JPH0366138B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Two examples of conventional injection molding molds are shown in FIGS. 1 and 2, both of which are hot runner type injection molding molds. First, in FIG. 1, 101 is the fixed side mounting plate, 102 is the hot runner block,
103 and 4 are spacers, and 119 is also a spacer. 120 is a fixed side template, 21 is a movable side template, 2
2 is the movable side mounting plate, 23 is the molded product cavity, 1
24 is a gate, 102a is a resin inlet, and 102b is a resin passage.

Molten resin injected from an injection molding machine (not shown) flows from the resin inlet 102a and enters the resin passage 1.
02b, molded product cavity 2 via gate 124
3 is filled. The resin passage 102b in the hot runner block 102 is constantly filled with molten resin.

However, the mold shown in FIG. 1 had the following drawbacks. That is, there is a drawback that the molten resin in the hot runner block 102 drips from the gate 124 into the molded product cavity 23, and if the gate 124 is large, the molten resin in the vicinity of the gate 124 when injection filling into the molded product cavity 23 is completed. Excessive pressure is applied, causing defects such as distortion of the molded product.
Conversely, if the gate 124 is small, there will be a large resistance to the flow of the resin, resulting in large pressure loss and increased heat generation.

When molding an asymmetric molded product using multiple gates like the mold shown in Figure 1, it is necessary to change the amount of resin inflow from each gate, but to do this, the dimensions of the gate 124 must be changed. I had to. Changing the dimensions of the gate 124 had to be done by processing the gate by trial and error while trying to mold it, which had drawbacks such as being laborious and time-consuming and not being reliable.

Next, in the mold shown in FIG. 2, 201 is a fixed side mounting plate, 202 is a hot runner block, 203 and 4 are spacers, and 219 is also a spacer. 22
0 is a fixed side template, 224 is a gate, and 205 is a valve pin. Further, 217 is provided on the opening/closing cylinder fixed side mounting plate 201, and is attached to the opening/closing piston 20.
It has 8 built-in. Note that this cylinder is operated by hydraulic pressure or pneumatic pressure. 202a is a resin inlet;
202b is a resin passage.

However, in the case of the example shown in Fig. 2, the valve pin 20
5 is provided in each of the plurality of gates 224, some of the disadvantages in FIG. As in the case, valve pin 205
If the opening amount is large, excessive pressure will be generated near the gate 224, resulting in molded product defects.On the other hand, if the opening amount is small, the resin flow resistance will be large, resulting in excessive pressure loss, heat generation, etc. There were flaws.

In mold technology, determining the gate placement and size is the most difficult, and often requires modification even after the mold has been manufactured. Furthermore, in order to prevent excessive pressure near the gate of the molded product, conventional molds restrict the flow path with a gate, resulting in pressure loss and heat generation.

The present invention has been proposed in order to solve the above-mentioned conventional drawbacks, and includes a valve gate device having a valve pin provided at each gate of an injection molding mold that can open and close each gate at a free timing.
It is supported by an intermediate fixed fulcrum and is swingable, and one end is pivotally connected to the valve pin and the other end is pivotally connected to a connecting fitting that moves together with the opening/closing piston, and when the opening/closing piston operates, the tip of the valve pin is moved to close the gate. and a lever for moving the opening/closing piston to a fully open position; a mid-opening piston that is disposed on the side facing the opening/closing piston and has a state in which no pressure is applied and a state in which it is pushed out with a force greater than that of the opening/closing piston; A stopper plate is provided at the tip and faces the connection fitting, and when the valve pin is in the middle open position, the center-opening piston applies a larger force to the stopper plate than the opening/closing piston, and the center-opening piston acts on the stopper plate through the connection fitting and the lever. The valve pin is held in the mid-open position, and by closing the valve pin, it is possible to prevent so-called nasal drip from the gate, by fully opening the valve pin, it is possible to prevent pressure loss and heat generation at the gate, and by opening the valve pin fully, it is possible to prevent pressure loss and heat generation at the gate. It is possible to prevent excessive pressure near the molded product gate.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 3 is a side sectional view of the entire mold showing an embodiment of the present invention, and FIGS. 4 to 6 are detailed views of the valve gate showing three operating positions of the valve pin. FIG. 4 shows the valve pin closed, FIG. 5 shows the valve pin fully open, and FIG. 6 shows the valve pin halfway open.

In FIG. 3, 1 is a fixed side mounting plate, 2 is a hot runner block, which is heated by a heater (not shown), and the resin passage 2b is always filled with molten resin. Reference numeral 2a denotes a resin inlet, which comes into contact with the nozzle of the injection molding machine, into which molten resin is injected during the injection operation of the injection molding machine.

Reference numeral 20 denotes a stationary side mold plate, which is connected to the stationary side mounting plate 1 via a spacer 19. Further, the hot runner block 2 is assembled between the fixed side mounting plate 1 and the fixed side mold plate 20 via spacers 3 and 4.
21 is a movable side mold plate, 22 is a movable side mounting plate, and both are connected.

23 is a molded product cavity, and the mold is opened to the left and right with the cavity 23 as a border. 24 is the tip of the center hole of the sprue bushing 2c at the left end of the hot runner block 2, and is called a gate. 5 is a valve pin, the left end of which fits into the tip of the center hole of the sprue bushing 2c to seal the molten resin.
Further, the right end is connected to the lever 7 via a pin 12. A bracket 6 is attached to the hot runner block 2 and supports the lever 7 via a pin 13.

Reference numeral 17 denotes a center-open cylinder incorporated into the fixed side mounting plate 1, which houses a center-open piston 8, and the center-open piston 8 is screwed to the stopper plate 9. On the other hand 1
Reference numeral 8 denotes an opening/closing cylinder built into the stationary template 20, which has an opening/closing piston 11 inside.
1 is screwed to a connecting fitting 10. The connecting fitting 10 is connected to the lever 7 via a pin 14, but is free between it and the stopper plate 9. Further, 15 and 16 are covers.

Note that the cylinders 17 and 18 are driven by hydraulic pressure or pneumatic pressure. Further, as shown in FIG. 3, a valve gate is incorporated in each gate 24, and each valve gate has independent drive cylinders 17 and 18.

Next, the effect will be explained. First, when injection is started in FIG. 3, molten resin is injected from an injection molding machine (not shown) through the resin inlet 2a, and the molten resin flows into the molded product cavity 23 from each gate 24 through the resin passage 2b. do. Each gate 24 has a built-in valve gate that operates as described below, and the gate opening can be opened to the required degree at the required timing.

Next, the operation of one valve gate will be explained with reference to FIGS. 4 to 6. FIG. 4 shows the state before injection starts. Pressure is applied to the head side of the opening/closing piston 11 of the opening/closing cylinder 18, but no pressure is applied to the middle opening piston 8, so the force of the opening/closing piston 11 is applied to the connecting fitting 10, The valve pin 5 is pressed against the tip of the center hole of the sprue bush 2c via the lever 7. Therefore, even if there is resin pressure in the resin passage 2b, the resin will not leak to the gate 24.

Next, when injection starts, the valve pin 5 is moved to the right by moving the opening/closing piston 11 to the left as shown in FIG. 5, and the left gate opening of the valve pin 5 is fully opened. 24
The molten resin is allowed to freely flow into the molded product cavity 23 through the process. In this case, since the gate opening is fully opened, the pressure loss and heat generation of the resin flowing into the gate are small. Incidentally, when the resin continues to flow into the molded product cavity 23 in the state shown in FIG. 5 and the cavity is almost filled, it can be set in advance using a timer.

Next, as shown in FIG. 6, move the opening/closing piston 11 to the right to bring the connecting fitting 10 into contact with the stopper plate 9.
At this time, a force greater than that of the opening/closing piston 11 is exerted to the left on the middle opening cylinder 8, and the cylinder 8 is stopped in the state shown in FIG. In this state, the gate opening on the left side of the valve pin 5 is opened and narrowed to prevent excessive pressure from being applied to the vicinity of the gate 24 of the molded product.

When the injection (including injection holding) is completed, the state is returned to the state shown in Fig. 4, and after the molded product is taken out, the resin passage 2b is
This prevents resin from leaking into the molded product cavity 23 through the gate 24.

The present invention is configured as described in detail above, and by closing the valve pin, resin leakage from the gate can be prevented, and by fully opening the valve pin, pressure loss and heat generation of the resin flowing into the gate can be prevented. Further, in the present invention, when the valve pin is in the middle open position, a force greater than that of the opening/closing piston is applied to the stopper plate to hold the valve pin in the middle open position via the connecting fitting and lever, so that the valve pin can be easily held in the middle open position. The valve pin can be stably placed in the middle open position. Therefore, by opening the valve pin,
Excessive pressure near the molded product gate can be prevented, and by changing the timing of opening and closing the valve pin of each gate, the amount of resin flowing into each gate can be optimized. As described above, the present invention employs a three-position system for each gate of the mold: open, partially open, and closed, and because of this three-position system, the temperature of the resin passing through the gate and the pressure inside the mold can be easily controlled. Therefore, according to the present invention, an ideal gate for an injection mold can be realized.

[Brief explanation of drawings]

1 and 2 are side sectional views showing a conventional valve gate device for an injection mold, and FIG. 3 is a side sectional view of a valve gate device for an injection mold according to an embodiment of the present invention. 4, 5, and 6 are detailed views of the main parts in FIG. 3 in different operating states, respectively. Explanation of the main parts of the diagram, 2... Hot runner block, 2c... Sprue bush, 5... Valve piston, 7... Lever, 8... Center open piston, 9...
...Stopper plate, 10...Connection fittings, 11...Opening/closing piston, 17, 18...Cylinder, 24...Gate.

Claims (1)

[Claims] 1. In a valve gate device having a valve pin provided on each gate of an injection molding mold, which can open and close each gate at a free timing, the valve gate device is supported by an intermediate fixed fulcrum and is swingable, and one end is attached to the valve pin, The other end is pivotally connected to a connecting fitting that moves together with the opening/closing piston, and a lever that moves the tip of the valve pin to the closed and fully open positions of the gate by the operation of the opening/closing piston, and is disposed on the side facing the opening/closing piston; The center-open piston is provided with a state in which no pressure is applied at all and a state in which it is pushed out with a force greater than the opening/closing piston, and a stopper plate provided at the tip of the center-open piston and in contact with the connection fitting; A valve for an injection molding mold, wherein the piston applies a force larger than the opening/closing piston to a stopper plate when the valve pin is in the middle open position to hold the valve pin in the middle open position via the connecting fitting and lever. gate device.