JPH0464850B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an injection compression molding machine having a toggle type mold opening/closing mechanism.

In general, injection molding involves injecting plasticized resin into a mold, cooling and solidifying it in the mold to form a molded product in the desired shape, but the plasticized resin solidifies. It is well known that so-called casting shrinkage occurs during casting, and it is unavoidable that molded products undergo changes in thickness, deformation, etc. due to this casting shrinkage.

However, in recent years, molding of ultra-precision mechanical parts, optical parts, etc. by injection molding has become popular, and it has become inevitable to prevent deformation due to casting shrinkage.

As a means for preventing deformation due to casting shrinkage, a so-called compression molding method has been proposed in which the resin that has already been filled into the mold, leaving a compression allowance, is compressed again during the cooling and solidification process.

As this compression molding method, Japanese Patent Application Laid-Open No. 51-73058
As described in the issue, a special mold clamping cylinder is configured to enable multi-stage mold clamping, and the mold is first closed with a slight compression margin left, and then the mold is injected, and then the mold is clamped again to the final mold clamping position. In this method, a stopper or wedge is provided between the molds or the platen in advance, and the mold is first moved to the position regulated by the stopper or wedge (the position leaving a compression allowance). After closing and injecting, remove the stopper or wedge, etc., and clamp the mold again to the final position to obtain the desired molded product.Furthermore, there is a method in which a compression cylinder is installed in the mold in advance and the mold is clamped first. A known method is to obtain a desired molded product by activating a compression cylinder within the mold to compress the cavity surface after the mold is clamped and injected using a device.

However, the method described above requires a special mold clamping cylinder and performs multi-step mold clamping under hydraulic control, making it difficult to obtain accurate positioning accuracy of the mold clamping position. Although this method provides better positioning accuracy than the method of mechanically regulating the stroke of the mold clamping cylinder, it requires an in/out/adjustment mechanism such as a stopper or wedge, and mold clamping is performed using a direct pressure cylinder. Therefore, a large mold clamping cylinder is required.

Furthermore, in the method (2), the mold is clamped to the final mold clamping position in one go, so positioning the mold clamping position is relatively easy, and a direct pressure cylinder or a toggle mechanism can be used as the mold clamping device, so it is possible to use a toggle mechanism. Using a mechanism has the advantage of reducing mold clamping force, but since a compression cylinder is built into the mold, the mold structure becomes complicated, and the entire mold must be replaced every time the molded product changes. Yes, mold costs increase.

None of the methods were completely satisfactory.

This invention was made in view of the above, and
A fixed plate and a toggle support are provided at intervals in the axial direction of the tie bar, a movable plate is installed between the fixed plate and the toggle support, one end is attached to the toggle support, and the other end is attached to the movable plate. A nut is attached to the joint part of the toggle support of an injection molding machine having a toggle type mold opening/closing mechanism having a toggle mechanism attached to the toggle support and a mold opening/closing cylinder attached to the toggle support, and the nut and the tie bar are attached to the tie bar. A threaded portion is provided, and by rotating the nut, the axial position of the toggle support can be adjusted according to the thickness of the mold. A compression cylinder is attached to the stationary platen, and the This is an injection molding machine that has a toggle type mold opening/closing mechanism with a piston connected to a tie bar, and can perform compression molding without incorporating a compression cylinder into the mold.

The following will explain the embodiments shown in the drawings.

1 is a fixed plate, 2 is a movable plate, 3 is a toggle support, 4 is a toggle mechanism whose one end is attached to the movable plate 2 and the other end is attached to the toggle support 3, and 5 is a mold opening/closing cylinder attached to the toggle support 3. The piston rod 5' end of the cylinder 5 is attached to the toggle mechanism 4 , and the movable platen 2 is moved forward and backward relative to the fixed platen 1 via the toggle mechanism 4 by expansion and contraction of the mold opening/closing cylinder.

Reference numerals 6 and 6' denote molds, one of which is mounted on the fixed platen 1 side and the other on the movable platen 2 side, and these molds are opened and closed as the movable platen 2 moves forward and backward. Tie bars 7 and 7' connect the fixed platen 1 and the toggle support 3 to each other at a predetermined interval, and guide the movable platen 2.

Although the above configuration is similar to that of a conventional injection molding machine having a toggle type mold opening/closing mechanism, the following configuration is added in the present invention.

8, 8' are compression cylinders on the fixed platen 1 side (first,
2) or on the side opposite to the mold mounting surface of the toggle support 3 (not shown), and inside the cylinders 8, 8' are pistons 9, 9 connected to the tie bars 7, 7'. ' is inset. The pistons 9, 9' may be formed integrally with the tie bars 7, 7' at the ends of the tie bars 7, 7' as shown in the figure (first, second
(Figure) Alternatively, although not shown, the tie bars 7, 7' and the pistons 9, 9' may be formed separately, and both may be fixed together with a suitable fixture such as a bolt, and the pistons 9, 9'
9' is fitted into the cylinders 8, 8'. 10 is a tie bar 7, 7' insertion hole formed in the toggle support 3, and the tie bar 7, 7' is slidably inserted into the hole 10, and a nut 12 is screwed into the threaded portion 11 of the tie bar 7, 7'. 12' is rotatably mounted.

13, 13' are sprockets that are integrally attached to the nuts 12, 12';
3' is rotated by a drive motor 15 attached to the toggle support 3 via a chain 14 or a gear (not shown).

16 is a braking device such as an electromagnetic brake or a hydraulic brake provided on the output shaft side of the drive motor 15; 17;
Reference numeral 17' denotes a rotation extraction gear attached to the output shaft 18 of the drive motor 15. The rotation speed is detected by the encoder 19 via the gears 17, 17' to detect the amount of movement of the toggle support 3, and the encoder 19 is connected to a comparator (not shown), compares the setting amount input to the comparator with the amount detected by the encoder 19, and controls the amount of movement of the toggle support 3.

This invention has the configuration as described above.

Next, its effect will be explained.

The amount of movement of the movable platen 2 is determined in advance by the toggle mechanism 4 , so when the molds 6 and 6' to be used are determined, the amount of opening and closing of the molds is determined, so the thickness and compression amount α of the molds 6 and 6' are determined. Input the set amount based on the setting value into the setting device,
When the drive motor 15 is driven, the toggle support 3 is moved in the axial direction of the tie bars 7, 7' via the chain 14, sprockets 13, 13' and nuts 12, 12', and is stopped at a set position.

In this state, when the mold opening/closing cylinder 5 is operated to extend the toggle mechanism 4 and close the mold, the molds 6, 6'
is closed with the compression allowance α remaining.

After the mold is closed, an injection device (not shown) is operated to inject the plasticized resin into the molds 6, 6', and the inside of the compression cylinders 8, 8' is cooled and solidified in the molds 6, 6'. When the pistons 9, 9' are actuated to extend the tie bars 7, 7', the mold 6 or 6' is clamped so as to close the compression allowance α through the bars 7, 7'. The resin in 6' is compressed to complete the molding, and after the molding is completed, the mold opening/closing cylinder 5 is operated in the mold opening direction to contract the toggle mechanism 4 and the molded product is released from the mold.

One molding process is completed with the above steps, and the above steps are repeated thereafter.

When molding is completed using the same mold in this way and the mold is replaced, input the setting amount based on the mold thickness and compression amount of the new mold into the setting device and position the toggle support in the same manner as described above. After adjusting, molding is performed in the same molding process as described above.

This invention has the above-mentioned configuration, and the opening/closing amount of the mold is controlled by adjusting the position of the toggle support, and the compression of the mold is performed by the compression cylinder provided on the fixed plate, so the mold opening/closing is performed by the toggle mechanism. Since the mold opening due to the injection pressure during injection is prevented mechanically by a toggle mechanism, a mold opening/closing cylinder with a small capacity is required, saving energy and controlling the closing position of the mold. Since no stopper or wedge is required, the structure can be simplified.

In addition, since the compression cylinder is mounted on a fixed platen, the mold clamping stroke of the compression cylinder only needs to be equal to the compression allowance α, so the compression cylinder only needs to have a small capacity. Since there is no need to incorporate a cylinder, the mold structure can also be simplified.

[Brief explanation of the drawing]

1 and 2 are partially cutaway front views showing one embodiment of the present invention, and FIG. 1 is a state diagram of the mold closed, and FIG.
The figure is a state diagram of the mold opening, and FIG. 3 is a side view of the same. 1... Fixed plate, 2... Movable plate, 3... Toggle support, 4 ... Toggle mechanism, 5... Mold opening/closing cylinder, 7, 7'... Tie bar, 8... Compression cylinder,
11...screw part, 12, 12'...nut.

Claims (1)

[Claims] 1 A fixed plate and a toggle support provided at intervals in the axial direction of the tie bar, a movable plate arranged between the fixed plate and the toggle support, one end of which is attached to the toggle support, and the other end of which is movable. A nut is attached to the joint part of the toggle support of an injection molding machine having a toggle-type mold opening/closing mechanism having a toggle mechanism attached to the panel and a mold opening/closing cylinder attached to the toggle support, and the tie bar is provided with a nut. A threaded part is provided to be screwed into the toggle support, and by rotating the nut, the axial position of the toggle support can be adjusted, and a compression cylinder is attached to the fixed plate.
An injection compression molding machine having a toggle type mold opening/closing mechanism, characterized in that a piston connected to the tie bar is disposed within the compression cylinder.