Prosthetic hand having a conformal, compliant grip and opposable, functional thumb
View Patent ↗An anthropomorphic artificial hand having a mechanical system that allows for the digits to be compliant to pressure that tends to flex the digits, and provides for the digits to be self biasing to conform to the shape of the object being grasped. The hand comprises one to four fingers, with the fingers having up to three joints each. The hand may also comprise a thumb that can be rotated into and out of opposition of the fingers. The joints of the thumb are also self biasing to allow conformance to the object being grasped. The hand is of the voluntary closing operation, with all digits being self extending. This allows the hand to use two cables to operate if body powered (one for the fingers, one for the thumb). The hand may also be electronically powered using two channels for operating the fingers and thumb simultaneously.
1. An anthropomorphic prosthetic hand or robotic manipulator comprising:
(a) a base section forming the major frame, representing the carpal carpal-metacarpal section of the human hand, onto, or into, which other components are mounted;
(b) four individual digits appearing to be fingers attached to said frame, each having three joints allowing full, but not hyper-extension, individual movement of all joints;
(c) one digit appearing to be a thumb attached to said frame having three joints, one of which represents the metacarpal-carpal joint and allows the thumb to rotate into and out of opposition of said fingers, with all joints allowing full, but not hyper-extension, individual movement;
(d) a mounting point intended for the purpose of attaching said hand to the socket of the prosthetic system allowing donning of the device by the amputee;
(e) two actuation systems mounted within said frame and extending into said digits, that causes said fingers to flex, or said thumb to rotate into opposition and flex, with the first system actuating said four fingers, the second system actuating said thumb such that said fingers and thumb can be operated separately, yet simultaneously, these actuation systems providing a passive, self biasing, conformal grip for said digits, which also provides for movement of the digits in the direction of flexure compliant to any external force without such movement causing any damage or malfunction of said digits, or actuation systems, with the actuation systems comprising a combination of highly flexible cables, and sliding blocks which allow the cables to be self biasing, and provide for changes in direction of force;
(f) means to provide operating power for said actuation systems from outside of said hand;
(g) a resilient device in the form of a glove to return the digits to the extended position by the use of compression and tension within the resilient material of said glove, which by variations in thickness in specific points of the resilient material also controls the timing of the movement of said joints in relation to each other to provide natural appearing movement of said hand.
2. The hand of claim 1 in which an activation system comprises a highly flexible flexion cable, one end of which being attached within the distal end of said thumb, passing through said thumb on the palmer sided of the distal two joints, then passing externally about the third joint, again on the palmer side, then passing into the frame of said hand, such that pulling the cable into said frame causes the thumb to flex, the second end of the cable thereafter being attached to the power source.
3. The hand of claim 1 in which an activation system comprising a series of highly flexible flexion cables arranged such that one flexion cable being attached at one end within the distal segment of one finger, runs through said finger on the palmer side of all joints, into said frame of said hand, into and through a second finger in the manner of the first finger, then being attached within the distal end of the second finger, a second flexion cable being run in like manner through the third and fourth fingers of said hand.
4. The hand of claim 3 further comprising a highly flexible intermediate cable attached to said first and second flexion cables such that one end of the intermediate cable is loosely attached to said first flexion cable at the portion creating a loop within said frame by use of a sliding block, allowing said first flexion cable to slide through the attachment point with little resistance, the second end of the intermediate cable being attached to second said flexion cable in a like manner, allowing second said flexion cable the same freedom of movement as the first flexion cable, the intermediate cable having a third mounting point consisting of a sliding block located so as to slide freely between the two end mounting points, this mounting point being used for the attachment to the power source.
5. The hand of claim 1 which further comprises two drive cables, each attached to one said actuation system such that pulling the cable away from said frame drives said actuation system, with the cables being powered by an energy source external to the hand, or prosthesis, the means to attach the cables to said energy source, the source of energy being the body of the amputee, with the method of actuation commonly being a harness worn by the amputee.
6. The hand of claim 1 which further comprises two motors driven by electrical means, each attached to one actuation system by means of direct ridged mechanical linkage, or by means of a flexible linkage such as a cable, the means to connect the motor(s) to a power source external to the hand, with the power source commonly being the motor control circuits operated by batteries.
7. The hand of claim 1 further comprising said resilient glove shaped so as to provide for the hand to appear to be a natural human hand, both in appearance, and to the touch.
8. The hand of claim 1 further comprising said resilient glove in which said resilient glove is made of such a material so as to provide a hydrostatic grip.