Backrest and chair

Abstract

In a backrest where a tensioning material is stretched over a frame-like structure, the degree of freedom in shape is to be improved. [Solution] The backrest 7 comprises a frame-shaped body 80 that forms a through-hole on its inside that horizontally connects the seating space S and the space surrounding the chair, and a tensioning material stretched over the frame-shaped body 80 that closes the through-hole from the seating space S side and forms a load-bearing surface. The frame-shaped body 80 has an engaging recess 60 that opens on the opposite side of the through-hole and engages with the edge of the tensioning material. The frame-shaped body 80 has an upper rod portion 82 that extends left and right in a front view, a lower rod portion 83 that is located below the upper rod portion 82 and extends left and right in a front view, an upper groove-forming member 86 that overlaps the upper rod portion 82 in the front-rear direction and forms an upper engaging recess 61, and a lower groove-forming member 88 that overlaps the lower rod portion 83 in the front-rear direction and forms a lower engaging recess 63.

Description

Technical Field

[0001] The present invention relates to a backrest and a chair.

Background Art

[0002] There is a backrest in which a tension member forming a backrest surface is stretched on a closed-loop frame body. In this type of backrest, an engagement recess is provided in the frame body along its extending direction, and the tension member is stretched by engaging the edge portion of the tension member with the engagement recess (see, for example, Patent Document 1). Patent Document 1 discloses a chair in which a groove portion opening on the opposite side of a space portion is formed at the peripheral edge portion of a backrest frame having a space portion at the center, and an edge member provided at the peripheral edge portion of a tension member is folded back from the front surface side to the rear of the backrest frame and engaged with the groove portion, whereby the tension member is stretched over the entire periphery on the front surface side of the backrest frame.

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 the closed-loop frame body of the backrest is made of synthetic resin, it is common to form the frame body by injection molding and set the mold extraction direction in the front-rear direction during molding. However, in a configuration in which an engagement recess for engaging a tension member is provided in the frame body, when the engagement recesses are opened outward in the vertical direction at the upper side and the lower side of the frame body, it is difficult to form the engagement recesses in the mold cavity and the core. That is, there is a problem that it is necessary to provide a slide core that moves in the vertical direction in the mold, resulting in a complication and enlargement of the mold structure.

[0005] Furthermore, optional structures such as handles may be integrally formed on the upper edge of the frame-like body, and it is necessary to make the upper edge thicker in the front-to-back direction to secure the area for these optional structures. Also, since users often grasp the top of the backrest when moving the chair, it is necessary to make the upper edge thicker in the front-to-back direction to ensure the rigidity of the upper edge of the frame-like body. When making the upper edge thicker in the front-to-back direction in this way, it is desirable to remove material from the upper edge to suppress sink marks caused by injection molding. In addition, a connecting structure that connects to a seat or seat support may be provided on the lower edge of the frame-like body. It is difficult to form such material removal and connecting structures, along with engaging recesses, on the upper and lower edges of the frame-like body by injection molding, and even if it were possible, it would result in further complexity and enlargement of the mold structure. In other words, when engaging recesses are opened on the outward side in the vertical direction on both the upper and lower edges of the frame-like body, there is a problem that the degree of freedom in the design shape is reduced in exchange for suppressing the complexity and enlargement of the mold. Furthermore, since the seater's back is likely to come into contact with the upper part of the upholstery, it is necessary to more reliably prevent the upholstery from falling off at the upper edge of the frame-like structure, and it is desirable to strengthen the holding force of the upholstery. For this reason, it is desirable to improve the degree of freedom in the opening direction of the engaging recess, especially at the upper edge of the frame-like structure.

[0006] Therefore, the present invention aims to improve the degree of freedom in shape of a backrest in which a tensioning material is stretched over a frame-like body. Furthermore, it aims to provide a chair equipped with such a backrest. [Means for solving the problem]

[0007] A backrest according to a first aspect of the present invention comprises a frame-shaped body having a through portion formed on its inside that horizontally connects a seating space and the space surrounding the chair, and a tensioning material stretched over the frame-shaped body that closes the through portion from the seating space side and forms a back support surface, wherein the frame-shaped body has an engagement recess formed on the opposite side of the through portion, into which the edge of the tensioning material engages, and the frame-shaped body has an upper rod portion extending in the left-right direction when viewed from the front, a lower rod portion located below the upper rod portion and extending in the left-right direction when viewed from the front, an upper groove forming member that overlaps the upper rod portion in the front-rear direction and forms a first portion of the engagement recess, and a lower groove forming member that overlaps the lower rod portion in the front-rear direction and forms a second portion of the engagement recess.

[0008] According to the first embodiment, the first portion of the engagement recess is formed by overlapping the upper groove forming member on the upper rod in the front-rear direction. This allows the first portion of the engagement recess, which has depth in a direction intersecting the front-rear direction, to be formed without using a slide core of the injection molding die. Therefore, the complexity and size of the injection molding die for the upper rod can be suppressed. Moreover, since the upper groove forming member is overlapped on the upper rod in the front-rear direction, when a material removal is formed on the upper rod, the material removal can be opened on the upper groove forming member side in the front-rear direction and then closed by the upper groove forming member. This prevents the material removal from being exposed on the outer surface of the frame-like body, thus improving the appearance of the backrest. Furthermore, since the second portion of the engagement recess is formed by overlapping the lower groove forming member in the front-rear direction on the lower rod, the second portion of the engagement recess, which has depth in a direction intersecting the front-rear direction, can be formed without using a slide core for the injection molding die. For this reason, since the injection molding die for the lower rod does not require a slide core to form the second portion of the engagement recess, complex structures other than the engagement recess can be formed on the lower rod while suppressing the complexity and size increase of the die. As described above, in a backrest in which tension material is stretched over a frame-like body, it is possible to improve the degree of freedom in the shape of the backrest while suppressing the complexity and enlargement of the injection molding die.

[0009] A backrest according to a second aspect of the present invention is, in the backrest according to the first aspect described above, wherein the upper groove forming member is attached to the upper rod from one of the front-rear directions, the lower groove forming member is attached to the lower rod from one of the front-rear directions, and the tensioning material may overlap the upper groove forming member and the lower groove forming member in the front-rear direction.

[0010] According to the second embodiment, the upper groove-forming member and the lower groove-forming member are attached to the upper rod or the lower rod from the same front and rear sides. This allows the upper groove-forming member and the lower groove-forming member to be attached to each other from the same side while the upper rod and the lower rod are in place. Therefore, the workability during the assembly of the backrest can be improved. Furthermore, by overlapping the upper groove-forming member and the lower groove-forming member in the front-to-back direction, the exposure of the upper groove-forming member and the lower groove-forming member on the backrest's exterior can be suppressed. Therefore, the appearance of the backrest can be made even better.

[0011] A third aspect of the present invention is a backrest according to the second aspect, wherein the upper groove forming member may be attached to the upper rod portion from the front, and the lower groove forming member may be attached to the lower rod portion from the front.

[0012] According to the third embodiment, an upper groove-forming member is positioned in front of the upper rod, and a lower groove-forming member is positioned in front of the lower rod, and these upper and lower groove-forming members are covered from the front by a tensioning material. This allows the upper and lower groove-forming members to be covered by the tensioning material without having to stretch the tensioning material around the upper and lower rods. As a result, the outer portion of the backrest in plan view is exposed from the tensioning material, so when the chair moves on the floor or the backrest comes into contact with an object around the chair, contact between the tensioning material and the surrounding object can be suppressed. Therefore, damage to the tensioning material can be suppressed and the durability of the backrest can be improved.

[0013] A backrest according to a fourth aspect of the present invention is a backrest according to any of the first to third aspects described above, wherein the upper groove forming member is screwed to the upper rod and the lower groove forming member is screwed to the lower rod.

[0014] According to the fourth embodiment, the screw fastening portions in the upper groove-forming member and the lower groove-forming member are covered with tension material. Therefore, the appearance of the backrest can be made even better.

[0015] A backrest according to a fifth aspect of the present invention is a backrest according to any of the first to fourth aspects described above, wherein the frame-like body further comprises a pair of left and right lateral rods connecting the left and right ends of the upper rod and the lower rod on the same side, and each of the pair of lateral rods may have a third portion of the engaging recess formed therein.

[0016] According to the fifth embodiment, since the third portion of the engaging recess is formed on the lateral rod, no members other than the lateral rod are required to form the third portion of the engaging recess. Therefore, it is possible to suppress an increase in the number of parts of the frame-like body and improve the workability when assembling the backrest.

[0017] A chair according to the sixth aspect of the present invention is equipped with a backrest according to any of the first to fifth aspects described above.

[0018] According to the sixth embodiment, in a chair having a backrest on which a stretched material is stretched over a frame-like body, the degree of freedom in the shape of the backrest can be improved. [Effects of the Invention]

[0019] According to the present invention, in a backrest in which a tensioning material is stretched over a frame-like body, the degree of freedom in shape can be improved. [Brief explanation of the drawing]

[0020] [Figure 1] This is a perspective view of chair 1 according to this embodiment, seen from above. [Figure 2] Perspective view of the chair 1 according to the embodiment, seen from below. [Figure 3] Cross-sectional view of the chair 1 at a position corresponding to the line III-III in FIG. 6. [Figure 4] Cross-sectional view of the chair 1 at a position corresponding to the line IV-IV in FIG. 7. [Figure 5] Perspective view of the load support member 9 according to the embodiment. [Figure 6] Front view of the load support member 9 according to the embodiment. [Figure 7] Side view of the load support member 9 according to the embodiment. [Figure 8] Plan view of the load support member 9 according to the embodiment. [Figure 9] Cross-sectional view at the line IX-IX in FIG. 5. [Figure 10] Cross-sectional view at the line X-X in FIG. 5. [Figure 11] Cross-sectional view at the line XI-XI in FIG. 5. [Figure 12] Cross-sectional view at the line XII-XII in FIG. 5. [Figure 13] Rear view showing the middle part in the left-right direction of the upper connecting rod portion 45 of the embodiment. [Figure 14] Exploded perspective view of the load support member 9 according to the embodiment.

Mode for Carrying Out the Invention

[0021] 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.

[0022] Figure 1 is a perspective view of the chair 1 according to this embodiment, seen from above. As shown in Figure 1, the chair 1 of this 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.

[0023] Figure 2 is a perspective view of the chair 1 according to the 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 and a support base 15.

[0024] 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 can move on 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 5 from below. A lever for operating the gas spring is attached to the support base 15.

[0025] 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 backrest 7. The seat 5 comprises a seat plate 20 that receives the seating load and a cushion 23 positioned above the seat plate 20. The seat plate 20 is formed in a circular or rectangular shape in plan view such that its plan view shape substantially matches the plan view shape of the seat 5. The cushion 23 is positioned along the upper surface of the seat plate 20 and is supported by the seat plate 20. The cushion 23 is positioned so as to overlap the entire seat plate 20 when viewed from above.

[0026] Figure 3 is a cross-sectional view of chair 1 at the position corresponding to line III-III in Figure 6. Figure 4 is a cross-sectional view of chair 1 at the position corresponding to line IV-IV in Figure 7. As shown in Figures 2 to 4, the seat 5 further comprises a seat plate support member 26. The seat plate support member 26 supports the seat plate 20 from below. The seat plate support member 26 is connected to the seat plate 20 so as to be displaceable in the front-rear direction. The seat plate support member 26 is connected to the seat plate 20 so as not to be displaceable in the up-down and left-right directions.

[0027] 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.

[0028] Figure 5 is a perspective view of the load-supporting member 9 according to this embodiment. As shown in Figure 5, the load-supporting member 9 comprises a seating portion 30, a pair of left and right horizontal rod portions 35, a pair of left and right upright rod portions 40, an upper connecting rod portion 45, and a lower connecting rod portion 50.

[0029] As shown in Figures 3 to 5, the seat support portion 30 is coupled to the support structure 3 so as not to be displaceable in the vertical and horizontal directions. The seat support portion 30 is coupled to the seat 5 so as not to be displaceable in the vertical direction. The seat support portion 30 has a lower surface 30l that is supported by the support structure 3 and an upper surface 30u that supports the seat 5 from below. By coupling to the seat plate support member 26 of the seat 5 from below, the seat support portion 30 interposes between the seat 5 and the support base 15, indirectly connecting the seat 5 and the support base 15. The 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.

[0030] The upper wall portion 31 is the part of the seat support portion 30 that has a lower surface 30l and an upper surface 30u. 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, and the seat plate support member 26 is connected to it from above. The support base 15 and the seat plate support member 26 are fastened to the upper wall portion 31 by a common fastening member.

[0031] 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 in the front-rear direction, and a front wall portion and a rear wall portion extending in the left-right direction. The seating portion 30 is formed in a box shape with an opening at the bottom. The support base 15 is positioned inside the seating portion 30.

[0032] Figure 6 is a front view of the load-supporting member 9 according to the embodiment. As shown in Figures 5 and 6, the pair of horizontal rods 35 correspond one-to-one with the pair of side wall portions 32a. The horizontal rods 35 are connected to the side wall portions 32a. The horizontal rods 35 are formed integrally with the seat support portion 30. In this embodiment, the entire horizontal rod 35 is formed integrally with the entire seat support 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. It is preferable that the horizontal rod portion 35 is not in contact with the seat 5, but in configurations such as when the seat plate 20 is not displaced in the front-rear direction relative to the seat plate support member 26, the horizontal rod portion 35 may be in contact with the seat 5. The outer end of the horizontal rod portion 35 is located outside the seat 5 in a plan view.

[0033] 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 its longitudinal direction. The upper surface 35u of the horizontal rod portion 35 is connected to the upper surface 30u of the seating portion 30 via a stepped surface 32b provided on the side wall portion 32a that faces outward in the left-right direction. As a result, the upper surface 35u of the horizontal rod portion 35 extends outward in the left-right direction from a position lower than the upper surface 30u of the seating portion 30. Note that the normal direction of the stepped surface 32b does not have to be parallel to the left-right direction; it is sufficient that the normal vector of the stepped surface contains a component that points outward in the left-right direction.

[0034] Figure 7 is a side view of the load-supporting member 9 according to this embodiment. As shown in Figures 5 and 7, 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. From their lower ends, the upright rods 40 extend upward through 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 rods 35 and the upright rods 40. The upright rods 40 intersect the seat 5 in a side view from the left-right direction. The upper end of the upright rod portion 40 is within the formation range of the seat support portion 30 in the front-rear direction.

[0035] 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.

[0036] Figure 8 is a plan view of the load-supporting member 9 according to the embodiment. As shown in Figures 5 and 8, the upper connecting rod 45 connects the upper ends of a pair of upright rods 40. The upper connecting rod 45 is formed integrally with the upright rods 40. In plan view, the upper connecting rod 45 is formed in a U-shape that opens forward and is curved to be convex towards the rear. The upper connecting rod 45 is positioned to surround the seating space S from both 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 between the upright rods 40 and the upper connecting rod 45. The upper connecting rod 45 includes a pair of left and right armrests 46, a backrest 47, and an extension 48.

[0037] As shown in Figure 5, a pair of armrests 46 correspond one-to-one with a pair of upright rods 40. The armrests 46 have length in the front-rear 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-rear direction is a rectangle with one pair of sides extending vertically and the remaining pair of sides extending horizontally. The left-right outer and upper corners 46a of the armrests 46 are located at the outermost left-right position of the armrests 46 at any position in the front-rear direction of the armrests 46.

[0038] 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 middle portion in the left-right direction of the upper connecting rod portion 45 and connects to the rear ends of the pair of armrest portions 46. The backrest portion 47 only needs to include the middle portion in the left-right direction 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.

[0039] 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.

[0040] 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. A material retention opening 48a is formed in the extension portion 48. The material retention opening 48a is open to the front. The material retention opening 48a is closed from the front by the tensioning material 70.

[0041] As shown in Figure 7, the upper connecting rod 45 further includes a handle portion 49. The handle portion 49 is provided on the side of the chair 1 that faces the space surrounding the extension portion 48. The handle portion 49 has a convex shape in the cross-section of the upper connecting rod 45 so that the user can place their fingers on it (see Figure 9).

[0042] As shown in Figure 5, 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 6 and 7). 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.

[0043] 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 portion 45. The inner surface 45i is provided along the entire length of the upper connecting rod portion 45. That is, the inner surface 45i is provided continuously from the front end of the pair of armrest portions 46 to the backrest portion 47. The inner surface 45i is continuous with the inner surface 40i of the upright rod portion 40. Furthermore, the inner surface 45i is provided continuously from the backrest portion 47 to the extension portion 48. The portion of the inner surface 45i formed on the armrest portion 46 faces inward in the left-right direction when viewed from above (see Figure 8). The portion of the inner surface 45i formed on the backrest portion 47 and the extension portion 48 faces forward when viewed from above (see Figure 8). 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 9).

[0044] 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 to a point below the connection point with the upper connecting rod 45 on the upright rod 40. In other words, the lower connecting rod 50 is connected to the upper and lower intermediate part 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 seat 5 and has a gap in the vertical direction relative to the seat 5 when viewed from the front (see Figure 6). The lower connecting rod 50 is formed in a U-shape that opens forward when viewed from above and is curved to be convex towards the rear. The lower connecting rod 50 is positioned to surround the seating space S from both the left and right sides and the rear. The lower connecting rod 50 extends from its front end to the rear when viewed from the left or right in a side view. The middle portion of the lower connecting rod 50 in the left-right direction is located in front of the middle portion of the upper connecting rod 45 in the left-right direction.

[0045] As shown in Figures 5 and 6, the lower connecting rod portion 50 comprises a lower surface 50l facing downward 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.

[0046] The portion of the load-supporting member 9 consisting of the upper connecting rod 45, the pair of upright rods 40, and the lower connecting rod 50 is formed in a closed loop shape when viewed from the front. This closed loop portion is referred to as the frame-like body 80. Inside the frame-like body 80, surrounded by the upper connecting rod 45, the pair of upright rods 40, and the lower connecting rod 50, there is a through-hole that horizontally connects the seating space S and the space surrounding the chair 1.

[0047] Figure 9 is a cross-sectional view of the IX-IX line in Figure 5. Figure 10 is a cross-sectional view of the XX line in Figure 5. Figure 11 is a cross-sectional view of the XI-XI line in Figure 5. Figure 12 is a cross-sectional view of the XII-XII line in Figure 5. As shown in Figures 5 and 9 to 12, the frame-like body 80 has an engagement recess 60 into which the tensioning material 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 around the entire circumference of the frame-like body 80.

[0048] As shown in Figures 5, 9, and 10, the upper engagement recess 61 is formed in the upper connecting rod 45. The upper engagement recess 61 opens to the upper surface 45u of the upper connecting rod 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 45. The portion of the upper engagement recess 61 that extends in the left-right direction (for example, the backrest engagement recess 61b) opens upward and backward, and has depth downward and forward from the opening. The upper engagement recess 61 is provided continuously along the entire length of the upper connecting rod 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 recess 61a and the backrest engagement recess 61b are in direct communication with each other.

[0049] As shown in Figures 5 and 11, 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 open forward and have depth from the opening towards the rear. The side engagement recesses 62 extend along the extending direction 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. At the connection between the side engagement recess 62 and the upper engagement recess 61, the engagement recess 60 bends so that its curvature is at its maximum value and opens continuously upward from the front.

[0050] As shown in Figures 5 and 12, the lower engagement recess 63 is formed in the lower connecting rod 50. The lower engagement recess 63 opens to the lower surface 50l of the lower connecting rod 50. The lower engagement recess 63 extends along the extending direction of the lower connecting rod 50. The portion of the lower engagement recess 63 that extends in the left-right direction opens downward and rearward, and has depth from the opening upward and forward. 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 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. At the connection between the lower engagement recess 63 and the side engagement recess 62, the engagement recess 60 is bent so that its curvature is at its maximum value, and opens continuously from the front downward.

[0051] As shown in Figures 9 to 12, 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.

[0052] As shown in Figures 1 and 5, the upholstery material 70 is stretched over the load-bearing member 9 to form a load-bearing surface (back support surface) 8. The upholstery material 70 is stretched over the frame-shaped body 80 so that the load-bearing surface 8 faces the torso of the seated person from the outside in the horizontal direction. The upholstery material 70 comprises a sheet body 71 and an edge material. The sheet body 71 is made of a sheet material such as mesh fabric, knit fabric, or cloth. The sheet body 71 is formed by cutting the 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-bearing member 9, which consists of an upper connecting rod portion 45, a pair of upright rod portions 40, and a lower connecting rod portion 50.

[0053] 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 9 to 12). 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.

[0054] 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 also closes the through portion on the inside of the frame-like body 80 from the seating space S side.

[0055] Since the upper engagement recess 61 has depth extending downward and forward from its opening, when tension is applied to the sheet body 71, the upper edge portion 72 attempts to rotate within the upper engagement recess 61 with its rear end as a pivot point, and the sheet body 71 is strongly pressed against the opening edge of the upper engagement recess 61 from the rear. As a result, the tensioning material 70 frictionally engages with the opening edge of the upper engagement recess 61, making it difficult for it to fall out of the upper engagement recess 61. Also, since the lower engagement recess 63 has depth extending upward and forward from its opening, when tension is applied to the sheet body 71, the lower edge portion 74 attempts to rotate within the lower engagement recess 63 with its rear end as a pivot point, and the sheet body 71 is strongly pressed against the opening edge of the lower engagement recess 63 from the rear. As a result, the tensioning material 70 frictionally engages with the opening edge of the lower engagement recess 63, making it difficult for it to fall out of the lower engagement recess 63.

[0056] The component structure of the frame-shaped body 80 will now be described. Figure 14 is an exploded perspective view of the load-supporting member 9 according to the embodiment. As shown in Figure 14, the frame-shaped body 80 comprises a frame member 81 and an upper groove-forming member 86 and a lower groove-forming member 88 attached to the frame member 81.

[0057] The frame member 81 is provided as a strength member of the frame-shaped body 80 and is continuous around the entire circumference of the frame-shaped body 80. The frame member 81 is an injection-molded body made of resin material. The frame member 81 is formed by demolition in the front-to-back direction during molding. The frame member 81 is a single member comprising an upper rod portion 82 extending in the left-to-right direction when viewed from the front, a lower rod portion 83 located below the upper rod portion 82 and extending in the left-to-right direction when viewed from the front, and a pair of left and right lateral rod portions 84 connecting the left and right ends of the upper rod portion 82 and the lower rod portion 83 on the same side.

[0058] The upper rod portion 82 is the main part of the upper connecting rod portion 45. The upper groove forming member 86 overlaps the upper rod portion 82 from the front. The upper rod portion 82 cooperates with the upper groove forming member 86 to form the upper connecting rod portion 45. The upper rod portion 82 extends along the entire length of the upper connecting rod portion 45. The upper rod portion 82 forms the lower surface of the upper connecting rod portion 45, the outer surface facing the surrounding space of the chair 1, and the portion of the upper surface 45u that is horizontally outside the upper engagement recess 61. On the other hand, the upper rod portion 82 forms only a part of the inner surface 45i of the upper connecting rod portion 45. Material removal cutouts 82a are formed on the upper rod portion 82. Multiple material removal cutouts 82a are formed along the extending direction of the upper rod portion 82. All of the material removal openings 82a are open to the front. The material removal openings 82a are formed within the range in which the upper groove forming member 86 is positioned in the extending direction of the upper connecting rod portion 45.

[0059] The lower rod portion 83 is the main part of the upper connecting rod portion 45. The lower groove forming member 88 overlaps the lower rod portion 83 from the front. The lower rod portion 83 cooperates with the lower groove forming member 88 to form the lower connecting rod portion 50. The lower rod portion 83 extends along the entire length of the lower connecting rod portion 50. The lower rod portion 83 forms the upper surface of the lower connecting rod portion 50, the outer surface facing the surrounding space of the chair 1, and the portion of the lower surface 50l that is horizontally outside the lower engagement recess 63. On the other hand, the lower rod portion 83 forms only a part of the inner surface 50i of the lower connecting rod portion 50. Material removal cutouts 83a are formed on the lower rod portion 83. Multiple material removal cutouts 83a are formed along the extending direction of the lower rod portion 83. All of the material removal openings 83a are open to the front. The material removal openings 83a are formed within the range in which the lower groove forming member 88 is located in the extending direction of the lower connecting rod portion 50.

[0060] Each of the pair of lateral rods 84 independently forms a portion of the upright rod 40 on the same left and right side, between the connection portion with the upper connecting rod 45 and the connection portion with the lower connecting rod 50. Engaging recesses 60 are formed in the lateral rods 84. The engaging recesses 60 formed in the lateral rods 84 include a lateral engaging recess 62. The engaging recesses 60 formed in the lateral rods 84 include the connection portion between the lateral engaging recess 62 and the upper engaging recess 61, but do not include the connection portion between the lateral engaging recess 62 and the lower engaging recess 63. In other words, the engaging recesses 60 formed in the lateral rods 84 extend from the lateral engaging recess 62 to the front end of the upper engaging recess 61. Furthermore, the engaging recesses 60 formed in the lateral rods 84 are the portion of the entire engaging recess 60 that allows the core of the mold to be removed forward during injection molding.

[0061] The upper groove forming member 86 is attached to the upper rod portion 82. The upper groove forming member 86 overlaps the upper rod portion 82 in the front-rear direction. The upper groove forming member 86 is attached to the upper rod portion 82 from the front. The upper groove forming member 86 closes all of the material removal 82a of the upper rod portion 82 from the front. The upper groove forming member 86 cooperates with the upper rod portion 82 to form a smooth inner surface 45i of the upper connecting rod portion 45. The upper groove forming member 86 forms an engagement recess 60 between itself and the upper rod portion 82. The engagement recess 60 formed by the upper groove forming member 86 includes an upper engagement recess 61. The engagement recess 60 formed by the upper groove forming member 86 does not include the connection between the upper engagement recess 61 and the side engagement recess 62.

[0062] As shown in Figures 9 and 10, the upper groove forming member 86 comprises a base portion 86a and a groove forming wall portion 86b that protrudes from the base portion 86a toward the outside of the frame-shaped body 80 (opposite side of the through portion). The base portion 86a is provided along the entire length of the upper groove forming member 86. The base portion 86a forms the inner surface 45i of the upper connecting rod portion 45 and is in contact with the upper rod portion 82. The base portion 86a is screwed to the upper rod portion 82 using a screw or other threaded member. In this case, the threaded member is screwed into the upper groove forming member 86 from the tensioning member 70 side along the front-rear direction. The base portion 86a is restricted from downward movement when not fixed to the upper rod portion 82 by contacting the upward-facing stepped surface formed on the upper rod portion 82 from above.

[0063] The groove-forming wall portion 86b is provided along the entire length of the upper groove-forming member 86. The groove-forming wall portion 86b forms the inner surface 45i of the upper connecting rod portion 45 and has a gap with respect to the upper rod portion 82 along its entire length. The gap between the groove-forming wall portion 86b and the upper rod portion 82 is the upper engagement recess 61. That is, the groove-forming wall portion 86b forms the wall surface of the upper engagement recess 61 on the seating space S side, and the upper rod portion 82 forms the wall surface of the upper engagement recess 61 on the opposite side of the seating space S. Furthermore, since the base portion 86a protrudes further toward the upper rod portion 82 than the groove-forming wall portion 86b, the base portion 86a forms the bottom surface of the upper engagement recess 61. Furthermore, the portion of the upper engaging recess 61 formed by the upper groove forming member 86 includes an undercut when the mold removal direction is set to the front-to-back direction during injection molding of the upper connecting rod portion 45.

[0064] As shown in Figure 14, engaging pieces 86c are provided at the left and right front ends of the groove-forming wall portion 86b. The engaging pieces 86c protrude further than the base portion 86a in the direction of extension of the engaging recess 60. The engaging pieces 86c are inserted inside the upper end of the engaging recess 60 in the upright rod portion 40. The engaging pieces 86c engage with the wall portion of the engaging recess 60 on the seating space S side of the upright rod portion 40, restricting displacement toward the seating space S side. This restricts the bending of the upper groove-forming member 86 so that its front end separates from the upper rod portion 82 toward the seating space S side.

[0065] The lower groove forming member 88 is attached to the lower rod portion 83. The lower groove forming member 88 overlaps the lower rod portion 83 in the front-rear direction. The lower groove forming member 88 is attached to the lower rod portion 83 from the same front-rear side (i.e., the front) as the upper groove forming member 86. The lower groove forming member 88 closes all material removal 83a of the lower rod portion 83 from the front. The lower groove forming member 88 cooperates with the lower rod portion 83 to form a smooth inner surface 50i of the lower connecting rod portion 50. The lower groove forming member 88 forms an engagement recess 60 between itself and the lower rod portion 83. The engagement recess 60 formed by the lower groove forming member 88 includes a lower engagement recess 63. The engagement recess 60 formed by the lower groove forming member 88 includes a connection between the lower engagement recess 63 and the side engagement recess 62. In other words, the engagement recess 60 formed by the lower groove forming member 88 extends from the lower engagement recess 63 to the lower ends of each of the pair of side engagement recesses 62. For convenience, in the following explanation, the range of the engagement recess 60 formed by the lower groove forming member 88 will be referred to as the lower engagement recess 63.

[0066] As shown in Figure 12, the lower groove forming member 88 comprises a base portion 88a and a groove forming wall portion 88b that extends from the base portion 88a toward the outside of the frame-shaped body 80 (opposite side of the through portion). The base portion 88a is provided along the entire length of the lower groove forming member 88. The base portion 88a forms the inner surface of the lower connecting rod portion 50 and is in contact with the lower rod portion 83. The base portion 88a is screwed to the lower rod portion 83 using a screw or other threaded member. In this case, the threaded member is screwed into the lower groove forming member 88 from the tensioning member 70 side along the front-rear direction. The base portion 88a is screwed to the lower rod portion 83 at its left and right pair of front ends and at one or more locations between the pair of front ends. The front end of the base portion 88a is fixed to the lower rod portion 83, which restricts the bending of the lower groove forming member 88 so that its front end moves away from the lower rod portion 83 toward the seating space S. The base portion 88a is restricted from moving downward when not fixed to the lower rod portion 83 by contacting the downward-facing stepped surface formed on the lower rod portion 83 from below.

[0067] The groove-forming wall portion 88b is provided along the entire length of the lower groove-forming member 88. The groove-forming wall portion 88b forms the inner surface 50i of the lower connecting rod portion 50 and has a gap with respect to the lower rod portion 83 along its entire length. The gap between the groove-forming wall portion 88b and the lower rod portion 83 is the lower engagement recess 63. That is, the groove-forming wall portion 88b forms the wall surface of the lower engagement recess 63 on the seating space S side, and the lower rod portion 83 forms the wall surface of the lower engagement recess 63 on the opposite side of the seating space S. In the illustrated example, the base portion 88a forms the bottom surface of the lower engagement recess 63. Note that the portion of the lower engagement recess 63 formed by the lower groove-forming member 88 includes an undercut when the mold release direction is set to the front-rear direction during injection molding of the lower connecting rod portion 50.

[0068] As described above, the upper groove-forming member 86 does not form a connection between the upper engagement recess 61 and the side engagement recess 62. That is, the end of the upper groove-forming member 86 is located offset from the connection between the upper engagement recess 61 and the side engagement recess 62. Similarly, the lower groove-forming member 88 forms a connection between the lower engagement recess 63 and the side engagement recess 62. That is, the end of the lower groove-forming member 88 is located offset from the connection between the lower engagement recess 63 and the side engagement recess 62. In other words, the edges of each groove-forming member 86, 88 are located offset from the bend of the engagement recess 60.

[0069] As described above, the backrest 7 of this embodiment includes a frame-shaped body 80 that has a through-hole on its inside that horizontally connects the seating space S and the surrounding space of the chair 1, and a tensioning material 70 that is stretched over the frame-shaped body 80 and closes the through-hole from the seating space S side, forming a load-bearing surface 8. The frame-shaped body 80 has an engagement recess 60 that opens on the opposite side of the through-hole and engages with the edge of the tensioning material 70. The frame-shaped body 80 has an upper rod portion 82 that extends in the left-right direction when viewed from the front, a lower rod portion 83 that is located below the upper rod portion 82 and extends in the left-right direction when viewed from the front, an upper groove-forming member 86 that overlaps the upper rod portion 82 in the front-rear direction and forms an upper engagement recess 61, and a lower groove-forming member 88 that overlaps the lower rod portion 83 in the front-rear direction and forms a lower engagement recess 63.

[0070] According to the above configuration, the upper engagement recess 61 is formed by overlapping the upper groove forming member 86 on the upper rod portion 82 in the front-rear direction. This allows the upper engagement recess 61, which has depth in the vertical direction, to be formed without using a slide core of the injection molding die. Therefore, it is possible to suppress the complexity and size of the injection molding die for the upper rod portion 82. Moreover, since the upper groove forming member 86 is overlapped on the upper rod portion 82 in the front-rear direction, when forming a material removal section 82a on the upper rod portion 82, the material removal section 82a can be opened on the upper groove forming member 86 side (forward in this embodiment) in the front-rear direction, and the material removal section 82a can be closed by the upper groove forming member 86. This prevents the material removal section 82a from being exposed on the outer surface of the frame-like body 80, thus improving the appearance of the backrest 7.

[0071] Furthermore, since the lower engagement recess 63 is formed by overlapping the lower groove forming member 88 on the lower rod portion 83 in the front-rear direction, the lower engagement recess 63, which has depth in the vertical direction, can be formed without using a slide core for the injection molding die. For this reason, since the injection molding die for the lower rod portion 83 does not require a slide core to form the lower engagement recess 63, complex structures other than the engagement recess 60 can be formed on the lower rod portion 83 while suppressing the complexity and size increase of the die. As described above, in a backrest 7 in which a tensioning material 70 is stretched over a frame-like body 80, it is possible to improve the degree of freedom in the shape of the backrest 7 while suppressing the complexity and enlargement of the injection molding die.

[0072] In particular, in this embodiment, since the upper engagement recess 61 and the lower engagement recess 63 have depth in a direction inclined in the front-rear direction with respect to the vertical direction, it is difficult to form the upper engagement recess 61 and the lower engagement recess 63 with a slide core that moves in the vertical direction. Therefore, the effect of being able to form the upper engagement recess 61 and the lower engagement recess 63 without using a slide core can be effectively demonstrated.

[0073] The upper groove forming member 86 is attached to the upper rod portion 82 from the front. The lower groove forming member 88 is attached to the lower rod portion 83 from the front. The tensioning material 70 overlaps the upper groove forming member 86 and the lower groove forming member 88 in the front-rear direction. With this configuration, the upper groove forming member 86 and the lower groove forming member 88 are attached to the upper rod portion 82 or the lower rod portion 83 from the same side front-rear. This allows the upper groove forming member 86 and the lower groove forming member 88 to be attached to the frame member 81 from the same side while the frame member 81, including the upper rod portion 82 and the lower rod portion 83, is in a fixed position. Therefore, the workability during assembly of the backrest 7 can be improved.

[0074] Furthermore, since the tensioning material 70 overlaps the upper groove forming member 86 and the lower groove forming member 88 in the front-to-back direction, it is possible to prevent the upper groove forming member 86 and the lower groove forming member 88 from being exposed on the surface of the backrest 7. Therefore, the appearance of the backrest 7 can be made even better.

[0075] The upper groove forming member 86 is attached to the upper rod portion 82 from the front. The lower groove forming member 88 is attached to the lower rod portion 83 from the front. With this configuration, the upper groove forming member 86 is positioned in front of the upper rod portion 82, and the lower groove forming member 88 is positioned in front of the lower rod portion 83, and these upper groove forming member 86 and lower groove forming member 88 are covered from the front by the tensioning material 70. As a result, the upper groove forming member 86 and lower groove forming member 88 can be covered by the tensioning material 70 without having to stretch the tensioning material 70 so as to wrap around the upper rod portion 82 and lower rod portion 83. Therefore, the outer portion of the backrest 7 in plan view is exposed from the tensioning material 70, so when the chair 1 moves on the floor or the backrest 7 comes into contact with an object around the chair 1, it is possible to suppress the tensioning material 70 from coming into contact with the surrounding object. Therefore, damage to the upholstery 70 can be suppressed, thereby improving the durability of the backrest 7.

[0076] The upper groove-forming member 86 is screwed to the upper rod portion 82. The lower groove-forming member 88 is screwed to the lower rod portion 83. With this configuration, the screw-fastened portions of the upper groove-forming member 86 and the lower groove-forming member 88 are covered by the tensioning material 70. Therefore, the appearance of the backrest 7 can be made even better.

[0077] The frame-like body 80 further comprises a pair of left and right lateral rods 84 that connect the left and right ends of the upper rod 82 and the lower rod 83 on the same side. A side engagement recess 62 is formed in each of the pair of lateral rods 84. With this configuration, since the side engagement recess 62 is formed in the lateral rods 84, no members other than the lateral rods 84 are required to form the side engagement recess 62. Therefore, the increase in the number of parts of the frame-like body 80 can be suppressed and the workability during assembly of the backrest 7 can be improved.

[0078] Here, if the edge of the groove-forming member is located at the bend of the engagement recess 60, the wall portion of the engagement recess 60 on the seating space S side will be divided into two members at the bend. The wall portion of the engagement recess 60 on the seating space S side supports the tensioning material 70 by biting into it at the bend of the engagement recess 60, so if it is divided at the bend of the engagement recess 60, it can pierce the tensioning material 70. In this embodiment, since the edges of the groove-forming members 86 and 88 are located offset from the bend of the engagement recess 60, it is possible to prevent the wall portion of the engagement recess 60 on the seating space S side from piercing the tensioning material 70 at the bend of the engagement recess 60. Therefore, damage to the tensioning material 70 can be effectively suppressed.

[0079] 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 upper connecting rod 45 has an armrest 46 in addition to the backrest 47, but the configuration is not limited to this. That is, the upper connecting rod does not necessarily have to have an armrest.

[0080] In the above embodiment, the frame-like body 80 is connected to the seating portion 30 at the front end of the lower rod portion 83, but the position of the connection between the frame-like body and the seating portion is not particularly limited. For example, the frame-like body may be connected to the seating portion at the middle of the lower rod portion in the left-right direction.

[0081] In the above embodiment, the groove-forming members 86 and 88 overlap the frame member 81 from the front, but the configuration is not limited to this. At least one of the upper groove-forming member and the lower groove-forming member may overlap the frame member from the rear.

[0082] In the above embodiment, the screwing direction of the threaded member for attaching the upper groove forming member 86 to the upper rod portion 82 is parallel to the mounting direction (front-to-back direction) of the upper groove forming member 86 to the upper rod portion 82, but the configuration is not limited to this. That is, the screwing direction of the threaded member may be inclined with respect to the mounting direction of the upper groove forming member to the upper rod portion, and for example, the threaded member may be screwed into the upper groove forming member along the vertical direction. The same applies to the screw fastening structure of the lower groove forming member 88 and the lower rod portion 83.

[0083] In the above embodiment, material removal is formed in the upper rod portion 82 and the lower rod portion 83, but the configuration is not limited to this. That is, material removal does not have to be formed in at least one of the upper rod portion and the lower rod portion.

[0084] In the above embodiment, the upper groove-forming member 86 blocks all of the material removal 82a of the upper rod portion 82 from the front, but the configuration is not limited to this. The upper groove-forming member does not have to block at least a portion of the material removal of the upper rod portion. The same applies to the lower groove-forming member.

[0085] In the above embodiment, the upper groove-forming member 86 is screwed to the upper rod portion 82, but the method of fixing the upper groove-forming member 86 and the upper rod portion 82 is not particularly limited. The same applies to the method of fixing the lower groove-forming member 88 and the lower rod portion 83.

[0086] In the above embodiment, an upper engagement recess 61 is formed between the upper groove forming member 86 and the upper rod portion 82, but the configuration is not limited to this. The upper engagement recess only needs to be formed on the upper connecting rod portion when the upper groove forming member is attached to the upper rod portion, and may also be formed on the upper groove forming member itself. Also, in the above embodiment, a lower engagement recess 63 is formed between the lower groove forming member 88 and the lower rod portion 83, but the configuration is not limited to this. The lower engagement recess only needs to be formed on the lower connecting rod portion when the lower groove forming member is attached to the lower rod portion, and may also be formed on the lower groove forming member itself.

[0087] In the above embodiment, the side engagement recess 62 opens forward, but the configuration is not limited to this. For example, the side engagement recess may open outward in the left-right direction.

[0088] 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]

[0089] 1…Chair 7...backrest 8…Load-bearing surface (back support surface) 60…Engaging recess 61…Upper engagement recess (first part) 62... Side engagement recess (third part) 63…Lower engagement recess (second part) 70…Tension material 80...frame-like body 82…Upper rod part 83…Lower rod part 84…Lateral rod part 86… Upper groove forming member 88...Lower groove forming member S... Seating space

Claims

1. A frame-like body having an internal through-hole that connects the seating space and the space surrounding the chair in a horizontal direction, A tensioning material stretched over the frame-like body to close the penetration from the seating space side and form a back support surface, Equipped with, The frame-like body has an engagement recess formed on the opposite side of the through-hole, into which the edge of the tensioning material engages. The aforementioned frame-like body is The upper rod extends horizontally in a front view, A lower rod portion located below the upper rod portion and extending in the left-right direction when viewed from the front, An upper groove forming member that overlaps the upper rod portion in the front-rear direction and forms the first portion of the engagement recess, A lower groove forming member that overlaps the lower rod portion in the front-rear direction and forms the second portion of the engagement recess, Having, Backrest.

2. The upper groove forming member is attached to the upper rod portion from one of the front-rear directions. The lower groove forming member is attached to the lower rod portion from one of the front-rear directions. The tensioning material overlaps the upper groove forming member and the lower groove forming member in the front-rear direction. The backrest according to claim 1.

3. The upper groove forming member is attached to the upper rod portion from the front, The lower groove forming member is attached to the lower rod portion from the front. The backrest according to claim 2.

4. The upper groove forming member is screwed to the upper rod portion, The lower groove forming member is screwed to the lower rod portion. The backrest according to claim 2 or claim 3.

5. The frame-like body further comprises a pair of left and right lateral rods that connect the left and right ends of the upper rod and the lower rod on the same side, Each of the pair of lateral rods has a third portion of the engagement recess formed therein. A backrest according to any one of claims 1 to 3.

6. A chair having a backrest as described in any one of claims 1 to 3.

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