Voluntary opening prehension device

• US 4,685,925 A
• Filed: 10/22/1984
• Issued: 08/11/1987
• Est. Priority Date: 10/22/1984
• Status: Expired due to Term

• Current Assignee: Northwestern University
• Original Assignee: Northwestern University
• Inventors: Childress, Dudley, Strysik, John
• Primary Examiner(s): Picard, Leo P.
• Application Number:
  US06/663,154
• Time in Patent Office: 1,023 Days
• Field of Search: 3/12, 3/1.1, 623/25
• US Class Current: 623/25
• CPC Class Codes: A61F 2/588 Hands having holding devices shaped differently from human fingers, e.g. claws, hooks, tubes
• CPC Class Codes: A61F 2/72 Bioelectric control, e.g. myoelectric
• CPC Class Codes: A61F 2002/30525 Worm gears
• CPC Class Codes: A61F 2002/701 operated by electrically controlled means, e.g. solenoids or torque motors
• CPC Class Codes: A61F 2220/0025 Connections or couplings between prosthetic parts, e.g. between modular parts; Connecting elements
• CPC Class Codes: H02P 5/68 controlling two or more dc dynamo-electric motors H02P5/46, H02P5/60 take precedence

Abstract

A voluntary opening prehension device is constructed with a pivot member having a pair of fingers mounted thereon and extending distally from the pivot member. The fingers may be pivoted individually or simultaneously so as to selectively separate or converge at their distal ends. An electric motor is used to separate the fingers. A closing mechanism biases the fingers into contact with each other when the motor is not in operation. A battery supplies electrical power to the motor. A field effect transistor driver serves as a switch for actuating the electric motor when it is supplied with a myopulse of a specified threshold strength or greater. This reduces the amount of electrical power utilized to operate the device since the motor is actuated only when a clear signal is sent from the user. A control mechanism supplies the myopulse to the field effect transistor driver in response to a myoelectric signal generated by the user.

Claims

1. A voluntary opening prehension device comprising:

a pivot member;

a pair of finger members extending distally from said pivot member, at least one of said finger members being pivotally mounted thereon for selective separation and convergence of said finger members at their respective distal ends;

electric motor means for effecting said selective separation of said finger members;

closing means for biasing at least a portion of said finger members in contact with each other;

a battery member for supplying electrical power to said electric motor means;

field effect transistor driver means for actuating said electric motor means when supplied with a myopulse signal of a specified threshold strength or greater, so as to reduce the electric power necessary to operate said prehension device;

control means for supplying a myopulse to said field effect transistor driver in response to a myoelectric signal generated by the user;

said control means comprising a signal detector for detecting a myoelectric signal generated by the user;

a processor for processing said myoelectric signal into a myopulse which is directed to said field effect transistor driver for actuating said driver; and

a threshold detector for restricting actuating of said motor to those instances in which said myoelectric signal is of a specified minimum voltage strength or greater.

2. The voluntary opening prehension device as described in claim 1 wherein said field effect transistor driver means, said signal detector, said processor and said threshold detector are affixed to a module selectively removable from and connectable to said voluntary opening prehension device, for repair or replacement as desired.

3. The voluntary opening prehension device as described in claim 1 wherein said battery member is selectively removable from and connectable to the voluntary opening prehension device for recharging or replacement as desired.

4. The voluntary opening prehension device of claim 1 wherein a first one of said pair of finger members is fixedly attached to said pivot member and a second one of said pair of finger members is pivotally mounted on said pivot member whereby pivoting of said second one of said pair of finger members is effective to selectively separate or bring together said pair of finger members.

5. The voluntary opening prehension device as described in claim 1 wherein said electric motor means comprises:

a direct current micromotor electrically connected to said battery member, said micromotor having a linear shaft extending perpendicularly therefrom at a first end; and

a cable member connected to said linear shaft member at a first end and attached to one of said finger members at a second end whereby actuation of said direct current micromotor is effective to rotate said shaft member thereby winding said cable member about said shaft, which in turn pivots said finger member into an open position relative to the other of said finger members.

6. The voluntary opening prehension device of claim 1 wherein the threshold detector further comprises hysteresis means for providing hysteresis of the predetermined threshold value thereby preventing the threshold detector from cycling the motor means due to small fluctuations in the myoelectric signal when said myoelectric signal is near the specified minimum voltage strength.

7. The artificial hand of claim 6 wherein the threshold detection means further comprises hysteresis means for providing hysteresis of the predetermined threshold value thereby preventing cycling of the motor means due to small fluctuations in the value of the electrical signal when said value is near the predetermined threshold value.

8. An artificial hand comprising:

an artificial forearm member attachable to the arm of the patient;

a pivot member attached to the distal end of said forearm member;

a pair of finger members extending distally from said pivot member and pivotally mounted thereon, so as to permit selective contact of said finger members to each other proximate their respective distal tips;

electric motor means for selectively separating said finger members;

field effect transistor driver means for actuating said electric motor means when supplied with electrical current;

a battery member for supplying electrical current to said electric motor means;

closing means for urging at least a portion of each of said finger members into contact with each other; and

control means for selectively actuating said electric motor means, said control means including;

an electrode member affixed proximate to a voluntary muscle of the patient for detecting electrical activity generated by actuation of the voluntary muscle of the patient;

a bandpass amplifier electrically connected to said electrode member for amplifying an electrical signal as a result of said electrical activity;

an amplifier electrically connected to said signal detector for rectifying said electrical signal and fur supplying a myopulse to said field effect transistor driver; and

,

threshold detection means for comparing the myopulse to a predetermined threshold value and for inhibiting actuation of said electric motor means whenever the myopulse signal has a value less than the predetermined threshold value.

9. The artificial hand as described in claim 8 and further comprising:

socket means for rapid selective attachment or removal of said pivot member to said forearm member.

10. The artificial hand as described in claim 9 and further comprising:

an elastic resilient thermoplastic covering encompassing said finger members and formed in the shape of a hand so as to simulate the appearance and function of a natural hand and to urge said finger members into contact with each other.

11. The artificial hand as disclosed in claim 10 and further comprising:

a second pivot member interchangeably attachable to said socket member, and having a pair of fingers extending distally therefrom and pivotally mounted thereon, so as to provide selective attachment of;

(1) said pivot member with said thermoplastic covering encompassing said finger member or

(2) said socket member as desired.

12. The artificial hand as disclosed in claim 8 and further comprising:

retriggerable timer means for limiting actuation of said electric motor means to a selected time period, so as to reduce the power consumption of said artificial hand member.

13. The artificial hand as disclosed in claim 12 wherein said selected time period is 4 seconds.

14. The prosthetic device as described in claim 12 wherein said desired period of actuation is approximately four seconds, so as to allow time for grasping of an object and at the same time effect conservation of said electrical power.

15. The artificial hand as described in claim 8 wherein said field effect transistor driver comprises:

a vertical metal oxide semiconductor transistor having a voltage of 40-70 millivolts when driving said electric motor means, said vertical metal oxide semiconductor transistor being effective to reduce the voltage drop to said electric motor means and thereby to operate said artificial hand more efficiently.

16. The artificial hand as described in claim 8 wherein said amplifier comprises:

a complimentary metal oxide semiconductor bandpass amplifier.

17. The artificial hand as described in claim 8 wherein said closing means comprises:

an elastic band member connecting said finger members so as to resiliently retain said finger members in contact with each other.

18. The artificial hand as described in claim 8 and further comprising:

a smoothing circuit electrically connected to said signal detector for removing fluctuations in output current; and

a buffer circuit interposed between said amplifier and said electric motor means for electrical isolation of said processor.

19. The artificial hand as described in claim 8 and further comprising:

a thermoplastic covering encompassing said finger members and formed in the shape of a hand so as to simulate the appearance and function of a natural hand.

20. The artificial hand as described in claim 8 wherein said thermoplastic covering is selectively removable by the user.

24. The prosthetic device as described in claim 15 wherein said battery means comprises a 9-volt transistor battery.

21. A myoelectrically controller prosthetic device comprising:

a housing member;

means for attaching said housing member to the natural limb of the patient;

an artificial limb member extending distally from said housing member and movably attached thereto;

electric motor means for selective movement of said artificial limb member, relative to said housing member;

a battery member for supplying electrical power to said electric motor means;

control means for selectively actuating said electric motor means, in response to movement of one or more selected voluntary muscles of the patient;

a field effect transistor driver for actuating said electric motor means when a specified threshold signal has been detected from the patient;

said control means including a signal detector for detecting myoelectric signals generated by the user;

a processor for processing said myoelectric signal into a myopulse directed to said field effect transistor driver for actuation thereof; and

threshold detection means for comparing the myopulse signal to a predetermined threshold value and for inhibiting actuation of the field effect transistor whenever the myopulse has a value less than the predetermined threshold value.

22. The prosthetic device as described in claim 21 and further comprising:

timer means for deactivating said electric motor means after a desired period of actuation so as to conserve the electrical power of said battery.

23. The prosthetic device as described in claim 21, wherein said prosthetic device utilizes a quiescent current of 18 microamperes or less.

25. The prosthetic device as described in claim 21 and further comprising an easy access battery chamber for selective removal and replacement of said battery means, as required.

26. The myoelectrically controlled prosthetic device of claim 21 wherein the threshold detector means further comprises hysteresis means for providing hysteresis of the predetermined threshold value thereby preventing cycling of the motor means due to small fluctuations in the value of the myopulse when said value is near the predetermined threshold value.