JPH0618738B2 - Press molding machine - Google Patents

Description

TECHNICAL FIELD The present invention relates to a press molding machine for injecting a molten resin or a preheated resin into a mold in a semi-closed state and then pressing to obtain a molded product. It is a thing.

[Prior Art] With a conventional press molding machine, when molding a large-sized molded product, a mold equipped with a plurality of injection gates is used to start injecting resin from each injection gate at the same time to obtain approximately the same amount. The resin was injected into each cavity and then pressed.

[Problems to be Solved by the Invention] In the above-described conventional press molding machine, since a plurality of injection gates are respectively injected into the corresponding cavities with substantially the same amount of resin regardless of the shape of the injection cavities, a large capacity is achieved. The amount of resin in the cavity is insufficient, and the amount of resin in the small capacity is excessive, causing the resin to flow from one cavity to another and moving the resin over a long distance, requiring a large pressing force. come.
In addition, a difference in the forming pressure between the cavities causes defects such as warpage in the molded product, and depending on the fluidity of the molten resin and the wall thickness of the molded product, large-capacity cavities may be unfilled or small-capacity cavities. It has a drawback that it causes burr and defective filling.

The present invention has been made in view of the above-mentioned drawbacks of the conventional technique, and provides a press molding machine capable of controlling the amount of injected resin according to the capacities of cavities corresponding to a plurality of gates of a mold. To aim.

[Means for Solving the Problems] The present invention provides a press molding machine in which a molten resin or a preheated resin is injected into a mold in a semi-closed state, and then the mold is completely closed. A plurality of injection gates that can be freely opened and closed with respect to a single molded product provided in, and a resin amount control unit that controls the injection resin amount by adjusting the opening and closing timing of each injection gate. The control means includes a temperature sensor that detects the temperature of the cavity corresponding to each gate and outputs a gate closing signal for closing each injection gate when the temperature reaches a preset temperature.

In addition, in a press molding machine that completely injects a molten resin or a preheated resin into a mold in a semi-closed state, and then completely closes the mold, And a plurality of injection gates that can be opened and closed, and a resin amount control unit that controls the injection resin amount by adjusting the opening and closing timing of each injection gate, and the resin amount control unit is provided for the cavity corresponding to each gate. It is characterized in that it has a pressure detector which is installed at an appropriate position and outputs a gate closing signal for closing each injection gate when the resin pressure of the injected resin is detected and when each reaches a preset pressure. .

[Operation] After the mold is closed in a semi-closed state, when the resin is injected into the corresponding cavity from each gate, the opening / closing timing of each injection gate is adjusted to control the amount of injected resin. It is possible to inject an appropriate amount of resin according to the cavity capacity.

[Embodiment] Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing an example of a mold 100 relating to a press molding machine of the present invention, and FIG. 2 is a plan view showing a molded product 200 obtained by the mold 100 of FIG.

As shown in FIG. 1, the mold 100 includes first to third cavities 111, 112, 13 and injection gates 11, 1 which can be opened and closed and which correspond to the respective cavities.
2 and 13, and valves 1, 2 and 3 are provided at the respective gates. Resin is valve 1, respectively
By opening 2,3, each cavity 111,1
The injection amount is controlled by opening and closing the injection gates 11, 12, and 13, respectively. In addition, the first to third cavities 111, 112,
The relationship between the capacities of 113 is the molded product 200 shown in FIG.
As is clear from the above, the first cavity 111> the third cavity 111
Cavity 113> second cavity 112.

Next, a first embodiment of the present invention will be described with reference to FIG.

In this embodiment, the temperature sensor 41 is embedded in the mold 44, and the temperature sensor 41 is connected to a thermometer (not shown). This thermometer outputs a closing signal for the injection gate 43 when the temperature detected by the temperature sensor 41 reaches a preset temperature.

Now, when the injection gate 43 is opened and the molten resin is injected into the cavity 40, the temperature of the mold 44 rises due to the heat of the molten resin. Furthermore, as the amount of injected resin increases, the circular shape of the resin centering on the injection gate 43 increases, and the mold temperature of the embedded portion of the temperature sensor 41 also rises accordingly, and the temperature detected by the temperature sensor 41 is measured by the thermometer. When the set value is reached, the injection gate 43 is closed to stop the resin supply. The amount of resin injected into the cavity 40 in this embodiment can be increased or decreased by adjusting the set value of the thermometer described above. Although the temperature sensor is embedded in the mold in this embodiment, the temperature of the resin may be directly detected by exposing the tip of the temperature sensor to the surface of the cavity.

Further, a second embodiment of the present invention will be described with reference to FIG.

In this embodiment, a pin 51, which is pressed by resin pressure, is embedded at an appropriate position of the die 56.
1 is supported by a spring 52 and pushed up into the cavity 50. Further, a limit switch 53 that detects that the pin 51 is pressed down is provided below the pin 51.
When the press of 1 is detected, a closing signal of the injection gate 55 is output.

Now, when the injection gate 55 is opened and the injection of the molten resin proceeds, the injected resin reaches the pin 51. After that, when the resin injection further progresses and the resin pressure on the pin 51 reaches a preset pressure, the pin 51 is pushed down and the limit switch 53 operates to output a closing signal of the injection gate 55 to supply the resin. stop. The amount of injected resin in this embodiment can be increased or decreased by adjusting the strength of the spring 52.
It is also possible to embed a pressure sensor as a pressure detector for detecting the injection resin pressure in the mold and close the injection gate when the pressure detected by the pressure sensor reaches a preset pressure.

Further, instead of the above-mentioned molten resin, preheated resin can be injected into each cavity.

In each of the above embodiments, the temperature sensor and the pressure detector are provided for each cavity corresponding to each gate.

[Effect of the Invention] As described above, according to the present invention, the opening / closing timing of each injection gate for injecting the molten resin or the preheated resin into each cavity of the mold is determined by the pressure of the injection resin in each cavity. Alternatively, by detecting the temperature of the injected resin and controlling them as parameters, an appropriate amount of resin can be injected into the volume of each cavity.
There is an effect that resin does not flow between the cavities and an excessive pressing force is not required, and furthermore, cavity unfilling and overfilling can be prevented, and defective molding can be prevented.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a mold 100 relating to the press molding machine of the present invention, FIG. 2 is a plan view showing a molded product 200 when the mold 100 of FIG. 1 is used, and FIG. Is a sectional view showing the constitution of the first embodiment of the present invention, and FIG. 4 is a sectional view showing the constitution of the second embodiment of the present invention. 1,2,3,42,54 …… Valve 11,12,13,43,55 …… Injection gate 40,50,111,112,113 …… Cavity 41 …… Temperature sensor 44,56,100 …… Mold 51 …… Pin 52 …… Spring 53 …… Limit switch 200 …… Molded product

Claims (2)

[Claims] 1. A press molding machine for completely closing a mold (100) after injecting a molten resin or a preheated resin into the mold (100) in a semi-closed state. A plurality of injection gates (11, 12, 13) that can be opened and closed with respect to a single molded product
A resin amount control means for controlling the injection resin amount by adjusting the opening / closing timing of each injection gate is provided, and the resin amount control means detects the temperature of the cavity corresponding to each gate and is preset respectively. When the temperature is reached,
A press molding machine having a temperature sensor for outputting a gate closing signal for closing each injection gate. 2. A press molding machine for injecting a molten resin or a preheated resin into a mold (100) in a semi-closed state, and then completely closing the mold, wherein the mold (100) is provided. A plurality of injection gates (11, 12, 13) that can be opened and closed with respect to a single molded product
A resin amount control means for controlling the amount of injected resin by adjusting the opening / closing timing of each injection gate is provided, and the resin amount control means is installed at an appropriate position of the cavity corresponding to each gate and the injected resin is injected. And a pressure detector that outputs a gate closing signal for closing each injection gate when the resin pressures of the respective ones have reached preset pressures.