WO2010019117A1

WO2010019117A1 - Elevator vertical vibration absorber

Info

Publication number: WO2010019117A1
Application number: PCT/US2008/009711
Authority: WO
Inventors: Randall Keith Roberts; George Scott Copeland; Soumitra Borthakur; Vijay Jayachandran; Richard J. Ericson
Original assignee: Otis Elevator Company
Priority date: 2008-08-14
Filing date: 2008-08-14
Publication date: 2010-02-18

Abstract

A traction elevator system(lθ) includes a car(12), traction members (16) connected to the car, and a vibration absorber (20). The vibration absorber includes a first mass (30) connected to an elevator system mass other than the car and a resilient member (44). The resilient member is connected between the first mass and the elevator system mass. The natural frequency of the vibration absorber is approximately equal to an excitation frequency of the elevator system.

Description

ELEVATOR VERTICAL VIBRATION ABSORBER

BACKGROUND

The present invention relates to the improvement of ride quality in elevator systems. In particular, the present invention relates to a device for reducing vertical vibrations in an elevator system.

A typical traction elevator system includes an elevator car and a counterweight, each suspended on opposite ends of traction members, such as belts or ropes, in an elevator hoistway. In some systems, the elevator car is attached to a car frame to which the traction members are attached. The elevator system may also include rails extending the length of the hoistway and attached to opposite sides of the hoistway. A group of guides may be attached to the elevator car or car frame and guide the car (and frame) up and down the hoistway along the rails.

There are several factors that impact the quality of the elevator car ride in elevator systems. One such factor is vertical vibrations transmitted through the elevator system to the car. Vertical vibrations emanate from different sources in modern elevator systems. For example, a small imperfection in the drive sheave may cause a once per revolution excitation to the system. The excitation caused by the sheave imperfection can cause vibrations, which are transmitted through, for example, the traction members to the car. The vibration levels may be particularly high in cases where the excitation frequency matches a natural frequency of the system. In addition to drive sheaves, guide rail imperfections may cause vibrations as the elevator car is guided through the hoistway along the rails. Even slightly deflected rails and minimal discontinuity in guide rail segment joints can cause undesirable vibrations in the elevator car. Additionally, metal particles and debris on the rails generated during elevator installation and in-service wear may act to interfere with the guides moving along the rails and thereby cause vibrations in the car.

In an attempt to minimize vertical vibrations in elevator systems, elevator manufacturers have conducted mitigating activities, such as cleaning guide rails, adjusting car balance, and reducing drive and idler sheave runouts. Additionally, elevator systems commonly include vibration isolation/damping devices on various parts of the system. For example, roller guide assemblies commonly include a suspension and a damping system to reduce the impact of rail imperfections on car ride quality. However, a need still exists to improve car ride quality by making elevator systems less sensitive to vertical vibrations. SUMMARY

A traction elevator system includes a car, traction members connected to the car, and a vibration absorber. The vibration absorber includes a first mass connected to an elevator system mass other than the car and a resilient member. The resilient member is connected between the first mass and the elevator system mass. The natural frequency of the vibration absorber is approximately equal to an excitation frequency of the elevator system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a traction elevator system. FIG. 2 is a schematic of the elevator system of FIG. 1 including a vibration absorber according to the present invention incorporated into the elevator tie-down compensation. FIG. 3 is a schematic of the elevator system of FIG. 1 including a vibration absorber according to the present invention incorporated into the elevator counterweight.

FIG. 4A is a perspective view of one embodiment of the vibration absorber of FIG. 3.

FIGS. 4B-4D are detail views of different components of the vibration absorber of FIG. 4A.

FIG. 5A is a front view of an alternative embodiment of the vibration absorber of FIG. 3.

FIG. 5B is a detail view of the vibration absorber of FIG. 5 A. FIG. 6 is a front view of another alternative embodiment of the vibration absorber of FIG. 3.

FIG. 7 is a perspective view of yet another alternative embodiment of the vibration absorber of FIG. 3.

FIG. 8 is a graph of predicted vibration amplitude as a function of frequency for a baseline elevator system and a system with a vibration absorber according to the present invention.

FIGS. 9 A and 9B are graphs of predicted elevator car acceleration as a function of time for a baseline elevator system and a system with a vibration absorber according to the present invention, respectively. DETAILED DESCRIPTION

FIG. 1 is a perspective view of elevator system 10 including car 12, counterweight 14, traction members, such as traction members 16, drive machine 18, and tie-down compensation 20. Although FIG. 1 shows an elevator system with a 1 : 1 roping arrangement, embodiments of the present invention are equally applicable to elevator systems with other roping arrangements, for example, having a 2:1 or 3:1 suspension ratio. In FIG. 1, car 12 and counterweight 14 are connected to drive machine 18 and tie-down compensation 20 by traction members 16. Drive machine 18 includes motor 22, drive sheave 24, and deflector sheave 26. Tie-down compensation 20 includes compensation sheave 28 and compensation mass 30. Traction members 16 terminate on the top and bottom of car 12 and counterweight 14. Traction members 16 connected between the top of car 12 and the top of counterweight 14 wrap around drive sheave 24 and deflector sheave 26. Traction members 16 connected between the bottom of car 12 and the bottom of counterweight 14 wrap around compensation sheave 28. Motor 22 of drive machine 18 is powered to turn drive sheave 24, which engages traction members 16 to move car 12 (and thereby counterweight 14) up and down a hoistway (not shown).

Counterweight 14 is configured to counterbalance the weight of car 12, which in turn reduces the torque required by drive machine 18 to raise and lower car 12. Additionally, counterweight 14 contributes to maintaining the tension in traction members 16 necessary to allow drive sheave 24 to drive car 12 without slipping. Tie-down compensation 20 is configured to augment the tension in traction members 16 by employing compensation mass 30 connected to compensation sheave 28. Additionally, tie-down compensation 20 reduces the effects of car 12 and counterweight 14 jump caused by abrupt changes in the speed of car 12.

During operation, the ride quality of car 12 of elevator system 10 may be adversely affected by vertical vibrations. Vertical vibrations in elevator system 10 may be caused by, for example, an imperfection in drive sheave 24 that produces an excitation in system 10 once per revolution of drive sheave 24. The excitation can cause vibrations that travel through traction members 16 to car 14. Vibration levels may be particularly high when the excitation frequency matches a natural frequency of system 10. Embodiments of the present invention therefore employ tuned mass dampers incorporated into an existing elevator system mass other than the car, such as the counterweight or the compensation mass, to absorb undesirable vertical vibrations and thereby minimize the impact of the vibrations on the elevator car. The presence of a tuned damper ensures that disturbance energy in a relatively narrow frequency band is transferred to the relatively small damper mass, instead of the car mass, to minimize the car vibration levels. In addition, the presence of a tuned damper allows the inertia of a large system mass to be balanced by a comparatively lightweight damper mass. The tuned mass damper is configured in such a way that the system mass moves in one direction as the damper mass moves in the other, thus damping the system oscillation. Tuned mass dampers are engineered, or "tuned" to specifically counter harmful vibration frequencies, such as a system excitation frequency. The size of the damper mass necessary to absorb system vibrations is a function of the size of the system mass into which the damper mass is incorporated. It is therefore impractical to incorporate tuned mass dampers into the elevator car assembly, because such configurations would add an unacceptable amount of weight and cost to the elevator system.

FIG. 2 is a schematic of elevator system 10 of FIG. 1 including vibration absorber 40 incorporated into tie-down compensation mass 30. Vibration absorber 40 includes damper mass 42, resilient member 44, and damper 46. Damper mass 42 is connected to compensation mass 30. Resilient member 44 and damper 46 are connected between damper mass 42 and compensation mass 30. Vibration absorber 40 may be tuned to have a natural frequency substantially equal to an excitation frequency of elevator system 10. The natural frequency of vibration absorber 40 may be adjusted by varying one of the mass of the damper mass 42, the resiliency of resilient member 44, and the damping coefficient of damper 46. During elevator operation, vibration absorber 40 may substantially reduce the amount and magnitude of vibrations reaching car 12 by balancing the inertia of compensation mass 30 as compensation mass 30 encounters vertical vibrations in system 10.

FIG. 3 is a schematic of elevator system 10 of FIG. 1 including vibration absorber 50 incorporated into counterweight 14. Vibration absorber 50 includes damper mass 52, resilient member 54, and damper 56. Damper mass 52 is connected to counterweight 14. Resilient member 54 and damper 56 are connected between damper mass 52 and counterweight 14. Vibration absorber 50 may be tuned to have a natural frequency substantially equal to an excitation frequency of elevator system 10. The natural frequency of vibration absorber 50 may be adjusted by varying one of the mass of the damper mass 52, the resiliency of resilient member 54, and the damping coefficient of damper 56. During elevator operation, vibration absorber 50 may substantially reduce the amount and magnitude of vibrations reaching car 12 by balancing the inertia of counterweight 14 as counterweight 14 encounters vertical vibrations in system 10.

In embodiments of the present invention, it may be advantageous to permit as much vibration in the vibration absorber as possible. Therefore, the vibration absorbers may not include an engineered damper. Rather, damping may be achieved through system imperfections and environmental forces, for example, friction.

FIG. 4A is a perspective view of one embodiment according to the present invention including a vibration absorber 60 incorporated into the elevator counterweight 14. FIGS. 4B-4D are detail views of different components of vibration absorber 60. Counterweight 14 includes vibration absorber 60, counterweight masses 62, and counterweight frame 64. Vibration absorber 60 includes damper masses 66, absorber frame 68, springs 70, and brackets 72. In FIG. 4A, counterweight masses 62 and damper masses 66 are arranged generally vertically adjacent one another in counterweight frame 64. Damper masses 66 are disposed in absorber frame 68 within counterweight frame 64. Arranged underneath absorber frame 68, between damper masses 66 and counterweight masses 62, are helical springs 70. In the illustrative embodiment, springs 70 are arranged for vertical compression and are generally distributed equidistantly along the width of absorber frame 68. As shown in the detail view of FIG. 4B, each of springs 70 is arranged about post 74 connected to the bottom of absorber frame 68 and both spring 70 and post 74 are contained by cylindrical sleeve 76 connected to counterweight frame 64.

In FIG. 4A, brackets 72 are connected to counterweight frame 64 above damper masses 66 and absorber frame 68. Brackets 72 are configured to augment the action of springs 70 and simultaneously limit lateral, e.g. forward and backward, travel of vibration absorber 60 within counterweight frame 64. Brackets 72 may therefore be generally flexible in the vertical direction and substantially rigid in lateral directions. Brackets 72 may be, for example, steel brackets having a T-shape and including slots 78 for adjustable connection to counterweight frame 64 as shown in FIG. 4C. As shown in FIG. 4A and in greater detail in FIG. 4D, brackets 72 abut the top of absorber frame 68. In order to limit deflection and thereby prevent yielding of brackets 72, embodiments of the present invention may include bumper 79 connected to counterweight frame 64 as shown in FIG. 4D. Vibration absorber 60 does not include any engineered damping. Vibrations encountered by absorber 60 may be gradually attenuated as friction acts to oppose the force of the system vibrations on absorber 60.

FIG. 5A is a front view of counterweight 14 including vibration absorber 80. FIG. 5B is a detail view of vibration absorber 80 of FIG. 5A. Vibration absorber 80 is an alternative embodiment according to the present invention including a vibration absorber incorporated into the elevator counterweight. Counterweight 14 includes vibration absorber 80, counterweight masses 82, counterweight frame 84, and guide rails 86. Vibration absorber 80 includes damper masses 88, absorber frame 90, springs 92, and sliding guides 94. In FIG. 5A, counterweight masses 82 and damper masses 88 are arranged generally horizontally adjacent one another in counterweight frame 84. Damper masses 88 are disposed in absorber frame 90 within counterweight frame 84. As shown in greater detail in FIG. 5B, guide rails 86 are generally T-shaped beams extending the length of counterweight frame 84 and sliding guides 94 are channel-shaped members configured to slidably engage rails 86. Guide rails 86 are connected to counterweight frame 84 and absorber frame 90 is slidably connected to rails 86 by sliding guides 94.

In FIG. 5A, arranged below absorber frame 90 between damper masses 88 and counterweight masses 82 are helical springs 92. Springs 92 are arranged for vertical compression and are generally distributed equidistantly along the width of absorber frame 90. Springs 92 may be contained by sleeves and posts as shown in the embodiment of FIGS. 4A-4D, or any other containment device appropriate for use in the embodiment of FIGS. 5A and 5B. Vibrations encountered by vibration absorber 80 are damped by the friction between sliding guides 94 and rails 86. Friction will act to dampen oscillation of damper masses 88 after vibration absorber 80 absorbs vibrations generated in the elevator system and transmitted to counterweight 14. FIG. 6 is a front view of counterweight 14 including an alternative embodiment of a vibration absorber, wherein a vibration absorber 100 is incorporated into elevator counterweight 14. Counterweight 14 includes vibration absorber 100, counterweight masses 82, counterweight frame 84, and rods 102. Vibration absorber 100 includes damper masses 88, absorber frame 90, and springs 92. In FIG. 6, counterweight masses 82 and damper masses 88 are arranged generally horizontally adjacent one another in counterweight frame 84. Damper masses 88 are disposed in absorber frame 90 within counterweight frame 84. Rods 102 are connected to counterweight frame 84, and absorber frame 90 and damper masses 88 are slidably connected to rods 102 by, for example, bushings 104 configured to receive rods 102. Rods 102 extend along the length of counterweight frame 84 and are configured to constrain and guide motion of damper masses 88 in absorber frame 90. Helical springs 92 are arranged below absorber frame 90 between damper masses 88 and counterweight masses 82. Springs 92 are arranged for vertical compression and are generally distributed equidistantly along the width of absorber frame 90. Springs 92 may be contained by sleeves and posts as shown in the embodiment of FIGS. 4A-4D, or any other containment device appropriate for use in the embodiment of FIG. 6. Vibrations encountered by vibration absorber 100 are damped by the friction between rods 102 and bushings 104. Friction will act to dampen oscillation of damper masses 88 after vibration absorber 100 absorbs vibrations generated in the elevator system and transmitted to counterweight 14.

FIG. 7 is a perspective view of counterweight 14 including yet another alternative embodiment of a vibration absorber, wherein a vibration absorber 110 is incorporated into elevator counterweight 14. Counterweight 14 includes vibration absorber 110, counterweight masses 112, counterweight frame 114, and plates 116. Vibration absorber 110 includes damper masses 118, absorber frame 120, shock absorbers 122, and ball joints 124. In FIG. 6, counterweight masses 112 and damper masses 118 are arranged generally vertically adjacent one another in counterweight frame 114. Damper masses 118 are disposed in absorber frame 120 within counterweight frame 114. Shock absorbers 122 are connected between absorber frame 120 and counterweight frame 114 by ball joints 124. Shock absorbers 122 are configured for vertical compression as vibration absorber 110 encounters vibrations from the elevator system. Shock absorbers 122 may be configured to absorb energy using, for example, hydraulic fluid. Alternatively, shock absorbers 122 may contain springs placed in compression by the weight of vibration absorber 110. Ball joints 124 provide freedom of lateral movement for absorber 110 within counterweight frame 114. However, plates 116 provide a limit on lateral movement of vibration absorber 110 by containing absorber frame 120 generally within counterweight frame 114. Additionally, movement of vibration absorber 110 may be controlled by connecting absorber frame 120 to counterweight frame 114 with sliding guides (not shown) configured to receive guide rails (not shown) connected to counterweight frame 114. Vibrations encountered by vibration absorber 110 are damped by friction within shock absorbers 122 and ball joints 124, and the effect of gravity on absorber 110. The combination of friction and gravity will act to dampen oscillation of damper masses 118 after vibration absorber 110 absorbs vibrations generated in the elevator system and transmitted to counterweight 14.

A simulation study was performed to analyze the effect on elevator system vertical vibration of vibration absorbers according to the present invention. FIGS. 8, 9 A and 9B show results generated from the simulation study. FIG. 8 is a graph of vibration versus frequency ratio, where the magnitude of the vibration has been normalized based on the maximum expected vibration in a baseline system without an absorber. The frequency ratio is equal to the frequency of the vibration excitation divided by the natural frequency of the vibration absorber. In FIG. 8, curve 130 shows the vibration magnitude for varying frequencies of an elevator system without a vibration absorber, and curve 132 shows the vibration magnitude for varying frequencies of an elevator system with a vibration absorber according to the present invention. FIGS. 9A and 9B are graphs of elevator car acceleration over time for a simulated multi-floor run of the car. FIG. 9A shows the results for an elevator system without a vibration absorber and FIG. 9B shows the results for a system with a vibration absorber according to the present invention. In FIGS. 9A and 9B, the multi-floor run includes an acceleration phase leading to a constant speed phase 134 and ending in a deceleration phase. Vibration absorbers according to the present invention will be most effective in the constant speed phase 134. As can be seen by comparing curve 130 to curve 132 in FIG. 8 and the results in FIG. 9A to the results in FIG. 9B, vibration absorbers according to the present invention may reduce vertical vibrations in the elevator car by as much as approximately 50%.

Embodiments of the present invention substantially reduce vertical vibrations in the elevator car and thereby dramatically improve car ride quality. Vibration absorbers according to the present invention employ a tuned mass damper incorporated into an existing elevator system mass other than the car, such as the counterweight or the compensation mass, to absorb undesirable vertical vibrations before they reach the elevator car. Embodiments of the present invention therefore stabilize against motion caused by harmonic vibration by allowing the inertia of a large system mass to be balanced by a comparatively lightweight damper mass. Incorporating vibration absorbers according to the present invention into an existing system mass eliminates the need to add large amounts of weight to the elevator system and increases the adaptability of embodiments of the present invention to existing elevator system installations. Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. For example, although it is not shown in the embodiment of FIGS. 4A-4D, a rail and guide system may be used to facilitate movement of vibration absorber 60 in a similar fashion as shown in FIGS. 5A and 5B. Embodiments of the present invention include elevator systems with a vibration absorber incorporated into both the counterweight and the compensation mass, as well as elevator systems with a vibration absorber incorporated into one of the counterweight or the compensation mass. Additionally, vibration absorbers according to the present invention may employ hydraulic dampers, such as a shock absorber type damper utilizing a viscous hydraulic fluid in a sealed cylinder.

Claims

CLAIMS:

1. A traction elevator system comprising: a car; one or more traction members connected to the car; and a vibration absorber comprising: a first mass connected to an elevator system mass other than the car; and a resilient member; wherein the resilient member is connected between the first mass and the elevator system mass; and wherein a natural frequency of the vibration absorber is approximately equal to an excitation frequency of the elevator system.

2. The system of claim 1, wherein the elevator system mass comprises a counterweight configured to be connected to one or more traction members of the elevator system.

3. The system of claim 2 further comprising: a counterweight frame in which the counterweight and the first mass are disposed; a pair of guide rails connected to the counterweight frame; and a plurality of guide members connected to the first mass and disposed on the guide rails to guide movement of the first mass.

4. The system of claim 2, wherein the counterweight and the first mass are disposed vertically adjacent one another in the counterweight frame.

5. The system of claim 2, wherein the counterweight and the first mass are disposed horizontally adjacent one another in the counterweight frame.

6. The system of claim 2, wherein the resilient member comprises one or more springs arranged below the first mass.

7. The system of claim 6, wherein each of the springs is contained by a cylindrical sleeve connected to the counterweight frame.

8. The system of claim 6, wherein the resilient member further comprises one or more brackets connected to the counterweight frame above the first mass.

9. The system of claim 8, wherein the brackets are configured to be flexible in a direction of vibration and substantially rigid in one or more directions generally perpendicular to the direction of vibration.

10. The system of claim 8 further comprising a bumper connected to the counterweight frame above the brackets and configured to limit deflection of the brackets.

11. The system of claim 1, wherein the elevator system mass comprises a tie- down compensation mass configured to be connected to the traction members toward a bottom of a hoistway.

12. The system of claim 1, wherein the resilient member comprises one or more springs.

13. An elevator counterweight apparatus comprising: a counterweight configured to be connected to one or more traction members; and a vibration absorber comprising: a first mass connected to the counterweight; and a resilient member; wherein the resilient member is connected between the first mass and the counterweight; and wherein a natural frequency of the vibration absorber is tuned to an excitation frequency of the elevator system.

14. The apparatus of claim 13 further comprising: a counterweight frame in which the counterweight and the first mass are disposed; a pair of guide rails connected to the counterweight frame; and a plurality of guide members connected to the first mass and disposed on the guide rails to guide movement of the first mass.

15. The apparatus of claim 14, wherein the counterweight and the first mass are disposed vertically adjacent one another in the counterweight frame.

16. The apparatus of claim 14, wherein the counterweight and the first mass are disposed horizontally adjacent one another in the counterweight frame.

17. The apparatus of claim 14, wherein the resilient member comprises one or more springs arranged below the first mass.

18. The apparatus of claim 17, wherein each of the springs is contained by a cylindrical sleeve connected to the counterweight frame.

19. The apparatus of claim 18, wherein the resilient member further comprises two brackets connected to the counterweight frame above the first mass.

20. The apparatus of claim 17 further comprising a bumper connected to the counterweight frame above the brackets and configured to limit deflection of the brackets.

21. The apparatus of claim 13 further comprising: a counterweight frame in which the counterweight and the first mass are disposed; and a pair of rods connected to the counterweight frame; wherein the first mass is slidably connected to the rods.

22. The apparatus of claim 21 further comprising a plurality of bushings connected to the first mass and configured to receive the rods.

23. The apparatus of claim 13 further comprising: a counterweight frame in which the counterweight and the first mass are disposed; and a plurality of shock absorbers connected between the counterweight frame and the first mass and configured for compression under a weight of the first mass.

24. The apparatus of claim 23 further comprising a plurality of ball joints connecting the shock absorbers to the counterweight frame and the first mass.

25. An elevator tie-down compensation apparatus connected to an elevator system toward a bottom of a hoistway, the tie-down compensation apparatus comprising: a compensation mass configured to be connected to one or more traction members; and a vibration absorber comprising: a first mass connected to the compensation mass; and a resilient member; wherein the resilient member is connected between the first mass and the compensation mass; and wherein a natural frequency of the vibration absorber is tuned to an excitation frequency of the elevator system.

26. A method of absorbing vertical vibrations in an elevator system, the method comprising: attaching a first mass to an existing elevator system mass other than a car; connecting a resilient member between the first mass and the elevator system mass to form a tuned mass damper; and adjusting a natural frequency of the tuned mass damper to approximate or equal an excitation frequency of the elevator system.

27. The method of claim 26, wherein the natural frequency of the vibration absorber is adjusted by varying one or more of the mass of the first mass and a resiliency of the resilient member.

28. The method of claim 26, wherein the first mass is attached to a counterweight of the elevator system.

29. The method of claim 26, wherein the first mass is attached to a tie-down compensation mass of the elevator system.