Joining method and a device for operating a fastening tool

A device for operating a fastening tool for joining at least two plate-shaped workpieces of similar or different materials, comprising:

• a hydraulic cylinder having a cylindrical cavity,
• a main piston having a piston rod integrally connected to a punch for performing the joining operation,
• the main piston dividing the cavity of said cylinder into a piston rod remote work chamber and a piston rod adjacent work chamber such that the main piston has one side pressurized by pressure prevailing in said piston rod remote work chamber and has an axially opposite side pressurized by pressure prevailing in said piston rod adjacent work chamber,
• a clamp piston having a piston rod integrally connected to a clamp for exerting a clamping force upon the workpieces,
• said clamp piston along with its piston rod coaxially extending about the piston rod of said main piston and being displaceable with respect thereto, and
• each of said work chambers having a fluid pressure port selectively to be pressurized or depressurized,
• the improvement comprising:
• the clamp piston being disposed in said piston rod adjacent work chamber of said hydraulic cylinder and said piston rod adjacent work chamber has sections disposed on axially opposite sides of said clamp piston and communicating with each other by fluid flow passage means such that the axially opposite sides of said clamp piston both are pressurized by pressure prevailing in said piston rod adjacent work chamber.

A device for operating a joining tool for joining at least two plate-shaped workpieces of similar or different materials, comprising:

• a first hydraulic cylinder having a cylindrical cavity,
• a main piston having a piston rod integrally connected to a punch for performing a joining operation,
• the main piston dividing the cylindrical cavity of said cylinder into a piston rod remote work chamber and a piston rod adjacent work chamber each of which having a fluid pressure port selectively to be pressurized or depressurized,
• a second hydraulic cylinder including a clamp piston and a piston rod integrally connected to a clamp for exerting a clamping force, said clamp piston confining a single work chamber selectively to be pressurized by pressure fluid or depressurized,
• the improvement of which comprises:
• said single work chamber of said second hydraulic cylinder and said piston rod adjacent work chamber of said first cylinder being permanently connected to each other by fluid communication means.