For purposes of an exemplary showing, the present invention will be described in its application to moving walks or escalators. As will be abundantly apparent to one skilled in the art, the teachings of the present invention are equally apparent to one skilled in the art, the teachings of the present invention are equally applicable to moving walks of the type comprising an endless procession of tread segments or pallets or belts moving between a pair of balustrade skirts.
As is well known in the art, a typical escalator or moving walk includes a conveyor portion for transporting passengers between a first landing and a second landing. The transport conveyor is of the endless type, having an articulated belt which is driven about a closed path or loop. The transport conveyor typically includes an upper load bearing run upon which passengers stand while being transported between the landings. The conveyor further includes a lower return run and first and second turn-around portions that connect the load bearing and the return runs.
A typical escalator comprises a plurality of steps which are operatively joined together in a pivotal fashion to form an endless loop of steps. Each step typically comprises a pair of side frames which supports a substantially planar tread and an arcuate riser. Each step has a first pair of shaft mounted wheels located to either side thereof and substantially beneath the riser. Each step has a second pair of shaft mounted wheels located near the opposite end of the tread remote from the riser. The shaft of the second set of wheels is also operatively attached to a pair of drive chains which pass over an upper pair of corresponding sprocket wheels at the upper end of the escalator and a corresponding lower pair of sprocket wheels at the lower end of the escalator. Typically, one of the upper and lower sprocket wheel pairs is an idler pair, and the other of the upper and lower sprocket wheel pairs is a driven pair, driving the pair of chains and the plurality of steps attached thereto. Typically, the set of tracks for the first set of wheels is so configured that it assures that the treads of the steps in the passenger carrying flight are horizontal. The set of tracks for the first set of wheels is configured to assure that the treads assume a continuous belt-like configuration about the upper and lower sprocket wheel sets and throughout the length of the return flight. Typically, the second set of shaft mounted wheels rides upon its own separate set of tracks.
It is common practice to drive a passenger conveyor from one end or the other, with escalators usually being driven from the upper terminal. As mentioned previously, driving by means of one or more sprocket wheels in the turn-around portion has been widely used. Typical drive units include one or more drive motors and gear reducers operably linked to sprocket wheels which engage and propel the conveyor drive chains which in turn drive the endless belt about its guided path.
There are several different drive arrangements in the art that have been used to drive passenger moving walks and escalators. One such arrangement comprises a vertically or horizontally disposed electric motor having an input shaft being perpendicular to the sprocket wheel drive shaft. This arrangement is commonly used in order to transmit the necessary drive power and to achieve the necessary reduction in the speed of rotation by means of a worm gearing. Although the step-down ratio and the improved operational noise-levels achieved by operation of this drive configuration are desirable, there remains an undiminished need for a drive assembly exhibiting improved flexibility and a smaller structural size with the same, or possibly even increased, capacity for electric power. Given the limited amount of space that is available inside the area of return of the step band or truss envelopment, the orientation and height of this type of drive system limits its retrofit capabilities and makes it incompatible with many escalator or moving walk systems where available space for drive assemblies is somewhat limited.
The somewhat lower efficiency of the vertical worm gearing assembly and the cumbersome and limiting configuration of the vertical drive system in particular provided incentive to look for further solutions and improved drive means. One such alternative configuration is a horizontally disposed drive motor located within the region of reversal and inside the rotating step or pallet belt. A typical drive assembly of this configuration includes a drive shaft and planetary gearing arranged with axes parallel to the axes of the step or pallet drive shaft. Typically, a transmission output gear on the motor drive shaft is in direct engagement with a gear on the shaft of the step or pallet drive. Although this arrangement is somewhat more compact than a vertically disposed worm gear drive arrangement, it is not very flexible in that it must be disposed near the sprocket assembly so that the various gears are in communication.
It is clear that a need exists for an improved flexible drive assembly for escalators and moving walks capable of being disposed in a variety of configurations. Such a drive assembly would be relatively compact as compared with prior art systems and would achieve improved space utilization without sacrificing adequate power output.