US2598294A - Spray gun - Google Patents

Description

May 27 1952 D. J. PEI-:Ps 2,598,294

SPRAY GUN Filed March 22, 1950 3 Sheets-Sheet l INVENTOR DONALD J. PEEPs BY Lof @om ATTORNEY May 27, 1952 D. J. PEEPs 2,598,294

SPRAY GUN Filed March 22, 1950 3 Sheets-Sheet 2 "ll l., m 4 7 I. I

3.7/ ii, 158-/M 59 INVENTOR DONALD J. PE EPs BY @PQM ATTORN EY May 27, 1952 D. J. PEEPS 2,598,294

SPRAY GUN Filed March 22, 195o 3 sheets-sheet, :5

INVENTOR DONALD J. PEEPS BY WGW ATTORNEY Patented May 27, 1952 parte stares TENT FFICE SPRAY GUN Donald J. Peeps, Toledo, Ohio, assignor to The De Vilbiss Company, Toledo, Ohio, a corpora tion of Ghio.

l Claims. l

This invention relates to an automatic spray gun using air for an atomizing medium and for motivating a piston actuatingly associated with the needle valve controlling the discharge of spray material.

It relates particularly to such a spray gun designed to receive from a single supply hose atomization air and piston motivating air.

In such a spray gun the spraying operation is started and stopped by the opening and closing of a valve in the single air supply line. This control arrangement seems about as simplified as possible; however, a serious dimculty which the subject invention is designed to overcome has always been encountered with such guns in the past.

To terminate the spraying action of the gun the valve in the air supply line is closed. The air between the valve and the gun continues to Iiow through` the nozzle until the air pressure is lowered to a point where the pistonV spring moves the piston forwardly andthe material discharge Valve associated with it to closed or non-operation position. Until the material valve is closed, atomizing air at a progressively lower pressure flows to the nozzle to atomize material still being discharged from the nozzle at the regular rate. The reduced atomizing pressure at the final stage frequently is insuicient to properly atomize the material and the latter is then deposited in the form of rough spray or spatter seriously impairing the quality of the coating. Should the pistonv be inclined-.to stick or move sluggishly such an objectionable condition is intensified.

With single hose automatic guns poor atomization may also be associated with the start of each spraying action. This objectionable condition is derived from the fact that the air piston opens the material discharge valve before the air reaching the gun has attained full atomizing pressure.V

The primary object of this invention is to valve in the air line isshut off, immediately vents the air from the piston cylinder as soon as theair pressure is lowered to a point threatening proper atomization.

Otherobjects and purposes of the invention will become apparent upon a reading of the following specication. considered with the accompanying drawing. in which:

Figure 1 is a side elevational View of. a spray gun embodying'my invention; l

Figure 2 is a front elevational View of the spray gun;

Figure 3 is a rear 'elevational View thereof;

Figure 4 is a vertical section of the spray headv detached from the main body member of the 81111;

Figure 5 is a verticalisection of the body member without the spray head; in order to show the combination check and relief Valve and its communicating passages the lower rearward portion of this section is along a plane inclinedA laterally. to the left of Figure 3 as indicated by the line 5 5of this figure;

Figure 6 is a vertical section of the connector assembly for holding the spray head and body together. This includes an air valve for adjusting the air flow to the horn ports on the spray headair cap;

Figure '7 is a fragmentary vertical section of the rear portion of vthespray gun taken on the linezT-'l of 'Figure 3 through the air supply inlet andatomizing air valve housing;

Figure 8 is a fragmentary horizontal section taken on the line 8 8 of Figure 1.

The spray gunshown in the drawing consists of a. main body'portion l anda spray head 2 normally held together by hollow connecting screwfS. The body I` has an air cylinder i closed by cap 5 atits rear end. Below the cap 5 is air.= inlet 6 for supplying air both to the air cylinderand to the spray head. Through a boss Bonthe bodyis a threaded bore 9 for receiving a mounting rodinot shown) for supporting the sprayygun in anyA desired location.

From theforward end of the air cylinder 4. eX- tend'twovertical arms E53 and ll. These arms are joined by a narrow transverse section l2 in which there are upper and lower bores I3 and I 4*. The rear end ofA the spray head 2 is held between the forwardY portions oi the arms It andl II with the rear end wall of the air inlet I5 abutted against the forwardend wall of the upper bore i3. The inlet I5 is internally threaded at I6. The connector 3 holds the spray head'lon the body I by being inserted through the bore I3' and engagingthe threads I6. The connector^3 asrillustrated in Figure 6 has a tapered shoulder I1 which seatsv around the rearY edge of the-bore I3.

' On; the-lower side: of the spray head 2, is; the;-

spray material inlet I8. On the forward end of the spray head is an air atomizing cap I9.

Through the lower bore i4 in the transverse section l 2 extends the rear end of the spray material needle Valve as well as the packing nut 2l and the packing retaining nipple 22 within which the nut 2l is threaded.

Within the cylinder 4 as shown in Figure 5 is an air piston assembly. This consists of a supporting cup 24 around the periphery of which isheld the piston leather 25 by means of a disc 26. An axially positioned rod 21 is inserted from the rear through a central bore in the disc 26 until a shoulder on the rod abuts against the disc. The forward end of the rod 21 is threaded through a central bore in the cup 24 and beyond the cup has a threaded connection with trigger 30 which opens the spray material valve 20 and atomizing air valve 29.

As shown in Figure 5 this hollow trigger 35 has a lateral opening 3l near its forward end for receiving the head 32 on the rear end of the needle 2B. The opening 3l has an elongated portion 33 extending to the center of the forward end of the trigger for accommodating the shank of the needle 29 adjacent to the head 32. To impel the needle forwardly toward its seat in the spray head a spring 34 is located Within the hollow portion of the trigger.

This spring has its rearward thrust against the Y forward end of the rod 21 and its forward thrust against the needle through an intermediate Inovable disc 35. The bore of the trigger has a rearwardly facing shoulder 36 as may be seen in Figure 5 just behind the lateral hole 3l. This shoulder reduces the bore slightly below the diameter of the disc whereby the disc may not move forwardly beyond the shoulder. This keeps it from moving into the space ordinarily occupied by the needle head 32 and thus interfering with the reinsertion of the head. The trigger has a downwardly extending iinger 31 positioned to strike the stem 33 of the air valve 29 located in a casing 40 below the air cylinder (Figure '1).

In the operation of the spray gun it is rst mounted upon a rod having threaded engagement with bore 9. An air hose is fastened to the inlet nipple 6 and a spray material Supply hose connected to inlet i8. The flow of air entering nipple 6 is ordinarily controlled by a valve in the air supply line in synchronism with a conveyor carrying articles to be spray coated.

When an article is in position to be coated and the air supply valve opened the air enters nipple 6. travels through lateral passages 4l into bore i12 (see Figure 8). As soon as the pressure of the air is great enough to overcome the tension of spring 43 Valve 44 is moved rearwardly from its forward seat d5 to its rearward seat 46 letting the air enter annular chamber l1 and thence upwardly through passage 48 (refer to Figure 5) to the air cylinder 4.

The piston under the force of the air pressure upon the piston leather 25 moves rearwardly. After the initial movement of the piston the air also acts upon the forward face of the cup 24. The piston moves against the tension of spring 69 until the end of the rod 21 strikes against cylinder cap 5. The cap is set to stop the piston at a point where the piston will open the material needle, to which the piston is attached at its forwardend, to a degree suitable for the desired discharge of coating material.

The rearward piston movement draws the needle from its seat in the material discharge tip 50 allowing the material reaching the tip from the connection I8 to be discharged from the outlet port 5l of the tip. This material is atomized and shaped into an appropriate fan pattern by air discharged around it from annular opening 52 between the tip and the air cap I9 and from supplemental ports in the air cap.

The lair reaches the spray head from connection 6 past valve 29 which is opened against spring 53 by rearward movement of the downwardly extending nger 31 of the trigger. This air travels forwardly through the passage 54 which leads through the arm Il and terminates at opening 55 in the bore I3 shown in Figure 5. From here the air passes through ports 5E in the connector 3 and enters the spray head.

In order to insure the presence of atomizing air at the nozzle before the discharge of material the nger 31 contacts the air valve stem 38 before the head 32 of the vmaterial valve is moved rearwardly by the forward end wall of the axial bore in trigger 33. The air reaching the nozzle for atomization purposes is at proper pressure for effective atomization as the spring 43 is so tensioned by adjusting screw 51 that the air ahead of the valve 44 must be at a satisfactory atomizing pressure before the valve 44 is moved and permits air into cylinder 4 for actuating the piston.

When it is desired to interrupt the spraying action the valve in the air supply line is closed. As air will continue momentarily to pass the open atomizing air Valve 29 the pressure of the air reaching the spray gun decreases; however, as soon as the pressure is below that of the spring 43 the force of this spring promptly returns the valve M from its rearward seat 45. The air in the cylinder 4 is thus released to the atmosphere by way of the passages through valve contacting plug 58 and the port 59 in the adjusting screw 51.

The piston immediately moves forwardly rst seating the material valve and then allowing the atomizing air valve to return to its closed position. This action is so rapid that the pressure of the atomizing air reaching the nozzle is sustained at a satisfactory level until the ow of material is ended.

A further advantageous result is the locking in the air supply hose, between the check valve 44 and the air control valve in the supply hose, of air at a pressure approaching that desired for atomizing; consequently, when the valve in the air supply line is again opened little time is utilized in building up the additional pressure required for the operation of the gun.

It may be seen therefore that an automatic spray gun constructed according to this invention has means for checking piston actuating air from reaching the cylinder until the air pressure is satisfactory for atomization, means for rapidly evacuating air from the cylinder on reduction of air pressure and means for maintaining air under pressure in the air supply line between operations of the spray gun.

These means contribute individually and jointly to greatly improved results by eliminating poor atomization and by enabling rapid actuation of the spray gun.

While a particular embodiment has been herein presented, it should be understood that the principles of the invention may be utilized with various arrangements of air passages and valve construction.

I claim:

1. In a spray gun of the type described, a spray material discharge valve, an atomizing air valve, a reciprocable piston actuatingly connected to the discharge valve and the atomizing air valve, a spring thrust against the piston for moving it in one direction, the piston being subject to air pressure for movement in the opposite direction, a single air supply inlet for both atomizing and piston motivating air, a communicating bore between the inlet and the atomizing air valve, a separate passageway from the inlet to the piston, an air pressure movable check valve in said passageway, a passageway closingr seat therefor, a spring yieldably holding the check valve to said seat, means for adjusting the tension of said spring, whereby the pressure of the air from the air supply inlet required to open the check valve; against the spring tension may be set suciently p high to be suitable for atomization, a second seat for said check valve to which it is movable by the air pressure in the passageway when the pressure is suicient to overcome the spring tension, an atmospheric vent having communication with said passageway between the iirst seat and the piston, said check valve closing off said communication when upon its second seat. v

2. In an automatic spray gun of the type de scribed, a spray nozzle, an atomizing air passage leading thereto, an air valve in said atomizing passage, a passage for the material to be sprayed ond branch passage at a point between the check valve when it is in closed position and the airl pressure responsive means, said check valve, when moved to open position by the pressure of the air, cutting o' the communication between the atmospheric vent and the second branch passage.

3. In an automatic spray gun of the type described, an air pressure responsive spray controlling element, an air supply passage leading thereto, an atmospheric venting passage connected to said supply passage, an air pressure movable valve at the juncture of said passages, two opposed seats for said valve, a spring for yieldably holding the valve against one of the seats in which it closes the supply passage and opens the venting passage, adjustable means for varying the tension of the spring against the valve, the valve when moved to the other of said seats by the pressure of air within the supply passage opening said supply passage and closing said venting passage.

4. In an automatic spray gun of the type described, a material discharge valve, an air pressure responsive elementactuatingly associated with said discharge valve, an air supply passage, an atmospheric vent passage, a face-to-face near juncture of said supply and vent passages, closely spaced annular valve seats surrounding the adjacent ends of the supply and vent passages, valve means movable between said seats, a spring thrust against the valve means to hold it with a predetermined yieldable pressure upon the seat around the supply passage, said valve means movable by predetermined air pressure against the spring thrust to the seat surrounding the vent passage, and a laterally directed passage extension communicating with the space between the valve seats and leading to the air pressure responsive element, whereby the element receives a supply of motivating air in one seating position of the valve means and is vented in the other seating position of the valve means.

`DONALD J. PEEPS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,332,544 Davis Mar. 2, 1920 1,380,866 Day June 7, 1921 1,932,039 Hewitt Oct. 24, 1933 2,107,732 Gustafsson et al Feb. 8, 1938 2,208,464 Logette et al July 16, 1940 2,533,953 Peeps Dec. 12, 1950

Images