JPS5852105Y2 - Molding mold for reaction injection molding - Google Patents

Description

[Detailed description of the invention] This invention is a reaction injection molding of liquid thermosetting polyurethane.
This invention relates to a mold for injection molding (hereinafter referred to as RIM).

RIMe, for example, is a method in which liquid substances such as polyol and polyisocyanate are injected into a mold at high speed under low pressure and cured by high-speed reaction, and is widely used in Imada automobile bumpers and automobile interior parts. ing.

This is because RIM molding has features such as being able to perform small cycle molding, being easier to manufacture large molded products, and being lower in cost than normal injection molding.

In such RIM molding, the forming mold is usually manufactured by machining steel, aluminum, etc., but if it is made in the same way as a normal injection bottom mold, there will be a large amount of paris because it is liquid molding. Occurs at the joint surface of the lower mold.

In addition, the mold temperature during molding is usually around 45 to 75°C, so even if sufficient consideration is given to the alignment accuracy of the upper and lower molds when manufacturing the mold, thermal expansion of the mold will occur depending on the temperature during molding, resulting in parity. It is extremely difficult to eliminate it.

Therefore, after molding, a trimming operation to remove debris from the molded product is inevitably required.

FIG. 1 is a partial vertical cross-sectional view of the conventional molding mold for RIM as described above during mold clamping, in which 1 is the upper mold, 2 is the lower mold, and 3 is the cavity between the upper mold 1 and the lower mold 2. 4 indicates the joint surface of the upper and lower molds.

When a liquid substance is injected into the cavity 3, the iron liquid leaks out from a small gap in the joint surface 4, resulting in a gap 5.

At the same time, molding defects such as voids and sink marks occurred due to pressure loss.

The purpose of this invention is to improve the above-mentioned drawbacks, and to provide a mold for RIM circumferential shapes that does not cause particles to adhere to the molded product, does not require trim work, and improves the molding cycle. The feature is that a groove is provided on either the upper or lower mold over almost the entire circumference of the joint surface of the upper mold and lower mold, and the nested rubber elastic body is completely inserted into this groove through the elastic body. Installation, top, without filling
The RIM molding mold includes a pair of upper and lower molds so that the nested rubber elastic body can be pressed against the joint surface of the mold when the lower mold is clamped.

Hereinafter, specific embodiments of the present invention will be further described with reference to the accompanying drawings.

FIG. 2 is a schematic diagram of the upper mold illustrating the basic principle of the present invention, in which a rubber elastic body 16 is fitted along the groove 15 provided around the entire circumference of the upper mold 11, and the upper mold 11 is tightened using screws 17 or adhesive. Fixed.

In this case, the rubber elastic body 16 is made to protrude slightly from the mold surface 11a to have a compression allowance A, and when the upper and lower molds are clamped, the rubber elastic body 16 is deformed to eliminate the gap between the mold joint surfaces. Make it.

Usually, this rubber elastic body 16 is made of CR having heat resistance, abrasion resistance, etc. in consideration of the particular mold temperature.

Sail rubber such as EPDM, Teflon rubber, urethane elastomer, etc. are preferred.

In addition, the hardness of the rubber elastic body is generally determined based on the compression allowance, and this compression allowance is determined by the machining accuracy of the upper and lower molds, but if normal machining accuracy is assumed, the compression allowance is Range A O, 2-0.5 mm, 45-6
A range of 5° (Shoyer D type) is preferred.

The location where the rubber elastic body is fitted is approximately the entire circumference of the joint surfaces of the upper and lower molds.

Therefore, the upper mold 11 as described above is replaced with the lower mold 1.
When the mold is clamped into the mold 2, it becomes as shown in FIG. .

Therefore, when the mold is clamped, the elastic body 16 is deformed due to the compression allowance A of the rubber elastic body 16, and the gap between the upper mold 11 and the lower mold 12 disappears, so no leakage of liquid from the joint gap occurs. .

FIG. 4 shows an embodiment of a mold according to the present invention that more effectively embodies the above basic principle based on the above basic principle. There is a groove 25, and a plurality of springs 27 fixed to the upper mold 21 are provided in the groove 25, and a nested rubber elastic body 26 is inserted at the end of the spring 27 without completely filling the groove. Elastically connected.

That is, the nested rubber elastic body 26 is pushed in the direction of the arrow shown in the figure by the elastic force of the spring, and is pressed against the surface of the lower mold.

In this case, since the magnitude of the pressing force of the nested rubber elastic body 26 to the lower mold surface affects the occurrence of flash, it is necessary to consider the elastic modulus of the spring 27. The pressure force can be adjusted more easily than in Fig. 3.

However, when a spring and a nested rubber elastic body are used in combination like this, the mold can be clamped with a smaller compression force than the compression force when clamping the mold when only the rubber elastic body is used as shown in Figures 2 and 3. This avoids excessive distortion of the nested rubber elastic body, prevents aging, and extends lifespan.

In addition, since deformation of the rubber elastic body enters the cavity 23 and changes the shape of the molded product, the spring prevents this.
Further, it is preferable that the hardness of the rubber elastic body is as high as 80 to 90' (Shoyer D type).

FIG. 5 shows another embodiment of the present invention, in which the upper mold 2
1 is provided with a groove 25, and in place of the spring, a nested elastic body 26' is attached via a rubber elastic body 27' of low hardness.

Note that the nested elastic body 26' similarly protrudes slightly from the surface of the upper mold 21, and the rubber elastic body 27' fixes the upper mold 21 and the nested elastic body 26' with adhesive.

As described above, the RIMe mold of the present invention has a groove on either the upper or lower mold, and the nested rubber elastic body is completely inserted into this groove through an elastic body such as a spring or rubber elastic body. It is installed without filling, and the nested rubber elastic body is crimped to the joint surfaces of the upper and lower molds over almost the entire circumference of the joint surfaces of the upper and lower molds when the upper and lower molds are clamped. The compressive force of the nested rubber elastic body via the elastic body prevents liquid from leaking from the joint between the upper and lower molds, eliminates the occurrence of flakes in the molded product, eliminates the need for citrim work, and significantly improves the molding cycle. In addition to this, by interposing the elastic body, the compressive stress on the nested rubber elastic body is buffered, and unreasonable distortion is avoided, which has an excellent effect of preventing aging and improving lifespan.

In particular, the nested elastic body does not completely fill the groove, so it is suitable for moderately relieving the mold clamping compression force, and moreover, it is not necessary to use something like a guide rod only through the elastic body. This makes it possible to reliably prevent leakage of liquid in RIM molding, where liquid is injected into the cavity at high speed and high pressure from a place where the nested elastic body can completely adhere to the opposing mold surface. , exhibits great effectiveness in industrial applications.

[Brief explanation of the drawing]

Fig. 1 is a partial vertical cross-sectional view of a conventional RIM mold when tightened, and Fig. 2 is a diagram illustrating the basic principle of the present invention.
FIG. 3 is a partial vertical cross-sectional view of the mold for RIM shown in FIG. 2 when the mold for RIM is tightened, FIGS. 4 and 5. 1 is a partial vertical cross-sectional view of the RIM forming mold according to each embodiment of the present invention when it is tightened; FIG. 1.11.21...Top mold, 2. j2.2
2...Lower mold, 3,13.23...
・Cavity, 4, 14.24...Joint surface, 1
5.25... Groove, 16.26... Rubber elastic body, 26'... Nested elastic body, 17...
...Screw, 27...Spring, 27'...
・Rubber elastic body.

Claims (1)

[Scope of utility model registration request] In a mold consisting of a pair of upper and lower molds, over almost the entire circumference of the joint surface of the upper and lower molds,
A groove is provided in at least one of the upper and lower molds, and a nested rubber elastic body is installed in the groove through an elastic body without being completely filled, and when the upper and lower molds are clamped, the nested rubber elastic body A mold for reaction injection molding, characterized by having a structure in which a body is pressed into contact with a mold joint surface.