WO2015162508A1

WO2015162508A1 - Electrical switch

Info

Publication number: WO2015162508A1
Application number: PCT/IB2015/052264
Authority: WO
Inventors: Michael William LIEBENBERG
Original assignee: Circuit Breakers Ind Ltd
Current assignee: Circuit Breakers Ind Ltd
Priority date: 2014-04-25
Filing date: 2015-03-27
Publication date: 2015-10-29
Anticipated expiration: 2016-10-25

Abstract

This invention relates to an electrical switch and more particularly but not exclusively, to a make first break last electrical switch. The switch (10) includes an electrical contact set comprising a first, stationary contact (16) and a second, displaceable contact (22), the displaceable contact being displaceable between a connected position in which the contacts abut, and a disconnected position in which the contacts are spaced apart. The switch also includes a switching mechanism for displacing the second contact between the connected and disconnected positions, the switching mechanism including a handle arrangement (31) which is displaceable between an off position, in which the second contact (22) is in the disconnected position, and an on position, in which the second contact (22) is in the connected position. The second contact (22) is displaced from the disconnected position to the connected position before the handle arrangement (31) reaches the on position when displaced from the off position, and in that the second contact (22) is displaced from the connected position to the disconnected position when the handle arrangement (31) is already partially displaced away from the on position towards the off position.

Description

ELECTRICAL SWITCH

BACKGROUND TO THE INVENTION

THIS invention relates to an electrical switch and more particularly but not exclusively, to a make-first-break-last electrical switch.

In electrical engineering, a switch is an electrical component that can break an electrical circuit by interrupting the current or diverting it from one conductor to another. The most common form of switch is a manually operated electromechanical device with one or more sets of electrical contacts, which are connected to external circuits. Each set of contacts can be in one of two states. The set of contacts can be "closed", meaning the contacts are touching and electricity can flow between them, or "open", meaning the contacts are separated and the switch is non-conducting. The mechanism actuating the transition between these two states may take various forms, and can for example be toggle-type flip switch mechanism. A circuit breaker is a special kind of automatically operated electrical switch designed to protect an electrical circuit from damage caused by overload currents or short circuit faults. Its basic function is to detect a fault condition and interrupt current flow. Unlike a fuse, which is actuated once and must then be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation. in an electrical connector assembly comprising mating electrical connectors and having a power or signal circuit and a ground circuit (such as an electrical switch, and including a circuit breaker), it is desirable that the neutral and/or ground circuit should in certain circumstances be made before the power or signal circuit when the connectors are mated. On the other hand, when the connectors are unmated the power or signal circuit should be broken before the ground and/or neutral circuit. In other words, it is desirable for the neutral connection to be made first and broken last.

In practice a number of identical switches are located adjacent one another, with one switch being a dedicated neutral switch, and with the remainder of the switches being the dedicated live switches. It will be appreciated that if the neutral switch is mechanically identical and connected to the live switches, the neutral and live contacts will all be made at the same time if the flip switches are toggled at the same time. This can be undesirable, in that the flip switches of the adjacent switches are in practice connected to one another and the entire circuit breaker assembly is therefore toggled in one single action.

It is accordingly an object of the invention to provide an electrical switch that will, at least partially, alleviate the above disadvantages. it is also an object of the invention to provide an electrical switch which will incorporate a useful alternative switch with existing electrical switches in an integrated product SUMMARY OF THE INVENTION

According to the invention there is provided an electrical switch including: an electrical contact set comprising a first, stationary contact and a second, dispiaceable contact, the displaceable contact being dispiaceable between a connected position in which the contacts abut, and a disconnected position in which the contacts are spaced apart; and

a switching mechanism for displacing the second contact between the connected and disconnected positions, the switching mechanism including a handle arrangement which is displaceable between an OFF position, in which the second contact is in the disconnected position, and an ON position, in which the second contact is in the connected position;

characterized in that the second contact is displaced from the disconnected position to the connected position before the handle arrangement reaches the ON position when displaced from the OFF position, and in that the second contact is displaced from the connected position to the disconnected position when the handle arrangement is already partially displaced away from the ON position towards the OFF position. There is provided for the handle arrangement to displace the second contact from the disconnected position to the connected position when the handle arrangement is displaced about half of its travel from the OFF to the ON position. There is provided for the handle arrangement to displace the second contact from the connected position to the disconnected position when the handle arrangement is displaced about half of its travel from the on to the off position. There is provided for the handle arrangement to displace the second contact from the disconnected position to the connected position when the handle arrangement is displaced less than a corresponding handle arrangement of a conventional prior art switch. There is provided for the handle arrangement to displace the second contact from the connected position to the disconnected position when the handle arrangement is displaced more than a corresponding handle arrangement of a conventional prior art switch.

A linking arrangement may connect the handle arrangement to the second contact. The effective length of the linking arrangement may be adjustable.

Preferably the effective length is automatically and dynamically adjusted when the handle arrangement is displaced between the ON and ON positions. The effective length of the linking arrangement may be longer when the handle arrangement is in the Off position, than when the handle arrangement is in the OFF position.

Preferably the linking arrangement includes a rigid linking member.

Preferably the linking arrangement includes a resilient linking member.

A first end of the resilient linking member may be connected to the handle arrangement, and more particularly to a pin extending from the handle arrangement The second end of the resilient linking arrangement may be connected to the second contact, and more particularly to a pivotable arm on which the second contact is located.

A first end of the rigid linking member may include a slot In which the pin of the handling arrangement is slldeably received. The second end of the rigid linking member may be connected to the second contact, and more particularly to a pivotable arm on which the second contact is located. There is provided for the handle arrangement to exert a compressive force on the resilient linking member when the handle arrangement is displaced from the off position towards the on position, in order for the resilient linking member to displace the second contact, and in particular the pivotable arm of the second contact, from the disconnected position to the connected position. There is also provided for the resilient linking member to be compressed to the effective length of the rigid linking member upon further displacement of the handling arrangement towards the on position.

A further feature of the invention provides for the handling arrangement to include a handle, and a handle link, with the handle and the handle link being pivotably , but independently, mounted about the same pivot axis. The handle may have a lever end which is in use engaged by a user, and an actuating end which in use engages the handle link. The actuating end of the handle may be at least partially circular, and may include a triangular receiving aperture for receiving the end of the handle link therein, the receiving aperture approximating a removed sector of the circular actuating end. There is provided for the handle link to be pivotable inside the receiving aperture between a first position in which one side of the handle link abuts one side of the receiving aperture, and a second position in which an opposing side of the handle link abuts an opposing side of the receiving aperture. There is provided for the handle and the handle link to be angularly dispiaceabie relative to one another between 20 and 50 degrees, preferably between 30 and 45 degrees.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the invention is described by way of a non- limiting example, and with reference to the accompanying drawings in which: Figure 1 is a plan view of the electrical switch In accordance with the invention, the switch being in an ON position with the contact set connected; Figure 2 is a plan view of the electrical switch in accordance with the prior art, the switch being in an ON position with the contact set connected; Figure 3 is an enlarged perspective view of the linking arrangement of the electrical switch of Figure 1; Figure 4 is a plan view of the switch of Figure 1 in an OFF position; Figure 5 is a plan view of the switch of Figure 2 in an OFF position; Figure 6 is a plan view of the switch of Figure 1 with the handle arrangement being displaced from the OFF position towards the ON position up to the point where the contact set of the switch is in a connected position; Figure 7 is a plan view of the switch of Figure 2 with the handle arrangement being displaced from the OFF position towards the ON position up to the point where the contact set of the switch is in a connected position; Figure 8 is a plan view of the switch of Figure 1 with the handle arrangement being displaced from the ON position towards the OFF position, the handle arrangement being shown in the positon where the contact set of the switch is just about to be displaced to the disconnected position; Figure 9 is a plan view of the switch of Figure 2 with the handle arrangement being displaced from the ON position towards the OFF position, the handle arrangement being shown in the positon where the contact set of the switch is just about to be displaced to the disconnected position; Figure 10 is a perspective view of the handling arrangement of the electrical switch of Figure 1 , showing the handle link in a first position relative to the handle; and Figure 11 is a perspective view of the handling arrangement of the electrical switch of Figure 1, showing the handle link in a second position relative to the handle. DETAILED DESCRIPTION OF INVENTION

Referring to the drawings, in which like numerals indicate like features, a non-limiting example of an electrical switch in accordance with the invention is generally Indicated by reference numeral 10. It should be noted that the inventive concept can find application in various switches and switch configurations, and can specifically also be used in circuit breakers.

In order better to understand the invention, the prior art will first be described in more detail, with reference to Figures 2, 5, 7 and 9. The electrical switch shown in these figures are the same as that described with reference to the invention, with the exception of the design and configuration of the switching arrangement 30. The same numbering system will therefore be used for components that are identical. It should also be noted that components that are not required in order to explain the inventive concept are omitted for the sake of clarity. The electrical switch 10 shown in Figures 2, 5, 7 and 9 comprises a plastic housing which houses the contact set and the switching arrangement 100. A line terminal 12 is provided, and in use an external electric conductor (not shown) is connected thereto. The line terminal 12 is in electrical contact with a first contact 16 of the contact set. The first contact 16 is a stationary contact A load terminal 13 is provided in an opposite end of the casing, and in use an external electric conductor (not shown) is connected thereto. The load terminal 13 is in electric contact with a second contact 20 of the contact set via an electrical conductor 14 housed inside the housing 11.

A rigid and stationary carriage 15 is secured to the housing 11, and in use carries, inter alia, the switching arrangement 100 and the second contact arrangement 20. The second contact arrangement 20 includes a pivotable arm 21, with the contact 22 located on one end of the arm 21. An opposite end of the arm 21 is pivotably secured to the carriage 15 at a pivot point 21.1. A linking arm connecting point 21.2 is provided in a proximal zone of the pivotable arm. The pivotable ami is therefore pivotably displaceable between a connected position (Figure 2) in which the first contact 16 and the second contact 22 abut, and a disconnected position (Figure 5) in which the first contact 16 and the second contact 22 are spaced apart. The structure described above is the same for the invention and the prior art. The existing switching arrangement 100 known in the art will now be described in more detail. The switching arrangement 100 comprises a toggle type switch including a switch handle 101 and a switch body 102. The switch body is pivotably secured to the carriage 15, which allows the switch to be pivotably displaceable between an on position (Figure 2) and an off position (Figure 5). The switch handle 101 extends from the housing 11 in order to be accessible by a user of the switch. An actuating extension 103 extends radially outwardly from the circular switch body 102. A linking arm 104 connects the actuating extension 103 to the pivotable arm 21. More particularly, a first end 104.1 of the linking arm 104 is pivotably secured to the actuating extension, whereas an opposing second end 104.2 is pivotably secured to the connecting formation 21.2 provided on the pivotable arm 21 of the second contact arrangement 21. In use, displacement of the switch handle 101 translates in displacement of the actuating extension 103. The actuating extension 103 in turn pushes the pivotable arm downward (Figure 7) or upward (Figure 9) depending on the particular action that is taking place.

What is significant is that contact between the first contact 16 and the second contact 22 is made when the switching arrangement 100 has been displaced almost completely from the OFF position towards the ON position. Also, contact between the first contact 16 and the second contact 22 is broken almost immediately when the switching arrangement 100 is slightly displaced from the on position towards the OFF position. Making and breaking of the connections therefore occurs when the switch handle 101 is almost at the ON position. It follows that an accompanying neutral or ground switch needs to have slightly different switching characteristics if the set of switches are to adhere to the make-first-break-last characteristic. In particular, the same displacement of the switching arrangement 30 or 100 must result in the new switch (neutral / ground) making contact before the prior art switch (live), and also in the new switch (neutral / ground) breaking contact after the prior art switch (live). Making and breaking of the connection of the new switch must therefore take place when the switch handle 101 is located somewhere between the ON and OFF positions. The switching arrangement 30 that was designed to achieve this will be described in more detail below. The new and inventive electrical switch 10 shown in Figures 1 , 3, 4, 6, 8, 10 and 11 comprises a plastic housing which houses the contact set and the switching arrangement 30. A line terminal 12 is provided, and in use an external electric conductor (not shown) Is connected thereto. The line terminal 12 is in electrical contact with a first contact 16 of the contact set The first contact 16 is a stationary contact. A load terminal 13 is provided in an opposite end of the casing, and in use an external electric conductor (not shown) is connected thereto. The load terminal 13 is in electric contact with a second contact 20 of the contact set via an electrical conductor 14 housed inside the housing 11.

A rigid and stationary carriage 15 is secured to the housing 11, and in use carries, inter alia, the switching arrangement 100 and the second contact arrangement 20. The second contact arrangement 20 includes a pivotable arm 21, with the contact 22 located on one end of the arm 21. An opposite end of the ami 21 is pivotably secured to the carriage 15 at a pivot point 21.1. A linking arm connecting point 21.2 Is provided in a proximal zone of the pivotable arm. The pivotable arm is therefore pivotably dispiaceable between a connected position (Figure 1) in which the first contact 16 and the second contact 22 abut, and a disconnected position (Figure 4) in which the first contact 16 and the second contact 22 are spaced apart. The switch arrangement 30 of the new electrical switch 10 differs from the prior art switch arrangement 100 in a number of aspect, with the end goal being a configuration where the contacts connect or 'make' earlier compared to a conventional electrical switch during the OFF-ON switch sequence of the electrical switch 10, and where the contacts disconnect or 'break' later compared to a conventional electrical switch during the ON- OFF switch sequence of the electrical switch 10. The switch arrangement 30 includes a switch handle 31 extending from a disc-like switch body 32. The switch body 32 is located inside the housing 11 , and is pivotably connected to the carriage 15. The switch handle 31 protrudes from the housing 11 in order to be accessible by a user of the switch 10. As in the case of the prior art, the switch arrangement 30 also includes an actuating extension 34 (reference numeral 103 in the prior art switch) but in this case the actuating extension 30 is not integrally formed with the switch body 32. Instead, a first end 34.1 of the actuating extension is pivotably securable about the same pivot axis of the switch body 32. In addition, the switch body 32 includes a receiving aperture 33 for receiving the first end 34.1 of the actuating extension 34 therein. The receiving aperture 33 is in the form of an open sector that has been removed from the disc-like switch body 32. As can be seen in Figures 10 and 11 , the actuating extension 34 does not fit snugly inside this aperture 33, but can rather pivot between a first position in which one side of the actuating extension 34 abuts a first face 33.1 of the receiving aperture 33, and a second position in which an opposing side of the actuating extension 34 abuts an opposing, second face 33.2 of the receiving aperture 33. The importance of this configuration will become apparent when the displacement of the switching arrangement from an on (connected) position (Figure 1) to an OFF (disconnected) position (Figure 4) is discussed, as illustrated in Figure 8.

As is the case in the prior art switch, a linking arrangement 40 links the switch arrangement 30 with the second contact arrangement 20. However, the configuration of the link arrangement 40 is substantially different compared to the switch link 104 used in the prior art. In this case the linking arrangement comprises a first, resilient link member 41 and a second, rigid link member 42 that cooperate to form a composite link member having an automatically adjustable length. The resilient link member 41 has a first end 41.1 that is pivotably connected to the second end 34.2 of the actuating extension 34, and a second end 41.2 that is pivotably connected to the pivotabie arm 21 of the second contact arrangement 20, and more particularly to the connecting formation 21.2 on the pivotabie arm. In this example, the resilient link member is in the form of an undulating brass strip which can be lengthwise compressed when a sufficient compressive force Is exerted thereon. The rigid link member 42 has a first end 42.2 that is linked to the first end 41.1 of the resilient link member 41, and a second end 42.3 that is pivotably connected to the pivotabie arm 21 of the second contact arrangement 20, and more particularly to the connecting formation 21.2 on the pivotabie arm. As can be seen in Figure 3, a slot 42.1 is provided in the first end 42.2 of the rigid link member 42. A securing pin 43 that secures the first end 41.1 of the resilient link member 41 to the actuating extension 33 extends through this slot, and thus operatively links the rigid link member 42 and the resilient link member 41. The rigid link member 42 will therefore accommodate some compression (and hence contraction) of the resilient link member 41 , until the pin 43 abuts a bottom end of the slot 42.1, at which point the rigid link member 41 will act as a iimiter that will prevent further compression of the resilient link member 41. The effective length of the link arrangement 40 is therefore variable, and can vary between the length of the uncompressed resilient link member 41 (when the handle is in the off position) and the length of the rigid link member 42 (when the handle is in the on position). The effective length of the link arrangement is essentially variable because a resilient link member 41 is used. The rigid link member 42 acts as a limiter so as to provide a lower limit to the extent to which the length of the link arrangement can be reduced. The linking arrangement of the new switch is therefore longer than a conventional switch when the handle is in an off position, but the same length as a conventional switch then the handle is in an on position.

In use, when the switch handle 31 Is displaced from the off towards the on position (as seen in Figure 6) the effective length of the link arrangement will be that of the uncompressed resilient link member 41 , which is longer than the length of the conventional rigid link member 104 used in the prior art switch as described above. When the switch handle 31 is therefore displaced, the second contact arrangement 20 will be actuated early on in the displacement cycle between the off and on positions of the handle, and an early make or connection is ensured. The contact set connects when the handle is displaced roughly 20 degrees of the full 80 degree displacement. In other words, the second contact 22 will engage the first contact 16 when the switch handle 31 is displaced about 25% of the entire stroke of the switch handle 31. This is about 40 degrees before connection will take place when a conventional switch is used. The exact same handle displacement (if the two switches are placed side by side and the handles are displaced simultaneously) will thus result in the switch in accordance with the invention to make or connect before the conventional switch, resulting in a make first situation when the new switch is used for the neutral or ground connection.

Once the connection has been made, the pin 43 will engage the bottom of the slot 42.1, and further displacement of the switch handle 31 will not result in additional compression of the resilient link member 41. At the end of the cycle (Figure 1 and 2) the effective length of the link arrangement 40 mil be the same as the length of the switch link 104 of the conventional switch.

When the switch 10 is in the on position (Figure 1) the actuation extension 34 abuts the first face 33.1 of the receiving aperture 33 in the switch body 32, having been urged towards that position by said first face 33.1. When the switch handle 31 is now displaced towards the off position (Figure 8) the switch handle 31 will initially be displaced without any concomitant displacement of the actuating extension 34 due to the receiving aperture 33 allowing some relative movement of the switch handle 31 and the actuating extension 34. Only when the second face 33.2 of the receiving aperture engages the actuating extension 34 will the switch handle 31 begin to exert a force on the actuating extension 34. In this particular example this will happen at about a 50 degree (or 62%) displacement of the switch handle away from the on position. The distance or delay is determined by the included angle of the sector that defines the re ceiving aperture. With the conventional switch (Figure 9) the switching handle exerts a force onto the actuating extension immediately (the two components being integrally formed) and the break or disconnection takes place after a very small displacement of the switch handle. The exact same handle displacement (if the two switches are placed side by side and the handles are displaced simultaneously) will thus result in the switch in accordance with the invention to break or disconnect after the conventional switch, resulting in a break last situation when the new switch is used for the neutral or ground connection.

It will be appreciated that the above is only one embodiment of the invention and that there may be many variations without departing from the spirit and/or the scope of the invention.

Claims

CLAIMS: 1. An electrical switch including:

an electrical contact set comprising a first, stationary contact and a second, displaceable contact, the displaceable contact being displaceable between a connected position in which the contacts abut, and a disconnected position in which the contacts are spaced apart; and

a switching mechanism for displacing the second contact between the connected and disconnected positions, the switching mechanism including a handle arrangement which is displaceable between an OFF position, in which the second contact is in the disconnected position, and an ON position, in which the second contact is in the connected position,'

characterized in that the second contact is displaced from the disconnected position to the connected position before the handle arrangement reaches the ON position when displaced from the OFF position, and in that the second contact is displaced from the connected position to the disconnected position when the handle arrangement is already partially displaced away from the ON position towards the OFF position.

2. The electrical switch of claim 1 in which the handle arrangement displaces the second contact from the disconnected position to the connected position when the handle arrangement is displaced about half of its travel from the OFF to the ON position.

3. The electrical switch of claim 1 or claim 2 in which the handle arrangement displaces the second contact from the connected position to the disconnected position when the handle arrangement is displaced about half of its travel from the ON to the OFF position. The electrical switch of any one of the preceding claims in which the handle arrangement displaces the second contact from the disconnected position to the connected position when the handle arrangement is displaced to a lesser extent from the OFF position to the ON position than a corresponding handle arrangement of a conventional prior art switch. The electrical switch of any one of the preceding claims in which the handle arrangement displaces the second contact from the connected position to the disconnected position when the handle arrangement is displaced to a larger extent from the ON position to the OFF position than a corresponding handle arrangement of a conventional prior art switch. The electrical switch of any one of the preceding claims including a linking arrangement that connects the handle arrangement to the second contact. The electrical switch of claim 6 in which an effective length of the linking arrangement is adjustable. The electrical switch of claim 7 in which the effective length is automatically and dynamically adjusted when the handle arrangement is displaced between the off and on positions. The electrical switch of claim 7 or 8 in which the effective length of the linking arrangement is longer when the handle arrangement is in the off position, than when the handle arrangement is in the on position. The electrical switch of claim 7, 8 or 9 in which the linking arrangement includes a resilient linking member. The electrical switch of claim 10 in which a first end of the resilient linking member is connected to the handle arrangement. The electrical switch of claim 11 in which the first end of the resilient linking member is connected to a pin extending from the handle arrangement. The electrical switch of claim 10, 11 or 12 in which a second end of the resilient linking arrangement is connected to the second contact The electrical switch of claim 13 in which the second end of the resilient linking arrangement is connected to a pivotable arm on which the second contact is located. The electrical switch of claim 7 to 14 in which the linking arrangement includes a rigid linking member. The electrical switch of claim 15 in which a first end of the rigid linking member includes a slot in which a pin of the handling arrangement is slideably received. The electrical switch of claim 15 or 16 In which a second end of the rigid linking member is connected to the second contact. The electrical switch of claim 17 in which the second end of the rigid linking member is connected to a pivotable arm on which the second contact is located. The electrical switch of any one of claims 10 to 18 in which the handle arrangement is adapted to exert a compressive force on the resilient linking member when the handle arrangement is displaced from the off position towards the on position, in order for the resilient linking member to displace the second contact, and in particular the pivotable arm of the second contact, from the disconnected position to the connected position. The electrical switch of claim 19 in which the resilient linking member is compressed to the effective length of the rigid linking member upon further displacement of the handling arrangement towards the on position. The electrical switch of any one of the preceding claims in which the handling arrangement includes a handle and a handle link, with the handle and the handle link being pivotably, but independently, mounted about the same pivot axis. The electrical switch of claim 21 in which the handle has a lever end which is in use engaged by a user, and an actuating end which in use engages the handle link. The electrical switch of claim 22 in which the actuating end of the handle is at least partially circular, and includes a triangular receiving aperture for receiving the end of the handle link therein. The electrical switch of claim 23 in which the receiving aperture approximates a removed sector of the circular actuating end. The electrical switch of claim 24 in which the handle link is pivotable inside the receiving aperture between a first position in which one side of the handle link abuts one side of the receiving aperture, and a second position in which an opposing side of the handle link abuts an opposing side of the receiving aperture. The electrical switch of claim 25 in which the handle and the handle link are angularly displaceabte relative to one another between 20 and 50 degrees. The electrical switch of claim 26 in which the handle and the handle link are angularly displaceable relative to one another between 30 and 45 degrees.