Specification

Switching device, method of assembling or operating such switching device and electrical device comprising such switching device

The present invention relates to a switching device comprising at least one first contact member being moveable relative to at least one second contact member to reversibly electrically contact the at least one second contact member and to a method of assembling such a switching device. Furthermore, the present invention relates to a method of operating such a switching device, to an electrical circuit and an electrical device, both comprising such a switching device.

Switching devices such as contactors or relays are generally known and are generally electromagnetically actuated or, in rarer cases, gas pressure actuated.

In electromagnetic relays, an electromagnetic actuator can comprise an electromagnet and a corresponding armature or an electrifiable coil with a core, which is able to move in an electromagnetic field generated by the electrified coil, a so-called solenoid.

Known armatures are moveable in the electromagnetic field or are fixed relative to a moveable electromagnet and may themselves be a permanent magnet or an electromagnet .

Electromagnetic relays have been, in principle, known since 1926 and comprise a coil and iron core arrangement as electromagnet and a moveable armature, which is spaced apart from the electromagnet by a spring. An electromagnetic attractive force generated by the electromagnet, which is greater than a force generated by the spring -spring force-, moves the armature towards the electromagnet into an active position. A contact arm of the armature comprises a resiliently seated, moveable contact member. When the armature is in the active position, the moveable

contact member contacts a corresponding fixed contact member electrically conducting, such that, via both contact members , an electrical circuit is closed. The resilient seating of the moveable contact member provides an individual contact pressure.

The gap between the electromagnet and the armature causes an electromagnetic field loss, however, if the armature moves towards the electromagnet, the gap between the electromagnet and the armature decreases, such that the field loss is reduced. As a result, movement of the armature towards the electromagnet is accelerated, and, as movement of the armature causes movement of the moveable contact member towards the fixed contact member, undesired bounce of the contact members is caused, depending on the kinetic energy of the moveable contact member.

If an electrical current supplying the electromagnet is switched off, the electromagnetic field begins to collapse, resulting in reduction of the electromagnetic attractive force. As soon as the electromagnetic force falls below the spring force, the armature begins to move towards an inactive position due to the spring force. As a result, the moveable contact member is also moved towards an open position, such that the electrical circuit opens. However, normally the electromagnetic field is at least partially maintained for a certain span of time following the switch off of the electrical current, so that movement of the contact members into the open position, which results in opening of the electrical circuit, is undesirably delayed or even impossible.

Undesired opening of the contact members against an action of a contact spring of the moveable contact can result from a force, which is exerted by an electrical current in a conductor. The force is proportional to the current intensity, and whereas the current intensity increases linearly, the force is squared. Therefore, a contact spring force is a limiting factor regarding a maximum current flow through the conductor, if an undesired opening of the contact members based on the force exerted by the conducted electrical current is to be prevented. In order to bring the contact members in contact, i.e. close the contact, the

contact spring force must be overcome by the electromagnetic actuating means, by which an "allowed" contact spring force and also the maximum current flow through the conductor is limited.

As a result, the relays comprising such electromagnetic actuating means are generally large, have a high energy consumption and their manufacture is cost intensive. In addition, they suffer from an undesired dissipation of heat, and large dimensions of the electromagnetic actuators can result in electromagnetic interference, which may undesirably affect other electrical circuits and/or devices .

However, if the electromagnetic actuating means have reduced dimensions, the performance of the relay, particularly regarding a current carrying capacity of the electrical circuit and/or the contacts, is limited.

Furthermore, mechanical shock, vibration, electrical effects or the like can cause undesired opening of the contact, which can result in relay failure, breakdown of the current circuit, loss of contact material et cetera.

In addition, the loss of contact material and the reduction of a thickness of the contact members associated therewith results in a reduced contact spring force, which, again, causes an accelerated loss of contact material. Therefore, in order to prevent early failure of the relays, the contact member thickness is dimensioned such that a standard lifetime of the relay is not shortened. This adds to the manufacturing costs, particularly if the contact members consist of expensive materials such as silver or the like.

It is therefore desirable to have an alternative switching device which overcomes or at least alleviates at least one of the above mentioned disadvantages, which is achieved by the present invention.

In a first aspect of the invention there is provided a switching device, for example a contactor or relay, which may comprise at least one first contact member being moveable relative to at least one second contact member to reversibly contact the at least one second contact member, particularly to contact the second contact member electrically conducting. At least one latching means may be adapted to hold at least a part of the at least one first and second contact members in electrically conducting contact. This is particularly advantageous for reducing detrimental effects of external factors, which may be mechanical or physical factors, such as vibration, agitation, temperature, mounting direction of the switching device (e.g. upside down etc.) . Detrimental effects of electrical factors can also be reduced. Electrical factors, which can be tested by "make and break" tests etc. , include for example arcing in connection with undesired opening/and or closing of the contact, which results in reduction ^' of a contact member lifespan, or the like.

The term "electrically conducting contact" is to be understood as to relate to a contact having an ability to conduct an electrical current, and an expression similar to the term "to hold • the contact members in conducting contact" as to relate to at least partially assisting in holding the contact members in conducting contact, directly or indirectly. The first and second contact members contact, e.g. abut, each other in a closed position and enclose a gap if they are in an open position. The first contact member can be a moveable contact member and the second contact member can be a fixed or a moveable contact member. In addition, the term "connected with" is used to describe a direct connection or an indirect connection via at least one intermediate part or element, whereas the terms "connected to" and "engage" are used to describe a direct connection and/or interaction. Furthermore, if hereinbefore or hereinafter the term "first (/second) contact member" is used, this term shall be understood as to relate to at least one (first/second) contact member, e.g. one, two, three or a multiplicity of contact member (s) .

A first electrical circuit may be establishable or de-establishable, e.g. may be closed or opened, by moving the first and second contact members in the closed or open position, respectively .

Preferably, the first contact member is moveable by at least one first actuating means . The first actuating means may be an electromagnetical, electromechanical or mechanical actuating means. The dimensions of the first actuating means can be minimised or at least reduced, which results in a smaller size of the switching device, as the latching means holds the contact members in conducting contact. Furthermore, the "smaller" first actuating means has a reduced energy consumption and a heat dissipation is also advantageously reduced. As a result, manufacturing and operation costs are reduced.

If the first actuating means is an electromagnetical actuating means, it may comprise a first and second part or a moveable and a fixed part . At least one of the moveable or fixed part is adapted to generate a force, for example an electromagnetic force, resulting in relative displacement of the moveable part, e.g. at least one of the first and second parts. The first contact member can be directly or indirectly moved by the at least one moveable part, for example via at least one intermediate member. As will be appreciated, indirectly moving the first contact member advantageously provides a possibility to more flexible arrange components of the switching device and to adaptation of the switching device, a housing of the latter etc., to different requirements regarding size and/or shape.

The moveable or fixed part of the electromagnetical actuating means may be an electromagnet, e.g. comprise a coil and a core, and the fixed or moveable part may be a corresponding part, for example an armature such as an anchor or the like. Alternatively, the moveable and/or fixed part may be a permanent magnet.

The latching means is adapted to limit movement of the moveable part, the first contact member or a combination thereof, to hold

the first and second contact member in electrically conducting contact. Additionally or alternatively, the latching means may be adapted to limit movement of any other moveable part being actively or passively involved in relative movement of the first and second contact members, such that the first and second contact members are held in conducting contact.

In operation, the latching means can be connected with at least one of the first and second contact members to hold the first and second contact members in conducting contact. This is particularly advantageous, as an effect of mechanical factors such as shock, vibration or the like and/or of a mounting direction (e.g. upside down) on the conducting contact (s) is (are) minimised or at least reduced. Furthermore, as opening of the contact member (s) due to the force generated by the electrical current in the conductor is minimised or at least reduced, the contact member (s) have a prolonged lifetime and/or can have reduced dimensions, particularly a reduced thickness, which results in a cost reduction.

The latching means can be adapted to be connected with the first and second contact members, such that the latching means, particularly a retaining means of the latching means, is able to engage the first and second contact members . The retaining means may have at least one recess provided for receiving the first and second contact members when contacted. For example, the retaining means can be U-shaped such that, if the contacting first and second contact members are connected with the retaining means, a first part of an inner surface of the retaining means engages a top surface of the first contact member and/or a second part of the inner surface of the retaining means engages a bottom surface of the second contact member.

Advantageously, if the first and second contact members are held in conducting contact by the latching means, the first actuating means can be at least partially deactivated, which results in saving of energy and in a reduction of electromagnetic disturbance and/or heat generated by the first actuating means, or

by elements associated therewith, e.g. a first actuating means control circuit - main control circuit - or the like. Furthermore, as the first actuating means merely has a function in moving the first and second contact members and is not essentially required for, or is at least assisted by the latching means in, maintaining the contact of the contact members, the first actuating means can have smaller dimensions.

In embodiments, the at least one intermediate member is adapted to be connected with, e.g. to engage with, the first actuating means. For example, the intermediate member may be at least one transmission means, transmission assembly, lever, resilient means, or the like. Additionally, the intermediate member may be adapted to move the first contact member directly or indirectly. The latching means may be adapted to be connected with, e.g. to engage with, at least a part of the intermediate member and can thereby limit relative movement of the first contact member, such that the first and second contact members are held in conducting contact .

In a preferred embodiment, at least one second actuating means is adapted to actuate at least a part of the latching means. The second actuating means may be controlled by at least one control circuit, which is particularly advantageous for automatically or at least semi-automatically actuatable latching means.

The second actuating means may be an electromagnetical, an electromechanical and/or a mechanical actuating means . If the second actuating means is an electromagnetical actuating means, it may comprise at least one coil and core arrangement, e.g. an electromagnet, adapted to generate an electromagnetical force to actuate the latching means directly or indirectly. Advantageously, the second actuating means has a smaller size and/or a lesser energy consumption compared with the first actuating means, which results in a reduction of size and heat dissipation. This is particularly advantageous if the energy supply to the first actuating means, the second actuating means or both actuating means is switched off, if the first and second contact members

are held in conducting contact by the latching means. It will be appreciated that, if the energy supply to the latching means is switched off, the latching means will continue to hold the contact members in contact (active position) until a resetting of the latching means into a position in which the first contact member is moveable relative to the second contact member (an inactive position of the latching means) is triggered.

Alternatively, if the second actuating means is an electro- mechanical actuating means, it may be or may comprise at least one motor, for example an AC motor, a DC motor, a universal motor, an induction motor, a stepper motor, a linear motor or the like, or a combination thereof. A motor can be easily adapted to different applications and requirements. Furthermore, elec- tromagnetic interference with electrical circuits and/or electrical devices due to electromagnetic fields generated by electromagnets is reduced and/or can more easily be shielded.

If the motor is a stepper motor, it can advantageously be precisely controlled and/or positioned, and if the motor is a linear motor, a high acceleration is advantageously provided.

In a preferred embodiment, the first contact member is moveable by at least one first force and the latching means is adapted to exert at least one second force, i.e. a counterforce to the first force. Advantageously, if the counterforce equals or exceeds the first force, the first and second contact members are held in electrically conducting contact.

The first force may be applied by the first actuating means, e.g. at least one first resilient means, particularly a spring or the like.

Additionally or alternatively, the switching device may comprise at least one reset means, e.g. a second resilient means . The reset means is adapted to reset at least a part of the latching means into an inactive position. The resetting can be achieved by moving the latching means, or at least a part thereof, into a position,

in which the first contact member is moveable relative to the second contact member. Advantageously, at least a part of the latching means is moveable by the second actuating means from the inactive position into the active position, and is moveable from the active into the inactive position by the reset means . It will be appreciated that, if the second resilient means, e.g. a spring or the like, functions as the reset means, the energy consumption and undesired effects associated therewith, such as heat dissipation etc. , are advantageously reduced.

In a second aspect of the invention there is provided a method of assembling a switching device as hereinbefore and hereinafter described, comprising the step of mounting to the switching device at least one latching means. The at least one latching means is provided for at least partially holding the at least one first and second contact members in electrically conducting contact, particularly when the at least one latching means is activated. For example, the latching means can be mounted such that at least a part of the first and second contact members can be held in electrically conducting contact for a preset or variable time.

In a third aspect of the invention there is provided a method of operating the switching device as hereinbefore and hereinafter described, wherein the at least one latching means is holding the at least one first and second contact members in electrically conducting contact, particularly when the at least one latching means is activated. The latching means may be controlled by at least one control circuit. In addition, the at least one control circuit may be directly or indirectly connected with the main control circuit, such that activation and/or deactivation of one of the first actuating means and the latching means affects activation and/or deactivation of the other.

In a further aspect of the invention there is provided an electrical circuit comprising at least one switching device as hereinbefore and hereinafter described. In addition, the electrical circuit may comprise at least one electrical load.

In a still further aspect of the invention there is provided an electrical device, for example a control unit, automation system, control cabinet or the like, comprising at least one switching device as hereinbefore and hereinafter described and/or comprising an electrical circuit comprising at least one such switching device .

An embodiment of the present invention will hereinafter be described with reference to the accompanying drawings by way of example only, wherein

FIG 1 shows a schematic representation of a switching device according to the present invention,

FIG 2 shows a schematic longitudinal cut view of an assembly comprising an electromagnetic relay according to the state of the art,

FIG 3 shows a schematic longitudinal cut view of an embodiment of the switching device according to the present invention, having a first and second contact member in an open position,

FIG 4 shows a schematic longitudinal cut view of the switching device of FIG 3 having a first and second contact member in a closed position,

FIG 5 shows a schematic longitudinal cut view of a part of an alternative embodiment of the switching device according to the present invention having first and second contact members in an open position, and

FIG 6 shows a schematic longitudinal cut view of the switching device of FIG 5 having first and second contact members in a closed position.

PIG 1 shows a schematic representation of an assembly 10 comprising a switching device 12 according to the present invention. The switching device 12 comprises a first and a second contact member 14, 16 adapted to be moveable relative to each other by a first actuating means 18. The first actuating means 18 is controlled by a main control circuit 18a.

A first electrical circuit 20 is established (closed) , if the first and second contact members 14, 16 are in electrically conducting contact, i.e. in a closed position, and the first electrical circuit 20 is de-established (opened) , if the contact members 14, 16 are spaced apart such that they are not in electrically conducting contact, i.e. are in an open position. A latching means 22, at least a part of which is moveable by a second actuating means 24, is adapted to hold the first and second contact members 14, 16 in electrically conducting contact. The latching means 22 is under control of a control circuit 26 and is adapted to limit relative movement of the first contact member 14 directly, i.e. the latching means 22 can be adapted to be connected with at least a part of the first contact member 14, or indirectly, i.e. the latching means 22 can be adapted to be connected with at least a part of the first actuating means 18.

It will be appreciated that any movement of any other part or component of the assembly 10, by which relative movement of the first contact member 14 towards a position, in which the first and second contact members 14, 16 are not in electrically conducting contact, is facilitated, may be limited by the latching means 22.

In FIG 2, a schematic longitudinal cut view of the assembly 10 comprising an electromagnetic relay 28 according to the prior art is shown. The relay 28 opens or closes the first electrical circuit 20 (shown in FIG 1) , which is connected with the second contact member 16 via a first and second conductor 30, 32 of the assembly 10.

A first actuating means 18 of the relay 28 has a first part and a corresponding second part, shown here as a moveable and a fixed part 34, 36. The fixed part 36, which comprises an electromagnet

38 with a coil 40 and core 42, e.g. an iron core 42, is affixed to a base member 44 of a housing 45 of the assembly 10, and the moveable part 34 is a moveable armature, which is spaced apart from the electromagnet 38 by a resilient means 46, shown here as a spring.

The first contact member 14 is shown here as a contact bridge 48, which comprises a first and second moveable contact 50, 52, which are respectively located on opposite end portions of the contact bridge 48. The contact bridge 48 is connected with the moveable part 34 via a spring 54, which is connected to a top portion 56 of a connecting means 58 connected with the moveable part 34.

The second contact member 16 is shown here as a first and second fixed contact 60, 62 connected with the first and second conductor 30, 32, and the first fixed contact 60 corresponds with the first moveable contact 50 and the second fixed contact 62 corresponds with the second moveable contact 52.

In FIG 3 a schematic longitudinal cut view of the assembly 10 comprising an embodiment of the switching device 12 of the present invention is shown, wherein the moveable and fixed parts 34, 36 of the switching device are in an open position. In this example, the switching device 12 is partially similar to the relay 28 as shown in FIG 2.

The switching device 12 further comprises the latching means 22 adapted to hold the first and second contact members 14, 16 in electrically conducting contact. In FIG 3, the latching means 22 is shown in an inactive position, allowing relative movement of the moveable and fixed part 34, 36.

In this particular embodiment, a latching means housing 70 comprising the latching means 22 is affixed to the housing 45 of the assembly 10. However, the latching means 22 and/or the latching means housing 70 may be affixed to any other suitable part or component related to or being part of the assembly 10.

In this embodiment, the second actuating means 24 is shown as an electromagnetic actuating means comprising a coil - second coil 72 - and a moveable core - second core 74. A switch contact 76, which is shown in a closed position in which it is electrically contacting a first and second control contact 78, 80 of the main control circuit 18a, is located on one end of the second core 74, and a retaining means 82 is located on the opposite end. The retaining means 82 is inactive, such that the first contact member 14 can be moved relative to the second contact member 16. Switch contact 76 and first and second control contacts 78, 80 resemble a control switch for controlling the main control circuit 18a, with which an electrical energy source 84 is connected.

Alternatively, the first, second or both actuating means 18, 24 is, or comprises, at least one motor. Examples of a suitable electromotor include an AC motor, a DC motor, a universal motor, an induction motor, a stepper motor, a linear motor or a combination thereof .

In FIG 4 a schematic longitudinal cut view of the switching device

12 of FIG 3 is shown, wherein the first and second contact members 14, 16 are in electrically conducting contact. In the present example this is achieved by the moveable and fixed parts 34, 36

being in a closed position, i.e. contacting each other. However, it will be appreciated that the closed position of the moveable and fixed part 34, 36 can be any position in which the first and second contact members 14, 16 contact each other.

The latching means 22, particularly the retaining means 82 of the latching means 22, is active, i.e. the retaining means 82 engages a corresponding surface 86 of the moveable part 34. Thereby, a movement of the moveable part 34 towards the open position is limited, and, as a result, the first and second contact members 14, 16 (shown in FIG 1) are held in conducting contact. The latching means 22 exerts a second force which is a counterforce to the first force, by which the first contact member 14 is moveable .

When the latching means 22 is active, the switch contact 76 is spaced apart from the first and second control contacts 78, 80, such that the switch of the main control circuit 18a is opened. Due to the opening of the main control circuit 18a switch, the first actuating means 18 is deactivated.

A schematic longitudinal cut view of parts of an alternative embodiment of the switching device 12 having first and second contact members 14, 16 in an open position, is shown in FIG 5.

In principle, the switching device 12 is similar to the switching device 12 as shown in FIG 3, however, in this embodiment, one latching means 22 is adapted to hold three first contact members 14, 14a, 14b in contact with corresponding second contact members 16, 16a, 16b. The first contact members 14, 14a, 14b have first moveable contacts 50, 50a, 50b and the second contact members 16, 16a, 16b have first fixed contacts 60, 60a, 60b. The connecting means 58 is adapted to move the three first contact members 14, 14a, 14b relative to the second contact members 16, 16a, 16b.

The moveable second core 74 of the latching means 22 is connected to a moveable means 92, e.g. an elongate transmission member, which is connected with retaining means 82, 82a, 82b in an inactive position. Each of the retaining means 82, 82a, 82b in the inactive position is positioned such that relative movement of the first contact member 14, 14a, 14b is possible.

FIG 6 shows a schematic longitudinal cut view of the switching device 12 as shown in FIG 5 , with first and second contact members 14, 16 in a closed position.

As the first contact members 14, 14a, 14b electrically contacts the respective second contact members 16, 16a, 16b, electrical conduction via the contacting first moveable and second fixed contacts 50, 50a, 50b, 60, 60a, 60b possible.

The latching means 22 is activated, and the retaining means 82, 82a, 82b is positioned by the moveable means 92, such that each of the retaining means 82, 82a, 82b engages a corresponding first contact member 14, 14a, 14b, respectively. As a result, the first and second contact members 14, 14a, 14b, 16, 16a, 16b are held in conducting contact .

Operation of the latching means 22 will now be briefly described with reference to FIG 1.

Controlled by the main control circuit 18a, the first actuating means 18 is moved from an inactive to an active position. In connection with this movement, e.g. due to a direct or indirect coupling of the first actuating means 18 and the first contact member 14 , the latter is moved towards the second contact member 16 until the first and second contact members 14, 16 contact each other electrically conducting; the first electrical circuit 20 is closed. The latching means 22 is actuated by the second

actuating means 24 and is shown as having connected with the first contact member 14. Additionally or alternatively, the latching means 22 can be connected with at least a part of the first actuating means 18 and/or any other moveable part or component of the assembly 10, such that movement of the first contact member 14 into a position, in which the first and second contact members 14, 16 are not connected electrically conducting, is prevented. When the first and second contact members 14, 16 are held in conducting contact by the latching means 22, the first actuating means 18 can be deactivated, e.g. in connection with the activation and/or deactivation of the latching means 22.

For example, the latching means 22 engages the first contact member 14, when the latter is in conducting contact with the ^" second contact member 16. Thereby, the first and second contact members 14, 16 are held in conducting contact, if the first actuating means 18 is switched off.

In operation, the moveable part 34 of the first actuating means 18 is moved relative to the fixed part 36, such that the first contact member 14 is brought into contact with the second contact member 16. The latching means 22 engages the moveable part 34, such that the first and second contact members 14, 16 are held in conducting contact ; in particular, the retaining means 82 (e.g. shown in FIG 4) of the latching means 22 engages a corresponding surface 86 (as shown in FIG 4) of the moveable part 34. Thereby, movement of the moveable part 34 into the inactive position is inhibited or at least limited if the first actuating means 18 is switched off, and the first and second contact members 14, 16 are held in contact.

Referring to figures 3 and 4, an example of operation of the latching means 22 will now be briefly described.

The first actuating means 18 is deactivated in connection with the movement of the second core 74 of the latching means 22: The switch contact 76 is moved from a closed position, in which it contacts the first and second control contact 78, 80 of the main

control circuit 18a electrically conducting (the main control circuit 18a is closed) , into an open position, in which it does not contact the control contacts 78, 80 (the main control circuit 18a is open) .

A reset means, e.g. a second resilient means, such as a spring or the like, which may be comprised by the assembly 10, may move the retaining means 82, 82a, 82b from an active position into an inactive position, i.e. into a position in which the movement of the first contact member 14 is substantially not limited by the latching means 22. Particularly, the retaining means 82, 82a, 82b is rest by the reset means in connection with an activation of the first actuating means 18.

It will be appreciated that various modifications may be made to the invention as hereinbefore and hereinafter described without departing from the scope thereof.

In essence, the present invention relates to a switching device

12 comprising at least one first contact member 14 being moveable relative to at least one second contact member 16 to reversibly electrically contact the at least one second contact member 16, wherein at least one latching means 22 is adapted to hold the at least one first and second contact members 14, 16 in electrically conducting contact, to a method of assembling such a switching device 12 comprising the step of mounting to the switching device 12 at least one latching means 22, and wherein the latching means 22 is provided for at least partially holding the first and second contact members 14, 16 in electrically conducting contact, when activated, to a method of operating such a switching device 12, wherein the at least one latching means 22 is holding the at least one first and second contact members 14, 16 in electrically conducting contact, when activated, to an electrical circuit comprising at least one such switching device 12 and to an electrical device comprising at least one such switching device 12 and/or the electrical circuit.

Reference signs

10 assembly

12 switching device 14 first contact member

14a first contact member

14b first contact member

16 second contact member

16a second contact member 16b second contact member

18 first actuating means

18a main control circuit

20 first electrical circuit

22 latching means 24 second actuating means

26 control circuit

28 relay

30 first conductor 32 second conductor 34 moveable part

36 fixed part

38 electromagnet 40 coil

42 core 44 base member

45 housing

46 resilient means

48 contact bridge

50 first moveable contact 50a first moveable contact

50b first moveable contact

52 second moveable contact

54 spring

56 top portion

58 connecting means

60 first fixed contact0a first fixed contact0b first fixed contact

62 second fixed contact

70 latching means housing

72 second coil

74 second core

76 switch contact

78 first control contact

80 second control contact

82 retaining means 2a retaining means 2b retaining means

84 energy source

86 corresponding surface

92 moveable means