chair

Abstract

To provide a chair with excellent maintainability. [Solution] The chair 1 comprises a support structure 3 that contacts the floor surface, and a seat 5 and a backrest 7 supported by the support structure 3. The backrest 7 has a pair of left and right arm support parts 55 that stand upright on the left and right outer sides of the seat 5 and have armrest surfaces on which the seated person can rest their arms, and a back support part 56 that connects the pair of arm support parts 55 to each other and is formed integrally with the pair of arm support parts 55, forming a backrest surface that faces forward. The inner surfaces of each of the pair of arm support parts 55 and the front surface of the back support part 56 are continuous with each other. The seat 5 is positioned between the pair of arm support parts 55 and is movable in the front-rear direction relative to the support structure 3.

Description

Technical Field

[0001] The present invention relates to a chair.

Background Art

[0002] There is a chair in which a backrest having a pair of left and right armrests and a backrest portion connecting the pair of armrests is arranged so as to surround a seat (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, when a backrest having a pair of armrests and a backrest portion integrally is arranged so as to surround a seat, there is room for improvement in the workability of maintenance work that requires an operator to insert a hand between the lower part of the backrest and the seat.

[0005] Therefore, the present invention is to provide a chair having excellent maintainability.

Means for Solving the Problems

[0006] A chair according to a first aspect of the present invention comprises a support structure that contacts the floor surface, and a seat and backrest supported by the support structure, wherein the backrest has a pair of left and right arm support parts that stand upright passing outward in the left-right direction from the seat and have armrest surfaces on which a sitter can rest their arms, and a back support part that connects the pair of arm support parts and is formed integrally with the pair of arm support parts and forms a backrest surface facing forward, wherein the inner surfaces of each of the pair of arm support parts and the front surface of the back support part are continuous with each other, and the seat is positioned between the pair of arm support parts and is movable in the front-rear direction relative to the support structure.

[0007] According to the first embodiment, since the seat is movable in the front-to-back direction relative to the back support, it becomes easy to move the seat forward from the back support. Therefore, it becomes easy for a worker to insert their hand between the lower part of the back support and the seat. In addition, since a certain clearance is provided between the arm support and the seat in order to allow the seat to move in the front-to-back direction relative to the backrest, it becomes easy for a worker to insert their hand between the lower part of the arm support and the seat. Thus, a chair with excellent maintainability is obtained.

[0008] A chair according to a second aspect of the present invention is the chair according to the first aspect described above, wherein the backrest is positioned below the seat and further has an outward-facing portion that connects the pair of arm support portions and the support structure.

[0009] According to the second embodiment, the connection between the support structure and the backrest is positioned below the seat, so that the connection between the support structure and the backrest is positioned around the seat, avoiding the difficulty of inserting a hand between the seat and the backrest. Therefore, a decrease in maintainability can be suppressed.

[0010] A chair according to a third aspect of the present invention is a chair according to the first or second aspect described above, wherein the pair of arm support portions have a pair of left and right upright rod portions extending vertically along the left and right outer positions of the seat, the backrest has an intermediate connecting rod portion connecting the vertical intermediate portions of each of the pair of upright rod portions, and the upper surface of the seat may be located below the intermediate connecting rod portion.

[0011] According to the third embodiment, since the pair of upright rods are connected to each other by an intermediate connecting rod, the backrest can be made more robust. Furthermore, since the seat is positioned below the intermediate connecting rod, it becomes easier for the worker to reach between the intermediate connecting rod and the seat. Therefore, a decrease in maintainability can be suppressed.

[0012] A chair according to a fourth aspect of the present invention is a chair according to the third aspect described above, wherein the backrest may have an upper connecting rod that connects the upper ends of each of the pair of upright rods.

[0013] According to the fourth embodiment, the upper connecting rod cooperates with a pair of upright rods and intermediate connecting rods to form a closed loop structure. This makes it possible to create a robust backrest without forming it as a plate-like structure that extends from the back support to the arm support.

[0014] A fifth aspect of the present invention is a chair according to the first or second aspect of the present invention, wherein the backrest may include a pair of left and right upright rods provided on the pair of arm support parts and extending vertically along the left and right outer positions of the seat, a connecting rod connecting the pair of upright rods, and a single tensioning material stretched over the connecting rod to form the inner surfaces of each of the pair of arm support parts and the front surface of the back support part.

[0015] According to the fifth embodiment, the inner surfaces of each of the pair of arm support parts and the front surface of the back support part can be formed with tensioning material so as to be continuous with each other.

[0016] The chair according to the sixth aspect of the present invention is a chair according to any one of the first to fifth aspects, and includes a support portion that supports the seat. The seat may be such that the portion supported by the support portion changes in the front-rear direction as the seat moves in the front-rear direction with respect to the support structure.

[0017] According to the sixth aspect, compared with a configuration in which the seat is supported by a link mechanism or the like so as to be movable in the front-rear direction with respect to the support structure, the connection structure between the seat and the support portion can be simplified. Therefore, the configuration of the chair can be simplified.

Effects of the Invention

[0018] [[ID=IO]] According to the present invention, a chair having excellent maintainability can be provided.

Brief Description of the Drawings

[0019] [Figure 1] It is a perspective view of the chair 1 according to the first embodiment as seen from above. [Figure 2] It is a perspective view of the chair 1 according to the first embodiment as seen from below. [Figure 3] It is a cross-sectional view taken along line III-III in FIG. 11. [Figure 4] It is a cross-sectional view taken along line IV-IV in FIG. 12. [Figure 5] It is a perspective view of the seat receiving upper portion 80 according to the first embodiment. [Figure 6] It is a perspective view of the seat 5 and the seat receiving upper portion 80 according to the first embodiment as seen from below [Figure 7] It is a perspective view of the seat 5 according to the first embodiment as seen from below. [Figure 8] It is a cross-sectional view taken along line VIII-VIII in FIG. 6. [Figure 9] It is a cross-sectional view taken along line IX-IX in FIG. 6. [[ID=4S]] [Figure 10] It is a perspective view of the load support member 9 according to the first embodiment. [Figure 11] It is a front view of the chair 1 according to the first embodiment. [Figure 12]This is a side view of chair 1 according to the first embodiment. [Figure 13] This is a plan view of chair 1 according to the first embodiment. [Figure 14] Figure 13 shows a cross-sectional view along line XIV-XIV. [Figure 15] Figure 10 is a cross-sectional view along the XV-XV line. [Figure 16] Figure 10 shows a cross-sectional view along the line XVI-XVI. [Figure 17] This is a front view of the chair 101 according to the second embodiment. [Figure 18] This is a side view of the chair 101 according to the second embodiment. [Modes for carrying out the invention]

[0020] Embodiments of the present invention will be described below with reference to the drawings. In the following description, components having the same or similar functions will be denoted by the same reference numerals. Duplication of these components may be omitted. Furthermore, in the following description, directions such as front, back, up, down, left, and right will be the same as the direction of a person (seatee) seated in a chair in a normal posture. That is, the direction in which the seatee faces forward will be referred to as "front," and the opposite direction will be referred to as "rear." In each figure, the arrow UP indicates upward, the arrow FR indicates forward, and the arrow LH indicates left. In this embodiment, "integrally formed" means that at least a portion of all parts of the object are formed from a single member. That is, when multiple parts are integrally formed, a continuous member is provided for all parts of the object. However, a member other than the single member may be provided for a portion of the object.

[0021] (First Embodiment) Figure 1 is a perspective view of the chair 1 according to the first embodiment, seen from above. As shown in Figure 1, the chair 1 of the first embodiment comprises a support structure 3, a seat 5, and a backrest 7. The chair 1 has a seating space S above the seat 5.

[0022] Figure 2 is a perspective view of the chair 1 according to the first embodiment, seen from below. Note that in Figures 2 and subsequent figures, the upholstery material 70, which will be described later, may not be shown. As shown in Figures 1 and 2, the support structure 3 comprises a leg 10, a base 15, and a seating portion 17.

[0023] The leg body 10 comprises a multi-legged leg 11 and a leg column 12. Each leg of the multi-legged leg 11 is fitted with a caster that allows it to travel on the floor. However, the leg body does not need to have casters; it only needs to have a contact point that touches the floor. A footrest may be fitted to the multi-legged leg 11. The leg column 12 extends upward from the center of the multi-legged leg 11. The leg column 12 contains a gas spring, which is the lifting mechanism of the chair 1. The gas spring is configured such that an inner cylinder 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 column 12. The support base 15 is connected to the upper end of the leg column 12 (inner cylinder). The support base 15 supports the seat support 17 from below. A lever for operating the gas spring is attached to the support base 15.

[0024] Figure 3 is a cross-sectional view along line III-III in Figure 11. Figure 4 is a cross-sectional view along line IV-IV in Figure 12. As shown in Figures 2 to 4, the seat support portion 17 is provided at the upper end of the support structure 3. The seat support portion 17 supports the seat 5 from below. The seat support portion 17 is interposed between the seat 5 and the support base 15, indirectly connecting the seat 5 and the support base 15. The seat support portion 17 comprises a lower seat support portion 30 connected to the support base 15, and an upper seat support portion 80 connected to the lower seat support portion 30 and supporting the seat 5.

[0025] The lower seat support portion 30 is connected to the support base 15 so as not to be displaceable in the vertical and horizontal directions. The lower seat support portion 30 comprises an upper wall portion 31 that extends horizontally and a peripheral wall portion 32 that extends downward from the upper wall portion 31. The upper wall portion 31 and the peripheral wall portion 32 are formed integrally.

[0026] The upper wall portion 31 is plate-shaped with a rectangular plan view, having one pair of sides extending in the front-to-back direction and the remaining pair of sides extending in the left-to-right direction. The support base 15 is connected to the upper wall portion 31 from below. The peripheral wall portion 32 extends downward from the outer peripheral edge of the upper wall portion 31. The peripheral wall portion 32 is connected to the outer peripheral edge of the upper wall portion 31 all around. Thus, the peripheral wall portion 32 comprises a pair of left and right side wall portions 32a extending along the front-to-back direction, and a front wall portion and a rear wall portion extending along the left-to-right direction. The seat support lower portion 30 is formed in a box shape with an opening at the bottom. The support base 15 is positioned inside the seat support lower portion 30.

[0027] The upper part of the seat support 80 is fixed to the upper wall portion 31 from above. The upper part of the seat support 80, the base 15, and the upper wall portion 31 of the lower part of the seat support 30 are fastened to each other by a common fastening member. The upper part of the seat support 80 supports the seat 5 so that it can move linearly in the front-rear direction, but cannot move in the left-right direction or up-down direction.

[0028] Figure 5 is a perspective view of the upper part 80 of the seat support according to the first embodiment. As shown in Figure 5, the seat support upper part 80 is formed in a box shape with an upward opening. The seat support upper part 80 has a rectangular plan view shape in which one pair of sides extend in the front-to-back direction and the remaining pair of sides extend in the left-to-right direction. The seat support upper part 80 is made of metal. The seat support upper part 80 comprises a horizontal part 81, a pair of left and right upright parts 82, a first engaging part 83, and a pair of front and rear auxiliary upright parts 84.

[0029] The horizontal portion 81 is positioned so as to overlap the upper wall portion 31 from above. The horizontal portion 81 is the part of the upper seat support portion 80 that is fastened to the lower seat support portion 30. The horizontal portion 81 is a flat plate that spreads horizontally and has thickness in the vertical direction. The horizontal portion 81 has a rectangular plan view shape that substantially matches the plan view shape of the upper seat support portion 80. The upper surface of the horizontal portion 81 does not have any structure that protrudes upward between at least one pair of upright portions 82.

[0030] A pair of upright portions 82 rise upward from both sides of the horizontal portion 81 in the left-right direction. The upright portions 82 are connected to the left and right edges of the horizontal portion 81 and extend along the front-rear direction. The upright portions 82 are flat plates with thickness in the left-right direction. The upright portions 82 are formed integrally with the horizontal portion 81 by bending or other processes. However, the upright portions 82 may also be joined to the horizontal portion 81 by welding or other means. The formation range of the upright portions 82 in the front-rear direction coincides with the formation range of the horizontal portion 81 in the front-rear direction. The formation of the upright portions 82 enhances the bending rigidity of the horizontal portion 81 by functioning as ribs. The upper end edge of the upright portions 82 extends parallel to the horizontal portion 81 along the entire length of the upright portions 82. In the left of the pair of upright portions 82, multiple engagement holes 82a (six in this embodiment) are formed, which penetrate the upright portion 82 in the left-right direction and are spaced apart in the front-rear direction. The multiple engagement holes 82a are arranged at equal intervals.

[0031] A pair of first engaging portions 83 are provided on both the left and right sides of the upper seat portion 80, corresponding to a pair of upright portions 82. The first engaging portions 83 extend inward in the left-right direction from the upright portions 82 on the same side, above the horizontal portion 81. That is, the first engaging portions 83 overlap the horizontal portion 81 with a gap in the vertical direction. The pair of first engaging portions 83 are provided with a gap between them in the left-right direction. The first engaging portions 83 are connected to the upper end edge of the upright portion 82. The first engaging portions 83 are flat plates that spread parallel to the horizontal portion 81 and have thickness in the vertical direction. The first engaging portions 83 have length in the front-rear direction. The first engaging portions 83 are formed integrally with the upright portion 82 by bending or other processes. However, the first engaging portions 83 may also be joined to the upright portion 82 by welding or other means. The first engaging portions 83 are formed by a plurality of first engaging pieces 83a arranged with a gap in the front-rear direction. In other words, one or more notches are formed on the inner edge in the left-right direction of each first engaging portion 83.

[0032] A pair of auxiliary upright sections 84 rise upward from the front and rear of the horizontal section 81. The auxiliary upright sections 84 are connected to the front and rear edges of the horizontal section 81 and extend along the left-right direction. The auxiliary upright sections 84 are flat plates with thickness in the front-rear direction. The auxiliary upright sections 84 are joined to the horizontal section 81 by welding or the like. However, the auxiliary upright sections 84 may be formed integrally with the horizontal section 81 by bending or the like. The formation range of the auxiliary upright sections 84 in the left-right direction coincides with the formation range of the horizontal section 81 in the left-right direction. The formation of the auxiliary upright sections 84 enhances the bending rigidity of the horizontal section 81 by having the auxiliary upright sections 84 function as ribs. The upper end edge of the auxiliary upright section 84 extends parallel to the horizontal section 81 at the same position in the vertical direction as the upper end edge of the upright section 82. Notches 84a cut downward are formed near both ends in the left-right direction of the upper end edge of each auxiliary upright section 84. A rib 92, described later, is positioned in the notch 84a so as to be movable in the front-rear direction. From a strength standpoint, it is desirable that the left and right edges of the auxiliary upright portion 84 be connected to the front-rear edges of the corresponding upright portion 82, for example, by welding.

[0033] As shown in Figures 1 and 2, the seat 5 supports the buttocks and thighs of the sitter. The seat 5 is indirectly supported by the base 15 of the support structure 3 via the seat support portion 17. The seat 5 comprises a seat plate 20 that receives the seating load and a cushion 22 positioned above the seat plate 20. The seat plate 20 is made of a hard material such as synthetic resin or metal. The seat plate 20 is formed in a circular or rectangular shape in plan view so that its plan view shape substantially matches the plan view shape of the seat 5. The cushion 22 is positioned along the upper surface of the seat plate 20 and is supported by the seat plate 20. The cushion 22 is positioned so as to overlap the entire seat plate 20 when viewed from above.

[0034] Figure 6 is a perspective view of the seat 5 and seat support upper part 80 according to the first embodiment, viewed from below. Figure 7 is a perspective view of the seat 5 according to the first embodiment, viewed from below. As shown in Figures 6 and 7, the lower surface of the seat plate 20 has a bulge 90 that bulges downward and a recess 91 that sinks upward. The bulge 90 is formed in the center of the lower surface of the seat plate 20. The bulge 90 is formed in the shape of a truncated square pyramid, having a top portion 90a that extends horizontally in the center and a peripheral portion that extends upward as it moves outward horizontally from the outer edge of the top portion 90a.

[0035] The recess 91 is formed in the center of the lower surface of the seat plate 20 and is open downwards. In this embodiment, the entire recess 91 is formed at the top 90a of the bulge 90. The recess 91 has a constant width in the left-right direction and extends in the front-rear direction. The seat plate 20 includes a pair of left and right side walls 20a that define the recess 91 from both sides in the left-right direction, a front wall 20b that defines the recess 91 from the front, and a rear wall 20c that defines the recess 91 from the rear. The recess 91 is capable of receiving the upper seat support 80. The side walls 20a face the upright portion 82 of the upper seat support 80 from the outside in the left-right direction. The front wall 20b and the rear wall 20c face the auxiliary upright portion 84 of the upper seat support 80 from the outside in the front-rear direction. Furthermore, the distance between the front wall portion 20b and the rear wall portion 20c is wider than the front-rear size of the upper seat support portion 80, and the recess 91 accommodates the upper seat support portion 80 so as to be movable in the front-rear direction. The downward-facing bottom surface of the recess 91 may be in slidable contact with the first engagement portion 83. In a configuration in which the seat plate 20 and the upper seat support portion 80 are in direct sliding contact, the portion of the seat 5 that is supported by the upper seat support portion 80 changes in the front-rear direction as the seat 5 moves in the front-rear direction relative to the support structure 3.

[0036] Figure 8 is a cross-sectional view along the line VIII-VIII in Figure 6. As shown in Figures 7 and 8, the seat plate 20 includes a pair of left and right ribs 92 that protrude downward from the lower surface of the seat plate 20, and a second engaging portion 93 that protrudes outward in the left-right direction from the ribs 92.

[0037] A pair of ribs 92 are positioned between a pair of side wall portions 20a. That is, the pair of ribs 92 are positioned in the recess 91. The pair of ribs 92 extend in the front-rear direction and are connected to the front wall portion 20b and the rear wall portion 20c. The pair of ribs 92 are spaced apart in the left-right direction. The pair of ribs 92 are positioned between a pair of upright portions 82 of the seat support upper portion 80. Each rib 92 is close to the upright portion 82 on the same side of the pair of upright portions 82 and faces it from the inside in the left-right direction. The lower edge of each rib 92 faces the upper surface of the horizontal portion 81 of the seat support upper portion 80. The lower edge of the rib 92 has a gap in the vertical direction with respect to the horizontal portion 81. However, the lower edge of the rib 92 may be in slidable contact with the horizontal portion 81. The pair of ribs 92 pass through the notch 84a of the auxiliary upright portion 84 of the seat support upper portion 80 so as to be displaceable in the front-rear direction. The pair of ribs 92 contact the edges of the notches 84a of the auxiliary upright portion 84 in the left-right direction, thereby restricting the relative left-right displacement of the seat plate 20 and the lower seat support portion 30.

[0038] A pair of left and right second engaging portions 93 are positioned between a pair of upright portions 82, corresponding to a pair of first engaging portions 83. The pair of second engaging portions 93 are supported by the same rib 92 on the left and right sides of a pair of ribs 92. The second engaging portions 93 extend outward in the left-right direction from the rib 92 at a position above the horizontal portion 81. The second engaging portions 93 are flat plates that spread parallel to the horizontal portion 81 and have thickness in the vertical direction. The second engaging portions 93 have length in the front-rear direction and are connected to the rib 92 along their entire length. The second engaging portions 93 are positioned lower than the first engaging portions 83 in the vertical direction. The second engaging portions 93 are formed by a plurality of second engaging pieces 93a arranged at intervals in the front-rear direction. The first engaging pieces 83a can pass through the gaps in front of and behind each second engaging piece 93a in the vertical direction. Also, each second engaging piece 93a can pass through the gaps in front of and behind the first engaging piece 83a in the vertical direction. This allows the upper part of the seat support 80 to approach the seat plate 20 from below, and the first engaging portion 83 of the upper part of the seat support 80 to be positioned above the second engaging portion 93 of the seat plate 20. The second engaging piece 93a faces the first engaging piece 83a from below when the seat 5 is in a fixed position relative to the upper part of the seat support 80 (described later).

[0039] As shown in Figures 6 and 8, the seat plate 20 has a fixing part 25 that secures the seat plate 20 and the seat support upper part 80 to each other. The fixing part 25 is positioned close to the upright part 82 (the left upright part 82 in this embodiment) of the pair of upright parts 82 of the seat support upper part 80 in which the engagement hole 82a is formed. The fixing part 25 is positioned facing the upright part 82 from the outside in the left-right direction. The fixing part 25 comprises a shaft part 26, an engagement projection 27, and an operating part 28.

[0040] Figure 9 is a cross-sectional view of the IX-IX line in Figure 6. As shown in Figures 8 and 9, the shaft portion 26 extends in the front-rear direction. Both ends of the shaft portion 26 are rotatably supported by the seat plate 20. The shaft portion 26 is not displaceable in the front-rear direction relative to the seat plate 20. The shaft portion 26 is positioned outward and above the engagement hole 82a in the left-right direction.

[0041] The engaging projection 27 is a convex portion that protrudes inward in the left-right direction. The engaging projection 27 is connected to the shaft portion 26, is immovable relative to the shaft portion 26, and rotates integrally with the shaft portion 26. At least one engaging projection 27 is provided. If multiple engaging projections 27 are provided, they are arranged with spacing between them in the front-rear direction. Each engaging projection 27 is inserted into an engaging hole 82a (see Figure 5) and engages with the upright portion 82, restricting the relative displacement of the seat plate 20 and the seat support upper portion 80 in the front-rear direction. The engaging projection 27 can detach outward in the left-right direction from the engaging hole 82a as it rotates integrally with the shaft portion 26. When the engaging projection 27 detaches from the engaging hole 82a, the seat plate 20 becomes movable in the front-rear direction relative to the seat support upper portion 80. The number of engagement holes 82a is greater than the number of engagement projections 27, and the engagement hole 82a into which each engagement projection 27 is inserted is changed according to the position of the seat plate 20 in the front-rear direction relative to the seat support upper part 80. As a result, multiple fixing positions of the seat plate 20 in the front-rear direction relative to the seat support upper part 80 are set, and the fixing position of the seat plate 20 in the front-rear direction can be selected from multiple positions. Although not shown in the figures, when the seat support upper part 80 is received in the recess 91 on the lower surface of the seat plate 20, a restricting member is provided in the recess 91 that contacts the seat support upper part 80 to restrict the range of movement of the seat plate 20 in the front-rear direction relative to the seat support upper part 80, so that the first engagement piece 83a and the second engagement piece 93a, which are facing each other in the vertical direction, do not shift in the front-rear direction and the seat plate 20 does not become displaced upward.

[0042] As shown in Figures 6 and 8, the operating section 28 is connected to the shaft 26 and is immovable relative to the shaft 26. The operating section 28 extends outward in the left-right direction from the front of the shaft 26 so as to be away from the upper part of the seat support 80. The operating section 28 is a flat plate that spreads out substantially horizontally. The operating section 28 has a constant width in the front-rear direction and extends in the left-right direction. The operating section 28 protrudes outward in the left-right direction from the bulging portion 90. The left-right outer end of the operating section 28 (the left end in this embodiment) is positioned below the seat plate 20 with a vertical gap between it and the seat plate 20.

[0043] The fixed portion 25 is biased around the central axis of the shaft portion 26 by a biasing member (not shown). The fixed portion 25 is biased by the biasing member in the direction in which the engaging projection 27 is inserted into the engaging hole 82a. The fixed portion 25 rotates so that the engaging projection 27 disengages from the engaging hole 82a when the operating portion 28 is pulled up against the biasing force of the biasing member.

[0044] As shown in Figures 6 and 7, the seat plate 20 has a housing portion 95 for housing the fixing portion 25. The housing portion 95 includes a shaft housing recess 96 for housing the shaft portion 26 and an operating recess 97 for housing the operating portion 28.

[0045] The shaft housing recess 96 is formed at the top 90a of the bulge 90 on the lower surface of the seat plate 20 and is open downwards. That is, the shaft housing recess 96 is formed in the side wall portion 20a of the seat plate 20. The shaft housing recess 96 is adjacent to the recess 91 on the left-right side and communicates directly with the recess 91. The shaft housing recess 96 accommodates the shaft portion 26 and the engaging projection 27 of the fixing portion 25 so that they do not protrude downwards from the lower surface of the seat plate 20. Support arms 98 are provided at the front and rear ends of the shaft housing recess 96 to rotatably support the end of the shaft portion 26 (see Figure 9). The support arms 98 support the end of the shaft portion 26 from below.

[0046] The operating recess 97 is adjacent to the shaft housing recess 96 in the left-right direction from the opposite side of the recess 91 and communicates directly with the shaft housing recess 96. The operating recess 97 opens to the lower surface of the seat plate 20. The operating recess 97 extends in the left-right direction, connecting the inside of the shaft housing recess 96 with the space on the left-right outer side of the side wall portion 20a. The operating part 28 is positioned in the operating recess 97 so as to be movable upward. This allows the operating part 28 to be operated upward. The operating part 28 extends from the shaft housing recess 96 through the operating recess 97 to the space on the left-right outer side of the side wall portion 20a.

[0047] As shown in Figures 1 and 2, the backrest 7 is supported by the support structure 3. The backrest 7 has a load-bearing surface 8 that supports the weight of the seated person above the seat 5. The backrest 7 is not tiltable relative to the seat 5. The backrest 7 is formed substantially symmetrically. The backrest 7 comprises a load-bearing member 9 and an upholstery member 70.

[0048] Figure 10 is a perspective view of the load-supporting member 9 according to the first embodiment. As shown in Figure 10, the load-supporting member 9 comprises a pair of left and right horizontal rods 35, a pair of left and right upright rods 40, an upper connecting rod 45, and a lower connecting rod 50.

[0049] Figure 11 is a front view of chair 1 according to the first embodiment. As shown in Figures 10 and 11, the pair of horizontal rods 35 correspond one-to-one with the pair of side wall portions 32a of the seat support lower portion 30. The horizontal rods 35 are connected to the side wall portions 32a. The horizontal rods 35 are formed integrally with the seat support lower portion 30. In this embodiment, the entire horizontal rod 35 is formed integrally with the entire seat support lower portion 30. The horizontal rods 35 are connected to the intermediate portion in the front-rear direction of each side wall portion 32a. That is, the horizontal rods 35 are connected to a location in the front-rear direction that is spaced apart from the front and rear ends of each side wall portion 32a. The horizontal rods 35 extend outward in the left-right direction from each side wall portion 32a. The horizontal rods 35 extend along the left-right direction in the space below the seat 5. The horizontal rods 35 are non-contact with the seat 5. The outer end of the horizontal rod portion 35 is located outside the base 5 in a plan view. The cross-sectional shape of the horizontal rod portion 35 perpendicular to the left-right direction is rectangular, with the front-to-back direction as the longitudinal direction.

[0050] Figure 12 is a side view of chair 1 according to the first embodiment. As shown in Figures 10 and 12, a pair of upright rods 40 correspond one-to-one with a pair of horizontal rods 35. The upright rods 40 are connected to the horizontal rods 35. The upright rods 40 are formed integrally with the horizontal rods 35. In this embodiment, the upright rods 40 are formed integrally with the entire horizontal rods 35. The upright rods 40 have length in the vertical direction. The upright rods 40 have lower ends connected to the left-right outer ends of each horizontal rod 35. The lower ends of the upright rods 40 are indirectly connected to the support structure 3 via the horizontal rods 35. The upright rods 40 extend upward from their lower ends into the left-right outer space of the seat 5 in a front view. The load-supporting member 9 is smoothly bent so that its outer surface is continuous at the connection between the horizontal rod portion 35 and the upright rod portion 40. The upright rod portion 40 intersects the seat 5 in a side view from the left and right directions. The upper end of the upright rod portion 40 is within the formation range of the seat support lower portion 30 in the front-rear direction.

[0051] The cross-sectional shape of the upright rod portion 40 perpendicular to the vertical direction is rectangular, with the front-to-back direction as its longitudinal direction. The upright rod portion 40 has a rectangular cross-sectional shape, which improves its rigidity against loads from vertically above. The upright rod portion 40 comprises a front surface 40f facing forward and an inner surface 40i facing the seating space S. For example, the front surface 40f is defined by the area of ​​the outer surface of the upright rod portion 40 that is visible from the front. The front surface 40f is provided along the entire length of the upright rod portion 40. The inner surface 40i is provided along the entire length of the upright rod portion 40. The inner surface 40i is continuous with the upper surface 35u of the horizontal rod portion 35.

[0052] Figure 13 is a plan view of chair 1 according to the first embodiment. As shown in Figures 10 and 13, the upper connecting rod 45 connects the upper ends of the pair of upright rods 40. The upper connecting rod 45 is integrally formed along its entire length between the connection points with each of the pair of upright rods 40. The upper connecting rod 45 is integrally formed with the upright rods 40. The upper connecting rod 45 extends rearward from each upright rod 40. In plan view, the upper connecting rod 45 is formed in a U-shape that opens forward and is curved to be convex rearward. The upper connecting rod 45 extends between the connection points with each upright rod 40 without having any bends in plan view. That is, the upper connecting rod 45 is formed along its entire length by either a portion that extends linearly in plan view, or a portion that is curved in plan view, or both. The upper connecting rod 45 is positioned to surround the seating space S from both the left and right sides and the rear. In a side view from the left and right directions, the upper connecting rod 45 extends upward and backward from its front end (see Figure 7). The load-supporting member 9 is smoothly bent so that its outer surface is continuous at the connection point between the upright rod 40 and the upper connecting rod 45. The upper connecting rod 45 comprises a pair of left and right armrests 46, a backrest 47, and an extension 48.

[0053] As shown in Figure 10, a pair of armrests 46 correspond one-to-one with a pair of upright rods 40. The armrests 46 have length in the front-to-back direction. The armrests 46 have front ends connected to the upper ends of the upright rods 40. The front ends of the pair of armrests 46 are the front ends on both the left and right sides of the upper connecting rod 45. The armrests 46 extend rearward from their front ends in a plan view. The cross-sectional shape of the armrests 46 perpendicular to the front-to-back direction is a rectangle with one pair of sides extending vertically and the remaining pair of sides extending horizontally. The left-to-right outer and upper corners 46a of the armrests 46 are located at the outermost left-to-right position of the armrests 46 at any position in the front-to-back direction of the armrests 46.

[0054] The backrest portion 47 is connected to a pair of armrest portions 46. The backrest portion 47 is formed integrally with the pair of armrest portions 46. The backrest portion 47 extends between the rear ends of the pair of armrest portions 46. The backrest portion 47 extends outward in the left-right direction from the left-right intermediate portion of the upper connecting rod portion 45 located behind the seating space S, and connects to the rear ends of the pair of armrest portions 46. The backrest portion 47 only needs to include the left-right intermediate portion of the upper connecting rod portion 45 and have a region that extends along the left-right direction, and the boundary between the armrest portion 46 and the backrest portion 47 does not need to be uniquely defined. However, for example, if the upper connecting rod portion has a clearly bent portion in a plan view, that bent portion may be used as the boundary between the armrest portion and the backrest portion.

[0055] The cross-sectional shape of the backrest portion 47 perpendicular to the left-right direction is a quadrilateral shape in which one pair of sides extend along the vertical direction and the remaining pair of sides extend upward towards the rear. The upper and rear corner 47a of the backrest portion 47 is the rearmost position of the backrest portion 47 at any position in the front-rear direction of the backrest portion 47. The upper and rear corner 47a in the middle of the backrest portion 47 in the left-right direction is the rear upper end of the upper connecting rod portion 45. The upper and rear corner 47a of the backrest portion 47 is continuous with the outer and upper corner 46a of the armrest portion 46 in the left-right direction. That is, the outer and upper corner 45a in the horizontal direction of the upper connecting rod portion 45 is the edge that is located furthest outward in the horizontal direction of the upper connecting rod portion 45. In this embodiment, the horizontally outer and upper corner 45a of the upper connecting rod portion 45 is located furthest outward in the horizontal direction from the seat 5 and the load-supporting member 9.

[0056] The extension portion 48 extends downward from the middle of the backrest portion 47 in the left-right direction. The entire extension portion 48 is formed integrally with the backrest portion 47. The extension portion 48 extends in the left-right direction along the backrest portion 47. The lower end surface of the extension portion 48 is inclined with respect to the horizontal direction and faces downward and rearward (see Figure 14).

[0057] The upper connecting rod portion 45 comprises an upper surface 45u facing upward and an inner surface 45i facing the seating space S. For example, the upper surface 45u is defined as the area of ​​the outer surface of the upper connecting rod 45 that is visible from above. The upper surface 45u is provided along the entire length of the upper connecting rod 45. That is, the upper surface 45u is provided continuously from the front end of the pair of armrests 46 to the backrest 47. The upper surface 45u is continuous with the front surface 40f of the upright rod 40. In this embodiment, the upper surface 45u is a continuous plane along its entire length, except for the rounded portions on both side edges. The upper surface 45u faces forward and upward. That is, the upper surface 45u faces upward and forward when viewed from the left and right directions (see Figures 11 and 12). The upper surface 45u may also face upward when viewed from the left and right directions. The portion of the upper surface 45u formed on the armrest 46 is the armrest surface on which the seated person rests their arms (including elbows). The armrest surface of this embodiment can support the portion of a seated person's arm from the forearm to the elbow. However, it is sufficient that the armrest surface can support at least the seated person's forearm or elbow. The armrest surface may face upward and inward in the left-right direction, or upward and outward in the left-right direction, when viewed from the front-back direction.

[0058] The inner surface 45i is a concave curved surface that extends in a U-shape in plan view, corresponding to the plan view shape of the upper connecting rod 45. The inner surface 45i is provided along the entire length of the upper connecting rod 45. That is, the inner surface 45i is provided continuously from the front end of the pair of armrests 46 to the backrest 47. The inner surface 45i is continuous with the inner surface 40i of the upright rod 40. Furthermore, the inner surface 45i is provided continuously from the backrest 47 to the extension 48. The portion of the inner surface 45i formed on the armrest 46 faces inward in the left-right direction when viewed from above (see Figure 13). The portion of the inner surface 45i formed on the backrest 47 and the extension 48 faces forward when viewed from above (see Figure 13). Of the inner surface 45i, the region located within the formation range of the extension portion 48 in the left-right direction extends forward as it goes downward (see Figure 14).

[0059] The lower connecting rod 50 connects the pair of upright rods 40. The lower connecting rod 50 is positioned below the upper connecting rod 45. The lower connecting rod 50 is connected above the lower end of the upright rod 40 and below the connection point with the upper connecting rod 45. In other words, the lower connecting rod 50 is connected to the vertically intermediate part of the upright rod 40. However, the vertically intermediate part of the upright rod 40 does not have to be equidistant from the upper and lower ends of the upright rod 40. The lower connecting rod 50 is formed integrally with the upright rod 40. The lower connecting rod 50 is positioned above the upper surface of the seat 5 and has a vertical gap with respect to the seat 5 when viewed from the front (see Figure 11). The lower connecting rod 50 extends rearward from each upright rod 40. The lower connecting rod 50 is formed in a U-shape that opens forward in a plan view and is curved so as to be convex to the rear. The lower connecting rod 50 extends between the connection points with each upright rod 40 without having any bends in a plan view. The lower connecting rod 50 is positioned to surround the seating space S from both the left and right sides and the rear. In a side view taken from the left and right directions, the lower connecting rod 50 extends rearward from its front end. The front end of the middle portion of the lower connecting rod 50 in the left-right direction is located in front of the front end of the middle portion of the upper connecting rod 45 in the left-right direction. The middle portion of the lower connecting rod 50 in the left-right direction overlaps with the rear of the seat 5 in a plan view (see Figures 12 and 13).

[0060] In this embodiment, substantially the entire load-bearing member 9 and the seat support portion 30 are formed from a single member. As a result, the seat support portion 30, the pair of horizontal rods 35, the pair of upright rods 40, and the upper connecting rod 45 are integrally formed. Furthermore, because the load-bearing member 9 is integrally formed with the seat support portion 30, the backrest 7 is immovable relative to the seat support portion 17. In other words, the support structure 3 in this embodiment includes a part of the backrest 7, and the seat 5 is supported via the seat support portion 17 so as to be able to move relative to the backrest 7 in the front-rear direction.

[0061] As shown in Figures 10 and 11, the lower connecting rod portion 50 comprises a downward-facing lower surface 50l and an inner surface 50i facing the seating space S. For example, the lower surface 50l is defined by the area of ​​the outer surface of the lower connecting rod portion 50 that is visible from below. The lower surface 50l is provided along the entire length of the lower connecting rod portion 50. The inner surface 50i is a concave curved surface that extends in a U-shape in plan view, corresponding to the plan view shape of the lower connecting rod portion 50. The inner surface 50i is provided along the entire length of the lower connecting rod portion 50. The inner surface 50i is continuous with the inner surface 40i of the upright rod portion 40. The inner surface 50i is located in the middle of the load-supporting member 9 in the left-right direction, forward of the entire inner surface 45i of the upper connecting rod portion 45 (see Figure 14).

[0062] Figure 14 is a cross-sectional view along the line XIV-XIV in Figure 13. Figure 115 is a cross-sectional view along the line XV-XV in Figure 10. Figure 16 is a cross-sectional view along the line XVI-XVI in Figure 10. As shown in Figures 10 and 14 to 17, the load-supporting member 9 has an engagement recess 60 into which the tensioning member 70 engages. The engagement recess 60 comprises an upper engagement recess 61 formed in the upper connecting rod portion 45, a pair of left and right side engagement recesses 62 formed in each upright rod portion 40, and a lower engagement recess 63 formed in the lower connecting rod portion 50. The engagement recess 60 extends continuously in an annular shape.

[0063] As shown in Figures 10, 14, and 15, the upper engagement recess 61 is formed in the upper connecting rod portion 45. The upper engagement recess 61 opens to the upper surface 45u of the upper connecting rod portion 45. The upper engagement recess 61 opens to the edge of the upper surface 45u on the seating space S side. The upper engagement recess 61 extends along the extending direction of the upper connecting rod portion 45. The upper engagement recess 61 is continuously provided along the entire length of the upper connecting rod portion 45. The upper engagement recess 61 includes a pair of left and right armrest engagement recesses 61a located in the armrest portion 46 and a backrest engagement recess 61b located in the backrest portion 47. The armrest engagement recesses 61a and the backrest engagement recesses 61b are in direct communication with each other.

[0064] As shown in Figures 10 and 16, the side engagement recesses 62 are formed in each upright rod portion 40. The side engagement recesses 62 open to the front surface 40f of the upright rod portion 40. The side engagement recesses 62 extend along the direction of extension of the upright rod portion 40. The side engagement recesses 62 extend along the edge of the front surface 40f on the seating space S side. The upper end of the side engagement recess 62 is connected to the end of the upper engagement recess 61. Thus, the side engagement recess 62 is in direct communication with the upper engagement recess 61. The lower end of the side engagement recess 62 opens continuously from the front downwards.

[0065] As shown in Figures 10 and 14, the lower engagement recess 63 is formed in the lower connecting rod portion 50. The lower engagement recess 63 opens to the lower surface 50l of the lower connecting rod portion 50. The lower engagement recess 63 extends along the extending direction of the lower connecting rod portion 50. The lower engagement recess 63 extends along the edge of the lower surface 50l on the seating space S side. The lower engagement recess 63 is provided continuously along the entire length of the lower connecting rod portion 50. The end of the lower engagement recess 63 is connected to the lower end of the side engagement recess 62. Thus, the lower engagement recess 63 is in direct communication with the side engagement recess 62.

[0066] As shown in Figures 14 to 16, the load-bearing member 9 is provided with a communication recess 65 that connects the engagement recess 60 and the seating space S. The communication recess 65 is adjacent to the engagement recess 60 from the seating space S side. The communication recess 65 is formed to be stepped down together with the engagement recess 60 with respect to the surface of the load-bearing member 9 from which the engagement recess 60 opens. The communication recess 65 extends along the entire length of the engagement recess 60. The communication recess 65 opens from the surface of the load-bearing member 9 from which the engagement recess 60 opens to the inner surface facing the seating space S side. For example, the portion of the communication recess 65 adjacent to the upper engagement recess 61 opens from the upper surface 45u of the upper connecting rod 45 to the inner surface 45i, and is stepped down downward from the upper surface 45u. As a result, the opening end of the engagement recess 60 is open to the seating space S side through the communication recess 65. Furthermore, the communication recess 65 is formed to be shallower than the engagement recess 60 when the surface in the load-supporting member 9 from which the engagement recess 60 opens is used as a reference.

[0067] As shown in Figures 1 and 10, the upholstery 70 is stretched over the load-bearing member 9 to form a load-bearing surface 8. The upholstery 70 is stretched over the load-bearing member 9 so that the load-bearing surface 8 faces the torso of the seated person from the outside in the horizontal direction. The load-bearing surface 8 faces forward and includes a backrest surface that supports the back of the seated person. The upholstery 70 is stretched over a frame consisting of an upper connecting rod 45, a pair of upright rods 40, and a lower connecting rod 50. The upholstery 70 is stretched along the vertical direction so as to span between the upper connecting rod 45 and the lower connecting rod 50. The upholstery 70 extends in a U-shape in plan view between the pair of upright rods 40. The upholstery 70 comprises a seat body 71 and an edge material. The seat body 71 is made of a seat material such as mesh fabric, knit fabric, or cloth. The sheet body 71 is formed by cutting a sheet material into a desired shape. In this embodiment, the sheet body 71 is formed in a rectangular shape, corresponding to the shape of the frame-shaped portion of the load-supporting member 9, which consists of the upper connecting rod portion 45, a pair of upright rod portions 40, and the lower connecting rod portion 50.

[0068] Edge members are attached to the edges of the sheet body 71. The edge members form the edges of the tensioning member 70. For example, the edge members are provided around the entire circumference of the edges of the tensioning member 70. The edge members are made of a material with higher rigidity than the sheet body 71. The tensioning member 70 engages with the engagement recess 60 by inserting the edge members into the engagement recess 60 (see Figures 14 to 17). The edge members are provided on the upper edge 72, the left and right side edges 73, and the lower edge 74 of the tensioning member 70. The upper edge 72 of the tensioning member 70 engages with the upper engagement recess 61. The left and right side edges 73 of the tensioning member 70 engage with the side engagement recess 62. The lower edge 74 of the tensioning member 70 engages with the lower engagement recess 63. The outer peripheral edge of the tensioning member 70 is inserted into the engagement recess 60 around its entire circumference.

[0069] The seat body 71 is pulled out from the engaging recess 60 through the communication recess 65 toward the seating space S. The tensioning material 70 is positioned so that the seat body 71 does not protrude from the surface in which the engaging recess 60 of the load-supporting member 9 opens, as the seat body 71 passes through the communication recess 65. The seat body 71 is positioned so that it does not cover the horizontal outer and upper corner 45a of the upper connecting rod 45, as it is pulled out from the engaging recess 60 toward the seating space S. The tensioning material 70 exposes the majority of the upper surface 45u over its entire length so as to expose the outer edge of the upper surface 45u of the upper connecting rod 45 in a plan view. In this embodiment, the tensioning material 70 exposes the entire portion of the upper surface 45u of the upper connecting rod 45 that is outside the width center in a plan view (opposite side from the seating space S) at all positions in the extending direction of the upper connecting rod 45. The seat body 71 covers the inner surface 45i of the upper connecting rod portion 45, the inner surface 40i of the pair of upright rod portions 40, and the inner surface 50i of the lower connecting rod portion 50 from the seating space S side. The seat body 71 closes the inner space of the frame consisting of the upper connecting rod portion 45, the pair of upright rod portions 40, and the lower connecting rod portion 50 from the seating space S side.

[0070] Here, as shown in Figure 1, the portion of the backrest 7 that stands upright, passing outside the seat 5 in the left-right direction, and has an armrest surface, is referred to as the left and right pair of arm support portions 55. The arm support portions 55 are the portions of the backrest 7 that extend downward from the armrest portion 46 of the upper connecting rod portion 45. The arm support portions 55 include the upright rod portion 40, and a portion of the lower connecting rod portion 50 and the upholstery material 70. The seat 5 is positioned between the pair of arm support portions 55. The portion of the backrest 7 that connects the pair of arm support portions 55 and forms the backrest surface is referred to as the back support portion 56. Since the back support portion 56 includes the backrest surface, it is the portion of the backrest 7 that extends downward from the backrest portion 47 of the upper connecting rod portion 45. The back support portion 56 includes the entire portions of the lower connecting rod portion 50 and the tensioning material 70 that are not included in the arm support portion 55. The back support portion 56 is formed integrally with the pair of arm support portions 55. The inner surfaces of the pair of arm support portions 55 and the front surface of the back support portion 56 are continuous with each other as a load-bearing surface 8 formed by a single tensioning material 70. The load-bearing surface 8 has a gap in the vertical direction relative to the seat 5, regardless of the front-to-back position of the seat 5, because the lower connecting rod portion 50 is positioned above the upper surface of the seat 5. As a result, the entire back support portion 56 has a gap relative to the seat 5. On the other hand, the upright rod portion 40 of the arm support portion 55 faces the outer peripheral edge of the seat 5 from the outside in the horizontal direction.

[0071] As described above, the backrest 7 of the chair 1 in this embodiment has a pair of left and right arm support parts 55 that stand upright on the left and right outer sides of the seat 5 and have armrest surfaces on which a seated person can rest their arms, and a back support part 56 that connects the pair of arm support parts 55 to each other and is formed integrally with the pair of arm support parts 55, forming a backrest surface that faces forward. The inner surfaces of each of the pair of arm support parts 55 and the front surface of the back support part 56 are continuous with each other. The seat 5 is positioned between the pair of arm support parts 55 and is movable in the front-rear direction relative to the support structure 3. With this configuration, since the seat 5 is movable in the front-rear direction relative to the back support part 56, it becomes easy to move the seat 5 forward away from the back support part 56. Therefore, it becomes easy for a worker to insert their hand between the lower part of the back support part 56 and the seat 5. Furthermore, a certain clearance is provided between the arm support 55 and the seat 5 so that the seat 5 can move in the front-to-back direction relative to the backrest 7, making it easy for a worker to insert their hand between the lower part of the arm support 55 and the seat 5. Thus, a chair 1 with excellent maintainability is obtained.

[0072] The backrest 7 is positioned below the seat 5 and further has a horizontal rod 35 that connects a pair of armrests 55 to the support structure 3. With this configuration, the connection between the support structure 3 and the backrest 7 is positioned below the seat 5, thus avoiding the situation where the connection between the support structure and the backrest is positioned around the seat, making it difficult to insert a hand between the seat and the backrest. Therefore, a decrease in maintainability can be suppressed.

[0073] The pair of arm support sections 55 have a pair of left and right upright rods 40 that extend vertically along the left and right outer positions of the seat 5. The backrest 7 has a lower connecting rod 50 that connects the vertical intermediate portions of each of the pair of upright rods 40. The upper surface of the seat 5 is located below the lower connecting rods 50. With this configuration, the pair of upright rods 40 are connected to each other by the lower connecting rods 50, making the backrest 7 robust. Furthermore, since the seat 5 is positioned below the lower connecting rods 50, it becomes easy for a worker to insert their hand between the lower connecting rods 50 and the seat 5. Therefore, a decrease in maintainability can be suppressed.

[0074] The backrest 7 has an upper connecting rod portion 45 that connects the upper ends of each of the pair of upright rod portions 40. With this configuration, the upper connecting rod portion 45 cooperates with the pair of upright rod portions 40 and the lower connecting rod portion 50 to form a closed loop structure. This makes the backrest 7 robust without having to be formed in a plate-like shape that extends from the back support portion to the arm support portion.

[0075] The backrest 7 is stretched over the upper connecting rod 45 and the lower connecting rod 50 and comprises a single tensioning material 70 that forms the inner surfaces of each of the pair of arm support sections 55 and the front surface of the back support section 56. With this configuration, the inner surfaces of each of the pair of arm support sections 55 and the front surface of the back support section 56 can be formed by the tensioning material 70 in a continuous manner with respect to each other.

[0076] Chair 1 is equipped with a seat support upper part 80 that supports the seat 5. As the seat 5 moves in the front-rear direction relative to the support structure 3, the point at which it is supported by the seat support upper part 80 changes in the front-rear direction. With this configuration, the connection structure between the seat 5 and the seat support upper part 80 can be simplified compared to a configuration in which the seat is supported so as to be movable in the front-rear direction relative to the support structure by a link mechanism or the like. Therefore, the structure of chair 1 can be simplified.

[0077] (Second Embodiment) In the first embodiment, the load-bearing surface 8 of the backrest 7 has a gap with respect to the seat 5. In contrast, the second embodiment differs from the first embodiment in that the load-bearing surface 108 of the backrest 107 is positioned along the seat 105. Other configurations are the same as in the first embodiment, except as described below.

[0078] Figure 17 is a front view of the chair 101 according to the second embodiment. Figure 18 is a side view of the chair 101 according to the second embodiment. As shown in Figures 17 and 18, the chair 101 comprises a support structure 103, a seat 105, and a backrest 107.

[0079] The support structure 103 comprises a leg body 110 having a leg column, and a support base 115 connected to the upper end of the leg column. The support base 115 supports the seat 105 from below via a sliding mechanism 130. The sliding mechanism 130 connects the support base 115 and the seat 105 so that they can move relative to each other in the front-rear direction. The seat 105 has multiple fixed positions in the front-rear direction relative to the support base 115. The fixed positions of the seat 105 in the front-rear direction can be selected from multiple positions.

[0080] The backrest 107 comprises a pair of left and right arm support sections 155 that stand upright on the left and right outer sides of the seat 105, and a back support section 156 that connects the pair of arm support sections 155. Each arm support section 155 has an armrest surface. The seat 105 is positioned between the pair of arm support sections 155. The back support section 156 forms the backrest surface. The pair of arm support sections 155 and the back support section 156 are integrally formed. The inner surfaces of the pair of arm support sections 155 and the front surface of the back support section 156 are continuous with each other as a load-bearing surface 108. The load-bearing surface 108 may be made of a flexible sheet material or a hard material such as synthetic resin. The lower part of the load-bearing surface 108 faces the outer peripheral edge of the seat 105 from the outside in the horizontal direction. The lower part of the load-bearing surface 108 is positioned along the outer edge of the seat 105 so as not to form a substantial gap with respect to the seat 105 when the seat 105 is in its rearmost position relative to the support structure 103. When the seat 105 moves forward from its rearmost position, a gap is formed between the lower front surface of the back support portion 156 and the outer edge of the seat 105. However, even when the seat 105 moves forward from its rearmost position, a gap does not necessarily have to be formed between at least a portion of the lower inner surface of the arm support portion 155 and the outer edge of the seat 105.

[0081] This embodiment provides the same effects as the first embodiment. Furthermore, in this embodiment, the lower part of the load-bearing surface 108 of the backrest 107 is positioned along the outer edge of the seat 105. With this configuration, it is difficult for a worker to insert their hand between the back support portion 156 of the backrest 107 and the seat 105, making it possible to create a chair 101 that is suitable for achieving the above-mentioned effects.

[0082] It should be noted that the present invention is not limited to the embodiments described above with reference to the drawings, and various modifications are conceivable within its technical scope. For example, in the above embodiment, the tensioning material 70 is stretched over the entire frame of the load-supporting member 9, which consists of the upper connecting rod portion 45, the pair of upright rod portions 40, and the lower connecting rod portion 50, but the configuration is not limited to this. That is, the tensioning material may be stretched over only a part of the frame. For example, the tensioning material may be stretched over only the upper connecting rod portion and the lower connecting rod portion, leaving a gap between them and the pair of upright rod portions.

[0083] In the above embodiment, the seat 5 is linearly movable in the front-rear direction relative to the seat support 17, but the configuration is not limited to this. The direction of movement of the seat relative to the seat support only needs to be along the front-rear direction, and for example, the direction of movement of the seat may be inclined in the vertical direction with respect to the front-rear direction. Also, the seat does not have to move linearly relative to the seat support, and for example, the trajectory of the seat's movement in the front-rear direction may be curved in a side view.

[0084] In the above embodiment, the load-bearing surface 8, including the backrest surface, is formed by a single tensioning material 70, but the configuration is not limited to this. The backrest may have a pair of arm support parts and a back support part formed integrally with the pair of arm support parts. For example, the backrest may have a shell that extends from the back support part to the pair of arm support parts and a cushion positioned in front of the shell at the back support part, wherein the shell is formed to be continuous with the inner surface of the arm support parts and a part of the front surface of the back support part, and the front surface of the cushion may form the remaining part of the front surface of the back support part.

[0085] Furthermore, it is possible to replace the components in the above-described embodiments with well-known components as appropriate, without departing from the spirit of the present invention. [Explanation of symbols]

[0086] 1,101... chair 3,103…Support structure 5,105…za 7,107...backrest 35… Crossbar section (outward-facing section) 40…Erecting pole section 45… Upper connecting rod (connecting rod) 50… Lower connecting rod (middle connecting rod, connecting rod) 55,155…wrist support 56,156…back support department 70… Zhang Cai 80… Seat upper part (support part)

Claims

1. A support structure that makes contact with the floor surface, The seat and backrest are supported by the aforementioned support structure, Equipped with, The aforementioned backrest is, A pair of left and right arm support parts extend outwards from the left and right sides of the seat and have armrest surfaces on which the seated person rests their arms, A back support portion connects the pair of arm support portions and is formed integrally with the pair of arm support portions, forming a backrest surface that faces forward, It has, The inner surfaces of each of the pair of arm support parts and the front surface of the back support part are continuous with each other. The seat is positioned between the pair of arm support portions and is movable in the front-rear direction relative to the support structure. chair.

2. The backrest is positioned below the seat and further has an outward-facing portion that connects the pair of arm support portions and the support structure. The chair according to claim 1.

3. The pair of arm support parts have a pair of left and right upright rods that extend vertically along the left and right outer positions of the seat, The backrest has an intermediate connecting rod that connects the vertical intermediate portions of each of the pair of upright rods, The upper surface of the seat is located below the intermediate connecting rod. The chair according to claim 1 or claim 2.

4. The backrest has an upper connecting rod that connects the upper ends of each of the pair of upright rods. The chair according to claim 3.

5. The aforementioned backrest is, A pair of left and right upright rods are provided on the pair of arm support parts, and the left and right outer positions of the seat extend along the vertical direction, A connecting rod that connects the pair of upright rods, A single tensioning material stretched over the connecting rod, forming the inner surfaces of each of the pair of arm support parts and the front surface of the back support part, Equipped with, The chair according to claim 1 or claim 2.

6. The seat is provided with a support portion that supports the seat, As the seat moves in the front-to-back direction relative to the support structure, the portion of the seat supported by the support changes in the front-to-back direction. The chair according to claim 1 or claim 2.

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