US3636483A

US3636483A - Electromagnetic relay

Info

Publication number: US3636483A
Application number: US67287A
Authority: US
Inventors: Karl Evert Jambrink; Per Harry Elias Claesson; Rolf Albin Zander
Original assignee: Individual
Current assignee: Individual
Priority date: 1970-08-26
Filing date: 1970-08-26
Publication date: 1972-01-18
Anticipated expiration: 1989-01-18

Abstract

An electromagnetic relay of the miniature relay type with a contact spring group and a magnetic circuit which comprises a substantially rectangular loop formed by a magnetic core and a magnetizing coil surrounding a part of the core. The core part surrounded by the coil is the armature of the relay, the armature being pivoted at one end and movable in a direction transversally to the axial direction of the coil and to the longitudinal direction of the armature.

Description

United States Patent J ambrink et al.

ELECTROMAGNETIC RELAY Inventors: Karl Evert Jambrink, Grumsgatan 3, Farsta; Per Harry Elias Claesson,

Osterhagens Gard, Drevviken; Roll Albln Zander, Storhagsvagen 28'A, Alvsjn, all of Sweden Filed: Aug. 26, 1970 Appl. No.: 67,287

' Related US. Application Data Continuation of Ser. No. 723,451, Apr. 23, 1968,

abandoned.

Foreign Application Priority Data I May 3, 1967 Sweden "62 81/67 Jan. 31, 1968 Sweden .1251/68 us. c|...'. .335/135, 335/276 Int. Cl. ..no1n 50/26 F1eldofSearch.. .335/135, 128, 124,187,203,

[451 Jan. 18, 1972 References Cited UNITED STATES PATENTS 2,692,314 10/1954 Lawrence ..335/129 3,260,818 7/1966 Fisher et al. ..335/274 3,431,521 3/1969 Kusano .....335/124 Primary Examiner-Harold Broome Attorney-Strauch, Nolan, Neale, Nies & Kurz [57] ABSTRACT An electromagnetic relay of the miniature relay type with a contact spring group and a magnetic circuit which comprises a substantially rectangular loop formed by a magnetic core and a magnetizing coil surrounding a part of the core. The core.

part surrounded by the coil is the armature of the relay, the armature being pivoted at one end and movable in a direction transversally to the axial direction of the coil and to the 1ongitudinal direction of the armature.

' 21 Claims, 17 DrawingFigures PATENTED M18197? 3,636,483

SHEET 1 BF 4 INVENTORS KARL EVERT JARNBRINK BYPER HARRY ELIAS CLAESSON ROLF ALBIN ZANDER PATENTEQ .mn 81972 3.838.483

sum 2 OF 4 /5 &

s a F79. 7 3 :5 1 I m 1/ y 1 '51 E INVENTORS KARL svsm .mmenmx PER HARR'Y ELIAS CLAESSON ROLF ALBIN ZANDER ATTORNEYS PATENTEDJANISIWZ 3.636.483

SHEET 3 OF 4 KARL EVERT JARNBRINK HYPER HARRY ELIAS CLAESSON ROLF ALBIN ZANDER ATTORNEYS PATENTEUJANTSIQTZ asset-483 saw u or 4 Fly. /7

INVENTORS KARL EVERT JARNBRINK BYPER HARRY ELIAS CLAESSON ROLF ALBIN ZANDER JMWM m ATTORNEYS 23, 1968, now abandoned.

' LE TR MAG ETI RE AY This is a continuation of application No. 723

,451 filed Apr.

The present invention relates to an electromagnetic relay of very small dimensions.

More specifically, the invention relates to an electromagnetic relay which has one or more contact spring groups, a magnetic circuit and a coil surrounding a part of the magnetic circuit. The magnetic circuit comprises a ferromagnetic core which has the shape of a substantially rectangular loop. One side of the loop constitutes a movable armature and is pivoted by one end thereof to the adjacent end of the rest of the loop, whichforrns the stationary part of the core. The other end of the movable armature forms a working airgap with the other end of the stationarycore part.

Further, there is anactuating rib in mechanical engagement with the armature near the working alrgap. The actuatingrib is arranged to transmit movement from the armature to the movable contact spring or springs of the contactspring group or groups.

.SUMIMARY or THEIINVENTION A primary object of theinvention resides in the provision of a novel electromagnetic relay withsmall dimensions and high degree of reliability. I I A further object of the invention resides in the provision of a novel small relay, the magnetic circuit of which exerts a great traction force to the armature, in spite of the small dimensions, while maintaining the current consumption at a small value, so that the heating of the relay coil will not exceed allowable limits. A t

The invention, according to one aspect thereof, is substantially characterized by the fact, that the relay armature is SUI? rounded by the core with an airgap between the inner walls of the coil andat least one side of the armature and that the armature is movable in the coil transversally to the longitudinal axis thereof and that the stationary core part is fixed relatively to the coil and adapted to substantially close the magnetic circuitat one single side of the coil. I According to another aspect of the invention, if the available area for the winding ofthe coil inside the loop formed by the magneticcircuit is A and the width of the core part inside the coil is B, andits thickness is T,.the following dimensional relations should be fulfilled:

' B-T/A 0.l I T/B 0.2 By such dimensioning arather distinguished maximum of the pulling force for a given volume of the relay and a given power dissipation is surprisingly obtained. I In order to obtain such optimal'function, it is also suitable to I 8 ows .a side view ofa, el y. partly i sec iom or ing to a modified form of the present invention. I

FIG. 9 shows a front end view of therelay according to FIG. 8,

FIG. 10 is a top view of the same relay, FIG. 11 is a top view of an-armature assembly used in any of the relays according to FIGS! to 3. and '4 to 6,

FIG. 12 is a side view of the samearma'ture assembly,

FIG. 13 is a top view of a pole sheet forming an airgap spacer comprised in the armature assembly according to FIGS. 11 and 12, I

FIG. .1 4 is a side view of? contact spring group intended for any of the relays according to FIGS! to 3, FIGS.'4 to'6 or FIGS. 8 to 10, I

FIG. 15 is a front end view of the contact spring group according'to FIG. 14,

FIG. 16 is a side view of anothercontact spring group intended for the same relays, and I FIG. 17 is a curve showing the traction force ofthe armature as a function of certain specific dimensions of a relay according to any of the Figures. I I v In FIGS. 1 to 3 there is illustrated anelectromagnetic relay I relating to the kind of relays called miniature relays. The relay is mounted on a bracket 1 which is made from plastic or similar material. The bracket 1 is designed to serve as a support for a contact spring group 4 and also to serve as a support design the magnetic coil so that when the nominal actuating .voltage is impressed to its terminal, the maximum allowable power should be dissipated in thecoil in consideration of the allowable heating of the coil.

Further, the present invention relates to means and methods for assembling a relay of the type referred to and to contactspring groups and actuating ribs for such relays.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 6 is a top view of one of the contact spring groups used I in'the relay according to FIG. 4, I

FIG. 7 illustrates a part of the relay according to FIGS. 4 to 6 during one stage of its asembling,

for and be integral with a coil bobbin of a magnetizing coil 2.

I The relay comprises also a magnetic circuit consisting of two

parts

3, 7. One of said parts 3, which is the stationary core part, is rigidly connected to that part of the bracket 1 which is integral with the coil bobbin. The other of said magnetic circuit parts, which is the movable part or the armature 7, is by one end 74 thereof in contact'with one end 3a of the fixed part 3 while the other end 7b of said movable part or armature is so located, that a working airgap 1 6,is formed between the other end 3b of the fixed part 3. and said other end 7b of the movable part 7. K It is apparent from] FIG. 1, that the armature 7 is movable transversally within the aperture-in 'the magnetizing coil 2 and that the stationary magnetic core part 3forms a substantially closed magnetic loop with the armature 7. Said magnetic loop is closed at one side only of the'magnetizing coil 2.

A contact spring group-4 is rigidly mounted on the stationary core part 3 by means of a screw 5.0. The contact springs comprised in said contact spring group 4 have rear ends 4a which are intendedto be connected to an external circuit e.g., a printed circuit) by, for example, soldering. Said ends extend through apertures in an upstanding part vlb integral with the bracket 1.

The front ends (not shown) of the movable contact springs in said contact spring group 4 are actuated by an actuating rib 107 the lower end of which is in engagement with the armature 7 in order to transmit movement from the armature 7 to said contact springs.

The upper end 1074 of the actuating rib 107 penetrates through an aperture in an upper plate 412. and is guided in said The rear end 3a of the stationary magnetic core part 3 is received in a pocket in the bracket 1. The front end 3b of said core part 3 is fastenedto the front flange 2f of the bobbin for the magnetizing coil 2 by means of a screw 1 11.

The lower end of the actuating rib 107 has two legs 1070 and 107d which are guided in lateral recesses (not shown) in the front end 3b of the stationary core part 3.

In FIGS. 4 to 6 there is illustrated a second embodiment of the invention, which is in all essential similar to the embodiment already described. I

In a'coil bobbin belonging to the bracket 1 which has a rear flange 14 and a front flange 12, a winding 2 is provided. A U- shaped stationary iron core part 3 has rear and

front legs

34 and 3b, respectively, and carries two contact spring groups 4 which are fastened to said core part by means of screws 5. The

movable contact springs of said contact spring group are actuated by an actuating rib 107, which will be described more in detail later. I I I When the relay is assembled, (see FIG. 7), an opening 11 which is-provided in the front leg 3b of said stationary core part 3 is forced over a projection 13 provided on the front flange 12 of the coil bobbin belonging to the bracket 1, and, thereafter, the rear leg 3a of said core part 3 is pushed down in a pocket behind the coil bobbin 2 and in front of an upstanding part 15 of said bracket I. Said projection 13 should preferably be slightly conical in order to facilitate the mounting, and, by this means, the core part 3 and the front wall of the bobbin 2 will be rigidly fastened to each other.

Alternatively, the projection 13 may be smaller than the aperture 11 in the bridge 3. In this case the stationary core part 3 and the bobbin 1 can be fixed to each other by melting the outermost end of the projection 13 by a heat tool. Altematively, the projection can be fixed in the aperture by glueing. But before this fastening is made, a fixture should be pushed into the airgap 16 to accurately determine the size of said airgap in a simple way.

As an alternative, it is, of course, possible to provide an aperture in the flange 12 of the bobbin and a corresponding projection on the leg 3b of the core part 3, if this should be preferred for some reason.

Inside the coil 2, the armature 7 is movably located. The armature 7 is provided with a fastening spring 8 which, when the armature is pushed into the bobbin, engages the front leg 3b of the stationary core part 3 and thus locks the armature within the bobbin, so that the armature is prevented from sliding out of the bobbin in an opposite direction to the direction, in which it was pushed in. The armature is prevented from sliding out from the bobbin in the other direction by the upstanding part 15 of said bracket 1. The rear end of the armature 7 is in contact with the rear leg 3b of the stationary iron core part 3. The distance between the front end of the armature 7 and the end of the front end 3a of the core part 3 forms the working airgap 16. When the armature is in its unactuated or rest posi-' tion, its location is determined by the bottom surface of said armature 7. As illustrated, said surface rests on the inner wall surface of the coil bobbin.

When the armature 7 is actuated or, after actuation, is restored to its rest position, there will be, during the movement of the armature, an air cushion which is compressed within a limited volume between the armature and the walls of the coil bobbin. This air cushion is highly damping the movement of the armature and prevents the armature from bouncing when it reaches any of its end positions, and by such bouncing to inadvertently actuate the springs in the contact spring group. This damping is very effective, especially if the width of the armature is only slightly less than the width of the opening in the coil bobbin.

It has been mentioned in the foregoing, and it will be obvious from FIG. 4, that the location of the armature 7 in its rest position is determined by a wall in the coil bobbin. Further, said coil bobbin, according to the foregoing, is fastened to the stationary core part 3. Therefore, the size of the working airgap l6 will be accurately determined.

The stationary core part 3 and its rear leg 3a will be fixed to the coil bobbin by the contact spring group 4, because said contact spring group will be fixed relative to the bracket 1 by means of the connection ends of the contact springs which penetrate apertures in the upstanding part 15 of said bracket 1.

The mounting of the contact spring group in this embodiment of the relay is carried out in the following way.

First, the contact spring group is pushed backwards as far as possible on the relay whereby the connection ends of the contact springs penetrate the apertures in the upstanding part 15 of the bracket 1 of the relay. Thereafter, the actuating rib 107 is put into place between the front leg 3b of the stationary core part 3 and the front flange 12 of the coil bobbin. When the contact spring group 4 thereafter is pushed forwards, to its final position, the movable contact springs will penetrate the actuating rib 107 and will be moved to their correct positions in relation to the different supporting surfaces of the actuating rib, which will be described more in detail in connection with the description of the contact spring functions.

The actuating rib 107 has an upper portion which is bifurcated and has two upstanding projections l07b and 107C. Said legs are guided in recesses 25a and 25b, respectively (FIG. 6) in a top plate 25 belonging to the contact spring group. At its bottom end, the actuating rib 107 is provided with two

legs

107d and 107f which project downwards between the front end of the bobbin of the magnetic coil 2 and

lateral projections

30 and 3d of the front end 3b of the stationary core part 3. The bottom ends of said legs 3c and 3d are in engagement with

side projections

70 and 7d, respectively of the armature 7, as will be apparent from FIGS. 4 and 5. The lateral projections 3c and 3d of the stationary core part 3 and the corresponding

lateral projections

70 and 7d of the armature form pole-shoes which enlarge the magnetic surfaces between which the working airgap is formed. As already stated, this allows for such dimensioning of the magnetic circuit, that other parts of the core and armature may bemagnetically saturated during normal use of the relay. This is another condition for obtaining maximum pulling force fora given size and a given power dissipation.

In FIGS. 8 to 10 a modified embodiment of the invention is described.

According to this embodiment, the stationary iron core part 3 is located inside the coil bobbin for the magnetic coil 2 and the movable core part or the armature 7 is located outside the coil.

The stationary core part 3 is kept in place by the coil bobbin. The armature 7 is pivoted at its rear end 7a. It is inserted into a suitable opening 1d of the rear flange of the coilbobbin. It is forced into said opening 1d in the somewhat elastic flange. There are two lateral recesses (not shown) in said armature 7 in which the edges-defining the opening 1d are received after pushing in said armature. By this means, the armature is kept in place in its inserted position. I

At the front end of the relay, the armature 7 is guided and transversally movable in an opening 1e in the front flange of said coil bobbin.

Both the stationary core part 3 and the armature 7 are L shaped and identical to each other.

A contact spring group 4 is fastened to a sheet metal plate by a screw or rivet 101. Said plate 100 has a down-bent rear flap 102 which is received in a pocket in the bracket 1 and abuts against the rear, upper side of the stationary core part 3. Therefore, the position of the spring group 4 is always accurately defined relative to the magnetic circuit and independent of dimensional alterations in the insulation material of the bracket 1. i

The plate 100 has bent-down side portions. The lowermost edges of said side portions are bent inwards to be received in recesses in the front wall of the front flange of the coil bobbin as shown at 100a and 10% in FIG. 9.

The contact spring group is actuated by an actuating rib 107 which is of similar construction and functions similarly to the actuating rib 107 in FIGS. 1 to 3.

For facilitating the release of the relay while the residual magnetism in the magnetic circuit is still rather strong (which is necessary for obtaining a rapid releasing function) it is necessary to provide a nonmagnetic pole-pin or pole-sheet in the working airgap between the armature 7 and the stationary core part 3. i

The armature 7 with its

side projections

70 and 7d and with a fastening spring 8 and a pole sheet 21 attached to it, is illus trated in FIGS. 11 and 12. The pole sheet 21 is illustrated separately in FIG. 13.

The fastening spring 8 is fastened to the armature 7 in the vicinity of the pivoting point, near the end 7a of said armature. This fastening can be made by, for example, spot-welding. Said spring 8 is pretensioned so that its free end near the working airgap is bent upwards. When the armature is inserted into the relay, the end of said spring part 8 will be in engagement with the inside of the front end 3a of the stationary part 3, and thus lock the armature 7 in inserted position. Said free end of the spring 8 inside the coil bobbin is preferably broader than the armature. By this means, the armature 7 will be locked against lateral movements and the armature will be free from engagement with the inner sides of the coil bobbin so that friction between the sides of the armature and the adjacent parts of the coil bobbin will be avoided.

For fastening the pole-sheet 21 to the armature assembly illustrated in FIGS. 11 and 12, said pole-sheet is provided with a narrow middle portion 21a which is pushed into an opening 19 in the-fastening spring 8 as illustrated. I

The relay according to FIGS. 4 to 6 has a contact spring group 4 which is illustrated in detail in FIG. 4. Said contact spring group has three changeover contacts which is apparent from FIG. 4. One of said changeover contacts comprises the contact springs 27, 28 and 29 and a supporting spring 30. The supporting spring as well as the contact spring 27 are rigid as compared to the springs 28 and 29. The contact spring 28 is bent towards the contact spring 27, so that the desired contact pressure is obtained. Further, the contact spring 29 is bent towards the supporting spring 30, so that, when the contact spring 28, through actuation by the part 31 of the actuating rib 107 is moved upwardly so as to lift the spring 29 from the spring 30, a desired contact pressure between the contact springs 28 and 29 will be obtained. The movement by spring action of the rigid contact springs 28 and 30 should, of course, be small as compared to the movement of the springs 28 near the part 31 of the contact rib 107 when the armature is actuated. Another changeover contact in the same contact spring group comprises the contact springs 37 to 40. This changeover contact is identical to the just described changeover contact and, therefore, this changeover contact need not be described more in detail here.

A third changeover contact in the same contact spring group comprises one rigid spring 32,'one moveable contact spring 33 and one fixedcontact spring 34 and, in addition to that, one rigid supportingspring 35. This changeover contact isfunctioning in the same way as the just described changeover contacts. It will be apparent from FIG} 4, however, that the rigid spring 32 is double bent to have the shape of a z, in

, the direction towards the movable spring 33 at the end 'where the contacts are provided. Similarly, the fixed spring 34 is double bent in the same way in the direction towards the spring 33, at the end where the contacts are provided. By this means, the heights of the solid contact parts isconsiderably decreased as compared to the solid contact parts of the contact springs 27, 30 in the changeover contact previously described, and, therefore, the quantity of contact material in said solid contacts is considerably decreased. In case that a precious metal is used for the contacts, it is of course advantageous from an economical point of view, to need rather small quantities of material for the solid contacts. The quantity of material should be determined by the quantity of material which is required because of the loss of material due to migration (contact erosion) and not by the distance between the contact springs, which is determined by the thickness of the insulation spacing washers between the contact springs. The thickness of said washers is, in turn, determined by the requirements of insulation between the contact springs.

In order to obtain good contacts, the changeover contact springs 28 33 and 37 and the upper springs 29., 34 and 39 ought to be bifurcated so that twin contacts are obtained in a manner known per se. In order to eliminate vibrations or contact bounces, when the contacts are closed or broken, the shanks of the bifurcated portions should be tapering forwardly in a direction from the nonbifurcated portion towards the contacts. Further, those parts of the actuating rib 6 which are engaging the movable contact springs as well as the supporting points, where the supporting

springs

30, 35 and 40 cooperate with the associated contact springs, ought to be as close to the contacts as possible. Therefore, said parts of the actuating rib towards the contacts, which will be apparent from FIG. 4.

As will be apparent from FIG. 5, which illustrates the relay as viewed from the rear end thereof, two contact spring groups may be mounted on the core part 3. The contact spring groups are assembled in a manner known per se by means of insulating spacing washers between the springs. Each contact spring assembly is clamped together by means of a hollow rivet 4! (FIG. 6).

In FIGS. 14 and 15 there is illustrated a contact spring group comprising one break contact and one double make contact. The contact spring group comprises one rigid contact spring 46, one movable contact spring 47, two fixed contact springs 48 and 50 and two rigid supporting springs 49 and 51.

Because the actuating rib 107 has the shape of a ladder, the

located more close to the clamping part of the spring. How the I contact spring group functions, when the part 45 of the actuating rib 107 is displaced by the armature, may be apparent from FIG. 14 without detailed explanation.

The contact spring group according to FIG. 16 comprises one break contact and one continuous changeover contact. The contact spring group contains one rigid, fixed contact spring 46, one movable contact spring 52, and, further, one rigid contact spring 53 and one bendable, fixed contact spring 54.As in the embodiment according to FIG. 14, the contacts belonging to one contact function (the make contact function of the continuous changeover contact) are located inside the contact actuating rib 107 in order to obtain great contact movements.

In order that the rigid springs, such as the springs 27 and 30 in FIG. 4 should not be appreciably bent when they are loaded by the contact pressure, which would bring about contact bounces and improper contact functions, such rigid springs In order to'avoid contact bounces, the movable contact springsand the supported'fixed contact springs should have a very low mass, i.e., they should be rather thin, so that the maximum bending stress exceeds 20 kgJmm. (2,-800 pounds per square'inch) and, as previously stated, the supporting surfaces and the actuating surfaces of the actuating rib should be adapted to cooperate with the contact springs close to the contacts.

In known constructions of contact spring groups for relays of the miniature relay type, the fixed contact springs comprised in the'break function of the changeover contact (cor responding to

springs

27, 32 and 37 in FIG. 4) have had the form of double springs, viz one rather soft contact spring and one rather rigid supporting spring. According to the present invention, only one rigid spring is required for the same purpose which, of course, decreases the production costs for the relay. Similarly, the contacts which correspond to the spring 46 in FIG. 14 and 46 and 53in FIG. 16 have usually comprised two springs each, but according to the present invention, such contacts have been simplified to comprise only one contact spring each.

By the dimensioning rule indicated in the foregoing, i.e., that the ratio between the cross section area of the magnetic core and the area of the opening for the magnetizing coil should exceed 0.1 and preferably be between 0.2 and 1.0 and that the ratio of the thickness to the width of the core part inside the magnetizing coil should be more than 0.2, the benefit would be obtained, among others, that a better cooling will be achieved, provided that the compared relays have similar total dimensions. In an ordinary relay of the L-shaped armature type, and with a length of 30 mm. a height of 30 mm. and a width of 19 mm., there was obtained a temperature increase of 66 C. when the coil was supplied with a constant voltage, giving a dissipated power of 1.85 watts in the relay coil at 20 C.

-ambient temperature. The ratio mentioned in the foregoing vertical axis indicates the effective power supplied to the magnetizing coil and the abscissa or horizontal axis indicates the ratio between the core area and the area of the opening available for the cross section of the winding of the magnetizing coil, located between the

core parts

3 and 7. The curve indicates said ratio provided that the volume of the whole magnetizing circuit is constant. Further the curve is valid for a certain, favorable value of the ratio of the thickness to the width of the rectangular core in the coil. This means, of course, that when the volume of the

parts

3 and 7 increases, there will be a correspondingdecrease of the volume of the coil winding. The indicated values of the vertical axis is in watts, i.e., the maximum effect is indicated to be about 1.5 watts. The curve is computed and tested for suitable dimensions of the magnetic circuit of the relay where the

core parts

3 and 7 and the winding with the coil bobbin included has the following dimensions: length 27 mm., width 17 mm. (the width of the coil) and height 17 mm. For a value on the horizontal axis of 0.56 a pulling force of 640 grams will be obtained, when the working airgap is 0.18 mm. and the supplied efiective power is 0.64 watts. The pulling force is 320 grams, when the airgap is 0.36 mm. and the effective power is 0.85 watts. These values are calculated for a circuit without pole shoes. The dotted curve is calculated for the

parts

3 and 7 being provided with pole shoes which extend substantially along the whole width of the outer flange of the coil bobbin. It is evident from the curves, that a pronounced minimum point is obtained, when the ratio between the core area and the opening for the magnetizing winding is between 0.2 and 0.6 but it is also evident from the curve that said ratio ought to be greater than 0.1. Very acceptable values are obtained even if the ratio is allowed to vary between 0.1 to 2.0. l

It should, however, be emphasized that about three times as great pulling force will be obtained under similar conditions by, said dimensioning rule as compared to relays, which at present are available in the market. It is obvious, however, that the curve shown in FIG. 17 would be somewhat altered, if other fixed dimensions are used as base values. Thus, a still better optimal value will be obtained, if the length of the circuit is somewhat greater.

It has been stated in the foregoing, that the stationary core part 3 and the armature 7 should have substantially equal cross section areas. In this connection it should be mentioned that a certain leakage field always is present around the coil and, therefore, the part which is enclosed in the coil has always a slightly greater magnetic field than the other part. The difference in field intensity in the case now discussed is supposed to be ofthe order of 10 percent. This means, that for obtaining an optimal dimensioning, the part outside the coil should have slightly greater cross section area than the part inside the coil. The expression substantially equal cross section area for these parts is meant to include such minor differences between the areas of the two parts.

It should be noted, that by making one of the parts U- shaped, the benefit is obtained that the legs of such part can be ground simultaneously for providing a good contacting surface against the other part with well defined dimensions. It should also be noted, that such grinding will not alter the pole surface area. i

It is a known fact that when the relay should be used in dusty surroundings, contact faults will easily occur if the dust has access to the contacts. For avoiding such contact faults, attempts have been made to cover the relays by suitable caps. But in this case there will be a risk for a so-called activating of the contacts, due to the vapors, especially carbon hydrogen vapors, which are generated by the insulation material in the relay. According to this invention, both of the last-named disadvantages are avoided by enclosing the relay by a cap, an envelope or the like, which is provided with at least one opening in which a dust filter is inserted.

In FIG. 4, there is a cap 17 illustrated, preferably made from plastic, which is pushed over the relay from the front end thereof, i.e., the end where the contacts are located. At the other rear end of the relay, there is a backplate which is designated as a washer 18, preferably of a porous material, for example foam rubber or some other material, which has dustfiltering characteristics. Washer 18 has apertures for the connection ends of the contact springs of the relays. The connection ends should hermetically penetrate the apertures, so that dust would not be able to penetrate through the apertures. Washer 18 can be located inside or outside the upstanding part 15 of the bracket 1 which is integral with the coil bobbin.

Alternatively, an air ventilation may be arranged at other locations in the walls of the cap, for example in the neighborhood of the contacts. Thus, the cap 17 is shown to have one or more ventilation openings 17a, in which units 17b made from air filter material of a known type are inserted and fastened by means of, for example, glueing. The last-mentioned filter does not exclude the simultaneous use of other filters of the type described above at the rear end of the relay.

What is claimed and desired to be secured by Letters Patent is:

1. An electromagnetic relay comprising: at least one contact spring group; a magnetic circuit; and a coil surrounding a part of said magnetic circuit; said magnetic circuit comprising a ferromagnetic assembly which has the shape of a substantially rectangular loop, one side of said loop constituting a movable armature; means mounting one end of said armature in pivotal disposition to the adjacent end of a stationary loop part constituted by the rest of said magnetic loop and providing a working airgap between the other end of said armature and the respective adjacent, other end of said stationary loop part; an actuating rib in mechanical engagement with the other end of said armature near said working airgap, said actuating rib being disposed to transmit movement from the armature to any movable contact spring of a said associated contact spring group, said armature being disposed through said coil with an airgap between the inner walls of the coil and at least one side I of said armature, said armature being pivotably movable in said coil transversally to the longitudinal axis thereof; and said stationary loop part being fixed relatively to said coil and adapted to substantially close the magnetic circuit at one single side of said coil.

2. An electromagnetic device comprising: a stationary magnetic circuit part; a magnetizing coil and a movable armature, characterized by the fact, that the stationary part is located wholly outside said coil and extends parallel to the axis of the coil from one end of the coil to the other, and that said movable armature is located inside said coil and being pivoted at one end adjacent to an end of said fixed stationary part at one end of said coil; space within said coil enabling pivotal shift of said armature; and the other end of said armature disposed outside the other end of said coil and forming a working airgap with said stationary part.

3. An electromagnetic device according to claim 2, characterized by the fact, that said stationary part is parallel to the coil axis and located only at one side of said coil and that said armature is disposed so its said other end shifts to and from said stationary part and by such movement the size of the working airgap is decreased and increased respectively.

4. An electromagnetic relay device according to claim 2, characterized by the fact that a coil bobbin is provided; at one side of said armature a leaf spring is disposed within said coil, said spring having a free end which abuts against the inside wall surface of said coil bobbin and keeps said movable armature in such a position that a working airgap is situated 15. A relay according to claim 13, characterized by the fact, that said cover is provided by at least one aperture in the vicinity of the contacts, in which a dust filter is inserted.

16. A relay according to claim 1, said relay comprising: at least one changeover contact, characterized by the fact that said changeover contact comprises one movable contact terized by the fact that said leaf spring is provided with an aperture, a strip of nonmetallic sheet material is inserted through said aperture, one end of said strip extending to the airgap and forming a nonmetallic pole-sheet, for preventing the pole surfaces from making direct contact with each other.

7. A relay according to claim 6, characterized by the fact that said aperture in said leaf spring is elliptic and that said strip has a portion of reduced width adapted upon assembly to be located in said aperture for fixing said strip in a predetermined, longitudinal position. i

8. An electromagnetic device according to claim 2, characterized by the fact, that the cross-sectional areas of said fixed corepart and said movable armature have such dimensions that there will be magnetic saturation simultaneously in said core parts when normal actuation current is passed through said coil that by such actuation a normal heating of said coil will occur within usual safety margins.

9. An electromagnetic device according to claim 3 charac-. terized by a coil bobbin, and the fact, that said stationary part is U-shaped, with the legs thereof bent towards said movable armature, that cooperating lug aperture means on a leg of said stationary part and said bobbin interlock said stationary core part to said coil bobbin.

10. A relay according to claim 1, comprising a coil bobbin for the magnetizing coil having a flange provided with an extension at one side, said extension enabling support for one end of contact springs belonging to said contact spring group.

.11. A relay according to claim 10, characterized by the fact, that said extension has apertures therethrough, and circuit connection ends of said contact springs penetrate through said extension apertures.

12. A relay according to claim 1, wherein the contact spring groups are characterized by the fact, that at least one contact set of the contact springs is located in an aperture in said actuating rib.

13. An electromagnetic relay according to claim 1, comprising a cover for said relay, characterized by the fact, that said cover is provided with at least one opening in which a dust filter is inserted.

14. A relay according to claim 13, characterized by the fact, that said dust filter comprises a porous washer located at the rear part of said relay, remote from the relay contacts, and that said filter is provided with openings into which the exter nal connection parts of the springs are tightly fitted.

spring and one fixed contact spring and that said fixed contact spring is considerably stiffer, by at least approximately ten times, than the movable spring, and that the contact means of said movable contact spring rests against the contact means of said fixed spring so that a breaking contact is obtained, and that said changeover contact further comprises a second fixed contact spring and a supporting spring, the supporting spring supporting said second fixed spring and being at least about ten times stiffer than said second fixed contact spring thus providing the make function of the changeover contact, and

finally that the supporting surface by which said supporting spring supports sat second fixedcontact spring and a so the surface of that partof the actuating rib which actuates the movable contact spring are located immediately adjacent to the contacts of said springs.

17. A relay according to claim 16, characterized by the fact,

that said fixed spring for the break function and said fixed spring for the make function are double bentto have the shape of a z in the vicinity of the contacts thereof, towards the associated movable contact springs, so that the height of the solid contacts of said springs is considerably less than the thickness of insulating spacing washers located between said contact springs.

18. An electromagnetic device comprising: a stationary magnetic circuit part; a magnetizing coil and a movable armature; said stationary part being disposed outside said coil and extending parallel to the axis of said coil from one end of said coil to the other end of said coil; said movable armature being disposed inside said coil; means pivoting said movable armature at one end adjacent to an end of said fixed stationary part at one end of said coil, the space within said coil enabling pivotal shift of said armature; and the other end of said armature being disposed outside the other end of said coil and forming a working airgap with said stationary part; the cross I section area of said armature divided by the area A of the space between the armature and the stationary part, available for the cross section of the winding of said coil, is greater than 0.1 and that the thickness of said armature divided by its width is greater than 0.2. I

19. An electromagnetic device as defined in claim 18, wherein the thickness T of the armature divided by its width B is greater than 0.35 and preferably between 0.35 and 0.5.

20. An electromagnetic device as defined in claim 18,

wherein the cross section area of the armature divided by the area A of the space between the armature and the stationary part, available for cross section of thewinding of said coil, is greater than 0.2 and preferably between 0.2 and 1.0.

21. An electromagnetic device as defined in claim 20, wherein the thickness T of the armature divided by its width B is greater than 0.35 and preferably between 0.35 and 0.5.

Claims

1. An electromagnetic relay comprising: at least one contact spring group; a magnetic circuit; and a coil surrounding a part of said magnetic circuit; said magnetic circuit comprising a ferromagnetic assembly which has the shape of a substantially rectangular loop, one side of said loop constituting a movable armature; means mounting one end of said armature in pivotal disposition to the adjacent end of a stationary loop part constituted by the rest of said magnetic loop and providing a working airgap between the other end of said armature and the respective adjacent, other end of said stationary loop part; an actuating rib in mechanical engagement with the other end of said armature near said working airgap, said actuating rib being disposed to transmit movement from the armature to any movable contact spring of a said associated contact spring group, said armature being disposed through said coil with an airgap between the inner walls of the coil and at least one side of said armature, said armature being pivotably movable in said coil transversally to the longitudinal axis thereof; and said stationary loop part being fixed relatively to said coil and adapted to substantially close the magnetic circuit at one single side of said coil.

4. An electromagnetic relay device according to claim 2, characterized by the fact that a coil bobbin is provided; at one side of said armature a leaf spring is disposed within said coil, said spring having a free end which abuts against the inside wall surface of said coil bobbin and keeps said movable armature in such a position that a working airgap is situated between said armature and said stationary part; said spring structurally cooperating with said movable armature and said bobbin to maintain said armature in a predetermined longitudinal position in relation to said stationary part.

5. An electromagnetic relay according to claim 4, characterized by the fact, that said leaf spring at the free end thereof is broader than said armature and fits snug within said bobbin so that said leaf spring centers said armature inside the opening of said coil.

6. An electromagnetic relay according to claim 4, characterized by the fact that said leaf spring is provided with an aperture, a strip of nonmetallic sheet material is inserted through said aperture, one end of said strip extending to the airgap and forming a nonmetallic pole-sheet, for preventing the pole surfaces from making direct contact with each other.

7. A relay According to claim 6, characterized by the fact that said aperture in said leaf spring is elliptic and that said strip has a portion of reduced width adapted upon assembly to be located in said aperture for fixing said strip in a predetermined, longitudinal position.

8. An electromagnetic device according to claim 2, characterized by the fact, that the cross-sectional areas of said fixed core part and said movable armature have such dimensions that there will be magnetic saturation simultaneously in said core parts when normal actuation current is passed through said coil that by such actuation a normal heating of said coil will occur within usual safety margins.

9. An electromagnetic device according to claim 3, characterized by a coil bobbin, and the fact, that said stationary part is U-shaped, with the legs thereof bent towards said movable armature, that cooperating lug aperture means on a leg of said stationary part and said bobbin interlock said stationary core part to said coil bobbin.

11. A relay according to claim 10, characterized by the fact, that said extension has apertures therethrough, and circuit connection ends of said contact springs penetrate through said extension apertures.

14. A relay according to claim 13, characterized by the fact, that said dust filter comprises a porous washer located at the rear part of said relay, remote from the relay contacts, and that said filter is provided with openings into which the external connection parts of the springs are tightly fitted.

15. A relay according to claim 13, characterized by the fact, that said cover is provided by at least one aperture in the vicinity of the contacts, in which a dust filter is inserted.

16. A relay according to claim 1, said relay comprising: at least one changeover contact, characterized by the fact that said changeover contact comprises one movable contact spring and one fixed contact spring and that said fixed contact spring is considerably stiffer, by at least approximately ten times, than the movable spring, and that the contact means of said movable contact spring rests against the contact means of said fixed spring so that a breaking contact is obtained, and that said changeover contact further comprises a second fixed contact spring and a supporting spring, the supporting spring supporting said second fixed spring and being at least about ten times stiffer than said second fixed contact spring thus providing the make function of the changeover contact, and finally that the supporting surface by which said supporting spring supports said second fixed contact spring and also the surface of that part of the actuating rib which actuates the movable contact spring are located immediately adjacent to the contacts of said springs.

17. A relay according to claim 16, characterized by the fact, that said fixed spring for the break function and said fixed spring for the make function are double bent to have the shape of a ''''z'''' in the vicinity of the contacts thereof, towards the associated movable contact springs, so that the height of the solid contacts of said springs is considerably less than the thickness of insulating spacing washers located between said contact springs.

18. An electromagnetic device comprising: a stationary magnetic circuit part; a magnetizing coil and a movable armature; said stationary part being disposed outside said coil and extending parallel to the axis of said coil from one end of said coil to the other end of said coil; said movable armature being disposed inside said coil; means pivoting said movable armature at one end adjacent to an end of said fixed stationary part at one end of said coil, the space within said coil enabling pivotal shift of said armature; and the other end of said armature being disposed outside the other end of said coil and forming a working airgap with said stationary part; the cross section area of said armature divided by the area A of the space between the armature and the stationary part, available for the cross section of the winding of said coil, is greater than 0.1 and that the thickness of said armature divided by its width is greater than 0.2.

20. An electromagnetic device as defined in claim 18, wherein the cross section area of the armature divided by the area A of the space between the armature and the stationary part, available for cross section of the winding of said coil, is greater than 0.2 and preferably between 0.2 and 1.0.