US2832640A - Heat fusible material spray gun - Google Patents

Description

April 29, 1958 SHEPARD 2,832,640

HEAT FUSIBLE MATERIAL SPRAY GUN Filed Dec. 9, 1954 2 Sheets-Sheet l INVENTOR ARTHUR H SHEPARD ATTORNEY April 29, 1958 A. P.SHEPARD 2,332,640

HEAT FUSIBLE MATERIAL SPRAY GUN Filed Dec. 9, 1954 2 Sheets-Sheet 2 INVENTOR ARTHUR. F. SHEPARD ATTORNEY United Stflt$, Patent HEAT FUSIBLE MATERIAL SPRAY Arthur P. Shepard, Flushing, N. Y., assignor to Metallizing Engineering Co., Inc., Westbury, N. Y., a corporation of New Jersey Application December 9, 1954, Serial No. 474,155

5 Claims. (Cl. 299-28.8)

' This invention relates to an improved heat fusible material spray gun. The invention more particularly relates to a gun construction for blast gas spraying heat fusible materials, which utilizes the combustion gases as the blast gas.

Heat fusible material spray guns of the blast gas type are devices in which such material is fed into a melting zone in which it is melted, being thereafter sprayed from the gun in subdivided form by a blast of gas. The materials to be sprayed are fed into the melting zone either in the form of powder or in the form of an elongated member such as a rod or wire. A mixture of fuel gas and combustion supporting gas, such as a mixture of acetylene or propane and oxygen, is fed to the melting zone by suitable means, where the same is ignited, causing the melting or heat softening of the material to be sprayed. The material to be sprayed usually is metal, and devices of this sort are commonly called metal spray guns. The metal is usually solid metal in the form of a rod or wire though sometimes rods or wires composed of finely divided metal bonded together by a plastic material are used. Upon heating, this plastic material softens or disintegrates, releasing the metal in the melting zone so that the metal particles may be heated and expelled by a blast of gas. In cases where a solid wire or rod is used, air or another gas is forcibly directed against the molten material at the tip of the rod'or wire in such a manner that it impinges sharply against the tip, thereby substantially blasting the material into fine particles.

The known construction of heat fusible metal spray guns of this type includes a combustible gas nozzle or burner tip which is provided with a material feeding conduit and a multiple number of combustible gas jets, substantially surrounding the axis of the feeding conduit, and a blast gas nozzle surrounding the combustible-gas nozzle and the feeding conduit.

The prior known metal spray guns of the blast gas type have required a relatively large amount of air or other blast gas. This requirement has limited the use of such guns to installations where a relatively large supply of pressurized air or other blast gas was available or the relatively few and important installations where the additional installation of large capacity air compression equipment was warranted.

These known metal spray guns of the blast gas type have also been characterized by low thermal efliciency.- In such designs, only a small amount of metal, such as a short length of wire, is exposed to the flame, and therefore most of the heat from the flame is wasted. Furthermore, these known metal spray guns of the blast gas type have generally caused excessive oxidation of the metal or other material being sprayed, due to the fact that the blast gas used is either air or if not air itself rapidly mixes due to turbulence with atmospheric air so that in either case the hot particles of material being sprayed come into contact with oxygen.

, Attempts have been made in the-past to overcome some of the above disadvantages and particularly the dis- 2,832,640 Patented Apr. 29, .1955

advantage of the requirements for large amounts of air or other blast gas. One such attempt (see Shephard U. S. Patent No. 2,539,487), for instance, elongated the chamber between the combustible gas nozzle and the blast gas nozzle in an attempt to utilize some of the energy from the combustion of the gases to aid the blast gas in atomizing the metal or other material. No such attempts, however, have been successful in eliminating the requirement for a separate blast gas.

Prior known metal spray guns of the blast gas type and all attempted improvements thereof have not only failed to eliminate a separate blast gas but have also all been characterized by a structure in which the fusible material being sprayed is contacted by an oxidizing gas. One object of this invention is to overcome the above limitations and disadvantages.

A further object of this invention is a metal spray gun of the blast gas type which utilizes the products of combustion from the combustible and combustion supporting gases for the blast gas. I

A still further object of this invention is a meta v spray gun of the 'blast gas type which utilizes the products of combustion from the combustible and combustion supporting gases to such an extent that satisfactory atomization of the material being sprayed is obtained without the use of other blast gas. A still further object of this invention is a metal spray gun of the blast gas type which has a higher thermal etficiency than hitherto used metal spray guns of the blast gas type.

=A .still further object of this invention is a metal spray gun of the blast gas type which has a sufliciently higher thermal efliciency than hitherto used .metal spray guns of the blast gas type so that they may utilize air, instead of oxygen, for the combustion supporting :g'as

for spraying higher melting point materials.

A still further object of this invention is a metal spray gun of the blast gas type in which the material being sprayed is surrounded in an atmosphere of relatively inert gases so as to substantially reduce, the-oxidation of e the atomized material.

These and still further objects of theinvention will be more fully understood from the following descriptions The construction in accordance with this invention, which will be hereinafter more fully set forth, utilizes for the first time the energy contained in the expanding gaseousproducts of combustion to perform the entire function of the blast gas.

In the past, metal spray gun constructions have utilized the combustible and combustion supporting fluids only for theprovision of the necessary heating effect which results from the combustion of such gas mixtures, or at most to aid somewhat the blast gas function. The construction in accordance with this invention makes possible the complete elimination of the blast gas previously required by the utilization of the energy from the combustion gases to perform the entire blasting and propelling function. g

The construction in accordance with this invention so increases the thermal efficiency of the gun that less expensive and more readily available fluids may be used for the'combustible and the combustion. supporting fluids.v

Previously, acetylene and oxygen or, for lower melting point metals, propane and oxygen have been required. With the construction in accordance with this invention, mixtures of propane and air may be used even for the higher melting point metals.

This invention is broadly addressed to heat fusible ma-' terial spray guns in which the feed material is in divided form or in the form of an elongated member, such as a wire or rod. Within the preferred embodiments ofthe invention, however, the same will be hereinafter described more specifically in connection with guns in which the heat fusible material is metal in wire or rod form.

The heat fusible material spray gun in accordance with the invention comprises means such as a barrel defining an enclosed combustion chamber with a throttle nozzle opening at its forward end. This combustion chamber, in which the heat is generated for the melting of the fusible material to be sprayed, is made sutficiently large so that heat softening of the material and atomization of the material if the same is in the form of an elongated member may takeplace substantially within the chamber. Means are provided for passing a combustible fluid and a combustion supporting fluid into the combustion chamber, where the same are ignited and combustion takes place. Means are also provided for feeding divided fusible material or an elongated member of fusible material to be sprayed into the combustion chamber toward the'throttle nozzle opening, whereby, upon combustion of-the combustible and combustion supporting fluids in the chamber, the heat produced will heat soften (including melting) the material and the expanding combustion gases will act as blast gas conveying the heat softened material through the throttle nozzle at a high velocity. Since the combustion gases may build up pressure in the combustion chamber, the thermal efiiciency may be substantially increased. Due to the fact that the combustion process substantially completely takes place within the enclosed chamber, the heat produced is very efiiciently utilized and the walls of the combustion chamber will confine and concentrate the heat and heat up and ef ficiently radiate heat to aid in the combustion and melting processes.

' For purposes of illustration, and not limitation, the invention will be described in further detail with reference to preferred constructional embodiments as shown in the drawings, in which:

Fig. 1 is a partial section of an embodiment of a metal spray gun in accordance with the invention for feed material in the form of a rod or wire;

Fig. 2 is a vertical section showing in further detail the burner assembly of the gun shown in Fig. 1;

Fig. 3 is a front elevation of the gun shown in Fig. 1; Fig. 4 is a' front elevation of the multiple orifice nozzle plate shown in Fig. 2; V

Fig. 5 is a front elevation of the gas mixing plate shown in Fig. 2;.and

Fig. 6 is a diagrammatic showing of a further embodiment of a metal spray gun in accordance with the invention for feed material in divided form such as powder.

Referring to the drawings, 1 designates the metal or other fusible material to be sprayed which, as shown, is in the form of a metal rod or wire. The wire passes in through the back of the gun and through the feed rolls 21 and 22 which are mounted to contact and feed the rod or wire 1 forward through the metal spray gun into the combustion chamber. Feed rolls 21 and 22 are driven by the electric motor 23. This feed mechanism for the wire will be recognized as being more or less of a conventional feed mechanism for wire-type metal spray guns. In this connection, anyof the known or conventional feed mechanisms and/or drives may be used. Some of the priorknown metal spray guns utilize gas turbines which were actuated by the blast gas to drive the feed rolls. While such an arrangement would, of course, be operable, since the spray gun in accordance with the invention does not require a separate blast gas supply, it is preferable to use a motor such as the electric motor shown which does not require such a gas supply for its motive force. The wire 1.fed by the feed rolls 21 and 22 passes through a' central conduit in the body of the gas head 2. A rear wire guide 10, equipped with a packing seal 11, is' positioned at the rear of the body of the gas head 2. The seal 11 prevents leakage of pressure back along the infeeding wire.

f The body of the gas spray head 2 additionally has conduit 3 for the combustion supporting fluid such as air, and the conduit 4 for a combustiblefluid, such as propane, acetylene, natural gas, etc.

The forward end of the central conduit through the body of the gas head 2, through which the rod or wire passes, terminates in a forward wire guide 9.

The conduit 3 for the combustion supporting fluid terminates at the forward end of the body of the gas head in an annular groove 17, and the conduit 4 terminates in the annular groove 15.

A gas mixing plate 6 is positioned abutting against the forward end of the body of the gas head 2. The gas mixing plate 6 has a manifold in the form of the annular channel 5. A multiple number of orifices 18 communicate the channel 5 with the groove 17, and a multiple number of correspondingly radially positioned orifices 16 of smaller diameter communicate the groove 15 with the channel 5. The construction of the mixing plate may best be seen from Fig. 5.

In front of the mixing plate 6, a nozzle orifice plate 7 is positioned. This plate has a relatively large number of nozzles which surround the front wire guide 9 and which may best be seen from Fig. 4.

A barrel 14 is screwed over the forward end of the body'of the gas head 2. The inner surface of the barrel 14 defines the combustion chamber 13. A throttle nozzle 12 of ceramic or other heat-resistant material, such as refractory material, defines a central opening through the forward end of the barrel 14, and thus a passage out of the combustion chamber 13.

A spark plug 32 is' screwed through the side wall of the barrel 14.

In operation, the gun may be held by the handle 24 or positioned in any suitable holding means. The elongated member of heat-fusible material, such as the metal wire 1 of any conventional metal which may be sprayed, is passed in through the back of the gun and through the feed rolls 21 and 22, the wire passage 10, the central conduit of the spray head body and through the forward wire guide 9 into the combustion chamber 13. The tip of the wire 1 is preferably positioned in the nozzle 12 though the same may be positioned somewhat behind or forward of the same. In operation, as the tip is meltedofi from the wire, the wire will be continuously automatically fed forward by means of the electric motor 23 driving the feed rolls 21 and 22. Feeding may, of course, be effected in any known or conventional manner and may, for example, be semi-automatic or manual.

A combustion supporting fluid such as oxygen or air is passed from a conventional source of supply such as a pressure bottle, compressor or the like through the valve 19 and passes through the conduit 3 into the annular groove 17. v

A combustible fluid as, for example, propane, acetylene, etc'., is passed as, for example, from a conventional pressure bottle, or the like, through the valve 20 and the conduit 4 into the annular groove 15. The combustible fluid passes from the groove 15 through the openings 16 into the channel 5 and the combustion supporting material passes from the groove 17 through the openings 18 into the channel 5. The streams passing through the openings 16 and 1S impinge each other and an intimate mixing of the combustible fluid and combustion supporting'fluid is thus'eifected in the channel .5. The mixed fluid, such as the mixed air and propane or acetylene,

is then passed through the nozzles 8 of the orifice nozzle plate 7 into the combustion chamber 13. The combustible mixture in the combustion chamber 13 is then initially ignited by passing a spark across the gap of the spark plug 32. It is also possible, for example, to ignite the mixture in any other suitable manner as, for example, through the nozzle 12. Once the ignition has been effected, the combustion process is self-supporting and no further use of the spark plug is made.

combustion chamber 13, the gases, of course, rapidly ex pand. By adjusting the ratio of the combustible fluid to the combustion supporting fluid by means of adjustment of the valves 19 and 20, the combustion will continue smoothly, even with the increase in volume in the combustion chamber 13. The expanding gases will also, of course, flow rapidly out through the throttle nozzle 12.

With the embodiment shown, using, for example, a mixture of air and propane, the pressure in the combustion chamber should, for example, exceed 15, and preferably 25, pounds per square inch gauge. Excellent results have been obtained using a ratio of propane to air of between 1:22 and 1:40, and preferably about 1:30.

The volume of the combustion supporting fluid and the combustible fluid will, of course, vary with the throttle nozzle size. Thus, for example, with a throttle nozzle diameter of .157 inch, a pressure of 30 pounds per square inch gauge in the combustion chamber may be obtained with, for example, about 0.21 cubic foot per minute of propane and 4.81-8.23 cubic feet per minute of air.

In the initial stages of the ignition and initial building up of pressure in the combustion chamber 13, some lack of flame stability may occur when the walls of the chamber 13 are still cold. Flame stability, however, rapidly occurs as the walls of the chamber heat up sufliciently to maintain steady and continuous combustion. Alternately, this condition may be eliminated altogether by preheating the combustion chamber barrel 14, either by torch, electric heating elements or other suitable means.

With the rapid expansion of the combustion mixture in the chamber 13 and the building up of pressure in this chamber, the gas flows out through the throttle nozzle 12 at a relatively high velocity inthe manner of a jet discharge.

The outrushing combustion gases will impinge on the tip of the wire 1 which is melted or softened by the heat generated in the combustion chamber. The gases as they flow past the tip will atomize the metal and carry the atomized particles through the throttle nozzle 12, projecting the same at a relatively high velocity so that the same may be sprayed in the same manner as previously required a blast air or gas.

Since the combustion is effected in the substantially confined chamber 13, the heat produced is concentrated and efliciently utilized for the melting of the wire and the expansion of the gases. further increased by the turbulence and mixing of the combustible and combustion supporting gases in the annular channel 5 and as the same pass through the orifices 8. The thermal eificiency is still further increased due to the fact that the combustion takes place under pressure in the combustion chamber 13.

Of particular importance for the thermal efliciency is the fact that the inner surfaces of the walls of the combustion chamber 13 defined by the barrel 14 will reflect and concentrate the heat produced during the combustion process and heat up and efliciently radiate heat. Due to the importance of this thermal radiation, it is preferable that the barrel 14 or the inner surface of the combustion chamber 13 be constructed of a material which will efliciently radiate the heat absorbed back into the combustion chamber as, for example, micro crystalline alumina. It is also preferable that the combustion chamber be shaped to efficiently radiate heat toward the wire 1. The combustion gases in the chamber 13 are substantially inert, since very little oxygen or combustible fluid remains unreacted. These inert blast gases, consisting of the combustion gases, surround the tip of the wire and surround each of the individual atomized particles of metal for a considerable time after blasting through the throttle nozzle 12. Thus, the metal at the tip of the wire and each individual particle of atomized metal is protected from exposure to the oxidizing effect of the surrounding atmospheric air.

The thermal efliciency is I The exact shape or size of the combustion chamber 13 is not critical, though the same should be large enough to allow substantially the complete combustion to be effected within its interior. The throttle nozzle 12 allows a pressure to be built up in the chamber 13 as the combustion gases expand and rush out through the nozzle. The combustion chamber 13 preferably has a decreasing cross sectional diameter leading to the throttle nozzle 12, as, for example, a frusto'conical shape shown.

The tip of the rod or wire 1 should be positioned in the combustion chamber 13 or in the nozzle 12 so that, as the expanding combustion gases rush out through the nozzle 12, the same will impinge on'the tip, causing atomization. For this purpose, the tip of the rod or wire 1 should be directed axially toward the nozzle 12 and should preferably be coaxial withthe axis of the nozzle.

While the combustible fluid and/or the combustion supporting fluid may be conveniently fed through the gas head in gaseous form, the same may also be in another state as, for example, in the liquid state, pro vided they are converted to the gaseous form before or during the combustion.

While it is preferable that the feed material be in the form of an elongated member such as a rod or wire as described above, the same may also be in any known or conventional form for use in a heat fusible material spray gun such as a metal spray gun.

In the embodiment shown in Fig. 6, the feed material is in divided, such as powdered, form. The gun construction is substantially identical to that shown in connection with Figs. 1 through 5, except that, in place of the means for feeding the elongated member such as the rod or wire 1, means are provided for feeding the material to be sprayed in divided form such as in the form of powder into the combustion chamber 13'. In this embodiment, the feed rolls 21, 22 as shown in Fig. '1 are no longer necessary and the central conduit through the gas head body is replaced by a conduit 25' for passing gas entrained, divided solid fusible material into the combustion chamber. A conduit 26 is connected by the gas-, tight connection 27 to the conduit 25. A container'28 for divided fusible material with a jet feed arrangement 29 is connected to the conduit 26. Compressed gas as, for example, from compressed gas bottle 31 is connected to the jet arrangement by means of a conduit 30. In all other respects, the construction of the gun is identical to Figs. 1 and 2.

In operation, compressed gas from the bottle 31 which may comprise the combustible fluid, the combustion supporting fluid or a mixture thereof is passed through the conduit 30 to the jet 29. Finely divided heat fusible material to be sprayed is stored in the container 28. As the gas from the conduit 30 passes through the jet arrangement 29 the divided material from the container 28 is entrained with the gas stream and carried along through the conduit 26, connection 25 and central conduit 27 into the combustion chamber 13. The gas and pressure requirements for this function are relatively small. A combustion supporting fluid such as air is passed in through the valve 19 and conduit 3 while the combustible fluid is passed in through valve 20 and conduit 4 in the identical manner as described in connection with Figs. 1 through 4.

In all other respects, the operation is identical with the gun described in Figs. 1 through 5, except that the combustion in the combustion chamber 13 of the combustible and combustion supporting fluids will heat soften the divided fusible material and the expanded combustion gases will convey this divided heat softened material through the nozzle 12 at high velocity as blast gas.

Due to the fact that gas used for entraining and conveying the divided fusible material into the combustion chamber 13 may be a portion of the combustible and/or aasaeeo 7 combustion supporting fluids, a corresponding lesser amount of this fluid may be-conveyed to the valves 19 or 20 by suitable adjustment thereof or through the conduits 3on4 or nozzles by'a' suitable reduction in the dimensions thereof.

The means for entraining and/ or feeding the divided material to the combustion chamber dismay be any means known or conventionally used for this purpose in connection with heat fusible material spray guns.

The foregoing description is furnished by Way of illustration, and not limitation, and it is therefore my intention that the invention be limited only by the appended claims or their equivalents, wherein l have endeavored to claim broadlyall inherent novelty.

I claim:

1. A heat fusible material spray gun comprising a barrel defining antenclosed combustion chamber with a substantially centrally positioned throttle nozzle opening defined through its forward end, means for passing a combustible mixture of gases into said chamber, means for feeding an elongated member of heat fusible material to be sprayed into said chamber toward said nozzle opening, said combustion chamber and throttle nozzle being dimensioned so that upon combustion in said chamber, the heat produced will heat-soften the tip of said elongated member and the expanding combustion gases will act as blast gas atomizing the heat-softened material and conveying the same through said throttle nozzle at high velocity, said means for passing said combustible mixture of gases into said combustion chamber including a nozzle plate substantially closing the rear end of said chamber, said plate defining a multiple number of orifices therethrough, and said means for feeding said elongated member into said combustion chamber including a guide defining an axial passage for said elongated member through said plate into said combustion chamber.

. 2. A spray gun according to claim 1 including a mix ing plate behind said nozzle plate defining at least one manifold communicating with said orifices and means defining at least two separate fluid conduits terminating in said manifold.

3. A spray gun according to claim 1 in which. said means for feeding said elongated member and said means "'8 for passing said combustible mixture include a gas head body behind said combustion chamber, an axial central conduit through said body, a first fluid conduit defining a path of flow through said body terminating in a first annular groove, a second fiuid conduit defining a path of fiow through said body terminating in said second annular groove, a mixing plate in front of said body defining at least one manifold, a multiple number of annularly positioned passageways through said mixing plate, connecting said first annular groove and said second annular groove with said manifold, a nozzle plate in front of said mixing plate defining a multiple number of orifices therethrough communicating with said manifold and guide means defining a continuation of said second conduit through said mixing plate and nozzle plate into said combustion chamber.

4. A spray gun according to claim 3 in which said passageways communicating said annular grooves with said manifold are positioned so that the gas passing therethrough from said first annular groove will impinge on and mix with fluid passing therethrough from said seeond annular groove.

5. A spray gun according to claim 4 including sealing means at the rear end of said central conduit for sealing contact with an elongated member passing through said central conduit.

References Cited in the file of this patent UNITED STATES PATENTS 2,136,024 Schneider Nov. 8, 1938 2,137,442 Callan Nov. 22, 1938 2,231,247 Bleakley Feb. 11,1941 2,502,947 Hess Apr. 4, 1950 2,539,487 Shepard Jan. 30, 1951 2,556,193 Kenshol June 12, 1951 2,671,689 Wett Mar. 9, 1954 2,714,563 Poorman et a1. Aug. 2, 1955 2,727,126 Guest et a1. Dec. 13, 1955 FOREIGN PATENTS 553,099 Great Britian May 7, 1943

Images