SHOCK-ABSORBING STRUCTURE AND FLOOR MATERIAL

Abstract

The shock-absorbing structure includes a top plate including an upper surface to receive a load, and at least one leg extending in the Z-axis direction from the lower surface of the top plate and has a cross-sectional shape convexly flexed toward one side in the X-Y plane. When the load is applied from the upper surface side of the top plate in the shock-absorbing structure, the legs contract in the Z-axis direction to absorb the load until the load exceeds the threshold load, and once the load exceeds the threshold load, the legs become soft by bending toward the opposite side and being displaced largely while spreading their convexly-flexed cross-sectional surfaces in the Z-Y plane, and after the displacement, the legs can further absorb the load by abutting the upper side and the lower side of the side surface to contract in the Z-axis direction.

Claims

1. A shock-absorbing structure for mitigating an impact, comprising: a top plate including an upper surface to receive a load; and at least one leg extending in a first direction directed away from a lower surface of the top plate and having a cross-sectional shape convexly flexed toward one side in a second direction in a plane that intersects with the first direction, wherein the at least one leg is tilted toward an opposite side in the second direction relative to the lower surface of the top plate, and is formed from an elastic material so that it buckles toward the opposite side in the second direction when a load equal to or more than a threshold load is applied on the top plate.

2. The shock-absorbing structure according to claim 1, wherein the at least one leg includes a leading end having a shape similar to the cross-sectional shape.

3. The shock-absorbing structure according to claim 1, wherein the at least one leg has a cross-sectional shape convexly bent toward the one side of the second direction.

4. The shock-absorbing structure according to claim 1, wherein the at least one leg includes a concave portion formed on at least part of a corner on the one side of the second direction.

5. The shock-absorbing structure according to claim 4, wherein the concave portion is formed in a region spanning from a base end to a leading end of the at least one leg.

6. The shock-absorbing structure according to claim 1, wherein the at least one leg includes a plurality of legs arranged along a circumference of the top plate with the second direction defined as a radial direction having a reference point at a center of the top plate and the one side and an opposite side to the one side defined as an outside and an inside, respectively, associated with the radial direction.

7. The shock-absorbing structure according to claim 6, wherein each of the plurality of legs has a cross-sectional shape convexly flexed toward the outside of the radial direction, and is tilted toward the inside of the radial direction relative to the lower surface of the top plate.

8. The shock-absorbing structure according to claim 7, wherein two legs adjacent to each other among the plurality of legs form a gap therebetween.

9. The shock-absorbing structure according to claim 8, wherein the gap between the two legs becomes wider in the first direction from the lower surface of the top plate.

10. The shock-absorbing structure according to claim 7, wherein the top plate has a frame shape with an opening at a center.

11. The shock-absorbing structure according to claim 7, wherein the top plate has a rectangular shape, and each of the plurality of legs is arranged at a corner of the top plate.

12. The shock-absorbing structure according to claim 7, wherein the top plate includes an overhang portion that overhangs toward an outside from a location to which the plurality of legs are connected.

13. The shock-absorbing structure according to claim 12, wherein a thickness of the overhang portion is equal to or smaller than a thickness of the plurality of legs.

14. The shock-absorbing structure according to claim 12, wherein at least one of the plurality of legs includes a rib formed between its side surface on an outside and a lower surface of the overhang portion.

15. The shock-absorbing structure according to claim 12, wherein a plurality of top plates, each being identical to the top plate, are arrayed by joining the overhang portions with each other and at least in one of the second direction or a third direction that intersects with each of the first direction and the second direction, and the plurality of legs are provided in each of the plurality of top plates.

16. The shock-absorbing structure according to claim 15, further comprising: a sliding rib that is formed so as to extend in the first direction from an overhang portion of a top plate located at an outermost part in the plurality of top plates on an outside surface of a leg adjacent to the overhang portion among the plurality of legs provided on the top plate and so as to be tilted toward the outside surface of the leg adjacent to the overhang portion, wherein the sliding rib includes an end surface extending in the first direction from a side surface of the overhang portion of the top plate.

17. The shock-absorbing structure according to claim 15, wherein the top plate includes a claw portion which engages with a claw-reception portion of a top plate of another shock-absorbing structure and/or a claw-reception portion with which a claw portion of a top plate of another shock-absorbing structure engages.

18. The shock-absorbing structure according to claim 7, further comprising: a bottom surface connected to a leading end of each of the plurality of legs.

19. The shock-absorbing structure according to claim 18, wherein the bottom surface includes a central portion located at a center of the plurality of legs and a plurality of joint portions each of which being joined from the central portion to the leading end of each of the plurality of legs.

20. The shock-absorbing structure according to claim 18, wherein the top plate includes an engagement member that extends toward an outside of the top plate from between two legs adjacent to each other among the plurality of legs and has a shape with a leading end wider than a gap between the two legs.

21. The shock-absorbing structure according to claim 1, wherein the at least one leg includes a plurality of legs arranged adjacently near a center of the top plate with the second direction defined as a radial direction having a reference point at the center of the top plate and the one side and an opposite side to the one side defined as an inside and an outside, respectively, associated with the radial direction.

22. A floor material comprising: a surface material; and the shock-absorbing structure according to claim 1 that supports the surface material and is arranged on a subfloor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] FIG. 1 shows an overall structure of a shock-absorbing structure according to the present embodiment in a perspective view.

[0010] FIG. 2A shows an overall structure of a unit structure that constitutes the shock-absorbing structure in a perspective view.

[0011] FIG. 2B shows an internal structure of the unit structure, partially omitted in a perspective view.

[0012] FIG. 2C shows a structure of the unit structure in a top view.

[0013] FIG. 2D shows the structure of the unit structure in a bottom view.

[0014] FIG. 2E shows the structure of the unit structure in a side view.

[0015] FIG. 3A shows the shock-absorbing structures in a stacked state.

[0016] FIG. 3B shows the shock-absorbing structure in a wound state.

[0017] FIG. 4 shows a structure of a sliding rib.

[0018] FIG. 5A shows a function of the sliding rib (a state in which an end of the shock-absorbing structure is lifted onto an end of another shock-absorbing structure).

[0019] FIG. 5B shows the function of the sliding rib (a state in which the end of the shock-absorbing structure slides on a sliding rib of another shock-absorbing structure).

[0020] FIG. 5C shows the function of the sliding rib (a state in which the shock-absorbing structure is arranged side-by-side with another shock-absorbing structure).

[0021] FIG. 6A shows a structure of a reinforcement rib in a side view.

[0022] FIG. 6B shows the structure of the reinforcement rib in a bottom view.

[0023] FIG. 7A shows a structure of a joint structure in a perspective view.

[0024] FIG. 7B shows the structure of the joint structure in a side view.

[0025] FIG. 8A shows a state in which two shock-absorbing structures (two unit structures) are joined by the joint structure, in a perspective view.

[0026] FIG. 8B shows a state in which two shock-absorbing structures (two unit structures) are joined by the joint structure, in a side view.

[0027] FIG. 9A shows a shock-absorbing principle of the shock-absorbing structure (unit structure) (in the unloaded state).

[0028] FIG. 9B shows the shock-absorbing principle of the shock-absorbing structure (unit structure) (in the contracted state).

[0029] FIG. 9C shows the shock-absorbing principle of the shock-absorbing structure (unit structure) (in the buckled state).

[0030] FIG. 9D shows the shock-absorbing principle of the shock-absorbing structure (unit structure) (in the collapsed state).

[0031] FIG. 10 shows a cross-sectional structure of a floor material including the shock-absorbing structure according to the present embodiment.

[0032] FIG. 11 shows a shock-absorbing property of the shock-absorbing structure.

[0033] FIG. 12 shows an overall structure of another unit structure that constitutes the shock-absorbing structure in a perspective view.

[0034] FIG. 13A shows a second deformation mode of the shock-absorbing structure (unit structure) (in a legs-closed state).

[0035] FIG. 13B shows the second deformation mode of the shock-absorbing structure (unit structure) (in the legs-most-closed state).

[0036] FIG. 14A shows a third deformation mode of the shock-absorbing structure (unit structure) (in a legs-opened state).

[0037] FIG. 14B shows a third deformation mode of the shock-absorbing structure (unit structure) (in the legs-most-opened state).

[0038] FIG. 15A shows an overall structure of a unit structure according to a modification example in a perspective view.

[0039] FIG. 15B shows an internal structure of the unit structure according to the modification example, partially omitted in a perspective view.

[0040] FIG. 15C shows a structure of the unit structure according to the modification example in a top view.

[0041] FIG. 15D shows the structure of the unit structure according to the modification example in a bottom view.

[0042] FIG. 15E shows the structure of the unit structure according to the modification example in a side view.

[0043] FIG. 16 shows a structure of a sliding rib in the unit structure according to the modification example.

[0044] FIG. 17A shows a structure of an engagement member in the unit structure according to the modification example in a perspective view.

[0045] FIG. 17B shows a state in which the unit structure according to the modification example is joined to another unit structure by the engagement member, in a perspective view.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0046] Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the invention according to the claims. In addition, not all of the combinations of features described in the embodiments are essential to the solving means of the invention.

[0047] In an embodiment of the present invention, a size of a member may be described using approximately. Note that this means the size is accurate at least in significant figures (significant digits) and includes an inaccuracy in the extent of non-significant figures. For example, approximately 1 mm includes an inaccuracy in the extent of 0.1 mm.

[0048] FIG. 1 shows an overall structure of the shock-absorbing structure 100 according to the present embodiment in a perspective view. Here, a thickness direction of the shock-absorbing structure 100 is defined as a Z-axis direction and directions orthogonal to each other in a plane that is orthogonal to the Z-axis direction are defined as an X-axis direction and a Y-axis direction. As an example, the shock-absorbing structure 100 constitutes a floor material that supports a floor surface on a subfloor S (see FIG. 9A and the like) and mitigates impact applied to the floor surface. Here, the subfloor S may be one that includes a walking surface on which a person walks, such as a plane of a floor slab (concrete slab) in a reinforced concrete building, a surface on which flooring or the like is installed, a floorboard in a wooden building, or ground. Particularly, the shock-absorbing structure 100 is a structure that is firm against small loads during walking to allow stable walking, while being soft against large impacts upon falling over to allow the impact to be absorbed to prevent fractures.

[0049] The shock-absorbing structure 100 is configured by arraying a plurality of unit structures 10, each having a thickness in the Z-axis direction, in line in the X-axis direction or in the Y-axis direction or in a matrix-like manner in the XY direction, by joining the overhang portions 11b of the top plates 11 integrally with each other. Note that, although the shock-absorbing structure 100 according to the present embodiment is constituted by nine unit structures 10 in total that are arrayed three by three in the X-axis direction and the Y-axis direction, the number of unit structures 10 that are arrayed in each of the X-axis direction and the Y-axis direction can be arbitrarily determined, and thus the length of the shock-absorbing structure 100 in each of the X-axis direction and the Y-axis direction can also be determined arbitrarily.

[0050] FIG. 2A to FIG. 2E show the structures of the unit structures 10 constituting the shock-absorbing structure 100. The unit structure 10 is a minimal constitutional unit that constitutes the shock-absorbing structure 100. Here, FIG. 2A shows an overall structure of the unit structure 10 in a perspective view, FIG. 2B shows an internal structure of the unit structure 10, partially omitted in a perspective view, FIG. 2C shows a structure of the unit structure 10 in a top view, FIG. 2D shows the structure of the unit structure 10 in a bottom view, and FIG. 2E shows the structure of the unit structure 10 in a side view. The unit structure 10 includes a top plate 11 and legs 12.

[0051] The top plate 11 is a member that includes an upper surface to receive a load. In the present embodiment, the top plate 11 has a rectangular shape (particularly a square shape). Note that, the shape of the top plate 11 may be, for example, hexagonal or other polygonal shapes, as long as it is suitable to array the plurality of unit structures 10 in one axis direction or two axis directions. When the unit structure 10 is rectangular or hexagonal, it can be densely arrayed.

[0052] The size of the top plate 11 is determined to be sufficiently smaller than an area to which a load is applied when a person (including not only an adult but also a child) walks on the floor surface, i.e. the area of one's sole abutting the floor surface during walking or the area of one's knee that strikes against the floor surface when falling over. In the present embodiment, the length W.sub.11 of one side of the top plate 11 is defined to be approximately 15 mm, as an example. Accordingly, even when not only an adult but also a child falls over on the floor surface, the load applied to the floor surface can be absorbed by the plurality of unit structures 10 to prevent injuries such as fractures.

[0053] Note that, as will be described below, the shape of the top plate 11 may not be limited to the plate shape extending throughout a plane but may have a frame shape with an opening 11a at the center, as long as the top plate 11 can receive the load applied to the unit structure 10 via the surface material 120 and the like, because the top plate 11 supports a surface material 120 and the like that forms the floor surface on the shock-absorbing structure 100. The shape of the opening 11a may be circular (oval may also be possible), rectangular (including square), hexagonal, or other polygonal shapes. The top plate 11 having a plate shape has somewhat high rigidity and the legs 12 are difficult to tilt relative to the top plate 11 while the top plate 11 having a frame shape has moderately low rigidity and the legs 12 tilt easily to buckle relative to the top plate 11, thus allowing itself to become soft against the large impact upon falling over to absorb the impact.

[0054] FIG. 3A shows the shock-absorbing structures 100 in a stacked state. By the top plates 11 including the openings 11a, the legs 12 of a plurality of unit structures 10 included in the shock-absorbing structure 100 can each be inserted between the legs 12 of a plurality of unit structures 10 included in another shock-absorbing structure 100 through the openings 11a of the top plates 11, and the legs 12 of the plurality of unit structures 10 included in another shock-absorbing structure 100 can each be further inserted between the legs 12 of a plurality of unit structures 10 included in still another shock-absorbing structure 100 through the openings 11a of the top plates 11, thus allowing the plurality of shock-absorbing structures 100 to be stacked with a small thickness.

[0055] In the present embodiment, the top plate 11 has a rectangular (particularly square) frame body including a rectangular opening 11a at the center. The top plate 11 includes an overhang portion 11b that overhangs toward the outside (in X direction and Y direction) from a location to which the legs 12 are connected as described below, that is, in the case of the present example, from an inner edge portion which sections the opening 11a. The width W.sub.11b of the overhang portion 11b (see FIG. 2E) may be almost the same as or more than the width of the inner edge portion to which the legs 12 are connected. As an example, in the present embodiment, the width of the inner edge portion is defined to be approximately 1 mm, which is almost equal to the thickness d.sub.12 of the leg 12, and the width of the overhang portion 11b is defined to be approximately 1 mm. That is, the frame width W.sub.11 of the top plate 11 is defined to be approximately 2 mm. Accordingly, a large support surface is obtained and the upper surface layer 120 or the like can be stably supported.

[0056] In addition, the thickness d.sub.11 of the overhang portion 11b (see FIG. 2E) may be defined to be equal to or smaller than the thickness d.sub.12 of the leg 12. In the present embodiment, it is defined to be 1 mm, which is almost equal to the thickness d.sub.12 of the leg 12. Accordingly, due to the relatively small thickness of the overhang portion 11b, the rigidity of the top plate 11 becomes moderately low and the legs 12 easily tilt to buckle relative to the top plate 11, thus allowing the deformation stroke by which the top plate 11 is displaced in the Z-axis direction to be larger.

[0057] FIG. 3B shows the shock-absorbing structure 100 in a wound state. As described above, the shock-absorbing structure 100 is integrally configured by joining the overhang portions 11b with each other from the plurality of unit structures 10. The top plate 11 has a low rigidity at a location where overhang portions 11b are joined with each other between the adjacent unit structures 10. Hence, by arraying the unit structures 10 in a matrix-like manner, the shock-absorbing structure 100 can be flexed at the joint location and easily wound up in the array direction of the unit structure 10. At this time, the shock-absorbing structure 100 can be wound up in a small thickness by inserting the legs 12 of the unit structure 10 into the openings 11a of the top plates 11 of another unit structure 10.

[0058] The leg 12 is a member that extends in Z direction from the lower surface of the top plate 11 and supports the top plate 11 on the subfloor S. At least one leg 12 is provided in each of the top plates 11 of the plurality of unit structures 10 constituting the shock-absorbing structure 100, preferably a plurality of legs 12 are provided in each top plate 11, and particularly the plurality of legs 12 are arranged along the circumference of each top plate 11. Note that, when the top plate 11 has a polygonal shape, the legs 12 are each arranged near one of a plurality of corners and when the top plate 11 has a circular shape, the legs 12 are each arranged at at least three or more locations at an arbitrary interval. Accordingly, the top plate 11 can be stably supported since a load is distributed among the plurality of legs 12 when the load is applied to the top plate 11.

[0059] The height H.sub.12 of the leg 12 can be determined according to the deformation stroke required to absorb a load in one unit structure 10. In the present embodiment, the height H.sub.12 of the leg 12 is defined to be approximately 9 mm, as an example.

[0060] Each leg 12 is tilted toward the center of the top plate 11 (or the unit structure 10) relative to the lower surface of the top plate 11. In the side view associated with the X-axis direction (see FIG. 2E), the tilt angle .sub.12 of the leg 12 relative to the Z-axis is 6 to 13 degrees, preferably 8 to 11 degrees, more preferably approximately 9.5 degrees. The same applies to the tilt angle of the leg 12 in the side view associated with the Y-axis direction. Accordingly, the leg 12 easily buckles toward the center of the top plate 11.

[0061] Note that, the leg 12 may be perpendicular to the lower surface of the top plate 11 as long as it buckles when a large impact upon falling over is applied. In addition, the leg 12 may be tilted toward the outside of the top plate 11. In such a case, the tilt angle of the leg 12 may be the same as the tilt angle when it is tilted toward the center of the top plate 11.

[0062] Each leg 12 has a cross-sectional shape flexed convexly toward one side in the X-Y plane. The leg 12 may be convexly curved toward one side and is preferably convexly bent toward one side. Accordingly, a shift between deformation modes of the leg 12 when the load is applied to the leg 12, i.e. a shift from a contraction mode to a buckling mode or a shift from the buckling mode to the contraction mode, becomes more obvious. That is, a characteristic shift becomes more obvious in which the leg 12 remains firm until the load exceeds the threshold strength and becomes soft once the load exceeds the threshold strength. Here, a threshold load at which the deformation mode shifts is adjusted by selecting the thickness d.sub.12 of the leg 12 (see FIG. 2B). In the present example, the thickness d.sub.12 is defined to be approximately 1 mm as an example.

[0063] Since the top plate 11 of the present embodiment has a rectangular shape, the four legs 12 are each arranged near one of the four corners of the top plate 11 with their convexly-flexed outside surface facing outwardly in a radial direction having a reference point at the center of the unit structure 10 (or of the top plate 11) in the top view. In other words, the leg 12 arranged near an X, Y corner of the top plate 11 is bent outwardly from the center of the top plate 11, i.e. bent convexly at 90 degrees in an X, Y direction (in an L-shaped manner from the X direction to the +Y direction), and is joined at its upper end to the lower surface of the X, Y corner of the top plate 11 with its inside surface flush with the interior surface of the X, Y corner of the top plate 11. In addition, the leg 12 arranged near an X, +Y corner of the top plate 11 is bent outwardly from the center of the top plate 11, i.e. bent convexly at 90 degrees in an X, +Y direction (in an L-shaped manner from the +Y direction to the +X direction), and is joined at its upper end to the lower surface of the X, +Y corner of the top plate 11 with its inside surface flush with the interior surface of the X, +Y corner of the top plate 11. In addition, the leg 12 arranged near an +X, +Y corner of the top plate 11 is bent outwardly from the center of the top plate 11, i.e. bent convexly at 90 degrees in an +X, +Y direction (in an L-shaped manner from the +X direction to the Y direction), and is joined at its upper end to the lower surface of the +X, +Y corner of the top plate 11 with its inside surface flush with the interior surface of the +X, +Y corner of the top plate 11. In addition, the leg 12 arranged near an +X, Y corner of the top plate 11 is bent outwardly from the center of the top plate 11, i.e. bent convexly at 90 degrees in an +X, Y direction (in an L-shaped manner from the Y direction to the X direction), and is joined at its upper end to the lower surface of the +X, Y corner of the top plate 11 with its inside surface flush with the interior surface of the +X, Y corner of the top plate 11. Accordingly, the top plate 11 is supported by the plurality of (four in the present example) legs 12, arranged along its circumference, and the legs 12 can be prevented from spreading toward the outside and interfering with the legs 12 of adjacent unit structures 10 by buckling toward the inside in the radial direction when the load equal to or more than the threshold load is applied to the top plate 11.

[0064] The leg 12 includes a leading end that has a similar shape to the convexly-flexed cross-sectional shape as described above. That is, no end surface is provided which is parallel to the X-Y plane that connects the insides of the leading ends flexed at 90 degrees at each of the legs 12, no bottom surface is provided which is parallel to the X-Y plane that connects the leading ends of four legs 12, but a space 12c is formed which is open in the Z-axis direction among the leading ends of the four legs 12. Accordingly, the four legs 12 deform to spread respective body portions (the middle associated with the Z-axis direction) to equal to or more than 90 degrees in the X-Y plane (provision of the end surface or the bottom surface would increase the rigidity and cause difficulty in spreading), and then buckle entirely toward the center of the top plate 11, thus allowing the top plate 11 to be largely displaced in the Z-axis direction. In addition, since the unit structure 10 has a through hole in the Z-axis direction, air is allowed to pass through easily.

[0065] With such a shape of the leg 12, despite the small volume of the member occupying the space, the rigidity of the leg 12 can be maintained until it buckles, while deformation stroke associated with the Z-axis direction can also be increased as much as possible due to the reduced volume of the member.

[0066] Each leg 12 has a concave portion 12a formed on at least part of the corner on the outside in the radial direction having a reference point at the center of the unit structure 10 (or of the top plate 11) in the top view. Accordingly, bending of each leg 12 starting from the concave portion 12a toward the inside in the radial direction can be induced when the load equal to or more than the threshold load is applied to the top plate 11 of the unit structure 10.

[0067] The concave portion 12a is located in the middle of the leg 12 associated with the Z-axis direction. Particularly, the concave portion 12a is formed to have a wedge shape with the deepest portion at the middle of the leg 12, in a region spanning from the base end (i.e. the upper end that is connected to the lower surface of the top plate 11) to the leading end (i.e. the lower end) of the leg 12. The maximum width W.sub.12a of the concave portion 12a (see FIG. 2E) is defined to be approximately 1 mm, as an example. Accordingly, the upper edge and the lower edge of the concave portion 12a are prevented from interfering with each other and the bending angle, i.e. the deformation stroke of the leg 12 associated with the Z-axis direction, is not restricted when the leg 12 is bent, allowing buckling thereof in its entirety to maximize the deformation stroke. Note that, the concave portion 12a may be formed into a concave-surface shape. In addition, a plurality of concave portions 12a may be arranged side by side in the Z-axis direction.

[0068] Two adjacent legs 12 among the plurality of legs 12 form a gap 12b therebetween. The gap 12b is the smallest on the upper-end side of the two legs 12 and the minimum width w.sub.12 is defined to be approximately 2 mm, as an example. Note that, the adjacent legs 12 of the plurality of legs 12 may be joined with each other at their upper ends. In such a case, the minimum width W.sub.12 of the gap 12b is determined at a position immediately below the joint location. Accordingly, when the plurality of legs 12 buckle, the air inside the unit structure 10 easily flows through the gap 12b to the outside, and an air-damping effect is decreased moderately to cause the leg 12 to buckle easily.

[0069] Moreover, the shape of the side surface of the leg 12 is determined to make the gap 12b between the two adjacent legs 12 become wider from the lower surface of the top plate 11 (or the joint location of the two adjacent legs 12) in the Z direction. In the side view in the X-axis direction, an angle .sub.12 of the side surface of the leg 12 relative to the Z-axis (see FIG. 2E) is 3 to 10 degrees, preferably 5 to 8 degrees, more preferably approximately 6.3 degrees. Accordingly, the gap 12b becomes wider from the lower surface of the top plate 11 or the joint location to the lower end, in a range of, for example, approximately 2 to approximately 4 mm. Note that, the length W.sub.12 (see FIG. 2E) of one side of the leg 12 is approximately 4 mm. Accordingly, the deformation stroke of the top plate 11 associated with the Z-axis direction can be restricted by the two adjacent legs 12 interfering with each other when they buckle when the load equal to or more than the threshold load is applied to the top plate 11.

[0070] FIG. 4 shows a structure of the sliding rib 13 of the unit structure 10. The sliding rib 13 is provided on an outermost unit structure 10 of the plurality of unit structures 10 constituting the shock-absorbing structure 100, and is formed to extend from the overhang portion 11b of the top plate 11 in the Z direction on the outside surface of the leg 12 and to be tilted toward the outside surface of the leg 12. Accordingly, an end surface 13a that extends from the side surface of the overhang portion 11b in the Z direction is formed, and an inclined surface 13b which is connected to the outside surface of the leg 12 is formed thereunder. Note that, the width w.sub.13 of the sliding rib 13 is defined, for example, to be approximately 1 mm.

[0071] FIG. 5A to FIG. 5C show a function of the sliding rib 13. When two shock-absorbing structures 100 are to be arranged side by side on the subfloor S, the end (i.e. overhang portion 11b) of the outermost unit structure 10 of the shock-absorbing structure 100 on the right-hand side may be lifted onto the end (i.e. the overhang portion 11b) of the shock-absorbing structure 100 on the left-hand side as shown in FIG. 5A. At this time, the inclined surface 13b of the sliding rib 13 of the unit structure 10 on the right-hand side is lifted onto the overhang portion 11b of the unit structure 10 on the left-hand side.

[0072] Hence, a load is applied downwardly on the top plate 11 of the unit structure 10 on the right-hand side (in the direction of an outlined arrow). Accordingly, an end of the overhang portion 11b of the unit structure 10 on the left-hand side slides over the inclined surface 13b of the sliding rib 13 of the unit structure 10 on the right-hand side, and the unit structure 10 on the right-hand side is pushed downwardly while being shifted to the right-hand side as represented by a black-colored arrow.

[0073] Accordingly, as shown in FIG. 5B, the unit structure 10 on the right-hand side is positioned relative to the unit structure 10 on the left-hand side in the left and right direction, and the end surface 13a of the sliding rib 13 of the unit structure 10 on the right-hand side is in surface contact with the end surface 13a of the sliding rib 13 of the unit structure 10 on the left-hand side. Moreover, the load is applied downwardly on the top plate 11 of the unit structure 10 on the right-hand side (in the direction of an outlined arrow). Accordingly, the end surface 13a of the sliding rib 13 of the unit structure 10 on the right-hand side slides over the end surface 13a of the sliding rib 13 of the unit structure 10 on the left-hand side, and the unit structure 10 on the right-hand side is pushed further downwardly as represented by a black-colored arrow.

[0074] Finally, as shown in FIG. 5C, the unit structure 10 (i.e. the shock-absorbing structure 100) on the right-hand side is arranged side by side with the shock-absorbing structure 100 on the left-hand side on the subfloor S. In this manner, by utilizing the end surface 13a and the inclined surface 13b of the plurality of shock-absorbing structures 100 (unit structures 10), it is possible to position the plurality of shock-absorbing structures 100 in the lateral direction and to array them on the subfloor S so that their upper surfaces of the top plates 11 are flush with each other.

[0075] FIG. 6A and FIG. 6B show a structure of a reinforcement rib 14 of the shock-absorbing structure 100 in a side view and a bottom view, respectively. The reinforcement rib 14 may be provided between two adjacent unit structures 10 of the plurality of unit structures 10 constituting the shock-absorbing structure 100. The reinforcement rib 14 is formed to join the lower surfaces of overhang portions 11b by which two adjacent unit structures 10 are joined and the outside surfaces of the legs 12 of the two unit structures 10 that face each other across the overhang portions 11b in a bottom view. The width d.sub.14 and the height h.sub.14 of the reinforcement rib 14 are defined to be approximately 1 mm and approximately 2 mm, respectively as an example. By providing the reinforcement rib 14 between the top plate 11 and the leg 12, the rigidity of the leg 12 can be adjusted.

[0076] Note that, the reinforcement rib 14 may be provided between the outside surfaces of the legs 12 facing each other in all the unit structures 10, or alternatively, it may only be provided between the outside surfaces of the legs 12 facing each other in some of the unit structures 10.

[0077] In order to join the adjacent shock-absorbing structures 100 with each other when arraying the plurality of shock-absorbing structures 100 on the subfloor S, a joint structure may be provided on the outermost unit structure 10 of the plurality of unit structures 10 constituting the shock-absorbing structure 100. Multiple joint structures may be provided in one shock-absorbing structure 100.

[0078] FIG. 7A and FIG. 7B show the joint structure of the shock-absorbing structure 100 (unit structure 10) in a perspective view and a side view, respectively. The joint structure includes a claw portion 15 provided on one of the adjacent shock-absorbing structures 100 (unit structures 10a) and a claw-reception portion 16 provided on another of the shock-absorbing structures 100 (unit structures 10b). Here, the joint structure is exemplified that joins the +Y end of the outermost unit structure 10a of one of the shock-absorbing structures 100 and the Y end of the outermost unit structure 10b of another of the shock-absorbing structures 100, although the joint structure can be provided on an outer edge (+X edge, X edge, +Y edge, or Y edge) of any outermost unit structure 10 of the two shock-absorbing structures 100.

[0079] The claw portion 15 is a member that engages with the claw-reception portion 16 formed on the top plate 11 of the unit structure 10b. The claw portion 15 extends, in the +Y direction, from the top plate 11 and the upper-end side of the outside surface on the +Y side of the leg 12 on the +X, +Y side of the unit structure 10a, and includes a grooved portion 15a extending in the X-axis direction formed on the lower surface near the leading end and a grooved portion 15b extending in the X-axis direction formed at the base end side on the upper surface, forming an S-shape in the side view. Note that, the claw portion 15 may be formed between the top plate 11 and the leg 12 on the X, +Y side of the unit structure 10a.

[0080] The claw-reception portion 16 is a member that are engaged with the claw portion 15 formed on the top plate 11 of the unit structure 10a. The claw-reception portion 16 is provided on the +X, Y side of the unit structure 10b, instead of the leg 12, and includes a step portion 16b, a block body 16d, and engagement blocks 16c, 16e. The step portion 16b is formed to protrude toward the X side from the inner edge of the top plate 11 on the +X side. The block body 16d is formed to extend out toward the +Y side from the inner edge of the top plate 11 on the Y side. The engagement block 16c is formed integrally with a part of the top plate 11 on the Y, +Z side between the step portion 16b and the block body 16d so as to connect them. The engagement block 16e is formed on the +Y, Z side between the step portion 16b and the block body 16d so as to connect them. By the presence of the engagement blocks 16c, 16e, an S-shaped space 16a is formed between the step portion 16b and the block body 16d in a side view associated with the X-axis direction.

[0081] FIG. 8A and FIG. 8B show a state in which two shock-absorbing structures 100 (two unit structures 10a, 10b) are joined by the joint structure in a perspective view and a side view, respectively. First, the claw portion 15 of the unit structure 10a is inserted into the space 16a in the claw-reception portion 16 of the unit structure 10b, from below the engagement block 16c to above the engagement block 16e. Then, the engagement block 16e of the claw-reception portion 16 is fitted into the grooved portion 15a of the claw portion 15, and the engagement block 16c of the claw-reception portion 16 is fitted into the grooved portion 15b of the claw portion 15. Then, the overhang portion 11b on the +Y side of the top plate 11 of the unit structure 10a and the overhang portion 11b on the Y side of the top plate 11 of the unit structure 10b are abutted with each other, and the two unit structures 10a, 10b are arranged side-by-side so that their top plates 11 are flush with each other. Accordingly, the two unit structures 10a, 10b, i.e. two shock-absorbing structures 100 are joined.

[0082] Note that, one of the shock-absorbing structures 100 may include the unit structure 10b provided with the claw-reception portion 16 in addition to the unit structure 10a provided with the claw portion 15. In addition, another of the shock-absorbing structures 100 may include the unit structure 10a provided with the claw portion 15 in addition to the unit structure 10b provided with the claw-reception portion 16. That is, the shock-absorbing structure 100 may include one or more unit structures 10a provided with the claw portion 15 and one or more unit structures 10b provided with the claw-reception portion 16.

[0083] FIG. 9A to FIG. 9D show a shock-absorbing principle of the shock-absorbing structure 100 (unit structure 10). Note that, one unit structure 10 of the plurality of unit structures 10 constituting the shock-absorbing structure 100 is exemplified. An upper section and a lower section of FIG. 9A show the unit structure 10 in the unloaded state in a top view and a side view, respectively. The unit structure 10 is installed on the subfloor S. The top plate 11 of the unit structure 10 is supported at its height H.sub.12 (see FIG. 2E) by the four legs 12.

[0084] An upper section and a lower section of FIG. 9B show the unit structure 10 in the contracted state in a top view and a side view, respectively. A load is applied downwardly (in the direction of an outlined arrow) from the upper surface side of the top plate 11. However, the load is smaller than a predetermined threshold load. In such a case, the four legs 12 supporting the top plate 11 contract to some extent in the Z-axis direction and cause the top plate 11 to be lowered to some extent downwardly (in the direction of a black-colored arrow) to absorb the load.

[0085] An upper section and a lower section of FIG. 9C show the unit structure 10 in the buckled state in a top view and a side view, respectively. It is assumed that the load (the white-colored arrow) applied to the top plate 11 has increased to exceed the threshold load. In such a case, the four legs 12 supporting the top plate 11 bend (i.e. buckle) toward the inside of the unit structure 10 (in the direction of a small black-colored arrow) and are displaced largely in the Z-axis direction while spreading their convexly-flexed cross-sectional surfaces in the X-Y plane, thus causing the top plate 11 to be largely lowered downwardly (in the direction of a large black-colored arrow).

[0086] An upper section and a lower section of FIG. 9D show the unit structure 10 in the collapsed state in a top view and a side view, respectively. It is assumed that the load (the white-colored arrow) applied to the top plate 11 has further increased. The four legs 12 supporting the top plate 11 cause the top plate 11 to be further lowered downwardly (in the direction of a large black-colored arrow) to absorb the load by completely spreading their convexly-flexed cross-sectional surfaces in the X-Y plane, further bending toward the inside of the unit structure 10 (in the direction of a small black-colored arrow) to be soft, and abutting the upper side and the lower side of the outside surface to contract in the Z-axis direction.

[0087] In this manner, the shock-absorbing structure 100 (the unit structure 10) is firm against small load applied during walking which is smaller than the threshold load, providing stability during walking, and is soft against large impact upon falling over which is equal to or more than the threshold load, allowing large displacement to absorb the impact.

[0088] FIG. 10 shows a cross-sectional structure of a floor material 200 including the shock-absorbing structure 100 according to the present embodiment. The floor material 200 include a surface material 120, an intermediate material 110, and the shock-absorbing structure 100.

[0089] The surface material 120 is a layer material that includes an upper surface which forms the floor surface (i.e. a surface for walking). The surface material 120 may be made of a hard material such as wood, plywood, stone, sheet-vinyl floor made of vinyl chloride, tile, carpet, cork, continuous sheet or the like, so as to be provided with walkability. Note that, the surface material 120 may be integrally configured with the intermediate material 110.

[0090] The intermediate material 110 is a layer material that is arranged between the surface material 120 and the shock-absorbing structure 100 to flatten surface irregularities on the upper surface of the shock-absorbing structure 100 arrayed on the subfloor S. As the intermediate material 110, a foam layer may be adopted that is molded using foam materials such as polyurethane, as an example. The intermediate material 110 is arranged to cover at least two shock-absorbing structures 100. Accordingly, the load locally applied to the surface material 120 is distributed among the plurality of shock-absorbing structures 100.

[0091] The multiple shock-absorbing structures 100 are arrayed on the subfloor S and support the surface material 120 and the intermediate material 110. The shock-absorbing structure 100 is configured as described above, and absorbs the load applied via the surface material 120.

[0092] The shock-absorbing structure 100 according to the present embodiment can be manufactured by an injection molding method. Here, the top plate 11 and the legs 12 are integrally molded. The shock-absorbing structure 100 is formed from an elastic material such as NR rubber or thermoplastic elastomer so that the buckled legs 12 are restored and stand upright when they are released from the load. Accordingly, the legs 12 have rubber hardness of 10 to 100, preferably 50 to 80.

[0093] FIG. 11 shows a shock-absorbing property of the shock-absorbing structure 100 (example). In the numerical simulation according to the finite element method, a temporal transition of the load (arbitrary unit) was analyzed which was applied to the femur when a person weighing 40 kg fell over from an upstanding state and struck their femur against the floor surface (i.e. the upper surface of the surface material 120). As a comparative example, the shock-absorbing property of a carpet is also shown. Note that, the carpet was used that included piles made from polyester on the upper surface of a low-resistance urethane layer of approximately 10 mm. In the case of the carpet, the load applied to the femur gradually increases to reach the peak at approximately 0.02 seconds, and then is gradually damped. Here, by the load exceeding a fracture strength (a dash-dotted line) before reaching the peak, the fracture of the femur occurs. On the other hand, in the case of the shock-absorbing structure 100 according to the present embodiment, the load applied to the femur relatively quickly increases to reach the peak at approximately 0.012 seconds, remains constant until 0.02 seconds, and then is gradually damped. It is observed that the peak load is smaller than the peak load in the case of the carpet, and the load does not exceed the fracture strength by the legs 12 buckling before the load reaches the fracture strength.

[0094] With the floor material 200 configured as described above, when the load is applied from the upper surface side of the top plate 11 in the shock-absorbing structure 100 arranged with their legs 12 extending upright on the subfloor S, the legs 12 contract in the Z-axis direction to absorb the load until the load exceeds the threshold load, and once the load exceeds the threshold load, the legs 12 become soft by bending (i.e. buckling) toward the inside of the unit structure 10 and being displaced largely while spreading their convexly-flexed cross-sectional surfaces in the X-Y plane, and after the displacement, the legs 12 further absorb the load by abutting the upper side and the lower side of the outside surface to contract in the Z-axis direction. Accordingly, the floor material 200 is firm against the small load applied during walking, providing stability during walking, and is soft against the large impact upon falling over, allowing for large displacement to absorb the impact.

[0095] The shock-absorbing structure 100 according to the present embodiment includes a top plate 11 including an upper surface to receive a load, and at least one leg 12 that extends in the Z-axis direction from the lower surface of the top plate 11 and has a cross-sectional shape convexly flexed toward one side in the X-Y plane. According to this, when the load is applied from the upper surface side of the top plate 11 in the shock-absorbing structure 100 arranged with their legs 12 extending upright on the subfloor S, the legs 12 contract in the Z-axis direction to absorb the load until the load exceeds the threshold load (the contraction mode), and once the load exceeds the threshold load, the legs 12 become soft (the buckling mode) by bending (i.e. buckling) toward the opposite side and being displaced largely while spreading their convexly-flexed cross-sectional surfaces in the Z-Y plane, and after the displacement, the legs 12 can further absorb the load by abutting the upper side and the lower side of the side surface on the one side to contract in the Z-axis direction.

[0096] The floor material 200 according to the present embodiment includes the surface material 120 and the shock-absorbing structure 100 that supports the surface material 120 and is arranged on the subfloor S. By supporting the surface material 120 by the shock-absorbing structure 100 on the subfloor S, the floor material 200 is firm against the small load applied during walking, providing stability during walking, and is soft against the large impact upon falling over, allowing for large displacement to absorb the impact.

[0097] Note that, the shock-absorbing structure 100 according to the present embodiment is described to include a plurality of unit structures 10, each of which is defined as a constitutional unit that includes the top plate 11 of a rectangular frame shape and four legs 12 each provided near one of four corners of the top plate 11, although it is not limited to this, and the shock-absorbing structure 100 can be described to include a plurality of unit structures 10d (see FIG. 1), each of which is defined as a constitutional unit that includes the top plate 11d of cross shape and four legs 12 each provided near one of four internal corners of the top plate 11d. In such a case, as shown in FIG. 12, each of the four legs 12 extends in the Z direction from the lower surface of the top plate 11d, has a cross-sectional shape convexly flexed toward the inside in the radial direction having a reference point at the center of the top plate 11d (center of the cross) in the X-Y plane, and is arranged at one of four internal corners adjacently near the center of the top plate 11d. Accordingly, a high rigidity can be provided against a force applied in the direction of the X-Y plane by the top plate 11d being supported by the four legs 12 that are arranged adjacently near the center with their convexly-flexed portions facing each other.

[0098] Note that, in the shock-absorbing structure 100 according to the present embodiment, the leg 12 exhibits a hybrid deformation (referred to as a first deformation mode) in which the deformation mode is shifted between the contraction mode against the load smaller than the threshold load and the buckling mode against the load equal to or more than the threshold load, although it is not limited to this, and the leg 12 may exhibit other deformation modes.

[0099] FIG. 13A and FIG. 13B show a second deformation mode (legs-closed mode) of the shock-absorbing structure 100 (unit structure 10). Note that, one unit structure 10 of the plurality of unit structures 10 constituting the shock-absorbing structure 100 is exemplified. The unit structure 10 is installed on the subfloor S as shown in FIG. 9A, and the load is to be applied in this state.

[0100] An upper section and a lower section of FIG. 13A show the unit structure 10 in the legs-closed state in a top view and a side view, respectively. A load is applied downwardly (in the direction of an outlined arrow) from the upper surface side of the top plate 11. However, the load is smaller than a predetermined threshold load. The four legs 12 supporting the top plate 11 tilt at joints to the top plate 11 and deform so as to close their leading ends toward the inside. At this time, the four legs 12 cause the top plate 11 to be lowered downwardly (in the direction of a large black-colored arrow) to some extent to absorb the load by sliding their leading ends in the horizontal direction (in the direction of a small black-colored arrow) on the subfloor S.

[0101] An upper section and a lower section of FIG. 13B show the unit structure 10 in the legs-most-closed state in a top view and a side view, respectively. It is assumed that the load (the white-colored arrow) applied to the top plate 11 has increased to exceed the threshold load (the load may not necessarily exceed the threshold load). The four legs 12 supporting the top plate 11 further tilt at the joints to the top plate 11 and deform so as to close their leading ends toward the inside. Accordingly, the four legs 12 slide their leading ends in the horizontal direction (in the direction of a small black-colored arrow) on the subfloor S and interfere with each other at the center of the unit structure 10. Subsequently, the four legs 12 cause the top plate 11 to be further lowered downwardly (in the direction of the large black-colored arrow) to absorb the load by contracting in the Z-axis direction.

[0102] FIG. 14A and FIG. 14B show a third deformation mode (legs-opening mode) of the shock-absorbing structure 100 (unit structure 10). Note that, one unit structure 10 of the plurality of unit structures 10 constituting the shock-absorbing structure 100 is mainly exemplified. The unit structure 10 is installed on the subfloor S as shown in FIG. 9A, and the load is to be applied in this state.

[0103] An upper section and a lower section of FIG. 14A show the unit structure 10 in the legs-opened state in a top view and a side view, respectively. A load is applied downwardly (in the direction of an outlined arrow) from the upper surface side of the top plate 11. However, the load is smaller than a predetermined threshold load. The four legs 12 supporting the top plate 11 tilt at the joints to the top plate 11 and deform so as to open their leading ends toward the outside. At this time, the four legs 12 cause the top plate 11 to be lowered downwardly (in the direction of the large black-colored arrow) to some extent to absorb the load by sliding their leading ends in the horizontal direction (in the direction of a small black-colored arrow) on the subfloor S.

[0104] An upper section and a lower section of FIG. 14B show the unit structure 10 in the legs-most-opened state in a top view and a side view, respectively. It is assumed that the load (the white-colored arrow) applied to the top plate 11 has increased to exceed the threshold load (the load may not necessarily exceed the threshold load). The four legs 12 supporting the top plate 11 further tilt at the joints to the top plate 11 and deform so as to open their leading ends toward the outside. Accordingly, the four legs 12 slide their leading ends in the horizontal direction (in the direction of the small black-colored arrow) on the subfloor S and interfere with the leading ends of the legs 12 of the adjacent unit structure 10. Subsequently, the four legs 12 cause the top plate 11 to be further lowered downwardly (in the direction of the large black-colored arrow) to absorb the load by contracting in the Z-axis direction.

[0105] Note that, each of the plurality of unit structures 10 constituting the shock-absorbing structure 100 may deform in any of the first to third deformation modes. That is, one or more unit structures 10 may deform in the first deformation mode, another one or more unit structures 10 may deform in the second deformation mode, and still another one or more unit structures 10 may deform in the third deformation mode. In addition, each of the four legs of one unit structure 10 of the plurality of unit structures 10 constituting the shock-absorbing structure 100 may deform in any of the first to third deformation modes. That is, one or more legs 12 of the four legs of one unit structure 10 may deform in the first deformation mode, another one or more legs 12 of the four legs of one unit structure 10 may deform in the second deformation mode, and still another one or more legs 12 of the four legs of one unit structure 10 may deform in the third deformation mode.

[0106] Note that, in the plurality of unit structures 10 constituting the shock-absorbing structure 100 according to the present embodiment, the space 12c opened in the Z-axis direction is formed among the leading ends of the four legs 12, although alternatively, a bottom surface 17 connected to each leading end of the four legs 12 may be provided in such a case in which the body portion of the leg 12 has an appropriate rigidity to spread in the X-Y plane and deform.

[0107] FIG. 15A to FIG. 15E shows a structure of the unit structure 10d2 according to a modification example. The unit structure 10d2 is a minimal constitutional unit that constitutes the shock-absorbing structure 100. Here, FIG. 15A shows an overall structure of the unit structure 10d2 in a perspective view, FIG. 15B shows an internal structure of the unit structure 10d2, partially omitted in a perspective view, FIG. 15C shows a structure of the unit structure 10d2 in a top view, FIG. 15D shows the structure of the unit structure 10d2 in a bottom view, and FIG. 15E shows the structure of the unit structure 10d2 in a side view. The unit structure 10d2 includes a top plate 11, the legs 12, and the bottom surface 17. Here, the top plate 11 and the legs 12 are the same as those described above.

[0108] The bottom surface 17 is a plate-like member that is provided among the leading ends of the respective four legs 12 to form the bottom surface of the unit structure 10d2. The bottom surface 17 includes a central portion 17a and four joint portions 17b.

[0109] The central portion 17a is located at the center of the four legs 12 in the top view, and has a size and shape that roughly closes the inner space of the unit structure 10d2. In the present example, the central portion 17a has a rectangular shape and its four corners are arranged to be adjacent to the leading ends of the respective four legs 12.

[0110] Each of the four joint portions 17b joins each corner of the central portion 17a to each leading end of the adjacent legs 12. As an example, the joint portion 17b has a width that is equal to the width of the leading end of the leg 12 when viewed in the direction in which the joint portion 17b extends from the corner of the central portion 17a. Accordingly, a slit 17c connected to the gap 12b is formed between the two joint portions 17b adjacent to each other among the four joint portions 17b.

[0111] The bottom surface 17 has a substantially cross shape by including the central portion 17a and the four joint portions 17b in the top view. Particularly, by providing the appropriately sized central portion 17a, the unit structure 10d2 can be adhered and fixed to the subfloor S (see FIG. 10). In addition, by providing the bottom surface 17, an influence of friction with the subfloor S can be avoided and the deformation mode of the unit structure 10 can be limited to the contraction and buckling mode only (see FIG. 9A to FIG. 9D).

[0112] FIG. 16 shows a structure of the sliding rib 13 in the unit structure 10d2 according to the modification example. The sliding rib 13 is provided on the outermost unit structure 10d2 of the plurality of unit structures 10d2 constituting the shock-absorbing structure 100. The configuration of the sliding rib 13 is the same as that described above. By utilizing the end surface 13a and the inclined surface 13b of unit structures 10d2, it is possible, as described above, to position the plurality of shock-absorbing structures 100 in the lateral direction and to array them on the subfloor S so that their upper surfaces of the top plates 11 are flush with each other.

[0113] Note that, in the unit structure 10d2 according to the modification example, the reinforcement rib 14 may also be provided between the two adjacent unit structures 10d2 of the plurality of unit structures 10d2 constituting the shock-absorbing structure 100 (see FIG. 6A and FIG. 6B). Accordingly, the rigidity of the leg 12 can be adjusted.

[0114] FIG. 17A shows a structure of the engagement member 25 in the unit structure 10d2 according to the modification example in a perspective view. Note that, the engagement member 25 can be provided on the outer edge (+X edge, X edge, +Y edge, or Y edge) of any outermost unit structure 10d2 of the shock-absorbing structure 100. The engagement member 25 includes a base 25c, an extension portion 25b, and a leading end portion 25a.

[0115] The base 25c is a block-like member to fix the engagement member 25 to the unit structure 10d2, and as an example, it extends from immediately below the middle of the overhang portion 11b on the X side of the top plate 11 to the upper part of the gap 12b between the two legs 12 adjacent to each other on the X side, and is molded integrally with the top plate 11 and the two legs 12.

[0116] The extension portion 25b is a prism-like member that extends toward the outside of the top plate 11 in the X direction from between the two legs 12, that is, from the X surface of the base 25c, as it is provided between the two legs 12 in the present example, to support the leading end portion 25a. The width of the extension portion 25b associated with the Y-axis direction is smaller than the minimum width w.sub.12 of the gap 12b. In addition, the length of the extension portion 25b associated with the X-axis direction is slightly larger than the frame width of the top plate 11 in the top view. Note that, the extension portion 25b may not be limited to have a prism shape but may have a columnar body of any shape such as a cylindrical shape.

[0117] The leading end portion 25a is a member that engages with the two legs 12 of another unit structure 10d2, is fixed to the X edge of the extension portion 25b and has a shape widened in both +Y directions. The width of the leading end portion 25a in the Y-axis direction is larger than the minimum width W.sub.12 of the gap 12b.

[0118] FIG. 17B shows a state in which the unit structure 10d2 according to the modification example is joined by the engagement member 25 to the unit structure 10d2 included in another shock-absorbing structure 100, in a side view. First, the unit structure 10d2 is turned by 90 degrees in the Y-Z plane relative to the unit structure 10d2 to orient the leading end portion 25a of the engagement member 25 in the Z-axis direction. Then, an end of one side of the leading end portion 25a is inserted into the slit 17c of the unit structure 10d2 in the +Z direction, the extension portion 25b is moved to the upper part of the gap 12b connected to the slit 17c, and the leading end portion 25a is entirely put into the inner space of the unit structure 10d2. Finally, the unit structure 10d2 is turned by 90 degrees in the Y-Z plane and arranged so that its top plate 11 is flush with that of the unit structure 10d2. Accordingly, the unit structure 10d2 is joined to the unit structure 10d2 by the engagement member 25 of the unit structure 10d2 being engaged with the two legs 12 of the unit structure 10d2.

[0119] Note that, the shock-absorbing structure 100 may be configured to include both the unit structure 10 and the unit structure 10d2 according to the modification example. In other words, a part of the plurality of unit structures constituting the shock-absorbing structure 100 may be the unit structures 10 each of which has four legs 12 of free end, while the rest of the plurality of unit structures may be the unit structures 10d2 according to the modification example, each of which is provided with the bottom surface 17 among the leading ends of the four legs 12.

[0120] While the present invention has been described above by using the embodiments, the technical scope of the present invention is not limited to the scope of the above-described embodiments. It is apparent to persons skilled in the art that various alterations or improvements can be made to the above described embodiments. It is also apparent from the described scope of the claims that the embodiments added with such alterations or improvements can be included the technical scope of the present invention.

[0121] It is noted that the operations, procedures, steps, stages, or the like of each process performed by a device, system, program, and method shown in the claims, specifications, or drawings can be performed in any order as long as the order is not indicated by prior to, before, or the like and as long as the output from a previous process is not used in a later process. Even if the process flow is described using phrases such as first or next in the claims, specifications, or drawings, it does not necessarily mean that the process must be performed in this order.

Explanation of References

[0122] 10, 10a, 10b, 10d, 10d2 . . . unit structure, 11, 11d . . . top plate, 11a . . . opening, 11b . . . overhang portion, 12 . . . leg, 12a . . . concave portion, 12b . . . gap, 12c . . . space, 13 . . . sliding rib, 13a . . . end surface, 13b . . . inclined surface, 14 . . . reinforcement rib, 15 . . . claw portion, 15a, 15b . . . grooved portion, 16 . . . claw-reception portion, 16a . . . space, 16b . . . step portion, 16c, 16e . . . engagement block, 16d . . . block body, 17 . . . bottom surface, 17a . . . central portion, 17b . . . joint portion, 17c . . . slit, 25 . . . engagement member, 25a . . . leading end portion, 25b . . . extension portion, 25c . . . base, 100 . . . shock-absorbing structure, 110 . . . intermediate material, 120 . . . surface material, 200 . . . floor material, S . . . subfloor.