Patent ID: 8256963

Claim:
A roll machining apparatus for machining the surface of a roll while supporting and rotating the roll in a horizontal position, the apparatus comprising: a first spindle configured to be detachably coupled to a first end of the roll; a second spindle, disposed opposite to the first spindle on the same axis, configured to be detachably coupled to a second end of the roll; a first hydrostatic radial bearing configured to receive a radial load of the first spindle and configured to rotatably support the first spindle; a hydrostatic thrust bearing configured to receive a thrust load of the first spindle and configured to limit axial movement of the first spindle; a second hydrostatic radial bearing configured to receive a radial load of the second spindle and configured to rotatably support the second spindle; a floating thrust comprising: a thrust bearing comprising an outer race having two sides and a bearing case, the thrust bearing configured to receive a thrust load of the second spindle: a housing comprising a cylinder chamber, a hole configured to receive the thrust bearing and comprising a step portion formed within the hole, and a bearing case, movable only in an axial direction; a spacer and nut configured to fix the thrust bearing to the rear end of the second spindle; a pair of pistons, each of the pair of pistons comprising a cylinder chamber formed on a back side of the piston, one of the pair of pistons being disposed on each side of the outer race of the thrust bearing, each of the pair of pistons fitted movably into the hole, the pair of pistons configured to press the thrust bearing in an axial direction when a pressurized fluid is supplied to the cylinder chambers; wherein the floating thrust is configured to selectively operate in a first mode and a second mode, the floating thrust configured to limit axial movement of the thrust bearing to fix the position of the second spindle in an axial direction in the first mode, and the floating thrust configured to permit the thrust bearing to displace freely according to an expansion and/or contraction of the roll in the second mode; and a switching valve configured for switching a flow path of the pressurized fluid supplied to the cylinder chamber so as to selectively allow each piston to operate either to permit axial movement of the thrust bearing or to limit axial movement of the thrust bearing and fix it at a predetermined position, wherein the step portion in the hole is configured to limit forward movement of each piston to a forward limit position, and wherein each piston is configured to hold the bearing case of the thrust bearing to fix the thrust bearing at the predetermined position when each piston is in its forward limit position.