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Electromagnetic actuator comprising at least two distinct magnetic circuits

  • US 4,686,501 A
  • Filed: 10/11/1984
  • Issued: 08/11/1987
  • Est. Priority Date: 10/14/1983
  • Status: Expired due to Term
First Claim
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1. An electromagnetic actuator comprising:

  • an outer armature having a cylindrical shape and comprising a base;

    an inner armature positioned substantially along the axis of the outer armature, the two armatures being moveable relative to each other, during a stroke of the actuator, between a first position in which the movable armature is at a maximum distance from the base, and a second position in which the moveable armature is located at the end of the stroke toward the base;

    said inner and outer armatures defining a principal magnetic circuit having an air gap comprised of a variable portion between the inner armature and the base of the outer armature, and an essentially constant portion between the two armatures;

    the reluctance of said principal circuit having a maximum value when the inner armature is at the maximum distance from the base of the outer armature, and a minimum value when the inner armature is located at the end of the stroke toward the base of the outer armature,a ferro-magnetic separator including a radial portion within the outer armature, said magnetic separator establishing a secondary magnetic circuit in which lines of flux pass through the radial portion of the magnetic separator,the magnetic separator cooperating with the movable armature to establish a variable air gap to cause a variation of reluctance of the secondary magnetic circuit which is shifted along the stroke with respect to the variation of reluctance of the principal magnetic circuit, the variations of reluctance of the principal and secondary magnetic circuits during the course of an operating stroke of the actuator being monotone variations in the same direction, andfirst and second coil elements within the outer armature, andwherein the magnetic separator has the form of an annular washer of substantially constant thickness e, and when the air gap of the main magnetic circuit is at a minimum, the variable portion of the air gap is constituted by a single cylindrical space of substantially constant width E defined by the separator.

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