Cylinder device with force multiplier

A cylinder device with a force multiplier, which is configured so as to carry out lock driving downward with respect to an output rod (27) that is inserted in a housing (4) so as to be movable vertically, comprising:

• a first piston (41) which is inserted in a lower part of a cylinder hole (34) formed in the housing (4) and which is connected to a bottom of the output rod (27);
• a second piston (42) which is inserted in an upper part of the cylinder hole (34) and which is fitted on the output rod (27) so as to be movable vertically;
• a lock chamber (44), provided between the first piston (41) and the second piston (42), into which a pressurized fluid is supplied or from which the pressurized fluid is discharged;
• a first release chamber (51), provided below the first piston (41), into which a pressurized fluid is supplied or from which the pressurized fluid is discharged;
• a second release chamber (52), provided above the second piston (42), into which a pressurized fluid is supplied or from which the pressurized fluid is discharged;
• a force multiplier (64) provided in the second release chamber (52) so that (i) a force, which causes the pressurized fluid supplied into the lock chamber (44) to push the second piston (42) upward, is converted into a downward force while being subjected to force multiplication and (ii) the downward force thus converted is transmitted to the output rod (27), the force multiplier (64) including (a) a force-multiplying portion (70) provided on the second piston (42) and (b) a plurality of engaging balls (69) which are provided in a circumferential direction at predetermined intervals and with respect to which the force-multiplying portion (70) carries out wedged-driving inward in a radial direction;
• and
• a retaining spring (60) being provided in the lock chamber (44) between the first piston (41) and the second piston (42) and biasing the second piston (42) upward.