GB2030368A - Electromagnetic Cut-out Device Used as a Relay or for Short Circuit Protection - Google Patents

Abstract

An electromagnetic cut-out device is described in which magnetically held fixed (2) and movable (3) contacts are separated by magnetic repulsion by energizing the excitation circuit (52) of a magnetic device (11, 13), this circuit may include said two contacts so that separation of the latter automatically breaks the excitation circuit, the contacts being maintained in the separated configuration by means of a permanent magnet (9). A second similar electromagnetic arrangement may be provided which has an excitation circuit including said movable contact (3) and a further fixed contact (1) in contact therewith in the above mentioned separated configuration so that by energizing the circuit at contacts (51) the movable contact 3 is repelled once more to assume its original configuration, at the same time breaking the excitation circuit of the second electromagnetic arrangement. The cut-out device may also be used to replace fuses in electrical plugs or sockets, or as a short circuit protective arrangement to be included in circuit breakers. <IMAGE>

Description

SPECIFICATION Electromagnetic Cut-Out Device used as a Relay or for Short Circuit Protection This invention refers to an electromagnetic cutout device which may be embodied either as an electromagnetic relay having distinct advantages over known electromagnetic relays or as a device for providing protection against short circuits.

Electromagnetic relays of the prior art usually comprise a blade or arm carrying a movable contact which cooperates with a fixed contact to complete a load circuit when an electromagnetic coil is energized. Evidently it is necessary to have the current flowing continuously through the coil winding to keep the load circuit closed. This means a constant additional power consumption, and many times the use of a separate low voltage circuit to control the relay was found to be more convenient.

Other relays have their coils energized only when it is desired to connect the circuit (for example, by means of a push button), the fixed contact being maintained in the closed circuit position by mechanical means. This type of relay has the disadvantage that when the circuit is connected, an accidental closure or defect of the push button or other electric switch controlling the current in the coil may result in a constant flow of that current. This frequently burns out the coil which was not designed for a prolonged flow of current.The relay according to this invention combines the advantages and eliminates the disadvantages of the majority of known relays, because it has the following characteristics: a) the circuit for controlling or energizing the electro-magnetic means used to switch the relay can be connected to the same power supply network (AC or DC) which serves the load or loads being switched; b) the relay is maintained in its two positions by means of one or more permanent magnets, which means there is no consumption of electricity, while at the same time mechanical devices such as springs and similar objects are avoided; and c) when the relay is switched, it is impossible to make the current flow again through the corresponding coil unless the relay first reverts to its initial condition.

In accordance with this invention, an electrical cut-out device comprising at least one fixed contact, one movable contact mounted on an element capable of assuming a first configuration in which the movable contact is separated from said fixed contact, and a second configuration of contact between the movable contact and the fixed contact, first means to make the said element assume and maintain said first configuration and second means to make said element assume and maintain said second configuration, is characterized in that said first means comprises an electromagnetic device to make said element assume the first configuration by forces of repulsion and a permanent magnet so as to maintain said element in the first configuration by forces of attraction.

In the case of the cut-out device comprising a relay, the electromagnetic device of the first means has an energizing circuit including the movable contact and the fixed contact. Moreover, the second said means for making the element assume and maintain the second configuration may comprise a second electromagnetic device to make the element assume the second configuration by means of forces of repulsion.

According to another aspect of the invention the cut-out device thereof may be utilized for protection against short circuits and as such may be used instead of fusion in electrical plugs or sockets for domestic use or in circuit breakers.

Thus an electrical plug or socket according to this invention, including the above defined cut-out device and comprising a housing of insulating material wherein are mounted a pair of terminals for connection to two electrical leads and a pair of main contacts for cooperation with the contacts of another socket or plug respectively, is characterized in that one of said terminals is directly connected to one of said main contacts and the other of said terminals is connected to the other main contact through a series connection comprising said electromagnetic device and said movable and fixed contacts, said electromagnetic device comprising a low resistance winding of a reduced number of turns about a core of ferromagnetic material whereby said cut-out device separates said contacts to assume said first configuration only when a short circuit current passes through said winding.

Equally, a circuit breaker according to the present invention comprises an input terminal connected to an output terminal through a pair of contacts controlled by a bimetal element to protect against overloads and is characterized by including a relay device according to claim 1 in which said electromagnetic device comprises a low resistance winding of a reduced number of turns about a core of ferromagnetic material and connected between said input and output terminals in series with said bimetal element and said movable and fixed contacts of the cut-out device whereby said cut-out device separates itself to assume said first configuration only when a short circuit current passes through said winding.

The invention will now be described in more detail, by way of example, with reference to the attached drawings, in which: Figure 1 is a schematic illustration of a relay in accordance with a first embodiment of this invention, including the energizing and load circuits; Figure 2 is similar to Figure 1, but shows a second embodiment of the invention; Figure 3 is a top plan view of a shaft and blade arrangement for use in a modification of the relay shown in Figure 2; Figure 4 is a detail of still another relay constructed in accordance with this invention, showing a different switching system; Figures 5, 6 and 7 show schematically three other embodiments of this invention, similar to the one shown in Figure 1, but with different energizing circuits;; Figure 8 is a schematic view of a transverse section of an electrical supply socket, incorporating a device for protection against short circuits, constructed in accordance with the present invention; Figure 9 shows another embodiment of the present invention when incorporated in an electric plug; Figure 10 shows schematically a circuit cut-out device provided with a device for protection against short circuits in accordance with the present invention; and Figure 11 shows a relay according to the first aspect of this invention, provided with a cut-out device constructed in accordance with the second aspect thereof.

Referring now to Figure 1 of the drawings, a first embodiment of the invention comprises a relay with first and second fixed contacts 1 and 2 and, cooperating with said contacts, a movable contact 3 fixed at the free end of a metal blade 4, mounted in cantilever at 5. The fixed contacts 1 and 2 have terminals 6 and 7 respectively, while a terminal 8, in electrical contact with the supported end of blade 4, serves the movable contact 3.

The relay shown in Figure 1 also has a permanent magnet 9, fixed on blade 4, with a north pole facing the first fixed contact 1 and a south pole facing the second fixed contact 2.

Immediately above and below the permanent magnet 9, there are mounted upper and lower fixed coils 10 and 1 1,with cores 12 and 13 of soft iron or similar material.

When the relay is used, the first terminal 6 is connected through a first load C1 to be switched to a line 14 of the AC power supply network, the second terminal 7 being connected to the same line 14 through a second load C2, which can be an open circuit if switching of only one load is desired. Terminals 6 and 7 are also connected to the respective ends of coils 10 and 1 ,the other ends of which are connected to line 14 through switches S1 and S2. Terminal 8, which serves the movable contact 3 is, in its turn, connected to the other line 13 of the AC power supply network.

When the relay has the configuration illustrated in Figure 1, with a movable contact 3 engaged with the second fixed contact 2, the alternating current flows through load C2, the attraction between the permanent magnet 9 and the core of soft iron 13 maintaining blade 4 in this position. The current flows from line 1 5 to terminal 8, along blade 4, through contacts 3 and 2 and, finally, through load C2 to the other line 14 of the network.

It should be noted that it is of no use to operate switch S 1, as this will not complete the circuit that energizes coil 10. By pushing the button of switch S2, however, a circuit is closed from line 15 to line 14, through terminal 8, blade 4 and the contacts 3 and 2, coil 11 and switch S2. The magnetic field then induced in core 13 of coil 11 is an alternating field, so that in the first half cycle of the current in lines 14 and 15 which produces a south pole in the upper end of this core, the permanent magnet 9 (whose south pole faces downwards) is strongly impelled upwardly. When driven upwardly, the magnet 9 will evidently also take blade 4 with it, separating contacts 3 and 2 and disconnecting the current energizing the coil.

The upward impulse experienced by permanent magnet 9 causes it to reach core 12 of the upper coil 10 and remain there held by magnetic attraction. This, in turn, causes engagement of contacts 1 and 3 so that the current starts to flow through load C1.

It should again be noted that the described switching will not be affected in any way if the operator continues pressing the push button of switch S2, because one cycle at the most, i.e. up to the first half-cycle that produces a south pole in the upper end 13, is sufficient to interrupt the circuit between contacts 2 and 3. The circuit is, therefore, self-protecting.

In order to disconnect load C1 and connect load C2 again, the operation is repeated, except that switch S1 is closed to make blade 4 and the permanent magnet move downward in the first half-cycle of the network which produces a north pole in the bottom end of core 12 of coil 10, until the configuration of Figure 1 is assumed again.

Turning now to Figure 2, this shows schematically the presently preferred embodiment of the invention. As far as possible, the reference numbers in Figure 2 are the same as those used in Figure 1. There are, therefore, first and second contacts 1 and 2 and a movable contact 3a cooperating with them. Contact 3a, however, is mounted on blade 4 which, instead of being mounted in cantilever as in Figure 1, is fixed to a rotary shaft 5a at the mid-point between its ends. The other end of blade 4 carries a second movable contact 3b which cooperates with fixed upper and lower contacts 16 and 17 connected in common to terminal 8.

The relay shown in Figure 2 was designed for use with only one load C2, for which reason terminal 6 and the fixed contact 1 are only used to define the deactivated position of the relay and to energize coil 12, completing a circuit going from line 14, through switch 51, coil 12, terminal 6, contacts 1 and 3a, blade 4, contacts 3b and 16 and terminal 8, to line 1 5. Since there is no danger of the contacts getting welded in the position of C2 disconnected, one relatively small coil 12 is sufficient. If, however, the relay is deactivated when heavy currents flow through load C2, it has proved desirable to use two coils 1 a and 1 b with their respective soft iron cores 1 3a and 1 3b. These coils are connected in parallel between switch S2 and fixed contact 7.

For this reason, there are also two permanent magnets 9a and 9b, so that when switch S2 is closed, the relay switches in the first half-cycle that induces a south pole in the upper end of core 1 3a and a north pole in the lower end of core 13b.

Care should be taken, of course, to check that the coils 11 a and 11 b are properly connected so that this occurs in the same half-cycle.

Although Figure 2 shows the permanent magnets 9a and 9b mounted on the same blade as the movable contacts 3a and 3b, it is to be understood that another actuating blade suitable to turn the shaft 5a at a desired angle could be used, and even simplify the structure. By way of example, Figure 3 shows a plan view of a shaft and blade arrangement. In this case, the shaft 5a, of isolating material, is mounted for rotation between centers 1 8 and 19. Five parallel blades 20,21,22,23 and 24 are mounted transversally on the shaft. Blades 21,22 and 23 carry at each end movable contacts 3a and 3b, as in Figure 2, whereas the outermost blades 20 and 24 are actuating blades carrying permanent magnets 9a and 9b.These magnets work in cooperation with coils similar to those of Figure 2, always remembering that one end of each coil should be connected to one or more of the fixed contacts (not shown in Figure 3). In this embodiment there are, therefore, four magnets, two smaller coils (equivalent to coil 10 in Figure 2) and four bigger coils (equivalent to coils 11 a and 11 b in Figure 2).

All the relays described with reference to Figures 1 to 3 have the characteristic of a permanent magnet on the blade, which cooperates with an energized coil for repulsion and with the core of a non-energized coil, for attraction. It should be understood, however, that other ways do exist of obtaining the same effect and that Figure 4 is a detail of an alternative for the system, for example, of Figure 2.

With reference now to Figure 4, the permanent magnet 9b and the coil 11 b of Figure 2 are substituted by a fixed magnet 25 and a solenoid 26. Blade 4, in its turn, has a tooth 27 of soft iron which functions as a movable core and enters solenoid 26 in the configuration- shown. The solenoid is connected in a manner identical to that of coil 11 b of Figure 2. When the solenoid is not energized, the metal of the blade 4 itself is attracted by the permanent magnet 25, maintaining the contacts 3b and 1 6 closed.When the solenoid is energized and in the first half of the cycle of the network current that produces such effect, tooth 27 is expelled from its interior, disconnecting contacts 3b and 1 6 and driving blade 4 to assume the other configuration where it will be held by another fixed permanent magnet (not shown) similar to magnet 25.

With reference now to Figure 5, the circuit illustrated is basically similar to the one shown in Figure 1, except that there is only one fixed contact 2 with only one load C2 and the connections of coils 10 and 11 are different. In the case of Figure 5, the two coils 11 and 10 are connected in series between the fixed contact 2 and a line 28. The first end of the coil 11 is connected to the fixed contact 2 and line 28 can be connected to the phase line 1 5 through the switch S1 anda rectifier 29. Line 28 can also be connected to the neutral line 14 by means of switch S2 and a rectifier R. In the position shown in Figure 5 load C2 is connected with current flowing through the arm 4 and contacts 2,3.On closing switch S2, the coils 10 and 11 are connected in series between lines 14 and 1 5 by means of a circuit including arm 4 and contacts 2,3 of the relay. In the first cycle that induces a magnetic field in core 13 of coil 11, to repel the permanent magnet 9, arm 4 is driven upward, cutting said circuit, so as to make magnet 9 assume a position in contact with core 12 of coil 10.

When it is desired to connect the circuit again, it is only necessary to press switch 51. A current polarized by rectifier 29 now flows through line 15, through coils 10 and 11 and through load C2.

The coils 10 and 11 are wound so that the polarized current flowing in coil 10 repels magnet 9, while this same polarized current flowing through coil 11 attracts it. When contacts 10, 2 and 3 are disconnected normally, i.e. when the magnet 9 is in contact with core 13, even if switch S1 remains closed, the current stops flowing in the coils because they are by-passed by arm 4 of the relay, whose terminal 8 is also connected to the phase line 15.

The relay shown in Figure 6 is also similar to the one shown in Figure 1, but has different controls and connections. In this case, terminal 8 in the pivot of arm 4 is connected to the two lines 14 and 1 5 of the supply through the two loads C2 and C1, respectively. The two coils 10 and 11 are connected in series between, on the one hand, terminal 8, and on the other, switches S1 and S2, whose other terminals are connected to lines 1 5 and 14 respectively through appropriate resistors.

In the illustrated position load C2 is connected, but load C1 is not, since its two sides are connected through arm 4 of the relay to the same line 15 of the network. When switch S2 is pressed, current flows from line 14 through switch S2 and through the coils 11 and 10 in series, along arm 4 and through contacts 3 and 2 to the line 1 5. With the first half cycle that induces a magnetic field in the core 13 of coil 11 to repel the permanent magnet 9, arm 4 is driven upwards until the movable contact 3 meets fixed contact 1. In this configuration, the terminal 8 and the arm 4 are connected directly to line 14 so that even in the hypothesis that switch S2 remains closed, no current can pass directly through coils 10 and 11.In this second position, therefore, the load C2 is disconnected and load C1 is connected between lines 14 and 1 5 by means of a circuit including arm 4 and the fixed contact 1. When the switch S1 is pressed, an identical operation takes place in contrary direction.

Figure 7 shows still another possibility of making the connection of the relay of Figure 1. In this case the coils 10 and 11 are also connected in series between the lines 14 and 15, but a tap at 30 between the two coils is connected to terminal 8, so that in the configuration with load C2.connected, as illustrated, the actuation of the switch C2 connects only coil 11 in a circuit going from line 14, through switch 22, the coil itself 11, the tap 30, the terminal 8 and the fixed and movable contacts 2, 3, to the line 1 5. When arm 4 is driven upwardly, the coil 11 energizing circuit is cut again and when contact 3 assumes its other configuration against the fixed contact 1, switch S2 is of no more effect.In such configuration, of course, load C1 is connected, but can be disconnected again by the switch S1 functioning in a way similar to that described with reference to load C2.

Although the circuits illustrated in Figures 1, 5 6 and 8 have two loads C1 and C2, it is evident that one of the loads is merely optional and can be eliminated without modifying the function of the relay.

Although the relays constructed in accordance with this invention are destined mainly for use in CA systems where the switching power is supplied by the main supply itself, they can also be used in CC systems, except that in this case, it is essential to check the polarities and the directions winding of the coils to ensure repulsion between the magnets and the cores when the corresponding cores are energized.

Referring now to the second aspect of the invention, Figure 8 is a diagrammatical cross section of a wall socket provided with a short circuit protective device according to a first embodiment thereof. The switch shown in this Figure comprises a housing 31 of insulating material having two orifices 32 and 33 through its outward facing surface, for receiving the two pins of a plug as indicated in dashed lines. Within housing 31 two socket contacts 34 and 35 are mounted for contact with the pins of the plug and two terminals 36 and 37 for the wires 38 and 39 of the electrical installation.

Instead of connecting terminals 36 and 37 directly to their respective socket contacts 34 and 35, as would be the case with an ordinary socket without the protective device according to the present invention, terminal 36 is connected to a movable contact 40 at the end of a rigid arm 41 of insulating material, pivoted on the housing on a pin 42 at its other end, while terminal 37 is connected to contact 35 by a wire 43 wound several times (six times in Figure 8) around a soft iron core 44. A small contact 34 is fixed to the side of socket contact 35 for cooperation with movable contact 40 in the position illustrated.

A permanent magnet 46 mounted at a point between the ends of arm 41 is attracted in the position illustrated to core 44 which is below it.

Also mounted ithin housing 41, above permanent magnet 46, is a small plate 47 of ferromagnetic material which cooperates with the magnet to maintain arm 41 raised, with contacts 40 and 45 separated. The centre of plate 47 is orificed, as is also the centre of the upper part of housing 31, with the holes in register. A pin 48 having a shoulder 49 in its mid-section, passes through the two holes and is biased downwardly by means of a compression spring 50 operating between the shoulder and the inner surface of housing 31 so that, when contacts 40 and 45 are closed with arm 41 lowered, the lower end of pin 18 projects beyond the lower surface of plate 47, while the upper end of same is well within the hole in the housing. At least the upper end of the pin is red or a colour suitable for indicating that there is a defect.

If there is a short circuit during use, the instantaneous high current in wires 38 and 39 also passes through the winding in wire 43, creating a strong magnetic field in core 44. If the current is d.c. then the winding must be such that it induces a magnetic field in core 44 which repels permanent magnet 46, throwing it upwardly until it is attracted by plate 47, where it remains. At the same time, contacts 40 and 45 open, assuring that the circuit will be instantaneously broken, when a short circuit occurs.

When the magnet 46 is thrown upwards, it also forces up pin 48 (against spring 50) until its lower end remains in the plane of the lower surface of plate 47. In this position, the red upper end of pin 48 is flush with the external surface of housing 31 so that, on removing the male plug, it can immediately be seen that there has been a short circuit.

After repairing the defect which provoked the short circuit, a matchstick or other thin element should be introduced into the orifice in housing 41, pressing the permanent magnet 46 downwardly until it is attracted by core 43 once more to close contacts 40 and 45. On replacing the male plug and connecting the circuit, the normal current passing through wires 38, 39 and 43 is not sufficient to create a significant magnetic field in core 44.

In the normal case in which the current in wires 38, 39 and 43 is a.c. and not d.c. (that is, in domestic sockets) when there is a short circuit, the magnetic field induced in core 44 is also alternating. In the first half-cycle, therefore, which induces a magnetic field to repel permanent magnet 46, it is thrown upwards, immediately opening the circuit (contacts 40 and 45) exactly as described with reference to d.c current.

The socket shown in Figure 8 can be modified in many details, without departing from the present invention. Some of these modifications are incorporated in the male plug shown in Figure 9, where the same reference numbers are used, where appropriate, to facilitate understanding.

The plug of Figure 9 also has a housing 31 within which are received its pins 51 and 52 in contact terminals 34 and 35. In this case, however, terminal 47 is connected directly with contact 35, while the wire winding 43 around core 44 is connected in series with movable and fixed contacts 40 and 45 respectively between the other terminal 36 and the other contact terminal 34.

Arm 41' of the plug of Figure 9 is made of flexible metal and mounted in cantilever in housing 31, as indicated at 42'. A terminal 43' in the fixture 42' is used to effect an electrical connection between wire 43 and arm 41' on which movable contact 40 is mounted.

Apart from the above described small differences between the socket and plug of Figures 8 and 9, the other characteristics as well as the operation, are identical, making further description unnecessary.

Figure 10 shows another application of the present invention in a circuit cut-out device. A circuit cut-out device serves to disconnect a circuit when there is a current overload, that is to say, when the circuit is inadequate for the load applied to it. A normal type of cut-out is based on the action of a bimetal element which heats when conducting an overload current, so as to disconnect the circuit. The action of the bimetal, however, is relatively slow and the circuit does not provide sufficient protection against short circuits.

The circuit breaker 53 of Figure 9 comprises, therefore, terminals 54 and 55, between which is connected a device 56 whose circuit cut-out operation is based on a bimetal element. For the purpose of protecting the circuit against short circuits, circuit breaker 53 is provided with a suitable core of ferromagnetic material 44, around which are wound several turns of wire 43 connected in series with the bimetallic device 56.

Wire 43 is further provided with a fixed contact 45 which cooperates with a movable contact 40 mounted at the end of a rigid electrically conductive metal arm 41, pivoted at 42. Point 42 constitutes a terminal connected to one of the outlet terminals 55 of circuit breaker 53.

As in the embodiments described with respect to Figures 8 and 9, arm 41 also carries a permanent magnet 46, normally attracted by core 44. When a short circuit occurs, magnet 46 is thrown upwards, separating contacts 40 and 45, and being maintained in the suspended position by attraction to the ferromagnetic plate 47 which is provided with a pin 48, similar to that of Figures 8 and 9.

Figure 11 shows yet another embodiment of the present invention, when applied as a protective device against short circuits in a relay of the type illustrated in Figure 1. Figure 11 therefore shows a relay in which the circuit of load C is in series with a winding of several turns 57 around a core 44, and a pair of fixed and movable contacts 45 and 40, respectively, the latter being carried by a conductive metal arm 41 pivoted at point 42. Arm 41 also carries a magnet 46 which cooperates with core 44 to maintain contacts 40 and 45 closed, and also an actuating element 58 on its free end. Although the functioning of the relay illustrated in Figure 10 will not be described again in detail, it will be recalled that arm 59 of the relay, in the position illustrated, completes the circuit of load C between the two c.c. supply lines 60 and 61.On closing a switch S2, the repulsion between two permanent magnets 62 and 63 on the one hand, and the cores of two coils 64 and 65 on the other, causes arm 59 to rotate in an anti-clockwise sense, until the magnet is attracted by the core of the other coil 65. When a short circuit occurs, magnet 46 is repelled, with respect to core 44, rapidly impelling actuator 58 upwards. This, in its turn, strikes relay arm 59, rotating it until it assumes a disconnected position, with magnet 62 adhering to the core of coil 63. Immediately after, due to the separation of contacts 40 and 45, and the consequent disappearance of the magnetic field induced in core 44, arm 41 and the actuator fall under the force of gravity, again closing contacts 40 and 45.

Once the defect which originated the short circuit has been repaired, it is sufficient to press switch S1, so that the magnetic field induced in the core of coil 66 repels permanent magnet 62 on relay arm 59 which will once more assume the connected configuration, as illustrated in Figure 10. In case the short circuit has not been repaired, actuator 58 will again be thrown upwards, disconnecting the relay.

Although the present invention has been described in relation to presently preferred embodiments, it will be understood by those versed in the art that many modifications can be effected, both regarding the construction and the application, without departing from the true scope of the invention as defined in the attached claims.

Claims (34)

Claims

1. Electromagnetic cut-out device comprising at least one fixed contact, one movable contact mounted on an element capable of assuming a first configuration in which the movable contact is separated from said fixed contact, and a second configuration of contact between the movable contact and the fixed contact, first means to make the said element assume and maintain said first configuration and second means to make said element assume and maintain said second configuration, characterized in that said first means comprise an electromagnetic device to make said element assume the first configuration by forces or repulsion and a permanent magnet so as to maintain said element in the first configuration by forces of attraction and the second means includes a permanent magnet to maintain the element in the second configuration by means of forces of attraction.

2. Electromagnetic cut-out device according to claim 1, characterized in that said electromagnetic device of said first means has an energizing circuit including the movable contact and said fixed contact.

3. An electrical relay comprising a cut-out device according to claim 2 characterized in that said second means further comprises a second electromagnetic device to make said element assume the second configuration by means of forces of repulsion.

4. A relay in accordance with claim 3, characterized by the fact that each electromagnetic device comprises a fixed coil containing in its interior a core of ferromagnetic material, preferably soft iron.

5. A relay in accordance with claim 3 or 4, characterized by the fact that said element comprises a metal blade which carries said movable contact at one of its ends, said first and second electromagnetic devices being aligned with each other on opposite sides of said blade and between the ends thereof.

6. A relay in accordance with claim 5, characterized by the fact that a single permanent magnet is common to said first and second means, being used for maintaining the blade in each one of said configurations, said magnet being aligned with said electromagnetic devices to accompany the displacement of the blade between the two configurations, one magnetic pole facing the first electromagnetic device and the other pole facing the other electromagnetic device.

7. A relay in accordance with any one of claims 2 to 6, comprising a second fixed contact which is engaged by the movable contact in the first configuration, characterized by the fact that the second electromagnetic device has an energizing circuit comprising the movable contact and the first fixed contact.

8. A relay in accordance with claim 7, characterized by the fact that one end of the winding of the first coil is connected to the first fixed contact, its other end being connectable to one side of the power supply network, serving as a source of supply for a load to be controlled by the relay, while one end of the second coil is connected to the second fixed contact, its other end being connectable to the same said side of the network.

9. A relay in accordance with claim 5 or 6, characterized by the fact that said blade is mounted in cantilever at the opposite end to that having the movable contact, the blade having a terminal at its fixed end.

10. A relay in accordance with claim 6, characterized by the fact that said magnet is mounted on the blade.

11. A relay in accordance with claim 5 or 6, characterized by the fact that said blade is freely pivoted about a fixed point.

12. A relay in accordance with claim 11, characterized by the fact that said pivot point is along the length of said blade which is equipped with a second movable contact at one opposite end to the first movable contact, said relay also comprising third and fourth movable contacts in the first and second configurations, respectively, which are determined by two angular positions of pivoting of said blade.

13. A relay in accordance with claim 12, characterized by the fact that said third and fourth fixed contacts are both connected to a terminal to be connected to a power supply network which supplies both the load or loads being controlled by the relay and the energizing circuits of the electromagnetic devices.

14. A relay in accordance with claim 12 or 13, characterized by the fact that said pivot point is determined by a transverse shaft means on which the referred plate is mounted, at least one separate actuating blade carrying said permanent magnet being mounted transversely on said shaft means in association with said electromagnetic devices.

1 5. A relay in accordance with claim 14, characterized by the fact that said actuating blade has a permanent magnet mounted on each of its ends, said first electro-magnetic device comprising two coils with respective ferromagnetic nuclei, mounted permanently on the opposite sides of the actuating blade, at its opposite ends, for cooperating with the referred permanent magnets, respectively.

1 6. A relay in accordance with claim 15, characterized by the fact that each one of said two coils has one end of its winding connected to the second fixed contact and its other end connectable to one side of the power supply network.

1 7. A relay in accordance with claim 12 or 13, characterized by the fact that each one of said means for making said blade assumes and maintains the first or second configuration respectively, comprising a fixed solenoid, a movable core and a permanent magnet, said movable core being mounted so as to accompany the movement of said plate and said permanent magnet cooperating, in the respective configuration, with a metallic part which also accompanies the movement of said blade.

1 8. Electrical plug or socket comprising a housing of insulating material wherein are mounted a pair of terminals for connection to two electric leads and a pair of main contacts for cooperation with the contacts of another socket or plug respectively, characterized in that said pair of terminals is connected to respective ones of said pair of main contacts through a cut-out device according to claim 1 so that on completing a circuit when said plug or socket is coupled to a corresponding socket or plug, there is a series connection including said terminals, said main contacts, said electromagnetic device and said movable and fixed contacts of the cut-out device comprising a low-resistance winding, said electromagnetic device comprising a lowresistance winding of a reduced number of turns about a core of ferromagnetic material whereby said cut-out device separates said contacts to assume said first configuration only when a short circuit current passes through said winding.

1 9. Electrical plug or socket according to claim 1 8 characterized in that said low-resistance winding is connected between one of said terminals and its associated main contact whereas said fixed and movable contacts of the cut-out device are arranged to complete, in said second configuration, a connection between the other of said terminals and its associated main contact.

20. Electrical plug or socket according to claim 1 8 characterized in that one of said terminals is directly connected to its corresponding main contact and the other of said terminals is connected to its associated main contact through a series connection comprising said lowresistance winding and the fixed and movable contacts of the cut-out device.

21. Electrical plug or socket according to claim 1 8 or 1 9 characterized by a single permanent magnet carried on said element, said magnet cooperating with said core to maintain said element in the second configuration and cooperating with a fixed member of ferromagnetic material to maintain said element in the first configuration.

22. Electrical plug or socket according to claim 21 characterized by manually operable means to remove said element from said first configuration and to assume said second configuration under the force of attraction between the said magnet and the said core.

23. Circuit breaker comprising an input terminal connected to an output terminal through a pair of contacts controlled by a bimetal element to protect against overloads characterized by including a cut-out device according to claim 1 in which said electromagnetic device comprises a low-resistance winding of a reduced number of turns about a core of ferromagnetic material and connected between said input and output terminals in series with said bimetal element and said movable and fixed contacts of the cut-out device whereby said cut-out device separates itself to assume said first configuration only when a short circuit current passes through said winding.

24. A relay substantially as herein described with reference to and as illustrated by Figure 1 of the accompanying drawings.

25. A relay substantially as herein described with reference to and as illustrated by Figure 2 of the accompanying drawings.

26. A relay as claimed in claim 25 but modified substantially as herein described with reference to and as illustrated by Figure 3 of the accompanying drawings.

27. A relay substantially as herein described with reference to and as illustrated by Figure 4 of the accompanying drawings.

28. A relay substantially as herein described with reference to and as illustrated by Figure 5 of the accompanying drawings.

29. A relay substantially as herein described with reference to and as illustrated by Figure 6 of the accompanying drawings.

30. A relay substantially as herein described with reference to and as illustrated by Figure 7 of the accompanying drawings.

31. An electrical supply socket substantially as herein described with reference to and as illustrated by Figure 8 of the accompanying drawings.

32. An electric plug substantially as herein described with reference to and as illustrated by Figure 9 of the accompanying drawings.

33. A relay provided with a cut-out device substantially as herein described with reference to and as illustrated by Figure 11 of the accompanying drawings.

33. A circuit cut-out device substantially as herein described with reference to and as illustrated by Figure 10 of the accompanying drawings.

34. A relay provided with a cut-out device substantially as herein described with reference to and as illustrated by Figure 11 of the accompanying drawings.

New Claims or Amendments to Claims filed on 3 December 1979.

Superseded Claims 1 to

34.

New or Amended Claims:

1. Electromagnetic cut-out device comprising at least one fixed contact, one movable contact mounted on an element capable of assuming a first configuration in which the movable contact is separated from said fixed contact, and a second configuration of contact between the movable contact and the fixed contact, an electromagnetic device to make said element assume said first configuration by forces of repulsion and a permanent magnet to maintain said element in the first configuration by forces of attraction, said electromagnetic device having an energizing circuit which includes the movable contact and said fixed contact, and second means to make said element assume and maintain said second configuration, including a permanent magnet to maintain the element in the second configuration by forces of attraction.

2. An electrical relay comprising a cut-out device according to claim 1 characterized in that said second means further comprises a second electromagnetic device to make said element assume the second configuration by means of forces of repulsion.

3. A relay in accordance with claim 2, characterized by the fact that each electromagnetic device comprises a fixed coil containing in its interior a core of ferromagnetic material, preferably soft iron.

4. A relay in accordance with claim 2 or 3, characterized by the fact that said element comprises a metal blade which carries said movable contact at one of its ends, said first and second electromagnetic devices being aligned with each other on opposite sides of said blade and between the ends thereof.

5. A relay in accordance with claim 4, characterized by the fact that a single permanent magnet is common to said first and second means, being used for maintaining the blade in each one of said configurations, said magnet being aligned with said electromagnetic devices to accompany the displacement of the blade between the two configurations, one magnetic pole facing the first electromagnetic device and the other pole facing the other electromagnetic device.

6. A relay in accordance with any one of the claims 1 to 5, comprising a second fixed contact which is engaged by the movable contact in the first configuration, characterized by the fact that the second electromagnetic device has an energizing circuit comprising the movable contact and the first fixed contact.

7. A relay in accordance with claim 6, characterized by the fact that one end of the winding of the first coil is connected to the first fixed contact, its other end being connectable to one side of the power supply network, serving as a source of supply for a load to be controlled by the relay, while one end of the second coil is connected to the second fixed contact, its other end being connectable to the same said side of the network.

8. A relay in accordance with claim 4 or 5, characterized by the fact that said blade is mounted in cantilever at the opposite end to that having the movable contact, the blade having a terminal at its fixed end.

9. A relay in accordance with claim 5, characterized by the fact that said magnet is mounted on the blade.

10. A relay in accordance with claim 4 or 5, characterized by the fact that said blade is freely pivoted about a fixed point.

11. A relay in accordance with claim 10, characterized by the fact that said pivot point is along the length of said blade which is equipped with a second movable contact at one opposite end to the first movable contact, said relay also comprising third and fourth movable contacts in the first and second configurations, respectively, which are determined by two angular positions of pivoting of said blade.

12. A relay in accordance with claim 11, characterized by the fact that said third and fourth fixed contacts are both connected to a terminal to be connected to a power supply network which supplies both the load or loads being controlled by the relay and the energizing circuits of the electromagnetic devices.

13. A relay in accordance with claim 11 or 12, characterized by the fact that said pivot point is determined by a transverse shaft means on which the referred plate is mounted, at least one separate actuating blade carrying said permanent magnet being mounted transversely on said shaft means in association with said electromagnetic devices.

14. A relay in accordance with claim 13, characterized by the fact that said actuating blade has a permanent magnet mounted on each of its ends, said first electromagnetic device comprising two coils with respective ferromagnetic nuclei, mounted permanently on the opposite sides of the actuating blade, at its opposite ends, for cooperating with the referred permanent magnets, respectively.

1 5. A relay in accordance with claim 14, characterized by the fact that each one of said two coils has one end of its winding connected to the second fixed contact and its other end connectable to one side of the power supply network.

1 6. A relay in accordance with claim 11 or 12, characterized by the fact that each one of said means for making said blade assumes and maintains the first or second configuration respectively, comprising a fixed solenoid, a movable core and a permanent magnet, said movable core being mounted so as to accompany the movement of said plate and said permanent magnet cooperating, in the respective configuration, with a metallic part which also accompanies the movement of said blade.

1 7. Electrical plug or socket comprising a housing of insulating material wherein are mounted a pair of terminals for connection to two electric leads and a pair of main contacts for cooperation with the contacts of another socket or plug respectively, characterized in that said pair of terminals is connected to respective ones of said pair of main contacts through a cut-out device according to claim 1 so that on completing a circuit when said plug or socket is coupled to a corresponding socket or plug, there is a series connection including said terminals, said main contacts, said electromagnetic device and said movable and fixed contacts of the cut-out device comprising a low-resistance winding, said electromagnetic device comprising a lowresistance winding of a reduced number of turns about a core of ferromagnetic material whereby said cut-out device separates said contacts to assume said first configuration only when a short circuit current passes through said winding.

1 8. Electrical plug or socket according to claim 1 7 characterized in that said low-resistance winding is connected between one of said terminals and its associated main contact whereas said fixed and movable contacts of the cut-out device are arranged to complete, in said second configuration, a connection between the other of said terminals and its associated main contact.

1 9. Electrical plug or socket according to claim 1 7 characterized in that one of said terminals is directly connected to its corresponding'main contact and the other of said terminals is connected to its associated main contact through a series connection comprising said lowresistance winding and the fixed and movable contacts of the cut-out device.

20. Electrical plug or socket according to claim 1 7 or 1 8 characterized by a single permanent magnet carried on said element, said magnet cooperating with said core to maintain said element in the second configuration and cooperating with a fixed member of ferromagnetic material to maintain said element in the first configuration.

21. Electrical plug or socket according to claim 20 characterized by manually operable means to remove said element from said first configuration and to assume said second configuration under the force of attraction between the said magnet and the said core.

22. Circuit breaker comprising an input terminal connected to an output terminal through a pair of contacts controlled by a bimetal element to protect against overloads characterized by including a cut-out device according to claim 1 in which said electromagnetic device comprises a low-resistance winding of a reduced number of turns about a core of ferromagnetic material and connected between said input and output terminals in series with said bimetal element and said movable and fixed contacts of the cut-out device whereby aid cut-out device separates itself to assume said first configuration only when a short circuit current passes through said winding.

23. A relay substantially as herein described with reference to and as illustrated by Figure 1 of the accompanying drawings.

24. A relay substantially as herein described with reference to and as illustrated by Figure 2 of the accompanying drawings.

25. A relay as claimed in claim 24 but modified substantially as herein described with reference to and as illustrated by Figure 3 of the accompanying drawings.

26. A relay substantially as herein described with reference to and as illustrated by Figure 4 of the accompanying drawings.

27. A relay substantially as herein described with reference to and as illustrated by Figure 5 of the accompanying drawings.

28. A relay substantially as herein described with reference to and as illustrated by Figure 6 of the accompanying drawings.

29. A relay substantially as herein described with reference to and as illustrated by Figure 7 of the accompanying drawings.

30. An electrical supply socket substantially as herein described with reference to and as illustrated by Figure 8 of the accompanying drawings.

31. An electric plug substantially as herein described with reference to and as illustrated by Figure 9 of the accompanying drawings.

32. A circuit cut-out device substantially as herein described with reference to and as illustrated by Figure 10 of the accompanying drawings.