US1632225A - Electric elevator system - Google Patents

Description

June 14, 1927, 1,632,225

G. B. GROSVENOR ELECTRIC ELEVATOR SYSTEM Filed May 23, 1922 4 Sheets-Sheet l INVEETQR June 14,1927. 7 r 1,632,225

G. B- GROSVENOR ELECTRIC ELEVATOR SYSTEM Filed May 23, 1922 4; Sheets-Sheet. 2

% iNVENTOR June 14,1927. 1,632,225

G. B. GROSVENOR ELECTRIC ELEVATOR SYSTEM Filed May 25, 1922 4 Sheets-Sheet 3 INVENTOR Agra m un 4 1927. e 1 G. B. GROSVENOR ELECTRIC ELEVATOR SYSTEM Patented June 14, 1927 UNITED STATES PATENT OFFIQE.

GRAHAM B. GROSVENOR, OF CHICAGO, ILLINOIS, ASSIGNOR TO OTIS ELEVATOR COM- PANY, OF JERSEY CITY, NEW JERSEY, A CORPORATION OF NEW JERSEY.

ELECTRIC ELEVATOR SYSTEM.

Application filed my 23, 1922.v Serial No. 563,094.-

I and retardation was accomplished automatically by means controlled by the operator. Later automatic means for levelling the floor of the elevator even with the landings" in .stopping were applied. In certain of the 1 most successful elevator systems of the present day, the operator may run the elevator at a plurality of approximately fixed speeds,

but in ordinary operation he will move the car switch to full speed position on startingv up and willavail himself of the automatic control of acceleration. In stopping he will bring the car switch to the" neutral position at a distance from the landing corresponding to that which he has found by experience 2 will bring the car to rest by-the automatic retarding means within the zone, of action of, the levelling devices.

The distance from the landing at which the operator must initiate the automatic stopping in order to reach the landin in the least possible time is variable and depends on the speed of the elevatorand the load, as well as on the particular means for retarding the elevator. Hence, in systems of the above type the skill of the operator is an important factor in securing a high average speed of the elevator.

- The highestpossible average speed will be obtained when the elevator is started at the maximum permissibleacceleration, run at full speed, and then stopped with maximum permissible retardation so as to bring the floor of the car level with the landing. This may be regarded as a goal toward which elevator systems have striven.

()ne object of my present invention is to provide an automatic slow-down, which will come into action at varying distances from the landing, to automatically bring the ele-' vator from the speed'at which it is moving toa definite low speed. The distance from the landing at which the automatic slow: down device comes into operationis proportioned to the speed of the elevator so that in such a manner that, by the action of devices suitably located in the hatchway to out off the. power and apply the brake ata fixed distance from the landing, the elevator will always come to rest approximately level with the landing. Other objects will appear from the detailed description.

To accomplish the first of these objects, 'I may, for example, use a pair of strips arranged to move in accordance with the move ments of the elevator, but on a reduced scale. Suitable contacts are provided in the strips and stationary brushes corresponding with the landings are arranged to contact with the strips. A governor, provided with a plurality of pairs of contacts adapted to be closed successively as the speed of the governor increases, is driven by the elevator mechanism. These pairs of contacts are each connected in series with a'contact in one of the strips and under proper conditions controlthe full speed operation of the elevator. Thus, as the elevator approaches a landing, when the controller is in the proper position for automatic slow-down, a circuit is com leted throu 'h those particular contacts of t e strip and overnor that correspond to the position and speed of the car.

The second object is attained, for example, by usinga motor-generator to supply current to the elevator motor and so designing the generator that its voltage will be greater when the elevator motor islifting a load (whether in car or in counterweight) than when it is lowering it. In this way the speed of the elevator may be higher when the elevator is ascending loaded or descending light than it is when the elevator isascending. light or descending loaded. Then by taking advantage of the fact that. the greater the load the elevator motor is lifting, the shorter the distance required to stop, and coordinating this with the speed characteristics as described above, the elevatorwill be brought to rest in substantially the same distance under allconditions'ofloading.

-In 1n copendingapplication Serial No;

541,815, tiled March" 7th,,1922, I have decable to other elevator systems.

In order that my invention may be fully understood, it will be described by way of example in connection with the accompanying drawings, in which Figure 1 is a schematic view showing the general arrangement of the apparatus of a system embodying my automatic slow-down and stop.

Figure 2 is a wiring diagram illustratin the action of my automatic slow-down and stop in connection with the system according to my application Serial No. 541,815.

Figure 3 is a longitudinal section of my automatic slow-down controller.

Figure 4 is a development of the cylindrical surface of the controller of Figure 3, showing the contacts and strips Figure 5 is a vertical cross-section of the car switch used by the operator in the elevator to control its movements.

Referring more particularly to the drawings, the motor 4, Figure 1, operates from the supply mains and drives generator 5 through shaft 6. Generator 5 is separately excited and a resistance 7 is included in its field circuit. Motor 4 and generator -5 are kept running during such periods as the elevator is in service. series field 8 for generator 5 is connected in the circuit lead ing to the reversing switch 9, from the armature terminals of generator 5. Elevator niotor 10 is supplied with current for its arma ture through reversing switch 9, whereas-its field is separately excited. On an extension of the shaft of elevator motor 10 is mounted sheave 11 over which runs the supporting cable 12 of elevator 13 and counterweight 14. Brake drum 15 of electro-mechanical brake 16 is also fastened on the extension of the shaft of motor 10. Brake 16 is so constructed that when the solenoid 115 is not energized, the shoe 20 is held against the drum 15 by spring 21 and the elevatormotor 10 is brought to rest if moving, or held stationar if at rest. WVhen solenoid 115 is energize spring 21 is compressed and the brake released The automatic slow-down controller 18 is shown as being driven by gear 19 from gear 17 which is mounted on the extension of the,

shaft of motor 10. The gears 17 and 19 are selected to give a reduction of motion "to the slow-down controller that will cause its total travel to correspond to the total'travel of the elevator. Controller 18 may be driven by any other means such as are commonly employed for operating floor controllers. Such drives comprise as an essential element means for rectifying errors in the required fixed relation between the motion of the controller and of the car, due to slip or creepage of the cable.- One well known means of accomplishing this is indicated at 29 where gear 17 is driven by friction produced by the pressure of spring 30. The controller 18 is so-constructed that it can travel only the distance corresponding to the full travel of the elevator between the upper and lower landings. Consequently any errors due to slip or creepage will be corrected at the ends of each trip of the elevator.

At some suitable point, preferably at the top of the hatchway, is located a governor 22, which runs-at a speed corresponding to the speed of the elevator. It is here shown as a centifugal governor driven by cable 23 which is attached at both ends to the elevator 13 and runs over sheaves 24, 25, 26 and 27. The function of governor 22 is to close contacts in the circuit of the slow-down device 18, as will be described hereinafter. Governor 22 may be the usual governor which serves to actuate the safety devices for stopping the elevator in case of 0verspeed.

Automatic stopping switch 28 serves to bring the car to rest from low speed approximately level with the landing. It is here shown as a solenoid-operated switch in which the solenoid is mounted at a suitable point on the elevator car, whereas the armature 31 is mounted at a point in the hatchway in such relation that when the elevator floor is level with the landing, the armature 31 is opposite the cooperating part of the solenoid core.

Car switch 32 is mounted in the elevator car within easy reach of the operator.

Referring to Figure 2, the shunt motor 4 is connected tothe mains 33, 34 through the usual starting box 160. Motor 4 is of the constant speed type and drives the armature 35 of the generator 5 as described in connection with Figure 1. The field coil 36 of generator 5 is connected in series with the resistance 37 across mains 33, 34 by wires 38 and 39.

Field coil 40 of elevator motor 10 is connected through resistance 41 to mains 33, 34 by wires 42 and 43.

A control panel 44 is located at a suitable point, preferably in the motor room, and all the motor circuit closing switches are mounttoo ed on it. These switches are solenoid-operis determined by adjusting the resistance 37'. a

If the handle 45 of the car switch 32' be moved in the up direction U, so that com tact 46 covers contacts 47 and 48, a circuit will'be closed from main 34 through wires 39, 49, 50, contacts 47, 46, 48, wires 51, 52, solenoid winding 53 of magnetic stopping switch 28, wire 54, contacts 55, 56 and wires 57, 38 to main liy energizing solenoid 53 its core is attracted by the armature 31 and contacts 58, 59 and 60, 61 are opened. Stopping switch 28 may be constructed in various ways to accomplish this result. 1 have shown it as having, for example, a core 62 pivotally mounted at its lower-end on the frame 63 which is attached to the elevator car. An arm 64 extends from core 62 toward .the iron armature 31 which is fixed in the hatchway. Stop 65 prevents the arm 64 from coming into contact with armature 31 when solenoid 53 is energized and spring 66 moves core 62 away from armature 31 to close contacts 58, 59 and 60, 61 when solenoid 53 is deenergized. Contacts 59 and 61 are insulated'from each other and from core 62 to which they are attached.

By a further movement of handle 45, whereby contacts 47, 48 and 67 are covered by contact 46, an open circuit is set (to be closed, as will be described later) from main 34 through wires 39, 49, 50, contacts 47, 46

and 67, resistance 68,'wire 69, contacts 60, 61

(which however are open, due to the action of the stopping switch as last described) wire 70, solenoid winding 71 and wires 72, 73 and 42 to main 33.

Still further movement of handle 45 to cover contact 74 by contact 46 results in setting a circuit from main 34 through wires 39, 49 and 50, contacts47, 46 and 74, wire 75, resistance 76, wire 77, solenoid winding '78, wires 79 and 80,- resistance 81, contacts 82,

83, wires 84and 85, contacts 86, 87 of the Y direction switch (which are still open) and wire 38 to main 33. At the same time a circuit is set from main 34 through wires 39, 49 and 50, contacts 47, 46 and 74, wire 75, resistance 88, wire 89, solenoid coil 90, wires 91 and 92, contact 93, bridge contact 94, insulating block 252, strip 95 of the .=low down controller, brush 272, wire 96, contacts 97, 9 which are adapted to close at the same time as the direction switch, and wires 99, 72, 73 and 42 to main 33.

' Still further movement of handle 45 to cover contact by contact 46 closes a circuit from main 34 through wires 39, 49 and 50, contacts47, 46, 100, wires 101, 102 and 70, solenoid winding 71 of the direction switch, and wifes 72, 73 and 42 to main 33. The closing of this circuit energizes winding 71 and closes contacts 86, 87 and contacts 103, 104 of the direction switch which is of auv usual form of-solenoid-operated switch that is held closed when-its solenoid is energized and opened for example by gravity when the solenoid is deenergized; A circuit now extends from the armature 35 of genercontacts 87, 86, wires 85 and 34, contacts 83,

82, resistance 81, wires 80, and 111, contacts 112, 113. wire 114, winding of clertroniechauical brake l6 and wire 43 to main 34. The energizing of winding 115 releases the electromechanical brake 16 and the elevator now starts in the up direction at low speed. lVhen the brake is entirely released, contacts'112, 113 open; (see Figure 1) land resistance 151 is no longer short-circuited. Resistance 151 is so selected that when it. is in the circuit of the solenoid, the current will be reduced to a minimum required to hold the brake elf. This results in a saving of power since the full current is flowing through the solenoid circuit only at starting. Simultaneously with the closing of the up direction switch, contacts 116, 117 are closed and resistance 41 in series with the field winding 40 of elevator motor 10 is shortcircuited through wire 161, contacts 116,117, wires 118, 119, branch circuits through contacts 120, 121 and contacts 122, 123, and wire 73. This gives full field strength for elevator inotor 10 in starting up, hence maximum starting torque. The act of closing the up direction switch simultaneously opens, contacts 124, 125 thereby disconnecting resistance 81 from across the tern'iinal. of armature 400 of elevator motor-10. It is to be observed that the circuit trom'the car switch through winding 78 has now been closed by the closing of the direction switch and solenoid winding 78 is energized, Due to the resistance 76 in its circuit, however, it does not close contacts 126, 127 and contacts 128, 129 of the high speed switch since resistance 1'6 is so adjusted that it will not pass sufficient current to close the high speed switch but will allow suflicient current to pass through the solenoid, to hold the latter closed if it has been previously closed.

Still further movement of car switch handle 45 to cover contact 130 by contact 46 short circuits resistance 76 through wires 131 and 132, and'soleno-id winding 78 of the high speed switch is fully energized. Contacts 126, 127 are thereby closed and restance 37 in the field circuit of generator 5 is short circuited through wire 134, contacts 12". 126 and wires 133 and 38. The voltage at the terminals oi generator 5 will then increase at a rate dependent on the design of the generator and elevator motor 10 will increase in speed. Simultaneously with the closing of contacts 128. 129 and 1:26, 127 of the high speed switch, contacts 122. 123 are opened. Contacts 55, 56 are also opened,

lit)

thereby deenergizing the winding 53 of the stopping switch'28.

W en the voltage at the terminals of generator 5 has built up to a certain percentage (generally about 50%) of the normal full voltage, solenoid 135-is sutliciently energized to open. contacts 120, 121. Since contacts 122, 123 have been previously opened by high speed switch solenoid 78, the short circuit across resistance 41 in the field circuit of elevator motor 10 is opened and elevator motor 10 will have a weaker field which will cause it to speed up. The voltage at which resistance 41 is inserted in the field circuit of elevator motor 10 may be adjusted by changing resistance 136. It is to be noted that re-' sistance 136 and solenoid winding 135 are connected across the terminals of armature is now from main 33 through wires 38, 105,.

35 of generator 5 through wires 137, 138 and 139, 38.

When the voltage at the terminals of generator 5 has built up to a certain percentage (generally about 75%) of the normal full voltage solenoid 140 is sufiiciently energized to close contacts 108, 141 and contacts 142, 143. The voltage at which this takes place may be governed by changing the resistance 162 in the circuit of solenoid winding 140. This results in placing both generator 5 and elevator motor 10 directly across the mains 33, 34. The armature circuit of generator 5 arn'i'ature 35, wire 137 contacts 142, 143 and wire 39 to main 34. Series field 8 is shortcircuited in order that driving motor 4 and generator 5, which is now running as a motor, may have similar characteristics for parallel operation. This is advisable because motor 4 and genera-tor 5 are mechanically coupled. The armature circuit of elevator motor 10 is now from main 33 through wire 38, contacts 87, 86, wire 85, armature 400,

Wire 105, contacts 104, 103, wires 106, 107,-

. contacts 108,141, and wire 39 to main 34.

Thus the elevator motor 10 is being supplied with current directly from the mains 33, 34. This is advantageous in that whenever the elevator is running .at full speed, power consumption is kept to a minimum since the generator 5 and .motor 4 will only require that amount of. power necessary to turn them over.

Having described the circuits as they are successively closed in bringing the car switch to the'fullspeedup position, I will briefly describe the action in moving the car switch handle back to neutral (neglecting the control by the automaticslow-down controller and stop, which will be described. later).

By moving handle 45 back to uncover contact 130 of the car switch 32 the elevator will still run at full speed since solenoid 78 ot' the high speed w tch is still suflicientlv cnergizcd to hold the switch closed. Moving handle 45 to uncover contact 100 will result in no ch-ange since the direction switch is still held inby solenoid 71 by the circuit through the contacts 60, 61 of themagnetic stopping switch 28. Resistance '68 inthis circuit is so I thereupoi'i opens. Armature 400 of elevator motor 10 is then connected across armature 35 of generator 5 and the field of elevator motor 10 is restored to full strength. At the same time, the circuit short-circuiting resistance 37 in the hold of generator 5 is opened and the voltage at the terminals of armature 35 drops. Since the elevator is running at full speed the generator will act as a dynam ic brake for the elevator motor and will slow it down until its voltage corresponds to the low voltage delivered by the generator. By uncovering contact 67 the circuit through resistance 68, contacts 60, 61 and solenoid 71 of the direction switch is opened and the solenoid dcenergized. The direction switch opens and the elevator comes to rest through the dynamic braking action of resistance 81 Y which is connected across the armature terminals of elevator motor 10 by the closing of contacts 124, 125. Resistance 81 may be made very low so that a strong brakin action is applied. The opening of the irection switch also opens the circuit through the electromechanical brake 16 and allows it to act to assist in bringing the elevator to rest and to hold it stationary when it has stopped. It is to be noted that resistance 150 is shunted across the solenoid winding 115 of brake 16. This resistance serves to discharge the solenoid winding 115 when it is disconnected from its supply of current and by selecting the proper resistance the time required for full application of the brake can be governed. Further movement of handle 45 of the car switch to uncover contact 48 opens the circuit through solenoid 53 of the magnetic stopping switch and finally uncovering contact 47 opens the circuit from the main 34 to contact 46 on the car switch handle.

Although I have described the circuits set or closed as the car switch movable contact- 46 covers each contact, it is not intended that the operator will avail himself of all the contacts in the ordinary operation of the elevator. By means of my" automatic slow-down and stop in connection with other features of my system, the operator is enabled to normally control the elevator by moving the car switch handle to one of three positions which I have designated as 1-, 2 and 3 (Figures 1 and 2).

Position 1 isneutral and there is no electrical connection to contact 46 of the car switch handle 45. Handle 45 is self-centermamas ing and tends to return to the neutral position whenever the operator removes his hand. This may be accomplished by the torsionspring 200 (Figure 5) one end of which is fastened to an enlargement 201 of the shaft 202 and the other end to the car switch body. When in the neutral position the spring has no tension. To move the handle in either the up or down direction it is necessary for the operator to move the grip 203 lengthwise in order to disengage the latch 204 from the notch 205. Grip 203 is slidably mounted on tube 206 which is securely screwed into handle 45. An enlargement 207 on latch 204 serves to attach it to grip 203. A compression spring 208 is mounted over tube 206, an enlargement of which serves as an abutment for the spring which at all times will tend to engage the latch.

Assuming normal operation in which it is desired to bring the elevator from one landing to another landing above it in the shortest time, the operator will release the latch 204 by sliding grip 203 longitudinally and move the car switch handle 45 to its extreme position (position 3) in the up direction so that the latch 204 will rest against the edge 209 of notch 210 (Figure 1). All contacts for up direction will then be closed 'on the car switch and the elevator will accelerate to full speed and run at that speed as long as the operator keeps the latch 204 pressed against the edge 209 of notch 210.

.switchis in position 2.

The principles of operation of slow-down controller 18 will be understood from the diagrammatic illustration shown in Figure 2, and a practical construction will be described later in connection with Figures 3 and 4. Two parallel strips 250 and 251 are mounted in such a manner that they will move together longitudinally in accordance with the movements of the elevator. Strip 250 is made up of a metallic portion 95, an insulatingportion 252, and a second metallic portion 253. The insulatin portion 252 is located at the point midwayiietween the two ends of the strip. Strip 251 consists of a metallic portion 254 extending from one end toward the middle and another metallic portion 255 extending from the other end toward the middle. At definite distances from the center are mounted contacts 256 and 257 which are insulated from each other and from the strip 251 by insulators 258, 259 and 260. Contact 93 is located at the center otthe strip and is of a definite length. Contacts 2G1 and 262 are similarly arranged on the other end of strip 251. Strips 250 and 251 are insulated from each other and from the mechanism that moves them. \Vhen the elevator is ascending, the strips move in the direction of the arrowdesignated up. Posts 263, 264 and 265 are mounted in fixed positions along the path of motion of the strips at intervals corresponding to the distance between landings. Each otthese posts, as indicated at post 263, is provided with two brushes 266 and 267 which contact respectively with strips 250 and 251. The two brushes and post form'a conducting bridge from one strip to the other and each set is insulated from the others.

lVith the elevator ascending at full speed and approaching the landing corresponding to post 263, at which it is desired to stop, the operator permits or causes the car switch to move from position 3 to position 2. The elevator will continue to run at full speed since the direction switch and high speed switch are still in until contact 256 on strip 251' comes under brush 267. Under the conditions just described, contacts 269 and 270 will be closed, due to the setting of centrifugal governor 22, which is driven from the elevator mechanism. Governor 22 is so set that contacts 269, 270 close when the elevator is nearly up to full speed and remain closed until the speed hasdropped a small amount below full speed. A circuit will then be established from main 34 through Wires 39, 49 and 50, contacts 47, 46 and 74, wire 75, resistance 88, wire 89, .solenoid winding 90, wires 91, 268, contacts 269. 270, wire 271, contact 256, brushes 267, 266, strip section 95, brush 272, which is mounted to contact on strip 250, wire 96, contacts 97, 98 and wires 99, 72, 73 and 42 back to main 33. Thus the high speed switch solenoid is energized by the current flowing in this circuit as well as by that flowing in the circuit of which solenoid winding 78 forms a part. Vinding 90, however, is wound in the reverse sense to winding 78 so that the effects of the two windings are neutralized and the high speed switch will open. As previously described. the generator voltage will immediately decrease and the elevator motor will be retarded by the dynamic braking action of the generator until it has reached the low speed corresponding to the low generator voltage.

Contact 256 is placed in strip 251 in such position that it will come under brush 267 at a time when the elevator is distant from the landing, the minimum required to brin the elevator from full speed to low speed lit] open. Elevator motor is thereby discon-- nected from the generator and resistance-81 is connected across the armature terminals of motor 10 by the closing of contacts 124, 125. At the same time, solenoid 115 of electromechanical brake 16 is deenergized and the brake is applied. In order to provide a quicker action of the electromechanical sition 2 until brake in automatically stopping, resistance 150 may be divided into two sections, one of which is normally short-circuited by contacts 287, 288 of the magnetic stopping switch 28 through wires 286 and 289. \Vhen the arm 64 comes-opposite armature 31, contacts 287, 288 are opened and the resistance across coil 115 is increased, thereby applying the brake in less time.

The elevator will now be at rest with its floor approximately level with the landing and the operator may place the car switch handle in neutral position or leave it in pohe desires to move the elevator car again.

Considering now the case in which the elevator is running at say three-quarters full speed and it is desired to stop at a landing: fiuch'a case might be where the elevator is proceeding from one floor to the second floor above. The operator will place the car switch handle in position 2, and if the elevator is accelerating it will continue to do so,-as full'speed conditions in the control circuits still obtain. 'As the elevator is not up to full speed, contacts 269, 270 con-,

trolled by the centrifugal governor willnot be closed and contact 256 of the slow-down controller will pass under brush 267 without causing any change. Contacts 273, 274, however, are adjusted so that they will be closed by the governor 22 when the elevator is running at three-quarters full speed. Consequently the elevator will continue toward the landing, and strips 250 and 251 of the slow-down controller will continue toward post 263. \Vhen contact 257- comes under brush 267, the circuit through contacts 274, 273 and solenoid winding will be closed and the high speed switch will be opened. It is to be noted that the slow-down in this case is initiated at a time when the elevator is nearer the landing than in the case where the elevator was running at full speed. The

distance from the landing at which slow down is initiated is controlled by the location of contact 257 in strip 251 and is de- 'ing the car switch in neutral position, the

operator will move it to position 3 and immediately return it to position 2. Although the control circuits will be set for full speed operation, it is unlikely that the elevator will-reach full speed and it is probable that the speed will be below threequarters full speed. Strips 250 and 251 of the floor controller will, therefore, move in accordance 'the governor and operates to initiate auto- .to slow speed, as in the previous cases. Al-

through I have shown but three contacts in the slow-down controller corresponding to three elevator speeds, it is apparent that any other number may be used under the same principles of operation.

In all cases when the elevator is brought to rest at a landing, the post corresponding to that particular landing will be central with insulating block 252 and contact 93. In Figure 2, post 264 is so shown. Insulating blockv 252 is shorter than contact 93 so that in slowing down a circuit may be made from contact 93 through the bridge contacts of the posts to portion 95 or 253 of strip 250. Insulating block 252, however, serves the purpose of keeping the circuit through solenoid winding 90 of the high speed switch open at the time of starting the elevator from a landing, so that. high speed operating conditions may be initiated inin'iediately on bringing the car switch to full speed position.

I have found that vin stopping a certain elevator from a full speed of six hundred loo I feet per minute by means of my automatic lamiling previous to the landing at which he desires to stop, in which to initiate the automatic stint-clown and'in addition a distance above the previous landing equivalent to one-half the length of insulating block 252 which may also be about three feet. If he moves the car switch to position 2 at any point within this six foot zone, he will make a perfect stop in a minimum of time. This is of great advantage over the controlling means heretofore in common use where it has been necessary for the operator to initiate the stopping at a definite dista-nce -itrom the landing in order to have the car come to rest exactly at the landing, without the use of levelling devices.

lVhether-the system is provided with an automatic stop or a manually controlled stop, the automatic slow-down represents an important improvement in the operation of elevators. It is peculiarly advantageous, however, in connection with an automatic stop, as will be apparent, and I regard the combination as a specific subject of invention in addition to the broad principles of the automatic slow-down per se.

It the operator desires-to stop the elevator at any time, whether at a landing or between landings, without utilizing the automatic slow-down and stop, he may do so by placing the car switch handle in the neutral position in which the automatic slow-down and stop are cut out. The elevator will then he brought to rest by the dynamic brake and electromechanical brake as though the automatic slow-down were not present.

Under certain conditions of operation, I may use push- buttons 300 and 301 to move the elevator for short distances at low speed. These are mounted immediately over the car switch in the elevator car. Push-button 300 is for up motion and push-button 301 for down motion, and they are mechanically interlocked by mounting one on each end of lever 302 so that both cannot be used at the same time. A contact 303 is provided on switch handle 45, but insulated from it, and is adapted to contact with a contact 304 (mounted on the car switch) when the handle 4.5 is in the neutral position. By pressing push-button 300, a circuit is closed from main 3st through wires 39, 49, 305, contacts 303. 304. wire 306, contacts 307, 308, 309, wires 102, 70,.solenoid 71 of the up dircction switch and wires 72, 73 and 42 to main 33. The direction switch will close, brake it; will be released and the elevator will ascend at low speed as long as the operator keeps pressure on push-button 300.

It will be understood that down motion, both hy-the push-button 301 and bythe car switch 32 in connection with the slow-down controller and magnetic stopping switch, is controlled in an exactly similar manner to that described for up motion.

sprocket or gear 339 and plate 34.0. Drum 341 is driven by In Figure 3, showii-ig one form of slowdown controller, atrame-325 supports a shaft 326, which is kept from turning by set screw 32? and key 328. A worm 329 is fixed on the shaft 320 between the two standards of frame 323. Slip rings 330, 331 and 332 are also secured to shaft 326. These slip ri'ngsare insulated from each other and from their supporting member 333. Spider 334 is rotatably mounted -on shal't 326 and in bearing The hub :36 oi spider 334 extends through bearing 335 and is driven by through bolts 338 and not studs 34:2 and 3 :3 which are secured in spider 334 and pass through holes in spokes to -cure ot the ring 349. hen located they are locked in place by bolts 35 fh-"" Posts 355. 350 and 357 are mountedfol-lengthwise adjustment respectively in arms 351, 352 and 353. (tn the outer cylindrical surface of drum 3-11" are mounted the strips 250 and of Figure 2 in the form of a helix having the same pitch as the worm 329. The strips are insulated from the drum by insulation Brush 272 is mounted on post 355 and as shown in Figure 3. the brid e contact 94 is mounted on post'35'T. Post 306 holds the brush corresponding to brush 272 for down motion of the elevator. It will be understood that posts 263 and 265 (Figure 2) are mounted in suitable relation to post 3570a ring 3 10. It is app rent that as the drum 341 rotates the brughes will be maintained on the proper strip Figure 4 shows the developed surface of the drum 341 and diagrammatically the electrical connections andarrangements of contacts for a slow-down controller designed for three landings. This is the condition illustrated in Figure 2 and the same numerals are used in connection with Figure t. As the operation was described in detail in connection with Figure 2, it is thought unnecessary to repeat it. Although I have described 'the slow-down controller as designed for three landings, it may he used For any number by proportioningthe speed of the controller to that of the/elevator so that when the elevator, moves the full length of the hatchway the controller .will rotate an amount that will cause the portion 05 of strip 250. to move under brush 272 from a point near insulating block 252-to a point cap be placed at any point in the circuinnear its end. In designing the controller it is also necessary to locate contacts 256, 257

and 93 in strip 251 so as to initiate slowdown at the proper distance from the landing.

Having described my improved system of elevator control I desire to point out that it atfords means for maintaining the highest possible average elevator speed and for do- 10 ing away with the necessity of highly skilledoperators. To do thisI employ automatically controlled acceleration and retardation, which can be made as rapid as desired and, in addition, I automatically determine the point at which the elevator will start to slow down so that regardless of its speed it will always reach a prescribed low speed at approximately the same distance from the landing. Further I automatically stop the elevator from the low speed approximately level with the landing without over-running.

My control system enables the operator to select, while the car is in motion, the landing at which he desires to automatically stop and he has quite a range of distancein which to manipulate the car switch to accomplish this. Consequently his skill is not constantly taxed nor does he become so quickly fatigued.

I have found that in bringing elevators to rest, there is some variation in the distance required to stop them from any given speed, depending on the load in the elevator. The same considerations apply in bringing an elevator from any given speed to a lower speed. It is customary to counterbalance elevators and forty percent of the full load 7 is a common amount. Considering an ele-' vator for a maximum lifting capacity of two 4 thousand five hundred (2500) pounds, coun terbalanced forty percent, the maximum unbalanced load when the elevator is ascending fully loaded will be one thousand five hundred (1500) pounds, and the maximum unbalanced load when the elevator is descending light will be one thousand (1000) pounds. These amounts represent the weights the elevator motor must lift under the extreme conditions. In additionthe motor must accelerate the total mass of the elevator, counterweights, cables, etc.. and the brakes must retard these masses. Then the elevator motoris lifting the unbalanced load,

*as when the elevator is ascending loaded or descending light, the elevator car will stop in a shorter distance after the power is turned off and the brakes applied. than it will stop when the unbalanced load is being lowered by the elevator motor.

To compensate for this variation in the distance required to stop, I provide means for controlling the speed of the elevator so that it will be in some direct proportion to the load on the elevator motor at both full and low speeds. In this way the tendency of the elevator to stop or slow down to a. definite low speed in a shorter distance under conditions of load on the elevator motor is counteracted by the tendency to travel a greater distance due to increased speed. This is particularly important in the low speed operation of the elevator as it is from the low speed that the elevator is brought to rest at a landing. The means I employ to give an elevator speed that will be greater as the load on the motor increases, is the impressing on the armature terminals of the elevator motor 10 of a voltage that will be higher as the load on the motor increases. This voltage characteristic is produced by properly designing the generator 5 and particularly proportioning the series field 8 in reference to the separately excited field 36 to give the desired results.

I have obtained excellent results in automatically stopping an elevator under different conditions of loading by means of the invention described. As an example, the greatest variation in conditions for a. particular elevator were found to be between stopping while ascending and stop ing while descending with the elevator fillly loaded and an unbalanced loadof one thousaid five hundred (1500) pounds. Under such conditions I was able to stop this ele- "ator from low speed within one inch of the landing when approaching from either direction by making the prescribed low speed sixty feet per minute when the elevator was ascending and thirty-eight feet per minute when the elevator was descending. The voltages at the generator terminals corresponding to these speeds were 57 and 9 respectively. With the load in the car just balancing the counterweight, which is the average running condition, stops were made with1n oneeighth of an inch of the landing in either direction and the voltage was 34 for up motion and 32 for down motion.

This is an important improvement 1n elevator practice, where heretofore the speed has always been slower when the motor was 11fting a load than when it was retarding it, and offers many advantages in automatic control, as has been pointed out.

I claim 1. An elevator system comprising, an elevator, a motor for raising and lowering the elevator, a source of curei'nt for said motor, means for automati ally initiating a reduction of the voltage of said source to a delinite low value to cause a reduct ion of the elevator speed. and means for automatically causing said definite low value of voltage to be in some direct proportioirto the load on said motor.

2. An elevator system. comprising, an elevator, a motor for raising and lowering the elevator, a generator for supplying current to said motor, and means for automaticall initiating a reduction of the terminal E. F. of said generator to a definite low value to cause a reduction of the elevator speedvsaid genera or having a series field winding constructed and arranged to cause said delinitelow value oi generator terminal E. llLli. to be in some direct proportion to the load on said motor.

3. An electric elevator system comprising .in combination, an elevator, a motor for' raising and lowering the elevator, a generator :for supplying current to said motor, means for automatically determining the speed of said motor directly in some proportion to the load thereon, said means comprising said generator, and meansffor automatically stopping the elevator at a landing.

4. An electric elevator system comprising in combination, an elevator, a motor for raising and lowering the elevator, a. generator for supplying current to said motor, means for automatically determining the speed of said motor directly in some propor tion to the load thereon, said means comprising said generator, and means for automatically discontinuing the supply of current to said motor and applying a brake at a fixed distance from the landing to stop the elevator at the landing.

5. An electric elevator system comprising 1n combinatlon, an elevator, a motor for raising andlowering the elevator, a generator for supplying current to said motor, said generator having a series field winding, and means to automatically cause the elevator speed to be directly in some proportion to the unbalanced weight being lifted, said means comprising said generator.

6'. An electric elevator system comprising in combination, an elevator, a motor for raising and lowering the elevator, a generator for supplying'current to said motor, said generator having a series field winding, and means to automatically cause the elevator speed to be inversely in some proportion to the unbalanced Weight being lowered, said means comprising said generator.

7. An elevator system comprising, motive means for raising and lowering the elevator, means for automatically initiating a reduction of the elevator speed to a definite low speed at difi'erent, distances from a landing and means for causing the definite low speed i of the elevator to be. directly in some propor- Y as tion to the load on said motive means.

8. An elevator system comprising, means for automatically initiating a reduction of the elevator speed to a definite low speed at different fixed distances from the desired landing, and means for causing the definite low speed of the elevator to be directly in some proportion to the unbalanced weight being ifted.

9. An elevator system comprising, means for automatically initiating a. reduction of the elevator speed to a definite low speed/at difi'erent fixed distances from the desired landing, and means for causing the definite low speed of the elevator to be inversel in some proportion to the unbalanced weight being lowered.

10. An elevator system comprising, motive means for raising and lowering the elevator, means for automatically initiating a reduction of the elevator speed to a definite low speed as it approaches a selected landing, automatic means for rendering said initiating means effective at different distances from the selected landing, and means for causing said definite low speed to be directly in some proportion to the load on said motive means.

11. An elevator system comprising, motive means for raising and lowering the elevator, means for causing the elevator to be brought from rest to full speed, means for automatically initiatin a reduction of the elevator s eed to a de nite low s eed at a variable istance from the desire landing,

said initiating means comprisin means for a landing for automatically initiating a reduction of the elevator speed to a definite low speed at a variable distance from the selected landing, said initiating means comprising means responsive to the speed of the elevator for determining said distance, and means for causing said definite low speed to be directly in some proportion to the load on said motive means.

13. An elevator system comprising, means for bringing the elevator from rest to full speed, means rendered operative by the operator in selecting a landing -for automatically initiating slowing down of the elevator to a definite low speed at different fixed distances from the landin selected, means for automatically determining the fixed distance at which the initiating means becomes effective, and means to automatically cause the definite low speed of the elevator to be directl in some proportion to the unbalanced weig t being lifted.

14:. An elevator system comprising, means for bringing the elevator from rest to full speed, means rendered operative by the operator in selecting a landing for automatically initiating slowingdown of the elevator to a definite low speed at different fixed distances from the landing selected, means for automatically determining the fixed distance at which the initiat'lngmeans becomes effective, and means to automatically cause the definite low speed of the elevator to be inversely in some proportion to the unbalanced weight being lowered.

15. An electric elevator system comprising in combination, means normally under control of the operator for bringing the elevator from rest to full speed, means for automatically initiating a reduction ot. the elevator speed to definite low speed at. a distance from the desired landing, depending upon the momentary speed of the elevator, and means to automatically cause the delinite low speed of the elevator to be directly in some proportion to the unbalanced Weight being lifted;

16. An electric elevator system comprising in combination means normally under control of the operator for bringing the elevator from rest to'full speed, means for automatically initiating a reduction of the elevator speed to definite low speed at a distance from the desired landing, depending upon the momentary speed of the elevator, and means to automatically cause the definite low speed of the elevator to be inversely in some proportion to the unbalanced weight being lowered.

17. An electric elevator system comprising in combination, means normally under control of the operator for bringing the elevator from rest to full speed, means for automatically initiating a reduction of the elevator speed to definite low speed at a distance from the desired landing, depending upon the momentary speed of the elevator, and means to automatically cause the definite low speed of the elevator to be directly in some proportion to the unbalanced weight being lifted'and inversely in some proportion to the unbalanced weight being lowered.

18. An electric elevator system comprising in combination, means normally under control of the operator for bringing the elevator from rest to full speed. means for automatically initiating a reduction of the elevator speed to definite low speed at a listance from the desired landing. depending upon the momentary speed of the elevator, means to automatically cause the deli- .nite low speed of the elevator to be directly vator from rest to full speed, means for automatically initiating a reduction of the elevator speed to definite low.speed at a distance from the desired landing, depending upon the momentary speed of the elevator, means to automatically cause the definite low speed of the elevator to be inversely in some proportion to the unbalanced weight being lowered, and means for automatically initiating stopping of the elevator'at a fixed distance from a landing to bring the elevator to rest approximately level with the landing. 20. An electric elevator system compris ing in combination, means normally under control of the operator for bringing the elevator from rest to full speed, means for automatically initiating a reduction of the elevator speed to definite' low speed at a distance from the desired landing, depend ing upon-the momentary speed of the elevator, means to automatically cause the definite low speed of the elevator to be directly in some proportion to the unbalanced weight being lifted and inversely in some proportion to the unbalanced weight being lowered, and means for automatically ini tiating stopping of the elevator at a fixed distance from a landing to stop the elevator approximately level with the landing.

GRAHAM B. GROSVENOR.

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