JPH0558246U - Injection mold - Google Patents

Abstract

(57) [Summary] [Purpose] In order to reduce the difference in wall thickness of the boss, a boss is provided at the base of the boss so that the undercut part can be removed by the mold structure. [Structure] A meat recess 3 is provided at the base of a boss Z provided at the center of the molded product 1, and a thick rib 5 of the molded product 1 and the boss Z are connected by a reinforcing rib 4 to provide the meat recess 3. , Prevents local increase in wall thickness.

Description

[Detailed description of the device]

[0001]

[Industrial application]

 The present invention relates to a structure of an injection molding die for preventing sink marks of a boss in a plastic molded product.

[0002]

[Prior Art]

 Conventionally, a round boss was directly provided inside the molded product.

[0003]

[Problems to be solved by the device]

 In the above-mentioned prior art, since the round boss is provided directly on the thick portion of the molded product, the root portion of the boss can locally have a thick portion. An analysis of the injection molding process revealed that after the resin was filled and pressure was applied, the resin began to shrink as the resin temperature decreased in the cooling process, and the greater the difference in wall thickness, the more the shrinkage progressed and the wall thickness increased. Larger sink marks are large. Therefore, sink marks were unavoidable at the boss. The purpose of the present invention is to reduce the difference in wall thickness of the boss portion by providing a flesh steal at the base of the boss so that the undercut portion can be pulled out by the mold structure.

[0004]

[Means for Solving the Problems]

 In order to achieve the above-mentioned object, the present invention has a structure in which a boss portion has a sleeve projecting structure in order to remove an undercut at the base of the boss portion in an injection molding die, and the sleeve projecting pin is divided into two parts so that the divided parts are elastically deformed. I made it open and close.

[0005]

[Action]

 The tip of the sleeve protruding pin is divided into two parts, and the tip is open when no load is applied. When the mold is assembled and clamped in the mold, the tip of the sleeve is held in close contact by a hole that fits into the sleeve protruding pin. In this state, the tip portion is in a bent state and adheres closely. At the time of projecting, the tip part comes out of the fitted hole, so that the elastic recovery occurs and the tip part is left open. Since there is a structure that utilizes the elasticity of the sleeve protruding pin material, there is no other alternative.

[0006]

【Example】

 An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a plan view of an example of a molded product according to the present invention, and FIG. 2 is a sectional view thereof. The base portion of the boss 2 provided in the center of the molded product 1 has a meat recess 3 and the thick portion 5 of the molded product 1 and the boss 2 are connected by a reinforcing rib 4. By providing this meat stealing, the wall thickness is prevented from locally increasing. In addition, in the mold, since the meat steal 3 is an undercut, the molded product 1 cannot be ejected. FIG. 3 shows a sleeve projecting pin 6 for removing this undercut. The boss portion of this pin is divided into two and has tip portions 7 and 8. The sleeve protruding pin 6 is made of a metal material having spring elasticity. Further, in the unloaded state, the tip portions 7 and 8 are open as shown in the figure. FIG. 4 is a cross-sectional view of an injection molding die according to the present invention, showing a state when the die is clamped. The sleeve protruding pin 6 is housed in the fitting side 10 of the movable side mold plate 9, and in this state, the tip portions 7 and 8 of the sleeve protruding pin 6 are in a closed state. The shape of the boss 2 is formed. By filling the resin in this state, the boss of the molded product 1 shown in FIGS. 1 and 2 can be obtained. FIG. 5 is a cross-sectional view of the mold showing a state in which the molded product 1 is projected after the resin is filled and cooled and solidified. The sleeve projecting pin 6 is projected by the projecting plate 11, and the tip portions 7, 8 are projected from the fitting holes 10 of the movable side mold plate 9. Accordingly, the tips 7 and 8 are opened by elastic recovery, and the undercut of the molded product 1 is removed, and the molded product can be taken out. According to this embodiment, the undercut at the boss root of the molded product can be removed, so that a molded product with an excellent appearance without sink marks can be obtained.

[0007]

[Effect of the device]

 According to the present invention, since the undercut provided at the base of the boss of the molded product can be removed, it is possible to steal the boss and prevent sink marks. In addition, since it is possible to prevent the wall thickness from locally increasing, the cooling period can be shortened.

[Brief description of drawings]

FIG. 1 is a plan view of a molded product.

FIG. 2 is a vertical sectional view of a molded product.

FIG. 3 is a perspective view of a sleeve protruding pin of the present invention.

FIG. 4 is a vertical cross-sectional view showing a mold clamped state of the mold.

FIG. 5 is a vertical cross-sectional view of a mold showing a state where a molded product is projected.

[Explanation of symbols]

1 ... Molded product, 2 ... Boss, 3 ... Meat stealing, 4 ... Rib, 5 ... Wall thickness, 6 ... Sleeve protruding pin, 9 ... Movable side template, 11 ...
Protruding plate.

Claims (1)

[Scope of utility model registration request] 1. An injection molding die, comprising a plastic molding having a boss at the base of a boss portion, wherein an undercut is removed by a sleeve protruding pin utilizing elastic deformation.