Patent Publication Number: US-10773923-B2

Title: Method for avoiding unwanted safety gear tripping in an elevator system, controller adapted to perform such a method, governor brake and elevator system each having such a controller

Description:
FIELD OF THE INVENTION 
     The present invention relates to a method for avoiding unwanted safety gear tripping in an elevator system, a controller adapted to perform such a method, a governor brake and an elevator system each having such a controller. 
     RELATED BACKGROUND ART 
     The following description of background art and examples may include insights, discoveries, understandings or disclosures, or associations, together with disclosures not known to the relevant prior art, to at least some examples of embodiments of the present invention but provided by the invention. Some of such contributions of the invention may be specifically pointed out below, whereas other of such contributions of the invention will be apparent from the related context. 
       FIG. 15  shows an elevator system  101  according to the related background art. This elevator system  101  comprises an elevator car  106  which is connected to a counterweight  107  via suspension ropes  113  which go over a traction wheel  112  driven by a hoisting machine (not shown). The elevator car  106  and the counterweight  107  are both guided vertically by respective guide rails inside a shaft (both not shown). In the following, the elevator car  106  and the counterweight  107  are referred to as the moving mass. 
     The elevator system  101  further comprises a safety circuit having a plurality of normally closed safety switches for monitoring the safety status of the elevator in normal operation. If the safety of the elevator is somehow compromised, at least one of the safety switches is opened, the hoisting machine is de-energised and machinery brakes  116  are engaged so as to decelerate the moving mass for quick stop. These safety switches can be opened in the event of opening an emergency exit hatch of the elevator car  106 , arrival at an extreme limit of permitting movement in the shaft, opening of a door of the elevator car  106  and so on. 
     The elevator system  101  further comprises an overspeed governor system  102  for the elevator car  106 , which has a governor rope loop  103  directed up from the elevator car  106 , over an overspeed governor pulley  108 , then down and under a tension weight pulley  109  connected to a tension weight  110  and then up again to the elevator car  106  to be connected to a synchronization linkage  114  for tripping an elevator car safety gear  104 . A corresponding overspeed governor system  152  can be attached to the counterweight  107 . The elements of the overspeed governor system  152  are provided with reference signs which are obtained by adding the value 50 to the values of the reference signs of the overspeed governor system  102  for the elevator car  106 . 
     The synchronization linkage  114  has synchronization levers which make the safety gear  104  of the moving mass to engage the guide rails of the moving mass when at least a predetermined force is applied to the synchronization linkage  114  by the governor rope  103 . This predetermined force is acting against spring forces of synchronization lever springs such that the synchronization lever engages the safety gear when the force applied by the governor rope  103  exceeds the synchronization lever spring force. 
     The overspeed governor system  102  supervises the speed of the moving mass, and, if this speed exceeds a predetermined tripping speed which is above a rated speed of the elevator, it opens a further safety switch of the above explained safety chain to activate the machinery quick stop operation described above and, simultaneously, decelerates the governor rope  103 . This deceleration of the governor rope  103  acts against the spring forces of synchronization lever springs such that the synchronization lever engages the safety gear  104 , bringing the elevator car  106  into an emergency stop. 
     To summarise, a quick stop operation of the machinery is initiated whenever the elevator safety circuit indicates a compromised safety status of the elevator. 
     Additionally, if the compromised safety status is a result of an overspeed condition of the moving mass, detected by overspeed governor, an emergency stop operation is activated by engaging the safety gear of the moving mass. 
     However, in high rise elevators, the elevator travel and speed increase such that the inertia of the governor rope  103  increases substantially. This brings a new challenge during elevator quick stops carried out by the hoisting machine brakes  116 . Namely, when the governor rope  103  having the increased length decelerate during the above explained quick stop, a large force is applied to the synchronization linkage  114 , because the inertia of the governor rope  103  is large. As a result, the decelerating governor rope  103  is capable of producing forces to the synchronization linkage  114  which exceed the needed force to engage the safety gear  104  when the moving mass is decelerated. In other words, the safety gear  104  might be unwantedly engaged or tripped during quick stop although the speed of the moving mass has not exceeded the predetermined tripping speed for engaging the safety gear  104 . 
     One solution for preventing unwanted safety gear tripping is to increase the synchronization lever spring force. However, this has an effect on the design of the overspeed governor since EN-81 codes require that the pull through force of the governor rope is twice as big as the force needed to engage the safety gear via the synchronization linkage. Stronger synchronization leads to bigger overspeed governor pull-through forces and, consequently a stronger and, thus, heavier overspeed governor rope due to required safety factor. It is evident that this will finally lead to elevator systems in which there is no more feasible design window for overspeed governor and safety gear system. 
     Hence, it is the object of the present invention to provide a measure for preventing the overspeed governor rope inertia from unwantedly engaging the safety gear. 
     BRIEF DESCRIPTION OF THE INVENTION 
     According to the present invention, the above object is solved with a method for avoiding unwanted safety gear tripping in an overspeed governor system of an elevator system, the overspeed governor system having a governor rope connected to a moving mass of the elevator system, a machinery brake for decelerating the moving mass so as to perform a quick stop of the moving mass, a safety gear mounted to the moving mass, a synchronization linkage for tripping the safety gear and a synchronization linkage blocking device for blocking the synchronization linkage and/or a governor brake for braking the governor rope, the method comprising the step of determining whether a quick stop of the moving mass is performed, and activating the governor brake and/or the synchronization linkage blocking device when the quick stop of the moving mass is performed. 
     According to this method, when a quick stop of the moving mass is performed, and thus the deceleration of the governor rope exceeds an allowable deceleration, the governor brake is activated according to a first alternative. By activating the governor brake, the kinetic energy of the governor rope is dissipated such that the force applied to the synchronization linkage is reduced. As a result, the safety gear is not unwantedly tripped during deceleration of the elevator car. According to a second alternative, the synchronization linkage blocking device is activated when the quick stop of the moving mass is performed. As a result, although a large force might be applied to the synchronization linkage, the synchronization levers are prevented from movement such that the safety gear is not unwantedly tripped during deceleration of the elevator car. 
     According to a preferable embodiment, the elevator system comprises a safety circuit configured to indicate that the safety of the elevator system is jeopardized if a safety circuit switch of the safety circuit is open, wherein the method further comprises determining whether the safety circuit indicates jeopardized safety, and concluding that the quick stop of the moving mass is performed if said jeopardized safety indication is present. According to this embodiment, the already existing safety circuit can be used for concluding about whether a quick stop is performed without the need of providing a separate means for determining whether the quick stop is performed. In other words, if the safety circuit is open, the elevator system carries out a quick stop which results in that the deceleration of the elevator car exceeds the allowable deceleration. 
     According to a further preferable embodiment, the elevator system comprises a controller for controlling stopping of the moving mass at a terminal floor and a normal terminal slowdown device configured to output a normal terminal slowdown signal if stopping of the moving mass at the terminal floor by control of the controller is jeopardized, wherein the method further comprises determining whether the normal terminal slowdown signal is output, and concluding that the quick stop is performed if the normal terminal slowdown signal is output. According to this embodiment, the already existing normal terminal slowdown device (NTS device) can be used for concluding about whether the quick stop is performed without the need of providing a separate means for determining whether the quick stop is performed. In other words, if the normal terminal slowdown signal, i.e. if the NTS device is activated, the elevator system carries out a quick stop which results in that the deceleration of the elevator car exceeds the predetermined deceleration limit. 
     According to a further preferable embodiment, the elevator system comprises an elevator car and a counterweight each acting as a moving mass, wherein one overspeed governor system is provided for the elevator car and another overspeed governor system is provided for the counterweight, further comprising determining whether the elevator car moves up or down, and if the elevator car moves up, the governor brake and/or the synchronization linkage blocking device of the overspeed governor system for the elevator car is activated, and if the elevator car moves down, the governor brake and/or the synchronization linkage blocking device of the overspeed governor system for the counterweight is activated. Here, in case the elevator car moves up, there is a risk of unwanted safety gear tripping at the elevator car. By contrast, in case the counterweight moves up, i.e. the elevator car moves down, there is a risk of unwanted safety gear tripping at the counterweight. Hence, the respective governor brake and/or the respective synchronization linkage blocking device is activated thus avoiding to unnecessarily activate the governor brake and/or block the synchronization linkage where there is no risk of unwanted safety gear tripping. As a result, the service life of the governor brake and that of a device for blocking the synchronization linkage can be made longer. 
     The object is further solved with an unwanted safety gear tripping avoiding controller for avoiding unwanted safety gear tripping in an elevator system, the unwanted safety gear tripping avoiding controller being adapted to perform the above explained method steps. With this controller, the same advantages as those described above can be obtained. 
     The object is further solved with a governor brake for braking a governor rope so as to avoiding unwanted safety gear tripping in an elevator system, wherein the elevator system comprises an overspeed governor system having at least a governor rope connected to a moving mass of the elevator system, a machinery brake for decelerating the moving mass so as to perform a quick stop, and a safety gear mounted to the moving mass, the governor brake further comprising the above explained unwanted safety gear tripping avoiding controller. By means of this governor brake, the invention can easily be implemented into existing elevator systems and overspeed governor systems. Since, the governor brake already comprises the unwanted safety gear tripping avoiding controller, it is not necessary for the controllers of the elevator systems and overspeed governor systems to be replaced because the control can entirely be done by the unwanted safety gear tripping avoiding controller of the governor brake. 
     According to a further preferable embodiment, the unwanted safety gear tripping avoiding controller of the governor brake is adapted to monitor the safety circuit and/or the normal terminal slowdown device of the elevator system so as to conclude about that the quick stop of the moving mass is performed. This allows the governor brake to use information of the safety circuit and/or the normal terminal slowdown device for concluding about whether the quick stop of the moving mass is performed without the need of a separate device dedicated to this conclusion. 
     According to a further preferable embodiment, the governor brake further comprises an elevator movement detecting device for detecting an elevator deceleration of the governor rope, wherein the unwanted safety gear tripping avoiding controller is adapted to monitor the elevator movement detecting device so as to conclude about whether the quick stop of the moving mass is performed. This allows to provide a fully independent system without the need of providing modifications or new features for the elevator control system. 
     According to a further preferable embodiment, the elevator movement detecting device is a speed sensor which is adapted to measure the speed of the governor rope, or an accelerometer or a gyroscope adapted to measure the deceleration of the governor rope, directly or indirectly. 
     Furthermore, the object is solved with an elevator system comprising an overspeed governor system having at least a governor rope connected to a moving mass of the elevator system, a machinery brake for decelerating the moving mass so as to perform a quick stop of the moving mass, a safety gear mounted to the moving mass, a synchronization linkage for tripping the safety gear, a synchronization linkage blocking device for blocking the synchronization linkage and/or a governor brake for braking the governor rope, and an unwanted safety gear tripping avoiding controller having the above explained features. 
     According to a further preferable embodiment the elevator system further comprises an elevator car controller and the unwanted safety gear tripping avoiding controller is implemented in the elevator controller. This allows to implement the invention into the existing elevator controller. When the existing elevator car controller uses a low latency bus such as LAN or CAN, the reaction time for activating the governor brake or blocking the synchronization linkage is not affected. 
     According to a further preferable embodiment, the governor system further comprises an OSG brake controller (overspeed governor brake controller) and the unwanted safety gear tripping avoiding controller is implemented in the OSG brake controller. 
     According to a further preferable embodiment, the elevator system comprises an elevator car and a counterweight each acting as a moving mass, wherein one overspeed governor system is provided for the elevator car and another overspeed governor system is provided for the counterweight, wherein the elevator system further comprises an elevator controller and the overspeed governor system further comprises an overspeed governor system controller both constituting the unwanted safety gear tripping avoiding controller, wherein the elevator controller is adapted to determine whether the elevator car moves up or down and to determine whether the moving speed of the elevator car exceeds a predetermined speed limit, and the elevator car controller is adapted to send an activation signal and a moving direction signal to the OSG brake controller if the moving speed of the elevator car exceeds the predetermined speed limit, wherein the OSG brake controller is adapted to, upon receipt of the activation signal and the moving direction signal, determine whether the quick stop is performed, and when the quick stop is performed, to activate the governor brake and/or the synchronization linkage blocking device of the overspeed governor system for the elevator car, if the moving direction signal indicates that the elevator car moves up, and to activate the governor brake and/or the synchronization linkage blocking device of the overspeed governor system for the counterweight if the moving direction signal indicates that the elevator car moves down. According to this embodiment, the elevator controller determines whether the moving speed of the elevator car is above a predetermined speed limit above which there is a risk of unwanted gear tripping due to the elevator car being decelerated. Thus, when the moving speed of the elevator car is below this speed limit, there is no risk of unwanted safety gear tripping such that there is no need of activating the overspeed governor system controller. If, however, the moving speed of the elevator car is above the speed limit, the overspeed governor system controller is activated and further receives the moving direction signal. On the basis of this information, the overspeed governor system controller can then activate the governor brake and/or the synchronization linkage blocking device of the correct moving mass, namely that of the elevator car in case the elevator car is moving up, and that of the counterweight in case the elevator car is moving down. This allows to avoid unnecessary activation of the governor brake or blocking of the synchronization linkage of the other, the incorrect moving mass. As a result, the service life of the governor brake of the blocking device can be increased. 
     Also according to this embodiment, the determination whether the quick stop is performed can be made on the basis of whether the safety circuit is open or whether the normal transportation slowdown device is activated. 
     According to a further embodiment, the speed governor system further comprises an overspeed governor pulley and a tension weight pulley, and the governor brake is a brake device acting on the overspeed governor pulley, a brake device acting on the governor rope or a brake device acting on tension weight pulley. 
     Furthermore, the object is solved with a synchronization linkage blocking device for blocking a synchronization linkage so as to avoid unwanted safety gear tripping in an elevator system, wherein the elevator system comprises an overspeed governor system having at least a governor rope connected to a moving mass of the elevator system via the synchronization linkage, a machinery brake for decelerating the moving mass so as to perform a quick stop of the moving mass, and a safety gear mounted to the moving mass, the synchronization linkage blocking device further comprising the above described unwanted safety gear tripping avoiding controller. 
     According to a further preferable embodiment, the unwanted safety gear tripping avoiding controller of the synchronization linkage blocking device is adapted to monitor the safety circuit and/or the normal terminal slowdown device of the elevator system so as to conclude about whether the deceleration of the elevator car exceeds the predetermined deceleration limit. This allows the synchronization linkage blocking device to use information of the safety circuit and/or the normal terminal slowdown device for concluding about whether the deceleration of the elevator car exceeds the predetermined deceleration limit without the needs of a separate device dedicated to this conclusion. 
     According to a further preferable embodiment, the synchronization linkage blocking device further comprises an elevator movement detecting device for detecting an elevator deceleration of the governor rope. This allows to provide a fully independent system without the need of providing modifications or new features for the elevator control system. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other objects, features, details and advantages will become more fully apparent from the following detailed description of embodiments of the present invention which is to be taken in conjunction with the appended drawings, in which: 
         FIG. 1  shows an elevator system according to a first embodiment of the present invention; 
         FIG. 2  shows a modification of the elevator system shown in  FIG. 1 ; 
         FIG. 3  shows a further modification of the elevator system shown in  FIG. 1 ; 
         FIGS. 4A to 4D  show examples of the governor brakes shown in  FIGS. 1 to 3 ; 
         FIG. 4E  shows a synchronization linkage of the elevator system shown in  FIGS. 1 to 3 . 
         FIG. 5  shows a controller scheme of the elevator system and the OSG system according to the first embodiment; 
         FIG. 6  shows a flow chart of a control of the elevator car controller shown in  FIG. 5 ; 
         FIG. 7  shows a flow chart of the governor brake controller and the elevator car controller monitoring device shown in  FIG. 5 ; 
         FIG. 8  shows a controller scheme of an elevator system according to a second embodiment; 
         FIG. 9  shows a flow chart of the elevator system shown in  FIG. 8 . 
         FIG. 10  shows a controller scheme of an OSG system according to a third embodiment; 
         FIG. 11  shows a flow chart of the OSG system shown in  FIG. 10 ; 
         FIG. 12A  shows synchronization lever angle at bottom of the shaft without governor brake and  FIG. 12B  shows synchronization lever angle at bottom of the shaft with governor brake; 
         FIG. 13A  shows synchronization lever angle at middle of the shaft without governor brake and  FIG. 13B  shows synchronization lever angle at middle of the shaft with governor brake; 
         FIG. 14A  shows synchronization lever angle at top of the shaft without governor brake and  FIG. 14B  shows synchronization lever angle at top of the shaft with governor brake; 
         FIG. 15  shows an elevator system according to the background art; 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     In the following, description will be made to embodiments of the present invention. It is to be understood, however, that the description is given by way of example only, and that the described embodiments are by no means to be understood as limiting the present invention thereto. 
     In particular, different exemplifying embodiments will be described using, as an example of an elevator system to which the embodiments may be applied, an elevator system as depicted and explained in connection with  FIGS. 1 to 3 . 
     It is to be noted that the following examples and embodiments are to be understood only as illustrative examples. Although the specification may refer to “an”, “one”, or “some” example(s) or embodiment(s) in several locations, this does not necessarily mean that each such reference is related to the same example(s) or embodiment(s), or that the feature only applies to a single example or embodiment. Single features of different embodiments may also be combined to provide other embodiments. Furthermore, terms like “comprising” and “including” should be understood as not limiting the described embodiments to consist of only those features that have been mentioned; such examples and embodiments may also contain features, structures, units, modules etc. that have not been specifically mentioned. 
     The general elements and functions of described elevator systems, details of which also depend on the actual type of elevator system, are known to those skilled in the art, so that a detailed description thereof is omitted herein. However, it is to be noted that several additional devices and functions besides those described below in further detail may be employed in an elevator system. 
       FIG. 1  shows an elevator system  1  having an elevator car  6  and a counterweight  7 , which are both acting a moving mass and are connected to each other by suspension ropes  13 . The suspension ropes  13  are going around a traction wheel  12  which is driven by a hoisting machine (not shown). Because of the heavy mass hanging on both ends of the suspension ropes  13 , the suspension ropes  13  do not slide on the traction wheel  12 . When the traction wheel  12  is driven by the hoisting machine and rotates, the elevator car  6  and the counterweight  7  move. The elevator car  6  and the counterweight  7  are guided by guide rails (not shown) which are mounted to the walls of the shaft (not shown) in which the elevator system  1  is provided. 
       FIG. 1  further shows an overspeed governor (OSG) system  2  for the elevator car  6 , which comprises a governor rope  3  both ends of which are connected to the elevator car  6  (the moving mass). The governor rope  3  goes around a governor pulley  8  on the top side of the elevator system and goes around a tension weight pulley  9  connected to a tension weight  10  on the bottom side of the elevator system. The governor rope  3  is connected to the elevator car  6  via a synchronization linkage  14  having synchronization levers for tripping a safety gear  4  against both guide rails of the elevator car  6 . 
       FIG. 1  further shows an overspeed governor (OSG) system  52  for the counterweight  7 , which comprises a governor rope  53  both ends of which are connected to the counterweight  7  (the moving mass). The governor rope  53  goes around a governor pulley  58  on the top side of the elevator system and goes around a tension weight pulley  59  connected to a tension weight  60  on the bottom side of the elevator system. The governor rope  53  is connected to the counterweight  7  via a synchronization linkage  64  having synchronization levers for tripping a safety gear  54  against both guide rails of the counterweight  7 . 
     Furthermore,  FIG. 1  shows that the OSG systems  2 ,  52  are provided with a governor brake  5 ,  55  which is configured to reduce the force applied to the synchronization linkage  14  by the governor rope  3 ,  53  when the governor brake  5 ,  55  is operated. In more detail, the governor brake  5 ,  55  is configured to dissipate the kinetic energy of the governor rope  3 ,  53 .  FIG. 1  schematically shows that the governor brake  5 ,  55  acts on the governor pulley  8 ,  58 . However, according to  FIG. 2 , the governor brake  5 ′,  55 ′ can act directly on the governor rope  3 , and according to  FIG. 3 , the governor brake  5 ″,  55 ″ can act on the tension weight pulley  9 ,  59 . 
       FIGS. 4A to 4C  show alternative embodiments of the governor brakes  5 ,  5 ′ and  5 ″ which apply also to the governor brakes  55 ,  55 ′ and  55 ″. According to  FIG. 4A , in the governor brakes  5  and  5 ″, which act on the governor pulley  8  or the tension weight pulley  9 , the brake force can act on the pulley side. According to  FIG. 4B , in the governor brakes  5  and  5 ″, which act on the governor pulley  8  or the tension weight pulley  9 , the brake force can act on the pulley groove edge. According to  FIG. 4C , in the governor brakes  5  and  5 ″, which act on the governor pulley  8  or the tension weight pulley  9 , the brake force can act on the governor rope  3  on the groove. According to the approaches of  FIGS. 4A and 4B , the rope friction in the groove is the dimensioning factor on the brake force. According to the approach of  FIG. 4C , the rope robustness against damage is the dimensioning factor. 
       FIG. 4D  shows details of the governor brake  5 ′ of the elevator system shown in  FIG. 2 . This brake device is a standalone device acting on the governor rope  3 , similar mechanism like OSG rope clamp acting on the rope but with smaller force than OSG tripping force. 
       FIG. 4E  shows the synchronization linkage  14 ,  64  in more detail. According to one embodiment, the synchronization linkage  14 ,  64  is provided with a synchronization linkage blocking device  15  which is adapted to block the operation of the synchronization linkage  14 ,  64 . 
     Thus, by means of one of the governor brakes  5 ,  5 ′  5 ″ and/or by means of the synchronization blocking device  15 , unwanted tripping of the safety gear  4 ,  54  can be prevented. Hence, if there is a situation which requires to prevent unwanted tripping of the safety gear  4 ,  54 , either the governor brakes  5 ,  5 ′,  5 ″ or the synchronization blocking device  15  can be operated. Alternatively, both of them can be operated simultaneously. 
     In the following, the control schemes according to a first embodiment are described with reference to  FIGS. 5, 6 and 7 . 
       FIG. 5  shows a control scheme of the elevator system  1  according to the first embodiment. Here, in addition to the above described constituents, the elevator system  1  comprises a safety circuit  21 , and a NTS (normal terminal slowdown) device  22  as well as an elevator controller  23 . 
     The safety circuit  21  comprises a plurality of safety switches as the one explained for the background art. The safety switches are normally closed and are opened during a functional nonconformance of the elevator system  1 . When one of the safety switches is open, the safety circuit  21  indicates a functional nonconformance of the elevator system  1 , meaning that the safety of the elevator system is jeopardized. The elevator controller  23  receives this indication from the safety circuit and activates hoisting machine brake  16  of the elevator system  1  so as to perform a quick stop of the elevator car  6 . 
     Furthermore, the elevator controller  23  is adapted to control stopping of the elevator car  6  at a terminal floor which is the uppermost or the lowermost floor. However, if the elevator car  6  fails to stop at the terminal floor, the normal terminal slowdown device  22  outputs a normal terminal slowdown signal. The normal terminal slowdown signal is sent to the elevator controller  23  which cuts the power from hoisting machinery and activates the hoisting machine brake  16  of the elevator system  1  so as to perform a quick stop of the elevator car  6 . 
     Furthermore, the control scheme comprises an OSG brake controller  30  having a governor brake controller  31  and an elevator controller monitoring device  32 . The governor brake controller  31  is configured to operate the governor brake  5 ,  5 ′ or  5 ″. The governor brake controller  31  can be replaced or complemented by a synchronization blocking device controller which is configured to operate the synchronization blocking device  15 . 
       FIG. 6  shows a flow chart of a control procedure carried out by the elevator controller  23  of  FIG. 5 . According to step S 1 , the elevator car controller  23  determines whether the elevator car  6  is moving up or down and whether the moving speed of the elevator car exceeds a predetermined speed limit. In step S 2 , if the moving speed of the elevator car exceeds the predetermined speed limit, the control proceeds to step S 3  (yes in S 2 ) and sends an activation signal and a moving direction signal to the OSG system controller  30 . The moving direction signal indicates whether the elevator car  6  is moving up or down. 
     The above mentioned predetermined speed limit can be 0.5 m/s, for example, which corresponds to an inspection drive of the elevator. In this case, the activation of the governor brake or the blocking of the synchronization linkage of the safety gear is disabled during inspection drive. However, the invention is not limited to that the moving speed of the elevator car  6  exceeds a predetermined speed limit and the activation of the governor brake or the blocking of the synchronization linkage of the safety gear can also be done without referring to a speed limit. According to a first modification of the first embodiment, the speed limit can be 0.0 m/s. In this case, an activation signal is sent to the OSG brake controller in step S 3  of  FIG. 6  when the elevator car is moving at all, i.e. also during the inspection drive. 
     Meanwhile, as is shown in  FIG. 7 , the OSG brake controller  30  shown in  FIG. 5  monitors in step S 11  whether the activation signal is received from the elevator controller  23 . According to the above mentioned first modification, the activation signal is received if the elevator car moves at all, i.e. also during the inspection drive. If the activation signal is received (yes in step S 11 ), the elevator controller monitoring device  32  shown in  FIG. 5  is activated in step S 12 . In other words, the elevator controller monitoring device  32  monitors whether the safety circuit  21  of the elevator system  1  is open, i.e. whether one of the safety switches of the safety circuit  21  is open such that a quick stop will be carried out by the elevator controller  23 . Furthermore, the elevator controller monitoring device  32  monitors whether the NTS-device is triggered such that a quick stop will be carried out by the elevator controller  23 . In both cases, the quick stop will result in a strong deceleration of the elevator car  6 . 
     If the elevator controller monitoring device  32  determines that the safety circuit  21  is open or the NTS device is activated or triggered (yes in step S 13 ), the control proceeds to step S 14 . Otherwise, the control turns back to step S 12 . 
     In step S 14 , it is determined whether the moving direction signal indicates that the elevator car  6  moves upward. If this is the case (yes in Step S 14 ), the control proceeds to step S 15  in which the governor brake  5  of the OSG system  2  for the elevator car  6  is activated by the governor brake controller  31 . In a complementary or alternative embodiment, the synchronization linkage  14  of the OSG system  2  for the elevator car  6  is blocked by activating the respective blocking device  15  by the governor brake controller  31  or a separate blocking device controller (not shown). 
     On the other hand, if the moving direction signal indicates that the elevator car  6  moves downward (no in step S 14 ), the control proceeds to step S 16  in which the governor brake  55  of the OSG system  52  for the counterweight  7  is activated by the governor brake controller  31 . Complementary or alternatively, the synchronization linkage  64  of the OSG system  52  for the counterweight  7  is blocked by activating the respective blocking device  15  by the governor brake controller  31  or a separate blocking device controller (not shown). 
     By means of this control, the OSG brake controller  30  is informed by the elevator controller  23  about the upcoming event of a quick stop of the elevator car  6  when the speed of the elevator car  6  is high enough that the quick stop will result in a certain degree of deceleration of the elevator car  6 . 
     Furthermore, when the elevator car  6  moves upward and is then decelerated, the inertia of the governor rope  3  acts on the synchronization linkage  14  of the elevator car  6  such that there is a risk of unwanted tripping of the safety gear  4  of the OSG system for the elevator car  6 . Hence, in this case, when quick stop is performed and thus, the deceleration of the elevator car  6  exceeds a certain deceleration, the governor rope  3  of the OSG system for the elevator car  6  is braked by activating the governor brake  5  of the OSG system for the elevator car  6 . Hence, the inertia of the governor rope  3  is dissipated such that the synchronization linkage  14  of the OSG system for the elevator car  6  does not unwantedly engage the safety gear  4 . Complementary or alternatively, the blocking device  15  is activated such that the operation of the synchronization linkage  14  of the OSG system for the elevator car  6  is blocked such that the safety gear  4  is not engaged even if the inertia of the governor rope  3  would be high enough for operating the synchronization linkage  14 . 
     By contrast, when the elevator car  6  moves downward and is then decelerated, the inertia of the governor rope  53  acts on the synchronization linkage  64  of the counterweight  7  such that there is a risk of unwanted tripping of the safety gear  54  of the OSG system  52  for the counterweight  7 . Hence, in this case, when the quick stop is performed and thus, the deceleration of the elevator car  6  exceeds a certain deceleration, the governor rope  53  of the OSG system  52  for the counterweight  7  is braked by activating the governor brake  55  of the OSG system  52  for the counterweight  7 . Hence, the inertia of the governor rope  53  is dissipated such that the synchronization linkage  64  of the OSG system  52  for the counterweight  7  does not unwantedly engage the safety gear  54 . 
     Complementary or alternatively, the blocking device  15  is activated such that the operation of the synchronization linkage  64  of the OSG system  52  for the counterweight  7  is blocked such that the safety gear  54  is not engaged even if the inertia of the governor rope  53  would be high enough for operating the synchronization linkage  64 . 
     In the following, the control schemes according to a second embodiment will be described with respect to  FIGS. 8 and 9 . 
     In the first embodiment, the claimed unwanted safety gear tripping avoiding controller is implemented in both the elevator controller  23  and the OSG system controller  30  in a shared manner. This is, the OSG brake controller  30  uses information regarding the elevator speed from the elevator controller  23  and monitors the safety circuit  21  and the NTS device  22  of the elevator controller  23  for concluding that the quick stop is performed, resulting in a certain degree of deceleration of the elevator car  6 , so as to take a measure against unwanted tripping of the safety gear. 
     By contrast, in the second embodiment, the governor brake  5  and/or the blocking device  15  are fully controlled by the elevator controller  203 . Hence, as is shown in  FIG. 8 , elevator system  1  comprises a governor brake controller  204  in addition to the safety circuit  201 , the NTS-device  202  and the elevator controller  203 . Unlike the first embodiment, there is no separate OSG brake controller  30  with elevator controller monitoring device  32  in the second embodiment. 
       FIG. 9  shows a flow chart of a control procedure carried out by the elevator controller  203  of  FIG. 8 . According to step S 200 , the elevator controller  203  determines whether the elevator car  6  is moving up or down and sends a moving direction signal to the governor brake controller  204  to indicate whether the elevator car  6  is moving up or down. 
     Furthermore, the elevator car controller  203  monitors whether the safety circuit  201  of the elevator system  1  is open, i.e. whether one of the safety switches of the safety circuit  201  is open such that a quick stop will be carried out by the elevator controller  203 . Furthermore, the elevator controller  203  monitors whether the NTS device  202  is triggered such that a quick stop will be carried out. In both cases, the quick stop will result in a strong deceleration of the elevator car  6 . 
     If the elevator controller  203  determines that the safety circuit  21  is open or the NTS device is activated (yes in step S 201 ), the control proceeds to step  202 . Otherwise, the control procedure returns to start (see no in step S 201 ). 
     In step S 202 , it is determined whether the moving direction signal indicates that the elevator car  6  moves upward. If this is the case (yes in Step S 202 ), the control proceeds to step S 203  in which the governor brake  4  of the OSG system  2  for the elevator car  6  is activated by the governor brake controller  204 . In a complementary or alternative embodiment, the synchronization linkage  14  of the OSG system  2  for the elevator car  6  is blocked by activating the respective blocking device  15  by a blocking device controller (not shown). 
     On the other hand, if the moving direction signal indicates that the elevator car  6  moves downward (no in step S 203 ), the control proceeds to step S 204  in which the governor brake  55  of the OSG system  52  for the counterweight  7  is activated by the governor brake controller  204 . Complementarily or alternatively, the synchronization linkage  64  of the OSG system  52  for the counterweight  7  is blocked by activating the respective blocking device  15  by a blocking device controller (not shown). 
     By means of this control, the elevator controller  203  determines whether there is the event of a quick stop of the elevator car  6  which might result in a certain degree of deceleration of the elevator car  6 . Furthermore, when the elevator car  6  moves upward and is then decelerated, the inertia of the governor rope  3  acts on the synchronization linkage of the elevator car  6  such that there is a risk of unwanted tripping of the safety gear  4  of the OSG system for the elevator car  6 . Hence, in this case, when a quick stop is performed and thus, the deceleration of the elevator car  6  exceeds an allowable deceleration, the governor rope  3  of the OSG system for the elevator car  6  is braked by activating the governor brake  5  of the OSG system for the elevator car  6 . Hence, the inertia of the governor rope  3  is dissipated such that the synchronization linkage  14  of the OSG system for the elevator car  6  does not unwantedly engage the safety gear  4 . Complementarily or alternatively, the blocking device  15  is activated such that the operation of the synchronization linkage  14  is blocked such that the safety gear is not engaged even if the inertia of the governor rope  3  would be high enough for operating the synchronization linkage  14 . 
     By contrast, when the elevator car  6  moves downward and is then decelerated, the inertia of the governor rope  53  acts on the synchronization linkage  64  of the counterweight  7  such that there is a risk of unwanted tripping of the safety gear  54  of the OSG system  52  for the counterweight  7 . Hence, in this case, when the quick stop is performed and thus, the deceleration of the elevator car  6  exceeds a certain deceleration due to the quick stop, the governor rope  53  of the OSG system  52  for the counterweight  7  is braked by activating the governor brake  55  of the OSG system  52  for the counterweight  7 . Hence, the inertia of the governor rope  53  is dissipated such that the synchronization linkage  64  of the OSG system for the counterweight  7  does not unwantedly engage the safety gear  54 . Complementarily or alternatively, the blocking device  15  is activated such that the operation of the synchronization linkage  64  is blocked such that the safety gear  54  is not engaged even if the inertia of the governor rope  53  would be high enough for operating the synchronization linkage  64   
     As in the first embodiment, the elevator controller  203  can additionally determine in step S 200  whether the elevator speed exceeds a predetermined speed limit. In this modification, the step S 201  will only be carried out if the actual elevator speed exceeds the predetermined speed limit. Otherwise, the control can be terminated. Hence, the governor brake  5  and/or the blocking device  15  will only be activated if the elevator speed is above the predetermined speed limit upon the event of the quick stop. Thus, the governor brake  5  or the blocking device  15  will only be activated if the deceleration during the quick stop is large enough for resulting in a correspondingly large inertia force of the governor rope  3  such that there is a risk of unwantedly tripping the safety gear  4 . Hence, if there is no risk of unwanted safety gear tripping because the elevator speed is below the predetermined speed limit, the governor brake  5  or the blocking device  15  does not need to be operated. 
     The above mentioned predetermined speed limit can be 0.5 m/s, for example. 
     In the following, the control schemes according to the third embodiment will be described with respect to  FIGS. 10 and 11 . 
     In contrast to the first and second embodiment, in the third embodiment, the governor brake  5  and/or the blocking device  15  are fully controlled by the OSG brake controller  300 . Hence, as is shown in  FIG. 10 , the OSG brake controller  300  comprises an elevator movement detecting device  301  and a governor brake controller  302 . 
     The elevator movement detecting device  301  can be a speed sensor, an accelerometer or a gyroscope and is suitable for deriving or detecting the elevator speed, the moving direction of the elevator and the acceleration and deceleration of the elevator car  6  and the counterweight  7  and thus of the governor ropes  3 ,  53 . 
       FIG. 11  shows a flow chart carried out by the OSG brake controller  300  of  FIG. 10 . According to step S 300 , the elevator movement detecting device  301  determines whether the elevator car  6  is moving up or down and detects the deceleration of the elevator car  6 . 
     In step S 301 , it is determined whether the deceleration of the elevator car  6  exceeds a predetermined deceleration limit. If the detected deceleration exceeds the predetermined deceleration limit, the control proceeds to step S 302 . Otherwise, the control is terminated. 
     In step S 302 , it is determined whether the elevator car  6  moves upward. If this is the case (yes in Step S 302 ), the control proceeds to step S 303  in which the governor brake  5  of the OSG system  2  for the elevator car  6  is activated by the governor brake controller  302 . Complementarily or alternatively, the synchronization linkage  14  of the OSG system  2  for the elevator car  6  is blocked by activating the respective blocking device  15  by a blocking device controller (not shown). 
     On the other hand, if it is determined that the elevator car  6  moves downward (no in step S 302 ), the control proceeds to step S 304  in which the governor brake  55  of the OSG system  52  for the counterweight  7  is activated by the governor brake controller  302 . Complementarily or alternatively, the synchronization linkage  64  of the OSG system  52  for the counterweight  7  is blocked by activating the respective blocking device  15  by a blocking device controller (not shown). 
     By means of this control, the elevator movement detection device  301  determines whether the deceleration of the elevator car  6  is above the predetermined deceleration limit. Furthermore, when the elevator car moves upward and is then decelerated, the inertia of the governor rope  3  acts on the synchronization linkage  14  of the elevator car  6  such that there is a risk of unwanted tripping of the safety gear of the OSG system for the elevator car  6 . Hence, in this case, when the deceleration of the elevator car  6  exceeds a predetermined deceleration limit due to the quick stop, the governor rope  3  of the OSG system  2  for the elevator car  6  is braked by activating the governor brake  5  of the OSG system for the elevator car  6 . Hence, the inertia of the governor rope  3  is dissipated such that the synchronization linkage  14  of the OSG system for the elevator car  6  does not unwantedly engage the safety gear  4 . Complementarily or alternatively, the blocking device  15  is activated such that the operation of the synchronization linkage  14  is blocked such that the safety gear  4  is not engaged even if the inertia of the governor rope  3  would be high enough for operating the synchronization linkage  14 . 
     By contrast, when the elevator car  6  moves downward and is then decelerated, the inertia of the governor rope  3  acts on the synchronization linkage  64  of the counterweight  7  such that there is a risk of unwanted tripping of the safety gear  54  of the OSG system  52  for the counterweight  7 . Hence, in this case, when the deceleration of the elevator car  6  exceeds a predetermined deceleration limit due to the quick stop, the governor rope  53  of the OSG system  52  for the counterweight  7  is braked by activating the governor brake  55  of the OSG system  52  for the counterweight  7 . Hence, the inertia of the governor rope  53  is dissipated such that the synchronization linkage  64  of the OSG system  52  for counterweight  7  does not unwantedly engage the safety gear  54 . Complementarily or alternatively, the blocking device  15  is activated such that the operation of the synchronization linkage  64  is blocked such that the safety gear  4  is not engaged even if the inertia of the governor rope  53  would be high enough for operating the synchronization linkage  64 . 
     The system according to the third embodiment is fully independent from the elevator control system. For example, the control of the third embodiment can be implemented directly into the governor brake  5 ,  55  or into the blocking device  15  of the synchronization linkage  14 ,  64 . 
     In the above embodiments, the elevator system has a safety circuit and an NTS-device. However, according to a modification, the elevator system has only one of the safety circuit and the NTS device. 
     In the above embodiments, the moving direction of the elevator car is determined (see S 1  in  FIG. 6  and S 14  in  FIGS. 7 , S 200  and S 202  in  FIG. 9 , and S 300  and S 302  in  FIG. 11 ), and the governor brake is activated for the elevator car or for the counter weight depending on the moving direction of the elevator car, or the synchronization linkage of the safety gear is blocked for the elevator car or for the counter weight depending on the moving direction of the elevator car. However, according to modifications of the embodiments, the steps of determining the moving directions can be omitted and the governor brakes for both of the elevator car and the counterweight can be activated, or the synchronization linkages of the safety gears for both of the elevator car and the counterweight can be blocked if the safety circuit is open, the NTS-device is triggered or the elevator deceleration exceeds a predetermined limit. 
     DESCRIPTION OF EXAMPLES 
     According to the above embodiments, one way to absorb the governor rope kinetic energy is to stop OSG pulley and/or tension weight diverting pulley by a separate brake and to decelerate the governor rope by rope traction. Therein, the pulley traction capability is depending on rope forces which can be obtained as follows. 
     Traction at Governor Pulley 
     
       
         
           
               
             
               { 
               
                 
                   
                     
                       
                         
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                         + 
                         
                           F 
                           2 
                         
                       
                       = 
                       
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                         ⁡ 
                         
                           ( 
                           
                             
                               m 
                               TW 
                             
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                           f 
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                           ⁢ 
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     By solving these formulas, the traction force and energy during deceleration is obtained: 
     
       
         
           
             
               Δ 
               ⁢ 
               
                   
               
               ⁢ 
               
                 F 
                 OSG 
               
             
             = 
             
               
                 g 
                 ⁡ 
                 
                   ( 
                   
                     
                       m 
                       TW 
                     
                     + 
                     
                       2 
                       ⁢ 
                       
                         Hm 
                         r 
                       
                     
                   
                   ) 
                 
               
               - 
               
                 2 
                 ⁢ 
                 g 
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                       m 
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                     + 
                     
                       2 
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                     + 
                     1 
                   
                 
               
             
           
         
       
       
         
           
             
               W 
               OSG 
             
             = 
             
               Δ 
               ⁢ 
               
                   
               
               ⁢ 
               
                 F 
                 OSG 
               
               ⁢ 
               s 
             
           
         
       
     
     Same equations apply for tension weight pulley, but here, the mass of the governor rope is zero. 
     The total energy absorbed is then
 
 W   tot   =W   OSG   W   div  
 
     Below is given an example calculation of pulley traction absorption capabilities at two different travel height. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 OSG and tension weight pulley traction capability 
               
            
           
           
               
               
               
               
            
               
                   
                 Travel H [m] 
                 400 
                 750 
               
               
                   
               
            
           
           
               
               
               
               
            
               
                   
                 Governor rope kinetic energy at 
                 12.8 
                 24.8 
               
               
                   
                 10 m/s [kJ] 
                   
                   
               
               
                   
                 OSG traction force 
                 1242 
                 1538 
               
               
                   
                 Diverting pulley traction force 
                 884 
                 884 
               
               
                   
                 Total traction force 
                 2126 
                 2421 
               
               
                   
                 Energy from OSG traction [kJ] 
                 14.9 
                 18.5 
               
               
                   
                 energy from div pulley traction [kJ] 
                 10.6 
                 10.6 
               
               
                   
                 Total [kJ] 
                 25.5 
                 29.1 
               
               
                   
               
            
           
         
       
     
     A quick stop simulation for the overspeed governor system  2  including the synchronization linkage  14  was performed. The travel distance of the elevator car  6  was chosen to be 750 m and the rated speed was 10 m/s. During the quick stop, a linear deceleration of 5 m/s 2  is assumed. The simulation was run at three different locations in the shaft, namely at the bottom, the middle and the top of the shaft. The simulations were also run with and without the additional governor rope brakes  5 . The braking forces were chosen as calculated with the above formulas and given in table  1 . Hence, for OSG traction force  1538 N was used and for diverting pulley at tension weight  884 N was used. The synchronization linkage  14  was dimensioned such that ˜ 1100 N force from OSG rope is enough to activate the safety gears. 
     In the  FIGS. 13 to 15  is shown the synchronization lever angle as a function of time and quick stop for elevator is activated at t=0 s. The lower horizontal line represents the lower limit of the synchronization lever (normal position) and the upper horizontal line is the angle where the safety gear is assumed to be activated. In the simulation the braking action of the safety gear is not taken into account, i.e. the contact between the safety gear wedges/brake pads and the elevator guide rails is not included. 
     For all synchronization locations in the shaft, the unintentional safety gear tripping is possible, when the OSG system does not include the additional governor brakes. In all of the above mentioned shaft locations, the synchronization lever angle reaches the upper horizontal line almost immediately after the quick stop is performed. 
     When additional governor brakes are activated, the unwanted tripping of the safety gear is not possible, as the synchronization lever angle does not reach the upper horizontal line.