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US 2003/0197582 A1Published application
Electromagnetic actuator having a permanent magnet
AssigneeSerac Group
InventorBertrand Gruson
Life of this patent
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AssigneeSerac Group
InventorBertrand Gruson
Estimating the term…
The electromagnetic actuator comprises a coil, a magnetic actuator member mounted in the coil, at least one ring of magnetic material placed around the coil, and at least one permanent magnet adjacent to one end of the ring and disposed overlying a portion of the outside surface of the coil, the permanent magnet having a magnetic field that extends in an axial direction of the coil, the magnetic actuator member being slidably mounted in a non-magnetic guide member extending inside the coil, and the ring having an end opposite from the magnet which is spaced apart from the non-magnetic guide member by a non-magnetic gap.
1/ An electromagnetic actuator comprising a coil, a magnetic actuator member mounted in the coil, at least one ring of magnetic material placed around the coil, and at least one permanent magnet adjacent to one end of the ring and disposed overlying a portion of the outside surface of the coil, the permanent magnet having a magnetic field that extends in an axial direction of the coil, wherein the magnetic actuator member is slidably mounted in a non-magnetic guide member extending inside the coil, and wherein the ring has an end opposite from the magnet which is spaced apart from the non-magnetic guide member by a non-magnetic gap.
2/ An electromagnetic actuator according to claim 1, wherein the permanent magnet is a ring surrounding the coil.
3/ An electromagnetic actuator according to claim 1, wherein the permanent magnet is interposed between two rings of non-magnetic material.
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From the US filing history. Foreign family members aren’t listed.
Backward citations are indexed for grants only.
With armatures: magnetic constructions
Armatures entering the winding: armatures or stationary parts of magnetic circuit having permanent magnet
Guiding or setting position of armatures, e.g. retaining armatures in their end position: by permanent magnets
Magnets
Term end not estimated
The present invention relates to an electromagnetic actuator having a permanent magnet.
Document U.S. Pat. No. 4,295,111 discloses an electromagnetic actuator comprising a coil placed around a magnetic body in which a magnetic actuator member is mounted. A permanent magnet is placed around the coil and has a magnetic field extending along an axial direction of the coil.
The permanent magnet is interposed between two rings of magnetic material which are in contact with the magnetic body. This serves to concentrate the magnetic field and to develop a high level of force. In contrast, the stroke of the actuator member is relatively short, and for long strokes, it is necessary to increase the axial dimensions of the actuator.
Other characteristics and advantages of the invention appear on reading the following description of a particular, non-limiting embodiment of the invention given with reference to the sole accompanying FIGURE which is an axial section view of an electromagnetic actuator of the invention.
With reference to the FIGURE, the electromagnetic actuator of the invention comprises in conventional manner: a coil 1 fixed around a tube of non-magnetic material 2 in which a magnetic actuator member 3 is slidably mounted. The coil 1 is connected by a power supply wire 4 to power supply means (not shown) enabling the coil to be excited or de-excited in order to drive the magnetic actuator member.
In accordance with the invention, in the preferred embodiment shown, a ring 5 forming a permanent magnet, e.g. a ferrite ring whose permanent magnetic field extends in an axial direction of the ring, is placed around the coil so as to overlie the central portion of the outside surface of the coil. The field generated by the ring 5 thus extends in an axial direction of the coil 1. The ring 5 is disposed between two rings 6 of magnetic material, e.g. of soft iron.
In addition, the two ends of the coil 1 are covered by annular plates 7 each having a peripheral edge in contact with the inside surface of the corresponding ring 6. The annular plates 7 are pierced by respective central orifices of diameter greater than the diameter of the non-magnetic tube 2. The magnetic rings 6 are thus spaced apart from the non-magnetic tube 2 by a non-magnetic gap.