Lubricated thrust bearings for pump and motor units

Abstract

A glandless pump and wet motor unit for circulating water in a boiler has an axially movable shaft which is rotatable in a liquid-filled housing of the motor and carries a disk disposed between electromagnets which are energizable to produce an electromagnetic field serving to maintain the shaft through magnetic bearings in a selected axial position when the electromagnets are energized. At least one mechanical auxiliary thrust bearing is provided in the housing and becomes effective in response to deenergization of the electromagnets. The auxiliary bearing may be a Kingsbury bearing which is spaced apart from the electromagnetic thrust bearing, or the auxiliary bearing may include the disk which cooperates with adjacent surfaces of the electromagnets or with adjacent surfaces of the housing when the shaft is subjected to axial stresses while the electromagnets are deenergized. Each bearing is preferably a double-acting bearing, and the auxiliary bearing or bearings are also surrounded by the liquid which is confined in the housing. The disk of the electromagnetic thrust bearing has one or more radial channels which circulate liquid in the housing when the shaft rotates to drive the impeller of the pump.