Seal for a joint or juncture – Seal between relatively movable parts – Diverse and distinct dynamic seals
Reexamination Certificate
1998-10-23
2001-04-03
Knight, Anthony (Department: 3626)
Seal for a joint or juncture
Seal between relatively movable parts
Diverse and distinct dynamic seals
C277S377000, C277S377000, C277S402000, C277S394000
Reexamination Certificate
active
06209879
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a sealing apparatus used in a shaft sealing section of various devices and appliances, particularly a sealing apparatus provided with a sealing lip made of a rubber-like elastic material and a sealing lip made of a resin.
2. Description of the Related Art
A conventional sealing apparatus of this type comprises a metal ring having a cylindrical portion and an inward flange portion folded from the open-air side end of this cylindrical portion radially inward, a first sealing member, made of a rubber-like elastic material, formed integral with the metal ring, and a second sealing member, made of a resin material, held between the inward flange portion of the metal ring and the first sealing member. The first sealing member has a first sealing lip which extends to the axial direction sealing liquid side and has a lip leading end slidably in sealing contact with the surface of a rotary member. The second sealing member has a second sealing lip which is located in a gap between the open-air side surface of the first sealing lip and the rotary member and has an inner periphery slidably in sealing contact with the surface of the rotary member.
The second sealing lip made of resin supports the first sealing lip, and inhibits an excessive deformation of the first sealing lip when pressure of the sealing liquid becomes excessively high. Double sealing is ensured by the first sealing lip and the second sealing lip by causing the inner periphery of the second sealing lip to come into sealing contact with the rotary member.
In the conventional art as described above, however, the first sealing lip made of rubber is easily susceptible to wear, and cannot sufficiently prevent leakage of the sealing liquid.
Leakage of the liquid having leaked from the first sealing lip on the open air side is prevent to some extent by the second sealing lip of resin. However, the main role of the second sealing ring made of resin is to inhibit deformation of the first sealing lip made of rubber, resulting in an insufficient sealing property.
The second sealing lip made of resin, requiring rigidity to some extent with a view to fully causing it to display the deformation inhibiting function of the first sealing lip, is poor in flexibility and has only an insufficient follow-up property relative to axial eccentricity of the rotary member.
Since the first sealing lip has a foot shape which permits only drawing a curvature simply from the radial direction to the axial direction, the bend at the foot of the second sealing lip made of resin bending along such a curvature has only a small degree of freedom of bending.
This causes an increase in tension with the rotary member upon occurrence of axial eccentricity, accelerating wear, and produced wear powder of the resin causes deposition of sludge. This forms a cause of occurrence of liquid leakage from interruptions of the lip line of the second sealing lip made of resin.
The deformation inhibiting function of the first sealing lip provided by the second sealing lip made of resin is limited to a certain extent, and deformation of the first sealing lip under a high sealing liquid pressure cannot sufficiently be inhibited.
SUMMARY OF THE INVENTION
The present invention was developed to solve the above-mentioned problems in the conventional art, and has an object to provide a sealing apparatus having a simple configuration and excellent in air-tightness.
Another object of the invention is to provide a sealing apparatus capable of improving eccentricity follow-up property of a second sealing lip made of a resin.
Still another object of the invention is to provide a manufacturing method of a sealing apparatus which facilitates fabrication of the second sealing lip, permits high-accuracy assembly in the manufacturing process, and allows to display a satisfactory sealing property.
To achieve the above objects, the present invention provides, in one aspect, a sealing apparatus, which is applied to a rotary member, comprising:
a metal ring having a cylindrical portion and an inward flange portion extending radially inward from an open-air side end of the cylindrical portion;
a first sealing member made of a rubber-like elastic material, the first sealing member having a radial portion connected to the cylindrical portion and disposed to a portion opposing to the inward flange portion of the metal ring and a first sealing lip axially extending from the radial portion to a sealing liquid side and having a lip leading end tightly contacting a surface of the rotary member to be slidable;
a second sealing member made of a resin material, and having a flange-shaped interposed portion held between the inward flange portion of the metal ring and the radial portion of the first sealing member and a second sealing lip extending from an inner-diameter end portion of the flange-shaped interposed portion towards the axial sealing liquid side and being positioned in a gap defined between the open-air side of the first sealing lip and the rotary member so that an inner peripheral portion thereof tightly contacts the surface of the rotary member to be slidable;
a first screw pump means provided on a sliding surface of the first sealing lip and adapted to provide a pumping function for transporting a liquid between sliding surfaces under an effect of a rotational sliding motion to the rotary member; and
a spiral or ring-shaped slit groove formed on the sliding surface of the second sealing member.
Therefore, even when wear of the first sealing lip progresses and the sealing liquid leaks to the open-air side, the liquid is pushed back by the first pump acting portion. Further, when the liquid leaks from the first sealing lip to the open air side, seal is provided by the spiral slit groove or a plurality of annular slit grooves arranged on the sliding surface of the second sealing lip. In the case of the spiral slit groove, the liquid is returned to the sealing side by the action of the screw pump. In the case of the annular slit grooves, on the other hand, a peak of surface pressure occurs for each slit groove, and this provides a higher sealing property than in the type with no groove.
Formation of the slit groove(s) on the sliding surface of the second sealing lip leads to a decrease in rigidity of the second sealing lip under the effect of the slit groove(s) and a higher follow-up property for the axial eccentricity of the second sealing lip. Because this configuration comprises only slits (cuts), even forming in a spiral shape can give a high sealing property at standstill. When annular slit grooves are formed it is possible to completely seal leakage at standstill.
The first screw pump acting portion should preferably have a configuration in which a plurality of screw slots inclining in opposite directions relative to a plane including a center axis are arranged in the circumferential direction, and a spiral slit groove should preferably be provided on the second sealing lip.
This combination is selected for improving sealing properties including durability.
More specifically, the screw slots inclining in the opposite directions of the first sealing lip displays a pumping function for rotation in the both directions of the rotary member. The screw slots has an object to increase the amount of pumping, and the amount of pumping is larger in the one-direction screw than in the two-direction screw [amount of pumping: one-direction screw>two-direction screw>no screw]. Wear resistance is the most excellent in the absence of screw, followed by the two-direction screw and then the one-direction screw, in this order (wear resistance: one-direction screw<two-direction screw<no screw). For the first sealing lip made of rubber, therefore, the two-direction screw giving a good balance between the amount of pumping and wear resistance is selected.
The spiral slit groove of the second sealing lip, on the other hand, in which sealing is in only one direction, provides an advantage of improving s
Ikeda Yasuhiro
Mizunoya Koichi
Munekata Shinobu
Watanabe Tatuhiko
Yamanaka Satoshi
Armstrong, Westerman Hattori, McLeland & Naughton
Eagle Industry Co. Ltd.
Knight Anthony
Williams Mark
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