Patent Publication Number: US-2023143819-A1

Title: Safety brake system

Description:
FOREIGN PRIORITY 
     This application claims priority to European Patent Application No. 21383003.7, filed Nov. 5, 2021, and all the benefits accruing therefrom under 35 U.S.C. § 119, the contents of which in its entirety are herein incorporated by reference. 
     TECHNICAL FIELD 
     This disclosure relates to a safety brake system for use within a conveyance system such as an elevator system, and to a method of operating a safety brake in a safety brake system. 
     BACKGROUND 
     Many elevator systems include a hoisted elevator car, a counterweight, a tension member, which connects the hoisted elevator car and the counterweight, and a sheave that contacts the tension member. During operation of such an elevator system, the sheave may be driven by a machine to move the elevator car and the counterweight through the hoistway, with their movement being guided by guide rails. Typically a governor is used to monitor the speed of the elevator car. According to standard safety regulations, such elevator systems must include an emergency braking device (known as a safety brake or “safety gear”) which is capable of stopping the elevator car from moving downwards, even if the tension member breaks, by gripping a guide rail. 
     The risks associated with freefall of an elevator car in an elevator system are particularly acute for elevator systems employed in high-rise buildings, where more significant over speed may occur due to the increased drop. The actuation of the safety brake is usually mechanically controlled. An elevator system employing a mechanical governor and mechanically-actuated safety brake is shown in  FIG.  1   , and described in greater detail below. 
     Electromechanical actuators have also been proposed, wherein a safety controller is in electrical communication with an electromagnetic component that can be controlled to effect movement of the safety brake via a mechanical linkage. It is an aim of the present disclosure to provide an improved safety brake system. 
     SUMMARY 
     According to a first aspect of this disclosure there is provided a safety brake system for use in a conveyance system including a guide rail and a conveyance component moveable along the guide rail, the safety brake system comprising: a safety brake moveable between a non-braking position where the safety brake is not in engagement with the guide rail and a braking position where the safety brake is engaged with the guide rail; a linkage mechanism; and an actuator for the safety brake, the actuator being configured to be mounted to the conveyance component and positioned between first and second ferromagnetic components, the actuator comprising: an array of magnetic components comprising a first magnetic component adjacent to and arranged between two second magnetic components, wherein the first magnetic component comprises one of a permanent magnet and an electromagnet and wherein the second magnetic components each comprise the other of a permanent magnet and an electromagnet, wherein the magnetic components of the array are arranged such that when the electromagnet of the first or second magnetic components is in a first state, the actuator is held in a first position against the first ferromagnetic component, wherein when the electromagnet of the first or second magnetic components is switched from the first state to a second state, the magnetic field between the array and the first ferromagnetic component is reduced and the magnetic field between the array and the second ferromagnetic component is augmented so as to move the actuator from the first position to a second position against the second ferromagnetic component, and wherein the linkage mechanism is coupled between the safety brake and the actuator such that movement of the actuator from the first position to the second position when the electromagnet is switched from the first state to the second state causes the safety brake to move into the braking position. 
     As the actuator is moved from the first position to the second position when the electromagnet is switched from the first state to the second state, a simple and reliable safety brake system may be provided which may be triggered even if a relatively large distance is provided between the first and second ferromagnetic components. 
     It will be appreciated by those skilled in the art that the first and second magnetic components may be arranged in the array of magnetic components such that the direction of the magnetic field of the first magnetic component is substantially perpendicular to the direction of the magnetic field of the two second magnetic components. The first of the two second magnetic components may be arranged such that the direction of its magnetic field is opposite to the direction of the magnetic field of the second of the two second magnetic components. In this regard, the first and second magnetic components may be arranged such that each next component of the array of magnetic components follows a spatially rotating pattern of magnetization. 
     In other examples, the first and second magnetic components may be arranged in the array of magnetic components such that the direction of the magnetic field of the first magnetic component is at an angle to the direction of the magnetic field of the two second magnetic components, where the angle may for example be between 45° and 90°. The first of the two second magnetic components may be arranged such that the direction of its magnetic field is at an angle of between 90° and 180° to the direction of the magnetic field of the second of the two second magnetic components. In this regard, the first and second magnetic components may be arranged such that each next component of the array of magnetic components follows a spatially rotating pattern of magnetization, wherein the magnetic field of each next component is rotated by an angle of, for example, between 45° and 90° relative to the previous component. 
     The array of magnetic components may act as a one-sided flux structure when the electromagnet(s) of the first component or the second magnetic components is in the second state. The array of magnetic components may form a Halbach array when the electromagnet(s) of the first component or the second magnetic components is in the second state. 
     It will be understood that when the electromagnet of the first or second magnetic components is switched from the first state to the second state, the magnetic field between the array and the first ferromagnetic component may be reduced such that there is no attractive force or there is negligible attractive force between the array of magnetic components and the first ferromagnetic component. 
     It will further be understood that when the electromagnet of the first or second magnetic components is switched from the first state to the second state, the actuator is moved from the first position to the second position due to the attractive magnetic force between the array of magnetic components and the second ferromagnetic component. 
     In one set of examples, the electromagnet of the first or second magnetic components may be switched from the first to the second state, for example, if the conveyance component is detected to be moving too fast or accelerating at too great of a rate. 
     It will be understood that when the first magnetic component is a permanent magnet, the two second magnetic components are electromagnets and when the first magnetic component is an electromagnet, the two second magnetic components are permanent magnets. 
     In examples wherein the two second magnetic components each comprise an electromagnet, references made to the electromagnet of the first or second magnetic components is to be understood as describing a first and a second electromagnet. 
     In some embodiments, the components of the array of magnetic components may be in contact with one another. In other embodiments, the components of the array of magnetic components may be spaced apart from one another. 
     In a set of examples, movement of the actuator from the first position to the second position when the electromagnet of the first or second magnetic components is switched from the first state to the second state causes the safety brake to move into the braking position directly. In another set of examples, movement of the actuator from the first position to the second position when the electromagnet of the first or second magnetic components is switched from the first state to the second state causes the safety brake to move into the braking position indirectly. 
     It will further be understood that, in some examples of the disclosed safety brake system, there is no dependence on frictional forces to actuate the safety brake. Rather, the linkage mechanism may be caused to move to actuate the safety brake as a direct result of the movement of the actuation component, in other words, by the movement of the actuation component from the first position to the second position when the electromagnet is switched from the first state to the second state being transferred to the safety brake via the linkage mechanism. 
     The disclosed safety brake system may require fewer components than prior art mechanical safety brake devices which may therefore reduce the space required by the safety brake system. In addition, the reduction in the number of components may reduce the cost of installation and service. The disclosed safety brake system may further provide a system which is simple to maintain and provides robust performance. 
     In one set of examples, when in the first state, the electromagnet of the first or second magnetic component may not be energised. In these examples, the actuator may be held in the first position against the first ferromagnetic component by the permanent magnet of the first or second magnetic components. 
     In this set of examples, the actuator may be held in the first position by an attractive magnetic force between the permanent magnet of the first or second magnetic components and the first ferromagnetic component. In this set of examples, electric current need not be supplied to the electromagnet of the first or second magnetic components while the actuator is in the first position thus achieving a reliable and energy efficient system. 
     In a set of examples, the magnetic components of the array may be arranged such that when the actuator is in the second position, and when the electromagnet of the first or second magnetic components is not energised, the permanent magnet of the first or second magnetic components act to hold the actuator in the second position against the second ferromagnetic component. 
     In this set of examples, the actuator may be held in the second position by an attractive magnetic force between the permanent magnet of the first or second magnetic components and the second ferromagnetic component. In this set of examples, electric current need not be supplied to the electromagnet of the first or second magnetic components while the actuator is in the second position thus achieving a reliable and energy efficient system. 
     In a set of examples, when in the second state, the electromagnet of the first or second magnetic component may be energised with a first polarity and, when in the first state, the electromagnet of the first or second magnetic component may be energised with a second, opposite polarity. 
     In this set of examples, when the electromagnet is in the first state, the magnetic field between the array and the first ferromagnetic component is augmented and the magnetic field between the array and the second ferromagnetic component is reduced. In this regard, the actuator is held in the first position against the first ferromagnetic component by the attractive force between the array of magnetic components and the first ferromagnetic component. In this set of examples, when the electromagnet is in the first state there may be no attractive magnetic force or there may be negligible attractive magnetic force between the array of magnetic components and the second ferromagnetic component. Thus, the actuator may be less susceptible to false actuation. 
     In a set of examples, when the electromagnet of the first or second magnetic components is switched to a third state, the magnetic field between the array and the first ferromagnetic component may be augmented and the magnetic field between the array and the second ferromagnetic component may be reduced so as to move the actuator from the second position to the first position. 
     In a set of examples, the electromagnet of the first or second magnetic components may be energised with a first polarity in the second state, and may be energised with a or the second, opposite polarity in the third state. 
     It will be understood, that when the electromagnet is energised with a first polarity the magnetic field between the array and the first ferromagnetic component may be augmented and the magnetic field between the array and the second ferromagnetic component may be reduced such that the actuator is moved towards the first ferromagnetic component or is held against the first ferromagnetic component. In addition, when the electromagnet is energised with a second, opposite polarity the magnetic field between the array and the second ferromagnetic component may be augmented and the magnetic field between the array and the first ferromagnetic component may be reduced such that the actuator is moved towards the second ferromagnetic component or is held against the second ferromagnetic component, 
     In a set of examples, the safety brake system may further comprise a mount for attaching the actuator to the conveyance component. In this set of examples, the first ferromagnetic component may be part of or may be fixed to the mount. 
     In a set of examples, the array may comprise a plurality of first magnetic components and each first magnetic component may be arranged between two second magnetic components. In this set of examples, the first and second ferromagnetic components may be spaced apart in a first direction and the magnetic components of the array may be aligned in a direction perpendicular to, or generally perpendicular to the first direction, for example, within 25° of perpendicular to, the first direction. It will be understood however that in other sets of examples, the magnetic components of the array may be arranged differently and need not be aligned in the direction described above. 
     In this set of examples, each next magnetic component of the array of magnetic components follows a spatially rotating pattern of magnetization. In some examples, the magnetic component of the array of magnetic components are arranged such that each next magnetic component in the array alternates between a first magnetic component and a second magnetic component. In some examples, the array of magnetic components comprises an odd number of magnetic components. 
     In one set of examples, the second ferromagnetic component may be the guide rail. 
     In another set of examples, the second ferromagnetic component may be part of or may be fixed to the mount. In this set of examples, the second ferromagnetic component is fixed with respect to the first ferromagnetic component. 
     In a set of examples, the actuator may further comprise a contact portion configured to be spaced apart from the guide rail when the actuator is in the first position and configured to be in contact with the guide rail when the actuator is in the second position. In examples, the contact portion may comprise a high friction surface. In examples, the safety brake system may be configured such that when the conveyance component is moving downwards relative to the guide rail, movement of the actuator to the second position creates an upwards reaction force transmitted by the linkage mechanism to move the safety brake into the braking position. 
     In examples of the present disclosure, the safety brake device may find use in a variety of conveyance systems, such as elevator systems, people conveyors, goods transporters, etc. The conveyance component that is moveable along a guide rail may be a platform, a counterweight or a cab for transporting goods or people. In some examples, the conveyance system is an elevator system and the conveyance component is an elevator car. 
     In examples, the actuator may further comprise a ferromagnetic support structure housing the magnetic components of the array so as to guide the magnetic flux produced by the magnetic components of the array to flow through the ferromagnetic support structure. 
     According to a second aspect of this disclosure there is provided an elevator system comprising: an elevator car driven to move along at least one guide rail; and the safety brake system of any of the above examples, wherein the safety brake is arranged to be moveable between the non-braking position where the safety brake is not in engagement with the guide rail and the braking position where the safety brake is engaged with the guide rail. 
     In some examples, the actuator may be configured to move relative to the elevator car. 
     In one set of examples, the elevator system may further comprise a speed sensor and a controller arranged to receive a speed signal from the speed sensor and to selectively switch the electromagnet of the first or second magnetic component from the first state to the second state upon detecting an overspeed or over-acceleration condition for the elevator car based on the speed signal. 
     In this or another set of examples, the elevator system may further comprise an accelerometer and a controller arranged to receive an acceleration signal from the accelerometer and to selectively switch the electromagnet of the first or second magnetic component from the first state to the second state upon detecting an over-acceleration condition for the elevator car. 
     In some examples, the controller may be arranged to receive both a speed signal and an acceleration signal from a speed sensor. In other examples, the controller may be arranged to receive both a speed signal and an acceleration signal from an accelerometer. 
     Therefore, when the elevator car is travelling at overspeed or over-acceleration, selectively switching the electromagnet from the first state to the second state will actuate the safety brake to engage with the guide rail, preventing further motion of the elevator car. 
     According to a second aspect of this disclosure there is provided a method of operating a safety brake in a safety brake system, the safety brake moveable between a non-braking position where the safety brake is not in engagement with a guide rail and a braking position where the safety brake is engaged with the guide rail, the safety brake system comprising: an actuator mounted to a component moveable along a guide rail and configured to move between first and second ferromagnetic components, the actuator comprising: an array of magnetic components comprising a first magnetic component adjacent to and arranged between two second magnetic components, wherein the first magnetic component comprises one of a permanent magnet and an electromagnet and wherein the second magnetic components each comprise the other of a permanent magnet and an electromagnet; and a linkage mechanism coupled between the safety brake and the actuator, the method comprising: operating the electromagnet of the first or second magnetic component in a first state in a normal mode such that the actuator is held in a first position against the first ferromagnetic component; and operating the electromagnet of the first or second magnetic component in a second state in an emergency stop mode such that the magnetic field between the array and the first ferromagnetic component is reduced and the magnetic field between the array and the second ferromagnetic component is augmented so as to move the actuator from the first position to a second position against the second ferromagnetic component, wherein the linkage mechanism is coupled between the safety brake and the actuator such that movement of the actuator from the first position to the second position when the electromagnet is switched from the first state to the second state causes the safety brake to move into the braking position. 
     In examples of the present disclosure, the steps of operating the electromagnet of the first or second magnetic components are executed by a controller. 
     In some examples, operating the electromagnet of the first or second magnetic components comprises supplying a pulse of electric current to the electromagnet. In some examples, operating the electromagnet of the first or second magnetic components comprises supplying continuous electric current to the electromagnet. In some examples, current is supplied to the electromagnet of the first or second magnetic components for a pre-determined duration. 
     In examples, the method may further comprise detecting an overspeed or over-acceleration of the component and initiating the emergency stop mode by switching the electromagnet of the first or second magnetic component from the first state to the second state. 
     In one set of examples, the method may further comprise operating the electromagnet of the first or second magnetic component in a first state in a normal mode such that the electromagnet is not energised. 
     In this set of examples, the actuator may be held in the first position against the first ferromagnetic component by the permanent magnet of the first or second magnetic components. In this set of examples, in the normal mode electric current is not supplied to the electromagnet of the first or second magnetic components thus achieving a reliable and energy efficient system. 
     In a set of examples, in the emergency mode, the permanent magnet of the first or second magnetic components acts to hold the actuator in the second position against the second ferromagnetic component. 
     In this set of examples, the actuator may be held in the second position by an attractive magnetic force between the permanent magnet of the first or second magnetic components and the second ferromagnetic component. In this set of examples, electric current is not supplied to the electromagnet of the first or second magnetic components thus achieving a reliable and energy efficient system. 
     In a set of examples, operating the electromagnet of the first or second magnetic components in the first state in the normal mode may comprise energising the electromagnet with a first polarity and operating the electromagnet of the first or second magnetic components in the second state in the emergency mode may comprise energising the electromagnet with a second, opposite polarity. 
     In this set of examples, when the electromagnet is in the first state, the magnetic field between the array and the first ferromagnetic component is augmented and the magnetic field between the array and the second ferromagnetic component is reduced. In this regard, the actuator is held in the first position against the first ferromagnetic component by the attractive force between the array of magnetic components and the first ferromagnetic component. In this set of examples, there is no attractive magnetic force or there is negligible attractive magnetic force between the array of magnetic components and the second ferromagnetic component. Thus the actuator is less susceptible to false actuation. 
     In a set of examples, the method may further comprise operating the electromagnet of the first or second components in a third state such that the magnetic field between the array and the first ferromagnetic component is augmented and the magnetic field between the array and the second ferromagnetic component is reduced so as to move the actuator from the second position to the first position. 
     In a set of examples, operating the electromagnet of the first or second magnetic components in the second state in emergency mode may comprise energising the electromagnet with a first polarity, and operating the electromagnet of the first or second magnetic component in the third state may comprise energising the electromagnet with a second, opposite polarity. 
     It will be understood, that when the electromagnet is energised with a first polarity the magnetic field between the array and the first ferromagnetic component may be augmented and the magnetic field between the array and the second ferromagnetic component may be reduced such that the actuator is moved towards the first ferromagnetic component or is held against the first ferromagnetic component. In addition, when the electromagnet is energised with a second, opposite polarity the magnetic field between the array and the second ferromagnetic component may be augmented and the magnetic field between the array and the first ferromagnetic component may be reduced such that the actuator is moved towards the second ferromagnetic component or is held against the second ferromagnetic component, 
     In a set of examples, the method may further comprise attaching the actuator to the conveyance component by a mount. In this set of examples, the first ferromagnetic component may be part of or may be fixed to the mount. 
     In a set of examples, operating the electromagnet of the first or second magnetic component in the second state in the emergency stop mode so as to move the actuator from the first position to a second position against the second ferromagnetic component may further comprise moving a contact portion of the actuator to be in contact with the second ferromagnetic component, wherein the contact portion is configured to be spaced apart from the guide rail when the actuator is in the first position and configured to be in contact with the guide rail when the actuator is in the second position, and wherein the second ferromagnetic component is a guide rail. In examples, the contact portion may comprise a high friction surface. In examples, the safety brake system may be configured such that when the conveyance component is moving downwards relative to the guide rail, movement of the actuator to the second position creates an upwards reaction force transmitted by the linkage mechanism to move the safety brake into the braking position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic diagram of an elevator system employing a mechanical governor; 
         FIG.  2    is a schematic view of a safety brake system according to an example of the present disclosure; 
         FIG.  3    is a schematic cross-sectional view of part of a safety brake system according to an example of the present disclosure; 
         FIG.  4    is a different schematic cross-sectional view of the part of a safety brake system of  FIG.  3   ; 
         FIG.  5    is a schematic cross-sectional view of part of a safety brake system according to an example of the present disclosure with the actuator in a first position and with the safety brake in a first, non-braking position; 
         FIG.  6    is a schematic diagram of an actuator of a safety brake system according to an example of the present disclosure; 
         FIG.  7    is a schematic cross-sectional view of the part of the safety brake system of  FIG.  5    with the actuator in a second position and with the safety brake in the first, non-braking position; 
         FIG.  8    is a schematic cross-sectional view of the part of the safety brake system of  FIG.  5    with the actuator in a third position and with the safety brake in a second, braking position; 
         FIG.  9    is a schematic cross-sectional view of part of a safety brake system according to another example of the present disclosure; 
         FIG.  10    is a schematic block diagram of emergency braking control for an elevator system and safety brake system according to an example of the disclosure; 
         FIG.  11 A  is a schematic cross-sectional view of a safety brake system according to another example of the present disclosure with the safety brake in a first, non-braking position; and 
         FIG.  11 B  is a schematic cross-sectional view of the safety brake system of the example of  FIG.  11 A  with the safety brake in a second, braking position. 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    shows a conveyance system, in this example an elevator system, generally indicated at  10 . The elevator system  10  includes cables or belts  12 , a car frame  14 , a conveyance component, in this example an elevator car  16 , roller guides  18 , guide rails  20 , a governor  22 , and a pair of safety brakes  24  mounted on the elevator car  16 . The governor  22  is mechanically coupled to actuate the safety brakes  24  by linkages  26 , levers  28 , and lift rods  30 . Governor  22  includes a governor sheave  32 , rope loop  34 , and a tensioning sheave  36 . Cables  12  are connected to car frame  14  and a counterweight (not shown in  FIG.  1   ) inside a hoistway. Elevator car  16 , which is attached to car frame  14 , moves up and down the hoistway by force transmitted through cables or belts  12  to car frame  14  by an elevator drive (not shown) commonly located in a machine room at the top of the hoistway. Roller guides  18  are attached to car frame  14  to guide the elevator car  16  up and down the hoistway along the guide rails  20 . Governor sheave  32  is mounted at an upper end of the hoistway. Rope loop  34  is wrapped partially around governor sheave  32  and partially around tensioning sheave  36  (located in this example at a bottom end of the hoistway). Rope loop  34  is also connected to elevator car  16  at lever  28 , ensuring that the angular velocity of governor sheave  32  is directly related to the speed of elevator car  16 . 
     In the elevator system  10  shown in  FIG.  1   , the governor  22 , a machine brake (not shown) located in the machine room, and the safety brakes  24  act to stop the elevator car  16  if it exceeds a set speed as it travels inside the hoistway. If elevator car  16  reaches an over-speed or over-acceleration condition, the governor  22  is triggered initially to engage a switch, which in turn cuts power to the elevator drive and drops the machine brake to arrest movement of the drive sheave (not shown) and thereby arrest movement of elevator car  16 . If, however, the elevator car  16  continues to experience an over speed condition, governor  22  may then act to trigger the safety brakes  24  to arrest movement of elevator car  16 . In addition to engaging a switch to drop the machine brake, governor  22  also releases a clutching device that grips the governor rope  34 . Governor rope  34  is connected to the safety brakes  24  through mechanical linkages  26 , levers  28 , and lift rods  30 . As elevator car  16  continues its descent, governor rope  34 , which is now prevented from moving by actuated governor  22 , pulls on the operating levers  28 . The operating levers  28  actuate the safety brakes  24  by moving linkages  26  connected to lift rods  30 , which lift rods  30  cause the safety brakes  24  to engage the guide rails  20  to bring the elevator car  16  to a stop. 
     Mechanical speed governor systems are being replaced in some elevators by electronically-actuated systems. A safety brake system is described herein that is suitable for electronic or electrical control of actuating and resetting a safety brake in an elevator system. It will be understood that the safety brake system of the present disclosure could be used in an elevator system  10  of the type shown in  FIG.  1   . However, this is only one example of a system in which the safety brake system of the disclosure could be used. The safety brake system of the present disclosure could also be used in any other suitable type of conveyance system. Such other types of conveyance system may include (but are not limited to) hydraulic elevator systems and ropeless elevator systems such as pinched wheel or linear motor propulsion elevator systems. 
       FIG.  2    shows an example of a safety brake system  40  having a safety brake  42 , and an actuator  44 . The safety brake system  40  can be mounted onto the elevator car  16  of  FIG.  1    to actuate the safety brake  42  without relying on a mechanical coupling to the governor  22 . The safety brake system  40  of the example includes a mount  48 , which may be mounted on the elevator car frame  14 . In other examples, the mount  48  may be mounted on an external surface of the elevator car  16  instead. The mount  48  includes apertures  52 , which enable fixation of the mount  48  to the car frame  14 . The mount  48  comprises an actuator mounting portion  49  and a safety brake mounting portion  50 . In this example, the actuator mounting portion  49  and the safety brake mounting portion  50  are separate components as shown in  FIG.  2   . In other examples, the actuator mounting portion  49  and the safety brake mounting portion  50  could both be parts of the same component. The actuator mounting portion  49  and the safety brake mounting portion  50  of this example both include apertures  52 , which enable fixation of the respective mounting portions to the car frame  14 . The safety brake system of this example further comprises a guide rail channel  54 , which extends along the length of the safety brake  42  and is configured to accommodate the guide rail  20  (not shown in  FIG.  2   ). 
     The safety brake  42  of the safety brake system  40  is moveable between a non-braking position where the safety brake  42  is not in engagement with the guide rail  20 , and a braking position where the safety brake  42  is engaged with the guide rail  20 . In the example of  FIG.  2   , the safety brake  42  is a roller-type safety brake comprising an angled surface and a roller moveable along the surface from a non-braking position to a braking position where the roller is brought into engagement with the guide rail  20 . As shown, the safety brake  42  is located below the actuator  44  in this example such that linkage mechanism  56  can act to pull the roller upwardly along the angled surface to move the safety brake  42  into the braking position. However, it will be appreciated that the safety brake  42  may take any suitable form and could instead comprise a wedge-shaped brake pad instead of the roller, or a magnetic brake pad. In some examples, the safety brake may be located above the actuator  44  instead such that, for example, the linkage mechanism can act to push the roller upwardly along the angled surface to move the safety brake into the braking position. Various roller-type safety brakes such as those described above are well-known in the art, for example as seen in U.S. Pat. No. 4,538,706. 
     Regardless of the exact form of the safety brake  42 , the safety brake is coupled to the actuator  44  via a linkage mechanism  56 . The actuator  44  is positioned between a first ferromagnetic component and a second ferromagnetic component. In the example of  FIG.  2   , the first ferromagnetic component is a backing plate  60  for the actuator  44 . The backing plate  60  of this example extends outwardly from and perpendicular to the actuator mounting portion  49  in a direction away from the car frame  14 . The second ferromagnetic component in the example of  FIG.  2    is the guide rail  20  (not shown in  FIG.  2   ). 
     With reference to  FIG.  3    and  FIG.  4   , the safety brake system  40  further comprises a cover  61  attached to actuator mounting portion  49  so as to define a channel  58  between the cover  61  and the actuator mounting portion  49 . The actuator  44  is located in the channel  58  between the actuator mounting portion  49  and the cover  61  such that lateral movement of the actuator  44  in relation to the guide rail  20  is restricted by the actuator mounting portion  49  in one direction and by the cover  61  in the opposite direction. Thus, the actuator  44  may be configured to move toward and away from the guide rail and be restrained or limited against movement in other lateral directions such as the direction perpendicular to the direction of movement toward and away from the guide rail. A back end  57  of the channel  58  is at least partially defined by backing plate  60 . Backing plate  60  limits movement of the actuator in a direction away from the guide rail  20 . A front end  59  of the channel  58  is open as to allow movement of the actuator  44  towards the guide rail  20  and/or contact of the actuator  44  with the guide rail  20 . The actuator  44  is free to move along the channel  58  in a direction along the guide rail  20  between a first axial end  64  and a second axial end  65  of the channel  58 . The first axial end  64  comprises at least one opening (not shown) through which the linkage mechanism  56  extends. In the example described, the first axial end  64  of the channel  58  and the second axial end  65  of the channel  58  are defined by the cover. In other examples, the first axial end  64  of the channel  58  and the second axial end  65  of the channel  58  may be defined at least partially by the mounting portion  49 . 
     The actuator  44  of the safety brake system  40  of  FIG.  2    is shown in greater detail in  FIG.  5   . The actuator  44  comprises an array of magnetic components and is configured to be moved from a first position, adjacent the backing plate  60  (the first ferromagnetic component of this example) to a second position adjacent the guide rail  20  (the second ferromagnetic component of this example). The array of magnetic components comprises at least one first magnetic component and at least two second magnetic components. The first magnetic component is adjacent to and arranged between the two second magnetic components. The first magnetic component comprises one of a permanent magnet and an electromagnet and the second magnetic components each comprise the other of a permanent magnet and an electromagnet. Thus, when the first magnetic component is a permanent magnet, the two second magnetic components are electromagnets and when the first magnetic component is an electromagnet, the two second magnetic components are permanent magnets. 
     In some examples, for example as shown in  FIG.  5   , the first and second ferromagnetic components are spaced apart from each other in a first direction and the magnetic components of the array are aligned in a direction perpendicular to the first direction, or a direction generally perpendicular to the first direction, for example in a direction within 25° of perpendicular to the first direction. The magnetic components of the array are orientated with respect to their magnetic fields so as to form a Halbach array when current is supplied to the electromagnet(s) of the first or second magnetic components. 
     In the example of  FIG.  5   , the array of magnetic components comprises one electromagnet  66  (the first magnetic component) and two permanent magnets  68  (the second magnetic components). The electromagnet  66  is adjacent to and arranged between the two permanent magnets  68  such that the magnetic components are stacked in the direction of the guide rail  20  (generally in the direction perpendicular to the first direction). 
     The array of magnetic components is configured such that the magnetic fields of the two permanent magnets  68  are opposite in direction to each other. The magnetic field generated by the electromagnet  66  when electric current is supplied to it has a direction substantially perpendicular to that of the two permanent magnets  68 . As a result, the magnetic fields generated by electromagnet  66  and the two permanent magnets  68  interact such that the array of magnetic components generates an augmented magnetic field on one side of the array and a reduced magnetic field on another side of the array. 
     In a set of examples, such as the example of  FIG.  5   , the north pole of the first of the two permanent magnet  68  faces the north pole of the second of the two permanent magnets  68  such that the magnetic fields of the two permanent magnets  68  are opposite in direction to each other. In the example of  FIG.  5   , each of the two permanent magnets is orientated with respect to its poles such that the north pole is adjacent to (or faces towards) the electromagnet  66  while the south pole faces away from the electromagnet  66 . The polarity of the electromagnet  66  is determined by the direction of current supplied to the magnet. The electromagnet  66  can be energised with a first polarity such that the north pole of the electromagnet  66  faces the guide rail  20  or with a second polarity such that the south pole of the electromagnet  66  faces the guide rail  20 . 
     The actuator  44  of this example further comprises a support structure  70  which houses the electromagnet  66  and the two permanent magnets  68 . The support structure  70  can take any suitable shape and, in this example, comprises a frame. In the example of  FIG.  5   , the frame comprises ferromagnetic material and part of the frame extends through a coil of the electromagnet  66  in order to form the ferromagnetic core of the electromagnet  66 . In other examples, the electromagnet  66  may comprise a separate ferromagnetic component as a core. The electromagnet  66  and the two permanent magnets  68  are fixed relative to one another via the support structure  70  such that the electromagnet  66  and two permanent magnets  68  move as a single unit. The electromagnet  66  is located between the two permanent magnets  68  such that the array extends in a vertical direction or, in other words, in a direction parallel to the guide rail  20 . 
     In the example of  FIG.  5    and with reference to  FIG.  6   , the support structure  70  defines a first outer component  71 , a middle component  72  and a second outer component  73 . The first outer, middle and second outer components  71 ,  72 ,  73  extend in a direction generally parallel to the first direction. The first outer, middle and second outer components  71 ,  72 ,  73  are substantially parallel to one another. The first outer, middle and second outer components  71 ,  72 ,  73  are spaced apart from one another in a direction generally perpendicular to the first direction. The first outer, middle and second outer components  71 ,  72 ,  73  each comprise a first end  71   a,    72   a,    73   a  and a second end  71   b,    72   b,    73   b.  When the actuator  44  is in position in the elevator system, the first ends  71   a,    72   a,    73   a  of the first outer, middle and second outer components  71 ,  72 ,  73  are positioned to face the guide rail  20  and to be closer to the guide rail  20  than the second ends  71   b,    72   b,    73   b  of the first outer, middle and second outer components  71 ,  72 ,  73 . The second ends  71   b,    72   b,    73   b  of the first outer, middle and second outer components  71 ,  72 ,  73  are positioned to face the backing plate  60  and to be closer to the backing plate  60  than the first ends  71   a,    72   a,    73   a  of the first outer, middle and second outer components  71 ,  72 ,  73 . 
     The support structure  70  further defines a front component  74  and a back component  75  extending in a direction generally perpendicular to the first direction. The front and back components  74 ,  75  are substantially parallel to one another. The front and back components  74 ,  75  are spaced apart in a direction generally parallel to the first direction. The front and back components  74 ,  75  are each connected to each of the first outer, middle and second outer components  71 ,  72 ,  73 . The front component  74  connects the first ends  71   a,    72   a,    73   a  of the first outer, middle and second outer component  71 ,  72 ,  73  to one another. The back component  75  connects the second ends  71   b,    72   b,   73   b  of the first outer, middle and second outer components  71 ,  72 ,  73  to one another. 
     As shown in  FIG.  5    and with reference to  FIG.  6   , a portion of the first end  71   a  of the first outer component  71  extends beyond the front component  74  in the first direction (in this example towards the guide rail  20 ), thus defining a first outer front prong  76   a.  A portion of the first end  72   a  of the middle component  72  extends beyond the front component  74  in the first direction (in this example towards the guide rail  20 ), thus defining a middle front prong  77   a.  A portion of the first end  73   a  of the second outer component  73  extends beyond the front component  74  in the first direction (in this example towards the guide rail  20 ), thus defining a second outer front prong  78   a . A portion of the second end  71   b  of the first outer component  71  extends beyond the back component  75  in the first direction (in this example towards the backing plate  60 ), thus defining a first outer back prong  76   b.  In some examples, a portion of the second end  72   b  of the middle component  72  may extend beyond the back component  75  in the first direction (in this example towards the backing plate  60 ), thus defining a middle back prong  77   b.  A portion of the second end  73   b  of the second outer component  73  extends beyond the back component  75  in the first direction (in this example towards the backing plate  60 ), thus defining a second outer back prong  78   b.    
     In the example of  FIG.  5   , no middle back prong  77   b  is provided. In such examples, the energy required to augment the magnetic field between the guide rail  20  and the actuator  44  to cause the actuator  44  to move to the second position may be less than the energy required to augment the magnetic field between the backing plate  60  and the actuator  44  in order to move the actuator  44  back to the first position from the second position. In other words, in such examples, the energy required to trip or actuate the actuator  44  may be less than the energy required to reset the actuator  44 . 
     As shown in  FIG.  5    and with reference to  FIG.  6   , the coil  69  of the electromagnet  66  is wound around the middle component  72 . The middle component  72  thus forms the electromagnetic core of the electromagnet  66 . One of the two permanent magnets is located at a generally equal distance between the first outer component  71  and the middle component  72 . The other of the two permanent magnets is located at a generally equal distance from the second outer component  72  and the middle component  73 . A first end of each of the two permanent magnets is housed by the front component  74 . A second, opposite end of each of the two permanent magnets is housed by the back component  75 . 
     In the example of  FIG.  5    and with reference to  FIG.  6   , the support structure  70  is configured to guide the magnetic flux of the magnetic components of the array of magnetic components. In other words, the magnetic flux produced by the magnetic components of the array is directed to flow preferentially through the ferromagnetic support structure  70  so as to optimise the interactions between the magnetic fields of the electromagnet  66  and the two permanent magnets  68 . The front prongs  76   a,    77   a,    78   a  of the first outer, middle and second outer components  71 ,  72 ,  73  are configured to guide the magnetic flux generated by the magnetic components of the array of magnetic components. The back prongs  76   b,    78   b  of the first outer and second outer components  71 ,  73  are configured to guide the magnetic flux generated by the magnetic components of the array of magnetic components. In some examples, a back prong  77   b  of the middle component  72  may also be provided and configured to guide the magnetic flux generated by the magnetic components of the array of magnetic components. 
     While the support structure  70  has been described in relation to  FIG.  5    and  FIG.  6   , other configurations are envisaged and it will be understood that such a support structure having all or some of the features described in relation to this example could be provided with any example of an actuator according to the disclosure. 
     The actuator  44  may further comprise one or more contact portions  80  provided on the frame for contacting the guide rail  20  when the actuator  44  is in the second position. In some examples (not shown), the contact portions may comprise high friction surfaces. In other examples, the one or more contact portions  80  may be provided as a separate component(s) attached to the actuator  44 . 
     In  FIG.  5   , the actuator  44  is shown in the first position, corresponding to when the safety brake  42  is in a non-braking position, e.g. upon installation or after reset. The safety brake system  40  is mounted onto the car frame  14  (not shown in  FIG.  5   ) via the mount, in this example mounting portion  49 , such that the safety brake system  40  moves with the elevator car  16  in use along the guide rail  20 . In the first position, the actuator  44  is magnetically attached to the backing plate  60  and is spaced away from the guide rail  20  as will be described further below. 
     The electromagnet  66  is in a first state when the actuator  44  is in the first position as shown in  FIG.  5   . In this example, no electric current is being supplied to electromagnet  66  and thus when the electromagnet  66  is in the first state, the electromagnet  66  does not generate a magnetic field. As a result, the array of magnetic components does not generate an augmented magnetic field on a first side and a reduced or cancelled magnetic field on another, opposite side. The actuator  44  (the frame in the example shown) is held against backing plate  60  due to the attractive magnetic force between the two permanent magnets  68  and the backing plate  60 . The actuator  44  is therefore held away from the guide rail  20 , defining a gap  45  between the actuator  44  and the guide rail  20 . 
     A safety controller  79  (as shown in  FIG.  10    and described in further detail below) is in electrical communication with the electromagnet  66 . If a freefall, over-speed, or over-acceleration condition of the elevator car  16  is detected by the governor  22 , the safety controller  79  is configured to switch the electromagnet  66  to a second state by supplying a pulse of electric current to the electromagnet  66  in a first direction of current flow. In alternative examples, the safety controller  79  may be configured to provide a continuous supply of electric current so as to maintain the electromagnet  66  in the second state after it has switched from the first state to the second state. In either example, the safety controller  79  is configured to energise the electromagnet  66  with a first polarity. When the electromagnet  66  is in the second state, the magnetic fields generated by the respective components of the array interact such that the magnetic fields generated by the magnetic components on a first side of the array are summed together to provide an augmented magnetic field on the first side of the array. In contrast, the magnetic fields generated by the magnetic components on a second, opposite side of the array are opposed and so sum together to provide a reduced magnetic field on the second, opposite side of the array. Thus, the array can be configured such that when the electromagnet  66  is in the second state, an attractive magnetic force between the array and the backing plate  60  is reduced or cancelled and an attractive magnetic force between the array and the guide rail  20  is strong or augmented. Thus, as will be described in further detail below with reference to  FIG.  7   , the actuator  44  (in this example, the frame) will be moved into the second position in contact with the guide rail  20  by the attractive magnetic force between the array of magnetic components and the guide rail  20 . 
     In  FIG.  7   , the actuator  44  of  FIG.  5    is shown in the second position in contact with the guide rail  20  after the electromagnet  66  has been switched to the second state. In the example of  FIG.  6   , the electromagnet  66  reverts back to the first state once the safety controller  79  ceases supplying the electric current to the electromagnet  66 . It will be understood that once the electromagnet  66  ceases generating a magnetic field, the magnetic fields generated by the respective components of the array can no longer interact such that the magnetic fields generated by the magnetic components on the first side of the array are augmented while the magnetic field on the second opposite side are reduced or cancelled. Therefore, when the actuator  44  is in the second position and the electromagnet  66  has reverted to the first state, in which no current is supplied to it, the actuator  44  is held in the second position against the guide rail  20  by the attractive magnetic force between the permanent magnets  68  and the guide rail  20 . In other words, the actuator  44  is magnetically attached to guide rail  20  in the second position. 
     In other examples, the safety controller  79  may instead be configured to provide a continuous supply of electric current to the electromagnet  66  so that the actuator  44  is held in the second position against the guide rail  20  by the attractive magnetic force between the array of magnetic components and the guide rail  20 . In other words, the safety controller  79  may be configured to maintain the electromagnet  66  in the second state while the actuator  44  is in the second position. 
     Once the actuator  44  is magnetically attached to the guide rail  20 , movement of the elevator car  16  downwards relative to the guide rail  20  causes the actuator  44  to move upwards relative to the elevator car  16  to a third position. This is due to the downwards motion of the elevator car  16  and the actuator mounting portion  49  which is fixed to the elevator car  16  via the frame  14 , and the fixed position of the guide rail  20 . In some examples, this is at least in part due to the friction force produced between the guide rail  20  and the contact portions  80  (or support structure  70 ) which are held against the guide rail  20  by magnetic force, the friction force opposing the movement of the elevator car, thus resulting in an upwards reaction force. In other examples, the high friction surface of contact portions  80  may increase the friction force between the contact portions  80  and the guide rail  20  by having a higher coefficient of friction. This may act to hold the actuator  44  against the guide rail more reliably. 
     In  FIG.  8   , the actuator  44  of  FIG.  5    is shown in the third position. When the actuator  44  is moved to the third position, the resulting upwards reaction force is applied to the linkage mechanism  56  (not shown), which is connected between the actuator  44  and the safety brake  42 . The linkage mechanism  56  transmits the upwards reaction force to the roller of the safety brake  42  to move the roller upwards along the angled surface into the braking position such that it engages the guide rail  20  and prevents further downwards motion of the elevator car  16 . Therefore, when an over-speed or freefall condition of an elevator car  16  is detected by a safety controller  79 , the safety brake system  40  acts to prevent further downwards motion of the elevator car  16 . 
     To reset the safety brake  42  and the actuator  44 , the elevator car  16  is moved upwards. The elevator car  16  is moved upwards until the safety brake  42  is released and the actuator  44  is aligned with the backing plate  60 . In some examples, aligning the actuator  44  with the backing plate  60  (i.e. the first ferromagnetic component) corresponds to moving the actuator  44  from the third position to the second position. The safety controller  79  is configured to then switch the electromagnet to a third state by suppling a pulse of electric current to the electromagnet  66  in a second direction of current flow. In other words, the safety controller  79  is configured to energise the electromagnet  66  with a second polarity. In this respect, the current flow supplied to switch the electromagnet  66  to the third state is opposite in direction to the current flow supplied to switch the electromagnet  66  to the second state and, consequently, the second polarity of the electromagnet  66  when the electromagnet  66  is in the third state is opposite to the first polarity of the electromagnet  66  when the electromagnet  66  is in the second state. When the electromagnet  66  is in the third state, the magnetic fields generated by the respective components of the array interact such that the magnetic fields generated by the magnetic components on the second side of the array are summed together to provide an augmented magnetic field on the second side of the array. In contrast, the magnetic fields generated by the magnetic components on the first, opposite side of the array are opposed and so sum together to provide a reduced magnetic field on the first side of the array. Thus, the array can be configured such that when the electromagnet  66  is in the third state, an attractive magnetic force between the array and the guide rail  20  is reduced or cancelled and an attractive magnetic force between the array and the backing plate  60  is strong or augmented. Thus, the actuator  44  (in this example, the frame) will be moved into contact with the backing plate  60  to the first position by the attractive magnetic force generated between the array of magnetic components and the backing plate  60 . Once the electromagnet ceases to be supplied with electric current and so returns to its first state, the actuator  44  is held in the first position by the magnetic force between the permanent magnets  68  and the backing plate. 
     A further example of a safety brake system  140  according to the disclosure is described in relation to  FIG.  9   . The safety brake system  140  operates in substantially the same way as described above and can be used with a safety brake  142  and linkage mechanism  156  in the manner described above. However, the actuator  144  of the example of  FIG.  9    has an array of magnetic components comprising a permanent magnet  168  arranged between two electromagnets  166 . In this example, the array is configured such that the magnetic fields, generated by the two electromagnets  166  when electric current is supplied by the safety controller  79 , are opposite in direction to each other. The magnetic field generated by the permanent magnet  168  has a direction substantially perpendicular to the magnetic fields of the two electromagnets  166 . As a result, the magnetic fields generated by the two electromagnets  166  and the permanent magnet  168  interact such that the array of magnetic components generates an augmented magnetic field on one side of the array and a reduced magnetic field on another side of the array. 
     In the example of  FIG.  9   , the support structure  170  defines a first outer component  171  and a second outer component  173 . The first outer and second outer components  171 ,  173  extend in a direction generally parallel to the first direction. The first outer and second outer components  171 ,  173  are substantially parallel to one another. The first outer and second outer components  171 ,  173  are spaced apart from one another in a direction generally perpendicular to the first direction. The first outer and second outer components  171 ,  173  each comprise a first end  171   a,    173   a  and a second end  171   b,    173   b.  When the actuator  144  is in position in the elevator system, the first ends  171   a,    173   a  of the first outer and second outer components  171 ,  173  are positioned to face the guide rail  20  and to be closer to the guide rail  20  than the second ends  171   b,    173   b  of the first outer and second outer components  171 ,  173 . The second ends  171   b,    173   b  of the first outer and second outer components  171 ,  173  are positioned to face the backing plate  60  and to be closer to the backing plate  60  than the first ends  171   a,    173   a  of the first outer and second outer components  171 ,  173 . 
     The support structure  170  further defines a front component  174  and a back component  175  extending in a direction generally perpendicular to the first direction. The front and back components  174 ,  175  are substantially parallel to one another. The front and back components  174 ,  175  are spaced apart in a direction generally parallel to the first direction. The front and back components  174 ,  175  are each connected to each of the first outer and second outer components  171 ,  173 . The front component  174  connects the first ends  171   a,    173   a  of the first outer and second outer component  171 ,  173  to one another. The back component  175  connects the second ends  171   b,    1   73   b  of the first outer and second outer components  171 ,  173  to one another. 
     As shown in  FIG.  9   , a portion of the first end  171   a  of the first outer component  171  extends beyond the front component  174  in the first direction (in this example towards the guide rail  20 ), thus defining a first outer front prong  176   a.  A portion of the first end  173   a  of the second outer component  173  extends beyond the front component  74  in the first direction (in this example towards the guide rail  20 ), thus defining a second outer front prong  178   a.  A portion of the second end  171   b  of the first outer component  171  extends beyond the back component  175  in the first direction (in this example towards the backing plate  60 ), thus defining a first outer back prong  176   b.  A portion of the second end  173   b  of the second outer component  173  extends beyond the back component  175  in the first direction (in this example towards the backing plate  60 ), thus defining a second outer back prong  178   b.    
     As shown in  FIG.  8   , the coils  169  of the electromagnets  166  are wound around the first outer component  171  and the second outer component  173  respectively. The first outer component  171  and the second outer component  173  thus form the electromagnetic cores of the electromagnets  166  respectively. The permanent magnet  168  is located at a generally equal distance between the first outer component  171  the second outer component  173 . A first end of the permanent  168  magnets is housed by the front component  174 . A second, opposite end of the permanent magnets  168  is housed by the back component  175 . 
     In the example of  FIG.  8   , the support structure  170  is configured to guide the magnetic flux of the magnetic components of the array of magnetic components. In other words, the magnetic flux produced by the magnetic components of the array is directed to flow preferentially through the ferromagnetic support structure  170  so as to optimise the interactions between the magnetic fields of the two electromagnets  166  and the permanent magnets  168 . The front prongs  176   a,    178   a  of the first outer and second outer components  171 ,  173  are configured to guide the magnetic flux generated by the magnetic components of the array of magnetic components. The back prongs  176   b,    178   b  of the first outer and second outer components  171 ,  173  are configured to guide the magnetic flux generated by the magnetic components of the array of magnetic components. While the support structure  170  has been described in relation to  FIG.  8   , other configurations are envisaged and it will be understood that such a support structure having all or some of the features described in relation to this example could be provided with any example of an actuator according to the disclosure. 
     In a further set of examples of a safety brake system according to the disclosure, the safety brake system may be as shown in the example of  FIGS.  5  to  7    or  FIG.  9    and may operate in substantially the same way as described above. Further, it may be used with a safety brake and linkage mechanism in the manner described above. However, in these examples, when the electromagnet(s) of the first magnetic component or of the two second magnetic components is in a first state, the electromagnet(s) is supplied with an electric current in a first direction of current flow such that the magnetic fields generated by the magnetic components on a first side of the array are summed together to provide an augmented magnetic field on the first side of the array and the magnetic fields generated by the magnetic components on the second, opposite side of the array are summed together to provide a reduced magnetic field on the second, opposite side of the array. In other words, when the electromagnet(s) is in the first state, the actuator is held in a first position against the first ferromagnetic component by the augmented magnetic force on the first side of the array. 
     In this set of examples, the actuator is moved to the second position by reversing the direction of current flow of the electric current supplied to the electromagnet(s), the switching the electromagnet(s) to a second state. In the second position, the actuator is held in position against the second ferromagnetic component by an augmented magnetic force on the second side of the array. It will be appreciated that, in this set of examples, the safety controller is configured to continuously supply current to the electromagnet(s) and that switching the electromagnet(s) from the first state to the second state is achieved by reversing the direction of the current flow supplied. Therefore, in this set of examples the electromagnet(s) is either in the first state or the second state. To reset the safety brake and the actuator, the elevator car  16  is moved upwards until the safety brake is released and the actuator is aligned with the first ferromagnetic component. In some examples, aligning the actuator with the first ferromagnetic component corresponds to moving the actuator from the third position to the second position. The safety controller  79  is configured to then switch the electromagnet(s) to a third state (corresponding here to switching the electromagnet back to the first state) by suppling electric current to the electromagnet(s) in the first direction of current flow. 
     In any of the examples disclosed above, the linkage mechanism  56 ,  156  may take any suitable form for mechanical transmission of the upwards reaction force. Although the linkage mechanism  56 ,  156  has been illustrated in the form of a bar, it could be a wire, or a series of link members, or a plate, for example. In addition, although the safety brake  42  has been illustrated as being positioned below the actuator  44 , it could instead be located above the actuator  44  with the upwards reaction force being transmitted as described. 
     Further, all the examples shown are configured for vertical movement of the elevator car  16  along a guide rail  20 . It will be appreciated however that the examples of the disclosure could equally apply to an elevator or conveyance system in which the conveyance component is configured to move horizontally or in another non-vertical direction. Thus, the safety brake system according to various examples of the disclosure could be used to stop movement of a conveyance device in an upwards direction or in another, non-vertical direction, engagement of the actuator with guide rail causing a reaction force in a direction opposite to the direction of motion of the conveyance device relative to the guide rail, the reaction force causing the linkage to move the safety brake into engagement with the guide rail. 
       FIG.  10    shows a schematic block diagram of emergency braking control for the elevator system  10  and the safety brake systems  40 ,  140 . The elevator system  10  further comprises a speed sensor  92 , accelerometer  94  and a safety controller  79 . The speed sensor  92  measures the speed of descent and ascent of the elevator car  16 . The accelerometer  94  measures the acceleration of the elevator car  16 . The safety controller  79  is arranged to receive a speed signal  96  from the speed sensor  92 , and an acceleration signal  98  from the accelerometer  94 , and to control an electrical power supply  99  to the at least one electromagnet  66  in the safety brake system  40 ,  140 . The safety controller  79  will selectively supply electric current to the at least one electromagnet  66  or each electromagnet  166 , e.g. upon the safety controller  79  detecting an overspeed condition for the elevator car  16  based on the speed signal  96 , or upon the safety controller  79  detecting an over-acceleration condition for the elevator car  16  based on the speed signal  96  or the acceleration signal  98 . In some examples, the safety controller  79  will selectively supply a pulse of electrical current to the electromagnet(s)  66 ,  166  of the first magnetic component or the two second magnetic components. In other examples, the safety controller  79  will selectively supply continuous electrical current to the electromagnet(s)  66 ,  166  of the first magnetic component or the second magnetic components such as to maintain the electromagnet(s) in a given state. 
       FIGS.  11 A and  11 B  show a further example of a safety brake system  240  having an actuator  244  and a safety brake  242  with the safety brake being shown in a first, non-braking position in  FIG.  11 A  and in a second, braking position in  FIG.  11 B . Although the safety brake illustrated in  FIGS.  11 A and  11 B  is a roller-type safety brake, it will be appreciated that the safety brake  242  may take any suitable form. The safety brake system  240  may be mounted to the elevator car frame  14  substantially in the same way as with the example of  FIG.  2   . In the example shown, the mount  249  comprises a single component. It will be understood however, that separate mounting components could be provided as in the earlier examples shown. 
     Regardless of the exact form of the safety brake  242 , the safety brake  242  is coupled to an actuator  244  via a linkage mechanism  256 . The actuator  244  comprises an array of magnetic components and is configured to be moved from a first position, adjacent to a first ferromagnetic component to a second position adjacent a second ferromagnetic component. The array of magnetic components comprises at least one first magnetic component and at least two second magnetic components. The first magnetic component is adjacent to and arranged between the two second magnetic components. The first magnetic component comprises one of a permanent magnet and an electromagnet and the second magnetic components each comprise the other of a permanent magnet and an electromagnet. Thus, when the first magnetic component is a permanent magnet, the two second magnetic components are electromagnets and when the first magnetic component is an electromagnet, the two second magnetic components are permanent magnets. 
     In the example of  FIG.  11 A and  11 B , the array of magnetic components comprises one electromagnet  266  (the first magnetic component) and two permanent magnets  268  (the second magnetic components). The electromagnet  266  is adjacent to and arranged between the two permanent magnets  268  such that the magnetic components are stacked in the direction perpendicular to the guide rail  20 . 
     The actuator  244  is configured to move relative to the mount  249  along an axis parallel to the guide rail  20  between the first position the second position. The actuator  244  is therefore configured to provide movement to the linkage mechanism  256 , thus moving the safety brake  242  between the non-braking and braking positions. The linkage mechanism  256  is coupled at one end to the roller  282  and extends along an axis  283  parallel to the guide rail or generally parallel to the guide rail  20  such as, for example, within 10° of parallel to the guide rail  20 . As seen, the safety brake  242  is located below the actuator  244  in this example such that the linkage mechanism  256  can act to pull the roller  282  upwardly along the “wedge” surface  284  to move the safety brake  242  into the braking position. The roller  282  in the example shown is pulled upwardly along a braking axis, which in the example shown corresponds to the axis  283 . 
     The safety brake system  240  further includes a housing  262  which is fixed to the mount  249  and encloses the actuator  244 . The housing  262  may take any suitable shape and, in the example shown, comprises a hollow body, having a longitudinal axis A-A and first and second closed ends  262   a,    262   b.  A safety lever  285  is provided, and in the example shown, is formed as a continuation of the linkage mechanism  256 . In any example of the disclosure, the safety lever  285  may alternatively be a separate component from the linkage mechanism  256 . The safety lever  285  extends into the housing  262  through the first closed end  262   a  thereof along a lever axis, which in the example shown corresponds to the longitudinal axis A-A of the housing  262  and extends parallel to the guide rail  20 . 
     The actuator  244  is substantially the same as the actuator of the example of  FIGS.  2  and  5   .  FIG.  11 A  shows the safety brake system  240  in a non-braking position when the actuator  244  is in the first position, e.g. upon installation or after reset. In this position, the actuator  244  is held in contact with the first closed end  262   a  of the housing  262  (the first ferromagnetic component) by the attractive magnetic force between the permanent magnets  268  and the first closed end  262   a.  In the first position, actuator  244  is spaced from the second closed end  262   b  of the housing  262  (the second ferromagnetic component). In the first position, the electromagnet  266  is in a first state, in this example receiving no electric current and thus not generating a magnetic field. 
     A safety controller  79  (as show on  FIG.  10   ) is in electrical communication with the electromagnet  266 . If a freefall, over-speed, or over-acceleration condition of the elevator car  16  is detected by the governor  22 , the safety controller  79  is configured to switch the electromagnet to a second state by suppling a pulse of electric current to the electromagnet  266  in a first direction of current flow. In other words, the safety controller  79  is configured to energise the electromagnet  266  with a first polarity. When the electromagnet  266  is in the second state, the magnetic fields generated by the respective components of the array interact such that the magnetic fields generated by the magnetic components on a first side of the array are summed together to provide an augmented magnetic field on the first side of the array. In contrast, the magnetic fields generated by the magnetic components on a second, opposite side of the array are opposed and so sum together to provide a reduced magnetic field on the second, opposite side of the array. Thus, the array can be configured such that when the electromagnet  266  is in the second state, an attractive magnetic force between the array and the first closed end  262   a  is reduced or cancelled and an attractive magnetic force between the array and the second closed end  262   b  is strong or augmented. Thus, the actuator  244  (in this example, the frame  270 ) will be moved into contact with the closed end  262   b,  in other words to the second position, by the attractive magnetic force generated between the array of magnetic components and the closed end  262   b.  In the example of  FIG.  11 B , the actuator  244  is stopped by and/or rests against the second closed end  262   b  of the housing  262  when in the second position. 
     The safety lever  285  is connected to the actuator  244  and is thus moved along the axis  283  in the direction of travel of the actuator  244 . The safety lever  285  is continuous with or coupled to the linkage mechanism  256  as described above in relation to  FIGS.  11 A and  11 B . The linkage mechanism  256  is linked to the roller  282  or a similar component of the safety brake  242  such that the movement of the safety lever  285  pulls the roller  282  or other safety brake component upwardly in the example shown (but more generally in a direction opposite to the direction of movement of the elevator car  16  during a freefall, over-speed, or over-acceleration condition). The safety lever  285  thus acts to move the safety brake  242  into the braking position such that it engages the guide rail  20  and prevents further downwards motion of the elevator car  16 . In other words, the safety brake  242  is actuated as a result of the electromagnet  266  being switched by the controller  79  from a first state when the electromagnet  266  is not supplied with an electric current to a second state when the electromagnet  266  is supplied with an electric current in a first direction. 
     In  FIG.  11 B , the actuator  244  of  FIG.  11 A  is shown in the second position after the electromagnet  266  has been switched to the second state. The electromagnet  266  reverts back to the first state once the safety controller  79  ceases supplying the pulse of electric current to the electromagnet  266 . It will be understood that once the electromagnet  266  ceases generating a magnetic field, the magnetic fields generated by the respective components of the array can no longer interact to augment the magnetic fields generated by the magnetic components on the first side of the array and to cancel the magnetic field on the second opposite side. When the actuator  244  reverts to the first state, the actuator  244  is held in the second position against the second closed end  262   b  by the magnetic attraction between the permanent magnets  268  and the closed end  262   b.  In other words, the actuator  44  is magnetically attached to the closed end  262   b  in the second position. 
     To reset the safety brake  242  and the actuator  244  of the safety brake system  240  from the braking to the non-braking position, the safety controller  79  is configured to switch the electromagnet  266  to a third state by suppling a pulse of electric current to the electromagnet  266  in a second direction of current flow, wherein the second direction of current flow is opposite to the first direction of current flow. When the electromagnet  266  is in the third state, the magnetic fields generated by the respective components of the array interact such that the magnetic fields generated by the magnetic components on the second side of the array are summed together to provide an augmented magnetic field on the second side of the array. In contrast, the magnetic fields generated by the magnetic components on the first, opposite side of the array are opposed and so sum together to provide a reduced magnetic field on the first side of the array. Thus, the array can be configured such that when the electromagnet  266  is in the third state, an attractive magnetic force between the array and closed end  262   b  is reduced or cancelled and an attractive magnetic force between the array and the first closed end  262   a  is strong or augmented. Thus, the actuator  244  (in this example, the frame  270 ) will be moved into contact with the closed end  262   a  to the first position by the attractive magnetic force between the array of magnetic components and closed end  262   a.  Once the electromagnet  266  ceases to be supplied with electric current, the actuator  244  is held in the first position by the magnetic force between the permanent magnets  268  and the first closed end  262   a.  In this and other examples, the elevator car  16  may optionally be moved along the guide rail  20  in a direction opposite to the direction of movement of the elevator car  16  during a freefall, over-speed, or over-acceleration condition prior to the electromagnet  266  being switched by the safety controller  79  so as to reset the safety brake. 
     With reference to  FIG.  10   , the elevator system  10  comprises a safety controller  79 . The elevator system  10  further comprises a speed sensor  93  and an accelerometer  94 . The speed sensor  92  measures the speed of descent and ascent of the elevator car  16 . The accelerometer  94  measures the acceleration of the elevator car  16 . The safety controller  79  is arranged to receive a speed signal  96  from the speed sensor  92 , and an acceleration signal  98  from the accelerometer  94 , and to control an electrical power supply  99  to the at least one electromagnet  266  in the safety brake system  240 . In a set of examples, the elevator system  10  may comprise either a speed sensor  93  or an accelerometer  94 . In some examples, the speed sensor  93  may measure the acceleration and the speed of descent and ascent of the elevator car  16 . In other examples, the accelerometer  94  may measure the acceleration and the speed of descent and ascent of the elevator car  16 . 
     The safety controller  79  will selectively supply electric current to the at least one electromagnet  266 , e.g. upon the safety controller  79  detecting an overspeed condition for the elevator car  16  based on the speed signal  96 , or upon the safety controller  79  detecting an over-acceleration condition for the elevator car  16  based on the speed signal  96  or the acceleration signal  98 . In some examples, the safety controller  79  will selectively supply a pulse of electrical current to the electromagnet(s)  266  of the first magnetic component or the two second magnetic components. In other examples, the safety controller  79  will selectively supply continuous electrical current to the electromagnet(s)  266  of the first magnetic component or the second magnetic components so as to maintain the electromagnet(s) in a given state. 
     In a further set of examples of a safety brake system according to the disclosure, the safety brake system may be as shown in the example of  FIGS.  10 A and  10 B  and may operate in substantially the same way as described above. Further, it may be used with a safety brake and linkage mechanism in the manner described above. However, in these examples, the actuator comprises an array of magnetic components comprising a permanent magnet arranged between two electromagnets. In these examples, the array is configured such that the magnetic fields, generated by the two electromagnets when electric current is supplied by the safety controller, are opposite in direction to each other. The magnetic field generated by the permanent magnet has a direction substantially perpendicular to the magnetic fields of the two electromagnets. As a result, the magnetic fields generated by the two electromagnets and the permanent magnet interact such that the array of magnetic components generates an augmented magnetic field on one side of the array and a reduced magnetic field on another side of the array. 
     In a further set of examples of a safety brake system according to the disclosure, the safety brake system may be as shown in the example of  FIGS.  11 A and  11 B  and may operate in substantially the same way as described above. Further, it may be used with a safety brake and linkage mechanism in the manner described above. However, in these examples, when the electromagnet(s) of the first magnetic component or of the two second magnetic components is in a first state, the electromagnet(s) is supplied with an electric current in a first direction of current flow such that the magnetic fields generated by the magnetic components on a first side of the array are summed together to provide an augmented magnetic field on the first side of the array and the magnetic fields generated by the magnetic components on the second, opposite side of the array are summed together to provide a reduced magnetic field on the second, opposite side of the array. In other words, when the electromagnet(s) is in the first state, the actuator is held in a first position against the first ferromagnetic component by the augmented magnetic force on the first side of the array. 
     In this set of examples, the actuator is moved to the second position by reversing the direction of current flow of the electric current supplied to the electromagnet(s), the switching the electromagnet(s) to a second state. In the second position, the actuator is held in position against the second ferromagnetic component by an augmented magnetic force on the second side of the array. It will be appreciated that, in this set of examples, the safety controller is configured to continuously supply current to the electromagnet(s) and that switching the electromagnet(s) from the first state to the second state is achieved by reversing the direction of the current flow supplied. Therefore, in this set of examples the electromagnet(s) is either in the first state or the second state. To reset the safety brake and the actuator, the elevator car  16  is moved upwards until the safety brake is released. The safety controller is configured to then switch the electromagnet(s) back to the first state by suppling electric current to the electromagnet(s) in the first direction of current flow. 
     It will be appreciated by those skilled in the art that the disclosure has been illustrated by describing one or more examples thereof, but is not limited to these examples; many variations and modifications are possible, within the scope of the accompanying claims. For example, the safety brake system may be used in a roped or ropeless elevator system, or another type of conveyance system.