Patent ID: 7121554

Claim:
In a high-pressure cylinder with a wall, adapted to receive therein an axially moveable plunger, a seal assembly for sealing the gap between said wall and said plunger, comprising an annular internal recess in said wall, the recess being bounded radially by the cylinder wall and axially by an open end and a bottom opposite thereto, a plunger-sealing ring, a cylinder-sealing ring, a resilient low-pressure ring, and an annular seal holder, wherein the resilient low-pressure ring is fitted on the plunger and is disposed at the recess bottom; the cylinder sealing ring is disposed in the recess around the low-pressure ring, and is tightly fitted against the cylinder wall; the plunger sealing ring is tightly fitted on the plunger and is disposed in the recess, extending radially along the cylinder sealing ring and the low-pressure ring; the seal holder is inserted into the open end of the recess, abutting the plunger-sealing ring, and being tightened to the cylinder wall to urge the plunger-sealing ring against the cylinder-sealing ring and the low-pressure ring, and to urge the latter two rings against the recess bottom and against each other; both the plunger sealing-ring and the cylinder-sealing ring being metallic, their mutual contact surfaces being fitted to each other, the plunger sealing ring having sufficient section modulus to ensure that under high pressure the contact and bending deformations at said mutual contact surfaces be sufficiently small as to keep a tight fit therebetween, wherein high-pressure sealing of the gap between the plunger and the cylinder wall is provided entirely by said two metallic rings across the following interfaces: between the plunger and the plunger-sealing ring; between the plunger-sealing ring and the cylinder-sealing ring; and between the cylinder-sealing ring and the cylinder wall.