCLUDES PARTLY FILLING A MOLD WITH FIRST MOLTEN METAL HAVING FIRST PROPERTIES, THEN COOLING THE EXPOSED SURFACE OF THE FIRST METAL TO ABOUT THE SOLIDUS FOR THE FIRST METAL WHILE MAINTAINING MOLTEN METAL BELOW THE SURFACE SO THAT THERE IS NOW ON THE SURFACE OF MOLTEN FIRST METAL A NONLIQUID BARRIER WHICH PREVENTS THE FLOW OF MOLTEN METAL THERETHROUGH, THEN POURING ONTO THE BARRIER SECOND MOLTEN METAL HAVING SECOND AND DIFFERENT PROPERTIES SO THAT THERE IS NOW A NON-LIQUID BARRIER BETWEEN TWO BODIES OF MOLTEN METAL, THEN MELTING THE BARRIER TO FORM A SINGLE MASS OF MOLTEN METAL HAVING PORTIONS OF DIFFERENT PROPERTIES WHILE MIXING THE TWO MOLTEN METALS IN THE SPACE OCCUPIED BY THE BARRIER AND SOLIDIFYING SAID SINGLE BODY OF MOLTEN METAL.