Chair

The present invention relates to an office chair and, in particular, to a chair that can naturally adopt either of two positions, a serious working position and a relaxed reclining position, when a person is seated upon it.

The typical office chair that has long been used is provided with a gas spring and a coil spring as attached energy means on the underside of a seat thereof, and the configuration is such that large inclinations of a back rest are implemented by the gas spring whereas small adjustments of the inclination of the back rest in the final stages are implemented by the coil spring.

However, since a gas spring is used as the reclining mechanism for the seat, the manufacturing costs are inevitably high, and thus it is extremely difficult in the prior art to provide an inexpensive chair, despite all efforts to reduce the costs of other components.

In addition, since adjustment of the seat back reactive force in the prior art makes use of a spring such as a coil spring with a single type of spring characteristic, it is difficult to implement a natural reclining state. In other words, the fault occurs that, just by the person sitting, the seat portion and back rest of the chair recline backwards, making it difficult to achieve a working position, on the other hand, if the reactive force of the coil spring is made stronger, this makes it difficult to recline backwards, and in that state reclining becomes so difficult it is not possible to relax.

The present invention was devised in the light of the above described problems and has as an objective the provision of a chair that is inexpensive and has a structure such that it can naturally adopt either a serious working position or a relaxed reclining position, and which is designed to remove the defects of the prior art.

In order to achieve the above objective, the present invention concerns a chair in which a base member is fitted onto an upper portion of a leg comprising a plurality of castors in contact with a floor together with support members for these castors, and a seat portion and a back rest are provided on an upper portion of a support plate attached to the base member so as to be is capable of reclining with respect thereto. In accordance with this invention, this chair is also provided with a cam-shaped link capable of rotating about the periphery of a pin provided in the base member, an upper portion of the link protrudes towards the support plate side, and a corresponding elastic member that is compressed by the rotation of the link is provided in a bottom portion of the base member. A shaft portion in contact with the link, and which causes the link to change profile in response to the reclining action of the support plate, is provided within the support plate. A stopper lever is also provided in the base member to maintain the upright state of the link.

With the above described configuration, the inclination of the base member causes the shaft portion to compress the link of the base member that it is in contact with, and thus a cushion state can be maintained. Operation of the stopper lever holds the link in its upright state, and thus the inclination of the seat portion and back rest of the chair can be locked in a simple manner.

FIG. 1 is a side view of the exterior of an embodiment of a chair in accordance with the present invention;

FIG. 2 is a side view of a frame portion of the chair shown in FIG. 1;

FIG. 3 is a side view of the frame portion of FIG. 2 when it is in reclined state;

FIG. 4 is a plan view of the frame portion of FIG. 2;

FIG. 5 is a side view of an embodiment of vital components of the chair in accordance with the present invention;

FIG. 6 is a side view of the vital chair components of FIG. 5 when in an inclined state;

FIG. 7 is a side view of the vital chair components of FIG. 5 in a state when they are locked by a stopper lever; and

FIG. 8 is a perspective view of the stopper lever.

An embodiment of the present invention will be described below with reference to the accompanying drawings.

In a chair 1 of the present invention, shown in FIG. 1 and FIG. 2, a base member 3 is fitted onto an upper portion of a leg 2 comprising a plurality of radially arranged castors 2a in contact with a floor together with support members 2b for these castors 2a, and a seat portion 5 and a back rest 6 are provided on a support plate 4 that is capable of reclining with respect to the base member 3.

As shown in FIG. 4 and FIG. 5, the configuration is such that a cam-shaped link 8 wherein its back surface has a cam-shaped surface 8b is rotatably attached around the periphery of a pin 7 that is provided in the base member 3, an upper portion of the link protrudes towards the support plate 4 side, and a corresponding elastic member 9 that is compressed by the rotation of the link 8 is provided in a bottom portion of the base member 3. A shaft portion 10 in contact with the link 8, and which causes the link 8 to change profile in response to the reclining action of the support plate 4, is provided within the support plate 4. A stopper lever 11 is also provided in the base member 3 to maintain the upright state of the link 8.

The seat portion 5 and back rest 6 of the chair 1 of the present invention are designed to able to recline backwards from a solid-line position to a dotted line position shown in FIG. 1, in the same manner as a prior art chair. The frame structure of this chair is such that the support plate 4 of the upper portion thereof rotates with respect to the base member 3 about a pivot of a pin 12 affixed to a front portion of the chair, as shown in FIG. 2 and FIG. 3, the back frame 13 rotates about a pivot of the shaft portion 10 provided in the support plate 4, and the base member 3 and back frame 13 are further linked together by a pin 14 that passes through an elongated hole.

A plan view of the structure of FIG. 2 is shown in FIG. 4, and a detailed side view thereof is shown in FIG. 5, illustrating that the base member 3 is within the support plate 4, and the back frame 13 is provided in a rear portion of the base member 3. A coil spring 15, the link 8 that is a vital component of the present invention, the elastic member 9 formed of a material such as polyurethane rubber, and a cushion receptacle 16 that holds the elastic member 9 are provided within the base member 3, and a collar 10a is provided straddling over the shaft portion 10 between the wall surfaces of the support plate 4. Reference number 3a denotes a hole for inserting the leg 2. As shown in FIG. 5, the stopper lever 11 is provided in a lower portion (on the front left side) of the assembly. In an upper portion (on the front right side) thereof, there is a lever 17 for raising and lowering the chair 1, with a lever cap 18 for raising and lowering the seat portion being provided at a leading end thereof.

The cam-shaped surface 8b of the link 8 is ordinarily placed in contact with the collar 10a attached to the shaft portion 10, there are projections 8a in the front side thereof at the center and at each end, the pin 7 is inserted into a lower portion thereof, and the upper portion thereof rotates about the pin 7. This ensures that, when the back rest is inclined forward, the projections 8a first come into contact with the elastic member 9 made of a material such as polyurethane rubber and then compress it.

The stopper lever 11 of the chair in accordance with the present invention, shown in perspective in FIG. 8, has a shape such that two end portions 11a and 11b thereof are bent into mutually opposite directions with respect to a central portion 11c thereof, the central portion 11c is supported on a stopper lever stay 19 provided in a base portion of the base member 3 in such a manner that the entire lever can rotate upward or downward. The end portion 11a on the outer side is provided with a handle 20. A V-shaped notch 16a is provided in an upper portion of the 10 cushion receptacle 16. When the end portion 11b at the inner side of the stopper lever 11 rotates and enters the notch 16a, it comes into contact with the link 8 in such a manner that it releases the forward inclination. In FIG. 5, reference number 4a denotes a cutout for preventing the stopper lever 11 from moving upward, reference number 21 denotes a slide guide, and reference number 22 denotes an elongated hole into which a peg 23 provided on the stopper lever 11 is inserted so that it can move either up or down, for fixing the stopper lever 11 in position.

The operation of the chair in accordance with the present invention will now be described.

When a person sits on the seat portion 5 with the chair in the state shown in FIG. 5, the support plate 4 reclines backward with respect to the base member 3. This causes the collar 10a that is ordinarily in contact with the cam-shaped surface 8b of the link 8 to be pushed down while sliding over the outer periphery of the link 8, so that the link 8 compresses the forward-inclined elastic member 9 and reaches the state shown in FIG. 6. Thus the chair 1 receives a reactive force not only from the coil spring 15 but also from the elastic member 9, and can thus take up a more natural reclining position.

Next, to change the reclining position shown in FIG. 6 to a working position, the user returns the back portion to its foremost inclined position (the state shown in FIG. 5), then operates the end portion 11a of the stopper lever 11 having the handle 20 in the upward direction, as shown by the arrow, so that the other end portion 11b enters the notch 16a of the cushion receptacle 16. Thus the stopper lever 11 stops the rotation of the link 8, even if the link 8 has been inclined forward by the person sitting down on the seat portion 5. The backward inclination of the seat portion 5 and back rest 6 of the chair 1 is locked. Then the stopper lever 11 is fixed at the upper side of the elongated hole 22. To release the lock, the user can operate the stopper lever 11 in the downward direction.

As described above, in the chair in accordance with the present invention, a base member is fitted onto an upper portion of a leg comprising a plurality of radially arranged castors in contact with a floor together with support members for these castors, and a seat portion and a back rest are provided on an upper portion of a support plate that is capable of reclining with respect to the base member. The chair is also provided with a cam-shaped link capable of rotating about the periphery of a pin provided in the base member, an upper portion of the link protrudes towards the support plate side, and a corresponding elastic member that is compressed by the rotation of the link is provided in a bottom portion of the base member. The provision within the support plate of a shaft portion in contact with the link, and which causes the link to change profile in response to the reclining action of the support plate, ensures that the shape of the link can be selected and fabricated as appropriate and the reactive force of the chair can be set to any required level by compression of the elastic member 9 formed of a material such as polyurethane rubber. Therefore, the weight of the user can be supported in a natural manner throughout the entire use of the chair. Since the movement of the link can be stopped by a simple mechanism, the chair's position while the user is working can be maintained, and the working position can be locked.