US3729969A

US3729969A - Barrel forming press

Info

Publication number: US3729969A
Application number: US00173028A
Authority: US
Inventors: J Gibson; D Videtto; R Linse
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1971-08-19
Filing date: 1971-08-19
Publication date: 1973-05-01
Anticipated expiration: 1990-05-01

Abstract

A numerically controlled apparatus and method for forming barrels of a desired diameter by successively advancing incremental portions of flat metal stock along a longitudinal path, and transversely deforming each portion with a ram reciprocally disposed in a vertical plane and acting against an oppositely disposed non-uniform concave die, the apparatus including a sensor and feedback system responsive to determine magnitude of permanent deformation and to actuate the ram in relation thereto to correct for errors, and including the provision for transversely retracting the ram to allow for removal of a completed cylinder.

Description

States Patent 1191 can nite [111 3,729,969 Gibson et al. 1 May 1, 1973 [54] BARREL FORMING PRESS. 1,968,455 7/1934 Jones ..72 133 [75] Inventors: James W; Gibson; Donald A. xiii Videtto, both of North East; Richard V Lmse E an of Primary Examiner-Charles W. Lanham [73] Assignee: General Electric Company, Erie, Assistant ExaminerM. J. Keenan Pa. Att0rney-Walter C. Bernkopf et al. [22] Filed: Aug. 19, 1971 [57] I ABSTRACT [21] Appl' N07 173028 A numerically controlled apparatus and method for forming barrels of a desired diameter by successively [52] US. Cl. ..72/127, 72/7, 72/379, advancing incremental portions of fiat metal stock 72/702, 113/120 L along a longitudinal path, and transversely deforming B B210 d 51/00 each portion with a ram reciprocally disposed in a ver- [58] Field of Search ..72/8, 9, 7, 21, 22, i l la nd acting against an oppositely disposed non-uniform concave die, the apparatus including a 1 113/1 1 120 R, 120 L sensor and feedback system responsive to determine magnitude of permanent deformation and to actuate References Cited the ram in relation thereto to correct for errors, and UNITED STATES PATENTS including the provision for transversely retracting the ram to allow for removal of a completed cylinder. 1,573,810 '2/1926 Cunningham 72/384 3,057,394 lO/l962 Vuillien 36 Clams, Drawmg'Flgures 2,763,924 9/1956 Bellometti ..72/368 Patented May 1, 1 973 9 Sheets-Sheet 1 INVENTORS DONALD A. VIDET O RICHARD C UNSE JAMES \/J. GIBSON blr/h fim a THUR ATTORNEY Patented May 1, 1973 9 Sheets-Sheet 2 Patented May 1, 1973 9 Sheets-Sheet 5 Patented May 1, 1973 9 Sheets-Sheet 4 DESIRED BEND POINT (INCHES) Pafented Ma 9 Sheets- Sheet 9 A FULLY RETRACTED-DATUM PLANE B CLEARANCE 'DESIRED BEND POINT -OVERBEND COMPENSATION FOR SPRINGBACK WORKPIECE ADVANCEMENT mcREM ADDVI'IVE INCREF'IEN'I" CORRECTION POSITION FIGS .ENTSE (8| INCRENENTS) 6 I E l l I XK /m INCREI'IENTS an mcREnENTs" T 5 i 5. 5 F7 F8 2'0 2'! WORKPI ECE ADVANCEMENT" INCREMENTS BAR (2| mcREMENTs) v FIG. IO

REL

BARREL FORMING PRESS BACKGROUND OF THE INVENTION This invention relates generally to metal deforming presses and in particular to numerically controlled presses having relatively reciprocating, non-complementary tool faces for forming barrels from flat metal stock.

The art of forming rounds and curvilinear sections from flat work pieces is well-known and has generally been accomplished by one of three basic methods, the most common of which is the rolling method.

Inherent in the process of rolling flat stock into curvilinear shapes is the requirement that during the time a bending force is being exerted on the stock, the force imparting element is necessarily rotating and the stock is frictionall y engaged and moving relatively thereto, thus necessitating a driving power of greatmagnitude. This is particularly true of heavy plate where exceptionally high loading or bending effort is required to bend to small diameters. It is a characteristic feature of rolling that the operation is slowed down considerably when plates near the maximum capacity are being rolled due to the high friction effect on the bearings of the machine, thus leaving sometimes less than half the power of the machine for actual bending.

Another difficulty arising in the stock rolling method is that of forming the portions near the ends of the plate. Theoretically, it is impossible to bend the end of the piece, and to even approach the end requires a much greater force than the central portions because of the extremely short lever arm. Although this dilemma is present in any metal forming operation, it is of particular interest in the rolling process wherein greater forces are required due to factors discussed hereinbefore. Generally, a separate crimpting process is applied to the stock end before the rolling process is begun.

Further, it should be noted that rolling machines have severe restrictions as to the diarneter-to-thickness ratios of the work stock, and as a result if a wide range of sizes are deSired a plurality of machines will be required with the attendant additionalcosts.

A second method of forming rounds from flat metal stock involves the bending of the stock piece around a ram so as to cause it to conform to the shape thereof. The inherent qualities of spring back whichare present in the metal prevent the forming ofa shape which conforms exactly to the shape of the ram, and the degree of spring back will vary considerably as it is affected by many factors. In addition, the use of a specific ram is required in obtaining a specific diameter shape and the operation is considerably limited by the diameter-to thickness ratio of the metal stock.

The third method which is in common use is that of forming metal work pieces with a press brake by progressively bending incremental portions thereof. Various devices have been developed in the line with this principle, most of which employ the use ofa pair of spaced contact members adapted to engageone side of a work piece, and an oppositely and centrally disposed ram adapted to engage the opposite side of the work piece. The portion of the work piece lying between the spaced members is bent by the movement of the ram relative to the pair.

Factors which determine the degree of stock deformation include the distance between the spaced pair of contacts as well as the distance the central ram is moved relative to the plane of the spaced pair. The extent to which the portion being bent approaches a uniform curvilinear form depends additionally on the radius of curvature of the ram contact surface and the proximity of the ram workpiece engagement point relative to the point intermediate the spaced pair. Generally, a ram having a greater radius of curvature will effect a more uniform bend, but will require a greater force to do so; a compromise is therefore generally settled upon with the ram having a diameter considerably smaller than the distance between the spaced pair. As for the ram work piece engagement point, it is generally maintained as near as possible to the midpoint of the pair;"however, there are times, such as when bending near the ends of a work piece as hereinbefore discussed, when it is advantageous to vary this point of engagement from the midpoint.

In the process of forming a barrel or complete cylinder, these factors must therefore be taken into account and for optimum efficiency the combination varied to accommodate the particular application. The subject invention is designed to provide this versatility.

Another consideration involved! in the relatively reciprocating tool arrangement is that of the flapping of stock ends in a direction transverse to the direction of feed and in particular the flapping of the unformed end. One solution has been to provide a rigid holding device to be temporarily secured to the work piece during the bendingstroke, thus requiring a separate operation of disengagement and engagement for each time the stock is advanced. A holding device which maintains a constant engagement with the work piece has been used, but under certain conditions it must undergo great stresses.

A further obstacle encountered in the forming of barrels, i.e., of forming a complete 360 shell, without unnecessary removal and reversal at the midpoint, and that of providing a means to remove the shell upon completion of the operation. The first obstacle is overcome by allowing the formed portion of the work piece to circumvent the ram. The formed work piece can then be removed as long as the space between the formed end and the unformed end exceeds that of the ram width. However, the formation of a 360 barrel must cause this distance to approach zero, and an al ternate methodof removal must be provided.

It is therefore an object of this invention to provide an improved metal bending press adapted to deform flat stock into curvilinear shapes having any of a multitude of diameters using a single die and ram combination.

Yet another object of this invention is the provision for a metal bending press operating under variable loads-to function with a minimum of power.

Still another object of this invention is the provision for a metal bending press which maintainspositive engagement and control of a work piece during its forming cycle therethrough.

A further object of this invention is the provision in a metal bending apparatus for the reduction of transverse movement of the unformed end of a metal work piece during the forming of adjacent portions thereof.

Yet another object of this invention is the provision in a metal bending press for numerically controlling the longitudinal movement of a metal work piece being formed and the reciprocal movement of a ram relative to a counteracting die.

Still another object of thisinvention is the provision in a metal bending press for sensing degree of permanent deformation of a metal work piece and providing feedback to actuate the press in correcting to meet predetermined deformation desires.

A further object of this invention is the provision in a metal forming press for progressively bending a metal work piece into a form approximating a cylinder without removal until completion.

Still another object of this invention is the provision in a barrel forming press for longitudinally aligning the work piece to ensure having at least one edge aligned in a single plane.

Still a further object of this invention is the provision for a metal forming press which is durable and economical in construction and extremely functional in use.

These objects and other features and advantages become more readily apparent upon reference to the following description when taken in conjunction with the appended drawings.

SUMMARY OF THE INVENTION This invention is a metal bending hydraulic press wherein a work piece is incrementally advanced under numerical control and progressively deformed by interaction between a concave die of non-uniform curvature and a semicircular mandrel. Reciprocation of the mandrel relative to the die is automatically controlled in coordination with work piece advancement to produce a regular polygon which closely approximates a circle having any of a multitude of desired diameters. A device sensitive to mandrel displacement is used to determine permanent deformation of each increment and to provide automatic feedback in reactuating the mandrel to correct for metal spring back and errors due to individual work piece peculiarities. Positive control of the work piece is maintained by a feed mechanism moving on an inclined feed table, the entire feed and deforming cycle being automatically coordinated by a control unit using either a taped program input or an operator input. Input variables include work piece thickness and barrel diameter which are functions of feed rate and mandrel stroke distance. Upon completion of the automatic cycle, the mandrel is transversely retracted and the formed barrel is vertically removed, wherein its abutting ends can be easily welded together to complete the cylinder.

In the drawings as hereinafter described, a preferred embodiment is depicted; however various other modifications and alternate constructions can be made thereto without departing from the true spirit and scope of the invention.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a perspective view of the barrel forming press with its associated equipment.

FIG. 2 is a side plan view of the installed preferred embodiment with a sectional view of the mandrel portion and with a portion of the floor broken away to show features extending below the supporting floor.

FIG. 3 is a rear view of the preferred embodiment showing a partial sectional view of the mandrel support arrangement.

FIG. 4 is a top plan view of the preferred embodiment.

FIG. 5 is an enlarged fragmentary sectional view of the feed transmission unit portion of the invention.

FIG. 6A is an enlarged fragmentary side view of the mandrel/die relationship with a work piece in place.

FIG. 6B is a view thereof wherein the work piece has been longitudinally advanced.

FIG. 7 is an enlarged fragmentary sectional view of the mandrel and pulldown with included sensor device.

FIGS. 8A and 8B are simplified schematic views of the electrical and hydraulic control of the press.

FIG. 9 is a schematic view of specific ram stroke positions as measured from a reference plane.

FIG. 10 is a graphic representation of desired bend points of the ram as plotted against work piece advancement increment in a particular forming operation.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings the press apparatus is shown at 10 in FIG. 1 and comprises the major components of a feed table 11, a loading assembly 12, a stock feeder 13, a die 14, a frame 15, a ram 16, a control unit 17 and a hydraulic power unit (not shown). Movement of the ram 16 and stock feeder 13 are effected by a hydraulic power system, the movements being controlled and coordinated by the control unit 17, to form a Hat metal work piece 20 into a curvilinear shape.

The feed table 11 as shown in FIGS. 1, 2 and 4 is of the support type and has a top 19, sides 21, a front end 22, a feed end 23 and support legs 24. The support legs 24 are of such varying lengths as to align the table top 19 in an inclined position discussed hereinafter.

Disposed on the front end of the table is a servocontrolled hydraulic feed motor 25 (FIG. 4) which is electrically connected to the control unit 17 and mechanically connected at its shaft ends through reduction gears 26 to a pair of elongated ball screws 27 extending longitudinally along each side of the table 11. Journal bearings 28 (FIGS. 2 and 4) rigidly secured to the table near its feed end provide rotatable support for the opposite ends of the ball screws 27. Also secured to the table front end 22 is a shield 29 (FIGS. 1 and 2) extending upwardly and over the motor reduction gear combination to provide a protective covering therefor.

Movably mounted to the upper surface of the table top 19 is the stock feeder 13 (FIGS. 1, 2 and 4) comprising a carriage 31, a pair of subcarriages 32 and 33 and a pair of transmission units 34 (FIG. 5). The carriage extends transversely across the table beyond the sides 21 and has transmission units 34 extending downwardly on each side to threadably engage the ball screws 27. The construction of one of the two transmission units 34 is best seen in FIG. 5 with the unit comprising a rectangular housing 36 rigidly secured at its Abutting the outer side of the wall is a plate 38 which is secured thereto by four bolts 39, each bolt having a coil spring 41 biasing the plate 38 against the housing 36. The plate 38 has a central passage 42 in which the ballscrew is rotatably disposed, and has a rigidly secured ball-nut 43 with associated balls 44, extending axially into the housing to provide a threadable connection to the ball-screw. In operation the transmission units 34 allow the carriage 31 to top longitudinally with respect to the table top 19 without putting a tensile stress on the ball-nut and screw combination. The long bolts 39 and associated springs 41 allow the housing 36 to tilt relative to the screw 27 while the plate 38 remains unchanged in its alignment. A turning of ball screws 27 by the motor 24 causes the plate 38 and hence the feeder carriage 31 to move longitudinally along the table in the appropriate direction. A pulse generator (not shown), operably attached to each of the screws may be utilized to sense the position of the stockfeeder and to communicate this to the control unit.

The carriage 31 comprises a pair of spaced tracks 46a and 46b and a central screw member 40 extending transversely across the table 19. The screw.member 40 has on its opposite ends right and left hand screw threads 40a and 40b threadably engaged with screw blocks 45a and 45b, respectively. The screw blocks are thus coordinated to move inwardly and outwardly together as the screw is turned by the handle 50.

The subcarriages 32 and 33 are slidably adjustable on the carriage tracks and are frictionally engaged with the transverse sides of the screw block 45a and 45b respective by a tongue-and-groove relationship. The screw blocks and. subcarriages are interconnected by the cylinder-and-

piston combinations

47 and 48, the piston having its end secured to the screw block and the cylinders being secured to the respective subcarriages. The hydraulic cylinder 48 has a greater diameter than that of cylinder 47 for reasons hereinafterdiscussed. The subcarriages 32 and 33'have pivotably secured to and extending toward the feed end of the table,

jaws

49 and 51, respectively, thejaws pivotal movement being controlled by leverably connected

hydraulic clamp cylinders

52 and 53 respectively, which are pivotably secured to the subcarriages, and adaptedto force the jaw free ends toward the table top surface. Near the free ends of the

jaws

49 and 51 are integrally secured the opposing inwardly extending pivot spurs 54 and 56 (FIG. 4) adapted to pivotally engage the longitudinal edges of a flat metal work piece near its end, and to thereby control its relationship with respect to the table top 19. The work piece is in this manner positively held throughout its forming operation. The fluid flow to the four

hydraulic cylinders

47, 48, 52and 53 is controlled with the control unit 18.

In operation the metal stock piece is placed on the table between the

jaws

49 and 51. The jaws are then moved inwardly equal distances, by the turning of the screw handle 50 so that the spurs 54 and 56 approach the sides of the stock piece. A guage means (not shown) is located on the one subcarriage 32 to indicate its transverse position on the carriage 31. A simple graduated scale on the carriage would be one way to accomplish this. Final adjustment is now made with the hydraulic cylinders, with both cylindersmaking an initial movement inwardly until the spurs engage the stock piece, then the larger cylinder 48 overpowers the smaller 47 to cause the associated subcarriage 32 to return to its guaged position. Thus, positive control of the stock piece is established while aligning one longitudinal side thereof with respect to the table side 21.

The loading assembly 12 (FIGS. 1 and 4) is pivotally connected to one of the table sides 21 and is employed to transfer a piece of flat metal stock20 to a position on the table top surface wherein the

jaws

49 and 51 may be attached thereto for subsequent control and move ment. A plurality of appendages 57 extend normally outward from the table side 21, each having at its end a journaled hole 58 formed therein, the holes 58 being axially aligned and having a common pivot member 59 extending therethrough. The pivot member 59 is rotatable within by operation of a hydraulic torque motor 61 mechanically connected at its one end. A number of radially extending spaced arms 62 are attached to the pivot member 59, the two nearest the rear of the press being rigidly secured to the pivot member 59, and the remaining three being engagable therewith through independently and manually operated collar and pin arrangements 63. When operating with short work pieces it isnt necessary to use all arms 62 and thus one or more of those toward the front end may be disengaged and allowed to remain idle. Attached longitudinally to each of the arms 62 is an electromagnet 64 for maintaining a temporary attractive engagement with a work piece. The electromagnets are independently activated and deactivated by the operator at the control unit 17.

The press frame 15 (FIGS. 2 and 3) is secured to the table feed end 23 by bolts 71 and rests on the floor surface 72 with a portion being suspended in a lower cavity 73. lntegrally secured to the frame is a centrally disposed main cylinder 74 with its associated piston and rod 76 (FIG. 3) the combination fluidly connected to the hydraulic power unit 18 and controlled by the control unit 17. A pair of spaced vertical pulldowns 77 are reciprocally disposed in the frame 15 and are connected to the piston 76 through a key platen 78, which is bolted to the end of the piston 76 and has its ends engaging inner key ways 79 in the pulldowns 77. A movement of the piston 76 downwardly causes the pulldowns 77 to move downwardly an equal distance. The pulldowns 77 are raised by a separate hydraulicsystem comprising a pairof pull-back cylinders 81 attached to opposite sides of the frame 15, each having an operable piston 82 and associated clevis 83 extending downwardly and interconnecting to the outer side of a pulldown 77 by a connecting member 85. Both the main cylinder and the pull-back cylinder hydraulic systems are powered by the hydraulic unit 18 which receives its orders from the control unit 17. A single cylinder having a double acting piston arrangement may replace the combination described; however. the function of raising and lowering the pulldown would be essentially identical in nature.

Secured to the outer side of and near the upper end of each of the pulldowns 77 is an elongated ram housing, 84 and 86 respectively, (FIGS. 2, 3, and 4) extending horizontally outwardly and adapted to contain the large and small rams l6 and 88 respectively. The housing 84 has longitudinal walls 89 and an'end wall 91 parallel to the pulldowns 77. A passage 92 is formed in the pulldown opposite the end wall 91 which permits the movement of the large ram 16 therethrough to an operating position as shown in FIG. 3. A screw 93 extends longitudinally through the housing 84 from the end wall 93 to a point just beyond the inner side of the pulldown 91. The screw is rotatably secured in the end wall 91 and is turned by a hydraulic large ram motor 94 which is activated by the control unit 17.

The large ram 16 (FIGS. 2 and 3) comprises an upper portion 96, semicircular in cross-section, and having a longitudinal hole formed therein for threadable engagement with the screw 93; and a lower portion 97, rectangular in cross-section, and having a width less than that of the upper portion. It is vertically supported by two rollers 98 mounted on each of opposite sides of the ram walls 89, the rollers engaging the upper portion as shown in FIG. 3. A pair of rollers 99 is similarly disposed in the same plane on each of the four pulldowns. The ram upper portion 96 extends inwardly beyond the inner end of the lower portion so as to allow for supportable engagement with the pulldown on the side of small ram 88 when in an operating position as shown in FIG. 3. A large mandrel 100 is mounted in a longitudinal key-way 101 on the under side of the lower portion, the mandrel having a profile of uniform curvature on its lower surface.

The opposite ram housing 86 is a mirror image of the one hereinbefore described, having longitudinal walls 102, an end wall 103, a screw 104, and a hydraulic small ram motor 106. Similarly, a passage, 105 is formed in the pulldown which is similar to that formed in the other pulldown member. The small ram 88 however comprises a shortened upper portion 107 threadably engaging the screw 104; a longer middle portion 108, having a rectangular cross-section; and a lower portion 109, having a width less than that of the middle portion. A small mandrel 1 11 is mounted to the lower portion 109 with a keyway and has a profile of uniform curvature on its lower surface. Roller pairs 112 are mounted along the walls 102 for rollably engaging the middle portion 108, and roller pairs 113 on the pulldowns provide similar support.

In practice either the large ram 16 or small ram 88 may be independently moved into or out of the position between the pulldowns by selective rotation of the

screws

93 and 104. When both of the rams are retracted into their respective housings, the space between the upper ends of the pulldowns is free for the passing of material therethrough. When either ram is inthe central position as one is shown in FIG. 3, the inner ends will be overlapping so as to provide meta] engagement and support. An operator thus may easily select one of two mandrel sizes to suit the required specifications. The choice of mandrel size used is dependent on the size of the work piece being formed. Although either mandrel may be used to form any ofa number of diameters, the greater forces required when forming metal work pieces of greater thicknesses makes it prudent to use a larger mandrel. Accordingly, two sizes are provided to best meet the requirements as effected by" work piece thickness and barrel diameter.

A sensor device 114 (FIGS. 3 and 7) is situated in the passage 105, being secured to the pulldown 77 at its transverse center line and extending downwardly to a specific point wherein it may engage the periphery of either the large ram or the small ram, identified by the numeral 87 in FIG. 7, depending on which is in the protracted position. The designed allowance for the sensor occupied space is such that the sensor 114 will not engage either the large ram 16 or small ram 88 when one is in the protracted position unless they are displaced upwardly by an outside force. The sensor 114, which is a normally-open switch, is closed whenever there occurs any appreciable vertical displacement of the ram relative to the pulldown 77, and the closed circuit causes a signal to go to the control unit 17. As described hereinafter, the signal causes the ram to make another stroke, and return to the check position where the relative displacement is again sensed and the sensor either closes to repeat the process or it remains open to allow the subsequent steps to proceed. It should be noted that the sensor device may be located at various other locations. The preferred location arrangement described allows the sensor to remain relatively free from accumulations of dirt and metal particles.

The die 14 (FIGS. 1, 2 and 6) is integrally secured to the frame 15 with its entrance end 117 abutting the table feed end 23 to form an extension thereof. The longitudinal profile of the die in relation to the ram movement axis is shown in FIG. 6 with a work piece inserted therebetween. The die is of non-uniform curvature, with a large portion (a) proximate the entrance end 117 extending in the plane of the feed table top 19 and having a constant slope which is preferably I5V2 in respect to a line orthogonal to the axis of ram travel, a segment (b) having uniform curvature with its radius centered on the ram center line, a portion (c) having a constant slope, preferably of 22.5 and a larger portion (d) having a reversed uniform curvature with a larger radius than the radius of segment 6. It was found empirically that the inclination angle of l5 /2 for the table and loading end resulted in the most desirable mandrelwork piece relationship. Deviation in either direction from this angle causes greater whip in the unformed end of the work piece 20 when the mandrel is lowered to a forming position. It should be noted that the work piece will always contact the die 14 or die and table combination at two displaced points, but these points will vary longitudinally as the work piece proceeds along the die. It should also be noted that the longitudinal point at which the work piece 20 first contacts the mandrel also varies as the work piece is moved along its path, the initial contact points being on the en trance side of the mandrel center line, and the final contact points being on the exit side of the center line. Likewise, for each stroke of the mandrel, the work piece first engages it on one side of its center line, and as the mandrel is further lowered, contact is progressively made with its surface in a direction toward the mandrel center line.

For example, in FIG. 6(a) the stock 20 has been fed into the first incremental position and is supported at one point M on the die 14 and at one point on the table (not shown) which forms an extension thereof. The point at which the work piece first contacts the mandrel in its downward stroke is point R, and after completion of the stroke, wherein the mandrel has moved a distance Y, the work piece 20 has established contact at points proximate the centerline of the mandrel. This rolling effect across the mandrel surface will effect a desired bend with a minimum amount of power being exerted.

Referring now to FIG. 6 (b), the work piece 20 has been advanced to a second position wherein it engages the die at a point N as well as at a point on the table. As the mandrelis lowered, it first contacts the work piece at a point T and then further lowers a distance YY to establish contact at the point S on the mandrel center line. In this example the points R and T are substantially the same; however, as the work piece proceeds along its progression, and in particular where it nears completion of its cycle, the point at which it initially contacts the mandrel will vary.

As the work piece is advanced to the first bending position it may be canted somewhat from the longitudinal path, which, if left uncorrected would result in the making of a barrel having somewhat of a helical twist, with the two ends misaligned for proper joining. A guide unit 119 (FIGS. 2 and 4) is thus provided on the frame to align the work piece relative to its direction of movement. Its construction is similar to the feed unit hereinbefore described having spaced transverse tracks 121a and 121b, a central-screw member 122, screw blocks 123a and 123b, subcarriage 124 and 125, and hydraulic cylinder-and-

piston combination

126 and 127, the cylinder of 127 being larger than that of 126. A pair of spaced

parallel fingers

128 and 130 are secured to the subcarriages 124 and 125 respectively, and extend forwardly toward the table, and downwardly into a position contiguous with the die working surface.

i In operation, the guide mechanism is transversely adjusted in the same manner as the feed mechanism wherein the initial adjustment 75 is made by the screw handle 120 and final adjustment is made with the hydraulic cylinders. A gauge means on the guide mechanism allows the subcarriage 124 to betransversely adjusted to correspond to the position of the feed mechanism subcarriage 32, thus ensuring that one stock piece edge is aligned throughout its length with a table side 21.

The guide mechanism does not maintain contact with the workpiece throughout its movement as does the feed mechanism. Rather, only at the beginning of the stock-piece cycle is engagement made to align the piece, and then it is released to permit it to slide freely in its longitudinal path between the fingers.

The hydraulic power unit 18 is of the conventional type, being fluidly connected to the various cylinders hereinbefore described with the flow thereto. being controlled by the control unit 18.

The control unit 18 is of the type which is commercially available, having three different modes of operation: automatic, wherein it functions in accordance with a predetermined program such as a taped program; manual, wherein the parameters are inserted by the use of thumb wheel switches or the like; and jog, wherein the use of push buttons causes functional movements, the movements continuing as long as the buttons remain depressed.

FIG. 8 is a schematic illustration ofthe electrical and hydraulic circuits controlling the press. In operation, the work piece 20 is moved by the stock feeder l3 and its position sensed by pulse generators 129 operably attached to the screws 27, with the carriage logic 131 being sent to a feed back counter 132 for comparison with a command counter 133 which receives parametersover line 135 from a system control 134 of the control unit 17. Any difference between the two values is sent from the comparator 136 to an output buffer 137 and then to a servo-amplifier 138 where the signal is increased in magnitude for actuating the servo valve 139 and hence causing the feed motor 25 to move the stock feeder 13.

The mandrel position is similarly controlled by the main cylinder 74 and the pull back cylinders 81, wherein hydraulic pressure is delivered to both by a variable pitch pump 141, and a pulse generator 142 is responsive to the ram position. The ram direction logic 143 then passes to the ram feed back counter 144 and a corresponding value sent to the comparator 146 for equation with predetermined values received from the system control 134 through the ram position command counter 147. The value difference passes to the output buffer 148, servo amplifier 149 servo valve 151 and hence to the variable pitch pump 141 for controlling the flowof fluid.

The predetermined parameters are operator injected in either the .jog or manual mode of operation, whereas in the automatic mode the values are received from a tape reader 152 through a decoder 153. To facilitate the manual and jog modes a description of the ram s position is indicated on a ram position read-out 154 through a ram feedback counter 156 interconnected between the pulse generator 142 and the control unit 17 where a datum position originates and can be operatively varied as will be described hereinafter.

The auxiliary control by the control unit 17 includes that of valve control to the

loader subcarriage cylinders

47 and 48, their clamp cylinders 52 and-53, the

guide cylinders

124 and 126, and the

ram motors

94 and 106. Each of the movements are initiated by the operator through the control unit with pressure valves regulating the terminal position of the loader clamp and guide cylinders. The auxiliary pump 155 is driven by an electric motor 165. It should be noted that various alternative types of control systems may be utilized to obtain the desired results, and that the system described in the preferred embodiment is only one of such systems. Further, it should, be kept in mind that a forming operation may be performed without such control where the degree of accuracy is not critical and where manual controlled operation of the mandrel and feeder is sufficient for a particular purpose.

Th e'parameters injected by either the operator or by the program tape includes those controlling the stroke of the ram for any increment position of the work piece. FIG. 9 shows the various positions that must be defined with respect to the ram position. Position A represents the reference plane for the ram stroke and generally remains constant. However, as previously stated it may be varied slightly by the operator to compensate for varying thicknesses of a particular work piece, the change being made with a simple thumb wheel. Position D is the distance from the reference plane that the ram moves on its firststroke against the work piece. This point is precalculated to include compensation for spring back and if correct it is the lowest point to which the ram is lowered. Following the first stroke the ram is raised to point C the desired position of the bent portion of the work piece, wherein if the desired bend has been effected, the ram mandrel will maintain contact with the work piece, but will have little contact force exerted therebetween. If the force is insufficient to actuate sensor 114, the ram will raise to clearance position B, and the work piece will be longitudinally advanced another increment to repeat the process. However, if the bend was insufficient, to meet the precalculated degree of deformation the resultant upward force on the ram will displace it upwardly closing the sensor switch and causing the ram to commence another stroke.

in this case, the ram will descend in its second stroke to point B which is below point D by an additional increment, such increment being a constant injected by the tape or operator. The ram again raises to point C where the ram displacement is checked and the process repeated until the desired bend is effected and the sensor 114 is actuated; at which time the ram raises to point B and the work piece is longitudinally advanced by a predetermined increment.

The desired bend point can be calculated for each bend location on the work piece, the principal factors being the desired diameter of the formed work piece and the work piece thickness. As discussed hereinbefore, variation in work piece thickness is another factor effecting this point and can be compensated for by the operator, but will generally be negligible. However, the desired bend point (point C in FIG. 9) will vary considerably along the complete length of the work piece as can be seen in FIG. 10, which indicates values characteristic of a specific work piece diameter and thickness. The smooth curve (a) represents the values of the desired bend points when using 81 advancement intervals along the length of the work piece, thereby very closely approximating a cylinder. As can be seen, at the first advancement point the mandrel is required to be lowered to its lowest point, with the following advancement points requiring desired bend points of decreasing value. Following the sixth advancement interval the corresponding desired bend point becomes nearly constant and remains so until the work piece trailing end approaches the mandrel (increment 77). There is, however, a slight progressive increase in the desired-bend point when proceeding from the fifth increment to the seventy seventh, the reason being that the contact point of the work piece on the table is progressively moving downwardly thereon, and consequently the mandrel must correspondingly move further downwardly. As the work piece approaches the final intervals the desired bend point is progressively increased to a maximum at the last interval.

Referring now to the straight-line graph (b) the total number of increments has been reduced to twenty-one (21) so as to less closely approximate a cylinder, but to result in a production time saving. The desired-bend points are then constant at all points except for the first and last intervals wherein an end crimp is required and wherein the mandrel must be lowered to a further point. The mandrel operation is thus much simplified and a constant desired-bend point can be employed for a given barrel diameter and plate thickness, provided that the degree of cylindrical approximation is not critical.

A third alternative which would combine the best of the two methods discussed above would involve advancing the work piece in shorter increments near its ends, and in longer increments along its mid portion. In this manner, a high degree of cylindrical approximation may be attained in a minimum of time.

Various alternative arrangements for sensing work piece deformation may be employed; however, that described in the preferred embodiment is considered to be superior over other considered methods. The method of measuring curvature by measuring angular displacement of the work piece free-end requires certain basic assumptions as discussed in U.S. Pat. No. 3,333,445 issued to Harry W. Mergler and Erik Trostmann on Aug. 1, 1967. A combination of methods is described in U.S. Pat. No. 3,459,018 issued to Neil S. Miller on Aug. 5, 1969, wherein the angular displacement method is supplemented by that of using a gauging means which is adjustable with respect to a tangent of the curved work piece. The gauging means is contiguous with the work piece and is susceptible to accumulation of dirt and scale. The gauging means described in the preferred embodiment is on the other hand a simple system which measures displacement on a fixed axis and which locates the sensor in a position removed from danger of breakage and dirt accumulation.

What is claimed as new and desired to secure by Letters Patent of the United States is:

1. A press apparatus for successively bending to a desired shape presented portions of a metal workpiece at successive points displaced longitudinally along the work piece during longitudinal movement thereof, said apparatus comprising in combination:

a. a work piece die means adapted for supporting said work piece, said die means comprising a first portion having a constant inclined slope and including a feed surface, and a second portion having a substantially concave surface, which is immediately adjacent and tangentially contiguous to said first portion;

. feed means for incrementally advancing said work piece on said feed surface toward said second portion whereby said work piece is supported by a first support point on said first portion and a second support point on said second portion;

c. mandrel means movably disposed adjacent said second portion of said die means and adapted to reciprocate along an axis to predetermined positions relative thereto, to engage and cause defor mation of the stock portions;

. mandrel support means disposed adjacent to said second portion and secured to said mandrel means; and,

e. power means for selectively moving said mandrel support means in a direction parallel to the axis of reciprocal movement of saidmandrel means.

2. A press apparatus as defined in claim 1 wherein said mandrel means, in longitudinal cross-section, is convex in form relative to said second portion of said die means, and wherein for each stock advancement in initial point of engagement of said mandrel means with the stock is distal to the longitudinal center line, of said mandrel, while continued downward movement in deforming the stock portions causes the relative engagement point to approach the longitudinal center line of said mandrel means.

3. A press apparatus as defined in claim 1 wherein said second portion of said die means is of constantcurvature form and wherein said axis of mandrel movement is coincident with a radial axis of said second por tion.

4. A press apparatus as defined in claim 3 wherein said die means includes a third portion, said third portion having a constant slope and being tangentially contiguous with said second portion of said die means at l the opposite end thereof from said first portion.

5. A press apparatus as defined in claim 3 wherein the angle subtended by the plane of said first portion of said die means and said axis of mandrel movement is substantially 15 /2".

6. A press apparatus for longitudinally bending to a desired curvature a portion of metal stock said apparatus comprising in combination:

a. die means, said die means being longitudinally concave in form and adapted to provide support for the stock portions at the longitudinal ends thereof, wherein a portion of said die means is of uniform curvature;

b. mandrel means movably disposed adjacent said uniform curvature portion of said die means, and adapted to reciprocate along a radial axis of said uniform curvature portion to predetermined positions relative thereto, to engage and cause deformation of the stock portion;

c. pulldown means secured to said mandrel means and adapted to provide support therefor;

(1. power means for selectively moving said pulldown means in a directionparallel to the axis of reciprocal movement of said mandrel means;

e. sensing means disposed on said axis of reciprocal movement and responsive todetermine the dis placement of the stock portion along said axis of reciprocal movement in relation to afixed plane normal to said axis; v

f. comparing means adapted to receive a pre-registered desired displacement value and to compare it with the actual displacement of the stock portion as determined by said sensing means;

g. feedback means for actuating said power means in response to said comparing means;

. wherein the actual displacement of the stock portion is compared with a pre-registered desired displacement and additional deforming is accomplished until the two values become comparable.

7. The press apparatus as defined in claim 6 including a feed means adapted to present successive longitudinal portions of stock for successive longitudinal bending thereof, wherein the displacement of each of said successive longitudinal portions is determined by said sensing means in relation to the same fixed plane.

8. The press apparatus as defined in claim 6 wherein said pulldown means comprises a pair of spaced pulldown members having aligned passages formed therein for receiving said mandrel means extending normally therebetween, and wherein said sensing means is disposed in one of said passages adjacent the top surface of said mandrel means so as to be responsive to up ward movement of said mandrel means relative to said pulldown means.

9. A press apparatus for successively bending to a desired shape presented portions of metal stock during longitudinal movement thereof, said apparatus comprising in combination:

a. a planar table adapted to support the stock during its longitudinal movement thereover; feed means for progressively advancing the stock at predetermined increments along said table;

c. a longitudinally concave die comprising a first portion of constant slope communicating with, and coincident with the plane of, said planar table, and a second portion having a substantially concave configuration adapted to slidably receive and frictionally engage along a line thereon, the stock for which it providessupport, the position of the line of engagement varying longitudinally as the stock is advanced along its path;

. pulldown means movably disposed adjacent said die;

e. a first mandrel secured to said pulldown means, said first mandrel being disposed above said second portion of said die means and adapted to move toward said die in a radial axis of said second portion;

f. power means operably connected to said pulldown means for moving said first mandrel to predetermined positions relative to said second surface of said die.

10. A press apparatus as defined in claim 9 wherein said radial axis along which said first mandrel moves is in a vertical plane and said planar table is inclined to substantially 15% from the horizontal plane, with the lower end of said planar table being integrally secured to said die.

1]. A press apparatus as defined in claim 9 and including means for retracting said first mandrel in a direction transverse to both the longitudinal axis of said table and said radial axis, to retract said first mandrel to one longitudinal side of said table and die and permit removal ofa deformed work piece.

12. A press apparatus as defined :in claim 11 wherein said pulldown means comprises first and second, spaced vertically aligned pulldown members, one disposed on each side of said die, said pulldown members having aligned passages formed therein for engagably receiving said first mandrel extending normally therebetween, said first mandrel being retractable along the axis of said passages to disengage said second pulldown members and extend outwardly from said first pulldown member on the longitudinal side opposite said die.

13. A press apparatus as defined in claim 12 and including:

a. a second mandrel adapted to extend normally between said first and second pulldowns and to be engagably received in said passages formed therein when said first mandrel is in a retracted position, said second mandrel being adapted to move toward said die in a radial axis of said second portion thereof;

b. and means for retracting said second mandrel along the axis of said passages to disengage said first pulldown member and extend outwardly from said second pulldown member on the longitudinal side opposite said die.

14. A press apparatus as defined in claim 9 and in- I cluding a guide mechanism adjacent said die and opposite said table with respect to said pulldown means, said guide mechanism comprising:

a. a transverse track aligned transversely to both the longitudinal axis of said table and said radial axis;

b. a pair of spaced, longitudinal, fingers adapted to be moved along said transverse track, said fingers having oppositely disposed contact surfaces thereon, said contact surfaces being adapted to engage opposite longitudinal edges of a metal stock piece near the leading end thereof;

c. a pair of biasing means for biasing said fingers inwardly toward each other on said track to engage and move the stock leading end to longitudinally align the metal stock with respect to said table; means for pre-aligning one of said fingers with respect to a longitudinal side of said table; and

e. means for releasing said pair of biasing means to allow said fingers to disengage from the stock piece and permit the stock piece to be advanced longitudinally along said table.

15. A press apparatus as defined in claim 14 wherein one of said pair of biasing means is substantially unequal in biasing force to the other one of said pair to biasing means and wherein the force of one biasing means is completely overcome by the force of the opposite biasing means, wherein the finger connected to the weaker biasing means is permitted to initially engage said stock piece while at one position on the transverse track and to subsequently be moved to said prealigned position on said track.

16. A press apparatus as defined in claim 9 wherein said feed means is adjacent to said planar table and comprises:

b. a pair of spaced jaws adapted to be moved along said transverse track, said jaws having opposing spurs thereon said spurs being adapted to engage opposite longitudinal edges of a metal stock piece near the trailing and thereof;

c. a pair of biasing means for biasing said jaws inwardly toward each other on said track to engage and move the stock trailing end to longitudinally align the metal stock with respect to said table;

d. means for pre-aligning one of said jaws with respect to a longitudinal side of said table;

e. means for moving said track longitudinally on said table, toward said pulldown means, so as to maintain alignment of said stock piece; and

f. means to release said jaws from engagement with said stock piece when the trailing edge of the stock piece approaches said pulldown means.

17. A press apparatus as defined in claim 16 wherein one of said pair of biasing means is substantially unequal in biasing force to the other one of said pair of biasing means and wherein the force of one biasing means is completely overcome by the force of the opposite biasing means, wherein the jaw connected to the weaker biasing means is permitted to initially engage said stock piece while at one position on the transverse track and to subsequently be moved to said prc-aligned position on said track.

18. A press apparatus as defined in claim 14 wherein said feed means is adjacent to said planar table and comprises:

0. a pair of biasing means for biasing said jaws inwardly toward each other of said track to engage and move the stock trailing end to longitudinally align the metal stock with respect to said table;

means for pre-aligning one of said jaws with respect to a longitudinal side of said table;

f. means to release said jaws from engagement with said stock piece when the trailing edge of the stock piece approaches said pulldown means; wherein said pre-aligning means for said feed means is coordinated with said pre-aligning means for said guide mechanism to align one longitudinal edge of a stock piece with a longitudinal side of said table.

19. A press apparatus for forming regular polygon barrels approximating a cylinder by progressively bending presented portion of flat metal stock during longitudinal movement thereof, the apparatus comprising in combination:

a. feed means for advancing the stock predetermined increments along a longitudinal path;

b. a die surface adapted to provide two support points for frictional engagement and support of the stock portions at the longitudinal ends thereof, said support points varying over the longitudinal length of said die surface asthe stock is advanced;

c. a mandrel movably disposed adjacent said die surface and adapted to reciprocate to pre-determined positions relative thereto, to engage and cause deformation of the stock portions;

. pulldown means secured to said mandrel means and adapted to provide support therefor;

e. power means for selectively moving said pulldown means in a direction parallel to the axis of reciprocal movement of said mandrel means;

f. means for preselecting said increments of stock advancement for a particular diameter barrel; and

g. means for preselecting particular mandrel posi' tions corresponding to the particular advancement positions of the stock along said longitudinal path; wherein the diameter of the cylindrical elements is determined by selection of a particular stock advancement interval and of particular mandrel positions in relation to the advancement positions of the stock along said longitudinal path.

20. A press apparatus as defined in claim 19 wherein said pulldown means comprises a pair of spaced vertically aligned pulldown members, one disposed on each side of said die surface, said pulldown members having said mandrel extending normally therebetween, parallel to the axis of the barrel being formed, thus allowing the formed portion of the stock to circumvent said mandrel to form a complete cylinder.

' therein for axially receiving said mandrel, and including means for axially retracting said mandrel from one of said passages and from the cylindrical barrel, to allow the barrel to be removed from the apparatus in a direction normal to said axis.

22. A method of forming a substantially planar workpiece into a predetermined profile wherein the workpiece is supported on two displaced contact surfaces and a mandrel is lowered to impinge on a portion of the workpiece intermediate said surfaces to deform the workpiece comprising the steps of:

a. supporting the workpiece in an entrance plane tangent to the entrance side of a concave portion of a continuous die surface;

b. advancing the workpiece longitudinally a predetermined distance along said die surface to rest on an exit portion thereof, so as to suspend a portion of the workpiece between a surface of said exit portion and a surface of said entrance plane;

0. lowering a mandrel having a convex impingement surface a predetermined distance toward the workpiece on an axis displaced by a major angle from said entrance plane;

d. engaging the suspended portion of the workpiece with said convex surface of said mandrel and bending the workpiece a predetermined distance toward but not coincident with the concave portion of the die surface;

e. raising said convex mandrel; and

f. advancing the workpiece sequential increments and repeating the above steps at each increment position until the desired workpiece profile is ob tained; and

g. removing the workpiece from said die surface.

23. A method as set forth in claim 22 wherein said exit portion of said continuous die surface. is convex with respect to the workpiece, thereby allowing a rolling engagement there-between as the mandrel is lowered.

24. A method as set forth in claim 22 wherein said concave portion of said continuous die surface is of substantially uniform curvature thereby allowing for smooth advancement of the workpiece andpreventing stress concentration in said die surface.

25. A method as set forth in claim 22 wherein said major angle between the entrance plane and the mandrel lowering axis is in therange of 60-80.

26. A method as set forth in claim 22 and including a prelininary step of pre-registering the associated predetermined distances of stock advancement and mandrel-lowering for each sequential increment to obtain the desired workpiece profile.

27. A method as set forth in claim 24 wherein at each sequential increment the workpiece is permanently deformed in accordance with the pre-registered distance and wherein after lowering of the mandrel at each increment the following steps are performed:

a. raising the mandrel to a pre-determined desiredbend-point and establishing whether the workpiece portion has been permanently deformed to said bend point;

b. lowering the mandrel to a position closer to said die surface than that of the previous lowering for that increment, provided that the workpiece portion has not been permanently deformed to said bend point; and

c. repeating the above steps until the workpiece portion has been permanently deformed to said bend point.

28. A method as set forth in claim 25 wherein the establishing of whether the workpiece portion has been permanently deformed to said bend point is accomplished by:

a. allowing the mandrel to be displaced upwardly by reaction to contact pressure from the workpiece;

and

b. sensing any upward displacement of said mandrel by a pressure sensitive device disposed thereabove.

29. A method as set forth in claim 22 wherein the process includes the establishing and maintaining of positive continuous control of the workpiece by a feeder means mounted on the entrance plane so as to be movable on that plane in both the longitudinal and transverse directions.

30. A method as set forth in claim 27 and including the step of transversely aligning the workpiece so that one of the longitudinal edges thereof coincides with the longitudinal path of advancement.

31. A method as set forth in claim 24 wherein transverse forces are applied to opposite longitudinal edges of the workpiece with the force on one edge being greater than the force on the opposite edge, thereby allowing the workpiece to be transversely positioned with its opposite edge coincident with a desired reference plane.

32. A method as set forth in claim 22 wherein the workpiece is removed in the following manner:

a. retracting the mandrel in a direction normal to both the path of advancement and the mandrellowering axis; and I b. removing the workpiece in a plane formed by themandrel lowering axis and the path of advancement.

33. A method of forming a substantially planar workpiece into a regular polygon barrel approximating a cylinder having a predetermined diameter, wherein the workpiece is supported on two displaced contact surfaces and a mandrel is lowered to impinge on a portion of the workpiece intermediate said surfaces to deform the workpiece comprising the steps of:

a. supporting the workpiece in an entrance plane tan- 1 gent to the entrance side of a concave portion of a continuous die surface;

advancing the workpiece longitudinally a predetermined distance along said die surface to rest on an exit portion thereof, so as to suspend a portion of the workpiece between a surface of said exit portion and a surface of said entrance plane;

engaging the suspended portion of the workpiece with said convex surface of said mandrel and bending the workpiece a predetermined distance toward but not coincident with. the concave portion of the die surface;

e. raising said convex mandrel;

f. advancing the workpiece sequential increments and repeating the above steps at each increment position until the workpiece has been formed in a 360 polygon;

g. retracting the mandrel from within the barrel in a direction parallel with the barrel axis; and

h. removing the barrel in a direction normal to the barrel axis.

34. A method as set forth in claim 33 wherein the predetermined distances of advancement are varied with the longitudinal position of the workpiece, and further wherein they are varied such that the sequential increments proximate the longitudinal beginning and end of the workpiece are shorter than those increments near the intermediate portions thereof.

35. A method as set forth in claim 33 and including a preliminary step of preregistering the associated predetermined distances of stock advancement and mandrel-lowering for each sequential increment to obtain the desired predetermined diameter for a workpiece having a specific thickness.

36. A method as set forth in claim 33 wherein at the initial increment position the intermediate portion of the workpiece is supported on said entrance plane and the leading end thereof is supported on said concave portion; and at the final increment position, the intermediate portion is supported at said die exit portion and the trailing end thereof is supported on said concave portion, thereby allowing the workpiece to be deformed proximate its ends.

Claims

1. A press apparatus for successively bending to a desired shape presented portions of a metal workpiece at successive points displaced longitudinally along the work piece during longitudinal movement thereof, said apparatus comprising in combination: a. a Work piece die means adapted for supporting said work piece, said die means comprising a first portion having a constant inclined slope and including a feed surface, and a second portion having a substantially concave surface, which is immediately adjacent and tangentially contiguous to said first portion; b. feed means for incrementally advancing said work piece on said feed surface toward said second portion whereby said work piece is supported by a first support point on said first portion and a second support point on said second portion; c. mandrel means movably disposed adjacent said second portion of said die means and adapted to reciprocate along an axis to predetermined positions relative thereto, to engage and cause deformation of the stock portions; d. mandrel support means disposed adjacent to said second portion and secured to said mandrel means; and, e. power means for selectively moving said mandrel support means in a direction parallel to the axis of reciprocal movement of said mandrel means.

3. A press apparatus as defined in claim 1 wherein said second portion of said die means is of constant-curvature form and wherein said axis of mandrel movement is coincident with a radial axis of said second portion.

4. A press apparatus as defined in claim 3 wherein said die means includes a third portion, said third portion having a constant slope and being tangentially contiguous with said second portion of said die means at the opposite end thereof from said first portion.

5. A press apparatus as defined in claim 3 wherein the angle subtended by the plane of said first portion of said die means and said axis of mandrel movement is substantially 15 1/2 *.

6. A press apparatus for longitudinally bending to a desired curvature a portion of metal stock said apparatus comprising in combination: a. die means, said die means being longitudinally concave in form and adapted to provide support for the stock portions at the longitudinal ends thereof, wherein a portion of said die means is of uniform curvature; b. mandrel means movably disposed adjacent said uniform curvature portion of said die means, and adapted to reciprocate along a radial axis of said uniform curvature portion to predetermined positions relative thereto, to engage and cause deformation of the stock portion; c. pulldown means secured to said mandrel means and adapted to provide support therefor; d. power means for selectively moving said pulldown means in a direction parallel to the axis of reciprocal movement of said mandrel means; e. sensing means disposed on said axis of reciprocal movement and responsive to determine the displacement of the stock portion along said axis of reciprocal movement in relation to a fixed plane normal to said axis; f. comparing means adapted to receive a pre-registered desired displacement value and to compare it with the actual displacement of the stock portion as determined by said sensing means; g. feedback means for actuating said power means in response to said comparing means; h. wherein the actual displacement of the stock portion is compared with a pre-registered desired displacement and additional deforming is accomplished until the two values become comparable.

8. The press apparatus as defined in claim 6 wherein said pulldown means comprises a pair of spaced pulldown members having aligned passages formed therein for receiving said mandrel means extending normally therebetween, and wherein said sensing means is disposed in one of said passages adjacent the top surface of said mandrel means so as to be responsive to upward movement of said mandrel means relative to said pulldown means.

9. A press apparatus for successively bending to a desired shape presented portions of metal stock during longitudinal movement thereof, said apparatus comprising in combination: a. a planar table adapted to support the stock during its longitudinal movement thereover; b. feed means for progressively advancing the stock at predetermined increments along said table; c. a longitudinally concave die comprising a first portion of constant slope communicating with, and coincident with the plane of, said planar table, and a second portion having a substantially concave configuration adapted to slidably receive and frictionally engage along a line thereon, the stock for which it provides support, the position of the line of engagement varying longitudinally as the stock is advanced along its path; d. pulldown means movably disposed adjacent said die; e. a first mandrel secured to said pulldown means, said first mandrel being disposed above said second portion of said die means and adapted to move toward said die in a radial axis of said second portion; f. power means operably connected to said pulldown means for moving said first mandrel to predetermined positions relative to said second surface of said die.

10. A press apparatus as defined in claim 9 wherein said radial axis along which said first mandrel moves is in a vertical plane and said planar table is inclined to substantially 15 from the horizontal plane, with the lower end of said planar table being integrally secured to said die.

11. A press apparatus as defined in claim 9 and including means for retracting said first mandrel in a direction transverse to both the longitudinal axis of said table and said radial axis, to retract said first mandrel to one longitudinal side of said table and die and permit removal of a deformed work piece.

12. A press apparatus as defined in claim 11 wherein said pulldown means comprises first and second, spaced vertically aligned pulldown members, one disposed on each side of said die, said pulldown members having aligned passages formed therein for engagably receiving said first mandrel extending normally therebetween, said first mandrel being retractable along the axis of said passages to disengage said second pulldown members and extend outwardly from said first pulldown member on the longitudinal side opposite said die.

13. A press apparatus as defined in claim 12 and including: a. a second mandrel adapted to extend normally between said first and second pulldowns and to be engagably received in said passages formed therein when said first mandrel is in a retracted position, said second mandrel being adapted to move toward said die in a radial axis of said second portion thereof; b. and means for retracting said second mandrel along the axis of said passages to disengage said first pulldown member and extend outwardly from said second pulldown member on the longitudinal side opposite said die.

14. A press apparatus as defined in claim 9 and including a guide mechanism adjacent said die and opposite said table with respect to said pulldown means, said guide mechanism comprising: a. a transverse track aligned transversely to both the longitudinal axis of said table and said radial axis; b. a pair of spaced, longitudinal, fingers adapted to be moved along said transverse track, said fingers having oppositely disposed contact surfaces thereon, said contact surfaces being adapted to engage oppOsite longitudinal edges of a metal stock piece near the leading end thereof; c. a pair of biasing means for biasing said fingers inwardly toward each other on said track to engage and move the stock leading end to longitudinally align the metal stock with respect to said table; d. means for pre-aligning one of said fingers with respect to a longitudinal side of said table; and e. means for releasing said pair of biasing means to allow said fingers to disengage from the stock piece and permit the stock piece to be advanced longitudinally along said table.

15. A press apparatus as defined in claim 14 wherein one of said pair of biasing means is substantially unequal in biasing force to the other one of said pair to biasing means and wherein the force of one biasing means is completely overcome by the force of the opposite biasing means, wherein the finger connected to the weaker biasing means is permitted to initially engage said stock piece while at one position on the transverse track and to subsequently be moved to said pre-aligned position on said track.

16. A press apparatus as defined in claim 9 wherein said feed means is adjacent to said planar table and comprises: a. a transverse track aligned transversely to both the longitudinal axis of said table and said radial axis; b. a pair of spaced jaws adapted to be moved along said transverse track, said jaws having opposing spurs thereon said spurs being adapted to engage opposite longitudinal edges of a metal stock piece near the trailing and thereof; c. a pair of biasing means for biasing said jaws inwardly toward each other on said track to engage and move the stock trailing end to longitudinally align the metal stock with respect to said table; d. means for pre-aligning one of said jaws with respect to a longitudinal side of said table; e. means for moving said track longitudinally on said table, toward said pulldown means, so as to maintain alignment of said stock piece; and f. means to release said jaws from engagement with said stock piece when the trailing edge of the stock piece approaches said pulldown means.

17. A press apparatus as defined in claim 16 wherein one of said pair of biasing means is substantially unequal in biasing force to the other one of said pair of biasing means and wherein the force of one biasing means is completely overcome by the force of the opposite biasing means, wherein the jaw connected to the weaker biasing means is permitted to initially engage said stock piece while at one position on the transverse track and to subsequently be moved to said pre-aligned position on said track.

18. A press apparatus as defined in claim 14 wherein said feed means is adjacent to said planar table and comprises: a. a transverse track aligned transversely to both the longitudinal axis of said table and said radial axis; b. a pair of spaced jaws adapted to be moved along said transverse track, said jaws having opposing spurs thereon said spurs being adapted to engage opposite longitudinal edges of a metal stock piece near the trailing and thereof; c. a pair of biasing means for biasing said jaws inwardly toward each other of said track to engage and move the stock trailing end to longitudinally align the metal stock with respect to said table; d. means for pre-aligning one of said jaws with respect to a longitudinal side of said table; e. means for moving said track longitudinally on said table, toward said pulldown means, so as to maintain alignment of said stock piece; and f. means to release said jaws from engagement with said stock piece when the trailing edge of the stock piece approaches said pulldown means; wherein said pre-aligning means for said feed means is coordinated with said pre-aligning means for said guide mechanism to align one longitudinal edge of a stock piece with a longitudinal side of said table.

19. A press apparatus for forming regular polygon barrels approximating a cylinder by progressivelY bending presented portion of flat metal stock during longitudinal movement thereof, the apparatus comprising in combination: a. feed means for advancing the stock predetermined increments along a longitudinal path; b. a die surface adapted to provide two support points for frictional engagement and support of the stock portions at the longitudinal ends thereof, said support points varying over the longitudinal length of said die surface as the stock is advanced; c. a mandrel movably disposed adjacent said die surface and adapted to reciprocate to pre-determined positions relative thereto, to engage and cause deformation of the stock portions; d. pulldown means secured to said mandrel means and adapted to provide support therefor; e. power means for selectively moving said pulldown means in a direction parallel to the axis of reciprocal movement of said mandrel means; f. means for preselecting said increments of stock advancement for a particular diameter barrel; and g. means for preselecting particular mandrel positions corresponding to the particular advancement positions of the stock along said longitudinal path; wherein the diameter of the cylindrical elements is determined by selection of a particular stock advancement interval and of particular mandrel positions in relation to the advancement positions of the stock along said longitudinal path.

21. A press apparatus as defined in claim 20 wherein said pulldown members have aligned passages formed therein for axially receiving said mandrel, and including means for axially retracting said mandrel from one of said passages and from the cylindrical barrel, to allow the barrel to be removed from the apparatus in a direction normal to said axis.

22. A method of forming a substantially planar workpiece into a predetermined profile wherein the workpiece is supported on two displaced contact surfaces and a mandrel is lowered to impinge on a portion of the workpiece intermediate said surfaces to deform the workpiece comprising the steps of: a. supporting the workpiece in an entrance plane tangent to the entrance side of a concave portion of a continuous die surface; b. advancing the workpiece longitudinally a predetermined distance along said die surface to rest on an exit portion thereof, so as to suspend a portion of the workpiece between a surface of said exit portion and a surface of said entrance plane; c. lowering a mandrel having a convex impingement surface a predetermined distance toward the workpiece on an axis displaced by a major angle from said entrance plane; d. engaging the suspended portion of the workpiece with said convex surface of said mandrel and bending the workpiece a predetermined distance toward but not coincident with the concave portion of the die surface; e. raising said convex mandrel; and f. advancing the workpiece sequential increments and repeating the above steps at each increment position until the desired workpiece profile is obtained; and g. removing the workpiece from said die surface.

23. A method as set forth in claim 22 wherein said exit portion of said continuous die surface is convex with respect to the workpiece, thereby allowing a rolling engagement there-between as the mandrel is lowered.

24. A method as set forth in claim 22 wherein said concave portion of said continuous die surface is of substantially uniform curvature thereby allowing for smooth advancement of the workpiece and preventing stress concentration in said die surface.

25. A method as set forth in claim 22 wherein said majoR angle between the entrance plane and the mandrel lowering axis is in the range of 60*-80*.

27. A method as set forth in claim 24 wherein at each sequential increment the workpiece is permanently deformed in accordance with the pre-registered distance and wherein after lowering of the mandrel at each increment the following steps are performed: a. raising the mandrel to a pre-determined desired-bend-point and establishing whether the workpiece portion has been permanently deformed to said bend point; b. lowering the mandrel to a position closer to said die surface than that of the previous lowering for that increment, provided that the workpiece portion has not been permanently deformed to said bend point; and c. repeating the above steps until the workpiece portion has been permanently deformed to said bend point.

28. A method as set forth in claim 25 wherein the establishing of whether the workpiece portion has been permanently deformed to said bend point is accomplished by: a. allowing the mandrel to be displaced upwardly by reaction to contact pressure from the workpiece; and b. sensing any upward displacement of said mandrel by a pressure sensitive device disposed thereabove.

32. A method as set forth in claim 22 wherein the workpiece is removed in the following manner: a. retracting the mandrel in a direction normal to both the path of advancement and the mandrel-lowering axis; and b. removing the workpiece in a plane formed by the mandrel lowering axis and the path of advancement.

33. A method of forming a substantially planar workpiece into a regular polygon barrel approximating a cylinder having a predetermined diameter, wherein the workpiece is supported on two displaced contact surfaces and a mandrel is lowered to impinge on a portion of the workpiece intermediate said surfaces to deform the workpiece comprising the steps of: a. supporting the workpiece in an entrance plane tangent to the entrance side of a concave portion of a continuous die surface; b. advancing the workpiece longitudinally a predetermined distance along said die surface to rest on an exit portion thereof, so as to suspend a portion of the workpiece between a surface of said exit portion and a surface of said entrance plane; c. lowering a mandrel having a convex impingement surface a predetermined distance toward the workpiece on an axis displaced by a major angle from said entrance plane; d. engaging the suspended portion of the workpiece with said convex surface of said mandrel and bending the workpiece a predetermined distance toward but not coincident with the concave portion of the die surface; e. raising said convex mandrel; f. advancing the workpiece sequential increments and repeating the above steps at each increment position until the workpiece has been formed in a 360* polygon; g. retracting the mandrel from within the barrel in a directIon parallel with the barrel axis; and h. removing the barrel in a direction normal to the barrel axis.