JPH0361578B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to a method for filling raw materials in foam molding, and by performing staggered filling from two or more raw material fillers to a pair of mold cavities, it is possible to fill without cracking and to produce good foam molded products with little difference in specific gravity. This is a method that makes it possible to provide In the conventional method of filling raw materials in foam molding, raw material fillers were operated simultaneously, and raw materials were fed into the mold cavity at the same time. A conventional piping system is shown in Fig. 1, where 1 is a cavity frame, 2 is a core frame, 3 is a cavity mold, 4 is a core mold, and 5a-
5d is the raw material filling device, 6 is the main air piping, 7
is a filter, 8 is an on-off solenoid valve for the raw material filler,
9 is an air pipe for closing the filling machine, 10 is a stop valve for the main pipe, 11 is an air pipe for opening the filling machine, 12 is a solenoid valve for feeding air, 13 is a pipe for feeding air, 14, 15, 16 is a stop valve, 17
18 is a hopper shutter, and 19 is a feed hose. First, the solenoid valve 8 for opening and closing the filling device is activated, and the filling devices 5a to 5d are opened at the same time, and the solenoid valve 12 for feeding air is also opened. Air is blown out to blow away the water remaining on the surfaces of both molds 3 and 4. Next, in the filling process, hopper shutter 1
8 is opened, and the mold cavities between both molds 3 and 4 are filled with raw material expandable thermoplastic resin particles all at once by the air supplied from the filling devices 5a to 5d, which are already open. This filling is controlled by a timer. When filling is completed, the filler opening/closing electromagnetic valve 8 is activated, and the fillers 5a to 5d are closed, but the inlet air continues to come out and the raw material remaining in the inlet hose 19 is returned to the hopper 17. Next, the incoming air solenoid valve 12 and the hopper shutter 18 are closed to complete the filling process. The above conventional time chart is shown in Table 1 below.

[Table] That is, in the conventional filling method, the raw material filling devices were operated simultaneously, and therefore the raw materials were filled into the mold cavities at the same time. According to such a method, mutual interference of the air introduced for filling the raw material causes parts where it is difficult for the raw material to enter, and it is not possible to obtain a good foamed molded product by filling without cracking. Therefore, as a conventional solution, the so-called cracking method is generally adopted, in which the mold is opened by about 2 to 7 mm when filling the raw material, and the injected air is released to the outside.
However, the resulting foamed molded product had a difference in specific gravity between the bottom and side views. That is, in the method employing cracking, there was no problem in filling the bottom part, but the filling in the side parts was poor.
In particular, in the case of box-shaped foam molded products such as fish boxes, if the side parts are not evenly filled with raw materials, the physical properties will be weak and accidents such as collapse of the cargo may occur. At the same time, there was a demand for non-cracking filling in order to promote weight reduction of foam molded products. This invention is based on the problems of the prior art and has developed a raw material filling method that can be adapted to the above-mentioned current demands. In this method, two or more raw material fillers are provided for a pair of mold cavities, and the same kind of resin is filled into the mold cavity. In order to fill the particles without cracking, each raw material filler is operated at different times. Next, embodiments of the present invention will be illustrated below with reference to the drawings. 21 in Fig. 2 is a cavity frame, 2
2 is a core frame, 23 is a cavity mold that is one of a movable type and a fixed type, 24 is a core mold that is the other of a movable type and a fixed type, 25a to 25d are raw material fillers, 26 is a main air pipe, 27 is a filter, 28 and 29 are solenoid valves for incoming air,
30, 31 are supply air pipes, 32, 33, 3
8, 39, 41, 44 are stop valves, 34, 35
36 and 43 are air piping for opening the filling device, 37 and 42 are air piping for closing the filling device, 45 is a hopper, 46 is a hopper shutter, and 47 is a feed hose. There is. In order to carry out the alternate filling of the present invention using the filling piping system described above, the solenoid valves 34, 3 for opening and closing the filling device are used.
5 and fillers 25a, 25b, 25c,
Open 25d at the same time. At the same time, open the solenoid valves 28 and 29 for incoming air, and open the cavity mold 2.
Air is blown into the mold cavity formed by the core mold 24 and the core mold 24, and water remaining on the surfaces of both the molds 23 and 24 is blown away. Next, the filler on-off valve 34 is activated, and the filler 2
At the same time as 5b and 25d are closed, the inlet air valve 28
Also, the filling devices 25b and 25d stop supplying air to the mold cavity. First step of filling (Table 2 below)
filling), open the filling devices 25a and 25c,
Air continues to be supplied to the mold cavity by the opening of the supply air valve 29, and at this time the hopper shutter 46 is opened.
Approximately 80 to 90% of the mold cavities are filled with raw resin particles by the injected air. After this filling, the filler opening/closing solenoid valve 35 is activated to fill the fillers 25a, 25c.
closes. At this time, the inlet air valve 29 remains open and the raw material remaining in the inlet hose 47 is removed from the hopper 4.
I'll change it back to 5. Then, close the inlet air valve 29 and fill the first
The process ends. At this time, the filling devices 25b and 25d
In order to prevent a delay in the opening operation, the filler opening/closing electromagnetic valve 34 may be operated to open the fillers 25b and 25d in advance. Then the second filling
In the process (filling in Table 2 below), the filling device 25b,
25d and the inlet air valve 28 is opened to fill the remaining 10% to 20% of the mold cavity with the raw material by the inlet air. Next, the electromagnetic valve 34 for opening and closing the charger is operated, and the fillers 25b and 25d are closed. At this time, the feed air valve 28 remains open and the raw material remaining in the feed hose 47 is returned to the hopper 45. After this, the inlet air valve 28 is closed, and the hopper shutter 46 is also closed at the same time, completing the second filling step. At the same time, the entire filling process ends. The time chart for the above alternate filling is shown in Table 2 below.

[Comparative example]

When 12 filling devices were simultaneously operated using the conventional method in a 6-cavity mold, cracking 5 was obtained when using the same equipment as the raw material made of expanded polystyrene with an apparent specific gravity of 0.020 as in the example.
mm, a foamed molded product with a good appearance was obtained, but there was a difference in specific gravity of 0.0042 between the bottom part specific gravity of 0.023 and the side part specific gravity of 0.0188. However, when the above-mentioned foam molding was performed without cracking, some filling defects were observed on the side surfaces of the foam molded products obtained from molds No. 2, No. 3, and No. 6. Partial contraction had occurred. (Effects of the Invention) As is clear from the above-mentioned Examples and Comparative Examples, in the method of this invention, two or more raw material fillers are provided for a pair of mold cavities, and the same kind of material is filled in the mold cavity. In order to fill the resin particles without cracking, each raw material filler is used at different times to perform the filling operation, which makes it possible to fill without cracking and mass-produce good foam molded products with little difference in specific gravity. It will be suitable for

[Brief explanation of drawings]

In the figure, Fig. 1 is a piping system diagram for explaining the conventional filling method, Fig. 2 is a piping system diagram for explaining alternate filling according to the present invention, and Figs. FIG. 4 is a filling schematic diagram of the second embodiment, and FIG. 5 is a layout diagram of the filling machine. 25a to 25d... Raw material filling device, 28, 29...
...Inlet air valve, 34, 35...Filler opening/closing valve,
45...Hopper, 46...Hopper shutter, 47...Feeding hose.

Claims (1)

[Scope of Claims] 1. In a method for filling the mold cavities of a pair of foam molding molds consisting of a movable mold and a fixed mold with the same kind of foam molding thermoplastic resin particles serving as a raw material, In foam molding, in which two or more raw material fillers are provided, and each raw material filler is operated at a time difference in order to fill the same type of resin particles into the mold cavity without cracking. How to fill raw materials. 2. A method for filling raw materials in foam molding according to claim 1, wherein each feed air valve corresponding to each raw material filling device is opened alternately to fill the raw materials.