Holding magnet assembly with permanent magnet annular disc - has flat tray pole yoke with bottom projection forming third pole surface

摘要

The holding magnet provides a very high ratio of holding force to its own weight. The annular permanent magnetic disc is held in a pole yoke in shape of a flat tray, from the bottom of which the permanent magnet protrudes in the direction of the tray peripheral wall, forming the first pole surface. The tray bottom has a lug-shaped protrusion (12b) forming a third pole surface (22). The annularly shaped permanent magnet (10) surrounds the protrusion concentrically. Preferably the permanent magnet is of a rare earth - cobalt alloy with a specific energy content of at least 100 mWs cm-3, while the inner diameter of the disc is at least 20 mm. The pole surface of the protrusion may have the same extent as that of the peripheral wall pole surface.