Abstract: There is provided a prosthetic leg with an extension auxiliary mechanism 1100 capable of generating an extension torque only when an angle of bending of the knee is small. A knee joint 80 of a thigh prosthesis 170 is of a multi-axis structure, and a front and a rear link 130, 150 together with an upper thigh member 110 and a lower thigh member 120 constitutes a constrained chain. An extension auxiliary mechanism 1100 having a compression spring is supported between the lower thigh member 120 and the rear link 150. An extension torque generated by the extension auxiliary mechanism 1100 is determined by a product of a force caused by biasing of the compression spring and a distance from a line of action of the force to the center of rotation of the rear link 150. Here, at a stage where the bending angle of the knee exceeds, for example, 15 degrees, an axis of the compression spring is brought generally into alignment with a connecting portion 170O between the rear link 150 and the lower thigh member 120.

Abstract: Paying attention to the mechanical play between the first and second support members for supporting opposite end portions of a knee axis and a brake block located between the support members, the present invention chiefly aims at removing the play in the direction of an axis of the knee axis in an effective and a reliable manner. In order to achieve this object, according to the present invention, a plurality of spacer members are inserted between each support member and the brake block such that the spacer members may slide on the mutual abutment surface. Each spacer member is of a ring type. The spacer members are fitted to and supported by the knee axis in a state that the spacer members are overlaid one upon another in the axial direction of the knee axis. In order to enhance the smooth sliding on the abutment surface, the spacer members are preferably made of resin material.

Abstract: An artificial limb provides for positional relation between a first pin for rotatably connecting one end of an air cylinder device to a lower member and a second pin for rotatably connecting the other end of the air cylinder device to an upper member. The attaching position of the second pin is set to satisfy certain predetermined conditions when an artificial limb is in a completely extended state. The position of an air cylinder device (particularly, the attaching position of the second pin) is changed in conformity with a walking speed which is variable in phase such as normal walking, quick walking, and running with small steps. The artificial limb further comprises a pin position change capable of changing the position of a second pin rotatably connected to an upper member in conformity with variation of walking speed.

Abstract: In an artificial leg for a person having an upper thigh cut and a knee joint lost, a cylinder disposed between upper and lower leg members, which are coupled through a pivotable joint, for controlling bending and straightening of the joint by an air cushion for convenience of walking. The cylinder includes a cylindrical sleeve closed at both ends and a piston having a piston rod and sliding in the sleeve, and has its structure improved by using as a cushion one of two inner cavities separated by the piston, which encloses the piston rod, thereby buffering butting between the upper and lower leg members to remove unpleasant shock resulting at the end of straightening the joint.