JPH03193320A - Injection molding die - Google Patents

Abstract

PURPOSE:To improve the molding workability, realize favorable external appearance and consequently eliminate finishing process by a method wherein resin is injected under pressure through submarine gates in a cavity under the condition that a pair of a fixed mold and a movable mold are registered and pins for forming through hole are fittingly installed in order to mold a product having a hole, which pierces along the mold opening direction of a die. CONSTITUTION:The cavity 1 of a product 10 is formed at the parting faces of a fixed mold 2 and of a movable mold 3. Further, pins 4 and 5 for producing a through hole 11, which is to recessedly provided on vertical wall surface at the edge face of the product 10, are installed so as to separably abut against each other at a PL face, which is normal to the mold parting direction, in the cavity 1. Furthermore, submarine gates 6 are provided at least on one abutting face of the pin 4 so as to be open and communicate with the cavity 1 and a sprue 7, which communicates with the gates 6, is provided. The submarine gates 6 are formed by producing notched grooves, which communicates with a plurality of positions on the outer peripheral edge of the pin 4, at the tip face of the fixed side pin 4. Conical or curved surface-shaped recessed part 8 and projected part 9 may well be opposedly provided so as to correspond to the central part of the pins. In addition, the abutting area of the movable side pin 5 is set no to exceed that of the fixed side pin 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a mold for injection molding synthetic resin products having through holes using a split mold.

[Conventional technology]

Conventionally, injection molded products made of synthetic resin always have a gate, and the gate method used during molding has often been the side gate method or the submarine gate method, which makes the gate marks less noticeable.

This side gate method is suitable for molding even thick products because the gate cross section can be made into a circle with a diameter of 2 to 5 mm or a rectangular shape with a side of 2 to 5 mm. However, on the other hand, it requires a finishing process such as cutting the remaining gate part with a saw etc. after molding, removing the tread remaining on the cut surface and wiping off the chips, which has the disadvantage of being relatively expensive. Gate cutting is a disadvantage of side gate methods such as
In order to avoid processes that are difficult to automate, such as finishing processes, the submarine gate method has been widely adopted.

This is because in this submarine gate method, when the surface provided with the gate is parallel to the mold release direction of the product, that is, perpendicular to the PL plane, cut pieces of the gate are unlikely to remain on the product.

Problems to be solved by the invention C) However, with the conventional submarine gate method, products whose end surfaces are spherical or curved close to it have the following problems:
If the surface of the product with the gate is not perpendicular to the PL surface, cut pieces of the gate may remain, and even if these cut pieces remain as protrusions, they may have a negative impact on the tactile sensation. Not only does it give a bad impression, but it also looks bad and affects the value of the product, so a finishing process was needed to make it less noticeable.

Furthermore, if a submarine gate is used, even if finishing the gate remains is unnecessary, installation is impossible if the product is too thin. In other words, if the height distance of the product from the PL plane at the gate part is less than 3 dragons, and the cross section of the product does not have a surface perpendicular to or close to the PL plane, the submarine gate itself cannot be used. In addition, conventional film gates used to create gates in holes used a thin film-like gate and punched it out, but holding pressure could not be applied and there was debris on the cut surface of the gate. This is a problem because the resin that is injected from the gate flies directly onto the surface of the mold, leaving behind marks.
The jetting phenomenon, which significantly impairs the appearance of the product, is more likely to occur than side gates.Furthermore, if a submarine gate is provided on the fixed side mold, the gate will be cut when the mold is opened, but the cutting resistance will be large and the product will be damaged. There were still problems such as sometimes remaining in the mold cavity on the fixed side.

The present invention solves the various problems of these conventional methods, improves the appearance after molding, eliminates the need for a finishing process, provides a good feeling of use, and offers a degree of freedom in design, greatly increasing the product value. In addition, it significantly improves workability during molding,
It is an object of the present invention to provide an injection mold that easily enables cost reduction.

[Means for resolving issues]

The present invention is a mold for molding a product having a hole passing through the mold in a direction along the mold opening direction using a split mold that can be opened and closed, and in which a pin forming the through hole is inserted into the cavity. The pins are arranged so as to collide in a separable manner, and a submarine gate is provided on at least one abutment surface of the pin to communicate an opening into the cavity, and the pin is provided with a sprue that communicates with the submarine gate. This is an injection mold.

[For production]

In the injection mold of the present invention, when a pair of fixed molds and a movable mold are fitted together, a pin for forming a through hole is fitted and pressed against each other, and resin is injected and press-fitted into the cavity from the submarine gate, the product is manufactured. At the same time as the molding, a wall perpendicular to the PL surface was recessed, so that the cut surface of the gate
Even if some protrusion remains on the gate, the protrusion will not come out and will remain within the through hole and will not be directly touched by the hand, and will not adversely affect the feel during use.

In addition, if a pin for forming a through-hole is provided and a submarine gate is provided on the fixed side mold, the gate will be cut when the mold is opened, but the product will not come out (separated) from the fixed side mold cavity. Mold) Resistance is large and the product often remains in the stationary mold, but the through-hole forming pin of the stationary mold prevents the product from being released from the cavity of the stationary mold when the mold is opened. This reduces resistance and allows the product to stay in the cavity of the moving mold.

〔Example〕

An embodiment of the present invention will be described with reference to the drawings. In FIG. 1, a perpendicular through hole 11 is recessed in the end face of a synthetic resin product 10, and this through hole 11 is formed into a pair of divided parts that can be opened and closed. A mold 2.3 is a molding mold for molding a product 10 in a cavity 1 having a hole 11 penetrating in the direction along the mold opening direction of the mold, and a pin 4.3 forming the through hole 11.
A submarine gate 6 is provided on at least one abutting surface of the pin 4 so that the opening communicates with the cavity 1 and with the submarine gate 6. A sprue 7 is provided on the pin 4.

The pin is composed of a fixed side pin 4 and a moving side pin 5, and a submarine gate 6 is formed by forming a notch-shaped groove on the tip surface of the fixed side pin 4 that communicates with a plurality of places on the outer periphery of the pin. A sprue 7 is provided passing through the fixed side pin 4, the contact surfaces of the pins 4 and 5 are the PL plane perpendicular to the mold release direction of the product, and sprue 7 is provided at the center of the pins so as to correspond to each other. It is preferable that the submarine gate 6 is provided with conical or curved concave and convex portions 8.9 facing each other.

Furthermore, the molding die is made up of a pair of stationary mold 2 and movable mold 3, and the cavity 1 of the product 10 is formed on the mating surface (PL surface) of these, and the PL surface is formed in the end surface of the product. Pins 2 and 3 are provided in which a through hole 11 is formed for recessing a wall surface perpendicular to the wall surface.

In this case, the submarine gate 6 is positioned as a concave groove on the fixing pin 4 side with a distance of more than I In to the PL surface side, so that it is easy to process the gate cut part of the mold, and the gate remains on the product. It's best to avoid giving out.

Further, when the resin is injected into the cavity 1 from the submarine gate 6, the resin collides with the convex portion 9 of the pin 5 for forming the through hole 11, and the shefting trace remains only inside the through hole 11 and its vicinity. , the appearance of the product will be good.

The through-hole forming pin 4.5 is composed of a fixed side pin 4 inserted into the fixed side mold 2 and a movable side pin 5 inserted into the movable side mold 3, as shown in the first diagram. I can do it. In that case, the diameters of both may be the same, or the diameter on the movable pin side may be slightly smaller, or the cutting toward the PL surface may have a slope, and as shown in the first figure, the submarine gate 6 is sheared during die cutting and cutting is prevented. Care was taken to prevent it from coming out, and to reduce the resistance to release from the cavity.

The submarine gate 6 may be provided across both the pins 4 and 5, or may be provided with a concave and convex portion to smoothly guide the resin flow, so that the submarine gate 6 can be injected not only from one location but also from multiple locations. Deployed to the pin so that it can be used. For example, product 1
The pins 4 and 5 to be inserted into the through hole 11 of 0 are divided into two parts, and the fixed side is
Push the pin from the moving side into the hole, inject resin from the sprue 7 provided through the pin on the fixed side, and then press the pin from the fixed side (
or/and moving side) into the cavity 1 from the submarine gate 6, which has a part of the tip of the pin cut out.
In order to facilitate the movement of the pin during gate cutting, the pin 5 on the movable side is designed not to exceed the size (in plane) of the pin 4 on the fixed side. In addition, resin is injected into the mold cavity 1, and after it cools down, the fixed side pin 4 and the movable side pin 5 are
The fixed mold 2 and the movable mold 3 are left in abutment, and the PL surface of the parting surface that contacts the fixed mold 2 and the movable mold 3 remains closed, and the fixed mold 2 and the movable mold 3 are moved in the direction of arrow A. It is preferable to operate the gate so that the fixed side pin 4 and the movable side pin 5 move in the direction of arrow B relative to the product 10 so that the gate can be easily cut.

〔Effect of the invention〕

According to the present invention, the gate of a synthetic resin product with a through hole is located inside the hole, so the cut surface of the gate is not noticeable, does not impair the usability, and the product surface has a smooth finish, such as printing finish, etc. It has a good appearance, has flexibility in design, and can increase product value.Also, it can be easily adopted even for thin products, making mold processing easier, maintaining strength, and reducing product separation. The mold can also be easily made,
Since the cross section of the gate can be relatively large, it is easy to apply holding pressure after resin injection, which contributes to stable dimensional accuracy of the product, is effective in preventing sink marks, and improves workability during molding.
This has many beneficial effects such as easy cost reduction.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing one embodiment of the present invention. 1... Cavity, 2, 3... Mold, 4, 5...
Pin, 6... Submarine gate, 7... Sprue,
8... Concave portion, 9... Convex portion, 10... Product, ■... Through hole.

Claims (3)

[Claims] (1) A mold for molding a product having a hole passing through the mold in a direction along the mold opening direction using a split mold that can be opened and closed, wherein the pin forming the through hole is separated in the cavity. A submarine gate is provided on at least one abutment surface of the pin to communicate an opening into the cavity, and the pin is provided with a sprue that communicates with the submarine gate. Molding mold. (2) The pin consists of a fixed side pin and a movable side pin, and a submarine gate is formed by forming a notch-shaped groove on the tip surface of the fixed side pin that communicates with a plurality of locations on the outer periphery of the pin, The injection mold according to claim 1, further comprising a sprue extending through the fixed side pin. (3) The injection mold according to claim 1 or 2, wherein the contact area of the movable pin is slightly smaller than the contact area of the fixed pin.