US3369633A - Electrical control for a hydraulic elevator system - Google Patents

Description

Feb. 2o, 1968 ELECTRICAL CONTROL FIOR A HYDRAULIC ELEVATOR SYSTEM 'R. F. MARTIN Filed April 8, 1964 ...l-Psw Nc I I l I Il u | I I I .1 I I I 00h/N HLA CFLL/ oook OPER/772W? U ooo@ OPER/170A? MOTOR l?? @Qi/fifa@ United States Patent Ofi-ice 3,369,633 Patented Feb. 20, 1968 3,369,633 ELECTRICAL CONTROL FOR A HYDRAULIC ELEVATQR SYSTEM Richard F. Martin, Rock Island, Ill., assignor to Montgomery Elevator Company, a corporation of Delaware Filed Apr. 8, 1964, Ser. No. 358,201 9 Claims. (Cl. IS7- 29) 'ABSTRACT 0F THE DISCLOSURE A hydraulic elevator control circuit that includes a protective timer which is started each time the motor and pump start, and which has a cycle slightly greater than the time required Afor the elevator to make a single trip from the bottom terminal to the top terminal without intermediate stops. If the timer cycle is completed before the car stops at the top terminal the motor is stopped and the valves are operated to lower the car to the bottom terminal.

Hydraulic elevators have come into widespread use in recent years for relatively fast passenger service in buildings having two to four floors. Modern installations require relatively high rates of fluid flow to produce the required high speeds, and this in turn increases the complexity of the valves required to control the movement of the elevator, and in particular to provide a smooth slow down at a floor and accurate stopping at the floor level.

The more sophisticated modern'hydraulic elevator systems have caused an increase in the possibility that a car will stall during upward travel when it is in the leveling zone .and traveling at a very low speed which is commonly between 3 and 10 feet per minute. The reason is clear when it is recognized that a hydraulic elevator uses a constant speed, constant displacement pump, so the reduction in elevator speed from normal running speed to leveling speed must be accomplished by partially opening a bypass valve that permits a predetermined portion of the hydraulic fluid to be bypassed back to the reservoir, so that only a small fraction of the full flow is used to elevate the car at a slow rate for accurate leveling. Accordingly, in the leveling zone a change in viscosity of the oil, a lchange in valve characteristics, or even slight slippage of the belt between the electric drive motor and the pump may be sufficient to cause the car to stall in the leveling Zone. A

lThe consequences of stalling a car in the up leveling zone are not too serious in a freight elevator, because the elevator operator can ordinarily reach the door interlock of the floor which the car was approaching when it stalled, open the door and get out of the elevator, whereupon he can take the necessary steps to ycut out the elevator circuit and thus preventl damage to the motor, the pump or the valves. On the other hand, in a passenger elevator with automatic doors which can open only when the elevator is stopped .at floor level, and particularly in automatic passenger operated elevators, if a car stalls in the up leveling zone it can cause panic among the passengers, and may also severely damage the motor, pump, or valves before information concerning the malfunction can be transmitted to a person who can stop the -pump drive.

In accordance with the present invention, the elevator control circuit includes a protective timer which is started each time the motor and the pump start. The

timer is set to continue operating for the full time necessary for the elevator to make a single full trip from the bottom terminal to the top terminal without intermediate stops, plus a short additional time to aiford a safety factor. The safety factor may be only a few seconds. The timer runs only when the motor and pump run, .and reeycles each time the pump motor starts.

The system includes a contactor relay which closes to start the pump motor .and which remains closed as long as the pump motor and pump are in operation. I-f the up contactor relay remains closed for a time longer than the predetermined time on the protective timer, the timer contacts operate to complete a safety circuit which stops the pump motor and operates the elevator control valves to return the elevator car to the bottom terminal. When the car reaches the bottom terminal it parks with its door open, and at the same time the protected service, or fused switch which controls the entire electrical control system is automatically opened tothrow the car out of service.

At the same time that the protective circuit stops the motor and opens the down travel valve it drops out of the control circuit the service circuit that includes the car and hall call registering pushbuttons, and the indicator circuit which shows the position and direction of travel of the elevator car. Thus, the car expresses to the bottom terminal without stopping to answer lany calls for service, and the position and direction indicator at the bottom terminal which would normally indicate to prospective passengers that the car is ready to travel up, are also disabled.

The control System is illustrated diagrammatically in the accompanying drawing in which those portions of the control system which are old and known in the art .are illustrated only by appropriately labeled blocks. Thus, for example, the up hall call registration-momory-and cancelling circuits 10 include a pushbutton service call switch on the bottom terminal floor and each ioor below the top terminal floor, .and all the necessary relays or equivalent elements for registering the presence of the up call on the controller, retaining the call for service until the car stops during upward travel to answer the call for service, and for cancelling the service call after the car has stopped. Such circuitry is very old and well known to those skilled in the elevator art, .and is basic to all elevator systems whether electric or hydraulic.

Similarly, the car call-registration-memory-andeconcelling circuits 12 provide all the conventional controls which are required to register a call for service to a particular floor by a passenger entering the car, hold the call for service until the car stops at the desired iioor, and cancel the call.

Likewise, the down hall call-registrtion-memory-andcancelling circuits 14 include the components similar to those in the up hall call circuits except, of course, that there is a down call switch at the top terminal and none .at the bottom terminal except in those buildings having a basement served by the elevator.

Elevator position and direction determining circuits 16 are also entirely old and well known, and may include the lantern for each vloor which is illuminated to indicate the approach of .a car in a particular direction of travel when a passenger on the oor has registered a call for service in that direction by pressing a hall call button, and the direction lanterns at the terminal oors which, when a car is parked, indicate the availability of the car for travel in the indicated direction.

Likewise, the door operator pilot relay and timer circuits 18 include the customary components which prevent the door from being opened until the elevator is stopped at a floor, the .controls which cause the door operator motor 20 to start opening the door the moment4 the car is stopped at the door, the timer which causes the door to remain open for only a predetermined length of time after which it closes automatically, and the safetyl where it would be dangerous for the door to close and the car to start.

The circuit shown in the drawing is illustrated in an across-the-line form of diagram. No key is given for the relays and associated contacts as the drawing is relatively simple, all on one sheet, and the relationship of the contacts and relays is believed readily apparent.

The control circuit is energized from a suitable source, as 110 volt alternating current, through a protected or fused master or service switch 22. One side of the source is connected with line 23 and the other with line 24. Hydraulic pump motor 25 is connected across the line through normally open contacts U associated with up contactor relay U. The down valve solenoid is connected across the line through normally open contacts D yassociated with down contactor relay D. Door operator motor 20, which is reversible in operation, is connected for operation to open the car doors through contacts O associaated with open relay O and to close the doors through conta-cts C associated with door close relay C.

Specific circuitry for registering car calls is illustrated in the car call registration-memory and cancelling circuits 12. The elevator car is provided with a series of pushbuttons as PB-N and PB-l representing each of the floors the car serves. The designation PB-N represents all of the floors other than the lower terminal iioor. On closure of pushbutton PB-N, a circuit is completed energizing car call relay NC in turn closing contacts NC-1 and NC-2. Contact NC-ll completes a holding circuit for the relay while Contact NC-2 provides information to the elevator direction determining circuit 16 to establish the necessary movement of the elevator to answer the car call. The car call circuitry for the other oors operates in the same manner.

The up direction relay U is energized at the'time it is desired to cause the car to leave from a oor in the up direction, as a car leaves the lower terminal in response to a call car or a hall call from an upper floor. After the doors are closed, relay U is energized closing contact U and starting the pump motor to deliver hydraulic fluid to the ram and lift the car. In accordance with the invention, the timer PT is connected in parallel with relay U and is energized at the same time. The contacts associated with timer PT are shown in the condition they have before the timer has timed out. When the timer times out each of the PT contacts is reversed in condition. The time of timer PT is set to be slightly longer than the time required for the elevator to travel from the lowest floor to the highest oor without intermediate stops. At each stop the pump motor is deenergized, and since PT is in parallel with U, the timer is also deenergized. When the up direction relay U is energized for the next up travel of the car, the timer PT is also energized and again starts its cycle; and this occurs whether the car is at the bottom terminal or an intermediate floor. Thus, whether the car parks at a floor or reverses its travel, the energization circuit for relay PT is broken and the timer resets automatically, assuming it has not yet reached the end of its timing period.

If the timer PT times out before the car reaches its destination and the pump stops, the safety circuitry is placed in operation. This may occur through a malfunction or failure of a. portion of the elevator system. The contacts associated with timer PT affect the operation of several portions of the circuit. Contact PT-1 times closed, completing a holding circuit for the timer. Contact PT-S opens breaking the energization circuit .for up direction relay U. Contact PT-Z times open breaking the energization circuit for the up and down hall call circuits and 14 and affecting a portion of the call car circuitry, as will appear.

The circuitry representing a first floor car call is actuated by closure of contact PT-4 connnected in parallel with PBA. The resulting closure of contact lC-Z acts through the direction determining circuitry to energize down direction relay D. This in turn energizes the down solenoid valve and causes the hydraulic fluid in the cylinder to bleed slowly therefrom to lower the elevator. The elevator is caused to by-pass all other hall calls as the car call circuitry for floors other than the first Hoor are connected with line 23 through contact PT-2 which opens on timing out of the timer PT.

When the car nears the lower terminal, a zone switch is actuated closing contacts 1Z-2 in parallel with contacts PT-S. Contacts O associated with relay O close, energizing door operator motor 20 to open the car doors permitting the passengers to leave. It is necessary that the car doors be prevented from reclosing in this direction of the system. Contacts lZ-ll open in the circuit of door close relay C. Timer contacts PT-G, parallel with contact lZ-l are also opened, and relay C cannot be energized regardless of the actuation of other circuitry associated with the door operator pilot relay and timer.

Timer PT is maintained in its condition through holding contact PT-l. It cannot be reset until the protected service switch 22 is opened, breaking the power circuit for the entire system. The switch is accessible only to authorized service personnel who, before the car is returned to operation, can remedy the fault in the System which caused the actuation of the protective timer. When switch 1-2 is opened, relay PT is deenergized and all of the con- -tacts associated therewith are returned to the positions illustrated in the drawings. The timer is reset upon deenergization, as described above.

The foregoing detailed description is given for clearness of understanding only and no unnecessary limitations should be understood therefrom, as modifications will be obvious to those skilled in the art.

I claim:

1. In a hydraulic elevator system that has a ram and an elevator car on the ram serving a plurality of floors that include a bottom terminal and a top terminal, an electric motor driven pump to deliver fluid under pressure from a reservoir to the ram, and valve means to control flow of fluid between the pump and ram to raise and lower the ram .and stop the car at the fioors served by it, electric control means comprising: call means operable to register calls for service in an up direction; means responsive to operation of the call means for starting the electric pump motor and operating the valve means to raise the ram; timing means which times out after a time that is somewhat in excess of the maximum time required to move the car from the bottom terminal to the top terminal; and means responsive to the timing out of said timing means for stopping the electric pump motor and actuating the valve means to lower the ram and move the car to the bottom terminal.

2. The control means of claim 1 which includes indicator circuit means for indicating the position and direction of travel of the car, and means responsive to timing out of the timing means for dropping the indicator circuit out of the control circuit.

3. The control means of claim 1 which includes service circuit means having call registering means at floors served by the elevator and in the elevator car for registering calls for service, .and means responsive to timing out of the timing means for dropping the service circuit means out of the control circuit.

4. The control means of claim 1 which includes indicator electric circuit means continuously indicating the position and direction of travel of the car, service circuit means having call registering means at floors served by the elevator and in the elevator car for registering calls for service, and means responsive to timing out of the timing means for dropping the service circuit means out of the control circuit.

5. The ycontrol means of claim 1 that includes a master switch, and means responsive to opening of the master switch for `dropping the timer actuated means out of the circuit and thereby returning the service circuit means and the indicator circuit means to the control circuit.

6. In a hydraulic elevator system that has a ram and an elevator car on the ram serving a plurality of oors that include a bottom terminal floor and a top terminal floor, a door for controlling access to the car at each oor, an electric motor `driven pump to deliver fluid under pressure from .a reservoir to the ram, and valve means to control ilow of fluid between the pump and ram to raise and lower the ram and stop the car at the floors served by it, electric controlmeans comprising: call means operable to register calls for service in `an up direction; means responsive to operation of the up call means for closing the door, starting the electric pump motor and operating the valve means to raise the ram; timing means which times out after a time that is somewhat in excess of the maximum time required to move the car from the bottom terminal to the top terminal; means responsive to the timing out of said timing means for stopping the electric pump motor `and actuating the valve means to lower the ram and move the car to the botto-m terminal; and means responsive to stopping of the car at the bottom terminal for opening the door at said terminal.

7. The control means of claim 6 that includes a door operating circuit responsive to actuation of a service circuit call registering means for closing the `door at the bottom terminal oor, and means responsive to timing out of the timer for dropping the Idoor operating circuit out of the control circuit.

8. The control means of claim 7 which includes indicator electric circuit means for indicating the position and direction of travel of the car, service circuit means having call registering means at floors served by the elevator .and in the elevator car for registering calls for service, and means responsive to timing out `of the timing means for dropping the service circuit means out of the control circuit.

9. The control means of claim 8 that includes a master switch, and means responsive to opening of the master switch for dropping the timer actuated means out of the circuit and thereby returning the service circuit means and the indicator circuit means to the control circuit.

References Cited UNITED STATES PATENTS 2,647,590 7/1953 Anderson 187-29 2,695,077 11/1954 Suozzo 187-29 ORIS L. RADER, Primary Examiner.

T. LYNCH, Assistant Examiner.

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