Abstract:
A passenger conveyor drive belt assembly ( 40 ) includes a belt support ( 60 ) that facilitates proper engagement between the drive belt ( 42 ) and corresponding links ( 32 ) of a step chain ( 30 ) under selected conditions such as a full brake application. The belt support ( 60 ) preferably is positioned between a drive sheave ( 50 ) and an idler sheave ( 52 ) within the loop traveled by the drive belt. The belt support ( 60 ) includes at least one moveable support member ( 62 ) that does not contact the inner surface of the drive belt during normal operation conditions. In one example, the belt support ( 60 ) comprises a plurality of rollers ( 62 ).

Description:
FIELD OF THE INVENTION 
   This invention generally relates to passenger conveyor drive systems. More particularly, this invention relates to a drive belt assembly for a passenger conveyor. 
   DESCRIPTION OF THE RELATED ART 
   Passenger conveyors such as escalators or moving walkways typically include a plurality of steps or pallets that move in a loop pattern. A drive assembly for moving the steps typically is supported within a building structure underneath the corresponding floor or enclosed so that it is hidden from view. Over the years, there has been a desire to move away from overly complicated and large machinery. Those skilled in the art have strived to improve passenger conveyor drive systems to make them easier to incorporate into building structures and more economical, for example. 
   One difficulty associated with many escalator drive systems is the need for frequent maintenance or repair. Not only does this introduce costs for maintaining escalator systems, but it also presents a difficulty to maintenance technicians. The need to hide escalator drive components underneath floors or within other structures of a building necessarily places constraints on the ability to readily access components for repair or replacement. 
   There is a need for an improved escalator drive system. There are a variety of challenges and obstacles to be overcome in successfully designing such a drive system. This invention provides a unique belt drive arrangement that has a support assembly for ensuring satisfactory performance of the drive system in a variety of circumstances. 
   SUMMARY OF THE INVENTION 
   In general terms, this invention is an assembly for driving a passenger conveyor system. A drive assembly designed according to this invention includes a drive belt that has a cogged surface that is adapted to engage correspondingly configured links of a step chain associated with a plurality of steps. The drive belt forms a loop. A drive sheave is positioned at one end of the loop and engages an inner surface of the drive belt to move the belt around the loop. An idler sheave is positioned at an opposite end of the loop and engages the inner surface of the drive belt. The idler sheave moves with the belt responsive to movement of the drive sheave. A belt support is positioned between the drive sheave and the idler sheave. The belt support has at least one moveable element spaced from the inner surface of the belt yet close enough to engage the belt inner surface as the belt moves toward the belt support under certain conditions to ensure a desired engagement between the cogged surface of the drive belt and the links of the step chain links near the belt support. 
   The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiments. The drawings that accompany the detailed description can be briefly described as follows. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  diagrammatically illustrates an escalator system. 
       FIG. 2  schematically illustrates selected portions of an example embodiment of a drive assembly designed according to this invention. 
   

   DETAILED DESCRIPTION 
     FIG. 1  shows a passenger conveyor system  20  that includes a plurality of steps  22  that are adapted to carry passengers between landings  24  and  26  in a conventional manner. An escalator is illustrated in  FIG. 1  as an example passenger conveyor. This invention is equally applicable to moving walkways or other passenger conveyors. 
   Referring more particularly to the broken away portion of  FIG. 1  and  FIG. 2 , a  25  step chain  30  is associated with the steps  22 . The step chain  30  includes a plurality of step chain links  32  having teeth  34  that cooperate with a drive module  40  to provide the desired movement of the steps  22 . The step chain  30  is associated with the steps  22  and any of a variety of known manners. 
   The drive module  40  includes a belt  42  having a toothed, outer engaging surface  44  with a plurality of teeth  46  that cooperate with the teeth  34  on the step chain links  32 . The belt  42  preferably includes reinforcing members such as steel cords or polymer strands encased in a polymer material. As the belt  42  moves around a loop, the teeth  46  on the outer surface  44  engage the teeth  34  on the step chain links  32  to provide the desired movement of the step chain  30  and the steps  22 . 
   The loop around which the belt  42  travels has a drive sheave  50  at one end and an idler sheave  52  at the other end. A drive machine  54  having a conventional motor and brake arrangement propels the drive sheave  50  such that a toothed surface  56  on the drive sheave  50  engages teeth  57  on an inner surface  58  of the belt  42  to propel the belt around the loop. 
   Under normal operating conditions, the teeth  46  on the belt  42  cooperate with the teeth  34  on the step chain links  30 . According to this invention, the belt  42  is in proper, desired engagement with the step chain links  32  under normal operating conditions. There are situations, however, where unusually high loads are imposed on the step chain  30  and consequently the belt  42  where separation forces tend to separate the teeth  46  from the teeth  34 . An example of such a situation is where a full brake application to stop the escalator occurs when there are passengers present on the escalator. 
   For such situations, the inventive arrangement includes a belt support  60  that operates to maintain proper engagement between the belt  42  and the step chain links  32  even under such unusual operation conditions. The belt support  60  includes at least one moveable member that is spaced from the inner side  58  of the belt  42  in a region of the belt between the drive sheave  50  and the idler sheave  52 . 
   In the illustrated embodiment, the belt support  60  includes a plurality of rollers  62  that are supported on a bracket  64 , which is supported by the structure supporting other portions of the drive module, which is associated with the escalator truss structure (not illustrated) in one example. The rollers  62  normally do not engage the inner surface  58  of the belt  42 . Under selected operating conditions, such as a full brake application when separation forces tend to urge the belt  42  away from the step chain links  32 , the belt  42  moves toward the belt support  60  until the inner surface of the belt  42  contacts the belt support  60 , which maintains proper engagement between the teeth  46  on the belt  42  and the teeth  34  on the step chain links  32 . 
   The illustration exaggerates the preferred spacing between the rollers  62  and the inner side of the belt  42 . In one example, the outside surface of the rollers  62  that is closest to the inner side  58  of the belt  42  are separated by a distance in a range from approximately 0.5 to 1 millimeter. Such a spacing between the rollers  62  and the inner side of the belt  42  keeps the rollers from contacting the belt under normal operating conditions. Under the more severe operating conditions, such as the stop with a fall brake load, the rollers engage the belt and maintain the desired engagement between the belt  42  and the step chain links  32 . 
   The rollers  62  in one example have an axial length that is equal to a width of the belt  42 . The rollers  62  preferably have an outside dimension (i.e., diameter) that is substantially larger than a spacing between the teeth  58  on the inner side of the belt  42 . The rollers  62  in one example have a smooth outside surface. A variety of materials may be selected for making the rollers  62 , depending on the particulars of the belt  42 . 
   The inventive arrangement has advantages compared to an arrangement where a belt support continuously engages the drive belt, for example. With this invention, there is no noise or vibration introduced by the backup rollers  62  during normal system operation. Additionally, the rollers and bearings can be less expensive components as they only operate under limited circumstances where noise or vibration are not a primary concern. The inventive arrangement, therefore, provides cost savings and enhanced system operation characteristics such as smoother and quieter movement. 
   Given this description, those skilled in the art will be able to realize appropriate support structures for maintaining the belt support  60  in a preferred location so that it operates as needed for a particular situation. The illustrated example includes a plurality of rollers  62  associated with each side of the belt loop. 
   Such arrangements are particularly useful where the step chain  30  and the belt  42  are engaged on both sides of the belt loop. 
   The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not depart from the essence of this invention. The scope of legal protection given to this invention can only be determined by studying the following claims.