JP4707060B2 - Chair - Google Patents

Description

  The present invention relates to a chair suitably applied in an office or the like, and relates to a back support device, a seat support device, and a chair that provide a backup function adapted to the behavior of a worker.

  For chairs used in offices, etc., taking into account long-time desk work, etc., to back up the body properly, the shape and angle of the back seat, refresh and rest so that the body during work is not burdened Various ingenuity has been devised, such as the tilt function and the locking function.

  However, in offices, you can rest on one elbow, for example, rest, turn around while sitting and interact with the workers from the side or diagonally, and move documents and other items to the periphery. There are many cases. In such a case, in a conventional chair made with an emphasis on the movement in the front-rear direction, the back can often hinder the movement.

Although it is not a chair used in an office, it is possible to back up body movements necessary for rearward confirmation etc. in a car, as shown in Patent Document 1, considering the movement of the body different from the conventional one. The function of the car seat has been proposed. This seat is provided with a rotation shaft at a position that cuts the center in the width direction, and the upper half of the back that is provided independently of the lower half is rotated around this rotation shaft, so that the body can be twisted. It is a thing.
Japanese Utility Model Publication 4-34111

  However, such a seat function may be suitable as a backup for the operation of turning while holding the steering wheel, but is not necessarily appropriate as a function for backing up an operation performed in an office or the like. In offices and the like, the movement described in the above-mentioned patent publication, such as twisting the body around the spine without moving the spine when moving to the rest or accessing the surroundings when sitting, is rather unnatural. It is accompanied by the behavior of tilting the body while raising and lowering.

  Based on such knowledge, the present invention intends to provide a new and useful chair that can be better adapted to the movement of a seated person in the office.

In order to achieve this object, the present invention takes the following measures.
That is, the chair of the present invention is provided with a base point that can be a pivotal fulcrum at the right and left edges near the lower end of the backrest, and either the left or right base point is the pivotal fulcrum and the other is the floating point. The center that crosses the center in the width direction of the backrest by rotating the fulcrum between the left and right base points according to the direction of the biasing force that acts on the backrest in accordance with the seated person's behavior The backrest is movable so that the line can tilt to the left and right following the behavior of the seated person rising to the right or descending to the right.

If the center of gravity of the body is moved in the width direction while sitting on a general chair, the spine tilts to the left and right as the right shoulder rises and descends. According to the present invention, it is possible to maintain the relative relationship between the seated person and the backrest by causing the backrest to perform exactly such an operation, and the backrest does not get in the way even if the seated person moves, And it becomes possible to maintain an appropriate support state. In addition, since the fulcrum is positioned on the left or right side of the waist that does not move much when the seated person tilts the body to the left or right, the backrest can appropriately follow the back movement. it can.

In order to cope with the movement of the pivoting fulcrum between the left and right base points, the base point is a shaft part fixed to the backrest, and this shaft part is pivotally supported by a bearing provided on the back support base side. It is preferable that the shaft portion serving as the floating point is released from the bearing portion while the shaft portion serving as the pivot fulcrum is pivotally supported on the bearing portion during the rotation.

As a preferred embodiment in this case, the bearing portion is set at the lower end of the long hole of the support member having a long hole, and the floating shaft portion moves freely along the long hole to the upper end of the long hole. Is mentioned.

Alternatively, as another configuration for responding to the operation in which the rotation fulcrum is switched between the left and right base points, the base point is a bearing portion provided on the backrest, and the shaft portion provided on the back support rod side. It is also preferable that the bearing portion that becomes the pivot point when the backrest is pivoted and the bearing portion that becomes the floating point is released from the shaft portion while being pivotally supported on the shaft portion. .

As a preferred embodiment in this case, the bearing portion is set at the upper end of the support member having a long hole, and the floating bearing portion causes the shaft portion to move freely along the long hole to the lower end of the long hole. Is mentioned.

In order to enable appropriate use according to the purpose and application, the shaft portion also serves as a fastener, and the backrest can be selectively fixed by fastening the fastener to the support member. It is desirable to keep it.

As a chair having another configuration of the present invention, by providing a constricted portion that promotes the tilting motion of the backrest at the side edge near the lower end of the backrest, the center line that vertically cuts the center in the width direction of the backrest is Even if the backrest is flexible so that it can tilt or curve to the left and right following the behavior of rising right shoulder or descending right shoulder, the same effects as described above can be achieved.

In order to respond more accurately to the movement of the seated person, the twisting action of the counterclockwise in plan view accompanying the movement of the seated person to the right shoulder or the twisting action of clockwise turning in the plan view accompanying the behavior of the seated person to lower the right shoulder It is desirable that the backrest can change its direction in its twisting direction.

In order to realize such a function simply, the movable surface formed on the back surface of the backrest contacts the backup surface formed on the back support side under different curvatures and rolls in the width direction. What is composed is effective.

  Since the present invention is configured as described above, even if the seated person leans in the direction in which he / she wants to rest or in the direction he / she wants to access, he / she follows the backrest without disturbing him / her, thereby maintaining an appropriate backup state. It is possible to provide a new and useful back support device that can be used.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

The chair of the present embodiment shown in FIGS. 1 and 2 supports a backrest 3 on a back support 1 via a back support device 2, and the back support device 2 is a seated person seated on a seat 8. The backrest 3 is provided with a function of supporting the backrest 3 so as to be movable in the same direction in order to adapt to the twisting operation to the side or obliquely rearward and the tilting operation to the side. In addition, this chair includes a lumbar support 4, and the lumbar support 4 can be directly adjusted to a desired protrusion amount and height position through a simple structure and operation.

  More specifically, the back support rods 1 are rearward and upwardly projecting in pairs, and a backup member 12 is horizontally mounted on the projecting end via a bracket 11, which is shown in FIG. As shown in the figure, a curved plate 12y having a predetermined curvature is formed by plastic deformation processing in a region reaching the left and right end portions adjacent to the central flat portion 12x and having a front surface as a backup surface 12a. Yes. Further, a bearing member 14 shown in FIGS. 2 and 4 and the like is attached to the back support rod 1 in the vicinity of the lumbar portion corresponding to the lumbar spine 1 via a bracket 13. The bearing member 14 has a standing wall 141 having a long hole 141 a extending in a substantially vertical direction, and the standing wall 141 is positioned at a portion facing the lower side edge of the backrest 3.

  On the other hand, as shown in FIGS. 1 and 2, the backrest 3 has a cushion material (not shown) attached to the front side of a relatively hard resin-made backrest inner shell 31 having elasticity, and is stretched from above. The ground 33 is covered up to the portion extending over the back surface, and when the backrest inner shell 31 is formed, the movable member 34 shown in FIGS. 3 and 5 is integrally formed in the corresponding portion of the backup member 12. The movable member 34 has a plate shape with a rear surface as a movable surface 34a, and a curved portion 34y having a predetermined curvature larger than that of the backup surface 12a is formed in a region reaching the left and right ends adjacent to the central flat portion 34x. is doing. And this movable surface 34a is arrange | positioned in the position which faces the said backup surface 12a. That is, the facing distance d between the backup surface 12a and the movable surface 34a is set so as to gradually widen as the curved portions 12y and 34y are displaced in the width direction from the center, and the both surfaces 12a and 34a are in contact with each other. In this state, the movable surface 34a rolls with respect to the backup surface 12a while changing the contact position as shown in FIGS. 3 to 5, for example, so that the backrest 3 can change its direction as indicated by an arrow in FIG. .

  Further, in the present embodiment, as shown in FIGS. 2, 3, 6, and 7 and the like, an auxiliary member 35 having an angular cross section is integrally formed at a position continuous with the movable member 34 when the backrest inner shell 31 is formed. is doing. The auxiliary member 35 is provided with a regulating surface 35a at a position where a predetermined gap P (see FIG. 7) is formed between the auxiliary surface 35a and the regulating surface 35a in a region extending from the center in the width direction to the end. Two gently curved surfaces that protrude rearward are connected to each other, and the gap P is released downward. Then, by covering the movable member 34 and the auxiliary member 35 on the backup member 12 from above, the backup surface 12a is accommodated in the gap P between the movable surface 34a and the regulating surface 35a so as to be capable of relative swinging. That is, in the state of FIG. 3 in which the movable surface 34a is not oscillating, a clearance C is secured at least in a portion other than the center in the width direction between the backup surface 12a and the regulating surface 35a, and the oscillating end shown in FIG. The restricting surface 35a is brought into contact with the backup surface 12a to restrict further swinging of the movable surface 34a. In the drawing, the edge 35ax of the regulating surface 35a is locally in contact with the backup surface 12a, but it may be made to contact widely along the curve. Further, an urging means 36 made of a compressible material such as urethane or a spring material is interposed in the central portion in the width direction between the backup surface 12a and the regulating surface 35a. The movable surface 34a is pressed against the backup surface 12a by urging.

Further, as shown in FIGS. 2 and 4, the backrest 3 is provided with a shaft portion 37, which is a base point that can be a pivotal fulcrum on the right and left edges near the lower end, on the back support 1 side. It is fixed after passing through a long hole 141a extending in the substantially vertical direction of the bearing member 14 provided, and using the lower end of the long hole 141a as the bearing portion 14x, By using one as a rotation fulcrum and the other as a floating point, the backrest 3 can be rotated left and right as indicated by an imaginary line in FIG. Then, the shaft portion 37 serving as a floating point is disengaged from the bearing portion 14x and can be allowed to float along the long hole 141a to the upper end of the long hole 141a. Further, in the present embodiment, the shaft portion 37 is formed in a bolt shape to also serve as a fastener, and the backrest 3 is selectively tilted to the bearing member 14 by being tightened toward the standing wall 141. It can be fixed impossible.

The backrest 3 configured in this way is fixed at least in the front-rear direction to the back support 1 side via the shaft portion 37 and the bearing member 14 even when the backrest 3 is tiltable. The movable surface 34a is basically not constrained other than at least contacting the backup surface 12a in the front-rear direction. For this reason, when a biased load as shown by an arrow W in FIG. 5 acts on a position displaced from the center in the width direction with respect to the backrest 3 from the seated person, the backrest inner shell mainly constituting the backrest 3 The upper surface of the backrest 3 is twisted and deformed downward using the elasticity of 31 and the movable surface 34a is rolled while moving the contact portion with respect to the backup surface 12a. The direction of the upper part of will be changed to the left and right.

In addition, when the seated person performs a behavior of rising right shoulder or descending right shoulder, and a biasing force (for example, an arrow T in FIG. 4) in the direction of turning clockwise or counterclockwise in the back view acts on the backrest 3. The backrest 3 rotates through the shaft portion 35 and the bearing member 14, and the centerline m that vertically cuts the center in the width direction is shown as an imaginary line in FIG. It is designed to be able to be tilted by following the downward movement of the shoulder. The tilted backrest 3 may be returned to the normal position by placing a resin spring or the like at an appropriate site.

In addition to such a configuration, the present invention for positioning the lumbar support 4 and guiding it in the vertical direction using the bracket 13 as shown in FIG. The guide member 5 which is a guide part which concerns on is attached. This guide member 5 is made of a resin, and a metal support shaft 6 for wearing a lumbar support shaft is inserted into a long hole 5a formed between opposing walls 51 and 52 which are paired in the front and rear as shown in FIG. A part thereof constitutes a vertical positioning mechanism A for the lumbar support 4 in cooperation with the support shaft 6.

The vertical positioning mechanism A is a partially cylindrical recess provided at an intermittent position along the vertical direction on the front surface of the opposing wall 52 of the guide member 5 to engage the support shaft 6 with the support shaft 6. 53. In this recess 53, the space between the opposing walls 51 and 52 is expanded in the front-rear direction.

When the plate-like elastic body 54 provided at a part of the guide member 5, specifically, at the intermediate position in the width direction of the front facing wall 51 is viewed from the insertion direction of the support shaft 6, the elongated hole 5 a is narrowed. Even if the support shaft 6 is engaged with any of the recesses 53, the support shaft 6 is elastically biased toward the recess 53 as shown in FIG. At the same time, the support shaft 6 can move between the recesses 53 and 53 against the elastic body 54 as shown in FIG. The elastic body 54 of the vertical positioning mechanism A imparts rotational resistance to the support shaft 6 by pressing the support shaft 6 against the recess 53, making it difficult to turn, so that not only the vertical position of the lumbar support 4 but also the rotation angle is provided. Temporarily holds the action.

On the other hand, the backrest 3 side is elastically deformable by providing a U-shaped slit 31b in the lumbar region 31a of the backrest inner shell 31 as shown in FIGS. The outer wall is fixed to the back support rod 1 so as to correspond to the side of the lumbar region 31a, and the lumbar support 4 is positioned so as to correspond to the lumbar region 31a. That is, the lumbar support 4 is disposed at a position where the cushion material 32 is pressed forward while elastically deforming the lumbar region 31a. Needless to say, a part of the back inner shell 31 is cut out and a resin plate that can be elastically deformed is disposed so as not to hinder the corresponding structure.

With such a configuration, when the support shaft 6 moves up and down, the support shaft 6 is engaged in each recess 53 and positioning in the height direction is performed. Since the recess 53 exists in a direction urged by the elastic body 54, if a load is applied to the backrest 3 from the seated person, the support shaft 6 is more strongly pressed against the recess 53 and engaged.

  And the grip-like operation part 7 shown in FIG.1 and FIG.10 is provided in the right-and-left both ends of this support shaft 6 in the vicinity of the right and left edges of the backrest 3, and the arm is moved backward while the seated person is seated. The left and right operation parts 7 are gripped so that the support shaft 6 can be moved up and down.

  At this time, the support shaft 6 is intermittently engaged with the left and right recesses 53 as the support shaft 6 moves in the vertical direction. Therefore, the engagement between the support shaft 6 and the recess 53 serves as a clue to move the support shaft 6 while keeping the horizontal position if viewed from a different viewpoint than the positioning function. Further, since the recess 53 described above has a partially cylindrical surface extending horizontally, the shape of the recess 53 can also give a clue for guiding the support shaft 6 horizontally.

  On the other hand, as shown in FIG. 2 and the like, the lumbar support 4 in this embodiment includes a prismatic block portion 41 and a support shaft mounting portion 42 formed at a portion displaced from the column axis n of the block portion 41 as a resin. It is formed by integral molding, and is provided with an anti-rotation portion 43 by a screw or the like for axially attaching the support shaft 6 to the support shaft mounting portion 42, and the substantially flat surface of each block portion 41 is shown in FIGS. A support surface S (S (1), S (2), S (3), S (4)) as shown in (d) is provided, and a rounded corner R is provided between the adjacent support surfaces S, S. ing. The support shaft 6 is attached to the support shaft mounting portion 42, and both are fixed by a rotation preventing portion 43 so as to be integrally rotatable.

That is, each support surface S is a pressure receiving surface that receives the load F evenly as shown in FIG. 11A at a predetermined rotational position, and as shown by an arrow V in FIG. When the support 4 is to be rotationally displaced, the region that moves forward by the rotation (the lower half of the support surface S in the figure) approaches the backrest 3 and moves backward by the rotation (the upper surface of the support surface S). The load F is received with priority over the half). In other words, when each support surface S is a pressure receiving surface, the lumbar support 4 is stabilized in a posture in which the portion having the smallest distance from the support shaft 6 is the center position of the pressure reception, and from there, the lumbar support 4 is supported by the support shaft 6. If the occupant tries to rotate in the direction that increases the distance from the occupant, a pressing force is generated in the direction that reduces the distance from the seated person to the lumbar support 4, and the lumbar support 4 attempts to return to a stable direction. The operation of stably holding the lumbar support 4 at the predetermined rotational position is performed. Since the distance L (L (1), L (2), L (3), L (4)) from the support shaft 6 of the support surface S is basically different as shown in FIG. The protrusion amount (that is, L) of the support surface S can be changed depending on whether the surface S (S (1), S (2), S (3), S (4)) is a pressure receiving surface.

  When the above-described operation unit 7 is seated and gripped with both hands and a rotation operation is performed, the lumbar support 4 rotates together with the support shaft 6 so that a desired support surface S can be selected.

Even when no load is applied to the backrest 3 from the seated person, even when the support surface S (3) having the smallest protrusion amount becomes the pressure receiving surface, the resin plate 31a on the back surface of the backrest 3 is pressed to provide a cushioning material. The position of the support shaft 6 is defined so that 32 is in a slightly compressed state. Further, the support surfaces S (2) and S (4) are set at the support shaft 6, and the distances L (2) and L (4) therefrom are the same in this embodiment (FIG. 12). (See (b) and (d)), since the height position with respect to the support shaft 6 when these become the pressure receiving surface is different, it has a simple height position changing function using rotation. it can.

  Although not shown, the back support rod 1 is attached with an outer shell that conceals the mechanical parts attached to the back of the back support rod 1 and the backrest 3. As one form of this outer shell, it has a wall part which protrudes in the shape of a circle toward backrest 1 in a part of the inner shell, and a back support rod is provided at a position that is an outer wall of the wall part and can be concealed from the rear. A structure in which the above-mentioned mechanism part is accommodated in the inner cavity is conceivable. In this case, the above-mentioned tension 33 is wound around the backrest to surround the wall portion so as to surround it. It is preferable to attach in such a state.

As described above, the chair according to the present embodiment is provided with the base point that can serve as a pivot point on the right and left edges near the lower end of the backrest 3 by the shaft part 37, and any of the shaft parts 37 that can serve as the left and right base points. The backrest 3 pivots left and right with one of them as a pivot point and the other as a floating point, and the pivot point is a left and right base point depending on the direction of the urging force acting on the backrest 3 according to the behavior of the seated person By switching between the (shaft portion 37), the center line m that cuts through the center of the backrest 3 in the width direction can be tilted to the right and left following the behavior of the seated person rising to the right or descending to the right. The backrest 3 is movable.

That is, when moving the center of gravity in the width direction while the seated person is seated, the spine is usually tilted left and right while the right shoulder is raised and lowered. According to the present embodiment, by causing the backrest 3 to perform exactly such an operation, the relative relationship between the seated person and the backrest 3 is kept constant, and the backrest 3 follows even if the seated person moves. It is possible to achieve useful effects such as maintaining an appropriate support state without being in the way.

Further, as described above, the backrest 3 of the right side edge portions near the lower end and the base that may be the pivot point at the left edge is provided by the shaft portion 37, either one of the pivot point of the left and right shaft portion 37, on the other hand the base rotation fulcrum depending on the orientation of the urging force of the right and left acting on the backrest 3 with the turning operation on the behavior of the row have and occupant to the backrest 3 is left as a floating point (shaft portion 37) between Then as replaced by, occupant would be positioned a fulcrum less immobile left side edge or right side edge of the waist per Rino sites when performing a behavior to tilt the body to the left and right, the backrest 3 on the back of the movement It can be made to follow appropriately.

The shaft portion 37 is pivotally supported by a bearing portion 14x provided on the back support rod 1 side, and the shaft portion 37 which is a pivotal fulcrum when the backrest 3 is rotated is supported while being pivotally supported by the bearing portion 14x. Since the shaft portion 37 serving as a point is separated from the bearing portion 14x, an operation in which the rotation fulcrum is instantaneously transferred between the left and right base points can be easily realized.

At this time, the bearing portion 14x is set at the lower end of the long hole of the bearing member 14 having the long hole 141a, and the freely moving shaft portion 37 is moved to the upper end of the long hole along the long hole 141a. In addition to guiding the shaft portion 37 to be operated, an appropriate operating resistance can be given between the shaft portion 37 and the bearing member 14, and the movable end is restricted to effectively limit the movable range of the backrest 3. be able to.

Further, since the shaft portion 37 also serves as a fastener and the backrest 3 can be selectively fixed by fastening the fastener to the bearing member 14, depending on the purpose and application, or Whether to use the tilting function of the backrest 3 can be easily selected according to the preference of the seated person.

In particular, the backrest support device 2 can follow the movable surface 34a by changing its direction from side to side when the load W applied to the backrest 3 from the seated person is biased in the same direction from the center of the backrest 3 in the width direction. In combination with the above-described tilting motion of the back, the twisting motion in the counterclockwise direction in plan view accompanying the rising motion of the seated person's right shoulder, or the right view in plan view accompanying the motion of the seated person in descending right shoulder The backrest 3 can be changed in posture in the twisting direction following the torsional motion around.

Therefore, even when the tilting motion of raising the right shoulder or lowering the right shoulder is performed while twisting the body when the seated person is resting or accessing the surrounding area, the backrest 3 is more accurately followed by the seated person's behavior. It becomes possible to make it.

In particular, when twisting the body, it is a natural movement that the part of the back parallel to the spine moves away from the spine as the body rolls while contacting the backrest 3. The movable surface 34a formed on the back surface of the backrest 3 is configured to roll on the backup surface 12a formed on the back support 1 side under different curvatures and roll in the width direction. It is possible to cause the backrest 3 to follow the back movement appropriately by giving the backrest 3 almost the same movement as the seated person.

The specific configuration of each unit is not limited to the above-described embodiment.

For example, as shown in FIG. 13, a bearing portion 114 x is provided on the backrest 3 as a base point, and this bearing portion 114 x is pivotally supported by a shaft portion 137 provided on the back support rod 1 side so that the backrest 3 is rotated. The bearing portion 114x serving as the floating point may be released from the shaft portion 137 while the bearing portion 114x serving as the rotation fulcrum is pivotally supported on the shaft portion 137. Even with such a configuration, it is possible to easily and reliably give an operation in which the rotation fulcrum shifts between the left and right base points.

In this case, the bearing portion 114x is set at the upper end of the bearing member 14 having the long hole 141a, and the floating bearing portion 114x is configured to move the shaft portion 137 to the lower end of the long hole along the long hole 141a. In addition to supporting the floating bearing portion 114x, an appropriate operating resistance can be given between the shaft portion 137 and the bearing member 14 as in the above embodiment, and the back end 3 is restricted by regulating the floating end. Can be effectively defined.

Further, instead of tilting the backrest 3, as shown in FIG. 14, the center line m that vertically cuts the center of the backrest 3 in the width direction follows the movement of the seated person to the right shoulder or to the right shoulder. Even if the backrest 3 is made flexible so that it can be tilted or curved left and right, the same effect as described above can be obtained. In this case, the entire backrest 3 may be configured to be deformable flexibly, but by providing a constricted portion 3p that promotes the tilting action of the backrest 3 at the side edge near the lower end of the backrest 3 as shown in the figure, The required operation can be effectively realized while maintaining the self-supporting shape of the backrest 3 itself to some extent.

Other configurations can be variously modified without departing from the spirit of the present invention.

The perspective view of the chair concerning one embodiment of the present invention. The exploded perspective view. The top view which fractured | ruptured the same part. The rear view. FIG. The side view which fractured | ruptured the same part. The principal part enlarged view of FIG. The expansion perspective view of the guide member in the embodiment. Action | operation explanatory drawing of the vertical positioning mechanism in the embodiment. Explanatory drawing of the operation part in the same embodiment. Action | operation explanatory drawing of the lumbar support in the embodiment. Action | operation explanatory drawing of the lumbar support in the embodiment. The figure which shows the modification of this invention. The figure which shows the other modification of this invention.

Explanation of symbols

3 ... Backrest 37 ... Base point (shaft)
m ... center line

Claims (9)

A base point that can be a rotation fulcrum is provided at the right edge and the left edge near the lower end of the backrest, and the backrest can rotate left and right with one of the left and right base points as the rotation fulcrum and the other as the floating point. The center line that runs through the center of the backrest in the width direction is the right side of the seated person's right shoulder as the rotation fulcrum is switched between the left and right base points according to the direction of the urging force acting on the backrest in accordance with the behavior of the seated person. A chair characterized in that the backrest is movable so that it can tilt to the left and right following the upward movement or the downward shoulder movement. The base point is a shaft part fixed to the backrest, and this shaft part is pivotally supported by a bearing part provided on the back support side, and the shaft part that becomes a pivotal fulcrum when the backrest rotates is used as the bearing part. The chair according to claim 1, wherein the shaft portion serving as a floating point is separated from the bearing portion while being pivotally supported . The chair according to claim 2, wherein the bearing portion is set at the lower end of the long hole of the support member having a long hole, and the floating shaft portion moves freely along the long hole to the upper end of the long hole . The base point is a bearing portion provided on the backrest, and this bearing portion is pivotally supported on a shaft portion provided on the back support rod side, and the bearing portion that serves as a pivotal fulcrum when the backrest rotates is used as the shaft portion. The chair according to claim 1, wherein a bearing portion that becomes a floating point is made free from the shaft portion while being pivotally supported . The chair according to claim 4, wherein the bearing portion is set at an upper end of a support member having a long hole, and the floating bearing portion allows the shaft portion to move freely along the long hole to the lower end of the long hole . The chair according to any one of claims 2 to 5, wherein the shaft portion also serves as a fastening device, and the backrest can be selectively fixed by fastening the fastening device to the support member . By providing a constricted part that promotes the tilting movement of the backrest at the side edge near the lower end of the backrest, the center line that runs through the center in the width direction of the backrest is the behavior of the seated person rising or descending A chair characterized by having a flexible backrest so that it can tilt or curve from side to side following the movement. The backrest is directed in the direction of torsion following the counterclockwise torsional motion in the plan view accompanying the movement of the seated person's right shoulder or in the clockwise direction of the plan view accompanying the behavior of the seated person to lower the right shoulder. The chair according to any one of claims 1 to 7, wherein the chair can be changed . The chair according to claim 8, wherein the movable surface formed on the back surface of the backrest is configured to roll in the width direction while contacting a back surface formed on the back support rod side under different curvatures .

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