Pump and method of driving same

Abstract

A fluid transfer device such as a reciprocating pump, preferably of the diaphragm type suitable for use with an airless spray-gun for painting and the like, having a pumping side for the fluid to be pumped and a driving side driven through a piston through a solution or mixture of liquid and gas, such as oil and air. Under throttled or standby operation conditions, reduced diaphragm movement is accommodated without changing the piston stroke by reducing the volume of the driving liquid and by releasing gas from the reduced volume of liquid to prevent vaporization and condensation of the driving fluid itself. A dead space is provided on the pumping side allowing some diaphragm movement into the pumping side even when completely closed so that only a small proportion of driving liquid is released and only a small amount of gas is freed from the driving liquid to accommodate the reduced diaphragm movement during the full piston stroke. The loading and unloading of the driving fluid on the power and suction strokes of the piston is controlled so that the driving fluid is always above its vapor pressure. The gas is released from the driving liquid according to Henry's Law.

I claim as my invention: 
     
       1. A driven fluid pump device adapted to be throttled and stopped without throttling or stopping the driving input which comprises, means defining a pumping chamber and a .[.driven.]. .Iadd.driving .Iaddend.fluid chamber, a fluid propelling member separating said chambers, a driving fluid in said driving fluid chamber actuating said member and composed of liquid and gas, driving means for alternately pressure loading and unloading said driving fluid, means for releasing some of said driving fluid when loaded above a predetermined pressure to provide a reduced driving volume for reduced actuation of said propelling member, and means maintaining minimum pressure on the driving fluid above the vapor pressure of said fluid whereby any expansion of the reduced driving volume upon unloading will be accommodated by the remaining liquid and gas released therefrom. 
     
     
       2. The device of claim 1 wherein the driving fluid is a liquid having a gas dissolved therein which is released therefrom according to the law of Henry. 
     
     
       3. The device of claim 2 wherein the liquid is a lubricant and the gas is air. 
     
     
       4. The device of claim 1 wherein the fluid propelling member is a diaphragm. 
     
     
       5. The device of claim 1 wherein the driving means is a piston. 
     
     
       6. The device of claim 5 wherein the piston has a uniform stroke. 
     
     
       7. The device of claim 5 wherein the piston is driven by an eccentric member. 
     
     
       8. The pump device of claim 1 wherein the fluid propelling member receives pumpage on one side and said driving fluid on the other side.Iadd., the pumping chamber has a dead space on the pumpage side .Iaddend.and an inlet valve controls flow of pumpage to .Iadd.thereby .Iaddend.maintain .[.a.]. .Iadd.said .Iaddend.space on the pumpage side of said fluid propelling member accommodating movement of the member to lessen reduction of the driving volume of said driving fluid during standby operation when no flow of pumpage occurs. 
     
     
       9. The device of claim 8 wherein the fluid propelling member is a diaphragm having a pumpage chamber on one side and a driving fluid chamber on the other side, an inlet valve controls flow of pumpage into the pumpage chamber, a check valve controls flow out of the pumpage chamber, and said two valves cooperate to prevent the pumpage chamber from being completely filled to maintain .[.a.]. .Iadd.said .Iaddend.dead space .[.of.]. .Iadd.for .Iaddend.compressible fluid accommodating movement of the diaphragm into the pumpage chamber during throttling or stopping of the pumping. 
     
     
       10. The device of claim 1 including a supply chamber for driving fluid and a spring loaded valve controlling release of driving fluid to said supply chamber. 
     
     
       11. The device of claim 10 wherein a passageway selectively connects the supply chamber with the driving fluid chamber ahead of the driving means for replenishing said chamber. 
     
     
       12. A driven pump adapted to be throttled or stopped without throttling or stopping the driving input comprising a housing defining a pumping chamber and a driving liquid chamber, a fluid propelling .Iadd.diaphragm .Iaddend.member separating said chambers, driving means acting on liquid in the driving liquid chamber to actuate said propelling member for pumping fluid through the pumping chamber, a relief valve controlling maximum pressure in said driving liquid chamber and releasing excess liquid from the chamber to accommodate throttled movement of the diaphragm, and means controlling the driving means to maintain pressure on the remaining liquid in the driving liquid chamber above the vapor pressure of the liquid. 
     
     
       13. The pump of claim 12 having a source of driving liquid containing gas dissolved therein communicating with said relief valve to receive excess driving liquid from the driving liquid chamber, and means connecting said source with the driving liquid chamber to replenish the chamber whenever pressure therein is below the pressure of the source. 
     
     
       14. The pump of claim 12 wherein the pumping chamber is fed through an inlet valve biased to closed position to maintain a dead space accommodating movement of the fluid propelling member into the pumping chamber even when the chamber is closed. 
     
     
       15. The pump of claim 12 wherein .[.the fluid propelling member is a diaphragm and.]. the driving means is a constant stroke piston. 
     
     
       16. A driven diaphragm pump adapted to be throttled and stopped without throttling or stopping the driving input which comprises a housing having a diaphragm chamber, a diaphragm in said housing spanning said chamber and dividing the chamber into a pumping chamber .Iadd.having a dead space .Iaddend.and an opposed driving liquid chamber, a spring biased inlet valve for admitting pumpage to said pumping chamber, an outlet valve controlling flow of pumpage from said pumping chamber, a source of lubricating liquid having air dissolved therein, means bleeding liquid from said source to said driving chamber, a relief valve controlling flow of liquid from the driving chamber back to the source, a piston acting on liquid in said driving chamber to load and unload said liquid for reciprocating said diaphragm to draw pumpage through the inlet valve into said pumping chamber and to discharge pumpage from the pumping chamber through the outlet valve, means driving said piston through a stroke to act through the liquid for forcing a full stroke of the diaphragm whenever pressure in the pumping chamber is below the pressure of the driving liquid, said relief valve releasing driving liquid from the driving chamber back to the source when pressure in the pumping chamber exceeds pressure on the driving liquid, the spring load on said inlet valve to the pumping chamber being effective to .Iadd.limit flow of pumpage to .Iaddend.maintain .[.a.]. .Iadd.said .Iaddend.dead space in the pumping chamber accommodating movement of the diaphragm into the pumping chamber even when the outlet valve is closed thereby minimizing release of driving liquid through the relief valve upon throttled operation of the pump, and means limiting the stroke of the piston to maintain the driving liquid volume less than a volume occupied by the liquid and available air from the liquid to always sustain the liquid above its vapor pressure whereby reduced throttled diaphragm strokes are accommodated by reducing the volume of driving liquid and releasing air from the reduced volume of liquid to prevent vaporization of the liquid. 
     
     
       17. The pump of claim 16 wherein the piston closes the bleeding means except at the end of its suction stroke. 
     
     
       18. The pump of claim 16 wherein the piston is spring biased against a wobble plate providing the driving input. 
     
     
       19. The pump of claim 16 wherein the outlet valve is in a spray-gun receiving pumpage from the pumping chamber. 
     
     
       20. A diaphragm pump comprising a housing defining a chamber for a source of lubricating liquid containing dissolved air, a driving chamber for said liquid and a pumping chamber, a diaphragm separating said driving and pumping chambers, a piston separating said source and driving chambers, means reciprocating said piston to load and unload liquid in said driving chamber, a passageway venting the source chamber to the driving chamber only when the piston unloads the liquid in the driving chamber, a relief valve releasing liquid from the driving chamber to the source chamber when pressure in the pumping chamber exceeds pressure in the driving chamber, means biasing the piston in an unloading direction to reduce pressure in the driving chamber following release of liquid therefrom, and means limiting the unloading stroke of the piston to maintain a volume in the driving chamber filled only by the liquid therein and the air released from said liquid. 
     
     
       21. The diaphragm pump of claim 20 having .Iadd.a dead space in said pumping chamber and .Iaddend.an inlet valve limiting liquid flow into the pumping chamber on the suction stroke of the diaphragm to maintain .[.a.]. .Iadd.said .Iaddend.dead space in the pumping chamber accommodating some movement of the diaphragm into the pumping chamber even when said pumping chamber is closed. 
     
     
       22. The diaphragm pump of claim 20 wherein the means limiting the unloading stroke of the piston maintains a pressure in the driving chamber substantially above the vapor pressure of the liquid therein so that any air released from said liquid follows the law of Henry. 
     
     
       23. A method of pumping fluids under variable flow conditions without varying or stopping the driving input which comprises driving a fluid pumping member with a driving fluid composed of liquid and gas, alternately pressure loading and unloading said driving fluid, releasing some of the driving fluid to provide a reduced driving volume for reduced actuation of said pumping member, and maintaining the pressure on the reduced volume of driving liquid above the vapor pressure thereof to accommodate any expansion of the reduced volume by separation of gas from the liquid. 
     
     
       24. The method of pumping a liquid through full flow, throttled and intermittently stopped conditions without throttling or stopping the driving input which comprises driving a liquid propelling member with a driving fluid composed of liquid and gas, releasing some of the driving fluid to accommodate throttling and intermittent stopping of the pumping, and maintaining minimum pressure on the driving fluid above the vapor pressure of the liquid. 
     
     
       25. The method of pumping through a wide range of flow rates and intermittent stopping of flow without changing driving input which comprises thrusting a driving liquid against a pumping diaphragm, unloading said liquid whenever pumping pressures exceed a predetermined level, and maintaining the liquid at all times above its vapor pressure. 
     
     
       26. The method of diaphragm pumping throughout a wide flow range without changing the driving input which comprises driving a diaphragm with a liquid containing a gas dissolved therein and releasing gas from the liquid under the law of Henry to accommodate throttled and intermittent stoppage of the pumping operation. 
     
     
       27. The method of diaphragm pumping a liquid throughout a wide range of flow and intermittent stopped conditions without throttling the driving input which comprises driving the diaphragm with a liquid containing a dissolved gas, controlling the flow of liquid into the diaphragm pumping chamber to maintain a dead space in the chamber accommodating movement of the diaphragm into the chamber even when the chamber is sealed, loading and unloading the driving liquid to reciprocate the diaphragm, releasing driving liquid to accommodate reduced reciprocation of the diaphragm during throttling and intermittent stopping of the pumping, and releasing air from the driving liquid on the suction stroke following the release of excess driving liquid to maintain pressure of the driving liquid always above its boiling point. .Iadd. 28. A driven fluid pump device adapted to be throttled and stopped without throttling or stopping the driving input which comprises, means defining a pumping chamber and a driving fluid chamber, a fluid propelling member separating said chambers, a driving fluid in said driving fluid chamber actuating said member and composed of liquid and gas, driving means for alternately pressure loading and unloading said driving fluid, means for releasing some of said driving fluid when loaded above a predetermined pressure to provide a reduced driving volume for reduced actuation of said propelling member, means maintaining minimum pressure on the driving fluid above the vapor pressure of said fluid whereby any expansion of the reduced driving volume upon unloading will be accommmodated by the remaining liquid and gas released therefrom, and means agitating at least portions of the driving fluid to add gas thereto. .Iaddend..Iadd. 29. A driven fluid pump device adapted to be throttled and stopped without throttling or stopping the driving input which comprises, means defining a pumping chamber and a driving fluid chamber, a fluid propelling member separating said chambers, a driving fluid in said driving fluid chamber actuating said member and composed of liquid and gas, driving means for alternately pressure loading and unloading said driving fluid, means for releasing some of said drive fluid when loaded above a predetermined pressure to provide a reduced driving volume for reduced actuation of said propelling member, means maintaining minimum pressure on the driving fluid above the vapor pressure of said fluid whereby any expansion of the reduced driving volume upon unloading will be accommodated by the remaining liquid and gas released therefrom, and means adding gas to the driving fluid. .Iaddend..Iadd. 30. A driven fluid pump device adapted to be throttled and stopped without throttling or stopping the driving input which comprises, means defining a pumping chamber and a driving fluid chamber, a fluid propelling member separating said chambers, a driving fluid in said driving fluid chamber actuating said member and composed of liquid and gas, driving means for alternately pressure loading and unloading said driving fluid, means for releasing some of said driving fluid when loaded above a predetermined pressure to provide a reduced driving volume for reduced actuation of said propelling member, means maintaining minimum pressure on the driving fluid above the vapor pressure of said fluid whereby any expansion of the reduced driving volume upon unloading will be accommodated by the remaining liquid and gas released therefrom, a supply chamber for driving fluid, a spring-loaded valve controlling release of driving fluid to said supply chamber, and agitating means in the supply chamber agitating the driving liquid in the chamber adding gas to said driving liquid. .Iaddend. .Iadd. 31. The device of claim 30 wherein the supply chamber has a vent communicating the chamber with an exterior atmosphere effective to supply atmospheric gas to the chamber. .Iaddend..Iadd. 32. A driven pump adapted to be throttled or stopped without throttling or stopping the driving input comprising a housing defining a pumping chamber and a driving liquid chamber, a fluid propelling diaphragm member separating said chambers, driving means acting on liquid in the driving liquid chamber to actuate said propelling member for pumping fluid through the pumping chamber, a relief valve controlling maximum pressure in said driving liquid chamber and releasing excess liquid from the chamber to accommodate throttled movement of the diaphragm, means controlling the driving means to maintain pressure on the remaining liquid in the driving liquid chamber above the vapor pressure of the liquid, a source of driving liquid containing gas dissolved therein communicating with said relief valve to receive excess driving liquid from the driving liquid chamber, means connecting said source with the driving liquid chamber to replenish the chamber whenever pressure therein is below the pressure of the source, and means associated with the source adding gas to the driving liquid. .Iaddend..Iadd. 33. A driven pump adapted to be throttled or stopped without throttling or stopping the driving input comprising a housing defining a pumping chamber and a driving liquid chamber, a fluid propelling diaphragm member separating said chambers, driving means acting on liquid in the driving liquid chamber to actuate said propelling member for pumping fluid through the pumping chamber, a relief valve controlling maximum pressure in said driving liquid chamber and releasing excess liquid from the chamber to accommodate throttled movement of the diaphragm, means controlling the driving means to maintain pressure on the remaining liquid in the driving liquid chamber above the vapor pressure of the liquid, and said driving means being a constant stroke piston, said piston being driven by a driving device having at least portions thereof located in a source chamber for said driving liquid, the source chamber at least partially filled with driving liquid, a gas in said source chamber, and said portions agitating said driving liquid effective to entrain gas in the driving liquid. .Iaddend..Iadd. 34. The device of claim 33 wherein the portions include a rotating wobble plate in the source chamber partially submerged in the driving liquid. .Iaddend..Iadd. 35. The device of claim 34 wherein the wobble plate is driven by a motor located external of the source chamber. .Iaddend..Iadd. 36. A diaphragm pump comprising a housing defining a chamber for a source of lubricating liquid containing dissolved air, a driving chamber for said liquid and a pumping chamber, a diaphragm separating said driving and pumping chambers, a piston separating said source and driving chambers, means reciprocating said piston to load and unload liquid in said driving chamber, a passageway venting the source chamber to the driving chamber only when the piston unloads the liquid in the driving chamber, a relief valve releasing liquid from the driving chamber to the source chamber when pressure in the pumping chamber exceeds pressure in the driving chamber, means biasing the piston in an unloading direction to reduce pressure in the driving chamber following release of liquid therefrom, means limiting the unloading stroke of the piston to maintain a volume in the driving chamber filled only by the liquid therein and the air released from said liquid, said means reciprocating said piston having a portion thereof located in the source chamber effective to entrain additional air in said liquid by agitation thereof, said liquid with said additional air supplied to said driving chamber through said passageway. .Iaddend..Iadd. 37. A driven fluid pump device adapted to be throttled and stopped without throttling or stopping the driving input which comprises: means defining a pumping chamber and a driven fluid chamber, a fluid propelling member separating said chambers, a driving fluid in said driving fluid chamber actuating said member and composed of liquid and gas, means for adding gas to said liquid, driving means for alternatively pressure loading and unloading said driving fluid, means for releasing some of said driving fluid when loaded above a predetermined pressure to provide a reduced driving volume for reduced actuation of said propelling member, and means maintaining minimum pressure on the driving fluid above the vapor pressure of said liquid whereby any expansion of the reduced driving volume upon unloading will be accommodated by the remaining liquid and gas released therefrom. .Iaddend..Iadd. 38. A driven pump adapted to be throttled or stopped without throttling or stopping the driving input comprising a housing defining a pumping chamber and a driving liquid chamber, a fluid propelling member separating said chambers, driving means acting on liquid in the driving liquid chamber to activate said propelling member for pumping fluid through the pumping chamber, a relief valve controlling maximum pressure in said driving liquid chamber and releasing excess liquid from the chamber to accommodate throttle movement of the diaphragm, and means controlling the driving means to maintain pressure on the remaining liquid in the driving liquid chamber above the vapor pressure of the liquid, the liquid including gas dissolved and entrained therein. .Iaddend..Iadd. 39. A driven pump device adapted to be throttled or stopped without throttling or stopping the driving input comprising in combination: a housing having a working chamber, a fluid propelling diaphragm dividing the chamber into a pumping chamber and opposed driving liquid chamber, a source of driving liquid, said source including a source chamber only partially filled with said driving liquid, means supplying gas to said source chamber, means in said source chamber agitating said driving liquid to entrain gas therein, piston driving means acting on said driving liquid in said driving chamber to alternately pressure load and pressure unload said driving liquid in said driving chamber to actuate said diaphragm for pumping fluid through the said pumping chamber, a relief valve controlling maximum pressure in said driving chamber and releasing excess driving liquid from the driving chamber to the said source chamber to accommodate throttled movement of the diaphragm when the driving liquid in the driving chamber is loaded above a predetermined pressure to provide a reduced driving volume of liquid in the driving chamber for reduced actuation of the diaphragm, passage means between said source chamber and the said driving chamber supplying driving liquid from said source chamber to the said driving chamber ahead of said piston for replenishing said driving chamber, and means maintaining minimum pressure on the driving liquid in the driving chamber above the vapor pressure of said liquid whereby any expansion of the driving liquid in the driving chamber upon pressure unloading will be accommodated by release of gas from the driving liquid in the driving chamber. .Iaddend..Iadd. 40. A diaphragm pump comprising a housing defining a chamber for a source of lubricating liquid containing dissolved air, a driving chamber for said liquid and a pumping chamber, a diaphragm separating said driving and pumping chambers, a piston separating said source and said driving chambers, means reciprocating said piston to load and unload liquid in said driving chamber, a passageway venting the source chamber to the driving chamber only when the piston unloads the liquid in the driving chamber, a relief valve releasing liquid from the driving chamber to the source chamber when pressure in the pumping chamber exceeds pressure in the driving chamber, means biasing the piston in an unloading direction to reduce pressure on the driving chamber following release of liquid therefrom, means limiting the unloading stroke of the piston to maintain a volume in the driving chamber filled only by the liquid therein and the air released from said liquid, and means in the source chamber agitating lubricating liquid therein and effective to entrain additional air in said lubricating liquid. .Iaddend..Iadd. 41. The pump of claim 40 wherein the means in said source chamber is operatively connected to said means reciprocating said piston. .Iaddend..Iadd. 42. The device of claim 41 wherein the means reciprocating said piston includes a rotating wobble plate positioned in said source chamber, the piston being spring biased against a face of said wobble plate, the wobble plate being only partially submerged in lubricating liquid in said source chamber, a vent in said source chamber communicating said source chamber to an outside atmosphere and effective to supply said atmosphere to said source chamber, and said wobble plate effective to agitate liquid in said source chamber to entrain atmospheric gas therein. .Iaddend..Iadd. 43. A method of pumping fluids under variable flow conditions without varying or stopping the driving input which comprises driving a fluid pumping member with a driving fluid composed of liquid and gas, positively adding gas to said liquid, alternately pressure loading and unloading said driving fluid, releasing some of driving fluid to provide a reduced driving volume for reduced actuation of said pumping member, and maintaining the pressure on the reduced volume of driving liquid above the vapor pressure thereof to accommodate any expansion of the reduced volume by separation of gas from the liquid. .Iaddend..Iadd. 44. The method of pumping a liquid through full flow, throttled and intermittently stopped conditions without throttling or stopping the driving input which comprises driving a liquid propelling member with a driving fluid composed of liquid and gas, agitating said liquid at a liquid-gas interface, adding gas to said liquid by said agitation, releasing some of the driving fluid to accommodate throttling and intermittent stopping of the pumping, and maintaining minimum pressure on the driving fluid above the vapor pressure of the liquid. .Iaddend..Iadd. 45. The method of diaphragm pumping a liquid throughout a wide range of flow and intermittent stopped conditions without throttling the driving input which comprises providing a liquid containing a dissolved gas, agitating said liquid and adding gas thereto, driving the diaphragm with the liquid containing the gas, controlling the flow of the liquid containing the gas into the diaphragm pumping chamber to maintain a dead space in the chamber accommodating movement of the diaphragm into the chamber even when the chamber is sealed, loading and unloading the driving liquid containing the gas to reciprocate the diaphragm, releasing driving liquid containing the gas to accommodate reduced reciprocation of the diaphragm during throttling and intermittent stopping of the pumping, and releasing portions of the air from the driving liquid on the suction stroke following the release of excess driving liquid to maintain pressure of the driving liquid in the diaphragm pumping chamber always above its boiling point. .Iaddend..Iadd. 46. A driven diaphragm pump adapted to be throttled and stopped without throttling or stopping the driving input which comprises a housing having a diaphragm chamber, a diaphragm in said housing spanning said chamber and dividing the chamber into a pumping chamber having a dead space and an opposed driving liquid chamber, a spring biased inlet valve for admitting pumpage to said pumping chamber, an outlet valve controlling flow of pumpage from said pumping chamber, a source of lubricating liquid having air dissolved therein, means bleeding liquid from said source to said driving chamber, a relief valve controlling flow of liquid from the driving chamber back to the source, a piston acting on liquid in said driving chamber to load and unload said liquid for reciprocating said diaphragm to draw pumpage through the inlet valve into said pumping chamber and to discharge pumpage from the pumping chamber through the outlet valve, means driving said piston through a stroke to act through the liquid for forcing a full stroke of the diaphragm whenever pressure in the pumping chamber is below the pressure of the driving liquid, said relief valve releasing driving liquid from the driving chamber back to the source when pressure in the pumping chamber exceeds pressure on the driving liquid, the spring load on said inlet valve to the pumping chamber effective to limit flow of pumpage to maintain said dead space in the pumping chamber accommodating movement of the diaphragm into the pumping chamber even when the outlet valve is closed thereby minimizing release of driving liquid through the relief valve upon throttled operation of the pump, means limiting the stroke of the piston to maintain the driving liquid volume less than a volume occupied by the liquid and available air from the liquid to always sustain the liquid above its vapor pressure whereby reduced throttled diaphragm strokes are accommodated by reducing the volume of driving liquid and releasing air from the reduced volume of liquid to prevent vaporization of the liquid, said means driving said piston having portions thereof received in a chamber which is partly filled with said lubricating fluid and provides said source of lubricating fluid, said portions of the piston being only partly submerged in said lubricating fluid, said chamber being supplied with gas, and said portions of the piston agitating the lubricating liquid and adding gas thereto. .Iaddend..Iadd. 47. The method of pumping through a wide range of flow rates and intermediate stopping of flow without changing driving input which comprises providing a driving liquid, entraining a quantity of gas in said liquid by agitation thereof to provide a driving liquid-gas combination, thrusting the combination against a pumping diaphragm, unloading the combination whenever pumping pressures exceed a predetermined level, releasing portions of the gas from the combination during unloading and maintaining the liquid at all times above its vapor pressure. .Iaddend. .Iadd. 48. The method of claim 47 including the step of reentraining portions of the released gas in the combination during thrusting.