Patent GB-125318-A (GB)
Title: Improvements in Artificial Hands.
Inventor: DILWORTH OTTO LEGRAND
IPC: A61F2/58
Filed: 1918-02-25
Abstract: 125,318. Dilworth, O. L. Feb 25, 1918. Limbs, artificial.-Comprises a construction of hand in which the pull on a single cord bends both the tip and middle sections of all the fingers and the thumb to any desired extent, and locks them automatically in the bent position until they are released and restored to their original position by a repetition of the pull on the cord. Finger-bending mechanism. The pull on a cord 90, which is connected to shoulder harness as described in Specification 123,571, is transmitted through mechanism hereinafter described to a main transverse finger-actuating rod 135, Figs. 2 and 6. The pull on the cord moves the rod rearwardly in inclined guides 85 and thus also moves the attached finger levers 124 rearwardly to bend the finger tips about the pivots 125. The inclination of the guides also causes the finger-levers to rock about the middle joint pivots 120 as fulcrums, and thus bend the middle sections of the fingers by the base of the levers acting on cross rods 128. The bending of the middle sections accelerates the bending movement of the fingertips, and this latter movement is still further accelerated by cam surfaces 129 on.the levers coacting with the pivots 120 to force the levers rearwardly during the rocking movement. Mechanism connecting the operating cord to the main finger-actuating rod. This mechanism comprises three main superposed members, consisting of a main lateral support, a ,swinging plate or bar above the support, and a sliding plate above the swinging plate. The angular movement of the swinging plate serves to operate the main finger-operating rod, while the movement of the sliding plate controls the locking and unlocking of the fingers in the bent position. The swinging plate or bar 91, Figs. 6 and 7, is pivoted at 99 to the main lateral support 89. The longitudinallysliding plate 93 slides in guides in the upper surface of the swinging plate. A boss on the swing- ing plate passes through a clearance space in the sliding plate and carries a loose ratchet wheel having actuating teeth 95 and retaining or detent teeth 96. The pull on the cord 90 rotates a lever 102 about the pivot 99 and through the medium of the attached pawl 105 rotates the ratchet-wheel one tooth. This movement frees the pawl 97 and allows it to enter the space between two detent teeth under the influence of the spring 98. A pin 101 on this pawl is connected to the sliding plate 93 which is thus moved along the swinging plate urtil a pawl 106 carried by it engages with fixed teeth 133. By this time, the lever 102 has attained the position such that, on further rotation, the pin 103 will also be moved and thus the swing- ing plate will be rotated against the action of a spring 136 and locked against backward movement by the pawl 106 and teeth 133. The swinging plate is linked to a member carrying a series of eyes 111 through which the main finger-operating rod passes, so that the swinging movement of the plate is converted into a rearward pull on the operating-rod. To prevent excessive axial movement of the operating-rod due to this conversion of motion, the eye-carrying member is provided with a further sliding pivotal connexion with the support 89. One end of the support 89 can move laterally in the framework of the hand to a slight extent, against the action of the spring 132. This is stated to give flexibility to the finger-actuating mechanism. When the pull on the cord 90 is released, the lever 102 moves back until it is held by the pin 103, and the pawl 105 engages a new tooth on the ratchet-wheel. This backward movement of the lever is caused by a spring connecting the pawl 105 to the pivot 94. A further pull on the operating-cord then rotates the ratchet-wheel another tooth and thus re-engages the pawl 97 with a tooth on the detent wheel. The movement of the pawl 97 moves the sliding frame and disengages the locking-pawl 106. If the pull on the cord is then released, the swinging plate and the lever 102 return to their original positions and straighten the fingers. Construction and operation of the thumb. The thumb comprises a pivoted tip 77, a pair of middle plates 75, and a two-part cylindrical base member 70 all connected together as shown in plan in Fig. 5. The base member fits into a socket formed on the hand as shown in Figs. 2 and 4, and may be rotated by hand in the socket to any desired ex- .tent. A screw and annular groove retain the base member in the socket. In one position, a spring 79 can rotate the member 75 so that a lug thereon engages a notch 121, Fig. 2, to retain the thumb lightly. A bending cord 80, Fig. 4, is connected to the tip section and is connected to the swinging plate that operates the fingers on the opposite side of the pivot to the finger-actuating gear. The middle plates bend about the base member at the same time through the operation of the spring 79. The cord 80 is not actuated in the reverse direction for positively unbending the thumb, as the straightening movement of the fingers increases the space between the fingers and thumb sufficiently tb release any object grasped.