Constant flow fluid pump

• US 6,227,807 B1
• Filed: 02/02/1999
• Issued: 05/08/2001
• Est. Priority Date: 02/02/1999
• Status: Expired due to Term

• Current Assignee: Becton, Dickinson & Co
• Original Assignee: Becton, Dickinson & Co
• Inventors: Chase, Eric
• Primary Examiner(s): Walberg, Teresa
• Assistant Examiner(s): FASTOVSKY, LEONID M
• Application Number:
  US09/241,654
• Time in Patent Office: 826 Days
• Field of Search: 210/656, 210/634, 318/685, 417/20, 417/478, 417/38, 417/22, 417/44, 417/44.1, 417/44.3, 417/46, 417/2, 417/36
• US Class Current: 417/44.1
• CPC Class Codes: F04B 11/0041 by piston speed control F04B11/0058 takes precedence
• CPC Class Codes: F04B 49/065 and making use of computers
• CPC Class Codes: G01N 15/1404 Handling flow, e.g. hydrodynamic focusing

Abstract

The present invention is a means and method for providing constant output flow from a fluid pump. The invention does this by controlling the radial speed of the pump motor during discreet segments of the motor'"'"'s 360° angular/radial path through a revolution of the pump. The electric pump motor is controlled throughout the 360° radial path by employing a control means for controlling the speed of actuation of the radial steps of a stepper motor throughout the 360° path of rotation of the stepper motor. Control means for controlling the speed of the discreet steps of the stepper motor comprises at least a memory means, a counting means and an amplification means.

Claims

1. A constant flow fluid pump, including a single fluid pump means having a single linear moving piston actuated by a rod and a crankshaft within a single cylinder for pumping a fluid through said single cylinder, comprising:

a motor disposed in mechanical communication with said crankshaft of said single pump means; and

control means in electrical communication with said motor for energizing said motor at predetermined differing rates at discrete steps through the 360°

rotation of said motor to provide for rotating said crankshaft at fluctuating speeds and thereby drive said single moving piston at a constant linear speed during the upstroke of said single piston, and to minimize the drown stroke time of said single piston.

2. The constant flow pump of claim 1 wherein the control means energizes the motor at predetermined differing rates by supplying uniform current/power to the motor at predetermined differing times.

3. The constant flow pump of claim 2, wherein said control means includes memory means, counting means, converting means, amplifying means and reset means.

4. The constant flow pump of claim 3 wherein the memory means includes an EPROM programmed with a predetermined series of numbers each representing a different time between motor steps.

6. The means for controlling the linear speed of a rod driven by a reciprocating crank shaft of claim 1, wherein said control means further includes a preprogrammed forward control memory means for storing a series of numbers, each of said numbers being representative of a discreet signal to said stepper motor to articulate a discreet step in said 360°

rotation of said stepper motor, a counting means for selecting the numbers stored in said memory means, a conversion means for converting said number to a time interval before the next step command is given, and a driving means responsive to the output step command signals of said conversion means for outputting electrical power to said stepper motor for energizing said stepper motor to articulate the next step for each of said steps around said 360°

rotation.

8. The constant flow pump of claim 3 wherein the memory means includes means for storing 400 numbers, each number representing the velocity of the motor at each of 400 discrete steps around the 360°

rotation of the motor.

9. The constant flow pump of claim 8 wherein the counter means includes means for counting the number of half steps during which the motor has advanced, said counter means further includes means for counting the advancing 400 half step advances during one revolution of the motor prior to being reset by the reset means.

10. The constant flow pump of claim 9 wherein the conversion means further includes an internal conversion means and includes means for taking each of the 400 numbers representing motor velocity from the memory means and loading said number into said internal conversion means, said internal conversion means includes means for counting down from said number at a constant rate and outputting a pulse to the counter means for advancing the counter means by one step and for outputting a pulse to the amplifier means.

11. The constant flow pump of claim 10 wherein the amplifier means includes means to convert and amplify said conversion means pulse into suitable half step energization current for causing the motor to advance a half step.

12. The constant flow pump of claim 11 wherein the reset means includes an optical sensor means having a reset flag disposed on the motor so as to rotate with the motor'"'"'s output shaft, which optical sensor means sends a reset signal to the counter means when said optical sensor means senses said reset flag, to provide for synchronizing said counter means with the actual position of the motor to provide for resetting the counter means when the piston is in the correct position within the cylinder at the beginning of the next stroke.

5. A means for controlling the linear speed of a piston rod that is being driven by a rotating crank shaft, comprising:

a) a stepper motor means in rotatable communication with said rotating crank shaft for turning said crank shaft in discreet steps throughout the full 360°

rotation; and

b) control means for controlling the predetermined incident speed of said stepper motor throughout said 360°

rotation.

7. A control means for converting a position controlled device into a speed controlled device, comprising:

a) a memory means for storing a series of numbers, each of said numbers being representative of a discreet signal to a stepper motor to articulate a discreet step in the 360°

rotation of said stepper motor and the speed of articulating said discreet step;

b) a counting means for selecting the numbers stored in said memory means, a conversion means for converting said numbers to a time interval before the next motor step and for outputting a signal representative of the incidence of the discreet step of said stepper motor of said 360°

rotation; and

c) a driving means responsive to the output signals of said conversion means for outputting electrical power to said stepper motor for energizing said stepper motor to articulate each of said steps around said 360°

rotation.