US3733569A - Magnetic switching assembly - Google Patents

Magnetic switching assembly Download PDF

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Publication number
US3733569A
US3733569A US00247319A US3733569DA US3733569A US 3733569 A US3733569 A US 3733569A US 00247319 A US00247319 A US 00247319A US 3733569D A US3733569D A US 3733569DA US 3733569 A US3733569 A US 3733569A
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United States
Prior art keywords
magnet
switching
magnetic
magnetic field
switching assembly
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Expired - Lifetime
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US00247319A
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English (en)
Inventor
N Yanagisawa
T Murata
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Alps Alpine Co Ltd
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Alps Electric Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H36/00—Switches actuated by change of magnetic field or of electric field, e.g. by change of relative position of magnet and switch, by shielding
    • H01H36/0006—Permanent magnet actuating reed switches
    • H01H36/0013—Permanent magnet actuating reed switches characterised by the co-operation between reed switch and permanent magnet; Magnetic circuits

Definitions

  • ABSTRACT A magnetic switching assembly is disclosed in which the magnet stroke for operative switching is reduced while maintaining reasonably wide tolerances in the relative positioning of the components thereby to provide faster and more accurate switching at low cost.
  • an actuating magnet is positioned adjacent a reed switch for movement toward and away from the switch contacts to provide operative switching in both directions.
  • a second permanent magnet is disposed at right angles to the actuating magnet and is effective to deflect the magnetic field associated therewith thereby to provide a steeper magnetic field strength gradient in the direction of the magnet stroke. The magnet stroke is thereby minimized while maintaining the positioning tolerances of the reed switch and magnet at values permitting low cost manufacture.
  • the second magnet which serves to deflect the magnetic field of the driving magnet is formed integral with the driving magnet in an L-shaped configuration.
  • FIG 75 FIG. 74
  • This invention relates to magnetically actuated switches and more particularly to an improved actuating means for a magnetically actuated switch of the pushbutton type.
  • Magnetic switching devices are used in a variety of applications particularly in the communications and data processing fields where rapid and reliable manually actuatable switching is required.
  • the most commonly utilized switching device in this category is the reed switch which comprises a pair of contacts encapsulated in glass or the like, those contacts being movable into and out of electrical engagement with each other in response to the variation in magnetic field.
  • a permanent magnet is positioned adjacent the operative switching device and is movable relative thereto,.thereby to vary the magnetic field strength in the vicinity of the switch contacts.
  • those contacts are resilient and overlappingly disposed within the glass casing in spaced relationship to provide a resiliently biased normally open circuit between the output leads extending from opposite ends of the casing.
  • the permanent magnet As the permanent magnet is moved closer to the switch contacts, the magnetic field strength or flux density in the vicinity of those contacts increases and the spaced contacts are magnetically attracted to one another. That magnetic attraction increases in response to the movement of the permanent magnet until it is sufficient to overcome the resilient bias of the contacts whereupon those contacts are drawn into operative physical and electrical engagement to close the circuit between the output switch terminals.
  • the reverse effect results the magnetic field strength decreases resulting in a loss of magnetic attraction between the contact arms, whereby those contact arms spring back to their normally open positions.
  • reed switches of the pushbutton type typically utilize a movable bar magnet having opposite magnetic poles at either end.
  • the magnetic field strength gradient lines of the magnet extend outwardly from either pole in an arcuate configuration, the field strength decreasing in a radially outwardly direction. If the reed switch is disposed opposite one pole of the magnet with the magnet movable toward or away from I the switch contacts, a maximum lateral tolerance for alignment is achieved.
  • this arrangement involves relative movement of the magnet along its minimum magnetic field strength gradient (the lowest rate of change of field strength) thereby requiring a maximum travel stroke of the magnet to effect operative switching in both directions.
  • the magnet may be positioned closer to the reed switch and movable past the reed switch in a direction parallel to a plane through the switch contacts thereby to take advantage of the steeper magnetic field strength gradient in that direction.
  • This arrangement requires the manufacture of parts and positioning thereof to extremely close tolerances to insure that the magnet is close enough to the switch contacts to effect switching yet to insure against contact with the fragile glass casing. The manufacturing cost is accordingly significantly increased.
  • the present invention comprises a reed switch assembly including a pair of normally spaced resilient contact arms encased within an elongated housing, said switching device being actuated by the movement of a permanent magnet movably positioned closely adjacent thereto.
  • the permanent magnet comprises an L-shaped magnetic assembly having a first pole on one leg thereof and a second pole on the other leg thereof. That L-shaped magnet assembly is mounted with its inwardly facing operative surface spaced from the reed switch casing and movable in a direction parallel to one of its legs.
  • the magnetic field associated with the other leg of the magnet is effective to provide operative switching of the resilient contact arms between their normally open position and a closed position resulting from the magnetic attraction of those contact arms effected by an increase in the magnetic field strength as the permanent -magnet is moved toward the reed switch.
  • the magnetic field associated with the second leg of the assembly interferes with the magnetic field associated with the operative switching leg of the magnet and deflects it to a flattened condition, thereby to significantly increase the magnetic field strength gradient in the direction of movement toward and away from the reed switch. Accordingly, this arrangement results in a reduced travel stroke required for effective switching while at the same time maintaining a rather wide lateral tolerance for the positioning of the magnet relative to the reed switch.
  • FIGS. 1 and 1A are perspective views of two embodimerits of permanent magnets commonly used in prior art reed switches;
  • FIGS. 2A, 2B and 2C show three embodiments of prior art reed switch assemblies utilizing the permanent magnet of FIG. 1A wherein the permanent magnet is movable in the direction parallel to the plane of the reed switch;
  • FIG. 3 is an illustration similar to that of FIGS. 2A, 2B and 2C of another prior art reed switch assembly employing the permanent magnet of FIG. 1A wherein the magnet is movable toward and away from the reed switch in a direction perpendicular to its axis.
  • FIG. 4 is a graphical illustration of the switching operation of a reed switch as a function of magnetic field strength
  • FIG. 5A is a schematic illustration of the magnetic field associated with two permanent magnets disposed at right angles to each other;
  • FIG. 5B is a side elevational view, partly in section, of one embodiment of the present invention employing two permanent magnets disposed at right angles to each other in contiguous relationship;
  • FIG. 5C is a side elevational view, partly in section, of a second embodiment of the present invention utilizing a pair of permanent magnets having different dimensions;
  • FIG. 6A is a side elevational view, partly in section, of a third embodiment of the present invention utilizing an integral L-shaped permanent magnet
  • FIG. 6B is a perspective view of the permanent magnet used with the embodiment of FIG. 6A;
  • FIG. 7A is a side elevational view, partly in section, of a fourth embodiment of the present invention utilizing an integral L-shaped permanent magnet.
  • FIG. 7B is a perspective view of the permanent magnet used in the embodiment of FIG. 7A.
  • the conventional reed switch comprises a pair of electrically conductive contact arms 12 and 14 mounted in slightly spaced overlapping relationship within a housing or capsule 1 I typically made of glass.
  • the overlapped ends of the contact arms 12 and 14 define the operation contact surfaces, the other ends of those arms extending in opposite directions through the opposite ends of the housing 11 to form the operative output terminals T1 and T2 of the switch.
  • the contact arms 12 and 14 are typically made of a resilient metallic material and in absence of external influences are disposed in the slightly spaced or open position illustrated in FIG. 2C, thereby to define an open circuit between the output switch terminals T1 and T2.
  • the switch is closed by causing the contact arms to move towards each other into operative engagement. This is accomplished by the application of a magnetic field of sufficient strength to provide a magnetic attraction between the contact arms sufficient to overcome their natural resiliency which normally maintains them in the spaced or open position.
  • FIG. 4 The switching action of a reed switch as a function of magnetic field strength (i.e. intensity or flux density through the contacts) is illustrated schematically in FIG. 4.
  • the magnetic field strength here represented by flux density B
  • B2 the magnetic field strength
  • the magnetic field strength is thereafter reduced below the B2 value (as represented by the upper horizontal line 18 moving to the left)
  • the contacts do not resile back to their open position (FIG.
  • the difference between the magnetic field strengths B1 and B2 represents the minimum variation in flux density which will efiect operative switching in both directions. That variation is produced in a manually actuated reed switch by the reciprocal movement of a permanent magnet.
  • FIG. 1A there is illustrated a permanent bar magnet 10 of the type used to actuate the conventional reed switch comprising an elongated bar of magnetized material (i.e. ferro-magnetic iron) having a north pole N at one end and a south pole S at its other end.
  • a planar four-pole magnet 10A such as that illustrated in FIG. 1B, may be utilized.
  • the reed switch assemblies of FIGS. 2 and 3 are illustrated in connection with an actuating magnet of the two-pole bar type as illustrated in FIG. 1A. It will be appreciated, however, that the principles discussed below apply equally to the use of alternate conventional actuating magnets such as that illustrated in FIG. 1B.
  • the magnetic field strength (flux density) associated with a pennanent magnet varies as a function of the distance from its poles-the flux density decreases in a direction away from the operative pole.
  • the variation in magnetic field strength is illustrated by the solid gradient line B2 which represents the connection between all points having a flux density value of B2 and the broken gradient line B1 which represents the connection of all points having a lower flux density value of B1. Accordingly, when the contact arms 12 and 14 are positioned outside of the area bounded by broken gradient line B1, the contacts are open, as illustrated by the solid line position of the switch 11 in FIG. 3.
  • the magnet In order to switch from that open position to the closed position of the contacts, the magnet must be moved downwardly in the X direction by a distance sufficient to bring the contact arms within the area bounded by the solid line B2 within which area the flux density is greater than the value E2, the value sufficient to close the switch contacts (see FIG. 4). Conversely, in order to again open the switch contacts, the magnet 10 must be moved upwardly in the Y direction by a distance sufficient to position the contact arms 12 and 14 outside of the area bounded by the broken gradient line B1 which represents the area within which the magnetic flux density is greater than the value B1. Accordingly, when the reed switch 11 is aligned directly beneath the pole of the magnet 10 as illustrated in solid lines in FIG.
  • the distance D between the lines B1 and B2 along the XY axis represents the minimum distance which the magnet 10 must be adapted to move in order to effect operative switching in both directions (the thickness of the contacts and space therebetween is here neglected for the sake of simplicity).
  • the maximum latitude or tolerance L of positioning of the reed switch relative to the magnet 10 in a direction perpendicular to the XY axis is defined between the vertical broken lines L1 and L2.
  • the reed switch may be positioned anywhere within the broken vertical boundary lines L1 and L2 and still be in registration with at least a portion of the magnetic field within the gradient line B2.
  • the magnet 10 must be movable by a minimum distance of D In'order to minimize the distance D by which the magnet must be moved to accomplish switching, the magnet may be positioned for movement in a direction parallel to a plane through the axis of the switch.
  • FIGS. 2A-2C Three such prior art arrangements are illustrated in FIGS. 2A-2C.
  • FIG. 2A the magnet 10 is disposed with its north and south poles vertically spaced while the reed switch is horizontally disposed closely adjacent the magnet 10.
  • the magnetic field within the solid line B2 associated with the north pole encompasses the contact arms 12 and 14, thereby to close same and upon movement in the opposite Y direction those contacts resile to the open position upon crossing the broken gradient line B1. Since the lines B1 and B2 are closer at the point of crossing of the contacts 12 and 14 in this embodiment (the flux density gradient is steeper in this region), the distance D or D defining the required magnet stroke for operative switching (for the precisely aligned and maximum lateral tolerance conditions, respectively) is reduced. However, in this embodiment the maximum lateral tolerance L of positioning the reed switch relative to the magnet in a direction perpendicular to the XY axis is quite small and accordingly the cost of manufacture is prohibitive.
  • the magnet is disposed with its north and south poles horizontally spaced in a direction parallel to the axis of the reed switch 11.
  • the magnet is again movable vertically in the XY direction past the reed switch and the operation is substantially identical to that illustrated and described with respect to FIG. 2A.
  • the reed switch 11 and magnet 10 are both disposed vertically and the magnet is movable vertically in the XY direction. Again, the operation is as described above. It should be noted, however, that in the embodiments of FIGS. 2A, 2B and 2C (as opposed to the embodiment of FIG. 3), the reed switch must be positioned much closer to the magnet so that the allowable tolerances are even further reduced in order to prevent the magnet from actually contacting the fragile glass casing of the reed switch. Moreover, in the embodiments of FIGS. 2A and 2C where the magnet is moved in the direction of its north-south axis, the upper end of the magnet stroke must be quite accurately limited in order to prevent inadvertent closing of the switch contacts by the lower or south pole of the magnet.
  • FIGS. 2A-2C provide for faster switching in less space (i.e. shorter magnet strokes) but at substantially increased cost (resulting from the requirement of closer tolerances) while the lower cost of the reed switch assembly of FIG. 3 (resulting from the wider tolerances permitted) is attained at the sacrifice in speed of operation and space requirements (i.e. longer magnet stroke).
  • the present invention provides a magnetic switching assembly adapted to provide the shorter magnet stroke of the embodiments of FIGS. 2A-2C for faster switching in less space while at the same time maintaining the wide tolerances for positioning the reed switch relative to the permanent magnet which enables the construction of the assembly at low cost.
  • FIG. 5A is a schematic illustration (in end view) of two permanent bar magnets 20 and 22 disposed at right angles to each other in spaced relationship.
  • the magnetic fields associated with these magnets do not interfere with one another.
  • the reed switch 11 is positioned below the south pole of the horizontally disposed actuating magnet 20, that magnet being movable vertically along the XY axis toward and away from the reed switch 11.
  • the maximum lateral tolerance L within which the reed switch may be positioned and still be in registration with at least a portion of the magnetic field within the gradient line B2 is considerably larger than that of the embodiments of FIGS. 2A-2C.
  • the required magnet stroke D, for this rather large lateral tolerance L is still considerably smaller than that of the embodiment of FIG. 3. Accordingly, by providing a magnet assembly comprising two bar magnets disposed at right angles and mounted in a suitable framework (not shown) for movement toward and away from the reed switch as illustrated in FIG. B, the advantages of the prior art structures of both FIGS. 2A-2C and FIG. 3 are achieved.
  • FIG. 5C A further modification is illustrated in FIG. 5C.
  • the vertically disposed or biasing magnet 22' is considerably smaller than the actuating magnet and accordingly the reed switch 11 may be positioned closer to that biasing magnet thereby reducing the lateral dimension of the switch.
  • this savings in lateral space is accomplished at some sacrifice in the extent to which the magnet stroke may be minimized since the smaller the biasing magnet, the smaller the deflection of the field associated with the driving magnet and the larger the distance between the gradient lines B1 and B2 in the direction of the XY axis.
  • FIGS. 6 and 7 a single integral L-shaped magnet having appropriately positioned poles is substituted for the two magnet assemblies of FIGS. 58 and 5C.
  • the magnet 24 in the embodiment of FIG. 6 is generally equivalent in operation to the two-magnet assembly of FIG. 5B whereas the design of the magnet 26 of the embodiment of FIG. 7 is similar to that of the assembly of FIG. 5C.
  • the use of an integral one-piece magnet eliminates the need for a mounting frame to maintain the magnets of FIGS. 58 and SC in operative relative positions and accordingly substantially reduces the cost of manufacture and assembly. It will be appreciated that the embodiments of FIGS. 5B, 5C, 6 and 7 all provide an improved reed switch assembly which may be assembled at reasonable cost while at the same time providing a substantially increased speed and reliability of operation while minimizing space requirements.
  • a magnetic switching assembly comprising switching means movable between at least two operative switch positions under the influence of a magnetic field, said switching means being movable from a first to a second position upon entering a magnetic field having an intensity greater than a first value and being movable from said second position back to said first position upon moving into a magnetic field having a second intensity less than a second value, said first intensity value being greater than said second intensity value, first permanent magnet means disposed adjacent common plane with said switching means in a first direction toward and away from same, said first magnet means having a normal magnetic field intensity which decreases from a value greater than said first intensity value to a value less than said second intensity value in said first direction, whereby said switching means may be operatively switched between said first and second operative switch positions by a reciprocating movement of said permanent magnet toward and away from said switch means in said first direction by a given minimum distance, the improvement comprising second permanent magnet means adjacent said first permanent magnet means and having a magnetic field extending in a second direction angularly disposed to said first direction
  • said first and second magnet means comprises the angularly disposed legs of a single integral permanent magnet.
  • said first and second magnet means comprises the angularly disposed legs of a single integral permanent magnet.

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  • Switches That Are Operated By Magnetic Or Electric Fields (AREA)
  • Push-Button Switches (AREA)
US00247319A 1971-05-10 1972-04-25 Magnetic switching assembly Expired - Lifetime US3733569A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP46030964A JPS5228994B1 (enrdf_load_stackoverflow) 1971-05-10 1971-05-10

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US3733569A true US3733569A (en) 1973-05-15

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US00247319A Expired - Lifetime US3733569A (en) 1971-05-10 1972-04-25 Magnetic switching assembly

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US (1) US3733569A (enrdf_load_stackoverflow)
JP (1) JPS5228994B1 (enrdf_load_stackoverflow)
DE (1) DE2203168C3 (enrdf_load_stackoverflow)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4144568A (en) * 1976-09-17 1979-03-13 Hiller Alexander J Exercise recorder

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3133173A (en) * 1960-07-15 1964-05-12 Int Standard Electric Corp Rotating magnetic reed switch
US3356948A (en) * 1962-10-20 1967-12-05 Int Standard Electric Corp Electrical switching unit, controlled through permanent magnets with a reed contact, having a freely movable armature

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3133173A (en) * 1960-07-15 1964-05-12 Int Standard Electric Corp Rotating magnetic reed switch
US3356948A (en) * 1962-10-20 1967-12-05 Int Standard Electric Corp Electrical switching unit, controlled through permanent magnets with a reed contact, having a freely movable armature

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4144568A (en) * 1976-09-17 1979-03-13 Hiller Alexander J Exercise recorder

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DE2203168C3 (de) 1980-06-26
DE2203168A1 (de) 1972-11-23
DE2203168B2 (de) 1979-10-11
JPS5228994B1 (enrdf_load_stackoverflow) 1977-07-29

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