Chair seat structure

Abstract

To provide a chair seat structure that can improve seating comfort. [Solution] The chair seat structure includes a pair of shaft members 42 extending along the depth direction of the seat 4 and provided at both ends in the width direction of the seat 4, a pair of rotating bodies 43 that can rotate around the shaft members 42 as axes of rotation, and a seat plate 7 connecting the pair of rotating bodies 43 and that can bend and deform in the thickness direction of the seat 4.

Description

Technical Field

[0001] The present invention relates to a seat structure of a chair, and particularly to a seat structure of a chair including a seat plate that can be elastically deformed in the thickness direction of the seat.

Background Art

[0002] As a means for ensuring comfort when sitting on a chair seat, it is common to arrange a sponge-like cushioning material on the seat plate (see, for example, Patent Document 1). Here, the cushioning material has predetermined physical properties such as softness and resilience. Therefore, depending on the physique and weight of the user, it may be too soft or conversely too hard. Therefore, in the chair of Patent Document 1, a plurality of cushioning slits are provided in the seat plate to bend the seat plate itself, thereby improving the cushioning of the seat.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the conventional seat structure of a chair, although the elastic deformation of the central portion of the seat plate is allowed by the cushioning slits, the deformation of both end portions in the width direction of the seat plate fixed to the seat support (for example, the seat outer member) is not allowed, and there is room for improvement in sitting comfort.

[0005] The present invention has been made to improve such a situation, and an object thereof is to provide a seat structure of a chair that can improve sitting comfort.

Means for Solving the Problems

[0006] The present invention relates to a chair seat structure, comprising: a pair of shaft members extending along the depth direction of the seat and provided at both ends in the width direction of the seat; a pair of rotating bodies rotatable around the shaft members as axes of rotation; and a seat plate connecting the pair of rotating bodies and capable of bending and deforming in the thickness direction of the seat.

[0007] According to the present invention, in response to the load when seated, the rotating body rotates, causing both ends of the seat plate in the width direction to displace toward the center in the width direction, and the seat plate sinks downward and flexes to envelop the buttocks and thighs of the seated person, thereby improving seating comfort.

[0008] In the chair seat structure of the present invention, a return mechanism may be provided that applies a rotational force to the shaft member in a direction toward the outward direction in the width direction by deformation of an elastic member.

[0009] In this configuration, the elastic member of the return mechanism deforms when seated, allowing the seat plate to have appropriate elasticity in its deflection deformation, further improving seating comfort.

[0010] Furthermore, in the seat structure of the chair according to the present invention, the upper surface of the seat plate may constitute the seating surface of the seat.

[0011] In this configuration, by using the upper surface of the seat board as the seating surface, the seat board flexes and deforms to envelop the sitter's buttocks and thighs, resulting in a comfortable seating experience while reducing manufacturing costs compared to configurations that include a seat cushion.

[0012] Furthermore, in the seat structure of the chair according to the present invention, a cushioning material may be provided on the upper surface of the seat plate.

[0013] In this configuration, the seat board flexes and deforms to envelop the sitter's buttocks and thighs, and the cushioning material deforms to conform to the sitter's buttocks and thighs, thereby further improving seating comfort. [Effects of the Invention]

[0014] The seat structure of the chair of the present invention can improve the sitting comfort because both end portions in the width direction of the seat plate are displaced toward the center in the width direction and the seat plate sinks downward and deflects in accordance with the load during sitting.

Brief Description of the Drawings

[0015] [Figure 1] It is an external view of the chair according to the embodiment, where (A) is a front view and (B) is a perspective view. [Figure 2] (A) of the chair is a plan view and (B) is a rear view. [Figure 3] (A) of the chair is a right side view and (B) is a right side view in the rocking state. [Figure 4] It is an exploded perspective view of the seat. [Figure 5] It is a plan view showing the seat receiving member and the rocking mechanism. [Figure 6] It is an exploded perspective view of the rocking mechanism. [Figure 7] It is a longitudinal sectional view at the X-X position in Fig. 2(A). [Figure 8] It is a longitudinal sectional view showing the rocking state. [Figure 9] It is a longitudinal sectional view showing the sitting state. [Figure 10] (A) is a right side view of the seat and (B) is a conceptual diagram for explaining the deformation of the seat inner shell during sitting. [Figure 11] It is a diagram for explaining the rotation support unit. [Figure 12] It is a longitudinal sectional view for explaining the rotation support unit.

Modes for Carrying Out the Invention

[0017] (1). Overview of the chair First, the overview of the chair will be mainly described based on FIGS. 1 to 3. This embodiment is applied to a swivel chair frequently used for office work and the like. The chair has a leg support 1 and a leg device 2 having casters, a base body 3 fixed to the upper end of the leg support 1, a seat 4 disposed on the base body 3, and a backrest 5 on which a seated person can lean. The base body 3, the seat 4, and the backrest 5 are provided substantially symmetrically about the left and right.

[0018] The base body 3 is formed in a box shape that opens upward. The backrest 5 is provided in a substantially U-shaped opening facing forward so as to surround the rear edge portion of the seat of the seat 4 and the left and right seat side edge portions in plan view, and includes a back plate portion 51 and left and right side plate portions 52. Although details will be described later, the backrest 5 is supported by the base body 3 so as to be tiltable backward.

[0019] (2). Overview of the seat For example, as shown in FIG. 4, the seat 4 includes a seat receiving member 6 made of a metal plate attached to the base body 3. A resin seat inner shell 7 is connected and supported to the seat receiving member 6 via a rotation support mechanism 40. In this embodiment, the seat inner shell 7 constitutes a seat plate. A seat cushion material 8 is stacked on the upper surface of the seat inner shell 7. The seat cushion material 8 is covered with a skin material 10 such as cloth.

[0020] The seat inner shell 7 is provided so as to be bendable and deformable in the thickness direction, and the left and right seat inner side edge portions 71 are supported by the seat receiving member 6 via the rotation support mechanism 40, and the central portion is configured to be able to sink downward by the weight of the seated person. For example, a number of slits 7a are provided in the seat inner shell 7 so as to freely bend according to the sitting posture of the seated person. The arrangement area of the slits 7a, the shape and size of each slit 7a, etc. can be appropriately changed. Note that the seat inner shell 7 may not include the slits 7a.

[0021] The rotation support mechanism 40 comprises left and right rotation support units 41 provided at the left and right edges of the seat 4. In this embodiment, two sets of rotation support mechanisms 40, each having left and right rotation support units 41, are provided front and rear, at the front and rear edges of the seat 4.

[0022] The rotational support mechanism 40 supports the left and right inner seat edge portions 71 of the seat inner shell 7 so that they can rotate around a rotation axis extending in the depth direction (front-to-back direction) of the seat 4. The left and right rotational support units 41 extend along the depth direction of the seat 4 and include left and right shaft members 42 provided at both ends in the width direction of the seat 4, and left and right rotating bodies 43 that can rotate around the shaft members 42 as a rotation axis. The left and right rotating bodies 43 are connected to the left and right inner seat edge portions 71 of the seat inner shell 7. In other words, the seat inner shell 7 connects the left and right rotating bodies 43.

[0023] In this embodiment, of the four rotation support units 41 that constitute the front and rear rotation support mechanism 40, the two rotation support units 41 positioned front and rear near the left and right edges of the seat 4 are arranged so that the axes (rotation axes) of the shaft members 42 are on the same straight line. The front and rear shaft members 42 are connected by a connecting shaft 50 that extends along the axis of the shaft members 42, so that they can rotate relative to each other around the axis.

[0024] A lower cushioning material 9 is provided between the seat inner shell 7 and the seat support member 6. The material of the lower cushioning material 9 is not particularly limited, but for example, recycled cushioning (chip urethane) or a three-dimensional mesh fiber structure can be used. The lower cushioning material 9 is housed in a receiving recess 61 provided at the rear of the central part of the seat support member 6. In this embodiment, the receiving recess 61 is provided at a location below the seated person's buttocks 100 (see Figure 9).

[0025] As shown in the conceptual diagram of Figure 10(B), when a person sits on the seat 4, a downward force is applied to the seat inner shell 7 (seat plate) in accordance with the load at the time of sitting, and the rotating body 43 of the rotation support mechanism 40 rotates around the axis of the shaft member 42 so as to displace the portion 71 near the side edge of the seat inner towards the center in the width direction. As a result, the seat inner shell 7 sinks downward and flexes to envelop the buttocks 100 and thighs 101 of the person sitting, thereby improving the sitting comfort. Note that the seat cushion material 8 is not shown in Figure 10(B).

[0026] Here, since the left and right shaft members 42 of the left and right rotation support units 41 constituting the rotation support mechanism 40 can rotate independently of each other around their axes, the amount of inward displacement of the portion 71 near the side edge of the inner seat 4 can be made different on both the left and right edges of the seat 4 when seated. As a result, the amount of displacement of the portion 71 near the side edge of the inner seat 7 on both sides can be made different depending on the seated position and posture of the sitter on the seat 4, causing the inner seat shell 7 to flex and deform, thus providing a better seating experience.

[0027] Furthermore, this embodiment includes two sets of rotational support mechanisms 40, one located near the front edge and the other near the rear edge of the seat inner shell 7. Since each of the four rotational support units 41 constituting the two sets of rotational support mechanisms 40 is provided to rotate independently around its axis, the amount of inward displacement of the seat inner side edge portion 71 can be made different at the front and rear of the seat 4 when seated. This allows for more flexible deflection deformation of the seat inner shell 7, resulting in an even better seating experience.

[0028] Furthermore, in this embodiment, since the seat cushion material 8 is arranged on the upper surface of the seat inner shell 7, in addition to the seat inner shell 7 bending and deforming to envelop the seated person's buttocks 100 and thighs 101, the seat cushion material 8 also deforms to conform to the seated person's buttocks 100 and thighs 101, thereby further improving seating comfort.

[0029] Furthermore, as shown in Figure 9, when a person sits on the seat 4, the seat cushion material 8 undergoes elastic compression deformation, and the seat inner shell 7 sinks in, causing the lower cushion material 9 to undergo elastic compression deformation accordingly. In this embodiment, the seat 4 undergoes elastic deformation of both the seat cushion material 8 and the lower cushion material 9 when seated, thus improving cushioning and preventing the seat inner shell 7 from bottoming out even if it deforms significantly, thereby improving seating comfort.

[0030] Furthermore, since the seat 4 can withstand the seating load with the lower cushioning material 9, the seat inner shell 7 can sink in well (become more prone to bending deformation), creating a comfortable seat that envelops the buttocks when seated. In addition, by appropriately selecting the elastic force of the lower cushioning material 9, the amount of compressive deformation of the lower cushioning material 9 when seated, i.e., the amount of sinking of the seat 4, can be controlled.

[0031] As shown in Figure 7, etc., in this embodiment, the upper surface 91 of the lower cushion material 9 (the contact surface with the seat inner shell 7) is slightly curved in a concave shape. By appropriately designing the shape of the upper surface 91 of the lower cushion, the shape of the seat inner shell 7 when seated can be controlled not only by the restorative force of the seat inner shell 7 itself but also by the restorative force of the lower cushion material 9, and the shape of the seat inner shell 7 when seated can be designed to be a desired shape.

[0032] In this embodiment, the seat support member 6 and the seat inner shell 7 are connected in a way that prevents detachment and allows for disassembly by fasteners such as screws (not shown). This makes it possible to replace the lower cushion material 9, allowing users to select their preferred level of cushioning by replacing the lower cushion material 9, thus making it user-friendly. Furthermore, when the cushioning of the lower cushion material 9 deteriorates due to aging or other reasons, the cushioning of the seat 4 can be restored by replacing the lower cushion material 9 with a new one.

[0033] (3) Overview of backrests As shown in Figures 3 and 7, the backrest 5 is connected to the base body 3 via a back connecting arm 12 and a back connecting member 13 so as to be able to tilt backward. As described above, the backrest 5 comprises a back plate portion 51 along the rear edge of the seat 4 and left and right side plate portions 52 along the left and right side edges of the seat 4. The lower end portion 51a of the back plate portion 51 and the lower end portion 52a of the side plate portions 52 are positioned at a height below the upper surface of the seat 4. In this embodiment, the lower ends 51a and 52a of the backrest 5 are curved inward from the side of the seat 4 diagonally downward and are positioned below the rear edge and left and right side edges of the seat 4.

[0034] Although detailed illustrations are omitted, the backrest 5 comprises a core material, a back cushion material covering at least the inward-facing surface of the core material, and a surface material such as cloth covering the entire surface of the backrest 5. A back connecting member 13 is fixed to the inward-facing surface of the lower end 51a of the backrest. The backrest 5 is supported by the base body 3 by the connection of the back connecting member 13 and the back connecting arm 12.

[0035] (4) Overview of the locking mechanism As shown in Figures 4 to 6, a rocking mechanism 20 for supporting the backrest 5 so that it can tilt backward is housed inside the metal base body 3. The base body 3 has a base body bottom 31 which is roughly rectangular in plan view, and left and right base body sides 32 which extend upward from the left and right edges of the base body bottom 31. An arm housing portion 33 for housing the back connecting arm 12 is recessed and bulges downward in the left-right center of the rear part of the base body bottom 31. A cylindrical leg support connecting portion 34 into which the upper end of the leg support 1 is inserted and fixed is provided integrally with the front surface of the arm housing portion 33 on the lower surface of the base body bottom 31.

[0036] The locking mechanism 20 is generally arranged symmetrically. The rear connecting arm 12, which constitutes a part of the locking mechanism 20, comprises a rear arm 12a extending in the left-right direction, a pair of forward-facing arms 12b extending forward from both ends of the rear arm 12a, and a connecting arm 12c extending in the left-right direction and connecting the intermediate parts of the left and right forward-facing arms 12b.

[0037] The rear arm 12a is made of metal and has a U-shaped cross-section with a downward-facing opening. The back connecting member 13 is connected to the upper surface of the rear arm 12a by fasteners such as screws. The forward arm 12b is formed of an upward-facing, roughly V-shaped metal plate, with its rear end fixed to the rear arm 12a and its front end rotatably connected to a support shaft 21 that extends in the left-right direction.

[0038] The support shaft 21 is made of a metal rod and is fixed to the base body 3 in a horizontal position by a support shaft fixing device 22 provided inside the arm housing portion 33 of the base body 3. The front part of the forward-facing arm 12b, which is pivotally supported on the support shaft 21, is located inside the arm housing portion 33, while the rear part of the forward-facing arm 12b and the rear arm 12a are located near the outside of the rear of the base body 3. The forward-facing arm 12b is positioned in an inclined position with the front lower and the rear higher. The rear connecting arm 12 is connected to the base body 3 so as to be rotatable around the support shaft 21.

[0039] The connecting arm 12c is made of metal and is provided in a roughly box shape with an upward opening. It is provided to be longer in the left-right direction than the distance between the left and right forward-facing arms 12b, and both left and right ends of the connecting arm 12c protrude outward from the left and right forward-facing arms 12b. The left and right side portions of the connecting arm 12c are provided with rear pin support portions 12d that extend upward. The rear pin support portions 12d have rear pin support holes 12e that open in the left-right direction for supporting the left and right inner ends of the rear pin member 23 that extends in the left-right direction.

[0040] Within the base body 3, a pair of left and right load-applying arms 24 extending in the front-rear direction are arranged along the side portion 32 of the base body. The load-applying arms 24 are made of metal and have a linear shape, extending from near the front edge to near the rear edge of the base body 3. The front half portion 24a of the load-applying arms 24 is provided with a roughly U-shaped cross-section with a downward opening, and the rear half portion 24b of the arms is provided as a pair of left and right plate-like structures extending rearward from the left and right side portions of the front half portion 24a, respectively.

[0041] The rear end of the rear half 24b of the arm is provided with a pair of left and right rear pin support holes 24c through which the rear pin member 23 is inserted, and is positioned on the left and right outer sides of the rear pin support portion 12d of the back connecting arm 12. By inserting the horizontally elongated rear pin member 23 through the rear pin support holes 12e and 24c and supporting it so that it cannot be removed, the load-applying arm 24 and the back connecting arm 12 are connected so that they can rotate relative to each other around the rear pin member 23.

[0042] A front pin member 25 extending in the left-right direction is horizontally mounted on the front half 24a of the load-applying arm 24, between the left and right side portions. Upward-facing convex load-applying arm connecting portions 35 are provided protruding from each of the left and right front corner portions of the base body bottom portion 31. The load-applying arm connecting portion 35 is made of metal and has a front pin support elongated hole 35a that opens in the left-right direction and extends in the front-rear direction. In this embodiment, the front pin support elongated hole 35a is formed of a resin or resin bushing member supported by the load-applying arm connecting portion 35.

[0043] The front half 24a of the load-applying arm 24 is placed over the load-applying arm connecting portion 35 from above, while the front pin member 25 is inserted through the front pin support elongated hole 35a. As a result, the load-applying arm 24 is supported with respect to the load-applying arm connecting portion 35 so as to be rotatable around the front pin member 25 and so as to be able to move back and forth. The front pin support elongated hole 35a restricts the range of movement of the load-applying arm 24 in the back and forth direction between a forward movement limit position where the front pin member 25 is positioned at the front end of the front pin support elongated hole 35a and a backward movement limit position where the front pin member 25 is positioned at the rear end of the front pin support elongated hole 35a.

[0044] The front half 24a of the left and right load-applying arms 24 are connected by a front spring support member 26 that extends in the left-right direction. The front spring support member 26 is formed, for example, from a metal rod, and both of its left and right ends are connected to the portion of the left and right front half 24a of the arms that supports the front pin member 25.

[0045] On the base body 3, at the bottom 31 of the base body, metal rear spring support members 27 are erected on the left and right sides of the base body, respectively, which in a plan view enclose the leg support connecting portion 34. Between the pair of left and right rear spring support members 27 and the front spring support member 26, a pair of left and right spring bodies 28 are arranged. The spring bodies 28 are for providing resistance to the backward tilting of the backrest 5, and in this embodiment, they are composed of compression coil springs arranged to be inclined in a front-high, rear-low posture along the front-rear direction. The spring bodies 28 are interposed in a compressed state between the front and rear spring support members 26 and 27, with their front ends abutting against the left and right edges of the front spring support member 26 and their rear ends abutting against the front surface of the rear spring support member 27.

[0046] As shown in Figure 7, the rocking mechanism 20 biases the front spring receiving member 26 forward by the elastic force of the spring body 28, thereby positioning the left and right load-applying arms 24 at their forward movement limit positions, and maintaining the backrest 5 in an upright position (initial position when unloaded).

[0047] As shown in Figure 8, when a seated person leans against the backrest 5 and a rearward load is applied to the backrest 5, the backrest connecting arm 12 and backrest connecting member 13 rotate downward around the pivot shaft 21. Then, the load-applying arm 24 connected to the backrest connecting arm 12 and the front spring-receiving member 26 fixed to the load-applying arm 24 rotate around the front pin member 25 and are pulled rearward, causing the spring body 28 to compress and deform. In this way, the rocking mechanism 20 supports the backrest 5 so that it can tilt backward against the elastic force of the spring body 28.

[0048] The range of backward tilt of the backrest 5 is limited by a front pin member 25 that is movable in the front-rear direction within the front pin support elongated hole 35a. As shown in Figures 1 to 3 and Figure 7, when the backrest 5 is in its initial position with no load, the lower end 52a of the side plate portion 52, which tilts backward together with the back plate portion 51, is located below the upper surface of the seat 4. Furthermore, even when the backrest 5 is in its maximum backward tilt position (see Figure 8), the lower end 52a of the side plate of the backrest 5 is configured to be located below the upper surface of the seat 4.

[0049] In other words, the backrest 5 is supported by the base body 3 so as to be able to tilt backward, such that the lower end 52a of the side plate does not remain above the upper surface of the seat 4 even when the backrest 5 changes its position. This prevents foreign objects from getting caught between the side plate 52 of the backrest 5 and the seat 4 when a person sitting on the seat 4 tilts the backrest 5 backward, thus ensuring safety and making it user-friendly. In addition, when the backrest 5 is in its initial position without load, the lower end 52a of the side plate of the backrest 5 is positioned below the seat 4, making the base body 3 less visible when the chair is viewed from the side, thus providing a good appearance.

[0050] (5) Seat configuration As described above, the seat 4 comprises a seat support member 6, a rotation support mechanism 40, a seat inner shell 7, a seat cushion material 8, and a surface material 10 (see Figures 4 and 7, etc.). As shown in Figure 7, the seat cushion material 8 is made of an elastic material such as urethane and has a seat cushion recess 81 on its lower surface that accommodates the seat inner shell 7.

[0051] The seat cushion recess 81 is provided to a depth that accommodates the upper part of the base body 3 when the seat cushion material 8 is attached to the seat support member 6 with the seat inner shell 7 and rotation support mechanism 40 interposed therebetween. The seat cushion material 8 may be integrally molded with the seat inner shell 7 by insert molding, or the seat inner shell 7 may be housed and positioned in the seat cushion recess 81 after molding. Furthermore, the seat cushion material 8 is not limited to a molded product, but may be a sheet-like elastic material stretched over the seat inner shell 7.

[0052] As shown in Figures 4 and 5, the four rotational support units 41 that constitute the two sets of front and rear rotational support mechanisms 40 are arranged at the four corners of the seating member 6, which is roughly rectangular in plan view. In this embodiment, the four rotational support units 41 have the same structure. The left and right side edge portions 66 of the seating member 6 on which the rotational support units 41 are arranged are stepped down from the center in the left-right direction and extend in the front-rear direction, and are arranged on the left and right outer sides of the base body 3.

[0053] Figure 11 shows a rotary support unit, where (A) is a plan view, (B) is a side view, (C) is a side view seen from the return mechanism side, and (D) is a side view seen from the shaft member side. Figure 12(A) is a longitudinal section view showing the support base cross section separated at position AA in Figure 11(A), (B) is a longitudinal section view at position BB in Figure 11(B), and (C) is a longitudinal section view at position CC in Figure 11(B).

[0054] As shown in Figures 11 and 12, the rotating support unit 41 comprises a shaft member 42 extending in the front-rear direction, a rotating body 43 rotatable about the axis of rotation of the shaft member 42, a support base 44 that rotatably supports the shaft member 42 about its axis, and a return mechanism 46 that applies rotational force to the shaft member 42 in a direction toward the outside in the width direction of the seat 4 by deformation of an elastic member 45. The axis of the shaft member 42 extends toward the depth direction of the seat 4 and, in this embodiment, is provided along the front-rear direction. However, the axis of the shaft member 42 may be inclined with respect to the front-rear direction. For example, the axis of the shaft member 42 may extend slightly diagonally downward toward the depth direction of the seat 4, or slightly inward to the left and right.

[0055] The shaft member 42 is made of metal, for example, and has a substantially cylindrical main shaft portion 42a extending in the front-rear direction, and a substantially cylindrical small-diameter shaft portion 42b extending along the axis from one end of the main shaft portion 42a. A cam bevel portion 42c is provided around the base end of the small-diameter shaft portion 42b, formed by cutting out a substantially triangular convex shape from one end face of the main shaft portion 42a toward the other end. In this embodiment, the cam bevel portion 42c has six substantially isosceles triangular recesses (which can also be called six substantially isosceles triangular protrusions) of the same shape, arranged continuously to surround the base end of the small-diameter shaft portion 42b when viewed from the circumferential direction of the main shaft portion 42a.

[0056] A pair of left and right axial movement restricting portions 42d are integrally formed on the side surface of the main shaft portion 42a near one end, projecting in the left-right direction (away from the axis). The axial movement restricting portions 42d have a substantially rectangular parallelepiped shape and, when viewed from the left-right direction, protrude outward from the lower half of the side surface of the main shaft portion 42a. The lower surface 42e of the restricting portion 42d is inclined diagonally downward from the left and right outer sides inward.

[0057] A pair of left and right rotation range restricting portions 42f are integrally formed on the side surface of the shaft main portion 42a near the other end, protruding in the left and right directions. The rotation range restricting portions 42f have a roughly trapezoidal shape in which the upper side is shorter than the base side when viewed from above, and protrude outward in a roughly horizontal position from the side surface which is slightly deviated downward with respect to the axis of the shaft main portion 42a when viewed from the left and right directions.

[0058] A connecting hole 42g is drilled along the axis of the other end face of the main shaft portion 42a for inserting and supporting the end of the connecting shaft 50. For example, the connecting hole 42g is formed as a female threaded hole into which the threaded portions formed at both ends of the connecting shaft 50 are screwed.

[0059] As shown in Figures 5 and 11, a rotating body 43 having a vertically penetrating screw insertion hole 43a is fixed to the upper surface of the main shaft portion 42a by screw fastening. The rotating body 43 is interposed between the main shaft portion 42a and the inner seat edge portion 71, and is formed of a metal member that is larger in the left-right direction than the main shaft portion 42a. The rotating body 43 is fastened to the upper surface of the main shaft portion 42a by screw 49, which is inserted from above into the screw insertion hole 71a provided in the inner seat edge portion 71, with the screw shaft of the screw 49 being inserted into the screw insertion hole 43a, and the rotating body 43 together with the inner seat edge portion 71 by screw 49. As a result, the rotating body 43 and the inner seat edge portion 71 are provided so as to be rotatable with the axis of the shaft member 42 as the axis of rotation.

[0060] The rotating body 43 also functions as a spacer member to ensure the distance between the main shaft portion 42a and the portion 71 near the inner edge of the seat. The rotating body 43 may be integrally molded with the main shaft portion 42a. Furthermore, since the screw 49 is provided so as to be rotatable with the axis of rotation of the shaft member 42, it can be said to constitute the rotating body of the seat structure of the present invention.

[0061] The return mechanism 46 includes a cylindrical cam member 47 that is rotatably fitted onto the small-diameter shaft portion 42b of the shaft member 42, an elastic member 45 consisting of a compression coil spring that is loosely fitted onto the small-diameter shaft portion 42b at the tip side of the small-diameter shaft portion 42b, and a pressing force adjuster 48 that adjusts the load applied by the elastic member 45 to the cam member 47.

[0062] The cam member 47 is made of resin, for example, and integrally comprises a pair of left and right rotation restricting portions 47b projecting in the left-right direction from the outer surface of the cylindrical portion 47a, and a cam portion 47c provided on one end surface of the cylindrical portion 47a so as to abut against the slope of the cam slope portion 42c of the shaft member 42. The rotation restricting portions 47b have a substantially rectangular parallelepiped shape and project outward to the left and right from a portion near the other end of the outer surface of the cylindrical portion 47a. The cam portion 47c has six substantially isosceles triangular protrusions along the circumferential direction that engage with the cam slope portion 42c of the shaft member 42. The other end surface of the cylindrical portion 47a (the end surface opposite to the cam portion 47c) constitutes a spring seat that supports one end of the elastic member 45.

[0063] The pressing force adjuster 48 is formed by a screw that engages with a female screw hole drilled along the axis on the end face of the small-diameter shaft portion 42b of the shaft member 42. After fitting the cam member 47 and the elastic member 45 onto the small-diameter shaft portion 42b, the screw shaft of the pressing force adjuster 48 is screwed into the female screw hole of the small-diameter shaft portion 42b, and the elastic member 45 is interposed between the cam member 47 and the screw head of the pressing force adjuster 48. By adjusting the degree to which the pressing force adjuster 48 is screwed in, the amount of deflection of the elastic member 45 can be appropriately set. This allows adjustment of the load that the elastic member 45 applies to biasing the cam portion 47c of the cam member 47 toward the cam inclined surface portion 42c of the shaft member 42.

[0064] The support base 44 of the rotating support unit 41 comprises a first base portion 44a that supports the shaft member 42, and a second base portion 44b that holds the return mechanism 46 and is connected to the first base portion 44a so as not to move relative to it. The first base portion 44a has a substantially box-shaped form that is long in the axial direction of the shaft member 42, and comprises a shaft support portion 44c that houses and supports the main shaft portion 42a of the shaft member 42, and a restricting portion housing portion 44d that houses the axial movement restricting portion 42d.

[0065] The shaft support portion 44c and the regulating portion housing portion 44d are recessed in the upper surface of the first base portion 44a, opening upward. The shaft support portion 44c is provided as a roughly U-shaped groove with a groove width slightly larger than the diameter of the main shaft portion 42a. Both longitudinal ends of the shaft support portion 44c open onto both longitudinal sides of the first base portion 44a.

[0066] The restricting section housing 44d is provided in a roughly box shape, extending left and right across the shaft support section 44c, at a position closer to the second base section 44b of the first base section 44a. The restricting section housing 44d is provided in a depth greater than that of the shaft support section 44c, and its axial length is formed to be slightly greater than the axial length of the axial movement restricting section 42d of the shaft member 42. The restricting section housing 44d restricts the axial movement of the shaft main section 42a relative to the axial movement restricting section 42d of the shaft member 42, which is located within the first base section 44a, while holding it so that it can rotate around its axis.

[0067] The second base portion 44b of the support base 44 has a substantially rectangular parallelepiped shape that is elongated in the axial direction of the first base portion 44a, and includes a return mechanism housing portion 44e with a circular cross-section that extends in the axial direction and opens to both longitudinal sides of the second base portion 44b. The inner diameter of the return mechanism housing portion 44e is set to be slightly larger than the outer diameter of the cam member 47. A pair of left and right groove-shaped recesses 44f are formed on the inner circumferential surface of the end of the return mechanism housing portion 44e on the first base portion 44a side, which accommodate the left and right rotation restricting portions 47b of the cam member 47.

[0068] The groove-shaped recess 44f extends along the axial direction of the cam member 47, with one end opening on the side of the second base portion 44b on the first base portion 44a side, and the other end positioned midway along the axial direction of the return mechanism housing portion 44e. The groove depth of the groove-shaped recess 44f is set to be greater than the protruding length (radial dimension) of the rotation restricting portion 47b. The groove width of the groove-shaped recess 44f is set to be slightly greater than the thickness dimension (height dimension) of the rotation restricting portion 47b.

[0069] The cam member 47, elastic member 45, and pressing force adjuster 48 constituting the return mechanism 46 are mounted on the small-diameter shaft portion 42b of the shaft member 42, and then inserted into the return mechanism housing portion 44e of the second base portion 44b from the side facing the first base portion 44a, with the pressing force adjuster 48 leading. The left and right rotation restricting portions 47b of the cam member 47 are inserted into the left and right groove-shaped recesses 44f of the return mechanism housing portion 44e. As a result, the cam member 47 is held in the second base portion 44b so as to be slidable along the axial direction while its rotation around the axis is restricted. The small-diameter shaft portion 42b of the shaft member 42 is held in the second base portion 44b so as to be rotatable around its axis via the cam member 47.

[0070] The small-diameter shaft portion 42b is held by the second base portion 44b, and the first base portion 44a is brought closer to the main shaft portion 42a of the shaft member 42 held by the second base portion 44b from below, and the main shaft portion 42a of the shaft member 42 and the axial movement restricting portion 42d are housed in the shaft support portion 44c and restricting portion housing portion 44d of the first base portion 44a. Then, the first base portion 44a and the second base portion 44b of the support base 44 are connected so that they cannot move relative to each other by a connecting mechanism (not shown). The configuration of the connecting mechanism is not particularly limited, but can be realized by, for example, protrusions or claws formed on the base portions 44a and 44b respectively that engage with each other.

[0071] In the rotating support unit 41, the shaft member 42 is restricted from moving in the axial direction by the axial movement restricting portion 42d being housed in the restricting portion housing portion 44d, while rotation around the axis is permitted. Here, the rotation of the shaft member 42 around the axis is limited by the range of rotational angle by the lower surface 42e of the restricting portion 42d contacting the bottom surface of the restricting portion housing portion 44d. In this embodiment, the rotational angle range of the shaft member 42 is limited, for example, to about 25 degrees clockwise and counterclockwise from the horizontal position of the axial movement restricting portion 42d.

[0072] As shown in Figures 4, 5, and 10(A), the support bases 44 of the rotation support unit 41 are fixed to the four corners of the seating member 6, for example, by mounting screws (not shown). The left and right rotation support units 41 constituting the front rotation support mechanism 40 are positioned with the first base portion 44a facing forward (the second base portion 44b facing backward), and the axis of the shaft member 42 is oriented in the front-rear direction. On the other hand, the left and right rotation support units 41 constituting the rear rotation support mechanism 40 are positioned with the second base portion 44b facing forward (the first base portion 44a facing backward), and the axis of the shaft member 42 is oriented in the front-rear direction. The shaft members 42 of the front and rear rotation support units 41 are connected so as to be able to rotate relative to each other by a connecting shaft 50, which has its axis on the same straight line and is inserted and supported through connecting holes 42g.

[0073] As described above, the portion 71 near the inner seat edge is connected to the upper surface of the main shaft portion 42a of the shaft member 42 of each rotating support unit 41 by a screw 49, with a rotating body 43 interposed between them. The rotating body 43, the portion 71 near the inner seat edge, and the screw 49 are all rotatably mounted so as to the axis of rotation of the shaft member 42 of the rotating support unit 41.

[0074] Furthermore, with the rotating body 43 and the seat inner shell 7 connected to the rotating support unit 41 attached to the seat receiving member 6, the degree to which the pressing force adjuster 48 is screwed in by inserting a screwdriver or other screw-driving tool from the other end of the return mechanism housing portion 44e of the rotating support unit 41 can be adjusted, thereby adjusting the pressing force of the cam member 47 against the cam inclined surface portion 42c due to the elastic force of the elastic member 45. Note that the elastic member 45 and the pressing force adjuster 48 may be located outside the return mechanism housing portion 44e.

[0075] When a downward load is applied to the seat inner shell 7 when seated, inward forces act on the part 71 near the side edge of the seat inner. The shaft member 42 rotates around its axis in a direction that displaces the part 71 near the side edge of the seat inner and the rotating body 43 inward, against the elastic force of the elastic member 45. As the shaft member 42 rotates around its axis, the cam inclined surface 42c displaces the cam member 47 away from the cam inclined surface 42c, causing the compression coil spring constituting the elastic member 45 to undergo compression deformation.

[0076] As a result, in response to the load when seated, the portion 71 near the side edge of the inner seat 4 is displaced toward the center in the width direction of the seat 4, and the inner seat shell 7 sinks downward and flexes to envelop the seater's buttocks and thighs, thus providing a good seating experience. When the downward load on the inner seat shell 7 is released, the shaft member 42 returns to its initial position (the state in which no downward load is applied to the inner seat shell 7) by the return mechanism 46 (restoring force of the elastic member 45) of the rotation support unit 41.

[0077] In this embodiment, since two rotational support units 41 are provided at the front and rear of each inner seat edge portion 71, the return force of the return mechanism 46 can be made different for the front and rear rotational support units 41. This allows the cushioning to be appropriately adjusted between the front and rear of the seat 4 according to the user's preference and intended use, making it user-friendly. It is also possible to make the return force of the return mechanism 46 different for the left and right rotational support units 41 that constitute the rotational support mechanism 40.

[0078] In this embodiment, the rotatable range of the shaft member 42 is limited by the contact between the axial movement restricting portion 42d or the rotation range restricting portion 42f on the left and right inner sides of the shaft member 42 and the bottom surface of the restricting portion housing portion 44d or the seat receiving member 6. Here, when the axial movement restricting portion 42d or the rotation range restricting portion 42f is in contact with the bottom surface of the restricting portion housing portion 44d or the seat receiving member 6, if an inward force is applied to the portion 71 near the inner side edge of the seat, an upward rotational force acts on the shaft member 42 with the restricting portion 42d or 42f as the pivot point. Therefore, an upward movement restricting member may be provided on the support base 44 or the seat receiving member 6 to prevent the shaft member 42 from lifting up, for example by covering the upper surface of the shaft member 42.

[0079] Next, the structure around the lower cushion material 9 will be described. As shown in Figures 4 and 5, the seat support member 6 is roughly rectangular in plan view and has a receiving recess 61 in the center for accommodating the lower cushion material 9. The receiving recess 61 is provided in the left and right center of the seat support member 6, extending from the front to the rear, and the first receiving recess 62 provided in the rear is formed to be deeper than the second receiving recess 63 provided in the front. The seat support member 6 has a shape in which the center of the front edge is cut out and the left and right front edge side ends 64 protrude forward, and the front edge of the receiving recess 61 is open toward the front.

[0080] As shown in Figures 7 and 8, the receiving recess 61 is provided in the seat support member 6 in a downwardly convex concave shape so as not to interfere with the locking mechanism 20. In this embodiment, the receiving recess 61 is provided extending from the front edge to the rear edge portion of the center of the seat support member 6 in the left-right direction. The first receiving recess 62, recessed in the rear edge portion, is provided above the arm receiving portion 33 at a depth that does not interfere with the back connecting arm 12. The second receiving recess 63, recessed in the front edge portion, is provided above the left and right spring bodies 28 and the space between them at a depth that does not interfere with the spring bodies 28. The first receiving recess 62 is provided deeper than the second receiving recess 63.

[0081] In the seat 4, the first accommodating recess 62 is located below the seater's buttocks 100 (see Figure 9). The second accommodating recess 63 is located in the center of the seat 4, connected to the front of the first accommodating recess 62. The seat support member 6 has openings 65 on the left and right sides of the first accommodating recess 62 that open in the vertical direction. The left and right openings 65 ensure ventilation between the seat cushion material 8 and the base body 3 through the slits 7a of the seat inner shell 7.

[0082] As shown in Figures 4 and 7, the lower cushion material 9 housed in the housing recess 61 is approximately rectangular in plan view and comprises a first lower cushion portion 92 housed in the first housing recess 62 and a second lower cushion portion 93 housed in the second housing recess 63. The first lower cushion portion 92 is thicker than the second lower cushion portion 93. That is, the thickness of the first lower cushion portion 92, which is positioned below the seated person's buttocks 100 (see Figure 9), is greater than the thickness of the second lower cushion portion 93 (the other part). The left and right edges of the first lower cushion portion 92 housed in the first housing recess 62 are positioned to overlap the opening 65 without interfering with the rocking mechanism 20.

[0083] As described above with reference to Figure 9, when a person sits on the seat 4, the seat cushion material 8 undergoes elastic compression deformation and the seat inner shell 7 sinks in, and the lower cushion material 9 undergoes elastic compression deformation in response. In this embodiment, the thickness of the first lower cushion portion 92, which is positioned below the seater's buttocks 100, is greater than the thickness of the second lower cushion portion 93 (other parts). By increasing the thickness of the lower cushion material 9 in the area of ​​the seat 4 where a large seating load is applied, the seating load can be reliably supported by the lower cushion material 9, and the cushioning when seated can be improved.

[0084] In the above embodiment, the seat 4 is provided with a seat cushion material 8 on the upper surface of the seat inner shell 7 which serves as the seat plate, but the upper surface of the seat plate may also constitute the seating surface of the seat 4. In this case, the seat plate does not need to have slits 7a for improving cushioning. Also, the upper surface of the seat plate that constitutes the seating surface may be covered with a surface material such as cloth.

[0085] The above describes specific examples of the present invention, but the present invention can be implemented in various other ways. For example, the shaft members 42 of the front and rear rotation support units 41 may be formed as a single unit. Furthermore, the elastic member 45 of the return mechanism 46 is not limited to a compression coil spring, but can be any type of spring body such as a torsion bar, leaf spring, or rubber, as long as it can apply rotational force to the shaft member 42 in a direction that causes the rotating body 43 to move outward in the width direction.

[0086] Furthermore, the rotating body 43 may be integrally formed with the shaft member 42. Also, the portion 71 of the inner seat shell 7 near the inner seat edge may be in contact with and supported by the shaft member 42 of the rotation support mechanism 40. In this case, the member for connecting the portion 71 near the inner seat edge and the shaft member 42 may be integrally formed with the portion 71 near the inner seat edge, the shaft member 42, or both.

[0087] Furthermore, the lower cushioning material 9 may be made of other elastic materials such as sliced ​​urethane, not just recycled cushioning (chip urethane) or a three-dimensional mesh fiber structure, or it may be a configuration in which multiple elastic materials are laminated.

[0088] Furthermore, the lower cushioning material 9 comprises a first lower cushioning portion 92 and a second lower cushioning portion 93 which are integrally formed, but the first lower cushioning portion 92 and the second lower cushioning portion 93 may be provided separately. In this case, the first lower cushioning portion 92 and the second lower cushioning portion 93 may be made of different materials. Also, the shape of the lower cushioning material 9 can be changed as appropriate; for example, the lower cushioning material 9 may be formed with a uniform thickness. Also, the lower cushioning material 9 may be positioned so as to protrude from the receiving recess 61. Furthermore, the shape and depth of the receiving recess 61 can be changed as appropriate.

[0089] Furthermore, the shape of the seat 4 and backrest 5 can be arbitrarily set as needed. In addition, the rocking mechanism 20 can employ not only a compression coil spring as a means of providing resistance to the backward tilting of the backrest 5, but also various spring bodies (elastic bodies) such as torsion bars, leaf springs, and rubber, or a locking means such as a gas cylinder to control the backward tilting position of the backrest 5. Moreover, the seat structure of the chair of the present invention can be applied to chairs without a rocking function or a chair without a swivel function, and can also be applied to floor chairs without support legs. [Explanation of Symbols]

[0090] 4 seats 7. Seat inner shell (seat plate) 8. Seat cushion material 42 Shaft member 43. Solids of revolution 45 Elastic members 46 Return mechanism

Claims

1. The seat structure of a chair, A pair of shaft members extending along the depth direction of the seat and provided at both ends in the width direction of the seat, A pair of rotating bodies that can rotate around the aforementioned shaft member as a rotation axis, A seat plate connecting the pair of rotating bodies and capable of bending and deforming in the thickness direction of the seat, The seat structure of a chair.

2. The device includes a return mechanism that, through the deformation of an elastic member, applies a rotational force to the shaft member in a direction toward the outward direction in the width direction of the rotating body. The seat structure of a chair according to claim 1.

3. The upper surface of the aforementioned seat board constitutes the seating surface. The chair seat structure according to claim 1 or 2.

4. The upper surface of the aforementioned seat plate is provided with cushioning material. The chair seat structure according to claim 1 or 2.

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