US1011215A - Tension leverage for rope-drive elevators. - Google Patents

Description

D. L. LINDQUIST. TENSION LEVERAGE FOR ROPE DRIVE ELEVATORS.

APPLICATION FILED MAY 7, 1908.

Patented Dec. 12, 1911.

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DAVID L. LINDQUIST, OF YONKERS, NEW YORK, ASSIGNOR T0 OTIS ELEVATOR COM- PANY, OF JERSEY CITY, NEW JERSEY, A CORPORATION OF NEW JERSEY.

TENSION LEVERAGE FOR ROPE-DRIVE ELEVATORS.

Specification of Letters Patent.

Application filed May 7, 1908.

To all whom it may concern:

Be it known that I, DAVID L. LINDQUIST, a subject of the King of Sweden, residing at Yonkers, in the county of Westchester and State of New York, have invented a new and useful Improvement in Tension Leverage for Rope-Drive Elevators, of which the following is a specification.

My invention relates to improvements in traction or rope drive elevator apparatus, and one of its objects is the provision of novel means for varying the traction on the driving cables as the load on the car varies.

Other objects of my invention will appear hereinafter, the novel combinations of elements being set forth in the claims hereunto annexed.

In the accompanying drawing which illustrates an elevator embodying my invention, Figure 1 is an elevation view of the elevator; Fig. 2 is a side elevation of the motor;

Fig. 3 is a sectional plan View taken substantially on the line a-a; of Fig. 1., and showing a floating lever and means for adjustably connecting the cables thereto; Fig. 4: is a sectional view of the floating lever and associated parts.

M designates an electric motor arranged to drive a grooved traction sheave S which is preferably mounted directly upon the motor shaft 10. The driving cables 11 are in frictional engagement with the traction sheave S and are connected at one end to a suspended beam 12 by an eye-bolt or eyebolts 13, or other fastening means. The other ends are connected to a counterbalance weight W. Other cables 14 are connected to this counterbalance weight W and pass up over a pulley 15 which is supported by suitable bearings 16 mounted upon a stationary beam 17. The cables 14 are also connected to the suspended beam 12 by eye-bolts 18. A weight W is suspended by cables 19 which pass over a stationary pulley 20 and are connected to the suspended beam 12 near one end thereof by eye-bolts 21.

C designates an elevator car which is adapted to travel on the usual guide rails 22, 22, and is suspended near the opposite end of the beam 12 by the eye-bolt 23. The

beam 12 is provided with slots 21, 18 and 23, to provide for the adjustment of the fastenings 21, 18 and 23, respectively.

The movement of the elevator car 0 is controlled from within the same by means of a manually operated switch 24: which is arranged to eifect the operation of a controlling device 25 wherein a pivoted arm 26 is adapted to electrically engage a series of contacts 27, and thus effect the starting, stopping, and reversing of the motor M in a well known way.

28 designates a source of electrical energy, such as a dynamo or other generator of electricity. Any other desired form of motor and system of control may be used in connection with my invention.

The suspended beam 12 is in effect a floating lever and is subjected to various forces acting in difierent directions at different locations thereon. At the point of suspension 23 the car and its load are exerting a downward pull. At the point 18 the counterbalance weight W is exerting an upward pull. The point 13 is held stationary by the driving cables 11 when the motor is at rest, while at 21 there is an upward pull due to the weight W.

Assuming the motor M to be at rest and the various parts in the relative positions shown in the drawing, the suspended beam 12 is held in a state of equilibrium. Assuming, further, the point 18 as a fulcrum, it is seen that the tension on the driving cables 11 lying on the right-hand side of the traction sheave S is due to the weight of the car and its load and the weight W, each producing an upward pull upon the cables 11 at the point 13. This upward pull at 13, however, is in excess of the combined weights of the car and its load and the weight W, owing to the leverage obtained by these weights operating about the point 18 as a fulcrum.

In order to illustrate the effect of the 9 various weights on the tension of the driving cables, let the following conditions be assumed: the weight of the empty car 2,000 lbs., the weight of the counterbalance weight W 1,500 lbs, and the weight of the auxiliary weight W 500 lbs.; the horizontal distances between the suspension points 21-13, 13-18, and 1823, 1 foot, 1 foot, and 2 feet, respectively. The weight of the lever 12 is here neglected, although it may also be relied on to assist the car and load in bending the driving cables onto the driving sheave. Now, considering the point 18 as a fulcrum, the tension on the cables 11 at the point 13 due to the weight of the car alone is 1,000

lbs, or double that of the car itself, since the length of the lever arm between the points 18 and 23 is double that of the arm between the points 18 and 13. In a similar manner the tension on the cables 11 at this same point 13 due to the weight W, is double that of the weight of WV, or 1,000 lbs. The total tension upon the cables 11 at the point 13 or upon the right-hand side of the traction sheave S is therefore 4,000 lbs.+1,000 lbs, or 5,000 lbs. It is evident that the tension upon the cables 14 at the point 18 is equal to the weight of the car added to the tension upon the cables 11 at the point 13, less the weight WV, which expressed in figures will be 2,000 lbs.+5.-000 lbs.500 lbs.:6,500 lbs. The tension upon the driving cables 11 adjacent to. the lefthand side of the traction sheave S equals the tension upon the cables 14 at the point 18, less the weight of the counterbalance weight W, or 6,500 lbs.-1,500 lbs.:5,000 lbs. Thus it is seen that in the example given the tension of the driving cables 11 upon either side of the traction sheave S is equal to 5,000 lbs., making a total upward pull upon this sheave of 10,000 lbs. which is considerably in excess of the combined weights of the car, counterbalance and auxiliary weight IV, their combined Weight being only 4,000 lbs. It should also be noted that both leads are put under the same strain so that there is no tendency for the cable 11 to slip on the driving sheave. If a load of 500 lbs. is now added to the weight of the car it is readily ascertained by proceeding as in the above example that the tension on the driving cables 11 on the right-hand side of the traction sheave S is 6,000 lbs. and on the left-hand side 6,500 lbs, the total tension or upward pull upon the traction sheave being therefore 12.500 lbs. -By comparing this result with that found in the case of an empty car, viz,

10,000 lbs, it becomes apparent that the increase in total tension upon the traction sheave caused by the load of 500 lbs. in the car, is the difference between 12,500 lbs. and 10,000 lbs., or 2,500 lbs. The ratio. between the total tension (12,500 lbs.) on the traction sheave and the car and load 2,500 lbs.) is therefore 5 to 1, and this ratio is true in every instance where the load in the car is the only quantity varying from the conditions specified in the above examples. If the car is empty, the ratio is 10,000 to 2,000 or 5 to 1, also.

In order to increase the ratio between the load on the car and the total tension on the traction sheave, the point of suspension 18 may be placed closer to the point 13, there by increasing the leverage of both the car and auxiliary weight W. Utilizing the same weights as before in the case of an empty car and moving the point 18 six inches nearer the point 13, it is found that the tension on either side of the traction driving sheave S is 11,500 lbs. making a total tension of twice 11,500 lbs. or 23,000 lbs. By now adding a load of 500 lbs. to the car, it will be found that the tension on the left side of the traction sheave is 14,500 lbs. and on the right side 14,000 lbs., making a total tension of 28,500 lbs. The corresponding total tension in the case of an empty car was 23,000 lbs., making a difference of 5,500 lbs. due to the load of 500 lbs. placed in the car. Where the ratio before was 5 to 1, the ratio under the new conditions is 11 to 1, the difference between the two ratios being caused by merely moving the suspension point 18 a distance of six inches. The important feature of the invention, however, is that the difference in tension in leads extending from the driving sheave as compared with the total tension in said leads varies but little with increase of load. Under certain conditions of practice, if this diiference should exceed 50% of the tension on the lead having the lesser tension there would be slipping, but it will be seen that even if the load were increased to 8,000 lbs, the tension in the left-hand lead would be 29,000 lbs. and in the righthand lead 21,000 lbs., the difference being 8,000 lbs. or about 38.1% of 21,000 lbs. the

tension on the right hand lead. Therefore, starting with a car weighing 2,000 lbs, the difference in the tensions in the leads ex tending from the driving sheave would never be sufiiciently great in practice to efiect any slipping of the driving ropes on the driving sheave.

From the foregoing examples it is readily seen that by varying the position of the cable fastening 18, or by varying any of the other suspension points, any desired ratio between the tension on the driving cables and the load on the car may be obtained.

In this manner a powerful traction may be produced between the driving motor and driven cables where a relatively light car and counterbalance are used. The suspended beam 12 may be of any desired length.

and arranged to travel in the hatchway upon suitable guides.

Although in the examples given the weight of the two counterweights W and W taken together is equal to the weight of the car, so that the system is balanced when the car is empty, it will be understood that this ratio need not be maintained and that in practice the car is usually overbalanced so that an average load on the car is required to balance the counterweights.

If desired, the auxiliary weight W may be dispensed with entirely and the same re sults obtained by a readjustment of the other parts. To illustrate this, let it be assumed that the weight of the parts and their arrangement is the same as in the example first given, and the 500 pound counterweight IV removed and 500 lbs. added to the counterweight WV. This will not disturb the equilibrium of the system, as the Weight W will then balance the empty car. But the tension on the hoisting cables will be reduced. The tension on the cable 11 at the point 13 is now simply that due to the weight of the car acting about the point 18 as a fulcrum, that is, 4,000 lbs. To increase this tension to 5,000 lbs. as in the first example, the fulcrum point 18 is moved nearer to the point 13, so that the ratio between the two lever arms 13, 18 and 18, 23 is 2 to 5. The tension on the cable 11. at the point 13 is then 5,000 lbs; the tension on the cable 14 is 5,000 lbs. plus the weight of the car, or 7,000 lbs; the tension on the cable 11 below the counterweight W is 7,000 lbs. less the weight W, or 5,000 lbs. It is thus seen that a balance is maintained and the same tension on the hoisting cable obtained without the auxiliary weight W, by a proper adjustment of parts. The auxiliary weight W, however, forms a ready means for adjusting the tension on the hoisting cables. The tension on the leads extending from both sides of the driving sheave can be increased or decreased by adding to or taking from the weight W. By making the distance between the points 18 and :21 great as compared with the distance between the points 13 and 18, a wide variation in the tension of the hoisting cables may be obtained by a small increase or decrease in the weight W. It will also be observed that by transferring a portion of the auxiliary weight WV to the main counterweight W, or vice versa, the tenison on the hoisting cables may be adjusted without disturbing the balance of the system in the least.

While the foregoing examples are theoretically correct, it should be understood that they are given merely as illustrations, as there are various conditions met with in practice which would modify the results to a certain extent. Such conditions are fully recognized by those skilled in the art, and due allowance could readily be made there- While I have shown an operative embodiment of my invention, I desire not to be limited to the precise construction and arrangement of parts as herein shown, since various modifications are possible without departing from the spirit and scope of my invention.

What I claim as new and desire to have protected by Letters Patent of the United States is 1. In an elevator, the combination with a motor, of a car, a hoisting cable, a counterweight, a lever forming a connection be tween the car and counterweight, and a weight connected to the lever to increase the tension on the hoisting cable.

2. In an elevator, the combination with a motor, of a car, a hoisting cable, a lever connected to the car and cable, and a device connected to said lever for increasing the tension on the hoisting cable.

3. In an elevator, the combination with a motor, of a car, a hoisting cable, a beam from which the car is suspended, connections between the cable and beam for supporting the beam and car and placing a tension on the cable proportional to the weight of the car, and a weight. having connections with the beam for increasing the tension on the hoisting cable and also partially counterbalancing the weight of the car.

4. In an elevator, the combination with a motor, of a car, a hoisting cable, connections between the car and cable, and a weight associated with said parts, movable at the same speed as the car and increasing the tension on the hoisting cable an amount greater than said weight.

5. In an elevator, the combination with a motor, of a horizontal beam, a cable connected at its ends to intermediate points on the beam, a car suspended from one end of the beam, and a counterweight connected to the other end of the beam and exerting an upward tension thereon.

6. The combination with a driving member, of a load carrying device, a hoisting cable, a device forming aconnection between said load carrying device and said cable and operable to maintain tension on the cable, and a weight connected to said connecting device and operable to increase the tension on the cable.

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

DAVID L. LINDQUIST.

Witnesses CHAS. M. NISSEN, JAMES D. IvERs.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, I). 0.

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