Dual-piston fluid pump

Abstract

A multi-piston fluid pump system includes a pump head, a motor unit, and a processor, the pump head having two or more cylinders and a piston disposed within each cylinder, the motor unit configured to provide bi-directional actuation of the pistons in each cylinder in response to control signals from the processor in order to minimize fluctuations in pressure and/or flow rate at the outlet of the fluid pump system.

What is claimed is: 
     
         1 . A fluid pump system comprising:
 a pump head comprising
 a first cylinder and a second cylinder, the first cylinder having a first piston disposed within, and the second cylinder having a second piston disposed within; 
 a first inlet fluidly coupled to the first cylinder, and a second inlet fluidly coupled to the second cylinder; 
 an outlet fluidly coupled to the first cylinder and to the second cylinder; 
   a motor unit operatively coupled to the pump head, the motor unit comprising a first motor and a second motor, the first motor configured to actuate the first piston bi-directionally within the first cylinder, and the second motor configured to actuate the second piston bi-directionally within the second cylinder;
 and 
   a processor configured to control the motor unit such that a total delivered flow rate of fluid from the outlet of the pump head is maintained at a target flow rate, the processor configured to:
 during a first phase, cause the motor unit to actuate the first piston in a first delivery direction to deliver fluid from the first cylinder through the outlet at the target flow rate, while causing the motor unit to actuate the second piston in a second filling direction to draw fluid into the second cylinder through the second inlet; and 
 during a second phase, cause the motor unit to actuate the first piston in the first delivery direction to deliver fluid from the first cylinder through the outlet at a first decreasing flow rate, while causing the motor unit to actuate the second piston in a second delivery direction to deliver fluid from the second cylinder through the outlet at a second increasing flow rate such that the total delivered flow rate of fluid from the outlet of the pump head is maintained substantially at the target flow rate during the second phase. 
   
     
     
         2 . The fluid pump system of  claim 1  wherein the processor is further configured to:
 during a third phase, cause the motor unit to actuate the first piston in a first filling direction to draw fluid into the first cylinder through the first inlet, while causing the motor unit to actuate the second piston in the second delivery direction to deliver fluid from the second cylinder through the outlet at the target flow rate; and 
 during a fourth phase, cause the motor unit to actuate the second piston in the second delivery direction to deliver fluid from the second cylinder through the outlet at a second decreasing flow rate, while causing the motor unit to actuate the first piston in the first delivery direction to deliver fluid from the first cylinder through the outlet at a first increasing flow rate such that the total delivered flow rate of fluid from the outlet of the pump head is maintained substantially at the target flow rate during the fourth phase. 
 
     
     
         3 . The fluid pump system of  claim 2  wherein the processor is configured to actuate the first motor independently of the second motor. 
     
     
         4 . The fluid pump system of  claim 3  wherein the first motor and the second motor are each comprised of one of a rotary motor with a lead screw and a linear motor. 
     
     
         5 . The fluid pump system of  claim 3  wherein the pump head is a disposable component of the fluid pump system. 
     
     
         6 . The fluid pump system of  claim 3 , further comprising:
 a first valve for controlling fluid flow between the first inlet and the first cylinder;   a second valve for controlling fluid flow between the first cylinder and the outlet;   a third valve for controlling fluid flow between the second cylinder and the outlet; and   a fourth valve for controlling fluid flow between the second inlet and the second cylinder.   
     
     
         7 . The fluid pump system of  claim 6  wherein at least one of the first, second, third, and fourth valves is a check valve. 
     
     
         8 . The fluid pump system of  claim 6  wherein at least one of the first, second, third, and fourth valves is an actively-controlled valve. 
     
     
         9 . The fluid pump system of  claim 8  wherein the at least one actively-controlled valve is configured to be controlled by the processor. 
     
     
         10 . The fluid pump system of  claim 9  wherein the pump head is a disposable pump head, and wherein at least one of the actively-controlled valves is a pinch valve assembly configured to act upon a portion of the disposable pump head. 
     
     
         11 . The fluid pump system of  claim 3  wherein the processor is configured to cause the first, second, third, and fourth phases to repeat in succession. 
     
     
         12 . The fluid pump system of  claim 3  wherein each of the first increasing flow rate, the first decreasing flow rate, the second increasing flow rate, and the second decreasing flow rate are comprised of one of a linearly changing rate and an exponentially changing rate. 
     
     
         13 . The fluid pump system of  claim 3  wherein the processor is configured to modify an operating parameter or condition of the fluid pump system in response to information about a condition of the fluid pump system comprising one of: (a) a first position of the first piston within the first cylinder, (b) a second position of the second piston within the second cylinder, (c) an elapsed time since the initiation of the current phase, (d) an amount of fluid remaining in the first cylinder or the second cylinder, and (e) any logical combination of conditions (a) through (d). 
     
     
         14 . The fluid pump system of  claim 6  wherein the processor is configured to modify an operating parameter or condition of the fluid pump system in response to information about a condition of the fluid pump system comprising one of: (a) a first position of the first piston within the first cylinder, (b) a second position of the second piston within the second cylinder, (c) an elapsed time since the initiation of the current phase, (d) an amount of fluid remaining in the first cylinder or the second cylinder, (e) a position of one or more of the first, second, third, and fourth valves, and (f) any logical combination of conditions (a) through (e). 
     
     
         15 . The fluid pump system of  claim 8  further comprising a sensor proximate the outlet, the sensor configured to provide a sensor signal to the processor, and the processor configured to modify either or both of a motor unit operating parameter and a position of any of the first, second, third, or fourth valves in response to the sensor signal. 
     
     
         16 . The fluid pump system of  claim 15  wherein the sensor is a pressure sensor, and the processor is configured to modify either or both of the motor unit operating parameter or the position of any of the first, second, third, or fourth valves to avoid exceeding a maximum pressure limit. 
     
     
         17 . The fluid pump system of  claim 15  wherein the sensor is a flow sensor, and the processor is configured to modify either or both of the motor unit operating parameter or the position of any of the first, second, third, or fourth valves to achieve the target flow rate at the outlet. 
     
     
         18 . The fluid pump system of  claim 15  wherein the processor is configured to modify the timing of changes to the positions of any of the first, second, third, or fourth valves to minimize fluctuations in flow or pressure at the outlet. 
     
     
         19 . The fluid pump system of  claim 9  wherein information about the disposable pump head is provided to the processor and used to determine one or more initial operating parameters of the fluid pump system. 
     
     
         20 . A method of operating a multi-cylinder fluid pump system, the method comprising:
 delivering fluid from a first cylinder at a target flow rate while a second cylinder is being filled, and   delivering fluid from the first cylinder at a decreasing flow rate while delivering fluid from the second cylinder at an increasing flow rate,   wherein the sum of the increasing flow rate and the decreasing flow rate equals the target flow rate, and   wherein an operating parameter or condition of the multi-cylinder fluid pump system is modified in response to information about a condition of the fluid pump system.