INFUSION SYSTEM

• US 3,739,943 A
• Filed: 02/04/1971
• Issued: 06/19/1973
• Est. Priority Date: 02/04/1971
• Status: Expired due to Term

• Current Assignee: Sherwood Medical Company (Medtronic Plc)
• Original Assignee: Jack L. Wilhelmson, Theodore E. Weichselbaum, Vernon F. Braun
• Inventors: Wilhelmson, Jack L., Weichselbaum, Theodore E., Braun, Vernon F.
• Primary Examiner(s): Freeh, William L.
• Assistant Examiner(s): Winburn, John T.
• Application Number:
  US05/112,691
• Time in Patent Office: 866 Days
• Field of Search: 417/416,417,418 222/70,76,59 128/DIG.13,230
• US Class Current: 222/59
• CPC Class Codes: A61M 5/1452 pressurised by means of pistons
• CPC Class Codes: A61M 5/1458 Means for capture of the plunger flange
• CPC Class Codes: A61M 5/172 electrical or electronic A61M5/16804, A61M5/16831 take precedence
• CPC Class Codes: A61M 5/365 Air detectors A61M5/1684 takes precedence; in extracorporeal blood circuits A61M1/3626
• CPC Class Codes: Y10S 128/13 Infusion monitoring

Abstract

A portable infusion system uses a disposable piston-type syringe and a disposable two-way valve as a positive displacement pump. The syringe piston is reciprocally driven by a bidirectional DC motor under control of a battery powered circuit. Different selectable rates of pumping are maintained by controlling the width of bidirectional DC pulses coupled to the DC motor and by monitoring the motor back EMF during the off time of the pulses. Safety circuits protect against deleterious conditions such as the passage of an air bubble, an over-pressure condition, or an excess pumping rate as could be caused by a component failure.

Claims

1. In a system having pump means for pumping fluid from a fluid source to an outlet, a rate monitor, comprising:

control means for controlling said pump means and for providing a control signal representative of a selected rate of flow for the fluid;

sensing means for generating a monitor signal representative of the rate of flow produced by said pump means;

first circuit means coupled to said control means and said sensing means for comparing said control and said monitor signals for generating an error signal when a comparison of the control signal and the monitor signal indicates that the produced rate of flow has varied by a predetermined amount from the selected rate of flow; and

second circuit means coupled to said first circuit means and responsive to said error signal for disabling said pump means upon the occurrence of said error signal.

2. The rate monitor of claim 1 wherein said pump means includes fluid channel means interconnecting said fluid source and said outlet and including a pump chamber, and drive means including a piston slidably mounted within the pump chamber for reciprocation under control of said control means to pump fluid through said fluid channel means, said sensing means generating said monitor signal in response to a predetermined motion of said drive meaNs.

3. In a system having pump means for pumping fluid from a fluid source to an outlet, a rate monitor, comprising:

control means for controlling said pump means and for providing a control signal representative of a selected rate of flow for the fluid;

sensing means for generating a monitor signal representative of the rate of flow produced by said pump means;

circuit means for generating an error signal when a comparison of the control signal and the monitor signal indicates that the produced rate of flow has varied by a predetermined amount from the selected rate of flow, said pump means including fluid channel means interconnecting said fluid source and said outlet and including a pump chamber, and drive means including a piston slidably mounted within the pump chamber for reciprocation under control of said control means to pump fluid through said fluid channel means, said drive means including link means cyclically driven through a path, said sensing means generating said monitor signal in response to a predetermined motion of said drive means, said sensing means including position responsive means for sensing cyclically recurring positions of said link means whereby said monitor signal is cyclically recurring.

4. The rate monitor of claim 3 wherein said control means provides a fixed value control signal for a given selected rate of flow, said circuit means includes time constant means for producing a time varying signal having a value dependent on the value of said fixed control signal and the time duration thereof, and means for time comparing said time varying signal with said cyclically recurring monitor signal to detect said predetermined amount of rate variation.

5. The rate monitor of claim 4 wherein said time constant means includes capacitor means and a charging path therefore coupled to said fixed value control signal, and said time comparing means includes gate means for discharging said capacitor means for each occurrence of said cyclically recurring monitor signal.

6. The rate monitor of claim 3 wherein said sensing means comprises switch means actuated once for each repetitive cycle of said link means.

7. The rate monitor of claim 6 wherein said switch means comprises a magnetically actuable contact means which changes state in the presence of a magnetic field, and said link means includes magnetic field generating means carried thereby for actuating the contact means.

8. In a system having pump means for pumping fluid from a fluid source to an outlet, a rate monitor, comprising:

control means for controlling said pump means and for providing a control signal representative of a selected rate of flow for the fluid;

said control means including selector means for selecting different pumping rates, and motor means responsive to said selector means for controlling the cyclic rate of driving the pump means;

sensing means for generating a monitor signal representative of the rate of flow produced by said pump means; and

circuit means for generating an error signal when a comparison of the control signal and the monitor signal indicates that the produced rate of flow has varied by a predetermined amount from the selected rate of flow;

said circuit means including means responsive to said selector means for generating a different value control signal for each selectable rate, and means for comparing the different value control signals with the monitor signal.

9. The rate monitor of claim 8 wherein said comparing means generates the error signal when the rate of flow produced by the motor means exceeds by a predetermined range the selected rate of flow, and safety means responsive to said error signal for disabling said motor means.

10. In an infusion system having pump means for pumping fluid from a fluid source to a patient, and control means for controlling the pump means to establish a desired pumping operation, a monitor, comprising:

sensing means associated with said pump means for providing a monitor signal representative of The actual pumping operation of the pump means;

circuit means for generating an analog waveform having a predetermined relation to the monitor signal when the actual pumping operation corresponds to the desired pumping operation;

detector means responsive to a change in the predetermined relation between the monitor signal and the analog waveform for generating an error signal; and

safety means for disabling the pump means in response to said error signal.

11. The monitor of claim 10 wherein said pump means comprises a positive displacement pump having a piston slidably mounted within a pump chamber for reciprocation along a predetermined path, and said sensing means generates a recurring monitor signal for at least each cycle of reciprocation.

12. The monitor of claim 11 wherein said circuit means generates a recurring analog waveform having a voltage level synchronized with the occurrence of the monitor signal when the actual rate of pumping corresponds to the desired rate of pumping, and said detector means is responsive to a time advance in the occurrence of the monitor signal for generating said error signal to thereby prevent an excessive pumping rate.

13. The monitor of claim 10 wherein said control means includes selector means for selecting different pumping rates for the pump means, said circuit means includes capacitor means, a plurality of circuit paths each having a different time constant, and charging means controlled by said selector means for connecting one of said circuit paths between a potential source and said capacitor means to form said analog waveform across said capacitor means, said detector means includes means for time comparing the charge of the capacitor means with the occurrence of the monitor signal to detect for said predetermined relation.

14. The monitor of claim 13 wherein said detector means further includes discharge means responsive to each occurrence of the monitor signal for discharging said capacitor means.