Abstract:
An elevator system includes an elevator car and a counterweight fixed to a traction device. A drive pulley moves the traction device. A bottom tensioning apparatus is fixed to the counterweight and to the elevator car. A tensioning weight tensions the bottom tensioning apparatus. In an end position of the counterweight, the elevator car can continue to move when the traction device is moved further by the drive pulley. This moves the tensioning weight at half the speed of the elevator car, for example. A measuring device is provided for the tensioning weight for detecting such a motion of the tensioning weight. This allows a triggering of an emergency stop of the elevator car.

Description:
FIELD OF THE INVENTION 
     The invention relates to an elevator system with at least one elevator car drivable by a drive pulley by way of a traction means, wherein apart from the traction means a bottom tensioning means or apparatus, which is tensioned by a tensioning means weight, for the elevator car is provided. In particular, the invention relates to the field of elevator systems in which the occurrence of slip of the traction means at the drive pulley is prevented. In addition, the invention also relates to a method of operating such an elevator installation. 
     BACKGROUND OF THE INVENTION 
     An elevator system with an elevator car, a counterweight and a traction means, which connects the elevator car with the counterweight, is known from EP 0 619 263 A1. In that case the movement of the drive pulley is transmitted by way of the traction means to the elevator car and the counterweight. Also provided are tensioning means by way of which the elevator car is acted on against the force of the counterweight by a tensioning force. In the case of, in particular, high-rise elevator systems it is thereby possible to provide compensation for imbalance, which arises due to the weight of the traction means, at the drive pulley so that slip of the traction means at the drive pulley is prevented and the loading of a drive motor unit driving the drive pulley is reduced. 
     The elevator system known from EP 0 619 263 A1 has the disadvantage that in a state in which the counterweight rests in its end setting on a buffer a further raising of the elevator car is possible. Particularly in the case of elevator systems of very high construction the weight of the traction means, which engages the drive pulley from the side of the counterweight, can be sufficient to ensure the friction, which required for raising the elevator car, at the drive pulley. Since this represents a significant safety risk, the constructional height of known elevator systems is, for safe operation, limited. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to create an elevator system in which safety is improved and which, in particular, an excessive lifting of an elevator car is prevented. 
     It is to be noted that the traction means also has the function, apart from transmission of the force or torque of a drive motor unit to the elevator car in order to actuate the elevator car, of supporting the elevator car. By actuation of the elevator car there is understood, in particular, raising or lowering of the elevator car, wherein the elevator car can be guided by one or more guide rails. 
     It is advantageous that a measuring device detects a vertical movement of the tensioning means weight and outputs a measurement variable, particularly a measurement voltage. For that purpose the measuring device comprises travel, speed or acceleration detecting means. In the present case use is preferably made of a measuring device with speed detecting means or a speed detecting device. The measurement voltage issued by the speed detecting device in that case proportionally increases with increasing vertical speed of the tensioning means weight. The detection of the speed of the tensioning means weight has the advantage that changes in length, which occur over relatively lengthy periods of time, of the tensioning means weight have no influence on the detection. For example, the length of the traction means and the length of the bottom tensioning means can increase due to the permanent load, which can lead to changes in position of the tensioning means weight. However, movement of the elevator car, which is not in accordance with operation, relative to the counterweight when, for example, the counterweight is stationary has the effect of movement of the tensioning means weight, so that detection of the speed of the tensioning means weight makes possible the detection of an undesired operating state regardless of the initial position of the tensioning means weight. 
     It is advantageous if the speed detecting device comprises a magnet rod, which is constructed at least in part to be magnetic, and at least one coil element, which surrounds the magnet rod in sections, and if the magnet rod and the coil element are so arranged that a movement of the tension means weight causes a relative movement between the magnet rod and the coil element. The magnet rod can, for example, be connected by means a bracket or the like with the tensioning means weight so that the magnet rod moves together with the tensioning means weight. The coil element can in this case be arranged in stationary position and, for example, be connected by way of a support with a floor or wall of an elevator shaft or another form of boundary of the travel region of the elevator car, such as, for example, a foundation of a framework construction. 
     In advantageous manner, a control device is provided which is connected with the speed detecting device, wherein the control device stops the elevator car when a threshold value is exceeded. This threshold value is predetermined with respect to a maximum permissible speed of movement of the tensioning means weight. In operation of the elevator system specific relatively small movements of the tensioning means weight can arise in operation of the elevator system when, for example, the elevator car starts off or the counterweight runs against a hydraulic buffer. Moreover, vibrations can propagate to the tensioning means weight. It is possible by the threshold value to reliably prevent response of a safety device in such normal cases. In the event of exceeding of the threshold value, the control device can, for example, actuate a safety relay for a safety chain for triggering an emergency stop. The threshold value is, in particular, fixable at such a level that the speed detecting device responds when the elevator car or the counterweight travels onto a buffer or when the elevator car or counterweight is blocked. 
     It is also advantageous if the speed detecting device is connected with an evaluating device and that the control device is connected by means of a bus system with the evaluating device connected with the speed detecting device. The detected speed of the tensioning means weight or a measurement variable correlated with the speed of the tensioning means weight can be issued by way of the bus system to the control device. In addition, the control device can also access the evaluating device and, by way of this, optionally the speed detecting device in order to, for example, perform a function check. 
     It is advantageous if a second elevator car and a second counterweight associated with the second elevator car, which are suspended at a second traction means connected with the second elevator car and the second counterweight, are provided. In addition, a second bottom suspension means is suspended on the one hand at the second counterweight and on the other hand at the second elevator car. Similarly, a second tensioning means weight which tensions the second bottom tensioning means is provided. Finally, a second measuring device is provided, preferably a second speed detecting device, for the second tensioning means weight and serves for detecting movement of the second tensioning means weight. The safety equipment can thus be used even with elevator systems with two elevator cars and, in corresponding manner, also with elevator systems with more than two elevator cars. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       Preferred embodiments of the invention are explained in more detail in the following description by way of the accompanying drawings, in which corresponding elements are provided with corresponding reference numerals and in which: 
         FIG. 1  shows an elevator system with two elevator cars in a schematic illustration in correspondence with a first embodiment of the invention; 
         FIG. 2  shows an elevator system with an elevator car in a schematic illustration in correspondence with a second embodiment of the invention; 
         FIG. 3  shows an illustration, in the form of a detail, of an elevator system which shows, inter alia, a tensioning means weight; 
         FIG. 4  shows a speed detecting device for the tensioning means weight shown in  FIG. 3 , with a control device in correspondence with one possible embodiment of the invention; 
         FIG. 5  shows the speed detecting device, which is shown in  FIG. 4 , in a detailed schematic illustration; and 
         FIG. 6  shows a speed detecting device for the tensioning means weight, which is shown in  FIG. 3 , with an evaluating device connected with a control device by way of a bus system, in correspondence with another possible embodiment of the invention. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 1  shows an elevator system  1  which is arranged in an elevator shaft  2  bounded by lateral walls  3 ,  4  as well as a floor  5  and a ceiling  6 . The elevator system  1  can, in particular, be of very high construction and, for example, have an elevator shaft  2  with a height of 300 meters or more. 
     The elevator system  1  comprises a first elevator car  7  and a second elevator car  8 , wherein the first elevator car  7  is arranged below the second elevator car  8 . The two elevator cars  7 ,  8  are movable upwardly and downwardly independently of one another along a travel path usable by both elevator cars  7 ,  8 . In that case the travel path is disposed in the elevator shaft  2 , wherein one or more elevator car guide rails or the like can be provided, which for simplification of the schematic illustration are not illustrated. 
     The lower, first elevator car  7  is suspended at a traction means or device  10  with two traction means runs  10 . 1 ,  10 . 2  in substantially point-symmetrical manner with diagonally opposite force introduction regions and in the ratio 1:1. The traction means  10  also has the function of a support means. The first traction means run  10 . 1  of the first elevator car  7  has a first end  11 . 1  and a second end  12 , which are fastened to the elevator car  7  and an associated counterweight  18 , respectively. In that case a first auxiliary roller  16 . 1 , around which the first traction means run  10 . 1  is guided, is mounted in the upper region of the elevator shaft  2  in the vicinity of the ceiling  6 . Moreover, the first traction means run  10 . 1  runs around a first drive pulley  17 . 1 , which is similarly mounted in stationary position in the vicinity of the ceiling  6  at the top in the elevator shaft  2 , i.e. is connected with a drive motor unit fastened in the elevator shaft  2 . From the first drive pulley  17 . 1  the first traction means run  10 . 1  finally runs to the associated counterweight  18 , to which the first traction means run  10 . 1  is fastened. 
     The second traction means run  10 . 2  of the first elevator car  7  has a first end  11 . 2  and a second end  12 , which are fastened to the elevator car  7  and the associated counterweight  18 , respectively. In that case a second auxiliary roller  16 . 2 , around which the second traction means  10 . 2  is guided, is mounted at the upper region of the elevator shaft  2  in the vicinity of the ceiling  6 . Moreover, the second traction means run  10 . 2  runs around a second drive pulley  17 . 2 , which is similarly mounted in stationary position in the vicinity of the ceiling  6  at the top in the elevator shaft  2 , i.e. is connected with a drive motor unit fastened in the elevator shaft  2 . From the second drive pulley  17 . 2  the second traction means run  10 . 2  finally runs to the associated counterweight  18 , to which the second traction means run  10 . 2  is fastened. 
     The first and second drive pulleys  17 . 1 ,  17 . 2  preferably lie on a common drive axis. In a particularly preferred embodiment the two drive pulleys  17 . 1 ,  17 . 2  are constructed as an integral drive pulley, which has corresponding guide grooves for receiving the two traction means runs  10 . 1 ,  10 . 2 . In both preferred embodiments the two drive pulleys  17 . 1 ,  17 . 2  or the integral drive pulley is or are drivable by a drive motor unit. 
     In addition, a bottom tensioning means or device  19  is provided, wherein a first end  20  of the bottom tensioning means  19  is suspended at the bottom at the first elevator car  7  and a second end  21  of the bottom tensioning means  19  is suspended at the bottom at the first counterweight  18 . The bottom tensioning means  19  is tensioned by means of a tensioning means weight  22 . For this purpose, a roller arrangement  23  with rollers  24 ,  25  is provided, the arrangement being connected with the tensioning means weight  22  so that the bottom tensioning means  19  runs around the roller arrangement  23 . 
     The second elevator car  8  is centrally suspended at a second traction means or device  30 , which also serves as support means, in a 1:1 suspension. A first end  31  of the traction means  30  is fastened to the second elevator car  8 , preferably at the ceiling thereof. A second end  32  of the traction means  30  is fastened at the top to a second counterweight  33 , which is associated with the second elevator car  8 . In addition, the traction means  30  is guided around an auxiliary roller  34  and around a drive pulley  36 , wherein the drive pulley  35  is arranged at the top in the elevator shaft  2  in the region of the ceiling  6  and is connected with a fixedly mounted drive motor unit. 
     Moreover, a second bottom tensioning means or device  36  with two tensioning means runs  36 . 1 ,  36 . 2  is provided. A first end  37  of the first and second tensioning means runs  36 . 1 ,  36 . 2  is fastened to a second associated counterweight  33 . From its first end  37 , the first and second tensioning means runs  36 . 1 ,  36 . 2  are guided around a roller arrangement  39 , which receives a second tensioning means weight  42 . The first tensioning means run  36 . 1  is in that case guided by two rollers  40 . 1 ,  41 . 1 . The second tensioning means run  36 . 2  is guided by two further rollers  40 . 2 ,  41 . 2 . In addition, a second end  47 . 1  of the first tensioning means run  36 . 1  as well as a second end  47 . 2  of the first tensioning means run  36 . 2  are fastened to the underside of the second elevator car  8  in substantially point-symmetrical manner with diagonally opposite fastening points. 
     The tensioning means weight  22  is associated with the first elevator car  7 . The second tensioning means weight  42  is associated with the second elevator car  8 . In addition, the tensioning means weights  22 ,  42  are arranged in the region of the floor  5  of the elevator shaft  2 , i.e. at the bottom in the elevator shaft  2 . 
     A measuring device  80  for the tensioning means weight  22  is associated with the tensioning means weight  22 . In addition, a measuring device  51  for the tensioning means weight  42  is associated with the tensioning means weight  42 . The measuring devices  80 ,  61  are schematically illustrated in  FIG. 1 , wherein the embodiment is also explained in further detail on the basis of  FIGS. 2 to 6  by way of possible embodiments of the measuring device as a speed detecting device  80 . 
     In further variants of embodiment the measuring devices  80 ,  51  can also be designed as position detecting or acceleration detecting devices. For this purpose the measuring devices  80 ,  51  are equipped with position or acceleration detecting means such as, for example, position transmitters or light barriers on the one hand or acceleration or inertia sensors on the other hand. 
       FIG. 2  shows an elevator system  1 ′ in correspondence with a second exemplifying embodiment of the invention in a schematic illustration. The elevator system  1 ′ in this exemplifying embodiment comprises an elevator car  7  which is connected with the counterweight  18  by way of the traction means  10 . The traction means  10  runs over the drive pulley  17 , which is connected with a drive motor unit  17 ′ mounted in stationary position. 
     Buffer devices  60 ,  61 , from each of which a respective hydraulically damped cylinder  62  or  63  projects, are arranged in the elevator shaft  2 . In that case, in  FIG. 2  a situation is illustrated in which the counterweight  18  is deposited on the cylinder  62  of the buffer device  60 , wherein during the deposit a deceleration of the counterweight  18  is carried out in order to prevent an abrupt impact with the buffer device  60 . Moreover, the drive pulley  17  rotates in the rotational direction  64  so that a traction force is exerted on the traction means  10  in the rotational direction  64 . 
     When the counterweight  18  rests by way of the cylinder  62  on the buffer device  60  then the length of traction means  10  between the counterweight  18  and the drive pulley  17  is relieved of load. In the case of conventional elevator systems  1  of low construction the traction means  10  can slip through at the drive pulley  17  due to the relief of load. However, in the case of elevator systems  1  of high construction in which the elevator shaft  2  has, for example, a height of approximately 300 meters, the length of the traction means  10  between the counterweight  18  and the drive pulley  17  already has a high intrinsic weight. This intrinsic weight acts in a direction  65  on the traction means  10  in the region of the drive pulley  17 . A slack cable  66  or the like thereby forms, as is illustrated in  FIG. 2 . The elevator car  7  is in that case raised further upwardly in a direction  67 , although the counterweight  18  is already stationary. The formation of slack cable  66  or the like can also take place already during the deceleration of the counterweight  18 , which is caused by pressing of the hydraulically damped cylinder  62  into the buffer device. 
     The formation of slack cable  66  or the like, i.e. an over-traction, can occur in the case of use of polyurethane-encased cables as traction means  10  or in the case of use of wedge-ribbed belts as traction means  10  even with relatively low build heights of the elevator installation  1 , for example in the case of build heights of approximately 100 meters or approximately 30 meters. In the case of polyurethane-encased traction means use can also be made of aramid fibers. The occurrence of over-traction is therefore promoted by high build heights of the elevator system  1  and by a relatively large friction between the drive pulley  17  and the traction means  10 . 
     Since the counterweight  18  is at rest, but the elevator car is actuated further in the direction  67 , the tensioning means weight  22  with the roller arrangement  23  moves at half the speed of the elevator car  7  in a direction  68 . The movement in the direction  68  can in that case even begin during deceleration of the counterweight  18 . 
     A critical state arises if with deposited counterweight  18  increasing slack cable  66  or the like is formed. In this case the tensioning means weight  22  together with the roller arrangement  23  moves in the direction  68  at half the speed of the elevator car  7 . The measuring device  80 , which is fastened on the one hand to a guide  69  for the tensioning means weight  22  and on the other hand to the tensioning means weight  22 , serves for detecting the movement of the tensioning means weight  22 . The design of the measuring device  80  as a speed detecting device  80  is explained in the following in further detail with reference to  FIGS. 3 to 6 . 
       FIG. 3  shows a detail illustration of an elevator system  1 , which depicts a tensioning means weight  22  in a guide  69 . The guide  69  is connected with the floor  5  of the elevator shaft  2 . Moreover, in this exemplifying embodiment the roller arrangement  23  is integrated in the tensioning means weight  22 . The tensioning means weight  22  is guided by the guide  69 , wherein it is movable upwardly and downwardly as is illustrated by the double arrow  70 . The movement of the tensioning means weight  22  is in that case limited by a lower abutment  71  and an upper abutment  72 . 
     A bracket  73  is fastened to the tensioning means weight  22 . A magnet rod  74 , which is at least partly of magnetic construction and which is arranged in sections in a protective tube  75 , is connected with the bracket  73 . The protective tube  75  is connected with a support of the guide  69 . The magnet rod  74  together with the tensioning means weight  22  thus moves, but the protective tube  75  is arranged in stationary position. A movement of the tensioning means weight  22  in a direction  70  therefore causes a relative movement between the magnet rod  74  and the protective tube  75 . The magnet rod  74  and the protective tube  75  are part of a speed detecting device  80 , which on the basis of this relative movement detects a movement of the tensioning means weight  22 . The protective tube  75  of the speed detecting device  80  comprises coil elements  81 ,  82  ( FIG. 5 ) which are connected by way of lines  83 ,  84  with a control device  85 . The coil elements  81 ,  82  are in that case arranged within the protective tube  75 . 
       FIG. 4  shows a speed detecting device  80  for the tensioning means weight  22 , which is shown in  FIG. 3 , with a control device  85  in correspondence with a possible embodiment of the invention. In that case, the magnet rod  74  has at least one magnetic section  86 . The coil elements  81 ,  82  of the speed detecting device  80  are provided in the region of the magnetic section  86 . The coil elements  81 ,  82  in this exemplifying embodiment are connected in series by way of a connecting line  87 . In the case of a relative movement between the magnetic section  86  and the coil elements  81 ,  82 , i.e. in the case of a movement of the tensioning means weight  22 , a measurement variable in the form of a voltage or measurement voltage is generated between the lines  83 ,  84 , as is explained in detail on the basis of  FIG. 5 . The coil elements  81 ,  82  are connected by way of the lines  83 ,  84  with a comparator  90 , which is designed as a voltage comparator and which compares that between the lines  83 ,  84  with a threshold value voltage, which is provided by a settable threshold value store  91 . The settable threshold value store  91  can be designed as, for example, a settable resistance. If the measurement voltage between the lines  83 ,  84  exceeds the threshold value voltage, then the comparator  90  activates a safety relay  92 . The safety relay  92  is connected in a line  93  of a safety chain  93 ′, wherein in the case of interruption of the safety chain  93 ′ an emergency stopping device  94  obliges an emergency stop of the elevator car  7 . 
     Moreover, a voltage supply  95  is provided for the control device  85 . In addition, the control device  85  comprises a sensor testing device  96  serving for testing the functional capability of the speed detecting device  80 . In particular, the sensor testing device  96  can check whether a current flow is possible by way of the lines  83 ,  84  as well as the coil elements  81 ,  82  and the connecting line  87 . Furthermore, a self-testing device  97  is provided, by which a self-testing of the comparator  90  is possible. Furthermore, a manually actuable reset button  98  is provided. After triggering of an emergency stop by the emergency stopping device  94  an appropriate operative must be called for checking the elevator system. After the check, the speed detecting device  80  can be reset to its initial state by way of the reset button  98 , whereby the safety relay  92  closes the safety chain  93 ′. 
     Alternatively or in addition, the speed detecting device  80  can be reset under remote control, for example by service personnel of a monitoring center. For that purpose the elevator system is connected by signal transmission means, such as a line or by radio, with the monitoring center. 
       FIG. 5  shows a detail of the speed detecting device  80 , which is shown in  FIG. 4 , in a detailed, schematic illustration. In that case the magnetic section  86  arranged within the coil elements  81 ,  82  is illustrated. On movement of the magnetic section  86  relative to the coil elements  81 ,  82 , as is illustrated by the double arrow  70 , induction voltages U 1  and U 2  are generated between the respective ends of the coil elements  81 ,  82  by magnetic induction. In this embodiment the coil elements  81 ,  82  are connected in series by way of the connecting line  87  so that the individual voltages U 1  and U 2  summate to a form a total voltage U 1 +U 2 . However, it is also possible for the induction voltages U 1  and U 2  to be separately evaluated by a control device  85 . For this purpose, a line  87 ′ can be additionally led to the control device  85 . In a given case, it is also possible to provide, instead of one line  87 ′, two lines  83 ′,  84 ′ ( FIG. 6 ) so as to be able to evaluate the two induced voltages U 1  and U 2  completely separately from one another. Through the separate measurement of the induced voltages U 1  and U 2  of the coil elements  81 ,  82  safety can be increased as a consequence of redundancy and mutual comparison of the signals. In both cases the mode of function can be checked by a suitable sensor testing device  96 . 
     The sum voltage U 1 +U 2  can thus serve as measurement voltage for the speed detecting device  80  or use can be made of two measurement voltages, namely the individual voltages U 1  and U 2 . 
     The design of the coil elements  81 ,  82  with respect to the magnetic section  86  can be such that the generated voltages U 1  and U 2  are at least substantially proportional to the speed of the tensioning means weight  22 . This sensor has a high functional integrity, since it operates contactlessly and no electrical energy supply for the speed detecting device  80  is required. The voltage supply  95  for the control device  85  can be stored by battery or accumulator, wherein the activation of the safety relay  92  can be such that in the absence of functional capability, particularly in the case of failure of the supply voltage, the control device  85  interrupts the safety chain  93 ′. 
     The control device  85  can be designed without a microprocessor and corresponding software. A simpler construction is thereby possible and a high level of reliability can be guaranteed. If the speed of the tensioning means weight  22  is too high, particularly when the speed of the tensioning means weight  22  is equal to half the speed of the elevator car  7 , then the safety relay  92  opens the safety chain  93 ′. The threshold value, which is required for this purpose, of the threshold value store  91  is set so low that response of the control device  85  takes place with consideration of a safety margin. 
     The length of the magnet rod  74  can, for example, be equal to the length of the possible stroke of the tensioning means weight  22  plus a specific length for fastening to the bracket  73 . Damage of not only the magnet rod  74 , but also the coil elements  81 ,  82  is prevented by the protective tube  75 . 
       FIG. 6  shows the speed detecting device  80 , which is illustrated in  FIG. 4  and which is connected by way of an evaluating device  100  and a bus system  101  with a control device  102 , in correspondence with a further possible embodiment of the invention. In this exemplifying embodiment the coil elements  81 ,  82  are connected with the evaluating device  100  by way of the lines  83 ,  83 ′ or  84 ,  84 ′. The induced voltages U 1 , U 2  can be separately detected by the separate connection of the coil elements  81 ,  82  with the evaluating device  100 , whereby safety is improved. The evaluating device  100  evaluates the induced voltages U 1 , U 2 , for example by means of a suitable analog-to-digital converter, and issues these data by way of the bus system  101  with respect to, for example, a bus cycle of the bus system  101 . In that case the evaluating device  100  can be connected at one side, as is illustrated by the data arrow  103 , with the bus system  101 . However, it is also possible for the evaluating device  100  to receive data from the bus system  101 , as is illustrated by the data arrow  104 . The evaluating system  100  is thus coupled at least in one direction with the bus system  101 . In addition, the bus system  101  is linked with the control device  102 , which can access data transmitted by way of the bus system  101  and can transmit data by way of the bus system  101  to further devices, particularly to the evaluating device  100 . The control device  102  can evaluate the data obtained from the evaluating device  100  and in a given case cause an emergency stop of the elevator car  7 . 
     In that case it is also possible for the evaluating device  100  to already undertake a far-reaching evaluation of the induced voltages U 1  and U 2  of the coil elements  81 ,  82 , wherein, in particular, the comparator  90  and a threshold value store  91 , as are described on the basis of  FIG. 4 , can be integrated in the evaluating device  100 . In this case the evaluating device  100  can report by way of the bus system  100  whether or not an emergency stop is required. 
     In the absence of data of the evaluating system  100  the control device  102  can thereby conclude that there is a fault in the evaluating device  100 . 
     The invention is not restricted to the described embodiments. 
     In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiment. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.