[1]United States Patetit Office 3,136,484 ANGULAR BLAST GAS CAP Ferdinand J. Dittrich, Bellmore, N.Y., assignor to Metco Inc., a corporation of New Jersey Filed June 22, J960, Ser. No. 38,031 5 Claims. (Cf. 239-79) This invention relates to an angular blast gas cap for a heatfusible material spray gun. Heat-fusible material spray gtms are devices in ,vhich a heat-fusible material is fed into a heating zone, where the same is melted or at least heat-softened, and then propelled in finely divided form, as for exarnple, against a surface to be coated. The heat-fusible material may be fed to the heating zone in a finely divided or powdered form, in which case the ,-Un is genera-Uy referred to, as a "powder type gun," or in the form of a rod or wire (the term "wire" being used generically to define both of these elements), in which case the gun may generally be referred to as a wire typ-gun. In heat-fusible material spray guns of the wire type the wire is fed into, the heating zone, in which the tip of the wire is melted or at least heat-softened, and a blast gas, such as air, is directed against the tip of the wire thus heated in order to, atomize fine particles from the wire and propel the sarne in the form of a spray. The blast gas is -enerally directed against the tip of the wire by means of a blast gas cap, often referred to as an "air cap," as air is usuauy used as the blast gas. The most common commerciafly utilized heat-fusible material spray guns utilize a combustion flaine for heating, and frequently an additional blast gas for atoniizing and propelling is used. Thus, for example, the heat in the heating zone may be generated by the buriling of a fuel gas, such as acetylene or propane, with air or oxygen, and the blasting where a separate blast gas is provided, may be effected with air, nitrogen or the like. A typical heat-fusible material spray gun of the wire type is, for example, described in U.S. Patent 2,340,903. Less common types of spray guns do not provide for blast gas but utilize the expanding combustion gases as a blast gas by allowing the same to expand from a confined combustion zone through a throttle nozzle or to expand throu.-h an elongated nozzle or the like. In accordance with newer constructions, the heat for 'the melting or heat-softening of the heat-fusible material is produced by a plasma flame, i.e., a flame in the energy state above the gas state, with elee-trons being actually stripped fror@i the atoms of the material forming the gas. The plasma is most commonly generated utilizing an electric arc and most usually a constricted arc. The plasma flame may be used for spraying in a manner similar to the combustion flame, and a separate blast gas may be used for atomizing and propelling the material being sprayed, if desired. Other modes have been known or proposed for generating the heat for heat-fusible material spray guns. These include electric heating, as for example electric resistance heating or induction heating or ordinary arc heating. With the use of an ordinary electric arc two separate heatfusible material wires may be fed forwaxd at a converging angle and an electric are struck therebetween. A blast gas may then be propelled against the arc, atomizing the wires as they are consumed and melted in the are, and propelling the atomized material away from the are in the form of a spray. Alternatively the wire or powder may be, for example, fed through an electric arc formed from separate electrodes. In heat-fusible material spray guns of the powder type the powdered heat-fusible material is generally fed, entrained in a smau stream of carrier gas, into a flamq where the same is heated to heat-softened or molten conPatented June 9, 1964 2 dition and propelled by the velocity of the combustion gases from the flame or by means of a separate blast gas to the surface being sprayed. For certain applications it is necessary to change the direction of the heat-fusible material spray. Thus, when spraying in confined spaces, such as interior surfaces, as for example when spraying the interior of tubes or cylinders, it is necessary to deflegt the spray at an angle to its nonnal direction so that the spray gun nozzle, as 10 such, or at the end of an extension may be inserted in the tube or cylinder, in the general direction of its axis, and effect the spraying of a sprayed coating on the walls of the tube or cylinder. For this purpose the spray was generoy directed against a solid deflector surface which 15 would deflect the spray and project the same against the tube or cylinder side wall. The solid deflector surface was generally formed as part of a special blast gas or air cap, known as an angular blast gas or air cap. This angular aircap would have the construction of a conventional 20 blast gas or air cap except that its outlet opening was offset to one side at an angle to its normal axis, and the interior adjacent its outlet opening was in the form of a rounded and smooth deflector surface. Thus, in effe-ct, the outlet opening was, for example, directed at an angle 25 of 45' from the normal axis, and the interior of the cap was constructed as a rounded deflector surface in order to deflect the spray streatn and direct the same out through the outlet opening at this angle. The cap and the portion forming the deflector were generally constructed of metal. 30 These angular caps presented various difficulties in operation and were very sensitive to flame conditions, wire speed and air pressure adjustinents. In order for the same to function properly, it was necessary that the molten tip of the wire be preeisely positioned at a fixed 35 spot with respect to the deflector surface. If this tip would be too close to the deflector surface, sprayed heatfusible material, such as the metal, would deposit on the surface, causing sticking, spattering and the like. If the tip were too far away from the deflector surface, the angle 40 of spray would change and the work would not ba evenly coated. The difficulty of maintaining the tip at this exact required position may be readily appreciated when considering the dynamic conditions encountered during operation, with the wire constantly being moved and with 45 metal being constantly melted and atomized off from the tip at a fairly rapid rate. A very slight change in the flame characteristics, the air flow or even the metallurgy or crystal structure of the wire will affect the position of the wire tip and thus can cause difficulties as mentioned 50 above. Even when the wire tip is precisely maintained at the desired positi6n with respect to the deflector surface of the cap, the caps still have a tendency to loading with spray metal, which of course changes the flow character55 isti6s around the deflector section, catising difficulties. A frequent interruption of operation, with cleaning and polishing of the caps, is thus generally required in operation. Furthermore the caps, particularly with respect to the deflector section, must be manufactured with preci60 sion and maintained in this condition, for if the same contains burrs, pits or roughnesses, turbulent flow may be caused which in turn will permit the sprayed metal to deposit on the cap. This in turn will result in disturbance of the flame, flickering, and spattering of the spray, 65 and ultimately back-firing or sticking of the wire in the nozzle. In spite of these many disadvantages of lon.standing in the art, a more satisfactory solution for the deflection of the spray was not found. Attempts to effect the deflection of the sprayed stream by the use of 70 an additional blast gas or gas curtain in place of the solid deflector surface, did not prove practical. The spray stream from the heat-fusible material spray gun is not
[2]3 homog-,rieous and there is a higher percenlage of larger particles in the ceiter of the stream, with most of the finer particles being concentra@,Cd at the outside of the stream. These fine particles in turn contain a higher percentage of oxides, which are deleterious to the coatings. In -.iormal sprayiig procedi-ires ttiese fine part-leles are blown away by deflection of the gas stream as it stiikes the work, and thus are not deposited in harmful quantities on the work 8urface@ When attp-mpts were mad--, ho@,vever, to deilect the normal direction of the spray stream with the use of an auxiliary blast @as stream or curtain of gas, the origi-.ial distribution of the partic'les is disrupted, so that ' he finer particles with the deleterious oxides are no loiger deficefed frorri the surface, but will be deposited, producing an inferior coating. Furlhermore, the lar.-er particles are given an asymmetrical distribution paitern, Nvhich results in an uneven coating when, for example, spraying is effected in the conventional manper, i.e., t@.e surface is sprayed with overlapping stripes. One object of this invention is to overcome these d@'@fficulties. A further object of this innelition, is a novel angular blast gas cap whichovereo-nes these d,',fnculties. These and still further objects will become apparent from the following description read in conjunction with the drawings in which: FIG@ 1 is a vertical section of an embodimen, of an angular blast gas cap in accordance with the invention; FIG. 2 is a cross-sect:lo-i of the embodiment shown in FIG. 1; , FIG. 3 is a partial. vertical section showing the air cap of FIG. I as positioned on a metal flame spray gun; FIG. 4 is a plan view of the embod,.Ment sh6wn in FIG. 3; FIG. 5 is a plar. view of a portio@i of a further embodiment of aii angular cap in accordance with the invention; FIG. 6 is a plan view of a portion of a still futther embodime@it of an angular cap in accordance with the invention; and F'IG. 7 diagrammatically shows a vertical, cross-sectional view of a portion of a powder giin in accordance with the invention. The invention is particularly applicable to flame spray guns of the wire type, but as hereinafter described is also applicabl.- to other types of heat-fusible material spray guns. In accorda-.ico with the invention it has been surprisingly discovered that the deflection of the stream of heatfusible material bein.- sprall Ted may be effected by a separate blast gas stream without the disadvantages previously encountered if this separate blast gas stream is of a cross-sectional shape approximating that of a trough, with the plane of the base of the trough bisecting the axis of th,- normal spray direction at an angle between about 60 and 90' and preferably at about 90'. If the side walls of the troughshaped blast gas stream extend in the normal spray direction, the shape of the stream will not b.- appreciably distorted. If these side walls, however, extend opposite the normal spray direction, i.e., point upstream of the normal spray direction' then the deflected spray stream will be distorted into a fan shape but will still produce an excellent quality coating, and this distorted shape may be useful in certain instances. The deflecting trough-shaped blast -as strcain is preferably generated by passing a blast gas throu,-h a multiple nurinber of jets having a corresvonding trough-shaped configuration, but may be generated in any other known or desired manner. A preferred embodiment of the invention comprises an angular blast gas or air cap which, in contra-distinction to th-- conventional angular air cap, docs not have a-.i offset outlet opening or nozzle, but an outlet or nozzle extending in the normal axial direction and is provided with means, such as a multiple number of j-,ts of the proper cor.1'@,-uration off to o-tic side fbereof@ for d:irecling a trough-shaped blast of -as traiisversely 3,136,484 4 across 'Lhe outlet opening, with the plane of the bas-. of the trough bisectirg tl-.e axis of tiie blast gas rlow passag-through tl-ic cap at an angle between about 60 and 90'. Referring to ti@e em. bodiment shown in FIGS. 1-4 of the drawin.@, the angular blast gas cap in accordarce with the invention coir@prises a housing 1, of metal or other suitable material conventionally used for tb.e co-qstruction of air caps, defining a blas@. -as flow passage 2 extending substantially axially therein and termi-.iatiil10 at a forwardly direct,-d ou'Llet opening or nozzle 3 and an inlet opening 4 at its rear end poi-tion. This port;on ol the construction as thus far defined is substantially identical to that of a conventional blast gas or air cap, i.e., as contrasted to, an angular cap. In accordance with the 15 :i-.Ivcntion tLe cap has an extendin@- I;p 5 on one sidf,-, this lip extendilig past the outlet opening 3. A mult@ple nl,.mber 6f blast gas jets 6 extend throi-igh this lip in a directio-ti substanti,,d'iy norn-ial to the axis of the blast gas flow passa,@e 2. Thes-, J;ets are in a trough-shaned con20 fi@L,.ra'c;on, as may best be seen fro-m FIG. 4.. Ttie uilder-side of the extendin-@ lip 5 is shaped to deflile the hollow air chamber 7 provided with ah open bottom wh:@ch ill turn is sealed by the closure plate S. A multiple number of gas flow passages 9 ext-,nd c6axially w;tll 25 the bore of the passage 2 into tnis cnamber 7. The cap is positioned on a heat-i'Usible material spray gun, as for example a flame spray gun of the w@re type, in the conventional manner as shown in FIG. 3. The cap is thus I secured in the g,-,n housing 10 in the con30 ventional manner. The nozzle body 11 ol the gun extends inlo the passage 2. This nozzle body 11 is provided with a central axial wire fe,-ding orifice iL2, a wire guide bushing 13, and a mult@@ple number of converging burner jets 14. An annular -roove 15 is cut in th-, 35 rear face of the nozzle body so that the sarne intersects the burner jets 14. The rear face of the nozzle body 11 is machined flat and pressed a@-ainst a correspondin@flat surface of the -Un head 16 by means of the nut 17. The gun head 16 has an annular groove 18 which co.-re40 snonds to and, mates with the groove 15, in the nozzle body' A gas feed passa,-e 19 leads into the groove 18. The head 16 also has an axial bore or orifice 20 which corresponds to and mates with the wire feeding orifice 12. In operation a wire 21 of heat-fusi'ole material, as 45 for example a conventional metallizing rod or wire of metal, is fed through the gun, through the orifice 20, the wire feeding orifice 12 and the -tiide bushing 13, through the passage 2 to the position shown. The feeding of the wire r@iay be effected in any known or co@iventional man50 ner as for example by feed rolls driven by any known or @onventional drive means, such as a gas turbine actuated by blast gas, an electric motor or the like, or even manually pushed through. A combustible gas mixture o,4, for example, acetylene and oxy,@en, acetylene aiid a,.r, 55 propane and air, propane and oxy,@en, or the like, is fed, for example, throtigh a mixing chamber through the fuel, gas passage 19 and passes into the annular groova 18 to the annular groove 15 through the burner jets 14, where the same is ignited in front of the nozzle body 60 11, forming a heating zone. The flame from the jets 14 impinges on the tip of the wire 21, melting the same. A blast gas, such as compressed air, is fed through the space 22, passes through the openings 23 in the nut 17, through the inlet opening 14 of the cop and through the 65 blast gas flow passage 2 of the cap out through the outlet opening or nozzle 3, where the sa,-ne : impinges on the tip of the rod 21, atomizing n-iaterial from this melting tip and propelling '@he sarne in the form of a fine spray away from the gun in the conventional manner, in 70 a d".rection coaxial with the passa ge 2 and direction of feed of the wire 21. A portion of the blast gas passing through the space 22 will pass through the gas passages 9 into the chamber 7@ From the chamber 7 the gas will B-ow out of the jets 6 in the for.,n of a tro@,igh-shaped 75 blast of gas corresponding in cross-sectior,.al shape tG the
[3]5 trough-shaped configuration of the jets 6, as may be seen from FIG. 4. This troughshaped blast of gas will pass transversely across the outlet opening or nozzle 3. The direction of this blast is such that it would normally bisect the axis of the blast -as flow passage 2 at an angle of about 90' though the jets 6 could be so constructed that the plane of the base of this trough-shaped blast of gas would bisect the axis of the passage 2 at any angle between about 60' and 90'. This trough-shaped blast of gas will deflect the spray so that the same will change its direction to pass at an angle to the axis of the passage 2 and wire 21, as for example at a 45' angle, thus enabling the spraying of a surface extending in the direction of the wire 21. In this manner, for example, the interior of tubes or cylinders may be sprayed in the conventional manner, as when using conventional prior art angular air caps. While the blast gas from the jets 6 is normally directed so that the same will bisect the axis of the blast gas flow passage 2 at an angle between about 70' and 90', the component flow, due to the deflection of fne spray, will of course be at a different angle. When reference, however, is made herein and in the claims to the angle of 60'-90', the sarne is meant to define the normal angle if the blast of gas would extend from the jets unimpeded, i.e., the angle at which the same is directed, rather than the angle that the same actually crosses the outlet opening. Very surprisingly the deflected spray will produce a homogeneous, high qual4ty coat-'@ng, and for som-, unexplained reason the deposit efficienoy is increased even in comparison with the undeflected spray. Noiie of the disadvantages previously encountered when atten-ipting to deflect the spray with a gas stream or curtain occur, and of course none of the disadvantages which were encountered when using a solid deflecting surface, as for example in a conventional ari,- ular air cap occur, there being of course no solid deilecting surface on which sprayed metal could deposit or on which suriace imperfections could occur, causing difficulties. The jets 6 are preferably in the trough configuration as shown in FIG. 4, with two rows of staggered jets and two outermost jets forming the walls of the trough, which extend in the normal spraying direction, i.e., with the base of the trou.-h directed toward or facin.- the spray. In place of having the jets 6 in a trough-shaped configuration, the same may be directed so as to form the troli,@h-shaped blast of gas. Thus, for example, the j may be in an cven row, with the outer jets incli slightly forward so as to form the trough waus. In place of individual jets any other means for forming the trough-shaped blast gas may be used, as for example the slot-shaped opening as shown in FIG. 5. With the side walls of the trough directed in the normal direction of spray, the spray pattern as deposited on the sprayed surface will not bematerially changed as compared with an undeflected spray. If, however, the walls of the trough are directed inwardly toward the spray, using for example an array of jets as shown in FIG. 6, then the spray pattern will be flattened out into a fan shape, so that the spray will be deposited in narrower bands of a greater length which may be desirable in certain instances. The exact shape of the troughshaped blast gas is not critical as long as the same has this over-all cross-sectional shape. Preferably the height of the side walls of this trough-shaped blast above the inside trough base when initially formed, should be at least 15% and preferably at least 30% of the width of the trough. Thus, in the embodiment shown in FIG. 4, the distance of the outermost row of the jets 6, i.e., the two outermost jets which form the wall of the trough from the next adjacent row, should be at least 15% and preferably 30% of the average length of the other rows of jets. 3,136,484 6 The following is a practical exarnple of operation given by way of illustration and not limitation: Example 5 In this example a metallizing flame spray gun having the construction corresponding to that shown in FIG. 3 and commercially sold by the Metallizing Engineering Co. Inc. of,Westbury, Long Island, as a Model "K!' gun, was used. The air cap I had an over-all length of 10 1.17", the diameter of the outlet opening 3 was .305" and of the opening 4 .573". The lip 5 was positioned .285" from the central axis of the cap and had a length of 3/s". The jets 6 were .0315" in diameter, with each row being spaced .078" apart. The centers of the in15 dividual jets of each row were spaced .0625" apart and 'Lhe distance between the outermost jets forming the wall of the trough-shaped blast was .375". The innermost row of jets was positioned .125" from the face of the cap. The passages 9 were Ylr," in diameter, with their 20 centers 3/32" apart. The gun was operated with air at an air pressure of between 90 and 100 p.s.i. as the blast gas, and with acetylene as the combustion gas and oxygen as the oxidizing gas, the oxygen being maintained at 40 p.s.i. and the acetylene at 15 p.s.i. The wire feed speed 25 was maintained at 8 lbs. per hr., the air at a flow rate of 37 cu. ft. per min., oxygen at a flow rate of 97 cu. ft. per min., and the acetylene at a flow rate of 35 cu. ft. per min. With these values the spray was deflected at an angle of abotit 45' from the axis of the passage 30 2. The interiors of engine cylinders were successfully sprayed with steel, bronze, aluminum, zinc and molybdenum, with this set-up. The wire size used for the spraying was 'Is" and in all cases an excellent, homogeneous coating was obtained with a higher deposit effi35 ciency than would be indicated for the spray without the deflection, a-qd a deposit efficiency substantially higher than that which could be obtained with a conventional angular air cap having a solid nietal deflecting surface. Even after continuous operation there was no deposit 40 build-up on the cap and no conditions occurred which would interfere with continuous operation. While, as mentioned, the invention is particularly suitable for use in connection with wire type flame spray guns, and in particular as a novel blast gas or air cap 45 construction therefor, the invention is also applicable for deflecting heat-fusible material sprays in general, including all of the various types as previously mentioned herein. For this purpose the spray is effected in the conventional manner and the trough-shaped blast of gas 50 is passed transversely across the normal spray pattern at an angle of between about 60'-90' with respect to the axis thereof for the deflection. FIG. 7 diagrammatically shows an embodiment of the invention in connection with a powder spray gun. The 55 gun has a conventional spray nozzle 24 provided with an outlet passage 25 for the powdered material, and an annular ring of combustion gas jets 26. Heat-fusible material in powdered form, such as powdered metal or the like, is fed through the conduit 27 from a hopper or 60 container or the like, and a stream of a carrier gas, such as air, is passed through the passage 28. This gas passes through the outlet orifice 29 and entrains a small quantity of the powder, carrying the same out through the passage 25. Combustion gas and combustion supporting 65 gas, such as acetylene and oxygen, or propane and oxygen, are passed through the jets 26 and ignited at the face of the nozzle. The heat-fusible powder entrained in the carrier gas passes into the flarne and is heat-softened and propelled in the form of a spray by the expanding com70 bustion gases. A lip 5 of the construction previously described is positioned on one side of the nozzle and provided with jets 6 of the configuration previously described, the chamber 7, and the passages 9. A blast gas is passed through the passages 9 from the tube 30 75 and flows from the jets 6 in the form of the trough-
[4]7 shaped blast of gas, deflecting the spray at an angle to the axis of the passage 2 and the normal spray direction. The jets 6 may have any desired shape or configuration, as previously described, capable of produe: g tWs trough.n shaped blast. The required velocity of the blast may be Very easily empirically determined for the particular angle of deflection desired. While the invention has been described in detail with reference to certain specific enibodiments, various changes and inodifications which fall witwn the spirit of fne invention and scope of the appended claims will become apparent to the skilled artisan. The invention is therefore only intended to be liniited by the appended claims or their equivalents, wherein I have endeavored to claiin all inherent novelty. I
