GB2149211A - Electrical relays - Google Patents

Abstract

The armature (14) of a relay is pivotably arranged in a coil (3) and operates contact sets (2) via a insulating link members (19). The armature pivots about an axis which is perpendicular to both the winding axis of the coil (3) and the direction in which the relay terminals (29, 30, 31, 12) project from the relay housing (1). The contact force of the contact set (2) is enhanced by means of a permanent magnet (7) located between two yoke pieces (6, 5), each having bent-over portions providing pole faces (15, 16, 17, 18), coupled thereby. In a monostable version (as illustrated) the pole faces (15, 16, 17, 18) of the pole pieces via which magnetic coupling to the armature (14) occurs are different in size, so that when the coil (3) is de-energised the armature (14) will always restore to the same position corresponding to the larger pole faces (15, 17 as illustrated). In a bistable version the pole face areas are the same so that the armature is held in its last set position upon coil de-energisation. <IMAGE>

Description

SPECIFICATION Electrical relays This invention relates to electrical relays and to methods of manufacturing them.

According to one aspect of the present invention there is provided an electrical relay comprising an electrically-insulating housing; a coil disposed in the housing; an armature extending through the coil and pivotable therein upon passage of a current through the coil; at least one contact set disposed in the housing and arranged to be operated by pivotable movement of the armature; a permanent magnet disposed in the housing and serving to enhance the contact force of the at least one contact set; and first and second yoke pieces disposed in the housing, the permanent magnet being disposed in a coupling relation between the yoke pieces whereby to induce poles of opposite type therein, wherein a respective end portion of the armature extends from each end of the coil, wherein each pole piece has a respective pole face for each end portion of the armature, each end portion of the armature being disposed between pole faces provided by yoke pieces, wherein terminals associated with the contact set extend generally in one direction from the housing, wherein the coil is wound about an axis perpendicular to the one direction, and wherein the armature pivots about an axis perpendicular to both the one direction and the coil axis.

According to a second aspect of the present invention there is provided an electrical relay comprising in an electrically-insulating housing: a coil; an armature extending through the coil and pivotable therein upon passage of a current through the coil; at least two contact sets disposed on one side of the coil, each being associated with a respective end of the armature and arranged to be operated by pivotable movement of the armature; first and second planar yoke pieces disposed on second and third sides respectively of the coil and a permanent magnet disposed on the fourth side of the coil to induce poles of opposite types in the yoke pieces, wherein a respective end portion of the armature extends from each end of the coil between bent-over portions of the yoke pieces providing pole faces for each end portion of the armature.

According to a third aspect of the present invention there is provided an electrical relay comprising an electrically-insulating housing; a coil disposed in the housing; an armature extending through the coil and pivotable therein upon passage of a current through the coil; at least two contact sets disposed in the housing, each being associated with a respective end of the armature and arranged to be operated by pivotable movement of the armature; a permanent magnet disposed in the housing and serving to enhance the contact force of the contact sets; and first and second yoke pieces disposed in the housing, the permanent magnet being disposed in a coupling relation between the yoke pieces whereby to induce poles of opposite type therein, wherein a respective end portion of the armature extends from each end of the coil, wherein at each end of both yoke pieces there is a bent-over portion providing a respective pole face for each end portion of the armature, each end portion of the armature being disposed between pole faces provided by both pole pieces, wherein terminals associated with the contact sets extend generally in one direction from the housing, wherein the coil is wound about an axis perpendicular to the one direction, and wherein the armature pivots about an axis perpendicular to both the one direction and the coil axis.

According to a fourth aspect of the present invention there is provided an electrical relay comprising an electrically-insulating housing; a coil disposed in the housing; an armature extending through the coil and pivotable therein upon passage of a current through the coil; four contact sets disposed in the housing, two contact sets being associated with each end of the armature, the contact sets being isolated from one another and arranged to be operated by pivotable movement of the armature, the contacts of the four contact sets all being disposed on one side of the coil; yoke means; and a permanent magnet disposed in the housing and serving to enhance the contact force of the contact sets, the permanent magnet being disposed in a coupling relation with the yoke means, which provides two pole faces for each end of the armature, such as to induce poles of opposite type in the two pole faces at each end of the armature.

According to a fifth aspect of the present invention there is provided a method of making an electrical relay comprising providing a housing with holes in a face thereof corresponding to the intended positions of external connection terminals; providing a coil wound about a first axis on a bobbin and connected to a pair of external connection terminals mounted thereon; arranging an armature in the coil such that it is pivotable therein about a second axis perpendicular to the first axis upon passage of a current through the coil; providing at least one side wall of electrically insulating material, each side wall having embedded therein a conductor frame providing external connection terminals and supporting fixed and moving contacts of a contact set; arranging a magnet in the housing whereby to serve for enhancement of the contact force of the contact set; inserting the coil wound on the bobbin and with the armature therein into the housing so that the pair of connection terminals locate in a pair of said holes; insert ing the at least one side wall in a respective gap between the coil and an outer wall of the housing so that the external connection terminals of the conductor frame locate in respective holes in the housing and extend generally in one direction from the face of the housing which is perpendicular to both the first and second axis.

Embodiments of the invention will now be described with reference to the accompanying drawings, in which: Fig. 1 illustrates, somewhat schematically, a partial part-sectional side view of an embodiment of relay; Fig. 2 illustrates, somewhat schematically, a plan view of a relay sub-assembly located in a casing therefor with the switch sets omitted; Fig. 3 illustrates, somewhat schematically, an end view of the relay of Fig. 1 as seen in the direction of arrow A with the casing end wall and the switch sets omitted; Figs 4a, 4b and 4c show, respectively a left hand end view, a side view and a right hand end view of one pole piece of the relay of Fig.

1; Figs 5a, 5b and Sc show, respectively, a left hand end view, a side view, and a right hand end view of the other pole piece of the relay of Fig. 1.

Figs 6a, 6b, and 6c, respectively show schematically three armature shapes, together with corresponding pole piece shapes and indicating pivoting of the armature in the coil bobbin; and Fig. 7 shows a partially exploded view of part of a relay according to the present invention and specifically indicating two contact switch sets and their relation to a coil in the overall structure.

Referring firstly to Figs. 1, 2, 3 and 7, the relay comprises a plastics moulded housing or casing 1 which has in its underneath face (base) la two rows of holes such as 29a, 30a, 31 a, 1 2b to accommodate external connection terminals of the relay. In the 4C/O version illustrated there are seven holes per row in order to accommodate a total of fourteen terminals, three for each of the four switch sets 2 plus two for a coil 3. A yoke assembly 4 comprises two yoke pieces 5 and 6 which are coupled by a permanent magnet 7. The magnet is polarised transversely to its length so that one longitudual face is south seeking (S) (Fig.3). The configuration of each of the yoke pieces 5 and 6 can be appreciated more clearly from Figs 4 and 5. The magnet 7 extends between the yokes along the entire length thereof.In the embodiment illustrated the yoke piece 5 is polarised by the N face of magnet 7 whereas the yoke piece 6 is polarised by the S face of magnet 7. The coil 3 is wound on a bobbin 8 which has a central longitudinal aperture 9 therethrough. The aperture 9 has a rectangular section in the embodiment illustrated. Extending through the aperture 9 and pivotable therein is an armature 14. The armature and/or the aperture may be designed to enable the pivoting, examples of which will be described in more detail hereinafter, particularly with reference to Figs 6a, 6b and 6c. The armature 14 is pivotable about an axis 21 intermediate its ends which is transverse to its length and extends generally parallel to the plane of base 1 a of casing 1.Thus when considering the casing mounted to a printed circuit board disposed in a horizontal plane the armature will perform a see-saw movement involving up and down (vertical) movement relative to a horizontal axis. In more general terms, if the terminals of the relay extend generally in one direction from the casing, and the coil is wound about on axis perpendicular to the one direction, then the armature pivots about an axis perpendicular to the one direction and the coil axis. Each end of the armature 14 is disposed between a respective pair of pole faces of the yokes 5 and 6.Each of the pole faces 1 7 and 18 of yokes 5 are disposed below the corresponding pole faces 15 and 1 6 of yoke piece 6 and below the armature 14, that is the pole faces 1 7 and 1 8 are innermost in the casing 1. Pole faces 1 5 and 1 8 are adjacent one another and pole faces 1 6 and 1 7 are adjacent one another. The pole faces are provided as bent-over end portions of the yoke pieces.

The coil 3 in the embodiment illustrated is wound on a bobbin 8 which has two separate sections 10 and 11 due to the presence of a central plate 1 3 formed integrally with the bobbin 8. The coil 3 is electrically continuous between the two sections 10 and 11 and wound in the same direction in both sections.

The ends of coil 3 are each coupled to a respective coil terminal 1 2 of a pair of such terminals disposed at the central plate 1 3.

The yoke pieces 5 and 6 and the armature 14 are manufactured from soft magnetic materials having high permeability and low remanence.

Since the areas of the pole faces of the yoke pieces 5 and 6 compared to the armature ends are different, pole face 1 7 of yoke piece 5 being larger in area than pole face 18 of yoke piece 5 and pole face 15 of yoke piece 6 being larger than pole face 1 6 of yoke piece 6, the force acting on the armature 14 due to the permanent magnet is greater in one pivoting direction of movement of the armature (clockwise in Fig.1) than the other.

Thus when the coil 3 is de-energised, the armature will always return to the same position, corresponding to the larger area pole faces 1 5 and 17, and hence the device illustrated is monostable.

Each end of the armature 14 is operatively linked to the switch sets 2 via insulating link members 19, for example of a plastics material. In the 4C/0 version the members 1 9 may be comprised, as illustrated, by generally rectangulary-shaped apertured plastics links as illustrated in Fig 7 which each serve to operate two switch sets. The members 1 9 couple the armature to the movable blades (contact springs) 20 of the switch sets 2. The movable blades 20 extend generally in a plane substantially parallel to the base 1 a of the casing and are all disposed, together with the contacts of the switch sets, on one (upper) side of the device, which side will be subsequently covered by a dust cap (not shown) clipped over ledge 1 b on the upper side of the casing 1.The blades 20 of the sets at the both ends of the device are biased towards the lower fixed contacts 23 so that they are reliably contacted when the blades are not pushed towards the upper fixed contacts 22 by the members 19, which are disposed between the pole faces at the ends of the yoke pieces and the ends of the coil.

When the coil 3 is energised, whereby to operate the relay, the direction of current flow is such as to cause magnetic polarities to be induced at either end of the armature 14 which are the same and thus oppose the polarities existing at the contacted pole faces 1 5 and 1 7 of the yoke pieces 6 and 5, respectively, due to the magnet 7, and thus the armature 14 is caused to move pivotally due to repulsion. At a point in the travel of the armature its induced poles will be attracted to the opposite poles, due to the permanent magnet, existing at the other pole faces 1 6 and 1 8 of the yoke pieces. Thus during the armature travel both repulsion and attraction forces act on the armature to provide high acceleration.When the gap between the armature and the pole faces is very small, even a low value of remanence is sufficient to delay the release of the armature when the coil is de-energised. For this reason remanence slugs (not shown) of non-magnetic material, for example copper or brass, may be used to maintain a small non-magnetic gap between the parts to overcome the effects of remanence. In a monostable version the remanence slugs would be mounted to the pole faces of the pole pieces which are contacted when the relay is operated, that is the smaller area pole faces 16 and 18.

A bistable version of the relay may be achieved by arranging for the pole faces 1 5,16,1 7 and 18 to be of the same area, so that the permanent magnet force will retain the armature in the last position to which it was set, as dictated by the direction of the coil flux. If the relay is to be used with current reversing electronics then a single coil can be used which will switch the armature with reversal of the current in the coil. Once reversed it is not necessary to maintain the coil current as the permanent magnet force will be sufficient to hold the armature in position. If only unidirectional currents are available from the electronics with which the relay is to be used, then flux reversal can be achieved either by the use of reversing contacts, or by the use of two coils wound in different directions.For two coil versions a respective set of coil terminals will be required for each coil.

Whereas Fig.1 illustrates an embodiment in which respective pairs of pole faces 1 5,1 8 and 16,17 are parallel and the armature ends are tapered for maximum contact area when the armature is pivoted, this is not the only possibility. As indicated in Fig 6a, the armature may taper towards each end from a central region 24 so that by suitable choice of the dimensions of the armature and the bobbin aperture the central region 24 may itself define the pivot. In such an arrangement the yoke assembly 4 involves parallel pole faces.

The arrangement of Fig. 6b also involves parallel pole faces but to reduce the cost of manufacturing of the armature only the ends thereof are tapered and another version of pivot is employed. This may simply be comprised by suitably shaped projections deformed from the armature material by, for example, punching, or it may be comprised by a pair of opposed knife edges 25,26 disposed centrally of the aperture as indicatedin Fig. 6b. The cost of tapering even just the ends of the armatures to the required tolerances is likely to be high and thus the alternative arrangement of Fig 6c may be attractive.

This arrangement uses a rectangularly sectioned flat strip of magnetic material for the armature 14 and the pole faces of the yoke assembly 4' are angled in order to provide maximum contact area. Such angling may either be achieved by deforming the pole pieces illustrated in Figs. 4 and 5 after machining thereof, or alternatively by modifying the design of those pole pieces to include the required angling. In this case also the pivot may be provided by a pair of opposed knife edges or projections punched from the armature material.

The monostable and bistable relays described above are particulary suitable for manufacture in a miniature form in a DIL (dual-inline) outline package (30 per type, using three pins for each of the four contact sets plus two pins for the coil, the remaining pins being omitted). Such a DIL package is 1Omm high, 35mm long and 10mum wide. The design of the monostable and bistable versions of the relay is the same except for two piece parts, the yoke pieces, thus facilitating manufacture.

The relay design is also particulary suitable for automated assembly and adjustment may be performed with ease.

As may be appreciated from Fig. 7 the fixed contacts 22,23 and the mount 27 for movable contact 20 are embedded in a plastics side wall 28. The contacts are all formed from a conductive frame which has been stamped from a continuous strip of conductive frame material. After embedding in the plastics side wall the conductive frame is trimmed so that the contacts are electically separated, fixed contacts 22,23 and the mount 27 are each have a respective external connections terminals 29,31 and 31 which, when the side wall 28 is inserted in the gap between the outer wall 1 c of casing 1 and the adjacent side of the coil 3, will project through the aforementioned holes in the underside of the casing 1.

The coil connection terminals 1 2 project through corresponding holes in the casing 1 and are mounted to the central plate 1 3 of the bobbin. The upper end 1 2a of each of these connection terminals 12 forms a wiring tag for a corresponding end of coil 3. The bobbin 8 may be moulded from plastics material. The terminals 12 can have a tangled stake which bites in a groove in plate 1 3 or can alternatively be embedded therein during the bobbin moulding process. Either way they are firmly irremovably held to the motor unit.

This enables the coil to be automatically wound and terminated using a very fine wire.

Once the winding has been wound and terminated (tagged) the terminations are soldered.

The tagged ends 1 2a are bent inwardly to detension the wire ends of the coil. With the coil 3 wound on the bobbin 8 and inserted in the casing 1 so that the terminals 1 2 project through the respective holes (12b) in the underside face of the casing, four gaps, two on either side of the central plate 13 on both sides of the coil, are left which are exactly the right size to accommodate side walls such as 28. As is apparent from Fig. 7 there are lefthanded and right-handed versions of the switch sets, two of each being required for each relay in the 4C/O version.

The sequence of operations for the assembly of the relay, which is suitable for automation, is as follows. A yoke piece assembly 4 is assembled and a bobbin 8 on which coil 3 has been wound and terminated located centrally between the projecting ends of the yoke pieces providing the pole faces. A respective insulating link 19 is disposed at each end of the bobbin with the aperture therein aligned with the bobbin aperture.An armature 14 is slid in from one end of the yoke piece assembly to adopt the position shown in Fig. 1 extending between the pole faces 15 and 18, through one insulating link, through the bobbin 8, through the other insulating link and between the pole faces 1 6 and 1 7. This subassembly, which is held together by the armature 14, is inserted in a casing 1 so that the coil terminals 1 2 project through the respective holes 12b. The insulating links 1 9 may be split as at 33, in which case they need not be located relative to the armature until after the bobbin is disposed in the casing.Side walls 28 with their embedded terminals and fixed and moving contacts are then slid into the respective gaps between the coil and the casing walls so that their terminals extend through the respective casing holes 29a,3Oa,31a. Sprags 32 on the terminals serve to positively lock the terminals in the plastics casing 1. An ultrasonic force can be superimposed on the direct insertion force to help overcome friction and partially fluidise the plastics material to ease insertion. The holes 29a, 30a, 31 a and 1 2b may taper from the inside towards the outside of the casing, being larger than required for the terminal size at the inside of the casing in order to facilitate location of the terminals therein.The side walls 28 may then be glued to fix their position in the casing and to seal the terminals in the holes in the underside of the casing 1. At this point the relay may be tested and the bias of the movable blades adjusted as appropriate. Finally a dust cap (not shown) is clipped over the ledge 1 b on the upper side of casing 1, and may be glued or ultrasonically welded in place, to complete the relay.

We have previously employed side walls in which the three switch set terminals, but not a coil terminal, are embedded for other types of relay, as described in our co-pending Application No. 8128565 (Serial No. 2106716A) (A.L. Freeman-B.H Taylor-R.E.R. Smith 71-2). The same side walls as manufactured for that relay type can be employed in the single magnet/vertically pivoting armature relay described above, thus facilitating manufacture thereof.

The relays proposed by the present invention have high sensitivity, large contact clearances and are highly efficient. The high efficiency is achieved by placing the moving armature within the coil and using the permanent magnet to enhance the contact force. Typically for such a miniature TTL compatible polarised DIL relay the contact force is greater than 3 grams (for four changeover contact (switch) sets), the contact clearance is 0.75mm, the operate time is less than 10 msec and the release time (TTL connected) is less than 10 msec. Whereas the embodiments of relays described above employ four contact sets, two at each end of the armature, versions for the operation of a single contact set, or two contact sets can be similary constructed.

Claims (27)

1. An electrical relay comprising an electrically-insulating housing; a coil disposed in the housing; an armature extending through the coil and pivotable therein upon passage of a current through the coil; at least one contact set disposed in the housing and arranged to be operated by pivotable movement of the armature; a permanent magnet disposed in the housing and serving to enhance the contact force of the at least one contact set; and first and second yoke pieces disposed in the housing, the permanent magnet being dis posed in a coupling relation between the yoke pieces whereby to induce poles of opposite type therein, wherein a respective end portion of the armature extends from each end of the coil, wherein each pole piece has a respective pole face for each end portion of the armature, each end portion of the armature being disposed between pole faces provided by yoke pieces, wherein terminals associated with the contact set extend generally in one direction from the housing, wherein the coil is wound about an axis perpendicular to the one direction, and wherein the armature pivots about an axis perpendicular to both the one direction and the coil axis.

2. A relay as claimed in claim 1, wherein in a first pivotable position of the armature one end portion of the armature is in contact with the adjacent first pole piece and the other end portion of the armature is in contact with the adjacent second pole piece, and wherein in a second pivotable position of the armature the one end portion of the armature is in contact with the adjacent second pole piece and the other end portion of the armature is in contact with the adjacent first pole piece.

3. A relay as claimed in claim 2 and adapted for monostable operation, wherein the pole pieces in contact with the armature for one of said first and second pivotable positions, a rest position, are larger than the other pole pieces, and wherein the direction of current flow through the coil in use of the relay serves to induce poles in the armature end portions of the same type as the induced poles of the pole pieces contacted in the rest position.

4. A relay as claimed in claim 3 including remanence slugs mounted to the pole pieces which are not contacted in the rest position.

5. A relay as claimed in claim 2 and adapted for bistable operation, wherein the pole pieces in contact with the armature for either of said first and second pivotable positions are of equal contact area.

6. A relay as claimed in claim 5 and including a second coil coaxial with the firstmentioned coil and in which the armature is also pivotable, the armature being pivoted into onepivotable position by the passage of current through the first-mentioned coil and into the other pivotable position by passage of the current through the second coil.

7. A relay as claimed in any one of the preceding claims, wherein the armature operates the at least one contact set by insulating link means coupled between the armature and a movable contact of the at least one contact set.

8. A relay as claimed in claim 1, wherein the magnet is elongate, at least as long as the armature and extends parallel to the coil axis, the magnet having one longitudinal face which is N-pole seeking and an opposite longitudinal face which S-pole seeking, wherein the first and second yoke pieces are elongate and extend parallel to the coil axis, each being in contact with a respective longitudinal face of the magnet throughout its length.

9 A relay as claimed in claim 8, wherein at each end of both yoke pieces there is a bentover portion providing the respective pole piece.

1 0. A relay as claimed in claim 8 or claim 9, wherein the pole faces of the pole pieces at one armature end portion are disposed in parallel planes and wherein the one armature end portion is tapered whereby to enable contact to be made with the pole faces over the whole area of the adjacent surfaces upon pivoting of the armature in either direction.

11. A relay as claimed in claim 8 or claim 9, wherein the opposing faces of one armature end portion which are to contact respective pole faces upon pivoting of the armature are in parallel planes, and wherein the pole faces are disposed in planes at respective angles to said parallel planes whereby to enable contact to be made over the whole area of the adjacent surfaces upon pivoting of the armature in either direction.

1 2. A relay as claimed in any preceding claim, including four contact sets, two arranged at each end of the armature.

1 3. A relay as claimed in any one of the preceding claims wherein the armature is pivotable about a fixed pivot arranged substantially centrally of the first mentioned coil.

14. A relay as claimed in any one of the preceding claims wherein the magnet is elongate and is disposed in the housing with its longitudinal axis parallel to the coil axis and generally to one side of the coil and wherein a movable contact of the at least one contact set extends generally parallel to the coil axis and in a plane on the side of the coil opposite the one side.

15. A relay as claimed in any one of the preceding claims and including for each contact set a side wall member of electrically insulating material having embedded therein a conductor frame providing the terminations and supporting the fixed and moving relay contacts of the contact set, the coil being wound on a bobbin and connected to a pair of external connection terminals mounted thereon which project through the housing in the first direction, the side wall members being disposed in the housing between the coil and outer walls of the housing.

1 6. An electrical relay comprising in an electrically-insulating housing: a coil; an armature extending through the coil and pivotable therein upon passage of a current through the coil; at least two contact sets disposed on one side of the coil, each being associated with a respective end of the armature and arranged to be operated by pivotable movement of the armature; first and second planar yoke pieces disposed on second and third sides respec tively of the coil and a permanent magnet disposed on the fourth side of the coil to induce poles of opposite types in the yoke pieces, wherein a respective end portion of the armature extends from each end of the coil between bent-over portions of the yoke pieces providing pole faces for each end portion of the armature.

1 7. An electrical relay comprising an electrically-insulating housing; a coil disposed in the housing; an armature extending through the coil and pivotable therein upon passage of a current through the coil; at least two contact sets disposed in the housing, each being associated with a respective end of the armature and arranged to be operated by pivotable movement of the armature; a permanent magnet disposed in the housing and serving to enhance the contact force of the contact sets; and first and second yoke pieces disposed in the housing, the permanent magnet being disposed in a coupling relation between the yoke pieces whereby to induce poles of opposite type therein, wherein a respective end portion of the armature extends from each end of the coil, wherein at each end of both yoke pieces there is a bent-over portion providing a respective pole face for each end portion of the armature, each end portion of the armature being disposed between pole faces provided by both pole pieces, wherein terminals associated with the contact sets extend generally in one direction from the housing, wherein the coil is wound about an axis perpendicular to the one direction, and wherein the armature pivots about an axis perpendicular to both the one direction and the coil axis.

18. An electrical relay comprising an electrically-insulating housing; a coil disposed in the housing; an armature extending through the coil and pivotable therein upon passage of a current through the coil; four contact sets disposed in the housing, two contact sets being associated with each end of the armature, the contact sets being isolated from one another and arranged to be operated by pivotable movement of the armature, the contacts of the four contact sets all being disposed on one side of the coil; yoke means; and a permanent magnet disposed in the housing and serving to enhance the contact force of the contact sets, the permanent magnet being disposed in a coupling relation with the yoke means, which provides two pole faces for each end of the armature, such as to induce poles of opposite type in the two pole faces at each end of the armature.

1 9. An electrical relay comprising an electrically-insulating housing, a coil disposed in the housing; an armature extending through the coil and pivotable therein upon passage of a current through the coil; at least two contact sets disposed in the housing, each being associated with a respective end of the armature and arranged to be operated by pivotable movement of the armature, the contacts of the contact sets all being disposed on one side of the coil, yoke piece means; a permanent magnet disposed in the housing in a coupling relation with the yoke piece means, which provides two pole faces for each end of the armature, such as to induce poles of opposite type in the two pole faces at each end of the armature; and insulating links disposed between the pole faces and the ends of the coil for operating the contact sets.

20. A method of making an electrical relay comprising providing a housing with holes in a face thereof corresponding to the intended positions of external connection terminals; providing a coil wound about a first axis on a bobbin and connected to a pair of external connection terminals mounted thereon; arranging an armature in the coil such that it is pivotable therein about a second axis perpendicular to the first axis upon passage of a current through the coil, providing at least one side wall of electrically insulating material, each side wall having embedded therein a conductor frame providing external connection terminals and supporting fixed and moving contacts of a contact set; arranging a magnet in the housing whereby to serve for enhancement of the contact force of the contact set; inserting the coil wound on the bobbin and with the armature therein into the housing so that the pair of connection terminals locate in a pair of said holes, inserting the at least one side wall in a respective gap between the coil and an outer wall of the housing so that the external connection terminals of the conductor frame locate in respective holes in the housing and extend generally in one direction from the face of the housing which is perpendicular to both the first and second axis.

21. A method as claimed in claim 20, wherein the magnet is disposed in a coupling relation with first and second yoke pieces such as to induce poles of opposite type therein, and wherein the magnet, yoke pieces, coil wound on the bobbin and the armature are assembled together and inserted into the housing as a unit, in which unit respective end portions of the armature extend from each end of the coil and between respective pole faces of the first and second pole pieces in which are induced poles of opposite type.

22. A method as claimed in claim 20 or claim 21 wherein the at least one side wall is permanently fixed in the housing.

23. A method as claimed in any one of claims 20 to 22, wherein ultrasonic energy is applied during insertion of the at least one side wall to ease insertion.

24. A method as claimed in any one of claims 20 to 23 including the step of adjusting the moving contact of the respective contact set after insertion of the at least one side wall.

25. A method of making an electrical relay substantially as herein described with reference to the accompanying drawings.

26. An electrical relay made by a method as claimed in any one of claims 20 to 25.

27. An electrical relay substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.