GB2066577A - Electromagnetic relays - Google Patents

Abstract

An electromagnetic, polarized relay has a core (1) comprising a web (2) and arms (3 and 4) providing pole surfaces (6 and 7); a permanent magnet (8); and a shunt (9), embedded in a block (23). A relay armature (10) is pivotally mounted on the block for engagement and disengagement with the pole surfaces (6 and 7). <IMAGE>

Description

SPECIFICATION An electromagnetic, polarized relay The present invention relates to an electromagnetic, polarized relay.

Relays with an iron circuit moulded into some insulation material are already known. In these relays, a movable armature is arranged in a cavity in the moulded mass or body.

According to the present invention, there is provided an electromagnetic, polarized relay, an iron circuit of which, with the exception of an armature, is embedded in a block, the relay further comprising a core with a coil and pole surfaces, the armature co-operating with the pole surfaces and a permanent magnet, wherein the core and the permanent magnet are embedded in the block, and the armature is mounted on the block for engagement and disengagement with the pole surfaces.

The present invention will now be described by way of example with reference to the accompanying drawings, in which: - Figures 1 to 4 illustrate items included in an iron circuit, i.e. the magnetic circuit excluding air gaps, in a relay and an advantageous arrangement of the items in the iron circuit; Figure 5 illustrates a plastics coating of a core included in the iron circuit; Figure 6 shows a preferred embodiment of embedding of the core of the iron circuit, a permanent magnet and a shunt and the arrangement of an armature of the iron circuit after embedding; Figures 7a, b and c illustrate a preferred embodiment of a spring group adapted for cooperation with the moulded body according to Figure 6; and Figure 8 illustrates an example of a spring group for carrying out several relay functions.

In contradistinction to known relays, the following examples are characterized in that a core and a permanent magnet are embedded in a block, where there can be openings for pole surfaces lying close under an outside surface on one side of this block, and that an armature is mounted on the block outside the said surface for engagement and disengagement with the pole surfaces. The block has holes left by the locating pins which oriented the embedded items.

The relays to be described are intended particularly for telephony purposes, and in that 'connection for mounting on circuit boards, when the relays must have small dimensions.

The iron circuit embedded in the block and consisting of the core and permanent magnet, with the armature placed in a guide bearing on a side of the block, form a unit. By placing the armature on the outside of the block, the latter can be completely or partly filled so that there are no moving parts therein. This is essential with the small items envisaged here and in the miniaturization of the relay, as this creates increased demands on the form and correct mutual relation of the items for the right cooperation between the items in the iron circuit, especially in a polarised relay with its greater sensitivity. The block also has the advantage that it can be made completely sealed, such occurrences as the penetration of gases into the relay during soldering on a circuit board thus being prevented.

Figure 1 is a perspective view of a core 1 included in an iron circuit. The core is substantially U-shaped with a web portion 2 formed as a shaft and plate-form arms 3 and 4. The core is suitably produced by bending or folding a straight member.

The web portion is substantially quadratic in cross-section, the corner edges being rounded off.

The web portion constitutes a winding part for a core coil 5 (see Figures 2 and 3) and the longer side edge surfaces 6 and 7 on the arms 3 and 4 constitute pole surfaces of the core.

As is apparent from the plan view in Figure 2 and side view in Figure 3 seen from the left in Figure 2, a permanent magnet 8 of the iron circuit is situated between the core arms 3 and 4 to one side of the coil 5 and parallel thereto.

The permanent magnet further abuts against a piece of iron 9, serving as a magnetic shunt for the permanent magnet. Also, the permanent magnet as well as the shunt are closer to the arm 4 than to the arm 3. This gives an effect which will be more closely described later in conjunction with measures for forming a monostable relay. A similar effect is obtained when in one embodiment of the core, the distances from the axial centre of the winding portion to the respective pole surfaces are somewhat different. This effect will also be described in conjunction with the said measures.

Figure 3 also illustrates the placing and mounting of a plate-form armature 10 for cooperation with the pole surfaces 6 and 7. The armature is pivotably mounted on a bearing surface 11 disposed centrally between the arms and parallel thereto. This surface can be formed at a casing around the core, e.g. as illustrated in Figure 6. The armature works as a see-saw for engagement with one or other pole surface.

The armature suitably comprises a substantially rectangular plate and could be as illustrated in Figure 4 for co-operation with the mounting illustrated in Figure 6. In this embodiment, tongues 12 and 13 project out from the middles of the long sides of the rectangular armature, these tongues constituting guides in the armature mounting. On its upper side opposite the mounting 11 , the armature is provided with plastics ridges 14 and 1 5 serving as lifting means for movable metal springs to carry out the relay functions, e.g. springs arranged in a spring group of the kind illustrated in the Figures 7 and 8.The armature also has portions 1 6 and 1 7 projecting from its short sides, and the reason for this will be explained in conjunction with the description of the embodiment according to Figure 6, for which the armature illustrated in Figure 4 is specially formed.

The above-described relay has a substantially U-shaped core, with large pole surfaces 6 and 7 and simultaneously an elongate winding portion, with the permanent magnet situated in the space between the core arms and the plate-form armature mounted above a plane through the pole surfaces and working as a see-saw for contact with one or other of the core pole surfaces. This structure enables a substantial miniaturization of the relay.

With reference to Figures 5 and 6, it will now be described how the above-described iron circuit, apart from the armature, is moulded into a plastics body.

The core is provided with a plastics coating in a tool. The core with platics coating is illustrated in Figure 5 in plan view. The plastics coating is provided to obtain insulation for the coil winding and attachment of welding lugs. With the aid of the plastics coating, pole tags can be formed for the armature, forming the armature's contact surfaces for the energized and unenergized states of the relay.

In the core of Figure 5, the web portion 2 is completely covered with plastics apart from a narrow strip 1 8 through the insulation where supporting means of the moulding tool have been in engagement against the core 1. The free end portion of the one of the arms of the core, as illustrated for the arm 3, this portion being used for location in the moulding toul, is not plasticscoated. The other arm 4, on the other hand, has its free end portion coated during moulding as well, whereby some length variation of the core is taken up within the dimensions of the moulding tool .The pole surfaces 6 and 7 do not have a plastics coating, with the exceptions of small areas covered by plastics flaps 19 and 20 respectively, constituting the above-mentioned pole tags for the armature.The plastics coatings on the side surfaces of the arms are preferably taken up to the same height as for the plastics tags, so as to form stop or engagement surfaces for the armature, together with the tags. The plastics coating is further provided with holes 21 and 22 on the outsides of the arms, for soldering lugs (not shown).

Figure 6 illustrates, in a view corresponding to Figure 3, moulding of the core 1, the permanent magnet 8 and the shunt 9 in a block 23 of plastics material with an armature 10 (illustrated in Figure 4) mounted on the upper side 24 of the block. The core, permanent magnet and shunt, shown by dashed lines, are embedded so that a block completely or partly filled with platics material is formed. The portions of the pole surfaces 6 and 7 not covered by the plastics tags 1 9 and 20, and the plastics tags, lie substantially in the upper plane of the block. Before embedding, the core with the coil, shunt and permanent magnet could have been placed in a holder (not shown), included inside the block, this holder being formed and adapted for correct positioning of these items.For mounting the armature 10, the upper surface of the block at respective ones of two opposite edges has two projecting upwardly curved nodules 25 and on outside each of these a pair of upstanding edges 26, the distance between the edges 26 being somewhat greater than the width of the side locating tongues 1 2 and 13.

These side locating tongues could (see Figure 4) be of different widths as well as, in such a case, the distances between the edges 26, with the object of obtaining correct location of the armature. The nodules 25 provide a bearing line for the planar underside of the armature, i.e. they correspond to 11 in Figure 3. The lower edges of the projecting portions 1 6 and 1 7 described in conjunction with Figure 4 at the short sides of the armature constitute the stops for the armature movement towards the upper side of the block.

For reasons given in conjunction with Figures 7a to 7c, the block has shoulders 27 on its four side surfaces, of which one, indicated by the line 28, is offset relative the others.

The iron circuit forms a unit comprising the core 1 with its coil, the permanent magnet 8 and the shunt 9 embedded in the block, with the armature 10 placed in its bearing guides 25 and 26 on the upper side of the block. By placing the armature on the outside of the block, the latter can, if so desired, be completely filled so that there is no cavity in it and no moving parts, or it can be partly filled. This is essential with the small items in question here for the desired miniaturization of the relay, as miniaturization involves increased demands on the forming of the items and their correct mutual relation for the correct cooperation between the items in the iron circuit, especially in a polarized relay with its greater sensitivity.The block also has the advantage that is completely sealed off, whereby the penetration of gases into the block during soldering on a circuit board is prevented.

The unit can be tested in respect of stroke, the positions of the plastics ridges 14 and 1 5 above the upper side of the block for energized and deenergized armature as well as the relay pulling force. The upper side of the block can constitute a reference plane from which all dimensions can be taken, both internally and externally.

As previously described in conjunction with Figure 4, the plastics ridges 14 and 1 5 of the armature 10 serve as lifting means for movable metal springs for performing the relay functions.

Figures 7a and 7c and 8 illustrate an advantageous embodiment of such springs kept together in a group. A spring group will now be described in the following as an example while referring to Figures 7a to 7c in an embodiment adapted to the block 23. The spring group comprises a plastics frame 29 shown in plan in Figure 7a, of which sections 1-1 and Il-lI are shown in Figures 7b and 7c respectively. The frame has substantially the same outside dimensions as the block 23. The inner dimensions of the frame are adapted for placing the frame on the shoulders 27 and 28 of the block, the frame having a shorter side wall 30 filling out the shorter shoulder 28 in one side wall of the block, while the remaining side walls 31 of the frame are equally as long and fill out the shoulders 27 in the remaining side walls of the block.This ensures that the spring group will be correctly fitted to the block. When the frame is fitted, support surfaces 32, preferably comprising a nodule or the like in each corner, rest against the upper side 24 of the block.

A plurality of planar metal springs are moulded straight through into two opposite side walls of the frame, the springs being directed towards each other for overlapping in pairs. One such pair is illustrated in Figure 7a, for the sake of simplicity.

In each pair there is a short spring 33, which thus is practically immovably attached, and a long resiliently movable spring 34. As is apparent from Figure 7c, it is preferable that the short springs 33 are moulded-in so that they lie in a plane parallel to a plane through the support surfaces 32, while the long springs are moulded-in so that they form an angle to this plane. Figure 7c also shows contacts 35 and 36 on mutually opposite surfaces at the free ends of the short and long springs respectively. The armature co-operating with a spring group displaces the long springs into contact with the short springs when the relay comes into operation. For example, in the armature 10 described above, its plastics ridges act on the long spring when the relay comes intc action.

The portions of the springs extending outside the frame are bent through 900 and formed into soldering lugs. The spring group forms a unit which can be measured and adjusted with respect to positions, contacting forces, etc. of the springs with the four supporting surfaces 32 as a reference plane.

By the arrangement of a spring group as described above, the spring pairs are arranged side by side in a plane immediately above an armature and can perform several functions after actuation by the armature. Figure 8 illustrates an example of such a spring group.

As schematically illustrated in the embodiment according to Figure 8, seven spring pairs are arranged in the spring group in the plastics frame 29. The middie spring pair lacks contacts, while remaining spring pairs have the contacts 35 and 36. The contact functions for these pairs provided with contacts are arranged such that at one frame wall there are four terminals S and at the opposite frame wall there are two terminals S. Depending on the position of the armature, energized or deenergized, there is thus obtained a relay with four makes and two breaks. The middle spring pair without contacts, which functions as do the contact springs on actuation by the armature, is arranged to serve as an extra spring bias on the armature when energized.

A construction of a relay in accordance with the invention could lead to a bistable relay, in which the armature with the force of the permanent magnet maintains its position just as well in the de-energized as in the energized state. In a preferred embodiment, a relay in accordance with the invention will function as a monostable relay, i.e. it will close or make when current is applied to the coil and open or break when the current is interrupted.

The bistable condition is effected by placing the magnet 8 and/or the shunt 9 asymmetrically in relation to the core 1, as is illustrated in Figures 2 and 3, for example. The pulling force will be then unequally great at the pole surfaces 6 and 7.

By loading an armature, e.g. the armature 10, with more functions on one side than on the other side thereof, e.g. four and two functions as illustrated in Figure 8, different pulling forces are required at energizing and de-energizing.

By introducing extra springs without contacts, e.g. the middle spring pair in Figure 8, an additional bias is obtained, whereby the spring group characteristic can be formed in good conformity with the form of the pulling force graphs, and an extra load obtained on the side of the armature where there are more functions.

By selecting different thicknesses of the pole tags for the pole surfaces, e.g. the plastics tags 1 9 and 20 illustrated in Figure 5, and as a result thereof having different distances from the axial centre of the winding portion 2 to the pole surfaces 6 and 7; as desribed in conjunction with Figure 3, the pulling force is altered for the energized and de-energized states.

In summary, the relay can be given a monostable function by taking one or a combination of some or all of the following steps: - the permanent magnet is asymmetrically placed; - the permanent magnet shunt is asymmetrically placed; - the contact spring load is asymmetric; - a spring pair not having contacts is provided; - the pole tags are given different thicknesses; - the permanent magnet is given a distorted magnetization; -the armature mounting is asymmetrically located between the pole surfaces.

Such steps, singly or in a combination, are used to make a monostable relay from the bistable basic construction. At the same time, they are also used to obtain good agreement between the slope of the graphs and thereby permit increased manufacturing tolerances.

Claims (10)

1. An electromagnetic, polarized relay, an iron circuit of which, with the exception of an armature, is embedded in a block, the relay further comprising a core with a coil and pole surfaces, the armature co-operating with the pole surfaces and a permanent magnet, wherein the core and the permanent magnet are embedded in the block, and the armature is mounted on the block for engagement and disengagement with the pole surfaces.

2. A relay as claimed in claim 1, wherein, before embedding, the core was provided with a plastics coating to insulate the coil winding, and to form layers partially covering the pole surfaces and providing stop surfaces for the armature.

3. A relay as claimed in claim 2, wherein the core is substantially U-shaped with a web portion from which arms extend, the coil being wound round the web portion, and side edge surfaces facing in the same direction on the arms provide the said pole surfaces, wherein the plastics coating also covers the remaining sides of one of the arms and at least partially the corresponding sides of the other of the arms, the plastics coating on the outsides of the arms being formed to create attachments for soldering lugs.

4. A relay as claimed in claim 3, wherein the plastics coating on the outside and inside of the arms extends up to a level with the covering layers on the pole surfaces.

5. A relay as claimed in any of claims 2 to 4, wherein the covering layers on the pole surfaces are substantially in the same plane as a side of the block.

6. A relay as claimed in any preceding claim, wherein the pole surfaces extend adjacent and parallel to two opposite edges of a side of the block and the armature has extensions having widths substantially conforming to the lengths of the pole surfaces and is pivoted like a see-saw about an axis substantially parallel to the pole surfaces.

7. A relay as claimed in claim 3 or any of claims 4 to 6 as dependent on claim 3, wherein the permanent magnet is situated between the arms of the core.

8. A relay as claimed in claim 7, wherein the permanent magnet is situated closer to one of the core arms than the other.

9. A relay as claimed in any preceding claim, wherein a magnetic shunt is embedded in the block and engaging against the side of the permanent magnet facing away from the armature.

10. An electromagnetic, polarized relay, substantially in accordance with any example herein described with reference to the accompanying drawings.