Mechanical-hydraulic fastening device

Claim 1

A MECHANICAL-HYDRAULIC GRIPPING APPARATUS, COMPRISING: A FIXED JAW AND A MOVABLE JAW AND MEANS SUPPORTING SAID FIXED AND MOVABLE JAWS IN CONFRONTING RELATION TO EACH OTHER SO THAT WORK CAN BE GRIPPED THEREBETWEEN; A SPINDLE HAVING AN AXIAL OPENING THERETHROUGH CONNECTED TO SAID MOVABLE JAW FOR EFFECTING MOVEMENT THEREOF TOWARD AND AWAY FROM SAID FIXED JAW, SAID SPINDLE HAVING AN END PORTION OF LARGER SIZE AT THE END THEREOF REMOTE FROM SAID MOVABLE JAW, SAID END PORTION HAVING A CHAMBER THEREIN; A PRIMARY PISTON AND A SECONDARY PISTON SLIDABLY DISPOSED IN SAID CHAMBER IN SPACED APART RELATIONSHIP WITH A PRESSURE LIQUID IN THE SPACE BETWEEN SAID PISTONS; MEANS FOR MOVING SAID PRIMARY PISTON TOWARD AND AWAY FROM SAID SECONDARY PISTON WHEREBY HYDRAULIC PRESSURE IS APPLIED TO SAID SECONDARY PISTON; AND A PISTON ROD CONNECTED TO SAID SECONDARY PISTON AND SLIDABLY EXTENDING THROUGH THE OPENING IN SAID SPINDLE AND ENGAGEABLE WITH SAID MOVABLE JAW WHEREBY THE FORCE URGING SAID MOVABLE JAW TOWARD SAID FIXED JAW IS RESPONSIVE TO THE PRESSURE APPLIED TO SAID SECONDARY PISTON.