US3478287A - Magnetic reed contact assemblies - Google Patents

Magnetic reed contact assemblies Download PDF

Info

Publication number
US3478287A
US3478287A US712454A US3478287DA US3478287A US 3478287 A US3478287 A US 3478287A US 712454 A US712454 A US 712454A US 3478287D A US3478287D A US 3478287DA US 3478287 A US3478287 A US 3478287A
Authority
US
United States
Prior art keywords
reed
electrode
voltage
counterbalancing
arrangement
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US712454A
Other languages
English (en)
Inventor
Thomas Harrett
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
International Standard Electric Corp
Original Assignee
International Standard Electric Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by International Standard Electric Corp filed Critical International Standard Electric Corp
Application granted granted Critical
Publication of US3478287A publication Critical patent/US3478287A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H51/00—Electromagnetic relays
    • H01H51/28—Relays having both armature and contacts within a sealed casing outside which the operating coil is located, e.g. contact carried by a magnetic leaf spring or reed
    • H01H51/287—Details of the shape of the contact springs

Definitions

  • the invention relates to magnetic reed contact as--" semblies for incorporation in magnetic reed switches.
  • assemblies normally take the form of a pair of contact members of magnetic material,- one or both of which are cantilevers, sealed in a glass envelope which, commonly, is evacuated. In operation the assembly is inserted I in a solenoid or otherwise arranged so that when a magnetic field is applied across the gap between the contact members they are attracted together and'close a circuit path.
  • tact gap are concerned, a typical construction should be 'able to withstand several kilovolts. If an attempt be made mature closure at high voltages. We are: not concerned with vthe magnetic design, nor, indeed, with theproblemof using a magnetic reed switch to break a high voltage circuit under load. a
  • a magnetic reed contact assembly including a cantilever reed of magnetic material, the .free end of which overlaps another electrode ofi-Inagnetic material and is arranged to be attracted to and contact the other electrode when a magnetic field is applied between them and to be urged to a normal, out-of contact,.position by the elasticity of the reed when the magnetic'field is removed, the contact assembly further including an electrostatic.counterbalancing electrode ofnonmagnetic material positioned opposite. and connected to the said: other electrode withthe the" reed and the counterbalancing electrode substanthe accompanying drawings in which:
  • FIG. 1 is a diagrammatic sketch illustratingthe feasembly according to the invention
  • FIG. 2 is a diagrammatic sketch for assistance in discussing the electrostatic behaviour of a conventional single reed switch
  • FIG. 3 are curves illustrating the variation of elastic and electrostatic forces on the movable reed of FIG. 2;
  • FIG. 4 illustrates an arrangement, according to the invention, for counteracting the electrostatic force on the reed of a single reed switch
  • FIG. 5 illustrates a modification of the arrangement of FIG. 4
  • FIGS. 6, 7 and 8 are graphs showing the variation of the ratio of electrostatic force to elastic force in different single reed embodiments of the invention.
  • FIG. 9 illustrates a further modification of the arrangement of FIG. 4 as applied to a double reed contact assembly.
  • a pair of leads 1 and 2 are sealed through the respective ends of an evacuated glass envelope 3. These leads are normally of magnetic material. At the end of each lead is welded a thin reed 4, 5, respectively, of magnetic material. Each reed thus constitutes a cantilever. The free ends of these cantilevers overlap one another and form the contacts of the assembly.
  • the contacts may be plated or be provided with raised contact areas (not shown), to cooperate with one another.
  • each reed is associated with two further members, both of nonmagnetic material, brazed to the same lead 1 or 2 as the case may be.
  • the first of these additional members is a other reed lies approximately midway between reed and counterbalancing electrode, but slightly closer to the counterbalancing electrode.
  • the other member is a backing member 7 against which the reed rests when in its normal position.
  • the members -6 and 7 should be substantially rigid and, to illustrate this, are drawn much thicker than the reeds.
  • the functions of the counterbalancing electrode 6 and backing member 7 and the ,balancing electrodes are each 0.5 inch while the reeds are 0.010 inch in thickness and separated, in their normal position, by a gap also of 0.010 inch.
  • a reed 8 is shown cantilevered from a support 9, represented as a wall, and arranged to cooperate with a rigid fixed contact member 10. Let it be assumed that the free end of the reed 8 overlaps the fixed contact member 10 by a'distance a and that, in the normal position of the reed, the opposing surfaces of the members 8 and 10 are a distance d apart.
  • Points C and D correspond to points of equilibrium but, whereas C represents a point of stable equilibrium, at D the equilibrium is unstable.
  • the restoring force f is greater than the deflecting force 1, and so the reed, if deflected to a position between points C and D, will tend to return to the equilibrium position C. If it be deflected beyond the point D, however, the electrostatic force is greater than the restoring force and the contacts will close.
  • an electrostatic counterbalancing electrode 11 of non-magnetic material is placed opposite the fixed contact member 10 so that the reed 8 is midway between them in its normal position.
  • the electrodes 10 and 11 are strapped together so as to be at the same potential. It is evident that with the reed in its normal position the electrostatic forces are exactly counterbalanced.
  • FIG. 5 differs from those previously discussed in that, as the applied voltage is increased, the reed will merely be pressed more firmly against its backing member. It is true that this implies some increase in the magnetic field which must be applied to close the contacts, but the positional unbalance need only be slight. As the reed is moved inward, the electrostatic unbalance decreases until the reed is midway between the counterbalancing electrode and the other contact member, after which its behaviour can be expected to be similar to that of the balanced arrangement.
  • FIG. 5 An analysis of the arrangement of FIG. 5 may be made on somewhat similar lines to those for FIGS. 2 and 4 by substituting the following where the distance between the normal position of the reed and the counterbalancing electrode is rd, as indicated in FIG. 5.
  • V A V
  • V corresponds to the maximum voltage for the balanced arrangement
  • the corresponding graphs would differ only by 'an upward shift of the scale of ordinates.
  • the behaviour generally, is thus similar to the uncompensated case of FIG. 2 with the reed moving outward instead of inward as applied voltage is increased.
  • the reed moves in the same direction as in the arrangement of FIG. 2 when voltage is applied.
  • Equation 13 defines the maximum applied voltage for stability under dynamic conditions.
  • a 0.875 at 0.23
  • the critical dynamic voltage is thus, as is to be expected, somewhat less than the maximum static voltage for stability and its application causes the reed to deflect to somewhat beyond the position of limiting static stability before reversing its motion. Since, at its maximum deflection under dynamic conditions, the reed is momentarily stationary, the position of maximum deflection is that of the corresponding limiting deflection, at the reduced voltage, in the static case.
  • FIG. 1 is basically that of FIG. 5 except that, in place of one fixed contact member and one movable reed, there are two movable reeds each similarly provided with its own counterbalancing electrode and its own backing member. If desired the backing members could be omitted; the numerical design values would differ somewhat from those given above, but the general behaviour is similar.
  • the counterbalancing electrode is of the same efiective length as its reed. This is not essential; it would in fact be possible, instead of making a gap between a reed and its counterbalancing electrode smaller than that between the reed and its fellow contact member, to increase the overlap of the counterbalancing electrode and so increase the outward electrostatic force.
  • FIG. 9 shows a double reed arrangement with a second reed 8a replacing the fixed contact member 10 of FIGS. 4 and 5.
  • the reed 8a and the counterbalancing electrode 11 are both supported from a wall 9a and the reed 8a is arranged similarly to the reed 8 with a counterbalancing electrode 11a electrically connected to reed 8 through wall 9 and carrying dielectric material 13a interposed between it and its cooperating reed 8a. If the dielectric constant be k, the presence of the insulating material increases the outward com ponent of electrostatic force on each reed by the factor k.
  • the outer gaps may be increased by the factor k
  • the outer gaps would be 2.24 X the inter-reed gap, with the consequent advantage of lower electric intensity at the cost of some lowering of insulation resistance due to the presence of the solid dielectric.
  • a high voltage magnetic reed contact assembly including a cantilever reed of magnetic material the free end of which overlaps another electrode of magnetic material and is arranged to be attracted to and contact the other electrode when a magnetic field is applied between them and to be urged to a normal, out of contact, position by the elasticity of the reed when the magnetic field is removed, the contact assembly further including an electrostatic counterbalancing electrode of non-magnetic material position opposite and connected to the said other electrode with the free end of the reed in between them, the arrangement being such that when a high voltage is applied between the reed and the said other electrode, the reed being in its normal position, the electrostatic attraction between .the reed and the counterbalancing electrode substantially counteracts that between the reed and the said other electrode.
  • An assembly as claimed in claim 1 including a rigid non-magnetic backing member against which the free end of the reed rests when in its normal position.

Landscapes

  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Non-Mechanical Conveyors (AREA)
  • Switches That Are Operated By Magnetic Or Electric Fields (AREA)
US712454A 1967-03-17 1968-03-12 Magnetic reed contact assemblies Expired - Lifetime US3478287A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB02677/67A GB1164696A (en) 1967-03-17 1967-03-17 Magnetic Reed Contact Assemblies

Publications (1)

Publication Number Publication Date
US3478287A true US3478287A (en) 1969-11-11

Family

ID=10009104

Family Applications (1)

Application Number Title Priority Date Filing Date
US712454A Expired - Lifetime US3478287A (en) 1967-03-17 1968-03-12 Magnetic reed contact assemblies

Country Status (4)

Country Link
US (1) US3478287A (de)
CH (1) CH474827A (de)
FR (1) FR1569764A (de)
GB (1) GB1164696A (de)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20120235774A1 (en) * 2011-03-16 2012-09-20 Kabushiki Kaisha Yaskawa Denki Reed switch
US20170194119A1 (en) * 2014-09-26 2017-07-06 Deqiang Jing Magnetic reed switch

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2450499A (en) * 1945-09-21 1948-10-05 Bell Telephone Labor Inc Circuit maker and breaker
US2922856A (en) * 1956-12-20 1960-01-26 Siemens Ag Electromagnetic switch

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2450499A (en) * 1945-09-21 1948-10-05 Bell Telephone Labor Inc Circuit maker and breaker
US2922856A (en) * 1956-12-20 1960-01-26 Siemens Ag Electromagnetic switch

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20120235774A1 (en) * 2011-03-16 2012-09-20 Kabushiki Kaisha Yaskawa Denki Reed switch
US8659375B2 (en) * 2011-03-16 2014-02-25 Kabushiki Kaisha Yaskawa Denki Reed switch
US8760246B2 (en) 2011-03-16 2014-06-24 Kabushiki Kaisha Yaskawa Denki Reed switch
US20170194119A1 (en) * 2014-09-26 2017-07-06 Deqiang Jing Magnetic reed switch
US10217584B2 (en) * 2014-09-26 2019-02-26 Deqiang Jing Magnetic reed switch

Also Published As

Publication number Publication date
FR1569764A (de) 1969-06-06
GB1164696A (en) 1969-09-17
CH474827A (de) 1969-06-30

Similar Documents

Publication Publication Date Title
US2907846A (en) Polarized switching contact device
US3365592A (en) Piezoelectric relay
US2290320A (en) Circuit breaker mechanism
US3356948A (en) Electrical switching unit, controlled through permanent magnets with a reed contact, having a freely movable armature
US4595855A (en) Synchronously operable electrical current switching apparatus
US3478287A (en) Magnetic reed contact assemblies
US3470341A (en) Vacuum switch with liquid filled bellows operation
US2834848A (en) Electric switch
US3331040A (en) Miniature diaphragm relay
US3015707A (en) Relay
US3236965A (en) Sealed switch for strong currents
US3155804A (en) Mercury amalgam electrical contacts
US3053938A (en) Electromagnetically actuating relays in coordinate switches
US2983792A (en) Coordinate switching devices
US3068333A (en) Control device
US3166652A (en) Magnetic reed switch with latching feature
US2960585A (en) Electrically actuated contacting device
US2785241A (en) Electric circuit controllers
US3259715A (en) Locally biased reed switches
US3292121A (en) Bistable switching device
US1990348A (en) Electric switch
US2117047A (en) Circuit controlling device
US3211857A (en) Polarized electromagnetic relay
US2771527A (en) Snap action switch
US3316513A (en) Sealed contact reed switch having contoured reeds