Fastening apparatus and control systems therefor

Claim 1

In an apparatus operable to fasten together overlying metal sheets or webs, wherein a co-operating piercing-and-forming punch and die set is operable partially to sever and to displace a localised region of said sheets out of the planes thereof, and a flattening punch is then operable to spread the displaced region and thus fasten the sheets together with a clenching action, the improvement comprising: a die mounting section on which said piercing-and-forming die is mounted; a punch mounting section on which said flattening punch is mounted; first and second hydraulically-operated piston and cylinder arrangements by which said die and punch mounting sections are respectively and separately operable, in sequence, for required movements relatively to said piercing-and-forming punch; first and second lever arms which share a common intermediate pivot axis and at adjacent ends of which said piercing-and-forming die and said flattening punch are respectively mounted, said piston and cylinder arrangements including hydraulic pistons acting at the other ends of said first and second arms; and a third lever arm with which each of said first and second lever arms has a scissor relationship, which is fixed with respect to hydraulic cylinders of said piston and cylinder arrangements, and which mounts said piercing-and-forming punch.