The invention relates to a switching device comprising a first contact for making contact to a first circuit and a second contact for making contact to a second circuit.

In a low voltage distribution system switchgear is placed in a housing. The switchgear comprises a switching device. The switching device is a withdrawable unit in the form of a drawer that can be inserted into a cabinet that is placed in a housing. The switching device comprises a set of main contacts and a set of auxiliary contacts. Both sets are placed on a backside of the device. The main contacts are for making contact to vertically arranged pairs of distribution bus bars in the rack. The auxiliary contacts are for making contact to auxiliary cable side contacts connected to cables of an auxiliary circuit.

The switching device provides for a number of connection states which are selected by a main disconnect switch and by partially or completely withdrawing the switching device from the cabinet. The states are indicated in the table below.

State unit Main Main Auxiliary Test button disconnect contacts contacts light

Connected Inserted Closed Connected Connected Off on

Connected Inserted Open Connected Connected Off off

Test Withdrawn Open Disconnected Connected On

30 mm

Disconnected Withdrawn Open Disconnected Disconnected Off

45 mm

Removed Removed

from the rack The switching device is arranged such that a change of state can only be to one or two of the other states corresponding to moving up or down a row in the table. This is arranged for safety reasons. Thus, for the transition between the connected off state and the test state, the main disconnect must be opened by the main disconnect switch. For this a special mechanism is present.

To remain connected in both the "connected on" and the "test" state, the auxiliary cable side contacts of the auxiliary circuit extend at least 30 mm in the direction in which the drawer is withdrawn. The auxiliary contacts slide along the auxiliary cable side contacts when the drawer is withdrawn from the "connected on" to the "test" state or inserted further into the cabinet from the "test" state to the "connected on" state. Sliding contacts however are less reliable as they wear out and as they may become contaminated.

Moreover, there is a risk that the drawer may be accidentally closed or that it may change from the position in which it is withdrawn by 45 mm to a position in which it is withdrawn by only 30 mm. Such an accidental closure or change of position may for instance occur when someone or something falls against the drawer or leans against it. Such an accidental change in position corresponds to a change in the state and therefore is dangerous. For instance, in case of a change from being withdrawn by 45 mm to 30 mm, the auxiliary circuit is either connected or disconnected.

It is an object of the invention to provide a switching device that at least partially reduces or obviates this problem. According to a first embodiment of the invention, there is provided a switching device comprising

- a first contact for making contact to a first circuit;

- a second contact for making contact to a second circuit;

- a first transfer mechanism;

- a second transfer mechanism comprising a sector gear and a rack gear, the rack gear connected to the second contact and the sector gear arranged to transfer rotation of a rotable drive member to movement of the rack gear; - the rotable drive member comprising a first range of orientations wherein the first transfer mechanism drives the first contact between a first connected position and a first disconnected position and wherein the sector gear is out of engagement with the rack gear; and comprising a second range of orientations wherein the rack gear is in engagement with the sector gear and drives the second contact between a second connected position to a second disconnected position.

As will be appreciated by the person skilled in the art, a sector gear comprises a sector with teeth and a toothless sector and that a rack gear comprises teeth. The skilled person will also appreciate that in a combination of a sector gear with a rack gear, the orientation of the sector gear with respect to the rack gear determines if the sector gear engages with the rack gear and the rack gear is driven or is out of engagement with the rack gear and the rack gear is not driven. This is because the sector gear can only move the rack when the sector with teeth engages with the rack, i.e. wherein the teeth of that sector mesh with the teeth of the rack gear. Therefore on rotation of the sector gear the rack gear is driven intermittently on continuous rotation of the rotable drive member. The first range of orientations corresponds to the toothless sector facing the rack gear and the second range of orientations corresponds to the sector with teeth facing the rack gear and the teeth of that sector meshing with the teeth of the rack gear.

Since the rotable drive member also drives the first transfer mechanism, the connection status of both the first contact and the second contact can be controlled by the drive member such that the first contact can be disconnected while the second contact remains connected. Here, the rotable drive member indirectly drives the first contact between the first connected position and the first disconnected position while rotating in a first range of orientations. In the first range of orientations the sector gear is out of engagement with the rack gear (i.e. the teeth of the sector with teeth of the sector gear do not mesh with the teeth of the rack gear). Therefore, in the first range of orientations the rack gear does not move and thus the second contact does not move.

As the rotable drive member drives the first transfer mechanism and the second transfer mechanism by rotating, the switching device can be operated by inducing rotational motion of the rotable drive member. This is preferable as rotational motion can easily be provided by a motor or by a dial arranged to be handled by a user.

According to a second embodiment of the invention the switching device of the first embodiment is provided wherein rotation of the rotable member in a first direction corresponds to moving the second contact from the second disconnected position to the second connected position and to moving the first contact from the first disconnected position to the first connected position. In this embodiment the second and the first contact are connected sequentially when the drive member is rotated over a sufficient angle. Obviously, by rotating in a direction opposite to the first direction will sequentially disconnect the first contact and then the second contact.

According to a third embodiment of the invention, the first transfer mechanism comprises a sector gear and a further rack gear connected to the first contact, the sector gear comprised by the first transfer mechanism arranged to transfer rotation of the rotable drive member to movement of the further rack gear wherein the sector gear of the first transfer mechanism is out of engagement with the further rack gear when the rotable drive member is in the second range of orientations.

The further rack gear and the sector gear comprised by the first transfer mechanism convert to rotational motion of the rotable drive member to a linear movement of the first contact.

Because the further rack gear is out of engagement with (i.e. does not mesh with) the sector gear of the first transfer mechanism when the rotable drive member is in the second range of orientations, i.e. when the second contact is moved between the second connected position and the second disconnected position, the switching device can remain relatively small. This is because when in stead the further rack gear would mesh with the sector gear of the first transfer mechanism, the first contact would continue its linear movement so that space would be required to accommodate this linear movement. In an advantageous, forth embodiment of the invention, the switching device is according to the third embodiment and the sector gear comprised by the first transfer mechanism is the sector gear comprised by the second transfer mechanism and the teeth of the sector gear span a sector corresponding to less than 180 degrees and the rack gear and the further rack gear are arranged diametrically around the sector gear.

By placing the rack gear and the further rack gear at diametrical positions around the sector gear with teeth in less than half the circumference, the teeth of the sector gear will not mesh with the rack gear and the further rack gear simultaneously. Therefore the first contact and the second contact do not move simultaneously.

By using one sector gear for both the first transfer mechanism and the second transfer mechanism the switching gear requires little space. In addition this is a relatively cheap solution.

According to a fifth embodiment of the invention the sector gear is arranged to rotate around a sector gear axis, and a connection rod is hingeably connected to the rack gear at a first end and hingeably connected to a drive rod at a second end, the drive rod being connected to second contact; the connection rod arranged to pivot around an axis parallel to the sector gear axis.

An advantage of this embodiment is that a motion of the rack gear in a certain direction corresponds to a motion of the drive rod having a component in the opposite direction.

Therefore a rotation of the sector gear in one direction corresponds to the first contact and the second contact being moved in the same direction, instead of in opposite directions.

According to a sixth embodiment of the invention the sector gear is arranged to rotate around a sector gear axis, a first pin connects a connection rod to the rack gear, a second pin connects the connection rod to a drive rod connected to the second contact, the first pin arranged to rotate and to slide through a first slot of the connection rod, the second pin arranged to rotate and slide through a second slot of the connection rod, wherein the connection rod is arranged to pivot around an axis parallel to the sector gear axis. An advantage of this embodiment is that a motion of the rack gear in a direction corresponds to a motion of the drive rod having a component in the opposite direction. Therefore a rotation of the sector gear in one direction (over a sufficient angle) corresponds to the first contact and the second contact being moved in the same direction, instead of in opposite directions.

Additionally, as the pins can rotate within the respective slots and can slide in the respective slots, the connection rod only transfers forces parallel to the direction of the movement of the second rack. Moreover, the second contact is moved in a direction parallel to the direction of movement of the second rack without necessarily being exposed to a force driving it in a direction perpendicular direction.

Preferably, the drive rod is guided by a guide to induce the sliding movement of the pins in their respective slots.

According to a seventh embodiment of the invention the teeth of the rack gear and the teeth of the further rack gear point in the same direction and the sector gear and the further sector gear are arranged to rotate in the same direction when the rotable drive member (15) rotates in a first direction.

Because the teeth of the rack gear and the teeth of the further rack gear face in the same direction, the rack gear and the further rack gear are parallel. Because the sector gear and the further sector gear are arranged to rotate in the same direction and the rack gear and the further rack gear are parallel, the rack gear is arranged to move the first contact in a direction parallel to the direction in which the further rack gear is arranged to move the second contact. Moreover, a rotation of the drive member (over a sufficient angle) results in a movement of the first contact and the second contact in the same direction, not in opposite directions.

According to an eight embodiment of the invention, the switching device comprises a torsion spring arranged to push the first contact toward the first connected position or the first disconnected position or to push the second contact towards the second connected position or the second disconnected position. The torsion spring may be arranged to have a first leg and a second leg, whereby the second leg in contact, either directly or indirectly such as via a roller bearing, with the first contact or as the case may be the second contact. The second leg thereby exerts a spring force against the first contact or as the case may be the second contact. The orientation of the second leg changes when the first contact moves between the first connected position and the first disconnected position or as the case may be when the second contact moves between the second connected position and the second disconnected position. The first leg of the torsion spring may remain its orientation while the orientation of the second leg changes, such that the torsion changes and the spring force changes. By using spring force, the position of the first contact or the second contact is stabilized and vibrations are dampened. For increasing the spring force a plurality of additional torsion springs may be used, all arranged similarl to the torsion spring. According to a ninth embodiment of the invention, the switching device comprises a roller bearing arranged between the torsion spring and the first contact or the second contact.

The roller bearing prevents wearing by for instance abrasion of the first contact or the second contact.

Preferably, the switching device of the above embodiments is for switching low voltage circuits, i.e. circuits suitable for handling around 1000 V or 1500 V DC.

Examples of embodiments the invention will now be described with reference to the accompanying schematic drawings. Corresponding reference symbols in the schematic drawings indicate corresponding parts. The schematic drawings are not necessarily to scale and certain features may be exaggerated to better illustrate and explain the present invention. Certain features may not be shown to better illustrate and explain certain aspects of the present invention. Further, the examples are not intended to be exhaustive or otherwise limit or restrict the invention to the precise configurations shown in the drawings and disclosed in the following detailed description. Figure 1 cabinet for a low voltage distribution system

Figure 2 switching device according to a first example of the invention

Figure 3 switching device according to a second example of the invention

Figure 4 switching device according to a third example of the invention Figure 5 side view of a first contact and a locking mechanism Figure 6 side view of a first contact and a locking mechanism First example

For the purpose of explaining the invention, use is made of an x-direction, a y-direction and a z-direction, which are all perpendicular and chosen in right-handed orientation. A

corresponding Cartesian coordinate system is used as well.

In the following examples of the invention, the positive z-direction is a vertical upward direction. In a first example of the invention, there is an encapsulating housing comprising switchgear for a low voltage distribution system. The encapsulating housing comprises a number of cabinets (1) placed side by side against each other (figure 1). Each cabinet has a front side (parallel to the x-direction) that is accessible for personnel. The cabinets (1) each comprise a main bus bar compartment (2). The main bus bar compartments of neighbouring cabinets are connected by openings (3). Four main bus bars (4) are housed in a main bus bar compartment. The four main bus bars run parallel to the x- direction and are connected to four distribution bus bars per cabinet. The four distribution bus bars are vertically placed (i.e. they run parallel to the z-direction) in an insulated bus bar chamber at the backside of the cabinets. Each of the four distribution bus bars is housed in a separate glass-fibre reinforced polyester bus bar duct running parallel to the z-direction. The four distribution bus bars are each connected to one of the horizontal main bus bars by connection bars.

The cabinets (1) comprise multiple switchgear and control gear compartments aligned to the left walls of the compartments. On the right side of the cabinets (1) is a cable connection compartment (5).

One of the switchgear compartments is occupied by a drawer (6) comprising a switching device (7) according to the invention (figure 2). The switching device comprises a first contact (8) with four conductors that are isolated from each other by walls of glass-fibre reinforce polyester. The first contact (8) can be moved along the y-direction to connect (positive y-direction) or disconnect (negative y-direction) the four conductors with the four distribution bus bars.

The switching device also comprises a second contact (9) with four auxiliary conductors that are isolated from each other by walls of glass-fibre reinforce polyester. The second contact (9) can be moved along the y-direction to connect (positive y-direction) or disconnect (negative y-direction) the four auxiliary conductors with corresponding cables of an auxiliary circuit. Within the switching device, the four conductors of the first contact (8) are electrically connected to the four conductors of the second contact (9).

The switching device (7) comprises a first rack gear (10) and a second rack gear (11). The first rack gear (10) and the second rack gear (11) are arranged at diametrical positions around a sector gear (12), in this example at different x-coordinates. The sector gear (12) is arranged to rotate around a sector gear axis (13). The sector gear comprises teeth in a sector of the circumference. The sector spans less than 180 degrees. The rest of the circumference is toothless. The first rack gear (10) and the second rack gear (11) are arranged at a distance from the sector gear axis (13) such that they can engageably mesh with the teeth of the sector gear (12). The first rack gear (10) and the second rack gear (11) have a tangential orientation to the sector gear (12) and as they are at diametrical positions, they have parallel orientations with respect to each other. In this example the first rack gear (10) and the second rack gear (11) extend in the y-direction. Where the first rack gear (10) and the second rack gear (11) face each other, the teeth of the first rack gear (10) point in the direction of the second rack gear (11) and the teeth of the second rack gear (11) point in the direction of the first rack gear (10). The switching device further comprises a first gear wheel (14) and a second gear wheel (15). The first gear wheel (14) is arranged concentrically with the sector gear (12) and is fixed to the sector gear (12). The second gear wheel (15) is arranged to mesh with the first gear wheel (14). The switching device further comprises a first bevel gear (16) and a second bevel gear (17) meshing with the first bevel gear (16). The first bevel gear (16) is arranged concentrically with the second gear wheel (15) and is fixed to the second gear wheel (15). The second bevel gear (17) forms an end of a drive shaft (18) extending in y-direction. The drive shaft (18) is in turn driven by a motor or by a user via a dial.

The first rack gear (10) is connected to the first contact (8). The second rack gear (11) is connected to a first end of a connection rod (19) by a first hinge (20). The connection rod (19) is mounted on a pivot (21) to pivot around an axis in the z-direction. A second end of the connection rod (19) is connected to a drive rod (22) by a second hinge (23). The drive rod (22) is connected to the second contact (9) by a third hinge (24).

In a first state of the switching device (7) the first contact (8) is in a first connected position and the second contact (9) is in the second connected position, i.e. their respective y- coordinates have maximum values.

The state of the switching device (7) wherein the first contact (8) is in a disconnected position and the second contact (9) is a connected position, is herein referred to as a second state. Herein, the third state of the switching device (7) refers to the state wherein the first contact (8) is in the first disconnected position and second contact (9) is in the second disconnected position. In the third state, the respective y-coordinates of the both the first contact (8) and the second contact (9) are at their smallest values.

The switching device (7) further comprises a main disconnect and a test button light. The main disconnect is closed in the first state of the switching device and is open in the second and third state. The main disconnect is opened between the first state and the second state. The main disconnect may be driven by the drive shaft (18). The test light is illuminated only when the switching device (7) is in the third state, otherwise it is off.

The drawer (6) does not change position during the three states of the switching device.

Spring force of a locking mechanism is used to keep the first contact (8) in connected position (i.e. the position corresponding to a maximum value of the y-coordinate). A torsion spring (39) comprises a first leg (40) and a second leg (41). The first leg (40) is attached to the drawer (6). A roller bearing (42) is mounted on the second leg (41). The torsion spring (39) is positioned such that when the first contact (8) is in the connected position, the roller bearing (42) is in contact with a backside surface (43) of the first contact (8) facing in negative y-direction (figure 5). In this position the torsion spring (39) exerts a spring force in positive y-direction to the first contact (8), i.e. it forces the first contact (8) towards the position wherein the y-coordinate is maximal. The connected position corresponds to the position wherein the y-coordinate is maximal. The spring force therefor dampens possibly occurring vibrations of the first contact (8) and prevents unwanted displacement of the first contact (8).

When the first contact (8) has a smaller y-coordinate than in the first connected position, the angle between the second leg (41) and the first leg (40) is widened and the roller bearing (42) may contact a bottom side surface (44) of the first contact (8) (figure 6). By decreasing the y- coordinate of the first contact (8) the contact moves to a disconnected position. The bearing helps in reducing friction when the first contact (8) is slid over the clip between the connected and the disconnected position. As friction is reduced, abrasion is reduced. A similar torsion spring and roller bearing is placed similarly at the second contact (9) with similar purpose and results.

The switching device according to the first example is easy to manufacture, cost effective, compact and robust. Moreover, precise motion control can be obtained by sizing the different gears (12,14,15,16,17).

Second example

A second example (figure 3) of the invention differs only in how the second rack gear (11) is connected to the second contact (9). For instance the switching device (7) is comprised in a drawer (6), which in turn is placed in a cabinet (1). The switching device can switch between the first state, the second state and the third state. The switching device also comprises the main disconnect and the test button. Furthermore, the switching device (7) comprises torsions springs (39) and roller bearings (42) to lock the first contact (8) and the second contact (9) in their respective first and second connected positions. It also comprises the sector gear (12) and the first racking gear (10) and the second racking gear (11) and the first racking gear (10) and the second racking gear (11) have the same position and orientation with respect to each other and the sector gear (12). The second rack gear (11) is connected to a first end of a connection rod (19) by a first cylindrical pin (25) extending in the z-direction. The first cylindrical pin engages in a first slot (26) of the connection rod (19). The connection rod (19) is mounted on a pivot (21) to pivot around an axis in the z-direction. A second end of the connection rod (19) is connected to a drive rod (22) by a second cylindrical pin (28) engaging with a second slot (27) of the connection rod (19). The drive rod (22) is connected to the second contact (9) and is guided by a guide (29).

Third example

A third example (figure 4) of the invention differs from the first example and the second example in how the drive shaft (18) drives the first rack gear (10) and the second rack gear (11). For instance the switching device (7) is comprised in a drawer (6), which in turn is placed in a cabinet (1). The switching device can switch between the first state, the second state and the third state. The switching device also comprises the main disconnect and the test button. Furthermore, the switching device (7) comprises torsions springs (39) and roller bearings (42) to lock the first contact (8) and the second contact (9) in their respective first and second connected positions.

In the third example, a second bevel gear (17) forms an end of a drive shaft (18) extending in the y-direction. The second bevel gear (17) meshes with a first bevel gear (16) arranged to rotate around an axis extending in the z-direction. The first bevel gear is arranged

concentrically on a third gear wheel (30).

A first toothed belt (31) loops around the third gear wheel (30) and a forth gear wheel (32) and engages with the teeth of the third gear wheel (30) as well as the teeth of the forth gear wheel (32). A first sector gear (33) is concentrically attached to the forth gear wheel (32). The toothed sector of the first sector gear (33) spans less than 180 degrees. The first sector gear (33) is arranged to be in engagement with a first rack gear (10) that extends in the y-direction. When the first sector gear (33) is in engagement with the first rack gear (10) the teeth of the toothed sector of the first sector gear (33) mesh with teeth of the first rack gear (10). The first rack gear (10) is attached to the first contact (8). A second toothed belt (34) loops around the forth gear wheel (32) and a fifth gear wheel (35). The second toothed belt (34) meshes with the teeth of the forth gear wheel (32) and the fifth gear wheel (35). The fifth gear wheel (35) has the same dimensions as the forth gear wheel (34) to make it rotate with the same angular speed as the forth gear wheel (34). A second sector gear (36) is concentrically attached to the fifth gear wheel (35). The toothed sector of the second sector gear (36) spans less than 180 degrees. The second sector gear (36) is arranged to be in engagement with a second rack gear (11) that extends in the y-direction. When the second sector gear (36) is in engagement with the second rack gear (11) the teeth of the toothed sector of the second sector gear (36) mesh with teeth of the second rack gear (11). The second rack gear (11) is attached to the second contact (9). The first sector gear (33) and the forth gear wheel (32) are arranged to rotate around a first sector gear axis (37). The second sector gear (36) and the fifth gear wheel (35) are arranged to rotate around a second sector gear axis (38). The x-coordinate of the first rack gear (10) is larger than the x-coordinate of the first sector gear axis (37). The teeth of the first rack gear (10) are directed to the negative x-direction.

The x-coordinate of the second rack gear (11) is larger than the x-coordinate of the second sector gear axis (38). The teeth of the second rack gear (11) are directed to the negative x- direction.

In variants of the third example, the combinations of toothed belts and gear wheels may be replaced by combinations of chains and sprocket wheels or by combinations of belts or cables with pulleys. In the variants, the function is the same as in the third example and the transmission rations correspond to the third example as well. Combinations of toothed belts and gear wheels and combinations of chains and sprocket wheels are preferred over combinations of belts or cables and pulleys.

For example, in a first variant of the switching device according to the third example, a first pulley is used instead of the third gear wheel (30) and a first belt or a first cable is used instead of the first toothed belt (31). A second pulley is used instead of the forth gear wheel (32).

In this variant, a second belt or second cable loops around the second pulley. A third pulley is used instead of the fifth gear wheel (35).

In yet another variant of the switching device according to the third example, a first sprocket wheel is used instead of the third gear wheel (30) and a first chain is used instead of the first toothed belt (31). A second sprocket wheel is used instead of the forth gear wheel (32).

In this variant, a second chain loops around a third sprocket wheel and a forth sprocket wheel The third sprocket wheel is concentrically placed with the second sprocket wheel (at another z-coordinate) and has the same dimensions as the second sprocket wheel. The forth sprocket wheel is used instead of the fifth gear wheel.

The switching device according to the third example and its variants is easy to assemble and design, easily maintainable. Relatively light and small parts can be used for the third example and its variant.