Electromagnetic Relay Structure

The invention relates to the construction of an electromagnetic relay containing an armature inside the body of a coil holder which consists of two substantially tightly fitting components.

It is known that the armature of an electromagnetic relay may be advantageously located within the coil holder body, thereby obviating the requirement for the otherwise necessary core. Moreover, stray magnetic flux is least in the centre of the coil so that the maximum magnetic flux generated by the energised coil will directly act on the armature. The device of German Patent Specification No. 1,213,917 is aimed at securing these advantages. However, when such relays are built in practice there production cost is fairly high because of the multitude of different operations and/or the large number of different parts which are involved.

It has been proposed in German Patent Specification No. 1,909,940 to accommodate all functional parts of a relay in two matching but different halves of the body of a coil holder, both halves having contacts and terminals and one half in addition being provided with an adjustable contact terminal and associated contact blade. Although this idea has proved practicable it is suitable neither as a multiple contact relay nor for handling heavier currents or voltages. It also has the drawback that the spacing of the contacts is affected by tolerance variation from the design dimensions of the two halves of the coil holder body.

The present invention not only eliminates these defects but also makes available new possibilities for the manufacture and application of such relays. The invention consists in contriving only one of the parts of the coil holder body in such a way that it forms a contact holder in which the contact terminals projecting therefrom to the outside and the fixed contacts are embedded and thus firmly located, whereas the other part at least partly encloses the contact chamber in the form of a cover. In a further development of this idea all functional parts are positively located in relatively fixed positions in the coil holder body and the bearings are also not subject to tolerance variations, a feature which also enables substantial advantages to be secured, even in applications involving an undivided coil holder body. Yet another feature of the invention resides in that the coil holder body is composed of two identical contact holders. The identical nature of the contact holders provides to some extent for the mutual compensation of all tolerance variations of the coil holder halves which affect the contact spacing, and by using sprung contact elements the residual tolerances are rendered substantially ineffective.

The invention will be more particularly described with reference to a number of embodiments shown in the drawings in which:

FIGS. 1 to 6 depict an unpolarised relay containing an armature mounted in its axis of inertia wherein:

FIG. 1 is a section taken on the line A -- A' in FIG. 3,

FIG. 2 is a section taken on the line C -- C' in FIG. 1,

FIG. 3 is a section taken on the line B -- B' in FIG. 1,

FIG. 4 is a section taken on the line D -- D' in FIG. 1,

FIG. 5 is a perspective view of the armature 1 which is partly embedded in a sheath of insulating synthetic plastic material applied by extrusion, injection moulding or press moulding in such a way that armature bearings 12 and guide pins 13 which serve for operating the spring contact blades are integrally formed in the moulding, and

FIG. 6 is a section taken on the line E -- E' in FIG. 1.

FIGS. 7 to 12 illustrate a polarised relay having a permanent magnet armature 1b mounted in its axis of inertia wherein:

FIG. 7 is a section taken on the line A -- A' in FIG. 12,

FIG. 8 is a section taken on the line D -- D' in FIG. 7,

FIG. 9 is a section taken on the line E -- E' in FIG. 10,

FIG. 10 is a section taken on the line B -- B' in FIG. 12,

FIG. 11 is a section taken on the line F -- F' in FIG. 10, and

FIG. 12 is a section taken on the line C -- C' in FIG. 7.

FIGS. 13 to 20 illustrate the application of the invention to a polarised relay containing a soft iron armature 1c mounted in its axis of inertia, and a fixed permanent magnet 50c, 50c', wherein:

FIG. 13 is a section taken on the line H -- H' in FIG. 14,

FIG. 14 is a section taken on the line G -- G' in FIG. 19,

FIG. 15 is a section taken on the line E -- E' in FIG. 14,

FIG. 16 is a section taken on the line D -- D' in FIG. 17,

FIG. 17 is a section taken on the line F -- F' in FIG. 19,

FIG. 18 is a section taken on the line C -- C' in FIG. 17 and FIG. 19,

FIG. 19 is a section taken on the line B -- B' in FIG. 17, and

FIG. 20 is a section taken on the line A -- A' in FIG. 17.

FIGS. 21, 22 and 23 illustrate the further application of the invention to a polarised relay having only one change-over contact and an armature 1d which conducts the electric current wherein:

FIG. 21 is a diagrammatic view in the direction A of FIG. 22,

FIG. 22 is a section taken on the line B -- B' in FIG. 23, and

FIG. 23 is a section taken on the line C -- C' in FIG. 22.

FIG. 24 is a longitudinal section of a relay in which the contact holder 21e is formed with a pivot pin 49, bearing shoulders 51, 51e being also formed on the contact holder 21e and on the cover 22e for locating the armature 1e in the vertical direction. Since in this case the bearing bore traverses a soft iron armature 1e it is desirable in some applications not to make the pivot pin 49 of a synthetic plastics material but rather of a bearing metal, the metal pin being then secured by conventional methods or by pressing or riveting. FIG. 24 also shows a rigid connection between the cover 22e and the contact holder 21e by rivets 48, 48' at two or more points.

FIGS. 25 and 26 illustrate a further embodiment of the invention in the case of an unpolarised relay in which the body 2f of the coil holder is of undivided integral construction and forms a contact holding base.

FIG. 25 is a section taken on the line B -- B' in FIG. 26, and

FIG. 26 is a section taken on the line A -- A' in FIG. 25.

FIGS. 27 and 28 show the spring contact blade 31f used in this embodiment.

FIGS. 29 to 32 and 33 to 38 are further developments of the invention exemplified for two polarised relays each comprising two identical halves of a body which serves as a contact holder.

FIG. 29 is a section taken on the line C -- C' in FIG. 30,

FIG. 30 is a section taken on the line B -- B' in FIG. 32,

FIG. 31 is a section taken on the line D -- D' in FIG. 30,

FIG. 32 is a section taken on the line A -- A' in FIG. 30,

FIG. 33 is a section taken on the line C -- C' in FIG. 34,

FIG. 34 is a section taken on the line B -- B' in FIG. 36,

FIG. 35 is a section taken on the line D -- D' in FIG. 34, and

FIG. 36 is a section taken on the line A -- A' in FIG. 34.

FIGS. 37 and 38 illustrate details, H--H.

The relay illustrated in FIGS. 1 to 6 is diametrically symmetrical about its centre lines X and Z and in many instances particular reference numbers are shown only once for convenience. According to the invention, the coil holder 2 of the relay comprises a bottom member forming a contact holder 21 and an upper member forming a cover 22. Bearings 23, 23' or sockets for the armature, for instance as described in German Patent Specification No. 1,010,640, are moulded into each part of the coil holder body.

The armature 1 is partly contained inside an injection moulded or extruded synthetic plastics sheath 11 which is integrally formed with pivot pins 12, 12' as well as with guide pins 13, 13' for cooperation with spring contact blades 31, 31' and actuating bosses 14, 14' having inclined flanks 43, 43' to facilitate assembly. The tolerance limits are very close because the features which are of importance to the relay, namely the positions of the bearings and of the actuating means, are positively fixed in the production tool, and the production costs are low because all these functional elements as well as a V-shaped slot 55 provided for assembly are produced in one operation without waste of material. Finally, the partial sheath 11 also provides electrical insulation in relation to the spring contact blades 31, 31'. Likewise dimensionally fixed in relation to the bearings 23, 23' is a recess 42 in the contact holder 21 and a recess 42' in the cover 22 for the firm reception therein of poleshoes 4, 4'. An armature restoring spring 41 is riveted to each poleshoe 4, 4' preferably with the aid of pronounced round-headed rivets. The necessary bias is imparted to the armature restoring spring 41 by a V-shaped notch 56 when the armature is inserted into the bearing 23'. The contact holder 21 which constitutes the lower portion of the coil holder consists of a dimensionally stable synthetic plastics material. Fixed contacts 32, 32' as well as contact terminals 33 and 33' and coil terminals 53, 53' are embedded by an extruding, injection or press moulding operation. In a further development of the invention the fixed contacts 32, 32' as well as the contact and winding terminals 32a, 33, 33', 53, 53', 53a are of similar shape so that their external pins 32a, 53a are spaced at so-called `fives` pitched standard intervals 2T for conductor plates, whereas in the interior facing of the cover 22 they are located in a bank Y at intervals T known as a 2.5 pitch.

The fixed contacts 32, 32' contain a metal faceplate, such as Ag, AuNi, AgPd or the like on the side facing the movable contacts 3, 3'. Moreover, the terminal pins preferably consist of German silver for the sake of easy soldering or spot welding.

The spring blades 31, 31' are connected to the inside terminals 33, 33' preferably by spot welding or brazing. These spring blades are folded back upon themselves and splayed at their ends in such a way that during deflection they bear against the guide pin 13 or the actuating boss 14 with a predetermined amount of spring pressure. When the relay is energised, as in the drawing, the actuating boss 14 lifts off the spring blade 31 and a predetermined spring pressure is applied by contact 3 to the fixed contact 32. When the relay is not energised, the armature 1 is urged by the biased restoring spring 41 into its position of rest which is not shown in the drawing. The contact 3 is thus withdrawn from contact 32 by the actuating boss 14, and the guide pin 13 lifts off the spring contact blade 31 as soon as the contact 3' strikes the fixed contact 32', contact pressure being again provided by the bias of the spring blade 31.

For supporting the spring blades 31, 31' and to permit the armature 1 to be conveniently introduced into the bearing sockets 23' V-shaped ribs 44, 44' are so moulded on the contact holder 21 that the distance f between the vertix of a V-shaped rib 44' and the V-shaped slot 55 is less than the amount e whereby the pivot pin 12' tapers in relation to its bearing socket 23'.

In the cover 22, which forms the upper part of the coil holder, and which consists of an insulating synthetic plastics material, locating studs 24, 24' are moulded on the cover for cooperation with corresponding recesses 75, 75' in the contact holder 21. The two parts (21, 22) are thus fixed together and connected. A particularly economical connection is achieved by providing the locating studs 24, 24' with slots 26 which impart spring to the split ends of the studs. A similar connection is shown in FIGS. 14, 18, 19 and 20.

A split 26c in FIG. 14 divides a locating stud 24c into a sprung end 57c and a stiff end 58c and is slightly shorter than the depth of penetration of the locating stud 24c into the contact holder 21c in order to prevent the tightness of fit of the contact holder 21c in the cover 22c from being impaired by the sprung ends of the locating pin 57c yielding and the resin from flowing through the slit 26c into the interior of the relay when the latter is being sealed with castable resin.

In order to facilitate fitting the cover 22c to the contact holder 21c the upper end of the recess 75c is provided with a chamfer 59 and/or further chamfering 60 having an angle .alpha..sub.2 is provided on the end of the locating stud 57c, 58c. In order to prevent the sprung end 57c of the locating stud from being impaired in its function by friction with the wall of the recess 75c and 75c' this is either formed with sloping flanks .beta. (FIG. 20) or arranged to have clearance a in relation to the wall of the recess 75c' and 75c " (FIG. 20). The sprung end 57c of the locating stud is provided with a projection d (FIG. 14) which snaps into an enlargement in the recess 75c. In order to compensate any tolerances which might impair a tight fit between the cover 22c and the contact holder 21c the projection d has a bevel of angle .alpha..sub.1 at the point of engagement. If this angle is say 15.degree. and the projection d = 0.6 mm, a tolerance of d x tan .alpha..sub.1 = 0.16 can be compensated. The forces which arise are similarly satisfactory.

In the case of a spring deflection f of 0.8 mm provided by appropriate shaping, for instance by chamfering the sprung end of the locating stud, a sprung length l of 8 mm, a thickness h = 1 mm, a width b = 1 mm and a Young's moldulus of 850 kg/sq.mm, the spring force is P.sub.s = f .sup.. E .sup.. b .sup.. h.sup.3 / 4 .sup.. l.sup.3 = 0.33 kg. Assuming that .alpha..sub.1 = .alpha..sub.2 = 15.degree. and a coefficient of friction .mu. = 0.1 for the synthetic plastics materials which are here practicable (e.g. "Delrin", diallyl phthalate, "Crastine"), then the force needed for the insertion of four such locating studs would be P.sub.M = 4.sup.. P.sub.s (sin .alpha..sub.2 + .alpha. cos .alpha..sub.2) = 0.47 kg. The cover 22c pulls itself into the contact holder 21c with a force P.sub.H .about. 4P.sub.s .sup.. (cot .alpha..sub.1 - .mu.).about.4.8 kg, i.e. about 4000 times its own weight.

This example shows that the application of little effort in manual assembly without the use of tools permits a sufficiently stable connection to be achieved and that the forces involved can be varied very considerably by slight variations of the angles .alpha..sub.1, .alpha..sub.2 and/or of the thickness h or the length l, bearing in mind that the forces vary with the third power of these parameters.

Demands for very small relays possessing high breakdown and insulation resistance can thus be met by providing the cover 22 with partitions 28, 28' (FIGS. 2, 3, 4) and the contact holder 21 with notches 45 or recesses 62. The partition 28 is therefore not yet present when the spring contact 31 is fitted and is not in the way. Another requirement which miniature relays of relatively high current breaking performance are often required to satisfy is ability to handle alternating current. A.c.-energised relays usually contain a short-circuiting ring at the pole face of the core. However, since relays according to the present invention lack a core, a short circuiting ring 95 and/or 95', consisting for instance of copper, is pressed into suitable recesses either in the armature 1 facing the polesholes 4, 4' or into a suitable location in the pole-shoes 4 and/or 4'. However, since high resistance of the windings is needed for operation with a mains voltage of 220 volts, calling for very thin wires in the case of miniature relays containing little winding space, the coil holder 2 contains recesses 25, 25' in which components (such as resistors, capacitors or diodes) for smoothing the a.c. or for attenuating the energising current are accommodated. In order to provide a relay which is specially suitable for a.c. excitation the said smoothing devices may be used alone or in combination with one or two short circuiting rings 95, 95'. The flanges of the cover 22 and/or contact holder 21 contain slots 29, 29' for the ends of the windings so that they cannot be electrically or mechanically influenced by neighbouring turns of the winding.

Another advantage of this invention is that the windings 52, which must naturally be different for every voltage, can be fitted to the relay after it has been mounted. Consequently more generous plans can be laid for large scale production without incurring the risk of no outlet being found for lengthy periods for relays having particular windings.

When the coil holder has been wound and connected the relay need merely be closed by fitting a cap 39 which in conventional manner engages a nib 61 on the contact holder 21. The cap 30 consists of ferromagnetic material and in view of the proposed disposition of the poleshoes 4, 4' of which two faces I, II make contact with the cap it forms a very effective return path for the magnetic flux. The proposed polarised relays in FIGS. 7 to 12, 13 to 20, 21 to 23, 29 to 32 and 33 to 36 are illustrated with their armature 1b,1c, 1d, 1g, 1h in central position. They are likewise symmetrically constructed with reference to the centre lines X, Z with the exception of one adjusting facility 17, 35 (FIG. 12) which is asymmetrical with respect to the Z-axis. The polarised relay according to FIGS. 7 to 12 contains an H-section armature 1b which is symmetrically composed of a permanent magnet 50 and two adjacent poleshoes 4b, 4b'. According to the invention this three-part armature 1b is held together in its inertial axis Z by an embracing plastics sheath 11b which is also formed with pivot pins 12b, 12b'. The plastics sheath 11b continues over the two outer faces 1f of the poleshoes 4b, 4b', and actuating bosses 14b, 14b' are formed on the outer ends as well as angle pieces 35, 35' between the inertial axis Z and the actuating bosses 14b", 14b'", the angle pieces partly embracing the spring contact blades 31b, 31b' without touching them and serving as stops for the free ends of adjusting leaf springs 17, 17'.

The contact holder 21b which forms the bottom part of the coil holder differs from the contact holder 21 (FIG. 1) principally by the presence of half of a flange 8 in the middle which is formed with the bearing 23b as well as with one half shell of an internal thread 38.

For locating the adjusting spring blades 17, 17' there are provided, on the sides of the core member of the contact holder 21b which forms part of the coil body, shoulders 63, 63' having walls 36, 36' which are kept free to provide horizontal abutments, and which contain the nose 64 of the adjusting spring blade 17, 17'. Round pips 37, 37' are also provided to form a fixed rest when the adjusting spring blades 17, 17' are flexed by the adjusting screws 65, 65'.

Similarly, the cover 22b which forms the upper part of the coil holder body differs from the cover 22 (in FIG. 1) principally by the presence of a flange half 8' in the middle which besides a bearing socket 23b' also contains one half of an internal screw thread 38' which matches the thread 38 of the other half to form a complete and continuing thread when assembled. Preferably the threads of the two halves 38, 38' may be slightly staggered, since this constitutes an easy method of ensuring a firm frictional fit of the adjusting screws 65, 65' in the thread.

The inside contact terminals 33b, 33b' are centrally spot welded or brazed to the spring contact blades 31b, 31b'. The pressure with which the contact 3b, 3b' bears against a fixed cooperating contact 32b, 32b depends not only upon the geometry and spring properties of the spring blade 31b, 31b' but also upon the bias which results from the height of the contact 3b,3b' and the thickness of the fixed counter-contact 32b, 32b', bearing in mind that the fixed contacts 32b, 32b' and the contact terminal 33b, 33b' are coplanar.

The assembly of the relay illustrated in FIGS. 7 to 12 comprises the following steps:

a. Spot weld or braze spring contact blades 31b, 31b' to the inner end of the terminals 33b, 33b'.

b. Introduce adjusting leaf springs 17, 17' into the contact holder 21b in such a way that the nose 64 comes to lie between the walls 36' of the shoulder 63.

c. When inserting the armature 1b into the bearing sockets 23b the spring blades 31b, 31b' are flexed as already explained in the previous embodiment. Any additional bias of the spring blades 31b, 31b' that may be required and the simultaneous adjustment of the contact spacing is effected by bevel edges of the actuating bosses 14b, 14b', 14b", 14b'", such as a bevel 43' being shown for instance in FIG. 5.

d. Insert counter-poleshoes 40, 40' into fixed recesses 42b in the contact holder 21b.

e. Insert cover 22b into contact holder 21b causing four locating studs 24b on the cover 22b to engage the contact holder 21b with tension, as has already been described with reference to the relay illustrated in FIGS. 1 to 6 and with reference to FIGS. 14, 18, 19 and 20. This automatically causes the upper pivot pin 12b' of the armature 1b to enter the socket 23b' whereas the counter-poleshoes 40, 40' enter the fixed recesses 42b' in the cover 22b and thus assume their exactly prescribed positions.

f. Wind and connect up the coils 5b, 5b' which are insulatedly separated by the central flange of the coil holder.

g. Affix the cap 39b of ferromagnetic material, which then comes into contact with the faces Ib, IIb, Ib', IIb' of the counter-poleshoes 40, 40'.

h. Adjust relay for one-sided or two-sided position of rest of the armature and/or for threshold of response by adjusting screws 65, 65'.

In FIG. 12 the adjusting screw 65' is shown in adjusted position. It causes the free end of the adjusting spring blade 17 to bear against the angle piece 35 and thus to determine the forces needed for moving the armature, and hence the response and/or release thresholds of the relay. Finally the relay may be evacuated, filled with a protective gas atmosphere and made airtight by embedment in a castable resin. However, the openings in the cap 39b for the adjusting screws 65, 65' must also be covered to ensure that a smooth seal is created and the adjusting screws 65, 65' are locked.

The polarised relay according to FIGS. 13 to 20 is an embodiment of the invention containing a soft iron armature 1c and fixed magnets 50c, 50c'. The partial armature sheath 11c, the bearings 12c, 23 and the shape of the coil holder 2c are substantially similar to those described with reference to the preceding examples. For vertically locating the permanent magnets 50c, 50c' and for the simultaneous location of the poleshoes 4c, 4c', the contact holder 21c is formed with ribs 67, 67'. These ribs 67, 67' are so contrived that clearance remains between them, permitting a rib 68 in a different plane which likewise vertically locates the permanent magnet 50c to be formed in one and the same operation. The cover 22c contains a corresponding complete rib 69 since upward and lateral location is provided by the plastics cap 39c.

The central flange 8c on the contact holder 21c is formed with locating pins 70, 70' for locating an adjusting spring 64c, the pins engaging cooperating holes in the adjusting spring 64c. When assembled the end of the adjusting spring 64c located by the locating pins 70, 70' (FIG. 16) is urged against the contact holder 21c by an appropriate boss 96 formed inside the cover 22c. The adjusting spring 64c is thus positioned. If the locating pins 70, 70' consist of a thermoplastic material they may just as readily be used for hot welding the root of the adjusting spring 66 to the contact holder 21c. A conventional riveted joint would also be feasible. The relay is adjusted by radial flexure of the root end 66 of the two-bladed adjusting spring 64c of a fork-like tool.

In the embodiment shown in FIG. 19 the adjusting spring 64c has been set so that one of its spring ends bears on the biased spring contact blade 31c which bears on the actuating boss 14c. This has the advantage that the thrust of the adjusting spring 64c provides a supplementary force transmitted by the spring blade 31c to the contact pair 3c/32c as soon as the actuating boss 14c is withdrawn from the spring blade 31c. In this state the armature 1c will have left its centre position and, since in such permanent magnet systems, as described for instance in U.S. Pat. No. 1,255,133, any effect of the adjusting spring 64c continuing substantially beyond the centre position of the armature 1c is always undesirable, the proposed arrangement ensures not only improved contacting reliability, but also a simple method of adjustment, particularly when a second adjusting spring of the same kind is available on the mirror symmetrically opposite side so that the operate response and the release response of the relay can be cleanly preset completely independently the one from the other.

A major advantage which the proposed form of construction of the relay also offers is that according to the desired sensitivity of response and/or insensitivity to vibrations one, two, three or four permanent magnets 50c, all of like dimensions and shape, can be inserted into pockets provided in the coil holder 2c without necessitating modifications in design.

Similarly magnets having different properties can be used in combination.

For instance, assuming that two or three barium ferrite magnets are combined with correspondingly two or one AlNiCo magnets, which are well known to have widely different temperature coefficients, then the conditions for a good compensation of the effect of ambient temperature on the response voltage of the relay are good, particularly in conjunction with the above-described effects of the contact spring 31c and adjusting spring 64c. The two poleshoes 4c, 4c' are off-angled from the yoke 5c, 5c' and located between the rib 69 on the cover 22c and on the one hand the ribs 67, 67' of the contact holder 21c and on the other hand the webs 71, 71' which form the contact chamber 54c, 54c' and which are parts of the contact holder. If a second adjusting spring 64c is provided, then the large recess 25c' which is intended in the contact holder for other components, must be dispensed with to enable this second adjusting spring together with the locating pins 70, 70' to be located in a mirror symmetrical position to the spring on the opposite side. After adjustment has been made the remaining space in the recess 25c may also be used for accommodating the previously mentioned components. In a relay with symmetrically positioned terminals it is advisable to make arrangements to prevent mistakes in assembly. For this reason the contact holder 21c is provided, according to the invention, with a locating pin 89 having a relatively thin wall, above which is a locating hole 90. If an additional terminal pin, either for earthing the relay or as a terminal for components 7c inside the relay or for other integrated circuit arrangements, is needed, then this locating pin 89 can be broken off to make the locating hole 90 available for the insertion thereinto of an additional terminal pin which may be located by a tight friction fit or by pinching together the contact holder 21c and/or the cover 22e.

The polarised relay in FIGS. 21, 22, 23 is another development of the invention in which the coil holder 2d is an undivided single component and is merely formed at its flanges with contact holder elements 21d, 21d' for fixed contacts 31d, 31d'. A slightly extended flange on the coil holder 2d contains slots 29d, 29d', whereas a recess 75d is provided in the contact holder member 21d' for the reception of the two limbs of the U-shaped yoke 4d or of a third limb perpendicularly branching from the yoke 4d for the purpose of forming a centre contact terminal 33d.

This relay is designed for rupturing heavier loads and its armature deflection is therefore fairly large, the contact forces are high and the conductor cross sections considerable. Nevertheless, this relay is also intended to be inexpensive to make and to function reliably. These requirements are satisfied for the following reasons:

a. The fixed contacts 31d, 31d' consist of ferromagnetic material and merely have a faceplate 99 made of contact material simultaneously serving as a magnetic separator. Also, the armature 1d of ferromagnetic material is likewise provided at points facing the fixed contacts 31d, 31d' with faceplates 3d, 3d' also serving as magnetic separators.

b. The fixed contacts 31d, 31d' are inclined towards the centre axis X in such a way that when the faces of the contacts 3d, 3d' close with the faces of the fixed contacts 31d, 31d' they will both be coplanar. This means that burn-off will be distributed over a relatively wide contact face. The fact which may at first sight be thought a drawback that the thickness of the separators becomes thinner as burn-off progresses actually has the inherent advantage that with continuing burn-off which raises the contact resistance, the contact-making forces rise in accordance with the decreasing width of the air gap and thus counteract the increase in contact resistance due to burn-off.

c. According to the angularity of the fixed counter-contacts 31d, 31d' which also form poleshoes, the abutting surfaces of the permanent magnets 50d, 50d' which consist of electrically insulating barium ferrite are chamfered. This has the advantage that the permanent magnets 50d, 50d' can be easily inserted between the stationary fixed contacts 31d, 31d' forming the pole-shoes and the two ends of the U-shaped yoke 4d and then keyed in together with the permanent magnets, so that tolerational differences compensate and a good magnetic flux transfer is assured.

d. The soft iron armature 1d is T-shaped, the cross members 73, 73' of the Tee being formed with a knife edge 15 and with two wings 76, 76' in one operation. The knife edge 15 rests in a Vee-notch formed in the yoke 4d and is urged into the notch by an armature-retaining spring 6d having ends engaging angles in the bottom of the yoke 4d.

e. One end of each two adjusting springs 17d, 17d' is anchored, preferably by riveting, to the bottom of the yoke 4d whereas the other ends are flexed by adjusting springs 65d, 65d' in such a way that the armature wings 76 and 76' underneath are selectably sufficiently loaded to keep the armature 1d in stable position on one or both sides to operate or to release at the desired response levels.

The problem which arises when a relatively high current is to be carried from the current conducting armature through the yoke to the contact terminal 33d is solved by providing as many points of contact between the electrically conducting armature and the yoke carrying the current to the contact terminal 33d.

In the illustrated example these are the two knife edges 15 on the T-member 73, 73' which is pressed with considerable force into the Vee notch in the yoke 4d, the contact point of the armature-retaining spring 6d, and the contact points between the adjusting springs 17d, 17d' and the armature wings 76, 76'.

Finally it should be mentioned that the armature 1d is located with relatively little clearance in an opening 97 which is in the plane of the yoke 4d.

FIGS. 25 and 26 illustrate an unpolarised relay of symmetrical design in the energised position. The invention is here applied to an integral undivided coil holder containing an armature 1f mounted in the inertial axes X and Z. The armature 1f is provided with a partial sheath 11f which at its ends is formed with actuating bosses 14f, 14f' and it has a bore with a funnel-shaped opening 43f.

As in the preceding embodiments contact holding elements 21f, 21f' are formed on the two flanges of the integral coil holder body 2f. A contact blade 31f, 31f' is shown in side view in FIG. 27 and in a section taken on the line A -- A in FIG. 28. The spring is formed with a lateral locating web 77 which cooperates with a locating slot 29f centrally formed in the coil holder body 2f. The contact blades proper 31f, 31f' project from each side of the locating web 77, the off-angled blades being strengthened by the provision of flutings 78, 78'. This geometry permits the armature 1f to be inserted into the coil holder body 2f, without being obstructed, after the locating web 77 has first been electrically and mechanically firmly connected to the terminal 33f which is embedded in a fixed position in the contact holding element. A spring member which serves as an armature restoring spring 16f extends at an angle of about 10.degree. from one flank provided with an indentation 78' in a direction opposite to that of the contact spring and, when assembled, one end of this spring member bears against the insulating partial sheath 11f enclosing the armature 1f, applying a thrust P.sub.f (FIG. 26) which in the non-energised state of the relay (not shown) maintains contact between 3f and 32f by the action of the boss 14f formed on the partial sheath 11f of the armature 1f, bearing in mind that the point of application of the force P.sub.f is on the opposite side of the pivot bearing (12f, 23f) of the armature 1f constituting the rest contact force.

The socket opening 18f in the centre of the coil holder 2f which serves as a pivot bearing, and which is formed with a funnel-shaped entry 43f' to facilitate insertion of the pivot pin 12f and the shoulder 51f which keeps the armature 2f in a vertical position are moulded in one operation in the upper part of the injection or pressure mould producing the coil holder body 2f. Preferably, the bearing 23f is a pressed-in cup for the reception of the pivot pin 12f to permit an insulation of the shoulder 51f' from the coil windings 5f to be dispensed with and clearance maintained.

The poleshoes 4f, 4f' are preferably spot welded to the cap 39f, which also consists of ferromagnetic material, to provide a closed iron circuit for the magnetic flux when the windings are energised.

The relay in FIGS. 29 to 32 illustrates a novel concept in which the two parts of the coil holder body are two identical contact holder members containing poleshoes 4g, 4g', terminals 53g, 53g' for the windings, fixed contacts 32g, 32g' and a centrally disposed contact terminal 33g for a two-bladed contact 31g. Magnets 50g, 50g' are inserted, and an armature 1g which substantially corresponds to the armature 1c is mounted between these two identical contact holders 21g, 21g'. When the two identical contact holders 21g, 21g' have been fitted together so that the spring ends 57g, 57g' engage, as has already been described in detail with reference to the embodiments illustrated in FIGS. 14, 18, 19 and 20 in the case of contact holder 21c and its associated cover 22c, two fully operative change-over contacts are automatically created. The armature 1g is made of soft iron and has a relatively large cross section. It therefore lacks spring elastic properties and it is mounted in its axis of inertia.

As the magnetic air gap between the ends of the armature and the poleshoes 4g, 4g' need not be identical with the spacing of the contacts any tolerance variations in the width of the air gaps between the armature 1g and the poleshoes 4g, 4g' and the contact spacings are less critical.

Adjustment of the relay is effected at the contact terminal 33g or by one of the described methods using corresponding means.

FIGS. 33 to 38 illustrate yet another embodiment of the invention in the case of a polarised relay which has a coil holder body 2h consisting of two identical halves in the form of contact holders 21h, 21h', and in which pivot bearings 23h, 23h' as well as pockets 80, 80' for the reception of permanent magnets 50h, 50h', 50h", 50h'" are formed. These pockets 80, 80' contain abutments 81, 81', formed in the mould, for precisely fixing the distances between the permanent magnets 50h", 50h'" as well as the width of the air gap s.sub.h between the poles of the armature 1h and the permanent magnets 50h, 50h' respectively 50h" and 50h'". The usual tolerances of the permanent magnets 50h, 50h' are rendered ineffective by a holding spring 82 which consists of ferromagnetic material, and which serves both as a poleshoe 4h, 4h' where it makes contact with the magnets as well as a yoke 5h from which the poleshoes are off-angled, also bearing in mind that the position of the poleshoes 4h, 4h' has relatively little effect on the functioning of the relay.

Moulded into the contact holder 21h which forms one half of the coil holder body are four, preferably round, locating pins 13h, 13h', 13h", 13h'" and a similar number of holes 83 in mirror symmetrical disposition thereto. FIG. 37 illustrates the detail H of FIG. 36. In other words, when the two identical contact holders 21h are fitted together with their ends reversed, the locating pins 13h will also register with corresponding holes 83. A similar arrangement holds in the case of the locating studs 24g and the cooperating recesses 75g in the preceding embodiment, but a connection by locating pins 13h and holes 83 is better suited for achieving a tight frictional fit.

Again in a manner corresponding to the preceding embodiments the terminal pin 33h of contact holder 21h is connected in the middle by spot welds or brazing to a spring blade 31h. As illustrated in FIG. 37 the spring blade 31h has a central offset so arranged that the sides which slope towards the offset at an angle .gamma. have a self-centering effect in assembly on the spring in relation to the contact terminal pin 33h. Preferably the spring blade 31h is attached to that side of the contact terminal pin 33h which faces the armature 1h, and its spring portions are so angled that, when the armature 1h is inserted into the bearing sockets 23h, 23h', they will bear with pressure against the actuating bosses 14h, 14h'. This improves the reliability of contact making because of the horizontal fixation thus obtained and because of the bias of the spring blade 31h which bears on the contact terminal pin 33h with the combined thrust generated by its two biased spring members, so that satisfactory functioning of the relay would be assured even if there were no fixed connection between the two contact elements 31h and 33h.

In order to take up unwanted tolerances a bearing bush 79 may be fitted over each pivot pin 12h, 12h' which are both integrally moulded with the partial sheath 11h. This detail is shown in FIG. 34 and again illustrated on a larger scale in FIG. 38. The bearing bush 79, 79' provides the necessary bearing clearance even if the two half shells forming the sockets 23h, 23h' press on the bush 79.

The use of bearing bushes 79 is also on advantage whe integrally moulded pivot pins 12h, 12h' are replaced by a pivotal pin 12f (FIG. 25) which transverse the armature 1h. The pivot pin 12f will then have slight clearance inside the walls 98, 98' of the sockets 23h, 23h' and the bearing bush 79, 79' will have slight clearance in relation to the walls 98, 98' and to the armature 1h so that it can also perform the function of a bearing shoulder.

The relay illustrated in FIG. 33 to FIG. 38 is assembled as follows:

a. Affix the spring blades 31h to the contact terminal pin 33h embedded in the contact holder member 21h.

b. Insert the permanent magnets 50h, 50h' into the pockets in the contact holder member 21h.

c. Insert the armature 1h into the bearing sockets 23h, 23h'.

d. Fit together two identical contact holder elements 21h which have both been pre-assembled as stated in (a) and (b). This automatically biases the spring contact blades.

e. Insert the holding spring 82 until its off-angled ends 84, 84' snap into engagement with premoulded shoulders 85 (FIG. 33) in the assembled coil holder body 2h.

f. Wind the coils 52h, 52h' and connect their ends to the winding terminals 53h, 53h'.

g. Adjust the operate and release thresholds at the ends of the contact terminal 33h which are accessible through openings in the centre flange 8h.

h. Cover the recesses 25 in the central coil holder flange with a retaining spring 82' which in the illustrated embodiments is identical with the retaining spring 82 serving as yoke, poleshoe and magnet locating means.

e. As a magnetic shield and for reducing the magnetic stray flux a cap 39h of ferromagnetic material may be fitted over the relay.

Intermediately between assembly operations (b) and (d) the faces of the contact holder 21h which later abut may be provided with an adhesive, for instance by the so-called screen printing technique and the retaining springs 82, 82' may be coated if the contact-containing chamber 54h is to be airtight and sealed from the environment. Similarly, after assembly operation (i) the relay may be cast in resin to prevent moisture from entering the coil and to improve the mechanical protection of the relay.

In the preceding embodiments (cf. for instance FIGS. 2, 3, 4, 16) of the invention, it has been explained that the contact holder 21, 21c is formed with moulded recesses 25, 25c for the space-saving accommodation of components 7, 7', 7h. In the embodiment illustrated in FIGS. 33, 34, 35 a wider employment of such components is rendered possible by the addition of a conductor plate 86 for their reception. In such a case the upper ends of the coil terminals 53h, 53h' are electrically connected to the circuit on the conductor plate 86 and at least one of the ends of a coil terminal 53h projecting from the relay is isolated to prevent an undesirably high potential from entering the conductor plate circuit 88. On the other hand the conductor plate circuit 88 will usually require one or two additional terminals. For this purpose, the contact holder, as described with reference to FIG. 16, contains at least one locating hole 90 which permits an additional terminal pin to be fitted. The invention can then be further developed by providing the contact holder 21h with lateral sloping faces 91 for mounting a potentiometer 87. If this potentiometer is connected in series with the coil 52, it can be used to adjust the operate and/or release thresholds exactly. The oblique affixation of the potentiometer 87 to the relay has the advantage that it is accessible for adjustment in any position of the relay, even when this is contained in a pocket in a control system. Accordingly, a cap for such an arrangement must be provided with a window 93 in a sloping face 92 of the cap which is substantially parallel to the sloping mounting face 91 of the contact holder 21h. However, if the cap is to be universally applicable, it is advisable to provide a window 94 in the edge of the cap facing the potentiometer.

As demonstrated by the description of only seven embodiments, the present invention opens up fresh paths of development in the technology of relay design. It has been repeatedly emphasized that special features of one embodiment can be nearly always applied with the same advantages to other embodiments, so that combinations of the several features described in different contexts of the above specification should also be considered as being within the scope of the present invention.

While specific embodiments of the invention have been shown and described in detail to illustrate the application of the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.