AUTOMATIC GRINDING VALVE

摘要

A grinding valve for grinding scale build up of a valve seat in the valve is disclosed. The valve has a stem (18) which extends through a yoke (16). A yoke bush (36) is arranged in the yoke (18). A first spur gear (52) is arranged on the stem (18) for rotating the stem (18). The first spur gear (52) is connected to the shaft (18) by a key slot so that the shaft (18) can move in its longitudinal direction relative to the first spur gear (52). A second spur gear is coupled to the yoke bush (36) for rotating the yoke bush (36). First and second pinion gears (80) and (94) are connected in mesh engagement with the first and second spur gears so that drive can be selectively supplied to the first and second spur gears to rotate the stem (18) and yoke bush (36) so that the manner in which the stem (18) moves in a longitudinal direction and its speed of rotation can be selected so as to cause a grinding of a valve element (22) carried by the stem (18) against a valve seat (26) to grind scale build up off the valve seat (26).