Vertical drive mechanism for a cutting apparatus

摘要

A vertical drive mechanism is provided for a cutting apparatus. The cutting apparatus can be used for in place machining of a valve seat which may include an annular turntable adapted to be rotatably mounted on the valve above the valve seat. A feed shaft is mounted through the turntable so as to be rotatable therewith, and a bottom of the feed shaft is adapted to receive a cutter for machining the valve seat. The vertical drive mechanism is mounted on the feed shaft and includes a nut threaded on the feed shaft and a gear combination. The gear combination may include a first portion which is fixedly connected to the nut, a second portion which operatively engages the first gear portion, and a third portion which operatively engages the second gear portion, the third gear portion being mounted for rotatable slidable friction engagement about the nut. With this arrangement, rotation of the turntable causes the vertical drive mechanism to rotate therewith as a unit, however, upon stopping the third gear portion, the latter will rotate relative to the turntable and the remainder of the vertical drive mechanism to turn the second gear portion, then the first gear portion, then the nut, then drive the feed shaft vertically.