JPH0155975B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for preventing leakage of accumulated material in injection molding, and its purpose is to prevent the leakage of accumulated material in injection molding. The purpose is to prevent the leakage of retained material from the gate, which is called nasal drip.

To describe an illustrative embodiment of the invention:
Reference numeral 1 denotes a mold, and a nozzle contact surface 2 to which a nozzle (not shown) is brought into close contact communicates with a cavity 6 via a sprue 3, a runner 4, and a gate 5. Reference numerals 7 and 8 are cutoff valves divided into two parts with slopes disposed in the vicinity of the nozzle contact surface 2 in the passage of the sprue 3 so as to be slidable in a transverse direction so as to be able to cut off the sprue 3; The shut-off valves 7 and 8 are formed with a through hole 9 that coincides with and communicates with the sprue 3 under each joined state, and after the molding material is injected and supplied to the mold 1, the shut-off valves 7 and 8 are closed. A negative pressure chamber 10 is created in the gap between the shutoff valves 7 and 8 which are separated from each other at the same time as they are separated to the left and right to cut off the sprue 3, and the negative pressure chamber 10 is configured to communicate with the passage on the gate 5 side of the sprue 3. . Further, the shutoff valves 7 and 8 are connected to springs 1 through rods 11 and 11 at their rear ends, respectively.
2 and 12 connect the driven bodies 13 and 13 which are biased to retreat, and the driving bodies 14 and 14 which are in inclined contact with the driven bodies 13 and 13 are moved downward by the biasing force of springs 15 and 15 when the mold is opened. It is configured like this. 16 is a mold matching surface, 17 is a knockout pin, and 18 is a heater.

To explain the operation of the present invention, FIG. 1 shows a state in which molding material is injected and supplied from a nozzle into a mold 1, and the two-split shutoff valves 7 and 8 are in a joined state, and the through hole 9 is spun out. The molding material is press-fitted into the cavity 6 through the sprue 3, runner 4, and gate 5. After the molded product in the cavity 6 has cooled and solidified, when the mold 1 is opened to take out the molded product as shown in FIG. Driven body 1 that comes into contact with the slope
3 and 13 are also retracted by the biasing force of springs 12 and 12, whereby the two-split shutoff valves 7 and 8 slide apart to the left and right, respectively. Here, one of the shutoff valves 7 shuts off the sprue 3 and at the same time creates a negative pressure chamber 10 having a required volume in the gap between the two shutoff valves 7 and 8 which are separated. Since the negative pressure chamber 10 communicates with the gate 5 side passage of the sprue 3, some of the material staying in the passage from the gate 5 side passage of the sprue 3 to the runner 4 and the gate 5 is transferred to the negative pressure chamber 10.
Since the internal pressure in the passage section is completely removed, there is no possibility that the material staying between the sprue 3, the runner 4 and the gate 5 will leak out from the gate 5 due to its surface tension. do not.

After the molded product is removed, the mold is closed and the first
When the mold mating surfaces 16 are joined as shown in the figure, the driving bodies 14, 14 rise against the springs 15, 15, and the driven bodies 13, 13, which are in contact with the slopes thereof, move back against the springs 12, 12. Then, both shutoff valves 7 and 8, which had been separated, are joined together. As a result, the accumulated material sucked into the negative pressure chamber 10 is compressed by both the shutoff valves 7 and 8, and all of it is completely pushed back into the sprue 3.
The through hole 9 formed in the sprue 3 is connected to the passage of the sprue 3 to return to the state shown in FIG. 1 in which molding material can be injected and supplied, and then the above-mentioned operations are repeated in sequence.

Note that when the mold 1 is small and the volume of the passage leading to the sprue 3, runner 4, and gate 5 is small, and therefore the volume of the material staying in the passage is small, the two-part shutoff valve 7 is used. , 8 without sliding them apart.
It is also possible to set and operate the volume of the negative pressure chamber 10 to be small by fixing the shutoff valve 7 and sliding only the other shutoff valve 7 apart.

The present invention is as described above, and the two-split shutoff valves 7 and 8 are disposed in the passage of the sprue 3.
The gate is called a nasal drip because it can cause the negative pressure chamber 10 to be opened, and the material staying in the passage leading to the sprue 3, runner 4, and gate 5 can be sucked in and the internal pressure in that passage can be completely removed. It is possible to completely prevent leakage of the accumulated material from the negative pressure chamber 10, and when the shutoff valves 7 and 8 are moved back and connected, all of the accumulated material sucked into the negative pressure chamber 10 can be completely pushed back. Therefore, the injection and supply operation of molding material can be repeated smoothly.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and Fig. 1 is a longitudinal cross-sectional view of the shutoff valve in the connected state during injection and supply of molding material, and Fig. 2 shows the cutoff valve in the separated state when the mold is opened to take out the molded product. FIG. 1...Mold, 2...Sprue, 4...Runner, 5
... Gate, 6 ... Cavity, 7, 8 ... Shutoff valve, 9 ... Through hole, 10 ... Negative pressure chamber.

Claims (1)

[Claims] 1 In the passage of the sprue 3 of the mold 1, the two-split shutoff valves 7 and 8 are slidably disposed so as to be able to separate and open, and the shutoff valves 7 and 8 match the sprue 3 in the state of being joined. After drilling a communicating through hole 9 and injecting and supplying molding material to the mold 1, the shutoff valves 7 and 8 are opened to shut off the sprue 3, and a negative pressure chamber is generated in the gap between the shutoff valves 7 and 8, which are opened at the same time. 10 is configured to communicate with the gate 5 side passage of the sprue 3. A leakage prevention device for retained material in injection molding.