JP2744392B2 - Synthetic resin legs in chairs - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synthetic resin leg for an office chair or the like.

[0002]

2. Description of the Related Art A leg device for an office chair generally includes a leg having a plurality of leg rods extending radially in a plan view to support a pillar such as a gas spring so as not to fall down. The seat is attached to the upper end of the pillar. In order to improve the appearance and simplify the manufacturing process, the legs are integrally formed of synthetic resin.
Conventionally, a cylindrical portion having a flat bottom plate connected to the lower end is formed substantially at the center of the leg, and the pillar is supported by the flat bottom plate in the cylindrical portion.

[0003]

However, as described above,
In the configuration in which the column is supported by the flat bottom plate in the cylindrical portion of the leg, the load acting via the column is mainly acting as a bending force on the bottom plate, and the support strength for the column is not sufficient. In other words, there is a problem that the durability of the legs is low.

[0004] To solve this problem, for example,
It is considered that the thickness of the bottom plate in the cylindrical portion should be increased as described in JP-A-91048. However, when the legs are integrally molded by a pair of dies using an injection molding method or a reaction molding method, there is a problem in that the gate sealing time becomes longer and the molding time becomes longer. In addition, in order for the resin filled in the cavity of the mold to be solidified in an even state, there is an appropriate value for the thickness of each part of the leg, and therefore, the bottom plate of the cylindrical portion has an appropriate value. When the thickness is increased, the shape of the legs is not uniform when the legs are formed, which causes another problem that distortion may occur due to a difference in shrinkage.

[0005] It is an object of the present invention to improve the durability of a leg without causing molding problems.

[0006]

In order to achieve this object, according to the present invention, there is provided a synthetic resin leg having a cylindrical portion into which a pillar for supporting a seat is fitted. Of these, a rib-shaped or step-shaped support portion for the pillar is formed at an appropriate height. According to a second aspect of the present invention, in a synthetic resin leg provided with a cylindrical portion into which a pillar for supporting a seat is fitted, an upwardly convex bottom plate supporting the pillar is provided on an inner peripheral surface of the pillar. Was connected.

[0007]

According to the present invention, a rib-shaped or step-shaped support portion is formed on the inner peripheral surface of the cylindrical portion, and the leg is supported by the rib-shaped or step-shaped support portion. With this configuration, the upper and lower lengths of the ribs and the steps can be lengthened, so that the support strength for the pillars can be remarkably improved as compared to the case where the pillars are supported by the bottom plate, and the ribs The step-like or step-like support portion can be formed without changing the thickness of the cylindrical portion.

According to a second aspect of the present invention, when the pillar is supported by the bottom plate formed in an upwardly convex shape,
By supporting the pillars not only by bending stress but also by compressive stress, the supporting strength can be greatly improved compared to the case where the bottom plate is formed as a flat plate, so change the thickness of the bottom plate and the thickness of the cylindrical part Without this, the supporting strength of the pillar can be remarkably improved.

As described above, according to the present invention, it is possible to improve the supporting strength for the pillars without changing the thickness of the cylindrical portion and the bottom plate, and it is said that distortion occurs after molding and the molding efficiency decreases. This has the effect of improving the durability of the legs without causing any problems.

[0010]

Next, an embodiment of the present invention will be described with reference to the drawings. 1 to 5 show a first embodiment. In these figures, a chair indicated by reference numeral 1 is composed of a seat 2 and a backrest 3.
And a leg device 4. The leg device 4 includes a synthetic resin leg 5 having a plurality of leg rods 5a extending radially in a plan view. An approximately protruding portion 6a and a bottom plate A gas spring 8 as an example of a pillar is held by a bush 7 fitted to an upwardly projecting portion 6a of the cylindrical portion 6 so as not to fall down. A caster 9 is provided at the tip of each leg 5a.

The gas spring 8 has a cylinder 10 and a downwardly facing piston rod 11 fitted therein. The upper end of the cylinder 10 is fixed to the seat body 2, while a small diameter formed at the lower end of the piston rod 11. A washer 12 is fitted to the portion 11a, and the washer 12 is supported by a plurality of rib-shaped support portions 13 projecting inward from a portion of the inner peripheral surface of the cylindrical portion 6 above the bottom plate 6b. .

Small-diameter portion 11a of piston rod 11
Are locked to the bottom plate 6b by a snap ring 14. An operating pin 10 protrudes from the upper end of the cylinder 10. When the operating pin 10 is pressed to release the lock on the piston rod 11, the seat 2 can be raised and lowered. The leg 5a of the leg 5 is formed in a hollow shape with a downward opening, and a plurality of connecting ribs 15 are formed in order to improve strength.

In the above configuration, the load of the seat body 2 and the backrest 3 of the chair 1 or the person sitting on the chair acts on the gas spring 8 and the washer 12 as a downward load, and is supported by the rib-shaped support portion 13. You. Since the rib-like support portion 13 extends upward from the bottom plate 6b and has a long vertical length and thus has a strong strength against a downward load, it acts via the gas spring 8 and the washer 12. It has high durability against a downward load.

On the other hand, when the legs 5 are integrally formed by an injection molding method or a reaction molding method using a pair of dies, it is necessary to uniformly solidify the resin filled in the cavities of the dies.
The thickness of each portion of the leg 5 has an appropriate value, and if the thickness is out of the appropriate value, distortion is likely to occur due to a difference in shrinkage when the resin hardens. However, the rib-shaped support portion 13 merely protrudes inward from the inner peripheral surface of the cylindrical portion 6, and in order to form the rib-shaped support portion 13, the thickness of the cylindrical portion 6 and the thickness of the bottom plate 6 b are reduced. Since it is not necessary to change the length, when the leg 5 is molded, no distortion occurs due to a difference in shrinkage when the resin is hardened,
Also, the molding time does not become long.

In the second embodiment shown in FIG. 6, the cylindrical portion 6 is formed with a small diameter from the lower end to an appropriate height portion without changing the thickness of the cylindrical portion, so that the inside of the cylindrical portion 6 is reduced. A stepped support portion 16 is formed on the peripheral surface, and the piston rod 11 is supported at the position of the stepped support portion 16. In this case, the bottom plate 6b is formed at the position of the step-like support portion 16, and the piston rod 11 is locked to the bottom plate 6b by the snap ring 14.

In the second embodiment, the portion of the cylindrical portion 6 below the step-like supporting portion 16 has a small diameter.
The support strength for the piston rod 8b can be remarkably improved, and there is no need to change the thickness of the cylindrical portion 6, so that no distortion occurs during molding. FIG.
FIG. 8 shows a third embodiment in which the bottom plate 6b is formed in an upwardly convex arch shape so that the piston rod 11 is supported by the bottom plate 6b, and FIG.
This is a fourth embodiment in which the bottom plate 6b is formed to have a substantially gate-shaped cross section, and the piston rod 11 is supported by the bottom plate 6b.

In any of the third and fourth embodiments, the load acting downward through the piston rod 11 acts not only on the bottom plate 6b but also as a compressive force on the bottom plate 6b. 6b can improve the supporting strength without increasing its thickness. FIG.
When the washer 12 is formed so as to be fitted on the bottom plate 6b as shown by a solid line in FIG.
b and the contact area of the seat 12 with the
Since it is possible to apply a load evenly to b,
The support strength of the bottom plate 6b can be further improved.

In FIGS. 7 and 8, the bottom plate 6b does not necessarily need to be provided at the lower end of the cylindrical portion 6, but may be provided at an intermediate height position on the inner peripheral surface of the cylindrical portion 6.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a leg device according to a first embodiment.

FIG. 2 is a perspective view of a chair.

FIG. 3 is a bottom view of the leg.

FIG. 4 is a sectional view taken along line IV-IV of FIG.

FIG. 5 is a sectional view taken along line VV of FIG. 1;

FIG. 6 is a sectional view of a main part showing a second embodiment.

FIG. 7 is a cross-sectional view illustrating a main part of a third embodiment.

FIG. 8 is a sectional view of an essential part showing a fourth embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Chair 4 Leg device 5 Leg 6 Cylindrical part 6b Bottom plate 8 Gas spring as an example of a pillar 12 Washer 13 Rib-shaped support part 16 Step-shaped support part

Claims (2)

(57) [Claims] 1. A synthetic resin leg provided with a tubular portion into which a pillar for supporting a seat body fits, wherein a rib-like shape or a rib for the pillar is provided at an appropriate height on an inner peripheral surface of the tubular portion. A synthetic resin leg for a chair, wherein a stepped support portion is formed. 2. A synthetic resin leg having a cylindrical portion into which a pillar for supporting a seat is fitted, wherein an upwardly convex bottom plate supporting the pillar is connected to an inner peripheral surface of the pillar. A chair made of synthetic resin in a chair characterized by the following.