GB1566933A

GB1566933A - Electro-magnetic relay

Info

Publication number: GB1566933A
Application number: GB1854377A
Authority: GB
Original assignee: FEME
Current assignee: FEME
Priority date: 1977-02-02
Filing date: 1977-05-03
Publication date: 1980-05-08
Also published as: DE2719870A1; FR2379904A1; IT1075619B; FR2379904B1; DE2719870C2

Description

(54) AN ELECTRO-MAGNETIC RELAY (71) We, FEME FABRICA EQUIPAGGIAMENTI MECCANICO ELETTRICI S.p.A. of 1 Via le Certosa, Milan, Italy; a firm duly organized under Italian law do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention concerns electromagnetic relays in general and in particular relays of the flat type, occupying very little space in depth, intended in particular for use on parallel printed circuit boards mounted opposite to each other with a small space between them.

Electro-magnetic relays in general, as is well known, may have spring contact plates secured at one end to an insulating body, and are secured by screwing or by clamping as an insert in the insulating body itself or by force fitting using convex or raised zones or tabs, formed on the plates themselves, into slots or grooves of the insulating body, which are then sometimes filled with cast resin.

Whilst securing the plates by screwing has no operational disadvantages, it occupies a certain minimum space, and the other two methods of securing may cause permanent deformations of the plates and hence may require an adjustment of the spring plates themselves to take into account the characteristic parameters necessary for reliable and durable operation, such as the spaces between the contacts and the contact pressures.

For reasons of cost it is advisable for the method of securing the spring plates to be simple and rapid, without requiring adjusting work.

Another important feature required is to obtain sensitive, regular operation over a long period, so that the displaceable parts of the relay should be subjected to minimum and a constant degree of wear over a given period.

According to the present invention there is provided an electromagnetic relay comprising an insulating support means, contact springs mounted in respective slots provided in said insulating support means, on the opposed walls of each of which slots, alternate projections are provided, disposed transversely to the longitudinal axis of the contact spring with their summits engageable with the contact spring, so as to produce an elastic deformation of the portion of the contact spring inserted in the slot thereby securing the contact spring to the insulating support, the remaining length of the contact spring being free to elastically oscillate.

The connection of the springs with the insulating support is ensured by the particular shape of the support itself which permits rapid assembling of the contact springs on the relay and effects the reliable securing thereof without requiring any other means, such as screws or moulded or cast resin.

Among other things, this makes it possible to exactly define the free length of the springs themselves, thus facilitating obtaining the ratio of the distances and the contact pressures suitable for good operation.

These features permit production with maximum constancy of quality whilst reducing to the minimum the individual preparation of the apparatus.

Each spring plate is inserted in a respective slot and, due to engagement by the projections, preferably three, is subjected to an elastic deformation which thus generates the desired pressure which holds it in its inserted position, whilst allowing elastic oscillation of the remaining free length which is precisely defined in this manner.

The said three alternate projections formed on the opposing walls of each slot have a proportionate depth so as to dispose each displaceable contact spring at an incline relative to the longitudinal axis of the slot, thus elastically initially tensioning it against an opposing fixed contact plate in order to ensure the necessary and desired contact pressure without requiring any previous adjustment or bending of the contact spring itself.

A further advantage of the present invention resides in the feature that the dimensions of the slots, due to the presence of the alternate projections, have no adverse effects on the connection of the contact springs and consequently may be provided in values suitable for moulding in thermosetting plastics material, which is the type normally employed for the insulating supports of relays.

The present invention will be described further with reference to an electromagnetic relay of flat type having four double changeover contact sets, given by way of example only, illustrated in the accompanying drawings, in which: Figure 1 is a front view of the relay, with its cover removed; Figure 2 shows a section of the relay including its cover taken on the line II - II of Figure 1; Figure 3 shows the front view of a displaceable contact spring assembled on the relay, but not initially tensioned, and not showing the inserted and opposing fixed contact plate; and Figure 4 shows a detail - on an enlarged scale and in section - illustrating a variant for the connection of the displaceable contact spring.

The relay, illustrated on an enlarged scale in the drawings, has a magnetic circuit formed by a support yoke member 1 of soft iron bent L-shaped and encased in a casing 2 of thermo-setting material, a core 3 of soft iron, riveted onto the member 1 and a movable planar armature 4 of soft iron for closing the magnetic circuit which armature 4 can rotate about a fulcrum 5, formed by a knife edge of the support 1. The armature 4 is held in engagement with the fulcrum 5 by means of a small wire spring 6, located in the casing 2. The spring 6 due to the round shape of the wire, produces a minimum and constant degree of wear on a limited area of engagement on the armature over a given time, thus obtaining sensitive, regular operation over a long period. Mounted on the core 3 is a coil former 7 of thermo-plastics material which carries a winding 8 of thin wire, the ends of which are electrically connected to two terminals 9 and 10 for connection to an external circuit.

The casing 2 also serves as an insulating support for fixed and displaceable contacts of the relay, complete with terminals for connection to the external circuit. Eight fixed contact plates are provided, four of which 11, 12, 13 and 14 have the same shape, and four of which 15, 16, 17 and 18 each also having the same shape but having a different shape from the first four, which are mounted in slots in the casing 2. One side of the plates abuts the bottom of the casing 2 itself and the other side abuts against the inside of a cover 19 of thermoplastics material which is mounted on the casing 2, the function of which is to afford protecton against dust.

Four displaceable contact springs 20, 21, 22 and 23, each having the same shape, are mounted in four identical slots 24, 25, 26 and 27 of the casing 2, which have a special shape, characterised by the presence of three alternate projections 28, 29 and 30 formed on the opposing walls of each slot and disposed therein transversely to the longitudinal axis of each spring and with their summits coming into contact with the springs. Each displaceable contact spring 20, 21, 22 and 23 mounted in said slots in engagement with said projections, is subjected to elastic deformation, and hence produces the desired pressure which secures it in its respective slot whilst maintaining unimpaired the possibility of elastic oscillation of the remaining free length. Thus, fixture of the displaceable springs is assured even in the absence, on the springs themselves, of convex portions and tabs which may cause initial permanent deformation, and without also requiring other cooperating securing means, such as screws or resin, moulded or cast. The three alternate projections 28, 29 and 30, formed in each slot 24, 25, 26 and 27, have a relative height sufficient for receiving each displaceable contact springs 20, 21, 22 and 23 at an incline relative to the longitudinal axis of the slot itself, thus elastically initially tensioning it against the respective opposing fixed contact plates 15, 16, 17 and 18 in order to ensure the necessary and desired contact pressure without having to make any adjustment or initial bending of the plate itself.

Figure 3 shows one of the four displaceable contact springs 20, 21, 22 and 23, namely the plate 20, forced into engagement with the three alternate projections or prominences 28, 29, and 30, but not initially tensioned, the opposing fixed contact plate 15 not being shown. Figure 4 shows a variant in which the corner 24' takes the place of the projection or prominence 30.

Movement is transmitted from the armature 4 to the displaceable contact springs 20, 21, 22 and 23 by means of a thrust member 31 of insulating material, shown in section in Figure 1, guided by slots in the casing 2 and connected to the armature by means of a slot 32 therein.

WHAT WE CLAIM IS:

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. each displaceable contact spring at an incline relative to the longitudinal axis of the slot, thus elastically initially tensioning it against an opposing fixed contact plate in order to ensure the necessary and desired contact pressure without requiring any previous adjustment or bending of the contact spring itself. A further advantage of the present invention resides in the feature that the dimensions of the slots, due to the presence of the alternate projections, have no adverse effects on the connection of the contact springs and consequently may be provided in values suitable for moulding in thermosetting plastics material, which is the type normally employed for the insulating supports of relays. The present invention will be described further with reference to an electromagnetic relay of flat type having four double changeover contact sets, given by way of example only, illustrated in the accompanying drawings, in which: Figure 1 is a front view of the relay, with its cover removed; Figure 2 shows a section of the relay including its cover taken on the line II - II of Figure 1; Figure 3 shows the front view of a displaceable contact spring assembled on the relay, but not initially tensioned, and not showing the inserted and opposing fixed contact plate; and Figure 4 shows a detail - on an enlarged scale and in section - illustrating a variant for the connection of the displaceable contact spring. The relay, illustrated on an enlarged scale in the drawings, has a magnetic circuit formed by a support yoke member 1 of soft iron bent L-shaped and encased in a casing 2 of thermo-setting material, a core 3 of soft iron, riveted onto the member 1 and a movable planar armature 4 of soft iron for closing the magnetic circuit which armature 4 can rotate about a fulcrum 5, formed by a knife edge of the support 1. The armature 4 is held in engagement with the fulcrum 5 by means of a small wire spring 6, located in the casing 2. The spring 6 due to the round shape of the wire, produces a minimum and constant degree of wear on a limited area of engagement on the armature over a given time, thus obtaining sensitive, regular operation over a long period. Mounted on the core 3 is a coil former 7 of thermo-plastics material which carries a winding 8 of thin wire, the ends of which are electrically connected to two terminals 9 and 10 for connection to an external circuit. The casing 2 also serves as an insulating support for fixed and displaceable contacts of the relay, complete with terminals for connection to the external circuit. Eight fixed contact plates are provided, four of which 11, 12, 13 and 14 have the same shape, and four of which 15, 16, 17 and 18 each also having the same shape but having a different shape from the first four, which are mounted in slots in the casing 2. One side of the plates abuts the bottom of the casing 2 itself and the other side abuts against the inside of a cover 19 of thermoplastics material which is mounted on the casing 2, the function of which is to afford protecton against dust. Four displaceable contact springs 20, 21, 22 and 23, each having the same shape, are mounted in four identical slots 24, 25, 26 and 27 of the casing 2, which have a special shape, characterised by the presence of three alternate projections 28, 29 and 30 formed on the opposing walls of each slot and disposed therein transversely to the longitudinal axis of each spring and with their summits coming into contact with the springs. Each displaceable contact spring 20, 21, 22 and 23 mounted in said slots in engagement with said projections, is subjected to elastic deformation, and hence produces the desired pressure which secures it in its respective slot whilst maintaining unimpaired the possibility of elastic oscillation of the remaining free length. Thus, fixture of the displaceable springs is assured even in the absence, on the springs themselves, of convex portions and tabs which may cause initial permanent deformation, and without also requiring other cooperating securing means, such as screws or resin, moulded or cast. The three alternate projections 28, 29 and 30, formed in each slot 24, 25, 26 and 27, have a relative height sufficient for receiving each displaceable contact springs 20, 21, 22 and 23 at an incline relative to the longitudinal axis of the slot itself, thus elastically initially tensioning it against the respective opposing fixed contact plates 15, 16, 17 and 18 in order to ensure the necessary and desired contact pressure without having to make any adjustment or initial bending of the plate itself. Figure 3 shows one of the four displaceable contact springs 20, 21, 22 and 23, namely the plate 20, forced into engagement with the three alternate projections or prominences 28, 29, and 30, but not initially tensioned, the opposing fixed contact plate 15 not being shown. Figure 4 shows a variant in which the corner 24' takes the place of the projection or prominence 30. Movement is transmitted from the armature 4 to the displaceable contact springs 20, 21, 22 and 23 by means of a thrust member 31 of insulating material, shown in section in Figure 1, guided by slots in the casing 2 and connected to the armature by means of a slot 32 therein. WHAT WE CLAIM IS:

1. An electro-magnetic relay comprising an insulating support means, contact springs mounted in respective slots provided in said insulating support means, on the opposed walls of each of which slots, alternate projection are provided, disposed transversely to the longitudinal axis of the contact spring with their summits engageable with the contact spring, so as to produce an elastic deformation of the portion of the contact spring inserted in the slot thereby securing the contact spring to the insulating support, the remaining length of the contact spring being free to elastically oscillate.

2. An electro-magnetic relay as claimed in Claim 1, in which the number of projections is at least three.

3. A relay according to Claim 1 or 2, in which the alternate projections have a relative height so as to dispose the displaceable contact springs at an incline relative to the longitudinal axis of the slots, so as to initially tension them elastically against opposing fixed contact plates, so as to ensure a predetermined contact pressure.

4. A relay according to Claims 1, 2 or 3 in which the alternate projections are formed on raised portions of the insulating support.

5. A relay according to Claims 1 to 4, in which the alternate projections are provided on opposing walls of slots, open on three sides, formed on the insulating support.

6. A relay according to Claims 1 to 5, in which at least one of the alternate projections is replaced by a corner of the slot.

7. A relay according to Claim 5, in which the slots are formed betwen pairs of ribs formed on the insulating support.

8. An electro-magnetic relay substantially as herein described with reference to and as illustrated in Figures 1 to 3 and 4 of the accompanying drawings.