Artificial foot for leg prostheses

Abstract

An artificial foot made of synthetic materials with an integrally cast metallic base plate having a forward downwardly depending offset portion of a unique configuration, the rear end of the base plate being supported by a tab.

Description

The present invention relates to an artificial foot made of foamed synthetic materials that are foamed within a mold, for leg prostheses.

In the operational behaviour of a leg prothesis, the foot and the functional characteristics of the same are of considerable importance. The foot must allow the amputated patient to tread on the ground with a maximum of dampening, in simultaneously providing a rigid linkage for the prothesis and maintaining, during walking, the highest possible degree of resiliency of the rolling motion resistance.

For quite some time have been known artificial feet made of felt and rubber, with a wooden reinforcement. In the course of development, artificial feet of this type have been replaced by artificial feet made of resilient plastic or synthetic materials. The preferred materials employed have been foamed polyurethanes that were advantageous because of their low weight. The foot functions were provided by adhesively bonding several foamed materials of different hardness. The connecting element for connecting the foot with the prosthetic leg member was as before manufactured of wood. There has also been proposed to provide aluminium plates as connecting members for attachment to the highly resilient foam at the sole of the foot. These proposals, however, encountered difficulties since the prior art aluminium plates were not adapted properly to the foot function.

Heretofore known artificial feet were unsatisfactory because of the insufficient aging resistance of adhesively bonded foam materials, the humidity absorption properties of the wooden core and the unfavorable roll-off motion function of the molded-in aluminium plates whereby this function was delimited in a central region of the foot.

It is now the object of the present invention to provide an artificial foot for leg prostheses in which the above pointed out drawbacks are eliminated and the full operational functions of the foot are provided.

For achieving this object, there is now proposed, in accordance with the present invention, an artificial foot made of foamed synthetic materials that are foamed within a mold, for leg prostheses, and this artificial foot is characterized by a metallic base plate disposed in the area of the sole of the foot within the foamed foot member, a forwardly extending portion of the metallic base plate defining a downwardly depending offset portion, the configuration of the offset portion of the base plate adapted to the roll-off motion of the ball of the foot, the offset portion secured to a forefoot core made of a homogeneous plastic material, the configuration of the forefoot core corresponding to the shape of the point of the foot, and a rearwardly extending portion of the metallic base plate supported by a portion of a tab made of a homogeneous plastic material, the tab being disposed within the heel portion of the foot.

According to another characteristic of the present invention, a recess is provided in a rearward portion of the foot and extends from the top surface of the artificial foot down to the upper surface of the metallic base plate and adapted to receive articulation and attachment members.

The drawing illustrates a longitudinal vertical sectional view of an artificial foot in accordance with a preferred embodiment of the present invention.

A metallic base plate 10 is provided in the area of the sole of the foot. The metallic base plate 10 is adapted to the configuration of the sole of the foot within the area of the ball of the foot 12 by means of a downwardly depending offset portion 11. The offset portion 11 allows to perform the rolling motion functions of the foot within a transverse sectional area located substantially in a region intermediate a first and a second third at the forward end of the foot when assuming the foot to be subdivided, along its length, into three longitudinal portions of approximately equal lengths. This transverse area is predetermined by nature itself and substantially coincides with the line of articulation of the toes. To adapt the rolling motion resistance of the artificial foot to the natural foot function, a forefoot core 14 made of a homogeneous elastomer material is prevulcanized to the downwardly depending offset portion 11 of the base plate 10. The lower boundary of the forefoot core 14 corresponds to the outer configuration of the ball of the foot. This forefoot core 14 is of a non-foamed structure and is perfectly resistant to aging. Therefore the rolling motion resistance may be predetermined and will not alter during extended periods of time. Within the heel portion of the artificial foot, a tab 15 likewise made of a homogeneous elastomer material is prevulcanized to the metallic base plate 10 and forms a reinforcement member. The thus formed functional core of the foot comprising the metallic base plate 10, the forefoot core 14 and the tab 15 may be readily adapted to any size of foot and to different heel heights.

The actual foot body 16 is integrally foamed of a cellular material about the functional foot core, in order to preserve a low weight of the foot. A recess 17 may be provided within a rearward portion of the artificial foot. This recess 17 may extend from the top surface of the foot body down to the upper surface of the metallic base plate 10 and allows to threadedly attach articulation and attachment members directly to the metallic base plate 10.

Claims

What is claimed is:

1. An artificial foot made of foamed synthetic materials that are foamed within a mold, for leg prostheses, characterized by a metallic base plate disposed in the area of the sole of the foot within the foamed foot member, a forwardly extending portion of said metallic base plate defining a downwardly depending offset portion, the configuration of said offset portion of said base plate adapted to the roll-off motion of the ball of the foot, said offset portion secured to a forefoot core made of a homogeneous plastic material, the configuration of said forefoot core corresponding to the shape of the point of the foot, and a rearwardly extending portion of said metallic base plate supported by a portion of a tab made of a homogeneous plastic material, said tab being disposed within the heel portion of the foot.

2. An artificial foot as in claim 1, further characterized by a recess in a rearward portion of the foot, said recess extending from the top surface of said artificial foot down to the upper surface of the metallic base plate and adapted to receive articulation and attachment members.

3. An artificial foot as in claim 2, further characterized in that said forefoot core and said tab are made of a homogeneous elastomer material.

4. An artificial foot as in claim 3, further characterized in that the foot body is integrally foamed of a cellular resilient material about the functional core of the foot consisting of said metallic base plate, said forefoot core and said tab.