JP4818506B2 - Tilt device for backrest in chair - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a tilting device for a backrest in a chair, and more particularly to a support structure for the backrest and a biasing force adjusting means for biasing means for biasing the backrest forward.
[0002]
[Prior art]
A conventional chair that allows the backrest to be tilted backward is pivotally attached to the front end of the pair of left and right dorsal fins that support the backrest with a shaft that faces in the left-right direction. In general, the backrest is always urged with a compression coil spring or a gas spring so that the backrest is directed to the standing position.
In addition, there is a type in which a shaft that pivotally supports the front end portion of the backrest is used as a cylinder shaft, and a torsion bar that biases the backrest toward an upright position is provided therein.
[0003]
[Problems to be solved by the invention]
In the conventional structure as described above, since the shaft hole facing the left and right direction provided at the front end of the dorsal fin is externally fitted to the shaft protruding from the side surface of the support base, stress is applied to the front end of the dorsal fin. In particular, it is vulnerable to twisting of the dorsal fin, and therefore the front end of the dorsal fin is made thick or made of a hard metal material or the like, resulting in high costs. Further, rattling or the like tends to occur between the front end portion of the dorsal fin and the shaft, and the tilting of the dorsal back may be unsmooth.
[0004]
Furthermore, in the case of using a conventional torsion bar, in order to secure the amount of bending of the torsion bar, one end of the torsion bar facing in the left-right direction having a length substantially equal to the interval between the left and right dorsal fins is fixed to the support base side, The other end is fixed to one dorsal fin, and the other dorsal fin is in a so-called scooping state in which the urging force of the torsion bar does not act directly. Therefore, there is a problem that the rigidity of the backrest and the backrest must be increased.
[0005]
In view of the above-mentioned problems of the prior art, the present invention is firmly attached to the support base so that the front end portion of the dorsal fin can be stably and smoothly rotated without rattling or the like. It is an object of the present invention to provide a tilting device for a backrest in a chair that can be supported by a torsion bar and can be urged in a balanced manner by a torsion bar, and has a simple structure and can be manufactured at low cost. It is said.
[0006]
[Means for Solving the Problems]
According to the present invention, the above problem is solved as follows.
(1) A pair of left and right cylinders facing left and right are provided on both side walls of a box-like support supported on a pedestal, and the outer ends of a pair of left and right cylinder shafts supported in both cylinders. Is fixedly fitted to the front end portions of a pair of left and right dorsal fins extending forward from the lower part of the backrest, and the backrest and both dorsal fins are integrated with the cylindrical shaft so that the central axis of the cylindrical body The two ends of the torsion bar, which are pivotally supported around and pivoted around the support base and are loosely fitted in both cylinder shafts and facing the left-right direction, are relatively unrotatable to the front ends of both dorsal fins. The base end of the adjustment plate is fixed to the middle part of the torsion bar between the inner ends of the left and right cylinder shafts, and the center axis of the torsion bar is centered between the front end of the adjustment plate and the support base the angle adjusting means for adjusting the angular position of the adjustment plate to be provided, on both sides of the adjusting plate, have a through hole capable of loosely torsion bar And a pair of bearings made of a synthetic resin having a recess inner ends of each cylindrical shaft outside surface may rotatably fitted, provided as relatively non with respect to said adjustment plate.
[0007]
(2) In the above item (1), the two bushes fitted on the respective cylinder shafts are rotatably fitted to the inner surfaces of both end portions of the cylinder so that the respective cylinder shafts are rotatably provided in the cylinder. .
[0008]
(3) In the above item (2), the outer shape of the cylinder shaft is a polygon, and the fitting hole formed in the front end portion of the back for fitting the cylinder shaft and the fitting hole of the bush are used as the outer shape of the cylinder shaft. And the complement of the polygon.
[0009]
(4) In any one of the above items (1) to (3), the angle adjusting means is screwed into a screw hole provided at the tip of the adjustment plate so that the tip contacts the upper wall of the support base. With adjustment screw.
[0010]
(5) In any one of the above items (1) to (4) , on the inner surface of the left and right bearings, through the hole or notch provided in the adjustment plate, A projecting shaft to be fitted is provided, and both the bearings are engaged with the adjustment plate so as not to be relatively rotatable.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.
As shown in FIGS. 1 and 2, a caster (2) is provided at the tip of the support leg (1) extending radially from the center, and the leg is located at the center of the support leg (1). A column (3) is erected and a support base (4) is fixed to the upper end of the leg column (3).
[0012]
The support base (4) has an L-shape in a side view, extends rearward and upward, and has a pair of left and right dorsal fins (6) that support the backrest (5). The backrest (5) and the backrest (6) are pivotally mounted so as to be pivotable about an axis that faces the direction, and the backrest (5) and the backrest (4) are provided with an elastic reclining mechanism (7) and a tilting range as will be described later. The adjusting device (8) can be tilted backward from the standing position as shown in FIG. 1 within the range defined by the tilting range adjusting device (8).
[0013]
Above the support base (4), the seat (9) moves rearward and downward via the seat support (10) in conjunction with the back tilt (5) and the back lean (6). It is supported in this way. Note that the support structure of the seat (9) and the linkage mechanism with the backrest of the seat (9) are not directly related to the present invention, so detailed description thereof will be omitted.
[0014]
On both sides of the seat receiver (10), armrests (12) are provided via supports (11) extending in the left-right direction.
[0015]
Next, details of the elastic reclining mechanism (7) and the tilting range adjusting device (8) provided in the support base (4) will be described with reference to FIG.
[0016]
The support base (4) has a box shape with an open bottom surface, and its rear portion is fitted to the upper end of the pedestal (3) and is supported on the pedestal (3) so as to be slightly inclined upward. ing.
[0017]
Tapered cylindrical bodies (13) and (14) are formed integrally on the front and rear portions of both side walls (4a) of the support base (4).
[0018]
A pair of left and right cylinder shafts (16) in the form of a hexagonal cylinder are provided in the through hole (15) penetrating each rear cylinder (14) and the side wall (4a) of the support base (4). A pair of bushes (17) and (18) are rotatably supported. The outer ends of the left and right cylinder shafts (16) projecting outward from the cylinder (14) are located on the inner end face of the lateral truncated cone-shaped receiver (19) formed at the front end of the dorsal fin (6). It is fitted into the formed hexagonal hole (20) and fixed by a set screw (21).
[0019]
The inner ends of the left and right cylinder shafts (16) are separated from each other.
In the left and right cylinder shafts (16), a series of elongated torsion bars (22) made of a stack of a plurality of leaf springs are loosely fitted, and both ends of the torsion bar (22) It is press-fitted in a rectangular hole (23) formed at the back end of the hexagonal hole (20) in the receiver (19) of 6), and is fastened by a set screw (not shown) as necessary.
[0020]
In the gap between the inner ends of the left and right cylindrical shafts (16), there is an adjustment plate (25) facing forward, in which the central portion of the torsion bar (22) is inserted into the square hole (24) formed in the base end portion. It is arranged.
[0021]
A cylindrical portion (27) in which a screw hole (26) facing substantially up and down is formed is fixed to the front end of the adjustment plate (25) facing forward.
[0022]
An adjustment screw (29) having a rotary handle (28) at the lower end is screwed into the screw hole (26), and the upper end protruding upward from the screw hole (26) is connected to the upper wall (4b) of the support base (4). ) And the torsion bar (22) when the backrest (5) is in the upright position by adjusting the distance from the upper wall (4b) to the tip of the adjustment plate (25) By adjusting the initial torsion amount, the urging force for returning the backrest (5) to the standing position can be adjusted.
[0023]
Angle adjusting means for adjusting the angular position of the adjusting plate (25) about the central axis of the torsion bar (22) is formed by the screw hole (26) and the adjusting screw (29).
[0024]
The angle adjusting means, the torsion bar (22), the cylindrical shaft (16), the cylindrical body (14), and the like form an elastic reclining mechanism (7).
[0025]
A round hole (30) and a U-shaped notch (31) are provided at a point-symmetrical position around the square hole (24) in the adjustment plate (25).
[0026]
On both sides of the base of the adjustment plate (25), there is an insertion hole (32) through which the torsion bar (22) passes in the center, and the inner end of the cylindrical shaft (16) is rotatably fitted on the outer surface. A pair of bearings (34) made of synthetic resin in which circular recesses (33) to be joined are formed, and bosses (35) projecting from the inner side surfaces thereof are connected to round holes (30 ) And a notch (31), and a projecting shaft (36) projecting on the inner surface of the opposing bearing (34) has an engagement hole (37) drilled in the center of the boss (35). Is provided so that it cannot rotate relative to the adjustment plate (25).
[0027]
On the outside of the inner end of the left and right cylindrical shafts (16) fitted in the recess (33) of the bearing (34), the base end (rear end) of a pair of left and right arms (38) facing forward The hexagonal hole (39) provided in is fitted. A shaft (40) facing in the left-right direction is provided at the tip end portion (front end portion) of both arms (38) so as to protrude to both sides.
[0028]
As shown in FIGS. 3 to 9, on the right side of both arms (38) in the support base (4), there is a first main component of the maximum back tilt angle adjusting means (41) of the backrest (5). Similarly, on the left side, the second regulating member (44) which is the main part of the angle adjusting means (43) of the standing position (initial position) of the backrest (5) is provided on the left side. (4) The upper wall (4b) and the bottom plate (46) screwed to the lower ends of a pair of front and rear bosses (45) suspended from the lower surface thereof are sandwiched from above and below, and each regulating member (42) A groove (47) formed in the upper end of (44) facing in the front-rear direction is slidably engaged with a guide protrusion (48) facing in the front-rear direction formed in the lower surface of the upper wall (4b) of the support base (4). They are arranged so as to match.
[0029]
By moving forward on the inner side surface of the first restricting member (42), the amount of protrusion of the right end portion of the shaft (40) into the vertical turning locus gradually increases, and the shaft (40) In addition, a generally wedge-shaped contact portion (49) is formed so as to make the upward rotation range of the arm (38) small.
[0030]
In this example, the lower surface of the contact portion (49) that is inclined forward and upward is stepped, and the receiving surface (50) of the shaft (40) at each step is arc-shaped close to the outer diameter of the shaft (40). is there.
[0031]
An upper portion of the first restricting member (42) is formed with a hollow hole (51) communicating with the groove (47) from the outer surface, whereby an elastic bending piece (52) is formed on the upper portion, A plurality of concave portions provided with a hemispherical protrusion (53) formed on the central upper surface thereof on one side lower surface of the upper wall (4b) of the support base (4) at the same pitch as the pitch of each receiving surface (50) By selectively engaging with (54), each receiving surface (50) is stably held at a position where it is aligned with the shaft (40).
[0032]
A rectangular step (55) is formed at the front upper corner of the outer surface of the first restricting member (42), and an engagement hole (56) facing in the left-right direction is formed at the back end. It has been drilled. An inwardly bent portion (57a) at the rear end of the rod (57) facing in the front-rear direction for linking to a first operation lever (60) described later is fitted into the engagement hole (56). Yes.
[0033]
A cylindrical shaft (58) facing left and right is rotatably supported in the left cylinder (13) at the front portion of the support base (4), and in the same direction in the cylindrical shaft (58). The core shaft (59) that faces is inserted so as to be relatively rotatable.
[0034]
The left and right ends of the cylindrical shaft (58) and the core shaft (59) projecting outward from the cylindrical body (13) have the same outer diameter in the first and second operating levers (60) and (61). The cylindrical portions (60a) and (61a) are fitted so that the cylindrical portions (60a) are in contact with each other, and the outer cylindrical portion (60a) is fixed to the core shaft (59) with a set screw (62). It is worn.
[0035]
In the first operating lever (60), the operating piece (60b) extends forward from the outer periphery of the cylindrical portion (60a), and the right end of the operating piece (60b) is connected to the second operating lever (61 ) Extends in the direction of the cylindrical portion (61a) by the same length as the cylindrical portion (61a).
[0036]
In the second operating lever (61), the operating piece (61b) extends rearward from the outer periphery of the cylindrical portion (61a), and the left end of the operating piece (61b) is connected to the first operating lever (60). ) Extends in the direction of the cylindrical portion (60a) by the same length as the cylindrical portion (60a).
[0037]
The core shaft (59) protruding from the right end of the cylindrical shaft (58) extends to the vicinity of the right side wall (4a) of the support base (4). A shaft hole (63a) drilled in the base end of (63) is fitted and fixed with a set screw (64).
[0038]
The core shaft (59) moves to the left when the left side surface of the operating arm (63) contacts the right side surface of the bifurcated piece (65) that hangs down from the lower surface of the upper wall (4b) of the support base (4). Is prevented from coming off from the cylinder (13).
[0039]
The inwardly bent portion (57b) at the front end of the rod (57) is fitted in the engaging hole (63b) formed in the distal end of the operating arm (63) and facing in the left-right direction.
[0040]
Thus, by rotating the first operating lever (60) downward, the core shaft (59) and the operating arm (63) are rotated counterclockwise in FIG. 6, and the operating arm ( 63), the rod (57) is pulled forward, and the first restricting member (42) is stepped by engaging the protrusions (53) one by one with each recess (54). The maximum back tilt angle of the backrest (5) can be limited to progressively smaller angles.
[0041]
Conversely, by rotating the first operating lever (60) upward, the first restricting member (42) is gradually moved backward by the reverse operation to the above, and the backrest (5). The maximum rearward tilt angle can be gradually increased.
[0042]
By means of the first regulating member (42), the rod (57), the operating arm (63), the core shaft (59), the first operating lever (60), etc., the maximum back tilt angle adjusting means (5) 41) is formed.
[0043]
By moving backward on the inner side surface of the second restricting member (44), the amount of protrusion of the left end portion of the shaft (40) into the vertical rotation locus gradually increases, and the shaft (40) In addition, a generally wedge-shaped abutting portion (66) is formed so as to make the downward rotation range of the arm (38) small.
[0044]
In this example, the upper surface of the abutting portion (66) that slopes backward and downward is stepped, and the receiving surface (67) of the shaft (40) in each step is arc-shaped close to the outer diameter of the shaft (40). .
[0045]
The rear upper part and the front lower part of the outer side surface (left side surface) of the second restricting member (44) have a large-diameter projecting shaft (69) having a transverse hole (68) facing in the front-rear direction and a small-diameter shaft. A projecting shaft (70) is provided to project.
[0046]
The small-diameter projecting shaft (70) has a front end of a tension coil spring (72) that is locked to a projection (71) projecting outward from the rear end outside of the left bottom plate (46). It is locked.
[0047]
In the lateral hole (68) of the large-diameter protruding shaft (69), it is formed at the rear end of the tension coil spring (73) that has a stronger biasing force than the tension coil spring (72), that is, has a large spring constant. The L-shaped locking portion (73a) thus inserted is inserted and locked.
[0048]
The front end of the tension coil spring (73) is linked to the second operation lever (61) as will be described later.
[0049]
A non-circular fitting portion (58a) formed at the left end portion of the tube shaft (58) is placed in the small diameter tube portion (61c) formed at the right end of the tube portion (61a) of the second operation lever (61). ) And the second operating lever (61) is coupled to the cylindrical shaft (58) while being prevented from rotating.
[0050]
A spur gear (74) is integrally formed at the right end of the cylindrical shaft (58), and this spur gear (74) is formed on the lower surface of the upper wall (4b) of the support base (4) immediately above. An integral sector gear (77) meshes with a shaft (76) rotatably fitted in the provided semi-cylindrical bearing recess (75) (see FIG. 8).
[0051]
An upper end portion of an operating arm (78) having a substantially semicircular arc when viewed from the side is integrally fixed to or integrally formed with the right side surfaces of the shaft (76) and the sector gear (77).
[0052]
An elastic tongue piece (79) is integrally formed in the middle portion of the operating arm (78), and the operating arm (78) is most watched about the axis (76) as shown in FIG. When rotating in the direction, the upper part of the operating arm (78) and the elastic tongue piece (79) elastically grip the portion of the core shaft (59) immediately after exiting the right end of the cylindrical shaft (58), (78) prevents it from turning counterclockwise due to paranoia from that position.
[0053]
The front end portion of the tension coil spring (73) is fixed to the pin (80) protruding rightward from the lower end portion of the operating arm (78).
[0054]
Thus, when the second operating lever (61) faces rearward and upward, as shown in FIG. 7, the operating arm (78) is held in a state in which the core shaft (59) is pressed and gripped. The restricting member (44) is located at the front limit.
[0055]
In this state, the shaft (40) and the arm (38) are in contact with the upper surface of the bottom plate (46) without being blocked by the contact portion (66) of the second restricting member (44). The backrest (5) is, for example, made to face substantially vertical, for example.
[0056]
From this state, when the second operation lever (61) is rotated rearward and downward, for example, stopped in an intermediate substantially horizontal state, the second operation lever (61), the cylinder shaft (58) and its spur gear (74) is rotated clockwise in FIG. 7, and accordingly, the operating arm (78) is rotated counterclockwise around the axis (76) together with the sector gear (77). By rotating the pin (80), the tension coil spring (73) is pushed in the loosening direction.
[0057]
At this time, when the backrest (5) is located at a substantially vertical standing position and the shaft (40) is at the position shown in FIG. 7, the rear end surface of the abutting portion (66) abuts on the front end, and The second restricting member (44) is prevented from moving backward and is held in the position shown in FIG.
[0058]
After that, when the backrest (5) is tilted backward by the seated person and the arm (38) and the shaft (40) are turned upward, the second restricting member (44) is not The two strong and weak tension coil springs (72) and (73) are moved backward to a position where the urging forces of the two springs are balanced.
[0059]
Thereafter, when the backrest (5) is raised, the shaft (40) comes into contact with, for example, the middle receiving surface (67) in the contact portion (66) of the second restricting member (44) moved rearward, It can no longer descend. Therefore, after that, the standing position (return position) of the backrest (5) is a position slightly inclined backward from the vertical state described above.
[0060]
When the second operating lever (61) is rotated to the maximum rearward and downward, the second restricting member (44) has the shaft (40) and the arm (38) turned upward by the same action as described above. After waiting to move, it moves to the rear limit as shown in FIG. 9, and at this time, the backrest (5) can return only to a position tilted considerably backward.
[0061]
When the second operating lever (61) is turned upward from a position facing downward in the rear direction to a desired position, the operating arm (78) is rotated clockwise about the axis (76) in FIG. The front end of the tension coil spring (73) is pulled forward by the pin (80).
[0062]
However, at this time, if the shaft (40) abuts one of the receiving surfaces (67) and the second restricting member (44) is pressed downward, the second restricting member (44) is immediately Does not move, waits for the backrest (5) to be tilted backward by the occupant, moves forward, and makes the standing position of the backrest (5) a desired angle.
[0063]
When the second operating lever (61) is rotated to the upper limit facing rearward and upward, the operating arm (78) elastically grips the core shaft (59) by the elastic tongue piece (79) as shown in FIG. After that, the second restricting member (44) waits for the backrest (5) to be tilted backward, then returns to the front limit, and thereafter, the standing position of the backrest (5) Will be almost vertical.
[0064]
Thus, after the backrest (5) tilts slightly backward, the second restricting member (44) moves to a position where the urging forces of the two tension coil springs (72) and (73) are balanced. Therefore, it is possible to prevent the receiving surfaces (67) of the second restricting member (44) from being worn or damaged.
[0065]
Further, by using the spur gear (74) and the sector gear (77), the rotation stroke of the second operating lever (61) and the operating arm (78) The required amount of rotation can be harmonized.
[0066]
A second restricting member (44), a tension coil spring (72) (73), an operating arm (78), a sector gear (77), a cylindrical shaft (58) provided with a spur gear (74), a second operating lever (61 ) And the like, the angle adjustment means (43) for the standing position is formed, and the tilt range adjustment means (8) for the backrest (5) is formed by this and the above-mentioned maximum rearward inclination angle adjustment means (41). Yes.
[0067]
By restricting the range of movement of the shaft (40) from above and below by means of the maximum rearward tilt angle adjusting means (41) and the angle adjusting means (43) of the standing position, the backrest (5) can be changed to a desired rearward tilt angle. Can be fully restrained.
[0068]
A shaft (82) of the operating lever (81) is pivotally supported in the cylinder (13) at the right front portion of the support base (4), and this shaft (82) serves as a height adjusting means for the seat (9). Although linked, these configurations are not directly related to the present invention, and detailed description thereof will be omitted.
[0069]
As shown in FIG. 10, a pin (83) projecting from a part of the inner end surface of the cylindrical shaft (58) is provided in a vertically long direction provided immediately below the shaft (76) of the operating arm (78). Engage with the hole (84) and rotate the operating arm (78) about the axis (76) via the pin (83) and the long hole (84) as the cylinder shaft (58) rotates. Thus, the spur gear (74) and the sector gear (77) can be omitted.
[0070]
【The invention's effect】
According to the present invention, the following effects can be achieved.
According to the first aspect of the present invention, the left and right dorsal fins are fixed to the cylindrical shaft rotatably supported in the cylindrical body provided on the both side walls of the support base and rotate integrally. It is firmly and stably supported by the support base, and the backrest and backrest can be smoothly rotated without rattling or the like.
Further, the torsion bar can urge the left and right dorsal fins in a well-balanced manner, and the urging force can be adjusted with a simple structure.
Further, the positional relationship among the inner end portion of the cylindrical shaft, the adjustment plate, and the central portion of the torsion bar is stabilized, and the relative movement (rotation) thereof becomes smooth.
[0071]
According to the second aspect of the present invention, the support of each cylindrical shaft is stable, and the backrest can smoothly rotate together with the cylindrical shaft.
[0072]
According to the third aspect of the present invention, only the cylindrical shafts are fitted into the fitting holes of the dorsal fin, so that they are prevented from rotating together, and there is no need to provide special rotation preventing means. Therefore, the structure can be simplified.
[0073]
According to the fourth aspect of the present invention, the structure of the means for adjusting the back biasing force by the torsion bar can be simplified.
[0074]
According to the fifth aspect of the present invention, the left and right bearings can be easily assembled to the adjustment plate, and after assembly, it is possible to reliably prevent the two bearings from being displaced relative to the adjustment plate.
[Brief description of the drawings]
FIG. 1 is a side view of a chair provided with an embodiment of the present invention.
FIG. 2 is an exploded perspective view of the same.
FIG. 3 is an exploded perspective view similarly showing the internal structure of the support base.
4 is an enlarged cross-sectional plan view taken along line IV-IV in FIG. 1. FIG.
5 is a longitudinal side view taken along line VV in FIG. 4. FIG.
6 is a longitudinal side view taken along line VI-VI in FIG. 4;
7 is a longitudinal side view taken along line VII-VII in FIG.
FIG. 8 is an enlarged vertical front view taken along line VIII-VIII in FIG.
9 is a vertical side view similar to FIG. 7, showing another operating state. FIG.
FIG. 10 is an enlarged longitudinal sectional side view of the main part showing a modification of the means for linking the cylinder shaft and the operating arm.
[Explanation of symbols]
(1) Support legs
(2) Casters
(3) pedestal
(4) Support base
(4a) Side wall
(4b) Upper wall
(5) Backrest
(6) Backpack
(7) Elastic reclining mechanism
(8) Tilt range adjustment device
(9) Seat
(10) Seat receiver
(11) Support
(12) Armrest
(13) (14) Tube
(15) Through hole
(16) Tube shaft
(17) (18) Bush
(19) Receiver
(20) Hexagon hole
(21) Set screw
(22) Torsion bar
(23) Square hole
(24) Square hole
(25) Adjustment plate
(26) Screw hole
(27) Tube part
(28) Rotation handle
(29) Adjustment screw (angle adjustment means)
(30) Round hole
(31) Notch
(32) Insertion hole
(33) Recess
(34) Bearing
(35) Boss
(36) Projection shaft
(37) Engagement hole
(38) Arm
(39) Hexagon hole
(40) axis
(41) Maximum backward tilt angle adjustment means
(42) First regulating member
(43) Standing position angle adjustment means
(44) Second regulating member
(45) Boss
(46) Bottom plate
(47) Groove
(48) Guide ridge
(49) Contact part
(50) Reception surface
(51) Meat hole
(52) Elastic flexure
(53) Protrusion
(54) Recess
(55) Step
(56) Engagement hole
(57) Rod
(57a) (57b) Inward bending part
(58) Cylinder shaft
(58a) Mating part
(59) Core shaft
(60) First control lever
(61) Second control lever
(60a) (61a) Tube
(60b) (61b) Operation piece
(61c) Small diameter cylinder
(62) Set screw
(63) Actuating arm
(63a) Shaft hole
(63b) Engagement hole
(64) Set screw
(65) Fork
(66) Contact part
(67) Reception surface
(68) Side hole
(69) Projection shaft
(70) Projection shaft
(71) Protrusion
(72) (73) Tension coil spring
(73a) Locking part
(74) Spur gear
(75) Bearing recess
(76) axis
(77) Sector gear
(78) Actuating arm
(79) Elastic tongue
(80) Pin
(81) Control lever
(82) axis
(83) Pin
(84) Long hole

Claims (5)

A pair of left and right cylinders facing left and right are provided on both side walls of a box-shaped support base supported on the pedestal, and the outer ends of the pair of left and right cylinder shafts supported in both cylinders are connected to the back. It fits in the front ends of a pair of left and right dorsal fins that extend forward from the lower part of the fin, and the dorsal fin and both dorsal fins are united with the cylinder shaft and rotated around the central axis of the cylinder. Both ends of the torsion bar facing left and right fitted loosely in both cylinder shafts are attached to the front ends of both dorsal fins so as not to rotate relative to each other. Between the inner ends of the left and right cylinder shafts, fix the base end of the adjustment plate to the middle of the torsion bar, and adjust the center axis of the torsion bar between the front end of the adjustment plate and the support base provided angle adjustment means for adjusting the angular position of the plate, on both sides of the adjustment plate has an insertion hole capable of loosely fitting the torsion bar, One on the outer surface the inner end of each cylindrical shaft a pair of bearings made of a synthetic resin having a recess which can be rotatably fitted, characterized in that provided as a relatively non-rotatable with respect to said adjustment plate A tilting device for the backrest of a chair.   2. The backrest of the chair according to claim 1, wherein the two bushes that are externally fitted to the respective cylinder shafts are rotatably fitted to the inner surfaces of both end portions of the cylinder so that the respective cylinder shafts are rotatably provided in the cylinder. Tilting device.   The outer shape of the cylinder shaft is a polygon, and the fitting hole formed in the front end portion of the back that fits the cylinder shaft and the fitting hole of the bush are polygons that complement the outer shape of the cylinder shaft. A tilting device for a backrest in the chair according to Item 2.   The angle adjusting means includes an adjusting screw that is screwed into a screw hole provided at a tip portion of the adjusting plate, and that has a tip abutting against the upper wall of the support base. A tilting device for the backrest of a chair. Protruding shafts that fit into the engagement holes drilled in the opposing bearings are provided on the inner surfaces of the left and right bearings through holes or notches provided in the adjustment plate, and the two bearings cannot be rotated relative to the adjustment plate. The tilting device for the backrest in the chair according to any one of claims 1 to 4, wherein the tilting device is engaged.

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