JPH0242428Y2 - - Google Patents

Description

[Detailed description of the invention] [Technical field to which the invention pertains] This invention relates to a hydraulic device that opens and closes a mold valve gate of an injection molding machine, etc., and particularly improves the hydraulic circuit of a hydraulic cylinder that opens and closes a mold valve gate. Regarding.

[Prior art and its problems]

2. Description of the Related Art Conventionally, a hydraulic circuit configured as shown in FIG. 2 is known as a hydraulic circuit for controlling a hydraulic cylinder for opening and closing a mold valve gate of an injection molding machine. That is, in FIG. 2, reference numeral 10 indicates a mold valve gate part, and a rod 14 is inserted through a part of the molten resin passage 12, and the valve gate is opened and closed by moving the rod 14 forward and backward. configured. However, the rod 14 is connected to a piston 18 of a hydraulic cylinder 16 located adjacent to the molten resin passageway 12. Therefore, the hydraulic circuit for this hydraulic cylinder 16 includes a hydraulic pump 20, a pressure reducing valve 22, a directional switching valve 24,
It is connected to the piston side oil chamber 16A of the hydraulic cylinder 16 via the flow control valve 26. On the other hand, the rod side oil chamber 16B of the hydraulic cylinder 16 is connected to the tank 30 through a flow rate control valve 28 and a direction switching valve 24.
is connected to. Therefore, if the directional control valve 24 is not energized now, the hydraulic circuit is maintained in the state shown in FIG. 2, and the hydraulic cylinder 1
At 6, the piston 18 advances the rod 14 to hold the mold valve gate 10 closed.
Next, when the direction switching valve 24 is energized, the supply of pressure oil to each oil chamber 16A, 16B of the hydraulic cylinder 16 is reversed, the hydraulic pump 20 communicates with the rod side oil chamber 16B, and the piston side oil chamber 16A communicates with the tank. Connects with 30. As a result, the rod 14 moves back to open the mold valve gate section 10.

However, since this type of mold valve gate is generally integrated with a hydraulic cylinder, the molten resin passage and piston are close to each other, and the oil chambers to which pressure oil is supplied are both exposed to high temperatures. being exposed to For this reason, as described above, in the conventional system in which pressure oil remains in the high temperature oil chamber of the hydraulic cylinder 16, the pressure oil is provided at the sliding part between the hydraulic cylinder 16 and the rod 14, or the sliding part of the piston 18, for example. Seal parts were exposed to high temperatures, resulting in significant damage, and high temperatures accelerated oxidative deterioration of the hydraulic oil.

[Purpose of invention]

The purpose of this invention is to provide hydraulic pressure for opening and closing mold valve gates that can effectively prevent thermal damage to seal parts and thermal deterioration of hydraulic oil for hydraulic cylinders installed in mold valve gates of injection molding machines, etc. We are here to provide you with the equipment.

[Key points of the idea]

A hydraulic device for opening and closing a mold valve gate according to the present invention is a hydraulic device for opening and closing a mold valve gate, which is configured such that a rod is connected to a piston of a hydraulic cylinder and the rod opens and closes a mold valve gate. Both oil chambers defined by the pistons are switchably connected to a hydraulic pump and a tank via a directional control valve, and furthermore, hydraulic lines are connected to both oil chambers of the hydraulic cylinder via a check valve and a throttle valve, respectively. These hydraulic lines are also connected to the tank via a common relief valve.

In the hydraulic system for opening and closing the mold valve gate, the hydraulic pump is connected to one of the oil chambers of the hydraulic cylinder via a directional control valve, and is connected to the oil chamber via a pressure reducing valve and a flow rate control valve. It is preferable to set the set pressure of the valve to a pressure slightly lower than the set pressure of the pressure reducing valve.

Further, it is preferable that a heat exchanger is connected to a hydraulic line that communicates the directional control valve and the relief valve with the tank.

[Embodiment of the invention] Next, an embodiment of the hydraulic device for opening and closing a mold valve gate according to the invention will be described in detail below with reference to the accompanying drawings.

Figure 1 shows the hydraulic circuit of a hydraulic cylinder that opens and closes the mold valve gate.It is a circuit added to the conventional hydraulic circuit shown in Figure 2, and its basic configuration is the same as that shown in Figure 2. It's the same. Therefore, for convenience of explanation, the same reference numerals are given to the same components as in the circuit configuration shown in FIG. 2, and detailed explanation thereof will be omitted. That is, in this embodiment, the hydraulic lines 32 and 34 are led out from the piston side oil chamber 16A and the rod side oil chamber 16B of the hydraulic cylinder 16, respectively.
check valves 36, 38 and throttle valve 40, respectively.
42 and, via a common relief valve 44, to a part of a hydraulic line 46 that connects the directional control valve 24 and the tank 30.

Further, a heat exchanger 48 is provided on the tank 30 side of the hydraulic line 46 that is connected to the hydraulic lines 32 and 34 .

Next, the operation of the hydraulic system of this embodiment configured as described above will be explained.

Now, in the illustrated state, assuming that the directional switching valve 24 is not energized, the pressure oil supplied from the hydraulic pump 20 is transferred to the pressure reducing valve 22, the directional switching valve 2
4. The oil is supplied to the piston side oil chamber 16A of the hydraulic cylinder 16 via the flow rate control valve 26, while the rod side oil chamber 16B is communicated with the tank 30. As a result, the rod 14 moves forward and the mold valve gate part 10
to the closed state. At this time, the pressure oil supplied to the piston side oil chamber 16A of the hydraulic cylinder 16 is further supplied to the check valve 36 and the throttle valve 40 from the hydraulic line 32.
The pressure is maintained at a pressure slightly lower than the set pressure of the pressure reducing valve 22 through the relief valve 44 and the mold valve gate 10 is kept closed, and the excess oil is passed through the hydraulic line 46 to the heat exchanger 48. The water is cooled down and returned to the tank 30. Further, in this case, since the hydraulic line 32 is at high pressure, the check valve 38 of the hydraulic line 34 is closed, and the oil in the rod side oil chamber 16B of the hydraulic cylinder 16 is transferred to the flow rate control valve 28, the directional switching valve 24, and the heat exchanger. 48 and is returned to tank 30.

Next, when the directional switching valve 24 is energized, the pressure oil supplied from the hydraulic pump is supplied to the rod side oil chamber 16B of the hydraulic cylinder 16 via the directional switching valve 24 and the flow rate control valve 28, while the pressure oil is supplied to the rod side oil chamber 16B of the hydraulic cylinder 16. 1
6A is communicated with the tank 30. As a result, the rod 14 moves back and the mold valve gate section 10 is opened. At this time, the oil supplied to the rod-side oil chamber 16B of the hydraulic cylinder 16 is further maintained at a predetermined set pressure from the hydraulic line 34 via the check valve 38, throttle valve 42, and relief valve 44, as described above. Excess oil is returned to tank 30 via hydraulic line 46 and cooled by heat exchanger 48 . Further, in this case, since the hydraulic line 34 becomes high pressure, the check valve 36 of the hydraulic line 32 is closed, and the piston side oil chamber 16A of the hydraulic cylinder 16 is closed.
The oil is returned to tank 30 via flow control valve 28, directional valve 24 and heat exchanger 48.

[Effect of idea]

As is clear from the embodiments described above, according to the present invention, in the oil chamber on the side where the pressure oil of the hydraulic cylinder is supplied, pressure oil is constantly circulated to the tank, so the hydraulic cylinder is kept under low-temperature pressure. Oil is supplied, and adverse effects such as thermal damage to seal parts and oxidative deterioration of pressure oil due to high temperatures can be easily and reliably prevented.

In addition, the oil returned to the tank via the directional control valve and the pressure oil supplied to one oil chamber of the hydraulic cylinder and circulated to the tank via the relief valve are returned to the tank via a heat exchanger. , cooling of the oil in the tank can be achieved extremely efficiently.

Although the preferred embodiments of the present invention have been described above, it goes without saying that various changes can be made without departing from the spirit of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a hydraulic system diagram showing an embodiment of a hydraulic system for opening and closing mold valve gates according to the present invention, and FIG. 2 is a hydraulic system diagram of a conventional hydraulic system for opening and closing mold valve gates. 10... Mold valve gate part, 12... Molten resin passage, 14... Rod, 16... Hydraulic cylinder, 16A... Piston side oil chamber, 16B... Rod side oil chamber, 18... Piston, 20... ... Hydraulic pump, 22 ... Pressure reducing valve, 24 ... Directional switching valve, 2
6, 28...flow control valve, 30...tank, 32
...Hydraulic line, 34...Hydraulic line, 36,3
8... Check valve, 40, 42... Throttle valve, 44
...Relief valve, 46...Hydraulic line, 48...
Heat exchanger.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) In a hydraulic device for opening and closing a mold valve gate, which is configured such that a rod is connected to the piston of the hydraulic cylinder and the rod opens and closes the mold valve gate, The two defined oil chambers are switchably connected to a hydraulic pump and a tank via a directional control valve, and a hydraulic line is led out from both oil chambers of the hydraulic cylinder via a check valve and a throttle valve, respectively. A hydraulic device for opening and closing a mold valve gate, characterized in that these hydraulic lines are connected to a tank via a common relief valve. (2) Utility Model Registration In the mold valve gate opening/closing hydraulic system described in claim 1, the hydraulic pump connected to one oil chamber of the hydraulic cylinder via a directional control valve has a pressure reducing valve and a flow control valve. A hydraulic device for opening and closing a mold valve gate, which is connected to the oil chamber via a valve, and has a relief valve set at a pressure slightly lower than the pressure reducing valve. (3) A hydraulic system for opening and closing a mold valve gate as described in claim 1 of the utility model registration claim, in which a heat exchanger is connected to a hydraulic line that communicates a directional control valve and a relief valve with a tank. Hydraulic device for opening and closing valve gates.