Sealing device

[Problem] To provide a sealing device having high pressure resistance and durability for a reciprocating shaft.[Solution] A sealing device comprising an oil seal member and a dust seal member. The oil seal member and the dust seal member each comprise a rigid ring provided inside a shaft hole and an elastic ring attached to the rigid ring, wherein the elastic ring has formed thereon a lip that slidably contacts a reciprocating shaft. The rigid ring of the dust seal member is detachably fitted in the rigid ring of the oil seal member. The sealing device further comprises another rigid ring provided between the elastic ring of the oil seal member and the elastic ring of the dust seal member in a direction parallel to the axial direction of the reciprocating shaft. This rigid ring is detachably fitted in a concave portion formed radially inward of the rigid ring of the dust seal member and reinforces the elastic ring of the dust seal member.

TECHNICAL FIELD

The present invention pertains to a sealing device to be used for sealing the area around a shaft of an instrument having a reciprocating shaft.

BACKGROUND ART

In instruments having reciprocating shafts such as hydraulic cylinder devices and shock absorbers, a sealing device for sealing an annular interval between a reciprocating shaft and a shaft hole inner surface is provided between the reciprocating shaft and the shaft hole inner surface.

Patent document 1 discloses a sealing device for a shock absorber of a vehicle suspension device. This sealing device has: a metal reinforcement ring; a main lip disposed on an inner peripheral portion of the reinforcement ring and provided on an oil chamber side; and a dust lip disposed on the inner peripheral portion of the reinforcement ring and provided on an outer space side. The main lip and the dust lip are formed from an elastic material such as fluororubber and are adhered to the reinforcement ring. More precisely, an elastic body part comprising the main lip and an elastic body part comprising the dust lip are adhered, respectively, to the two surfaces of the reinforcement ring. Further, a thin elastic body part for coupling these elastic body parts is adhered to the inner periphery surface of the reinforcement ring.

Patent document 2 discloses a sealing device for a shock absorber, said sealing device having provided therein a back-up ring for reinforcing the main lip.

PRIOR ART DOCUMENTS

Patent Documents

Patent Document 1: Japanese Patent No. 4332703 B

Patent Document 2: JP 2005-090569 A

SUMMARY OF INVENTION

Technical Problem

Accompanying the greater variation in vehicle driving environments and ways of being driven, the usage conditions of sealing devices for shock absorbers have become harsher. Further, when internal oil pressure is high such as in a monotube-type shock absorber, designing requires consideration of the pressure resistance and the durability of the sealing device.

Here, the objective of the present invention is to provide a sealing device that has high pressure resistance and durability.

Solution to Problem

The sealing device according to the present invention is a sealing device to be provided between a reciprocating shaft and an inner surface of a shaft hole in which the reciprocating shaft is provided, wherein the sealing device comprises: an oil seal member comprising a liquid-side rigid ring made of a rigid body and provided inside the shaft hole, and a liquid-side elastic ring made of an elastic body and attached to the liquid-side rigid ring, the liquid-side elastic ring having formed thereon an oil lip that is provided radially inward of the liquid-side rigid ring and slidably makes sealing contact with the reciprocating shaft; a dust seal member comprising an atmosphere-side rigid ring made of a rigid body and detachably fitted in the liquid-side rigid ring, and an atmosphere-side elastic ring made of an elastic body and fixed to the atmosphere-side rigid ring, the atmosphere-side elastic ring having formed thereon a dust lip that is provided radially inward of the atmosphere-side rigid ring and slidably contacts the reciprocating shaft; and an intermediate rigid ring that is made of a rigid body, is detachably fitted in a concave portion formed radially inward of the atmosphere-side rigid ring, is provided between the liquid-side elastic ring and the atmosphere-side elastic ring in a direction parallel to the axial direction of the reciprocating shaft, and reinforces the liquid-side elastic ring.

In this sealing device, the oil seal member and the dust seal member are separate members, the oil seal member and the dust seal member each comprise a rigid ring provided inside the shaft hole and an elastic ring attached to the rigid ring, and the elastic ring has formed thereon a lip that slidably contacts the reciprocating shaft. Between the liquid-side elastic ring of the oil seal member and the atmosphere-side elastic ring of the dust seal member, an intermediate rigid ring, which is separate to the foregoing members, is provided in a direction parallel to the axial direction of the reciprocating shaft, and the liquid-side elastic ring is reinforced by the intermediate rigid ring which is made of a rigid body. The liquid-side elastic ring which has an oil lip formed thereon is reinforced by the liquid-side rigid ring, and the atmosphere-side elastic ring which has a dust lip formed thereon is reinforced by the atmosphere-side rigid ring, and furthermore, the liquid-side elastic ring is supported by the intermediate rigid ring, the intermediate rigid ring being fitted in a concave portion of the atmosphere-side rigid ring fitted in the liquid-side rigid ring, and rigidly supported with a strong supporting force by the atmosphere-side rigid ring and the liquid-side rigid ring. Therefore, it is possible to enhance the pressure resistance and the durability of the sealing device.

In a sealing device in one embodiment of the present invention, the intermediate rigid ring is detachably fitted in a concave portion formed radially inward of the liquid-side elastic ring. In this case, after the intermediate rigid ring is fitted in the concave portion of the atmosphere-side rigid ring, it is easy to assemble the liquid-side elastic ring of the oil seal member to the intermediate rigid ring.

In a sealing device in one embodiment of the present invention, at least the inner peripheral surface of the intermediate rigid ring is formed from a metal that is softer than the outer peripheral surface of the reciprocating shaft. In this case, it is possible to use the intermediate rigid ring as a guide for guiding the reciprocal movement of the reciprocating shaft.

In a sealing device in one embodiment of the present invention, an elastic material is not fixed to the inner peripheral surface of the intermediate rigid ring. In this case, there is no risk of an elastic material peeling from the inner peripheral surface of the intermediate rigid ring, and further, it is possible to set a smaller gap between the intermediate rigid ring and the reciprocating shaft. Accordingly, it is possible to further enhance the pressure resistance and the durability of the sealing device.

Advantageous Effects of Invention

In the present invention, between the liquid-side elastic ring of the oil seal member and the atmosphere-side elastic ring of the dust seal member, an intermediate rigid ring, which is different to the foregoing members, is provided in a direction parallel to the axial direction of the reciprocating shaft, and the liquid-side elastic ring is reinforced by the intermediate rigid ring which is made of a rigid body. The liquid-side elastic ring which has an oil lip formed thereon is reinforced by the liquid-side rigid ring, and the atmosphere-side elastic ring which has a dust lip formed thereon is reinforced by the atmosphere-side rigid ring, and furthermore, the liquid-side elastic ring is supported by the intermediate rigid ring, the intermediate rigid ring being fitted in a concave portion of the atmosphere-side rigid ring fitted in the liquid-side rigid ring, and rigidly supported with a strong supporting force by the atmosphere-side rigid ring and the liquid-side rigid ring. Therefore, it is possible to enhance the pressure resistance and the durability of the sealing device. Further, the oil seal member, the dust seal member, and the intermediate rigid ring are mutually separate members, and therefore, it is possible to exchange any of these members for a suitable member or select a suitable member according to the circumstances. For example, if the oil seal member has degraded due to age, it is possible to exchange only the oil seal member. Further, it is possible to prepare several kinds of oil seal members and several kinds of dust seal members having different sizes, shapes, structures, or other details, and to select a suitable oil seal member or dust seal member according to the environment in which the sealing device is to be used.

DESCRIPTION OF EMBODIMENTS

Below, various embodiments of the present invention are described with reference to the attached drawings.

First Embodiment

FIG. 1shows the first embodiment of the present invention, and shows a portion of a shock absorber, which is an instrument that has a reciprocating shaft, and a sealing device disposed in the shock absorber.

A shock absorber1comprises a cylindrical housing2and a columnar reciprocating shaft4. The reciprocating shaft4is formed from a metal such as steel. The housing2is cylindrical and comprises a shaft hole2A having the reciprocating shaft4provided therein. Oil, that is, a liquid L, has been put into the shaft hole2A. An end wall3having an opening3A formed in the center thereof is formed at a lower end of the housing2.

A sealing device6, which is an oil seal, and a rod guide8are provided inside the housing2. Although the details are not shown, the rod guide8is fixed to the housing2. The rod guide8guides the reciprocal movement of the reciprocating shaft4in the vertical direction inFIG. 1(that is, the axial direction of the reciprocating shaft4) and presses the sealing device6to the end wall3.

The sealing device6is provided inside the housing2, and the movement of the sealing device6in the lateral direction inFIG. 1is restricted by the inner peripheral surface of the housing2. Further, the sealing device6is sandwiched by the rod guide8and the end wall3, and the movement of the sealing device6along the axial direction of the reciprocating shaft4is restricted. The sealing device6is provided between the reciprocating shaft4and the inner surface of the shaft hole2A in which the reciprocating shaft4is provided, and prevents or reduces leakage of the liquid L from a liquid L side to an atmosphere A side.

The reciprocating shaft4is columnar, the shaft hole2A is cross-sectionally circular, and the sealing device6is substantially annular, butFIG. 1shows only the left half of these parts.FIG. 1shows a central axis C which is common to the reciprocating shaft4, the shaft hole2A, and the sealing device6.

In this embodiment, the sealing device6comprises three separate members, i.e., an oil seal member10, a dust seal member12, and a rigid ring (intermediate rigid ring)14. If necessary, seeFIG. 2which is an exploded cross-sectional view dearly showing these three members.

The oil seal member10comprises: a liquid-side rigid ring16provided inside the shaft hole2A and attached to the shaft hole2A; and a liquid-side elastic ring18fixed to the liquid-side rigid ring16. The liquid-side rigid ring16is formed from a rigid body such as a metal. The liquid-side rigid ring16has an L-shaped cross-section and comprises an annular portion16aand a cylindrical portion16bextending from an outer edge of the annular portion16a.

The liquid-side elastic ring18is formed from an elastic material such as an elastomer and is fixed to the inner peripheral edge of the annular portion16aof the liquid-side rigid ring16. The liquid-side elastic ring18has formed thereon an oil lip20provided radially inward of the liquid-side rigid ring16. The oil lip20makes sealing contact with the outer peripheral surface of the reciprocating shaft4and prevents or reduces leakage of a liquid from the liquid L side to the atmosphere A side. When the reciprocating shaft4moves in the direction of the central axis C, the reciprocating shaft4slides with respect to the oil lip20.

The liquid-side elastic ring18is mainly fixed to a liquid L-side surface of the liquid-side rigid ring16of the liquid-side rigid ring16, but is also fixed to the inner peripheral surface of the liquid-side rigid ring16, and furthermore, a region18qwhich is a section of the liquid-side elastic ring18is also fixed to an atmosphere A-side surface of the liquid-side rigid ring16. The region18qis compressed by the dust seal member12.

Moreover, the oil seal member10comprises an outer gasket19. The outer gasket19is formed from an elastic material such as an elastomer and is fixed in close adherence with the annular portion16aand the cylindrical portion16bof the liquid-side rigid ring16. The liquid-side rigid ring16applies a supporting force on the outer gasket19radially outwardly, that is, toward the inner peripheral surface of the shaft hole2A, and the outer gasket19is compressed by the inner peripheral surface of the shaft hole2A and the liquid-side rigid ring16. Thus, the outer gasket19prevents or reduces leakage of a liquid through an outer portion of the shaft hole2A from the liquid L side to the atmosphere A side.

Although the outer gasket19and the liquid-side elastic ring18may be separate, in this embodiment, they are coupled via a thin film portion21. That is, the liquid-side elastic ring18, the outer gasket19, and the thin film portion21constitute a continuous integrated elastic portion formed from the same material. The thin film portion21is also fixed in close adherence with the liquid-side rigid ring16. In this embodiment, a protrusion8aof the rod guide8is caused to contact the thin film portion21of the oil seal member10and a pressing force is applied to the sealing device6toward the end wall3of the housing2.

With respect to the oil seal member10, “attached to the shaft hole2A” means being attached directly or indirectly to the shaft hole2A. These may be attached to the shaft hole2A directly (for example, by press-fitting), and may also be attached to the shaft hole2A indirectly (for example, as in this embodiment, by being pressed to the end wall3by the rod guide8).

The dust seal member12comprises: an atmosphere-side rigid ring22detachably fitted in the liquid-side rigid ring16of the oil seal member10; and an atmosphere-side elastic ring24fixed to the atmosphere-side rigid ring22. The atmosphere-side rigid ring22is formed from a rigid body such as a metal. The atmosphere-side rigid ring22is a circular ring and is provided in an internal space defined by the annular portion16aand the cylindrical portion16bof the liquid-side rigid ring16, with one side surface of the atmosphere-side rigid ring22being contacted by the annular portion16a, the other side surface thereof being contacted by the end wall3, and the external peripheral surface being caused to contact the inner peripheral surface of the cylindrical portion16b.

The atmosphere-side elastic ring24is formed from an elastic material such as an elastomer and is fixed to the inner peripheral edge of the atmosphere-side rigid ring22. The atmosphere-side elastic ring24has formed thereon a dust lip26provided radially inward of the atmosphere-side rigid ring22. The dust lip26contacts the outer peripheral surface of the reciprocating shaft4and predominantly fulfills a role of preventing foreign matter (for example, mud, water, dust) from entering from the atmosphere A side to the liquid L side. When the reciprocating shaft4moves in the direction of the central axis C, the reciprocating shaft4slides with respect to the dust lip26. The dust lip26may make sealing contact with the outer peripheral surface of the reciprocating shaft4so as to fulfill a role of preventing or reducing leakage of a liquid.

This sealing device6comprises a garter spring30wound around the atmosphere-side elastic ring24. The garter spring30applies a force on the dust lip26that presses the dust lip26to the reciprocating shaft4. However, the garter ring30is not essential. Further, a garter spring may be wound around the liquid-side elastic ring18in order to press the oil lip20to the reciprocating shaft4.

In order to contact the outer peripheral surface of the reciprocating shaft4, the oil lip20and the dust lip26are caused to elastically deform radially outwardly more than the state shown inFIG. 1.FIG. 1shows a state in which a sealing device1is not provided around the reciprocating shaft4(the reciprocating shaft4is shown by a dotted line) and does not show deformation of these lips20,26.

A concave portion22A is formed radially inward of the atmosphere-side rigid ring22of the dust seal member12. The concave portion22A is columnar and open on the liquid L side.

The concave portion22A has detachably fitted therein a rigid ring14(intermediate rigid ring14) formed from a rigid body such as a resin (for example, polytetrafluoroethylene) or a metal. In this embodiment, the intermediate rigid ring14is back-up ring and has formed in the center thereof a through-hole into which the reciprocating shaft4is inserted. Further, when the sealing device6is assembled, the intermediate rigid ring14always contacts the liquid-side elastic ring18of the oil seal member10and reinforces the liquid-side elastic ring18.

More specifically, the intermediate rigid ring14is detachably fitted in the liquid-side elastic ring18of the oil seal member10in a concave portion18A formed radially inward of a region near the dust seal member12. As shown in the drawings, at least one groove is formed in the concave portion18A, and a protrusion to be press-fitted in the groove may be formed on the intermediate rigid ring14. Due to the intermediate rigid ring14, it is possible to enhance the pressure resistance and the durability of the sealing device36, and in particular of the oil lip20. In this embodiment, one intermediate rigid ring14is used, but the intermediate rigid ring14may also be configured from a plurality of rigid members.

The atmosphere-side elastic ring24comprises a region24qfixed to the inner peripheral surface of the atmosphere-side rigid ring22, and the intermediate rigid ring14is also caused to contact the region24q.

In this embodiment, the inner diameter of the intermediate rigid ring14is smaller than the inner diameter of a region in the liquid-side elastic ring18of the oil seal member10that contacts the intermediate rigid ring14, and also smaller than the inner diameter of the region24qin the atmosphere-side elastic ring24of the dust seal member12that contacts the intermediate rigid ring14. Accordingly, the rigid ring14is provided between the liquid-side elastic ring18and the atmosphere-side elastic ring24in a direction parallel to the axial direction of the reciprocating shaft4.

In this embodiment, between the liquid-side elastic ring18of the oil seal member10and the atmosphere-side elastic ring24of the dust seal member12, the intermediate rigid ring14, which is separate from the liquid-side elastic ring18and the atmosphere-side elastic ring24, is provided in a direction parallel to the axial direction of the reciprocating shaft4, and the liquid-side elastic ring18is reinforced by the intermediate rigid ring14which is made of a rigid body. The liquid-side elastic ring18which has an oil lip20formed thereon is reinforced by the liquid-side rigid ring16, and the atmosphere-side elastic ring24which has a dust lip26formed thereon is reinforced by the atmosphere-side rigid ring22, and furthermore, the liquid-side elastic ring18is supported by the intermediate rigid ring14, the intermediate rigid ring14being fitted in the concave portion22A of the atmosphere-side rigid ring22fitted in the liquid-side rigid ring16, and being rigidly supported with a strong supporting force by the atmosphere-side rigid ring22and the liquid-side rigid ring16. Due thereto, the liquid-side rigid ring16, the atmosphere-side rigid ring22, and the intermediate rigid ring14work as an integrated rigid body and can firmly reinforce the liquid-side elastic ring18and the atmosphere-side elastic ring24. Therefore, it is possible to enhance the pressure resistance and the durability of the sealing device6, and in particular of the oil lip20.

In this embodiment, the intermediate rigid ring14is detachably fitted in the concave portion18A formed radially inward of the liquid-side elastic ring18. Accordingly, after the intermediate rigid ring14is fitted in the concave portion22A of the atmosphere-side rigid ring22, it is easy to assemble the liquid-side elastic ring18of the oil seal member10to the intermediate rigid ring14.

In the same manner as an intermediate rigid ring47of a third embodiment described below, at least the inner peripheral surface of the intermediate rigid ring14may be formed from a metal that is softer than the outer peripheral surface of the reciprocating shaft4. In this case, it is possible to use the intermediate rigid ring14as a guide for guiding the reciprocal movement of the reciprocating shaft4. In this case, the eccentricity of the sealing device6with respect to the reciprocating shaft4decreases and it is possible to prevent or reduce abrasion of or damage to the lips20,26from becoming significant in places.

In this embodiment, when the sealing device6is provided between the reciprocating shaft4and the inner surface of the shaft hole2A, both the liquid-side elastic ring18and the atmosphere-side elastic ring24always contact the intermediate rigid ring14. Accordingly, when the sealing device6is being used, both the liquid-side elastic ring18and the atmosphere-side elastic ring24are always reinforced by the intermediate rigid ring14.

Furthermore, in this embodiment, between the liquid-side elastic ring18of the oil seal member10and the atmosphere-side elastic ring24of the dust seal member12, the intermediate rigid ring14, which is separate from the liquid-side elastic ring18and the atmosphere-side elastic ring24, is provided in a direction parallel to the axial direction of the reciprocating shaft4, and therefore, it is possible to reduce the size of a gap between the outer peripheral surface of the reciprocating shaft4and the inner peripheral surface of the intermediate rigid ring14. Since this gap is small, there is little risk of the oil lip20or the dust lip26entering this gap with the reciprocal movement of the reciprocating shaft4, even if the pressure of the liquid L is high. Thus, it is possible to further enhance the pressure resistance and the durability of the sealing device6.

Although an elastic material such as an elastomer may be fixed to the inner peripheral surface of the intermediate rigid ring14, such a material is unnecessary and is not provided in this embodiment. Due thereto, there is no risk of an elastic material peeling from the inner peripheral surface of the intermediate rigid ring14, and further, it is possible to set a smaller gap between the intermediate rigid ring14and the reciprocating shaft4.

To produce the oil seal member10, an elastic member comprising the liquid-side elastic ring18, the outer gasket19, and the thin film portion21may, for example, be adhered to the liquid-side rigid ring16using an adhesive. To produce the dust seal member12, the atmosphere-side elastic ring24may, for example, be adhered to the atmosphere-side rigid ring22using an adhesive. Or, the seal member10or12may be produced by arranging the rigid ring16or22inside a mold, pouring a liquid elastic material into the mold, and allowing to harden to form the elastic ring18or24.

Second Embodiment

FIG. 3is a cross-sectional view of a sealing device36according to a second embodiment. Drawings fromFIG. 3onwards show the same constituent elements as those already described, and therefore the same reference signs are used and no detailed description is provided regarding these constituent elements.

This sealing device36comprises, instead of the liquid-side elastic ring18of the first embodiment, a liquid-side elastic ring39which is indirectly attached to the liquid-side rigid ring16. An oil seal member37of the sealing device36comprises: a liquid-side rigid ring16; an outer gasket19fixed in close adherence with the liquid-side rigid ring16; an intermediate elastic ring38fixed in close adherence with the liquid-side rigid ring16; a thin film portion21which couples the outer gasket19and the intermediate elastic ring38; and a liquid-side elastic ring39. The thin film portion21is also fixed in close adherence with the liquid-side rigid ring16.

Although the outer gasket19and the intermediate elastic ring38may be separate, in this embodiment, they are coupled via the thin film portion21. That is, the intermediate elastic ring38, the outer gasket19, and the thin film portion21constitute a continuous integrated elastic portion formed from the same elastic material (for example, an elastomer). In this embodiment, the annular portion16aof the liquid-side rigid ring16is smaller than that of the first embodiment. The intermediate elastic ring38is fixed in close adherence with the inner peripheral surface of the annular portion16a.

Although the liquid-side elastic ring39is formed from an elastic material (for example, an elastomer), it is a separate member from the abovementioned elastic portion and is detachably attached to the intermediate elastic ring38. A V-shaped groove38A is formed on the inner peripheral surface of the intermediate elastic ring38, and a protrusion39aof the liquid-side elastic ring39is fitted in this groove38A.

The liquid-side elastic ring39has formed thereon an oil lip40provided radially inward of the liquid-side rigid ring16. The oil lip40makes sealing contact with the outer peripheral surface of the reciprocating shaft4and prevents or reduces leakage of a liquid from the liquid L side to the atmosphere A side. When the reciprocating shaft4moves in the direction of the central axis C, the reciprocating shaft4slides with respect to the oil lip40.

In this embodiment, too, it is possible to achieve the same effects as those of the first embodiment.

As is clear fromFIG. 1andFIG. 3, the different abovementioned embodiments have the dust seal member12and the intermediate rigid ring14in common, while the details of the oil seal member differ. It is possible to prepare several kinds of oil seal members having different sizes, shapes, structures, or other details, and to select a suitable oil seal member according to the environment in which the sealing device is to be used. That is, in the present invention, the oil seal member, the dust seal member, and the intermediate rigid ring are mutually separate members, and therefore, it is possible to customize the sealing device according to the circumstances. Several kinds of dust seal members having different sizes, shapes, structures, or other details may be prepared and a suitable dust seal member may be selected according to the environment in which the sealing device is to be used. Further, if the oil seal member or dust seal member has degraded due to age, it is possible to exchange only the degraded member.

Third Embodiment

FIG. 4is a cross-sectional view of a sealing device46according to a third embodiment. This sealing device46comprises an intermediate rigid ring47instead of the intermediate rigid ring14, which is a back-up ring, of the first embodiment. The intermediate rigid ring47is detachably fitted in the columnar concave portion22A that is formed radially inward of the atmosphere-side rigid ring22of the dust seal member12and in which the liquid L side is open.

The intermediate rigid ring47is a bush, in other words a circular ring, formed from a rigid body such as a resin or a metal, preferably a metal. The inner peripheral surface of the intermediate rigid ring47is subjected to a smoothing process and it is possible to use the intermediate rigid ring47as a guide for guiding the reciprocal movement of the reciprocating shaft4. Thus, by using the intermediate rigid ring47of the sealing device46as a guide, the eccentricity of the sealing device46with respect to the reciprocating shaft4decreases and it is possible to prevent or reduce abrasion of or damage to the lips20,26from becoming significant in places.

In order to minimize abrasion of the reciprocating shaft4, it is preferable that at least the inner peripheral surface of the intermediate rigid ring47is formed from a metal that is softer than the external peripheral surface of the reciprocating shaft4.

For example, the intermediate rigid ring47may be formed by sintering from a powder of a copper alloy and a powder of an iron alloy. In this case, being formed into a porous body having multiple minute vacancies is more preferable.

Or, the intermediate rigid ring47may be formed from bronze. At least one of lead and polytetrafluoroethylene may also be mixed in the bronze, or the bronze may be impregnated with one of lead and polytetrafluoroethylene.

Or, the intermediate rigid ring47may be formed from aluminum or aluminum oxide. The aluminum oxide may also be impregnated with polytetrafluorothylene.

As shown inFIG. 5, the intermediate rigid ring47may comprise an outer ring47A and an inner ring47B fitted inside of the outer ring47A. It is preferable that the inner ring47B is formed from a metal that is softer than the external peripheral surface of the reciprocating shaft4as described above. It is preferable that the outer ring47A is formed from a metal that has a higher compression strength than the material of the inner ring47B. The number of parts of the intermediate rigid ring47may be three or more.

In this embodiment, too, it is possible to achieve the same effects as those of the first embodiment.

Unlike the first embodiment, in this embodiment the liquid-side elastic ring18of the oil seal member10does not have formed thereon a concave portion (corresponding to the concave portion18A of the first embodiment) for receiving the intermediate rigid ring47. However, the same as in the first embodiment, even in this embodiment when the sealing device46is assembled, the intermediate rigid ring47always contacts the liquid-side elastic ring18and reinforces the liquid-side elastic ring18.

In this embodiment, the intermediate rigid ring47is not fitted in the liquid-side elastic ring18. Accordingly, after the intermediate rigid ring47is fitted in the concave portion22A of the atmosphere-side rigid ring22, it is easy to assemble the liquid-side elastic ring18of the oil seal member10to the intermediate rigid ring47.

Although an elastic material such as an elastomer may be fixed to the inner peripheral surface of the intermediate rigid ring47, such an elastic material is unnecessary and is not provided in this embodiment. Due thereto, there is no risk of an elastic material peeling from the inner peripheral surface of the intermediate rigid ring47, and further it is possible to minimize a gap between the intermediate rigid ring47and the reciprocating shaft4. Since this gap is small, there is little risk of the oil lip20or the dust lip26entering this gap with the reciprocal movement of the reciprocating shaft4, even if the pressure of the liquid L is high, and it is possible to further enhance the pressure resistance and the durability of the sealing device46.

Fourth Embodiment

FIG. 6is a cross-sectional view of a sealing device56according to a fourth embodiment. This sealing device56comprises, instead of the liquid-side elastic ring18of the third embodiment, a liquid-side elastic ring39which is indirectly attached to the liquid-side rigid ring16. An oil seal member37of the sealing device56comprises: a liquid-side rigid ring16; art outer gasket19fixed in close adherence with the liquid-side rigid ring16; an intermediate elastic ring38fixed in close adherence with the liquid-side rigid ring16; a thin film portion21which couples the outer gasket19and the intermediate elastic ring38; and a liquid-side elastic ring39. The thin film portion21is also fixed in close adherence with the liquid-side rigid ring16.

Thus, the fourth embodiment is a modification of the third embodiment, and this modification is the same as the modification in the second embodiment with respect to the first embodiment. For details, see the description of the second embodiment. As shown inFIG. 5, in this embodiment, too, the intermediate rigid ring47may also be configured from a plurality of parts. In this embodiment, too, it is possible to achieve the same effects as those of the third embodiment.

As is clear fromFIG. 4andFIG. 6, the third embodiment and the fourth embodiment have the dust seal member12and the intermediate rigid ring47in common, while the details of the oil seal member differ. It is possible to prepare several kinds of oil seal members having different sizes, shapes, structures, or other details, and to select a suitable oil seal member according to the environment in which the sealing device is to be used. That is, in the present invention, the oil seal member, the dust seal member, and the intermediate rigid ring are mutually separate members, and therefore, it is possible to customize the sealing device according to the circumstances. Several kinds of dust seal members having different sizes, shapes, structures, or other details may be prepared and a suitable dust seal member may be selected according to the environment in which the sealing device is to be used. Further, if the oil seal member or dust seal member has degraded due to age, it is possible to exchange only the degraded member.

Various embodiments of the present invention have been described above, but the above descriptions do not limit the present invention and, in the technical scope of the present invention, various modifications can be considered, including deletion, addition, and exchange of constituent elements.

For example, the present invention is not limited to a shock absorber and may also be applied in a sealing device used in another instrument having a reciprocating shaft such as a hydraulic cylinder device.

The shape of the lips and other details are not limited to the embodiments that are shown. Further, a garter spring may be provided to one or both of the oil seal member and the dust seal member.

REFERENCE SIGNS LIST