chair

Abstract

To provide a chair which has a preferable structure capable of attaching an option to a backrest.SOLUTION: A backrest E of a chair comprises a nut holding recess nt comprising: an upper opening part kh1; a lower opening part kh2; and a front opening part kh3. A nut member J comprises: a boss part j1 on which a screw groove is arranged; and a flange part j2 which is continuous to the upper part of the boss part j1 and may engage to a flange engagement part nt3 being a part forming the upper opening part kh1. As an option, there is provided a screw insertion hole penetrating in a vertical direction, and by screwing a screw inserted into the screw insertion hole from a lower side with respect to the boss part j1, the option can be fitted to the backrest E.SELECTED DRAWING: Figure 25

Description

[Technical field]

[0001] The present invention relates to a chair. [Background technology]

[0002] 2. Description of the Related Art There are known chairs to which options such as a headrest and a hanger can be attached to the backrest (see, for example, Patent Document 1).

[0003] By the way, many backrests to which options can be attached are equipped with polygonal nuts. The nuts have polygonal outer peripheries and are fitted into nut fitting holes drilled in the corresponding square holes. The options are attached to the backrest by screwing a screw into the nut on the backrest side.

[0004] However, in conventional methods, precise alignment of the nut with the nut fitting hole is required to fit a polygonal nut into a square-shaped nut fitting hole, making it difficult to carry out the work smoothly.

[0005] In addition, when a polygonal nut is to be provided on the frame material of the backrest, a square nut fitting hole must be provided on the frame material, which necessitates a certain thickness dimension in the front-to-rear direction of the frame material. In other words, in the case of conventional chairs, when options are attached to the backrest, the degree of freedom in designing a frame material with a restricted thickness dimension in the front-to-rear direction is limited.

[0006] Needless to say, the options are not limited to headrests and hangers as long as they can be attached to the backrest. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP2010-099108A Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been made in light of the above circumstances, and has as its object to provide a chair having a suitable structure that allows at least an option to be attached to the backrest. [Means for solving the problem]

[0009] That is, the present invention has the following configuration.

[0010] The invention described in claim 1 is a chair in which an option can be attached to the backrest, the backrest being provided with a nut holding recess formed with an upper opening portion open upward, a lower opening portion open downward, and a front opening portion open forward, capable of holding a nut member, the nut member being provided with a boss portion housed in the nut holding recess and having a threaded groove on its inner surface, and a flange portion connected to the boss portion and capable of engaging with a portion forming the upper opening portion, the option being provided with a screw insertion hole penetrating in the vertical direction, and the chair being configured so that the option can be attached to the backrest by screwing a screw inserted into the screw insertion hole from below into the boss portion.

[0011] The invention described in claim 2 is the chair described in claim 1, wherein the boss portion is accommodated in the nut retaining recess through the front opening portion.

[0012] The invention described in claim 3 is the chair described in claim 1 or 2, wherein the option is provided with a movement restricting portion that can restrict forward movement by engaging with the backrest.

[0013] The invention described in claim 4 is a chair described in claim 1, 2 or 3, wherein the backrest is formed by tensioning a tensioning member that can form a backrest surface against the frame-shaped portion, and the nut retaining recess is provided in an upper frame material extending in the left-right direction that forms the frame-shaped portion.

[0014] The invention described in claim 5 is a chair described in claim 4, in which the upper frame material has an outer frame portion having a tension member mounting groove formed therein for mounting the tension member, and an inner frame portion arranged below this outer frame portion, and the nut retaining recess is provided in the inner frame portion.

[0015] The invention described in claim 6 is the chair described in claim 1, 2, 3, 4 or 5, wherein the flange portion extends longitudinally in the left-right direction from an upper end portion of the boss portion.

[0016] The invention described in claim 7 is the chair described in claim 1, 2, 3, 4, 5 or 6, in which the option is a backrest extension member for extending the backrest or a hanger for hanging clothes. Effect of the Invention

[0017] As described above, according to the present invention, it is possible to provide a chair having a suitable configuration that allows at least an option to be attached to the backrest. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a perspective view showing an embodiment of the present invention. [Diagram 2] FIG. [Diagram 3] FIG. [Figure 4] FIG. [Diagram 5] FIG. [Figure 6] FIG. [Figure 7] FIG. [Figure 8] FIG. [Figure 9] FIG. [Figure 10] FIG. [Figure 11] FIG. [Figure 12] FIG. 4 is a plan view of an adjustment lever (reaction force adjustment lever) in the embodiment. [Figure 13] Cross-sectional view taken along line AA in FIG. 9(a). [Figure 14] FIG. [Figure 15] FIG. [Figure 16] FIG. [Figure 17] FIG. [Figure 18] FIG. [Figure 19] Cross-sectional view of line BB in Figure 2. [Figure 20] Cross-sectional view taken along line CC in FIG. 2. [Figure 21] Cross-sectional view of line DD in Figure 2. [Figure 22] FIG. [Figure 23] FIG. [Figure 24] FIG. [Diagram 25] FIG. [Figure 26] An enlarged view of part E in FIG. [Figure 27] 20 is a cross-sectional view taken along line FF in FIG. 19. [Figure 28] FIG. [Figure 29] FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, one embodiment of the present invention will be described with reference to FIGS.

[0020] In this embodiment, the present invention is applied to a swivel chair for business use (hereinafter simply referred to as a "chair") suitable for use in an office or the like.

[0021] The chair comprises legs A, a support base B which is a support member supported rotatably relative to the legs A, a seat C disposed on the support base B, a backrest E supported so as to be able to tilt backward relative to the support base B via a back support member (not shown), and a backrest surface extension member F and a hanger G which are options which can be selectively attached to the backrest E.

[0022] <<Legs A>> The leg A includes a plurality of leg blades a1 arranged radially, each having a caster a11 at its tip, and a leg support a2 erected at the base end of the leg blade a1.

[0023] The leg support a2 is configured to be extendable and retractable in the vertical direction. The leg support a2 is capable of supporting the support base B by a gas spring (not shown) so that the vertical position can be changed.

[0024] <<Support base B>> The support base B is mainly composed of a support base main body 1 which is integrally formed from synthetic resin. The support base B is attached onto the leg A.

[0025] <Support base body 1> The support base main body 1 comprises a foundation bottom structure 11 having a downward surface and attached to the leg support a2, an inclined bottom wall 12 having a downward surface facing diagonally downward and rearward and extending diagonally downward and forward from the front end of the foundation bottom structure 11, a front bottom wall 13 having a downward surface, extending forward from the front end of the inclined bottom wall 12 and inclined so as to gradually position upward as it moves forward, left and right side walls 14 in an upright position extending upward from the left and right ends of the foundation bottom structure 11, the inclined bottom wall 12, and the front bottom wall 13, respectively, and a front wall 15 in an upright position connecting the front ends of the left and right side walls 14.

[0026] A reaction force generating unit (not shown) is disposed inside the support base main body 1 to generate a reaction force for the backrest E that can tilt backward. The reaction force generating unit is disposed between a reaction force adjusting lever K pivotally supported on the support base B and a back support (not shown) pivotally supported on the support base B and connected to the backrest E. The reaction force generating unit is mainly composed of a spring material.

[0027] A reaction force adjusting lever K, which is an adjustment lever for adjusting the reaction force of the backrest E, is rotatably supported on the support base B.

[0028] <<Reaction force adjustment lever K>> The reaction force adjustment lever K is rotatably supported on the support base 1. The reaction force adjustment lever K is pivotally supported on the support base 1 so that its longitudinal axis is in the left-right direction. The reaction force adjustment lever K is rotated by the user's hand, and the degree of compression of the spring material that constitutes the reaction force generating part can be adjusted in accordance with the rotation.

[0029] The reaction force adjustment lever K is equipped with an operating part k1 which is provided at the tip, which is one end portion, and is gripped by a user to apply a rotational operating force, an intermediate connecting part k2 which is connected to the operating part k1 with its axis js aligned and has a shape in which the outer diameter dimension becomes shorter as it moves away from the operating part k1, and a lever base shaft part k3 which is connected to the intermediate connecting part k2 with its axis js aligned and has a retained shaft part k31 which is a part which is pivotally supported on the support base main body 1.

[0030] The reaction force adjusting lever K is made up of an operating portion k1, an intermediate connecting portion k2, and a lever base shaft portion k3 which are integrally formed from synthetic resin.

[0031] <Operation section k1> The operation unit k1 includes an operation unit body k11 having a generally cylindrical shape that is open to the outside, and a protruding portion k12 that is a mark portion provided at an end of the operation unit body k11 and extends toward the center of the operation unit body k11. The protruding portion k12 is a single portion that protrudes from the inner peripheral surface of the operation unit body k11 toward the center of the operation unit body k11.

[0032] [Operation unit body k11] The operation unit body k11 can form a substantially cylindrical space s1 inside. The operation unit body k11 is configured such that the outer peripheral surface of the tip portion k111 is positioned in a direction that gradually approaches the tip. In addition, a plurality of grooves k112 for preventing finger slippage are provided along the axis js on the outer peripheral surface of the tip portion k111 of the operation unit body k11.

[0033] A mark recessed portion k114 having a width dimension substantially equal to the thickness dimension of the protruding portion k12 is formed on the outer peripheral surface of the tip portion k111 of the operation portion main body k11 corresponding to the protruding portion k12. That is, the recessed portion k114 is provided on the outer peripheral surface of the tip portion k111 located directly behind the inner peripheral surface of the operation portion main body k11 from which the protruding portion k12 is protruded.

[0034] [Protruding part k12] The protrusion k12 protrudes from the inner circumferential surface of the operation unit main body k11 toward the axis js. The protrusion k12 is in the form of an upright wall extending along the longitudinal direction of the reaction force adjustment lever K. When viewed from the axis js direction, the protrusion k12 has a tip k121 which is a shaped portion that gradually narrows toward the axis js. In this embodiment, the gradually narrowing shaped portion is only present at the tip k121 of the protrusion k12. More specifically, the tip k121 of the protrusion k12 is in the form of a semicircular arc in a side view.

[0035] The protruding portion k12 has an outwardly facing end surface k122 for use as a marker on the outwardly facing end edge of the operation portion main body k11, that is, on the outer side of the opening edge k113 of the operation portion main body k11.

[0036] <Intermediate connection part k2> The intermediate connecting part k2 has a shape in which the outer diameter dimension gradually decreases from the side having the operating part k1 toward the side having the lever base part k3. That is, the intermediate connecting part k2 has a partial cone shape interposed between the operating part k1 and the lever base part k3.

[0037] A substantially conical inner space s2 is formed inside the intermediate connecting part k2, which is continuous with the cylindrical space s1 of the operating part main body k11. A protrusion k12 provided on the operating part main body k11 is connected to the inner peripheral surface of the tip side part of the intermediate connecting part k2, i.e., the inner peripheral surface on the operating part k1 side.

[0038] <Lever base part k3> The lever base shaft portion k3 is provided with a retained shaft portion k31 which is connected to the intermediate connecting portion k2 with its axis js aligned and journaled on the support base B, an engaging protrusion k32 which can engage with a protrusion (not shown) for regulating the rotation range provided on the support base B, and a cam portion k33 which can engage with a reaction force generating portion (not shown) arranged inside the support base B.

[0039] A plurality of held shaft portions k31 are arranged on the lever base shaft portion k3. Among the plurality of held shaft portions k31 arranged on the lever base shaft portion k3, the diameter of the held shaft portion k31 at the base end is set to be the smallest, and the diameter of the held shaft portion k31 at the tip side (operation portion k1 side) is set to be the largest. In other words, the lever base shaft portion k3 is arranged with a plurality of held shaft portions k31 having different diameters from the base end to the tip side, and the diameter at the tip side is set to be larger than that at the base end side.

[0040] The engaging protrusions k32 are disposed at two positions on the left and right sides of the lever base shaft k3, spaced apart from each other. The engaging protrusions k32 are adapted to engage with a protrusion (not shown) for restricting the rotation range provided on the support base B, thereby restricting the rotation range of the reaction force adjusting lever K, which receives the operating force from the user, around the axis js.

[0041] The cam portions k31 are disposed at two positions on the left and right sides of the lever base shaft portion k3, spaced apart from each other.

[0042] <<Location C>> The seat C includes a seat support c1 and a seat body c2 that is provided on the seat support c1 so that its front-rear position can be changed.

[0043] An operating piece L that acts on a gas spring (not shown) and can expand and contract the leg support a2 in the up and down direction is pivotally supported at the bottom of the seat support c1 so as to be capable of flapping.

[0044] The seat body c2 is configured to be able to slide in the front-rear direction relative to the seat support c1.

[0045] <<Back support>> The back support, not shown, is interposed between the support base B and the backrest E. The back support comprises a pair of left and right arms that extend in the front-rear direction and are pivotally supported on the support base main body 1 via a main shaft, not shown, and a connecting member that connects the rear parts of the pair of left and right arms. The connecting member is provided with a nut portion to which a screw for attaching the backrest E is screwed. In other words, a backrest attachment portion to which the backrest E is attached is provided at the rear part of the back support.

[0046] A rearward tilt degree setting lever H, which can selectively set the rearward tilt degree of the backrest E, is rotatably supported on the back support body.

[0047] The back support is covered and concealed by a cover body I which is integrally formed from a synthetic resin.

[0048] <<Backrest E>> The backrest E comprises a back frame M attached to the backrest mounting portion of the back support, and a mesh-like stretching member P stretched over the back frame M. The backrest E has a backrest surface pm that supports the back of a seated person from behind, and is formed by the stretching member P mainly made of mesh fabric.

[0049] The chair of this embodiment is configured so that an optional backrest surface extension member F and a hanger G can be selectively attached to the upper frame material 3 of the backrest E.

[0050] <Back frame M> The back frame M comprises left and right side frame members 2 each having a tension member mounting groove mz opening outward, an upper frame member 3 having a tension member mounting groove mz opening upward and connecting the upper parts of the left and right side frame members 2, a lower frame member 4 connecting the lower parts of the left and right side frame members 2, and an intermediate connecting frame member 5 having a tension member mounting groove mz opening downward and connecting the left and right side frame members 2 together while forming an upper cavity sa between the upper frame member 3 and a lower cavity sb between the lower frame member 4.

[0051] The left and right side frame members 2, the upper frame member 3, and the lower frame member 4 are integrally molded from synthetic resin. The intermediate connecting frame member 5 is attached to the left and right side frame members 2 with screws.

[0052] The back frame M comprises an upper frame-shaped portion w1 which is formed with an upper cavity sa therein by left and right side frame members 2, an upper frame member 3, and an intermediate connecting frame member 5, and a lower frame-shaped portion w2 which is formed with a lower cavity sb therein by left and right side frame members 2, a lower frame member 4, and an intermediate connecting frame member 5.

[0053] The backrest E in this embodiment is configured such that a tension member P capable of forming a backrest surface pm is tensioned to an upper frame portion w1 which is a frame portion provided on a back frame M.

[0054] [Left and right side frame material 2] The left and right side frame members 2 extend in the vertical direction. On the outer surfaces of the left and right side frame members 2, tension member attachment grooves mz are formed, which continue from the upper ends of the left and right side frame members 2 to a height position approximately corresponding to the lower edges of the intermediate connecting frame members 5.

[0055] [Top frame material 3] The upper frame material 3 extends in the left-right direction. The upper frame material 3 has an outer frame portion 31 in which a tension member mounting groove mz that opens upward for mounting a tension member P is formed, and an inner frame portion 32 disposed below the outer frame portion 31. The upper frame material 3 is provided with a nut holding recess nt in which a nut member J for mounting an option can be held, as will be described in detail later.

[0056] The outer frame portion 31 constitutes the upper portion of the upper frame material 3. The front surface of the outer frame portion 31 forms the portion that is attached to the rear surface of the tension member P, i.e., the portion that backs the tension member P.

[0057] The inner frame portion 32 constitutes the lower portion of the upper frame material 3. The inner frame portion 32 is located more inward than the outer frame portion 31. In other words, the inner frame portion 32 is provided in a location that is covered by the tension member P when viewed from the front.

[0058] The inner frame portion 32 includes a hanging wall 321 that is arranged to hang downward from the rear of the outer frame portion 31, a lower end wall 322 that extends forward from the lower end of the hanging wall 321, and a plurality of connecting walls 323 that form upright walls connecting between the lower end wall 322 and the outer frame portion 31, and between the lower end wall 322 and the hanging wall 321.

[0059] The back surface of the hanging wall 321 is substantially flush with the back surface of the outer frame portion 31. The bottom end wall 322 is provided at a distance in the up-down direction from the outer frame portion 31. The connecting walls 323 are provided to increase the connecting strength between the bottom end wall 322 and the outer frame portion 31, and a plurality of them are provided at regular intervals in the left-right direction.

[0060] The inner frame portion 32 is provided with a nut holding recess nt that is formed with an upper opening portion kh1 that is open upward, a lower opening portion kh2 that is open downward, and a front opening portion kh3 that is open forward and that can hold the nut member J. The nut holding recess nt is provided at a plurality of positions on the inner frame portion 32.

[0061] The nut retaining recess nt is provided in the lower end wall 322 of the inner frame portion 32. The nut retaining recess nt has left and right standing wall portions nt1 and a rear standing wall portion nt2 connecting rear portions of the left and right standing wall portions nt1. The nut retaining recess nt has a generally U-shaped hole shape that is open to the front when viewed from the bottom.

[0062] The nut retaining recess nt is formed by left and right upright wall portions nt1 and a rear upright wall portion nt2, which define an upper opening portion kh1 that is open upward, a lower opening portion kh2 that is open downward, and a front opening portion kh3 that is open forward.

[0063] In addition, the nut retaining recess nt forms a portion that can form an upper opening portion kh1 by the upper edges of the left and right upright wall portions nt1 and the upper edge of the rear upright wall portion nt2, and also forms a flange engagement portion nt3 that can engage with the underside of the flange portion j2 of the nut member J.

[0064] A gap sk capable of accommodating the flange portion j2 of the nut member J is formed between the nut holding recess nt and the outer frame portion 31.

[0065] In this embodiment, the inner frame portion 32 is provided with four nut holding recesses nt spaced apart in the left-right direction. The pair of nut holding recesses nt located on both the left and right outer sides are used when attaching a backrest surface extension member F for extending the backrest surface pm, and the pair of nut holding recesses nt located on both the left and right inner sides are used when attaching a hanger G for hanging clothes.

[0066] The nut member J held in the nut holding recess nt is made of metal. The nut member J includes a boss portion j1 ​​that is accommodated in the enclosed space of the nut holding recess nt and has a screw groove j11 on its inner peripheral surface, and a flange portion j2 that is connected to the boss portion j1 ​​and can engage with a flange portion engagement portion nt3 whose lower surface forms the upper open portion kh1.

[0067] The nut member J has a generally T-shape. That is, the flange portion j2 extends longitudinally outward in the left-right direction from the upper end of the generally cylindrical boss portion j1.

[0068] The method of holding the nut member J in the nut holding recess nt provided in the backrest E and attaching the optional backrest surface extension member F and optional hanger G will be described in detail later.

[0069] [Bottom frame material 4] The lower frame member 4 has a portion that connects the lower portions of the left and right side frame members 2 and is connected to the back support member. The lower frame member 4 is provided with a back support member connecting portion 41 that is recessed and open forward, for fitting externally to a backrest mounting portion provided on the back support member and connecting the backrest mounting portion.

[0070] [Intermediate connection frame material 5] The intermediate connecting frame member 5 extends in the left-right direction. The intermediate connecting frame member 5 is installed between the portions of the left and right side frame members 2 that are tilted forward when viewed from the side. The intermediate connecting frame member 5 is separate from the other frame members that make up the back frame M, i.e., the left and right side frame members 2, the upper frame member 3, and the lower frame member 4.

[0071] The left and right ends of the intermediate connecting frame member 5 are screwed to the left and right side frame members 2. The intermediate connecting frame member 5 has a curved shape that is convex toward the rear in a plan view. The intermediate connecting frame member 5 is formed with a tension member mounting groove mz that opens downward.

[0072] <Upholstery material P> The upholstery member P is mainly made of a mesh-like fabric capable of forming the backrest surface pm.

[0073] The tensile member P is adapted to be attached at its peripheral portion to a tensile member attachment groove mz provided in the upper frame-shaped portion w1 of the back frame M. The tensile member P is stretched over the front side of the upper frame-shaped portion w1 of the back frame M.

[0074] <<Backrest extension member F>> The backrest surface extension member F is for providing an extended backrest surface fm as a contact surface that can contact the user on the backrest surface pm formed by the backrest E. The backrest surface extension member F in this embodiment is called a "shoulder support" because the user's shoulders can mainly contact the extended backrest surface fm.

[0075] The backrest surface extension member F includes a pad body f1 having an extended backrest surface fm, the front surface of which is a contact surface that can come into contact with the user, and a base body f2 that can support the pad body f1.

[0076] The backrest surface extension member F has an upper frame material arrangement recess fu formed between the lower part of the base body f2 and the lower end part of the pad body f1, the upper frame material arrangement recess fu being open to the front and both the left and right sides.

[0077] The backrest surface extension member F is provided with a movement restricting portion ks, which is located on the rear side of the upper frame material 3 in the backrest E and can restrict forward movement by engaging with the rear portion of the upper frame material 3, at a position facing the upper frame material arrangement recess fu.

[0078] <Pad body f1> The pad body f1 includes a pad body main body f3 attached to a pad body attachment portion f6 provided on the base body f2, and a front cover material f4 covering the front surface and peripheral edge portion of the pad body main body f3.

[0079] The pad body f1 has a generally rectangular shape with its elongated sides in the left-right direction when viewed from the front. The pad body f1 has a generally symmetrical shape when viewed from the front. The edges of both the left and right sides of the pad body f1 are gently curved so as to convex outward when viewed from the front. The extended backrest surface fm, which is the front surface of the pad body f1, is set to be generally flush with the backrest surface pm formed by the upholstery member P.

[0080] The vertical dimension of the pad body f1 is shorter than the vertical dimension of the base body f2. The position of the upper edge of the pad body f1 is approximately aligned with the position of the upper edge of the base body f2. The shape of the side edge of the pad body f1 in a front view is approximately aligned with the shape of the side edge at the same height position of the base body f2. The lower edge of the pad body f1 is set at a position that approximately abuts against the upper frame member 3.

[0081] [Pad body f3] The pad body f3 includes a pad base f31 formed of synthetic resin in the shape of a generally upright plate, and a cushion f32 made of urethane foam attached to the front surface of the pad base f31.

[0082] The pad base f31 has a pair of hook engaging portions f311 spaced apart from each other in the left-right direction at the center of the back side of the pad base f31 in the vertical direction. The hook engaging portion f311 has an engaging hole f314 that is open in the vertical direction.

[0083] The hook engaging portion f311 has an engaging hole f314 penetrating in the vertical direction, which is formed by left and right protruding walls f312 protruding rearward and a connecting wall f313 connecting the rear portions of the left and right protruding walls f312. The hook engaging portion f311 can engage with the base body f2 by inserting a hook f61, which is an engaging portion protruding from the pad body mounting portion f6 of the base body f2, into the engaging hole f314.

[0084] The lower part of the rear side of the pad base f31 is provided with left and right fitting protrusions f315 and a central fitting protrusion f316 as engagement parts at three locations on the left, right and center. Each fitting protrusion f315, f316 is substantially arrow-shaped and protrudes rearward. Each fitting protrusion f315, f316 can be engaged with a protrusion fitting part f62 as an engagement part provided on the pad body mounting part f6 of the base body f2. The left and right fitting protrusions f315 are set in a different position from the central fitting protrusion f316. More specifically, the left and right fitting protrusions f315 are set in a position rotated 90 degrees from the central fitting protrusion f316 in rear view.

[0085] [Front skin material f4] The front skin f4 is made of a fabric having an area larger than the front part of the pad body f3. The edge part f4e of the front skin f4 can be stored between the pad body f3 and the base body f2 so as not to be visible from the outside. The front skin f4 can form an extended backrest surface fm provided on the backrest surface pm of the upholstery member P.

[0086] <Base body f2> The base body f2 comprises a base plate-shaped portion f5 having an approximately upright plate shape, a pad body mounting portion f6 provided on the front side of the base plate-shaped portion f5 and to which the pad body f1 is attached, an upper frame member mounting portion f7 provided below the pad body mounting portion f6 and attached to the upper frame member 3 using a fastener screw v1, and a rear skin material f9 that covers the peripheral portion and rear portion of the base plate-shaped portion f5.

[0087] The base plate portion f5, the pad body mounting portion f6, and the upper frame member mounting portion f7 that constitute the base body f2 are integrally formed from synthetic resin.

[0088] In this embodiment, the backrest surface extension member F is configured so that only the rear skin material f9 covering the base plate portion f5 of the base body f2 can be seen in the rear view. In other words, the backrest surface extension member F is configured so that no members other than the rear skin material f9 can be seen in the rear view.

[0089] [Base plate part f5] The base plate portion f5 has a generally rectangular shape with its elongated sides in the left-right direction in rear view. The edges of the left and right sides of the base plate portion f5 are gently curved so as to convex outward in rear view. The rear surface of the base plate portion f5 is covered with a rear skin material f9.

[0090] The front side of the base plate-shaped portion f5 is provided with an upper horizontal rib f52 extending in the left-right direction, the tip of which can abut against the rear surface of the pad base f31, and a plurality of vertical ribs f53 extending in the up-down direction, the tip of which can abut against the rear surface of the pad base f31. The vertical ribs f53 are arranged at intervals in the left-right direction. A lower horizontal rib f54 extending in the left-right direction, the tip of which can abut against the upper frame material 3 of the backrest E, is provided at the lower part of the front side of the base plate-shaped portion f5.

[0091] In this embodiment, the movement restriction portion ks is mainly composed of the components located behind the upper frame material 3, i.e., the tip of the lower horizontal rib f54 and the tip of the vertical rib f53 located below the lower horizontal rib f54, and can restrict the forward movement of the backrest surface extension member F by engaging with the back surface of the upper frame material 3.

[0092] [Pad body mounting part f6] The pad body mounting portion f6 has a hook f61 protruding at a position corresponding to the hook engagement portion f311 of the pad base f31, and a protruding engagement portion f62 protruding at positions corresponding to the left, right and center engagement protrusions f316 of the pad base f31.

[0093] The pad body f1 is attached to the base body f2 by engaging the hook engagement portion f311 with the hook f61 provided on the pad body mounting portion f6, and then engaging the left, right and central engaging protrusions f315, f316 with the protrusion engaging portions f62 provided on the pad body mounting portion f6.

[0094] [Upper frame mounting part f7] The upper frame member mounting portion f7 is mainly composed of a portion protruding forward from the lower end of the base plate portion f5. The upper frame member mounting portion f7 has an upward surface f71 that extends in the left-right direction and serves as the mounting base surface for the upper frame member 3.

[0095] The upper frame member mounting portion f7 has two screw holes h1 that penetrate vertically at the left and right. The backrest surface expansion member F is configured to be mounted to the upper frame member 3 by screwing the screw v1 inserted through the screw hole h1 into the nut member J disposed in the nut holding recess nt in the upper frame member 3.

[0096] The upper frame material mounting portion f7 has a convex wall portion f72 at the upper end of the front part corresponding to the portion where the screw insertion hole h1 is formed, which can be positioned in the front opening portion kh3 of the nut retaining recess nt provided in the upper frame material 3.

[0097] A storage groove f8 that is open downward and outward and can store the edge portion f9e of the rear skin f9 is formed in the lower part of the base body f2, i.e., between the upper frame member mounting portion f7 and the base plate-shaped portion f5. Groove-forming walls f73 are erected at the rear ends of both sides of the upper frame member mounting portion f7 to form the storage groove f8 between them and the peripheral portion of the base plate-shaped portion f5.

[0098] In addition, the front surface of the groove forming wall f73 can abut against the rear surface of the upper frame material 3, and also serves as a movement restricting portion ks that can restrict the forward movement of the backrest surface extension member F.

[0099] [Back skin material f9] The rear skin f9 is made of a material having an area larger than the rear surface of the base plate portion f5. The edge portion f9e of the rear skin f9 can be accommodated between the base plate portion f5 and the pad body f1, and can also be accommodated in an accommodating groove f8 provided between the lower peripheral edge of the base plate portion f5 and the upper frame member mounting portion f7.

[0100] << Hanger G >> The hanger G is for hanging the user's clothes, etc. The hanger G is attached to the upper frame member 3 of the back frame M.

[0101] The hanger G comprises a hanger body g1 extending in the left-right direction for hanging clothes, etc., a pair of left and right hanger legs g2 extending downward from the underside of the hanger body g1 and extending forward at the lower part, and a base portion g3 which connects the lower ends of the left and right hanger legs g2 and is provided with an upper frame member mounting portion g7 which is attached to the upper frame member 3.

[0102] The base portion g comprises a base portion main body g4 having an upper frame material mounting portion g7, and an upright wall g5 serving as a movement restricting portion ks that is erected at the rear of the base portion main body g4 and can engage with the rear surface of the upper frame material 3.

[0103] The upper frame material mounting portion g7 extends in the left-right direction and has an upward surface g71 which serves as the mounting base surface for the upper frame material 3.

[0104] The upper frame member mounting portion g7 is provided with two screw insertion holes h2 penetrating in the vertical direction at the left and right positions. The hanger G is configured to be mounted to the upper frame member 3 by screwing the screw v2 inserted into the screw insertion hole h2 into the nut member J disposed in the nut holding recess nt in the upper frame member 3.

[0105] The upper frame material mounting portion g7 has a convex wall portion g72 at the upper end of the front part corresponding to the portion where the screw insertion hole h2 is formed, which can be positioned at the front opening portion kh3 of the nut retaining recess nt provided in the upper frame material 3.

[0106] <<How to install the option (backrest extension part F)>> The chair of this embodiment is applied with a mounting structure that makes it easy to mount options to the backrest E. Hereinafter, a method of mounting the options to the upper frame material 3 of the backrest E will be described using the backrest surface extension member F as a specific example.

[0107] First, the nut member J is held in the nut holding recess nt that is open forward and provided in the upper frame member 3. A tension member P is stretched and provided in advance on the front side of the upper frame-shaped portion w1 of the back frame M.

[0108] The worker passes the approximately T-shaped nut member J through the upper cavity sa surrounded by the upper frame-shaped portion w1 from the rear to the front, and then holds the nut member J in the nut holding recess nt which is open to the front.

[0109] The boss portion j1 ​​of the nut member J is accommodated in the nut holding recess nt through the front opening portion kh3. The flange portion j2 of the nut member J is accommodated in the gap sk between the nut holding recess nt and the outer frame portion 31. The flange portion j2 of the nut member J engages with the flange portion engagement portion nt3, which is the portion that forms the upper opening portion kh1 in the nut holding recess nt, and cannot move downward. In other words, the nut member J is provisionally positioned relative to the upper frame material 3 by having the boss portion j1 ​​accommodated in the nut holding recess nt and the flange portion j2 disposed in the gap sk.

[0110] Next, the backrest surface extension member F is moved from rear to front, and disposed at a position where the upper frame material disposition recess fu surrounds the upper frame material 3.

[0111] Then, a screw v1 is inserted from the bottom to the top through a screw insertion hole h1 provided in the upper frame member mounting portion f7 of the backrest surface extension member F, and the screw v1 is screwed into the boss portion j1 ​​of the nut member J. By screwing the screw v1 into the nut member J, the upper frame member mounting portion f7 of the backrest surface extension member F and the inner frame portion 32 of the upper frame member 3 are fastened together.

[0112] Using the above mounting method, the backrest surface extension member F can be attached to the upper frame material 3 of the backrest E.

[0113] The nut holding recess nt provided in the upper frame material 3 is open in the forward and vertical directions, making it easy for an operator to attach (temporarily place) the nut member J. The operator can properly hold the nut member J in the nut holding recess nt by simply feeling the inner frame portion 32 of the upper frame material 3 from the rear side of the backrest E without having to closely check the nut holding recess nt which is covered by the upholstery member P and difficult to see.

[0114] In addition, the backrest surface extension member F is provided with a movement restriction portion ks that can restrict forward movement. Therefore, even if the backrest surface extension member F is pressed forward, the nut member J cannot move forward from the nut holding recess nt that is open to the front side.

[0115] With the above-described embodiment, it is possible to provide a chair having an operating unit main body k11 with an approximately cylindrical outer shape that suppresses complexity, while having a reaction force adjustment lever K that can preferably perform an indicator function of indicating the rotation posture by means of the protrusion k12.

[0116] Furthermore, in the above-described embodiment, the nut member J can be held in the nut retaining recess nt which is open above, below and to the front, making it possible to provide a chair having a suitable configuration in which options such as a backrest surface extension member F can be attached to the backrest E.

[0117] In the above-described embodiment, the backrest surface extension member F is attached to the upper frame member 3 of the backrest E. The backrest surface extension member F is configured such that only the rear skin material f9 covering the base plate-shaped portion f5 can be seen in the rear view, so that a preferable appearance based on the rear skin material f9 can be achieved in the rear view.

[0118] As described above, in the chair according to this embodiment, the backrest E can be fitted with optional backrest surface extension members F and hangers G (hereinafter simply referred to as "options").

[0119] The backrest E is provided with an upper opening portion kh1 that is open upward, a lower opening portion kh2 that is open downward, and a front opening portion kh3 that is open forward, and is provided with a nut retaining recess nt that can hold a nut member J.

[0120] The nut member J has a boss portion j1 ​​that is accommodated in the nut retaining recess nt and has a screw groove j11 on its inner surface, and a flange portion j2 that can engage with a flange portion engagement portion nt3 that is connected to the boss portion j1 ​​and forms the upper open portion kh1.

[0121] The option is provided with screw insertion holes h1, h2 that penetrate in the vertical direction, and the option can be attached to the backrest E by inserting screws v1, v2 from below into the screw insertion holes h1, h2 and screwing them into the boss portion j1.

[0122] Therefore, with this embodiment, it is possible to provide a chair having a suitable configuration that allows options to be attached to the backrest E.

[0123] That is, the nut member J can be held in the nut holding recess nt that is open only in the up-down and forward directions in the backrest E. Therefore, in this embodiment, the work of holding the nut member J in the nut holding recess nt can be smoothly performed, which contributes to reducing the time required for the worker to attach the nut member J. In other words, the chair of this embodiment can provide a suitable optional attachment structure for the backrest E.

[0124] Furthermore, if a nut retaining recess nt is formed in the upper frame material 3 of the backrest E, options can be attached. This allows for excellent freedom in designing the upper frame material 3, which is a frame material with a restricted front-to-rear dimension (front-to-rear width). Since the upper frame material 3 is a part that is easily visible to the user, if the upper frame material 3 has a restricted front-to-rear dimension, it can contribute to the creation of an excellent appearance.

[0125] The boss portion j1 ​​of the nut member J is received in the nut retaining recess nt through the front open portion kh3.

[0126] Therefore, an operator can easily attach the nut member J to the nut holding recess nt by utilizing the front open portion kh3.

[0127] In particular, in this embodiment, the backrest E is formed by tensioning the tension member P that can form the backrest surface pm to the upper frame portion w1 that is the frame portion. The nut holding recess nt is provided in the upper frame material 3 that extends in the left-right direction and forms the upper frame portion w1.

[0128] For this reason, the worker will attach the nut member J to the nut retaining recess nt of the upper frame material 3 from the rear side of the backrest E through the cavity (upper cavity sa) of the upper frame-shaped portion w1 so as not to be obstructed by the upholstery member P. However, with the configuration of this embodiment, the nut member J can be easily attached without having to be precisely aligned with the nut retaining recess nt.

[0129] The option is provided with a movement restricting portion ks that can restrict forward movement by engaging with the backrest E.

[0130] For this reason, even if a strong external force acts on the option, the nut member J held in the nut retaining recess nt will be maintained in the appropriate position without jumping out from the nut retaining recess nt toward the front opening portion kh3.

[0131] The upper frame material 3 includes an outer frame portion 31 having a tension member mounting groove mz formed therein for mounting the tension member P, and an inner frame portion 32 disposed below the outer frame portion 31. The inner frame portion 31 is provided with a nut holding recess nt.

[0132] As a result, the nut retaining recess nt can be covered and hidden by the tension member P when viewed from the front side, and is disposed in a suitable position that is not easily noticeable from the outside.

[0133] The flange j2 of the nut member J extends longitudinally in the left-right direction from the upper end of the boss j1. Therefore, even if the thickness dimension in the front-rear direction of the upper frame material 3 is short, a foothold that can support the flange j2 from below can be easily secured, and the flange j2 can be suitably engaged with the upper frame material 3.

[0134] Options include a backrest extension member F for extending the backrest pm or a hanger G for hanging clothes.

[0135] Therefore, the backrest extension member F or the hanger G can improve convenience for the user of the chair.

[0136] It should be noted that the present invention is not limited to the embodiment described above in detail.

[0137] The backrest may have any configuration. In other words, the backrest is not limited to the one in which a tension member is stretched over a frame-shaped portion as shown in the above-mentioned embodiment, but may have a backrest main body mainly made of synthetic resin, for example.

[0138] The option may be anything that can be attached to the backrest and used. The option is not limited to the backrest surface extension member and hanger as shown in the above embodiment, but may be, for example, a headrest.

[0139] The nut member may have any shape as long as it includes a boss portion and a flange portion, and the specific shape of the nut member may be set in various ways without departing from the spirit of the present invention.

[0140] The optional movement restricting feature may be any part capable of engaging with the backrest to restrict forward movement.

[0141] Furthermore, the specific configuration of each part is not limited to the above embodiment, and various modifications are possible without departing from the spirit of the present invention. [Explanation of symbols]

[0142] E…Backrest F…Backrest extension member (optional) G…Hanger (optional) nt…Nut retaining recess J…Nut material j1…Boss part j2…Tsubabe

Claims

1. A chair in which an option can be attached to the backrest, The backrest is provided with a nut holding recess that is formed with an upper opening portion that is open upward, a lower opening portion that is open downward, and a front opening portion that is open forward and that can hold a nut member, the nut member includes a boss portion that is accommodated in the nut holding recess and has a thread groove on its inner peripheral surface, and a flange portion that is connected to the boss portion and can engage with a portion that forms the upper opening portion, The option is provided with a screw insertion hole penetrating in the vertical direction, The chair is configured so that the option can be attached to the backrest by screwing a screw inserted into the screw insertion hole from below into the boss portion.

2. 2. The chair according to claim 1, wherein the boss portion is received within the nut retaining recess through the front opening.

3. 3. The chair according to claim 1, wherein the option includes a movement restricting portion that can restrict forward movement of the option by engaging with the backrest.

4. The backrest is provided with a tension member that can form a backrest surface and is tensioned against the frame-shaped portion, 4. The chair according to claim 1, 2 or 3, wherein the nut holding recess is provided in an upper frame member extending in the left-right direction and constituting the frame-shaped portion.

5. The upper frame member has an outer frame portion in which a tension member mounting groove for mounting the tension member is formed, and an inner frame portion disposed below the outer frame portion, 5. The chair of claim 4, wherein said inner frame portion is provided with said nut retaining recesses.

6. 6. The chair according to claim 1, 2, 3, 4 or 5, wherein the flange portion extends longitudinally in the left-right direction from an upper end portion of the boss portion.

7. 7. The chair according to claim 1, 2, 3, 4, 5 or 6, wherein the option is a backrest extension member for extending the backrest or a hanger for hanging clothes.

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