JPH10659A - Mold for injection molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the prevention of flash generation in the gate part of a molding by forming an inclined surface slanting to the axial direction of a slider pin at the end of the slider pin. SOLUTION: Even when a gap S is generated around a slide pin 6 after service for a long period and the gap S is filled with a thermoplastic resin R, since an inclined surface 61 is formed at the end of the pin 6, the thickness of the resin R in the gap S is smaller than that of the resin R in the second runner part 52. The pin 6 is kept for a while in the most advanced state to pressurize and hold the resin R in a cavity 4. When the resin in the cavity 4 is cooled and solidified, a moving mold 3 is moved and separated from a fixed mold, and a thermoplastic resin molding 1 in the cavity 4 is moved with the moving mold 3 to be separated from the fixed mold 2. An ejector pin is actuated, the molding 1 in the cavity 4 is removed from the moving mold 3, and cutting is started from the thin wall part of the gap S so that no flash is generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold for injection molding, and more particularly to a mold for preventing the formation of burrs on a gate portion of a molded product after molding.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Patent Application Laid-Open No. HEI 1-118423.
As described in Japanese Patent Application Laid-Open No. 5-261778, a cavity is provided between a fixed mold and a movable mold, a runner portion communicating with the cavity is provided, and the heat in the runner portion is provided in the runner portion. 2. Description of the Related Art There is known an injection molding die provided with a slider pin that press-fits a plastic resin into a cavity, shuts off the inside of a runner portion from the inside of the cavity, and presses and holds the thermoplastic resin in the cavity.

[0003]

As shown in FIG. 5, when a short tube 1 with a flange is formed by using such an injection mold, a fixed die 2 and a movable die 3 are not provided. As a result of the slider pin 6 reciprocating from the first runner 51 in the movable mold 3 to the second runner 52 in the fixed mold 2 through the cavity 4 formed therebetween, as a result of long-term use,
As shown in the enlarged view of FIG. 6, the vicinity of the first runner 51 and the second runner 52 in the fixed mold 2 is worn, and an annular gap S is generated around the slider pin 6. Will be filled.

As a result, the formed short pipe 1 with flange
7 is cut off in the middle of the resin R invading and filling the annular gap S near the location indicated by the arrow C.
As shown in (1), it is inevitable that thin-walled cylindrical burrs 13 are generated at the gate portion of the formed short tube 1 with flange, that is, at the corner between the short tube portion 11 and the flange 12.

The present invention has been made in view of such a problem in the conventional injection mold, and an object of the present invention is to solve the above-mentioned problem and to provide a flash on a gate portion of a molded product. It is an object of the present invention to provide an injection molding die capable of preventing occurrence of occurrence.

[0006]

In order to achieve the above object, an injection mold according to the present invention has a cavity provided between a fixed mold and a movable mold, and a runner portion communicating with the cavity. In the injection molding die provided with a slider pin for press-fitting the thermoplastic resin in the runner portion into the cavity into the runner portion and shutting off the inside of the runner portion and the cavity and pressurizing and holding the thermoplastic resin in the cavity, The tip of the slider pin is provided with an inclined surface inclined with respect to the axial direction of the slider pin.

[Effect] In the injection molding die of the present invention, the tip of the slider pin is provided with an inclined surface inclined with respect to the axial direction of the slider pin. Even if an annular gap is formed, the resin that penetrates and fills the annular gap has a thin portion near the connection point between the cavity and the runner, and when the molded product is released, the thin portion is cut from the thin portion. In addition, burrs do not occur on the molded product.

[0008]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing an example of the injection mold of the present invention. In FIG. 1, reference numeral 1 denotes a molded product molded by the injection molding die of the present invention, and the molded product 1 is a short pipe with a flange. Reference numeral 2 denotes a fixed mold of the injection molding die of the present invention, and reference numeral 3 denotes a movable die of the injection molding die of the present invention, which is a molded product 1 to be formed between the fixed die 2 and the movable die 3. A cavity 4 having a shape corresponding to the shape of the short pipe with a flange is provided.

Reference numeral 5 denotes a runner portion. The runner portion 5 includes a first runner portion 51, a second runner portion 52, and a third runner portion 53. First runner part 51
Is provided in the movable mold 2 and communicates with the cavity 4. The second runner part 52 is provided so as to be connected to the first runner part 51, and is provided on the fixed mold 2.

Reference numeral 6 denotes a slide pin.
Is slidably provided in the first runner section 51 and the second runner section 52 by operation of a hydraulic cylinder (not shown). As shown in an enlarged manner in FIG. 2, an inclined surface 61 which is inclined with respect to the direction of the axis OO of the slide pin 6 and faces the outer side surface is provided at the tip of the slide pin 6.

When the slide pin 6 moves forward in the first runner section 51, the first runner section 51 and the thermoplastic resin in the cavity 4 are compressed, and the slide pin 6 further advances the first runner section 51 to move the slide pin 6 forward. When the tip of the slide pin 6 reaches the inside of the second runner portion 52 and the tip of the slide pin 6 advances most,
The runner part 51 and the second runner part 52 are shut off.

When the leading end of the slide pin 6 is most retracted, the first runner 51, the second runner 52 and the cavity 4 communicate with each other, and the thermoplastic resin R from the third runner 53 is discharged from the second runner 53. The inside of the cavity 4 is filled via the first runner part 51 and the second runner part 51.

Next, an embodiment in which a short pipe with a flange, which is a molded article 1, is formed by using the injection mold of the present invention shown in FIG. 1 will be described. As shown in FIG. 1, in a state where the fixed mold 2 and the movable mold 3 are closed and the tip of the slide pin 6 is most retracted, the thermoplastic resin R melted from an injection molding machine (not shown) is not shown. It is injected and filled into the cavity 4 via the nozzle and the third runner section 53, and further via the second runner section 52 and the first runner section 51.

Next, the slide pin 6 is advanced by the operation of a hydraulic cylinder (not shown), and the thermoplastic resin R in the first runner portion 51 is pressed into the cavity 4 while being compressed by the advance of the slide pin 6. Slide pin 6
Is most advanced, the slide pin 6 cuts off the cavity 4 from the first runner portion 51 and the second runner portion 52, and the press-fitting of the thermoplastic resin in the first runner portion 51 into the cavity 4 is completed. I do.

Even if the gap S is formed around the slide pin 6 due to long-term use and the gap R is filled with the resin R,
Since the inclined surface 61 is provided at the tip of the slide pin 6, the resin in the gap S is thinner than the resin in the second runner 52. In this way, the state in which the slide pin 6 is advanced most is maintained for a while, and the thermoplastic resin in the cavity 4 is held under pressure.

When the thermoplastic resin in the cavity 4 is cooled and solidified, the movable mold 3 is moved and divided from the fixed mold 2, and the thermoplastic resin molded product 1 in the cavity 4 moves together with the movable mold 3 to move the fixed mold 2. Move away from

When the movable mold 3 is farthest from the fixed mold 2, a projecting pin (not shown) operates to release the molded product 1 in the cavity 4 from the movable mold 3. Is thin, so it is cut from the thin part,
As shown in FIG. 3, the molded article 1 has no burrs. Thereafter, the movable mold 3 closes to the fixed mold 2 again as shown in FIG. 1, and the same cycle is repeated.

FIG. 4 is an enlarged view showing the main part of another example of the injection molding die of the present invention. In the injection molding die of the present invention shown in FIG. Angled inclined surface 6 inclined to the axial direction of 6 and facing inward and outward
1 and 61 are provided.

Also in the injection molding die of the present invention shown in FIG. 4, since the inclined surfaces 61, 61 are provided at the tip of the slide pin 6, even if the gap S occurs due to long-term use, the gap S is formed. The resin R to be filled is thinner than the resin R to be filled in the second runner portion 52, and when the molded product is released from the mold, the resin R is cut from the thin portion, so that no burrs are generated on the molded product.

Although the embodiment of the present invention has been described with reference to the drawings, the configuration of the present invention is not limited to the illustrated embodiment, and design changes within the scope of the present invention are included in the present invention. It is. For example, as in the illustrated embodiment, instead of forming a short tube with a flange using the injection molding die of the present invention, a simple tube may be used, or another molded product may be used.

[0021]

According to the injection molding die of the present invention, the tip of the slider pin is provided with an inclined surface inclined with respect to the axial direction of the slider pin. Even if an annular gap is formed, a thin portion is formed near the connecting point between the cavity and the runner in the resin that penetrates and fills the annular gap, and the molded product is cut from the thin portion during mold release, Burrs do not occur on molded products.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of an injection mold according to the present invention.

FIG. 2 is an enlarged sectional view showing a part indicated by a circle A of the injection molding die of the present invention shown in FIG.

FIG. 3 is a sectional view showing a molded product formed by the injection molding die of the present invention shown in FIG. 1;

FIG. 4 is an enlarged sectional view of a main part showing another example of the injection mold of the present invention.

FIG. 5 is a cross-sectional view showing a conventional injection mold.

6 is an enlarged cross-sectional view showing a portion indicated by a circle B of the injection molding die shown in FIG. 5;

FIG. 7 is a sectional view showing a molded product formed by the injection molding die shown in FIG. 5;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Molded product 2 Fixed mold 3 Moving mold 4 Cavity 5 Runner 51 First runner part 52 Second runner part 53 Third runner part 51 Hydraulic cylinder 6 Slider pin

Claims (1)

[Claims] 1. A cavity is provided between a fixed mold and a movable mold, and a runner portion communicating with the cavity is provided.
In the injection molding die provided with a slider pin that press-fits the thermoplastic resin in the runner part into the cavity into the runner part, shuts off the inside of the runner part and the cavity, and pressurizes and holds the thermoplastic resin in the cavity. An injection molding die, characterized in that an inclined surface inclined with respect to the axial direction of the slider pin is provided at the tip of the pin.