Hydraulic clamp bushing having sigma shaped bushing ends

A hydraulic clamp bushing which is connectable to a rotary shaft for transmitting axial or rotary torques, said clamp bushing comprising:

• a closed circular sleeve having two sleeve walls and two bushing ends, at least one of said sleeve walls being formed as an expandable sleeve wall so as to expand radially outwards or inwards;
• a pressure medium chamber between said two sleeve walls having a hydraulic pressure medium trapped therein;
• a pressurizing means for pressurizing said hydraulic pressure medium to cause said expandable sleeve wall to expand radially outwards or inwards when said pressurizing medium is pressurized whereby the clamp bushing is adapted to be clamped to the rotary shaft;
• wherein said two bushing ends of said closed sleeve are shaped with a respective inwardly directed fold prior to pressurizing of said pressure medium, and said inward folds of said bushing ends are then straightened when said pressure medium is pressurized;
• and
• wherein said expandable sleeve wall has respective end parts at and adjacent respective said bushing ends and intermediate parts between said end parts, said end parts having a thickness of material which is less than a thickness of material of said intermediate parts whereby respective axial end edges at an intersection of said expandable sleeve and said respective bushing ends are adapted to be initially pressed against the rotary shaft as said pressure medium is first pressurized by said pressurizing means in order to straighten up the clamp bushing relative to the rotary shaft before said intermediate wall parts are pressed to the rotary shaft by said pressure medium.