Precision Fluid Dispensing Using Peristaltic Roller Control

Abstract

A precision fluid dispensing system that can be effectively used for accurate fluid dispensing in peristaltic pumps if roller control is used. Peristaltic pumps can be combined with pinch valves allowing a dispense tube to be open while a source tube is blocked. Controlled roller movement is used to move the next roller to the same starting position as the previous roller was on the previous dispense, the dispense pinch valve is closed and the source valve is opened. The system uses roller positioning where the each roller is properly positioned so that each dispense cycle starts in the same position. The precision and accuracy is better than 0.3% total.

We claim: 
     
         1 . A precision fluid dispensing system comprising:
 a peristaltic pump with a plurality of rollers on at least one rotor configured to execute a sequence of single dispenses;   a motor driving the rotor;   an encoder or external sensor cooperating with said rotor, the encoder or external sensor adapted to determine an absolute rotational position of the rotor;   wherein, after each single dispense in said sequence of single dispenses, the motor positions the rotor so a next roller is in an identical angular position as a previous roller before the dispense.   
     
     
         2 . The precision fluid dispensing system of  claim 1  wherein the sequence of single dispenses along with an optional partial dispense results in a total dispense of a predetermined quantity of fluid. 
     
     
         3 . The precision fluid dispensing system of  claim 1  wherein, the motor is a stepper motor. 
     
     
         4 . The precision fluid dispensing system of  claim 3  wherein the stepper motor has a fixed number of micro-steps per revolution; the peristaltic pump has a fixed number of rollers on the driven rotor, and the number of micro-steps in a single dispense equals the number of micro-steps per revolution divided by the number of rollers. 
     
     
         5 . The precision fluid dispensing system of  claim 3  wherein the optional partial dispense has a number of micro-steps equal to the total number of steps required for the total dispense modulo the number of steps in a single dispense. 
     
     
         6 . The precision fluid dispensing system of  claim 3  wherein the stepper motor has a fixed number of micro-steps per revolution; the peristaltic pump has a fixed number of rollers on a driven rotor, and the number of micro-steps per revolution divided by the number of rollers is not an integer, the number of micro-steps in each single dispense is the number of micro-steps per revolution divided by the number of rollers truncated to the next lower integer for each single dispense except the last single dispense in a motor revolution, with the last single dispense in the motor revolution containing a number of micro-steps needed to bring the total number of micro-steps per motor revolution to the fixed number of micro-steps per revolution. 
     
     
         7 . A precision fluid dispensing system comprising:
 a peristaltic pump with a plurality of rollers on a rotor configured to execute a sequence of single dispenses;   a stepper motor rotationally driving the rotor;   an encoder or external sensor cooperating with said rotor, the encoder or external sensor adapted to determine a circumferencial position of the rollers;   wherein, after each single dispense in said sequence of single dispenses, the motor positions the rotor so a next roller is in an identical angular position as a previous roller before the dispense;   wherein the sequence of single dispenses along with an optional partial dispense results in a total dispense of a predetermined quantity of fluid.   
     
     
         8 . The precision fluid dispensing system of  claim 7  wherein the stepper motor has a fixed number of micro-steps per revolution; the peristaltic pump has a fixed number of rollers, and the number of micro-steps in a single dispense equals the number of micro-steps per revolution divided by the number of driven rollers. 
     
     
         9 . The precision fluid dispensing system of  claim 7  wherein the stepper motor has a fixed number of micro-steps per revolution; the peristaltic pump has a fixed number of rollers, and the number of micro-steps per revolution divided by the number of rollers is not an integer, the number of micro-steps in each single dispense is the number of micro-steps per revolution divided by the number of rollers truncated to the next lower integer for each single dispense except the last single dispense in a motor revolution, with the last single dispense in the motor revolution containing a number of micro-steps needed to bring the total number of micro-steps per motor revolution to the fixed number of micro-steps per revolution. 
     
     
         10 . A precision fluid dispensing system comprising:
 a peristaltic pump with a plurality of rollers mounted on at least one rotor configured to execute a sequence of single dispenses;   a motor driving the rotor;   wherein, after each single dispense in said sequence of single dispenses, the motor positions the rotor so a next roller is in an identical angular position as a previous roller before the dispense;   
     
     
         11 . The precision fluid dispensing system of  claim 10  wherein, the motor is a stepper motor. 
     
     
         12 . The precision fluid dispensing system of  claim 11  wherein the stepper motor has a fixed number of micro-steps per revolution; the peristaltic pump has a fixed number of driven rollers, and the number of micro-steps in a single dispense equals the number of micro-steps per revolution divided by the number of driven rollers. 
     
     
         13 . The precision fluid dispensing system of  claim 11  wherein the stepper motor has a fixed number of micro-steps per revolution; the peristaltic pump has a fixed number of driven rollers, and the number of micro-steps per revolution divided by the number of rollers is not an integer, the number of micro-steps in each single dispense is the number of micro-steps per revolution divided by the number of rollers truncated to the next lower integer for each single dispense except the last single dispense in a motor revolution, with the last single dispense in the motor revolution containing a number of micro-steps needed to bring the total number of micro-steps per motor revolution to the fixed number of micro-steps per revolution.