GB2186428A - Clam-shell electromagnetic relay - Google Patents

Abstract

An electro-magnetic relay of flat configuration comprises a pair of pressed magnetic steel yoke members (3, 6), pivoted like a clam shell, and a spring member 10 welded to one of the yoke members (6). The pressed yoke members define a recess locating an energising coil (1) and the spring member (10) biasses the yoke members apart. Either a make operation or a break operation can be adopted. Either a current sensing relay or voltage operable relay can be made. A particularly cheap and rugged configuration, particularly suitable for automobile lamp failure circuits, is provided. <IMAGE>

Description

SPECIFICATION Clam-shell electromagnetic relay This invention relates to an electro-magnetic relay, particularly one of simple inexpensive construction which is nevertheless rugged and suitable for, for example, use in automobiles.

In an automobile it is necessary to indicate to the driver if a lamp hasfailed and one method of achieving this isto provide a current sensing relay in the lamp supply circuitwhich, if the lampfails, causes the relay to become de-energised thus changing the contact condition ofthe relay, in this particularex- ample a break only contact set to which a lamp failurewarning lamp would be connected and which would thus become energised when the contacts make when the relay has become de-energised on failure of the lamp circuit.

One object of the present invention is to provide a relay construction which is suitable, although not exclusivelyso,forsuch an application.

According to the present invention there is provided an electro-magnetic relay comprising an energising coil having a diameterwhich is large in comparison with its axial thickness, a pair of plate-like magnetic yoke members having co-operating pole faces and extending over respective opposite sides of the coil, the yoke members being operable like a clam shell by energisation of the coil to change the contact condition.

According to anotheraspectofthe presentinvention there is provided a method of making an electromagnetic relay comprising providing an energising coil having a diameter which is large in comparison with its axial thickness, providing a pair of plate-like magnetic yoke members having co-operating pole faces, locating the energising coil so that the yoke members extend over respective opposite sides of the coil, whereby the yoke members will be operable like a clam shell by energisation of the coil to change the contact condition.

Conveniently at least one of the plate-like mem berscomprisesa pressed magnetic steel plate shaped to have a raised centre and a raised rim,the raised centre and rim forming the pole faces ofthe member. Although it is possible for the yoke members themselves to provide the contacts of the relay, it is preferable to provide at least one flatconducting spring which is secured to one of the plate-like members, e.g. by spot welding, and which carries one of the contacts. Preferably also the spring provides the means of biassing apart the plate-like members.

Conveniently the spring ata position remotefrom the contact, is held in an insulating block which also houses terminations for the energising coil.

In orderthatthe invention can be clearly understood reference will now be made to the accompanying drawings in which Figures 1A and IB show respectively a diametral cross-section and a plan view of a current flow sensor relay according to an embodiment of the present invention; Figures2A and 2B show respectively a diametral cross-section and a plan view of a currentflow sensor relay according to a second embodiment of the present invention; Figures 3A and 3B show respectively a diametral cross-section and a plan view of a voltage relay for switching relatively high currents, according to a further embodiment ofthe present invention and, Figures 4shows diagrammatically the stages in manufacturing and assembling a relay similar to that shown in Figures 3A and 3B.

Referring to Figure 1 ofthe drawings the relay comprises a pancake-shaped winding 1 which is spirallywound and located within an annular recess 2 of a coined magnetic steel yoke member 3. The yoke member 3 has a raised central portion 4 and a raised rim 5 forming pole faces.

A co-operating yoke member 6 also made of magnetic steel is flat and thus provides a flat pole face co-operating with the pole faces 4 and 5 of the yoke member 3.

Both yoke members 3 and 6 are located for re lativelypivotal movement in an insulating block 7 made of plastics material and having respective recesses 8 and 9 to receive the respective yoke members 3 and 6. The yoke members operate somewhat afterthe style of clam shells and reference herein to that style is intended to give a general indication only of the style of structure ofthe relay. The yoke member3 is fixed relative to the block7 and the yoke member 6 is pivotable within its recess 8, and a con ductivespring 10 madeforexample of phosphor bronze, isspotwelded at 11 to the yoke member 6.

The spring 10 extendsthrough the block7 and its remote end 1 OA provides a connection terminal.

Yoke member 6 has a contact 6A at the side remote from the terminal 1 OA and this contact 6A makes contactwhen the relay is energised with the cooperating pole face 5 of the yoke member 3. Prefer ably the pole faces 5 is plated to provide a good con- tact making surface.

The spring 10 normally biassestheyoke members 3 and 6 apart about their pivoting axes which is located adjacent the periphery of the coil 1 and lies sub stantially parallel to a diameterofthe coii 1.

As shown in Figure 1 B the pivot axis extends in substantially a north and south direction as viewed in the drawing.

The yoke member3 has an extension 3Aforming a second connection terminal for the contact making surface of the pole face 5.

Athird connection terminal 1Aisformed byone end ofthewinding extending outofthe recess 2and through the block 7. Thus the connection terminal 1 OA is common for the coil and for the make-only switch contact.

The relay describes acts as a currentflow sensing relay and has a low coil resistance (approximately 50mfl and has a single make contact set. The coil is formed bywinding aspiralwinding ofthewireand placing the wire into the recess 2 between the yoke members.

In use in a motorvehiclethe coil is connected in the power line to a lamp filament. When the lamp circuit is energised currentflows through the winding 1 which operates the relay and closes the signal contact set. Should the lamp fail the current is interrup ted and the switch contact is opened. This switch contact is used to control a voltage to either a "lamp on" indicator on the dashboard or the controlling cir cuitry which in turn reacts to the lamp failure.

The switch contact set indicating by the reference numeral 6A and the plated surface of the rim 5, can be formed anywhere around the circumference provided it is reasonably remote from the pivot axis so that a sufficientopening between the contacts can be obtained.

In an alternative construction a break-only contact set can be provided. This is illustrated in Figures 2A and 2B in which similar reference numerals indicate the same of similar parts to those described with re reference to Figures 1A and 1 B.

Referring to Figures 2A and 2B the only modifications overthe embodiment of Figure 1, lie in the contacts. In this embodiment the conductive spring 10 has been elongated and providessupportforthe contact 6Awhich is now located on the outside ofthe yoke member 6. In addition instead of a plated surface of pole face 5 being used as a second contact of the contact set, the second contact is now provided by a second spring member 3B which is secured by welding at SAto the underside of the rim 5.

The other modification is an insulating sheet 12 which covers the recess 2 and the pole face 5 and 4.

This insulating sheet 12 prevents electrical contact between the two yoke members.

Thus when the winding 1 is energised the contact set (contacts lOB and 3B) breakwhich can be used to triggerthe controlling circuitry which reacts to a lamp failure indicated by the trigger.

In all other respects the embodiments of Figures 1 and 2 are the same.

Referring now to Figures 3A and 3B the relay there shown comprises a pair of magnetic steel yoke members 21 and 22, both having been pressed to provide a raised central portion 21 A and 22A respectively and raised rims 21 B and 22B respectively. These raised portions form pole faces which co-operate with each other.

Each yoke member is secured to a respective conductive spring member 23 and 24 which as shown in Figure 3B, is of a "Y" configuration.

Within the annular recess 25 formed between the pressed steel yoke members, is located an energising winding 26 wound on an annular plastics bobbin 27.

As with the previous embodiments the coil diameter is large in comparison with its axial depth orthickness.

The springs 23 and 24 are secured in an insulating block28alongwiththe lead outwires 29 and 30 of the energising winding 26.

At the opposite end the springs 23 and 24 support a pair ofcontacts 23B, 24B and the springs are welded to the associated yoke member, as indicated at weldpointsW1 andW2.

As in the previous embodiments the spring member (in this case there are two members 23 and 24) bias the yoke members apart about pivoting axes located in a generally north south direction as viewed in Figure 3B and adjacent the outer periphery of the energising winding 26. The axes are indicated generally by the reference symbols Al and A2.

The relay has normally-open contacts 23B, 24B and when the winding is energised the yoke members are drawn together by the magnetic flux across the gap between the centre portions 21A and 22A and the rim portions 21 B and 22B.

In the embodiment described the winding had l2S0turnsof0.O88inch diameterwire giving a wind- ing of 1660hms. At 12 volts the current was 72mA.

The iron yoke members were made of 0.7mm thick sheet material and the plastic block 28 is made in two identical parts which are designed to snap together to locate the springs and lead outs in between them.

The whole assembly would be housed in a plastics box (not shown) whose side walls also are effective to limit the outward movement of the yoke members caused by the biassing effect of the springs 23 and 24. This relay can switch to 30 amps at 12 volts.

Referring now to Figure 4 there is described one method and manufacturing procedure for making a relay similar to the one shown in Figure 3 exceptthat the springs 23 and 24are rectangular in shape rather than "Y" shaped.

Referring to Figure 4Athere is shown a brass strip lead frame 30 which has been punched to produce L-shaped connection terminals 31. A second lead frame 32 of thin phosphor bronze material has been punched to provide rectangular contact springs 33.

Contacts of e.g. cadium-copper 34 and 35 are welded to the rectangular contact springs 33 and the two lead frames are passed under a welding station wherethecontactspring 33 is welded to the Lshaped connection terminals 31 and at the next station the contact spring is guillotined from the strip 32.

At the next station halfthe plastics insulating block 36 is moulded overthe contact spring and in the moulding operation is incorporated a coil connection pin 37.

The yoke members are made from iron strip 38 which is passed through a coining station which coins the annular recess 39 with a passageway 40.

At a subsequent station the yoke is punched from the strip but still held by a neck portion 41.

The yoke is then offered up to the contact spring with the half housing 36 and welded to it. The yoke is subsequently guillotined from the iron strip 38.

This sub-assemblythen is amalgamated with the identical sub-assembly by clipping the two housing halves 36 together and between the open jaws ofthe clam-like yoke members, the wound bobbin 42 is inserted.

The lead outwires 43 and 44 of the wound bobbin 42 are soldered to the pins such as 37 and the spring members such as 33 are then set.

A moulded plastic cover 44 is slid overthe assembly and is sealed with resin in known manner.

Finallythe arms 31 are guilotined from the strips 30 to provide the finished relay.

Claims (11)

1. An electro-magnetic relay comprising an energising coil having a diameter which is large in comparison with its axial thickness, a pair of plate-like magnetic yoke members having co-operating pole faces and extending over respective opposite sides of the coil, the yoke members being operable iike a clam shell by energisation ofthe coil to changethe contact condition.

2. A relay as claimed in claim 1 ,wherein at least one of the plate-like yoke members comprises a pressed magnetic steel plate having a raised centre and a raised rim forming the pole faces ofthe member.

3. A relay as claimed in any preceding claim wherein at least one of the plate-like members is spot welded two a conducting spring on which a contact is mounted.

4. A relay as claimed in claim 3 wherein the end of the spring remote from the contact is secured in an insulating blockwhich also houses terminations of the energising coil.

5. A relay as claimed in claim 3 or claim 4, wherein the spring also provides a biassing force tending to bias the yoke members apart.

6. A relay substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

7. A method of making an electro-magnetic relay comprising providing an energising coil having a diameter which is large in comparison with its axial thickness, providing a pair of plate-like magnetic yoke members having co-operating pole faces, locating the energising coil so that the yoke members extend over respective opposite sides ofthe coil, whereby the yoke members will be operable like a clam shell by energisation of the coil to changethe contact condition.

8. Amethodasclaimed inclaim7,whereinthe yoke members are secured to respective contact springs which support contacts of the relay and provide a biassing force tending to bias the yoke members apart.

9. A method as claimed in claim 8, wherein each spring member has an insulating block moulded on it, said blocks being adapted to snap together to hold the yoke members and springs in the desired mutual relationship.

10. Amethod as claimed in claim 9, wherein the energising winding is wound on a bobbin which is pushed into a recess defined between the yoke members.

11. A method of making a relay substantially as hereinbefore described with reference to and as illustrated in Figure4 of the accompanying drawings.