As will be seen from the illustration, the work- 

 ing parts of the Otis Electric Traction Elevator 

 have been reduced to the simplest possible elements. 

 The elevator engine consists essentially of a motor, 

 traction driving sheave and a brake pulley, the 

 latter enclosed with a pair of powerful spring actu- 

 ated, electrically released brake shoes, all compactly 

 grouped and mounted on a heavy iron bed plate. 



Instead of the high speed motor used with the 

 geared electric elevator, a slow speed shunt wound 

 motor designed especially for the service is used. 



The armature shaft, which is of high tensile steel 

 of unusually large diameter, is also the driving shaft, 

 and on it are mounted the brake pulley and the trac- 

 tion driving sheave. 



The introduction of the direct drive, and conse- 

 quent elimination of all intermediate gearing between 

 the motor and the driven member, results in a machine 

 of remarkably high efficiency, and the use of the slow 

 speed motor, together with the carefully designed con- 

 troller, gives starting, accelerating, retarding and stop-, 

 ping effects unexcelled by the far more costly, high 

 grade hydraulic equipments. The stopping, partic- 

 ularly, is accomplished with the greatest ease, and 

 with absolutely no disagreeable effects to the passen- 

 ger, this resulting from the comparatively low mo- 

 mentum of moving parts following the use of the slow- 

 speed motor. 



The driving cables, from one end of which is sup- 

 ported the car, and from the other end the counter- 

 weight, pass partly around the trac- 

 tion driving sheave, in lieu of a 

 drum, continuing around an idler 

 leading sheave, thence again around the driving 

 sheave, thereby forming a complete loop around these 

 two sheaves, this arrangement securing the necessary 

 tractive effort for lifting the car. One of the striking 

 advantages resulting from this arrangement of cables 

 and the method of driving them is the decrease in 

 traction which follows the landing on the bottom 

 of the shaft of either the car or the counterweight, 

 and the consequent minimizing of the lifting power 

 of the machine until normal conditions are resumed. 

 Inasmuch as, in any properly constructed elevator, 

 the parts are so arranged that the member (car or 

 counterweight) which is at the bottom of the shaft 

 must come to rest before the other member can pos- 

 sibly come in contact with the overhead work, it will 

 be readily seen that the above mentioned decrease 

 in lifting effort is a very valuable and effective safety 

 feature inherent to this type of elevator. 



[47 



DRIVING 

 CABLES 



The cables are arranged with straight leads, 

 thereby increasing their life through the elimination 

 of much of the usual bending and reverse bending, 

 and their durability is further materially increased 

 by the use of ball-bearing shackles or hitches, both 

 on the car and counterweight ends, which are ar- 

 ranged to allow the cables to twist and untwist freely, 

 following their natural strong tendency to do so 

 under the starting and stopping strains, which tend- 

 ency if restrained results in severe torsional stresses 

 in the cables. 



The controller is so designed in connection with 

 the motor that the initial retarding of the car and 

 THF CflNTRfll bringing same to a stop is indepen- 

 dent of the brake, the latter being 

 LING DEVICES , , , . 



required only to bring the car to 



final positive stop and to hold it at the landings. 



The motor is also so governed, electrically, as to 

 prevent its attaining any excessive speed with the 

 car on the down motion, no matter what the load 

 may be. 



In designing the controlling equipment, one of 

 the features demanding greatest consideration, in 

 view of the high speed at which the car runs, was 

 the automatic retarding of its speed and its final 

 positive stopping, automatically, at the upper and 

 lower terminals of travel. This result is very satis- 

 factorily attained with the installation, in the elevator 

 hatchway, of two groups of switches, located respec- 

 tively at the top and bottom of the shaft, each switch 

 in the series being opened one after another, as the 

 car passes, each operation resulting in a reduction 

 of speed until the opening of the final switch brings 

 the car to a positive stop, applying the brake. This 

 operation is entirely independent of the operator in 

 the car and is effective even though the car operating 

 device be left in the full speed position. The failure 

 of any one of these switches would result merely in 

 the stopping of the car, which could not be run until 

 the switch was put in commission again. 



An elementary feature of security of the greatest 

 interest and importance is provided in the Otis Oil 

 Cushion Buffers. These are placed 

 in the hoistway, one under the car 

 and one under the counterweight, 

 and are arranged to bring either the car or the counter- 

 weight to a positive stop, through the telescoping of 

 the buffer this telescoping occurring at a carefully 

 calculated rate of speed, which is regulated by the 

 escapement of oil from one chamber of the buffer 

 to another. The buffers have been proved capable, 



THE SAFETY 

 DEVICES 



