Inductive proximity switch having an oscillator magnetic core and a permanent magnet forming a saturation-sensitive magnetization area

Claim 1

An inductive proximity switch comprising oscillator circuit means including an oscillator coil wound on a magnetic core for generating a magnetic field, electronic switch means connected to the oscillator circuit means and adapted to be actuated in dependence upon a damping of the oscillations of the oscillator circuit means, at least one auxiliary magnet having at least one pole surface forming an active surface of the proximity switch and the pole axis of said pole surface being substantially transversely directed with respect to the active surface so that the auxiliary magnet produces a sensor field having flux extending out from the active surface, a trip device fashioned of a permeable material and being moveably supported so as to be movable toward said active surface, and said auxiliary magnet being connected to the magnetic core of said oscillator circuit means so as to form a permeable unit, the flux of said magnetic core of said oscillator circuit means being completely closed by the auxiliary magnet, and wherein said permeable unit has a reduced cross-sectional area in which the magnetic fluxes of the auxiliary magnet and the magnetic core of said oscillator circuit means heterodyne, said reduced cross-sectional area forming a saturation-sensitive magnetization area, said reduced cross sectional area being adapted to be operated in saturation by a reduction in the magnetic resistance in the sensor field which occurs when the trip device is introduced into the sensor field, thereby damping the flux of the magnetic core of said oscillator circuit means.