US2119016A - Rubber heel - Google Patents

Description

May 31, 1938. c. LAMB 2,119,016

RUBBER HEEL Filed Dec. 20, 1957 Patented May 31, 1938 UNITED STATES PATENT' OFFICE 2 Claims.

This invention relates to the orthopedic art and particularly to heels made of rubber or other elastic material.

Extensive experimentation has been carried on from time to time with the object of providing a rubber heel which when used will tend to correct or mitigate the condition of fallen arches commonly known as fiat feet. While engaged for many years in the manufacture of orthopedic rubber heels, I have made an intensive study of this problem, and have noted that one of the main differences of all these so-ca11ed orthopedic corrective rubber heels has been first that they did not supply a sufficient degree of resiliency in the main body of the heel, and secondly, that they were subject to a relatively rapid wearing down of the rear outer corners of the heels. The low degree of resiliency present in the main body of most of these heels had a tendency to defeat whatever advantage there is in a rubber heel in the way of correcting a. tendency towards fallen arches or in relieving such a condition after it has become acute. I also noted that the rapid wearing down of the rear outer corners of rubher heels generally resulted in rendering these practically valueless after a relatively short period of use in so far as any corrective tendency they might have. This is because of the fact that when so worn down the fulcrum point in the heel moves forwardly so that instead of causing the shoe to pull down and rearwardly the metatarsals of the foot, so that the constrictive action of the tendons under the foot would lift the internal cuniform and scaphoid structure-of the instep upwardly, the shoe would tend in fact to resist the forward turning movement about the fulcrum in the heel and the tendency would be for the weight of the body to be thrown downwardly on the instep structure with the ultimate result of straining this.

Beginning with the observation of these facts, I have proceeded by my experiments to the discovery that a new rubber heel having adequate resiliency in the main body thereof produces a distinctly beneficial effect resulting from corrective forces applied to the arch structure of the foot, tending to produce a high arch. Such a heel continues to produce this effect, however, only so long as it retains a substantially fiat lower surface and a substantially uniform degree of resiliency from the extreme rear of the heel to the front thereof.

It is, therefore, an object of my invention to provide an orthopedic rubber heel which shall possess a substantially high degree of resiliency throughout the main body thereof and which will tend when used to maintain over a relatively long period of use a substantially fiat lower surface.

It is a further object of my invention to provide an orthopedic rubber heel the reaction to use of which is such that this heel will retain a substantially high degree of resiliency in the rear outer portion of the heel over a relatively long period of use.

Yet another object of my invention is to provide an orthopedic rubber heel, the reaction to use of which will be such as to maintain the original shape of said heel to an extent that the fulcrum about which the foot is caused to rock, as this heel engages the ground, is maintained at a substantially maximum distance rearwardly, as when the said heel is new.

The manner of accomplishing the foregoing objects as well as further objects and advantages will be made manifest in the following description taken in connection with the accompanying drawing in which Fig. 1 is a side elevational view of a man striding and with the shoe of his foremost foot poised so that a rubber heel thereon is just about to engage the ground.

Fig. 2 is a perspective view of the preferred form of my invention when embodied in a rubber heel for the right foot.-

Fig. 3 is a rear elevational view of the heel shown in Fig. 2 when the latter is positioned as when applied to a shoe and is taken on the direction of arrow 3 in Fig. 2.

Fig. 4 is a front elevational view of the heel shown in Fig. 2, and is taken in the'direction of arrow 4 therein.

Fig. ,5 is a vertical sectional view taken on the line 5-5 of Fig. 2, and which shows the structure of said heel when it is new.

Fig. 6 is a diagrammatic cross-Sectional view similar to Fig. 5 and illustrating the condition thereof after it has been subjected to several months wear.

Fig. 7 is a longitudinal sectional view of an ordinary rubber heel after it has been given a similar amount of wear as that to which the heel of my invention was subjected before the latter exhibited a worn condition as shown in Fig. 6.

In searching for a solution to the problems referred to hereinabove, I discovered that the abnormal wearing away of the bottom face 01a rubber heel in the area of maximum wear may be greatly decreased by the provision of material on the other portions of the lower face of rapidly than the material used in the area of maximum wear.

As a preferred embodiment of my invention, therefore, I have provided a rubber heel III in which the main body ii of the heel is composed of highly resilient rubber and which also has a relatively high resistance to abrasion. The body of rubber ll forms a relatively thick upper layer in the heel ll of substantially uniform thickness throughout the heel except opposite the area of maximum wear l2 in which the rubber 0f the body ll extends downwardly to the lower face of the heel. The balance of the lower surface of the heel I0 I have divided into areas It and I, the area I! being that in which the wear is substantially uniform but less than the wear in area l2, and the area I being that in which the wear is substantially uniform but less than the wear in area i5.

In area II I provide an inlay ll of rubber which is somewhat less resilient than the body of rubber II and considerably more susceptible to abrasion. In the area II I provide an inlay ll of rubber which is still harder than the inlay l1 and which is even more susceptible yet to the abrasion than the inlay l1. In the manufacture of the heel II the body II and the inlays I1 and II are The result of the more rapid abrasion of the inserts l1 and I. is illustrated in Fig. 6. Here it is seen that the body ll opposite the area I! has been only very slightly beveled rearwardly, whereas substantially one-half of the thickness of the inlays I1 and "have been worn away. The

eifect of this in contributing towards the attain-- ment of the objective of my invention has been indicated by drawing lines A-A, BB and C-C in Figs. 5, 6 and '7, which designate respectively the planes on which the first pressural contact of the heel is had in placing the foot on the ground.

In Fig. 5 which shows the heel III of my invention when this was new it is seen that the plane of contact between the heel and the ground is such that this contact is maintained up to the place where the ball of the foot is entirely on the ground a rotational force is exerted by the resiliency of the rear portion of the heel tending to force the front portion of the shoe downwardly. The resistance to this force by the natural tenslng of the tendons beneath the foot and upwardly from the cuniform and scaphoid bones of the arch structure is to distribute the load of the foot between the heel and the ball of the foot and maintain the arch structure in healthful arched condition free from abnormal strain.

The location of line BB in Fig. 6 illustrates how in the heel of my invention the plane of contact between the rear portion of the heel and the ground is maintained practically up to the time the heel which would tend to wear away more the ball of the foot engages the ground even after the heel has suffered a considerable degree of wear over a relatively long period of use. At the same time it should also be-noted that while the highly resilient rubber body H has been worn down in area of maximum wear l2, this wear has been matched by corresponding wearing down of the inserts l1 and I8 over the balance of the lower surface of the heel so that the ultimate result is to prevent the abnormal beveling of the rear outer-corner of the heel and to keep the bottom of the heel substantially flat. It is clear from this that the beneficial results of the flat lower surface of a rubber heel are in my invention retained throughout a relatively long use of the heel.

In Fig. 7 I have illustrated an ordinary rubber heel 20 as it appears after a considerable period of use, the line 0-0 indicating the plane of initial contact between a rear lower face ll of the heel and the ground. This plane is seen to be such as to throw the fulcrum about which the shoe rotates away forward towards the middle of the heel. This effects a tendency to rotate the shoe in exactly the opposite direction as a new heel. In

other words the heel 20 after engaging the ground on the plane of line CC not only exerts no corrective force thereafter on the arch structure of the foot, but on the contrary produces a negative reaction applying undue strains on the arch.

The foregoing comparison can be demonstrated by anyone by alternately wearing a pair of shoes having new rubber heels and a pair of shoes which are badly run down at the outward rear portions thereof and carefully noting the exactly opposite reaction obtained.

What I claim is:

1. A heel comprising a body of rubber which includes: a base or upper layer of relatively high resiliency and abrasion resistance, said base layer extending down to the lower face of said heel in the area of maximum wear; and a lower layer of relatively low resiliency and abrasion resistance covering the areas of less than maximum wear, said layers being vulcanized into a unitary body, the resiliency and the power to resist abrasion of said lower layer decreasing progressively as it extends away from said area of maximum wear and towards an area of minimum wear.

2. A heel comprising a body of rubber which includes: a base or upper layer of relatively high resiliency and abrasion resistance, said base layer extending down to the lower face of said heel in an area of maximum wear at the rear outer corner of said heel; and a lower layer of relatively low resiliency and abrasion resistance covering the balance of said lower face, said lower layer comprising two or more sections of progressively less resiliency and abrasion resistance than said upper layer and than each other as said sections increase in distance from said area. the section of least resiliency and abrasion resistance being located in an area adjacent the inner forward corner of said heel, said layers being vulcanized into a unitary body.

CHARLES LAMB.

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