System and method for increased flow uniformity

• US 6,394,771 B2
• Filed: 02/26/2001
• Issued: 05/28/2002
• Est. Priority Date: 08/03/1998
• Status: Expired due to Term

• Current Assignee: Carefusion 303 Incorporated (Becton, Dickinson & Co)
• Original Assignee: ALARIS Medical Systems, Inc. (Becton, Dickinson & Co)
• Inventors: Butterfield, Robert D.
• Primary Examiner(s): Wolfe, Willis R.
• Assistant Examiner(s): Gimie, Mahmoud
• Application Number:
  US09/794,539
• Publication Number:
  US 20010007636A1
• Time in Patent Office: 456 Days
• Field of Search: 417/477.1,43,53,12,44.1,45,300 318/685 604/153
• US Class Current: 417/477.1
• CPC Class Codes: A61M 5/16831 Monitoring, detecting, signalling or eliminating infusion flow anomalies low-level float-valves causing cut-off A61M5/40; indicating or recording presence, absence or direction of flow in general G01P13/0066
• CPC Class Codes: F04B 2203/0213 Pulses per unit of time (pulse motor)
• CPC Class Codes: F04B 43/082 the tubular flexible member being pressed against a wall by a number of elements, each having an alternating movement in a direction perpendicular to the axes of the tubular member and each having its own driving mechanism

Abstract

A system for increasing the volumetric flow uniformity of fluid pumped through a conduit by an infusion pump. A pumping mechanism operates in identifiable step movements that are broken down into microstep movements that are then grouped into packets. The pumping mechanism controls the period of each microstep, so that the sum of the microstep periods in a packet is essentially equal to the packet period, with little or no waiting time on the motor. The motor preferably begins moving the assigned microsteps in each packet immediately upon the beginning of the time period, but controls the period of the microsteps for that packet.

Claims

1. An apparatus for increasing the uniformity of flow of fluid through a conduit comprising:

a drive device that moves in movement increments;

a pumping mechanism coupled to the drive device that pumps fluid through the conduit in volume increments in response to movement increments of the drive device, with each volume increment corresponding to a respective movement of the drive device, at least some of the volume increments differing from other volume increments;

an input device that provides a desired flow rate value;

a processor configured to;

receive the desired flow rate value;

group the movement increments into movement groups as a function of the volume increments corresponding to the respective movement increments, with each movement group having a total flow volume equal to the combined volume increments of the movement increments in the movement group, wherein the total flow volumes of all movement groups are approximately equal, and wherein the total flow volume of each movement group is a generally constant value for all desired flow rates within a specific range of flow rates and the total flow volume of each movement group is a function of the desired flow rate for flow rates outside the specific range of flow rates;

assign a group period to each movement group as a function of the desired flow rate, wherein the group periods of all movement groups are equal;

determine an increment period for each movement increment, wherein the combined increment periods of all movement increments in a movement group are approximately equal to the group period for the movement group; and

control the drive device to move in the movement increments, with the movement increments occurring at the assigned increment periods.

2. The apparatus of claim 1 wherein the processor is configured to control the drive device to cause the movement increment period of each movement increment within an increment group to be proportional to the fluid flow volume increment of the movement increment.

3. The apparatus of claim 1 wherein the processor is configured to control the drive device to cause the movement increment period of all movement increments within an increment group to be equal.

4. A parenteral fluid delivery system comprising:

a fluid delivery conduit;

a peristaltic pump, said pump having a plurality of peristaltic elements movable into and out of engagement with the conduit to control the flow of fluid through the conduit;

a drive device having a plurality of positions through which the drive device may move in incremental movements, said drive device coupled to the peristaltic elements of the pump, wherein the peristaltic elements pump fluid through the conduit in volume increments in responses to incremental movements of the drive device, each volume increment corresponding to a respective incremental movement of the drive device;

a position sensor that monitors the position of the drive device;

a memory that is configured to store data representing the volume increment of fluid flow corresponding to each incremental movement of the drive device;

an input device that provides a desired move selection; and

a processor in communication with the memory, said processor configured to receive the desired mode selection and select one of two or more operational modes, the processor in at least one, but not all, of said operational modes further configured to;

receive the drive device position signal and the fluid flow volume increment data;

assign incremental movements of the drive motor to incremental movement groups as a function of the fluid flow volume increment data for each incremental movement, with the combined fluid flow volume increments of all incremental movements within a movement group approximately equal to the combined fluid flow volume increments of other movement groups;

assign a timeslot for each incremental movement group, with all timeslots having an equal period; and

control the drive device to cause the movement increments in each movement group to be spread across the timeslot period for that movement group, with each movement increment having a period, with the sum of all movement increment periods in a movement group being equal to the movement group period.

5. The apparatus of claim 4 wherein the processor is configured to control the drive device to cause the movement increment period of each movement increment within an increment group to be proportional to the fluid flow volume increment of the movement increment.

6. The apparatus of claim 4 wherein the processor is configured to control the drive device to cause the movement increment period of all movement increments within an increment group to be equal.

7. The apparatus of claim 4 wherein the processor is configured to continuously move at high or maximum speed through a predetermined number of movement increments, the sum total of the increments of fluid flow indicated in memory corresponding to the respective movement increments being essentially zero.

8. The apparatus of claim 4 wherein the drive device comprises a cam shaft rotated by a step motor, said step motor moving in a series of motor steps, with each motor step corresponding to a movement increment.

9. The apparatus of claim 4 wherein the drive device comprises a cam shaft rotated by a step motor, said step motor moving in a series of motor steps, with said motor steps further divided into microsteps, wit each microstep corresponding to a movement increment.