Symmetrical belt tensioning system and apparatus for twin-belt continuous casting machines

A symmetrical belt tensioning system for use in a twin-belt continuous casting machine of the type in which a casting region is defined between spaced parallel portions of the two revolving endless casting belts, said system comprising:

• a frame for supporting and revolving an endless casting belt having a pair of main rolls at opposite ends, said rolls extending parallel to each other and also parallel to the plane of the casting region for defining an oval shaped path around which the casting belt is revolved,
• at least one of said main rolls being hollow,
• a rigid squaring shaft passing through said hollow roll from one end of the roll to the other,
• a pair of bearings encircling said squaring shaft for mounting said hollow roll on said squaring shaft, one of said bearings being mounted near each end of said hollow roll providing free rotation of said roll about said squaring shaft.
• a pair of parallel torque arms rigidly secured to opposite ends of said squaring shaft,
• a pair of pivot mountings positioned on opposite sides of the frame for mounting the respective torque arms on the frame,
• a pair of consistent, predictable force-applying means, one of said force-applying means being associated with each of said torque arms for urging both of said torque arms simultaneously to swing equally about said pivot mountings for moving said one roll in a direction away from the other roll for tightening the casting belt,
• said pair of consistent, predictable force-applying means being a pair of fluid power cylinders each having a piston rod extending from one end, said fluid power cylinders and piston rods acting along lines of thrust between said frame and points of application on the respective torque arms,
• each of said lines of thrust having essentially the same angular relationship with respect to a radius R.sub.2 in the respective torque arms from the effective centers of the pivot mountings to said points of application as the angular relationship between the direction of belt tension force exerted by the taut casting belt and a radius R.sub.1 in the respective torque arms from said effective pivot mounting centers to the axis of said hollow roll,
• whereby essentially the same effective lever mechanical advantage is maintained for each of the fluid power cylinders over the operating range of movement of said roll,
• thereby to maintain the tension of the endless belt essentially directly proportional to the fluid pressures in said cylinders regardless of the belt length over the operating range.