Solution pumping for maximizing output while minimizing uneven pumping pressures

• US 5,415,528 A
• Filed: 09/08/1994
• Issued: 05/16/1995
• Est. Priority Date: 12/18/1992
• Status: Expired due to Term

• Current Assignee: Hospira Incorporated (Pfizer Inc.)
• Original Assignee: Abbott Laboratories Incorporated
• Inventors: Tripp, Edward, Rudzena, William L., Ogden, John E.
• Primary Examiner(s): Bertsch, Richard A.
• Assistant Examiner(s): McAndrews, Jr., Roland G.
• Application Number:
  US08/303,279
• Time in Patent Office: 250 Days
• Field of Search: 417/19, 417/20, 417/28, 417/44.1, 417/44.3, 417/44.8, 604/151, 604/152, 604/153, 604/65, 604/67, 128/DIG. 12, 318/644, 318/645, 318/481, 222/63
• US Class Current: 417/28
• CPC Class Codes: A61M 2205/12 with interchangeable cassettes forming partially or totally the fluid circuit
• CPC Class Codes: A61M 2206/22 eliminating pulsatile flows, e.g. by the provision of a dampening chamber
• CPC Class Codes: A61M 5/142 Pressure infusion, e.g. using pumps
• CPC Class Codes: F04B 11/0041 by piston speed control F04B11/0058 takes precedence
• CPC Class Codes: F04B 43/04 Pumps having electric drive
• CPC Class Codes: Y10S 128/12 Pressure infusion

Abstract

A solution pumping system is disclosed which is embodied as a disposable pump cassette including a self-contained positive displacement pump, and an associated pump driver including a reciprocable pump piston for driving the pump of the cassette. This system is particularly suited for use in compounding in preparation of parenteral solutions for administration to patients. In order to promote high liquid output with minimum peak pumping pressures, the controls of the system operate to provide a "square" pumping pressure waveform, thus optimizing performance of the system. This is achieved by selectively varying the velocity of the pump piston during its operation.

Claims

1. A solution pumping system, comprising:

a pump driver including a reciprocable pump piston, and

associated pump means in operative association with said pump piston of said pump driver,

said system including a liquid inlet, a liquid outlet, and a liquid flow path for joining said inlet and outlet in fluid communication,

said pump means being joined with said flow path for pumping liquid from said inlet to said outlet, via said flow path, by reciprocation of said pump piston, wherein said pump piston cooperates with said pump means to pump means with liquid during an advancing stroke of said pump piston and to fill said pump means with liquid during a return stroke of said pump piston,

said system further including control means for controlling operation of said pump piston of said pump driver, said control means acting to minimize peak pressures created by said pump means while maximizing liquid output of said pump means, by selectively varying the velocity of the pump piston during the advancing stroke by accelerating the piston to a preselected maximum velocity and then decreasing the velocity for a selected time interval.

2. A solution pumping system in accordance with claim 1, wherein

said system includes pressure sensor means operatively associated with said pump means for sensing liquid pressure created by said pump means, said pressure sensor means being operatively connected with said control means to reduce the liquid pressure created by said pump means when the pressure exceeds a predetermined value.

3. A solution pumping system in accordance with claim 1, wherein

said pump means comprises a pump chamber, and a resilient pump diaphragm positioned adjacent to said chamber, said pump piston being engageable with said pump diaphragm so that during said advancing stroke of said pump piston, said diaphragm is displaced into said pump chamber for pumping liquid therefrom from said inlet to said outlet.

said pump chamber refilling with liquid during said return stroke as said resilient diaphragm creates a negative pressure within said pump chamber, said control means operating said pump piston during said return stroke so that said pump piston remains in engagement with said pump diaphragm.

4. A solution pumping system in accordance with claim 1, wherein

said pump driver includes a stepper motor operatively connected to said pump piston for advanced and retracting said pump piston by individual driving steps separated by dwell periods, said control means controlling the velocity of said pump piston by selectively varying the length of the dwell periods between successive driving steps of said stepper motor.

5. A solution pumping system, comprising:

a pump driver, said pump driver including a reciprocable pump piston, and a plurality of valve actuators; and

a pump cassette positionable in operative association with said pump driver, said pump cassette including at least one liquid inlet, at least one liquid outlet, a liquid flow path for joining said inlet and said outlet in fluid communication, and pump means operatively driven by the pump piston of said associated pump driver for pumping liquid from a selected liquid inlet to a selected liquid outlet via said flow path,

said pump means comprising a pump chamber, and a resilient pump diaphragm positioned adjacent the pump chamber for engagement with said pump piston, so that said diaphragm is displaced into said chamber during an advancing stroke of said pump piston, and said chamber is refilled with liquid during a return stroke of said pump piston as said resilient diaphragm creates a negative pressure within said chamber,

said system including control means for controlling operation of said pump means by controlling the velocity of said pump piston during said advancing stroke by accelerating the piston to a preselected maximum velocity and then decreasing the velocity for a selected time interval to act to minimize peak pressures created by said pump means while maximizing liquid output of said pump means.

6. A solution pumping system in accordance with claim 5, wherein

said pump driver includes pressure sensor means, including a probe engageable with said pump cassette, for sensing liquid pressure created by said pump means, said pressure sensor means being operatively connected with said control means to reduce the liquid pressure created by said pump means by varying the piston velocity when the pressure exceeds a predetermined value.

7. A solution pumping system in accordance with claim 6, wherein

said control means operates to control opening and closing of said liquid inlet and said liquid outlet by controlling selected ones of said valve actuators respectively operatively associated therewith,

said control means operating to delay closing of said liquid outlet and opening of said liquid inlet until the liquid pressure within said pump cassette returns substantially to zero subsequent to said advancing stroke of said pump piston, said control means operating to delay closing of said liquid inlet and opening of said liquid outlet until the liquid pressure within said pump cassette returns substantially to zero subsequent to the return stroke of said pump piston and refilling of said pump chamber.

8. A method of operating a solution pumping system including a pump driver having a reciprocal pump piston, and associated pump means in operative association with said pump piston, said method comprising the steps of:

reciprocally moving said pump piston for cooperation with said pump means, so that during an advancing stroke of said piston, liquid is pumped from said pump means, and during a return stroke of said piston said pump means refills with liquid, and

selectively varying the velocity of said pump piston by accelerating the piston to a preselected maximum velocity and then decreasing the velocity for a selected time interval to act to minimize peak pressures created by said pump means during said advancing stroke while maximizing liquid output of said pump means.

9. A method of operating a pumping system in accordance with claim 8, including:

sensing the pressure created by said pump means, and reducing the velocity of said pump piston during the advancing stroke thereof when liquid pressure within said cassette exceeds a predetermined value.

10. A method of operating a pumping system in accordance with claim 8, including

reciprocally moving said pump piston with a stepper motor operatively connected thereto, causing the pump piston not to move during at least one dwell period and controlling the velocity of said pump piston by selectively varying the dwell periods between successive driving steps of said stepper motor.

11. A method of operating a pumping system in accordance with claim 8, including

delaying successive advancing and return strokes of said pump piston until liquid pressure created by said pump means returns substantially to zero.