Digital pump with multiple outlets

Abstract

A pump system for coupling a positive displacement pump capable of supplying flow sequentially to a number of different volumes at different pressures. In some embodiments the pump output is coupled to multiple volumes that may be at the same or different pressures. The output of the pump is cycled between each such volume by on-off valves to maintain the required pressure in each volume, with the output of the pump being returned to its input when necessary to vent excess flow capacity. A controller may be used to control the on-off valves responsive to pressure sensors for each volume. In other embodiments the output of the pump is through on-off valves coupled to actuators as well as to a by-pass valve, and the valves are operated at high speed and with a duty cycle to provide controlled actuator velocities. Various embodiments are disclosed.

1 . A pump system comprising: 
 a positive displacement pump having an input and an output;    a plurality of on-off valves each having an input coupled to the output of the positive displacement pump;    the outputs of the plurality of on-off valves each being coupled to a respective control volume to be pressurized;    a bypass on-off valve also having an input coupled to the output of the positive displacement pump and having an output coupled to the input to the positive displacement pump;    the plurality of on-off valves being sequenced so that the positive displacement pump is connected to different control volumes at different times to provide the necessary flow at a required pressure for each control volume;    the by-pass on-off valve routing any excess pump flow back to the input to the positive displacement pump.    
     
     
         2 . The pump system of  claim 1  wherein one and only one of the plurality of on-off valves or the bypass valve is on at any one time.  
     
     
         3 . The pump system of  claim 2  wherein the turn off of one on-off valve and the turn on of the next on-off valve are phased so that one on-off valve is partially off as the next on-off valve is partially on.  
     
     
         4 . The pump system of  claim 2  wherein the turn off of one on-off valve and the turn on of the next on-off valve are phased to maintain flow from the positive displacement pump without a substantial pressure spike in the output of the positive displacement pump.  
     
     
         5 . The pump system of  claim 1  wherein each control volume includes a pressure sensor and wherein the plurality of on-off valves and the bypass on-off valve are controlled by a controller, the controller sequentially checking an output of each pressure sensor and controlling the plurality of on-off valves and the bypass on-off valve to provide the necessary flow at the required pressure for each control volume.  
     
     
         6 . The pump system of  claim 5  wherein the controller is responsive to at least one additional input.  
     
     
         7 . The pump system of  claim 5  wherein the pressure sensors are pressure switches.  
     
     
         8 . The pump system of  claim 5  wherein the pressure sensors are selected from the group consisting of linear and nonlinear pressure sensors.  
     
     
         9 . The pump system of  claim 8  wherein the pressure sensors are biased so as to only sense around the required pressures.  
     
     
         10 . The pump system of clam  5  wherein the plurality of on-off valves provide the necessary flow at the required pressure for each control volume, each with a predetermined hysteresis around the required pressure.  
     
     
         11 . The pump system of  claim 10  wherein the hysteresis is imposed by the controller.  
     
     
         12 . The pump system of  claim 1  wherein the on-off valves are solenoid operated spool valves  
     
     
         13 . A pump system for controlling one or more hydraulic actuators comprising: 
 a positive displacement pump having a hydraulic fluid pumping rate;    a controller coupled to receive actuator velocity control signals;    a plurality of on-off valves;    a bypass on-off valve having an input coupled to an output of the positive displacement pump and having an output coupled to an input to the positive displacement pump;    a first half of the plurality of on-off valves each being configured to couple an output of the positive displacement pump to a hydraulic actuator input;    a second half of the remaining plurality of on-off valves each being configured to couple a hydraulic actuator input to a low pressure vent, wherein each hydraulic actuator has a specific actuator velocity per unit hydraulic fluid flow rate;    the controller being configured to sequentially and repetitively couple selected ones of the plurality of on-off valves on and off with a duty cycle selected to provide a fluid flow rate through the selected on-off valves to cause an actuator velocity responsive to the actuator velocity control signals.    
     
     
         14 . The pump system of  claim 13  wherein one and only one of the first half of the plurality of on-off valves or the bypass valve is on at any one time.  
     
     
         15 . The pump system of  claim 14  wherein the turn off of each of the first half of the on-off valves and the by-pass valve and the turn on of the next valve of the first half of the on-off valves and the by-pass valve are phased so that one on-off valve is partially off as the next on-off valve is partially on.  
     
     
         16 . The pump system of  claim 14  wherein the turn off of each of the first half of the on-off valves and the by-pass valve and the turn on of the next valve of the first half of the on-off valves and the by-pass valve are phased to maintain flow from the positive displacement pump without a substantial pressure spike in the output of the positive displacement pump.  
     
     
         17 . The pump system of  claim 13  wherein the on-off valves are solenoid operated spool valves