chair

Abstract

To provide a chair that can meet desired design requirements for the upright member and backrest body while suppressing the need for larger manufacturing equipment. [Solution] A chair according to one aspect of the present invention comprises a seat having an upward-facing seating surface, a pair of upright members extending on both sides of the seat in the left-right direction when viewed from the front, and spanning the seat vertically when viewed from the side, and a backrest body having a forward-facing backrest surface and positioned above the seat and behind the upright members. The backrest body is connected to the pair of upright members via connecting parts and comprises an inner shell that forms the skeleton of the backrest body from a different material than the upright members, and an outer material that constitutes the backrest surface and covers the inner shell and connecting parts together.

Description

Technical Field

[0001] The present invention relates to a chair.

Background Art

[0002] Conventionally, a chair having a backrest member in which a backrest portion and a pair of armrest portions are integrally formed has been known (see, for example, Patent Document 1 below). In this type of chair, the armrest portion extends upward through the side of the seat from a mounting portion provided below the seat. The backrest portion connects between the upper end portions of the pair of armrest portions above 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 above-described conventional technology, since the backrest portion and the armrest portion are integrally formed of a synthetic resin material, there is a problem that it is difficult to manufacture them so as to satisfy the desired design requirements. Further, there is also a problem that integrally forming the backrest portion and the armrest portion leads to an increase in the size of the mold.

[0005] The present invention provides a chair that can satisfy the desired design requirements for the upright member and the backrest body while suppressing an increase in the size of the manufacturing equipment.

Means for Solving the Problems

[0006] In order to solve the above problems, the present invention adopts the following aspects. (1) A chair according to one aspect of the present invention comprises a seat having an upward-facing seating surface, a pair of upright members arranged at a distance from the seat in the left-right direction on both sides of the seat, or in front of the seat, and extending so as to straddle the seat in the vertical direction in a side view, and a backrest body having a forward-facing backrest surface and positioned above the seat and behind the upright members, wherein the backrest body is connected to the pair of upright members via connecting parts and comprises an inner shell that forms the skeleton of the backrest body from a different material than the upright members, and an exterior material that constitutes the backrest surface and covers the inner shell and the connecting parts together.

[0007] According to this embodiment, by forming the upright member and the inner shell from different materials, unlike when the upright member and the inner shell are formed from the same material, it is possible to design each to satisfy desired design requirements. In this case, the inner shell, which constitutes the frame of the backrest, can be made of a softer material (for example, a synthetic resin material) than the upright member, while the upright member, which supports the load applied to the backrest body, can be made of a more rigid material than the inner shell, thereby improving the degree of design freedom. Furthermore, since the upright member and the inner shell can be manufactured separately, it is possible to suppress the increase in size of manufacturing equipment compared to when the upright member and the inner shell are integrally molded. Furthermore, in this embodiment, since the connecting portion that links the upright member and the inner shell is covered by the exterior material, it is possible to prevent the additional connecting portion, which would be added by making the upright member and the inner shell separate components, from being exposed to the outside of the chair. This improves the appearance of the chair.

[0008] (2) In the chair according to the embodiment of (1) above, it is preferable that the inner shell and the upright members are connected to each other by the connecting portion above the seat. According to this embodiment, the connection work between the upright member and the inner shell can be performed above the seat. This makes it easier to secure working space compared to connecting the upright member and the inner shell below the seat, and allows the connection work to be performed with the chair in an upright position. As a result, assembly workability can be improved.

[0009] (3) In the chair according to the embodiment of (2) above, the inner shell preferably comprises a shell body that supports the backrest surface from the rear, and a pair of shell protrusions that protrude forward from both ends in the left-right direction of the shell body, and the pair of upright members preferably each has an overlapping portion that overlaps in a plan view with the corresponding shell protrusion of the pair of shell protrusions and is connected to the shell protrusion by the connecting portion. According to this embodiment, the inner shell and the upright member are fixed in an overlapping state in a plan view. Therefore, compared to cases where, for example, the inner shell and the upright member are fixed together in a buttock-like position in the front-to-back direction, it is easier to withstand loads acting from above on the connection between the inner shell and the upright member.

[0010] (4) In the chair according to the embodiment of (3) above, it is preferable that the connecting portion comprises a bolt that penetrates the shell protrusion and the overlapping portion from below in a vertical direction, and a nut that is provided above the shell protrusion and the overlapping portion and is fastened to the bolt. According to this embodiment, by using bolts and nuts to fix the shell protrusions and connecting rods together, it is easy to ensure the connection strength between the shell protrusions and connecting rods. Furthermore, since the parts of the bolts and nuts that protrude from the connection between the shell protrusions and connecting rods can be covered with the exterior material, the shape of the bolts and nuts can be suppressed from being visible on the outer surface of the backrest body. As a result, the appearance can be improved.

[0011] (5) In the chair according to the embodiment of (4) above, the upright member comprises a vertical rod portion extending in the vertical direction and an overlapping portion extending rearward from the upper end of the vertical rod portion, wherein the dimension of the overlapping portion in the vertical direction is smaller than the dimension of the vertical rod portion in the vertical direction and the dimension of the vertical direction is larger than the dimension of the vertical rod portion in the vertical direction. According to this embodiment, since the vertical dimension of the connecting rod is smaller than the vertical dimension of the vertical rod, a shorter bolt can be used compared to when a bolt is driven vertically through the vertical rod. This makes assembly easier. Also, since the front-to-back dimension of the connecting rod is larger than the front-to-back dimension of the vertical rod, the degree of freedom regarding the outer diameter and number of bolts can be increased. This makes it easier to ensure the connection strength between the connecting rod and the shell projection. Furthermore, the rigidity of the connection between the inner shell and the upright member can be increased by the length of the front-to-back overlap. Therefore, at the connection between the inner shell and the upright member, unlike when rigidity is ensured by the inner shell alone, it is no longer necessary to incorporate design elements to increase the rigidity of the inner shell. In other words, the design of the inner shell can be simplified.

[0012] (6) In the chair according to the embodiment of (5) above, it is preferable that the vertical rod portion has a larger dimension in the front-to-back direction than in the left-to-right direction. According to this embodiment, even if the vertical rod portion is set to span the seat in the vertical direction, it is easier to withstand the load acting backward on the upright member due to the seating load acting on the backrest.

[0013] (7) In a chair according to any of the embodiments described in (1) to (6) above, it is preferable that the upright member is made of a material with higher rigidity than the inner shell. According to this embodiment, the upright member is more resistant to the load acting backward on it due to the seating load acting on the backrest. Since the inner shell is made of a softer material than the upright member, it can provide a flexible seating feel to the sitter's back.

[0014] (8) In the chair according to any one of the above aspects (7), a support structure for supporting the seat from below is provided, and the upright member is preferably connected to the front end portion of the support structure at the lower end portion and extends obliquely rearward as it goes upward. According to this aspect, since the upright member is formed of a material having high rigidity with respect to the inner shell, the connecting portion between the upright member and the support structure can be arranged away from the backrest surface in the front-rear direction. Thereby, the appearance of the chair can be improved.

Effects of the Invention

[0015] According to each of the above aspects, while suppressing the enlargement of manufacturing equipment, it is possible to satisfy desired design requirements for the upright member and the backrest body.

Brief Description of the Drawings

[0016] <00所望の設計要件を満たすことができる。It is a perspective view of the chair seen from the right rear. [[ID=所望の設計要件を満たすことができる。 [Figure 2] It is a partial side view of the chair. [Figure 3] It is a cross-sectional view corresponding to line III-III of FIG. 1. [Figure 4] It is a view of FIG. [Figure 5] It is a cross-sectional view corresponding to line V-V of FIG. 4. [Figure 6] It is an exploded perspective view of the upper structure. [Figure 7] It is a cross-sectional view corresponding to line VII-VII of FIG. 2. [Figure 8] It is a perspective view around the connecting rod portion. [Figure 9] It is a cross-sectional view corresponding to line IX-IX of FIG. 8. [Figure 10] It is a cross-sectional view corresponding to line X-X of FIG. 2. [Figure 11] It is a cross-sectional view of the chair showing the reclining state. [Figure 12] It is a perspective view showing another configuration of the chair. [Modes for carrying out the invention]

[0017] Next, embodiments of the present invention will be described with reference to the drawings. In the embodiments and modifications described below, corresponding components may be denoted by the same reference numerals and their descriptions omitted. In the following description, expressions indicating relative or absolute arrangements such as "parallel," "orthogonal," "center," and "coaxial" will not only strictly represent such arrangements, but will also represent states in which the surfaces are relatively displaced by an angle or distance that allows for tolerances or the same function to be obtained. Furthermore, in this embodiment, "facing each other" is not limited to cases where the orthogonal directions (normal directions) of the two surfaces coincide with each other, but also includes cases where the orthogonal directions intersect.

[0018] [Chair 1] Figure 1 is a perspective view of chair 1 from the right rear. Figure 2 is a partial side view of chair 1. As shown in Figures 1 and 2, the chair 1 comprises a support structure 2, a seat 3, an upper structure 4, and an operating unit 5. The chair 1 is configured such that the seat 3 is displaced backward and downward in conjunction with the reclining movement of the upper structure 4. In the following description, directions such as front, back, up, down, left, and right are the same as the direction of a person (sitter) sitting in the chair 1 in a normal posture. In this case, the arrow UP in the figures indicates upward, the arrow FR indicates forward, and LH indicates left. Also, in the following description, in the front-back, up-down, and left-right directions, the side away from the center of the chair 1 may be referred to as the outside, and the side toward the center of the chair 1 may be referred to as the inside.

[0019] <Support structure 2> The support structure 2, while in contact with the floor surface F, supports the seat 3 and the upper structure 4 from below. The support structure 2 comprises a leg 11 and a base 12. The leg body 11 comprises a multi-branched leg 15 and a leg column 16. Each leg of the multi-legged structure 15 is fitted with a caster 17 that allows it to move on the floor surface F. However, the casters 17 are not an essential component. For example, the leg body 11 may be in contact with the floor surface F via adjusters or the like instead of casters 17.

[0020] Figure 3 is a cross-sectional view corresponding to the line III-III in Figure 1. As shown in Figures 1 and 3, the leg column 16 extends upward from the central part of the multi-legged leg 15. The leg column 16 has a gas spring 18 built into it, which is the lifting mechanism of the chair 1. The gas spring 18 is configured such that an inner cylinder 18a is supported so as to be able to move up and down and rotate relative to an outer cylinder (not shown) provided inside the leg cover 19, for example. An operating pin 18b for extending and retracting the gas spring 18 protrudes upward from the inner cylinder 18a. In other words, the gas spring 18 can extend and retract (move forward and backward relative to the outer cylinder) when the operating pin 18b is pushed in.

[0021] Figure 4 is a view taken from arrow IV in Figure 2, showing a portion of the support base 12 broken away. As shown in Figures 3 and 4, the support base 12 is a box-shaped support mechanism (support base) that is connected to the seat 3 and the superstructure 4 at the upper end of the support structure 2. The support base 12 comprises a casing 21, a tilting mechanism 22, and a linkage mechanism 23.

[0022] The casing 21 is connected to the upper end of the leg column 16 (inner cylinder 18a). In the side view shown in Figure 2, the casing 21 is formed in a box shape that is flattened vertically. As shown in Figure 3, a housing hole 21b is formed at the rear end of the casing 21, penetrating vertically through the bottom wall portion 21a of the casing 21. The upper end of the leg column 16 is inserted into the casing 21 from below through the housing hole 21b. As a result, the casing 21 is cantilevered to the leg column 16, tilting upward as it moves forward. The operating pin 18b of the gas spring 18 protrudes into the casing 21 through the housing hole 21b.

[0023] In the plan view shown in Figure 4, the casing 21 is formed in a triangular shape, with its width gradually increasing in the left-right direction towards the front. As shown in Figures 2 and 4, a lateral connecting port 21c is formed at the front end of the casing 21, allowing the inside and outside of the casing 21 to communicate in the left-right direction. The lateral connecting port 21c is formed by opening a portion of the side wall portion 21d located on both sides of the casing 21 in the left-right direction.

[0024] As shown in Figure 3, an upward-opening upper connection port 21e is formed at the front of the casing 21. The upper connection port 21e communicates with a lateral connection port 21c. The portion of the casing 21 located behind the upper connection port 21e constitutes the top wall portion 21f. In a plan view, the top wall portion 21f faces the lower surface of the base 3 with a vertical gap between them, at least in the portion that overlaps with the leg column 16.

[0025] In the bottom wall portion 21a, a pair of left and right support walls 24 are provided in the portion located between the housing hole 21b and the lateral connecting port 21c. The support walls 24 extend upward from the bottom wall portion 21a with the left-right direction as the thickness direction. The support walls 24 may be integrally formed with the casing 21, or separate support walls 24 may be fixed to the casing 21.

[0026] The tilting mechanism 22 connects the base 12 and the seat 3, and the base 12 and the superstructure 4. In other words, in the chair 1 of this embodiment, the seat 3 and the superstructure 4 are connected to each other via the base 12. The tilting mechanism 22, together with the seat 3, constitutes a so-called four-bar linkage mechanism. The tilting mechanism 22 includes a front link 25 and a rear link 26.

[0027] As shown in Figures 3 and 4, the front link 25 is provided at the front end of the casing 21. Specifically, the front link 25 comprises a front base 28 and a pair of overhangs 29 (see Figure 4). The front base 28 is housed at the front end of the casing 21. The front base 28 is supported at its rear end by the casing 21 via the main shaft 31 (see Figure 3). The main shaft 31 is provided to traverse the casing 21 in the left-right direction. Specifically, both ends of the main shaft 31 in the left-right direction pass through the support wall 24 in the left-right direction and are then supported by the portion of the side wall 21d located behind the lateral linkage opening 21c. As a result, the front link 25 is provided so as to be rotatable relative to the casing 21 around the axis of the main shaft 31 (main axis C1). In this embodiment, the front link 25 is rotatable so as to be displaceable in the vertical direction at its front end.

[0028] As shown in Figure 4, the protruding portions 29 each project outward in the left-right direction from the front end of the front base 28. Each protruding portion 29 projects outward from the casing 21 through the corresponding lateral connection opening 21c.

[0029] As shown in Figure 3, the rear links 26 are located within the casing 21, behind the front links 25. The rear links 26 are provided in pairs, left and right. Each rear link 26 extends in a manner that is inclined backward as it extends upward. The rear links 26 are supported at their lower ends by the support wall 24 via a lower shaft member 33. In the illustrated example, the lower shaft member 33 is located in the support wall 24, behind and above the main shaft 31. The lower shaft member 33 is located in front of the leg column 16. The rear links 26 are rotatable relative to the support wall 24 (casing 21) around the axis of the lower shaft member 33 (lower axis C2).

[0030] The linkage mechanism 23 is a mechanism for linking the operating unit 5 and the gas spring 18. The linkage mechanism 23 is located in the casing 21 in a part that is rearward of the lower shaft member 33. The linkage mechanism 23 is located above the housing hole 21b and is rotatable around an axis that runs in the left-right direction. The linkage mechanism 23 rotates in conjunction with the operation of the operating unit 5, thereby pushing in the operating pin 18b.

[0031] <Location 3> As shown in Figures 1 and 4, the seat 3 is formed in a circular or rectangular shape in plan view, and supports the seater's buttocks and thighs from below on its upward-facing seating surface 3a. The seat 3 comprises a seat support member 38 and a seat body 39.

[0032] As shown in Figures 3 and 4, the seating member 38 is connected to the support base 12 while covering the casing 21 from above. Specifically, the seating member 38 comprises a seating plate 41, a pair of outer connecting pieces 42, and a pair of inner connecting pieces 43. The seat support plate 41 is positioned above the support base 12, with its thickness oriented vertically. The seat support plate 41 protrudes outward in the left-right direction relative to the casing 21.

[0033] The outer connecting piece 42 protrudes downward from the seat plate 41, spaced apart in the left-right direction. The outer connecting piece 42 extends over the entire front-rear area of ​​the seat plate 41, excluding the front and rear ends. In a side view, the outer connecting piece 42 covers at least a portion of the rear link 26 described above from the outside in the left-right direction. The length of the outer connecting piece 42 in the front-rear direction can be changed as appropriate.

[0034] The front end of the outer connecting piece 42 is connected to the front end of the front base 28 via the seat support shaft 45 within the upper linkage opening 21e. The seat support shaft 45 extends parallel to the main shaft 31 in a portion located in front of and above the main shaft 31. The seat support shaft 45 is rotatably connected to the outer connecting piece 42 and the front base 28 around an axis (seat support axis C3) that runs along the left-right direction. The seat receiving member 38 is configured to be rotatable around the seat support axis C3 relative to the front link 25 and to revolve around the main axis C1 relative to the support base 12. That is, the front end of the seat 3 is rotatable so as to be displaced vertically and longitudinally relative to the support base 12. Specifically, the front end of the seat 3 is displaceable upward and backward relative to its initial state. The position of the seat support shaft 45 relative to the main shaft 31 can be changed as appropriate. That is, the seat support shaft 45 may be coaxial with the main shaft 31, or it may be positioned rearward or below the main shaft 31.

[0035] The inner connecting piece 43 protrudes downward from a portion located inward in the left-right direction relative to the pair of outer connecting pieces 42 at the center of the seat plate 41 in the front-rear direction, with a gap in the left-right direction. At least a portion of the inner connecting piece 43 is covered by the outer connecting piece 42 from the outside in the left-right direction when viewed from the side. As shown in Figure 3, the inner connecting piece 43 is connected to the upper end of the rear link 26 via the upper shaft member 46 within the upper linkage opening 21e. The upper shaft member 46 extends parallel to the lower shaft member 33 in a portion located rearward and above the lower shaft member 33. The upper shaft member 46 is connected so as to be rotatable relative to the inner connecting piece 43 and the upper end of the rear link 26 around an axis (upper axis C4) that runs along the left-right direction. That is, the rear end of the seat 3 can be displaced downward and rearward in relation to the upward and rearward displacement of the front end of the seat 3 from its initial state. The position of the lower shaft member 33 relative to the upper shaft member 46 can be changed as appropriate.

[0036] The seat body 39 is supported from below by the seat support member 38. The seat body 39 comprises a main part 39a and a downward-sloping front part 39b. The main portion 39a is the part that constitutes the plan view outline of the seat 3. The main portion 39a protrudes from the seat support member 38 on both sides in the left-right direction and to the rear. The rear end edge of the main portion 39a is located behind the rear end of the support base 12. The downward-sloping portion 39b is the part that extends downward from the front end of the main portion 39a. In a front view, the downward-sloping portion 39b overlaps with the front end of the support base 12. Of the seat body 39, at least the portion from the upper surface of the main portion 39a to the front surface of the downward-sloping portion 39b functions as the seating surface 3a when seated.

[0037] Here, since the seat 3 (seat support member 38) is connected to the rear link 26 at its central part in the front-rear direction, a vertical gap is created between the rear of the seat 3 and the rear of the support base 12. In other words, the rear of the seat 3 extends backward from the support base 12 as if it were cantilevered. Note that it is sufficient for a vertical gap to exist between the seat 3 and the support base 12 at least at a position where it overlaps with the leg column 16 in a plan view.

[0038] Figure 5 is a cross-sectional view corresponding to the VV line in Figure 4. As shown in Figures 3 and 5, the seat body 39 comprises a seat shell 50, a cushioning material 51, and a surface material 52. The seat shell 50 is formed from a hard material such as synthetic resin or metal, and functions as a structural member of the seat body 39. The seat shell 50 is formed over the main portion 39a and the downward-sloping front portion 39b of the seat body 39. The cushioning material 51 is provided on at least the portion of the seat shell 50 that faces (overlaps with) the seating surface 3a, and elastically supports the sitter. In this embodiment, the cushioning material 51 covers the upper surface of the seat shell 50 and also covers the outer peripheral portion of the lower surface of the seat shell 50 by wrapping around the outer peripheral edge of the seat shell 50 to the lower surface of the seat shell 50. The surface material 52 forms the outer surface of the seat body 39, including the seating surface 3a, and covers the seat shell 50 and cushioning material 51 together.

[0039] <Superstructure 4> Figure 6 is an exploded perspective view of the superstructure 4. As shown in Figures 1 and 6, the upper structure 4 incorporates the functions of both an armrest 100 and a backrest 101. The upper structure 4 comprises a pair of upright members 60, a backrest body 61, and a connecting part 62. Each of the upright members 60 is a molded product integrally formed from, for example, a metal material (such as aluminum). Each upright member 60 connects the base 12 and the backrest body 61. Each upright member 60 is provided on both sides in the left-right direction relative to the seat 3. Each upright member 60 has a symmetrical configuration. Therefore, the details of the upright members 60 will be described below using one of the upright members 60 on the left-right side as an example.

[0040] The upright member 60 is formed in an L-shape in both a plan view and a side view. Specifically, the upright member 60 comprises a horizontal rod portion 65, a vertical rod portion 66, and a connecting rod portion 67. As shown in Figures 4 and 6, the transverse rod portion 65 extends in the left-right direction below the seat 3. The transverse rod portion 65 has an insertion opening 65a that opens inward in the left-right direction. The protruding portion 29 of the front link 25 is fixed to the transverse rod portion 65 by being inserted into the transverse rod portion 65 through the insertion opening 65a. As shown in Figure 3, the upright member 60 can revolve around the main axis C1 as the front link 25 rotates around the main axis C1. The transverse rod portion 65 extends from below the seat 3 to the side, inclining upward as it moves outward in the left-right direction. In the illustrated example, the lower surface of the transverse rod portion 65 smoothly connects to the lower surface of the casing 21. Also, as shown in Figure 2, the transverse rod portion 65 is close to or in contact with the front downward portion 39b from the rear. In this case, at least a portion of the horizontal rod portion 65 is covered from the front by the downward-sloping portion 39b when viewed from the front.

[0041] As shown in Figures 2 and 6, the vertical rod portion 66 extends upward from the left-right outer end of the horizontal rod portion 65. The vertical rod portion 66 extends in the left-right outer region relative to the seat 3, and in a side view, it straddles the seat 3 in the vertical direction. The vertical rod portion 66 extends with a backward inclination as it goes upward. In a side view, the inclination angle of the vertical rod portion 66 with respect to the front-rear direction is the same as the inclination angle of the downward-sloping front portion 39b with respect to the front-rear direction. In addition, the front-rear dimension of the vertical rod portion 66 gradually increases as it goes upward. Note that the portion of the inner surface of the vertical rod portion 66 that intersects with the seat 3 (seat body 39) may be in contact with the surface of the seat body 39 that faces outward in the left-right direction. In this case, the inner surface of the vertical rod portion 66 may be in contact with the seat body 39 in such a way that it presses it inward in the left-right direction. However, there may be a gap between the inner surface of the vertical rod portion 66 and the seat body 39 that is small enough to prevent fingers or other objects from entering (for example, about 5 mm).

[0042] Figure 7 is a cross-sectional view corresponding to the line VII-VII in Figure 2. As shown in Figures 6 and 7, the vertical rod portion 66 is formed in a flattened shape with the front-to-back direction as the longitudinal direction and the left-to-right direction as the short direction in a cross-sectional view perpendicular to the vertical direction. In the illustrated example, the vertical rod portion 66 extends with its outer surface curving inward in the left-to-right direction as it moves forward, so that the left-to-right dimension gradually decreases as it moves forward. The cross-sectional shape of the vertical rod portion 66 can be changed as appropriate, such as to be rectangular or circular.

[0043] Figure 8 is a perspective view of the area around the connecting rod 67. As shown in Figures 6 and 8, the connecting rod portion 67 functions as a connecting portion between the backrest body 61 and the upright member 60. The connecting rod portion 67 protrudes upward from a part of the upper end surface of the vertical rod portion 66 and extends backward from the vertical rod portion 66. The connecting rod portion 67 is flattened in the left-right direction and extends cantilevered backward from the vertical rod portion 66. Of the upper end surface of the vertical rod portion 66, the portions extending forward from both sides in the left-right direction relative to the connecting rod portion 67 (the portions that do not overlap with the connecting rod portion 67 in a plan view) constitute a stepped surface 66a.

[0044] Figure 9 is a cross-sectional view corresponding to the IX-IX line in Figure 8. As shown in Figures 8 and 9, the connecting rod 67 is formed in a frustoconical shape, with its dimensions gradually decreasing in the front-to-back and left-to-right directions as it extends upward. The vertical dimension H67 (maximum dimension) of the connecting rod 67 is smaller than the vertical dimension H66 of the vertical rod 66 (see Figure 2). Note that the dimension H66 of the vertical rod 66 shown in Figure 3 is the dimension in the extending direction of the vertical rod 66.

[0045] The connecting rod portion 67 has a dimension T67 in the front-rear direction that is greater than the dimension T66 of the vertical rod portion 66 in the front-rear direction. In this embodiment, the dimension T67 of the connecting rod portion 67 and the dimension T66 of the vertical rod portion 66 are the maximum dimensions in the front-rear direction. In the example in Figure 9, the upper surface of the connecting rod portion 67 is formed as a flat surface perpendicular to the vertical direction. On the other hand, the lower surface of the connecting rod portion 67 is formed as an inclined surface that extends upward as it approaches the rear.

[0046] Figure 10 is a cross-sectional view corresponding to line XX in Figure 2. As shown in Figure 10, in a cross-sectional view perpendicular to the vertical direction, the connecting rod 67 extends with its outer surface curving inward in the left-right direction as it moves forward, so that its left-right dimension gradually decreases as it moves forward.

[0047] As shown in Figures 1 and 6, the backrest body 61 connects the upright members 60 to each other by wrapping around the seat 3 from the rear end above it. The backrest body 61 comprises an inner shell 70 and an outer material 71. The inner shell 70 forms the framework of the backrest body 61. The inner shell 70 is made of a different material than the upright member 60. In this embodiment, the inner shell 70 is a molded product integrally formed by, for example, stamping a synthetic resin material. That is, in the upper structure 4, the upright member 60 is made of a material with higher rigidity than the inner shell 70. The inner shell 70 may also be formed by injection molding or the like.

[0048] As shown in Figures 6 and 10, the inner shell 70 comprises a shell body 75 and a shell projection 76. The shell body 75 is the part of the inner shell 70 that mainly forms the frame of the backrest 101. In a plan view, the shell body 75 is positioned so that at least a part of it overlaps with the rear end of the seat 3. In a plan view, the shell body 75 extends in the left-right direction, following the shape of the rear end of the seat 3. The shell body 75 has its thickness in the front-back direction and extends in the up-down direction. In a side view, the shell body 75 extends while sloping backward as it goes upward, and then extends further upward. In a front view, the shell body 75 extends outward in the left-right direction while curving downward as it goes downward. Note that the shell body 75 may extend linearly in the left-right direction in a plan view, for example, as long as it has at least a surface facing forward.

[0049] Each shell projection 76 is located at the lower end of the shell body 75 and protrudes forward from both ends in the left-right direction. Each shell projection 76 has a symmetrical configuration. Therefore, the details of the shell projection 76 will be described below using one of the shell projections 76 in the left-right direction as an example.

[0050] The shell projection 76 comprises an outer plate 81 and a bulging portion 82. The outer plate 81 is the part of the inner shell 70 that mainly forms the frame of the armrest 100. The outer plate 81 extends forward from the shell body 75 so as to be continuous with the outer surface of the shell body 75. The outer plate 81 is flattened in the left-right direction and extends in the front-back direction. Specifically, in a plan view, the outer plate 81 extends outward in the left-right direction as it moves forward, and then extends inward in the left-right direction as it moves further forward. In the illustrated example, the outer plate 81 is formed in a curved shape with a projection on the left-right outward side.

[0051] The lower end surface of the outer plate 81 is flush with the lower end surface of the shell body 75, and together with the lower end surface of the shell body 75, it constitutes the lower end surface of the inner shell 70. As shown in Figures 3 and 8, the lower end surface of the inner shell 70 extends along the upper edge of the seat 3, leaving a gap between it and the upper edge of the seat 3 in both the side view and the front view. Also, as shown in Figure 6, the upper end surface of the outer plate 81 curves upward as it is directed towards the rear. The upper end surface of the outer plate 81 smoothly connects with the left-right outer end surfaces of the shell body 75.

[0052] The bulge portion 82 bulges inward in the left-right direction at the front end of the outer plate 81. The lower end surface of the bulge portion 82 is flush with the lower end surface of the outer plate 81. The bulge portion 82 has a base surface 82a located below the upper end surface of the outer plate 81. The base surface 82a is a flat surface extending in the front-rear direction.

[0053] As shown in Figures 5, 8, and 9, the shell projection 76 has a receiving recess 76a that opens downward. The receiving recess 76a is a recess formed to conform to the outer shape of the connecting rod 67. The receiving recess 76a is formed spanning the outer plate 81 and the bulging portion 82. The connecting rod 67 is housed in the receiving recess 76a from below. The upper end surface of the connecting rod 67 abuts against the top surface of the inner surface of the receiving recess 76a, thereby positioning the inner shell 70 in the vertical direction relative to the upright member 60. When the connecting rod 67 is housed in the receiving recess 76a, the portion of the lower end surface of the shell projection 76 that overlaps with the vertical rod 66 in a plan view is close to or in contact with the stepped surface 66a. On the other hand, the portion of the lower end surface of the shell projection 76 that does not overlap with the vertical rod portion 66 in a plan view is located below the lower end surface of the connecting rod portion 67.

[0054] The connecting portion 62 is for connecting the upright member 60 and the inner shell 70 between the connecting rod portion 67 and the shell projection portion 76. The connecting portion 62 includes a mounting seat 85 and a fastening member 86. The mounting base 85 is a plate made of metal or the like. The mounting base 85 is positioned on the base surface 82a. The mounting base 85 may be fixed to the bulging portion 82 by screws 87 (see Figure 9) or the like.

[0055] The fastening member 86 connects the bulging portion 82 and the connecting rod portion 67 with the mounting seat 85 in between. The fastening member 86 is, for example, a bolt 86a and a nut 86b. The fastening member 86 connects the bulging portion 82 and the connecting rod portion 67 by tightening a nut 86b from above onto the mounting seat 85 with a bolt 86a that penetrates the connecting rod portion 67, the bulging portion 82, and the mounting seat 85 from below. In other words, the fastening member 86 connects the upright member 60 and the inner shell 70 above the seat 3. In this embodiment, multiple fastening members 86 (for example, two) are provided at intervals in the front-rear direction. The head of the bolt 86a is housed in a recess that opens onto the lower end surface of the connecting rod portion 67, and is therefore located above the lower end surface of the connecting rod portion 67. Furthermore, the shaft portion of the bolt 86a and the nut 86b are covered from the outside in the left-right direction by the outer plate 81 above the bulging portion 82.

[0056] The exterior material 71 comprises a cushioning material 91 and a surface material 92. The cushioning material 91 mainly covers the inner surface (front and inward-facing surfaces in the left and right directions) and the upper end surface of the inner shell 70. In this case, the cushioning material 91 is also housed within the stepped portion 93 surrounded by the outer plate 81 and the bulging portion 82, thereby covering the mounting seat 85 and the fastening member 86 (the shaft portion of the bolt 86a and the nut 86b). In other words, the exterior material 71 collectively covers at least a portion of the inner shell 70 and the connecting portion 62.

[0057] The outer material 92 covers the cushioning material 91 and the inner shell 70 together. Specifically, the outer material 92 is provided so as to overlap the inner shell 70 from above. As a result, the cushioning material 91 and the inner shell 70 are covered by the outer material 92 from both sides in the front-to-back direction, both sides in the left-to-right direction, and from above. At its lower end, the outer material 92 is fixed to the lower end surface of the inner shell 70 or the inner surface of the housing recess 76a by staples T (see Figures 5 and 9). In this case, the fixing portion (staples T) between the outer material 92 and the inner shell 70 is provided within the housing recess 76a, and the connecting rod portion 67 is housed within the housing recess 76a, so it is not exposed to the outside of the chair 1. Furthermore, by housing the connecting rod portion 67 within the housing recess 76a, its periphery (at least above and on both the front, back, left, and right sides) is surrounded by the shell projection portion 76. Furthermore, since the shell projection 76 is surrounded by the surface material 92, the connecting rod 67 is also surrounded by the surface material 92.

[0058] In the superstructure 4, the shell projection 76 of the backrest body 61, the connecting rod 67, and the portion of the exterior material 71 that covers the shell projection 76 constitute the armrest 100. In this case, the portion of the exterior material 71 that constitutes the upper surface of the armrest 100 functions as an elbow support surface 100a that supports the elbow of the seated person. In the superstructure 4, the shell body 75 of the backrest body 61 and the portion of the exterior material 71 that covers the shell body 75 constitute the backrest 101. In this case, the portion of the exterior material 71 that constitutes the front of the backrest 101 functions as a backrest surface 101a that supports the back of the seated person. In this embodiment, the backrest 100 is connected to the upright member 60 via the armrest 101. That is, the seating load acting on the superstructure 4 is transmitted to the support base 12 via the upright member 60.

[0059] <Operation unit 5> As shown in Figures 2, 4, and 5, the operating unit 5 is for operating the gas spring 18 via the linkage mechanism 23. The operating unit 5 is provided on the underside of the seat 3 via a lever stay 110. The lever stay 110 is a fixing bracket for fixing the operating unit 5 to the seat 3. As shown in Figure 4, the lever stay 110 is fixed to the right end of the seat support plate 41, in a portion located behind the upright member 60. A portion of the lever stay 110 protrudes outward (to the right) from the seat support plate 41 in the left-right direction.

[0060] The operating part 5 is a lever. The operating part 5 is located on the underside of the seat 3, in a side view, behind the horizontal rod 65 and the vertical rod 66, and in front of the leg column 16. Therefore, the operating part 5 is located in front of the rear end of the support base 12. Alternatively, the operating part 5 is located on the underside of the seat 3, in a plan view, to the right of the center in the left-right direction. In this case, in a plan view, the operating part 5 is located in a position shifted to the right of the support base 12, and the entire unit overlaps the seat 3.

[0061] The operating unit 5 comprises a base member 120 and an operating element 121. The base member 120 is fixed to the portion of the lever stay 110 that protrudes from the seat support plate 41. That is, the operating part 5 overlaps with the seat body 39 in a plan view in the portion located outward in the left-right direction from the seat support member 38. The base member 120 extends in the front-rear direction along the right edge of the seat support plate 41. As shown in Figure 5, the upper surface of the base member 120 is formed as an inclined surface that extends upward as it moves outward in the left-right direction, following the lower surface of the seat body 39.

[0062] The control element 121 is the part operated by the seated person or the like when raising or lowering the seat 3. The control element 121 is positioned below the base member 120, overlapping at least a portion of the base member 120 in the vertical direction. In a plan view, the control element 121 is formed in a fan shape, with its width gradually increasing in the left-right direction towards the rear. At its front end, the control element 121 is supported by the base member 120 so as to be rotatable around an operating axis O that runs along the vertical direction.

[0063] In the cross-sectional view perpendicular to the front-to-back direction shown in Figure 5, the operator 121 is formed in a stepped shape, with the vertical dimension gradually increasing as it moves outward in the left-to-right direction. The connecting surface of the upper and middle sections of the operator 121 constitutes a first handle portion 121a facing inward in the left-to-right direction. The connecting surface of the middle and lower sections of the operator 121 constitutes a second handle portion 121b facing inward in the left-to-right direction. Each handle portion 121a and 121b is a part on which a seated person or the like can hook their fingers when operating the operator 121.

[0064] The operator 121 is connected to the linkage mechanism 23 via the wire W shown in Figures 3 and 4. The operation unit 5 operates the linkage mechanism 23 when the wire W is displaced by the rotational operation of the operator 121 around the operating axis O.

[0065] <Height adjustment of seat 3> When raising or lowering the seat 3, the occupant inserts their hand from above the armrest 100, through the left and right outer side of the upright member 60, and under the seat 3. In this position, they hook their fingers into either the handgrip portion 121a or 121b and pull the operator 121 outwards in the left and right direction. As a result, the operator 121 rotates outwards in the left and right direction around the operating axis O from its initial position, which activates the linkage mechanism 23 via the wire W. Consequently, the operating pin 18b is pushed in via the linkage mechanism 23, enabling the gas spring 18 to extend and retract.

[0066] In other words, the seat 3 can be raised and lowered by rotating the operator 121. Specifically, by applying a load to the seat 3 that is greater than the biasing force of the gas spring 18, the gas spring 18 compresses and the seat 3 descends. On the other hand, if the load applied to the seat 3 is less than the biasing force of the gas spring 18, the gas spring 18 extends and the seat 3 rises. When the operator 121 is released, the operator 121 returns to its initial position due to the biasing force of a biasing member (not shown) interposed between the operator 121 and the base member 120. This releases the pushing operation of the operating pin 18b by the linkage mechanism 23. As a result, the extension and retraction movement of the gas spring 18 is restricted.

[0067] <Reclining motion of seat 3> Figure 11 is a cross-sectional view of chair 1 in the reclined position. In Figure 11, the dashed line indicates the initial state (before reclining) of the seat 3 and upper structure 4. As shown in Figures 3 and 11, when a person sits on the seat 3 of the chair 1 in its initial state and leans against the backrest 101 via the backrest surface 101a, the seating load acting on the backrest 101 is transmitted to the front link 25 via the upright member 60. As a result, the front link 25 rotates around the main axis C1, causing the entire upper structure 4 to rotate backward and downward.

[0068] As the front link 25 rotates around the main axis C1, the seat support axis C3 revolves around the main axis C1, causing the front end of the seat 3 to rotate backward and upward. Meanwhile, the seat 3 is connected to the base 12 via the rear link 26 at its center in the front-rear direction. Therefore, in accordance with the displacement of the front end of the seat 3, the rear link 26 rotates so that the upper axis C4 revolves around the lower axis C2. Consequently, in accordance with the displacement of the front end of the seat 3, the rear end of the seat 3 rotates backward and downward. In other words, in the chair 1 of this embodiment, the seat 3 is displaced backward and downward in accordance with the reclining operation of the upper structure 4.

[0069] In this embodiment, the distance between the lower axis C2 and the upper axis C4 is shorter than the distance between the main axis C1 and the seat support axis C3. Therefore, the amount of rotation of the seat 3 around the main axis C1 is smaller than the amount of rotation of the upper structure 4 around the main axis C1.

[0070] Reference numeral 125 in Figure 11 indicates a reaction spring mechanism that biases the seat 3 and the upper structure 4 to their initial state via the front link 25. The reaction spring mechanism 125 is interposed between the support wall 24 and the front link 25. That is, when the seating load acting on the backrest 101 is released, for example, when the seated person moves away from the backrest surface 101a, the front link 25 rotates around the main axis C1 due to the biasing force of the reaction spring mechanism 125. This returns the upper structure 4 and the seat 3 to their initial state. The chair 1 may also be equipped with a tilting operation unit that switches between a locked state that restricts the rotation of the upper structure 4 and the seat 3 via the tilting mechanism 22, and an unlocked state that allows the rotation of the upper structure 4 and the seat 3.

[0071] The chair 1 of this embodiment comprises a seat 3 having a seating surface 3a, a pair of upright members 60 positioned at a distance from the seat 3 in the left-right direction on both sides of the seat 3 or in front of the seat 3, and extending so as to straddle the seat 3 in the vertical direction when viewed from the side, and a backrest body 61 having a backrest surface 101a facing forward, positioned above the seat 3 and behind the upright members 60. The backrest body 61 is connected to the pair of upright members 60 via connecting parts 62 and comprises an inner shell 70 that forms the skeleton of the backrest body 61 from a different material than the upright members 60, and an exterior material 71 that constitutes the backrest surface 101a and covers the inner shell 70 and the connecting parts 62 together. With this configuration, by forming the upright member 60 and the inner shell 70 from different materials, it is possible to design each to meet desired design requirements, unlike when the upright member 60 and the inner shell 70 are formed from the same material. In this case, the inner shell 70, which constitutes the frame of the backrest 101, can be made of a softer material (for example, synthetic resin) than the upright member 60, while the upright member 60, which supports the load applied to the backrest body 61, can be made of a more rigid material than the inner shell 70, thereby improving the degree of design freedom. Furthermore, since the upright member 60 and the inner shell 70 can be manufactured separately, it is possible to suppress the increase in size of manufacturing equipment compared to when the upright member 60 and the inner shell 70 are integrally molded. Furthermore, in this embodiment, since the connecting portion 62 that connects the upright member 60 and the inner shell 70 is covered by the exterior material 71, the connecting portion 62, which is added by making the upright member 60 and the inner shell 70 separate components, is not exposed to the outside of the chair 1. This improves the appearance of the chair 1.

[0072] In the chair 1 of this embodiment, the upright member 60 and the inner shell 70 are connected to each other by a connecting portion 62 above the seat 3. With this configuration, the connection work between the upright member 60 and the inner shell 70 can be performed above the seat 3. This makes it easier to secure working space compared to when the upright member 60 and the inner shell 70 are connected below the seat 3, and the connection work can be performed with the chair 1 in an upright position. As a result, assembly workability can be improved.

[0073] In the chair 1 of this embodiment, the inner shell 70 comprises a shell body 75 located behind the backrest surface 101a, and a pair of shell protrusions 76 projecting forward from both ends of the shell body 75 in the left-right direction. The pair of upright members 60 each have a connecting rod (overlapping portion) 67 that overlaps in a plan view with the corresponding shell protrusion 76 of the pair of shell protrusions 76 and is connected to the shell protrusion 76 by a connecting portion 62. In this configuration, the inner shell 70 and the upright member 60 are fixed in a state where they overlap in the vertical direction. Therefore, compared to, for example, the case where the inner shell 70 and the upright member 60 are fixed together in the front-to-back direction, this configuration is more resistant to loads acting from above on the connection between the inner shell 70 and the upright member 60.

[0074] In the chair 1 of this embodiment, the connecting portion 62 includes a bolt 86a that penetrates the shell projection 76 and the connecting rod portion 67 from below in a vertical direction, and a nut 86b that is provided above the shell projection 76 and the connecting rod portion 67 and is tightened onto the bolt 86a. With this configuration, the connection strength between the shell projection 76 and the connecting rod 67 can be easily ensured by using bolts 86a and nuts 86b to fix the shell projection 76 and the connecting rod 67 together. Furthermore, since the parts of the bolts 86a and nuts 86b that protrude from the connection between the shell projection 76 and the connecting rod 67 can be covered by the exterior material 71, the shape of the bolts 86a and nuts 86b can be suppressed from being visible on the outer surface of the superstructure 4. As a result, the appearance can be improved.

[0075] In the chair 1 of this embodiment, the upright member 60 includes a vertical rod portion 66 extending in the vertical direction and a connecting rod portion 67 extending rearward from the upper end of the vertical rod portion 66. The connecting rod portion 67 has a vertical dimension H67 that is smaller than the vertical dimension H66 of the vertical rod portion 66, and a front-to-back dimension T67 that is larger than the front-to-back dimension T66 of the vertical rod portion 66. With this configuration, the vertical dimension H67 of the connecting rod 67 is smaller than the vertical dimension H66 of the vertical rod 66, allowing the use of shorter bolts 86a compared to when the bolts 86a are passed vertically through the vertical rod 66. This simplifies assembly. Furthermore, since the front-to-back dimension T67 of the connecting rod 67 is larger than the front-to-back dimension T66 of the vertical rod 66, the degree of freedom regarding the outer diameter and number of bolts 86a can be increased. This makes it easier to ensure the connection strength between the connecting rod 67 and the shell projection 76. In addition, the rigidity of the connection between the inner shell 70 and the upright member 60 can be increased by the length of the connecting rod 67 in the front-to-back direction. Therefore, at the connection between the inner shell 70 and the upright member 60, unlike when rigidity is ensured by the inner shell 70 alone, it is no longer necessary to incorporate design elements to increase the rigidity of the inner shell 70. In other words, the design of the inner shell 70 can be simplified.

[0076] In the chair 1 of this embodiment, the vertical rod portion 66 has a larger dimension in the front-to-back direction compared to its dimension in the left-to-right direction. With this configuration, even if the vertical rod portion 66 is set to span the seat 3 in the vertical direction, it can easily withstand the load acting backward on the upright member 60 due to the seating load acting on the backrest 101.

[0077] In the chair 1 of this embodiment, the upright member 60 is made of a material with greater rigidity than the inner shell 70. With this configuration, even if a load is applied to the upright member 60 from the seating load acting on the backrest 101, deformation of the upright member 60 can be suppressed. Since the inner shell 70 is made of a softer material than the upright member 60, it can provide a flexible seating feel to the sitter's back.

[0078] In the chair 1 of this embodiment, a support structure 2 is provided to support the seat 3 from below, and the upright member 60 is connected to the front end of the support structure 2 at its lower end and extends inclined towards the rear as it goes upward. With this configuration, since the upright member 60 is made of a material with higher rigidity than the inner shell 70, the connection between the upright member 60 and the support structure 2 can be positioned away from the backrest surface 101a in the front-rear direction. This improves the appearance of the chair 1.

[0079] (Other variations) While preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments. Additions, omissions, substitutions, and other modifications are possible without departing from the spirit of the present invention. The present invention is not limited by the above description, but only by the appended claims. In the embodiment described above, a configuration was described in which the inner shell 70 and the upright member 60 are connected in a state where they are overlapped in the vertical direction, but the configuration is not limited to this. The inner shell 70 and the upright member 60 may be connected in a state where they are overlapped in the front-to-back direction or the left-to-right direction. In this case, the portion of the upright member 60 that abuts against the inner shell 70 functions as an overlapping portion.

[0080] In the embodiment described above, a configuration was described in which the inner shell 70 and the upright member 60 are connected above the seat 3, but the configuration is not limited to this. The inner shell 70 and the upright member 60 may be connected below the seat 3. In the embodiment described above, a configuration was described in which the upper structure 4 has the functions of both an armrest 100 and a backrest 101, but the configuration is not limited to this. The upper structure 4 only needs to have the function of at least a backrest 101. In the above-described embodiment, the exterior material 71 was described as comprising a cushioning material 91 and a surface material 92, but the configuration is not limited to this. The exterior material 71 may be configured to cover the inner shell 70 and the connecting portion 62 together. In this case, the exterior material 71 does not need to cover the upright member 60.

[0081] In the embodiment described above, a configuration in which the bolt 86a and nut 86b are fastened in the vertical direction was described, but the configuration is not limited to this. The bolt 86a and nut 86b may also be fastened in the horizontal direction. In the embodiment described above, a configuration in which the connecting portion 62 includes a bolt 86a and a nut 86b was described, but the configuration is not limited to this. In addition to fastening members 86 other than bolts 86a and nuts 86b, fittings using dowels, engagements using claws, joining with adhesives, etc., can be appropriately selected for the connecting portion 62. In the above-described embodiment, a configuration was described in which the rigidity of the upright member 60 is higher than that of the inner shell 70, but the configuration is not limited to this. The rigidity of the upright member 60 and the inner shell 70 can be changed as appropriate. For example, the rigidity of the inner shell 70 may be higher than that of the upright member 60. In the embodiments described above, a configuration in which the upright member 60 extends at an inclination was described, but the invention is not limited to this configuration. The upright member 60 may extend perpendicular to the horizontal direction. In the embodiments described above, a configuration in which the upright member 60 comprises a horizontal rod portion 65 and a connecting rod portion 67 was described, but the invention is not limited to this configuration. The upright member 60 only needs to have at least a vertical rod portion 66. In the embodiment described above, a configuration was described in which a pair of upright members 60 are connected below the seat 3 via a support base 12 (front link 25), but the configuration is not limited to this. As shown in the chair 1 in Figure 12, the pair of upright members 60 may be integrally connected below the seat 3 via a connecting part 200 that connects the horizontal rods 65. In other words, the pair of upright members 60 and the connecting part 200 may constitute a single upright unit 201. In this case, the upright unit 201 may be connected to the lower surface of the seat 3 via the connecting part 200 and may not rotate relative to the seat 3.

[0082] In the embodiments described above, the upper structure 4 was described as being reclinable, but the configuration is not limited to this. The upper structure 4 may be non-reclinable. In the embodiments described above, the operating unit 5 was described as being located on the underside of the seat 3, behind the upright member 60, but the configuration is not limited to this. The operating unit 5 can be provided at any position on the chair 1. In this case, the operating unit 5 may be provided, for example, on the side of the vertical rod 66. In the embodiment described above, the exterior material 71 was configured to cover the shaft portion of the bolt 86a, the nut 86b, and the mounting seat 85 of the connecting portion 62, but the configuration is not limited to this. The exterior material 71 only needs to cover at least a part of the connecting portion 62, and may cover the entire connecting portion 62, including the head of the bolt 86a. In the above-described embodiment, the upright member 60 (vertical rod portion 66) is described as extending outward from the seat 3 in the left-right direction, overlapping (crossing) the seat 3 in a side view, but the configuration is not limited to this. The upright member 60 (vertical rod portion 66) may be positioned in front of the seat 3 in a side view, as long as it is positioned outward from the seat 3 in the left-right direction in a front view. Furthermore, when the upright member 60 is positioned in front of the seat 3, the pair of upright members 60 may be provided in positions that overlap both ends of the seat 3 in the left-right direction in a front view. In other words, the pair of upright members 60 only need to extend so as to straddle the seat 3 in the vertical direction in a side view, and if they are provided in a position that overlaps the seat 3 in a side view, they should be positioned on both sides in the left-right direction relative to the seat 3, and if they are provided in front of the seat 3 in a side view, they should be positioned in front of the seat 3 with a gap between them in the left-right direction.

[0083] Furthermore, without departing from the spirit of the present invention, the components in the embodiments described above can be replaced with well-known components as appropriate, and the modifications described above can be combined as appropriate. [Explanation of Symbols]

[0084] 1: Chair 2: Support structure 3: Za 3a: Seat surface 60: Upright member 61: Main unit 62:Connection part 66: Vertical rod section 67: Connecting rod (overlapping part) 70: Inner shell 71: Exterior materials 75: Shell body 76: Shell protrusion 86a: Bolt 86b: Nut 101a: Backrest side H66: Dimensions H67: Dimensions T66: Dimensions T67: Dimensions

Claims

1. A seat having an upward-facing seating surface, A pair of upright members are arranged on both sides of the seat in the left-right direction, or in front of the seat, with a gap between them in the left-right direction, and extending so as to straddle the seat in the vertical direction when viewed from the side, It comprises a backrest body having a backrest surface facing forward, positioned above the seat and behind the upright member, The aforementioned backrest body is, An inner shell is connected to a pair of the upright members via a connecting portion, and is made of a different material from the upright members to form the frame of the backrest body. A chair comprising an exterior material that constitutes the backrest surface and covers the inner shell and the connecting portion together.

2. The chair according to claim 1, wherein the inner shell and the upright members are connected to each other by the connecting portion above the seat.

3. The aforementioned inner shell is A shell body that supports the aforementioned backrest surface from the rear, The shell body comprises a pair of shell protrusions that project forward from both ends in the left-right direction, The chair according to claim 2, wherein each of the pair of upright members has an overlapping portion that overlaps in a plan view with the corresponding shell protrusion of the pair of shell protrusions and is connected to the shell protrusion by the connecting portion.

4. The aforementioned connecting portion is A bolt that penetrates the shell protrusion and the overlapping portion from below in an up-and-down direction, The chair according to claim 3, further comprising a nut provided above the shell projection and the overlapping portion, and fastened to the bolt.

5. The aforementioned upright member is, A vertical rod extending in the vertical direction, The structure comprises the overlapping portion extending rearward from the upper end of the vertical rod portion, The chair according to claim 4, wherein the overlapping portion has a vertical dimension smaller than the vertical dimension of the vertical rod portion, and a front-to-back dimension larger than the front-to-back dimension of the vertical rod portion.

6. The chair according to claim 5, wherein the vertical rod portion has a larger dimension in the front-to-back direction than in the left-to-right direction.

7. The chair according to any one of claims 1 to 6, wherein the upright member is formed of a material with higher rigidity than the inner shell.

8. The seat is provided with a support structure that supports it from below, The chair according to claim 7, wherein the upright member is connected to the front end of the support structure at its lower end and extends inclined toward the rear as it goes upward.

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