US3644854A - Reed switch - Google Patents

Abstract

A reed-type switch having two contact tongues, at least one of which is provided with a permanent magnet polarized transversely of the longitudinal direction of the contact tongues and parallel to the direction of movement thereof. By said permanent magnet the adjoining part of the contact tongue concerned is magnetically saturated by a flux passing consecutively through the contact tongues and produced by external means. The direction of said flux at the contact area is opposite that of the flux of the permanent magnet. The value of said flux is such that the difference between the two fluxes is capable of moving the contact tongues from the open state into the closed state. When the contact tongues are closed, the magnet will maintain the closed condition.

Description

United States Patent 5] Feb. 22, 1972 Steenmeijer [54] REED SWITCH [72] Inventor: Jan Paul Steenmeijer, l-lilversum, Netherlands [73] Assignee: U.S. Philips Corporation, New York, N.Y.

[22] Filed: Apr. 20, 1970 [21] Appl. No.: 29,888

[30] Foreign Application Priority Data May 9, 1969 Netherlands ..6907099 [52] US. Cl ..335/ 153 [Si] Int. Cl. ..H0lh l/66 [58] Field ofSearch ..335/l53, 154, 83, 196

[56] References Cited UNITED STATES PATENTS OTHER PUBLICATIONS Bozorth, Ferromagnetism, 1951, page 282.

Primary Examiner-Hemard A. Gilheany Assistant Examiner-F. E. Bell Attorney-Frank R. Trifari [57] ABSTRACT A reed-type switch having two contact tongues, at least one of which is provided with a permanent magnet polarized transversely of the longitudinal direction of the contact tongues and parallel to the direction of movement thereof. By said permanent magnet the adjoining part of the contact tongue concerned is magnetically saturated by a flux passing consecutively through the contact tongues and produced by external means. The direction of said flux at the contact area is opposite that of the flux of the permanent magnet. The value of said flux is such that the difference between the two fluxes is capable of moving the contact tongues from the open state into the closed state. When the contact tongues are closed, the magnet will maintain the closed condition.

3,070,677 12/1962 Lowry ..335/l54 2,245,391 6/1941 Dickten ..335/ 83 4 Claims, 2 Drawing Figures 3 I, V/IY/JQIQW/IIA?2%%@@A@%E%A%AQA%A% PATENTEDFB22 1912 I INVENTOR. JAN P. STEENMEIJER zwwde R AGENT REED swr'rca The invention relates to a reed-type switch having two contact tongues and provided with at least one permanent magnet whose field holds the contact tongues closed once in the closed position.

In known switches of the kind set forth a permanent magnet is arranged near the contact tongues. If the contact tongues are housed in a hermetically closed envelope, the permanent magnet is located outside the envelope. A switch having a permanent magnet arranged in the proximity of the contact tongues has the disadvantage that a portion of the flux passes through the contact tongues, whereas a considerable portion merely extends through the air so that it does not contribute to holding the contact tongues in the closed state.

The invention has for its object to reduce materially said disadvantage.

The invention is characterized in that the permanent magnet is arranged on the side of one of the contact tongues facing the other contact tongue near the range of overlap of the two contact tongues, the direction of polarization of the permanent magnet being transverse of the direction of length of the contact tongues and parallel to their direction of movement thereof, while a considerable portion of the flux of the permanent magnet passes through the free end of said other contact tongue.

Because at least one of the contact tongues is provided in the manner described with a permanent magnet polarized transversely of the direction of length of the contact tongues, only a comparatively small portion of the flux of the permanent magnet passes solely through the air so that permanent magnets oflower strength and smaller size can be employed.

Switches of the kind set forth are intended for use as make contacts or break contacts in accordance with the strength of the permanent magnet.

In the make contact form the strength of the permanent magnet is insufficient for moving the contact tongues from the open state into the closed state without the assistance of an externally produced magnetic flux, but it is sufficient to hold the contact tongues once closed in the closed state without the assistance of an externally produced magnetic flux. The interruption of a contact once established and solely maintained by the field of the permanent magnet is performed by the application of an externally produced magnetic flux whose direction at the contact area is opposite that of the flux of the permanent magnet at the contact area and whose value is at least equal to the flux of the permanent magnet. With an external flux either produced by an energizing coil or by a permanent magnet it may readily occur that the flux required for interrupting the established contact is exceeded to an extent such that without taking countermeasures the contacts close again after having been interrupted or the contact may remain in the closed state and not be interrupted even for a short time.

In the form of a break contact the strength of the permanent magnet is sufiicient to move the contact tongues from the open state into the closed state without the assistance of an externally produced magnetic flux. The interruption of the closed contact is performed by the application of an externally produced magnetic flux whose direction at the contact area is opposite that of the flux of the permanent magnet at the contact area and whose value is at least equal to the flux of the permanent magnet. Also in the form of a break contact it may readily occur that the flux required for the interruption is exceeded to an extent such that without taking countersteps after the interruption the contacts close again or even remain in the closed state.

An advantageous embodiment of the magnetic tongue contact according to the invention is characterized in that with an externally produced magnetic flux passing consecutively through the contact tongues, whose direction at the contact area is opposite to that of the flux of the permanent magnet(s) and whose value is such that the difierence between the said two fluxes is capable of moving the contact tongues from the open state into the closed state, the magnet adjoining part of the contact tongue becomes unambiguously saturated.

The invention will be described more fully with reference to the drawing.

FIG. 1 shows schematically on a greatly enlarged scale an advantageous embodiment of a magnetic tongue contact in accordance with the invention, one of the contact tongues being provided with a permanent magnet.

FIG. 2 shows schematically a further advantageous embodiment of a magnetic tongue contact in accordance with the invention, the two contact tongues being provided with a per manent magnet.

The magnetic tongue contact 1 shown in FIG. 1 comprises two contact tongues 5 and 7, accommodated in a hermetically closed envelope 3 and overlapping each other in part and made of magnetizable material. The contact tongue 5 is provided with a cylindrical magnet 9, which is fastened to the side of the contact tongue 5 facing the contact tongue 7 near the free end of the contact tongue 7. The dimension of the permanent magnet 9 transverse of the contact tongue 5 (perpendicular to the plane of the drawing) is equal to the width of the contact tongue 5. It should be noted that said transverse dimension of the permanent magnet may also exceed the width of the contact tongue. The permanent magnet 9 is arranged at such a distance from the free end of the contact tongue 7 that a considerable portion of the flux of the permanent magnet 9 passes through said free end. The direction of polarization of the permanent magnet 9 is transverse of the direction of length of the contact tongues 5 and 7 and parallel to the direction of movement thereof, and in the situation shown (the reverse is also possible) the magnetic south pole is located near the part of the permanent magnet 9 joining the contact tongue 5 and the magnetic north pole is located near the part of the permanent magnet 9 opposite the former part. The field lines of the permanent magnet 9 mainly extend as is shown in FIG. 1. The flux from the permanent magnet 9 in the contact opening is insufficient to move the contact tongues 5 and 7 from the open state (as shown in the drawing) into the closed state without the assistance of an externally produced flux from an energizing coil 11 surrounding the envelope 3, whereas it is sufficient to hold the contact tongues 5 and 7 in the closed state without the contribution of a flux produced by the energizing coil so that the tongue contact 1 forms a makecontact. The establishment of the closed state of the contact tongues 5 and 7 is performed by means of a flux produced by the energizing coil 11 in the direction P (see FIG. 1), the direction of said flux at the area of the opening 13 between the contact tongues 5 and 7 being equal to that of the flux already prevailing in said area and originating from the permanent magnet 9. When the coil 11 is no longer energized, the contact tongues 5 and 7 remain in the closed state because, as stated above, the permanent magnet 9 has sufficient strength for holding the contact tongues in the closed state. The interruption of the contact maintained solely by the permanent magnet 9 is performed with the aid of a flux produced by the energizing coil 11 in the direction Q (see FIG. 1).

The contact tongue 5 has two zones 15 and 17, which are premagnetized by the permanent magnet 9 in the directions A and B respectively. The premagnetization of the zones 15 and 17 is amplified or attenuated in accordance with the direction of a flux passing consecutively through the two contact tonguesS and 7 and obtained by external means, such as a current through the coil 11 or a permanent magnet (not shown) arranged near the contact tongues. By an externally produced flux in the direction P, which contributes to the flux of the permanent magnet 9 in the contact opening 13 the premagnetization in the zone 17 is amplified and that in the zone 15 is in a first instance attenuated. The inverse applies to a flux in the direction 0, opposite the direction P. By an appropriate choice of the strength of the permanent magnet 9 in the tongue contact shown in FIG. 1 the premagnetization in the zone 17 is such that with an externally produced flux in the direction P, which moves the contact tongues 5 and 7 into the closed state,

(hereinafter termed make-flux) the zone 17 is not yet saturated, whereas the premagnetization in the zone 15 is such that with an externally produced flux in the direction O, which is required for moving the contact tongues 5 and 7 from the closed state into the open state, (hereinafter termed breakflux) the zone is saturated. If the externally produced flux passing consecutively through the contact tongues and having a direction at the contact area opposite that of the flux of the permanent magnet has such a value that the difierence between the two said fluxes is capable of moving the contact tongues from the open state into the closed state, the zone 15 is distinctly saturated. Because the value of the portion of the externally produced overall magnetic flux, which traverses as a break-flux or as a make-flux the contact tongues 5 and 7 in series (the remaining portion passes a path through the air) is determined by the premagnetized zone of the highest premagnetization, which thus forms the highest magnetic reluctance, the break-flux passing consecutively through the contact tongues 5 and 7 in the direction Q, even when the externally produced overall magnetic flux is comparatively largely exceeded owing to the saturation of the zone 15, will not attain such a high value that after the contact is interrupted the contacts would close again, whereas the make-flux passing consecutively through the contact tongues 5 and 7 in the direction P, owing to the nonsaturation of the zone 17, is always sufficiently strong for closing the contact. By the said arrangement of the permanent magnet 9 on the contact tongue 5 and by the premagnetization of the zones 15 and 17 a magnetic tongue contact is obtained, whose dimensions do not exceed those of conventional tongue contacts, the contacts being closed after interruption only at the occurrence of a comparatively strong, externally produced flux.

It will be apparent that if the magnetic tongue contact 1 is constructed in the form of a break-contact the aforesaid result is also obtained.

It should be noted that also when a displaceable permanent magnet is used instead of a coil the overall flux to be externally produced required for obtaining the break-flux can be readily exceeded, for example, due to inaccuracies involved in prac tice in the displacement of such a magnet so that also in this case a premagnetization obtained by a permanent magnet arranged on one of the contact tongues obviates the risk of a return to the closed state.

FIG. 2 shows only the essential part of the other advantageous embodiment of the magnetic tongue contact 19 in accordance with the invention. The magnetic tongue contact 19 comprises two partly overlapping contact tongues 21 and 23 of magnetizable material. The contact tongues 21 and 23 are provided with identical permanent magnets 25 and 27 respectively, which are arranged on the side of the contact tongue concerned facing the other contact tongue. The permanent magnets 25 and 27 are fastened at equal distances from the free ends of the contact tongues 21 and 23 near the free ends of the contact tongues 23 and 21 respectively. The directions of polarization of the two permanent magnets are transverse of the longitudinal directions of the contact tongues and parallel to the direction of movement thereof and are the same for the two magnets, the magnetic north and south poles being located at the places indicated in FIG. 2 and the field lines mainly extending as is illustrated in FIG. 2. The strength of the identical permanent magnets 25 and 27 in common is sufficient to hold the contact tongues 21 and 23 in the closed state without the need for an externally produced flux, but it is not sufficient to move the contact tongues from the open state (see FIG. 2) into the closed state without the aid of an externally produced magnetic flux. The magnetic tongue contact 19 is therefore a make-contact. By the permanent magnet 25 two zones 29 and 31 in the contact tongue 21 are premagnetized. The direction C of premagnetization in the zone 29 is opposite the direction D of premagnetization in the zone 31. In the'contact tongue 23 the permanent magnet 27 provides the premagnetization of two zones 33 and 35, the direction E of premagnetization in the zone 33 being opposite the direction F of premagnetization in the zone 35.

The contact tongues 21 and 23 are moved into the closed state by means of a magnetic make-flux externally produced (for example by a coil) in the direction P (see FIG. 2), whose direction at the area of the contact opening 37 between the contact tongues 21 and 23 is equal to that of the flux already produced there by the permanent magnets 25 and 27. The externally produced flux is eliminated when the contact tongues 21 and 23 are in the closed state. The interruption of the contact maintained solely by the permanent magnets 25 and 27 is performed by means of a break-flux externally produced in the direction Q. (see FIG. 2).

The strength of the permanent magnets 25 and 27 is such that with a make-flux externally produced in the direction P the premagnetized zones 33 and 31 are not yet saturated, whereas with a break-flux externally produced in the direction Q the premagnetized zones 29 and 35 are saturated. Even when the overall flux to be externally produced in the direction Q is comparatively largely exceeded, the zones 29 and 35 then saturated prevent the break-flux passing consecutively through the contact tongues 21 and 23 from attaining such a value that after the interruption the contact tongues close again.

Like the tongue contact 1 of FIG. 1, the tongue contact 19 of FIG. 2 has no larger dimensions than the conventional tongue contacts.

If by an appropriate choice of the strength of the permanent magnets 25 and 27 the magnetic tongue contact 19 forms a break-contact, the aforesaid result will, of course, also be obtained.

If the magnetic tongue contact is proportioned so that a comparatively strong premagnetization is required, it is preferred to use a magnetic material for the permanent magnet(s) which contains about 50 atom percent of platinum and about 50 atom percent of cobalt. This magnetic material permits of manufacturing comparatively small permanent magnets of high field strength.

For illustrating the dimensions of one embodiment of a tongue contact in accordance with the invention the essential dimensions are designated in FIG. 2 by the characters a, b, c, d, e, and f, wherein a=0.33 mm.

b=0.85 mm.

c=l .00 mm.

d=0.l0 mm.

e=0. 10 mm.

The permanent magnets used in this embodiment contain 50 atom percent of platinum and 50 atom percent of cobalt and after being secured to the contact tongues they are magnetized with the aid of a field having an inductance of about 2.5 Weber/m3.

It should be noted that the tongue contact of FIG. 2 has a symmetrical structure. This is, however, not at all required.

What is claimed is:

l. A switch comprising a hermetically sealed envelope, two contact tongues mounted within'said envelope, at least one permanent magnet arranged on the side of one of the contact tongues facing the other contact tongue near the area where the two contact tongues overlap each other, the magnetic field of said permanent magnet being sufficient to hold the contact tongues together once they have been closed, the direction of polarization of the permanent magnet being transverse of the direction of length of the contact tongues and parallel to the direction of movement thereof, thereby producing premagnetized zones within at least one of said contact tongues, a considerable portion of the flux of the permanent magnet passing through the free end of said other contact tongue, and means external of said envelope for actuating the switching operation.

2. The switch according to claim 1 wherein a permanent magnet is arranged on the side of each of said contact tongues facing the other and arranged near the area of contact overlap between the tongues, said magnets being polarized in the same directions.

contact tongues from the open state into the closed state, the magnet adjoining part of the contact tongue thereby becoming saturated.

4. The switch according to claim 1 wherein magnetic material of the permanent magnet contains about 50 atom percent of platinum and about 50 atom percent of cobalt.

Claims (4)

1. A switch comprising a hermetically sealed envelope, two contact tongues mounted within said envelope, at least one permanent magnet arranged on the side of one of the contact tongues facing the other contact tongue near the area where the two contact tongues overlap each other, the magnetic field of said permanent magnet being sufficient to hold the contact tongues together once they have been closed, the direction of polarization of the permanent magnet being transverse of the direction of length of the contact tongues and parallel to the direction of movement thereof, thereby producing premagnetized zones within at least one of said contact tongues, a considerable portion of the flux of the permanent magnet passing through the free end of said other contact tongue, and means external of said envelope for actuating the switching operation.

2. The switch according to claim 1 wherein a permanent magnet is arranged on the side of each of said contact tongues facing the other and arranged near the area of contact overlap between the tongues, said magnets being polarized in the same directions.

3. The switch according to claim 2 wherein said means external of said envelope produces magnetic flux passing consecutively through said contact tongues, the direction of said flux at the contact area being opposite to that of the flux of the permanent magnets and whose value is such that the difference between said flux produced by said external means and the flux of the permanent magnet is capable of moving the contact tongues from the open state into the closed state, the magnet adjoining part of the contact tongue thereby becoming saturated.

4. The switch according to claim 1 wherein magnetic material of the permanent magnet contains about 50 atom percent of platinum and about 50 atom percent of cobalt.

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