Integrally cast shoe sole containing stiffener member

A shoe sole structure in which a metallic stiffener member having generally the form of an elongated plate is encapsulated within a solid body of elastomeric material. The elastomeric material provides a ground-engaging surface underneath the stiffener member, a foot-supporting surface above the stiffener member, and also provides a toe-supporting portion which extends forwardly of the stiffener member and is free to flex vertically as needed.

RELATED APPLICATION 
The invention disclosed in the present application is an improvement over 
that disclosed in my copending application Ser. No. 155,589 filed June 2, 
1982, now U.S. Pat. No. 4,348,821. 
BACKGROUND OF THE INVENTION 
In recent years there have been many innovations relating to shoes, some of 
which are of decorative or appearance value only, while others relate to 
the mechanical or utilitarian qualities of the product. The invention 
disclosed in my above-referenced patent is in the latter category. 
In the manufacture of any product, cost is always an important 
consideration. Shoes are no exception. Thus it is advantageous to 
construct a shoe sole in such a way that it will provide superior 
performance, but yet its manufacturing cost is reduced. 
The object of the present invention, therefore, is to provide a shoe sole 
structure which is of superior quality, but yet lends itself to 
manufacturing by machine methods at low cost. 
SUMMARY OF THE INVENTION 
According to the present invention a shoe sole structure is made from a 
solid mass of elastomeric material within which a metallic stiffener 
member is imbedded. More specifically, the stiffener member has generally 
the form of a flat plate which is of sufficient length to extend from the 
heel portion of the shoe to the metatarsal arch region, and has a 
plurality of holes or perforations formed therein. 
Thus, the solid mass of elastomeric material includes one portion which 
lies beneath the stiffener member for engaging the ground, and another 
portion which lies above the stiffener member for supporting the foot of 
the wearer. The elastomeric material is cast as a solid body extending 
through the holes or perforations in the stiffener member, so that its 
upper and lower portions are adequately secured together. 
Further, in accordance with the invention, the same mass of elastomeric 
material extends forwardly from the forward extremity of the stiffener 
member, so as to provide a toe-supporting portion of the shoe sole 
structure. Thus the stiffener member performs the traditional function of 
an arch support, while the portion of the shoe sole structure that extends 
forwardly of the metatarsal arch region is free to flex and bend as 
needed. 
According to the presently preferred form of the invention the stiffener 
member is not absolutely flat, but has a downward protrusion or kink at 
one point along its length. The purpose of the downward protrusion is to 
reduce the resilience of the ground-engaging portion of the elastomeric 
material, at that particular point along the length of the shoe sole 
structure.

DETAILED DESCRIPTION 
Reference is made to FIGS. 1 through 5 of the drawing illustrating the 
presently preferred form of the invention. 
The complete shoe sole structure S includes a solid mass of elastomeric 
material 10 and a metallic stiffener member 20. The elastomeric material 
may, for example, be soft rubber. The stiffener member may, for example, 
be made of an aluminum alloy. 
Elastomeric member 10 has a substantially flat upper surface which is 
adapted to have the conventional form of shoe upper secured upon it. Thus, 
the upper surface 11 is a foot-supporting surface, although it supports 
the foot indirectly, through a conventional shoe upper, rather than 
directly. Around the entire circumferential edge of the upper surface 11 
there is an upwardly turned flange 12. 
Elastomeric member 10 also has a ground-engaging bottom surface designated 
generally as 15. At the rearward or heel end of the sole structure S, the 
elastomeric member 10 provides a rounded heel 16. Near the longitudinal 
center of sole structure S, but slightly to the rear of that longitudinal 
center, elastomeric member 10 provides a central pedestal 17, the under 
surface of which is also rounded in the longitudinal direction. That 
portion of the elastomeric member which underlies the metatarsal arch 
portion of the shoe is especially identified by numeral 18, while the 
toe-supporting portion is identified by numeral 19. The central pedestal 
17 is a unique structural feature disclosed in my above-identified patent. 
Stiffener member 20 has the general configuration of an elongated flat 
plate. Its upper surface is designated by numeral 21 while its lower 
surface is designated by numeral 22. The rearward or heel end of stiffener 
member 20 is rounded at 23 as best seen in FIG. 1. Its forward end has a 
substantially square cut as designated by numeral 24, but being slightly 
dished across the width of the sole structure S. The length of stiffener 
member 20 is such that it extends above the heel portion 16 of the 
elastomeric material, above the central pedestal 17, and into the 
metatarsal arch region 18. It does not extend into the toe-supporting 
portion 19 of the shoe sole, which is therefore free to flex vertically as 
needed. 
In the presently preferred form of the invention the stiffener member 20 
has a number of troughs or corrugations 25 formed in a longitudinal 
direction. The purpose of these corrugations is to enhance the resistance 
to bending movements in a lengthwise direction. Stiffener member 20 also 
has a number of holes or perforations 27 formed in it. See FIGS. 1 and 5. 
These holes or perforations permit the elastomeric material to be case as 
an integral member in which that portion of the elastomeric material below 
the stiffener is secured to the portion above the stiffener through the 
openings. The elastomeric material also completely surrounds and encloses 
the edges of stiffener member 20. 
Thus it will be seen that in accordance with the general concept of the 
invention a metallic stiffener member, similar to a traditional arch 
support, is completely encapsulated within an elastomeric member that is 
cast as a single body. The ground-engaging surface of the elastomeric 
member lies beneath the stiffener member, while the foot-supporting 
surface lies above it. And the toe-supporting portion of the elastomeric 
member extends forwardly of the stiffener member and is free to flex 
vertically as needed. 
However, the present invention provides more than simple encapsulation of a 
metallic stiffener member inside an integrally cast elastomeric member. 
Thus, at one point along its length the stiffener member 20 has a downward 
protrusion or kink 26 formed in it. The purpose of the protrusion or kink 
is to alter the mechanical characteristics of the ground-engaging surface 
of the elastomeric member. Specifically, according to the presently 
preferred embodiment of the invention, the protrusion or kink 26 lies 
immediately above the central pedestal portion 17 of the elastomeric 
member. As a result of this arrangement, the mechanical action of central 
pedestal 17 is relatively stiff while the mechanical action of the rounded 
heel 16 is quite resilient. Comparing the thicknesses of the resilient 
material which lies beneath the stiffener member 20, it will be noted that 
the heel portion 16 is several times as thick as the central pedestal 17. 
These relationships are as described in my above-identified patent. 
It will be understood, however, that the present invention is not 
restricted to having the kink or protrusion in the stiffener member 
located at the location of central pedestal 17. In accordance with the 
invention such a kink or protrusion may, if desired, be located in the 
heel portion of the shoe sole structure S.