Backrest and chair

Abstract

A backrest is provided with a frame-shaped back frame having an opening that opens in the front-rear direction, the back frame being provided with: a pair of side frame members provided on both sides in the left-right direction; and a connecting member extending in the left-right direction and connecting the pair of side frame members to each other, the side frame members including: a first side frame portion constituting an upper portion of the side frame members and extending in the up-down direction; a second side frame portion extending downward and inward in the left-right direction from the lower end portion of the first side frame portion; and a lower side frame portion extending downward from the lower end portion of the second side frame portion toward the outside in the left-right direction and forward.

Description

Technical Field

[0001] This disclosure relates to backrests and chairs. Background Technology

[0002] For example, Patent Document 1 discloses a backrest having a frame-shaped backrest that is generally rectangular when viewed from the front. The backrest has a pair of rods extending in the vertical direction, a lower frame spanning the lower ends of the pair of rods, and a connecting frame disposed between the upper ends of the pair of rods. The backrest is mounted to the seat of a chair via a support mounting portion formed at the lower front of the lower frame.

[0003] Existing technical documents Patent documents Patent Document 1: Japanese Patent No. 6765182 Summary of the Invention

[0004] (a) Technical problems to be solved However, for chair backrests, to improve seating comfort, it is desirable for the back frame to flex to a certain extent in the fore-and-aft direction when the occupant leans back. In this case, the stress generated by the fore-and-aft load of the occupant acts on the back frame. Due to the effect of this stress, it is possible to apply a load to the support mounting portion.

[0005] In contrast, if the rigidity of the back frame is increased in order to reduce the load on the support mounting part of the back frame, the back frame will be difficult to bend when the occupant leans against it, and the seating comfort will be impaired.

[0006] This disclosure was made to solve the above-mentioned problems, and its purpose is to provide a backrest and chair that can reduce the load on the support mounting parts in the backrest frame and provide good seating comfort.

[0007] (II) Technical Solution To solve the above-mentioned technical problems, this disclosure adopts the following approach.

[0008] (1) One aspect of the present disclosure is a chair back, comprising: a back frame, which is frame-shaped and has an opening in the front-to-back direction; and a load-bearing surface, which covers the back frame at least from the front and supports the upper body of the seated person, the back frame comprising: a pair of side frame members disposed on both sides in the left-right direction; and a connecting member extending in the left-right direction to connect the pair of side frame members to each other, the side frame members comprising: a first side frame portion constituting the upper part of the side frame member and extending in the vertical direction; a second side frame portion extending downward and inward in the left-right direction from the lower end of the first side frame portion; and a third side frame portion extending downward and outward in the left-right direction and forward from the lower end of the second side frame portion.

[0009] According to this method, if the occupant leans against the backrest, the load from the occupant's upper body (mainly the spine) acts via tension material from front to back and diagonally downward on the first side frame portion of a pair of side frame members located on the upper part of the backrest frame. Consequently, the pair of side frame members undergo elastic deformation such that the upper end of the first side frame portion displaces rearward with the lower end of the second side frame portion as its center. At this time, the load acting on the side frame members is transmitted from top to bottom.

[0010] Therefore, in this configuration, the second side frame extends inward in the left and right directions as it faces downward, while the third side frame extends outward in the left and right directions and forward as it faces downward.

[0011] According to this structure, the second side frame and the third side frame are connected via a shape-changing portion (bending portion). Therefore, for example, compared to the case where the second side frame and the third side frame are connected in a straight line, the load transmitted to the third side frame can be reduced. Therefore, for example, when seated, the stress acting on the structural parts of the chair connected to the backrest due to the front-rear loads acting on the first side frame and the second side frame can be reduced.

[0012] This provides a backrest that reduces the load on the lower part of the backrest frame, such as the mounting parts for support installation, and provides good seating comfort.

[0013] Furthermore, in the second side frame section, a portion of the side frame component temporarily extends inward in the left-right direction. Therefore, while suppressing the overall left-right dimensions of the backrest, it is easy to set the angle of the third side frame section relative to the vertical direction to an angle that makes it difficult to transmit loads to the third side frame section. Thus, design flexibility is also improved.

[0014] (2) In the backrest of the manner described in (1) above, preferably, the connecting member has a first connecting part that connects the upper ends of the first side frame to each other.

[0015] According to this method, for example, a load acting on one side frame member can be easily transmitted to the other side frame member via the first connection. Therefore, the support load can be distributed throughout the entire back frame. Thus, the stress acting on the boundary between the second and third side frame members can be reduced.

[0016] (3) In the backrest of the manner described in (1) or (2) above, preferably, the connecting member has a second connecting portion that connects the boundary portions of the second side frame portion and the third side frame portion of the pair of side frame members to each other.

[0017] According to this method, for example, the load transmitted to the second side frame due to the seating load is also transmitted to the second connecting portion, thereby reducing the stress acting on the boundary portion between the second and third side frames. As a result, the influence of stress can be suppressed from spreading to the lower side frame portion below the second connecting portion.

[0018] (4) In the backrest of the manner described in (3) above, preferably, the thickness of the second connecting part in the vertical direction gradually increases from the rear to the front.

[0019] According to this method, compared to the case where the second connecting part is a thin plate with a constant thickness in the vertical direction from rear to front, the thickness of the second connecting part gradually increases from rear to front, thereby increasing the rigidity of the second connecting part relative to torsion. Therefore, for example, it is possible to effectively resist the stress acting on the boundary portion between the second and third side frames and on the second connecting part due to seating loads.

[0020] (5) In the backrest of either (3) or (4) above, preferably, the connecting member has a third connecting part that connects the lower ends of the third side frame to each other.

[0021] According to this method, the lower part of the back frame is formed into a robust ring shape through a pair of third side frames, a second connecting part, and a third connecting part. As a result, the load transmitted to the third side frames is also transmitted to the third connecting part, thereby distributing the load transmitted to the third side frames through the lower part of the back frame. Consequently, the stress acting on the structural parts of the chair connected to the backrest can be reduced.

[0022] (6) In the backrest of the manner described in (5) above, preferably, the third connecting part has a support connecting part, which is connected to the support of the chair that supports the backrest.

[0023] According to this method, as described above, the load transmitted to the third side frame can be distributed and supported in the lower part of the back frame, thereby reducing the stress acting on the structural parts of the chair connected to the backrest.

[0024] (7) In any of the backrests described in (1) to (6) above, preferably, the third side frame portion has an armrest mounting portion for armrest mounting.

[0025] According to this method, the load from the occupant's back during seating can be supported by the first and second side frame portions, and the load acting from the occupant's elbows can be supported by the third side frame portion. Therefore, compared to, for example, connecting the armrest to the first and second side frame portions, the required rigidity of the first and second side frame portions can be reduced.

[0026] (8) In any of the above (1) to (7) backrests, preferably, the first side frame extends diagonally forward from the upper end toward the lower end, and the second side frame extends diagonally backward from the upper end toward the lower end.

[0027] According to this method, the first side frame extends diagonally forward from the upper end toward the lower end, thereby supporting the upper body of the seated person from both sides and providing a comfortable seating experience. The second side frame, connected to the lower end of the first side frame, extends diagonally backward from the upper end toward the lower end, so that when viewed from the side, the extension direction of the second side frame can be appropriately configured relative to the direction of the load from the upper body of the seated person.

[0028] (9) The chair of this type has a backrest of any of the above (1) to (8).

[0029] According to this method, a chair with a backrest that can reduce the load on the lower part of the back frame, such as the mounting part for the support, and provide good seating comfort can be provided.

[0030] (III) Beneficial Effects According to the above methods, the load on the lower part of the back frame, such as the mounting part for mounting to the support, can be reduced, and good seating comfort can be provided. Attached Figure Description

[0031] Figure 1 This is a perspective view of the chair in the embodiment of this disclosure, viewed from the left rear.

[0032] Figure 2 This is a rear view of the chair.

[0033] Figure 3 This is a perspective view of the back frame of this embodiment.

[0034] Figure 4 yes Figure 2 Sectional view in direction II.

[0035] Figure 5 This is a view of the lower part of the back frame from the front. Detailed Implementation

[0036] Next, embodiments of the present disclosure will be described based on the accompanying drawings. In the embodiments and variations described below, corresponding structures may sometimes be denoted by the same reference numerals and the description thereof may be omitted. In addition, in the following description, expressions indicating relative or absolute configurations such as "parallel", "orthogonal", "center", "coaxial", etc. not only strictly represent such configurations, but also represent states where there are tolerances and angular or distance displacements relative to each other to the extent that the same functions can be obtained. In addition, in the present embodiment, "relative" does not only refer to the case where the orthogonal directions (normal directions) of the two surfaces coincide with each other, but also includes the case where the orthogonal directions cross each other.

[0037] [Chair 1] Figure 1 is a perspective view of Chair 1 as viewed from the left rear. Figure 2 is a rear view of Chair 1.

[0038] As Figure 1 、 Figure 2 shown, Chair 1 includes a support structure 2, a seat 3, a backrest 4, and armrests 5. In the following description, the front-back, up-down, left-right orientations, etc. are the same as those of a person (the sitter) sitting on Chair 1 in a regular posture. In this case, the arrow UP in the figure indicates the upper side, the arrow FR indicates the front side, and LH indicates the left side. In addition, in the following description, in the front-back direction, up-down direction, and left-right direction, the side away from the center of Chair 1 may sometimes be referred to as the outer side, and the side toward the center of Chair 1 may be referred to as the inner side.

[0039] <Support structure 2> The support structure 2 includes leg bodies 11 and a support 12.

[0040] The leg bodies 11 include multiple legs (Japanese: multi-branched legs) 13 and leg columns 14.

[0041] Rollers 15 capable of moving on the ground F are installed on each leg of the multiple legs 13.

[0042] The leg column 14 extends upward from the central part of the multiple legs 13. An air spring 16 serving as a lifting mechanism for Chair 1 is provided inside the leg column 14. The air spring 16 is structured such that, for example, the inner cylinder 16a 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 14.

[0043] The support 12 is connected to the upper end portion of the leg column 14 (inner cylinder 16a). The support 12 supports the seat 3 from below. The support 12 supports the backrest 4 so as to be able to tilt.

[0044] <Seat 3> The seat 3 is formed in an arc shape protruding downward when viewed from the front, and supports the part from the sitter's buttocks to the thighs from below. As Figure 1As shown, the seat 3 has a seat shell 30 and a seat body 31.

[0045] The housing 30 is a resin-molded plate-shaped component that forms the skeleton of the seat 3. The housing 30 is installed on the support 12 so as to cover the entire support 12 from above. The seat body 31 is supported from below by the housing 30. The seat body 31 has a cushioning material provided on the upper surface of the housing 30 and a skin material covering the cushioning material from above.

[0046] <Backrest 4> The backrest 4 supports the occupant's waist and back from behind. The backrest 4 is connected to the support 12 in a way that allows it to tilt about an axis in the left-right direction. However, the backrest 4 can also be connected to the support 12 in a way that prevents it from tilting.

[0047] Figure 3 This is a perspective view of the back frame 41 of this embodiment.

[0048] like Figure 1 , Figure 3 As shown, the backrest 4 has a back frame 41 and a tension material 42.

[0049] The back frame 41 is a structural member that forms the shape of the backrest 4. The back frame 41 is integrally molded from a resin material or similar material. When viewed from above, the back frame 41 forms a rearward-protruding arc shape, and when viewed from the side, it forms an S-shape. Figures 1-3 As shown, in the back frame 41, the upper frame portion 41A and the lower frame portion 41B are connected vertically, forming a figure-eight shape when viewed from the front. Specifically, the back frame 41 includes a pair of side frame members 43, a first connecting part (connecting member) 51, a second connecting part (connecting member) 52, a third connecting part (connecting member) 53, and a support connecting part 56 (see reference). Figure 3 ) and handrail installation part 57.

[0050] A pair of side frame components 43 each have an upper side frame portion 44 and a lower side frame portion 45.

[0051] The upper side frame portion 44 has a first side frame portion 46 and a second side frame portion 47. The first side frame portion 46 forms the upper part of the side frame member 43 and extends in the vertical direction. When viewed from the side, the first side frame portion 46 extends obliquely forward from the upper end to the lower end. The second side frame portion 47 extends downward from the lower end of the first side frame portion 46. When viewed from the side, the second side frame portion 47 extends obliquely backward from the upper end to the lower end. The second side frame portion 47 is shorter in the vertical direction than the first side frame portion 46. Therefore, at the portion where the lower end of the first side frame portion 46 connects to the upper end of the second side frame portion 47, the upper side frame portion 44 has a curved portion in the lower part compared to the center in the vertical direction.

[0052] In addition, such as Figure 2 , Figure 3 As shown, the first side frame portion 46 extends downwards and outwards in the left-right direction. The second side frame portion 47 extends downwards and inwards in the left-right direction from the lower end of the first side frame portion 46. Thus, when viewed from the front, the left-right spacing between the pair of first side frame portions 46 gradually widens downwards. In addition, the left-right spacing between the pair of second side frame portions 47 gradually narrows downwards.

[0053] The lower side frame portion (third side frame portion) 45 extends downward from the boundary between the upper side frame portion 44 and the second connecting portion 52. The upper end of the lower side frame portion 45 is connected across the lower end of the upper side frame portion 44 and the lower wall portion 52d of the second connecting portion 52. When viewed from the side, the lower side frame portion 45 extends downward and forward from the lower end of the second side frame portion 47. That is, the lower side frame portion 45 extends diagonally forward from the upper end to the lower end. Thus, when viewed from the side, the connection between the lower end of the second side frame portion 47 and the upper end of the lower side frame portion 45 bends backward. Figure 1 As shown, when viewed from the side, the angle θ1 formed by the lower end of the second side frame portion 47 and the upper end of the lower side frame portion 45 is preferably an obtuse angle.

[0054] The lower side frame portion 45 extends downward and outward in the left-right direction from the lower end of the second side frame portion 47. Therefore, when viewed from the front, the left-right spacing between the pair of lower side frame portions 45 gradually widens downward. When viewed from the front, the connection between the lower end of the second side frame portion 47 and the upper end of the lower side frame portion 45 bends inward in the left-right direction. Figure 2 As shown, when viewed from the front, the angle θ2 formed by the lower end of the second side frame portion 47 and the upper end of the lower side frame portion 45 is preferably an obtuse angle.

[0055] like Figure 1 , Figure 2 As shown, the middle portion of the lower side frame 45 in the vertical direction coincides with the outer end of the base 3 in the horizontal direction when viewed from the front. The lower end of the lower side frame 45 is located lower than the base 3. The front end of the lower side frame 45 is located further forward than the curved portion of the upper side frame 44.

[0056] like Figures 1-3 As shown, the first connecting portion 51 forms the upper end of the back frame 41. The first connecting portion 51 connects the upper ends of the first side frame portions 46 to each other. When viewed from above, the first connecting portion 51 extends in the left-right direction in an arc shape that bulges backward. The vertical dimension of the first connecting portion 51 gradually increases as it faces forward.

[0057] Figure 4 yes Figure 2Sectional view in direction II.

[0058] The second connecting portion 52 connects the lower end of the second side frame portion 47 to the boundary portion of the lower side frame portion 45. When viewed from above, the second connecting portion 52 extends in a rearward-protruding arc shape in the left-right direction. Figure 4 As shown, the thickness of the second connecting portion 52 in the vertical direction gradually increases from the rear to the front. In cross-sectional view, the second connecting portion 52 is formed in a C-shape with the rear ends of the upper wall portion 52t and the lower wall portion 52d connected to each other and opening forward. The upper surface of the upper wall portion 52t of the second connecting portion 52 is formed as an inclined surface that slopes upward as it faces forward. On the other hand, the lower surface of the lower wall portion 52d of the second connecting portion 52 is formed such that the vertical distance between it and the upper surface of the upper wall portion 52t gradually increases as it faces forward. However, it can also slope forward and upward as long as the angle (angle of elevation) between the lower surface of the second connecting portion 52 and the horizontal plane is smaller than the angle (angle of elevation) between the upper surface and the horizontal plane.

[0059] Figure 5 This is a view of the lower part of the back frame 41 from the front.

[0060] like Figure 4 , Figure 5 As shown, a forward-facing recess 52a is formed on the front end face of the second connecting portion 52. Specifically, the front opening of the forward-facing recess 52a faces diagonally forward and downward. When viewed from the side, the forward-facing recess 52a is a triangular shape whose vertical dimensions gradually decrease as it faces backward. In this embodiment, the forward-facing recess 52a is integrally formed throughout the left-right direction of the second connecting portion 52. By forming the forward-facing recess 52a, the second connecting portion 52 achieves improved formability and weight reduction.

[0061] like Figure 5 As shown, a plurality of longitudinal ribs 58 are formed on the inner side of the forward recess 52a. The longitudinal ribs 58 are spaced apart in the left-right direction within each forward recess 52a. Each longitudinal rib 58 connects the downward surface 52c and the upward surface 52b, which are opposite each other in the vertical direction, on the inner surface of the forward recess 52a. The downward surface 52c faces downward in the upper wall portion 52t, and the upward surface 52b faces upward in the lower wall portion 52d. The longitudinal ribs 58 extend along the entire length in the front-rear direction within the forward recess 52a. These multiple longitudinal ribs 58 reinforce the second connecting portion 52 where the forward recess 52a is formed.

[0062] In addition, such as Figure 4As shown, a tension material holding member 70 is embedded in the forward recess 52a. The tension material holding member 70 has an upper contact surface 70a that contacts the lower surface 52c of the forward recess 52a and a lower contact surface 70b that contacts the upper surface 52b. The tension material holding member 70 is configured such that, when viewed from the side, the vertical distance between the upper contact surface 70a and the lower contact surface 70b gradually decreases as it moves rearward. The tension material holding member 70 extends in the left-right direction, is embedded from the front into the entire left-right portion of the forward recess 52a, and is fixed to the second connecting portion 52 by bolts or the like (not shown).

[0063] The lower end of the leading edge of the tension material holding member 70 protrudes further forward than the downward surface 52c of the second connecting portion 52. The tension material holding member 70 has an engagement groove 71 that engages with a portion of the periphery of the second connecting portion 52 and the tension material 42. The engagement groove 71 is integrally formed throughout the left-right direction of the tension material holding member 70. The engagement groove 71 opens downward at the lower end of the leading edge of the tension material holding member 70. When viewed from the side, the engagement groove 71 opens obliquely downward in a rearward direction.

[0064] The second connection portion 52 is reinforced by mounting such a tension material retaining member 70 to the forward recess 52a.

[0065] like Figures 1-3 As shown, the upper frame portion 41A is composed of a first connecting portion 51, an upper side frame portion 44, and a second connecting portion 52. The upper frame portion 41A has an opening portion 41p that opens in the front-rear direction.

[0066] like Figure 2 , Figure 3 , Figure 5 As shown, the third connecting portion 53 extends in the left-right direction and connects the lower ends of the lower side frame portions 45 to each other. When viewed from the front, the third connecting portion 53 is formed into a downward-protruding arc shape. When viewed from the side, the third connecting portion 53 is located further forward than the second connecting portion 52. Figure 3 , Figure 5 As shown, the thickness of the third connecting portion 53 in the vertical direction gradually increases from the rear to the front. The upper surface 53t of the third connecting portion 53 is formed as an inclined surface that slopes downward as it moves forward. On the other hand, the lower surface 53d of the third connecting portion 53 is formed as an inclined surface that slopes downward as it moves forward, and the vertical distance between the lower surface 53d and the upper surface 53t gradually increases as it moves forward.

[0067] In the third connecting portion 53, a forward-facing recess 53a is formed on the front end face of the third connecting portion 53. The formation of the forward-facing recess 53a improves the formability and reduces weight in the third connecting portion 53. Specifically, the front opening of the forward-facing recess 53a opens obliquely forward and downward. When viewed from the side, the forward-facing recess 53a is formed as a triangular shape whose vertical dimension gradually decreases as it faces rearward. In this embodiment, the forward-facing recesses 53a are formed on both sides of the third connecting portion 53, excluding the central portion in the left-right direction.

[0068] Multiple longitudinal ribs 59 are formed on the inner side of the forward recess 53a. The longitudinal ribs 59 are spaced apart in the left-right direction within each forward recess 53a. Each longitudinal rib 59 connects the opposing surfaces (the upward-facing surface 55b and the downward-facing surface 55c) in the vertical direction of the inner surface of the forward recess 53a. The longitudinal ribs 59 extend along the entire length in the front-rear direction within the forward recess 53a. These multiple longitudinal ribs 59 reinforce the third connecting portion 53 on which the forward recess 53a is formed.

[0069] The support connecting portion 56 is located at the center of the third connecting portion 53 in the left-right direction. The support connecting portion 56 is integrally formed with the third connecting portion 53. The support connecting portion 56 is connected to the support 12. The support connecting portion 56 protrudes upward from the third connecting portion 53 and is formed into a box shape with an opening to the front. The inner side of the support connecting portion 56 forms an insertion groove 56a for inserting a part of the support 12.

[0070] The handrail mounting part 57 is located at the lower end of the lower side frame part 45. The handrail mounting part 57 protrudes to the left and right sides relative to the third connecting part 53.

[0071] like Figure 1 , Figure 2 As shown, the tension material 42 forms a load-bearing surface 42f, which supports the upper body of the seated person, specifically, the waist and back. The tension material 42 is configured to cover the opening 41p of the upper frame portion 41A from the front. The tension material 42 is constructed of a membrane-like component, such as a mesh material or fabric, and is capable of elastic deformation. The outer periphery of the tension material 42 is fixed to the outer surface of the upper frame portion 41A (first connecting portion 51, upper side frame portion 44, and second connecting portion 52) in a manner that surrounds the upper frame portion 41A. Alternatively, the backrest 4 may be a structure in which cushioning material and a skin material cover the back frame 41 instead of the tension material 42.

[0072] <Armrest 5> The armrest 5 is connected to the back frame 41. The armrest 5 is installed in each armrest mounting part 57, supporting the occupant's elbows and forearms from below. The armrest 5 includes an armrest support part 80 and an armrest body 81.

[0073] The handrail support member 80 is a component that connects the handrail mounting portion 57 to the handrail body 81, and functions as a strength component of the handrail 5. When viewed from the front, the handrail support member 80 is L-shaped. The lower end of the handrail support member 80 is mounted to the handrail mounting portion 57 from the left and right sides.

[0074] The handrail body 81 is supported so that it can move up and down relative to the handrail support member 80. The handrail body 81 includes a handrail support 82 and a handrail portion 83.

[0075] The handrail support 82 is inserted into the insertion hole 80a from above the handrail support member 80, the insertion hole 80a extending through the handrail support member 80 in the vertical direction. The handrail support 82 is configured to move vertically along the insertion hole 80a.

[0076] An armrest portion 83 is provided at the upper end of the armrest support 82. The armrest portion 83 is formed, for example, by covering the outer shell with a skin material and a padding material. The upper surface of the armrest portion 83 forms an elbow rest surface supporting the seated person's elbow. The armrest portion 83 covers the armrest support 82 from above and is installed on the armrest support 82 in a state of extending relative to the armrest support 82 in both the front-back and left-right directions. Alternatively, the armrest 5 can also be installed on the seat 3 or the support 12. Furthermore, the armrest 5 can also be a structure that does not move vertically.

[0077] <Lumbar support 100> A lumbar support member 100 is provided at the center of the second connecting portion 52 in the left-right direction to support the lumbar region of the seated person. The lumbar support member 100 protrudes upward from the second connecting portion 52 such that it is located within the upper frame portion 41A. Furthermore, the lumbar support member 100 is not an essential structure in the chair 1 of this embodiment, and can be omitted. The chair includes a lumbar support member body 101 and a mounting portion 130.

[0078] The lumbar support body 101 abuts against the back of the seated person through the tension material 42, supporting the load of the seated person from behind. The mounting part 130 is a component that mounts the lumbar support body 101 to the chair body 1A. The mounting part 130 is mounted at the center of the second connecting part 52 in the left-right direction.

[0079] In the backrest 4 of this embodiment, the backrest frame 41 has a pair of side frame members 43 including a first side frame portion 46, a second side frame portion 47 extending downward from the lower end of the first side frame portion 46 and inward in the left and right direction, and a lower side frame portion 45 extending downward from the lower end of the second side frame portion 47 and outward in the left and right direction and forward.

[0080] According to this structure, if the occupant leans against the backrest 4, the load from the occupant's upper body (mainly the spine) (seating load) acts from the front to the rear and diagonally downwards via the tension material 42 on the first side frame portion 46 of a pair of side frame members 43 disposed on the upper part of the backrest frame 41. As a result, the pair of side frame members 43 undergo elastic deformation in such a way that the upper end of the first side frame portion 46 is displaced rearwards with the lower end of the second side frame portion 47 as the center. At this time, the load acting on the side frame members 43 is transmitted from top to bottom.

[0081] Therefore, in this embodiment, the second side frame portion 47 extends inward in the left and right directions as it faces downward, while the lower side frame portion 45 extends outward in the left and right directions and forward as it faces downward.

[0082] According to this structure, the second side frame portion 47 and the lower side frame portion 45 are connected via a shape-changing portion (bending portion). Therefore, for example, compared to the case where the second side frame portion 47 and the lower side frame portion 45 are connected in a straight line, the load transmitted to the lower side frame portion 45 can be reduced. Therefore, for example, when seated, the stress acting on the structural part of the chair 1 connected to the backrest 4 due to the front-rear load acting on the upper frame portion 41A (first side frame portion 46, second side frame portion 47) can be reduced.

[0083] In this way, a backrest 4 can be provided that can reduce the load on the structural part of the chair 1 connected to the backrest 4 at the lower part of the backrest frame 41, and can provide good seating comfort.

[0084] Furthermore, in the second side frame portion 47, a portion of the side frame member 43 is temporarily extended inward in the left-right direction. Therefore, while suppressing the overall left-right dimension of the backrest 4, it is easy to set the angle of the lower side frame portion 45 relative to the vertical direction to an angle that makes it difficult to transmit loads to the lower side frame portion 45. Thus, the degree of design freedom can also be improved.

[0085] In the backrest 4 of this embodiment, the upper ends of the first side frame portions 46 are connected to each other by the first connecting portion 51.

[0086] According to this structure, for example, the load acting on one side frame member 43 can be easily transmitted to the other side frame member 43 via the first connecting part 51. Therefore, the support load can be distributed throughout the back frame 41. Therefore, the stress acting on the boundary between the second side frame part 47 and the lower side frame part 45 can be reduced.

[0087] In the backrest 4 of this embodiment, the boundary portions of the second side frame portion 47 and the lower side frame portion 45 are connected to each other by the second connecting portion 52.

[0088] According to this structure, for example, the load transmitted to the second side frame portion 47 due to the seating load is also transmitted to the second connecting portion 52, thereby reducing the stress acting on the boundary portion between the second side frame portion 47 and the lower side frame portion 45. As a result, the influence of stress can be suppressed from spreading to the lower side frame portion 45 below the second connecting portion 52.

[0089] In the backrest 4 of this embodiment, the thickness of the second connecting portion 52 in the vertical direction gradually increases from the rear to the front.

[0090] According to this structure, compared to the case where the second connecting portion 52 is a thin plate with a constant thickness in the vertical direction from rear to front, the thickness of the second connecting portion 52 gradually increases from rear to front, thereby increasing the rigidity of the second connecting portion 52 relative to torsion. Therefore, for example, it is possible to effectively resist the stress acting on the boundary portion between the second side frame portion 47 and the lower side frame portion 45, and on the second connecting portion 52, due to seating loads.

[0091] In the backrest 4 of this embodiment, it is configured to have a third connecting part 53 that connects the lower ends of the lower side frame parts 45 to each other.

[0092] According to this structure, the lower part of the back frame 41 is formed into a robust ring shape via a pair of lower side frame portions 45, a second connecting portion 52, and a third connecting portion 53. Thus, the load transmitted to the lower side frame portions 45 is also transmitted to the third connecting portion 53, thereby enabling the lower part of the back frame 41 to distribute and support the load transmitted to the lower side frame portions 45. As a result, the stress acting on the structural parts of the chair 1 connected to the backrest 4 can be reduced.

[0093] In the backrest 4 of this embodiment, the third connecting part 53 is configured to have a support connecting part 56.

[0094] According to this structure, as described above, the load transmitted to the lower side frame 45 can be distributed and supported in the lower part (lower frame 41B) of the back frame 41, thereby reducing the stress acting on the structural part of the chair 1 connected to the backrest 4.

[0095] In this embodiment, the backrest 4 is configured such that the lower side frame portion 45 has an armrest mounting portion 57.

[0096] According to this structure, the load from the back of the seated person can be supported by the upper frame portion 41A (first side frame portion 46, second side frame portion 47), and the load acting from the elbow of the seated person can be supported by the lower frame portion 41B (lower side frame portion 45). Thus, compared with, for example, connecting the armrest to the upper frame portion 41A, the rigidity required for the upper frame portion 41A can be reduced.

[0097] In the backrest 4 of this embodiment, the first side frame portion 46 extends diagonally forward from the upper end toward the lower end, and the second side frame portion 47 extends diagonally backward from the upper end toward the lower end.

[0098] According to this structure, the first side frame portion 46 extends diagonally forward from the upper end toward the lower end, thereby supporting the upper part of the seated person's upper body from both sides via the tension material 42, resulting in a good seating feel. The second side frame portion 47, which is connected to the lower end of the first side frame portion 46, extends diagonally backward from the upper end toward the lower end, so that when viewed from the side, the extension direction of the second side frame portion 47 can be appropriately configured relative to the direction of the load from the seated person's upper body.

[0099] The chair 1 of this embodiment has the backrest 4 described above.

[0100] According to this structure, a chair 1 with a backrest 4 can be provided, which can reduce the load on the lower part of the backrest frame 41, the mounting part for the support, etc., and can provide good seating comfort.

[0101] (Other variations) The preferred embodiments of this disclosure have been described above, but this disclosure is not limited to these embodiments. Additions, omissions, substitutions, and other modifications to the structure are possible without departing from the spirit of this disclosure. This disclosure is not limited by the foregoing description, but only by the appended claims.

[0102] In the above embodiment, the first side frame portion 46 extends downward and outward in the left and right directions, but is not limited to this. The first side frame portion 46 may extend only in the vertical direction, or it may extend only downward (vertically downward) when viewed from the front. Alternatively, the first side frame portion 46 may extend downward and inward in the left and right directions. However, it is preferable that the angle at which the first side frame portion 46 tilts downward and inward in the left and right directions is smaller than the angle at which the second side frame portion 47 tilts downward and inward in the left and right directions.

[0103] In the above embodiment, the second side frame portion 47 extends obliquely rearward from the upper end toward the lower end when viewed from the side, but it is not limited to this. The second side frame portion 47 may also extend vertically downward or obliquely forward from the upper end toward the lower end when viewed from the side.

[0104] In the above embodiment, a structure having a first connecting portion 51, a second connecting portion 52, and a third connecting portion 53 as connecting members has been described; however, the structure can be appropriately modified. For example, at least one of the first connecting portion 51, the second connecting portion 52, and the third connecting portion 53 may be omitted. Furthermore, other connecting members besides the first connecting portion 51, the second connecting portion 52, and the third connecting portion 53 may be included. Moreover, the vertical position and shape of the connecting members can be appropriately modified.

[0105] In the above embodiments, the structure of each part of the chair body 1A has been described, but its structure can be appropriately modified.

[0106] In the above embodiment, the structure of the chair 1 having armrests 5 has been described, but the armrests 5 are not a necessary structure.

[0107] Furthermore, without departing from the spirit of this disclosure, the constituent elements in the above embodiments can be appropriately replaced with known constituent elements, and the above variations can also be appropriately combined.

[0108] Explanation of reference numerals in the attached figures 1 chair 4. Backrest 5 Handrails 41 Back Frame 41p opening 42f Load support surface 43 Side frame components 46 First side frame 47 Second side frame 51 First connecting part (connecting component) 52 Second connecting part (connecting component) 53 Third connecting part (connecting component) 56 Support Connection Part 57 Handrail Installation Department

Claims

1. A backrest, which is the backrest of a chair, having: The back frame is frame-shaped and has an opening in the front-to-back direction; and The load-bearing surface, which covers the back frame at least from the front, supports the upper body of the seated person. The back frame has: A pair of side frame components, positioned on either side in the left-right direction; and A connecting component, extending in the left-right direction, connects the pair of side frame components to each other. The side frame component includes: The first side frame portion, which constitutes the upper part of the side frame component, extends in the vertical direction; The second side frame portion extends downward and inward in a left-right direction from the lower end of the first side frame portion; and The third side frame extends downward from the lower end of the second side frame and outward in the left and right directions and forward.

2. The backrest according to claim 1, characterized in that, The connecting component includes a first connecting portion. The first connecting part connects the upper ends of the first side frame parts to each other.

3. The backrest according to claim 1 or 2, characterized in that, The connecting component includes a second connecting portion. The second connecting portion connects the boundary portions of the second side frame portion and the third side frame portion of the pair of side frame components to each other.

4. The backrest according to claim 3, characterized in that, The thickness of the second connecting part in the vertical direction gradually increases from the rear to the front.

5. The backrest according to claim 3, characterized in that, The connecting component includes a third connecting portion that connects the lower ends of the third side frame portions to each other.

6. The backrest according to claim 5, characterized in that, The third connecting part includes a support connecting part, which is connected to the support of the chair that supports the backrest.

7. The backrest according to claim 1 or 2, characterized in that, The third side frame has a handrail mounting section for installing handrails.

8. The backrest according to claim 1 or 2, characterized in that, The first side frame extends diagonally forward from the upper end toward the lower end. The second side frame extends diagonally backward from the upper end toward the lower end.

9. A chair having a backrest as described in claim 1 or 2.

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