US3716810A - Reed switch - Google Patents

Reed switch Download PDF

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Publication number
US3716810A
US3716810A US00206013A US3716810DA US3716810A US 3716810 A US3716810 A US 3716810A US 00206013 A US00206013 A US 00206013A US 3716810D A US3716810D A US 3716810DA US 3716810 A US3716810 A US 3716810A
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United States
Prior art keywords
reed
reeds
contact
switch
reed switch
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
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US00206013A
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English (en)
Inventor
T Hara
T Oguma
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Fujitsu Ltd
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Fujitsu Ltd
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Publication date
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Publication of US3716810A publication Critical patent/US3716810A/en
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Expired - Lifetime legal-status Critical Current

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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

  • ABSTRACT A reed switch comprises apair of reeds positioned so that the locus of operation of the freeend of at least one of the reeds does not cross the other of the reeds.
  • Contact material is provided in the area of the free I end of each of the reeds. The contact material on at least one of the reeds is mounted to deviate from the free end of the one of thereeds.
  • the present invention relates to-a reed switch. More particularly,theinvention relates, to areed switch used to close and open. an electri'c circuit.
  • the reed switch of the, invention comprisesa pair of.
  • the reed, switch is positioned in a JOiLtb providefa reed relay.
  • the principalobjefct of theyinventionn is:- toprovide a new. and, improved Freed; .switchiwhi'ch overcomes th disadvantagesof knowniypesofi reed-switch-
  • n0 Protectivecircuit utilized to prevent such; adhesion-1
  • Another. objectof the-invention is,to p'rovide a reed switch which may -.be utilizedas a.;threshold limit element.
  • s iAnotherobjectlof theinvention istoprovide a reed switchhavinga largecontactfgap; thick contacts and long slidingjatthe. contacts, which: reed. switch is par- I ticularlysuitablefor useg-in telecommunication equipment, telephone exchangeequjpmentand.various electronicv equipment andlfunctions; therein with long life, high reliability, efficiencyand,effectiveness.
  • Another object. of-the,inivention isato.provide. a, reed switch, having thesam'eworkingv ampere-turns and releasing ampere turns, so. that it-.is-.utili'zable asareed relay and asathresholdlimitelement.
  • areed switch comprises-a,pair-of;reeds.:positionedfl-so that'the locus of operation of; the, free-,end of at1least -one of the .reeds does not cross, theothenofathe reeds.
  • Contact material is, provided in -the area. of the ,ireeaendof each of the reeds.
  • the contact-material.on.:at leastpone of the reeds is mountedgto .deviatefromthe' free .;end .;of the one of the reeds.
  • the free ends of thereedsiar'e spaced from each other in every one of the reeds extends beyondthefre'e end of the one of-the reeds toward the other of the reeds.
  • the contact material on the one of the reeds comprises a spring.
  • FIG. 3 is a graphicalprese'ntation of the magneticf characteristics of a reed switch of the prioraart
  • FIG. .4 is a perspective view of the contact area of an embodiment of the reed switch of the invention.
  • FIG. 5a is a schematic diagram of the-contact area of another embodiment of the reed'switch of the invention.
  • FIG. 5b is aschematic diagram of thecontact area of still another embodiment of the reed switch of themvention.
  • FIG. 6 isa graphical presentationof the magnetic characteristics of the reed" switch of the invention.
  • FIGKI is a graphical presentation of the magnetic characteristics of reed switches of the priorart andthe reed switch of the invention.
  • FIGS 8a, '8b,-8c,-8d and 8e are perspective views of differentsmodifications of yet another embodiment of the reed switch ofthe invention.
  • FIG. 1 illustrates a known type. of reed switch:
  • reeds 1' and-2 are of rod-like configuration and comprise, for example, 52 alloy. g
  • the free ends of the .reeds land 2, which are to bear the'contact material, are melted down in order to provide them with an appropriate spring or resiliency characteristic.
  • the free. end 3 of the: reed-1' is plated with the contact'material.
  • the free end 4of the reed 2 is plated with thecontactmaterial.
  • the contact material comprises precious metals.
  • the reeds 1 and 2 are sealed in a glass tube 51in the.
  • the reedswitch may be inserted 7 into a coil or winding 6whichrnay be woundon a bob condition'ofthe, switch-and-the contact material on the bin 7, thereby providing a reed relay.
  • F IG. 2 illustrates the area'of the contacts of a known type-of reedswitch.
  • FIG. 2' isa representation of the contact area of the reed switch of FIG. 1 on a considerably enlarged scale.
  • the area 8 is the melted down partofthereed'l andthe area 9 is the melted down partof the reed 2.
  • the reedl has a contact part 11, which'is the free end of said reed, plated v with precious metals.
  • the reed 2 has a contact part-12', which-is the free endof said'reed; plated withpreciousmetals. 1
  • the contact areas 11 and 12 are positioned adjacent each other in a manner whereby the locus of operation of each crosses the other.
  • the contacts 11 and 12 are spaced from each other by a distance x,.
  • the force of 'magnetic attraction on the reeds l and 2 in their contact areas 11 and 12 is directly proportional to the gap or space '16,.
  • the space x may thus not be increased since a large attractive force is required.
  • the distance .1 is from 50 to 120 microns.
  • the contact areas are usually formed 'by thin non-magnetic material applied by plating or sputtering.
  • the contact material is thus very restricted. Since the contacts 11 and 12 are thin, they suffer erosion, transfer and wear due to the impact ,of said contacts and the current flowing between said contacts at the instant of make and break after a specific number of operations. This results in bad contact or improper release. Furthermore, uneve'ness in the contacts due to the transfer is increased in accordance with the'magnitude of the current'flowing between said contacts.
  • Improper-release may be caused b'y'minute-unevenness in aknown reed relay in which the gap x, between the contacts cannot be made large. Furthermore, it is obvious that make and break of the large current which increases unevenness due to the transfer becomes impossiblenln a conventional reed relay the release is non-abrupt in the structure of FIG. 1, so that improper release is inevitable.
  • FIG. 3 illustrates the magnetic characteristic of a known reed switch.
  • the abscissa represents the excitation in ampere-turns and. the ordinate represents the magnetic flux density dz.
  • working ampere-turns are illustrated at a point m and the release ampere-turns are illustrated at a point n.
  • the release ampere-turns are less than the working ampere-'tums. This is due to the magnitude of the'demagnetizingfield. That is, the magnitude of the demagnetizing field is proportional to its length, provided that the material and cross-sectional area are the same. f
  • the produced demagnetizing field is determined by the length of each reed, whereas when thecontacts are closed or in contact, the produced demagnetizing field is determined by the sum of the length of each reed. Accordingly, the
  • FIG. 4 shows a reed switch of the invention.
  • the structure of the reed switch is the same as that of the known reed switch, except that the free endsof the reeds are spaced from each other and the free end of one of the reeds is extended in a direction toward the other.
  • the free ends of a first reed 41 and a second reed 42 are spaced from each other by and 42 thus does not come into contact with that of the other in any condition of the switch.
  • the reeds 41 and 42 comprise magnetic material.
  • a contact 43 is provided in the area of the free end of the first reed 41.
  • a contact 44 is provided in the area of the free end of the second reed 42.
  • the contacts may be affixed to the corresponding reeds by any suitable means such as, for example; welding.
  • the contact 44 of the reed 42 extends beyond-the free end of said reed toward the reed 41.
  • the reeds 41 and 42 comprise magnetic material such as, for example, 52 alloy.
  • the contacts 43 and 44 comprise materials such as, for example, nickel, tungsten, molybdenum, lead, gold and silver, and palladium and mercury.
  • the thickness of the contact 44 is selected for suitable or appropriate stiffness so that said contact functions as a spring or resilient body. Since the free ends of the reeds 41 and 42 do not overlap, the gap x between the contacts 43 and 44 thereof may be made large.
  • the bottom surfaceof the reed 42 is spaced a distance x;, from the bottom surface of the reed 41.v
  • the reed switch of the present invention functions in the following manner.
  • the contact 44 of the reed 42 abruptly approaches the contact 43 of the reed 41 and said'contacts come into contact with each other.
  • the free end of each of the reeds 41 I The release force operates as the contact force between the contacts 43 and 44.
  • the total release force is the sum of the release force based upon the displacement of the reeds 41 and 42 and the release force of the contact 44.
  • Stabilization may be provided at the point where the total release force and the attractive force of the reeds 41 and 42 come to a balance. These are primarily the vertical components of such forces.
  • the point of balance is a point at which the reeds 41 and 42 slip slightly up and down. That is, the balance is maintained under a magnetically biased condition.
  • the reed switch of the invention permits a greater make and break of the current than that of a'conventional reed switch by making the contact gap at, the same as the contact gap x of the conventional reed switch.
  • FIG. 6 illustrates the magnetic characteristic of the reed switch of the invention.
  • the abscissa represents the excitationin ampere-turns and the ordinate represents the magnetic flux density (b.
  • a point P in FIG.'6 represents the working ampere-turns and the releasing ampere-turns, which are equal to each other.
  • the working and releasing ampere-turns are equal, because of the difference of thereed switch of the invention over a conventional reed switch, which difference is that there is no contact between the reeds opposite each other and the magnitude of demagnetization is constant independent of the release and closing of the contact. Accordingly, the reed switch of the invention may be utilized as a threshold limit element, thereby expanding the utilization of the reed switch.
  • the speed of release of the contacts 43 and 44 of the reed switch of FIG. 4, after the release of the bent contact 44, is great compared tothe speed of .release of the contacts of a conventional reed switch, as shown in FIG. 2, for example. Thisis due to the addition of the release energy of the contact member 44 in the reed switch of FIG. 4.
  • the reed switch of the invention provides impulsive release. Since the reed switch of the invention provides impulsive release, the force of contact and the force of release between the contacts are great, so that adhesion or sticking of the contacts is eliminated.
  • FIG. 7 illustrates theattractive force characteristics and explains the contact gap.
  • the abscissa represents the displacement of the reed in millimeters and the ordinate represents the attractive force in grams.
  • x is the displacement of the reeds l and 2.
  • the reeds 41 and 42 are displaced by the distance x;,.
  • the distance x is substantially vertical, extending up and down.
  • a curve 7l shows the attractive force characteristic of the conventional reed switch.
  • a curve 72 shows the attractive force characteristic of the reed switch of the invention.
  • the reeds comprise a square bar of 52 alloy having'a cross-sectional area of 0.37 mm. The thickness of the bar was 0.54 mm and the width of the bar was 0.82 mm. The gap t in the reed switch of the invention, as shown in FIG. 4, was 0.01 mm.
  • a curve 711 of FIG. 7 shows the release force I characteristic of the conventional reed switch.
  • a curve 721 shows the release force characteristic of the reed grams attractive force. If the attractive force charac-.
  • teristic 71 is selected in-anticipation' of a small surplus, the gap x, between the reeds l and 2 is approximately 0.15 mm.
  • the release force characteristic shown by the curve 721 of FIG. 7 may be selected toward the same release force of 5 grams,in which case the displacement x between the reeds 41 and 42 (FIG. 4) is approximately 0.34 mm.
  • the displacement of thereed switch of the invention is more than double the displacement of :the conventional read switch, so that the contactgap is greatly improved.
  • FIGS. andSb show another embodiment of the reed switchiof the invention.
  • the .reeds 51 and 52"c'omprise magneticmaterial such as, for example, 52 alloy.
  • a contact 53 or 53 is affixed to the reed 51 and a spring 54 or 54' extends from the reed 52 toward the reed 51.
  • a contact 55 or 55' is affixed to the spring 54 or 54' in each of FIGS. 5a and 5b.
  • the contacts 53 and 55 are thin and there is a sufficient contact gap between them.
  • the contact gap may, however, become insufficient due to the necessity for using-thick contacts under the particular circumstances which determine the use of the reed switch.
  • the thick contacts 53' and 55' of FIG. 5b may be utilized.
  • the desired contact gap may be provided by bending the spring 54' away from the contact 53 but extending said spring substantially linearly over the-
  • the reeds 801 and 802 are rods of magnetic material such as, for example, 52 alloy.
  • a substantially spherical contact 805 is affixed to the first read 801 by anysuitable means such as, for example, welding.
  • a contact 806 is affixed to the substantially flat portion 804 of the second reed 802 at an end 807 thereof.
  • the contact 806 is resilient and functions as a spring.
  • the contact 806 comprises a precious metaLsuch as, for example, tungsten,-nickel; molybdenum, gold and silver, gold and lead, palladium, silver and palladium, and copper and palladium.
  • the contact 805 comprises a precious metal of the same group of metals as the contact 806. I 1
  • the first reed 801 comprises a tube having an axial bore extending therethrough, instead of a rod, as in the embodiments of FIGS. 8a and 8b.
  • the first reed 801 of FIG. 8c may thus be utilized for replacing inert gas of nitrogen and hydrogen, or reducing gas such as hydrogen and carbon monoxide, for the air in the glass housing 803 after said housing is sealed. That is, an inert or reducing gas is supplied'through the axial bore of the reed 801. After the gas exchange is completed,the bore of the reed'80l is sealed by any suitable-means such as, for example,
  • the first and second reeds 801'. and 802 have the configuration of plates.
  • the first and second reeds comprise 52 alloy. The free end of the second.
  • welding and may have a cylindrical configuration.
  • FIG. 8d The difference between the embodiments of FIGS. I 8d and 8e is'that in FIG. 8d, a slot 811 is provided in the free end of the contact area 808' to form twin contact parts 812 and 813.
  • a slot 811 is provided in the free end of the contact area 808' to form twin contact parts 812 and 813.
  • one of the contact parts 812 and 813 such as, for example, the contact part 813, has an oxide film.
  • the contact part 813 is bent. In this case, the other contact part 812 contacts the contact 809 and results in reliable contact and switching.
  • the magnetic attraction structure of the invention is applicable to general electromagnetic switches. Furthermore, the aforedescribed embodiments relate to a reed switch having a make contact. The invention, however, is applicable to'a reed switch having a break contact by means of a simple well known technique.
  • a reed switch comprising a pair of reeds of ferromagnetic material, at least one of said reeds being movable, said reeds having free ends spaced from one another in every condition of the switch, a first contact member secured to one of said reeds and passing beyond the free end if said one reed to extend over the free end of the other reed, and a second contact member secured to said other reed, said switch being opened and closed at said contact members by the displacement of at least one of said reeds.
  • a reed switch as claimed in claim 2 wherein said spring is flexed when said contact members are closed during operation of the switch.
  • a reed switch as claimed in claim 1 wherein said second contact member is secured to said other reed at a position displaced from the free end of said other reed.
  • a reed switch as claimed in claim 1 wherein said first contact member is .bent away from said second contact member but extends substantially linearly over said second contact member.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Contacts (AREA)
  • Transmission And Conversion Of Sensor Element Output (AREA)
  • Switches That Are Operated By Magnetic Or Electric Fields (AREA)
US00206013A 1970-12-11 1971-12-08 Reed switch Expired - Lifetime US3716810A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP45109398A JPS4911511B1 (nl) 1970-12-11 1970-12-11

Publications (1)

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US3716810A true US3716810A (en) 1973-02-13

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Application Number Title Priority Date Filing Date
US00206013A Expired - Lifetime US3716810A (en) 1970-12-11 1971-12-08 Reed switch

Country Status (6)

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US (1) US3716810A (nl)
JP (1) JPS4911511B1 (nl)
DE (1) DE2158875A1 (nl)
FR (1) FR2117621A5 (nl)
GB (1) GB1373225A (nl)
NL (1) NL158646B (nl)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4085392A (en) * 1976-01-14 1978-04-18 Gordos Corporation Reed switch construction
US5969311A (en) * 1995-01-12 1999-10-19 Siemens Aktiengesellschaft Mechanical inertia switch
US20020130740A1 (en) * 2001-03-13 2002-09-19 Takamisawa Electric Co.,Ltd Switch operable under a predetermined condition, external magnetic field generating unit, combination of such a switch and an external magnetic field generating unit and electronic apparatus incorporating the same
US20140049346A1 (en) * 2011-03-16 2014-02-20 Kabushiki Kaisha Yaskawa Denki Reed switch

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS547705U (nl) * 1977-06-16 1979-01-19
GB2204449A (en) * 1986-08-23 1988-11-09 Stc Plc Reed relay contacts

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2892052A (en) * 1956-02-15 1959-06-23 G M Giannini & Co Inc Magnetically operated sealed switch apparatus
US3327263A (en) * 1966-03-30 1967-06-20 Allis Chalmers Mfg Co Liquid means for improving current carrying capacity of reed type switch

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2892052A (en) * 1956-02-15 1959-06-23 G M Giannini & Co Inc Magnetically operated sealed switch apparatus
US3327263A (en) * 1966-03-30 1967-06-20 Allis Chalmers Mfg Co Liquid means for improving current carrying capacity of reed type switch

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4085392A (en) * 1976-01-14 1978-04-18 Gordos Corporation Reed switch construction
US4148000A (en) * 1976-01-14 1979-04-03 Gordos Corporation Reed switch construction
US5969311A (en) * 1995-01-12 1999-10-19 Siemens Aktiengesellschaft Mechanical inertia switch
US20020130740A1 (en) * 2001-03-13 2002-09-19 Takamisawa Electric Co.,Ltd Switch operable under a predetermined condition, external magnetic field generating unit, combination of such a switch and an external magnetic field generating unit and electronic apparatus incorporating the same
US6972651B2 (en) * 2001-03-13 2005-12-06 Takamisawa Electric Co., Ltd Switch operable under a predetermined condition, external magnetic field generating unit, combination of such a switch and an external magnetic field generating unit and electronic apparatus incorporating the same
US20140049346A1 (en) * 2011-03-16 2014-02-20 Kabushiki Kaisha Yaskawa Denki Reed switch
US8760246B2 (en) * 2011-03-16 2014-06-24 Kabushiki Kaisha Yaskawa Denki Reed switch

Also Published As

Publication number Publication date
DE2158875A1 (de) 1972-06-29
NL7116859A (nl) 1972-06-13
GB1373225A (en) 1974-11-06
NL158646B (nl) 1978-11-15
FR2117621A5 (nl) 1972-07-21
JPS4911511B1 (nl) 1974-03-18

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