US3559891A

US3559891A - Spray gun

Info

Publication number: US3559891A
Application number: US816191A
Authority: US
Inventors: Kurt Herman Liedberg; Lars Gunnar Torbjorn
Original assignee: Atlas Copco AB
Current assignee: Atlas Copco AB
Priority date: 1968-04-19
Filing date: 1969-04-15
Publication date: 1971-02-02
Anticipated expiration: 1988-02-02
Also published as: DE1919427A1; JPS4819857B1; GB1244235A; SE318506B

Abstract

In a spray gun with pressure fluid actuated servo motor for moving the coating material valve and with servopiston means in the servo motor to be pressurized for movement against or relieved for displacement by unidirectional force bias under the control of a control valve, a setting valve provides, when open, arresting of the servopiston means by pressure fluid in a position corresponding to closed position of the coating material valve irrespective of the position of the control valve. Such safety setting may be used for blowing live pressure fluid via the control valve to a blowing opening for blowing the workpiece clean preparatory to spraying.

Description

O United States Patent l 13,559,891

[72] Inventors Kurt Herman Liedberg; [56] References Cited Lars Gunnar Torbjorn Christensson, UNITED STATES PATENTS [2 1] App No g z'f f 2,864,649 12/1958 Adams 239/526X [22] Filed Apr. 15, 1969 3,327,949 6/1967 Eull 239/412 [45] Patented Feb. 2, 1971 Primary Examiner-M. Henson Wood, J r. [73] Assignee Atlas Copco Aktiebolag Assistant Examiner-Th0mas C. Culp, Jr.

Nacka, Sweden AnomeyBauer & Goodman a corporation of Sweden [32] Priority Apr. 19, 1968 [33] Sweden ABSTRACT: In a spray gun with pressure fluid actuated servo [31] 5521/68 motor for moving the coating material valve and with servopiston means in the servo motor to be pressurized for move- 54] SPRAY GUN merit against or relieved for displacement by unidirectional force bias under the control of a control valve, a setting valve 9 Claims, 1 Drawing Flg.

provides, when open, arresting of the servoplston means by [52] U.S. Cl 239/443, pressure fluid in a position corresponding to closed position of 239/412, 239/526, 239/569, 239/583 the coating material valve irrespective of the position of the Cl B control valve. Such safety setting may be used for blowing live [50] Field of Search 239/412, pressure fluid via the control valve to a blowing opening for 41 l 410, 526, 583, 413, 4l6.2, 443 blowing the workpiece clean preparatory to spraying.

SPRAY GUN This invention relates to spray guns and more particularly to spray guns in which a coating material valve is operated by a pressure fluid-actuated servomotor. Via a control valve the servomotor is supplied with or relieved from pressure fluid. This moves a servopiston means in the motor respectively against or in the direction of a unidirectional force bias active thereagainst and produced by fluidic or metallic spring means. The servopiston means is connected to and operates the coating material valve.

Such spray guns are normally used for high-pressure spraying without atomizing assistance of pressure fluid. Particularly in manually operated spray guns of this type any accidental actuation of the control valve must be prevented during handling of the gun and it is followingly a desideratum to include some means in the spray gun whereby it can be set at safety between the spraying operations. Conventionally one resorts in connection herewith to a variety of movable stops or catches for the control valve which, however, take up considerable space around the trigger of the spray gun and are a hindrance in handling.

it is therefore an object of the invention to replace such prior stop devices by a safety means using the pressure fluid in the gun for arresting the servopiston means therein at safety. Another object of the invention is to provide a safety means which does not affect the accessibility of the trigger. A further object of the invention is to provide, on the basis of such safety means, a combination thereof with a device for blowing the working piece clean from dust and debris before the spraying operation. A still further object of the invention is to provide an improved control valve for the servomotor of the spray gun.

For the above and other purposes there is according to the invention provided a spray gun comprising a housing, nozzle means forwardly on said housing, means for supplying coating material under pressure to said nozzle means, a coating material valve in said housing movable between closed and open position for controlling the flow of such material through said noule means, a source of pressure fluid, a pressure fluidactuated servomotor in said housing, servopiston means connected to said coating material valve and sealingly guided in said motor for reciprocating movement between a first and a second position corresponding respectively to said closed and open position of said coating material valve, means in said motor for maintaining unidirectional force bias on said servopiston means, a supply passage in said housing connected to said source of pressure fluid, an exhaust passage in said housing, a control valve in said housing connected to said supply and exhaust passages and to said servomotor and movable between a first and a second position for connecting said motor respectively to said supply passage or to said exhaust passage to cause movement of said servopiston means respectively against or in the direction of said force bias, a branch pa sage in said housing extending between said supply passage and said servomotor, and a setting valve in said branch pasage movable independently of said control valve between closed and open position to keep, in the latter of them, said servopiston means permanently arrested by pressure fluid in the first position thereof regardless of the position of said control valve.

The above and other purposes of the invention will become obvious from the following description and from the accompartying drawing in which an embodiment of the invention is illustrated by way of example. It should be understood that this embodiment is only illustrative of the invention and that various modifications thereof may be made within the scope of the claims.

In the drawing is illustrated a longitudinal section through a spray gun for high-pressure spraying.

The spray gun has a handle carrying a forwardly directed gun body H on which a trigger 12 is pivotally journaled on a pivot 13. A coating material chamber 14 is fonned forwardly in the body 11 and is supplied with liquid surface coating material under high pressure from a suitable pump, not shown,

via a suitable hose and a nipple 15. The chamber 14 is bordercd forwardly by a valve seat 18 threadedly fastened to the gun body 11. Against the valve seat 18 a conventional spray nozzle 16 is clamped by a hollow nut 17. In the valve seat 18 is arranged an outlet orifice 18 which is closed or opened by a coating material valve 19 movable between corresponding positions. The coating material valve 19 is carried by a stem 20 extending out of the chamber 14 to the rear through a washer 21, a packing 22, and a gland nut 23 threadedly received in the gun body 11.

The stem 20 is fixed as by a stop screw within a piston rod 24 included in a pressure fluid-actuated servomotor generally designated by 25 and disposed in the rear portion of the gun body 11.

The servomotor 25 includes a servopiston means as of differential type which may be a single-headed piston but preferably is formed as a tandem piston having a core body 26 and front and

rear pistonheads

27, 28. The core body 26 is screwed to the piston rod 24 and clamps thereagainst the front pistonhead 27. The rear pistonhead 28 is affixed to the rear end of the core body 26. The core body 26 is guided sealingly and slidably in a partition 29 fixed in a bore 36 within the gun body 11, there being fixed working cylinders in the bore 36 at both sides of the partition 29, one within a frontpiece 30 and the other in a backpiece 31. The rear pistonhead 28 divides the working cylinder of the backpiece 31 into a forward working chamber 32 around the core body 26 and a rear working chamber 33. In the frontpiece 30 a working chamber 34 is formed between the partition 29 and the front pistonhead 27. Via passages 35 in the core body 26 the working chamber '34 is in permanent communication with the working chamber 33 of the backpiece 31. The interior of the front piece 30 forwardly of the front pistonhead 27 communicates freely with the atmosphere via the clearance around the piston rod 24.

A supply passage 37 in the handle 10 communicates the working chamber 32 of the backpiece 31 directly with a suitable source of pressure fluid, not shown, preferably a source of compressed air which via a hose, not shown, and a nipple 37 is connected to the supply passage 37. A branch or safety passage 38 starts from the supply passage 37 adjacent to the nipple 37 with a passage portion 38 extending to a safety or setting valve 39 which at 41 is threadedly received in the end of the handle 10 and may be screwed tight to the closed position depicted in the figure or be loosened and unscrewed to open position by turning of a knob 40. in the open position of the setting valve 39 the passage portion 38' communicates with the main portion of the branch passage 38 which latter opens into a valve chamber 42 adjacent the trigger 12 of the spray gun. The branch passage 38 is continued by a short passage 38 at the other side of the chamber 42 and connected to the working chamber 34 of the servomotor 25 in the frontpiece 30. The inner end of the chamber 42 is connected to the supply passage 37 by a bore forming a valve seat 43 in said chamber and taking up a valve spring 44. A ball valve 45 operating as a two-position three-way control valve cooperates with the valve seat 43 and can be moved sealingly onto the seat 43 against the action of the valve spring 44 by depression of a valve pin 46 by means of the trigger 12. The valve pin 46 is guided in a valve seat body 47 carrying a second valve seat 48 within the chamber 42 onto which latter the ball valve 45 is moved by the valve spring 44 when the trigger 12 is released. From'the opening defined by the valve seat 48 there extend

exhaust bores

49, 50 to a reduced forward portion of bore 36 forwardly of frontpiece 30 from which an exhaust passage 51 is extended through the gun body 11 in forward direction to a forwardly pointing blowing opening 52 above the spray nozzle 16.

With the supply passage 37 receiving pressure fluid, the working chamber 32 of the backpiece 31 around the core body 26 will be pressurized. This pressure acts as a permanent force bias of fluidic spring means on the

tandem piston

27, 28 and strives to move the

tandem piston

27, 28 from a first or closed position thereof, shown in the figure, to a second open position. in which the coating material valve 19 is open. in the first position of the

tandem piston

27, 29 pressure fluid enters from the supply passage 37 via the open seat 43 of the ball valve 45 into the main pan of the branch passage 38 and is supplied via the short passage 38 to the working chamber 34 of the front piece 30 and thense to the working chamber 33 of the backpiece 31 via the passages 35 of the core body 26. The pressure acting in the

working chambers

33, 34 maintains the

tandem piston

27, 28 in the first position thereof against the action of the force bias in the working chamber 32. Since the ball valve 45 is kept under forward thrust against the valve seat 48 by the valve spring 44, the pressure level in the

working chambers

33, 34 is on as long as the trigger 12 stays inactuated.

When the trigger 12 is depressed. the valve pin 46 lifts the ball valve 45 from the seat 48 pushing the ball valve 45 against the opposite valve seat 43. Followingly, the pressure fluid supply from the supply passage 37 to the chamber 42 is interrupted simultaneously with the

working chambers

34, 33 and thebranch passage 38 being relieved via the

exhaust passages

49,50, 51 to the atmosphere via the blowing opening 52. As a result the force bias produced by the pressure acting in the working chamber 32 against the rear head 28 can displace the

tandernpiston

27, 28 to the second position thereof, to the right in the figure, the piston rod 24 pulling the valve stem 20 and opening the orifice 18 of the coating material valve 29 for purposes of spraying paint or other coating liquid. As soon as the trigger 12 is released, the seat 43 of the ball valve 45 is reopened by the valve spring 44 and the previously displaced parts of the spray gun return to the positions thereof shown in the figure.

When the spray gun is to be set at safety, the setting valve 39 is opened by the knob 40. As a result the bore 42 is permanently pressurized via the safety passage 42 regardless of the fact whether the trigger 12 is depressed or released. Although in the depressed position of the trigger 12 the connection via the valve seat 48 and the

exhaust passages

49, 50 51 is open to the atmosphere at blowing opening 52, these passages are flooded by pressure fluid and dimensioned such as to maintain a high-pressure level in the chamber 42 so that the servomotor 25 stays at safety in the closed position shown in the figure regardless of the position of the ball valve 45. The air jet emitted from the flowing opening 52 and produced when the trigger 12 is depressed, is used as blowing air for cleaning the workpiece before spraying. As soon as spraying is again desired, the safety valve 39 is screwed tight closed at which time the pneumatic safety setting obviously ceases.

Blowing of the workpiece may in certain cases be brought about without opening of the setting valve 39 by careful partial depression of the trigger 12. This causes the ball valve 45 to lighten on the seat 48 without closing the seat 43. Such adjustment, however, requires great experience for avoiding unintentional opening of the paint valve 19 and blowing, therefore, is during production spraying normally always performed only by using the pneumatic safety setting with the setting valve 39 open.

We claim:

1. A spray gun comprising a housing, nozzle means forwardly on said housing, means for supplying coating material under pressure to said noule means, a coating material valve in said housing movable between closed and open position for controlling the flow of such material through said nozzle means, a source of pressure fluid, a pressure fluid actuated servomotor in said housing, servopiston means connected to said coating material valve and sealingly guided in said motor for reciprocating movement between a first and a second position corresponding respectively to said closed and open position of said coating material valve, means in said motor for maintaining unidirectional force bias on said servopiston means, a supply passage in said housing connected to said source of pressure fluid, an exhaust passage in said housing, a control valve in said housing connected to said supply and exhaust passages and to said servomotor and movable between a first and a second position for connecting said motor respectively to said supply passage or to said exhaust passage to cause movement of said servopiston means respectively against or. in the direction of said force bias, a branch passage in said housing extending between said supply passage and said servomotor. and a setting valve in said branch passage movable independently of said control valve between closed and open position to keep, in the latter of them, said servopiston means permanently arrested by pressure fluid in the first position thereof regardless of the position of said control valve.

2. A spray gun according to claim 1 inwh'ich said first position of said servopiston means corresponds to said control valve taking said first position thereof.

3. A spray gun according to claim 1 in which the connection of said control valve with said servomotor is also in communication with the portidn of said branch passage controlled by said setting valve.

4. A spray gun according to claim 3 in which there is provided a blowing opening on said housing pointing in the forward direction thereof, and in which said exhaust passage extends to said blowing opening.

5. A spray gun according to claim 1 in which said control valve is a two-position three-way valve including a valve chamber communicating with said servomotor, a ball valve in said valve chamber, two opposed valve seats in said valve chamber sealingly cooperating with opposite sides of said ball valve and between which said ball valve is reciprocable, one of said valve seats defining a connection between said valve chamber and said supply passage and the other a connection between said valve chamber and said exhaust passage, and means carried by said housing for selectively moving said ball valve sealingly onto one or the other of said seats.

6. A spray gun according to claim 5 in which said valve chamber is connected to the portion of said branch passage controlled by said setting valve.

7. A spray gun comprising a housing, nozzle means forwardly on said housing, means or supplying coating material under pressure to said nozzle means, a coating material valve in said housing movable between closed and open position for controlling the flow of such material through said nozzle means, a source of pressure fluid, a pressure fluid actuated servomotor in said housing, servopiston means connected to said coating material valve and sealingly guided in said motor for reciprocating movement between a first and a second position corresponding respectively to said closed and open position of said coating material valve, means in said motor for maintaining a unidirectional force bias on said servopiston means, a supply passage in said housing connected to said source of pressure fluid, an exhaust passage in said housing, a blowing opening on said housing pointing in the forward direction thereof and disposed at the outlet end of said exhaust passage therein, a control valve in said housing connected to said supply an exhaust passages and to said servomotor and movable between a'first and a second position for connecting said motor respectively to said supply passage or to said exhaust passage to cause movement of said servopiston means respectively against or in the direction of said force bias, a branch passage in said housing extending between said supply passage and said servomotor, a setting valve in said branch passage movable independently of said control valve between closed and open position to keep, in the latter of them, said servopiston means arrested by pressure fluid in the first position thereof regardless of the position of said control valve, and said branch passage also communicating with said control valve at the connection thereof with said servomotor for directing pressure fluid via said supply, branch and exhaust passages directly to said blowing opening with said setting in said open and said control valve in said second position thereof.

8. A spray gun according to claim 7, in which said control valve is a two-position three-way valve including a valve chamber communicating with said servomotor, a ball valve in said valve chamber. two opposed valve seats in said valve chamber scalingly cooperating with opposite sides of said ball valve and between which said ball valve is reciprocablc, one of said valve seats defining a connection between said valve chamber and said supply passage and the other a connection between said valve chamber and said exhaust passage. and means carried by said housing for selectively moving said ball valve sealingly onto one or the other of said seatsv 9. A spray gun comprising a housing, nozzle means on said housing, means for supplying coating material under ressure to said nozzle means, a coating material valve in said housing movable between closed and open position for controlling the flow of such material through said nozzle means, a source of pressure fluid a pressure fluid actuated servomotor in said housing, servopiston means connected to said coating material valve and sealingly guided in said motor for reciprocating movement between two alternative positions corresponding to said closed and open position of said coating material valve. means in said motor for maintaining unidirectional force bias on said servopiston means. a supply passage in said housing connected to said source of pressure fluid, an exhaust passage in said housing, a valve chamber in said housing connected to said servomotor, a ball valve in said valve chamber. two opposed valve scats in said valve chamber sealingly cooperating with opposite sides of said ball valve and between which said ball valve is reciprocable, one of said valve seats defining a connection between said valve chamber and said supply passage and the other a connection between said valve chamber and said exhaust passage and connecting in one position of said ball valve said valve chamber to said supply passage and in the other position of said ball valve said valve chamber to said exhaust passage to cause movement of said servopiston means respectively against or in the direction of said force bias, and means carried by said housing for selectively moving said ball valve sealingly onto one or the other of said seats UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 559,891 Dated February 2, 1971 Inventor(s) KURT HERMAN LIEDBERG and LARS GUNNAR TORBJORN CHRISTENSSON It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown -below:

Claim 7, line 2 "or" should read --for--;

line l, "an" should read "and";

Signed and sealed this 25th day of May 1971 (SEAL) Attest:

WARD M.FIEI'GHER JR. WILLIAM E. SGHUYLER, JR fitesting Officer Commissioner of Patents

Claims

1. A spray gun comprising a housing, nozzle means forwardly on said housing, means for supplying coating material under pressure to said nozzle means, a coating material valve in said housing movable between closed and open position for controlling the flow of such material through said nozzle means, a source of pressure fluid, a pressure fluid actuated servomotor in said housing, servopiston means connected to said coating material valve and sealingly guided in said motor for reciprocating movement between a first and a second position corresponding respectively to said closed and open position of said coating material valve, means in said motor for maintaining unidirectional force bias on said servopiston means, a supply passage in said housing connected to said source of pressure fluid, an exhaust passage in said housing, a control valve in said housing connected to said supply and exhaust passages and to said servomotor and movable between a first and a second position for connecting said motor respectively to said supply passage or to said exhaust passage to cause movement of said servopiston means respectively against or in the direction of said force bias, a branch passage in said housing extending between said supply passage and said servomotor, and a setting valve in said branch passage movable independently of said control valve between closed and open position to keep, in the latter of them, said servopiston means permanently arrested by pressure fluid in the first position thereof regardless of the position of said control valve.

2. A spray gun according to claim 1 in which said first position of said servopiston means corresponds to said control valve taking said first position thereof.

3. A spray gun according to claim 1 in which the connection of said control valve with said servomotor is also in communication with the portion of said branch passage controlled by said setting valve.

7. A spray gun comprising a housing, nozzle means forwardly on said housing, Means or supplying coating material under pressure to said nozzle means, a coating material valve in said housing movable between closed and open position for controlling the flow of such material through said nozzle means, a source of pressure fluid, a pressure fluid actuated servomotor in said housing, servopiston means connected to said coating material valve and sealingly guided in said motor for reciprocating movement between a first and a second position corresponding respectively to said closed and open position of said coating material valve, means in said motor for maintaining a unidirectional force bias on said servopiston means, a supply passage in said housing connected to said source of pressure fluid, an exhaust passage in said housing, a blowing opening on said housing pointing in the forward direction thereof and disposed at the outlet end of said exhaust passage therein, a control valve in said housing connected to said supply an exhaust passages and to said servomotor and movable between a first and a second position for connecting said motor respectively to said supply passage or to said exhaust passage to cause movement of said servopiston means respectively against or in the direction of said force bias, a branch passage in said housing extending between said supply passage and said servomotor, a setting valve in said branch passage movable independently of said control valve between closed and open position to keep, in the latter of them, said servopiston means arrested by pressure fluid in the first position thereof regardless of the position of said control valve, and said branch passage also communicating with said control valve at the connection thereof with said servomotor for directing pressure fluid via said supply, branch and exhaust passages directly to said blowing opening with said setting in said open and said control valve in said second position thereof.

8. A spray gun according to claim 7, in which said control valve is a two-position three-way valve including a valve chamber communicating with said servomotor, a ball valve in said valve chamber, two opposed valve seats in said valve chamber sealingly cooperating with opposite sides of said ball valve and between which said ball valve is reciprocable, one of said valve seats defining a connection between said valve chamber and said supply passage and the other a connection between said valve chamber and said exhaust passage, and means carried by said housing for selectively moving said ball valve sealingly onto one or the other of said seats.

9. A spray gun comprising a housing, nozzle means on said housing, means for supplying coating material under pressure to said nozzle means, a coating material valve in said housing movable between closed and open position for controlling the flow of such material through said nozzle means, a source of pressure fluid a pressure fluid actuated servomotor in said housing, servopiston means connected to said coating material valve and sealingly guided in said motor for reciprocating movement between two alternative positions corresponding to said closed and open position of said coating material valve, means in said motor for maintaining unidirectional force bias on said servopiston means, a supply passage in said housing connected to said source of pressure fluid, an exhaust passage in said housing, a valve chamber in said housing connected to said servomotor, a ball valve in said valve chamber, two opposed valve seats in said valve chamber sealingly cooperating with opposite sides of said ball valve and between which said ball valve is reciprocable, one of said valve seats defining a connection between said valve chamber and said supply passage and the other a connection between said valve chamber and said exhaust passage and connecting in one position of said ball valve said valve chamber to said supply passage and in the other position of said ball valve said valve chamber to said exhaust passage to cause movement of said servopiston means respectivelY against or in the direction of said force bias, and means carried by said housing for selectively moving said ball valve sealingly onto one or the other of said seats.