JP2005177180A - Chair - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a chair capable of reducing the manufacturing cost and permitting firmly attaching a bearing to a support without rattling of the bearing, adaptable to the change of the size of a component member. <P>SOLUTION: The support 3 mounted at the upper end of a leg pole has a nearly half-box-shaped support base 4 whose top is open. A U-shaped notch 18 is formed at the upper edge of each side piece 4a of the support base 4, and a plurality of flange-like ribs 24 and 25 are mounted on the outer surface of each bearing 17 at intervals in the axial direction of the bearing 17. The bearing 17 is inhibited from moving in the right or left direction by mounting the bearing 17 on the support base 4 with the edge of the notch 18 in the side piece 4a clasped between the adjacent ribs 24 and 25. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention provides a chair having a pair of left and right bearings pivotally supported on a support base provided at the upper end of a pedestal, with a shaft facing in the left-right direction for pivotally supporting a constituent member of the chair such as a seat and a backrest, In particular, the present invention relates to a bearing support structure.

Some conventional reclining chairs are configured such that the seat moves rearward and downward in conjunction with the backward inclination of the backrest (see, for example, Patent Document 1).
In such a reclining chair, it is necessary to firmly pivot the backrest and the seat on the support base provided at the upper end of the pedestal with the axis facing the left-right direction.
JP 2003-245154 A

  In the chair described in Patent Document 1, since the support base is formed of a molded product such as a synthetic resin material or an aluminum light alloy, a recessed portion for fitting a bearing that pivotally supports the shaft is provided. It can be formed with high accuracy, and rattling of the bearing can be prevented.

However, since it is expensive to form a large support base with high accuracy using a synthetic resin material or the like, it is considered to manufacture the support base at low cost by pressing a sheet metal.
If the support base is made of sheet metal, it is difficult to finish the recess for fitting the bearing as described above with high accuracy, and the bearing may be rattled in the support base. Also, if you try to increase the accuracy, it is rather expensive.

  In addition, when providing a plurality of types of chairs with different backrest and seat dimensions in the left-right direction, it is desired to share parts such as a support base.

  In view of the above-mentioned problems of the prior art, the present invention can reduce the manufacturing cost, can be firmly attached to the support base without rattling the bearing, and can be used to change the dimensions of the constituent members. The purpose is to provide a chair that can be used.

According to the present invention, the above problem is solved as follows.
(1) In a chair in which a shaft facing in the left-right direction is pivotally supported on a support base provided at the upper end of a pedestal with a pair of left and right bearings, and a component member of the chair is rotatably mounted on the shaft. The support base includes a substantially semi-cylindrical support base whose upper surface is open, and a substantially U-shaped cutout is provided on the upper edge of each side piece of the support base. By attaching each bearing to the support base so that the ribs are provided at intervals in the axial direction of the bearing, and the edge of the notch in the side piece is sandwiched between two adjacent ribs, The movement of each bearing in the left-right direction is prevented.

(2) In the above item (1), two bearings adjacent to each other are selected from at least three ribs, and the notch edge of the side piece is sandwiched between the ribs so that each bearing is supported on the support base. By attaching to, it is possible to adjust the amount of protrusion of each bearing outward from the support base.

(3) In a chair in which a shaft facing in the left-right direction is pivotally supported by a support base provided at the upper end of the pedestal with a pair of left and right bearings, and a component member of the chair is rotatably mounted on the shaft. The bearing is sandwiched between a receiving metal fitting provided on the support base and a holding metal fitting attached thereto, and a positioning protrusion is provided on one of the outer peripheral surface of the bearing and the opposite surface of the receiving metal fitting or the holding metal metal fitting facing the bearing, On the other hand, a plurality of positioning holes are provided side by side in the axial direction of the bearing so that the positioning protrusions can be selectively fitted.

(4) In the above items (1) to (3), a concave portion is provided on each of the opposing surfaces of the receiving metal fitting provided on the support base and the holding metal fitting attached thereto, and a bearing is provided in the space formed by the opposing concave parts. The outer peripheral edge of the rib provided on the outer peripheral surface of the bearing is brought into contact with the inner surface of the concave portion, whereby the bearing is held by the receiving metal fitting and the holding metal fitting.

(5) In the above items (1) to (4), the bearing is formed by superposing two semicircular arc-shaped half bearing members facing each other.

(6) In the above items (1) to (5), the shaft is pivotally attached to a support base at a portion extending forward from the lower end of the backrest of the backrest that supports the backrest.

(7) In the above items (1) to (6), the shaft is for pivotally supporting the front portion of the seat as a support base.

(8) In the above item (7), the bearing hole formed in the bearing is a long hole whose longitudinal direction faces the rear lower side.

According to the present invention, the following effects can be achieved.
(a) According to the invention described in claim 1, each bearing is mounted on the support base so that the notch edge of the side base of the support base is sandwiched between two adjacent ribs. Can be prevented from moving in the left-right direction, and can be firmly attached to the support base without rattling the bearing.
Further, the support base can be manufactured at low cost by sheet metal.

(b) According to the invention described in claim 2, each of two ribs adjacent to each other is selected from at least three ribs, and the edge of the notch in the side piece of the support base is sandwiched therebetween, By mounting the bearing on the support base, the amount of protrusion of each bearing from the support base to the outside can be adjusted, and thus the change in the dimensions of the constituent members can be accommodated.

(c) According to the invention described in claim 3, the amount of protrusion of each bearing outward from the support base is adjusted by selecting the positioning hole into which the positioning protrusion fits and mounting the bearing on the support base. Therefore, it is possible to cope with a change in the dimensions of the constituent members.
Also, by fitting the positioning protrusions into any of the positioning holes, it becomes possible to easily align the bearing with the support base. Is prevented.

(d) According to the invention described in claim 4, the rib provided on the bearing not only increases the rigidity of the bearing, but also the outer peripheral edge of the rib abuts against the inner surface of the recess between the receiving metal fitting and the holding metal fitting. Even if the precision of the metal fittings and the holding metal fittings is somewhat poor, it is possible to reliably prevent the bearings from rattling or rotating together with the shaft.
Further, since the receiving metal fitting and the holding metal fitting can be manufactured at low cost by sheet metal, the manufacturing cost can be reduced.
Furthermore, the presser fitting can be removed from the receiving fixture, and the bearing can be easily detached from the support base.
And since it can isolate | separate easily for every member from which material differs, it can also contribute to the separate collection | recovery for every material at the time of disposal.

(e) According to the invention described in claim 5, since the bearing is formed by superposing two semi-arc-shaped half bearing members facing each other, both the half bearing members are separated from each other or vice versa. By assembling in the manner, the shaft can be detached not only from the axial direction of the shaft hole but also from the direction orthogonal thereto, and convenience can be improved.
And since it can isolate | separate easily for every member from which material differs, it can also contribute to the separate collection | recovery for every material at the time of disposal.

(f) According to the invention described in claim 6, the backrest that supports the backrest can be firmly pivotally attached to the support base, and the backrest can be reclined smoothly and stably.

(g) According to the invention described in claim 7, the front part of the seat can be pivotally supported by the support base, and the rear part of the seat can be rotated up and down in conjunction with the tilting of the backrest or the like.

(h) According to the invention described in claim 8, the seat can be moved rearward and downward in conjunction with the tilting of the backrest, etc., and the movement of the seat during reclining can be optimized.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a side view of a reclining chair to which the present invention is applied, and FIG. 2 is an exploded perspective view of an essential part thereof.
This reclining chair has a pedestal (2) erected at the center of five radial legs (1), and a long support base (3) in the front-rear direction rotates at the upper end of the pedestal (2). It is installed freely.

The support base (3) includes a lower metal support base (4) and a synthetic resin support base cover (5) that covers the support base (4).
As shown in FIG. 3 and subsequent figures, the support base (4) has a semi-cylindrical shape with an open upper surface, and a substantially horizontal upper surface plate (6) is formed at the upper end of the rear end on both sides of the support base. It is fixed by welding to the inner surface of the upward side piece (4a) in (4).

As shown in FIG. 7, a fitting hole (7) is provided at the center of the rear portion of the upper plate (6), and a cylindrical body (8) facing vertically is fitted into the fitting hole (7) from below. The diameter-enlarging flange (8a) provided at the lower end of the cylinder (8) is fixed to the lower surface of the upper plate (6) by welding. The upper portion of the cylindrical body (8) has a fitting hole (10) drilled in the upper wall of a lid-like reinforcing material (9) opened at the lower end fixed to the upper surface of the upper plate (6) by welding. The outer peripheral portion is welded to the edge of the fitting hole (10) and reinforced.
An upper end of a gas spring (11) for adjusting the height of the support base (3) provided in the pedestal (2) is fitted into the cylinder (8) from below, whereby the support base ( 3) is supported by a pedestal (2), more specifically a gas spring (11), so that the height can be adjusted.

  At the rear end of the upper surface plate (6), there is a protrusion protruding rearward through a rectangular notch (12) provided in the center of the upper edge of the upward rear piece (4b) in the support base (4). 6a) is formed, and the back of the back of each side piece (6b) (6b) that hangs along the rear side of the rear piece (4b) of the support base (4) from both side ends of the projection (6a) A bearing hole (13) for receiving a shaft (62a) pivotally supporting the front lower end of the tilting gas spring (62) (see FIGS. 1 and 2) is provided. The upper end of the gas spring (62) is connected to the middle part of the backpack (20) with a shaft (62b).

  A front wall (6c) and a front piece (6d) facing the front upper side from the upper end thereof are provided at the front portion of the upper surface plate (6). As shown in FIG. 10, a presser fitting (14) having a substantially U shape in a side view is attached.

  The holding bracket (14) consists of a horizontal piece (14a) that is long in the left and right direction, side pieces (14b) and (14c) that hang from the front and rear edges, and a pair of left and right protrusions that protrude forward and backward from both sides of the lower end. Mounting pieces (14d), (14d), (14e) and (14e), and the horizontal pieces (14a) and the both side pieces (14b) and (14c) form an upward recess. The front side piece (14b) is shorter than the rear side piece (14c) and is slightly inclined forward and downward.

  The presser bracket (14) has its front mounting pieces (14d) and (14d) abutted against the upper surface of the front piece (6d) of the upper surface plate (6) and the rear mounting pieces (14e) and (14e) The face plate (6) is attached to the upper surface of the front portion of the upper face plate (6) by coming into contact with a portion slightly behind the standing wall (6c) and fastening with a screw (15).

As shown in FIG. 3 to FIG. 5 and FIG. 7 to FIG. 10, the left and right sides of the space (16) formed between the presser fitting (14) and the upper plate (6) are substantially square in a side view. A pair of bearings (17), (17) is provided. In addition, a U-shaped notch (18) is cut from the upper end of a portion of the support base (4) that is continuous with the space (16) in both side pieces (4a), through which a bearing (17 ) Can protrude outward.
This bearing (17) (17) is a portion of the pair of left and right dorsal fins (20) (20) supporting the backrest (19) that extends forward from the lower end of the backrest (19). This is for pivotally supporting the left and right shaft (21) provided at the front end portion on the support base (3) (see FIGS. 1 and 2).

  The bearing (17) is composed of a pair of upper and lower half bearing members (22) and (22). Each half bearing member (22) includes a semi-bearing portion (23) having a semicircular arc shape in a side view and an outer periphery of the outer circumference. A plurality of (here, two) semi-circular bowl-shaped ribs (24) provided in the part, and a plurality (eight in this case) provided in the inner part in the side view are substantially rectangular bowls. It consists of a rib (25).

  The ribs (24) and (25) are oriented in a direction perpendicular to the axis of the semi-bearing portion (23), and are appropriately spaced in the direction of the axis. The distance between the second and third ribs (24) and (25) from the outside, and the distance between the fourth and fifth ribs (25) and (25) from the outside are the sides on the support base (4). It is almost equal to the thickness of the piece (4a) (see FIGS. 4 and 8).

In this example, the side shape of each rib (25) of the upper semi-bearing member (22) is a substantially trapezoidal shape with a narrow upper end, and is U-shaped in plan view at the inner end of the semi-bearing portion (23). The upper half bearing member (22) may have the same shape as the lower half bearing member (22), and the upper half bearing member (22) may be simply inverted up and down. .
Incidentally, the notch (26) is provided so as not to interfere with the operation lever for operating the gas spring (11) (not shown).

  The upper and lower semi-bearing members (22) and (22) are fitted into the void (16) in a state where they face each other and overlap each other, and the outer peripheral edge of each rib (25) is a substantially square void ( By contacting the inner surface of 16), rattling in the up-down direction and the front-rear direction is prevented.

  In addition, a notch (25a) is provided in the corner portion of each rib (25) facing the inner surface of the corner portion of the void (16), and the outer peripheral edge of each rib (25) is the corner of the void (16). Since it does not come into contact with the inner surface of the part, there is no need to increase the processing accuracy of the bent part of the presser fitting (14) and the top plate (6), which are difficult to process with high accuracy, and processing becomes easier. Manufacturing cost can be reduced.

  Also, between the second and third ribs (24) and (25) from the outside in the upper and lower half bearing members (22) and (22), or between the fourth and fifth ribs (25) and (25) from the outside. (The latter in the examples of FIGS. 5 and 8), by engaging the edge of the U-shaped notch (18) in each side piece (4a) of the support base (4), each half bearing member The amount of protrusion from each side piece (4a) of the support base (4) in (22) can be selected in two stages, and the edge of the notch (18) is engaged between the two ribs By doing so, the movement and backlash of the half bearing members (22), (22) in the left-right direction with respect to the support base (3) are prevented.

  In this example, as shown in FIG. 10, depending on the range from the front piece (6b) on the top plate (6) to the portion where the rear attachment piece (14e) of the presser fitting (14) is attached, the bearing (17 ) Is formed with a recess for receiving from below. That is, in this example, the receiving metal fitting (27) is formed integrally with the support base (3).

  The upper and lower half bearing members (22) and (22) face each other and overlap each other so that the circular bearing hole (28) formed between the upper and lower half bearing portions (23) and (23) (20) A shaft (21) pivotally supporting (20) is rotatably fitted.

  As shown in FIG. 3, FIG. 4, FIG. 6, and FIG. 7, the U-shaped portion similar to the notch (29) at the rear is formed at the front part of the both side pieces (4a) (4a) of the support base (4). A notch (18) is provided on the inside, and a presser fitting (31) and a receiving metal fitting that are fixed in the support base (4) by sandwiching a bearing (30) with an upper and lower split structure from above and below. (32) is provided.

  The holding metal fitting (31) and the receiving metal fitting (32) have the same shape with a concave portion (33) formed at the center of the metal plate.

  The presser fitting (31) will be described in detail. The presser fitting (31) includes a horizontal piece (34) that is long in the left-right direction, side pieces (35) and (36) that hang from the front and rear edges, and each side piece. (35) (36) with mounting pieces (37) and (38) protruding forward and rearward from the lower end of the rear mounting piece (38) to the rear side piece (36) and the front end of the horizontal piece (34) A notch (39) having a square shape in plan view is formed in the central portion until the end.

On both side edges of the notch (39) in the horizontal piece (34), there are projecting pieces (41) and (41) provided with horizontally long engagement holes (40) for locking the support cover (5). Three positioning holes (42) are arranged in the left-right direction on both sides of the notch (39) in the horizontal piece (34).
Screw insertion holes (43) and screw holes (44) are provided side by side on both sides of the front and rear mounting pieces (37) and (38) so as to form a pair on the left and right.

Since the receiving metal fitting (32) has the same structure and shape as the above-described holding metal fitting (31), the same parts are denoted by the same reference numerals as described above, and are not illustrated in detail, and detailed description thereof is omitted. To do.
That is, the receiving metal fitting (32) is the same as the holding metal fitting (31) rotated by 180 degrees about the axis facing the front-rear direction, and both projecting pieces (41) (41) are provided on the support base (4). One of the positioning holes (42) (in this example, the outermost) is fitted in a recess (45) provided in the center of the front of the support base (4). It is welded to the support base (4) so as to engage with a short positioning pin (45a) (see FIG. 4) projecting from the upper surface of both sides.

  When the presser fitting (31) is placed in a proper position on the receiving bracket (32), the screw hole (44) of the receiving bracket (32) is located directly below the screw insertion hole (43) of the presser fitting (31). Therefore, the four corners of the presser fitting (31) can be received and fastened to the fitting (32) by screwing the screw (46) from above into the screw hole (44) through the screw insertion hole (43).

  The bearing (30) is formed by superposing two upper and lower half bearing members (47) and (47) having the same shape so as to face each other, and each half bearing member (47) divides an oval into two in the longitudinal direction. Shaped semi-bearing portion (48), a plurality (two in this case) of four semi-elliptical bowl-shaped ribs (49) provided on the outer periphery of the outer periphery, and half bearing portion (48) It is composed of a plurality of (in this case, five) substantially triangular ribs (50) provided before and after the outer periphery of the inner portion, and the outer shape in a side view is a concave portion of the presser fitting (31) or the receiving metal fitting (32) ( It is almost complementary to the inner shape of 33).

  Each rib (49) (50) is oriented in a direction perpendicular to the axis of the semi-bearing portion (48) and has an appropriate interval in the direction of the axis. Further, a notch (51) is provided at the tip of each rib (50) facing the inner surface of the corner of the recess (33).

  Further, on the outer peripheral surface of the half bearing portion (48) in each half bearing member (47), there are two of the three positioning holes (42) in the holding fitting (31) or the receiving fitting (32). A positioning projection (52) having a cross shape in a plan view is provided at a position corresponding to.

  The upper and lower half bearing members (47) and (47) are in a state where they are overlapped with each other, and both concave portions (33) and (33) are formed by joining the presser fitting (31) and the receiving fitting (32) to face each other. By fitting into the space (53) formed by the above, a half-hole-shaped bearing hole (54) inclined slightly rearward and downward is formed by the two semi-bearing portions (48) facing each other. Since the outer peripheral edge of each rib (50) is in contact with the inner surface of the substantially rectangular space (16), rattling in the vertical direction and the front-rear direction is prevented.

  As described above, the notch (52) is provided at the tip of each rib (50) facing the inner surface of the corner of the recess (33), and the outer peripheral edge of each rib (50) is the recess (33). Because it does not come into contact with the inner surface of the corner, it is not necessary to increase the processing accuracy of the bent part of the presser fitting (31) or the receiving metal fitting (32), which is difficult to process with high accuracy, making it easy to process Thus, the manufacturing cost can be reduced.

  In addition, two positioning projections (52) provided on each half bearing member (47) are arranged closer to the outside of the three positioning holes (42) in the holding metal fitting (31) or the receiving metal fitting (32). It is possible to select the amount of protrusion from each side piece (4a) of the support base (4) in each bearing (30) in two stages by selecting and engaging the two of them or the two closer to the inside In addition, it is possible to easily align the half bearing member (47) and the receiving metal fitting (32) or the holding metal fitting (31) at the time of assembling. The movement and backlash of the semi-bearing members 47, 47 with respect to 3) in the front-rear direction and the left-right direction are prevented.

  Further, according to the amount of protrusion from the side surface of the support base (4) of each half bearing member (47) determined by which positioning hole (42) the two positioning protrusions (52) are engaged with. Any one of the grooves (55) formed between the plurality of ribs (49), (50) in each half bearing member (47) is placed in front of each side piece (4a) of the support base (4). By engaging with the edge of the U-shaped notch (29) at the center, the lateral movement and rattling of the semi-bearing members (47) (47) with respect to the support base (3) can be prevented more reliably. can do.

  In the bearing hole (54) formed by the front bearing (30), the front horizontal support shaft (59) facing the left-right direction in the square frame-like seat frame (58) supporting the seat (57) Are fitted so as to be rotatable around the axis and slidable downward in the longitudinal direction of the bearing hole (54).

The rear horizontal support shaft (60) facing the left-right direction of the seat frame (58) is connected to the upper surface of the middle portion of the pair of left and right dorsal fins (20, 20) close to the shaft (21) (61) ( 61).
Therefore, when the backrest (19) and the backrest (20) (20) are tilted backward, the rear horizontal support shaft (60) in the seat frame (58) is moved rearward and downward together with the rear portion of the seat (57). Accordingly, the front horizontal support shaft (59) of the seat frame (58) is moved rearward and downward along the bearing hole (54) together with the seat (57).

  The backrest (19) is in a standing position between the lower end of the both side pieces (6b) and (6b) protruding rearward in the upper surface plate (6) and the middle portion of the dorsal fins (20) and (20). A gas spring 62 (see FIGS. 1 and 2) for urging in the direction of is provided, and the front end of the upper surface plate 6 in the support base 4 and the front of the seat frame 58 A compression coil spring (63) for urging the horizontal support shaft (59) forward and an adjusting means (64) for adjusting the urging force are provided between the horizontal support shaft (59) of the portion. However, since they are not directly related to the present invention, a detailed description is omitted.

  The present invention relates to a support structure for the bearings (17) and (30) among the structures of the reclining chair described above, and has the above-described effects of the invention by the configuration described in each claim of the claims. There is an effect.

  In the support structure of the rear bearing (17), as in the support structure of the front bearing (30), the bearing (17) is sandwiched from above and below with a presser fitting and a receiving metal fitting having a vertically symmetrical structure, The support bracket is fixed to the support base (4) or the upper plate (6), or the upper and lower half bearing members (22) and (22) are opposed to the presser fitting (14) or the upper plate (6) opposite thereto. A positioning protrusion similar to the positioning protrusion (52) may be provided on any one of the surfaces, and a positioning hole into which the positioning protrusion is fitted may be provided on the other.

  In addition, the bearing hole (54) of the front bearing (30) is a perfect circle similar to the bearing hole (28) of the rear bearing (17), and the seat ( 57) may be rotated only about the horizontal support shaft (59) without sliding in the front-rear direction.

It is a side view of a reclining chair to which the present invention is applied. Similarly, it is a disassembled perspective view of the principal part. Similarly, it is the perspective view which looked at the support base when the support cover was removed from the rear upper side. Similarly, it is a disassembled perspective view of a support base and a rear bearing. Similarly, it is a partial enlarged perspective view when the rear bearing is mounted on the support base. Similarly, it is a support part of a support base and a front bearing, and an exploded perspective view. Similarly, it is a center vertical side view of only the main members of the support base and the seat frame. Similarly, it is a longitudinal front view longitudinally cut along a vertical plane including the center line of the support shaft at the rear portion of the seat frame. It is a vertical side view of the main member along the IX-IX line of FIG. Similarly, it is an enlarged view of the principal part of FIG.

Explanation of symbols

(1) Leg
(2) Pillar
(3) Support base
(4) Base basis
(4a) Side piece
(4b) Rear piece
(5) Support cover
(6) Top plate
(6a) Projection
(6b) Side piece
(6c) Standing wall
(6d) Front piece
(7) Mating hole
(8) Tube
(8a) Expanded flange
(9) Reinforcing material
(10) Mating hole
(11) Gas spring
(12) Notch
(13) Bearing hole
(14) Presser bracket
(14a) Horizontal piece
(14b) (14c) side piece
(14d) (14e) Mounting piece
(15) Screw
(16) Empty space
(17) Bearing
(18) Notch
(19) Backrest
(20) Backpack
(21) axis
(22) Half bearing member
(23) Half bearing
(24) (25) Rib
(25a) Notch
(26) Notch
(27) Bracket
(28) Bearing hole
(29) Notch
(30) Bearing
(31) Presser bracket
(32) Bracket
(33) Recess
(34) Horizontal piece
(35) (36) side piece
(37) (38) Mounting piece
(39) Notch
(40) Engagement hole
(41) Projection
(42) Positioning hole
(43) Screw insertion hole
(44) Screw hole
(45) Recess
(45a) Locating pin
(46) Screw
(47) Half bearing member
(48) Half bearing
(49) (50) Rib
(51) Notch
(52) Positioning protrusion
(53) Empty space
(54) Bearing hole
(55) Groove
(57) Seat
(58) Seat frame
(59) (60) Horizontal support shaft
(61) Connecting bracket
(62) Gas spring
(63) Compression coil spring
(64) Adjustment means

Claims (8)

In a chair in which a shaft directed in the left-right direction is pivotally supported by a pair of left and right bearings on a support base provided at the upper end of the pedestal, and a constituent member of the chair is rotatably mounted on the shaft.
The support base includes a substantially semi-cylindrical support base whose upper surface is open, and a substantially U-shaped notch is provided on the upper edge of each side piece of the support base, and a plurality of outer circumferences of the bearings are provided. By mounting flanges on the support base so that ribs are provided at intervals in the axial direction of the bearing, and the edge of the notch in the side piece is sandwiched between two adjacent ribs. A chair characterized in that it prevents movement of each bearing in the left-right direction.   At least two ribs adjacent to each other are selected from among at least three ribs, and the bearings are mounted on the support base so that the notch edge of the side piece is sandwiched between them. The chair according to claim 1, wherein the amount of protrusion outward from the base base is adjustable. In a chair in which a shaft directed in the left-right direction is pivotally supported by a pair of left and right bearings on a support base provided at the upper end of the pedestal, and a constituent member of the chair is rotatably mounted on the shaft.
The bearing is sandwiched between a receiving metal fitting provided on the support base and a holding metal fitting attached thereto, and a positioning protrusion is provided on one of the outer peripheral surface of the bearing and the opposite surface of the receiving metal fitting or the holding metal fitting opposite thereto. On the other hand, the chair is characterized in that a plurality of positioning holes are provided in the axial direction of the bearing so that the positioning protrusions can be selectively fitted.   Recesses are provided on the facing surfaces of the receiving metal fitting provided on the support base and the holding metal fitting attached thereto, and the bearings are fitted into the spaces formed by the opposing concave parts, and the ribs provided on the outer peripheral surface of the bearing are provided. The chair according to any one of claims 1 to 3, wherein the outer peripheral edge is brought into contact with the inner surface of the recess to hold the bearing by the receiving metal fitting and the holding metal fitting.   The chair according to any one of claims 1 to 4, wherein the bearing is configured by superposing two semi-arc-shaped half bearing members facing each other.   The chair according to any one of claims 1 to 5, wherein the shaft is pivotally attached to a support base at a portion extending forward from the lower end of the backrest of the backrest that supports the backrest.   The chair according to any one of claims 1 to 6, wherein the shaft is for pivotally supporting the front portion of the seat on a support base.   The chair according to claim 7, wherein the bearing hole formed in the bearing is a long hole whose longitudinal direction faces the rear lower side.

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