ESCALATOR, the name applied to a con tinuous carrier designed for conveying pas sengers from one level to another within a limited time. The various units making up the escalator are so arranged that on the incline they present the familiar zigzag appearance of an ordinary stairway, and may be used as such. The escalator consists of an endless series of steps connected together by a heavy sprocket chain which, at the proper place, engages with the driving sprocket wheel. Each step is es sentially a four-wheel truck, bolted to a shaft, which, in turn, is connected to the links of the driving chain. There are two wheels at each end of the truck traveling on separate tracks, so placed that the steps remain horizontal at all points of the ascent. At the landing, at the top and the bottom of the escalator, the trucks travel in the same plane so that the steps there become a moving platform. Ample opportunity is thus given, even to the infirm, to board the de vice before the ascent begins and at the top to step off again. A traveling hand-rail moving at the same speed as the steps further simplifies its use. Should a,person fail for any reason to step off at the upper landing, a device called a shunt removes him from it. This consists of a box-like affair, triangular in plan, placed about 10 feet from the top of the escalator with the apex pointing against the direction of the mov ing platform. In the lower part, set in a ver tical position, are two belts running backwards from the apex. Anything coming in contact with these belts is gently brushed to one side. Every part of the escalator is made to microm eter measurements of one thousandth of an inch by special machinery designed for the pur pose. As a result of this unusual precision, the various steps fit together so nicely that a piece of paper cannot be forced between them. To secure practically noiseless operation, the wheels on which the trucks move are deadened, raw hide pinions are used in driving gear, and the tracks are built up of wood and steel. The links of the sprocket chain are made of two 18-inch cast steel shrouds, with steel pins between them at 3 inches between centres. The ends of the links are bushed with
phosphor-bronze in which graphite is inlaid, thus providing lubrication of the bearing sur faces, and the heels are similarly provided with a constant lubrication of graphite. The escala tor is driven by an electric motor located within the structure of the upper landing and suitably geared to the large driving sprocket wheel by a combination of worm and spur gearing. All parts of the numing gear are made of crucible cast steel, the axles and link pins being of cold drawn steel. Each casting is subjected to a test of many times the working-strain to come upon it.
While there are no mechanical limitations to the rate of speed with which the escalator may be driven, it has been found that a speed of about 100 feet per minute is satisfactory to the public. At this rate of driving, 4,000 steps per hour arrive at the landing and the maximum capacity of the machine depends upon the width of the steps used. The escalators which have been installed for railroad stations, large depart ment stores and other localities where a large capacity is necessary, have been a little over five feet in width and as each step readily ac commodates three people the maximum capacity of such a construction is 12,000 people per hour. For the smaller department stores and for use in railroad stations where the traffic is not heavy the escalator is made of such width as to ac commodate one person on each step, and the capacity is therefore 4,000 per hour. It should be noted that the escalator is a perfectly. re versible machine, operating equally well in either direction. In the "duplex° type, the steps dur ing the descent are again guided into the fatniliar.zigzag position by suitably placed tracks and thus the same machine serves to carry pas sengers both up and down. In a third modifica tion of the device designed especially for the London underground railroad, where the dif ference between levels is considerable, the steps ascend in one spiral and descend in another spiral below the first.