US1972015A - Push button elevator control system - Google Patents

Description

ug. 28, 1934. Hl B GQLDMAN 1,972,015

RUSH BUTTON ELEVATOR CONTROL SYSTEII Filed July 20, 1932 L- Ll'l'flif' 32 55 34 M@ me; A

Fifi@ T l Patented Aug. 28, 1934 Unirse STATES tenais PATENT PUSH BUTTON ELEVATOR CONTROL SYSTEM 21 Claims.

lViy invention relates to pushbutton control systems for electric elevators, and it has particular relation to certain hereinafter-mentioned improvements which, while not limited to any particular use, are primarilyand especially adapted for hold-down or constant-pressure pushbutton control systems in which the pushbutton must be pressed down constantly as long as the elevator is to run. By the term elevator I mean to include a vertically moving cage, car or platform for' freight, passenger or dumbwaiter use.

One of the objects of my invention is to provide a non-interference switch adapted for a constant-pressure pushbutton control-system for elevators, in order to safeguard the persons using the elevators, so as to give them time to load and unload, vAccording to my invention, the non-interference switch-contacts are in series with the landing pushbuttons, as in my pending application Serial No. 408,982, led November 22, 1929,v for Automatic elevator controls. These switch-contacts are openedv whenever the elevator motor is energized, but first they are shunts ed by an auxiliary contact-device which was not provided in my pending application abovementioned. The shunt-connected auxiliary contact-device keeps the landing pushbuttons live so that a constant-pressure control system may be used. As soon as the elevator-motor is deenergized, theY auxiliary contact-device instantly opens, and the non-interference switch begins to`close, being retarded by a dash-pot or the like, meanwhile killing the landing pushbuttons and giving the operator time to load or unload, or time to open a rguard-device which automatically locks out the elevator-motor controls.

Another object of my invention is to provide a non-interference switch which is mechanically interlocked with the reversing contactors of an electric elevator system of the constant pressure pushbutton type,

A further object of my invention is to provide elevator control system utilizing barriers or guard-devices, the opening of which will lock out the elevator motor so that the elevator-car cannot be moved until the barrier is manually closed, supplemented by means of automatically ringing alarm whenever someone depresses a button at another landing when the barrier at the elevator-car has been leftv open, so that the operator at the car-landing will close the barrier again.

With the foregoing and other objects in View, my invention consists in the elements, combinations, systems and methods hereinafter described and claimed, and illustrated in the accompanying drawing, wherein Figure 1 is a simplified diagrammatic View of circuits and apparatus illustrating a preferred form of embodiment of my invention, and

Figs. l2 and 3 are similar views showing modiiications.

An elevator car is raised and lowered by a reversible electric motor 2, shown as a threephase induction motor, which is controlled by two main up and down electromagnetic reversing contactors U and D for energizing it in either direction of rotation. The accelerationof the motor, on starting,r may be controlled by two starting resistances 5, which may be cut out by an accelerating relay 6 energized from a timing relay 7. The motor may be stopped by the usual brake, as shown, for example, in my aforementioned pending application.

Each of the reversing contactors U and D has an energizing coil 8, two main contacts 9 for the motor circuit, a normally open auxiliary contact l1, and preferably also a normally closed auxiliary contact 12, although the latter may be omitted if the contactors are provided, as is common, with electrical or mechanical interlocks for preventing the simultaneous actuation of both contactors, as indicated at 13.

Current is supplied to the contactor-coils 8 from the supply-line l through a switch 16 having an auxiliary contact 17 for the contactorcoil circuit. An overspeed switch 18 on the motor shaft is also included in thecontactor-coil cirouit,vas well as a nal up limit switch 19, a final down limit switch 29, a car-gate Contact 21 and a car safety switch 22.

One of the supply-leads 23 of the contactorcoil circuit is connected to a control-means in the car, preferably one which cannot be moved to the up and down positions at the same time, being either a car switch or mechanically interlocked up and down pushbuttons 24 and 25, preferably having a mechanical interlock 26 for preventing both buttons from being depressed at the same time.

In the normal at rest position of the controlmeans 24 and 25 in the car, a circuit is completed to a landing-pushbutton supply-lead 27 leading to a plurality of up and down landing pushbuttons 29 and 30, each landing having one up pushbutton and one down pushbutton.

The up pushbuttons 24 and 29 in the car and at the landings, when depressed, connect the supply-'lead 23 to an up conductor 31 which leads to the electromagnet-coil 8 of the up contaeter U, through an up stop limit switch 32. The down pushbuttons and 30, when depressed, connect the supply-lead 23 to a down conductor 33 which leads to the electromagnetcoil 8 of the down contactor D, through a down stop limit switch 34. The car pushbuttons 24 and 25 are so arranged that, when either one is actuated, the landing-pushbutton supplylead 27 is deenergized, as shown.

The arrangement just described is what I call a constant-pressure or hold-down pushbutton control, in which the up or down contactor U or D, which energizes the motor 2, isA

held closed only as long as the pushbutton is held down. Such constant-pressure control systems, lacking the automatic control features which are provided for some elevators, are inherently less expensive than the automatic systems, and every eort must be made to keep down the expense by using the simplest possible control circuit and apparatus.

As pointed out in my above-mentioned'automatic elevator control case, Serial No. 408,982, it is desirable to provide a non-interference switch to kill the landing pushbuttons for a few seconds after the car stops, so ask to prevent anyone else from interfering with the operators control over the car before he has time to enter or leave the car or to operate a door or barrier such as the above-mentioned car-gate contact 21 which opens and thus kills all control over the elevator-*noten When an efort is made to apply a non-interference switch to a constant-pressure elevator control, difficulty is involved because of the vnecessity for keeping the landing pushbuttons 29 and 30 live until the motor stops, because the motor cannot'be kept going if vthe pushbutton circuit is interrupted. Furthermore, economic considerations, as above pointed out, lead to a Vdesire for as few relays as possible, even avoiding the necessity for the electromagnetic or relay-type of non-interference switch which is shown in my above-mentioned pending application.

In view of the foregoing considerations, I have devised a mechanical non-interference switch and I have shunted its contacts 37 byY means of the normally open auxiliary contacts 11 on the reversing contactors U and D. When the normally closed contacts 12 are utilized, the normally open contact l1 of each contactor is connected in series with the normally closed contact 12 of the other contactor, so that there can be no possibility of erroneous operation. l

The non-interference switch-contacts v37 are connected in series with the landing-pushbutton supplf-iead V2'?. f

The non-interference switch 36 is'operated by means of a mechanical connection to the two reversing contactors U and D, preferably including resilient connections or springs: 41, 42, carried by the respective contactors, so that, when either contactor is raised or energized, it lifts the non-interference switch 36 and opens the contacts 37. The mechanical connection is such, however, that before the contacts 37 aire opened the normally open auxiliary contact ll of the actuated contactor 'is closed, so that a shtmting circuit is made around the contacts 37 in order toavoid even a momentary break inthe pushbutton circuit. This is an importantprecaution in a'constant-pressure pushbutton system, as above described. l

The non-interference switchg36 is provided with a dashpot 44 or equivalent time-delay device for retarding its action, and this device may retard the switch more strongly when it is closing than when it is opening, as indicated by the inclination of the piston-packing in the drawing.

When the energized reversing contactor U or D is deenergized, it immediately drops, thus permitting the non-interference switch to begin to drop,'moving slowly on account of the dashpot. However, the auxiliary contact 11, which was closed when the contactor was energized, is immediately opened, so that the landing-pushbutton-circuit is opened during the time required for the non-interference switch-contact 37 to close, thereby safeguarding the operator as previously described.

It is noted that my use of a mechanical nonvinterference switch, instead of an electromagnetic-non-interference relay, may be applied to automatic, as well as constant-pressure, pushbutton control systems.

In addition to, or instead of, the car-gate contact 21 already mentioned, I prefer to use landing doors or barriers, carrying switches or contacts which are all connected in series, so that I the elevator cannot be operated unless all barriers are properly closed, and I also desire to provide signal means that will operate, without any additional wiring or equipment, (so as to cut down expense), whenever a landing pushbutton 29 or 30 is depressed, to summon the elevator car, when one or more of the barriers or doors are open.

To this end, I provide a door-contact relay 52 which performs the double function of placing a i break in the up and down contactor-coil circuits, when one door or barrier is open, and transferring the energizing circuit from the up or down contactor-coil 8 to a bell or other signal54, when one door or barrier is open.

The door-contact or barrier-contact relay 52 is provided with an actuating coil 53 which is energized whenever all of the door contacts 50 are closed. This causes the relay to pick up, closing two normally open contacts 55 and 56 which are in series with the "up and down conductors 31 and 33, respectively, for the two contactorcoils -8, and at the same time opening two normally closed contacts 57 and 58 which are connected between the bell or signal device 54 and said up and down conductors 31 and 33, respectively.

When the door-contact relay 52 is not properly energized, the up and down conductors 31 and 33 are thus caused to actuate the bell 54, in-

stead of actuating the contactor-coils 8, so that when a pushbutton is depressed under these circumstances the bell automatically rings, thus summoning the person who left the door open,

so that he will close the door and permit someone j vide, for the protection of the operator in the fa.

car,- anemergency-release switch 59 in the car, which must be held down to be effective, and which will short-circuit all ofthe door contacts andkeep the operator from being stuck between two landings.

However, j, L -4 It will be noted that my double-purpose doorcontact and signal relay 52 not only avoids the use of extra equipment for signalling purposes, but it also avoids the necessity for a separate circuit for the sole purpose of signalling, which, under union regulations, could not be installed by the elevator Workmen, but must be installed by electricians, and, according to some safety codes, must use wires lying in separate conduits. All of these difiiculties, as well as improved automatic and instantaneous signalservice, are obtained by my relay 52 which avoids the necessity for a separate signalling pushbutton at each landing.

While I have shown and described my invention in a preferred form of embodiment, I do not desire to be limited altogether thereto. For example, in dumb-waiters, the control equipment 2e and 25 in the car would be omitted, as well as the car-gate contact 21 and the car safety switch 22, The foregoing and other changes can be made without departing from the essential spirit of my invention. I desire, therefore, that my appended claims shall be accorded the broadest interpretation consistent with their language and the prior art.

As another exemplary modification, it may sometimes be desirable to provide landing pushbuttons so arranged that, if the car is at the top of its shaftway, and two or more down buttons are pressed at different landings at the same time, the car will stop at the last button reached, when it is released, regardless of how the down buttons are actuated at higher landings, and if the car is in the basement and two or more up buttons are pressed at dii'erent landings at the same time, the car will stop when the lowest button is released, instead of keeping on traveling until the last up landing button is released, as in Fig. 1.

For this purpose, I may provide long-stroke, double-contact up and down buttons 61 and 62 at the landings, as shown in Fig. 2, connecting them so that the energizing current, after passing through the non-interference switch 37, is led irst to the top and bottom contacts of one of the buttons, as 62, at the lowest landing, then from the top contacts of this button to the top and bottom contacts of theother button 61 at the same landing, then from the top contacts of the last-mentioned button to the top and bottom contacts of one of the buttons of the next higher landing, and so on through all the landing buttons. The bottom contacts of the down buttons 62 at the landings lead to the down conductor 33 which supplies the down contactor as in Fig. 1, whe the bottom contacts of the up buttons 61 at the landings, in Fig. 2, lead to the up conductor 31. Long- stroke buttons 61 and 62 will have to be used to provide time, after a button 61 or 62 has been released, for the main up and down contacter, as the case may be, to drop down, thereby open-circuiting the auxiliary non-interference contacts 11 and killing all of the landing buttons before the top contacts of the released buttonl are closed so as to energize the buttons at the higher landings.

1f it desired to have the elevator stop at the nrst down button that is reached on descendiing in response to a call from a plurality oi landing 'out-tons, instead of continuing on to the bottom one, as in Fig. 2, 1 may utilize the connections shown in 3, wherein the supply current coming from the non-interference switch 37 goes to the up button y51 at the lowest landing, and

thence on through the other up buttons 61, in order, as indicated at 71, While a branch circuit 72 leads from the non-interference switch 37 and goes rst to the down button 62 at the top landing, and thence on through the other down buttons 62, in order, as indicated at 73.

I claim as my invention:

1. A pushbutton elevator-control system; comprising, in combination with an elevator car and a reversible electric elevator motor; electromagnetic up and down reversing contactors, energizing means for the energizing coils of said reversing contactors, said energizing means comprising a source oi supply and control circuits including pushbuttons at the landings; a delayed-action non-interference switch having contacts in series with the energizing circuits for said landing pushbuttons, means responsive to the energization of either of said reversing contactors for rst closing a by-pass circuit around said non-interference switch-contacts and then causing said non-interference switch-contacts to open, and for respondng to the deenergization of the energized contactor for opening said by-pass circuit and then causing said non-interference switchcontacts to close only after a predetermined timedelay.

2. A pushbutton elevator-control system; cornprising, in combination with an elevator car and a reversible electric elevator motor; electromagnetic up and down reversing contactors having energizing coils, main contacts for the elevator motor circuit, a normally closed auxiliary contact and a normally open auxiliary Contact; energizing means for the energizing coils of said reversing contactors, said energizing means comprising control circuits including pus'nbuttons at the landings and control means in the car; and non-interference means for giving the user of the elevator time to enter or leave the car after it has reached its landing before anyone else can summon the car from another landing; characterized by said non-interference means comprising a delayed-action relay having normally closed contacts which open after a slight delay 7" when either of said reversing contactors is actuated and which close after a longer delay when the actuated contacter is released, said delayed-action relay-contacts being in series with the landing bushbuttons and being shunted by the normally closed auxiliary contact of the up contactor in series with the normally open auxiliary contact of the down contactor, and being also shunted by the normally open auxiliary contact of the up contactor in series With the normally closed auxiliary contact oi the down contacter.

3. A constant-pressure pushbutton elevatorcontrol system; comprising, in combination with an elevator car and a reversible electric elevator motor; electromagnetic up and down reversing contactors; control means in the car for energizing either of said reversing contactors at will and vlor instantly discontinuing the energization thereof upon the return of said control means to its normal inoperative position; and constantthen causing said non-interference switch-contacts to open, and forresponding to the denergization of the energized contactor for opening said by-pass circuit and then causing said noninterference switch-contacts to close only after a predetermined time-delay.

4. A pushbutton elevator-control system; comprising, in combination with an elevator car and a reversible electric elevator motor; electromagnetic up and down reversing contactors having energizing coils, main contacts for the elevator motor circuit, and a normally open auxiliary contact; energizing means for the energizing coils ofY said reversing contactors, said energizing means comprising control circuits including pushbuttons at the landings, a retarded noninterference switch having contacts in series with the energizing circuits for said landing pushbuttons, connections for connecting each of the normally open auxiliary contacts of the two reversing contactors in parallel to said non-interference switch, means responsive to the energization of either of said reversing contactors for causing said `non-interference switch-contacts to open after the closure of one of said shunting auxiliary contacts, and means responsive to the deenergzation of the energized contactor for causing said non-interference switch-contacts to close only after a predetermined time-delay.

5. A pushbutton control-system for an electric elevator comprising a car, barriers for the safeguarding of people, and barrier-operated switches for the prevention of elevator-movement when said barriers are not properly positioned, characterized by electromagnetic up and down" reversing contactors; up and down pushbuttons at the landings for energizing said up and down contactors, respectively; and a retarded non-interference switch having contacts in series with the energizing circuits for said landing pushbuttons, means responsive to the energize.- tion of either or' said reversing contactors for rst closing a by-pass circuit around said non-interference switch-contacts and then causing said non-interference switch-contacts to open, and for responding to the deenergization of the energized contactor for opening said by-pass circuit and then causing said non-interference switch-contacts to close only after a predetermined timedelay sufcient for the person in control of the elevator to operate one of said barriers.

6. The invention as specified in claim 5, characterized by a barrier-contact relay having an energizing coil in series with a plurality of said barrier-operated switches, whereby said barriercontact relay is energized only when said serially connected barrier-operated switches are all closed, said barrier-contact relay having normally open contacts connected in series with an energizing circuit of both of the reversing contactors, so as to prevent the operation of either contacter' when one or more of the barriers are improperly positioned, and signal means connz'ted to be effectively energized in lieu of the .up or down reversing contacter when a pushbutton is depressed While the barrier-contact relay is deenergized.

7. The invention as specied in claim 5, characterized by a barrier-contact relay having an energizing coil in series with a plurality of said barrier-operated switches, whereby said barriercontact relay is energized only when said serially connected barrier-operated switches i are Yall closed, said barrier-contact relay having a pair of normally openV main contact circuits'connected in series with the respective energizing circuits of the up and down reversing contactors, and a signal means, said barrier-contact relay having a vpair of auxiliary contact circuits which are closed when said barrier-contact relay is unenergized, for completing an energizing circuit from the up and down pushbutton circuits to said signal means to energize the latter whenever a pushbutton is depressed when one of said serially connected barrier-operated switches is open.

8. A pushbutton control-system for an electric elevator comprising a car, barriers for the safeguarding of people, and barrier-operated switches for the prevention of elevator-movement when said barriers are not properly positioned, characterized by electromagnetic up and down reversing contactors; up and down pushbuttons at the landings for energizing said up and down contactors, respectively; a barrier-contact relay having an energizing coil in series with a plurality of said barrier-operated switches, whereby said barrier-contact relay is energized only when Vsaid serially connected barrier-operated switches are all closed, said barriercontact relay having -apair of normally open main contact circuits connected in series with the respectiveenergizing circuits or" the up and down reversing contactors, .and a signal means, said barrier-contact relay having a pair or" auX- iliary contact circuits which are closed when said barrier-contact relay is unenergized, for completing .an energizing circuit from the up and fdown pushbutton circuits to said signal means to energize the latter whenever a pushbutton is depressed when one of said serially connected barrier-operated switches is open.

9. A pushbutton control-system for an electric elevator comprising a car, barriers for the safeguarding of people, and barrier-operated switches for the prevention of elevator-movement when said barriers are not properly positioned; characterized by electromagnetic up and down reversing contactors; up and down pushbuttons at the landings for energizing said up and down contactors, respectively; a signal means; and means responsive to an open position of one or more barrier-switches for making an energizing circuit connection from one or more landing pushbuttons to said signal means.

10. A pushbutton control-system for an electric elevator comprising a car, barriers for the safeguarding of people, and barrier-operated switches for the prevention of elevator-movement when said barriers are not properly positioned; characterized by electromagnetic up and down reversing contactors having energizing coils, energizing means for the energizing coils of said reversing contactors, said energizing means comprising control circuits including pushbuttons at the landings, and a retarded non-interference switch having contacts in series with the energizing circuits for said landing pushbuttons, means responsive to the energization of either of said reversing contactors for first closing a bypass circuit around said non-interference switchcontacts and then causing said non-interference switch-contacts to open, and for responding'to the deenergization oi the energized contactor for opening said by-pass circuit and then` causing said non-interference switch-contacts to close only after a predeterminedtime-delay suiicient for the person in control of the elevator to operate one of said barriers.

, 11. The invention as specified in claim l0, characterized by a barrier-contact relay having an ifi() energizing' coil in series with a plurality of said barrier-operated switches, whereby said barriercontact relay is energized only when said serially connected barrier-operated switches are all closed, said barrier-contact relay having normally open contacts connected in series with an energizing circuit of both of the reversing contactors, so as to prevent the operation of either contactor when one or more of the barriers are improperly positioned, and signal means connected to be eiectively energized in lieu of the up or down reversing contactor when a pushbutton is depressed while the barrier-contact relay is deenergized.

l2. The invention as specied in claim l0, characterized by a barrier-contact relay having an energizing coil in series with a plurality of said barrier-operated switches, whereby said barriercontact relay is energized only when said serially connected barrier-operated switches are all closed, said barrier-contact relay having a pair of normally open main contact circuits connected in series with the respective energizing circuits of the up and down reversing contactors, and a signal means, said barrier-contact relay having a pair or auxiliary contact circuits which are closed when said barrier-contact relay is unenergized, for completing an energizing circuit from the up and down pushbutton circuits to said signal means to energize the latter whenever a pushbutton is depressed when one of said serially connected barrier-operated switches is open.

13. A pushbutton control-system for an electric elevator comprising a car, barriers for the safeguarding of people, and barrier-operated switches for the prevention of elevator-movement when said barriers are not properly positioned; characterized by electromagnetic up and down reversing contactors having energizing coils; energizing means for the energizing coils of said reversing contactors, said energizing means comprising control circuits including pushbuttons at the landings; a barrier-contact relay having an energizing coil in series with a plurality of said barrier-operated switches, whereby said barriercontact relay is energized only when said serially connected barrier-operated switches are all closed, said barrier-contact relay having a pair of normally open main contact circuits connected in series with the respective energizing circuits of the up and down reversing contactors, and a signal means, said barrier-contact relay having a pair of auxiliary Contact circuits which are closed when said barrier-contact relay is unenergized, for completing an energizing circuit from the up and down pushbutton circuits to said signal means to energize the` latter whenever a pushbutton is depressed when one of said serially connected barrier-operated switches is open.

lll. A pushbutton control-system for an electric elevator comprising a car, barriers for the safeguarding of people, and means including barrieroperated switches for the prevention of elevatormovement when said barriers are not properly positioned; characterized by means, including electromagnetic up and down reversing contactors having energizing coils, for controlling the operation of the car; energizing means for the energizing coils of said reversing contactors, said energizing means comprising control circuits including pushbuttons at the landings; a signal means, and means responsive to an open position of one or more barrier-switches for making an energizing circuit from one or more landing pushbuttons to said signal means.

l5. The invention as specified in claim 4, characterized by a mechanical connection between said non-interference switch and the reversing contactors whereby said non-interference switch is lifted whenever either one of the reversing contactors is lifted into energized position.

16. A pushbutton elevator-control system; comprising, in combination with an elevator car and a reversible electric elevator motor; electromagnetic up and down reversing contactors, energizing means for the energizing coils of said reversing contactors, said energizing means comprising control circuits including pushbuttons at the landings; a delayed-action non-interierence switch having contacts in series with the energizing circuits for said landing pushbuttons, means for actuating said non-interference switch when either of the reversing contactors is energized, to open its contacts, whenever one of the reversing contactors is energized, and quick-acting means for shunting said non-interference switch contacts when either' or the reversing contactors is energized.

17. A pushbutton elevator-control system; comprising, in combination with an elevator car and a reversible electric elevator motor; electromagnetic up and down reversing contactors, energizing means for the energizing coils of said reversing contactors, said energizing means coniprising control circuits including pushbuttons at the landings; a retarded non-interference switch having contacts in series with the energizing circuits or said landing pushbuttons, a resilient mechanical connection between said non-interference switch and the reversing contactors whereby said non-interference switch is lifted whenever either one of the reversing contactors is lifted into energized position, and a time-delay device for retarding the lowering of said noninterference switch upon the deenergization of the energized contactor, and quick-acting means for shunting said non-interference switch contacts when either of the reversing contactors is energized.

18. A pushbutton control-system for an electric elevator comprising a car, barriers for the safeguarding of people, and barrier-operated switches for the prevention of elevator-movement when said barriers are not properly positioned, characterized by electromagnetic up and down reversing contactors having energizing coils, main contacts for the elevator motor circuit, and a normally open auxiliary contact; energizing means for the energizing coils of said reversing contactors, said energizing means cornprising control circuits including pushbuttons at the landings, a retarded non-interference switch having contacts in series with the energizing circuits for said landing pushbuttons, a mechanical connection between said non-interference switch and the reversing contactors whereby said noninterierence switch is lifted whenever either one of the reversing contactors is lifted into energized position, a dashpot for retarding the lowering of said non-interference switch upon the deenergization of the energized contacter, and connections for connecting each of the normally open auxiliary contacts of the two reversing contactors in parallel to said non-interference switch.

19. The invention as specified in claim 1, characterized by long-stroke, double-contact down buttons at the several landings, connected in series with each other, in order, and long-stroke double-contact up buttons at the several landings, connected in series with each other, in order, whereby, upon the simultaneous depression of two up landing buttons, or two down landing buttons,.the car is under the control of the button closest to the source of supply.

20. A constant-pressure pushbutton electric control system for elevators comprising up and. down control-circuit means, a supply circuit therefor, double-contact up buttons at the several landings, energized from said supply circuit in series with each other, in order, for energizing said up control-circuit means when an up button is depressed, and double-contact down buttons at the several landings, energized irom said supply circuit in series with each other, in order, for energizing said down control-circuit means when a down button is depressed, whereby, upon the simultaneous depression of two up landing buttons, or two down landing buttons,

the car is under the vcontrol of the button closest to the source of supply.

21. A constant-pressure pushbutton electric control system for elevators comprising up and down control-circuit means, a supply Circuit therefor, double-contact up buttons at the several landings, energized from said supply circuit in series with each other, in order, starting with the lowest landing, for energizing said up control-circuit means when an up button is depressed, and double-contact down buttons at the several landings, energized from said supply circuit in series with each other, in order, starting with the top landing, for energizing said down control-circuit means when a down button is depressed, whereby upon the simultaneous depression of two up landing buttons, or two down landing buttons, the car is under the control of the button closest to the source of 511191313.

' HARRY BENJAMIN GOLDMAN.

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