Clamp apparatus

A clamp apparatus, comprising a clamp main body, an output rod that is fitted in the clamp main body so as to move freely upward and downward therein and capable of projecting out from an upper end of the clamp main body, and a vertically oriented cylinder bore formed within the clamp main body, and further comprising:

• a sliding piston member that vertically partitions the cylinder bore and is made of a single member separate from the output rod;
• first and second fluid pressure operation chambers defined in the cylinder bore below and above the piston member;
• a fluid passage configured to cause, during an upward light-load stroke of the piston member due to fluid pressure in the first fluid pressure operation chamber, a back pressure in the second fluid pressure operation chamber to be received by the output rod, so that said output rod is advanced thereby;
• a force multiplication mechanism configured so that, during a heavy-load stroke of the piston member at the conclusion of raising operation thereof, the force multiplication mechanism multiplies a force acting on the piston member due to the fluid pressure in the first fluid pressure operation chamber, and transmits this force to the output rod;
• and
• a link mechanism configured so that, during unclamping lowering operation of the piston member, the link mechanism links together the output rod and the piston member after lowering by a predetermined stroke amount.