FR2698538A1 - Foot replacement prosthesis with internal energy storage springs - has pair of independently-reacting spring blades enclosed within elastic body of foot prosthesis, secured together below ankle recess - Google Patents

Abstract

The prosthesis has a foot-shaped body (1) of flexible material, with an ankle recess (2) at its upper part for attachment to a leg or leg prosthesis. A pair of spring blades (3, 4) are embedded within the body of the prosthesis to allow elastic deformation independent of one another. A first blade (3) extends from below the ankle recess towards the toe end of the prosthesis, inclined downwardly towards the toe. The second blade (4), which is U-shaped, is arranged below the rear end of the first blade, to which it is rigidly secured at its upper part. ADVANTAGE - Utilises energy stored in spring blades to reduce force and fatigue on lower leg.

Description

NEW PROSTHETIC FOOT STRUCTURE WITH RESTITUTION
OF ENERGY.

 The present invention relates to a new prosthetic foot structure with energy restitution, intended to limit fatigue in walking of an amputee of a lower limb equipped with such a foot.

 We already know in the art, various prosthetic foot structures in which a spring blade, suitably shaped, flexes under the weight of the patient, when the latter puts his weight on the blade, to then restore the stored energy, when the walker lifts the foot.

 The present invention relates to a structure of this type in which two leaf springs, of a particular shape, are combined so as to ensure a double effect of energy restitution, both when the prosthetic foot is in contact with the ground by its posterior part than by its anterior part, and thus allowing a smooth movement of the patient equipped with this foot.

 The subject of the invention is therefore a prosthetic foot structure comprising a body made of a flexible material, the shape and aesthetics of which reproduce those of a human foot, this body having at its upper part, in line with the usual position of the heel, a malleolar recess, intended to receive a socket fitted to the leg stump of the user or a component of a leg prosthesis, while inside this body is housed at least one blade forming spring, elastically deformable during the walking of the person equipped with this prosthetic foot, this structure being characterized in that it comprises two separate spring blades, deformable independently of one another, the first blade extending substantially from the bottom of the malleolar recess to the front end of the body and being inclined from the rear towards the front of the body, while the second blade is arranged at the rear rier of this body, substantially below the malleolar recess, and has, in section through a longitudinal vertical plane, a lying U-shaped section, the two branches of which are directed towards the rear, the upper branch being in contact with the lower or upper face of the rear part of the first blade and being rigidly integral with the latter.

In this structure, there is therefore a double effect of energy restitution
- on the one hand, by the first blade, when the front end of the prosthetic foot is raised, and that, simultaneously, the second blade is compressed at the back
- on the other hand, by the second blade, when the rear end of the prosthetic foot is raised and that, simultaneously, the first blade is compressed.

 Advantageously, the lower branch of the U-shaped section blade will be slightly curved towards the other branch, for example by making an angle of about 70 with the horizontal, so as to define a rolling profile.

 The combination of the two elastically deformable blades, one of which, the second U-shaped blade, is arranged at the rear of the prosthetic foot and turned towards the rear, has the effect that the middle part of the foot has a relatively stiffness important.

 On the other hand, at the heel attack, it is the rear end of the lower branch of the second blade farthest from the pseudo-rolling or pivoting center of this blade, which is compressed in the first place and the a very soft attack is thus obtained on contact with the prosthetic structure and the ground. As the step of the user progresses, the point of contact of the prosthetic foot with the ground approaches the pivot center of this second blade and this results in a significant increase in damping.

This damping effect can advantageously be reinforced by using a body made of an expanded plastic material, for example a polyurethane foam, in which the elastically deformable blades are embedded. This expanded material, compressed between the two branches of the sectional blade
U and between the blade directed forwards and the ground, will thus help to dampen the movement of the prosthetic foot.

 Between the two branches of the U-shaped section blade, a recess can advantageously be made in the expanded plastic material, so as to allow the latter to deform easily. This recess may, for example, be cylindrical and be arranged in line with the malleolar recess, for example coaxially with this recess.

 As indicated, the central part of the foot is sufficiently rigid and thus lends itself to easy use of the foot at rest.

 In order to favor its use for walking, the front part of the foot should have a rapidly decreasing stiffness from the central part to the front end. For this purpose, the first blade inclined towards the front, will preferably have a thickness which will decrease in a substantially regular manner from the malleolar recess to its front end. The second blade may also have a decreasing thickness from its part in contact with the first blade to the free end of its lower branch, so as to be able to modulate its flexibility.

 The blades used may be made of any elastically deformable material, having the required flexibility characteristics. The Applicant has advantageously used for this purpose a composite material consisting of glass fibers and / or woven carbon fibers, possibly embedded in a thermoplastic or thermosetting resin, which make it possible to give the blades, by varying the orientation of the fibers, a rigid structure in the longitudinal direction and relatively flexible in the transverse direction. Any other material offering a spring effect can be used.

 The prosthetic foot according to the invention therefore provides amputees of the lower limb with unequaled comfort of use, due to its energy restoring effect, the damping of movements carried out longitudinally and transversely, and its adaptation to the inequalities of ground. It ensures a smooth running of the user's step and behaves towards him as if he were equipped with a malleolar joint.

 It will be noted, in this regard, that the fact of bending slightly upwards the free end of the lower branch of the rear blade of U-section has the effect, during walking, of exerting a rolling action and to propel the foot in the direction of travel, without causing any significant constraint at the level of the stump of the user housed in the malleolar recess.

 The envelope of the prosthetic foot will preferably have a shape that best approximates that of a foot. In particular, there may be provided, for this purpose, a part simulating a big toe separated from the mass of the other toes and a longitudinal recess will be provided for this purpose at the front end of the blade inclined forward, in order to separate from the body thereof a part which will strengthen the mass of the big toe.

The appended schematic drawings, which are not limiting, illustrate one form of implementation of the invention. On these drawings
- Figure i is a longitudinal section of the prosthetic foot structure
- Figure 2 is a top view of the first longitudinal blade inclined forward
- Figure 3 is a perspective view from below of the second U-section blade.

 As can be seen in FIG. 1, the prosthetic foot structure according to the invention comprises a body 1 made of an expanded plastic material, for example made of polyurethane, the shape of which reproduces that of a human foot. The body i may be covered with a film, not shown, forming the skin.

 At the upper part of this foot is a malleolar recess 2, of substantially cylindrical shape, with a vertical axis, intended to receive a socket fitted to the stump of the user or a member of a leg prosthesis.

 Inside the mass of the body i are embedded two leaf springs, 3 and 4, made of an elastically deformable material.

 The blade 3 extends substantially along the entire length of the foot and it leaves the base of the recess 2, of which it is substantially contiguous to extend to the front end of the foot. As seen in Figure 2, a recess 5 is provided at the front end of the blade 3, to define a part 6 there, intended to reinforce a part of the body 1 simulating a big toe.

 This blade 3 has a thickness which decreases regularly from the base of the recess 2 to its front end, so as to have increased flexibility from the middle part of the foot to its end.

 The blade 4, arranged at the rear of the foot, below the malleolar recess 2, has, in a vertical longitudinal plane, a section in a reclining U, the two branches of which are directed towards the rear of the foot. The upper branch of the blade 4 is applied against the underside of the blade 3 and is made integral with this by gluing and / or by a screw (not shown), which is engaged in slots 7, 8, of the two blades arranged opposite recess 2 and which cooperates with a nut. It will be noted that in order to be able to engage the screw or the nut, a substantially cylindrical recess 9 is formed in the body i, in line with the openings 7 and 8, from the recess 2 to the base of the body 1. This recess 9 can be coaxial with the recess 2. Similarly, to allow passage to the screw or the nut, a light 10 is provided in the lower branch of the blade 4, directly above the lights 7 and 8.

 The free end of the lower arm of the U-shaped blade 4 is very slightly curved upwards, for example by an angle of 70, in order, as explained above, to be able to produce a rolling effect when the rear part of the foot presses on the ground.

The lower branch of the blade 4 thus pivots, exerting a damping effect and opposing an increasing resistance as the step progresses, when the foot comes into contact with the ground.

 The central part of the foot is the one which exhibits the least flexibility and this again increases as far as the front end of the blade 3, due to the reduction in thickness of the latter.

 The expanded plastic material from which the body 1 is made can absorb the unevenness on the ground. In addition, it naturally contributes to the damping effect, since it is compressed between the two branches of the U of the blade 4 and between the blade 3 and the ground. The recess 9 made in the plastic material moreover promotes the deformation of the latter between the branches of the part 4.

 The blade 4 may also have a decreasing thickness from the part in contact with the blade 3 to the free end of the lower branch, in order to be able to modulate its flexibility.

 As indicated above, the blades 3 and 4 may advantageously be made of woven carbon and / or glass fibers, possibly embedded in a thermoplastic or thermosetting material, so as to be able to influence the orientation of the plies of fibers to obtain a certain stiffness in the longitudinal direction of the foot and a flexibility in the transverse direction.

 The recess 2 makes it possible to adapt the foot as well to the stump of a person amputated of a lower limb as to an organ of a prosthesis of the leg.

 It will be noted that the rolling effect of the blade 4 and the increasing flexibility of the foot, from its middle part, towards the front, on the one hand, towards the rear, on the other hand, confer on this foot properties comparable to those which would result from the use of a malleolar joint, while the means used in accordance with the present invention are much simpler than those of the prior art.

Claims (8)

 1. Prosthetic foot structure comprising a body (1) of a flexible material, the shape and aesthetics of which reproduce those of a human foot, this body having at its upper part, in line with the usual position of the heel , a malleolar recess (2), intended to receive a socket fitted to the user's leg stump or a component of a leg prosthesis, while inside this body is housed at least one blade forming a spring , elastically deformable during the walking of the person equipped with this prosthetic foot, this structure being characterized in that it comprises two distinct leaf springs (3, 4), deformable independently of one another, the first blade (3) extending substantially from below the malleolar recess (2) to the front end of the body (1) and being inclined from the rear to the front of the body (1), while the second blade (4) is arranged at the rear of this body s, substantially below the malleolar recess (2), and has, in section through a longitudinal vertical plane, a lying U-shaped section, the two branches of which are directed towards the rear, the upper branch being in contact with the lower or upper face of the rear part of the first blade (3) and being rigidly integral with the latter.  2. prosthetic foot structure according to claim 1, characterized in that the lower branch of the second blade (4) with U section is slightly curved towards the other branch, so as to define a rolling profile.  3. prosthetic foot structure according to one of claims 1 and 2, characterized in that the second blade (4) has a decreasing thickness from its part in contact with the first blade (3) to the free end of the lower branch.  4. prosthetic foot structure according to one of claims 1 and 2, characterized in that the first blade (3) has a thickness decreasing in a substantially regular manner from its part in contact with the upper branch of the second blade (4) to its front end.  5. prosthetic foot structure according to one of claims 1 to 4, characterized in that the spring blades (3, 4) are made of woven glass and / or carbon fibers, optionally impregnated with a thermoplastic or thermosetting resin, and in that the layers of fibers are oriented so as to have a certain rigidity in the longitudinal direction of the foot and a certain flexibility in the transverse direction.  6. Prosthetic foot structure according to one of claims 1 to 5, characterized in that the body (1) is made of an expanded plastic.  7. prosthetic foot structure according to one of claims 1 to 6, characterized in that the body (1) has a recess (9) perpendicular to the malleolar recess (2).  8. Prosthetic foot structure according to one of claims 1 to 7, characterized in that the front end of the first leaf spring (2) has a recess (5) defining a part (6) engaged as a reinforcement piece in a part of the body (1) in the shape of a big toe.