Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Leg – Ankle
Reexamination Certificate
1999-10-21
2001-10-23
Willse, David H. (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Leg
Ankle
C623S027000
Reexamination Certificate
active
06306178
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a prosthetic device for a lower leg or foot for use by a below-the-knee amputee.
2. Description of the Related Art
Although prosthetic devices have been in use for centuries, not until relatively recently have efforts been made to design prosthetic legs and feet to react dynamically to the cyclic loading and unloading of the foot during movement to simulate more closely natural gait. To this end, prosthetic devices typically are configured to store and release energy during normal body movements. Typical prosthetic feet include a spring plate arranged longitudinally approximately within the sole of a shoe. The spring plate is usually arranged so as to provide flexure of the foot while walking.
Materials undergo a certain amount of deformation when they are stressed. If a mechanical element experiences a steady deformation when acted upon by steady forces, it is exhibiting compliance which is the basic characteristic of a spring. A translational spring is a mechanical element which deforms by steady amounts when loaded by steady forces. A linear spring has a proportional relation between deformation and force. Thus, the spring stores work as energy associated with its deformation. This stored energy is called translational potential energy. Hence, the energy stored in the spring depends directly on the force transmitted to the spring. In other words, the work done by any force acting on a spring during a specified displacement is equal to the change in the kinetic energy of the spring. This statement is the basic work-energy principle of body dynamics in physics.
The single spring plate of the prior art may have varying thicknesses along its length to give varying compliances across the spring plate in order to simulate more closely the curling movement of a foot during a walking motion. Improvements to the spring plate have included multiple plates of different thicknesses attached or adhered to each other within the prosthetic foot in order to create different compliances along the length of the foot. However, these attempts to achieve different compliances by varying the thicknesses have not been successful because it has been found that spring plates are inherently limited in their simulation of the natural motion of a foot. In particular, as a prosthetic foot using such a spring plate is curled, as it is during a normal walking or running motion, the effort required to curl the prosthetic foot increases, thereby inhibiting the full range of motion. Therefore, it is desirable to provide a prosthetic device that provides a more natural simulation of the motion of a leg or a foot.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a prosthetic device which more naturally simulates the motion of a user's leg or foot.
According to the invention, the prosthetic device is provided with a base portion, a leaf spring attached to the base portion, a lever member hingedly attached to the leaf spring, a rocking member attached to the base portion, and a line having a first end attached to a front end of the leaf spring and having a second end attached to a back end of the lever member. The line has a middle portion, between the first and second ends, that is attached to the rocking member. The prosthetic device can convert a pivoting motion of the lever member into a deflection of the leaf spring, thereby storing energy imparted by the lever member to the leaf spring.
Preferably, the rocking member is an eccentric body, such as a cam-shaped wheel. The line is fixed to the eccentric body such that, as the lever member pivots, the amount of deflection caused in the leaf spring by the pulling of the line changes through the range of foot motion. Accordingly, the eccentric body can be configured such that the deflection of the leaf spring changes over the range of pivoting of the lever member.
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Kania Bruce
Zimmerman David
Fountainhead
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Stewart Alvin
Willse David H.
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