JP2677142B2 - Core pin structure of injection mold - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a core pin structure of an injection molding die used for molding synthetic resin parts and the like.

[0002]

2. Description of the Related Art Conventionally, injection molding machines have been used for molding resin parts. The injection molding machine heats a thermoplastic resin to plasticize it, injects the molten resin into the closed mold, and then opens the mold to take out the solidified resin molded product. ing. The mold has a core and a cavity, and a molding space for injecting a molten resin is formed between the mutually facing surfaces of the core and the cavity.

In a resin component having a boss 102, such as a resin molded product 100 (only a part of which is shown) shown in FIG. 6, in order to mold the boss hole 103 to a predetermined inner diameter and depth,
Core pins are provided on the core of the mold. For example, in the case of the core pin structure 110 of the conventional die 109, a part of which is shown in FIG. 4, a molding space 113 is provided between the cavity 111 and the core 112, and the boss molding cavity 114 on the core 112 side is Core pin
The tip of 120 is positioned.

As in the resin molded product 100, the slanted portion 105
When the boss 102 is provided on the inner wall 106 of the boss hole 103,
If is formed in a flat shape that is orthogonal to the axis of the boss 102, a thick portion 107 with a large change in wall thickness is formed in the vicinity of the boss 102, and the wall thickness locally increases. When the resin is hardened at the location, "sink marks" of the resin may occur as shown by the broken line in the figure, which causes deterioration of the appearance.

To cope with the above-mentioned problems, the boss hole 103
It is necessary to incline the back wall 106 of the slanted part by an angle according to the slanted angle of the slanted part 105. Therefore, in the conventional core pin structure 110 shown in FIG. 4, the tip end surface 121 of the core pin 120 is formed obliquely. In this case, the core pin 120 is
It is necessary that 121 is held by the core 112 in a posture in which it faces a predetermined direction. In such a core pin structure 110, the rotation stopping means 125 for restricting the rotation of the core pin 120 is adopted.

For example, in the core pin structure 110,
The flange-shaped base 126 of the core pin 120 is provided with a rotation-stop pin 127 protruding in the radial direction, and a core pin insertion hole.
Detent groove 131 where detent pin 127 fits next to 130
By providing the core pin 120 with respect to the core 112
I was trying to make a detent. This core pin 120
Is fixed to the core 112 by a set screw 133 screwed into the female screw portion 132 of the core pin insertion hole 130.

[0007]

However, in the above-described conventional core pin structure 110, it is necessary to provide the core pin 120 with the detent pin 127 and the core 112.
Since it is necessary to provide the detent groove 131 on the core pin 12,
It takes time and labor to manufacture the 0 and the detent groove 131, which causes the cost to increase. Moreover, the core pin 120
Since it is necessary to obliquely cut the tip surface 121 of the core pin 120 at an accurate position, when manufacturing the core pin 120, the core pin 120 is molded to a certain length as shown by the broken line in FIG. With the core assembled to the core 112, the tip surface 121 is obliquely formed by grinding or the like. For this reason, the processing is extremely troublesome, the work is difficult, and the time required for the processing is not negligible.

Therefore, it is an object of the present invention that the core pin can be easily manufactured, and the rotation preventing means for the core pin can be eliminated, so that it is not necessary to provide a rotation preventing pin or a rotation preventing groove as in the prior art. An object is to provide a core pin structure of an injection molding die.

[0009]

The present invention, which was developed to achieve the above object, has an oblique molding space extending obliquely with respect to the mold opening direction between the mutually facing surfaces of a cavity and a core. In an injection molding die in which a void portion for molding a boss portion continuous to the oblique molding space is provided on the core side, the tip side is inserted into a core pin insertion hole provided in the core and the tip side is for molding the boss portion. The core pin structure of the injection-molding die is characterized in that it has a core pin projecting to the side of the oblique molding space through the void portion and the tip end surface of the core pin is hemispherical.

[0010]

In the core pin structure of the present invention, the tip end surface of the core pin is formed in a hemispherical shape, and this hemispherical end surface projects toward the oblique molding space side. Therefore, the vicinity of the boss portion of the molded resin molded product It is avoided that the thickness of the
It is possible to suppress the occurrence of “sink” after curing. Since such a core pin may be oriented in any rotation direction, a rotation preventing means for the core pin is unnecessary.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. A mold 10 for injection molding, a part of which is shown in FIG. 3, includes a fixed-side unit 11 located on the right side in the figure and a movable-side unit 12 located on the left side in the figure. Eye bolts 13 and 14 for lifting are provided above the units 11 and 12, respectively.

The fixed side unit 11 includes a fixed side mounting plate 20.
And a cavity 21 and the like. The cavity 21 is provided with a well-known locate ring 22, spool bush 23, and the like. Spool bush 2
A nozzle 25 on the runner side is joined to the resin injection port 24 of No. 3. A molding surface 26 is formed on the end surface of the cavity 21 in accordance with the outer surface shape of a resin molded product to be molded (for example, a resin bumper of an automobile).

The movable unit 12 includes a movable mounting plate 30.
, Spacer block 31, core 32, support pin 33, guide pin 34, and ejector plate 3
5, 36, an ejector pin 37, and the like. A molding surface 39 corresponding to the inner surface shape of the resin molded product to be molded is formed on the end surface of the core 32. Molding in which molten resin is injected between the molding surface 39 and the molding surface 26 of the cavity 21. A space 45 for use is formed. The molding space 45 includes an oblique molding space 46 that extends obliquely with respect to the mold clamping direction (the lateral direction in the drawing). The oblique forming space 46 may be curved in an arc shape.

Core pins 50 and 51 are provided at appropriate locations on the core 32, that is, locations where the boss portions are formed. These core pins 50 and 51 are inserted into core pin insertion holes 52 and 53 provided in the core 32. The positions and the numbers of the core pins 50 and 51 are determined according to the resin molded product to be molded, and needless to say, are not limited to the illustrated examples.

The first core pin 50 located on the upper side in the drawing
Has a shape as shown in FIGS. 1 and 2. The core pin 50 includes a flange-shaped base portion 55, a cylindrical body portion 56, and a small diameter portion 57 formed on the distal end side of the body portion 56. Around this small diameter portion 57, a boss molding space is formed. The portion 58 is formed.

The tip surface 60 of the small diameter portion 57 is formed in a hemispherical shape. In FIG. 2, the dimension R is the radius of curvature of the tip surface 60. The core pin 50 has a core pin insertion hole 5
When it is inserted into the No. 2, the hemispherical tip surface 60 passes through the boss forming cavity 58 and projects toward the oblique forming space 45 side.

An internal thread portion 61 is provided at the entrance of the core pin insertion hole 52. A set screw 62 is screwed into the female screw portion 61 from the rear side of the base portion 55 of the core pin 50. The core pin 50 is fixed to the core 32 by the set screw 62 in a state where the core pin 50 is fully inserted in the core pin insertion hole 52.

The second core pin 51 also comprises a flange-shaped base portion 70, a cylindrical body portion 71, a small diameter portion 72 formed on the tip side of the body portion 71, and the like. An internal thread 75 is provided at the rear of the core pin insertion hole 53.
A set screw 76 is screwed into the core 5 from the rear side of the base portion 70 of the core pin 51. The core pin 51 is fixed by a set screw 76 in a state where the core pin 51 is fully inserted into the core pin insertion hole 53, and the tip end surface 77 of the core pin 51 projects to a predetermined position in the molding space 45.

In the mold 10, as in the conventional case, a molten resin (for example, polypropylene) heated by an injection molding machine is pressurized and injected from the nozzle 25 into the molding space 45 through the spool bush 23. The molten resin is used in the oblique molding space 46 and the boss 58 for molding the boss.
Also flows into. Then, after the resin is cured, the core 32 is separated from the cavity 21, and the ejector pin 3
The molded product is extruded by 7.

The inclined molding space 46 of the mold 10 and the void portion 58 for molding the boss portion integrally mold the boss portion in the inclined portion of the resin molded product, and the outside of the small diameter portion 57 of the core pin 50. A boss hole having a size corresponding to the diameter and the length is formed. In this case, the inner wall of the boss hole is formed in a shape corresponding to the hemispherical tip surface 60 of the core pin 50. Therefore, it is possible to avoid a portion where the wall thickness changes extremely near the molded boss portion, and to suppress the occurrence of "sink" after the resin is cured.

With the core pin structure of the above-described embodiment, the hemispherical tip surface 60 can be finished when the core pin 50 is manufactured, and a long product manufactured in advance as in the prior art is ground to a desired length in another process. No complicated post-processing such as finishing is required. Further, since it does not matter even if the core pin 50 can be freely rotated, the detent pin 127 and the detent groove 131, which are required in the past, are not required, and the structure is simplified and the cost is reduced as compared with the conventional core pin structure. Can contribute.

[0022]

According to the present invention, the structure of the core pin and the core, etc. can be simplified, and the core pin can be easily manufactured as compared with the conventional one having the slanted end face, and the detent groove is formed on the core side. It is not necessary to provide the core pin or the rotation stop pin on the core pin, which is a great effect in reducing the cost.

[Brief description of the drawings]

FIG. 1 is a sectional view of a core pin structure showing an embodiment of the present invention.

FIG. 2 is a side view of a core pin used in the core pin structure shown in FIG.

FIG. 3 is a sectional view of a part of an injection molding die including the core pin structure shown in FIG.

FIG. 4 is a sectional view of a conventional core pin structure.

5 is a perspective view of a core pin used in the conventional core pin structure shown in FIG.

FIG. 6 is a partial cross-sectional view of a conventional resin molded product having a boss portion.

[Explanation of symbols]

10 ... Mold, 21 ... Cavity, 32 ... Core, 46 ... Oblique molding space, 50 ... Core pin, 52 ... Core pin insertion hole,
58 ... Void for molding boss, 60 ... Hemispherical tip surface.

Claims (1)

(57) [Claims] 1. A slanting molding space extending obliquely with respect to a mold opening direction is provided between mutually facing surfaces of a cavity and a core, and a boss molding void continuous with the slanting molding space is provided on the core side. In the injection mold provided in
The core pin is inserted into a core pin insertion hole provided in the core, and the tip side has a core pin projecting to the oblique molding space side through the void for molding the boss portion, and the tip end surface of the core pin is hemispherical. A core pin structure of an injection molding die, which is characterized in that