Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Arm or component and actuator or connector therefor – Finger actuator embodied in simulated hand
Patent
1996-09-06
1999-03-30
Willse, David H.
Prosthesis (i.e., artificial body members), parts thereof, or ai
Arm or component and actuator or connector therefor
Finger actuator embodied in simulated hand
A61F 254
Patent
active
058882464
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to hand prostheses and in particular to such prostheses with movable gripping fingers.
BACKGROUND OF THE INVENTION
The design of such hand prostheses presents formidable problems in achieving gripping light enough to handle fragile objects and strong enough to provide a secure grip to objects where it is desired to apply substantial forces. These problems are further compounded by the limited spaced available, especially within the fingers themselves, and where it is required to provide for independent movement of different fingers to a greater or lesser extent, and/or varying the rate of movement of individual fingers.
A particular problem arises with the fitting of hand prostheses in patients with relatively long hand stumps. Conventional electrical hand prostheses use an electric motor mounted in the body structure of the hand itself. Some versions have the motor mounted axially parallel to the long axis of the arm and others have the motor at 90 degrees to this axis. A variety of transmission systems are used to link motor and fingers e.g. lead screw and nut, or bevel and spur gears. Without exception these types of hand prosthesis require precise alignment between motor and transmission system. This is usually achieved by locating all the parts within a hand body consisting of an investment casting or other moulded structure. Such an arrangement is relatively cumbersome and the motor cannot be readily accommodated within the limited space available in the main body of the prosthesis attached to the patient's hand stump. Another disadvantage is that patients with some residual digits cannot have any functional restoration at all because of the space constraints. The operational characteristics of such devices also tend to be restricted e.g. allowing only a single gripping pattern to be employed.
SUMMARY OF THE INVENTION
It is an object of the present invention to avoid or minimise one or more of the above disadvantages.
The present invention provides a prosthesis for providing at least one mechanically operable finger member, said prosthesis having at least one said finger member extending generally tangentially with respect to a fixed worm gear wheel means on a support body of said prosthesis and mounted for rotation about the worm gear wheel spindle, said finger member having a drive motor with a worm extending generally longitudinally of the finger member and in engagement with the gear teeth of said worm gear wheel so that when said drive motor is operated, in use of the prosthesis, said finger member moves around said worm gear wheel towards or away from another finger member and/or a natural finger for closing and opening of a hand grip.
Thus the hand prosthesis of the present invention uses a particularly compact form of finger drive which also can allow improved operational flexibility.
As used herein the expression "finger member" includes a "thumb member". Whilst it is possible to provide a useful hand grip defined by just one movable finger member and one fixed member, it is generally preferred to have a hand prosthesis with a plurality of movable finger members, most preferably with control means formed and arranged so as to permit more or less, independence of movement of the finger members or groups of finger members, e.g. to allow higher speed lower torque movement of a "thumb" finger member, and slower speed higher torque movement of the other finger(s), and/or to permit the provision of different gripping patterns with different combinations of individual/group finger movement characteristics.
Conveniently a root portion of said at least one said finger member provided with a drive motor is connected by a linkage means to the root portion of at least one other (motor-less) finger member mounted for pivotal movement on said support body, said linkage means being formed and arranged for transmitting drive to said other finger member so as to pivotally move said other finger member towards or away from said at least one finger me
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patent: 4505166 (1985-03-01), Tesar
patent: 4623354 (1986-11-01), Childress
patent: 4792338 (1988-12-01), Rennerfelt
patent: 4923477 (1990-05-01), Horvath
Royal Infirmary of Edinburgh NHS Trust
Willse David H.
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