Athletic Training Shoe Having Foam Core and Apertured Sole Layers

The subject matter of the present invention relates generally to athletic shoes and in particular to athletic shoes having multi-layered soles including an apertured sole layer and/or a foam core sole layer positioned between a harder, wear resistant outer sole layer and the shoe upper.

In the preferred embodiment, the apertured sole layer is a heel lift layer positioned below an intermediate sole layer having a softer resilient foam core surrounded by a harder resilient border portion and provided within an elongated opening extending longitudinally beneath the heel, arch and metatarsal bones of the wearer's foot for greater comfort and support. The shoe is built on a straight last and is provided with flared sides on the intermediate sole layer and heel lift layer for greater lateral stability along with a flat planar beveled heel which insures proper foot position during initial contact with the ground, sometimes called "heel strike." This insures proper foot placement from heel strike to toe off. The shoe of the present invention is especially useful as a training shoe for running, exercise and conditioning, since it prevents injury to the foot and leg.

Previously it has been proposed in spike track shoes used by jumpers, to provide an aperture in the heel lift sole layer for cushioning the heel, as shown in U.S. Pat. No. 3,290,801 of Bente, granted Dec. 13, 1966. However, such shoes employed a single opening in the heel lift layer of a sufficient size to receive the downward projection of the heel bone of the foot to prevent injury to the heel of the jumper. It is also old to provide conventional street shoes with an apertured middle sole for ventilation, as shown in U.S. Pat. No. 231,398 of Bussey, granted Aug. 24, 1880 and U.S. Pat. No. 3,050,875 of Robbins, granted Aug. 28, 1962. Unlike the present invention, a plurality of apertures arranged in three staggered rows are not provided in the heel lift layer to provide both support and cushioning. In addition, there is no intermediate sole layer provided above the heel lift layer which contains a softer resilient foam core within an elongated opening extending beneath the heel, arch and metatarsal bones of the foot as is employed in the training shoe of the present invention. Furthermore, there is no indication that such athletic shoe should be made with a straight last. However, it should be noted that conventional street shoes have previously been made with straight lasts, as shown in U.S. Pat. No. 2,034,243 of Maxwell, granted Mar. 17, 1936.

Previously it has been proposed in U.S. Pat. No. 3,793,750 of Bowerman to provide an athletic shoe with a nylon fabric upper and cushion middle sole layer covered by a harder outer sole including polygon-shaped studs. Athletic shoes have also been made with flared sides and beveled rear heel surfaces. Unlike the present invention, such athletic shoes were not provided with an apertured heel lift layer or an intermediate sole layer having an inserted core of softer foam cushioning. These sole layers give the athletic shoe of the present invention the advantages of excellent comfort and support, while at the same time providing a relatively lightweight shoe of long useful lifetime and good traction.

It is therefore one object of the present invention to provide an improved athletic shoe having intermediate sole layers which provide better cushioning, comfort and support.

Another object of the invention is to provide such a shoe of good lateral stability which guides the foot at the time of initial contact by the heel of the shoe with the ground and during continued contact of the bottom of the sole until final contact by the toe of the shoe with the ground in order to prevent injury by insuring proper foot placement during running even when the wearer is fatigued.

A further object of the invention is to provide such a shoe as a training shoe which is relatively lighter in weight and has a long useful lifetime while at the same time providing good traction.

An additional object of the present invention is to provide such an athletic shoe employing an apertured heel lift layer and an intermediate sole layer having a core insert of soft foam cushioning material provided within an opening extending beneath the heel, arch, and metatarsal bones of the foot and in communication with at least some of the apertures in such heel lift layer.

Another object of the invention is to provide such a shoe in which the heel lift layer and the intermediate sole layer are covered by an outer sole layer of harder, resilient, wear-resistant material which may have polygon-shaped studs molded in its outer bottom surface.

Still another object of the invention is to provide such an athletic shoe in which the intermediate sole layer and the heel lift layer are provided with side surfaces which flare outwardly and are provided with inwardly slanting rear heel surfaces forming a flat planar beveled heel.

A still further object of the invention is to provide such a shoe in which the shoe upper and sole is in the shape of a straight last for greater comfort and prevention of injury.

Other objects and advantages of the present invention will be apparent from the following detailed description of a preferred embodiment thereof and from the attached drawings of which:

FIG. 1 is a side elevation view of a shoe in accordance with the preferred embodiment of the present invention;

FIG. 2 is a top elevation view of the shoe of FIG. 1;

FIG. 3 is a rear elevation view of the shoe of FIGS. 1 and 2;

FIG. 4 is a vertical section view taken along the line 4--4 of FIG. 2;

FIG. 5 is a vertical section view taken along the line of 5--5 of FIG. 2;

FIG. 6 is an enlarged vertical section view of the shoe upper taken along the line 6--6 of FIG. 1;

FIG. 7 is a bottom elevation view of the shoe of FIG. 1 with parts broken away for clarity to show the internal construction of the sole layer; and

FIG. 8 is a diagrammatic view looking down on the top of the shoe of FIG. 2, showing the foot of the wearer within such shoe.

As shown in FIG. 1, one embodiment of the athletic shoe of the present invention includes a shoe upper 10 of leather or synthetic plastic fabric, such as nylon, secured to a multilayered sole including an outer sole layer 12 of hard resilient wear-resistant rubber material, an apertured heel lift layer 14 of resilient lightweight foam cushioning material and an intermediate sole layer 16 of similar cushioning material but having a softer foam core for greater cushioning, as hereafter described. The heel lift layer 14 is preferably positioned between the intermediate sole layer 16 and the outer sole layer 12, such heel lift layer extending longitudinally beneath the heel, arch and metatarsal bones of the foot of the wearer, while the intermediate layer extends the full length of the foot. However, it is also possible to reverse the positions of the heel lift layer 14 and intermediate sole layer 16 in some instances. The heel lift layer 14 is of approximately the same maximum thickness of about 1/4 inch as the intermediate sole layer 14 in the heel area, as shown in FIG. 4, but such heel lift tapers to a smaller thickness under the arch and metatarsal bones until it terminates slightly in front of the metatarsal heads.

The intermediate sole layer 16 includes an outer border portion 18 extending around the rim of the intermediate sole layer and surrounding a softer foam inner core 20. The foam core 20 has a substantially flat continuous upper surface and is contained within a single elongated opening passing through the intermediate sole layer and extending longitudinally beneath the heel, arch and toes of the foot for cushioning. The border portion 18 of harder foam material is provided with flared side surfaces 22 on opposite sides of the sole which flare downwardly and outwardly. Each of the flared side surfaces 22 is aligned with a similar flared surface 24 on the side of the heel lift layer 14, as shown in FIG. 4. Thus, the two flared side surfaces 22 and 24 are aligned and form an acute included angle B with the top surface 26 of the bottom portion of the outer sole layer 12 normally engaging the ground. The flare angle B is in the range of 45.degree. to 75.degree. and is preferably about 60.degree.. The flared sides 22 and 24 of sole layers 16 and 14 provide the shoe with greater lateral stability to prevent sprained ankles and other injuries to the foot. In order to achieve this lateral stability, the border portion 18 of the intermediate sole layer and the entire heel lift layer 14 are made of a relatively hard, dense, resilient foam material, such as a closed cell synthetic or natural foam rubber including polyisoprene microcellular sponge rubber, having a density of about 42 lbs./cu. ft. at a temperature of 76.degree. F. and a hardness of about 42 to 46 durometer, A-type, at 68.degree. F. It should be noted that the hardness and density values were obtained by the standard tests A.S.T.M. D2240 and A.S.T.M. D1565 of the American Society of Testing and Materials. Also to provide greater cushioning, the intermediate sole layer 16 is also provided with the inner core 20 of a softer, lower density, resilient, closed cell foam material, such as a synthetic plastic of polyethylene of ethylene vinyl acetate copolymer, whose cells may be filled with nitrogen or other foaming gas. The ethylene vinyl acetate core may have a density of 8.3 lbs./cu. ft. at 76.degree. F. and a hardness of 26 to 29 durometer, A-type, at 68.degree. F., while the polyethylene core may have a density of 2.4 lbs./cu. ft. at 76.degree. and a hardness of 11 durometer, A-type, at 68.degree. F. However, other synthetic plastic or rubber foam materials can be employed for sole elements 14, 18 and 20.

The apertured heel lift layer 14 is provided with three rows of apertures 26, 28 and 30 which extend longitudinally along such layer. The middle row of apertures 28 is staggered out of alignment with the apertures of the outer two rows of apertures 26 and 30. The back aperture in the middle row of apertures 28 is closest to the rear of the heel portion of the shoe while the two front apertures of the outer two rows of apertures 26 and 28 are closest to the front of the heel wedge portion and overly the heads of the metatarsal bones of the foot, as shown in FIG. 8, for greater comfort and cushioning. At least some of the apertures, including the entire middle row 28, are in alignment with the foam core 20 of the intermediate layer, such apertures extending completely through the heel lift layer into communication with the foam core. It should be noted that the apertures are circular, have a diameter in the range of 1/2 to 1 inch, preferably about 3/4 inch diameter which is greater than the maximum thickness of the heel lift layer 14, and have a longitudinal spacing between adjacent apertures in the same row of approximately twice the diameter of the apertures or 11/2 inches for the preferred size, as shown in FIG. 7. In this case the rows 26, 28 and 30 consist of three apertures each.

As shown in FIGS. 1, 3 and 7, the outer sole layer 12 includes a plurality of polygon-shape studs 32 extending downwardly from the lower surface of the outer sole layer and formed of hard rubber molded integrally therewith, such as shown in U.S. Pat. No. 3,793,750 referred to previously. These studs provide the shoe with good traction and additional cushioning. Of course, the outer sole is made of a harder, more wear-resistant rubber or other resilient material, than the cushioning layers 14 and 16. This outer sole of about 1/8 inch thickness is thinner and harder than the cushioning layers 14 and 16 and can be replaced when such outer sole layer wears out.

The outer sole layer, the heel lift layer and the intermediate sole layer are bonded together in a conventional manner by a waterproof glue such as rubber cement or other suitable bonding material. In addition, the top surface of the boundary portion 18 of the intermediate sole layer 16 is bonded to a pair of inner edges 34 and 36 of the shoe upper, as shown in FIG. 4. An inner platform layer 38 of fiberboard or cardboard provided within the shoe is similarly bonded over the edges 34 and 36 of the upper, and is also bonded over the foam core 20 of the intermediate sole layer. A resilient foam insole layer 40, such as closed cell Neoprene foam rubber, having a fabric bonded to its upper surface, is provided within the shoe over this platform layer to prevent blisters on the foot.

Flat, planar heel surfaces 42 and 44 are provided at the rear ends of the intermediate sole layer 16 and the heel lift layer 14, as shown in FIGS. 1 and 7. These planar heel surfaces are aligned to form a beveled heel which slants downwardly and inwardly to form an obtuse, included angle A of preferably about 120.degree. with the upper surface of the bottom portion of the outer sole layer 12 which normally engages the ground when the wearer is standing still. The outer sole layer 12 includes an upper portion 46 which extends up from the bottom portion over the beveled heel surfaces 42 and 44 to cover the beveled heel, as shown in FIG. 3. The beveled heel insures proper foot placement during initial contact with the ground, sometimes called "heel strike," while the flared sides 20 and 24 of the sole layers provide lateral stability and maintain the bottom of the sole on the ground until final contact with the ground by the toe of the shoe, sometimes called "toe off." This, together with the cushioning and support of the foot by the heel lift layer and the intermediate sole layer, prevent injury to the wearer's foot and leg. Such guiding of the shoe to insure proper foot position at all times, as well as provide support for the arch and cushioning for the entire foot, is extremely important when running long distances such as during training because when a runner becomes fatigued his foot placement tends to become sloppy.

Another feature which helps achieve good comfort and proper foot position is the straight last of the shoe, as shown in FIG. 8. The shoe upper and sole layers are formed on a straight last, having a last axis 48 which extends between the forward most point 50 and the rearward most point 52 of the sole. This last axis 48 corresponds to the weight bearing line of the foot and extends along a line which bisects the heel of the foot and passes through the second metatarsal head 54. This straight last axis passes along the second metatarsal bone and in this regard is different from the last axis shown in FIG. 1 of the U.S. Pat. No. 2,034,243, referred to above.

As shown in FIG. 6, the shoe upper 10 may be made of a multiple layer fabric including an outer layer 56 of nylon fabric of open mesh, an inner layer 58 of a different synthetic fabric of closed mesh and a middle layer 60 of open cell, synthetic foam such as polyurethane. This multiple layer fabric is strong, comfortable and provides good air ventilation. The inner layer 60 prevents small cinders, rocks or other objects from passing through the fabric which might otherwise be transmitted through the outer layer 56 because of the smaller mesh openings in the inner layer.

It will be obvious to those having ordinary skill in the art that changes may be made in the above described preferred embodiment without departing from the spirit of the invention. For example, the front end of the heel lift layer 14 could terminate at or behind, rather than in front of, the metatarsal heads to provide greater sole flexibility at the metatarsal joint. Also, it should be understood that while the shoe of the present invention prevents injury in the sense that it greatly reduces the chance of injury, no shoe can eliminate all injury. Therefore, the scope of the present invention should be determined by the following claims.