Abstract: A composite seal including multiple seal elements is disclosed along with corresponding methods and seal structures. In one embodiment, the composite seal may include a first, substantially annular seal element having an upper body portion, a neck portion, and an axial protrusion. The upper body portion includes opposing inclined surfaces extending toward the neck portion defining a first angle. The axial protrusion includes opposing inclined surfaces extending towards an axial end of the axial protrusion defining a second angle, wherein the first angle and the second angle are substantially similar. The composite seal may further include a second, substantially annular seal element having a mouth portion, a neck portion and a recess portion, wherein the axial protrusion is configured to be complementarily engaged with the recess portion in an interlocking manner.

Abstract: A sleeve element having at least one end region configured to be biased into a laterally adjacent recess formed in one of the piston element surface and the bore surface is disclosed. A seal assembly is disclosed including two sleeve elements, each sleeve element having at least one end region disposed adjacent a recess formed in one of the piston element surface and the bore surface, the at least one end region being configured for deflection thereinto. A seal assembly including one sleeve element wherein the sleeve element includes end regions thereof, each end region disposed adjacent a recess formed in one of the piston element surface and the bore surface, the end region being configured for deflection thereinto. Further, an energizer may be disposed generally within a recess. Pressure relief and equalization structures for a sleeve element and seal assembly are also disclosed, as is a method of sealing.