DIRECT-CONNECTED ELECTRIC ELEVATORS

Direct-Connected Belted Electric Elevator. The second step taken in the development of the electric elevator was the elimination of the countershaft and the tight and loose pulley and the substitution therefor of a belt connecting the motor directly with the elevator machine. The mechanisms used in belt elevators for shifting the belt then became superfluous. Although the elimination of the countershaft seems a small and natural step to take, it makes a great change in the working conditions of the elevator, since in the belt-shifting types the motor starts without load, which is applied only after the motor has attained its normal speed; while in the direct-connected type the motor must start under load. There is nothing gained by hav

the motor being mounted on the same base with the machine.

Motors. Since in direct-connected electric elevators the motor starts under load and must therefore have a strong torque, it must also get up speed rapidly though gradually. Of these two conditions the last-named one is fulfilled by peculiar controlling devices that are described below, while the first named one is fulfilled by the construction of the motor itself, which is generally of the compound-wound typea series-field coil serving to give the necessary torque at starting and the shunt coil steadying the field. The series coils are generally cut out when the motor has attained normal speed, after which the motor runs as a simple shunt-wound motor.

Of alternating current motors, only

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the two-phase or three-phase induction motors prove satisfactory for directconnected electric elevators, since they will start under load with sufficient torque. These motors behave, as far as their action in the elevator combination goes, just like shunt-wound continuous-current motors.

Transmitting Devices.-The transmitting devices between the motor and car consists, with few exceptions, of worm-gearing, drum and rope. The worm shaft is almost invariably coupled to the motor shaft by a flange coupling, serving at the same time as

a brake pulley. Both single worm and double worm-gearing are used, as will be seen from the illustrations given farther on, the double worm being used mostly on heavy machines, to avoid the end thrust of the worm shaft. Such heavy machines are also frequently provided with back gearing. Ordinarily, however, single work-gearing is used, great care and ingenuity being

ropes, hand wheels, and levers. Electrical operating devices are being introduced, however, with success in connection with the magnet system of control.

Motor Safeties.-Motor safeties are used in various forms; they are either mechanical or electrical or both.

Examples of Electric Elevators.— The examples of electric elevators here given do not represent all the various designs in the market, nor does the order in which they are described indicate any superiority of design of one make over another. A careful study of these will give a person enough insight into the construction and operation of this class of machinery to enable him to handle other makes of machines.

FIG. 2.

displayed in the design of the step bearings for the worm.

Counterbalancing.-Direct-connected electric elevators of the drum type are always overbalanced.

Controlling Devices.-The power control of direct-connected electric elevators is entirely electrical, there being no belts to shift or similar mechanical operations to perform; but besides breaking the current, the motor must be reversed. Hence, besides the simple snap switch and rheostat already mentioned in connection with belt-shifting electric elevators, a reversing switch switch or pole changer is needed.

In elevator practice, the complete apparatus necessary to control the electric motor-the power control, as we have called it, is called a controller, especially if the various parts of it are built together in such a way as to make a separate self-contained piece of machinery. A number of different forms of such controllers are used by the various manufacturers of electric elevators.

Brakes. The breaking arrangements used are either entirely mechanical, that is, such as are used in connection with belt and steam elevators, or electrical mechanical, or wholly electrical.

Operating Devices. In the majority of electric elevators the operating devices are mechanical, such as hand

FIG. 3.

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ELEKTRON ELEVATORS

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Motors. Fig. 1 is an end and side elevation of an electric elevator made by the Elecktron Manufacturing Company. The motor is the well known Perret multipolar machine, shuntwound.

Transmitting Devices. The transmitting devices are single worm-gearing, drum and rope. The arrangement of the step bearing of the worm is

shown in Fig. 2. Alternate phosphorbronze and steel disks are used to distribute the wear. The worm-shaft is attached to the motor shaft by means of a flange coupling F, which serves at the same time as a brake pulley.

Simple Controller.-The Elektron Manufacturing Company uses various kinds of controllers for various kinds of elevators. The simplest arrangement used is a double-throw switch attached to the hub of a shipper sheave S, Fig. 1, and a solenoid rheostat placed anywhere conveniently near the machine.

The switch consists of a casting A, Fig. 1, supported on the frame of the machine and carrying four sets of clips C1, C2, and C, C2, to which the necessary line, field, armature, solenoid and electric-brake connections are made. The switch blades B1, B2 attached to the shipper sheave engage the

in these machines is, for ordinary service, a simple mechanical one, which is released by a cam on the shipper sheave through a system of levers and applied by a weight, as with belt elevators. For passenger service, an electrical-mechanical brake is used, which is released by an electromagnet and applied by gravity. This arrangement is shown in Fig. 1, in which the brake magnet is marked B; the rapidity of action of the same is regulated by a dashpot D.

Fig. 4 is a diagram of the electrical connections between the switch, rheostat, brake and motor. It will be useful to follow out these connections. The lines are connected through the fuses f, f and the doublepole switch s to the elevator switch at the binding posts L, and L. Supposing the blades of the switch to be thrown to the right, that is, across

clips C1, C2, or C,', C,' for the up trip and the down trip, respectively. In Fig. 1 the blades are shown in their neutral position; that is, when the elevator is at rest. It will be seen that to start the elevator up or down, the sheave with the blades must be turned through an arc of 135°, the clips being set at right angles. This long travel is given for the purpose of giving the rheostat arm time to fall back into its starting position before the current in the armature can possibly be reversed; it also helps to reduce sparking and flashing at the clips.

Ordinary Brake.-The brake used

the clips C, and C2, and the current to enter at the binding post L., then it passes first to clip 1 of the set C,, whence it divides by means of the switch blade among the clips 2, 3 and 4. From 2 it passes to binding post L, thence through the field windings of the motor, back to the binding post L,, thence to the clip b of set C2, over the blade crossing this set of clips to clip a, thence to binding post L, and to the line, thus completing the shunt circuit for the field. From clip 3 the current goes to the binding post L., through the solenoid windings of the rheostat R to the binding post r, of

the rheostat to the binding post L, of the switch, to clip c of set C2 over the blade of the clip a, to the building post L to the line, thus completing the circuit through the solenoid. From clip 4 the current goes to binding post L2, thence through the armature of the motor to the binding post r, of the rheostat, through the lower half of the resistance, through the rheostat arm and the upper half of resistance to binding post r,, to L1, c, a, L., and line, thus completing the armature circuit. Throwing the blades to the left, we will find, in following out the three circuits again, that the current traverses the field circuit in the same direction as before, but that the current in the armature is reversed, thus reversing the motor. The electromagnet windings. of the brake are in shunt with the solenoid circuit, as is easily seen from the diagram.

The operation of this elevator is as follows: When the shipper sheave is thrown over to the right or left, the brake magnet is energized and tends to slowly release the brake, since the dashpot prevents too sudden a release; at the same time the solenoid is energized. This tends to slowly cut out the resistance from the armature circuit; the dashpot prevents too quick an action, and it is so adjusted that all the resistance will be cut out by the time the motor reaches its normal speed. Upon breaking the circuits, the brake is at once applied and the resistance arm drops back into its original position, ready for another

start.

Dynamic Brake.-On high speed elevators, in order to get a particularly smooth stop, the Elektron Manufacturing Company uses, in addition to the electrical mechanical brake, a so-called dynamic brake, which, indicated in Fig. 1 at R, is usually placed on a bracket between the shipper sheave and the worm-gear case. It is shown in detail in Fig. 5 and consists of a switch lever L, actuated by a cam on the operating sheave, and a variable resistance.

This resistance is so connected to the system that the armature is short

motor slows down, the cam operating the lever L being so constructed as to first cut in all the resistance at the instant the main circuit is broken; on being turned farther by the operator, the switch lever is caused to brush over the resistance contacts, thus gradually cutting the resistance. down to zero. Of course this short circuit is opened before the elevator is started again. As has been said, the dynamic brake is used only in addition to the ordinary brake, the latter being necessary to hold the car stationary after it has been stopped.

Fig. 6 shows diagrammatically the connections when the dynamic brake. is used. The field must necessarily remain excited after the armature cir

sistance is short-circuited, thus giving the fields the full current due to its windings and consequently, the full torque available. When the elevator is stopped, the resistance is cut in, choking the field current, but leaving it strong enough to give sufficient magnetism to get a dynamic-brake effect.

Speed Regulating Controller.Another type of controller used by the Elektron Manufacturing Company is shown in Figs. 7 and 8, while the diagram of connections is given in Fig. 9. It is evident that the combinations described in the previous article do not allow of any regulation of speed, the motor being simply shunt-wound with an unchangeable field. The purpose of the arrangement now to be described is to give speed regulation, which is accomplished by a changeable resistance in the field. The controller is mechanically operated.

As seen in Fig. 7, there are two cams I and II operating the armature and field-resistance arms A, and A,

switches. All these cams are mounted on the shipper-sheave shaft S. The brake is the same as in the previous design.

Fig. 9 is a diagram of the connections for this controller. (a) shows the external connections between motor, brake and connection board B; (b) gives the internal connections between the connection board B and the various clips and resistance blocks inside the controller. By swinging the shipper sheave to the right or left, switch blades connect the clips a and b, c and d, and e and f, completing the circuits. Thus, supposing the current to enter the system from the line at the binding post I, it goes to the clip e, over a blade or knife to the clip f, thence to the pivot p, of the pole changer, where it divides. One branch goes through the polechanger arm r, and the armature resistance to binding post 2, thence through the armature back to the binding post 3, thence through the other pole-changer arm r2, to the pole-changer pivot P2, to the clip b,