US2287770A - Metal spray gun - Google Patents

Description

June 30, 1942.

Egg.

F. O. ALBERTSON METAL SPRAY GUN 5 Sheets-Sheet l 4/22 160 j jzg 22 122 126 E 131 "1557 7; 1 3 t 23 June 30, 1942. R Q ALBERTSQN 2,287,770

METAL SPRAY GUN Filed Jan. ll, 1959 5 Sheets-Sheet 2 June 30, 1942. O. ALBERTON 2,287,770

METAL S PRAY GUN Filed Jan. 11, 1939 Sheets-Sheet 4 j I J31 32 1R June 30, 1942. o, ALBERTSQN 2,287,770

METAL SPRAY GUN Filed Jan. 11, 1959 5 Sheets-Sheet 5 Patented June 30, 1942 I METAL SPRAY GUN Frans O. Albertson, Sioux City, Iowa, assignor to Albertson & Company, Inc.,

corporation of Iowa Sioux City, Iowa, a

Application January 11, 1939, Serial No. 250,292

/ 3 Claims.

The present invention relates to metal spray guns, and is particularly concerned with metal spray guns of the type adapted to melt electrically a supply of meltable metal and to spray it by means of compressed air.

The present application relates to improvements in the metal spray guns covered by my priorpatent, No. 2,058,653, issued October 27,

1936, on Metal spray guns.

The metal spray guns constructed according to my prior patent and according to the present invention have been subjected to very hard usage. Although constructed solely for melting and spraying metal, operators appear to have a tendency to use the end of the gun as a hammer for flattening out parts of metal, and have also been known to hammer the gun about or jar it for the purpose of loosening metal in the nozzle.

One of the objects of the invention is the provision of an improved metal spray gun which is tion of the gun for striking blows against the sprayed metal.

Another object of the invention is the provision of an improved metal spray gun which is so constructed that the handle is cooler and the heat is concentrated at the metal well so as to 1 conserveheat and apply the heat more effectively to the work at hand, thereby facilitating the continuous use of the gun with a smaller heating element.

Another object of the invention is the provision of an improved metal spray gun, in which the ends of the nozzles are protected against injury and the air nozzle and metal nozzle are so arranged that they are automatically placed in predetermined relationto each other when the gun is assembled.

Some difliculty has been encountered due to operators of the guns endeavoring to adjust the location of the air nozzle, and this adjustment is something which should be done only'by experts.

Another object of the invention is the provision of an improved metal spray gun connection in which the air nozzle is not adjustably mounted with respect to the metal nozzle, and in which the air nozzle is provided with means for assuring its location in a predetermi'nedposition with respect to the metal nozzle so that air nozzles can be replaced by those unskilled in the assembly of such guns.

Another object of the invention is the provision of an improved unit construction of guns of this type, in which the gun is constructed of a plurality of units so that they are readily replaceable and can be replaced by one unskilled in the assembly of such guns, by merely ordering a new replacement unit from the factory.

Another object of the invention is the provision of an improved gun construction from which all frangible parts have been eliminated and in which all units of the construction have been made so sturdy and serviceable that they may be used for a long period of time without necessity for replacement or repair and so that there is no possibility of porcelain particles getting between the contacts of the switch.

Another object of the invention is the provision of an improved metal spray gun having improved means of controlling the operation of the gun, so that as soon as the gun is used for spraying there is an immediate increase in the heat supplied to the gun, which is necessary, due to the melting of metal in the spraying operation.

When the spraying operation begins, the continuous supply of mold metal to the gun requires a greater amount of heat, as the cold metal must not only be raised to the melting temperature, but the heat of fusion must be applied thereto,

and this additional supply of heat required for continuous operation of the gun under the best conditions is insured by the controlling devices included in the present construction.

Other objects and advantages of the invention will be apparent from the following description and the accompanying drawings, in which similar characters of reference indicate similar parts throughout the several views.

Referring to the five sheets of drawings accompanying this specification,

Fig. 1 is a side elevational view of a metal spray gun constructed according to the invention;

Fig. 2 is a front elevational view of the gun, shown in full size;

Fig. 3 is a top plan view of the gun;

Fig. 4 is a vertical sectional view, taken on a plane passing vertically through the center of the spray gun, showing the details of construction thereof;

Fig. 5 is a sectional view, taken on the plane of the line 55 of Fig. 4, looking in the direction of the arrows;

Fig. 6 is an enlarged sectional view, taken on the same plane as Fig. 4, but showing the thermostatic switch in section also;

Fig.7 is an. enlarged sectional view, taken on the plane of the line 1-1 of Fig. 4, looking in the direction of the arrows;

Fig. 8 is an enlarged sectional view, taken on the plane of the line 6-8 of Fig. 4, looking in Fig, 11 is a fragmentary sectional view, takenon the same plane as Fig. 4, showing the details of construction of the air control valve unit, and the valve locked in open position;

Fig. 12 isa fragmentary sectional view, taken on the plane of the line l2--|2 of Fig. 4, looking in the direction of the arrows, showing the trigger, obtained in the unlatched position;

Fig. 13 is a fragmentary sectional view, taken on the plane of the line i3--|3 of Fig. 11, showing the trigger, with the trigger shown in the latched position;

Fig. 14 is a fragmentary elevational view of the cable anchor, seen from the inside of the housing 22, and taken on the plane of the line "-44 of Fig. 4;

Fig. 15 is a fragmentary sectional view, similar to Fig. 4. showing a modified and preferred form of cable anchor, which may also be utilized with my metal spray gun;

Fig. 16 is a similar view with the cable anchor in section, on the same plane;

Fig. 17 is a view in-perspective of the stirrup used in the cable anchor;

Fig. 18 is a sectional view on the plane of the line l 3l8 of Fig. 16;

Fig. 19 is a fragmentarysectional view showing the mode of support of the gun on its handle unit;

Fig. 20 is a similar view of a modification.

Referring to Fig. 1. 20 indicates in its entirety a metal spray gun constructed according to the invention. The gun may consist of a plurality of separable units, such as, for example, the handle unit 2|, a rear housing unit 22, a front housing unit or metal melting unit 23, an insulating unit 24, and an air nozzle unit 25.

The handle unit 2| may consist of a cast metal member ,(Fig. 4) provided with a closed lower end wall26, handle side walls 21, and an upper entrigger control mechanism, and the upwardly extending flange 36 has a groove 4| in its rear wall for receiving a complementary projecting portion of the valve supporting body 42.

The air control mechanism may be constructed as a separate unit carried by the valve support-- At its forward end the valve supporting body 42 has an upward extension 50 for extending a conduit upward to meet the air nozzle unit 25. The body 42 is formed at its rear end with a threaded bore 5| for receiving a standard air conduit fitting 52, which is connected to the air hose 53. I

The air hose 53 is connected to a source of air under pressure, which is preferably at from 65 to '70 pounds per square inch pressure, butwhich may vary considerably, as the standard air supply which is used for filling tires may be used.

The threaded bore 5| communicates with a diagonally upwardly extending conduit 54, which communicates with the vertical, cylindrical bore 48. Conduit 54 Iscontinued on the opposite side of the vertical bore 48 by conduit 55, and communicates with an upwardly extending conduit casting 42.

/ bored from the right end of the casting and the largement 23. The handle walls may consist of the front and rear curved handle walls 29, 39 and the fiat and parallel side handle walls 3|,-32 integrally joined together to form a tubular member adapted to have a substantial fit in the hand.

At the lower end of the front curved wall 29 of the handle there is a forwardly projecting lug 33 which engages below thelowermost finger and serves to keep the handle from slipping upward in the hand.

The enlargement 28 comprises a backwardly and.upwardly extending curved wall 34 and a fiat bottom wall 35, both of which carry the upwardly extending boundary flange 36, providing a relatively shallow chamber 31 in the upper open end of the handle for receiving the valve mechanism. I i

The handle unit is provided with an aperture or slot 33 in the flange 35 and extending downwardly into the front handle wall 39 for receiving the trigger of the valve control mechanism. It is also provided with an aperture 39 (Fig. l) for projection of the latching button 40 of the conduit 55 from the top of the casting 42.

Conduit 56 communicates with a horizontal bore 51, which is adapted to receive the end of the air nozzle unit 25 and is bored from the left end of casting 42 (Fig. 4).

The metal tube 58 of the nozzle unit 25 has a close sliding fit in the bore 51 so that it effects a substantially air-tight joint between the tube 58 and the bore 51. The valve unit 49 may comprise a tubular brass member 59, having a relatively small bore 60 at its lower end. communicating with a larger bore H at the transverse bore 62.

There is a frusto-conical valve seat 63 at the lower end of the enlarged bore 6| and at the upper end of the tubular body 59 there is a threaded counterbore 54 for receiving the threaded plug 65, which closes the upper end of the valve body.

The valve 49 is, provided with a valve member in the bore 6|, comprising a substantially cylindrical valve member 65, having a frusto-conical seating surface 51 and a cylindrical stem 68 slidably mounted in the bore 60 and projecting therefrom.

A compression coil spring 69 engages the upper end of the valve member 65, and has its opposite end seated against the end of the plug 65. The

valve member 66 effects a substantial closure of the air bore 62, inasmuch as the body 55 is interposed between the ends of the bores 62 and has a substantial fit in its valve socket. The fit, however, is such as to permit a sliding movement of the valve member 63, and the valve member may be opened by means of a trigger 10, which acts on the stem 68 and lifts the valve body 65 until there is communication between the bores 52.

According to the present construction the elec-- tric heating element of the gun is controlled by means of a thermostatic switch, and energization of the'conductors leading to the thermostatic switch is controlled by merely plugging in an electric wall plug connected to the cable conductors, which are housed in the rubber covered cable II. The cast metal valve-supporting body 42 may support a sheet metal bracket I2, which carries the trigger mechanism. The bracket I2 has a horizontal attaching flange I3, which is secured by means of a screw bolt I4, passing through the flange and threaded into the body 42. It also has an aperture I5 for passing the valve stem 68, and it has a downwardly extending flat bod I6 for supporting the trigger mechanism.

The trigger mechanism is also preferably provided with means for latching the trigger with the valve in the open position, which may com- The body I2 has a pair of forwardly extending parallel sheet metal flanges H, which pivotaliy support the trigger I8 and have apertures I8 for passing the trigger pintle I9.

The trigger I8 may comprise a sheet metal member having a curved forward'yoke 88 and a pair of parallel side walls 8|, '82 (Fig. 1 and Fig. 4),. The side walls-8|, 82 have the pintle I9 riveted in them after the pintlehas been assembled with the bearing flanges TI. The body flange I6 of the bracket I2 may also support a curved guide member 83, comprising a flange which is a sliding fit between the side walls 8|, 82 of the trigger, but which is shorter than'the open space below the end of the trigger, so as to be spaced from the yoke I0, and permit the actuation of the trigger. The curved guide flange 83 is secured to a body flange 84, which is secured to the body flange "I8 by a threaded stud 85. I

The stud 85 is threaded into a bore in the body flange 84 and passes through a bore in the 1 body flange I8, and is locked in place by means of a nut 86. The length of the stud 85 is such that its end engages the opposite or rear curved wall 38 of the handle in order to prevent the bending of the bracket I2, and to hold the bracket in proper position.

The body flange 84 has its'upp'er end fitting between the bearing flanges 11 so that only one screw bolt 85 is necessary to secure these parts together.

The side flanges 8|, 82 of the trigger have a pair of rearward extensions 81, which havea pin 88 extended through them, and projecting laterally at each side, so that one end of each of the two springs 89 may be hooked over each end of the pin 88. The body flange I8 of bracket I2 has a pair of laterally extendinglugs 98 so that the opposite end of each of the two springs 89 may be hooked over a lug 98.

Thus, by means of the springs 89, the pin 88 and extensions 81 of the trigger are drawn downward, and the trigger I8 is urged outward to the position of Fig. 4. The pin 88 also extends through a valve-actuating bar 9|, comprising a small metal bar, having an aperture for the pin 88, and having its body slidably engaging the body flange I8 of the bracket 12.

The valve-actuating bar 9| is substantially rectangular in cross-section and of smaller cross-section at its upper end, the upper end being confined between the bracket [2 and the push button pin 92, which carries the push button 48.

The valve-actuating bar 9| is adapted to be slid upward by means of pin 88, when the trigger 18 is pulled back. In its upward movement the end of the bar 9| engages the stem 88 of the valve and opens the valve. The bar 9| is, however, urged downward by the two springs 89, which also urge the trigger I8 outward.

prise the pin 92. The bracket 12 is provided with a pair of rearwardly extending flanges 93, having apertures for slidably receiving the pin 92, which carries the push button 48 at one end. At its opposite end the pin 48 has a stop washer secured between a shoulder on thepin and the rivet end of the pin.

A coil spring 94 is compressed between the button 48, and one of the flanges 93, and surrounds the pin 92 (Fig. 12). Thus the push button is urged into the position of Fig. 12 by the spring 94, but after the trigger 18 has been pressed, the push button may be moved inward to the position of Fig. 13,

The trigger has an extension 95 on one of its side flanges 82, which reaches up into position to engage with the pin 92. The extension 95 has a stop surface 98 on its rear side so that when the push button 48 is pressed to the position of Fig. 13, after the trigger has been pressed,

' the stem 92 will engage the stop surface 98 and hold the trigger in that position.

The stem 92 is furthermore held in that position itself by means of the washer '91, which engages the outside of the flange 95, as in Fig. 13. Thus the trigger may be pulled and latched in the position of Fig. 13, that is, with the valve open, by means of the push button 48.

If, thereafter, the trigger is again pulled, its

flange will move out from under the washer 91, and the spring 94 will immediately snap the latch and pin 92, from the position of Fig. 13 to that of Fig. 12, so that the trigger is released by an auxiliary pull and subsequent release of the trigger.

Thus the air valve mechanism 69 may be latched in the closed position, if desired, or it may be left subject to control solely by means of the trigger I8,

The valve and trigger mechanism carried by the body 42 may be inserted in the upper, open end, or chamber 3'! of the handle unit 2|, as a unit; and may be secured therein by a plurality of screw bolts, such as, for example, the screw bolt I88, which extends through the forward wall 29 of the handle, and is threaded into the bracket I2 by means of the two screw bolts H, which pass through the lower flange 35 of the upper handle extension and are threaded into the body of the casting 42.

The unit construction of this trigger and valve mechanism is illustrated as shown in Fig. 11. The upper, open end of the handle may be closed by means of a metal plate I82, which substantially fits over the chamber and engages the outer wall 36thereof, and has a centrally located rectangular aperture I83 for passing the upwardly projecting valve parts, as shown in Fig.

trigger, the user of the gun may send to the fac-- tory for a valve and handle replacement unit, which can be immediately shipped and substituted in his spray gun with a minimum amount of effort, and with the assurance that the parts can be assembled very easily and will operate perfectly.

In some embodiments of the invention, as shown, for example, in the modification of Fig. 19, the plate I02 may be made of insulating material and secured to the handle by a plurality of screw bolts I04 passing through apertures in the plate and threaded into threaded bores in the bottom flange 35 of the handle chamber 31.

The handle is also provided with thickened walls at I05, at each of the four corners of the handle chamber 35, the-walls having through apertures I06 for receiving screw bolts I01, which secure the handle unit to the rest of the metal spray gun. The structure at one of the corners of the handle is shown in detail in Fig. 19, the heads of the bolts I01 being disposed in the bores I06, and the heads of the screw bolts I01 engaging the under side of the metal plate I02.

Referring to Fig. 20, this shows a modification in which the handle unit is provided with bores I09 slightly smaller than the heads of screw bolts I01, and with a counterbore IIO for receiving the heads of the screw bolts I01 at the top.

The insulating plate III, which may be made of the same material as the insulation 24, is provided with bores II2 for passing the screw bolts I01, and is secured to the handle unit 2| by a plurality of screw bolts I04, as previously described. In this case the bolts I01 will be retained in the handle assembly by means of the plate III, so that the handle may be removed with its bolts intact, and difficulty in assembly,

due to the bolts dropping out, is avoided.

plate I02 at each of the four corners of the handle unit, and the spacer members are preferably formed with radially extending fins II6. The spacer members comprise tubular metal members having a plurality of radially extending fins for radiating heat which is conducted to this part of the metal spraygun from the electric heating element.

Above the spacer elements,bolts I01 preferably support another heat radiating plate II1, which is provided with apertures for passing each of the bolts I01, and with a centrally located rectangular aperture IIO for passing the valve assembly 49 and upwardly extending lug 50.

The plate 1 is preferably constructed of metal, and is adapted also to radiate heat, and is spaced from both the rear housing 22 of the gun and the handle structure, so that air may pass between these parts, and such heat as is conducted to the parts may be dissipated.

Immediately above the plate II1 the bolts I01 support additional similar spacer members H9,

similar in structure to the spacers II5, for spacing the plate II1 from the rear housing member 22.

The rear housing member 22 may consist of a cast metal member, such as aluminum, which is open at the bottom and at the front end. It is provided with two side walls (Fig. 3) which are joined by a top wall I22 of substantially U shape, and by a rear wall I23, which may be substantially flat. i

The end I24 of the rear housing 22 is open, as is also the lower side' I25 (Fig. 1) The walls of the rear housing 22 are thickened adjacent the ends of each of the screw bolts I01, and provided with threaded bores for receiving the screw bolts At its upper side the rear housing 22 may be provided with a plurality of ventilation slots I26 for the purpose of permitting the air to pass through this housing from the open bottom I25,

up through the slots I26, in order that heat may be dissipated. The upper wall 22 curves gradually upward from the flat rear vall I23, and is provided at its forward end with a pair of sheet metal right angle brackets I21, I23, which are provided with a transverse aperture I20 adapted to be used to hang up the gun.

The angle brackets I21, I 28 have their vertical flanges welded together at I30, and ha e their horizontal flanges secured to the rear hous ing 22 by the screw bolts I3 I, which pass through apertures in the horizontal flanges, and are threaded into the metal body of housing member 22.

' The rear housing member 22 may serve as a junction box or a connection box for the electrical conductors, and for this purpose the rear wall I23 is provided with an aperture I32 for passing a rubber hose I33, which is a close fit on brass wire, which is clamped about the hose I 33 -so tightly that it forms a groove therein, and

causes the hose to clamp the rubber covered cable 1I. Thus the hose I33 is suitably anchored to the rubber'covered cable H by the ring I34, so that the gun may be liftedgby means of the hose, if desired, and the cable is caused to assume an easy bend where it emerges from the rear housing 22 inside the hose I33.

The ring I34 also serves as a shoulder for engaging outside of the wall I23 and determining the position of the hose I33 with respect to the housing 22.

The wire I 35 is similar in structure except that its two ends I36, I31 are bent radially outward and engage on both sides of the head of a screw bolt I38, which is threaded into a threaded bore from the inside of the housing 22 immediately adjacent the aperture I32. Radial portions I36, I31 of the wire ring I35 serve to prevent rotation of the hose I33 and conductor cable 1| in the housing bore I32.

The ring I35 also clamps the hose I33, forms connect the heating element of the gun with the ordinary lighting circuit. A third insulating cable I43 is utilized for. grounding the gun, and at the plug end of the cable 1I may b connected to the conduits which house the wires of the lighting system, which are, of course, grounded. Porcelain sleeves may surround conductors I40, I42,

The conductor I43is grounded on the housing I22 by means of being connected to a screw bolt I44, which is threaded into a threaded bore in the housing 22. The insulating unit 24 preferably comprises a block of electrical insulation which is also adapted to withstand heat impact without damage.

The insulating block 24 is substantially rectangular in cross-section and provided with rounded corners so that its outer surface I50 is flush with the outer surface of the housing member 22 and housing member'23.

The block 24 is provided with substantially fiat front and rear surfaces II, I52, except that these surfaces are preferably provided with a multiplicity of radially extending grooves I53 leading to a central flat recessed field I54, I55 on the back and the front for the purpose of permitting the egress of air from the interior of the housing.

The front side I5I of the block 24 is also provided with a substantially cylindrical bore I56 to provide space for the switch member, which has an axially projecting adjustment screw I 51.

The insulating block 24 is provided adjacent each side with a transverse bore I58, I59, for passing the screw bolts I60, which pass through bores IIiI, I62 in the front housing member 23 and are threaded into threaded bores I63, I64 in the rear housing member 22 (Fig. 8). Block 24 may consist of a heat treated composition comprising asbestos and a phenolic resin binder molded to shape.

Thus the insulating block and two housing members are secured together by two screw bolts I80, and the spray gun may be taken apart merely by removingthese bolts. block 24 is tightly clamped between the two housing members 22, 23, and it is adapted to withstand impacts to which either housing member may be subjected, without damage.

The front housing member 23 of the spray gun preferably comprises a member of cast aluminum or other metal of high heat conducting capacity, and the housing member is substantially rectangular in front elevation, but provided with rounded upper corners and with a convexly curved tip I14 tapers, being provided with an external frusto-conical surface I16, and it is provided with an internal frusto-conical recess I11, terminating in a relatively small cylindrical bore I18, which is the nozzle aperture. The nozzle I14 may also be threaded into the bore I13.

The frusto-conical bore I11 provides a continuation of the frusto-conical metal well I1.I. The metal well "I is centrally located with regard to the substantial body of metal, of which the front housing member 23 is constructed, and embedded in the metal of the member 23 is a helically coiled electric heating element I80 (Fig. 4).

This heating element I80 is of the type having an outer metal jacket I 8| of copper or brass, or other suitable metal, and having an inner resistance wire I82, which is helically coiled inside the jacket I8I, the turns of wire being insulated from each other and from the jacket I8I by a suitable refractory insulating composition, initially in the form of a powder.

The helical heating element I80 has a pair of rearwardly projecting straight extensions I83, I 84 (Fig. 4), which are necessary to extend the connections to the rear part of the spray gun, and

I for the reason that the end portions of the heat- The insulating lower surface I655; The rear surface I56 of the front housing member 23 is substantially flat and fits against the insulating block 24 with the outer surface of the front housing member 23 flush with the outer surface of the block 24.

At the front lower corner of the front housing member 23 it is preferably provided with an angular recess I66 defined by the side walls I51, I68, rear wall I69, and top wall I10. The recess I66 is for the purpose of housing the ends of the metal nozzle and air nozzle and preventing damage to these nozzles, which it accomplishes, since the nozzles do not project beyond the boundaries of the recess I86.

The front housing member 23 is preferably formed with a metal well comprising a downwardly tapering frusto-conical bore I1 I, the upper end of which is substantially larger than the diameter of the solder sticks or wires I12 of the metal to be melted.

The lower end of the casting is preferably smaller than the diameter of the solder sticks,

and it communicates with a larger co'unterbore' I13, which is adapted to receive the metal nozzletip I14. The metal nozzle tip I14 is constructed of high speed steel adapted to withstand the high temperatures to which it is subjected, and it has an external cylindrical surface I15 which is a tight frictional lit in the bore I13. The nozzle ing element are not readily bendable.

The end portions of the heating element have metal connectors I90 extending therefrom for engagement with the wires of the circuit, and the connectors I90 are insulated from the metal jacket I8I by layers of mica I 9| or other suitable insulation.

In other embodiments of the invention the insulating block 24 may support electric socket connectors I90 attached to the conductors I40 and I42, and the heating element I may be so arranged that its end connectors slidably engage in the socket connectors carried by the insulating block 24.

The heating element I80 may be purchased in straight form on the open market, and preliminary to its incorporation in the metal body 23 it is coiled in helical form on a mandrel with its coils spaced from each other and provided with the straight extensions I83, I84. The heating element is held in a suitable jig, and the metal body 23 is cast about the heating element I80 so that the heating element is embedded in the body 23 surrounding the metal well "I and having the extensions I83, I84 projecting therefrom.

The insulating block 24 has suitable apertures I92, I93 for passing the extensions I83, I84. At its lower end the metal body 23 is provided with a horizontal bore I94 for supporting the air nozzle 25 and having an enlarged counterbore I95, leaving a. clearance about the major portion of the air nozzle 25.

This clearance prevents direct transmission of heat from the body 23 to the air nozzle 25 and over the length of the counterbore I95.

The air nozzle 25 is preferably constructed as a unit, and provided with means for detachably mounting it in the metal spray gun in proper position with respect to the metal nozzle I14. so that users of the guns cannot adjust the air nozzle and get it out of its proper position.

It is preferable that this position be determined at the factory.

The air nozzle unit 25 comprises a metal tube 58, which extends from the bore 51; forward through the insulating block 24, counterbore I95, and bore I94. At its left end (Fig. v4) adjacent the metal nozzle I14, the air nozzle unit 25 is provided with an arcuate aperture 200, the shape of which is best shown in Fig. 2. The arcuate air to embrace the space at the end of the metal nozzle 1'14, the two nozzles being arranged to converge toward the same point, except that the air nozzle directs an arcuate stream of air against the metal emerging from the metal nozzle. The metal is thereby atomized and sprayed in a horizontal direction I In order to predetermine the location of the air nozzle unit 25 with respect to the metal nozzle, the tube 58 is preferably fixedlysecured to a rectangular metal block 201, which is. adaptedto fit in a complementary socket or slot 202 in the metal body 23.

The block 201 is confined in the slot 202 by means of the insulating block 24, which engages on the rear side of the block 201,

The vertical walls of the slot 200 determine the rotative position of the tube 58 and nozzle 200 with respect to the metal nozzle 114. The positionof the block 201 on the tube 58 also serves,

to determine the longitudinal adjustment of the air nozzle unit with respect to the metal nozzle.

The air nozzle unit 25 is'very conveniently inserted as a unit or removed as a unit, and replacements may be kept on hand so that it is unnecessary to make any adjustments, and a gun which needs repair in this respect canbe repaired very quickly by providing it with a new air nozzle unit.

The metal body 23 is provided with a bore 203, which communicates with the counterbore 195. The bore 203 extends beyond the counterbore 195 to the bottom of the metal member 23, for the reason that the hole is drilled-through from the bottom to a thermostat chamber 204.

The air tube 58 is provided with relatively small pin hole 205 for the purpose of permitting the leakage of air under pressure from the air tube 58 into the thermostat chamber 24, where the cooling air is directed against the thermostat for a purpose further to be described.

This takes place, of course, only when the valve member 66 is moved to open position, and,

in the present metal spray gun the air valve is completely closed when the trigger is in the position of Fig. 4, as distinguished from some of the The supporting base 211 has a plurality of cylindrical metal posts 215 fixedly secured therein by means of an annular shoulder 216, a reduced cylindrical portion 211, and a riveted portion 218 secured in a bore in the body 212.

The posts 215 may be four in number and equally spaced from each other, and provided with annular slots 219. The annular slots 219 are adapted to receive the edge of a bi-metallic thermostatic member .220 of the type having a predetermined concavity formed therein, so that when the bi-metallic element 220 is heated to a predetermined temperature, the expansion of one of its metals is resisted until a predetermined stress is set up, when the bi-metallic element 220 snaps from a downward concavity to an upward concavity in Fig. 8.

The clearance between. the slots 219 and the bi-metallic member 220 permits this without placing undue strain upon'the bi-metallic element. The bi-metallic element 220- is fixedly secured at its center to a switch-actuating post 221, which has an annular shoulder 222 and a washer 223, and its end portion is riveted over at 225, which has a threaded bore engaging the threads of post 221. Thecross-head 225 may be locked in position by a lock nut 226, and further secured in place by fusing material 221 about the end of the post 221 and nut 226.

devices of the'prior art, in which constant leakage of air was contemplated for the purpose of cooling the gun.

The air aperture 205 is so located that it may act as a nozzle, directing air through the enlarged aperture 203 against the thermostat 220 of a thermostat switch.

The air tube 58 is provided with an aperture 265, which is downwardly directed when the air nozzle is in proper position, and which registers with the bore 56. The close fit of the air nozzle 58 in the bore 51 effectively closes the upper end of the bore 56 and places the air tube 58 in airtight communication with the bores 55 and 56,

leading to the suppl of air under pressure.

, The metal spray gun is provided with a thermostatic switch for the purpose of controlling the energization of the electric heating'element 180, and the thermostatic switch structure is best shown in Figs. 6, 7, and 8. v

The thermostatic switch comprises a unit 210, whichispreierably supported upon a sheet metal base 211. 'I-hebase 211 may have a flat sheet metal body 212 and a pair of side flanges213, 214 at rightan'gles to the body 212 (Fig. 8). The base 212 has a frictional fit in the socket 204 of the housing member 23.

The cross-head 225 is shown in Fig. '7, and it may comprise a circular metal member having a pair of apertures 230, 231 for receiving the guide posts 232, 233. These guide posts are fixedly secured to the base 212 by riveted'formations similar in character to the mode of securing the posts 215.

The cross-head 225 may also support a pair of contact members, comprisingthe discs 235,

236. The discs 235, 236 are preferably insulated from the cross-head 225 by the following means. Each contact 235 or236 is secured by means of a rivet 231, which passes through the contact and through a mica washer 238, second mica. washer 239, and metal washer 240. The crosshead 225 has a clearance at 241 about the rivet 231 so that the rivet is electrically insulated from the cross-head 225.

The disc 242 has a lower convex surface 242' so that the contact 236 has a limited universal movement and tends to engage tw-o fixed contacts equally. The fixed contacts are shown in Fig. '7 and indicated at 243-246.

The base 211 of the switch may carry a plurality of connector posts 241-250. Each connector post is again insulated from the base by means of mica in the same manner as described with respect to the rivet 231, having mica above and below the metal body 212 and a clearance between the aperture in the metal body 212 and a centrally located rivet 251. Each of these posts is similar in structure, and therefore only on need be described.

The metal rivet 251 is surrounded in the posts 248 and 249 by a tubular spacer 252, and the posts 248, 249 are connected by a metal connec-v tor band 253. The posts 241-250 may, however,

be solid metal posts secured in the same manner to the base 21 1 above the mica plate'254 (Fig; 8)

Each of the posts 241-260 is connected to the fixed contacts 243-246, respectively.

The fixed contacts may comprise sheet metal strips of suitable metal, arranged so that the pairs of contacts are adapted to be engaged by the movable contacts 235, 236, which bridge the fixed contacts, as shown by the over-lapping portions in Fig. '7. The posts 241 and 250 are provided with connector screws 255, located in threaded bores in the posts and adapted to clamp wires to the posts.

The connections are readily seen from Fig. 4. The ground connection of the conductor I43 of the cable has already been described. The conductor 440 is connected to'a conductor 26!], which is connected to the binding post 250 of the thermostatic switch. Thence the circuit may be traced through the contacts 245, bridging the contact 235, fixed contact 246, binding post 249, strip conductor 253, binding post 248, fixed contact 244, removable contact 236, fixed contact .243, binding post 241, conductor 26l, heating b contacts 235, 236.

Referring to Fig. 15, this is a fragmentary sectional view similar to Fig. 4, but showing the preferred form of cable anchor which has been utilized in later commercial embodiments of the invention.

In this case the bore 210 receives a conventional junction box fitting 2" of the type having a threaded shank 212 which passes through the bore 210, and secured by means of a nut 213.

The fitting 21! has a clamping member 214 actuated by a screw bolt 215 for clamping the rubber hose and forcing it into tight engagement with the rubber covered cable contained therein. Thus the hose and cable are both anchored to the spray gun by means of the fitting 2'.

The operation of the metal spray gun is as follows: The conductor cable H is provided with a conventional plug, which may be plugged in at any lighting circuit socket, and controlled with other switches, if desired. The plugging in.of the gun energizes the gun and, as the thermostatic switch is in closed position when the gun is cool, the circuit is closed through the heating element.

This causes the gun to heat up, and heat is transmitted directly from the heating element to the metal body 23, which has the heating element embedded within it, and heat is most effectively. applied to the metal I12, to be melted in the metal well IN.

The heating of the gun continues until it reaches a predetermined temperature, at which the thermostatic switch is actuated to open the circuit. During this time the gun may or may not have its hose connected to the air under pressure, but the air is shut off at the valve 66 during the preliminary heating up of the gun, and air is only turned on when the gun is in use.

In the preliminary heating up of the gun, the heating element isturned off at, for example,

approximately 750 degrees F.

The gun is now sufliciently heated so that it can be used at any time by putting the meltable solder in the well and turning on the air to eflect a spraying action. It is at a suitable temperature for the melting of the solder, but not at the preferred temperature for continuous operation.

when the gun is permitted to cool with the air turned oif, it is found that the switch is again closed at approximately 600 degrees F. Since the air is turned on by means of the actuation of the trigger 10, air under pressure issues from the air nozzle 200 and from the bleeder nozzle 205.

The cooling efiect of the air from the nozzle 205 on the thermostat causes it to move the switch to closed position at once, and an immediate supply of additional heat is provided for supplying the heat of fusion of the meltable metal and keeping the gun at the desired temperature for continuous operation.

When the current is turned on and the air is turned on, the gun is maintained at a temperature of from substantially 800 to 850 degrees F. As soon as the air is turned off and the spraying of metal ceases, the air ceases to discharge against the thermostat, and the thermostat is soon heated by the heat from the gun and heating element to a point where it shuts off the current, but maintains the gun at a predetermined preliminary temperature.

The operation of the gun from the point of view of spraying is substantially the same as described in my prior applications. The meltable metal issues from the metal nozzle H4, and is engaged and atomized by the air under pressure issuing from the arcuate air nozzle 200, and the metal is sprayed against an adjacent surface.

The present gun is so sturdy that it can be subjected to hammering, which frequently occurs when the guns are handled by unskilled operators.

ticles of porcelain which would otherwise get in between the switch contacts and prevent the energization of thegun and the insulating block 24 isof such material that it cannot be broken by the hard usage to which these guns are put.

The thermostatic-switch is adapted to maintain the gun at one temperature in readiness for use, and at a second operating temperature during its use. By means of the discharge of cooling air upon the thermostatic switch the thermostatic switch is caused to be closed at once when the air is turned on and the spraying operation begun, and an additional supply of heat is pro-' vided for the heat of fusion of the metal to be melted.

The gun is maintained at a suitable temperature. during operation, for continuous operation, so that there will be no interruption in the spraying of metal and no chance for metal to oxidize before additional metal is applied to it.

The present gun is more sturdy and may be,

more economically manufactured and provided with better heat insulation than the devica of the prior art,and the air nozzle and other units ay more conveniently be replaced, by users, so that the operators may be supplied with spare parts, and do not have to send the spray guns back to the factory for repair.

'The units of the gun are so arranged that the spare parts automatically fit into proper position, and no adjustment is necessary.

-While I have illustrated a preferred embodiment of my invention, many modifications may be made without departing from the spirit of the invention, and I do not wish to be limited to the precise details of construction set forth, but desire to avail myself of all changes within the scope of the appended claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent 01 the United States, is:

1. In a spray gun for metal having a nozzle for metal, an air nozzle unit comprising a metal tube having means at oneend for connection to an air conduit, and having an air nozzle disposed at the opposite end, said air nozzle having a narrow, arcuate aperture, said tube having intermediate its ends, a metal alignment block located in predetermined longitudinal position on said tube for determining the spacing of said nozzle from said metal nozzle, and said block having shoulders for engaging complementary shoulders on said gun for determining the rotative position of said nozzle and tube with respect transverse bore registering with said first-mentioned conduit, a valve member in said valve body for interrupting communication 01 said conduit by closure of said bore in said valve body,

saidvalve body having a downwardly projecting i connection to an air conduit, and having an air nozzle disposed at the opposite end, said air nozzle having a narrow, arcuate aperture, said tube having intermediate its ends, a metal alignment block located in predetermined longitudinal position on said tube for determining the spacing of said nozzle from said metal nozzle, and said block having shoulders for engaging complementary shoulders on said gun for determining the rotative position of said nozzle and tube with respect to said metal nozzle.

FRANS O. ALBERTSON.

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