Reclining chair and elasticity adjusting device used for the same

Abstract

To provide a technology to perform adjustment pleasantly in an elasticity adjusting device for changing reclining resistance by changing a contact position of a spring unit with respect to an arm member.SOLUTION: A spring unit 30 includes a compression coil spring 51, a fixed side spring receiver 52, a movable side spring receiver 53, and a case member. The case member includes right and left side plates 55 and an upper lid member 56, and a stopper shaft 92 provided in the movable side spring receiver 53 is fitted into a frame body 94 fixed to the side plates 55. When a cam 40 rotates, a slider 46 moves back and forth, and the spring unit 30 rotates up and down through an inclined guide frame 47. Since the stopper shaft 92 and the frame body 94 are made of metal plate, back and forth positions of the movable side spring receiver 53 do not change even if used over a long period of time, and the state of slidingly contacting an arm member 33 lightly is maintained over a long period of time.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a reclining chair in which a backrest tilts backward against a spring means and an elasticity adjusting device used therein, and more particularly to a technique for adjusting the resistance to the backward tilting movement of the backrest. [Background technology]

[0002] Reclining chairs have a spring means that provides resistance to the backward tilting of the backrest, but they often also have an elasticity adjustment means that changes the magnitude of the spring means' resistance to the backward tilting of the backrest (i.e., the magnitude of the backrest's reaction force acting on the body when reclining). Compression coil springs are often used as the spring means. On the other hand, elasticity adjustment devices are classified into two types: a stepless type that uses a rotary screw, and a step type that uses a cam or lever.

[0003] Mechanisms for changing the resistance of the spring means are roughly divided into a method for changing the initial pressure applied to the spring means and a method for changing the moment acting on the spring means. As the latter method, the applicant of the present application disclosed in Patent Document 1 a method for changing the inclination angle of a rotating spring unit by a cam.

[0004] In Patent Document 1, the rotation center of the spring unit is located at the front end and is in a left-right longitudinal position, so the load caused by the tilting of the backrest acts on the spring unit from behind via the load support arm. On the other hand, the cam is a peripheral cam that is located above the rear of the spring unit so as to rotate around the left-right longitudinal axis, and when the cam is rotated by operating a lever, the position of the spring unit in a side view changes, and the resistance to the backward tilting of the backrest changes. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2013-22082 A Summary of the Invention

[0006] A common elasticity adjustment means for chairs involves receiving one end of a compression coil spring with a rotating hand and adjusting the initial compression force of the coil spring by rotating a handle. However, with this method, the repulsive force of the coil spring acts directly on the handle, which has the problem that there is a large resistance to rotating the handle, and because the resistance is so large, the handle must be rotated many times, making adjustment time-consuming.

[0007] In contrast, in Patent Document 1, the load of the backrest caused by tilting the backrest backward acts as a force to compress the spring unit, but since the direction of the load of the backrest differs from the direction in which the cam abuts against the spring unit, the load of the backrest does not act directly on the cam. Therefore, the cam can be rotated with a light force to easily adjust the elasticity.

[0008] Although Patent Document 1 has these advantages, the inventors of the present application found room for improvement through their research. For example, in Patent Document 1, the movable spring receiver of the spring unit faces an arm-shaped pusher (arm member) that rotates around the rotation axis of the backrest, and the contact position of the movable spring receiver with respect to the pusher is adjusted by rotating the spring unit, but it was anticipated that a situation would occur in which the movable spring receiver would come into strong contact with the pusher in a non-reclining state, making it difficult to rotate the cam smoothly.

[0009] In other words, in Patent Document 1, a coil spring is pretensioned and housed in a synthetic resin case, and the movable spring bearing is attached to the case so that it can move back and forth by a specified stroke. In the non-reclining state, there is a very small clearance between the movable spring bearing and the pusher, or they are lightly abutted against each other, so that the cam can be rotated with a light force. However, there is a concern that the end of the long hole will wear down over time, causing the movable spring bearing to hit the pusher hard in the non-reclining state, making it difficult to rotate the cam.

[0010] The present invention aims to prevent this phenomenon from occurring in advance. [Means for solving the problem]

[0011] Now, why does the movable spring bearing hit the pusher so hard when it is fully advanced? This is because the case constituting the spring unit is made of synthetic resin. In Patent Document 1, the stroke of the movable spring bearing is regulated by inserting a slide pin provided on the movable spring bearing into an elongated hole provided in the case, but if the case is made of synthetic resin, the end of the elongated hole will wear down, albeit very slightly, due to the pressing action of the slide pin during use, and as a result, the forward position of the movable spring bearing in the non-reclining state will be greater than the design value, and there is a risk of it hitting the pusher hard.

[0012] The present invention was made based on such knowledge, and typical examples are specified in each claim. The invention in claim 1 is directed to a reclining chair, and first, "A seatback that can be tilted backward and an elastic adjustment means that provides resistance to the backward tilt of the backrest, The elasticity adjustment means includes an arm member extending in a direction perpendicular to the pivot axis of the backrest, a compression coil spring that expands and contracts in a substantially longitudinal direction to provide resistance to the pivoting of the arm member, a movable spring bearing that moves in a substantially longitudinal direction following the pivoting of the arm member, a fixed spring bearing that supports the compression coil spring on the opposite side to the movable spring bearing, and a case member that holds both spring bearings and the compression coil spring in a state in which the movable spring bearing can move back and forth by a predetermined stroke. This is the structure.

[0013] In addition to the above configuration, "When the case member rotates around the end portion on the fixed spring bearing side as a fulcrum, the contact position of the movable spring bearing against the arm member changes in the vertical direction, thereby changing the elastic resistance to the backward tilting movement of the backrest." The configuration is added, and further features include: "The stopper means for holding the movable spring receiver in the fully advanced position by the compression coil spring is made of metal." It has the following configuration.

[0014] The invention of claim 2 is an example of the development of claim 1. "The case member has metal side plates arranged on both the left and right sides of the compression coil spring, and the left and right side plates are formed with elongated holes through which metal stopper shafts protruding from the movable spring bearing on both the left and right sides can slide freely. The stopper shaft is caused to abut against one end face of the elongated hole, thereby functioning as the stopper means. The structure is as follows.

[0015] The invention of claim 3 is an example of the development of claim 2, "The stopper surface where the stopper shaft and one end face of the elongated hole come into contact has a shape that is long in a direction perpendicular to the moving direction of the stopper shaft in a side view." The structure is as follows.

[0016] In this case, being long in a direction perpendicular to the movement direction of the stopper shaft includes, for example, a straight line in side view, a gentle bow shape, a V shape that spreads out at a large angle, etc. If the stopper shaft is a rectangular corner, the stopper surface will be in the form of a straight line in side view.

[0017] The invention of claim 4 is a development example of claim 2 or 3, "Furthermore, a synthetic resin guide frame is provided to guide the slide of the stopper shaft, The guide frame includes an outer plate that overlaps the outer surface of the side plate and a guide rib that fits into an elongated hole in the side plate, and the outer plate is fixed to the side plate with a screw. The structure is as follows.

[0018] The invention of claim 5 is an example of the development of claim 2, "The case member has a top cover member fixed to the left and right side plates with screws, The upper cover member is provided with a guide means for rotating the case member by an external operation. The structure is as follows.

[0019] The invention of claim 6 is an example of the development of claim 5. "The fixed side spring bearing and the left and right side plates have bearing holes through which hollow shafts for rotating the case member are inserted, and positioning parts are formed to maintain the relative positions of the case members. Furthermore, the case member including the fixed side spring bearing and the left and right side plates is disposed in a space formed in the base, which is a molded product, so as to be immovable from side to side, and is rotatably connected to the base by a support shaft inserted into the hollow support shaft. The structure is as follows.

[0020] The invention of claim 7 is an example of the development of claim 6. "As the positioning portion, a cylindrical boss protruding outward to the left and right and a protruding portion located below the cylindrical boss are formed on the fixed side spring bearing, and the side plate is fitted into the cylindrical boss, and the front portion of the side plate rests on the protruding portion." The structure is as follows.

[0021] The invention of claim 8 is directed to an elasticity adjusting device, "An elastic adjustment device that provides resistance to the backward tilt of a backrest, a movable spring bearing that moves back and forth by rotation of an arm member extending in a direction intersecting the rotation axis of the backrest; a compression coil spring that is compressed by the movable spring bearing; a fixed-side spring bearing that supports the compression coil spring from a side opposite to the movable-side spring bearing; a case member that holds both the spring bearings and the compression coil spring in a state in which the movable spring bearing can move back and forth by a predetermined stroke, In a configuration in which the case member rotates in the vertical direction around the end portion of the fixed spring bearing as a fulcrum, the contact position of the movable spring bearing with respect to the arm member changes in the vertical direction, thereby changing the elastic resistance to the backward tilting movement of the backrest, The stopper means for holding the movable spring receiver in the fully advanced position by the compression coil spring is made of metal. The structure is as follows. Effect of the Invention

[0022] In the present invention, the stopper means of the movable spring bearing is made of metal, so the stopper means will not wear out even with long-term use, and the movable spring bearing can be held in a specified forward position. Therefore, when adjusting the elasticity by using a cam or the like to rotate the case member, it can be operated with light force for a long period of time. In addition, the clearance (or contact condition) between the arm member and the movable spring bearing can be maintained at the design value with high precision, so rattling of the arm member can be prevented.

[0023] The stopper means can have various configurations, but if a combination of a metal stopper shaft and a metal side plate is used as in claim 2, the case material necessary for holding the compression coil spring is utilized, thereby ensuring the stopper function with a simple structure.

[0024] In claim 2, it is possible to form the stopper shaft into a circle as in Patent Document 1, but if the stopper shaft is set to move smoothly, the radius of the stopper shaft becomes smaller than the radius of curvature of the end of the long hole, causing the stopper shaft and the end of the long hole to come into one-sided contact and become susceptible to wear. In this regard, by adopting the configuration of claim 3, even if the stopper shaft slides smoothly through the long hole, the stopper surface (contact surface) between the stopper shaft and the end of the long hole can be lengthened to reliably prevent wear.

[0025] Therefore, it is possible to prevent sagging and wear without making the side plates excessively thick, and to maintain high stopper function while making the product as light as possible (maintaining high quality and durability). Forming the stopper shaft into a square shape as in the embodiment is particularly advantageous because it allows the use of commercially available square bars (square wire rods).

[0026] By adopting the configuration of claim 4, the slide of the stopper shaft is guided by a guide frame made of synthetic resin, so that metal parts do not rub against each other and generate abnormal noises, allowing the chair to be used comfortably.

[0027] In the configuration of claim 5, the case member is made of three parts, so it is easier to process than a one-piece molded product. In addition, it is also possible to freely combine sheet metal processed products and resin molded products, which is excellent in terms of design freedom. Since the case member rotates using the upper cover member that constitutes it, it is possible to reduce the number of parts in the entire device, and there is also the advantage that the movement can be made more reliable by eliminating play between the parts.

[0028] To allow rotation, the case member needs to be pivotally supported at one end by a component of the chair, but if it is connected to the base using a pivot as in claim 6, it can be easily adapted even if the base is a molded product such as a die cast product, since it can be placed inside the base with the pivot removed and then the pivot inserted. Also, since the fixed side spring bearing and the side plate are held in their respective positions by the positioning part, they can be firmly fixed with a small number of screws. In this case, adopting the configuration of claim 7 has the advantage that rattling of the side plate can be firmly prevented by the double positioning of the cylindrical boss and the overhanging part.

[0029] The present invention also includes the elasticity adjustment device of claim 8. If each component is preassembled and made into a unit, it is preferable to reduce the labor required for assembling the chair. In addition, by making it into a unit, high dimensional accuracy can be ensured, which has the advantage of preventing quality variations due to the skill level of the workers. [Brief description of the drawings]

[0030] [Figure 1]1A is a front perspective view, FIG. 1B is a rear perspective view from below, and FIG. 1C is a partially separated rear perspective view showing the appearance of a chair according to an embodiment. [Diagram 2] (A) is a side view in the neutral state, (B) is a side view in the reclining state, and (C) is an exploded perspective view. [Diagram 3] 13(A) and 13(B) are exploded perspective views of the main parts. [Figure 4] FIG. [Diagram 5] FIG. [Figure 6] FIG. 2A is a perspective view of a spring unit as viewed from below, and FIG. 2B is a perspective view of the spring unit as viewed from above. [Figure 7] 1A is an exploded perspective view of the spring unit, and FIG. 1B is a perspective view of the cam in a horizontal position. [Figure 8] 13(A) and (B) are diagrams for explaining the operation, and (C) is a partially separated side view of the side plate and the guide frame. [Figure 9] 1A is a partially separated perspective view of a spring unit, FIG. 1B is a top perspective view showing the support structure of an outer shell, and FIG. 1C is a bottom perspective view showing the support structure of an outer shell. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] Next, an embodiment of the present invention will be described with reference to the drawings. In the following, the terms front, back, left and right are used to specify directions, but these directions are defined as directions seen from a person normally sitting on the chair. The front view is a view seen from the direction opposite the seated person.

[0032] (1) Overall Overview First, an overview of the chair will be described with reference to Figures 1 and 2. This embodiment is applied to a swivel chair that is widely used in offices. The chair comprises a leg device 1, a seat 2, and a backrest 3 as basic elements. The leg device 1 has a structure in which a leg support 4 made of a gas cylinder is erected in the center of a base having five leg blades, and a caster is provided at the tip of each leg blade.

[0033] 1 and 2, a base 5 is fixed to the upper end of the leg support 4, and the lower tips of left and right first tilting frames 6 are connected to the base 5 by first support shafts 7. As shown in Figs. 1(B) and (C), the first tilting frame 6 extends rearward from the base 5 and rises up, spreading outward on the left and right, and the upper part of the first tilting frame 6 constitutes the lower side members 8a of the lower back frame 8. Left and right long lower members 8b that constitute the lower end of the lower back frame 8 are connected to the lower ends of the left and right lower side members 8a.

[0034] 1(B) and (C), an upper back frame 9 with a loop structure that is open in the front and rear directions is connected to the upper ends of the left and right lower side members 8a by a second support shaft (pin) 10 on the left and right longitudinal sides. The lower end of the upper back frame 9 is composed of a lower frame part 9a that protrudes backward, and a second tilting frame (center frame) 11 is disposed between the left and right intermediate parts of the lower frame part 9a and the rear end part of the base 5, and the second tilting frame 11 is connected to the lower frame part 9a and the base 5 by a third support shaft and a fourth support shaft (neither of which are shown in the figures) on the left and right longitudinal sides.

[0035] Therefore, the first tilting frame 6, the second tilting frame 11 and the back frames 8, 9 rotate relative to each other while tilting backward as a whole. Specifically, as can be seen from Figures 2(A) and (B), due to the difference in the front-back position and the up-down height of each support shaft 7, 10, the upper back frame 9 rotates forward relative to the lower back frame 8 during reclining. The backrest 3 includes a back panel 12 made of a flexible resin material such as elastomer, and an upholstery 12a stretched on the front surface of the back panel 12. A top rest 13 that supports the head and neck of a seated person is attached to the upper end of the upper back frame 9 in a height-adjustable manner. A lumbar support device 14 that supports the back panel 12 from the front is attached to the lower part of the second tilting frame 11.

[0036] As shown in Fig. 2(C), the seat 2 comprises a resin inner shell (seat plate) 15 and a cushion 16 placed on top of it, and the inner shell 15 is supported from below by a resin outer shell (seat support member) 17. The front part of the inner shell 15 is formed with a plurality of rows of left and right longitudinal slits to form a deformation-permitting part 15a that can be rolled up downward, while the outer shell 17 is fitted with a movable support 18 connected to the front end of the deformation-permitting part 15a so as to be movable back and forth. For example, as shown in Figs. 1(A) and (B), a depth adjustment handle 19 for moving the movable support 18 back and forth is arranged on the left side of the outer shell 17.

[0037] For example, as shown in Figures 1(B) and (C), the first tilting frame 6 is formed with support arms 20 that extend outward to the left and right and have their front ends protruding upward, and a rear bearing portion 21 provided at the rear of the outer shell 17 is connected to the support arms 20 with left and right long pins 22 (see Figure 2(C)). On the other hand, as shown in Figure 3(A), a pair of left and right front mounts 23 are disposed at a portion near the front of the base 5, and the front portion of the outer shell 17 is connected to the front mounts 23 via a joint member 24 so as to be movable forward and backward and not to be separated upward. Therefore, when the backrest 3 tilts backward, the seat 2 moves backward as a whole.

[0038] (2) Overview of the support mechanism Next, the elasticity adjusting device that provides elastic resistance to the backward tilting movement of the backrest 3 and the structure around it will be described. Referring mainly to the drawings, FIG.

[0039] For example, the structure of the base 5 is shown in Figures 3 to 5. The base 5 is, for example, an aluminum die-cast product, and includes left and right side plates 5a and a rear block portion 5b that is integrally connected to the rear portions of the left and right side plates 5a, as shown in Figure 4. A tapered hole 26 penetrates the rear block portion 5b from above and below so that the upper end of the leg support 4 fits into it from below.

[0040] A rear bearing portion 5c protrudes rearward from the rear block portion 5b. The lower end of the second tilting frame 11 is connected to the rear bearing portion 5c via a two-split bearing 27 shown in FIG. 3B, a fourth support shaft (not shown), and a pressing member 27a. A rear bracket 28 for connecting a gas cylinder for rearward tilt control is provided on the rear bearing portion 5c.

[0041] A middle top plate 5d projects forward from the upper end of the rear block portion 5b, and a center boss 29 projects upward from the middle top plate 5d. A frame-shaped front joint portion 5e having a front wall, a front top plate, and left and right side walls is integrally connected to the front portions of the left and right side plates 5a. The inside of the base 5 is a downward-opening cavity surrounded by the left and right side plates 5a, the rear block portion 5b, and the front joint portion 5e, and the cavity also opens upward between the front joint portion 5e and the middle top plate 5d.

[0042] 4 and 5, the spring unit 30 is inserted from below into the base 5. The front end of the spring unit 30 is connected to the side wall of the front joint part 5e by the left and right long front support shafts 31. Meanwhile, the left and right first support shafts 7 are inserted from the outside into the lower part of the middle top plate 5d of the side plates 5a of the base 5 and are rotatably held. The first support shaft 7 has hexagonal parts (square parts) 7a, 7b on both sides of a circular journal part, and the front end of the first tilting frame 6 is fitted into the outward hexagonal part 7a so as not to rotate relative to the first tilting frame 6, and is fixed to the first tilting frame 6 by the bolts 32 shown in FIG. 2(C) and FIG. 3.

[0043] For example, as shown in Fig. 4, the inward hexagonal portions 7b of the left and right first support shafts 7 are fitted in hexagonal holes provided in the upper ends of the arm members 33 that are substantially vertically long so as not to rotate relative to each other. Therefore, when the backrest 3 and the first tilting frame 6 are tilted backward, the arm members 33 rotate forward with the first support shaft 7 as a fulcrum. The forward rotation of the arm members 33 is supported by the spring unit 30, and as the spring unit 30 rotates up and down with the front support shaft 31 as a fulcrum, the support position of the spring unit 30 with respect to the arm members 33 changes up and down, and the resistance (hardness) to the arm members 33 is adjusted. The first support shaft 7 is rotatably held on the base 5 via, for example, a bush 34 shown in Fig. 4.

[0044] For example, as shown in Fig. 4, the cavity of the base 5 is closed from below by a lower cover 35. In addition, an upper cover 36 is also fixed to the base 5. As shown in Fig. 3, a link-like member 37 that unlocks the leg support 4 is attached to the rear block portion 5b of the base 5, and a hole 38 that exposes the link-like member 37 upward is formed in the upper cover 36. The link-like member 37 is operated by a wire with a tube (not shown).

[0045] (3) Basic structure of the elasticity adjustment device For example, as shown in Fig. 4, a cam 40 having multiple cam surfaces formed on its outer periphery is held by center boss 29 so as to be horizontally rotatable as a member for rotating spring unit 30. Cam 40 has an upward cylindrical portion 40a, and a disk 41 is fixed by a screw 42. A pair of wires 43 are wound around upward cylindrical portion 40a in opposite directions. As shown in Fig. 4 (also see Fig. 7(A)), a pair of ball retaining holes 44 are formed inside upward cylindrical portion 40a of cam 40. Wires 43 are pulled out to the outside from a notched groove communicating with ball retaining hole 44.

[0046] The wires 43 are each inserted into a tube (not shown), and the ends of the tubes are held immovably by receiving seats 45 provided on the base 5. Although not shown, an elasticity adjustment handle (not shown) is rotatably disposed on the right side of the outer shell 17. When the elasticity adjustment handle is rotated, the pair of wires 43 are pulled in opposite directions, causing the cam 40 to rotate horizontally.

[0047] The horizontal rotation of the cam 40 is converted into the rotation of the spring unit 30 by a slider 46 that can move back and forth, and an inclined guide frame 47 that is in a rearward-leaning position and is provided on the spring unit 30. For example, as can be seen from Figure 4, the slider 46 is made of synthetic resin and has an angular shape in a plan view, and is held by a metal plate enclosure member 48 that covers the slider 46 from above, preventing it from moving upward or sideways, but allowing it to move back and forth.

[0048] The surrounding member 48 has flanges 48a on the left and right, and the flanges 48a are fixed to the base 5 with screws 49. For this reason, the base 5 is provided with an inward step 5f on which the flanges 48a overlap, at the same height as the middle top plate 5d. Also, the surrounding member 48 is formed with a cut-out groove 50 that exposes the inclined guide frame 47 upward.

[0049] As shown in FIG. 7(A), the spring unit 30 includes a compression coil spring 51 that expands and contracts approximately in the front-to-rear direction, a fixed side spring holder (front spring holder) 52 that supports the compression coil spring 51 from the front, a movable side spring holder (rear spring holder) 53 that supports the compression coil spring 51 from the rear and against which the arm member 33 abuts, an auxiliary plate 54 overlapping in front of the movable side spring holder 53, left and right side plates 55 made of metal plate (steel plate), and an upper cover member 56 that covers the compression coil spring 51 from above.

[0050] The fixed-side spring bearing 52 is made of synthetic resin (or may be an aluminum die-cast product) and is formed into a block shape, through which the left and right long front support shafts 31 are inserted. Therefore, the fixed-side spring bearing 52 is formed with a bearing hole 52a through which the front support shafts 31 pass. The front end of the side plate 55 is fixed to the fixed-side spring bearing 52 with a bolt 57, in which case a cylindrical boss 58 protrudes from the fixed-side spring bearing 52 and a fitting hole 59 at the front end of the side plate 55 is fitted into the cylindrical boss 58.

[0051] An upward engaging rib 60 is provided on the cylindrical boss 58, while an engaging groove 61 that engages with the engaging rib 60 is cut out and formed in the fitting hole 59 of the side plate 55. Also, the fixed-side spring receiver 52 is formed with a lateral protruding portion 62 on which the side plate 55 rests from above. The cylindrical boss 58, engaging rib, engaging groove 61, and lateral protruding portion 62 are specific examples of positioning portions that position the fixed-side spring receiver 52 and the side plate 55.

[0052] 3(B) and 9(C), front mounts 23 overlap front stage portions 63 formed on both the left and right sides of the front joint portion 5e of the base 5, and a circular positioning boss 64 is protrudingly provided on the front stage portions 63. The front mount 23 is fixed to the base 5 by a screw 64a that is screwed into the positioning boss 64 from above. The front support shaft 31 is held by the left and right front mounts 23 so that it cannot come off.

[0053] Therefore, the front spindle 31 is held in place without any special means for preventing it from coming off. For example, as shown in Fig. 9(B), a positioning groove 65 is formed in the portion of the side wall of the front joint part 5e through which the front spindle 31 is inserted, while a positioning protrusion 66 that fits into the positioning groove 65 is formed on the front mount 23.

[0054] 9(B) and 3(B), the joint member 24 is connected to the outer shell 17 by utilizing its elastic deformation. Also, a foot 24a that is L-shaped when viewed from the front and provided on the joint member 24 fits into a dovetail groove 67 formed in the front mount 23, so that the front part of the outer shell 17 is held in the front mount 23 so as to be unable to come off and to be movable back and forth.

[0055] (4) Spring unit details For example, Fig. 7(A) shows a top cover member 56. The top cover member 56 is made of synthetic resin and is arranged so as to partially cover the compression coil spring 51 from above, and the left and right side plates 56a are fixed to the side plate 55 by two screws 68, one at the front and one at the back. Therefore, the side plate 55 has two tapped holes 69, one at the front and one at the back. Also, as shown in Fig. 7(A), the top cover member 56 is formed with a downward groove 70 that fits with the upper edge of the side plate 55.

[0056] In this embodiment, the case member recited in the claims is constituted by the side plate 55 and the top cover member 56, and the inclined guide frame 47 having an oblong hole in an inclined posture is integrally formed on both the left and right sides of the top cover member 56. The spring unit 30 is inclined downward toward the rear as a whole, and therefore the inclined guide frame 47 is also inclined downward toward the rear. The slider 46 is formed with a cut groove 71 into which the inclined guide frame 47 fits from below, and the slider 46 and the inclined guide frame 47 are connected by a left-right long slide pin 72.

[0057] The slide pin 72 is inserted into the front end of the slider 46, but since the slider 46 only moves back and forth and does not rotate, the slide pin 72 also only moves back and forth and does not move up and down. Therefore, the slide pin 72 is held in place by the enclosing member 48 so that it cannot come out. The inclined guide frame 47 constitutes a part of the guide means recited in the claims.

[0058] For example, as shown in Fig. 7(A), the front part of the side plate 55 is fixed to the fixed-side spring bearing 52 with a bolt 57, and, as shown in Fig. 6(A), the upper edge is fixed to the upper cover member 56 with two screws 68, one at the front and one at the back. Therefore, the fixed-side spring bearing 52, the side plate 55, and the upper cover member 56 form a single structure. Therefore, the case member consisting of the side plate 55 and the upper cover member 56 has a robust structure.

[0059] 7, the cam 40 is roughly D-shaped in plan view, and has first to ninth cam surfaces 74 to 82 formed on its outer circumferential surface. The cam surfaces 74 to 82 are recessed in the axial direction in plan view, and the distance (height) from the axial center varies in the clockwise direction so as to increase from the first cam surface 74 to the ninth cam surface 82. On the other hand, a support protrusion 73 that selectively comes into contact with any of the cam surfaces 74 to 82 is provided at the rear end of the slider 46 so as to protrude backward.

[0060] Forming the cam surfaces 74-82 as concave surfaces as in the embodiment allows the posture of the cam 40 to be stabilized. When transitioning from a higher cam surface to a lower cam surface, the support protrusions 73 climb over the ridges at the locations of the cam surfaces 74-82, and therefore the cam 40 will not rotate unless a certain amount of force is applied. On the other hand, there is inherent resistance to transitioning from a lower cam surface to a higher cam surface, and therefore, in this case as well, the cam 40 will not rotate unless a certain amount of force is applied. Therefore, the cam 40 is stably held in the set posture.

[0061] As shown in Fig. 7(A), a rearward-facing flange 84 is provided at the lower end of the slider 46 where the support protrusion 73 is provided, and an upward-facing engagement protrusion 85 is provided on the flange 84, while as shown in Fig. 7(B), an engagement groove 86 into which the engagement protrusion 85 is slidably fitted is formed long in the circumferential direction on the lower surface of the cam 40. To be precise, the engagement groove 86 is formed in the range of the cam 40 where the cam surfaces 74 to 82 are formed.

[0062] Since the engagement projection 85 of the slider 46 and the engagement groove 86 of the cam 40 are always held in an engaged state, the slider 46 moves back and forth in conjunction with the rotation of the cam 40, regardless of whether the cam 40 rotates in the forward or reverse direction. Therefore, a phenomenon does not occur in which the cam 40 rotates during reverse rotation and the slider 46 does not move backward, and the posture of the spring unit 30 can be accurately changed. Also, in this example, a spring for returning the spring unit 30 to its original posture is not required, which has the advantage of simplifying the structure.

[0063] It is also possible to form the engagement groove 86 on the upper surface of the cam 40 and provide the engagement protrusion 85 so that it protrudes downward. Furthermore, instead of the engagement groove 86, it is also possible to provide a downward or upward rib along the outer periphery of the cam 40. That is, in the engagement groove 86, it is the outer periphery surface that functions to prevent the slider 46 from separating, and the inner periphery surface is not necessarily required, so a rib alone will suffice.

[0064] For example, Fig. 6(A) shows arm member 33, which is a metal die-cast product, and is fixed to inward hexagonal portion 7b of first support shaft 7 with screws 87. On the other hand, for example, Fig. 7(A) shows movable-side spring retainer 53, which is a synthetic resin molded product (or a metal die-cast product) formed in a triangular shape when viewed from the side, and metal auxiliary plate 54 on which movable-side spring retainer 53 overlaps from behind has left and right long positioning holes 88 and left and right round positioning holes 89, while movable-side spring retainer 53 has a horizontally long positioning protrusion 90 and a circular positioning round hole 91 protruding rearward.

[0065] 7(A), for example, a square bar-shaped (rectangular) stopper shaft 92 as an example of a stopper means is inserted into the movable-side spring bearing 53 so as to be held in place so as not to come off. The stopper shaft 92 protrudes from both the left and right sides of the movable-side spring bearing 53, and these protruding portions are inserted into elongated holes 95 formed in the side plate 55 in the front-rear direction, and are also inserted into a guide frame 94 fixed to the side plate 55 with screws 93.

[0066] The guide frame 94 is made of synthetic resin and has an outer plate 94a overlapping the outer surface of the side plate 55, a guide rib 94b that is U-shaped in side view and fits into an elongated hole 95 provided in the side plate 55, and an inner plate 94c that overlaps the inner surface of the side plate 55 behind the elongated hole 95 of the side plate 55, and the inner plate 94c is integrally continuous with the rear end of the guide rib 94b. The exposed portion of the stopper shaft 92 is slidably inserted between the upper and lower guide ribs 94b.

[0067] 8(C), for example, the inner plate 94c of the guide frame 94 is located behind the rear end surface (one end surface) 95a of the elongated hole 95 in the side plate 55. Therefore, the stopper shaft 92 does not hit the inner plate 94c, and the retracted position of the stopper shaft 92 is regulated by the rear end surface 95a of the elongated hole 95. Also, since the inner plate 94c of the guide frame 94 overlaps the inner surface of the side plate 55, even if only the front portion is fixed to the side plate 55 with a single screw 93, it is firmly fixed to the side plate 55.

[0068] (5) Summary When the cam 40 is rotated, the slider 46 moves forward and backward, but since the inclined guide frame 47 is inclined backward and downward, the spring unit 30 rotates vertically around the front support shaft 31 as a fulcrum in accordance with the forward and backward movement of the slider 46. Then, the contact position of the movable side spring bearing 53 with the arm member 33 changes vertically. In other words, when the spring unit 30 rotates, the load support span of the arm member 33 changes. Therefore, the strength of the resistance to the backward tilting movement of the backrest 3 changes.

[0069] Specifically, when cam 40 changes from a low position to a high position, slider 46 advances and spring unit 30 rotates downward, and the load support span by arm member 33 increases, thereby reducing resistance to reclining (the spring becomes softer). The front surface of arm member 33 is gently curved so as to be concave forward in side view, so that the relationship with movable side spring bearing 53 does not change in the unloaded state even when spring unit 30 rotates.

[0070] The compression coil spring 51 is pretensioned, but the front-to-rear positional relationship between the cam 40 and the arm member 33 is set so that no or almost no spring force acts on the arm member 33 when the cam 40 is fully retracted (the spring unit 30 is fully extended) without the weight of the person acting on the backrest 3.

[0071] Specifically, when the backrest 3 is pulled forward, there is a very small amount of clearance between the arm member 33 and the cam 40 (because the center of gravity of the backrest 3 is behind the first support shaft 7, the arm member 33 hits the cam 40 due to the backrest 3's own weight even when no person is leaning against the backrest 3, but the spring force of the arm member 33 is set not to act on the arm member 33).

[0072] Therefore, the cam 40 can be rotated easily, but because the metallic stopper shaft 92 is positioned by the metallic side plate 55, the front-to-rear position of the stopper shaft 92 does not change even with long-term continuous use, allowing easy and continuous adjustment of the elasticity for reclining. If the movable side spring bearing 53 is made of synthetic resin, it is preferable to prevent the generation of rubbing noise when it comes into sliding contact with the arm member 33.

[0073] The forward and backward movement of the stopper shaft 92 is guided by a guide frame 94 made of synthetic resin, so no rubbing noise is generated when reclining, making it possible to use the chair comfortably. The forward position of the stopper shaft 92 is restricted by a front wall 94d of a guide rib 94b in the guide frame 94, but because the front wall 94d is made of synthetic resin, no impact noise is generated even if a person leans vigorously against the backrest 3. This also makes the chair comfortable to use.

[0074] On the other hand, when the seat is moved away from the backrest 3, the elastic force of the compression coil spring 51 causes the stopper shaft 92 to hit the rear end surface 95a of the elongated hole 95, but since the spring force decreases as the stopper shaft 92 moves backward, the stopper shaft 92 does not hit the rear end surface 95a of the elongated hole 95 violently. Therefore, no abnormal noise is generated when the backrest 3 is raised.

[0075] While manufacturing the side plate 55 from a metal plate as in the embodiment is beneficial in terms of improving strength, constructing the case member from the side plate 55 and the top cover member 56 provides a case member with excellent strength and functionality, since the side plate 55 is made of sheet metal and ensures high strength, while the top cover member 56 is made of resin and can easily be integrated with the inclined guide frame 47. In the embodiment, the side plate 55 is formed into a three-dimensional structure by forming outward bulges 55a, 55b at the upper and lower parts, and forming it in this manner has the advantage of contributing to increased strength by increasing resistance to bending and twisting.

[0076] While the stopper shaft 92 is made of a square bar, the stopper surface consisting of the rear surface of the stopper shaft 92 and the rear end surface 95a of the elongated hole 95 forms a straight line in a side view. For this reason, even if the vertical width of the stopper shaft 92 is made slightly smaller than the vertical distance between the upper and lower guide ribs 94b to allow the stopper shaft 92 to move smoothly, the stopper shaft 92 abuts against the rear end surface 95a of the elongated hole 95 over the entire vertical width of its rear end surface. Therefore, the impact caused by the expansion and deformation of the compression coil spring 51 is supported by the entire vertical width of the stopper shaft 92, preventing wear.

[0077] 6(A), it is also possible to connect the rear ends of the left and right side plates 55 with a reinforcing member such as a spacer 96 below the compression coil spring 51. With this configuration, the robustness of the spring unit 30 can be further improved.

[0078] Although the embodiment of the present invention has been described above, the present invention can be embodied in various other ways. For example, mechanisms other than cams can be used as adjustment means for rotating the spring unit. When a cam is used, it is also possible to rotate it about a horizontal axis (in this case, it is also possible to rotate the cam directly with a handle or via a gear without using a wire). When a cam that rotates horizontally is used, it is also possible to rotate it using a worm gear or bevel gear mechanism without using a wire.

[0079] The stopper means may be a bolt or a bolt-like headed rod inserted into the stopper shaft from behind. When a bolt is used, the positional relationship between the arm member and the movable spring bearing can be fine-tuned by adjusting the degree to which it is screwed into the case member.

[0080] The case member can also be formed in a cylindrical shape similar to that of Patent Document 1. In this case, the case member can be an aluminum die-cast product. Furthermore, although the spring unit is disposed in front of the arm member in the embodiment, the spring unit can also be disposed behind the arm member, for example, in a form in which the arm member extends upward from a rotation fulcrum. When the spring unit is disposed behind the arm member in this way, the spring unit can be rotated around its rear end portion as a fulcrum.

[0081] The rear surface of the stopper shaft and the rear surface of the elongated hole can be formed into an arch shape or a large-angle V shape in side view. In this case, it is preferable that the arch shape or V shape is concave toward the rear. It is also possible to make the entire case member or the side plates from synthetic resin, fix a metal stopper frame, and receive the stopper shaft with this stopper frame. In this case, the stopper frame forms part of the stopper means. [Industrial Applicability]

[0082] The present invention can be embodied in a chair, and therefore has industrial applicability. [Explanation of symbols]

[0083] 2nd seat 3. Backrest 5. Bass 6 Tilting Frame 7 1st spindle 8 Lower back frame 9 Upper back frame 17 Outer Shell 23 Front Mount 30 Spring unit 31 Front support shaft 33 Arm component (pusher) 40 Cam 46 Slider constituting the guide means 47 Inclined guide frame constituting the guide means 51 Compression coil spring 52 Fixed side spring holder 53 Movable side spring support 55 Side plate constituting the case member (and stopper means) 56 Upper cover member constituting the case member 58 Cylindrical boss constituting the positioning portion 59 Side panel fitting hole 62 Horizontal protrusion constituting the positioning part 73 Support protrusion 74~82 Cam surface 92 Stopper shaft constituting the stopper means 93 Bis 94 Guide Frame 94a Outer shell 94b Guide rib 94c inner plate 95 Slotted hole in side panel 95a: Rear end surface (one end surface) functioning as a stopper means

Claims

1. The seatback has a backrest that can be tilted backward, and an elastic adjustment means that applies resistance to the backward tilting of the backrest. The elasticity adjustment means includes an arm member extending in a direction perpendicular to the pivot axis of the backrest, a compression coil spring expanding and contracting in a substantially longitudinal direction to provide resistance to the pivoting of the arm member, a movable spring bearing that moves in a substantially longitudinal direction following the pivoting of the arm member, a fixed spring bearing that supports the compression coil spring on the opposite side to the movable spring bearing, and a case member that holds both spring bearings and the compression coil spring in a state in which the movable spring bearing can move back and forth by a predetermined stroke, a reclining chair in which the case member rotates about an end portion of the fixed spring bearing as a fulcrum, thereby changing a contact position of the movable spring bearing with respect to the arm member in a vertical direction, thereby changing an elastic resistance to a backward tilting movement of the backrest, a stopper means for holding the movable spring bearing in a position where it is fully advanced by the compression coil spring, the stopper means being made of metal; Reclining chair.

2. the case member has metallic side plates arranged on both the left and right sides of the compression coil spring, and the left and right side plates are formed with elongated holes through which metallic stopper shafts protruding from the movable-side spring bearing to both the left and right sides can slidably pass, The stopper shaft is caused to abut against one end surface of the elongated hole, thereby functioning as the stopper means.

2. The reclining chair according to claim 1.

3. a stopper surface where the stopper shaft and one end surface of the elongated hole come into contact has a shape that is long in a direction perpendicular to a moving direction of the stopper shaft in a side view; 3. A reclining chair as claimed in claim 2.

4. Further, a guide frame made of synthetic resin is provided to guide the sliding of the stopper shaft, The guide frame includes an outer plate overlapping an outer surface of the side plate and a guide rib that fits into an elongated hole in the side plate, and the outer plate is fixed to the side plate with a screw.

4. A reclining chair according to claim 2 or 3.

5. the case member has a top cover member fixed to the left and right side plates with screws, The upper cover member is provided with a guide means for rotating the case member by an external operation.

3. A reclining chair as claimed in claim 2.

6. The fixed-side spring bearing and the left and right side plates are provided with bearing holes through which hollow support shafts for rotating the case member are inserted, and positioning portions are formed to maintain the respective positions of the case members. The case member including the fixed side spring bearing and the left and right side plates is disposed in a space formed in a base which is a molded product so as to be immovable to the left and right, and is rotatably connected to the base by a support shaft inserted into the hollow support shaft.

6. A reclining chair as claimed in claim 5.

7. As the positioning portion, a cylindrical boss protruding outward to the left and right and a protruding portion located below the cylindrical boss are formed on the fixed side spring bearing, and the side plate is fitted into the cylindrical boss, and a front portion of the side plate is placed on the protruding portion.

7. A reclining chair according to claim 6.

8. An elasticity adjustment device that provides resistance to the backward tilt of a backrest, a movable spring bearing that moves back and forth by rotation of an arm member extending in a direction intersecting the rotation axis of the backrest; a compression coil spring that is compressed by the movable spring bearing; a fixed-side spring bearing that supports the compression coil spring from a side opposite to the movable-side spring bearing; a case member that holds both the spring bearings and the compression coil spring in a state in which the movable spring bearing can move back and forth by a predetermined stroke, In a configuration in which the case member rotates in the vertical direction around the end portion of the fixed spring bearing as a fulcrum, the contact position of the movable spring bearing with respect to the arm member changes in the vertical direction, thereby changing the elastic resistance to the backward tilting movement of the backrest, a stopper means for holding the movable spring bearing in a fully advanced position by the compression coil spring, the stopper means being made of metal; Elasticity adjustment device for chairs.

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