Abstract:
A passenger conveyor drive belt assembly includes a belt support that facilitates proper engagement between the drive belt and corresponding links of a step chain. The belt support preferably is positioned between a drive sheave and an idle sheave within the loop traveled by the drive belt. The belt support includes at least one moveable support member that moves responsive to movement of the drive belt while urging the drive belt into proper engagement with the step chain links.

Description:
BACKGROUND 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. 
     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 also 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 overall drive system. 
     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 idle sheave is positioned at an opposite end of the loop and engages the inner surface of the drive belt. The idle sheave moves with the belt responsive to movement of the drive sheave. A belt support is positioned between the drive sheave and the idle sheave. The belt support has at least one moveable element engaging the inner surface of the belt and maintaining a desired position of the belt near the belt support to insure a desired engagement between the cogged surface of the drive belt and the links of the step chain 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 a preferred embodiment of a drive assembly designed according to this invention. 
     FIG. 3 illustrates selected portions of another example drive assembly designed according to this invention. 
     FIG. 4 illustrates selected portions of another example drive assembly designed according to this invention. 
     FIGS. 5A and 5B illustrate selected portions of a belt support arrangement of another example drive assembly designed according to this invention. 
     FIGS. 6A and 6B illustrate a modified version of the example embodiment of FIGS. 5A and 5B. 
     FIG. 7 illustrates selected portions of another modification of the embodiment of FIGS. 5A and 5B. 
     FIG. 8 schematically illustrates another example assembly designed according to an embodiment of this invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A passenger conveyor system  20  includes a drive assembly  22  for moving a plurality of steps  24  in a desired direction. A handrail  26  moves with the steps  24  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. 
     A drive assembly  22  designed according to this invention includes a drive belt  30 . A drive sheave  32  preferably engages an inner side of the drive belt  30  to move the belt  30  around a loop. An idle sheave  34  preferably is positioned at an opposite end of the loop from the drive sheave  32 . A drive mechanism  36  is schematically shown for moving the drive sheave  32  in the desired direction and at the desired speed. The drive mechanism  36  may include a braking mechanism as known in the art, for example. 
     The belt  30  preferably includes reinforcing members such as steel cords or polymer strands encased in a polymer material. An outer surface  40  on the drive belt  30  preferably is cogged while an inner surface  42  preferably is also cogged. The inner surface is shaped to interface with the drive sheave  32 . The cogged surfaces are also referred to as having teeth in this description. The outer surface  40  preferably cooperates with a plurality of step chain links  44 , which are associated with the steps  24  in a known manner. The cogged pattern on the outer surface  40  preferably corresponds to the pattern of teeth on the step chain links  44 . As the drive sheave  32  moves the belt  30 , engagement between the cogged surface  40  and the step chain links  44  results in the desired movement of the steps  24 . 
     A belt support  50  preferably is positioned between the drive sheave  32  and the idle sheave  34 . The belt support  50  avoids any sagging of the belt in a central portion of the loop where the drive belt  30  may otherwise become disengaged from the step chain links  44 . In the example of FIG. 2, the belt support  50  includes a plurality of rollers  52  that engage the inner surface  42  on the belt  30 . Each of the rollers  52  preferably includes an outer surface having a plurality of spaced spines  54  and grooves  56 . The configuration of the outer surface on the rollers  52  preferably complements the configuration of the inner surface  42  on the belt  30 , which permits the rollers  52  to support the belt  30  between the teeth. The rollers  52  preferably extend axially across the width of the belt  30  and freely rotate about their respective axes  58 . 
     The belt support  50  preferably is supported on an escalator truss structure. It is also possible to arrange the belt support  50  to be supported by the building structure, which may be particularly useful for moving walkways. In one example the rollers  52  are supported on fixed axles that extend between parallel plates, which are securely positioned to maintain desired roller positions. Given this description, those skilled in the art will be able to realize appropriate support structures for maintaining the belt support  50  in a preferred location so that it operates as needed for a particular situation. 
     The rollers  52  preferably are positioned to cause the belt  30  to have a desired amount of engagement with the step chain links  44  in the vicinity of the support  50 . To get maximum support, the rollers preferably are as small as practical given the belt tooth pitch. The space between the sheaves and between the top and bottom of the belt loop impacts how many rollers will provide the desired support. Given this description, those skilled in the art will be able to determine the proper number of rollers needed and their optimum placement to meet the needs of a particular situation. The rollers  52  preferably are positioned to insure proper engagement between the belt  30  and the step chain links  44  without interfering with such engagement or introducing undesirable wear or temperature increases on the belt  30 . 
     A belt support  50  designed according to this invention preferably distributes the load across the teeth on the cogged surface  40  of the belt as evenly as possible over a plurality of the teeth. In one example, the load is distributed across approximately twelve teeth. A belt support  50  designed according to this invention also eliminates the need for any special tooth configurations that otherwise might be necessary to avoid clash at the engagement between the teeth on the belt and the corresponding surfaces on the step chain links. With a belt support designed according to this invention, the teeth on the belt  30  may include nearly vertical faces, which requires minimal engagement force and renders the overall drive system more efficient. 
     A belt support designed according to this invention therefore provides for a more evenly distributed load over the belt surface along the entire loop, which improves the belt life and the performance of the drive system. 
     FIG. 3 illustrates another example belt support  50 A. This example includes a support chain  60  that engages the inner surface  42  on the drive belt  30 . The links of the chain  60  have associated rollers  61  that follow tracks  62  and  64 . The rollers  61  follow a loop that is smaller than the loop of the drive belt  30 . Along a portion of the loop formed by the tracks  62  and  64  (i.e., the top and bottom portions according to the illustration) the support chain  60  ensures that the drive belt  30  is in a position to properly engage the step chain links  44 . In one example, the support chain  60  includes a generally flat surface that is received against the inner surface  42  on the drive belt  30 . In another example, the support chain includes a cogged surface that corresponds to and engages the cogged inner surface  42  of the belt so that the chain moves about its own loop as the drive belt  30  moves above its loop. Those skilled in the art who have the benefit of this description will be able to select an appropriate loop size and an appropriate support chain design to meet the needs of their particular situation. 
     FIG. 4 shows another example belt support  50 B. Only portions of selected components are shown diagrammatically for simplicity. In this example, a support chain  70  follows a loop that is smaller than the loop of the drive belt  30 . In this example, the support chain  70  is held in a desired position by rollers  72  and  74 . The rollers preferably are positioned to force the chain  70  into contact with the drive belt  30  along a portion of the length of the loop of the chain  70  as desired. 
     The support chain  70  preferably is designed to pivot in one direction but not in an opposite direction. Each link  76  preferably is constructed so that an adjacent link pivots about an axis  78  in only one direction preferably up to an angle of approximately 90 degrees. This is schematically illustrated by the direction arrow  79 , which shows the permissible movement between adjacent links. The structure of each link prevents any pivoting in an opposite direction. 
     Of course, there is some limitation on the ability to construct the links to prevent all pivoting in the one direction. In one example, the chain preferably is designed so that any deflection of the chain in the direction opposite to the pivot direction corresponds to an arc having an eight meter radius. Such an arrangement accommodates the physical limitations on designing a chain to prevent pivoting in one direction while maintaining the desired amount of contact between the drive belt  30  and the step chain links  44  along a given portion of the drive belt loop. 
     In the examples of FIGS. 3 and 4 the support chain provides the advantage of distributing the load for urging the drive belt into engagement with the step chain links over a chosen length of the belt rather than causing point contact. The loop of the support chain preferably is arranged so that the chain does not cause engagement between the belt and step chain links at the locations where the support chain turns about a radius of the support rollers or pulleys. This eliminates clash issues between the belt  30  and teeth on the links  44 . Additionally, these arrangements allow the belt deflection angle to be limited to approximately one degree. This limits the force on the engagement system, produced by the belt tension, to around 300 N, even when the tension on the belt is approximately 10,000 N. 
     In the region where the drive belt  30  is effectively squeezed between the support chain and the links  44 , the center teeth of the belt surface  40  are fully engaged whereas the teeth near the end of the engagement area (i.e., at the sides of the support) are disengaged by up to approximately one millimeter. 
     The tracks or rollers that guide the support chain preferably are designed to allow for some oscillatory motion at the turning points to allow for the polygon effect of the support chain links when moving around a loop. 
     FIGS. 5A and 5B illustrate another example belt support  50 C designed according to this invention. In this example, a plurality of rollers  80  are spaced about the undersurface  42  of the belt  30 . The rollers  80  are supported on a plurality of axes  81  that are appropriately supported by an escalator truss structure. The belt  30  preferably is machined so that the undersurface  42  includes a plurality of flat portions  82  along which the rollers  80  contact the belt  30 . In the illustrated example, a plurality of rollers  80  preferably are spaced apart axially and in a transverse direction so that the rollers  80  are staggered to more evenly distribute the load across the surface of the belt in the area of the support  50 C. Those skilled in the art who have the benefit of this description will be able to chose the number of rollers used and the spacing needed to meet the needs of their particular situation. 
     FIGS. 6A and 6B illustrate a modification to the embodiment of FIGS. 5A and 5B. In this example, a belt support  50 D includes a plurality of sets of rollers  90  that are spaced laterally in similar fashion to the rollers  80  of the previous example. In this example, a plurality of support belts  92  are received about the sets of rollers  90 . Each support belt  92  is received about a row of rollers  90  as seen in the direction of belt travel. The support belts  92  may be made from a polymer material. The support belts  92  preferably engage flat portions  94  that are machined on the inner side  42  of the belt  30 . In this example, the support belts  92  better distribute the load on the belt  30  compared to rollers that directly contact the drive belt  30 . 
     The example of FIG. 7 includes a belt support  50 E that includes support belts  92  that travel along a loop that is approximately the same size of the loop of the drive belt  30 . In this example, a plurality of support belts  92  engage a plurality of flat portions machined on the inner side of the belt  42  like that shown for the previous example. The support belts  92  preferably travel about the drive sheave  32  and the idle sheave  34 . The surfaces of the sheaves preferably are machined to accommodate the support belts  92  along with the drive belt  30 . In one example, the sheave surfaces are machined to include flats corresponding to the positions of the support belts  92 . Between the sheaves  32  and  34  the support belts  92  are supported by rollers  90  to maintain a desired amount of contact between the support belts  92  and the drive belt  30  along the entire loop. 
     The example of FIG. 8 illustrates a belt support  50 F having a plurality of rollers  100 . A support belt  102  travels about a loop around the rollers  100  and engages the inner surface  42  of the drive belt  30 . In this example, there are no machined flat portions upon which the support belt rides. Instead, the support belt  102  directly engages the outermost portion of the cogs on the inner surface  42  of the belt  30 . The rollers  100  and support belts  102  preferably are arranged like the alignment shown in FIGS. 6A and 6B (with the exception of flats on the belt  30 ). 
     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.