JPH04216906A - Mold clamping device - Google Patents

Abstract

PURPOSE:To obtain the above mold clamping device, in which a seal ring is not damaged due to rubbing and which prevent the leakage of compressed oil from a cylinder front chamber at the time of mold clamping, by fitting the thin seal ring having a U-shaped cross section onto the outer circumferential surface of a piston and mounting an oil path communicating the inside of the seal ring and a cylinder post chamber into the piston. CONSTITUTION:A seal ring 8 is passed through the terminal section of a flowing clearance, a stroke is changed over to mold clamping, the supply of compressed oil to a booster ram 6 is stopped, a cylinder post chamber 4 is boosted, and a seal section 8b is swollen, and pushed against the inwall surface of a cylinder. Consequently, the periphery of a piston is interrupted completely, and the outflow of compressed oil is prevented completely, thus also holding mold clamping force easily for a prolonged time. When mold opening by the booster ram is conducted, the seal section 8b of the seal ring 8 is restored to an original state, and separated from the inwall surface of the cylinder, thus generating no rubbing.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulically operated mold clamping device used in an injection molding machine or the like.

0002

[Prior Art] As a means of reducing hydraulic resistance to the piston in the cylinder and speeding up the movement of the piston, pressure oil flows around the piston in the cylinder from the rear chamber of the cylinder to a part of the front chamber of the cylinder. A mold clamping device provided with a gap is described in Japanese Patent Application Laid-open No. 128925/1983.

[0003] In this conventional device, as the piston moves by the rapid-feeding cylinder, a portion of the pressure oil in the chamber existing in the movement direction flows out from the circulation gap on the outer circumference of the piston to the oil chamber on the opposite side. This movement supplements the oil in the rear chamber of the cylinder, which has expanded, and prevents the generation of negative pressure.

0004

[Problems to be Solved by the Invention] The problem with such a mold clamping device is that the terminal end of the circulation gap in the cylinder front chamber is a step, so it is designed to be in close contact with the inner circumferential surface of the cylinder front chamber. The seal ring on the outer circumferential surface of the piston is rubbed strongly every time it passes through the steps, and is easily damaged. Although it is effective in speeding up mold opening and closing, it cannot withstand long-term use. That's true.

[0005] The present invention was devised to solve the problem of such conventional devices, and its purpose is to prevent the seal ring from rubbing due to friction even if the end portion of the above-mentioned flow gap is a stepped portion. It is an object of the present invention to provide a mold clamping device having a new structure that is free from damage, has good contact with the inner circumferential surface of a cylinder front chamber, and can prevent leakage of pressure oil from the cylinder front chamber during mold clamping.

[0006] The features of the present invention for the above-mentioned purpose are that a pressure oil circulation gap extending from the rear chamber of the cylinder to a part of the front chamber of the cylinder is provided on the outer periphery of the piston in the cylinder, and that the outer periphery of the piston has a U-shaped cross section. A thin reel ring is fitted into the piston, and an oil passage is provided inside the piston to communicate the inside of the seal ring with the rear chamber of the cylinder.

[0007]

[Operation] In the above structure, when the piston moves to the cylinder front chamber to close the mold, a part of the pressure oil in the cylinder front chamber is pushed by the piston and flows out from the circulation gap to the cylinder rear chamber. When the piston moves to the end of the flow gap, it becomes difficult for pressure oil to flow out from the flow gap, resistance increases, and the movement of the piston slows down.

When the pressure in the cylinder rear chamber is increased and the mold is clamped, the oil passage inside the piston makes the pressure in the seal ring the same as that in the cylinder rear chamber, causing the seal ring to expand and increase the pressure inside the cylinder front chamber. Pressed against the surrounding surface. This completely isolates the area around the piston and prevents pressure oil from leaking from the cylinder front chamber.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a cylinder having a mold clamping ram 2 movable back and forth inside. This mold clamping ram 2 is integrated with a piston 5 that partitions the inside of the cylinder into a front chamber 3 and a rear chamber 4, and a movable platen located opposite to a fixed platen is connected to the tip end, although omitted in the drawing, and a movable platen located opposite to a fixed platen is connected to the tip end. A booster ram 6 is inserted from the rear end of the cylinder.

Concave grooves are provided on all sides of the inner circumferential wall of the cylinder 1, extending from the rear end of the cylinder rear chamber 4 to a part of the cylinder front chamber 3. 7,7 is formed.

A metal seal ring 8 is fitted on the outer peripheral surface of the piston 5. This seal ring 8 has both side edges 8a thick and a seal portion 8b thin.
It consists of a ring with a U-shaped cross section and a recess that forms the oil chamber 9 on the inside.

This seal ring 8 is fitted from the rear end into a stepped portion 10 on the outer periphery of the piston, and is fixed to the piston 5 by a pusher fitting 11 that is fitted into the corner of the stepped portion and secured to the rear end of the piston with a bolt or the like. There is.

Further, an oil passage 12 is bored in the piston to connect the cylinder rear chamber 4 and the oil chamber 9 inside the seal ring, and the pressure oil flowing into the oil chamber 9 from this oil passage 12 causes , the thin seal portion 8b located a little away from the cylinder inner wall surface bulges toward the cylinder inner wall surface.

In the above structure, when the mold clamping ram 2 is moved forward by the booster ram 6 to close the mold, the pressure oil in the cylinder front chamber 3 flows out into the hydraulic path 13. Further, a part of the pressure oil is pushed out from the circulation gaps 7, 7 and flows into the cylinder rear chamber 4, and together with the pressure oil supplied from the hydraulic path 14, supplements the expanding pressure oil in the cylinder rear chamber 4.

When the piston 5 reaches the terminal end of the flow gaps 7, 7, the flow of pressure oil from the flow gaps 7, 7 is restricted;
As a result, the hydraulic resistance on the cylinder front chamber side increases, and the movement of the mold clamping ram 2 by the booster ram 6 slows down.

After the seal ring 8 has passed the end of the flow gap, the process is switched to mold clamping, the supply of pressure oil to the booster ram 6 is stopped, and the pressure in the cylinder rear chamber 4 is increased. The pressure inside the seal ring is also increased by the pressure oil, and the seal portion 8b bulges out and is pressed against the inner wall surface of the cylinder.

[0016] As a result, the area around the piston is completely shut off and leakage of pressure oil is completely prevented, making it easier to maintain mold clamping force over a long period of time.

[0017] Besides the hydraulic pressure in the cylinder rear chamber 4, when the mold is opened by the booster ram 6, as the hydraulic pressure in the cylinder rear chamber 4 decreases, the hydraulic pressure in the seal ring also decreases. However, the seal portion 8b of the seal ring 8 returns to its original state and separates from the cylinder inner wall surface.

When the piston 5 moves backward together with the piston 5, it is away from the inner wall surface of the cylinder and no friction occurs, so even if the end portions of the flow gaps 7, 7 are stepped, the seal portion 8b will come into contact with the stepped portions. It will not cause any damage.

In the above embodiment, the flow gaps 7, 7 are formed by grooves provided in the inner wall of the cylinder, but unlike the conventional device, the inner wall of the cylinder other than the front part of the front chamber of the cylinder is formed by the piston. The diameter may be larger than that to form a flow gap.

Further, although the illustrated seal ring 8 has a single oil chamber 9, if the seal ring 8 is wide, a partition may be provided in the center to form a plurality of oil chambers 9.

[0021]

As described above, the present invention provides a pressure oil circulation gap 7 on the outer periphery of the piston 5 in the cylinder 1 extending from the cylinder rear chamber 4 to a part of the cylinder front chamber 3.
A thin reel ring 8 with a U-shaped cross section is attached to the outer peripheral surface of the piston 5.
, and an oil passage 12 is provided in the piston 5 to communicate the inside of the seal ring with the cylinder rear chamber 4.

[0022] There is no rubbing of the seal ring due to the step formed at the end of the flow gap, and the seal part is less likely to be damaged, so it can be used for a long period of time, and it is necessary to replace the seal ring frequently as in the past. Since there is no oil, the time and labor required for repairs, replacements, etc. are saved, and the surrounding area is less contaminated by oil during replacement.

In addition, the pressure oil in the rear chamber of the cylinder acts on the seal ring and bulges out the seal portion, thereby sealing off the area around the piston, so the sealing performance is better than when the seal ring is simply pressed, and the movement of the piston is prevented. Since the sliding resistance during operation is also extremely small, it has the advantage of being very convenient for high-speed opening and closing.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional side view of one embodiment of a mold clamping device according to the present invention.

FIG. 2 is a sectional view taken along line AA in FIG. 1;

FIG. 3 is an enlarged longitudinal sectional side view of main parts.

[Explanation of symbols]

1 Cylinder 2 Mold clamping ram 3 Cylinder front chamber 4 Cylinder rear chamber 5 Piston 6 Booster ram 7. Flow gap 8 Seal ring 8b Seal part 9 Seal ring oil chamber 10 Stepped section 11 Presser metal fittings 12 Oil road

Claims (1)

[Claims] Claim 1: A pressure oil circulation gap extending from the rear chamber of the cylinder to a part of the front chamber of the cylinder is provided on the outer periphery of the piston in the cylinder, and a thin reel ring with a U-shaped cross section is fitted on the outer periphery of the piston. A mold clamping device characterized in that an oil passage is provided in the piston to communicate the inside of the seal ring and the rear chamber of the cylinder.