Fluid pressure operated sensing system

Claim 1

AN EDGE ALIGNMENT CONTROL SYSTEM COMPRISING (A) AN EDGE ALIGNMENT CONTROL MEANS FOR CONTROLLING THE POSITION OF A MOVING WEB OF MATERIAL AND CAPABLE OF ACTUATION IN RESPECTIVE OPPOSITE SENSES TO TEND TO MOVE THE WEB LATERALLY IN RESPECTIVE OPPOSITE DIRECTIONS, (B) AN EDGE POSITION SENSING HEAD HAVING FLUID PRESSURE OUTPUT MEANS FORT SENSING EDGE POSITION AND GENERATING RESPECTIVE FIRST AND SECOND DIFFERENTIAL PRESSURE OUTPUTS IN RESPONSE TO ERRORS OF WEB POSITION IN RESPECTIVE OPPOSITE DIRECTIONS FROM A CORRECT POSITION OF THE WEB DEFINED BY SAID HEAD, (C) FIRST AND SECOND FLUID PRESSURE RESPONSIVE DEVICES COUPLED TO SAID FLUID PRESSURE OUTPUT MEANS OF SAID HEAD AND RESPONSIVE TO SAID FIRST AND SECOND DIFFERENTIAL PRESSURE OUTPUTS RESPECTIVELY TO PROVIDE RESPECTIVE FIRST AND SECOND MECHANICAL OUTPUTS, (D) FIRST AND SECOND MECHANICALLY ACTUATED SWITCHING DEVICES COUPLED RESPECTIVELY TO SAID FIRST AND SECOND FLUID PRESSURE RESPONSIVE DEVICES AND ACTUATED RESPECTIVELY BY SAID FIRST AND SECOND MECHANICAL OUTPUTS THEREFROM, AND (E) MEANS FOR CONNECTING SAID FIRST AND SECOND MECHANICALLY ACTUATED SWITCHING DEVICES TO SAID EDGE ALIGNMENT CONTROL MEANS FOR ACTUATION THEREOF IN RESPECTIVE OPPOSITE DIRECTIONS IN RESPONSE TO SAID FIRST AND SECOND MECHANICAL OUTPUTS TO TEND TO MAINTAIN SAID WEB IN SAID CORRECT POSITION AS DEFINED BY SAID HEAD.