US3580435A

US3580435A - Spray gun with pressure operated valve

Info

Publication number: US3580435A
Application number: US721304A
Authority: US
Inventors: Alf Georg Bertilsson
Original assignee: Atlas Copco AB
Current assignee: Atlas Copco AB
Priority date: 1968-04-15
Filing date: 1968-04-15
Publication date: 1971-05-25
Anticipated expiration: 1988-05-25

Abstract

In a spray gun the supply of coating material to the nozzle means of the gun is controlled by a pressure fluid-actuated differential servo piston means dividing the cylinder thereof in a first cylinder chamber around the stem and a second cylinder chamber opposite to the first cylinder chamber. During both strokes of the servo piston means the first cylinder chamber is pressurized by pressure fluid. A maneuvering valve is provided for either supplying pressure fluid to the second chamber for producing one of the strokes of the servo piston means against the action of pressure fluid in the first chamber, or relieving the pressure fluid in the second chamber for releasing the other stroke of the servo piston means under the action of said pressure fluid in the first chamber. More particularly the servo piston means may be of tandem design for quick actuation.

Description

United States Patent [72] lnventor Alt Georg Bertilsson Harlingstorp, Axvall, Sweden [21] Appl. No. 721,304 [22] Filed Apr. 15, 1968 [45] Patented May 25, 1971 [73] Assignee Atlas Copco Aktiebolag Nacka, Sweden [54] SPRAY GUN WITH PRESSURE OPERATED VALVE 3,248,879 5/1966 Natho 92/134X FOREIGN PATENTS 821,648 10/1959 Great Britain 91/416 850,490 10/1960 Great Britain 91/416 Primary Examiner-Stanley H. Tollberg Assistant Examiner-H. S. Lane Attorney-Bauer and Goodman ABSTRACT: In a spray gun the supply of coating material to 6 Claims, 5 Drawing Figs.

the nozzle means of the gun is controlled by a pressure fluid- [52] US. Cl 222/504, actuated diff ti l Servo piston means dividing the cyiinder 9l/41625l/31 thereof in a first cylinder chamber around the stern and a [51] Int. Cl B67d 5/06 Second cylinder chamber opposite to the fi t cylinder [50] Field of Search 222/504; chamben During both Strokes f the Servo piston means the 92/134; 251/31 63-5; 91/416 first cylinder chamber is pressurized by pressure fluid. A maneuvering valve is provided for either supplying pressure [56] References Cited fluid to the second chamber for producing one of the strokes UNITED STATES PATENTS of the servo piston means against the action of pressure fluid 2,746,425 5/ 1956 Schafer 91/416X in the first chamber, or relieving the pressure fluid in the 3,083,913 4/1963 Coffman et a1. 239/412X second chamber for releasing the other stroke of the servo 2,479,454 8/1949 Annin 92/134X piston means under the action of said pressure fluid in the first 2,582,512 1/1952 Stueland. 92/134X chamber. More particularly the servo piston means may be of 2,983,922 5/ 1961 Juilfs 92/134X tandem design for quick actuation.

28 I3 4 26 [2 ll 3 7 /A B 17 l l IO 29 6 l5 PATENTEUHAYZ IQYI 3,580,435

SHEET 3 [IF 3 36 24 34 I6 23 l3 l2 INVIz'N'l'OR.

SPRAY GUN WITH PRESSURE OPERATED VALVE This invention relates to spray guns for coating materials and more particularly to spray guns having pressure fluid-actuated servo piston means in the housing of the gun for the control of the coating material valve therein. Such spray guns are normally used for airless spraying of coating material under high pressure and for remotely controlling automatic spraying equipment intended for similar or other spraying operations. Conventionally the servo piston means are moved by a spring during one of the strokes in the reciprocation thereof and by pressure fluid during the other stroke.

It is an object of the invention to provide in spray guns of the above type, a simplified servo piston means in which both strokes of the servo piston means are powered by pressure fluid without actuation of the servo piston means by springs. A further object of the invention is to provide in spray guns of the above type a servo piston means of a design more efficient in utilizing the pressure fluid power acting thereagainst for quick opening or closing of the coating material valve. A still further object is to provide in spray guns of the above type a servo piston means of tandem design without actuating springs.

For the above and other purposes there is according to the invention provided 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 for controlling the flow of such material through said nozzle means, a source of pressure fluid, a cylinder in said housing, differential servo piston means connected to said coating material valve and having a stem portion thereon sealingly but slidably guided in said housing, said differential servo piston means being movable in said cylinder to perform alternately opening and closing strokes therein under the action of pressure fluid from said source for controlling said coating material valve, said differential servo piston means dividing said cylinder in a first cylinder chamber around said stem and a second cylinder chamber opposite to said first cylinder chamber, means for keeping said first cylinder chamber pressurized by pressure fluid from said source during the strokes of said servo piston means, a maneuvering valve, and means controlled by said maneuvering valve for either supplying pressure fluid from said source to said second chamber for producing one of the strokes of said servo piston means against the action of said pressure fluid in said first chamber, or relieving the pressure fluid in said second chamber for releasing the other stroke of said servo piston means under the action of said pressure fluid in said first chamber.

The above and other purposes of the invention will become obvious from the following description and from the accompanying drawings in which three embodiments of the invention are illustrated by way of example. It should be understood that these embodiments are only illustrative of the invention and that various further modifications thereof may be made within the scope of the claims.

In the drawings FIG. 1 shows a longitudinal section through a remotely controlled automatic spray gun according to one embodiment of the invention. As depicted in FIG. 1 pressure fluid is supplied to the spray gun via a diagrammatically illustrated maneuvering valve such as to keep the coating material valve of the spray gun closed. FIG. 2 shows the spray gun in FIG. 1 in another position with the maneuvering valve in relief position and the coating material valve open. FIG. 3 shows a longitudinal section through an automatic spray gun of modified embodiment with the coating material valve therein closed FIG. 4 shows a longitudinal section corresponding to FIG. 3 but with the coating material valve open. FIG. 5 shows a longitudinal section through a spray gun according to a third embodiment of the invention.

In FIGS. 1 and 2 the housing of the spray gun is designated by and is provided with a servo piston means consisting of a differential piston 13 controlling the flow of paint from/a first, or paint cylinder chamber 20. The piston 13 has a stem portion 13 thereon sealingly but slidably guided in the housing 10 in a bore 29 in free communication with the atmosphere. The piston 13 is journaled for reciprocation in a cylinder 14 provided in a backhead 14 which is screwed to the rear end of the spray gun housing 10. The differential piston 13 consists of a resilient packing cup 15 slidably cooperating with the cylinder 14 and a washer 30 retaining the packing cup 15 against a rear shoulder on the steam 13. The washer 30 is locked by a tightening nut screwed onto the stem 13. The packing cup 15 divides the cylinder 14 in two second and

third cylinder chambers

16, 12 of which said chamber 16 is disposed around the stem 13 and said third chamber 12 is at the end thereof opposite to chamber 16. By means of a conduit 17 the second cylinder chamber 12 is connectable via a maneuvering valve 11 alternatively to a supply hose and a source 37 of pressure fluid such as compressed air or to the atmosphere.

By means of a stop screw there is affixed to the stem 13 of differential piston 13 the stem 18 of a coating material valve 19. The valve 19 is disposed in a coating material or paint chamber 20 in the front portion of the housing 10. At the traverse into the paint chamber 20 the coating material valve stem 18 is surrounded by a sealing ring 28 of packing material which is compressed by the aid of a packing nut 27. Via a conduit 21 the paint chamber 20 is supplied with coating material under high pressure of the order of magnitude of 300 atmospheres. The paint chamber 20 has an outlet orifice 31 controlled by the valve 19. An atomizing nozzle means 25 is kept in place coaxially with and in front of the outlet orifice 31 by means of a retaining nut 22.

The housing 10 is provided with a cross bore 26 disposed proximate to the coating material valve axis and serving as a suspending or fixation hole for the housing 10 when the spray gun is to be mounted for automatized work. I

In FIG. 1 the maneuvering valve 11 is set to a position in which pressure fluid is supplied from the source 37 via the maneuvering valve 11 and conduit 17 to the cylinder chamber 12. The differential piston 13 is thus power biased in forward direction towards the outlet orifice 31 and the paint valve 19 is maintained firmly on its seat around the outlet orifice 31. The edge of the packing cup 15 is turned towards the cylinder chamber 16 and in the position depicted in FIG. 1 the cup 15 consequently acts as a check valve means allowing pressure fluid to flow to the cylinder chamber 16 while the cylinder chamber 12 is pressurized. When the maneuvering valve 11 is switched to exhaust cylinder chamber 12, FIG. 2, the charge of pressure fluid trapped in cylinder chamber 16 expands, acts against piston packing cup 15 and displaces the differential piston 13 rearwardly away from the outlet orifice 31. The opening stroke of the coating material valve 19 thus started is amplified by coating material pressure in the paint chamber 20 which acts on the valve 19 and valve stem 18 axially in the opening direction thereof.

As soon as the maneuvering valve 11 is returned the position indicated in FIG. 1, the cylinder chamber 12 is again filled by pressure fluid and the differential piston 13 is moved in its closing stroke forwardly overcoming the counter pressure in cylinder chamber 16. Cylinder chamber 16 is charged at the initial stage simultaneously with chamber 12 by pressure fluid entering chamber 12 and flowing past the packing cup 15. During the closing stroke the differential piston 13 closes the coating material valve 19 and compresses simultaneously therewith the pressure fluid charge in cylinder chamber 16 to a pressure slightly higher than line pressure.

In the embodiment depicted in FIGS. 3 and 4 the servo piston means which at the stem end thereof is affixed to the coating material valve stem 18, is of tandem design. In the spray gun housing 32 the servo piston means is thus provided with an outer tandem piston head 13 affixed to a stem 13 and sealingly but slidably guided in a partition 34 within the housing 32. Similar to the embodiment in FIGS. 1, 2 piston head 13 and stem 13 provide a differential piston guided in a bore 14' in a backhead 14. In the housing 32 there is provided coaxially with the bore 14 a bore 33 in which is slidable an intermediate pistonhead 36 incorporating a packing cup 35. The intermediate pistonhead 36 is affixed to the stem 13 of the pistonhead 13 and is kept in position thereagainst by an extension stem 13 which is screwed onto the forward end of stem 13 Between the intermediate pistonhead 36 and the partition 34 there is formed a third cylinder chamber 24 disposed in the bore 33. The second cylinder chamber 12 in the backhead 14 communicates via inner passages 23 provided in the stem 13' with the third cylinder chamber 24.

When pressure fluid is supplied from the source 37 via the maneuvering valve 1 1 to cylinder chamber 12 in the backhead 14, the packing cup 15 will as before act in check valve manner and cylinder chamber 16 between the outer pistonhead 13 and the partition 34 will thus be charged simultaneously with pressure fluid entering cylinder chamber 12. As a result the pistonhead 12 will be actuated by an axial force to perform the closing stroke of the tandem piston in the direction of the outlet orifice 31 of the coating material valve 19. This force is amplified by the cylinder chamber 24 between the packing cup 35 of pistonhead 36 and the partition 34 becoming pressurized simultaneously with chamber 12 via the passages 23, and the tandem piston will thus perform its closing stroke under pressure bias against both

pistonheads

13, 36.

As soon as the maneuvering valve 11 is switched to exhaust position, FIG. 4, the

cylinder chambers

24 and 12 will be exhausted. Pressure fluid trapped in cylinder chamber 16 behind the packing cup 15 will now be free to expand for performing the opening stroke of the tandem piston and for opening the coating material valve 19. The opening movement is amplified by coating material pressure starting to act in the paint chamber on the coating material valve 19 in the opening direction thereof as soon as the valve 19 has left its seat around orifice 31. The tandem design of the servo piston means increases the total piston area available for the closing stroke and reduces the dimensions of the servo piston means allowing quick operation.

in the embodiment exemplified in FIG. 5 the servo piston means in the spray gun housing 38 is identical in operation with the embodiment depicted in FIGS. 3,4 The backhead 14, however, is closed at the rear end thereof by means of a plug 39 and pressure fluid is supplied to the tandem piston for closing purposes from the source 37 directly to both

cylinder chambers

24, 16. The supply of pressure fluid is controlled by a maneuvering valve 40 which is actuated by a trigger 41 and may be moved against the action of a spring 42 from a position a in which the source 37 is connected to both

cylinder chambers

24, 16 to a position b in which cylinder chamber 16 is connected to the source 37 whilst the cylinder chamber 24 is exhausted via a conduit 43. Via the passages 23 cylinder chamber 12 is of course exhausted simultaneously with cylinder chamber 24. In connection with the depicted valve arrangement it is particularly suitable to arrange the maneuvering valve 40 in a pistol type grip 44, diagrammatically depicted by broken lines in FIG. 5, by which the spray gun housing 38 may be directed and used manually.

I claim:

1. A spray gun comprising a housing, nozzle means on said housing, meansfor supplying coating material under pressure to said nozzle means, a piston operating in said housing, a coating material valve mounted on an end of said piston within a first cylinder chamber for controlling the flow of such material through said nozzle means, a source of pressure fluid, an additional cylinder in said housing, a differential servo pistonhead connected to said piston at an end opposite to said coating material valve, said piston having an intermediate stem portion thereon sealing but slidably guided in said housing, said differential servo pistonhead being movable in said additional cylinder to perform alternately opening and closing strokes therein under the action of pressure fluid from said source for controlling said coating material valve, said differential servo pistonhead dividing said additional cylinder in a second cylinder chamber around said stern and a third cylinder chamber ad'acent to said second cylinderchamber, a passage connected etween said second and third cylinder chambers, a one-way valve means arranged in said passage for controlling the flowing of pressure fluid only in the direction from said third cylinder chamber into said second cylinder chamber, means for flowing pressure fluid from said source into said third cylinder chamber and from thence through said one-way valve means into said second cylinder chamber, a maneuvering valve, and means controlled by said maneuvering valve for'either supplying pressure fluid from said source to said third chamber for producing said closing stroke of said servo piston head against the action of said pressure fluid in said first and second chambers, or relieving the pressure fluid in said third chamber for releasing said servo piston head for said opening stroke thereof under the action of pressure fluid in said first and second chambers.

2. A spray gun according to claim 1 in which said maneuvering valve has a first position adapted to cause said means controlled thereby to supply pressure fluid to all three of said cylinder chambers and a second position adapted to supply pressure to said first cylinder chamber only and to relieve the pressure in said third cylinder chamber.

3. 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 for controlling the flow of such material through said nozzle means, a source of pressure fluid, a cylinder in said housing, a tandem piston having a stem portion thereon connected to said coating material valve, said tandem piston having an intermediate and an outer piston head thereon and being movable in said cylinder to perform alternately opening and closing strokes therein under the action of pressure fluid from said source for controlling said coating material valve, a partition in said housing between said piston heads for sealingly but slidably receiving said stem portion therein, said tandem piston dividing said cylinder in a first cylinder chamber between said partition and outer head, a second cylinder chamber outwardly of said outer head, and a third cylinder chamber between said partition and intermediate head, passage means permanently communicating said second and third cylinder chambers, means for keeping said first cylinder chamber pressurized by pressure fluid from said source during the strokes of said tandem piston, a maneuvering valve, and means controlled by said maneuvering valve for either supplying pressure fluid from said source to said second and third chambers for producing one of the strokes of said tandem piston against the action of said pressure fluid in said first chamber, or relieving the pressure fluid in said second and third chambers for releasing the other stroke of said tandem piston under the action of pressure fluid in said first chamber.

4. A spray gun according to claim 3 in which said means for keeping said first cylinder chamber pressurized are check valve means on said outer head opening for pressure fluid flow from said second to said first cylinder chamber, said check valve means being provided by a resilient packing cup included in said outer head.

5. A spray gun according to claim 3 in which said passage means are provided in said stem portion.

6. A spray gun according to claim 3 in which said maneuvering valve has a first position adapted to cause said means controlled thereby to supply pressure fluid to all three of said cylinder chambers and a second position adapted to supply pressure to said first cylinder chamber only and to relieve the pressure in said second and third cylinder chambers.

Claims

1. A spray gun comprising a housing, nozzle means on said housing, means for supplying coating material under pressure to said nozzle means, a piston operating in said housing, a coating material valve mounted on an end of said piston within a first cylinder chamber for controlling the flow of such material through said nozzle means, a source of pressure fluid, an additional cylinder in said housing, a differential servo pistonhead connected to said piston at an end opposite to said coating material valve, said piston having an intermediate stem portion thereon sealing but slidably guided in said housing, said differential servo pistonhead being movable in said additional cylinder to perform alternately opening and closing strokes therein under the action of pressure fluid from said source for controlling said coating material valve, said differential servo pistonhead dividing said additional cylinder in a second cylinder chamber around said stem and a third cylinder chamber adjacent to said second cylinder chamber, a passage connected between said second and third cylinder chambers, a one-way valve means arranged in said passage for controlling the flowing of pressure fluid only in the direction from said third cylinder chamber into said second cylinder chamber, means for flowing pressure fluid from said source into said third cylinder chamber and from thence through said one-way valve means into said second cylinder chamber, a maneuvering valve, and means controlled by said maneuvering valve for either supplying pressure fluid from said source to said third chamber for producing said closing stroke of said servo piston head against the action of said pressure fluid in said first and second chambers, or relieving the pressure fluid in said third chamber for releasing said servo piston head for said opening stroke thereof under the action of pressure fluid in said first and second chambers.