Patent ID: 7066699

Claim:
A tensioning apparatus comprising: a shank member for carrying a tensioning force along a longitudinal axis for preloading an assembly, the shank member comprising a first diameter along a portion in a tensioned state carrying the tensioning force and a second diameter greater than the first diameter along the portion in a relaxed state not carrying the tensioning force; an annular member comprising a surface in contact with the assembly and an opening sized to receive the shank member portion with an interference fit for transferring the tensioning force from the shank member through the annular member into the assembly to preload the assembly, the shank member first diameter and the annular member opening providing an interference fit sufficient to prevent relative movement there between under the influence of transferring the tensioning force; a fluid passageway for delivering a pressure between the shank member and the annular member for selectively expanding the opening to relax the interference fit; a tensioner responsive to a pressure to apply the tensioning force to the shank member; wherein a first pressure is required in the fluid passageway to relax the interference fit with the shank member in the relaxed state, and a second pressure lower than the first pressure is required in the fluid passageway to relax the interference fit with the shank member in the tensioned state; and wherein the tensioner is selected to provide the tensioning force to the shank member at the second pressure so that a single pressure is used to pressurize the fluid passageway and to pressurize the tensioner to pre-load the assembly.