Search Images Maps Play YouTube News Gmail Drive More »
Sign in
Screen reader users: click this link for accessible mode. Accessible mode has the same essential features but works better with your reader.


  1. Advanced Patent Search
Publication numberUS3218523 A
Publication typeGrant
Publication dateNov 16, 1965
Filing dateJul 29, 1963
Priority dateJul 29, 1963
Publication numberUS 3218523 A, US 3218523A, US-A-3218523, US3218523 A, US3218523A
InventorsEugene Benson Hector
Original AssigneeEugene Benson Hector
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Electromagnetic device having a permanent magnet armature
US 3218523 A
Abstract  available in
Previous page
Next page
Claims  available in
Description  (OCR text may contain errors)

Nov. 16, 1965 H. E. BENSON 3,218,523

ELECTROMAGNETIC DEVICE HAVING A PERMANENT MAGNET ARMATURE Filed July 29, 1963 I O I I I INVENTOR H20 for E, fielzs'on W ab Eh I BY ATTORNEYS United States Patent 3,218,523 ELECTROMAGNETIC DEVICE HAVING A PERMANENT MAGNET ARMATURE Hector Eugene Benson, Cheveley, Newmarket, England Filed July 29, 1963, Ser. No. 298,250 2 Claims. (Cl. 317172) This invention relates to direct-current tractive electromagnet devices, of which solenoids, relays and the like are common forms.

It is normal practice to make iron parts of electromagnets entirely of ferrous material which is magnetized by the excitation of a coil or coils and which ceases to be magnetized when the current is switched off. The armature or plunger of such an electromagnet device, therefore, requires the continuous passage of current through the coil in order to hold it in the closed position, unless otherwise achieved by a mechanical latch.

It is an object of the present invention to enable the armature or plunger of a DC. electromagnet device, once closed by brief coil excitation, to remain closed with current switched off and without the aid of a mechanical device, and to be released by a further coil pulse of reversed polarity.

According to the invention, the moving armature or plunger of the electromagnet device consists wholly or partly of a permanent magnet, which in the open position lies sufficiently far away from a fixed pole piece in the electromagnet coil, not to move spontaneously towards the fixed pole piece under influence of its own permanent magnetism, or which in the open position magnetically attaches itself to a fixed piece of ferrous material in order to restrain it from spontaneous closing.

Energizing of the electromagnet coil with direct current of the correct polarity causes the permanent magnet armature to close by interaction of the permanent magnet and electromagnet fields, and in closing to exert external mechanical force in the manner known for tractive electromagnets of which solenoids and relays are common forms.

Once closed, the permanent magnet armature will contact the fixed pole piece and because of its magnetism, will be attracted thereto and remain closed, sustaining whatever mechanical load is within its power, without further passage of current in the coil.

The armature or plunger is restored to the open position by energizing the coil with current of reverse polarity to the closing current, so that interaction of permanent magnet and electromagnet fields results in mutual repulsion of the fixed and moving parts.

One manner of using this principle is to apply reverse current of the same strength as the closing current, to produce definite repulsion of the armature or plunger. An alternative manner is to apply a reverse current weaker than the closing current, sufiicient to cancel attraction of the fixed and moving parts but without repelling force.

The present invention will now be described in greater detail by way of example with reference to the accompanying diagrams, wherein:

FIG. 1 is a diagrammatic view of a form of the invention wherein a coil encircles a fixed pole piece to which a moving armature is pivotally attached;

FIG. 2 is a diagrammatic view of a form of solenoid electromagnet wherein the moving plunger enters the coil; and

FIG. 3 illustrates a modified form of switching arrangement.

In each of the illustrated embodiments a yoke 1 or 1a defines a fixed pole 2 or 2a and is energized by a coil 3 or 3a. The armature 4 or plunger 4a is composed either wholly or partly of a permanent magnet, the effect in either case being to present magnetic poles of unlike polarity at opposite ends of the moving part. Characters 5 and 5a identify stops of ferrous material to which the armature or plunger may releasably attach itself by magnetic attraction when in the open position. The stops 5 or 5a are mounted on any suitable fixed support (-not shown).

It will be evident that in each form, the coil may be energized with direct current applied in such direction as to, selectively, attract or to repel the permanent magnet armature or plunger.

The ganged switching arrangement shown at 6 and 6a illustrates one way in which current may be sent through coils 3 or 3a in either desired direction and the modified switching arrangement 6b of FIG. 3 illustrates a resistor 7 in one side of the circuit so that more current will flow in one direction than in the other.

The above described examples have been found to have the following advantages:

Only a momentary coil pulse is required to close or to open the electromagnet, which by permanent magnet attraction will sustain its load without current, without coil heating, and without the tendency to deterioration of insulating materials caused by coil heating.

The repelling effect of the reverse-polarity opening current can drive the armature or plunger out to the open position, and take the place of the spring return frequently necessary with conventional electromagnets.

The same repelling effect can be used to achieve a double-acting solenoid which without the benefit of this invention, necessitates the use of two separate coils each with its own iron circuit.

The same repelling effect can give much faster opening than is possible in a conventional D.C. electromagnet in which it is necessary to wait for the decay of flux in the magnetic circuit before the armature or plunger can drop out.

I claim:

1. An electromagnetic device comprising: a coil; means for selectively directing electric current to flow in either direction through said coil; a ferromagnetic pole piece in said coil and having a pole face therein; a member mounted adjacent said pole piece for movement of at least one portion of said member toward and from said pole face; said member being a permanent magnet and said one portion being one magnetic pole thereof, said pole piece having another pole face adjacent another portion of said member which comprises the other magnetic pole thereof; a ferromagnetic stop member, separate from said pole piece, fixed in spaced relation to said pole face and said coil; said member being engageable with said pole piece or with said stop member, selectively, to be magnetically held thereby in either of two positions.

2. A device as defined in claim 1 wherein said pole piece comprises a generally U-shaped member with said coil surrounding one leg thereof; said member being piv otally mounted on the other leg of said pole piece, in the region of its said other magnetic pole.

References Cited by the Examiner UNITED STATES PATENTS 2,740,956 4/1956 Hatton 317-172 X 3,119,940 1/1964 Pettit et al 31717l X 3,126,501 3/1964 Flora 317171 X BERNARD A. GILHEANY, Primary Examiner.

JOHN F. BURNS, Examiner.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2740956 *Oct 19, 1951Apr 3, 1956IttPolarized magneto signal device
US3119940 *May 16, 1961Jan 28, 1964Sperry Rand CorpMagnetomotive actuators of the rectilinear output type
US3126501 *Dec 23, 1960Mar 24, 1964International Business Machines CorporationFlora
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3504315 *Dec 5, 1967Mar 31, 1970Plessey Co LtdElectrical solenoid devices
US3530454 *Oct 9, 1967Sep 22, 1970Ite Imperial CorpDrop annunciator with pivotally-mounted target indicator bearing a permanent magnet
US3544933 *Dec 12, 1968Dec 1, 1970Baldwin Co D HCombination stop action
US3683239 *Jun 17, 1971Aug 8, 1972Sturman Oded ESelf-latching solenoid actuator
US3747370 *Mar 19, 1971Jul 24, 1973Northrop Carolina IncPattern jack actuator means for circular knitting machines
US3914723 *Jul 15, 1974Oct 21, 1975Price Edison IncPositive action magnetic latching relay
US4259653 *Nov 22, 1977Mar 31, 1981Magnetic Laboratories, Inc.Electromagnetic reciprocating linear actuator with permanent magnet armature
US4737750 *Dec 22, 1986Apr 12, 1988Hamilton Standard Controls, Inc.Bistable electrical contactor arrangement
US4978935 *Jan 25, 1988Dec 18, 1990Jerzy HoffmanElectromagnetic relay
US5272458 *Oct 17, 1989Dec 21, 1993H-U Development CorporationSolenoid actuator
US8183964 *May 22, 2012General Electric CompanyCurrent trip unit for circuit breaker
US8912871 *Nov 15, 2010Dec 16, 2014Schneider Electric Industries SasElectromagnetic actuator with magnetic latching and switching device comprising one such actuator
US9183976Mar 15, 2013Nov 10, 2015Hanchett Entry Systems, Inc.Springless electromagnet actuator having a mode selectable magnetic armature
US20090153276 *Feb 18, 2009Jun 18, 2009General Electric CompanyCurrent trip unit for circuit breaker
US20140145801 *Jan 29, 2014May 29, 2014Abb Technology AgMagnetic actuator with rotatable armature
DE19608953A1 *Mar 8, 1996Sep 11, 1997Harting KgaaBistabiler Kleinmagnet
U.S. Classification335/234, 335/281
International ClassificationH01F7/122, H01H50/22, H01F7/08, H01H50/16, H01H51/22, H01F7/14, H01F7/16
Cooperative ClassificationH01F7/14, H01H51/2236, H01F7/1615, H01F7/122, H01H50/22
European ClassificationH01H50/22, H01F7/16A1, H01F7/14, H01H51/22D