Seal for a joint or juncture – Seal between relatively movable parts – Piston ring or piston ring expander or seat therefor
Reexamination Certificate
2000-10-05
2002-09-24
Knight, Anthony (Department: 3626)
Seal for a joint or juncture
Seal between relatively movable parts
Piston ring or piston ring expander or seat therefor
C277S928000
Reexamination Certificate
active
06454273
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an improvement of a seal structure, particularly a seal structure to be used with a hydraulic cylinder or the like.
BACKGROUND ART
Heretofore, there have been seal structures of a bearing section of a hydraulic cylinder or the like which has been disclosed in Japanese Utility Model Laid-Open Publication No. Hei 4-138160 and in which a backup ring is installed so as to prevent a heel section of a seal ring from projecting, and which has been disclosed in Japanese Patent Publication No. Hei 6-100202 and in which an unloading pressure control valve (buffer ring) is provided so as to reduce a pressure which acts on a seal ring.
However, in such conventional seal structures, for example, in the one which is disclosed in Japanese Utility Model Laid-Open Publication No. Hei 4-138160, the inner diameter and the outer diameter of an insertion groove of the seal ring are parallel to each other. A pressure receiving area of the seal ring in an axial direction extends over an entire surface of the inner diameter and outer diameter of a lip, whereby a supporting area of the heel section is almost the same as the pressure receiving area.
Thus, there have been problems such that a pressure of the heel section becomes high when a pressure is high and a deformation projecting into a sliding surface and a pressure grade to the sliding surface are great. Thus, a capacity of scraping of a hydraulic operating fluid film is great and oil leakage arises resulting from the scraping.
Further, the constitution is such that the higher a pressure becomes, the greater the capacity of scraping of a hydraulic operating fluid film becomes. Therefore, there will be problems such that a sliding section enters a non-lubricating state, friction increases, further frictional heat arises, thermal decomposition of the sliding section arises, and abnormal abrasion arises.
Further, in the constitution which is disclosed in Japanese Patent Publication No. Hei 6-100202 and in which the buffer ring and the seal ring are combined, the buffer ring is not constituted such that the buffer ring is completely airtight so as to secure a hydraulic operating fluid film. Therefore, there will be problems such that for example, in a flow regenerative circuit in which the pressure of an oil room on the side of a rod becomes high in either case of the expansion and shrinkage of a hydraulic cylinder, a pressure between the seal ring and the buffer ring is accumulated and it is impossible to prevent a high pressure from acting on the seal ring when a load pressure operates for a long period of time.
An object of the present invention is to provide a seal structure which solves these problems.
DISCLOSURE OF THE INVENTION
In order to solve the problems mentioned above, the present invention is made and characterized in that in seal structure which is composed of a sliding member, a supporting member for supporting the sliding member slidably, and a seal ring provided between the sliding member and the supporting member, the seal ring is stored in a storage concavity section and has a lip section on which a pressure of a hydraulic operating fluid acts and a heel section for supporting on a side wall surface of the storage concavity section a pressure which acts on the seal ring, and an annular pressure receiving area between an inner circumference and an outer circumference of the lip section is rendered to be smaller than an annular supporting area between an inner circumference and an outer circumference of the heel section.
The constitution is such that the seal ring is provided either at the supporting member or the sliding member.
Thus, since the pressure receiving area of the lip section is smaller than the supporting area of the heel section, when a pressure of the hydraulic operating fluid acts on the lip section, thrust to deform the seal ring becomes small. Moreover, since the supporting area of the heel section is larger than the pressure receiving area of the lip section, a pressure which arises at the heel section is reduced. Thus, it is possible to prevent the heel section from projecting into a sliding surface, whereby reliability on resistance to oil leakage can be enhanced. Further, since a pressure of the heel section can be reduced in a constant ratio, it is possible to prevent the heel section from coming into contact with the sliding surface when a high pressure acts and the friction can be reduced. Also, since a pressure of the heel section is rendered to be small, it is possible to make a critical working pressure of the seal ring higher and to eliminate a pressure reducing mechanism, such as a buffer ring. Therefore, a size of the seal in a sliding direction can be reduced and entire seal structure can be miniaturized. Since a shape of the seal is not symmetrical, it is possible to expect such effects that an error in assembling the seal ring can be prevented and sealing performance can certainly be secured.
Since the heel section of the seal ring is composed of a tapered surface which is away from the lip section in an opposite direction toward the sliding surface of the seal ring, deformation force of the seal is released in a direction of a bottom of a groove when a high pressure acts on the seal, the pressure is more uniformly distributed over the supporting surface, and it is possible to prevent the heel section from projecting into or sticking to the sliding surface.
It is constituted such that the heel section of the seal ring and a retaining member to retain the heel section are provided at the storage concavity section, and a space which becomes larger in an opposite direction toward the sliding surface of the heel section is provided when a pressure of a hydraulic operating fluid is not acting on a contact surface of the heel section and the retaining member. Therefore, the seal is certainly deformed in an opposite direction toward the sliding surface and a deformation of the seal on the sliding member side is suppressed, whereby a pressure and a pressure grade to the sliding member is hardly affected by a working pressure and a very stable sealing function can be realized.
It is constituted such that a tapered surface is formed at an outer circumference of a middle section which connects the lip section and the heel section of the seal ring. Therefore, a pressure of the lip section does not directly act on the supporting surface of the heel section, the distribution of a pressure is dispersed along the tapered surface, and it is possible for the heel section to have a uniform distribution of the pressure extending over an entire supporting surface of the heel section.
There is provided a hydraulic operating fluid draining groove for leading to the heel section a hydraulic operating fluid which exists between the tapered surface of the middle section and an inner circumferential section of the storage concavity to store the seal ring. Therefore, even though a high pressure which acts on the lip section leaks out to the tapered surface, it is possible to discharge the pressure to the side of the heel section under an atmospheric pressure using the hydraulic operating fluid draining groove. Thus, it is possible to prevent the tapered surface from being added to a pressure receiving area of the lip section on which a high pressure acts.
A space is provided between an inner circumference on the heel section side and a piston rod, and also a predetermined space for absorbing a deformation of the seal ring is formed between an outer circumference of the heel section and an inner circumference of the storage concavity section.
A space is provided between an inner circumference on the heel section side and the piston rod, a pressure receiving area of the lip section and a supporting area of the heel section are almost identically formed, and a predetermined space for absorbing a deformation of the seal ring is formed between an outer circumference of the heel section and an inner circumference of the storage concavity section.
It is constituted such that a total
Hara Sadaaki
Kanda Masahide
Kashima Mituhiro
Mitushima Koji
Beres John L.
Kayaba Kogyo Kabushiki Kaisha
Knight Anthony
Rabin & Berdo
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