US3188425A - Electromechanical switch for use as a crosspoint for conversation circuits - Google Patents

Description

June 8, 1965 A. J. HENQUET ETAL 3,188,425 ELECTROMECHANICAL SWITCH FOR USE AS A CROSSPOINT FOR CONVERSATION CIRCUITS Filed June 4, 1962 lnuenlorg AJ HE/VQUE T E S lLEl-ZME By M/ A ttorn e y 3,188,425 LECTROMECHANICAL SWITCH FOR USE AS A CRQSSPOINT FOR CONVERSATIGN CIRCUHTS Andr Jean Henquet and Fernand Silerme, Boulogne- Billancourt, France, assignors to International Standard Electric Corporation, New York, N.Y., a corporation of Delaware Filed June 4, 1962, Ser. No. 199,916 Claims priority, application France, June 14, 1961, 864,957, Patent 1,299,665 4 Claims. (Cl. 200-87) The present invention relates to an electromagnetic switch, and particularly to a memory suitable for use as switch crossp'oints controlled by electronic circuits in telephone or other systems.

Semi-conductors have not yet fulfilled the various requirements present in telephone switching systems, and more particularly in the cross points placed in the conversation circuits. On the other hand, electromagnetic relays are not suitable for crosspoint usage as the operation time thereof is relatively long, and the memory function has to be added thereto through means such as locking contacts and circuits. One object of this invention is to provide a switch which may be defined as a magnetic memory relay and may be controlled by relatively short pulses the duration of which is of the order of microseconds rather than on the order of milliseconds as is common for conventional relays. The duration of the mechanical movement of such a relay caused by the magnetic flux could be longer than the pulse which sets said magnetic flux.

Magnetic switches are known which utilize magnetic cores wherein the flux may be reversed by a pulse for producing the remanent fluxes which set the switch in either position. In a switch of this type, ferrite cores carrying windings have been combined in such a way that when opposite fluxes were established in the cores, the resultant flux set the switching element in energized position, whereas when fluxes in series were established in said cores, the switching element was moved to its manual unoperated position. In another known switch of this type, one of the cores was constituted by a permanent magnet, yet it was in such a magnetic circuit that the fluxes in series were acting to set the switching element in energized position were as the opposite energization would substantially suppress the flux.

Another object of the present invention is to provide a switch of the fast acting electromagnetic type arranged to operate in equipment racks without mutual influence with the neighbouring magnetic relays or switches.

According to a feature of the invention, the magnetic circuit of the switch comprises a branch containing a permanent magnet which produces a nearly constant flux,

. anotherbranch comprising a reversible magnet, preferably a metallic one (as opposed to ferrites), carrying a winding being able to reverse the flux thereof, and a branch comprising the switching element. The latter branch responds to the resultant flux when the reversible magnet has an opposite flux to the flux of permanent magnet to set the switching element in the energized position. The branch structures are such that the fluxes of the two first branches do not substantially pass over the third branch when they are in series, and this resets the switching member in the position of rest. Preferably, a fourth branch may be provided having a magnet keeper being able to control the reluctances of the three other branches.

According to another feature of the invention, the magnetic circuit is provided with a magnetic casing constituted by a side which hugs the reversible magnet and constitutes the said magnet keeper, and two sleeves which surround the respective ends of said three branches of the circuit.

United States. Patent Patented June 8, 1965 In a preferred embodiment, the envelope is constituted by a permeable magnetic material tube having a portion cut out adjacent the permanent magnet and mobile magnetic members of the said switch.

The switching member may be of the well-known magnetic reed contact type enclosed in a glass tube. If necessary, one or several tubes may be provided.

According to another feature of the present invention, the magnetic path between said reed contacts and the other branches of the magnetic circuit is established without metallic or other magnetic contact, by means of pole pieces externally encompassing a large portion of the reed contacts. This arrangement provides a sufficient magnetic permeance together with a complete electric insulation.

The above-mentioned and other features and objects of this invention will become more apparent by reference to the following description taken in conjunction with the accompanying drawing, in which:

FIGURE 1 represents the internal members of the switch, in elevation and in the relative position they have in the switch,

FIGURE 2 represents in perspective a magnetic yoke,

FIGURE 3 represents in elevation the members of FIG- URE 1 together with two magnetic yokes placed in position,

FIGURE 4 represents in elevation the above mentioned members enclosed in the magnetic envelope,

FIGURES 5 and 6 represent a front view and a plane View or" the switch of FIGURE 4.

The switching member is constituted by two switching elements 1 (only one being shown in the elevation view of FIGURE 1) of a known type wherein two magnetic reeds 2, 3 are enclosed in a glass tube 4 in order to constitute an electrical contact when their adjacent ends are attracted by a magnetic flux flowing through said reeds. The over-all length of these elements may be mm.

On one side of these tubes is placed a permanent magnet 5. This magnet must have a relatively high coercive force so that its magnetic flux will not be substantially modified during switch operations. An alloy known by the trade name Ticonal (containing 8 to 35% of titanium, 15 to 30% of cobalt, 10 to 25% of nickel and about 5% of aluminum) may be provided. This alloy has a coercive field of 800 oersteds and a remanent induction of 10,000 gauss. Magnet 5 may have a length of 25 mm. and a section of 20 mm. so that it has a coercive force of 2,000 oersteds and a remanent flux of about 2,000 M. An alloy known by the trade name Alnico, for instance, may be also utilized, such alloy containing about 6% of ti taniurn, 12% of cobalt, 15 to 30% of nickel and 8 to 10% of aluminium, the remainder being iron. This alloy has a coercive field of about 500 oersteds and a remanent induction of about 7,000 G.

On the other side of the tubes, opposite magnet 5, a small bar 6 is positioned which constitutes a reversible magnet carrying a magnetizing coil 7. This small bar has also a high permeability, but a much lower coercive force, and a substantially rectangular hysteresis loop. The material in this bar 6 could be heat treated iron at high content of chromium and carbon with an addition of silicon. The alloy utilized may have a coercive field of 70 to 80 oersteds and a remanent induction of 9,500 gauss. The length of the small bar may be 62 mm., the section 28 mm. so that the coercive force will be about 460 oersteds and the remanent flux about 2,600 M.

The three branches of the magnetic circuit constituted by the above mentioned members are magnetically coupled by two yokes 3, one of which is shown in FIGURE 2, the other members and their yokes being shown in PEGURE 3. Yoke 8 comprises bush 9 enclosing the extremity of small bar 6 and two bushes It enclosing tubes 4. These bushes are linked by blades 11, the whole structure being formed by punching and bending a permeable magnetic material sheet, for instance ductile iron. It will be noted that the yokes are not in contact with the magnetic reeds 2, and thus do not need to be electrically insulated therefrom. Bushes which constitute pole pieces are relatively long so as to give a large surface to the air gap between them and reeds 2 to enhance the passage of the magnetic flux. The utilization of small bars 5 and 6 having a great coercive force and a large remanent flux, insures the correct operation of the switch under these conditions. Magnet 5 tangentially contacts bushes 10, but its main magnetic circuit will be completed by the outer envelope.

Envelope 12, shown in FIGURE 4 encompasses coil 7 and two bushes 14. An aperture is cut out in the middle of envelope 12. Lugs 16 formed near the edges of this aperture may be welded to the extremities of permanent magnet 5, so that flux from the magnet passes through the magnetic shunt constituted by bushes 1d and side 13. As represented in FIGURE '6, bushes 1% surround inner yokes 940 with a certain space, so that the magnetic shunt also afforded by the envelope to bar 6 comprises a large air gap. The space between bushes 14 and yokes 8 contains insulating plugs 17 (FIGURE 5) for housing the electrical connections of the switching reeds and the winding of coil 7.

In operation, the switch may have two energized states and two corresponding remanent states. When the switch is in the de-energized remanent state, the magnetization of bar 6 is in a reverse position with respect to that of permanent magnet 5 (FIGURE 1), results in their magnetic fluxes being linked in series aided by yokes 8. Taking into account the magnetic shunt afforded by envelope 12, a very small flux passes through reeds 2, and the switches remain unoperated. At the moment when an operating pulse is applied to Winding 7, the magnetization of bar 6 is reversed. If the pulse is a shoit one, the 7 is applied bar 6 will resume its original magnetization and y will keep it after the termination of the pulse. The fluxes, in series, will avoid reeds 2-3 the easier as an air gap is left between them and yokes 8. The reeds will move aside and will open the electrical contacts.

The establishment of the magnetic circuit according to the invention, with its members having a high permeability and a high coercive force in spite of their small size, its air gap and its magnetic shunt, ensures a reliable operation, the conservation of the permanent magnet, a good insulation of the conducting reeds together with an economic construction and a fairly reduced size,

While the principles of the invention have been described in connection with a specific embodiment, it is to he clearly understood that this description is made only by way of example and not as a limitation on the scope of the invention. a

We claim:

1. An electromechanical switch for use as a crosspoint comprising: at least one set of magnetic reed contacts; means including a permanent magnet of relatively high coercive force for providing a substantially constant flux within operating limits of said reed contacts; an electromagnetic device having a core made of material with a low coerciveforce, high permeability and a square hysteresis loop; means for reversing the direction of magnetization of said core responsive to electrical pulses of short duration; magnetic circuit means coupling said inagnet and said core for carrying substantially no flux when the magnet and core flux are in series aiding and for carrying a high level. of flux when the magnet and core flux are in series opposing; and yoke means for completing said magnetic circuit; said yoke means having three branch means, a first of said branch means providing an air gap surrounding one of said contacts, a second branch means providing an air gap surrounding another of said contacts, and a third of said branch means receiving and holding said core.

2. The switch of claim 11 wherein each of said sets of contacts is sealed in a glass tube, and said first and second branch means surround and hold said glass tube, said air gap being the space between the inside of the glass tube and said contacts.

3. The switch of claim 2 and a magnetic envelope enclosing at least a portion of said magnetic reed contacts, there being a magnetic contact between said permanent magnet and said envelope, said envelope providing mag netic shielding for said switch.

4. The switch of claim 3 wherein said magnetic envelope comprises a side passing along said core and terminating at either end in a magnetic brush, saidbrushes surrounding said yoke without touching said yoke, said brushes also surrounding and forming an opening intermediate the ends of said envelope, said contacts and said permanent magnet being adjacent said opening.

References Cited by the Examiner UNITED STATES PATENTS 2,902,55s 9/59 Peek 200- s7 2,938,982 5/60 Brown et al. 2004,? 3,002,066 9/61 Ketchledge et al. 200-s7 3,008,019 11/61 Scheidig 200-87 3,056,868 10/62 Jacobson et al. 200-87 3,061,696 10/62 Peek 200 s7 FOREIGN PATENTS 617,984 4/61 Canada.

BERNARD A. GILHEANY, Primary Examiner. ROBERT SCHAEFER, Examiner.

Claims (1)

1. AN ELECTROMECHANICAL SWITCH FOR USE AS A CROSSPOINT COMPRISING: AT LEAST ONE SET OF MAGNETIC REED CONTACTS; MEANS INCLUDING A PERMANENT MAGNET OF RELATIVE HIGH COERCIVE FORCE FOR PROVIDING A SUBSTANTIALLY CONSTANT FLUX WITHIN OPERATING LIMITS OF SAID REED CONTACTS; AN ELECTROMAGNETIC DEVICE HAVI NG A CORE MADE OF MATERIAL WITH A LOW COERCIVE FORCE, HIGH PERMEABILITY AND A SQUARE HYSTERESIS LOOP; MEANS FOR REVERSING THE DIRECTION OF MAGNETIZATION OF SAID CORE RESPONSIVE TO ELECTRICAL PULSES OF SHORT DURATION; MAGNETIC CIRCUIT MEANS COUPLING SAID MAGNET AND SAID CORE FOR CARRYING SUBSTANTIALLY NO FLUX WHEN THE MAGNET AND CORE FLUX ARE IN SERIES AIDING AND FOR CARRYING A HIGH LEVEL OF FLUX WHEN THE MAGNET AND CORE FLUX ARE IN SERIES OPPOSING; AND YOKE MEANS FOR COMPLETING SAID MAGNETIC CIRCUIT; SAID YOKE MEANS HAVING THREE BRANCH MEANS, A FIRST OF SAID BRANCH MEANS PROVIDING AN AIR GAP SURROUNDING ONE OF SAID CONTACTS, A SECOND BRANCH MEANS PROVIDING AN AIR GAP SURROUNDING ANOTHER OF SAID CONTACTS, AND A THIRD OF SAID BRANCH MEANS RECEIVING AND HOLDING SAID CORE.

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