Athletic shoe midsole design and construction

Abstract: A midsole assembly for an athletic shoe comprises a midsole formed of soft elastic material and a corrugated sheet disposed in the heel portion of a midsole. A plurality of through holes are formed at portions where a midsole contacts a corrugated sheet. In this case, transverse deformation of the heel portion of a midsole can be prevented by the wave formed portion of a corrugated sheet and running stability of a shoe can be ensured. Also, the cushioning properties of a shoe can be improved at the aperture formed portions where vertical deformation becomes easier.

Description: The present invention relates to a midsole assembly of an athletic shoe. More particularly, the invention relates to a midsole assembly comprising a midsole formed of soft elastic material and a corrugated sheet disposed in the midsole. The sole of an athletic shoe used 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 is required in athletic shoes. Consequently, there is need to prevent shoes from being deformed excessively in the lateral or transverse direction when contacting the ground. As shown in Japanese Utility Model Examined Publication No. 61-6804 and in the document US-A-4 561 195, the applicant of the present application proposes a midsole assembly having a corrugated sheet therein, which can prevent such an excessive lateral deformation of shoes. The midsole assembly shown in the above publications incorporate a corrugated sheet in the heel portion of a midsole, thereby producing a resistant force that prevents the heel portion of a midsole from being deformed laterally or transversely when a shoe contacts with the ground. Thus, transverse deformation of the heel portion of a shoe is prevented and running stability can be ensured. Generally, by inserting a corrugated sheet, the heel portion of a midsole tends to be less deformed in the transverse direction and running stability can be improved. However, when the corrugated sheet is formed especially of high elastic material the heel portion of a midsole tends to be less deformed in the vertical direction as well. Thus, by using a corrugated sheet, a portion where adequate cushioning properties is required on landing may show less cushioning properties. EP-A-0 878 142 was cited, under Article 54(3) EPC as a novelty only citation, during examination of the present application. EP-A-0 878 142 discloses a midsole assembly for an athletic shoe comprising: a midsole formed of soft elastic material; and a corrugated sheet disposed in a heel portion of the midsole, wherein a hole is formed adjacent the corrugated sheet and penetrates an outsole and the midsole, and is provided over a generally oval region in the centre of the heel. It is desirable to provide a midsole assembly for an athletic shoe that can ensure not only running stability but also cushioning properties. The present invention provides a midsole assembly for an athletic shoe comprising: a midsole formed of soft elastic material; and a corrugated sheet disposed in at least a heel portion of said midsole; wherein a hole is formed between said corrugated sheet and said midsole, and said hole extends in a direction of a crest line or a trough line of a wave configuration of said corrugated sheet. The present invention also provides an athletic shoe comprising the midsole assembly as described in the preceding paragraph. In one embodiment, a midsole assembly comprises a midsole formed of soft elastic material and a corrugated sheet disposed in at least a heel portion of the midsole. A hole is provided at a portion of the midsole contacting the corrugated sheet. In a second embodiment, the hole is formed on the concave surface side of the wave configuration of the corrugated sheet. In a third embodiment, the hole is formed on the convex surface side of the wave configuration of the corrugated sheet. In a fourth embodiment, the hole is formed on the inclined surface between the convex and concave surfaces of the wave configuration of the corrugated sheet. The hole may extend in the shoe width direction, as described in a fifth embodiment, or it may extend radially, as described in a sixth embodiment. The hole may be a through hole, as described in a seventh embodiment, or it may be a hole with a bottom, as described in an eight embodiment. The hole may be formed only on the inner side surface of the midsole, as described in a ninth embodiment. In alternative, the hole may be formed only on the outer side surface of the midsole, as described in a tenth embodiment, or it may be formed only in the heel central portion of the midsole, as described in an eleventh embodiment. According to the embodiments, since a corrugated sheet is disposed in at least a heel portion of the midsole, transverse or lateral deformation of the heel portion of the midsole can be prevented, and thus, the stability of a shoe on landing can be ensured. Moreover, in this case, because there is provided a hole at the portion of a midsole contacting with a corrugated sheet, deformation of the corrugated sheet against a vertical compressive force is made easier on this hole formed portion. Thereby, cushioning properties on landing can be secured. Furthermore, by forming a hole in the midsole, the whole midsole can be made lightweight. Additionally, "a hole" in this case includes both a through hole and a hole with a bottom, as is clear from the description of the embodiments, and besides, it also includes a so-called air reservoir that has not an opening end on the circumferential surface of a midsole. The sectional shape of a hole can be any kinds of shape and may be a narrow slit formed between the midsole and the corrugated sheet. The hole may be formed on the concave surface side or the convex surface side of the wave configuration of a corrugated sheet. In alternative, the hole may be formed on the inclined surface between the adjacent concave and convex surface sides of the wave configuration of a corrugated sheet. The hole may extend radially or in the shoe width direction. In the case of a radial extension of a hole, the radiant point may be placed inside or outside the heel portion of a midsole, or on the edge portions of an outer circumference, and the radiant angle may be set at any angle. Moreover, when the hole is a through hole, the cushioning properties of the whole midsole can be improved and the whole midsole can be made further lightweight. In order that the present invention may be well understood, various embodiments thereof, which are given by way of example only, will now be described with reference to the accompanying drawings, in which: Figure 1 is a side view of an athletic shoe incorporating a midsole construction, or assembly; Figure 2 is a top plan view of the left side of the midsole construction; Figure 3 is a side view of the midsole construction of Figure 2 where (a) is an outer side view and (b) is an inner side view; Figure 4 is a cross sectional view taken along line IV-IV of Figure 2; Figure 5 is a schematic illustrating a first alternative of the midsole construction of Figure 3; Figure 6 is a schematic illustrating a second alternative of the midsole construction of Figure 3; Figure 7 is a schematic illustrating a first alternative of the midsole construction of Figure 4; Figure 8 is a schematic illustrating a second alternative of Figure 4; Figure 9 is a schematic illustrating a third alternative of Figure 4; Figure 10 is a schematic illustrating a first alternative of the midsole construction of Figure 2; and Figure 11 is a schematic illustrating a second alternative of Figure 2. Turning now to the drawings, Figure 1 illustrates an athletic shoe incorporating a midsole construction, or assembly. The sole of this athletic shoe 1 comprises a midsole 3, a corrugated sheet 4 and an outsole 5 directly contacting with the ground. The midsole 3 is fitted to the bottom of the uppers 2. The corrugated sheet 4 having a wavy configuration is disposed in the midsole 3. The outsole 5 is fitted to the bottom of the midsole 3. The midsole 3 is provided in order to absorb a shock load imparted on the heel portion of the shoe 1 when landing on the ground. The midsole 3 is comprised of an upper midsole 3a and a lower midsole 3b which are respectively disposed on the top and bottom surfaces of the corrugated sheet 4. That is, the corrugated sheet 4 is interposed between the upper midsole 3a and the lower midsole 3b, and the sheet 4 is integrated with the upper and lower midsoles 3a, 3b. 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 are used. The corrugated sheet 4 is formed of thermoplastic resin such as thermoplastic polyurethane(TPU) of comparatively rich elasticity, polyamide elastomer(PAE), ABS resin and the like. Alternatively, the corrugated sheet 4 is formed of thermosetting resin such as epoxy resin, unsaturated polyester resin and the like. Generally, in this midsole construction, the pressure imparted from the upper midsole 3a in landing is dispersed by the corrugated sheet 4 and the pressured area of the lower midsole 3b becomes enlarged. As a result, compressive hardness throughout the midsole construction is made higher. Moreover, in this embodiment, there are provided a plurality of holes between the midsole 3 and the corrugated sheet 4. A corrugated sheet 4, as shown in Figure 2, extends from the heel portion to the planter arch portion of a midsole 3. The corrugated sheet 4 is comprised of a heel portion 4a having a wave configuration and a planter arch portion 4b, which is generally flat and integrally formed with the heel portion 4a. A broken line L in the drawing indicates the crest or trough line of the wave configuration of the corrugated sheet 4. These holes 6 extend in the direction of the crest line or the trough line of the wave configuration. In this embodiment as shown in Figure 3, each of the holes 6 formed in the midsole 3 is provided on the trough side or concave surface side 41 of the wave configuration of the corrugated sheet 4. These holes 6 are through holes penetrating the midsole 3 in the width direction, as shown in Figure 4. In this case, since the corrugated sheet 4 is provided at least on the heel portion in the midsole 3, lateral or transverse deformation of the heel portion of the midsole 3 can be prevented and thus, stability of the shoe 1 on landing can be secured. Furthermore, in this embodiment, a plurality of holes 6 are formed at the portions of the midsole 3 contacting the corrugated sheet 4. With the provision of holes 6 , deformation of the midsole 4 against the vertical compressive pressure can be made easier, thus securing the cushioning properties on landing. Moreover, by forming a hole 6 in the midsole 3, the whole midsole 3 can be made lightweight and besides, the wave configuration of the corrugated sheet 4 is emphasized and appearance of the whole shoe is improved. In addition, all the holes 6 formed in the midsole 3 are through holes and the cushioning properties of the whole midsole 3 in the lateral direction can be improved and the weight of the midsole 3 can be made further lightweight. As shown in Figure 5, a hole 6 may be formed on the crest side or the convex surface side 42 of the wave configuration of the corrugated sheet 4, or as shown in Figure 6, it may be formed on the inclined surface 43 between the adjacent convex and concave surfaces of the wave configuration of the corrugated sheet 4. A hole 6 is not limited to a through hole. As shown in Figures 7 to 9, a hole 6 may include a hole with a bottom i.e. is closed at one or both of its ends, as shown in Figures 7 to 9. In Figure 7, a hole 6 is formed only on the inner surface side of the midsole 3 and in Figure 8, a hole 6 is formed only on the outer surface side of the midsole 3. In Figure 9, a hole 6 is provided only in the heel central portion of the midsole 3. That is, a hole 6 in Figure 9 takes the form of an air reservoir. In these cases, a shock load on landing can be relieved by the provision of each of the holes 6 and the cushioning properties can be improved. Thus, control of the cushioning properties according to the athletics and the athletes can be realized. For example, in athletics such as tennis or basketball where athletes land more frequently from the heel inner side portions, a hole 6 is formed only on the midsole inner surface side, whereas in athletics where athletes land more frequently from the heel outer side portions, a hole 6 is formed only on the midsole outer surface side. Moreover, in athletics where athletes land more frequently from the whole heel portions, a hole 6 is formed only on the heel central portion of the midsole. On the other hand, at portions without a hole 6, the original function of the corrugated sheet 4 can be fully developed and the compressive hardness or hardness to deform against the compressive force is maintained, thereby preventing the heel portion of a foot from lying. As a result, over-pronation and over-supination can be prevented, and damages to the feet of athletes can be prevented. In the embodiments shown in Figures 1 to 4, the holes 6 elongate in the shoe width direction, but the present invention is not limited to these examples. The holes 6 may elongate radially, as shown in Figures 10 and 11. In Figure 10, the radiant point O is disposed in the heel central portion and in Figure 11, the radiant point O' is disposed on the outer circumference edge portions of the heel portion. In addition, the radiant angle may be obtuse, as shown in Figure 10, or it may be an acute angle, as shown in Figure 11. In addition to these examples, the hole formed direction may be any angles including the combination of the width direction and the radiant direction. Those skilled in the art to which the invention pertains may make modifications and other embodiments employing the principles of this invention without departing from its spirit or essential characteristics particularly upon considering the foregoing teachings. 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.

Claims: A midsole assembly for an athletic shoe comprising: a midsole (3) formed of soft elastic material; and a corrugated sheet (4) disposed in at least a heel portion of said midsole, characterised in that a hole (6) is formed between said corrugated sheet and said midsole, and said hole extends in a direction of a crest line (L) or a through line (L) of a wave configuration of said corrugated sheet. A midsole assembly as claimed in claim 1, wherein said hole (6) is formed at a concave surface (41) of the wave configuration of said corrugated sheet (4). A midsole assembly as claimed in claim 1, wherein said hole (6) is formed at a convex surface (42) of the wave configuration of said corrugated sheet (4). A midsole assembly as claimed in claim 1, wherein said hole (6) is formed on an inclined surface (43) between adjacent convex (42) and concave surfaces (41) of the wave configuration of said corrugated sheet. A midsole assembly as claimed in claim 1, wherein said hole (6) extends in a shoe width direction. A midsole assembly as claimed in claim 1, wherein said hole (6) extends radially. A midsole assembly as claimed in claim 1, wherein said hole (6) is a through hole extending through said midsole (3). A midsole assembly as claimed in claim 1, wherein said hole (6) is closed at one or both of its ends. A midsole assembly as claimed in claim 1, wherein said hole (6) is formed on an inner side surface of said midsole (3). A midsole assembly as claimed in claim 1, wherein said hole (6) is formed only on an outer side surface of said midsole (3). A midsole assembly as claimed in claim 1, wherein said hole (6) extends only in the heel central portion of said midsole (3). An athletic shoe (1) comprising a midsole assembly as claimed in any one of the preceding claims.

Inventors: KITA KENJIRO, KITA, KENJIRO
Applicants: MIZUNO KK, MIZUNO CORPORATION
Application year: 1999
Main classification: A43B13
IPC codes: A43B21, A43B13