JP5313013B2 - Tunnel gate mold - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mold for molding of a resin which solves problems associated with a tunnel gate while retaining advantages of employment of a tunnel gate. <P>SOLUTION: A tunnel gate type molding die is so constructed that a molten resin injected into a sprue 54 flows from a runner 56 inclined with respect to the parting plane 30 of the mold, passes through the tunnel gate 58 and reaches each cavity 32. A hollow sprue bush 14 is incorporated into a fixed mold 10, and a heater 40 for heating the molten resin is incorporated in the sprue bush 14. The space portion between the sprue bush 14 and the heater 40 constitutes the sprue 54 and runners 56 going from the sprue 54 to individual cavities 32. Tunnel gates 58 each connecting a runner 56 to a cavity 32 are arranged in the sprue bush 14. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a tunnel gate type mold in which molten resin injected into a sprue reaches a cavity from a runner through a tunnel gate.

  As a mold for resin molding using this type of tunnel gate, for example, the technique disclosed in Patent Document 1 is already known. As shown in this technology, in the mold where the molten resin injected into the sprue flows from the runner through the tunnel gate and into the cavity, the product and gate part are automatically cut by the mold opening after molding, and the gate Since the trace is not conspicuous, there is an advantage that finishing is not necessary.

JP-A-6-328511

  However, since the tunnel gate has a small diameter of 0.8 to 2.0 mm, the gate seal accompanying the hardening of the resin is fast and it is difficult to apply pressure in the cavity. Further, when molding a thin product, chipping is likely to occur from the gate portion.

  The present invention is intended to solve the above-described problems, and an object of the present invention is to solve the problems of the tunnel gate while maintaining the advantages of adopting the tunnel gate.

The present invention is for achieving the above object, and is configured as follows.
According to a first aspect of the present invention, a plurality of cavities are formed in a two-plate mold composed of a fixed mold and a movable mold, and the molten resin injected into the sprue of the fixed mold is a parting surface of the mold. A tunnel gate type mold configured to reach individual cavities from a runner inclined with respect to the tunnel gate. A hollow sprue bushing is incorporated in the fixed die and melted in the sprue bushing. A heating body for heating the resin is incorporated. The space between the sprue bushing and the heating element constitutes a sprue and a runner from the sprue toward the individual cavities. And the tunnel gate which leads to each cavity from each runner is comprised by the sprue bush, respectively.

  In this configuration, a tunnel gate with a small passage diameter is generally used, but the resin in the runner and tunnel gate is melted by the heating element even when the resin enclosed in the cavity begins to harden. Can be kept in a state. As a result, it is difficult to apply pressure to the inside of the cavity, which is a disadvantage of the tunnel gate, while maintaining the advantages of automating the gate cut, which is an advantage of the tunnel gate, and eliminating the need for finishing the gate trace. Problems such as chipping can be solved.

According to a second invention, in the first invention, the end portion of the sprue bush incorporated in the fixed die is a fitting portion that protrudes from the parting surface and fits into the movable concave portion.
As a result, the sprue bush can also be used as a cotter pin of the mold, and the structure of the mold can be simplified.

It is sectional drawing showing the tunnel gate type metal mold | die. FIG. 2 is an enlarged cross-sectional view of a part of FIG.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
The molding die shown in FIG. 1 is a two-plate type including a fixed die 10 on the upper side of the drawing and a movable die 20 on the lower side of the drawing. These fixed mold 10 and movable mold 20 are fixed to individual mounting plates 12 and 22. The fixed mold 10 has a sprue 54 configured as described later, and a plurality (4 to 6) of cavities 32 are formed by the fixed mold 10 and the movable mold 20 around the sprue 54. Resin products 60 are respectively molded by encapsulating molten resin in these cavities 32 and curing them.
A product 60 shown in the drawing is an acrylic map lamp lens in an in-vehicle overhead console.

  The movable mold 20 can be operated in a direction perpendicular to the parting surface 30 of the mold (downward in the drawing) through the mounting plate 22, whereby the mold is changed from the mold-clamped state shown in the drawing to the mold-opened state. Switched. A predetermined space is secured by the spacer 24 between the movable mold 20 and the mounting plate 22. The protruding plate 26 incorporated in this space can move relative to the operation of the movable mold 20. Further, the two protrusion plates 26 are combined, and thereby the base ends of the plurality of protrusion pins 28 are fixed. These protruding pins 28 penetrate through the movable mold 20, and the respective leading ends thereof reach the bottom surfaces of the corresponding cavities 32 on the movable mold 20 side.

A hollow sprue bushing 14 is incorporated in the fixed mold 10. The sprue bushing 14 is inserted into the fixed mold 10 from the upper surface side. The sprue bushing 14 is fixed in a state where the upper end flange portion 16 is sandwiched between the fixed mold 10 and the mounting plate 12, and the lower end fitting portion 18 is fitted in the concave portion 34 of the movable mold 20. Matching. Therefore, the fitting portion 18 of the sprue bush 14 in the mold open state of the mold protrudes from the parting surface 30 of the fixed mold 10.
The outer peripheral surface of the fitting portion 18 and the inner peripheral surface of the concave portion 34 are tapered cone surfaces, and the fitting portion 18 fits into the concave portion 34 when the mold is clamped. Functions as a cotter pin for the mold.

  The sprue bushing 14 is generally referred to as “nesting”, and has a structure that is vertically divided into two. Inside the sprue bush 14, a sprue 54 and a runner 56 heading from the sprue 54 to the individual cavities 32 are configured together with the heating body 40 described below. Further, as is apparent from FIG. 2, a tunnel gate 58 for communicating each runner 56 and each cavity 32 is formed on the peripheral wall of the sprue bush 14. As described above, the sprue bush 14 needs to be processed to form the sprue 54, the runner 56, and the tunnel gate 58. However, since the sprue bush 14 is divided vertically, high-precision processing is required. Is possible.

A heating body 40 is incorporated in the hollow of the sprue bushing 14. The base 42 of the heating body 40 is fixed to the fixed mold 10 on the upper surface side of the mounting plate 12. The base 42 is provided with an injection port 50 through which molten resin is injected from a nozzle of an injection mechanism (not shown), and a passage 52 leading from the injection port 50 to the sprue 54 in the sprue bushing 14 (FIG. 1).
The shaft portion 44 integrated with the base portion 42 incorporates an electric heater in an insulated state. The shaft portion 44 is positioned coaxially with the sprue bushing 14 in the sprue bushing 14, and the tip end portion 48 of the shaft portion 44 extends from the inner surface side to the shaft center portion of the fitting portion 18 in the sprue bushing 14. It is supported by fitting. In addition, the shaft portion 44 includes a hook-shaped protruding portion 46 that protrudes from the outer peripheral surface near the tip thereof toward each cavity 32.

  A space between the inner peripheral surface of the sprue bushing 14 and the outer peripheral surface of the shaft portion 44 of the heating body 40 is a sprue 54 that forms a flow path of the molten resin in the mold. Further, the inside of the sprue bush 14 has a shape in which each protruding portion 46 of the shaft portion 44 in the heating body 40 is accommodated, and these space portions are runners 56 respectively. Each runner 56 is set to have a predetermined inclination angle (about 45 °) with respect to the parting surface 30 by the outer surface shape of the protruding portion 46 and the inner surface shape of the sprue bushing 14. Each runner 56 communicates with each cavity 32 through a tunnel gate 58 having a small diameter (0.8 to 2.0 mm in diameter).

Next, resin molding will be described.
In the mold clamping state shown in the drawing, the molten resin injected into the sprue 54 from the injection port 50 through the passage 52 flows into the individual cavities 32 from the runners 56 through the tunnel gates 58. At this time, the molten resin flowing through the sprue 54 and the runner 56 is kept heated by the heating body 40 (shaft portion 44), and the molding die functions as a “hot runner system”.

The molten resin filled in each cavity 32 is cured as it cools, whereby a plurality of products 60 are formed simultaneously. After the molding, the movable mold 20 is operated downward in FIG. 1, whereby the movable mold 20 is separated from the fixed mold 10 on the parting surface 30 and the mold is opened. As a result of the mold opening, each product 60 remaining on the movable mold 20 side and each runner 56 on the fixed mold 10 side are automatically cut from each other at the respective tunnel gates 58.
At the same time, as the movable mold 20 is operated, the protruding plate 26 is relatively displaced upward in FIG. 1, and the individual products 60 are pushed up from the molding surface of the movable mold 20 by the protruding pins 28. And demolded.

  As described above, by using the tunnel gate 58 and the hot runner method in combination, the resin in the runner 56 and the tunnel gate 58 is kept in a molten state even when the molten resin starts to cool and harden in the cavity 32. be able to. For this reason, it becomes possible to delay the gate seal and apply a sufficient holding pressure in the cavity 32, and even if the product 60 is thin, the problem of chipping from the location of the gate portion when the mold is opened is also eliminated. . The advantages of adopting the tunnel gate 58, that is, the advantage that the gate cutting is automated or the gate trace is inconspicuous and the finishing process is not required are maintained.

DESCRIPTION OF SYMBOLS 10 Fixed type 14 Sprue bush 20 Movable type 30 Parting surface 32 Cavity 40 Heating body 54 Sprue 56 Runner 58 Tunnel gate

Claims (2)

A runner in which a plurality of cavities are formed in a two-plate mold consisting of a fixed mold and a movable mold, and the molten resin injected into the sprue of the fixed mold is inclined with respect to the parting surface of the mold A tunnel gate type mold configured to reach individual cavities from the tunnel gate,
A hollow sprue bushing is incorporated in the fixed mold, and a heating body for heating the molten resin is incorporated in the sprue bushing, and the sprue and the sprue are separated by a space between the sprue bushing and the heating body. Runners heading to individual cavities, and tunnel gate molds with sprue bushings that are connected to individual cavities from each runner. The tunnel gate type molding die according to claim 1,
A tunnel gate molding die in which the end of a sprue bush incorporated in a fixed mold is a fitting part that protrudes from a parting surface and fits into a concave part of a movable mold.

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