JP2024050312A - Chair - Google Patents

Abstract

[Problem] To provide a chair with a suitable structure that allows the backrest to be easily attached and detached from the back support. [Solution] A chair equipped with a detachment prevention mechanism P that is provided between the back support L and the backrest M and prevents the backrest M from being detached from the back support L. The detachment prevention mechanism P is configured to include an operating member p1 that is provided on the back support L and can be reversibly operated by a human operating force between an engaging position that prevents the backrest M from being detached and a retracted position that allows the backrest M to be detached, and an engaged portion p2 that is provided on the backrest M and can be engaged with an engaging portion p11 provided on the operating member p1 in the engaged position. [Selected Figure] Figure 9

Description

The present invention relates to a chair.

Chairs have been known that have a relative movement prevention means for engaging the back shell with the mounting member of the back support rod and maintaining this engaged state (see, for example, Patent Document 1).

However, in conventional designs, the attachment and detachment of the back shell is performed exclusively by the manufacturer using special tools, etc., and is not designed to be easily attached and detached by the end user.

Japanese Patent Application Laid-Open No. 11-128022

The present invention was made in light of the above circumstances, and aims to provide a chair with a suitable configuration that allows the backrest to be easily attached and detached from the back support.

That is, the present invention has the following configuration.

The invention described in claim 1 is a chair comprising a back support, a backrest that is detachable from the back support, and a mechanism for preventing the backrest from being removed from the back support, the mechanism being provided between the back support and the backrest, the mechanism for preventing the backrest from being removed from the back support. The mechanism for preventing the backrest from being removed from the back support comprises an operating member provided on either the back support or the backrest, the operating member being reversibly operable by a human operating force between an engaging position that prevents the backrest from being removed and a retracted position that allows the backrest to be removed, and an engaged portion provided on the other of the back support and capable of engaging with an engaging portion provided on the operating member in the engaging position.

The invention described in claim 2 is the chair described in claim 1, which is provided with a positioning mechanism for positioning the backrest relative to the back support, and the positioning mechanism includes a protrusion provided on either the back support or the backrest, and a recess provided on the other with which the protrusion can engage.

The invention described in claim 3 is the chair described in claim 2, in which the protrusion and the recess can be engaged in the vertical direction, and the operating member, in the engaged position, prohibits vertical movement of the backrest relative to the back support.

The invention described in claim 4 is the chair described in claim 1, in which the operating member is provided with an operated part that directly receives an operating force from a person at least when moving from the engaged position to the retracted position.

The invention described in claim 5 is the chair described in claim 4, in which a space into which fingers can be inserted is provided between the back support and the backrest, and the operated part is disposed in a position facing the space.

The invention described in claim 6 is the chair described in claim 1, in which the operating member is rotatably supported on either the back support or the backrest.

The invention described in claim 7 is the chair described in claim 1, in which the operating member is biased in the direction of the engagement posture by a biasing member.

The invention described in claim 8 is the chair described in claim 1, in which the operating members are provided in pairs on the left and right sides of the back support, and the engaged parts are provided in pairs on the left and right sides of the backrest.

The invention described in claim 9 is a chair according to claim 8, in which the back support comprises a back support body that supports the operating member and a cover member that is attached to the back support body, the operating member is provided with an operated part that directly receives a pressing force of a finger when moving from the engaging position to the retracted position, and the cover member covers the operating member so that only the engaging part and the operated part are exposed to the outside.

As described above, the present invention provides a chair with a suitable configuration that allows the backrest to be easily attached and detached from the back support.

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. 15 is an enlarged view of the lower part of FIG. FIG. FIG. 2 is a rear view of the back upholstery in the same embodiment with a portion cut away. FIG. 2 is a front view of the back upholstery in the same embodiment with a portion cut away. FIG. 4 is a perspective view of first and second belt-shaped members in the embodiment. FIG. FIG. FIG. FIG. 4 is a plan view for explaining the operation of the operating member in the embodiment. FIG. 4 is a plan view for explaining the operation of the operating member in the embodiment. 5 is a cross-sectional plan view for explaining the operation of the operating member in the embodiment. FIG. 5 is a cross-sectional plan view for explaining the operation of the operating member in the embodiment. FIG. 5 is a view taken in the direction of the arrow X in FIG. 4 . FIG. FIG. FIG. FIG. FIG. FIG. FIG. FIG. 4 is a perspective view of the seat body from below in the same embodiment. FIG. 4 is a central cross-sectional view of the seat body in the embodiment. FIG. FIG. FIG. FIG. FIG. FIG. 8 is an explanatory diagram of the attachment operation of the seat body to the seat support in the embodiment; FIG. 8 is an explanatory diagram of the attachment operation of the seat body to the seat support in the embodiment; FIG. 8 is an explanatory diagram of the attachment operation of the seat body to the seat support in the embodiment; FIG. 8 is an explanatory diagram of the attachment operation of the seat body to the seat support in the embodiment; FIG. 8 is an explanatory diagram of the attachment operation of the seat body to the seat support in the embodiment; FIG. 5A to 5C are explanatory views of a method for forming an opening in the embodiment. 5A to 5C are explanatory views of a method for forming an opening in the embodiment. 5A to 5C are explanatory views of a method for forming an opening in the embodiment. 5A to 5C are explanatory views of a method for forming an opening in the embodiment. 5A to 5C are explanatory views of a method for forming an opening in the embodiment. FIG. 4 is an enlarged view of the embodiment after the opening is formed.

One embodiment of the present invention will be described below with reference to Figures 1 to 53.

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

The leg A has multiple leg blades a1 with casters at their lower ends, and a leg support a2 that stands up from the part where the upper ends of the leg blades a1 meet. The leg support a2 is configured to be extendable and retractable in the vertical direction.

The support base B is attached to the upper end of the leg A. Inside the support base B, a support mechanism (not shown) is provided to support the seat C and back support L.

The seat C in this embodiment is described in detail below.

<<Seat C>>
The seat C is supported by a support base B disposed on the legs 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.

Seat C comprises a seat support 1 and a seat body D that has an upward facing seat surface and is detachable from seat support 1.

The outer periphery of seat C, i.e., the outer periphery of seat support 1 and seat body D, is smoothly continuous to form a partial sphere.

<Seat Receptacle 1>
The seat support 1 supports the seat body D. The upper surface of the seat support 1 is adapted to engage with the shell body 3 that constitutes the seat body D. In other words, the shell body 3 is adapted to be placed on the upper surface of the seat support 1.

The seat support 1 is made of synthetic resin and formed into a shell shape. The seat support 1 has a partially spherical shape. The outer peripheral surface of the seat support 1 that is visible to the user is formed to have a spherical surface shape.

The outer peripheral surface of the front part of the seat support 1 is configured to smoothly connect to the underside of the front part of the support base B. In addition, the outer peripheral surface of the seat support 1 is configured to smoothly connect to the outer peripheral surface of the seat body D.

A downwardly open recess 11 is provided in the lower part of the center of the seat support 1 in the left-right direction, where the support base B can be placed.

The upper part of the seat support 1, i.e., the part of the seat support 1 facing upward, is provided with a shell body mounting part 12 having a connection part with the shell body 3 of the seat main body D. The rear end part of the shell body mounting part 12 is provided with a notch 122 to avoid interference with the operating lever k2 provided on the shell body 3.

The shell body mounting section 12 is provided with shaped parts that form a detachable engagement structure (central positioning section G, vertical engagement mechanism H, horizontal engagement mechanism I, and reverse restriction mechanism K) that allows the seat body D to be detached, as described in detail below.

The outer peripheral edge 1e of the seat support 1 is formed so that it is gradually positioned downward (concave downward) from both left and right ends toward the center in the left-right direction when viewed from the front and back. Also, the outer peripheral edge 1e of the seat support 1 is formed so that it is gradually positioned upward (convex upward) from both front and back ends toward the center in the front-to-rear direction when viewed from the side.

The upper end of the seat support peripheral wall portion 121, which is erected inside the outer peripheral edge 1e of the seat support 1, is arranged to extend in a substantially horizontal direction when viewed from the front, back, and side.

<Seat body D>
The seat body D includes a seat cushion Dq, a shell body 3 for supporting the cushion, which is a support member attached to the underside of the seat cushion Dq, and a seat upholstery Dh that covers the upper part and peripheral part of the seat cushion Dq and covers the peripheral part of the shell body 3. The seat body D is provided with a seat surface on the upper surface that is substantially circular in plan view.

[Seat cushion Dq]
The seat cushion Dq is mainly made of a urethane foam material. The seat cushion Dq is formed so that the width dimension gradually increases toward the top. The lower surface of the seat cushion Dq is attached to the shell body 3.

The seat cushion Dq is shaped to fit over the shell body 3 from above. When viewed from the bottom, the seat cushion Dq is larger than the shell body 3. The dimensions of the seat cushion Dq in the front-rear and left-right directions are set to be longer than the dimensions of the shell body 3 in the front-rear and left-right directions.

[Shell body 3]
The shell body 3 is generally disk-shaped and attached to the lower surface of the seat cushion Dq. The shell body 3 is integrally formed from synthetic resin.

The shell body 3 comprises a shell body main body 31 having a disk-shaped portion whose upper surface is bonded to the underside of the seat cushion Dq, a support wall portion 33 that is connected to extend downward from the peripheral edge of the shell body main body 31 and whose outer surface is in contact with the inner surface of the peripheral portion of the seat cushion Dq, an end wall portion 34 that extends diagonally upward and outward from the lower end of the support wall portion 33 and supports the lower end of the peripheral portion of the seat cushion Dq, and a peripheral wall portion 32 that is suspended downward from the underside of the peripheral portion of the shell body main body 31 inside the support wall portion 33.

The lower end of the peripheral wall portion 32 is arranged to extend substantially horizontally when viewed from the front, rear, and side.

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

The shell body main body 31 has a central protrusion g1 that protrudes downward from the center in the front-rear and left-right directions. The shell body main body 31 has a plurality of locking projection engagement portions hk that are spaced at regular intervals in the circumferential direction on the inside of the peripheral wall portion 32.

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

The peripheral wall portion 32 is disposed on the peripheral edge of the shell body 3. More specifically, the peripheral wall portion 32 is disposed closer to the center than the support wall portion 33 of the shell body 3. The peripheral wall portion 32 has an outward surface 32m against which the edge portion de of the seat upholstery Dh that encases the seat cushion Dq can come into contact.

The peripheral wall portion 32 is arranged in a substantially circular ring shape when viewed from the bottom. In other words, the peripheral wall portion 32 is arranged continuously on a circular path, except for one location at the rear where the operating lever k2 is arranged, so that the peripheral wall portion 32 is located on a virtual circumferential line that forms a perfect circle centered on the central protrusion g1 when viewed from the bottom.

The peripheral wall 32 has outward extensions 321 that extend outward and restrict the downward movement of the edge de of the seating material Dh. The outward extensions 321 are protruding pieces arranged at regular intervals around the peripheral wall 32.

The peripheral wall 32 has an inwardly protruding portion it on the inner surface at three locations on the front end and both left and right end portions, i.e., the inner surface at the center of the front portion of the peripheral wall 32 in the left-right direction, and the inner surface at the center of the front-rear direction on both left and right end portions of the peripheral wall 32. The inwardly protruding portion it constitutes the horizontal engagement mechanism I, which will be described in detail later.

Ribs rv are connected to the inner surface of the peripheral wall 32, which are vertically attached to the shell body main body 31 and extend outward from the center of the shell body main body 31. The ribs rv are arranged radially on the underside of the shell body main body 31.

The operating lever k2 is supported on one side by the shell body main body 31. That is, the shell body 3 is provided with the operating lever k2, which is a cantilevered lever member that engages with the seat support 1. The operating lever k2 has a wall-like portion k21 that constitutes part of the peripheral wall portion 32 and stands upright from the base end portion of the operating end portion k22.

The operating lever k2 is disposed 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.

Between the base end ke and the operating end k22, the operating lever k2 has a downwardly protruding protrusion kt that can engage with the upward recess k1 provided in the seat support 1. The recess k1 of the seat support 1 and the protrusion kt of the operating lever k2 constitute the reverse movement prevention mechanism K, which will be described in detail later.

The lower end edge 3e of the support wall portion 33 of the shell body 3 is formed so as to be gradually positioned downward (so as to be convex downward) from both the left and right ends toward the center in the left-right direction in front and rear views. Also, the lower end edge 3e of the support wall portion 33 of the shell body 3 is formed so as to be gradually positioned upward (so as to be convex upward) from both the front and rear ends toward the center in the front-to-rear direction in side views.

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

[Seat upholstery Dh]
The seat upholstery Dh is mainly made of a stretchable fabric that covers the seat cushion Dq.

The seating fabric Dh has a ring-shaped edge portion de. The seating fabric Dh is configured in a bag shape that is open downward. The seating fabric Dh is provided with a string-like member (not shown) for reducing the diameter of the edge portion de and bringing the edge portion de into contact with the outward surface 32m of the peripheral wall portion 32 of the shell body 3.

<<Attachment/detachment structure of seat body D to seat support 1>>
The seat body D is configured to be horizontally rotatable 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.

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

Between the seat support 1 and the seat body D, there are provided a central positioning section G that positions the seat body D so that its axis coincides with that 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 reversal prevention mechanism K that prevents the seat body D in the mounting position (F) from reversing toward the retracted position (E).

<Central positioning part G>
The central positioning portion G is capable of positioning the seat support 1 and the shell body 3 of the seat main body D so that they approximately coincide with the common axis cj.

The central positioning portion G is cylindrical and has a downwardly protruding central protrusion g1 provided at the center of the shell body 3 of the seat body D, and a hole-shaped central protrusion engagement portion g2 provided at the center of the seat support body 1 with which the central protrusion g1 engages so as to be able to rotate relative to the seat body D.

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

The vertical engagement mechanism H has a locking protrusion hp, which is a first engagement part provided on the seat support 1, and a locking protrusion engagement part hk, which is a second engagement part provided on the shell body 3 and can engage with the locking protrusion hp of the seat support 1.

The seat body D can take the mounting position (F) by tightly engaging the locking protrusion hp and the locking protrusion engagement portion hk.

The locking projections hp of the seat support 1 and the locking projection engagement portions hk of the shell body 3 are arranged at regular intervals along an imaginary circumferential line centered on the common axis cj.

[Lock protrusion hp (first engagement portion)]
The locking protrusions hp constitute a protruding structure protruding in a direction intersecting the common axis cj. The locking protrusions hp protrude substantially horizontally inward, i.e., toward the center of the common axis cj, from the seat support peripheral wall 121, which is erected on the peripheral edge of the seat support 1 in a substantially annular shape in a plan view.

The locking protrusion hp can engage in the vertical direction with the guide inclined surface hm provided on the locking protrusion engagement portion hk. More specifically, the locking protrusion hp can press the guide inclined surface hm of the locking protrusion engagement portion hk downward. In other words, the locking protrusion hp moves the seat body D downward during the process of the seat body D rotating from the retracted position (E) to the attached position (F).

[Lock protrusion engagement portion hk (second engagement portion)]
The locking projection engaging portion hk has an upwardly directed guide inclined surface hm with which the locking projection hp can engage. The locking projection engaging portion hk is provided so as to protrude downward from the shell body main body 31 which is in the shape of a circular plate.

The locking projection engagement portion hk includes a support wall hs that hangs downward from the shell body main body 31, and an engagement portion main body hg that is supported by the support wall hs and has an upwardly facing guide inclined surface hm on its upper surface.

The support wall hs has 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.

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 width dimension shorter than that of the first support wall portion ha and is connected to the base end edge, which is one circumferential end edge of the engagement portion body hg.

The engagement body hg is a plate-like member that is in a fallen position and extends in the circumferential direction. The inner edge and base edge of the engagement body hg are connected to the support wall hs. The upward guide inclined surface hm on the engagement body hg is inclined so as to be positioned gradually upward from the tip side toward the base end side. Here, the tip side of the engagement body hg refers to the edge side that forms the tip of the direction in which it advances when rotating from the retracted position (E) to the attached position (F).

The locking protrusions hp and guide inclined surfaces hm of the vertical engagement mechanism H configured as described above are configured to gradually increase in close contact as the seat body D rotates from the retracted position (E) to the attached position (F).

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

First, as shown in FIG. 43, the seat body D is moved downward from a position spaced above the seat support 1 while its horizontal position is positioned on the common axis cj by the central positioning part G.

Next, as shown in FIG. 44, the seat body 43 that has been moved downward is rotated around the common axis cj.

After that, as shown in FIG. 45, when the seat body D reaches the mounting position (F), the locking protrusion hp and the locking protrusion engagement portion hk are engaged so as to be in close contact with each other in the vertical direction.

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

The horizontal engagement mechanism I is provided with an inward protrusion it, which is a second engagement part provided on the shell body 3, and an outward guide inclined surface im, which is a first engagement part provided on the seat support body 1 and can engage with the inward protrusion it, which is a horizontal protrusion of the shell body 3.

The inward protrusion it of the shell body 3 and the outward guide inclined surface im of the seat support body 1 are arranged at regular intervals along an imaginary circumferential line centered on the common axis cj.

[Inward protruding portion it (second engagement portion)]
The inward protrusion it constitutes a protruding structure protruding in a direction intersecting the common axis cj. The inward protrusion it protrudes inward, i.e., in the direction of the common axis cj, from the peripheral wall portion 32, which is a hanging wall-like wall erected on the shell body 3 so as to form a substantially annular shape in a plan view.

In addition, from the portion of the peripheral wall 32 where the inward protrusion it is provided, an outward extension 321 extends in the opposite direction, i.e., outward, to engage with the edge de of the seating material Dh.

The inward protrusion it can horizontally engage with the outward guide inclined surface im provided on the seat support 1. More specifically, the inward protrusion it can press inward against the outward guide inclined surface im provided on the seat support peripheral wall portion 121 of the seat support 1.

[Outward guide inclined surface im (first engagement portion)]
The outward inclined guide surface im is provided on the outer peripheral surface of the seat support peripheral wall portion 121, which is an upright wall erected on the peripheral edge portion of the seat support 1. The outward inclined guide surface im faces outward, which is the horizontal direction in which it can engage with the inward protrusion it. The outward inclined surface is inclined so as to be positioned gradually outward as it moves clockwise.

The inward protrusion it and outward guide inclined surface im of the horizontal engagement mechanism I configured as described above are configured to gradually increase the degree of intimacy as the seat body D rotates clockwise from the retracted position (E) to the attached position (F).

<Reverse regulation mechanism K>
The reversal prevention mechanism K is provided between the seat body D and the shell body 3 of the seat support 1, and prevents the seat body D in the mounting position (F) from reversing toward the retracted position (E).

On the other hand, the reversal prevention mechanism K can release the state in which the seat body D cannot rotate relative to the seat support 1 by operating the operating lever k2 so as to deform it upward against the elastic restoring force of the shell body 3, and the seat body D can be rotated from the mounting position (F) to the retracted position (E) and removed from the seat support 1.

The reverse-back prevention mechanism K is equipped with 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).

The protrusion kt of the reversal prevention mechanism K is provided on a cantilever-shaped operating lever k2 provided on the shell body 3. The protrusion kt of the operating lever k2 is disengaged from the recess k1 provided on the seat support 1 by moving the operating end k22, which receives the operating force from the user's fingers, upward using the elastic deformation of the member, and the seat body D can be rotated from the mounting position (F) to the retracted position (E).

The upper surface of the rear end of the seat support 1 is provided with a guide inclined surface km adjacent to the recessed portion k1, which can engage with the protruding portion kt of the operating lever k2. The guide inclined surface km is inclined so that it gradually rises upward as it approaches the recessed portion k1. The top of the inclined surface is set to be located above the bottom of the recessed portion k1.

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

When the seat body D moves from the retracted position (E) to the attached position (F), the protruding portion kt overcomes the guide inclined surface km and engages with the recessed portion k1 due to the elastic return force of the operating lever k2.

In this embodiment, when the reversal prevention mechanism K moves from the retracted position (E) to the attached position (F), the protrusion kt is raised by the pivoting movement of the shell body 3, running up the inclined guide surface km of the seat support body 1, so there is no need to apply an operating force to the operating lever k2. At this time, when the protrusion kt of the operating lever k2 has climbed up the inclined guide surface km, the elastic return force of the operating lever k2 automatically fits into the recess k1. In other words, no special operation of the operating lever k2 is required when the reversal prevention mechanism K moves from the retracted position (E) to the attached position (F).

In addition, on both sides of the peripheral wall 32 of the shell body 3 adjacent to the operating lever k2, downward protrusions 32t are provided that extend downward to the same position as the lower end position of the operating lever k2.

These downward protrusions 32t are designed to prevent the operating lever k2 from being pushed upward by the placement surface when the seat body D or the shell body 3 is placed independently on a placement surface such as a floor surface for the purpose of using it as a replacement part, etc.

In other words, the downward protrusions 32t provided on the left and right sides of the operating lever k2 can suppress the operating lever k2 from being pushed up by the placement surface, which can effectively prevent the operating lever k2 from developing a bending tendency that would impair the intended elastic deformation.

The back support L of this embodiment is described in detail below.

<<Back support L>>
The back support L includes a back support body 5 and a cover member 6 attached to the back support body 5.

The back support L supports left and right operating members p1 that can be changed between an engagement position (U) in which the backrest M is engaged and a retracted position (N) in which the backrest M is retracted. The left and right operating members p1 constitute a disengagement prevention mechanism P, which will be described in detail later.

[Back support body 5]
The back support body 5 comprises a base end portion 51 which is rotatably connected to the support base B, left and right standing frame portions 52 which are connected to the base end portion 51 and extend in the vertical direction in a pair on the left and right, and an upper frame portion 53 which extends approximately horizontally and is connected to the upper ends of the left and right standing frame portions 52.

A recess q2 that constitutes the positioning mechanism Q is provided on the front side of the upper end of the left and right standing frame parts 52, i.e., on the front side of the connection part between the left and right standing frame parts 52 and the upper frame part 53. The recess q2 will be described in detail later.

The upper frame portion 53 is partially annular and curved to form a convex rearward shape in plan view. The upper frame portion 53 cooperates with the cover member 6 that forms the upper half of the half-split shape that corresponds to the upper frame portion 53 to form a circular shape with both left and right end faces facing forward, and the overall outer shape is a cylinder curved into a partially annular shape.

In other words, the upper frame portion 53 constitutes the lower half of a cylindrical exterior shape curved into a partial ring shape. In other words, the upper frame portion 53 and the cover member 6 constitute the upper frame body 5a that has circular forward end faces at both the left and right ends, has a curved shape that is convex backward in plan view, and has an overall generally cylindrical shape curved into a partial ring shape.

The upper frame portion 53 is provided with a number of screw insertion holes h1 through which screws v1 are inserted to attach the cover member 6 to the upper frame portion 53, penetrating vertically.

The rear side of the upper frame portion 53 is provided with a rear biasing member engaging portion 532 having a recessed shape that supports the rear portion of a coil spring p3, which is a biasing member that biases the operating member p1 forward, i.e., in the direction of the engaged posture (U).

A boss portion 533 is provided on the upper frame portion 53, and a screw member v2 is screwed into the boss portion 533 to regulate the vertical movement of the operating member p1. The boss portion 533 and the screw member v2 constitute the vertical movement regulation portion 53k.

The boss portion 533 is disposed in a long hole portion p14 provided at the rear of the engagement portion p11 of the operating member p1. The head of the screw member v2 can engage near the upper opening edge of the long hole portion p14 of the operating member p1 to prevent the operating member p1 from moving upward.

[Cover member 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.

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

The cover member 6 is provided with a window frame portion 6w that surrounds the engagement portion p11 of the operating member p1, which can be protruded and retracted 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 engagement portion p11 of the operating member p1, and side wall portions 62 that partially cover both the left and right sides.

The window frame portion 6w cooperates with the outer peripheral wall q21 that constitutes the recess q2 of the positioning mechanism Q to form a rectangular window frame-shaped portion when viewed from the front.

The front side of the cover member 6 is provided with a notch 6k for exposing the operated portion p13 of the operating member p1. The notch 6k is provided adjacent to the inside of the window frame portion 6w.

The backrest M of this embodiment is described in detail below.

<<Backrest M>>
The backrest M is a generally horizontally elongated rectangular shape with both left and right ends rounded. The backrest M has a backrest surface on the front side against which the back of a seated person can abut. The backrest M in this embodiment is configured to be detachable from the back support L by a simple operation by the user. The backrest M has a backrest main body 7, which is a structural body, and a back upholstery 8, which is a covering body that can cover the backrest main body 7.

<Backrest body 7>
The backrest body 7 includes a backrest base 71 made of synthetic resin and having a substantially horizontally elongated rectangular shape, and a back cushion 72 attached to the front surface of the backrest base 71. A single storage groove 7m that opens downward and extends in the left-right direction is provided at the lower end of the backrest base 71 in the backrest body 7.

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

The inside of the accommodation groove 7m, i.e., the inner surfaces of the pair of groove forming walls 7f, 7r, are provided with a number of engagement protrusions t(f), t(r). Both of the pair of groove forming walls 7f, 7r are provided with engagement protrusions t(f), t(r) that protrude forward or backward.

In this embodiment, the engagement protrusions t(f), t(r) are provided alternately on both groove forming walls 7f, 7r arranged to face each other in the extension direction of the accommodation groove 7m. In other words, the engagement protrusions t(f) of one groove forming wall 7f and the engagement protrusions t(r) of the other groove forming wall 7r are provided alternately from one end to the other end in the longitudinal direction of the accommodation groove 7m so that they do not collide.

The back side of the backrest base 71 that constitutes the backrest main body 7 is provided with an engaged part p2 and a protruding part q1, which are connecting structures for connecting to the back support L. The engaged part p2 constitutes the detachment prevention mechanism P. The protruding part q1 constitutes the positioning mechanism Q.

<Back cover 8 (covering body)>
The back upholstery 8 is composed of a front covering portion 8f that covers the front side of the backrest main body 7 and a back covering portion 8r that covers the back side of the backrest main body 7, and is bag-shaped and open downward.The back upholstery main body 80 is also equipped with first and second belt-shaped members 81, 82 arranged at the lower opening end of the back upholstery main body 80.

The back upholstery 8 is provided with 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 belt-shaped member 81 that is attached by sewing 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 belt-shaped member 82 that is attached by sewing 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.

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 a pair of openings 8s provided on the left and right sides of the back side.

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

A space capable of accommodating the backrest body 7 is formed inside the back upholstery body 80. A lower opening 8k is formed at the lower end of the back upholstery body 80, i.e., between the lower end of the front covering part 8f and the lower end of the back covering part 8r, and is open downwards to allow the backrest body 7 to be inserted into the internal space.

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

The opening 8s is mainly composed of a through hole 8t provided in the back covering portion 8r, which is a 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 ring-shaped member T that forms a continuous ring and is attached by sewing to the through hole peripheral portion 8e.

Through holes 8t are formed at two locations on the left and right of the rear covering portion 8r, at positions corresponding to the protrusions q1 protruding from the rear side of the backrest body 7.

The ring-shaped member T is made of a flexible synthetic resin sheet material in the shape of a square frame with a hole th in the center. The ring-shaped member T is configured to be flexible. The ring-shaped member T is sewn to the through-hole periphery 8e in the back-side covering portion 8r. In the installation completion position (Ta), the back-side covering portion 8r covers the ring-shaped member T so that everything except the hole th cannot be seen from the outside.

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 installation completion position (Ta) are covered by the through-hole peripheral portion 8e adjacent to the through-hole 8t in the back covering portion 8r, and the through-hole peripheral portion 8e is fixed only to the inner surface t3 of the annular member T in the installation completion position (Ta).

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

[Regarding the engagement between the first and second belt-shaped members 81, 82 and the accommodation groove 7m of the backrest main body 7]
A first belt-shaped member 81 sewn to the lower end of the front covering portion 8f and a second belt-shaped member 82 sewn to the lower end of the back covering portion 8r are adapted to be inserted into a single storage groove 7m provided at the lower end of the backrest main body 7.

The first and second belt-shaped members 81, 82 are overlapped with each other and inserted together into the storage groove 7m.

When the first and second belt-shaped members 81 and 82 are inserted to a predetermined position in the accommodation groove 7m, the engaging protrusions t(f) and t(r) protruding from the groove forming walls 7f and 7r of the accommodation groove 7m can engage with the through holes 81a and 82a provided in the belt-shaped members 81 and 82. More precisely, only the through holes 81a and 82a at the positions corresponding to the engaging protrusions t(f) and t(r) of the inserted first and second belt-shaped members 81 and 82 can be engaged with the engaging protrusions t(f) and t(r).

As a result, after the first and second belt-shaped members 81, 82 that make up the edge of the back upholstery 8 penetrate to a specified depth in the single storage groove 7m, their downward movement (reverse movement/slip-out) is restricted by the engagement protrusions t(f), t(r), so that they are unlikely to easily slip out to the outside even when subjected to a pulling force from the back upholstery main body 80.

In addition, the engagement protrusions t(f) protruding from one groove forming wall 7f and the engagement protrusions t(r) protruding from the other groove forming wall 7r are arranged alternately along the extension direction of the storage groove 7m, so that the first and second belt-shaped members 81, 82 can be smoothly inserted into the storage groove 7m without excessive interference from the engagement protrusions t(f), t(r).

<<Method of forming opening 8s in back upholstery 8 (covering body)>>
An opening 8s is provided in the back upholstery 8. The opening 8s includes a back covering portion 8r, which is a fabric material having a through hole 8t, and an annular member T that has a continuous ring shape and is attached to the through hole peripheral portion 8e and is disposed so as not to be visible from the outside without impairing the front-rear communication function of the hole portion th.

In this embodiment, the opening 8s in the back upholstery 8 is formed through a preparation process S1, an outer surface side attachment process S2 of the annular member, a first annular member inversion process S3, and a second annular member inversion process S4, as shown below.

<Preparation step S1>
As shown in Figure 48, the preparation process S1 involves preparing a back upholstery main body 80, which is the fabric material that constitutes the back upholstery 8 in which the opening 8s is to be formed, and a ring-shaped member T in an initial position (Tb).

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

<Annular member outer surface side mounting process S2>
Following the preparation process, as shown in Figures 49 and 50, a process of attaching annular member T in an initial position (Tb) to the outer surface side of the through hole peripheral portion 8e of the back side covering portion 8r, which is the base material, is performed (annular member outer surface attachment process S2).

In this embodiment, the annular member T in the initial position (Tb) is sewn to the through-hole peripheral portion 8e while being pressed against the outer surface of the through-hole peripheral portion 8e. In other words, the annular member T in the initial position (Tb) is fixed to the outer surface of the through-hole peripheral portion 8e via the sewn portion tx.

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

<First annular member inversion step S3>
After the annular member mounting process, as shown in Figure 51, a process (first annular member inversion process S3) is performed in which the annular member T in the initial position (Tb), in which the annular member T is attached to the outer surface side of the through hole peripheral portion 8e, is flexibly deformed so as to rotate its inner peripheral edge side toward the inner surface side of the back covering portion 8r, and the annular member T is inverted back and forth to be disposed on the inner surface side of the back covering portion 8r.

<Second annular member inversion step S4>
After the first annular member inversion process S3, as shown in Figure 52, a process (second annular member inversion process S4) is performed in which the annular member T in the intermediate position (Tc) is inverted back and forth while further bending and deforming the inner edge side toward the inner surface side of the back covering portion 8r, so that the entire annular member T is covered from the outer surface side by the back covering portion 8r.

In this embodiment, by going through the method of forming the opening 8s in the back upholstery 8 (covering body) that includes each of the steps described above, an opening 8s is formed in the rear covering portion 8r of the back upholstery 8, reinforced by the annular member T in the installation completion position (Ta) that is inverted 360° from the initial position (Tb).

The first and second annular member inversion steps S3 and S4 are carried out smoothly and continuously due to the flexural deformation of the annular member T.

<<Attachment/detachment structure of the backrest M to the back support L>>
The chair of this embodiment is configured so that the backrest M can be easily attached and detached to the back support L without the use of tools by not only the manufacturer but also the end user, to facilitate maintenance such as cleaning and replacement, as well as storage and transportation.

The attachment/detachment structure of the backrest M includes a positioning mechanism Q that positions the backrest M relative to the back support L, and a detachment prevention mechanism P that prevents the backrest M, which has been positioned in the correct attachment position by the positioning mechanism Q, from being detached from the back support L.

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

The positioning mechanism Q has a protrusion q1 provided on the backrest M and a recess q2 provided on the back support L with which the protrusion q1 can engage. The protrusion q1 provided on the backrest main body 7 and the recess q2 provided on the back support L can engage in the vertical direction.

[Protrusion q1]
The protrusions q1 are provided in pairs on the left and right sides of the backrest M. The protrusions q1 protrude from the rear side of the backrest main body 7 and are exposed to the outside through an opening 8s in the back upholstery 8.

The protrusion q1 is provided with a wall-shaped engaging portion q11 that extends vertically in rear view, with the width dimension gradually decreasing downward and positioned gradually rearward in side view, and a connecting portion q12 that connects the backrest body 7 and the left-right middle portion of the wall-shaped engaging portion q11 and is provided so that the front-rear dimension gradually increases downward. The upper end of the wall-shaped engaging portion q11 is connected to the backrest body 7.

The protrusion q1 is provided below the engaged portion p2 that constitutes the anti-detachment mechanism P recessed in the backrest body 7.

[Recess q2]
The recess q2 is provided on the front side of the upper end of the left and right standing frame parts 52 constituting the back support L. The recess q2 is open upward. The recess q2 is designed to fit the protrusion q1 of the backrest M inserted from above.

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 the outer peripheral wall q21, which has a bottom wall portion qt and left and right side wall portions qs erected upward from both left and right side 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.

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 on the left and right, and is provided with a front recess portion qm in which a first space qa is provided between the pair of front wall portions q22 and in which the connecting portion q12 of the protrusion q1 is disposed.

The recess q2 also has a rear recess qr that is formed behind the front recess qm, i.e., behind the pair of front wall portions q22, and between the left and right side wall portions qs erected on the bottom wall portion qt, and in which a second space qb is provided in which the wall-like engaging portion q11 of the protrusion q1 is disposed.

In this embodiment, the protrusion q1 of the backrest M, which constitutes the positioning mechanism Q, moves vertically, or more precisely, from a diagonally upper-front direction to a diagonally lower-rear direction, while engaging with the recess q2 of the back support L. The load of the seated person on the backrest acts upward, backward, and downward, but hardly acts forward. Therefore, by configuring the protrusion q1 to be inserted into the recess q2 from a diagonally upper-front direction to a diagonally lower-rear direction, the backrest M is less likely to come off the back support L, and the backrest M can be securely fixed to the back support L.

<Release prevention mechanism P>
The separation prevention mechanism P is provided between the back support L and the backrest M and prevents the backrest M from separating from the back support L.

The detachment prevention mechanism P is provided with an operating member p1 that is provided on the back support L and can be operated reversibly by human operating force between an engagement position (U) that prevents the backrest M from detaching and a retracted position (N) that allows the backrest M to detach, i.e., can rotate in the forward and backward directions, and an engaged portion p2 that is provided on the backrest M and can be engaged with an engaging portion p11 provided on the operating member p1 in the engagement position (U).

[Operation member p1]
The operating member p1, in the engaged position (U), prohibits the up-down movement of the backrest M relative to the back support L. The operating member p1 is rotatably supported by the upper frame portion 53 of the back support body 5. The operating members p1 are disposed in pairs on the left and right sides of the back support L.

The operating member p1 is provided with an axial hole pa penetrating in the vertical direction at the inner end, which is the base end, into which the axial portion 531 erected on the upper frame portion 53 is inserted; an engagement portion p11 protruding forward at the outer end, which is the tip end; a biasing member engagement portion p12 provided on the rear side between the axial hole pa and the engagement portion p11 before engaging with the front portion of the coil spring p3, which is a biasing member; an operated portion p13 provided on the front side between the axial hole pa and the engagement portion p11 and which directly receives a human operating force, i.e., a rearward pressing force by the fingers, when moving from the engagement position (U) to the retracted position (N); and an elongated hole portion p14 provided on the rear of the engagement portion p11 and which engages with a vertical movement regulating portion 53k provided on the upper frame portion 53.

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

The position of the operating member p1 can be changed from the engaged position (U) to the retracted position (N) by pressing the operated part p13 backward with the user's finger. 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.

As shown in FIG. 27, a space sp is provided between the back support L and the backrest M into which fingers can be inserted. The operated part p13 is disposed in a position facing the space between the back support L and the backrest M. This allows the user to effortlessly press the operated part p13 like a push button.

In addition, only the outer surface of the operated portion p13 of the operating member p1 in the engaged position (U) is exposed between the back support L and the backrest M. 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 with each other. Therefore, although the operated portion p13 is arranged so as to be operable from the outside, it is arranged in an inconspicuous location and has a substantially flush form so as to be less noticeable in relation to the cover member 6.

[Engaged portion p2]
The engaged portion p2 constitutes a portion that can be engaged with the engaging portion p11 of the operating member p1 supported by the back support L. The engaged portion p2 is adapted to be engaged with the engaging portion p11 of the operating member p1 in the engaging posture (U).

The engaged parts p2 are provided in pairs on the left and right sides of the backrest M. The engaged parts p2 are recessed on the back side of the backrest main body 7 so as to open backward. The engaged parts p2 recessed in the backrest main body 7 are exposed to the outside through an opening 8s in the back upholstery 8.

The engaged portion p2 is provided on the protruding portion q1 that constitutes the positioning mechanism Q protruding from the backrest body 7.

After the backrest M is positioned in the correct 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 cannot move upward relative to the back support L, and as a result, it is prohibited from being detached from the back support L.

The above-described embodiment makes it possible to provide a chair having a suitable configuration in which the backrest M can be easily attached and detached from the back support L using the operating member p1 that can be reversibly operated by a human operating force.

In addition, in the above-described embodiment, the seat body D is configured to be horizontally rotatable about the common axis cj relative to the seat support 1 between a retracted position (E) in which the seat body D can be detached from the seat support 1 and an attachment position (F) in which the seat body D is attached to the seat support 1. This makes it possible to provide a chair with a suitable configuration in which the seat body D can be easily attached and detached from the seat support 1 without using special tools.

In the above-described embodiment, the peripheral wall portion 32 is provided on the periphery of the shell body 3 and has an outward surface 32m against which the edge portion de of the seating fabric Dh can abut, and is arranged in a substantially annular shape when viewed from the bottom. This makes it possible to provide a chair in which the edge portion de of the seating fabric Dh covering the seat cushion Dq can be suitably abutted against the peripheral wall portion 32 of the shell body 3 with a substantially uniform pressing force.

In the above-described embodiment, the backrest body 7, which is the main structure, is provided with a storage groove 7m with engaging protrusions t(f), t(r), and the back upholstery 8 is provided with first and second belt-shaped members 81, 82 with through holes 81a, 82a that engage with the engaging protrusions t(f), t(r) of the storage groove 7m. This makes it possible to provide a chair with a configuration that allows the edge of the back upholstery 8 to be easily and less likely to come loose and be attached to the storage groove 7m of the backrest body 7, which is the main structure.

The above-described embodiment can provide a method for suitably forming a reinforced opening 8s with a desirable appearance in the back upholstery 8, which is a covering that can cover a member. The above-described embodiment can be applied to the back upholstery 8, etc., and can provide a chair having a covering with a reinforced opening 8s with a desirable appearance.

As described above, the chair according to this embodiment includes a back support L, a backrest M that can be attached to and detached from the back support L, and a detachment prevention mechanism P that is provided between the back support L and the backrest M and prevents the backrest M from detaching from the back support L.

The detachment prevention mechanism P includes an operating member p1 that is provided on the back support L and can be reversibly operated by a human operating force between an engagement position (U) that prevents the backrest M from detaching and a retracted position (N) that allows the backrest M to detach, and an engaged portion p2 that is provided on the backrest M and can be engaged with an engaging portion p11 provided on the operating member p1 in the engagement position (U).

This makes it possible to provide a chair with a suitable configuration that allows the backrest M to be easily attached and detached from the back support L.

A positioning mechanism Q is provided to position the backrest M relative to the back support L. The positioning mechanism Q has a protrusion q1 provided on the backrest M and a recess q2 provided on the back support L with which the protrusion q1 can engage.

This makes it possible to provide a chair with a suitable configuration that allows the backrest M to be easily positioned relative to the back support L by engaging the protrusion q1 and the recess q2.

The protrusion q1 and recess q2 can be engaged in the vertical direction, allowing the user to easily engage the backrest M with the back support L.

In particular, in this embodiment, the protruding portion q1 of the backrest M moves from a diagonally upper front direction to a diagonally lower rear direction while engaging with the recessed portion q2 of the back support L. Since the load of the seated person on the backrest acts upward, backward, and downward, but hardly acts forward, by configuring the protruding portion q1 to be inserted into the recessed portion q2 from a diagonally upper front direction to a diagonally lower rear direction, the backrest M is less likely to come off the back support L, and the backrest M can be securely fixed to the back support L.

In addition, since the operating member p1 prohibits the backrest M from moving vertically relative to the back support L in the engaged position (U), it is possible to effectively prohibit the backrest M and the back support L, which are engaged vertically by the protrusion q1 and the recess q2, from coming apart.

The operating member p1 is provided with an operated part p13 that directly receives a human operating force when moving from the engagement position (U) to the retracted position (N).

This allows the end user or other user to easily remove the backrest M.

A space is provided between the back support L and the backrest M into which fingers can be inserted, and the operated part p13 is disposed at a position facing that space.

For this reason, the operated part p13 is disposed at a location where a person's fingers can be inserted without difficulty, and is disposed at a location that is difficult to see and is not noticeable when viewed from the periphery of the chair.

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

For this reason, the operating member p1 is provided in a suitable configuration that makes it easy to assume the engaged position (U) and the retracted position (N).

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

This allows the operating member p1 to be stable in the engaged position (U).

The operating members p1 are provided in pairs on the left and right sides of the back support L. And the engaged parts p2 are provided in pairs on the left and right sides of the backrest M.

As a result, the backrest M is stably supported by the back support L.

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

As a result, the operating member p1 is adequately covered by the cover member 6 without its functionality being impaired.

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

The operating member constituting the removal prevention mechanism may be provided on the back support or the backrest. In other words, the operating member is not limited to being provided on the back support as in the above-mentioned embodiment, but may be provided on the backrest.

It goes without saying that the specific shape of the operating member can be set as appropriate without departing from the spirit of the present invention.

The engaged portion constituting the disengagement prevention mechanism may be provided on the backrest or the back support. In other words, the engaged portion is not limited to being provided on the backrest as in the above-mentioned embodiment, but may be provided on the back support.

It goes without saying that the specific shape of the engaged portion can be set as appropriate without departing from the spirit of the present invention.

The operating member may be any member that can be reversibly moved by a human operating force between an engagement position that prohibits the backrest from being removed and a retracted position that allows the backrest to be removed. In other words, the operating member may be of any configuration as long as it is supported so as to be reversibly operable. For example, the operating member may be configured to be slidable between the engagement position and the retracted position.

The protrusion constituting the positioning mechanism may be provided on the back support or the backrest. In other words, the protrusion is not limited to being provided on the backrest as in the above-mentioned embodiment, but may be provided on the back support.

It goes without saying that the specific shape of the protrusion can be set as appropriate without departing from the spirit of the present invention.

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

It goes without saying that the specific shape of the recess can be set as appropriate without departing from the spirit of the present invention.

The protrusion and recess are not limited to those that can engage in the up-down direction, but may also be ones that can engage in the front-back or left-right direction.

The operated portion provided on the operating member is not limited to the configuration shown in the above embodiment.

For example, the operated part may be a lever.

The operated portion does not have to be exposed on the front side of the back support. The operated portion may be exposed on the back side or bottom side of the back support.

The operating member may be configured so that it is not biased in the direction of the engagement posture by a biasing member.

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.

L: back support M: backrest P: separation prevention mechanism p1: operation member p11: engagement portion p2: engaged portion

Claims (9)

A chair comprising a back support, a backrest detachable from the back support, and a separation prevention mechanism provided between the back support and the backrest to prevent the backrest from separating from the back support,
The chair is characterized in that the detachment prevention mechanism comprises an operating member provided on either the back support body or the backrest, which is reversibly operable by a human operating force between an engagement position which prevents the backrest from detaching and a retracted position which allows the backrest to detach, and an engaged portion provided on the other body with which an engaging portion provided on the operating member can engage in the engagement position. A positioning mechanism is provided to position the backrest relative to the back support,
2. The chair according to claim 1, wherein the positioning mechanism comprises a protrusion provided on one of the back support and the backrest, and a recess provided on the other with which the protrusion can be engaged. The protrusion and the recess can be engaged in a vertical direction,
3. The chair according to claim 2, wherein the operating member, in the engaged position, prohibits vertical movement of the backrest relative to the back support. The chair according to claim 1, wherein the operating member is provided with an operated part that directly receives an operating force from a person at least when moving from the engaged position to the retracted position. The chair according to claim 4, in which a space into which fingers can be inserted is provided between the back support and the backrest, and the operated part is disposed at a position facing the space. The chair according to claim 1, wherein the operating member is rotatably supported on either the back support or the backrest. The chair according to claim 1, wherein the operating member is biased in the direction of the engagement position by a biasing member. The operating members are provided in pairs on the left and right sides of the back support,
2. The chair according to claim 1, wherein the engaged portions are provided in pairs on the left and right sides of the backrest. The back support member includes a back support body that supports the operating member, and a cover member that is attached to the back support body,
the operating member is provided with an operated portion that directly receives a pressing operation force of a finger when the operating member moves from the engagement position to the retracted position,
9. The chair according to claim 8, wherein the cover member covers the operating member so that only the engaging portion and the operated portion are exposed to the outside.

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