PURPOSE: To eliminate backlash in a gear train as well as to make a degree of gear cutting accuracy improvable, by installing a pressing device, which makes gear surfaces themselves at the opposite side to a contact tooth surface between a worm and a worm wheel contact with each other, and a braking device for a worm shaft.
CONSTITUTION: A gear 11 being attached to a driving shaft of a motor 10 is engaged with a gear 9, forming a pressing device, and a table 3 is energized in a direction of rotation by the motor 10 via these gears 11 and 9 whereby tooth surfaces themselves paired with a contact tooth surface at the opposite side are made contact with each other at a time when a work wheel 5 is driven by a master work 4. In addition, a brake 12 is attached to the tip of a work shaft 7, and the brake is operated so as to prevent this work shaft from rotating by force out of the work wheel 5 due to pressing force or the like of cutting force or the pressing device. Thus, backlash in a gear train 6 between a gear hob 2 and the worm 4 is eliminated and, what is more, even if inverse-wind conventional hob cutting takes place, any drawbacks due to the backlash between the worm 4 and the work wheel 5 will not occur there, thus accuracy is well improved.
NAKAI SEIGO
NABEKURA MASAKAZU
