chair

Abstract

To provide a chair with enhanced workability for which a spring member to be used for return of a backrest can be easily compressed and assembled due to a simple constitution.SOLUTION: A compression coil spring 60 is arranged with its energization directed in a cross direction and comprises a front side engagement part 62 arranged in the front part of the spring and a rear side engagement part 63 arranged in the rear part of the spring. A backrest 20 has a rear side spring receiving part 65 which is engaged with the rear side engagement part 63. A seat receiving member 50 has a front side spring receiving part 55 which is arranged in front of the rear side attachment part 53, above the rear side spring receiving part 65, and is engaged with the front side engagement part 62. A long hole penetrates the seat receiving member 50 in a vertical direction and extends in the cross direction. A support base 40 has an engagement projection which is engaged with the long hole to be relatively movable in the cross direction. The compression coil spring 60 is provided to be more compressed than its natural length between the front side spring receiving part 55 and the rear side spring receiving part 65, with the engagement projection located at the rear end part of the long hole.SELECTED DRAWING: Figure 5

Description

[Technical Field]

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

[0002] Conventionally, a chair back used for office work, etc., has been known that includes a back supported on a support structure so as to be rotatable about an axis along the width direction of the support structure, and a biasing means that biases the back in a direction returning the back to its initial state.

[0003] The chairs described in Patent Documents 1 and 2 have a backrest that is tiltably supported on a support structure, and a spring member that is disposed behind the backrest's position relative to the support structure. In Patent Document 1, a compression spring is disposed in a compressed state between the backrest and the support structure. Patent Document 2 describes a configuration in which the compression spring is disposed within a strength member that constitutes part of the seat, and when the compression spring is assembled, an initial reaction force of the compression spring is applied to the backrest when the compression spring is positioned in the correct position. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4848099 [Patent Document 2] Patent No. 5724063 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the chair described in Patent Document 1 requires a process of manually placing the compression spring between the two components while pressing it against the spring force, which reduces workability and leaves room for improvement in this regard. Furthermore, in the case of the chair described in Patent Document 2, the compression spring is disposed inside the seat, which causes a problem in that the component configuration of the seat becomes complicated.

[0006] Therefore, the present invention has been made in consideration of the above circumstances, and provides a chair in which the spring member used to return the backrest can be easily compressed and assembled with a simple structure, thereby improving workability. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention employs the following means. That is, the chair according to the present invention comprises a support structure, a backrest rotatably supported on the support structure around a first axis in the chair width direction and displaceable in the front-rear direction between an upright state and a tilted state, a seat having a front supported portion supported so as to be movable relative to a front portion of the support structure in the front-rear direction and a rear supported portion supported at a position above the first axis and displaceable in the front-rear direction as the backrest displaces relative to the support structure, and a spring member provided in a compressed state between the support structure or the seat and the backrest, which deforms as the backrest displaces in the front-rear direction to urge at least the backrest in a direction returning it to the upright state, and the spring member has a biasing direction in the front-rear direction. and a front engaging portion disposed at the front of the spring and a rear engaging portion disposed at the rear of the spring, the support structure or the backrest having a rear spring receiving portion that engages with the rear engaging portion, the seat being arranged forward of the rear supported portion and above the rear spring receiving portion, and having a front spring receiving portion that engages with the front engaging portion, the front supported portion being an elongated hole that passes through the seat in the vertical direction and extends in the front-to-rear direction, the support structure having an engaging protrusion that engages with the elongated hole so as to be movable relative to the front-to-rear direction, and the spring member being arranged in a state compressed from its natural length between the front spring receiving portion and the rear spring receiving portion with the engaging protrusion located at the rear end of the elongated hole.

[0008] In a chair configured in this manner, when the spring member is compressed and attached to a predetermined position in the spring assembly space between the support structure and the seat, the front of the seat is opened by moving the front of the seat upward from the front of the support structure, and the spring member is inserted into the spring attachment space through the opening between the support structure and the seat. The rear engaging portion of the spring member then engages with the rear spring bearing portion provided on the backrest, and the front engaging portion of the spring member is supported by the front spring bearing portion of the seat. The seat is then lowered downward so that it approaches the front of the support structure, allowing the engaging protrusion on the support structure to be inserted into and engaged with the elongated hole that forms the front supported portion of the seat. This allows the spring member to be attached to a predetermined position in a compressed state.

[0009] In this invention, the front supported portion, which serves as a positioning means between the seat and the support structure, is an opening consisting of a long hole that penetrates in the vertical direction. Therefore, when the seat is dropped from above to be supported by the support structure during assembly, the action of dropping the seat allows the engaging protrusion on the support structure to be inserted into and engaged with the long hole in the seat. In other words, there is no need for a special action or a complex structure for the seat, and the engagement structure is simple, as it engages with the engaging protrusion on the support structure, thereby improving work efficiency. In addition, since the front supported portion of the seat is a long hole, the seat can be positioned using the long hole when the seat is fixed to the support structure and the spring member is in the correct position and an initial compression force is applied.

[0010] In addition, the chair of the present invention may be characterized in that the long holes are provided in a pair at a distance from each other in the chair width direction of the seat, and the front spring support portion is provided between the pair of long holes.

[0011] In a chair configured in this way, the elongated hole in the seat and the front spring bearing portion can be spaced apart in the width direction of the chair. This means that the movement of the engaging protrusion of the support structure that engages with the elongated hole within the elongated hole (movement in the front-to-back direction) is less affected by the compressive reaction force of the spring member. This allows for greater freedom in the design of both the elongated hole and the front spring bearing portion.

[0012] In addition, the chair according to the present invention may be configured such that the seat is provided with a reinforcing wall that is disposed between the front spring receiving portion and the elongated hole and extends in the vertical direction.

[0013] In a chair configured in this way, a reinforcing wall extending in the vertical direction is disposed between the front spring bearing portion and the elongated hole, which increases the rigidity of the seat near the front spring bearing portion, which is affected by the biasing force of the spring member. This prevents the moment caused by the biasing force that the front spring bearing portion constantly receives from the spring member from being transmitted to the area near the elongated hole. [Effects of the Invention]

[0014] According to the chair of the present invention, the spring member used to return the backrest to its original position can be easily compressed with a simple structure, thereby improving workability during assembly. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a perspective view of a chair according to an embodiment of the present invention, seen obliquely from the front. [Figure 2] 1 is a perspective view of a chair according to an embodiment of the present invention with upholstery removed, seen obliquely from the rear. FIG. [Figure 3] 1 is an exploded perspective view of a chair according to an embodiment of the present invention. [Figure 4] 1 is a partially exploded side view showing the configuration of a seat, a backrest, and a support base of a chair according to an embodiment of the present invention. [Figure 5] 11 is a vertical cross-sectional view of the configuration in FIG. 4, taken along the line X1-X1 in FIG. 10. [Figure 6] FIG. 2 is a perspective view of the seat support member as seen from diagonally above the front. [Figure 7] FIG. 4 is a plan view of the seat support member as viewed from above. [Figure 8] FIG. 6 is an enlarged view of the main part shown in FIG. 5. [Figure 9] FIG. 10 is a perspective view of a support base provided with a compression coil spring and a portion of a backrest, viewed obliquely from above and in front. [Figure 10] FIG. 10 is a plan view of the configuration shown in FIG. 9 as seen from above. [Figure 11] 11 is a cross-sectional view taken along the line X2-X2 shown in FIG. 10. [Figure 12] 11 is a cross-sectional view taken along the line X3-X3 shown in FIG. 10. [Figure 13] FIG. 2 is a perspective view of the adjustment means and the operating means as seen obliquely from behind. [Figure 14] 1A and 1B are diagrams showing the rotational states of the backrest, in which (a) is a diagram showing the upright state and (b) is a diagram showing the tilted state. [Figure 15] 1(a) to 1(c) are diagrams illustrating the assembly process of a compression coil spring. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, a chair according to an embodiment of the present invention will be described with reference to the drawings. In the following explanation, for the sake of convenience, the direction in which a seated person sitting in a normal posture on seat 5 faces forward will be referred to as "forward," and the opposite direction will be referred to as "rear." Furthermore, the up / down and left / right directions in the following explanation refer to directions that match the direction of the seated person when sitting in a normal posture on seat 5 with the seated person at the center. In the following explanation, the left / right direction in this case will also be referred to as the width direction (chair width direction). Note that an arrow FR pointing forward, an arrow UP pointing upward, and an arrow LH pointing to the left are shown in appropriate places in the drawings.

[0017] As shown in Figure 1, the chair 1 of this embodiment comprises legs 10 placed on the floor surface F, a box-shaped support base 40 placed on top of the legs 10, a seat 5 attached to the top of the support base 40, a backrest 20 attached to the rear of the support base 40 to support the back of the seated person, and armrests 19 extending from both sides of the lower side of the seat 5 to the upper side of the seat 5 on which the seated person's elbows and arms can be rested.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] The plate surface of the inner member 31 faces substantially in the front-to-rear direction. The inner member 31 has an inner vertical extension portion 33 and an inner upper protruding portion 34. The inner vertical extension portion 33 has an inner curved upper portion 331, an inner curved lower portion 332, an inner lower portion 333, and an inner lower fixing portion 334.

[0023] 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.

[0024] The backrest support member 30 of the backrest 20 is fixed to the inner member 31 and the outer member 32, and is provided with a rotating member 38 at the rear of the support base 40 that is rotatable around a first axis C1 in the width direction (left-right direction) via a rotating main shaft 42 (see Figures 4 and 5). The inner member 31 and the outer member 32 are integrated and fixed to the rotating member 38 by inserting a bolt 38a from the mounting recess 353a of the outer lower part 353 of the outer member 32 to the mounting hole 353b, through the mounting hole 334a of the inner lower fixing part 334 of the inner member 31, and through the mounting hole formed in the rotating member 38, and tightening a nut (not shown) onto this bolt 38a.

[0025] 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.

[0026] The backrest 20 configured in this manner is supported rotatably around the first axis C1 (main pivot axis 42) relative to the support base 40, as shown in Figures 1 and 2, and is displaceable in the front-to-rear direction from an upright state P1 (see Figure 14(a)) in which the upper end 20a is positioned relatively forward to a tilted state P2 (see Figure 14(b)) in which the upper end 20a is positioned relatively backward.

[0027] 4 and 5, the seat 5 is provided so as to be displaceable in the front-to-rear direction in accordance with the displacement of the backrest 20 relative to the support base 40. The seat 5 includes a seat body 51 and a seat support member 50 that supports the seat body 51 from below.

[0028] The seat support member 50 is formed in a rectangular shape in plan view from above, so that the seat body 51 can be attached to the upper edge. 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.

[0029] As shown in Figures 5 and 6, the seat support member 50 has an elongated hole 52 (front supported portion) that is supported so as to be movable relative to the front part of the support base 40 in the front-to-rear direction, a rear mounting portion 53 (rear supported portion) that is supported so as to be movable relative to the front part at a position above the first axis C1, and a front spring support portion 55 that rotatably engages with the front part of the compression coil spring 60 described later. The seat support member 50 is positioned forward of the rear mounting portion 53 and above the third axis C3 described later, and is rotatably engaged with the front portion of the compression coil spring 60 around the fourth axis C4 described later.

[0030] 5 to 7, the seat support member 50 has a bottom wall 501 and a side wall 502 standing upright from the periphery of the bottom wall 501. The above-mentioned seat body 51 (see FIG. 4) is attached to the upper end of the side wall 502. The bottom wall 501 extends in the front-rear direction along the outer shape of the compression coil spring 60, which is disposed below, so as not to interfere with the compression coil spring 60, which will be described later, and has a protruding convex portion 503 formed on the upper side.

[0031] 5 and 8, the rear attachment portion 53 is rotatably connected to the rotating member 38 of the backrest support member 30 around a shaft member 39 that extends in the width direction, which will be described later. Here, the central axis of the shaft member 39 is defined as a second axis C2.

[0032] As shown in FIG. 8, the rear attachment portion 53 protrudes downward from the lower rear end of the seat support member 50 and has a rotation shaft hole 531 penetrating in the width direction. The shaft member 39 is rotatably inserted into the rotation shaft hole 531. The rear attachment portion 53 (i.e., the seat support member 50) is rotatable around the shaft member 39 relative to the rotating member 38 (see FIG. 5). That is, as shown in FIG. 5, the seat support member 50 moves rearward relative to the support base 40 when the backrest 20 changes from the upright position P1 (see FIG. 14(a)) to the tilted position P2 (see FIG. 14(b)). Here, an arrow E1 shown in FIG. 5 indicates the movement direction of the seat support member 50 when changing from the upright position P1 to the tilted position P2.

[0033] As shown in Figures 6 and 7, a pair of elongated holes 52 are provided at a distance from each other on both sides in the width direction in the front portion of the bottom wall portion 501. An engaging protrusion 43 (see Figures 9 and 10) protruding upward from the front portion of the support base 40 is slidably engaged with each of the pair of elongated holes 52 along the longitudinal direction (front-rear direction) of the elongated hole 52 while its downward movement is restricted so that it does not slip out of the elongated hole 52. When the backrest 20 tilts, the elongated hole 52 slides rearward relative to the engaging protrusion 43 provided on the support base 40, and the seat support member 50 moves rearward. In other words, when the seat support member 50 moves rearward, the position of the engaging protrusion 43 in the front-rear direction relative to the elongated hole 52 moves from the rearward side to the frontward side.

[0034] 9 to 12, the front spring bearing portion 55 has a pair of fixing portions 551 provided on both sides in the width direction and fixed to the underside of the bottom wall portion 501 of the seat bearing member 50, and a front spring reaction force receiving shaft 552 that connects the pair of fixing portions 551 to each other in the width direction and receives the spring reaction force. Here, the central axis of the front spring reaction force receiving shaft 552 is defined as a fourth axis C4. The front spring bearing portion 55 is provided between a pair of elongated holes 52 that are spaced apart in the width direction.

[0035] The fixed portion 551 is a member formed by bending a plate material into a U-shape and has a pair of reinforcing walls 551A facing each other in the width direction. The reinforcing walls 551A are disposed so that their surfaces are perpendicular to the fourth axis C4 and extend in the up-down direction. A front spring reaction force receiving shaft 552 penetrates each pair of reinforcing walls 551A of the pair of fixed portions 551. The front spring reaction force receiving shaft 552, which is positioned between the pair of reinforcing walls 551A of the fixed portion 551, supports the front portion (front engagement portion 62) of the compression coil spring 60, which will be described later. In this manner, in this embodiment, the reinforcing wall 551A is disposed between the front spring receiving portion 55 and the elongated hole 52.

[0036] The front spring reaction force receiving shaft 552 is a rod member with a circular cross section. The front spring reaction force receiving shaft 552 is inserted through multiple (four) reinforcing walls 551A and is fixed so as not to move in the left-right direction relative to these reinforcing walls 551A. The front engagement portion 62 of a compressed compression coil spring 60 is supported on the front spring reaction force receiving shaft 552 of each fixing portion 551.

[0037] As shown in Figure 3, the support base 40 comprises a support base body 41 (support structure) fixed to the upper part of the leg pillar 12 (see Figure 1), a pivot main shaft 42 that supports the pivot member 38 of the backrest support member 30 rotatably around the first axis C1 in a direction that tilts the pivot member 38 relative to the support base body 41, and an engaging protrusion 43 (see Figures 9 and 10) that supports the seat support member 50 slidably in the front-to-rear direction.

[0038] 5, the support base body 41 has a bottom wall 411 that forms a bottom shielding surface 411a, and a pair of side walls 412 that extend upward from both the left and right sides of the bottom wall 411, and is formed into a bowl shape that opens upward as a whole. In other words, a space (first internal space S1) is formed above the bottom wall 411 and between the pair of left and right side walls 412. The bottom shielding surface 411a is located below the rear engagement portion 63. Two compression coil springs 60 (spring members) are arranged in parallel in the width direction and housed in a first internal space S1 (see FIG. 9) above the support base body 41. The rear end 41a of the support base body 41 protrudes rearward beyond the rear upper parts 412a of the side walls 412. The support base body 41 is provided on the rear upper parts 412a of the side walls 412 located on both the left and right sides so as to be non-rotatable relative to the rotation main shaft 42.

[0039] 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. As shown in Fig. 10, the rotating shafts 42 provided on each of the side walls 412 on both sides in the width direction are coaxial with each other on a first axis C1. Note that the rotating shafts 42 may be provided so as not to be rotatable relative to the rotating member 38.

[0040] 9 and 10, the engaging protrusions 43 are provided on the front upper ends 412b of the side walls 412 on both the left and right sides of the support base body 41 so as to protrude upward. The engaging protrusions 43 have a protruding portion 431 and a sliding portion 432 that is provided on the upper end of the protruding portion 431 and has a larger diameter than the protrusion. The protruding portion 431 is formed in a circular cross section with a diameter that is approximately the same as the width of the elongated hole 52 (see FIGS. 6 and 7) of the seat receiving member 50. The protruding portion 431 of the engaging protrusion 43 is inserted into the elongated hole 52, and the sliding portion 432 is disposed inside the seat receiving member 50.

[0041] The sliding portion 432 of the seat support member 50 is located on the upper surface of the bottom wall portion 501 and between the pair of side wall portions 502. The sliding region of the sliding portion 432 in the inner portion of the seat support member 50 is located at a position that avoids the convex portion 503 (see FIG. 5) that protrudes upward in a shape that follows the outer shape of the compression coil spring 60 described above, and provides a space where the sliding portion 432 does not interfere with other portions. In other words, the position of the elongated hole 52 and the sliding region of the sliding portion 432 are located at positions on both the left and right sides that avoid the pair of compression coil springs 60 when viewed from above.

[0042] The support base body 41 of the support base 40 and the pivoting member 38 are provided with a compression coil spring 60 (spring member) that biases the backrest 20, which is in the tilted state P2 (see Figure 14(b)), and the seat 5, which is displaced in the direction indicated by the arrow E1 in conjunction with the tilting of the backrest 20, in a direction returning to the upright state P1 (see Figure 14(a)), an adjustment means 70 that adjusts the biasing force of the compression coil spring 60, and an operating means 80 that is connected to the adjustment means 70 and operates the adjustment means 70.

[0043] 8 to 10, the rotating member 38 has a rear wall 381 and a pair of side walls 382 (side pieces) extending perpendicularly from both left and right ends of the rear wall 381 and spaced apart in the width direction. A second internal space S2 is formed between the pair of side walls 382. 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 60 is supported in the front part of the second internal space S2.

[0044] A pair of side walls 382 of the rotating member 38 are rotatably supported by the main rotating shaft 42 relative to the rear upper portion 412a of the side wall 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 main rotating shaft 42 in the rotating member 38. The rotating member 38 supports the main rotating shaft 42 at its front portion. The rotating member 38 also includes a shaft member 39 at its rear portion to which the rear mounting portion 53 of the seat receiving member 50 is attached. The rotating member 38 supports an operating shaft 81 of the operating means 80 at a portion intermediate between its front and rear portions.

[0045] 8, the shaft member 39 that constitutes the second axis C2 extends in the width direction. Both sides of the shaft member 39 in the width direction are supported by the side walls 382. A rear attachment portion 53 of the seat support member 50 is rotatably supported by the shaft member 39. In other words, the rear portion of the seat support member 50 is rotatably supported with respect to the rotating member 38.

[0046] 5 and 9 to 12, the compression coil spring 60 is disposed with its biasing direction facing the front-to-rear direction. The compression coil spring 60 is provided in a compressed state between the backrest 20 and the seat 5 (seat support member 50), and is deformed in accordance with the displacement of the seat support member 50 in the front-to-rear direction, thereby biasing the backrest 20 and the seat 5 in a direction returning them to the upright state P1. In other words, the compression coil spring 60 has a restoring force that, by its biasing force, returns the backrest 20 and the seat 5 to their original positions (the upright state P1 shown in FIG. 8) after they have been tilted by a load input from the front to the backrest main body 23 (a load input when the seated person leans their back against the backrest main body 23). The compression coil spring 60 has a front engaging portion 62 provided at one end (front portion) of the compression coil spring 60, and a rear engaging portion 63 provided at the other end (rear portion).

[0047] When the compression coil spring 60 is compressed in the front-to-rear direction, the front engagement portion 62 is displaced rearward and the rear engagement portion 63 is displaced forward. Two compression coil springs 60, with their biasing direction facing the front-to-rear direction, are housed side by side in the width direction in the first internal space S1 of the support basic body portion 41. The pair of compression coil springs 60 are attached in a constantly compressed and biased state whether the backrest 20 is in the upright position P1 (see FIG. 14(a)) or the tilted position P2 (see FIG. 14(b)). More specifically, the compression coil spring 60 is arranged in a state compressed from its natural length (symbol L3 shown in FIG. 15(a)) (a state compressed by symbol L4 shown in FIG. 15(c)) between the front spring bearing portion 55 and the rear spring bearing portion 65 with the engaging protrusion 43 positioned at the rear end of the elongated hole 52.

[0048] The front engagement portion 62 has an outer cylinder 62b that extends toward the rear engagement portion 63 in the axial direction of the compression coil spring 60. The compression coil spring 60 is fitted onto the spring shaft 64. A front portion 64a of the spring shaft 64 is slidably inserted into the outer cylinder 62b of the front engagement portion 62, and a rear portion 64b is engaged with a spring bearing portion 64A that is fixed to the rear engagement portion 63. The rear end of the spring bearing portion 64A has a flange portion 64d that supports the rear end of the compression coil spring 60 from the rear. The peripheral surface of the spring shaft 64 on the rear portion 64b side is provided with a protrusion 64c that protrudes radially outward. The protrusion 64c abuts against a front end 64e of the spring bearing portion 64A from the front side, thereby restricting rearward movement of the spring shaft 64. The front portion of the compression coil spring 60 is fitted onto the outer cylinder 62b of the front engagement portion 62, and the rear portion is fitted onto the spring receiving portion 64A. As the compression coil spring 60 compresses and expands, the outer cylinder 62b of the front engagement portion 62 and the spring receiving portion 64A on the rear engagement portion 63 side move closer to or farther away from each other, thereby changing the distance between them.

[0049] The front engagement portion 62 abuts against the front end of the compression coil spring 60 from the front. The front engagement portion 62 is formed in a U-shape that opens forward when viewed in the width direction. The U-shaped recess 62a (first recess) engages with the front spring reaction force receiving shaft 552 of the front spring receiving portion 55 provided on the seat receiving member 50, pressing it from behind. In other words, the front spring reaction force receiving shaft 552 bears the reaction force of the compression coil spring 60 whether the backrest 20 is in the upright position P1 or the tilted position P2. The front spring receiving portion 55 is positioned rearward of an appropriate position within the front-rear direction range of the elongated hole 52.

[0050] The rear engagement portion 63 abuts against the rear end of the compression coil spring 60 from behind. The rear engagement portion 63 has a through-hole 63a (see FIG. 5) that penetrates in the width direction. A shaft portion 712 of an operating shaft 71 that extends in the direction of a third axis C3 in the width direction of an adjustment means 70 (described later) is inserted into and supported in the through-hole 63a. The backrest 20 is engaged with the rear engagement portion 63 of the compression coil spring 60 so as to be rotatable about the third axis C3. The rear engaging portion 63 may have a second recessed portion that opens rearward instead of the through hole 63a. In this case, the second recessed portion is engaged with the shaft portion 712 from the front in a rotatable state.

[0051] The rear engagement portion 63 is in a state in which a spring force is applied from the front to the operating shaft 71. In other words, the operating shaft 71 bears the reaction force of the compression coil spring 60 whether the backrest 20 is in the upright position P1 or the tilted position P2.

[0052] 5, 8, and 9, the rotating member 38 of the backrest 20 is provided with a rear spring bearing portion 65 that supports the compression coil spring 60 rotatably about the third axis C3 relative to the rear engagement portion 63 at the rear of the compression coil spring 60 via the shaft portion 712 of the operating shaft 71. In other words, the rear engagement portion 63 of the compression coil spring 60 and the rear spring bearing portion 65 are provided rotatably about the third axis C3, with the shaft portion 712 serving as the common third axis C3.

[0053] The rear spring receiving portion 65 is disposed in surface contact with a forward inclined surface 38c (forward surface) facing upward and forward, which is formed on the rotating member 38 of the backrest 20. The rear spring receiving portion 65 is provided so that its position can be adjusted in the vertical direction with respect to the forward inclined surface 38c by an adjustment means 70, which will be described later, and has a receiving surface 65a that is in surface contact with the forward inclined surface 38c.

[0054] The forward inclined surface 38c may have a vertically extending groove formed therein for engaging the receiving surface 65a. The receiving surface 65a is in surface contact with the bottom surface of the groove. In this case, the rear spring receiving portion 65 is movable in the vertical direction but is restricted from moving in the width direction. In other words, the groove allows the rear spring receiving portion 65 to be positioned in the width direction.

[0055] 8, the rear spring receiving portion 65 includes a spring engaging portion 651 that engages with the rear engaging portion 63 of the compression coil spring 60 so as to be relatively movable in response to vertical displacement, and a receiving portion 652 that is disposed rearward of the spring engaging portion 651 and has the above-mentioned receiving surface 65a. Both widthwise side surfaces of the spring engaging portion 651 are disposed at a distance in the widthwise direction from the side walls 382 of the pivoting member 38 of the support structure or backrest 20.

[0056] 9 and 10, the adjustment means 70 has the function of adjusting the biasing force of the compression coil spring 60 and adjusting the restoring force of the backrest 20 in the tilted state P2 (see FIG. 14(b)). The adjustment means 70 is housed in the second internal space S2 between the side walls 382 of the rotating member 38 of the backrest 20. The adjustment means 70 adjusts the position of the rear engagement portion 63 of the compression coil spring 60 in the vertical direction. 9 to 13, the adjustment means 70 includes an action shaft 71 that acts on the biasing force of the compression coil spring 60, an adjustment shaft 72 that movably supports the action shaft 71, and a support member 73 that rotatably supports the adjustment shaft 72 with respect to the operating means 80. The adjustment shaft 72 (central portion, intermediate piece) is located in the center in the width direction.

[0057] 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 operating means 80, which will be described later, so that by operating the operating means 80, 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 along the entire axial direction, with which the operating shaft 71 is threadedly engaged.

[0058] 11, in the upright position P1, the adjustment shaft 72 is disposed such that its axial direction is angled obliquely so that the length gradually increases from the front to the rear as it moves from the lower shaft end 72b to the upper shaft end 72a in a side view. The lower shaft end 72b is located below the rotation main shaft 42 (first axis C1). The upper shaft end 72a is located above and rearward of the rotation main shaft 42. In other words, the operating shaft 71, which moves along the adjustment shaft 72, i.e., the rear engagement portion 63 provided at the rear end of the compression coil spring 60 connected to the operating shaft 71, is configured to move between a position below the rotation main shaft 42 (indicated by the two-dot chain line in FIG. 14(a)) and a position above and rearward of the rotation main shaft 42 (indicated by the solid line in FIG. 14(a)).

[0059] 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 60 rotates around the front engagement portion 62 (first axis C1), and therefore only the angle viewed from the width direction changes.

[0060] 8 and 13, the support member 73 extends in the vertical direction and includes a fixed plate 731 fixed to the rear wall 381 of the rotating member 38 with screws (not shown), and an upper support plate 732 and a lower support plate 733 extending forward from the upper and lower ends of the fixed plate 731. The adjustment shaft 72 is disposed between the upper support plate 732 and the lower support plate 733. As shown in FIG. 11, the adjustment shaft 72 has an upper end 72a rotatably supported by the upper support plate 732 and a lower end 72b rotatably supported by the lower support plate 733.

[0061] 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. As shown in FIG. 10 , the rear engagement portion 63 of the spring member 60 is connected to the shaft portion 712.

[0062] 9, the operating means 80 is provided on the rotating member 38. The operating means 80 has an operating shaft 81 extending in the left-right direction, an operating lever 82 provided at the tip (one end) of the operating shaft 81 that protrudes outward from a side wall 382, ​​and a first transmission gear 83 made of a bevel gear 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 portion of the operating shaft 81 in the width direction that protrudes widthwise from the side wall 382, ​​while the inner end portion in the width direction is positioned within the second internal space S2 and connected to the adjustment means 70.

[0063] The operating shaft 81 is disposed in a state where it protrudes outward from the upper part of the side wall 382 of the rotating member 38. 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.

[0064] A first transmission gear 83 provided in the axial middle of the operating shaft 81 meshes with a 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.

[0065] The operating lever 82 is located to the side in the width direction of the side wall 382 of the rotating member 38, and behind the seat support member 50. In other words, the operating lever 82 is located above and behind the seat support member 50, and is in a position that is easily accessible by the hands of an occupant sitting on the seat 5 on the seat support member 50.

[0066] In the chair 1 configured in this manner, when adjusting the reaction force (returning force) of the backrest 20, first, the operating lever 82 of the operating means 80 is rotated, and the action shaft 71 located at the rear engagement portion 63 of the compression coil spring 60 moves up and down along the adjustment shaft 72. For example, by rotating the operating lever 82 in one direction, the adjustment shaft 72 rotates in one direction via the first transmission gear 83 and the second transmission gear 721, and the nut portion 711 that screws onto the adjustment shaft 72, i.e., the action shaft 71, moves up along the adjustment shaft 72.

[0067] 14(a) and 14(b), the operating shaft 71 moves on the adjustment shaft 72, which changes the distance between the front engagement portion 62 and the rear engagement portion 63 of the spring member 60, thereby adjusting the compression amount of the compression coil spring 60, i.e., the biasing force (reaction force) of the compression coil spring 60. In other words, the return force when the backrest 20 returns from the tilted state P2 to the upright state P1 can be adjusted.

[0068] 14(a) shows the backrest 20 in an upright position P1, and FIG. 14(b) shows the backrest 20 in a tilted position P2. The compression coil spring 60 shown by the solid line in FIG. 14(a) and (b) indicates the upper limit position T1 when the adjustment means 70 is used, and the compression coil spring 60 shown by the two-dot chain line indicates the lower limit position T2 when the adjustment means 70 is used.

[0069] The upper limit position T1 of the rear engagement portion 63 (third axis C3) of the compression coil spring 60, which is adjusted by the adjustment means 70, is set to a position above the first axis C1. As shown in Fig. 5, the upper limit position T1 of the rear engagement portion 63 (third axis C3) is set forward and below the rear attachment portion 53 (second axis C2). Furthermore, the distance L5 between the first axis C1 and the rear engagement portion 63 (third axis C3) at the upper limit position T1 is set to be shorter than the distance between the first axis C1 and the rear attachment portion 53 (second axis C2).

[0070] In this way, the adjustment means 70 of this embodiment is configured so that the position of the action shaft 71, i.e., the position of the rear engagement portion 63 of the compression coil spring 60, is changed by moving the action shaft 71 on the adjustment shaft 72, thereby adjusting the biasing force of the compression coil spring 60 (the return force of the backrest 20). In this embodiment, 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.

[0071] Next, the positional relationship between the above-mentioned axes C1, C2, C3, and C4 will be described in more detail. As shown in Figures 14(a) and (b), in the chair 1 of this embodiment, the first distance L1 between the third axis C3 and the fourth axis C4 is set to be smaller than the second distance L2 between the second axis C2 and the fourth axis C4.

[0072] 15(a), in the chair 1, in the pre-assembly state where the seat receiving member 50 is opened upward with the elongated hole 52 of the seat 5 relative to the front part (engaging protrusion 43) of the support base part 41 of the support base 40, the seat receiving member 50 is configured to open up to a first position N1 where the first distance L1 is greater than the natural length L3 of the compression coil spring 60. In other words, when the seat receiving member 50 is in the first position N1, the front engaging part 62 of the compression coil spring 60, whose natural length L3 is engaged with the rear engaging part 63 of the backrest 20, can be engaged with the front spring receiving part 55 of the seat receiving member 50.

[0073] 15(c), in the assembled state where the seat receiving member 50 is engaged and closed with the elongated hole 52 of the seat 5 against the front part (engaging protrusion 43) of the support base 41 of the support base 40, the first distance L1 is set to a second position N2 where it is shorter than the natural length L3 of the compression coil spring 60. In other words, in the assembled state, the compression coil spring 60 is attached in a state where it has an initial reaction force where a compressive force (symbol F1 shown in FIG. 15(c)) is applied from the front engaging part 62.

[0074] 15(b) shows the state before assembly of the compression coil spring 60, which is at a third position N3 between the first position N1 and the second position N2, where the first distance L1 is shorter than the natural length L3 of the compression coil spring 60. Even in this third position N3, a compressive force (denoted by symbol F1 in FIG. 15(c)) acts on the compression coil spring 60 from the front engagement portion 62.

[0075] In the chair 1 configured as described above, when the compression coil spring 60 is mounted in a compressed state at a predetermined position in the spring assembly space between the support base 41 and the seat-receiving member 50 of the support base 40, the front portion of the seat-receiving member 50 is moved upward away from the front portion of the support base 41 to open the seat-receiving member 50, and the compression coil spring 60 is inserted into the spring assembly space through the opening between the support base 41 and the seat-receiving member 50. Then, the rear engaging portion 63 of the compression coil spring 60 engages with the rear spring receiving portion 65 provided on the backrest 20, and the front engaging portion 62 of the compression coil spring 60 is supported by the front spring receiving portion 55 of the seat-receiving member 50. Thereafter, the seat-receiving member 50 is lowered downward so as to approach the front portion of the support base 41, whereby the engaging protrusion 43 of the support base 41 is inserted into the elongated hole 52, which is the front supported portion of the seat-receiving member 50, and the seat-receiving member 50 is engaged with the engaging protrusion 43 of the support base 41. This allows the compression coil spring 60 to be attached in a predetermined position in a compressed state.

[0076] In this embodiment, the front supported portion, which serves as a positioning means for the seat support member 50 and the support base 40, is an opening consisting of an elongated hole 52 that penetrates in the vertical direction. Therefore, when the seat support member 50 is dropped from above to be supported by the support base 40 during assembly, the action of dropping the seat support member 50 allows the engaging protrusion 43 of the support base 40 to be inserted into and engaged with the elongated hole 52 of the seat support member 50. In other words, there is no need for a special action or for the seat support member 50 to have a complex structure, and the seat support member 50 has a simple engagement structure in which it engages with the engaging protrusion 43 on the support base 40 side, thereby improving work efficiency. Furthermore, since the front part of the seat support member 50 is formed as a long hole 52, the seat support member 50 can be positioned using the long hole 52 when the seat support member 50 is fixed to the support base 40 and the compression coil spring 60 is in the correct position and an initial compression force is applied.

[0077] In this embodiment, a pair of elongated holes 52 are provided at an interval in the width direction of the seat support member 50. The front spring support portion 55 is provided between the pair of elongated holes 52. In the chair 1 configured in this manner, the elongated holes 52 provided in the seat support member 50 and the front spring support portion 55 can be arranged with a distance in the width direction. In other words, the movement of the engaging protrusion 43 of the support base 40 engaged with the elongated hole 52 within the elongated hole 52 (movement in the front-rear direction) is less affected by the compression reaction force of the compression coil spring 60. This increases the degree of freedom in the design of the elongated hole 52 and the front spring support portion 55.

[0078] Furthermore, in the chair 1 of this embodiment, a reinforcing wall 551A extending in the vertical direction is disposed between the front spring receiving portion 55 and the elongated hole 52, which increases the rigidity of the seat receiving member 50 near the front spring receiving portion 55, which is affected by the biasing force of the compression coil spring 60. This prevents the moment caused by the biasing force that the front spring receiving portion 55 always receives from the compression coil spring 60 from being transmitted to the portion near the elongated hole 52.

[0079] The technical scope of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

[0080] For example, in the embodiment described above, the rear engaging portion 63 of the compression coil spring 60 is provided on the backrest 20, but it may also be configured to be provided on the support base body portion 41 (support structure).

[0081] In addition, in this embodiment, a compression coil spring 60 is used as the spring member, but this is not limited to this and other spring members such as a torsion coil spring can also be applied. Furthermore, the spring is not limited to a compression spring and a tension spring such as a tension coil spring can also be used.

[0082] In addition, in this embodiment, a first recess 62a is formed in the front engagement portion 62 of the compression coil spring 60, and the front spring support portion 55 has a front spring reaction force receiving shaft 552 that is coaxial with the fourth axis C4 and engages with the first recess 62a, but the first recess may also be provided in the front spring support portion 55.

[0083] In addition, in this embodiment, the rotating member 38 of the backrest 20 has a pair of side walls 382 spaced apart in the width direction, and the adjustment means 70 is arranged in the space between the side walls 382 (second internal space S2), but the rotating member 38 may be configured without a pair of side walls 382.

[0084] Furthermore, in this embodiment, the second internal space S2 is part of the first internal space S1, but this is not limited to this, and the first internal space S1 and the second internal space S2 may be separate and not overlap each other.

[0085] Furthermore, it is possible to appropriately change the specific configurations and arrangements of the spring member 60, the adjustment means 70, and the operating means 80. For example, although the pair of compression coil springs 60 are used as the spring members in this embodiment, other biasing members may also be used.

[0086] In addition, within the scope of the spirit of the present invention, the components in the above-described embodiments may be replaced with well-known components as appropriate, and the above-described modifications may be combined as appropriate. [Explanation of symbols]

[0087] 1 chair 20 Backrest 20A Backrest structure 30 Backrest support member 38 Rotating member 39 Shaft member 40 base 41 Support body (support structure) 42 Rotating shaft 43 Engagement protrusion 50 Seat support member 51 Seat body 52 Long hole (front supported part) 53 Rear mounting portion (rear supported portion) 55 Front spring support 60 Compression coil spring (spring component) 62 Front engagement part 63 Rear engagement part 65 Rear spring support 70 Adjustment means 71 Axis of action 72 Adjustment axis 80 Operating means 411a Lower shielding surface 552 Front spring reaction bearing shaft C1 First axis center C2 Second axis C3 3rd axis C4 Fourth axis

Claims

1. a support structure; a backrest supported by the support structure so as to be rotatable about a first axis in the chair width direction and displaceable in the front-rear direction between an upright state and a tilted state; a seat having a front supported portion supported so as to be movable relative to the front portion of the support structure in the front-rear direction, and a rear supported portion supported at a position above the first axis, the seat being displaceable in the front-rear direction in accordance with displacement of the backrest relative to the support structure; a spring member that is provided in a compressed state between the support structure or the seat and the backrest, and that deforms in accordance with the displacement of the backrest in the front-rear direction to bias at least the backrest in a direction to return it to the upright state; the spring member is disposed with a biasing direction facing the front-rear direction, and includes a front engaging portion disposed at a front portion of the spring and a rear engaging portion disposed at a rear portion of the spring; the support structure or the backrest includes a rear spring receiving portion that engages with the rear engaging portion, the seat is disposed forward of the rear supported portion and above the rear spring receiving portion, and includes a front spring receiving portion that engages with the front engaging portion, the front supported portion is a long hole that penetrates the seat in the up-down direction and extends in the front-rear direction, the support structure includes an engaging protrusion that engages with the elongated hole so as to be relatively movable in the front-rear direction, The spring member is arranged in a compressed state from its natural length between the front spring receiving portion and the rear spring receiving portion with the engaging protrusion positioned at the rear end of the elongated hole.

2. The long holes are provided in a pair at an interval in the chair width direction of the seat, The chair according to claim 1 , wherein the front spring receiving portion is provided between the pair of elongated holes.

3. 3. The chair according to claim 2, wherein the seat is provided with a reinforcing wall that is disposed between the front spring receiving portion and the elongated hole and extends in the vertical direction.

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