Athletic shoe midsole design and construction

Abstract: A midsole assembly for an athletic shoe comprises an upper midsole 3a and a lower midsole 3b formed of soft elastic material and a corrugated sheet 4 having a heel portion 4a formed with corrugation. The corrugated sheet 4 is interposed between the upper and lower midsoles 3a, 3b. Upwardly and downwardly extending walls 6, 7 and 8 are formed at the medial and lateral sides of the corrugated sheet 4. Thereby, transverse or lateral deformation of the heel portion of the midsole 3 can be securely prevented and running stability can be further improved.

Description: The present invention relates to a midsole assembly for an athletic shoe and, more particularly, to an improved assembly comprising a midsole and a corrugated sheet inserted into the midsole. The sole of an athletic shoe for use in various sports is generally comprised of a midsole and an outsole. The midsole is typically formed of soft elastic material in order to ensure adequate cushioning properties. The outsole is fitted under the midsole and directly contacts with the ground. Running stability as well as adequate cushioning properties are required in athletic shoes. There is a need to prevent athletic shoes from deflecting or deforming excessively in the lateral or transverse direction when the shoe lands on the ground. As shown in Japanese Utility Model publication No. 61-6804, the applicant of the present invention proposes a midsole assembly having a corrugated sheet therein. Such a midsole construction including a corrugated sheet at the heel portion of a midsole produces a resistant force, which prevents the heel portion of a midsole from being deformed laterally or transversely when the shoe lands on the ground. Thereby, excessive transverse or lateral deformation of the heel portion of a shoe is prevented and running stability is secured. On the other hand, in athletics such as tennis or basketball where rapid lateral movement is included, there has been a strong request that lateral deflection of shoes during games be more securely prevented and running stability be further improved. It is desirable to provide a midsole assembly for an athletic shoe that can more securely prevent lateral deflection or deformation after athletes land on the ground. It is also desirable to provide a midsole assembly for an athletic shoe that cannot only prevent lateral deflection securely but improve cushioning properties. EP-A-0 963 711 and EP-A-0 966 895 were cited under Article 54(3) during examination. Both of these documents and US-A-5 224 280 disclose a midsole assembly according to the preamble of claim 1. The present invention provides a midsole assembly for an athletic shoe for use in various sports, such as running, track, basketball, football, baseball, volleyball, soccer, tennis, golf, biking, and the like Then present invention provides a midsole assembly for an athletic shoe, comprising: a midsole formed of soft elastic material and including a midsole heel portion that comprises an upper midsole portion and a lower midsole portion below said upper midsole portion; and a corrugated sheet disposed at least in said midsole heel portion between said upper midsole portion and said lower midsole portion; characterised in that said corrugated sheet has a corrugated configuration including a plurality of crests and troughs having respective crest and trough lines which extend across the width of said midsole; said crests and said troughs each have a convex surface and a concave surface; and a respective wall portions extend upwardly from the convex surfaces of said crests and/or respective wall portions extend downwardly from the convex surfaces of said troughs; said plurality of wall portions are provided at the medial side and the lateral side of said midsole heel portion; and there are no wall portions extending downwardly from the concave surfaces of the crests. Other preferred aspects of the invention are defined in the accompanying claims. An embodiment referred to hereinafter provides a midsole assembly where an aperture is formed at the contact area between the upper or lower midsole and the corrugated sheet. The aperture may be formed at a convex or concave surface of the corrugated sheet. The aperture may be a through hole penetrating through the upper or lower midsole. In the embodiment, because the corrugated sheet is interposed between the upper and lower midsoles at least at the heel portion, lateral deflection or deformation of the heel portion of the midsoles can be prevented. Moreover, in this case, when the corrugated sheet has upwardly extending walls at its medial and lateral sides, the medial and lateral sides of the upper midsole sandwiched between the oppositely disposed walls. When the corrugated sheet has downwardly extending walls at its medial and lateral sides, the medial and lateral sides of the lower midsole are sandwiched between the oppositely disposed walls. Thus, when the heel portion of the upper and lower midsoles are going to deflect in the lateral direction after the shoe lands on the ground, the upwardly and/or downwardly extending walls prevent the heel portion of the upper and lower midsoles from being deformed in the lateral direction, which further improves the running stability. In the embodiment, because the upper or lower midsole has an aperture at the contact region with the corrugated sheet, the corrugated sheet is easy to be deformed relative to the vertical load at a region where an aperture is formed. Thereby, cushioning properties is advanced. In addition, when an aperture is a through hole, cushioning properties can be improved across the whole width of the midsole. The present invention may be well understood the described embodiment thereof, wich is given by way of example only, and will now be described with reference to the accompagnying drawings (which are not to scale), in which : FIG. 1 is a side view of an athletic shoe employing the midsole construction of an embodiment of the present invention; FIG. 2 is a top plan view of the midsole assembly of a left shoe according to the embodiment; FIG. 3A is a lateral side view of the midsole assembly of FIG. 2; FIG. 3B is a medial side view of the midsole assembly of FIG. 2; FIG. 4 is a perspective view of a corrugated sheet; FIG. 5 is a cross sectional view of the midsole assembly of FIG. 2 taken along line V-V. FIG. 6 is a cross sectional view of the midsole construction of FIG. 2 taken along line VI-VI. Turning now to the drawings, FIG. 1 illustrates an athletic shoe incorporating a midsole assembly of an embodiment of the present invention. The sole of this athletic shoe 1 comprises a midsole 3 attached under an upper 2, a corrugated sheet 4 disposed in the midsole 3 and an outsole 5 attached under the midsole 3 and directly contacting with the ground. The midsole 3 is provided in order to absorb shock load imparted on the heel portion of the shoe 1 when the shoe lands on the ground. The midsole 3 is comprised of an upper midsole 3a and a lower midsole 3b that are respectively disposed on the top and bottom surfaces of the corrugated sheet 4. The midsole 3 is generally formed of soft elastic material having good cushioning properties. Specifically, thermoplastic synthetic resin foam such as ethylene-vinyl acetate copolymer (EVA), thermosetting resin foam such as polyurethane (PU), or rubber material foam such as butadiene or chloroprene rubber is used. The corrugated sheet 4 is formed of thermoplastic resin such as thermoplastic polyurethane (TPU) of comparatively rich elasticity, polyamide elastomer (PAE), ABS resin or the like. Alternatively, the corrugated sheet 4 may be formed of thermosetting resin such as epoxy resin, unsaturated polyester resin or the like. As shown in FIG. 2, the corrugated sheet 4 extends from the heel region to the midfoot region of the midsole 3. The corrugated sheet 4 is comprised of a heel portion 4a having corrugations and a generally planar midfoot portion 4b integrally formed with the heel portion 4a. In FIG. 2, a broken line L extending in the width direction at the heel portion 4a indicates a crest or trough line of corrugations of the corrugated sheet 4. As shown in FIGS. 3A and 3B, a plurality of upwardly extending walls, or wall portions, 6 are formed at the inner and outer sides of the corrugated sheet 4 (see FIG. 4). These walls 6 extend upwardly from the convex surfaces of respective crests of the corrugated sheet 4. As shown in FIG. 5, the inner and outer side faces of the upper midsole 3a are sandwiched between the oppositely disposed walls 6. At the trough or concave side of the corrugations of the corrugated sheet 4 there are a plurality of slightly upwardly extending walls, or wall portions, 7 (see FIGS. 3A, 3B and 4). As shown in FIG. 6, the inner and outer side faces of the upper midsole 3a are also sandwiched between the oppositely disposed walls 7. At the convex surface of the troughs of the corrugated sheet 4, there are respective slightly downwardly extending walls, or wall portions, 8 (see FIGS. 3A, 3B and 4). As shown in FIG. 6, the inner and outer side faces of the lower midsole 3b are sandwiched between the oppositely disposed walls 8. Walls 7 and 8 extend slightly (only a small amount) upwardly and downwardly repectively. Moreover, a plurality of apertures 9 are formed at the contact area of the lower midsole 3b with the corrugated sheet 4. These apertures 9 are provided at the concave side of the corrugations of the corrugated sheet 4. As shown in FIG. 5, the apertures 9 are through holes penetrating the lower midsole 3b in the width direction. In addition, as shown in Figs 5 and 6, the lower midsole 3b is formed with a vertically extending through hole 10 for improvement of its cushioning properties. In this case, the heel portion 4a of the corrugated sheet 4 placed at the heel region prevents the heel region of the midsole 3 from being deflected and deformed in the lateral or transverse direction after the shoe lands on the ground. Furthermore, the deflecting movement of the heel region of the upper midsole 3a is also prevented by the upwardly extending walls 6, 7, and the deflecting movement of the heel region of the lower midsole 3b is also prevented by the downwardly extending walls 8. Thereby, transverse deformation of the heel region is more securely prevented and running stability is further improved. Moreover, in this case, deformation of the corrugated sheet 4 relative to the vertical load is easier at the regions where the apertures 9 are formed. Thereby, cushioning properties are advanced. Additionally, because the apertures 9 are through holes, cushioning properties across the whole width of the midsole 3 are improved and the midsole 3 is lighter in weight. In a variation the upwardly extending walls of the corrugated sheet 4 are formed either at the convex side or at the concave side of the corrugations of the corrugated sheet 4. In a further variation, the downwardly extending walls 8 of the corrugated sheet 4 are formed at the concave side of corrugations of the corrugated sheet 4. Alternatively, the downwardly extending walls may be formed at both the convex side and the concave side. The apertures 9 may be formed in the upper midsole 3a. In the alternative, the apertures 9 may be formed at the convex side of corrugation of the corrugated sheet 4. Those skilled in the art to which the invention pertains may make modifications and other embodiments employing the principles of this invention. The described embodiments and examples are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. Consequently, while the invention has been described with reference to particular embodiments and examples, modifications of structure, sequence, materials and the like would be apparent to those skilled in the art, yet still fall within the scope of the invention as defined in the claims.

Claims: A midsole assembly for an athletic shoe, comprising: a midsole (3) formed of soft elastic material and including a midsole heel portion that comprises an upper midsole portion (3a) and a lower midsole portion (3b) below said upper midsole portion; and a corrugated sheet (4) disposed at least in said midsole heel portion between said upper midsole portion and said lower midsole portion; characterised in that said corrugated sheet has a corrugated configuration including a plurality of crests and troughs having respective crest and trough lines (L) which extend across the width of said midsole; said crests and said troughs each have a convex surface and a concave surface; respective wall portions (6) extend upwardly from the convex surfaces of said crests and/or respective wall portions (8) extend downwardly from the convex surfaces of said troughs; said plurality of wall portions (6, 8) are provided at the medial side and the lateral side of said midsole heel portion; and there are no wall portions extending downwardly from the concave surfaces of the crests. A midsole assembly according to claim 1, wherein said wall portions (6, 8) each have a curved contour extending upwardly from the convex surfaces of said crests or downwardly from the convex surfaces of said troughs. A midsole according to claim 1 wherein, said plurality of wall portions (8) extend downwardly only slightly from the convex surfaces of the troughs. A midsole assembly according to claim 1, wherein said corrugated sheet (4) is formed of thermoplastic resin such as thermoplastic polyurethane (TPU), polyamide elastomer (PAE), or ABS resin; or the corrugated sheet (4) is formed of thermosetting resin such as epoxy resin, or unsaturated polyester resin. A midsole assembly according to claim 1, further having an aperture (9) which extends along said lines (L) in the width direction at the contact area between said corrugated sheet (4) and said soft elastic material of said upper or said lower midsole (3). A midsole assembly according to claim 5, wherein said aperture (9) is formed at a said convex surface of said corrugated sheet (4). A midsole assembly according to claim 5, wherein said aperture (9) is formed at a said concave surface of said corrugated sheet (4). A midsole assembly according to claim 7, wherein said aperture (9) is a through hole that penetrates through said midsole from said lateral side to said medial side between said corrugated sheet (4) and said soft elastic material of said upper or said lower midsole (3). An athletic shoe comprising a midsole assembly as claimed in any of the preceding claims.

Inventors: KIMURA TAKAYA, KITA KENJIRO, KIMURA, TAKAYA, KITA, KENJIRO
Applicants: MIZUNO KK, MIZUNO CORPORATION
Application year: 2000
Main classification: A43B13
IPC codes: A43B5, A43B13, A43B21