Chair and its backrest

Abstract

To secure body stability by holding shape retention while securing high cushioning and fitting properties by having a soft-elastomer backboard.SOLUTION: A backboard 2 is provided with high flexibility by having a large number of through holes 21 and is deformable by following up movement of a user. An upper reinforcement member 13 is fastened in an upper end part in a rear face of the backboard 2, and so is a lower reinforcement member 16 in a lower end part in the rear face of the backboard 2. The upper reinforcement member 13 is connected to an upper support 11 of a back frame 3, while the lower reinforcement member 16 is fixed on a lower support 12 of the back frame 3. The upper support 11 is capable of performing horizontal rotation against resilience. The backboard 2 is deformable by following up the movement of the user while retaining the entire shape. Therefore, the chair can secure high fitting and cushioning properties while securing stability of the user's body.SELECTED DRAWING: Figure 6

Description

Technical Field

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

Background Art

[0002] Chairs come in various forms. The swivel chair commonly used in offices mainly consists of a leg device with casters, a seat, and a backrest. Optional accessories such as armrests, headrests, and hangers are attached.

[0003] Also, many swivel chairs have a reclining function where the backrest can recline. With such a reclining function, the sitter can relax the body and continue to use it for a long time.

[0004] Important factors for maintaining comfort in a chair are the fit, cushioning, and softness of the backrest. Therefore, the front surface of the backrest is made of cushioning material or the body is supported by a mesh material. The mesh material also has the advantage of preventing sweating due to its excellent breathability.

[0005] Now, when the sitter leans on the backrest, the center line of the upper body is not always aligned with the center line of the backrest. The sitter may lean with the upper body tilted to the right or left, or twist the body while leaning on the backrest and face backward. In these cases, the pressing force (body pressure) due to the sitter's leaning acts strongly and is biased towards the left or right side of the backrest.

[0006] And basically, the backrest of a chair often has rigidity such that it hardly deforms under the pressing force of the sitter. However, if the backrest has a rigid structure, a part of the sitter's body will strongly hit a part of the backrest, resulting in a loss of comfort.

[0007] Therefore, a chair has been proposed that allows the backrest to bend and deform (torsional deformation) due to the pressure applied by the sitter, and one example of such a chair is disclosed in Patent Document 1. Patent Document 1 relates to the applicant's prior application, and the upper end of the back support has left and right longitudinal Upper Support It is mounted to rotate horizontally against the spring, Upper Support The left and right ends of the backrest are connected to both ends of the backrest, and if the user's weight is unevenly distributed to either the left or right side, Upper Support The backrest twists and deforms as it rotates horizontally. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2020-58759 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] In Patent Document 1, the backrest bends and deforms (twistes) due to the pressure applied by the seated person. Therefore, when the upper body is shifted to the right or left and leaning against the backrest, the backrest deforms to follow the movement. Consequently, it is possible to accommodate the movement of the seated person's body and to soften the contact of the backrest with the body. As a result, it can be said that comfort can be improved.

[0010] In order to improve the cushioning and fit of the backrest, it is beneficial to construct the back panel from a soft material such as elastomer. However, because soft materials such as elastomer lack rigidity, simply replacing the backrest in Patent Document 1 with elastomer may not guarantee the shape retention of the backrest.

[0011] The present invention has been made in view of the current situation and aims to suitably expand upon Patent Document 1. [Means for solving the problem]

[0012] The present invention comprises many components, and typical examples are specified in each claim. Of these, the invention of claim 1 is: "A soft material that flexes and deforms under the pressure of the person sitting on it." Synthetic resin It comprises a back panel made of a certain material, and a back frame to which the back panel is attached, The backrest includes upper and lower edges on the left and right longitudinal sides, and left and right edges on the top and bottom longitudinal sides, the upper and lower edges being retaining edges that attach to the back frame, and the left and right side edges being freely deformable parts that can stretch and deform due to the pressure applied by the seated person. Ori , The upper edge of the aforementioned back panel is attached to the back frame via long, plate-shaped upper reinforcing members that overlap the upper edge from the rear. It is the backrest of a chair, The aforementioned upper reinforcing member is made of synthetic resin and is separate from the back frame, while the upper edge of the back plate and the upper reinforcing member are integrated and fixed to each other, The lower edge of the back plate has left and right long reinforcing members that overlap from the rear. There are " This is the structure.

[0013]

[0014] The invention of claim 2 is, " It comprises a backrest made of a soft material that flexes and deforms under the pressure of the seated person, and a back frame to which the backrest is attached. The backrest includes upper and lower edges on the left and right longitudinal sides, and left and right edges on the top and bottom longitudinal sides, the upper and lower edges being retaining edges that attach to the back frame, and the left and right side edges being freely deformable parts that can stretch and deform due to the pressure applied by the seated person. The upper edge of the back panel has upper reinforcing members, which are long on both sides and in a plate-like shape, integrally formed and overlapping from the rear, while the lower edge of the back panel has lower reinforcing members, which are long on both sides and overlapping from the rear. In this basic configuration, "The aforementioned back frame has a back support column located in the middle of the left and right sides, and arm portions extending to the left and right from its upper end, The arm portion is attached to the back support column in a manner that allows it to rotate horizontally against elasticity, and the left and right ends of the upper reinforcing member are connected to both the left and right ends of the arm portion. This is the structure.

[0015] Invention of Claim 3 In the same basic configuration as claim 2, "The upper reinforcing member has upper boss portions that protrude rearward and downward at both left and right ends, and the left and right ends of the arm portion of the back frame are connected to the upper boss portions, The lower reinforcing member is also formed integrally with the back plate, and upward-facing protrusions are formed at both the left and right ends of the lower reinforcing member, which are joined integrally with the back plate. It is configured as follows.

[0016] The invention according to claim 4 In the same basic configuration as claim 2, "On the back plate, a group of slits that are open in the front and rear directions in the vertical longitudinal direction are formed in multiple rows and multiple stages in the left - right direction and the vertical direction, At the upper part of the back plate where the upper reinforcing member overlaps, a concave groove continuous with the slit is formed, and the back plate is thinner at the location of the concave groove." It is configured as follows.

[0017] The invention according to claim 5 relates to a chair, and the chair " A seat on which a person sits and , legs that support the seat, Claim Choose one of 1-4 the backrest described in ,of and includes." It is configured as follows.

Advantages of the Invention

[0018] In the present invention, even if the back plate is made of a soft material such as an elastomer, the back plate is shaped by the reinforcing member, so that while stabilizing the shape of the back plate, deformation due to the body pressure of the seated person can be tolerated. Therefore, even if a group of punched holes is formed in the back plate, the freedom of design such as the shape and pattern of the punched holes can be improved, and the fit and cushioning properties of the back plate can be improved. Synthetic resin Moreover, since elongation deformation of the back plate due to the body pressure (pressing force) of the seated person is tolerated, the back plate can be deformed following the movement of the user's body,

[0019] Also, the fit and cushioning properties can be further improved. Furthermore, in the present invention hand

[0020] Claim 2By adopting this configuration, the shape retention of the backrest can be ensured while allowing the backrest to deform to follow the twisting of the user's body. In other words, the upper reinforcing member prevents the backrest from deforming excessively, while appropriately supporting the body and allowing the backrest to follow the body's movements. Therefore, the features of Patent Document 1 can be improved, and the value of the chair can be enhanced.

[0021] Claim 3 By adopting this configuration, the integration between the upper reinforcing member and the back panel, as well as the integration between the lower reinforcing member and the back panel, can be improved, thereby enhancing the shape-retaining function of the back panel.

[0022] Claim 4 By forming numerous cutouts in the back panel as shown, the back panel can be configured to deform appropriately. Furthermore, since reinforcing members are placed on top of the upper edge of the back panel, cutouts cannot be formed in the areas where the reinforcing members overlap. However, because the recessed grooves make it appear as if the group of cutouts extends to the upper edge of the back panel, it is possible to prevent a gap from appearing at the upper edge of the back panel and improve the aesthetics.

[0023] Furthermore, claims 4 Therefore, because the grooved areas are thin, the upper edge of the back panel is allowed to flex and deform together with the upper reinforcing member. Consequently, it has excellent cushioning properties. [Brief explanation of the drawing]

[0024] [Figure 1] The diagram shows the chair of the embodiment, with (A) being a perspective view from the front, (B) a side view, (C) a top view, and (D) a perspective view from the rear. [Figure 2] This is a front view with the seat omitted. [Figure 3] (A) is a rear perspective view of the back panel, and (B) is a side view of the back panel. [Figure 4] (A) is a separated perspective view of the back seen from the rear, and (B) is a separated perspective view of the back seen from the front. [Figure 5] (A) is a diagram showing the lower reinforcing member in an inverted state, and (B) is a diagram showing the relationship between the lower support and the back plate. [Figure 6] (A) is a separate perspective view of the upper section, (B) is a diagram showing the relationship between the upper reinforcing member and the clip body, (C) is a separate perspective view of the upper reinforcing member in an inverted state, and (D) is a perspective view of the clip body. [Modes for carrying out the invention]

[0025] Next, embodiments of the present invention will be described based on the drawings. In the following, the terms front, back, left, and right will be used to specify directions, but these directions are specified as those viewed from a person who is normally seated. The front view direction is the direction opposite to the seated person.

[0026] (1) Overview of the chair First, let's describe the chair's overview. This embodiment is applied to swivel chairs commonly used in offices and other similar settings. As shown in Figures 1 and 2, the chair comprises, as its main components, a seat 1, a backrest 2, a back frame 3 to which the backrest 2 is attached, and a leg assembly 4. The backrest 2 is made of a material such as elastomer. Soft synthetic resin material It consists of the following. In this embodiment, the back plate 2 is synonymous with the backrest. The back frame 3 is an example of a back frame.

[0027] The leg assembly 4 has a group of branch legs equipped with casters (only some of the casters are shown in Figures 1(A) and 1(D)). Also, as shown in Figure 2, the base body 6 is fixed to the leg support column (gas cylinder) 5 located in the center, and the back frame 3 is connected to the base body 6 via a joint member 7 so as to be able to tilt backward. More precisely, a forward-facing portion 3a is integrally provided at the lower end of the back frame 3, and the forward-facing portion 3a is fixed to the joint member 7, and the joint member 7 is connected to the base body 6 via left and right longitudinal support shafts 8 so as to be able to tilt backward.

[0028] The support shaft 8 is rotatably held to the base body 6 via a torsion bar, which is an example of a spring mechanism. Therefore, the chair in this embodiment is a reclining type in which the backrest 2 tilts backward against an elastic mechanism. The seat 1 has a structure in which cushioning material is layered and held in an inner shell (not shown) and covered with an outer shell. The inner shell is attached to the outer shell 9 shown in Figure 1(B). The outer shell 9 is connected to the base body 6 and the joint member 7 so as to be rotatable relative to each other. Therefore, when the backrest 2 tilts backward, the seat 1 tilts backward in conjunction with the backrest 2 (synchronized).

[0029] As shown in Figure 4, the back frame 3 has vertically elongated back support columns 10 located in the middle of the left and right sides, horizontally rotatable upper supports 11 attached to the upper ends of the back support columns 10, and left and right lower supports 12 integrally provided at the lower ends of the back support columns 10. The upper supports 11 are Specific examples of the arm section The back support 10 rotates horizontally against a spring built into it. The back support 10 and upper support 11 are made of synthetic resin, but aluminum die-cast or sheet metal parts can also be used.

[0030] For example, as shown in Figure 4, the upper support 11 has a portion that faces left and a portion that faces right from the axis of the back support 10, and these two portions are connected as one unit, with both left and right ends being free ends. Furthermore, the upper support 11 has a curved shape in plan view, concave towards the front (bulging towards the back), and the left and right ends of the back plate 2 are connected to its left and right ends. Consequently, there is a large space between the upper support 11 and the back plate 2. Due to the existence of this space, the upper end of the back plate 2 (Upper part) It is permitted for the seat to stretch and deform backward (concave) due to the pressure (body pressure) applied by the seated person.

[0031] The rear surface of the upper end of back panel 2 has the left and right longitudinal sections It is a plate-shaped synthetic resinThe upper reinforcing member 13 is integrally fixed by insert molding or two-color molding, and the left and right ends of the upper reinforcing member 13 are connected to the upper support 11 via clip bodies 14. Upper boss portions 15 that overlap the upper support 11 are provided projecting backward and downward from both the left and right ends of the upper reinforcing member 13.

[0032] On the other hand, as clearly shown in Figure 4, the lower support 12 is curved such that its upper and lower surfaces become higher towards the tip when viewed from the rear, and the lower surface formed by the lower surfaces of the left and right lower supports 12 and the lower surface of the back support 10, etc. (i.e., the lower surface of the back frame 3) is also a curved surface that bulges downward. Therefore, the back frame 3 as a whole has a shape similar to an anchor.

[0033] As shown in Figure 1(D), for example, the lower support 12 extends forward in a way that embraces the rear of the seat when viewed from above, and the armrest device 6 is attached to its tip. The width of the lower support 12 decreases towards the tip when viewed from above and from behind.

[0034] Lower end of back panel 2 The part (lower edge) is elongated on both sides and bulges downwards, and On the rear surface, left and right longitudinal lower reinforcing members 16 are integrally fixed by insert molding or two-color molding, and the left and right ends of the lower reinforcing members 16 are fixed to the tip of the lower support 12 with screws 17 (see Figures 3 and 5). Lower bosses 18 that fit into the lower support 12 are provided projecting backward from the left and right ends of the lower reinforcing members 16. The upper and lower reinforcing members 13 and 16 are made of synthetic resin such as polypropylene, nylon resin, or polycarbonate.

[0035] As can be seen from Figure 4, the back of the back frame 3 is covered by a center cover 19 and a side cover 20. Specifically, the center cover 19 covers the entire back support 10 and a portion of the lower support 12, while the side cover 20 covers the back of the front half of the lower support 12. When the side cover 20 is removed, an armrest device can be attached to the lower support 12.

[0036] The backrest 2 is designed to bend and deform easily under the pressure exerted by a seated person leaning back. To facilitate this deformation, the backrest 2 has multiple rows of perforations 21. The lower end of the backrest 2 is fixed immovably to the lower support 12, while the upper end is attached to both ends of the horizontally rotatable upper support 11. Therefore, when a person sitting in the chair twists their upper body, the lower support 12 rotates horizontally, causing the backrest 2 to elastically deform, bending or indenting backward, in accordance with the body's twist. Consequently, the upper reinforcing member 13 can also elastically deform (bend) under the user's pressure.

[0037] Furthermore, the lower support 12 rises higher than the seat 1. Therefore, as shown in Figures 1(A) and 1(B), left and right raised sections 1a are formed at the rear of the seat 1. Consequently, the seat 1 provides enhanced support to the user's waist (buttocks).

[0038] (2) Fixing structure between the back plate and the lower support As shown in Figure 5(A), the lower reinforcing member 16 has a shell shape that curves along the lower support 12 and opens forward, and is provided with numerous reinforcing ribs inside. Therefore, the lower support 12 has a rigid structure that does not deform even when pressed by the pressure of a seated person, and thus the lower edge of the back plate 2 is firmly fixed to the lower support 12 via the lower reinforcing member 16.

[0039] Furthermore, truncated pyramidal lower boss portions 18 are provided at both the left and right ends of the lower reinforcing member 16. It is attached facing backward. Meanwhile, the tips of the left and right lower supports 12 are provided with recesses 23 into which the lower boss portion 18 is fitted, and screws 17 inserted from the outside into the recesses 23 are screwed into the lower boss portion 18 of the lower reinforcing member 16. As shown in Figure 5(A), A nut 23a into which a screw 17 is threaded is attached to the lower boss portion 18 of the lower reinforcing member 16. In Figure 5(A), nut 23a is shown on the lower support 12, but nut 23a is actually attached to the lower boss portion 18.

[0040] Although not shown in the diagram, the lower reinforcing member 16 is provided with multiple positioning protrusions on the left and right sides, while the lower support 12 has positioning holes into which the positioning protrusions fit. By fitting the positioning protrusions with the positioning holes, the lower reinforcing member 18 can be firmly fixed to the lower support 12 even when fixed with two screws 17 on the left and right sides.

[0041] As shown in Figures 4(A) and 5, the lower reinforcing member 16 has spatula-shaped upward protrusions 24 integrally formed on both the left and right ends, while the back plate 2 has recesses 25 on both the left and right ends into which the upward protrusions 24 of the lower reinforcing member 16 fit. ke The lower reinforcing member 16 is integrally molded to the back plate 2 by insert molding or two-color molding, but the presence of the upward protrusion 24 allows for adhesion. (Joining) Because the surface area has increased, the lower reinforcing member 16 can be firmly fixed to the back plate 2.

[0042] (3) Fixing structure between the back panel and the upper support As shown in Figures 6(A) and 6(C), the upper boss portion 15 protrudes from the rear and downward of the upper reinforcing member 13, and therefore the upper boss portion 15 is below Directional protrusion too It is composed of the upper boss section 15 The downward-facing part The rear surface overlaps with the front surface of the upper support 11. On the other hand, downward-facing projections 26 are provided at both the left and right ends of the upper support 11 so as to overlap with the upper boss portion 15. The upper boss portion 15 has a vertical width more than twice that of the upper reinforcing member 13 and has a large surface area, so it is firmly fixed to the back plate 2.

[0043] Furthermore, a downward-facing hook-shaped engaging claw 27 is formed on the rear surface of the upper boss portion 15, while bag-shaped portions 28 into which the engaging claw 27 fits are formed at both the left and right ends of the upper support 11. By forming an engaging hole 29 into which the engaging claw 27 fits from above at the bottom 28a of the bag-shaped portion 28, the upper boss portion 15 and the upper support 11 are held in a manner that prevents them from separating in the front, back, left, and right directions. (Consolidated) They are doing it.

[0044] Furthermore, a forward-facing opening groove 31 is formed in the partition wall 30 that constitutes the bag-shaped portion 28, and the claw portion 14a of the clip body 14 is inserted into the opening groove 31 from the inside in the left-right direction. The clip body 14 has a base portion 14b located inside the partition wall 30, and the claw portion 14a can be inserted into the opening groove 31 by pushing the base portion 14b outward with a fingertip to the left and right.

[0045] The claw portion 14a of the clip body 14 is bent into a U-shape laterally. After elastically deforming, it enters the cutting groove 31. Once fully engaged in the cutting groove 31, the U-shaped tip surface 14c disengages from the cutting groove 31 and contacts the outer surface of the partition wall 30. As a result, the clip body 14 cannot be removed from the cutting groove 31.

[0046] With the clip body 14 fitted into the cut-open groove 31, the claw portion 14a of the clip body 14 overlaps the upper surface of the engaging claw 27 of the upper reinforcing member 13. Therefore, the engaging claw 27 of the upper reinforcing member 13 is held in an upward position by the claw portion 14a of the clip body 14. In addition, the front end surface of the partition wall 30 in the upper support 11 overlaps the upper boss portion 15 of the upper reinforcing member 13, and the cut-open groove 31 is blocked by the upper boss portion 15 of the upper reinforcing member 13, so the forward movement of the clip body 14 is prevented by the upper boss portion 15 of the upper reinforcing member 13.

[0047] As can be seen from Figure 6(B), the upper boss portion 15 of the upper reinforcing member 13 is provided with a stopper 32 that abuts against or closely contacts the claw portion 14a of the clip body 14 from the front. Also, as can be seen from Figure 6, the upper support 11 has a trough-shaped structure that opens forward and has reinforcing ribs inside. As shown in Figure 6(C), a center boss portion 33 is formed in the left and right middle part of the upper support 11, which is attached to the back support column 10 so as to be able to rotate horizontally.

[0048] (4) Summary In this embodiment, the back plate 2 Lower end (bottom edge)Since the lower support 12 is fixed to the lower support 12 via the rigid lower reinforcing member 16, the lower end of the back plate 2 does not undergo elastic deformation even when the user's body pressure is applied. Therefore, the user's lower back (buttocks) is always firmly supported, and the lower back is always kept in a stable state.

[0049] On the other hand, the back plate 2 is made of elastomer and is highly flexible, bending and deforming to conform to the user's pressing force, but a rigid upper reinforcing member 13 is fixed to the upper end. The left and right sides (lateral edges) are unrestricted deformation-allowing areas. Therefore, the back panel is set to 2. hand While maintaining its basic shape, it stretches backward and twists and deforms in a plan view. Therefore, it can stably support the user's body while deforming to follow their movements, ensuring a high level of fit and cushioning.

[0050] Furthermore, in this embodiment, the upper reinforcing member 13 also bends and deforms to some extent, so it can bend and deform in response to the user's pressing force, ensuring high cushioning. Also, by forming a large number of cutouts 21 in the back plate 2 as in this embodiment, the flexibility of the back plate 2 can be increased, further improving the fit and cushioning. By selecting various shapes and arrangement patterns of the cutouts 21, the range of designs can be expanded while ensuring a good fit and cushioning.

[0051] Although embodiments of the present invention have been described above, the present invention can be implemented in various other ways. For example, if the upper support rotates horizontally as in the embodiment, the upper reinforcing member can also be configured as a rigid structure. ru.

[0052] under The reinforcing members do not necessarily need to be integrally molded with the back panel by insert molding or the like; they can be fixed to the back panel with fasteners such as screws. stomach. [Industrial applicability]

[0053] The present invention can be implemented in a chair. Therefore, it can be used industrially. [Explanation of symbols]

[0054] 2 Back plate 3 Backframe (Back frame) 10 Back strut 11 Upper Support (Arm section) 12 Lower Support 13 Upper reinforcing member 14 Clip type 15 Upper Boss Section 16 Lower reinforcing member 18 Lower Boss Section 24 Upward projection 27 Engaging claws 29 Engagement holes 30 Bulkhead 31 Cut holes

Claims

1. It comprises a backrest made of soft synthetic resin that flexes and deforms under the pressure of the seated person, and a back frame to which the backrest is attached. The backrest includes upper and lower edges on the left and right longitudinal sides, and left and right edges on the top and bottom longitudinal sides, the upper and lower edges being retaining edges that attach to the back frame, and the left and right side edges being freely deformable parts that can stretch and deform due to the pressure applied by the seated person. The upper edge of the aforementioned back panel is attached to the back frame via long, plate-shaped upper reinforcing members that overlap the upper edge from the rear, forming the backrest of the chair. The aforementioned upper reinforcing member is made of synthetic resin and is separate from the back frame, while the upper edge of the back plate and the upper reinforcing member are integrated and fixed to each other, The lower edge of the aforementioned back panel has left and right longitudinal lower reinforcing members overlapping it from the rear. The back of a chair.

2. A backrest made of a soft material that flexes and deforms under the pressure of a seated person, and a back frame to which the backrest is attached, The backrest includes upper and lower edges on the left and right longitudinal sides, and left and right edges on the top and bottom longitudinal sides, the upper and lower edges being retaining edges that attach to the back frame, and the left and right side edges being freely deformable parts that can stretch and deform due to the pressure applied by the seated person. The chair backrest is formed such that the upper edge of the back plate has upper reinforcing members in the shape of plates, which are long on both sides and overlap from the rear, and the lower edge of the back plate has lower reinforcing members, which are long on both sides and overlap from the rear, The aforementioned back frame has a back support column located in the middle of the left and right sides, and arm portions extending to the left and right from its upper end. The arm portion is attached to the back support column in a manner that allows it to rotate horizontally against elasticity, and the left and right ends of the upper reinforcing member are connected to both the left and right ends of the arm portion. The back of a chair.

3. A backrest made of a soft material that flexes and deforms under the pressure of a seated person, and a back frame to which the backrest is attached, The backrest includes upper and lower edges on the left and right longitudinal sides, and left and right edges on the top and bottom longitudinal sides, the upper and lower edges being retaining edges that attach to the back frame, and the left and right side edges being freely deformable parts that can stretch and deform due to the pressure applied by the seated person. The chair backrest is formed such that the upper edge of the back plate has upper reinforcing members in the shape of plates, which are long on both sides and overlap from the rear, and the lower edge of the back plate has lower reinforcing members, which are long on both sides and overlap from the rear, Upper boss portions are formed at both the left and right ends of the upper reinforcing member, projecting rearward and downward, and the left and right ends of the arm portion of the back frame are connected to the upper boss portions, The lower reinforcing member is also formed integrally with the back plate, and upward-facing protrusions are formed at both the left and right ends of the lower reinforcing member, which are joined integrally with the back plate. The back of a chair.

4. A backrest made of a soft material that flexes and deforms under the pressure of a seated person, and a back frame to which the backrest is attached, The backrest includes upper and lower edges on the left and right longitudinal sides, and left and right edges on the top and bottom longitudinal sides, the upper and lower edges being retaining edges that attach to the back frame, and the left and right side edges being freely deformable parts that can stretch and deform due to the pressure applied by the seated person. The chair backrest is formed such that the upper edge of the back plate has upper reinforcing members in the shape of plates, which are long on both sides and overlap from the rear, and the lower edge of the back plate has lower reinforcing members, which are long on both sides and overlap from the rear, The aforementioned back panel has a group of slits that are vertically elongated and open in the front-to-back direction, formed in multiple rows and stages in the left-to-right and up-to-down directions. In the upper part of the back plate where the upper reinforcing member overlaps, a groove continuous with the slit is formed, and the back plate is thinner in the area of ​​the groove. The back of a chair.

5. A seat on which a person sits, Legs supporting the aforementioned seat, A backrest as described in any of claims 1 to 4, A chair equipped with [a specific feature / feature].

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