US1725402A - Elevator-cable equalizer - Google Patents

Description

Allg- 1929- D. L. LINDQUIST 1,725,402

ELEVATOR CABLE EQUALIZER Original Filed June 11, 1927 33M W INVEHTOI? F/af BY ATTORNEY Patented Aug. 20, 1929.

UNITED STATES DAVID L. LINDQUIST, OF HARTSDALE,

NEW YORK, ASSIGNOR TO COMPANY, OF NEW YORK, N. Y., A CORPORATION OF NEW OTIS ELEVATOR JERSEY.

\ ELEVATOR-CABLE EQUALIZER.

Application filed June 11, 1927, Serial No. 198,075.

This invention relates to equalizers for elevator hoisting ropes.

In traction elevator systems wherein solid hitches are employed for connecting the hoisting ropes to the elevator car and its counterweight, these ropes may sustain unequal portions of the load. This inequality of load distribution may be due to various factors, such as difference in the diameters of the grooves of the driving sheave or un equal stretching of the ropes. lVhere such inequality exists, the ropes carrying the greater portion of rapid wear and possible breaking.

One feature of the invention is the provision of equalizers on both the car and the counterweight ends of the hoisting ropes, which equalizers tend to maintain equal ten sion in all the ropes at any point.

Another feature of the invention is the provision of equalizers on both the car and the counterweight ends of the hoisting ropes in which the equalizing members of each equalizer are biased to definite positions relative to each other.

A third feature is to provide equalizers of a construction that may be arranged for any number of hoisting ropes.

Still another feature resides in the provision of equalizers that are of simple construction, easily installed, and which occupy a minimum of overhead space.

Other features and advantages will become apparent from the specification, taken in connection with the accompanying drawings wherein one embodiment of the invention is illustrated.

In the drawings Figure 1 is a schematic representation of an elevator system illustrating the applica-' tion of hoisting; rope equalizers to the elevator car and to the counterweight.

Figure 2 is an enlarged detail view taken along the line 22 of Figure 1.

Figure 3 is an enlarged detail view taken along the line 33 of Figure 1.

Figure is a diagrammatic representation of a portion of a hoisting rope equalizer wherein four hoisting ropes are employed.

Referring to Figure 1, the hoisting motor 1 drives the sheave 2 for effecting the raising and lowering of the elevator car 3 and counterweight 4, three hoisting ropes 6 being shown for convenience of description. An

theload are subjected to.

9 (see also Figure 1).

Renewed March 12, 1929.

electromagnetic brake 5 is a plied to the motor shaft for the purpose of bringing the hoisting motor, and therefore the car and counterweight, to a stop.

According to the preferred arrangement, the ends of the hoisting ropes 6 are secured to thimble rods 7 of hoisting rope equalizers 8 and 10. Equalizer 8 is secured to the car 3 and equalizer 10 is secured to the counter-' weight4. Since hoisting rope equalizers 8 and 10 are of the same construction, only one of these equalizers, namely equalizer 8, will be described.

As illustratedin Figure 2, equalizer 8 comprises a frame having a top plate 11 and a bottom plate 15, the bottom plate being connected to the car! framework by clamps These plates are joined .by vertically extending rods 14. These rods are secured to the top plate 11 as by nuts 16 threaded on the rods and positioned on both sides of the plate. Similarly, these rods are secured to the bottomplate 15 as by nuts 17 threaded on the rods and positioned on both sides of the plate. The thimble rods 7 extend downwardly apertures provided in top plate 11 and are secured at their lower ends to sheave blocks 13, one for each thimble rod. Each of these thimble rods is provided with a compression spring 12, these springs surrounding their respective rods and extending between the sheave blocks and the top plate. Each of the sheave blocks is flanged outwardly, these flanged portions being provided with bearing apertures through which rods 14 extend. By this arrangement, the sheave blocks are restricted to vertical movement, the rods 14 serving as guides for the blocks.

Each of the sheave blocks is provided with depending arms 26 between which a sheave 25 is rotatably mounted. Two additional sheave blocks 21 and 23 are pivotally secured to the bottom plate 15. Each of these sheave blocks is provided with upwardly extending arms 27. A sheave 20 is rotatably mounted between arms 27 of block 21 while a sheave through 22 is rotatably mounted between the arms 27 of block 23. One end of 18 is secured as by a hitch 19 to the bottom plate 15. From the hitch 19,'the equalizer rope extends upwardly and around one of the sheaves 25. From this sheave, rope 18 extends downwardly and around sheave 20.

an equalizer rope In a similar manner, rope 18 is 'led from sheave 2O upwardly. and around another of sheaves 25, thence downwardly and around sheave 22 and thence upwardly and around the remaining sheave 25. From this last sheave, rope 18is led downwardly to the bottom plate where it is secured as by a hitch 24. With such arrangement of the equalizer rope, sheaves 20 and 22 are positioned at an angle with respect to sheaves 25. Hitches 19 and 24: may be adjusted so as to lengthen or shorten the equalizer rope.

' Inasmuch as the'equalizer rope 18 extends around all of the sheaves 25, the tension in the equalizer rope is equal at all points and each sheave carries equal load.

In Figure 4: the equalizer is shown developed in a single plane in order that the manner in which the equalizer rope is extended around the various sheaves may be readily seen. In this figure, four hoisting ropes are illustrated, instead of three as in the other figures, to demonstrate that the equalizer may be arranged for other numbers of hoisting ropes. It is believed that the operation of the system may be more readily understood by reference to this figure. The

same reference characters will be employed,

namely, 6 for the hoisting ropes, 18 for the equalizer rope, 12 for the springs, 25 for the V upper sheaves and 20 and 22 for two of the lower sheaves, the additional lower sheave being designated 28.

In order that the operation and advantages of the equalizer arrangement may be readily understood, assume that only one of the movable bodies, for example the elevator car, is provided with an equalizer and that the springs 12 are omitted. With such arrangement, although the' tension in the hoisting ropes on the car side of the driving sheave is equalized, there is no equalization weight side of the sheave.

of the tension in-these ropes on the counter- For example, should the diameter of one of the grooves of the driving sheave be greater than that of the other grooves, during lifting of the counterweight, the rope running in that groove is caused to bear the greatest portion of the load. The portion of the load carried by this rope increases as the upward movement of the counterweight continues until rope slippage occurs at the driving sheave.

Assume now that both the car and the counterweight are provided with equalizers and that the springs 12 are omitted. Without the springs, the equalizers are in a state of unstable equilibrum. That is, no forces exist tending to maintain the upper sheaves 25 in any particular relative positions. With the car and counterweight at rest, the system may be adjusted so as to place the sheaves 25 of each equalizer in any desired relative positions, for example in horizontal alignment as illustrated in Figure 4. So long as ency o would expand.

the car and counterweight remain at rest, these relative positions are maintained, as the existingforces are balanced. When the car and counterweight are started in operation, any resulting unbalance ,of forces, even though slight, causes relative movement of sheaves 25 to other positions, dependent on how the forces are unbalanced. This relative shifting of the sheaves 25 of bothequalizers may continue until the limit of movement of one or more of the sheaves is reached in which event the equalizers are no longer capable of equalizing thetension in all the hoisting ropes. By way of specific example, assume that in operation the left-hand hoisting rope of Figure 4 creeps on the driving vented while the equalizers act at all times,

tending to equalize the-tension in thehoisting ropes. These springs tend to maintain the sheaves 25 of each equalizer in definite positions with respect to each other. preferred to employ springs of the same size so as to tend to maintain the sheaves in horizontal alignment. These springs are in effect biasing springs and may be rather weak.

In order that the action of the springs may be readily understood, assume that the car and the counterweight are at rest at equal distances from the driving Isheave, that the hoisting ropes are of the same length and that the sheaves 25 of each equalizer are in horizontal alignment. Should there be a slight unbalance of forces when the system is in operation such as is caused by a tendone of the hoisting ropes to creep, the springs act to prevent unrestrained shifting of the sheaves which might eventually result in all the clearance for the sheave 25 for that rope being taken up and consequently the equalizers being rendered ineffective. For example, should the left-hand hoisting rope 6 tend to creep to the counterweight side of the driving sheave when the tis' system is in operation, spring 12 of the car equalizer for that rope would be compressed while the other springs of the car equalizer Also spring 12 of the counterweight equalizer for that rope would expand while the other springs of that equalizer would be compressed. The movement of the sheaves in causing the differences of spring compressions also tends'to cause equalization of the tension in the hoisting 25 of both the car ropes. Thus,

hoisting ropes and sheaves '25 as before,

ropes act as bufi" a condition is reached where the unequal tensions of the hoisting ropes are balanced by the unequal spring compressions. Owing to the fact that the unbalance of forces due to rope creepage is relatively small, this shifting of the sheaves and change of spring compression is very slight. Also, owing to the fact that the springs are relatively weak, the change in rope tension is verysmall so that substantially complete equalization is obtained.

With the assumption as regards relative car and counterweight relative positions of assume now that the diameter of the groove in the driving sheave,

for the left-hand rope 6 is larger than that of the others. Assuming that the car is started in the up direction, during its upward movement, the left-hand rope 6 on the car side of the driving sheave tends gradually to assume an increasing portion of the load. The equalizers act, however, to equalize the tension of the hoisting ropes, there being a slight difference due to the inequality of spring compressions resulting from the shifting of the sheaves 25. As previously pointed out, the springs 12 are relatively weak so'that the inequality of rope tensions is not very marked. Upon the reversal of car travel, the equalizers act oppositely so as to cause the sheaves 25 to resume their horizontal alignment upon the car and counterweight again being equidistant from the driving sheave.

Should one of the hoisting ropes stretch, for example the left-hand rope 6, springs 12 of both the car and the counterweight equalizers for this rope expand equally to compensate for this change of length. Owing to the fact that both the car and counterweight sheaves 25 for this rope move downwardly, the remaining sheaves 25 move upwardly. In this manner, the tension in the hoisting ropes tends to become equal.

Should a hoisting rope'break, the sheaves and counterweight. equalizers for the remaining hoisting ropes move upwardly, compressing their springs. Thus, the springs for the;.intact ers preventing any shock which might result from the engagement of the sheave blocks 13 with [top plate 11.

Should the equalizer rope of one of the.

respective eqpalizer act as buffers to eliminate the shockinertia in starting and sto ing.

As many changes could he, made in the above construction widely different embodiments of this invention could be made the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

WVhat is claimed is:

positions, lengths of ,said elevator car; vdevlce connecting for equalizing the 'ing the car end of a counterweight; hoisting ropes extending from said car to said counterweight; an equalizing device connecting said ropes to an additional equalizing said ropes to said-counterweight; and means associated with said equalizing devices for biasing the hoistin ropes to definite one another.

2.In an elevatorsystem; an'elevator can; a counterweight; hoisting ropes extending from said car to said coimterweight; means positions with respect to for equalizing the tension in the hoisting ropes,

said means comprising a set tively movable equalizing member of relaconnecting the car end of the hoisting ropes to the car and an additional set of relatively movable equalizing members connecting the counterweight end ofgthe hoisting ropes to the counterweight; and means for biasingthe equalizing members of each set to certain definite positions relative to each other.

3. In an elevator system; an elevator car; a counterweight; hoisting ropes extending from said car to said counterweight; means for equalizing the tension in the hoisting ropes, said means comprising a set of relatively movable equalizing members connect ing the car end of the hoisting ropes to the car and an additional set of relatively movable equalizing members connecting the counterweight end of the hoisting ropes to the counterweight the equalizing members of each set to horizontal alignment.

4. In an elevator system; an elevator car; a counterweight; hoisting ropes extending from said car to said counterweight; means tension in the hoisting ropes, said'means comprising a set of relatively movable equalizing members connectthe hoisting ropes to the car and an additional set of relatively movable equalizing members connecting the tendency for the car to bounce due to itsand means for biasing I and many apparently without departing from 1. In an elevator system; an elevator car;

counterweight end-of the hoisting ropes to a for equalizing the tension in the. hoisting I hoisting ropes extending. said counterweight; means ropes, and means connecting the sheaves "of a the second set to the counterwelght in such manner as to permit their relative movement; and a plurality of springs, one for each sheave of each set, for biasing the sheaves of each set to horizontal alignment.

6. In an elevator system; a movable body;

a hoisting ropes; equalizing means attaching said ropes to said movable body and arranged to permit relative movement of said ropes;

and resilient means tending to restrain said relative movement.

.hoisting ropes comprising a plurality of d counterweight endsofthe hoisting ropes in 7. In an elevator system; a movable body; v

hoisting ropes; a plurality of sheaves, each attached to a different one of said hoisting ropes; a .plurality of additional sheaves attached to said movable body; roping led around said first and said additional sheaves in alternation; and resilient means extending between saidfirst mentioned sheaves and said movable body.

8. A suspension device for connecting a movable body of an elevator system to the hoisting ropes comprising; a plurality of sheaves, each attached to a different one of said hoisting ropes; a plurality of sh'eaves,

one less in number thansaid first mentioned sheaves, attached to said movable body; an equalizing rope secured at both ends to said movable body and led around said first and second mentioned sheaves in alternation between its ends; and resilient means for biasing said first mentioned sheavesto definite positions with respect to each other.

9. A suspension device for connecting a movable body of an elevator system to the sheave blocks, one for each of said ropes an connected'thereto; a plurality of sheaves, one for each sheave block, said sheaves being 'ournaled in their respective blocks; a plurality of additional sheaxze b1o cks, one less' in number than the first mentioned sheave blocks, said additional sheave blocks being pivotally connected to said movable body; a plurality of additional sheaves, one for each additional sheave block, said additional sheaves being journaled in their respective blocks; an equalizing rope anchored at both ends, said rope being led around said first mentioned and additional sheaves in alternation between its ends; a member arranged above said first mentioned sheave blocks and secured to said movable body; and a plurality of compression springs, one for each of said first mentioned sheave blocks,'s'aid springs extending between their respective sheave .blocks and said member.

between its ends around the sheaves connected to the car ends of the hoisting ropes and the sheaves carried by the car; springs tending to maintain the sheaves connected to the car ends of the hoistin ropes in definite positions relative to each 0t er; an additional sheave for each hoisting rope and connected to the counterweight end thereof; sheaves carried by the counterweig t; roping connected at each end to the counterweight and extending between its ends around the sheaves connected to the counterweight ends of the hoisting ropes and the sheaves carried by the counterweight; and'springs tending to maintain the sheaves connected to the definite positions relative to each other.

In testimony whereof, I have signed my 95:

name to this specification.

DAVID L. LINDQUIST.

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