Elevator safety system

Abstract

An elevator safety system for an elevator car 11 has an edge device 13, mounted to the car door or a landing door, the edge device having one or more visible light emitters 134. A levelling sensor 15,

Description

FIELD The technology relates to safety systems for elevators, and in particular to a system for detecting an offset or misalignment between an elevator car and a landing. BACKGROUND Misalignment of an elevator car with a corresponding landing can cause an offset between the floor of the car and the floor of the landing, thereby posing a safety risk to users. The offset may cause a user to trip, for example. There is, therefore, a need to detect such offsets as early as possible. WO2020044030 discloses an elevator levelling sensor system for determining misalignment between an elevator car floor and a landing floor using an auxiliary sensor. A safety system for detecting misalignment between an elevator car floor and a corresponding landing floor is required. BRIEF DESCRIPTION OF THE INVENTION Disclosed is an elevator safety system for use with an elevator car configured to move between a plurality of landings, the elevator safety system including: an edge device configured to be mounted to an elevator car door or a landing door, the edge device including one or more visible light emitters; a levelling sensor configured to be mounted with respect to an the elevator car andor a landing of the plurality of landings, and configured to determine a distance to a portion of the landing and / or a distance to a portion of the elevator car in use; and a controller configured to use the determined distance(s) to determine a vertical offset between an elevator car floor and a landing floor, and to control operation of at least a portion of the visible light emitters to provide a visual representation of the determined offset. The controller may be configured to determine the vertical offset by: (i) comparing the distance to the portion of the elevator car with the distance to the portion of the landing; and / or (ii) comparing the distance to the portion of the elevator car to a predetermined distance, the levelling sensor being mounted in a substantially fixed vertical position with respect to the landing floor; and / or (iii) comparing the distance to the portion of the landing to a predetermined distance, the levelling sensor being mounted in a substantially fixed vertical position with respect to the elevator car floor. The controller may be further configured to control operation of at least a portion of the visible light emitters to provide a visual representation of a status of the elevator car door. The levelling sensor may be mounted to the edge device. The levelling sensor may be slidable with respect to the edge device such that the position of the levelling sensor with respect to the edge device is adjustable. The levelling sensor may be configured to determine the distance to at least one of: (i) a portion of the landing floor located in a gap between the elevator car door and the landing door; (ii) a portion of the elevator car floor located in the gap between the elevator car door and the landing door; (iii) a header of the elevator car; (iv) a header of the landing; (v) a feature on the elevator car door; and / or (vi) a feature on the landing door. Also disclosed is an elevator safety system for use with an elevator car configured to move between a plurality of landings, the elevator car having an elevator car floor and an elevator car door, the elevator safety system including: a levelling sensor mounted with respect to an the elevator car and ora landing of the plurality of landings, each having a floor and a door, the levelling sensor configured to determine a distance to at least one of: (i) a portion of the a landing floor located in a gap between the elevator car door and the a landing door; (ii) a portion of the elevator car floor located in the gap between the elevator car door and the a landing door; (iii) a header of the elevator car; (iv) a header of the a landing; (v) a feature on the elevator car door; and / or (vi) a feature on the a landing door; and a controller configured to use the determined distance(s) to determine a vertical offset between the elevator car floor and the a landing floor, and to output an indication of the determined offset to a user. The controller may be configured to determine the vertical offset by: (i) comparing the distance to at least one of the portion of the landing floor, header of the landing, or feature on the landing door, with the distance to at least one of the portion of the elevator car floor, header of the elevator car, or feature on the elevator car door; and / or (ii) comparing the distance to the portion of the elevator car floor, header of the elevator car, or feature on the elevator car door to a predetermined distance, the levelling sensor being mounted in a substantially fixed vertical position with respect to the landing floor; and / or (iii) comparing the distance to the portion of the landing floor, header of the landing, or feature on the landing door to a predetermined distance, the levelling sensor being mounted in a substantially fixed vertical position with respect to the elevator car floor. The system may further include an edge device mounted to the elevator car door, wherein the levelling sensor is mounted to the edge device, and wherein the levelling sensor is configured to determine a distance to at least one of (i) a portion of the landing floor located in a gap between the elevator cardoorand the landing door; (ii) a header of the landing; and / or (iii) a feature on the landing door. The edge device may include one or more visible light emitters and the controller may be configured to control operation of at least a portion of the visible light emitters to provide a visual representation of the determined offset to the user. The controller may be further configured to control operation of at least a portion of the visible light emitters to provide a visual representation of a status of the elevator car door. The levelling sensor may be slidable with respect to the edge device such that the position of the levelling sensor with respect to the edge device is adjustable. Also disclosed is an elevator safety system including: a door sensor configured to be mounted to an elevator car door and / or a landing door to detect an obstruction blocking the elevator car door and / or landing door; a levelling sensor slidably mounted to the door sensor and configured to determine a distance to a portion of the landing and / or a portion of the elevator car; and a controller configured to use the determined distance(s) to determine a vertical offset between an elevator car floor and a landing floor, and to output an indication of the determined offset to a user. The controller may be configured to determine the vertical offset by: (i) comparing the distance to the portion of the elevator car with the distance to the portion of the landing; and / or (ii) comparing the distance to the portion of the elevator car to a predetermined distance, the levelling sensor being mounted in a substantially fixed vertical position with respect to the landing floor; and / or (iii) comparing the distance to the portion of the landing to a predetermined distance, the levelling sensor being mounted in a substantially fixed vertical position with respect to the elevator car floor. The door sensor may include one or more visible light emitters, and the controller may be configured to control operation of at least a portion of the visible light emitters to provide a visual representation of the determined offset. The controller may be further configured to control operation of at least a portion of the visible light emitters to provide a visual representation of a status of the elevator car door. The levelling sensor may be configured to determine the distance to at least one of: (i) a portion of the landing floor located in a gap between the elevator car door and the landing door; (ii) a portion of the elevator car floor located in the gap between the elevator car door and the landing door; (iii) a header of the elevator car; (iv) a header of the landing; (v) a feature on the elevator car door; and / or (vi) a feature on the landing door. The levelling sensor may further include a clamping mechanism to fix the position of the levelling sensor with respect to the edge device. BRIEF DESCRIPTION OF THE FIGURES In orderthatthe present disclosure may be more readily understood, preferable embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings, in which: Fig. 1 shows a schematic simplified view of an elevator system; Figs. 2a-d show a simplified view of an elevator car door opening; Fig. 3 shows a schematic simplified view of a door sensor; Fig. 4 shows a door sensor and other elevator system components; Fig. 5 shows a levelling sensor mounted to a door sensor; Fig. 6 shows a close-up view of the levelling sensor of Fig. 5; and Fig. 7 shows a simplified view of the levelling sensor and door sensor in use. DETAILED DESCRIPTION OF THE DISCLOSURE With reference to figure 1, for example, an elevator system 1 may include one or more elevator cars 11 each provided in a respective elevator shaft 12. The elevator system 1 may be fitted to a building or other facility which has a plurality of different levels 21. The elevator system 1 may be configured to serve each of the plurality of levels 21 to allow users and / or objects to travel between levels 21. The or each elevator car 11 includes an elevator door 111 which can be moved between open and closed configurations to enable access to the elevator car 11 selectively. The elevator door 111 may be a sliding door which moves between the open and closed configurations through a linear movement. The elevator door 111 may be provided in at least two parts which retract in opposing directions when moving from the closed to the open configuration, and extend towards each other when moving from the open to the closed configuration (i.e. a centre opening arrangement). Each part of the elevator door 111 may be provided as a plurality of sections, each section may move in a linear manner with respect to one or more other sections of the same part of the elevator door 111 (in a sliding movement). A similar arrangement of sections may be used for a side opening (or single door) arrangement of an elevator door 111 - i.e. an elevator door 111 which includes a single part, which may be formed of multiple sections, which extends across the entire door opening when in the closed configuration. Accordingly, a relatively large door aperture 111a may be provided by the overlapping position of the door sections when in the open configuration (the door aperture 111a being the opening of the door 111 at any given time and so reaches a maximum with the elevator door 111 in its open configuration and a minimum with the elevator door 111 in its closed configuration). This can be seen in figures 2a-2d, for example. The elevator door 111 may be configured to interact with an elevator shaft door, also referred to as a landing door, such that the elevator door 111 operates synchronously with the elevator shaft door or landing door (moving between the open and closed configurations) when the elevator door 111 is adjacent the elevator shaft door or landing door. An elevator shaft door may be associated with each level 21 which is served by the elevator system 1. Accordingly, when the elevator car 11 stops at a particular level 21, the elevator door 111 may be generally adjacent an elevator shaft door for the level 21. The elevator door 111 and adjacent elevator shaft door may then operate synchronously to allow access between the elevator car 11 and the level 21 - i.e. to allow users and / or objects to enter or leave the elevator car 11. The disclosed technology includes an elevator safety system. The safety system may include an edge device 13 which may be a door sensor 13 - see figures 3-7, for example. The or each elevator door 111 may be associated with the door sensor 13. The door sensor 13 may be configured to detect one or more objects which would obstruct the movement of the elevator door 111 (and / or the elevator shaft door) to the closed configuration. In other words, the door sensor 13 associated with the or each elevator door 111 may be configured to detect an object which may be hit by the movement of the elevator door 111 towards the closed configuration. The door sensor 13 may include a light curtain, for example. The or each door sensor 13 may be communicatively coupled to a door controller 111b which is, in turn, communicatively coupled to a door driving mechanism 111c which is configured to drive the movement of the elevator door 111 from the open to the closed configuration (and potentially also from the closed to the open configuration). On the sensing of an obstruction, the door sensor 13 which sensed the obstruction may send a signal to the door controller 111b which may, in turn, operate the door driving mechanism 111 c to cease movement of the elevator door 111 towards the closed configuration and / or to reverse the movement of the elevator door 111 back towards the open configuration. The or each door sensor 13 may be provided to prevent or reduce the risk of injury or damage to users or objects which may obstruct the operation of the elevator door 111. Indeed, users may even deliberately place an object or a part of their body in the path of the elevator door 111 whilst it is moving towards its closed configuration in order to cause the elevator door 111 to re-open -relying on the aforementioned operation of the door sensor 13. The door sensor 13 may be mounted to the elevator car 11 (e.g. to the elevator door 111 (such as to the parts of the elevator door 111 or to the part of the elevator door 111 and to a slam post)). The door sensor 13 may be mounted to the leading edge or edges of the elevator door 111. As will be appreciated, if the elevator door 111 has only one part, then the slam post may effectively be a second (albeit stationary) leading edge of the elevator door 111. Alternatively, the door sensor 13 may be mounted to the elevator shaft door(s), also referred to as landing door(s). Mounting the door sensor 13 to the elevator car 11 means that the same door sensor 13 is used irrespective of the level 21 at which the elevator car 11 is located. If a door sensor 13 is mounted to each elevator shaft door, then there will need to be multiple door sensors 13 (one for each level 21 for each elevator shaft 12). The edge device 13 could take a number of different forms. For example, the door sensor 13 may comprise an infrared door sensor 13 which has at least one infrared transmitter 131 (located on a first side of the door aperture 111a) and at least one infrared receiver 132 (located on a second, opposing, side of the door aperture 111a). An obstruction between the transmitter 131 and receiver 132 will be detected due to a change in received infrared light by the receiver 132. A corresponding signal will then be provided to the door controller 111b, as described herein. The transmitter 131, whether using the infrared spectrum or some other part of the electromagnetic spectrum, may include a plurality of discrete emitter devices 131 a-each emitter device 131a being configured to emit a signal for receipt by the receiver 132. Accordingly, in some versions, each emitter device 131a may include one or more light emitting diodes (which may each be configured to output infrared light in some versions). The emitter devices 131a may form a linear array. Similarly, the receiver 132, whether using the infrared spectrum or some other part of the electromagnetic spectrum, may include a plurality of discrete receiver devices 132a - each receiver device 132a being configured to receive a signal emitted by the transmitter 131. Accordingly, in some versions, each receiver device 132a may include one or more phototransistors or photodiodes (which may each be configured to receive infrared light in some versions). The receiver devices 132a may form a linear array. The edge device 13 may include one or more visible light emitters 134 which are each configured to emit light in the visible light spectrum - see figures 2b-2d and 3, for example (figures 2b-2d provide a graphical representation of the light emitted by the emitters 134 in some versions). The or each visible light emitter 134 may be configured to direct light into the elevator door aperture 111a. The light emitted by the or each visible light emitter 134 may convey information to the user(s) of the elevator car 11 - e.g. by using different colours to indicate status or operational information. The or each visible light emitters may be used to provide a visual representation of a status of the elevator car door(s) 111. The statuses may include open, opening, closed, closing, unobstructed, and / or obstructed, for example. The status may be determined using the door sensor 13 (e.g. obstructed / unobstructed), and / or may be provided by the door controller 111b (e.g. door open, opening, closed, closing). The or each visible light emitter 134 may be configured to emit a different colour of visible light to indicate whether the door sensor 13 has detected an obstruction (compared to the light emitted when no obstruction is detected), for example. Similarly, the or each visible light emitter 134 may be configured to emit a different colour of visible light to indicate whether the door is open / opening, compared to the light emitted when the door is closed / closing, for example. In some versions the edge device 13 may include the visible light emitters 134 but may not include the transmitter 131 or receiver 132. In such versions, therefore, the edge device 13 may include one or more visible light emitters 134 configured to provide a visual representation of a status of the elevator car door 111, which may be provided by the door controller 111b, for example. For example, the edge device 13 may illuminate in a first colour (e.g. green) to indicate the door 111 is open and / or opening, and may illuminate in a second colour (e.g. red) to indicate the door 111 is closed and / or closing. In some versions the edge device includes both the transmitter 131 and receiver 132, and the visible light emitters 134. The edge device 13 may include a housing 130. The housing 130 may be an elongate housing and may be generally in the shape of an elongate cuboid. The housing 130 may house the transmitter devices 131a and / or receiver devices 132a and / or visible light emitters 134. A first housing 130 may house the transmitter devices 131a and a first set of visible light emitters 134 and a second housing 130 may house the receiver devices 132a and a second set of visible light emitters 134. The edge device 13 may, therefore, include a pair of housings 130. In versions in which the edge device 13 does not include the transmitter 131 or receiver 132, the housing 130 may house the visible light emitters 134, which may be used to represent door statuses. The housing 130 may be configured for mounting to the elevator car door(s) 111 and / or elevator shaft door(s), also referred to as landing doors. The housing 130 may, therefore, include one or more mounting points, which may be configured to receive a fixing member such as a screw or bolt, for example. The housing 130 may be mounted to a leading edge of the elevator car door 111 or landing door in use (and this arrangement may provide good visibility of the visible light emitters 134). The housing may include a transparent portion associated with the transmitter devices 131a and / or receiver devices 132a and / or visible light emitters 134. In some versions, the door sensor 13 may include both transmitters 131 and receivers 132 on the same side of the door aperture 111a, and such transmitter and receiver 131,132 arrangements may be provided on both sides of the door aperture 111a. In some versions, the door sensor 13 may be configured to detect one or more objects or users adjacent but not yet obstructing the operation of the elevator door 111. To this end, the door sensor 13 may include one or more auxiliary transmitters and / or one or more auxiliary receivers. The or each auxiliary transmitter and / or receiver may be of the same type as described above in relation to the transmitters 131 and receivers 132. The one or more auxiliary transmitters and / or receivers may be configured to direct and receive light (such as infrared light) along respective axes which are angled with respect to each other and are directed generally outwardly with respect to the elevator car 11. An object or user located generally in front of the elevator door 111 may, therefore, be detected through analysis of the light received at the one or more auxiliary receivers. This is generally referred to herein as 3D object detection because of the ability to detect objects (and users) which are not within the generally 2D plane of the elevator door aperture 111a. Other forms of 3D object detection may also be possible. The safety system may include a levelling sensor 15. The levelling sensor 15 may be configured to determine a distance from the levelling sensor 15 to an object within its field of view. The output from the levelling sensor 15 may be used by the door sensor controller 133 to determine an offset, which may in particular be a vertical offset in use, between an elevator car floor and a landing floor. The levelling sensor 15 may be a ranging sensor, such as a time-of-flight sensor. An example of such a sensor is the VL53L5CX Time-of-Flight 8x8 multizone ranging sensor supplied by STMicroelectronics. The levelling sensor 15 may include a housing 150 within which the sensor is housed. In some versions, the levelling sensor 15 is mounted for movement with the elevator car 11 within the elevator shaft 12, such that the same levelling sensor 15 can be used on more than one level 21 (e.g. without requiring a levelling sensor to be provided on each level). The levelling sensor 15 may be mounted such that a field of view of the levelling sensor 15 encompasses a region generally adjacent the elevator door 111 (i.e. an approach to the elevator car 11) and outside of the elevator car 11 (i.e. a region of a landing of the level 21, for each such level 21 - a landing being a part of the level 21 at which objects can enter or leave the elevator car 11). The mounting of the levelling sensor 15 could take a number of different forms. For example, the levelling sensor 15 may be mounted so that it is partially or substantially entirely within the confines of the elevator car 11. The levelling sensor 15 may be mounted to a ceiling of the elevator car 11. The levelling sensor 15 may be mounted to part of the surround of the elevator door 111. The levelling sensor 15 may be mounted to a header 113 of the elevator car 12. The levelling sensor 15 may be mounted to an elevator door 111 or to the door slam post or to an elevator floor, for example. The levelling sensor 15 may, therefore, be mounted separately from the edge device 13. However, in some versions, the levelling sensor 15 may be mounted to the edge device 13 (and may therefore be mounted to the door sensor 13). The levelling sensor 15 may be mounted to the housing 130. The levelling sensor 15 may be slidably mounted to the edge device 13 (e.g. the housing 130). The levelling sensor 15 may include a clamping mechanism to fix the position of the levelling sensor 15 with respect to the edge device 13. The levelling sensor 15 may include a slot 151 for receiving a fixing member 152 such as a screw. The slot 151 may be defined in a flange of the housing 150, for example. The edge device 13 may include a corresponding receiving portion for receiving the fixing member 152, which may facilitate the mounting of the levelling sensor 15 to the edge device 13. The fixing member 152 may, therefore, be movable within the slot 151 such that the levelling sensor 15 is slidable with respect to the edge device 13. The fixing member 152 may act as the clamping mechanism to fix the position of the levelling sensor 15 with respect to the edge device 13. The adjustable coupling of the levelling sensor 15 to the edge device 13 may provide flexibility in the installation of the levelling sensor 15 and may enable the levelling sensor 15 to be mounted at an optimum position for determining a distance to an object. This may provide easier installation in different elevator systems, for example. In some versions the levelling sensor 15 may be mounted directly to a printed circuit board of the edge device 13, and may therefore be located inside the housing 130. The levelling sensor 15 may be mounted to the printed circuit board via a bracket, for example such that the field of view of the levelling sensor 15 is directed towards a floor. A field of view of the levelling sensor 15 may extend forwardly from the sensor 15. The levelling sensor 15 may be configured to determine a distance to an object within its field of view. The levelling sensor 15 may be generally fixed with respect to the elevator car 12. The levelling sensor 15 may be mounted to the edge device 13, for example, which may itself be mounted to a leading edge of the elevator car door 111. The field of view of the levelling sensor 15 may face generally downwardly and forwardly from the levelling sensor 15. In use, the field of view of the levelling sensor 15 may include a portion of the landing floor, which may be located in a gap between the elevator car door 111 and the landing door; a portion of the elevator car floor, which may be located in the gap between the elevator car door 111 and the landing door; a header 113 of the elevator car 12; a header of the landing; a feature on the elevator car door 111; and / or a feature on the landing door. The feature on the elevator car door 111 may include a protrusion or depression, and may include a door bracing strut, for example. The feature on the landing door may include a protrusion or depression, and may include a door bracing strut, for example. The levelling sensor 15 may be mounted in a substantially fixed vertical position with respect to the landing floor, and in such versions the field of view may include a portion of the elevator car floor, which may be located in the gap between the elevator car door 111 and the landing door; a header 113 of the elevator car 12; and / or a feature on the elevator car door 111. The levelling sensor 15 may, therefore, be configured to determine a distance to a part of the elevator car 12. The levelling sensor 15 may be mounted in a substantially fixed vertical position with respect to the elevator car floor, and in such versions the field of view may include a portion of the landing floor, which may be located in the gap between the elevator car door 111 and the landing door; a header of the landing; and / or a feature on the landing door. The levelling sensor 15 may, therefore, be configured to determine a distance to a part of the landing. The levelling sensor 15 may be generally located centrally with respect to a width of elevator door aperture 111a. In some versions in which the elevator door 111 is a side opening door 111, the location of the levelling sensor 15 may be offset such that the levelling sensor 15 is located closer to the door slam than to the opposing part of the elevator door aperture 111a (with the elevator door 11 open). The levelling sensor 15 may, in such versions, be mounted to the header 113 of the elevator car 12. The levelling sensor 15 may be an infrared sensor, a microwave sensor, a visible light sensor, or an acoustic sensor. In some versions, the levelling sensor 15 is a radar sensor. As will be appreciated, different sensors will have different characteristics. A microwave radar sensor may demonstrate good characteristics for use as the levelling sensor 15. For example, the levelling sensor 15 may be a mmWave sensor and some such suitable devices are available from Texas Instruments Incorporated. The levelling sensor 15 may use an electromagnetic wave and may operate in the frequency range of about 30GHz to about 300GHz. The levelling sensor 15 may be generally referred to, in some versions, as a ranging sensor as it may be configured - in those versions - to determine the range of another object from the levelling sensor 15. The ranging sensor as the levelling sensor 15 may be a time-of-flight sensor which is configured to emit a signal (e.g. an electromagnetic or acoustic signal) and to receive a reflected signal (that signal having been reflected from the object). The time between the emission of the signal and the receipt of the reflected signal may, therefore, allow the distance of the object from the levelling sensor 15 to be determined. The field of view of the levelling sensor 15 may be separated into at least two zones. Each zone may represent a region of the field of view. The zones may form an array, for example, such as in the case of an 8x8 multizone ranging sensor 15. The levelling sensor 15 may be configured to sense objects selectively within different zones of the field of view of the levelling sensor 15. In other words, the levelling sensor 15 may be configured to activate sensing with respect to the zones selectively - such that objects in an inactive zone are ignored and objects within an active zone may be sensed. In other words, the levelling sensor 15 may have selectively controllable sensing regions (e.g. the aforementioned zones) and sensing may be limited to one or more sensing regions during operation. The active and inactive zones may be determined in a calibration step, for example. At least one active zone may include a portion of the elevator car 12 and / or at least one active zone may include a portion of the landing (e.g. the landing floor). The field of view of the levelling sensor 15 may encompass a region generally adjacent the elevator door 111 outside of the elevator car 11 (i.e. a region of a landing of the level 21, e.g. a part of the floor of that landing). Accordingly, in some versions, the field of view of the levelling sensor 15 includes a part inside the elevator car 11 and a part outside of the elevator car 11 (this part including a portion of the landing). In some versions, the door sensor 13 includes one or more audible information devices 135 such as a buzzer, alarm, or speaker. The or each audible information device 135 may be configured to provide an audible indication of whether or not an obstruction has been detected, and / or whether the elevator door 11 is moving from the closed to the open configuration or from the open to the closed configuration. In some versions, the audible information is provided in spoken words and / or an alarm, siren or beeping sound. In some versions, the one or more audible information devices 135 include an internal device 135a configured to provide audible information inside the elevator car 11. In some versions, the one or more audible information devices 135 include an external device 135b configured to provide audible information outside the elevator car 11 (e.g. to one or more users near the elevator car 11 on a particular level 21). The audible information device 135 may be configured to provide an audible indication of a vertical offset detected between the elevator car 12 floor and the landing floor. The safety system may include a door sensor controller 133. The door sensor controller 133 may be part of the door sensor 13. The door sensor controller 133 may be configured to control one or more aspects of the operation of the door sensor 13. These one or more aspects may include the operation of the transmitter 131 and / or receiver 132, and / or operation of the auxiliary transmitter and / or receiver, and / or the or each visible light emitter 134, and / or the or each audible information device 135,135a,135b, and / or any communication of the door sensor 13 to the door controller 111b (to control the operation of the door driving mechanism 111c), and / or the operation of the levelling sensor 15. The door sensor controller 133 may also be referred to as an edge device controller 133 and may control the operation of the visible light emitters 134 both in versions in which the edge device 13 includes, and does not include, the transmitter 131 and / or receiver 132. The door sensor controller 133 may be communicatively coupled (e.g. by a wired or wireless communication channel) to the door controller 111b and / or a main elevator controller 3 of the elevator system 1 which is configured to control the operation of one or more aspects of the elevator system 1. The main elevator controller 3 may include various inputs and outputs, as well as configuration interfaces, and the like, which enable the main elevator controller 3 to control the operation of the elevator system 1 and to allow an engineer to configure one or more parts of the elevator system 1. The main elevator controller 3 may be communicatively coupled to one or more other input interfaces. The one or more other input interfaces may include a car operating panel 112. The car operating panel 112 may be provided within the elevator car 11 and may include a plurality of buttons (which may be individual buttons of the panel or parts of a graphical user interface (which may be provided on a touchscreen, for example)). The car operating panel 112 may be configured to receive user input (e.g. by actuation of one or more of the buttons thereof) and to send corresponding signals to the main elevator controller 3 and / or to the door controller 111b. The user input and corresponding signals may include instructions for the elevator car 11 to travel to a particular level 21, to cause the elevator door 111 to remain open, to cause the elevator door 111 to close, to cause the elevator door 111 to move towards the open position, to trigger an alarm, to activate an emergency intercom, and the like. Typically a car operating panel 112 includes a plurality of buttons, with each of the plurality representing a different level 21 and there being additional buttons of the or each other input, for example. The one or more other input interfaces may include one or more call buttons 121. The or each call button 121 may be provided on associated levels 21. Actuation of a particular call button 121 by a user may cause the sending of a call signal to the main elevator controller 3 requesting that an elevator car 11 is sent to a level 21 associated with that particular call button 121 - e.g. so that a user on that level 21 can enter the elevator car 11 and move to a different level 21 using the elevator car 11. The door sensor controller 133 may be configured to control the operation of the or each visible light emitter 134 - as mentioned above. For example, the door sensor controller 133 may be configured to cause the or each visible light emitter 134 to emit a first colour of visible light when the elevator door 111 is open and not closing, and / or a second colour of visible light when the elevator door 111 is closing, and / or a colour of visible light (which may be the first or a third colour of visible light) when the door sensor 13 detects an object. The first, second, and third colours of visible light may be different colours of visible light, for example. The door sensor controller 133 may be configured to control the operation of the or each visible light emitter 134 based the sensed configuration and / or operation of the elevator door 111 - as sensed using the door sensor 13 (e.g. the infrared transmitter(s) and receiver(s) 131,132). In some versions, the door sensor controller 133 may be communicatively coupled to the door controller 111b such that the door controller 111b may provide information about the current configuration of the elevator door 111 and / or any currently underway or future changes in that configuration (e.g. from the open to the closed configuration or vice versa). This communicative coupling may be referred to, for example, as door controller feedback and may be provided by a wired or wireless communications link. In some versions, as described herein, an operation of the elevator door 111 may be determined, at least in part, based on information generated about the operation of the elevator door 111 by the door sensor 13 (e.g. the state of or changes in configuration). The door sensor 13 may generate this information using, for example, the or each infrared transmitter and receiver 131,132 and / or may use other elements (which may include an acceleration or a separate position sensor mounted with respect to (e.g. on) the elevator door 111). In some versions, the infrared transmitter and receiver 131,132 may be used to determine a distance between the leading edges of the elevator door 111 (one of which may be the door slam post). In other words, the infrared transmitter and receiver 131,132 may be used to determine a width of the elevator door aperture 111a. This may be achieved by, for example, monitoring the strength of the received infrared signals sent from the transmitter 131 to the receiver 132 (e.g. the magnitude of the received signal), when there is no obstruction (or in relation to a part in which there is no obstruction). A lookup table may be provided to match signal strengths to distances (i.e. widths) - the content of the lookup table having been generated in a prior calibration process. Accordingly the infrared transmitter and receiver 131,132 may operate as a position sensor (as well as detecting obstructions). Other forms of position sensor are also envisaged and may be included - such position sensors being configured to determine a configuration of the elevator door 111 (i.e. whether the elevator door 111 is open or closed and, in some versions, the width of the elevator door aperture 111a). In some versions, the door sensor controller 133 may be communicatively coupled to the car operating panel 112 such that one or more user inputs to the car operating panel 112 may be communicated to the door sensor controller 133. These one or more user inputs may be, for example, an input to request the elevator door 111 to open, to close, or to remain open, for example. This communicative coupling may be referred to, for example, as car operating panel feedback and may be provided by a wired or wireless communications link. In some versions, the door sensor controller 133 is configured to determine when an expected (i.e. future) operation of the elevator door 111 will or is likely to occur. This operation may be a change in the configuration of the elevator door 111 such as a change from the open to the closed configurations (i.e. when the change in configuration will or is likely to occur), and / or may be another operation such as a nudge operation. The door sensor controller 133 may be configured to determine when an expected (i.e. future) configuration of the elevator door 111 will be achieved). The door sensor controller 133 may be configured to determine not only when the expected operation or configuration will occur but what that expected operation or configuration will be. The operations of the elevator door 111 are typically controlled by the door controller 111b based on a computer program executed by that controller 111b. The computer program defines a number of rules which determine which operations of the elevator door 111 are executed and when they are executed. Typically, these rules will include predetermined delays which cause the elevator doors 111 to be held in a particular configuration for the predetermined delay period before another operation is executed. For example, when an elevator door 111 is opened, the rules may specify a predetermined delay period before a close operation (i.e. a movement of the elevator door 111 towards the closed configuration) is executed. As part of that close operation, the rules may require the presence (or absence) of an obstruction to be determined (using the door sensor 13). If an obstruction is detected, then the rules may specify a predetermined delay period before the close operation is re-attempted. Similar predetermined delay periods are typically defined in relation to all or substantially all changes in the operation of the elevator doors 111 (during normal use (i.e. outside of fault conditions or maintenance operations). Therefore, the door sensor controller 133 may be configured to determine when an expected (i.e. future) operation of the elevator door 111 will or is likely to occur based on one or more delay periods stored by the door sensor controller 133. The door sensor controller 133 may, as will be understood, have no direct access to the predetermined delay periods used by the door controller 111b. Therefore, the door sensor controller 133 may retain stored delay period(s) independently of the door controller 111b. The or each delay period stored by the door sensor controller 133 may include one or more of: a period the elevator door 111 is held in the open configuration; a period the elevator door 111 is held in the open configuration after detection of an obstruction; a period the elevator door 111 is held in the open configuration after a user input on the car operating panel (that input being to open or hold open the elevator door 111)-some car operating panels 112 may provide for multiple different user inputs in this regard, each associated with a different period, and the period stored by the door sensor controller 133 may be one, some, or all of the associated delays depending on which user input is received; a period the elevator door 111 takes to move from the open configuration to the closed configuration; a period the elevator door 111 takes to move from the closed configuration to the open configuration; and a period of time for which an obstruction is detected before a nudge operation is activated. The door sensor controller 133 may use the door sensor 13 (and / or the communicative coupling to the car operating panel 112) in order to determine when a particular operation commences and / or how long a particular configuration of the elevator door 111 has been maintained. The door sensor controller 133 may store the or each delay period, therefore, in association with at least one trigger event and / or at least one subsequent operation or configuration of the elevator door 111. The door sensor controller 133 may be configured to detect the or each trigger event. As will be appreciated, therefore, the aforementioned delay periods stored by the door sensor controller 133 may be based on one or more predetermined events determined using the door sensor 13 and / or the communicative coupling to the car operating panel 112. The detection of the or each predetermined event may cause (e.g. trigger) the door sensor controller 133 to determine the associated delay period from the or each stored delay period. The door sensor controller 133 may then monitor the time elapsed since detection of the or each predetermined event to determine when (or when it is expected) that an operation of the elevator door 111 will be caused by the door controller 111b. The door sensor controller 133 may store the or each delay period in association with the predetermined trigger event and the expected change in operation or configuration of the elevator door 111. Therefore, the door sensor controller 133 may be configured to determine not only when there will be an expected change in the operation or configuration of the elevator door 111 but also what that operation or configuration of the elevator door 111 is expected to (or will) be. A trigger event may effectively comprise a plurality of sub-events which comprise the conditions for the occurrence of that event. For example, a trigger event may comprise a sub-event that the elevator door 111 is in the open configuration and a sub-event that there has been one attempted movement of the door to the closed configuration but that this was prevented by a sensed obstruction. The or each delay period, the associated trigger event, and / or the associated subsequent operation or configuration, may be stored during an initial setup of the door sensor controller 133. This information will be generally referred to herein as the door operating period information. Therefore, the door sensor controller 133 may be configured to store the door operating period information (e.g. as part of the commissioning of the elevator system 1 and / or the door sensor 13). This may be entered by an engineer, for example, using a computing device temporarily connected to the door sensor controller 133 for such purposes. In some versions, the door sensor controller 133 is configured to learn the door operating period information. In particular, the door sensor controller 133 may be configured to monitor the configuration and / or operation of the elevator door 111 using the door sensor 13 (which may include use of the or each infrared receiver and transmitter 131,132, the or each auxiliary transmitter and receiver, and / or the acceleration sensor of the door sensor 13). The door sensor controller 133 may be configured to determine the occurrence of one or more trigger events (as described herein), the occurrence of a subsequent operation or configuration of the elevator door 111, the period between the trigger event and the subsequent operation / configuration, and (in some versions) the subsequent operation / configuration which occurred. This information may then be stored as the door operating period information by the door sensor controller 133. The learning performed by the door sensor controller 133 may be implemented as part of a setup process for the door sensor controller 133. This setup process may be initiated on installation of the door sensor controller 133. The learning may be initiated periodically thereafter to update and / or confirm the stored door operating period information. In some versions, the learning is performed substantially continuously and the door operating period information updated and / or confirmed relatively frequently as a result. Therefore, the door sensor controller 133 may have a learning mode of operation which may be implemented on installation, periodically, or substantially continuously. The learning mode may be implemented instead of or in combination with an operational mode (this being the mode in which the expected operation and / or configuration of the elevator door 111 is determined. The door sensor controller 133 may be configured to control the operation of the or each visible light emitter 134 based at least in part on the expected operation and / or configuration of the elevator door 111 and when the operation and / or configuration of the elevator door 111 is expected to occur. The door sensor controller 133 may be configured to use the or each visible light emitter 134 to provide an indication of the expected operation and / or configuration of the elevator door 111 and / or when that operation and / or configuration of the elevator door is expected to occur. The door sensor controller 133 may be configured, for example, to use the colour of the or each visible light emitter 134, the illumination or non-illumination of the or each visible light emitter 134, flashing of the or each visible light emitter 134, a sequence of flashing of the or each visible light emitter 134, a frequency of flashing of the or each visible light emitter 134, a duration of illumination or non-illumination of the or each visible light emitter 134, and the like. As described herein, there may be a plurality of visible light emitters 134 provided in a generally linear arrangement on the elevator door 111 (e.g. on a leading edge of an elevator door 111, or on each of the opposing edges the door aperture 111a). Therefore, there may be one or more linear arrangements of visible light emitters 134 provided according to some versions. The door sensor controller 133 may be configured to control the or each linear arrangement of visible light emitters 134 to indicate, for example, when the expected operation and / or configuration will occur. The door sensor controller 133 may be configured to provide a countdown for example to when the operation / configuration will occur. This countdown may be provided by the sequential illumination or extinguishing of the illumination (i.e. changing from illumination to non-illumination) of the visible light emitters 134 of the or each liner arrangement of visible light emitters 134 (e.g. in an upward to downward direction, or vice versa, or towards a central point). Likewise, instead of illumination or non-illumination, the door sensor controller 133 may use sequential changes in colour in the same manner. This countdown may be provided by a rain-effect in which the visible light emitters 134 are illuminated and extinguished such that there is the appearance of an illuminated element dropping down (or rising) along the or each linear arrangement of visible light emitters 134. The countdown may be conveyed by the illuminated element reaching the bottom (or top) of the or each linear arrangement of visible light emitters 134. The countdown may be conveyed by the frequency at which a series of such illuminated elements drop down (or rise) along the or each linear arrangement of light emitters 134. Again, instead of illumination and non-illumination, there may be a colour change in the same manner. This countdown may be provided by increasing (or decreasing) the frequency of flashing of the visible light emitters 134 (e.g. of all of the visible light emitters of one or more linear arrangements). The flashing may be between illuminated and non-illuminated states or may be between colours, for example. In some versions, a countdown may be provided, therefore, to the closing of the elevator door 111 or to the initiation of a nudge operation. The countdown may be provided from when the elevator door 111 begins a close operation to when the close configuration is achieved. Indeed, a countdown could be provided to any detectable operation of the elevator door 111 to the achievement of configuration of the elevator door 111. The countdown operations as described herein are intended to provide the user with a visual indication of when an operation or configuration is expected to occur. The countdown may not be linear but may appear to accelerate as the expected operation or configuration becomes imminent - e.g. to convey greater urgency. Accordingly, the frequency of any change in the operation (e.g. flashing) of the or each visible light emitter 134 may increase at a faster rate as the expected operation or configuration approach or approach completion. The door sensor controller 133 may be configured to use the or each visible light emitter 134 to display additional information to a user. For example, the door sensor controller 133 may be configured to use the or each visible light emitter 134 to display an intended direction of travel to the user. This may be achieved in a number of different ways. For example, the direction of a raineffect (as described above, or other sequential effect) may be downward indicating a downward intended direction of travel of the elevator car 11 or upward indicating an upward intended direction of travel of the elevator car 11. In some examples (which could be in addition to or instead of a rain-effect), the door sensor controller 133 may be configured to control at least one visible light emitter 134 towards an upper part of the door aperture 111a to be in a different illumination state than at least one visible light emitter 134 towards a lower part of the door aperture 111a. These different states of illumination may be used to indicate an intended direction of travel. The states of illumination could be a different brightness of illumination, illuminated and not illuminated, or illumination in different colours of visible light. Likewise, the states of illumination could include different frequencies of flashing of the or each visible light emitter 134 The door sensor controller 133 may be configured to control the or each visible light emitter 134 to indicate a direction of travel without indicating any other information or in combination with other information as described herein. The door sensor controller 133 may be configured to determine the intended direction of travel for the elevator car 11 (i.e. the direction of travel of the car 11 after it leaves the current level 21) from the main elevator controller 3. This intended direction of travel information may be received, for example, through the communicative coupling between the door sensor controller 133 and the main elevator controller 3. The intended direction of travel for the elevator car 11 may, in some versions, be obtained by the door sensor controller 133 from the car operating panel 112 which may, in turn, receive this information from the main elevator controller 3 - e.g. so that this information can be presented to occupants of the elevator car 11 on a screen or other display device within the elevator car 11 (which may be part of or coupled to the car operating panel 112). In some versions, the operation of the or each visible light emitter 134 is at least partially dependent on an operation of the elevator door 111. In some versions, the operation of the or each visible light emitter 134 is at least partially dependent on an operation (or intended operation) of the elevator car 11. In some versions, the operation of the or each visible light emitter 134 is at least partially dependent on an operation (or intended operation) of the elevator car 11 and on an operation of the elevator door 111. In some versions, the operation of the or each visible light emitter 134 is not dependent on an operation of the elevator door 111 and, in such versions, the door sensor controller 133 as described herein may comprise two controllers - a controller which provides information to the door controller 111 b for use in controlling the operation of the elevator door 111 and a controller which operates the or each visible light emitter 134. In some versions in which the operation of the or each visible light emitter 134 is not dependent on an operation of the elevator door 11, the door sensor controller 133 may be configured to determine when to operate the or each visible light emitter 134 based on information received (directly or indirectly - see above) from the main elevator controller 3 (such as location information for the elevator car 11), so that the or each visible light emitter 134 are only operated when the elevator car 11 is at a level 21 and not between levels 21. Likewise, the or each visible light emitter 134 may be extinguished after a predetermined period in which the elevator car 11 does not move - indicating a lack of use. This predetermined period may be determined by the main elevator controller 3 or, indeed, by the door sensor controller 133 or the door controller 111b. In some versions, the visual indication provided to the user is also associated with a corresponding audible indication - which may be a beeping, buzzing, or similar sound which is operated in a corresponding manner (e.g. at a corresponding frequency) to visual indication provided by the or each visible light emitter 134. The audible indication may be provided by the audible information device 135. As will be understood, the or each visible light emitter 134 may be provided on at least part of an elevator door 111 and may be provided as part of a leading edge of that door 111 or door part. The or each visible light emitter 134 may be provided in the same housing as at least part of the door sensor 13 (e.g. in the same housing as one or more infrared transmitters 131 and / or in the same housing as the one or more infrared receivers 132). The or each visible light emitter 134 may be provided as part of an edge device for an elevator door 111 which may be configured to provide a light curtain (e.g. across the door aperture 111a). The audible information device 135 may be similarly located in the same housing at least part of the door sensor 13 (e.g. in the same housing as one or more infrared transmitters 131 and / or in the same housing as the one or more infrared receivers 132). The or each visible light emitter 134 may be a relatively simple light emitter or cluster of light emitters. In some versions, the or each visible light emitter 134 (whether considered individually or collectively) is not capable of displaying letters or words. In some versions, the operation of door sensor controller 133 to control the or each visible light emitter 134 is comparatively simple. In particular, in some versions, the door sensor controller 133 need not receive (e.g. from the door controller 111 b or the main elevator controller 3) complex information about the operation and future operation of the elevator door 111. Instead, in some versions, the door sensor controller 133 may determine when these operations and configurations are likely to be completed based on a trigger event and the door operating period information. This may make the door sensor controller 133 suitable for operation, for example, with a large number of different elevator systems 1 - rather than, for example, having to have a completely different arrangement for each different make and / or model of elevator system 1. Likewise, in some versions, these abilities are retrofittable to an existing elevator system 1 (even if that elevator system 1 was not designed to allow such an arrangement to be implemented). As will be appreciated, the visual indication provided by some versions provides an implied, but direct, instruction to a user regarding the operation of the elevator system 1 and what actions they should take (e.g. remove an obstruction) or not take (e.g. cause an obstruction) to avoid disrupting the operation of the elevator system 1. As will also be appreciated, versions may seek to provide a visual indication of an internal operation of the elevator system 1 which is otherwise unknown and unknowable to the user. The operation of the levelling sensor 15 may, in some versions, be determined at least in part by the expected operation and / or configuration of the elevator door 111. For example, the sensing region or regions currently active may be determined at least in part by the expected operation and / or configuration of the elevator door 111. In some versions, the operation of the levelling sensor 15 (e.g. the size and / or location of the sensing region (or zone)) is determined at least in part based on the current width of the elevator door aperture 111a, and this may be determined by use of the signal strength between the transmitter 131 and receiver 132 (or another form of position sensor). In some versions, however, the levelling sensor 15 is not part of the door sensor 13 as such. In versions such as these, the levelling sensor 15 may have its own controller and this controller may receive information regarding the current configuration of the elevator door 111 (e.g. the width of the elevator door aperture 111a). This information may be received from the door sensor 13, which may be communicatively coupled to the controller of the levelling sensor 15. The controller of the levelling sensor 15 may be configured to output a signal to trigger the opening of the elevator door 111 (or to indicate that the elevator door 111 should remain open) based on the information from the levelling sensor 15 and the information about the current configuration of the elevator door 111. This signal may be output to the door controller 111b (the door controller 111b may be configured to receive this as a separate input to a signal triggered by the door sensor 13, for example) or may be output to another controller or interface which is configured to interleave or otherwise combine signals from that controller and from the door sensor 13 (e.g. from the door sensor controller 133). In other words, there may be multiple controllers and these controllers associated with the levelling sensor 15 and the door sensor 13 may be communicatively coupled to provide an output to the door controller 111b. Accordingly, the door sensor 13 may be referred to as a door sensor arrangement in which the door sensor arrangement includes the levelling sensor 15 and the other parts of the door sensor 13 described herein. The levelling sensor 15 may be configured to determine a distance from the levelling sensor 15 to an object within its field of view. This may include, for example, the floor of the elevator car 11 and / or the landing. These distances may be compared in order to determine an offset between the vertical alignment of the elevator car 11 and the landing (i.e. between the floor of the elevator car 11 and the floor of the landing at the level 21 at which the elevator car 11 is stopped). The levelling sensor 15 may be configured to determine the distance to at least one of: (i) a portion of the landing floor located in a gap between the elevator car door and the landing door; (ii) a portion of the elevator car floor located in the gap between the elevator car door and the landing door; (iii) a header of the elevator car; (iv) a header of the landing; (v) a feature on the elevator car door; and / or (vi) a feature on the landing door. The levelling sensor 15 (e.g. using its controller) or the door sensor controller 133 or another controller, may be configured to convert (i.e. calculate) the distance information generated by the levelling sensor 15 such that the offset can be determined. In particular, levelling sensor 15 may be configured to determine the distance to the landing and / or elevator car 11 floor along respective axes which are at an angle to a vertical axis. In some versions, these respective axes may be angles of different magnitudes from the vertical. This or these angles may be predetermined such that the vertical distance to the elevator car 11 floor and the landing floor may be determined. In some versions, the respective angles are of the same magnitude and the distances along the axes can be directly compared to determine if there is an offset with or without determining the respective vertical distances. In some versions, the magnitude of the respective angles is small (e.g. less than 10 degrees or less than 5 degrees or less than 2 degrees from vertical) - i.e. the axes are near-vertical (which may also aid to simplify any calculations (e.g. by taking the distance along these axes as an approximation of the vertical distance). The expected distance(s) to be determined by the levelling sensor 15 may be set in a calibration stage, and the distances(s) determined in use may be compared to the expected distance(s) to determine the offset. In some versions, the distance measured to the elevator car 11 floor is a distance to the floor close to the elevator doors 111 and the distance measured to the landing floor may be similarly close to the elevator doors 111 (e.g. a part of the landing floor over which the elevator shaft doors may pass when opening and closing, and which may not be visible when the elevator shaft doors are closed). The levelling sensor 15 may in particular be configured to determine the distance to a portion of the landing floor located in a gap between the elevator car door and the landing door, and / or a portion of the elevator car floor located in the gap between the elevator car door and the landing door. As such portions are sequestered between the elevator car door 111 and the landing door, they are protected from interference, for example by people or goods entering or leaving the elevator car. The levelling sensor 15 (e.g. using its controller) or the door sensor controller 133 or another controller, may be configured to compare any determined offset (which may have been determined by subtracting the measured distances or the calculated vertical distances, for example) to a predetermined threshold. If the predetermined threshold (i.e. an offset threshold) is exceeded then it may be determined that the offset is too great and a maintenance alert may be issued. The maintenance alert (in some versions including other information to identify the elevator car 11, and / or the landing level 21, and / or the offset determined, and / or the distances which were compared and / or measured), may be sent to the remote maintenance system and / or to the main elevator controller 3 and / or to the maintenance device of the elevator system 1. In some versions, the levelling sensor 15 is configured to output the distance measurements and / or the calculated vertical distances and / or the determined offset to the remote maintenance system and / or to the main elevator controller 3 and / or to the maintenance device of the elevator system 1 and the comparison to a threshold may be performed by one or more of those systems, controllers, or devices remotely from the levelling sensor 15. In some versions, the calculated vertical distances are also remotely determined by one or more of these systems, controllers, or devices. A maintenance alert may trigger a maintenance action - such as a maintenance personnel call-out to travel to the location of the elevator system 1 and perform a maintenance operation (which may be preventative). The maintenance action may include enhanced monitoring - such as ongoing monitoring (remotely or locally) of the offset, or the measured or calculated distances. In some versions, the determined offset may be visually represented using the visual light emitters 134. The edge device controller 133, for example, may be configured to control the illumination of one or more of the visual light emitters 134 to provide a visual representation of the determined offset. In use, the edge device 13 may be configured such that a first end of the array of visual light emitters 134 is located adjacent the floor of the elevator car 11 and / or landing, and a second end of the array may be located distant from the floor. The second end may therefore be opposite the first end. The visual light emitters 134 may therefore form a generally vertical linear array in use. The offset may be visually represented by the illumination of a particular number of visual light emitters 134, and / or the illumination of visual light emitters 134 in a particular location in the array, and / or flashing of the visual light emitters 134, and / or the illumination of the visual light emitters 134 in a particular colour, sequence, and / or pattern. For example, with the edge device 13 mounted to form a generally vertical linear array in use, a portion of the visual light emitters at or towards the bottom end of the array may be illuminated to provide a visual representation of the offset. For example, a warning portion of the visual light emitters 134 at the bottom end of the array may be illuminated in a particular colour or flashing mode to indicate the existence of the determined offset, and the number of visual light emitters included in the warning portion may increase as the determined offset increases, e.g. such that the length of the warning portion increases as the offset increases. The visual representation may therefore provide an easy-to-understand indication of the size of the offset and may warn users of the presence of the offset such that greater care can be taken when entering and exiting the elevator car 11. In some versions the visual representation may include the illumination of at least a portion of the visual light emitters 134 to provide a warning when the determined offset exceeds a predetermined threshold, and the warning may not be provided when the offset falls below the predetermined threshold. This may, therefore, provide an easy-to-understand representation of the compliance (or non-compliance) of the elevator system with an acceptable tolerance, for example, while warning users of the presence of the offset. In some versions, the levelling sensor 15 is mounted is a fixed vertical position with respect to the landing floor (i.e. the levelling sensor 15 does not travel with the elevator car 11 in the elevator shaft) and, in such versions, only the distance to the elevator car 11 floor may be measured or calculated, for example (and then compared to a predetermined distance which may be based on the known distance to the landing floor). In some versions, the levelling sensor 15 is mounted is a fixed vertical position with respect to the elevator car 11 floor (i.e. the levelling sensor 15 does travel with the elevator car 11 in the elevator shaft) and, in such versions, only the distance to the landing floor may be measured or calculated, for example (and then compared to a predetermined distance which may be based on the known distance to the elevator car 11 floor). In some versions the elevator safety system may include a plurality of levelling sensors 15. The plurality of levelling sensors 15 may be mounted on the edge device 13, for example at regular intervals along the edge device 13. There may be two, three, or four levelling sensors 15 mounted on the edge device 13, for example. Each levelling sensor 15 may, therefore, produce a corresponding depth map. The depth maps may be provided to a controller (e.g. the edge device controller 133) which may learn the relationship between the depth maps and the vertical offset between the elevator car 11 floor and the landing floor. This may include a calibration phase in which the depth maps are associated with a corresponding offset. In some versions, the levelling sensor 15 may be operated (e.g. by a controller) to measure the or each distance (for use in determining vertical misalignment) when the elevator doors 111 are determined to be open or at least partially closed. Taking measurements when the elevator doors 111 are open may enable multiple measurements to be taken, for example, across the door aperture 111a. This may enable an average to be taken (e.g. mean, median, or modal distance) to reduce other objects (i.e. other than the floors) causing incorrect vertical offset measurement or problem detection. Taking measurements when the elevator doors 111 are partially open (which may be when they are opening or closing) may still allow multiple measurements to be taken as mentioned above, but may also reduce the risk of other objects causing incorrect vertical offset measurement or problem detection (as there are likely to be fewer such obstructions as the elevator doors 111 open and close). In some versions, the or each measurement is taken when it is determined that there is no obstruction of the elevator doors 111 and this may be determined by the door controller 111 b or door sensor controller 133, for example - which may provide an indication that there is or is not an obstruction to the levelling sensor 15 or an associated controller. The or each controller described herein (e.g. the door sensor controller 133, the door controller 111b, and the main elevator controller 3) may comprise a respective computing device. The or each computing device may include a processing unit which is communicatively coupled to memory (i.e. a computer readable storage medium). The operations of the or each controller may be provided as instructions stored on their readable storage medium and which, when executed, cause the process to be performed. In relation to the door sensor controller 133, the door operating period information may be stored on the computer readable medium of the door sensor controller 133. Whilst the door sensor controller 133 and the door controller 111b have been described as separate controllers, they may - in some versions - be integrated into a single controller. When used in this specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components. The invention may also broadly consist in the parts, elements, steps, examples and / or features referred to or indicated in the specification individually or collectively in any and all combinations of two or more said parts, elements, steps, examples and / or features. In particular, one or more features in any of the embodiments described herein may be combined with one or more features from any other embodiment(s) described herein. Protection may be sought for any features disclosed in any one or more published documents referenced herein in combination with the present disclosure. Although certain example embodiments of the invention have been described, the scope of the appended claims is not intended to be limited solely to these embodiments. The claims are to be construed literally, purposively, and / or to encompass equivalents.

Claims

1. An elevator safety system for use with an elevator car configured to move between a plurality of landings, the elevator safety system including:an edge device configured to be mounted to an elevator car door or a landing door, the edge device including one or more visible light emitters;a levelling sensor configured to be mounted with respect to the elevator car or a landing of the plurality of landings, and configured to determine a distance to a portion of the landing and / or a distance to a portion of the elevator car in use; anda controller configured to use the determined distance(s) to determine a vertical offset between an elevator car floor and a landing floor, and to control operation of at least a portion of the visible light emitters to provide a visual representation of the determined offset.

2. A system according to claim 1, wherein the controller is configured to determine the vertical offset by:(i) comparing the distance to the portion of the elevator car with the distance to the portion of the landing; and / or(ii) comparing the distance to the portion of the elevator car to a predetermined distance, the levelling sensor being mounted in a substantially fixed vertical position with respect to the landing floor; and / or(iii) comparing the distance to the portion of the landing to a predetermined distance, the levelling sensor being mounted in a substantially fixed vertical position with respect to the elevator car floor.

3. A system according to any preceding claim, wherein the controller is further configured to control operation of at least a portion of the visible light emitters to provide a visual representation of a status of the elevator car door.

4. A system according to any preceding claim, wherein the levelling sensor is mounted to the edge device.

5. A system according to claim 4, wherein the levelling sensor is slidable with respect to the edge device such that the position of the levelling sensor with respect to the edge device is adjustable.

6. A system according to any preceding claim, wherein the levelling sensor is configured to determine the distance to at least one of: (i) a portion of the landing floor located in a gap between the elevator car door and the landing door; (ii) a portion of the elevator car floor located in the gap between the elevator car door and the landing door; (iii) a header of the elevator car; (iv) a header of the landing; (v) a feature on the elevator car door; and / or (vi) a feature on the landing door.

7. An elevator safety system for use with an elevator car configured to move between a plurality of landings, the elevator car having an elevator car floor and an elevator car door, the elevator safety system including:a levelling sensor mounted with respect to the elevator car or a landing of the plurality of landings, the levelling sensor configured to determine a distance to at least one of:(i) a portion of a landing floor located in a gap between the elevator car door and a landing door;(ii) a portion of the elevator car floor located in the gap between the elevator car door and a landing door;(iii) a header of the elevator car;(iv) a header of a landing;(v) a feature on the elevator car door; and / or(vi) a feature on a landing door; anda controller configured to use the determined distance(s) to determine a vertical offset between the elevator car floor and a landing floor, and to output an indication of the determined offset to a user.

8. A system according to claim 7, wherein the controller is configured to determine the vertical offset by:(i) comparing the distance to at least one of the portion of the landing floor, header of the landing, or feature on the landing door, with the distance to at least one of the portion of the elevator car floor, header of the elevator car, or feature on the elevator car door; and / or(ii) comparing the distance to the portion of the elevator car floor, header of the elevator car, or feature on the elevator car door to a predetermined distance, the levelling sensor being mounted in a substantially fixed vertical position with respect to the landing floor; and / or(iii) comparing the distance to the portion of the landing floor, header of the landing, or feature on the landing door to a predetermined distance, the levelling sensor being mounted in a substantially fixed vertical position with respect to the elevator car floor.

9. A system according to claim 7 or 8, further including an edge device mounted to the elevator car door, wherein the levelling sensor is mounted to the edge device, and wherein the levelling sensor is configured to determine a distance to at least one of (i) a portion of the landing floor located in a gap between the elevator car door and the landing door; (ii) a header of the landing; and / or (iii) a feature on the landing door.

10. A system according to claim 9, wherein the edge device includes one or more visible light emitters and the controller is configured to control operation of at least a portion of the visible light emitters to provide a visual representation of the determined offset to the user.

11. A system according to claim 10, wherein the controller is further configured to control operation of at least a portion of the visible light emitters to provide a visual representation of a status of the elevator car door.

12. A system according to any of claims 9-11, wherein the levelling sensor is slidable with respect to the edge device such that the position of the levelling sensor with respect to the edge device is adjustable.

13. An elevator safety system including:a door sensor configured to be mounted to an elevator car door and / or a landing door to detect an obstruction blocking the elevator car door and / or landing door;a levelling sensor slidably mounted to the door sensor and configured to determine a distance to a portion of the landing and / or a portion of the elevator car; anda controller configured to use the determined distance(s) to determine a vertical offset between an elevator car floor and a landing floor, and to output an indication of the determined offset to a user.

14. A system according to claim 13, wherein the controller is configured to determine the vertical offset by:(i) comparing the distance to the portion of the elevator car with the distance to the portion of the landing; and / or(ii) comparing the distance to the portion of the elevator car to a predetermined distance, the levelling sensor being mounted in a substantially fixed vertical position with respect to the landing floor; and / or(iii) comparing the distance to the portion of the landing to a predetermined distance, the levelling sensor being mounted in a substantially fixed vertical position with respect to the elevator car floor.

15. A system according to claim 13 or 14, wherein the door sensor includes one or more visible light emitters, and wherein the controller is configured to control operation of at least a portion of the visible light emitters to provide a visual representation of the determined offset.

16. A system according to claim 15, wherein the controller is further configured to control operation of at least a portion of the visible light emitters to provide a visual representation of a status of the elevator car door.

17. A system according to any of claims 13-16, wherein the levelling sensor is configured to determine the distance to at least one of: (i) a portion of the landing floor located in a gap between the elevator car door and the landing door; (ii) a portion of the elevator car floor located in the gapbetween the elevator car door and the landing door; (iii) a header of the elevator car; (iv) a header of the landing; (v) a feature on the elevator car door; and / or (vi) a feature on the landing door.

18. A system according to any of claims 13-17, wherein the levelling sensor further includes a5 clamping mechanism to fix the position of the levelling sensor with respect to the edge device.30

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