US2924297A - Elevator safety controls - Google Patents

Description

Feb. 9, 1960 c. BRANDON ELEVATOR SAFETY CONTROLS Filed Sept. 25, 1956 4 Sheets-Sheet l IN V EN TOR. CWPL 5214/1 00 Feb. 9, 1960 c. BRANDON 2,924,297

ELEVATOR SAFETY CONTROLS Filed Sept. 25, 1956 4 Sheets-Sheet 2 V INVENTOR C994 ERR/V00 Feb. 9, 1960 c. BRANDON 2,924,297

I ELEVATOR SAFETY CONTROLS Filed Sept. 25, 1956 4 Sheets-Sheet 3 i l p I I I l l l i IN V EN TOR.

(H/9A BAA/VDO/V Feb. 9, 1960 c. BRANDON 2,924,297

ELEVATOR SAFETY CONTROLS Filed Sept. 25, 1956 v 4 Sheets-Sheet 4 mvgNToR. 04,94 ERA/v0 04 A TTO/P/Vifi United States Patent ELEVATOR SAFETY CONTROLS Carl Brandon, Detroit, Mich, assignor, by mesne assignments, to Elevator Construction & Service (10., Detroit, Mich., a corporation of Delaware Application September 25, 1956, Serial No. 612,033

3 Claims. Cl. 187-28) The present invention relates to an elevator safety control, and more particularly to an elevator control device which fails safe by gravity actuation in response to any one of several operating conditions constituting safety hazards.

This application is a continuation-impart of my earlier copending application, Serial No. 540,455, filed October 14, 1955 and abandoned upon the filing of this application.

The use of hydraulic elevators has been limited by the difficulty in safely controlling their operation. A loss of hydraulic pressure, as upon valve failure or cylinder rupture, can have disastrous consequences. Less spectacular, but equally dangerous, is a gradual uncontrolled descent of the elevator car from an open hatchway door. The loss of electric power, for driving the hydraulic pump, also can have serious after effects.

The present invention provides a new, novel, and extremely effective safety control system for an elevator. This system is equally applicable to either electrically or hydraulically operable elevators, but the system is illustrated and described herein as specifically applied to a hydraulic elevator.

Generally, this system employs a brake applicable to a safety cable or rope attached to an actuating arm for dogs engageable with the hatchway guides of the elevator car. If the car is descending and the cable is halted, the dogs will engage the guides to stop the car abruptly and positively.

The brake means, in the preferred and illustrated form of the invention, includes a brake shoe engageable with the cable as it is lapped about the periphery of a guide sheave or the like, the shoe being movable eccentrically of the sheave so as to be self-energizing when released. Thus, the brake fails safe when released, since it is overbalanced toward an applied position but restrained from application by the control system.

The brake restraining means biases the brake from application by the use of an electromotive or other force overcoming the graviational apply force constantly ex erted on the brake. Interruption of the restraining force by any means will apply the brake, and this interruption can be accomplished by or in response to any number of operating conditions.

I have found that interruption of the restraining force and resultant application of the brake in response to the following operating conditions will be sufficient to safeguard users of the elevator:

(1) Actuation of a manual emergency switch.

(2) Loss of hydraulic pressure.

(3) Loss of electric power.

(4) Uncontrolled car descent from a hatchway opening.

(5) Excessive car down speed.

It is,'the'refore, an important object of this invention to provide a new and improved safety control system for an elevator.

Another important object is the provision vofan ele- See 2 vator safety control which fails safe in response to dangerous operating conditions through the application of a positive braking element.

A further object is to provide an elevator control in which a normally gravity-applied brake is restrained from application by a control system sensitive to any one of several dangerous operating conditions.

it is still another object of this invention to provide a control for an elevator in which the descent of an elevator car is accommodated by the release of a brake through an electrical control circuit incorporating electromotive force means energized only under normal operating conditions and operative to release the brake for self-energized application upon interruption of the control circuit.

Yet another object is the provision of an elevator control system responsive to any one of several operating conditions, including actuation of a manual switch, a loss of hydraulic or electrical actuating forces, uncontrolled car descent, or excessive car down speed, to immediately and positively halt the car in the hatchway.

On the drawings:

Figure 1 is a schematic representation of the hydraulic actuating system for an elevator employing a safety corn trol system of the present invention;

Figure 2 is a broken, elevational, somewhat diagrammatic illustration of a complete elevator actuating mechanism utilizing the safety control system of the present invention;

Figure 3 is an enlarged elevational view of one form of a specific brake mechanism utilized with the elevator of Figure 2;

Figure 4 is a different form of brake mechanism similar to that illustrated in Figure 3;

Figure 5 is a fragmentary elevational view further illustrating the details of connection between the safety control cable and the dog actuation arm of the elevator;

Figure 6 is a wiring diagram illustrating the brake actuation system for utility in connection with the em bodiment of the brake shown in Figure 3 of the drawings;

Figure 7 is a Wiring diagram similar to that of Figure 6 but illustrating the control circuit utilizable in connection with the brake illustrated in Figure 4 of the drawings. 1

As shown on the drawings:

In Figure 1, reference numeral 10 refers generally to the actuating piston of an elevator indicated at 2th in Figure 2, the piston being vertically operable within a cylinder 11.

The cylinder 11 receives pressured fluid from a pump 12, which is preferably electrically driven to transfer fluid from a reservoir or container 13 and through a one way check valve 14 and a passage 15 to the cylinder 11.- A gate valve 16 controls the flow of fluid through a reservoir return line 17, the valve 16 being controlled through a linkage 19 actuated by a solenoid 18. The solenoid 18 and its associated valve 16 form a part of the conventional hydraulic elevator control mechanism, and as such form no part of the present invention. A hand pump 19a located between a pair of one way check valves may be utilized for manually raising the elevator in the event that power actuation of the pump 12 failsor to lift the elevator off the dog stop (hereinafter described) in the event of power failure.

As best shown in FigureZ, the piston 10 is connected directly to the floor or platform 20a of the elevator 20, so that, upon operation of the pump 12 to fill the cylinder 11 with pressured fluid, upward movement of the cylinder 10 will effect elevation of the platform 20a. Alternately, upon actuation of the solenoid 18 and turning of the gate valve 16, fiuid from the cylinder will be bled back through the passages 15 and 17 into the reservoir 13 to accommodate lowering of the platform 20a.

Vertical movement of theplatform 20a is guided by a pair of vertically extending, laterally spaced guides 21 having a central vertical rib 21a engaged by vertically spaced guide elements 22 on the elevator platform 20a and carried by spaced vertical .posts 22a forming apart of the elevator 20.- It will be appreciated that in Figure 2, only one vertical guide21'is illustrated, but it will be evident that two such guides are provided in laterally spaced relation and an additional set of guide elements 22 are provided for engagement with the other guide 21.

A safety cable or rope 23 is attached to the elevator 20 through an attachment bracket 24. The cable 23 forms, in efiect, a closed loop and is lapped about vertically spaced sheaves or the like 25 and 26 which are disposed adjacent the upper and lower extremities, respectively, of the elevator travel. The upper sheave 25 is disposed upon a lateral shaft 25a which is supported upon uprights 25b which, in turn, are mounted upon a :structural member 25c forming a part of the building in which the elevator is utilized. The other sheave 26 is disposed upon a shaft 26a journaled in a vertically slidable frame 26b which is freely movable on vertical support rods 26c carried by arms 26d projecting laterally from the guide posts 21. The Weight of the sheave 26 and its carriage 26b maintains the cable 23 taut.

The actual connection of the cable 23 with the elevator car 20 is best shown in Figure 5, from which it will be seen that the connecting arm 24 is provided with an aperture 24a through which a vertically slidable rod 24b extends. This rod 24b carries an abutment 24c and confined between the abutment 24c and the arm 24 is a coiled compression spring 24d which effectively urges the rod 24b downwardly to the position shown in Figure 5.

The lower end of the rod 24b is connected to adog actuation arm 24c, the other end of the arm 24e being keyed to a shaft 24 which extends transversely of the elevator 20 to carry at either extremity thereof a dog 24g engageable with the vertical rib 21a of the vertical guides 21. Obviously, counterclockwise movement of the lever 24e will cause the same movement of the dogs 24g, so that the dogs will engage the rib 21a to prevent further downward displacement of the car 20. The upper end of the rod 24b is connected to both ends of the cable 23, as at 23a and 23b.

The operation .of the dogs will be readily appreciated, since halting of the cable 23 and continued downward movement of the car 20 will cause the cable 23 to move the rod 24b upwardly against the compression of the spring 24d, thus causing counterclockwise movement of the lever 24a and the dogs 24g, so that the dogs engage the guide rib 21a. scent of the elevator car 20 will be prohibited. Once the cable 23 is again released for movement, the spring 24d will return the arm of 24a to its illustrated position, and the dogs 24g will be released.

The braking means for the cable 23 is illustrated in Figures 3 and 4 of the drawings, wherein it will be seen that a self-energizing brake shoe 27 is disposed upon a brake actuating arm 27a, the arm 27a being in the form of a yoke straddling the pulley or sheave 25 and being pivotal about a pivot axis 29a which is displaced vertically from the shaft 25a of the sheave 25. Movement. of the yoke 29 about the center 29a will cause the brake shoe 27 to move toward the periphery of the sheave 25. The sheave 25 is, of course, grooved to receive the cable 23 thereabout, and the shoe 27 is of such size as to fit in this groove and to engage the cable 23. After engagementbetween the shoe 27 and the cable 23, further continued clockwise rotation of the sheave 25 will serve to further engage the brake shoe 27 with the cable 23. Thus, the brake shoe 27 is said to be self-engaging.

Preferably, the arms 29 oi: the yoke carrying the shoe 27 are keyed to a shaft'29b which defines the pivot axis for the yoke, and also securedto-this shaft 29b is a laterally extending, generally triangular lever 30. That Thus, downward movement or deface of the lever 30 remote from the shaft 29b is .arcuate, so as to be concentric with'the axis 29a, and the face is provided with gear teeth 33. The teeth 33 meshwith a sector gear 33b mounted upon the driven shaft 33a of a torque motor 31 which is energizable through electrical lead lines 32 in a manner. to be hereinafter more fully described.

The lever 30 is of such size and weight that it is gravitationally urged .in a clockwise direction. This weight of the lever 30 biases the yoke29 in a clockwise direction and thereforebiases the brake shoe 27 toward engagement with the cable 23. If the lever 30 were not a 23 could not accommodate downward movement of the elevator car 20, since the restraint against this movement of the cable would constantly apply the dogs 24g.

The yoke 29 can also be moved so asto apply the brake shoe 27 to the cable 23 by a plurality of centrifuw gally actuated dogs or levers 28.. These dogs 28 are pivoted to the sheave 25and :are movable radially outwardly in response to excessive rotational speeds of the sheave to engage the inner surfaces of yoke 29 urging it clockwise overcoming the electrical or other holding means and thereby apply the brake. 1 Such centrifugal actuation ofthe brake is conventional and is not claimed as a feature of the present invention.

The wiring diagram of Figure 6 of the drawings shows the control for the torque motor 31. The windings of i z the motor 31 are illustrated schematically in the circuit as being energized by the three lead lines 32 hereinbefore described. This torque motor is of conventional type and is designed to exert a predetermined rated torque without danger to the motor when the motor is stalled.

:1: The motor 31 is of a capacity and torque rating such that 0% is de-energized, the weight of the lever 30 will apply the it can exert a torque sufficient, when acting through the.

gears 33 and 33b, to prevent the application of the brake 27 to the cable 23. So long as the motor 31 is energized,

the brake will not be applied. However, once the motor brake. i

Thus, the torque forceof themotor restrains the brake from application, the electromotive force of the motor overcoming the gravitational apply force constantly errerted on the brake by the lever 30. As illustrated in Figure 6, several abnormal operating conditions may be utilized to interrupt the actuation of the motor 31 so as to apply the brake.

More specifically, in Figure 6 current applied to the windings of the motor 31 from one of the lead lines 32 passes through a pair of relay contacts 40 which are under the control of a. relay R1. Thisrelay R1 is in circuit with a pair of contacts 41 which are adapted to be closed by a pressure responsive switch 42 having a cylin- 7 der 42a subject to the pressure in they hydraulic conduit out of contact with the contacts 41 by a compression 15 (Figure 1)'. So long as hydraulic pressure is present in the conduit 15,piston 43 is depressed to close the contacts 41. Once the pressure in the conduit 15 falls below a predetermined minimum, the piston 43 is urged spring 44. Thus, a failure of hydraulic pressure in the conduit 15 will de-energize the relay R1 to open the relay 3 contacts 40, thus de-energizing the motor 31 and allowing the brake 27 to be applied by the gravitational lever 30. To insure setting of the brake even when the pressure loss is momentary, a holding circuit can be provided for the relay R1.

A different phase of the motor 31 is energized through a manual emergency switch 45 which is normally closed,

- but which can beopened by the elevator operator ora passenger in the elevator to de-energize the. motor 31 and apply theebrake 27.1 i

To further control the operation of the elevator, specifically to halt the elevator in the event of a gradual leak in the system such that the elevator may drift downwardly or gradually settle from an open hatchway door, a cam actuated limit switch 46 is provided. This switch 46 is in parallel with a pair of elevator movement control switches 486T and 48b, which control the downward and upward movement of the elevator through the solenoid 18 for controlling the gate valve 16 and through the pump 12.

The switch 46 is controlled by a cam follower arm 47 (Figure 2) which is mounted on the car beneath the platform 20:! thereof for contact with a cam surface 48 attached to a floor or other elevator station 50 of the biulding in which the elevator is movable. So long as the switch 46 is closed by the cooperation of the cam 48 with the cam arm 47, the brake 27 will not be applied, inasmuch as the motor 31 is still operable. Thus, the brake is not applied when the elevator is stopped at a floor 50 and neither the upswitch 4811 nor the downswitch 48b is closed. However, in the event that neither the switch 48a nor the switch 48b is closed and the elevator platform drifts downwardly sufiiciently to remove the arm 47 from the cam 48, the switch 46 will be open and the corresponding phase of the motor 31 will be deenergized, thus cutting off the motor and accommodating the gravity application of the brake 27 to the cable 23.

In that embodiment of the invention illustrated in Figures 4 and 5, identical reference numerals refer to identical portions of the apparatus illustrated in Figure 3 of the drawings. It will be noted that the triangular geared lever 30 has been replaced with a straight lever 36 which cooperates with the yoke 29 to define a bell crank controlling application of the brake 27 to the cable 23. This lever 36 is overbalanced in the same manner as the lever 30 heretofore described, and the lever is retained against clockwise movement by a solenoid 34 connected to the extreme end of the lever 36 through a link 35.

The solenoid 34 is adapted to be energized through a circuit illustrated in Figure 7 of the drawings. It will be noted that this circuit again includes the pressure switch 42 and the relay R1 for controlling the relay contacts 40. Here, however, the relay 34 is provided with an upper switch plate 51 adapted to close contacts 52 when the relay is de-energized, which contacts form a switch for shorting out a relay resistance 53 which is in the circuit through the emergency switch 45 and the cam switch 46. The solenoid switch 51-52 is normally open when the solenoid coil 54 is energized. Thus, current from the switches 45 and 46 and through the contacts 40 must necessarily pass through the resistance 53 36. The smaller current flow through the resistance 53 is suflicient to retain the arm 36 in its elevated position.

I claim:

1. In an elevator construction having a plurality of elevator stations and elevator braking means, control circuit comprising elevator up and down switches which are closed respectively for moving said elevator up and down, switch means, tripping means, said tripping means being engaged with said switch means to close said switch means when said elevator is at a station and disengaged when said elevator has moved an increment away from said station, a power circuit including power means for restraining application of said elevator braking means, said elevator up and down switches and said switch means being in said power circuit with said circuit being broken when all of said switches and switch means are open but closed when any one of said switches or switch means is closed.

2. A' safety control for an elevator car actuatable vertically along a guide rail, comprising a brake dog on the car engageable with the rail, a cable operatively connected to the brake dog to apply the dog upon halting of the cable and continued descent of the car, a fixed axis sheave passed over by said cable, a self-energizing cable brake arm mounted on a parallel fixed axis spaced from said sheave fixed axis having a brake shoe adapted to brakingly engage said cable while passing around said sheave, a lever arm connected to said brake arm biased to urge said brake arm and shoe into braking position, an electric torque motor operatively connected to said lever arm adapted when energized to hold said brake arm and shoe in a disengaged position and when de-energized to permit movement thereof to said braking position, an energizing circuit for said torque motor, a plurality of safety control switches interposed in said energizing circuit the opening of any one of which in response to any of a plurality of different emergency operating conditions such as uncontrolled car descent from a normal stopping position or manual actuation of an emergency switch in the elevator car will de-energize said torque motor causing engagement of said cable brake, halting of said cable, actuation of said brake dog and braking of said elevator car. 7

3. A safety control as set forth in claim 2 applied to an elevator actuated by hydraulic pressure wherein means are included for opening one of said safety control switches in response to a drop in hydraulic actuating pressure below a predetermined minimum elevator operating pressure.

References Cited in the file of this patent UNITED STATES PATENTS Sprague Jan. 15, 1935

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