JP2744373B2 - Method of forming legs in chair - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of molding a synthetic resin leg to which a support for supporting a seat in a chair is fitted so as not to slip off.

[0002]

2. Description of the Related Art Japanese Utility Model Publication No. 56-5965 and Japanese Utility Model Publication No.
In Japanese Patent Laid-Open Publication No. 1-16836, a lower end of a columnar column for supporting a seat body of a chair is formed in a truncated conical shape with a smaller diameter as going downward, while a plurality of leg arms of the leg are arranged at the center. The leg portion is formed so as to extend radially in a plan view, a caster is attached to each leg arm tip portion, and the lower end portion of the truncated cone is fitted to the tapered post receiving portion at the central portion. Has been proposed.

In the above prior art, the leg is made of metal and thus is sturdy, but the base of the leg arm must be welded to the column receiving part, which increases the number of manufacturing steps and increases the manufacturing cost. In recent years, Japanese Patent Application Laid-Open
As disclosed in Japanese Patent Application Laid-Open No. 0813, this leg is integrally injection-molded with a thermoplastic synthetic resin material.

In this case, between a pair of molds for injection molding,
A communicating cavity (gap) corresponding to a central column supporting portion of the leg body and a plurality of (four or five) leg arms extending radially therefrom is formed, and a molten synthetic resin material is formed in the cavity. At a predetermined pressure.
Like the above-mentioned legs, it has a pillar support portion at the center in plan view, and a substantially point-symmetrical shape in which a plurality of leg arms extend radially therefrom, the molten state from the nozzle of the injection machine to the cavity. Considering the fluidity of the synthetic resin and the control of the flow direction of the synthetic resin, it is preferable that the portion to be filled with the synthetic resin is on the center side of the support receiving portion.
In addition, since it is necessary to form the hole surface of the column receiving portion in a tapered shape, a nested body for forming the inner diameter surface of the column receiving portion is inserted into the one mold so as to face the inside of the cavity. This is the usual molding method.

[0005] However, as a conventional molding method, FIG.
As shown in the figure, the inner diameter (center) of the nested body 102 located inside the pair of molds 100 and 101 communicates from the nozzle (not shown) of the injection machine to the cavity 103 corresponding to the support receiving portion. A gate 104 (referred to as a molten synthetic resin filling passage, a sprue gate or a direct gate) will be provided, so that the bottom plate 105 is connected to the lower end of the tapered column receiving portion of the molded product. It will be molded into.

[0006] As shown in FIG.
In order to make contact with substantially the entire inner diameter surface of the tapered post receiving portion 109 at 08, the diameter D1 of the large diameter portion and the diameter of the small diameter portion of the nested body 102 correspond to the shape of the lower end portion 107. D2 and length H1 may be set to predetermined values. In addition, the nested body 10 after injection molding is used.
The solidified resin portion 110 of the gate 104 in FIG.
0 is cut out together with the center of the bottom plate 105.

[0007]

By the way, the thickness of the support receiving portion 109 in the synthetic resin leg cannot be made too large. Then, when the downward load of the person sitting on the seat body repeatedly acts on the tapered column receiving portion 109 via the column 106, the diameter of the column receiving portion 7 is increased and deformed, and the column 106 is moved to the initial position. There was a problem that it would sink much more than this.

In order to solve this problem, the lower end 10 of the support 106 is attached to the upper surface of the bottom plate 105 formed at the time of molding.
7 so that the lower surface contacts the initial state.
If it is desired to change the dimensions and shape of the lower end portion 107 of the support column 106, particularly when the length of the lower end portion 107 is short, It is necessary to change the shape of the nested body 12 without changing the pair of molds 100 and 101, particularly to shorten the length. Then, the thickness of the bottom plate 105 becomes excessively large compared with the thickness of the cylindrical portion of the support receiving portion 109, and this portion is a portion that enters the cavity 103 from the gate 104, and excessive molding occurs when the synthetic resin is solidified. There is a problem that cracks and deformations are apt to occur due to residual stress such as application of pressure and injection molding becomes difficult. Therefore, conventionally, although the outer dimensions of the legs are the same, if the outer dimensions of the pillars are changed, it is necessary to recreate the mold itself, and there has been a problem that the manufacturing cost becomes extremely high.

An object of the present invention is to solve these problems.

[0010]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a support for supporting a lower end portion of a support in a chair, and a plurality of radially extending radially connected to the outer surface of the support. A cavity for forming a leg having a leg arm is formed between a pair of molds, and an inner diameter surface of the column receiving portion is formed in a downward constricted shape toward the lower part of the leg in the cavity. A method of providing a locking portion protruding in the radial center direction at a position closer to the lower portion of the column receiving portion on the inner diameter surface, wherein a lower end outer peripheral edge of a nesting body for forming the inner diameter surface of the column receiving portion; Inserting the nested body and the ring body into the cavity with a space corresponding to the locking portion formed between the ring body detachably attached to the lower end of the body, and then the inner diameter of the nested body Synthetic tree in cavity through section After filling the is obtained by employing the method of removing said nesting body and cover the surface of the opposite side of the ring body synthetic resin and the ring member.

In place of the above method, a ring body larger than the outer diameter of the lower end of the nested body is detachably attached to the lower end of the nested body for forming the inner diameter surface of the column receiving portion. After inserting the body and the ring body into the cavity and then filling the cavity with the synthetic resin through the inner diameter of the nest, the nest and the synthetic resin covering the inner diameter of the ring are removed. You may do it.

[0012]

According to the first method, the engagement projection can be integrally formed on the inner diameter surface of the support member. According to the second method, the engagement surface can be formed on the inner surface of the support member. The ring body buried in the hole serves as an engagement protrusion. According to this method, by changing the shape and dimensions of the nesting body without changing the external dimensions of the legs, it is possible to adapt the shape to the lower end of the pillar having any shape and size, and in particular, the engagement protrusions This makes it easy to change the position where the ring is provided or the position where the ring body is attached, and even in such a case, the leg can be formed without changing the forming performance. Therefore, there is also an effect that the work of changing the dimensions of the columns in the chair can be extremely easily performed.

Further, when the outer dimensions of the legs are the same, and the outer dimensions of the pillars, especially the shape and dimensions of the lower end portion, can be dealt with only by changing the dimensions and shapes of the nested body and the ring body. Has a remarkable effect of being inexpensive.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will now be described. The seat 2 in the chair 1 shown in FIG.
Are supported by legs 4 made of synthetic resin. The gas cylinder 3 is configured such that an elevating shaft 6 that moves up and down with respect to a lower support 5 can be held at an appropriate height position by an operation lever (not shown). Attach to the underside of.

The legs 4 are, as shown in FIGS.
6 is formed integrally with a synthetic resin such as nylon, polycarbonate, polyacetal resin, etc.
In the center of the column, as shown in FIG. 6, there is provided a column receiving portion 7 having an inner diameter surface 7a of a tapered cross-section square or round hole having a constricted shape having an angle of θ with respect to a vertical line. Three or more (five in this embodiment) leg arms 8 are radially extended on the outer periphery of the column receiving portion 7 in plan view, and a caster 9 is attached to the tip of each leg arm 8.

The lower end 5a of the column 5 in the gas cylinder 3 is inserted into the column receiving portion 7.
Therefore, the lower end portion 5a is formed in a truncated cone shape or a truncated pyramid shape so as to have the same taper angle as θ and to have a smaller diameter as going downward. Next, a method of manufacturing the leg 4 by injection molding will be described.
FIGS. 3 to 5 show a first embodiment of the present invention, in which a cavity 10 for forming the leg 4 is formed between a pair of dies 11 and 12. In order to form the inner diameter surface 7a of the column receiving portion 7 in a downward constricted shape as it goes below the leg 4 in the cavity 10, the nest 14 is made to face the cavity 10 and the base of the nest 14 is formed. Is detachably attached to one of the molds 11. A vertically elongated gate 15 is formed in the center of the inner diameter of the nested body 14 so as to penetrate vertically (from the base to the free end). Reference numeral 16 denotes an annular concave portion for integrally forming a ring-shaped locking portion 13 protruding in the radial center direction at a portion of the inner diameter surface 7a near the lower portion of the column receiving portion 7, and reference numeral 17 denotes an inner diameter portion of the ring body 18. This is a fitting step portion for supporting. This ring body 18 is
7, the nesting member 14 and the ring member 18 are put into the cavity 10, and the gate 15 is filled with a molten synthetic resin (see FIG. 4).

At this time, the ring body 18 is
A support pin 19 projecting from one surface of the ring body 18 toward the inner surface of the other mold 12 so as not to be accidentally dropped inside.
(See dashed lines in FIGS. 3 and 4). Alternatively, the ring body 18 may be inserted upward into the cavity 10 so as to be supported by the fitting step 17 of the nesting body 14, or the mating surfaces of the pair of dies 11, 12 may be substantially vertical ( The axis of the nesting member 14 may be laterally oriented).

After the synthetic resin is solidified in the cavity 10, the two dies 11, 12 are separated from the mating surface.
The leg 4 in a state where the nesting member 14 and the ring member 18 are fitted to each other is formed in the inner diameter portion of the column receiving portion 7. Then, FIG.
In the above, when the bottom plate 20 portion of the support receiving portion 7 is removed with a cutting tool or the like larger than the outer diameter of the ring body 18 and the edge of the nested body 14 at the tip of the gate 15 and the resin portion 21 is cut, And the nesting member 14 can be separated and removed.

In this way, the inner diameter surface 7a has
A ring-shaped locking portion 13 protruding in the radial center direction can be integrally formed at a predetermined lower portion of the column receiving portion 7. Therefore, when the lower end portion 5a of the support is inserted into the inner diameter hole of the support receiving portion 7, the lower end 5a contacts the upper surface of the ring-shaped locking portion 13, and even if a downward load acts on the support,
The strut 5 does not sink much to the leg 4.

FIGS. 7 and 8 show a second embodiment of the manufacturing method, in which a small-diameter fitting step 17 is provided at the lower end of a nesting member 14 for forming the inner diameter surface of the column receiving portion 7 of the leg 4. The fitting step 1 has a lower end outer diameter D of the nesting body 14.
A ring body 22 having an outer diameter D4 larger than 3 is detachably attached. In this state, the nested member 14 and the ring member 22 are inserted into the cavity 10 between the pair of molds 11 and 12, and then melted into the cavity 10 through the gate 15 at the inner diameter of the nested member 14. After the synthetic resin is filled and the synthetic resin is solidified, the nesting member 14 and the synthetic resin covering the inner diameter of the ring body 22 are removed. In other words, only the ring body 22 is left on the inner diameter of the portion near the lower portion of the column receiving portion 7. In this case, the ring body 22 plays a role of a locking portion that can support the lower end 5a of the column 5 inserted into the inner diameter hole of the column receiving portion 7.

It is needless to say that the integrally formed locking portions 13 need not be ring-shaped, but may be provided at appropriate intervals in the circumferential direction. Further, in order to prevent the settlement, the outer peripheral surface of the lower end portion 5a of the support may be knurled to provide a rough surface portion of knurls.

[Brief description of the drawings]

FIG. 1 is a perspective view of a chair.

FIG. 2 is a bottom view of a main part of a leg.

FIG. 3 is a partially cut-away side sectional view of the nested body and the ring body of the first embodiment.

FIG. 4 is an enlarged sectional view of a cavity part in a mold.

FIG. 5 is a partially cutaway side sectional view of a manufacturing process.

FIG. 6 is a cross-sectional view of a state in which a support is mounted on a support receiving portion.

FIG. 7 is an enlarged sectional view of a cavity part in a mold according to a second embodiment.

FIG. 8 is a cross-sectional view of a state in which a support is mounted on a support receiving portion.

FIG. 9 is an enlarged sectional view of a cavity in a mold according to the related art.

FIG. 10 is a cross-sectional view of a state in which a support in the related art is mounted on a support receiving portion.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Chair 2 Seat 3 Gas cylinder 4 Leg 5,106 Column 5a Lower end 7,109 Column receiving part 7a Inner diameter surface 8 Leg arm 10,103 Cavity 11,12,100,101 Mold 13 Locking part 14,102 Nested body 15, 104 Gate 16 Annular recess 17 Fitting step 18, 22 Ring body 20 Bottom plate

Claims (2)

(57) [Claims] A pair of cavities for forming a leg having a column receiving portion for supporting a column lower end portion of a chair and a plurality of radially extending leg arms connected to an outer surface of the column receiving portion. In the cavity, the inner diameter surface of the strut receiving portion is formed in a constricted shape as it goes below the leg in the cavity, and the inner diameter surface has a radius near the lower portion of the strut receiving portion. In the method of providing a locking portion protruding in the center direction, a method is provided between an outer peripheral edge of a lower end of a nesting body for forming an inner diameter surface of the column receiving portion and a ring body detachably attached to a lower end of the nesting body. With the cavity corresponding to the locking portion formed, insert the nested body and the ring body into the cavity, and then fill the cavity with the synthetic resin through the inner diameter of the nested body, Table of ring body opposite to nested body Method of molding the leg in the synthetic resin and chair and removing a ring covering the. 2. A pair of cavities for forming a leg having a column receiving portion for supporting a column lower end portion of a chair and a plurality of leg arms connected to an outer surface of the column receiving portion and extending radially. In the cavity, the inner diameter surface of the strut receiving portion is formed in a constricted shape as it goes below the leg in the cavity, and the inner diameter surface has a radius near the lower portion of the strut receiving portion. In the method of providing a locking portion protruding in the center direction, a state in which a ring body larger than the outer diameter of the lower end of the nesting body is detachably attached to the lower end of the nesting body for forming the inner diameter surface of the column receiving part. Then, after inserting the nested body and the ring body into the cavity, and then filling the cavity with the synthetic resin through the inner diameter part of the nested body, the nested body and the synthetic resin covering the inner diameter part of the ring body And remove Method of molding the leg in the chair, wherein the door.