Seal for a joint or juncture – Seal between relatively movable parts – Relatively rotatable radially extending sealing face member
Reexamination Certificate
1998-04-17
2001-05-01
Knight, Anthony (Department: 3626)
Seal for a joint or juncture
Seal between relatively movable parts
Relatively rotatable radially extending sealing face member
C277S361000, C277S388000
Reexamination Certificate
active
06224061
ABSTRACT:
This invention relates to mechanical seals and especially to non-metallic mechanical seals.
A mechanical shaft seal for separating a first liquid fluid from a second fluid includes a rotary assembly for mounting on a rotatable shaft for rotation therewith and a stationary assembly for securing to a fixed structure within which the rotary assembly is located. Such a seal includes a “floating” component which is mounted axially movably around the rotary, shaft of, for example a pump and a “static” component which is axially fixed, typically being secured to a housing. The floating component has a flat annular end face or seal face which is directed towards a complementary seal face of the static component. The floating component is urged towards the static component, usually by means of one or more springs, to close the seal faces together to form a sliding face seal. One of the floating and static components forms part of the rotary assembly and the other forms part of the stationary assembly.
Those seals whose floating component form part of the rotary assembly are described as rotary seals. If the floating component forms part of the stationary assembly the seal is referred to as a stationary seal.
If the sliding seal between the rotary and stationary components are assembled and preset prior to despatch from the mechanical seal manufacturing premises, the industry terminology for this is “cartridge seal”. If the rotary and stationary components are despatched individually (unassembled) from the mechanical seal manufacturing premises, the industry terminology for this is “component seal”.
Non-metallic mechanical seals commonly have, as a minimum, the “wetted” components (the components which are in contact with the sealed product) manufactured using a non-metallic material.
Non-metallic mechanical seals are therefore employed when the sealed product attacks metallic materials.
A non-metallic mechanical seal may include a non-metallic end cap associated with the rotary assembly and which separates the sealed product from other components of the seal, particularly those components which are metallic. However such a non-metallic end cap is prone to distortion due to the hydraulic forces acting on it being unbalanced, that is to say different at one longitudinal end of the end cap compared with the other end.
According to the present invention there is provided a mechanical shaft seal for separating a first liquid from a second fluid comprising:
(a) a rotary assembly for mounting on a rotatable shaft for rotation therewith;
(b) a stationary assembly for securing to a fixed structure within which the rotary assembly is located;
(c) said rotary assembly and said stationary assembly each carry a respective mating seal face;
(d) one of said seal faces being located on a floating component mounted for axial movement with respect to said shaft;
(e) means for urging the floating component in a direction towards the other of said seal faces; and
(f) a non-metallic end cap which, in use, separates the first fluid from other components of the seal and which is arranged such that, in use, it is subjected to substantially balanced hydraulic loading.
Preferably the end cap is secured to the rotary assembly and sealing means are located between said end cap and said rotary assembly, said sealing means being positioned such that hydraulic pressure from said first fluid is exerted substantially equally on opposed longitudinal ends of said end cap. The sealing means preferably comprise first and second sealing members associated with respective first and second longitudinal ends of the end cap, said sealing members bearing against surfaces which are equally distanced from the longitudinal axis of the shaft seal.
The second fluid may be a gas or a liquid. In the case where it is a liquid, it is preferred that further sealing means are located between said end cap and said rotary assembly, said further sealing means being positioned such that hydraulic pressure from said second fluid is exerted substantially equally on opposed longitudinal ends of said end cap. Preferably the further sealing means comprise a third sealing member associated with a longitudinal end of the end cap, said first and third sealing members bearing against surfaces which are equally distanced from the longitudinal axis of the shaft seal.
A shaft seal of the present invention may be of rotary or a stationary mechanical seal. Furthermore it may be a single, double or triple mechanical seal.
A shaft seal of the invention may incorporate a barrier fluid system in which case the second fluid is a barrier fluid.
REFERENCES:
patent: 4509762 (1985-04-01), Garrett
patent: 4538820 (1985-09-01), Duffee
patent: 5067733 (1991-11-01), Nagai et al.
patent: 5213340 (1993-05-01), Aziber et al.
patent: 5324048 (1994-06-01), Carmody
patent: 5441282 (1995-08-01), Ciotola
patent: 5667356 (1997-09-01), Whittier et al.
patent: 5713576 (1998-02-01), Wasser et al.
patent: 5727792 (1998-03-01), Rockwood
patent: 5794939 (1998-08-01), Parkin
patent: 2325031 (1998-11-01), None
patent: 55-051166 (1980-04-01), None
AES Engineering Limited
Knight Anthony
Myers Bigel & Sibley & Sajovec
Pickard Alison K.
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