Apparatus for perforating a workpiece

An apparatus for perforating an elongate workpiece, comprising:

• conveyor means for longitudinally transporting said workpiece along a predetermined path;
• a main slide carrying tool means for perforating a workpiece confronted thereby;
• an ancillary slide adjacent said main slide carrying sensing means for detecting a reference surface of said workpiece, said sensing means including a pair of closely juxtaposed elements relatively offset in a direction transverse to said path, each of said elements having an output emitting a detection signal in a predetermined approach position relative to said reference surface;
• mutually independent first and second drive means for respectively displacing said main and ancillary slides in said transverse direction;
• switch means connected to the outputs of said elements for operating said second drive means to advance said ancillary slide toward said path in the absence of a detection signal from both of said elements and to retract said ancillary slide in the presence of detection signals from both said elements;
• and
• correlating means for determining a relative displacement of said slides and controlling said first drive means to restore said main slide to a predetermined position relative to said ancillary slide while holding the latter stationary by immobilizing said second drive means.