A magnetically coupled pump including a housing partitioned into a pump chamber and a motor chamber by a partition wall. An impeller is mounted in the pump chamber. The stator of the motor is mounted in the motor chamber. The rotating shaft of the impeller is received in a recess formed in the partition wall.Vacuum pumps The rotating shaft is held by a bearing mounted in the recess. An annular permanent magnet is mounted to the side of the body of the impeller which faces the partition wall and arranged about the rotating shaft. An annular sliding contact portion is formed at an end of the bearing and makes a sliding contact with the side of the body of the impeller facing the partition wall. A pair of annular auxiliary sliding contact portions are formed in a part of the rotating shaft and in a part of the bearing, respectively. Magnetic pumpsThe auxiliary sliding contact portions start to make a sliding contact with each other when the annular sliding contact portion is worn by a given amount. When the pump is driven, the impeller is rotated, rotating the annular sliding contact portion of the bearing while pushing it by the thrust-direction component of a magnetic attraction. The sliding contact portions are gradually worn with use. If the amount of wear reaches a given amount after prolonged use of the pump, the annular sliding contact portions begin to make a sliding contact with each other. Then, the auxiliary portions sustain the thrust-direction component of the magnetic attraction, as well as the sliding contact portions. Contact between the impeller and the partition wall is prevented. Decreases in the flow rate of the pump are suppressed. The life of the pump can be prolonged.

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2011-11-28

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