Patent Publication Number: US-7583170-B2

Title: Switching device with switch latch

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application claims priority of European application No. 06020611.7 EP filed Sep. 29, 2006, which is incorporated by reference herein in its entirety. 
   FIELD OF INVENTION 
   The invention relates to a switching device comprising a switch latch for mechanical activation of the switching device, a first tripper for overload protection, a second tripper for short-circuit protection, and a handle for activation of the switch latch, and to a method for displaying the disconnection cause of a switching device of said kind. 
   BACKGROUND OF INVENTION 
   In order to protect electrical loads, e.g. motors, use is routinely made of a circuit breaker having a tripper with time delay for overload protection and a tripper without time delay for short-circuit protection. Because the switch latch of the circuit breaker is mechanically coupled to the trippers, the trippers can interrupt the circuit by opening switching contacts automatically and effect the disconnection of the electrical load. The switching contacts can also be opened or closed manually by means of a handle of the circuit breaker, the handle being mechanically coupled to the switch latch or integrated in the switch latch. At the same time, the ON state (circuit breaker switched on) and the OFF state (circuit breaker switched off) are visible by virtue of the position of the handle. 
   It is already known that a circuit breaker has a handle which is arranged outside of the switch housing. The handle is moved to an intermediate position, also known as a tripped position, between ON and OFF positions if the circuit breaker is disconnected by a tripper in order to protect against overload or short circuit. In this case only the disconnection of the circuit breaker is shown by the position of the handle, but it is not possible to distinguish between overload and short circuit. In order to make the cause identifiable, the tripper that caused the trip is visibly indicated in some devices by means of a lamp, an attachable add-on module, or an integrated additional display. The use of an attachable add-on module or an integrated additional display is unfavorable in terms of the manufacturing costs of circuit breakers and hinders the simplification of the structure or the miniaturization of the size of circuit breakers. 
   SUMMARY OF INVENTION 
   The invention addresses e.g. the problem of visibly differentiating between the disconnection causes of a switching device. 
   The problem can be solved by means of a switching device as claimed in independent claims and by means of a method as claimed in a further independent claim. The dependent claims describe further advantageous embodiments of the invention. 
   The invention addresses the problem of indicating the trip cause by means of the position of the handle in a switching device. Assuming a switching device which has a switch latch for mechanical activation of the switching device, a first tripper for overload protection, a second tripper for short-circuit protection and a handle for activation of the switch latch, in order to indicate the disconnection cause of the switching device, the switching device is embodied in such a way that the handle is moved to a first position if the first tripper is tripped due to an overload, and the handle is moved to a second position if the second tripper is tripped due to a short circuit, with the first and the second positions being different. In the case of a disconnected switching device it is thus possible to make the trip cause identifiable in a simple manner and without an additional display. It is also unnecessary to provide additional space for further display elements on the small visible surface on the switch housing. 
   According to an advantageous embodiment of the invention, the handle for manually activating the switching device is provided. In this case the handle for activation of the switch latch is embodied in such a way that the switching device is switched on if the handle is moved to a third position, and that the switching device is switched off if the handle is moved to a fourth position. All four positions are different. If the switching device is used in a switch cabinet, a housing or similar, in addition to the ON and OFF state, the disconnection reasons of the switching device are also indicated by the position of the handle externally on the switch cabinet door or the housing. 
   In an advantageous embodiment the switching device is embodied in such a way that the handle arrives at the four positions by means of a rotational movement. Each of the four positions can be represented by a symbol or a sign and arranged in a circle, for example, in the case of a rotatable handle. The handle can come to rest in any position as a result of a rotational movement, and indicate the states and disconnection causes of the switching device. 
   The switching device advantageously has a switch gearwheel which is embodied to produce the rotational movement of the handle. By virtue of the switch gearwheel the rotational movement of the handle can be transferred to the switch latch or vice versa. 
   According to a further advantageous embodiment of the invention, the switch latch is embodied in such a way that the handle is moved to the first position and locked in the first position when the first tripper is tripped, and is moved to the second position and locked in the second position when the second tripper is tripped. The handle can also be moved to the third or fourth position and locked in the respective position when the switching device is switched on or off. 
   The handle advantageously has at least one toothed segment which is embodied in conjunction with the switch gearwheel to lock the handle in one of the four positions. 
   A switching device of said kind is normally used as a power switch or as a device which includes a power switch, in order to protect the current paths between an electrical supply and loads. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is described and explained in greater detail below with reference to the exemplary embodiments that are illustrated in the figures, in which: 
       FIG. 1  shows an illustration of the handle of a switching device which has been switched on, 
       FIG. 2  shows an illustration of the handle of a switching device which has been tripped due to short circuit, 
       FIG. 3  shows an illustration of the handle of a switching device which has been tripped due to overload, 
       FIG. 4  shows an illustration of the handle of a switching device which has been switched off, 
       FIG. 5  shows a schematic illustration of the OFF state of the switching device, 
       FIG. 6  shows a schematic illustration of the ON state of the switching device, 
       FIG. 7  shows a schematic illustration of the disconnection of the switching device due to short circuit, and 
       FIG. 8  shows a schematic illustration of the disconnection of the switching device due to overload. 
   

   DETAILED DESCRIPTION OF INVENTION 
     FIGS. 1 to 4  show in each case a handle  4  of a switching device which is used for the protection of an electrical load, e.g. a motor, against short circuit or overload. The switching device can also be switched on or off manually by rotating the handle  4 . In order to visually indicate the switch states—switched on or off—and the disconnection cause (short circuit or overload) of the switching device, a total of four positions  10 ,  11 ,  12  and  13  are provided for the handle  4 . The four positions  10 ,  11 ,  12  and  13  represent respectively the ON state, the OFF state, the disconnection due to overload and the disconnection due to short circuit for the switching device. The first position  12  and the second position  13  of the handle  4  are situated between the third position  10  and fourth position  11 , with the angle of rotation of the handle  4  between the third position  10 , in which the handle indicates the ON position of the device, and the fourth position  11 , in which the handle  4  indicates the OFF position, being 90°. Each position  10 ,  11 ,  12  and  13  is also depicted differently by a symbol (or inscription) for greater ease of identification. 
   If the handle  4  is rotated to the ON position  10  ( FIG. 1 ), the switching device is switched on. Conversely, if the handle  4  is rotated to the OFF position  11  ( FIG. 4 ), the switching device is switched off. In addition, the handle  4  can automatically move to position  12  or  13  and be locked or held there ( FIGS. 3 and 2 ) if the switching device automatically disconnects due to overload or short circuit. If the switching device is disconnected, e.g. due to overload, the handle  4  moves from the ON position  10 , past the position  13  which indicates tripping due to short circuit, to the position  12  and is locked in this position  12  in order to prevent a further rotation to the OFF position  11 . It is therefore possible, using the handle  4  alone, clearly to indicate the disconnection causes of the switching device in addition to the ON and OFF state, without any need to use an additional component. 
     FIG. 5  shows the schematic construction of a switching device as cited above which has been switched off. The switching device has a first tripper  2  for overload protection and a second tripper  3  for short-circuit protection. The first tripper  2  is preferably a thermobimetal tripper with time delay, and the second tripper  3  is preferably an electromagnetic tripper without time delay and additionally having a coil  17  and an armature  16 . Furthermore, the switching device has a switch latch  1  for mechanical activation of moving contacts  14  of the switching device and a handle  4  for activating the switch latch  1 . The handle  4  has a toothed segment  6 , and the switch latch  1  comprises a switch gearwheel  5  which is mounted on a fixed spindle and at least one connection lever  7 . By virtue of a toothed segment  6  engaging in the switch gearwheel  5 , the handle  4  is mechanically coupled to the switch latch  1 . The switch latch  1  is mechanically coupled to the trippers  2  and  3  respectively via two levers  8  and  9 . A spring  15  is provided in order to exercise a force on the lever  9 , such that the switch latch  1  can activate the trippers  2  and  3  or the handle  4  by means of its mechanical movement, the reverse applying analogously. 
   If the handle  4  is rotated to the position  11 , the handle  4  engages in the switch gearwheel  5  by means of the toothed segment  6  and rotates the switch gearwheel  5 . As a result of the rotation of the switch gearwheel  5 , the switch latch  1  can open the switching contacts  14 . The switching device is consequently switched off, and at the same time the handle  4  indicates the OFF state of the switching device in the OFF position  11 . 
   An identical switching device which is switched on is schematically illustrated in  FIG. 6 . If the handle  4  is rotated to the ON position  10 , the handle  4  activates the switch latch  1  in the same way. The switching contacts  14  are closed in order to switch the switching device on again, while the handle  4  indicates the ON state of the switching device in the ON position  10 . 
   In  FIG. 7 , the switching device has been disconnected due to a short circuit. In normal operation the lever  9  rests on the spring  15  and compresses the spring  15 . In the case of a short circuit, the armature  16  plunges into the coil  17  of the tripper  3  and the lever  9  is consequently freed. The lever  9  is pressed against the handle  4  by the released spring force and locks the handle  4  in the position  13 . At the same time the switching contacts  14  are opened via the switch latch  1 . The switching device is thus disconnected and at the same time the handle  4  shows the disconnection cause as a short circuit in the position  13 . 
   In  FIG. 8 , the switching device has been disconnected due to an overload. In the case of overload, the bimetal of the tripper  2  heats up. As a result of the deflection of the bimetal, the switch latch  1  is activated via the lever  8 . The handle  4 , which is coupled to the switch latch  1 , is moved to the position  12  by means of said switch latch  1  and locked there. The switching contacts  14  are then open. The switching device is thus disconnected and the handle  4  shows the disconnection cause as overload in the position  12 .