Hydraulic tensioning device

A hydraulic tensioning device comprising two relatively axially displaceable annular metallic bodies effecting an annular piston and cylinder arrangement including a fluid chamber defined between radially innermost and radially outermost walls comprising the cylinder,

• said radially outermost cylinder wall surrounding an associated radially outermost piston wall and said radially innermost cylinder wall being surrounded by an associated radially innermost piston wall,
• said radially outermost and radially innermost piston walls being formed with corresponding annular metallic webs, extending axially into the fluid chamber and tapering along their whole lengths to edges and providing, by operative engagement with their associated cylinder walls in response to fluid pressure in the chamber, sole sealing means of the arrangement,
• the radially innermost web being thinner than, and having a shallower taper than, the radially outermost web at their edges and at corresponding distances from their edges to confer greater flexibility on said radially innermost web, said webs between themselves defining, for part of the chamber, asymmetry in elevational cross section relative to an axial direction.