Seal for a joint or juncture – Seal between relatively movable parts – Circumferential contact seal for other than piston
Reexamination Certificate
1998-07-07
2001-01-16
Knight, Anthony (Department: 3626)
Seal for a joint or juncture
Seal between relatively movable parts
Circumferential contact seal for other than piston
C277S589000, C277S572000, C277S554000
Reexamination Certificate
active
06173964
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a seal assembly. More particularly, the present invention relates to a seal assembly for sealing a clearance space between first and second relatively displaceable surfaces, where such seal assembly has particular applicability to down-hole oil field applications.
BACKGROUND OF THE INVENTION
The use of seal assemblies in down-hole oil field applications is known. In one particular application, an oil drilling completion, and/or measurement tool is run down into an oil well lined with casing, and the equipment includes an annular groove within which an annular seal assembly is positioned to seal the space between the inner diameter of the casing and the outer diameter of the equipment. In the prior art, such a seal assembly typically comprised an annular seal element having annular coil springs molded into the two corners of the outer diameter (in toroidal cross-section), where the springs themselves act to prevent extrusion of the seal element in the region of such outer diameter corners.
Such a prior art seal assembly was found to work well under lower pressures and lower temperatures, for example up to 5,000 psi and 250° F. However, it is now typical in down-hole oil fields apparatus to have higher pressures and higher temperatures, on the order of 20,000 psi and 450° F., respectively. As one skilled in the art will appreciate, at such higher temperatures and pressures, the seal element of such prior art seal assembly, which is typically a rubber-like material, tends to flow and extrude through the springs, thereby resulting in a loss of seal element material and eventual seal failure.
Accordingly, it has been proposed to employ as a seal assembly in the aforementioned down-hole oil field application a T-shaped seal element (in toroidal cross-section) and a pair of annular back-up or anti-extrusion elements, one on each axial side of the T-shaped seal element. Such proposed T-seal seal assembly is known in the prior art and has been used in one form or another in other applications such as hydraulic or pneumatic systems for both rod- and piston-type seals. Generally, each back-up element is positioned adjacent the T-shaped element and the contact point thereof such that when higher pressure is applied to the opposite axial side of the T-shaped seal element, the respective back-up element prevents extrusion of the T-shaped seal element, in the area of such contact point.
However, it has been found that such prior art T-seal seal assemblies do not work well in the previously described high temperature and high pressure environment of a down-hole oil field application. In particular, it has been found that one or both of the back-up elements tends to become displaced from the T-shaped seal element, thereby failing to provide the desired back-up function such that the T-ring seal assembly eventually fails. Accordingly, a need exists for a T-ring seal assembly that works well under high pressure and high temperature, whereby the back-up elements do not become displaced with regard to the T-shaped seal element.
BRIEF SUMMARY OF THE INVENTION
To satisfy the aforementioned need, the present invention provides a seal assembly for sealing a generally cylindrical clearance space between first and second generally coaxial members. The seal assembly is for installation in a generally coaxial annular groove in the first member. The groove has a mouth, first and second side walls, and a base wall extending generally axially between the side walls.
The seal assembly comprises a generally annular seal element formed from an elastomeric material, a generally annular anti-extrusion back-up element formed from a non-elastomeric material, and a generally annular biasing element. The seal element has in toroidal cross-section a generally axially extending leg and a generally radially extending leg. The axial leg extends generally axially along the base wall of the groove, and includes generally axial end portions and a mid-portion between the end portions. The radial leg extends generally radially from the mid-portion of the axial leg and toward and through the mouth of the groove. The radial leg has opposing generally radially extending side surfaces and a contact surface between the side surfaces. The contact surface is positioned outside the mouth of the groove and sealingly contacts the second member.
The back-up element is positioned adjacent one of the side surfaces of the radial leg of the seal element. The back-up element functions to prevent extrusion of the seal element when pressure is applied adjacent the other side surface. The back-up element defines a generally annular channel that opens away from the adjacent side surface of the seal element and toward the respective side wall of the groove. The biasing element is positioned in the channel of the back-up element such that the biasing element provides a generally radial force on at least a portion of the seal element and the back-up element toward the base wall of the groove. The biasing element prevents the back-up element from becoming displaced with respect to the seal element when pressure is applied to the seal assembly.
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Bell Merle L.
Gravill Ian
Akin Gump Strauss Hauer & Feld L.L.P.
Greene Tweed of Delaware, Inc.
Knight Anthony
Peavey Enoch
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