US2752450A - Electromagnetic light current contact making relays - Google Patents

Description

June 26, 1956 c. H. FOULKES ET AL ELECTROMAGNETIC LIGHT CURRENT CONTACT MAKING RELAYS Filed Dec. 29, 1951 Inventor CH. FOULKES' .A.CH]LDS- R.E.SM|TH Ailorney United States Patent ELECTROMAGNETIC LIGHT CURRENT CONTACT MAKING RELAYS Christopher Henry Foulkes, Percy Arthur Childs, and Raymond Ernest Smith, London, England, assignors to International Standard Electric Corporation, New York, N. Y.

Application December 29, 1951, Serial No. 264,084

Claims priority, application Great Britain January 3, 1951 12 Claims. (Cl. 200-87) The present invention relates to light current contact making electromagnetic relays.

The main feature of the present invention comprises a light current contact-making electromagnetic relay having an energising coil or coils and a sealed contact assembly which comprises an enclosure bounded by two parallel buttons of insulating material, a fixed contact member sealed into each of said buttons so that it passes through and forms part of the enclosure, and a movable contact formed by an internally extending radial finger of resilient material attached to and forming part of a circular spacer which is sandwiched between said buttons with the end of its contact finger between said contact members, in which said spacer is of greater thickness than the contact finger, whereby the difference in thickness between the spacer and the contact finger defines the contact gaps between said contact finger and the ends of said fixed contact members.

The invention will be described with relation to the accompanying drawings, in which:

Fig. 1 shows the basic form of relay to which the present invention is applicable.

Fig. 2 is an enlarged end view of a sealed contact structure according to the present invention.

Fig. 3 is a cross section along the line IIIIII of Fig. 2.

Fig. 4 is an enlarged, exploded view of the contact structure of Figs. 2 and 3 with the casing in which it fits; while Figs. 5 and 6 show two combinations of coils and magnets for use in accordance with the contact structure according to Figs. 2, 3 and 4.

In the type of relay shown schematically in Fig. 1 a flexible contact finger 1 is located between two contact members 2 and 3 which are in line with each other. Magnetic fields can be generated by coils and/or permanent magnets 4 and 5, and the magnetic circuits are so arranged that the magnetic fields in the two circuits both traverse the armature, which therefore carries the dif ferential flux component. The resultant flux in armature 1 and the member 6 to which it is connected links with whichever field of those due to 4 and 5, respectively, is the greater. Therefore the armature 1 moves into contact with whichever of members 2 and 3 forms part of the magnetic circuit whose flux is greater. The members 1, 2, 3 and 6 form part of both the electrical and the magnetic circuits and members 2, 3 and 6 are electrically insulated from the remainder of the magnetic circuit.

The contact structure according to the invention will now be described with reference to Figs. 2, 3 and 4. The conductor members 2 and 3 and the moving armature 1 are located within a tubular metal casing 7. Each conductor member 2, 3 is a rod or stem of an alloy having good electrical and magnetic conducting properties and which is capable of being sealed to glass. Such an alloy may be a nickel cobalt iron alloy. Each memher 2 and 3 is sealed to the centre of a glass button 8 and 9. The glass buttons 8 and 9 are each sealed to flanged sleeve members 10 and 11 in such a way that the members 2 and 3 are respectively concentric with the sleeve members 10 and 11. The flanges 12 and 13 of the sleeves 10 and 11 are flush with the surfaces of the glass buttons 8 and 9.

The armature 1 is formed with an annular extension 15 whose outside diameter corresponds to that of the sleeves 10 and 11. The armature 1 and sleeves 10 and 11 are made of an alloy such as nickel-iron-cobalt which has good electrical and magnetic properties and which is capable of being sealed to glass.

The outer surface of each glass button, its contact member and the flange of the sleeve to which the button is sealed are flush. Thus the flange and the corresponding central conductor are coplanar. The annular extension 15 only of the armature 1 is increased in thickness by, say electro-plating, until the increased thickness gives the required contact gap. The sleeves with contact members are then assembled in the casing 7 with the armature sandwiched therebetween, the annular extension serving, due to its increased thickness as a spacer. This it is which determines the gap between the faces of the contact members 2 and 3, and thus determines the contact gap with a high degree of accuracy.

The armature should, in the embodiment of the invention described, be free from any mechanical bias toward either fixed contact to avoid distortion, which would otherwise result if the relay is used, as, say, a telegraph relay. Since there can be no question of adjustment after assembly, it is necessary to ensure that the armature is flat when assembled and free from any internal strain. This flatness may be achieved by a suitable heat treatment such as annealing, under pressure between flat blocks. The armature has a thickness of 9 mils, and the plating on the annular portion is of a thickness of about 1 mil on each side so that it extends 1 mil on each side of the armature. If the armature finger is midway between the fixed contacts this gives a contact gap of 1 mil on each side. In practice the armature will rest on one contact as a result of residual magnetisation, which gives an actual contact gap of 2 mils.

The thickened portions of the armatures annular extension may be of copper, as this is a convenient metal for electro-deposition on iron. The armature is any magnetic material which has a high saturation flux density and suitable mechanical properties. A suitable material is high purity iron.

To ensure clean surfaces the contacts may be heat treated in a reducing atmosphere after sealing to the glass buttons to remove oxide films. Alternatively the contact surfaces may have applied thereto by, for example, electro-plating a coating of gold or other suitable material to a thickness suflicient to prevent the formation of oxide films during storage and handling. This coating need not be thick enough to remain intact during the life of the relay since any base metal exposed to wear would be clean. Further, since the contacts are in a sealed enclosure when in use, it is not possible for contaminating films to form on the contacts.

The sleeves 10 and 11 are sealed to the tubular casing 7 by brazing or other suitable means at the extreme ends 16. A metal tubulation 17 is fitted to the casing 7 at a point in line with the armature and this is squashed on final sealing off. The chamber can be evacuated, or is preferably filled with an inert or reducing gas.

A typical relay which is not shown to scale in the drawings, has a diameter of about one inch and an overall length of between one and two inches. The contact gap, which is determined by the thickness of the metal electro-plated onto the annulus 15 is in one specific speci a on one fixed contact.

men, two thousandths of an inch when the armature is 3 have a diameter of 6.680 inch. The magnetic sleeves are of the order of mils thick and the outer casing about mils thick. The contact rods project beyond the ends of the relay so that contact therewith can made. From the dimensions it will be seen that a relay constructed according to the present invention is considerably smaller than known forms of relay.

A magnetic circuit of the type described can be excited by a variety of combinations of coils and/or mt nets arranged in various parts of the magnetic cir uit. Two such arrangements will be described.

Fig. 5 is a three-terminal arrangement suitable for operation from a pair of thermionic or gas filled tubes V1, V2 either of the hot or cold cathode type. They may for example, be part of a flip-flop circuit. Two coils 18 and 19 are fitted inside the sleeves it? and embracing the members 2 and 3, and sensed as shown. The magnetic circuit is completed by yokes 2d and 21. Each yoke Ztl, 21, is a flanged disc of magnetic material approaching close to one of the conductor members 2, 3 at its centre and also approaching close to the wall of the appropriate sleeve in, 11. Each flange disc is insulated from the appropriate sleeve by a short gap having a large surface area, the total surface area of the flange. This gives electrical insulation between the members 2 and 3 serving as conductors to the fixed contacts and the casing 7 which is used as an electrical conductor to the moving contact and armature 1. Since the insulating portion is a short gap of large cross section it has a low magnetic reluctance. These insulating gaps each contain a spacer of insulating material.

If both coils have equal numbers of turns the field flux in the device arises from the sum of the currents in the coils, while the exciting flux, which operates the relay, arises from the difference of these currents. I

Fig. 6 shows a two terminal arrangement which can be operated from a source of pulses of alternating polarity which is shown as an A. C. generator. The coils 1% and 19 are sensed as shown. The magnetic circuit is completed, as in Fig. 5, except that the yokes are replaced by two permanent magnets 22, 23 in the form of discs magnetised from centre to perimeter each in the same sense, as shown. These two magnets generate the field flux, all of which passes through the armature. The coils 18 and 19 together generate the exciting flux which flows through the conductor members 2, 3, through the magnets 22, 23 and through the casing. The combination of field flux and exciting flux operates the armature to either contact according to the polarity of the coil excitation.

If the two magnets are magnetised radially in opposite directions the armature can be normally biassed to one of the fixed contacts.

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

What we claim is:

1. A light current contact-making electromagnetic relay having a sealed contact assembly comprising a pair of insulating buttons, conductive enclosing means for supporting said buttons in parallel spaced relation to each other and sealed to said buttons, so as toform an enclosure therewith, a fixed contact member of magnetic material sealed in each button and extending therethrough, a movable contact of magnetic material movablymounted between said buttons, so as to be engageable alternately with said fixed contacts, said movable contact being connected to said conductive enclosing means, and magnetic means for energizing said fixed contact members for selectively controlling the movement The contact member rods 2 and 7 of said movable contact into engagement with predetermined of said fixed contacts.

2. A relay, as defined in claim 1, further comprising a conductive spacing member for mounting the movable contact between the buttons, said spacing member having a greater thickness than said movable contact and being in contact with said buttons, so as to determine the spacing therebetween, and being connected electrically to the conductive enclosing member.

3; A rela as claimed in claim 2 and in which each fixed contact member sealed into one of said buttons is formed by the end of a rod-like member of material having good electrical and magnetic conducting properties, and further comprising a sleeve member for each button of material having good electrical and magnetic duct lg properties, each button being sealed in its ssoci d sleeve member and each contact rod being wt bin and coaxial with its associated sleeve member, while the spacing member sandwiched between and electrical contact each of said sleeve members.

4. A relay, as claimed in claim 3 further comprising an energising coil embracing each of said rod-like members within the sleeve members, and yokes of magnetic material to closing the ends of the chambers formed by said sleeve members, and means for electrically insulating the contact members from said sleeve members.

5. A relay, as claimed in claim 4, in which the means for insulating the rod-like members from the sleeve members comprise a cylindrical opening in each magnetic yolte, slightly larger in diameter than the associated rodlike member, and with a relatively large surface adjacent said rod-like member, thus forming a short magnetic gap of large cross-section between the rod-like member and the yoke through which it passes.

6. A relay, as claimed in claim 5 and in which both of the yokes are discs permanently magnetised radially in opposite directions whereby the contact finger is normally biassed to one of the fixed contacts.

7. A relay, as claimed in claim 5, and in which both of said yoltes are discs magnetised in the same radial direction so that on de-energisation of the coils the contact finger remains in the position to which it was last operated.

8. A relay, as claimed in claim 1, in which the spacing member is circular and has an aperture in its circumference and the conductive enclosing member is provided with a tubulation aligned with said aperture, whereby the tubulation and the aperture in the spacer may be used during manufacture for evacuation or evacuation and filling with an inert or reducing atmosphere, after which the tubulation may be sealed off.

9. A sealed-contact light current electromagnetic relay having a single change over contact comprising two axially aligned rods of material having good electrical and magnetic conducting properties one end of each forming one of the fixed contacts, two buttons of insulating material through each of which is sealed one of said rods, two flanged magnetic sleeves to each of which is sealed one of said buttons in such a way that each rod is within and coaxial with its sleeve and the button to which a rod is sealed, the end of that rod and the flange of the sleeve to which that button is sealed being substantially flush, an internally extending radial finger of resilient material having good electrical and magnetic conducting properties, a circular spacer of greater thickness than said finger attached to and forming part of said finger, an outer casing, a pair of energising coils, a pair of disc shaped magnetic material yokes, the sleeves and spacer being assembled within the casing with the buttons facing each other and the spacer sandwiched between and in electrical contact with flanges of the associated sleeves, the contact finger having its end between the ends of said rods, the difference in thickness between spaced and contact finger defining the contact gaps, said casing, sleeves and buttons being sealed together to form a sealed contact chamber each of said coils being positioned so as to embrace one of said rods within its sleeve, the ends of the sleeves being closed by said yokes, each of said rods passing through one of said yokes and being electrically insulated therefrom by a short gap of large cross section.

10. A relay, as claimed in claim 1, wherein the contact surfaces are plated with a metal which does not readily oxidise, so that they are protected from oxidation during handling.

11. A process for making a relay, as claimed in claim 1, in which the movable contact and spacer are of high purity iron and are annealed under pressure between flat blocks to ensure that they are substantially dead fiat, after which the spacer is electroplated with a conductive metal to the required thickness.

12. A light current contacbmaking electromagnetic relay having a sealed contact assembly comprising a pair of insulating buttons, conductive enclosing means for supporting said buttons in parallel spaced relation to each other and sealed to said buttons, so as to form an enclosure therewith, a rod-like fixed contact member of material having good electrical and magnetic conducting properties sealed in each button and extending therethrough, a sleeve member for each button also of material having good electrical and magnetic conducting properties, each button being sealed in its associated sleeve member and each rod-like member being within and coaxial with its associated sleeve member, a movable contact of magnetic material movably mounted between said buttons so as to be engageable alternately with said fixed contact members, a conductive spacing member for mounting said movable contact between said buttons,

said spacing member having a greater thickness than said movable contact and being in contact with said buttons so as to determine the spacing therebetween and being connected electrically to said sleeve members, an energising coil embracing each of said rod-like members within the sleeve members, yokes of magnetic material closing the ends of said sleeve members, means for insulating said rod-like members from said sleeve members comprising a relatively large surface of each magnetic yoke adjacent the associated rod-like member but spaced therefrom forming a short magnetic gap of large cross-section between each rod-like member and the yoke through which it passes, said spacing member being circular and having an aperture in its circumference, and a tubulation on said conductive enclosing member aligned with said aperture, whereby the tubulation and the aperture in the spacer may be used during manufacture for evacuation or evacuation and filling with an inert or reducing atmosphere, after which the tubulation may be sealed ofi.

References Cited in the file of this patent UNITED STATES PATENTS 1,836,725 Proctor Dec. 15, 1931 1,941,273 Prince Dec. 26, 1933 2,009,892 Leece July 30, 1935 2,360,941 Eitel et al Oct. 24, 1944 2,342,527 Bucklen Feb. 22, 1944 FOREIGN PATENTS 245,715 Germany Apr. 16, 1912

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