JPH02265720A - Die for molding plastic - Google Patents

Abstract

PURPOSE:To enhance molding effect by increasing the diameter of a gate as compared with a conventional one by providing a fixed die and a movable die and forming a gate into a tunnel type gate by the core provided in the fixed die without providing a gate protruding pin. CONSTITUTION:A gate 8 is provided to a fixed die 1 as a tunnel type gate. The gate 8 pierces the ridge part 21 provided to the fixed die 1 so as to protrude in a semicircular shape and communicates with a runner 7 at the rear end thereof and also communicates with a cavity 9 at the leading end thereof and becomes gradually tapering from the rear end to the leading end thereof. A material is injected in the cavity through a spool 6, the runner 7 and the gate 8 and, after the material is solidified, mold opening is performed. At the time of this mold opening, the spool part (a), the runner part (b) and a molding A are separated from the fixed die 1 along with a movable die 3 and the gate part (c) positioned in the gate 8 is pulled by the runner part (b) and the gate 8 is cut at the connection part (d) with the cavity 9 by the cutting force based on the molding opening force acting on said connection part (d) and separated from the fixed die 1 along with the runner part (b).

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION This invention relates to plastic molding, particularly injection molds.

2. Prior Art Conventionally, when molding a plastic molded product A as shown in FIG. Since the spool a and runner part were separated from the molded product A by manually cutting the gate part C using scissors, post-processing work was required for gate processing, and as a result, the molding work was There was a problem of poor efficiency.

Problems to be Solved by the Invention Therefore, a tunnel gate method has been proposed as a solution to such problems, and in this method, when the mold is opened, the molded product A and the runner part are protruded with a runner ejecting pin. Gate section C was cut.

However, in this method, the cutting of the gate part C is performed by the speed and force of the ejector pin, and normally these cannot be made too large due to the structure of the mold, so the gate part C is completely cut and not left inside the gate. Clogging occurred and tedious work was required to remove it.

In order to avoid this, the diameter of the gate should be made smaller, but there is a problem that if the diameter of the gate is small in this way, the injection time becomes longer and the working efficiency deteriorates.

The purpose of this invention is to solve the problems in the conventional gate method, to prevent the gate from clogging the gate, thereby increasing the diameter of the gate, and to cut the gate when opening the mold. To provide a mold for plastic molding which can be performed automatically, eliminating the need for post-processing and increasing work efficiency.

Means for Solving the Problems In order to achieve the above-mentioned objects, the present invention provides a tunnel-type gate in which the gate is fixedly provided without providing a gate projecting pin.

Furthermore, this gate has a smaller diameter on the tip side than on the runner side.

Function In the above-mentioned molding die, when the mold is opened, the spool a and the runner part, together with the moving mold, cause mold layering from the fixed mold, but at that time, the gate part C is not fixed. It is located within the gate provided in the mold, and therefore a large force is applied to the gate portion C to open the mold, making it easy to cut the molded product A.

In this case, since the gate has a smaller diameter on the cavity side than on the runner side, the gate portion C can be reliably cut from the molded product A.

Example An embodiment of the invention shown in FIGS. 1 to 3 will be described.

In this embodiment, no gate protruding pin is provided;
Since this mold is the same as a conventional mold of this type except for the special gate, the description of the same parts will be omitted.

1 is a fixed type, 2 is a fixed type mounting plate, 3 is a movable type, 4 is a movable type mounting plate, 5 is a back plate, 6 is a spool bush, 7 is a runner, 8 is a gate, 9 is a cavity, 11 is a 1 slide core, 12 a second slide core oriented perpendicular to it, 13
is an angular pin.

14 is an extrusion plate, 15 is a runner extrusion pin, 16 and 17 are extrusion pins, and 18 is a support.

In the second embodiment, the gate 8 is provided in the fixed mold 1 in the form of a tunnel, the details of which are shown in FIGS. 2 and 3.

In these, 20 indicates the parting surface, and the gate 8
is a protrusion portion 21 provided on the fixed mold 1 in a semicircular shape.
It passes through in the axial direction, communicates with the runner 7 at the rear end, communicates with the cavity 9 at the tip, and gradually tapers from the rear end to the tip.

The drawing shows the mold closed state, and the material is injected into the cavity 9 of such a mold via the spool 6, runner 7, and gate 8, and when it solidifies, the mold is opened.

When opening the mold, the spool a, the runner part and the molded product A are separated from the fixed mold 1 together with the movable mold 3, and the gate part C located inside the gate 8 is pulled by the runner part. The gate 8 is cut at this point by a cutting force based on the mold opening force acting on the connecting portion d (FIG. 3) with the cavity 9, and is separated from the fixed mold 1 together with the runner section.

During this time, the slide core 11.12 moves in the same direction as the conventional one, and when the movable die 3 moves to a predetermined position, the ejector pins 15, 16, 17 move the spool a, runner part b, gate part C, Molded product A is separated and taken out of the mold.

Effects of the Invention This invention is as described above, and eliminates the gate projecting pin required in conventional molds, and uses a tunnel type gate provided in a fixed mold, so that the gate part and Cutting from the molded product is done by using a large mold opening force, so there is no possibility that the gate remains in the gate and clogs it after the mold is opened, and the gate diameter is reduced. The molding effect can be increased compared to the conventional one, and the molding effect can be enhanced, and the structure for this purpose is simple and manufacturing is easy.

Furthermore, by making the diameter of the gate smaller on the cavity side than on the runner side, there is also the effect of making cutting of the gate part more reliable.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a main part of an embodiment of the present invention, Fig. 2 is a cross-sectional view taken along line 2-2 of the same, Fig. 3 is a cross-sectional view taken along line 3-3 of the same, and Fig. 4 is a cross-sectional view of the invention. FIG. 2 is a perspective view of an example of a product molded by the method. 1...Fixed type 3...Movable type 6...Spool 7...Runner 8...Gate
9...Cavity it, 12...Slide core 15
．． 16.17...Extrusion pin 20...Parting surface 21...Protrusion portion Fig. 1

Claims (1)

[Scope of Claims] 1. It has a fixed mold and a movable mold, and is characterized in that the gate is made into a tunnel-type gate by a nest provided in the fixed mold without providing a gate protruding pin. Plastic mold. 2. The plastic molding die according to claim 1, wherein the gate has a smaller diameter on the cavity side than on the runner side.