Flow rate accuracy of a fluidic delivery system

• US 8,141,844 B2
• Filed: 10/22/2008
• Issued: 03/27/2012
• Est. Priority Date: 10/26/2005
• Status: Active Grant

• Current Assignee: Medos International Sarl (Johnson & Johnson)
• Original Assignee: Codman Neuro Sciences Sarl
• Inventors: Ginggen, Alec, Bork, Toralf, Crivelli, Rocco
• Primary Examiner(s): Fristoe, Jr., John
• Application Number:
  US12/255,666
• Publication Number:
  US 20090140185A1
• Time in Patent Office: 1,252 Days
• Field of Search: 251/129.01, 251/129.05, 251/129.06
• US Class Current: 251/129.05
• CPC Class Codes: A61M 2205/0294 Piezoelectric materials
• CPC Class Codes: A61M 2205/70 with testing or calibration facilities
• CPC Class Codes: A61M 2205/702 automatically during use
• CPC Class Codes: A61M 2205/8212 with means or measures taken for minimising energy consumption
• CPC Class Codes: A61M 39/22 Valves or arrangement of valves A61M39/02, A61M39/0247, A61M39/16 take precedence; regulating valves in infusion systems A61M5/16881; in devices worn by the patient for the reception of urine, faeces, catamenial or other discharge, or in colostomy devices A61F5/4405
• CPC Class Codes: A61M 5/14276 specially adapted for implantation
• CPC Class Codes: A61M 5/16881 Regulating valves on-off valves, e.g. clamps A61M39/28
• CPC Class Codes: A61M 5/172 electrical or electronic A61M5/16804, A61M5/16831 take precedence
• CPC Class Codes: F16K 1/34 Cutting-off parts, e.g. valve members, seats F16K1/06, F16K1/12, F16K1/14, F16K1/26 take precedence
• CPC Class Codes: F16K 31/006 having a free end
• CPC Class Codes: H10N 30/802 Drive or control circuitry or methods for piezoelectric or electrostrictive devices not otherwise provided for
• CPC Class Codes: Y10T 137/86389 Programmer or timer

Abstract

Improving the accuracy of the flow rate of a valve in a fluidic delivery device in which a desired flow rate may be achieved by varying the duty cycle of the valve. The flow rate of fluid delivery from the valve over its lifetime is stabilized by minimizing the voltage OPENING time of the valve to account for valve and piezoelectric actuator drift. Also, the valve OPENING time of one or more fluidic parameters that impact on the flow rate delivery by the valve and differ among fluidic delivery devices is compensated to optimize the flow rate accuracy.

Claims

1. A valve assembly with optimized flow rate accuracy over its lifetime, comprising:

a power supply;

charge pump circuitry powered by the power supply;

a piezoelectric actuator charged by the charge pump circuitry, the charge applied across the piezoelectric actuator reaching a predetermined threshold voltage over a rise time; and

a valve transitioning from a CLOSED state to an OPEN state when the piezoelectric actuator exceeds the predetermined threshold voltage;

the charge pump circuitry receives as input a PWM charge input signal subdivided into a plurality of PWM units, together comprising a PWM group, each of the plural PWM units having its own associated PWM parameters applied to that PWM unit so as to minimize a valve OPENING time and optimize the flow rate accuracy over the lifetime of the valve.

2. The valve assembly in accordance with claim 1, wherein each of the plural PWM units in the PWM group are equal in duration.

3. The valve assembly in accordance with claim 1, wherein the plural PWM units in the PWM group are not all equal in duration.

4. The valve assembly in accordance with claim 1, wherein the charge pump circuitry comprises a transistor electrically connected to an inductor.

5. The valve assembly in accordance with claim 4, the PWM charge pump input signal being generated by a processor is received as input to the transistor for establishing transistor ON time when the PWM charge pump input signal is high and transistor OFF time when the PWM charge pump input signal is low.

6. The valve assembly in accordance with claim 5, wherein when the power supply is substantially constant, among the plural PWM units in a particular PWM group, the transistor ON time remains constant, while the transistor OFF time is varied over time due to increasing charge built up across the piezoelectric actuator.

7. The valve assembly in accordance with claim 6, wherein with depleting voltage supplied by the power supply over time, among the plural PWM units in a particular PWM group, the transistor OFF time remains constant, while the transistor ON time is varied over time to compensate for the depleting voltage supplied by the power supply.

8. The valve assembly in accordance with claim 5, wherein with depleting voltage supplied by the power supply over time, among the plural PWM units in a particular PWM group, the transistor OFF time remains constant, while the transistor ON time is varied over time to compensate for the depleting voltage supplied by the power supply.