chair

Abstract

To provide a chair having a suitable structure which can easily attach / detach a backrest to / from a back support body.SOLUTION: A chair includes a detachment prohibiting mechanism P disposed between a back support body L and a backrest M, and prohibiting detachment of the backrest M from the back support body L. The detachment prohibiting mechanism P includes: an operation member p1 which is disposed in the back support body L and can be reversibly operated by the operational force of a person between an engaging posture of prohibiting detachment of the backrest M and an evacuation posture of permitting detachment of the backrest M; and an engaged part p2 which is disposed in the backrest M and with which an engaging part p11 disposed in the operation member p1 can be engaged in the engaging posture.SELECTED DRAWING: Figure 9

Description

Technical Field

[0001] The present invention relates to a chair.

Background Art

[0002] Conventionally, there has been known a chair provided with a relative movement preventing means for engaging a back shell with an attachment member of a back support rod and maintaining the engaged state (see, for example, Patent Document 1).

[0003] However, the conventional configuration is such that the attachment and detachment of the back shell are exclusively performed by the manufacturer using a dedicated tool or the like, and it has not been configured to be easily attachable and detachable by the user who is the end user.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present invention has been made paying attention to the above circumstances, and an object thereof is to provide a chair having a suitable configuration capable of easily attaching and detaching a backrest to and from a back support at least.

Means for Solving the Problems

[0006] That is, the present invention has the following configuration.

[0007] The invention according to claim 1 is a chair including a back support, a backrest detachable from the back support, and a detachment prohibiting mechanism provided between the back support and the backrest for prohibiting detachment of the backrest from the back support, wherein the detachment prohibiting mechanism is provided on the back support Rotatably supportedAn operating member that can be reversibly operated by human force between an engaged position that prevents the backrest from detaching and a retracted position that allows the backrest to detach, The aforementioned backrest It is provided with an engaged portion that can be engaged with an engaging portion provided on the operating member in the engagement position. Furthermore, the operating member is biased in the direction of the engagement position by a biasing member separate from the operating member, and the operating member is provided with an operating portion having an outer surface that directly receives a backward pressing force from the fingers against the biasing force of the biasing member, at least when moving from the engagement position to the retracted position. It is a chair.

[0008] The invention described in claim 2 is a chair according to claim 1, wherein a positioning mechanism is provided for positioning the backrest with respect to the back support, and the positioning mechanism comprises a protrusion provided on either the back support or the backrest, and a recess provided on the other that can engage with the protrusion.

[0009] The invention described in claim 3 is the chair according to claim 2, wherein the protrusion and the recess can engage in the vertical direction, and the operating member prevents the vertical movement of the backrest relative to the back support in the engaged position.

[0011] The invention described in claim 4 is characterized in that a space is provided between the back support and the backrest into which fingers can be inserted, and the operated part is positioned facing that space. 1 This is the chair described.

[0014] Claim 5 The invention described is a chair according to claim 1, wherein the operating members are provided in pairs on the left and right sides of the back support, and the engaged portions are provided in pairs on the left and right sides of the backrest.

[0015] Claim 6 The invention described herein is characterized in that the back support comprises a back support body that supports the operating member and a cover member attached to the back support body, wherein the cover member covers the operating member such that only the engaging portion and the operated portion are exposed to the outside. 1 or 5 This is the chair described. [Effect of the Invention]

[0016] As described above, according to the present invention, it is possible to provide at least a chair having a suitable configuration that allows a backrest to be easily attached to and detached from a back support. [Brief Description of the Drawings]

[0017] [Figure 1] Perspective view showing an embodiment of the present invention. [Figure 2] Front view in the same embodiment. [Figure 3] Rear view in the same embodiment. [Figure 4] Left side view in the same embodiment. [Figure 5] Right side view in the same embodiment. [Figure 6] Plan view in the same embodiment. [Figure 7] Bottom view in the same embodiment. [Figure 8] Exploded perspective view in the same embodiment. [Figure 9] Exploded perspective view in the same embodiment. [Figure 10] Perspective view from the rear in the same embodiment. [Figure 11] Rear view of the backrest in the same embodiment. [Figure 12] Left side view of the backrest in the same embodiment. [Figure 13] Bottom view of the backrest in the same embodiment. [Figure 14] Central longitudinal sectional view of the backrest in the same embodiment. [Figure 15] Enlarged view of the lower part in FIG. 14. [Figure 16] Exploded perspective view of the backrest in the same embodiment. [Figure 17] Rear view of a partially broken backrest ground in the same embodiment. [Figure 18] Front view of a partially broken backrest ground in the same embodiment. [Figure 19]Perspective views of the first and second strip-shaped members in the same embodiment. [Figure 20] A bottom view of the backrest body in the same embodiment. [Figure 21] A perspective view of the back support in the same embodiment. [Figure 22] An exploded perspective view of the back support in the same embodiment. [Figure 23] A plan view illustrating the operation of the operating member in the same embodiment. [Figure 24] A plan view illustrating the operation of the operating member in the same embodiment. [Figure 25] A plan view illustrating the operation of the operating member in the same embodiment. [Figure 26] A plan view illustrating the operation of the operating member in the same embodiment. [Figure 27] View in the direction of the arrow in the X direction in Figure 4. [Figure 28] A perspective view of the seat support in the same embodiment. [Figure 29] A plan view of the seat support in the same embodiment. [Figure 30] A perspective view of the rear of the seat support in the same embodiment. [Figure 31] Front view of the seat support in the same embodiment. [Figure 32] Rear view of the seat support in the same embodiment. [Figure 33] Left side view of the seat support in the same embodiment. [Figure 34] Right side view of the seat support in the same embodiment. [Figure 35] A perspective view from below of the seat body in the same embodiment. [Figure 36] A central cross-sectional view of the seat body in the same embodiment. [Figure 37] A central vertical cross-sectional view of the seat body in the same embodiment. [Figure 38] A plan view of the shell body in the same embodiment. [Figure 39] A bottom view of the shell body in the same embodiment. [Figure 40] Front view of the shell body in the same embodiment. [Figure 41] Rear view of the shell body in the same embodiment. [Figure 42] Right side view of the shell body in the same embodiment. [Figure 43] A diagram illustrating the operation of attaching the seat body to the seat support in the same embodiment. [Figure 44] A diagram illustrating the operation of attaching the seat body to the seat support in the same embodiment. [Figure 45] A diagram illustrating the operation of attaching the seat body to the seat support in the same embodiment. [Figure 46] A diagram illustrating the operation of attaching the seat body to the seat support in the same embodiment. [Figure 47] A diagram illustrating the operation of attaching the seat body to the seat support in the same embodiment. [Figure 48] A diagram illustrating the method for forming an opening in the same embodiment. [Figure 49] A diagram illustrating the method for forming an opening in the same embodiment. [Figure 50] A diagram illustrating the method for forming an opening in the same embodiment. [Figure 51] A diagram illustrating the method for forming an opening in the same embodiment. [Figure 52] A diagram illustrating the method for forming an opening in the same embodiment. [Figure 53] An enlarged view of the same embodiment after the opening has been formed. [Modes for carrying out the invention]

[0018] Hereinafter, one embodiment of the present invention will be described with reference to Figures 1 to 53.

[0019] The chair comprises legs A, a support base B supported by legs A, a seat C supported by support base B, a back support L supported by support base B, and a backrest M supported by back support L.

[0020] Leg A comprises multiple leg blades a1 equipped with casters at their lower ends, and a leg support column a2 that rises from the point where the upper ends of the leg blades a1 converge. The leg support column a2 is configured to be extendable and retractable in the vertical direction.

[0021] The support base B is attached to the upper end of leg A. Inside the support base B is a support mechanism (not shown) for supporting the seat C and back support L.

[0022] The seat C of this embodiment will be described in detail below.

[0023] <<Location C>> The seat C is supported by a support base B, which is positioned on top of the leg A. The lower surface of the support base B and the outer circumferential surface of the seat C are configured to be smoothly continuous when viewed from the front.

[0024] The seat C comprises a seat support 1 and a seat body D having an upward-facing seat surface and being detachable from the seat support 1.

[0025] The outer circumferential surfaces of seat C, that is, the outer circumferential surfaces of seat support 1 and seat body D, are smoothly continuous, forming a partially spherical shape.

[0026] <Seat receiver 1> The seat support body 1 supports the seat body D. The upper surface of the seat support body 1 is configured to engage with the shell body 3 that constitutes the seat body D. In other words, the shell body 3 is mounted on the upper surface of the seat support body 1.

[0027] The seat support body 1 is formed in a shell shape from synthetic resin. The seat support body 1 has a partially spherical shape. The outer surface of the seat support body 1, which is visible to the user, is formed to have a spherical surface shape.

[0028] The outer circumferential surface of the front portion of the seat support 1 is configured to smoothly connect with the lower surface of the front portion of the support base B. Furthermore, the outer circumferential surface of the seat support 1 is configured to smoothly connect with the outer circumferential surface of the seat body D.

[0029] The lower part of the center of the seating body 1 in the left-right direction is provided with a recess 11 that is open downwards and can accommodate a support base B.

[0030] The upper portion of the seat support 1, that is, the upward-facing portion of the seat support 1, is provided with a shell body mounting portion 12 that has a connection portion with the shell body 3 of the seat body D. The rear end of the shell body mounting portion 12 is provided with a notch 122 to avoid interference with the operating lever k2 provided on the shell body 3.

[0031] The shell mounting section 12 is provided with a shaped portion that constitutes a detachable engagement structure (central positioning section G, vertical engagement mechanism H, horizontal engagement mechanism I, and reverse return restriction mechanism K) that allows the seat body D to be attached and detached, as will be described in detail later.

[0032] The outer edge 1e of the seat support body 1 is formed so that, in front and rear views, it is gradually positioned downward from both the left and right ends toward the center in the left-right direction (forming a concave shape downwards). In addition, in side views, the outer edge 1e of the seat support body 1 is formed so that it is gradually positioned upward from both the front and rear ends toward the center in the front-rear direction (forming a convex shape upwards).

[0033] The upper end of the seat support periphery wall portion 121, which is erected inward from the outer peripheral edge 1e of the seat support 1, is provided to extend substantially horizontally in the front view, rear view, and side view.

[0034] <Seat body D> The seat body D comprises a seat cushion Dq, a support shell 3 attached to the underside of the seat cushion Dq, and seat upholstery Dh covering the upper part and peripheral edge of the seat cushion Dq and the peripheral edge of the shell 3. The seat body D has a seat surface on its upper surface that is approximately circular in shape when viewed from above.

[0035] [Seat cushion Dq] The seat cushion Dq is primarily made of polyurethane foam. The seat cushion Dq is shaped so that its width gradually increases towards the top. The underside of the seat cushion Dq is attached to the shell body 3.

[0036] The seat cushion Dq is shaped to fit onto the shell body 3 from above. When viewed from below, the seat cushion Dq is larger than the shell body 3. The dimensions of the seat cushion Dq in the front-to-back and left-to-right directions are set to be longer than the dimensions of the shell body 3 in the front-to-back and left-to-right directions.

[0037] [Shell body 3] The shell body 3 is a roughly disc-shaped object attached to the underside of the seat cushion Dq. The shell body 3 is integrally formed from synthetic resin.

[0038] The shell body 3 comprises a shell body main body 31 having a disc-shaped portion whose upper surface is adhered to the lower surface of the seat cushion Dq; a support wall portion 33 which is connected to the peripheral edge of the shell body main body 31 so as to extend downward and whose outer surface is in contact with the inner surface of the peripheral edge of the seat cushion Dq; an end wall portion 34 which extends diagonally upward and outward from the lower end of the support wall portion 33 and supports the lower end of the peripheral edge of the seat cushion Dq; and a peripheral wall portion 32 which is suspended downward from the lower surface of the peripheral edge of the shell body main body 31 located inside the support wall portion 33.

[0039] The lower end of the peripheral wall portion 32 is provided to extend substantially horizontally in the front view, rear view, and side view.

[0040] The shell body 3 is integrally provided with an operating lever k2, which has a cantilevered shape and a protrusion kt that engages with the seat support body 1 to prevent relative rotation from the mounting position (F).

[0041] The shell body 31 is provided with a central projection g1 that protrudes downward from the center in the front-rear and left-right directions. The shell body 31 is provided with a plurality of locking projections hk that are spaced at regular intervals in the circumferential direction, inside the peripheral wall 32.

[0042] The central protrusion g1 constitutes the central positioning part G, and the locking projection engagement part hk constitutes the vertical engagement mechanism H, which will be described in detail later.

[0043] The peripheral wall portion 32 is located on the periphery of the shell body 3. More specifically, the peripheral wall portion 32 is located on the central side of the shell body 3 than the support wall portion 33. The peripheral wall portion 32 has an outward-facing surface 32m that can come into contact with the edge portion de of the seat upholstery Dh that encloses the seat cushion Dq.

[0044] The peripheral wall portion 32 is arranged in a substantially annular shape when viewed from below. That is, the peripheral wall portion 32 is continuously arranged on a circular trajectory, except for one point at the rear where the operating lever k2 is located, so that when viewed from below, it is located on a virtual circumference that forms a perfect circle with the central protrusion g1 at its center.

[0045] The peripheral wall portion 32 is provided with outwardly extending portions 321 that extend outward and can restrict the downward movement of the edge portion de of the upholstery Dh. The outward extending portions 321 are multiple projections arranged at regular intervals in the circumferential direction on the peripheral wall portion 32.

[0046] Furthermore, inwardly bulging inward protrusions it are provided on the inner surfaces of three locations on the peripheral wall portion 32: the front end and both left and right ends, specifically the inner surface of the central left-right portion of the front of the peripheral wall portion 32, and the inner surface of the central front-rear portions of both left and right sides of the peripheral wall portion 32. These inward protrusions it constitute the horizontal engagement mechanism I, which will be described in detail later.

[0047] Ribs rv are attached to the inner surface of the peripheral wall portion 32, perpendicular to the shell body 31 and extending outward from the central part of the shell body 31. The ribs rv are arranged radially on the lower surface of the shell body 31.

[0048] The operating lever k2 is cantilevered to the shell body 31. That is, the shell body 3 is provided with an operating lever k2, which is a lever member that is cantilevered and engages with the seating body 1. The operating lever k2 has a wall-like portion k21 that extends from the base portion of the operating end portion k22 and forms part of the peripheral wall portion 32.

[0049] The operating lever k2 is located at the rear of the shell body 31. The base end ke of the operating lever k2 is integrally connected to the shell body 31, and the outer end is provided with an operating end k22 that receives the operating force from the user's fingers.

[0050] The operating lever k2 has a protrusion kt projecting downward between its base end ke and operating end k22, which can engage with an upward-facing recess k1 provided in the seating body 1. The recess k1 of the seating body 1 and the protrusion kt of the operating lever k2 constitute the reverse-reverse restricting mechanism K, which will be described in detail later.

[0051] In the shell body 3, the lower edge 3e of the support wall portion 33 is formed so as to be gradually positioned downward from both the left and right ends toward the center in the left-right direction when viewed from the front and rear (convex downward). In addition, in the shell body 3, the lower edge 3e of the support wall portion 33 is formed so as to be gradually positioned upward from both the front and rear ends toward the center in the front-rear direction when viewed from the side (convex upward).

[0052] The lower end edge 3e of the support wall portion 33 in the shell body 3 is set to follow the outer peripheral end edge 1e of the seat support body 1 when the seat body D is in the mounting position (F).

[0053] [Sitting area Dh] The seat upholstery Dh is primarily composed of a stretchable fabric that covers the seat cushion Dq.

[0054] The seat upholstery Dh has an annular edge portion de. The seat upholstery Dh is constructed in a bag-like shape that is open downwards. The seat upholstery Dh is provided with a string-like member (not shown) that reduces the diameter of the edge portion de and brings the edge portion de into contact with the outward-facing surface 32m of the peripheral wall portion 32 of the shell body 3.

[0055] <<Attachment and detachment structure of the seat body D to the seat support 1>> The seat body D is configured to be able to rotate horizontally around a common axis cj relative to the seat support 1, between a retracted position (E) in which it is detachable from the seat support 1 and an attached position (F) in which it is attached to the seat support 1.

[0056] In this embodiment, the chair is configured so that the seat body D can be easily attached to and detached from the seat support 1 without the use of tools, not only by the manufacturer but also by the end user (user), in order to facilitate maintenance such as cleaning and replacement, as well as storage and transportation.

[0057] Between the seat support 1 and the seat body D, there is a central positioning part G that positions the seat body D so that its axis aligns with the axis of the seat support 1, a vertical engagement mechanism H that tightly engages the seat support 1 and the shell body 3 in the vertical direction when the seat body D is in the mounting position (F), a horizontal engagement mechanism I that tightly engages the seat support 1 and the shell body 3 in the horizontal direction when the seat body D is in the mounting position (F), and a reverse-reverse restricting mechanism K that restricts the seat body D from returning to the retracted position (E) when it is in the mounting position (F).

[0058] <Central positioning section G> The central positioning unit G can position the shell body 3 of the seat support 1 and the seat body D so that they substantially align with the common axis cj.

[0059] The central positioning portion G is cylindrical and includes a downwardly projecting central protrusion g1 provided in the center of the shell body 3 of the seat body D, and a central protrusion engaging portion g2 provided in the center of the seat receiving body 1 and forming a hole that allows the central protrusion g1 to rotate relative to it.

[0060] <Vertical engagement mechanism H> The vertical engagement mechanism H engages the shell body 3 of the seat support 1 and the seat body D in the vertical direction so as to pull them together.

[0061] The vertical engagement mechanism H comprises a locking projection hp, which is a first engagement portion provided on the seating body 1, and a locking projection engagement portion hk, which is a second engagement portion provided on the shell body 3 and capable of engaging with the locking projection hp of the seating body 1.

[0062] The seat body D can assume the mounting position (F) by the close engagement of the locking projection hp and the locking projection engagement portion hk.

[0063] Multiple locking projections hp of the seating body 1 and locking projection engagement portions hk of the shell body 3 are arranged at regular intervals along a virtual circumference centered on the common axis cj.

[0064] [Locking projection hp (first engagement part)] The locking projection hp constitutes a protruding structure that is provided in a direction intersecting the common axis cj. The locking projection hp is provided approximately horizontally inward, that is, towards the center where the common axis cj is located, from the upright wall-shaped seat body peripheral wall portion 121, which is erected on the periphery of the seat body 1 in a substantially annular shape in a plan view.

[0065] The locking projection hp can engage in the vertical direction with the guide inclined surface hm provided on the locking projection engagement portion hk. More specifically, the locking projection hp can press the guide inclined surface hm of the locking projection engagement portion hk downwards. In other words, the locking projection hp moves the seat body D downwards during the process of the seat body D being rotated from the retracted position (E) to the mounted position (F).

[0066] [Latching protrusion engaging part hk (second engaging part)] The locking projection engagement portion hk has an upward-facing guide inclined surface hm that can engage with the locking projection hp. The locking projection engagement portion hk protrudes downward from the circular plate-shaped shell body 31.

[0067] The locking projection engagement portion hk comprises a support wall hs that is suspended downward from the shell body 31, and an engagement portion body hg that is supported by the support wall hs and has an upward-facing guide inclined surface hm on its upper surface.

[0068] The support wall hs comprises a first support wall portion ha extending in the circumferential direction and a second support wall portion hb connected to the first support wall portion ha and extending in a direction substantially perpendicular to the first support wall portion ha.

[0069] The first support wall portion ha is connected to the inner edge of the engagement portion body hg, which extends in the circumferential direction. The second support wall portion hb has a shorter width dimension than the first support wall portion ha and is connected to the base edge, which is one circumferential edge of the engagement portion body hg.

[0070] The engaging part body hg is a plate-like structure that extends circumferentially in a reclined position. The inner edge and base edge of the engaging part body hg are connected to the support wall hs. The upward-facing guide inclined surface hm provided on the engaging part body hg is inclined so as to be gradually positioned upward from the tip side to the base side. Here, the tip side of the engaging part body hg refers to the edge side that forms the tip in the direction of movement when rotating from the retracted position (E) to the mounted position (F).

[0071] The locking projection hp and guide inclined surface hm of the vertical engagement mechanism H, which has the above configuration, are configured such that the degree of contact gradually increases as the seat body D pivots from the retracted position (E) to the mounted position (F).

[0072] The procedure for attaching the seat body D to the seat support 1 is as follows:

[0073] First, as shown in Figure 43, the seat body D is moved downward from a position separated above the seat support 1, while the central positioning unit G positions it horizontally on the common axis cj.

[0074] Next, as shown in Figure 44, the seat body 43, which has been moved downward, is rotated around the common axis cj.

[0075] Subsequently, as shown in Figure 45, when the seat body D reaches the mounting position (F), the locking projection hp and the locking projection engagement portion hk engage so that they are in close contact in the vertical direction.

[0076] <Horizontal engagement mechanism I> The horizontal engagement mechanism I engages the seat support 1 and the shell 3 of the seat body D in the horizontal direction.

[0077] The horizontal engagement mechanism I comprises an inward projection it, which is a second engagement portion provided on the shell body 3, and an outward-facing guide inclined surface im, which is a first engagement portion provided on the seating body 1 and capable of engaging with the inward projection it, which is a horizontal projection portion of the shell body 3.

[0078] Multiple inwardly protruding portions it of the shell body 3 and outwardly oriented guide inclined surfaces im of the seating body 1 are arranged at regular intervals along a virtual circumference centered on the common axis cj.

[0079] [Inwardly protruding part it (second engaging part)] The inward projection it constitutes a protruding structure that extends in a direction intersecting the common axis cj. In a plan view, the inward projection it extends inward, that is, toward the common axis cj, from a hanging wall-shaped peripheral wall portion 32 that is erected on the shell body 3 in a substantially annular shape.

[0080] Furthermore, an outward extension 321 extends from the peripheral wall portion 32, where the inward projection it is provided, in the opposite direction, i.e., outward, to which the edge portion de of the upholstery Dh is locked.

[0081] The inward projection it can engage horizontally with the outward-facing guide inclined surface im provided on the seating body 1. More specifically, the inward projection it can press inward against the outward-facing guide inclined surface im provided on the seating body peripheral wall portion 121 of the seating body 1.

[0082] [Outward-facing guide inclined surface im (first engagement portion)] The outward-facing guide inclined surface im is provided on the outer circumferential surface of the seat-receiving body periphery wall portion 121, which is an upright wall erected on the periphery of the seat-receiving body 1. The outward-facing guide inclined surface im faces outward, which is the horizontal direction that allows it to engage with the inward projection portion it. The outward-facing inclined surface is inclined so that it gradually moves outward as it moves clockwise.

[0083] The inward projection it and outward guide inclined surface im of the horizontal engagement mechanism I, which has the above configuration, are configured such that the degree of contact gradually increases as the seat body D rotates clockwise from the retracted position (E) to the mounted position (F).

[0084] <Reverse Regulatory Mechanism K> The reverse movement restriction mechanism K is provided between the seat body D and the shell body 3 of the seat support 1, and restricts the seat body D from moving backward in the retracted position (E) direction from the mounting position (F).

[0085] On the other hand, the reverse-returning restraint mechanism K can release the state in which the seat body D is unable to rotate relative to the seat support 1 by operating the operating lever k2 so as to deform upward against the elastic restoring force of the shell body 3, thereby allowing the seat body D from the mounting position (F) to be rotated to the retracted position (E) and detached from the seat support 1.

[0086] The reverse-reverse restricting mechanism K comprises a recess k1 provided on the upper surface of the rear end of the seat support 1, and an operating lever k2 provided on the shell body 3 and having a protrusion kt that can engage with the recess k1 only in the mounting position (F).

[0087] The protrusion kt of the reverse-reverse regulating mechanism K is provided on the cantilevered operating lever k2 provided on the shell body 3. The protrusion kt of the operating lever k2 releases the engagement with the recess k1 provided on the seat support body 1 by using the elastic deformation of the material to move the operating end k22, which receives the operating force from the user's fingers, upward, thereby allowing the seat body D to rotate from the mounting position (F) to the retracted position (E).

[0088] Furthermore, the upper rear end surface of the seat support 1 is provided with a guide inclined surface km adjacent to the recess k1, which can engage with the protrusion kt of the operating lever k2. The guide inclined surface km is inclined so as it approaches the recess k1, gradually rising upwards. The uppermost part of the inclined surface is set to be above the bottom of the recess k1.

[0089] When the seat body D is in the retracted position (E), the protrusion kt of the operating lever k2 is positioned at the lowest point on the inclined surface. Then, when the seat body D rotates from the retracted position (E) to the mounted position (F), the protrusion kt is gradually pushed upward by the guide inclined surface km against the elastic restoring force of the operating lever k2.

[0090] Furthermore, when the seat body D moves from the retracted position (E) to the mounted position (F), the protruding portion kt overcomes the guide inclined surface km and engages with the recessed portion k1 by the elastic restoring force of the operating lever k2.

[0091] In this embodiment, when the reverse-return restricting mechanism K moves from the retracted position (E) to the mounted position (F), the rotational movement of the shell body 3 causes the protrusion kt to climb up the inclined guide surface km of the seating body 1, thus eliminating the need to apply any operating force to the operating lever k2. At this point, once it has climbed over the inclined guide surface km, the protrusion kt of the operating lever k2 automatically engages with the recess k1 due to the elastic restoring force of the operating lever k2. In other words, the reverse-return restricting mechanism K does not require any special operation of the operating lever k2 during the process from the retracted position (E) to the mounted position (F).

[0092] Furthermore, downward projections 32t are provided on both sides of the peripheral wall portion 32 of the shell body 3 adjacent to the operating lever k2, extending downward to the same position as the lower end of the operating lever k2.

[0093] These downward protrusions 32t are designed to prevent the operating lever k2 from being pushed upward by the mounting surface when the seat body D or shell body 3 is placed independently on a mounting surface such as the floor for purposes such as replacement parts.

[0094] In other words, the downward protrusions 32t provided on the left and right sides of the operating lever k2 can suppress the upward pushing of the operating lever k2 by the mounting surface, thereby effectively preventing the operating lever k2 from developing a bending tendency that would impair its intended elastic deformation.

[0095] The back support L of this embodiment will be described in detail below.

[0096] <<Back support L>> The back support L comprises a back support body 5 and a cover member 6 attached to the back support body 5.

[0097] The back support L supports left and right operating members p1 that can change their position between an engaged position (U) in which they engage with the backrest M and a retracted position (N) in which they are retracted from the backrest M. The left and right operating members p1 constitute a release prevention mechanism P, which will be described in detail later.

[0098] [Back support body 5] The back support body 5 comprises a base end portion 51 that is rotatably connected to the support base B, left and right upright frame portions 52 that are connected to the base end portion 51 and extend vertically in pairs on the left and right, and an upper frame portion 53 that extends substantially horizontally and is connected to the upper ends of the left and right upright frame portions 52.

[0099] Recesses q2, which constitute the positioning mechanism Q, are provided on the front side of the upper ends of the left and right upright frame sections 52, that is, on the front side of the connection portion between the left and right upright frame sections 52 and the upper frame section 53. The recesses q2 will be described in detail later.

[0100] The upper frame portion 53 has a partially annular shape that curves to convex towards the rear in a plan view. The upper frame portion 53 works in cooperation with the cover member 6, which forms the upper half of the upper frame portion 53, to form a circular shape with both left and right end faces facing forward, and the overall shape is a cylindrical shape that is curved in a partially annular manner.

[0101] In other words, the upper frame portion 53 constitutes the lower half of a cylindrical outer shape that is partially curved in an annular shape. To put it another way, the upper frame portion 53 and the cover member 6 have circular forward-facing end faces at both the left and right ends, and have a curved shape that is convex to the rear in a plan view, and as a whole constitute an upper frame body 5a that is partially curved in an annular shape.

[0102] The upper frame portion 53 is provided with a plurality of screw insertion holes h1 that penetrate vertically and through which screws v1 for attaching the cover member 6 to the upper frame portion 53 are inserted.

[0103] On the rear side of the upper frame portion 53, there is a rear biasing member engagement portion 532 which has a recessed shape and supports the rear of a coil spring p3, which is a biasing member that biases the operating member p1 forward, i.e., in the engagement position (U) direction.

[0104] A boss portion 533 is erected on the upper frame portion 53, to which a screw member v2 capable of restricting the vertical movement of the operating member p1 is screwed. The boss portion 533 and the screw member v2 constitute the vertical movement restricting portion 53k.

[0105] The boss portion 533 is disposed within the elongated hole portion p14 provided at the rear of the engaging portion p11 of the operating member p1. The screw member v2 is configured such that its head can engage with the vicinity of the upper opening edge of the elongated hole portion p14 of the operating member p1 in order to prevent the operating member p1 from moving upward.

[0106] [Cover component 6] The cover member 6 constitutes approximately the upper half of the curved cylindrical upper frame body 5a. The cover member 6 is attached to the upper frame portion 53 by screws v1 so as to cover the left and right operating members p1.

[0107] The cover member 6 covers the operating member p1 such that only the engaging portion p11 and the operated portion p13 provided on the operating member p1 are exposed to the outside.

[0108] The cover member 6 is provided with a window frame portion 6w that surrounds the engaging portion p11 of the operating member p1, which can extend and retract from the upper frame portion 53. The window frame portion 6w has an upper wall portion 61 that partially covers the upper side of the engaging portion p11 of the operating member p1, and side wall portions 62 that partially cover both the left and right sides.

[0109] Furthermore, the window frame portion 6w can cooperate with the outer peripheral wall q21 that constitutes the recess q2 of the positioning mechanism Q to form a rectangular window frame shape when viewed from the front.

[0110] Furthermore, a notch 6k is provided on the front side of the cover member 6 to expose the operated portion p13 of the operating member p1. The notch 6k is located adjacent to the inside of the window frame portion 6w.

[0111] The backrest M of this embodiment will be described in detail below.

[0112] <<Backrest M>> The backrest M has a roughly elongated rectangular shape overall, with rounded ends on both sides. The backrest M has a backrest surface on its front that can come into contact with the back of the person sitting. In this embodiment, the backrest M is configured to be easily attached to and detached from the back support L by a simple operation by the user. The backrest M has a backrest body 7, which is the main structure, and a back upholstery 8, which is a covering that can cover the backrest body 7.

[0113] <Backrest body 7> The backrest body 7 comprises a roughly horizontally elongated rectangular backrest base 71 made of synthetic resin and a back cushion 72 attached to the front surface of the backrest base 71. At the lower end of the backrest base 71 of the backrest body 7, a single storage groove 7m is provided, which opens downward and extends in the left-right direction.

[0114] The storage groove 7m is composed of a pair of front and rear groove-forming walls 7f and 7r arranged so that their inner surfaces face each other in the front-to-back direction. The first and second strip-shaped members 81 and 82, which are provided at the lower edge of the back upholstery 8 that covers the backrest body 7, are inserted into a single storage groove 7m.

[0115] Multiple engaging protrusions t(f) and t(r) are provided inside the accommodating groove 7m, that is, on the inner surfaces of the pair of groove-forming walls 7f and 7r. Engaging protrusions t(f) and t(r) are provided on both the pair of groove-forming walls 7f and 7r, projecting either forward or backward.

[0116] In this embodiment, the engaging protrusions t(f) and t(r) are alternately provided on both groove-forming walls 7f and 7r, which are arranged to face each other front and back along the extension direction of the accommodating groove 7m. In other words, the engaging protrusions t(f) on one groove-forming wall 7f and the engaging protrusion t(r) on the other groove-forming wall 7r are arranged to protrude alternately from one end to the other in the longitudinal direction of the accommodating groove 7m so as not to collide.

[0117] On the back side of the backrest base 71, which constitutes the backrest body 7, there is an engaging portion p2 and a protruding portion q1, which are connecting structures for connecting to the back support L. The engaging portion p2 constitutes a detachment prevention mechanism P. The protruding portion q1 constitutes a positioning mechanism Q.

[0118] <Back upholstery 8 (covering body)> The back upholstery 8 comprises a back upholstery body 80 which is a bag-like structure open downwards and includes a front covering portion 8f that covers the front side of the backrest body 7 and a back covering portion 8r that covers the back side of the backrest body 7, and first and second strip-shaped members 81 and 82 disposed at the lower open end of the back upholstery body 80.

[0119] The back upholstery 8 comprises a front covering portion 8f that covers the front side of the backrest body 7, a back covering portion 8r that covers the rear side of the backrest body 7, a first strip-shaped member 81 that is sewn to the lower end of one end of the front covering portion 8f and inserted into the storage groove 7m of the backrest body 7, and a second strip-shaped member 82 that is sewn to the lower end of one end of the back covering portion 8r and inserted into the storage groove 7m of the backrest body 7.

[0120] The back upholstery 8 exposes the engaging portion p2 and the protruding portion q1, which are connecting structures provided on the backrest body 7, to the outside through openings 8s provided on the left and right sides of the back side.

[0121] [Back upholstery fabric 80] The back upholstery body 80 is formed into a bag-like shape that is open downwards by sewing together the peripheral edges of the front covering portion 8f and the back covering portion 8r, which are made of stretchable fabric, excluding the lower ends.

[0122] A space is formed inside the back upholstery body 80 that can accommodate the backrest body 7. Between the lower end of the back upholstery body 80, that is, the lower end of the front covering portion 8f and the lower end of the back covering portion 8r, a lower opening 8k is formed that opens downwards and allows the backrest body 7 to be inserted into the internal space.

[0123] In this embodiment, the back of the back upholstery body 80, i.e., the back covering portion 8r, is provided with a pair of openings 8s on the left and right sides that expose the engaged portion p2 and the protruding portion q1 of the backrest body 7 to the outside.

[0124] The opening 8s is mainly composed of a through hole 8t provided in the back covering portion 8r which is made of fabric material, a through hole peripheral portion 8e which is the peripheral region of the through hole 8t in the back covering portion 8r, and a synthetic resin annular member T which forms a continuous ring and is attached to the through hole peripheral portion 8e by sewing.

[0125] Through holes 8t are formed at two locations on the left and right sides of the back covering portion 8r, corresponding to the protruding portion q1 that is provided on the back side of the backrest body 7.

[0126] The annular member T is formed in a rectangular frame shape from a flexible synthetic resin sheet material and has a hole th in the center. The annular member T is configured to be deformable by bending. The annular member T is sewn to the peripheral edge 8e of the through hole in the back covering portion 8r. In the completed mounting position (Ta), the annular member T is covered by the back covering portion 8r so that everything except the hole th is not visible from the outside.

[0127] In this embodiment, the entire outer surface t1, the entire inner end t2, and at least a portion of the inner surface t3 of the annular member T in the completed mounting position (Ta) are covered by the through-hole periphery 8e adjacent to the through-hole 8t in the back covering portion 8r, and the through-hole periphery 8e is fixed only to the inner surface t3 of the annular member T in the completed mounting position (Ta).

[0128] [First and second strip-shaped members 81, 82] The first and second strip-shaped members 81 and 82 are made of synthetic resin, are strip-shaped, and extend in the left-right direction. In this embodiment, the first and second strip-shaped members 81 and 82 have substantially the same structure. Each of the first and second strip-shaped members 81 and 82 is provided with a plurality of through holes 81a and 82a arranged in a row, into which the engaging projections t(f) and t(r) can engage.

[0129] [Regarding the relationship between the first and second strip-shaped members 81 and 82 and the storage groove 7m of the backrest body 7] The first strip-shaped member 81, sewn to the lower end of the front covering portion 8f, and the second strip-shaped member 82, sewn to the lower end of the back covering portion 8r, are inserted into a single storage groove 7m provided at the lower end of the backrest body 7.

[0130] The first and second strip-shaped members 81 and 82 are superimposed on each other and inserted together into the 7m storage groove.

[0131] When the first and second strip-shaped members 81 and 82 are inserted to their predetermined positions within the housing groove 7m, the engaging projections t(f) and t(r) protruding from the groove-forming walls 7f and 7r of the housing groove 7m can engage with the through holes 81a and 82a provided in the respective strip-shaped members 81 and 82. More precisely, when the first and second strip-shaped members 81 and 82 are inserted, only the through holes 81a and 82a located at positions corresponding to the engaging projections t(f) and t(r) can be locked against the engaging projections t(f) and t(r).

[0132] As a result, the first and second strip-shaped members 81 and 82 that constitute the edges of the back upholstery fabric 8 are restricted from moving downward (reverse / coming out) by the engaging projections t(f) and t(r) after they have entered the predetermined depth of the single storage groove 7m, making it difficult for them to easily come out even when subjected to tensile force from the back upholstery fabric body 80.

[0133] Furthermore, since the engaging projection t(f) protruding from one groove-forming wall 7f and the engaging projection t(r) protruding from the other groove-forming wall 7r are arranged alternately along the extension direction of the accommodating groove 7m, the first and second strip-shaped members 81 and 82 can be inserted smoothly and without force into the accommodating groove 7m without being excessively obstructed by the engaging projections t(f) and t(r).

[0134] <<Method for forming an opening 8s in the backing fabric 8 (covering)>> The back upholstery 8 is provided with an opening 8s. The opening 8s comprises a back covering portion 8r, which is a fabric material with a through hole 8t, and an annular member T that forms a continuous ring and is attached to the peripheral edge 8e of the through hole, and is arranged so as not to be visible from the outside without impairing the front-to-back communication function of the hole th.

[0135] In this embodiment, the opening 8s of the backing fabric 8 is formed by going through the following steps: preparation step S1, annular member outer surface attachment step S2, first annular member inversion step S3, and second annular member inversion step S4.

[0136] <Preparation process S1> Preparation step S1, as shown in Figure 48, involves preparing the back upholstery body 80, which is the fabric material that constitutes the back upholstery 8 in which the opening 8s is to be formed, and the annular member T in the initial position (Tb).

[0137] A through-hole 8t is provided in the back covering portion 8r of the back upholstery body 80 by an appropriate method. The annular member T is a flexible, thin plate frame that can be sewn to the back upholstery body 80. In this embodiment, the annular member T is made of synthetic resin and is formed in a substantially rectangular annular shape.

[0138] <Attachment process S2 to the outer surface of the annular member> Following the preparation process, as shown in Figures 49 and 50, the annular member T in its initial position (Tb) is attached to the outer surface of the through-hole periphery 8e of the back covering portion 8r, which is the fabric material (annular member outer surface attachment process S2).

[0139] In this embodiment, the annular member T in the initial position (Tb) is attached to the outer surface of the through-hole periphery 8e and is sewn to the through-hole periphery 8e. In other words, the annular member T in the initial position (Tb) is fixed to the outer surface of the through-hole periphery 8e via the sewing portion tx.

[0140] In other words, the annular member outer surface attachment process S2 involves sewing the annular member T to the outer surface of the through-hole peripheral edge 8e, which is the edge portion of the through-hole 8t.

[0141] <First annular member inversion process S3> Following the annular member mounting process, as shown in Figure 51, the annular member T, which is in its initial position (Tb) attached to the outer surface of the through-hole periphery 8e, is reversed front to back while being deformed so that its inner periphery rotates toward the inner surface of the back covering portion 8r, thereby positioning the annular member T on the inner surface of the back covering portion 8r (first annular member reversal process S3).

[0142] <Second annular member inversion process S4> Following the first annular member inversion step S3, as shown in Figure 52, the annular member T in the intermediate position (Tc) is inverted front to back while further bending and deforming its inner edge toward the inner surface of the back covering portion 8r, thereby covering the entire annular member T from the outer surface with the back covering portion 8r (second annular member inversion step S4).

[0143] In this embodiment, by going through the method for forming an opening 8s in the back covering fabric 8 (covering body) which includes the steps described above, an opening 8s is formed in the back covering portion 8r of the back covering fabric 8, which is reinforced by an annular member T in the completed mounting position (Ta) that has been reversed 360° from the initial position (Tb).

[0144] Furthermore, the first and second annular member inversion processes S3 and S4 are carried out smoothly and continuously due to the bending deformation of the annular member T.

[0145] <<Detachable structure of back support M to back support L>> In this embodiment, the chair is configured so that the backrest M can be easily attached to and detached from the back support L by both the manufacturer and the end user (user) without the use of tools, which facilitates maintenance such as cleaning and replacement, as well as storage and transportation.

[0146] The attachment and detachment structure of the backrest M includes a positioning mechanism Q for positioning the backrest M relative to the back support L, and a detachment prevention mechanism P for preventing the backrest M, which has been positioned in the correct mounting position by the positioning mechanism Q, from detaching from the back support L.

[0147] <Positioning mechanism Q> The positioning mechanism Q positions the backrest M to a predetermined mounting position relative to the back support L.

[0148] The positioning mechanism Q comprises a protrusion q1 provided on the backrest M and a recess q2 provided on the back support L into which the protrusion q1 can engage. The protrusion q1 provided on the backrest body 7 and the recess q2 provided on the back support L can engage in the vertical direction.

[0149] [Protrusion q1] The protruding parts q1 are provided in pairs on the left and right sides of the backrest M. The protruding parts q1 are located on the back side of the backrest body 7 and are exposed to the outside through the opening 8s in the back upholstery 8.

[0150] The protruding portion q1 comprises a wall-like locking portion q11 that extends vertically in a rear view, gradually decreasing in width towards the bottom, and positioned to gradually move backward towards the bottom in a side view, and a connecting portion q12 that connects the backrest body 7 and the left-right intermediate portion of the wall-like locking portion q11, and is provided so as to gradually increase in length in the front-rear direction towards the bottom. The upper end of the wall-like locking portion q11 is connected to the backrest body 7.

[0151] The protruding portion q1 is located below the engaged portion p2, which constitutes the detachment prevention mechanism P recessed in the backrest body 7.

[0152] [Recess q2] The recess q2 is provided on the front side of the upper end of the left and right upright frame portions 52 that constitute the back support L. The recess q2 is open upward. The recess q2 is designed so that the protruding portion q1 of the backrest M, which is inserted from above, can be fitted into it.

[0153] The recess q2 is provided inside the outer peripheral wall q21 that protrudes forward from the upper ends of the left and right upright frame portions 52. The recess q2 is composed of an outer peripheral wall q21 having a bottom wall portion qt and left and right side wall portions qs erected upward from both left and right edges of the bottom wall portion qt, and a pair of left and right front wall portions q22 erected in front of the bottom wall portion qt.

[0154] The recess q2 has a pair of left and right front wall portions q22 erected on the bottom wall portion qt so as to be spaced apart from each other, and a front recess portion qm is provided between the pair of front wall portions q22, with a first space qa where the connecting portion q12 of the protruding portion q1 is disposed.

[0155] Furthermore, the recess q2 is formed behind the front recess portion qm, i.e., behind the pair of front wall portions q22, and includes a rear recess portion qr, which is provided with a second space qb between the left and right side wall portions qs erected on the bottom wall portion qt, where the wall-like locking portion q11 of the protruding portion q11 is disposed.

[0156] In this embodiment, the protrusion q1 of the backrest M, which constitutes the positioning mechanism Q, moves vertically, or more precisely, from diagonally forward-upward to diagonally rear-downward, while engaging with the recess q2 of the back support L. Since the backrest load of the seated person acts upward, backward, and downward, but hardly acts forward, by configuring the protrusion q1 to be inserted into the recess q2 from diagonally forward-upward to diagonally rear-downward, the backrest M becomes difficult to detach from the back support L, and the backrest M can be securely fixed to the back support L.

[0157] <Withdrawal Prevention Mechanism P> The detachment prevention mechanism P is provided between the back support L and the backrest M and prevents the backrest M from detaching from the back support L.

[0158] The detachment prevention mechanism P comprises an operating member p1 provided on the back support L that is reversibly operable by human operating force between an engaged position (U) that prohibits the detachment of the backrest M and a retracted position (N) that allows the detachment of the backrest M, i.e., rotatable in the front-rear direction, and an engaged portion p2 provided on the backrest M that can engage with an engaging portion p11 provided on the operating member p1 in the engaged position (U).

[0159] [Operating component p1] The operating member p1 prevents vertical movement of the backrest M relative to the back support L in the engaged position (U). The operating member p1 is rotatably supported on the upper frame portion 53 of the back support body 5. The operating members p1 are arranged in pairs on the left and right sides of the back support L.

[0160] The operating member p1 comprises a shaft hole pa that penetrates vertically and is inserted into a shaft portion 531 erected on the upper frame portion 53, which is provided at the inner end which is the base end; an engaging portion p11 that protrudes forward at the outer end which is the tip end; a biasing member engaging portion p12 provided on the rear side between the shaft hole pa and the engaging portion p11, which engages with the front part of the coil spring p3, which is a biasing member; an operated portion p13 provided on the front side between the shaft hole pa and the engaging portion p11, which directly receives the operating force of a person, i.e., the backward pressing force by the fingers, when moving from the engaged position (U) to the retracted position (N); and an elongated hole p14 provided at the rear of the engaging portion p11 that engages with the vertical movement restricting portion 53k provided on the upper frame portion 53.

[0161] The operating member p1 is constantly biased in the engaged position (U) direction by a coil spring p3. The user can change the position of the operating member p1 to the retracted position (N) by pressing the operated portion p13 of the operating member p1, which is in the engaged position (U), against the biasing force of the coil spring p3 in the retracted position (N) direction (the direction in which the engaging portion p11, which is the rotating end, moves backward).

[0162] The change in the position of the operating member p1 from the engaged position (U) to the retracted position (N) is performed by pressing the operated part p13 backward with the user's fingers. In other words, the user can move the operating member p1 to the retracted position (N) by pressing the operated part p13 backward like a push button.

[0163] As shown in Figure 27, a space sp into which fingers can be inserted is provided between the back support L and the backrest M. The operable part p13 is positioned facing the space between the back support L and the backrest M. Therefore, the user can easily press the operable part p13 like a push button.

[0164] Furthermore, the back support L and the backrest M are configured to expose only the outer surface of the operated portion p13 of the operating member p1 in the engagement position (U). In other words, the outer surface of the operated portion p13 and the outer surface of the cover member 6 are configured to be substantially flush. Therefore, although the operated portion p13 is provided to be operable from the outside, it is provided in an inconspicuous location and is configured to be substantially flush with the cover member 6 so as not to be conspicuous.

[0165] [Engaged part p2] The engaged portion p2 is the part that the engaging portion p11 of the operating member p1, which is supported by the back support L, can engage with. The engaging portion p11 of the operating member p1, which is in the engaged position (U), engages with the engaged portion p2.

[0166] The engaging portions p2 are provided in pairs on the left and right sides of the backrest M. The engaging portions p2 have a recessed shape that is provided on the back side of the backrest body 7 so as to open to the rear. The engaging portions p2 recessed in the backrest body 7 are exposed to the outside through the opening 8s in the back upholstery 8.

[0167] The engaged portion p2 is located on a protruding portion q1 that constitutes a positioning mechanism Q, which is projected from the backrest body 7.

[0168] After the backrest M is positioned in its proper mounting position by the positioning mechanism Q, when the engaging portion p11 of the operating member p1 engages with the engaged portion p2, the backrest M becomes unable to move upward relative to the back support L, and as a result, detachment from the back support L is prohibited.

[0169] In the embodiment described above, it is possible to provide a chair having a suitable configuration in which the backrest M can be easily attached to and detached from the back support L using an operating member p1 that can be reversibly operated by human force.

[0170] Furthermore, in the embodiment described above, the seat body D is configured to be able to rotate horizontally around a common axis cj relative to the seat support 1, between a retracted position (E) in which it can be detached from the seat support 1 and an attached position (F) in which it is attached to the seat support 1. Therefore, it is possible to provide a chair with a suitable configuration that allows the seat body D to be easily attached to and detached from the seat support 1 without the use of any special tools.

[0171] Furthermore, in the embodiment described above, the shell body 3 is provided with a peripheral wall portion 32 that has an outward-facing surface 32m to which the edge portion de of the upholstery Dh can abut, and is arranged in a substantially annular shape when viewed from the bottom. Therefore, it is possible to provide a chair that can suitably abut the edge portion de of the upholstery Dh covering the seat cushion Dq against the peripheral wall portion 32 of the shell body 3 with substantially uniform pressure.

[0172] Furthermore, in the above-described embodiment, the backrest body 7, which is the main structural body, is provided with a receiving groove 7m having engaging protrusions t(f) and t(r), and the back upholstery 8 is provided with first and second strip-shaped members 81 and 82, which have through holes 81a and 82a that engage with the engaging protrusions t(f) and t(r) of the receiving groove 7m. Therefore, it is possible to provide a chair with a configuration that allows the edge of the back upholstery 8 to be easily and securely attached to the receiving groove 7m of the backrest body 7, which is the main structural body.

[0173] Furthermore, according to the above-described embodiment, it is possible to provide a method for suitably forming a reinforced opening 8s having a suitable appearance in the back upholstery 8, which is a covering body that can cover the member. Furthermore, according to the above-described embodiment, it is possible to provide a chair having a covering body that is applicable to the back upholstery 8, etc., and has a reinforced opening 8s having a suitable appearance.

[0174] As described above, the chair according to this embodiment comprises a back support L, a backrest M that is detachable from the back support L, and a detachment prevention mechanism P provided between the back support L and the backrest M to prevent the backrest M from detaching from the back support L.

[0175] The detachment prevention mechanism P comprises an operating member p1 provided on the back support L that can be reversibly operated by human force between an engaged position (U) that prohibits the detachment of the backrest M and a retracted position (N) that allows the detachment of the backrest M, and an engaged portion p2 provided on the backrest M that can engage with an engaging portion p11 provided on the operating member p1 in the engaged position (U).

[0176] Therefore, it is possible to provide a chair with a suitable configuration that allows the backrest M to be easily attached to and detached from the back support L.

[0177] A positioning mechanism Q is provided for positioning the backrest M relative to the back support L. The positioning mechanism Q comprises a protrusion q1 provided on the backrest M and a recess q2 provided on the back support L that the protrusion q1 can engage with.

[0178] Therefore, by engaging the protruding portion q1 and the recessed portion q2, it becomes possible to provide a chair with a suitable configuration that allows for easy positioning of the backrest M relative to the back support L.

[0179] Since the protruding portion q1 and the recessed portion q2 can engage in the vertical direction, the user can suitably perform the operation of engaging the backrest M with the back support L.

[0180] In particular, in this embodiment, the protruding portion q1 of the backrest M moves from an oblique forward-upward direction to an oblique rear-downward direction, engaging with the recess q2 of the back support L. Since the backrest load of the seated person acts upward, rearward, and downward, but hardly acts forward, by configuring the protruding portion q1 to be inserted into the recess q2 from an oblique forward-upward direction to a rear-downward direction, the backrest M becomes difficult to detach from the back support L, and the backrest M can be securely fixed to the back support L.

[0181] Furthermore, since the operating member p1 prevents vertical movement of the backrest M relative to the back support L in the engaged position (U), the protrusion q1 and recess q2 effectively prevent the backrest M and back support L from separating in the vertical direction.

[0182] The operating member p1 is provided with an operated part p13 that directly receives the operating force of a person when moving from an engaged position (U) to a retracted position (N).

[0183] Therefore, the design allows end-users and other users to easily remove the backrest M.

[0184] A space is provided between the back support L and the backrest M into which fingers can be inserted, and the operable part p13 is positioned facing this space.

[0185] Therefore, the operable part p13 is positioned in a location where a person's fingers can be easily inserted, and also in a location that is difficult to see and inconspicuous from the outer perimeter of the chair.

[0186] The operating member p1 is rotatably supported on the back support L.

[0187] Therefore, the operating member p1 is provided in a suitable configuration that allows for easy adoption of both an engaged position (U) and a retracted position (N).

[0188] The operating member p1 is biased in the direction of the engagement position (U) by the biasing member, which is a coil spring p3.

[0189] Therefore, the operating member p1 can be stabilized in the engaged position (U).

[0190] The operating members p1 are provided in pairs on the left and right sides of the back support L. The engaging parts p2 are provided in pairs on the left and right sides of the backrest M.

[0191] Therefore, the backrest M is stably supported by the back support L.

[0192] The back support L comprises a back support body 5 that supports the operating member p1, and a cover member 6 attached to the back support body 5. The operating member p1 is provided with an operated portion p13 that directly receives the pressing force of the fingers when moving from an engaged position (U) to a retracted position (N). The cover member 6 covers the operating member p1 so that only the engaged portion p11 and the operated portion p13 are exposed to the outside.

[0193] Therefore, the operating member p1 is suitably covered by the cover member 6 without its function being impaired.

[0194] However, the present invention is not limited to the embodiments described in detail above.

[0196] It goes without saying that the specific shape of the operating member can be appropriately set without departing from the spirit of the present invention.

[0198] It goes without saying that the specific shape of the engaged portion can be appropriately set without departing from the spirit of the present invention.

[0200] The protruding portion constituting the positioning mechanism may be provided on the back support or backrest. In other words, as in the embodiment described above, the protruding portion is not limited to being provided on the backrest, but may also be provided on the back support.

[0201] It goes without saying that the specific shape of the protruding portion can be appropriately set without departing from the spirit of the present invention.

[0202] The recess constituting the positioning mechanism may be provided in the backrest or back support. In other words, as in the embodiment described above, the recess is not limited to being provided in the back support, but may also be provided in the backrest.

[0203] It goes without saying that the specific shape of the recess can be appropriately set without departing from the spirit of the present invention.

[0204] The protruding portion and the recessed portion are not limited to being able to engage in the vertical direction, but may also be able to engage in the front-to-back direction or the left-to-right direction.

[0205] The operated portion provided on the operating member is not limited to the configuration shown in the above-described embodiment.

[0209] Furthermore, the specific configuration of each part is not limited to the above embodiments, and various modifications are possible without departing from the spirit of the present invention. [Explanation of symbols]

[0210] L...back support M...backrest P...Withdrawal Prevention Agency p1...Operating component p11…Engagement part p2...Engaged part

Claims

1. A chair comprising a back support, a backrest detachable from the back support, and a detachment prevention mechanism provided between the back support and the backrest to prevent the backrest from detaching from the back support, The aforementioned detachment prevention mechanism comprises an operating member rotatably supported on the back support and reversibly operable by human operating force between an engaged position that prevents the detachment of the backrest and a retracted position that allows the detachment of the backrest, and an engaged portion provided on the backrest that can engage with an engaging portion provided on the operating member in the engaged position. The operating member is biased in the direction of the engagement position by a biasing member separate from the operating member, The chair is provided with an operating portion having an outer surface that directly receives a backward pressing force from the fingers against the biasing force of the biasing member, at least when moving from the engaged position to the retracted position.

2. The chair according to claim 1, wherein a positioning mechanism is provided for positioning the backrest relative to the back support, and the positioning mechanism comprises a protrusion provided on either the back support or the backrest, and a recess provided on the other that can engage with the protrusion.

3. The protruding portion and the recessed portion can engage in the vertical direction. The chair according to claim 2, wherein the operating member, in the engaged position, prevents the backrest from moving vertically relative to the back support.

4. The chair according to claim 1, wherein a space is provided between the back support and the backrest into which fingers can be inserted, and the operated part is positioned facing that space.

5. The operating members are provided in pairs on the left and right sides of the back support, The chair according to claim 1, wherein the engaged portions are provided in pairs on the left and right sides of the backrest.

6. The aforementioned back support comprises a back support body that supports the operating member and a cover member attached to the back support body. The chair according to claim 1 or 5, wherein the cover member covers the operating member such that only the engaging portion and the operated portion are exposed to the outside.

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