Release type electromagnetic device

• US 4,020,433 A
• Filed: 01/07/1975
• Issued: 04/26/1977
• Est. Priority Date: 01/18/1974
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Taguchi, Tetsuya, Uchidoi, Masanori, Mashimo, Yukio, Watanabe, Satoshi, Miyakawa, Hideaki
• Primary Examiner(s): Harris, George
• Application Number:
  US05/539,048
• Time in Patent Office: 840 Days
• Field of Search: 335/229, 335/230, 335/234
• US Class Current: 335/230
• CPC Class Codes: G03B 7/083 for control of exposure time
• CPC Class Codes: H01F 2007/1692 Electromagnets or actuators with two coils
• CPC Class Codes: H01F 7/064 Circuit arrangements for actuating electromagnets circuit arrangements for obtaining special operating characteristics H01F7/18; driving circuits for electromagnets making use of a switching regulator H01H47/325
• CPC Class Codes: H01F 7/122 by permanent magnets H01F7/1615, H01F7/1646 take precedence
• CPC Class Codes: H01F 7/1646 Armatures or stationary parts of magnetic circuit having permanent magnet

Abstract

The device includes a permanent magnet for attracting a movable iron armature. A pair of elongated rectilinear magnetic bodies have planar pole faces at one end facing the iron armature, and the permanent magnet is sandwiched between these two magnetic members intermediate their ends, with the permanent magnet extending perpendicularly to the magnetic members. Respective magnetizing windings embrace each magnetic member between the permanent magnet and the pole faces of the members, to produce a magnetic flux in the magnetic members opposing the flux provided by the permanent magnet so as to release the iron armature. In one embodiment of the invention, the other ends of the members, projecting beyond the permanent magnet, are angled to face each other to provide an air gap therebetween. In a second embodiment of the invention, the magnetic members or yokes have respective second windings thereon, beyond the permanent magnet, and the ends of these yokes, beyond the second windings, are formed with planar pole faces for operative association with a second iron armature. Both iron armatures are spring biased to disengage the magnetic yokes or members. As the permanent magnet engages the yokes intermediate their ends, the magnetic flux path due to the magnetizing windings does not include the permanent magnet and therefore an effective armature releasing magnetic flux can be provided with only a relatively small current supplied to the magnetizing windings.

Claims

1. A release type electromagnetic device comprising, in combination, two relatively elongated, substantially rectilinear pole pieces arranged in spaced substantially parallel relation;

a permanent magnet positioned between said pole pieces and having its magnetizing direction substantially perpendicular to the longitudinal extent of said pole pieces;

a normally deenergized electromagnetic means operatively associated with said pole pieces and operable, when energized, to generate a magnetic flux opposing the magnetic flux of said permanent magnet;

a movable magnetizable armature adjacent corresponding first ends of said pole pieces, forming pole faces, and normally attracted against said pole faces by the flux of said permanent magnet when said electromagnetic means is deenergized;

spring means biasing said armature to disengage said pole faces; and

means forming a magnetizable flux path adjacent said permanent magnet and opposing the flux path including said permanent magnet and said armature;

said magnetizable flux path forming means, said pole pieces and said armature forming a closed magnetic circuit for the flux of said electromagnetic means, said closed magnetic circuit by-passing said permanent magnet.

2. A release type electromagnetic device, according to claim 1, in which said closed magnetic circuit includes a member having a smaller magnetic reluctance than the magnetic reluctance of said permanent magnet.

3. A release type electromagnetic device, according to claim 1, in which said magnetizable flux path has a magnetic resistance less than the magnetic resistance of said permanent magnet.

4. A release type electromagnetic device, according to claim 1, in which said electromagnetic means includes coil means wound on said pole pieces.

5. A release type electromagnetic device, according to claim 1, in which said closed magnetic circuit includes magnetic flux adjusting means operable to adjust the amount of magnetic flux from said electromagnetic means.

6. A release type electromagnetic device, according to claim 1, in which said permanent magnet is positioned between said pole pieces intermediate the ends of said pole pieces, so that said pole pieces have second ends extending beyond said permanent magnet in a direction opposite to the extend of said first ends from said permanent magnet;

said electromagnetic means comprising coil means on said pole pieces between said permanent magnet and said first ends of said pole pieces;

said second ends of said pole pieces constituting projections from said permanent magnet and forming part of the closed magnetic circuit, for the flux of said electromagnetic means, by-passing said permanent magnet.

7. A release type electromagnetic device, according to claim 6, in which said second ends of said pole pieces are bent toward each other to define an air gap therebetween.

8. A release type electromagnetic device, according to claim 1, in which said permanent magnet is positioned between said pole pieces intermediate the ends of said pole pieces;

said pole pieces having corresponding second ends forming second pole faces;

a second movable magnetizable armature adjacent said corresponding second ends of said pole pieces and normally attracted against said second pole faces by the flux of said permanent magnet when said electromagnetic means is deenergized;

second spring means biasing said second armature to disengage said second pole faces;

said electromagnetic means comprising first coil means wound on said pole pieces between said permanent magnet and said first ends thereof, and second coil means wound on said pole pieces between said permanent magnet and said second ends thereof;

said second coil means being operable, when energized, to generate a magnetic flux opposing the magnetic flux of said permanent magnet exerted on said second armature;

whereby two closed magnetic circuits for the flux of said electromagnetic means are formed in by-passing relation with said permanent magnet, one closed magnetic circuit including said pole pieces, said second armature, said first coil means and said first armature, and the other closed magnetic circuit including said pole pieces, said first armature, said second coil means and said second armature.