Seal for a joint or juncture – Seal between fixed parts or static contact against... – Contact seal for other than internal combustion engine – or...
Reexamination Certificate
2001-12-27
2004-05-18
Pickard, Alison K. (Department: 3676)
Seal for a joint or juncture
Seal between fixed parts or static contact against...
Contact seal for other than internal combustion engine, or...
C277S644000, C277S650000, C277S910000, C220S234000, C220S239000
Reexamination Certificate
active
06736407
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to fluid seals, and in particular, to devices and systems for sealing fluids at very high pressures.
2. Description of the Related Art
Sealing fluids at extremely high pressures, i.e., pressures in excess of 15,000 psi, can be extremely difficult and complicated.
FIG. 5
illustrates a high pressure seal according to the prior art. In the illustrated example, a plug
10
is engaged with a cylinder wall
12
having a circular mouth. An exterior surface
14
of the plug
10
is closely conformed to an interior surface
16
of the cylinder wall
12
. A circular gap
18
is formed between the plug
10
and the cylinder wall
12
. An annular recess
20
is formed in the external surface
14
of the plug
10
at a distal end
22
of the plug.
A metallic ring
24
with a triangular cross-section is positioned within the recess
20
with its right-most edge
26
abutting a complementary angled wall
28
of the recess. The metallic ring
24
is sized to slide with the plug
10
with respect to the internal surface
16
of the cylinder wall
12
when the system is not pressurized. This allows the plug
10
to be inserted and removed from the cylinder wall
12
to provide access to a cavity
30
.
A polymeric backup ring
32
(sometimes referred to as a seal) is positioned to the left of the metallic ring
24
, as viewed in FIG.
5
. An angled, left-most edge
34
of the metallic ring
24
abuts a complementary tapered edge
36
on the polymeric backup ring
32
.
An O-ring
38
is positioned on the side of the polymeric backup ring
32
opposite the metallic ring
24
. The O-ring
38
is large enough to extend from the recess
20
to the internal surface
16
of the cylinder wall
12
. The O-ring
38
seals the cavity
30
.
When a fluid in the cavity
30
is pressurized, the O-ring
38
is urged against the polymeric backup ring
32
which, in turn, is urged against the metallic ring
24
. The tapered edge
36
of the polymeric backup ring
32
presses against the angled, left-most edge
34
of the metallic ring
24
, creating an upward force that urges the metallic ring against the internal surface
16
of the cylinder wall
12
. In addition, as the metallic ring
24
is urged toward the right, as viewed in
FIG. 5
, the wall
28
of the recess
20
also urges the right-most edge
26
of the metallic ring upward against the internal surface
16
of the cylinder wall
12
. In addition, the pressurized fluid operates on the left-most edge
34
of the metallic ring
24
, adding to the force urging the metallic ring against the internal surface
16
of the cylinder wall
12
.
As a result of the combined forces described above, the metallic ring
24
is urged against the internal surface
16
of the cylinder wall
12
with a very high force. As a result, the force the metallic ring
24
exerts on the internal surface
16
is so great that relative movement between the two galls and scratches one or both of the contacting surfaces.
When the fluid in the cavity
30
is pressurized to extremely high pressures (i.e., over 15,000 psi), or more so when the fluid is pressurized to even greater pressures (e.g., over 75,000 psi or over 100,000 psi), the cylinder wall
12
expands outward and the plug
10
compresses toward the right as viewed in FIG.
5
. The expansion and movement of these parts results in relative movement between the metallic ring
24
and the internal surface
16
of the cylinder wall
12
. Every time the pressure in the cavity
30
is cycled, the metallic ring
24
expands and contracts, further galling and scratching either the metallic ring and/or the cylinder wall
12
. Eventually, scratches or other damage allows fluid to escape from the cavity
30
, ultimately resulting in seal failure. In addition, it has been recorded that after a number of cycles, the metallic ring
24
can become lodged against the cylinder wall
12
, requiring further repair and replacement of parts of the system.
Attempts have been made to coat the metallic ring
24
with materials that prevent or delay damage. It has been found, however, that such coatings are only temporary and, ultimately, the metallic ring
24
again fails, as described above.
BRIEF SUMMARY OF THE INVENTION
The present invention is directed toward seals and seal systems for use with high pressure fluid containment systems. Embodiments of the invention allow a plug or other closure to be easily, manually engaged with and disengaged from a pressure vessel, while affecting a fluid seal at extreme elevated pressures. Embodiments of the invention will not scratch or gall the seal or the internal surface of the pressure vessel, and will not become lodged within the pressure vessel, as were commonly experienced with prior art seals.
One embodiment of the present invention incorporates a metallic ring having inner and outer surfaces. The inner surface is adapted to be received within a recess in a plug or other closure, and the outer surface is adapted to closely conform with an internal surface of a mouth on a pressure vessel. The maximum unstressed diameter of the metallic ring is equal to or slightly less than the diameter of the mouth to allow the closure to be manually inserted into and removed from the mouth when fluid in the pressure vessel is not pressurized. An edge on the metallic ring is adapted to sealingly conform to a complementary edge on the recess when the seal is subject to an elevated pressure. The metallic ring is made from a material having a modulus of elasticity that is sufficiently low such that, when the fluid is pressurized, the fluid pressure expands the metallic ring against the wall of the pressure vessel with a force sufficient to prevent extrusion of an O-ring. At the same time, however, the modulus of elasticity of the material of the metallic ring is small enough such that the force between the metallic ring and the wall is insufficient to generate a shear load great enough to gall the metallic ring when the metal ring moves with respect to the wall.
In another embodiment of the present invention, the seal incorporates a metallic ring having an inner surface, an outer surface, and an edge similar to those described above. In this embodiment, however, the metallic ring has a specific width that is selected to provide a desired pressure area. The width corresponds to the portion of the outer surface that contacts the wall of the pressure vessel. In the present invention, the width is large enough such that, when the fluid is pressurized, the metallic ring expands against the wall of the mouth with a force sufficient to prevent O-ring extrusion. At the same time, however, the width is small enough such that the force is insufficient to generate a shear load great enough to gall the metallic ring when the metallic ring moves with respect to the internal surface.
In another embodiment of the present invention, the metallic ring incorporates a first ring and a second ring. The first ring can be configured according to either of the above embodiments. The second ring is spaced apart from the first ring and is configured to retain at least one O-ring in the space between the first and second rings. In some alternate embodiments of this invention, the first and second rings are connected by an elongated neck of metallic material. The length and thickness of the neck are selected such that the mass of the second ring does not adversely affect the performance of the first ring.
The present invention is also directed toward pressure vessels incorporating the above-described seals.
REFERENCES:
patent: 2456356 (1948-12-01), Aber
patent: 2739855 (1956-03-01), Bruning
patent: 3144162 (1964-08-01), Morris
patent: 3223427 (1965-12-01), Gerard et al.
patent: 3419180 (1968-12-01), Homrig et al.
patent: 3514132 (1970-05-01), Peabody
patent: 3854735 (1974-12-01), Maurer et al.
patent: 4192519 (1980-03-01), Buggele
patent: 4346903 (1982-08-01), Heiermann
patent: 4883336 (1989-11-01), Bock et al.
patent: 4936512 (1990-06-01), Tremoulet, Jr.
pate
Hashish Mohamed
Raghavan Chidambaram
Svensson Lennart
Tremoulet, Jr. Olivier L.
Flow International Corporation
Pickard Alison K.
Seed IP Law Group PLLC
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