US2361420A - Spray metal gun of the gas blast type - Google Patents

Description

' Get. 31, 1944. A. P. SHEPARD 2,361,420

SPRAY METAL GUN OF THE GAS BLAST TYPE I Filed Nov. 4, 1941 JL Juga5 44 43 J6 51 I 34 3/ 41 51 32, F ,JZ J

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- lrfhurPS/Effldl'd ATTORNEY Patented Oct. 31, 1944- UNITED STATES PATENT OFFICE SPRAY METAL GUN OF THE GAS BLAST TYPE- Arthur P. Shepard, Forest Hills, N. Y., assignor to Metallizing Engineering Company, Inc., Long Island City, N. Y., a corporation of- New Jersey Application November 4, 1941, Serial No. 417,771 6 Claims. (01. 91-122) 4 This invention relates to new and'useful improvements in spray metal guns of the gas blast type.

In spray metal guns of the gas blast type, .a metal wire is usually fed continuously into a heating zone in which the tip of the wire is melted and from which metal particles in a finely subdivided state are propelled by a blast of gas to the object to be sprayed. In guns of this type, it has been common practice to bleed air into the passage leading the wire to the heating zone. The bleeding of air or other blast gas is accomplished by means of a single-aperture opening into the wire passage. Spray metal guns of the gas blast type, and conventionally including a gas blast bleeding aperture, are characterized by the fact that the tip of the'wire, at the point of its melting, fluctuates considerably and appears to move in and out longitudinally during the spraying operation. This requires that the-wire speed be reduced sufficiently so that the tip of the wire where it melts off in its outermost position does not extend far enough to cause a rough" or spattery type of spray. Such reduction in wire speed is conducive of ineconomi'cal operation'of the gun. In addition to the necessity for reducing speed, another disadvantage which results from this construction is that occasionally the wire sticks in the tip of the-nozzle.

The construction in accordance with the instant invention satisfactorily overcomes the aforementioned disadvantages and drawbacks present in the conventionally construed spraymetal guns of this type. The invention will bemore fully understood and'these as well as other objects will become evident from' the foregoing description read in conjunction with the drawing in which I Fig. 1 is a cross-section through part of aspray metal gun construction embodying my invention on the line |l of Fig. 2 in the direction of the arrow;

Fig. 2 is a vertical section through part of a spray metal gun construction embodying my invention; and

4 Fig. 3 is a vertical section through the construction illustrated in Fig. 1 in the plane III-III thereof.

Referring to the drawing, I (Fig. 2) indicates the inlet for oxygen or other combustion supporting gas, 2 the inlet for acetylene or other combustible gas, and 3 the inlet for-air or other gas for atomization of the metal, projection of the metal spray and driving of the turbine. When plug 4 of valve 5' is in the position shown, each position, which is at 'a right angle to the showing inFig; 2, first some combustible gas passes into duct and thence to the burner outlet to enable the burner-to be lighted. Some air passes simultaneously into manifold I 9 to enable the turbine to come up to speed. Alternatively, all the valve passages may beopen'ed" but at such rates of flow as to establish favorable lighting conditions which are different from the conditions obtain ing when the gun is in operation. This position of the valve is called' the lighting position. After the burner has been lighted, movement of handle 8 causes oxygen to flow through duct ill" which establishes a melting flame with the ignited gas and the final movement of handle 8 to the position shown in Fig. 2' permits air to flow into duct l5 and thence into chamber Hi to project the sprayed metal'upon thesurface tobe covered.

Thexconstruction of that part of the gun by which the rod or wire ismelted'and projected will be explained by reference to Fig. 1. The'wire 31 moves forward to guide 31' and through duct 32 to the interior 33 of the burner tip'341 The mixture of gas and oxygenmov'e forward through the 5 duct H, which is immediately behind duct 32 and into the annular space 3'5. From this annular space 35 the combustible mixture moves forward through a number of holes to be discharged through convergent orifices 36 against the wire. This forms a zone of gases undergoing combustion, whereby'the' wire 31 melts as rapidly as it is progressively advanced into the zone, for which reason this zone is referred to as a melting zone. The air from chamber l6 advances through the 5 annular space 40 surrounding burner tip 34 and tions in the characteristics of the air blast. When a satisfactory adjustment has been made, the tip 4| is locked in position by the lock nut 44. It will be noted that the air in passing forward from the chamber 16 goes through the constricted annular space 45 which exerts a definite control over the volume of air passing. As a result of this construction and the orifice efl'ect thereby created, the adjustment of air tip 4| modifies the characteristics of the air blast without so great a modification of the volume of air passing thereto as would otherwise result, which is decidedly advantageous in the adjustment and operation of the gun. The wire 31 is fed through the pas,- sage or duct 32 to the melting zone by means of suitable wire feeding means (not illustrated) such as driven bursor the like mechanism known in the art.

Blast gas bleeder ducts 50 lead, in combination with blast gas chamber Hi, from the annular neck or groove 5| into the wire duct or passage 32..

The bleeder holes in accordancewith our invention are preferably so arranged thatthey are substantially evenly spaced with respect to each other inside the wire passage or duct. Instead of individual bleeder ducts it is possible to provide for one or more common or intercommunicating ducts from which the requisite number of bleeder holes issue into the wire passage. Though as a rule two bleeder holes accomplish the desired result, three bleeder holes are preferred. In general, unless special circumstances, or considerations of construction prevail rendering the use of more than three bleeder holes desirable, a number of bleeder holes in excess of three will normally not confer any material advantage over the use of three such holes.

The dimensions of the bleeder holes should be suchthattheir aggregate cross-sectional area permit the blast gas or compressed air supply to bleed into the wire passage at a pressure sufiicient to overcome the .back pressure obtaining at the burner nozzle tip and insufficient to interfere with the temperature requirements of the melting zone.

My'invention is not limited to'the construction of a spray gun illustrated in the foregoing examples and may be used in connection with any other suitable gun construction of the gas blast wire feed type, including those having other heating or melting means for the wire, such as an are or the like and further including those constructions of this type in which multiple wires are fed to the heating zone.

The foregoing description is by way of illustration and not of limitation, and it is, therefore my intention that the invention be limited only by the appended claims or their equivalent, in which I have endeavored to claim broadly all inherent novelty. a

.I claim:

1. In a metal spray gun of the wire'feed gas blast type, having a gas blast duct and a wire feed duct for feeding a metal wireto'the melting zone of saidgun, the improvement comprising a gas blast bleederholes being spaced apart a conf. siderable distance from each other to substantially reduce wire tip fluctuation in said melting zone.

2. In a metal spray gun of the Wire feed gas blast type, theimprovement in accordance with claim 1 in which said holes and said passages are each three in number.

3. In a metal spray gun of the wire feed gas blast type having a gas blast duct and a wire feed duct for feeding a metal wire to the melting zone of such gun, the improvement comprising in communication with said gas blast duct a multiple number of blast gas bleeder holes around the wire feed duct of said gun, said gas blast bleeder holes being spaced apart a considerable distance from each other to substantially reduce wire tip fluctuation in said melting zone.

4. In a metal spray gun of the wire feed gas blast type having a gas blast duct and a wire feed duct for feeding a metal wire to the melting zone of such gun, the improvement comprising a multiple number of holcsaround the wire feed duct of said gun. and a multiple number of bleeder gas passages at least one for each of said holes zone of such gun,-the improvement comprising a multiple number of evenly spaced holes in substantially radial arrangement in said wire feed duct of said gun, and a multiple number of bleeder gas passages at least one for each of said holes and connecting said holes with said gas blast duct, said holes and said passages being positioned, and dimensioned to bleed blast gas into said wire feed duct sufiicient to overcome back pressure at the nozzle tip of said gun.

6. In a metal spray gun of the wire feed gas blast type, the improvement in accordance with claim 5 in which said holes are three in number.

ARI'HUR P. SHEPARD.

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