JPH0138651B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a vertical clamping device for a molding machine.

(B) Conventional technology A conventional vertical mold clamping device of a general molding machine has a fixed platen, a movable platen that is movable up and down relative to the fixed platen, and a mold opening/closing device that moves the movable platen up and down. It has a cylinder and a mold clamping cylinder that applies mold clamping force between the movable platen and the fixed platen. The movable molds attached to the movable platen are moved toward or away from each other with the mold opening/closing cylinder relative to the fixed mold attached to the fixed platen, and the molds are opened and closed. Immediately before closing, a mold clamping force is applied by a mold clamping cylinder.

(C) Problems to be Solved by the Invention However, the vertical mold clamping device of such a conventional molding machine has the problem of requiring a large mold opening/closing cylinder and the problem of generating shock during operation. , and that it is difficult to control the delicate mold clamping force.

In other words, in a vertical mold clamping device, the weight of all movable parts such as the movable platen and the movable mold attached to it must be raised and lowered, so a horizontal mold clamping device is hardly affected by gravity. Compared to this, a much larger mold opening/closing force is required. For this reason, the mold opening/closing cylinder becomes large, and the hydraulic device that supplies hydraulic pressure to it also becomes large, resulting in an increase in the price of the device and increased energy consumption. For example, if the mold opening/closing cylinder is directly driven by a hydraulic pump, the capacity of the hydraulic pump and the electric motor that drives it must be increased, and if an accumulator is used, it must be operated with a small rate of pressure fluctuation. In order to
An accumulator that can accommodate about 10 times the volume of gas is required. Furthermore, when the molding cycle is short, it is necessary to increase the capacity or number of hydraulic pumps for accumulating pressure in the accumulator. Furthermore, when a hydraulic pump and an accumulator are used together, the hydraulic system becomes larger and the price increases for the same reason as above.

As heavy objects such as the movable platen and the movable molds attached to it move vertically at high speed, large shocks are applied to the equipment, which can easily cause loosening of attached parts and oil leakage from piping, which requires maintenance and inspection. As the work increases, the operating rate tends to decrease as well.

In addition, when using a vertical mold clamping device as an injection compression molding device, it is necessary to control the clamping speed and mold clamping force step by step just before the mold closes, but in the case of a vertical mold clamping device, Because the weight of movable parts such as movable platens and movable molds directly acts as mold clamping force,
It is difficult to control the delicate mold clamping force.

The present invention aims to solve the above problems.

(d) Means for Solving the Problems The present invention solves the above problems by providing a balance cylinder and an accumulator with predetermined characteristics capable of supporting the weight of a movable part. That is, in the present invention, the fixed platen 10 and the movable platen 12 are arranged vertically, the movable platen is moved in the vertical direction by the mold opening/closing cylinder 18, and the mold 1 is moved by the mold clamping cylinder.
This is a vertical mold clamping device for a molding machine that applies mold clamping force to the molds 4 and 16, and includes a balance cylinder 20 provided between a fixed platen and a movable platen, an oil chamber 24a partitioned by a piston, and It has an accumulator 24 having a gas chamber 24b, and an oil passage 22 that connects the oil chamber 20a of the balance cylinder and the oil chamber 24a of the accumulator, and the volume of the gas chamber of the accumulator changes depending on the stroke of the piston of the balance cylinder. This is based on the assumption that the pressure receiving area of the balance cylinder piston, the pressure receiving area of the accumulator piston, and the gas pressure of the gas chamber will change significantly (approximately twice) at the lower limit of the mold opening/closing stroke of the movable platen. The balance cylinder is characterized in that the weight of the entire movable part that moves together with the movable platen is supported by the balance cylinder. Note that the reference numerals in parentheses indicate corresponding members in the embodiments described later.

(e) Action The stroke of the piston of the accumulator causes a large change in the volume of the gas chamber. A balance cylinder installed separately from the mold opening/closing cylinder operates at the lower limit of the mold opening/closing stroke (near the mold closing position).
In this case, almost all of the weight of the moving parts is supported, and at the upper limit of the mold opening/closing stroke, for example, 1/2 of the weight of the moving parts is supported.
The capacity of the accumulator is set to support. Therefore, the proportion of the weight of the movable part that is shared by the balance cylinder changes depending on the stroke position of the mold opening/closing cylinder. The required load of the mold opening/closing cylinder is reduced by the load shared by this balance cylinder. At the lower limit of the mold opening/closing stroke, almost all of the weight of the movable part is supported by the balance cylinder, so the shared load of the mold opening/closing cylinder becomes almost zero. Further, near the upper limit of the mold opening/closing stroke, about half of the weight of the movable part is supported by the balance cylinder, and the rest is shared by the mold opening/closing cylinder. Therefore, the mold opening/closing cylinder can be downsized, and the amount of melt of the hydraulic pump and electric motor that drive it can also be reduced. Furthermore, since the weight of the movable part is supported by the balance cylinder, the shock generated even if the movable part moves at high speed is extremely small. Furthermore, at the lower limit of the mold opening/closing stroke, almost all of the weight of the movable part is supported by the balance cylinder, so when performing injection compression molding, for example,
It is possible to accurately control the molding force, making it possible to precisely control the mold clamping force.

(f) Example FIG. 1 shows an example of the present invention. A movable platen 12 movable in the vertical direction is arranged to face a fixed platen 10 arranged vertically.
A fixed die 14 is attached to the fixed platen 10, and a movable die 16 is attached to the movable platen 12. The movable platen 12 is moved up and down by a pair of mold opening/closing cylinders 18, that is, the movable mold 16 is moved up and down by the fixed mold 1.
It can be moved closer or further away from 4. Furthermore, a pair of balance cylinders 20 are provided between the movable platen 12 and the fixed platen 10. Oil chamber 2 of balance cylinder 20
0a is connected to an oil chamber 24a of an accumulator 24 by an oil passage 22. Gas chamber 24b of the accumulator 24 at the upper limit of the mold opening/closing stroke
The volume of the gas chamber is twice the volume of the oil chamber 20a of the two balance cylinders 20, which changes during the stroke between the upper limit of the mold opening/closing stroke and the lower limit of the mold opening/closing stroke. 24
The gas pressure sealed in b is set to a value that can support 1/2 of the weight of the entire movable part including the movable platen 12 and the movable mold 16 at the upper limit of the mold opening/closing stroke of the movable platen 12. The oil pressure discharged by the pump 26 is transferred to the oil chambers 18a and 18b of the mold opening/closing cylinder 18 via the switching valve 28 to the oil passage 3, respectively.
0 and oil passage 32. A relief valve 34 is provided in the oil passage 30. Note that this vertical mold clamping device has a mold clamping cylinder that applies a mold clamping force between the fixed platen 10 and the movable platen 12, but this is not shown.

Next, the operation of this embodiment will be explained. 1st
The figure shows the vertical mold clamping device in the mold opening state.
That is, the hydraulic pressure from the pump 26 is supplied to the oil chamber 18a of the mold opening/closing cylinder 18 through the oil passage 30, and the movable platen 12 is at the upper limit of the mold opening/closing stroke. In this state, the gas pressure in the gas chamber 24b of the accumulator 24 is
The pressure is such that it supports 1/2 of the weight of the entire moving part such as 6. From this state, the switching valve 28 is switched, and the oil chamber 1 of the mold opening/closing cylinder 18 is opened from the oil passage 32 side.
8b to start the mold closing stroke, the oil chamber 24a of the accumulator 24 passes through the oil passage 22 in the oil chamber 20a of the balance cylinder 20.
gradually returned to the inside. Therefore, the gas volume in the gas chamber 24b of the accumulator 24 gradually decreases, the gas is compressed, and its pressure gradually increases. When the movable platen 12 moves to the lower limit of the mold opening stroke (mold closing position), the gas volume in the gas chamber 24b of the accumulator 24 becomes 1/2 of the initial state.
The pressure will double. The entire weight of the movable part is supported by the hydraulic pressure corresponding to this gas pressure. Next, a predetermined mold clamping force is applied between the fixed mold 14 and the movable mold 16 by operating a mold clamping cylinder (not shown). Injection molding is performed in this state. After injection molding is completed, the mold clamping force of the mold clamping cylinder is removed, and the switching valve 28 is switched to switch the direction of hydraulic pressure supply to the mold opening/closing cylinder 18.
The movable platen 12 is raised. As the movable platen 12 rises, the hydraulic oil in the oil chamber 24a of the accumulator 24 passes through the oil passage 22 to the oil chamber 2 of the balance cylinder 20.
gas chamber 2 of the accumulator 24.
The gas pressure in 4b gradually decreases. Eventually, the state returns to the state shown in FIG. 1, and the balance cylinder 20 is in a state where it supports 1/2 of the total weight of the movable parts. The remaining weight of the movable part is shared by the mold opening/closing cylinder 18.

As mentioned above, the mold opening/closing cylinder 18 only needs to support 1/2 of the total weight of the movable parts such as the movable platen 12 and the movable mold 16 even under the heaviest load, and the capacity of the mold opening/closing cylinder 18 can be reduced compared to the conventional one. It can be about half. As a result, the hydraulic pump that drives this can also be downsized, and the power required for mold opening/closing operations can be significantly reduced. In the case of a direct drive method using a hydraulic pump, when comparing the method according to the present invention and the conventional method (one without a balance cylinder), as shown by the broken line in FIG. While constant power is required until the mold is opened,
In the case of this embodiment, as shown by the solid line, the required power is 0 at the start of mold opening, and the required power at the end of mold opening is also 1/2 that of the conventional one. Therefore, the required power in the case of this embodiment is 1/2 that of the conventional one even at the maximum,
On average, it will be reduced to 1/4, resulting in significant savings in operating costs. In addition, the capacity of the electric motor is approximately 1/2 that of conventional models.
It turns out that it can be done.

Furthermore, when comparing the case of a conventional method in which a pump and an accumulator are used together to drive a mold opening/closing cylinder, as shown in Fig. 3, the maximum required power in the case of this embodiment is almost the same as that of the conventional method. However, the average required power is approximately 1/4. As a result, it can be seen that in the case of this embodiment, the required number or capacity of the accumulator and hydraulic pump can be reduced.

Even though the movable parts with large weight move when the mold is opened and closed, they are balanced by the balance cylinder 20, so the shock generated is extremely small. This eliminates oil leaks due to loose fittings and loose piping, and reduces the labor required for maintenance and inspection.

In addition, as mentioned above, at the lower limit of the mold opening/closing stroke, the entire weight of the movable part is supported by the balance cylinder 20, so the mold clamping force can be accurately controlled without being affected by the weight of the movable part. can do. Therefore, in the case of compression molding, for example, it is possible to finely control the molding pressure.

(G) Effects of the Invention As explained above, according to the present invention, a balance cylinder and an accumulator are provided, and the force obtained by the balance cylinder at the lower limit of the mold opening/closing stroke of the movable platen is applied to the movable platen, the movable mold Since the weight of the movable parts is balanced, the mold opening/closing cylinder can be downsized, and the hydraulic device and electric motor that drive it can also be downsized, reducing equipment costs and operating costs. Furthermore, since the shock caused by the movement of the movable parts is reduced, parts and piping do not come loose even when the mold is operated at the desired opening/closing speed. In addition, it becomes possible to accurately and delicately control mold clamping force when performing compression molding. Further, the accumulator may be a small one whose gas chamber volume changes greatly, and a large air tank or the like is not required.

[Brief explanation of drawings]

Fig. 1 is a diagram showing a vertical mold clamping device of a molding machine according to the present invention, Fig. 2 is a diagram showing the effect of the present invention in the case of direct pump drive, and Fig. 3 is a diagram showing the present invention in the case of combined use of a pump and an accumulator. FIG. 10... Fixed plate, 12... Movable plate, 14... Fixed mold, 16... Movable mold, 18... Mold opening/closing cylinder, 20... Balance cylinder, 22... Oil path, 24... Accumulator, 26...Pump,
28...Switching valve, 30...Oil passage, 32...Oil passage,
34...Relief valve.

Claims (1)

[Claims] 1. A fixed platen 10 and a movable platen 12 are arranged vertically, the movable platen is moved vertically by a mold opening/closing cylinder 18, and the mold 14 is moved by a mold clamping cylinder.
It is a vertical mold clamping device for a molding machine that applies mold clamping force to a molding machine 16, and includes a balance cylinder 20 provided between a fixed platen and a movable platen, and an oil chamber 24a and a gas chamber partitioned by a piston. 24b, and an oil passage 22 that connects the oil chamber 20a of the balance cylinder and the oil chamber 24a of the accumulator, and the volume of the gas chamber of the accumulator changes greatly according to the stroke of the piston of the balance cylinder. The relationship between the pressure-receiving area of the balance cylinder piston, the pressure-receiving area of the accumulator piston, and the gas pressure in the gas chamber is such that at the lower limit of the mold opening/closing stroke of the movable platen, the weight of the entire movable part that moves with the movable platen is A vertical mold clamping device for a molding machine, characterized in that it is set in a relationship such that it is supported by a balance cylinder.