JPS5869029A - Synthetic resin molded body and mold apparatus therefor - Google Patents

Abstract

PURPOSE:To obtain a resin product having no weldline, by injecting a synthetic resin material along the entire periphery of the inner peripheral edge of an opening into a cavity when a synthetic resin product having an opening in the center is to be injection molded. CONSTITUTION:When a synthetic resin product 11 having an opening 12 in the center is to be molded by injection molding, a melted resin is injected in the cavity 21 defined by a movable mold 23 having a pin 22 for forming the opening 12 and a stationary mold 26 having an injection port 25 for introducing the melted resin into the cavity 21, and is cooled and solidified to obtain the desired product. In this case, the injection port 25 provided to the mold 26 is formed in the shape of a ring along the pin 22.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a synthetic resin molded article formed by injection molding and a mold apparatus used for molding the synthetic resin molded article.

Conventionally, synthetic resin molded bodies such as sealing caps, cylindrical parts, gears, etc., which are formed by injection molding of synthetic resin, have been molded using a mold apparatus as shown in FIG. This mold apparatus shown in FIG. A synthetic resin material is injected into the synthetic resin molding part 1 and a passage 4 which is in contact with the surface of the mold 3 on which the synthetic resin molding part 1 is provided and through which the synthetic resin material injected from a predetermined hopper flows. The second mold 8 on the fixed side is provided with an injection port 5.

By the way, in the conventional mold device shown in Fig. 1, -
Several synthetic resin injection ports 5 are provided at appropriate intervals in the synthetic resin molded part 1, and the plane of one end surface 7 of one synthetic resin molded body 6 molded by the synthetic resin molded part 1. It is located so that it faces the area. In the mold device configured in this way, the synthetic resin material injected from each injection port 5 flows in the direction of the arrow, centering on each injection port 5, as shown in FIG. The synthetic resin is injected into the molded part 1. Therefore, within the synthetic resin molded part 1, abutting portions of the synthetic resin injected from each injection port 5 are generated. The synthetic resins injected from each injection port 5 are slightly cooled while they collide with each other, and do not completely fuse at the abutting portions. As a result, so-called weld lines 9, which are weak joints with insufficient mechanical strength, occur in the resulting synthetic resin molded body 6.

When the synthetic resin molded body 6 in which such a weld line 9 occurs is configured, for example, as a cap for sealing a dry cell battery, the purpose of providing a fragile portion to release excess pressure within the dry cell main body is It makes you lose your mind. In other words, when there is excessive pressure inside the battery,
The weld line 9 opens before the weakened portion that is actively provided to release the pressure opens, making it impossible to form a sealing cap for protection against excessive pressure as desired.

In addition, when the synthetic resin molded body 6 is used to constitute a transparent plate constituting a cassette half of a tape cassette r, the above-mentioned weld line? When this occurs, this weld line? In this case, opaque and random streaks occur on the transparent plate, making it impossible to obtain a transparent plate that is transparent over the entire surface, and furthermore, it becomes extremely unsightly in terms of aesthetics.

Furthermore, in the mold apparatus shown in FIG. It is not possible to mold a synthetic resin molded body 6 with an accurate shape corresponding to the above. Therefore, it is extremely difficult to mold gears and the like that require highly accurate roundness.

Therefore, the present invention has weak mechanical strength as described above,
The object of the present invention is to provide a synthetic resin molded article that can be formed by injection molding with extremely high molding precision without producing weld lines that impair the aesthetic appearance, and to provide a mold device for forming this synthetic resin molded article. .

That is, the present invention is a synthetic resin molded body formed by injection molding, which is formed by injecting synthetic resin from the entire periphery of the inner peripheral edge of an opening provided in the synthetic resin molded body. It is.

Specific examples of the synthetic resin molded article according to the present invention will be described with reference to the drawings.

FIG. 3 shows an example in which the synthetic resin molded article 11 according to the present invention is applied to a cap for sealing a dry battery.The cap 11 formed by injection molding of this synthetic resin material has a carbon rod in the center. It has an opening 12 through which it is inserted, and is generally formed into a disk shape as a whole. This cap 1
1 is the opening 1 at the inner circumferential edge of the opening 12, that is, at the one end surface 11a side of the cap 11, as shown in FIG.
An injection port for the synthetic resin material is made to face the entire periphery 13 of the inner peripheral side edge 2 of 2, and the molten synthetic resin material is injected from the entire periphery 13 to be molded.

In addition, the synthetic resin molded bodies formed by the present invention include, in addition to the above-mentioned gears and knobs for sealing dry batteries, small gears having openings for inserting support shafts, and tapes having openings on the inner peripheral surface. The present invention can also be applied to a rectangular member having a hole for inserting a reel shaft, such as a transparent plate forming a window of a tape counter of a recorder or a cassette half of a tape cassette.

As a mold device for molding the above-mentioned synthetic resin molded article, one configured as described below is used.

As shown in FIG. 5, this mold device has a synthetic resin molding section 21 corresponding to a desired synthetic resin molding, and an opening that projects into the synthetic resin molding section 21 and is formed in the synthetic resin molding. A first mold 23 on the movable side is provided with pins 22 corresponding to the portions thereof, and a first mold 23 on the movable side is in contact with the surface of the first mold 23 on which the synthetic resin molded portion 21 is provided, and is injected from a predetermined hopper. The mold 26 comprises a synthetic resin material injection passage 24 through which the synthetic resin material flows, and a fixed-side second mold 26 provided with an injection port 25 through which the synthetic resin material is injected into the synthetic resin molding section 21.

In this mold apparatus, the injection port 25 provided in the second mold 26 is formed in a ring shape, and the injection port 25 provided in the second mold 26 is formed in a ring shape.
It is facing the side facing 3.

This injection port 25 is connected to the synthetic resin molded body 11 molded in the plastic molding section 21 when the first mold 23 is inserted.
The entire outer periphery of the pin 22 that protrudes into the synthetic resin molded part 21 so as to face the entire inner peripheral edge 13 of the opening 12 formed in the synthetic resin molded body 11 on the one end surface 11a side. It is provided so as to be open over the entire length.

By using the mold device configured in this manner, a synthetic resin molded body can be molded by injecting synthetic resin material from the entire inner peripheral edge of the opening provided in the synthetic resin molded body as described above. can be formed.

The synthetic resin molded body molded by this mold device is formed by injecting synthetic resin material radially around the inner peripheral edge of the opening provided in the inner surface portion. , it becomes possible to mold without creating weld lines that are generated when synthetic resin materials injected from different directions butt against each other. Therefore, it is possible to prevent the occurrence of weak parts in a synthetic resin molded product in which synthetic resin material is uniformly injected at any location, and furthermore, in products where weak parts are actively provided, such as caps for sealing dry batteries, it is possible to prevent the occurrence of weak parts. , without impairing the function of this vulnerable part. In addition, because so-called weld lines do not occur, it may impair the aesthetic appearance when applied to the transparent plate that forms the window of the tape counter of a tape recorder, or the cassette half of a tape cassette that has a transparent part. do not have. Furthermore, according to the mold apparatus according to the present invention, the synthetic resin material can be injected uniformly around the injection port, so a highly accurate synthetic resin molded body that corresponds precisely to the synthetic resin molded part can be formed. It can also be applied to items that require extremely high machining accuracy, such as small gears. Further, according to the mold device according to the present invention, by separating the second mold on the movable side from the first mold on the fixed side, the injection port can be removed without leaving any debris or the like. Therefore, a desired synthetic resin molded article can be obtained without any post-treatment. In the above embodiment, the injection port for the synthetic resin material is exposed to the periphery of one end surface of the opening of the synthetic resin molded body. It may be arranged so that it faces the inner side of the opening to the extent that it does not leave any debris and does not affect the synthetic resin molded product even if flakes or the like occur.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing a conventional mold device, and the second
The figure is a schematic view showing a state in which synthetic resin material is injected by the mold device. FIG. 3 is a perspective view showing a synthetic resin molded article according to the present invention, FIG. 4 is a sectional view showing an injection state of the synthetic resin material from which this synthetic resin molded article is molded, and FIG. 5 is a perspective view showing a synthetic resin molded article according to the present invention. 1 is a schematic cross-sectional view showing a mold device used for molding a synthetic resin molded body according to the present invention. 11...Synthetic resin molded body 12...
...Opening part 21...Synthetic resin molded part 22...
...Pin 23...First mold 25...River...Inlet 26...Song Second mold patent applicant Sony Corporation representative Person Patent Attorney Kodo Koike 1) Sakae Mura - 1° 22. . No. 31a Figure 5 6 3 Procedural amendment (voluntary) January 20, 1980 Commissioner of the Japan Patent Office Shima 1) Haruki Tono1, Indication of the case 1982 Patent Application No. 1677572, Title of invention case Related Patent Applicant Address: 6-7-35, Kitashina-yo, Tokyo Parts-Yo-ku Name (21
8) Sony Corporation (Name) Representative Kazuo Iwama 4, Agent Address 105 Address 2-6-4 Toranomon, Minato-ku, Tokyo Voluntary

Claims (2)

[Claims] (1) A synthetic resin molded body formed by injection molding, which is a synthetic resin molded by injecting a synthetic resin material from the entire inner peripheral edge of an opening provided in the synthetic resin molded body. Molded object. (2) A first mold having a synthetic resin molded part and provided with a pin protruding from the synthetic resin molded part, and a surface having a synthetic resin material injection passage and facing the first mold. and a second mold provided with a synthetic resin material injection port facing toward the mold, and the synthetic resin material injection port is opened over the entire outer circumference of the pin protruding into the synthetic resin molded part. A mold device for forming synthetic resin molded bodies.