Pulse-free escalator

#The present invention relates to an escalator system having pulse-free turnarounds and transition zones and a method for designing the escalator system.

#The step assembly of an escalator forms a chain of rigid links. The links are supported by rollers which move around a smooth closed track. At the top and bottom of the escalator, the tracks “turn around”, reversing the direction of travel. Typically, the velocity of the step entering the turnaround differs from the velocity of the step having exited the turnaround. This is experienced as a cyclical velocity pulsation at the link passage frequency. As part of this experience, the rollers may periodically lift off the track or the joints and rollers may be subject to excessive loads alternately binding and stretching. This “polygon-effect” vibration can result in unacceptable ride quality. The same effect can occur to a lesser degree in the transition regions between the escalator rise and the upper and lower landings.

#Polygon-effect vibration is typically addressed by defining roller paths with sufficiently large radii for turnarounds and transitions. Haruta et al., in the article “A Super High-Rise Escalator With a Horizontal Mid-Section”, Elevator Technology 6, Proceedings of ELEVCON '95, March 1995, pp. 78-87, describe a design method for choosing optimal constant radii for minimization of the polygon effect. Despite the existence of this design method, there remains a need for a design method and an escalator which has a truly pulse-free turnaround.

#FIG. 1 is a schematic representation of a roller path for an escalator system showing transition and turnaround regions;

#FIG. 2 is a side view of a turnaround section of a track system used in the escalator system of FIG. 1;

#FIG. 3 is a schematic representation of a four bar linkage going through a turnaround section of a track in accordance with the present invention;

#As discussed above, the present invention relates to an escalator system 10 having pulse free turnaround and/or transition sections. As used herein, the term “pulse-free” means that if the links in one straight section are moving at a constant rate, the links in the return section move at the same constant rate. Pulse-free allows both sides to have the same constant velocity. The escalator system 10 includes a pair of spaced apart guide tracks 12, and a pair of spaced apart link assemblies 14 for supporting a plurality of steps (not shown). Each link assembly 14 includes a plurality of links 16 joined together by pins or the like. Each link 16 has at least one roller 18 for engaging a respective one of the guide tracks 12 and for following the path defined by the respective guide track 12. A typical guide path 20 for each roller 18 is shown in FIG. 1. As shown therein, the guide path 20 includes first and second spaced apart turnaround portions 22 and 24 and four transition sections 26, 28, 30, and 32. Any suitable conventional drive system known in the art may be used to drive the link assemblies 14 and hence the rollers 18.

#Referring now to FIG. 2 of the drawings, a portion of one of the guide tracks 12 is illustrated. It should be recognized that the guide track 12 on the opposite side of the escalator 10 has the same construction and has the same relationship of guide track, rollers, and links. The guide track portion shown in FIG. 2 includes turnaround portion 22 and transition sections 26 and 28. As can be seen in this figure, a plurality of rollers 18 attached to links 16 travel along the guide path defined by the guide track 12 which is entirely closed, particularly in the turnaround portion 22.

#In order for the turnaround portion 22 to be pulse free, the speed of the link exiting the turnaround portion 22 must be the same as the speed of the link entering the turnaround portion 22. Such a pulse-free turnaround portion is shown in FIG. 3. As shown therein, the pulse free turnaround portion 22 has a linear entry section 34, a first known trajectory section 36 adjacent the linear section 34, a linear exit section 38, and a second known trajectory section 40 adjacent the linear exit section 38. The first and second known trajectory sections 36 and 40 may have any desired configuration. For example, each of the sections 36 and 40 may be constant radius curved sections having a radius R. Alternatively, the sections 36 and 40 may have different curved configurations. The pulse-free turnaround portion 22 exemplified in FIG. 3 also has a pulse free section 42 intermediate the constant radius sections 36 and 40. As shown in FIG. 4, the pulse free section 42 does not have a constant radius curvature as shown by curve 43.