JPH0321943Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an injection mold, and more particularly to an injection mold having a submarine gate feature.

(Prior technology) Submarine gates are suitable for fully automatic molding because they can be cut automatically when the molded product is ejected, and gate marks can be reduced, and in some cases, the gate can be placed inside the annular molded product. It is widely used in injection molds because it can attach

This type of submarine gate is generally described in "Introduction to Plastic Molding Processing" (published by Nikkan Kogyo Shimbun).
As shown on pages 92 and 93, either a fixed or movable mold is provided with a gate that reaches the wall of the molded product, or a secondary runner is provided with a pin that has a gate that penetrates the mold. and is configured to communicate with the cavity through the cavity.

Therefore, although this type of mold has the above-mentioned advantages, it also has the problem that it is more difficult to manufacture and more expensive than a normal mold having a gate portion on the dividing surface.

(Purpose) The present invention was created in view of the above problem, and its purpose is to be easy to manufacture,
Moreover, it is an object of the present invention to provide a new injection mold that hardly requires treatment of gate marks.

(Means for Achieving the Object) In other words, in order to achieve the object, the present invention forms a recess in the joint surface of the movable mold that communicates the runner and the cavity, and a recess on both sides of the part of the recess closer to the cavity. forming a fitting recess with a smaller diameter than the recess, and embedding and fixing in the fitting recess an embedded member whose top portion is flush with the joint surface and whose outer peripheral surface on the runner side is arcuate so as to straddle the recess; A submarine gate with a large runner opening and a small cavity opening is formed between the runner and the cavity by the recess and the embedded member.

(Example) The details of the present invention will be explained below based on the illustrated example.

Fig. 1 shows an embodiment of the present invention, in which a fixed mold 1 attached to a fixed die plate (not shown) of an injection molding machine has a runner 4 and a cavity connected to a spool 3 on its dividing surface PL. 2 are formed separately through a flat surface 5.

On the other hand, a movable mold 6 is attached to a movable die plate (not shown) of the injection molding machine and faces the fixed mold 1.
A cavity 7 and a runner part 8 are recessed in the dividing surface PL so as to correspond to those on the fixed mold 1, and a submarine gate is formed between the cavity 7 and the runner part 8. Cylindrical recess 9
is recessed with an appropriate width. This recess 9
As shown in FIG. 3, the dividing plane
The concave portion 9 is formed as a substantially semicircular cross-section drilled from the PL, and one end of the recess 9 communicates with the runner portion 8, and the other end communicates with the cavity 7 via a sharp edge portion 2e.

Further, on both sides of this recess 9, mounting recesses 10, 10 having a semicircular cross section with a diameter smaller than that of the recess 9 are recessed in a portion closer to the cavity 7 than the boundary line a. A semi-cylindrical body 11 having a cross section is fitted so that its flat top surface is on the same plane as the upper surface of the movable mold 6 and straddles the cylindrical recess 9, and then bolts 12, 12 or welding, etc. It is integrally installed by.

Therefore, in the gate formed by the cylindrical recess 9 and the semi-cylindrical body 11, as shown in FIG. The runner opening 14 is large, the cavity opening 13 is a small gate, and the cross section is shaped like a "Magadama ball".
When the cylindrical recess 9 and the cavity 7 meet, a material guiding path is formed continuously with the circular arc surface 2a inside the cavity of the fixed mold 1, and a sharp edge is provided at the contact point between the cylindrical recess 9 and the cavity 7 to cause stress concentration. 2b is formed.

In the figure, reference numeral 15 indicates a protruding pin that protrudes the spool 3 side of the runner R, and 16 indicates a protruding pin that protrudes the molded product W.

Therefore, when the fixed mold 1 and the movable mold 6 configured in this way are joined together and the molten resin material is fed from the spool 3 to the runner 4, the resin material enters the cylindrical recess 9 through the wide runner opening 14. , further guided by the outer circumferential surface 11a of the semi-cylindrical body 11, and flows into the cavity 2 through the narrow cavity opening 13.

When the runner 4, the gate part, and the cavity 2 are filled with the resin material in this way, the movable mold 6 is separated from the fixed mold 1, and each of the protruding pins 15 and 16 is molded with the runner R. The product W is released from the movable mold 6 (FIG. 2). At this time, the runner R whose spool 3 side is pushed up by the ejecting pin 15 rotates clockwise in the figure while being guided by the outer peripheral surface 11a of the semi-cylindrical body 11 as a fulcrum. The molded product W that has been pushed up is pushed upward as it is. For this reason, the runner R that is integrated with the molded product W has
Tensile force and shearing force act at the cavity opening 13, and this acts as a stress concentration at the edge 2b between the runner 8 and the cavity 7, and as a result, both are reduced to the extent that no post-treatment is required in this area. cut sharply.

In the embodiment described above, a part of the cylindrical recess 9 is filled with a semi-cylindrical body 11 provided biased toward the cavity 7 side to form a submarine gate. In the case where the gate part g on the molded product is provided far away from the joint surface PL, a recess 19 is provided between the cavity 17 and the runner 18 to reach the gate part g, and this recess 19 It is also possible to configure a submarine gate in which the cavity opening 23 is narrow and the runner opening 24 is large by embedding a column 21 having a substantially quarter-circular cross section.

(Effects) As described above, according to the present invention, a recess is provided in the joint surface of the movable mold to connect the cavity and the runner, and a member whose top surface is flush with the joint surface is biased toward the cavity. This type of submarine gate can be easily formed by using a recess formed in the joint surface and a fitting member fixed so as to straddle this recess. Not only can you do it, but
Even if the gate opening becomes deformed or deteriorated due to long-term use, it can be easily repaired or corrected by simply replacing the fitting member. Moreover, since this fitting member is provided in the part of the recess near the cavity, when releasing the mold, simply pushing up the runner slightly using this member as a fulcrum will cause a large misalignment between the molded product and the molded product. In addition, the runner can be easily and reliably separated from the molded product to the extent that no post-processing is required while causing stress concentration at the joint with the cavity.

[Brief explanation of the drawing]

Figures 1 and 2 are cross-sectional views of an apparatus constituting an embodiment of the present invention, showing the operating states of molding and mold release, and Figure 3 is an enlarged view of the main parts of the same apparatus.
Figure a is its cross-sectional view, figure b is its top view, and
The figure is a sectional view of a device showing another embodiment of the present invention. 1... Fixed type, 2... Cavity, 3... Runner, 6... Movable type, 7, 17... Cavity,
8, 18...Runner part, 9, 19...Recessed part, 1
1, 21...Semi-cylindrical body, 15, 16...Protruding pin.

Claims (1)

[Scope of utility model registration request] A recess for communicating the runner and the cavity is formed in the joint surface of the movable mold, and fitting recesses having a smaller diameter than the recess are formed on both sides of the portion of the recess closer to the cavity, and a top portion is formed in the fitting recess. An embedded member whose outer peripheral surface on the runner side is flush with the joint surface and whose outer peripheral surface on the runner side is arcuate is embedded and fixed so as to straddle the recess, and between the runner and the cavity, the recess and the embedded member are fixed. An injection mold characterized by a large runner opening and a small cavity opening forming a submarine gate.