Interlocking mechanism for switching devices

An interlocking mechanism for interlocking a first and a second low voltage switching devices, wherein each of the switching devices includes a movable contact part, a stationary contact part and, an actuating unit for operating the movable contact part in a direction and making connection or disconnection with the stationary contact part. The interlocking mechanism includes a first and a second housing connected to each other, a first and a second sliding bar. The first sliding bar is arranged on the first housing and connects to the actuating unit of the first switching device. The second sliding bar is arranged on the second housing and connects to the actuating unit of the second switching device. A sliding plane is defined and has a X- and Y-axis, the Y-axis being defined in the direction of motion of the actuating unit of the switching devices.

FIELD OF THE INVENTION

The present invention relates to an interlocking mechanism for mechanically locking one of two low-voltage switching devices when the other switching device is in a closed position, wherein the two switching devices are placed side by side. Each of the switching devices comprises a movable contact part, a stationary contact part and, an actuating unit for operating the movable contact part in a direction and making connection or disconnection with the stationary contact part. The interlock is connected to the actuating unit. In particular, the invention relates to a mechanical interlock. Such a switching device may be arranged to operate a low voltage application, wherein the low-voltage is in a range of 1000 V AC or 1500 V DC.

BACKGROUND OF THE INVENTION

Depending on the requirement of an application, it is sometimes required to connect an electrical device to the same power source via two switching devices or contacting devices. In this case, it is important to provide reliable power to the electrical device. Therefore, an interlock mechanism is provided when the switching devices are used, which means that the switching devices won't be closed simultaneously for avoiding short-circuiting connected electrical devices.

FIG. 6illustrates a perspective view of a mechanical interlock for interlocking a first and second switching devices according to the prior art, wherein the interlocking mechanism comprising a first and a second housing60,60′ connected to each other. The moving contact parts of the switching devices are movable between open and closed positions. A first and a second sliding bar610,610′ are arranged on the first housing and second housing respectively and are further connected to the corresponding actuating unit of each of the switching devices. The sliding bars are arranged to slide along a sliding plane defined by an X′- and Y-axis. The Y-axis is defined in the direction of motion of the actuating unit of the switching devices and each of the sliding bars is configured to slide in the Y-axis direction of the sliding plane. The interlock further includes a shaft and a cam integrated with the shaft as one piece640. This integrated part is disposed between the first and second housing and the cam is configured to be only rotatable when both switching devices are in open position. Furthermore, the cam is adapted, following the motion of the actuating unit and thereby the movable contact part of the first switching device, to rotate to a position wherein for retaining the second switching devices in an open position.

This type of an interlock requires the housings be well connected during operations. During their life, switching devices may however make numerous contacting operations, each of which results a rotation of the cam. The rotations however result in frictions between the shaft-cam assemble and the housings, which consequently results displacement between the housings. This may result in simultaneous closure of both of the switching devices, which consequently results a short-circuit fault. Therefore, a more reliable interlock is desired.

SUMMARY OF THE INVENTION

One object of the present invention is to provide an improved interlocking mechanism for locking out one of two switching devices when the other is in a closed position, which is reliable, compact, easily to be installed.

This object is achieved by the interlocking mechanism, characterized in that the shaft is disposed to be perpendicular to the sliding plane so that the shaft is perpendicular to the direction of motion of the actuating unit of the switching devices, the cam further comprises a first and a second locking element for blocking the first and second sliding bar respectively, each of the locking elements protruding laterally in the X-axis direction, each of the sliding bars comprises an opening at one end of the bar, and the opening is configured for retaining the corresponding locking element when the corresponding switching device is in a closed position.

By disposing the shaft perpendicularly to the sliding plane and adapting the structures of the cam and sliding bars to it, the present invention solves the aforesaid problem. Because the rotating motion of the cam has been changed in another dimension with 90°, the frictions between the shaft-cam assemble and the housings during operations have been significantly reduced, which further reduces the displacement between the housings. Therefore, the invention prevents the switching devices from being short-circuited, which enables a safer and more reliable operation.

Another advantage is that the invention extends the lifetime of the interlock. This is because that, due to disposing the shaft perpendicularly to the sliding plane, a contacting force generated by a connecting operation of a switching device becomes more centered on the shaft, which further reduces the wear of the housing.

According to one embodiment of the invention, the cam is mountable on the shaft. Alternatively, the cam is formed with the shaft as one piece. A holder may be provided on the first and second housing respectively for retaining the shaft.

According to another embodiment of the invention, the cam has a curved outline. It is advantageous to provide a curved outline in that this optimized shape saves space between the first and second housing, which enables a compact interlocking mechanism. Preferably, the curved outline is arc-shaped.

When in use, such an interlocking mechanism may be arranged between the first and the second switching devices that have the same size.

By providing a third housing arranged between the first and second housings and adapting the first sliding bar to the size of the first switching device, the interlocking mechanism may be applied to the first and the second switching devices of different size.

According to yet another embodiment of the invention, the first and second housing may further respectively comprise a sliding track and the corresponding sliding bar is arranged to slide thereon.

DETAILED DESCRIPTION OF THE INVENTION

With reference toFIG. 1,1a-bandFIG. 2, an interlocking mechanism1for interlocking a first200and a second200′ switching devices comprises a first2and a second2′ housing connected to each other, a first10and a second10′ sliding bar, a shaft30disposed between the first2and the second2′ houses and a cam40configured to be rotatable about the shaft30. Each of the housing2,2′ has an inner side5,5′ and an outer side6,6′ and the first and the second housing2,2′ are connected with their inner sides against to each other.

Each of the switching devices200,200′ may comprise a movable contact part, a stationary contact part and an actuating unit (they are not shown) for operating the movable contact part in a direction and making connection or disconnection with the stationary contact part.

The first sliding bar10is arranged on the inner side5of the first housing2and connecting to the actuating unit of the first switching device200and the second sliding bar10′ is arranged on the inner side5′ of the second housing2′ and connecting to the actuating unit of the second switching device200′. In this example, a recess9,9′ is provided in the inner side5,5′ of each of the housing2,2′ for retaining the corresponding sliding bar10,10′. A sliding plane P is defined and has an X- and Y-axis, wherein the Y-axis is defined in the direction of motion of the movable parts of the switching devices. Each of the sliding bars10,10′ are configured to slide in the Y-axis direction of the sliding plane P. A sliding track7,8may be further provided in the recess9of a housing2for facilitating the sliding motion of the sliding bar10.

Moreover, an actuating connector14,14′ is provided on each of the sliding bars10,10′ for connecting the sliding bar10,10′ to the actuating unit of the corresponding switching device200,200′. An opening24,24′ is further provided on each of the recesses9,9′ to allow the actuating connector14,14′ to extend therethrough. Therefore, as the movable contact part of the switching device200,200′, the sliding bars10,10′ are also operated by the actuating unit.

A holder, in this example in form of a recess23,23′, is further provided on the inner side of a housing2,2′ for retaining the shaft30. The shaft30is disposed to be perpendicular to the sliding plane P, which therefore means that the shaft30is perpendicular to the direction of motion of the actuating unit of the switching devices200,200′.

It is advantageous that the shaft30is arranged to be perpendicular to the sliding plane P, it is possible to make a form bound measurement in a molding tool to be used to make the recess23,23′. The form bound measurement in the molding tool enables a more accurate recess and reduces the gap between the shaft and the recess.

Furthermore, to prevent simultaneous closure of the switching devices200,200′, the cam40is configured to be only rotatable about the shaft30when both switching devices200,200′ are in open positions.

With reference toFIG. 5a-c, the cam40includes two sides opposite to each other. A first and a second locking element42,42′ are further provided on each of the sides of the cam40and is protruding laterally in the X-axis direction. The cam may be rotatable about the shaft in a range of 80°-100°, preferably about 90° in the direction of the X-axis, or R. In this example, the cam40is mountable on the shaft30. In this case, a through hole43is provided on the cam40. Alternatively, the cam may be formed with the shaft as one piece. The cam and shaft may be made of metal, for example steel, and/or hard plastics.

In this example, the cam30has a curved outline so that the cam may rotate in a relatively small space, a compact interlock is therefore achieved. Preferably, the curved outline is arc-shaped. It should be understood that other structures of a cam may be applicable to the invention.

Furthermore, an opening12,12′ is provided at one end of each of the sliding bars10,10′ for retaining the corresponding locking element42,42′ when the corresponding switching device is in a closed position. The opening has a width W arranged to be able to retain the cam. In this example, the opening12further comprises an outer portion15facing the housing2and has a smaller width W1than W. The outer portion is further configured to retain the locking element42when the corresponding switching device200is in a closed position.

FIG. 5d-eshow a plan and a side view of the interlock1in an interlocking position, where the first switching device200is in a closed position and the second locking element42′ is blocking the second sliding bar10′ to prevent the second switching device200′ from a connecting operation.

With reference toFIG. 5f-g, following a connecting/closing operation of the second switching device200′, the second sliding bar10′ is actuated by the actuating unit and moves towards a closed position. The motion of the second sliding bar10′ is further transformed to a rotating motion of the cam40so that the cam40rotates to a position wherein the second locking element42′ is retained in the outer portion of the opening12′ whereas the first locking element42is blocking the first sliding bar10to prevent the first switching device200from a connecting/closing operation.

In this example, the first and second locking elements42,42′ are disposed to be perpendicular to each other. However, other dispositions of the locking elements may be also possible.

As shown inFIG. 2, when in use, such an interlocking mechanism may be arranged between two identical switching devices200,200′ that have the same size.

With reference toFIGS. 3,3aand4, to be able to interlock switching devices of different size, a third housing3is provided to be arranged between the first and the second housings2,2′. The first sliding bar110is further adapted to the size of the first switching device210. In this way, switching devices210,200′ of different sizes may be interlocked by the interlock1′.

Optionally, a snap catch15is provided and protrudes inwards from one edge of the housing and is arranged to be cooperated with the snap hook16arranged on the other end of the sliding bar. This snap-fit joint enables a non-movable sliding bar at installation and connection of the interlock11′ with the switching devices200/210,200′ and therefore allows an easy installation. Both the snap catch15and the snap hook are made of flexible material, for example thermoplastics, that will be deflected briefly during joining operation. It is understood that other kinds of snap-fit joints may be also applicable.

Further advantages of the invention are easily installation, compact size, ease of manufacturing due to less components, and therefore less production cost.