Abstract:
A switching device for an elevator door provides a door contact signal. The switching device includes a magnet, a plurality of proximity sensors, and a detection area, which area is adjoined by the proximity sensors and in which the magnet can be moved. A sensor signal can be generated by each of the proximity sensors in at least one position of the magnet in the detection area, wherein the sensor signals are dependent on the distance from the magnet to the proximity sensors. A method for providing the door contact signal utilizes the switching device.

Description:
FIELD 
     The invention relates to a switching device for an elevator door for providing a door contact signal. The invention additionally relates to a method of providing such a door contact signal by means of such a switching device. 
     BACKGROUND 
     Elevator installations comprise an elevator car and elevator doors, particularly a car door and shaft doors. For example, a shaft door is provided with at least one door contact switch by means of which it is monitored whether the shaft door is unlocked. Such door contact switches arranged at each individual shaft door are incorporated in a safety circuit. If one of these shaft doors is unlocked, the safety circuit is interrupted. In that way the elevator car can be moved only when all shaft doors of the elevator installation are locked. Moreover, further settings of such an elevator door can be monitored by means of door contact switches, particularly an open setting or closed setting. 
     WO 2006036146 shows a switching device for monitoring a door leaf belonging to an elevator door. The elevator door comprises, apart from the door leaf, a door surround, wherein the door leaf is lockable to the door surround. The switching device comprises a plurality of magnets and an equal number of proximity sensors. The magnets are arranged at the door leaf and the proximity sensors fastened to the door surround. Each of these proximity sensors is associated with exactly one individual magnet. In that case, the magnets have a defined geometric arrangement relative to one another. This defined geometric arrangement is equally imaged by the proximity sensors in such a way that the magnets simultaneously activate the proximity sensors on transition of the door leaf to its locked setting. This means that each proximity sensor has the same spacing from the magnet associated therewith. By means of a switching device defined in such a way it is possible to avoid simulation by an unauthorized person, by way of a permanent magnet held at the proximity sensors, a locked setting of the relevant elevator door even though this elevator door is, for example, still open. 
     It is problematic with such a switching device that such a spacing, which triggers the unlocked setting, of the magnets from the proximity sensors associated therewith can equally be influenced by faulty settings of, for example, a damaged door leaf. This means that a deviation of the magnets from their intended movement path near the locked setting of the door leaf signifies a displacement of the locked setting itself, which in turn can lead to failure of the elevator door and consequently to shutdown of the elevator installation. 
     SUMMARY 
     It is therefore an object of the invention to create a switching device for an elevator door with reduced probability of failure. 
     The object is fulfilled by a switching device for an elevator door, for providing a door contact signal, the switching device comprising a detection space, a plurality of proximity sensors, wherein the proximity sensors are arranged to adjoin the detection space, and a magnet movable in the detection space, wherein in at least one setting of the magnet in the detection space a sensor signal generated by this magnet can be produced by each of the proximity sensors in order to provide compensation, on the basis of evaluation of the sensor signals, for faulty settings of the magnet in the detection space, wherein the sensor signals are dependent on the spacing of the magnet from the proximity sensors. 
     The object is equally fulfilled by an elevator door with such a switching device. 
     The object is also fulfilled by a method for providing a door contact signal, wherein the method is performed by means of a switching device comprising a magnet, a plurality of proximity sensors and a detection space, and the proximity sensors are arranged at the detection space, with the following method steps:
         producing a first sensor signal, which is dependent on the spacing of the magnet from a first one of the proximity sensors, in a setting of the magnet in the detection space and   producing a second sensor signal, which is dependent on a spacing of the magnet from a second one of the proximity sensors, in the same setting of the magnet in the detection space.       

     Current circuits, which are switchable by means of magnets, of elevator doors can cause faulty functions when solely one defined switching spacing of the magnet from the proximity sensor represents the criterion for switching of the corresponding door contact. A relevant spacing from elevator door components, in which the switching process is to take place, can be reliably established in such a way only if the magnet moves with respect to the proximity sensor along that movement path to which the switching device has been adjusted. 
     However, is not unusual that different components of the elevator door in the course of its operation are changed in such a way by external influences that the magnet no longer moves along its intended movement axis with respect to the proximity sensor. This can be caused by, for example, deformation of the door leaf or wear of individual guide elements guiding the door leaf. In correspondence with a thus-changed movement of the magnet in the environment of the proximity sensor the relevant spacing of the elevator door components from the instant of the switching process can be changed. 
     It was accordingly sought to so change the design of the switching device that a change of the elevator door of that kind has, to the largest extent, no influence on the relevant spacing. It is possible, by means of a plurality of proximity sensors each producing a sensor signal in dependence on the specific spacings thereof from the individual magnet, to trigger the switching process at this predetermined relevant spacing independently of changes to the elevator door by external influences. Accordingly, compensation for faulty settings of the magnet in the detection space can be provided on the basis of evaluation of the sensor signals. 
     In a development of the switching device the proximity sensors are formed by Hall sensors. Hall sensors are proximity sensors of simple construction and accordingly function with corresponding reliability. 
     In a development of the switching device the proximity sensors are arranged substantially on one side of an axis of movement of the magnet. Alternatively thereto the proximity sensors can be arranged substantially on both sides of this axis of movement of the magnet. By means of these alternatives, possibilities are given for evaluating the sensor signals in simple mode and manner. 
     A development of the switching device comprises two proximity sensors or three proximity sensors, which are preferably not arranged along a straight line. Depending on how the external influences act on the elevator door, a specific minimum number of proximity sensors is necessary in order to be able to determine the position of the magnet within the detection space and thus adhere in the long term to the described relevant spacing of the elevator door components during the switching process of the switching device. If it is anticipated that the axis of movement of the magnet displaces, due to the external influences, in the detection space in the switching device only along a plane, merely two proximity sensors are necessary for that purpose. However, if the elevator door components due to external influences are changed in such a way that the axis of movement of the magnet in the detection space can vary in any manner, three proximity sensors are necessary in order to maintain in the long term the relevant spacing of the elevator door components during the switching process of the switching device. 
     A development of the switching device comprises an evaluating unit which is constructed in such a way that by means of evaluation of the sensor signals a door contact is switched in the case of a predetermined depth of penetration of the magnet into the detection space. In that way a possibility is provided for processing the sensor signals, which relate to a position of a magnet in the detection space, of the proximity sensors and thus produce the door contact signal. 
     The evaluating unit can be constructed in such a way that reference signal values, which are signal values of the sensor signals produced in a reference setting of the magnet, can be stored in the evaluating unit and the reference signal values can be compared with the signal values of the sensor signals produced in an instantaneous setting of the magnet. In that way the effect of external influences on the elevator door can be determined. At the same time, a change, which is excessively large for this reason, of the instantaneous setting of the magnet from the reference setting of the magnet in the detection space can be detected or also precluded. Thus, failures of the elevator door can be precluded by preventative maintenance. 
     In a development of the switching device comprising the evaluating unit a minimum value can be stored in the evaluating unit and the evaluating unit can be constructed in such a way that the door contact is switched only when the signal values exceed the minimum value. Faulty functions of the switching device can be precluded by means of such an additional safety aspect if, for example, all other criteria for the switching process of the switching device are fulfilled. 
     A development of the switching device comprises a self-testing unit producing a magnetic pulse, wherein the self-testing unit acts in such a way on at least one of the proximity sensors that a signal value is produced by means of such a pulse. Functional disturbances of the switching device which occur can be recognized by means of such a self-testing unit acting on the sensor signal of the proximity sensor. In the case of full functionality of the switching device, the magnet pulse of the self-testing unit causes a signal value of the proximity sensor. The sensor signal is correspondingly influenced by this signal value. If an evaluation of the sensor signal has the result that the sensor signal is not influenced or is influenced in an unexpected way by the self-testing unit, a functional disturbance, which can be eliminated by a service engineer, of the switching device can, for example, be the cause. 
     A development of the elevator door comprises a locking device comprising two components to be locked relative to one another, wherein the components to be locked relative to one another are preferably a catch and a stop, or at least two components which are movable relative to one another, wherein the at least two components movable relative to one another are at least one door leaf and a door surround, wherein the proximity sensors are attached to a first one of the components and the magnet to a second one of the components. An arrangement of the proximity sensors and the magnet of that kind enables monitoring of a closed, open or any operational setting of the door leaf or a locked setting of the elevator door. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The invention is explained in more detail in the following by way of figures, in which: 
         FIG. 1  shows an elevator door with a locking device; 
         FIGS. 2A, 2B  show a switching device of an elevator door according to the prior art; 
         FIG. 3  shows a switching device for an elevator door; 
         FIG. 4A  shows a switching device of an elevator door according to a first variant of embodiment; 
         FIG. 4B  shows a signal plot of the switching device shown in  FIG. 3A ; 
         FIG. 5A  shows a switching device of an elevator door according to a second variant of embodiment; 
         FIG. 5B  shows a signal plot of the switching device shown in  FIG. 5A ; and 
         FIG. 6  shows a switching device of an elevator door according to a third variant of embodiment. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows an elevator door  2  arranged in an elevator installation. The elevator door  2  can be constructed as a car door or as a shaft door arranged at a floor  12 . The elevator door  2  comprises a door surround  8  and a first door leaf  6 . 1 . In addition, the elevator door can comprise a second door leaf  6 . 2  and/or a locking device  10  for locking the door leaf  6 . 1 . 
     The locking device  10  comprises a catch  16  and a mechanical stop  14 . The catch  16  can, for example, be coupled with the first door leaf  6 . 1  and the stop  14  can be fastened to the second door leaf  6 . 2  or to the door surround  8 . When the catch  16  is in engagement with the mechanical stop  14  an opening movement of the first door leaf  6 . 1  and optionally the second door leaf  6 . 2  is prevented. A switching device  4  (see  FIGS. 2A, 2B, 3, 4A, 5A and 6 ) for monitoring the locked setting can be arranged at the locking device  10 . 
     A switching device  4  of an elevator door  2  according to the prior art is illustrated in simplified form in  FIGS. 2A, 2B . The elevator door  2  comprises a door leaf  6 , which is shown in its closed setting, and a door surround  8 . The switching device  4  for monitoring the closed setting of the door leaf  6  comprises a magnet  20  and a proximity sensor  22 . The magnet  20  is fastened to the door leaf  6 . The proximity sensor  22  is fastened to the door surround  8  and has a detection spacing SA. The detection spacing SA characterizes the maximum distance between the magnet  20  and the proximity sensor  22 , sufficient for producing a door contact signal S. 
       FIG. 2A  shows the elevator door  2  in the state in accordance with an adjustment, which has been carried out, of the switching device  4  by a service engineer. The service engineer had at the moment of the adjustment the possibility of determining the fastening position of the proximity sensor  22  and/or the magnet  20  in such a way that a door contact signal S detecting the closed signal is issued when the door leaf  6  has a maximum gap spacing W from the door surround  8 . Such an adjustment is based on the detection spacing SA. Correspondingly, the door contact signal S is interrupted when the door leaf  6  is moved in opening direction O in such a way that the spacing between the magnet  20  and the proximity sensor  22  is greater than the detection spacing SA. In correspondence with the adjustment, the magnet  20  moves, in the case of the movement of the door leaf  6  in opening direction O or closing direction C, along its intended axis B of movement. 
       FIG. 2B  shows the door leaf  6  in its closed setting, after external influences have produced a change of components of the elevator door  2 . For example, such changes can be caused by deformations of the door leaf  6  produced by elevator passengers or by wear of guide elements of the door leaf  6 . Accordingly, in the case of movement of the door leaf  6  in opening direction O or closing direction C the magnet  20  no longer moves along its intended axis B of movement, but moves along a changed axis B′ of movement. Due to the detection spacing SA, which is substantially unchanged since the moment of adjustment of the switching device  4  by the service engineer, there is therefore the result according to  FIG. 2B  that the switching process of the switching device takes place at a maximum gap spacing W′ changed with respect to the maximum gap spacing W. Accordingly, the door contact signal S is issued only when the changed maximum gap spacing W′ is exceeded. In the least favorable case the door leaf  6  can adjoin the door surround  8  without a door contact signal S which detects the closed setting of the door  6 , because the resulting spacing of the magnet  20  from the proximity sensor  22  is greater than the detection spacing SA. If this door contact signal S is essential for continued operation of the elevator installation this leads to a temporary failure of the elevator installation until the switching device  4  is readjusted by a service engineer. 
     An exemplifying switching device  4  according to the invention is shown in  FIG. 3 . A switching device  4  comprises a magnet  20 , a detection space DR and at least two proximity sensors  22   a ,  22   b .  22   c . In addition, the switching device  4  can comprise an evaluating unit  26 . The proximity sensors  22   a ,  22   b ,  22   c  are arranged adjacent to the detection space DR. For example, the switching device  4  comprises a switch body  21  to which the proximity sensors  22   a ,  22   b ,  22   c  are fastened. 
     In the case of monitoring of the locking setting explained in accordance with  FIG. 1  the magnet  20  can be arranged, preferably fastened, at the catch and the proximity sensors  22   a ,  22   b ,  22   c  can be arranged, preferably fastened, at the stop, or vice versa. Alternatively thereto, the switching device  4  can be provided for monitoring an open or a closed setting or any operational setting of the door leaf. For this purpose, the proximity sensors  22   a ,  22   b ,  22   c  can be arranged, preferably fastened, at the first door leaf and the magnet  20  can be arranged, preferably fastened, at the optionally present second door leaf or at the door surround, or vice versa. If the door leaf or the catch is in the setting to be monitored or in the immediate vicinity thereof, the magnet  20  has a depth ET of penetration into the detection space DR. Accordingly, the magnet  20  enters at least partly into the detection space DR. The switching device  4  is constructed or adjustable in such a way that a door contact is switched in the case of a predetermined penetration depth ET* into the detection space DR. 
     In correspondence with the spacing of the magnet  20 , which has entered at least partly into the detection space DR, from each individual one of the proximity sensors  22   a ,  22   b ,  22   c , at least one of the proximity sensors  22   a ,  22   b ,  22   c  produces a sensor signal  24   a ,  24   b ,  24   c  which can be associated with the respective proximity sensor  22   a ,  22   b ,  22   c . The at least one sensor signal  24   a ,  24   b ,  24   c  can be communicated to the evaluating unit  26 . If at least two sensor signals  24   a ,  24   b ,  24   c  are present a penetration depth ET of the magnet  20  can be determined by evaluation of these sensor signals  24   a ,  24   b ,  24   c  and optionally the current direction of movement of the door leaf. For example, this evaluation can be carried out with the help of mathematical algorithms which describe a dependence of the sensor signal  24   a ,  24   b ,  24   c  on the spacing of the magnet  20  from the associated proximity sensors  22   a ,  22   b ,  22   c . If the penetration depth ET of the magnet  20  corresponds with the predetermined penetration depth ET*, a door contact can be switched by means of issue of a door contact signal S. The door contact signal S accordingly signals that the door leaf has reached or passed the closed, open or locked setting or the previously arbitrarily established operating position. 
       FIGS. 4A, 5A, 6  show components of an elevator door with a switching device  4  according to different variants of embodiment. The elevator door comprises the components of the elevator door illustrated in  FIG. 1 . The switching device  4  comprises a magnet  20 , a detection space DR and at least two proximity sensors  22   a ,  22   b ,  22   c ,  22   d  and can include an evaluating unit  26 . The proximity sensors  22   a ,  22   b ,  22   c ,  22   d  are arranged adjacent to the detection space DR. The magnet  20  is fastened to the door leaf  6  and the proximity sensors  22   a ,  22   c  are fastened to the door surround  8  ( FIG. 4A ) or vice versa ( FIG. 6 ). Alternatively thereto the magnet  20  can be fastened to a first door leaf  6 . 1  and the proximity sensors  22   a ,  22   b  to a second door leaf  6 . 2  ( FIG. 5A ). 
     In the case of a closing movement C of the at least one at least partly opened door leaf  6 ,  6 . 1 ,  6 . 2  the magnet  20  enters the detection space DR. The magnet  20  is in that case moved along a predetermined axis B of movement with respect to the detection space DR, in which case external influences can lead to a changed axis B′ of movement. The proximity sensors  22   a ,  22   b ,  22   c ,  22   d  each produce a sensor signal  24   a ,  24   b ,  24   c ,  24   d , which can be associated with the respective proximity sensor  22   a ,  22   b ,  22   c ,  22   d  when the magnet  20  is in the detectable vicinity of the respective proximity sensor  22   a ,  22   b ,  22   c ,  22   d . The sensor signals  24   a ,  24   b ,  24   c ,  24   d  can be communicated to the evaluating unit  26  and evaluated within the evaluating unit  26 . If the evaluation, in a given case a comparison, of the sensor signals  24   a ,  24   b ,  24   c ,  24   d  by the evaluating unit  26  has the result that the door leaf  6 . 1  in accordance with the purpose of the switching device  4  is locked or closed or opened or adopts a defined operating position the door contact signal S is issued. Such a door contact signal S can be used for, for example, switching a safety circuit of the elevator installation. If the evaluation of the sensor signals  24   a ,  24   b ,  24   c ,  24   d  by the evaluating unit  26  has the result that the door leaf  6 . 1  is no longer locked or closed or opened or adopts the defined operating position, the door contact signal S is stopped. 
     A number of at least two proximity sensors  22   a ,  22   b ,  22   c  is necessary if it can be assumed that the movement axis B′ of the magnet  20  in the detection space DR, even after occurrence of the influences changing the elevator door components, is changed substantially only along a plane such as, for example, the plane of illustration shown in accordance with  FIGS. 4A, 5A . Thereagainst, a number of at least three proximity sensors  22   a ,  22   b ,  22   c  (for example  FIG. 6 ), preferably not arranged along a straight line, is necessary if the magnet  20  after occurrence of the influences changing the elevator door components can have in the detection space DR a movement axis B′ changed in any way. 
       FIG. 4A  shows the switching device  4  according to a first variant of embodiment in which the proximity sensors  22   a ,  22   c  are arranged substantially at both sides of the movement axis B, B′, which is changed in certain circumstances by means of external influences, of the magnet  20 . 
       FIG. 5A  shows the switching device  4  according to a second variant of embodiment in which the proximity sensors  22   a ,  22   b  are arranged substantially on one side of the movement axis B, B′, which is changed in certain circumstances by means of external influences, of the magnet  20 . 
       FIGS. 4B and 5B  show signal plots of the switching devices  4  shown in  FIGS. 4A and 5A . Signal values, particularly the signal strengths, of the sensor signals  24   a ,  24   b ,  24   c  in dependence on the penetration depth ET of the magnet  20  into the detection space DR are depicted in these signal plots. In that case, a higher signal strength in the illustrated  FIGS. 4A, 5A  corresponds with a reduced spacing of the magnet  20  from the relevant proximity sensor  22   a ,  22   b ,  22   c . It is known on the basis of the sensor characteristic of the individual proximity sensors  22   a ,  22   b ,  22   c  which spacing the magnet  20  has from the corresponding proximity sensor  22   a ,  22   b ,  22   c  for the detected signal value  24   a ,  24   b ,  24   c . Accordingly, a position of the magnet  20  in the detection space DR can be detected from the sensor signals  24   a ,  24   b ,  24   c  of at least two proximity sensors  22   a ,  22   b ,  22   c . In that way it is made possible by means of evaluation of the sensor signals  24   a ,  24   b ,  24   c  within the evaluating unit  26  to switch the door contact by means of the door contact signal S in the case of a predetermined penetration depth ET* of the magnet  20  into the detection space DR. 
     The evaluating unit  26  can be constructed in such a way that, on adjustment of the switching device  4 , signal values  24   a ,  24   b ,  24   c  of the proximity sensors  22   a ,  22   b ,  22   c  at a predetermined penetration depth ET* of the magnet can be stored as reference signal values  25   a ,  25   b ,  25   c . The reference signal values  25   a ,  25   b ,  25   c  therefore characterize a reference setting of the magnet  20  for the predetermined penetration depth ET*. 
     Through comparison of the signal values, which occur at the predetermined penetration depth ET* in the course of operation of the elevator door, of the sensor signals  24   a ,  24   b ,  24   c  with the reference signal values  25   a ,  25   b ,  25   c  it is possible to determine to what extent the instantaneous position of the magnet  20  departs from the position of the magnet  20  at the time of adjustment of the switching device  4  for the predetermined penetration depth ET*. Accordingly, it can be recognized to what extent external influences have contributed to deformation of the elevator door. Moreover, it can be estimated within which period of time readjustment of the elevator door has to be carried out without risk of failure of the elevator door due to faulty functioning of the elevator door. Through issue of an adjustment request signal in the case of a predeterminable departure of these signal values of the sensor signals  24   a ,  24   b ,  24   c  from the reference signal values  25   a ,  25   b ,  25   c  such a failure of the elevator installation can be prevented. In the case of determination of the difference leading to an adjustment request signal it is possible to take into consideration, for example, mass tolerances of components and the size of the detection space DR of the switching device  4 . 
     In  FIG. 5B  exemplifying plots of those signal values of the sensor signals  24   a ′,  24   b ′ resulting from movement of the magnet  20  along its changed axis B′ of movement are shown by dotted line. According to the depicted illustration the switching device  4 , in the case of an arrangement of the proximity sensors  22   a ,  22   b  substantially on one side of the movement axis B, B′— which is changed in certain circumstances—of the magnet  20 , can be so adjusted that the criterion for issue of the door contact signal S is signal values  24   a ,  24   b ;  24   a ′,  24   b ′, which are of the same level, of the proximity sensors  22   a ,  22   b . A minimum value M stored in the evaluating unit  26  is required in the case of such an evaluation in order to prevent issue of the door contact signal S when the signal values  24   a ,  24   b ,  24   a ′,  24   b ′ are smaller than this minimum value M. 
       FIG. 6  shows a switching device  4  of an elevator door according to a third variant of embodiment. The switching device  4  can, when an evaluating unit  26  is present, comprise a self-testing unit  28 . 1 ,  28 . 2 . The self-testing unit  28 . 1 ,  28 . 2 —for example comprising at least one electromagnet acting on the proximity sensors  22   a ,  22   b ,  22   c ,  22   d —produces magnetic pulses at predeterminable frequency. Magnetic pulses act on the proximity sensors  22   a ,  22   b ,  22   c ,  22   d , whereupon the proximity sensors  22   a ,  22   b ,  22   c ,  22   d  produce signal values corresponding with the pulses. These signal values produced by means of the pulses are superimposed on the signal plots, which are generated on the basis of the detection of the magnet  20 , of the sensor signals  24   a ,  24   b ,  24   c ,  24   d . It can accordingly be recognized by means of evaluation of the sensor signals  24   a ,  24   b ,  24   c ,  24   d  within the evaluating unit  26  whether the proximity sensors  22   a ,  22   b ,  22   c ,  22   d  process or the switching device  4  processes these produced pulses in an anticipated manner. If this is not the case, that can mean a functional disturbance of the switching device  4 . Accordingly, a fault signal can be produced, which generates, for example, a servicing request for servicing of the switching device  4 . 
     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.