chair

Abstract

To provide a chair capable of improving feeling of sitting even when a body is inclined in a longitudinal direction.SOLUTION: A backrest structure 13 comprises a backrest support body 31 connected to a seat part structure, and a backrest body 32 for supporting a back receiving member 33. The backrest support body 31 comprises: a lower support part 42 connected to the seat part structure; pillar parts 43a, 43b extending upward from the lower support part 42; and an upper support part 46 positioned above the pillar parts 43a, 43b. The backrest body 32 comprises an upper fixed part 51 fixed to the upper support part 46, and a lower connection support part 52 supported on the lower support part 42 via a rocking support mechanism 45. The rocking support mechanism 45 supports the lower connection support part 52 on the lower support part 42 rockably in the longitudinal direction.SELECTED DRAWING: Figure 4

Description

[Technical Field]

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

[0002] BACKGROUND ART As described in Patent Document 1 and the like, some chairs equipped with backrests have a backrest position that can be adjusted in the front-to-rear direction to suit the physique and posture of the seated person. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6651799 Summary of the Invention [Problem to be solved by the invention]

[0004] However, a person sitting in a chair may tilt their body left or right while sitting. A backrest that moves forward and backward has difficulty following the movement of the person sitting in either the left or right direction. If the backrest does not follow the movement when the person sitting in the chair tilts left or right, it is difficult to further improve the comfort of the seat. [Means for solving the problem]

[0005] A chair that solves the above problem is a chair with a backrest structure, the backrest structure including a backrest support connected to a seat structure and a backrest main body supported by the backrest support, the backrest support including a lower support portion connected to the seat structure, a support column extending upward from the lower support portion, and an upper support portion located above the support column, the backrest main body including an upper fixed portion fixed to the upper support portion and a lower connection support portion supported by the lower support portion via a swing support mechanism, the swing support mechanism supporting the lower connection support portion so that it can swing left and right relative to the lower support portion. With this configuration, when a user leans their torso left and right, the backrest structure also swings in the same direction. This allows the backrest structure to follow the user's movement, improving sitting comfort.

[0006] The chair may further include a swing shaft provided on one of the lower support portion and the lower connecting support portion, and a receiving portion provided on the other portion, the receiving portion through which the swing shaft is inserted. According to the above configuration, a structure for swinging the backrest body relative to the backrest support member can be realized with a simple configuration.

[0007] In the chair described above, the swing support mechanism may include, in the one portion, a wall portion that defines a space around the swing shaft portion to accommodate the protrusion having the receiving portion formed thereon, and a plate that is placed on a tip surface of the wall portion to close the space. With the above configuration, the backrest main body is prevented from rattling in the front-rear direction relative to the backrest support body.

[0008] In the chair, the support pillar may be configured to have flexibility so that it bends in the swinging direction when the chair swings left and right. According to the above configuration, the support pillar bends when the weight of the user is applied, making it easier for the backrest body to swing.

[0009] In the chair, the pair of support columns may be configured to have narrow portions that bend toward each other, thereby narrowing the gap between them more than the gap between the lower columns. With this configuration, the pair of support columns can be bent so that the amount of displacement of the upper columns is greater than the amount of displacement of the lower columns. [Effects of the Invention]

[0010] With the above-described configuration, the seating comfort can be improved even when the trunk is tilted to the left or right. [Brief explanation of the drawings]

[0011] [Figure 1] This is a perspective view of the chair seen from the front side. [Figure 2] FIG. 2 is a rear view of the chair shown in FIG. [Figure 3] FIG. 2 is a side view of the chair shown in FIG. [Figure 4] 2 is a perspective view of the chair back structure shown in FIG. 1, seen from the rear side. FIG. [Figure 5] FIG. 2 is an exploded perspective view of a swing support mechanism in the chair shown in FIG. [Figure 6] FIG. 2 is an enlarged exploded perspective view of a rocking support mechanism in the chair shown in FIG. [Figure 7] FIG. 10 is a rear view showing a state in which a seated user has tilted their torso left and right. [Figure 8] 10 is a rear view showing the state of the backrest structure when a seated user tilts their torso left or right. FIG. [Figure 9] This is a rear view of the main part of a modified swing support mechanism that does not use a swing shaft portion, showing the backrest body standing upright relative to the backrest support body. [Figure 10] 10 is a rear view of the main part of the swing support mechanism shown in FIG. 9, showing a state in which the backrest main body is tilted relative to the backrest support member. FIG. [Figure 11] FIG. 10 is a rear view of a modified swing support mechanism in which the through-hole of the support piece is configured as a horizontally elongated hole. [Figure 12]FIG. 10 is a cross-sectional view of a modified swing support mechanism in which the tip end surface of the upper wall that contacts the support piece is configured as a convex arc surface. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, a specific embodiment of a chair will be described with reference to FIGS. 1 to 12. FIG. (Overall chair configuration) As shown in Figures 1 and 2, chair 1 includes leg members 11, a seat structure 12, and a backrest structure 13. In this embodiment, chair 1 has seat 22 of seat structure 12 open to allow sitting. This open side is the front side, and the side of seat structure 12 on which backrest structure 13 is located is the rear side. In this embodiment, the left and right directions when viewing seat structure 12 from the front side are the right and left sides, the seat side relative to leg members 11 is the upper side, and the leg member 11 side relative to seat 22 is the lower side.

[0013] The leg member 11 is a leg member with casters. The leg member 11 is provided with a leg post 11a. Leg portions 11b extend radially from the lower end of the leg post 11a. Casters 11c are attached to the tips of the leg portions 11b. A gas spring is built into the leg post 11a. This gas spring adjusts the height of the support base 21 in response to the operation of an operating lever 16 provided on the seat structure 12.

[0014] The seat structure 12 includes a support base 21 and a seat 22. The seat 22 is attached to the top of the support base 21. The seat 22 is configured by layering a cushioning material such as urethane foam on a seat plate and covering it with cloth or the like.

[0015] (Backrest structure) 2 and 3, the backrest structure 13 has a symmetrical shape when viewed from the front-to-rear direction. The backrest structure 13 includes a backrest support 31 and a backrest main body 32. The backrest main body 32 includes a back support member 33.

[0016] The backrest support 31 is connected to the seat structure 12 by a connecting member 39. The backrest support 31 includes a lower support portion 42, a support pillar portion 43, and an upper support portion 46. The connecting member 39 connects the seat structure 12 and the lower support portion 42, and extends below the pedestal 21 from the rear to the front, reaching close to the leg pillar 11a. The connecting member 39 is fixed to the lower support portion 42 by a fixing member such as a screw. The connecting member 39 and the lower support portion 42 may be formed as a single, integrally formed member.

[0017] The lower support portion 42 extends in the left-right direction behind the seat portion 22. The length of the lower support portion 42 in the left-right longitudinal direction is approximately the same as or shorter than the rear edge of the seat portion 22. As shown in FIG. 4, the connecting member 39 of the lower support portion 42 is fixed to the longitudinal center on the surface facing the leg pillar 11a. A swing support mechanism 45 that swingably supports the backrest main body 32 is provided on the rear surface of the lower support portion 42 in the longitudinal center. The swing support mechanism 45 is provided on the opposite side of the connection portion of the connecting member 39. The swing support mechanism 45 will be described in detail below.

[0018] The support column 43 includes a pair of first and second support columns 43a and 43b. The pair of support columns 43a and 43b extend upward from the lower support column 42 while gently curving. Specifically, the pair of support columns 43a and 43b extend upward from below, diagonally rearward, with a gap between them (first gap C1). Next, the pair of support columns 43a and 43b extend upward while the gap between them narrows toward the front (second gap C2). After that, the pair of support columns 43a and 43b extend upward at approximately the same gap (third gap C3). Then, the pair of support columns 43a and 43b open in the left-right direction to form the upper support column 46. That is, a first curved portion 47a is formed in the portion forming the first gap C1, bulging diagonally rearward to widen the gap between them. The portion that defines the second interval C2 defines a second curved portion 47b that bulges forward. The pair of support portions 43a, 43b curve toward each other from the first curved portion 47a to the second curved portion 47b, so that the interval therebetween narrows from the lower first interval C1 to the upper second interval C2. As a result, the portion above the second curved portion 47b is narrower than the first curved portion 47a.

[0019] The upper support portion 46 connects the upper ends of the first support portion 43a and the second support portion 43b and protrudes outward in the left-right direction. That is, the upper support portion 46 includes a connecting portion 46a connecting the upper end of the first support portion 43a and the upper end of the second support portion 43b, a first extension portion 46b extending in one direction from the upper end of the first support portion 43a, and a second extension portion 46c extending in the other direction from the upper end of the second support portion 43b.

[0020] The connecting portion 46a is configured with a component mounting portion for mounting accessories such as a headrest or a jacket hanger. The component mounting portion is configured by closing a component mounting recess provided in the connecting portion 46a with a separate cap 48a. The component mounting recess has its open end facing rearward and is provided in a location that is difficult to see from the front. The component mounting recess is provided with screw holes or the like for fixing the accessory. When attaching an accessory, the cap 48a is removed and the accessory is fixed to the component mounting recess.

[0021] The first extension 46b is provided with a first fixed support portion 48b that fixedly supports the backrest main body 32. The first fixed support portion 48b uses a first fastener to fix the upper fixed portion 51 of the backrest main body 32 to the first extension 46b. The second extension 46c is also provided with a second fixed support portion 48c that fixedly supports the backrest main body 32. The second fixed support portion 48c uses a second fastener to fix the upper fixed portion 51 of the backrest main body 32 to the second extension 46c.

[0022] The backrest main body 32 has, as an example, an annular frame shape. The backrest main body 32 includes an upper fixing portion 51, a lower connecting support portion 52, and first and second vertical frame portions 53a and 53b that connect the left and right sides of the upper fixing portion 51 and the left and right sides of the lower connecting support portion 52. The upper fixing portion 51 has a curved shape that follows the curve of the upper support portion 46 of the backrest support body 31. The vertical frame portions 53a and 53b extend diagonally forward from the upper fixing portion 51 toward the lower connecting support portion 52. The lower connecting support portion 52 has a U-shape, and both sides of the lower connecting support portion 52 protrude forward beyond the left and right sides of the upper fixing portion 51, and is curved so that the center protrudes backward. The left and right sides of the lower connecting support portion 52 are connected to the lower sides of the vertical frame portions 53a and 53b. In the curved lower connection support part 52, a protrusion 54 constituting the swing support mechanism 45 protrudes downward from the central part located at the rearmost part.

[0023] A back support member 33 is tensioned across the backrest body 32 (see FIG. 1). The back support member 33 is, for example, a tension member. The back support member 33 has, for example, a mesh shape, and is tensioned across the upper fixing portion 51, the lower connecting support portion 52, and the vertical frame portions 53a and 53b so as to be able to suitably receive a load from the front.

[0024] (swinging support mechanism) 5, the swing support mechanism 45 includes, as components provided in the lower support portion 42 of the backrest support body 31, a swing shaft portion 61, a wall portion 62 that forms a space 62a around the swing shaft portion 61, and a plate 63 that closes the space 62a. The swing support mechanism 45 includes, as components provided in the lower connection support portion 52 of the backrest body 32, a protrusion 54 and a through-hole 54a formed in the protrusion 54.

[0025] 6, the swing shaft 61 is a cylindrical boss integrally formed on a bottom wall 61a that is part of the lower support part 42, and has a central axis that extends in the front-to-rear direction. The swing shaft 61 protrudes rearward from the flat bottom wall 61a.

[0026] The wall portion 62 includes a lower wall 64a, a pair of vertical walls 64b, 64c located on either side of the lower wall 64a, and an upper wall 64d located above the lower wall 64a. The space 62a is defined by the walls 64a, 64b, 64c, and 64d erected on the bottom wall 61a. A first fixed boss 65a and a second fixed boss 65b are formed on the bottom wall 61a, respectively, on the left and right sides of the pivot shaft portion 61. Both the first fixed boss 65a and the second fixed boss 65b are cylindrical and include insertion holes extending in the front-rear direction. A bolt 69 serving as a fixing member is inserted through the insertion hole. The upper wall 64d includes a recess 66 cut out toward the bottom wall 61a. The protrusion 54 is disposed in the recess 66.

[0027] The tip surfaces of the lower wall 64a and the vertical walls 64b, 64c are at the same height from the bottom wall 61a. The tip surfaces of both sides of the recess 66 in the upper wall 64d are one step lower than the tip surfaces of the lower wall 64a and the vertical walls 64b, 64c. The wall portion 62 has an inner rib 64e formed adjacent to the lower wall 64a on the inside of the lower wall 64a. The inner rib 64e connects the fixing bosses 65a, 65b to the lower wall 64a and the vertical walls 64b, 64c. The inner rib 64e reinforces the fixing bosses 65a, 65b. The tip surfaces of the fixing bosses 65a, 65b are one step lower than the tip surfaces of the lower wall 64a and the vertical walls 64b, 64c. The tip surfaces of the fixing bosses 65a, 65b are at the same height as the tip surfaces of both sides of the recess 66 in the upper wall 64d. The recess 66 of the upper wall 64d is configured as a double wall. That is, the recess 66 of the upper wall 64d is configured as a low wall 64f and a high wall 64g, with the upper wall being the low wall 64f and the lower wall being the high wall 64g. The high wall 64g is the wall that directly contacts the outer surface of the protrusion 54, and the low wall 64f reinforces the high wall 64g. The outer surface of the protrusion 54 is configured as a flat surface, and the tip surface of the high wall 64g is also configured as a flat surface. As a result, the protrusion 54 swings left and right while being guided by the tip surface of the high wall 64g. Shutters may be further provided in the low wall 64f to close the gap between the upper wall 64d on both sides of the recess 66 and the swinging protrusion 54.

[0028] The upper side of the recess 66 is provided with an extension piece 67 that extends upward from the bottom wall 61a. The extension piece 67 overlaps with the protrusion piece 54 supported by the swing shaft portion 61, and is located on the front side of the protrusion piece 54, i.e., on the seat portion 22 side. As a result, the extension piece 67 hides the protrusion piece 54 when viewed from the seat portion 22 side, and also makes it difficult for foreign objects to enter the swing support mechanism 45 from the front.

[0029] The protrusion 54 is a flat plate-shaped piece that protrudes downward from the center of the lower connection support part 52. A through hole 54a is formed in the center of the protrusion 54 as a receiving part. The swing shaft part 61 also has a perfect circle in cross section in a direction perpendicular to the central axis. The through hole 54a is a perfect circle with a larger diameter than the outer diameter of the swing shaft part 61. When the swing shaft part 61 is inserted into the through hole 54a, the protrusion 54 supports the swing shaft part 61 so that it can rotate in the left-right direction, although there is some play with respect to the swing shaft part 61. The protrusion 54 is located within the recess 66 and can rotate in the left-right direction within the range of the left-right width.

[0030] The plate 63 is, for example, made of sheet metal and has a shape corresponding to the shape of the opening surrounded by the wall portion 62. The plate 63 has fixing holes 68 at three locations: a position corresponding to the tip end surface of the pivot shaft portion 61, a position corresponding to the tip end surface of the first fixing boss 65a, and a position corresponding to the tip end surface of the second fixing boss 65b. The plate 63 is placed on the tip end surfaces of the inner rib 64e and the fixing bosses 65a and 65b, and on the tip end surfaces on both sides of the recess 66 in the upper wall 64d. Bolts 69, which serve as fixing members, are inserted through the fixing holes 68 and the insertion holes of the pivot shaft portion 61 and the fixing bosses 65a and 65b. The bolts 69 are tightened by nuts provided on a mounting plate located on the opposite side of the bottom wall 61a from the space 62a. As a result, the space 62a is closed by the plate 63. The plate 63 is fixed to the wall portion 62 after the swing shaft portion 61 is inserted into the through hole 54a of the protrusion 54. As a result, the protrusion 54 is accommodated in the space 62a, and the space 62a is closed by the plate 63, thereby restricting back and forth rattle.

[0031] The relationship between the backrest support member 31 and the backrest main body 32 will be explained using Figure 4. The upper side of the backrest main body 32 is fixed to the backrest support member 31 by the first fixed support member 48b and the second fixed support member 48c, and the lower side can swing left and right from the position of the swing shaft member 61. The support members 43a and 43b of the backrest support member 31 are positioned to extend in the vertical direction between the vertical frame members 53a and 53b of the backrest main body 32. Both the backrest support member 31 and the backrest main body 32 are made of reinforced plastic, for example, a synthetic resin such as nylon containing glass fiber, but the backrest main body 32 is made to be more flexible than the backrest support member 31 to improve sitting comfort.

[0032] However, at least the support pillars 43a and 43b of the backrest support body 31 have flexibility to the extent that they bend in the swinging direction when swinging. When the backrest main body 32 swings left and right around the swing shaft 61, the support pillars 43a and 43b also bend left and right because the backrest main body 32 and the backrest support body 31 are fixed at the top. The backrest main body 32 bends in accordance with the posture of the user 100 at that time. Furthermore, when the user 100 leaves the seat, the backrest main body 32 and the support pillars 43a and 43b elastically return to their upright position.

[0033] (Chair operation explanation) A case will be described in which user 100, seated in chair 1, tilts his or her torso left or right. As shown in FIG. 7 , user 100 bends his or her spine from pelvis 101 to either the left or right. The spine as a whole arches, contracting the half of the body on the twisting side and extending the other side. At this time, user 100 starts moving from head 104, followed by movements of thoracic vertebrae 103, lumbar vertebrae 102, and pelvis 101. The tilt is such that displacement amount B around thoracic vertebrae 103 is greater than displacement amount A around lumbar vertebrae 102 near pelvis 101, and displacement amount C of head 104 above thoracic vertebrae 103 is even greater. That is, the displacement amount of user 100's torso increases from pelvis 101 toward head 104.

[0034] In response to such lateral movement of the user 100, the backrest structure 13 operates as follows. As shown in FIG. 8 , the backrest main body 32 is in contact with the back of the user 100 via the back support member 33. When the user 100 displaces their torso to either the left or the right, the backrest main body 32 swings in the same direction as the torso, with the swing shaft 61 of the backrest support 31 as a fulcrum. At this time, the support columns 43a and 43b of the backrest support 31, which are connected to the backrest main body 32 by being fixed at the upper side, also bend in the same direction. As a result, the entire backrest tilts in the direction of the tilt of the torso. Furthermore, the displacement of the support columns 43a and 43b near the upper support 46 is greater than the displacement of the portion near the lower support 42. In other words, the direction of displacement of the user 100's spine and the direction of displacement of the support columns 43a and 43b are approximately the same.

[0035] According to the above embodiment, the following effects can be obtained. (1) When the user 100 tilts their torso to the left or right, the backrest structure 13 also swings in the same direction. Specifically, the backrest main body 32, on which the back support member 33 is tensioned, swings relative to the backrest support body 31 around the swing shaft 61. This improves the sitting comfort of the user 100.

[0036] (2) The swing support mechanism 45 allows the backrest main body 32 to swing relative to the backrest support 31 by inserting the swing shaft portion 61 on the backrest support 31 side into the through-hole 54a of the backrest main body 32. The swing support mechanism 45 can realize a structure for swinging the backrest main body 32 relative to the backrest support 31 with a simple configuration.

[0037] (3) The protrusion 54 in which the through hole 54a is formed is disposed in the space 62a surrounded by the wall portion 62, and the space 62a is closed by the plate 63. This prevents the backrest main body 32 from rattling in the front-to-rear direction relative to the backrest support body 31.

[0038] (4) The support pillars 43 are strong enough not to bend unless a load equivalent to at least the weight of the user 100 is applied. When such a load is applied, the backrest main body 32 swings relative to the backrest support 31 with the weight of the user 100 being applied. In other words, it is possible to prevent the backrest main body 32 from easily swinging relative to the backrest support 31 with a light load, which would otherwise make the seating uncomfortable.

[0039] (5) The pair of support pillars 43 have a second curved portion 47b above the first curved portion 47a, and the upper portion is made narrower, so that the upper portion can be bent so that the amount of displacement is greater than the amount of displacement below.

[0040] The first embodiment can be modified as follows. The swinging of the backrest body 32 relative to the backrest support 31 is not limited to the configuration of the swing shaft 61 and the through-hole 54a.

[0041] 9 and 10 show a modified example of the swing support mechanism 45 that does not use the swing shaft 61 and the through-hole 54a. In this modified example, the wall 71 of the backrest support 31 that comes into contact with the lower end surface of the protrusion 54 on the backrest main body 32 has a first arc-shaped surface 72 with a first radius. In contrast, the lower end surface of the protrusion 54 on the backrest main body 32 also has a second arc-shaped surface 73. The second arc-shaped surface 73 has a second radius that is smaller than the first radius. In other words, the first arc-shaped surface 72 has a gentler arc-shaped surface than the second arc-shaped surface 73.

[0042] 9 shows the backrest main body 32 in an upright position. In this state, the second central axis 73a of the second arcuate surface 73 is vertical and coincides with the first central axis 72a of the first arcuate surface 72. The position of the first central axis 72a of the first arcuate surface 72 is the point of contact 74 with the second arcuate surface 73.

[0043] 10 shows a state in which the backrest main body 32 is tilted approximately 10 degrees relative to the backrest support body 31. In this case, the second central axis 73a is tilted in the same direction as the first central axis 72a, and the contact point 74 between the first arcuate surfaces 72 moves in the direction in which the backrest main body 32 is tilted. This type of swing support mechanism 45 also makes it possible to support the backrest main body 32 swingably relative to the backrest support body 31.

[0044] 11 shows a modified example of the through-hole 54a formed in the protrusion 54 of the backrest main body 32. The through-hole 54a shown in FIG. 6 and elsewhere is a perfect circle with a larger diameter than the outer diameter of the swing shaft 61. In contrast, the through-hole 75 shown in FIG. 11 is a horizontally elongated hole with its major axis in the left-right direction. This allows the swing shaft 61 to move more freely within the through-hole 75 than in the case of the through-hole 54a. This allows the backrest main body 32 to swing more freely in the left-right direction relative to the backrest support 31.

[0045] 12 shows a modified example of the upper wall 64d of the wall portion 62. The tip surface 76 of the upper wall 64d that contacts the outer surface of the protrusion 54 is configured as a convex arcuate surface with the highest point in the center. The outer surface of the protrusion 54 is flat. As a result, when the protrusion 54 swings, it also tilts in the front-to-back direction following the tip surface 76. This allows the backrest main body 32 to swing not only left-to-right but also front-to-back relative to the backrest support 31. With this configuration, if the through-hole 75 is elongated as shown in FIG. 11, the protrusion 54 can swing more easily in the front-to-back and left-to-right directions.

[0046] The pair of support pillars 43a, 43b may not necessarily have a configuration in which the second curved portion 47b is provided above the first curved portion 47a and the upper portion is narrower. As an example, the pair of support pillars 43a, 43b may be linear and extend straight upward from the lower support portion 42. In this case, the distance between the pair of support pillars 43a, 43b is constant. The curved portions 47a, 47b may have a gently curved shape or an angular shape.

[0047] The flexibility of the pair of support pillars 43a, 43b may be adjusted by the material, by the shape such as the thickness, or by a combination of these. The number of support pillars 43 may be one or three or more.

[0048] The swing support mechanism 45 may be configured without the wall portion 62 for defining the space 62a for arranging the protrusion 54. In this case, the protrusion 54 is exposed. The swing shaft 61 may be provided on the backrest main body 32 side, such as on the protrusion 54, and the through-hole 54a may be provided on the backrest support 31 side, such as on the bottom wall 61a.

[0049] The protruding piece 54 may be omitted, and the through hole 54a may be provided in the lower connection support part 52. The through hole 54a serving as the receiving portion may be a hole with a bottom into which the pivot shaft portion 61 is engaged.

[0050] The plate 63 may be provided with a wall portion 62 to form a space 62a. The wall portion 62 may be a single wall instead of a double wall formed by providing the inner rib 64e. In this case, the wall portion 62 will have the same height except for the recessed portion 66, and the plate 63 will be placed on its tip end surface. In this case, the plate 63 may be placed so as not to protrude from the single wall portion 62.

[0051] The outer peripheral edge of the plate 63 may have a protruding portion that at least partially protrudes from the wall portion 62 . The swing support mechanism 45 can also be configured to be covered with a cover so that it is not easily visible from the outside. In this case, the cover has a size that covers the wall portion 62 and the plate 63. The cover is preferably configured to have hooks on its inner surface so that the hooks can be engaged with the protruding portion of the plate 63. This allows the cover to be attached to the lower support portion 42 without using screws or the like. Of course, the cover may also be fixed to the lower support portion 42 with screws, adhesive, or the like.

[0052] The back support member 33 stretched over the backrest main body 32 is not limited to a mesh sheet, but may be the same fabric upholstery as that used for the seat portion 22. The backrest main body 32 may also be a cushion type such as urethane. In the case of a cushion type, the backrest main body 32 is constructed by placing a cushion material such as urethane on a plate-like or perforated plate and covering it with an impermeable fabric upholstery. In other words, the backrest main body 32 is constructed integrally with the back support member 33. The backrest main body 32 only needs to have at least an upper fixing part 51 and a lower connecting support part 52.

[0053] The chair 1 may have legs that do not include casters 11c. The seat 22 may also be provided with armrests. [Explanation of symbols]

[0054] 1. Chair 12...Seat structure 13...Backrest structure 31...Backrest support 32...Backrest body 33...Back support member 39...Connecting member 42...Lower support part 43(43a,43b)...Strut part 45...Swing support mechanism 46...Top support part 47a...First curved section 47b...Second curved section 48a...Cap 48b...First fixed support part 48c...Second fixed support part 51...Top fixed part 52...Lower connection support part 53a, 53b...Vertical frame section 54...projection piece 54a...Through hole 61...Oscillating shaft 62...Wall part 62a…space 63...Plate 65a, 65b... Fixed boss 66...recess 69...Bolt

Claims

1. A chair having a backrest structure, The backrest structure includes a backrest support connected to the seat structure and a backrest body supported by the backrest support, The backrest support includes a lower support portion connected to the seat structure, a support column portion extending upward from the lower support portion, and an upper support portion located above the support column portion, The backrest body includes an upper fixing portion fixed to the upper support portion and a lower connecting support portion supported by the lower support portion via a swing support mechanism, The swing support mechanism supports the lower connection support part so that the lower connection support part can swing left and right relative to the lower support part, and the support part has flexibility to bend in the swing direction when swinging left and right. chair.

2. The swing support mechanism includes: a swing shaft portion provided in one of the lower support portion and the lower connection support portion; a receiving portion provided in the other portion, the receiving portion through which the swing shaft portion is inserted; The chair of claim 1.

3. The swing support mechanism includes: a wall portion defining a space around the pivot shaft portion in the one portion, the space accommodating the protruding piece having the receiving portion formed thereon; a plate that closes the space by being placed on the tip end surface of the wall portion.

3. The chair of claim 2.

4. The support pillars are a pair, The pair of support pillars are provided with narrow portions that bend toward each other, making the gap between them narrower than the lower portion. A chair according to any one of claims 1 to 3.

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