JPH043781Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) This invention is applicable to injection molding machines, die casting machines,
The present invention relates to a mold clamping cylinder applied to a mold clamping device in a so-called molding machine such as a press.

(Prior Art) Hereinafter, the conventional technology will be explained using a mold clamping device of an injection molding machine as an example.

FIG. 7 shows a hydraulic circuit of a mold clamping device in a conventional injection molding machine.

In the figure, 1 is a mold clamping cylinder, which is a hydraulic cylinder for closing or opening a mold 4. A clamp ram 2 is slidably inserted into the inside of the mold clamping cylinder 1. A piston ring 5 is placed in a groove carved in the circumferential direction of the piston circumferential surface.
is loaded.

The movable platen 3 is a platen on which a mold 4 is attached, and is connected to the clamp ram 2. Reference numeral 8 denotes an opening/closing operation switching valve for switching the oil passage to open/close the mold 4.

A pilot check valve 12 is provided between the mold clamping side chamber 6 of the mold clamping cylinder 1 and the switching valve 8 for opening/closing operation, and a passage of the pilot check valve 12 is opened when pressure oil is supplied from a pilot pressure source 15. It's summery. The pilot check valve 12 is operated by a switching valve 19. Further, there is another pilot check valve 13 between the mold opening side chamber 7 on one side of the mold clamping cylinder 1 and the switching valve 8 for opening/closing operation.
When pressure oil is supplied from the pilot pressure source 10, the passage of the pilot check valve 13 is opened. The switching valve 11 operates a pilot check valve 13.

On the other hand, both the pilot check valves 12,
13 and the passages leading to the mold clamping side chamber 6 and the mold opening side chamber 7 are provided with an oil passage, and the oil passage is also provided with a switching valve 16. The switching valve 16 opens and closes the oil passage between the two chambers.

The operation of the conventional device having such a configuration will be described as follows.

Mold closing process: When the solenoid a of the switching valve 8 for opening/closing operation is energized, oil is sent from the hydraulic source 14 through the pilot check valve 12 to the mold clamping side chamber 6, and moves the clamp ram 2 and movable platen 3 forward. let Note that since the solenoid e is energized at this time, no oil is sent to the mold opening side chamber 7.

Mold clamping pressure increase process... After the movable platen 3 moves forward and closes the mold, the solenoid e is turned off and oil is also sent to the mold opening side chamber 7, causing hydraulic pressure to rise in both chambers.

Mold clamping block process...Solenoid c after pressure increase,
When d is energized, the pilot pressure to the pilot check valves 12 and 13 is cut off, and the check valves 12 and 13 work together to enter a blocked state.

Mold opening process...When solenoid b is energized,
Pressure oil from the hydraulic source 14 passes through the pilot check valve 13 and is sent to the mold opening side chamber 7. At this time, the solenoid c is de-energized, and since the solenoid c is de-energized, the pilot check valve 12 is opened and the oil from the mold clamping side chamber 6 is returned to the tank through there. Further, at this time, the oil passage between the mold clamping side chamber 6 and the mold opening side chamber 7 is cut off because the solenoid e of the switching valve 16 is energized.

Incidentally, in the conventional device described above, the piston ring 5 has a step-shaped abutment portion as shown in FIGS. 8 and 9, and the clamp ram 2
If hydraulic pressure is applied in the direction of arrow A as shown in Fig. 10, leakage of pressure oil will occur through the gap 5a at the joint as shown by arrow B indicated by the broken line. do. On the other hand, if hydraulic pressure acts in the direction opposite to the direction of arrow A, leakage of pressure oil will occur in the direction opposite to arrow B through the other gap 5b. When the mold is opened, hydraulic pressure is applied to the mold opening side chamber 7 as described above, but at this time it is necessary to suppress leakage from the piston rings 5, and for this purpose, the number of piston rings 5 is increased to suppress the leakage. This is the current situation.

In addition, during mold clamping, it is necessary to simultaneously send oil to both the mold clamping side chamber 6 and the mold opening side chamber 7, and it is necessary to separately install a switching valve 16 for this purpose. valve 16
This led to the problem of rapid pressure drop due to leakage from the pipe.

Further, due to the structure of the mold clamping cylinder 1, there is a large difference in volume between the mold clamping side chamber 6 and the mold opening side chamber 7, and therefore, it is necessary to control the flow rate of pressure oil in order to simultaneously increase the oil pressure. However, since the difference in volume at this time varies depending on the operating conditions, it may be impossible to control the flow rate using a fixed orifice.

(Problems to be solved by the invention) In this way, in the conventional mold clamping cylinder, a large number of piston rings are installed, and a switch is installed to connect and disconnect the oil passage connecting both chambers on the mold clamping side and the mold opening side. It is necessary to install a separate valve, and there is a problem that leakage from this valve tends to cause a pressure drop during the mold clamping block, and furthermore, there is a problem in controlling the flow rate when trying to apply hydraulic pressure to both chambers at the same time. There is also the problem that it is difficult.

Therefore, the present invention aims to solve these problems by eliminating the switching valve and having a simple structure.

(Means for solving the problem) Therefore, the present invention divides the inside of the cylinder into a mold-clamping side chamber and a mold-opening side chamber through a piston having a piston ring, and also provides a mold having a clamp ram housed in a reciprocating manner. In the clamping cylinder, the piston ring is of a one-way type that allows pressure oil to leak only from the mold-clamping side chamber to the mold-opening side chamber, thereby solving the above-mentioned problem.

(Function) The present invention is characterized in that the piston ring used has a directionality for sealing.

That is, a piston ring is used that has poor sealing performance from the mold-clamping side chamber to the mold-opening side chamber, and excellent sealing performance from the mold-opening side chamber to the mold-clamping side chamber in the opposite direction. At the same time, remove the oil passage connecting both chambers and the switching valve for the oil passage.

In this way, even if the extra oil passages and switching valves are eliminated, the special piston ring structure allows oil to be sent from the mold clamping side chamber through the piston ring to the mold opening side chamber when the mold clamping pressure increases, and the oil is sent to both chambers. stand up. At this time, there may be a large amount of leakage from the piston ring.

When the mold is opened, the piston ring has excellent sealing performance from the mold opening side chamber toward the mold closing side chamber, so that the mold opening operation is performed smoothly.

(Example) Hereinafter, an example of the present invention will be specifically described according to an example shown in the drawings.

Fig. 1 shows a hydraulic circuit when an embodiment of the present invention is applied to a mold clamping device, and Figs. 2 and 3 show structural examples of a piston ring joint part applied to this embodiment. FIGS. 4 to 6 show the behavior of pressure oil when oil pressure is applied to the same piston ring.

Now, as mentioned above, the mold clamping cylinder of the molding machine according to the present invention is characterized by a piston ring, and as a result of adopting the piston ring, redundant oil passages and switching valves are eliminated from the hydraulic circuit of the mold clamping device. It is possible.

Therefore, in the following explanation, the piston ring will be mainly described based on FIGS. 2 to 6.

In these figures, the piston ring 20 applied to the present embodiment has a cross section of one end at the abutment portion at a desired point on each of the long side and the short side of the rectangular cross section of the piston ring 20, as shown in the drawings. It has a triangular cross section formed by tying it together, and the cross section at the other end is formed into a pentagonal cross section after cutting off the triangular cross section.

Therefore, - at the center of the joint in Fig. 2
The cross section in the direction of the arrow shows the piston ring 2 as shown in FIG.
The end portions of 0 overlap each other at the sloped portion, and the whole has a rectangular cross section. Also, the gap at the joint is 20
a and 20b have cross-sectional shapes as shown in FIG. 4, FIG. 5, and FIG. 6, which show the cross section taken in the direction of the arrow in FIG. 2, and the cross section shown in the direction shown in the arrow, respectively.

Because of the above configuration, the piston ring 20 is of a one-way type with a directional seal.

To explain this with reference to FIGS. 4 to 6, when there is pressurized oil in the direction of arrow C in FIG. However, in the case of the present piston ring 20, the sealed portion is communicated through a gap 20a on one side of the abutment portion, so the pressure oil passes through this gap 20a as shown by arrow D. Conversely, when the pressure oil acts in the direction of arrow A shown in FIGS. 5 and 6, the piston ring 20 is pushed upward from the bottom in the figure and comes into close contact with the upper wall surface of the groove 2a in which the piston ring 20 is loaded. However, in this case, as is clear from both figures, both ends of the piston ring 20 are in close contact with the wall surfaces A and C and the cylinder bore surfaces B and D in the gaps 20a and 20b, so the same gap is 20
Pressure oil cannot pass through either a or 20b, and the pressure oil is completely sealed.

Considering the case where this piston ring 20 is applied to a mold clamping cylinder of an injection molding machine, if the mold clamping side chamber 6 is arranged in the upper part of the drawing and the mold opening side chamber 7 is arranged in the lower part in FIGS. 4 to 6, The sealing performance from the mold-clamping side chamber 6 to the mold-opening side chamber 7 is poor, and the sealing performance from the mold-opening side chamber 7 to the mold-clamping side chamber 6 in the opposite direction is excellent. In this way, this piston ring 20
If this is adopted, the seal from the mold opening side chamber 7 to the mold clamping side chamber 6 will be complete, and in the opposite case, it will be possible to apply hydraulic pressure to both chambers via the piston ring 20. The external oil passage and switching valve 16 connecting the two chambers as shown are no longer necessary, and therefore, in the present invention, the oil passage and switching valve 16 can be eliminated from the hydraulic circuit as shown in FIG.

Next, based on FIG. 1, the operation when the mold clamping cylinder of this embodiment is applied to an injection molding machine will be described as follows, focusing on the differences from the conventional machine.

Mold closing process...When solenoid a is energized,
Pressure oil is sent from the hydraulic source 14 through the pilot check valve 12 to the mold clamping side chamber 6, and the clamp ram 2 and movable platen 3 move forward. At this time, the pressure oil leaks into the mold opening side chamber 7 through the piston ring 20, but since the solenoid d is in a de-energized state and pilot pressure is built up in the pilot check valve 13, the pressure oil can freely pass through.
The oil in the mold opening side chamber 7 is returned to the tank through the same check valve 13.

Mold clamping pressurization step: Even after the clamp ram 2 is advanced the most, the oil flow is the same as in the mold closing step. However, in this case, oil pressure builds up in both chambers due to the supply pressure oil and leakage.

Mold clamping block process...Solenoids c and d are energized, and the pilot check valves 12 and 13 are activated.
work together to form a block state.

Mold opening process: Solenoid b is energized and solenoids c and d are de-energized as in the conventional method, and pressure oil is sent from the hydraulic source 14 to the mold opening side chamber 7 through the pilot check valve 13. At this time, the oil in the mold clamping side chamber 6 is returned to the tank through the pilot check valve 12. In this case, the piston ring 20 is in the state shown in FIGS. 5 and 6, and no pressure oil leaks from the mold opening side chamber 7 to the mold clamping side chamber 6.

(Effects of the invention) As explained in detail above, the present invention uses a one-way type piston ring provided on the piston of the clamp ram that allows pressure oil to leak only from the mold-clamping side chamber to the mold-opening side chamber, making it easy to prevent leakage. In addition to being able to achieve mold clamping, leaks on the mold opening side can be kept to a very small level, and extra oil passages and switching valves installed there are no longer required, which simplifies the hydraulic circuit and sequence. The number of parts such as piping, switching valves, piston rings, etc. can be reduced. Therefore, the number of leakage points is reduced, so that a sufficient holding time can be spent in the mold clamping block process.

[Brief explanation of drawings]

Figure 1 is a hydraulic circuit diagram of the mold clamping cylinder of the present invention.
Fig. 2 is a perspective view of the joint part of the piston ring adopted in the present invention, Fig. 3 is a sectional view of Fig. 2,
4 to 6 are explanatory sectional views showing the action of the piston ring in the mold clamping cylinder, FIG. 4 is a sectional view of FIG. 2, and FIG. 6 is a sectional view of FIG. 2, FIG. 7 is a hydraulic circuit diagram of a conventional mold clamping cylinder, FIG. 8 is a perspective view of a conventional piston ring abutment, and FIG. 9 is a sectional view of FIG. - Sectional view in Figure 8,
FIG. 10 is a sectional view of FIG. 8 showing the action of a conventional piston ring in a mold clamping cylinder. Explanation of the main parts of the figure, 1... mold clamping cylinder, 2
... Clamp ram, 6 ... Mold clamping side chamber, 7 ... Mold opening side chamber, 8, 9, 11 ... Switching valve, 20 ... Piston ring.

Claims (1)

[Scope of utility model registration request] The inside of the cylinder is divided into a mold closing side chamber and a mold opening side chamber via a piston having a piston ring, and
A mold for a molding machine, characterized in that, in a mold clamping cylinder having a clamp ram housed in a reciprocating manner, the piston ring is a one-way type that allows pressure oil to leak only from the mold clamping side chamber to the mold opening side chamber. Tighten cylinder.