Shock absorber, shoe sole and shoe

公开(公告)号:
US11832683B2
公开(公告)日:
2023-12-05
申请号:
US16/909119
申请日:
2020-06-23
授权日:
2023-12-05
受理局:
美国
专利类型:
授权发明
简单法律状态:
有效
法律状态/事件:
授权
IPC分类号:
A43B13/02 | A43B13/04 | A43B13/14 | A43B7/32 | A43B13/12 | A43B13/18 | A43B21/26 | B32B3/12 | F16F7/12
战略新兴产业分类:
-
国民经济行业分类号:
C1954 | C1953 | C1952 | C1951 | C2444 | C1761 | O8192 | C1959
当前申请(专利权)人:
ASICS CORPORATION
原始申请(专利权)人:
ASICS CORPORATION
当前申请(专利权)人地址:
1-1, MINATOJIMA-NAKAMACHI 7-CHOME, CHUO-KU, 650-8555, KOBE-SHI, HYOGO, JAPAN
工商统一社会信用代码:
-
工商登记状态:
其他
工商注册地址:
-
工商成立日期:
1977-01-01
工商企业类型:
-
发明人:
SAKAMOTO, MASANORI | IWASA, YUTARO | TANIGUCHI, NORIHIKO | SHIMOMURA, KOJI
代理机构:
STUDEBAKER & BRACKETT PC
代理人:
-
摘要:
A shock absorber includes a three-dimensional structure composed of a unit structure repeatedly, regularly and continuously arranged in at least one direction, the unit structure being a three-dimensional shape formed by a wall having an external shape defined by a pair of parallel planes or curved surfaces. When the unit structure occupies a cuboidal space representing a unit space and defined by mutually orthogonal three sides having a first side extending in an axial direction in which the shock absorber exhibits a shock absorbing function as the shock absorber receives a load and second and third sides each extending from one end of the first side in a direction orthogonal to the axial direction, and the first side has a length L1 and a longer one of the second and third sides has a length L2, the shock absorber satisfies 1.1≤L1/L2≤4.0.
技术问题语段:
However, when it is attempted to obtain large compressive stiffness in a shock absorber having such a structure, there is a problem, that is, an increased wall thickness results in an increased volume ratio and the shock absorber's weight is significantly increased.|In particular, when it is desired to locally increase the compressive stiffness of only a portion of the shock absorber, and that portion's wall thickness is increased, that portion's weight is significantly increased, and the shock absorber inevitably has an increased overall weight, which is a significant obstacle to weight reduction.
技术功效语段:
[0006]Herein, the shock absorber having a structure in which a thickness is added to a geometrical surface structure has a structural feature, that is, it achieves large compressive stiffness more easily than a shock absorber including a part having a lattice structure or a web structure. [0008]Accordingly, it is an object of the present invention to provide a shock absorber which is lightweight and has an excellent shock absorbing function, and can be used in various applications, a shoe sole comprising the shock absorber, and a shoe comprising the shoe sole.
权利要求:
1. A shoe sole comprising a shock absorber comprising a three-dimensional structure composed of a unit structure repeatedly, regularly and continuously arranged in three orthogonal axial directions, the unit structure being a three-dimensional shape formed by a wall having an external shape defined by a pair of parallel planes or curved surfaces, each unit structure having a cavity therein, an axial direction of the three orthogonal axial directions being orthogonal to a tread, the axial direction being a direction in which the shock absorber exhibits a shock absorbing function as the shock absorber receives a load, a cavity of any one unit structure communicating with any cavity of each of other unit structures adjacent to the one unit structure in the three orthogonal axial directions, in a direction in which the one unit structure is adjacent to each of the other unit structures, wherein such unit structures each occupy an approximate rectangular parallelopiped space representing a unit space and are defined by mutually orthogonal three sides having a first side extending in the axial direction and second and third sides each extending from one end of the first side in a direction orthogonal to the axial direction, and the first side has a length L1 and a longer one of the second and third sides has a length L2, the three-dimensional structure including the unit structure satisfying 1.1≤L1/L2≤4.0, the wall of the three-dimensional structure has a meandering portion which is a portion presenting a cross-sectional shape extending in a meandering manner when the three-dimensional structure is cut along at least a specific plane, the meandering portion has an integrally-formed reinforcement portion to reinforce a turning point of the meandering portion, and the integrally-formed reinforcement portion is an additional thickness portion of the wall consisting of the same material as the wall and provided at an internal corner portion of the turning point to make the turning point larger in thickness and in compressive stiffness than another portion of the wall. 2. The shoe sole according to claim 1, wherein such unit spaces aligned in the axial direction each have an equal L1/L2. 3. The shoe sole according to claim 1, wherein the three-dimensional structure is a triply periodic minimal surface with a thickness added thereto. 4. The shoe sole according to claim 3, wherein the three-dimensional structure has a Schwarz' P structure or a gyroid structure. 5. The shoe sole according to claim 1, wherein the three-dimensional structure is composed of a plurality of planes disposed to intersect with one another with a thickness added thereto so that the three-dimensional structure has a cavity therein. 6. A shoe comprising: a shoe sole according to claim 1; and an upper provided above the shoe sole. 7. The shoe sole according to claim 1, wherein the additional thickness portion of the wall comprises a protrusion at the internal corner portion of the turning point or a fill portion at the internal corner portion extending across the internal corner portion.
技术领域:
-
背景技术:
Field of the Invention [0002]The present invention relates to a shock absorber for absorbing shock, a shoe sole comprising the shock absorber, and a shoe comprising the shoe sole. Description of the Background Art [0003]Conventionally, various types of shock absorbers for absorbing shock have been known, and these various types of shock absorbers have been used depending on the application. For example, a shoe may have a shoe sole provided with a shock absorber in order to absorb shock caused upon landing. The shock absorber provided to the shoe sole is typically composed of a member made of resin or rubber. [0004]In recent years, there have also been developed shoes having a shoe sole provided with a part having a lattice structure, a web structure or the like so that not only a material but also a structure provides an enhanced shock absorbing function. A shoe comprising a shoe sole provided with a part having a lattice structure is disclosed for example in U.S. Patent Publication No. 2018/0049514. [0005]Japanese National Patent Publication No. 2017-527637 describes that a three-dimensional object which is manufactured in a three-dimensional additive manufacturing method can be manufactured by adding thickness to a geometrical surface structure, such as a polyhedron having a cavity therein or a triply periodic minimal surface, and discloses that composing the three-dimensional object of an elastic material allows the object to be applied for example to a shoe sole.
发明内容:
[0006]Herein, the shock absorber having a structure in which a thickness is added to a geometrical surface structure has a structural feature, that is, it achieves large compressive stiffness more easily than a shock absorber including a part having a lattice structure or a web structure. [0007]However, when it is attempted to obtain large compressive stiffness in a shock absorber having such a structure, there is a problem, that is, an increased wall thickness results in an increased volume ratio and the shock absorber's weight is significantly increased. In particular, when it is desired to locally increase the compressive stiffness of only a portion of the shock absorber, and that portion's wall thickness is increased, that portion's weight is significantly increased, and the shock absorber inevitably has an increased overall weight, which is a significant obstacle to weight reduction. [0008]Accordingly, it is an object of the present invention to provide a shock absorber which is lightweight and has an excellent shock absorbing function, and can be used in various applications, a shoe sole comprising the shock absorber, and a shoe comprising the shoe sole. [0009]A shock absorber in a first aspect of the present invention includes a three-dimensional structure composed of a unit structure repeatedly, regularly and continuously arranged in at least one direction, the unit structure being a three-dimensional shape formed by a wall having an external shape defined by a pair of parallel planes or curved surfaces. When the shock absorber in the first aspect of the present invention is such that each unit structure occupies a cuboidal space representing a unit space and defined by mutually orthogonal three sides having a first side extending in an axial direction in which the shock absorber exhibits a shock absorbing function as the shock absorber receives a load and second and third sides each extending from one end of the first side in a direction orthogonal to the axial direction, and the first side has a length L1 and a longer one of the second and third sides has a length L2, the shock absorber in the first aspect of the present invention satisfies 1.1≤L1/L2≤4.0. [0010]A shoe sole according to the first aspect of the present invention comprises the shock absorber according to the first aspect of the present invention described above. [0011]A shoe according to the first aspect of the present invention includes the shoe sole according to the first aspect of the present invention described above, and an upper provided above the shoe sole. [0012]A shock absorber according to a second aspect of the present invention includes a three-dimensional structure composed of a unit structure repeatedly, regularly and continuously arranged in at least one direction, the unit structure being a three-dimensional shape formed by a wall having an external shape defined by a pair of parallel planes or curved surfaces. In the shock absorber according to the second aspect of the present invention, when such unit structures each occupy a hexahedral space representing a unit space, the three-dimensional structure includes, as the unit structure, unit structures each occupying a unit space having an external shape with a different dimension. [0013]A shoe sole according to the second aspect of the present invention comprises the shock absorber according to the second aspect of the present invention described above. [0014]A shoe according to the second aspect of the present invention includes the shoe sole according to the second aspect of the present invention described above, and an upper provided above the shoe sole. [0015]The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.
具体实施方式:
[0060]Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following embodiments, identical or common portions are identically denoted in the figures, and will not be 165 described repeatedly. First Embodiment [0061]FIG. 1 is a partially cutaway perspective view of a shock absorber according to a first embodiment. FIG. 2 is a cross section of the shock absorber taken along a line II-II shown in FIG. 1. A shock absorber 1A according to the present embodiment will be described below with reference to FIGS. 1 and 2. [0062]As shown in FIGS. 1 to 2, shock absorber 1A includes a three-dimensional structure S having a plurality of unit structures U (see FIG. 1, in particular). The plurality of unit structures U each have a three-dimensional shape formed by wall 10 having an external shape defined by a pair of parallel curved surfaces. [0063]Herein, in FIG. 1, in order to facilitate understanding, reference character U does not denote the unit structure in a strict sense; rather, it denotes a cuboidal unit space occupied by the unit structure. [0064]The plurality of unit structures U are repeatedly, regularly and continuously arranged in each of the widthwise direction (the X direction indicated in the figure), the depthwise direction (the Y direction indicated in the figure), and the heightwise direction (the Z direction indicated in the figure). FIGS. 1 and 2 extract and show four unit structures U adjacent to one another in each of the widthwise and depthwise directions and two unit structures U adjacent to each other in the heightwise direction. [0065]While in the present embodiment, shock absorber 1A composed of a large number of unit structures U provided in each of the widthwise, depthwise and heightwise directions will be indicated as an example for the sake of illustration, how many unit structures U are repeated in the widthwise, depthwise and heightwise directions is not particularly limited, and two or more unit structures arranged in at least one of the three directions suffice. [0066]Shock absorber 1A according to the present embodiment is intended to exhibit a shock absorbing function in the heightwise direction (the Z direction shown in the figure). Accordingly, when shock absorber 1A receives a load, shock absorber 1A exhibits the shock absorbing function in an axial direction, which will match the heightwise direction described above. [0067]The plurality of unit structures U each have a three-dimensional shape formed by wall 10, as has been set forth above. Therefore, as the plurality of unit structures U are continuously connected to one another, three-dimensional structure S is also composed of a set of walls 10. [0068]Herein, three-dimensional structure S included in shock absorber 1A has a 200 structure in which a thickness is added to a geometrical surface structure. In shock absorber 1A according to the present embodiment, the surface structure is a Schwarz' P structure, which is a type of mathematically defined triply periodic minimal surface. Note that a minimal surface is defined as a curved surface of those having a given closed curve as a boundary that is minimal in area. [0069]As shown in FIG. 2, three-dimensional structure S that is a Schwarz' P structure with a thickness added thereto has a meandering portion 11 which is a portion presenting a cross-sectional shape extending in a meandering manner when three-dimensional structure S is cut along a specific plane. In the present embodiment, the specific plane is a plane orthogonal to the plane of the sheet of FIG. 1 and parallel to the line II-II. [0070]While there will be three types of meandering portions 11 in total in terms of the structure of three-dimensional structure S: one extending in the widthwise direction; one extending in the depthwise direction; and one extending in the heightwise direction, herein, meandering portion 11 which appears in the cross section shown in FIG. 2, that 215 is, extends in the heightwise direction (i.e., the Z direction), is noted. [0071]Meandering portion 11 extending in the heightwise direction has a plurality of turning points 12 located in the heightwise direction, and turning point 12 is provided with an internal corner portion 13 and an external corner portion 14. Of these portions, internal corner portion 13 is a portion which appears in the above cross-sectional shape to have a concave shape on a surface of wall 10, and external corner portion 14 is a portion which appears in the above cross-sectional shape to have a convex shape on a surface of wall 10. Herein, a distance between meandering portion 11 extending in the heightwise direction and meandering portion 11 adjacent thereto varies depending on the location in the heightwise direction, and the distance periodically increases and decreases in the heightwise direction. [0072]As shown in FIG. 1, in shock absorber 1A according to the present embodiment, unit structure U has a shape elongate in the height direction. More specifically, unit structure U is configured such that when each unit structure U occupies a cuboidal space representing a unit space and defined by mutually orthogonal three sides having a first side extending in the heightwise direction (that is, the Z direction), a second side extending in the widthwise direction (that is, the X direction) and a third side extending the depthwise direction (that is, the Y direction), the first side is the longest side. The longest or first side is a side extending in the aforementioned axial direction in which the shock absorbing function is intended to be exhibited. [0073]Herein, in the present embodiment, the second side and the third side are adjusted to be equal in length. Therefore, as shown in the figure, when the first side has a length L1 and the second and third sides have a length L2, shock absorber 1A of the present embodiment satisfies 1.1≤L1/L2≤4.0. [0074]This configuration allows the shock absorber to be lightweight and have an excellent shock absorbing function, which will more specifically be described hereinafter. When the second side and the third side are different in length, the length of the longer one of the second and third sides may be represented as L2, and the above relational expression may be satisfied. [0075]Herein, while shock absorber 1A may be manufactured in any method, it can be additively manufactured using a three dimensional additive manufacturing apparatus for example. [0076]While shock absorber 1A may basically be formed of any material having a large elastic force, it is preferably formed of a resin material or a rubber material. More specifically, when shock absorber 1A is formed of resin, shock absorber 1A can be formed for example of thermoplastic resin such as ethylene-vinyl acetate copolymer (EVA) or can be formed for example of thermosetting resin such as polyurethane (PU). When shock absorber 1A is formed of rubber, it can be formed for example of butadiene rubber. [0077]Shock absorber 1A can be composed of a polymer composition. In that case, an example of a polymer to be contained in the polymer composition includes olefinic polymers such as olefinic elastomers and olefinic resins. Examples of the olefinic polymers include polyolefins such as polyethylene (e.g., linear low density polyethylene (LLDPE), high density polyethylene (HDPE), and the like), polypropylene, ethylene-propylene copolymer, propylene-1-hexene copolymer, propylene-4-methyl-1-pentene copolymer, propylene-1-butene copolymer, ethylene-1-hexene copolymer, ethylene-4-methyl-pentene copolymer, ethylene-1-butene copolymer, 1-butene-1-hexene copolymer, 1-butene-4-methyl-pentene, ethylene-methacrylic acid copolymer, ethylene-methyl methacrylate copolymer, ethylene-ethyl methacrylate copolymer, ethylene-butyl methacrylate 265 copolymer, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-butyl acrylate copolymer, propylene-methacrylic acid copolymer, propylene-methyl methacrylate copolymer, propylene-ethyl methacrylate copolymer, propylene-butyl methacrylate copolymer, propylene-methyl acrylate copolymer, propylene-ethyl acrylate copolymer, propylene-butyl acrylate copolymer, ethylene-vinyl acetate copolymer (EVA), propylene-vinyl acetate copolymer, and the like. [0078]The polymer may be an amide-based polymer such as an amide-based elastomer and an amide-based resin. Examples of the amide-based polymer include polyamide 6, polyamide 11, polyamide 12, polyamide 66, and polyamide 610. [0079]The polymer may be an ester-based polymer such as an ester-based elastomer and an ester-based resin. Examples of the ester-based polymer include polyethylene terephthalate and polybutylene terephthalate. [0080]The polymer may be a urethane-based polymer such as a urethane-based elastomer and a urethane-based resin. Examples of the urethane-based polymer include polyester-based polyurethane and polyether-based polyurethane. [0081]The polymer may be a styrene-based polymer such as a styrene-based elastomer and a styrene-based resin. Examples of the styrene-based elastomer include styrene-ethylene-butylene copolymer (SEB), styrene-butadiene-styrene copolymer (SBS), a hydrogenated product of SBS (styrene-ethylene-butylene-styrene copolymer (SEBS)), styrene-isoprene-styrene copolymer (SIS), a hydrogenated product of SIS (styrene-ethylene-propylene-styrene copolymer (SEPS)), styrene-isobutylene-styrene copolymer (SIBS), styrene-butadiene-styrene-butadiene (SBSB), styrene-butadiene-styrene-butadiene-styrene (SBSBS), and the like. Examples of the styrene-based resin include polystyrene, acrylonitrile styrene resin (AS), and acrylonitrile butadiene styrene resin (ABS). [0082]Examples of the polymer include acrylic polymers such as polymethylmethacrylate, urethane-based acrylic polymers, polyester-based acrylic polymers, polyether-based acrylic polymers, polycarbonate-based acrylic polymers, epoxy-based acrylic polymers, conjugated diene polymer-based acrylic polymers and hydrogenated products thereof, urethane-based methacrylic polymers, polyester-based methacrylic polymers, polyether-based methacrylic polymers, polycarbonate-based methacrylic polymers, epoxy-based methacrylic polymers, conjugated diene polymer-based methacrylic polymers and hydrogenated products thereof, polyvinyl chloride-based resins, silicone-based elastomers, butadiene rubber (BR), isoprene rubber (IR), chloroprene (CR), natural rubber (NR), styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), butyl rubber (IIR), and the like. [0083]As has been described above, shock absorber 1A according to the present embodiment will be lightweight and have an excellent shock absorbing function. This is significantly attributed to a structural feature (a feature in shape) of shock absorber 1A. Hereinafter, this point will be described in detail based on a result of a first verification test conducted by the present inventor. [0084]FIG. 3 is a graph showing a result of simulating the shock absorbing functions of shock absorbers according to Comparative Example 1 and Example 1. [0085]In the first verification test, models for the shock absorbers according to Comparative Example 1 and Example 1 were specifically designed and a case in which these models received an external force in a prescribed direction was assumed, and how the models would behave in that case was simulated and their behaviors were individually analyzed. More specifically, a so-called stress-strain curve was obtained for each of these models. [0086]Herein, the shock absorber according to Example 1 is exactly shock absorber 1A according to the present embodiment, and satisfies 1.1≤L1/L2≤4.0. While the shock absorber according to Comparative example 1 is approximate in configuration to shock absorber 1A according to the present embodiment, it does not satisfy 1.1≤L1/L2≤4.0. [0087]More specifically, the shock absorber according to Comparative Example 1 includes unit structure U having widthwise, depthwise and heightwise dimensions each of 10 mm and L1/L2 is 1.0. Wall 10 has a thickness of 2.36 mm, in which case a volume ratio V of about 50% is provided. [0088]In contrast, the shock absorber according to Example 1 includes unit structure U having widthwise and depthwise dimensions each of 5 mm and a heightwise dimension of 10 mm and L1/L2 is 2.0. Wall 10 has a thickness of 1.36 mm, in which case a volume ratio V of about 50% is provided. [0089]Further, the shock absorbers according to Comparative Example 1 and Example 1 both received external force in the axial direction described above or the heightwise direction. It was assumed that the shock absorbers according to Comparative Example 1 and Example 1 were both formed of a urethane-based acrylic polymer having an elastic modulus of 0.5 MPa. [0090]To increase compressive stiffness to provide an enhanced shock absorbing function, unit structure U may typically have wall 10 increased in thickness. However, when wall 10 is increased in thickness, volume ratio V will also increase accordingly, so that the larger wall 10 is in thickness, the larger volume ratio V is, resulting in the shock absorber being heavier. That is, there is a so-called trade-off relationship between ensuring compressive stiffness and reducing weight. [0091]However, as shown in FIG. 3, despite having the same volume ratio as that of the shock absorber according to Comparative Example 1, the shock absorber according to Example 1 has a larger compressive stiffness than the shock absorber according to Comparative Example 1. It is believed that this is because unit structure U is reduced in length in the widthwise direction, and accordingly, wall 10 acts more like a partition and thus contributes to enhancing compressive stiffness. [0092]Therefore, according to the result of the first verification test, it can be seen that the shock absorber according to Example 1 can obtain large compressive stiffness with a smaller volume ratio (that is, without increasing wall 10 in thickness), and as a result can be lightweight and have an excellent shock absorbing function. [0093]Shock absorber 1A according to the present embodiment described above can thus be a shock absorber which is lightweight and has an excellent shock absorbing function, and can be used for various applications. [0094](First and Second Variations) [0095]FIGS. 4A and 4B are schematic cross sections showing the shapes of main portions of shock absorbers according to first and second variations. Hereinafter, shock absorbers 1A1 and 1A2 according to the first and second variations based on the first embodiment will be described with reference to FIGS. 4A and 4B. [0096]As shown in FIG. 4A, shock absorber 1A1 according to the first variation is provided with a plurality of additional thickness portions 15 at prescribed positions on wall 10. The plurality of additional thickness portions 15 are each provided in the form of a protrusion at internal corner portion 13 of a turning point 12 of meandering portion 11. The plurality of additional thickness portions 15 also each extend across internal corner portion 13. [0097]Additional thickness portion 15 is provided to allow turning point 12 to be larger in thickness than another portion, and functions as a reinforcement portion that reinforces turning point 12 at which stress easily concentrates as shock absorber 1A1 significantly deforms when an external force is applied thereto. When additional thickness portion 15 is provided, larger compressive stiffness can be ensured, and when an external force is applied, and once turning point 12 has been deformed thereby to some extent, additional thickness portion 15 will physically prevent further deformation of turning point 12, and can thus suppress stress concentration caused at turning point 12. [0098]As shown in FIG. 4B, shock absorber 1A2 according to the second variation is provided with a plurality of additional thickness portions 15′ at prescribed positions on wall 10. The plurality of additional thickness portions 15′ are each different from additional thickness portion 15 that shock absorber 1A1 has, as described above, that is, each not in the form of a protrusion, and instead provided to fill internal corner portion 13 of turning point 12 of meandering portion 11. The plurality of additional thickness portions 15′ also each extend across internal corner portion 13. [0099]Additional thickness portion 15′ is provided to allow turning point 12 to be larger in thickness than another portion, and functions as a reinforcement portion that reinforces turning point 12 at which stress easily concentrates as shock absorber 1A1 significantly deforms when an external force is applied thereto. When additional thickness portion 15′ is provided, larger compressive stiffness can be ensured, and when an external force is applied, and once turning point 12 has been deformed thereby to some extent, additional thickness portion 15′ will physically prevent further deformation of turning point 12, and can thus suppress stress concentration caused at turning point 12. [0100]Although not described specifically, shock absorbers 1A1 and 1A2 according to the first and second variations also satisfy 1.1≤L1/L2≤4.0. [0101]Thus shock absorbers 1A1 and 1A2 according to the first and second variations provides the effect of shock absorber 1A according to the first embodiment, and in addition, will be able to suppress local stress concentration, and can thus be enhanced in durability and further enhanced in compressive stiffness. Second Embodiment [0102]FIG. 5 is a partially cutaway perspective view of a shock absorber according to a second embodiment. A shock absorber 1B according to the present embodiment will be described below with reference to FIG. 5. [0103]As shown in FIG. 5, shock absorber 1B includes three-dimensional structure S having a plurality of unit structures U. The plurality of unit structures U each have a three-dimensional shape formed by wall 10 having an external shape defined by a pair of parallel curved surfaces. [0104]The plurality of unit structures U are repeatedly, regularly and continuously arranged in each of the widthwise direction (the X direction indicated in the figure), the depthwise direction (the Y direction indicated in the figure), and the heightwise direction (the Z direction indicated in the figure). FIG. 5 extracts and shows four unit structures U adjacent to one another in each of the widthwise and depthwise directions and two unit structures U adjacent to each other in the heightwise direction. [0105]As has been described above, the plurality of unit structures U each have a three-dimensional shape formed by wall 10. Therefore, as the plurality of unit structures U are continuously connected to one another, three-dimensional structure S is also composed of a set of walls 10. [0106]Herein, three-dimensional structure S included in shock absorber 1B has a structure in which a thickness is added to a geometrical surface structure. In shock absorber 1B according to the present embodiment, the surface structure is a gyroid structure, which is a type of triply periodic minimal surface mathematically defined. [0107]While shock absorber 1B according to the present embodiment includes unit structures U each occupying a cuboidal space representing a unit space and defined by first to third sides having lengths L1 and L2 (in the present embodiment as well, the second and third sides are equal in length), the shock absorber of the present embodiment, as well as the first embodiment, satisfies 1.1≤L1/L2≤4.0. [0108]Thus shock absorber 1B of the present embodiment, as well as the first embodiment, can be lightweight and have an excellent shock absorbing function, and can be used in various applications. Third Embodiment [0109]FIG. 6 is a partially cutaway perspective view of a shock absorber according to a third embodiment. A shock absorber 1C according to the present embodiment will be described below with reference to FIG. 6. [0110]As shown in FIG. 6, shock absorber 1C includes three-dimensional structure S having a plurality of unit structures U. The plurality of unit structures U each have a three-dimensional shape formed by wall 10 having an external shape defined by a pair of parallel curved surfaces. [0111]The plurality of unit structures U are repeatedly, regularly and continuously arranged in each of the widthwise direction (the X direction indicated in the figure), the depthwise direction (the Y direction indicated in the figure), and the heightwise direction (the Z direction indicated in the figure). FIG. 6 extracts and shows eight unit structures U adjacent to one another in each of the widthwise and depthwise directions and four unit structures U adjacent to one another in the heightwise direction. [0112]As has been described above, the plurality of unit structures U each have a three-dimensional shape formed by wall 10. Therefore, as the plurality of unit structures U are continuously connected to one another, three-dimensional structure S is also composed of a set of walls 10. [0113]Herein, three-dimensional structure S included in shock absorber 1C has a structure in which a thickness is added to a geometrical surface structure. In shock absorber 1C according to the present embodiment, the surface structure is a Schwarz' D structure, which is a type of mathematically defined triply periodic minimal surface. [0114]While shock absorber 1C according to the present embodiment includes unit structures U each occupying a cuboidal space representing a unit space and defined by first to third sides having lengths L1 and L2 (in the present embodiment as well, the second and third sides are equal in length), the shock absorber of the present embodiment, as well as the first embodiment, satisfies 1.1≤L1/L2≤4.0. [0115]Thus shock absorber 1C of the present embodiment, as well as the first embodiment, can be lightweight and have an excellent shock absorbing function, and can be used in various applications. Fourth Embodiment [0116]FIG. 7 is a partially cutaway perspective view of a shock absorber according to a fourth embodiment. A shock absorber 1D according to the present embodiment will be described below with reference to FIG. 7. [0117]As shown in FIG. 7, shock absorber 1D includes three-dimensional structure S having a plurality of unit structures U. The plurality of unit structures U each have a three-dimensional shape formed by wall 10 having an external shape defined by a pair of parallel planes. [0118]The plurality of unit structures U are repeatedly, regularly and continuously arranged in each of the widthwise direction (the X direction indicated in the figure), the depthwise direction (the Y direction indicated in the figure), and the heightwise direction (the Z direction indicated in the figure). FIG. 7 extracts and shows only two unit structures U adjacent to each other in each of the widthwise and depthwise directions. [0119]As has been described above, the plurality of unit structures U each have a three-dimensional shape formed by wall 10. Therefore, as the plurality of unit structures U are continuously connected to one another, three-dimensional structure S is also composed of a set of walls 10. [0120]Herein, three-dimensional structure S included in shock absorber 1D has a structure in which a thickness is added to a geometrical surface structure. In shock absorber 1D according to the present embodiment, the surface structure is a cubic octet structure formed of a plurality of planes disposed to intersect with one another to have a cavity therein. [0121]While shock absorber 1D according to the present embodiment includes unit structures U each occupying a cuboidal space representing a unit space and defined by first to third sides having lengths L1 and L2 (in the present embodiment as well, the second and third sides are equal in length), the shock absorber of the present embodiment, as well as the first embodiment, satisfies 1.1≤L1/L2≤4.0. [0122]FIG. 8 is a graph showing a result of simulating the shock absorbing functions of shock absorbers according to Comparative Example 2 and Example 2. Hereinafter, with reference to FIG. 8, a second verification test conducted to verify an effect 485 obtained when shock absorber 1D according to the present embodiment is used will be described. [0123]In the second verification test, models for the shock absorbers according to Comparative Example 2 and Example 2 were specifically designed and a case in which these models received an external force in a prescribed direction was assumed, and how the models would behave in that case was simulated and their behaviors were individually analyzed. More specifically, a so-called stress-strain curve was obtained for each of these models. [0124]Herein, the shock absorber according to Example 2 is exactly shock absorber 1D according to the present embodiment, and satisfies 1.1≤L1/L2≤4.0. While the shock absorber according to Comparative Example 2 is approximate in configuration to shock absorber 1A according to the present embodiment, it does not satisfy 1.1≤L1/L2≤4.0. [0125]More specifically, the shock absorber according to comparative example 2 includes unit structure U having widthwise, depthwise and heightwise dimensions each of 20 mm and L1/L2 is 1.0. Wall 10 has a thickness of 1.6 mm, in which case a volume ratio V of about 50% is provided. [0126]In contrast, the shock absorber according to example 2 includes unit structure U having widthwise and depthwise dimensions each of 10 mm and L1/L2 is 2.0. Wall 10 has a thickness of 0.8 mm, in which case a volume ratio V of about 50% is provided. [0127]Further, the shock absorbers according to Comparative Example 2 and Example 2 both received external force in the axial direction described above or the heightwise direction. It was assumed that the shock absorbers according to Comparative Example 2 and Example 2 were both formed of a urethane-based acrylic polymer having an elastic modulus of 9 MPa. [0128]As shown in FIG. 8, despite having the same volume ratio as that of the shock absorber according to Comparative Example 2, the shock absorber according to Example 2 has a larger compressive stiffness than the shock absorber according to Comparative Example 2. It is believed that this is because, as well as in verification test 1, unit structure U is reduced in length in the widthwise direction, and accordingly, wall 10 acts more like a partition and thus contributes to enhancing compressive stiffness. [0129]Shock absorber 1D according to the present embodiment described above can thus be a shock absorber which is lightweight and has an excellent shock absorbing function, and can be used for various applications. Fifth Embodiment [0130]FIG. 9 is a partially cutaway perspective view of a shock absorber according to a fifth embodiment. A shock absorber 1E according to the present embodiment will be described below with reference to FIG. 9. [0131]As shown in FIG. 9, shock absorber 1E includes three-dimensional structure S having a plurality of unit structures U. The plurality of unit structures U each have a three-dimensional shape formed by wall 10 having an external shape defined by a pair of parallel planes. [0132]The plurality of unit structures U are repeatedly, regularly and continuously arranged in each of the widthwise direction (the X direction indicated in the figure), the depthwise direction (the Y direction indicated in the figure), and the heightwise direction (the Z direction indicated in the figure). FIG. 9 extracts and shows only two unit structures U adjacent to each other in each of the widthwise and depthwise directions. [0133]As has been described above, the plurality of unit structures U each have a three-dimensional shape formed by wall 10. Therefore, as the plurality of unit structures U are continuously connected to one another, three-dimensional structure S is also composed of a set of walls 10. [0134]Herein, three-dimensional structure S included in shock absorber 1E has a structure in which a thickness is added to a geometrical surface structure. In shock absorber 1E according to the present embodiment, the surface structure is a cubic structure formed of a plurality of planes disposed to intersect with one another to have a cavity therein. [0135]While shock absorber 1E according to the present embodiment includes unit structures U each occupying a cuboidal space representing a unit space and defined by first to third sides having lengths L1 and L2 (in the present embodiment as well, the second and third sides are equal in length), the shock absorber of the present embodiment, as well as the first embodiment, satisfies 1.1≤L1/L2≤4.0. [0136]Thus shock absorber 1E of the present embodiment, as well as the first embodiment, can be lightweight and have an excellent shock absorbing function, and can be used in various applications. Sixth Embodiment [0137]FIG. 10 is a partially cutaway perspective view of a shock absorber according to a sixth embodiment. A shock absorber 1F according to the present embodiment will be described below with reference to FIG. 10. [0138]As shown in FIG. 10, shock absorber 1F includes three-dimensional structure S having a plurality of unit structures U. The plurality of unit structures U each have a three-dimensional shape formed by wall 10 having an external shape defined by a pair of parallel planes. [0139]The plurality of unit structures U are repeatedly, regularly and continuously arranged in each of the widthwise direction (the X direction indicated in the figure), the depthwise direction (the Y direction indicated in the figure), and the heightwise direction (the Z direction indicated in the figure). FIG. 10 extracts and shows only two unit structures U adjacent to each other in each of the widthwise and depthwise directions. [0140]As has been described above, the plurality of unit structures U each have a three-dimensional shape formed by wall 10. Therefore, as the plurality of unit structures U are continuously connected to one another, three-dimensional structure S is also composed of a set of walls 10. [0141]Herein, three-dimensional structure S included in shock absorber 1F has a structure in which a thickness is added to a geometrical surface structure. In shock absorber 1F according to the present embodiment, the surface structure is an octet structure formed of a plurality of planes disposed to intersect with one another to have a cavity therein. [0142]While shock absorber 1F according to the present embodiment includes unit structures U each occupying a cuboidal space representing a unit space and defined by first to third sides having lengths L1 and L2 (in the present embodiment as well, the second and third sides are equal in length), the shock absorber of the present embodiment, as well as the first embodiment, satisfies 1.1≤L1/L2≤4.0. [0143]Thus shock absorber 1F of the present embodiment, as well as the first embodiment, can be lightweight and have an excellent shock absorbing function, and can be used in various applications. Seventh Embodiment [0144]FIG. 11 is a perspective view of a shoe sole and a shoe comprising the shoe sole according to a seventh embodiment, and FIG. 12 is a side view of the shoe sole shown in FIG. 11. FIGS. 13A to 13E schematically show an example of how a shock absorber is arranged in the shoe sole shown in FIG. 11. Herein, FIG. 13A is a schematic cross section of the shoe sole taken along a line XIIIA-XIIIA shown in FIG. 12. Hereinafter, a shoe sole 110A and a shoe 100A including shoe sole 110A according to the present embodiment will be described with reference to FIGS. 11, 12, and 13A to 13E. Shoe sole 110A according to the present embodiment includes shock absorber 1A according to the first embodiment. [0145]As shown in FIG. 11, shoe 100A includes shoe sole 110A and an upper 120. Shoe sole 110A is a member that covers the sole of a foot and has a generally flat shape. Upper 120 has a shape that at least covers the entirety of a portion on a side of the bridge of a foot inserted in the shoe, and is located above shoe sole 110A. [0146]Upper 120 includes upper body 121, tongue 122, and shoelace 123. Of these, tongue 122 and shoelace 123 are both fixed to or attached to upper body 121. [0147]Upper body 121 has an upper portion provided with an upper opening for exposing an upper portion of an ankle and a portion of the bridge of a foot. Upper body 121 has a lower po
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