US2676843A

US2676843A - Spray gun

Info

Publication number: US2676843A
Application number: US307355A
Authority: US
Inventors: Curtis H Parsons; Rudolph J Perme
Original assignee: Fansteel Inc
Current assignee: Fansteel Inc
Priority date: 1952-08-30
Filing date: 1952-08-30
Publication date: 1954-04-27
Anticipated expiration: 1971-04-27

Description

April 27, 1954 c. H. PARSONS ErAL SPRAY GUN Filed Aug. 30, 1952 iihmi all Patented Apr. 27, 1954 UNITED STATES OFFICE SPRAY GUN New York Application August 30, 1952, Serial No. 307,355

11 Claims. 1

This invention relates to a spray gun, and particularly to a spray gun for handling materials at elevated temperatures. The spray gun to be hereinafter described is particularly adapted for handling low melting metals or alloys in molten form, plastics at elevated temperatures, or any viscous material to be thinned by heating.

Spray guns for handling molten metal are particularly susceptible to freezing of the metal at the nozzle, also to burning of the metal in the gun body due to excessive oxidation of the metal and consequent formation of scum or dross on the surface.

Our new spray gun is characterized by structural simplicity which makes the same easy to manufacture, assemble, disassemble and clean. Furthermore, our newl spray gun has features therein which make for trouble-free and satisfactory operation for long periods of time. Other and additional advantages will be pointed out in connection with the detailed description of the new spray gun. An exemplary embodiment of one form of new spray gun embodying our invention will now be described in connection with the drawings, it being understood that variations in construction may be made without department from the spirit of the invention.

Referring therefore to the drawings:

Figure l is a top plan view of a spray gun embodying our invention;

Figure 2 is a sectional elevation along line 2-2 of Figure l.

The spray gun comprises handle grip I l rigidly attached to gun body generally indicated by numeral i l, from the body of which depends nozzle assembly i3 and to the side of which there is attached junction box l5. Handle l may have any desired shape and is here shown as being of the pistol grip type.

Handle lo carries pivot pin l1 upon which is carried trigger or control handle I8. The movement of trigger handle i8 around pivot l1 is limited by stop screw i9 and lock-nut 25 mounted in part 2l of the handle extending toward the gun body. Between handle portion 2l and the sun body generally indicated by numeral ll is housing 23. The bottom of housing 23 carries an. air valve having body 24 provided with a suitable inlet fitting 25 for air. Air valve 24 may be of any desired construction and as here shown has valve rod 26 cooperating with spring-pressed valve member 2l. Valve member 2l normally rests against valve seat 28 and may be moved to open position by actuation of valve rod 25. Valve rod 26 is actuated by plunger 30 which slides in ing rings to prevent leakage of air. Plunger 3f!` extends above the top of valve body 24 and is actuated by nger 33 of vertically sldable rod 34 disposed in housing 25. Tip position 35 of the trigger cooperates with finger 33 for controlling the valve. The air valve has outlet 3l connected by screw ttings 33 and pipe 39 to nozzle assembly I3.

Referring now to gun body il, this comprises magazine or tank 40 of suitable refractory metal or material. For many purposes, tank 40 may be of stainless steel. Other metals or nonmetallic materials, such as glass, porcelain or ceramic may be used. Tank 40 may have any desired shape and as shown here has straight sides 4I and 42 with

rounded sides

43 and 44. The bottom of the tank is stepped and will be described in detail later.

Within tank 4B is electric heating element 46 having coils extending to the bottom of the tank. Electric heater 46 is metal clad and may be any one of a number of heaters well known on the market and used in electric stoves and other devices. Generally, such heating elements consist of resistance wire, such as Nichrome, buried in solidied insulation material and the whole surrounded by metal conduit or pipe. The heating element should be capable of withstanding both the temperature and any corrosive or alloying action of the material heated within the tank. Electric heating element 45 has the two end portions thereof extending into junction box l5 for connection to suitable electric receptacles.

Tank 40 has bottom portion 49 adjacent rounded side 43. Bottom portion 49 is provided with fittings 5|] and 5| dening chamber 52 within which is disposed thermocouple 53. Thermocouple 53 is inside of hollow tting 5l near the bottom of the tank and will thus be responsive to the temperature of the heated or molten material in the tank. Thermocouple 53 is connected by cable 54 to suitable switch control means for maintaining a desired constant temperature within the tank. Inasmuch as such thermostatically controlled systems are well known, no description thereof is deemed necessary.

Bolted to opposite straight portions 4I and 42 of the tank is baffle plate 56 extending into tank 40 down 'close to the bottom thereof. Rigidly bolted to baille plate 56, as by a clamp, is thermocouple 5l' connected by cable 58 to an alarm, such as a gong. Thermocouple 51 extends for a substantial desired distance into tank 40 and is adapted to actuate an alarm in the event that the temperature surrounding the therrnocouple falls to a lower value than normal during operating conditions. This will occur when the level of the material, such as metal, becomes too low in the tank. Thermocouple 5l therefore will control a low level alarm system. In addition, the low level alarm will function as a supervisory alarm for indicating whether the entire tank heating system is operating.

Bolted between baffle plate 58 and housing 23 is supporting block 8i! of suitable metal, such as iron or stainless steel. Block 88 carries pivot pin iii upon which is mounted rocker arm 62. Rocker arm 82 has finger 83 extending into housing 23 and disposed within slot 54 of vertically movable rod 3d. Rocker arm B2 has actuating end 58 pivotally secured at 61 to tubular push rod 58. Tubular push rod 58 works in well 18 in support block El) and the tubular push rod is biased downwardly by coil spring 1l extending between the bottom of the well and anchor block 12 within the push rod.

Tubular push rod 58 extends into the tank and should therefore be made of material, such as stainless steel, to withstand the temperature as well as any corrosive effects of the material within the tank. Tubular push rod 88 has the bottom part thereof closed by shouldered plug 14 rigidly attached thereto as by a press iit or by welding or the like. shouldered plug 'i4 has axial channel 15 therethrough, the upper portion of the channel being threaded and the lower portion of the channel being smooth and reduced in dimension. The threaded upper portion of channel 15 accommodates threaded head 15 of needle valve 18. Threaded head 18 may be adjusted to any desired position in plug 1li after which stop screw 8U, extending laterally of the plug, may be tightened to lock the threaded needle valve head into position.

The bottom of tank 40 bounded by curved side 44 and the right hand parts of straight sides di and 42, as seen from the top in Figure 1, is formed as a downwardly extending circular flange 8| having the outside thereof threaded. As is clearly shown in Figure 2, flange il extends down below tank bottom 49 at the left thereof. The entire nozzle assembly I3 is bolted to the bottom of the tank by shouldered ring nut 82.

The nozzle assembly i3 includes generally conical cup member 83 having an outwardly extending iiange bearing against the bottom of flange 8| of the tank and engaged by the shoulder of ring 82 and pressed firmly against the tank. flange. Conical cup 83 of the nozzle assembly is hollow and at the bottom carries inner and

outer sleeves

34 and 85. Sleeve 84 has the bottom end counterbored and threaded to receive nozzle tip 86. Conical cup 85 and

sleeves

84 and 85 are formed of metal, such as stainless steel, which will withstand the temperature of the molten or hot material in the gun tank. Cup 83 and sleeve 85 have jacket 81 intimately and permanently joined thereto. Jacket 81 is of metal and may be cast on cup 83 and sleeve 85. For many applications, jacket 81 may be of aluminum. However, it may be of a higher meltting metal or alloy, such as copper or brass, for example, if that is necessary.

Embedded within jacket 81 is electric heating element 88 generally of the same construction as heating element 45 for the tank. Heating element 88 is preferably disposed on the inside portion of the jacket and close to outer Sleeve 85. Transversely through the jacket is 'fitting @dior receiving the end of air pipe 39. Fitting 88 provides an air channel through the jacket and registers with an opening in outer sleeve 85. Between outer sleeve and inner sleeve 84 is annular channel 9|, through which air passes to the nozzle tip 8,5.

Jacket 81 has chamber 93 near the bottom thereof in which is thermocouple 94 maintained therein by fitting 95. The thermocouple is connected by cable 96 to a suitable switching sys tem for controlling heater 88 to maintain the nozzle assembly at a desired temperature.

Needle valve 18 has a pointed tip cooperating with the needle valve seat in nozzle tip 85. The outside of the nozzle tip is protected by cap 98 carried by ring nut 99 engaging the externally threaded end of nozzle tip 88. The construction of the needle valve and various sleeves and seats are conventional. The nozzle tip has a number of air channels |88 registering with annuiar air channel 8l.

The entire nozzle assembly including the jacketing may be quickly removed from the gun proper by disconnecting air pipe 39 from iitting @il and loosening ring nut 82. It is clear that the needle valve itself may be easily adjusted or replaced. Nozzle tip 86 may be changed to vary the air or needle valve discharge openings and thus provide for different gun operation or accommodate different materials to be sprayed.

To operate the gun, a quantity of material such as a low melting metal or alloy, such as lead, for example, or tin or any other desired material, may be dropped into tank 40. The heating elements within the tank will melt the material and maintain the same in molten condition. Baiiie plate 56 will prevent undesired dross or scum from entering the Well of the tank from which material flows to the needle valve. As a rule, any metal or material to be melted or heated will be deposited in the tank to the left of the baille plate 58 as seen in Figure 1 or Figure 2. Preferably, the surface of the molten or hot material is covered with a layer of inert liquid, such as a high boiling oil or some noninflammable liquid which will protect the surface of the metal being melted, or protect the surface of the material being heated, from undesired interaction with atmosphere.

Assuming that the gun is properly loaded and is ready for use, trigger I8 is rocked on pivot I1. This causes member 34 to be moved downwardly, opening the air valve and raising the needle from its seat.

The large mass of material forming nozzle assembly I3 provides a substantial thermal lag and insures proper heating of the air, as well as a desired temperature of the molten material around the needle valve. Freezing of the needle valve is rendered impossible. In practice, nozzle tip 85 may be of copper or brass or other metal having excellent heat conductivity. The threaded part of the nozzle tip extending inwardly of inner sleeve 84 insures good heat transfer to the nozzle tip and thus insures the maintenance of desired temperature conditions at the needle valve seat. If desired, jacket 31 may extend down around the nozzle tip to insure a more intimate connection between the body of the nozzle assembly and the nozzle tip itself.

In order to conserve heat, the outside of the tank may be covered with suitable heat insulation |03 of material like asbestos. It is also possible to cover the nozzle assembly with a heat insulation. Air supplied to the gun may be preheated.

Instead of loading the gun tank by dropping material therein, it is possible to have a central supply tank for a number of guns. Each gun may be connected to the central supply tank by hose having means to heat the hose to prevent chilling. The central supply tank would have heating means, thermostatic control, and low level alarm as desired. With such a central tank, each gun could have the molten or hot material fed directly to the needle valve and the individual gun tank, tank heater, low level alarm and tank thermostat could be eliminated.

We claim:

l. A spray gun for handling material to be maintained at an elevated temperature prior to spraying, said gun comprising a body including a tank for retaining a quantity of material to be sprayed, electric heating means disposed in said tank for maintaining said material at an elevated temperature, a nozzle assembly carried by said body, said nozzle assembly including an elongated needle valve member and needle valve sleeve having an end channeled to provide a seat and discharge opening for said spray material, an electric heater surrounding said needle valve sleeve and a massive metal jacket around said heating means, said jacket having sufficient mass to endow the nozzle assembly with substantial thermal lag, thermostatic means disposed in said jacket for controlling the heating element to maintain the nozzle assembly at a substantially constant elevated temperature, an air supply including a discharge opening adjacent the discharge opening of the spraying material, said air supply also including an air valve and manual means for operating simultaneously both the air valve and needle valve.

2. The spray gun according to claim 1 wherein said air supply includes an inlet through the nozzle jacket and air channels within the nozzle assembly providing air paths through the nozzle assembly.

3. The spray gun according to claim 1 wherein said nozzle assembly includes a nozzle tip having the valve seat for the needle valve member, said nozzle tip being removable from the nozzle assembly.

4. The spray gun according to claim 1 wherein said jacket is of cast aluminum.

5. A spray gun for handling material to be maintained at an elevated temperature prior to spraying, said gun comprising a body including a tank for the spraying material, an electric heating element within said tank, said tank having a two level bottom, a nozzle assembly detachably secured to the lower tank level and forming the closure therefor, said nozzle assembly including a cup-shaped member having a depending sleeve, an elongated needle valve member disposed in said sleeve, an actuating member carrying said needle valve member and extending upwardly through the tank to the top thereof, said nozzle assembly including an electric heating element wound around said sleeve and a massive cast metal jacket around said heating element and around the outside of said cup-shaped member, thermostat means carried by said jacket for controlling the nozzle assembly temperature, a nozzle tip detachably secured to the bottom free end of said nozzle assembly sleeve, said nozzle tip having a channel therethrough with a needle valve seat for cooperation with said needle valve member, means providing air passages through said nozzle assembly and terminating adjacent the discharge region kof said nozzle tip, an air supply coupled to said nozzle assembly air passage means, said air supply including a manually controlled air valve, and manual means for simultaneously opening said air valve and moving said actuating member carrying the elongated needle valve to open the needle valve.

6. The spray gun according to claim 5 wherein said tank is provided with a vertically disposed baffle extending for a substantial distance into the tank and dividing the same into two compartments, said baiile having the lowest part thereof terminating at a distance above the elevated tank bottom.

'7. The spray gun according to claim 5 wherein the tank is provided with a vertically disposed baie dividing the same into two compartments, the one compartment having the bottom formed by said nozzle assembly, the other compartment having a, thermostatic means extending upwardly from the bottom for controlling the tank heater.

8. The spray gun according to claim 5 wherein said tank is provided with a vertically disposed baiiie extending short of the bottom but dividing the tank generally into two compartments, one compartment having the bottom formed by the nozzle assembly, and thermostatic means carried by said baffle and extending for a substantial distance into the tank, said last-named thermostatic means being adapted to function as part of a low level spraying material alarm.

9. A spray gun for handling material to be maintained at an elevated temperature prior to spraying, said gun comprising a body including a tank for storing a supply of spray material, electric heating means for said tank for maintaining said spray material at a desired elevated temperature, a nozzle assembly carried by said body and including an elongated needle valve member and sleeve surrounding said elongated needle valve member, said sleeve having a channeled portion providing a seat and discharge opening for said needle valve member, said needle valve sleeve being supplied by spraying material from the tank, an air inlet for said nozzle assembly, an air supply for said inlet, said air supply including an air valve carried by said gun body, manual means for simultaneously opening said air valve and said needle valve, electric heating means for said nozzle assembly surrounding said needle valve sleeve for maintaining said nozzle assembly and needle valve at an elevated temperature, said tank having a baflie plate dividing same into two compartments, said baille plate being vertical in the normal gun position with said compartments being in side by side relation and being joined near the tank bottom, said needle valve member and sleeve extending from the bottom of one compartment and the other compartment being adapted to receive fresh material for spraying.

10. A spray gun for handling material to be maintained at an elevated temperature prior to spraying, said gun comprising a body including a tank for storing a supply of spray material, electric heating means for said tank for maintaining said spray material at a desired elevated temperature, a nozzle assembly carried by said body and including an elongated needle valve member and sleeve surrounding said elongated needle valve member, said sleeve having a channeled portion providing a seat and discharge opening for said needle valve member, said needle valve sleeve being supplied by spraying material from the tank, an air inlet for said nozzle assembly, an air supply for said inlet, said air supply including an air valve carried by said gun body, manual means for simultaneously opening said air valve and said needle valve, electric heating means for said nozzle assembly surrounding said needle valve sleeve for maintaining said nozzle assembly and needle valve at an elevated temperature, and thermostatic means disposed in said tanks at a predetermined depth, said thermostatic means being adapted to function in connection with an alarm system for indicating a loW level of spraying material.

11. A spray gun for handling material to be maintained at an elevated temperature prior to spraying, said gun comprising a body including a tank for storing a supply of spray material, electric heating means for said tank for maintaining said spray material at a desired elevated temperature, a nozzle assembly carried by said body and including an elongated needle valve member and sleeve surrounding said elongated needle valve member, said sleeve having a chan neled portion providing a seat and discharge opening for said needle valve member, said needle valve sleeve being supplied by spraying material from the tank, an air inlet for said nozzle assembly, an air supply for said inlet, said air supply including an air valve carried by said gun body, manual means for simultaneously opening said air valve and said needle valve, electric heating means for said nozzle assembly surrounding said needle valve sleeve for main taining said nozzle assembly and needle valve at an elevated temperature, said tank having a vertically disposed baille plate in the normal gun position to divide the tank into two compartments disposed side by side, said compartments being connected at the bottom of the tank below said baie plate and thermostatio means carried by said baille plate, said thermostatic means ex tending for a predetermined depth into the tank and being adapted to cooperate with an alarm system for controlling the same to indicate a lovv level of spraying material.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 2,058,971 Foi-ton Oct. 27, 2,276,232 Gilbert Mar. l0, i942 2,434,911 Denyssen Jan. 27, llle 2,5`5l,078 Wing May l., i951 FOREIGN PATENTS Number Country Date 66,337 Norway Mar. 2li, 1942