TRACTION ELEVATOR SYSTEM HAVING MULTIPLE MACHINES

Abstract: An elevator system having multiple machines and flat ropes is disclosed. In one embodiment, the machines are engaged in a series manner with a single set of ropes to drive the car and counterweight. In another embodiment, each machine is engaged with a separate set of ropes to drive the car and counterweight.

Description: Description Traction Elevator System Having Multiple Machines Technical Field The present invention relates to elevator systems and, more particularly, to traction elevator systems having multiple machines. Background of the Invention A typical traction elevator system includes a car and a counterweight disposed in a hoistway, a plurality of ropes that interconnect the car and counterweight, and a machine having a traction sheave engaged with the ropes. The ropes, and thereby the car and counterweight, are driven by rotation of the traction sheave. The machine, and its associated electronic equipment, along with peripheral elevator components, such as a governor, are housed in a machineroom located above the hoistway. A recent trend in the elevator industry is to eliminate the machineroom and locate the various elevator equipment and components in the hoistway. An example is JP 4-50297, which discloses the use of a machine located between the car travel space and a wall of the hoistway. Another example is U.S. Patent 5,429,211, which discloses the use of a machine located in the same position but having a motor with a disc-type rotor. This configuration makes use of the flatness of such a machine to minimize the space needed for the machine in the hoistway. This machine disclosed also makes use of permanent magnets in the rotor in order to improve the efficiency of the machine. These types of machines, however, are limited to relatively low duties and low speeds and, for the disc-type rotor, the machines can be very expensive. The above art notwithstanding, scientists and engineers under the direction of Applicants' Assignee are working to develop elevator systems that efficiently utilize the available space within a building. Disclosure of the Invention According to the present invention, an elevator system includes one or more ropes, a first machine having a traction sheave engaged with the ropes and a second machine having a traction sheave engaged with the ropes. Having two traction machines rather than the conventional single traction machine permits each of the machines to be more compact than the single machine. As a result, for an elevator system without a machineroom the hoistway layout is more flexible. Each of the machines may be located in positions that the larger single machine cannot fit into. In addition, in the event of a failure of one of the machines, the other machine may be used temporarily to operate the elevator system and evacuate passengers. According to one embodiment of the present invention, an elevator system includes a first machine having a traction sheave and a second machine having a traction sheave, with both traction sheaves engaged with and driving the same set of ropes. In this configuration, the machines are arranged in series, i.e., the machines are driving the ropes in the same direction. An advantage of this embodiment is that the angle of wrap of the ropes with the traction sheave may be less than 180 degrees for each sheave since the total angle of wrap is the sum of both sheaves. Another advantage is the elimination of diverting sheaves needed in conventional elevators to align the ropes with the engagement points on the car and counterweight. According to another embodiment of the present invention, an elevator system includes one or more flat ropes, a first machine having a traction sheave engaged with the flat ropes, and a second machine having a traction sheave engaged with the flat ropes. The use of flat ropes, which are defined as having an aspect ratio greater than one, permits the diameter of the traction sheaves to be dramatically reduced and results in significantly smaller motors to drive the sheaves. As a result, the machines are more compact and, by combining this feature with an elevator system having multiple machines, results in an elevator system layout that is very flexible. The foregoing and other objects, features and advantages of the present invention become more apparent in light of the following detailed description of the exemplary embodiments thereof, as illustrated in the accompanying drawings. Brief Description of the Drawings Figure 1 is a schematic illustration of one embodiment of the present invention. Figures 2 and 3 are side and top views, respectively, of a second embodiment of the present invention. Figures 4 and 5 are side and top views, respectively, of a third embodiment of the present invention. Figure 6 is a sectional, side view of a traction sheave and a plurality of flat ropes, each having a plurality of cords. Figure 7 is a sectional view of one of the flat ropes. Best Mode for Carrying Out the Invention Illustrated in Figure 1 is an elevator system 10 having a car 12 and counterweight 14 interconnected by one or more ropes 16, and two machines 18, 20 engaged with the ropesl 6. Each of the machines 18, 20 includes a motor 22 and a traction sheave 24. One machine is disposed above the counterweight 14 and the other machine 20 is disposed above the car 12. Various other hoistway equipment, such as guide rails, have been omitted from Figure 1 for clarity. In this embodiment, the machines 18, 20 are engaged with the ropes 16 in a series manner in that they are engaged with the same set of ropes 16 and drive the ropes 16 in the same direction. The operation of the motors 22, and thereby the machines 18, 20, is synchronized electronically by a controller 26. Although illustrated as having a controller 26 for electronically synchronizing the operation of the machines 18, 20, it should be noted that the machines 18, 20 may also be mechanically synchronized, such as by having a synchronizing belt engaged with the shaft of the two machines or any other manner of mechanical synchronization. Electrical synchronization in the electrical control system 26 may be devised based on constant torque output of the two motors 22, to ensure equal torque sharing in the event of any differential slip of the ropes on either of the traction sheaves. In addition, the control system may be a based upon closed loop, constant torque control of the motors. In the event of a very light car or high rise building, the two motors may have to be rotating at slightly different speeds to maintain equal torque, due to the differential traction slip on one traction sheave being slightly different than the other traction sheave. This would be most noticeable when car was fully loaded or empty, and therefore experiencing the maximum imbalance in car side versus the counterweight side rope tensions. The ropes 16 are flat ropes, which are defined as ropes having an aspect ratio greater than one, wherein aspect ratio is defined as the ratio of the width "w" of the ropes to the thickness "tl"of the ropes (see Figure 7), and preferably much greater than one. Each of the flat ropes 16 includes one or more load-carrying cords encased within a high friction elastomeric jacket. The ropes 16 are engaged with each of the traction sheaves 24 with an angle of approximately 90 degrees, so that the total angle of wrap between the ropes 16 and the sheaves 24 is approximately 180 degrees. The ropes 16 are terminated at the car 12 and counterweight 14 and are non-continuous, i.e., they do not form an endless loop. In the alternative, idler sheaves may be incorporated into the elevator system in order to increase the angle or wrap on either or both traction sheaves, if desired. Such a configuration may be used to increase the traction in order to permit lighter cars to be used with the elevator system. During operation of the elevator system 10, both motors 22 are driven in the same rotational direction such that the ropes 16 are driven in a common direction. In normal operation, each machine 18,20 provides sufficient traction to provide the motive force for approximately half of the unbalanced load of the car 12 (including passenger and/or freight load) and counterweight 14. Therefore, the size of each machine 18,20 is reduced as compared to conventional single traction machine elevator systems. In the event of a failure of one of the machines 18,20, the other machine 18,20 may be used to move the car 12 to a nearby landing to evacuate passengers. In order to reduce their size further, the machines 18, 20 do not include brakes. Brakes to stop or hold the car 12 during normal operation may be incorporated onto the car 12. Although illustrated in Figure 1 as having two machines in fixed locations relative to the hoistway, it should be apparent to one skilled in the art that the machines may also be located on the car and/or the counterweight. For instance, one machine may be located on the car and the other machine may be located on the counterweight, with the operation of the machines synchronized to move the car and counterweight in opposite directions. Illustrated in Figures 2 and 3 is another embodiment of the present invention. In this embodiment, an elevator system 28 includes a car 30 and a pair of counterweights 32,34, with each counterweight 32,34 interconnected with the car 30 by a set of ropes 36,38. The elevator system 28 also includes a pair of machines 40,42, with each machine 40,42 engaged with one of the sets of ropes 36,38. The machines 40,42 are located above the car 30 and the ropes 36,38 extend down along the sides of the hoistway to the car 30 and to the counterweights 32,34. As with the embodiment of Figure 1, this embodiment uses flat ropes to reduce the size of the machines 40,42 such that they can be fit conveniently above the car 30 and, as in the embodiment of Figure 1, the machines 40, 42 are synchronized either electronically or mechanically (not shown). In this configuration, the counterweights 32,34 are each half the mass of conventional counterweights and the load of the elevator system 28 is split between the two machines 40,42. The combination of multiple machines and flat ropes minimizes the size of the machines 40,42 such that they can be located above the car 30 without significantly impacting the space requirements of the elevator system 28. During operation, each of the machine shafts 44 rotates in the opposite rotational direction of the other machine shaft 44 in order to raise and lower the car 30 and counterweights 32,34. It should be noted that the location of one of the counterweights could be moved to the opposite side of its associated machine so that the machine shafts would rotate in the same rotational direction. In addition, even though shown in Figures 2 and 3 as having conventional guide rails for the counterweight, it should be apparent that other means of guiding the counterweight may be used, such as guiding the counterweights within hollow column-like guides. Illustrated in Figures 4 and 5 is another embodiment of the present invention. This embodiment is similar to that shown in Figures 2 and 3, except that the machines 40,42 are moved from above the car 30 to a position above the hoistway doors 46 of one of the landings. As a result, diverter sheaves 50 are needed to provide the desired rope drops to the car 30 and counterweights 32,34. In this embodiment, the combination of the features of multiple machines and flat ropes makes the machines compact enough that they can fit within the confined space above the hoistway doors. An advantage of this particular embodiment is the accessibility of the machines for maintenance. In addition to the use of multiple machines, another feature of the present invention is the flatness of the ropes used in the above described elevator system. The increase in aspect ratio results in a rope that has an engagement surface, defined by the width dimension "w", that is optimized to distribute the rope pressure. Therefore, the maximum rope pressure is minimized within the rope. In addition, by increasing the aspect ratio relative to a round rope, which has an aspect ratio equal to one, the thickness "tl"of the flat rope (see Figure 7) may be reduced while maintaining a constant cross-sectional area of the portions of the rope supporting the tension load in the rope. As shown in Figure 6 and 8, the flat ropes 722 include a plurality of individual load carrying cords 726 encased within a common layer of coating 728. The coating layer 728 separates the individual cords 726 and defines an engagement surface 730 for engaging the traction sheave 724. The load carrying cords 726 may be formed from a high-strength, lightweight non-metallic material, such as aramid fibers, or may be formed from a metallic material, such as thin, high-carbon steel fibers. It is desirable to maintain the thickness "d" of the cords 726 as small as possible in order to maximize the flexibility and minimize the stress in the cords 726. In addition, for cords formed from steel fibers, the fiber diameters should be less than .25 millimeters in diameter and preferably in the range of about .10 millimeters to .20 millimeters in diameter. Steel fibers having such diameter improve the flexibility of the cords and the rope. By incorporating cords having the weight, strength, durability and, in particular, the flexibility characteristics of such materials into the flat ropes, the traction sheave diameter "D" may be reduced while maintaining the maximum rope pressure within acceptable limits. The engagement surface 730 is in contact with a corresponding surface 750 of the traction sheave 724. The coating layer 728 is formed from a polyurethane material, preferably a thermoplastic urethane, that is extruded onto and through the plurality of cords 726 in such a manner that each of the individual cords 726 is restrained against longitudinal movement relative to the other cords 726. In addition, the coating layer is preferably flame retardant to minimize damage to the coating layer and cords in the event that the belt is exposed to flames or damaging heat. Other materials may also be used for the coating layer if they are sufficient to meet the required functions of the coating layer: traction, wear, transmission of traction loads to the cords and resistance to environmental factors. It should be understood that although other materials may be used for the coating layer, if they do not meet or exceed the mechanical properties of a thermoplastic urethane, then the benefits resulting from the use of flat ropes may be reduced. With the thermoplastic urethane mechanical properties the traction sheave 724 diameter is reducible to 100 millimeters or less. As a result of the configuration of the flat rope 722, the rope pressure may be distributed more uniformly throughout the rope 722. Because of the incorporation of a plurality of small cords 726 into the flat rope elastomer coating layer 728, the pressure on each cord 726 is significantly diminished over prior art ropes. Cord pressure is decreased at least as n " ' , with n being the number of parallel cords in the flat rope, for a given load and wire cross section. Therefore, the maximum rope pressure in the flat rope is significantly reduced as compared to a conventionally roped elevator having a similar load carrying capacity. Furthermore, the effective rope diameter 'd' (measured in the bending direction) is reduced for the equivalent load bearing capacity and smaller values for the sheave diameter 'D' may be attained without a reduction in the D/d ratio. In addition, minimizing the diameter D of the sheave permits the use of less costly, more compact, high speed motors as the drive machine. A traction sheave 724 having a traction surface 750 configured to receive the flat rope 722 is also shown in Figure 6. The engagement surface 750 is complementarily shaped to provide traction and to guide the engagement between the flat ropes 722 and the sheave 724. The traction sheave 724 includes a pair of rims 744 disposed on opposite sides of the sheave 724 and one or more dividers 745 disposed between adjacent flat ropes. The traction sheave 724 also includes liners 742 received within the spaces between the rims 744 and dividers 745. The liners 742 define the engagement surface 750 such that there are lateral gaps 754 between the sides of the flat ropes 722 and the liners 742. The pair of rims 744 and dividers, in conjunction with the liners, perform the function of guiding the flat ropes 722 to prevent gross alignment problems in the event of slack rope conditions, etc. Although shown as including liners, it should be noted that a traction sheave without liners may be used. Although the invention has been shown and described with respect to exemplary embodiments thereof, it should be understood by those skilled in the art that various changes, omissions, and additions may be made thereto, without departing from the spirit and scope of the invention. For instance, although shown in each embodiment as having two machines, additional machines may be used.

Claims: CLAIMS What is claimed is: 1. An elevator system having a car and a counterweight interconnected by one or more ropes for travel within a hoistway, each of the ropes being non- continuous, the elevator system further including a first machine having a traction sheave engaged with and providing motive force to the one or more ropes, and a second machine having a traction sheave engaged with and providing motive force to the one or more ropes. 2. The elevator system according to Claim 1 , wherein the car and counterweight are suspended from the one or more ropes. 3. The elevator system according to Claim 1, wherein the first and second machines drive the ropes concurrently. 4. The elevator system according to Claim 1 , wherein the first and second machines are engaged with the one or more ropes in a serial manner. 5. The elevator system according to Claim 1 , wherein the angle of wrap of the one or more ropes with the traction sheave of the first machine is approximately ninety degrees. 6. The elevator system according to Claim 5, wherein the angle of wrap of the one or more ropes with the traction sheave of the second machine is approximately ninety degrees. 7. The elevator system according to Claim 1, wherein each of the one or more ropes has a width w, a thickness t measured in the bending direction, and an aspect ratio, defined as the ratio of width w relative to thickness t, greater than one. 8. The elevator system according to Claim 1, wherein the first machine and the second machine are electronically synchronized. 9. The elevator system according to Claim 1 , wherein the first machine and the second machine are mechanically synchronized. 10. The elevator system according to Claim 1, wherein the first machine is fixed relative to the hoistway. 11. The elevator system according to Claim 10, wherein the second machine is fixed relative to the hoistway. 12. The elevator system according to Claim 1, further including an elevator brake used to hold the car in position during normal operation of the elevator system, wherein the elevator brake is disposed on the car. 13. An elevator system having a car and counterweight interconnected by one or more ropes, wherein each of the one or more ropes has a width w, a thickness t measured in the bending direction, and an aspect ratio, defined as the ratio of width w relative to thickness t, greater than one, the elevator system further including a first machine having a traction sheave engaged with and providing motive force to the one or more ropes, and a second machine having a traction sheave engaged with and providing motive force to the one or more ropes. 14. The elevator system according to Claim 13, wherein the one or more ropes includes a first set of ropes and a second set of ropes, and wherein the first machine is engaged with the first set of ropes and the second machine is engaged with the second set of ropes. 15. The elevator system according to Claim 13, wherein the car and counterweight are suspended from the one or more ropes. 16. The elevator system according to Claim 13, wherein the first and second machines drive the ropes concurrently. 17. The elevator system according to Claim 13, wherein the first and second machines are engaged with the one or more ropes in a serial manner. 18. The elevator system according to Claim 13 , wherein the angle of wrap of the first set of ropes with the traction sheave of the first machine is approximately ninety degrees. 19. The elevator system according to Claim 18, wherein the angle of wrap of the second set of ropes with the traction sheave of the second machine is approximately ninety degrees. 20. The elevator system according to Claim 13, wherein the first machine and the second machine are electronically synchronized. 21. The elevator system according to Claim 13, wherein the first machine and the second machine are mechanically synchronized. 22. The elevator system according to Claim 13, wherein the first machine is fixed relative to the hoistway. 23. The elevator system according to Claim 22, wherein the second machine is fixed relative to the hoistway. 24. The elevator system according to Claim 13, further including an elevator brake used to hold the car in position during normal operation of the elevator system, wherein the elevator brake is disposed on the car.

Inventors: ADIFON LEANDRE, ERICSON RICHARD J, ADIFON, LEANDRE, ERICSON, RICHARD, J.
Applicants: ADIFON LEANDRE, ERICSON RICHARD J, OTIS ELEVATOR CO, ADIFON, LEANDRE, ERICSON, RICHARD, J., OTIS ELEVATOR COMPANY
Application year: 1999
Main classification: B66B11
IPC codes: B66B7, B66B9, B66B11, B66B13, B66B17, D07B1