Seal for a joint or juncture – Seal between relatively movable parts – Relatively rotatable radially extending sealing face member
Reexamination Certificate
2000-04-06
2001-10-23
Mah, Chuck Y. (Department: 3626)
Seal for a joint or juncture
Seal between relatively movable parts
Relatively rotatable radially extending sealing face member
C277S379000, C277S370000, C277S373000
Reexamination Certificate
active
06305693
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to a rotary shaft seal and more particularly to a shaft seal suitable for high speed operations. The invention is further directed to a rotary seal of the type described wherein the face pressure with which the moving part contacts the stationery seal face may be set with precision. The invention is further directed to a seal assembly characterized in that it may be readily mounted and de-mounted from the drive shaft and wherein the substitute sacrificial moving part may be readily installed without the necessity of returning the seal assembly to the factory.
2. Description of the Prior Art
The use of rotary seals has, by and large, replaced the use of stuffing box seals. In a conventional rotary seal, a rotating member is pressed against a static surface whereby fluids are precluded from passing through the interface between the static and rotating components of the seal.
Rotary seals are capable of accommodating a significant degree of shaft eccentricity, a capability not found in stuffing boxes.
In high-speed applications, it is desirable that the rotary component of the seal engage the static component with a precisely determined force. In order to provide a long working life, since wear is significant in seals of this sort, it is conventional to employ as a rotary component wear-resistant substances such as carbides, sintered carbon, etc. A deficiency of such substances is their susceptibility to chipping or cracking unless handled with extreme care. In view of the fragility of such substances, a significant amount of damage occurs in the course of shipping and handling the fully assembled seal.
Conventional seals of the type described typically comprise a mounting collar adapted to be coupled to the shaft and a seal-face carrier member. The seal-face carrier is shiftable axially relative to the drive collar. Drive fingers extend from the collar to the seal-face carrier to provide a rotary driving connection between the two components. The respective components are biased apart by a plurality of coil springs, the respective ends of which are mounted in aligned apertures in the collar and seal-face carrier.
As will be apparent from the foregoing, when the seal-face is worn to the point that an unacceptably low sealing force is exerted, it is necessary to separate the seal-face from the collar and substitute a new seal carrier member. This substitution involves aligning the ends of each of the springs (often 20 or more) with a pair of the opposed apertures in the seal-face and the mounting collar. The complexity of effecting this re-mounting usually requires the return of the entire assembly to the factory.
PRIOR ART
The most closely related prior art is considered to be a seal manufactured by the A.W. Chesterton Company of Stoneham, Mass. and is identified by that company as the 880 seal. This seal employs a structure as generally described above including sixteen coil springs interposed between the drive collar and the seal carrier rings. A drive connection between the mounting collar and the seal carrier is provided by fingers on the carrier extending into slots on the collar.
Also relevant are rotary seal structures assigned to or licensed to the assignee of the instant application, namely U.S. Pat. No. 5,409,241 disclosing a double seal-faced arrangement wherein seal-face pressure is generated by axial expansion of an elastomeric ring, U.S. Pat. Nos. 3,988,026; 4,217,980; 4,365,707; 4,809,992 and 4,822,056 all of which refer to rotary shaft seals utilizing elastomeric expansion to generate seal face force.
SUMMARY OF THE INVENTION
The present invention may be summarized as directed to a simple and readily installed and refurbished rotary seal assembly. More particularly the invention is directed to a single-face seal assembly wherein the rotary seal face is urged against the stationery seal face by a plurality of coil springs aligned with the shaft axis, the springs being radially spaced about the shaft. The springs are mounted over drive fingers which extend axially and are slideably mounted within complemental apertures formed in the drive collar. The outer ends of the drive pins are slideably received in complemental apertures formed in the portion of the rotating seal face remote from the stationery seal. The inner ends of the drive fingers are fixed to an annular ring spaced inwardly from the collar.
The described structure includes numerous advantageous not found in known seal structures. Specifically, in order to achieve a precise seal face pressure it is possible, at the factory, to compress the springs to a precisely desired amount and interpose a removable clip or tab between the collar and the annular ring spaced inwardly from the collar. The spring force will retain the clips or tabs in position until after installation is effected, following which removal the of the tabs will result in application of the desired quantum of pressure.
A further and important advantage of the described seal resides in the fact that the drive fingers extend slideably into complemental apertures formed in the rotating seal member, the rotating seal being endwisely removable and replaceable without the necessity of aligning springs. This is so since the springs are captured between the drive collar and a pusher ring through which the pins pass.
It is accordingly an object of the invention to provide a rotary seal which may be factory set to exert a predetermined pressure following mounting. A further object of the invention is the provision of a seal of the type described wherein the rotary seal component may be endwisely removed from the remaining components of the seal. The facile endwise removability and replaceability of the rotary seal component enables the rotary seal to be separately packaged for shipment, reducing the susceptibility of damage to the fragile seal face component. A further object of the invention is the provision of a device of the type described wherein a new rotary seal component may be readily applied without the use of jigs or like-assembly devices since the rotary component may be simply axially slipped over the projecting ends of the drive fingers. In the device of the invention, the drive fingers serve the multiple purposes of providing a driving connection between the shaft and the rotary seal component and as a mounting guide for the springs.
REFERENCES:
patent: 2374353 (1945-04-01), Jacobson
patent: 2571035 (1951-10-01), Hastings
patent: 5188377 (1993-02-01), Drumm
patent: 5275421 (1994-01-01), Hornsy
patent: 5863047 (1999-11-01), Ellis
patent: 6017036 (2000-11-01), Murphy
Magidoff Barry G.
Mah Chuck Y.
Peavey Enoch E
Sutton Paul J.
Woodex Bearing Company, Inc.
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