JPH0414040Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an oblong leg rod made of synthetic resin for furniture such as chairs and desks.

[Conventional technology]

Generally, as shown in FIG. 6, the legs of the chair are arranged above the floor surface from the support part 21 for the guide tube 20 that supports the seat support rod (not shown) in a height-adjustable manner. The horizontally long leg rods 22 extend radially, and the distal end of each horizontally long leg rod 20 is grounded directly or via casters 21. By integrally molding the entire leg body or only each oblong leg rod 22 with hard synthetic resin,
It is well known that efforts are being made to reduce costs, reduce weight, or improve appearance. In this case, weight reduction is achieved by forming the horizontally long leg rods 22 in a downward-opening U-shape in cross section.

In that case, the horizontally long leg rod 22 is formed by filling a pair of male and female molds 24 and 25 with molten resin, making them individual, and then cutting them out. Therefore, conventionally, in order to facilitate mold cutting, the inner surface of the horizontally long leg rod 20 was formed into a tapered surface that widened downward at a considerably large angle (α0), while the outer surface was also formed with a taper angle similar to that of the inner surface. The side plate 20a of the horizontally long leg rod 20 is formed into a tapered surface that widens downward at an angle (β0) smaller than (α0).For this reason, conventionally, the side plate 20a of the horizontally long leg rod 20 has a lower wall thickness (t1) than a wall thickness (t1) at the upper end. It had a cross-sectional shape with a thin wall thickness (t2).

[Problem that the invention attempts to solve]

Therefore, a bending moment that causes the longitudinal axis of the horizontally long leg rod 20 to curve downward acts on the horizontally long leg rod 20, so that compressive stress is generated at the upper end of the side plate 20a of the horizontally long leg rod 20, and tensile stress is generated at the lower end. However, if the cross-sectional shape is made thinner at the lower end as in the past, the height of the neutral plane of stress (h1) will be the height of the side plate 20a (h0), as shown in FIG. Since it is located considerably above the midpoint of the side plate 20a and is far away from the lower end surface of the side plate 20a, the tensile stress at the lower end increases.

However, since hard synthetic resins are generally strong against compressive force but weak against tensile force, in the conventional form, the tensile strength at the lower end of the horizontally long leg rod 20 is significantly reduced. In addition, since the lower end portion is thin, it is weak against impact force from the lateral direction. Therefore, if a hard object collides with the lower end portion while a load is applied to the side plate 20a, the side plate 20a is likely to be damaged or cracked. There was a problem.

To solve this problem, the tensile strength and impact strength at the lower end can be increased by making the entire side plate 20a thicker, or the outer surface of the side plate 20a can be Countermeasures such as protruding reinforcing ribs 26 along the lower edge can be considered, but the former countermeasure increases the amount of resin used, resulting in additional problems of increased weight and cost. Furthermore, even with the latter measure, the amount of resin used increases, resulting in an increase in weight and cost, and a new problem arises in that the ribs 25 protrude to the outside, resulting in poor appearance.In any case, it is not a good idea. do not have.

The object of the present invention is to make it possible to improve the strength without deteriorating the appearance or increasing the weight when molding the oblong leg rod from hard synthetic resin.

[Means for solving problems]

For this reason, the present invention provides an oblong leg rod made of hard synthetic resin that protrudes laterally from the lower end of the furniture body and has a grounding part on the floor surface at the tip. The outer surfaces of both side plates of the horizontally long leg rod are formed into tapered surfaces such that the distance between them widens downward, while the inner surfaces of the both side plates of the horizontally long leg rod are formed such that the distance between them is parallel to each other. Alternatively, it is formed into a tapered surface that widens downward at an angle smaller than the taper angle between the outer surfaces.

[Function and effect of invention]

With this structure, the side plates of the horizontally long leg rod have a thin upper end and a thicker lower end, which improves the strength against impact forces that act from the lateral direction on the lower ends of the side plates. , 8th
As shown by the dashed line in the figure, the neutral plane of the cross section approaches the lower end of the side plate, which reduces the tensile stress generated at the lower end of the side plate, so the strength at the lower end of the side plate is greater than that of the conventional one. This will result in a dramatic increase.

On the other hand, the compressive stress at the upper end of the side plate of the horizontally long leg rod will increase slightly, but hard synthetic resin is strong against compressive force, and since the horizontally long leg rod has a U-shaped cross section, Since it is difficult to deform, the upper end part is not easily damaged.

The outer surfaces of both side plates are tapered surfaces with a downwardly widening interval, and the inner surfaces are tapered surfaces with parallel or downwardly widening intervals, which makes it difficult to cut out the mold during molding. There is no problem, and there is no problem with manufacturing.

Therefore, according to the present invention, when molding oblong leg rods for supporting furniture from hard synthetic resin,
Even if the cross-sectional area of the side plate of the horizontally long leg rod is the same as that of the conventional one, the tensile strength and impact strength at the lower end of the side plate can be improved, so there is no possibility of chipping when an object hits the lower end of the side plate of the horizontally long leg rod. It has the effect of reliably preventing or reducing defects such as cracking without causing new problems such as deterioration of appearance, increase in weight, or increase in cost.

〔Example〕

Next, an embodiment in which the present invention is applied to the legs of a chair will be explained based on the drawings (Figs. 1 to 4). The leg body 1 has five oblong leg rods 3 extending radially from the support part 1a into which the guide tube 2 is fitted. A caster 4, which is an example of a ground contact part, is attached to the tip of the rectangular oblong leg rod 3. The leg body 1 is integrally molded from a hard synthetic resin such as glass fiber reinforced plastic (FRP), such as a mixture of 66 nylon and glass fiber at a weight ratio of 67:33, or polycarbonate.

Each of the horizontally long leg rods 3 is formed hollow in a U-shaped cross section with a downward opening, and a rib 6 having an X-shape when viewed from the bottom is provided in succession between the inner surfaces of the side plates 5, 5.
Ribs 8 extending parallel to the side plates 5 are provided on the lower surface of the top plate 7 to protrude downward to provide reinforcement against bending moments acting in the vertical and horizontal directions and torsion around the axis.

And each side plate 5 in each horizontally long leg rod 3,
The inner surface of 5 is formed into a tapered surface that widens downward at a small angle α, while the outer surface of
By forming the tapered surfaces that widen downward at an angle β larger than the taper angle α of the inner surface, each side plate 5 can
The wall thickness of the lower end portion 5b is greater than the wall thickness t3 of the upper end portion 5a.
Form so that t4 is thick. For example, α=
Set to approximately 1° and β = 3°. Note that the inner surfaces may be formed parallel to each other (that is, α=0°).

In this way, when the side plate 5 of the horizontally long leg rod 3 is formed so that its lower end 5b is thick, the impact strength from the side against the lower end 5b is improved, and as shown by the dashed line in FIG. As the height h2 of the neutral plane of bending stress approaches the lower end of the side plate 5, the tensile stress at the lower end 5b can be reduced compared to the conventional example, so the cross-sectional area is the same as that of the conventional example. Even if there is, the tensile strength and impact resistance at the lower end portion 5b will be significantly improved.

However, as the neutral plane of stress moves downward, the compressive stress at the upper end 5a of the side plate increases slightly compared to the conventional one, and the upper end 5a slightly increases.
There is a concern that the strength will decrease at point a, but this type of hard synthetic resin is strong against compressive force and is difficult to deform due to its U-shaped cross section, so there is plenty of strength. Therefore, the strength at the upper end portion 5a is sufficiently maintained.

In addition, since the inner surfaces of the side plates 5 are parallel to each other or extend downward, and the outer surfaces of the side plates 5 are tapered surfaces extending downward, the mold will not become impossible to remove during molding, and the mold can be reliably removed. It can be molded.

Therefore, damage or cracking at the lower end portion 5b of the side plate 5 of the oblong leg rod 3 can be prevented without deteriorating the appearance or increasing the weight.

In addition, in the embodiment, the entire leg body 1 was integrally molded with each of the horizontally long leg rods 3 being connected to each other.
Of course, the attachment portion 1a for the guide tube 2 and the oblong leg rod 3 may be formed separately (the support portion 1a may be made of metal). In addition, this invention
It can be used not only for chair legs, but also for desk or table legs 9 and 10 as shown in Fig. 5, support legs for supporting display poles, or support legs for movable blackboards. Needless to say, the present invention can be applied to various types of horizontally long leg rods that are attached to the lower end of the furniture body and extend laterally.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention; FIG. 1 is a partially cutaway front view of the legs of a chair, and FIG.
3 is a bottom view of FIG. 2, FIG. 4 is a sectional view of FIG. 2, and 5 is a bottom view of FIG.
6 is a perspective view of a conventional leg of a chair, FIG. 7 is a cross-sectional view taken from FIG. 6, and FIG. 8 is a stress distribution diagram on the side plate of an oblong leg rod. It is. DESCRIPTION OF SYMBOLS 1... Leg body, 1a... Support part, 3... Oblong leg rod, 4... Caster, 5... Side plate, 5a... Upper end of side plate, 5b... Lower end of side plate.

Claims (1)

[Scope of utility model registration request] In a horizontally long leg rod made of hard synthetic resin that protrudes laterally from the lower end of the furniture body and has a ground contact portion on the floor at its tip, the horizontally long leg rod is formed into a U-shape with a downward opening in cross section. The outer surfaces of both side plates in the leg rod are formed into tapered surfaces in which the distance between them widens downward, while the inner surfaces of the both side plates in the horizontally long leg rod are formed so that the distance between them is parallel or the outer surfaces are tapered. An oblong leg rod made of synthetic resin for furniture, characterized in that it is formed with a tapered surface that widens downward at an angle smaller than the corner.