Chairs and backrests

Abstract

To provide a chair that can reduce impact on a connection part of a backrest which is caused by an input load to the backrest, and to provide the backrest.SOLUTION: A chair includes: a lower support structure; a tilting member supported to the lower support structure so as to be capable of tilting about an axis line in a horizontal direction and projecting backward from the lower support structure; and a backrest connected to the tilting member. The backrest includes: a backrest body having a load support surface facing forward; a cylindrical part formed into a cylindrical shape that is open forward, and connected to the tilting member while the tilting member is stored inside thereof; and a connection part provided on side walls on both right and left sides of the cylindrical part and connecting the backrest body to the cylindrical part.SELECTED DRAWING: Figure 2

Description

Technical Field

[0004]

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

Background Art

[0002] For example, Patent Document 1 below discloses a chair having a seat on a support base and supporting a backrest via a back support on the support base. The backrest includes a frame-shaped back frame. The back frame is an integrally molded product having left and right side frame members, an upper frame member connecting between the upper parts of these left and right side frame members, and a lower frame member connecting between the lower parts of the side frame members. The lower frame member of the back frame includes a flat lower frame member body. This lower frame member body is overlapped on the backrest attachment portion of the back support. Bolt insertion holes corresponding to the nut portions of the back support are formed in the lower frame member body. The back frame is attached to the back support by screwing bolts inserted through these bolt insertion holes into the nut portions of the back support, respectively.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] [[ID=​​​​This invention has been made in view of the above-mentioned problems, and aims to reduce the effect that input load to the backrest has on the connection points of the backrest. [Means for solving the problem]

[0006] To solve the above problems, the present invention employs the following embodiments. (1) A chair according to one aspect of the present invention comprises a lower support structure, a tilting member supported by the lower support structure so as to be tiltable about an axis in the left-right direction and projecting rearward from the lower support structure, and a backrest connected to the tilting member, wherein the backrest comprises a backrest body having a load-bearing surface facing forward, a cylindrical portion formed in the shape of a cylinder opening toward the front and connecting to the tilting member with the tilting member housed inside, and connecting portions provided on the left-right side walls of the cylindrical portion and connecting the backrest body and the cylindrical portion. The connecting portion has a reinforcing portion that extends outward from each side wall in the left-right direction and extends in the front-rear direction, and a pair of extending portions that extend outward from each side wall in the left-right direction and are located upward as they move outward in the left-right direction, the reinforcing portion protrudes forward from each of the pair of extending portions, the reinforcing portion is provided in a pair on each side wall spaced apart in the vertical direction, and the pair of reinforcing portions includes a lower reinforcing portion that runs along the lower edge of the extending portion and is connected to the lower edge of the cylindrical portion . According to this embodiment, for example, when a seated person turns their head to one side, the backrest tilts in conjunction with the tilting member. This applies a load to the backrest that includes a component in the left-right direction. This applied load is transmitted to the side wall of the cylindrical part via the connecting part. As a result, the side wall deforms in the left-right direction, absorbing the load that would cause the tilting member to tilt from a horizontal position to the left-right direction. Furthermore, because the cylindrical part is formed in a cylindrical shape, the applied load can be distributed throughout the entire cylindrical part. This improves the connection strength between the tilting member and the backrest. Therefore, according to this embodiment, the effect of the applied load on the backrest on the connection point of the backrest can be reduced. According to this embodiment, the reinforcing portion makes the connection portion strong against loads that twist in the front-rear direction. Therefore, the reinforcing portion can absorb a large portion of the load applied to the backrest before it is transmitted to the cylindrical portion. According to this embodiment, the strength of the connection can be improved compared to the case where only one reinforcing part is provided on each side wall. In addition, the reinforcing part can be molded at the same time as the cylindrical part that opens forward is molded. According to this embodiment, the extensions can improve the strength of each reinforcing section. Furthermore, the pair of extensions can individually guide the load applied to the left side of the backrest to the left side wall, and the load applied to the right side of the backrest to the right side wall. This can suppress excessive stress concentration in the left-right center of the cylindrical section.

[0010] ( 2A backrest according to one aspect of the present invention is a backrest that is tiltably supported by a lower support structure so as to be tiltable about an axis in the left-right direction and connected to a tilting member that protrudes rearward from the lower support structure, comprising: a backrest body having a load-bearing surface facing forward; a cylindrical portion formed in the shape of a cylinder that opens toward the front and connects to the tilting member when the tilting member is housed inside; and connecting portions provided on the left-right side walls of the cylindrical portion and connecting the backrest body and the cylindrical portion. The connecting portion has a reinforcing portion that extends outward from each side wall in the left-right direction and extends in the front-rear direction, and a pair of extending portions that extend outward from each side wall in the left-right direction and are located upward as they move outward in the left-right direction, the reinforcing portion protrudes forward from each of the pair of extending portions, the reinforcing portion is provided in a pair on each side wall spaced apart in the vertical direction, and the pair of reinforcing portions includes a lower reinforcing portion that runs along the lower edge of the extending portion and is connected to the lower edge of the cylindrical portion . According to this embodiment, the connection strength between the tilting member and the backrest can be improved. Therefore, the influence of the input load on the backrest on the connection point of the backrest can be reduced. According to this embodiment, the reinforcing portion makes the connection portion strong against loads that twist in the front-rear direction. Therefore, the reinforcing portion can absorb a large portion of the load applied to the backrest before it is transmitted to the cylindrical portion. According to this embodiment, the strength of the connection can be improved compared to the case where only one reinforcing part is provided on each side wall. In addition, the reinforcing part can be molded at the same time as the cylindrical part that opens forward is molded. According to this embodiment, the extensions can improve the strength of each reinforcing section. Furthermore, the pair of extensions can individually guide the load applied to the left side of the backrest to the left side wall, and the load applied to the right side of the backrest to the right side wall. This can suppress excessive stress concentration in the left-right center of the cylindrical section. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a chair and a backrest that can reduce the effect of the input load on the backrest on the connection point of the backrest. [Brief explanation of the drawing]

[0012] [Figure 1] This is a front view of a chair according to the first embodiment of the present invention. [Figure 2] This is an exploded perspective view showing the base and backrest in the first embodiment of the present invention. [Figure 3] This is a cross-sectional view showing the connection between the tilting member and the backrest in the first embodiment of the present invention. [Figure 4] This is a perspective view showing the connection between the tilting member and the backrest in the first embodiment of the present invention. [Figure 5] This is a front view showing the connection between the tilting member and the backrest in the first embodiment of the present invention. [Figure 6] This is a side view showing the connecting portion in the first embodiment of the present invention. [Figure 7] This is a cross-sectional view showing the connecting portion in the first embodiment of the present invention. [Figure 8] Perspective view showing the backrest in the second embodiment of the present invention.

Mode for Carrying Out the Invention

[0013] (First Embodiment) Hereinafter, referring to the drawings, the first embodiment of the backrest 4 and the chair 1 according to the present invention will be described.

[0014] FIG. 1 is a front view of the chair 1 in the first embodiment of the present invention. The chair 1 in this embodiment is a furniture that supports a seated person in a seated posture. The chair 1 is used, for example, in an office or a store. <000009​​​​​​​​​​​​​​​​​​​​The leg column 14 is erected in the center of the multi-branch leg 13 and extends upward from the center of the multi-branch leg 13. The leg column 14 has an outer cylinder 14a and an inner cylinder 14b. The outer cylinder 14a is fixed to the multi-branch leg 13. The lower part of the inner cylinder 14b is connected to the outer cylinder 14a. The inner cylinder 14b is connected to the outer cylinder 14a so as to be movable in the vertical direction D3. The inner cylinder 14b is supported by a spring (not shown) housed inside the leg column 14. The upper end of the inner cylinder 14b is fixed to the support base 11. Such a leg column 14 supports the seat 12 so as to be movable in the vertical direction D3 via the support base 11.

[0020] Figure 2 is an exploded perspective view showing the base 11 and backrest 4 in the first embodiment of the present invention. Figure 3 is a cross-sectional view showing the connection between the tilting member 3 and the backrest 4 in the first embodiment of the present invention. The cross-section in Figure 3 is a cross-section showing the central part of the backrest 4 in the left-right direction D2. The cross-section in Figure 3 is aligned with the front-back direction D1 and the up-down direction D3. The support base 11 is a box-shaped part located above the leg portion 10. The support base 11 is provided with a tilting member 3, which will be described later. As shown in Figures 2 and 3, the support base 11 has an upper housing 11a that opens downward and a lower housing 11b that is fitted into the upper housing 11a from below. The lower housing 11b is box-shaped and opens upward. The rear surface 11c of the lower housing 11b is inclined so that it gradually moves forward as it goes downward. Furthermore, a seat 12 is installed on the support base 11. The seat 12 is the part on which the sitter sits directly. The seat 12 has a seat body 12a and a surface material 12b. The seat body 12a is attached to the support base 11. The surface material 12b covers the upper surface of the seat body 12a. A cushioning material (not shown) is placed inside the surface material 12b (between the surface material 12b and the seat body 12a).

[0021] As shown in Figures 2 and 3, the tilting member 3 is provided inside the support base 11. A tilting shaft 5 that supports the tilting member 3 is also provided inside the support base 11. The tilting shaft 5 extends in the left-right direction D2. Hereafter, the axis O of the tilting shaft 5 may be simply referred to as "axis O". The tilting member 3 is supported by the base 11 of the lower support structure 2 so as to be able to tilt around the axis O in the left-right direction D2. The tilting member 3 protrudes rearward from the base 11 of the lower support structure 2.

[0022] Figure 4 is a perspective view showing the connection between the tilting member 3 and the backrest 4 in the first embodiment of the present invention. Figure 5 is a front view showing the connection between the tilting member 3 and the backrest 4 in the first embodiment of the invention. As shown in Figures 3 to 5, the tilting member 3 includes a tilting plate 50, a first plate 51, and a second plate 52.

[0023] The tilting plates 50 are attached one at each end of the tilting shaft 5 in the left-right direction D2. The tilting plates 50 protrude rearward from the rear wall of the upper housing 11a that constitutes the support base 11. The tilting plate 50 has a front plate 53 and a rear plate 54 connected to the rear end of the front plate 53. The upper edge of the rear plate 54 is inclined to gradually move downward as it moves towards the rear. An insertion hole 50a is provided at the rear end of the rear plate 54, penetrating in the left-right direction D2. The tilting shaft 5 is inserted through the insertion hole 50a. The pair of tilting plates 50 are rotatable around the tilting shaft 5.

[0024] The first plate 51 spans the rear ends of the tilting plates 50. The first plate 51 is a flat plate extending in the left-right direction D2. The thickness direction of the first plate 51 coincides with the vertical direction, or is slightly inclined with respect to the vertical direction. Through holes 51a are formed in the first plate 51, penetrating in the thickness direction. In this embodiment, three through holes 51a are formed at intervals in the left-right direction D2. Of the three through holes 51a, the through hole 51a in the middle of the left-right direction D2 is formed further forward than the other two through holes 51a. The through holes 51a on both outer sides of the left-right direction D2 are formed at the same front-rear direction D1 position.

[0025] The second plate 52 is placed on top of the upper surface of the first plate 51. The second plate 52 is a flat plate with a thickness similar to that of the first plate 51. Through holes 52a are formed in the second plate 52, penetrating in the thickness direction. The number of through holes 52a in the second plate 52 is the same as the number of through holes 51a in the first plate 51, and they are positioned to overlap with the through holes 51a of the first plate 51 in the vertical direction D3.

[0026] The tilting member 3 described above is connected to the backrest 4. As shown in Figures 1 and 2, the backrest 4 comprises a backrest body 20 and a connecting part 6.

[0027] The backrest body 20 is located behind the seat 12. The backrest body 20 supports the sitter's back by wrapping it around from the rear and from both sides D2. The backrest body 20 has a shell 21, an outer covering material 22, and a lower frame 24.

[0028] The shell 21 is formed in a plate shape that extends in the vertical direction D3. The shell 21 is slightly inclined so that it is positioned towards the rear as it extends upward. Furthermore, the shell 21 is curved so that it is positioned towards the front as it extends from the center in the left-right direction D2 outwards in the left-right direction D2.

[0029] The upholstery material 22 is provided at least on the front surface of the shell 21. A cushioning material (not shown) is placed inside the upholstery material 22 (between the upholstery material 22 and the shell 21). The surface of the upholstery material 22 faces forward and functions as a load-bearing surface 23 that supports the load of the occupant from the rear. The upholstery material 22 may cover only the front surface of the shell 21, or it may be provided to cover the entire shell 21 except for the lower part, including the rear surface.

[0030] As shown in Figure 5, the lower frame 24 is fixed to the shell 21 by being inserted into a mounting hole 21a formed at the lower end of the shell 21. In this embodiment, the lower frame 24 is integrally formed with the connecting part 6, which will be described later, by resin molding.

[0031] Figure 6 is a side view showing the connecting portion 6 in the first embodiment of the present invention. As shown in Figures 5 and 6, the connecting portion 6 extends downward from the lower end of the lower frame 24. The connecting portion 6 is shaped to wrap around the lumbar region of a person seated in a normal posture on the seat 12 from the rear, below, and both sides in the left-right direction D2. The outer shape of the connecting portion 6 is formed in a U-shape that opens upward when viewed from the front-rear direction D1. The rear surface 6a of the connecting portion 6 is formed in a curved shape.

[0032] As shown in Figure 2, the connecting portion 6 comprises a cylindrical portion 30, a connecting portion 40, a central reinforcing portion 7, and a rear reinforcing portion 9. The cylindrical portion 30 is formed in a cylindrical shape that opens toward the front. The outer shape of the cylindrical portion 30 extends in the front-rear direction D1 and the left-right direction D2, and is formed in a thin rectangular parallelepiped shape in the up-down direction D3. The rear end of the cylindrical portion 30 is closed by a rear reinforcing portion 9 (see Figure 3), which will be described later. The tilting member 3 is housed inside the cylindrical portion 30. The cylindrical portion 30 is connected to the tilting member 3 with the tilting member 3 housed inside.

[0033] The cylindrical portion 30 has an upper wall 31, a lower wall 32, a side wall 33, a thickened portion 35 (see Figure 5), and a lower wall rib 36 (see Figure 6). As shown in Figures 3 and 4, slits 31a are formed in the upper wall 31. The slits 31a are provided at both ends of the upper wall 31 in the left-right direction D2. The slits 31a penetrate the upper wall 31 in the up-down direction D3 and open forward. The rear plate 54 of the tilting member 3 is inserted through each slit 31a from the front. Therefore, the upper portion of each rear plate 54 is sandwiched between the corresponding slits 31a from both sides in the left-right direction D2. Also, as described above, the upper edge of the rear plate 54 is inclined to be located downward as it moves towards the rear. Therefore, the rear end of the rear plate 54 is housed inside the cylindrical portion 30.

[0034] Grooves 32a, opening upward and forward, are formed at both ends of the lower wall 32 in the left-right direction D2. The rear plate 54 of the tilting member 3 is inserted through the grooves 32a from the front. As a result, the lower portion of each rear plate 54 is sandwiched in the grooves 32a from both sides in the left-right direction D2.

[0035] Furthermore, the first plate 51 of the tilting member 3 is placed on top of the lower wall 32. Through holes 32b are formed in the lower wall 32, penetrating in the plate thickness direction. The same number of through holes 32b are formed in the lower wall 32 as the number of through holes 51a in the first plate 51 and the second plate 52a, and are positioned to overlap with the through holes 51a in the first plate 51 and the second plate 52a in the vertical direction D3. Bolts 8 are inserted from below through the through holes 32b, 51a, and 52a that overlap in the vertical direction D3. The lower wall 32 is fastened and fixed to the first plate 51 and the second plate 52 of the tilting member 3 by these bolts 8.

[0036] The side walls 33 constitute the ends of the cylindrical portion 30 on both sides in the left-right direction D2. The side walls 33 connect the ends of the upper wall 31 and the lower wall 32 in the left-right direction D2 to the vertical direction D3.

[0037] As shown in Figure 5, the thickened portion 35 is provided at both ends of the lower wall 32 in the left-right direction D2. The thickened portion 35 protrudes downward from the lower surface of the lower wall 32. A hole 35a opening forward is formed at the front end of the thickened portion 35. As shown in Figures 3 and 5, the lower wall rib 36 is provided between the thickened portions 35 on both sides of the lower wall 32 in the left-right direction D2. The lower wall rib 36 protrudes downward from the lower surface of the lower wall 32. The lower wall rib 36 has a plurality of first lower wall ribs 36a and a plurality of second lower wall ribs 36b. The first lower wall ribs 36a are ribs that extend in the front-rear direction D1, and the second lower wall ribs 36b are ribs that extend in the left-right direction D2. The first lower wall ribs 36a and the second lower wall ribs 36b intersect in a grid pattern. The second lower wall ribs 36b connect the thickened portions 35 on both sides of the left-right direction D2.

[0038] Furthermore, as shown in Figure 3, from another perspective, the lower surface 30a of the front end of the cylindrical portion 30 is inclined to gradually move rearward as it extends downward. That is, the lower surface 30a of the front end of the cylindrical portion 30 is inclined to move rearward away from the rear surface 11c of the support base 11, which is opposite to the front-rear direction D1, as it extends downward.

[0039] As shown in Figures 2 and 5, the connecting parts 40 are provided on the side walls 33 on both sides D2 in the left-right direction of the cylindrical part 30. The connecting parts 40 connect the lower end portion 20a (lower frame 24 in this embodiment) of the backrest body 20 to the cylindrical part 30. The connecting portion 40 has an extended portion 41 and a reinforcing portion 42.

[0040] The extensions 41 are provided on the side walls 33 on both sides of the cylindrical portion 30 in the left-right direction D2. The pair of extensions 41 are spaced apart in the left-right direction D2. The pair of extensions 41 are arm-shaped members that extend outward from each side wall 33 in the left-right direction D2. Each extension 41 is positioned upward as it moves outward in the left-right direction D2. The upper end of each extension 41 is connected to the lower end 20a (lower frame 24 in this embodiment) of the backrest body 20. In this embodiment, the combined outer shape of the pair of extended portions 41 and the cylindrical portion 30 is formed in a U-shape that opens upward when viewed from the front-rear direction D1.

[0041] The reinforcing parts 42 are provided on the side walls 33 on both sides of the cylindrical part 30 in the left-right direction D2. The reinforcing parts 42 extend outward from each side wall 33 in the left-right direction D2 and extend in the front-rear direction D1.

[0042] Figure 7 is a cross-sectional view showing the connecting portion 6 in the first embodiment of the present invention. The cross-section in Figure 7 is a cross-section of the reinforcing portion 42 of the connecting portion 6. The cross-section in Figure 7 is aligned along the front-rear direction D1 and the up-down direction D3. In this embodiment, as shown in Figure 7, the reinforcing portion 42 is formed as a rib protruding forward from each of the pair of extension portions 41. Furthermore, as shown in Figure 5, the reinforcing portion 42 is formed along the extension portion 41 so as to be positioned upward from the cylindrical portion 30 toward both sides in the left-right direction D2. The upper end of each reinforcing portion 42 is connected to the lower end portion 20a (lower frame 24 in this embodiment) of the backrest body 20.

[0043] Furthermore, a pair of reinforcing sections 42 are provided on each side wall 33, spaced apart in the vertical direction D3. Hereinafter, of the pair of upper and lower reinforcing sections 42, the upper reinforcing section 42 will be referred to as the upper reinforcing section 43, and the lower reinforcing section 42 will be referred to as the lower reinforcing section 44.

[0044] The upper reinforcing portion 43 is formed in a curved shape along the upper edge of the extended portion 41. The length L1 of the upper reinforcing portion 43 in the front-rear direction D1 (see Figure 7) gradually increases in the left-right direction D2 as it moves toward the cylindrical portion 30. The lower end portion 43a of the upper reinforcing portion 43 is connected to the upper edge of the side wall 33 of the cylindrical portion 30 (see Figure 4).

[0045] The lower reinforcing portion 44 is formed in a curved shape along the lower edge of the extended portion 41. The length L2 of the lower reinforcing portion 44 in the front-rear direction D1 (see Figure 7) gradually increases in the left-right direction D2 towards the cylindrical portion 30. The lower end portion 44a of the lower reinforcing portion 44 is connected to the lower side of the side wall 33 of the cylindrical portion 30 and to the thickened portion 35 (see Figure 4). The lower end portion 44a of the lower reinforcing portion 44 is provided over substantially the entire length of the cylindrical portion 30 in the front-rear direction D1.

[0046] The front end of the lower end 44a of the lower reinforcing portion 44 is located in front of the front end of the lower end 43a of the upper reinforcing portion 43. Also, the thickness W2 (see Figure 7) of the lower reinforcing portion 44 in the vertical direction D3 is greater than the thickness W1 (see Figure 7) of the upper reinforcing portion 43 in the vertical direction D3.

[0047] Thus, in this embodiment, the connecting portion 40 has an extended portion 41 with the shape described above and a reinforcing portion 42. For this reason, as shown in Figure 7, the cross-sectional shape of the connecting portion 40 along the vertical direction D3 and the front-rear direction D1 is U-shaped, opening towards the front. Furthermore, a pair of connecting parts 40 provided on both sides D2 in the left-right direction are connected by a central reinforcing part 7.

[0048] As shown in Figures 5 and 6, the central reinforcing section 7 is provided behind the cylindrical section 30 and is integrally formed with the cylindrical section 30 and the connecting section 40. The central reinforcing section 7 extends upward from the rear of the cylindrical section 30. The upper end of the central reinforcing section 7 is connected to the lower end 20a (lower frame 24 in this embodiment) of the backrest body 20. A through-hole 7a is formed in the center of the central reinforcing section 7 in the left-right direction D2, extending through in the front-back direction D1. The dimension of the through-hole 7a in the left-right direction D2 gradually decreases as it moves downward. The lower end of the central reinforcing section 7 (hereinafter referred to as the central lower reinforcing section 7b) extends to both the left and right sides. The upper edge of the central lower reinforcing section 7b is slightly curved so as to protrude downward along the lower edge of the through hole 7a when viewed from the front. The central lower reinforcing section 7b is connected to the rear reinforcing section 9 (see Figure 3). The rear reinforcing portion 9 is a member that closes the rear opening of the cylindrical portion 30. The rear reinforcing portion 9 is provided over the entire area of ​​the rear opening of the cylindrical portion 30. The rear reinforcing portion 9 improves the strength of the rear end of the cylindrical portion 30 against loads in the vertical direction D3 and the left-right direction D2. The rear reinforcing portion 9 extends rearward from the rear end of the cylindrical portion 30. The rear reinforcing portion 9 also has a thickness in the vertical direction D3 that is approximately the same as that of the cylindrical portion 30. The rear reinforcing portion 9 is integrally formed with the cylindrical portion 30, the connecting portion 40, and the central reinforcing portion 7.

[0049] According to this embodiment, the following effects and benefits are achieved.

[0050] In this embodiment, the chair 1 comprises a lower support structure 2, a tilting member 3, and a backrest 4. The tilting member 3 is supported by the lower support structure 2 so as to be tiltable around an axis O in the left-right direction D2, and protrudes rearward from the lower support structure 2. The backrest 4 is connected to the tilting member 3. The backrest 4 comprises a backrest body 20, a cylindrical portion 30, and a connecting portion 40. The backrest body 20 has a load-bearing surface 23 facing forward. The cylindrical portion 30 is formed in a cylindrical shape that opens toward the front, and is connected to the tilting member 3 with the tilting member 3 housed inside. The connecting portion 40 is provided on the side walls 33 on both sides of the cylindrical portion 30 in the left-right direction D2, and connects the backrest body 20 and the cylindrical portion 30.

[0051] As a result, when a seated person moves their body, for example by twisting their body, the backrest 4 tilts in conjunction with the tilting member 3. This applies a load to the backrest 4 that includes a component in the left-right direction D2. This input load is applied to the side wall 33 of the cylindrical portion 30 via the connecting portion 40. The side wall 33 then deforms in the left-right direction D2, absorbing the load that would cause the tilting member 3 to tilt from a horizontal position to the left-right direction D2. In this embodiment, the tilting member 3 is connected to the cylindrical portion 30 at the lower wall 32 of the cylindrical portion 30, but the left-right deformation of the side wall 33 prevents the tilting member 3 and the cylindrical portion 30 from being pulled apart vertically by the moment caused by this input load. Furthermore, since the cylindrical portion 30 is formed in a cylindrical shape, the input load can be distributed throughout the entire cylindrical portion 30. This improves the connection strength between the tilting member 3 and the backrest 4. Therefore, according to this embodiment, the influence of the input load on the backrest 4 on the connection point of the backrest 4 can be reduced.

[0052] Furthermore, in this embodiment, the connecting portion 40 has a reinforcing portion 42 that extends outward from each side wall 33 in the left-right direction D2 and extends in the front-rear direction D1.

[0053] As a result, the reinforcing portion 42 makes the connecting portion 40 strong against loads that twist in the front-rear direction D1. Therefore, the connecting portion 40 can absorb a large portion of the load before it is transmitted to the cylindrical portion 30, thanks to the reinforcing portion 42. Thus, the connection strength between the tilting member 3 and the backrest 4 can be further improved. This makes the backrest 4 more robust.

[0054] In this embodiment, the reinforcing parts 42 are provided in pairs on each side wall 33, spaced apart in the vertical direction D3.

[0055] This improves the strength of the connection portion 40 compared to the case where there is only one reinforcing portion 42 on each side wall 33. Therefore, the connection strength between the tilting member 3 and the backrest 4 can be further improved. In addition, since the reinforcing portion 42 can be molded at the same time as the cylindrical portion 30 that opens forward is molded, manufacturing efficiency can also be improved.

[0056] Furthermore, in this embodiment, the connecting portion 40 has a pair of extensions 41 that extend outward from each side wall 33 in the left-right direction D2 and are located upward as they extend outward in the left-right direction D2. The reinforcing portion 42 protrudes forward from each of the pair of extensions 41.

[0057] As a result, the extension 41 improves the strength of each reinforcing section 42. Furthermore, the pair of extension sections 41 can individually guide the load applied to the left side of the backrest 4 to the left side wall 33, and the load applied to the right side of the backrest 4 to the right side wall 33. This suppresses excessive stress concentration in the center of the cylindrical section 30 in the left-right direction D2. Therefore, the connection strength between the tilting member 3 and the backrest 4 can be further improved. As a result, the backrest 4 becomes even more robust.

[0058] In this embodiment, the backrest 4 is provided with a central reinforcing portion 7 located at the rear of the cylindrical portion 30. A pair of left and right connecting portions 40 are connected by the central reinforcing portion 7. As a result, each connecting portion 40 and cylindrical portion 30 is reinforced by the central reinforcing portion 7. Furthermore, a through hole 7a is formed in the center of the central reinforcing portion 7 in the left-right direction D2, penetrating in the front-rear direction D1. Therefore, the pair of connecting portions 40 on both sides in the left-right direction D2 are spaced apart in the left-right direction D2 at least in the middle portion of the vertical direction D3. As a result, the load transmitted from the backrest 4 is distributed in the left-right direction D2, and stress concentration in the center of the left-right direction D2 is suppressed. Thus, it is possible to reinforce each connecting portion 40 and cylindrical portion 30 while suppressing stress concentration in the center of the left-right direction D2. This further improves the connection strength between the tilting member 3 and the backrest 4, making the backrest 4 even more robust.

[0059] Furthermore, in this embodiment, the lower surface 30a of the front end of the cylindrical portion 30 is inclined so as it extends downward, it moves backward from the rear surface 11c of the support base 11 that faces the front-rear direction D1. As a result, even if the backrest 4 tilts backward, the lower surface 30a of the cylindrical part 30 and the rear surface 11c of the support base are maintained at a sufficient distance from each other. Therefore, the occupant's fingers will not get caught between the cylindrical part 30 and the support base 11, improving safety.

[0060] (Second Embodiment) Next, a second embodiment of the present invention will be described. In this description of the second embodiment, parts that are the same as those of the first embodiment described above will be omitted or simplified.

[0061] Figure 8 is a perspective view showing the backrest 104 in a second embodiment of the present invention. As shown in Figure 8, in the chair 101 and backrest 104 of this embodiment, the backrest body 120 includes a backrest frame 121 and a mesh material 122. The backrest frame 121 is formed in a frame shape with a through hole 121a that penetrates in the front-rear direction D1. The mesh material 122 is a sheet-like member attached to the front side of the backrest frame 121. The through hole 121a of the backrest frame 121 is closed by this mesh material 122. In this embodiment, the front surface of the mesh material 122 faces forward and functions as a load-supporting surface 123 that supports the load input by the user from the rear.

[0062] Furthermore, in this embodiment, a connecting portion 6 having the same configuration as in the first embodiment is provided at the lower end 120a of the backrest body 120 (the lower end of the backrest frame 121). Therefore, the chair 101 and backrest 104 of this embodiment can exhibit the same effects and advantages as those of the first embodiment described above.

[0063] While preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments. Additions, omissions, substitutions, and other modifications are possible without departing from the spirit of the present invention. The present invention is not limited by the above description, but only by the appended claims.

[0064] In the embodiments described above, the case in which the cylindrical portion 30 is formed in a rectangular parallelepiped shape extending in the front-rear direction D1 and the left-right direction D2 was explained, but the configuration is not limited to this. The cylindrical portion 30 may be formed in a polygonal cylindrical shape with five or more sides, for example. Alternatively, the cylindrical portion 30 may be formed in a cylindrical shape.

[0065] In the embodiment described above, the case in which the rear end of the cylindrical portion 30 is closed was explained, but the configuration is not limited to this. The cylindrical portion 30 may be open not only at the front but also at the rear.

[0066] The above-described embodiment explains the case where a pair of reinforcing parts 42 are provided on each side wall 33 spaced apart in the vertical direction D3, but the configuration is not limited to this. The number of reinforcing parts 42 provided on each side wall 33 can be changed as appropriate. Only one reinforcing part 42 may be provided on each side wall 33. [Explanation of Symbols]

[0067] 1: Chair 2: Lower support structure 3: Tilting member 4: Backrest 20: Backrest 23:Load supporting surface 30: Cylindrical part 33: Side wall 40: Connection part 41: Extension part 42: Reinforcement 101: Chair 104: Backrest 120: Backrest body 123: Load bearing surface D1: Anteroposterior direction D2: Left / right direction D3: Vertical direction O: Axis line

Claims

1. Lower support structure, A tilting member is supported by the lower support structure so as to be tiltable around an axis in the left-right direction, and protrudes rearward from the lower support structure, A backrest connected to the tilting member, Equipped with, The aforementioned backrest is, A backrest body having a load-bearing surface facing forward, A cylindrical portion formed to open forward, which connects to the tilting member while the tilting member is housed inside, The cylindrical portion is provided with connecting parts on both the left and right side walls, which connect the backrest body and the cylindrical portion. The aforementioned connection part is Each of the aforementioned side walls extends outward in the left-right direction and has a reinforcing portion that extends in the front-rear direction, A pair of extensions extending outward from each of the aforementioned side walls in the left-right direction, and positioned upward as they move outward in the left-right direction, It has, The reinforcing portion protrudes forward from each of the pair of extension portions, The reinforcing parts are provided in pairs on each of the side walls, spaced apart in the vertical direction. A chair comprising a pair of reinforcing parts, each including a lower reinforcing part that runs along the lower edge of the extended part and is connected to the lower edge of the cylindrical part.

2. A backrest that is supported by a lower support structure so as to be tiltable around a left-right axis and connected to a tilting member that protrudes rearward from the lower support structure, A backrest body having a load-bearing surface facing forward, A cylindrical portion formed to open forward, which connects to the tilting member while the tilting member is housed inside, The cylindrical portion is provided with connecting parts on both the left and right side walls, which connect the backrest body and the cylindrical portion. The aforementioned connection part is Each of the aforementioned side walls extends outward in the left-right direction and has a reinforcing portion that extends in the front-rear direction, A pair of extensions extending outward from each of the aforementioned side walls in the left-right direction, and positioned upward as they move outward in the left-right direction, It has, The reinforcing portion protrudes forward from each of the pair of extension portions, The reinforcing parts are provided in pairs on each of the side walls, spaced apart in the vertical direction. A backrest comprising a pair of reinforcing portions, including a lower reinforcing portion that runs along the lower edge of the extended portion and is connected to the lower edge of the cylindrical portion.

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