Seal for a joint or juncture – Seal between relatively movable parts – Circumferential contact seal for other than piston
Reexamination Certificate
1998-09-03
2001-04-10
Knight, Anthony (Department: 3626)
Seal for a joint or juncture
Seal between relatively movable parts
Circumferential contact seal for other than piston
C277S565000, C277S566000, C277S562000, C277S571000
Reexamination Certificate
active
06213476
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
This invention relates generally to radial lip seals for use with relatively rotatable members such as wheel axle applications, and in particular to lip seals wherein the contacting lip is formed of two dissimilar materials.
2. Related Prior Art
Lip-type fluid seals typically employ a flexible sealing member that is fixed to an outer metallic case and includes one or more sealing lips along a radially inward edge thereof. The selection of the sealing member material is determined by a number of factors, including the environment in which the seal will be operating. Elastomeric materials, such as rubber, are often employed as the sealing lip material in applications where the lip seal is exposed to a dirty environment. For example, seals used in heavy equipment applications for sealing axle bearings are exposed on the air or atmosphere side of the seal to various contaminants which would be harmful to the bearings, including water, salt, and abrasives such as dust, mud, sand, etc. In other applications, contaminants may be present in lubricant on one side of the seal. In either case, elastomers are generally preferred as the sealing lip material over other materials, such as polytetrafluoroethylene (PTFE) materials, as the elastomers are far more resistant to wear under such contaminated conditions than those of the PTFE materials, which generally perform poorly.
Environmental conditions which favor PTFE materials over the elastomers for the selection of the sealing member include low and high temperature and/or dry or low lubricant running conditions. The PTFE materials are generally more wear resistant than elastomers under such conditions.
Difficulties arise, however, when seals operate in environments that favor neither material. For example, in the heavy equipment application described above, it is not uncommon for the seal to be subjected not only to a contaminated environment, but also to low or high temperature and/or low lubricity conditions. In the past, the elastomers were selected over PTFE materials, as the elastomers are more tolerant of low or high temperature and/or low lubricity conditions than are the PTFE materials of a contaminated running condition. Thus, there is a need in the industry for a lip seal that performs well in a contaminated environment and low or high temperature and/or low lubricity operating conditions.
SUMMARY OF THE INVENTION AND ADVANTAGES
A fluid seal assembly for a relatively rotatable member having a cylindrical sealing surface comprises a rigid annular case, a sealing member formed of elastomeric material fixed to the case including an annular seal lip having a contaminated side and an opposite side and an annular elastomeric lip portion disposed on the contaminated side having an annular elastomeric lip edge supported for sealing engagement with the sealing surface of the relatively rotatable member. The invention is characterized by the sealing lip including an insert formed of PTFE material bonded to the elastomeric lip portion in axially adjacent relation thereto on the opposite side of the sealing lip having an annular PTFE lip edge supported for simultaneous sealing engagement with the sealing surface of the relatively rotatable member.
According to a further aspect of the invention, a unitized fluid seal assembly is provided having an outer metal case, an inner wear sleeve, a sealing member having a body formed of elastomeric material fixed to the case including a radially inwardly projecting annular sealing lip having a contaminated side and an opposite side and an elastomeric lip portion having an annular elastomeric lip edge disposed on the contaminated side in sealing engagement with the wear sleeve. The invention is characterized by the sealing lip including a PTFE insert bonded to the lip portion and having an annular PTFE lip edge disposed on the opposite side in simultaneous sealing engagement with the wear sleeve and sealed from the contaminated side by engagement of the elastomeric lip portion with the wear sleeve.
The invention also contemplates a method of manufacturing such fluid seals wherein a PTFE insert is bonded to an elastomeric lip portion to provide a PTFE lip portion. The elastomeric and PTFE lip portions are trimmed to provided common axially adjacent elastomeric and PTFE lip edges disposed on the contaminated and opposite sides, respectively of the seal and supported for simultaneous sealing engagement with a sealing surface of a relatively rotatable member.
The invention thus provides a fluid seal having a sealing lip with a composite elastomeric/PTFE lip edge. The elastomeric lip edge is disposed on the contaminated side of the lip and the PTFE lip edge is disposed on the opposite side of the lip and are support for simultaneous contact with the corresponding sealing surface of a relatively rotatable member, such as a wear sleeve.
Such a composite seal configuration is particularly well suited in applications where the operating conditions favor neither a lip seal fabricated of only elastomeric or PTFE material. In a heavy equipment axle bearing seal application, the elastomeric lip edge on the contaminated side of the sealing lip is exposed to contaminants during operation, while the PTFE lip edge is on the opposite side shielded from the contaminating atmosphere by the elastomeric lip edge. In operating conditions where, in addition to the contaminating environment, there exists also low or high temperature and/or low lubricity operating conditions, the PTFE lip edge comes into play to maintain a good fluid seal with the sealing surface of the relatively rotatable member. The simultaneous contact of the wear-resistant PTFE lip edge advantageously limits the degree of wear of the elastomeric lip edge to that of the PTFE lip edge, thereby enabling the elastomeric lip edge to continue shielding the PTFE lip edge from contaminants even under unfavorable conditions of extreme temperatures and/or low lubricity conditions.
A further advantage of the PTFE/elastomeric lip edge combination is that the PTFE material has a higher modulus of elasticity than that of the elastomeric material. During operation, reversible hydrodynamic surface deformations are imparted to the elastomeric lip portion to assist in the exclusion of contaminants. It has the further advantage of providing such hydrodynamic aids without having to form them during the manufacturing process. This simplifies the manufacture of such seals, particularly those requiring bi-directional hydrodynamic capabilities. Still a further advantage is that the bi-modulus imparted hydrodynamic surface deformations are not permanent like those of the molded, embossed, or cut type, which are prone to entrapping contaminants thereby reducing the effect of the hydrodynamic features and in some cases causing premature wear of the seal and/or scoring of the sealing surface of the relatively rotatable member.
REFERENCES:
patent: 4274641 (1981-06-01), Cather
patent: 4300777 (1981-11-01), Symons
patent: 4822058 (1989-04-01), Butler et al.
patent: 4969653 (1990-11-01), Breen
patent: 5183271 (1993-02-01), Wada
patent: 5431872 (1995-07-01), Sink
patent: 5577741 (1996-11-01), Sink
patent: 5649710 (1997-07-01), Kanda
patent: 6050570 (2000-04-01), Otto
Carr Stephen J.
Chandler Jon A.
Drake Gary B.
Federal-Mogul World Wide Inc.
Knight Anthony
Peavey Enoch E
Reising Ethington, Barnes, Kisselle, Learman & McCulloch, P.C.
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