Seal for a joint or juncture – Seal between relatively movable parts – Circumferential contact seal for other than piston
Reexamination Certificate
1997-01-21
2001-05-01
Mah, Chuck Y. (Department: 3626)
Seal for a joint or juncture
Seal between relatively movable parts
Circumferential contact seal for other than piston
C277S641000, C277S643000, C277S644000, C251S306000
Reexamination Certificate
active
06224064
ABSTRACT:
BACKGROUND—FIELD OF INVENTION
This invention relates to seal designs used in butterfly valves.
BACKGROUND—DESCRIPTION OF PRIOR ART
Many butterfly valve designs have been implemented which incorporate the basic attribute of a disc which has an outside contour of a section of a sphere which imposes a compressive deformation on a surrounding plastic or elastomeric ring shaped seat when it closes in order to effect the seal. Unfortunately, all such designs are subject to loss of valve seal during use due to seat wear occurring during repetitive open to close cycling and/or due to compressive set of the seat which can be caused by material compressive and or hoop tension creep, seat contraction or expansion and concurrent material softening or hardening due to temperature changes, disc movement during high pressure application and/or disc/seat misalignment. These conditions will cause loss of seat sealing force which will limit the valve life and operating conditions. The disclosed
FIG. 1
design is intended to greatly remedy these problems. To explain the benefits of the disclosed invention, a detailed description of how the various modes of operation of a spherical disc butterfly valve can lead to seal damage is provided. Before this detailed description is provided, a brief description of the disclosed
FIG. 1
design is given.
OBJECTS AND ADVANTAGES
The subject butterfly valve seal as shown in
FIG. 1
is designed for use on a butterfly valve with a spherical disc as shown in
FIGS. 4 through 6
or other suitable valve. This seal
11
has several advantages over the other currently used seal designs for this type of valve.
The
FIG. 1
seal
11
is unique in that it combines the features of a fixed side of the seal base on the valve preferred side with a cavity on the other side of the base which contains a resilient, compressed spring or bushing
12
.
The compressed region of the base of the seal
11
provides secure restraint of the seal
11
in the valve body. Also, the seal
11
has a lip above the groove on the side opposite the fixed region which is cupped by a lip on the retainer
13
. Together, the lip and fixed region of the seal
11
provide secure restraint of the seal
11
such that it will not dislodge due to flow impingement in either direction or extrude into the gap between the disc
15
and the valve when the disc
15
is not full closed but accumulating pressure such that the seal
11
would otherwise extrude into the gap between the disc
15
and the valve body
16
.
Moreover, and uniquely beneficial, the seal design provides a fixed portion about which the remainder of the ring shaped seal
11
can cantilever flex in a toroidal manner. The toroidal flexure is resisted by the bushing or spring mechanism
12
contained in the cavity on the opposite side of the base of the seat
11
. The combined resistance to toroidal flexure is thereby achieved by a combination of cantilevering of the seal
11
about its fixed base region and the simultaneous radial force developed by the compressed and/or dilated bushing or spring
12
which is contained in the radially expanding and/or sectionally decreasing cavity region upon disc
15
closure. This combination of a fixed region of the seat
11
base adjacent to a cavity region containing a spring or bushing
12
which is compressed and/or expanded in diameter due to flexure of the seat
11
about the opposite fixed region of the seat base is the essential claim herein. In addition to this claim, several attributes of the design have been arrived at which enable the arrangement to be installed easily, to be secured in the valve firmly, to enable it to work properly are part of the subject invention. The design provides a cavity feature which would facilitate secure and easy installation of the seal
11
while effecting spring/bushing
12
pre-compression in the cavity.
REFERENCES:
patent: 3654950 (1972-04-01), Hamm
patent: 3718338 (1973-02-01), Traub
patent: 4513765 (1985-04-01), Rishovd et al.
patent: 2605189 (1976-08-01), None
patent: 2031124 (1980-04-01), None
patent: 2121513 (1983-12-01), None
patent: 0157867 (1982-09-01), None
Ackerman William
Mah Chuck Y.
St. Germain Stephen V.
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