JPH0645140B2 - Pre-fill valve for mold clamping device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a prefill valve for a mold clamping device such as a synthetic resin molding machine.

[Prior Art] In a conventional mold clamping device capable of opening and closing a mold at high speed, as shown in FIG. 6 as an example, a flow passage 3 of an oil tank is connected to a rear oil chamber 2 of a mold clamping cylinder 1. A prefill valve 4 for opening and closing the flow passage 3 on the rear oil chamber side is provided.

The prefill valve 4 includes a hydraulic cylinder 5 provided on the flow path side, a valve body 7 attached to the tip of a piston 6,
Pressure oil is supplied to the rapid-feed cylinder 10 from the rapid-feed ram 11 which is composed of the valve seat 8 provided at the opening of the rear oil chamber 2 and is inserted into the rapid-feed cylinder 10 in the mold-clamping ram 9 from the rear end of the mold-clamping cylinder. When the mold clamping ram 9 moves forward at high speed in the mold clamping direction, or when pressure oil is supplied to the front oil chamber 12 and the mold clamping ram 9 moves backward at high speed in the mold opening direction. Valve to supply or discharge pressure oil.

In the cylinder of the prefill valve 4, as shown in FIG. 7, the rear end of the piston 6 is in contact with the ram 14 which is elastically pressed backward by the coil spring 13, and the ram 14 is hydraulically moved to the ram 14. Is opened and the piston 6 is moved forward to open the valve.

[Problems to be Solved by the Invention] In such a conventional prefill valve 4, the degree of opening and closing of the valve body 7 is constant, and only full opening and full closing can be performed.

Therefore, the valve body 7 is fully opened regardless of the mold opening / closing speed, and the pressure oil passes through the prefill valve 4 without resistance. Therefore, the speed change of the mold clamping ram 9 is caused by the rapid feed cylinder 1
Either 0 or the amount of pressure oil supplied to the front oil chamber 12 is changed.

However, in such a speed change, due to the action of the inertial force due to the weight of the movable plate, the mold, etc., the switching from the high speed to the low speed is poor and there is a problem in efficiency.

Another problem is that it takes time for the valve body 7 to be completely closed until it is completely closed, and it takes time to pressurize the rear oil chamber after completion of mold closing.

Furthermore, when a die opening spring is used in the die, the die may suddenly open due to the elastic force of the spring during the initial die opening. This is because the prefill valve 4 is fully opened after the pressure is released, and the hydraulic resistance on the rear oil chamber side is removed.

The present invention has been conceived in order to solve the problems of the above-described conventional prefill valve, and an object thereof is to newly open a prefill valve in multiple stages by a simple hydraulic means. Another object of the present invention is to provide a prefill valve for a mold clamping device.

[Means for Solving the Problem] The feature of the present invention according to the above-mentioned object is to provide a valve body for opening and closing a flow path of an oil tank connected to a rear oil chamber of a mold clamping cylinder on the rear oil chamber side, and a tip of a main piston. The hydraulic cylinder of the main piston is provided with a hydraulic cylinder having a short-stroke auxiliary piston that presses the main piston.

[Operation] In the above-described configuration, the valve body is fully opened by the operation of the main piston, and the pressure oil is quickly introduced into or discharged from the rear oil chamber. Further, the main piston is pressed by the operation of the sub piston, the valve body is opened apart from the valve seat by the stroke of the sub piston, and the inflow or outflow of the pressure oil in the rear oil chamber is restricted.

[Embodiment] FIGS. 1 to 4 show a prefill valve according to the present invention.
In the embodiment, 20 is an opening of a rear oil chamber, 21 is a seat of a prefill valve 22 provided in the opening 20, and a pressure oil flow hole 23 is formed in the seat 21. A valve seat 24 is provided inside the so as to face the opening 20.

An oil tank flow path 25 is connected to the outside of the seat body 21, and the prefill valve 22 is provided at the center of the flow path 25.
The hydraulic cylinder 26 is fixedly installed on the seat 21.

Inside the hydraulic cylinder 26, the valve seat 2
A main piston 28 having a valve main body 27 which contacts and separates from the No. 4 at the tip is housed by actuating a coil spring 29 for closing the valve.

A hydraulic cylinder 31 accommodating a short-stroke auxiliary piston 30 is connected to the end of the hydraulic cylinder 26.
The sub piston 30 penetrates through the partition wall and the main piston 2
It is in contact with the head of No. 8.

The valve body 27 is constantly operated by the elastic force of the coil spring 29 via the main piston 28.
As shown in FIG. 1, the valve closed state is maintained (at the time of pressurization).

When the hydraulic oil is pressed into the cylinder from the passage 32 on the side of the cylinder, the main piston 28 moves to the coil spring 29.
Is compressed and moved forward, and as shown in FIG. 2, the valve body 27 is fully opened (when the high speed mold is opened and closed).

Further, in the valve closed state or the fully opened state, when hydraulic oil is press-fitted into the hydraulic cylinder 31 from the side passage 33 into the cylinder, and the auxiliary piston 30 is pushed out or pushed out,
In the valve closed state, the main piston 28 is pushed out by the short stroke, and in the fully opened state, the return of the main piston 28 is blocked, and the valve body 27 separates from the valve seat 24, so that the stroke is reduced. With the same size, as shown in FIG. 3, a slight opening 34 occurs (when the low speed mold is opened and when the initial mold is opened).

The hydraulic operation of the two hydraulic cylinders 26 and 31 is the fourth.
This is performed by operating two switching valves A and B in the hydraulic circuit shown in the figure.

The oil chamber on the opposite side of each hydraulic cylinder 26, 31 is in communication with the flow path 25 by a passage shown by a dotted line.

FIG. 5 shows the mold clamping process in the mold clamping device, and the valve switching based on the process is as follows.

EFFECTS OF THE INVENTION As described above, according to the present invention, a hydraulic cylinder of a main piston provided with a valve body at its tip is provided with a hydraulic cylinder provided with a sub-piston having a short stroke for pressing the main piston. Since the piston allows a slight opening of the valve, the following effects are achieved.

At the time of mold opening and closing, the valve body is in the fully open state, but at the same time as switching to a low speed, the auxiliary piston is operated to control the return of the main piston, and the full opening is switched to a slight open valve. Since resistance can be generated, outflow of pressure oil from the rear oil chamber is controlled and movement of the mold clamping ram due to inertial force is also controlled, resulting in slower movement of the mold clamping ram than in the case of full opening. .

Since it is possible to switch from full opening to a slight opening at the time of low speed switching, the valve closing operation at the time of high pressure mold clamping thereafter is quick and the boosting time of the rear oil chamber is shortened.

Even if the hydraulic pressure in the rear oil chamber is released, the valve body will not be fully opened and resistance will be created.Even if the elastic force of the mold spring acts on the mold clamping ram, the mold clamping ram will retract and Initial mold opening can be performed slowly without the mold opening suddenly.

[Brief description of drawings]

1 to 4 show one embodiment of the prefill valve of the mold clamping device according to the present invention. FIG. 1 is a vertical sectional view when the valve is closed, and FIG. 2 is a vertical sectional view when the valve is fully opened. 3 and 4 are longitudinal sectional views when the valve is slightly opened, FIG. 4 is an explanatory view showing the relationship with the switching valve, FIG. 5 is a mold clamping stroke diagram, and FIG. 6 is a conventional prefill valve. A schematic longitudinal sectional view of the mold clamping cylinder provided,
FIG. 7 is a vertical sectional view of a conventional prefill valve. 20 ... Opening of rear oil chamber 21 ... Seat 22 ... Prefill valve 23 ... Flow hole 24 ... Valve seat 25 ... Flow passage 26 ... Hydraulic cylinder 27 ... Valve body 28 ... Main piston 29 ... Coil spring 30 ... Sub piston 31 ... Hydraulic cylinder 34 ... Slight opening

Claims (1)

[Claims] 1. A valve body for opening and closing a flow path of an oil tank connected to a rear oil chamber of a mold clamping cylinder is provided at a tip of a main piston, and the main piston is connected to a hydraulic cylinder of the main piston. A prefill valve for a mold clamping device, comprising a series of hydraulic cylinders provided with a sub-piston having a short stroke for pressing a piston.