Chair whose seat swings in a front-rear direction and a left-right direction

Abstract

A chair is realized which takes specific measures to suppress movement of a seat in a front-rear direction when the seat swings in the front-rear and the left-right directions with respect to a support base. For the purpose, the chair wherein a seat 5 swings in the front-rear and left-right directions with respect to a support base 2, the chair is configured such that swinging of the seat 5 in front-rear direction with respect to the support base 2 is capable of being suppressed at one or a plurality of predetermined positions, or arbitrary position via operation of operation member 152.

Claims

1. A chair, wherein a seat swings in front-rear and left-right directions with respect to a support base, the chair is configured such that swinging of the seat in the front-rear direction with respect to the support base is capable of being suppressed at one or a plurality of predetermined positions, or arbitrary position via an operation of an operation member, the chair comprising: an engaged part provided at a support base side or a seat side, the engaged part comprising a front-rear direction groove part extending in the front-rear direction and a left-right direction groove part extending in the left-right direction, the front-rear direction groove part crossing the left-right direction groove part to form a center crossing part where a groove depth is deeper than any other portion of the front-rear direction groove part and the left-right direction groove part, and an engaging part that engages the engaged part at the support base side or the seat side, the engaging part provided at the seat side or the support base side, and the engaging part at the seat side or the support base side elastically protruding toward the engaged part at the support base side or the seat side by the operation of the operation part, wherein the engaging part engages one of the front-rear direction groove part or the left-right direction groove part of the engaged part in accordance with swinging of the seat to the front-rear and left-right directions and swinging to one direction is regulated, and then, by further swinging to another direction, whereby the engaging part engages the crossing part and swinging in both front-rear and left-right directions is regulated.

2. A chair, wherein a seat swings in front-rear and left-right directions with respect to a support base, the chair is configured such that swinging of the seat in the front-rear direction with respect to the support base is capable of being suppressed at one or a plurality of predetermined positions, or arbitrary position via an operation of an operation member, wherein a front-rear swinging part is provided between the seat and the support base supporting the seat, and a left-right swinging part is provided between the front-rear swinging part and the support base or between the seat and the front-rear swinging part, and the seat is swingably supported in front-rear and left-right directions by the front-rear swinging part and the left-right swinging part, and a front-rear stopper mechanism is provided between the left-right swinging part and the front-rear swinging part, or between the support base and the front-rear swinging part, or between the support base and the left-right swinging part, the front-rear stopper mechanism switches between allowance and suppression of swinging of the seat in the front-rear direction through engaging or disengaging an engaging part and an engaged part by operation of the operation member.

3. The chair according to claim 2, wherein a left-right stopper mechanism is further provided between the left-right swinging part and the front-rear swinging part, or between the support base and the front-rear swinging part, or between the support base and the left-right swinging part, the left-right stopper mechanism switches between allowance and suppression of swinging of the seat in the left-right direction through engaging or disengaging an engaging part and an engaged part by operation of the operation member.

4. The chair according to claim 3, wherein the front-rear stopper mechanism and the left-right stopper mechanism operate through operation of the operation member in common.

5. The chair according to claim 3, wherein the front-rear stopper mechanism and the left-right stopper mechanism operate by one operation.

6. The chair according to claim 2, wherein the engaged positions of the engaging part and the engaged part are provided at a plurality of the positions in the front-rear direction.

7. The chair according to claim 2, wherein it is possible to switch between suppression and no-suppression of swinging in front-rear direction on at least one predetermined position within the movement range in front-rear direction and it is possible to switch between suppression and no-suppression of swinging in left-right direction at a center reference position in left-right direction.

8. The chair according to claim 2, wherein the engaging part and the engaged part are engaged and the front-rear stopper mechanism works when the seat moves to the predetermined position after a swinging allowance operation is performed through the operation member.

9. The chair according to claim 2, wherein the chair includes a control mechanism configured to change the operation of a movable part between the allowed and suppressed states when the load applied by a seated person is received, and the control mechanism also changes the allowed/suppressed states of the operation of the movable part when an engagement state between the engaged part and the engaging part changes, and a recess of the control mechanism and a recess of the stopper mechanism are set at different positions in the front-rear direction.

10. The chair according to claim 2, wherein the operation member is provided at the front-rear swinging part and the operation member moves in accordance with the front-rear movement of the seat.

11. The chair according to claim 2, wherein the operation member is provided in the seat and the operation member swings in the front-rear and the left-right directions together with the seat.

12. The chair according to claim 2, wherein a fixed arm part is attached to the support base and the operation member is provided in the fixed arm part.

13. The chair according to claim 2, wherein a back frame configured to support a backrest is erected integrally behind the seat.

14. The chair according to claim 2, includes: a load detection part that detects a sitting load applied by a seated person; and an operation part that operates in accordance with a detection state of the load detection part, and the operation part is configured so as to input in the front-rear stopper mechanism in parallel with the operation of the operation member, even in a state where the engaging part and the engaged part of the front-rear stopper mechanism are not engaged via the operation of the operation member, when the load is not applied, the engaging part and the engaged part are engaged, and when the load is applied, they are disengaged.

15. The chair according to claim 14, wherein the seat is configured so as to automatically return to a reference position in the front-rear and left-right directions in a state where the load is not applied by the seated person.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a perspective view, as viewed obliquely from the front, of a chair according to an embodiment of the present invention.

(2) FIG. 2 is a perspective view thereof, as viewed obliquely from behind, in which a part of the chair is removed.

(3) FIG. 3 is an exploded perspective view of front, rear, right, or left support portions in the chair.

(4) FIG. 4 is a perspective view illustrating a state where a left-right swing part is incorporated in a support base part of the chair.

(5) FIG. 5 is a perspective view illustrating a state where a front-rear swing part is incorporated in the left-right swing part.

(6) FIG. 6 is a perspective view of a part of FIG. 5, as viewed obliquely from below.

(7) FIG. 7 is an enlarged perspective view illustrating a part of FIG. 4.

(8) FIG. 8 is a perspective view of a state where a left-right stopper mechanism is incorporated in FIG. 4.

(9) FIG. 9 is an operation explanatory diagram of the left-right swing part.

(10) FIG. 10 is an operation explanatory diagram of the left-right swing part.

(11) FIG. 11 is an operation explanatory diagram of the front-rear swing part, a part of which is illustrated transparently.

(12) FIG. 12 is an operation explanatory diagram of the front-rear swing part, a part of which is illustrated transparently.

(13) FIG. 13 is an operation explanatory diagram of the front-rear swing part, a part of which is illustrated transparently.

(14) FIG. 14 is an exploded perspective view illustrating a relationship between the front-rear swing part and a back.

(15) FIG. 15 is a perspective view illustrating a weight-receiving part provided on a seat.

(16) FIG. 16 is an exploded perspective view of a control mechanism and a front-rear stopper mechanism configured to suppress a front-rear operation.

(17) FIG. 17 is a perspective view of the assembled control mechanism and front-rear stopper mechanism configured to suppress a front-rear operation.

(18) FIG. 18 is a perspective view of FIG. 17, as viewed obliquely from below.

(19) FIG. 19 is an exploded perspective view of a left-right stopper mechanism configured to suppress a left-right operation.

(20) FIG. 20 is a perspective view of a partially assembled left-right stopper mechanism configured to suppress a left-right operation.

(21) FIGS. 21A to 21C are schematic views illustrating suppressing operations for the front, rear, right, or left.

(22) FIG. 22 is an operation explanatory diagram of the left-right stopper mechanism.

(23) FIG. 23 is an operation explanatory diagram of the left-right stopper mechanism.

(24) FIG. 24 is an operation explanatory diagram of the front-rear stopper mechanism.

(25) FIG. 25 is an operation explanatory diagram of the front-rear stopper mechanism.

(26) FIGS. 26A and 26B are operation explanatory diagrams of a control mechanism operating in accordance with a seating state.

(27) FIG. 27 is a partially broken perspective view illustrating an engaging portion of a bearing and a guide hole in the embodiment.

(28) FIGS. 28A to 28C are diagrams for explaining a processing procedure of the guide hole.

(29) FIG. 29 is an exploded perspective view illustrating an operating mechanism of the back.

(30) FIG. 30 is an exploded perspective view illustrating a configuration of the back.

(31) FIG. 31 is a cross-sectional view of the back including the operating mechanism.

(32) FIG. 32 is an explanatory diagram of a guide part included in the operating mechanism.

(33) FIG. 33 is an operation explanatory diagram corresponding to FIG. 31.

(34) FIG. 34 is an operation explanatory diagram corresponding to FIG. 31.

(35) FIG. 35 is an operation explanatory diagram according to a turning operation of a backrest.

(36) FIG. 36 is an exploded perspective view illustrating a restricting portion configured to restrict the operation of the back.

(37) FIG. 37 is a perspective view illustrating a lower surface of the seat.

(38) FIG. 38 is an exploded perspective view of the seat.

(39) FIG. 39 is an enlarged cross-sectional view of a front part of the seat.

(40) FIG. 40 is a diagram illustrating an operation of a deformation part.

(41) FIG. 41 is a diagram illustrating a recess configuring the front-rear stopper mechanism and the control mechanism according to modification of the present invention.

(42) FIG. 42 is a perspective view of a part of the front-rear stopper mechanism and the left-right stopper mechanism according to another modification of the present invention.

MODE FOR CARRYING OUT THE INVENTION

(43) An embodiment of the present invention will be described below with reference to the drawings.

(44) As illustrated in FIGS. 1 to 5, this chair is an office chair configured by erecting a leg supporting post 13 incorporating a lifting/lowering mechanism therein, in a central part of a leg vane 12 supported by a caster 11, and attaching a support base part 2 rotatably at an upper end side of the leg supporting post 13. In the support base part 2, a seat 5 being a movable part is supported via a front-rear swing part 3 as a one-direction operating part (movable part) operable any one of a front-rear direction (X-direction in the drawings) and a left-right direction (Y-direction in the drawings) being two directions crossing each other, and a left-right swing part 4 being an other-direction operating part (support part) operable in the other of the front-rear direction and the left-right direction and the seat 5 can swing in the front-rear direction and the left-right direction with respect to the support base part 2. Specifically, the front-rear swing part 3 is provided between the seat 5 and the support base part 2 configured to support the seat 5, and the left-right swing part 4 is provided between the front-rear swing part 3 and the support base part 2. Behind the seat 5, a back 6 is arranged.

(45) The support base part 2 functions as a structured body for receiving the load applied by seated person, and in the support base part 2, a left-right pair of arm attachment parts 23 is integrally formed with the support base part 2 via a bearing base part 22 on both left and right sides of a support base main body 21 including a through hole 21a along an up-down direction into which an upper end of the leg supporting post 13 is inserted. A shaft swing damper 21b is attached to the hole 21a opening on the surface of the support base main body 21 in the front-rear direction and upper ends of left-right swing links L1, L2 are attached to holes 22a opening on the front and rear surfaces of the bearing base part 22, via swing support shafts S1, S2.

(46) The left-right swing part 4 includes a pair of plate-shaped link bases 41 disposed separated from each other in the front-rear direction to perform a swinging operation in the left-right direction with respect to the support base part 2, and a left-right swing main body 42 configured to connect the pair of link bases 41, 41. At both left and right ends of the link bases 41, holes 41a, 41a are opened and the lower ends of the left-right swing links L1, L2 are attached via swing shafts S3, S4. FIG. 4 illustrates a state where the links L1, L2 are attached via the swing shafts S1 to S4. As illustrated in FIGS. 7 and 8, the left-right swing main body 42 is provided with a unit attached hole 42a penetrating in the up-down direction, and a later-described left-right lock part 7 is attached to the unit attached hole 42a. That is, the left-right swing main body 42 is disposed in a suspended state to be swingable to the left and right with respect to the support base part 2 via the left-right swing links L1, L2, and the left-right swing links L1, L2 are attached so that the distance between the lower ends is smaller than the distance between the upper ends, as illustrated in FIG. 4 and the like.

(47) That is, as illustrated in FIGS. 9 and 10, when the left-right swing part 4 swings, the link L2 (L1) located at the swing destination approaches a vertical posture and the other link L1 (L2) approaches a horizontal posture, as a result of which an operation is performed in which a center of gravity of the left-right swing part 4 is lifted while tilting so that a moving tip side is lower.

(48) A window 41c is opened at the center of the link base 41, a rolling damper 44 is positioned in the window 41c, and a swing range of the left-right swing part 4 is restricted to a range where the rolling damper 44 can perform a relative movement within the window 41c.

(49) The front-rear swing part 3 includes a pair of plate-shaped rail plates 31, 31 disposed separated from each other in the left-right direction to perform a swinging operation in the front-rear direction with respect to the left-right swing part 4, and an upper connection plate 32 and a front connection plate 33 configured to connect the pair of rail plates 31, 31. At a front side of the rail plates 31, a guide hole 34 is provided to penetrate the rail plates 31, a bearing 45a is engaged in the guide hole 34, and the bearing 45a is a rolling body 45 provided to be rollable independently to the left and right on a side surface at a front end side of the left-right swing main body 42. The reference sign 45z in the drawings indicates a spacer disposed on an inner surface side of the rail plate 31 and having a diameter larger than that of the bearing 45a. The rear end side of the rail plate 31 extends rearward and downward, a lower end of a link arm LA, being a swingable front-rear swing link, is attached via a swing shaft S5 to an extension end of the rail plate 31, and the upper end of the link arm LA is supported by the rear end of the left-right swing part 4 via a swing shaft S6. That is, the rear end of the front-rear swing part 3 is disposed in a suspended state to be swingable forward and rearward with respect to the left-right swing part 4 via the link arm LA. The guide hole 34 has a shape that is gently curved forward and downward from the rear end side toward the front end side, and at the rear end, there is provided a shockless part SL configured to mitigate a shock when the front-rear swing part 3 moves forward together with the seat 5. The upper connection plate 32 is provided with a unit attached hole 32a penetrating in the up-down direction, and a front-rear lock unit 8 described later based on FIG. 16 is attached to the unit attached hole 32a. Axles of the bearing 45a being the rolling body 45 in the example of the drawings are separated to the left and right. However, as long as the bearing 45a being the rolling body 45 is rollable independently to the left and right, the axle may be common.

(50) That is, when the front-rear swing part 3 moves rearward, as illustrated in FIG. 12, from the state of FIG. 11 where the upper surface of the front-rear swing part 3 takes a substantially horizontal posture, the bearing 45a performs a relative movement with respect to the front end side of the guide hole 34 at the front end of the front-rear swing part 3, so that the front end side of the front-rear swing part 3 is lifted to a high position, and the link arm LA approaches a vertical posture. As a result, an operation is performed where the rear end side of the front-rear swing part 3 is guided to a lower position. Conversely, when the front-rear swing part 3 moves forward, as illustrated in FIG. 13, from the state of FIG. 11, the bearing 45a performs a relative movement with respect to the rear end side of the guide hole 34 at the front end of the front-rear swing part 3, so that the front end side of the front-rear swing part 3 is guided to a lower position, and the link arm LA approaches a horizontal posture. As a result, an operation is performed where the rear end of the front-rear swing part 3 is lifted to a higher position. That is, the front-rear swing part 3 performs an inclining operation so that the moving tip side is also lower in the front-rear direction.

(51) On the front end side of the rail plate 31 included in the front-rear swing part 3, a pitching damper 31c formed by bending a part of the rail plate 31 is provided, and when swinging rearward, the front-rear swing part 3 abuts against a front end lower part 4z (see FIG. 3) of the left-right swing part 4 in the vicinity of the swing end to mitigate the shock at the rearward movement end.

(52) As illustrated in FIG. 14, a back frame 61 included in the back 6 is attached to a rear part of the upper connection plate 32 included in a front-rear swing part 3, and a seat outer shell 51 (see FIG. 15) included in the seat 5 is attached to the connection plate 32 from above. That is, when the back frame 61 configured to support a backrest 62 is erected integrally behind the seat 5 and the seat 5 swings in the front-rear and left-right directions with respect to the support base part 2, as indicated by X and Yin the drawing, the back frame 61 also moves together with the seat 5, but the backrest 62 according to the present embodiment operates separately from the back frame 61 and the seat 5, as described later.

(53) A front-rear stopper mechanism 8M utilizing the front-rear lock unit 8 illustrated in FIGS. 16 to 18 is provided to a swinging of the seat 5 in the front-rear direction relative to the support base part 2 at a predetermined position through an operation of an operating member 152 illustrated in FIG. 15. A left-right stopper mechanism 7M utilizing the left-right lock unit 7 illustrated in FIGS. 19 and 20 are provided to suppress a swinging of the seat 5 in the left-right direction relative to the support base part 2 at a position determined in advance through an operation of an operating member 151 (being an operating member common with the operating member 152 in practice) illustrated in FIG. 15.

(54) In this embodiment, the left-right swing part 4 is supported by the support base 2 and the front-rear swing part 3 is supported by the left-right swing part 4 so that a layered structure is formed in which the left-right stopper mechanism 7M is provided between the support base part 2 and the left-right swing part 4, and the front-rear stopper mechanism 8M is provided between the left-right swing part 4 and the front-rear swing part 3.

(55) The left-right stopper mechanism 7M is configured to switch between allowing and suppressing the swinging of the seat 5 in the left-right direction, by engaging or disengaging an engaging element 71 and an engaged element 72 illustrated in FIG. 21A when the operating member 151 illustrated in FIG. 15 is operated. Specifically, the left-right stopper mechanism 7M includes an engagement pin 71a being the engaging part 71 provided at the side of the left-right swing part 4 and a groove 72a being the engaged part 72 provided on a sliding surface 20, the engaged part 72 relatively operating at the side of the support base part 2 being a position facing the engagement pin 71a. The engagement pin 71a is configured to be elastically biased toward the sliding surface 20, and to be fitted in the groove 72a at a predetermined position. As illustrated in FIGS. 3 and 7, the groove 72a has a rectangular shape in plan view and is provided at a center reference position in the left-right direction of the support base part 2 exposed upward via an opening 4t of the left-right swing part 4, and the engagement pin 71a illustrated in FIG. 20 is engaged to and disengaged from the groove 72a. A coil spring 73a being an elastic member 73 functions to bias the engagement pin 71a in a direction where the engagement pin 71a protrudes toward the sliding surface 20. Further, the left-right stopper mechanism 7M includes a conversion mechanism 74 illustrated in FIGS. 19 and 20 configured to convert an operation of the operating member 151 into an operation in a direction in which the engagement pin 71a is separated from the sliding surface 20 and the conversion mechanism 74, the engagement pin 71a and the coil spring 73a are integrally incorporated into a casing 70 of the left-right lock unit 7 to form with unitized.

(56) As illustrated in FIG. 19, the casing 70 has a halved structure, and the engagement pin 71a is disposed to be liftable and lowerable in a state where a wide part 71aw of the engagement pin 71a is guided by inner surfaces of side walls 70a, 70b of the casing 70 while a tip end part 71as being a part of the engagement pin 71a protrudes from a lower end of the casing 70. The conversion mechanism 74 includes the above-described coil spring 73a provided elastically in a compressed state between an upper end of the engagement pin 71a and an upper wall 70p of the casing 70, a stopper operation arm 75 rotatably supported via a horizontal shaft 70c between the side walls 70a, 70b of the casing 70 at a position adjacent to the engagement pin 71a, a torsion coil spring 76 rotatably attached together with the stopper operation arm 75, and a wire tube 77 including a spherical wire tip end 77a to be attached to the stopper operation arm 75 and a tube tip end 77b locked to the casing 70. As illustrated in FIG. 15, the other end of the wire tube 77 is locked in the vicinity of an operation lever 151a being the operating member 151 provided in the seat 5 and a wire base end 77c drawn therefrom is connected to the operation lever 151a. A tip end 76b of the torsion coil spring 76 is engaged with a hole 71a1 provided on the engagement pin 71a.

(57) When the casing 70 is fitted into the unit attached hole 42a of a swing main body part 42 included in the left-right swing part 4 illustrated in FIG. 7 to achieve the state in FIG. 8, an attachment part 70m provided in the casing 70 is mounted on an upper surface of the swing main body part 42 and fixed by screwing. The left and right side walls 70a, 70b of the casing 70 are tightly accommodated between left and right side walls 42a1, 42a2 of the unit attached hole 42a and the engagement pin 71a is tightly guided in the casing 70 by the inner surfaces of the side walls 70a, 70b of the casing 70. In this way, a rattling of the engagement pin 71a to the left and right is suppressed, and thus, the unit attached hole 42a of a left-right swing part 4 illustrated in FIG. 7 includes merely the left and right side walls 42a1, 42a2, a rear wall 42a3, and an inclined front wall 42a4 to form the lower opening 4t without a bottom wall. The engagement pin 71a is configured to hang directly from the lower opening 4t of the unit attached hole 42a without being guided by the bottom wall to abut against the sliding surface 20, to engage with the groove 72a. Parts in the front-rear direction of the engagement pin 71a are supported by front and rear guide walls formed in the casing 70. The groove 72a is formed between longitudinal ribs r1, r1 provided in the support base part 2, lateral ribs r2 are provided around the longitudinal ribs r1, r1, and upper surfaces of the longitudinal ribs r1 and the lateral ribs r2 form the sliding surface 20 on which the engagement pin 71a slides until engaging with the groove 72a.

(58) As illustrated in FIG. 22, when the operation lever 151a is in an unlocked position, the wire tube 77 rotates the stopper operation arm 75 to compress the coil spring 73a while the engagement pin 71a is lifted upwards at a tip end 76b of the torsion coil spring 76. When the operation lever 151a is operated to a locked position, as illustrated in FIG. 23, the tip end 76b of the torsion coil spring 76 rotates together with the stopper operation arm 75 by the repulsive force of the coil spring 73a, the engagement pin 71a is pressed downward, and when the engagement pin 71a engages with the groove 72a of the support base part 2, the locked state in the left-right direction is realized.

(59) The front-rear stopper mechanism 8M is configured to switch between allowing and suppressing the swinging of the seat 5 in the front-rear direction, by engaging or disengaging an engaging element 81 and an engaged part 82 illustrated in FIG. 21B when the operating member 152 illustrated in FIG. 15 is operated. Specifically, a configuration is so that the front-rear stopper mechanism 8M includes an engagement pin 81a being the engaging part 81 provided at the side of the front-rear swing part 3 and a groove 82a being the engaged part-82 provided on a sliding surface 40, the engaged part 82 relatively operating at the side of the left-right swing part 4 being a position facing the engagement pin 81a. The engagement pin 81a is configured to be elastically biased toward the sliding surface 40, and to fit in the groove 82a at a predetermined position. As illustrated in FIG. 7, the groove 82a is provided on an upper surface of the swing main body part 42 of the left-right swing part 4 at one or more predetermined locations (one location in the present embodiment) within a movable range of the engagement pin 81a when the engagement pin 81a of the front-rear swing part 3 mounted on the upper surface of the swing main body part 42 moves in the front-rear direction, and thus, the groove 82a has a shape extending in the left-right direction and an upper surface of a swing main body part 42 forms the sliding surface 40. A coil spring 83a being an elastic member 83 functions to bias the engagement pin 81a in a direction where the engagement pin 81a protrudes toward the sliding surface 40, a conversion mechanism 84 illustrated in FIGS. 16 and 17 is provided, the conversion mechanism 84 converting an operation of the operating member 152 into an operation in a direction in which the engagement pin 81a is separated from the sliding surface 40, and the conversion mechanism 84, the engagement pin 81a, and the coil spring 83a are integrally incorporated into a half-piece of the casing 80 to form with unitized.

(60) The casing 80 has a flat saucer-shape opened upward, and thus, the engagement pin 81a is guided by a guide 80g1 in the casing 80, and is disposed to be liftable and lowerable with a part of the engagement pin 81a protruding from a lower end of the casing 80. The conversion mechanism 84 includes the above-described coil spring 83a provided elastically in a compressed state between an upper end of the engagement pin 81a and a cover 80a closing the upper opening of the casing 80, a stopper operation arm 85 rotatably supported by a horizontal shaft 80c disposed between side walls 80b, 80b of the casing 80 at a position adjacent to the engagement pin 81a, a torsion coil spring 86 rotatably attached together with the stopper operation arm 85, and a wire tube 87 having a spherical wire tip end 87a that is attached to the stopper operation arm 85 and a tube tip end 87b locked to the casing 80. As illustrated in FIG. 15, the other end of the wire tube 87 is locked in the vicinity of an operation lever 152a being the operating member 152 provided in the seat 5 and a wire base end 87c drawn therefrom is connected to the operation lever 152a. A tip end 86a of the torsion coil spring 86 is at all times smoothly slidably engaged with a downward-facing surface 81a1 of the engagement pin 81a.

(61) When the operation lever 152a illustrated in FIG. 15 is in an unlocked position, the wire tube 87 illustrated in FIG. 17 rotates the stopper operation arm 85 to compress the coil spring 83a while the engagement pin 81a is lifted upwards at a tip end 86a of the torsion coil spring 86, as illustrated in FIG. 24. When the operation lever 152a is operated to a locked position, the tip end 86a of the torsion coil spring 86 rotates, as illustrated in FIG. 25, together with the stopper operation arm 85 by the repulsive force of the coil spring 83a, the engagement pin 81a is pressed downward, and when the engagement pin 81a engages with the groove 82a of the left-right swing part 4, the locked state in the front-rear direction is realized.

(62) It is noted that, in the chair according to the embodiment, a control mechanism 8X configured to automatically suppress a movement of the seat 5 in the front-rear direction at a predetermined position when the seated person leaves the seat, is provided along with the half-piece of the front-rear lock unit 8 of the front-rear stopper mechanism 8M.

(63) First, to detect seating of the seated person, a configuration is such that a weight-receiving part 50 (see FIG. 15), the height position of which changes due to a person sitting on a seat surface, is provided substantially at a center position of the seat 5, the change of the height position is mechanically transmitted to the control mechanism 8X illustrated in FIGS. 16 and 18 configured to control an operation of the front-rear swing part 3 being the movable part, and the control mechanism 8X changes the operation of the front-rear swing part 3, that is, the front-rear operation of the seat 5, between allowed and suppressed states.

(64) The operation changer 8X changes the allowed/suppressed states of the operation of the front-rear swing part 3 when an engagement state of an engaging part 81X illustrated in FIG. 21C and provided in the front-rear swing part 3 being a movable part and an engaged part 82X provided in the left-right swing part 4 being a support part configured to support the front-rear swing part 3 changes due to the load applied by seated person, and returns, by the elastic member 83X, the state of the front-rear swing part 3 from an operation state where the operation of the front-rear swing part 3 is allowed to the original state where the operation of the front-rear swing part 3 is suppressed, when the load applied by seated person is removed.

(65) The chair is configured such that the engaged part 82X is a recess 82aX, and when the load applied by seated person is received in the state where the engaging part 81X is fitted into the recess 82aX, the fitted state is released, so that the engaging part 81X and the engaged part 82X are disengaged due to the load applied by seated person, and when the load applied by seated person is removed, the engaging part 81X and the engaged part 82X engage with each other by the elastic force to bring the front-rear swing part 3 into an operation-suppression state.

(66) The control mechanism 8X includes an engagement pin 81aX being the engaging part 81X; and a groove-shaped recess 82aX being an engaged part 82X provided on a sliding surface 40X relatively operating at a position facing the engaging pin 81X. The engagement pin 81aX is configured to be elastically biased toward the sliding surface 40X, and to fit in the groove-shaped recess 82aX at a predetermined position. Then, when the seat 5 detects received of the load applied by seated person in a central part, the control mechanism 8X illustrated in FIGS. 16 and 17 separates the engagement pin 81aX from the groove-shaped recess 82aX. A coil spring 83aX being an elastic member 83X functions to bias the engagement pin 81aX in a direction where the engagement pin 81aX protrudes toward the sliding surface 40X. The control mechanism 8X includes a conversion mechanism 84X configured to convert an operation of the weight-receiving part 50 due to a person sitting on the seat, into an operation in a direction where the engagement pin 81aX is separated from the sliding surface 40X, and the conversion mechanism 84X, the engagement pin 81aX, and the coil spring 83aX are integrally incorporated into an other-half part of the casing 80 illustrated in FIG. 16, to form with unitized.

(67) The engagement pin 81aX is disposed to be 1 liftable and lowerable along front, rear, right, and left guides 80g2 of the casing 80, in a parallel relationship with the engagement pin 81 in the flat casing 80 configuring the front-rear stopper mechanism 8M. Similarly in parts to the conversion mechanism 84, the conversion mechanism 84X includes the coil spring 83aX provided elastically in a compressed state between an upper end of the engagement pin 81aX and the cover 80a closing the upper opening of the casing 80, a safety operation arm 85X rotatably supported by the horizontal shaft 80c disposed between side walls 80b, 80b of the casing 80 at a position adjacent to the engagement pin 81aX, and a torsion coil spring 86X rotatably attached together with the safety operation arm 85X. On the other hand, the weight-receiving part 50 is, as illustrated in FIG. 15, a pressure-receiving plate 52a rotatably fitted and attached to the seat outer shell 51 included in the seat 5, and a convex part 52b provided below the pressure-receiving plate 52a is disposed at a position displaced from the center of rotation of the safety operation arm 85X, where the convex part 52b can press a pressed part 85xt illustrated in FIG. 16. A tip end 86aX of the torsion coil spring 86X is at all times smoothly slidably engaged with a downward-facing surface of the engagement pin 81aX. The pressure-receiving plate 52a is biased in a direction away from the safety operation arm 85X by a coil spring 52c being an elastic body illustrated in FIGS. 26A and 26B. As illustrated in FIG. 37, a hole part 53x configured to avoid interference with the pressure-receiving plate 52a is provided at a corresponding position of a seat inner shell 53.

(68) As illustrated in FIG. 26B, when the weight-receiving part 50 does not sense the weight of the seated person, the engagement pin 81X is pressed downward by the coil spring 83aX while a tip end 85aX of a torsion coil spring 86X rotates together with the safety operation arm 85X, and when the engagement pin 81X engages with a groove 82aX of the front-rear swing part 3, the locked state in the front-rear direction is realized. As illustrated in FIG. 26A, when the weight-receiving part 50 detects the weight of the seated person, when the engagement pin 81X is pulled upward at the tip end 86aX of the torsion coil spring 86X while compressing the coil spring 83aX, the engagement pin 81X is disengaged from the groove-shaped recess 82aX and the locked state in the front-rear direction is released.

(69) That is, when a user is seated, the control mechanism 8X is unlocked, and afterwards, whether or not the seated person locks a movement in the front-rear direction depends on the state of a front-rear fixing stopper mechanism 8M, through the operation of the operating member 152, and when the seated person leaves the seat, the state is maintained unless the front-rear fixing stopper mechanism 8M is unlocked, and if the front-rear fixing stopper mechanism 8M is unlocked, the control mechanism 8X actuates to lock the front-rear operation of the seat 5.

(70) In particular, in this chair, the seat 5 tilts at least back and forth, and when the seated person starts standing up, the seat 5 moves while tilting forward together with the front-rear swing part 3, as illustrated in FIG. 13. When the seated person leaves the seat in this state and the load applied by seated person is removed, the engagement pin 81aX being the engaging part 81X illustrated in FIG. 21C settles on the sliding surface 40X in the front of the recess 82aX being the engaged part 82X. Afterwards, the seat 5 starts moving while tilting rearward in accordance with a relationship of the center-of-gravity position between the back and the seat, due to the presence of the back 6. During this movement, it is expected that the engagement pin 81aX being the engaging part 81X engages with the recess 82aX being the engaged part 82X. As illustrated in FIG. 7, in the recess 82aX, grooves are provided in a linked manner in an orthogonal direction, and a buffer material 82z such as rubber is embedded. The buffer material 82z is for avoiding collision of the engagement pin 81aX with the wall of the recess 82aX and a shock or an abnormal noise caused, and after colliding with the buffer material 82z. The engagement pin 81aX collides with the buffer material 82z and fits into the recess 82aX.

(71) It is noted that, when a person sits on the seat, the engagement pin 81aX and the recess 82aX are disengaged, however, the engagement pin 81aX and the recess 82aX engage with a certain degree of resistance, and thus, the locked state is not released immediately after the person sits on the seat, but is released when the resistance decreases due to a small movement of the seat 5.

(72) That is, the control mechanism 8X switches the locked state of the seat 5 between when the seated person leaves the seat and when sitting on the seat, and thus, may be called a “seat-leaving and seat-sitting automatic stopper mechanism”.

(73) Next, the guide hole 34 illustrated in FIG. 3 will be described. Even if the rail plate 31 being a plate member PM is thickened or a separate member is attached to the rail plate 31 to provide the guide hole 34 for securing a pressure-receiving area, this may only lead to an increase in the number of parts and the cost and does not necessarily lead to improvement of strength and durability.

(74) Therefore, in the present embodiment, as illustrated in FIG. 27, a flange part 31b is provided on the plate member PM of the front-rear swing part 3 being the movable portion in which the guide hole 34 is provided, that is, on a vertical surface 31a of the rail plate 31, and a guide surface 31b1 for moving the bearing 45a being the rolling body 45 in the longitudinal direction is provided at a position extending in the lateral direction of the flange part 31b, that is, in the horizontal direction in the attached state.

(75) A lateral dimension w1 of the guide surface 31b1 is greater than a thickness t1 of the rail plate 31 being the plate member PM. The guide surface 31b1 is integrally formed of metal together with the rail plate 31. As illustrated in FIG. 3 and the like, the flange part 31b has a shape—that goes around the circumference of the guide hole 34 opened in the vertical surface.

(76) The flange part 31b according to this embodiment is configured by plastic deformation processing of the plate member PM around the guide hole 34, and specifically, by adopting burring processing. In general, in the burring processing, a pilot hole is opened in a plate member, the periphery of the pilot hole is fixed with a jig and in this state, the edge of the pilot hole is raised, by pressing with a tool larger than the pilot hole, to form a flange part, and thus, a cylindrical flange is generally formed. So far, burring processing has only been utilized for forming tapped holes and the like and has not been considered for producing a structure for guiding a rolling body.

(77) Therefore, in the present embodiment, based on this new perspective, as illustrated in FIG. 28A, to form an asymmetrical hole, or more specifically, the guide hole 34 extending with a substantially constant width, a pilot hole 34x corresponding to the shape of the guide hole 34 is opened with a slightly smaller size than the guide hole 34, as illustrated in FIG. 28B. Then, the periphery of the pilot hole 34x is fixed with a jig 34Z along the shape of the guide hole 34, and in this state, pressing is performed with a tool 34Y that is larger than the pilot hole 34x and corresponds to the inner circumferential shape of the guide hole 34. Thus, as illustrated in FIG. 27, the flange part 31b extending in the lateral direction via a portion R from the vertical surface 31a is formed over the entire circumference of the guide hole 34, and the flange part 31b directed in this lateral direction is substantially the pressure-receiving area. The lateral dimension of the guide surface 31b1 is substantially uniform over the entire circumference.

(78) The manufacturing means for the guide hole 34 is selected based on the conditions that the guide surface 31b1 is smooth, the guide surface 31b1 has strength, and the manufacturing cost is low. Fine blanking processing and other processing were also tried, however, it turned out that, even though the fine blanking processing relatively likely to be selected was excellent in forming a smooth guide surface, the plate member needed to have a considerable thickness to obtain strength. Thus, the fine blanking processing could not be adopted due to its inappropriate cost and other processing also did not satisfy the conditions above. Overall, it turned out that burring processing met these conditions very suitably.

(79) However, when a shortest distance D from the guide hole 34 to the nearest edge of the plate member PM is narrow in the burring processing, the plate member PM is deformed during the processing or due to the load applied during the processing. As a result of attempting various tests in this embodiment, it was found that it was necessary and sufficient, as a condition for obtaining a stable shape, to set the shortest distance D (see FIG. 28) from the guide hole 34 to the edge of the plate member PM at an appropriate position to at least 15 mm or more for 2 to 6 mm of a thin plate.

(80) As illustrated in FIG. 27, when viewing the entire chair, the flange part 31b formed in this way extends outward from the pair of rail plates 31, 31, rather than inward in the left-right direction, and the guide surface 31b1 being a rolling surface is formed outside the rail plates 31. Further, to mitigate a shock caused from a collision with the bearing 45a being the rolling body 45, one end (the front end or the rear end) of the guide hole 34 is formed with a so-called shockless part in which the radius of curvature is changed, so that as the bearing 45a approaches the end due to an operation of the seat 5, the operation speed of the seat 5 is reduced by performing control so that the center of gravity of the seat 5 is lifted. The flange part 31b1 made by burring is designed to withstand the shock caused during this time.

(81) Further, when a left-right support state of the front-rear swing part 3 for the left-right swing part 4 becomes unbalanced, a lower region of the guide hole 34 causes the bearing 45a being the rolling body 45 to abut against the lower region of the guide hole 34 to support the bearing 45a and the flange part 31b contributes to supporting the load during this time.

(82) Generally speaking, as illustrated in FIG. 28C, the flange part 31b includes an upper-side first flange area A1 supporting the back and forth movement of the bearing 45a being the rolling body 45 when the seat 5 operates back and forth, a front-side second flange area A2 supporting a portion where the bearing 45a being the rolling body 45 reaches the front end of the guide hole 34 when the seated person leans against the back 6, and a rear-side third flange area A3 supporting a portion where the bearing 45a being the rolling body 45 reaches the rear end of the guide hole 34 when the seated person leans forward. Further, the flange part 31b includes a lower-side fourth flange area A4 supporting the bearing 45a being the rolling body 45 when the left-right support state is unbalanced. This structure remains similar, even if the guide hole 34 is formed at the side of the support portion and the bearing 45a being the rolling body 45 is disposed at the side of the movable portion.

(83) As described above, the guide hole 34 is formed in the vertical surface of the movable portion or the support portion of the chair and moves while receiving the load applied by seated person. The movable portion is supported at two locations on the front and rear side by the support portion including a guide structure configured by the rolling body 45 and the guide hole 34. In the present embodiment, the other movable portion of the chair is supported by the link arm LA, any one of the front and rear support structures is configured by the above-described rolling body 45 and the guide surface 31b1, and the other is configured by a different support structure, that is, in this embodiment, of the link structure.

(84) Next, the support mechanism of the back 6 will be described. As illustrated in FIGS. 2, 14, 30, and 29, in this chair, the back 6 is arranged behind the seat 5 and the backrest 62 is configured to be supported by the back frame 61 via the operating mechanism 6M. A back inner cover 63 is attached to the back frame 61, an opening 63a is provided in the back inner cover 63, and the backrest 62 is operatively supported by the back frame 61 via the opening 63a.

(85) The backrest 62 includes a cushion arranged on the front surface of a back plate 62a and the backrest 62 is entirely covered by an upholstery fabric. A lower end of the backrest 62 is disposed at a predetermined distance above the seat surface and the backrest 62 is supported on a back surface side by a back support part 61a at an upper end of the back frame 61 via the operating mechanism 6M.

(86) The operating mechanism 6M includes: a base part 64 fixed to or formed integrally with the back plate 62a included in the backrest 62 and including an elastic body 67 arranged on a back surface side of the base part 64; a tilting part 65 disposed at a position adjacent to the base part 64 and including a guide part 65a recessed in a tapered shape at the back surface side, the center of the guide part 65a being open in the front-rear direction; and a pressing tool 66 including a convex guide part 66a corresponding to the guide part 65a on the front surface side, the pressing tool 66 being fixed to the base part 64 via the opening of the tilting part 65 in a state where the guide part 66a is fitted into the guide part 65a, as illustrated by an arrow J in FIG. 29. As illustrated by arrows K in FIGS. 29 and 30, a configuration of the operating mechanism 6M is such that the tilting part 65 is pulled and passed through the opening of the back inner cover 63 to be fixed by a screw to the back support part 61a at the upper end side of the back frame 61. That is, as illustrated in FIG. 31, the pressing tool 66 is fixed to the base part with the tilting part 65 interposed therebetween, and thus, the pressing tool 66 is integrally formed with the base part 64 to form a part of the base part 64. The tilting part 65 can move freely in the gap between the base part 64 and the pressing tool 66, however, a configuration is such to allow for free movement of the tilting part 65, it is necessary to compress an elastic body 67 interposed between the tilting part 65 and the base part 64 against the elastic force. The elastic body 67 exerts a force on the guide part 65a of the tilting part 65 in a direction where the guide part 65a is constantly fitted in the guide part 66a of the pressing tool 66.

(87) More specifically, as illustrated in FIG. 32, the recess guide part 65a of the tilting part 65 has a substantially partially elliptical mortar-like shape including at least one valley line 65ax (two in this embodiment), the convex guide part 66a of the pressing tool 66 has a curved shape having at least one ridge line 66ax (two in this embodiment) fitted smoothly into the valley line 65ax, and the valley line 65ax and the ridge line 66ax can be fitted into each other. The convex guide part 66a is similar to a shape obtained by eliminating a part of an elliptical sphere, and the ridge line 66ax is formed along a line by a guide surface 66a intersected on the long axis side of the elliptical sphere. In a corresponding position of the matching recess guide part 65a, the valley line 65ax is also formed at the position where the guide surfaces 65a are intersected. The reason therefore is that a spherical body and a spherical surface-receiving seat do not have directionality and cannot perform a positioning function. In that sense, the convex guide part 66a and the recess guide part 65a are not limited to the mortar-like shape and the shape of the elliptical sphere, as long as they have different shapes that uniquely determine the directionality during fitting. However, in view of the smoothness of the guides, the guide parts 66a, 65a need to be configured of a smooth continuous surface. The ridge line 66ax and the valley line 65ax are provided to enhance the positioning function during fitting.

(88) In this embodiment, urethane is used for the elastic body 67, and as illustrated in FIG. 29, the elastic body 67 is arranged from the left and right corner parts to the upper edge portion of the upper half of the rectangular plate-shaped base part 64. As illustrated in FIG. 31, the thickness dimension of the elastic body 67 is set to achieve an appropriately compressed state in a state where the pressing tool 66 is attached to the base part 64, the tilting part 65 is attached to the back support part 61a of the back frame 61, and the guide part 66a of the pressing tool 66 and the guide part 65a of the tilting part 65 are fitted into each other. In view of the fact that the load is applied to a part above the center of the operating mechanism 6M when the seated person leans against the backrest 62, the elastic body 67 is not provided in the lower half of the base part 64 where there is little occasion to perform a function substantially, however, provision of the elastic body 67 in this position shall not be precluded.

(89) FIG. 33 illustrates a rearward tilted state when a load is applied to the upper part of the back 6, and FIG. 34 is a plane cross section thereof. Further, FIG. 35 illustrates a turning operation of the back 6 in a case where the seated person twists its body and the like.

(90) That is, the backrest 62 is disposed in a positional relationship where the backrest 62 moves against the elastic reaction force in the rearward direction and the turning direction while being supported by the elastic body 67, and a configuration is such that, when the elastic body 67 is deformed to the front, rear, right, or left in accordance with the amount of turning movement in the front, rear, right, or left directions, the reaction force returning the backrest 62 to a neutral position increases. The turning direction includes a turning movement in the left-right direction in front view, as illustrated in FIG. 35, and further, in a clockwise or counterclockwise direction in front view.

(91) The guide part 65a of the tilting part 65 and the guide part 66a of the pressing tool 66 included in the base part 64 are guided to and stopped in a reference position illustrated in FIG. 31 because of the shape of the guide parts 66a, 65a by pressure contact with the elastic body 67. Subsequently, when the pressure contact is loosened due to an elastic body 67 being compressed by a load being applied due to receiving pressure from the seated person, the guide part 65a of the tilting part 65 and the guide part 66a of the pressing tool 66 included in the base part 64 are at least partly separated, as illustrated in FIGS. 33, 34, and 35, so that the backrest 62 moves freely. The base part 64 and the tilting part 65 relatively move relative to the reference position in accordance with an amount of the received pressure and when the load is removed, the operating position is automatically returned, along the guide parts 66a, 65a, to the neutral position of FIG. 31 where the ridge line 66ax and the valley line 65ax coincide with each other. At this time, the backrest 62 is configured so that a gap SP between the guide parts 66a, 65a widens in accordance with a movement in the rear direction with respect to the back frame 61, and as a result, a turning range in the left-right direction expands and a return reaction force generated when the load is removed increases in accordance with the amount of turning movement in both the left and right directions.

(92) It is noted that, as illustrated in FIG. 36, the base part 64 and the tilting part 65 are provided with engaging parts 64b, 65b configured to restrict a relative movement of the base part 64 and the tilting part 65 in collaboration with the guide parts 65a, 66a. The base part 64 includes an upright wall 64c at a peripheral edge, and a window 64b1 to be the engaging part 64b opens in a rectangular shape in the upright wall 64c. On the other hand, in the tilting part 65, an L-shaped claw 65b1 to be the engaging part 65b is formed at a position displaced downward on the front side. Then, the base part 64 and the tilting part 65 are assembled with the claw 65b1 loosely fitted in the window 64b1, and a movable range of the tilting part 65 with respect to the base part 64 is restricted to a range where the claw 65b1 can move in the window 64b1. When the movable range is restricted, a part of the backrest load is also supported in this restriction portion.

(93) As described above, the left-right turning operation of the back 6 occurs with respect to the back frame 61 and the seat 5 is attached to the front-rear swing part 3 to which the back frame 61 is attached, and thus, the back frame 61 and the seat 5 integrally swing in the left-right direction in front view, however, the backrest 62 further performs a different movement separately from the left-right turning operation of the seat 5 and the back frame 61.

(94) It is noted that, in this embodiment, the base part 64 is attached to the backrest 62 and the tilting part 65 is attached to the side of the back frame 61, however, a configuration may be so that the base part 64 is attached to the side of the back frame 61 and the tilting part 65 is attached to the side of the backrest 62.

(95) Next, a front support mechanism of the seat will be described.

(96) As described above, in this chair, the seat 5 is configured to be supported to be swingable to the front, rear, right, or left with respect to the support base part 2, however, a feeling of pressure on a femoral region of the left and right legs of the seated person sitting on the chair configured to swing to front, rear, right, or left, may change to be unbalanced depending on the posture of the seated person. Further, in this chair, the back 6 is provided to tilt rearward behind the seat 5 and when the back 6 tilts rearward, the seat 5 moves together with the back 6 and performs an operation in which the front part of the seat 5 rises relative to the back part of the seat 5 which descends, and as a result, the seated person may experience a feeling of pressure on the femoral region of the legs when leaning rearward and anxiety or instability due to the legs of the seated person being lifted in the air.

(97) Thus, as illustrated in FIGS. 38, 37, and 39, this chair is provided with a deformation part 5X configured to change its shape in the up-down direction when receiving the load applied by seated person on a front part 5f of the seat 5.

(98) The deformation part 5X is provided at a position receiving the weight of the legs of the seated person, and is configured to deform downward when receiving the weight of the legs and to return upward when the weight of the legs is removed.

(99) Specifically, as illustrated in FIG. 38, in the seat 5, a cushion material 54 covered by a non-illustrated upholstery fabric is arranged on the seat inner shell 53, and the seat outer shell 51 is attached below the seat inner shell 53. The seat inner shell 53 is configured by connecting a rear part 53a and a front part 53b with a resin hinge part 53c, and the front part 53b is elastically deformed with respect to the rear part 53a with the resin hinge part 53c as a boundary. Together with this deformation, the cushion material 54 is also deformed, and thus, these portions configure the deformation part 5x.

(100) Then, the seat outer shell 51 is fixed to the front-rear swing part 3, and the rear part 53a of the seat inner shell 53 is attached above the seat outer shell 51. Thus, the deformation part 5x including the front part 53b of the seat inner shell 53 is deformed toward the seat outer shell 51.

(101) In this embodiment, a front seat lower cover 55 is attached to the front part 53b forming the deformation part 5X of the seat inner shell 53, with the seat outer shell 51 interposed therebetween. Although FIG. 15 gives the impression that the front seat lower cover 55 is attached to the front part of the seat outer shell 51, the front seat lower cover 55 is actually arranged below the front part of the seat outer shell 51 in a non-connected state and is coupled to the deformation part 5X of the seat inner shell 53 above, as illustrated in FIGS. 39 and 40. As illustrated in FIG. 15, the left-right dimensions of the front seat lower cover 55 correspond substantially to the left-right dimensions of the front part 53b of the seat inner shell 53, and thus, a base end 55a of the front seat lower cover 55 is attached to an engaged part 53b1 (refer to FIGS. 39 and 40) set in the front part 53b of the seat inner shell 53, with the seat outer shell 51 interposed therebetween and a rear end 55b of the front seat lower cover 55 is shaped to extend rearward and downward along the seat outer shell 51.

(102) At two locations on the left and right of the front part of the seat outer shell 51, compression springs 56 being elastic bodies are arranged at positions compressed between the front part 53b of the seat inner shell 53 and the front part of the seat outer shell 51.

(103) When the deformation part 5X at the side of the seat inner shell 53 approaches the seat outer shell 51, as illustrated in FIGS. 39 and 40, that is, when the deformation part 5x of the seat inner shell 53 is deformed downward while compressing the compression spring 56, an appropriate portion of the front part 53b of the seat inner shell 53 abuts against an upper front surface of the seat outer shell 51 (abutment point T1). Conversely, when the front part 53b of the seat inner shell 53 moves upward in a direction where the deformation of the deformation part 5x is eliminated by the compression springs 56, as illustrated in FIGS. 40 and 39, the front seat lower cover 55 abuts against a lower front surface of the seat outer shell 51 (abutment point T2). That is, a deformable range of the deformation part 5x of a seat inner shell 53 is restricted both downward and upward.

(104) Here, as illustrated in FIGS. 37 and 39, a resin hinge part 53c is shaped as a corrugated plate having a series of uneven portions, and the deformation part 5X has a structure that easily causes, in accordance with an unbalanced load received in a left-side region and a right-side region of the seat 5, regardless of the up-down direction, torsional deformation so that one side of the seat 5 in the left-right direction is lifted higher than the other side.

(105) It is noted that, in the chair according to the present embodiment, as illustrated in FIGS. 1 and 2, a fixed attachment part 91 extending upward is attached to an arm attachment part 23 of the support base part 2 to bypass the seat 5 and even if the seat 5 swings to the front, rear, right, or left, the fixed attachment part 91 remains in a fixed position that does not interfere with the seat 5. Further, a movable cover mechanism 92 in which a plurality of covers are combined, is disposed below the seat 5 to not interfere with the relative operation of the front-rear swing part 3 and the left-right swing part 4 and to hide the front-rear swing part 3 and the left-right swing part 4.

(106) As described above, the chair according to the present embodiment in which a seat 5 swings in the front-rear and the left-right directions with respect to a support base 2, the chair is configured such that swinging of the seat 5 in front-rear direction with respect to the support base 2 is capable of being suppressed at one or a plurality of predetermined positions, or arbitrary position (one position in the present embodiment) via an operation of an operation member 152. Therefore, swinging of the seat 5 in the front-rear and left-right directions allows a seated person to sit on the seat under an appropriate weight balance in accordance with the sitting posture and to obtain the feeling of use conventional chairs do not have. Furthermore, the swinging of the seat 5 in the front-rear direction is capable of being suppressed while such a swinging operation is performed. Therefore, the seated person can receive a support to keep a desirable posture with respect to the front-rear direction.

(107) Further, a front-rear swinging part 3 is provided between the seat 5 and the support base 2 supporting the seat 5, and a left-right swinging part 4 is provided between the front-rear swinging part 3 and the support base 2, and the seat 5 is swingably supported in front-rear and left-right directions by the support base 2 via these front-rear swinging part 3 and the left-right swinging part 4, and a front-rear stopper mechanism 8M is provided between the left-right swinging part 4 and the front-rear swinging part 3, and the front-rear stopper mechanism switches between allowance and suppression of swinging of the seat 5 in the front-rear direction through engaging or disengaging an engaging part 81 and an engaged part 82 by operation of the operation member 152. Therefore, the movable configuration in the front-rear and the left-right directions and the movement suppression structure in front-rear direction are capable of being effectively compatible.

(108) Further, a left-right stopper mechanism 7M is further provided between the support base 2 and the left-right swinging part 4, and the left-right stopper mechanism 7M switches between allowance and suppression of swinging of the seat 5 in the left-right direction through engaging or disengaging an engaging part 71 and an engaged part 72 by operation of the operation member 151. Therefore, in the above-described configuration, movement suppression structure in left-right direction is capable of being effectively realized.

(109) Further, it is possible to switch between suppression and no-suppression of swinging in front-rear direction on at least one predetermined position within the movement range in front-rear direction and it is possible to switch between suppression and no-suppression of swinging in left-right direction at a center reference position in left-right direction. Therefore, if the left-right swinging is suppressed at the center reference position and the front-rear swinging is suppressed at the predetermined position in front-rear direction, the fixing state same as one of the normal chairs can be obtained.

(110) Further, the front-rear stopper mechanism 8M and a left-right stopper mechanism 7M operate through operation of the operation members 151, 152 in common. Therefore, operation is easily performed.

(111) Further, the front-rear stopper mechanism 8M and the left-right stopper mechanism 7M operate by one operation in a different timing. Therefore, an operation is easily performed and it is possible to ensure an appropriate movement.

(112) Further, the engaging part 81 and the engaged part 82 are engaged and the front-rear stopper mechanism 8M works when the seat 5 moves to the predetermined position after a swinging allowance operation is performed through the operation member 152. Therefore, the operation of the operation member 152 and the operation timing of the front-rear stopper mechanism 8M can be adjusted.

(113) Further, the operation member 152(151) is provided in the seat 5 and the operation member 152(151) swings in the front-rear and left-right directions together with the seat 5. Therefore, even if the seated person changes his/her posture in the front-rear and left-right directions, the position of the operation member 152(151) is not changed and the operability is in good condition.

(114) Further, a back frame 61 configured to support a backrest 62 is erected integrally behind the seat 5. Therefore, when the seat 5 tilts in the left-right direction and the back frame 61 tilts in the same direction, the moving directions of a part of the back 6 and the seat 5 are the same and the back and the seat can integrally effortlessly move following the movement of the seated person.

(115) Further, the seat 5 is configured so as to automatically return to the reference position in the front-rear and left-right directions in a state where the load is not applied by the seated person. Therefore, even if the freedom degree of the seat 5 movement is higher, the seat 5 can stay at the predetermined position when the seated person sits on the seat.

(116) Although an embodiment of the present invention was explained above, the specific configuration of each part is not limited to those in the embodiment described above.

(117) For example, according to the above-described embodiment, the engaging part and the engaged part are engaged with recess and convex. However, a configuration may be applied that the engaging part is considered as a friction member and the engaged part is as a sliding surface, and the sliding is suppressed by the sliding resistance when the friction member is pressed to the sliding surface.

(118) Further, according to the above-described embodiment, the position of the recess 82aX being the engaged part configuring the control mechanism 8X and the position of a groove 82a being the engaged part 82 configuring the front-rear stopper mechanism 8M are aligned in the front-rear direction (X direction), and it is configured that the position to lock the seat 5 when a seated person sits on a seat and the position to lock the seat 5 when the seated person leaves the seat are the same position. However, as illustrated in FIG. 41, a configuration may be applied that the seat is locked at separate position by misaligning the position of the recess 182aX being the engaged part 182X configuring the control mechanism 108X and the position of the groove 182a being the engaged part 182 configuring the front-rear stopper mechanism 108 in the front-rear direction. With such a configuration, the movable part can be s0011uppressed in accordance with the seating state, and the seated person can sit on and leave the seat with stability and at ease. At this time, the front-rear position at which the seat is suppressed when the seated person leaves the seat and the front-rear position at which the seat is suppressed by manual operation can be appropriately set, respectively.

(119) Further, for example, it is also effective that the grooves 182a of the front-rear stopper mechanism 108 are provided at a plurality of the positions in front-rear direction and the position locked by fitting the engaging part can be selected. Adversely, the mode may be also applied that the engaging parts which engaging each groove are provided at a plurality of the positions. In this way, the movement of the seat can be suppressed at a plurality of the positions in front-rear direction with easy structure.

(120) Further, according to the above-described embodiment, the left-right swinger 4 is provided between the front-rear swinger 3 and the support base 2, and the front-rear stopper mechanism 8M is provided between the left-right swinging part 4 and the front-rear swing part 3, the front-rear stopper mechanism 8M switches between allowance and suppression of swinging of the seat 5 in the front-rear direction through engaging or disengaging the engaging part 81 and the engaged part 82 by operation of the operation member 152. However, a configuration may be applied that the left-right swinging part 4 is provided between the seat 5 and the front-rear swinging part 3 and the front-rear stopper mechanism 8M is provided between the support base 2 and the front-rear swinging part 3. In this way, it is possible to effectively realize the front-rear and left-right movable configuration and movement suppression structure in front-rear direction.

(121) Further, according to the above-described embodiment, the left-right stopper mechanism 7M is further provided between the support base 2 and the left-right swing part 4, the left-right stopper mechanism 7M switches between allowance and suppression of swinging of the seat 5 in the left-right direction through engaging or disengaging the engaging part 71 and the engaged part 72 by operation of the operation member 151. However, when the left-right swinging part is provided between the seat and the front-rear swinging part, the left-right stopper mechanism 7M that switches between allowance and suppression of the swinging of the seat 5 in the left-right direction through engaging or disengaging the engaging part 71 and the engaged part 72 by operation of the operation member 151, may be further provided between the left-right swing part 4 and the front-rear swing part 3. With the above-described configuration, it is possible to effectively realize the movement suppression mechanism in the left-right direction.

(122) Further, the operation member 152 of the front-rear stopper mechanism 8M and the operation member 151 of the left-right stopper mechanism 7M are configured to operate through operation of the operation member in common in practically. However, separate operation members are available.

(123) Further, a configuration may be applied that the operation member 152 is provided not in the seat 5 but in the front-rear swing part 3 and moves in accordance with the front-rear movement of the seat 5. In this way, since the position of the operation member is not changed even if the seated person changes his/her posture in the front-rear position, the operativity is in good condition and the unitization is also easily realized.

(124) Furthermore, according to the above-described embodiment, since the fixed arm part 91 is attached to the support base 2, it is also effective to provide the operation members 151, 152 in the fixed arm part 91. In this way, even if the seat 5 swings in the front-rear and left-right direction, the seated person can sit on the seat with stability at ease due to the fixed arm part 91. Further, if the operation members 151, 152 are provided in the fixed arm part 91, operation can be easily approached.

(125) Further, the fixed arm part 91 may be attached to the support base 2 and the operation members 151,152 may be fixed to the fixed arm part 91. In this way, even if the seat 5 swings in the front-rear and left-right directions, the seated person can sit on the seat with stability at ease due to the arm fixer 91. When the operation members are provided in the fixed arm part 91, operation can be easily approached.

(126) Further, chair includes: a load detector that detects the sitting load applied by the seated person; and an operation part that operates in accordance with the detection state of the load detection part. The operation part is configured so as to input in the front-rear stopper mechanism 8M in parallel with the operation of the operation member, even in a state where the engaging part 81 and the engaged part 82 of the front-rear stopper mechanism 8M are not engaged via the operation of the operation member 152, when the load is not applied, the engaging part and the engaged part are engaged, and when the load is applied, the engaging part and the engaged part are disengaged. In this way, the front-rear stopper mechanism 8M is shared and the front-rear swing part 3 being the movable part can be suppressed in accordance with the sitting state as well. Therefore, the seated person is able to sit on or leave the seat with easy configuration with stability at ease.

(127) Further, as illustrated in FIG. 42, the chair has the engaged part 200, the engaged part 200 is provided at the support base 202 or the seat 205 (the support base 202 in the drawing) and includes a groove 200a having a cross shape extending to the front-rear direction and left-right direction, the groove 200a has a deeper hole 200x than the groove 200a at the center crossing part 200a1 of front, rear, left ah right of the engaged part 200. An engaging part 210 that engages the engaged part 200 is provided at the seat 205 or the support base 202 (the seat 205 in the drawing), and the engaging part 210 elastically protrudes toward the engaged part 200 by the operation of the operation part 250, and the engaging part 210 engages one of a front-rear direction groove part 200am or a left-right direction groove part 200an of the engaged part 200 in accordance with swinging of the seat 205 to front-rear and left-right directions, and swinging to one direction is regulated, and then, by further swinging to another direction of the front-rear direction groove part 200am or the left-right direction groove part 200an, whereby the engaging part 210 engages the crossing part 200a1 and swinging in both front-rear direction and left-right direction is regulated. This configuration is also effective.

(128) With the above-described configuration, it can work with one groove and layered structure with a plurality of grooves is not required.

(129) Various other changes may be applied to other configurations without departing from the spirit of the present invention.

INDUSTRIAL APPLICABILITY

(130) Since the chair according to the present invention is configured as described above, the chair can be utilized especially suitably in an office and the like.

DESCRIPTION OF REFERENCE NUMERALS

(131) 2 . . . Support base 3 . . . Front-rear swing part 4 . . . Left-right swing part 5 . . . Seat 7M . . . Left-right stopper mechanism 8M . . . Front-rear stopper mechanism 61 . . . Back frame 62 . . . Backrest 71 . . . Engaging part 72 . . . Engaged part 81 . . . Engaging part 82 . . . Engaged part 151 . . . Operation member 152 . . . Operation member 108X . . . Control mechanism 182X . . . Engaged part 182aX . . . Groove 182 . . . Engaged part 182a . . . Groove 200 . . . Engaged part 200a . . . Cross-shaped groove 200a1 . . . Center crossing part 200x . . . Hole 210 . . . Engaging part 200am . . . Front-rear direction groove part 200an . . . Left-right direction groove part 202 . . . Support base 205 . . . Seat