Abstract:
A system for braking an escalator or moving walkway includes a handrail and passenger support in registration with one another so as to move together. A braking tensioner selectively increases tension in the handrail during operation. The increased tension serves to frictionally brake the handrail and hence the passenger support. The braking tensioner may be located in any of various locations depending upon system design, and may be driven in any suitable manner, e.g., hydraulically, electrically, electromagnetically, and so on. Frictional wear on the handrail is reduced by the fact that the described braking system spreads the frictional load over a large area of the handrail, e.g., the many locations where the handrail contacts the underlying support throughout its length.

Description:
TECHNICAL FIELD 
       [0001]    This patent disclosure relates generally to passenger conveyors and, more particularly to a braking system for passenger conveyors. 
       BACKGROUND 
       [0002]    As our world becomes faster and more automated, the need for all manner of passenger conveyors continues to increase, as does the load on existing conveyance devices. Within the built environment, several types of conveyors, namely elevators, escalators and moving walkways made larger and more efficient buildings possible throughout the last century. 
         [0003]    Nonetheless, as the demand for passenger conveyance continues to increase and the existing infrastructure in place continues to age, the requirement to periodically halt and repair or modify escalators and walkways in particular has become significant. Moreover, whatever the state of repair may be, an escalator may occasionally need to be stopped for emergency reasons, such as when a passenger is experiencing trouble with the system. 
         [0004]    When an escalator is stopped, two things must occur. First, the motor powering the escalator, typically a powerful electrical motor, is deactivated. Secondly, at essentially the same time a brake is applied to prevent movement of the escalator until it is reactivated for use. Because of the importance of proper braking, it is typical to equip passenger conveyor systems with two braking systems, namely, an operational brake and an auxiliary brake. The operational brake is typically located in the drive system and is used for routine stopping and holding of escalators. The auxiliary brake, in contrast, is an additional safety brake, usually found in the main drive assembly in the upper landing area, and is activated in accordance with local safety codes when conditions warrant. Each of these braking systems requires space for installation and operation, and also requires periodic inspection, repair, and maintenance. 
         [0005]    Thus, while braking of the passenger conveyor is important, the way in which braking is accomplished in modern passenger conveyors may be improved to reduce the space requirements and financial cost imposed by braking systems as well as to improve reliability. To this end, the inventor describes a new braking system for passenger conveyors as discussed below. 
         [0006]    It will be appreciated that this background description has been created by the inventor to aid the reader, and is not to be taken as a reference to prior art, nor as an indication that any of the indicated problems were themselves appreciated in the art. 
       SUMMARY 
       [0007]    In overview, the described system provides in one embodiment a passenger conveyor having an improved braking system. The passenger conveyor includes a passenger support configured to support one or more passengers and a continuous handrail linked to the passenger support so that the two portions move in registration with one another. The handrail may be guided on its path by a handrail guide. A drive system is provided for driving the passenger support and handrail while conveying one or more persons standing on the passenger support. A brake system selectively prevents movement of the handrail and thus the passenger support portion via a tensioner for selectively increasing a tension in the continuous handrail such that friction between the handrail and the underlying support is increased and the handrail is precluded from moving, thereby stopping the movement of the passenger support. 
         [0008]    The passenger conveyor may be any one of a number of device types, including escalators and moving sidewalks. Similarly, the passenger support may employ a linked plurality of treadplates, such as steps or pallets, or a conveyor belt. 
         [0009]    In an embodiment of the invention, the tensioner includes a tension bow adjacent the handrail and a forcing member associated with the tension bow for forcing the tension bow against the handrail. The tension bow may be a roller bow, a sliding bow, or other mechanism for engaging the handrail. 
         [0010]    The handrail may traverse first and second turnaround portions where the continuous handrail turns substantially one hundred and eighty degrees, transition curve portions, as well as one or more linear portions wherein the continuous handrail moves in a linear fashion. The tensioner may be located at any one of these locations, or may be located adjacent a handrail drive pulley or at any other convenient location along the path of the handrail. The forcing member associated with the tension bow may be hydraulically actuated, electrically actuated, electro-magnetically actuated, or spring actuated. 
         [0011]    In another embodiment of the invention, a method is provided for braking a passenger conveyor having a passenger support and a handrail linked to the passenger support such that the passenger support and the continuous handrail move in registration with one another. The method includes detecting a need to brake the passenger conveyor and selectively increasing a tension of the handrail to increase the friction between the handrail and underlying support until the handrail is precluded from moving, thus also stopping the passenger support portion. 
         [0012]    The passenger conveyor in accordance with this embodiment of the invention may be an escalator or a moving sidewalk, for example, and the passenger support may include one of a conveyor belt and a linked plurality of treadplates, such as steps or pallets. 
         [0013]    In an aspect of this embodiment of the invention, the passenger conveyor includes a tension bow adjacent the handrail and a forcing member associated with the tension bow. In this case, selectively increasing a tension of the handrail is executed by forcing the tension bow against the handrail via the forcing member. 
         [0014]    As with other embodiments of the invention, the tension bow may be, for example, a roller bow or a sliding bow. The tension bow may be forced against the handrail at any suitable location including at a turnaround portion where the handrail turns one hundred and eighty degrees, transition curve portions, adjacent a handrail driving pulley, or in a linear portion or at any other convenient location along the path of the handrail. 
         [0015]    As with other embodiments, the forcing of the tension bow against the handrail may be carried out by any one or more of a hydraulic mechanism, an electro-magnetic mechanism, an electrical mechanism, and a spring mechanism. 
         [0016]    In a further embodiment of the invention, a brake system for application to a passenger conveyor is provided. In this embodiment, a tension element configured to engage the passenger handrail of the passenger conveyor is provided to selectively increase tension therein. A forcing member is linked to the tension element and configured to selectively force the tension element against the passenger handrail for slipping engagement when actuated to provide a braking force resulting from increased tension of the handrail. 
         [0017]    As in other embodiments, the tension element may for example be one of a roller bow and a sliding bow, and the forcing member may be actuated via one of hydraulic, electro-magnetic, electrical, and spring force. 
         [0018]    It will be appreciated that different embodiments of the invention are not mutually exclusive, and that elements from any embodiment may be combined with one or more elements from any other embodiment, and that the division of the discussion into embodiments is made in order to break the disclosure down for reader convenience and not to signify different mutually exclusive inventions. Further and alternative aspects and features of the disclosed principles will be appreciated from the following detailed description and the accompanying drawings, of which: 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1  is a schematic elevation view of an escalator within which embodiments of the disclosed principles may be implemented; 
           [0020]      FIG. 2  is a detailed schematic elevation view of a handrail movement system with respect to which embodiments of the disclosed principles may be implemented; 
           [0021]      FIG. 3  is a perspective cut away view of a handrail drive mechanism for use in installations having an opaque balustrade; 
           [0022]      FIG. 4  is a schematic detail view of a handrail drive portion of an escalator as used in a glass balustrade installation; 
           [0023]      FIG. 5  is a schematic view of a lower linear handrail portion having a braking tension system; and 
           [0024]      FIG. 6  is a simplified schematic view of a handrail and associated drive system showing certain alternative friction zones wherein tensioning may be implemented to provide braking in keeping with the described principles. 
       
    
    
     DETAILED DESCRIPTION 
       [0025]    This disclosure relates to passenger conveyors having a moving step or standing portion, such as steps or floor segments, linked to one or more coordinated moving handrails for passenger support. The handrails are typically located on either side of the conveyor, within arm&#39;s reach of passengers on the conveyor. Typical embodiments include escalators and incline moving walkways for both vertical and horizontal movement of passengers as well as horizontal moving walkways for horizontal movement of passengers. The former may be used to move passengers between a limited number of contiguous floors in a building, while the latter may be used to quickly move passengers throughout a large flat space such as between airport terminals in an airport. 
         [0026]    In overview, the described system provides an improved braking system that serves the role of either the operational brake system or the auxiliary brake system or both. The described braking system can be installed as a part of a new installation or may be provided as a retrofit to an existing installation. In either case, the handrail friction, which is typically minimized, is selectively employed to provide a strong braking force. Due to the mechanical link between the handrail and the conveyor, the stopping of the handrail also serves to reliably stop the conveyor itself. 
         [0027]    Turning now to the details of certain exemplary embodiments,  FIG. 1  is a schematic elevation view of an escalator as summarized in the brief description of drawings above. The illustrated escalator  10  includes a frame  12 , drive system  14 , step chain  16 , steps  18 , roller tracks  20 , and balustrade assemblies  22 . The frame  12  includes truss section  24  on both the left and right hand sides of frame  12 , although only one side is visible in the figure. Each truss section  24  has two end sections  26  parallel to one another, connected by an inclined midsection  28 . The end sections  26  form upper landing  30  at upper elevation  32  and lower landing  34  at lower elevation  36 . Matching pairs of roller tracks  20  are attached on the inside of each truss section  24 , i.e. the side of truss section  24  facing the other truss section  24 . The region between inclined midsection  28  and landings  30 ,  34  in which the slope of roller track  20  is changing from the slope of incline  28  to the slope of landings  30 ,  34 , is defined to be transition region  38 . 
         [0028]    The upper landing  30  houses the escalator drive  14 , between truss sections  24 . The drive  14  powers a pair of step chain sprockets  40 , which in turn impart linear motion to step chains  16 . Steps  18  are connected to step chains  16  and guided along roller tracks  20  as they are driven along with step chains  16  by escalator drive  14 . Step chains  16  and steps  18  travel through closed loop path  42  (shown in phantom in  FIG. 1 ), running from one elevation to the other elevation ( 32 ,  36 ), and back. The regions of the closed loop path through which step chains  16  and steps  18  travel include two turnarounds  44  as chain  16  and steps  18  travel around two sprockets  40  or one sprocket and one turnaround track at upper and lower landings  30 ,  34 . 
         [0029]    As noted above, the drive  14  powers step chain sprocket  40  being associated with the upper landing  30 . In an embodiment, the step chain sprocket  40  associated with the upper landing  30  has affixed thereto a handrail drive sprocket  46  for driving a handrail movement system  48 , which will be described in greater detail below. In an embodiment, the handrail drive sprocket  46  is a double sprocket configured to drive the handrail movement system  48  via two chains in parallel. 
         [0030]    Turning to  FIG. 2 , a schematic elevation view of the handrail movement system  48  and related components and systems is shown in greater detail. As noted, the handrail movement system  48  is driven from a paired sprocket on the main drive assembly step chain sprocket  40  via handrail drive chain  50 , which may be a single multiplex chain or multiple chain strands in order to transfer sufficient force to both drive the handrail and brake the main drive assembly. Within the handrail movement system  48 , the handrail drive chain  50  is linked via a driven sprocket  52  to a handrail drive pulley  54  affixed to the driven sprocket  52 . 
         [0031]    The handrail drive pulley  54  is positioned and configured to drive the handrail of the escalator in driving condition. However, it is driven by the handrail in the braking condition. In particular, a pair of outer roller guides  56  in cooperation with a wrapping roller guide  58  serve to partially wrap the handrail  60  on the handrail drive pulley  54 . In this way, when the handrail drive pulley  54  rotates, the handrail  60  is pulled forward or backward. Because the handrail  60  forms a continuous loop around the escalator side structure, the entire handrail  60  moves. The gearing relationships of the rotating parts and the size of the handrail drive pulley  54  are used to establish the speed at which the handrail  60  moves relative to rotation of the drive system  14 . In this way, the movement of the handrail  60  is registered with the movement of the steps  18 , for both driving and braking the two components synchronously. 
         [0032]    While the arrangement of  FIG. 2  for moving the handrail  60  serves to hide the handrail driving mechanism in installations having a glass balustrade, other arrangements may be used as well.  FIG. 3  is a perspective cut away view of a handrail drive mechanism for use in installations having an opaque balustrade. Most of the handrail  60  has been omitted for clarity in this view. 
         [0033]    As can be seen, the handrail  60  rides on and is retained by an underlying structure such as handrail guide  62 . The handrail  60  is propelled by drive pulley  64  positioned in the illustrated embodiment as a turnaround at the upper landing. The drive pulley  64  is driven by chain drive  66  registered with a step drive system (not shown in this figure) similar to the drive arrangement shown in  FIG. 1 . It will be appreciated that a roller guide system  68  is beneficial in this arrangement as well in order to ensure continued registration of the handrail  60  with the drive pulley  64  and the handrail guide  62 . 
         [0034]    The handrail drive pulley  64  is positioned and configured to drive the handrail of the escalator in driving condition and transfer braking forces from the handrail in the braking condition. With respect to the driving condition, the handrail  60  will have been initially adjusted during installation or repair to transfer enough driving force by frictional coupling between handrail  60  and handrail drive pulley  64 . Similarly, braking force is transferred from the handrail  60  to the handrail drive pulley  64  via frictional engagement between handrail  60  and handrail drive pulley  64 . In this way, when the handrail drive pulley  64  rotates, the handrail  60  is pulled forward or backward. Because the handrail  60  forms a continuous loop around the escalator side structure, the entire handrail  60  moves. 
         [0035]    The gearing relationships of the rotating parts and the size of the handrail drive pulley  64  are used to establish the speed at which the handrail  60  moves relative to rotation of the drive system  14 . In this way, the movement of the handrail  60  is registered with the movement of the steps  18 , for both driving and braking the two components synchronously. 
         [0036]    In the illustrated arrangements as well as other drive arrangements, the handrail experiences frictional resistance with the underlying guide structure. This frictional resistance can cause substantial loss of efficiency of the entire escalator if the tension of the handrail is not properly set. At the same time, if the handrail tension is set too low, the handrail may lose lateral registration with the underlying guide structures and/or may lose registration with the steps by slipping, e.g., on the drive pulley. 
         [0037]    Although handrail friction has always been viewed as a problem requiring minimization, the inventor has found that he can manipulate the handrail tension to provide a beneficial braking action. In particular, handrail friction is a function of normal force between the handrail and an underlying guide surface, and that the normal force is a function of the tension in the handrail. Therefore, increased handrail tension results in increased friction forces that can be used to brake the handrail, and with it, the passenger-bearing elements as well. Thus, while the handrail tension should still be set to maximize efficiency, i.e., to reduce running friction to the lowest possible level, a separate additional mechanism is included in an embodiment for selectively increasing the tension of the handrail and thus increasing the frictional resistance experienced by the handrail. 
         [0038]    Although the initial tension of the handrail may indeed be increased to a level sufficient to prevent movement of the escalator, the regular operation of the escalator requires that the handrail and steps be free to move. Thus, the initial tension of the handrail must be set to a conventional lower level that allows such movement, and a system is provided in an embodiment for selectively increasing the handrail tension only when braking is desired. 
         [0039]      FIGS. 4 and 5  illustrate two configurations by which the handrail tension may be selectively increased to facilitate operational and/or auxiliary braking of the escalator. Referring to  FIG. 4  specifically, this figure shows a schematic detail view of the handrail drive portion of an escalator as used in a glass balustrade installation. The illustrated portion includes a handrail drive pulley  62  driving handrail  74 . The handrail  74  is guided by roller bow assemblies  76 . In the illustrated embodiment, at least one of the roller bow assemblies  76  (tension element) is linearly actuated via a driver  78  (forcing element) toward or away from the handrail drive pulley  62  so as to increase or decrease the tension of the handrail  74 . 
         [0040]    The driver  78  may be mechanical, hydraulic or magnetic, and/or may include a spring for actuation. Examples of mechanical drives include screw drives, rack and pinion drives, and so on, while examples of hydraulic drives include hydraulic rams and scissor drives among others. A magnetic drive may use magnetic force either to hold the roller bow  76  in the non-braking position until actuated, or may use magnetic force to drive the roller bow  76  toward the handrail drive pulley  72  at the time of actuation. In any event, the braking system may be triggered automatically or manually. Similarly, after actuation, the roller bow  76  may be returned to the non-braking position manually or automatically. In the illustrated embodiment, the necessary force to apply to the roller bow will be dependent on the specific design of the passenger conveyor, handrail length, type of friction surfaces, incline angle, materials used, etc. 
         [0041]    In another embodiment, the tension system for braking is located in the linear portion of the handrail run. This situation is illustrated in  FIG. 5 , which is a schematic view of a lower linear handrail portion having a braking tension system. In the illustrated embodiment, the handrail  80  in normal operation is surrounded by a plurality of roller guides  82  beneath it and a tension bow  84  above it. The tension bow may be of a roller or sliding type, with the required braking tension to be adjusted accordingly as described above. 
         [0042]    During braking operation, the tension bow  84  pushes downward on the handrail  80 , which is constrained from beneath by the plurality of roller guides  82 . In this way, the tension P o  of the handrail may be increased to the required braking level. As with the prior embodiment, the tension bow  84  may be actuated in any number of ways, including mechanical, hydraulic, magnetic, spring, etc. (not shown). The force with which the tension bow  84  must be actuated depends upon the angle of the handrail under the tension bow  84  during actuation. 
         [0043]    The tension bow  84  acting on the handrail  80  displaces the handrail  80  and forces a bend of angle α into the handrail  80 . In general, the larger the angle α, up to 180° (i.e., the flatter the handrail in the region of displacement), the lower the applied force (F) requirement. Although the handrail  80  under the tension bow  84  is initially at 180°, it will deflect slightly to a final angle α that determines a fractional multiplier for the applied force required. Exemplary values for the multiplier are as follows: 
         [0000]                                                          α (deg)   F(N)                                        80   153.2% × P 0             90   141.4% × P 0             100   128.6% × P 0             110   114.7% × P 0             120   100.0% × P 0             130    84.5% × P 0             140    68.4% × P 0             150    51.8% × P 0             160    34.7% × P 0             170    17.4% × P 0                          
Thus, for example, a curvature of 150° serves to reduce the applied force by about 50% of the required initial handrail tension force (P 0 ) to stop the passenger conveyor, while a curvature of 170° reduces the applied force by more than 80%. This leverage effect is due to the fact that a force applied along the base of a right triangle toward the hypotenuse results in a geometrically amplified resultant force along the hypotenuse, with the lowest amplification being essentially one (when the hypotenuse and base leg are essentially equal) and the highest amplification approaching infinity as the base leg (displacement) approaches zero. Quantitatively, given the geometric arrangement shown in  FIG. 5 , the amplification factor is (sin(90°−α/2)) −1 .
 
         [0044]    Because of the shallow bend in the handrail  80  allowed in the embodiment of  FIG. 5 , this embodiment is capable of providing a leverage advantage over the arrangement shown in  FIG. 4 . However, there are yet other ways in which the required braking force may be applied in keeping with the described principles.  FIG. 6  shows a number of alternative arrangements, but should not be taken as an exhaustive illustration of all remaining brake tension application configurations. 
         [0045]    In particular,  FIG. 6  is a simplified schematic view of a handrail  88  and associated drive system  90 , also showing certain alternative friction zones wherein tensioning may be implemented to provide braking in keeping with the described principles. The illustrated tension zones include a lower turn-around zone  92  and an upper turn-around zone  94 . In addition, the illustrated schematic also shows transition zone  96 . 
         [0046]    The handrail tensioners in the various zones  92 ,  94 ,  96  may be implemented in any suitable fashion to increase handrail tension to a point where braking results. In an embodiment, handrail tensioners at the turn-around zones  92 ,  94  are implemented via roller or sliding turn-around bows  98 ,  100  located at the escalator ends. The handrail tensioner  102  located in the transition zone  96  is also illustrated as a roller or sliding bow. Although multiple handrail tensioner devices  98 ,  100 ,  102  are shown, it will be appreciated that a single tensioner may be used to increase the tension of the entire handrail, or a combination of tensioners may be used to provide both an operational brake and a redundant auxiliary brake. 
         [0047]    As with the previously described embodiments, the handrail tensioners  98 ,  100 ,  102  may be tensioned via any suitable forcing mechanism. In various embodiments, the forcing mechanism includes one or more of a hydraulic piston or scissor, an electrical actuator such as a worm drive or other drive, an electro-magnetic drive, or a spring drive. 
         [0048]    The described system has the additional benefit of spreading the frictional wear on the handrail over a large percentage of the area of the handrail instead of concentrating wear on a small area or element. In particular, although the increased handrail tension may be caused by a tensioner in a single area, the friction that results from the increase in tension occurs essentially every place the handrail contacts the underlying support throughout its length. 
         [0049]    It will be appreciated that tensioner types and forcing systems other than those expressly mentioned herein may be used in keeping with the described principles. In addition, while the illustrated examples describe primarily escalator systems, it will be appreciated that the described principles apply equally to moving walkways and other passenger conveyor systems having a moving step or standing portion linked to a coordinated moving handrail portion. 
         [0050]    Moreover, although the illustrations herein generally show a single handrail and certain aspects and features of the handrail, it will be appreciated that a passenger conveyor such as an escalator or moving sidewalk will typically have two such handrails, both of which are linked to the moving step portion of the device. Thus, it will be appreciated that the described tensioning systems may be implemented on a single one of, or both, such handrails. Further, it is contemplated that while tensioning systems implemented on both handrails will typically match, such is not required, and different tensioning systems may be used on different handrails of the same passenger conveyor without departing from the scope of the described principles. 
         [0051]    Further, although illustrated as being implemented in either a pulley drive system as shown in  FIG. 2  or a turnaround drive in  FIG. 3 , it will be appreciated that the described principles apply equally to other types of handrail drives systems, such as linear handrail drive systems. 
         [0052]    Thus, it will be appreciated that the foregoing description provides useful examples of the disclosed system and technique. However, it is contemplated that other implementations of the disclosure may differ in detail from the foregoing examples. All references to the disclosure or examples thereof are intended to reference the particular example being discussed at that point and are not intended to imply any limitation as to the scope of the disclosure more generally. All language of distinction and disparagement with respect to certain features is intended to indicate a lack of preference for the features of interest, but not to exclude such from the scope of the disclosure entirely unless otherwise specifically indicated.