1. Field of the Invention
The present invention relates generally to a passenger conveyor such as an escalator, and more particularly to a terminal rail for a passenger conveyor capable of reducing noises and vibrations generated due to the impact produced from the terminal rail during its operation.
2. Description of Related Art
A passenger conveyor typically includes a series of passenger platforms which are driven in an endless path between horizontally spaced landings. The most common types of passenger conveyors are escalators and horizontal walkways. In case of the escalator, the platforms are steps which are driven between an upper landing and a lower landing to facilitate the conveyance of passengers, cargo, and the like. The passenger conveyor also includes hand rails which are movable along and supported by opposite sides of a main frame of the conveyor.
The passenger platforms are normally connected in a circle by a pair of drive chains which extend along opposite sides of the passenger conveyor and which engage a powered sprocket assembly mounted on at least one end of the conveyor to effect continuous movement of the steps between the upper and lower landings. The steps extend laterally across the conveyor between the opposite sides of the main frame to define a step band that is a spatial envelope between the upper and lower landings and between the opposite handrails through which the steps travel. The steps, which convey passengers toward an off-load landing, travel above the sprocket assembly to define an upper step band, while the inverted steps which return to the on-load landing, travel below the sprocket assembly to define a lower band.
Conventional passenger conveyors as described above are disclosed in, for example, U.S. Pat. No. 5,161,668 issued to Datema et al. on Oct. 10, 1992, U.S. Pat. No. 5,170,875 issued to Kubota on Dec. 15, 1992, and U.S. Pat. No. 5,224,580 issued to Nurnberg et al. on Jul. 6, 1993.
Meanwhile, another conventional passenger conveyor is illustrated in FIGS. 1 to 4. Referring to FIGS. 1 and 2, the conventional passenger conveyor comprises a pair of horizontally spaced circulating hand rails 1, a plurality of steps 2 which passengers get on and off, and a transmission system 3 for driving the handrails 1 and the steps 2. The transmission system 3 generally includes a motor 4 for driving the steps 2, a reduction gear for transferring the driving force between the motor and a drive sprocket 7, and drive chains 6 operatively engaged with the drive sprocket 7.
In the above passenger conveyor, the drive sprocket 7, a drive terminal gear 8, a drive shaft 12 and a terminal rail 13 constitute a drive system. And, the steps 9, endless step chains 10, and front and back wheels 14 and 15 which are engaged to the steps 9 constitute a moving system.
FIG. 3 is a perspective view of the terminal rail 13 having inner and outer guide rails 18 and 19, and FIG. 4 is a view illustrating an engaged state of the terminal rail 13, wherein the end of the inner guide rail 18 is engaged to a secondary rail 17.
Such a conventional terminal rail 13 performs only the role of guiding the back wheel 15 of the step 9. The terminal rail is provided with no special device or method to eliminate or constrain noises or vibrations. However, a method for accurately machining the inner and outer guide rails 18 and 19 of the terminal rail 13 along which the back wheel 15 of the step travels to reduce the clearance between them as small as possible, and to relieve the impact is mainly adopted. For instance, the Kubota patent discloses an expansion/contraction joint mechanism For adjusting the length of the guide rail.
When the electric power is supplied to the passenger conveyor as constructed above, the driving force produced from the motor 4 which is disposed in the transmission system 3 is transferred to a speed reducer 5. The driving force produced from the speed reducer 5 is transferred to the drive sprocket 7 through the drive chains 6. Accordingly, the drive terminal gear 8 engaged on the same axis of the drive sprocket 7 drives the step chains 10 connected with the steps 9, so that the steps 9 continuously move along the drive and driven terminal gears 8 and 11.
At that time, the front wheel roller 14 of the step moves along a primary rail 16, and the rear wheel roller 15 moves straight along the secondary 17 and turns along the terminal rail 13 on the upper and lower portions of the conveyor.
In particular, on the upper and lower portions of the conveyor, the front wheel roller 14 of the step rotates along the periphery of the terminal gear 8, and the rear wheel roller 15 of the step rotates along the turning section of the terminal rail 13 as shown in FIG. 4. At that time, the rear wheel roller 15 of the step 9 moves along the inner guide rail 18, and rotates along the inside of the outer guide rail 19.
When the conventional passenger conveyor with the terminal rail 13 engaged as described above operates, noises and vibrations are greatly produced due to the impact occurring near the terminal rail 13 positioned on the upper and lower portions of the conveyor.
The noises and vibrations caused by the impact have been the chronic and inherent problem of the conventional conveyor in spite of continuous efforts to solve it.
In order to examine all possible factors of the above noises and vibrations, the noise measuring test was carried out by using so-called Taguji method.
FIG. 5 is a graph showing the influence of each noise factor obtained by using the Taguji method. Referring to FIG. 5, it appears that as the inclination becomes greater, the influence of the factor for retaining the noises also becomes greater.
The testing result has revealed that the source of the noises and vibrations at the upper and lower turning sections of the conveyor is the terminal rail 13. Meanwhile, a factor "C" has been proved to have merely the relation to the increase/decrease of the noises and vibrations produced from the terminal rail.
In order to examine the mechanism of the noises and vibrations produced by the terminal rail 13 and the impact position therein, a red lead has been used. The rear wheel roller 15 of the step travels on the inner guide rail 18 of the terminal rail 13 through the trace on the terminal rail as shown in FIG. 6 and deviates from a turning section B. At the same time, the roller 15 strikes against a section A (the position at about 45 degrees counter-clockwise to the straight line of the inner guide rail of the terminal rail 13), and rotates along the inside of the inner guide rail 19 of the terminal rail 13.
The reason why the roller is not abutted against the inside of the outer guide rail 19 corresponding to the straight line of the inner guide rail 18, but rises toward the section A and impacts thereto is that the steps 9 are operated by the terminal gear 8. In view of the test results induced from the trace of the existing terminal rail 13, it has been confirmed that the outer guide rail 19 of the terminal rail 13 is applied with a lot of pressure and impact.
The trace of the rear wheel roller 15 of the step during turning is always constant, and thus the rear wheel roller 15 of the step impacts against the section A of the terminal rail 13, thereby producing the noises and vibrations; that is to say,
1. Every time the rear wheel roller 15 of the step impacts against the section A, the noises are significantly produced. PA1 2. Every time the rear wheel roller 15 of the step impacts against the section (0.8 seconds per step), the vibrations of the step 9 are increased by an increasing of the pulsating phenomenon. PA1 3. Since the rear wheel 15 of the step impacts directly upon the terminal rail 13, the life of these components is shortened. PA1 4. In case of the outer guide rail 19 of the terminal rail 13 having an interior surface with a coarse finish, the impact noises are increased.
In the structure of the conventional terminal rail, the dimensional clearance of the terminal rail 13 has to be maintained very precisely to reduce the noises and vibrations produced due to the above reason 1, thereby rising the cost and deteriorating the productivity thereof.