Method and apparatus for a passive knee joint

An artificial knee configured to be worn by a person during a walking cycle, the artificial knee comprising:

• a thigh link configured to move in unison with a thigh of the person;
• a shank link configured to move in unison with a shank of the person, the shank link being rotatably coupled to the thigh link,
• wherein knee extension motion is straightening of the artificial knee, and
• wherein knee flexion motion is bending of the artificial knee opposite of the knee extension motion;
• a compression spring rotatably coupled to the thigh link at a first end of the compression spring;
• a follower link rotatably coupled to a second end of the compression spring from a first end of the follower link, the follower link being rotatably coupled to the shank link from a second end of the follower link such that the thigh link, the shank link, the follower link, and the compression spring form a four bar linkage;
• and
• a constraint configured to constrain a motion of the follower link relative to the shank link during a first phase of the walking cycle and a second phase of the walking cycle,
• wherein during the first phase of the walking cycle, the constraint constrains the motion of the follower link such that the compression spring provides a torque between the thigh link and the shank link that resists knee flexion motion of the shank link relative to the thigh link,
• wherein during the second phase of the walking cycle, the constraint constrains the motion of the follower link such that the compression spring provides a torque between the thigh link and the shank link that encourages knee flexion motion of the shank link relative to the thigh link, and
• wherein the first phase of the walking cycle corresponds to a phase of the walking cycle in which an angle of the artificial knee is between an engagement angle and a toggle angle, wherein the second phase of the walking cycle corresponds to a phase of the walking cycle in which the angle of the artificial knee is between the toggle angle and a release angle, wherein the engagement angle is greater than a minimum angle of the artificial knee during the walking cycle but less than a maximum angle of the artificial knee during a stance phase of the walking cycle, wherein the toggle angle is greater than the maximum angle of the artificial knee during the stance phase of the walking cycle but less than an angle of the artificial knee at a toe off point of the walking cycle, and wherein the release angle is greater than the angle of the artificial knee at the toe off point of the walking cycle but less than a maximum angle of the artificial knee during the walking cycle.

An artificial knee configured to be worn by a person during a walking cycle, the artificial knee comprising:

• a thigh link configured to move in unison with a thigh of the person;
• a shank link configured to move in unison with a shank of the person, the shank link being rotatably coupled to the thigh link,
• wherein knee extension motion is straightening of the artificial knee, and
• wherein knee flexion motion is bending of the artificial knee opposite of the knee extension motion;
• a compression spring rotatably coupled to the thigh link from a first end of the compression spring, the compression spring being rotatably coupled to the shank link from a second end of the compression spring;
• and
• a constraint configured to constrain a motion of a follower link relative to the shank link during a first phase of the walking cycle and a second phase of the walking cycle,
• wherein when the follower link is moved from a singular point toward the constraint, the constraint constrains a motion of the follower link, and the compression spring provides a torque between the thigh link and the shank link that resists knee flexion motion of the shank link relative to the thigh link,
• wherein when the follower link is moved from the singular point away from the constraint, the constraint does not constrain the motion of the follower link, and knee flexion motion and knee extension motion of the thigh link relative to the shank link is unimpeded, and
• wherein when the follower link is moved from the singular point away from the constraint, the constraint does not constrain the motion of the follower link, and knee flexion motion and knee extension motion of the thigh link relative to the shank link is unimpeded, wherein the first phase of the walking cycle corresponds to a phase of the walking cycle in which an angle of the artificial knee is between an engagement angle and a toggle angle, wherein the second phase of the walking cycle corresponds to a phase of the walking cycle in which the angle of the artificial knee is between the toggle angle and a release angle, wherein the engagement angle is greater than a minimum angle of the artificial knee during the walking cycle but less than a maximum angle of the artificial knee during a stance phase of the walking cycle, wherein the toggle angle is greater than the maximum angle of the artificial knee during the stance phase of the walking cycle but less than an angle of the artificial knee at a toe off point of the walking cycle, and wherein the release angle is greater than the angle of the artificial knee at the toe off point of the walking cycle but less than a maximum angle of the artificial knee during the walking cycle.

An artificial knee configured to be worn by a person during a walking cycle, the artificial knee comprising:

• a thigh link configured to move in unison with a thigh of the person;
• a shank link configured to move in unison with a shank of the person, the shank link being rotatably coupled to the thigh link,
• wherein knee extension motion is straightening of the artificial knee, and
• wherein knee flexion motion is bending of the artificial knee opposite of the knee extension motion;
• a compression spring rotatably coupled to the thigh link from a first end of the compression spring, the compression spring being rotatably coupled to the shank link from a second end of the compression spring,
• wherein during a first phase of the walking cycle, the compression spring provides a torque between the thigh link and the shank link that resists knee flexion motion of the shank link relative to the thigh link, and
• wherein during a second phase of the walking cycle, the compression spring provides a torque between the thigh link and the shank link that encourages knee flexion motion of the shank link relative to the thigh link;
• a follower link rotatably coupled to the second end of the compression spring from a first end of the follower link, the follower link being rotatably coupled to the shank link from a second end of the follower link such that the thigh link, the shank link, the follower link, and the compression spring form a four bar linkage;
• and
• a constraint configured to constrain a motion of the follower link relative to the shank link near a singular point, wherein the singular point is a point where the compression spring and the follower link are in line with each other,
• wherein when the follower link is moved from the singular point toward the constraint, the constraint constrains the follower link, and the compression spring generates a force such that the force passes through a joint of the artificial knee during the first phase and second phase of the walking cycle,
• wherein when the follower link is moved from the singular point toward the constraint, the constraint constrains the follower link, and the compression spring generates a force such that the force passes through a joint of the artificial knee during the first phase and second phase of the walking cycle,
• wherein the first phase of the walking cycle corresponds to a phase of the walking cycle in which an angle of the artificial knee is between an engagement angle and a toggle angle, wherein the second phase of the walking cycle corresponds to a phase of the walking cycle in which the angle of the artificial knee is between the toggle angle and a release angle, wherein the engagement angle is greater than a minimum angle of the artificial knee during the walking cycle but less than a maximum angle of the artificial knee during a stance phase of the walking cycle, wherein the toggle angle is greater than the maximum angle of the artificial knee during the stance phase of the walking cycle but less than an angle of the artificial knee at a toe off point of the walking cycle, and wherein the release angle is greater than the angle of the artificial knee at the toe off point of the walking cycle but less than a maximum angle of the artificial knee during the walking cycle.