Abstract:
An elevator brake monitoring system includes a car ( 12 ); a machine ( 18 ) configured to actuate movement of the car; and a brake ( 32 ) configured to decelerate the car; wherein the system is configured to operate the machine to move the car at a pre-determined speed, engage the brake, measure a braking parameter and compare the measured braking parameter to a reference braking parameter.

Description:
BACKGROUND OF INVENTION 
       [0001]    The invention relates generally to an elevator and, more specifically, to a system and method for monitoring the capability of a brake of the elevator to sufficiently decelerate the elevator during emergency stopping thereof. 
         [0002]    An elevator brake may be tested periodically to assure that the brake has sufficient braking capability (i.e., the capability of the brake to decelerate and stop an elevator car). In older elevators, the braking capability is readily determined because the brake is used to actively control the elevator car during normal operations. For example, the braking capability may be tested implicitly at each stop of the car by verifying that the elevator decelerates and/or levels as expected when the brake is applied. 
         [0003]    Modern elevators use a motor to both decelerate the elevator car and hold the elevator car in position (e.g., at a landing). In modern elevators, normal deceleration and leveling of the elevator car may be performed by varying drive signals applied to the motor. The brake is typically engaged only in certain situations to hold or secure the elevator car in a stopped position. Thus, the brake capability is not easily detectable or verifiable through normal use. Brake shoe tests are part of regular safety code required tests. During these tests, a service person activates/deactivates the individual brake shoes. These tests are cumbersome and put excessive strain on the brake, leading to an accelerated decline of the brake capability. 
       BRIEF DESCRIPTION OF INVENTION 
       [0004]    According to an exemplary embodiment of the invention, an elevator brake monitoring system includes a car; a machine configured to actuate movement of the car; and a brake configured to decelerate the car; wherein the system is configured to operate the machine to move the car at a pre-determined speed, engage the brake, measure a braking parameter and compare the measured braking parameter to a reference braking parameter. 
         [0005]    In addition to one or more of the features described above or below, or as an alternative, further embodiments may include the measured braking parameter being braking distance. 
         [0006]    In addition to one or more of the features described above or below, or as an alternative, further embodiments may include the system being configured to determine the braking distance in response to the position encoder. 
         [0007]    In addition to one or more of the features described above or below, or as an alternative, further embodiments may include the measured braking parameter being braking time. 
         [0008]    In addition to one or more of the features described above or below, or as an alternative, further embodiments may include the system being configured to determine a braking capability of the brake in response to comparing the measured braking parameter to the reference braking parameter. 
         [0009]    In addition to one or more of the features described above or below, or as an alternative, further embodiments may include the braking capability being unsatisfactory when the measured braking parameter exceeds the reference braking parameter. 
         [0010]    In addition to one or more of the features described above or below, or as an alternative, further embodiments may include the braking capability being satisfactory when the measured braking parameter is below the reference braking parameter. 
         [0011]    In addition to one or more of the features described above or below, or as an alternative, further embodiments may include the braking capability being stored locally or in an external service system. 
         [0012]    In addition to one or more of the features described above or below, or as an alternative, further embodiments may include the measured braking parameter being stored locally or in an external service system. 
         [0013]    According to another r exemplary embodiment of the invention, a method for monitoring a braking capability of a brake of an elevator, the elevator including a car, a machine configured to actuate movement of the car, and the brake configured to decelerate the car, the method including operating the machine to move the car at a predetermined speed; engaging the brake; measuring a braking parameter; and comparing the measured braking parameter to a reference braking parameter. 
         [0014]    In addition to one or more of the features described above or below, or as an alternative, further embodiments may include the measured braking parameter being braking distance. 
         [0015]    In addition to one or more of the features described above or below, or as an alternative, further embodiments may include the measured braking parameter being braking time. 
         [0016]    In addition to one or more of the features described above or below, or as an alternative, further embodiments may include determining a braking capability of the brake in response to comparing the measured braking parameter to the reference braking parameter. 
         [0017]    In addition to one or more of the features described above or below, or as an alternative, further embodiments may include the braking capability being unsatisfactory when the measured braking parameter exceeds the reference braking parameter. 
         [0018]    In addition to one or more of the features described above or below, or as an alternative, further embodiments may include the braking capability being satisfactory when the measured braking parameter is below the reference braking parameter. 
         [0019]    In addition to one or more of the features described above or below, or as an alternative, further embodiments may include storing the braking capability locally or in an external service system. 
         [0020]    In addition to one or more of the features described above or below, or as an alternative, further embodiments may include storing the measured braking parameter locally or in an external service system. 
         [0021]    In addition to one or more of the features described above or below, or as an alternative, further embodiments may include emptying the car of load prior to operating the machine to move the car at the predetermined speed. 
         [0022]    A technical effect of the invention is the ability to automatically test the braking capability of an elevator brake without requiring service personnel to visually and/or physically inspect the brake. Results of the braking capability test may be stored and notifications and/or reports may be generated based on the braking capability test. 
     
    
     
       BRIEF DESCRIPTION OF DRAWING 
         [0023]    The subject matter that is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawing in which: 
           [0024]      FIG. 1  is a perspective view of an elevator in which an elevator brake monitoring system according to an exemplary embodiment may be implemented; 
           [0025]      FIG. 2  is a perspective view of a machine for controlling movement of an elevator car in an exemplary embodiment; and 
           [0026]      FIG. 3  is a flow diagram of a method for monitoring the braking capability of a brake of the machine illustrated in  FIG. 2  in an exemplary embodiment. 
       
    
    
     DETAILED DESCRIPTION OF INVENTION 
       [0027]      FIG. 1  is a perspective view of an elevator  10  including a car  12 , a counterweight  14 , roping  16 , a machine  18 , a position encoder  20 , and a controller  22 . The car  12  and counterweight  14  are connected to each other by the roping  16 . The roping  16  may include, for example, ropes, steel cables, or coated-steel belts. The counterweight  14  balances a load from the car  12  and facilitates movement of the car  12  concurrently and in an opposite direction with respect to the counterweight  14  within a hoistway  24 . 
         [0028]    The roping  16  engages the machine  18 , which is part of an overhead structure of the elevator  10  and controls movement between the car  12  and counterweight  14 . The position encoder  20  may be mounted on an upper sheave of a speed-governor system  26  and configured to provide position signals related to a position of the car  12  within the hoistway  24 . In other embodiments, the position encoder  20  may be directly mounted to a moving component of the machine  18 . 
         [0029]    The controller  22  is located, for example, in a controller room  28  of the hoistway  24  and controls operation of the elevator  10 . The controller  22  provides drive signals to the machine  18  to control the acceleration, deceleration, leveling, and stopping of the car  12 . The controller  22  is also configured to receive the position signals from the position encoder  20 . 
         [0030]      FIG. 2  is a perspective view of the machine  18  for controlling the movement of the car  12  and the counterweight  14 . The machine  18  includes a motor  30 , a brake  32 , a rotating member  34 , and a sheave  36 . In an exemplary embodiment, the rotating member  34  is a drive shaft  34  that projects from the motor  30 . The sheave  36  is fixedly disposed on the drive shaft  34  and mechanically engages the roping  16 . The brake  32  is disposed adjacent to the motor  30  at an end of the drive shaft  34  opposite the sheave  36 . It should be readily appreciated that the brake  32  can have any suitable relationship with the motor  30 , the drive shaft  34 , and the sheave  36 . 
         [0031]    The drive shaft  34  is rotatably driven by the motor  30 , which causes the sheave  36  to rotate. This rotation causes linear movement of the car  12  and the counterweight  14  due to the engagement between the roping  16  and the sheave  36 . The motor  30  drives the drive shaft  34  based upon the drive signals received from the controller  22 . The magnitude and direction of the force (i.e., torque) provided by the motor  30  on the roping  16  controls the acceleration, deceleration, direction, and speed of the car  12 . When the brake  32  engages the drive shaft  34 , the car  12  is stopped or secured in place to prevent movement of the car  12 . 
         [0032]    It should be readily appreciated that the brake  32  can be any suitable type of brake and engage and disengage from the drive shaft  34  in any suitable manner. It should be readily appreciated as well that, although the elevator  10  is disclosed herein as including the rotating sheave  36  and motor  30 , the elevator  10  can be implemented with other drive systems, such as a linear motor-driven elevator (e.g., a ropeless, self-propelled elevator). Embodiments are not limited to use of the machine  18  of  FIG. 2 . 
         [0033]      FIG. 3  is a flow diagram for a method for monitoring the braking capability of the brake  32  to sufficiently decelerate the car  12  according to an exemplary embodiment of the invention. With the method, an automatic test of the braking capability is initiated under defined conditions. 
         [0034]    At step  38 , the car  12  is emptied of load to provide a consistent mass. It is understood that the braking capability test may be performed with a load in the car  12 . It is desirable, however, to use the same car load across multiple braking capability tests. Emptying car  12  is just one example of a technique to provide a consistent mass. The elevator  10  may include, for example, at least one weight sensor to determine when there is no load in the car  12 . At step  40 , the unloaded car  12  is positioned in the hoistway  24  at a reference position (for instance, at an upper landing L of the hoistway  24 ). It is understood that step  40  may precede step  38 . The reference position is used so that subsequent braking capability tests are performed under similar circumstances. 
         [0035]    At step  42 , the machine  18  is operated to move the car  12  at a predetermined speed. More specifically, the motor  30  drives the drive shaft  34  and sheave  36  to provide movement of the car  12  at the predetermined speed. In an exemplary embodiment, the predetermined speed is less than or equal to a nominal speed of the car  12  during normal operations. In an exemplary embodiment, the nominal speed is about one meter/second, and the predetermined speed is about half of the nominal speed. The motor  30  drives the drive shaft  34  and sheave  36  for a short period of time (e.g., not more than a few seconds). In this way, noise and wear of the brake  32  are maintained at a low level during the test. 
         [0036]    It should be readily appreciated that the nominal speed can be any suitable speed and the predetermined speed can be any suitable speed that is less than or equal to the nominal speed. For example, the predetermined speed may vary from about 20% of the nominal speed to about 70% of the nominal speed. 
         [0037]    Once the car  12  is traveling at the predetermined speed, the brake  32  is engaged as shown at step  44 . More specifically, the controller initiates the brake  32  to decelerate the car  12  in a simulated “emergency” stop condition. 
         [0038]    At step  46 , the brake  32  has decelerated the car  12  to a completely stopped position. At step  48 , a measured braking parameter is determined by the controller  22 . It is understood that step  48  may be performed concurrently as the car  12  decelerates, and step  48  need not occur until after the car  12  has come to a stop. The measured braking parameter may be a braking distance the car  12  traveled from the application of the brake  32  at step  44  to the stopping of the car  12  at step  46 . The controller  22  may use position signals from position encoder  20  to determine the braking distance traveled from the application of the brake  32  at step  44  to the stopping of the car  12  at step  46 . In another exemplary embodiment, the measured braking parameter may be a braking time elapsed from the application of the brake  32  at step  44  to the stopping of the car  12  at step  46 . The controller  22  may use an internal clock to determine the braking time from the application of the brake  32  at step  44  to the stopping of the car  12  at step  46 . 
         [0039]    At step  50 , the measured braking parameter is compared to a reference braking parameter. If the measured braking parameter exceeds the reference braking parameter, flow proceeds to step  52  where the braking capability of the brake  32  is designated as unsatisfactory. This indicates that the measured braking parameter was excessive (e.g., too long of a distance or too long of a time to bring the car to a stop). At step  50 , if the measured braking parameter does not exceed the reference braking parameter, flow proceeds step  54  where the braking capability of the brake  32  is designated as satisfactory. 
         [0040]    At step  56 , the measured braking parameter can be stored locally on controller  22  or at an external service system. The braking capability determined through step  50  (e.g., satisfactory or unsatisfactory) may also be stored locally on controller  22  or at an external service system. A report including the results of the brake test of  FIG. 3  may be generated periodically to provide proof of compliance with certain regulations or codes requiring brake inspection. An alert or notification may be generated if the measured braking parameter exceeds the reference braking parameter to notify service personnel to inspect brake  32 . 
         [0041]    The exemplary system and method allow for automatic monitoring of performance of the brake  32  by applying the brake  32  and measuring stopping distance/time of the elevator car  12  under defined test conditions. The exemplary system and method allow for the brake  32  to be monitored regularly (e.g., every day). In addition, the exemplary system and method allow for simplification of maintenance and service of the elevator  10  since the exemplary system and method do not require a mechanic to perform a brake test. Moreover, the exemplary system and method allow for early and regular diagnostics of performance of the brake  32 . 
         [0042]    While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions, or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various non-limiting embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.