GB2166596A - Miniature relay - Google Patents

Abstract

An electromagnetic relay has an energising winding (1) and a surrounding magnetic yoke (2) providing opposed pole faces (3,4), and has two pivotally mounted, armature (5a,5b) extending through the winding. The armatures (5a,5b) have like poles induced in their three ends and this causes a repulsive force driving them apart, and this force assists in moving the moveable contacts (11,12). <IMAGE>

Description

SPECIFICATION Miniature relay This invention relates to minature relays.

Aconventional electro-magnetic relay has a yoke, a winding, and a moveable armature which, when the winding is energised, is attracted towards a pole face on the yoke and this movement is used to actuate one or more moveable contacts to change the contact conditions.

It is an object ofthe present invention to increase the force available at least over part ofthe operation of the relay.

According to the present invention there is provided an electro-magnetic relay comprising an energising winding, an armature extending through thewinding, a yoke providing a pole face cooperating with one end ofthe armature and completing a magnetic circuit around the winding between opposite ends of the armature, and a moveable contact moveable bythe armature on energisation to change a contact condition, characterised in that the armature is in longitudinally split parts and at least some of the force for moving the moveable contact is derived from magnetic repulsion between the parts on energisation ofthe winding.

In orderthatthe invention can be clearly understood reference will now be made to the accompanying drawings. In the drawings:- Fig. lisa graph of force versus distance for the electro-magnetic relay of Fig.2; Fig. 2 shows diagrammatically a relay illustrating the principles ofthe present invention; Fig. 3 shows a general arrangement partly in section of one embodiment of the relay of Fig. 2; Fig.4showsthe bobbinforthe relayof Fig.3; Fig. 5showstheyoke/pole pieceforthe relay of Fig.

3,and Fig 6 shows a detail ofthe relay of Fig. 3.

Referring to Fig. 2 ofthe drawings the relay comprises a winding 1 having a yoke 2 providing opposed pole faces 3 and 4 at one end ofthe relay.

Within the coil lisa split armature comprising armature parts 5a and 5b. These parts are pivotally mounted at 6.

Upon energisation ofthe coil 1 north poles will be induced in the free ends ofthe armature parts 5a and 5b and, through the yoke 2, south poles will be induced on the pole faces 3 and 4. These poles that are induced are indicated by the reference letters n and s.

Therefore the armature parts 5a and 5b repel one another attheirfree ends and the parts are at the same time attracted by the south poles ofthe poles pieces 3 and4.

Referring nowto Fig. 1 ofthe drawings, the graph shows the attractive force applied to the armature and how it changes with the armature position as the armature moves from its rest position to a position adjacentthe pole face of the yoke. With the normallyclosed contacts NC ofthe change over contact set closed and the armature at rest the attractive force increases as shown bythe curve A as the armature moves and closes the normally open contacts NC. The lever spring force is shown by curve L. This force increases substantially linea rlyfrom the point where the normal "undertravel" has been taken up to the point where the normally closed contacts just open.

This occurs at point NC. The curve Lthen changes slope to a more gentle linear slope until the normally open contacts just changes to a closed condition at NO.

The curve Lthen proceeds up a steeper slope as the normally-open contacts ofthe relay having been closed are then pushed further into contactto achieve the required contact pressure at point C. The slope of this part ofthe curve is similarto but not exactlythe same asthefirst partto point NC.

As can be seen at some points along the curve Athe attractive force due to the magnetism ofthe electromagnet has to be greaterthan the spring force of any ofthe contact springs required to be moved.

Howevertheforce of repulsion initially between the two a rm atu re parts 5a and 5b, which initially are lying together, is shown on the graph of Fig. 1 by curve R which combines with curve Ato give the combined curve R+A,which at any point, is greaterthan the spring force.

Referring now to Fig. 3 there is shown a plan view of one embodiment of a relay incorporating the principle of Fig 2. Parts having the same function are given the same reference numerals in Figs. 2 to 6. In Fig. 3 armature parts 5a and 5b are pivotally mounted at one 6 within an aperture7 in yoke part2.A plastics moulded bobbin 8 carries the energising winding (not shown) and a soft iron bentyoke 2 provides the poles faces 3 and 4. The yoke is shown in greater detail in Fig. 5.

Respective combs 9 and 10 actuate respective moveable contact springs 11 and 12 from a normally closed contact 13 and 14to a normally open contact 15 and 16. Contactsprings 11 and 12carrycontacts 11a and 12a.

The arrangement is seated in a base member 13 and covered by a lid 14. Movement ofthe armatures is in a plane at right angles to the terminals carrying the contacts which extend through the base 1 3to form a DlLfootprintforexternal connection.

Referring to Fig. 4there is shown in section the bobbin 8 shown in Fig. 3, and comprising a rectangu lartubular portion on which thewinding iswound and end cheeks 8a and 8b. Cheek 8b has the recess 8c in which is received the back portion of the yoke member 2.

Referring tq Fig. 5 there is shown the soft iron yoke ofthe relay. It is stamped out of a soft iron sheet and the polefaces3 and 4are bentup into a U configuration. Also bent up is the back portion 2A having the aperture 7 in which the ends ofthe armature parts 5a and 5b will be seated. Across the back ofthe back portion 2A is a small bar2B which acts as a backstop to prevent the armature parts 5a and 5b falling backthrough the pivot hole 7.

Although the pole faces 3 and 4 are shown parallel in The drawing(s) originally filed was (were) informal and the print here reproduced is taken from a later filed formal copy.

the particular embodiment described, and particularly in Figs. 3 and 5, nevertheless it would be possible for the polefacesto be non-parallel and have a diverging pair ofsurfaces, that is diverging in a direction projecting away from the relay. In the embodiment described the free end of the armature parts 5a and 5b are slightlytapered so that the mating surfaces between the pole faces 3 and 4 and the ends of the armature parts, are parallel in the energised condition.

this can be achieved by slightlyflattening the ends of the armature parts to produced the desired taper.

In orderto ensurethatthe armature parts move away from each other upon energisation ofthe relay, in a symmetrical manner, a comb link arrangement is provided and is shown in detail in Fig. 6. This part can be integrally moulded of plastics material and provides the combs 9 and 10 which transfer movement from the armature to the moving contact springs 11 and 12, sliding plungers 20 and 21 and V-shaped link arms linking the plungers 20 and 21 to the combs 9 and 10. these link arms are designated 20A and 20B for plunger 20 and 21A and 21 B for plunger 21. Shown in broken line are the armature parts 5a and 5b. The lateral double headed arrows indicate the direction of movement ofthe ends ofarmature parts 5a and 5b and ofthe combs 9 and 10.The combs are fixed to the armature parts and they are constrained to slide in a fixed common plane which is at right angles to the direction of movement of the plungers 20 and 21. Thus the integral plunger and comb arrangement ensures thatthe armature parts 5a and 5b move symmetrical away from one another on energisation ofthe relay.

This symmetrical movement is governed by the constraint ofthe plungers and the links.

Provision forthe integral comb and plunger and link arrangement shown in Fig. 6 is not shown in detail in Fig. 3 butthe slide ways forthe plungers 20 and 21 could for example be grooves moulded in the end cheek8a ofthe bobbin.

The improved sensitivity achieved in this relay enables low power (no morethan 200mW) in a miniature relay with a DIL "footprint" measuring 20mm by 10mm by8mm high,to achieve a contact force in the range 4-5 grams.

Claims (6)

1. An electro-magnet relay comprises an energising winding, an armature extending through the winding, a yoke providing a poleface cooperating with one end ofthe armature and completing a magnetic circuit around the winding between opposite ends ofthe armature, and a moveable contact moveable bythe armature on energisation to change a contact condition, characterised in that the armature is in longitudinally split parts and at least some ofthe force for moving the moveable contact is derived from magnetic repulsion between the parts on energisation ofthewinding.

2. A relay as claimed in claim 1, characterised in thatthe armature has two longitudinally split parts which are pivotally mounted at one end and linked for symmetric movement towards and away from a central axis ofthe armature.

3. A relay as claimed in claim 1 or claim 2, characterised in that each armature part is associated with a change over contact set on respective opposite sides of the relay.

4. An electro-magnetic relay as claimed in claim 1, claim 2, or claim 3, characterised in thattheyoke comprises a flat metal part which has been bent up at one end to form a pair of opposed pole faces lying in planes generally parallel to the axis of the relay, and has been bent up atthe opposite end in a plane transversetothefirst mentioned planes for providing a magneticflux path between the yoke and the opposite ends ofthe armature parts.

5. A relay as claimed in claim 4, characterised in thatthe armature parts are pivotally mounted in an aperture in the bent up end ofthe yoke.

6. A relay substantially as herein described with referenceto and as illustrated intheaccompanying drawings.