JPH0716415Y2 - Injection mold - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to an injection molding die used for molding a synthetic resin or the like.

(B) Conventional Technology Many injection molds of the type in which an undercut portion is formed in a molded product using an extrusion core have been proposed so far. JP 60-220722 A, JP 60-51020
Publications 60-159610, 63-170207, 64-4
An example is that described in Japanese Patent No. 2115.

(C) Problems to be solved by the invention Extruded cores can be formed into different patterns without remanufacturing the entire mold if this part is replaced, so it is limited to forming undercut parts. Widely used for molding small parts. FIG. 3 shows an example of the application. In the figure, 101 is a movable die, 102 is a movable die 10.
Mounting plate for attaching 1 to the molding machine, 103 is an extrusion core, 104 is an ejector plate, 105 is an extrusion core 103
Is a rod for connecting to the ejector plate 104. The extruded core 103 is used to form a molded product 106 having an L-shaped cross section. A through hole 107 is also provided in the molded product 106. In this case, since the separating direction (arrow) of the molded product 106 and the direction in which the through-hole 107 exits are the same, the molded product can be manufactured without any special consideration.
Separation of 106 is possible.

However, it is a different story when the shape of the molded product is as shown in FIG. Here, the bent portion of the molded product 106 is not a right angle but an acute angle, which is an undercut in the mold opening direction. Therefore, the molded product 106 is separated in the direction of the arrow, but this time the core portion for removing the through hole 107 hinders the separation. Therefore, the through hole 107 is formed by the core pin 108 fixed to the movable die 101. In this way, when the extruded core 103 is extruded, the core pin 108 is
It does not come out of 6 and hinder the separation of the molded product 106.
However, in this case, the core pin 108 may come out of the push core 103 depending on the push stroke of the push core 103. Core pin 10 that has fallen out
It is difficult to insert 8 into the through-hole 109 of the extruded core 103 together with the mold closing, and the through-hole 109 should be inserted to facilitate insertion.
Even if the inlet of the core is widened in a taper shape, there is a problem that the tip of the core pin 108 is worn and burr is generated in the through hole 107 as the mold is repeatedly opened and closed.

The present invention has been made in view of such a point, and in the case of using the extrusion core and the core pin, even if the stroke of the extrusion core becomes large, the tip of the core pin can still remain in the extrusion core. The object is to provide a simple mold structure.

(D) Means for Solving the Problems In the present invention, the core pin is attached to the ejector plate so as to be movable in a certain range in the axial direction, and at the time of mold clamping, the core pin is pushed to form a through hole or a recess in the molded product. A contact portion is provided on the movable mold side to maintain the shape at a position to be formed. A spring is inserted between the core pin and the movable die.

(E) Action When the mold is clamped, the core pin hits the contact portion on the movable mold mounting plate side and is pushed toward the fixed mold, and is maintained at a position where a through hole or a recess is formed in the molded product. After molding, the mold is opened, and when the ejector plate approaches the movable die, the spring between the core pin and the movable die begins to be compressed, and the core pin moves relative to the ejector plate. When the relative movement reaches the limit, the tip of the core pin is removed from the molded part, but still remains in the extruded core. After that, the stroke end of the ejector plate is suppressed while maintaining this positional relationship.

(F) Embodiment An embodiment will be described with reference to FIGS. 1 and 2. In the figure, 1 is a fixed mold, 2 is a cavity 3 between the fixed mold 1 and
Movable molds 4 for forming are molds that are molded by injecting molten resin into the cavity 3. Molded product 4 is
An undercut portion 6 bent at an acute angle is continuously provided at an end of a flat plate-shaped main portion 5, and the main portion 5 has a through hole 7. 8 is an extrusion core arranged in the movable die 2 for molding the undercut portion 6, 9 is a rod for connecting the extrusion core 8 to the ejector plate 10, and 11 is the movable die 2
And a core pin that penetrates the extrusion core 8. The base of the core pin 11 is attached to the ejector plate 10 so as to be movable in the axial direction. That is, a large-diameter portion 12 is provided at the base of the core pin 11, and this portion enters the cylinder portion 15 formed at the joint between the plates 13 and 14 constituting the ejector plate 10. The cylinder portion 15 has a transmission pin whose shape is such that the positional relationship between the large diameter portion and the small diameter portion of the core pin 11 is reversed.
16 is held, and its small diameter portion can be projected to the outside of the plate 14. The length of the cylinder part 15 is the core pin
It is longer than the thickness of the large diameter portions of 11 and the transmission pin 16 overlapped with each other, and the core pin 11 can move relative to the ejector plate by the difference. 17 is a movable mounting plate,
When the mold is clamped, the transmission pin 16 hits this. That is, the movable mounting plate 17 itself is the contact part,
In consideration of wear, another member may be replaceably attached. Reference numeral 18 is a compression coil spring arranged outside the core pin 11. One end of the compression coil spring 18 is received by the ring 19 fitted to the core pin 11.

The operation of the above mold is as follows. In the mold clamping state shown in FIG. 1, the transmission pin 16 hits the movable die mounting plate 17, and the core pin 11 is pushed out through the transmission pin 16 to a position where the tip of the core pin 11 contacts the fixed die 1. If molding is performed in this state, the product 4 having the through holes 7 is formed. If the core pin 11 is kept at a position where the tip does not reach the fixed mold 1, the recessed portion, not the through hole, remains in the molded product 4. When the mold is opened after molding, the ejector plate 10 starts to approach the movable mold 2 in the process. Then the compression coil spring 18
Since it hits the movable die 2 and tries to hold down the core pin 11, the core pin 11 is displaced relative to the ejector plate 10. On the other hand, extruded core 8 and ejector plate 10
Since the interval between and does not change to, the tip of the core punch 11 is pulled out from the molded product 4 and pushed into the core 8. When the relative displacement of the core pin 11 is stopped, the compression coil spring 18 thereafter permits the movement of the ejector plate 10 by the compression deformation of itself until the end of the stroke, and the state shown in FIG. 2 is reached. Even at this point, the tip of the core pin 11 remains in the extruded core 8.

(G) Effect of the Invention According to the present invention, the core pin moves out together with the extruded core after it is removed from the molded product, so that the fitting between the core pin and the extruded core is always maintained, and the core pin is completely removed from the extruded core. There will be no inconvenience caused by missing

[Brief description of drawings]

1 and 2 are partial cross-sectional views showing an embodiment of the present invention in a state when the mold is clamped and when the mold is opened, and FIGS. 3 and 4 are mold structures in which the present invention is not implemented. FIG. 1 ... Fixed type, 2 ... Movable type, 3 ... Cavity, 4 ...
... Molded product, 6 ... Undercut part, 7 ... Through hole, 8 ...
… Extruded core, 9… Rod, 10… Ejector plate, 11… Core pin, 17… Movable mounting plate (contact part), 18… Compression coil spring (spring).

Claims (1)

[Scope of utility model registration request] 1. An injection molding die comprising the following components: a. Fixed die. b. A movable mold that forms a cavity with the fixed mold. c. An extruded core arranged on the movable mold to form an undercut portion on the molded product. d. A rod connecting the extruded core to the ejector plate. e. A core pin that penetrates the movable die and the extrusion core and is attached to the ejector plate so as to be capable of relative movement in the axial direction within a certain range. f. A contact portion on the movable die mounting plate side that presses the core pin during mold clamping and maintains the core pin at a position where a through hole or a recess is formed in the molded product. g. A spring that is inserted between the core pin and the movable mold, and when the mold is opened, the core pin is relatively displaced so that the tip of the core pin pushes into the core and does not come out of it.