Athletic shoe midsole design and construction

Abstract: A midsole assembly for an athletic shoe comprises a midsole and a corrugated sheet. The midsole is formed of soft elastic material. The corrugated sheet is disposed in the heel portion of a midsole. The front end of the corrugated sheet extends from the plantar arch portion to the forefoot portion of the midsole. A sheet comprised of fiber reinforced plastics is bonded at from the outer circumference portion to the plantar arch portion of the heel portion of the corrugated sheet. A meshed sheet portion is formed in the center of the heel portion. Thus, lateral deformation of the shoes after contacting with the ground can be prevented at the outer circumference of the heel portion and the plantar arch portion having higher compressive hardness and running stability can be ensured. The shock load on landing can be absorbed at the heel central portion having lower compressive hardness and cushioning properties can be secured.

Description: The present invention relates to a midsole assembly for an athletic shoe. More particularly, the invention relates to a midsole assembly, which is comprised of 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, which is fitted under the midsole and directly contacts with the ground. The midsole is typically formed of soft elastic material in order to ensure adequate cushioning properties. Generally, running stability as well as adequate cushioning properties is required in athletic shoes. 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, there is proposed 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 publication incorporates a corrugated sheet in a heel portion of a midsole and it can produce resistant force preventing the heel portion of a midsole from being deformed laterally or transversely when a shoe contacts with the ground. Thus, the transverse deformation of the heel portion of a shoe is prevented. In such a way, by inserting a corrugated sheet into a midsole, the heel portion of a midsole tends to be less deformed in the transverse direction. When the corrugated sheet is formed especially of higher elastic material the heel portion of a midsole tends to be less deformed in the vertical direction as well. Therefore, by inserting a corrugated sheet, the heel portion of a midsole where adequate cushioning properties is required may show less cushioning properties in contacting the ground. On the other hand, when a relatively lower elasticity material is used as a corrugated sheet cushioning properties can be achieved to some degree at the time of contacting with the ground, whereas in athletics such as tennis or basketball where players move more often in the transverse direction, the transverse deformation of the heel portion of the shoes cannot be adequately restrained and running stability cannot be fully secured. US 5, 720, 118 discloses a midsole assembly for an athletic shoe according to the preamble of claim 1 herein. It is desirable to provide a midsole assembly for an athletic shoe which can secure cushioning properties as well as the running stability. The present invention provides a midsole assembly for an athletic shoe comprising: a midsole formed of soft elastic material; a corrugated sheet disposed in a heel portion of the midsole, the front end of the corrugated sheet extending from the plantar arch portion to the forefoot portion of the midsole; characterised in that an elastic member having a higher modulus of elasticity than said corrugated sheet is provided at the outer circumference of the heel portion of the corrugated sheet and further extends to the plantar arch portion of the corrugated sheet. Other preferred aspects of the invention are defined in the accompanying claims. An elastic portion having a lower modulus of elasticity than the corrugated sheet may be provided in the heel central portion of the corrugated sheet. The elastic member may comprise a fiber reinforced plastic sheet. The elastic member may comprise a metal plate. The elastic member may be bonded to the corrugated sheet. The elastic member may be injection molded together with the corrugated sheet. The elastic portion may be comprised of a plurality of holes formed in the corrugated sheet. The elastic portion may comprised of a meshed sheet, which is injection molded together with the corrugated sheet. The elastic portion may be comprised of titanium. The elastic portion may be comprised of superelastic material. The titanium may be insert molded together with the corrugated sheet. The titanium may be meshed, or comprised of a plurality of fibers or plates of titanium. The superelastic material may be insert molded together with the corrugated sheet. The superelastic material may be meshed, or comprised of a plurality of fibers or plates of superelastic material. A second elastic portion having a modulus of elasticity lower than the corrugated sheet may be provided at the forefoot portion of the corrugated sheet. The second elastic portion may be comprised of a plurality of holes formed In the corrugated sheet. The second elastic portion may be comprised of a meshed sheet, which is injection molded together with the corrugated sheet. The second elastic portion may be comprised of titanium. The second elastic portion may be comprised of superelastic material. The titanium or superelastic material may be insert molded together with the corrugated sheet. The titanium or superelastic material may be meshed, or comprised of a plurality of fibers or plates of titanium or superelastic material. The forefoot portion of the corrugated sheet may include a laterally extending groove. A described in the embodiments hereinafter, a compressive hardness (or resistance to deformation by compressive force) is made higher along the outer circumference of the heel portion, and as a result, transverse deformation of shoes after landing can be prevented and running stability can be ensured even in the athletics where athletes move more often in the transverse direction. Moreover, since the heel portion of a foot can be restrained from sinking unnecessarily into the midsole, loss of the athletic power is lessened. Furthermore, flexibility of the midsole is maintained to some degree in the heel central portion, which has a relatively low compressive hardness as compared to the outer circumference of the heel portion. Therefore, cushioning properties can be ensured in this heel central portion. Additionally, in this case, when a material of relatively low elasticity is used as a corrugated sheet more flexibility of the heel central portion of the midsole can be acquired and cushioning properties can be improved. When the higher elastic member (i.e. the elastic member with a higher modulus of elasticity than the corrugated sheet) is placed along the outer circumference of the heel portion of the corrugated sheet, and a lower elastic portion (i.e. the elastic portion with a lower modulus of elasticity than the corrugated sheet) is placed in the heel central portion of the corrugated sheet, transverse deformation after landing can be prevented at the outer circumference of the heel portion, which has a comparatively high compressive hardness, and cushioning properties on landing can be ensured at the heel central portion of a relatively low compressive hardness. When the lower elastic portion is comprised of titanium itself or superelastic material itself, as described in relation to the embodiments, a higher impact resilience and a lighter weight can be acquired. The front end of the corrugated sheet extends from the plantar arch portion to the forefoot portion of the midsole, and the higher elastic member is placed from the outer circumference of the heel portion to the plantar arch portion of the corrugated sheet. Thus, after landing, the heel portion to the planter arch portion of the midsole can be prevented from deforming transversely and the running stability can be ensured. Moreover, cushioning properties on landing can be ensured at the heel central portion of a relatively low compressive hardness. In the embodiments comprising a higher elastic and a lower elastic portion, lateral deformation of shoes after landing can be prevented at both the outer circumference of the heel portion and the plantar arch portion, and the cushioning properties on landing can be ensured at the heel central portion. In the embodiment in which the front end of the corrugated sheet extends from the plantar arch portion to the forefoot portion of the midsole and a lower elastic portion is provided at the forefoot portion of the corrugated sheet, compressive hardness of the forefoot portion decreases and as a result, cushioning properties of the forefoot portion is maintained. Moreover, flexibility of the forefoot portion can be ensured and turnability of the forefoot portion is improved. Further, when the forefoot portion of the corrugated sheet includes a laterally extending groove, flexibility of the forefoot portion of the midsole can be further improved. In order that the present invention may be used 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: The structures of figures 1 to 4 are not part of the invention Figure 1 is a side view of an athletic shoe incorporating a midsole construction; Figure 2 is a schematic illustrating the midsole construction of the first example given for information purposes only, wherein (a) is a top plan view of the midsole construction of a left side shoe; and (b) is an inside side view thereof; Figure 3 is a schematic illustrating the midsole construction of the second example, wherein (a) is a top plan view of the midsole construction of a left side shoe; and (b) is an inside side view thereof; Figure 4 is a schematic illustrating the midsole construction of the third example, wherein (a) is a top plan view of the midsole construction of a left side shoe; and (b) is an inside side view thereof; Figure 5 is a perspective view of the left side midsole construction of the first embodiment of the present invention. The elastic member is not represented in figure 5; Figure 6 is an outside side view of the left side midsole construction of the first embodiment of the present invention. The elastic member is not represented in figure 6; Figure 7 is a perspective view of a corrugated sheet in the left side midsole construction of the first embodiment of the present Invention; Figure 8 is a perspective view of a corrugated sheet in the midsole construction of the fourth example, which is not part of the invention; Figure 9 is a perspective view of a corrugated sheet in the midsole construction of the second embodiment of the present invention; Figure 10 is a perspective view of the midsole construction of the fifth example, which is not part of the invention; Figure 11 is a perspective view of a corrugated sheet in the midsole construction of the fifth example; Figure 12 is a schematic illustrating an alternative of Figure 11. This alternative is not part of the invention; Figure 13 is a perspective view of a corrugated sheet in a midsole construction comprising a second elastic portion that can be used in a fourth embodiment of the present invention. The structures of figures 14 to 18 are not part of the invention. Figure 14 is a bottom view of an athletic shoe incorporating the midsole construction of the sixth example; Figure 15 is a perspective view of a corrugated sheet having a lower elastic portion formed of meshed titanium; Figure 16 is a perspective view of a corrugated sheet having a lower elastic portion formed of laterally extending titanium fibers; Figure 17 is a perspective view of a corrugated sheet having a lower elastic portion formed of longitudinally extending titanium fibers; and Figure 18 is a perspective view of a corrugated sheet having a lower elastic portion formed of titanium plates. Turning now to the drawings, Figure 1 illustrates an athletic shoe in which a midsole construction of any of the embodiments can be incorporated. 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 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 bottom portion of the shoe 1 when an athlete 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. 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. Referring to Figures 2-14, there are shown various kinds of midsole assemblies, some of which constitute embodiments of the present invention, and some of which are examples given for information purposes only, as will be appreciated from the description hereinafter. In the following, the same reference numerals indicate the same or corresponding portions. In Figures 2 to 4, the corrugated sheet 4 is placed only at the heel portion of the midsole 3. In the remaining Figures, the corrugated sheet 4 is placed at the heel portion of the midsole 3 and the front end of the corrugated sheet 4 extends from the planter arch portion to the forefoot portion of the midsole 3. Additionally, the following drawings show the left side midsole donstruction Figure 2shows the first example given for information purposes only. In the drawing, (a) a top plan view of the midsole construction, and (b) is an inner side view of the midsole construction. In this first example, a fiber reinforced plastic sheet 41 is provided along the outer circumference of the heel portion of the corrugated sheet 4. This fiber reinforced plastic sheet 41 is formed of fiber reinforced plastics (FRP), which is comprised of reinforcement fiber and matrix resin. The reinforcement fiber may be carbon fiber, aramid fiber, glass fiber or the like. The matrix resin may be thermoplastic or thermosetting resin. Thus, a compressive hardness (or resistance to deformation by a compressive force) of the midsole 3 is greater at the outer circumference of the heel portion, and as a result, even in the athletics where athletes move more frequently in the transverse direction, the transverse deformation of the shoes after landing can be prevented and running stability can be secured. Moreover, since the unnecessary sinking of the heel of a foot into the midsole 3 can be restrained, loss of the athletic power is decreased. On the other hand, flexibility of the midsole 3 is maintained to some degree in the heel central portion, which has a relatively low compressive hardness as compared to the outer circumference of the heel portion. Thereby, cushioning properties on landing is maintained at this heel central portion. Additionally, in this case, when a relatively low elastic material is used as a corrugated sheet 4, the heel central portion of the midsole 3 is made more flexible and the cushioning properties can be improved. The fiber reinforced plastic sheet 41 may be bonded to the corrugated sheet 4, or it may be injection molded together with the corrugated sheet 4. Alternatively, a metal plate, which is made of stainless steel (SUS), superelastic alloy or the like, may be substituted for the fiber reinforced plastic sheet 41. Moreover, a sheet formed of other plastic materials may be utilized if it is a higher elastic member (or it has a larger modulus of elasticity) than the corrugated sheet 4. Figure 3 shows the midsole construction of the second example given for information purposes only. In the drawing, (a) is a top plan view of the midsole construction, and (b) is an inner side view of the midsole construction. In this second example, a plurality of holes are formed in the heel central portion of the corrugated sheet 4 and the heel central portion is meshed. This meshed portion 42 decreases the compressive hardness of the heel central portion of the midsole 3, and thus, flexibility of the midsole 3 is maintained and cushioning properties on landing can be increased. On the other hand, the outer circumference of the heel portion of the midsole 3 has a relatively high compressive hardness as compared to the heel central portion and it can prevent a shoe from deforming transversely and ensure the running stability. The shape of the holes formed in the heel central portion may be circular, rectangular, slit or any other configuration. Moreover, a meshed portion 42 is not limited to a plurality of holes formed in the heel central portion, of the corrugated sheet 4. A meshed portion 42 may be formed by injection molding a corrugated sheet 4 together with a meshed sheet that is formed in another process. Alternatively, a meshed portion 42 may be formed by using a relatively low elasticity (low modulus of elasticity) aterial than the corrugated sheet 4. Figure 4 shows the midsole construction of the third example given for information purposes only. In the drawing, (a) is a top plan view of the midsole construction and (b) is an inside side view of the midsole construction. In this third example, a fiber reinforced plastic sheet 41 is disposed along the outer circumference of the heel portion of the corrugated sheet 4 and a plurality of holes are formed in the heel central portion of the corrugated sheet 4 and the heel central portion is meshed. By employing such a structure, transverse deformation on landing can be prevented at the outer circumference of the heel portion having a large compressive hardness and cushioning properties on landing can be secured at the heel central portion having a small compressive hardness. Figures 5 to 7 show the midsole construction of the first embodiment of the present invention. Figure 5 is a perspective view of the midsole construction, Figure 6 is an outsize side view of the midsole construction, and Figure 7 is a perspective view of a corrugated sheet. In this first embodiment, the front end portion 4a of the corrugated sheet 4 extends from the planter arch portion to the forefoot portion of the midsole 3. The fiber reinforced plastic sheet 41' is placed at the outer circumference of the heel portion and from the outer circumference of the heel portion to the forefoot portion. Thus, after landing, transverse deformation of the heel portion to the planter arch portion of the midsole 3 can be prevented and running stability can be ensured. Also, cushioning properties on landing can be ensured at the heel central portion having a relatively small compressive hardness. The fiber reinforced plastic sheet 41' may be bonded to the corrugated sheet 4, or it may be injection molded together with the corrugated sheet 4. Moreover, a metal plate made of stainless steel (SUS) or superelastic alloy can be substituted for the fiber reinforced plastic sheet 41'. Furthermore, a sheet formed of other plastic materials may be employed if it is a higher elasticity member than the corrugated sheet 4. Figure 8 shows a corrugate sheet that is applied to the midsole construction of the fourth example given for information purposes only. In this fourth example, the front end portion 4a of the corrugated sheet 4 extends from the planter arch portion to the forefoot portion of the midsole 3 and a multiple of holes are formed in the heel central portion of the midsole and the heel central portion is meshed. By forming this meshed portion 42', cushioning properties on landing can be secured at the heel central portion with a lower compressive hardness. On the other hand, since compressive hardness of the midsole at the outer circumference of the heel portion is relatively large as compared to the heel central portion, transverse deformation of the shoe after landing can be prevented and running stability can be ensured at this outer circumference of the heel portion. In addition, holes formed in the heel central portion of the corrugated sheet 4 may be circular, rectangular, slit or any other configuration. Moreover, as a meshed portion 42', the corrugated sheet 4 that is injection molded together with a meshed sheet formed in a different process may be substituted for a plurality of holes. Furthermore, the meshed portion 42' may be formed by using a lower elastic member than the corrugated sheet 4. Figure 9 shows the midsole construction of the second embodiment of the present invention. In this second embodiment, the front end portion 4a of the corrugated sheet 4 extends from the planter arch portion to the forefoot portion of the midsole 3, and a fiber reinforced plastic sheet 41' is fitted to the outer circumference of the heel portion and from the outer circumference of the heel portion to the planter arch portion of the corrugated sheet 4. Moreover, the heel central portion of the corrugated sheet 4 is meshed. By forming these sheet 41' and meshed portion 42', transverse deformation of the shoe on landing can be prevented at the outer circumference of the heel portion and planter arch portion with higher compressive hardness, and cushioning properties on landing can be ensured at the heel central portion with a lower compressive hardness. Figures 10 and 11 show the midsole assembly of the fifth example given for information purposes only. Figure 10 is a perspective view of the midsole assembly, and Figure 11 is a perspective view of the corrugated sheet. In this fifth example, a plurality of holes are formed at the center of the heel portion and the tip portion of the front end portion 4a (or forefoot portion) of the corrugated sheet 4. The heel central portion and the tip portion of the front end portion 4a are meshed. By forming these meshed portions 42' and 43, cushioning properties on landing can be secured at the heel central portion, and flexibility of the forefoot portion with lower compressive hardness can be maintained and turnability of the forefoot portion can be improved. In addition, holes formed in the tip portion of the front end portion 4a of the corrugated sheet 4 may be circular, rectangular, slit or any other shape. The meshed portion, or second elastic portion, 43 may be formed in each tip portion of the front end portion 4a of the corrugated sheet 4 shown in Figure 7 and 9, and such a midsole constitues a third embodiment of the present invention. Moreover, in forming a meshed portion 43, a meshed sheet formed in another process may be injection molded together with the corrugated sheet 4. Alternatively, a meshed portion 43 may be formed by using a lower elasticity member than the corrugated sheet 4. The shape of the meshed portion 42' formed in the heel central portion of the corrugated sheet 4 is not limited to an elongated aperture as shown in Figures 8, 9 and 11. Various shapes such as a generally hourglass-shaped aperture as shown in Figure 12 can be employed. Figure 13 shows the corrugated sheet, with a second elastic portion which is employed in the midsole assembly of the fourth embodiment of the present invention. In this fourth embodiment, a meshed portion 43 is formed on the tip portion of the front end portion 4a of the corrugated sheet 4 and a plurality of grooves extending laterally are formed on the meshed portion 43. These grooves improves further the flexibility of the forefoot portion of the midsole 3. In addition, a groove 44 formed on the front end portion 4a preferably are plural but a single groove may be adopted. Figure 14 is a bottom view of the athletic shoe employing the midsole construction of the sixth example given for information purposes only. In this sixth example, a fiber reinforced plastic sheet 45, which extends longitudinally in a band form, is provided on the central portion of the planter arch portion of the corrugated sheet 4. This sheet 45 develops a so-called "shank effect" and thus, rigidity of the planter arch portion can be improved. As a results, after landing, lateral deformation of the planter arch portion of the midsole can be prevented and running stability can be secured. The fiber reinforced plastic sheet 45 may be bonded to the corrugated sheet 4, or it may be injection molded together with the corrugated sheet 4. A metal plate made of SUS, superelastic alloy, or the like can be substituted for the fiber reinforced plastic sheet 45. Furthermore, a sheet made from other plastic materials may be employed if it is a higher elastic member than the corrugated sheet 4. In addition, the fiber reinforced plastic sheet 45 may be placed covering the planter arch portion. In each of the second, third, and fourth, embodiments, a low elastic portion is formed of a plurality of holes, but the application of the current invention is not limited to these embodiments. The low elastic portion may be formed of titanium itself or superelastic material itself such as titanium alloy. The titanium or superelastic material may be insert molded together with the corrugated sheet, and meshed or comprised of a plurality of fibers or plates of titanium or superelastic material. Figures 15 to 18 show four corrugated sheets which are given for information purposes only, and which each have a lower elastic portion in the heel central portion. In Figure 15, the lower elastic portion 50 is formed of meshed titanium. In Figures 16 and 17, the lower elastic portion 50 is formed of a plurality of titanium fibers. In Figure 16, the titanium fibers extend laterally or in the shoe with direction, and in Figure 17, the titanium fibers extend longitudinally or in the length direction. In Figure 18, the lower elastic portion 50 is formed of a plurality of titanium plates. Those skilled in the art to which the invention pertains may make modifications and other embodiments particularly upon considering the foregoing teachings. The described embodiments 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, modifications of structure, sequence, materials and the like falling within the scope of the invention as defined in the claims may be apparent to those skilled in the art.

Claims: A midsole assembly for an athletic shoe comprising: a midsole (3) formed of soft elastic material; a corrugated sheet (4) disposed in a heel portion of said midsole, the front end of said corrugated sheet extending from the plantar arch portion to the forefoot portion (4a) of said midsole; characterized in that an elastic member (41) having a higher modulus of elasticity than said corrugated sheet is provided at the outer circumference of the heel portion of the corrugated sheet and further extends to the plantar arch portion of said corrugated sheet. A midsole assembly as claimed in claim 1, comprising: an elastic portic (42') having a lower modulus of elasticity than said corrugated sheet (4), said elastic portion being provided in the center of the heel portion of said corrugated sheet. A midsole assembly as claimed in claim 1 or 2, wherein said elastic member (41') comprises a sheet that is composed of fiber-reinforced plastics. A midsole assembly as claimed in claim 1 or 2, wherein said elastic member (41') comprises a metal plate. A midsole assembly of claim 1 or 2, wherein said elastic member (41') is bonded to said corrugated sheet (4). A midsole assembly as claimed in any of claims 1 to 3, wherein said elastic member (41') is injection molded with said corrugated sheet (4). A midsole assembly as claimed in claim 2, wherein said elastic portion (42') is comprised of a plurality of holes formed in said corrugated sheet (4). A midsole assembly as claimed in claim 2, wherein said elastic portion (42') is comprised of a meshed sheet, said meshed sheet being injection molded with said corrugated sheet (4). A midsole assembly as claimed in claim 2, wherein said elastic portion (42') is comprised of titanium. A midsole assembly as claimed in claim 2, wherein said elastic portion (42') is comprised of superelastic material. A midsole assembly as claimed in claim 9 or 10, wherein said titanium or superelastic material is insert molded with said corrugated sheet (4). A midsole assembly as claimed in claim 11, wherein said titanium or superelastic material is meshed, or comprised of a plurality of fibers or plates of titanium or superelastic material. A midsole assembly as claimed in any preceding claim, comprising: a second elastic portion (43) having a modulus of elasticity lower than said corrugated sheet, said second elastic portion being provided at the forefoot portion (4a) of said corrugated sheet (4). A midsole assembly as claimed in claim 13, wherein said second elastic portion (43) is comprised of a plurality of holes formed in said corrugated sheet (4). A midsole assembly as claimed in claim 13, wherein said second elastic portion (43) is comprised of a meshed sheet, said meshed sheet being injection moulded with said corrugated sheet (4). A midsole assembly as claimed in claim 13, wherein said second elastic portion (43) is comprised of titanium. A midsole assembly as claimed in claim 13, wherein said second elastic portion (43) is comprised of superelastic material. A midsole assembly as claimed in claim 16 or 17, wherein said titanium or superelastic material is insert molded with said corrugated sheet (4). A midsole assembly as claimed in claim 18, wherein said titanium or superelastic material is meshed, or comprised of a plurality of fibers or plates of titanium or superelastic material. A midsole assembly as claimed in claim 13, wherein the forefoot portion (4a) of said corrugated sheet (4) includes a groove (44) extending in the lateral direction. 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: A43B5, A43B13