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. The inner surface side of the corrugated sheet has a double structure. Since the compressive hardness of the midsole is higher on the inner surface side including a double structure, transverse deformation of a shoe on landing can be prevented and over-pronation can be restrained on this inner surface side and the loss of athletic power can be decreased. On the other hand, flexibility of the midsole is maintained on the outer surface side without a double structure and thus, cushioning properties can be secured on this outer surface side.

Description: The present invention relates to midsole assembly for 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 with the ground. As shown in Japanese Utility Model Examined Publication No. 61-6804, the applicant of the present invention proposes a midsole assembly having a corrugated sheet therein, which can prevent such an excessive lateral deformation of shoes. US-A- 5, 720, 118 discloses a midsole assembly according to the preamble of claim 1 hereinafter. The midsole assembly shown in the above publication incorporates a corrugated sheet in the heel portion of a midsole, thereby producing resistant force that prevents the heel portion of a midsole from being deformed laterally or transversely when a shoe comes in contact with the ground. Thus, transverse deformation of the heel portion of a shoe is prevented. However, it depends on the kind of athletics or athletes whether athletes land on the ground more frequently from the medial portions or from the lateral portions of the heels at the onset of landing. For example, since tennis or basketball players move more often in the transverse direction and the medial portions of their heels tend to first contact with the ground, the heels lean outwardly and so-called supination often occurs. On the other hand, since runners or joggers tend to land on the ground from the lateral portions of their heels and the load moves toward the toes, the heels lean inwardly and so-called pronation often occurs. These pronation and supination are normal movements when a shoe comes in contact with the ground. But over-pronation or over-supination may cause damages to the ankle, knee and hip of an athlete. In the conventional midsole design, there is provided a corrugated sheet having a constant wave configuration in both the transverse direction and the longitudinal direction of the heel portion. Therefore, the prior art midsole has a constant compressive hardness (hardness to deform against the compressive force) throughout the whole midsole and as a result, it cannot control effectively pronation and supination of the foot of an athlete although controlling them is required according to the kind of athletics. Generally, by inserting a corrugated sheet, the heel portion of a midsole tends to be less deformed in the transverse direction. When the corrugated sheet is formed especially from 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. On the other hand, good cushioning properties is indispensable requirements of athletic shoes, but too high cushioning properties may absorb an athletic power such as propellant or jumping power of an athlete It is desirable to provide a midsole assembly for an athletic shoe that can restrain over-pronation and over-supination on landing by preventing a shoe from being deformed in the transverse direction according to the kind of athletics and that can not only ensure adequate cushioning properties on landing but also prevent an athletic power from being lessened. 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, characterised in that at least a portion of the outer edge of said corrugated sheet having a multiple-layered structure in which the layers are spaced apart to define at least one predetermined opening in the midsole assembly. In one embodiment described hereinafter, 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. At least a portion of the outer circumference side, or edge, of the corrugated sheet has a double structure. The double structure is comprised of two sheets of corrugated sheets. These corrugated sheets are spaced apart by a predetermined distance in the thickness direction. The double structure may be formed only on the medial side of the midsole or only on the lateral side of the midsole, or on both the medial and lateral side of the midsole. The double structure may be formed on either or both the crest side and the trough side of the wave configuration of the corrugated sheet. Alternatively, the double structure is formed on an inclined surface between the adjacent crest and trough of the wave configuration of the corrugated sheet. The crest line or trough line of the wave configuration of the corrugated sheet may extend substantially in the shoe width direction. or alternatively may extend radially. Two or more layers may be provided at the outer circumference side of the corrugated sheet to form a multiple structure. Each of the corrugated sheets is spaced apart by a predetermined distance in the thickness direction. At a portion where a double, or multiple, structure is provided, rigidity of the corrugated sheet is further increased and the compressive hardness of the midsole is made greater. Thereby, transverse deformation of a shoe can be prevented and unnecessary sinking of the heel of a foot into a midsole can be restrained, and as a result, loss of athletic power can be decreased. In contrast, at other portions where a double structure is not provided, compressive hardness is relatively lower as compared to the portion of a double structure and flexibility of a midsole is maintained to some extent, and thus, shock load on landing is relieved and the cushioning properties can be secured. When the double structure is formed only on the medial side of the midsole, the compressive hardness of a midsole is higher on the medial side and flexibility of a midsole is maintained on the lateral side. Thereby, in athletics where athletes land more frequently from the heel lateral portion, shock load on landing is effectively relieved and the cushioning properties can be ensured, and besides, transverse deformation of a heel portion after landing can be prevented. Moreover, when the heel of a foot pronates after landing, the heel of a foot is restrained from unnecessarily sinking toward the medial side of a midsole by a heel medial side portion having a larger compressive hardness. Thereby, over-pronation can be prevented. When the double structure is formed only on the lateral side of the midsole, the compressive hardness of a midsole is higher on the lateral side and flexibility of a midsole is maintained on the medial side. Thereby, in athletics where athletes land more frequently from the heel medial portion, shock load on landing is effectively relieved and the cushioning properties can be ensured, and besides, transverse deformation of a heel portion after landing can be prevented. Moreover, when the heel of a foot supinates after landing, the heel of a foot is restrained from unnecessarily sinking toward the lateral side of a midsole by a heel lateral side portion having a larger compressive hardness. Thereby, over-supination can be prevented. When the double structure is formed on both the medial and lateral sides of the midsole, the compressive hardness of a midsole is higher on the medial and lateral sides and flexibility of a midsole is maintained on the central portion. Thereby, the cushioning properties on landing can be ensured on the heel central portion, and besides, transverse deformation of a heel portion after landing can be prevented and the running stability can be improved. As previously mentioned, the double structure can be formed on either the crest side or the trough side, or both the crest side and the trough side of the wave configuration of the corrugated sheet. When the double structure is formed on both the crest and trough sides of the wave configuration, the compressive hardness of a midsole can be made further greater on these crest and trough sides. In addition, the double structure may be If the crest line or the trough line of the wave configuration extends radially, the center of radiation or radiant point may be placed inside or outside the heel portion of a midsole, or on the edges of the outer circumference. The radiant angle may be acute or obtuse. When more than two layers are provided in the multiple structure, rigidity of the corrugated sheet can be further increased and the compressive hardness of the midsole is made further greater. Thereby, transverse deformation of a shoe can be prevented more effectively. In order that the present invention may be well understood, some embodiments thereof, which are given by way of example only, will now be described with reference to the accompanying drawings, which are not to scale and in which: Figure 1 is a side view of an athletic shoe incorporating the midsole assembly according to an embodiment of the present invention; Figure 2 is a top plan view of the left side midsole assembly as shown in Figure 1. Figure 3 is a side view of the midsole assembly of Figure 2, where Figure 2(a) is an outer side view and Figure 2(b) is an inner side view; Figure 4 is a top plan view of the corrugated sheet constituting the midsole assembly of Figure 2; Figure 5 is an outside end view of the corrugated sheet of Figure 4. Figure 6 is an inside end view of the corrugated sheet of Figure 4; Figure 7 is a cross sectional view taken along line VII-VII of Figure 4; Figure 8 is a schematic illustrating a first alternative of Figure 4. Figure 9 is a schematic illustrating a second alternative of Figure 4; Figure 10 is a cross sectional view taken along line X-X of Figure 9; Figure 11 is a schematic illustrating a first alternative of Figure 6; Figure 12 is a schematic illustrating a second alternative of Figure 6; Figure 13 is a schematic illustrating a third alternative of Figure 4; Figure 14 is a schematic illustrating a fourth alternative of Figure 4; and Figure 15 is a schematic illustrating a fifth alternative of Figure 4. Turning now to the drawings, Figure 1 illustrates an athletic shoe incorporating a midsole assembly, or construction. 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 a shoes wearer lands 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 on 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 whole midsole construction is made higher. Moreover, in this embodiment, there are provided a double structure, which has a double corrugated sheets 4 spaced apart at a predetermined space, on the trough side of the wave configuration of a 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. A broken line L in the drawing indicates the crest or trough line of the wave configuration of the corrugated sheet 4. In this case, the lines L extends radially and radiant point is disposed apart from the outer side edge of the midsole 3. As shown in Figures 3 to 7, the midsole medial side of the corrugated sheet 4 has a double-layered structure 41 where the corrugated sheet 4 has two layers which are spaced apart to define a predetermined clearance or aperture (opening) 6 in the thickness direction of the midsole assembly. This double structure 41 is formed on the trough side of the wave configuration. In this case, since the double structure 41 of the corrugated sheet 4 is formed only on the medial side of the midsole 3, the compressive hardness, or resistance to deformation by compressive force, of a midsole 3 is higher on the medial side, whereas the compressive hardness of a midsole 3 is relatively lower on the lateral side and flexibility of a midsole 3 is maintained on the lateral side. Thereby, in athletics where athletes land more frequently from the heel lateral portion, shock load on landing is effectively relieved and the cushioning properties can be ensured, and besides, transverse deformation of a heel portion after landing can be prevented. Moreover, when the heel of a foot pronates after landing it is restrained from unnecessarily sinking toward the midsole medial side by a heel medial side portion of a larger compressive hardness. Thereby, over-pronation can be prevented and loss of athletic power can be lessened. As shown in Figure 8, the double structure 41 may be formed only on the lateral side of the midsole 3. In this case, the compressive hardness of a midsole 3 is higher on the lateral side, whereas the compressive hardness of a midsole 3 is relatively lower on the medial side and flexibility of a midsole 3 is maintained on the medial side. Thereby, in athletics where athletes land more frequently from the heel medial portion, shock load on landing is effectively relieved and the cushioning properties can be ensured, and besides, transverse deformation of a heel portion after landing can be prevented. Moreover, when the heel of a foot supinates after landing, it is restrained from unnecessarily sinking toward the lateral side of a midsole 3 by a heel lateral side portion of a larger compressive hardness. Thereby, over-supination can be prevented and loss of athletic power can be decreased. As shown in Figures 9 and 10, the double structure 41 of a corrugated sheet 4 may be formed on both the medial and lateral sides of the midsole 3. In this case, the compressive hardness of a midsole 3 is higher on the medial and lateral sides, whereas the compressive hardness of a midsole 3 is relatively lower on the heel central portion and flexibility of a midsole 3 is maintained on this heel central portion. Thereby, the cushioning properties on landing can be ensured on the heel central portion, and besides, transverse deformation of a heel portion after landing can be prevented and the running stability can be improved. Moreover, in this case, over-supination as well as over-pronation can be effectively prevented. In the above-mentioned embodiments, the double structure 41 is formed on the trough side of the wave configuration of the corrugated sheet 4. However the application of the present invention is not limited to these examples. As shown in Figure 11, the double structure 41 may be formed on the crest side of the wave configuration of the corrugated sheet 4, or it may be formed on the inclined surface between the adjacent crest and trough of the wave configuration of the corrugated sheet 4, as shown in Figure 12. In the above embodiments, the crest and trough line L of the corrugated sheet 4 extend radially and the radiant point is disposed apart from the outer circumference edge of the midsole 3, but the application of the current invention is not limited to these examples. As shown in Figure 13, the radiant point O may be placed in the heel central portion. In alternative, as shown in Figure 14, the radiant point O' may be placed on the outer circumference edge portion of the heel portion. Furthermore, the radiant angle may be obtuse, as shown in Figure 13, or it may be an acute angle, as shown in Figure 14. In both cases, the double structure 41 is formed on both the crest and trough sides of the wave configuration of the corrugated sheet 4. In addition, the crest and trough lines L of the wave configuration may be parallel to each other and extend in the heel width direction, as shown in Figure 15. The embodiments have been described with reference to a double-layered structure 41, but a triple-layered structure may be substituted for the double-layered structure 41, and the present invention covers a multiple-layered structure having a plurality of layers which are spaced apart to define predetermined openings in the midsole assembly. Those skilled in the art to which the invention pertains may make modifications and other embodiments 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 falling within the scope of the invention as defined in the appended claims may be apparent to those skilled in the art.

Claims: A midsole assembly for an athletic shoe (1) 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 at least a portion of the outer edge of said corrugated sheet having a multiple-layered structure (41) in which the layers are spaced apart to define at least one predetermined opening (6) in the midsole assembly. A midsole assembly as claimed in claim 1, wherein said multiple-layered structure has two layers which are spaced apart to define a predetermined opening in the midsole assembly. A midsole assembly as claimed in claim 1 or 2, wherein said multiple-layered structure (41) is formed only on the medial side of said midsole assembly. A midsole assembly as claimed in claim 1 or 2, wherein said multiple-layered structure (41) is formed only on the lateral side of said midsole assembly. A midsole assembly as claimed in claim 1 or 2, wherein said multiple-layered structure (41) is formed on both the medial and lateral sides of said midsole assembly. A midsole assembly as claimed in any one of claims 1 to 5, wherein said multiple-layered structure (41) is formed on either or both the crest side and the trough side of the wave configuration of the corrugated sheet (4). A midsole assembly as claimed in any one of claims 1 to 5, wherein said multiple-layered structure (41) is formed on an inclined surface between the adjacent crest and trough of the wave configuration of said corrugated sheet (4). A midsole assembly as claimed in any preceding claim, wherein the crest line (L) or trough line (L) of the wave configuration of said corrugated sheet (4) extends in the shoe width direction. A midsole assembly as claimed in claim 1. wherein the crest line (L) or trough line (L) of the wave configuration of said corrugated sheet (4) extends radially. A shoe comprising a midsole assembly as claimed in any preceding claim.

Inventors: KITA KENJIRO, KITA, KENJIRO, Kita, Kenjiro, c/oMizuno Corp.
Applicants: MIZUNO KK, MIZUNO CORPORATION
Application year: 1999
Main classification: A43B13
IPC codes: A43B13, A43B21, A43B5