Abstract:
An electronic safety system for an elevator with a controller, which is coupled to a motor for driving an elevator car, a safety controller and a bus by means of which the controller can communicate with bus nodes which receive data from at least one sensor. The controller can communicate with a safety circuit which can be put into an open state by the safety controller, as a result of which the motor is shut off, and the safety circuit has a means which notifies the controller of shut-off of the motor, or shut-off of the motor can be detected by the controller on the basis of the data transmitted from the bus nodes to the controller.

Description:
FIELD OF THE INVENTION 
     The invention relates to safety systems for elevators. 
     BACKGROUND OF THE INVENTION 
     EP 1 159 218 B1 discloses an electronic safety system for an elevator in which safety shut-off is performed when an unsafe state is determined. The electronic safety system comprises a safety control device and a communication bus which allows control and data signals to be interchanged between a control device based on a microprocessor and various components which comprise bus nodes. The bus nodes are in a form such that they form an interface for sensors, contacts and switches. A safety control device processes the data received from the bus nodes and determines whether there is an unsafe state. In the event of an unsafe state, the safety control device sends a stop signal to the drive and brake unit of the elevator, with a status signal which indicates the unsafe state also being sent to the control device. 
     In the case of the safety control device which is known from EP 1 159 218 B1, the control device of the elevator is not intended to process any information from the bus nodes, but rather the control device actually obtains the processed information from the bus nodes from the safety control device in order to allow a faster reaction by the control device of the elevator. The safety control device undertakes the safety tasks on its own and is assigned an elementary role. 
     BRIEF SUMMARY OF THE INVENTION 
     It is an object of the invention to obtain a fast and safe embodiment of an electronic safety system in which a safety component is relieved of a load, which results in access to more information and increased safety with a possible improvement in maintenance. 
     As a result, a safety component such as a safety controller is relieved of load by virtue of the controller of the elevator indeed not obtaining from the safety controller the notification that shut-off or transfer to a safe state is or has been performed for a possible hazard potential. 
     The invention is explained in more detail below with reference to the exemplary embodiments which are illustrated in the appended figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG. 1  schematically shows a block diagram of the drive of an elevator car. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a block diagram of an elevator. A controller  1  is provided for a schematically shown elevator car denoted by  2 . 
     A motor  21  for driving the elevator car  2  is coupled to a bus  3  by means of a frequency converter  20 . 
     The controller  1  communicates via the bus  3  by means of bus nodes with components which, by way of example, are indicated as a floor level switch  4 , door contact  5 , command transmitter  6  and safe actuator  7  for a door motor  8  of the elevator car  2 . The controller  1  receives signals from the components via the bus  3  by means of the bus nodes, which form an interface for the components, such as the request for a journey to a particular floor level via the command transmitter  6  in the elevator car  2 . 
     In addition, signals are obtained from floor level switches  4  which allow inferences about the floor level on which the elevator car  2  is situated. The door contacts  5  provide a signal regarding whether the door of the relevant floor level is closed or open. The door contact  5 ′ provides a signal regarding whether the door of the elevator car  2  is closed or open. The safe actuator  7  is used to drive the door motor  8  of the elevator car  2 , which door motor can be controlled by the controller  1  by means of appropriate signals which are sent via the bus  3 . 
     In addition, at least two ultrasound position systems or USP systems  9  or a two-channel USP system is/are provided which each use ultrasound to ascertain the position of the elevator car  2  in the elevator shaft. The USP systems  9  used are preferably systems from the Schmersal company, the operation of which is described in the product catalogue “Aufzugsschaltgeräte-Aufzugs-Positionssystem USP” [Elevator switchgear-elevator position system USP] dated 31 Oct. 2007. The two USP systems  9  or the one two-channel USP system allow(s) redundant ascertainment of the position, which meets stringent safety requirements by comparing the position of the elevator car  2  as ascertained by the two USP systems  9  or the position of the elevator car  2  as ascertained by the one two-channel USP system. In addition, the position of the elevator car  2  ascertained over time can be used by the two USP systems  9  or the one two-channel USP system to determine the speed of the elevator car  2  in the elevator shaft as a derivation of the local operation of the elevator car  2  in the elevator shaft on the basis of time. It goes without saying that it is also possible to use more than two USP systems  9 . With two, however, the requisite redundancy is already obtained. Similarly, a two-channel USP system likewise provides the redundancy. In the case of the two-channel USP system, for example, it is possible to use a transmitter with two receivers and corresponding two channels. 
     The bus  3  has a safety controller  10  coupled to it as Can safety controller, which is able to receive the signals from floor level switch  4 , door contact  5 ,  5 ′, command transmitter  6 , safe actuator  7 , door motor  8  and USP system  9  via the bus  3 . The floor level switch  4 , door contact  5 ,  5 ′, command transmitter  6 , safe actuator  7  and USP system  9  can to this extent be called sensors. 
     The controller  1  is connected to a safety circuit  11  which the safety controller  10  can open using a (safety) switch  12 . The safety controller  10  monitors the safety operation of the elevator. If the safety controller  10  determines an unsafe state, such as the fact that the door contact  5 ′ is indicating that the door of the elevator car  2  is open while travelling between two floor levels, the (safety) switch  12  is opened and the elevator shut down or put into a safe state. Opening the safety circuit  11  results in operation of the (safety) switch  22 , which switches off the motor  21 . 
     Provision may be made for a device  13  for monitoring the speed of the elevator car  2  to be able to open a (safety) switch  14  independently of the safety controller  10  in order to open the safety circuit  11 , for example when a predetermined threshold value for the speed of the elevator car  2  is exceeded. The device  13  for monitoring the speed of the elevator car  2  may be implemented independently of the USP systems  9  or by the latter. 
     Provision may be made for one or two limit switches  15  for monitoring the overshooting of a predetermined local position of the elevator car  2  to be able to open a (safety) switch  16  independently of the safety controller  10  in order to open the safety circuit  11 , for example when the elevator car  2  in the elevator shaft exceeds a predetermined limit position at the lower or upper end of the elevator shaft. The limit switch(es)  15  may be implemented independently of the USP systems  9  or the two-channel USP system or by the latter. 
     When the motor  21  is shut off, the controller  1  receives from the safety circuit  11  the acknowledgement that the safety circuit  11  has been opened and the (safety) switch  22  has been operated to stop the motor  21 . To this end, a means is provided which reports the open safety circuit  11  to the controller  1 . This means may be implemented by the (safety) switch  22 , for example. As an alternative or in addition, provision may be made for the controller  3  to evaluate the information from the components, such as floor level switch  4 , door contact  5 , command transmitter  6 , safe actuator  7 , door motor  8  and USP system  9 , and to determine that shut-off needs/needed to be performed by the safety controller  10 . Provision may also be made for the safety controller  10  to forward the signals received from the components to the controller  1 . 
     The controller  1  can evaluate signals from the individual components connected to the bus nodes in order to provide an improved diagnosis and maintenance opportunity. 
     By way of example, the safety controller  10  can ascertain the position of the elevator car  2  in the elevator shaft redundantly by virtue of the two USP systems  9  connected to the bus  3  or by virtue of the one two-channel USP system. 
     If a floor level door of the elevator shaft now does not close correctly and the door contact  5  is not closed, it is possible to move the elevator car  2  above or below the impaired door whose door contact  5  is not closed. The redundancy of the position-finding for the elevator car  2  by the two USP systems  9  or the one two-channel USP system is taken as safe information for which the elevator is not shut off while the elevator car  2  does not enter the floor level region with the impaired door, i.e. the open door contact  5 . The availability of the elevator is improved. 
     In addition, provision may be made for a speed information item for the elevator car  2  to be able to be determined by the safety controller  10  from the two USP systems  9  or the one two-channel USP system redundantly so that it is possible to “catch up” in the region of the door zones of the elevator car  2 , i.e. the safety controller  10  provides the safe actuator  7  on the elevator car  2  with an enable signal in the region of the door zones so that the door motor  8  can be operated in the region of the door zone. This allows the operation of the door zone monitoring to be integrated in the safety controller  10 .