US2340903A - Metal spray gun - Google Patents

Description

Patented F eb. 8,

UNi'rEo STATES PATENT oI-ric` METAL SPRAY GUN Arthur P. Shepard, Forest Hills, N. Y., assignor to Metaliizing Engineering` Company, Inc., Long Island City, N. Y., a corporation of New Jersey Application July 31, 1940, Serial No. 348,633

(Cl. Sil-12.2)

17 Claims.

This inventionY relates to improvements in metal spray guns.

Metal spray guns of the wire feeding .gas blest type are devices in which a. metal rod or wire is continuously fed into a melting zone in which the metal is melted, being thereafter finely divided and expelled from the gun in sub-divided form by a. blast of air or other ges. A mixture of combustible and combustion supporting gases,

, tip, provided with e. wire feeding orice end s.

multiple number oi burner iets, substentially surrounding the exis of said orice, end en sir cop, extending with e portion of its inner surface, edjacent the air oep tip, toin advance of seid ori- `iice, preferably in substentislly converging reletion to said exis, and defining with a. backwerdly extending portion of its inner surface nud with seid burner tip e gas blast passage. It is to such nozzle construction that the invention primarily relates.

The hitherto used metal spray guns of the wire feeding ges blast ere of relatively low spi-eying speed end emciency end ere subject to the danger of bog, i. e., 'the ignition of the combustible ges mixture inside the ges jets or the gas passages.

I have devised an improved nozzle construction for s. metal spray gun of the wire feeding gas blest type permitting a more emcient and higher speed spraying of metal with a materially reduced tendency to backfire, then wos hitherto possible with conventional devices.

The invention vwill be more fully understood from the following description read in conjunction with the drawing illustrating a preferred embodiment of the structure in accordance with the invention in whichl Fig. l is e vertical section through a preferred embodiment of s nozzle construction in sccord ance with my invention;

Fig. 2 is on end view of the construction illustrated in Fig. 1 in the plene indicated b II-II;

Fig. 3 is e sectional view of the burner tip pon` tion of the construction illustrated in Fig. 1 in the plane indicated by III-III, and

Fig. 4 represents e sectional view of .the burner tip and air cap portion of the construction illustrated in Fig. 1 on the plane indicated by IV-IV.

Referring to the drawing, l represents the inner nozzle or burner tip; 2 represents the air capwhich is adjustebly screwed by e. thread Si into e housing t. The housing il is secured to the gun head of which only part is shown in the drawing. The inner nozzle or burner tip i is Isented on the iiat seat t of heed 5 end is held there securely by nut l. Air cap 2 has two slots cut in its rim at i es illustrated in Figs. l and 4. Lock nut t is provided for securing oir csp 2 in eny desired position. A port it leeds from a mixing chamber for combustible end combustionsupporting gases (not shown), to circuler channel ii cut in the fiat seat t. Inner nozzle or burner tip i is provided with a multiple number of ges possoges i2. Communicating with these gas passages ere burner jets it and it. These burner jets it and ld ore alternately spaced es indicated in Fig. 3. Burner jets it extend to the tip of the inner nozzle, while burner jets it communicate with enlarged jet portions l5. Enlarged iet portions it extend to the discharge end of the inner nozzle or burner tip es indicated in Fig. i. Mounted et the discharge end of lnner nozzle or burner tip i is e. bushing it which l is set beck slightly from the burner jet openings.

Burner tip i is constructed with o substentislly cylindrical surface il' which extends into end is concentric with the cylindrical surface or bore l@ of the eir csp i. Part of the inner surface oi' sir csp 2 hes a conical surface it with o comparstively shallow angle of slope relative the air' csp axis or the axis of the wire feeding criiice. This rst conical surface i9 adioins s. second conical surface 2t, edit the air csp tip, with a comparatively steeper angle of slope relative such ems. The surface at the juncture of the two conical sections i9 end 2d is prefersbly curved slightly es et il. The rod-like shape of metei i2 extends through wire'ieeding orice formedby guide bushing it in the inner nozzle or burner tip i.' Y

In the practical operstion of the improved gun nozzle structure in accordance with my invention, e mixture of combustible and combustion supporting gases enters through gas passage it and thence through channel Il to ses pesssges i2 in the inner nozzle or burner tip l. Gas pessages I2, alternately connected with burner jets -tained by counterborlng I3 and I4 permit the combustible mixture of gases to flow to the discharge end of inner nozzle or burner tip I. The gas entering burner jets I3 passes directly to the discharge end of the burner tip whereas the gas entering burner jets I4 flows first through enlarged jet portions I5 before passing to the discharge end of the burner tip I. Burner jets I3 are larger in crosssectional area than burner jets I4, whereas enlarged burner jet portions I5, preferably obor countersinking burner jets I4, are of larger cross-sectional area than jets I4. In many cases it is of advantage and preferred to construct enlarged jet portions I5 also of larger cross-sectional area than burner jets I3. When resorting such construction the combustible gas mixture entering gas passages I3 from channel Il, under substantially the same pressure, permits a greater volume of gas to flow through the wider jets I3 than flows through the smaller jets I4. This particular distribution of the combustible gases substantially eliminates the shrill undesirable whistle which sometimes occures when the same .volume of gas is permitted to discharge from each of the burner jets which is especially noticeable when using propane as the combustible gas component of the mixture. In most instances a few thousandth.. of an inch difference between the cross-sectional areas of burner jets I3 and I4 will give the desired result. The names issuing from the enlarged jet portions, such as jet portions I5, are shorter than the flames issuing from the discharge end of the non-enlarged jets, such as jets I3. When enlarged jet portions are substantially evenly distributed among the burner .iets surrounding the axis of the wire feeding orifice and particularly when such enlarged burner jet portions alternate with non-enlarged burner jet openings, as illustrated in the preferred embodiment of the invention shown in the drawing, a substantially ribbed-like flame is produced with the hot tip of the flames, issuing from burner jets i3, projecting farther than the hot tips of the flames, issuing from the burner jets i5, inwhich manner the melting zone is considerably elongated. This longer heating zone permits a more rapid melting of the metal and even of relatively high melting point metals so that the metal wire 4or rod 22 passing through the Wire feeding orince as defined by the bushing IB may be fed more rapidly through the nozzle and permits a more eillcient and speedier spraying operation. As shown in the drawing, the wire feeding orice through the bushing Il is set back slightly relative the discharge ends or openings of burner iets I3 and I4. vSuch construction greatly reduces the hazards of backnring and thus permits the use of a greater combustible gas flow with a resultant increase in spraying speed and eilliency. When used in conjunction with other structural elements of the improvedconstruction in accordance with the invention, tending to enhance spraying speed and emciency or to reduce backre hazards, it will still further enhance these advantages.

Air or other blasting gas enters chamber 26 under pressure from an inlet duct (not shown). This blasting gas passes through a substantially annular pressure reduction orifice 23, .substantially donned' by the cylindrical surface I8, formed on the backwardly extending portion of the inner surface of the 'air cap 2, and the cylindrical surface I1, formed by a part of the backwardly extending surface of the inner nozzle or burner tip I. After passing the pressure reduction orifice 23 the blasting gas enters chamber 24 and flows thence through the space between the sloped inner surface I9 of air cap 2 and the surface of the conical end of the inner nozzle or burner tip I, defining annular orifice 25, and out through the discharge end of the air cap 2. The inner surface of the air cap 2, adjacent the discharge end thereof, has an average angle of slope, with respect to the axis of the wire feeding orifice, greater than the average angle of slope, with respect to such axis, of its adjoining inner surface portion IB. As illustrated, both surface portions I9 and 20 each form a conical surface, the conical surface 20 having a greater average angle of slope, with respect to the axis of the wire feeding orifice, than has the conical surface I9. The blasting gas, passing with relatively high velocity through annular orifice 25, is deflected at a relatively small angle to the axis of the wire feeding orifice by the lesser sloped surface I9 of air cap 2. This relatiyely shallow angle of surface I9 permits the blasting gas to pass outside of the envelope of flame in advance of the inner nozzle or burner tip I before being deected by the steeper angled inner air cap surface 20. The blasting gas will thus converge at the most desirable steep angle at a point sufnciently in advance of the flame envelopevto substantially avoid the building up of a detrimental back pressure at the discharge end of the inner nozzle or Iburner tip I. The rapid and relatively steep angled convergence of the blasting gas at the molten tip of the metal wire or rod produces a very fine and complete break-up or atomization of the metal and blasts the same forward in a strong ne spray.. In this manner a more eflicient and speedier spraying operation is realized and, when using such construction in conjunction with the burner jet construction in accordance with the invention. the increase in spraying efficiency and speed, already greatly improved by such jet construction, is still further enhanced by this inner surface double slope improvement in the air cap. The material reduction in back pressure at the discharge end of the inner nozzle or burner tip I, obtained when' using the inner surface double slope construction, in accordance with the invention, considerably lessens the tendency to backfire. This beneficial effect is still further enhanced by utilizing this construction in conjunction with other structural features of my improved nozzle construction which possess such backfire hazard reducing effect.

W'hen using the inner air cap surface double slope construction, in accordance with the invention, I have foundy it of advantage to utilize an average angle of slope, with respect to the axis of the wire feeding orice, of the surface portion adjacent the air cap tip, of approximately 5 to 15 degrees and preferably of 10 to 11 degrees and an average angle of slope, relative such axis, of the gas blast passage delimiting portion of its inner surface, of approximately 3 to l2 degrees and preferably of 51/2 to 6% degrees.

The provision of an air reduction orice of substantially constant cross-sectional area throughout a given longitudinal adjustment of the air cap permits the adjustment of the air cap 2 with respect to the discharge end of the burner tip I without materially affecting the quantity of now of the blasting gas and irrespective of whether the air cap is moved towards or away from the burner tip. This construction also aids in increasing the spraying emciency and speed and further aids in materially reducing the danger of backring as it tends to eliminate the building up of back pressure which would result when moving the air cap towards the burner tip in the -absence of the substantially constant cross-sectional area, pressure reduction orifice, in accordance with the invention.

Air cap 2 is preferably provided adjacent its threaded end 3 as shown in Figs. 1 and 4 with slots 8 to prevent the possibility of accidentally shutting off the gas blast supply from chamber 26 by screwing the air cap 2 back too far until the back. of its end strikes nut 7. With the provision of such slots 8 sumcient air will pass through these slots even if the air cap 2 is screwed back as far as it will go.

The foregoing description is furnished 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 equivalents wherein I have endeavored to claim broadly all inherent novelty.

I claim:

1. In the nozzle construction of a wire feeding metal spray gun of the gas blast type, including a burner tip provided with a wire feeding orifice, a multiple number of burner jets substantially surrounding the axis of said orifice and means to supply a combustible gas through said jets, the improvement comprising an air cap having a first inner surface portion immediately surnounding said burner tip, defining therewith at least one gas blast passage, start' at a pOint prior to said orifice and having only one other second inner surface portion extending said gas blast passage to in advance of said orifice, and directing gas blast, issuing fromisaid gas blast passage, against the molten tip of the wire feeding through said orifice, the average angle of slope, with respect to said axis of said second inner surface portion being greater than the average angle of slope, with respect to said axis, of said first inner surface portion.

2. The improvement in accordance with claim l in which said first and second inner surface portions each defines a conical surface.

3. In the nozzle construction of a Wire feeding metal spray gun of the `gas blast type, including a burner tip provided with a wire feeding orifice, a multiple number of burner jets substantially surrounding the axis of said orifice and means to supply 'a combustible gas through said jets, the

improvement comprising an air cap, substantially v longitudinally adjustable with respect to said burner tip and having a first inner surface portion immediately surrounding said burner tip dening therewith at least one gas blast passage, starting at a point prior to said orifice and having only one other second inner surface portion extending said gas blast passage to in advance of said orifice, and directing gas blast, issuing from said gas blast passage, against the molten tip of the wire feeding through said orifice, the average angle of slope with respect to said axis of said second inner surface portion being greater than the average angle of slope, with respect to said aids, of said first inner surface portion, said burner tip and said air cap having cooperating backwardly extending surfaces, and, in communica- 'tion with said gas blast passage, a blasting gas pressure reduction orifice of substantially constent cross-sectional area throughout a given longitudinal adjustment of said air cap, said pressure reduction orifice being defined by at least part of said backwardly` extending surfaces.

4. The improvement in accordance with claim 3 in which said blasting gas pressure reduction orifice is a substantially 'annular orifice and in which said backwardly-extending surfaces form substantially cylindrical surfaces substantially coaxially aligned with said burner tip.

5. In the nozzle construction of a wire feeding metal spray gun of the gas blast type, including a burner tip provided with a wire feeding orice, a multiple number of burner jets substantially surrounding the axis of said orifice and means to supply a combustible gas through said jets, the improvement comprising an air cap, substantially longitudinally adjustable with respect to said burner tip and having a flrst inner surface portion immediately lsurrounding said burner tip, defining therewith' at least one gas blast passage, starting at a point prior to said orifice and having only one other second inner surface portion extending said gas blast passage to in advance of said orifice, and directing gasvblast, issuing from said gas blast passage, against the molten tip of the Wire feeding through said orifice, said burner tip and said air cap having cooperating backwardly extending surfaces, and, in communication with said gas blast passage, a blasting gas pressure reduction orifice of substantially constant crosssectional area throughout ag'iven longitudinal adjustment of said air cap, said pressure reduction orifice being dened byat least part of said backwardly extending surfaces. L

6. The improvement in accordance with claim 5 in which said blasting gas pressure reduction. orifice `is a substantially annular orifice and in which said backwardly extending surfaces form substantially cylindrical surfaces substantially co-axially aligned with said burner tip.

'1. In the nozzle construction of a wire feeding metal spray gun of the gas blast type, including a burner tip provided With a wire feeding orifice, a multiple number of burner jets substantially surrounding the axis of said orifice and means to supply a combustible gas through said jets, the l improvement comprising an air cap, substantially longitudinally adjustable with respect to said burner tip and having a first inner surface portion immediately surrounding said burner tip, defining therewith at least one gas blast passage, starting at a point prior to said orifice and lhaving only one other secondA inner surface portion extending said gas blast passage to in advance of said orifice, and directing gas blast, issuing from said gas blast passage, against the molten tip of the wire feeding through said orifice, the average angle of slope, with respect to said axis of said second inner surface portion being greater than the average angle of slope, with respect to said axis,l of said first inner surface portion, and a multiple number of burner Jets, at least some of which being, at least at their end portions, adjacent the jet openings, of larger cross-sectional area than the remaining jets, at least at their end portions, adjacent the jet openings.

8. The improvement in accordance with claim 7 in which at least some of said burner jets are at their-end portions, adjacent the Jet openings, of larger cross-sectional area than the jet portions, extending backwardly therefrom.

9. The improvement in,accordance with claim 7 in which each alternate of said burner jets isl f at its end portion, adjacent the jet opening, of

larger cross-sectional area than its jet portion,

extending backwardly therefrom and of larger cross-sectional area than the corresponding jet portions of the other burner jets.

l0. Theimprovement in accordance with claim 'l in which each alternate of said burner jets is at its end portion, adjacent the jet opening, of larger cross-sectional area than its jet portion extending backwardly therefrom and in which said backwardly extending jet portion is of smaller in advance of said orifice, and directing gas blast, i

- issuing from said gas blast passage, against the molten tip of the wire feeding through said orince, the improvement comprising a multiple numbei of burner jets, at least some of which being, at least at their end portions, adjacent the jet openings, of larger cross-sectional area than the remaining jets, at least at their end portions, adjacent the jet openings.

12. In the nozzle construction of a wire feeding metal spray gun of the gas blast type, including 'a burner tip provided with a wire feeding orifice, a multiple number of burner jets substantially surrounding the axis of said orifice, means to supply a combustible gas through said jets and an air cap having a first inner surface portion immediately surrounding said burner tip defining therewith at least one gas blast passage and having a second inner surface portion extending to in advance of said orifice, and directing gas blast, issuing from said gas blast passage, against the molten tip of the wire feeding through said orifice, the improvement comprising a multiple number of burner jets, at least some of which being at their end portions, adjacent the jet openings, of larger cross-sectional area than the jet portions, extending backwardly` therefrom.

13. In the nozzle construction of a wire feeding metal spray gun of the gas blast type, including a burner tip provided with a wire feeding orifice, a multiple number of -burner jets substantially surrounding the axis of said orifice, means to supply a combustible gas through said jets and an air cap having a rst inner surface portion immediately surrounding said burner tip, defining therewith at least one gas blast passage, Startins surrounding the axis of said orice and means to supply a combustible gas through said jets, the improvement comprising anair cap, substantially longitudinally adjustable with respect to said burner tip and having a first inner surface portion immediately surrounding said burner tip, defining therewith at least one gas blast passage, starting at a point prior to said orifice and having only one other second inner surface portion extending said gas blast passage to vin advance of said orifice, and directing gas blast, issuing from said gas blast passage, against the molten tip of' the wire feeding through said orifice, the average angle of slope, with respect to said axis of said second inner surface portion being greater than the average angle of slope, with respect to said axis, of said first inner surface portion, a multiple number of burner jets, each alternate of which being at its end portionadjacent the jet opening, of larger cross-sectional area than its jet portion extending backwardly therefrom, said backwardly extending jet portion being of smaller crosssectional area than the jet portions of smallest cross-sectional area of the other burner jets, said burner tip and said air cap having cooperating backwardly extending surfaces, and, in communication with said gas blast passage, a substantially annular blasting gas pressure reduction orifice of substantially constant cross-sectional area throughout a given longitudinal adjustment of said air gap, said pressure reduction orifice being defined by at least part of said backwardly extending surfaces to form substantially cylindrical surfaces having a substantially common axis with said burner tip. .r

15. In the nozzle construction of a wire feeding metal spray gu'n of the gas blast type, including a burner tip provided with a wire feeding orifice, a multiple number of burner jets substantially surrounding the axis ofl said orifice and means to supply a combustible gas through said jets, the

improvement comprising an air cap, substantially longitudinally adjustable with respect to said burner tip and having a first inner surface portion immediately surrounding said burner tip, dening therewith at least one gas blast pasv sage, starting at a point prior to said orifice and at a point prior to said orifice and having; only one other second inner surface portion extending said gas blastfpassage to in advance of said orince, and directing gas blast, issuing from said gas blast passage, against the molten tio of the wire .feeding through said orifice, the improvement comprising a multiple number of burner jets, each alternate of which being at its end portion, adjacent the jet opening, of larger cross-sectional area than its jet portion extending backwardly there.-

' from, said backwardly extending jet portion being of smaller cross-sectional area than the jetportions of smallest cross-sectional area of the'other burner jets.

14. In the nozzle construction of a wire feeding metal spray gun o! the gas blast type, including a burner tip provided with a wire feeding orifice,

a multiple number of burner jets substantially having only one other second inner surface portion extending said gas blast passage to in advance of said orifice, and directing gas blast, issuing from said gas blast passage, against the molten tip of the wire feeding through said orifice, the average angle of slope, withl respect to said axis of said second inner surface portion being greater than the average angle of slope, 'with respect to said axis, of said rst inner surface portion, and a wire feeding orifice set back lative to at least some of the burner jet opengs. Y

16. In the nozzle construction of a wire feeding metal spray gun of the gas blast type. including a burner tip provided with a wire feeding orifice, a multiple number of burner jets substantially surrounding the axis of said orifice, means tc supply a combustible gas through said jets and an air cap having a first inner surface portion immediately surrounding said burner tip defining therewith at least one gas blast passage and having a second inner surface portion extending to in advance of said orifice, and directing gas blast, issuing from said gas blast passage, against the molten tip of the wire feeding through said orifice, the improvement comprising a wire feeding orice set back relative to at least some of tho '2,340,903 burner jet openings and the face of the burner 17. In the nozzle construction of a wire feeding metal spray gun of the gas blast type, including a burner tip provided with a wire feeding orice, a multiple number of burner jets substantially surrounding the axis of said oriiice and means to supply a combustible gas through said jets, the improvement comprising an air cap, substantially longitudinally adjustable with respect to said burner tip and having a rst inner surface por tion immediately surrounding said burner. tip,

dening therewith at least one gas blast passage, -h

starting at a point prior to said orifice and havmg only one other secondinner surface portion extending said gas blast passage to in advance of said orifice, and directing gas blast, issuing from said gas blast passage, against the molten tip of the wire feeding through said orifice, the average angle of slope, with respect to said axis, of said `second inner surface portion being'greater than the averagev angle of slope,'with respect to said axis, of said first inner surface portion, said first inner surface portion dening a irst conical surface and said second inner surface portion denn'- ing a second conical surface, a multiple number of burner iets, each alternate of which being at its end portion, adjacent its jet opening, of larger cross-sectional yarea than its jet portion extendv ing backwardly therefrom, said backwardly extending jet portion being of smaller cross-sectional area than the jet portions of 'smallest crosssectional area of the otherburner jets, a wire feeding orifice set back relative\the burner jet openings andthe face of the burner tip, said burner tip and said air cap having cooperating backwardly extending surfaces, and, in communication with said gas blast passage, a substantially

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