Chair

Abstract

To provide a chair having good operability and workability in assembling.SOLUTION: A support base (40); and a main pivot shaft (42) supported by the support base so as to be rotatable about an axis 42a (first axis) of the main pivot shaft (42) extending in a widthwise direction of the support base, A backrest that can be displaced from a normal state to a tilted state in which the backrest is tilted rearward, a regulation unit 93 that regulates rotation of the backrest around an axis 42a of a main pivot shaft 42, a return unit 92 that returns the backrest in the tilted state to the initial state, an operation member 95 (first operation member) for a seated person to operate the regulation unit 93, an operation unit 80 (second operation member) for the seated person to operate the return unit 92, and a base member 91 that supports the operation member 95 and the operation unit 80, the operation member 95 is supported by a first support portion 912 provided on one end side of the base member 91 in the width direction, and the operation unit 80 is supported by a second support portion 913 provided on the other end side of the base member 91 in the width direction.SELECTED DRAWING: Figure 11

Description

[Technical Field]

[0001] The present invention relates to a chair. [Background technology]

[0002] BACKGROUND ART Conventionally, chairs used for office work or the like have been known that have a backrest that is supported rotatably about an axis along the width direction of the chair with respect to a support structure that supports the backrest and seat. Such a chair is equipped with a restricting means for restricting the above-mentioned rotation of the backrest, a biasing means for storing a force for returning the backrest that has rotated around the above-mentioned axis to its initial state, and an adjusting means for adjusting the biasing means (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4848099 Summary of the Invention [Problem to be solved by the invention]

[0004] In the chair disclosed in Patent Document 1, the operating lever for operating the restricting means and the knob for the adjusting means are located at positions separated in the front-to-rear direction. Therefore, when operating the restricting means and the adjusting means in succession, the seated person needs to change their posture, which makes it difficult to operate. Furthermore, during assembly, the operating lever for operating the restricting means and the knob of the adjusting means cannot be assembled together, making it difficult to unitize them, and the workability during assembly is poor.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a chair that is easy to operate and to assemble. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the chair of the present invention comprises a support structure, a backrest that is rotatably supported on the support structure around a first axis extending in the width direction of the support structure and that can be displaced to a tilted state tilted backward from an initial state, a regulating means for regulating the rotation of the backrest around the first axis, a return means for returning the backrest in the tilted state to its initial state, a first operating member with which a seated person operates the regulating means, a second operating member with which the seated person operates the return means, and a base member that supports the first operating member and the second operating member, wherein the base member extends in the width direction, the first operating member is supported by a first support portion provided on one end side of the base member in the width direction, and the second operating member is supported by a second support portion provided on the other end side of the base member in the width direction.

[0007] In the present invention, the first operating member is supported on one widthwise side of the base member, and the second operating member is supported on the other widthwise side of the base member. This allows the seated occupant to operate the restricting means with one hand on one widthwise side while seated, and operate the returning means with the other hand on the other widthwise side without changing their posture, resulting in good operability. It also prevents interference between the first operating member and the second operating member. Furthermore, because the first operating member and the second operating member can be centrally located via the base member, they can be easily unitized, resulting in good workability during assembly.

[0008] In the chair according to the present invention, the base member may be in the form of a rod extending in the width direction.

[0009] With this configuration, the space occupied by the base member can be reduced, and a large space can be secured for arranging other members such as the restricting means and the returning means.

[0010] In addition, in the chair of the present invention, the base member may be an axis portion having a second axis extending in the width direction, and the first operating member and the second operating member may be arranged coaxially on the second axis.

[0011] With this configuration, the base member, the first operating member, and the second operating member are arranged side by side in the width direction, so that the space occupied by these members can be reduced.

[0012] In addition, in the chair of the present invention, the return means may have a biasing section that biases the backrest in the tilted state in a direction returning it to its initial state, and an adjustment section that is connected to the second operating member and adjusts the biasing force of the biasing section, and the base member may be rotatable around the second axis, the first operating member may be rotatable relative to the base member around the second axis, and the second operating member may be fixed to the base member so as not to be rotatable relative to the base member around the second axis.

[0013] With this configuration, the operating force of the second operating member can be directly transmitted to the biasing portion.

[0014] In the chair according to the present invention, the restricting means and the returning means may be disposed at positions sandwiching the base member therebetween when viewed in the width direction.

[0015] With this configuration, the restricting means and the returning means can be disposed in positions where they do not interfere with each other.

[0016] In addition, in the chair of the present invention, the backrest may have a pair of side walls spaced apart in the width direction, the first operating member may be supported by the side wall arranged on one side in the width direction, and the second operating member may be supported by the side wall arranged on the other side in the width direction.

[0017] With this configuration, the first operating member and the second operating member are arranged dispersedly in the width direction, which prevents the occupant from operating the first operating member and the second operating member by mistake, compared to when the first operating member and the second operating member are both arranged on one side in the width direction.

[0018] In addition, in the chair of the present invention, the base member may have an intermediate portion between the first support portion and the second support portion, and both ends of the intermediate portion in the width direction may be supported by a pair of flange portions provided on the chair.

[0019] With this configuration, the base member is reliably supported by the chair, and the first operating member and the second operating member can be operated in a stable state. [Effects of the Invention]

[0020] According to the present invention, a chair that is easy to operate and to assemble can be provided. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a perspective view of a chair according to an embodiment of the present invention. [Figure 2] This is a perspective view of the chair with the upholstery removed, seen from diagonally behind. [Figure 3] 1 is an exploded perspective view of a chair according to an embodiment of the present invention. [Figure 4] FIG. 1 is a side view with the rear cover removed. [Figure 5] FIG. 5 is a perspective view of FIG. 4 as seen from above. [Figure 6] FIG. 5 is a view of FIG. 4 as seen from above. [Figure 7] FIG. 4 is a perspective view showing a return means and a restricting means. [Figure 8] FIG. 8 is a plan view of FIG. [Figure 9] FIG. 2 is a perspective view showing a base member and a support member. [Figure 10] FIG. [Figure 11] FIG. 2 is an exploded perspective view illustrating a base member and an operating member. [Figure 12] FIG. 9 is a cross-sectional perspective view taken along line AA in FIG. 8. [Figure 13] FIG. 2 is an exploded perspective view illustrating a base member and an operating member. [Figure 14] FIG. 9 is a cross-sectional view taken along line BB in FIG. 8. [Figure 15] FIG. 2 is a perspective view illustrating a base member, a connecting member, and an operating member. [Figure 16] FIG. [Figure 17] 10A and 10B are diagrams illustrating the operation of the connecting member and the engaging member. [Figure 18] 10A and 10B are diagrams illustrating the operation of the engagement member. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, a chair according to an embodiment of the present invention will be described with reference to FIGS. In the following explanation, for the sake of convenience, the direction in which an occupant seated in a normal posture on the seat 17 faces forward will be referred to as "forward," and the opposite direction will be referred to as "rearward." Furthermore, the terms "up / down" and "left / right" in the following explanation refer to directions that correspond to the direction centered on the occupant when the occupant is seated in a normal posture on the seat 17. In the following explanation, the left / right direction in this case will also be referred to as the width direction. Note that an arrow FR pointing forward, an arrow UP pointing upward, and an arrow LH pointing leftward are shown in appropriate locations in the drawings.

[0023] 1, chair 1 according to this embodiment comprises legs 10 placed on floor surface F, box-shaped support base 40 placed on top of legs 10, seat 17 attached to the top of support base 40, backrest 20 attached to the rear of support base 40 to support the back of the seated person, and armrests 19 extending above seat 17 from both sides of the lower side of seat 17 on which the seated person's elbows and arms can be rested. Legs 10 and support base 40 correspond to the support structure of the present invention.

[0024] The leg 10 has a multi-leg 11 with casters 11a, and a base 12 that stands up from the center of the multi-leg 11 and has a built-in gas spring (not shown) that serves as a lifting mechanism. The base 12 has an outer cylinder 13 and an inner cylinder 14. The outer cylinder 13 is fitted and supported on the multi-leg 11 so as not to rotate. The lower part of the inner cylinder 14 is supported on the outer cylinder 13 so as to be rotatable in the horizontal direction. The upper part of the inner cylinder 14 is fixed to a support base 40. The support base 40 has a built-in lift adjustment mechanism for the base 12 and a tilting mechanism for the backrest 20.

[0025] The backrest 20 has a backrest structure 20A (see FIG. 2) and an upholstery material 26 that covers the backrest structure 20A. The backrest structure 20A supports the back of a seated occupant. As shown in FIG. 2, the backrest structure 20A has a backrest support 21 and a backrest main body 23 supported by the backrest support 21.

[0026] The backrest support 21 supports the back of the seated occupant. The backrest support 21 has a backrest support member 30 and a rear extension member 22.

[0027] 3, the backrest support member 30 has an inner member 31 and an outer member 32. The inner member 31 has a shape that is elongated in the vertical direction. The inner member 31 is formed in a flat plate shape.

[0028] The outer member 32 has an outer vertical extension portion 35 and an outer upper protruding portion 36. The outer vertical extension portion 35 has an outer curved upper portion 351, an outer curved lower portion 352, and an outer lower portion 353. The inner member 31 and the outer member 32 are connected by screws.

[0029] The backrest support member 30 is provided with a rotating member 38 that is fixed to the inner member 31 and the outer member 32 and is rotatable via a rotating main shaft 42 that extends in the axial direction along the width direction (left-right direction) at the rear of the support base 40. An axis 42a of the rotating main shaft 42 corresponds to the first axis of the present invention. As shown in FIG. 4, the rotating member 38 is rotatable about the axis in the left-right direction relative to the support base 40. As shown in FIG. 3, a bolt 38a is inserted from the mounting recess 353a of the outer lower part 353 of the outer member 32 to a mounting hole 353b, through a mounting hole 334a of the inner lower fixing part 334 of the inner member 31, and through a mounting hole formed in the rotating member 38, and a nut is fastened to the bolt 38a. As a result, the inner member 31 and the outer member 32 are fixed integrally to the rotating member 38.

[0030] As shown in FIG. 3, the rotating member 38 and the outer lower portion 353 of the outer member 32 are covered from behind by a rear cover 37.

[0031] As shown in Figures 1 and 2, the backrest 20 configured in this manner is supported on the backrest support member 30 so as to be rotatable around an axis along the width direction of the backrest support member 30, and is displaceable from an initial state in which the upper end portion 20a is positioned relatively forward to a tilted state (see Figure 11) in which the upper end portion 20a is positioned relatively rearward.

[0032] As shown in Fig. 4, a seat shell 51 that holds the seat 17 from below is provided below the seat 17. The seat shell 51 is provided on a seat support member 50 that is supported from below by the support base 40. The seat shell 51 is secured to a front edge 50a of the seat support member 50 with a securing means such as a screw, with a securing portion (not shown) provided on the underside of the rear end of the seat shell 51 being engaged with the seat support member 50 from behind.

[0033] The seat support member 50 includes the above-mentioned seat shell 51, a main body 52 that is rectangular in plan view and to which the seat shell 51 can be attached at its upper edge, a rear attachment portion 53 that extends diagonally downward and rearward from a rear end portion 52a of the main body 52, a pair of elongated holes 54 that extend in the front-rear direction on both the left and right sides of a front lower surface 52b of the main body 52, and a spring front end support portion 55 fixed to the front of the main body 52. ​​The seat support member 50 is a strong member made of a metal material such as drawn sheet metal or aluminum die-cast, and has a saucer shape that is open on the top in the vertical direction.

[0034] The seat support member 50 has a bottom wall portion 501 and a side wall portion 502 standing upright from the peripheral edge of the bottom wall portion 501. The above-mentioned seat shell 51 is attached to the upper end of the side wall portion 502. The bottom wall portion 501 is formed with a recessed portion 503 recessed upward in a shape that follows the outer shape of the compression coil spring 61 so as not to interfere with the compression coil spring 61 described below.

[0035] The rear attachment portion 53 is provided on the rotating member 38 of the backrest support member 30, and is rotatably connected to a countershaft 39 of an operating means 80 (second operating member) that extends in the left-right direction (described later). The rear attachment portion 53 (i.e., the seat support member 50) is rotatable around the countershaft 39 relative to the rotating member 38. In other words, when the backrest 20 is tilted from the initial state, the seat support member 50 moves rearward relative to the support base 40.

[0036] 5 and 6, a pair of elongated holes 54 are provided on both the left and right sides of the front part of the bottom wall 501. A slide engagement portion 43 protruding upward from the front part of the support base 40 (see FIG. 4) is slidably engaged with each of the elongated holes 54 along the longitudinal direction (front-rear direction) of the elongated holes 54 while being restricted from moving downward out of the elongated holes 54. When the backrest 20 tilts, the elongated holes 54 slide rearward relative to the slide engagement portion 43 provided in the support base 40, and the seat support member 50 moves rearward. In other words, when the seat support member 50 moves rearward, the front-rear position of the slide engagement portion 43 relative to the elongated holes 54 moves from the rearward side to the frontward side.

[0037] 7 and 8, the spring front end receiving portion 55 has a pair of fixing portions 551 provided on both left and right sides and fixed to the underside of the bottom wall portion 501, and a front spring reaction force receiving shaft 553 that extends axially in the left and right direction and is supported while being inserted through the pair of fixing portions 551. An insertion hole 551a through which the front spring reaction force receiving shaft 553 is inserted is formed in the fixing portion 551. The fixing portion 551 is provided at a position where it does not interfere with a compression coil spring 61 (described later) supported by the front spring reaction force receiving shaft 553.

[0038] The front spring reaction force receiving shaft 553 is a rod material with a circular cross section. Both axial ends of the front spring reaction force receiving shaft 553 are inserted into the insertion holes 551a of the fixing parts 551 and fixed, and the front spring reaction force receiving shaft 553 is provided so as not to move in the left-right direction relative to the pair of fixing parts 551. The front ends of two compression coil springs 61 that are biased in the compression direction from the rear are supported by the front spring reaction force receiving shaft 553.

[0039] The support base 40 comprises a support base body portion 41 fixed to the upper part of the leg pillar 12 (see Figure 1), a pivot main shaft 42 that rotatably supports the pivot member 38 of the backrest support member 30 in a tilting direction relative to the support base body portion 41, and a slide engagement portion 43 that supports the seat support member 50 so that it can slide in the front-to-rear direction.

[0040] The support base body 41 has a bottom plate 411 and side plates 412 extending upward from both the left and right sides of the bottom plate 411, and is formed into a bowl shape that is open upward as a whole. Two compression coil springs 61 are housed in a first internal space S1 above the support base body 41. As shown in FIG. 4, the rear end 41a of the support base body 41 protrudes rearward beyond the rear upper parts 412a of the side plates 412. The support base body 41 has rotational shafts 42 provided on the rear upper parts 412a of the side plates 412 located on both the left and right sides.

[0041] 4, 7 and 8, the front part of the rotating member 38 of the backrest support member 30 is rotatably supported by a rotating shaft 42 on the inside rear part of the support base body 41. The rotating shaft 42 is provided on each of the left and right side plates 412. The rotation centers of the left and right rotating shafts 42 are coaxial.

[0042] The slide engagement portions 43 are provided on the front upper ends 412b of the side plates 412 on both the left and right sides of the support base body 41 so as to protrude upward. The slide engagement portions 43 have a protrusion 431 and a sliding portion 432 that is provided on the upper end of the protrusion 431 and has a larger diameter than the protrusion 431. The protrusion 431 is formed in a circular cross section with a diameter that is approximately the same as the width of the elongated hole 54 (see FIGS. 5 and 6) of the seat support member 50. The protrusion 431 of the slide engagement portion 43 is inserted into the elongated hole 54, and the sliding portion 432 is disposed inside the seat support member 50. The inner portion of the seat support member 50 where the sliding portion 432 is disposed is above the upper surface of the bottom wall portion 501 and between the opposing surfaces of the side wall portions 502. The sliding region of the sliding portion 432 in the inner portion of the seat receiving member 50 is located away from the recessed portion 503 (see FIGS. 5 and 6) that is recessed upward in a shape that follows the outline of the compression coil spring 61, and provides a space where the sliding portion 432 does not interfere with other portions. That is, the sliding region of the elongated hole 54 and the sliding portion 432 is set at positions on both the left and right sides that avoid the pair of compression coil springs 61 when viewed from above.

[0043] As shown in Figures 7 and 8, the support base body 41 of the support base 40 and the rotating member 38 are provided with a return means 92 that returns the backrest 20, which is in a tilted state, to its initial state, and a regulating means 93 that regulates the rotation of the backrest 20 around the main rotating shaft 42.

[0044] The return means 92 includes a biasing means 60 (biasing section) having a compression coil spring 61 that biases the backrest 20 in a tilted state in a direction returning it to its initial state, an adjustment means 70 (adjustment section) that adjusts the biasing force of the compression coil spring 61, and an operating means 80 that is connected to the adjustment means 70 and operates the adjustment means 70.

[0045] The rotating member 38 has a rear wall 381 and a pair of side walls 382a, 382b that extend perpendicularly from both left and right ends of the rear wall 381 and are spaced apart in the width direction. The second internal space S2 on the front side of the rotating member 38 accommodates the adjustment means 70 and the operating means 80. In addition, the rear end of the compression coil spring 61 is supported in the front part of the second internal space S2.

[0046] A pair of side walls 382a, 382b of the rotating member 38 are rotatably supported by the rotating shaft 42 on the rear upper portion 412a of the side plate 412 of the support base portion 41. An adjustment means 70 and an operating means 80 are disposed in a second internal space S2 located rearward of the rotating shaft 42 in the rotating member 38. The rotating member 38 supports the rotating shaft 42 at its front portion. The rotating member 38 also has a countershaft 39 at its rear to which the rear mounting portion 53 (see FIG. 4) of the seat receiving member 50 is attached. The rotating member 38 supports an operating shaft 81 of an operating means 80 at an intermediate portion between its front and rear portions.

[0047] The counter shaft 39 extends in the left-right direction and is supported by the left and right side walls 382a, 382b. A connecting piece 532 (see FIG. 4) of the rear mounting portion 53 of the seat receiving member 50 is rotatably supported by the counter shaft 39. In other words, the rear portion of the seat receiving member 50 is rotatably supported with respect to the rotating member 38.

[0048] The biasing means 60 has a restoring force for returning the backrest 20 tilted by the biasing force to its original position (initial state). The biasing means 60 has a compression coil spring 61, a spring front end support portion 62 provided at one end (front end) of the compression coil spring 61, and a spring rear end support portion 63 provided at the other end (rear end).

[0049] The front end of the compression coil spring 61 is compressed rearward, and the rear end is compressed forward. Two compression coil springs 61, with their biasing direction facing the front-to-rear direction, are housed side by side in the left-right direction in the first internal space S1 of the support basic body 41. The pair of compression coil springs 61 are attached in a constantly compressed and biased state, whether the backrest 20 is in the initial state or the tilted state.

[0050] The spring front end support portion 62 and the spring rear end support portion 63 are connected by an expandable connecting shaft 64 that is inserted inside the compression coil spring 61. In the biasing means 60, the expandable connecting shaft 64 expands and contracts as the distance between the spring front end support portion 62 and the spring rear end support portion 63 changes due to the compression and extension of the compression coil spring 61.

[0051] The spring front end support portion 62 abuts against the front end of the compression coil spring 61 from the front. The spring front end support portion 62 is formed in a U-shape that opens forward when viewed from the left and right. The U-shaped recess 62a (see FIG. 7) is pressed against the front spring reaction force receiving shaft 553 of the spring front end receiving portion 55 provided on the seat receiving member 50 from behind and engages with it. In other words, the front spring reaction force receiving shaft 553 bears the reaction force of the compression coil spring 61 whether the backrest 20 is in the initial state or the tilted state.

[0052] The spring rear end support portion 63 abuts against the rear end of the compression coil spring 61 from behind. The spring rear end support portion 63 has a through hole 631 (see FIG. 7) that penetrates in the left-right direction. An action shaft 71 (shaft portion 712, see FIG. 8) of the adjustment means 70 (described later) that extends in the left-right direction is inserted into and supported in the through hole 631. The spring rear end support portion 63 is in a state in which a spring force is applied from the front to the action shaft 71. In other words, the action shaft 71 bears the reaction force of the compression coil spring 61 whether the backrest 20 is in the initial state or the tilted state.

[0053] The adjustment means 70 has the function of adjusting the biasing force of the compression coil spring 61 of the biasing means 60 and adjusting the restoring force of the tilted backrest 20. The adjustment means 70 is housed in the second internal space S2 between the side walls 382a, 382b of the rotating member 38 of the backrest 20. The adjustment means 70 includes an action shaft 71 that acts on the biasing force of the biasing means 60 (compression coil spring 61), an adjustment shaft 72 that movably supports the action shaft 71, and a support member 73 that rotatably supports the adjustment shaft 72 relative to the operating means 80.

[0054] A second transmission gear 721 consisting of a bevel gear is integrally provided at the upper end of the adjustment shaft 72. This second transmission gear 721 meshes with a first transmission gear 83 of the operation means 80, which will be described later, and when the operation shaft 81 of the operation means 80 is operated, a rotational force is transmitted from the first transmission gear 83 to the second transmission gear 721, causing the adjustment shaft 72 to rotate in both forward and reverse directions. A male thread is formed on the adjustment shaft 72 over the entire axial direction, with which the action shaft 71 is threadedly engaged. The adjustment means 70 is linked to the operation of the operation means 80.

[0055] In an initial state, the adjustment shaft 72 is disposed with its axial direction angled obliquely so that, in a side view, it gradually moves from the front to the rear as it moves from the lower shaft end 72b to the upper shaft end 72a. The lower shaft end 72b is located below the main turning shaft 42. The upper shaft end 72a is located above and rearward of the main turning shaft 42. In other words, the operating shaft 71, which moves along the adjustment shaft 72, i.e., the spring rear end support portion 63 provided at the rear end of the compression coil spring 61 connected to the operating shaft 71, is configured to move between a position below the main turning shaft 42 and a position above and rearward of the main turning shaft 42.

[0056] The adjustment means 70 is configured so that, as the adjustment shaft 72 rotates, the action shaft 71, which is threaded onto the male screw, moves in the axial direction of the adjustment shaft 72 according to the rotational position of the adjustment shaft 72. That is, the adjustment means 70 can adjust the position of the action shaft 71 by moving the action shaft 71 along the adjustment shaft 72. When the action shaft 71 moves on the adjustment shaft 72, the compression coil spring 61 rotates about the spring front end support portion 62, and therefore only the angle as viewed from the left and right changes.

[0057] The support member 73 includes a fixed plate 731 that extends in the vertical direction and is fixed to the rear wall 381 of the rotating member 38 with screws (not shown), an upper support plate 732 and a lower support plate 733 that extend forward from the upper and lower ends of the fixed plate 731, and a pair of side support plates 734, 735 (a pair of flanges) that extend upward from both left and right sides of the upper support plate 732. Of the pair of side support plates 734, 735, the left side support plate 734 will be referred to as the first side support plate 734, and the right side support plate 735 will be referred to as the second side support plate 735. The adjustment shaft 72 is disposed between the upper support plate 732 and the lower support plate 733. The adjustment shaft 72 has an upper shaft end 72a rotatably supported by the upper support plate 732 and a lower shaft end 72b rotatably supported by the lower support plate 733.

[0058] 6 and 7, the action shaft 71 includes a nut portion 711 having a female thread that screws onto the adjustment shaft 72, and a shaft portion 712 that extends to both the left and right sides of the nut portion 711. The nut portion 711 moves along the adjustment shaft 72 as the adjustment shaft 72 rotates. The spring rear end support portion 63 of the biasing means 60 is connected to the shaft portion 712.

[0059] 7, the operating means 80 is provided on the rotating member 38. The operating means 80 includes an operating shaft 81 that extends in the left-right direction and is inserted through a hole 382c formed in the right side wall 382a, an operating lever 82 that is provided at a protruding tip (one end) of the operating shaft 81 that protrudes outward (to the right) from the right side wall 382a, and a first transmission gear 83 that is a bevel gear that is provided in the middle of the operating shaft 81 and located in the second internal space S2. That is, the operating means 80 has an outer end in the width direction of the operating shaft 81 that protrudes in the width direction from the right side wall 382a, and an inner end in the width direction that is located in the second internal space S2 and is connected to the adjustment means 70.

[0060] The operating shaft 81 is rotatably supported on the right side wall 382a of the rotating member 38. A hole 382c through which the operating shaft 81 is inserted is formed on the upper side of the right side wall 382a. The operating shaft 81 is disposed above the adjustment shaft 72 so that the axis of the operating shaft 81 and the axis of the adjustment shaft 72 are positioned in the same plane. The operating shaft 81 is supported by a base member 91 that is supported by a support member 73. The support member 73 and the base member 91 will be described later.

[0061] The first transmission gear 83 provided in the axial middle of the operating shaft 81 meshes with the second transmission gear 721 provided on the adjustment shaft 72. In other words, the rotation of the operating shaft 81, i.e., the rotation of the first transmission gear 83 around its axis in the left-right direction, is converted into the rotation of the second transmission gear 721 around the axis of the adjustment shaft 72.

[0062] In chair 1 configured in this manner, when adjusting the reaction force (returning force) of backrest 20, first, operating lever 82 of operating means 80 is rotated, causing action shaft 71 located at spring rear end support portion 63 of compression coil spring 61 to move up and down along adjustment shaft 72. For example, by rotating operating lever 82 in one direction, adjustment shaft 72 rotates in one direction via first transmission gear 83 and second transmission gear 721, and nut portion 711 screwed onto adjustment shaft 72, i.e., action shaft 71, moves up along adjustment shaft 72.

[0063] In this way, by moving the action shaft 71 on the adjustment shaft 72, the distance between the spring front end support portion 62 and the spring rear end support portion 63 of the biasing means 60 changes, and the compression amount of the compression coil spring 61, i.e., the biasing force (reaction force) of the compression coil spring 61, can be adjusted. That is, it is possible to adjust the restoring force when the backrest 20 returns from the tilted state to the initial state.

[0064] In the adjustment means 70 of this embodiment, the position of the action shaft 71, i.e., the position of the spring rear end support portion 63 of the compression coil spring 61, is changed by moving the action shaft 71 on the adjustment shaft 72, thereby adjusting the biasing force of the compression coil spring 61 (the return force of the backrest 20). In this embodiment, as shown in Fig. 12, the action shaft 71, which moves on the adjustment shaft 72, can be adjusted to a position above the rotation main shaft 42 in the vertical direction.

[0065] 9, the first-side support plate 734 and the second-side support plate 735 of the support member 73 are flat plates with their plate surfaces facing the left-right direction, and are arranged with a gap in the width direction. The first-side support plate 734 and the second-side support plate 735 have holes 734a and 735a that penetrate the first-side support plate 734 and the second-side support plate 735 at positions facing each other in the width direction. The hole 734a formed in the first-side support plate 734 is referred to as the first hole 734a, and the hole 735a formed in the second-side support plate 735 is referred to as the second hole 735a. A base member 91 is inserted into the first hole portion 734a and the second hole portion 735a. The base member 91 supports the operating means 80 (second operating member) of the returning means 92 and an operating member 95 (first operating member) of the restricting means 93, which will be described later.

[0066] 9 and 10, the base member 91 is a rod-shaped member with an axis 91a extending in the left-right direction. The axis 91a of the base member 91 corresponds to the second axis of the present invention. The left end of the base member 91 protrudes leftward beyond the first-side support plate 734. The right end of the base member 91 protrudes rightward beyond the second-side support plate 735. The middle portion of the base member 91 in the lengthwise direction (left-right direction) is referred to as middle portion 911, the left side of middle portion 911 is referred to as first support portion 912, and the right side of middle portion 911 is referred to as second support portion 913.

[0067] The cross-sectional shape of the intermediate portion 911 is circular. The cross-sectional shape of the first support portion 912 is a circle that is smaller than the cross-sectional shape of the intermediate portion 911. At the boundary between the intermediate portion 911 and the first support portion 912, a first step portion 914 is formed where the outer periphery of the intermediate portion 911 protrudes radially beyond the outer periphery of the first support portion 912. The first step portion 914 is formed by an end face 911b on the right side (first support portion 912 side) of the intermediate portion 911 and the peripheral surface of the first support portion 912.

[0068] The cross-sectional shape of the second support portion 913 is a rectangle with rounded corners. The rectangle of the cross-sectional shape of the second support portion 913 is sized so that it is inscribed within the circular cross-sectional shape of the intermediate portion 911. Therefore, a second step portion 915 is formed at the boundary between the intermediate portion 911 and the second support portion 913, where the outer periphery of the intermediate portion 911 protrudes radially outward beyond the outer periphery of the second support portion 913. The second step portion 915 is formed by an end face 911c on the left side (second support portion 913 side) of the intermediate portion 911 and the circumferential surface of the second support portion 913.

[0069] A left end 911a of the intermediate portion 911 of the base member 91 is inserted into the hole 734a of the first-side support plate 734. A left end face 911b of the intermediate portion 911 protrudes slightly to the left beyond the left face 734b of the first-side support plate 734. In other words, the right end face 911b of the intermediate portion 911 is located slightly to the left of the left face 734b of the first-side support plate 734. The first hole 734a is a circular hole. The inner diameter of the first hole 734a is the same as or slightly larger than the outer diameter of the intermediate portion 911. The intermediate portion 911 inserted into the first hole 734a is rotatable around the axis 91a of the base member 91 relative to the first-side support plate 734. The first support portion 912 is disposed on the left side of the first-side support plate 734. A portion of the second support portion 913 of the base member 91 slightly to the right of the left end portion 913a of the second support portion 913 is inserted into the second hole portion 735a of the second-side support plate 735. The boundary between the second support portion 913 and the intermediate portion 911 is located to the left of the second-side support plate 735, i.e., on the first-side support plate 734 side. The second hole portion 735a is a circular hole. The inner diameter of the second hole portion 735a is larger than the outer diameter of the second support portion 913. The second support portion 913 inserted into the second hole portion 735a is rotatable around the axis 91a of the base member 91 relative to the second-side support plate 735.

[0070] The base member 91 is rotatable about its axis 91a relative to the support member 73 when inserted into the first hole 734a of the first side support plate 734 and the second hole 735a of the second side support plate 735. A first recess 736 and a second recess 737 are formed side by side in the circumferential direction (the direction around the axis 91a of the base member 91) on the upper edge of the first-side support plate 734. The first recess 736 is disposed forward of the second recess 737. A protrusion 738 is formed between the first recess 736 and the second recess 737. The first recess 736 and the second recess 737 are configured to receive the protrusion of a connecting member 94, which will be described later.

[0071] 11 and 12, a recess 811 extending in the left-right direction and opening to the left is formed in the left end portion 81a of the operating shaft 81. A portion of the second support portion 913 of the base member 91 that protrudes to the right beyond the second-side support plate 735 is inserted into the recess 811. The operating shaft 81 is not inserted into the second hole 735a of the second-side support plate 735. The cross-sectional shape of the recess 811 is rectangular, the same as the cross-sectional shape of the second support part 913. The second support part 913 is fitted into the recess 811, and the operating shaft 81 and the second support part 913, i.e., the base member 91, are fixed so as not to rotate relative to each other around the axis 91a of the base member 91.

[0072] The operating shaft 81 is inserted from the right side into a hole 382c in a right side wall 382a of the rotating member 38. The outer diameter of a left end portion 81a of the operating shaft 81 is smaller than the diameter of the hole 382c. The operating shaft 81 is formed with an expanded diameter portion 812 that protrudes radially at a position to the right of the left end portion 81a. The outer diameter of the expanded diameter portion 812 is larger than the diameter of the hole 382c. When the expanded diameter portion 812 comes into contact with the right surface of the side wall 382a while the operating shaft 81 is inserted into the hole 382c, it restricts leftward displacement of the operating shaft 81.

[0073] A groove 813 is formed in the operating shaft 81 over the entire circumferential direction at a position to the right of the left end portion 81a and to the left of the enlarged diameter portion 812. A bearing member 814 is fitted into the groove 813. The bearing member 814 is a C-shaped member obtained by removing a portion of an annular member, and can be fitted into the groove 813 of the operating shaft 81 from the outer periphery of the operating shaft 81. In this embodiment, the bearing member 814 can be fitted into the groove 813 of the operating shaft 81 from above. The bearing member 814 is provided with a flange 814a at its right end that protrudes radially outward.

[0074] The bearing member 814 is fitted into the groove 813 of the operating shaft 81 when the operating shaft 81 is inserted from the right side through the hole 382c in the right side wall 382a of the rotating member 38 and the enlarged diameter portion 812 is in contact with or has a small gap with the right surface of the side wall 382a. In this embodiment, a rib protruding to the right from the edge of the hole 382c is provided on the right surface of the side wall 382a, and the enlarged diameter portion 812 is in contact with or has a small gap with the rib. When the bearing member 814 is fitted into the groove 813 in this manner, the flange 814a is in contact with or has a small gap with the left surface of the side wall 382a. When the bearing member 814 comes into contact with the left surface of the side wall 382a, it restricts the rightward displacement of the operating shaft 81. Even when at least one of the enlarged diameter portion 812 and the bearing member 814 is in contact with the side wall 382a, the operating shaft 81 can rotate about its axis relative to the side wall 382a. The operating means 80 is restricted from moving in the left-right direction relative to the rotating member 38 by the enlarged diameter portion 812 of the operating shaft 81 and the flange 814a.

[0075] 12 and 13, the first transmission gear 83 has a gear main body 831 on which a gear is formed, and a gear fixing portion 832 that is provided coaxially with the gear main body 831 and fixed to the base member 91. The axis of the first transmission gear 83 extends in the left-right direction, and the gear main body 831 is disposed to the left of the gear fixing portion 832. A hole 833 that penetrates the first transmission gear 83 in the axial direction is formed. Of the hole 833, the portion that penetrates the gear main body 831 is referred to as a first hole 833a, and the portion that penetrates the gear fixing portion 832 is referred to as a second hole 833b. The first transmission gear 83 is disposed on the left side of the second-side support plate 735.

[0076] The base member 91 is inserted into the hole 833 of the first transmission gear 83. A portion of the second support portion 913 of the base member 91 on the left side of the second side support plate 735 is fitted into the first hole 833a. The cross-sectional shape of the first hole 833a is a rectangle with rounded corners, the same as the cross-sectional shape of the second support portion 913. A right end portion of the intermediate portion 911 of the base member 91 is fitted into the second hole 833b. The cross-sectional shape of the second hole 833b is a circle, the same as the cross-sectional shape of the intermediate portion 911.

[0077] The second support portion 913 of the base member 91 is inserted into the hole 833 of the first transmission gear 83. The first transmission gear 83 and the base member 91 are fixed so as not to rotate relative to each other around the axis 91a of the base member 91. The left end portion (on the intermediate portion 911 side) of the second support portion 913 of the first transmission gear 83 is inserted into the second support portion 913. As shown in FIG. 13, the left end face 83a of the first transmission gear 83 is disposed at the position of the second step portion 915 at the boundary between the intermediate portion 911 of the base member 91 and the second support portion 913 (see FIG. 9), and is adjacent to the left end face 911c (on the second support portion 913 side) of the intermediate portion 911 with a small gap therebetween. As a result, when the base member 91 attempts to displace to the right relative to the first transmission gear 83, i.e., the operating means 80, the left end face 911c of the intermediate portion 911 of the base member 91 comes into contact with the left end face 83a of the first transmission gear 83, thereby restricting this displacement. The base member 91 is restricted from displacing to the right relative to the operating means 80.

[0078] When the operating shaft 81 rotates around the axis 91a of the base member 91, the base member 91 also rotates integrally. When the base member 91 rotates around the axis 91a of the base member 91, the first transmission gear 83 also rotates integrally. In other words, when the operating shaft 81 rotates around the axis 91a of the base member 91, the first transmission gear 83 also rotates integrally. Since the base member 91 is rotatable about an axis 91a of the base member 91 relative to the support member 73, the support member 73 does not rotate even when the base member 91 rotates.

[0079] As described above, the restricting means 93 shown in Fig. 14 restricts the rotation of the backrest 20 around the rotation main shaft 42. The restricting means 93 includes an engaging member 96 having an engaging protrusion 961 that is inserted into one of the plurality of engaging recesses 44 provided in the support base 40, an operating member 95 (see Figs. 11 and 15) that operates the engaging member 96, and a connecting member 94 (see Figs. 11 and 15) that connects the engaging member 96 and the operating member 95. As shown in Figs. 11 and 15, the engaging member 96, the operating member 95, and the connecting member 94 are supported by the base member 91.

[0080] As shown in FIGS. 11 and 12, the operating member 95 is provided on the rotating member . The operating member 95 has an operating shaft 951 that extends in the left-right direction and is inserted into a hole 382d formed in the left side wall 382b, and an operating lever 952 that is connected to the left end of the operating shaft 951. The operating shaft 951 is rotatably supported on the left side wall 382b of the rotating member 38. A hole 382d through which the operating shaft 951 is inserted is formed on the upper side of the left side wall 382b.

[0081] The operating shaft 951 has a recess 953 formed in a right end portion 951a, which extends in the left-right direction and opens to the right. The first support portion 912 of the base member 91 is inserted into the recess 953. The right end face 951b of the operating shaft 951 is adjacent to the right end face 911b (on the first support portion 912 side) of the intermediate portion 911 of the base member 91, with a small gap between them. As a result, when the base member 91 attempts to displace to the left relative to the operating shaft 951, i.e., the operating member 95, the right end face 911b of the intermediate portion 911 of the base member 91 abuts against the right end face 951b of the operating shaft 951, thereby restricting this displacement. The base member 91 is restricted from displacing to the left relative to the operating member 95. As described above, the right end face 911b of the intermediate portion 911 is located slightly to the left of the left face 734b of the first-side support plate 734. Therefore, a small gap is formed between the right end face 951b of the operating shaft 951 and the right end face 911b of the intermediate portion 911.

[0082] The cross-sectional shape of the recess 953 is a circle that is the same as or slightly larger than the cross-sectional shape of the first support portion 912. The operating shaft 951 and the first support portion 912 are not restricted in relative rotation about the axis 91a of the base member 91. In other words, the operating shaft 951 is supported by the base member 91 so as to be rotatable about the axis 91a of the base member 91. The cross-sectional shape (outer shape) of right end portion 951a of operating shaft 951, where recess 953 is formed, is a rectangle with rounded corners. Portion 951c of operating shaft 951 to the left of right end portion 951a is a circle in cross-sectional shape. The square cross-sectional shape of operating shaft 951 on the right side of operating shaft 951 is sized so that it is inscribed in the circle of the cross-sectional shape of portion 951c to its left.

[0083] 13, a third step 951d is formed at the boundary between right end portion 951a and left portion 951c of operating shaft 951, where the outer periphery of left portion 951c protrudes radially beyond the outer periphery of right end portion 951a. A right end face 951e of left portion 951c of operating shaft 951 and the circumferential surface of right end portion 951a form third step 951d. A protrusion 954 extending in the left-right direction is formed on the outer periphery of the right end portion 951a of the operating shaft 951.

[0084] The operating shaft 951 is inserted from the left side into a hole 382d in a left side wall 382b of the rotating member 38. The outer diameter of a right end portion 951a of the operating shaft 951 is smaller than the diameter of the hole 382d. An expanded diameter portion 955 that protrudes radially is formed on the operating shaft 951 at a position to the left of the right end portion 951a. The outer diameter of the expanded diameter portion 955 is larger than the diameter of the hole 382d. When the operating shaft 951 is inserted through the hole 382d, the expanded diameter portion 955 comes into contact with the left surface of the side wall 382b, thereby restricting displacement of the operating shaft 951 to the right.

[0085] A groove 956 is formed over the entire circumferential direction of the operating shaft 951 at a position to the left of the right end portion 951a and to the right of the enlarged diameter portion 955. A bearing member 957 (see FIGS. 8 and 12) is fitted into the groove 956. The bearing member 957 is a C-shaped member obtained by removing a portion of an annular member, and can be fitted into the groove 956 of the operating shaft 951 from the outer periphery of the operating shaft 951. In this embodiment, the bearing member 957 can be fitted into the groove 956 of the third step portion 951d from above. The bearing member 957 is provided with a flange 957a at its left end that protrudes radially outward.

[0086] The bearing member 957 is fitted into the groove 956 of the operating shaft 951 when the operating shaft 951 is inserted from the left side through the hole 382d in the left side wall 382b of the rotating member 38 and the enlarged diameter portion 955 is in contact with or has a small gap with the left surface of the side wall 382b. In this embodiment, a rib protruding to the right from the edge of the hole 382d is provided on the left surface of the side wall 382b, and the enlarged diameter portion 955 is in contact with or has a small gap with the rib. When the bearing member 957 is fitted into the groove 956 in this manner, the flange 957a is in contact with or has a small gap with the right surface of the side wall 382b. When the bearing member 957 comes into contact with the right surface of the side wall 382b, it restricts leftward displacement of the operating shaft 951. Even when at least one of the enlarged diameter portion 955 and the bearing member 957 is in contact with the side wall 382b, the operating shaft 951 can rotate about its axis relative to the side wall 382b. The operation member 95 is restricted from moving in the left-right direction relative to the rotating member 38 by the enlarged diameter portion 955 of the operation shaft 951 and the flange 957a.

[0087] 11, 12, 15, and 16, the connecting member 94 has a first connecting portion 941 attached to the operating shaft 951, a second connecting portion 942 attached to the intermediate portion 911 of the base member 91, and a third connecting portion 943 provided between the first connecting portion 941 and the second connecting portion 942. The first connecting portion 941, the second connecting portion 942, and the third connecting portion 943 are integrally formed. The connecting member 94 is arranged in the order of the first connecting portion 941, the third connecting portion 943, and the second connecting portion 942 from left to right. The connecting member 94 is rotatable relative to the base member 91 around the axis 91a of the base member 91.

[0088] The first connecting portion 941 is cylindrical and disposed in a direction in which a hole 941a penetrates the first connecting portion 941 in the width direction. The cross-sectional shape of the hole 941a of the first connecting portion 941 is a rectangle with rounded corners, the same shape as the outer shape of the right end portion of the operating shaft 951. A groove 941b corresponding to the protrusion 954 of the operating shaft 951 is formed on the inner circumferential surface of the hole 941a. The right end portion 951a of the operating shaft 951 is fitted into the hole 941a of the first connecting portion 941. The protrusion 954 of the operating shaft 951 is inserted into the groove 941b of the hole 941a of the first connecting portion 941. The operating shaft 951 and the first connecting portion 941 do not rotate relative to each other. In other words, the connecting member 94 is fixed to the operating shaft 951 and does not rotate relative to each other around the axis 91a of the operating shaft 951 and the base member 91. The first support portion 912 of the base member 91 is inserted into the hole 941a of the first connection portion 941. The first connection portion 941 is rotatable relative to the base member 91 around the axis 91a of the base member 91.

[0089] A left end face 941c of the first connecting portion 941 is disposed at a third step 951d (see also FIG. 13) at the boundary between a right end portion 951a of the operating shaft 951 and the left portion 951c thereof. Of the left end face 941c of the first connecting portion 941 shown in FIG. 16, portions 941d that protrude radially inward on both circumferential sides of the groove 941b abut against a right end face 951e (see also FIG. 13) of the left portion 951c of the operating shaft 951, as shown in FIG. 15. The right end face 951e of the left portion 951c of the operating shaft 951 is a surface facing right that forms the third step 951d. This restricts the first connecting portion 941, i.e., the connecting member 94, from being displaced leftward relative to the operating shaft 951.

[0090] The second connecting portion 942 is cylindrical and has a hole 942a that extends widthwise. The cross-sectional shape of the hole 942a of the second connecting portion 942 is a circle that is the same as or slightly larger than the cross-sectional shape of the intermediate portion 911 of the base member 91. The intermediate portion 911 is inserted into the hole 942a of the second connecting portion 942. The second connecting portion 942 is rotatable around the axis 91a of the base member 91 relative to the base member 91.

[0091] The first transmission gear 83 is disposed on the right side of the second connection portion 942, i.e., on the right side of the connecting member 94. As described above, the first transmission gear 83 is fixed to the base member 91. If the connecting member 94 attempts to displace to the right relative to the base member 91, it comes into contact with the first transmission gear 83, and is therefore restricted from displacing to the right. Note that a small gap is provided between the right end face of the connecting member 94 and the left end face 83a of the first transmission gear 83, which is large enough to allow relative rotation between the connecting member 94 and the base member 91.

[0092] The third connecting portion 943 is rotatable around an axis 91a of the base member 91 relative to the base member 91. The third connecting portion 943 has a first plate portion 943a that is disposed to the left of the first-side support plate 734 and connected to the first connecting portion 941, a second plate portion 943b that is disposed to the right of the first-side support plate 734 and connected to the second connecting portion 942, and a connecting portion 943c that connects the first plate portion 943a and the second plate portion 943b. The connecting portion 943c is disposed above the first-side support plate 734. A convex portion 943d that protrudes downward is formed on the lower surface of the connecting portion 943c (the surface facing the first-side support plate 734). As shown in FIG. 17, the convex portion 943d is disposed in either the first recess 736 or the second recess 737 of the first-side support plate 734 as a result of the coupling portion 943c rotating around the axis 91a of the base member 91. In FIG. 17, the connecting member 94 in which the convex portion 943d is disposed in the second recess 737 is indicated by a two-dot chain line. The convex portion 943d elastically deforms when climbing over a convex portion 738 between the first recess 736 and the second recess 737. In this embodiment, the convex portion 943d has a slit 943e formed therein that extends in the direction of the axis 91a of the base member 91, and has a pair of elastic pieces 943f, 943f at the front and rear of the slit 943e. This allows the convex portion 943d to easily deform elastically when climbing over the convex portion 738.

[0093] When the operating member 95 is operated to rotate around the axis 91a of the base member 91, the connecting member 94 also rotates integrally with the operating member 95. The rotation of the operating member 95 stops at either the position where the convex portion 943d of the connecting member 94 fits into the first concave portion 736 or the position where the convex portion 943d fits into the second concave portion 737.

[0094] 14, 17, and 18 is a leaf spring. As shown in Fig. 17, when the convex portion 943d of the connecting member 94 to be connected fits into the first concave portion 736, the engaging member 96 is oriented so that the engaging convex portion 961 is inserted into the engaging concave portion 44, and when the convex portion 943d fits into the second concave portion 737, the engaging convex portion 961 is urged in a direction so that it is ejected from the engaging concave portion 44.

[0095] As shown in Figure 18, the engagement member 96 extends obliquely from the front to the rear, gradually moving upward. The engagement member 96 is supported at its heightwise intermediate portion by a shaft 962 having an axis extending in the left-right direction so as to be rotatable about the axis. The axis 962a of the shaft 962 supporting the engagement member 96 corresponds to the third axis of the present invention. The axis 962a of the shaft 962 is located below the axis 91a of the base member 91. The shaft 962 is supported by the rotating member 38. That is, the shaft 962 is supported by the backrest 20. The shaft 962 is positioned below the axis 91a of the base member 91 and above the engagement recess 44. The upper part of the engagement member 96 is curved forward. A base support part 965 is provided at the upper end of the engagement member 96, and is connected to the second connection part 942 of the connection member 94 via a link part 963. An engagement protrusion 961 is provided at the lower end of the engagement member 96.

[0096] The link portion 963 protrudes radially from the outer peripheral surface of the second connecting portion 942. The link portion 963 protrudes radially (in a direction intersecting the second shaft portion) beyond the operating member 95. The link portion 963 has a link shaft portion 963a at its tip. The link shaft portion 963a is cylindrical, and its axis extends in the left-right direction. The link shaft portion 963a is inserted in the left-right direction into a base support portion 965 at the upper end of the engaging member 96. The base support portion 965 and the link shaft portion 963a are rotatable relative to each other around the axis of the link shaft portion 963a. When the operating member 95 is operated, the link portion 963 rotates together with the connecting member 94 around the axis 91a of the base member 91. The base support portion 965 (engagement member 96) rotates together with the link shaft portion 963a around the axis 91a of the base member 91. Because the engagement member 96 is rotatably supported by the shaft portion 962, the base support portion 965 rotates together with the link shaft portion 963a around the axis 91a of the base member 91, while also rotating relatively to the link shaft portion 963a around its axis. The link portion 963 functions as an interlocking portion that transmits the operating force input to the operating member 95 to the engaging member 96 and interlocks the engaging member 96 with the operating member 95 .

[0097] 17, when the convex portion 943d of the connecting member 94 is fitted into the first recessed portion 736, the link portion 963 is located forward (shown by a solid line in FIG. 17), and when the convex portion 943d of the connecting member 94 is fitted into the second recessed portion 737, the link portion 963 is located rearward (shown by a two-dot chain line in FIG. 17). As a result, when the convex portion 943d is fitted into the first recessed portion 736, the engaging convex portion 961 at the lower end of the engaging member 96 is located further rearward than when the engaging convex portion 943d is fitted into the second recessed portion 737. When the engaging convex portion 961 moves rearward, it is inserted into the engaging recessed portion 44 (shown by a solid line in FIG. 17), and when it moves forward, it is disengaged from the engaging recessed portion 44 (shown by a two-dot chain line in FIG. 17). The state in which the convex portion 943d of the connecting member 94 fits into the first recess 736 and the engaging convex portion 961 is inserted into the engaging recess 44 is referred to as the locked state, and the state in which the convex portion 943d of the connecting member 94 fits into the second recess 737 and the engaging convex portion 961 protrudes from the engaging recess 44 is referred to as the detached state.

[0098] The engaging protrusion 961 is inserted into a hole 383 formed in the rear wall 381 of the rotating member 38. The engaging protrusion 961 never comes out of the hole 383 and is always inserted into the hole 383. The hole 383 is located forward and above the engaging recess 44. When the rear side of the engaging protrusion 961 protrudes rearward from the hole 383, it is inserted into the engaging recess 44 (shown by solid lines in FIGS. 17 and 18), and the rear side of the engaging protrusion 961 comes out of the engaging recess 44 (shown by two-dot chain lines in FIGS. 17 and 18) when it is inserted inside the hole 383. In the disengaged state, the engaging recess 44 and the hole 383 are misaligned. When a load is applied to the backrest 20 and the rotating member 38 is displaced, the engaging protrusion 961 is displaced in accordance with this displacement, or an external force acts in the direction in which the rotating member 38 is displaced.

[0099] When the operating member 95 is operated to change from the detached state to the locked state, the convex portion 943d of the connecting member 94 moves from the second recess 737 to the first recess 736. At this time, the upper side of the engaging member 96 above the shaft portion 962 moves forward and assumes the state shown by the solid lines in Figures 17 and 18, but the lower side below the shaft portion 962 remains in the detached state shown by the two-dot chain lines in Figures 17 and 18 because the engaging convex portion 961 is not inserted into the engaging recess 44. At this time, the engaging member 96 is elastically deformed and is biased in the direction in which the engaging convex portion 961 enters the engaging recess 44.

[0100] In this state, when the backrest 20 rotates around the axis 42a of the rotation main shaft 42 and the engaging recess 44 and the hole 383 overlap, the engaging protrusion 961 is inserted into the engaging recess 44, resulting in a locked state. At this time, the elastic deformation of the engaging member 96 is restored, and the biasing force is reduced or eliminated.

[0101] In the locked state, the axis of the hole 383 and the axis of the engagement recess 44 are misaligned, and the external force received from the side of the hole 383 (the pivoting member 38) and the external force received from the side of the engagement recess 44 (the support base 40) are in opposite directions. When a shear force acts on the engagement protrusion 961 as it is sandwiched between the side of the hole 383 and the side of the engagement recess 44, the engagement protrusion 961 cannot come out of the engagement recess 44 even if the upper side of the engagement member 96 moves forward. When the operating member 95 is operated to change from the locked state to the released state, the convex portion 943d of the connecting member 94 moves from the first recessed portion 736 to the second recessed portion 737. At this time, the upper side of the shaft portion 962 of the engaging member 96 moves rearward and assumes the state shown by the two-dot chain line in FIGS. 17 and 18, but the lower side of the shaft portion 962 remains in the locked state shown by the solid line in FIGS. 17 and 18, with the engaging convex portion 961 unable to come out of the engaging recessed portion 44. At this time, the engaging member 96 is elastically deformed and is biased in the direction in which the engaging convex portion 961 comes out of the engaging recessed portion 44.

[0102] In this state, when the backrest 20 moves and the engaging recess 44 overlaps with the hole 383, the engaging protrusion 961 comes out of the engaging recess 44 and enters a disengaged state. At this time, the elastic deformation of the engaging member 96 is restored, and the biasing force is reduced or eliminated.

[0103] As described above, the operating means 80 is restricted from being displaced left and right relative to the rotating member 38. The operating member 95 is restricted from being displaced left and right relative to the rotating member 38. The base member 91 is restricted from being displaced rightward relative to the operating means 80. The base member 91 is restricted from being displaced leftward relative to the operating member 95. The connecting member 94 is restricted from being displaced leftward relative to the operating shaft 951. The connecting member 94 is restricted from being displaced rightward relative to the base member 91. As a result, the engagement member 96 connected to the connecting member 94 is restricted from being displaced in the left-right direction relative to the rotating member 38. In other words, the above functions as a means for aligning the engagement protrusion 961 of the engagement member 96 with the engagement recess 44 provided in the rotating member 38 in the left-right direction.

[0104] Next, the function and effect of the chair described above will be explained with reference to the drawings. In the chair 1 according to the present embodiment described above, the operating member 95 (first operating member) of the restricting means 93 is supported on the left side of the base member 91, and the operating member 80 (second operating member) of the returning means 92 is supported on the right side of the base member 91. This allows the seated person to operate the restricting means 93 with their left hand while seated, and to operate the returning means 92 with their right hand without changing their posture, providing good operability. In particular, since the operating member 95 and operating member 80 are provided on the backrest 20, the seated person can operate the backrest 20 from a position close to the backrest 20. It is also possible to prevent interference between the operating member 95 and the operating means 80. Furthermore, since the operating member 95 and the operating means 80 can be provided together via the base member 91, they can be easily unitized and the workability during assembly is good.

[0105] In the chair 1 according to this embodiment, the base member 91 is in the shape of a rod extending in the width direction. With this configuration, the space occupied by the base member 91 can be reduced, and a large space can be secured for arranging other members such as the restricting means 93 and the returning means 92.

[0106] In addition, in the chair 1 according to this embodiment, the base member 91 is an axis portion having an axis 91a (second axis) extending in the width direction, and the operating member 95 and the operating means 80 are arranged coaxially on the axis 91a of the base member 91. With this configuration, the base member 91, the operating member 95, and the operating means 80 are arranged side by side in the width direction, so that the space occupied by these members can be reduced.

[0107] Furthermore, in the chair 1 according to this embodiment, the return means 92 has a biasing means 60 (biasing section) that biases the backrest 20 in a tilted state in a direction returning it to its initial state, and an adjustment means 70 (adjustment section) that is linked to the operating means 80 and adjusts the biasing force of the biasing means 60. The base member 91 is rotatable about an axis 91a of the base member 91, the operating member 95 is rotatable relative to the base member 91 about the axis 91a of the base member 91, and the operating means 80 is fixed to the base member 91 so as not to be rotatable relative to the base member 91 about the axis 91a of the base member 91. With this configuration, the operating force of the operating means 80 can be directly transmitted to the biasing means (biasing portion) 60.

[0108] In addition, in the chair 1 according to this embodiment, the pivoting member 38 of the backrest 20 has a pair of side walls 382a, 382b spaced apart on the left and right, and the operating member 95 of the regulating means 93 is supported on the left side wall 382a, and the operating means 80 of the return means 92 is supported on the right side wall 382b. With this configuration, the operating member 95 and the operating means 80 are arranged in a dispersed manner in the width direction, which prevents the seat occupant from operating the operating member 95 and the operating means 80 by mistake, compared to when the operating member 95 and the operating means 80 are both arranged on either the left or right side.

[0109] In addition, in the chair 1 according to this embodiment, the restricting means 93 and the returning means 92 are disposed at positions sandwiching the base member 91 therebetween when viewed in the width direction. By adopting such a configuration, the restricting means 93 and the returning means 92 can be disposed at positions where they do not interfere with each other.

[0110] In addition, in the chair 1 according to this embodiment, the base member 91 has an intermediate portion 911 between the first support portion 912 and the second support portion 913, and both widthwise ends of the intermediate portion 911 are supported by a first side support plate 734 and a second side support plate 735 (a pair of flange portions) provided on the chair 1. With this configuration, the base member 91 is reliably supported by the chair 1, and the operating member 95 and operating means 80 supported by the base member 91 can be operated in a stable state.

[0111] Although the embodiment of the chair according to the present invention has been described above, the present invention is not limited to the above embodiment and can be modified as appropriate within the scope of the gist of the present invention. For example, in the above embodiment, the base member 91 is provided on the backrest 20, but it may be provided on a member of the chair 1 other than the base member 91, such as the support base 40 or the seat 17. Furthermore, in chair 1 according to this embodiment, the base member is a rod-like member extending in the width direction, but it may be a plate-like or block-like member, or may be a member extending in the front-rear direction.

[0112] In addition, in chair 1 according to this embodiment, the base member is a shaft portion having an axis 91a extending in the width direction, and operation member 95 and operation means 80 are arranged coaxially on axis 91a of base member 91, but may be arranged at positions where the axes are offset. Operation of operation member 95 and operation means 80 may be configured so that they can be operated by sliding in addition to rotation.

[0113] Furthermore, in the chair according to this embodiment, the operating member 95 of the regulating means 93 is rotatable relative to the base member 91 about the axis 91a thereof, and the operating means 80 of the returning means 92 is fixed so as not to be rotatable relative to the base member 91 about the axis 91a thereof, but the operating member 95 may be fixed so as not to be rotatable relative to the base member 91 about the axis 91a thereof, and the operating means 80 may be rotatable relative to the base member 91 about the axis 91a thereof. Both the operating member 95 and the operating means 80 may be rotatable relative to the base member 91 about the axis 91a thereof.

[0114] Furthermore, in the chair according to this embodiment, the regulating means 93 and the returning means 92 are arranged at positions sandwiching the base member 91 between them when viewed from the width direction, but the arrangement of the regulating means 93 and the returning means 92 may be set as appropriate.

[0115] Furthermore, in the chair 1 according to this embodiment, the operating member 95 of the regulating means 93 is supported on the left side wall 382a, and the operating means 80 of the returning means 92 is supported on the right side wall 382b, but the configuration in which the operating member 95 and the operating means 80 are supported on the chair 1 may be other than the above.

[0116] Furthermore, in the chair according to this embodiment, the base member 91 is supported by the first side support plate 734 and the second side support plate 735, but the form in which the base member 91 is supported may be set appropriately. [Explanation of symbols]

[0117] 1 chair 17 seats 20 Backrest 40 Support base (support structure) 60 Urging means (urging portion) 70 Adjustment means (adjustment section) 80 Operating means (second operating member) 91 Foundation members 91a Axis line (second axis line) 92 Recovery Method 93 Regulatory measures 95 Operating member (first operating member) 382a side wall 382b sidewall 734 First side support plate (edge) 735 Second side support plate (edge) 911 Middle Section 912 First Support Department 913 Second Support Department 962 Shaft

Claims

1. Support structure and A backrest is supported by the support structure so as to be rotatable about an axis extending in the width direction of the support structure, and is displaceable from an initial state to a tilted state tilted backward, A restricting means for restricting the rotation of the backrest about the axis, A means for returning the backrest, which is in the tilted state, back to the initial state, A first operating member for the seated person to operate the regulating means, It has a second operating member for the seated person to operate the return means, The aforementioned backrest is, The backrest body and It has a back support that supports the aforementioned backrest body, The return means is supported by the back support, The first operating member is supported on one end of the back support in the width direction, The second operating member is a chair supported on the other end of the back support in the width direction.

2. The back support has a rotatable member that can rotate around the axis relative to the support structure, The return means is provided on the rotating member, The first operating member is provided on one end of the rotating member in the width direction, The chair according to claim 1, wherein the second operating member is provided on the other end side in the width direction of the rotating member.

3. The aforementioned back support has a pair of side walls that are spaced apart in the width direction, The first operating member is supported by a side wall located on one side in the width direction, The chair according to claim 1 or 2, wherein the second operating member is supported by a side wall located on the other side in the width direction.

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