JPH0796258B2 - Molding method for synthetic resin hollow wheels - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement in a method for molding a synthetic resin hollow wheel used for a light-duty vehicle such as a riding lawn mower by blow molding.

(Prior Art) Conventionally, as a method of molding a lightweight synthetic resin wheel that can be mass-produced, it is practical to mold a wheel portion having an axial hole and a tire portion integrally with each other by a synthetic resin such as polyethylene into a hollow shape. It is widely known in the publication such as −27420.

(Problems to be Solved by the Invention) However, when the synthetic resin wheel is molded by blow molding, it is difficult to sufficiently increase the thickness of the wheel portion forming the shaft hole. In addition to its insufficient strength, it is often necessary to separately fit and use bearing metal fittings at both ends of the shaft hole, which makes it impossible to efficiently form a strong wheel with thick bearing parts. There was a problem.

The present invention has been proposed to solve this problem, and an object of the present invention is to provide a method of molding a synthetic resin hollow wheel that is easy to mold, is lightweight, and has excellent strength.

(Means for Solving Problems) In order to solve the above problems, in the present invention, a substantially cylindrical insert member is projected from the vicinity of the center of the bottom surface of the recess formed on the inner surface of the blow molding die. The parison set in the mold is locally pressed against both sides of the parison set by the insert member when the mold is clamped, and the two parts of the parison near the central part facing each other are locally fused. The technical means is to form a hollow wheel body from the parison, form a bearing part from the insert member, and fix both at the same time by injecting air from the through hole protruding in the Is.

(Example) An example of the present invention will be described below.

FIG. 1 shows a mold for molding a hollow wheel. A recess (2) is provided on the inner surface of the blow molding mold (1), and the recess (2) protrudes from approximately the center of the bottom surface. An insert member (5) made of synthetic resin such as high-density polyethylene, which is formed in a substantially cylindrical shape, is loosely inserted outside the provided cylindrical protrusion (3), and the insert member (5) is a recess. It is held in a state of protruding toward the inside of the mold from the vicinity of the central portion of the bottom surface of (2).

FIG. 2 shows the mold (1) in a clamped state. The parison (6) made of synthetic resin such as high density polyethylene set in the mold (1) has left and right sides near the center. The tip (5a) of the insert member (5) is locally pressed, and its opposing central portions (6a) are in contact with each other and locally fused.

After that, an air blowing tube (not shown) is inserted into the through hole (4) protruding from the die (1), the wall of the parison (6) is ruptured at the tip of this tube, and then the air is blown into the parison ( 6) Blow in to mold a hollow molded product having an insert member.

Then, after cooling, the hollow molded product is taken out, and the fusion-bonded portion (6a) of the parison formed between the left and right insert members (5) is cut out to remove the left and right insert members (5).
A shaft hole communicating with the inside is formed.

FIGS. 3 and 4 show the synthetic resin hollow wheel formed as described above, and (11) is a hollow wheel body molded from the parison (6), which includes the web portion (12) and the tire. The part (13) and the hub part (14) are integrally formed.

Reference numeral (16) is a bearing portion formed from the insert member (5) and having a shaft hole (17) therein, and is integrally fixed to the hub portion (14) of the wheel body (11) at the same time during blow molding.

Unlike the above embodiment, the insert member may be made of a synthetic resin material different from the parison, or may be made of a metal material.

If necessary, a synthetic resin material or the like may be filled in the air injection hole (15) of the parison left in the wheel body (11) to close the hole.

Further, in the above-mentioned embodiment, the outer peripheral surface of the insert member (5) is made uneven so that it is fixed to the hub portion (14) of the wheel body (11) in a fitted state. It does not matter if the outer peripheral surface is formed smoothly.

Further, the tire body (11) of the wheel body (11) may be provided with an uneven surface without smoothing the outer peripheral surface thereof.

(Effects of the Invention) Since the present invention is configured as described above, it has the following effects.

When the bearing part with a shaft hole is formed from a parison without using an insert member, the bearing part cannot be made thick enough, so the strength in the radial and axial directions is inferior, whereas it is formed from a parison. Since the bearing portion made of an insert member separately molded can be integrally fixed to the inner circumference of the hub portion, the strength of the bearing portion can be significantly increased.

When the bearing part is formed from a parison, the dimensional accuracy cannot be sufficient due to the influence of delicate blow molding conditions, while the insert member that forms the bearing part can be precisely formed by injection molding separately.
The dimensional accuracy of the bearing can be made very good.

Since the bearing portion made of the insert member can be integrally fixed to the wheel body at the same time during the blow molding process of the wheel body, it is not necessary to perform the bearing fixing work separately from the wheel body molding work, and the manufacturing efficiency is excellent.

[Brief description of drawings]

The drawings show one embodiment of the present invention. FIG. 1 is a cross-sectional view of a mold used in the present invention, FIG. 2 is a cross-sectional view showing a mold clamping time, and FIG. 3 is a cross-section of a wheel molded according to the present invention. FIG. 4 is a side view thereof. (1) …… Mold, (2) …… Concave, (5) …… Insert member, (6) …… Parison, (11) …… Wheel body, (16) …… Bearing section.

Claims (3)

[Claims] 1. A blow molding die is held in a state in which a substantially cylindrical insert member is projected from the vicinity of a central portion of a bottom surface of a recess formed on the inner surface of the die, and both sides of a parison set in the die are held. Locally pressed by the insert member at the time of mold clamping, after locally fusing the neighboring central portions of the parison, by blowing air from the through hole punched in the mold, A method for molding a hollow wheel made of synthetic resin, characterized in that a hollow wheel main body is formed from the parison, a bearing portion is formed from the insert member, and both are fixed at the same time. 2. A method for molding a synthetic resin hollow wheel according to claim 1, wherein the insert member is made of synthetic resin. 3. The method of molding a synthetic resin hollow wheel according to claim 1, wherein the insert member is made of metal.