JPH1089480A - Dustproof mechanism of cylinder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily install a dustproof mechanism without restricting use by constituting a hollow member composed of a porous and freely extensible- contractible gas permeable material so as to elongate in the circumferential direction as well as to be compressed in the shaft direction even in a condition where a piston rod advances most. SOLUTION: A hollow member 10 composed of sponge is fitted around a piston rod 2, and is pressed against an end surface of a cylinder sleeve 1 by a head part 12 of the piston rod 2 through an annular presser plate 11 similarly fitted around the piston rod 2. In a natural condition before installation, an inside diameter of the hollow member 10 is set smaller than an outside diameter of the piston rod 2, and its shaft directional length is set larger than a height of a member housing space when the piston rod 2 advances most from the cylinder sleeve 1. When the hollow member 10 is installed, the screwing-in type head part 12 is removed, and presser plate 11 is removed. Since the hollow member 10 easily extends-contracts in the circumferential direction and the shaft direction, its installing work is facilitated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylinder dustproof mechanism for preventing dust from entering a cylinder sleeve from between a cylinder sleeve and a piston rod.

[0002]

2. Description of the Related Art In a cylinder, as shown in FIG. 5, a piston rod 2 inserted into a cylinder sleeve 1 is compressed by a pressure oil supplied to two oil chambers separated by a piston in the cylinder sleeve 1. It is driven forward and backward in the axial direction. A first seal 3 is provided between the inner surface of the cylinder sleeve 1 and the outer surface of the piston rod 2 to seal the pressure oil in the oil chamber in the cylinder sleeve 1. A second seal 4 is mounted on the outer surface of the piston to partition the oil chamber in the cylinder sleeve 1.

In such a cylinder, the cylinder sleeve 1 is moved from between the cylinder sleeve 1 and the piston rod 2.
There is a danger that the seal 3 may be damaged by dust invading the inside and the sealing state of the pressurized oil may be deteriorated, thereby causing oil leakage. For this purpose, a dustproof mechanism for preventing dust from entering the cylinder sleeve 1 is often provided.

The dustproof mechanism includes a seal 3 between an inner surface of a cylinder sleeve 1 and an outer surface of a piston rod 2.
A scraper 5 is provided outside of the scraper. A boot 6 called a bellows is mounted on the rod projecting side of the cylinder sleeve 1. The boot 6 is an airtight sleeve having a bellows structure that can be deformed in the axial direction, and the inside communicates with the outside via the filter 7 so as to smoothly follow the operation of the piston rod 2 that passes through the inside.

[0005]

In an environment where there is a lot of dust, the dustproof effect is not sufficient with the scraper 5 alone, and the dust that has penetrated the seal 3 has to be used together with the boot 6. However, the boot 6 has the following problem.

[0006] Since a mold is required for production, it is expensive in small lot production. Due to the large mounting dimensions, use is restricted when cylinders are closely arranged. Since one end of the boot 6 needs to be fastened to the piston rod 2 with a snap ring 8 or the like, it takes a lot of time to attach the cylinder, and if the cylinders are densely arranged, even if the use is not restricted, the Installation work is difficult. The filter 7 is likely to be clogged, causing dust to enter in a relatively short time.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a cylinder which has a simple structure, is inexpensive, has a long useful life, and can be easily mounted without restricting the use thereof even when cylinders are densely arranged. Another object of the present invention is to provide a dustproof mechanism.

[0008]

According to the present invention, a dustproof mechanism for a cylinder is mounted on a rod projecting side of a cylinder sleeve.
A hollow member made of a porous, stretchable and breathable material through which a piston rod is inserted is provided. The hollow member is mounted so as to extend in the circumferential direction and be compressed in the axial direction even when the piston rod is most advanced.

The porous, stretchable and breathable material is a material generally called a sponge. The hollow member made of a sponge has a simple structure as compared with a boot having a bellows structure, and is low in material cost and processing cost. In addition, since it extends greatly in the circumferential direction, it can be easily attached in a state where the inner surface is in close contact with the outer surface of the piston rod. Then, by attaching the piston rod to the axially compressed state with the piston rod most advanced, one end surface thereof is always in close contact with the end surface of the cylinder sleeve, and the gap between the cylinder sleeve and the piston rod is reliably sealed.

When the piston rod operates, the hollow member expands and contracts in the axial direction. Since the internal air is exhausted when contracting in the axial direction, dust is prevented from entering the cylinder sleeve. When extending in the axial direction, it sucks in external air,
Since the air is filtered, dust in the air is prevented from entering.

That is, the hollow member is a sponge-type seal spacer which also functions as a filter as a whole. This seal spacer has the same dust-proof effect as a bellows-type boot in a dry use environment where there is almost no water or oil, and is much simpler in structure and easier to install than the boot. Since the effective area is much larger than that of the filter provided in the filter, the effective use period before clogging occurs is very long.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view illustrating a cylinder provided with the dustproof mechanism of the present invention.

The cylinder itself is the same as the cylinder shown in FIG. 3 in that a hollow member 10 made of a sponge is mounted on the rod projecting side of the cylinder sleeve 1 instead of the boot. The hollow member 10 made of a sponge is externally fitted to the piston rod 2, and is pressed against the end face of the cylinder sleeve 1 by the head portion 12 of the piston rod 2 via an annular holding plate 11 which is also externally fitted to the piston rod 2. ing.

What is important here is that, in a natural state before mounting, the inner diameter of the hollow member 10 is smaller than the outer diameter of the piston rod 2 and its axial length is such that the piston rod 2 projects most out of the cylinder sleeve 1. This is a point larger than the height of the member accommodating space. As a result, the hollow member 1 mounted on the rod projecting side of the cylinder sleeve 1
0 is extended in the circumferential direction by the piston rod 2 penetrating the inside, so that the inner surface is in close contact with the outer surface of the piston rod 2. In addition, since the piston rod 2 is compressed in the axial direction irrespective of the operation of the piston rod 2, the lower end surface is always in close contact with the upper end surface of the cylinder sleeve 1. As a result, the gap between the cylinder sleeve 1 and the piston rod 2 is sealed by the hollow member 10.

The mounting of the hollow member 10 is carried out by removing the screw-in head 12 and the holding plate 11. Since the hollow member 10 easily expands and contracts in the circumferential direction and the axial direction, the mounting operation thereof is easy.

During use, the hollow member 10 expands and contracts in the axial direction following the operation of the piston rod 2, so that the operation is not hindered. By functioning as a filter during use, dust can be prevented from entering the cylinder sleeve 1 from the gap between the cylinder sleeve 1 and the piston rod 2. Since the effective area is much larger than that of the filter mounted on the boot, the effective use period until clogging occurs is extended. When the dust accumulates in the hollow member 10, the hollow member 10 is replaced with a new one.
The replacement can be easily performed.

The hollow member 10 in a natural state before mounting
Of the outer diameter of the piston rod 2 is 0.8 to 0.9.
Double is preferred. Further, the axial length of the hollow member 10 in the same state is preferably about 1.2 times the height of the member housing space when the piston rod 2 has advanced most from the cylinder sleeve 1. If the extension or compression of the hollow member 10 is insufficient, the adhesion to the cylinder is insufficient, and the sealing performance is reduced. Excessive elongation or compression of the hollow member 10 causes permanent deformation or cracking of the sponge.

2 to 4 are three views of an injection molding pressure equalizing apparatus suitable for applying the dustproof mechanism of the present invention.

The pressure equalizing device for injection molding is attached to the tip of a main cylinder for applying a molding pressure to a mold for injection molding. The pressure equalizing device includes a body 13 having a plurality of cylinder chambers formed therein, a piston rod 14 is inserted into each cylinder chamber, and a rod cover 15 is screwed. Among the plurality of cylinder chambers in the body 13, a top oil chamber communicates with each other through an oil passage 16, and a bottom oil chamber communicates with each other through an oil passage 17. The piston rod 14 inserted into each cylinder chamber also serves as a plunger and is inserted into each cavity of the mold. The oil chamber on the top side and the oil chamber on the bottom side of each cylinder chamber communicate with each other, so that the thrust of the main cylinder is evenly transmitted to each cavity via each piston rod 14.

The hollow member 10 made of a sponge is mounted on the piston rod 14 at the top side (rod projection side) of each cylinder. The pitch of the cylinders here is as small as, for example, about 30 mm, but the hollow member 10 can be securely and easily mounted on such densely arranged cylinders.

In the pressure equalizing device for injection molding, the piston rod of each cylinder is not forcibly driven, and its stroke is small. The sponge hollow member 10 has a relatively small amount of expansion and contraction in the axial direction as compared with a bellows-type boot, and is therefore particularly effective as a dust-proof mechanism for a small-stroke cylinder used in a pressure equalizer for injection molding.

[0022]

As described above, the dust-proof mechanism of the cylinder of the present invention uses a sponge-type hollow member, so that the boot-type dust-proofing mechanism has the same dust-proofing effect as the bellows-type boot-type. Simpler and cheaper than that. In addition, even in the case where the effective period is long and the cylinders are densely arranged, the mounting can be easily performed without restricting the use.

[Brief description of the drawings]

FIG. 1 is a vertical sectional view illustrating a cylinder provided with a dustproof mechanism of the present invention.

FIG. 2 is a front view of a pressure equalizer suitable for applying the dustproof mechanism of the present invention.

FIG. 3 is a plan view of the pressure equalizing device.

FIG. 4 is a side view of the equalizing device.

FIG. 5 is a vertical sectional view of a cylinder provided with a conventional dustproof mechanism.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder sleeve 2 Piston rod 10 Hollow member

Claims (1)

[Claims] 1. A hollow member which is mounted on a rod projecting side of a cylinder sleeve and made of a porous and stretchable air-permeable material through which a piston rod is inserted, the hollow member extends in a circumferential direction, and A dustproof mechanism for a cylinder, wherein the piston rod is mounted so that it is compressed in the axial direction even when the piston rod is most advanced.