Patent ID: 8464644

Claim:
A rotary table assembly comprising: a rotatable table having a through hole extending along an axis; a frame rotatably supporting the rotatable table from a back surface side of the rotatable table; a rotary joint including a hollow cylindrical center shaft having a plurality of rotatable-table-side fluid passages, and a distributor having a plurality of frame-side fluid passages and being inserted into a center bore of the center shaft, the rotary joint being disposed in the through hole to receive and supply fluid between the frame-side fluid passages and the rotatable-table-side fluid passages; and a sealing member interposed between an outer peripheral surface of the center shaft and a peripheral surface of the through hole, wherein the center shaft includes a rotatable-table-side center shaft that is inserted into the through hole from a front surface side of the rotatable table and has the outer peripheral surface making contact with the sealing member, and a frame-side center shaft that is inserted into the through hole from the back surface side of the rotatable table, wherein the frame-side center shaft and the rotatable-table-side center shaft are secured to the rotatable table and are hollow and cylindrical, the distributor includes a basal portion at a bottom end thereof adjacent to the frame and a top region axially extending from the basal portion, the top region is inserted from the back surface side of the rotatable table into a center bore of the frame-side center shaft and a center bore of the rotatable-table-side center shaft in succession, and the basal portion is secured to the frame, communication ports of first ones of the frame-side fluid passages formed on an outer peripheral surface of the top region are in communication with communication ports of first ones of the rotatable-table-side fluid passages formed on an inner peripheral surface of the rotatable-table-side center shaft, and communication ports of second ones of the frame-side fluid passages formed on the outer peripheral surface of the top region are in communication with communication ports of second ones of the rotatable-table-side fluid passages formed on an inner peripheral surface of the frame-side center shaft.