Chair

Abstract

The invention provides a chair which is not only provided with a body weight sensing type locking mechanism, but also can adopt a forward leaning posture. A chair is provided with: legs; a support base (B) attached to the upper end of the leg; a seat (C) disposed on the support base (B); and a back support body (D) rotatably supported by the support base (B) via a main shaft (j1) and having a seat engagement shaft (j3) disposed in front of the main shaft (j1) and capable of engaging with the seat (C), the chair being provided with a weight-sensing-type lock mechanism (Rc) configured so as to be capable of raising the seat (C) upward by means of the seat engagement shaft (j3) in accordance with the backward tilting movement of the back support body (D). The chair is provided with a seat forward leaning mechanism (G) capable of changing the posture of the seat (C) around a seat clamping shaft (j3) between a normal posture (M) and a forward leaning posture (F) leaning forward than the normal posture (M).

Description

Technical Field

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

[0002] Conventionally, various chairs used in offices are known (for example, refer to Patent Document 1).

[0003] Among such chairs, there are chairs whose seats can be tilted backward while moving in a manner of sinking backward and downward in conjunction with the backward tilting movement of the backrest. Moreover, recently, among such chairs, there have begun to appear chairs equipped with a function of being able to change postures between a normal posture in which the seat surface is set to be approximately horizontal and a forward tilting posture in which the seat surface is tilted forward from the normal posture.

[0004] However, in conventional chairs, since the rotation shaft for tilting the seat forward is disposed at the rear end of the seat, it is difficult to tilt the seat forward flexibly in accordance with the sitting posture of the seated person.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2015-180263 Summary of the invention

[0008] Problems to be solved by the invention

[0009] The present invention has been made in view of the above-mentioned situation, and at least provides a chair in which a seat can be appropriately tilted forward.

[0010] Means for solving problems

[0011] That is, the present invention has the following configuration.

[0012] The invention described in technical solution 1 is a chair, comprising: legs; a supporting base, which is mounted on the upper end of the legs; a seat, which is arranged on the supporting base; and a back support body, which is rotatably supported on the supporting base via a main shaft and has a seat engaging axis which is arranged at a position forward of the main shaft and can engage with the seat, the chair is provided with a weight-sensing locking mechanism, which is configured to lift the seat upward using the seat engaging axis as the back support body tilts backward, and the chair is provided with a seat forward tilt mechanism, which can change the posture of the seat around the seat engaging axis between a normal posture and a forward tilt posture that is tilted forward than the normal posture.

[0013] According to the chair described in Technical Solution 1, in the invention described in Technical Solution 2, a front axis extending in the left-right direction is interposed between the front part of the supporting base and the front part of the seat, and the seat forward tilting mechanism is configured to enable the front axis to be relatively displaced in the up-down direction relative to the seat supported so as to be rotatable around the seat engaging axis.

[0014] According to the chair described in Technical Solution 2, in the invention described in Technical Solution 3, the seat forward tilting mechanism is provided with a spring between the seat and the front axle, and the spring applies force to the seat in the direction of the normal posture with the front axle as a foothold. When the spring is compressed to overcome the force under the load of the seated person, the seat can adopt the forward tilting posture.

[0015] According to the chair described in Technical Solution 3, in the invention described in Technical Solution 4, the seat comprises: a seat supporting portion, the seat supporting portion has an axis retaining portion capable of retaining the seat engaging axis and has an upper spring supporting portion, the upper spring supporting portion supports the upper end portion of the spring; and a seat main body, the seat main body being supported by the seat supporting portion.

[0016] According to the chair described in Technical Solution 4, in the invention described in Technical Solution 5, the seat supporting part comprises: a seat supporting part main body; and an upper spring supporting component, the upper spring supporting component is constructed to be loadable and removable relative to the seat supporting part main body and has the upper spring supporting part.

[0017] According to the chair of claim 5, in the invention of claim 6, the upper spring receiving member is configured to be attachable to and detachable from the seat receiving portion main body without using a fixing member.

[0018] According to the chair described in Technical Solution 3, in the invention described in Technical Solution 7, a lower spring-receiving component is installed on the front axle, and the lower spring-receiving component has a lower spring-receiving portion, and the lower spring-receiving portion receives the lower end portion of the spring.

[0019] According to the chair described in Technical Solution 7, in the invention described in Technical Solution 8, the lower spring-bearing member has the lower spring-bearing portion at the upper part and has a seat engaging portion at the lower part, the front-to-rear width dimension of which gradually shortens toward the bottom when viewed from the side, and a lower spring-bearing member retaining portion is provided on the seat, and the lower spring-bearing member retaining portion is recessed in a manner corresponding to the shape of the seat engaging portion and is configured to be able to fit into the seat engaging portion in the normal posture.

[0020] According to the chair described in Technical Solution 8, in the invention described in Technical Solution 9, the supporting base has a supporting base main body, the supporting base main body has a bottom wall portion and left and right side wall portions erected from the left and right end portions of the bottom wall portion, and the lower spring bearing member retaining portion is arranged at a position closer to the outside than the left and right side wall portions.

[0021] Effects of the Invention

[0022] As described above, according to the present invention, it is possible to provide at least a chair in which the seat can be appropriately tilted forward. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a perspective view showing one embodiment of the present invention.

[0024] Figure 2 It is a front view of this embodiment.

[0025] Figure 3 is a rear view of this embodiment.

[0026] Figure 4 It is a right side view of this embodiment.

[0027] Figure 5 It is a left side view of this embodiment.

[0028] Figure 6 is a top view of this embodiment.

[0029] Figure 7 It is a bottom view of this embodiment.

[0030] Figure 8 It is a perspective view of this embodiment.

[0031] Fig. 9 It is an exploded perspective view of this embodiment.

[0032] Fig.10 It is an exploded perspective view of this embodiment.

[0033] Fig.11 It is an exploded perspective view of this embodiment.

[0034] Fig.12 It is an exploded perspective view of this embodiment.

[0035] Fig.13 It is an exploded perspective view of this embodiment.

[0036] Fig.14 It is a left side view of this embodiment.

[0037] Fig.15 It is a perspective view of this embodiment.

[0038] Fig.16 It is a right side view of this embodiment.

[0039] Fig.17 It is a left side view of this embodiment.

[0040] Fig.18 is a top view of this embodiment.

[0041] Fig.19 is a top view of this embodiment.

[0042] Fig. 20 It is a left side view of this embodiment.

[0043] Fig.21 It is a left side view of this embodiment.

[0044] Fig. 22 It is a left side view of this embodiment.

[0045] Fig.23 It is a left side view of this embodiment.

[0046] Fig.24 It is a working explanation diagram of the elbow rest in this embodiment.

[0047] Fig.25 It is a working explanation diagram of the elbow rest in this embodiment.

[0048] Fig.26 It is a working explanation diagram of the elbow rest in this embodiment.

[0049] Fig. 27 It is a working explanation diagram of the elbow rest in this embodiment.

[0050] Fig.28 It is a working explanation diagram of the elbow rest in this embodiment.

[0051] Fig.29 It is a working explanation diagram of the elbow rest in this embodiment.

[0052] Fig.30 It is a perspective view of this embodiment.

[0053] Fig.31 It is a perspective view of this embodiment.

[0054] Fig.32 It is an exploded perspective view of this embodiment.

[0055] Fig.33 yes Fig.30 AA line section view in.

[0056] Fig.34 It is a perspective view of this embodiment.

[0057] Fig.35 yes Fig.34 The view in direction B.

[0058] Fig.36 yes Fig.30 CC line section view in.

[0059] Fig.37 It indicates the state of the seat leaning forward. Fig.36 The corresponding cross-sectional view.

[0060] Fig.38 yes Fig.30 DD line section view in.

[0061] Fig.39 It indicates the state of the seat leaning forward. Fig.38 The corresponding cross-sectional view.

[0062] Fig.40 It is a perspective view of this embodiment.

[0063] Fig.41 It is a perspective view of this embodiment.

[0064] Fig.42 It is an exploded perspective view of this embodiment.

[0065] Fig.43 It is a perspective view of this embodiment.

[0066] Fig.44 yes Fig.41 EE line cross-sectional view.

[0067] Fig.45 It is an exploded perspective view of this embodiment.

[0068] Fig.46 It is an exploded perspective view of this embodiment.

[0069] Fig.47 It is a right side view of this embodiment.

[0070] Fig.48 It is a right side view of this embodiment.

[0071] Fig.49 It is a right side view of this embodiment.

[0072] Fig.50 It is a right side view of this embodiment.

[0073] Fig.51 It is an exploded perspective view of this embodiment.

[0074] Fig.52 It is an exploded perspective view of this embodiment.

[0075] Fig.53 yes Figure 2 FF line section view.

[0076] Fig.54 yes Fig.53 Enlarged view of part G in FIG.

[0077] Fig.55 It is a central cross-sectional view showing a headrest according to another embodiment.

[0078] Fig.56 It is an exploded perspective view of this embodiment.

[0079] Fig.57 It is an exploded perspective view of this embodiment.

[0080] Fig.58 It is a partially enlarged cross-sectional view for explaining the up-down position changing mechanism in this embodiment.

[0081] Description of Reference Numerals

[0082] A…Legs

[0083] B…Support base

[0084] C… Block

[0085] D…Back support

[0086] G…Seat forward tilt mechanism

[0087] j1…spindle

[0088] j2…front axle

[0089] j3…seat clamp shaft

[0090] Rc…locking mechanism

[0091] (M)…Usually

[0092] (F)…Forward Leaning Posture DETAILED DESCRIPTION

[0093] Below, refer to Figure 1 to Figure 54 An embodiment of the present invention will be described.

[0094] This embodiment applies the present invention to a swivel chair for office use (hereinafter simply referred to as a "chair") that is preferably used in an office or the like.

[0095] The chair comprises: legs A; a support base B, which is mounted on the upper end of the legs A and can rotate; a seat C, which is arranged on the support base B; a back support body D, which is rotatably supported on the support base B via a main axis j1 and has a seat engaging axis j3 which is arranged at a position forward of the main axis j1 and can engage with the seat C; a backrest E, which is supported on the back support body D; a headrest I, which is supported on the backrest E; and left and right armrests K, which are mounted on the seat C.

[0096] The chair is provided with a weight-sensing locking mechanism Rc and a seat forward tilting mechanism G. The weight-sensing locking mechanism Rc is configured to be able to lift the seat C upward using the seat engaging axis j3 as the back support body D tilts backward, and the seat forward tilting mechanism G is capable of changing the posture of the seat C around the seat engaging axis j3 between a normal posture (M) in which the seating surface is approximately horizontal and a forward tilting posture (F) that is tilted forward of the normal posture (M).

[0097] The chair body is mainly composed of legs A, a support base B, a seat C, a back support body D, and a backrest E. That is, the chair of this embodiment includes a chair body, and armrests K and a headrest I attached to the chair body. The backrest E includes a lumbar support e4 configured to be attachable and detachable to a front back frame e2 as a back frame without using a fixing member.

[0098] Hereinafter, each component of the chair will be described in detail.

[0099] <<Leg A>>

[0100] The legs A include a plurality of leg blades a1 having casters a3 at their top ends and leg struts a2 erected at the base ends of the leg blades a1. The leg struts a1 include gas springs (not shown). The leg struts a1 can be extended and retracted in the vertical direction by a seat lifting mechanism (not shown).

[0101] <<Support base B>>

[0102] The support base B supports the seat C, the back support body D and the backrest E.

[0103] The support base B is mainly composed of a support base body b1 which is an integrally molded product of synthetic resin and is open upward. The support base body b1 is connected to the upper end of the leg support a2.

[0104] The support base body b1 includes a bottom wall portion b2 connected to the upper end of the leg support a2, left and right side wall portions b3 erected from the left and right ends of the bottom wall portion b2, and a front wall portion b4 erected from the front end of the bottom wall portion b2 and arranged between the front ends of the left and right side wall portions b3.

[0105] The left and right side walls b3 are provided with a front axle support b5, which can support the front axle j2 so that it can slide and move in conjunction with the operation of the locking mechanism Rc. The front axle support b5 is in a rearwardly inclined posture and is provided in the shape of a long hole extending in the vertical direction. The support base B can support the front part of the seat C through the front axle j2 and the components of the seat forward tilting mechanism G so that it can sink.

[0106] <<Seat C>>

[0107] The seat C is arranged on the supporting base B.

[0108] The seat C is arranged so as to be movable and change its posture between a normal posture (M) and an upward posture (not shown) moved to a position higher and rearward than the normal posture (M) by the operation of a weight-sensing locking mechanism Rc.

[0109] The seat C is arranged so that, by the operation of the seat forward tilting mechanism G, it can be moved and its posture can be changed between a normal posture (M) and a forward tilting posture (F) that is tilted forward than the normal posture (M).

[0110] The seat C is a seat made of synthetic resin, and has a seat supporting portion c1 and a seat main body c2. The seat supporting portion c1 has a seat engaging shaft retaining portion 16 as an shaft retaining portion capable of retaining the seat engaging shaft j3 and has an upper spring supporting portion 21a. The upper spring supporting portion 21a supports the upper end portion of the spring wg constituting the seat tilting mechanism G. The seat main body c2 has a seating surface and is supported by the seat supporting portion c1.

[0111] The front portion of the seat C is movably supported via the front shaft j2 relative to the support base B. The front-rear center portion of the seat C is supported by the support base B via a back support body D that holds a seat engagement shaft j3.

[0112] The front-rear center portion of the seat C is rotatably supported about the seat engagement axis j3. The front portion of the seat C rotatably about the seat engagement axis j3 is vertically movable about the front axis j2.

[0113] <Seat receiving part c1>

[0114] The seat receiving portion c1 has a shell-like shape having a size capable of supporting the seat body c2 at the upper portion. The seat receiving portion c1 can support the seat body c2 so as to be slidable in the front-rear direction.

[0115] The seat supporting portion c1 comprises: a seat supporting portion main body 1, which constitutes the main part; an upper spring supporting member 2, which is configured to be loadable and unloadable relative to the seat supporting portion main body 1 and has an upper spring supporting portion 21a; and a retaining portion forming member 3, which is configured to be loadable and unloadable relative to the seat supporting portion main body 1 and forms a part of a seat engaging shaft retaining portion 16 which serves as a portion for retaining the seat engaging shaft j3.

[0116] A front axle arrangement space cs is provided at the front portion of the seat receiving portion c1 for enabling the front axle j2 to be relatively moved in the up-down direction with respect to the seat C. More specifically, a front axle arrangement space cs is provided at the front portion of the seat receiving portion c1 for enabling the front axle j2, which is arranged at the lower limit position of the front axle support portion b5 in the support base B in the normal posture (M) and is fixed at the lower limit position, to be relatively displaced in the up-down direction with respect to the seat C that rotates around the seat engagement axis j3.

[0117] [Seat receiving part main body 1]

[0118] The seat supporting part main body 1 comprises: a seat supporting part base 11, which has a lower supporting area formed on the upper surface thereof which can be attached to the lower surface of the supporting member c21; a front lower extension wall 12, which is arranged in the left-right central part of the front part of the lower surface side of the seat supporting part base 11; left and right lower extension walls 13, which are extended downward in pairs in the left-right central part of the lower surface side of the seat supporting part base 11 and extend toward the rear from both end parts of the front lower extension wall 12; and a rear lower extension wall 14, which is arranged in the left-right central part of the rear part of the lower surface side of the seat supporting part base 11 and is arranged to connect the rear parts of the left and right lower extension walls 13.

[0119] (Seat receiving portion base 11)

[0120] The seat receiving part base 11 is provided with a plurality of ribs extending in the front-back direction and the left-right direction for ensuring rigidity on the upper surface side. The seat receiving part base 11 is provided with a lower receiving area which can be attached and slidably connected to the lower surface of the supporting member c21 in the seat body c2 by using the upper end portions of the ribs erected on the upper surface side.

[0121] A front axle abutment portion 15a is provided at the front of the center portion in the front-rear direction of the seat receiving portion base 11. The front axle abutment portion 15a is capable of abutting against the front axle j2 when the seat C takes a forward tilting posture (F) at a position facing the front axle arrangement space cs. The front axle abutment portion 15a defines the limit position when the seat C is tilted forward (the lower limit position of the front portion of the seat C when the seat C is tilted forward).

[0122] The front axle contact portions 15a are formed in pairs at the lower end of the protruding portion 15 protruding downward from the seat receiving portion base 11. The front axle contact portions 15a are partially arc-shaped and recessed to correspond to the outer peripheral surface of the front axle j2 in a side view.

[0123] A seat engagement shaft holding portion 16 that can rotatably hold the seat engagement shaft j3 is provided on the lower surface side of the front-rear center portion of the seat receiving portion base 11. The seat engagement shaft holding portion 16 is provided inside the left and right lower extension walls 13.

[0124] In this embodiment, the seat engaging shaft retaining portion 16 is composed of a seat engaging shaft retaining portion 16a formed on one side of the seat receiving portion base 11, and a seat engaging shaft retaining portion 31 formed on the other side of the retaining portion forming member 3 which is separate from the seat receiving portion base 11 and mounted on the seat receiving portion base 11.

[0125] In this embodiment, the seat engaging shaft holding portion 16 is formed by cooperating not only the seat receiving portion main body 1 but also the holding portion forming member 3 which is a member separate from the seat receiving portion main body 1. Therefore, compared with a configuration in which the seat engaging shaft holding portion is formed only by an integrally formed product, not only can the seat engaging shaft j3 included in the back support body D be smoothly assembled to the seat engaging shaft holding portion 16 of the seat receiving portion c1, but also a minute gap which may cause looseness is unlikely to be generated between the seat engaging shaft j3 and the seat receiving portion c1.

[0126] The holding portion forming member 3 is installed on the seat receiving portion base 11 by being inserted into the holding portion forming member mounting portion 17 having a slit-shaped insertion port on the upper surface side of the seat receiving portion base 11. The operation of inserting the holding portion forming member 3 relative to the holding portion forming member mounting portion 17 is performed after the seat engaging shaft j3 is temporarily engaged with the seat engaging shaft holding portion 16a formed on one side of the seat receiving portion main body 1.

[0127] An upper spring receiving member mounting portion 18 for mounting the upper spring receiving member 2 constituting the seat forward tilt mechanism G is provided at the front portion of the seat receiving portion base 11. The upper spring receiving member mounting portion 18 is formed at a corresponding portion of the seat receiving portion base 11 in such a manner that the upper spring receiving member 2 can be disposed on the front axle j2.

[0128] The upper spring receiving member mounting portion 18 can support the upper spring receiving member 2 in a state where the spring wg constituting the seat forward tilting mechanism G is biased upward.

[0129] The upper spring-bearing member mounting portion 18 includes: a front retaining portion 18a, which can retain a front engaging portion 22 provided at the front portion of the upper spring-bearing member 2 so as to be unable to move upward; and a rear retaining portion 18b, which can retain a rear engaging portion 23 provided at the rear portion of the upper spring-bearing member 2 so as to be unable to move upward and to move in the front-rear direction.

[0130] The rear holding portion 18 b is provided with a protrusion engaging hole 18 c through which an engaging protrusion 25 protruding from the rear engaging part 23 of the upper spring receiving member 2 can be engaged and penetrated in the up-down direction.

[0131] (Left and right lower extension walls 13)

[0132] The left and right lower extension walls 13 are provided with lower spring receiving member holding portions 13 a that are recessed downward and open upward.

[0133] The lower spring receiving member holding portion 13 a is recessed to correspond to the shape of the seat engaging portion 42 provided at the lower spring receiving member 4 and is configured to be engageable with the seat engaging portion 42 in the normal posture (M).

[0134] That is, the lower portion of the lower spring receiving member holding portion 13 a is formed so that the inner dimension in the front-rear direction gradually becomes shorter toward the lower side when viewed from the side.

[0135] The lower spring receiving member holding portion 13 a is disposed on the left and right lower extending walls 13 located outside the left and right side wall portions b3 constituting the support base body b1 .

[0136] In addition, the structure of the lower spring receiving member 4 will be described in detail later.

[0137] [Upper spring receiving member 2]

[0138] The upper spring receiving member 2 is configured to be detachable relative to the seat receiving portion body 1 without using a fixing member. The upper spring receiving member 2 is arranged in pairs on the left and right. The upper spring receiving member 2 is configured to be detachable relative to the upper spring receiving member mounting portion 18, which is arranged in pairs on the left and right on the seat receiving portion base 11 in the seat receiving portion body 1.

[0139] The upper spring-bearing member 2 comprises: a spring-bearing member main body 21, which is arranged in the middle part in the front-to-back direction and has an upper spring-bearing portion 21a on the lower surface side for bearing the upper end of the spring wg; a front snap-fitting portion 22, which protrudes forward from the front end of the spring-bearing member main body 21; and a rear snap-fitting portion 23, which extends rearward from the rear end of the spring-bearing member main body 21 and has a snap-fitting protrusion 25 protruding upward at its extending end.

[0140] In this embodiment, the upper spring receiving portion 21 a has a substantially smooth surface shape.

[0141] [Retention portion forming member 3]

[0142] The holding portion forming member 3 is configured to be attachable to and detachable from the seat receiving portion main body 1 without using a fixing member. The holding portion forming member 3 is arranged in pairs on the left and right. The holding portion forming member 3 is configured to be attachable to and detachable from the holding portion forming member mounting portion 17 which is provided in pairs on the left and right of the seat receiving portion base 11 in the seat receiving portion main body 1.

[0143] The holding portion forming member 3 is substantially L-shaped when viewed from the side. The holding portion forming member 3 includes: a seat engaging shaft holding portion 31 on the other side, which is provided at the rear portion and has a partially arc-shaped edge portion that can abut against the outer peripheral surface of the seat engaging shaft j3; and an engaging portion 32, which is provided at the front portion and can engage with a not-shown anti-disengagement engaging portion provided on the holding portion forming member mounting portion 17.

[0144] <Seat body c2>

[0145] The seat body c2 is supported so as to be slidable in the front-rear direction with respect to the seat receiving portion c1.

[0146] The seat body c2 comprises: a supporting member c21, which is in a shell shape and has dimensions in the front-to-back direction and the left-to-right direction that are larger than the seat supporting portion c1; a seat cushion (not shown), which is supported by the supporting member c21 and has dimensions in the front-to-back direction and the left-to-right direction that are larger than the supporting member c21; and a seat tensioning fabric c22, which covers the seat cushion and the peripheral edge of the supporting member c21 from the outside.

[0147] <Front axle j2>

[0148] A front axle j2 extending in the left-right direction is interposed between the front portion of the support base B and the front portion of the seat C. The front axle j2 moves up and down at the long hole-shaped front axle support b5 extending obliquely from the left and right side walls b3 of the support base body b1 as the backrest E tilts backward.

[0149] In this embodiment, the lower spring receiving member 4 receiving the lower end of the spring wg constituting the seat forward tilt mechanism G is relatively rotatably mounted on the front axle j2. The lower spring receiving member 4 is mounted on both left and right ends of the front axle j2.

[0150] The lower spring bearing member 4 is provided with a front axle holding hole 43 which penetrates in the left-right direction and into which the front axle j2 is inserted. The lower spring bearing member 4 comprises: a lower spring bearing portion 41 which is provided at the upper portion and has a shape portion which engages with the lower end portion of the spring wg; and a seat engaging portion 42 which is provided at the lower portion and has the front axle holding hole 43 in the central portion in the front-rear direction and is formed so that the front-rear width dimension gradually shortens downward in a side view.

[0151] <Back support body D>

[0152] The back support body D is interposed between the support base B and the backrest E, and between the support base B and the seat C.

[0153] The back support body D comprises: a pair of left and right arms d1, which are in the shape of an upright plate extending in the front-to-back direction and are pivotally supported (pivotally supported) on the support base body b1 via a main shaft j1; a connecting member d2, which is in the shape of an upright plate connecting the rear parts of the pair of left and right arms d1; a seat engaging shaft j3, which is supported on the front and upper parts of the pair of left and right arms d1 and extends in the left-right direction; a pair of left and right supporting shaft supporting members d3, which are arranged on the central part side of the pair of left and right arms d1 in the left-to-right direction and the upper part is connected to the seat engaging shaft j3; and a supporting shaft d4, which is connected between the lower parts of the pair of left and right supporting shaft supporting members d3.

[0154] <arm d1>

[0155] The left and right arms d1 are disposed outside the left and right side walls b3 of the support base body b1.

[0156] The left and right arms d1 include: left and right arm bodies d11, which extend in the front-to-back direction and can support the main axis j1 at the front end; and left and right forearm parts d12, which extend integrally from the front end of the left and right arm bodies d11 obliquely forward and upward and support the seat engaging axis j3 engaged with the seat C at the upper end.

[0157] The rear parts of the left and right arm bodies d11 are connected by a connecting member d2. The rear ends of the left and right arm bodies d11 are provided with a protruding portion dt that protrudes backward from the connecting member d2. The protruding portion dt can be embedded in a back support body connecting portion (not shown) provided at the lower end of the backrest E.

[0158] <Joining member d2>

[0159] The left and right ends of the connecting member d2 are rigidly connected to the inner side of the left and right arm bodies d11 by welding. The connecting member d2 is provided with a nut portion n3 which is screwed with a screw (not shown) for attaching the backrest E.

[0160] Furthermore, the back support body D is provided with a backrest mounting portion d5 formed by rear portions of the left and right arm bodies d11 and the connecting member d2 in a substantially H-shape in a plan view or a bottom view.

[0161] <Seat card axis j3>

[0162] The seat engagement axis j3 extends in the left-right direction. The seat engagement axis j3 can move about the support axis j1 in conjunction with the rearward tilting movement of the backrest E, that is, can move upward and backward. The seat engagement axis j3 engages with a seat engagement axis holding portion 16 provided at the center of the seat receiving portion c1 in the front-back direction and the left-right direction.

[0163] <Support shaft support member d3>

[0164] The left and right support shaft support members d3 are plate-shaped. The left and right support shaft support members d3 support the support shaft d4 pressed by the reaction force spring wd. The left and right support shaft support members d3 are supported by the main shaft j1 and the seat engagement shaft j3. The left and right support shaft support members d3 rigidly connect the two ends of the support shaft d4 at the lower end.

[0165] <Support shaft d4>

[0166] The support shaft d4 extends in the left-right direction and is disposed inside the support base body b1. The support shaft d4 is a portion that directly receives the biasing force of the reaction force spring wd disposed inside the support base body b1.

[0167] <<Backrest E>>

[0168] The backrest E is connected to the back support body D. The entire backrest E can be tilted rearwardly about a main axis j1 provided in the support base B. The backrest E is supported by the back support body D so as to be rotatable about the main axis j1 of the support base B.

[0169] The backrest E comprises: a back frame e1; a front back frame e2, which is arranged on the front side of the back frame e1; a tensioning member e3, which is tensioned on the front back frame e2; a lumbar support e4, which is arranged behind the tensioning member e3 and mounted on the front back frame e2; and a positioning mechanism e5, which can change the position of the front back frame e2 supporting the lumbar support e4 and the tensioning member e3 relative to the back frame e1 in the front-to-back direction.

[0170] <Back frame e1>

[0171] The back frame e1 includes: left and right side frame portions e11, which extend in the up-down direction; an upper frame portion e12, which connects the upper end portions of the left and right side frame portions e11; left and right lower frame portions e13, which extend forward from the lower end portions of the left and right side frame portions e11, respectively; and a lower connecting portion e14, which connects the lower end portions of the left and right lower frame portions e13.

[0172] A bearing protrusion e15 having a shaft hole eh constituting a positioning mechanism e5 is provided on the upper surface side of the left and right lower frame portions e13 .

[0173] The lower end portion of the back frame e1, that is, the front end portions of the left and right lower frame portions e13 and the lower connecting portion e14 are attached to the backrest attachment portion d5 of the back support body D.

[0174] <Front back frame e2>

[0175] The front back frame e2 is supported by the back frame e1. The front back frame e2 has a continuous frame shape when viewed from the front.

[0176] The front back frame e2 can selectively take a front position (f), a rear position (r) located rearward of the front position (f), and an intermediate position (m) located between the front position (f) and the rear position (r) by the positioning mechanism e5.

[0177] The front back frame e2 includes left and right side frame portions e21 extending in the up-down direction, an upper frame portion e22 connecting the upper ends of the left and right side frame portions e21, and a lower frame portion e25 connecting the lower ends of the left and right side frame portions e21.

[0178] A shaft holding portion e23 is protrudingly provided at the lower end of the left and right side frame portions e21 for holding the distal end shafts L21 of the left and right links L constituting the positioning mechanism e5. The shaft holding portion e23 has a C-shaped portion in side view for holding the distal end shaft L21.

[0179] The lower frame portion e24 constituting the left and right side frame portions e21 is formed to gradually shift inward as it goes downward. An attachment structure PT for attaching the attachment portion e42 of the lumbar support e4 without using a fixing member is provided on the front surface side of the lower frame portion e24.

[0180] The mounting structure PT comprises: inner and outer insertion portions pt1, pt2 for mounting a substrate portion e45 of a mounting portion e42 in a lumbar support member e4; inner and outer clamping walls pt3, pt4 for clamping a front protrusion e46 of the mounting portion e42 in a lumbar support member e4; and an embedded portion pt5 capable of being embedded in a recessed portion e47 of the mounting portion e42 in a lumbar support member e4.

[0181] A tool insertion portion pt6 is formed in the middle portion in the left-right direction of the inner fitting portion pt5 protruding from the lower frame portion e24. The tool insertion portion pt6 is configured to be slot-shaped so that a tool (not shown) can be inserted when the mounting portion e42 of the lumbar support member e4 is removed from the front back frame e2. Since the tool insertion portion pt6 of the inner fitting portion pt5 is provided, the operation of removing the lumbar support member e4 from the front back frame e2 can be smoothly performed.

[0182] Furthermore, the front back frame e2 is configured so as not to be detached from the distal end shafts L21 of the left and right links L unless it takes a predetermined posture.

[0183] That is, Fig.50 As schematically shown in the figure, the structure is such that the connection between the axis retaining portion e23 of the front back frame e2 and the top axis L21 of the connecting rod L will not be released (the front back frame e2 will not be detached from the top axis L21) unless the following operation is performed: the left and right connecting rods L are brought into a front posture (F) and the upper frame portion e22 of the front back frame e2 is detached from the upper frame portion e12 of the back frame e1, and then the entire front back frame e2 is rotated to a certain extent around the top axis L21 in a forward-leaning manner.

[0184] <Tension member e3>

[0185] The tension member e3 is a member formed by fixing a peripheral member made of synthetic resin (not shown) to the peripheral edge of a mesh fabric that can form a backrest by sewing or the like. The tension member e3 is tensioned on the front surface of the front back frame e2 by inserting or attaching (joining) the end of the peripheral member into a mounting groove provided around the front back frame e2.

[0186] The tension member e3 is located in front of the lumbar support e4. The tension member e3 can restrict the lumbar support e4 from moving forward relative to the front back frame e2, that is, prevent the lumbar support e4 from falling off relative to the front back frame e2.

[0187] <Lumbar support e4>

[0188] The lumbar support member e4 is for emphasizingly supporting the lumbar portion of the seated person from the back side.

[0189] The lumbar support e4 is disposed between the left and right side frame portions e21 of the front back frame e2. Both ends of the lumbar support e4 are attached to the left and right lower frame portions e24 constituting the left and right side frame portions e21.

[0190] The lumbar support e4 includes a curved plate-shaped lumbar support body e41 that receives a load from a user, and mounting portions e42 provided at both ends of the lumbar support body e41. The lumbar support e4 is integrally molded from a synthetic resin.

[0191] The lumbar support body e41 includes a main portion e43 located in the middle of the left-right direction and having a substantially horizontally long rectangular shape when viewed from the front, and connecting portions e44 extending obliquely downward and outward from the left and right lower corners of the main portion e43. A mounting portion e42 is provided at the extending end of the connecting portion e44.

[0192] The mounting portion e42 is configured to be attachable and detachable relative to the front portion of the lower frame portion e24 without using a fixing member.

[0193] The mounting portion e42 comprises: a plate-shaped substrate portion e45, which is extended from the extending end of the connecting portion e44 with approximately the same width dimension; a front protrusion e46, which protrudes forward from the central portion in the width direction of the substrate portion e45; and a recessed portion e47, which is recessed in the central portion in the width direction of the rear surface side of the substrate portion e45.

[0194] The left and right end portions of the substrate portion e45 are inserted into the inner and outer insertion portions pt1 and pt2 formed in pairs on the inner and outer sides of the front portion of the lower frame portion e24 in the shape of slits. The front protrusion e46 is sandwiched between the inner and outer clamping walls pt3 and pt4, which also serve as walls for forming the insertion portions pt1 and pt2 provided on the inner and outer sides of the lower frame portion e24. The recessed portion e47 is externally fitted into the inner fitting portion pt5 protruding from the lower frame portion e24.

[0195] The lumbar support member e4 is mounted from the back side to the front back frame e2 in a state where the tension member e3 is tensioned. That is, the mounting portion e42 of the lumbar support member e4 is lowered while being pressed against the back side of the tension member e3 from the back side of the backrest E, inserted between the tension member e3 and the lower frame portion e24, and engaged with the mounting structure PT provided on the lower frame portion e24, whereby the lumbar support member e4 is mounted to the front back frame e2.

[0196] On the other hand, when detaching the lumbar support e4 from the front back frame e2, the operation can be performed smoothly by inserting the tip of a tool (such as a flat-blade screwdriver, etc.) into a groove-shaped tool insertion portion pt6 provided in the embedded portion pt5 formed in the lower frame portion e24 of the front back frame e2.

[0197] <Positioning mechanism e5>

[0198] The positioning mechanism e5 can selectively position the lower end of the front back frame e2 at a front position (not shown), an intermediate position (not shown), or a rear position (r) by changing the posture of the left and right links L.

[0199] The positioning mechanism e5 is provided between the left and right lower frame portions e13 of the back frame e1 and the lower end portion of the front back frame e2.

[0200] The positioning mechanism e5 comprises: left and right links L, each of which has a base end axis L11 axially supported on a bearing protrusion e15 of a back frame e1 at a base end portion, and has a top end axis L21 held on an axis holding portion e23 of a front back frame e2 at a top end portion, and is rotatably connected relative to the back frame e1 and the front back frame e2; a link operating rod L3, which is arranged on the outer side of the left and right links L and can be rotated in a manner that can change the posture of the left and right links L to a front posture (F), a middle posture (M) and a rear posture (R); and a rotation limiting mechanism P, which is arranged between the link operating rod L3 and the bearing protrusion e15 and limits the relative rotation of the left and right links L relative to the bearing protrusion e15 when the link operating rod L3 is not operated.

[0201] [Left and right link L]

[0202] The left and right links L can rotate between a front posture (F) tilted forward and a rear posture (R) tilted backward. The left and right links L in this embodiment can rotate relative to the bearing protrusion e15 in three postures, namely Fig.49 and the front posture (F) shown at 50, Figure 1 , Figures 3 to 5 , Figure 7 and Figures 45-47 The rear posture (R) shown and Fig.48 The posture is maintained in an intermediate posture (M) between the front posture (F) and the rear posture (R) shown.

[0203] When an operating force for rotating the left and right links L around the base axis L11 is applied to the link operating lever L3, the left and right links L can rotate in the front-rear direction around the base axis L11. The left and right links L are mainly composed of an inner link member L1 and an outer link member L2.

[0204] The base end of the inner link member L1 is provided with a base end shaft L11 inserted into the shaft hole eh of the bearing protrusion e15. The top end of the inner link member L1 is provided with a fitting hole L12, which can be fitted with the protruding end of the top end shaft L21 protrudingly provided at the top end of the outer link member L2. The middle position of the inner link member L1 is provided with a screw insertion hole h4 for inserting a screw v4 for connecting the inner link member L1 with the outer link member L2.

[0205] A space L22 is formed at the inner side of the base end of the outer link member L2 for arranging the engaging member p2, the coil spring wp and the shaft member p3 constituting the rotation limiting mechanism P. A cylindrical portion L23 is protrudingly provided at the outer side of the base end of the outer link member L2, the cylindrical portion L23 being open to the outside with the axis aligned with the base end axis L11. The rod base end L31 of the link operating rod L3 is mounted on the cylindrical portion L23 in a manner that allows movement along the axis direction.

[0206] A top end shaft L21 held by the shaft holding portion e23 is provided at the top end of the outer link member L2. The protruding end of the top end shaft L21 is engaged with the engagement hole L12 provided in the inner link member L1. A nut portion n4 is provided at the middle position of the outer link member L2 to be screwed with a screw v4 passing through a screw insertion hole h4 of the inner link member L1.

[0207] [Link operating lever L3]

[0208] The connecting rod operating rod L3 includes: a rod base end portion L31, which extends in the left-right direction and has a nut portion n5 on the inner side that can be screwed with the shaft member p3 that constitutes the rotation limiting mechanism P, and an engaging portion is provided near the nut portion n5 and can engage with the protrusion L24 protruding from the inner circumferential surface of the cylindrical portion L23; and an operating piece L32, which extends in a direction intersecting the rod base end portion L31.

[0209] The rod base end L31 is configured to be movable in the axial direction relative to the cylindrical portion L23 provided on the left and right links L. On the other hand, the link operating rod L3 is engaged with the protrusion L24 on the inner circumferential surface of the cylindrical portion L23 provided in the outer link member L2 through the engagement portion L33 of the rod base end L31, so that the link L can be rotated around the base end axis L11.

[0210] [Rotation restriction mechanism P]

[0211] The rotation limiting mechanism P is provided between the link operating lever L3 and the bearing protrusion e15, and can limit the relative rotation of the left and right links L relative to the bearing protrusion e15 when the link operating lever L3 is not operated, and allow the link L to rotate relative to the bearing protrusion e15 when the user rotates the link operating lever L3.

[0212] The rotation limiting mechanism P comprises: an annular engaging portion p1, which is recessed on the outer side surface of the bearing protrusion e15 and is provided with engaging recesses p11 open in the direction of the shaft hole eh at a certain interval in a manner of surrounding the periphery of the shaft hole eh; an engaging member p2, which is provided with mountain-shaped protrusions p21 engaged with the engaging recesses p11 at a certain interval on the outer peripheral edge; a coil spring wp, which is arranged between the end surface on the opposite side of the bearing protrusion in the engaging member p2 and a foothold wall L25 provided at a position of the arrangement space L22 of the connecting rod member L2 facing the outside, and applies force to the engaging member p2 in the direction of the bearing protrusion e15; and an axial member p3, which can support the engaging member p2 so that it can move along the axial direction relative to the connecting rod operating rod L3.

[0213] When the user does not rotate the link operating lever L3, the coil spring wp urges the engagement member p2 toward the annular engagement portion p1. Therefore, the left and right links L do not rotate even when receiving external force from the front back frame e2.

[0214] Regarding the positioning mechanism e5, since the rotation limiting mechanism P is in effect, even if the left and right links L are subjected to external force from the front back frame e2 when they are in the middle posture (M), they will not move in the forward posture (F) direction or the rearward posture (R) direction unless the link operating lever L3 is operated.

[0215] On the other hand, when the user rotates the link operating lever L3, the rotation limiting mechanism P engages the annular engaging portion p1 with the engaging member p2, and the engaging member p2 overcomes the force of the coil spring wp and temporarily moves away from the annular engaging portion p1, thereby enabling the link L to rotate to a predetermined posture.

[0216] <<Handrail K>>

[0217] The armrests K are provided in pairs on the left and right sides of the chair body. The lower end portions of the armrests K are attached to the lower surface of the seat C constituting the chair body, more specifically, to the lower surface of the seat receiving portion c1.

[0218] The armrest K includes an armrest base KB including an elbow support 5 attached to a chair body and an elbow support portion 6 supported by the elbow support 5, and an elbow support 7 provided to be movable in the front-rear direction relative to the armrest base KB.

[0219] The armrest K includes an elbow support 5 attached to the chair body and an armrest main body KH including an elbow rest 7 and an elbow rest support portion 6 and supported so as to be vertically positionally changeable relative to the elbow support 5 .

[0220] The armrest body KH is mainly composed of an elbow rest support portion 6 held vertically movable relative to the elbow support 5 and an elbow rest 7 disposed slidably relative to the elbow rest support portion 6 in the front-rear direction.

[0221] In the armrest K of this embodiment, an elbow support guide mechanism Q is provided between the armrest base KB and the elbow support 7 to guide the elbow support 7 so as to be movable in the front-rear direction, and a lifting mechanism T is provided to enable the armrest body KH to be raised and lowered in the up-and-down direction relative to the elbow support 5 and to lock the armrest body KH at a predetermined height position.

[0222] Hereinafter, each structure of the armrest K of this embodiment will be described in detail.

[0223] <Elbow support 5>

[0224] The elbow support 5 has a connection portion 511 at a base end portion connected to a seat receiving portion c1 of a seat C constituting a chair body. The connection portion 511 is screwed to the seat receiving portion c1. The elbow support 5 is interposed between the armrest body KH and the chair body.

[0225] The elbow support 5 is substantially L-shaped when viewed from the front and rear. The lower portion of the elbow support 5 extends in the left-right direction, and the upper portion of the elbow support 5 extends in the up-down direction. The upper portion of the elbow support 5 is in a shape that can hold the armrest body KH in a vertically movable shape, that is, in a cylindrical shape that is open upward.

[0226] The elbow support 5 includes an elbow support body 51 which is an integrally molded product and an interior member 52 which is disposed inside the elbow support body 51 .

[0227] [elbow support body 51]

[0228] The elbow support body 51 has a connection portion 511 screwed to the lower surface of the seat receiving portion c1 at a lower portion i3 extending in the left-right direction, and has a cylindrical portion 512 opened upward at an upper portion extending in the up-down direction.

[0229] [Interior components 52]

[0230] The inner member 52 is disposed along the inner peripheral surface of the cylindrical portion 512. The inner member 52 is inserted into the cylindrical portion 512 and is attached to the elbow support body 51 by means of screws v1.

[0231] At the rear of the interior member 52, a plurality of engaged portions 521 constituting the lifting mechanism T are arranged at regular intervals in the vertical direction. The engaged portions 521 are formed of holes penetrating in the front-rear direction. The protrusion 92 of the engaging member 9 constituting the lifting mechanism T can be engaged with the engaged portions 521.

[0232] Guide rails 522 extending in the vertical direction are protrudingly provided at the front and rear of the inner peripheral surface of the inner member 52. The guide rails 522 can engage with guide recesses 611 extending in the vertical direction recessed at the front and rear of the outer peripheral surface of the cylindrical portion 61 of the elbow rest support 6.

[0233] <Elbow support 6>

[0234] The elbow support portion 6 is supported so as to be movable up and down relative to the elbow support 5 .

[0235] The elbow support portion 6 comprises: a cylindrical portion 61, which is arranged in the cylindrical portion 512 of the elbow support body 51, can move up and down relative to the cylindrical portion 512 and extends in the up and down direction; and a supporting base portion 62, which is continuously arranged on the cylindrical portion 61 and has a first guide gap S1 and a fixed guide shaft j4 constituting the elbow support guide mechanism Q on the upper surface portion 62b.

[0236] A lower wire member placement space 63 is formed in the elbow rest support portion 6. The wire member wy can be placed in the lower wire member placement space 63.

[0237] [cylindrical portion 61]

[0238] The cylindrical portion 61 has an internal space formed therein in which the engaging unit TU constituting the lifting mechanism T can be disposed and in which the wire member wy can be accommodated.

[0239] The cylindrical portion 61 includes: a guide recess 611, which is recessed in the front and rear of the outer peripheral surface in a manner extending in the up-down direction; and a window hole portion 612, which is provided with a locking member 9 constituting a lifting mechanism T at the rear portion of the lower portion in a manner capable of forward and backward movements and penetrates in the front-to-back direction.

[0240] The cylindrical portion 61 has a protrusion engaging hole (not shown) on the front surface side of the lower portion thereof for engaging with the distal end protrusion 87 of the engaging arm provided on the unit base 8 and an engaging recess 614 provided at the lower end portion for engaging with the convex portion formed on the unit base 8 .

[0241] [Supporting base portion 62]

[0242] The support base portion 62 is formed to have a larger dimension in the front-rear direction than the cylindrical portion 61. The rear portion of the support base portion 62 is in a cantilevered shape extending backward from the cylindrical portion 61.

[0243] The supporting base portion 62 includes: a peripheral wall portion 62a, which is connected to the cylindrical portion 61 and is formed so that the front-to-rear dimension gradually becomes longer upward when viewed from the side; and an upper surface portion 62b, which is arranged in a manner to partially cover the open portion formed at the upper end of the peripheral wall portion 62a.

[0244] The first and second upper surface component members 64 and 65 that constitute the upper surface portion 62b and the nut portions n2 and n6 for attaching and fixing the guide shaft j4 are arranged inside the peripheral wall portion 62a.

[0245] The upper surface portion 62b can support the elbow rest 7 from below so as to be slidable in the front-rear direction. That is, the upper surface portion 62b functions as a base of the elbow rest 7 that is movable in the front-rear direction.

[0246] A first guide gap S1, a fixed guide shaft j4 and a lower wire member connecting hole 652 are provided on the upper surface portion 62b. The first guide gap S1 can guide the elbow rest 7 to a predetermined track by engaging with a movable guide shaft j5 provided on the elbow rest 7 and protruding downward. The fixed guide shaft j4 is located at a position rearward of the first guide gap S1 and protrudes upward. The lower wire member connecting hole 652 is located between the first guide gap S1 and the fixed guide shaft j4 and penetrates in the up and down directions and can allow a part of the wire member wy to pass through.

[0247] The upper surface portion 62b is composed of a first upper surface portion constituent member 64 and a second upper surface portion constituent member 65, wherein the first upper surface portion constituent member 64 has an inner plate portion 641 and an outer plate portion 642 surrounding the inner plate portion 641 and a first annular guide gap S1 is formed between these inner plate portion 641 and the outer plate portion 642, and the second upper surface portion constituent member 65 has a cover portion 651 covering the outer plate portion 642 in the first upper surface portion constituent member 64 at the front and a lower wire member connecting hole 652 and an axis insertion hole 653 are formed at a position rearward of the cover portion 651.

[0248] The shaft insertion hole 653 of the second upper surface portion constituent member 65 is provided to attach the fixed guide shaft j4 to the nut portion n2 provided in the peripheral wall portion 62a.

[0249] The first upper surface component 64 and the second upper surface component 65 are connected in a partially overlapping manner in the up-down direction by the engagement of the claw portion 654 provided on the second upper surface component 65 with the claw engagement portion 643 provided on the first upper surface component 64. The connected first upper surface component 64 and the second upper surface component 65 are attached to the upper end of the peripheral wall portion 62a by screwing the screw v2 inserted through the screw insertion hole h2 provided on the first upper surface component 64 and the nut portion n2 provided in the peripheral wall portion 62a.

[0250] The movable guide shaft j5 provided on the elbow rest 7 side is engaged with the first guide slit S1. The structure of the first guide slit S1 will be described in detail later.

[0251] The second guide slit S2 provided on the elbow rest 7 side engages with the fixed guide shaft j4. The fixed guide shaft j4 includes a shaft body j41 having a head and a synthetic resin spacer member j42 having an annular shape and attached to the shaft body j41.

[0252] The lower wire member communicating hole 652 is formed in a rectangular shape with long sides in the left-right direction. The lower wire member communicating hole 652 is provided over substantially the entire width direction of the upper surface portion 62b.

[0253] [Lower wire member arrangement space 63]

[0254] The lower wire member disposing space 63 is provided inside the elbow rest support portion 6, that is, inside the cylindrical portion 61 and the support base portion 62. The lower wire member disposing space 63 is configured as a part in which the wire member wy can be disposed.

[0255] <Elbow support 7>

[0256] The arm of the seated person is placed on the upper surface of the elbow rest 7. The elbow rest 7 is formed by extending in the front-back direction as a whole. The elbow rest 7 includes an elbow rest base 71 and an elbow rest pad 72 disposed on the elbow rest base 71.

[0257] An upper wire member installation space sp is provided inside the elbow rest 7, i.e., between the elbow rest base 71 and the elbow rest pad 72. The upper wire member installation space sp is an installation space in which a part of the wire member wy can be installed. In this embodiment, the elbow rest 7 is provided with an operating lever R for operating the armrest body KH so as to be able to be raised and lowered relative to the elbow support pillar 5.

[0258] [Elbow support base 71]

[0259] The elbow support base 71 is a synthetic resin member having a shape extending in the front-rear direction as a whole. An operating rod R is rotatably supported on the elbow support base 71, and the operating rod R constitutes a lifting mechanism T for lifting the armrest body KH up and down.

[0260] The elbow rest base 71 includes a bottom wall portion 711 having a substantially flat bottom surface slidable relative to the upper surface portion 62 b of the elbow rest support portion 6 , and a peripheral wall portion 712 erected from an outer peripheral edge portion of the bottom wall portion 711 .

[0261] The bottom wall portion 711 includes: an axis support portion 713, which is arranged at the front portion of the upper surface side and can support the left and right axis portions r11 protruding from the operating rod R so that they can rotate; a second guide gap S2, which is arranged at a position farther back than the axis support portion 713 and penetrates in the up and down directions; a claw bearing portion 714, which can engage with an engaging claw 725 provided on the elbow support pad 72; and a nut portion n1, which is arranged at a position farther forward than the second guide gap S2 and is used to install a movable guide shaft j5 protruding downward than the bottom surface portion.

[0262] A window hole 715 is provided at the front of the peripheral wall 712 so that the operation portion r2 of the operation lever R for the user's finger to be hooked protrudes forward and penetrates in the front-to-back direction. In addition, a protrusion engaging portion 716 capable of engaging with the engaging protrusion 726 provided on the elbow rest pad 72 is provided at the upper portion of the window hole 715 at the front of the peripheral wall 712.

[0263] The second guide slit S2 constitutes the elbow rest guide mechanism Q. The second guide slit S2 engages with a fixed guide shaft j4 protruding from the support base portion 62 of the elbow rest support part 6 .

[0264] The second guide slit S2 is convexly curved toward the inner side, that is, toward the center of the chair body in the left-right direction, when viewed from above. A front end region SE is provided at the front end of the second guide slit S2 so that the fixed guide shaft j4 is not located even when the elbow rest 7 is located at the most retracted position (R). The front end region SE is a portion where the wire member wy can communicate when the elbow rest 7 is located at the most retracted position (R).

[0265] An upper wire member communicating hole that penetrates in the vertical direction and through which a part of the wire member wy can pass is formed in the elbow support base 71. The second guide slit S2 that penetrates in the vertical direction also serves as the wire member communicating hole in this embodiment.

[0266] The first guide slit S1 provided on the side of the elbow support portion 6 engages with the movable guide shaft j5. The movable guide shaft j5 is provided at a position forward of the second guide slit S2. The movable guide shaft j5 is mounted on the nut portion n1 provided on the elbow support base 71. The movable guide shaft j5 is provided in a manner protruding downward from the lower surface of the bottom wall portion 711 at the center portion in the left-right direction when viewed from above. The movable guide shaft j5 comprises: a shaft body j51 having a head; and a synthetic resin spacer member j52, which is annular and mounted on the shaft body j51.

[0267] [Elbow support pad 72]

[0268] The elbow rest pad 72 has an upper surface for placing the arm of the seated person. The elbow rest pad 72 includes a cushioning pad body 721 disposed at the upper portion and having cushioning properties, and a main body receiving member 722 made of synthetic resin mounted below the pad body 721. In this embodiment, the pad body 721 and the main body receiving member 722 are integrally provided by insert molding.

[0269] The main supporting member 722 comprises: a supporting member body 723, which is in the shape of a plate and is added to the lower surface of the pad body 721; an elastic force-applying portion 724, which is arranged on the lower surface side of the supporting member body 723 and engages with the operating rod R supported by the elbow support base 71 to apply force to the operating rod R in the direction of the initial posture (D); and an engaging claw 725 and an engaging protrusion 726, which engage with the claw supporting portion 714 and the protrusion engaging portion 716 of the elbow support base 71.

[0270] The elastic urging portion 724 includes left and right support protrusions 727 projecting downward from the receiving member main body 723 , and a flexible portion 728 spanning between the left and right support protrusions 727 and having a corrugated plate shape.

[0271] The elastic urging portion 724 presses the engaging projection r12 provided at the base end portion r1 of the operating rod R forward by utilizing the elastic deformation of the flexible portion 728 spanning the left and right support protrusions 727 .

[0272] The engaging protrusion r12 is pressed forward by the flexible portion 728 , so that the operating lever R can take the initial posture (D), that is, the initial posture (D) in which the operating portion r2 of the operating lever R is tilted forward.

[0273] In addition, a spring wt for urging the engaging member 9 in the engaging position (F) direction is provided in the engaging unit TU constituting the lifting mechanism T. Therefore, the operating lever R connected to the engaging member 9 via the wire member wy is configured so that even in the absence of the elastic urging portion 724 of the elbow rest 7, the operating lever R can be restored to the initial position (D) direction by the urging force of the spring wt pressing the engaging member 9.

[0274] That is, the elastic urging portion 724 of this embodiment supplementarily applies the urging force for returning the operating rod R to the initial position (D) in consideration of the minute dimensional differences that may occur in the wire member wy for each product.

[0275] [Operation lever R]

[0276] The operating rod R is used to operate the armrest body KH so as to change the vertical position. The operating rod R is rotatably supported with respect to the elbow rest 7 that can slide in the front-rear direction. The operating rod R is disposed at the front end of the elbow rest 7.

[0277] The operating lever R is configured to be able to change its position between an initial position (D) in which no operating force from a user is applied and an operating position (not shown) in which the operating lever R is applied with an operating force from a user and takes a position different from the initial position (D).

[0278] The operating rod R includes a base end r1 having a shaft portion as a rotation axis, and an operating portion r2 extending forward from the base end r1 and receiving an operating force of a user's finger.

[0279] The base end portion r1 includes: left and right shaft portions r11, which are protruded in the left and right directions with their axes aligned; an engaging protrusion r12, which is protruded between the left and right shaft portions r11 in a manner that is located above the axes of the left and right shaft portions r11, constituting a portion pressed forward by the elastic force applying portion 724; and a wire connecting portion r13, which is protruded in a manner that is located below the axes of the left and right shaft portions r11 and is connected to one end of the wire member wy.

[0280] The operating portion r2 is plate-shaped and protrudes forward through the window hole 715 of the elbow support base 71.

[0281] <<Elbow support guide mechanism Q>>

[0282] The elbow rest guide mechanism Q is configured to enable the elbow rest 7 to slide between the most advanced position (F) and the most retracted position (R) on one elbow rest rail selected from a plurality of, namely, two, elbow rest rails, an outer elbow rest rail SW and an inner elbow rest rail UW.

[0283] The elbow rest guide mechanism Q is provided between the elbow rest support portion 6 and the elbow rest 7 constituting the armrest base KB.

[0284] The elbow rest guide mechanism Q includes a first guide slit S1 and a fixed guide shaft j4 provided on the armrest base KB side, a second guide slit S2 provided on the elbow rest 7 side and engaged with the fixed guide shaft j4, and a movable guide shaft j5 engaged with the first guide slit S1.

[0285] The elbow support guide mechanism Q is provided with an outer gap portion QS and an inner gap portion QU in the first guide gap S1 as two gap portions connecting a gap end Sf corresponding to the most advanced position (F) and a gap end Sr corresponding to the most retracted position (R).

[0286] The outer slit portion QS is disposed outside the inner slit portion QU. The inner slit portion QU is disposed inside the outer slit portion QS. The outer slit portion QS and the inner slit portion QU are provided only in the first guide slit S1 provided in an annular shape in a plan view.

[0287] The elbow support guide mechanism Q is configured to select an outer elbow support rail SW that enables the movable guide shaft j5 to engage with the outer slit portion QS to enable the elbow support 7 to move forward and backward, and an inner elbow support rail UW that enables the movable guide shaft j5 to engage with the inner slit portion QU to enable the elbow support 7 to move forward and backward.

[0288] <<Working Description of Elbow Rest Guide Mechanism Q>>

[0289] The elbow rest 7 can slide in the front-to-back direction relative to the elbow rest support portion 6. The elbow rest 7 can move forward and backward on two elbow rest rails (2WAY rails), namely, the outer elbow rest rail SW and the inner elbow rest rail UW, between the most retracted position (R) in which the elbow rest 7 takes a forward posture substantially parallel to the left-right center line of the chair body and the most advanced position (F) in which the elbow rest 7 takes a posture inward of the most retracted position (R).

[0290] <Outer elbow rail SW>

[0291] The outer elbow rest rail SW in the elbow rest 7 is realized by the cooperation of the outer gap portion QS of the first guide gap S1 as a fixed gap provided in the elbow rest support portion 6 and the movable guide shaft j5 provided in the elbow rest 7, and the cooperation of the second guide gap S2 as a movable gap provided in the elbow rest 7 and the fixed guide shaft j4 provided in the elbow rest support portion 6.

[0292] The outer slit portion QS used in the outer elbow rest rail SW is set in a mountain shape so as to gently bulge outward.

[0293] The elbow support guiding mechanism Q is constructed so that when the movable guide shaft j5 is engaged with the outer gap portion QS connecting the gap ends Sf and Sr on one side and the other side to slide the elbow support 7 in the front-to-back direction, the left-right swinging degree of the front part of the elbow support 7 becomes gentler than that of the inner elbow support rail UW.

[0294] <Inner gap QU>

[0295] The inner elbow rest rail UW in the elbow rest 7 is realized by the cooperation of the inner gap portion QU of the first guide gap S1 as a fixed gap provided in the elbow rest support portion 6 and the movable guide shaft j5 provided in the elbow rest 7, and the cooperation of the second guide gap S2 as a movable gap provided in the elbow rest 7 and the fixed guide shaft j4 provided in the elbow rest support portion 6.

[0296] The inner slit portion QU used in the inner elbow rest rail UW is set in a mountain shape so as to protrude inwardly. The inner slit portion QU protrudes inwardly more than the outer slit portion QS protrudes outwardly.

[0297] Therefore, the elbow support guiding mechanism Q is constructed so that when the movable guide shaft j5 is engaged with the inner gap portion QU connecting the gap ends Sf and Sr on one side and the other side to slide the elbow support 7 in the front-to-back direction, the left-to-right swing degree of the front portion of the elbow support 7 becomes greater than that of the outer elbow support rail SW.

[0298] The elbow support guide mechanism Q is set so that when the movable guide shaft j5 is located at the middle position QM in the inner gap portion QU which is closest to the center of the chair body in the left-right direction, the elbow support 7 is in an inward posture (M) with the front end portion located at the innermost position relative to the rear end portion.

[0299] <<Lifting Mechanism T>>

[0300] The lifting mechanism T can regulate the vertical position of the armrest body KH relative to the elbow support 5 by operating the operating lever R provided at the elbow support 7 configured to be slidable in the front-rear direction.

[0301] The lifting mechanism T is constructed to include: an operating rod R, which is arranged on the elbow support 7; an engaged portion 521, which is arranged in an array on the elbow support column 5; an engaging member 9, which is arranged on the elbow support support portion 6 and can move forward and backward between an engaging position (F) that can engage with the engaged portion 521 and a retreat position (not shown) that is not engaged with the engaged portion 521 in conjunction with the rotation operation of the operating rod R; and a wire member wy, which connects the operating rod R and the engaging member 9.

[0302] In this embodiment, the engagement member 9 constitutes an engagement unit TU in which a plurality of components are assembled so as to be handled integrally.

[0303] <Operation lever R>

[0304] The structure of the operating lever R has been described above and therefore will be omitted.

[0305] The operating lever R is configured to be able to change its posture between an initial posture (D) in which a plate-shaped operating portion r2 is tilted forward and an operating posture not shown in the figure in which the front end portion of the operating portion r2 is subjected to an operating force from a user and rotates around the left and right axis portions r11 and moves upward compared to the initial posture (D).

[0306] <Engaged portion 521>

[0307] The engaged portion 521 can be engaged with the engaging member 9 provided on the elbow support portion 6. The engaged portion 521 of this embodiment is in the shape of a window hole penetrating in the front-back direction. A plurality of engaged portions 521 are arranged in parallel at a certain interval in the vertical direction at the rear of the inner member 52 constituting the elbow support 5.

[0308] <Engagement Unit TU>

[0309] An engagement unit TU including the engagement member 9 is attached to the lower portion of the cylindrical portion 61 in the elbow rest support 6 .

[0310] The engaging unit TU comprises: a unit base 8, which is mounted on the elbow support portion 6; an engaging member 9, which is configured to be able to move forward and backward relative to the unit base 8 between an engaging position (F) capable of engaging with the engaged portion 521 of the elbow support 5 and a retreat position retreated from the engaging position (F); and a spring wt, which is arranged between the unit base 8 and the engaging member 9 and applies force to the engaging member 9 in the direction of the engaging position (F).

[0311] [Unit matrix 8]

[0312] The unit base 8 is mainly composed of a block-shaped portion that is set to a size that allows it to be attached to the cylindrical portion 61 of the elbow rest support 6 .

[0313] The unit base 8 comprises: a snap-fitting member holding portion 81, which has a housing space capable of housing the snap-fitting member 9 in a manner capable of advancing and retreating, and has a portion capable of holding the snap-fitting member 9 so as to protrude and retract in the front-to-back direction; a snap-fitting arm portion 82, which is extended from the lower end portion of the front portion in the shape of an elastically deformable arm, and has a top protrusion 87 at the extended end portion that can engage with a protruding engaging hole (not shown) provided on the elbow support portion 6; an engaging protrusion 83, which protrudes outward from the lower end portion and can engage with an engaging recess 614 provided on the elbow support portion 6; and a bending guide portion 84, which bends the wire member wy extending in the up-down direction in a direction extending in the front-to-back direction.

[0314] The locking member retaining portion 81 is provided with a groove portion 85 capable of engaging with the convex rail portion 911 of the locking member 9 on the top wall portion and the bottom wall portion facing the accommodating space, and a front spring retaining portion 86 is provided on the front wall portion facing the accommodating space. The front spring retaining portion 86 can retain the front end portion of the spring wt.

[0315] [Engaging member 9]

[0316] The engaging member 9 includes a base portion 91 and a protruding portion 92 which is an engaging end that protrudes rearward from the base portion 91 and can engage with the engaged portion 521 .

[0317] The base 91 includes: a convex rail portion 911, which is arranged at the upper and lower parts and extends in the front-to-back direction in a manner that it can engage with the groove portion 85 of the engaging member retaining portion 81; a rear spring retaining portion 912, which is arranged at the front and can retain the rear end portion of the spring wt; and a wire connecting portion 913, which is arranged adjacent to the rear spring retaining portion 912 and is connected to the wire member wy.

[0318] <Line component wy>

[0319] The wire member wy connects the operation rod R and the engagement member 9. The wire member wy transmits the operation force applied to the operation rod R by the user to the engagement member 9.

[0320] The engagement member 9 connected to the wire member wy is urged toward the engagement position (F) by the spring wt. Therefore, the operation lever R connected to the engagement member 9 via the wire member wy can take the initial position (D) when the user does not operate the operation lever R.

[0321] The wire member wy has one end connected to the wire connection portion r13 of the operating rod R disposed on the elbow rest 7 , and the other end connected to the wire connection portion 913 of the engaging member 9 disposed at the cylindrical portion 61 of the elbow rest support 6 .

[0322] <Regarding the Arrangement Location of the Wire Member wy>

[0323] The wire member wy connects the operating rod R with the engaging member 9 through the upper wire member arrangement space sp, the second guide gap S2, the lower wire member connecting hole 652, and the lower wire member arrangement space 63. The upper wire member arrangement space sp is arranged inside the elbow support 7, that is, between the elbow support base 71 and the elbow support pad 72. The second guide gap S2 also serves as the upper wire member connecting hole arranged at the elbow support base 71. The lower wire member connecting hole 652 is arranged on the upper surface portion 62b of the elbow support support portion 6. The lower wire member arrangement space 63 is the internal space of the hollow elbow support support portion 6.

[0324] <<Working Description of Lifting Mechanism T>>

[0325] The lifting mechanism T defines the vertical position of the armrest body KH relative to the elbow support 5 by selectively engaging the engaging member 9 disposed on the elbow support portion 6 with any of the engaged portions 521 disposed on the elbow support 5 .

[0326] The lifting mechanism T of this embodiment is provided on the elbow rest 7 in which the operating rod R can slide in the front-back direction. Therefore, the lifting mechanism T transmits the operating force of the operating rod R to the engaging member 9 by using the wire member wy, so that the armrest body KH can be moved up and down by operating the operating rod R regardless of where the elbow rest 7 is within the movable range in the front-back direction.

[0327] When the elbow rest 7 is at the most advanced position (F), the path between the operating rod R where the wire member wy is arranged and the engaging member 9 is the longest. On the other hand, when the elbow rest 7 is at the most retracted position (R), the path between the operating rod R where the wire member wy is arranged and the engaging member 9 is the shortest.

[0328] Therefore, in the elbow rest 7 of the present embodiment, at least an upper wire member arrangement space sp is provided in which the wire member wy is configured to be able to bend and deform when the elbow rest 7 is in the most retracted position (R).

[0329] In addition, a lower wire member connecting hole 652 extending in the left-right direction is provided on the upper surface portion 62b of the elbow rest support portion 6. Therefore, even when the wire member wy is forcibly moved in the left-right direction by the curved second guide slit S2 as the elbow rest 7 slides in the front-back direction, the lower wire member connecting hole 652 can smoothly guide the wire member wy into the elbow rest support portion 6.

[0330] <<Headrest I>>

[0331] The headrest I comprises: a headrest main body IH, which is provided with a supporting surface for supporting the head of the seated person; a base IK, which supports the headrest main body IH so as to be rotatable in the front-rear direction; a frame mounting portion IF, which is mounted on the upper frame portion e12 of the back frame e1 and supports the base IK; and an up-and-down position changing mechanism IC, which is provided between the frame mounting portion IF and the base IK and enables the base IK to slide and move relative to the frame mounting portion IF in the up-and-down direction so as to change its position.

[0332] <Headrest body IH>

[0333] The headrest body IH includes: a frame portion i1 having a substantially square frame shape when viewed from the front and rear, and having a mounting groove for mounting a tension member provided at the peripheral portion; and a tension member i2 forming a head support surface tensioned relative to the frame portion i1.

[0334] A shaft holding portion i11 for holding a shaft portion i42 that protrudes from the base portion IK is provided at a lower portion of the frame portion i1.

[0335] <Base IK>

[0336] The base IK comprises: a lower portion i3 having a lower plate-like portion i31 extending in the up-down direction and in the shape of a plate; and an upper portion i4 having an upper plate-like portion i41 extending forward from the upper end portion of the lower portion i3 and in the shape of a plate and having an axis portion i42 at the top end portion thereof which is retained by an axis retaining portion i11 provided on the frame portion i1.

[0337] [lower part i3]

[0338] The lower part i3 includes: a lower plate-like portion i31, which is formed so that the width dimension in the left-right direction gradually becomes shorter toward the bottom; a guide rail i32, which constitutes an up-and-down position changing mechanism IC, is formed on the front surface side of the lower plate-like portion i31, and extends in pairs in the up-and-down direction; and a snap-fit ​​member retaining portion i33, which constitutes the up-and-down position changing mechanism IC and is formed in the up-and-down center portion between the left and right guide rails i32 on the front surface side of the lower plate-like portion i31 and retains the snap-fit ​​member i7 that can be engaged with the frame mounting portion IF so as to be able to protrude and retract in the front-and-back direction.

[0339] The left and right guide rails i32 each include a base end portion ik extending forward from the lower plate-shaped portion i31 and a top end portion is protruding outward from the extension end of the base end portion ik. The left and right guide rails i32 are restricted from moving in the front-rear direction and the left-right direction by engaging with the left and right rail receiving portions i52 provided on the back side of the frame mounting portion IF, and can move in the up-down direction.

[0340] The engaging member holding portion i33 holds the engaging member i7 constituting the up-down position changing mechanism IC and the spring wi for urging the engaging member i7 forward. The engaging member holding portion i33 comprises: a frame-shaped portion iw protruding forward from the lower plate-shaped portion i31 in a substantially rectangular cylindrical shape; a guide protrusion it protruding inside the frame-shaped portion iw and engaging with the guide groove ig of the engaging member i7; and a rear spring holding portion id protruding forward from the lower plate-shaped portion i31 located inside the frame-shaped portion iw and holding the rear end of the spring wi.

[0341] <Frame Mounting Section IF>

[0342] The frame mounting portion IF comprises: a base member i5 having an upper engaging portion i51 on the front side of the upper portion thereof which engages with the upper portion of the upper frame portion e12 in the back frame e1, and having left and right rail receiving portions i52 extending in the up-down direction and an engaged portion i53 which is arranged between the left and right rail receiving portions i52 and has a plurality of engaging recesses ia arranged in the up-down direction and capable of being engaged with the engaging member i7 on the back side; and a lower mounting member i6 which is mounted on the base member i5 by screws not shown in the figure and has a lower engaging portion i61 which engages with the lower portion of the upper frame portion e12 in the back frame e1.

[0343] The frame mounting portion IF is supported by the back frame e1 by being sandwiched between the upper frame portion e12 of the back frame e1 by the upper engaging portion i51 and the lower engaging portion i61.

[0344] The left and right rail receiving parts i52 have a groove im extending in the up-down direction and opening inward. The top end of the guide rail i32 can be engaged with the groove im.

[0345] The engaged portion i53 is arranged in the up-down direction with a plurality of engaging recesses ia that can be engaged with the engaging member i7 formed in a mountain shape at the top end. The engaging recess ia is composed of an upper recess forming surface ix that is inclined in a manner that is gradually located backward toward the upper side and a lower recess forming surface iz that is inclined in a manner that is gradually located backward toward the lower side. In addition, the inclination of the lower recess forming surface iz with respect to the up-down direction imaginary line corresponding to the up-down movement direction of the base IK is set to be greater than the inclination of the upper recess forming surface ix.

[0346] <Up and down position changing mechanism IC>

[0347] The vertical position changing mechanism IC is configured to be able to change the position of the base portion IK and the headrest main body IH supported by the base portion IK in the vertical direction relative to the frame mounting portion IF.

[0348] The up and down position changing mechanism IC is mainly composed of a guide rail i32 and a snap-fitting component retaining portion i33 arranged on the base IK, a snap-fitting component i7 retained by the snap-fitting component retaining portion i33 and a spring wi for applying force to the snap-fitting component i7, and left and right rail supporting portions i52 and a snap-fitted portion i53 arranged at the frame mounting portion IF.

[0349] The overall appearance of the engaging member i7 is block-shaped. The engaging member i7 comprises: a top engaging portion, the top engaging portion having an upper inclined surface ib set at the top end to be able to engage with the upper concave portion forming surface ix in a planar manner and a lower inclined surface ic set to be able to engage with the lower concave portion forming surface iz in a planar manner; and a front spring retaining portion if having a receiving portion capable of accommodating the front portion of the spring wi and a retaining protrusion that retains the top end portion of the spring wi. A spring wi is interposed between the engaging member i7 and the lower plate-shaped portion i31. The spring wi applies force to the engaging member i7 in the direction of the front, i.e., the engaged portion i53, with the lower plate-shaped portion i31 as a foothold.

[0350] In the vertical position changing mechanism IC, the inclination of the lower concave portion forming surface iz is set to be larger than the inclination of the upper concave portion forming surface ix. Therefore, the base portion IK and the headrest body IH are configured to be movable with a lighter force when the position is changed upward, and to be movable with a heavier force when the position is changed downward than when the position is changed upward.

[0351] <About Modification Example of Up and Down Position Changing Mechanism IC>

[0352] The vertical position changing mechanism IC only needs to be provided between the frame mounting portion IF and the base portion IK and to allow the base portion IK to slide relative to the frame mounting portion IF so as to change its position in the vertical direction. Of course, its specific structure can be variously modified.

[0353] Below, refer to Figure 55 to Figure 58 A modified example of the up-down position changing mechanism IC applied to the headrest 1 will be described.

[0354] The up and down position changing mechanism IC is mainly composed of a guide rail i32 arranged on the base IK, an engaged portion i53 arranged on the base IK and having an engaging recess ia with which the top end portion of the engaging member i7 can be selectively engaged, left and right rail supporting portions i52 arranged on the frame mounting portion IF, an engaging member retaining portion i33 arranged on the frame mounting portion IF, an engaging member i7 retained by the engaging member retaining portion i33, and a spring wi for urging the engaging member i7 toward the engaged portion i53 of the base IK.

[0355] In this embodiment, compared with the above-described embodiment, the front-rear positional relationship between the engagement member holding portion i33 that holds the engagement member i7 and the engaged portion i53 with which the distal end portion of the engagement member i7 is engaged is reversed.

[0356] The locking component i7 includes: a top locking portion ie, which is directed toward the lower portion i3 in the base IK and is arranged in pairs on the left and right; a positioning protrusion ih, which is arranged between a pair of top locking portions i8 on the left and right; and a rear spring retaining portion if, which has a receiving portion that can accommodate the rear portion of the spring wi and a retaining protrusion that retains the rear end portion which is one end portion of the spring wi.

[0357] A spring wi is interposed between the engagement member i7 and the base member i5 of the frame mounting portion IF. The spring wi urges the engagement member i7 rearward, that is, in the direction of the engaged portion i53 provided on the base portion IK, with the frame mounting portion IF as a foothold.

[0358] The top end engaging portion ie of the engaging member i7 has an upper inclined surface ib set to be able to engage in a surface manner with the recess forming surface ix on the upper side of the engaging recess ia, and has a lower inclined surface ic set to be able to engage in a surface manner with the recess forming surface iz on the lower side of the engaging recess ia.

[0359] The positioning protrusion ih is engaged with a positioning groove i54 which is provided between a pair of left and right engaged portions i53 and extends in the up-down direction, thereby positioning the engaging member i7. The pair of left and right engaged portions i53 are protruding from the base KI and have an engaging recess ia.

[0360] The positioning protrusion ih includes left and right side wall portions ih1 and a bottom wall portion ih2 disposed between the lower ends of the left and right side wall portions ih1. The left and right side wall portions ih1 can be engaged with a movement restricting portion i55 protruding from the upper side of the engaged portion i53, and the left and right side wall portions ih1 and the bottom wall portion ih2 can be engaged with a movement restricting portion i56 protruding from the lower side of the engaged portion i53.

[0361] As in the above-mentioned embodiment, the inclination of the lower recessed portion forming surface iz of the vertical position changing mechanism IC is set to be larger than the inclination of the upper recessed portion forming surface ix. Therefore, the base portion IK and the headrest body IH are configured to be movable with a lighter force when the position is changed upward, and to be movable with a heavier force when the position is changed downward than when the position is changed upward.

[0362] <<Locking mechanism Rc>>

[0363] The weight sensing locking mechanism Rc is configured to tilt the backrest E according to the weight of the seated person. The weight sensing locking mechanism Rc is configured to move the seat C backward as the backrest E tilts backward and lift the seat C against the load of the seated person.

[0364] The weight-sensing locking mechanism Rc is mainly composed of a supporting base B, a seat C, a back support body D, a backrest E and a reaction force spring wd, wherein the supporting base B is installed on the upper end of the leg A, the seat C is arranged on the supporting base B and is constructed so that the front part can move relative to the supporting base B via the front axis j2, the back support body D is rotatably supported on the supporting base B via the main axis j1 and has a seat engaging axis j3 arranged at a position forward of the main axis j1 and capable of engaging with the central part of the seat C in the front-to-back direction, and a supporting axis d4 urged by the reaction force spring wd in a manner that can move as a whole, the backrest E is supported on the back support body D, and the reaction force spring wd is arranged between the supporting base B and the back support body D and can impart a reaction force relative to the rearward tilting action of the backrest E.

[0365] <<Seat forward tilt mechanism G>>

[0366] The seat forward tilt mechanism G can change the posture of the seat C about the seat engagement axis j3 between a normal posture (M) in which the entire seat surface is substantially horizontal and a forward tilt posture (F) in which the seat surface is tilted forward from the normal posture (M).

[0367] The seat tilt mechanism G is configured to displace the front axle j2 relative to the seat C supported to be rotatable about the seat engagement axis j3 in the vertical direction. In addition, when the seat tilt mechanism G is in effect, the front axle j2 is held at the lower end of the front axle support b5 in the support base B and cannot be lowered further.

[0368] The seat forward tilting mechanism G tilts the seat C flexibly forward when the load of the seat occupant acts on the front part of the seat C. That is, the seat forward tilting mechanism G is configured so that the rotation in the forward tilting posture (F) direction is not locked when the load of the seat occupant acts on the front part of the seat C relative to the seat C in the normal posture (M).

[0369] Furthermore, the seat forward tilting mechanism G is configured so as not to lock the seat C in the forward tilting posture (F) in this posture.

[0370] The seat forward tilt mechanism G has a spring wg interposed between the seat C and the front axle j2, and the spring wg applies force to the seat C in the direction of the normal posture (M) with the front axle j2 as a foothold. When the seat forward tilt mechanism G receives the load of the seated person and the spring wg is compressed against the force, the front part of the seat C descends, thereby enabling the seat to take the forward tilt posture (F).

[0371] The upper end portion of the spring wg constituting the seat forward tilt mechanism G is configured to engage with an upper spring receiving portion 21 a provided on the lower surface side of an upper spring receiving member 2 attached to the seat receiving portion main body 1 .

[0372] The lower end portion of the spring wg constituting the seat forward tilt mechanism G is configured to engage with a lower spring receiving portion 41 provided at an upper portion of a lower spring receiving member 4 attached to the front axle j2.

[0373] The lower spring receiving member 4 has a lower spring receiving portion 41 at the upper portion and a seat engaging portion 42 at the lower portion. The seat engaging portion 42 is formed so that the front-rear width dimension gradually shortens downward in a side view.

[0374] The seat C is provided with a lower spring receiving member holding portion 13a which is recessed in a manner corresponding to the shape of the seat engaging portion 42 provided at the lower spring receiving member 4 and is configured to be engageable with the seat engaging portion 42 in the normal posture (M).

[0375] The seat engaging portion 42 of the lower spring-bearing member 4 is formed so that the front-to-rear width dimension gradually becomes shorter toward the downward direction, and the lower spring-bearing member retaining portion 13a is recessed in a manner corresponding to the shape of the seat engaging portion 42. This is to enable the lower spring-bearing member retaining portion 13a separated from the seat engaging portion 42 to be smoothly engaged with the seat engaging portion 42 when the seat C returns from the forward tilted posture (F) to the normal posture (M).

[0376] The chair of the above-mentioned embodiment not only has the weight-sensing locking mechanism Rc, but also can rotate the seat C around the seat engagement axis j3, which is an essential component of the weight-sensing locking mechanism Rc, so that the seat C can take a forward tilting posture (F).

[0377] Furthermore, according to the chair of the above-described embodiment, it is possible to provide the armrest K configured so that the elbow rest 7 can be moved forward and backward in various manners relative to the armrest base KB.

[0378] Moreover, according to the chair of the above-described embodiment, it is possible to provide an armrest K capable of appropriately performing an operation for changing the up-and-down position of the armrest main body KH.

[0379] As described above, the chair of this embodiment comprises: legs A; a support base B, which is mounted on the upper end of the legs A; a seat C, which is arranged on the support base B; and a back support body D, which is rotatably supported on the support base B via the main axis j1 and has a seat engaging axis j3 which is arranged at a position forward of the main axis j1 and can engage with the seat C.

[0380] Furthermore, the chair is provided with a weight-sensing lock mechanism Rc, which is configured to be able to lift the seat C upward by the seat engagement shaft j3 as the back support body D tilts backward.

[0381] The chair is provided with a seat forward tilting mechanism G capable of changing the posture of the seat C about the seat engagement axis j3 between a normal posture (M) and a forward tilting posture (F) tilted forward from the normal posture (M).

[0382] Therefore, according to the present embodiment, a chair can be provided which not only has a weight-sensing locking mechanism Rc that helps to provide comfortable support for the seat occupant, but also can make the seat C assume a forward leaning posture (F) by rotating the seat C around the seat engaging axis j3 which is a suitable structure for lifting the seat C upward in the weight-sensing locking mechanism Rc.

[0383] A front shaft j2 extending in the left-right direction is interposed between the front portion of the support base B and the front portion of the seat C. The seat forward tilting mechanism G is configured to displace the front shaft j2 relative to the seat C supported so as to be rotatable about the seat engagement shaft j3 in the vertical direction.

[0384] Therefore, the seat forward tilting mechanism G realizes a configuration capable of rotating the seat C between the forward tilting posture (F) and the normal posture (M) in association with the front axis j2 interposed between the support base B and the seat C.

[0385] The seat tilt mechanism G has a spring wg interposed between the seat C and the front axle j2, which applies force to the seat C in the direction of the normal posture (M) with the front axle j2 as a foothold. When the spring wg is compressed by the load of the seat occupant and overcomes the force, the seat C can take a tilt posture (F).

[0386] Therefore, it is possible to provide a seat forward tilting mechanism G having an epoch-making structure in which the seat C is tilted forward using the front shaft j2 as a foothold of the spring wg.

[0387] The seat C comprises: a seat receiving portion c1 having a seat engaging shaft retaining portion 16 as a shaft retaining portion capable of retaining the seat engaging shaft j3 and having a spring receiving portion 21a on the upper side receiving the upper end portion of the spring wg; and a seat body c2 supported by the seat receiving portion c1.

[0388] Therefore, the seat receiving portion c1 of the seat C can play a function of receiving the upper end portion of the spring wg constituting the seat forward tilting mechanism G.

[0389] The seat receiving portion c1 includes a seat receiving portion main body 1 and an upper spring receiving member 2 which is configured to be attachable to and detachable from the seat receiving portion main body 1 and has an upper spring receiving portion 21 a .

[0390] Therefore, since the upper spring receiving member 2 is attachable to and detachable from the seat receiving portion main body 1, the degree of freedom in design for easily constructing the seat forward tilting mechanism G is excellent.

[0391] The upper spring receiving member 2 is configured to be attachable to and detachable from the seat receiving portion main body 1 without using a fixing member.

[0392] Therefore, it not only contributes to the smooth construction of the seat forward tilting mechanism G, but also contributes to the reduction of working man-hours and the number of parts.

[0393] A lower spring receiving member 4 is attached to the front axle j2. The lower spring receiving member 4 has a lower spring receiving portion 41 that receives the lower end of the spring wg.

[0394] Therefore, an appropriate structure for making the front axle j2 a foothold of the spring wg is achieved.

[0395] The lower spring receiving member 4 has a lower spring receiving portion 41 at the upper portion and a seat engaging portion 42 at the lower portion, the front-rear width dimension of which is gradually shortened toward the lower side in a side view.

[0396] The seat C is provided with a lower spring receiving member holding portion 13a which is recessed in a manner corresponding to the shape of the seat engaging portion 42 and is configured to be engageable with the seat engaging portion 42 in the normal posture (M).

[0397] Therefore, the lower spring receiving member holding portion 13 a provided at the seat C is appropriately engaged with the seat engaging portion 42 of the lower spring receiving member 4 that is relatively displaced in the vertical direction relative to the seat C by the operation of the seat forward tilting mechanism G.

[0398] The support base B includes a support base body b1 including a bottom wall b2 and left and right side walls b3 rising from left and right ends of the bottom wall b2. The lower spring receiving member retaining portion 13a is provided outside the left and right side walls b3.

[0399] Therefore, the lower spring receiving and holding portion is disposed at an appropriate position that does not interfere with the support of the base body b1.

[0400] In addition, the present invention is not limited to the embodiments described in detail above.

[0401] The seat forward tilting mechanism may be any mechanism capable of changing the position of the seat about the seat engagement axis between a normal position and a forward tilting position that is tilted forward than the normal position, and is not limited to the configuration shown in the above embodiment.

[0402] The seat forward tilting mechanism may be configured without providing a spring that urges the seat in the direction of the normal posture.

[0403] The seat forward tilting mechanism may be configured such that a spring for biasing the seat in the direction of the normal posture uses a portion other than the front axle (for example, a support base, etc.) as a foothold.

[0404] The upper spring receiving portion may be provided on the seat receiving portion, and may be formed integrally with a member constituting a main part of the seat receiving portion, for example.

[0405] The seat body may not be able to slide relative to the seat receiving portion in the front-rear direction.

[0406] In addition, the specific configuration of each part is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention.

Claims

1. A chair comprising: legs; a support base, the support base being mounted on the upper ends of the legs; a seat, the seat being arranged on the support base; and a back support body, the back support body being rotatably supported on the support base via a main shaft and having a seat engaging shaft arranged at a position forward of the main shaft and engageable with the seat, the chair being provided with a weight-sensing locking mechanism, the weight-sensing locking mechanism being configured to be able to lift the seat upward using the seat engaging shaft as the back support body tilts backward, The chair is provided with a seat forward tilting mechanism capable of changing the posture of the seat about the seat engagement axis between a normal posture and a forward tilting posture that is tilted forward than the normal posture.

2. The chair according to claim 1, A front shaft extending in the left-right direction is interposed between the front portion of the support base and the front portion of the seat. The seat forward tilting mechanism is configured to be able to displace the front shaft relative to the seat supported so as to be rotatable about the seat engagement shaft in the up-down direction.

3. The chair according to claim 2, The seat forward tilting mechanism includes a spring disposed between the seat and the front axle, the spring applying force to the seat in the direction of the normal posture with the front axle as a foothold. When the spring is compressed against the force of the seat occupant under the load of the seat occupant, the seat can take the forward tilted posture.

4. The chair according to claim 3, The seat includes: a seat receiving portion having a shaft holding portion capable of holding the seat engagement shaft and an upper spring receiving portion receiving an upper end portion of the spring; and a seat main body supported by the seat receiving portion.

5. The chair according to claim 4, The seat receiving portion includes: a seat receiving portion main body; and an upper spring receiving member, the upper spring receiving member being configured to be attachable to and detachable from the seat receiving portion main body and having the upper spring receiving portion.

6. The chair according to claim 5, The upper spring receiving member is configured to be attachable to and detachable from the seat receiving portion main body without using a fixing member.

7. The chair according to claim 3, A lower spring receiving member is mounted on the front axle. The lower spring receiving member has a lower spring receiving portion that receives a lower end portion of the spring.

8. The chair according to claim 7, The lower spring receiving member has the lower spring receiving portion at the upper portion and has a seat engaging portion at the lower portion formed so that the front-rear width dimension gradually shortens downward in a side view. The seat is provided with a lower spring receiving member holding portion, the lower spring receiving member holding portion is recessed to correspond to the shape of the seat engaging portion and is configured to be engageable with the seat engaging portion in the normal posture.

9. The chair according to claim 8, The support base includes a support base body, and the support base body includes a bottom wall and left and right side walls erected from left and right ends of the bottom wall. The lower spring receiving member holding portion is provided at an outer side than the left and right side wall portions.

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