US3752368A

US3752368A - Airless liquid spraying device

Info

Publication number: US3752368A
Application number: US00188140A
Authority: US
Inventors: H Robertson
Original assignee: Individual
Current assignee: Individual
Priority date: 1971-10-12
Filing date: 1971-10-12
Publication date: 1973-08-14
Anticipated expiration: 1990-08-14

Abstract

A liquid spraying device employs compressed gas to urge a piston to slide in a tank and pressurize the liquid contained therein. The liquid is forced through a trigger operated liquid release valve and flows through a tip for mechanical atomization. Compressed gas is admitted into the tank through a pressure control valve which opens momentarily when a connected pushbutton is depressed and closes automatically in response to build up of pressure in a back pressure area. A commercially availiable cartridge is the preferred source of compressed gas and is supported by a holder part of the device.

Description

United States Patent Robertson Aug. 14, 1973 AIRLESS LIQUID SPRAYING DEVICE Primary Examiner-Samuel F. Coleman [76] Inventor. Barry L. Robertson, 210 N. p

Angeleno Ave., Azusa, Calif. 91702 g 22 Filed: on. 12, 1971 21 Appl. No.: 188,140 1 ABSTRACT A liquid spraying device employs compressed gas to urge a piston to slide in a tank and pressurize the liquid (5i. 222/3256 contained therein The liquid is fumed through a [58] Fieid 386 5 389 ger operated liquid release valve and. flows through a .5 tip for mechanical atomization. Compressed gas is admitted into the tank through a pressure control valve 5 6] References Cited which opens momentarily when a connected pushbutton is depressed and closes automatically in response to UNITED STATES PATENTS build up of pressure in a back pressure area. A com- 2,026,046 12/1935 Krannak 222/389 mercially availiable cartridge is the preferred source of 2,8 l X compressed gas and is supported a holder pan of the 3,321,110 5/1967 Price v 222/389 (lama 3,237,814 3/1966 Collar..... 222/389 X 2,446,501 8/1948 Weber 222/389 12 Claims, 3 Drawing Flgures Z3 /4/ 5/ I g a V iw 2 (g g 7; w.

A212 l 50 51 5g 74 i 1 a /24 99 /97 i a c 96\ L if A25 2 Sheets-Sheet l INVENTOR. my??? 4 ROBERTSON ATTORNEY S Patented Aug. 14, 1973 2 Sheets-Sheet 2 mNQ & m y w y hww NN\ \N\ \I@ SQ w J Q@ wm AIRLESS LIQUID SPRAYING DEVICE BACKGROUND OF THE INVENTION 1. Field of the Invention: This invention relates to a spray gun device and particularly to a gass pressure powered liquid spray gun.

2. Description of the Prior Art: Spray guns adapted to spray paint and other liquids have used compressed gas to force the liquid through a nozzle. Typically such spray guns are connected by tubular lines to a compressor or other bulky source of compressed gas. The gas is mixed with the liquid and the mixture sprays out of the nozzle. When such spray guns are connected to cylinders of compressed gas the cylinders have to be large because the gas is expended while the liquid is being sprayed. Since these sources of compressed gas are bulky they are not readily portable and consume a lot of storage space while not in use. In addition to being bulky, the compressor is expensive and is therefore generally suitable only for industrial or professional use.

SUMMARY OF THE INVENTION In the present invention a piston is slidably disposed in a tank which stores liquid to be sprayed. The piston divides the tank into two fluid-tight regions, an upper region for storing liquid and a lower region for storing compressed gas.

A port is provided in the tank bottom so that gas can enter the second region. A base connected to the tank bottom has interior passageways connecting the port in the tank bottom to a pressure control valve. The interior passageway cooperates with the lower region to form a completely closed chamber for confining gas while the pressure control valve is closed. The pressure control valve when opened admits a pulse of gas and thereafter closes automatically so tht the admitted gas is confined in a closed chamber.

The admitted gas urges the piston to slide in the tank and thereby pressurizes the liquid. A port is provided in a removable tank cap for liquid pressure driven out of the tank by the action of the piston. A spray gun assembly connected to the tank has a trigger-operated liquid release valve for controlling the flow of liquid to a spray tip which mechanically atomizes the liquid by breaking up the liquid into very fine droplets for spraymg.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevation view of the gas pressure powered spray gun of the present invention with a portion of the tank broken away to show the internal piston;

FIG. 2 is a partially exploded, vertical sectional view of the spray gun of FIG. 1 with the base removed and a portion of the gun body broken away for simplicity of the drawing;

FIG. 3 is a horizontal cross section taken along the line 3-3 of FIG. 1.

DESCRIPTION FIG. 1 shows the preferred embodiment of the gas pressure powered spray gun in an upright position with its forward or spraying end on the left. A flat bottom cylindrical tank appears in partial vertical cross section.

A tank cap 5 is removable from the tank so that liquid to be sprayed can be poured therein. A piston is slidable in the tank and partitions the tank into an upper reservoir 11 for storing the liquid and a lower reservoir 12. An O-ring 16 carried in a peripheral groove in the piston seals the piston to the tank to separate the liquid in the upper reservoir 11 from compressed gas which is introduced into the lower reservoir 12 as described in detail hereinafter. The compressed gas urges the piston to slide upwardly in the tank and thereby pressurizes the liquid. As indicated in FIG. 2 the inside diameter of the tank is uniform throughout its length. This feature has several advantages. First, all the liquid is purged from the tank when the piston reaches the upper end of its travel and there is little waste. Second, clean-up is greatly simplified with substantially all the liquid dispensed. Third, a safety feature is achieved. This safety feature arises because of the force of the piston against the tank cap makes it practically impossible to handtwist the tank cap unless the pressure in the lower reservoir is released in a manner described hereinafter. Thus there is no danger of having the liquid splatter incident to removing the tank cap while the device is still pressure-powered.

A base connects to the flat bottom 13 of the tank by means of a base mounting bushing 71 (FIG. 2). Two O-rings l8 encircle the bushing 71 for sealing it to the tank and the base respectively. A plunger pushbutton 125 extends rearwardly from the rear vertical surface 74 of the base to provide for manual actuation of a pressure control valve to initiate an operating cycle described hereinafter. An elongated cylindrical holder 51 extends rearwardly from the rear surface 74 and is lo cated behind the pushbutton in the aspect of FIG. 1. I-Iolder 51 provides support for a self-contained source of compressed gas 50 (FIG. 3).

A spray gun assembly, indicated generally at 20, is supported by a crown 6 on a tank cap 5. Spray gun assembly 20 includes a body 21 which, in the preferred embodiment, is a cast aluminum, substantially L- shaped piece. An elongated block portion 22 and a hand grip portion 23 are joined by an integral intermediate curved portion 24. A pivot pin 26 extends through a transverse bore in a curved portion 24 and pivotally mounts a tripper 27 to the spray gun body.

An aluminum spray tip is provided for atomizing liquid to be sprayed. A tip retaining cap 112 supports the spray tip at the forward end of the block.

As shown in FIG. 2, a tiered bore extends longitudinally through the block 22 and is formed by three axially aligned bores. The first or forward bore 28f extends a relatively short distance into the forward end of the block. The second or rear bore 28r has a smaller diameter than the forward bore 28f and extends a relatively short distance into the rear end of the block. The third or intermediate bore 281' extends between the forward and rear bores and has a diameter intermediate the forward and rear bores. An annular surface 29 formed at the junction of the intermediate and rear bores and facing the forward end provides a seat for one end of a helical compression spring 61.

A transverse bore 33 in the bottom portion of the block extends upwardly to open into the intermediate bore 28i and is internally threaded to connect to a mating boss 8 on the tank crown 6.

An aluminum plunger in the bore 28 has an elongated cylindrical portion 35f slidably disposed in the intermediate bore to form a liquid release valve between the transverse bore 33 and the forward bore 28f.

An O-ring 37 disposed in a peripheral groove located near the forward end of the cylindrical portion 35f seals the plunger to prevent leakage out to the forward end while the liquid release valve is closed. Another O-ring 37 disposed in a peripheral groove located near the rear end of the cylindrical portion 35f seals the plunger to the bore to prevent leakage out of the rear end of the bore. An elongated rod 351' integral with and having a smaller diameter than the cylindrical portion 35f projects out of the rear end of the block. An annular rearwardly facing surface 38 is formed at the junction of the cylindrical portion and the rod. The helical compression spring 61 is coiled around the rod and acts against the annular surface 38 to urge the liquid release valve to its closed position. The rod is threaded at its rear end to connect to an adjusting nut 39 (FIG. 1).

Trigger 27 (FIG. 1) in the presently preferred embodiment is a cast aluminum generally fork shaped piece. Each tine 22 of the fork has a transverse bore through it near its upper end to admit the pivot pin 26 for pivotal connection of the trigger to the gun body. The rod portion of the plunger projects rearwardly out of the bore 28 and passes between the two tines. When the trigger is pulled toward the grip, the tines act against the adjusting nut 39 to pull the connected plunger rearwardly to open the liquid release valve. When the trigger is released, the compression spring urges the plunger to move forwardly to close the liquid release valve.

The tank cap 5, shown in vertical cross section in F IG. 2, is a cast aluminum piece. A cylindrical side wall portion 4 of the tank cap is internally threaded to connect to the tank. A top wall portion is disk shaped and provides a fiat bottom surface 2. A circumferential groove 9 inside the side wall bore is axially located adjacent to the flat bottom surface 2. An O-ring l7 disposed in a groove 9 seals the tank cap to the tank. An integral, cyindrical spacing boss portion of the crown 6 projects upwardly from th top wall to provide a spacer between the gun block and the tank. The cylindrical connecting boss 8 is integral with and axially aligned with the spacing boss but has a smaller diameter. The connecting boss is externally threaded to connect to the transverse bore 33 in the gun block. A central bore 7 provides a passageway from the tank to the liquid release valve.

The aluminum spray tip 100 includes an elongated cylindrical shell 10] defining a passageway for liquid to be sprayed. A flange 102 integral with the cylindrical shell and located at the rear end portion of the spray tip has an exterior, forwardly facing annular surface 103 and an interior tapered surface 104 leading to the passageway to form a funnel shaped entry. A tapered circumferential wall 105 integral with the shell forms a hollow truncated cone projecting in the direction liquid is to be sprayed. A disk portion 106 is joined at its periphery to the circumferential wall forming the truncated cone and has an aperture 107 at its center. A pair of aligned, radially extending ridges project outwardly from the disk 106 and each ridge has parallel trapizoidal side surfaces. End surfaces 1 10 of the two ridges define a V shaped opening with the apex of the V open at the aperture of the disk portion. It has been found that the best spray is produced when the V shaped opening subtends an angle of approximately 60.

The tip retaining cap 112 comprises a hollow cylin drical portion 113 which is internally threaded to connect to a tip mounting bushing l 14. A ring 1 15 integral with the cylindrical portion 1 13 has an interior annular surface which extends radially inwardly and abuts the outwardly spacing surface 103 of the flange of the spray tip.

The tip mounting bushing 114 comprises a central ring 117; an elongated cylindrical wall 118 which is integral with one side of the central ring and threads into the forward bore 28f; a cylindrical wall 1 19 which is integral with the other side of the central ring and threads into the tip retaining cap 112; and a circumferential end surface which is tapered to fit tightly against the funnel shaped entry to the spray tip. Two O-rings 127 are provided to seal the tip mounting bushing and prevent leakage of liquid.

The base mounting bushing 71 is similar in construction to the tip mounting bushing. One end of the base mounting bushing threads into an axial tap through the flat bottom of the tank and the other end threads into a tank mounting hole in the base. Two O-rings are provided to seal the base mounting bushing and prevent leakage of gas.

Base shown in cross section in FIG. 3 is a die cast aluminum piece. The upper surface of the base faces the bottom surface 13 of the tank and is rectangular. The tank mounting hole 72 is a blind bore extending downwardly into the base and is internally threaded to connect to the base mounting bushing 71. The rear end surface 74 of the base is rectangular. A base inlet bore 75 is a blind bore extending a relatively short distance forwardly into the base which provides an inlet passage for gas escaping from the source of compressed gas 50. The base inlet bore is parallel and closely spaced to the right side 76.

A valve mounting hole 77 is a blind bore extending a relatively long distance forwardly into the base to provide a mounting hole for a pressure control valve body 80. The valve mounting hole is parallel to and closely spaced to the left side 79 of the base. A bore 78 transverse to and intersecting the base inlet bore 75 and the valve mounting hole 77 provides a passageway for the gas to enter pressure control valve. A valve plug 89 in the right end of the bore 78 prevents the gas from escaping. A bore 81 parallel to the bore 78 extends from the right surface 76, intersects the tank mounting hole and opens into the valve mounting hole 77. The portion of the bore 81 extending between the valve mounting hole and the base mounting hole provides a passageway for the gas to reach the tank from the pressure control valve. The portion of the bore 81 extending to the right surface 76 of the base provides the passageway to a pressure release valve 82. A countersunk hole 83 at the exit point of the bore 81 provides a seat for the pressure release valve. A bolt 85 threads into a portion of the bore 81 and an O-ring 84 disposed in a countersunk hole provides a gas tight seal while the bolt is screwed in tight. The gas is released simply by turning the bolt to loosen the O-ring 84.

The valve body is a die cast aluminum piece. An elongated cylindrical intermediate portion 91 of the valve body is press fitted into the valve mounting hole 77. A pair of

circumferential grooves

92 and 93 are longitudinally spaced apart on the valve body. An 0- ring 94 disposed in the groove 92 seals the valve body to the base to prevent leakage from the high pressure area to the outside. Another O-ring 94 disposed in the groove 93 seals the valve body to the base to prevent leakage from the high pressure area to the low pressure area. The forwardly disposed portion 96 of the valve body is cylindrical and has a smaller outer diameter than that of the intermediate press fitted portion. The forward end of the valve body is spaced apart from the blind end of the valve mounting hole. An annular shoulder portion 95 of the valve body abuts the rear surface 74 to assure the spacing.

A longitudinal bore 97 extends through the valve body. A valve inlet port 98 is a radially extending borethrough the valve body and is spaced forwardly of the shoulder 95 so as to be in communication with the transverse bore 78. A valve outlet port 99 is a radially extending bore through the valve body and is axially located so as to be in communication with the transverse bore 81.

An elongated aluminum plunger is slidable in the longitudinal bore 97. An elongated rod portion 121 of the plunger has a smaller diameter than the diameter of the longitudinal bore 97. A pair of circular flanges 122 integral with the rod portion 121 are located at the forwardly disposed end of the plunger 120. An O-ring 123 is provided between the flanges 122 for sealing the plunger to the valve body while the pressure control valve is closed. An O-ring 124 is provided between two circular flanges 125 to seal the plunger to the valve body and prevent gas from leaking out the rear end. The O-ring 124 is axially spaced apart from the O-ring 123 by a distance somewhat greater than the distance between the valve outlet port 99 and the valve inlet port 98.

The plunger pushbutton 125 is attached to the plunger and is manually movable to abutment with a plunger retaining cap 126.

The pressure control valve is shown in FIG. 3 in its closed position. In this position the forward end surface 160 of the plunger is spaced apart from the forward end of the valve mounting hole and the O-ring 123 seals the plunger to the valve body at a point rearwardly of the valve outlet port. A back pressure area 73 communicates with the bore 81 leading to the tank mounting hole. Thus a completely closed chamber is formed which includes the lower reservoir 12 (FIG. 1) in the tank, the bore 81 and the back pressure area 73. A high pressure area 130 communicates with the source of compressed gas 50. High pressure gas introduced into the high pressure area 130 acts equally-against the facing sides of the flanges 1.23 and 124 and thus the plunger is in equilibrium.

When the plunger pushbutton is depressed to open the pressure control valve the plunger slides forwardly in the longitudinal bore 97 to place the valve outlet port 99 in communication with the high pressure area 130. Gas flowing out of the valve outlet port 99 folds 'around the outside of the forwardly disposed portion 96 of the valve body and re-enters the bore 97 through the port at the entry to the back pressure area 73. As the pressure builds up in the back pressure area 73 it develops a thrust against the surface 160 which serves as a piston surface and thereby causes the plunger to return to its closed position. Thus the pressure control valve provides a means having an operating cycle for admitting a pulse of gas into the lower reservoir 12 and a means for containing the pulse of gas admitted therein.

The holder 51 is a hollow aluminum cylinder having an externally threaded, axially bored connecting boss for connection to the base inlet bore. An O-ring 141 seals the holder to the base. A holder retaining cap 153 is removable from the holder so that a source of compressed gas can be inserted into the holder. Preferably the source 50 is one of the commercially available cylindrical pellets or cartridges of compressed gas. Such pellets have a generally cylindrical body tapering into a nose and have a thin metal cap covering the nose. In one type of pellet the compressed gas is pressurized into about 5000 psi.

A puncture pin is provided for puncturing the thin metal cap of the pellet. Pin 150 has a portion press fitted into the axial bore of the connecting boss 140, a rim flange abutting the interior end surface of the holder, and a conical portion extending into the holder. An axial passageway through the pin 150 provides a path for gas flowing into the base inlet bore 75.

A hand operated plunger 155 is provided for forcing the pellet against the pin 150 so as to puncture the cap. An O-ring 156 seals the plunger to the inside circumferential walls of the holder. A feature of the holder is that it is long enough to accept either one of two standard size pellets. Also the O-ring 156 provides a gastight seal irrespective of which size pellet is used. I

The spray gun is prepared for use by assuring that the lower reservoir is not pressurized. To that end, pressure release valve 82 is opened. Now the tank cap can be removed with safety. The piston is then pushed toward the bottom of the tank. The piston has a cylindrical spacing skirtlSS, which prevents the piston from abutting the bottom of the tank. The skirt 15S serves two purposes. First, it acts as a guide to assure that the piston moves only in an axial direction. Second, it assures a minimum volume for the lower reservoir 12.

Liquid to be sprayed is then poured into the upper reservoir 11. Next the cap and spray gun assembly are reconnected. Now the pressure release valve 82 is closed and the operator screws in valve plug 89 if need be.

A pellet or cartridge is inserted into the holder and the plunger 155 is screwed in so that the pin 150 punctures the cap. The gas expands to fill the portion of the holder in front of the O-ring 156 which prevents the gas from escaping to the outside. The gas also flows through the puncture pin into the base inlet port and fills the bore 78 and the high pressure area 130.

The plunger pushbutton is then depressed. The pressure control valve responds by opening momentarily to admit a pulse or gas into the back pressure area 73 and the lower reservoir 12. The pressure increases in the back pressure area and develops a force (which is not countered balanced) against the forward end circular surface of the valve plunger. For a valve plunger having a we inch diameter end surface, a pressure of 150 psi develops 225 pounds of force and consequently the valve plunger moves back to its closed position even if the user continues to press against the pushbutton.

The compressed gas in the lower reservoir 12 acts against the piston to urge it upwardly and the piston responds by exerting a force against the liquid to pressurize it. Actuation of the trigger 27 opens the liquid re-' lease valve and the liquid flows at a relatively high pressure into the spray tip where it is atomized and sprays out.

As the contained volume of liquid is diminished by spraying, the piston slides upwardly and the volume displaced by the gas in the lower reservoir 12 increases.

Consequently the pressure decreases according to Boyle's Law. in one embodiment of the invention the volume displaced by the contained gas when the piston skirt abuts the bottom of the tank is about 10 cubic inches. The volume displaced when the piston abuts the inside surface of the tank cap is about 50 cubic inches. Thus the pressure drops from about 150 psi to 30 psi which is still substantially higher than atmospheric pressure. Of course, this pressure can be increased again as desired simply by pushing the plunger pushbutton.

After the liquid is depleted, the pressure release valve is opened and the gas escapes from the lower reservoir 12. Now the tank cap can be safely removed and another load of liquid can be poured into the tank to prepare for further spraying. Pushing the plunger pushbutton again repressurizes the spray gun.

A feature of the preferred embodiment resides in the fact that an exhausted cartridge is replaceable: without affecting the pressure in the lower reservoir. Consider for example the situation wherein it is desired to increase the pressure in the lower reservoir but the cartridge in the holder is exhausted or substantially so. To handle this situation, the operator unscrews the valve plug 89 to release the residual pressure on the inlet side of the pressure control valve. With the pressure control valve closed, the pressure in the lower reservoir is unaffected. Then the operator screws the valve plug 89 back in; installs and punctures a new cartridge; and then pushes the plunger pushbutton.

it should be noted that a number of modifications can be made to the above described preferred embodiment within the scope of the present invention. For example, the base can be provided with an adapter for connecting to a source of compressed gas other than a cylindrical pellet.

As another example the pressure control valve can be modified for automatic operation in maintaining a substantially constant pressure in the lower reservoir. To that end a compression spring can be installed in the longitudinal bore 97. between the flanges 125 and the cap 126 so as to urge the valve toward an open position. In operation so long as the pressure in the lower reservoir remains sufficiently high the valve remains closed by virtue of the force developed from back pressure. As soon as the back pressure drops below a predetermined amount, the urging force of the compression spring will cause the valve to open momentarily to admit a pulse of gas.

It should also be noted taht the base assembly 70 of FIG. 3 can be used to pressure-power portable cans of the type used commercially for hair sprays and the like. Such a use has the advantage that such cans can be reuseable and the waste incident to the disposal of such cans is eliminated.

I claim:

1. A gas pressure powered device for dispensing liquid, which comprises:

a tank having a first port and a second port;

a piston slidable in the tank and partitioning the tank into a first reservoir and a second reservoir, the first reservoir for storing liquid and being in liquid flow communication with the first port, the second reservoir for storing gas and being in gas flow communication with the second port;

first means having an operating cycle for admitting a pulse of pressurized gas into the second reservoir,

the first means including a gas controlvalve in gas flow communication with the second port for admitting the pulse of gas when opened and coope rating with the second reservoir when closed to from a gas-tight ciosed chamber for containing the admitted gas, the contained gas urging the piston to slide in the tank, the gas control valve including a member movable to start the operating cycle by opening the valve and having a surface against which the admitted gas develops a force to move the member to close the valve thereby terminating the operating cycle;

second means including a liquid control valve in liquid flow communication with the first port for spraying liquid driven out of the first reservoir when the liquid control valve is opened.

2. A device according to claim 1 including a pressure release valve openable to release the contained gas from the closed chamber while the gas control valve is closed.

3. A device according to claim 1 wherein the first means comprises a base connected to the tank and supporting the gas control valve, the device further comprising a holder connected to the base for holding a cartridge of compressed gas, a gas flow channel in the base for directing gas escaping from the cartridge into the lower reservoir while the control valve is open; and means for puncturing the cartridge to permit the gas to exit therefrom.

4. A device according to claim 3 wherein the volume of the closed chamber increases as the liquid is sprayed and the piston slides in the tank; and including means for limiting the minimum volume of the closed chamber such that the ratio of the minimum to the maximum volume of the closed chamber is sufficient to assure that the pressure of the gas admitted into the chamber remains substantially above atmospheric pressure.

5. A device according to claim 4 including means for assuring a minimum volume of the second reservoir.

6. A device according to claim 1 wherein the second means includes a spray tip for atomizing the liquid flowing through it when the liquid control valve is opened.

7. A device according to claim 6 wherein the spray tip has a V-shaped opening subtending an angle of about 8. A device according to claim 1 including sealing means around the periphery of the piston for sealing the piston to the tank to separate the gas in the second reservoir from liquid in the first reservoir.

9. A device according to claim 8 including a flat bottom removable tank cap having the first port therethrough and wherein the inside periphery of the tank is uniform along its length to permit the piston to slide into abutment with the flat bottom.

10. A device according to claim 1 wherein the gas control valve comprises a valve housing having a bore therein, an inlet port for admitting gas into the bore, an outlet port for admitting into the second reservoir gas flowing through the bore, and a return port communicating with the outlet port to readmit the gas into the bore; and wherein the movable member is a plunger piston that in response to manually applied pressure slides in the bore to open the valve and that defines said surface, the readmitted gas developing the thrust to close the valve.

11. A device according to claim 1 and including a base connected to the tank and supporting the gas control valve, a first flow channel in the base for directing gas flowing out of the gas control valve and into the lower reservoir; a second flow channel in the base for directing gas flowing into the gas control valve; a pressure release valve openable to release the contained gas from the closed chamber while the gas control valve is closed; and a valve openable to release gas from the second flow channel while the gas control valve is closed and thereby not affecting the pressure in the closed chamber.

12. A device according to claim 1 wherein the gas control valve comprises a valve housing having a bore therein through which said movable member moves, an inlet port in the housing transverse to the bore for admitting gas into the bore, an outlet port in the housing transverse to the bore providing for gas to flow out of the bore during the operating cycle, and a return port communicating with the outlet port to readmit the gas into the bore; and wherein the movable member is an elongated plunger piston slidable in the bore to open and close the valve so as to admit the pulse of gas into the second reservoir, the plunger piston defining said surface at one of its ends facing the return port and the readmitted gas developing the thrust to close the valve and terminate the operating cycle. i i i i l UNETED STATES PATENT OFFICE (IERTENCATE OF CORRECTKON Patent No. 3,752,368 Dated August 14, 1973 Inventor(s) Harry L. Robertson it is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Abstract line 10, availiable" should be --available- Column 1, line 2, "gass" should be --gas-- line 37, "tht" should be --that-- Column 3, line 19, "22" should be --32-- line 39, "th" should be --the-- Column 6, line 50, "or" should be ---of-- Column line 50, "taht" should be -thet- Column 8 line 1-, "from should be --form--. 7

(Claim 15 I Signed and sealed this 25th day of December 1973.

(SEAL) Attest: v

EDWARD M.PLETCHER,JR. RENE D. TEG'ISMEYER Attesting Officer Acting Commlssloner of Patents

Claims

1. A gas pressure powered device for dispensing liquid, which comprises: a tank having a first port and a second port; a piston slidable in the tank and partitioning the tank into a first reservoir and a second reservoir, the first reservoir for storing liquid and being in liquid flow communication with the first port, the second reservoir for storing gas and being in gas flow communication with the second port; first means having an operating cycle for admitting a pulse of pressurized gas into the second reservoir, the first means including a gas control valve in gas flow communication with the second port for admitting the pulse of gas when opened and cooperating with the second reservoir when closed to from a gas-tight closed chamber for containing the admitted gas, the contained gas urging the piston to slide in the tank, the gas control valve including a member movable to start the operating cycle by opening the valve and having a surface against which the admitted gas develops a force to move the member to close the valve thereby terminating the operating cycle; second means including a liquid control valve in liquid flow communication with the first port for spraying liquid driven out of the first reservoir when the liquid control valve is opened.

7. A device according to claim 6 wherein the spray tip has a V-shaped opening subtending an angle of about 60*.

8. A device according to claim 1 including sealing means around the periphery of the piston for sealing the piston to the tank to separate the gas in the second reservoir from liquid in the first reservoir.

12. A device according to claim 1 wherein the gas control valve comprises a valve housing having a bore therein through which said movable member moves, an inlet port in the housing transverse to the bore for admitting gas into the bore, an outlet port in the housing transverse to the bore providing for gas to flow out of the bore during the operating cycle, and a return port communicating with the outlet port to readmit the gas into the bore; and wherein the movable member is an elongated plunger piston slidable in the bore to open and close the valve so as to admit the pulse of gas into the second reservoir, the plunger piston defining said surface at one of its ends facing the return port and the readmitted gas developing the thrust to close the valve and terminate the operating cycle.