US 4,288,771 AGranted

Electromagnetic driven device

AssigneeMinolta Camera Kabushiki Kaisha

InventorsHiroshi Ueda, Shigeru Oyokota

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Abstract

An electromagnetically driven device has a coil and a plunger movably inserted in the coil between an inserted and ejected positions. An armature carrying a permanent magnet is provided at one end of the coil for holding the plunger in the inserted position by a magnetic attractive force developed between the armature and the plunger when the coil is deenergized. A yoke is provided between the permanent magnet and the armature for establishing a magnetic circuit therebetween with a predetermined reluctance developed between the armature and the yoke.

Claims16

Dependent claims

An electromagnetically driven device comprising:

a coil adopted to be energized by the application of an electric power thereto;
a plunger made of magnetic material and inserted in the hollow of the coil for movement in an axial direction of the hollow of the coil between an inserted position and an ejected position;
an armature made of magnetic material and having first, second and third faces, said first face of the armature being positioned to confront with one end of the coil, one end of the plunger contacting said first face of the armature when said plunger is moved to its inserted position;
a permanent magnet having first and second polar faces, said first polar face of the permanent magnet being held in contact with the second face of the armature for magnetizing the armature, said plunger being held in the inserted position, when said coil is deenergized, by a magnetic attractive force developed between the first face of the armature and the plunger, and said plunger being released from the magnetic attractive force in readiness for movement from the inserted position towards the ejected position when said coil is energized to counterbalance said magnetic attractive force;
a yoke made of a magnetic material and arranged for establishing a main magnetic circuit for the magnetic flux generated by said coil and said permanent magnet, and a bypass magnetic circuit for the magnetic flux generated by said permanent magnet, said main magnetic circuit being established through said yoke, said first and second faces of said armature and said first and second polar faces of said permanent magnet while said bypass magnetic circuit is established through said yoke, said second and third faces of said armature and said first and second polar faces of said permanent magnet;
means for presenting a predetermined reluctance between the third face of the armature and said yoke for bypassing predetermined flux emanated from the first polar face of the permanent magnet through the armature and the yoke without passing through the plunger to control the magnetic attractive force between the first face of the armature and the plunger.

3 more elements

Dependencies are inferred from the claim text.

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Abstract

An electromagnetically driven device comprising:

a coil adopted to be energized by the application of an electric power thereto;
a plunger made of magnetic material and inserted in the hollow of the coil for movement in an axial direction of the hollow of the coil between an inserted position and an ejected position;
an armature made of magnetic material and having first, second and third faces, said first face of the armature being positioned to confront with one end of the coil, one end of the plunger contacting said first face of the armature when said plunger is moved to its inserted position;
a permanent magnet having first and second polar faces, said first polar face of the permanent magnet being held in contact with the second face of the armature for magnetizing the armature, said plunger being held in the inserted position, when said coil is deenergized, by a magnetic attractive force developed between the first face of the armature and the plunger, and said plunger being released from the magnetic attractive force in readiness for movement from the inserted position towards the ejected position when said coil is energized to counterbalance said magnetic attractive force;
a yoke made of a magnetic material and arranged for establishing a main magnetic circuit for the magnetic flux generated by said coil and said permanent magnet, and a bypass magnetic circuit for the magnetic flux generated by said permanent magnet, said main magnetic circuit being established through said yoke, said first and second faces of said armature and said first and second polar faces of said permanent magnet while said bypass magnetic circuit is established through said yoke, said second and third faces of said armature and said first and second polar faces of said permanent magnet;
means for presenting a predetermined reluctance between the third face of the armature and said yoke for bypassing predetermined flux emanated from the first polar face of the permanent magnet through the armature and the yoke without passing through the plunger to control the magnetic attractive force between the first face of the armature and the plunger.

3 more elements