Rolling mills having hydraulic pressure control

Claim 1

IN A ROLLING MILL INCLUDING A PAIR OF ROLLS BETWEEN WHICH WORK CAN BE PASSED, A HYDRAULIC ROLLING PRESSURE CONTROL SYSTEM INCLUDING A RAM CYLINDER AND A PORTION PROJECTABLE THEREFROM INTO A ENGAGEMENT WITH ONE OF SAID ROLLS TO FORCE IT TOWARDS THE OTHER ROLL, AND HYDRAULIC FLOW MEANS CONNECTED WITH SAID CYLINDER AND WITH A SOURCE OF PRESSURE FLUID AND INCLUDING A REGULATOR VALVE HAVING A MEMBER DISPLACEABLE FOR CONTROLLING THE FLUID PRESSURE APPLIED FROM SAID SOURCE TO SAID RAM CYLINDER AND HENCE THE ROLLING PRESSURE, THE COMBINATION COMPRISING A ROLLING PRESSURE CONTROL MOTOR, A DRIVE TRANSMISSION CONNECTING SAID MOTOR TO SAID DISPLACEABLE VALVE MEMBER, MEANS FOR OPERATING SAID MOTOR TO DISPLACE SAID VALVE MEMBER FOR MAINTAINING A PRESCRIBED ROLLING PRESSURE IN THE RAM CYLINDER, AND A DIFFERENTIAL DEVICE INTERPOSED IN SAID DRIVE TRANSMISSION AND INCLUDING A FIRST INPUT CONNECTED FOR MOVEMENT BY THE MOTOR AND AN OUTPUT CONNECTED TO DISPLACE SAID VALVE MEMBER AND INCLUDING A SECOND INPUT OPERABLE FOR IMPARTING CORRECTIVE DISPLACEMENTS TO SAID VALVE MEMBER INDEPENDENTLY FROM THE DISPLACEMENTS IMPARTED BY SAID MOTOR.