Air-driven hydraulic pump with pressure control

Abstract

A hydraulically driven pump with driving pressure controlled within a predetermined range. The hydraulically driven pump has a driving-fluid port fluidly coupled to a compressed air source and ambient, a driven-fluid inlet port fluidly connected to a tank, and a driven-fluid outlet port. A pressure sensor is used for providing sensing values indicative to the driving pressure in the hydraulically driven pump, and the driving pressure is controlled in closed loop by releasing and filling air through the driving-fluid port. The hydraulically driven pump has a suction stroke, in which driven fluid is refilled into the pump, and a pressing stroke, in which driven fluid is pressed out. A hydraulic buffer is used to provide driving pressure during a suction stroke and two hydraulically driven pumps can work alternately in providing continuous pressure control.

1 . A hydraulically driven pump system comprising:
 a pump housing having a pump chamber therein and at least one driving-fluid port fluidly connected to said pump chamber;   a driving-fluid flow control means fluidly connected to said driving-fluid port and a first fluid for controlling supply and release of said first fluid, wherein said driving-fluid flow control means includes at least one electrically controlled solenoid valve;   a driven-fluid inlet port fluidly coupled to said pump chamber through a driven-fluid flow control means, which only allows a second fluid to flow into said pump chamber;   a driven-fluid outlet port though which said second fluid flows out from said hydraulically driven pump system under a driving pressure;   at least one pressure sensor for providing pressure sensing values indicative to said driving pressure; and   a closed-loop controller configured to control said driving pressure within a predetermined range by electrically energizing and de-energizing said at least one electrically controlled solenoid valve in said driving-fluid flow control means according to at least said pressure sensing values obtained from said at least one pressure sensor.   
     
     
         2 . The hydraulically driven pump system of  claim 1 , further comprising:
 a piston reciprocable in said pump chamber separating said pump chamber into a driving fluid chamber, which is fluidly connected to said driving-fluid port, and a driven fluid chamber, which is fluidly connected to said driven-fluid inlet port, and fluidly coupled to said driven-fluid outlet port.   
     
     
         3 . The hydraulically driven pump system of  claim 1 , wherein at least one electrically controlled solenoid valve in said driving-fluid flow control means is a three-way solenoid valve. 
     
     
         4 . The hydraulically driven pump system of  claim 1 , further comprising:
 a stroke controller configured to switch in between a suction stroke, in which said driving-fluid flow control means is controlled to release said first fluid from said pump chamber for drawing said second fluid into said pump chamber, and a pressing stroke, in which said driving-fluid flow control means is controlled to keep said second fluid from flowing into said pump chamber.   
     
     
         5 . The hydraulically driven pump system of  claim 4 , wherein said closed-loop controller is further configured to work only when said stroke controller is operating in said pressing stroke. 
     
     
         6 . The hydraulically driven pump system of  claim 4 , further comprising:
 a level sensor for providing level sensing values indicative to the volume of said second fluid in said pump chamber, wherein said stroke controller is further configured to switch in between said suction stroke and said pressing stroke according to at least said level sensing values obtained from said level sensor.   
     
     
         7 . The hydraulically driven pump system of  claim 4 , wherein said stroke controller is further configured to switch from said pressing stroke to said suction stroke according to at least said pressure sensing values obtained from said at least one pressure sensor. 
     
     
         8 . The hydraulically driven pump system of  claim 4 , wherein said stroke controller is further configured to switch from said pressing stroke to said suction stroke according to at least the release time of said second fluid from said driven pump system in said pressing stroke. 
     
     
         9 . The hydraulically driven pump system of  claim 1 , further comprising:
 a hydraulic buffer including a buffer chamber, a buffer inlet port, which is fluidly coupled to said pump chamber through a flow control means, which only allows fluid to flow from said pump chamber to said buffer chamber, and a buffer outlet port, which is fluidly connected to said driven-fluid outlet port.   
     
     
         10 . The hydraulically driven pump system of  claim 9 , wherein said at least one pressure sensor includes a pressure sensor providing sensing values indicative to the pressure in said buffer chamber; 
     
     
         11 . The hydraulically driven pump system of  claim 9 , wherein said hydraulic buffer further includes a piston reciprocable in said buffer chamber separating said pump chamber into an upper chamber and a lower chamber fluidly connected to said buffer inlet port and said buffer outlet port. 
     
     
         12 . The hydraulically driven pump system of  claim 11 , further comprising:
 a spring positioned in said upper chamber.   
     
     
         13 . The hydraulically driven pump system of  claim 11 , further comprising:
 a stroke controller configured to switch from a suction stroke, in which said driving-fluid flow control means is controlled to release said first fluid from said pump chamber for drawing said second fluid into said pump chamber, to a pressing stroke, in which said driving-fluid flow control means is controlled to keep said second fluid from flowing into said pump chamber, before said pressure sensing values indicate that said driving pressure is lower than a predetermined threshold.   
     
     
         14 . A hydraulically driven pump system comprising:
 a first pump housing having a first pump chamber therein, and at least one first driving-fluid port fluidly connected to said first pump chamber;   a second pump housing having a second pump chamber therein, and at least one second driving-fluid port fluidly connected to said second pump chamber;   a first driving-fluid flow control means fluidly connected to said first driving-fluid port and a first fluid for controlling supply and release of said first fluid, wherein said first driving-fluid flow control means includes at least one electrically controlled solenoid valve;   a second driving-fluid flow control means fluidly connected to said second driving-fluid port and said first fluid for controlling supply and release of said first fluid, wherein said second driving-fluid flow control means includes at least one electrically controlled solenoid valve;   a driven-fluid inlet port, which is fluidly coupled to said first pump chamber through a first driven-fluid flow control means that only allows a second fluid to flow into said first pump chamber, and fluidly coupled to said second pump chamber through a second driven-fluid flow control means that only allows said second fluid to flow into said second pump chamber;   a driven-fluid outlet port though which said second fluid flows out from said hydraulically driven pump system under a driving pressure;   at least one pressure sensor for providing pressure sensing values indicative to said driving pressure; and   a closed-loop controller configured to control said driving pressure within a predetermined range by electrically energizing and de-energizing said at least one electrically controlled solenoid valve in said first and second driving-fluid flow control means according to at least said pressure sensing values obtained from said at least one pressure sensor.   
     
     
         15 . The hydraulically driven pump system of  claim 14 , further comprising:
 a first driven-fluid flow control means fluidly connected to said first pump chamber and said driven-fluid outlet port for only allowing said second fluid to flow from said first pump chamber to said driven-fluid outlet port;   a second driven-fluid flow control means fluidly connected to said second pump chamber and said driven-fluid outlet port for only allowing said second fluid to flow from said second pump chamber to said driven-fluid outlet port; and   a pump controller configured to switch among at least a first suction mode, in which said first driving-fluid flow control means is controlled to release said first fluid from said first pump chamber for drawing said second fluid into said first pump chamber while said second driving-fluid flow control means is controlled to keep said second fluid from flowing into said second pump chamber, and a second suction mode, in which said second driving-fluid flow control means is controlled to release said first fluid from said second pump chamber for drawing said second fluid into said second pump chamber while said first driving-fluid flow control means is controlled to keep said second fluid from flowing into first second pump chamber.   
     
     
         16 . The hydraulically driven pump system of  claim 15 , wherein said pump controller is configured to operate in a third mode, in which said first driving-fluid flow control means is controlled to keep said second fluid from flowing into said first pump chamber, and said second driving-fluid flow control means is controlled to keep said second fluid from flowing into said second pump chamber. 
     
     
         17 . The hydraulically driven pump system of  claim 15 , wherein said at least one pressure sensor includes a first pressure sensor providing a first pressure sensing value indicative to the pressure inside said first pump chamber and a second pressure sensor providing a second pressure sensing value indicative to the pressure inside said second pump chamber, and said closed-loop controller is further configured to control said driving pressure by operating said second driving-fluid flow control means according to said second pressure sensing value, when said pump controller is in said first suction mode, and control said driving pressure by operating said first driving-fluid flow control means according to said first pressure sensing value, when said pump controller is in said second suction mode. 
     
     
         18 . The hydraulically driven pump system of  claim 17 , wherein said at least one pressure sensor includes a buffer pressure sensor providing sensing values indicative to the pressure in said buffer chamber. 
     
     
         19 . The hydraulically driven pump system of  claim 14 , further comprising:
 a hydraulic buffer including a buffer chamber, a buffer inlet port, which is fluidly connected to said first pump chamber through a first buffer flow control means that only allows said second fluid to flow from said first pump chamber to said buffer chamber, and fluidly connected to said second pump chamber through a second buffer flow control means that only allows said second fluid to flow from said second pump chamber to said buffer chamber, and a buffer outlet port fluidly connected to said driven-fluid outlet port.   
     
     
         20 . The hydraulically driven pump system of  claim 19 , wherein said hydraulic buffer further includes a piston reciprocable in said buffer chamber separating said pump chamber into an upper chamber and a lower chamber fluidly connected to said buffer inlet port and said buffer outlet port.