Prestressed rolling mill housing assembly with improved operational features

A cluster mill housing assembly comprising:

• a) an upper housing, wherein said upper housing has a roll cavity to receive a plurality of upper rolls for a rolling operation,
• b) a lower housing, wherein said lower housing has a roll cavity to receive a plurality of lower rolls for said rolling operation,
• c) wherein said rolling operation reduces the thickness of a flat metal strip to an exit gauge,
• d) four vertical prestress rods, wherein one said vertical prestress rod is located in each of four quadrants defined by the intersection of the two lines:
• i) the center lengthwise direction of said flat metal strip, and
• ii) lengthwise work roll contact point on said flat metal strip,
• e) wherein said upper housing moves vertically on said vertical prestress rods,
• f) wherein all of said vertical prestress rods are rigidly attached to said lower housing,
• g) an upper hydraulic cylinder on each said vertical prestress rod, wherein said upper hydraulic cylinders are connected to said upper housing,
• h) wherein the pistons of said upper hydraulic cylinders are connected to said vertical prestress rods,
• i) wherein said upper hydraulic cylinders are used to create a predetermined tensile load in said vertical prestress rods, wherein said predetermined tensile load is at least large enough to create a compression stress in both said upper housing and said lower housing during said rolling operation,
• j) at least two distance sensors connected to said upper housing and said lower housing, wherein said distance sensors measure the distance between said upper housing and said lower housing at two selected points,
• k) a lower hydraulic cylinder surrounding each said vertical prestress rod, wherein said lower hydraulic cylinders are connected to said lower housing and directly act upon said upper housing,
• l) wherein the pistons of said lower hydraulic cylinders move vertically and are capable of vertically separating said upper housing and said lower housing during said rolling operation to a predetermined gap,
• m) wherein said lower hydraulic cylinders are controlled by a lower hydraulic control system with sufficient control response to maintain said predetermined gap, and
• n) wherein said exit gauge of said flat metal strip during said rolling operation is substantially determined by a rotation of at least one support roll eccentric bearing on each side of said flat metal strip,
• wherein said cluster mill housing assembly is useful for reducing the gauge of said flat metal strip for commercial purposes.