Electrically driven artificial arm

• US 4,521,924 A
• Filed: 03/01/1983
• Issued: 06/11/1985
• Est. Priority Date: 03/01/1983
• Status: Expired due to Term

• Current Assignee: University of Utah (State of Utah)
• Original Assignee: University of Utah (State of Utah)
• Inventors: Jacobsen, Stephen C., Knutti, David F., Johnson, R. Todd
• Primary Examiner(s): Frinks, Ronald L.
• Application Number:
  US06/470,927
• Time in Patent Office: 833 Days
• Field of Search: 3/1.1, 3/12-12.8
• US Class Current: 623/20.11
• CPC Class Codes: A61F 2/58 Elbows; Wrists ; Other joints; Hands

Abstract

A prosthesis for a person with an amputation above the elbow is provided in which elbow motion is provided by an electrical motor contained within the prothesis. Operation of the motor is controlled by electric impulses from selected opposing muscle pairs on the amputee. The prosthesis is constructed with both internal and external modules which are readily replaceable. An electrically operated lock mechanism is provided for locking the elbow motion of the prosthesis. The locking mechanism is controlled by logic circuitry which in turn operates in response to electric impulses from the pair of muscles on the amputee. Novel means are also included which provide passive wrist movement and humeral rotation of the prosthesis. A removable battery module comprising rechargeable storage cells provides power for the motor and the electrically operated lock mechanism.

Claims

1. A prosthesis for a person with an amputation above the elbow, to provide a replacement for at least the lower arm and elbow of the person, with the prothesis being made from internal and external modules which are readily replaceable, said prosthesis comprising:

an upper arm or socket module which is adapted to be attached to the stump or shoulder portion of the person'"'"'s torso;

skin electrodes for monitoring the electromyographic signals from two antagonist muscles on the stump or torso of the person;

an elbow module having a hollow cavity therewithin, with a locking pin member mounted within the hollow cavity and an opening in the elbow module through which the locking pin is adapted to move, said elbow module further including means for moving the locking pin back and forth in the opening in the elbow module between an extended position in which the end of the locking pin extends outwardly from said opening in the elbow module and a retracted position in which the end of the locking pin is retracted so as to not extend outwardly from said opening;

means for connecting the elbow module to the socket module so that the elbow module can be rotated relative to the socket module about the longitudinal axis of the socket module;

a forearm module comprising a hinged member adapted to be pivotally attached to the elbow module, said hinged member having an enclosed hollow back portion and a forward portion formed of a substantially open framework, said forearm module further comprising an elongate forearm cover member which is open at both of its ends and is adapted to slide over the framework portion of the hinged member for attachment to the framework portion, with the rear end of the forearm cover abutting the enclosed back portion of the hinged member such that the combined cover member and hinged member have the general shape of a human forearm, said hinged member being open at its end adjacent to the hollow back portion thereof so that the elbow module can be received within the hollow back portion of the hinged member when the hinged member is pivoted about its attachment to the elbow module, said hinged member also having attached firmly to an inside surface of the hollow back portion thereof a curved elongate lock member which has a plurality of detent holes equally spaced along the length thereof, said lock member being positioned along the inside surface of the hinged member so that as the hinged member pivots about its attachment to the elbow module, the curved elongate lock member moves in an arc such that the detent holes therein move successively back and forth directly beneath the opening in the elbow module, whereby the hinged member, and thus the forearm module, can be locked in place with respect to the elbow module at various positions in the movement of the forearm module relative to the elbow module by activating the lock pin to extend from the opening in the elbow module to engage one of the detent holes in the lock member;

a motorized drive module for imparting pivotal movement of the forearm module relative to the elbow module, said drive module comprising a DC motor and gear reduction transmission mounted on a frame which is adapted to be removablyattached to the hinged member within the open framework of the hinged member, said drive module further including linkage means connected at one end thereof to the elbow module and at the other end thereof to the transmission, whereby the rotary motion of the motor is transmitted to substantially translational movement of the linkage which in turn imparts pivotal movement of the forearm module relative to the elbow module;

a wrist module attached to the forward end of the forearm cover, said wrist module being adapted to have a hook or simulated hand removably attached thereto, said wrist module further including means for rotating the hook or simulated hand relative to the forearm about the longitudinal axis of the forearm;

an electronic controller module adapted to receive the electromyographic signals from the skin electrodes to operate the DC motor of the motorized drive module; and

a battery pack module which is removably received within a receptacle in the prosthesis so as to be connected to the electronic controller module for providing electrical power thereto.

2. A prosthesis as claimed in claim 1, wherein said elbow module has a substantially flat upper end and further wherein said means for connecting the elbow module to the socket module comprises:

an annular fitting which is adapted to be attached to the end of the socket module, said annular fitting having a cylindrical end portion which extends away from the socket module and which has a substantially flat, circular end face, said cylindrical end portion being substantially coaxial with the longitudinal axis of the socket module, said cylindrical end portion further having a circumferencial flange or ring adjacent to the flat, circular, end face thereof;

an annular friction band having an annular recess formed around the inside surface at one end portion thereof so that the annular recess is adapted to engage the circumferential flange on said annular fitting, with the other end portion of the friction band adapted for attachment to the upper end of the elbow module to hold the flat upper end of the elbow module in parallel, closely spaced relationship with the flat, circular end of the annular fitting; and

an adjustable tension band adapted to encircle the friction band and to provide adjustable compression of the friction band,

whereby the ease with which the elbow module can be rotated relative to the socket module can be adjusted incrementally between essentially free rotation and various degrees of restrained rotation by adjusting the tension band to increase or decrease the compression exerted by the tension band on the friction band.

3. A prosthesis as claimed in claim 1, wherein the electronic controller module is mounted within the hollow cavity within the elbow module, and a portion of the exterior of the elbow module is removable so as to provide access to the cavity.

4. A prosthesis as claimed in claim 3 wherein the battery pack module is mounted within the cavity in said elbow module, with the battery pack module being adapted to be removably received within the cavity through an open space in the elbow module, with the outer end of the battery pack module being adapted to form a continuous surface for the open space in the elbow module when the battery pack module is positioned within the cavity of the elbow module.

5. A prosthesis as claimed in claim 1, wherein a wiring harness is provided for making electrical contact between electrical components of the prosthesis, said wiring harness comprising a flat ribbon of flexible material having conductor paths formed along the surface of the ribbon of flexible material, said conductor paths terminating in mutually corresponding contact pads adjacent various edges of the harness, and means are provided for connecting the electrical leads from the electrical components to corresponding contact pads on the harness.

6. A prosthesis as claimed in claim 5, wherein the wiring harness comprises a central portion and a plurality of ribbon-like extensions, with the conductor paths extending from the central portion to corresponding extensions and with the contact pads for the respective conductor paths being positioned at the terminal end portions of the extensions.

7. A prosthesis as claimed in claim 5, wherein the leads from the electrical components terminate in contact pads which are positioned on a substantially flat support member, and the means for connecting the electrical leads from the electrical components to corresponding contact pads on the harness comprises:

an elongate strip of resilient material positioned along at least one of the respective side edges of said harness and said flat support member when the harness and flat support member are positioned in side-by-side relationship with the pads on the harness abutting corresponding pads on the flat surface member;

and an elongate clip member adapted to clip firmly over the srip of resilient material and the side edges of the harness and the flat support member,

whereby the pads on the harness are held in firm electrical contact with correspondig pads on the flat support member.

8. A prosthesis as claimed in claim 1, wherein the means for moving the locking pin back and forth in the opening in the elbow module comprises:

a spring cantilevered at its one end to a rotatable base, with the other end of the spring being adapted to contact the locking pin;

means for rotating the rotatable base from a first position through an angle of about 180 degrees to a second position and vice versa about an axis coinciding with the attachment of the spring to the rotatable base,

whereby when the rotatable base is in its said first position, the spring biases the locking pin to move longitudinally to its extended position and when the rotatable base is in its said second position, the spring biases the locking pin to move longitudinally to its retracted position.

9. A prosthesis as claimed in claim 8, wherein the means for rotating the rotatable base includes:

a second DC motor;

a gear mechanism connecting the second DC motor to the rotatable base; and

means for operating the second DC motor.

10. A prosthesis as claimed in claim 9, wherein the means for operating the second DC motor comprises:

means for measuring the torque at the pivotal attachment of the forearm module to the elbow module;

means for measuring the rotational movement of the forearm module relative to the elbow module; and

wherein the electronic controller module comprises circuitry means for operating the second motor to rotate the rotatable base to its said first position only when the rotational movement of the forearm module is substantially zero and simultaneously the torque is above a predetermined value for a specified time interval, said electronic controller module further having circuitry means for operating the second motor to rotate the rotatable base to its said second position when a predetermined succession of electromyographic signals are received from the skin electrodes.

11. A prosthesis as claimed in claim 10, wherein the means for measuring the torque comprises means adapted to measure the force exerted on the elbow module by the linkage means of the motorized drive module, and the means for measuring the rotational movement of the forearm module comprises means for monitoring operation of the DC motor of the motorized drive module.

12. A prosthesis as claimed in claim 10, wherein the means for measuring said torque comprises:

an elongate stress member attached at one end thereof to the elbow module so as to displaced from and substantially parallel to the pivot axis about which the forearm module is attached to the elbow module, with the other end of the stress member being attached to the linkage means of the motorized drive module; and

a strain guage associated with the stress member to measure strain therein from the force exerted on the stress member by the linkage means,

and wherein the means for monitoring operation of the DC motor of the motorized drive module comprises;

an electrical generator driven from the drive shaft of the DC motor, whereby when the DC motor is operating, an output current is produced by the electrical generator.

13. A prosthesis as claimed in claim 1, wherein the frame on which the DC motor and the gear reduction transmission of the motorized drive module are mounted has at least three spaced projections extending therefrom, and the sides of the framework of the hinged member of the forearm module have a number of slots corresponding to the number of the projections on said frame, with the slots being adapted to receive the respective projections on the frame to effect attachment of the frame to the framework of the hinged member, and with the slots further being provided with removable end covers which prevent the projections on the frame from being removed from the slots until the removable end covers are removed from the slots.

14. A prosthesis as claimed in claim 13, wherein the spaced projections have a covering of resilient material about the end portion thereof, whereby the resilient material is compressed between the projections and the slots when the projections are positioned within their corresponding slots.

15. A prosthesis as claimed in claim 1, wherein the wrist module comprises:

a substantially cylindrical attachment member having external threads at one end thereof, with the other end of the attachment member being adapted to be secured to the forward end of the forearm cover;

an insert member comprising a cylindrical body which is open at one end and has an end cap at the other end thereof, said cylindrical body having a raised band circumscribing the central portion thereof, with the diameter of the raised band being of such size that the insert member with the raised band is adapted to fit coaxially within the one end of the cylindrical attachment member, said end cap having a bore therethrough which is coaxial with the cylindrical body of the insert member and which is adapted to receive attachment means for a hook or similated hand for attachment to said cap member;

an elastomeric o-ring adapted to fit circumferentially around the cylindrical body of the insert member between the one end of the cylindrical body and the raised band on the cylindrical body;

abutment means in the interior of the cylindrical attachment member, said abutment means adapted to fit over the cylindrical body of the insert member and to abut the o-ring when said one end of the insert member is fit within the cylindrical attachment member such that the o-ring is constrained between the raised band on the cylindrical body and the abutment means as the insert member is moved toward the abutment means; and

a screw ring adapted to be threaded on the external threads of the cylindrical attachment member and to advance the insert member toward the abutment means within the cylindrical attachment member as the screw ring is advanced on the threads of the cylindrical attachment member, thereby compressing the o-ring between the abutment member, the raised ring, the cylindrical body of the insert member, and the interior surface of the cylindrical attachment member to progressively inhibit rotational movement of the insert member relative to the attachment member as the screw ring is advanced on the threads of the cylindrical attachment member.

16. A prosthesis as claimed in claim 15, wherein the abutment means comprises:

an internal circumferential lip on the inside surface of the cylindrical attachment member and spaced from said one end thereof;

at least one longitudinal keyway in the cylindrical attachment member, said keyway extending from said one end of the cylindrical attachment member substantially to the lip on the inside surface of the cylindrical attachment member;

a bearing ring made of a polymeric material and adapted to fit within the cylindrical attachment member, with one end of the bearing ring abutting the lip on the inside surface of the cylindrical attachment member, said bearing ring also having a number of keys equal to the number of keyways in the cylindrical attachment member, with said keys, which extend from the outer periphery of the bearing ring, being adapted to be received in the corresponding keyways in the cylindrical attachment member.

whereby the other end of the bearing ring abuts said o-ring when the o-ring and insert member are positioned in the cylindrical attachment member.

17. A prosthesis as claimed in claim 16, wherein a second bearing ring made of polymeric material is adapted to fit between the insert member and the screw ring so that the screw ring presses against the second bearing ring and the second bearing ring in turn presses against the insert member when the screw ring is advanced on the threads of the cylindrical attachment member.

18. A prosthesis as claimed in claim 15, wherein the bore through the end cap of the insert member is threaded so as to be adapted to receive a threaded stud of a hook or simulated hand.

19. A prosthesis as claimed in claim 1, wherein the electronic controller module is adapted to operate the DC motor of the drive module over a range of speeds corresponding to the values of the electromyographic signals received from the skin electrodes, and circuitry means are provided for adjusting the sensitivity of the response of the electronic controller to the electromyographic signals received from the skin electrodes.

20. In a prosthesis for a person with an amputation above the elbow, said prosthesis including an upper arm socket which is adapted to be attched to the stump or shoulder portion of the person'"'"'s torso and an elbow and forearm section attached to said upper arm socket, an improved connection means between the upper arm socket and the elbow section which provides humeral rotation, said improved connection means comprising:

an annular fitting which is adapted to be attached to the end of the upper arm socket, said annular fitting having a cylindrical end portion which extends away from the upper arm socket and which as a substantially flat, circular end face, said cylindrical end portion being substantially coaxial with the longitudinal axis of the upper arm socket, said cylindrical end portion further having a circumferencial flange or ring adjacent to the flat, circular end face thereof;

providing the elbow section with a substantially flat upper end;

an annular friction band having an annular recess formed around the inside surface at one end portion thereof so that the annular recess is adapted to engage the circumferential flange on said annular fitting, with the other end portion of the friction band adapted for attachment to the upper end of the elbow section to hold the flat upper end of the elbow section in parallel closely spaced relationship with the flat, circular end of the annular fitting; and

an adjustable tension band adapted to encircle the friction band and to provide adjustable compression of the friction band,

whereby the ease with which the elbow section can be rotated relative to the upper arm socket can be adjusted incrementally between essentially free rotation and various degrees of restrained rotation by adjusting the tension band to increase or decrease the compression exerted by the tension band on the friction band.

21. In a prosthesis for a person with a amputation above the elbow, said prosthesis including an upper arm socket which is adapted to be attached to the stump or shoulder portion of the person'"'"'s torso, an elbow member attached to the upper arm socket and a forearm member hingedly attached to the elbow member, an improvement comprising means for locking the forearm member in place with respect to the elbow member, said improvement comprising:

a locking pin member mounted within a hollow cavity in the elbow member, with an opening in the elbow member through which the locking pin is adapted to move;

means for moving the locking pin back and forth in the opening in the elbow member between an extended position in which the end of the locking pin extends outwardly from said opening in the elbow member and a retracted position in which the end of the locking pin is retracted so as to not extend outwardly from said opening;

said forearm member having an enclosed hollow end portion which is pivotally attached to the elbow member, with an opening being provided in said hollow end portion of the forearm so that the elbow member is received within the hollow end portion of the forearm member when the forearm member is pivoted about its attachment to the elbow member, said forearm member also having attached firmly to an inside surface of the hollow end portion thereof a curved, elongate, lock member which has a plurality of detent holes equally spaced along the length thereof, said lock member being positioned along said inside surface so that as the forearm member pivots about its attachment to the elbow member, the curved, elongate, lock member moves in an arc such that the detent holes therein move successively back and forth directly beneath the opening in the elbow member through which the locking pin is adapted to move,whereby the forearm member can be locked in place with respect to the elbow member at various positions in the pivotal movement of the forearm member relative to the elbow member by activating the lock pin to extend from the opening in the elbow member to engage one of the detent holes in the lock member.

22. A prosthesis as claimed in claim 21, wherein the means for moving the locking pin back and forth in reciprocating motion in the opening in the elbow member comprises:

a spring cantilevered at its one end to a rotatable base, with the other end of the spring being adapted to contact the locking pin;

means for rotating the rotatable base from a first position through an angle of about 180 degrees to a second position and vice versa about an axis coinciding with the attachment of the spring to the rotatable base,

whereby when the rotatable base is in its firsrt position, the spring biases the locking pin to move longitudinally to its extended position and when the rotatable base is in its said second position, the spring biases the locking pin to move longitudinally to its retracted position.

23. A prosthesis as claimed in claim 22, wherein said means for rotating said rotatable base comprises:

a DC motor;

a gear mechanism connecting the DC motor to the rotatable base; and

means for operating the DC motor.

24. A prosthesis as claimed in claim 23, wherein the means for operating the DC motor comprises:

means for measuring the torque at the pivotal attachment of the forearm member to the elbow member;

means for measuring the rotational movement of the forearm member relative to the elbow member; and

electronic controller means including circuitry means for operating the DC motor to rotate the rotatable base to its said first position only when the rotational movement of the forearm member is substantially zero and simultaneously the torque is above a predetermined value for a specific time interval, said electronic controller means further having circuitry means for operating the DC motor to rotate the rotatable base to its said second position when a predetermined command is given by the person wearing the prosthesis.

25. In a prosthesis for a person with an amputation above the wrist, said prosthesis including a forearm member and a hook or simulated hand, an improved means simulating a wrist, said improved means comprising:

a substantially cylindrical attachment member having external threads at one end thereof, with the other end of the attachment member being adapted to be secured to the forward end of the forearm member;

an insert member comprising a cylindrical body which is open at one end and has an end cap at the other end thereof, said cylindrical body having a raised band circumscribing the central portion thereof, with the diameter of the raised band being of such size that the insert member with the raised band is adapted to fit coaxially within the one end of the cylindrical attachment member, said end cap having a bore therethrough which is coaxial with the cylindrical body of the insert member and which is adapted to receive attachment means for a hook or simulated hand for attachment to said cap member;

an elastomeric o-ring adapted to fit circumferentially around the cylindrical body of the insert member between the one end of the cylindrical body and the raised band on the cylindrical body;

abutment means in the interior of the cylindrical attachment member, said abutment means adapted to fit over the cylindrical body of the insert member and to abut the o-ring when said one end of the insert member is fit within the cylindrical attachment member such that the o-ring is constrained between the raised band on the cylindrical body and the abutment means as the insert member is moved toward the abutment means; and

a screw ring adapted to be threaded on the external threads of the cylindrical attachment member and to advance the insert member toward the abutment means within the cylindrical attachment member as the scew ring is advanced on the threads of the cylindrical attachment member, thereby compressing the o-ring between the abutment member, the raised ring, the cylindrical body of the insert member, and the interior surface of the cylindrical attachment member to progressively inhibit rotational movement of the insert member relative to the attachment member as the screw ring is advanced on the threads of the cylindrical attachment member.

26. A prosthesis as claimed in claim 25, wherein the abutment means comprises:

an internal circumferential lip on the inside surface of the cylindrical attachment member and spaced from said one end thereof;

at least one longitudinal keyway in the cylindrical attachment member, said keyway extending from said one end of the cylindrical attachment member substantially to the lip on the inside surface of the cylindrical attachment member;

a bearing ring made of a polymeric material and adapted to fit within the cylindrical attachment member, with one end of the bearing ring abutting the lip on the inside surface of the cylindrical attachment member, said bearing ring also having a number of keys equal to the number of keyways in the cylindrical attachment member, with said keys, which extend from the outer periphery of the bearing ring, being adapted to be received in the corresponding keyways in the cylindrical attachment member,

whereby the other end of the bearing ring abuts said o-ring when the o-ring and insert member are positioned in the cylindrical attachment member.

27. A prosthesis as claimed in claim 26, wherein a second bearing ring made of polymeric material is adapted to fit between the insert member and the screw ring so that the screw ring presses against the second bearing ring and the second bearing ring in turn presses against the insert member when the screw ring is advanced on the threads of the cylindrical attachment member.

28. A prosthesis as claimed in claim 25, wherein the bore through the end cap of the insert member is threaded so as to be adapted to receive a threaded stud of a hook or simulated hand.