Peristaltic pump with linear flow control

Abstract

A peristaltic pump includes a conduit having a first end for receiving a fluid from a reservoir and a second end for delivering the fluid. A plurality of fingers are disposed at respective locations along a segment of the conduit and are configured to alternately compress and release the conduit at the locations. A cyclical pump mechanism is coupled to move the fingers between respective compressed and released positions in a spatio-temporal pattern so as to drive a predetermined quantity of the fluid through the segment of the conduit in each pump cycle. A motor is coupled to drive the pump mechanism. A controller is coupled to activate and deactivate the motor in alternation during each pump cycle with a duty cycle that varies within the pump cycle.

1 . A peristaltic pump, comprising:
 a conduit having a first end for receiving a fluid from a reservoir and a second end for delivering the fluid;   a plurality of fingers, which are disposed at respective locations along a segment of the conduit and are configured to alternately compress and release the conduit at the locations;   a cyclical pump mechanism, which is coupled to move the fingers between respective compressed and released positions in a spatio-temporal pattern so as to drive a predetermined quantity of the fluid through the segment of the conduit in each pump cycle;   a motor, which is coupled to drive the pump mechanism; and   a controller, which is coupled to activate and deactivate the motor in alternation during each pump cycle with a duty cycle that varies within the pump cycle.   
     
     
         2 . The pump according to  claim 1 , wherein the pump cycle is characterized by a variation in a quantity of the fluid that is delivered per step of the motor during the pump cycle, and wherein the controller is operative to modulate the duty cycle so that the quantity of the fluid that is delivered through the conduit per unit time over the pump cycle is constant. 
     
     
         3 . The pump according to  claim 2 , wherein the controller is operative to activate and deactivate the motor by applying a waveform with a fixed period to the motor while varying a duration during which the motor is on during each period. 
     
     
         4 . The pump according to  claim 3 , wherein the pump cycle has first and second parts, such that the predetermined quantity of the fluid is driven through the segment during the first part, and wherein the controller is operative to drive the motor so as to cause the pump mechanism to complete the second part of the pump cycle during a single period of the waveform. 
     
     
         5 . The pump according to  claim 1 , wherein the controller is operative to activate and deactivate the motor by applying a waveform to the motor, and to adjust a flow rate through the conduit by modifying a characteristic of the waveform. 
     
     
         6 . The pump according to  claim 5 , wherein the characteristic is selected from a group of characteristics consisting of an average duty cycle of the waveform, a period of the waveform, and a number of steps of the motor per period of the waveform. 
     
     
         7 . The pump according to  claim 5 , wherein the controller is operative to activate and deactivate the motor in alternation to generate flow rates below a certain minimum level, and to run the motor continuously to generate flow rates above the minimum level. 
     
     
         8 . The pump according to  claim 1 , wherein the conduit comprises an elastic material, which exerts a first force against the fingers in response to compression of the conduit by the fingers, and wherein the fingers comprise magnets, and the pump comprises a ferromagnetic frame, which exerts a second force on the magnets, opposite to and balancing the first force during the pump cycle. 
     
     
         9 . The pump according to  claim 8 , wherein the pump mechanism comprises a camshaft, which is coupled to be driven by the motor and comprises multiple cams, each configured to drive a respective finger and having a crescent-shaped design for enhancing the balancing of the forces. 
     
     
         10 . The pump according to  claim 1 , and comprising a rotation sensor, which is configured to measure an angle of rotation of the motor and to provide feedback to the controller regarding the rotation of the motor. 
     
     
         11 . A method for fluid delivery, comprising:
 providing a peristaltic infusion pump comprising a cyclical pump mechanism and a motor coupled to drive the pump mechanism; and   driving the pump to deliver a fluid by activating and deactivating the motor in alternation during each pump cycle with a duty cycle that varies within the pump cycle.   
     
     
         12 . The method according to  claim 11 , wherein the pump cycle is characterized by a variation in a quantity of the fluid that is delivered per step of the motor during the pump cycle, and wherein driving the pump comprises modulating the duty cycle so that the quantity of the fluid that is delivered by the pump per unit time over the pump cycle is constant. 
     
     
         13 . The method according to  claim 12 , wherein modulating the duty cycle comprises applying a waveform with a fixed period to the motor while varying a duration during which the motor is on during each period. 
     
     
         14 . The method according to  claim 11 , wherein driving the pump comprises applying a waveform to the motor, and modifying a characteristic of the waveform in order to adjust a rate of flow of the fluid. 
     
     
         15 . The method according to  claim 14 , wherein the characteristic is selected from a group of characteristics consisting of an average duty cycle of the waveform, a period of the waveform, and a number of steps of the motor per period of the waveform. 
     
     
         16 . The method according to  claim 11 , wherein driving the pump comprises activating and deactivating the motor in alternation to generate flow rates below a certain minimum level, and running the motor continuously to generate flow rates above the minimum level. 
     
     
         17 . A peristaltic pump having a pump cycle and comprising:
 a conduit, comprising an elastic material, having a first end for receiving a fluid from a reservoir and a second end for delivering the fluid;   a plurality of fingers, which comprise magnets and are disposed at respective locations along a segment of the conduit and are configured to alternately compress and release the conduit at the locations, whereby the conduit exerts a first force against the fingers in response to compression of the conduit;   a ferromagnetic frame, which exerts a second force on the magnets, opposite to and balancing the first force during the pump cycle;   a cyclical pump mechanism, which is coupled to move the fingers between respective compressed and released positions in a spatio-temporal pattern so as to drive a predetermined quantity of the fluid through the segment of the conduit in each pump cycle;   a motor, which is coupled to drive the pump mechanism; and   a controller, which is coupled to activate and deactivate the motor in alternation during each pump cycle with a duty cycle that varies within the pump cycle.