Inverse symmetrical variable crown roll and associated method

A 2-hi rolling mill comprising:

• a housing for mounting rolls;
• an upper work roll having an inverse symmetrical profile positioned above a metal strip to be rolled;
• a lower work roll having an inverse symmetrical profile positioned below said metal strip to be rolled and oriented opposite from the upper work roll;
• a means for shifting the upper work roll and the lower work roll in relation to each other in said housing so as to create a family of strip profiles as a function of a roll shifting position;
• wherein the family of strip profiles created prior to shifting are strip profiles expressed by polynomial functions having terms of the n.sup.th order, where n is 4-5 inclusive, and the family of strip profiles produced by shifting the upper work roll having an inverse symmetrical profile and the lower work roll having an inverse symmetrical profile are strip profiles expressed by polynomial functions having terms of the (n-1).sup.th order, where n is 4-5, inclusive.

A rolling mill comprising:

• a housing for mounting rolls;
• an upper roll having an inverse symmetrical profile positioned above a metal strip to be rolled;
• at least one other roll above a metal strip to be rolled selected from the group consisting of a roll with an inverse symmetrical profile and a cylindrical roll;
• a lower roll having an inverse symmetrical profile positioned below said metal strip to be rolled;
• at least one other roll below a metal strip to be rolled selected from the group consisting a roll with an inverse symmetrical profile and a cylindrical roll;
• a means for shifting at least one roll having an inverse symmetrical profile above the metal strip to be rolled and at least one lower roll having an inverse symmetrical profile below a metal strip to be rolled, in relation to each other in said housing, so as to create a family of strip profiles as a function of a roll shifting position;
• wherein the family of strip profiles created prior to shifting are strip profiles expressed by polynomial functions having terms of the n.sup.th order, where n is 4-5 inclusive, and the family of strip profiles produced by shifting at least one upper roll having an inverse symmetrical profile and at least one lower roll having an inverse symmetrical profile are strip profiles expressed by polynomial functions having terms of the (n-1).sup.th order, where n is 4-5, inclusive.

A method of operating a rolling mill comprising:

• providing a rolling mill having:
• a housing for mounting rolls;
• at least one upper backup roll having an inverse symmetrical profile;
• an upper work roll oriented opposite from said at least one upper backup roll and contacting said at least one upper backup roll, the upper work roll having an inverse symmetrical profile;
• a lower work roll spaced from said upper work roll and having a cylindrical profile;
• at least one lower backup roll oriented opposite from the upper work roll and contacting the lower work roll, the at least one lower backup roll having an inverse symmetrical profile;
• a means for shifting the upper work roll and the lower work roll in relation to the at least one upper backup roll and the at least one lower backup roll in said housing so as to create a family of strip profiles as a function of a roll shifting position;
• and
• a means for regulating the vertical position of the at least one upper backup roll;
• shifting the upper work roll from a first position to a second position;
• measuring the distance from the first position to the second position;
• generating a first output signal based on the measured distance;
• calculating two standard reference signals from the means for regulating the vertical position of the at least one upper backup roll;
• adding the two standard reference signals to two actual position signals, representing the actual position of the means for regulating the vertical position of the at least one upper backup roll, to produce two total signals;
• comparing the two total signals with two actual cylinder feedback signals, representing the actual position of the means for vertical regulation after shifting the work roll;
• producing a differential signal based on comparing the two total signals with two actual cylinder feedback signals;
• and
• adjusting the vertical position of the upper backup roll based on the differential signal.