US3003702A

US3003702A - Feed control for metal spray guns and the like

Info

Publication number: US3003702A
Application number: US56744A
Authority: US
Inventors: Henry S Rondeau
Original assignee: Individual
Current assignee: Individual
Priority date: 1960-09-19
Filing date: 1960-09-19
Publication date: 1961-10-10
Anticipated expiration: 1978-10-10

Description

Oct. 10, 1961 s, RQNDEAU 3,003,702

FEED CONTROL FOR METAL SPRAY GUNS AND THE LIKE Filed Sept. 19, 1960 Pal. \\\\\W T 6 1 2 73 5 57 j 25 M r, 2 2 /6 I8 3 v V 77 6 M 5 j 26 3o 1 v14/ fjf INVENTOR.

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United States Patent Ofiice 3,003,702 Patented Oct. 10, 1961 3,003,702 FEED CONTROL FOR METAL SPRAY GUNS AND THE LIKE Henry S. Rondeau, 2865 Coventry Road, Cleveland, Ohio Filed Sept. 19, 1960, Ser. No. 56,744 19 Claims. (Cl. 239-84) This invention relates, as indicated, to a feed control for metal spray guns and the like and more particularly to a metal spray gun of the wire feed type which will give uniform atomization of the wire continually regardless of varying air pressures, imperfections in the wire, and fluctuations in the gas flame.

In metal spray guns wherein the usual gases, e.g., acetylene, oxygen and air are fed to a chamber together with the metal in wire form to be sprayed, the Wire feed mechanism may be driven as by an air motor connected with the air supply source. The turbine of such air motor drives feed rollers contacting the wire thus moving it into the combustion chamber. The melted Wire is sprayed by the flame and hot gases through the discharge nozzle of the gun. However, since the diameter of the discharge orifice of the nozzle is only slightly larger than the diameter of the wire, the improper feed of the wire with relation to the atomization of the tip thereof can cause pulsations, spattering, and other irregularities in the metal spray obtained. Obviously, if the wire is fed into the nozzle at an excessive lineal speed, it will not be completely melted whereby the resulting spray will include large unmelted particles and, on the other hand, if the wire is fed into the nozzle at an insufficient lineal speed, the productive capacity of the gun will suffer and furthermore may result in back-firing and sticking of the wire due to accumulation of metal at the nozzle tip and gas jets. Heretofore, manual controls of both the gas pressure and wire feed rate have been employed with the skill of the operator determining the most desirable conditions.

It is accordingly a principal object of the present invention to provide a feed mechanism for metal spray guns which will give uniform atomization at all times.

It is another object of the present invention to provide a metal spray gun of the wire feed type which will maintain the advancing melted-down conical tip of the wire in the portion of the nozzle at which most uniform and efficient melting and spraying is achieved.

It is yet another object of the present invention to provide a metal spray gun of the wire feed type which will give uniform results regardless of Varying air pressures, imperfections in the Wire, and fluctuations in the fusing flame.

Other objects and advantages of the present invention will become apparent as the following description proceeds.

To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawings setting forth in detail a certain illustrative embodiment of the invention, this being indicative, however, of but one of the various ways in which the principles of the invention may be employed.

In said annexed drawing:

FIG. 1 is a perspective View of a metal spray gun of the wire feed type in accordance with the present invention; and

FIG. 2 is a diagrammatic fragmentary sectional view of the feed control for such gun in accordance with the present invention.

Referring now to the annexed drawing and especially to FIG. 1, it will be seen that a metal spray gun of the wire feed type is provided wherein a wire is fed through two feed rollers 1 and 2 mounted for rotation on vertically extending axes and therefrom into a gas head 3. Such feed rollers 1 and 2 and the gas head 3 are mounted on a housing 4 which may be manually held or mounted on a fixture to have the gas head and metal spray issuing from the orifice 5 directed at the Work to be coated with the metallic spray. In order to melt or fuse the Wire W which is fed into the gas head 3, such gas head is supplied with a combustible gas, a combustion supporting gas, such as oxygen, and a blast gas such as compressed air. A typical combustion gas would be acetylene with the combustion supporting gas oxygen supplying an oxyacetylene flame to melt or fuse the tip 6 of the wire W to be sprayed through the orifice 5 by the blast gas or compressed air. A conical nozzle 7 may be secured as by nut 8 concentrically of the gas head 3 and such nozzle is provided with inlets 9 and 10 for the combustible gas and the combustion supporting gas. The blast gas or compressed air enters through passage 11 and flows into the gas head through several orifices such as that shown at 12. A branch passage 13 leads from the passage 11 through-pilot valve 14 and control valve 15 to motor 16. The motor 16 is in the form of a gas turbine effective to drive the shaft 17 and suitable gearing 18 vertically oppositely to rotate feed rolls 1 and 2 through shafts 19, thus feeding the Wire W therebetween into the gas head 3 to be sprayed through orifice 5.

A suitable plug valve 2% may be provided with control handle 21 simultaneously to govern the flow of the combustible gas through the passage 9, the combustion supporting gas through the passage Ill, and the blast gas through the passage 11. The inlets for these various passages may be provided at the bottom of vertically extending support or handle 22 as shown at 23. The valve 15 may be manually operated thus controlling the amount of air passing through the branch passage 13 to the motor 16 and thus the rate of feed of the wire W. Manual adjustments of the

valves

20 and 15 will produce initially the proper spray from the orifice 5. However, fiuctuations in the wire make-up, the pressure of the compressed air or oxyacetylene gases, will vary the set or desired atomized spray of the metal wire and heretofore only a manual adjustment could alleviate the difficulty incurred.

It will be apparent that if the wire tip 6 extends further to the right as seen in FIG. 2, such wire will tend to block the orifice 5 thus creating a higher back pressure in the combustion chamber 25 Within the gas head 3. Likewise, as the tip of the wire 6 moves to the left away from the orifice 5, the pressure within chamber 25 will drop. It has been found that the variation in the pressure in chamber 25 can be fed back to the motor 16 properly to control the feed of wire W and thus the position of tip 6 with respect to the center of the flame and the orifice 5 to obtain a uniform and proper atomization of the wire.

In order to obtain this feedback, the pilot type diaphragm valve 14 is provided which opens or closes with the increase or decrease of the air pressure in the chamber 25. Such pilot type diaphragm valve may include three

plates

25, 27 and 28, with the branch passage 13 extending through the plate 26 beneath ridge 29. The main diaphragm 30' is secured between

plates

26 and 27 and overlies an aperture 31 in plate 27 directly beneath ridge 29.

Secured between the

plates

27 and 28 is a secondary diaphragm 32 having a plastic member 33 secured thereto having a central upstanding portion 34 fitting within orifice or aperture 31 adapted to move and press diaphragm 30 toward ridge 29 restricting fluid flow within passage 13. A chamber 35 is provided between the plates -27 and 28 to allow for vertical movement of the diaphragm 32 and member 33 therein. The pilot chamber beneath the diaphragm is connected directly to the chamber 25 in the gas head through passage 36. An adjustable bleeder valve 37 having adjusting screw 38 is provided in the pilot passage 36 to exhaust air to atmosphere through orifice 39 to control the pressure Within pilot passage 36. This actuation of the pilot bleeder valve will control the actuation of the pilot valve to obtain the fine adjustments desired in the relation between the blast gas flow and the rate of feed of the wire W. It can now be seen that the pressure within the chamber 25 and thus the pressure in the lower portion of pilot cavity 35 beneath the relatively large area diaphragm 32 will cause vertical movement of the member 34 to control the fluid flow in branch passage 13, and thus the speed of turbine motor 16. Accordingly, the pointed end of the wire W itself acts as a valve needle when it goes forward through the nozzle into the orifice setting up a back pressure causing the pilot valve to reduce the fluid flow through branch passage d3 slowing down motor 16 and thus the rate of feed of the wire. The motor 16, of course, will slow down, moving the melted down tip 6 of the wire W away from the orifice 5 reducing the pressure in the chamber 25 and thus opening the valve 14. If, however, the wire pilot recedes too far from the air orifice 5, the back pressure in the chamber 25 will decrease and this time the valve 14 will open permitting more air to increase the turbine speed thus causing the Wire feed to speed up again and adjust itself into the center of the flame. if desired, a small orifice 40 may be employed to interconnect branch passage 13 and pilot conduit 36 preventing undue oscillations or sharp fluctuations in the operation of the valve.

It can now be seen that there has been provided an inverse feedback controlling the rate of feed of the wire W in response to the pressure within the chamber 25. Accordingly, the higher the back pressure in chamber 25, the slower the rate of feed of the wire W and inversely, the lower the back pressure in chamber 25, the higher the rate of feed of the wire W. With this type of device, closer and automatic control of the wire feed is obtained so that it cannot spray beyond the center of the flame and will give uniform atomization at all'times. This mechanism makes allowance for variations in air pressures, imperfections in the wire which create drag, and fluctuations in the oxyacetylene flame.

The spray Wire W employed in guns of this type may be steel, alloys of steel, bronze, aluminum, brass, and such metals may be used for coating, molding or bonding purposes. Wires of this type may be made of powdered or granulated metal held together by a plastic bond which easily disintegrates in the hot flame produced by the combustible and combustion supporting gases.

Whereas the invention has been illustrated as applied to a metal spray gun of the wire feed type, it will be readily understood that it is equally applicable to a spray gun for ceramic rod or to a spray gun of the powder feed type with the pressure in chamber 25 regulating and controlling the amount of powdered metal fed into the combustion chamber.

Other modes of applying the principles of the invention may be employed, change being made as regards the details described, provided the features stated in any of the following claims or the equivalent of such be employed.

1, therefore, particularly point out and distinctly claim as my invention:

1. A metal spray gun comprising a combustion chamber having a discharge metal spray orifice, means to feed metal into said chamber to be fused therein and sprayed through such discharge orifice; and inverse feedback means responsive to the pressure in said combustion chamber to control the rate of feed of said metal into Said chamber.

2. A metal spray gun as set forth in claim 1 including a blast gas conduit leading to said combustion chamber, and a branch conduit leading from said blast gas conduit to a gas turbine, said gas turbine driving said means to feed metal to said combustion chamber, said inverse feedback means controlling the passage of gas in said branch conduit.

3. A metal spray gun as set forth in claim 2 wherein said inverse feedback means comprises a pilot valve in said branch conduit, and means to open and close said pilot valve in response to the pressure in said combustion chamber.

4. A metal spray gun as set forth in claim 3 wherein said pilot valve includes two diaphragms, one said diaphragm controlling gas flow in said branch conduit in response to movement of the other said diaphragm.

5. A metal spray gun as set forth in claim 4 wherein the other said diaphragm has a large area exposed to a pilot chamber, the pilot conduit means interconnecting said pilot chamber and said combustion chamber.

6. A metal spray gun as set forth in claim 5 including substantially rigid plastic plate means interposed between said diaphragms.

7. A metal spray gun as set forth in claim 5 including a bleeder valve in said pilot conduit to bleed said pilot conduit to atmosphere.

8. A metal spray gun of the wire feed type comprising a combustion chamber having a discharge metal spray orifice, means to feed a wire into said chamber to be fused therein and sprayed through such orifice; and inverse feedback means responsive to the gas pressure in said chamber to control the rate of feed of said wire into said chamber.

9. A metal spray gun as set forth in claim 8 including feed rollers for said wire driven by a gas turbine, a gas supply to said combustion chamber, and branch conduit means leading from said gas supply to said gas turbine, said inverse feedback means controlling the flow of gas in said branch conduit thus to control the rate of feed of said wire.

10. A metal spray gun as set forth in claim 9 wherein said inverse feedback means comprises a pilot valve in said branch conduit to control the flow in said branch conduit, and means to open said pilot valve in response to a drop in pressure in said combustion chamber and to close said pilot valve in response to an increase in pressure in said combustion chamber.

11. A metal spray gun as set forth in claim 8 wherein said combustion chamber is frusto-conical in shape, said discharge orifice being at the small end thereof, and said orifice being of a diameter only slightly larger than the diameter of said wire.

12. A metal spray gun as set forth in claim 11 including means to supply a combustible and combustion supporting gas to said combustion chamber.

13. A metal spray gun of the wire feed type comprising a combustion chamber having a flame therein with a discharge metal spray orifice, means to feed a wire into said combustion chamber to be fused therein and sprayed through such orifice; and means responsive to the position of the tip of said wire in said combustion chamber to control the rate of feed of said wire into said chamber thereby to maintain the tip of said wire in the center of said flame to obtain a substantially uniform atomization of said wire in said combustion chamber.

14. In a metal spray gun of the wire feed type having a combustion chamber into which wire is fed to be melted and sprayed therefrom; means inversely to vary the rate of feed of said wire in relation to the pressure in said combustion chamber.

15. The combination set forth in claim 14 wherein said wire is fed by feed rolls driven by a turbine motor, and means inversely to control the rate of feed of said turbine motor in relation to the pressure in said combustion chamber.

16. In a metal spray gun of the type having a conical combustion chamber into which wire to be melted therein is fed and sprayed through an orifice at the smaller end thereof, means to supply such combustion chamber with a combustible gas, a combustion supporting gas, and a blast gas for forcing the atomized metal through such orifice, turbine driven means feeding said Wire to said combustion chamber, said turbine driven means being driven by a branch passage leading from the blast gas conduit leading to said combustion chamber; and pilot valve means in said branch passage controlling the speed of said turbine motor, and means interconnecting said pilot valve and said combustion chamber thereby inversely to vary the rate of feed of the Wire with respect to the pressure in said combustion chamber.

17. The combination set forth in claim 16 wherein said pilot valve includes a main diaphragm adapted to block the flow of fluid in said branch passage, 21 secondary diaphragm movable in response to the pressure in said combustion chamber.

18. The combination set forth in claim 17 wherein said wire is fed to such combustion chamber by juxtaposed feed rolls adapted to rotate about vertical axes, said feed rolls being driven through suitable gearing by said turbine motor.

19. The combination set forth in claim 18 including a manually adjustable valve in said branch passage thereby manually to control the speed of said turbine motor.

References Cited in the tile of this patent UNITED STATES PATENTS 1,262,134 Stolle Apr. 9, 1918 FOREIGN PATENTS 821,558 Great Britain Oct. 7, 1959