Control for roll gap of a rolling mill

Claim 1

Apparatus for control of the gap between a pair of rolls in a mill, the rolls of the pair having journals, comprising: a first carrier on one of said journals; a second carrier on the other one of the journals, the first and second carriers spaced apart; first means defining a pick-up inductance in the first carrier and including a U-shaped core having legs establishing a datum plane, and coil means on the core; second means defining an auxiliary inductance in the first carrier and disposed in vicinity of the pick-up inductance to be subjected to similar temperature; armature means in the second carrier and magnetically cooperating with the core of the first carrier but spaced from the datum plane, so that the distance between the first and second carrier determines an air gap in the inductance of the first means corresponding to the gap width between the rolls; third means, including first and second reference inductance means, at least one thereof being adjustable, both of them being connected to the inductance of the first and second means to define a bridge circuit; fourth means including a source of AC potential connected to electrically energizing the bridge circuit; fifth means connected to the bridge circuit to derive therefrom a control signal; and control means connected to be operated in response to the control signal to adjust the gap of the rolls so as to complete a control loop.