Elevator car isolation system and method

Information

  • Patent Grant
  • 6668980
  • Patent Number
    6,668,980
  • Date Filed
    Friday, July 6, 2001
    23 years ago
  • Date Issued
    Tuesday, December 30, 2003
    21 years ago
Abstract
The isolation system and method comprise suspending an elevator platform from an upper portion of an elevator sling with upper tension members. In addition to being suspended from the sling by upper tension members, the elevator car platform may be secured to a lower portion of the sling from with lower tension members. The tension members preferably have an in-use frequency of vibration below the frequencies of the elevator system vibrations. In an alternative embodiment, upper vibration attenuating tension members may be used to suspend the elevator car platform and the platform may be secured to the lower portion of the sling with standard isolation mounts instead of lower tension members. The tension members employed by the present invention may be manufactured from cables containing aramid fibers, such as Kevlar® rope.
Description




BACKGROUND OF THE INVENTION




1. Field of the Invention




The present invention relates to elevator systems. In particular, the present invention provides a method and apparatus for isolating elevator cars and platforms from vibrations.




2. Description of the Related Art




Vibrations are typically induced in elevator systems by a variety of sources. As elevator cars traverse elevator shafts, vibrations are induced by curves in the guide rails and by level differences in the guide rails. Moreover, an elevator hoist rope can transmit elevator lift motor vibrations to an elevator car. In addition, aerodynamic forces, braking forces and other mechanical sources induce a range of vibrations in an elevator system and these vibrations are often transmitted to an elevator car operating in the elevator system. In a modern elevator system, an elevator car sits on a platform that is mounted to an elevator sling. The platform is suspended from the sling by steel cables or brace rods. These cables or brace rods transmit the vibrations from the elevator system to the elevator platform and elevator car. The average power transmitted by these rods and/or cables is a function of their density, which, in the case of steel, is relatively high.




To prevent transmission of vibrational energy from the elevator system to the elevator car, most elevator manufacturers employ isolation devices, such as isolation pads, primarily manufactured from rubber, between the cables or brace rods and the elevator platform. In some applications, the platform may rest on a rubber pad that in turn rests on the elevator sling. While rubber isolation pads are relatively inexpensive and provide some attenuation to vibrations that occur in elevator systems, they have a relatively high natural frequency. Under standard loading conditions, rubber isolation pads and rod braces have a natural frequency of about 20 Hz. Attenuating media can only attenuate vibrations whose frequencies are greater than about 1.141 times the natural frequency of the attenuating media. Thus, rubber isolation devices can only attenuate vibrations over a relatively limited range of frequencies.




SUMMARY OF THE INVENTION




The present invention provides a vibration attenuated elevator car assembly and method for isolating an elevator car from vibrations having a range of frequencies that are typically encountered in elevator systems. According to one embodiment of the present invention, a vibration attenuated elevator car assembly for attenuating elevator system vibrations is used to secure an elevator car platform to an elevator sling that travels on elevator rails in an elevator shaft. The vibration attenuated elevator car assembly comprises an elevator car platform that is horizontally suspended from the elevator sling by upper tension members and that is also secured to a lower portion of the elevator sling by lower tension members. Thus, the elevator car platform is not indirect contact with the elevator sling.




Preferably, the elevator car is isolated from elevator system vibrations by suspending the elevator car platform from an upper portion of the elevator sling with tension members manufactured from synthetic fiber because synthetic fibers transmit significantly less energy at any tension, frequency, and amplitude than steel due to their lower density. Material containing aramid fibers, such as Kevlar® rope or Kevlar® cored rope with a Nomex® sheath, is particularly well-suited for use as a tension member because it has relatively low in-use natural frequencies. Vectran® and generic Aramid are also well-suited for use with the present invention.




As an alternative to using lower tension members, the elevator car platform may be secured to a safety plank or other lower structural member of the elevator sling with isolation mounts. In this embodiment, the car platform would still be suspended from the sling with upper tension members having an in-use natural frequency below that of the vibrations typically found in the elevator system.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

illustrates a prior art elevator car isolation system.





FIG. 2

illustrates a vibration attenuated car assembly according to the present invention, wherein the elevator car platform is fastened to an elevator sling with upper and lower tension members of the present invention.





FIG. 3

illustrates a vibration attenuated car assembly according to the present invention, wherein the elevator car platform is fastened to an elevator sling with upper tension members of the present invention and is fixed to a lower portion of the sling with isolation mounts.











DETAILED DESCRIPTION OF THE INVENTION





FIG. 1

illustrates the prior art elevator car isolation systems. Elevator platforms and cars are isolated from vibration by use of rubber isolation pads


1


. These rubber elements separate the isolated platform


4


from a structural platform


7


that is rigidly fixed to the elevator car frame. As is described in further detail below, the present invention may be used in conjunction with the prior art isolation systems or may be used alone.




As is shown in

FIG. 2

, a elevator car platform


21


for supporting an elevator car (not shown), having a front edge


22


with a left front corner


22


L and a right front corner


22


R and back edge


23


with a left back corner


23


L and a right back corner


23


R, is suspended from an upper portion of elevator sling


24


by a plurality of upper tension members


25


,


26


,


27


, and


28


. The upper portion of the sling


24


is that portion above the elevator car platform


21


. Conversely, any portion of the sling


24


below the elevator car platform


21


may be referred to as the lower portion the sling


24


. The sling


24


has a left stile


29


and right stile


30


. The left stile


29


and right stile


30


have upper portions


29


A and


30


A, respectively, and lower portions


29


B and


30


B, respectively. A crosshead


31


spans and connects the upper portions of the stiles


29


A and


30


A. And a safety plank


32


spans the lower portions of the stiles


29


B and


30


B. A fastening plate


33


is mounted in a center portion of and under the safety plank


32


. Those skilled in the art will recognize that the crosshead


31


need not be affixed at the exact upper ends of the stiles


29


and


30


and likewise the safety plank


32


need not be affixed at the exact bottom of the stiles


29


and


30


.




Upper tension member


25


secures the left front corner of the platform


22


L to the upper portion


29


A of the left stile


29


and is fastened to the platform


21


and stile


29


with standard fasteners. Upper tension member


26


secures the right front corner of the platform


22


R to the upper portion


30


A of the right stile


30


and is fastened to the platform


21


and stile


30


with standard fasteners. Upper tension member


27


secures the left back corner of the platform


23


L to the upper portion


29


A of the left stile


29


and is fastened to the platform


21


and the stile


29


with standard fasteners. Upper tension member


28


secures the right back corner of the platform


23


R to the upper portion


30


A of the right stile


30


and is fastened to the platform


21


and the stile


30


with standard fasteners.




In addition to being suspended from the upper portions


29


A and


30


A of the stiles


29


and


30


of the elevator sling


24


, the elevator car platform


21


may also be secured to the safety plank


32


by a plurality of lower tension members. Lower tension member


34


secures the right front corner of the platform


22


R to a fastening plate


33


and may be fastened to the fastening plate


33


and the platform


21


with standard fasteners. Lower tension member


35


secures the left front corner of the platform


22


L to the fastening plate


33


and may be fastened to the fastening plate


33


and the platform


21


with standard fasteners. Lower tension member


36


secures the right back corner of the platform


23


R to the fastening plate and may be fastened to the fastening plate


33


and the platform


21


with standard fasteners. A fourth lower tension member (not shown) secures the left back corner of the platform


23


L to the fastening plate


33


and may be fastened to the fastening plate


33


and the platform


21


with standard fasteners. The upper and lower tension members may, but need not, be fastened to the exact corners of the elevator car platform


21


. The upper and lower tension members may be fastened to the platform


21


in any manner that provides adequate support for the platform


21


.




The upper and lower tension members are preferably made of a material having a low ability to transmit power and have a low in-use natural frequency, preferably below the frequency of vibrations found in an elevator system, which is typically between 4 and 8 Hz. In general, the average power that can be transmitted is defined by the following equation:












P
_

=


1
2



μυω
2



y
m
2












Where density









μ
=

m
l





m
=

m





a





s





s





l
=

l





e





n





g





t






h
.















Where Wave velocity






υ
=



t





e





n





s





i





o





n

μ












Where frequency and amplitude are represented by Ω& y.




Cable or rope containing aramid fibers, such as Kevlar® rope or Kevlar® cored rope having a fire resistant sheath made from a material, such a Nomex® or a fire resistant coating, is particularly well-suited for use as a tension member because it has a low density. Spectra, graphite and fiberglass ropes or other composites structures may also be used as tension members. The ropes or cables that form tension members may comprise woven, bundled, or twisted fibers, and may in some, but not all embodiments, be covered with a sheath. Tension members should be sufficiently strong and stiff to support a fully loaded elevator car. Preferably, but not necessarily, the tension members should have a working load of 3000 pounds or greater. Often this requires the use of an aramid fiber rope having a 0.5 inch or greater diameter. The tension members should have a strength and a working load rating substantially equivalent to ⅝ inch diameter steel rods, which are typically used to suspend elevator car platforms. Typically, the upper tension members of the present invention are about 2 meters long. In some embodiments, it may be desirable to have tension members having a density of less than about 7.7 grams per cubic centimeter (“g/cc”) and preferably less than 2.5 g/cc. In one embodiment, where 0.5 inch diameter Kevlar® 49 sheathed rope is used, the tension members preferably have a linear mass density of about 0.138 kilograms per meter of length. In some situations, it may be advantageous to use different material for the upper and lower tension members. Likewise, the strength and other physical properties of the upper and lower tension members do not necessarily have to be identical and in certain situations better attenuation might be achieved by using upper tension members that have different properties than the lower tension members.




While the embodiment of the present invention described in the above example employs four upper tension members and four lower tension members, those of skill in the art will appreciate that the number and placement of the tension members may be varied depending upon other design criteria. Moreover, while it is often preferable to use materials for the tension members that cause the tension members to have low natural frequencies—to attenuate a large range of frequencies—it may, depending upon the frequency of vibrations that are to be attenuated, be desirable to use tension members having high, medium, low or ultra low natural frequencies. Likewise, the density of the tension member may vary.




As is shown in

FIG. 3

, an alternative embodiment of the present invention employs four upper tension members


25


,


26


,


27


, and


28


to suspend the platform


21


from the right and left stiles


29


and


30


of the elevator sling. Upper tension members


25


,


26


,


27


, and


28


are made from aramid fiber rope, such as Kevlar® cored rope and may be secured to the platform with standard means, such as isolation anchors


42


. The upper tension members


25


,


26


,


27


, and


28


should have a low in-use natural frequency, preferably a frequency below that of vibrations found in an elevator system. The platform


21


rests on platform isolation pads


40


that are mounted to the top of the safety plank


32


. In addition, the platform is secured to the stiles


29


and


30


with stile isolation pad and retainer brackets


41


.




The isolation pads and isolation anchors that may be used with the present invention may be standard rubber isolation pads, or they may be pads manufactured from other materials, including aramid fibers, that are inefficient at transmitting energy.




The present invention may be used in standard elevator systems, including roped and hydraulic systems, and in elevator systems that employ synthetic fiber hoist ropes, which also help dampen vibrations transmitted from the elevator system to elevator cars in the system.



Claims
  • 1. An elevator car assembly for attenuating elevator system vibrations in an elevator system, the elevator car assembly comprising:an elevator car sling for traveling in an elevator shaft and for supporting an elevator car platform, the elevator car sling having an upper portion and a lower portion; one or more upper tension members for suspending an elevator car platform from the upper portion of the elevator car sling, the upper tension members comprising synthetic fibers; one or more lower tension members comprised of synthetic fibers for securing an elevator car platform to the lower portion of the elevator sling; and said elevator car platform suspended horizontally from the upper portion of the elevator sling by the upper tension member(s) and secured to the lower portion of the elevator sling by the lower tension member(s).
  • 2. The elevator car assembly of claim 1, wherein the upper tension member(s) contain aramid fibers.
  • 3. The elevator car assembly of claim 1, wherein the upper tension member(s) contain a fire resistant coating.
  • 4. The elevator car assembly of claim 1, 2, or 3, wherein the upper tension member(s) have a vibrational frequency below the frequencies of the elevator system vibrations.
  • 5. The elevator car assembly of claim 1, 2, or 3, wherein the upper tension member(s) have a density of about 0.138 kg/m.
  • 6. The elevator car assembly of claim 1, wherein the lower tension member(s) contain aramid fibers.
  • 7. The elevator car assembly of claim 1, wherein the lower tension member(s) contain a fire resistant sheath.
  • 8. The elevator car assembly of claim 1, 6, or 7, wherein the lower tension member(s) have a vibrational frequency below the frequencies of the elevator system vibrations.
  • 9. The elevator car assembly of claim 1, 6, or 7, wherein the lower tension members have an in-use frequency below 8 Hz.
  • 10. The elevator car assembly of claim 1, wherein the upper and lower tension member(s) contain aramid fibers.
  • 11. The elevator car assembly of claim 1, wherein the upper and lower tension members contain a fire resistant sheath.
US Referenced Citations (27)
Number Name Date Kind
1907967 Himes May 1933 A
2246732 Hymans Jun 1941 A
3708991 Barkley Jan 1973 A
4412601 Cooper Nov 1983 A
4548297 Salmon et al. Oct 1985 A
4599832 Benton et al. Jul 1986 A
4657116 Gardner et al. Apr 1987 A
4766708 Sing Aug 1988 A
5005671 Aime et al. Apr 1991 A
5020639 Michel Jun 1991 A
5025893 Saito Jun 1991 A
5074382 Do Dec 1991 A
5181586 Yoo et al. Jan 1993 A
5230404 Klein Jul 1993 A
5325937 Suchodolski et al. Jul 1994 A
5490577 Yoo Feb 1996 A
5566786 De Angelis et al. Oct 1996 A
5584364 Sakita Dec 1996 A
5597988 Skalski Jan 1997 A
5611412 Yoo et al. Mar 1997 A
5811743 Kohara et al. Sep 1998 A
5832688 Crissey et al. Nov 1998 A
5845745 Lane Dec 1998 A
5881843 O'Donnell et al. Mar 1999 A
5881845 O'Donnell et al. Mar 1999 A
6164418 Chen et al. Dec 2000 A
6364063 Aulanko et al. Apr 2002 B1
Foreign Referenced Citations (7)
Number Date Country
0675066 Apr 1998 EP
352055145 May 1977 JP
352101547 Aug 1977 JP
354040451 Mar 1979 JP
404085275 Mar 1992 JP
405246658 Sep 1993 JP
9929610 Jun 1999 WO
Non-Patent Literature Citations (3)
Entry
Elevator World, V45, n6, Jun. 1997, p. 88-93.
Proceedings of the IEEE Conference on Control Applications, v2, 1994, IEEE, Piscataway, NJ, 94CH3420-7, p. 965-970.
Vibration Damping Workshop Proceedings, Long Beach, California, Feb. 27-29, 1984, AD-A152 547 pLL-1-LL-6, published Nov. 84.