Patent Publication Number: US-2017349405-A1

Title: Elevator brake monitoring

Description:
FIELD 
     The present disclosure relates to elevator brakes and particularly to a method and apparatus for detecting an unsafe operating condition which could potentially result in loss of brake torque and which could subsequently lead to uncontrolled car movement. 
     BACKGROUND 
     Typically, either a drum brake or a disc brake is provided to halt rotation of a motor shaft in traction elevators. In either case, at least one compression spring is generally employed to bias the brake into its closed or braking position and an actuator which is typically electromagnetically, hydraulically or pneumatically driven is provided to overcome the spring bias and move the brake into its open or released position, permitting the motor to commence rotation and thereby raise or lower an elevator car along a hoistway. These brakes are regarded as fail-safe systems since if, for example, power is lost to the actuator, the brakes under the influence of the biasing springs automatically assume the braking or closed position. 
     The disc or drum is splined or otherwise mounted to the shaft for concurrent rotation therewith. The shaft itself is rotatably supported via bearings provided in one or more support brackets. Depending on the specific application, the rated speed of shaft will vary widely depending on application, but generally the shaft may have a rated speed ranging from the tens to the hundreds of revolutions per minute. Furthermore, substantial loads are transmitted by the shaft, through the bearings and to the support brackets. Given the high work duty performed by the bearing, it is beneficial to lubricate them on a regular basis with oil or grease to ensure correct functionality and prolong lifespan. 
     Generally, the bearings are lubricated by a technician during call-outs or routine maintenance. However, given the manual nature of the task there is an inherent possibility that the bearings may be over-lubricated. This can pose an issue as any excess oil or grease may migrate onto the shaft and, given the high centrifugal forces operating thereupon, can consequently contaminate the disc or drum leading to loss of brake torque and the possibility of uncontrolled car movement. 
     JP-A-2013147279 discloses a system for monitoring the thickness of a brake lining within an elevator or conveyor. In a first example, featuring a brake disc arranged between an armature and a side plate, laser light is projected axially by a sensor from the side plate onto a zone of the armature which is circumferentially outwards from the brake disc. The sensor measures the time taken for the light to be reflected back to it from the zone and from the measured time can determine the axial distance between the armature and the side plate and thereby the thickness of the brake linings attached to opposing sides of the disc. In the brake drum arrangement of a second example, the sensor is mounted externally to a brake shoe so that it projects light through holes in the shoe and brake lining onto the brake surface on the drum. Again by measuring the time taken for the light to travel from the sensor to the brake surface of the drum and back to the sensor, the sensor can determine the thickness of the brake lining. 
     In a similar arrangement to the second example summarized above, WO-A1-2012/101091 describes a distance sensor mounted to the brake pad which projects electromagnetic radiation onto the brake surface of the drum and determines from the reflected radiation the distance travelled. The sensor has to be insensitive to most common duct, humidity, oil film and oil vapor. 
     Due to the location of the sensors of JP-A-2013147279 and WO-A1-2012/101091, they firstly cannot monitor for contamination such as any excess oil or grease that may migrate onto the shaft and, given the high centrifugal forces operating thereupon, that may consequently contaminate the disc or drum leading to loss of brake torque and the possibility of uncontrolled car movement. Furthermore, due to the very nature of the sensors used in JP-A-2013147279 and WO-A1-2012/101091, they cannot determine whether any contamination has occurred in the sensed zone as the sensor of JP-A-2013147279 relies purely on the time it takes for the light to travel to determine distance and the likewise sensor of WO-A1-2012/101091 needs to be insensitive to contamination. 
     EP-A1-1930275 describes an apparatus for detecting whether there is an abnormality in the operation of an elevator, and in one embodiment, a detector is provided for measuring a change in a pressure or viscosity of the oil injected into a bearing for rotatably supporting a rotating shaft. 
     The pressure sensors disclosed in EP-A1-1930275 may not be suitable for installation in an existing elevator installation. 
     SUMMARY 
     An objective of the present invention therefore is to provide an alternative solution for use in an elevator installation to detect an unsafe operating condition, which could potentially result in loss of brake torque and which could subsequently lead to uncontrolled car movement. The invention is, in particular, suited to the detection of over-lubrication of a bearing within the elevator. 
     In the method, an elevator brake having a rotatable component mounted to a shaft is monitored for contamination by projecting electromagnetic radiation onto the rotatable component or onto the shaft, and receiving reflected electromagnetic radiation. If an area or zone monitored by these steps becomes contaminated for example with oil or grease, the nature of the electromagnetic radiation reflected from the zone will change noticeably. 
     The degree of contamination step may be determined from the intensity of one or both of the projected and reflected electromagnetic radiations. 
     Preferably, a signal indicative of the intensity of the reflected electromagnetic radiation is compared with one or more thresholds. The signal may exceed an upper threshold indicating the presence of oil, grease or other contaminants. The signal may fall below a lower threshold indicating a fault with equipment. 
     Alternatively, a difference between the signal indicative of the intensity of the reflected electromagnetic radiation and a signal indicative of the projected electromagnetic radiation can be determined and again compared with one or more thresholds. 
     In either case, an elevator control can be informed if a threshold has been breached. It in turn can undertake remedial action. For example, the control can safely park an elevator car at a landing and open elevator doors to enable any passengers in the car to disembark. Furthermore, the control may also take the effected elevator out of commission and issue an alarm to a remote monitoring center indicating the situation and the need for maintenance. 
     The elevator installation according to the present invention comprises a shaft rotatably supported by a bearing, a brake having a rotatable component mounted to the shaft and a movable component to selectively engage a brake surface on the rotatable component, and a sensor projecting electromagnetic radiation onto and receiving reflected electromagnetic radiation from a zone located between the bearing and the brake surface. Again, the nature of the electromagnetic radiation reflected from the zone will change noticeably and dramatically as soon as the monitoring zone becomes contaminated. 
     Typically, the zone may be on the rotatable component or on the shaft. There is therefore a wide range of possibilities for selecting an appropriate position for mounting the sensor. 
     Preferably, the sensor included a transmitter, a receiver and a comparator. The comparator can either compare a signal indicative of the intensity of the reflected electromagnetic radiation with one or more thresholds or compare differences between the signal indicative of the intensity of the reflected electromagnetic radiation and a signal indicative of the projected electromagnetic radiation with one or more thresholds in order to detect an unsafe operating condition. In such a case, it is beneficial that the comparator is connected to an elevator control so that the control can undertake remedial action which may include informing a remote monitoring center. 
     The elevator brake can generally take any conventional form. For example, in one embodiment, the rotatable component is a brake disc and the movable component is a brake pad. Alternatively, the rotatable component could be a brake drum where the movable component is a brake lining. 
     Preferably, the movable component is biased by springs into engagement with the brake surface. 
     The movable component may be moved out of engagement with the brake surface by a hydraulic actuator or by an electromagnetic actuator. 
     Preferably, the electromagnetic radiation is in the form of ultraviolet light with the sensor being an ultraviolet sensor. Ultraviolet radiation has the benefit of being extremely good at exposing changes to the surface characteristics of the monitoring zone, particularly with regard to reflectivity and luminescence. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The invention is herein described by way of specific examples with reference to the accompanying drawings of which: 
         FIG. 1  is a schematic illustration of an exemplary embodiment of a typical elevator installation incorporating a method and apparatus according to the present invention; 
         FIGS. 2A and 2B  illustrate a plan and a side view, respectively, of an exemplary embodiment of a hydraulically actuated, elevator disc brake in conjunction with a sensor according to a first embodiment of the present invention; 
         FIGS. 3A and 3B  illustrate a plan and a side view, respectively, of an exemplary embodiment of an electromagnetically actuated, elevator drum brake in conjunction with a sensor according to a second embodiment of the present invention; 
         FIG. 4  illustrates components with a sensor according to an exemplary embodiment of the invention; 
         FIG. 5  is an exemplary graphical representation over time of the signal from the receiver to the comparator depicted in  FIG. 4 ; and 
         FIGS. 6A and 6B  are flowcharts illustrating monitoring procedures according to exemplary embodiments of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     A typical elevator installation  1  for use with the method according to the invention is shown in  FIG. 1 . The installation  1  is generally defined by a hoistway bound by walls within a building wherein a counterweight  2  and car  4  are movable in opposing directions along guide rails. Suitable traction means  6  supports and interconnects the counterweight  2  and the car  4 . In the present embodiment, the weight of the counterweight  2  is equal to the weight of the car  4  plus 40% of the rated load, which can be accommodated within the car  4 . The traction means  6  is fastened to the counterweight  2  at one end, passed over a deflecting pulley  5  positioned in the upper region of the hoistway, passed through a traction sheave  8  also located in the upper region of the hoistway, and fastened to the elevator car  4 . Naturally, the skilled person will easily appreciate other roping arrangements are equally possible. 
     The traction sheave  8  is driven via a drive shaft  10  by a motor  12  and braked by at least one elevator brake  14 ,  16 . The use of at least two brake sets is compulsory in most jurisdictions (see, for example, European Standard EN81-1:1998 12.4.2.1). Accordingly, the present example utilizes two independent, brakes  14  and  16 . Each of the brakes  14 ,  16  includes a spring-biased brake shoe releasable against a corresponding disc or drum mounted to the shaft  10  of the motor  12 . The brake may be hydraulically actuated to counteract the force of the biasing springs. Alternatively, the brake may include an electromagnet to open the brake against the springs. 
     Actuation of the motor  12  and release of the brakes  14 ,  16  is controlled and regulated by command signals C from a control system  18 . Additionally, signals S representing the status of the motor  12  and the brakes  14 ,  16  are continually fed back to the control system  18 . Movement of the drive shaft  10  and thereby the elevator car  4  is monitored by an encoder  22  mounted on brake  16 . A signal V from the encoder  22  is fed to the control system  18  permitting it to determine travel parameters of the car  4  such as position, speed and acceleration. 
     The control system  18  incorporates a modem and transponder  20  permitting it to communicate with a remote monitoring center  26 . Such communication can be wirelessly over a commercial cellular network, through a conventional telephone network or by means of dedicated line. 
       FIGS. 2A and 2B  illustrate a plan and a side view, respectively, of an exemplary embodiment of a hydraulically actuated, elevator disc brake  14  in conjunction with a sensor  40  according to a first embodiment of the present invention. Within the brake  14 , a brake disc  90  is splined or otherwise mounted to the shaft  10  for concurrent rotation therewith. The shaft  10  is rotatably supported via bearings  32  provided in one or more brackets  30 . A plurality of hydraulic brake actuators  70  surround and overlap the disc  90 . 
     In order to release the brake  14 , pressurized fluid is supplied via hydraulic circuits  71  to a brake cylinder  72  within each actuator  70 . The pressurized fluid acts on one side of a brake piston  74  to counteract the biasing force of a compression spring  76  acting on the other side of the piston  74 . Accordingly as the pressure of the fluid increases, the piston  74  moves to further compress the spring  76  (in the left direction in  FIG. 2B ) and thereby releases a piston mounted brake shoe  80  and an opposing brake shoe  82  from engagement with the opposing sides of a brake disc  90 . 
     Conversely, when the pressurized fluid within the hydraulic circuits  71  is drained, the pressure of the fluid with the brake cylinders  72  is no longer sufficient to counteract the biasing force of the compression springs  76  and the brake piston  74  and brake shoes  80 ,  82  will reassume their original positions to halt rotation of the brake disc  90  and thereby brake the shaft  10  of the elevator drive. 
     A brake surface A-B on the disc  90  against which the piston mounted brake shoe  80  and an opposing brake shoe  82  engage is defined as the area between the discrete circles A and B indicated in  FIG. 2A . 
     In order to detect any material that could possibly contaminate the brake surface A-B of the disc  90 , for example excess oil or grease migrating towards the brake disc  90  from the bearings  32 , a sensor  40  is provided which in this example is mounted on the support bracket  30 . The sensor  40  includes a transmitter  42  generating and directing ultraviolet light to a monitoring zone on the disc  90 . In this instance the monitoring zone is indicated with the dashed circle  50  in  FIG. 2A  and is located on the disc  90  between the shaft  10  and brake surface A-B. The sensor  40  also includes a receiver  44  to capture ultraviolet light reflected from the monitoring zone  50 . 
     Accordingly, migration of any oil or grease from the bearings  32 , along the shaft  10 , and radially outwards over the disc  90  and onto the monitoring zone  50 , will be detected by the sensor  40  as the characteristics of the ultraviolet light reflected from the monitoring zone  50  to the a receiver  44  will change noticeably as soon as the monitoring zone  50  become contaminated. 
     A further exemplary embodiment of the present invention will be descried with reference to  FIGS. 3A and 3B  which illustrate a plan and a side view, respectively, of an electromagnetically actuated, elevator drum brake  16  in conjunction with a sensor  40 . 
     The brake  16  includes a brake drum  92  either mounted directly on a shaft  10  either directly connected to a motor  12  or, alternatively, indirectly connected thereto via a gear. As in the previous embodiment, the shaft  10  is rotatably supported via bearings  32  provided in one or more brackets  30 . 
     Two brake arms  60  are provided at opposing sides of the drum  92  and are mounted at their lower ends on pivots  62  connected to a housing of either the motor  12  or the gear. Each arm  60  is fitted with a brake lining  63  and is biased by a pre-tensioned compression spring  64  towards the drum  92 . The forces imposed on the brake arms  60  by the springs  64  are illustrated by the arrows F s1  and F s2 , respectively. An electromagnetic actuator  65  is provided between and interconnects the upper ends of the brake arms  60 . The actuator  65  includes a housing  66  containing a series of solenoid coils  67  and a movable solenoid plunger  68  extending from the housing  66 . 
     In the closed position of the brake  16 , the electromagnetic actuator  65  is de-energized and therefore unable to resist the inward biasing forces F s1  and F s2  of the brake springs  64  on the arms  60 . Accordingly, the brake linings  63  frictionally engage with a brake surface A-B (defined between the dashed lined A and B in  FIG. 3B ) on the drum  92  to either halt rotation of the shaft  10  or retain the shaft  10  in a stationary position. 
     When the electromagnetic actuator  65  is activated or energized, as instructed by an elevator controller  18  (see  FIG. 1 ), current flows through the solenoid coils  67 , which results in the further extension of the solenoid plunger  68  from the housing  66 . This provides electromagnet opening forces illustrated by the arrows F e1  and F e2 , respectively, acting on the opposing brake arms  60 . The electromagnetic opening forces F e1  and F e2  open the brake  16  by further compressing the springs  64  to overcome the spring bias F s1  and F s2  and move the arms  60  and linings  63  away from the drum  92 , resulting in the provision of an air gap between the brake linings  63  and the drum  92  and thereby permitting rotation of the shaft  10 . 
     In order to detect any material that could possibly contaminate the brake surface A-B of the drum  92 , for example excess oil or grease migrating towards the brake drum  92  from the bearings  32 , a sensor  40  is provided, which in this example is mounted on the support bracket  30 . The sensor  40  again includes a transmitter  42  generating and directing ultraviolet light to a monitoring zone which in this instance is provided on the shaft  10 . The monitoring zone is indicated with the dashed circle  50  in  FIG. 3B  and is located on the shaft  10  between the bearings  32  and the brake surface A-B. The sensor  40  also includes a receiver  44  to capture ultraviolet light reflected from the monitoring zone  50 . 
     Accordingly, migration of any oil or grease from the bearings  32 , along the shaft  10 , and onto the monitoring zone  50 , will be detected by the sensor  40  as the characteristics of the ultraviolet light reflected from the monitoring zone  50  to the a receiver  44  will change noticeably as soon as the monitoring zone  50  becomes contaminated. 
       FIG. 4  illustrates the components of the sensor  40  according to an exemplary embodiment of the invention. As previously discussed, ultraviolet light UV 1  is sent from the transmitter  42  and incident upon the monitoring zone  50 . Thereafter ultraviolet light UV 2  is reflected from the monitoring zone  50  to the receiver  44 . The intensity of the reflected light UV 2  will naturally depend on the prevailing surface characteristics of the monitoring zone  50 . 
     The receiver  44  generates a signal UV in  that is indicative of the intensity of the light UV 2  reflected back to it from the monitoring zone  50 . This signal UV in  is fed from the receiver  44  to a comparator  46 , which compares it against an upper threshold value L 1  and a lower threshold value L 2  to determine whether there is an unsafe operating condition, which could potentially result in loss of brake torque. If an unsafe operating condition is detected, the comparator  46  issues a signal X to the elevator control  18  which, if required, will undertake remedial action. 
     An example is illustrated graphically in  FIG. 5  which shows the level of the signal UV in  over time. Initially, from time T 0  to T 1 , the signal UV in  remains within the boundaries defined by the upper threshold L 2  and the lower threshold value L 1 . 
     At time T 1 , however, the signal UV in  exceeds the upper threshold L 2  possibly indicating that oil or grease has migrated onto the monitoring zone  50 . In this instance, the comparator would issue a signal X to the elevator control  18  which, in response, may safely park the elevator car  4  at an appropriate landing and open elevator doors to enable any passengers in the car  4  to disembark. The control  18  may also take the effected elevator  1  out of commission and issue an alarm to the remote monitoring center  26  indicating the situation and the need for maintenance, e.g. cleaning off excessive oil or grease by a service technician. 
     At time T 2  in the graph of  FIG. 5 , the signal UV in  drops below the lower threshold L 1 , which could indicate that the light path between the transmitter  42  and the receiver  44  is obscured, perhaps by contamination to a lens of the transmitter  42  or receiver  44 . It could also indicate that at least one of the transmitter  42  and the receiver  44  is faulty. In this instance, the comparator would issue a signal X to the elevator control  18  which, in response, may issue an alarm to the remote monitoring center  26  indicating the situation and the need for maintenance. 
     As an alternative to the procedure described above, it is possible to determine whether there is an unsafe operating condition, which could potentially result in loss of brake torque by determining a difference Δ between the signal UV in  indicative of the intensity of the reflected ultraviolet light and a signal UV out  indicative of the projected ultraviolet light. Again, as in the previous procedure, if the difference Δ falls outside of the boundaries defined by an upper threshold and a lower threshold, the elevator control  18  can be informed and, if required, undertake remedial action. 
     The two alternate procedures outlined above for monitoring the brake illustrated in the flowcharts of  FIGS. 6A and 6B . Monitoring is commenced in step S 1  when the sensor  40  is initiated to transmit ultraviolet light UV 1  onto and receive ultraviolet light UV 2  reflected back from the monitoring zone  50 . In step S 2 , a signal UV in  indicative of the intensity of the ultraviolet light UV 2  reflected back from the monitoring zone  50  is determined. Next, in step S 3 , the signal UV in  is compared with an upper threshold L 2  and a lower threshold L 1 . If the signal UV in  lies within the threshold boundaries the procedure loops back to step S 2 . If not, the procedure in step S 4  notifies the control  18  that an unsafe condition has arisen with the brake. 
     In the alternate procedure shown in  FIG. 6B , monitoring is commenced in step S 11  when the sensor  40  is initiated to transmit ultraviolet light UV 1  onto and receive ultraviolet light UV 2  reflected back from the monitoring zone  50 . In step S 12 , a difference Δ between a signal UV out  indicative of the intensity of the ultraviolet light UV 2  transmitted to the monitoring zone  50  and a signal UV in  indicative of the intensity of the ultraviolet light UV 2  reflected back from the monitoring zone  50  is determined. Next, in step S 13 , the difference Δ is compared with an upper threshold L 2  and a lower threshold L 1 . If the difference Δ lies within the threshold boundaries the procedure loops back to step S 12 . If not, the procedure in step S 14  notifies the control  18  that an unsafe condition has arisen with the brake. 
     The procedure outlined can be performed continuously while the elevator in operation, or can be performed periodically. 
     Ultraviolet light has the benefit that it is extremely good at exposing changes to the surface characteristics of the monitoring zone  50 , particularly reflectivity and luminescence. However, it will be readily appreciated that other forms of electromagnetic radiation can be utilized by the invention. 
     Although in the exemplary embodiments specifically illustrated in  FIGS. 2B and 3B  the sensor  40  is mounted to the support bracket  30 , it will be easily appreciated that the sensor  40  can be mounted on any component so as the zone  50 , which it monitors is positioned between the bearings  32  and the braking surface A-B. 
     Having illustrated and described the principles of the disclosed technologies, it will be apparent to those skilled in the art that the disclosed embodiments can be modified in arrangement and detail without departing from such principles. In view of the many possible embodiments to which the principles of the disclosed technologies can be applied, it should be recognized that the illustrated embodiments are only examples of the technologies and should not be taken as limiting the scope of the invention. Rather, the scope of the invention is defined by the following claims and their equivalents. 
     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.