US2133504A - Metalizing spray gun - Google Patents

Description

Oct. 18, 1938. H. R.'F o 'roN 2, 3, 0

MEYI'ALIZING SPRAY GUN FiledOct. 2, 1935 v ,INVENTOR. xaraldfl. fi 'arfarz v Patented Oct; 18, 1938 UNITED STATES I PATENT OFF-ICE METALIZING SPRAY GUN Harold it. Foiton, Detroit, Mich. I Application October 2, 1935, Serial No. 43,164

5 Claims.

This invention relates to portable apparatus for melting, atomizing and spraying metals, having generally as its object the provision of an improved organization of parts adapted to apply in this manner a metallic coating to any suitable surface/by projection of the molten atomized metal against the work in a pressure-induced stream.

Various forms of apparatus for accomplishing these general ends have been known heretofore, and while some have worked satisfactorily for certainpurposeaall have been subject to shortcomings, and there has not to my knowledge been available heretofore a satisfactory small and portable implement, or one of any size manufacturable at low cost yet reliable in operation. It has also been considered necessary to utilize flaming'gases in the projection of the atomized metal, thus rendering impossible the coating of combustible substances. Further, where such flame-type projection is employed, a triple nozzle must be provided, that is, there must simultaneously be fed from as close to a common point as is practicable, molten metal, air under pressure, and the gases of combustion. This fact has made it impossible from a practical standpoint to reduce the size'of the nozzle and apparatus to proportions allowing ready portability and treatment of relatively small work, such as that required to be coated in the field, of mechanical dentistry. The present invention aims to overcome the mentioned difflculties, to provide eflicient operation without the use of flame projection,

and in a manner which enables use of a much smaller nozzle assembly, and consequent adaptation" of the apparatus to manufacture in much smaller, more easily handled and economical physical proportions, and of such ,size as to enable the performance of small and fine work.

A further object is the provision of such apparatus of the gun type, in which melting of the metal takes place entirely within the gun, and no storage or reservoir of molten metal is provided, the metal being projected immediately upon melting and consequently given .no opportunity to unduly oxidize.

A further important object is the provision of such apparatus in which air is used for projection of the molten metal, but cannot cool the metal before it leaves or cause congelation thereof in the nozzle.

Another important object is the provision in such a device of an improved combined crucible and nozzle element for the molten metal, which crucible element serves as a conveying tube rather than storage element for the molten metal, together with improved means for protecting the nozzle portion against engagement by the aspirating air, and consequent undesired conduction of heat therefrom.

A still further object involves the conduction of heated gases from the heating chamber around the crucible and over the nozzle to constantlyprotect the latter by a surrounding film of highly heated gases to assist in maintaining the temperature of the nozzle. t

A still further aim'of the present invention comprises the provision of improved heating means carried by and located entirely within the- Figure 1 is a side elevational view of an improved device incorporating the principles of my invention.

Figure 2 is a sectional view thereof taken substantiallyon' the line 22 of Figure 1 and looking in the direction of the arrows.

.Figure 3 is a longitudinal sectional elevation taken generally on the line 3-3 of Figure 2 and looking in the direction of the arrows.

Figure 4 is an enlarged detail sectional view of the nozzle portions.

Figure 5 is a sectional elevation thereof taken substantially as indicated on the line 5--5 of Figure 4 and looking in the direction of the arrows.

Figure 6 is an enlarged detail sectional view of one of the gas Jet nozzles.

Referring now to the drawings, reference char! acter i0 designates a generally cylindrical sheet metal housing, carriedbya handle l2 and having a back or upper wall and an open lower face in which the nozzle-projecting portions are supported. Its upper or back wall is apertured, as at H, to allow the escape of hot gases. Within the casing element is a framework carried thereby. comprising a generally cylindrical ring element l5 supported within the outer casing by screws I6, and a backing plate I! provided with a flue portion 20 arranged to discharge through the opening i l in the back wall of the casing. 4 The flue may be guarded as by a hat 22 arranged thereover to protect the user of the implement, whose head, or other portions of whose body might at times come close to the flue. The hat is shown as swingably attached, so that it may be moved same screws I6, is an annular element 25 provided with a circular feeding channel 21 for combustible gas, which is burned to provide the heat source. The front of element 25 is provided with a generally frusto-conical depression 29. The

depression. is closed and thus made to constitute an air delivery chamber by a front plate 30. In-

feed opening 32, guarding the nozzle 52 'thru which the molten metal is discharged against direct engagement by the aspirating air.

Air and gas delivery tubes 34-35 may be run through the hollow handle [2, and discharge into the air passage 29 and gas passage 21 respectively, while the metal to be sprayed may also be delivered through thehandle, preferably in ribbon form, as indicated at 31. Driving means for feeding the ribbon may comprise a pair of rollers 38-39 in frictional engagement therewith, and one, as'39, drivable by such means as worm and worm wheel ill-4|, the former in turn car- -"f'ried upon and drivable by flexible shaft 44,

which may project from the handle to any suitable source of power, as the electric motor diagrammatically indicated at 45'. The air and gas passages, or at least those portions thereof which project from the handle, are of course preferably flexible, as is the ribbon 31, and the air and gas supply couplings and the ribbon supply reel or the like (unshown) may be mounted upon the bench- (also unshown), or other support upon which the tool is to be used. It is preferable for the sake of convenience that the tool, if pro portioned for small work, such as the metalizing operations frequently desirable in mechanical dentistry, be used within a few feet of these connections and the motor, so that the connecting tubes, shaft and ribbon may not be unduly long and cumbersome.

A combined metal melting and delivery tube 50, which will for convenience be designated a crucible, is arranged substantially coaxially of and centrally within the casing, the upper end thereof being closed by a plug as while its ,lower delivery end carries the integral nozzle extension 52 which projects through but is somewhat smaller than the space within the cylindrical wall 26, as best indicated in Figure 4. The crucible is preferably formed of metal, although it may be of refractory material, but in either event is merely loosely positioned within the casing, not tightly secured in place, and provided with an annular pocket 53 surrounding the nozzle portion 52 at its area of connection with the body of the crucible, such pocket being thus connected to the space between the nozzle 52 and wall 26. The base portion of the crucible surrounding the pocket 53, and which rests upon the top wall of element 25, is not so finished as to tightly conform to and seal itself against such wall, as a result of which when, during operation, the aspirating air blast reduces the pressure in front of the nozzle assembly with respect to the pressure within the casing, a certain amount of the air and/or heated gases within the casing may leak between the base of the crucible and element 25, into thepocket 53, and out around the nozzle 52, such air being highly heated by its contact with the. crucible and forming a skin -of heated gases surrounding the nozzle and pre venting undue absorption of heat therefrom by the colder wall 26, thus assisting in maintaining the temperature of the nozzle, which effect is also aided by the shortness-of the nozzle and its integrality with the crucible. These factors facilitate ready heat conduction and guard against freezing of the metal within the nozzle. The base of the crucible and the surface of element 25 upon which it rests are not roughened or otherwise specially treated to allow the desired minutegas flow therearound, but are in my preferred construction simply machine finished. It may be that the slight flow necessary to maintain the skin of heated air about the nozzle is possible because of the vibration of the loose crucible due to the action thereupon of the flames, metal, and air flow. It is to be noted that the general effect of the suction, moreover, is to maintain the crucible seated, so that although vibration may allow a slight flow therebeneath, flaming gases cannot escape.

The metal ribbon is fed into the side of the crucible through a simple oversized opening 60, and is melted as fast as it enters by the flames from the gas jets 63, which are so focused as to concentrate the hottest portions of their flames upon the wall of the crucible. Six such jets are shown, a pair carried by each of three combined bolts and gas feed tubes 65, extended between element 25 and backing plate l8 and secured to each by suitably threaded coupling portions 66-- 61, the former providing a gas connection between thesupply chamber 21 and the gas channel 68 in each element 65, while a nut 69 may be se-' cured upon the portion 61 which projects through the backing plate. Each gas nozzle is axially drilled, as at 10, to provide gas connection with the passage 68, while air ports 'Il through the sides of the nozzles supply air in suitable quantitles to the larger mixing and discharge orifice 12, these parts being proportioned in accordance with the gassupply, and, as stated above, to focus the hottest part of the flame upon the crucible. The stem of each nozzle 63 may extend far enough into passage 68 to partly close the connection between it and the nozzle opening, thereby serving as a pressure reducing or metering orifice, which, particularly inthe case of the nozzle nearer the supply chamber 21, equalizes the gas supply pressure. The air supply for the burners enters the casing through the space 15 between element 25 and ring l5.

It will be seen that in event it is desired to remove the crucible it is merely necessary to swing hat 22 clear of the flue and remove the crucible therethrough, since it merely rests in place. I have found that a tool constructed in the manner described, and substantially in the propor tions shown, functions more satisfactorily than any similar device of which I am aware, and particularly embodies satisfactory operation in a much smaller construction, but it is necessary that the aspirating power of the air blast equal or exceed the rate of metal delivery, and that the heating also be rapid enough to melt the metal as fast as it is delivered. The heating of the crucible near the nozzle end is also important in maintaining the temperature of the metal and the nozzle.

It is also not possible, in accordance with my experience, to make the gun function properly, and to prevent clogging in the nozzle, if the crucible is tightly secured. The proportioning of the nozzle with respect to the air discharge and pressure, the rate of metal delivery and the heat, must of course be fixed, but once satisfactorily set no adjustments are necessary. It is best, if constant pressure air supply is not available, to utilize a controlling valve in the air line adapted to maintain the pressure reasonably constant.

The drawings accompanying this disclosure are, N

' gineer however, although it may be of further help to set forth that in connection with such a tool, utilizing a metallic ribbon oi tin-lead mixture, similar in composition to ordinary solder, and an air pressure of 35 pounds, the air discharge should be approximately 2 cubic feet per minute. A blast projection is then secured at the nozzle at a rate approximating 20,000 feet per minute. Due to the protection of the metal against loss of heat up to the very instant of its discharge, and the apparent tendency of each atomized particle to shield itself with a protecting skin of heated air which remains stagnant de spite the propagation of the particle, the blast will arrive at and adhere to the work in an homogeneously fused coating, even though projected through a considerable distance. The tool is ordinarily used in the horizontal position in which it is shown, but functions satisfactorily when tilted as much as forty-five degrees.

While it will be apparent that the illustrated embodiments of my inventionherein disclosed are well calculated to adequately fulfill the objects and advantages primarily stated, it is to be understood that the invention is susceptible to variation, modification and change within the spirit and scope 'of the subjoined claims.

What I claim is:

1. Means for spraying atomized molten metal comprising a housing incorporating a metal receiving crucible, heating means therefor and a discharge nozzle for melted metal directly connected to and integral with the receiving means,

means for maintaining the nozzle in a heated condition, a blast discharge nozzle surrounding the metal discharge nozzle and arranged when in operation to aspirate the molten metal from the first mentioned nozzle and atomize and project such metal, said first mentioned nozzle projecting loosely through the blast discharge nozzle, and the crucible being free to move with respect to the housing.

2. In a device of the character described, a housing having a heating chamber therein and an opening connecting the same with the exterior, a combined metal fusing and conducting element within and smaller than the heating chamber, a metal discharge nozzle portion carried by and connected to the interior of said element and projecting through but smaller than the. opening in the housing, means within the heating chamber for heating said element, means including a projection jet appurtenant the opening and adapted to discharge a projecting fluid under pressure to reduce the pressure at the mouth of the nozzle and induce molten metal within said element to flow therefrom, and means for feeding metal to said element, said element and nozzle being fitted loosely enough in the opening to allow a slight flow of heated gases from within the chamber through the spacebetween the nozzle and opening, to maintain in a highly heated condition the metal within the nozzle while preventing flame projection, said heating means, metal fusing and conducting element, nozzle and projection jet being so proportioned as to discharge the metal asfast as it is melted.

3. In a portable metalizing device, a casing having an opening therein, a combined metal fusing and conducting element within the casing having an inlet opening near one end thereof and an outlet nozzle portion connected to its other end and extending through the opening in the casing, means for feeding metal in strip form substantialiy continuously through the inlet opening and into said element, means. for heating other portions of said element, an atomizing jet orifice adjacent the nozzle and discharging in the same general direction for aspirating and projecting the metal, a wall between said nozzle and blast jet orifice for shielding the nozzle against direct impingement by the atomizing blast, said wall also providing a restricted passage between the interior of the casing and the nozzle to enable the heating of the latter by means of hot gases from the interior of the casing, and means appurtenant said first mentioned opening to prevent escape of flame through said passage.

4. In a device of the character described, a housing having a heating chamber and an opening therein, a combined metal fusing and conducting element in the heating chamber, a nozzle connected to' said element and discharging outside the chamber through said opening, means for delivering metal to said element substantially continuously, means for heating said element to melt the metal therein at a rate at least as fast as that at which it is delivered thereto, aspirating means including a jet surrounding the nozzle for discharging a gaseous projecting agent and drawing the molten metal from the crucible through the nozzle to form an atomized blast thereof, the

aspirating power of the jet being at least as great I as the rate of melting and delivery of the metal, said surrounding jet being spaced from the nozzle by a separate wall concentric with but spaced from the nozzle, the jet being arranged to draw heated gases through the space between said wall and nozzle to maintain the temperature of the nozzle, said element and nozzle constituting an assembly rested loosely in said housing and against said opening, and means for heating the nozzle without allowing flame projection.

5. In a device of the character described, a housing having a heating chamber and an opening therein, a combined metal fusing and conducting element in the heating chamber, a nozzle connected to said element and discharging outside the chamber through said opening, means for delivering metal to said element substantially continuously, means for heating said element to melt the metal therein'at a rate at least as fast as that at which it is delivered thereto, aspirating means including a jet surrounding the nozzle for discharging a gaseous projecting agent and drawing the molten metal from the crucible through the nozzle to form an atomized blast thereof, the aspirating power of the jet being at least as great as the rate of melting and delivery of the metal, said surrounding jet being spaced from the nozzle, and the nozzle being relatively short and constituting a unitary assembly with said element and resting loosely in said housing and against said opening, whereby eflicient heat conduction may take place between the element and nozzle, and whereby heated air may escape around the nozzle but escape of flame is inhibited, whereby the nozzle is heated by the'escaping air.

Images