US3018968A - Closed system recirculating assembly - Google Patents

Description

Jan. 30, 1962 G. s. LEVEY CLOSED SYSTEM RECIRCULATING ASSEMBLY 4 Sheets-Sheet 1 Filed Nov. 17, 1959 INVENTOR. GUSTAVE 5. LEVEY Jan. 30, 1962 e. s. LEVEY I 3,018,968

CLOSED SYSTEM RECIRCULATING ASSEMBLY Filed Nov. 17, 1959 4 Sheets-Sheet 3 INVENTOR. GUSTA V5 5- ZEVEY BY PIC/IE Y, MSNENNYJ FARR/N6 7' ON W 4/ A 770 NEYS Jan. 30, 1962 G. s. LEVEY 3,018,968

CLOSED SYSTEM RECIRCULATING ASSEMBLY Filed Nov. 17. 1959 4 Shets-Sheet 4 um)" 11: ER

IN V EN TOR.

61/5734 V5 5- LEVEY "3 Q BY IP/C H MSNEN/V :44 FA REV/VG TON ,4 77' OFNEYS United States Patent M 3,018,968 1 CLOSED SYSTEM RECIRCULATING ASSEMBLY Gustave S. Levey, Houston, Tex., assignor to The Spee- Flo Manufacturing Corporation, Houston, Tex., a corporation of Texas Filed Nov. 17, 1959, Ser. No. 853,638 8 Claims. (Cl. 239-124) This invention relates to liquid distribution and more particularly to a closed circuit spray painting system including a piston pump and a paint heater.

Recent developments in the spray painting field have resulted in the use of a device for heating the paint which is being conducted to the spray gun. The advantages of paint heating with respect to savings in solvent costs and the like are generally understood. In spray painting the dispensing of paint through the spray gun is usually an intermittent procedure and whenever the trigger on the spray gun is released so that the syray is not operating, the paint being circulated through the gun is returned to the paint supply. It is manifestly undesirable to raise the temperature of the entire paint supply in the barrel or tank which is being used and numerous expedients have been proposed to prevent the hot paint from the spray gum from being mixed with the main paint supply. The prior art efforts to solve this problem have included the use of two pumps, one pump for removing paint from the main supply and the other pump for recirculation of hot paint.

Difierent types of pumps have been used for withdrawing paint from the paint supply and pumping it through the paint heater to the spray gun. One of the most efficient types of pump for pumping paint is the airoperated cylinder and piston pump wherein a quantity of paint is discharged from the pump on both strokes of the piston in the cylinder.

Referring particularly to the pumping strokes in the pump of the type here referred to, a cylinder is provided with a paint inlet check valve at the bottom of the cylinci 40 der and a paint discharge port at the top. A piston an piston rod is reciprocated in the cylinder. The volume of the piston rod is proportioned with respect to the volume of the cylinder so that when the piston and piston rod are moved to the bottom of the cylinder adjacent the inlet, the piston and piston rod displace half of the paint contained in the cylinder. This results in one-half of a cylinder full of paint being discharged on the downstroke of the piston. When the piston and piston rod are moved upwardly, the check valve in the piston is closed and that quantity of paint above the piston is discharged from the pump. This quantity corresponds to one-half of the cylinder full of paint.

On the last-mentioned up stroke of the piston the check valve at the inlet of the pump is opened so that the cylinder is filled with paint and is ready for the next downstroke of the piston. The over-all result of this operation is that one-half of a cylinder full of paint is discharged on each of the up and down strokes of the pump. It is only on the up-stroke of the pump, however, that paint is drawn into the cylinder and the quantity being drawn into the cylinder is twice the quantity being discharged from the pump on the same stroke.

The problems presented by the use of such a pump in a paint system having a paint heater grow out of the fact that when the spray gun is closed paint is being returned toward the pump on each stroke of the pump. This is true regardless of the direction of the stroke of the piston. Since the cylinder of the pump is filled with paint only on the up-stroke of the pump, this means that the difference in volume between the hot paint returning to the pump and the ability of the pump to receive paint must be reconciled. The return volume is one-half a cylinder 3,018,963 Patented Jan. 30, 1962 full each stroke but the pump intake is limited to one cylinder full every other stroke.

It is among the objects of my invention to provide a closed circuit liquid distribution device having a main supply of liquid which is being pumped to a dispensing device by a single cylinder piston pump which discharges liquid at each stroke of the piston and wherein the system includes a return line and a secondary liquid reservoir constructed and arranged so that the returning liquid is isolated with respect to the main supply of liquid in the main reservoir.

It is a further object of my invention to provide a closed circuit paint distribution system including a pump, a paint heater and a spray gun and wherein a return line is provided from the spray gun back to the pump so as to maintain a continuous circulation of the heated paint and wherein the pump is characterized by a single cylinder and a piston which is reciprocated in the cylinder and which discharges substantially the same quantity of paint from the pump on each up and down stroke of the piston in the cylinder and wherein the pump inlet is connected to the main supply of paint and also to a reservoir for re ceiving heated paint coming from the spray gun on said return line.

It is a further object of my invention to provide a closed circuit paint distribution system comprising a main reservoir of paint, a single cylinder piston pump constructed to discharge substantially the same quantity of paint on the up and down stroke of the pump and wherein said pump inlet is connected to a secondary reservoir and wherein a line is provided for leading paint through a heater to a spray gun and a second line is provided leading paint from the spray gun back to said secondary reservoir and wherein said secondary reservoir is connected to the main supply of paint to supplement the paint in the secondary reservoir to make up for paint being used and, at the same time, prevent hot paint being returned to the pump from being mixed with the paint in the main supply.

It is a further object of my invention to provide a liquid distribution system having a pump characterized by continuous output and intermittent intake and wherein the pump is connected to a main supply of liquid and a secondary supply and wherein the secondary supply is liquid returned to the pump from a liquid dispensing device.

Further objects and advantages relating to low cost of manufacture, efiiciency' in operation and economies in use will appear from the following description and the appended drawings wherein:

FIG. 1 is a diagrammatic showing of a liquid distribution system made according to my invention;

FIG. 2 is an enlarged elevation with parts in section showing the pump with the piston on a down stroke and the reservoir ring at the base of the pump made according to my invention;

FIG. 3 is an elevation with portions in section similar to FIG. 2 but showing the piston of the pump on the upstroke;

FIG. 4- is a perspective view of the lower portion of the pump and the reservoir ring made according to my invention;

FIG. 4a is a perspective view with parts in section to illustrate the three-way connection forming a part of the reservoir ring at the base of the pump;

FIG. 5 is a diagrammatic perspective view showing the lower portion of the pump and the reservoir ring illustrating by legend the hot and cold bodies of paint in the reservoir ring;

FIG. 6 is a view similar to FIG. 5 illustrating the displacement of cold paint by hot paint being returned from the spray gun;

FIG. 7 is an elevation of a wall-mounted pump and liquid distributing system according to my invention;

FIG. 8 is an enlarged section showing of a modification of the secondary reservoir which is suited for use with the wall-mounted pump of FIG. 7;

FIG. 9 is a diagrammatic showing of a liquid distributing system for handling liquid resin;

FIG. 10 is a sectional view of a modified form of my invention; and

FIG. 11 illustrates a further modification wherein paint at high pressure is distributed to several locations in a factory.

Referring to the drawings, a container such as a barrel 6 is provided with a quantity of paint indicated at 7 and, for purposes of the description here, the container 6 and the quantity 7 will be referred to as the main reservoir of paint. The container 6 is provided with a cover 8 upon which is carried the pump assembly indicated in its entirety as at 10. The pump assembly includes an airoperated motor 11 and a paint cylinder 12 within which a piston is reciprocated by piston rod 13. The pump casting 14 mounted on the cover 8 includes a discharge port 15 and an inlet port 16. A line 17 conducts the paint being pumped to a paint heater 18 and thence through line 19 to the spray gun indicated at 20. Preferably the heater 18 is an electric heater having lines 1811 connected to an electric power line.

An air line 21 is connected to the pump motor 10 and an air line 22 is connected to the spray gun 20.

The details of the air motor 11, the paint heater 18 and the spray gun form no essential part of my invention and may be of any conventional type.

A return paint line 23 conducts paint from the spray gun to the inlet port 16 on the pump 10 and such return paint is led downwardly through a conduit 24 and connecting conduit 25 to a connector block 26 forming a part of the secondary reservoir indicated in its entirety as at 27.

In the normal operation of the assembly of FIG. 1 the piston rod 13 is reciprocated and pumps paint upwardly through a discharge pipe 28 to the discharge port 15, thence through line 17 through the paint heater where the paint is heated and thence through line 19 to the spray gun 20. Assuming the spray gun is intermittent-1y operated by means of the trigger 30, some of the paint will be discharged .in the form of a spray 31. When the trigger 30 is released, however, the unused paint will be returned in the direction of the arrows 32 through the line 23 to the inlet port 16. It is desirable to retain the paint which is heated and recirculate the hot paint rather than to mix the hot paint'being returned to the pump with the cold paint in the main reservoir 6. The recirculation prevents gravity separation in the paint.

The pump construction includes the cylinder 12 which is threaded at its lower end as at 33 into an inlet member 34 provided with a ball 35 which functions as an inlet check valve in the inlet seat 36. The lower end of the member 34- is provided with an inlet opening 37 and a screen 38 is mounted across the opening. The member 34 is secured within a hollow casing 39 by means of locking screws 40 which maintain the lower face of the member 34 spaced from the bottom plate 41 of the housing 39. The interior of the housing 39 is connected by means of a pipe 42 to the connector block 26. The hot paint return line 25 is connected to the connector block 26 at its upper face and the open end of the ring 43 is also connected to the connector block at a vertical face at right angles to the face receiving the pipe 42.

The ring 43 is interrupted at the connector block and one end only of the ring chamber opens into the connector block 26. The other end of the ring chamber is closed and is welded to a flat face of the block so as to form a continuous ring. The closed end of the ring 43 is notched as at 45 and in this way the circular chamber within the ring-43 is opened to the main supply of paint in the reservoir 6.

The upper end of the piston rod 13 is connected as at 46 and 47 to the piston rod 48 in the air motor 10. The lower end of the piston rod 13 is provided with a bore which is internally threaded as at 49. A piston 50 is exteriorly threaded at one end to be connected to the piston rod 13 by means of the threads 49. The piston 50 has an interior bore 51 throughout its length and a valve seat 52 at the upper end thereof adapted to be closed by a ball check valve 53. The piston rod is provided with lateral bores 54 so that on the down-stroke of the piston, as illustrated in FIG. 2, the paint in the cylinder 12 moves upwardly through the piston bore 51 past the ball check valve 53, out through ports 54 and thence into chamber 55 leading to the discharge pipe 28.

The diameter of the piston rod 13 is such that when the piston 50 and piston rod 13 reach the bottom of the stroke within the cylinder 12, the piston and piston rod displace half of the volume at the interior of the cylinder 12. This means that half of one cylinder full of paint has been moved through the chamber 55 and thence to the discharge pipe 28 and the other half of the cylinder full of paint is within the cylinder above the piston 50. In FIG. 2 the piston 50 and piston rod 13 are being moved down in the direction of the arrow 57 which means that the ball check 35 has closed the inlet port of the pump at 36 and the paint is being transferred through the bore 51 of the piston. On the upstroke of the pump, as illustrated by arrow 58 in FIG. 3, the piston ball check 53 is seated on the port 52 so that the paint above the piston 50 is being moved outwardly through chamber 55 to the discharge pipe 28. The volume being moved above the piston is one-half of a cylinder full of paint and on the upstroke of the piston the ball check 35 is lifted from its seat 36 so that paint from the interior of the chamber 39 moves up into the cylinder 12.

In the view of FIG. 5 the legend X indicates hot paint and the legend 0 indicates cold paint. The hot paint is being returned to the block 26 in the direction of the arrow 59. A cylinder full of hot paint has been drawn up into the cylinder 12 in the direction of arrow 60. The quantity of hot paint being moved down into the block 26 by way of the pipe 25 is one-half of a cylinder full of paint. Accordingly one-half of a cylinder full of hot paint moves in the direction of the arrow 61 from the ring 43 into the connector block 26 and thence through pipe 42 into the cylinder 12. It will be noted that this is hot paint in the ring 43 adjacent the connector block 26 and as this hot paint moves around the ring 43 and into the cylinder 12 cold paint comes in through the notches 45 to fill the ring. At the end of the up-stroke of the piston the line between the hot paint and the cold paint in thze ring 43 may be about at the point indicated by arrow 6 On the down-stroke of the piston 50 no hot paint moves through the pipe 42 into the pump. Hot paint, however, is being returned to the connector block 26 during the time of the down-stroke by way of the pipe 25. Since this hot paint cannot go into the pump by Way of line 42, it moves outwardly through the ring 43 and pushes the cold paint back to a point such as indicated by arrow 63. Thus the ring 43 serves as a secondary reservoir to store hot paint that cannot be accommodated by the pump. Such hot paint is stored in a chamber which isolates the hot paint from the cold paint in the main reservoir.

A modification of the liquid distributing system is illustrated in FIGS. 7 and 8 wherein the main paint reservoir is indicated at 75 and a secondary paint reservoir is indicated at 76. In this form of the invention the pump is of the wall-mounted type and the pump is connected to the paint reservoir 75 by a line 77 and pipe 78 apertured at 79 to withdraw paint 80 from the reservoir 75. This modification includes the air motor 81 having air line 82 elfective to reciprocate a piston rod 83 within a paint pump cylinder 84. In this form of the invention the casting at the base of the air motor 81, as indicated at 85, is provided with a discharge port 86 connected to a discharge line 87 coming from the pump. The paint line 88 leads from the port 86 through the heater .89, thence through line 90 to the spray gun indicated in its entirety as at 91. A return line 95 leads from the spray gun 91 to the secondary reservoir 76.

The base of the pump cylinder 84 is connected to an inlet member 96 which is provided with a ball check 97 constructed and arranged substantially as in the preferred embodiment. The secondary reservoir 76 is provided with a cold paint chamber '98 which has an opening in its upper wall as at 99 leading into a hot paint chamber 100. The cold paint line 77 coming from the main reservoir opens into the chamber 98 and the hot paint line 95 coming from the spray gun opens into the hot paint chamber 100. I The hot paint chamber is provided with a floating wall member 101 which is normally biased by spring 102 toward the pump inlet member 96. The floating wall member 101 is apertured as at 103 and this aperture is normally closed by a flat check plate 104.

In the modification of FIG. 7 the air motor 81 and the paint pump are constructed and arranged substantially as in the preferred embodiment. The hot paint returning from the spray gun 91 enters the chamber 100 and, assuming that the piston is moving on its down-stroke, the incoming hot paint will move the floating wall 101 downwardly against the bias of the spring 102. This will move cold paint underneath the floating wall 101 down through the opening 99 and thence back through the line 77 toward the main paint reservoir '75. When the piston in the cylinder 84 moves on its up-stroke drawing paint into the cylinder, the floating wall 101 will move upwardly and, if there is insufficient hot paint in the chamber 100 to fill the cylinder 84, cold paint will be moved upwardly through the opening 103 to supplement the paint supply in the secondary reservoir 76.

Although two forms of my invention have been described in connection with the distribution of paint, I am aware that my apparatus is well suited for the handling of other liquids.

In FIG. 9 I have illustrated my invention as used in connection with the distribution of liquid resin. In this modification the main reservoir 110 contains a supply of liquid resin such as an epoxy resin suited for fiber glass molding. The reservoir 110 is provided with a. pump assembly 112 corresponding substantially to that described in connection with the form of FIG. 1. A pump discharge line 113 leads to a catalyst adding device 114 constructed to add a catalytic agent to the resin being pumped through line 113. A dispensing station as at 115 is arranged with a valve 116 for dispensing the treated liquid resin to a molding device indicated at 117. When the valve 116 is closed at the dispensing station the liquid resin and catalyst therein is returned through line 118 through a cooling device 119 and thence back to the pump 112. It will be understood that the resin having the catalyst added is thereupon recirculated without being mixed with the resin supply in the container 110.

A system such as that illustrated in FIG. 9 is also suited for the handling of liquid foods wherein flavors, or other additives, are supplied in the recirculating system and where the modified liquids are to be isolated from the main liquid supply.

In FIG. of the drawings a modified form of installation using the wall-mounted pump is shown. This form is distinguished over the form illustrated in FIG. 7 in two respects, namely, the paint reservoir in the form of FIG. 10 is below the wall-mounted pump whereas in the form of FIG. 7 the paint container is above the foot valve of the pump. In the form of FIG. 7 a floating check valve assembly is contained within the housing 76 and the housing 76 is proportioned to serve as a-reservoir for the hot paint returned from the spray gun. In the form of FIG. 10, however, this type of reservoir at the foot valve of the pump is dispensed with and the paint supply line and the return line are connected to a T- connection at the foot valve of the pump.

Referring particularly to FIG. 10, the bulk container for the paint indicated at 200 is fitted with a cover 201 having a vent 203 and a pipe 204 apertured at its lower end as at 205 so as to permit the withdrawal of paint from the container 200. A line 206 leads upwardly from the container 200 to a T-fitting 207. The return line 208 from the spray gun is also connected to the T- fitting 207. The upper end of the T-fitting 207 is interiorly threaded to receive the foot valve 209 and the pump 210. In this form of the invention the line 206 serves as a reservoir for the paint which is being returned by way of line 208 during that phase of the pump operation wherein the paint coming from the spray gun exceeds the paint being withdrawn through the foot valve 2-09 by the pump 210.

The heated paint is characterized by a lower density than the cold paint in the container 200 and accordingly is maintained in the line 206 by the difference in gravity between the hot paint and the cold paint. Cold paint may move in and out of holes 205 as the volume of hot paint in the line 206 varies.

The installation embodying my invention shown in FIG. 11 is one suited for a factory paint system having several outlets at diiferent locations in the factory buildings.

The enclosure indicated at 300 represents a paint room having a large paint storage tank 301 in which paint is under pressure by means of the pump 302 and motor 303. The pressure applied to the paint in container 301 is a pressure considerably higher than that suited for use in paint spraying and such high pressures are desirable to facilitate distribution to various points throughout the plant where the paint is being used. The points of use may be at different elevations.

A main supply line 304 leads from the reservoir 301. The line 304 is tapped by various installations indicated by the branch lines 305, 306 and 307. A regulator 300 is connected in the line 305 so as to direct the paint along the regulator outlet 309 at a lower pressure than that at the inlet side of the regulator. It will be understood by those. skilled in the regulator art that the regulator 308 functions like a check valve in that it prevents flow from the low pressure side 309 to the high pressure side 305. A line 310 connects the line 309 carrying the paint from the regulator to a T-fitting 312. A tank 313 is connected as at 314 to the T-fitting 312 and a quantity of paint indicated at 315 is shown within the tank 313. The chamber within the tank 313 above the level of the paint 315 is indicated at 316 and this chamber contains air under pressure caused by the rising paint level in the tank 313.

A line 3117 leads from the fitting 312 into a fitting 318 mounted at the base of the foot valve 319 on the pump 320. The fitting 318 is also connected to the return line 321 leading from the spray gun 322. The pump 320 is operated by a motor illustrated at 323 and the output line of the pump 324 leads to the paint heater 325 and thence through hose 326 to the paint spray gun 322. The line 327 represents the air line operating the motor 323. The container 313 provides storage for hot paint returning from the spray gun, when such paint is not being drawn into the pump. The pump 320 corresponds in structure and mode of operation to the pump described in connection with the preceding forms. Accord ingiy on the down stroke of the pump the ball check valve within the foot valve indicated at 319 is closed and no hot paint is moving upwardly into the pumping cylinder of pump 320. During the down stroke of the pump, however, one-half of a cylinder full of paint is being moved to the spray gun 322 by way of the paint heater 325 and the lines 324 and 326. If the spray gun is closed and no paint is being used, however, this onehalf of a cylinder full of hot paint is being returned through line 321 into the fitting 318. Since the check valve within the foot valve 319 is closed, this hot paint returning by way of line 321 backs up through line 317 and into the container 313. On the next stroke of the pump (up stroke) more paint is being drawn into the pump cylinder of the pump 320 than is available by way of line 321 and accordingly one-half of a cylinder full of paint moves back into the pump from line 317 and the supply in container 313.

Although I have disclosed and described four forms of my invention in considerable detail, numerous modifications may be made therein without departing from the scope of the invention as defined in the following claims.

What is claimed is:

l. A paint distribution system comprising a container holding a quantity of paint, a cover for said container, a pump mounted on said cover, said pump comprising an air motor for reciprocating a piston rod, a paint cylinder immersed in the paint in said container, a piston in said cylinder connected to said piston rod, said piston having a check valve therein, a paint discharge port at the top of said piston, a paint reservoir at the bottom of said piston, a spray gun, a paint heater, a line connecting said pump outlet and said heater, a line connecting said heater and said spray gun, a return line connecting said spray gun and said reservoir, means connecting said reservoir to the paint supply in said container whereby one-half of a cylinder full of paint is discharged on each stroke of the piston and said cylinder is filled with paint on alternate strokes of the piston and heated paint coming from said spray gun is accommodated in said reservoir during the time that no paint is being drawn into the pump cylinder.

2. A paint distribution system comprising a container holding a quantity of paint, a cover for said container, a pump mounted on said cover, said pump comprising an air motor for reciprocating a piston rod, a paint cylinder in said container, a piston in said cylinder connected to said piston rod, said piston having a check valve therein, a paint discharge port at the top of said piston, a paint reservoir at the bottom of said piston, a spray gun, a paint heater, a line connecting said pump outlet and said heater, a line connecting said heater and said spray gun, a return line connecting said spray gun and said secondary reservoir, said piston and piston rod proportioned to displace half the volume of the cylinder and means connecting said reservoir to the paint supply in said container whereby one-half of a cylinder full of paint is discharged on each stroke of the piston and said cylinder is filled with paint on alternate strokes of the piston and heated paint coming from said spray gun is stored in said reservoir and isolated from the paint in the container.

3. A paint distribution system comprising a paint storage container, a pump assembly comprising an air motor for reciprocating a piston rod, a cylinder, a piston within the cylinder connected to said piston rod, an outlet at the top of said cylinder and an inlet at the bottom of said cylinder, conduit means connecting said outlet to a spray gun, a reservoir at the bottom of said cylinder, conduit means connecting said paint storage container to said reservoir, return conduit means connecting said spray gun to said reservoir, said pump inlet being in communication with the interior of said reservoir, said reservoir having means to prevent the paint returning from the top of said cylinder and an inlet valve at the bottom of said cylinder, a check valve in said piston, conduit means connecting said outlet to a spray gun, a reservoir at the bottom of said cylinder, conduit means connecting said paint storage to said reservoir, return conduit means connecting said spray gun to said reservoir, said pump inlet being in communication with said reservoir, movable means within said reservoir to prevent the paint returning from the spray gun being mixed with paint coming from said paint storage.

5. A liquid handling and distribution system comprising a container of liquid, a pump, said pump having a pumping cylinder and a reciprocating piston therein, a piston rod, motor means to reciprocate said piston rod and piston within said cylinder, said pump having an outlet, said pump having an inlet, said piston and piston rod having a volumetric displacement corresponding to halt the volume of said cylinder, a check valve in said pump inlet, a check valve in said piston whereby one-half of a cylinder full of liquid is discharged from said pump outlet on each reciprocation of the piston within the cylinder and one cylinder full of liquid enters said cylinder on alternate reciprocations of the said piston within said cylinder, said pump having a reservoir, said reservoir being connected to said main liquid supply at a first point, a liquid dispensing device, a liquid treating device, conduit means connected to said pump outlet and to said liquid treating device, conduit means connecting said liquid treating device to said dispensing device, return conduit means connecting said dispensing device to said reservoir at a second point spaced from said first point, said reservoir between said first and second points having a volume at least as great as one-half the volume of said cylinder whereby treated liquid returning from said dispensing device is isolated with respect to said main liquid supply and is recirculated, and whereby, as liquid is used at said dispensing device, liquid from said container is added through said reservoir.

6. A liquid distribution system comprising a main supply of liquid, a pump having a cylinder and a piston arranged to be reciprocated within the cylinder, means to reciprocate said piston, a check valve in said piston and a check valve for said cylinder effective to discharge onehalf of a cylinder full of liquid from the pump upon each stroke of the piston and draw one cylinder full into the cylinder on alternate strokes of the piston, a discharge line leading from said pump to a liquid dispensing device, a return line connected to said dispensing device, a secondary reservoir, means connecting said return line to said reservoir at one point, means connecting said reservoir to said pump cylinder check valve at a second point, means connecting said reservoir to said main supply of liquid at a third point, said reservoir being arranged to permit liquid flow from said first point and said third point toward said second point and to permit flow from said first point toward said third point, said reservoir having a volumetric capacity to receive between said first and third points a volume of liquid equal to the volume discharged by said pump on each stroke of the piston.

7. A liquid distribution system comprising a main supply of liquid, a pump having a cylinder and a piston arranged to be reciprocated within the cylinder, means to reciprocate said piston, a check valve in said piston and a check valve for said cylinder effective to discharge onehalf of a cylinder full of liquid from the pump upon each stroke of the piston and draw one cylinder full into the cylinder on alternate strokes of the piston, a discharge line leading from said pump to a liquid dispensing device, a return line connected to said dispensing device, a secondary reservoir, means connecting said return line to said reservoir at one point, means connecting said reservoir to said pump cylinder check valve at a second point, means connecting said reservoir to said main supply of liquid at a third point, said reservoir being arranged to permit liquid flow from said first point and said third point toward said second point and to permit flow from said first point toward said third point, said reservoir having a volumetric capacity to receive between said first and third points a volume of liquid equal to the volume discharged by said pump on each stroke of the piston and said reservoir having a smaller volume between said first and second points.

8. Means for spraying paint comprising a pump including a cylinder adapted to have its lower end immersed in a supply of paint, a piston rod reciprocaole through the upper end of said cylinder, a piston carried by said piston rod and having a check valve therein opening in the direction from the lower end of said cylinder toward the upper end thereof, the lower end of said cylinder having an inlet port with a check valve opening into the cylinder, means for reciprocating said piston rod to discharge paint on each stroke thereof and draw paint into the cylinder only on alternate strokes thereof, a paint discharge conduit opening into the upper end of said cylinder, a spray gun connected to said paint discharge conduit, a return conduit connecting said spray gun to said inlet port and a pipe connected to said return conduit adjacent the lower end of said cylinder and having an opening therein adapted to receive paint from said paint supply, the length of said pipe between said opening and its connection to said return conduit providing a volume at least as great as the volume of paint discharged on each stroke of said pump.

References Cited in the file of this patent UNITED STATES PATENTS

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