GB1583533A

GB1583533A - Electromagnetic relays

Info

Publication number: GB1583533A
Application number: GB1142/78A
Authority: GB
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 1977-01-13
Filing date: 1978-01-12
Publication date: 1981-01-28
Also published as: FR2377698A1; NL7800381A; FR2377698B1; IT1091959B; IT7819075A0; CH622382A5; SE7800360L; AT372216B; YU5278A; JPS5846817B2; JPS5388945A; ATA20878A

Abstract

The relay comprises a switching tongue (4) which interacts with other switching elements (5, 6) with its free end (4a). The elastic support (4b) of the switching tongue is attached to a ferromagnetic adjusting plate (8) which can be pivoted about a predetermined bending point (15) for its adjustment. This adjustment is carried out by a magnetic field (H) applied from the outside (17). During this adjustment, the adjustment plate (8) is deformed by individual magnetic pulses, the position or pretension of the switching tongue (4) being determined by measurements between the individual pulses. This method dispenses with adjusting screws or adjusting pliers which must be used for bending sheet metal parts. Such a relay can be adjusted automatically even if it is miniaturised, which saves much time. <IMAGE>

Description

(54) IMPROVEMENTS IN OR RELATING TO ELECTROMAGNETIC RELAYS (71) We, SIEMENS AKTIENGESELLSCHAFT. a German Company of Berlin and Munich. Federal Republic of Germany. 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 relates to electromagnetic relays and to methods of adjusting them.

With most electromagnetic relays provision is made for adjustment of a working gap in the magnetic circuit or a contact gap for the contact-making parts in the course of production so as to avoid an excessively wide spread of response values. In many cases. this adjustment is effected with the aid of adjusting screws or by bending sheet-metal components with the aid of adjusting tongs. this work requiring a great deal of care and manual skill and not being easy to automate.

With minaturised relays, the problem also arises that the parts to be adjusted are often very inaccessible with adjusting tools. With conventional relays having sealed contact systems later adjustment is effectively impossible. Even the relay described in German Patent Specification No. 1.243.271 designed to permit adjustment by means of screws in the casing wall through a spring adjusting arrangement does not provide a satisfactory solution to the problem since the spring adjusting arrangement is not only very costly but also ceases to be operable once the adjusting elements have been finally sealed off.

In connection with reed contacts it has also been suggested that after fusion in a glass enclosure a ferromagnetic switching tongue be subsequently deformed bevond its elastic bending limit by an externally applied magnetic field (US Patent Specification 3 242 557). However. very' strong magnetic fields are required to bend a spring tongue resting on the opposite contact, so that the desired adjustment cannot be obtained in a straightfoward manner. With this method.

the contact force cannot be set independently of the contact gap and this known method cannot provide any pre-loading against rigid opposing contacts.

An object of the invention is to provide an improved electromagnetic relay, and a method of adjusting it.

According to one aspect of the invention.

there is provided an electromagnetic relay comprising: an energising coil on a coil former; at least one switching contact; an elongate switching armature mounted for resilient movement bv energisation of said coil to produce switching by engagement of said armature with said contact; and a deformable elongate ferromagnetic member to which said armature is secured. a part of said member being secured to the former.

wherein between said secured part and the point of attachment of said armature. said ferromagnetic member is provided with a zone having relatively little resistance to deformation.

Preferably. said member extends generally parallel to said switching armature.

In one embodiment. said one end of said armature is secured to said member adjacent said secured part.

In a further embodiment. said one end of said armature is secured to the free end of said member.

Preferably, said deformation is bending deformation.

Preferably. said member is of a material having an elastic limit similar to that of soft iron.

Said switching armature may be constituted of spring material throtighout.

Said switching armature may form a substantially rigid armature and is connected to said ferromapnetic member via a leaf spring.

Said armature may form an armature con tact and is disposed within said coil former.

Expediently, said member is provided with two latcrally extending torsion mounts constituting respective zones of relatively little deformation resistance.

Expediently, said member is plate-like and said torsion mounts are in the main plane of said member and in its central region considered in the lengthwise direction.

Said torsion mounts may extend from said member to respective guide strips clamped in a further member of said relay on respective sides of said ferromagnetic member.

Said guide strips may form portions of a one-picce carrier.

Expediently, said ferromagnetic member, said torsion mounts and said carrier are formed from a common strip of sheet metal.

Said guide strips may be provided with respective shoulders at the secured part of said ferromagnetic member.

Preferably, the free ends of said guide strips are tapered to facilitate insertion in the relay.

Preferably, said carrier has an angled end provided with a connection extension.

Prefcrably, that part of said ferromagnetic member carrying said switching armature lics in a plane parallel to that of the remainder of said fcrromagnetic member and spaced therefrom in the direction of said armature.

Expediently. a free end of said ferromagnetic member is of spatulate form.

Expediently. said ferromagnetic member is provided with a longitudinally extending corrugation.

According to a further aspect of the invention there is provided a method for adjusting the relay of said one aspect. in which method the relay is disposed in a magnetic field whose lines of force make an angle greater than 0 and less than 90" with the longitudinal axis of said fcrromagnetic member, the krromagnetic member is deformed by a magnetic field impulse. and the position or bias of said switching armature is determined by electrical measurement.

Preferably. a plurality of said impulses are employed. and said measurement is made between two successive impulses.

Preferably. said angle is in the range of from 75" to 900. but less than 90".

For a better understanding of the invention, and to show how the same may be carried into effcct. preference will now be made.

by way of example. to the accompanying drawings. in which Figures I and 2 show a magnetically adjustable relay in a schematic view; Figures 3 and 4 show a magnetically adjustable resilient switching armature; Figures 5 and 6 shows a magnetically adjustable rigid armature; Figure 7 shows a magnetically adjustable contact spring; Figures 8, 9 and 10 show an adjusting plate with a switching armature in three views; Figures 11 and 12 show a miniature electromagnetic relay with the adjusting ferromagnetic member shown in Figures 8 to 10; and Figure 13 shows an adjusting process diagrammatically.

Figures 1 and 2 show an armature contact relay having a coil former 1 which carries a magnet system and a coil 2 and encloses a switching chamber 3. An armature contact is constituted by a ferromagnetic resilient tongue 4 which extends generally axially and makes switching movements with its free end 4a between two pole shoes 5 and 6. A permanent magnet 7 is disposed between ends of the pole shoes 5 and 6. Tongue 4 is attracted to one or the other of the pole shoes according to the direction of current flow in the coil 2. Pole shoes 5 and 6 also serve as opposed electrical contacts; (electrical connections to the pole shoes are not shown in the drawing).

Tongue 4 is not clamped directly in the coil former 1 by its end 4b but is secured to an adjusting plate 8 which extends generally parallel with tongue 4 and is made of a ferromagnetic material having a relatively low elastic limit. Adjusting plate 8 is clamped in the coil former 1 by mounts 9 and 10. To this end, coil former 1 has axial extending grooves 11 and 12 which are located on one side of chamber 3 either side of adjusting plate 8.

Between the fixing mounts 9 and 10, plate 8. has a punched-out lug 13 to which the spring tongue 4 is fixed. (for example by welding) at a point 14. Outside its clamping zone. each of fixing mounts 9 and 10 has a designed bending point (15 and 16 respectively) of reduced cross-section so that the adjusting plate 8 can be bent by an externally generated magnetic field with relatively little difficulty. When plate 8 is bent, the point of attachment 14 of the spring tongue 4 is moved so that the free end of tongue 4 rests against one or other of the two opposing poles 5 or 6 with a greater or lesser preloading or takes up a central position as desired. Adjusting plate 8 and tongue 4 are balanced through the limited rigidity of tongue 4 to such an extent that when the spring is bearing on pole plate 5 or 6 further deflection of plate 8 is not prevented.

The adjusting plate 8 can be bent by an externally applied magnetic field which is generated with a coil 17, for example (Figure 1). It is known that an elongate ferromagnetic component whose longitudinal axis is at an angle between 0 and 90" with the force lines of a magnetic field is subjected to a torque that tends to align the longitudinal axis with the force lines. The adjusting plate 8 is magnetised by the external fiel'd and acts as a dipole. Its magnetic dipole moment is p = I.V where I denotes the magnetisation and V the volume. Having a magnetic dipole moment p and making an angle a with the force lines (field strength H), plate 8 is subjected to a torque D given by D = p. H. sina If the component is clamped on one side, this torque corresponds to a force Fh acting at the end perpendicular to the largest face of the adjusting plate (of length 1) Fh = D 1 Thus the torque is dependent upon the sine of the angle between the adjusting plate to be bent and the magnetic lines of force. But since plate 8 cannot be magnetised with an angle a of 90 , the angle must be smaller than this. In practice, an optimum value for the torque is obtained with an angle a which is about 15 smaller than 90 .

Apart from the directional effect in a homogenous magnetic field, that force which seeks to move a ferromagnetic component in the direction of increasing field strength in an inhomogenous magnetic field (as a result of the attractive effect of the pole shoes) can also be utilised for magnetic adjustment.

This force Fi' can be approximated as Fi' = I . cos . , where v is in the field intensity.

Since this force acts in the direction of the field force lines, it still has to be multiplied by sina to obtain the components perpendicular to the adjusting plate. The force acts at the centre of gravity. With clamping at only one side, the resulting force Fi acting at the end of the adjusting plate is obtained by multiplying by 1/2 Fi = 2 I .4L, cos a. sin a.

A relay as in Figure 1 can be adjusted before permanent magnet 7 is fitted. The position of tongue 4 can be established between the individual magnetic field impulses by electrical measurement, e.g. with the aid of the capacitance between tongue 4 and opposite contacts or with the aid of the excitation required to deflect the tongue to the nearer pole plate. Another possibility for measurement is offered by the response and rejection strength of the polar system which is formed in the adjusting device by attaching an external permanent flux circuit. In the event of subsequent magnetic adjustment of the permanent magnet (if this is necessary) it must be ensured that the tongue adjustment is not affected. To this end, it may be advantageous to make the demagnetising field act at right angles to the direction of bias of the permanent magnet. However, it is usually better to make the adjustment to the finished relay. In this case the response Values of the assembled relay can serve as adjustment criteria. Then it is possible to set the response values precisely through a combined adjusting and balancing operation (the latter being for the permanent magnet). It is desirable that the two operations do not have any reciprocal effect. It is important that one of the two operations can be carried out without changing the final state produced by the other. If for instance the permanent magnet can be balanced without affecting the adjustment - by having the field lines of a demagnetising field running parallel with the coil axis - the adjustment is performed first and then the balancing.

Figures 3 and 4 show a form of adjusting plate 18 which is somewhat different from that shown in Figure 1. This can be incorporated in place of the adjusting plate 8 inside a relay, for instance in the coil former 1. It carries a contact tongue 20 secured at a point 19 and has two lateral projections 21 and 22 with which it can be mounted in a casing.

Like plate 8, adjusting plate 18 also has a deliberate bending point 23 of reduced cross-section.

In Figures 5 and 6 a rigid armature 24 is used in place of a resilient tongue, this armature being linked to a magnet core 26 by a leaf spring 25. This core 26 also serves as an adjusting plate. A deliberate weak bending zone 28 is provided between the portion 27, by which the core is secured in position, and the adjusting plate 26. As a result, adjustment can also be made by magnetic deformation of the adjusting plate 26.

Figure 7 shows a contact spring armature 31 which is not secured directly in a carrier 32 but is fixed to a ferromagnetic reinforcing plate 33. This reinforcing plate 33 can be deformed with a magnetic field for contact adjustment when a deliberate bending point 34 is again advantageously provided.

Figures 8 to 10 show a spring tongue 41 serving as an armature contact and fixed, (for example by welding) by one end to an extremity 42 of an adjusting plate 43. This adjusting plate 43 forms part of a ferromagnetic carrier 44 having two guide strips 45 and 46 on respective sides of plate 43 which carrier supports it with the aid of torsion members 47 and 48 disposed roughly in the centre. The end 42 of the adjusting plate 43 is bent in a stamping operation (see Figure 9) so that the parallel spring tongue has adequate clearance for its switching movements.

The free end 49 of the adjusting plate is widened and spatulate so as to be able to respond well during magnetic adjustment. A corrugation 50, which is pressed into the adjusting plate 43 in its centre, serves for stiffening.

For ease of insertion in guide slots provided in a relay casing, each guide strip is provided with slip faces 51 and 52 and also with insertion shoulders 53 and 54. Thus when pressing the guide strip into the relay casing, excessive bending which might otherwise occur at the carrier 44 when pressure is applied to the angled end 55, is avoided. This angled end 55 serves for magnetic attachment of the carrier 44 to a ferromagnetic casing cap. In addition it carries a moulded connecting prong 56 which is passed to the outside to serve as a plug or soldering connector and brought into the desired locating position by a bent section 57.

Figures 11 and 12 show a complete relay including tongue 41 and its carrier 44 from Figures 8 to 10. The casing is constituted by a coil former 58 which carries the coil 59 and forms a contact chamber 60. The tongue 41 acting as armature contact is disposed with its free end 41a between two angled pole plates 61 and 62 which are magnetically coupled at one end in each case to a permanent magnet 63. The carrier 44 for the adjusting plate 43 and the spring tongue 41 is inserted by means of the guides 45 and 46 into guide channels 64 and 65 in the coil former 58. It is coupled magnetically to a ferromagnetic casing cap 66 through its angled end 55.

Figure 13 illustrates the adjusting process with the relay of Figures 11 and 12 shown in schematic form. After assembly of the carrier 44 with the adjusting plate 43 and the spring tongue 41 in the relay and after sealing of the contact chamber, the spring tongue 41 tan still be adjusted. To this end a magnetic field is applied over between two poles 67 and 68, the force lines of said field passing through the adjusting plate 43 and exerting a force thereon. The adjusting plate 43 is twisted about the hinge axis constituted by the torsion mounts 47 and 48 by this magnetic field.

The arrows 70 and 71 indicate the direction of rotation. In this way tongue 41 can be brought into any desired resting position between the opposing pole plates 61 and 62, the relay characteristic being set by the permanent deformation of the torsion mounts 47 and 48.

Thus the adjusting member, serving as carrier for the switching component can be bent by means of a magnetic field applied from outside, which is particularly advantageous for hermetically sealed armatures or contact tongues. The switching component itself can be constituted as a spring tongue or mounted resiliently; it is not deformed itself during the adjusting operation, but the adjusting component constituted as its carrier is deformed, said component changing the mounting point of the switching member when it is bent. In this way the free end of the switching member can also be pre-loaded as desired relative to an opposing pole piece or an opposing contact as it is the tongue alone and not the deformable adjusting plate which rests on the counter stop.

The adjusting member may be disposed essentially parallel with the switching component the latter being fixed to the adjusting member in the vicinity of its clamped point.

In another advantageous embodiment the switching component can also be mounted resiliently flush with the adjusting member on the latter's free end. Expediently the adjusting member also has a designed bending point of reduced cross-section in the zone between its clamped point of reduced crosssection in the zone between its clamped point and the point of attachment of the switching component. In this way the magnetic forces needed for the adjustment can be kept small.

Preferably soft iron or a similar material having a resilience limit of the same order is used as material for the adjusting member. The switching component itself can be chosen as required and thus be made of springy contact material when it is a contact tongue or of ferromagnetic material when it is an armature. So this switching component can be an overall resilient, electrically and magnetically conductive armature contact tongue or in another case a rigid armature fixed by means of a hinge spring. The switching component can serve as an armature contact disposed inside the coil of the relay, when the coil former can form a hermetically sealed switching chamber for instance. In all these cases, the adjustment can still be carried out, by virtue of the invention, on a fully assembled, sealed and possibly still potted relay.

Provision may also be made for the adjusting member to be clamped in the relay casing by means of two lateral torsion mounts forming a hinge. The elongated adjusting member suspended by two torsion mounts alone can be deformed very favourably through the action of a magnetic field, the torsion mounts acting as a hinge in the process. The magnetic forces can be exploited particularly well for adjustment if the torsion mounts are disposed in the main plane of the adjusting member roughly at its centre lengthwise.

Expediently the torsion mounts are secured in the relay casing on either side of the part of The adjusting member to which the armature is secured by means of guide strips clamped without any play. These guide strips can enclose said part of the adjusting member in the manner of a fork as part of a one-piece carrier. Particularly favourable construction is obtained if the adjusting member with its torsion mounts and the carrier is made from one common strip of sheet material.

The switching component serving as armature is expediently fixed to one end of the adjusting member, preferably by welding.

This end is expediently so shaped by stamping or by bending that the switching component is sufficiently clear of the parallel adjusting member to have the required freedom of movement for the switching movements even after fitting and adjustment are completed. The free end of the adjusting member can be made wider and spatulate so as to be able to take in the largest possible number of lines of force for the adjustment. A corrugation stamped in the central zone of the adjusting plate serves to stiffen it so that the adjusting member does not bend in itself during the magnetic adjustment but is deflected as a whole.

In order that the guide strips be more easily insertable in corresponding guide slots in the casing, they exhibit slip faces at their ends. At the opposite ends the guide strips are expediently provided with widened insertion shoulders so that no bending moments are exerted on the guide strips at the moment of assembly. The carrier for the adjusting member can be angled following the path taken by the magnetic flux to link up with a ferromagnetic casing cap; if the magnetic parts, i.e. the carrier for the adjusting member and the switching component are part of the contact circuit at the same time, the carrier can be provided with a connecting prong formed integrally therewith.

WHAT WE CLAIM IS: 1. An electromagnetic relay comprising: an energising coil on a coil former; at least one switching contact; an elongate switching armature mounted for resilient movement by energisation of said coil to produce switching by engagement of said armature with said contact; and a deformable elongate ferromagnetic member to which said armature is secured, a part of said member being secured to the former, wherein between said secured part and the point of attachment of said armature, said ferromagnetic member is provided with a zone having relatively little resistance to deformation.

2. A relay according to claim 1 wherein said member extends generally parallel to said switching armature.

3. A relay according to claim l or 2 wherein said one end of said armature is secured to said member adjacent said secured part.

4. A relay according to claim 1 or 2 wherein one end of said armature is secured to said member.

5. A relay according to any one of claims 1 to 4 wherein said deformation is bending deformation.

6. A relay according to any one of claims l to 5 wherein said member is of a material having an elastic limit similar to that of soft iron.

7. A relay according to any one of Claims l to 6 wherein said switching armature is constituted of spring material throughout.

8. A relay switching to any one of Claims 1 to 6 wherein said switching armature forms a substantially rigid armature and is connected to said ferromagnetic member via a leaf spring.

9. A relay according to any one of Claims 1 to 8 wherein said armature forms an armature contact and is disposed within said coil former.

10. A relay according to any one of Claims 1 to 9 wherein said member is provided with two laterally extending torsion mounts constituting respective zones, of relatively little deformation resistance.

11. A relay according to Claim 10 wherein said member is plate-like, and said torsion mounts are in the main plane of said member and in its central region considered in the lengthwise direction.

12. A relay according to Claim 10 or It wherein said torsion mounts extend from said member to respective guide strips clamped in a further member of said relW on respective sides of said ferromagnetic member.

13. A relay according to Claim 12 wherein said guide strips form portions of a one-piece carrier.

14. A relay according to Claim 13 wherein said ferromagnetic member, said torsion mounts and said carrier are formed from a common strip of sheet metal.

15. A relay according to any one of Claims 12 to 14 wherein said guide strips are provided with respective shoulders at the secured part of said ferromagnetic member.

16. A relay according to any one of Claims 12 to 15 wherein the free ends of said guide strips are tapered to facilitate insertion in the relay.

17. A relay according to any one of Claims 13 to 16 wherein said carrier has an angled end provided with a connection extension.

18. A relay according to any one of Claims 10 to 17 wherein that part of said ferromagnetic member carrying said switching armature lies in a plane parallel to that of the remainder of said ferromagnetic member and spaced therefrom in the direction of said armature.

19. A relay according to any one of Claims 10 to 18 wherein a free end of said ferromagnetic member is of spatulate form.

20. A relay according to any one of Claims 10 to 19 wherein said ferromagnetic member is provided with a longitudinally extending corrugation.

2 1. An electromagnetic relay substantially as hereinbefore described with reference to the accompanying drawings.

22. A method for adjusting the relay of any one of the preceding claims, in which method the relay is disposed in a magnetic field whose lines of force make an angle greater than 0 and less than 90" with the longitudinal axis of said ferromagnetic member, the ferromagnetic member is deformed by a magnetic field impulse, and the position or

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. even after fitting and adjustment are completed. The free end of the adjusting member can be made wider and spatulate so as to be able to take in the largest possible number of lines of force for the adjustment. A corrugation stamped in the central zone of the adjusting plate serves to stiffen it so that the adjusting member does not bend in itself during the magnetic adjustment but is deflected as a whole. In order that the guide strips be more easily insertable in corresponding guide slots in the casing, they exhibit slip faces at their ends. At the opposite ends the guide strips are expediently provided with widened insertion shoulders so that no bending moments are exerted on the guide strips at the moment of assembly. The carrier for the adjusting member can be angled following the path taken by the magnetic flux to link up with a ferromagnetic casing cap; if the magnetic parts, i.e. the carrier for the adjusting member and the switching component are part of the contact circuit at the same time, the carrier can be provided with a connecting prong formed integrally therewith. WHAT WE CLAIM IS:

1. An electromagnetic relay comprising: an energising coil on a coil former; at least one switching contact; an elongate switching armature mounted for resilient movement by energisation of said coil to produce switching by engagement of said armature with said contact; and a deformable elongate ferromagnetic member to which said armature is secured, a part of said member being secured to the former, wherein between said secured part and the point of attachment of said armature, said ferromagnetic member is provided with a zone having relatively little resistance to deformation.

bias of said switching armature is determined by electrical measurement.

23. A method according to Claim 22 wherein a plurality of said impuses are employed, and said measurement is made between two successive impulses.

24. A method according to Claim 22 or 23 wherein said angle is in the range of from 75" to 900. but less than 90".

25. A method according to any one of Claims 22 to 24 for adjusting a relay according to any one of Claims l to 2 1 and including a permanent magnet. in which method said magnetic field is applied in such manner that said magnet is magnetised thereby.

26. A method for adjusting a relay, the method being in accordance with claim 22 and substantially as hereinbefore described.