Patent Publication Number: US-9422133-B2

Title: Elevator car control in a landing zone using a machine brake in response to undesired car movement

Description:
BACKGROUND 
     Elevator systems have several features that are intended to ensure efficient, reliable and comfortable service to passengers. For example, passengers want easy access to an elevator car. Control over the position of an elevator car parked at a landing makes it easier for passengers to board or exit the elevator car. 
     There are industry standards and codes that establish parameters that must be met when parking an elevator car at a landing. A recent revision to the EN81-1:1998 standard in Europe requires limiting movement of an elevator car at a landing when the car doors are open. U.S. Pat. Nos. 7,073,632; 7,137,484 and 7,775,329 each describe a proposal to limit movement of an elevator car under such conditions. It is not clear that such approaches will satisfy the recent standard revision or if such devices will provide an economical solution. 
     SUMMARY 
     An exemplary method is useful for controlling movement of an elevator car in an elevator system that includes a machine that selectively moves the elevator car and a machine brake that selectively resists movement of the elevator car. The method comprises determining whether the elevator car is near a landing and determining whether a door of the elevator car is open. A desired operation includes desired movement of the elevator car while the elevator car is near the landing and the door is open. A determination is made whether the elevator car moves other than according to the desired movement. The machine brake is applied for stopping movement of the elevator car responsive to elevator car movement other than the desired movement while the elevator car is near the landing and the door is open. 
     In an embodiment of the exemplary method of the preceding paragraph, determining whether the elevator car moves other than according to the desired movement may be based on an indication of a position of the elevator car relative to the landing. 
     Another embodiment of the exemplary method of either of the two previous paragraphs may include using a door zone detector for determining whether the elevator car is near the landing and for determining whether the elevator car moves other than according to the desired movement. 
     Another embodiment of the exemplary method of any of the three preceding paragraphs may include using a level position detector for determining whether the elevator car moves other than according to the desired movement. 
     In another embodiment of the exemplary method of any of the preceding paragraphs, the desired operation may comprise releveling the elevator car after the elevator car has stopped at the landing. 
     In another embodiment of the exemplary method of any of the preceding paragraphs, the desired operation may comprise approaching the landing and opening the door before the elevator car stops at the landing. 
     In another embodiment of the exemplary method of any of the preceding paragraphs, the desired operation may comprise departing from the landing before the door has closed. 
     An exemplary elevator system includes a hoistway having a plurality of landings. An elevator car is moveable within the hoistway to provide elevator service to any of the landings. The elevator car includes at least one door that is selectively opened or closed. A machine selectively causes movement of the elevator car. A machine brake selectively resists movement of the elevator car. A controller determines whether the elevator car is near a landing, whether a door of the elevator car is open and whether the elevator car moves other than according to a desired movement associated with a desired operation while the elevator car is near the landing and the door is open. The machine brake stops movement of the elevator car responsive to elevator car movement other than the desired movement while the elevator car is near the landing and the door is open. 
     In an embodiment of the exemplary system of the preceding paragraph, the controller may determine whether the elevator car moves other than according to a desired movement associated with a desired operation while the elevator car is near the landing and the door is open based on an indication of a position of the elevator car relative to the landing. 
     In another embodiment of the exemplary system of either of the two preceding paragraphs, the system may include a door zone detector near each landing. Each door zone detector may be configured to provide an indication of a position of the elevator car near the corresponding landing. The controller may use the indication from the door zone detector for determining whether the elevator car is near the landing and for determining whether the elevator car moves other than according to the desired movement. 
     In another embodiment of the exemplary system according to any of the three preceding paragraphs, the system may include a level position detector near each landing. Each level position detector may be configured to provide an indication of a vertical position of the elevator near the corresponding landing. The controller may use the indication for determining whether the elevator car moves other than according to the desired movement. 
     In another embodiment of the exemplary system of any of the preceding paragraphs, the desired operation may comprise releveling the elevator car after the elevator car has stopped at the landing. 
     In another embodiment of the exemplary system of any of the preceding paragraphs, the desired operation may comprise approaching the landing and opening the door before the elevator car stops at the landing. 
     In another embodiment of the exemplary system of any of the preceding paragraphs, the desired operation may comprise departing from the landing before the door has closed. 
     In another embodiment of the exemplary system of any of the preceding paragraphs, the controller is configured to prevent further movement of the elevator car subsequent to the machine brake stopping movement of the elevator car responsive to elevator car movement other than the desired movement while the elevator car is near the landing and the door is open until the controller is manually reset. 
     The various features and advantages of a disclosed example embodiment will become apparent to those skilled in the art from the following detailed description. The drawings that accompany the detailed description can be briefly described as follows. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  schematically illustrates selected portions of an example elevator system designed according to an embodiment of this invention. 
         FIG. 2  is a flow chart diagram summarizing an example control strategy useful in an embodiment of this invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  schematically shows selected portions of an elevator system  20 . Only selected portions are illustrated. Those skilled in the art will realize that many other components are included in an elevator system. Such components are omitted from the illustration and this discussion for the sake of brevity and because those skilled in the art are already aware of such components. 
     An elevator car  22  includes at least one door  24 . The elevator car  22  is moveable within a hoistway  26  to provide elevator service to a plurality of landings  28  and  30 , for example. The elevator car  22  is illustrated parked at the landing  28 . 
     In the illustrated example, a machine  32  selectively causes movement of the elevator car  22 . A brake  34 , which is associated with the machine, selectively resists movement of the elevator car by applying a braking force for purposes of stopping the elevator car  22  at one of the landings  28  or  30 , for example. In some examples, the brake  34  is also used for overspeed protection in an upward direction of car movement. A controller  40  controls the operation of the machine  32  and the machine brake  34 , respectively. 
     The disclosed example includes control features to control movement of the elevator car  22  when it is parked at a landing such as the landing  28 . Even though elevator cars remain essentially stationary when parked at a landing there are times when some movement is desired when the doors are not closed. For example, some movement is desired to relevel a car in response to a change in the load on the car that alters the relative position of the elevator car floor and the adjacent landing floor. Some elevator systems include features that are intended to reduce wait times for passengers such as allowing the doors to begin opening before the car has stopped at a landing or allowing the car to begin leaving a landing before the doors are fully closed, for example. Under such circumstances, the elevator car  22  is moving when the door  24  is open and the car  22  is near a landing. 
     The illustrated example provides the ability to relevel the elevator car  22  when it is parked at one of the landings  28  or  30 . A level sensor  42  is provided to inform the controller  40  when the elevator car  22  is at a desired level at a landing. If there is a significant change in the load on the car  22 , the car may move slightly out of the desired, leveled position. The level sensor  42  indicates this condition to the controller  40 , which responsively initiates a releveling operation. When releveling the elevator car  22 , there is a desired movement of the elevator car from the current position to the desired, leveled position at the corresponding landing. During a releveling operation, the brake  34  is released to allow for the desired movement of the elevator car  22 . The machine  32  typically causes the desired movement of the elevator car  22 . During a desired releveling operation, the elevator door  24  will be open and the elevator car  22  is near the landing  28 , for example. 
     Whenever the elevator car  22  is near a landing and the door is opened, the controller  40  ensures that any movement of the elevator car is consistent with a desired movement of the car under those conditions. A known door bypass circuit (not illustrated) allows car movement when a door is open. 
     The illustrated example provides the ability to begin opening the elevator car door  24  before the car has completely stopped at a landing. The illustrated example also includes the ability to begin departing from a landing before the elevator car door  24  is fully closed. Door zone detectors  44  provide an indication of when the elevator car  22  approaches within an appropriate distance from a landing to allow the car doors to begin opening. The door zone detectors  44  provide information regarding a position of the elevator car  22  relative to the corresponding landing. The controller  40  uses information from the door zone detectors  44  to perform desired elevator car operations for a given circumstance such as approaching a landing or departing from the landing and controlling a door operator (not illustrated) for opening or closing the elevator car door  24 . 
     The illustrated door zone detectors and level sensors may be realized using known sensing equipment and techniques for such purposes. The particular type of sensor or detector for a given elevator system may vary and those skilled in the art will realize how to select from among known components and techniques to meet their particular needs. 
     The controller  40  in this example maintains control over movement of the elevator car  22  including preventing uncontrolled movement of the elevator car  22  when it is near a landing and the car door  24  is open. For purposes of discussion, the car door  24  is considered open whenever it is not fully closed. 
       FIG. 2  includes a flowchart diagram  48  summarizing an example control approach; with flow diagram  50  starts at step  50 . From the start step  50 , the control protocol proceeds to step  52  at which the controller  40  determines whether the elevator car  22  is near a landing  28  or  30 , for example. If the determination in step  52  is “no”, the control protocol returns to start step  50 . If, however, the determination in step  52  is “yes”, the control protocol continues to step  54 . 
     At step  54 , the controller  40  determines whether the elevator car door  24  is open. If the determination in step  54  is “no”, the control protocol returns to start step  50 . If, however, the determination in step  54  is “yes”, the control protocol continues to step  56 . 
     At step  56  a determination is made whether a desired operation includes desired elevator car movement. Example desired operations include releveling the elevator car  22 , opening the car door  24  before the elevator car  22  comes to a complete stop at a landing, or beginning to move the elevator car  22  away from a landing before the door  24  has fully closed. During any of the three example desired operations, the brake  34  is released to allow the desired elevator car movement. If the determination in step  56  is “no”, the control protocol returns to start step  50 . If, however, the determination in step  56  is “yes”, the control protocol continues to step  58 . 
     At step  58 , the controller  40  determines whether the elevator car  22  is moving in a manner other than the desired movement associated with the desired operation. If such undesired movement occurs, such movement can be considered uncontrolled car movement. Accordingly, at step  58 , the controller  40  determines whether there is any such uncontrolled movement while the door  24  is open and the car  22  is near a landing. If the determination in step  58  is “no”, the control protocol returns to start step  50 . If, however, the determination in step  58  is “yes”, the control protocol continues to step  60 . 
     At step  60 , the controller  40  applies the machine brake  34  to stop any further movement of the elevator car  22 . In one example, when the machine brake  34  is applied under such circumstances, the controller  40  requires a manual resetting operation to be performed before the controller  40  will put the elevator car  22  back into normal service mode. 
     In one example, the controller  40  uses information from the doors zone detectors  44  to determine whether the elevator car  22  moves in a manner that is inconsistent with a desired movement when the car door  24  is open and the car  22  is near a landing. The doors zone detectors are used in this example to indicate when there is such motion of the elevator car  22  by providing an indication of the position of the elevator car  22  relative to the corresponding landing. In some cases, if a floor of the elevator car  22  moves more than a threshold distance from the level of the corresponding landing floor, the controller  40  is programmed or configured to apply the brake  34 . 
     One feature of using the door zone detectors  44  in this manner is that the illustrated example takes advantage of components already existing within the elevator system  20  and provides the additional ability of controlling movement of the elevator car  22  near a landing when the car door  24  is open by applying the machine brake  34  responsive to movement that is inconsistent with a desired movement of the elevator car  22 . 
     In another example, the controller  40  uses an indication from a level sensor  42  regarding a position of the elevator car  22  relative to a corresponding landing for determining whether any movement of the elevator car  22  near a landing when the door  24  is open is inconsistent with a desired movement. In one example, an existing door bypass circuit (not illustrated) operates responsive to the level sensor signals for realizing the control over the machine brake. 
     In another example, a combination of information from a door zone detector  44  and a level sensor  42  is used for monitoring any movement of the elevator car  22  near a landing with the car door  24  open. In either case, position information is used by the controller  40  to determine when the elevator car  22  has moved in a manner that requires applying the machine brake  34  to stop such movement. 
     Information regarding the position of the elevator car  22  relative to a landing is used as the indication that the machine brake  34  should be applied in one example. In another example, the position information is used to determine a speed of movement. Still another example includes a combination of speed and position information. Such information allows the controller  40  to determine when to apply the brake  34 , if the position or movement of the elevator car  22  is inconsistent with desired movement. 
     The illustrated example takes advantage of existing elevator system components and provides the ability to satisfy the requirements for preventing uncontrolled movement of an elevator car near a landing when the door is open. In one example, the controller  40  is part of elevator drive equipment that is responsible for machine control during normal elevator system operation. The disclosed example provides an economical solution to the requirement of maintaining control over movement of an elevator car near a landing when a car door is open that does not require any material change to existing elevator system components yet it provides an entirely new capability within such an elevator system. 
     In the disclosed example, once the brake is applied and the elevator car is stopped responsive to movement inconsistent with desired movement as described above, the car is taken out of service until an authorized individual resets the controller  40  to resume normal operation. This is shown at  62  in  FIG. 2 . Additional software is added to the controller  40  in one example to include such a required manual reset feature. In other examples software, firmware, hardware or a combination of these is added to the controller  40  to provide this additional feature. 
     The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this invention. The scope of legal protection given to this invention can only be determined by studying the following claims.