Curved escalator
This application is a continuation of application Ser. No. 647,650, filed Sept. 6, 1984, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to curved escalators. 
     As disclosed in Japanese Patent Publication No. 48-25559, a curved escalator which has a circular shape in plan view is provided on a framework with an endless stairway path including an inclined load-bearing run on the upper side of the loop path, a return run on the lower side of the loop, and turn-around portions at the opposite ends of the runs, and a plurality of segment-shaped steps are arranged in the stairway path with their step axles connected to an inner and an outer step chain loop defining the stairway path. In the curved escalator, an inner and an outer sprocket wheel having different diameter are mounted in the upper and the lower turn-around portions to engage and guide the inner and the outer step chain loops, respectively. The inner and the outer sprocket wheels in either the upper or the lower turn-around portion are driven by a drive mechanism for turning around the inner step chain at a radius smaller than that of the outer step chain, whereby the step axles connected to the inner and the outer step chain loops and hence treads of the steps are moved along a conical surface in the turn-around portions. 
     However, with the conventional curved escalator as described above, since the bottom surfaces between the teeth of the sprocket wheel are formed with no slope with respect to the axis of the sprocket wheel, since the step axles engage selected teeth of the sprocket wheel at a predetermined pitch, and the step axles turn around along a conical surface with their axes inclined with respect to the axis of the sprocket wheel, it has been difficult to cause the steps to smoothly and reliably turn around and a problem arises that the step chain oscillates, providing an uncomfortable ride. 
     SUMMARY OF THE INVENTION 
     Accordingly, an object of the present invention is to provide a curved escalator in which a driving force is transmitted to the step axles and the step chain, and the steps are smoothly turned around to provide a better ride. 
     Another object of the present invention is to provide a curved escalator in which the steps are stably and smoothly moved along the load bearing run of the stairway path and in which the abrasion of the guide rollers is minimized. 
     With the above objects in view, the curved escalator of the present invention comprises a plurality of segment steps having step axles connected to an inner and an outer endless loop of step chains so that the steps circulate along the endless loops, and inner and outer sprocket wheels having different diameters for turning around the step axles along a conical surface in turn-around portions of the loop which are in engagement with the inner and outer endless chain loops, with bottom surfaces of the teeth engageable with the step axles of the inner and outer sprocket wheels having bevelled surfaces that slope downwards so as to be parallel to the axis of the step axles in the turn-around portion, and with the teeth having the same pitch circle. 
     Since the bottom surfaces lying between the teeth engaging the step axles have surfaces sloped so as to be parallel to the axis of the step axles in the turn-around portion, and since the pitch circles of the teeth are the same, the driving force is transmitted to the step axles and the step chain, and the steps are smoothly turned around to provide a better ride. 
     Also, since each of the step axles comprises a roller mount rotatably mounted on ends of the step axle, a guide roller rotatably mounted on the roller mount with the guide roller being rotatable about an axis perpendicular to the step axle, and drive rollers mounted on both sides of the guide roller with the drive rollers being rotatable about an axis parallel to the step axle, the steps are stably and smoothly moved along the load bearing run of the stairway path and the abrasion of the guide rollers is minimized. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will become more readily apparent from the following detailed description of the the preferred embodiments taken in conjunction with the accompanying drawings, in which: 
     FIG. 1 is a schematic front view of the curved escalator of the present invention; 
     FIG. 2 is a plan view of the curved escalator shown in FIG. 1; 
     FIG. 3 is a side view of the upper turn-around portion of the stairway path of the embodiment of the present invention; 
     FIG. 4 is a partial sectional view showing how the step axle and the step chain are connected; 
     FIG. 5 is a partial plan view illustrating the steps and the step chains; 
     FIGS. 6 and 7 are sectional views taken along the lines VI--VI and VII--VII of FIG. 3; 
     FIG. 8 is a schematic diagram illustrating the upper turn-around portion of the curved escalator of another embodiment of the present invention; 
     FIG. 9 is a partial plan view of the steps and the step chains of the second embodiment of the present invention; 
     FIG. 10 is a side view of the steps and the outer step chain shown in FIG. 9; and 
     FIG. 11 is an enlarged plan view partially in section of the guide roller unit. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In FIGS. 1 and 2, a curved escalator of the present invention comprises a main frame 1 having defined therein a stairway path 2 that has a constant radius of curvature or is circular in plan throughout its entire length. The stairway path 2 includes a central, inclined section 2a, transient sections 2b, upper and lower horizontal landing sections 2c, and upper and lower turn-around portions 2d. The upper portion of the central inclined section 2a is a load-bearing run of an endless loop and the lower portion of the section 2b is a return run of the endless loop. A series of segment steps 3 each having a step axle 3a are connected to each other and disposed along the stairway path 2. The step axles 3a of the segment steps 3 are connected to inner and outer step chains 4 and 5, respectively, which are driven by a drive unit 6 mounted on the upper end of the main frame 1. The drive unit 6 transmits a driving force from a drive motor 6a through a chain 6b to a sprocket wheel shaft 6c. The shaft 6c is disposed at the center of the upper turn-around portion 2d of the stairway path 2 and has securely mounted thereon inner and outer sprocket wheels 6d and 6e which engage with the inner and outer step chains 4 and 5, respectively. In the lower landing section 2c, an outer tension sprocket wheel 7a engaging the outer chain 5 is mounted to define the lower turn-around portion 2d of the stairway path 2. Although not illustrated, an inner tension sprocket wheel is mounted concentrically with respect to the outer sprocket wheel 7a within the lower landing section 2c. The curved escalator also comprises a balustrade 8 including a handrail 9 thereon on each side of the stairway path as is well known in the art. 
     FIG. 3 shows an upper turn-around portion of the stairway path 2, in which the inner sprocket wheel 6d has a smaller diameter than the outer sprocket wheel 6e. These inner and outer sprocket wheels 6d and 6e are engaged by the step axles 3a at a predetermined pitch. It is seen that some of the tooth pairs, i.e., the tooth pairs between which the step axles 3a are received, are formed on the same pitch circles r 1  and r 2  as other teeth 6h and 6i and have bottom surfaces 6f and 6g inclined with respect to the sprocket shaft 6c and parallel to the step axles 3a in the turn-around portion. Other tooth pairs 6h and 6i have bottom surfaces have no slope with respect to the sprocket shaft 6c. Although not illustrated, the inner and outer tension sprockets in the lower turn-around portion 2d have a tooth arrangement similar to that of the upper inner and outer sprocket wheels 6d and 6e. 
     FIG. 4 illustrates the step axle 3a connected to the inner and outer step chains 4 and 5. The inner and outer step chains 4 and 5 have joint pieces engaged with end parts of each step axle 3a so that the step chains are allowed to deflect three-dimensionally, i.e., in three directions perpendicular to each other only at the connections to the step axles 3a. The joint pieces include links 4a and 5a placed over cylindrical rollers 4g and 5g and links 4b and 5b adjacent to the links 4a and 5a. The joint pieces further include rollers 4d and 5d having a spherical outer surface and carried by pins 4c and 5c mounted on the links 4a and 5a, and the rollers 4d and 5d are rotatably journaled by bearings 4e and 5e which have a concave spherical surface complementary to the outer surface of the spherical rollers 4d and 5d. The bearings 4e and 5e are supported within hollow cylindrical rollers 4f and 5f mounted at one end of adjacent link members 4b and 5b such that one end part of each joint piece containing the spherical roller 4d or 5d is connected to the end part having the cylindrical roller 4f or 5f of an adjacent link member 4b or 5b. 
     On the opposite ends of the step axle 3a of the step 3 are rotatably mounted drive rollers 3b and 3c rotatable about the axis of the axle 3a, and a guide roller 3d rotatable about the axis perpendicular to the step axle 3a is mounted on the outer end of the step axle 3a. As shown in FIG. 5, trailing rollers 3e are rotatably mounted on both sides of the step 3. The above-mentioned rollers 3b, 3c, 3d and 3e are guided and supported by various guide rails 10, 11, 12 and 13, respectively. 
     With the above-described arrangement, the drive unit 6 drives the sprocket wheels 6d and 6e to move the inner and outer step chains 4 and 5, thereby causing the circulating movement along the stairway path 2 of the steps 3 though the step axles 3a. 
     As shown in FIG. 3, the steps 3 are turned around in a vertical plane within the turn-around portions 2d of the stairway path 2. Since radii of the pitch circles of the inner and outer step chains 4 and 5 wound around the smaller inner sprocket wheel 6d and the larger sprocket wheel 6e are r 1  and r 2 , respectively, radii of curvature R 1  and R 2  of the inner and outer step chains 4 and 5 are expressed by r 1  :r 2  =R 1  :R 2 . Since the pitch circle radii r 1  and r 2  of the inner and outer sprocket wheels 6d and 6e are different, the step axles 3a are inclined at an angle θ and turn around along a conical surface as shown in FIG. 6. In the illustrated embodiment, the recessed portion between the teeth 6f and 6g within which the step axle 3a are received has inclined surfaces 6f and 6g, and the links 4a  and 5a engaging the step axle 3a of the inner and outer step chains 4 and 5 and the links 4b and 5b adjacent to the first-mentioned links 4a and 5a are deflectable in three directions perpendicular to each other, so that the rollers 4g and 5g rotatably mounted on the step axle 3a and the links 4a and 5a of the step chains 4 and 5 as well as the step axle 3a are inclined by the angle θ with respect to the sprocket wheel shaft 6c as shown in FIG. 6. Therefore, a desirable good contact is provided between the teeth 6f and 6g of the sprocket wheels 6d and 6e and the rollers 4g and 5g, as well as between the rollers and the step axle 3a, so that a driving force can be reliably transmitted from the sprocket wheels 6d and 6e to the step axle 3a and the step chains 4 and 5, and the steps 3 can be smoothly turned around through the use of the step axle 3a. 
     Within the inner and outer step chains 4 and 5, only the links 4a and 5a which the step axle 3a engages are allowed to deflect in three perpendicular directions as shown in FIG. 7. However, the next links 4b and 5b and the cylindrical connecting rollers 4f and 5f of the links 4b and 5b are not permitted to incline, similarly to the ordinary step chains. Also, as to the inner and outer sprocket wheels 6d and 6e, only the teeth 6f and 6g which engage the step axle 3a are provided with the inclined bottom surface and other teeth 6h and 6i are not inclined, similarly to the ordinary sprocket wheel. Since the teeth 6f, 6h, 6g and 6i are on a common pitch circle, the step chains 4 and 5 are driven around the sprocket wheels 6d and 6e on the same pitch circle and the same pitch, the step chains 4 and 5 are prevented from moving in a pulsating fashion, ensuring a comfortable ride on the moving steps 3. It is to be noted that although the description has been made in terms of the upper turn-around portion 2d of the stairway path 2, the present invention is similarly applicable to the lower turn-around portion 2d of the stairway. 
     FIGS. 8 to 11 illustrate another embodiment of a drive and guide roller assembly of the present invention. In the figures, a roller mount 14 is mounted at an outer end of the step axle 15 by a radial bearing 16 and a thrust bearing 17. The roller mount 14 is rotatable about the axis of the step axle 15 but is not movable in the direction of the axis of the step axle 15. Also, the roller mount 14 is disposed outside of the three-dimensionally deflectable outer step chain 5 coupled to the step axle 15. The roller mount 14 has mounted thereon a guide roller 18 rotatably mounted on a shaft 19 secured to the mount 14. The roller mount 14 has also mounted thereon a pair of outer drive rollers 20 rotatably mounted on a shaft 21 secured to the mount 14 on the front and rear sides of the guide roller 18. 
     On the inner end of the step axle 15 which extends outward beyond the three-dimensionally deflectable inner step chain 4 is mounted an inner drive roller 22 rotatable about the the axis of the axle 15. The step 3 is provided with trailing rollers 23 on the sides of the step 3. The trailing rollers 23 are rotatable about the axis parallel to the step axle 15 and are positioned on the inner side of the drive rollers 20 and 22. The inner and outer drive rollers 20 and 22 and the trailing rollers 23 are supported and guided by guide rails 10, 11, 12 and 13, respectively which are parallel to the stairway path 2, and the guide roller 18 is supported and guided by a guide rail 12 integral with the guide rail 11 and having a guide surface perpendicular to that of the guide rail 11 for the outer drive rollers 20. 
     In a curved escalator, since it is necessary that the steps 3 circulate along the stairway path 2 as described above and that the tread of the steps 3 be maintained horizontal at least in the load bearing run, the step axles 15 must be kept in a horizontal position during their movement. Therefore, it is required that the three-dimensionally deflectable inner and outer step chains 4 and 5 connected to the step axles 15 of the steps 3 be deflectable in any direction with respect to the step axles 15, and that the guide rollers 18 which are subjected to a radial component of a force due to the movement of the step axles 15 along the curved stairway path and determine the direction of movement of the step axles 15 be able to be directed to any direction relative to the step axles 15. As shown in FIG. 8, in the intermediate sloped section 2a of the stairway path 2, the angles of inclination θ 1 , θ 2  and θ 3  of the inner and the outer step chains 4 and 5 and the guide roller 18 disposed at the outer end of the step axle 15, respectively, are expressed as follows: 
     
         K.sub.1 tan θ.sub.1 =K.sub.2 tan θ.sub.2 =K.sub.3 tanθ.sub.3 
    
     where, K 1 , K 2  and K 3  are radii of curvature of the inner and the outer step chains and the guide roller, respectively as shown in FIG. 9, and θ 1 , θ 2  and θ 3  are angles of inclination of the inner and the outer step chains and the guide roller, respectively, as shown in FIG. 8. 
     As shown in FIG. 8, since the radii of curvature K 1 , K 2  and K 3  are different from each other, the angles of inclination θ 1 , θ 2  and θ 3  are also different from each other. However, since the step axles 15 move only horizontally within the horizontal landing sections 2c, all of the angles of inclination θ 1 , θ 2  and θ 3  are equal to 0. Explaining this relationship with reference to FIG. 8, in the horizontal section 2c which is a plane defined by A 1 , A 2 , B 1  and B 2 , the angles of inclination of the inner and the outer step chains as well as the guide roller are 0, while in the sloped section A 2 , A 3 , B 3  and B 2 , the angles of inclination θ 1 , θ 2  and θ 3  are different from each other. Therefore, it is required that the connecting portion of the inner and the outer step chains 4 and 5 and the guide roller 18 to the step axles 15 be freely rotatable independently of the step axles 15. 
     According to this embodiment of the present invention, the mount 14 is mounted so as to be rotatable about the axis of the step axle 15 at the outer end of the step axle 15, and the guide roller 18 is mounted so as to be rotatable about the shaft 19 that is perpendicular to the the step axle 15. The pair of outer drive rollers 20 is mounted on the mount 14 on the shaft 21 perpendicular to the shaft 19 of the guide roller 18, whereby the position of the mount 14 is regulated by two drive rollers 20 to restrict the angle of inclination of the guide roller 18. Therefore, by providing a predetermined angle of inclination in the guide rail 11 for the outer drive roller 20, the guide roller 18 may be directed in any direction with respect to the step axle 15. Therefore, the guide roller 18 is subjected to a radial component of tension in the step chain 4, satisfying the previously explained requirements for the step axles 15 of the curved escalator, and maintaining the step axles 15 horizontally in the load-bearing run of the stairway path 2, allowing the tread of the steps 3 to be kept horizontal and the steps 3 to be stably and smoothly moved along the stairway path 2. 
     Further, according to this embodiment, since the arrangement is such that the rolling contact surface of the outer drive roller 20 and the guide rail 11 have the same radius of curvature when seen in plan as the rolling contact surface of the guide roller 18 and the guide rail 12, the angle of inclination of the guide rail 12 and the angle of inclination of the guide roller 18 can be made equal, thus minimizing the slippage of the guide roller 18 which reduces the wear of the guide roller 18. 
     Also, since the step axles 15 are rotatable relative to the step chains 4 and 5, and the rollers 18 and 20, a torsion peculiar to the curved escalator does not act upon the step axles 15, enabling the step axles 15 to be compact. Further, the roller mount, the guide roller, and the pair of drive rollers may be disposed at the inner end of the step axle.