Switching apparatus for an electrical switching device

Abstract

A switching apparatus for an electrical switching device is provided, comprising: a fixed contact, a moving contact, and a switching lever movable between an on and an off position. In the on position, the fixed contact and the moving contact are in contact. In the off position, the fixed contact and the moving contact are separated. The switching lever comprises a bent portion. The switching apparatus further comprises an upper link, a lower link, and a cross-bar assembly. The upper link is coupled to a lower link, the lower link is coupled to the cross-bar assembly, and the moving contact is mounted on the cross-bar assembly such that it rotates with the movement of the cross-bar assembly. The upper link comprises a notch. When the switching lever is moved from the on position towards the off position in a weld state in which the fixed contact and moving contact are welded together, the notch is configured to engage with the bent portion to prevent the switching lever from moving to the off position.

Description

[0001] Switching Apparatus for an Electrical Switching Device

[0002] Field

[0003] This relates to a switching apparatus for an electrical switching device. In particular, this relates to a switching apparatus configured to indicate the true state of an electrical circuit and a method of controlling the switching apparatus.

[0004] Background

[0005] The use of electrical switching devices, such as a Moulded Case Circuit Breaker (MCCB), in electrical circuits is known. Electrical switching devices typically comprise a switching apparatus which is used to open or close electrical circuits by connecting contacts in an electrically conducting manner, or by separating contacts in an electrically isolating manner.

[0006] A switching apparatus for an electrical switching device typically comprises a switching lever movable between an on position and an off position to indicate that the electrical contacts are connected or separated respectively. The switching lever is typically coupled to the moving contact such that the contacts are connected or separated by moving the switching lever.

[0007] However, when a large current flows through the electrical circuit due to a fault such as a short circuit or overload condition(s), it is possible that arcing may occur between the electrical contacts as they are separated. The arcing can produce high temperatures, which can cause melting of parts of the contacts. As such, the electrical contacts may become welded together. In a state or condition in which the contacts are welded together, they are still physically and electrically connected even when the switching lever has moved from the on position towards the off position. Therefore, the switching lever may provide a false indication of the state of the electrical switching device. In this case, a user of the electrical switching device faces a risk of suffering from an electric shock.

[0008] Therefore, regulations mandate that it must not be possible to move the switching lever of a switching apparatus to the off position when the electrical contacts are welded, hereafter referred to as being in a "weld state". Further, the switching lever must return to the on position when the contacts are in the weld state, such that a true indication of the state of the electrical switching device is given. US 8,993,912 B2 provides a switching apparatus for an electrical switching device comprising a stop configured to interact with the switching lever when the contacts are in the weld state. However, the arrangement is complex and requires a plurality of separate components.

[0009] It is therefore desirable to provide an alternative switching apparatus for an electrical switching device which prevents the switching lever from moving to the off position, and returns the switching lever to the on position, when the electrical contacts are in the weld state. In particular, it can be desirable to provide a switching apparatus which has a simplified structure and improved reliability.

[0010] Summary

[0011] A switching apparatus for an electrical switching device is provided as defined in the appended independent claim 1, with optional features defined in the dependent claims appended thereto.

[0012] In the following specification, a switching apparatus is provided which is configured to prevent a switching lever from indicating that the electrical circuit is off and to indicate that the electrical circuit is on when the contacts are in the weld state.

[0013] According to an embodiment, a switching apparatus for an electrical switching device comprises a fixed contact, a moving contact, and a switching lever movable between an on and an off position. In the on position, the fixed contact and the moving contact are in contact, and in the off position, the fixed contact and the moving contact are separated. The switching lever comprises a bent portion. The switching apparatus further comprises one or more links coupled to the moving contact. One of the link(s) comprises a notch (or protrusion). When the switching lever is moved from the on position towards the off position in a weld state (in which the fixed contact and moving contact are welded together), the notch is configured to engage with the bent portion to prevent the switching lever from moving to the off position. The link may also be termed herein an "upper link".

[0014] Optionally, the switching apparatus comprises a series of links coupled to the moving contact, the series of links including the link (or upper link), a lower link, and a crossbar assembly.

[0015] As such, a switching apparatus with a simple mechanism may be provided to prevent the switching lever from moving to the off position when the contacts are in the weld state. By using a switching apparatus in accordance with the embodiment, an electrical switching device may be provided with improved safety.

[0016] Optionally, the switching lever is moved from the on position towards the off position in a normal state in which the fixed contact and the moving contact are not welded together, and the upper link is configured to rotate such that the notch or protrusion does not engage with the bent portion. This arrangement ensures that the notch and the bent portion do not engage, and therefore the motion of the switching lever is not interfered with, under normal operating conditions.

[0017] Optionally, the switching lever is coupled to the moving contact such that when a force is applied to the switching lever to move the switching lever towards the on position, a force is applied to the moving contact such that the moving contact moves towards the fixed contact.

[0018] Optionally, the switching lever is coupled to the moving contact such that when a force is applied to the switching lever to move the switching lever towards the off position, a force is applied to the moving contact to separate the moving contact from the fixed contact.

[0019] The weld state occurs when the moving contact is welded to the fixed contact due to a failure in the switching apparatus e.g. due to fault occurrence.

[0020] In some examples the switching lever is coupled to the moving contact by a biasing member, optionally a spring. The switching lever is prevented from moving to the off position and the force applied to the switching lever is removed, the biasing member acts to move the switching lever back to the on position. As such, a switching apparatus with a simple and reliable mechanism may be provided to return the switching lever to the on position when the contacts are in the weld state. Therefore, an electrical switching device may be provided which indicates the true state of the electrical circuit. That is, an electrical switching device may be provided with improved safety.

[0021] Optionally, the biasing member and the link (or upper link) are coupled to the moving contact; this coupling can be direct or indirect. Optionally, the biasing member and the link (or upper link) are coupled to the lower link at a common pivot point and to the moving contact through the lower link and the cross-bar assembly, wherein in the normal state the biasing member acts to toggle the upper link. Toggling the upper link causes the upper link to rotate such that the notch or protrusion does not engage with the bent portion.

[0022] In a weld state or condition, the notch is configured to engage with the bent portion to prevent the switching lever from moving to the off position. By arranging the notch and bent portion in this way, a secure means of engagement between the components is provided. As such, an electrical switching device may be provided with improved reliability and robustness. Optionally, the bent portion comprises a slot, and the switching apparatus further comprises a cradle configured to enter or engage with the slot when the electrical switching device is in a TRIP state.

[0023] Optionally, the notch is formed integrally with the upper link. This arrangement provides a switching apparatus with a reduced number of component parts. For example, there is no need for an additional pin as required in previous switching apparatus'. As such, an electrical switching device may be provided which has a simple manufacturing process and reduced costs.

[0024] Optionally, the notch protrudes from an edge of the upper link.

[0025] Optionally, the bent portion is formed integrally with the switching lever. This arrangement provides a switching apparatus with a reduced number of component parts. As such, an electrical switching device may be provided which has a simple manufacturing process and reduced costs.

[0026] According to another embodiment of the invention, a method of operating an electrical switching device is provided. The method comprises moving a switching lever between an on and an off position. In the on position, a fixed contact and a moving contact are in contact, and in the off position, the fixed contact and the moving contact are separated.

[0027] The method further comprises, in response to moving the switching lever towards the off position when the device is in a normal operating condition, moving the moving contact coupled to the switching lever by toggling a link.

[0028] The method further comprises, when moving the switching lever from the on position towards the off position in a weld state in which the fixed contact and moving contact are welded together, restricting toggling of the link and thereby engaging a notch of the link with a bent portion of the switching lever to prevent the switching lever from moving to the off position. Optionally, when the device is in a normal operating condition, moving the moving contact coupled to the switching lever comprises moving the moving contact, which is coupled indirectly to the switching lever through the link, a lower link, and a cross-bar assembly, by toggling the link.

[0029] Optionally, when the device is in the weld state and the moving contact is welded to the fixed contact, movement of the link, the lower link, and the cross-bar assembly is restricted, thereby restricting toggling of the link.

[0030] Optionally, the method further comprises returning the switching lever to the on position in the weld state by means of a biasing member coupled to the switching lever.

[0031] Optionally, the method further comprises, in response to moving the switching lever from the on position towards the off position in the normal state in which the fixed contact and the moving contact are not welded together, rotating, by the toggling, the link such that the notch does not engage with the bent portion.

[0032] Brief Description of the Drawings

[0033] Fig. 1 shows a side view of an example switching apparatus, the switching apparatus in an on state.

[0034] Fig. 2 shows a side view of the switching apparatus of Fig. 1 in an off state.

[0035] Fig. 3 shows a side view of the switching apparatus of Fig. 1 in a weld state.

[0036] Fig. 4 shows a perspective view of an example switching lever of the switching apparatus of Fig. 1.

[0037] Fig. 5 shows a front view of an example link (or upper link) of the switching apparatus of Fig. 1.

[0038] Fig. 6 shows a flowchart of a method of operating a switching apparatus as described herein.

[0039] Like reference numerals refer to like features.

[0040] Detailed Description

[0041] Embodiments of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the present disclosure are shown. The same reference numbers indicate the same components throughout the specification.

[0042] This disclosure may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present disclosure to those skilled in the art.

[0043] It will be understood that, although the terms "first", "second," etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are labels, and are only used to distinguish one element from another element. For instance, a first element discussed below could be termed a second element without departing from the teachings of the present disclosure. Similarly, the second element could also be termed the first element.

[0044] With reference to Figs. 1 to 5, an example switching apparatus for an electrical switching device is described. The switching apparatus is configured to prevent an operating handle from indicating that the electrical circuit is off when the electrical contacts are in a weld state; the switching apparatus is instead configured to indicate that the electrical circuit is on when the electrical contacts are in a weld state.

[0045] A switching apparatus comprises an operating handle 60 movable between an on position (Fig. 1) and an off position (Fig. 2). The mechanism described with reference to these figures is understood to be exemplary only, and any suitable mechanism may be used to achieve the desired outcome that the switching apparatus is configured to prevent an operating handle from indicating that the electrical circuit is off when the electrical contacts are in a weld state due to the engagement of a bent portion and a notch / protrusion as described herein.

[0046] The operating handle 60 may be moved between the on and the off position by applying a force to the operating handle 60. When a force is applied to one end of the operating handle 60 (e.g. at the end near an operating knob 60a), the operating handle 60 is configured to rotate around a point at or towards the other end of the operating handle 60.

[0047] In this example the switching apparatus comprises an operating knob 60a mechanically connected to the operating handle 60. The operating knob 60a is provided at the end of the operating handle 60 to which a force may be applied. The force may be applied to the operating knob 60a, for example, directly by a user. The operating knob 60a may be formed integrally with the operating handle 60.

[0048] The operating handle 60 is coupled to a switching lever 30. The switching lever 30 is also movable between an on and off position.

[0049] The operating handle 60 is coupled to the switching lever 30 via a connecting link. In this example, the connecting link is in the form of a rod. However, it is not limited thereto and any suitable coupling member may be used as the connecting link.

[0050] The connecting link is configured to transfer a force applied to the operating handle 60 to the switching lever 30 to rotate the switching lever 30 around a first rotation point Pl. In this way, the switching lever 30 is moved between the on and the off position in response to actuation of the operating handle 60. The first rotation point Pl is formed at one end of the switching lever 30 and the connecting link is coupled to the other end of the switching lever 30. The switching lever 30 and the connecting link may be coupled to each other using a common connection pin, for example, a floating pin. However, any suitable coupling means may be used.

[0051] The switching apparatus further comprises a fixed contact 10 and a moving contact 20, the switching lever 30 being coupled to the moving contact 20 to cause movement of the moving contact 20 during a making / breaking operation of the switching apparatus.

[0052] When the switching lever 30 is in the on position, the fixed contact 10 and the moving contact 20 are in contact in an electrically conducting manner (Fig. 1). When the switching lever 30 is in the off position, the fixed contact 10 and the moving contact 20 are separated in an electrically isolating manner (Fig. 2). In other words, current can flow through an electrical circuit to which the switching apparatus is connected when the switching lever 30 is in the on position and the contacts are closed or touching (i.e. in physical and electrical contact), and cannot flow when the switching lever 30 is in the off position and the contacts are open or separated (i.e. are physically and electrically separated).

[0053] The switching apparatus further comprises an upper link 40, a lower link 50, and a cross-bar assembly. The upper link 40, lower link 50, and cross-bar assembly form a series of links. The cross-bar assembly is coupled to or carries the moveable contact 20. The upper link 40 may also be referred to herein simply as a "link". The upper link 40 is configured to be rotatable (with respect to the switching apparatus and the lower link 50) around a second rotation point P2.

[0054] The lower link 50 is configured to be rotatable (with respect to the switching apparatus and the upper link 40) around a third rotation point P3. The lower link 50 is coupled to the upper link 40 at the third rotation point P3. The lower link 50 may be coupled to the upper link 40 via a toggle lever pin.

[0055] The lower link 50 is configured to be rotatable (with respect to the switching apparatus and the cross-bar assembly) around a fourth rotation point P4. The lower link 50 is coupled to the cross-bar assembly at the fourth rotation point P4. The crossbar assembly is configured to be rotatable around a fifth rotation point P5 or central point of the cross-bar assembly.

[0056] As discussed above, the moving contact 20 is coupled to the cross-bar assembly. As such, the moving contact 20 is configured to move towards or away from the fixed contact 10 as the cross-bar assembly rotates around the fifth rotation point P5.

[0057] The upper link 40, the lower link 50, and the cross-bar assembly are configured to form a four-bar linkage assembly (or four-bar mechanism). The four-bar linkage assembly is configured such that rotation of the upper link 40 (by the switching lever 30) causes rotation of the lower link 50, which in turn causes rotation of the cross-bar assembly. In other words, the upper link 40 corresponds to an input link, the lower link 50 corresponds to a coupling link, the cross-bar assembly corresponds to an output link, and a line between the second rotation point P2 and the fifth rotation point P5 corresponds to a fixed link of the four-bar linkage assembly.

[0058] That is, the cross-bar assembly is configured to be rotated by the lower link 50 when the upper link 40 rotates. In this way, the moving contact 20 coupled to the cross-bar assembly is configured to move towards or away from the fixed contact 10 as a result of rotation of the upper link 40 (or "link"). The upper link 40 is rotated by a force applied to it by or via the switching lever 30. In other words, the switching lever 30 is configured to apply a force to the upper link 40 to rotate the upper link 40 around the second rotation point P2. As such, a force applied to the operating handle 60 is transferred to the upper link 40 to rotate the upper link 40. In this way, a force applied to the operating handle 60 moves the moving contact 20 towards or away from the fixed contact 10 through the switching lever 30 and the four-bar linkage assembly.

[0059] A biasing member (not shown) is coupled to the switching lever 30. In this example the biasing member is a mechanism spring, referred to herein as a spring, but it is not limited thereto. The biasing member may be any suitable biasing member configured to act in the manner described. One end of the spring is coupled to the switching lever 30. The spring may be coupled to the switching lever 30 at substantially the same position at which the connecting link is coupled to the switching lever 30. The other end of the spring is coupled to the upper link 40. The spring may be coupled to the upper link 40 at a common pivot point with the lower link 50. That is, the spring may be coupled to the upper link 40 at the third rotation point P3.

[0060] When the operating handle 60 is moved from the on to the off position, or from the off to the on position, the spring is configured to toggle the upper link 40. That is, the spring is configured to apply a force to the upper link 40, for example at the common pivot point, such that the upper link 40 rotates around the second rotation point P2.

[0061] That is, when the switching lever 30 moves from the on to the off position, or from the off to the on position, in a healthy (or normal) operating state, the spring is tensioned and configured to transfer the force applied to the switching lever 30 to the upper link 40 such that the upper link (or simply "link" rotates). Past the toggle point of the upper link 40, the tensioning force on the spring is removed. The restoring force of the spring acts on the upper link 40 at the common pivot point. The restoring force acts to further rotate the upper link 40 and thereby move the moving contact 20. In particular, the restoring force generates a torque which acts on the upper link 40. As such, the upper link 40 rotates around the second rotation point P2.

[0062] In a healthy operating state, the switching apparatus is turned on by applying a force to the operating handle 60 to rotate it in an anticlockwise direction (as viewed in e.g. Fig. 2). This results in the rotation of the upper link 40 in the clockwise direction and, through the four-bar linkage assembly, the moving contact 20 is moved towards the fixed contact 10.

[0063] In the healthy (or normal) operating state, the switching apparatus is turned off by applying a force to the operating handle 60 to rotate it in a clockwise direction (as viewed in Fig. 1). This results in the rotation of the upper link 40 in the anticlockwise direction and, through the four-bar linkage assembly, the moving contact 20 is moved away from the fixed contact 10.

[0064] The switching apparatus may alternatively be configured such that it is turned on by applying a force to the operating handle 60 in the clockwise direction and turned off by applying a force to the operating handle 60 in the anticlockwise direction in a healthy operating state, as appropriate.

[0065] However, when the switching apparatus is not in the healthy operating state, such as a weld state in which the fixed contact 10 and the moving contact 20 are welded together, the moving contact 20 is not separated from the fixed contact 10 even when a force is applied to the operating handle 60 (and thereby to the switching lever 30). The weld state occurs when the moving contact 20 is welded to the fixed contact 10 due to a failure in the switching apparatus, such as a short circuit.

[0066] To prevent the switching lever 30, and thereby the operating handle 60, from being moved to the off position when the switching apparatus is in the weld state, a switching apparatus is provided comprising the following features.

[0067] The switching lever 30 of Fig. 1 comprises a bent portion 30a, to be described in more detail later with reference to Fig. 5. The bent portion 30a is configured to extend from the switching lever 30. The bent portion 30a extends from a second end of the switching lever 30. The second end is opposite the first end, i.e. distal from the rotation point Pl.

[0068] The upper link 40 (or link 40) comprises a notch 40a or a protrusion. The notch 40a is configured such that when the switching lever 30 is moved from the on position towards the off position in the weld state in which the fixed contact 10 and moving contact 20 are welded together, the notch 40a engages with the bent portion 30a to prevent the switching lever 30 from moving to the off position.

[0069] When the contacts 10, 20 are in the weld state, the upper link 40 is configured not to rotate around the second rotation point P2. That is, the upper link 40 is unable to rotate around the second rotation point P2 when the contacts are welded due to the four-bar linkage assembly. In particular, since the cross-bar assembly does not move when the contacts are welded, the normal operation of the four-bar linkage is hindered and the link 40 does not rotate in the manner described above. As such, when the switching lever 30, and thus the bent portion 30a, are moved towards the off position by operation of the operating handle 60, the notch 40a is configured to inhibit the movement of the switching lever 30 by engaging with the bent portion 30a of the switching lever 30 (see Fig. 3).

[0070] This is in contrast to the healthy or normal operating state in which, when the switching lever 30 is moved towards the off position, the upper link 40 is configured to rotate around the second rotation point P2. That is, the upper link 40 is configured such that it is able to rotate around the second rotation point P2 when the contacts are not welded (due to the movement of the cross-bar mechanism and underlying operation of the four-bar linkage). In this way, the notch 40a is rotated into a different position, away from the switching lever 30. As such, the notch 40a does not engage with the bent potion 30a in a normal state (see Fig. 2). This arrangement ensures that the notch 40a and the bent portion 30a do not engage, and therefore that the motion of the switching lever 30 is not interfered with, under normal operating conditions.

[0071] When in a weld condition or state, the notch 40a and the bent portion 30a may engage by coming into surface contact with each other. This may allow relatively large forces to be withstood, such that the engagement cannot be overcome by means of a large force applied to the operating handle 60 (and thereby to the switching lever 30). This arrangement prevents the switching lever 30 from moving to the off position when the contacts 10, 20 are in the weld state. As such, a false indication of the state of the electrical circuit is prevented from being given. In particular, the switching apparatus is prevented from indicating that the electrical circuit is in the off state when the contacts 10, 20 are welded together which corresponds to the on state.

[0072] In the weld state, the spring is tensioned when the switching lever 30 is moved from the on towards the off position. However, because the moving contact 20 (carried by the cross-bar assembly) and therefore the upper link 40 do not move, the spring remains tensioned (in the position of Fig. 3). When the switching lever 30 is prevented from moving to the off position and the force applied to the switching lever 30 is removed, the tensioned spring is configured to move the switching lever 30 back to the on position.

[0073] That is, in the weld state, when the force being applied to the switching lever 30 to move it from the on towards the off position is removed, the tension in the spring causes a restoring force of the spring to act on the switching lever 30 to return it to the on position (Fig. 1). As such, a simple and reliable mechanism may be provided to return the switching lever 30 to an on position when the contacts 10, 20 are in the weld state. Therefore, an electrical switching device may be provided which indicates the true condition of the contacts 10, 20 and state of the electrical circuit. An electrical switching device with improved safety may thus be provided.

[0074] In the healthy operating state, the spring is configured to toggle the upper link as set out above such that the upper link 40 rotates and notch 40a is prevented from engaging with the bent portion 30a of the switching lever 30 as it is moved from the on towards the off position (Fig. 2). Thus, the correct on or off position is indicated by the operating handle 60 in normal operation of the switching apparatus.

[0075] With reference to Fig. 4, a specific example of the bent portion 30a is described in more detail.

[0076] The bent portion 30a extends from the switching lever 30. The bent portion 30a of this example has an L shape, however it is not limited thereto. The bent portion 30a may be formed as a separate component which is fixed to the switching lever 30. Alternatively, the bent portion 30a may be formed integrally with the switching lever 30. By forming the bent portion 30a integrally with the switching lever 30, a switching apparatus may be provided with a reduced number of component parts. As such, an electrical switching device may be provided which has a simple manufacturing process and reduced costs.

[0077] In this example, the bent portion 30a and the notch 40a may engage by coming into direct surface contact but in other arrangements the bent portion 30a and the notch 40a may engage in any suitable manner. As such, an electrical switching device may be provided with improved reliability and robustness.

[0078] Typically, when there is a fault in an electrical circuit under healthy operating conditions, the electrical switching device is configured to separate the electrical contacts or enter a TRIP state. In other words, when the electrical switching device detects a fault in the electrical circuit to which it is connected, the electrical switching device goes from an ON state to a TRIP state. To reactivate the electrical switching device, the electrical switching device must go from a TRIP state to a RESET state or an OFF state. The electrical switching device may comprise a cradle 70 configured to move between different positions corresponding to an ON, a TRIP, a RESET, and an OFF state of the electrical switching device. The bent portion 30a in this specific example comprises a slot 30b. The slot 30b is configured to facilitate the movement of the cradle 70 when the electrical switching device goes from an ON state to a TRIP state. Similarly, the movement of the cradle 70 is facilitated by the slot 30b when the electrical switching device moves from a TRIP state to a RESET or on OFF state. The slot 30b is configured such that the cradle 70 can enter the slot 30b when the electrical switching device is changed from the ON state to the TRIP state. . The slot 30b may be configured to have a shape corresponding to that of the cradle 70, however it is not limited thereto.

[0079] With reference to Fig. 5, a specific example of the link (or upper link 40) is described in more detail.

[0080] The upper link 40 has a substantially triangular shape. The upper link 40 comprises a first corner 41, a second corner 42, and a third corner 43. The upper link 40 is configured to rotate around the second rotation point P2, which is formed in the first corner 41. The second corner 42 is coupled to the lower link 50. However, the shape of the upper link 40 is not limited to a triangular shape.

[0081] The notch 40a is configured to protrude from an edge of the upper link 40. However, it is not limited thereto, and the notch may additionally or alternatively protrude from a surface of the upper link 40, for example. The notch or protrusion 40a may be any suitable size or shape for engagement with the switching lever in a weld condition or state of the switching apparatus.

[0082] The notch 40a may be formed integrally with the upper link 40. By forming the notch 40a integrally with the switching lever, a switching apparatus may be provided with a reduced number of component parts. As such, an electrical switching device may be provided which has a simple manufacturing process and reduced costs.

[0083] A method of operating a switching apparatus for an electrical switching device is now described. The method can be performed with a switching device according to any embodiment or example provided herein.

[0084] According to a method of operating the switching apparatus, an operation S602 comprises moving the switching lever 30 from an on position and towards an off position. In the on position, the fixed contact 10 and the moving contact 20 are in electrical and physical contact. In the off position, the fixed contact 10 and the moving contact 20 are electrically and physically separated.

[0085] Operation S604 of the method comprises, in response to moving the switching lever 30 towards the off position, when the device is in a normal operating condition, moving (S604) the moving contact coupled to the switching lever by toggling a link (operation S606). Toggling the link at operation S606 can prevent the notch of the link from engaging with the bent portion of the switching lever in a normal state of the switching apparatus. In other words, operation S606 comprises, in response to moving the switching lever 30, rotating or toggling the upper link 40 coupled to the moving contact 20. Operation S606 can further comprise, by toggling or rotating the upper link 40, preventing a notch 40a of the upper link 40 from engaging with a bent portion 30a of the switching lever 30, thereby facilitating normal operation of the switching apparatus.

[0086] In some examples, the moving contact 20 is coupled indirectly to the switching lever 30 through a biasing member and a series of links comprising a link (or an upper link) 40, a lower link 50, and a cross-bar assembly, such that the moving contact 20 may be moved in response to moving the switching lever 30. Other mechanisms may be provided by which the switching lever 30 is configured to cause movement of the moveable contact 20, as the skilled person would understand, and operations S604, S606 are not limited to the use of any one particular mechanism.

[0087] As discussed above, operation S606 comprises, in response to moving the switching lever 30, rotating or toggling the upper link 40 coupled to the moving contact 20. This rotation / toggling may be by way of the biasing member coupled to the switching lever 30 as described above, or by any other suitable mechanism. In some examples, operation S606 can further comprise, in response to toggling the upper link 40, rotating the lower link 50 coupled to the upper link 40 at a third rotation point P3 and coupled to a cross-bar assembly at a fourth rotation point P4. Operation S606 can further comprise, in response to rotating the lower link 50, rotating the cross-bar assembly around a fifth rotation point P5 or central point of the cross-bar assembly.

[0088] In some examples, operation S604 can further comprise, in response to rotating the cross-bar assembly, moving the moving contact 20 assembled on the cross-bar assembly away from the fixed contact 10. The moving contact 20 may move away from the fixed contact 10 by rotating in the same direction as the rotation of the cross-bar assembly. In some examples, operation S604 can further comprise, in response to moving the switching lever 30 from an on position towards an off position under a healthy operating condition, moving the moving contact 20 to an ON position from an OFF position by means of the biasing member and the series of links.

[0089] Operation S608 comprises, when moving the switching lever from the on position towards the off position in a weld state in which the fixed contact and moving contact are welded together, restricting toggling of the link and thereby engaging a notch of the link with a bent portion of the switching lever to prevent the switching lever from moving to the off position. In some specific examples, such as described above, in response to moving the switching lever 30 from an on position towards an off position under a weld operating condition in which the fixed contact 10 and moving contact 20 are welded together, the method comprises restricting the rotation of the cross-bar assembly and thereby the rotation of the lower link 50 and toggling or rotation of the upper link 40.

[0090] Optionally, at operation S610, the switching lever 30 may be returned to the on position by means of the biasing member coupled to the switching lever 30.

[0091] List of reference numerals

[0092] 10 fixed contact 50 lower link

[0093] 20 moving contact 60 operating handle

[0094] 30 switching lever 60a operating knob

[0095] 30a bent portion 70 cradle

[0096] 30b slot Pl first rotation point

[0097] 40 (upper) link P2 second rotation point

[0098] 40a notch or protrusion P3 third rotation point (common pivot

[0099] 41 first corner point)

[0100] 42 second corner P4 fourth rotation point

[0101] 43 third corner P5 fifth rotation point

Claims

Claims1. A switching apparatus for an electrical switching device, comprising : a fixed contact (10); a moving contact (20); a switching lever (30) movable between an on and an off position, wherein in the on position the fixed contact and the moving contact are in contact, and wherein in the off position the fixed contact and the moving contact are separated; wherein the switching lever comprises a bent portion (30a); the switching apparatus further comprising a link (40) coupled to the moving contact; wherein the link comprises a notch (40a); wherein, when the switching lever is moved from the on position towards the off position in a weld state in which the fixed contact and moving contact are welded together, the notch is configured to engage with the bent portion to prevent the switching lever from moving to the off position.

2. The switching apparatus of claim 1, wherein when the switching lever is moved from the on position towards the off position in a normal state in which the fixed contact and the moving contact are not welded together, the link is configured to rotate such that the notch does not engage with the bent portion.

3. The switching apparatus of claim 1, wherein the switching lever is coupled to the moving contact such that when a force is applied to the switching lever to move the switching lever towards the on position, a force is applied to the moving contact such that the moving contact moves towards the fixed contact.

4. The switching apparatus of claim 1, wherein the switching lever is coupled to the moving contact such that when a force is applied to the switching lever to move the switching lever towards the off position, a force is applied to the moving contact to separate the moving contact from the fixed contact.

5. The switching apparatus of claim 1, wherein the weld state occurs when the moving contact is welded to the fixed contact due to a failure in the switching apparatus.

6. The switching apparatus of claim 3, wherein the link is an upper link, andwherein the switching lever is coupled to the moving contact by a biasing member (50), a lower link and a cross-bar assembly, optionally wherein the biasing member is a spring.

7. The switching apparatus of claim 6, wherein when the switching lever is prevented from moving to the off position and the force applied to the switching lever is removed, the biasing member acts to move the switching lever back to the on position.

8. The switching apparatus of claims 6 or 7, wherein: the biasing member and the upper link are coupled to the lower link at a common pivot point (P3), the lower link is coupled to the cross-bar assembly, the moving contact is assembled on the cross-bar assembly, and in the normal state, the biasing member acts to toggle the upper link such that the notch does not engage with the bent portion.

9. The switching apparatus of any of claims 1 to 8, wherein the notch is formed integrally with the link.

10. The switching apparatus of any of the preceding claims, wherein the notch protrudes from an edge of the link.

11. The switching apparatus of any of the preceding claims, wherein the bent portion is formed integrally with the switching lever.

12. A method of operating an electrical switching device, comprising : moving (S602) a switching lever from an on position and towards an off position, wherein in the on position a fixed contact and a moving contact are in contact, and in the off position the fixed contact and the moving contact are separated; in response to moving the switching lever towards the off position, when the device is in a normal operating condition, moving (S604) the moving contact coupled to the switching lever by toggling a link (S606); and when moving the switching lever from the on position towards the off position in a weld state in which the fixed contact and moving contact are welded together, restricting toggling of the link and thereby engaging (S608) a notch of the link with a- 18 - bent portion of the switching lever to prevent the switching lever from moving to the off position.

13. The method of claim 12, wherein: when the device is in a normal operating condition, moving (S604) the moving contact coupled to the switching lever comprises moving the moving contact, which is coupled indirectly to the switching lever through the link, a lower link, and a cross-bar assembly, by toggling (S606) the link; and when the device is in the weld state and the moving contact is welded to the fixed contact, movement of the link, the lower link, and the cross-bar assembly is restricted, thereby restricting toggling of the link.

14. The method of claim 13, further comprising : returning (S610) the switching lever to the on position in the weld state by means of a biasing member coupled to the switching lever.

15. The method of claim 13, further comprising, in response to moving the switching lever from the on position towards the off position in the normal state in which the fixed contact and the moving contact are not welded together, rotating, by the toggling, the link such that the notch does not engage with the bent portion.

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