JPH01182019A - Straight-hydraulic type clamping device - Google Patents

Abstract

PURPOSE:To lessen mechanical shock and prevent the generation of shock noise by providing a control means to keep a prefill valve constantly in the closed state at the time of pressure lowering and also providing a clamping circuit to gradually release the hydraulic pressure in a clamping cylinder. CONSTITUTION:A prefill valve 5a is retained and controlled in the 'closed' state only during the time required for the process of splitting a molding die or the time required for backward stroke of a clamping ram 4 to keep said process. Said action is carried out by an electromagnetic valve 8 successively to the pressure lowering process of clamping pressure. In said releasting process, the clamping ram 4 is going to move backward quickly just after releasing. At that time, the prefill valve 5a is in the 'closed' state, and pressure C in the pressurized space inside a clamping cylinder 3 rises quickly to control the quick movement of the ram 4. On the other hand, the pressure oil in the pressurized space C passes, for example, a throughhole 15 of the prefill valve 5a, and flows out from the throughhole of an auxiliary ram 14 into a tank 6 through a small opening D1 opened in the diameter direction of the auxiliary ram 4. Thus, the quick backward movement of the clamping ram 4 is relaxed.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a direct pressure type mold clamping device having a prefill valve in an injection molding machine, and in particular to a direct pressure type mold clamping device having a prefill valve for an injection molding machine. This relates to a pressure type mold clamping device.

(Prior Art) FIG. 5 shows an example of a conventional direct pressure type mold clamping device having a prefill valve. Melted and plasticized by injection/plasticization equipment (not shown)
Pressurized resin is injected into a mold 1, shaped into a molded product 2, and cooled.

The cooled molded product 2 is taken out by dividing the mold 1 into a core mold 1a and a cavity mold 1b as shown in FIG.

When cooling is completed, the molded product 2 is firmly stuck to the core mold 1a and the cavity mold 1b due to the contraction force of the resin, etc., and therefore the mold 1 changes from the state shown in FIG. 5 to the state shown in FIG. An extremely large amount of force is required to break it.

In the direct pressure type mold clamping device shown in Fig. 5, pressure oil is applied to the pressure receiving space A of the mold clamping ram 4 fitted in the mold clamping cylinder 3 in order to crack the mold 1, and the pressure is applied at a rate of about 1 to 2 cm/sec. Move the mold clamping ram 4 in the direction of arrow B at the same speed.

While this operation is being performed, the prefill valve 5 is in the "open" state, and the operation of the mold clamping ram 4 forces the working liquid in the pressure receiving space C back into the tank 6. Note that 7 indicates a movable platen.

The example shown in FIG. 7 shows a conventional prefill valve that is different from the mechanism described above, but its operation is exactly the same as the prefill valve described above.

Hereinafter, based on the example shown in FIG. 7, its operation will be explained in detail with reference to FIGS. 8 and 9.

When the mold clamping pressure is increased, the prefill valve 5a is in a "closed" state.

That is, when solenoid "A" of the solenoid valve 8 is excited, pressure oil is supplied from the hydraulic source 9 to the pressure receiving space F formed between the auxiliary ram 14 and the prefill valve 5a through the hole 11 made in the auxiliary ram 14. is supplied, and then the solenoid of the solenoid valve 10 “
When the opening is energized, the mold clamping cylinder 3 and prefill valve 5 are activated.
The pressure oil in the pressure receiving space E formed between the mold clamping cylinder 3 and the mold clamping cylinder 3 is released to the tank 13 through the hole 12 made in the mold clamping cylinder 3.
The prefill valve 5a moves to the right on the M plane and closes.

Next, the mold clamping pressure is reduced by de-energizing the solenoid "A" of the solenoid valve 8 and energizing the solenoid "C", and then the solenoid "port" of the solenoid valve 10 is de-energized to supply pressure oil to the mold clamping cylinder. 3 through the hole 12 made in the pressure receiving space E.
After the prefill valve 5a is moved to the left in the figure to the "open" state, pressure oil is supplied to the pressure receiving space A formed between the mold clamping cylinder 3 and the mold clamping ram 4, and the mold opening operation is performed. At this time, the hydraulic oil in the pressure receiving space C in the mold clamping cylinder 3 is easily pushed back into the tank 6 because the prefill valve 5a is open.

Here, in the case of the prefill valve shown in FIG. 7, the hole is formed in the auxiliary ram 14 when the prefill valve 5a advances to the "closed" state during the mold closing operation.

When the ram opens, a portion of the pressure oil from the hydraulic source 9 is transferred to the auxiliary ram 1.
4 through the through hole 15 of the prefill valve 5a to escape from the pressure receiving space C to the tank, thereby preventing shock when the forward speed of the prefill valve 5a decreases and the prefill valve 5a closes. There is. In the mold clamping device shown in Fig. 5, there are holes.

corresponds to Dl in FIG.

(Problem to be Solved by the Invention) A large force for breaking the mold 1 is normally required only when the gap between the core mold 1a and the cavity mold 1b reaches the range of several 11 to several centimeters. , is not necessary in the subsequent step of further opening the gap between the core mold 1a and the cavity mold lb.

Generally, there is a clear difference in the force required for the above two strokes, and at the point where the mold 1 is broken from the first stroke to the next stroke, the hydraulic pressure generated in the pressure receiving space of the mold clamping ram 4 is as shown in Figure 8. As shown in FIG.

The sudden change in force during mold release is due to the rapid expansion of the compressed liquid existing in the pressure receiving space A of the mold clamping ram 4.
causes a rapid retreat in direction B and an abrupt stop due to the low compressibility of the liquid. The core mold 1a is connected to the mold clamping ram 4 via the movable platen 7.
The total weight of these components cannot be ignored compared to the weight of the entire mold clamping device of an injection molding machine (20
~30%).

For this reason, the large change in force that occurs when the mold 1 is broken is sufficient to vibrate the entire device, which not only destroys the foundation that fixes the device, but also causes the instantaneous impact noise. Causes significant discomfort to the person operating the device.

The present invention was developed to suppress rapid speed fluctuations of the mold clamping ram due to large force fluctuations during mold release, and utilizes the mechanism originally possessed by direct pressure mold clamping devices. This is an attempt to solve the above problem by simply changing some of the movements.

(Means for Solving the Problems) Therefore, the present invention provides a direct pressure type mold clamping device equipped with a prefill valve, in which the pressure is reduced only for a predetermined time after the start of mold release or during a predetermined mold opening stroke necessary for mold release. control means for continuously keeping the prefill valve closed, and a throttle circuit for gradually releasing the hydraulic pressure in the mold clamping cylinder in order to alleviate the rapid retraction movement of the mold clamping ram that occurs immediately after mold release. This is intended to be a solution to the above problem.

(Function) Even after pressure reduction, the prefill valve is kept in the "closed" state only during the low-speed mold opening stroke section where cooling of the molded product is completed and the mold is divided into a core mold and a cavity mold. During this time, the increased pressure generated in the pressure-receiving space in the mold clamping cylinder gradually flows out into the tank through a throttle formed by a relatively small-diameter hole that communicates between the space and the tank.

This throttle creates a large resistance when the mold clamping ram moves at high speed, and suppresses rapid movement of the mold clamping ram.

(Example) Hereinafter, the present invention will be specifically explained based on illustrated embodiments.

The examples shown in FIG. 11'F and FIG. 3 utilize the conventional mold clamping device shown in FIG. 5 and FIG.
The prefill valve is controlled to be maintained in the "closed" state following the previous stroke, that is, the mold clamping pressure decreasing stroke, only during the time required for the stroke to divide the mold clamping pressure or during the backward stroke of the mold clamping ram to complete the same stroke.

In this mold release process, immediately after mold release, the mold clamping ram 4 tries to make a rapid retreat movement, but since the prefill valve is in the "closed" state, the pressure in the pressure receiving space C in the mold clamping cylinder 3 also rises rapidly. This suppresses the rapid movement of the ram 4.

On the other hand, the pressure oil in the pressure receiving space C is as follows in the case of FIG.
It gradually flows out into the tank 6 through the through hole of the auxiliary ram 14 through a small hole drilled in the radial direction of the auxiliary ram 14,
This will continue to suppress the backward movement of the mold clamping ram 4,
In addition, in the case of FIG. 3, the pressure oil passes through the through hole 15 of the prefill valve 5a, and the small hole D formed in the radial direction of the auxiliary ram 14.
It flows out from the through hole of the ram 14 into the tank 6 via the +, and as in the case of FIG. 1, the rapid backward movement of the mold clamping ram 4 is alleviated.

In the example shown in FIGS. 2 and 4, in the conventional mold clamping device shown in FIGS. Small-diameter holes Do and D+ are made in the mold clamping cylinder 3 to allow the water to flow directly into the tank 6 without any leakage.

Also in these embodiments, the prefill valve 5,
5a is maintained in a closed state, the pressure oil in the pressure receiving space C of the mold clamping cylinder 3 flows out through the small-diameter holes D;
While a is closed, rapid backward movement of the mold clamping ram 4 is inhibited.

Here, based on the embodiment shown in FIG. 3, the operations from mold closing to mold opening will be explained with reference to FIG. 10.

When the mold clamping pressure is increased, the prefill valve 5a is in a "closed" state.

That is, the solenoid "A" of the solenoid valve 8 is energized and pressure oil is supplied from the hydraulic source 9 (not shown) to the pressure receiving space F, and at the same time, the solenoid "A" of the solenoid valve 10 is energized and the pressure receiving space E is
Pressure oil is released to the tank 10, and the prefill valve 5a is closed.

Next, de-energize solenoid “A” and
If the solenoid "°" is kept energized during the mold opening low speed section G after the mold clamping pressure is lowered by energizing the solenoid "C", the prefill valve 5a continues to maintain the "closed" state. In this state, when pressure oil is sent to the pressure receiving space A and the mold 1 is broken and opened, the high pressure hydraulic oil in the pressure receiving space C passes through the through hole 15 of the prefill valve 5a and the small diameter hole D1 into the tank 6. However, the pressure loss generated when the hydraulic oil passes through the small diameter hole is added to the pressure receiving space C, which acts as a damper when the mold clamping ram 4 tries to move rapidly immediately after mold release. fulfill.

The small holes do not provide a large resistance when the mold clamping ram 4 moves at low speed, but are set so as to provide a large resistance when the mold clamping ram 4 moves at high speed.

After completing the mold opening low speed section G as described above, the solenoid valve 10
The solenoid "mouth" is de-energized, pressure oil is supplied to the pressure receiving space E through the hole 12, and the prefill valve 5a is kept in the "open" state to continue the mold opening operation.

At this time, since the oil pressure in the pressure receiving space A has returned to the normal low value, the mold clamping ram 14 is also retreated at the normal speed. In the other embodiments described above, the prefill valve maintains the "closed" state in the mold opening low speed section G, so that the same effect is achieved.

(Effects of the Invention) As described above in detail, according to the present invention, the temporary rapid backward movement of the mold clamping ram during mold release can be alleviated, and as a result, the following excellent effects can be achieved.

(1) The mechanical shock that was occurring in the entire device is greatly reduced, and there is no need to unnecessarily strengthen the foundation, etc.

(The impact noise generated at point 21-h is eliminated, improving the working environment for the workers.

[Brief explanation of the drawing]

1 to 4 are side sectional views showing different embodiments of the present invention when the mold is opened, FIG. 5 is a side sectional view showing an example of a conventional mold clamping device, and FIG. An explanatory diagram showing the state during molding, FIG. 7 is a partial configuration diagram showing the other side of the conventional similar mold clamping device, FIG. 8 is a diagram of mold opening pressure fluctuation during general mold opening,
FIG. 9 is an explanatory diagram of the conventional operation of the electromagnetic valve and prefill valve in each step from mold closing to mold opening, and FIG. 10 is a similar explanatory diagram of the operation according to the present invention. Description of the main parts of the figure 5.5a - Prefill valve 4 - Clamping ram Do, D +, Do, D+ - Small (bore) hole 6 - Tank

Claims (1)

[Claims] In a direct pressure type mold clamping device equipped with a prefill valve, a control means that keeps the prefill valve closed only during a predetermined period of time after the start of mold release or during a predetermined mold opening stroke necessary for mold release during pressure reduction; A direct pressure type mold clamping device characterized by having a throttle circuit that gradually releases hydraulic pressure in a mold clamping cylinder in order to alleviate rapid backward movement of a mold clamping ram that occurs immediately after mold release.