chair

Abstract

The mechanism for switching the tilt of the backrest is thin, allowing the seat to be lowered to a lower position, resulting in a chair with a sophisticated design. [Solution] The chair 1 according to the present invention comprises a main frame 2, a synchronous frame 10 rotatably attached to the main frame 2 and supporting a backrest 8, and a locking member 14 attached to the synchronous frame 10, configured to be able to move in and out to a predetermined position above a first portion 2d provided on the main frame 2, and restricting the rotation of the synchronous frame 10 relative to the main frame 2 by contacting the first portion 2d when it has moved to the predetermined position.

Description

Technical Field

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[0001] The present invention relates to a chair.

Background Art

[0002] Conventionally, chairs with a reclining backrest have been widely used. As an example, a chair has been developed that includes a mechanism for switching between a state where the backrest can recline and a state where it cannot (see Patent Document 1: Japanese Patent Application Laid-Open No. 2018-057633).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the chair exemplified in Patent Document 1 has problems that the part of the mechanism for switching the reclining of the backrest becomes thick (i.e., the dimension in the vertical direction is large), and the seat surface cannot be lowered to a low position, and the design lacks sophistication.

Means for Solving the Problems

[0005] In view of the above circumstances, the present invention aims to provide a chair in which the part of the mechanism for switching the reclining of the backrest is thin, the seat surface can be lowered to a lower position, and which has a sophisticated design.

[0006] The present invention solves the above problems by the following solution means.

[0007] The chair according to the present invention is required to include a main frame, a synchronous frame rotatably attached to the main frame and supporting a backrest, and a locking member attached to the synchronous frame, configured to be able to move in and out to a predetermined position above a first portion provided on the main frame, and which restricts the rotation of the synchronous frame relative to the main frame by contacting the first portion when it has moved to the predetermined position.

[0008] According to this, the mechanism for switching the tilt of the backrest can be realized with a thinner configuration.

[0009] Furthermore, it is preferable that the predetermined position is a position between the first portion and the second portion provided on the synchronous frame, and that the locking member restricts the rotation of the synchronous frame relative to the main frame by contacting the first portion and the second portion when the locking member has entered the predetermined position.

[0010] Furthermore, it is preferable that the locking member is rotatably mounted to the synchronous frame and that it moves in and out of the predetermined position by rotation.

[0011] Furthermore, it is preferable that the locking member has a first surface that contacts the first portion of the main frame and a second surface that contacts the second portion of the synchronous frame, and that when the chair is moved into the predetermined position, if no tilting force is acting on the backrest, the first surface contacts or a small gap is created with the first portion, and the second surface contacts or a small gap is created with the second portion, and when a tilting force is acting on the backrest, the first surface contacts the first portion and the second surface contacts the second portion, resulting in a clamped state.

[0012] Furthermore, it is preferable that the second surface is formed as an inclined surface on the rear end side of the first projection that protrudes from the lower surface of the tip of the locking member.

[0013] Furthermore, it is preferable that the first portion and the second portion are configured such that the surfaces that clamp the locking member are spaced apart in the direction in which the locking member enters the predetermined position.

[0014] Furthermore, it is preferable that the locking member has a second projection protruding from a side surface parallel to the rotating surface, and that the synchronous frame has a groove or hole that can engage with the second projection at the starting and ending positions of the rotation of the locking member.

[0015] Furthermore, it is preferable that the locking member has a screw hole drilled at a position facing the synchronous frame, and the synchronous frame has an insertion hole through which a screw can be inserted at a position corresponding to the screw hole. [Effects of the Invention]

[0016] According to the present invention, the mechanism for switching the tilt of the backrest can be made thinner. Therefore, it is possible to create a chair that allows the seat to be lowered to a lower position and has a sophisticated design. [Brief explanation of the drawing]

[0017] [Figure 1] This is a front perspective view showing an example of a chair according to an embodiment of the present invention. [Figure 2] Figure 1 is an exploded perspective view showing an example of a chair. [Figure 3] This is a rear perspective view showing an example of the lower structure of the chair in Figure 1. [Figure 4] Figure 1 is a front perspective view showing an example of the main frame of a chair. [Figure 5] Figure 1 is a front perspective view showing an example of a chair frame cover. [Figure 6]It is a front-side perspective view showing an example of the sync frame of the chair in FIG. 1. [Figure 7] FIG. 7(a) is a lower rear-side perspective view showing an example of the seat (seat main body) of the chair in FIG. 1, and FIG. 7(b) is an upper rear-side perspective view showing an example of the seat (seat receiving member) of the chair in FIG. 1. [Figure 8] It is an enlarged view showing an example of the seat operation lever of the seat of the chair in FIG. 1. [Figure 9] It is a front-side perspective view showing an example of the shell member of the backrest of the chair in FIG. 1. [Figure 10] It is a rear-side perspective view showing an example of the shell member of the backrest of the chair in FIG. 1. [Figure 11] It is a rear-side perspective view showing an example of the back plate of the backrest of the chair in FIG. 1. [Figure 12] It is an enlarged view showing an example of the lock member, rotation shaft, and tilt operation lever of the chair in FIG. 1. [Figure 13] It is an operation explanatory view for explaining the operation of the lock member of the chair in FIG. 1. [Figure 14] It is an operation explanatory view for explaining the operation of the lock member of the chair in FIG. 1. [Figure 15] It is an operation explanatory view for explaining the operation of the lock member of the chair in FIG. 1. [Figure 16] It is an enlarged view showing an example of the tip of the lock member of the chair in FIG. 1. [Figure 17] It is an enlarged view showing an example of the first part of the main frame of the chair in FIG. 1.

Mode for Carrying Out the Invention

[0018] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a perspective view (schematic view) from the upper left front showing an example of the chair 1 according to this embodiment, and FIG. 2 is an exploded perspective view (schematic view) of the chair 1 viewed from the same direction. For convenience of explanation, in the drawings, the directions of up and down, left and right, and front and back (directions from the viewpoint of the seated person) may be indicated by arrows. Also, in all the drawings for explaining the embodiments, members having the same function are denoted by the same reference numerals, and repeated explanations thereof may be omitted.

[0019] First, the overall configuration of the chair 1 according to this embodiment will be described. The chair 1 comprises legs 9, a main frame 2 attached to and supported by the upper end portion of the legs 9, a synchronous frame 10 rotatably attached to the main frame 2, a backrest 8 attached to the synchronous frame 10 (note that cushioning material and upholstery are not shown), and a seat 7 disposed above the main frame 2 and supported by the main frame 2.

[0020] As an overview of the operation of the chair 1 described above, the backrest 8, which is attached to a synchronous frame 10 that rotates relative to the main frame 2 and functions as a back support rod, is configured to be tiltable while receiving a repulsive force from a reaction force applying device 12. As will be described in detail later, the rotational movement of the synchronous frame 10 is restricted by a tilt lock mechanism, so the backrest 8 becomes immobile and is fixed in its initial position (in this embodiment, the position closest to the front). In addition, the seat 7, which is supported by the main frame 2, is configured to be able to be raised and lowered by the extension and retraction movement of the leg column 9a of the legs 9. As the extension and retraction movement of the leg column 9a is restricted by a lifting lock mechanism, the seat 7 becomes immobile and is fixed at any height position within the lifting range.

[0021] Next, the configuration of each part of chair 1 will be described. The legs 9 consist of a leg column 9a that supports the seat 7 via the main frame 2, a leg base on which the leg column 9a is erected in the center and which has multiple leg wings 9b, and casters 9c attached to the underside of the tip of each of the multiple leg wings 9b.

[0022] Here, the lifting and lowering locking mechanism for raising and lowering the seat 7 comprises a cylinder (not shown) fitted into the leg column 9a, a piston rod that moves up and down relative to the cylinder, a gas spring that is operated via a push valve 9e (also called a "push pin") provided at the tip of the piston rod and can be locked at any position, and a lifting and lowering operation lever 9d that operates the push valve 9e.

[0023] Next, as shown in Figure 4, the main frame 2 has a bottom plate portion 2A and a pair of left and right side wall portions 2B, 2B that extend continuously upward from each of the left and right ends of the bottom plate portion 2A and face each other in the left-right direction. The main frame 2 is covered by frame cover 3A, frame cover 3B, and frame cover 3C so as not to be exposed to the outside. Here, as shown in Figures 2 and 5, frame cover 3B and frame cover 3C are fitted together vertically on either side of the synchronizer frame 10.

[0024] Furthermore, the main frame 2 has through holes 2c formed in the bottom plate portion 2A into which the leg columns 9a are inserted and fixed. A leg column support bracket (not shown) is installed inside this through hole 2c.

[0025] The above-described leg support bracket is a component that fits and holds the portion of the leg 9a near the top (specifically, the portion near the tip of the piston rod of the gas spring that constitutes the leg 9a), and fixes it to the leg 9a. In other words, the leg 9a and the main frame 2 are connected via the leg support bracket, and the main frame 2 is fixed and attached to the upper end portion of the leg 9a.

[0026] Furthermore, the main frame 2 is configured such that the push valve 9e at the top of the leg column 9a is exposed at the upper end opening of the through hole 2c provided in the bottom plate portion 2A. As described above, the lifting operation lever 9d opens and closes this push valve 9e, thereby controlling the lifting movement of the seat 7.

[0027] Furthermore, elongated holes 2e are formed in the left and right side walls 2B, 2B of the main frame 2, near the front ends of each side wall, to support the seat support shaft 5 by passing it through in the left-right direction. The elongated holes 2e are formed with their longitudinal direction extending diagonally upward and backward from the front end of the main frame 2, and support the seat support shaft 5 so that it can move along this longitudinal direction.

[0028] Furthermore, holes 2f are formed in the left and right side walls 2B of the main frame 2, near the rear ends of each side wall, to support the rotating shaft 4 so that it can rotate on the axis by passing through it in the left-right direction. The synchronous frame 10 is rotatably connected to and attached to the main frame 2 by this rotating shaft 4.

[0029] Next, as shown in Figures 2 and 6, the synchronous frame 10 is a member that connects the main frame 2 and the backrest 8. It is rotatably mounted to the main frame 2 by a rotating shaft 4, and the backrest 8 is attached to its rear end. As a result, the synchronous frame 10 is connected to the main frame 2 in a way that allows it to rotate (oscillate), supporting the backrest 8 and functioning as a lever that tilts the backrest 8 using the rotating shaft 4 as a fulcrum.

[0030] Furthermore, the synchronous frame 10, which supports the backrest 8, transmits a force to the backrest 8 that attempts to push it back to its original position when the backrest 8 tilts backward, which is exerted by a reaction force applying device 12 interposed between the backrest 8 and the main frame 2.

[0031] The synchronous frame 10 has a pair of left and right frame portions 10A, 10A that are formed in the shape of flat plates and face each other in the left and right direction, and a backrest mounting portion 10B that is provided on the rear side of the pair of left and right frame portions 10A, 10A and spans between the pair of left and right frame portions 10A, 10A to which the backrest 8 is attached.

[0032] Each of the left and right frame portions 10A, 10A of the synchronous frame 10 has a hole 10e formed at its front end for supporting the fixed shaft 6 by passing it through in the left-right direction, a hole 10f formed behind the hole 10e for supporting the rotating shaft 4 by passing it through in the left-right direction, and further, a hole 10g formed behind the hole 10f for supporting the rotating shaft 14a of the tilt lock mechanism by passing it through in the left-right direction so that it can rotate on the shaft.

[0033] Here, the tilt lock mechanism related to the tilting movement of the backrest 8 comprises a main frame 2, a synchronous frame 10 rotatably mounted to the main frame 2 and supporting the backrest 8, a reaction force applying device 12 disposed at the rear end of the main frame 2 and interposed between the main frame 2 and the synchronous frame 10 to apply a reaction force so that the synchronous frame 10 rises relative to the main frame 2, that is, so that the backrest 8 rises (in other words, so that it returns from a reclined position to the initial upright position), and a locking member 14 that restricts the rotational movement of the synchronous frame 10 and fixes the backrest 8 so that it does not tilt backward. Details of the tilt lock mechanism will be described later.

[0034] Next, as shown in Figure 2, the seat 7 is composed of a seat support member 7A that is supported and attached to the main frame 2, and a seat body 7B that has an upward-facing seat surface and is detachably attached to the upper surface of the seat support member 7A. Here, a perspective view of the lower part of the seat body 7B viewed from the rear is shown in Figure 7(a), and a perspective view of the upper part of the seat support member 7A viewed from the rear is shown in Figure 7(b).

[0035] In this embodiment, the seat body 7B is configured to be able to rotate horizontally around a common axis C relative to the seat support member 7A, between a detachable position in which it can be separated from the seat support member 7A and an attached position in which it is attached to the seat support member 7A. Furthermore, a reverse-reverse restriction mechanism is provided to prevent the seat body 7B from returning to the detachable position when in the attached position. In this embodiment, the rotation direction is set to clockwise in a plan view when attaching and counterclockwise in a plan view when detaching.

[0036] The reverse-return restriction mechanism allows the seat body 7B to be released from its non-rotatable relative position relative to the seat support member 7A by operating the seat operating lever 7h so as to deform it upward against the elastic restoring force of the support member 7f, thereby allowing the seat body 7B from the mounted position to be rotated to the detached position and separated from the seat support member 7A.

[0037] The seat support member 7A is formed in a partially spherical shell shape using a resin material (such as polyamide resin). In particular, the outer surface of the seat support member 7A, which is visible to the user, has a spherical design.

[0038] The upper part (the upward-facing portion) of the seat support member 7A is provided with a seat mounting portion 7c to which the seat body 7B (specifically, the support member 7f described later) is attached. Furthermore, the rear end of the seat mounting portion 7c is provided with a notch 7d to avoid interference with the seat operating lever 7h provided on the seat body 7B.

[0039] The seat body 7B comprises a seat cushion 7e, a support member 7f attached to the lower surface of the seat cushion 7e to support it, and seat upholstery 7g covering the upper part and peripheral edge of the seat cushion 7e and the peripheral edge of the support member 7f. With this configuration, the upper surface of the seat body 7B becomes a seat surface that is approximately circular in plan view. For example, the seat cushion 7e is mainly made of polyurethane foam, which is a foamed material. The support member 7f is a roughly disc-shaped object attached to the lower surface of the seat cushion 7e. The support member 7f is integrally formed using a resin material (such as polyamide resin).

[0040] The support member 7f is provided with a seat operating lever 7h, which has a cantilevered, integrated structure and whose end (open end) is vertically movable. An enlarged view of the seat operating lever 7h is shown in Figure 8. The seat operating lever 7h has a protrusion 7i that protrudes downward, which engages with the seat receiving member 7A to restrict relative rotation from the mounting position to the removal position.

[0041] On the other hand, the seat support member 7A has a recess 7j drilled upward so that the protrusion 7i of the seat operating lever 7h can engage with it.

[0042] With the above configuration, by placing a finger on the seat operating lever 7h and moving it upward, the engagement between the protrusion 7i of the seat operating lever 7h and the recess 7j of the seat support member 7A can be released, and the seat body 7B can be rotated from the mounting position to the removal position.

[0043] The seat operating lever 7h according to this embodiment has a horizontal pushing portion 7ha at its end (open end side) that the operator can grip with their finger and push upward. The pushing portion 7ha is provided with a wall portion 7hb that is erected downward at the radially central end and a wall portion 7hc that is erected downward at the circumferential lateral end (specifically, the front side in the direction of rotating the seat body 7B from the mounting position to the removal position), which are mutually orthogonal continuous surfaces.

[0044] With this configuration, when removing the seat body 7B from the seat support member 7A in the mounting position, if one attempts to touch the push portion 7ha, which is located in a position that cannot be seen from the gap between the seat body 7B and the backrest 8, the presence of the walls 7hb and 7hc allows for a reliable determination of the position of the push portion 7ha, and the presence of the wall 7hc allows for a reliable determination of the direction in which to rotate the seat body 7B.

[0045] Next, as shown in Figure 2, the backrest 8 has a shell member 8A fixedly attached to the synchronous frame 10, a back plate 8B attached to the front of the shell member 8A, and upholstery with cushioning material on the side of the back plate 8B that faces the front (the upholstery including the cushioning material is not shown). Here, a perspective view of the shell member 8A seen from the front is shown in Figure 9, and a perspective view seen from the rear is shown in Figure 10. Also, a perspective view of the back plate 8B seen from the rear is shown in Figure 11.

[0046] The shell member 8A is constructed as a highly rigid member in order to ensure the strength required for the backrest 8. Specifically, to achieve high rigidity, the shell member 8A is formed using, for example, reinforced resins such as glass fiber reinforced nylon, polyacetal (POM), polypropylene (PP), and polyamide resins such as nylon, or materials other than resins such as iron, aluminum alloy, and stainless steel alloy.

[0047] The backrest 8B is a component that supports the back of the sitter's upper body (specifically, the back and lower back) with the intervening upholstery and cushioning material. Therefore, in order to conform to the back of the sitter's upper body when leaning against the backrest 8 and to achieve good comfort, it is constructed as a component with appropriate flexibility. Specifically, to give the backrest 8B appropriate flexibility, it is formed using resins such as polypropylene (PP) and nylon 6 (PA6).

[0048] In other words, the backrest 8 is constructed as a three-layer structure consisting of a shell member 8A with sufficient rigidity, a back plate 8B with appropriate flexibility, and a cushioning material that provides good shock absorption and breathability.

[0049] As an example, the connection structure between the shell member 8A and the back plate 8B is as follows. Mounting claws 8f are provided at the upper positions of the shell member 8A (for example, three locations on the left, center, and right), and mounting windows 8g are provided at the corresponding upper positions of the back plate 8B (for example, three locations on the left, center, and right). The mounting windows 8g are locked together by hooking them onto the mounting claws 8f. Furthermore, mounting protrusions 8h are provided at the lower positions of the back plate 8B (for example, three locations on the left, center, and right), and elastic engagement parts 8i are provided at the corresponding lower positions of the shell member 8A (for example, three locations on the left, center, and right). The mounting protrusions 8h are inserted into the elastic engagement parts 8i and elastically engaged, thereby connecting and fixing them together. In this embodiment, the mounting protrusions 8h are formed in a so-called house-shaped protrusion when viewed from the side, which can particularly enhance the effect of preventing damage when disconnecting the connection.

[0050] The shell member 8A is formed such that the portion that supports the seated person's upper body (referred to as the "upper body support portion 8d") is curved in a forward-facing convex shape in the middle of the vertical direction when viewed from the side and in the front-to-back longitudinal section, and curved in a backward-facing concave shape in the middle of the horizontal direction when viewed from the top and in the cross-section. The forward-facing portion of the shell member 8A is designed to support the area around the seated person's waist when viewed from the side.

[0051] On each of the left and right edges of the lower portion of the upper body support portion 8d of the shell member 8A, a pair of left and right armrest portions 8e, 8e are formed integrally with the upper body support portion 8d, projecting forward from each of these left and right edges and forming a circular shape.

[0052] As described above, the shell member 8A is constructed as a member with high rigidity, and therefore the integrated armrest portion 8e is also formed as a part with sufficient rigidity to support load.

[0053] The circle of the armrest portion 8e is formed by a generally horizontal upper edge that serves as an armrest, a front edge that extends diagonally downward and backward from the front end of the upper edge to the lower ends of the left and right edges of the upper body support portion 8d, and the left and right edges of the upper body support portion 8d between the rear end (in other words, the lower end) of the front edge and the rear end of the upper edge.

[0054] Furthermore, while a cantilevered armrest with single-point support at the rear end or a T-shaped armrest with single-point support in the middle can cause clothing pockets, for example, to get caught, the circular shape of the armrest prevents pockets from getting caught, thus improving comfort when using the chair. In addition, the circular shape of the armrest 8e makes it possible to improve stability and strength compared to cantilevered or T-shaped armrests.

[0055] The rear ends of the upper edges (i.e., the elbow rests) of the pair of left and right armrests 8e are connected to the part of the shell member 8A that protrudes the most forward in a side view.

[0056] At the lower end of the shell member 8A, a frame fixing portion 8c is formed, which opens downward (in other words, at the lower end) and serves as a space into which the backrest mounting portion 10B of the synchronous frame 10 and the frame portions 10A, 10A on both the left and right sides thereof are fitted. Furthermore, four through holes 8j are formed, which communicate from the front side of the shell member 8A to the space that serves as the frame fixing portion 8c.

[0057] Furthermore, four through holes 10c are formed in the backrest mounting portion 10B of the synchronous frame 10, in the same positional relationship as the through holes 8j formed in the frame fixing portion 8c of the shell member 8A.

[0058] Then, the upper part of the synchronous frame 10 is inserted through the opening at the lower end of the shell member 8A, and the backrest mounting part 10B is fitted into the frame fixing part 8c. Four screws are then inserted through each of the four through holes 8j formed in the frame fixing part 8c and into each of the through holes 10c formed in the backrest mounting part 10B, thereby directly fixing the frame fixing part 8c (and consequently the shell member 8A) to the backrest mounting part 10B. In this way, the backrest 8 is tiltably attached to the main frame 2 via the synchronous frame 10.

[0059] Next, the reaction force application device 12 is a device that applies a reaction force to the synchronous frame 10, which rotates relative to the main frame 2.

[0060] The reaction force device 12 is positioned between the rear end of the main frame 2 and the front end of the synchronous frame 10, and works to return the synchronous frame 10 to its initial position by biasing it in a direction that causes it to stand up (in other words, to be upright), thereby providing a repulsive force / reaction force to the movement of the backrest 8 and seat 7.

[0061] The initial position is defined as the state in which the rear side of the sync frame 10 is pushed upward and the backrest 8 attached to the backrest mounting portion 10B on the rear side of the sync frame 10 is pulled up as far as it will go and standing upright. For example, Figure 1 shows the initial position.

[0062] The reaction force applying device 12 comprises a pair of mounts arranged coaxially and facing each other, guided by a sliding shaft (not shown) to change the distance between them, and a compression coil spring interposed between the pair of mounts, with each of the mounts fitting into both ends.

[0063] Next, the tilt lock mechanism is a mechanism for fixing the backrest 8 in its initial position and releasing that fixation. In other words, the tilt lock mechanism controls the fixing and release of the posture of the backrest 8 attached to the synchronous frame 10 (in other words, the restriction and allowance of the tilting motion of the backrest 8) by restricting or allowing the rotational movement (specifically, the backward swinging motion) of the synchronous frame 10, which is rotatable relative to the main frame 2 with the rotation axis 4 as the pivot axis.

[0064] The tilt locking mechanism in this embodiment includes a locking member 14 that controls (i.e., switches) the restriction and allowance of the rotation of the synchronous frame 10 relative to the main frame 2. As an example, the locking member 14 has an inverted L-shape (i.e., hook shape) in side view and is formed with a thickness of about 20 mm in both the vertical and horizontal directions of its tip (however, it is not limited to this configuration). Furthermore, the rear end of the locking member 14 is fixed to a pivot shaft 14a that is rotatably supported on the synchronous frame 10 (specifically, a pair of left and right frame parts 10A, 10A). In addition, a tilting operation lever 14b for operating the pivot shaft 14a is attached to one end of the pivot shaft 14a. Here, an enlarged view of the locking member 14, the pivot shaft 14a, and the tilting operation lever 14b is shown in Figure 12.

[0065] For example, the locking member 14 is formed using a resin material (such as glass fiber reinforced nylon, polyacetal (POM), polypropylene (PP), or other polyamide resins) or a metal material (such as iron, aluminum alloy, or stainless steel alloy). On the other hand, the pivot shaft 14a is formed using a wire (rod) made of a metal material (such as iron or stainless steel alloy). However, the configuration is not limited to these.

[0066] The locking member 14 is configured to rotate its tip in an arc by operating the tilting lever 14b to rotate the pivot shaft 14a, allowing the tip to enter and exit a predetermined position. In this embodiment, the "predetermined position" is set to a position between the first part 2d provided on the main frame 2 and the second part 10d provided on the synchronous frame 10, above the first part 2d. Here, an enlarged view of the main frame 2 and the synchronous frame 10 is shown in Figure 13 as an explanatory diagram of the operation. Figure 14 shows a side cross-sectional view of the locking member 14 when it has entered the position between the main frame 2 (first part 2d) and the synchronous frame 10 (second part 10d), and Figure 15 shows a side cross-sectional view of it when it has exited. Figure 16 shows an enlarged view of the locking member 14, and Figure 17 shows an enlarged view of the main frame 2 (first part 2d).

[0067] In this embodiment, the first portion 2d provided on the main frame 2 is configured as a block portion extending outward in each of the left and right side wall portions 2B, 2B. The second portion 10d provided on the synchronous frame 10 is configured as a plate-like portion extending inward in each of the left and right frame portions 10A, 10A.

[0068] In this embodiment, when the locking member 14 is positioned between the first part 2d and the second part 10d, the lower surface of the tip of the locking member 14 ("first surface") is configured to be able to come into contact with the upper surface of the first part (block part) 2d of the main frame 2, and the upper surface of the tip of the locking member 14 ("second surface") is configured to be able to come into contact with the lower surface of the second part (plate-shaped part) 10d of the synchronous frame 10. By configuring the locking member 14 to enter between the first part (block part) 2d of the main frame 2 and the second part (plate-shaped part) 10d of the synchronous frame 10 in this way, the thickness shape (vertical dimension) of the tilting locking mechanism can be made thinner compared to conventional designs.

[0069] The operation of the tilt locking mechanism having the above configuration is as follows. Specifically, when the locking member 14 is positioned between the first part 2d and the second part 10d, if an attempt is made to rotate the synchronous frame 10 relative to the main frame 2, the lower surface of the tip of the locking member 14 ("first surface") comes into contact with the upper surface of the first part (block part) 2d of the main frame 2 in a way that catches on it, thus restricting rotation (i.e., the backrest 8 cannot be tilted backward). Note that if the load (force) applied to the backrest 8 is not very large, it is possible to restrict the rotation of the backrest 8 with the above configuration alone, but as the load (force) becomes larger, the strength of the locking member 14 becomes insufficient and the possibility of breakage increases. Therefore, in this embodiment, the upper surface of the tip of the locking member 14 ("second surface") is also provided in a configuration that presses against the lower surface of the second portion (plate-shaped portion) 10d of the synchronous frame 10, thereby also providing a rotational restriction effect. In this way, damage to the locking member 14 is prevented, and the rotation of the backrest 8 can be reliably restricted. On the other hand, when the locking member 14 has advanced from a position between the first portion 2d and the second portion 10d, if an attempt is made to rotate the synchronous frame 10 relative to the main frame 2, the locking member 14 does not come into contact with the first portion 2d and the second portion 10d, so rotation is permitted (i.e., the backrest 8 can be tilted backward).

[0070] In this embodiment, when the locking member 14 is positioned between the first part 2d and the second part 10d, and no tilting (rearward tilting) force is acting on the backrest 8, the first surface is in contact with the first part 2d or there is a slight gap, and the second surface is in contact with the second part 10d or there is a slight gap. On the other hand, when a tilting (rearward tilting) force is acting on the backrest 8, the first surface is in contact with the first part 2d and the second surface is in contact with the second part 10d, resulting in a compressed state.

[0071] Here, our research has revealed a new problem: when the locking member 14 is compressed between the first part 2d and the second part 10d, it may be pushed out from the position between them. This is due to the fact that the compressive force applied to the locking member 14 by the first part 2d and the second part 10d includes an expulsive component in the direction of action.

[0072] To address this issue, in this embodiment, the first portion 2d and the second portion 10d are configured such that the surfaces that clamp the locking member 14 (surfaces 2da and 10da) are spaced apart along the direction of entry into the space between the locking member 14 (i.e., from rear to front). Furthermore, in order to enable the second surface of the locking member 14 to contact (lock) with the second portion 10d configured in this way, the second surface is formed as an inclined surface 14d on the rear end side of the first projection 14c that protrudes downward from the lower surface of the tip of the locking member 14 (i.e., the inclined surface 14d is locked in close contact with surface 2da). These configurations make it possible to solve the problem.

[0073] Furthermore, in the locking mechanism according to this embodiment, the locking member 14 is provided with a second projection 14e protruding from a side surface parallel to the rotation surface, and the synchronous frame 10 is provided with a groove (or hole) 10h that can engage with the second projection 14e at the starting and ending positions of the rotation of the locking member 14. In addition, a biasing member (for example, a coil spring) 14f is provided that biases the locking member 14 in a direction in which the second projection 14e approaches the opposing groove 10h.

[0074] This configuration allows the tilting operation lever 14b to produce a click sensation, making it easier to understand when the tilting operation lever 14b is operated to the starting and ending positions of the rotation of the locking member 14, that is, to the allowable and restrictive positions for tilting (rearward tilting) of the backrest 8.

[0075] Furthermore, in the locking mechanism according to this embodiment, a screw hole 14g is provided in the locking member 14 at a position facing the synchronous frame 10 (in this embodiment, on the side parallel to the rotation surface), and when the synchronous frame 10 is in its initial position where it is not rotating (i.e., the initial position where the backrest 8 is not tilted backward), a through hole 10i is provided in the locking member 14 at a position corresponding to the screw hole 14g through which a screw can be inserted. The type of screw is not particularly limited, but a tapping screw can be preferably used.

[0076] With this configuration, the locking member 14 and the synchronized frame 10 can be fixed in place so that their relative positions do not change by inserting the screw through the insertion hole 10i of the synchronized frame 10 and screwing it into the screw hole 14g of the locking member 14. Therefore, a chair 1 without a tilting function for the backrest 8 can be easily constructed.

[0077] As explained above, the chair 1 according to this embodiment can have a thinner structure for the mechanism that switches the tilt of the backrest 8 (specifically, the main frame 2 and its surrounding parts) compared to conventional chairs exemplified in Patent Document 1, etc. Therefore, it is possible to lower the part of the mechanism to a lower position compared to conventional chairs, and consequently, it is possible to lower the seat to a lower position. Another effect is that the part of the mechanism becomes thinner and less conspicuous (i.e., the part that hinders the design is reduced), making it possible to realize a chair with a more sophisticated design.

[0078] It should be noted that the present invention is not limited to the embodiments described above, and various modifications are possible without departing from the scope of the invention. For example, other configurations can be applied to the seat 7, backrest 8, and legs 9. [Explanation of symbols]

[0079] 1 chair 2 Mainframe 3A, 3B, 3C Frame Covers 4 rotation axes 7 seats 8 Backrest 9 legs 10 Synchro Frame 14 Locking member

Claims

1. Mainframe and A synchronous frame is rotatably mounted to the main frame and supports the backrest, The synchronous frame is attached to the synchronous frame and is configured to be able to move in and out to a predetermined position above a first portion provided on the main frame, and a locking member that restricts the rotation of the synchronous frame relative to the main frame by contacting the first portion when the synchronous frame has moved into the predetermined position. A chair characterized by [this feature].

2. The predetermined position is located above the first portion and below the second portion provided on the sync frame, and is a position between the two. The locking member is configured to restrict the rotation of the synchronous frame relative to the main frame by contacting the first and second portions when it has entered the predetermined position. The chair according to claim 1, characterized by the following:

3. The locking member is rotatably mounted to the synchronous frame and is configured to move into and out of the predetermined position by rotation. A chair according to claim 1 or claim 2, characterized by the following:

4. The locking member is The main frame is provided with a first surface that contacts the first portion, and the sync frame is provided with a second surface that contacts the second portion, In the state in which the vehicle has entered the predetermined position, When no force is applied to the backrest in a tilting direction, the first surface comes into contact with the first part or a small gap is created, and the second surface comes into contact with the second part or a small gap is created. The configuration is such that when a force is applied to the backrest in a tilting direction, the first surface comes into contact with the first part and the second surface comes into contact with the second part, resulting in a compressed state. The chair according to claim 2, characterized by the following:

5. The second surface is formed as the inclined surface on the rear end side of the first projection that protrudes from the lower surface of the tip of the locking member. The chair according to claim 4, characterized by the following:

6. The first portion and the second portion are configured such that the surfaces that clamp the locking member are spaced apart in the direction in which the locking member enters the predetermined position. The chair according to claim 4, characterized by the following:

7. The locking member has a second projection that protrudes from a side surface parallel to the rotation surface, The synchronous frame has grooves or holes that can engage with the second projection at the starting and ending positions of the rotation of the locking member. A chair according to claim 1 or claim 2, characterized by the following:

8. The locking member has a screw hole drilled at a position facing the synchronous frame, The synchronous frame has through holes in positions corresponding to the screw holes through which screws can be inserted. A chair according to claim 1 or claim 2, characterized by the following:

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