Cushion structure and bathroom chair equipped therewith

Abstract

In the field of cushions made of synthetic resin foam, the objective is to provide a cushion structure that can achieve sufficient fit, cushioning, and pressure distribution to conform to the shape of the human body, such as the buttocks and thighs, while keeping the thickness of the cushion to a minimum. [Solution] According to the present invention, a cushion structure made of synthetic resin foam and a bathroom chair equipped therewith are provided, characterized in that the cushion structure comprises a top plate portion having a flat surface portion and a back portion, and a periphery portion that protrudes downward from the peripheral edge of the top plate portion and is formed to surround the four sides of the top plate portion, and a space is formed below the top plate portion that allows the top plate portion to bend downward due to the support of the periphery portion.

Description

Technical Field

[0001] The present invention relates to a cushion structure and a bathroom chair provided with the same, and particularly to a cushion structure made of a synthetic resin foam in which a peripheral dike portion protruding downward from the peripheral edge portion of the top plate portion of the cushion structure forms a space portion that allows the top plate portion to bend downward inside the peripheral dike portion, and a bathroom chair provided with the same.

Background Art

[0002] With the advent of an aging society, in order to assist the movements of the elderly and care recipients in the bathroom and bathtub, for example, as described in Japanese Unexamined Patent Application Publication No. 2023-56839 (Patent Document 1) and Japanese Unexamined Patent Application Publication No. 2018-15418 (Patent Document 2), there are known folding bathroom chairs and bathtub chairs with cushions made of foamed resin attached to the surface of the seat part and / or the backrest part.

[0003] By intervening between the contact surface of a human's buttocks and thighs and the seat part of a chair or the like, the cushion functions to relieve the impact from the seat part transmitted to the body such as the buttocks and to disperse the body pressure transmitted from the seat part to the buttocks and the like, making the sitting comfort good. Therefore, as a material for a cushion generally intended to be used in a bathroom or a bathtub, a flexible and water-resistant foamed resin is used, which is different from the seat part and backrest that are often formed of hard materials.

[0004] By the way, in order to make the sitting comfort of a cushion made of the above-mentioned foamed resin good, it is important to select an appropriate hardness and thickness of the cushion. Especially when the users of the cushion are the elderly and care recipients as assumed in Patent Documents 1 and 2, since their muscles and subcutaneous fat are thin, it is extremely important to select an appropriate hardness and thickness of the cushion so as not to cause damage such as rubbing, internal bleeding, and bruising to the buttocks and the like.

[0005] Furthermore, it is generally believed that to improve the comfort of a cushion, it is effective to increase its flexibility and fit by making it softer and thicker. This is because the softer the cushion and the thicker it is, the deeper the user's buttocks and thighs sink into the cushion, and the pressure on the contact surface with these areas is distributed, resulting in the cushion being able to support the user with lower pressure (reaction force).

[0006] However, many foamed resins, such as those used in the cushions described in Patent Documents 1 and 2, are known to shrink over time due to deterioration, and must be replaced periodically (see Patent Document 2). However, if the hardness of the cushion is softened and the thickness is increased for purposes such as improving the comfort of the cushion, it not only leads to increased costs due to increased weight, but also exacerbates the shrinkage of the cushion due to deterioration over time, resulting in the inconvenience of having to replace the cushion on a shorter cycle.

[0007] Therefore, as a method to improve the seating comfort of a cushion without changing its hardness or thickness, cushion structures such as those described in International Publication No. 2014 / 203891 (Patent Document 3) and Japanese Patent Application Publication No. 2021-45417 (Patent Document 4) have been developed.

[0008] The cushion structure described in Patent Document 3 improves the cushioning and fit of the cushion by providing a space below a support made of synthetic resin foam having a predetermined bending rigidity, and arranging the support in a row so that it can bend and deform downwards.

[0009] However, the cushion structure described in Patent Document 3 is a double-ended support beam structure in which both ends of a rod-shaped support (cushion) are supported from below by a pair of legs. Therefore, the deflection of the support, which is adjusted to improve the comfort of the cushion, is limited to deformation along a two-dimensional plane (vertical cross-section) including the support and the pair of legs, and it is almost impossible to deflect or deform in directions other than the aforementioned two-dimensional plane. As a result, the cushion structure described in Patent Document 3 cannot deflect or deform in all directions to conform to the three-dimensional shape of a person's buttocks, thighs, etc., and cannot obtain sufficient fit. In particular, it has the problem that it is not possible to improve the comfort of the cushion by distributing the body pressure transmitted from the seat to the buttocks, etc.

[0010] The cushion structure described in Patent Document 4 has a recess consisting of an annular groove in the center of the bottom surface and a protrusion in the center of the recess. When the recess is compressed and sinks due to sitting, the central protrusion rises relatively and contacts the perineum of the sitter from below, thereby improving the hold on the buttocks.

[0011] However, the cushion structure described in Patent Document 4 has the problem that the mold shape becomes complex and the manufacturing cost increases because the recess must be provided to correspond to the position of the seated person's ischial tuberosity and the protrusion must be provided to correspond to the position of the seated person's perineum. In addition, since the position of the ischial tuberosity and the perineum differs from person to person, there is a problem that it cannot be made suitable for everyone, including elderly people with reduced muscle and subcutaneous fat. [Prior art documents] [Patent Documents]

[0012] [Patent Document 1] Japanese Patent Publication No. 2023-56839 [Patent Document 2] Japanese Patent Publication No. 2018-15418 [Patent Document 3] International Publication No. 2014 / 203891 [Patent Document 4] Japanese Patent Publication No. 2021-45417 [Overview of the Initiative] [Problems that the invention aims to solve]

[0013] As mentioned above, making cushions softer or thicker to improve their comfort not only increases costs but also creates the problem of requiring cushion replacement at shorter intervals due to accelerated deterioration (shrinkage) over time.

[0014] Furthermore, in methods that enhance cushioning by supporting both ends of the cushion with a double-ended support beam structure, as described in Patent Document 3, the cushion cannot bend and deform in a specific direction, which is problematic because the cushion cannot flex in all directions to conform to the shape of a person's buttocks and thighs, thus failing to provide sufficient fit and pressure distribution.

[0015] Furthermore, in a method like the cushion structure described in Patent Document 4, where a protrusion is provided in the center of a circle and an annular recess is provided around it, and the recess is compressed when someone sits on it, causing the protrusion to rise relatively to fit the user's body shape, there is a problem in that the position of the ischial tuberosity and the perineum differs from person to person, making it impossible to make the cushion suitable for everyone.

[0016] Therefore, the present invention aims to provide a cushion structure that, in the field of cushions made of synthetic resin foam, can achieve sufficient fit, cushioning, and pressure distribution by conforming to the shape of the human body, such as the buttocks and thighs, while keeping the thickness of the cushion low. [Means for solving the problem]

[0017] The inventors of the present invention have diligently studied the fit, cushioning properties, and cushion structures that can enhance these properties of cushions made of synthetic resin foam. As a result, they have found that by providing the cushion with a top plate and a periphery that supports the top plate from its edges, the directionality of the deflection of the top plate is eliminated, allowing the top plate to deflect and deform in all directions, thereby solving the above problems and completing the present invention.

[0018] In other words, the present invention provides a cushion structure made of synthetic resin foam and a bathroom chair equipped therewith, characterized in that it comprises a top plate portion having a flat surface portion and a back portion, and a periphery portion that protrudes downward from the peripheral edge of the top plate portion and is formed to surround the four sides of the top plate portion, and a space is formed beneath the top plate portion that allows the top plate portion to flex downward due to the support of the periphery portion.

[0019] In the cushion structure of the present invention, the top plate is supported by a periphery that protrudes downward from its edge, surrounding all four sides of the top plate. When a user sits down, the top plate flexes and deforms in all directions to envelop the user's buttocks and thighs, resulting in a high degree of fit, and the high pressure distribution and cushioning provided by this fit. Furthermore, since the space formed beneath the top plate is open, the cushion structure of the present invention does not generate a high rebound force like an air cushion that exceeds the properties of the material, and the top plate can flex and deform sufficiently to conform to the shape of the user's buttocks and thighs. As a result, the cushion structure of the present invention can provide a good sitting experience while keeping the thickness of the cushion (top plate) to a minimum.

[0020] The top plate portion can be bent and deformed in all directions without choosing the bending direction inside the peripheral dike portion as long as it is supported by the peripheral dike portion so that substantially all four sides of the top plate portion are surrounded, whether continuous or discontinuous. Therefore, the peripheral dike portion does not necessarily need to be continuously formed over the entire circumference of the top plate portion. However, in order to make the bending deformation of the top plate portion in all directions more reliable and further prevent unnecessary substances such as dust and water from entering the space under the top plate portion from the outside of the cushion structure, it is preferable that the peripheral dike portion is formed over the entire circumference of the peripheral edge portion of the top plate portion.

[0021] In the present invention, on the back surface portion of the top plate portion of the cushion structure, convex portions may be provided locally so as to protrude downward from the surface of the back surface portion to reduce the bending allowance of the top plate portion in the space portion.

[0022] If the space under the top plate portion is too wide, the top plate portion itself will bend due to its own weight and it will not be possible to ensure sufficient bending allowance or sinking amount. Or when a user sits, the top plate portion will immediately collide with the seating surface such as a chair or a floor on which the cushion structure is installed, giving the user an uncomfortable feeling of having a bottom (feeling the shape and hardness of the seating surface). Therefore, by providing convex portions at appropriate positions on the back surface portion of the top plate portion to increase or decrease the substantial width of the space portion, the sinking amount and the repulsive force of the top plate portion can be changed, so that the fit and cushioning properties of the cushion structure can be adjusted. Also, by arranging convex portions on the back surface portion of the top plate portion, it is possible to intentionally form a portion with high cushioning properties and a portion without such properties in the top plate portion. Therefore, if convex portions are provided in the region where the buttocks hit, it is possible to effectively prevent giving the user an uncomfortable feeling of having a bottom.

[0023] There is no particular limitation on the shape of the convex portion, and it can be a plate-like body such as a rib and / or a columnar body such as a boss. However, in order to make the seating comfort of the cushion good by enabling the top plate portion to be bent and deformed in all directions, it is preferable that the protruding height of the convex portion is the same as the protruding height of the peripheral dike portion or lower than the protruding height of the peripheral dike portion.

[0024] In the present invention, in order to prevent foreign matters such as dust and water from entering the space part, the back surface part of the top plate part may be covered with a resin sheet so that the space part becomes a closed space. However, in order to obtain high cushioning properties, etc., it is not always desirable to make the space part a completely sealed space and function like an air cushion. Therefore, it is preferable to provide air vent holes or the like in the resin sheet covering the back surface part of the top plate part that allow air to enter and escape.

[0025] The synthetic resin foam forming the cushion structure can use elastomer materials such as PP (polypropylene) resin, PE (polyethylene) resin, bead foam, AS (acrylonitrile / styrene) resin, EVA (ethylene vinyl acetate copolymer) resin or urethane resin, etc. However, considering the properties such as cushioning property, flexibility, water resistance, and moldability of the material itself, it is preferable to use EVA resin.

[0026] Also, in the present invention, a second synthetic resin foam formed from the above resin material different from the cushion structure may be inserted into the space part of the cushion structure to adjust the cushioning property, body pressure dispersion property, etc. of the top plate part.

[0027] The cushion structure of the present invention can be installed on the floor or the like and used alone, or it may be used by being attached to a seating part such as a chair. Especially in the latter case, the cushion structure of the present invention has high fitting property, high body pressure dispersion property and cushioning property brought by the fitting property, and high water resistance can be obtained by using EVA resin as the material. Therefore, the above-described cushion structure of the present invention is suitable for use in a bathroom chair having a seating part body. Also, in order to make it possible to easily attach and detach the cushion structure to and from the seating part body, it is preferable to provide two or more circular fitting holes on the seating part body side of the bathroom chair, and provide a boss part on the cushion structure side that protrudes downward from the back surface part of the top plate part and fits into the fitting hole of the seating part body. Also, in order to effectively use the limited space, the boss part may be formed so as to overlap with the peripheral dike part of the back surface part of the top plate part and protrude downward from the lower surface (contact surface with the seating part body, etc.) of the peripheral dike part. [Effects of the Invention]

[0028] The present invention provides a cushion structure made of synthetic resin foam, comprising a top plate portion having a flat surface portion and a back portion, and a periphery portion that protrudes downward from the peripheral edge of the top plate portion and is formed to surround the top plate portion on all four sides, wherein a space is formed beneath the top plate portion that allows the top plate portion to flex downward due to support by the periphery portion.

[0029] According to the present invention, the top plate portion of the cushion structure is supported by a periphery portion that protrudes downward from its peripheral edge, surrounding all four sides of the top plate portion. When a user sits down, the top plate portion flexes and deforms in all directions to envelop the user's buttocks and thighs, resulting in a high degree of fit, and the high pressure distribution and cushioning provided by this fit. As a result, the cushion structure of the present invention can provide a good sitting experience while keeping the thickness of the cushion (top plate portion) to a minimum. [Brief explanation of the drawing]

[0030] [Figure 1] This is a top-down perspective view of a cushion structure and a bathroom chair equipped therewith according to one embodiment of the present invention. [Figure 2] Figure 1 is a perspective view of the bathroom chair shown from below. [Figure 3] Figure 1 is a top-down perspective view of the bathroom chair, showing the cushion structure and seat body separated. [Figure 4] Figure 3 is a perspective view from below of the cushion structure and seat body of the bathroom chair shown. [Figure 5] Figures 3 and 4 show (a) a plan view and (b) a front view of the cushion structure. [Figure 6] Figures 3 and 4 show (a) a bottom view and (b) a side view of the cushion structure. [Figure 7] Figure 5 is a cross-sectional view of the cushion structure shown in Figure 5. [Figure 8] Figure 5 is a cross-sectional view of the cushion structure shown in the diagram. [Figure 9] Figure 1 is a cross-sectional view AA of the cushion structure and seat body of the bathroom chair shown. [Figure 10] Figure 1 is a cross-sectional view of the cushion structure and seat body of the bathroom chair shown in Figure 1. [Figure 11] This shows the pressure distribution on the buttocks of a specific subject when they sit on each of the cushion structures of Example 1 and Comparative Examples 1 and 2. [Figure 12] The pressure distribution shown is the pressure exerted on the buttocks of a specific subject when they sit on the cushion structures of Comparative Examples 3 and 4, and, as a reference example, on the seat body of a chair (without the cushion structure). [Modes for carrying out the invention]

[0031] A cushion structure and a bathroom chair equipped therewith according to one embodiment of the present invention will be described in detail below with reference to the drawings. It should be noted that the present invention is not limited to the embodiments shown below, and various modifications are possible without departing from the technical spirit of the invention.

[0032] <Bathroom chair with cushioning structure> The cushion structure 3 according to one embodiment of the present invention can be installed on the floor or the like and used independently. Furthermore, the cushion structure 3 of this embodiment can be attached to the seat of a general chair or the like if a space 32 is formed beneath the top plate portion 30 of the cushion structure 3 in the installed state, allowing the top plate portion 30 to flex. In particular, the cushion structure 3 of this embodiment has a high degree of fit, and the high pressure distribution and cushioning properties provided by this fit, and if a resin such as EVA is used as the material, high water resistance can also be obtained, so it is suitable for use in a bathroom chair 1 used to assist the movements of the elderly or those requiring care in a humid bathtub. For this reason, in this embodiment, the cushion structure 3 of the present invention will be mainly described as a bathroom chair 1 equipped with it, but the forms of use of the cushion structure 3 of the present invention are not limited to that.

[0033] Figure 1 shows a top-down perspective view of a cushion structure 3 and a bathroom chair 1 equipped therewith according to one embodiment of the present invention, and Figure 2 shows a bottom-up perspective view of the bathroom chair 1 shown in Figure 1.

[0034] As shown in Figures 1 and 2, the bathroom chair 1 of this embodiment consists of a seat 2, a backrest 4, armrests 5, and legs 6. The legs 6 include a pair of front leg frames 60 that extend upward from below and support the back of the backrest 4, and a pair of rear leg frames 61 that are rotatably connected to the front leg frames 60 and extend upward from below to rotatably support the back of the seat 2. An armrest 5 is rotatably attached to each of the pair of front leg frames 60.

[0035] The front leg frame 60 and the rear leg frame 61 are both formed from hollow metal pipes, but the material is not limited to this. Sleeve-shaped movable front leg parts 600 and 610 are slidably mounted on the outer circumference of the front leg portion of the front leg frame 60 and the outer circumference of the rear leg portion of the rear leg frame 61, respectively, allowing adjustment of the length of the legs of the front leg frame 60 and the rear leg frame 61, in other words, the height of the seat 2. In addition, a resin cap 611 is attached to the tip of the movable rear leg part 610 to prevent scratching the floor and slipping, and a resin cap 601 with a roller is attached to the movable front leg part 600, which has a contact surface and rollers to prevent scratching the floor and slipping, as well as to facilitate opening and closing the legs of the bathroom chair 1.

[0036] By adopting the above configuration, the bathroom chair 1 of this embodiment can open and close the front leg frame 60 and the rear leg frame 61 between an open leg state where they are spaced apart from each other and a closed leg state where they are close together. In conjunction with the movement of the front leg frame 60 and the rear leg frame 61, the seat 2 can be rotated between a substantially horizontal unfolded state and a substantially vertical folded state. It should be noted that the bathroom chair 1 of this embodiment is merely an example, and the seat 2 may be a bathroom chair 1 without a backrest 4, or a bath chair that is normally used by being immersed in a bathtub, as long as it includes a seat body 20 and a cushion structure 3 that can be detachably attached to the seat body 20.

[0037] Figure 3 shows a top-down perspective view of the bathroom chair 1 shown in Figure 1, with the cushion structure 3 and seat body 20 separated, while Figure 4 shows a bottom-up perspective view of the bathroom chair 1 shown in Figure 3, with the cushion structure 3 and seat body 20.

[0038] As shown in Figures 3 and 4, the seat portion 2 of the bathroom chair 1 in this embodiment consists of a seat body 20 and a cushion structure 3 that is detachably attached to the upper surface of the seat body 20.

[0039] The seat body 20 is a hollow component made of polyethylene resin, taking into consideration water resistance and chemical resistance, but the material is not limited to this. The upper surface of the seat body 20 has a flat shape, and circular fitting holes 21 are formed at its four corners, penetrating the seat body 20 to receive the boss portions 34 of the cushion structure 3, which will be described later. Note that the fitting holes 21 do not necessarily have to penetrate the seat body 20, and may be recesses that can receive the boss portions 34. In addition, the upper surface of the seat body 20 has a "V" shaped drain groove 22 that is aligned to communicate with the drain holes 35 provided in the cushion structure 3 when the cushion structure 3 is attached, and drain holes 23 that communicate with the drain groove 22 and penetrate the seat body 20 are formed at both ends of the groove. Furthermore, a roughly rectangular cutout handle portion 24 is formed at the rear of the seat body 20 (the side closer to the backrest portion 4) for gripping when carrying the bathroom chair 1.

[0040] The backrest portion 4 of the bathroom chair 1 in this embodiment consists of a backrest body 40 and a flat backrest cushion 41 that is detachably attached to the surface of the backrest body 40.

[0041] The backrest body 40, like the seat body 20, is a hollow component made of polyethylene resin, taking into consideration water resistance and chemical resistance, but the material is not limited to this. The backrest body 40 has a small, curved, smooth surface, and circular backrest through holes 42 are formed at both ends to receive the backrest boss portion 410 of the backrest cushion 41 (see Figure 2).

[0042] The backrest cushion 41, like the cushion structure 3 of the seat 2, is made of EVA resin (ethylene vinyl acetate copolymer resin) with consideration for flexibility and water resistance, but the material is not limited to this. The backrest cushion 41 has a flat plate shape, and backrest boss portions 410 are formed at both ends of its back surface, protruding away from the back surface in accordance with the backrest through-holes 42 of the backrest body 40 described above.

[0043] <Cushion structure> Figure 5 shows (a) a plan view and (b) a front view of the cushion structure 3 shown in Figures 3 and 4, and Figure 6 shows (a) a bottom view and (b) a side view of the cushion structure 3 shown in Figures 3 and 4. Furthermore, Figure 7 shows a cross-sectional view (CC) of the cushion structure 3 shown in Figure 5, and Figure 8 shows a cross-sectional view (DD) of the cushion structure 3 shown in Figure 5.

[0044] The cushion structure 3 of this embodiment is formed from EVA resin (ethylene vinyl acetate copolymer resin) considering its high flexibility and water resistance, but the material is not limited to this. Other materials that can be used for the cushion structure 3 of this embodiment include PP (polypropylene) resin, PE (polyethylene) resin, bead foam, AS (acrylonitrile / styrene) resin, or urethane resin.

[0045] As shown in Figures 5-8, the cushion structure 3 of this embodiment comprises a top plate portion 30 having a flat surface portion 301 and a back portion 302, and a periphery portion 31 that protrudes downward from the peripheral edge portion 300 of the top plate portion 30 and is formed to surround the top plate portion 30 on all four sides. In this invention, "flat" of the top plate portion (front and back surfaces) does not mean a perfectly flat surface in the strict sense, but rather it is sufficient that the overall surface is flat enough to ensure a space 32 is maintained below the top plate portion 30 even when it flexes under its own weight, supported by the periphery portion 31. Therefore, as long as the overall surface is flat, it may have, for example, a mortar-shaped curved surface overall, or a surface with localized irregularities or openings.

[0046] The cushion structure 3 of this embodiment has boss portions 34 (Figures 6-8) at the four corners of its back surface 302 that protrude downward from the back surface 302 and fit into the fitting holes 21 of the seat body 20 when the cushion structure 3 is attached to the seat body 20. Furthermore, the back surface 302 has a substantially rectangular handle recess 36 (Figures 6(a), 8) at a position aligned with the handle portion 24 of the seat body 20. In addition, the rear part of the cushion structure 3 (the side closer to the backrest portion 4 of the bathroom chair 1) has a drain hole 35 (Figure 5(a)) for draining water accumulated on the upper surface of the cushion structure 3.

[0047] Figure 9 shows a cross-sectional view AA of the cushion structure 3 and seat body 20 of the bathroom chair 1 shown in Figure 1, and Figure 10 shows a cross-sectional view BB of the cushion structure 3 and seat body 20 of the bathroom chair 1 shown in Figure 1.

[0048] As can be understood by referring to Figures 9 and 10, the top plate portion 30 of the cushion structure 3 of this embodiment is supported by the circumferential portion 31, and a space 32 is formed below the top plate portion 30 and inside the circumferential portion 31, which allows the top plate portion 30 to bend downward.

[0049] As described above, in the cushion structure 3 of this embodiment, the top plate portion 30 is supported by a periphery portion 31 that protrudes downward from its peripheral edge portion 300 so as to surround all four sides of the top plate portion 30. Therefore, when a user sits down, the top plate portion 30 of the cushion structure 3 flexes and deforms in all directions to envelop the user's buttocks and thighs, providing a high degree of fit and resulting in high pressure distribution and cushioning. Furthermore, since the space portion 32 formed below the top plate portion 30 of the cushion structure 3 of this embodiment is open, it does not generate a high rebound force like an air cushion that is basically beyond the properties of the material, and the top plate portion 30 can flex and deform sufficiently to conform to the shape of the user's buttocks and thighs. As a result, the cushion structure 3 of this embodiment can provide good seating comfort while keeping the thickness of the cushion (top plate portion 30) down.

[0050] In this embodiment, the top plate portion 30 can bend and deform in all directions without choosing a direction of bending inside the periphery portion 31, as long as it is supported by the periphery portion 31 so that it is substantially surrounded on all four sides by the periphery portion 31, whether continuous or discontinuous. Therefore, the periphery portion 31 does not necessarily need to be formed continuously around the entire circumference of the top plate portion 30. Furthermore, there are no particular restrictions on the width dimension of the periphery portion 31; it should be a width dimension that allows the top plate portion 30 supported by the periphery portion 31 to form a space 32 into which it can bend downwards. However, in order to make the bending deformation of the top plate portion 30 in all directions more reliable, and to prevent unwanted objects such as dirt and water from entering the space 32 under the top plate portion 30 from outside the cushion structure 3 when it is attached to the seat body 20, it is preferable that the periphery portion 31 is formed around the entire circumference of the peripheral edge portion 300 of the top plate portion 30, as in this embodiment (Figure 6(a)).

[0051] The boss portion 34 provided on the underside 302 of the top plate portion 30 facilitates the attachment and detachment of the cushion structure 3 to the seat body 20, and after attachment, it functions to prevent the cushion structure 3 from shifting or detaching from the seat body 20. Furthermore, as shown in Figures 9 and 10, the boss portion 34 must maintain a space 32 between the top plate portion 30 and the seat body 20 even after being fitted into the fitting hole 21 of the seat body 20. For this reason, the protruding height of the boss portion 34 is formed to be higher than the protruding height of the perimeter portion 31, as shown in Figures 7 and 8, that is, the lowest end of the boss portion 34 is positioned below the lowest end of the perimeter portion 31.

[0052] Furthermore, when a user sits down, the boss portion 34 may be pressed down from above and excessively enter the fitting hole 21 of the seat body 20, potentially preventing it from returning to its original position while maintaining a low height in the space portion 32. For this reason, although not shown in the figures, the boss portion 34 may be made conical in shape to prevent it from excessively entering the fitting hole 21 even when pressed, or a step may be provided at its boundary to widen the diameter near the base beyond the diameter of the fitting hole 21. In addition, to make effective use of the limited space on the back surface 302 of the top plate portion 30, the boss portion 34 may be provided so as to overlap the circumferential ridge portion 31 formed on the back surface 302 and protrude downward from the lower surface of the circumferential ridge portion 31 (the contact surface with the seat body, etc.).

[0053] Furthermore, if the cushion structure 3 of this embodiment is not used by being attached to a specific chair equipped with a fitting hole 21 that engages with the boss portion 34, as is the bathroom chair 1 of this embodiment, but rather is used as a standalone unit placed on the floor or the seat of a general chair, then the boss portion 34 does not need to be provided on the back surface 302 of the cushion structure 3.

[0054] As shown in Figure 4, in this embodiment, the back surface 302 of the top plate portion 30 of the cushion structure 3 may be provided with a protrusion 33 that locally protrudes downward from the surface of the back surface 302, thereby limiting the height of the space portion 32 and reducing the deflection allowance of the top plate portion 30 in the space portion 32. However, the protrusion 33 is omitted in drawings other than Figure 4.

[0055] If the space 32 beneath the top plate 30 is too wide, the top plate 30 itself will sag under its own weight, preventing it from having sufficient flexibility and sinking depth. Alternatively, when a user sits down, the top plate 30 will immediately collide with the seat surface of the chair or floor on which the cushion structure 3 is installed, giving the user an unpleasant feeling of bottoming out (feeling the shape and hardness of the seat). Therefore, by increasing or decreasing the effective size of the space 32 by providing protrusions 33 at appropriate positions on the underside 302 of the top plate 30, the amount of sinking and rebound force of the top plate 30 can be changed, thereby adjusting the fit and cushioning of the cushion structure 3. Furthermore, by placing protrusions 33 on the underside 302 of the top plate 30, it is possible to intentionally create areas with high cushioning and areas without cushioning within the top plate 30. In particular, by providing protrusions 33 in areas where the buttocks make contact, it is possible to effectively prevent the user from feeling the bottoming out.

[0056] There are no particular limitations on the shape of the protrusion 33, and it may be a flap-like body such as a rib and / or a columnar body such as the boss portion 34 described above. The columnar body also includes a weight-shaped cylinder or prism with a tapered shape in the vertical direction. However, in order to improve the seating comfort of the cushion structure 3 by allowing the top plate portion 30 to flex and deform in all directions, it is preferable that the protruding height of the protrusion 33 is the same as the protruding height of the perimeter portion 31, or lower than the protruding height of the perimeter portion 31. That is, it is preferable that the lowest end of the protrusion 33 is at the same level as the lowest end of the perimeter portion 31, or is formed above the lowest end of the perimeter portion 31 on the side closer to the top plate portion 30.

[0057] In this embodiment, in order to prevent unwanted materials such as dust and water from entering the space 32, the underside 302 of the top plate 30 may be covered with a resin sheet (not shown) so that the space 32 becomes a closed space. However, in order to obtain a high level of cushioning, it is not necessarily desirable to make the space 32 a completely sealed space that functions like an air cushion. For this reason, it is preferable to provide air vents (not shown) that allow air to enter and leave the resin sheet covering the underside 302 of the top plate 30.

[0058] Furthermore, in this embodiment, a second synthetic resin foam, formed from a resin material different from that of the cushion structure 3, may be inserted into the space 32 of the cushion structure 3 to adjust the cushioning properties and pressure distribution of the top plate portion 30. [Examples]

[0059] <Fabrication and evaluation of cushion structures> The cushion structures of the embodiment and comparative example of the present invention were fabricated, and the pressure distribution on the buttocks of a subject when they sat down was measured and evaluated. The results will be described in detail below.

[0060] 1. Fabrication of the cushion structure [Example 1] A cushion structure of Embodiment 1 was manufactured that fits the seat body of a bathroom chair (product name: Rakuraku Open / Close Shower Bench CN, manufactured by Aron Kasei Co., Ltd.), and has a top plate portion with a thickness of approximately 16 mm and a top plate portion having the same planar shape as the seat body of the bathroom chair (maximum width: 37 mm, maximum depth: 33 mm), and the back surface of the top plate portion has a perimeter portion with a width of approximately 5 mm and a height of approximately 16 mm formed around its entire edge, and four boss portions with a diameter of approximately 30 mm and a height of approximately 20 mm formed at positions aligned with the fitting holes of the seat body. In other words, in the cushion structure of Embodiment 1, the perimeter portion is installed (placed) on the seat surface of the seat body, so the top plate portion is supported by the perimeter portion, and a space is formed beneath the top plate portion that allows the top plate portion to flex. Furthermore, to prevent the cushion structure of Example 1 from bending, it was placed directly on the test stand without the surrounding rim, and the hardness of the top plate was measured at 5 points using an Asker rubber hardness tester Type E (manufactured by Polymer Instruments Co., Ltd.). The average value was 36.

[0061] [Comparative Example 1] A cushion structure for Comparative Example 1 was fabricated with the same configuration as the cushion structure for Example 1, except that a perimeter was not formed on the underside of the top plate. In other words, the cushion structure of Comparative Example 1 is in close contact with the seat body of the bathroom chair, and no space is formed between the top plate and the seat body. Furthermore, when the cushion structure of Comparative Example 1 was attached to the seat of a bathroom chair, the average hardness of the top surface was measured at 5 points using an Asker rubber hardness tester Type E (manufactured by Polymer Instruments Co., Ltd.), and the average value was 36.

[0062] [Comparative Example 2] A cushion structure of Comparative Example 2 was fabricated with the same configuration as the cushion structure of Comparative Example 1, except that the thickness of the top plate was doubled to approximately 32 mm by laminating another cushion structure of Comparative Example 1 without a boss portion on top of the cushion structure of Comparative Example 1. In other words, the cushion structure of Comparative Example 2 is in close contact with the seat body of the bathroom chair, and no space is formed between the top plate and the seat body. Furthermore, when the cushion structure of Comparative Example 2 was attached to the seat body of a bathroom chair, the average hardness of the top plate (two top plates from Comparative Example 1) was measured at 5 points using an Asker rubber hardness tester Type E (manufactured by Polymer Instruments Co., Ltd.) was 37.

[0063] [Comparative Example 3] A cushion structure of Comparative Example 3 was fabricated with the same configuration as the cushion structure of Example 1, except that a perimeter ridge and boss were not formed on the underside of the top plate, and a pair of ridges, approximately 20 mm wide, with a front edge length of approximately 320 mm and a rear edge length of approximately 320 mm and a height of approximately 16 mm, were formed facing each other at two locations on the front and rear edges of the top plate and underside. In other words, the cushion structure of Comparative Example 3 has a double-ended support beam structure in which the top plate is supported from below by a pair of front and rear ridges, thereby creating a space beneath the top plate that allows the top plate to flex. Furthermore, since the top plate portion of the cushion structure in Comparative Example 3 has the same dimensions and is made of the same material as the cushion structure in Example 1, the hardness of the top plate portion of the cushion structure in Comparative Example 3 is also the same as that of the cushion structure in Example 1, at 36.

[0064] [Comparative Example 4] A cushion structure of Comparative Example 4 was fabricated with the same configuration as the cushion structure of Comparative Example 3, except that a pair of ridge sections, each approximately 20 mm wide, 260 mm long, and 16 mm high, were formed facing each other at two locations on the left and right edges of the top and bottom surfaces. In other words, the cushion structure of Comparative Example 4 has a double-ended support beam structure in which the top plate is supported from below by a pair of left and right ridges, thereby creating a space beneath the top plate that allows the top plate to flex. Furthermore, since the top plate portion of the cushion structure in Comparative Example 4 has the same dimensions and is made of the same material as the cushion structure in Example 1, the hardness of the top plate portion of the cushion structure in Comparative Example 4 is also the same as that of the cushion structure in Example 1, at 36.

[0065] [Reference example] Without attaching a cushion structure, the pressure distribution on the subject's buttocks was measured using the seat of a bathroom chair (product name: Rakuraku Open / Close Shower Bench CN, manufactured by Aron Kasei Co., Ltd.) as a reference example (maximum width: 37 mm, maximum depth: 33 mm) when the subject was seated. Furthermore, the average hardness of the seat of the reference example bathroom chair, measured at 5 points using an Asker rubber hardness tester Type D (manufactured by Polymer Instruments Co., Ltd.), was 65.

[0066] 2. Measurement of the pressure distribution on the cushion structure when the subject is seated. The cushion structures of Example 1 and Comparative Examples 1-4 were attached or placed on the seat body of a bathroom chair (product name: Rakuraku Open / Close Shower Bench CN, manufactured by Aron Kasei Co., Ltd.). Specifically, the cushion structures of Example 1 and Comparative Examples 3 and 4 were attached or placed on the seat body so that a predetermined space was formed between their respective top plates and the seat body, while the cushion structures of Comparative Examples 1 and 2 were placed so that their undersides were in close contact with the seat body. Next, a sensor mat (530mm x 530mm, with 16x16 arrangement of sensors (256 sensors)) of the pressure distribution measuring device FSA4.0 (manufactured by Takano Corporation) was placed on top of the cushion structure of Example 1 and the cushion structures of Comparative Examples 1-4, which were attached to or placed on a bathroom chair. The same subject (a male, 173cm tall, weighing 70kg, aged 39) then sat on the sensor mat, and the pressure distribution on the subject's buttocks was measured. The pressure distribution was measured at a sampling rate (number of samples taken per second) of 20Hz and within a measurable range of 0-300mmHg.

[0067] For the seat of the reference example bathroom chair (product name: Rakuraku Open / Close Shower Bench CN, manufactured by Aron Kasei Co., Ltd.), a sensor mat (530mm x 530mm, with 16x16 arrangement of sensors (256 sensors)) of the pressure distribution measuring device FSA4.0 (manufactured by Takano Co., Ltd.) was placed on the seat (without the cushion structure). The same subject (173cm tall, 70kg, 39-year-old male) as in the cushion structure of Example 1 sat on the sensor mat, and the pressure distribution on the subject's buttocks was measured. The pressure distribution was measured at a sampling rate (number of samples processed per second) of 20Hz and within a measurable range of 0-300mmHg.

[0068] 3. Measurement results and evaluation Figure 11 shows the measurement results of the pressure distribution on the subject's buttocks when the subject is seated for the cushion structure of Example 1 and the cushion structures of Comparative Examples 1 and 2. Figure 12 shows the measurement results of the pressure distribution on the subject's buttocks when the subject is seated for the cushion structures of Comparative Examples 3 and 4 and the seat body of the bathroom chair (without the cushion structure) of the Reference Example. In Figures 11 and 12, the unit of pressure on the sensor mat is shown in (mmHg), and the pressure distribution on the sensor mat is shown by the shades A to E and the height of the peaks. Shades "A" are 200 to 180 mmHg, "B" are 140 to 120 mmHg, "C" are 100 to 80 mmHg, "D" are 60 to 40 mmHg, and "E" are 40 to 20 mmHg.

[0069] Figures 11 and 12 show that the cushion structure of Example 1 exhibits the narrowest high-pressure areas A and B near the subject's buttocks (ischial tuberosity) compared to the cushion structures of Comparative Examples 1 to 4 and the seat body of the Reference Example, while conversely, the widest low-pressure areas C, D, and E near the subject's buttocks (ischial tuberosity). Therefore, the cushion structure of Example 1 exhibits significantly superior pressure distribution compared to the cushion structures of Comparative Examples 1 to 4 and the seat body of the Reference Example. Furthermore, it was found that the hardness of the top plate of the cushion structure of Example 1, which exhibits excellent pressure distribution, is preferably 30 to 40, as measured by an Asker rubber hardness tester Type E (manufactured by Polymer Instruments Co., Ltd.).

[0070] When the cushion structures of Comparative Examples 1 and 2 were compared with the cushion structure of Example 1, it was found that the cushion structures of Comparative Examples 1 and 2 showed almost no difference in pressure distribution due to the difference in cushion thickness, and the low-pressure regions C, D, and E were significantly narrower compared to the cushion structure of Example 1. As a result, the proportion of the high-pressure regions A and B in the pressure distribution was found to be extremely large. Furthermore, it was found that the pressure distribution of the cushion structures of Comparative Examples 1 and 2 was similar to the pressure distribution of the seat body of the reference example.

[0071] This is thought to be because, in the cushion structures of Comparative Examples 1 and 2, the cushion (top plate) is attached in close contact with the hard seat body, so when the subject sits down, they are more likely to receive the rebound force of the cushion itself. On the other hand, in the cushion structure of Example 1, a space is formed below the top plate, so when the subject sits down, the top plate flexes before the subject receives the rebound force of the cushion itself, so they are less likely to receive the rebound force of the cushion itself. In other words, in the case of the cushion structure of Example 1, the subject's buttocks and thighs sink deeply into the top plate of the cushion structure, and the pressure on the subject's body at the contact surface with these expanded areas is distributed, resulting in the subject being supported with lower pressure (reaction force).

[0072] When the cushion structures of Comparative Examples 3 and 4 were compared with the cushion structure of Example 1, it was found that in Comparative Example 3, the high-pressure areas A and B were wider in the left-right direction where the dam section was not located compared to the cushion structure of Example 1, while in Comparative Example 4, the high-pressure areas A and B were wider in the front-back direction where the dam section was not located compared to the cushion structure of Example 1. Furthermore, when the cushion structures of Comparative Examples 3 and 4 were compared with the cushion structure of Comparative Example 1, it was found that in Comparative Example 3, the low-pressure areas C, D, and E were wider in the front-back direction where the dam section was located compared to the cushion structure of Comparative Example 1, while in Comparative Example 4, the low-pressure areas C, D, and E were wider in the left-right direction where the dam section was located compared to the cushion structure of Comparative Example 1.

[0073] In the cushion structure of Comparative Example 3, the top plate is a double-ended beam structure in which both the front and rear ends are supported by a pair of ridges. As a result, it flexes in the front-to-back direction to fit the shape of the subject's buttocks, etc., and it is thought that the low-pressure areas C, D, and E, where body pressure is distributed, also expand in the front-to-back direction. On the other hand, in the double-ended beam structure described above, the top plate cannot flex sufficiently in the left-to-right width direction and cannot fit the shape of the subject's buttocks, etc. Therefore, it is thought that the high-pressure areas A and B, where body pressure is not distributed, expand in the left-to-right width direction by the amount of deformation of the buttocks.

[0074] In the cushion structure of Comparative Example 4, the top plate is a double-ended beam structure with both left and right ends supported by a pair of ridges. As a result, it flexes in the left-right width direction to fit the shape of the subject's buttocks, etc., and it is thought that the low-pressure areas C, D, and E, where body pressure is distributed, also expand in the left-right width direction. On the other hand, in the double-ended beam structure described above, the top plate cannot flex sufficiently in the front-back direction and cannot fit the shape of the subject's buttocks, etc. Therefore, it is thought that the high-pressure areas A and B, where body pressure is not distributed, expand in the front-back direction by the amount of deformation of the buttocks.

[0075] In contrast to the cushion structures of Comparative Examples 3 and 4, the cushion structure of Example 1 has a top plate that is supported by a perimeter that surrounds it on all four sides. As a result, it flexes and deforms in all directions to fit snugly around the subject's buttocks and thighs, and the increased contact surface with the buttocks and thighs evenly distributes the subject's body pressure. Consequently, the high-pressure areas A and B, where body pressure is not distributed, become smaller, while the low-pressure areas C, D, and E, where body pressure is distributed, expand in all directions.

[0076] As described above, according to the cushion structure of Example 1, the top plate is supported by a periphery that protrudes downward from its edge so as to surround all four sides of the top plate. Therefore, when a user sits down, the top plate flexes and deforms in all directions to envelop the user's buttocks and thighs, resulting in excellent effects such as a high degree of fit, and the high pressure distribution and cushioning provided by this fit. As a result, the cushion structure of the present invention also has the excellent effect of providing a good sitting experience while keeping the thickness of the cushion (top plate) low. [Explanation of Symbols]

[0077] 1...bathroom chair 2... Seat part 20..Seat body 21...Matching hole 22...Drain 23...Drain hole 24...Handle part 3. Cushion structure 30····Top panel 300... Peripheral area 301...Surface part 302...Back part 31... Surrounding embankment 32...Space part 33····Convex part 34.. Boss Section 35...Drainage holes 36. Handle recess 4. Backrest 40····Backrest 41. Backrest cushion 410... Backrest boss section 42... Hole through the backrest 5. Armrest 6... Legs 60····Front leg frame 600... Front leg movable part 601... Resin cap with roller 61...Rear leg frame 610... Rear leg movable part 611... Resin cap

Claims

1. A top plate having a flat surface and a back surface, It comprises a periphery portion that protrudes downward from the peripheral edge of the top plate portion and is formed to surround all four sides of the top plate portion, A cushion structure made of synthetic resin foam, characterized in that, due to the support provided by the surrounding rim, a space is formed beneath the top plate that allows the top plate to flex downward.

2. The cushion structure according to claim 1, characterized in that the periphery portion is formed over the entire circumference of the periphery of the top plate portion.

3. The cushion structure according to claim 1, characterized in that a protrusion is formed on the back surface of the top plate portion, which protrudes locally downward from the surface of the back surface portion, thereby reducing the deflection allowance of the top plate portion in the space portion.

4. The cushion structure according to claim 3, characterized in that the protruding height of the convex portion is the same as or lower than the protruding height of the perimeter levee portion.

5. The cushion structure according to claim 3, characterized in that the convex portion is a flap-shaped body and / or a columnar body.

6. The cushion structure according to claim 1, characterized in that the underside of the top plate portion is covered with a resin sheet so that the space portion forms a closed space.

7. The cushion structure according to claim 6, characterized in that a core material made of a material different from the cushion structure is inserted into the space.

8. The cushion structure according to claim 1, characterized in that the synthetic resin foam is formed from EVA resin.

9. The seat body and A bathroom chair comprising a cushion structure according to any one of claims 1 to 8 that is detachably attached to the seat body, The aforementioned seat body has two or more circular fitting holes, The cushion structure is characterized by having a boss portion that protrudes downward from the back surface of the top plate portion and engages with the fitting hole.

10. The bathroom chair according to claim 9, characterized in that the boss portion is formed to protrude downward from the lower surface of the perimeter portion.

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