US3400348A - Polarized reed relay wherein the permanent magnet is around the reed switch and in contact with the coil - Google Patents

Description

sept. 3, 196s T. DE PARRY 3,400,348

ROLARIZED REED RELAY WHEREIN THE PERMANENT MAGNET IS AROUND THE REED SWITCH AND IN CONTACT WITH THE COIL Filed July 5, 1961 /EXTERNAL CIRCUIT FIG. 3A FIG. 3B

INVENTOR.

THEODORE DE PARRY ATTY United States Patent 3,400,348 POLARIZED REED RELAY WHEREIN THE PERMA- NENT MAGNET IS AROUND THE REED SWITCH AND IN CONTACT WITH THE COIL Theodore De Parry, Elmhurst, Ill., assignor to Automatic Electric Laboratories, Inc., Northlake, Ill'., a `corporation of Delaware t Filed July 3, 1961, Ser. No. 121,534 3 Claims. (Cl. 335-153) This invention relates to relays, and more Particularly, to encapsulated polarized'dry reed relays.

Prior art relays of the above type typically use permanent magnets to maintain the reeds closed without the use of a continuous hold current. Normally these permanent magnets are attached to one or more of the contacts reeds inside of a sealed capsule. While the use of a permanent magnet inside of the glass capsule has successfully'solved the particular problem of maintaining the contact reeds closed without the need for continuous current through the energizing coil, a number of other problems have thereby been introduced in the design in the use of this type of reed relay. For instance, the incorporation of a permanent magnet or magnets inside of the glass capsule has materially increased the manufacturing cost and diiiiculties of constructing these reed relays. It also causes the reed relay to be appreciably larger than the reed relays which do not contain the permanent magnet. 4In addition, the incorporation of permanent magnets inside of the encapsulated relay is a major souree'of contamination of the vacuum. This results in contamination of the contact surfaces and thusmaterially effects the contact reliability and also materially increases contact microphonic noise generation.

Another :solution to the problem of maintaining the contact springs closed without the need for continuous current passage through the energizing coil has beenthe use of a permanent magnet positioned outside of the glass capsule containing the magnetic contact reeds. The reed relay so far invented utilizing this technique for maintaining the contact reeds closed have a, number of disadvantages and `difiiculties inherent in the design. For instance, the reed relays of this type have resulted in rather large structures with permanent magnets whose shape are extremely difficult to fabricate or manufacture. This of course has increased the manufacturing cost of the reed relay. In other reed relay designs wherein a permanent magnet of relatively simple shape have been utilized to maintain the magnetic contact reeds close, other difficulties and disadvantages have accrued. For instance, in these designs the use of multiple contact reeds, that is,

[three or more contact reeds, is essential to avoid completing circuits in which eddy currents can flow. In addition, it is necessary to carefully electrically insulate the permanent magnets from the contact springs to insure that the contact springs are not shorted out.

The reed relay of this invention is of the type wherein a permanent magnet holding the reeds in a closed condition without the use of a continuous current passage through the energizing coil is located outside of the glass tube.

Accordingly, an object of the invention is to provide a polarized dry reed relay whose cost of manufacture is minimized as a result of a simplified design.

Another object of the invention is to provide a dry reed relay which operates with a minimal energy signal.

Patented Sept. 3, 1968 ice Another object of the invention is to provide a polarized diy reed relay wherein eddy current generation is minimized.

lStill another object of the invention is to provide a polarized `dry reedrelay which is substantially not affected by external magnetic fields.

To accomplish these objectives the relay features in a general way: a dry reed switch capsule which supports on the external surface thereof a tubular-shaped permanent magnet which is placed coaxially over the capsule and which is made of plastic magnetic material, and an energizing coil which is in turn Wound on this permanent magnet.

These and other objects and features of the invention will be more" clearly understood from the following detailed description taken in conjunction with the drawings of which:

FIG. 1 is a cut vaway perspective view of a relay in accordance with the teachings of a first modification of the invention.

FIG. 2. is a cross sectioned side elevational view of a second modification of the invention.

FIG. 3a 4discloses a schematic of the magnetic circuit of the relay when the energizing current is of one polarity and,

FIG. 3b discloses a schematic of the magnetic circuit of the relay when the energizing current is of the reverse polarity. y

The relay as shown in FIG. 1 consists of; a pair of iiexible contact reeds 11 and 12 which are made of magnetic material, a hermetic vitreous tube 15 which is filled with an inert gas such as nitrogen, a permanent magnet 14 which is made of plastic magnetic material, and an energizing coil 13.

More specifically, reeds 11 and 12, constituting the magnetic armature and core for the relay, extend'from opposite ends of gas filled vitreous tube 15, one end of each reed being within the tube and the other end of each reed `being external of the tube. The latter ends 12a and 11a serve as connecting terminals for the corresponding external circuit being controlled by operation of the reeds. On the other hand, the ends Within the tube 11b and 12b respectively, are the longer of the two ends and are arranged so as to be in an overlapped and normally spaced apart relationship with each other. Accordingly, the contact area is limited to the overlapped portion of the two reeds. In applications where optimum contact operation is desired the contact area may be gold plated or gold diffused by conventional means. This technique reduces contact resistance between contact surfaces 116 and 126 to an absolute minimum and also minimizes corrosion.

The material from lwhich the reeds are constructed must possess certain physical characteristics for proper mechanical closure of the reeds at the contact areas 11b and 12b. These characteristics include light weight to increase the sensitivity of the relay; special rigidity to insure that the contacts do not bounce or close the contacts upon vibration of the relay; a high degree 0f resiliency to insure that proper contact pressure is obtained between the contact lareas 11b and 12b; and in addition, high fatigue strength so that the reed relay may be in service for millions of operations. p

Permanent magnet 14 is tubular-shaped and is coaxially l A003418 s 4 placed over the vitreous tube 15. The inside diameter of the ma-gnet 14 should be only slightly greater than t-he outside diameter of vitreous tube so that it may be slipped over the tube during manufacture of the relay yet maintain a tight or snug lit with the tube.

Permanent magnet 14 is preferably constructed out of a plastic magnetic material. This material is rubber bonded and of magnetic-ferrite composition. This material has a number of important characteristics which make it particularly suitable for application in reed relays of this invention. `One of its characteristics is that permanent magnets constructed from this material have exceptionally high coercivity and thus have a strong resist- -ance to dre-magnetization. In addition, the magnetization characteristics for this material produce essentially a square hysteresis curve. Another important characteristic of this material is the facility with which it may be machined or otherwise shaped. This results in great economy in manufacturing products utilizing this material.

Since in this material magnetic particles are bonded together by an insulating media, such as rubber or plastic, the material has an extremely high resistivity. This characteristic is extremely important in the operation of the high speed reed relay of this invention as will be discussed subsequently. In fact, the absence of this characteristic has prevented the construction of similar designs in the prior art. In addition this plastic magnetic material is of a very light weight which allows the product utilizing this material to also be of less weight than if the magnet were constructed from conventional cobaltnickel or steel magnets.

The magnetization of magnet 14 is such that the opposite poles are at the two end faces 17 and 18. Thus, the flux lines are directed generally in a longitudinal pattern over the tube 15. Around t-he magnet is an energizing coil 13 which activates a change in the relationship of the reeds 11 and 12 and thus operates the external circuit.

By way of example, a second modication of the invention may be las shown in FIG. 2. This modification displays substantially the same features as the lfirst modiication shown in FIG. 1 except for the additional feature of a plurality of pairs of reeds which are connected to a larger number of external circuits. The reeds are positioned 'within a corresponding larger hermetically sealed vitreous tube 30 which accordingly supports a larger permanent magnet 31 and energizing coil 32.

The operation of the relay Iwill now be described making reference to FIGS. l, 3a and 3b. With the contacts 11b and 12b open and no current flowing through coil 13, the magnetic field set up by permanent magnet 14 is axially through the vitreous tube. This magnetic field must not be sufficient at the air gap between contacts 11b and 12b to cause them to close. However, when 'an actuating current is passed through coil 13 in the direction to set up a magnetic field which aids the magnetic field of the permanent magnet 14 reeds 11 and 12 will close due to the magnetic force exerted by the two magnetic fields on the flexible reeds. The magnetic eld set up by the passage of current through coil 13 also causes the state of magnetism in the permanent magnet to reach its maximum full strength. It should be noted that since the particular permanent magnet used for this reed relay has very lar-ge resistance the eddy currents induced in the magnet are very small. In other words, the magnetic eld set up by the current to coil 13 is applied in full strength to achieve the desired effect and is not wasted in undesirable secondary effects.

Once the reeds are closed the current through coil 13 may be cut off. The reeds are maintained in a lmake or closed position by the action of the magnetic field alone.

To open the reeds it is necessary to pass a current through coil 13 of the opposite pulse polarity or in the opposite direction. This deactivating current through coil 13 must be sufficiently strong to reduce the magnetic field strength to a'value where the magnetic force of attraction between the contacts 11b and 12b is less than the mechanical bending moment in each reed forcin-g the reeds apart. However, it is imperative that the amount of current flowing through coil 13 does not set up a magnetic field strength to permanent magnet 14 sufficient to cause the flux state in the permanent magnet to reverse. Once contact surfaces 11b and 12b have opened the current through coil 13 may be shut off. When this occurs, the magnetic flux in permanent magnet 14 returns to its initial state. This flux state, as mentioned previously is alone insuflicient to again close the reeds against the resistive mechanical force of bending induced in the contact springs.

It is important to note in this operation that due to the high retentivity of the plastic ferrite material used for the tubular permanent magnet, the magnet does not act as a magnetic shield to the magnetizing field set up by the ow of current through the coil. On the other hand, the high retentivity of the material allows a sufficient magnetizing lield to be set up in the opposite direction by passage of current of the reverse polarity without changing the direction of magnetization of the permanent magnet. It is this combination of magnetization characteristics coupled with the low eddy current losses due to the high resistivity of the material which makes this material particularly suited to the application, and which distinguishes this invention from the prior art.

What is claimed is:

1. A magnetically operated high speed switch structure comprising:

an energizing coil,

a pair of cantilevered contact reeds extending within an elongated vitreous tube having Ian external surface and placed within said coil, said reeds activated in response to the energization of said coil;

and a plastic magnetic member, positioned directly on said external surface of said tube and in direct contact with said energizing coil, said member supporting said energizing coil and being in operative relation therewith to maintain said reeds activated after deenergization of said coil, yand to minimize the eddy currents generated by said coil.

2. An electromagnetic device comprising:

an energizing coil, f

a plurality of flexible contact reeds arranged in pairs and encapsulated by ra hermetically sealed vitreous tube having two ends and an external surface, said tube being placed within said coil, one reed of said pair extending through one end of said tube and the other reed of said pair extending through the opposite end of said tube, the opposite ends of said reeds extending within said tube and lying in an overlapping and normally spaced apart relationship to each other, said reeds closing in response to the energization of said coil with current of one polarity, and restoring in response to the energization of said coil with current of opposite polarity,

and a tubular shaped plastic magnetic member displaying both dielectric and permanent magnet properties positioned on said external surface of said tube and in direct contact with said energizing coil, said member supporting said energizing coil and being in operative relation therewith to maintain said reeds closed after deenergization of said coil `and to minimize the eddy currents generated by said coil.

3. A magnetically operated high speed switch structure comprising: an energizing coil, a pair of cantilevered contact reeds extendingwithin an elongated vitreous tube having an external surface and placed within said coil, said reeds activated in response to the energization of said coil; and a plastic magnetic member, positioned directly on said external surface of said tube and in direct contact with said energizing coil, said member supporting said energizing coil and being in operative relation therewith 5 6 to maintain said reeds closed after deenergization of said 3,024,392 3/1962 Baermann 317-159 coil, and to minimize the eddy currents generated by said 3,015,707 1/ 1962 Perreault 200-87 COIL R f C t d OTHER REFERENCES e ences l e 5 The Ferreed-A New Switching Device, Bell Tech- UNITED STATES PATENTS nical Journal, v01. XXXIX, No. 1, January 1960, pp. 1l, 2,877,315 3/1959 oliver 20o-87 12 and 19. 2,902,558 9/1959 Peek 200-87 2,978,556 4/1961 Lohs et al 200 87 BERNARD A. GILHEANY, Primary Examiner.

2,999,915 9/ 1961 Pfleiderer et ai 200-87 10 R. N. ENVALL, Assistant Examiner.

Claims (1)

1. A MAGNETICALLY OPERATED HIGH SPEED SWITCH STRUCTURE COMPRISING: AN ENERGIZING COIL, A PAIR OF CANTILEVERED CONTACT REEDS EXTENDING WITHIN AN ELONGATED VITREOUS TUBE HAVING AN EXTERNAL SURFACE AND PLACED WITH SAID COIL, SAID REEDS ACTIVATED IN RESPONSE TO THE ENERGIZATION OF SAID COIL; AND A PLASTIC MAGNETIC MEMBER, POSITIONED DIRECTLY ON SAID EXTERNAL SURFACE OF SAID TUBE AND IN DIRECT CONTACT WITH SAID ENERGIZING COIL, SAID MEMBER SUPPORTING SAID ENERGIZING COIL AND BEING IN OPERATIVE RELATION THEREWITH TO MAINTAIN SAID REEDS ACTIVATED AFTER DEENERGIZATION OF SAID COIL, AND TO MINIMIZE THE EDDY CURRENTS GENERATED BY SAID COIL

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