WO2005096719A2

WO2005096719A2 - Self-adjusting elevator hitch

Info

Publication number: WO2005096719A2
Application number: PCT/US2004/006833
Authority: WO
Inventors: Qinqian Zeng; John Ferrisi
Original assignee: Otis Elevator Company
Priority date: 2004-03-05
Filing date: 2004-03-05
Publication date: 2005-10-20
Also published as: WO2005096719A3

Abstract

An elevator system (10) includes an elevator car (12) supported for movement within a hoistway by a plurality of ropes (16) secured to the elevator car (12) by a corresponding plurality of hitch assemblies (14). Each hitch assembly (14) includes an adjustable member (18) for adjusting a biasing force exerted by a biasing member (20) on the elevator car (12). The adjustable member (18) varies the length of the biasing member (20) to distribute at least a portion of a supporting force among the plurality of ropes (16) to counter imbalanced loads on the elevator car (12).

Description

SELF-ADJUSTING ELEVATOR HITCH

FIELD OF THE INVENTION This invention generally relates to a hitch assembly for an elevator system, and more particularly to a self-adjusting elevator hitch assembly useful for compensating for imbalances within an elevator car.

DESCRIPTION OF THE RELATED ART An elevator car moving within a hoistway encounters many forces from differing sources. Preferably, the elevator car is balanced during movement within the hoistway to provide good ride quality and reduce wear on elevator system components. However, many sources of variation may cause unbalanced forces on the elevator car.

For example, changes in passengers, loads within the elevator car and a changing length of a traveling cable or compensation rope contribute to unbalanced forces on the elevator car. An unbalanced elevator car may degrade ride quality and cause undesirable noises or vibrations. It is therefore desirable to compensate for such unbalanced conditions to provide improved ride quality and eliminate undesirable noises and vibrations. Improved alignment and consistency of the guide rail can improve ride quality and reduce unbalanced loads on the elevator car. However, such improvements are costly, time intensive and provide limited improvements. One proposed counterbalance system includes weights that are shifted relative to sensed imbalances of the elevator car. Such systems add considerable weight to the elevator car, requiring larger duty machines to lift and move the elevator car. Further, such counterbalancing weights are limited to defined movement in specific directions and are therefore unable to fully compensate for imbalanced conditions in all directions. Accordingly, it is desirable to design a system for countering imbalance forces exerted on an elevator car in various directions to improve ride quality and eliminate undesirable noise and vibration. SUMMARY OF INVENTION The present invention is a hitch assembly for an elevator car that automatically adjusts a biasing force to redistribute a portion of a coupling force among a plurality of ropes supporting the elevator car. The hitch assembly includes an automatically adjustable member and a biasing member. In one example, the adjustable member changes the length of the biasing member to vary a corresponding biasing force exerted on the elevator car. Changing selected biasing forces distributes a portion of the coupling force among the plurality of ropes to counter imbalanced loads on the elevator car. Accordingly, the present invention provides a hitch assembly for countering imbalance forces exerted on an elevator car in various directions to improve ride quality and eliminate noise and vibration.

BRIEF DESCRIPTION OF THE DRAWINGS The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows: Figure 1 is a perspective schematic view of an elevator car with a hitch assembly designed according to this invention; Figure 2 is a schematic view of the elevator car of Figure 1 showing more detail of the hitch assembly in a first operating condition; Figure 3 is a partial schematic view of the example hitch assembly in a neutral position; Figure 4; is a partial schematic view of the example hitch assembly in a position to redistribute supporting forces; Figure 5, is a partial schematic view of another example hitch assembly in a position to redistribute supporting forces; and Figure 6, is a schematic top view of an elevator car including a hitch assembly designed according to this invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to Figures 1 and 2, an elevator system 10 includes an elevator car 12 supported for movement within a hoistway by a plurality of ropes 16. It should be noted that the term "rope" as used in this description includes belts, steel ropes, etc. The ropes 16 are secured to the elevator car 12 by a corresponding plurality of hitch assemblies 14. Each hitch assembly 14 includes an automatically adjustable member 18 and a biasing member 20. A length 34A, 34B (Shown in Figures 2, 3 and 4) of a selected biasing member 20 is adjustable to vary a corresponding coupling force exerted on the elevator car 12 to redistribute a portion of the coupling force to counter imbalanced loads on the elevator car 12. Referring to Figure 2, the biasing member 20 in this example is a coil spring having a spring force corresponding to a spring rate and the length 34A, 34B of the spring. The elevator car 12 is supported by the ropes 16. The hitch assemblies 14 include hitches 15 secured to an end of one of the plurality of ropes 16 in a known manner. Thimble rods 50 extend in a Icnown manner through a frame member 32 of the car 12. The biasing members 20 are disposed between a support 17 and the frame member 32 of the elevator car 12. The supporting force 22 suspending the car 12 is distributed among the plurality of ropes 16. The biasing members 20 apply a coupling force to the elevator car 12 by biasing the hitch assemblies 14 relative to the elevator car 12. Although, this description and the accompanying figures illustrate an elevator car 12 moving generally vertically, other directions of movement of an elevator car 12 are within the contemplation of this invention. The use of specific directions is not intended as limiting the disclosure, but is for discussion purposes only. Roller guide assemblies 26, associated with the elevator car 12, guide the elevator car 12 along guide rails 28 within an elevator hoistway. The elevator car 12, in some instances, may be imbalanced as caused by loads within the elevator car 12, structural irregularities within the guide rails 28, other forces exerted on the elevator car 12 during operation or a combination of these. A sensor 24 such as a known load cell, detects imbalance conditions on the elevator car 12. In one example, the sensor 24 is mounted to measure forces on a portion of the roller guide 26. Each sensor 24 communicates force information to a controller 30. The controller 30 may be dedicated to operation of the hitch assembly 14, or may be a portion of a system controller that governs operation of the elevator system 10. The controller 30 detects imbalanced loads on the elevator car 12 by analyzing force measurements from each of the sensors 24. Force measurements are used by the controller 30 to actuate the adjustable members 18 and change the length 34A, 34B of an associated biasing member 20. The change in length of the biasing member 20 changes the coupling force against the support 32 and redistributes a portion of the coupling force in a direction that will counter the detected imbalanced load or force. Those skilled in the art who have the benefit of this description will be able to program a controller to meet the needs of their particular situation. In one example, the adjustable members 18 are hydraulically actuated cylinders. In another example, electrical linear actuators are used. Other automatically moveable actuators may be used. The adjustable members 18 adjust the length of the corresponding biasing members 20 and thereby the bias of that member 20, which changes the coupling force exerted on the hitch. The differences between the biases of the plurality of biasing members 20 distributes a portion of the supporting force in a direction countering the detected imbalance force. Referring to Figure 3, the biasing members 20 and adjustable members 18 are initially disposed in a neutral position where all biasing members 20 are of a common length 34A and exert a common amount of biasing force to equally distribute the coupling force. The entire magnitude of the supporting force 22 is therefore evenly distributed between the hitches 14 coupling to ropes 16. Referring to Figure 4, upon detection of an imbalance load on the elevator car

12, the controller 30 controls movement of at least one of the adjustable members 18 to adjust a corresponding biasing member 20. As shown, the adjustable member 18 is actuated to decrease the length 34B of one spring 20, thereby increasing the biasing force exerted by the biasing member 20 and another hitch assembly 14 is adjusted to increase the length 34A, thereby decreasing the associated biasing force. The change in length of each biasing member 20 causes a proportional increase or decrease in biasing force to redistribute the total coupling force, thereby creating a moment, schematically shown at 38, that counters the detected imbalanced force such that the car 14 moves into a balanced position. Each of the plurality of biasing members 20 is adjusted individually to distribute the coupling force and counter balance the elevator car 12 against the imbalance force. Referring to Figure 5, another variable member 18' according to this invention is disclosed. The variable member 18 ' is disposed between the biasing member 20 and the support 32. The variable member 18' adjusts to change the length of the biasing member 20 such that different hitch assemblies 14 exert different coupling forces to balance the elevator car 12. A worker with the benefit of this disclosure would understand that placement of the variable member 18' for changing the biasing force exerted on the elevator car 12 can vary depending on the application. Referring to Figure 6, an example placement configuration of hitch assemblies 14 relative to each other allows for balancing the car 12 in side-to-side and front-to-back directions. The illustrated arrangement permits providing counter-balancing movements in more than one direction. The number of hitch assemblies 14 and the specific placement relative to the elevator car 12 are application specific, and a worker in the art who has the benefit of this description would understand how to configure the hitch assemblies 14 to support and counter imbalance forces on the elevator car 12. The hitch assembly 14 of this invention provides for countering imbalanced loads on an elevator car 12 without cumbersome and complicated mechanical components. Accordingly, the hitch assembly 14 of this invention provides a simplified mechanism and method of countering imbalance conditions on an elevator car 12 to improve ride quality, and decrease wear and fatigue on the elevator car 12 caused by imbalanced conditions. The foregoing description is exemplary and not just a material specification. The invention has been described in an illustrative manner. It should be understood that the terminology used is intended to be in the nature of words of description rather than of limitation. Many modifications and variations are possible in light of the above teachings. The preferred embodiment of this invention have been disclosed, however, one of ordinary skill in the art would recognize that certain modifications are within the scope of this invention. It is understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described. For that reason the following claims should be studied to determine the true scope and content of this invention.

Claims

1. An elevator system (10) comprising: an elevator car (12) ; and a plurality of hitch assemblies (14) for securing a corresponding plurality of ropes (16) to said elevator car (12), wherein each of said hitch assemblies (14) includes a biasing member (20) that biases the hitch assembly (14) relative to said car and an automatically adjustable member (18) that automatically varies a biasing force exerted by said biasing member (20).

2. The system (10) as recited in claim 1, comprising a sensor (42) for detecting an imbalance condition of said elevator car (12), at least one of said adjustable members varying a corresponding biasing force responsive to said sensor (42) detecting an imbalance condition.

3. The system as recited in claim 2, comprising at least one roller guide assembly (26) associated with the elevator car (12) for guiding said elevator car (12) along a guide rail (28) and wherein said sensor (42) measures a force on at least one portion of said roller guide assembly (26).

4. The system (10) as recited in claim 1, comprising a controller (30) that determines a balance condition of the car and controls said adjustable member (18) based upon the determined condition.

5. The system (10) as recited in claim 1, wherein a length of said biasing member (20) is proportional to a biasing force exerted by said biasing member (20) and wherein said adjustable member (18) is selectively movable to adjust a length of said biasing member (20).

6. The system as recited in claim 1, wherein said biasing member (20) comprises a coil spring.

7. The system (10) as recited in claim 1, wherein said adjustable member (18) comprises at least one hydraulic actuator operative to change a length of said biasing member (20).

8. The system (10) as recited in claim 1, wherein said adjustable member (18) comprises at least one electric actuator operative to change a length of said biasing member (20).

9. A hitch assembly (14) for securing a rope to an elevator car (12) comprising: a biasing member (20) for biasing the hitch assembly (14) relative to the elevator car (12); an adjustable member (18); and a controller (30) that controls said adjustable member (18) to automatically vary a biasing force exerted by said biasing member (20) on said support (32).

10. The assembly as recited in claim 9, comprising a sensor (42) for detecting an imbalanced condition on the elevator car (12).

11. The assembly as recited in claim 9, wherein a length of said biasing member (18) is proportional to said biasing force, and said adjustable member (18) changes said length of said biasing member (20) to adjust said biasing force exerted on said support (32).

12. The assembly as recited in claim 9, wherein said biasing member (20) comprises a coil spring.

13. The assembly of claim 9, comprising a plurality of hitch assemblies (14) disposed on a corresponding plurality of ropes (16) supporting the elevator car (12).

14. The assembly as recited in claim 9, wherein said adjustable member (18) comprises a hydraulic actuator operative to adjust a length of said biasing member (20).

15. The assembly as recited in claim 9, wherein said adjustable member (18) comprises an electric actuator operative to adjust a length of said biasing member (20).

16. A method of balancing an elevator car (12) comprising the steps of: a) detecting an imbalance condition of the elevator car (12); and b) redistributing at least a portion of a coupling force among a plurality of hitches and ropes attached to the elevator car (12).

17. The method as recited in claim 16, wherein said step b) comprises adjusting a biasing force exerted by at least one of a plurality of biasing members (20) corresponding to said plurality of ropes (16).

18. The method as recited in claim 17, wherein step b) comprises adjusting a length of the biasing member (20).

19. The method as recited in claim 18, wherein step b) comprises adjusting a length of each of said plurality of biasing members (20).

20. The method as recited in claim 16, comprising continuing to redistribute the coupling force until sensing a balanced condition of the elevator car (12).