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Saturable core proximity sensor including a flux director and a magnetic target element

  • US 5,351,004 A
  • Filed: 09/11/1992
  • Issued: 09/27/1994
  • Est. Priority Date: 10/15/1991
  • Status: Expired due to Term
First Claim
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1. A saturable core sensor comprising:

  • a magnetic target that includes;

    a magnet having a front face and a back face that produces a magnetic field in front of, in back of, and to the sides of the magnet;

    a plate positioned adjacent the magnet for reducing the magnetic field in the back of and at the sides of the magnet and for increasing the distance at which the magnetic field extends in a direction perpendicular to the front face of the magnet;

    sensor means for detecting said magnetic field and for indicating when said sensor means is positioned within a predetermined proximity of said magnetic target, said sensor means including;

    a core having a distal end and a proximal end and a longitudinal axis that is aligned substantially perpendicular to the front face of the magnet, wherein said core has a cross-sectional area in a plane perpendicular to the longitudinal axis that is substantially smaller than a cross-sectional area of the core along the longitudinal axis, said core becoming magnetically saturated when exposed to magnetic fields of a predetermined flux density that extend along the longitudinal axis of the core, but not saturating when exposed to magnetic fields of the predetermined flux density that extend in a direction substantially deviating from the longitudinal axis of the core;

    an inductive element surrounding said core that produces a second magnetic field that flows through the core and through an air gap that exists between the distal and proximal ends of the core; and

    a flux director disposed at the distal end of the core to intercept a fringing portion of the magnetic field of the magnetic target,wherein said core and inductive element have an inductance that decreases when said core is saturated by the magnetic field produced by the magnet and an inductance that increases when said core is not saturated by the magnetic field produced by the magnet, said change in inductance providing an indication of the proximity of the sensor means to the magnet target.

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