JPH06297527A - Toggle type clamping device - Google Patents

Abstract

PURPOSE:To prevent specific clamping force or over from acting on a toggle type clamping device. CONSTITUTION:A toggle type clamping device is composed of a movable platen 30, a fixed platen 32, a clamping housing 34, a tie-bar 36, a clamping cylinder 10, a toggle mechanism 12, etc. A movable side metal mold 38 is fixed to the movable platen, and further a fixed side metal mold 40 is fixed to the fixed platen. A clamping side oil chamber 10b of the clamping cylinder is connected to an oil pressure source 14 via the first piping 23, a pilot check valve 20, one side port of a main switching valve 18, and a flow rate regulation valve 16. A pilot port 20a of the pilot check valve is interconnected to or isolated from the first piping 23 with a pilot piping 33 and a pilot switching valve 22. The second piping 27 on a mold opening side oil chamber 10c side is connected to the other port of the main switching valve 18.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toggle type mold clamping device, and more particularly to a toggle type mold clamping device having an overload preventing function.

[0002]

2. Description of the Related Art As a conventional injection compression molding apparatus, there is one disclosed in Japanese Patent Laid-Open No. 61-253520. The injection compression molding apparatus shown therein is of a so-called direct-acting type, and a movable plate is directly attached to a piston rod of a mold clamping cylinder. That is, the movable plate can be moved at the same speed (the same amount of movement) as the piston rod.

[0003]

However, the conventional direct-acting injection compression molding apparatus as described above has a problem that it is troublesome to control the position of the movable plate. That is, in injection compression molding, it is necessary to apply compressive force stepwise by advancing the movable plate stepwise in the compression step of reducing the cavity volume with respect to the molten resin supplied to the mold cavity. In some cases, in order to remove the distortion of the molded product due to compression molding, a step of slightly increasing the cavity volume during the molding (strain removal step) may be necessary. In order to control the position of the movable platen, a high-precision sensor that accurately detects the position of the movable platen and a high-precision flow rate control device that stops the movable platen at a predetermined position are required. It becomes troublesome. As a solution to this, it is conceivable to perform compression molding using a toggle type mold clamping device. Even if the toggle type mold clamping device drives the crosshead part of the toggle mechanism at a constant speed, the moving speed on the link end side (movable plate side) increases as the link is bent in a linear shape and shortened. It has the characteristic that the moving speed on the movable platen side becomes slower as the extended state where the two extend straight to each other, and the movable platen stops at the position where the links of the toggle mechanism have completely extended linearly. . That is, it is possible to decelerate (stop) the movable platen side without decelerating the crosshead side (mold clamping cylinder side) of the toggle mechanism. The final pressing force (mold clamping force) corresponding to the force increase rate of the toggle mechanism is generated at the position where the links of the toggle mechanism are completely extended linearly. However, in the case of a toggle type mold clamping device, when the toggle mechanism links are completely extended in a straight line (the tie bar is extended), the mold plate temperature rises during use and other reasons. When the dimension between the movable plate and the movable plate becomes large (when the tie bar is further stretched),
There is a problem that a mold clamping force larger than a set value is applied to the mold, which may damage the mold clamping device and the mold. The present invention aims to solve such problems.

[0004]

The present invention solves the above problems by measuring the elongation of a tie bar of a mold clamping device and preventing the tie bar from being expanded beyond a preset amount of expansion. That is, the toggle type mold clamping device of the present invention is configured such that the hydraulic pressure source (14) sequentially passes through the main pipe (21), the flow rate adjusting valve (16), the main switching valve (18), and the first pipe (23) to perform mold clamping. Cylinder (10) mold clamping side oil chamber (10
By supplying hydraulic pressure to b), the mold clamping cylinder (1
0) of the piston rod (10a) via a toggle mechanism (12) connected to the tie bar (36) to apply a tension force to perform the mold clamping, the first pipe (2)
3) and a pilot check valve (20) having a pilot port (20a) and a first pipe (2)
3) and a pilot pipe (33) connecting the pilot port (20a) of the pilot check valve (20),
A pilot switching valve (22) which is provided in the pilot pipe (33) and is capable of switching the first pipe (23) and the pilot port (20a) of the pilot check valve (20) into either communication or cutoff; Tie bar (3
6) Tie bar elongation detection sensor (2
4) and a controller (26), the pilot check valve (20) has a pilot port (20).
When hydraulic pressure is not supplied to the a) from the first pipe (23), the mold clamping cylinder (10) is fed from the main switching valve (18) side.
Although the flow to the side is permitted, when the hydraulic pressure is supplied to the pilot port (20a) from the first pipe (23), the flow from the main switching valve (18) side to the mold clamping cylinder (10) side is allowed. The controller (26) stores the predetermined set amount of expansion of the tie bar (36) and allows the tie bar expansion detection sensor (24) to be arranged.
The signal of the measured elongation from is input to the controller (2
In 6), the pilot switching valve (22) is positioned at the shut-off position while the measured elongation is smaller than the set elongation, but when the measured elongation becomes equal to the restricted elongation,
A feature is that a command signal is output so as to position the pilot switching valve (22) at the communication position. A position detector (42) capable of measuring the position of a movable part such as the piston rod (10a) of the mold clamping cylinder (10) is provided, and the controller (26) has a mold clamping cylinder (10) in advance. ) The predetermined stroke position of is stored,
The signal of the measurement position from the position detector (42) is transmitted to the controller (2
6), the controller (26) compares the measured position with the set position, and when both positions match, the pilot switching valve (2) is operated for a preset time.
It is preferable to output a command signal for switching 2) to the cutoff position. The reference numerals in parentheses indicate the corresponding members of the embodiment.

[0005]

[Operation] During the mold clamping process, the tie bar elongation detector measures the elongation of the tie bar and outputs a signal (measured elongation) corresponding to the elongation to the controller. Amount is compared with the set stretch amount, no signal is output while the measured stretch amount is smaller than the set stretch amount, but if the measured stretch amount becomes equal to the set stretch amount, the main switching valve is turned off. The control signal is output to switch to the (neutral position), and the control signal is output to switch the pilot switching valve to the position where the mold clamping side oil chamber communicates with the pilot port of the pilot check valve. As a result, the supply of oil from the hydraulic pressure source side to the mold clamping cylinder was stopped, and the oil that tried to flow from the mold clamping side oil chamber of the mold clamping cylinder to the main switching valve side through the pilot check valve was also blocked. It becomes a state. Therefore, even if the mold or the like expands in the mold opening / closing axis direction due to a temperature rise, it is possible to prevent the toggle type mold clamping device from being overloaded with a predetermined load or more.

[0006]

【Example】

(First Embodiment) FIG. 1 shows a first embodiment of the present invention. A mold clamping housing 34 is arranged at a position facing the fixed platen 32. The movable platen 30 is arranged between the fixed platen 32 and the mold clamping housing 34. The mold clamping housing 34 and the movable platen 30 are connected by the toggle mechanism 12.
That is, one end of each of the plurality of links of the toggle mechanism 12 is connected to the mold clamping housing 34,
The other end side is connected to the movable platen 30, respectively. The fixed plate 32 and the mold clamping housing 34 include four tie bars 3
6 (however, only two are visible in the figure). The tie bars 36 penetrate the movable plate 30, respectively. That is, the movable plate 30 has the tie bar 36.
Is guided by the axial movement. A movable mold 38 is fixed to the movable plate 30, and a fixed mold 40 is fixed to the fixed plate 32. Mold clamping housing 3
A mold clamping cylinder 10 is attached to 4. The piston rod 10 a of the mold clamping cylinder 10 penetrates the center of the mold clamping housing 34 and is connected to the crosshead portion 12 a of the toggle mechanism 12. In the fixed portion facing the protruding end of the tie bar 36 on the mold clamping housing 34 side,
A tie bar elongation detector 24 is provided. The tie bar extension detection device 24 can detect the amount of extension of the tie bar 36 from the reference position. A controller 26 is provided for inputting a measurement position signal from the tie bar extension detection device 24. The controller 26 can control the switching positions of the switching valves 18 and 22 described later. A hydraulic pressure source 14 for supplying hydraulic pressure to the mold clamping cylinder 10 is provided. In the main pipe 21 of the hydraulic power source 14, the flow rate adjusting valve 1 is sequentially arranged toward the downstream side.
6 and the main switching valve 18 are connected. A branch pipe 25 is provided in the main pipe 21 at a position upstream of the position where the flow rate adjusting valve 16 is provided, and a relief valve 28 is provided therein. The return side of the relief valve 28 communicates with the tank 29. The relief valve 28 can set the upper limit pressure of the hydraulic pressure source 14. The main switching valve 18 is a three-position switching valve, and one port (the port on the upper left side in the figure) of the main switching valve 18 is connected via the first pipe 23 to the mold clamping cylinder 10.
Is connected to the mold clamping side oil chamber 10b. The first pipe 23 is provided with a pilot check valve 20 having a pilot port 20a. One end of a pilot pipe 33 is connected to the pilot port 20a of the pilot check valve 20. The other end of the pilot pipe 33 has a first
It is connected to the pipe 23. The pilot switching valve 22 is provided in the pilot pipe 33. That is, in the pilot check valve 20, when the pilot switching valve 22 is located at the symbol position (solenoid excitation position) opposite to the symbol position shown in the drawing, the pilot check valve 20 has its pilot port 20a at the mold clamping side oil chamber of the mold clamping cylinder 10. Although the hydraulic pressure from 10b is introduced to block the flow from the mold clamping cylinder 10 side to the main switching valve 18 side, when the pilot switching valve 22 is positioned at the symbol position (solenoid de-energized position) shown, this The pilot port 20a communicates with the tank 29 and allows a flow from a high pressure side to a low pressure side (normally, a flow from the main switching valve 18 side to the mold clamping cylinder 10 side). As a result, it is possible to limit the toggle mechanism 12 from stretching the tie bar 36 beyond the set value (to prevent overload). Main switching valve 18
The other port (the port on the upper right side in the figure) of the second pipe 2
It is connected to the mold opening side oil chamber 10 c of the mold clamping cylinder 10 via 7.

Next, the operation of the first embodiment will be described.
First, as a preparatory work, the set expansion amount of the tie bar 36 is input to the controller 26 as setting data. Further, the valve opening of the flow rate adjusting valve 16 is adjusted, and the relief valve 28 is set to a predetermined set relief pressure. This completes the preparation for injection compression molding.

Next, with the pilot switching valve 22 in the non-excited position (symbol position shown in FIG. 1), the main switching valve 1
8 is switched to the symbol position on the right side in the figure, and the oil whose flow rate is adjusted by the flow rate adjusting valve 16 from the hydraulic source 14 is supplied to the main pipe 2
1, the main switching valve 18, the first pipe 23, and the pilot check valve 20, and the mold clamping side oil chamber 10 of the mold clamping cylinder 10.
Then, the piston rod 10a and the crosshead 12a integral with the piston rod 10a are moved forward. That is, the mold closing operation is started. During mold closing, molten resin is injected into the mold cavity from a not-shown injection device at a predetermined timing,
The compression process is started. The expansion amount of the tie bar 36 is detected by the tie bar expansion detection device 24, and is input to the controller 26 as the measured expansion amount. The controller 26 is
The measured amount of elongation is compared with the set amount of elongation. While the two amounts of elongation do not match, no signal is output to the pilot switching valve 22 and the mold is clamped according to the normal molding process to perform compression molding. The product is molded. During the molding operation, the temperature of the molds 38, 40 rises for some reason and the molds 38, 40
When the dimension of the die opening / closing axis direction such as 40 becomes large, the toggle mechanism 12 is extended as set and the crosshead 12a is extended.
If is moved to a predetermined position, an excessive mold clamping force will be applied to the molds 38 and 40 (the tie bar 36 will be stretched beyond the limit elongation amount).
In the present invention, the expansion amount of the tie bar 36 is detected by the tie bar expansion detection device 24, and when the measured expansion amount matches the set expansion amount, a command signal is output from the controller 26 and the main switching valve 18 is illustrated. And the pilot switching valve 22 is switched to the excitation position. As a result, the hydraulic pressure is not supplied from the hydraulic pressure source 14 to the mold clamping cylinder 10, and the pressure in the mold clamping side oil chamber 10b of the mold clamping cylinder 10 is supplied to the pilot port 20a of the pilot check valve 20. As a result, the flow from the mold clamping side oil chamber 10b of the mold clamping cylinder 10 to the main switching valve 18 side is blocked. That is, the toggle mechanism 1
The state in which the tie bar 36 does not stretch the tie bar 36 beyond the limit elongation amount is maintained, and a predetermined compression force can be applied to the molds 38 and 40. Since the amount of dimensional change due to the temperature change of the mold during one shot is small, the influence of such expansion during one shot is ignored in the present invention.

(Second Embodiment) FIG. 2 shows a main part of a second embodiment of the present invention. The difference of the second embodiment from the first embodiment is that the mold clamping housing 34 is provided with a position detector 42 capable of measuring the moving position of the piston rod 10a of the mold clamping cylinder 10. The measurement position signal from the position detector 42 is input to the controller 26. The controller 26 includes a piston rod 10a of the mold clamping cylinder 10.
A plurality of stroke positions (setting positions) determined in advance are stored. The controller 26 compares the measured position with the set position, and when both positions match, switches the pilot switching valve 22 to the communicating position for a predetermined time. The other structure is the same as that of the first embodiment.

According to the operation of the second embodiment, the controller 26 receives the signal from the position detector 42, and the mold clamping cylinder 10 is operated.
The main switching valve 18 is switched to the neutral position and the pilot switching valve 22 is switched to the communicating position when it is judged that the piston rod 10a is located at the predetermined setting position. That is, the oil pressure in the mold clamping side oil chamber 10b of the mold clamping cylinder 10 is introduced into the pilot port 20a of the pilot check valve 20 and blocks the flow from the mold clamping cylinder 10 side to the main switching valve 18 side. As a result, the movable mold 38 stops at the predetermined position. After a lapse of a predetermined time, the main switching valve 18 is switched to the symbol position on the right side in the figure, the pilot switching valve 22 is switched to the shut-off position to move the movable mold 38, and the same movable operation is performed at each set stroke position. The side mold 38 is stopped and moved. As a result, a multistage compression molding operation is performed. Other operations are similar to those of the first embodiment.

In the description of each of the above embodiments, the internal leakage of the main switching valve 18 is treated as a problem when the main switching valve 18 is in the neutral position. If the leak is a problem,
A hydraulic circuit having the same pilot check valve and pilot switching valve as the first pipe 23 side can be added to the second pipe 27. Further, in the above description of the second embodiment, the position detector 42 detects the moving position of the piston rod 10a of the mold clamping cylinder 10, but another movable portion such as the crosshead 12a of the toggle mechanism 12 is used. It is also possible to detect the moving position of the. Further, although the present invention is applied to injection compression molding in the description of each of the above-described embodiments, the present invention can be applied to moldings other than injection compression molding.

[0012]

As described above, according to the present invention, the toggle type mold clamping device can prevent the mold clamping force of a magnitude larger than desired from acting on the mold, so that the mold is damaged. It is possible to prevent such troubles from occurring. Even in injection compression molding, it is not necessary to precisely control the flow rate supplied to the mold clamping cylinder.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 is a partial view showing a second embodiment of the present invention.

[Explanation of reference numerals] 10 mold clamping cylinder 10a piston rod 10b mold clamping side oil chamber 10c mold opening side oil chamber 12 toggle mechanism 12a crosshead 14 hydraulic power source 16 flow rate adjusting valve 18 main switching valve 20 pilot check valve 20a pilot port 21 main pipe Line 22 Pilot switching valve 23 First pipe 24 Tie bar expansion detector 25 Branch pipe 26 Controller 27 Second pipe 28 Relief valve 29 Tank 30 Movable plate 32 Fixed plate 34 Mold clamping housing 36 Tie bar 38 Movable side mold 40 Fixed side mold Type

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location B29C 45/82 7365-4F

Claims (2)

[Claims] 1. A mold of a mold clamping cylinder (10) which sequentially passes from a hydraulic pressure source (14) to a main pipe (21), a flow rate adjusting valve (16), a main switching valve (18), and a first pipe (23). By supplying hydraulic pressure to the clamping side oil chamber (10b), a tension force is applied to the tie bar (36) via the toggle mechanism (12) connected to the piston rod (10a) of the mold clamping cylinder (10). In a toggle type mold clamping device for performing mold clamping, a pilot check valve (20) provided in a first pipe (23) and having a pilot port (20a), a first pipe (23) and a pilot check valve (20). Pilot pipe (33) for connecting the pilot port (20a) of the pilot check valve (20a) to the pilot pipe (33), which is provided in the pilot pipe (33). ) Is connected or shut off, a pilot switching valve (22), a tie bar extension detection sensor (24) capable of detecting the amount of extension of the tie bar (36), and a controller (26). When the pilot check valve (20) is not supplied with the hydraulic pressure from the first pipe (23) to the pilot port (20a) of the pilot check valve (20), the pilot check valve (20) is connected to the mold clamping cylinder (10) from the main switching valve (18) side. ) Side, but the pilot port (2
0a) is supplied with hydraulic pressure from the first pipe (23), the mold clamping cylinder (10) is fed from the main switching valve (18) side.
It is arranged so that the flow to the side is not allowed. The controller (26) has a tie bar (3
The set elongation amount of 6) is stored, and the signal of the measured elongation amount from the tie bar elongation detection sensor (24) is input, and the controller (26) has the measured elongation amount smaller than the set elongation amount. During this period, the pilot switching valve (22) is located at the shutoff position. However, when the measured expansion amount becomes equal to the limit expansion amount, the command signal to position the pilot switching valve (22) at the communication position. The toggle type mold clamping device is characterized by outputting 2. A position detector (42) capable of measuring the position of a movable part such as a piston rod (10a) of a mold clamping cylinder (10) is provided, and the controller (26) is equipped with a mold clamping device in advance. Cylinder (10)
The predetermined stroke position of the controller is stored, and the signal of the measured position from the position detector (42) is stored in the controller (2
6), the controller (26) compares the measured position with the set position,
The toggle type mold clamping device according to claim 1, wherein when the two positions match, a command signal for switching the pilot switching valve (22) to the shut-off position is output for a preset time.