JPH0243697Y2 - - Google Patents

Description

[Detailed explanation of the invention] Technical field This invention relates to a molding device for foam molded products.
In particular, the present invention relates to a molding device for obtaining a foamed molded product with a smooth surface.

Conventional technology A foaming material is injected into the molding cavity while a gas such as nitrogen or air is introduced at a constant pressure into the molding cavity, and a foamed molded product is molded while the surface is smoothed by the action of the gas pressure. Devices that do this are known. When foamed material is injected into the molding cavity while gas is introduced, a dense film is formed on the surface of the injected material due to the action of gas pressure, and the film is then spread out along the molding surface. A foam molded product is formed in which only the inside is foamed.

Problems to be Solved by the Invention Incidentally, in such an apparatus, the gas introduced into the molding cavity escapes to the outside as the foamed material is filled into the cavity. However, if the molded product has protrusions such as ribs or bosses at predetermined locations, and the cavity has a recess corresponding to the protrusion,
The gas in the recess becomes trapped by the foamed material filled in the cavity. When gas is trapped in such a recess, the pressure of the gas makes it impossible for the foam material to fill the recess, resulting in a problem that a lack of thickness occurs in the molded product.

Means for Solving the Problems The present invention was made to solve these problems, and its gist is as follows:
Gas venting passages communicating with the recesses of the molded cavity are provided in a state that corresponds to each recess and are independent of each other, and valve means are respectively provided on the gas venting passages so that the gas is injected into the molded cavity. The gas trapped in the recesses by the foamed material is taken out to the outside through valve means provided corresponding to each recess.

Function and Effect of the Invention With this method, the gas in each recess of the mold can be vented through the corresponding gas vent passage, so that the gas trapped in these recesses can cause defects in the product. The occurrence of fleshy parts can be effectively prevented.

Moreover, in this way, the gas pressure in each recess can be controlled independently of each other by each corresponding valve means, so that the cooling rate of the foam material varies depending on the size and shape of the recess. It is now possible to adjust the gas pressure in each recess and, in turn, the filling speed of the foam material according to the It is possible to satisfactorily prevent the occurrence of an unfilling phenomenon due to early solidification, and to satisfactorily prevent the occurrence of underfilling due to unfilling of the foam material.

In other words, the forming apparatus of the present invention not only prevents the occurrence of under-walled parts caused by the gas trapped in the recesses, but also the occurrence of underfill parts in each recess caused by differences in size, shape, etc. of each recess. It is also possible to effectively prevent the occurrence of under-walled areas due to differences in the cooling rate of the foamed material. Therefore, even if the size and shape of the recesses are greatly different, cooling of the foamed material in those recesses can be effectively prevented. This has the advantage that even when the speeds differ greatly, it is possible to stably obtain a good product without any missing parts.

Further, according to the molding apparatus of the present invention, the gas pressure in each recess, and thus the filling speed of the foam material in each recess, can be individually and independently controlled by each corresponding valve means, so that each of the foam molded products can be individually controlled. Another advantage is that the thickness of the film layer on the surface of the convex portion can be adjusted individually depending on the purpose of the product.

Embodiments Next, embodiments of the present invention will be described in detail based on the drawings.

First, in FIG. 1, numeral 10 is a mold, which is composed of an upper mold 12 and a lower mold 14. A molding cavity 16 of a predetermined shape is formed in this molding die 10, and a molding cavity 16 of a predetermined shape is formed in the molding die 10.
The foamed material injected from 8 is injected into the molding cavity 16 through a material injection port 20. The mold 10 also includes a mold cavity 1.
Two through holes 22 and 24 are provided that open at the peripheral edge of the gas supply source 26 and 6.
The gas supplied through the gas passage 28 is introduced into the molded cavity 16 through the through hole 22, and the gas inside the molded cavity 16 is discharged to the outside through the through hole 24, the gas passage 30, and the electromagnetic valve 32. It's summery. Note that the gas passages 28 and 30
are communicated (bypassed) by a communication path 33, and the pressure of the gas in the molded cavity 16 is maintained at a constant pressure when the molded cavity 16 is partially filled with the foamed material. .

The molding cavity 16 is formed with recesses 34 and 36 in which rib portions are to be formed in the foamed molded product. Further, gas vent holes 38 and 40 are formed in the lower mold 14 and open into the recesses 34 and 36, and gas passages 4 are formed in the gas vent holes 38 and 40.
2,44 are connected. Gas passages 42, 44
On the top are throttle valves 46, 48 and a solenoid valve 50,
52 are provided.

Next, the operation of the above device will be explained.

First, the nozzle 18 of the injection device is pressed against the resin injection port 20 of the mold 10, and the electromagnetic valve 50,
52 is closed, the electromagnetic valves 26,
32 to guide gas supplied from the gas supply source into the molded cavity 16 and
Replace the inside with gas at a constant pressure. In this state, when a certain amount of foamed material is injected into the molding cavity 16 from the supply hole 20, the foamed material is injected into the molding cavity 16.
Due to the pressure of the gas inside, a dense coating layer (skin layer) is formed on the outer surface. Subsequently, by operating the electromagnetic valve 32 and injecting the foamed material from the injection port 20 while venting the gas inside the molding cavity 16, the foamed material expands the coating layer and fills the inside of the molding cavity 16. Go. At this time, the recess 3 of the molded cavity 16
The gas inside 4, 36 becomes trapped by the foam material. Therefore, the electromagnetic valves 50, 52
When opened, the gas in the recesses 34, 36 flows through the gas vent holes 38, 40, the gas passages 42, 44, the throttle valve 46,
48, and is gradually released to the outside via electromagnetic valves 50 and 52. Along with this, the foamed material is filled into the recesses 34 and 36 as shown in FIG. Here, each throttle valve 46, 48 is configured to control the cooling rate of the foam material in each recess 34, 36, which depends on the size and shape of each corresponding recess 34, 36, and in particular the purpose. The amount of squeezing is set in advance according to the thickness of the surface film layer.
Further, the electromagnetic valves 50 and 52 have respective corresponding recesses 3
4 and 36 at a timing corresponding to the formation position, size, shape, etc. In this way, the gas pressure when filling the foam material in each of the recesses 34 and 36 is adjusted according to the cooling rate of the foam material in the recesses 34 and 36 and the thickness of the desired surface film layer. Therefore, in each recess 34, 36, the desired filling can be achieved without causing filling defects due to early solidification of the foam material, that is, without causing insufficient parts due to early solidification of the foam material. This means that a surface film layer with a thickness of .

In addition, specifically, the electromagnetic valves 50 and 52 are as follows.
When the plunger of the injection device moves forward by a predetermined amount depending on the formation position, size, shape, etc. of each recess 34, 36, or after the start of injection, the formation position of each recess 34, 36 Each one opens when a predetermined time has elapsed depending on the size, shape, etc.

Once a predetermined amount of the foam material has been injected, the molding cavity 16 is filled with the foam material. At the same time, the foam material is foamed to form the cavity 1 as shown in FIG.
It is foam molded into the same shape as 6. At this time, foaming of the surface portion of the material in contact with the molding surface of the cavity 16 is suppressed, so that the surface of the molded product becomes smooth.
Since the surface portion of the foam material is formed as a dense coating layer, foaming is suppressed.

In this way, in the molding apparatus of this example,
Since the gas trapped in the recesses 34, 36 of the molding cavity 16 is extracted to the outside via the electromagnetic valves 50, 52, the injected foam material is not hindered by the gas in the recesses 34, 36. Since every corner of the cavity 16 can be filled, it is possible to effectively prevent the gas trapped in the recesses 34 and 36 from forming a hollow part in the foamed molded product.

In addition, by setting the throttle amount of the throttle valves 46 and 48 and setting the timing of the opening operation of the electromagnetic valves 50 and 52, the gas pressure when filling the foam material in each recess 34 and 36 can be appropriately controlled individually. In particular, the early solidification of the foam material due to the difference in the cooling rate of the foam material depending on the size and shape of the recesses 34, 36 is effectively prevented, and the occurrence of under-walled parts due to the early solidification is effectively prevented. In addition, a surface film layer of a desired thickness can be formed stably with high precision on each convex portion of the foam molded product molded within the recesses 34 and 36. Become.

Although the embodiments of the present invention have been described in detail above, the present invention can also be implemented in other forms.

For example, the present invention can be applied not only to molded products having rib portions as illustrated, but also to foam molded products having boss portions or other shaped protrusions. It is also possible to detect the pressure of the gas trapped in the recess of the molded cavity and open the electromagnetic valves 50, 52 based on the detected pressure. It is also possible to control the valve to maintain the pressure while allowing the gas to escape to the outside.

In addition, the present invention can be implemented with various modifications based on the knowledge of those skilled in the art without departing from the spirit thereof.

[Brief explanation of drawings]

FIG. 1 is a simplified cross-sectional view (partial circuit diagram) of a molding device that is an embodiment of the present invention;
3 are sectional views (partial circuit diagrams) of essential parts showing the apparatus shown in FIG. 1 in different operating states. 10: Molding mold, 16: Molding cavity, 34,
36: recess, 38: 40: gas vent hole 42, 44:
Gas passage, 46, 48: Throttle valve, 50, 52: Solenoid valve.

Claims (1)

[Claims for Utility Model Registration] A mold is provided with a concave portion corresponding to the convex portion in order to form a convex portion at a predetermined portion of a foam molded product,
With gas at a predetermined pressure introduced into the molding cavity of the mold, a foam material is injected into the molding cavity, and a foamed molded product is molded while smoothing the surface based on the smoothing effect of the gas. In the apparatus, gas vent passages communicating with the recesses of the molded cavity are provided in a state that is independent of each other and correspond to the respective recesses, and valve means are respectively provided on the gas vent passages, so that the gas vent passages communicate with the recesses of the molded cavity. A foam molded product characterized in that gas trapped in the recesses by the foam material injected into the molding cavity is taken out to the outside through valve means provided corresponding to each recess. molding equipment.