Device for locking workpieces on machine tools

A device for locking workpieces on machine tools, comprising:

• at least one base body fixable to a machine tool and provided with an oil hydraulic cylinder containing a pressurised oil hydraulic fluid;
• at least one rod extending along a main axis and partly inserted in said oil hydraulic cylinder slidably along said main axis when pushed by said pressurised oil hydraulic fluid, said rod comprising at least one inner portion inside said oil hydraulic cylinder and one outer potion outside said oil hydraulic cylinder;
• roto-translation means interposed between said oil hydraulic cylinder and said rod and designed to divide the motion of said rod into:
• at least one first stretch of roto-translation, in which said rod slides along said main axis and rotates about said main axis;
• and
• at least one second stretch of translation, in which said rod slides along said main axis without rotating;
• at least one clamp element associated with said outer portion f the rod for locking a workpiece to be machined on said machine tool, said clamp element being movable between:
• a home configuration, in which said clamp element is at a distance from said base body;
• an intermediate configuration, in which said clamp element is rotated and brought nearer to said base body compared with said home configuration following the motion of the rod along said first stretch;
• and
• an operating configuration, in which said clamp element is brought even nearer to said base body than in said intermediate configuration following the motion of said rod along said second stretch for locking said workpiece;
• wherein said device comprises at least one prismatic guiding body associated with said base body and prismatically couplable with said clamp element during the shifting of said rod along said second stretch.