JP2024065794A - Chair - Google Patents

Abstract

[Problem] To provide a chair with excellent design freedom, in which an upper frame is rotatably supported relative to a lower frame. [Solution] A chair back support D comprises a lower frame p1 having an axle J, and an upper frame p2 having a bearing K and rotatably supported relative to the lower frame p1. The axle J extends horizontally, and is configured such that its width dimension wj in the front-to-back direction is shorter than its width dimension in the up-to-down direction, and an axial curved surface jm is formed at the upper part of the axle J, which has a partially cylindrical curved surface shape and can indirectly engage with the bearing K via an intermediate member S. [Selected Figure] Fig. 12

Description

The present invention relates to a chair for use in an office, etc.

Various chairs have been known in the past in which the backrest is rotatably supported on the support base via a back support rod (see, for example, Patent Document 1).

In Patent Document 1, the upper back frame is supported on the lower back frame that constitutes the back support rod so that it can rotate in the front-rear direction. Between the lower back frame and the upper back frame, a metal support shaft (so-called steel shaft) that extends in the left-right direction is interposed.

In such a configuration, a structure for installing a metal support shaft between the lower and upper back frames is essential. This limits the design freedom that could reduce the number of parts and assembly labor.

JP 2009-165663 A

The present invention was made with the above in mind, and aims to provide a chair with excellent design freedom, at least in which the upper frame is supported rotatably relative to the lower frame.

In other words, the chair of the present invention has the following configuration.

The invention described in claim 1 is a chair in which a backrest is rotatably supported on a support base via a back support, the back support comprising a lower frame having either an axle or a bearing for receiving the axle, and an upper frame having the other of the axle and the bearing and rotatably supported on the lower frame, the axle extending horizontally and configured such that its width in the front-to-back direction is shorter than its width in the up-to-down direction, and either the upper or lower part of the axle has an axial curved surface that is partially cylindrical and can engage with the bearing directly or indirectly via another member.

The invention described in claim 2 is the chair described in claim 1, in which the lower frame is provided with the axle portion having the axial curved surface formed on the upper portion, and the upper frame is provided with the bearing portion.

The invention described in claim 3 is the chair described in claim 1, in which the upper frame or the lower frame including the axis portion is integrally formed from a synthetic resin.

The invention described in claim 4 is the chair described in claim 2, in which the lower frame is provided with an upper frame engagement portion including the axle portion, and the upper frame engagement portion includes a lower frame base, left and right support arms extending in pairs in the vertical direction from the left and right sides of the lower frame base, and a cross section that is installed between the left and right support arms and includes the axle portion.

The invention described in claim 5 is the chair described in claim 4, in which the cross section is provided with axle sections arranged in pairs on the left and right, each outer section of which is integrally connected to the left and right support arms, and a connecting section connecting these axle sections.

The invention described in claim 6 is the chair described in claim 2, in which a bearing recess that includes the bearing portion and is open downward is provided in the lower part of the upper frame.

The invention described in claim 7 is the chair described in claim 6, in which the other member is an intermediate member disposed in the bearing recess formed of a resin having greater sliding properties than the upper frame, and the axial curved surface formed on the upper part of the shaft engages with the bearing portion via the intermediate member.

The invention described in claim 8 is the chair described in claim 7, in which the resin is polyoxymethylene (POM) resin.

The invention described in claim 9 is the chair described in claim 6, in which the bearing recess includes a front wall portion, a rear wall portion disposed behind the front wall portion, and a connecting portion connecting the upper portions of the front wall portion and the rear wall portion, and the bearing portion is formed into a downward C-shape including the front wall portion, the rear wall portion, and the connecting portion.

The invention described in claim 10 is the chair described in claim 9, in which a reinforcing connection portion is provided that connects the left-right intermediate portions of the upper portions of the front wall portion and the rear wall portion.

As described above, the present invention provides a chair with excellent design freedom, at least in which the upper frame is rotatably supported relative to the lower frame.

FIG. 1 is a perspective view showing an embodiment of the present invention. FIG. FIG. FIG. FIG. FIG. FIG. FIG. FIG. FIG. FIG. FIG. FIG. FIG. FIG. FIG. FIG. Cross-sectional view taken along line AA in FIG. 8 . Cross-sectional view taken along line BB in FIG. 8 . Cross-sectional view taken along line CC in FIG. 8 . 19 is a cross-sectional view of a rearward tilting posture corresponding to the cut portion of FIG. 18 . FIG. FIG. FIG. Cross-sectional view taken along line D-D in FIG. 3 is an end view of line EE in FIG. 2 . FIG. 4 is a right side view illustrating assembly in the embodiment. FIG. 4 is a front view illustrating assembly in the embodiment. FIG. 4 is a front view illustrating assembly in the embodiment. FIG. 4 is a front view illustrating assembly in the embodiment. FIG. 4 is a front view illustrating assembly in the embodiment. 19 is a cross-sectional view of a mounting posture corresponding to the cut portion of FIG. 18 . FIG. 4 is a front view illustrating assembly in the embodiment. FIG. FIG.

One embodiment of the present invention will be described below with reference to Figures 1 to 35.

The chair comprises legs A, a support base B supported so as to be rotatable with respect to the legs A, a seat C disposed on the support base B, and a backrest E supported so as to be tiltable backwards with respect to the support base B via a back support D.

Between the support base B and the back support D, the chair is provided with a tilt-back setting mechanism I that can set the tilt-back degree of the backrest E using a tilt-back setting lever 5, which is an operating lever.

The individual components of the chair in this embodiment are described in detail below.

<<Leg A>>
The leg A is equipped with a plurality of leg blades a1 arranged radially and each having a caster at its tip, and a leg support a2 erected at the base end of the leg blade a1 and capable of extending and contracting in the vertical direction.

<<Support Base B>>
The support base B is attached on the leg A. The support base B is made of a material having excellent rigidity. The support base B is, for example, integrally molded from metal or synthetic resin. The support base B is in the shape of a box that is open upward.

The support base B is provided with a main shaft j1 extending in the left-right direction to rotatably support the back support D. A reaction spring F is disposed in the space within the support base B to provide a reaction force against the backward tilting movement of the back support D.

The space within the support base B contains the bearing shaft j4 that receives the rear end of the reaction spring F, the bearing shaft support member m3 that supports the bearing shaft j4, and the base end of the reaction adjustment lever G that acts on the front end of the reaction spring F.

<<Seat C>>
The seat C is provided on the support base B. The seat C includes a seat support c1 and a seat body c2 having a seating surface that contacts a seated person and is provided so that its front-rear position can be changed with respect to the seat support c1.

The front part of the seat C is supported so as to be movable up and down relative to the support base B via the front shaft j2. The middle part of the seat C in the front-rear direction is supported by the seat engagement shaft j3 provided on the back support D.

<<Back support body D>>
The back support D is interposed between the support base B and the backrest E. The back support D is capable of supporting the backrest E so as to be tiltable.

The lower part of the back support D is composed of the back support base M and the lower frame p1. The back support base M and the lower frame p1 that compose the lower part of the back support are fixed to each other. The lower part of the back support is supported rotatably around the main axis j1 with respect to the support base B between the initial state (N) and the backward tilted state (H).

As shown in FIG. 5, the upper frame p2 constituting the back support D is supported so as to be tiltable between an upright position (ps) and a backward tilted position (pr) relative to the lower part of the back support D.

The back support D is constantly biased in a direction that allows the backrest E to assume the initial state (N) by a reaction spring F attached to the support base B. A backward tilt setting lever 5 that can selectively set the backward tilt degree of the backrest E is rotatably supported on the back support D.

The back support D comprises a back support base M rotatably supported relative to the support base B via the main shaft j1, and a back support body P connected to the rear of the back support base M.

<Back support base M>
The back support base M is a metal structure interposed between the support base B and the backrest E, and between the support base B and the seat C.

The back support base M is equipped with left and right arms m1 arranged in a left-right pair and supported rotatably on the support base B via the main shaft j1, a connecting member m2 connecting the rear portions of the left and right arms m1, a seat engagement shaft j3 supported at the front portions of the left and right arms m1, left and right bearing shaft support members m3 arranged in a left-right pair and with their upper portions connected to the seat engagement shaft j3, and a bearing shaft j4 connected between the lower portions of the left and right bearing shaft support members m3.

The lower part of the back support base M is covered and concealed by the front cover body 6 made of synthetic resin.

[Left and right arms m1]
The left and right arms m1 are each shaped like an upright plate extending in the front-rear direction. The left and right arms m1 are disposed outside the support base B.

The left and right arms m1 are provided with left and right arm bodies m4 that extend in the front-rear direction and can support the main shaft j1 at their front parts, left and right front arm sections m5 that extend diagonally upward and forward from the front parts of the left and right arm bodies m4 and support the seat engagement shaft j3 at their upper parts, and a main shaft insertion hole (not shown) that is provided between the left and right arm bodies m4 and the left and right front arm sections m5 and penetrates in the left-right direction to hold the main shaft j1.

The rear portions of the left and right arm bodies m4 are rigidly connected by a connecting member m2. The left and right arm bodies m4 have rearward protruding portions mt that protrude rearward beyond the connecting member m2. The left and right rearward protruding portions mt are fitted into the fitting holes 111 of the back support base connecting portion 11 provided at the base end (front end) of the lower frame p1 that constitutes the back support body P.

[Connecting member m2]
The connecting member m2 is in the form of an upright plate extending in the left-right direction. Both left and right ends of the connecting member m2 are welded to the inside parts of the left and right arm bodies m4. The connecting member m2 is provided with a pair of left and right nuts n1 to which screws v1 for attaching the lower frame p1 are screwed.

The back support base connecting portion 11, which has a screw insertion hole h1, engages with the connecting member m2. The lower frame p1 is fixed to the back support base M by screwing the screw v1 inserted through the screw insertion hole h1 into the nut portion n1 of the connecting member m2.

[Seat engagement shaft j3]
The seat engagement shaft j3 extends in the left-right direction so as to be able to engage with the seat C. The seat engagement shaft j3 is disposed forward and above the main shaft j1. The seat engagement shaft j3 extends in the left-right direction and is held by a shaft holding portion (not shown) provided on the seat receiver c1.

[Bearing shaft support member m3]
The bearing shaft support members m3 are arranged in a pair on the left and right, inside the left and right front arm portions m5. The bearing shaft support members m3 are in the form of upright plates extending in the front-rear and up-down directions. The upper part of the bearing shaft support member m3 is connected to the seat engagement shaft j3. The lower part of the bearing shaft support member m3 is connected to the bearing shaft j4.

[Bearing axis j4]
The bearing shaft j4 is disposed forward and below the main shaft j1 and is biased rearward by a reaction spring F.

<Back support body P>
The back support body P supports the backrest E. The back support body P is connected to the upper and lower parts of the central part in the left-right direction of the backrest E. The back support body P is separated from the backrest E in a side view, except for the backrest engagement part 32 which is the upper connection part, and the backrest connection part 22a which is the lower connection part.

The back support body P includes a lower frame p1 having an axle J, an upper frame p2 having a bearing K that receives the axle J and supported on the lower frame p1 so as to be rotatable in the front-rear direction between an upright position (ps) and a backward tilted position (pr), a coil spring V that is a biasing member interposed between the lower frame p1 and the upper frame p2, and an intermediate member S that is interposed between the lower frame p1 and the upper frame p2.

In this embodiment, the chair has a back support base M and a lower frame p1 that constitute the lower back support. The lower back support can rotate with respect to the support base B between the initial state (N) shown in FIG. 2 and the backward tilted state (H) shown in FIG. 4, and can rotatably support the upper frame p2 so that it can take an upright position (ps) and a backward tilted position (pr) as shown in FIG. 5.

[Lower frame p1]
The lower frame p1 is fixed to the back support base M. That is, the lower frame p1 moves integrally with the back support base M.

The lower frame p1 is attached to the back support base M with a screw v1. The lower frame p1 is fixed to the back support base M. The lower frame p1 can support the upper frame p2 so that it can rotate in the front-rear direction. The lower frame p1 is connected to the lower part of the back side of the backrest E.

The lower frame p1 has a base structure 1 with a back support base connection part 11 at the front that is connected to the back support base M, and an upper frame engagement part 2 at the rear of the base structure 1.

(Foundation structure 1)
The base structure 1 comprises a back support base connecting portion 11 facing forward, and left and right side wall portions 12 extending linearly forward from both the left and right sides of the back support base connecting portion 11.

The back support base connection part 11 is provided with a pair of left and right fitting holes 111 that are open forward and fit into the left and right rear protruding parts mt protruding from the rear end of the back support base M, a connecting wall 112 that is disposed between the left and right fitting holes 111 and is attached to the connecting member m2 of the back support base M, and an arm engagement wall 113 that extends forward from the outside of each of the left and right fitting holes 111 and has portions that engage with the upper and lower edges of the left and right arm bodies m4.

The connecting wall 112 has a pair of screw insertion holes h1 on the left and right that penetrate in the front-to-rear direction. The lower frame p1 is fixed to the back support base M by screwing a screw v1 inserted from the rear into the screw insertion hole h1 of the connecting wall 112 into a nut n1 provided on the connecting member m2.

The left and right side wall portions 12 are in an upright position and are provided at the left and right front end portions of the lower frame p1. The left and right side wall portions 12 are arranged to follow the outer sides of the rear portions of the left and right arm bodies m4. The front portions of the left and right side wall portions 12 are provided with notched holes 121 that are open to the front.

The notch hole 121 has a partially circular shape (C-shaped in side view) with an end face that can engage with the base end (near the flange 523) of the cylindrical portion 521 of the rearward tilt degree setting lever 5. The flange 523 of the lever body 52 engages with the inner peripheral edge of the notch hole 121 in the left and right side walls 12.

(Upper frame engagement portion 2)
The upper frame engagement portion 2 is connected to the rear of the foundation structure portion 1. The upper frame engagement portion 2 extends in the vertical direction as a whole. The upper frame engagement portion 2 is formed so as to be positioned gradually upward as it goes rearward as a whole.

The upper frame engagement portion 2 includes a lower frame base 21 with a front spring bearing portion 211 provided in the left-right center, left and right support arms 22 extending in pairs in the vertical direction from the left and right of the lower frame base 21, a cross section 23 including an axle J that is installed between the vertical centers of the left and right support arms 22, and a restricting portion 24 that protrudes from the inside of the left and right support arms 22 and engages with the posture deformation portion s2 of the intermediate member S attached to the upper frame p2.

The lower frame base 21 is interposed between the foundation structure 1 and the left and right support arms 22. The front spring receiving portion 211 receives the front portion of the coil spring V. The front spring receiving portion 211 faces rearward so as to face the arrangement space sp between the base ends of the left and right support arms 22 in which the coil spring V is arranged.

The left and right support arms 22 are generally rectangular columns whose front-to-rear dimensions gradually become shorter as they move upward. The left and right support arms 22 each have an engagement portion 221 with a forward surface 22m that is provided at the top and engages with the upper frame p2 in a backward tilted position (pr), and a backrest connection portion 22a that is disposed below the engagement portion 221 and connects the lower portion of the left-to-right center of the backrest E.

Between the left support arm 22 and the right support arm 22, an arrangement space sp is formed in which the bearing recess 4, which is the lower frame engagement part protruding downward from the upper frame p2, can be arranged.

The engaging portion 221 is disposed above the shaft portion J. The engaging portion 221 is capable of positioning the rearward tilted posture (pr) of the upper frame p2. The front surface 22m of the engaging portion 221 is adapted to come into contact with the front wall portion 311 that constitutes the recessed portion 31 of the upper frame p2 in the rearward tilted posture (pr).

The backrest connecting portion 22a is the portion to which the lower portion of the backrest base e1 constituting the backrest E is screwed. The backrest connecting portion 22a protrudes forward from the engagement portion 221. The backrest connecting portion 22a is provided with a nut n2 that is screwed into a screw (not shown) that passes through a screw insertion hole (not shown) provided in the backrest base e1.

The horizontal section 23 is disposed below the backrest connecting section 22a. The horizontal section 23 is provided with left and right shaft sections J arranged in pairs on the left and right, with the outer sections integrally connected to the inner sections of the left and right support arms 22, and a connecting section 231 that integrally connects the lower sections of the left and right shaft sections J.

A downward recess 232 is formed in the center of the cross section 23 in the left-right direction so as to avoid the reinforcing connection section 44 that is provided in the shape of a rib in the bearing recess 4.

The shaft portion J has a curved shaft surface jm that extends in the left-right direction. The upper part of the shaft portion J has a curved shaft surface jm that is a partial cylindrical curved surface. In other words, the shaft portion J has a curved shaft surface jm that can indirectly engage with the bearing portion K of the upper frame p2 via the bearing cover portion s4 of the intermediate member S, which is another member.

The curved shaft surface jm formed on the upper part of the shaft portion J engages with the bearing portion K via the bearing cover portion s4 of the intermediate member S.

The shaft J is longer in the up-down direction than in the front-to-back width. The width dimension of the shaft J in the front-to-back direction (thickness dimension wj of the shaft J) is shorter than the width dimension in the up-to-down direction. The entire lower frame p1 including the shaft J is integrally formed from synthetic resin.

The restricting portion 24 is provided adjacent to the shaft portion J. The restricting portion 24 is provided on the inner surface of the left and right support arms 22. The restricting portion 24 is a portion that can engage with the posture deformation portion s2 of the intermediate member S. The restricting portion 24 is a block-shaped portion provided at the front and bottom of each of the left and right shaft portions J.

The restricting portion 24 has a forward surface 242 that faces forward and an inner surface 241 that is located behind the forward surface 242 and faces inward.

A sloped surface km is provided on the upper part of the inner surface 241, which is the inward-facing surface, and slopes downward gradually toward the left-right center of the lower frame p1 (gradually approaching the direction of the base s1 of the intermediate member S). The sloped surface km is provided in front of the shaft J. The portion of the inner surface 241 below the sloped surface km extends in a substantially vertical direction.

The forward surface 242 of the restricting portion 24 is adapted to come into contact with the posture deformation portion s2 that forms the second posture (Y) of the intermediate member S when the upper frame p2 forms the upright posture (ps).

The inner surface 241 of the restricting portion 24 is adapted to engage with the posture deformation portion s2 of the intermediate member S. The posture deformation portion s2 is adapted to deform from the second posture (Y) to the first posture (X) as the upper frame p2 in the mounting posture (T) approaches the lower frame p1.

In other words, as the bearing portion K of the upper frame p2 approaches the shaft portion J of the lower frame p1, which is the part to be assembled, the posture deformation portion s2 of the intermediate member S is guided by the inner surface 241 having the inclined surface portion km, and the tip portion s22, which is the tip portion, approaches the base portion s1, that is, it is elastically deformed from the second posture (Y) to the first posture (X).

The upper and lower parts of the lower frame p1 having the above configuration are covered by an upper cover body 7 and a lower cover body 8 made of synthetic resin.

[Upper frame p2]
The upper frame p2 is supported relative to the lower frame p1 so as to be rotatable about the shaft J. The upper frame p2 is provided with a bearing K configured to indirectly support the shaft J of the lower frame p1 via a bearing cover s4 of the intermediate member S. The upper frame p2 is a single column extending in the vertical direction, and is disposed behind the middle part of the backrest E in the left-right direction.

The upper frame p2 is configured to be rotatable around the axis J so that it can take an assembly position (T) in which the coil spring V can be attached between the upper frame p2 and the lower frame p1, and a normal position (U) that is a different position from the assembly position (T).

The assembly position (T) is a position that can only be taken when assembling or removing the upper frame p2 from the lower frame p1. The assembly position (T) of the upper frame p2 is set to a position that is more forward-leaning than the normal position (U).

The assembly position (T) of the upper frame p2 can only be taken when assembling it to the lower frame p1 and when removing it from the lower frame p1.

In other words, after the upper frame p2 has been transitioned from the assembly position (T) to the normal position (U) (after the assembly work of the upper frame p2 to the lower frame p1 is completed), it is configured not to return to the assembly position (T) unless a special operating force for disassembly is applied to the position deformation portion s2 of the intermediate member S.

The upper frame p2 is configured to be tiltable (tiltable) between a standing posture (ps) and a rearward tilt posture (pr) that is tilted further back than the standing posture (ps) when in the normal posture (U).

The upper frame p2 is made up of an upper frame main body 3 that extends in the vertical direction and constitutes the part that is visible to the user, and a downward protrusion (base end structural part) disposed below the upper frame main body 3, and is equipped with a bearing recess 4 that includes a bearing part K and is open downward and outward.

(Upper frame body 3)
Downwardly open recessed portions 31 are provided on both the left and right sides of the lower portion of the upper frame body 3. A backrest engaging portion 32 is protrudingly provided on the upper portion of the upper frame body 3 so as to be engageable with the backrest E so as to be movable up and down.

The upper parts of the left and right support arms 22 provided on the lower frame p1 are arranged inside the left and right recesses 31. The front surfaces 22m of the engagement parts 221 provided on the left and right support arms 22 engage with the front wall parts 311 that constitute the recesses 31, thereby determining the backward tilt position (pr) of the upper frame p2.

(Bearing insertion recess 4)
The bearing receiving recess 4 is provided in the lower part of the upper frame p2. The bearing receiving recess 4 is provided so as to be convex downward with respect to the upper frame main body 3 in the front and rear views. In other words, the left-right dimension of the bearing receiving recess 4 in the front and rear views is set to be shorter than the left-right dimension of the upper frame main body 3.

The bearing recess 4 has a front wall portion 41, a rear wall portion 42 disposed behind the front wall portion 41, and a connecting portion 43 connecting the upper portions of the front wall portion 41 and the rear wall portion 42.

The front wall portion 41 is a wall extending in the vertical and horizontal directions.

A rear spring bearing portion 411 is provided on the front side of the lower portion of the front wall portion 41. The rear spring bearing portion 411 faces forward so as to face the arrangement space sp in which the coil spring V (tilt spring) located between the base ends of the left and right support arms 22 is arranged.

A lower mounting portion 412 is provided at the lower end of the front wall portion 41 to which the front mounting portion s3 of the intermediate member S is attached. The lower mounting portion 412 has multiple protrusions that extend downward at different vertical positions. The lower mounting portion 412 has a central protrusion 41a and left and right side protrusions 41b that are located above the central protrusion 41a. The front mounting portion s3 of the intermediate member S is adapted to be fitted onto the lower mounting portion 412.

On the back side (rear-facing surface) of the front wall 41, multiple positioning ribs 413 are arranged in the left-right direction and protrude vertically to position the intermediate member S relative to the base s1 in the left-right direction.

The rear wall portion 42 is a wall extending in the vertical and horizontal directions. The rear wall portion 42 has a width dimension that is approximately the same as or shorter than the horizontal separation dimension between the left support arm 22 and the right support arm 22. The rear wall portion 42 has approximately the same horizontal width dimension as the front wall portion 41. The rear wall portion 42 has a vertically shorter dimension than the front wall portion 41. The rear wall portion 42 is arranged so that it gradually moves away from the front wall portion 41 in the downward direction as a whole (excluding the forward protruding portion 42b).

The rear wall 42 is provided with a rear mounting portion 421 to which the rear mounting portion s5 of the intermediate member S is attached. The rear mounting portion 421 of the rear wall 42 has a protrusion engagement portion 42a with which the multiple (four) engagement protrusions s51 arranged in parallel on the rear mounting portion s5 of the intermediate member S can engage, and a forward protruding portion 42b that fits into the fitting recess s52 provided on the rear mounting portion s5 of the intermediate member S.

The protruding engagement portion 42a is provided in multiple (four) through holes that are aligned in the left-right direction and penetrate in the front-rear direction.

The forward protruding portion 42b protrudes forward from the center in the left-right direction of the lower end of the rear wall portion 42.

The connecting portion 43 connects the upper portions of the front wall portion 41 and the rear wall portion 42 in the front-rear direction. The bearing recess 4 is open downward and outward by the front wall portion 41, the rear wall portion 42, and the connecting portion 43.

In addition, a reinforcing connecting portion 44 is provided in the left-right middle portion below the connecting portion 43 in the bearing recess 4, connecting the upper portions of the front wall portion 41 and the rear wall portion 42.

The bearing recess 4 is provided with left and right bearing parts K that receive the shaft part J of the lower frame p1. The bearing parts K are parts that engage with the shaft part J so as to be able to rotate relative to it. The bearing parts K are shaped like a downward C and include a front wall part 41, a rear wall part 42, and a connecting part 43. The left and right bearing parts K are provided on the left and right of the reinforcing connecting part 44.

The bearing recess 4 has an axial passage Z through which the axial portion J of the lower frame p1 can enter toward the bearing portion K only in the assembly position (T).

In this embodiment, the size of the shaft passage Z, i.e., the passage width wz, is determined by the cooperation of the front wall 41 of the bearing recess 4, which has a positioning rib 413, and the base s1 and rear mounting portion s5 (forward protruding portion/cross-section retaining portion) of the intermediate member S disposed in the bearing recess 4.

[Coil spring V (biasing member)]
The coil spring V constantly biases the upper frame p2 in the standing posture (ps). The coil spring V is a compression spring type. The coil spring V generates a reaction force for returning the upper frame p2 from the backward tilt posture (pr) to the standing posture (ps).

The front part of the coil spring V is supported by the front spring support part 211 provided on the lower frame p1 so as to be located below the shaft part J and the bearing part K.

The rear of the coil spring V is supported by the rear spring support 411, which is provided on the upper frame p2 so as to be located below the shaft J and bearing K.

As shown in FIG. 32, this embodiment is configured such that the coil spring V can be disposed between the front spring receiving portion 211 and the rear spring receiving portion 411 only when the upper frame p2 is in the assembly position (T).

In other words, the worker can easily place the coil spring V in the desired position using only his or her fingers without using any tools.

In other words, the back support body P in this embodiment is set so that the distance between the rear spring bearing portion 411 of the upper frame p2 in the assembled position (T) and the front spring bearing portion 211 of the lower frame p1 is greater in the front-to-rear direction than in the normal position (U).

[Intermediate member S]
The intermediate member S is disposed between the lower frame p1 and the upper frame p2. The intermediate member S is attached to the bearing receiving recess 4 of the upper frame p2. In other words, the main portion of the intermediate member S is attached to the inner surfaces of the front wall portion 41, the rear wall portion 42, and the connecting portion 43 which constitute the bearing receiving recess 4.

The intermediate member S is made of polyoxymethylene (POM) resin, which is more rigid than the upper frame p2 and has sliding properties.

The intermediate member S is capable of improving the sliding property with respect to the shaft portion J. In addition, the intermediate member S is capable of restricting the rotation of the upper frame p2, which has been changed from the assembly position (T) to the normal position (U), so that it cannot return to the assembly position (T).

The intermediate member S includes a base s1 located in the center in the left-right direction, a pair of posture deformation parts s2 extending from the left and right of the base s1 in the form of cantilever arms, a front mounting part s3 extending below the base s1 and fitting onto the lower mounting part 412 of the front wall part 41, a bearing cover part s4 connected to the top of the base s1 and covering the inner peripheral surface of the bearing part K while pressing against it, and a rear mounting part s5 extending downward from the rear end of the bearing cover part s4 and attached to the front side (inner surface side) of the rear wall part 42.

When viewed from the side, the intermediate member S has an inverted V-shape. That is, the intermediate member S has a front portion Sf including a base portion s1, a posture deformation portion s2, and a front mounting portion s3, a rear portion Sr including a rear mounting portion s5, and an upper portion Su including a bearing cover portion s4.

The intermediate member S, which has an inverted V shape when viewed from the side, can temporarily elastically deform so that the front portion Sf and rear portion Sr move toward each other when viewed from the side when it is attached to the bearing recess 4 of the upper frame p2.

In this embodiment, the temporary movement of the front portion Sf and the rear portion Sr toward each other is achieved mainly by elastic deformation of the ends of the left and right connecting arm portions s12 that are elongated in the vertical direction, i.e., the portions near the bearing cover portion s4.

(Base portion s1)
The base s1 is attached to the inner surface of the front wall 41 of the bearing recess 4. The base s1 includes a base main body s11 having a substantially rectangular shape when viewed from the front and rear, and left and right connecting arm portions s12 extending upward integrally from upper portions of both the left and right sides of the base main body s11 and having extending ends connected to the bearing cover portion s4.

A pair of reinforcing ribs rv extending vertically are provided in the center of the front side of the base body s11 in the horizontal direction. The reinforcing ribs rv are connected between the base body s11 and the front attachment part s3 to increase the overall rigidity of the front part Sf.

The reinforcing rib rv engages with the positioning rib 413 provided on the front wall 41 of the bearing recess 4 and also performs a left-right positioning function relative to the front wall 41.

The left and right connecting arm parts s12 are thin plates extending in the vertical direction, except for the parts near the bearing cover part s4. Only the parts of the left and right connecting arm parts s12 near the bearing cover part s4 are in the shape of a relatively thin column that can easily elastically deform in the front-rear direction.

(Posture transformation section s2)
The posture deformation portions s2 extend outward from both left and right side portions of the lower end portion of the base main body s11.

The posture deformation section s2 has a base end section s21 that extends outward from both the left and right sides of the base section s1, and a lump- or block-shaped tip section s22 that is connected to the upper end of the base end section s21 and has a larger left-right width dimension than the base end section s21.

The base end portion s21 is in the form of a plate that is easily elastically deformable. The base end portion s21 extends obliquely from both the left and right sides of the lower part of the base portion s1 toward the outside so that it is gradually positioned upward.

The base end portion s21 is the main portion that undergoes elastic deformation in the left-right direction when the posture deformation portion s2 engages with the restriction portion 24 during the work of assembling the lower frame p1 and the upper frame p2.

The posture transformation section s2 is configured to adopt a first posture (X) in the assembly posture (T) and a second posture (Y) different from the first posture (X) in the normal posture (U).

In other words, in the first position (X), the posture deformation portion s2 is elastically deformed in a direction such that the tip portion s22 approaches the base portion s1 by engaging with the inner surface 241 of the restriction portion 24 provided on the inner portion of the left and right support arms 22.

In addition, the posture deformation portion s2 is disposed at a location where it can engage with the forward surface 242 of the restricting portion 24 provided on the inner portion of the left and right support arms 22 in the second posture (Y).

That is, the tip portion s22 of the posture deformation portion s2 is arranged in front of the restricting portion 24 in the second posture (Y). In the second posture (Y), the posture deformation portion s2 can restrict the rearward rotation range of the portion of the upper frame p2 below the bearing portion K (the lower portion of the front wall portion 41) in order to determine the upright posture (ps) of the upper frame p2.

In the second position (Y), the positional deformation portion s2 is disengaged from the engagement relationship with the inner surface 241 of the restricting portion 24 that was established in the first position (X).

As the upper frame p2 transitions from the assembly position (T) to the normal position (U), the positional deformation part s2 transitions from the first position (X) to the second position (Y). At this time, the tip portion s22 of the positional deformation part s2 elastically returns to its original position in the left-right direction away from the base portion s1 as the base end portion s21 elastically deforms, and is disposed at a position where it can engage with the forward surface 242 of the restricting part 24 (in front of the restricting part 24).

The posture deformation portion s2 in the second posture (Y) is spaced forward from the forward surface 242 of the restricting portion 24 in the backward tilt posture (pr) and abuts against the forward surface 242 of the restricting portion 24 in the upright posture (ps).

In other words, the posture-deforming portion s2 in the second posture (Y) is configured to be supported between the restricting portion 24 and the front wall portion 41 when the upper frame p2 is in the upright posture (ps).

(Front mounting part s3)
The front mounting portion s3 has a central fitting recess s31 located in the center in the left-right direction, and side fitting recesses s32 provided on the left and right of the central fitting recess s31 so as to be located higher than the central fitting recess s31.

The central fitting recess s31 is adapted to fit the central protrusion 41a of the lower mounting portion 412 of the front wall portion 41. The side fitting recesses s32 are adapted to fit the left and right side protrusions 41b of the lower mounting portion 412 of the front wall portion 41.

(Bearing cover portion s4)
The bearing cover portion s4 has a partially cylindrical shape and is attached to each of the left and right bearing portions K. The bearing cover portion s4 is interposed between the shaft portion J provided on the lower frame p1 and the bearing portion K provided on the upper frame p2.

The bearing cover part s4 is supported by the backing of the bearing part K. The bearing cover part s4 is in direct contact with the shaft part J and can slide in association with the rotation of the upper frame p2.

The entire intermediate member S, including the bearing cover portion s4, is made of polyoxymethylene resin (POM), which has excellent sliding properties and rigidity. Therefore, by interposing the bearing cover portion s4 between the shaft portion J and the bearing portion K, the upper frame p2 can be rotated smoothly without the need to apply grease or the like to the lower frame p1.

In addition, the bearing portion K and the shaft portion J may be configured to directly engage with each other without providing a bearing cover portion s4 between them.

(Rear mounting part s5)
The rear mounting portion s5 comprises a wall-like portion sw extending in the vertical and horizontal directions, an engagement protrusion s51 protruding rearward from the lower portion of the wall-like portion sw, an engagement recess s52 provided on the rear side of the lower portion of the wall-like portion sw so as to be recessed forward, and a protruding portion st protruding forward from the lower portion of the wall-like portion sw, i.e., in the direction of the base s1, and capable of engaging with the cross portion 23.

The wall-like portion sw is integrally connected to the rear end of the bearing cover portion s4. A flange sg is integrally provided on the outer end of the bearing cover portion s4 and the wall-like portion sw to improve the strength of the connection. A cutout portion sk is provided in the left-right center of the bearing cover portion s4 and the wall-like portion sw to avoid interference with the reinforcing connection portion 44.

The engagement protrusions s51 are arranged in a row in the left-right direction (four in total). The engagement protrusions s51 are adapted to engage with the protrusion engagement portion 42a provided in the through-hole of the rear wall portion 42 of the upper frame p2.

The fitting recess s52 is provided on the rear side of the wall portion sw in the left-right center. The fitting recess s52 is adapted to engage with the forward protruding portion 42b protruding from the rear wall portion 42 of the upper frame p2.

The protruding portion st protrudes forward from the lower portion of the wall portion sw. The protruding portion st protrudes forward, approximately perpendicular to the wall portion sw.

The protruding portion st cooperates with the base portion s1 and the positioning rib 413 to determine the passage width wz of the shaft passage Z through which the cross section 23 of the lower frame p1 can pass toward the bearing portion K.

In other words, when the upper frame p2 is in the assembly position (T), the cross section 23 of the lower frame p1 can reach the bearing section K (bearing cover section s4) by passing through the shaft passage Z, which includes the protruding portion st.

When the upper frame p2 is in the normal position (U), the protruding portion st is disposed in a position that prevents the cross section 23 from slipping out of the bearing portion K. In other words, when the upper frame p2 is in the normal position (U), the protruding portion st is located at a position where it can engage with the lower edge of the cross section 23.

In other words, the protruding portion st engages with the lower frame p1, thereby preventing the upper frame p2 from disengaging (moving upward) from the normal position (U).

<<Rearward tilt degree setting mechanism I>>
The rearward tilt degree setting mechanism I is configured so that the user can select one of two or more rearward tilt degrees (four rearward tilt degrees in this embodiment) by rotating the rearward tilt degree setting lever 5 of the backrest E, which is supported so as to be able to tilt backward via the back support body D relative to the support base B.

The tilt-back setting mechanism I includes a tilt-back setting lever 5 rotatably supported on the back support D, a rotating member Q attached to the tilt-back setting lever 5 so as to be rotatable as one unit, a damper member (not shown) that is disposed on the support base B and against which the rotating member Q can abut, and a moderation engagement member R that is attached to the back support D and can moderately engage the rotating member Q.

<Rearward tilt degree setting lever 5 (operation lever)>
The rearward tilt degree setting lever 5 comprises a lever shaft portion 51 extending in the left-right direction and pivotally supported in an axial hole ma provided in the left and right arm bodies m4, and a lever body 52 which is attached so as not to rotate relative to the lever shaft portion 51 without the use of a fastener and has a portion which can be gripped by the user.

[Lever shaft portion 51]
The lever shaft 51 is made of metal. The lever shaft 51 is generally cylindrical and extends in the left-right direction. A protrusion 511 is provided at the protruding end of the lever shaft 51, protruding in a direction intersecting the axis of the lever shaft 51.

The lever shaft 51 is provided with a positioning plate 512 that is disk-shaped (donut-shaped) and whose inner surface is in contact with the outer surface of the right arm body m4. The positioning plate 512 is welded to the lever shaft 51.

The positioning plate 512 provided on the lever shaft 51 abuts against the outer surface of the right arm body m4, thereby restricting the leftward movement of the lever shaft 51 relative to the right arm body m4.

The flange 523 provided on the lever body 52 abuts against the outer surface of the positioning plate 512 provided on the lever shaft 51. In other words, the positioning plate 512 is interposed between the left arm body m4 and the flange 523 of the lever body 52.

[Lever body 52]
The lever body 52 is made of synthetic resin. The lever body 52 in this embodiment does not have a screw insertion hole for fixing to the lever shaft portion 51.

The lever body 52 includes a cylindrical portion 521 that extends in the left-right direction and has a receiving hole 52a formed therein in which the lever shaft portion 51 is disposed, a flange portion 523 that is integrally formed at the base end of the cylindrical portion 521, and a lever piece 522 that protrudes in a cantilever fashion from the cylindrical portion 521.

The cylindrical portion 521 has a receiving hole 52a that fits onto the lever shaft 51. The receiving hole 52a has a key groove 52b that can engage with the protrusion 511 provided on the lever shaft 51.

The flange 523 extends outward from the base end of the cylindrical portion 521. The flange 523 is disposed between the right arm body m4 of the back support base M and the side wall portion 12 of the lower frame p1 of the back support body P.

The flange 523 is provided around the entire circumference of the base end of the cylindrical portion 521. Only a specific portion of the flange 523 extends outwardly to correspond to the rotation range of the rearward tilt setting lever 5. In other words, the flange 523 is provided so that only the rear upper portion 52c, which can particularly engage with the peripheral portion of the cutout hole 121 in the side wall portion 12, protrudes outwardly.

In other words, in this embodiment, the lever body 52 is fitted onto the lever shaft 51 without using a fastener, so that the relative axial (left-right) movement of the lever body 52 with respect to the lever shaft 51 is restricted by the flange 523 provided on the lever body 52 directly or indirectly engaging with a component of the back support D.

The flange portion 523 is disposed between the right arm body m4 of the back support base M and the side wall portion 12 of the lower frame p1 in a manner that makes it difficult for it to shift sideways, so that the lever body 52 is appropriately supported relative to the lever shaft portion 51.

In this embodiment, the flange 523 is indirectly engaged with the right arm body m3, which is a component of the back support base M, via the positioning plate 512.

In other words, the flange portion 523 is positioned by being sandwiched between the positioning plate 512 of the lever shaft portion 51, which is in contact with the outer surface of the right arm body m4, and the peripheral portion of the cutout hole 121 in the side wall portion 12 of the lower frame p1.

The lever piece 522 protrudes from the tip of the cylindrical part 521 in a direction perpendicular to the longitudinal direction of the cylindrical part 521. The lever piece 522 is a protruding piece that makes it easier for the user to hook the fingers of the hand.

<Rotary member Q>
The rotating member Q is made of synthetic resin and is configured to rotate integrally with the rearward tilt degree setting lever 5. The rotating member Q is disposed between the left and right arm bodies m4 of the back support base M. The rotating member Q is biased by a spring qs in the direction of the moderation engagement member R attached to the inner surface of the right arm body m4.

<<Backrest E>>
The backrest E is supported by the back support D. The backrest E includes a shell-shaped backrest base e1 disposed on the back side, and a backrest main body e2 attached to the front side of the backrest base e1.

The lower part of the backrest base e1 is screwed to the upper part of the lower frame p1. The upper part of the backrest base e1 is supported so as to be movable relative to the upper frame p2 in the vertical direction.

The backrest body e2 has an inner shell and a back cushion (not shown), which are covered with a skin material.

<<Attachment of upper frame p2 to lower frame p1>>
The back support body P in this embodiment is configured so that the coil spring V can be manually arranged in a predetermined position between the lower frame p1 and the upper frame p2, and then the lower frame p1 and the upper frame p2 can be assembled in a single touch so that they cannot be separated.

In other words, although the back support body P requires the coil spring V to be interposed between the lower frame p1 and the upper frame p2, it is configured to be easily assembled by providing an intermediate member S that can exert a function of restricting the rotation range of the upper frame p2 relative to the lower frame p1.

An example of a process for assembling the upper frame p2 to the lower frame p1 will be described mainly with reference to Figures 27 to 32. Note that in Figures 28 to 31 and 33, the upper frame p2 is not shown in order to make it easier to see the operation of the intermediate member S. A part of the intermediate member S (the lower part) is also not shown.

<Preparation process>
First, prepare the lower frame p1, the coil spring V, the upper frame p2, and the intermediate member S that constitute the back support body P. The process of assembling the upper frame p2 to the lower frame p1 can be performed only by hand without using any tools.

There is no need to prepare grease. The intermediate member S is made of polyoxymethylene (POM) resin, which has excellent sliding and gliding properties as well as excellent rigidity, so assembly work can be carried out without applying grease between the members.

<Attachment of intermediate member S to upper frame p2>
Next, the intermediate member S is attached to the bearing receiving recess 4 of the upper frame p2. The mounting structure of the intermediate member S to the bearing receiving recess 4 has already been explained, so a description thereof will be omitted.

Here, in describing the process of assembling the upper frame p2 to the lower frame p1, for ease of explanation, the upper frame p2 with the intermediate member S attached may be referred to simply as the "upper frame p2."

<Movement of the upper frame p2 etc. in the assembly position (T)>
Next, as shown in FIG. 27, the upper frame p2 and the intermediate member S are changed to an assembly position (T) in which the upper frame p2 and the intermediate member S are tilted forward by about 15° from the normal position (U) relative to the lower frame p1 [about 15° from the upright position (ps)].

Then, as shown in Figures 27 and 28, the upper frame p2 and the lower frame p1 are moved relative to each other so that they approach each other so that the cross section 23 (shaft section J) of the lower frame p1 is disposed in the bearing recess 4 of the upper frame p2 in the specified assembly position (T).

When the upper frame p2 is in the assembled position (T), the cross section 23 (shaft J) of the lower frame p1 can move from the outside in the direction of the bearing section K through the shaft passage Z of the bearing recess 4, which has a passage width wz that is set to be approximately the same as or slightly longer than the thickness dimension (short side thickness dimension) of the cross section 23 (shaft J).

As shown in FIG. 29, in the initial stage in which the cross section 23 (shaft J) advances toward the rear (bearing K) of the bearing recess 4 in which the bearing K is provided, the outer surface of the base end portion s21 of the posture deformation section s2 in the second posture (Y) provided on the intermediate member S comes into contact with the inner surface 241 of the restricting section 24 protruding from the lower frame p1.

As shown in Figures 29 and 30, the base end portion s21 of the posture deformation portion s2 abutting against the inner surface 241 of the restricting portion 24 is pressed inward by engagement with the inner surface 241 of the restricting portion 24 fixed to the lower frame p1, and the posture is gradually changed from the second posture (Y) to the first posture (X).

The upper part of the inner surface 241 of the restricting portion 24 is provided with an inclined surface portion km. Therefore, the base end portion s21 of the posture deformation portion s2 of the intermediate member S is guided by the inclined surface portion km in the initial stage, and is smoothly and naturally deformed from the second posture (Y) to the first posture (X).

As shown in FIG. 31, when the cross member 23 (shaft J) is advanced to the rear of the bearing recess 4 (bearing K) and finally reaches a position supported by the bearing K (bearing cover s4), the upper frame p2 becomes rotatable around the shaft J relative to the lower frame p1. In addition, the deformation member s2 adopts a first position (X) in which it is elastically deformed by the inner edge 241 of the restricting member 24 so as to approach the base s1.

<Arrangement of coil spring V>
At this stage, as shown in FIG. 32, while maintaining the assembly posture (T) of the upper frame p2, the coil spring V is disposed between the front spring bearing portion 211 of the lower frame p1 and the rear spring bearing portion 411 of the upper frame p2.

When the upper frame p2 is in the assembly position (T), the arrangement space sp between the front spring receiving portion 211 and the rear spring receiving portion 411 has a sufficient separation space portion in the front-rear direction that allows the coil spring V to be arranged in the correct position by the worker's manual operation alone.

<Change in posture of upper frame p2 to normal posture (U)>
Then, after the coil spring V is arranged between the front spring receiving portion 211 and the rear spring receiving portion 411, the upper frame p2 is rotated around the axis portion J (the upper frame p2 is tilted backward) to change the position of the upper frame p2 from the assembly position (T) to the normal position (U).

As shown in Figure 33 (Figures 18 and 20), when the upper frame p2 is rotated from the assembly position (T) to the normal position (U), the position deformation portion s2, which was in the first position (X), moves forward relative to the regulating portion 24, and as a result, the elastic engagement with the inner surface 241 of the regulating portion 24 is released and the portion is positioned on the forward surface 242 side of the regulating portion 24.

In other words, the posture deformation portion s2, which was in the first posture (X), is disengaged from the inner surface 241 of the restricting portion 24, and moves outward due to elastic deformation (elastic return), changing its posture to the second posture (Y).

The tip portion s22 of the posture-deforming portion s2 in the second posture (Y) is adapted to engage with or be close to the inner surface portions of the left and right support arms 22. As a result, the tip portion s22 of the posture-deforming portion s2 in the second posture (Y) is disposed in front of the restricting portion 24.

In other words, the posture-deforming portion s2 in the second posture (Y) is disposed in a position where it can be supported between the lower frame p1 and the upper frame p2. When the upper frame p2 is changed from the assembly posture (T) to the normal posture (U), the posture-deforming portion s2 is automatically changed from the first posture (X) to the second posture (Y).

The postural deformation portion s2 in the second position (Y) is configured to move forward away from the restricting portion 24 when the upper frame p2 is in the backward tilting position (pr). On the other hand, the postural deformation portion s2 in the second position (Y) is sandwiched (supported) between the front wall portion 41 and the restricting portion 24 when the upper frame p2 is in the upright position (ps).

In other words, when the upper frame p2 assumes the standing posture (ps), it is prevented from assuming a further forward-leaning posture relative to the lower frame p1 by the posture deformation portion s2 of the second posture (Y).

In the normal position (U), the upper frame p2 cannot rotate backward by the amount of the thickness dimension in the front-to-rear direction at the tip portion s22 of the position deformation portion s2.

The upper frame p2 in the normal position (U) cannot return to the assembly position (T) in which the cross section 23 can come out of the bearing recess 4 unless a special operating force is applied to the positional deformation section s2 in the second position (Y), which is an obstruction member.

In other words, when the upper frame p2 is in the normal position (U), it cannot escape from the positional relationship in which the protruding portion st of the intermediate member S can engage with the lower edge of the cross section 23 (is located below the cross section 23), and the upper frame p2 cannot detach from the lower frame p1.

Through these steps, the attachment of the upper frame p2 to the lower frame p1 is complete.

When removing the upper frame p2 from the lower frame p1, the posture-deforming portion s2 in the second posture (Y) can be forcibly changed to the first posture (X) using fingers, a rod-shaped member, or the like.

In this embodiment, the coil spring V constantly biases the front wall portion 41 constituting the bearing recess 4 toward the rear. Therefore, by forcibly changing the position of the position-deforming portion s2 from the second position (Y) to the first position (X) using a finger or a rod-shaped member, it is relatively easy to change the position of the upper frame p2 from the normal position (U) to the assembly position (T).

In other words, in this embodiment, when the back support body P is in the normal position (U), the coil spring V always biases the upper frame p2 in the direction of the assembly position (T) (the direction that tends to tilt it forward).

Therefore, when the posture deformation portion s2, which is supported between the restricting portion 24 of the lower frame p1 and the front wall portion 41 of the upper frame p2, is forcibly moved from the second posture (Y) to the first posture (X), the coil spring V assists the rotation of the upper frame p2 so that it can move to the assembly posture (T).

The above-described embodiment makes it possible to realize a configuration in which the upper frame p2 is rotatably supported relative to the lower frame p1, without the need for a single steel shaft as in the conventional case.

For this reason, the chair of this embodiment not only facilitates design that contributes to improved aesthetics, but also provides excellent design freedom for supporting the upper frame p2 rotatably relative to the lower frame p1.

The above-described embodiment provides a configuration that allows the assembly of the upper frame p2 of the back support D, which is the second member configured to be rotatable relative to the lower frame p1 of the back support D, which is the first member, to be performed conveniently even in cases where a coil spring V, which is a biasing member, needs to be interposed between the lower frame p1 and the upper frame p2.

The above-described embodiment not only reduces the number of parts that make up the tilt-back setting lever 5, which is the operating lever, but also provides a chair with excellent design freedom that allows for a suitable appearance of the tilt-back setting lever 5.

As described above in detail, the chair of this embodiment has a backrest E rotatably supported on a support base B via a back support D. The back support D is equipped with a lower frame p1 having an axle J, and an upper frame p2 having a bearing K that receives the axle J and supported rotatably relative to the lower frame p1.

The shaft portion J extends horizontally, and its width in the front-to-back direction is shorter than its width in the up-to-down direction. At the upper part of the shaft portion J, a partially cylindrical curved shaft surface jm is formed, which can indirectly engage with the bearing portion K via an intermediate member S, which is another member.

This makes it possible to provide a chair with excellent design freedom, allowing the upper frame p2 to be rotatably supported relative to the lower frame p1.

In other words, in this embodiment, it is possible to realize a configuration in which the upper frame p2 is rotatably supported relative to the lower frame p1 without using a single steel shaft. This makes it easier to create a design that reduces the number of parts and contributes to improving the design.

The lower frame p1 is provided with a shaft portion J with a curved shaft surface jm formed on the upper portion, and the upper frame p2 is provided with a bearing portion K.

This allows the shaft portion J and the bearing portion K to be appropriately engaged via the intermediate member S.

The lower frame p1, which includes the shaft portion J, is integrally formed from synthetic resin.

This makes it possible to ideally realize a design that reduces the number of parts compared to conventional configurations that use a single steel shaft.

The upper frame engagement part 2, which includes the axis part J, is provided on the lower frame p1. The upper frame engagement part 2 includes a lower frame base part 21, left and right support arms 22 that extend in pairs in the vertical direction from the left and right sides of the lower frame base part 21, and a cross section 23 that is installed between the left and right support arms 22 and includes the axis part J.

For this reason, the shaft portion J included in the upper frame engagement portion 2 is provided in a manner that provides excellent rigidity.

The cross-bridge portion 23 is provided with axle portions J arranged in pairs on the left and right, with each outer portion integrally connected to the left and right support arms 22, and a connecting portion 231 connecting these axle portions J.

For this reason, the left and right shafts J included in the upper frame engagement portion 2 are provided in a manner that provides excellent rigidity.

A bearing recess 4 that includes a bearing portion K and is open downward is provided at the bottom of the upper frame p2.

For this reason, the upper frame p2 is configured so that the bearing portion K is appropriately engaged with the shaft portion J that is integral with the lower frame p1.

The other member, the intermediate member S, is made of a resin with better sliding properties than the upper frame p2 and is disposed in the bearing recess 4. The axial curved surface jm formed on the upper part of the shaft portion J engages with the bearing portion K via the intermediate member S.

As a result, the intermediate member S can slide smoothly against the shaft portion J without using a lubricant such as grease.

The resin is polyoxymethylene (POM). This gives the intermediate member S excellent strength and allows it to slide smoothly against the shaft portion J without the use of a lubricant such as grease.

The bearing recess 4 includes a front wall portion 41, a rear wall portion 42 disposed behind the front wall portion 41, and a connecting portion 43 connecting the upper portions of the front wall portion 41 and the rear wall portion 42. The bearing portion K is formed in a downward C-shape including the front wall portion 41, the rear wall portion 42, and the connecting portion 43.

For this reason, the bearing recess 4 has an ideal configuration for receiving the shaft portion J.

A reinforcing connection portion 44 is provided to connect the left-right middle portions of the upper portions of the front wall portion 41 and the rear wall portion 42.

For this reason, the front wall portion 41 and the rear wall portion 42 are configured with excellent strength due to the reinforcing connection portion 44.

The present invention is not limited to the embodiments described above.

The lower frame may be provided with a bearing portion that receives the shaft portion, and the upper frame may be provided with the shaft portion.

The lower part of the shaft may have a partially cylindrical curved shaft surface.

The shaft portion and the bearing portion may be engaged directly or indirectly via another member. In other words, there may be no intermediate member between the shaft portion and the bearing portion.

The shaft portion may be formed separately from the upper frame or the lower frame.

The entire left-right area of the cross section may constitute the shaft section.

The intermediate member that can exert the rotation restriction function may be provided between the support base and the back support.

In other words, the chair has a backrest rotatably supported on a support base via a back support, and one of the support base and the back support has an axle and the other has a bearing for receiving the axle. A biasing member is interposed between the support base and the back support. The back support is configured to be rotatable around the axle so that it can take an assembly position in which the biasing member can be attached between the support base and the back support, and a normal position which is a different position from the assembly position. An intermediate member may be provided between the support base and the back support to restrict the rotation of the back support that has been changed from the assembly position to the normal position so that it cannot return to the assembly position.

A more specific configuration of the above-mentioned invention is one in which the back support is configured to be tiltable between an upright position and a backward tilted position that is tilted further back than the upright position in the normal position, and the biasing member biases the back support in the direction of the upright position.

The intermediate member may be provided between the first member and the second member that constitute the chair. The first member and the second member may be any member that constitutes the chair.

In other words, the chair has a second member rotatably supported on a first member, one of the first member and the second member has an axle portion and the other has a bearing portion that receives the axle portion, a biasing member is interposed between the first member and the second member, the second member is configured to be rotatable around the axle portion so as to be able to adopt an assembly position in which the biasing member can be attached between the first member and the second member and a normal position that is a different position from the assembly position, and an intermediate member is provided between the first member and the second member that can restrict the rotation of the back support body that has been changed from the assembly position to the normal position so that it cannot return to the assembly position.

A more specific configuration of the above-mentioned invention is one in which the second member is configured to be tiltable between an initial position and a shifted position different from the initial position in the normal position, and the biasing member biases the second member in the direction of the initial position.

The specific configuration of each part is not limited to the above embodiment, and various modifications are possible without departing from the spirit of the present invention.

4... Bearing recess B... Support base D... Back support E... Backrest J... Shaft jm... Shaft curved surface K... Bearing P... Back support body p1... Lower frame (first member)
p2: Upper frame (second member)
V: Coil spring (biasing member)

Claims (10)

A chair in which a backrest is rotatably supported on a support base via a back support,
The back support includes a lower frame having either an axle portion or a bearing portion that receives the axle portion, and an upper frame having the other of the axle portion and the bearing portion and supported rotatably relative to the lower frame,
The shaft portion extends horizontally and has a width dimension in a front-rear direction shorter than a width dimension in a vertical direction,
A chair in which an axial curved surface having a partial cylindrical curved surface shape is formed on either the upper or lower part of the axis portion and which can engage with the bearing portion directly or indirectly via another member. The lower frame is provided with the shaft portion having the axial curved surface formed on an upper portion thereof,
2. The chair according to claim 1, wherein the bearing portion is provided on the upper frame. The chair according to claim 1, wherein the upper frame or the lower frame, including the axis portion, is integrally formed from synthetic resin. an upper frame engaging portion including the shaft portion is provided on the lower frame,
The chair of claim 2, wherein the upper frame engagement portion comprises a lower frame base, left and right support arms extending in a pair in the vertical direction from the left and right sides of the lower frame base, and a cross frame portion bridged between the left and right support arms and including the axis portion. The chair according to claim 4, wherein the cross-section comprises a pair of axles arranged on the left and right, each of whose outer parts is integrally connected to the left and right support arms, and a connecting part connecting these axles. The chair according to claim 2, wherein a bearing recess that includes the bearing portion and is open downward is provided in the lower part of the upper frame. the other member is an intermediate member disposed in the bearing receiving recess, the intermediate member being made of a resin having a higher sliding property than the upper frame,
7. The chair according to claim 6, wherein the axial curved surface formed on the upper portion of the shaft portion engages with the bearing portion via the intermediate member. The chair according to claim 7, wherein the resin is polyoxymethylene (POM) resin. the bearing recess includes a front wall portion, a rear wall portion disposed behind the front wall portion, and a connecting portion connecting upper portions of the front wall portion and the rear wall portion,
7. The chair according to claim 6, wherein the bearing portion is formed in a downward C-shape including the front wall portion, the rear wall portion, and the connecting portion. The chair according to claim 9, further comprising a reinforcing connection portion that connects the left-right middle portions of the upper portions of the front wall portion and the rear wall portion.

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