US2322774A - Counterweight apparatus for elevators - Google Patents

Description

June 29, 1943. s. L. POLACK COUNTERWEIGHT APPARATUS FOR ELEVATORS Filed May 6, 1941 2 Sheets-Shed 1 f /P w INVENTOR.

ATTORNEYS.

j L. POW

5. BY wfay June 29, 1943. s. L. POLACK COUNTERWEIGHT APPARATUS FOR ELEVATORS Filed May S, 1941 2 Sheets-Sheet 2 T u I I I I HP I II J; i e j O ATTORNEYS.

Patented June 29, 1943 OOUNTERWEIGHT APPARATUS FOR ELEVATORS Sidney L. Polack, Chicago, Ill. Application (i, 1941, Serial No. 392,119

11 Claims.

A great many equalizers have been devised for elevator cables to keep the tension on a plurality of cables equal in spite of variations in the amount which they stretch in the course of months. In most of these the range of satisfactory operation is quite narrow, and, because of their cost and size it has not been considered practical to use them on the counterweight end of the cables. Springs have been used at this point but mainly to absorb shock. They are incapable of maintaining equalization. If the cables are of slightly different diameters, or if the grooves of the driving pulley are not quite uniform, the cables will be drawn up and payed out unevenly and this can only be rendered harmless by equalization at both ends.

With the present elevator systems, the breakage of a single cable causes a great deal of trouble, particularly due to the fact that, as the car continues to run, the loose ends get tangled up in other cables and throw them off the driving drum, thus causing them all to break and drop the counterweight all the way to the bottom of the shaft.

According to the present invention, all of these defects are overcome simultaneously. Each cable carries an independent counterweight so that perfect equalization may be provided through any desired range. The dropping of a counterweight through the shaft when a single cable breaks is prevented by providing a floating framework carried by all of the counterweights jointly and capable of supporting any counterweight which is allowed to drop by a broken cable.

Damage from loose cable ends is prevented by an automatic switch which stops the elevator car when a counterweight is dropped within the frame by the broken cable. This automatic switch preferably operates in a normally closed circuit which has heretofore been provided for other purposes to stop the motor if the circuit is opened.

In the preferred form of the invention, means are provided for automatically providing a light,

or other signal in the motor room at the top of the shaft, when any cable stretches to such an extent that it approaches the limit of its equalized movement or when several of the cables stretch to such an extent that one of the other counter weights approaches in the opposite direction the limit of its relative equalized movement.

Suitable springs and cushion means are pro vided to absorb shocks in the case of breakage of a cable.

Additional advantages and objects of the in stretching of the cables.

that when new cables are applied to an elevator;

vention will be apparent from the following description and from the drawings, in which:

Fig. 1 is an elevation of the counterweight structure of this invention, partly broken away for the sake of illustration and illustrating its coaction with the counterweight guides.

Fig. 2 is a'circuit diagram for the preferred circuit connections of the counterweight shown in Fig. 1.

Fig. 3 is a vertical sectional view taken approximately on the line 3-3 of Fig. 1.

Fig. 4 is a transverse sectional view taken approximately on the line 44 of Fig. 3.

A preferred form of the invention has beenchosen for illustration and description, in com-. pliance with Section 4888 of the Revised Statutes, butpersons skilled in the art will readily perceive other means for accomplishing the same results, and the claims are therefore to be construed as broadly as possible, consistent with the prior art.

All commercial forms of elevators are balanced, and in fact usually overbalanced, by counterweights. A plurality of flexible cables ll extend from the elevator car over one or more sheaves at the top of the shaft and down-at the side of the shaft to a counterweight. One of the sheaves over which the cables run is usually a motore driven drum engaging each cable in a V-shaped groove for driving the cable, the motor for driving the drumbeing indicated at l2 in Fig. 2.

According to prior practice, there has been ineffect a single counterweight for each car, this counterweight being carried jointly by all of the cables. tribution of weight between the cables has usually, if not always, been provided, but such means have not been wholly satisfactory in all regards, particularly in the event of cable breakage.

According to the present invention, each cable- II is provided with a separate counterweight M. In normal operations these counterweights may be considered independent so that the weight supported by each cable is necessarily equal even though there may be a considerable differential It might be mentioned they always stretch in the course of use, but of course they rarely, if ever, stretch exactly the same amount and in some instances the variations in the amount of stretch may be substantial. It is important to keep an approximately even distribution of weight between the cables, not only because the entire weight on the cable which stretched least would be an unsafe strain but also because an excess of weight on a cable' Some means tending to equalize the dis-"'- with slotted extensions tends to stretch it more and make it thinner so that it will fit further into the grooves of the driving drum and produce a differential driving action, which in turn puts excess strain on a cable and increases the wear thereof.

With the plurality of counterweights I4 it is necessary to provide some means for guiding them. Ordinarily, the single counterweight is guided by vertically extending opposed T-shaped tracks l6. According to the present invention, a frame H is likewise guided, being provided l8 which slide on the guide track l6. It will be observed, however, that this frame is preferably not supported directly by the cables, but the cables extend freely through the frame and support the counterweights separately, the frame being carried jointly by the counterweights. Of course, if preferred for simplicity, the frame, if of about the weight of acounterweight, could be supported by one cable independently of the others, some of the advantages of the present invention being lost thereby.

There are various ways that the frame may be supported jointly by the counterweights. One way would'be to have a plurality of heavy but relatively long springs extending between each counterweight l4 and the frame I1. They could be either compression springs resting on the tops of the counterweights, or tension springs hanging from the counterweights. In installing the elevator, the cable lengths would be adjusted to place all of the counterweights at the same level with the result that the springs would be under equal tension and the weight of the frame would be divided equally between the counterweights. As the cables stretched differentially, however, some springs would be contracted and others expanded and the distribution of the weight of the frame on the counterweights would no longer be uniform. With a light frame this would still be satisfactory and much better than the present attempts at' equalization. The illustrated form of the invention is preferred, however, since it permits continued equal distribution of the weight of the frame in spite of differential stretching of the cables.

According to this form of the invention, each counterweight is provided at its bottom with a sheave 2|, and a plurality of sheaves 22 are secured to the bottom member 23 of the frame H. A cable 24 is threaded from the bottom member 23 through all of the sheaves 2| and 22 and back to the bottom member 23. It will be observed that in this way the weight of the frame l1 will be distributed evenly between the counterweights regardless of the relative positions of the counterweights, within their range of free movement. It will also be observed that the cable 24 is an idle cable in that it is not constantly running over the sheaves and hence there will be no appreciable wear on it. Since this cable merely supports the weight of the frame H, which may be much less than the weight of a counterweight, and since this weight is divided between the eight strands of the cable in the illustrated form, this cable may be quite light-- much lighter than the main cables II.

If one cable stretches considerably more than the other three, it will move relatively downwardly about three times as far as the other three move relatively upwardly with respect to the frame It is not always practical to provide unlimited room for differential movement between the counterweights since to do so might make the over-all height or width of the counterweight structure as a whole greater than the space available for it, particularly since it is desirable for the cables H to be quite close to one another so that they will hang nearly straight down from the grooves in the driving drum and not wear unevenly on the sides of the grooves. For this reason it is contemplated that in the present form of the invention under extreme conditions one of the counterweights M might reach the end of its independent movement and come to rest against the frame IT.

This would of course result in relieving some or all of the weight of this counterweight from its cable H and thus making the strains on the cables uneven. However, the relative movement between the counterweights and the frame I! I lends itself quite easily to the provision of means for preventing any danger of running the elevator under this condition. According to this invention, one or more switches are operated by any counterweight as it approaches a position of rest against the frame l1. These switches may either give a signal or stop the operation of the elevator motor without giving a signal. According to the preferred form, a signal is given first. This is accomplished by providing two switches 26 and 21 which are operated in sequence as a counterweight approaches the bottom member 23 of the frame l'l. They may be operated by means of a switch plunger 28 which may be positioned to be engaged either by the bottom of the counterweight, by one of the sheaves 2|, or by a yoke 29 which may also serve the purposes of mounting the sheave 2| on the counterweights and of furnishing a bumper to help absorbthe shock between the counterweight and the bottom member 23 in case of cable breakage.

As a counterweight l4 approaches the limit of its downward movement with respect to the frame it will first close one of the switches 26, there being one for each counterweight. As illustrated in Fig. 2, this will close a circuit from line L to line L through a light 3| or other signal which may be positioned in the motor room at the top of the shaft or in the engineers room or janitors room, or both. In the event that one of the cables breaks, its counterweight l4 would of course drop immediately and come to rest on the bottom member 23. Any suitable cushion or dashpot means may be provided for preventing damage to the counterweight or frame structure due to this drop. A pad 32 has been illustrated for this purpose. However, considerable damage to the equipment may result if the car continues to operate while the cable is severed and in fact such continued operation represents an actual danger. Not only is the weight of the car supported by less than the proper number of cables but there are necessarily two loose cable ends which by getting caught in the apparatus may do considerable damage. According to the present invention, all danger of accident or damage by continued operation of the elevator is avoided. Just before any counterweight 4 comes to rest on the bottom member 23, it will actuate one of the switches 27. These switches are normally closed and are all in series with each other and with the governor switch 33 in a circuit through coil 35 controlling the main cutout 34. The governor switch 33 and main cutout 34 are at present conventional so that it is merely necessary to extend the circuit through the switches 21. The main cutout 34 is normally maintained closed by the closed circuit through the switches 21 and 33, but, upon opening of that circuit, will shut off power to the motor l2. Normally this power reaches the motor l2 through the control relays 36. In short, the cutout 34 under the influence of the opening of any switch 21 opens the main power circuit forthe elevator. This is not objectionable from the standpoint of inconvenience to the persons riding in the elevator because it almost never happens and, when it does happen, the passengers can often climb out of the elevator even if they are not right at a floor and,

if not, it is a relatively short task to get them out of the elevator by means already conventional.

If all but one of the cables II should happen to stretch considerably more than the one, the result would be that the stretching cables would 'tend to lower the frame H with respect to the one counterweight, and in extreme cases the frame I1 might come to rest with its entire weight on the one counterweight. This would of course unbalance the distribution of weight between the cables and is therefore undesirable. To prevent it, switches 38 are provided above the counterweights to operate the signal 3| in the same manner as the switches 26. Thus, as any counterweight by relative motion upwardly with respect to the frame approaches the position of rest against the frame, it will operate the switch plunger 39 to close the associated switch 38 and close the circuit through the signal 3|. It might be noted, incidentally, that of course the voltage in the signal circuit and in the control circuit through relay coil 35 may be of reduced voltage as compared to the main line voltage for motor l2.

Of course, the switches 21 for stopping the car in the event of cable breakage can be provided even if the switches 26 and 38 are not provided. When both the switches 26 and 21 are provided, the switch 26 should operate before the switch 21, perhaps with the counterweight a half-inch higher than the position at which it operates the switch 21. Since the cables stretch very slowly, this will provide adequate time after the operation of signal 3| by switch 26 in which cable adjustments; can be made to avoid operation of switch 21. Even in private or semi-private installations where there is only occasional inspection, there will almost always be time to get the cables adjusted before further stretching causes a stoppage of service by opening a switch 21, since the stretching of the cables is very slow, especially after the first two or three inches.

With some future developments it may be desirable to use a plurality of independent counterweights without even having a joint frame for guiding them. For example, they could be so splined as to guide one another while still permitting slight relative vertical movement between one another, the outside counterweights of course being guided by guide rails. The signal and cutout means illustrated in Fig. 2 could be used wherever counterweights are independent, since each counterweight could be provided with a switch or switches operated by relative movement between it and adjacent counterweights. Likewise, in any equalizing apparatus with a single counterweight, a switch or switches could be provided to be operated by relative movement between the cables or between each equalizer link and some portion of the counterweight.

Although dimensions and details of the construction may of course be varied according to space available or even according to the whims of the designer, applicant contemplate having each counterweight approximately 2 inches by 10 inches in cross section and 8 to 9 feet lon with the counterweights approximately inch apart or even less if manufacturing tolerances permit. The counterweights may be provided with vertical holes 4| of approximately one inch in diameter extending all the way through the counterweights, each counterweight having two such holes. A rod 42 of about inch in diameter will extend through each hole 4|, the rods being secured to the top and bottom members of the frame I! and thus serving to guide the counterweights l4 within the frame. The frame may of course bemade up of any structure having adequate strength to withstand the blow of a dropping counterweight, although this does not require any enormous strength since the maximum distance that a counterweight can drop will probably be less than a foot. As a matter of fact, with the signal means provided in Fig. 2,

a frame large enough to proxide a maximum displacement of Weights relative to one another of 3 inches or even less would be quite satisfactory. If the signal 3| is not provided, a somewhat greater permissible movement would be desirable (if space limitations permit) so a to decrease the likelihood that a weight would come to rest on the frame or cause a shutdown of service. Counterweights are conventionally made of pig iron, and therefore the four counterweights in the range of size mentioned, together with the weight of the frame, would furnish adequate counterweighting for many cars and of course the dimensions or the number of counterweights would be varied for diiferent weights of cars. The pulleys 2| and 22 should be small enough not to strike one another if a weight drops onto the frame.

When the separate counterweights are centered far enough apart to cause an undesirable spacing of the cables II, the cables may extend around sheaves on the frame to bring them close together. I

The cables I I may each be secured to its associated counterweight in. any convenient manner, preferably adjustable. For example, the conventional shackle bolt 46 may be secured to the cable I l in a conventional manner and may be threaded into a sleeve 4'! which is swivelly secured to the counterweight H! by a plate 43 The plate 48 bears on a collar 49 formed integrally on the sleeve 41. The length of the cable can be adjusted by loosening lock nuts El and turning sleeve 4'1, the top of the sleeve preferably being hexagonal to facilitate turning it. After the cable has been adjusted to the proper length, the lock nuts 5| are tightened. To prevent the cable from becoming untwisted, the sleeve 47 is then secured against swiveling in any suitable manner, as by a setscrew 52.

Best results in the use of this inveniton will be obtained by using some equalizing means at the car end of the cables. However, if the cables and driving grooves in the drum are substantially uniform, a spring take-up between each cable and the car will ordinarily suilice. It is more important to have complete equalization between the cables on the counterweight end than on the car end because the counterweight, according to present practice, should be 40% heavier than a car loaded to rated capacity.

It should be mentioned that the switches 26,

21 and 38 are intended merely as diagrammatic representations of any snap-action switch, the switches 26 and 38 being normally open, as previously mentioned, and the switch 21 being normally closed.

From the foregoing it is seen that an elevator counterweight system has been provided which absolutely assures equalization of weight distribution between the various cables of the elevator. With the automatic shutoff system, damage to the apparatus upon breakage of one cable is positively prevented. With the preliminary signal systern there-is no danger that the provision of the automatic shutoff will cause a cessation of service except when the cable breaks.

I claim:

1. Elevator apparatus including a motor, a plurality ofcar-supporting cables operated by the motor, a counterweight frame adapted to be run on' guide means, a plurality of counterweight-s vertically movable with respect to said frame,

each guided with respect to said frame and each independently secured to a separate cable. a signal, switch means responsive to a substantial movement of any counterweight with respect to the frame to actuate the signal, and additional switch means responsive to a greater movement of any counterweight with respeotto said frame for stopping the motor.

2. Elevator apparatus including a motor, a plurality of car-supporting cables operated by the motor, a separate counterweight for each cable carried thereby, a frame carried jointly'by the cables, guiding the counterweights and supporting any counterweight Whose cable breaks, and

with respect to which a counterweight moves as the cables stretch differentially, means responsive to a substantial differential stretching of the cables to actuate a signal, and means responsive to further differential stretching of the cables or to the breaking of a cabl for stopping the motor.

3. Elevator apparatus including a motor, a plurality of car-supporting cables operated by the motor, a separate counterweight for each cable carried thereby, a frame carried jointly by the cables, guiding the counterweights and support-.

ing any counterweight whose cable breaks, and with respect to which a counterweight moves as the cables stretch differentially, means responsive to relative movement between the frame and a counterweight to actuate a signal, and means responsive'to further relative movement of the cables or to the breaking of a cable for stopping the motor.

4i. A counterweight for an elevator, including aframe adapted to run on guide means-a plurality of counterweights adapted to fit within the frame and each adapted to have a separate cable secured thereto, means for supporting the frame jointly from the counterweights in a manner to permit differential movement between the counterweights, switch means actuated upon a predetermined movement of any counterweight, and additional switch means actuated upon a further movement of said counterweight.

5. A counterweight structure for an elevator, including a frame adapted to run on counterweight guides, a plurality of separate counterweights within the frame adapted to be secured to separate cables, a sheave on each counterweight, an approximately equal number of sheaves on the frame, and a cable running through all. of said sheaves with its ends appropriately secured to support said frame from said counterweights jointly in a manner to permit differential movement of the counterweights while retaining a constant uniform distribution of the weight of the frame between the counterweights.

6. A counterweight structure for an elevator, including a frame adapted to run on counterweight guides, a plurality of separate counterweights within the frame adapted to be secured to separate cables, a sheave on each counterweight, an approximately equal number of sheaves on the frame, a cable running through all of said sheaves with its ends appropriately secured to support said frame from said counterweights jointly in a manner to permit differential movement of the counterweights While retaining a substantially constant uniform distribution of the weight of the frame between the counterweights, cushion means adapted to reduce the shock on the frame if a counterweight drops suddenly onto the frame, and switch means operable by relative movement between any counterweight and the frame.

7. A counterweight structure for an elevator, including a frame adapted to run on counterweight guides, a plurality of separate counterweights within the frame adapted to be secured to separate cables, a sheave on each counterweight, an approximately equal number of sheaves on the frame, a cable running through all of said sheaves with its ends appropriately secured to support said frame from said counterweights jointly in a manner to permit differential movement of the counterweights while retaining a substantially constant uniform distribution of the weight of the frame between the counterweights, and switch means operable by relative movement between any counterweight and the frame.

8. A counterweight structure for an elevator, including a frame adapted to run on counterweight guides, a plurality of separate counterweights within the frame adapted to be secured to separate cables, a sheave on each counterweight, an approximately equal number of sheaves on the frame, a cable running through all of said sheaves with its ends appropriately secured to support said frame from said counterweights jointly in a manner to permit differential movement of the counterweights while retaining a substantially constant uniform distributionof the weight of the frame between the counterweights, and cushion means adapted to reduce th shock on the frame if av counterweight drops suddenly onto the frame.

9. A counterweight structure for an elevator, including a frame adapted to run on counterweight guides, a plurality of separate counterweights within the frame adapted to be secured to separate cables, a sheave on each counterweight, an approximately equal number of sheaves on the frame, a cable running through all of said sheaves with its ends appropriately secured to support said frame from said counterweights jointly in a manner to permit differential movement of the counterweights while retaming a substantially constant uniform distribution of the weight of the frame between the. counter-weights, switch means operable by rela-\ tive movement between any counterweight and the frame, and additional switch means operable by further relative movement between the same counterweight and the frame.

10. A counterweight for an elevator, including.

a frame adapted to run on guide means, a plurality of counterweights adapted to fit within the frame and each adapted to have a separate cable secured thereto, means for supporting the frame jointly from the counterweights in a manner to permit differential movement between the counterweights, first switch means actuated by predetermined movement of any counterweight relative to the frame in eitheridirection, and additional switch means operable upon a movement of any counterweight downwardly with respect to the frame further than necessary to actuate the first switch means.

11. Elevator apparatus including a car, counterweight means, a plurality of cables secured to the counterweight means and to the car in a manner to permit difierential stretching of the cables while maintaining distribution of the load between the cables, a motor for operating the car, a signal, first switch means responsive to a predetermined difierential movement of cable portions for operating the signal, and second switch means responsive to further difierential movement of cable portions for stopping the 10 motor.

SIDNEY L. POLACK.

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