Peristaltic pump controller with scale factor that varies as a step function of pump inlet pressure

• US 5,947,692 A
• Filed: 10/30/1997
• Issued: 09/07/1999
• Est. Priority Date: 10/30/1997
• Status: Expired due to Term

• Current Assignee: Fenwal Incorporated (Fresenius SE & Co. KGaA)
• Original Assignee: Baxter International Inc.
• Inventors: Patno, Timothy J, Sahlin, Mark P
• Primary Examiner(s): Freay, Charles G.
• Assistant Examiner(s): Evora, Robert Z.
• Application Number:
  US08/960,676
• Time in Patent Office: 677 Days
• Field of Search: 604/66, 604/253, 604/27, 604/4, 417/307, 417/53, 417/477, 417/474, 417/478, 417/44.2, 417/44.3, 128/214, 128/213, 210/87
• US Class Current: 417/44.3
• CPC Class Codes: F04B 2203/0209 Rotational speed
• CPC Class Codes: F04B 2205/01 Pressure before the pump inlet
• CPC Class Codes: F04B 43/12 having peristaltic action
• CPC Class Codes: F04B 49/065 and making use of computers

Abstract

A controller for a peristaltic pump receives as an input pressure P_i sensed at the inlet of the pump. The controller derives a nonlinear scale factor S_Pi that varies as a step function with P_i. The scale factor S_Pi equals a first nonvariable value when P_i lays in a first defined zone of inlet pressures, and equals a second nonvariable value, different than the first nonvariable value, when P_i lays in a second defined zone of inlet pressures different than the first defined zone of inlet pressures. The controller generates a pump speed command based, at least in part, upon S_Pi.

Claims

1. A controller for peristaltic pump suited for processing blood and biological cellular suspensions and including a rotor assembly and a pump tube arranged to be engaged by the rotor assembly and having an inlet, the controller comprising

a sensing element for sensing pressure at the inlet and providing a sensed output P_i, and

a command module having an input coupled to the sensor to receive P_i, the command module including a processing element that derives a scale factor S_Pi that varies according to a step function of P_i and equals a first nonvariable value when P_i lays in a first defined zone of inlet pressures, and equals a second nonvariable value, different than the first nonvariable value, when P_i lays in a second defined zone of inlet pressures different than the first defined zone of inlet pressures, the command module also including an output that generates a pump speed command S based, at least in part, upon S_pi.

2. A controller according to claim 1

wherein the pump speed command S is derived, where

3. A controller for peristaltic pump suited for processing blood and biological cellular suspensions and including a rotor assembly and a pump tube arranged to be engaged by the rotor assembly and having an inlet, the controller comprising

a sensing element for sensing pressure at the inlet and providing a sensed output P_i, and

a command module having an input coupled to the sensor to receive P_i, the command module including a processing element that derives a pump calibration coefficient k, where:

space="preserve" listing-type="equation">k=f(C.sub.T, C.sub.R, S.sub.Pi)

and where;

f is a mathematical function,

C_T is a factor relating to the pump tube,

C_R is a factor relating to the rotor assembly, and

S_Pi is a scale factor that varies as a step function of P_i,

the command module also including an output that generates a pump speed command S, where

space="preserve" listing-type="equation">S=Q×

C.sub.T ×

C.sub.R ×

S.sub.Pi

and where;

Q is the desired flow rate.

4. A controller according to claim 3

wherein, according to the step function S_pi equals a first nonvariable value when P_i lays in a first defined zone of inlet pressures, and equals a second nonvariable value, different than the first nonvariable value, when P_i lays in a second defined zone of inlet pressures different than the first defined zone of inlet pressures.