US1242394A - Elevator safety device. - Google Patents

Description

I. H. VENN, ELEVATOR SA FETY DEVICE.

APPLICATION FILED FEB- 14; 1914,

1 Patented Oct. 9, 191.7.

2 SHEETS -SHEET I.

I JI I H l l l l l. H. VEN N. I ELEVATOR SAFETYDEVICE,

APPLICATION mzp ran. :4. m4.-

Patented; Oct. 9, 1917.

2 SHEETS-SHEET 2- INVE/VTUH:

WITNESSES.-

A OHNE UNITED s AEs ra'rnnr onnron.

ISAAC IL VENN, or YONKERS, YORK, easter ies. rro orls. erevaroa Q M Y. or JERSEY CITY, NEW master A ,coarqnermlr or essy.

' ELEVATOR sar'nrr EV-Ion.

Specification of Letters Patent.

. Pat nted ce 9., .91

Applieation filed February 1'4, 1914., Serial No. 818,7;95.

citizen of the United States, residing in Yonkers, in the county of Westchester and State of New. York, have invented a new and useful Improvement in Elevator Safety Devices, of which the following is a specification. V Y

My invention relates to safety devices for elevators, and has for an object the provision of means for applying a brake to an elevator car or its counterbalance weight, or both, in case of emergency, said brake automatically effecting a retarding action in accordance with the load.

-A further object of the invention is the provision of an elevator safety device which may be automatically operated with varying degrees of power depending upon condi: tions. V Other objects of the invention will appear hereinafter, the novel combinations of elements being pointed out in the appended claims. I

In the accompanying drawings, Figure 1 represents diagrammatically an elevator installation containing an embodiment of my invention; Fig. 2 is anenlarged detail view of the safety device as applied to the elevator car; Fig. 3 is a sectional end view of the safety plank; Fig. 4 is a view showing a modification. V Similar parts are designated by like reference characters in all of the figures.

Referring to Figs. 1, 2 and 3, an elevator car 0 is suspended by a cable or cables A which are associated with a drivingsheave M and idler sheave I, and are secured to a counterbalance weight W. The usual guide rails for the car and counterbalance weight are designated by B. Associated with the car and counterbalance weight aresafety planks S, S, which not only embodynovjel features in themselves, but also involve a novelty in the manner in which they are suspended and in which they. operate. 7 For example, the safety plank S under the car, is suspended from either end by means of cables 1, l, which may lead up' the side of the car and be connected to a, yoke? as shown. The latter isconnected to a cable 3, which leads over. the guide sheaves 4, 4, and is secured to the counterbalance weight W. The safety plank Swunder the counter-V i t s usp ree the ca le w iche e n t d t yok 6- h a t is connected to a cable 7 which leads over h g de sheaves 8,, 8, and is secured to, the top of the car. With this arrangement of the safety planks S, .S, the same normally will move up and down the hatchway with the car and counterweight, while under C n i ns h y'may have a la e movement thereto, respectively. The cables 3'ancl7 f-ro nwhich the car and counter? weight safety planks S, S, are suspended,

respectively, are adapted to be gripped by means of the clamps Qand '10, respectively, both of Whichclamps are connected to a rod 11, under the control of the speed governor G. The governor G may be driven from any convenient part ofthe elevator ap.p ar.a'

tus such as byasprocket chain or. belt 12 associated with the idler sheave I so that the governor rotate at a speed in accordance with that of the elevator car. Fig.

4 illustrates a common method of driving the governor direct from the car.

The safety planks S, S are substantially similartofle'ach other, and each comprises .a pair of channels 12, 12 (see Figs. and to which are secnred at either end apair .of massive 1 steel: blocks 13 .(Fig. 3) each of which is slotted out so as to receiventhe guiderail web'and a wedge 14. "The latter is provided with a: head 19 which normally rests'on top-of jthe blockfl3 and isfmaintain'ed .outof contact with the rail bymeans of a spring 17 and stud 16,-whichlatter is.

secured ,to the wed e and adapted :to slide in a groove 18 infile block 13 and one of the channelsl2. To each wedge 14,14is pivoted 'a lever 20fulc'rumed at'21 to a bracket 22 carried by the safety plank channels. The pivotal connection between the levers and each wedge is provided with a slight amount ofside play so as.to prevent cramping therebetween. The inner ends of the levers 20 on the car safety are slotted at 25 to receivea pin 26 carried by a rod 27 extending through the floor of the car and Pr v ded h a fo Pi 28,- A sp n 29 tends to move vthe rod 27 and inner ends of the levers 20 upwardlyand' to depress the wedges 14, 14. To the bottom :of the car are secured a pair of plungers 13 1, 31,;the lower ends of which are within a short dis.- tance of the plunger seats 30, 30,, carried by the levers 20, -20. Theplun'gers 31, ,31, are enlarged at, 32, 32 ,where they pass through the safety plank, and these enlarged portions are embraced by channels 35, 35, which act as a means for steadying the safety plank. Plates 3%, 34, are secured to the top of the safety plank and loosely surround the plungers so as to permit a relative movement of the car and safety plank within limits, but these plates will be engaged by the enlarged portions 32, 32 of the plungers in case the cables 1, 1, should part and thus prevent the safety plank from falling down the hatchway.

Whereas the levers 20, 20, are shown pivoted by pins 21, 21, to the center of the brackets 22, I provide other holes 23, 23, in each of the brackets and levers so that the pins 21, 21, may be removed from their present location and inserted in any one of the holes 23, 23. By this arrangement I provide a convenient means for varying the fulcrum of the levers 20 and thereby varying the power with whichthe wedges will engage the guide rails.

The operation of the safety device depends upon a relative movement between the car or counterbalance weight and its respective safety plank. This relative movement may be brought about in any one of several ways, namely, by manual means un der the control of the operator; by automatic speed controlled means; and automatically upon breakage of the hoisting cable or cables without regard to the speed.

In order to effect the operation of the car safety device by manual means, the operator depresses the rod 27 by means of the foot pedal 28 or by hand, and in so doing the levers 20 are simultaneosuly rocked upon their pivots 21, 21, and the wedges 1 1, 14, moved upwardly and into close engagement with the guide rails B. The safety plank S is now retarded in its further movement in a downward direction and the descending oar carries the plungers 31, 31, into engagement with the levers 20, 20, and thereby forces the wedges further into engagement with the guide rails. If the pivot or fulcrum 21, 21, of the levers 20, 20, is midway between the plunger seats 30, 30, and the points of connection between the levers and wedges, the latter will. be forced upwardly with a pressure substantially equal to the combined weight of the car and its load, whereas if the pivot or fulcrum 21 of each lever 20 be located in one of the holes 23 nearer the wedge than the plunger seat 30, the upward pressure on the wedges will be greater than the combined weights of the car and its load by an amount dependent upon the relative length of the lever arms. Should the pivot or fulcrum be located at one of the holes 23 nearest the plunger seat 30, the upward pressure on the wedges will be less than the combined weights of the car and its load.

In any event, the retardation of the car will be proportional to the load.

The operation of the safety device by speed controlled means is effected by the governor G in the following manner. when the car is operating up or down within normal speed limits, the governor G remains inactive and the cables S and 7 pass freely over their respective guide sheaves 4 and 8. If the car be descending, and for some reason its speed should become excessive, the governor balls will fly outwardly and depress the governor rod 11 and thereby actuate the eccentric clamps 9 and 10. The clamp 9 will immediatelv grasp the cable 3 and retard its further movement there through. Now, since the cable 3 suspends the safety plank S under the car. it follows that the latter will be arrested in its down ward. movement, and the descending car will settle upon the levers 20, 20, which will at once raise the wedges 14 into engagement with the guide rails, and the car will be graduallv arrested inaccordance with the load and finally stopped, the safety plank being carried downwardly with the car. It will be observed that the safety device on the counterbalance weight will not be operated bv the governor with a descending car, since the governor clamp .10 merely places a braking action on thecable 7, and as the counterbalance weight is moving up wardly at this time there will be no rela tive motion between the counterweight and its corresponding safety plank.

In the event of excessive speed with an ascending car, the governor clamp 10 will restrain the cable 7 which supports the counterweight safety plank, and the latter will be retarded, whereupon the counterweight will settle upon the levers of its safety plank and the corresponding wedges will operate to retard and arrest the counterweight. If the descending car is stopped. by its corresponding safety device, the driving traction between the sheave M and the hoisting cable becomes destroyed and the counterweight will not be further raised even though the sheave M continue to be driven. The same thing takes place when the counterweight safety operates with an ascending car. If the traction driving sheave be replaced by a winding drum and the car be arrested by its safety plank, there will be no danger of the counterweight being hoisted to the top of the hatchway, since the unbalanced weight of the counterweight will be in excess of the power of the hoisting engine or motor and the latter will be stalled. The same thing will take place if the car he ascending, to wit, the counterweight will be arrested by its safety plank, and the unbalanced load represented by the loaded .car will stall the motor.

It will be observed that I provide a stop 36 in connection with the governor Gr, the purpose of which is to prevent the clamps 9 and 10 frompositively locking the corresponding cables 3 and 7 Some arrangement of this kind is desirable since it ob-.

car or counterweight, as the case may be, to

settle on the said planks and actuatethe wedges. Other types of clamps may be used if desired other than the eccentric type as illustrated, but I prefer to use a clamp whose power may be predetermined so as to effect a known retardation of the cables '3 and 7 of which there are many kinds, the ones herein shown being merely by way of example. i

.As before pointed out, the safety device is arranged to be operated not only by the operator and also automatically in the event of excessive speed, but also incase the hoisting cable or cables part, regardless of whether the carbe in motion or not. This. feature in itself is of. the greatest impor-' tance sinceit insures thatin case the hoisting cable or cables part, both the car and counterweight immediately become locked to the safety device doesnot come into effectiveoperation until after the car has fallen a substantial distance and moreover is falling at a very high rate of speed. If the cables should part while the car were near the top of the hatchway, the safety clamps would have a chance to stop the car before it reached the bottom of the well, but if the cables should part with the car near the bottom of the well, the safetyidevice would not have an opportunity materially to check the speed of the car before it struck the bottom;

The counterweight in the meantime suffers a free. fall and in all likelihood-will do;

great damage.

By reason of myinvention I am enabled. to arrest both the carland counterweight 'in' case the hoisting cables part before either.

the car or counterweight'has had time to fall more than a very few-inches at'most,

so that all danger of a free 'fall athigh speed is absolutely done away withf Y Referring to Fig. 1, let us suppose that the car is at rest, and the hoistingcable or cablesA should part. The car and counterweight are now free to fall and will at once attempt to do so. As the counterweight moves downwardly it raises the safety plank S under thecar, while at the same time the car, in moving downwardly, raises the safety plank S under the counterweight, hence it will be seen that the car and its safetyplank are'carried in opposite directions toward eachother while the counterweight and its safety'plank are simultaneouslymoving in opposite directions toward each other. By reason of this operation the wedges on both of the safety planks will almost instantly be applied and both car and counterweight will be arrested before eitherv has moved more than an inch or two 'at the most and consequently long before either the car or counterweight have had time to attain even a moderate speed in a downward direction.

It will further be observed that the retarding power of the-wedges is greater in case the hoisting cables break than would be: the case if the safety device were operated by hand or by the governor. In the latter case the safety plank under the car isarrested by theg'overn'or clamp, and the car settling down on the levers 20, 20, applies the wedges with a power dependingupon the weight of the car and its load and also: upon the retardation of the safety plank inducedby the governorclamp. In case the hoisting cable or cables break, the total; power applied to the car safety wedges is that due not only to the weight of the car and its load acting through the levers 20,

20, but also to the added power due to the,

upward movement of the car safety plank, which upward movement will be effected by a considerable part of the weight of the counterbalance weight. To better illustrate the action of the car safety under these conditions, we may assume that the car and its load weighs 5000 lbs, while the counterweight weighs 4500 lbs.-. If the hoisting cable or cables should break, the car will set tleon the levers 20, 20 with a pressureof 5000 lbs. while the counterweight ispulling up: on the car safety plank with a force of4500 lbs., ignoring for the timebeing the action of, the a'counter'weight safety. The total force exerted on the levers .20, 20 willthere' fore be,;we may say, 5000 lbs. +4500 lbs,- or 9000 lbs; The same thing is taking placein connection with the counterweight, andits. safety device, and the; ultimate resultwill bethat the braking power of thewedge sis-far in exc'ess'of what it would i138: in "case the safety device were actuatedby the gov-- ernor under excess, speed conditions. WVhile the action of the 'safety'wedges under; the

of the safety wedges under the car will notv permit the entire weight of the car and its load to be available to raise the safety plank under the counterwelght, nevertheless a large portion of these weights is available to and counterweight will not be greater thanthat required to bring the unbalanced load to rest. This case calls for a safety device of moderate power. On the other hand, in case the hoisting cables part, the power of the safety devices will automatically be greatly increased so as to take care of the unbalanced car and counterweight which now represent a dead load. By this arrange ment the action of the safety when operated by hand or automatically by the governor will be moderate and in proportion to the load, so that the car will always come gradually and easily to a stop whatever the load maybe, and hence all shocks and jars to the elevator apparatus or discomfort to the passengers is avoided. When the hoisting cables part, the action of the safety device in stopping the car and counterweight is so extremely rapid that there can be no possibility of the car attaining any appreciable speed and hence there can be no shock or jar, notwithstanding the great power of the safety at this time.

lVhereas the parting of the hoisting cables of any elevator installation is but a very remote possibility when the apparatus is properly inspected from time to time, the likelihood of the car attaining an excessive speed from some disarrangement of its hoisting machinery, or in the case of an electric elevator, from some defective electric switch or false operation in the controlling circuits, or otherwise, is much more likely to occur and frequently does. In the generally accepted type of elevator safety device, the braking or retarding action of the same must be such that the car will be arrested smoothly and without shock or jar when the maasee the hatchway with little checking of speed until it strikes the bottom of the shaft with great force, which of course, is most likely to result in serious damage both to the car and its load of passengers.

By reason of my invention I am enabled to apply a braking action to either the car, counterweight, or both, which shall automatically be in proportion to the load. If the load be light, the braking action will be correspondingly gentle; if the load be heavy, the braking action will be correspondingly powerful. In each case the retarding action of the safety device is automatically increased or decreased in proportion as the load increases or decreases, the arresting of the car being effected gradually and gently without any possibility of shock or ar and regardless of load conditions. Furthermore since the retarding power of my safety device is proportional to the load, it follows that for a given speed the elevator car may always be stopped within a predetermined distance regardless of the load.

The pitch of the wedges 141-, should preferably be such that under no circumstances can the wedges be iminovably jammed be-' tween the guide rails and the steel blocks 13. The relative length of the arms of the levers 20 as determined by the position of the adjustable fulcrum 21 with respect to the plunger seat 30 and pivotal connection between the lever and the wedge, may best be determined by experiment so that the up ward pressure on the wedges will not be excessive. If desired, the pitch of the wedges and the length of the lever arms may be so proportioned that the resultant brake action will be just sufficient to bring the car and counterweight to a very slow speed so that the car will not be brought to rest, but may slowly slide down the guide rails and gently come to rest at the bottom of the hatchway. This feature is not found in elevator safety devices in present day use and is of great practical value. For example suppose an elevator be equipped with the usual safety device and a fire should break out in a building. The elevator, under these conditions would be operated as rapidly as possible and at the same time would in all likelihood be heavily overloaded on each downward trip. This condition is most favorable for excessive speed, and this speed might easily rise above that at which the speed governor is set to operate. Under these conditions the safety device will act and the car will be locked in the hatchway against movement, and the entire load of passengers consumed without any possibility of saving themselves or of receiving aid from an outside source. By reason of my invention the safety devices could be so adjustedthat the elevator car would not be brought to rest at an intermediate point in the hatchway, but would be gradually retarded to a slow speed regardless of the load and then permitted gently to slide down to the basement landing, where it would bottom without damage to itself or its live load.

It will be observed that the wedges will always operate simultaneously due to the slot and pin connection between the levers 20, 20, so that the brake action on each side of the car or counterweight is the same and comes into effect at the same time, so that there will never be a tendency for the car or counterweight to cant.

It may further be observed that the safety device is self resetting. For example: If the car be arrested by the manual operation of the safety device or automatically due to excessive speed in a downward direction, the hoisting motor may be reversed and the car lifted out of engagement with the levers I of its safety plank. The spring 29 will in all probability retract the wedges to their normal inactive position, but if this spring should lack the necessary power, a slight upward pull on the pedal 28 will efiect the desired result. In like manner, if the safety device on the counterweight be operated with an ascending car, and the hoisting motor be reversed, the spring associated with the counterweight safety levers 20, 20 will assist in returning the wedges to normal position out of engagement with the guide rails.

I desire not to be limited to the precise construction and arrangement of parts herein disclosed, since it is obvious that various changes and modifications could readily be made by one skilled in the art without departing from the spirit and scope of the invention.

What I claim is e 1. The combination with a car and con terweight and their respective guide rails, of a cable connecting the car and counterweight, a safety device under the car and counterweight, separate cables connected to the car and to the counterweight, respectively, for suspending each safety device independent of the first named cable connecting the car and counterweight and of each other, and means for efiecting the operation of said safety devices upon an abnormal relative bodily movement between the car and counterweight.

' 2. The combination with a car and counterweight and their respective guide rails, of a hoisting cable connecting the car and counterweight, a safety device under the car and counterweight, respectively, means for suspending said safety devices independently of said hoisting cable and of each other, and means operative upon breakage of the hoisting cable for effecting a movement toward each other of the car and its safety device and the counterweight and its safety device to effect the sudden actuation of both of said safety devices.

3. The combination with a car and counterweight and their respective guide rails, of a hoisting cable connecting the car and counterweight, a safety device under the car and counterweight respectively, means for suspending said safety devices independently of said hoisting cable and of each other, and automatic means operative upon excessive car speed for effecting a movement toward each other of the car and its safety device and the counterweight and its safety device to effect the actuation of said safety devices.

4;. The combination with a car and counterweight,of safety devices carried by the said car and counterweight, speed controlled means for effecting the operation of the safeties, a connection between the safety on the counterweight and the car, and an independent connection between the safety in the car and the counterweight, the car increasing the application of the safety of the counterweight through said connection, and the counterweight increasing the application of the safety to the car through the other connection.

5. The combination with a car and counterweight, of a cable connecting the car and counterweight, a safety for the counterweight, a separate safety for the car, a cable connecting the car with the safety on the counterweight, another cable connecting the safety on the car to the counterweight, these cables being independent of the first named cable, and adapted to apply the said safeties simultaneously to the car and counterweight.

6. The combination with a car and counterweight, of a cable connecting the car and counterweight, safety devices for the car and counterweight, a cable connecting the counterweight safety and car direct, another cable connecting the car safety and counterweight direct, and speed controlled means for operating one or the other ofsaid safeties in both directions of travel of the car.

In testimony whereof, I have signed my name to this specification in the presence of two subscribing witnesses.

ISAAC H. VENN.

Witnesses:

Gnonen D. Rosn,

SCHUYLER PHILLIPS.

copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, I). G.

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