JPS6134968B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mold apparatus for molding synthetic resin caps, and is intended to prevent the occurrence of so-called sink marks as much as possible after molding synthetic resin caps.

Synthetic resin caps, which are generally used for containers and the like, are obtained by filling a molding space formed by a cavity and a core with molten synthetic resin, and releasing the mold after the resin has cooled to a certain extent.

However, from the viewpoint of work efficiency, the molded cap is released from the core before it is completely cooled, so a so-called sink phenomenon appears on the outer surface of the cap due to an imbalance in shrinkage during cooling. I end up. This is particularly noticeable on the outer surface of the cap peripheral wall where the screw grooves are cut, and is a very serious defect in decorative caps where appearance is important.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The molding die device according to the present invention is capable of preventing sink marks to some extent on synthetic resin caps that are molded products, and one embodiment thereof will be described with reference to the drawings.

In the drawing, 10 is the cavity, 20 is the core,
S is the molding space for the cap that will become the product. In the present invention, the structure of the cavity side wall 11 is devised to achieve the above object.

First, a small radius R is provided at the back corner of the cavity 10, and the lowest position of this radius R is defined as position A, and the lowest position at the end of the cavity 10 is defined as position B, and the above positions A and B are The connected straight line is assumed to be a virtual straight line, and the intersection position of this virtual straight line and the extension line of the cavity top surface 12 is set as position C.

Next, the shape and size of the cap to be molded are determined.
The lowest position of the core packing land of the core 20 that is assembled into the cavity 10 in a predetermined positional relationship in view of the molding space S determined by the wall thickness etc. is a position D,
Further, a position between this position and the position C and on the virtual straight line is set as a position E, respectively;
Furthermore, the desired amount β, which is on the same plane as the position E on the plane perpendicular to the axis and is determined according to the wall thickness α of the peripheral wall of the product cap, is the thickness of the peripheral wall of the cap to be obtained as described above. The value of β is approximately 1/20 to 1/20 of the wall thickness α.
It is thought to be 1/50.

In such a position setting, the side wall 11 of the cavity 10 according to the present invention is formed into the following shape.

That is, position A and position F are smoothly connected to radius R to form a curved surface, and position F and position B are connected with a straight line to form the surface of side wall 11. be. In other words, the side wall 11 here is a surface that is hollowed out by the desired amount β at position E, rather than the surface formed by the imaginary straight line connecting position A and position B. be.

The mold device according to the present invention has the configuration described above. Therefore, in the present invention, the synthetic resin cap, which is molded by filling the space formed by the cavity and the core with molten resin, has a peripheral wall slightly expanded by the desired amount β immediately after the mold is released. Although it has an outwardly bulging shape, unbalanced shrinkage after mold release is avoided, so sink marks are prevented to some extent, and a synthetic resin cap with a beautiful appearance can be obtained.

[Brief explanation of the drawing]

The drawing is a half-sectional view of a cavity and a core according to the present invention. 10...Cavity, 11...Side wall, 12...Top surface,
20...Core.

Claims (1)

[Scope of Claims] 1. A mold device for molding a synthetic resin cap, which has a radius R formed at the back corner of the cavity 10.
The lowest position of the cavity 10 is A, the lowest position of the cavity 10 is B, the intersection position of the imaginary straight line connecting the positions B and A and the extension line of the cavity top surface 12 is C, the position C and the cavity 10 E is the intermediate position between the lowest position D of the core packing land of the core 20 that is assembled in a predetermined positional relationship with the core packing land, and is the position E on the virtual straight line, and is the same as the position E on the plane perpendicular to the axis. F is a position on a plane that is shifted outward from the position E by an amount β determined from 1/20α to 1/50α depending on the wall thickness α of the peripheral wall of the synthetic resin cap that is the product to be molded. The cavity side wall 11 is made of synthetic resin by forming the cavity side wall 11 by forming the position A and the position F into a gently continuous curved surface continuous with the radius R, and by connecting the position E and the position B in a straight line. Cap molding equipment.