Seal for a joint or juncture – Seal between relatively movable parts – Circumferential contact seal for other than piston
Reexamination Certificate
2000-02-11
2001-07-24
Dayoan, B. (Department: 3626)
Seal for a joint or juncture
Seal between relatively movable parts
Circumferential contact seal for other than piston
C277S572000
Reexamination Certificate
active
06264205
ABSTRACT:
The present invention generally relates to cartridge rotary seals that are pressed into a housing and provide a seal around a shaft at relatively low pressures under various fluid environments. More particularly, the present invention is directed to cartridge seals utilizing a separate metal retaining ring which provides axial and radial stress within a plastic sealing ring.
Cartridge rotary seals have been used for many years in a variety of applications for the sealing of various types of fluids and gases. Generally these seals use an elastomer as the seal material and such elastomer is molded and bonded to a supporting metal ring.
The materials described in this application utilize various types of plastics, such as ploytetrafluoroethylene PTFE because it exhibits relatively low friction and it is chemically inert and can withstand a variety of temperatures, thus enabling their use under conditions with no lubrication. Other plastic materials may be used, such as ultra high molecular weight polyethylene, but it has limited temperature capabilities and limited chemical compatibility with a high degree of friction.
The prior art cartridge seals utilized the elastomer in a bonded relationship and continuous tube bears around the shaft.
As here above noted, when plastics are utilized, like PTFE, the plastic is mechanically retained to the metallic ring and the entire assembly is pressed into the housing with a high degree of interference between the OD of the seal and the housing to permit retention of the seal assembly into the housing and at the same time, providing static sealing against the housing. Dynamic sealing between the seal and the shaft is provided by the contact between the plastic and the shaft.
A common problem with the prior art is that the elastomer when subjected to heat, produced a high degree of friction and wear and also have limited chemical compatibility that limits the life of the seal and can cause seal failure.
The present invention provides for a rotary cartridge seal including a separate plastic ring and retainer which are uniquely locked together in order to provide a residual force therebetween in order to maintain the components together within specific temperature parameters.
SUMMARY OF THE INVENTION
A rotary cartridge seal in accordance with the present invention generally includes a cold flowable plastic ring having a body for sealably engaging a housing bore and a lip for sealably engaging a shaft rotating within the housing bore. Importantly, as hereinafter discussed in greater detail, the usable plastic material must be cold flowable, such as, for example, polytetrafluoroethylene, PTFE. Compositions of PTFE and UHMW (ultra high molecular weight polyethylene). The use of these materials enable appropriate cold flow plastic to maintain radial and axial stability of the plastic ring between the housing and the shaft.
A separable metal retainer provides means for fixing the plastic ring within the housing bore and around the shaft. The separable metal retainer includes a surface of revolution with a rear portion having a diameter suitable for press fitting into the housing bore and a front portion of lesser diameter ending in a ring.
An internal groove is provided in the plastic ring body for engaging the metal ring therein in order to latch the plastic ring and metal ring together with a residual stress in a radial direction in the plastic ring body. This residual stress is created and maintained by specific configuration of the retainer. Specifically, the metal retainer includes a spring portion for providing the radial stress.
REFERENCES:
patent: 3037781 (1962-06-01), Peras
patent: 3658395 (1972-04-01), Hallerback
patent: 4053166 (1977-10-01), Domkowski
patent: 4335887 (1982-06-01), Benassi
patent: 5062648 (1991-11-01), Gomringer
patent: 5813676 (1998-09-01), Antonini et al.
patent: 6076645 (2000-06-01), Winkelmann et al.
Bal Seal Engineering Co., Inc
Beres John L.
Dayoan B.
Hackler Walter A.
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