GB2133626A - Electromagnetic relays - Google Patents

Abstract

A relay suitable for use in a circuit- breaker has a latch member resiliently baissed to lock the armature in one position but allow the armature to move from the other position. The latch member may be spring-loaded and the edge of the armature bevelled so that the latch urges the armature towards its locked position. <IMAGE>

Description

SPECIFICATION Electromagnetic Relays This invention relates to electromagnetic relays.

A known type of relay comprises an armature movable between open and closed positions and an electromagnet, the armature bearing an electrical contact or contacts which abuts a fixed contact or set of fixed contatcs when the armature is in its closed position and holds the contacts apart when the armature is in its open position. Alternatively the contact or contacts mounted upon the armature may abut a fixed or set of fixed contacts when the armature is in its open posi tion and hold the contacts apartwhen the armature is in its closed position. The armature is permanently urged towards one of these positions by a resilient deviceforexample a spring, but is moved to the other position by the magnetic field produced by the elec tromagnetwhen the latter is energised by an electric current.The relay may be of the "normally open" type, in which the armature remains in its closed position until the electromagnet is de-energised or the magnetic field is broken.

The contacts will form part of an electric circuit controlled by the relay, the circuit being established when the contacts are in their closed position and broken when the contacts are in their open position.

Such relays may be used in circuit-breakers, such as residual current circuit breakers in which a leakage current exceeding a given magnitude actuates the relay directly or indirectly by means of an electrical device or electronic circuit to open the contacts and break the circuit controlled by the relay. The contacts are then required to remain open until the fault causing the leakage current has been rectified. However there is commonly a risk that the contacts may change their state inadvertently by the action of mechanical shock, vibration of electrical malfunction.

The present invention is intended to provide a relay which, once operated to open or clói a circuit, remains locked in the opened or closed state until deliberate action is taken to unlock the relay.

According to one aspect of the invention there is provided an electric relay having an armature movable between an open and a closed position and a latch member resiliently biased to lock the armature in one of said positions but allow the armature to move from the other of said positions.

The relay may be of the normally open or the normally closed type. The latch member may be arranged to allow the armature to move from the closed to the open position and lock it in the open position, or alternatively to lock it in the closed position while allowing itto move from the open position.

The latch member may comprise a spring-loaded member arranged to abut an edge of the armature or an attachment to the armature when the armature is in one position,sothatthe member does not obstruct movement of the armature, but to move under the action ofthe latch spring into a locking position in the path of the armature or attachment when the latter has moved to its other position, so that the armature cannot return to its original position. The latch member may be moveable manually against the latch spring to unlock the armature.

A relay according to one embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a cross-section of a relay with the armature in its closed position, Figure 2 is a side view of the relay of Figure 1, Figure 3 is a front view of the relay of Figure 1, Figure 4 is a cross-sectiOn of the relay similar to Figure 1 but showing the armature in its open position.

Figure 5 is a view similar to Figure 2 with the armature in its open position, Figure 6 shows part of Figure 1 on a larger scale.

The relay shown in the drawings is a 2-pole relay comprising a metal frame 1 on which is mounted an armature 2 pivoted at 3 to rotate between a closed position shown in Figure 1 and an open position shown in Figure 4. The armature is urged towards its open position by a tension spring 4 mounted on the frame. The frame contains an electromagnet 5 which is magnetisable by wire windings (not shown in the drawings) which may be fed with electric current through terminals 6. On passage of current through the windings the electromagnet 5 is magnetised and urges the armature against the spring to its closed position; when this current is switched off the spring returns the armature to its open position.

A pair of fixed terminals 7 having contact surfaces 8 are mounted on the base 14 one on each side of the armature, and the armature carries corresponding contacts 9 arranged to engage the contact surfaces 8 when the armature is in its closed position. Contacts 9 are electrically connected to terminals 10 by cables 11 so that terminals 7 and 10 are electrically connected when the armature is in its closed position and disconnected when the armature is in its open position.

When terminals 7 and 10 form part of an electrical circuit operated by the relay the electrical circuit is thus opened and closed in response to the operating current supplied through terminals 6.

The frame and terminals are mounted on a base 14 of electrically insulating plastics material.

The armature has a central blade 15 which has a lower edge 16 which passes close to the upper surface of base 14 as the armature opens and closes. The base 14 is provided with a slot, located below the edge 16 of the blade 15 when the armature is closed.

A latch 17 extends through the slot and can slide up and down in the slot between the locking position shown in Figure 4 and the unlocking position shown in Figure 1. The lower end of the latch has a foot 18 which abuts the lower surface of base 14 when the latch is in its locking position and the latch is urged to its locking position by spring 19 which engages the lower surface of the foot.

The armature and latch are arranged such that when the armature is in its closed position the latch abuts the edge 16 of the armature blade 15 as shown in Figure 1. However when the armature moves into its open position as shown in Figure 4 the edge 16 of the armature blade 15 is clear of the slot and the latch 17 can move upwardly, driven by spring 19, to its locking position where it engages the side surface of the armature adjacent the magnet and prevents the armature returning to its closed position, thus preventing accidental closure of the relay.

The foot 18 has an outstanding lip 20 which can be pressed down manually to the position shown in Figure 1, thus lowering the latch and allowing the armature to return to its closed position when the electromagnet 5 is again energised.

As shown in Figure 6 the edge 16 of the armature blade which comes into contact with the latch 17 is bevelled to reduce the frictional force between the edge and the latch which would tend to prevent the armature opening. The angle between the plane defined by bevelled edge 16 and the tangent to the radius of rotation of the armature may be such that the resilient action of the latch urges the armature towards its open position, thus supplementing the opening action of the spring 4.

It will be appreciated that once the armature has moved to its open position it cannot be closed again until the latch is manually moved against spring 19 and there is no risk of the relay contacts being closed accidentally, for example underthe effect of mechanical shock, vibration or electrical control malfunction.

When the relay described above is used in a circuit-breaker the circuit to be protected includes terminals 7 and 10 and during normal operation an energising current fed through terminals 6 keeps the relay closed. In the event of a circuit malfunction, such as leakage to earth or overloading, the energising current is cut off and the relay opens, separating contact surfaces 8 and contacts 9 and breaking the circuit. Latch 17 then moves into its locking position and the relay cannot close until the latch is manually moved by depressing lip 20.

The armature and latch are dimensioned so that the latch moves into its locking position when the gap between the contacts reaches a desired value, suitably about 3 mm.

In the relay described above the latch 17 is reset to release the armature by manual pressure but it is also possible to provide an electro-mechanical device for resetting the latch, which may be operated by a push button, electrical device or electronic circuit. The relay described is of the normally open type but the same locking device may be used with a normally closed relay, for example a relay in which terminal 7 is on the side of the armature remote from the magnet so that the relay contacts are closed with the armature in the position shown in Figure 4.

The relay described is suitable for use in circuit breakers but it may also be used in many other situations in which a relay is to be automatically locked in an open or a closed position.

It will be appreciated that in the embodiment described when the magnetic circuit is de-energised, the armature will move towards its normally open position, (see Figure 4). The frictional drag present between the armature blade and latch is overcome by the profiled end 16 of the armature blade. When the armature has moved sufficiently to achieve a contact gap of 3 mm minimum, the latch moves upwards under the force of the spring 19. This status is shown in Figure 4. The latch will now stop the armature from closing until the latch is drawn from in front of the armature blade 15.

An application for this device is with a portable Residual Current operated Circuit Breaker, where once the device has tripped due to an earth leakage current or has been intentionally operated the breaker's contacts shall not be inadvertently closed by mechanical shock, vibration or electrical control malfunctions. Similarly, this mechanism could be used in any application where contact isolation is required to be guaranteed'and against mechanical shock, vibration or electrical control malfunctions.

CLAIMS (Filed on 8.2.83) 1. An electric relay having an armature movable between an open and a closed position and a latch member resiliently biased to lockthe armature in one of said positions but allow the armature to move from the other of said positions.

2. A relay according to Claim 1, in which the latch member comprises a spring-loaded latch member arranged to abut an edge of the armature or an attachment to the armature when the armature is in one position butto move into a locking position in the path of the armature or attachment when the armature has moved to its other position.

3. A relay according to Claim 2, in which said edge is bevelled and the resilient action of the latch urges the armature towards said other position.

4. A relay according to Claim 2 or 3, in which the latch member is movable manually against the latch spring to unlock the armature.

5. A relay, substantially as hereinbefore described with reference to the accompanying drawings.

6. A circuit breaker, comprising a relay according to any preceding claim.

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

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. armature returning to its closed position, thus preventing accidental closure of the relay. The foot 18 has an outstanding lip 20 which can be pressed down manually to the position shown in Figure 1, thus lowering the latch and allowing the armature to return to its closed position when the electromagnet 5 is again energised. As shown in Figure 6 the edge 16 of the armature blade which comes into contact with the latch 17 is bevelled to reduce the frictional force between the edge and the latch which would tend to prevent the armature opening. The angle between the plane defined by bevelled edge 16 and the tangent to the radius of rotation of the armature may be such that the resilient action of the latch urges the armature towards its open position, thus supplementing the opening action of the spring 4. It will be appreciated that once the armature has moved to its open position it cannot be closed again until the latch is manually moved against spring 19 and there is no risk of the relay contacts being closed accidentally, for example underthe effect of mechanical shock, vibration or electrical control malfunction. When the relay described above is used in a circuit-breaker the circuit to be protected includes terminals 7 and 10 and during normal operation an energising current fed through terminals 6 keeps the relay closed. In the event of a circuit malfunction, such as leakage to earth or overloading, the energising current is cut off and the relay opens, separating contact surfaces 8 and contacts 9 and breaking the circuit. Latch 17 then moves into its locking position and the relay cannot close until the latch is manually moved by depressing lip 20. The armature and latch are dimensioned so that the latch moves into its locking position when the gap between the contacts reaches a desired value, suitably about 3 mm. In the relay described above the latch 17 is reset to release the armature by manual pressure but it is also possible to provide an electro-mechanical device for resetting the latch, which may be operated by a push button, electrical device or electronic circuit. The relay described is of the normally open type but the same locking device may be used with a normally closed relay, for example a relay in which terminal 7 is on the side of the armature remote from the magnet so that the relay contacts are closed with the armature in the position shown in Figure 4. The relay described is suitable for use in circuit breakers but it may also be used in many other situations in which a relay is to be automatically locked in an open or a closed position. It will be appreciated that in the embodiment described when the magnetic circuit is de-energised, the armature will move towards its normally open position, (see Figure 4). The frictional drag present between the armature blade and latch is overcome by the profiled end 16 of the armature blade. When the armature has moved sufficiently to achieve a contact gap of 3 mm minimum, the latch moves upwards under the force of the spring 19. This status is shown in Figure 4. The latch will now stop the armature from closing until the latch is drawn from in front of the armature blade 15. An application for this device is with a portable Residual Current operated Circuit Breaker, where once the device has tripped due to an earth leakage current or has been intentionally operated the breaker's contacts shall not be inadvertently closed by mechanical shock, vibration or electrical control malfunctions. Similarly, this mechanism could be used in any application where contact isolation is required to be guaranteed'and against mechanical shock, vibration or electrical control malfunctions. CLAIMS (Filed on 8.2.83)

1. An electric relay having an armature movable between an open and a closed position and a latch member resiliently biased to lockthe armature in one of said positions but allow the armature to move from the other of said positions.

2. A relay according to Claim 1, in which the latch member comprises a spring-loaded latch member arranged to abut an edge of the armature or an attachment to the armature when the armature is in one position butto move into a locking position in the path of the armature or attachment when the armature has moved to its other position.

3. A relay according to Claim 2, in which said edge is bevelled and the resilient action of the latch urges the armature towards said other position.

4. A relay according to Claim 2 or 3, in which the latch member is movable manually against the latch spring to unlock the armature.

5. A relay, substantially as hereinbefore described with reference to the accompanying drawings.

6. A circuit breaker, comprising a relay according to any preceding claim.