Temperature compensation system for regulating flow through tubing in a pump

• US 6,869,425 B2
• Filed: 04/03/2002
• Issued: 03/22/2005
• Est. Priority Date: 06/12/1997
• Status: Expired due to Term

• Current Assignee: ICU Medical Incorporated
• Original Assignee: Hospira Incorporated (Pfizer Inc.)
• Inventors: Briggs, Kenneth D., Pryce, Dean C., Sampson, Russel M.
• Primary Examiner(s): Rodriguez, Cris L.
• Application Number:
  US10/115,311
• Publication Number:
  US 20020147425A1
• Time in Patent Office: 1,084 Days
• Field of Search: 604/500, 604 65- 67, 604/151, 604/131, 604/156, 604/32, 604/34, 604/30, 128/DIG.12, 417/19, 417/20, 417/32, 417/18, 417/14, 738/610.5, 738/610.6, 732/042.3, 732/025, 374132-135, 374/163, 374/165, 374/166
• US Class Current: 604/500
• CPC Class Codes: F04B 2205/09 Flow through the pump
• CPC Class Codes: F04B 43/08 having tubular flexible members F04B43/12 takes precedence
• CPC Class Codes: F04B 49/20 by changing the driving speed
• CPC Class Codes: G05D 7/0676 by action on flow sources G05D7/0688, G05D7/0694 take precedence

Abstract

A peristaltic pump is provided with a housing, a pump head in the housing, and a receiving path defined along a housing and pump head for receiving tubing. Two spaced-apart temperature sensors are provided. One temperature sensor is located adjacent the tubing in a heat conduction path along which heat flows between the sensor and the tubing. The other sensor is located outside of the heat conduction path for sensing ambient temperature. The pump operating speed is adjusted as a function of the sensed temperatures. This accommodates the temperature-dependent rate of recovery of the tubing from its peristaltically deformed configuration to its original configuration.

Claims

1. A process for regulating fluid flow through flexible tubing in a peristaltic pump where a length of the tubing which has been peristaltically deformed recovers to its original cross-sectional configuration at a rate dependent upon the temperature T_f of the fluid at the interior surface of the tubing, said process comprising the steps of:

(A) determining a temperature T_s by measurement with a first temperature sensor disposed on a heat transfer path adjacent to an exterior surface of said tubing, the heat transfer path being defined by a thermally conductive electrical insulator having a first surface disposed against said exterior surface of said tubing in said pump and a second surface bonded to said first temperature sensor by an interposed thermally conductive layer of bonding material;

(B) determining the ambient temperature T_a by measurement with a second temperature sensor disposed in said pump at a location thermally isolated from said heat transfer path;

(C) periodically calculating the temperature T_f of the fluid at the interior surface of the tubing according to the formula $T_f=\frac{\left(b<br><br>\text{\hspace{1em}<br><br>}<br><br>T_a\right)-T_s}{\left(b-1\right)}$

where b is an empirically predetermined constant equal to (T_f−

T_s)/(T_f−

T_a) calculated from a measured value of the temperature T_s when both temperatures T_f and T_a are fixed at selected values; and

(D) varying the pump operating speed inversely with, and as a function of, changes in the calculated temperature T_f.

2. A process for regulating fluid flow through flexible tubing in a peristaltic pump where a length of the tubing which has been peristaltically deformed recovers to its original cross-sectional configuration at a rate dependent upon the temperature T_f of the fluid at the interior surface of the tubing, said process comprising the steps of:

(A) determining a temperature T_s by measuring with a first temperature sensor disposed in said pump against a surface of an interposed thermally conductive structure which is located between, and in contact with, an exterior surface of said tubing and said first temperature sensor;

(B) determining the ambient temperature T_a by measuring with a second temperature sensor disposed in said pump at a location spaced and thermally isolated from said tubing and interposed thermally conductive structure;

(C) calculating the temperature T_f of the fluid at the interior surface of the tubing according to the formula $T_f=\frac{\left(b<br><br>\text{\hspace{1em}<br><br>}<br><br>T_a\right)-T_s}{\left(b-1\right)}$

where b is an empirically predetermined constant equal to (T_f−

T_s)/(T_f−

T_a) calculated from a measured value of the temperature T_s when both temperatures T_f and T_a are fixed at selected values; and

(D) operating the pump at a speed as a function of the calculated temperature T_f.

3. The process in accordance with claim 2 wherein said interposed thermally conductive structure is also an electrical insulator.

4. A process for regulating fluid flow through flexible tubing in a peristaltic pump where a length of the tubing which has been peristaltically deformed recovers to its original cross-sectional configuration at a rate dependent upon the fluid temperature, said process comprising the steps of:

(A) sensing the temperature at a location on a heat transfer path which includes a portion of said tubing inside the pump;

(B) sensing ambient temperature inside the pump at a location spaced from said tubing and thermally isolated from said heat transfer path; and

(C) adjusting the pump operating speed as a function of the two sensed temperatures.

5. A process for regulating fluid flow through flexible tubing in a peristaltic pump where a length of the tubing which has been peristaltically deformed recovers to its original cross-sectional configuration at a rate dependent upon the fluid temperature, said process comprising the steps of:

(A) sensing the temperature at a location on a heat transfer path which includes a portion of said tubing inside the pump;

(B) sensing ambient temperature inside the pump; and

(C) adjusting the pump operating speed as a function of the two sensed temperatures.