Patent ID: 8215198

Claim:
A backlash eliminator adapted to eliminate backlash in a gear train using helical gears when a workpiece whose tooth profile is to be machined by a cutting tool is rotated by the gear train, the backlash eliminator comprising: an input shaft coupled to a motor and having a drive gear; an output shaft disposed parallel to the input shaft, and to which the workpiece is fixed coaxially with the output shaft, and having a driven gear; and intermediate shafts disposed parallel to the input shaft and the output shaft, and each having a first intermediate gear meshing with the drive gear, and a second intermediate gear meshing with the driven gear, one of the intermediate shafts being supported to be stationary in an axial direction for positioning the output shaft in a rotating direction, and other of the intermediate shafts being supported to be movable in an axial direction for eliminating backlash between the other intermediate shaft and the output shaft; and pressing means which presses the other intermediate shaft in the axial direction thereof in a switchable manner to exert a backlash eliminating force between the driven gear and the second intermediate gear in a direction identical with a direction of generation of a cutting load generated in a circumferential direction of the workpiece during machining of the workpiece, wherein the other intermediate shaft is disposed such that a first clearance is formed between the casing and one end of the other intermediate shaft and a second clearance is formed between the casing and another end of the other intermediate shaft opposite to the first one end, and the pressing means selectively supplies air to the first clearance and the second clearance to press the other intermediate shaft in the axial direction thereof in a switchable manner.