Patent ID: 7175169

Claim:
A spring-lock type clamping apparatus, wherein an annular piston ( 5 ) is inserted into a housing ( 3 ) hermetically and axially movably, and an output member ( 8 ) is inserted into the annular piston ( 5 ) hermetically and axially movably, a lock chamber ( 11 ) is formed between the annular piston ( 5 ) and a base end wall ( 3 a ) of the housing ( 3 ), a release chamber ( 12 ) is formed between the annular piston ( 5 ) and a leading end wall ( 3 b ) of the housing ( 3 ), a spring ( 14 ) attached to the lock chamber ( 11 ) is adapted to move the annular piston ( 5 ) toward a leading end for locking, a pressurized fluid supplied to the release chamber ( 12 ) is adapted to move the annular piston ( 5 ) toward a base end for releasing, a pressing surface ( 38 ) is provided on a leading end portion of the annular piston ( 5 ), a first inclined surface ( 41 ), which gets closer to the axis toward the leading end, is provided on an inner periphery of a peripheral wall of the release chamber ( 12 ), a second inclined surface ( 52 ), which gets closer to the axis toward the base end, is provided on an outer periphery of the output member ( 8 ), a plurality of rolling members ( 55 ) are inserted between the pressing surface ( 38 ), the first inclined surface ( 41 ) and the second inclined surface ( 52 ) circumferentially at intervals, when the spring ( 14 ) moves the annular piston ( 5 ) toward the leading end for locking, the pressing surface ( 38 ) moves each rolling member ( 55 ) toward the leading end and radially inward via the first inclined surface ( 41 ), and each rolling member ( 55 ) moves the output member ( 8 ) toward the leading end via the second inclined surface ( 52 ), whereby a moving stroke (S 2 ) of the output member ( 8 ) is set larger than a moving stroke (S 1 ) of the annular piston ( 5 ) during the locking movement, followed by that the spring ( 14 ) is adapted to press an input surface ( 53 ) on an outer periphery of the output member ( 8 ) toward the leading end via the pressing surface ( 38 ) and the rolling members ( 55 ).