Patent GB-133833-A (GB)
IPC: A61F2/60
Filed: 1918-12-10
Abstract: 133,833. Amar, J. Dec. 10, 1918. No Patent granted (Sealing fee not paid). Limbs, artificial.-A knee-joint is controlled by the movement of the thigh bucket acting in conjunction with the bending of the foot. The thigh bucket is connected rigidly to a cam d mounted on the knee-joint pivot and formed with slots d<2>, d<3>. A front tendon with an interposed spring x<2> is pivoted to the bracket q<4> on the foot and carries a spindle w at the upper end engaging the slot d<2>. An inextensible rear tendon x<4>, pivoted to a spring lever y rigidly secured to the part of the foot in front of the pivot r, carries a spindle w<1> engaging the slot d<3>. Normally the spindle w<1> is held at the extreme end of its slot by the locking bar h operable 'by the knob 8. The spindle w is held nomally at the outwardlycurving end of its slot by cams m<3> mounted on side cheeks rigidly secured to and projecting upwards from the tubular framework of the leg. When the sound leg is moved forwards to take a step, the bending of the body causes the thigh socket a to be thrown forwards. The effect of the locking of the spindles wand w<1> in their slots is such that during this initial forward movement the thigh-piece and the leg move forwards as a whole about the foot pivot s. This action continues until the weight of the body is transferred to the artificial leg. The weight causes the knee-joint to collapse, and bend the lower leg rearwardly until a cross-bar o contacts with the end z<1> of a pivoted forked plate, also held against rotation by the locking-bar h. The following movements occur as the result of this rearward swing of the lower leg. (1) The cams m<3> roll against the spindle w, but still retain it at the limit of its slot. (2) The spring x<2> of the front tendon is stressed due to the bending movement. (3) The rear portion of the foot is raised, while the front portion remains on the ground. (4) The lever y, which remains practically stationary, is brought close to the raised' portion of the foot as shown in dotted lines. When the relative bending of the lower leg has reached its limit owing to contact being made with the member z<1>, the continued movement of the thigh in the forward direction swings the thigh and lower leg angularly as a rigid whole about the kneejoint pivot. During this action, the movement of the thigh is transmitted rigidly to the lower leg through the locking-bar h and tendon x<4> which causes an axial pull in the lever y. In addition, the lever y is raised by the angular movement of the spindle w<1> with respect to the kneejoint pivot f. The raising of the lever y raises the front portion of the foot until only the point of the toe rests on the ground. Finally, the continued forward movement of the thigh, in conjunction with the straightening of the sound leg as it finishes its step, raises the whole foot from the ground. During the forward movement of the raised foot to take a step, the spring x<2> gradually restores the bent lower leg into alinement with the thigh, but this restoration is not completed until after the leg has passed the vertical position and is inclined forwardly. The foot thus is prevented from striking the ground during the progress of the step. To sit down, the wearer raises the locking-bar h, thus allowing the cam to rotate independently of the lower leg. The spindle w<1> moves freely along the slot d<3> during this procedure, while the spindle w, after passing beyond the end of the cam m<3>, runs freely in the concentric portion of the slot d<2>. The thigh portion comprises a removable perforated socket b, of duralamin or other metal, which fits the stump exactly and engages frictionally with the main thigh socket a.