BACKGROUND OF THE INVENTION
This invention generally relates to load bearing members
for use in elevator systems. More particularly, this invention relates to an elevator
belt assembly having a specialized groove arrangement.
Elevator systems typically include a cab and counterweight
that move within a hoistway to transport passengers or cargo to different landings
within a building, for example. A load bearing member, such as roping or a belt
typically moves over a set of sheaves and supports the load of the cab and counterweight.
There are a variety of types of load bearing members used in elevator systems.
One type of load bearing member is a coated steel belt.
Typical arrangements include a plurality of steel cords extending along the length
of the belt assembly. A jacket is applied over the cords and forms an exterior of
the belt assembly. Some jacket application processes result in grooves being formed
in the jacket surface on at least one side of the belt assembly. Some processes
also tend to cause distortions or irregularities in the position of the steel cords
relative to the exterior of the jacket along the length of the belt.
Figure 8, for example, illustrates both of these phenomena.
As can be seen, the spacing between the exterior of the jacket 200 and the cords
210 varies along the length of the belt. As can be appreciated from the illustration,
the cords 210 are set within the jacket as if they comprise a series of cord segments
of equal length corresponding to the groove spacing. The illustration of Figure
8 includes an exaggeration of the typical physical cord layout for purposes of illustration.
The actual distortions or changes in the position of the cords relative to the jacket
outer surfaces may not be discernable by the human eye in some examples.
When conventional jacket application processes are used,
the manner in which the cords are supported during the jacket application process
tends to result in such distortion in the geometry or configuration of the cords
relative to the jacket outer surfaces along the length of the belt.
While such arrangements have proven useful, there is need
for improvement. One particular difficulty associated with such belt assemblies
is that as the belt moves in the elevator system, the grooves and the cord placement
in the jacket interact with other system components such as the sheaves and generate
undesirable noise, vibration or both. For example, as the belt assembly moves at
a constant velocity, a steady state frequency of groove contact with the sheaves
creates an annoying, audible tone. The repeated pattern of changes in the cord spacing
from the jacket outer surfaces is believed to contribute to such noise generation.
An alternative arrangement is required to minimize or eliminate
the occurrence of vibrations or an annoying tone during elevator system operation.
This invention addresses that need.
SUMMARY OF THE INVENTION
In general terms, this invention is a belt assembly for
use in an elevator system. The belt assembly includes a plurality of cords extending
generally parallel to a longitudinal axis of the belt. A jacket over the cords includes
a plurality of grooves that are situated to minimize the occurrence of an annoying
audible tone during elevator operation.
In one example, the grooves are longitudinally spaced such
that spacings between the grooves varies along the length of the belt. Having different
spacings between adjacent grooves eliminates the steady state frequency of groove
contact with other system components, which is a major contributor to the potential
for undesirable noise or vibration during elevator operation.
In another example, the grooves extend across the width
of the jacket. At least a portion of each of the grooves is aligned to be not perpendicular
to the longitudinal axis of the belt. In one example, the grooves comprise straight
lines. In another example, the grooves comprise a series of line segments, each
of which is at a different angle relative to the longitudinal axis of the belt.
A belt assembly designed according to this invention may
include the inventive different spacings, the inventive angular alignment of the
grooves or a combination of both. 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 embodiments. The drawings that accompany the detailed
description can be briefly described as follows.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure I schematically illustrates a portion of an example
belt assembly designed according to an embodiment of this invention.
Figure 2 is a cross-sectional illustration taken along
the lines 2-2 in Figure 1.
Figure 3 is a planar, schematic illustration of an alternative
groove alignment compared to the embodiment of Figure 1.
Figure 4 schematically illustrates another alternative
Figure 5 schematically illustrates another alternative
Figure 6 schematically illustrates another alternative
Figure 7 schematically illustrates a device and method
useful for making a belt assembly designed according to an embodiment of this invention.
Figure 8 schematically illustrates a typical cord geometry
relative to outer surfaces on a belt jacket according to the prior art.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Figures 1 and 2 schematically illustrate a belt assembly
20 that is designed for use in an elevator system. A plurality of cords 22 are aligned
generally parallel to a longitudinal axis of the belt assembly 20. In one example,
the cords 22 are made of strands of steel wire.
A jacket 24 covers over the cords 22. The jacket 24 preferably
comprises a polyurethane-based material. A variety of such materials are commercially
available and known in the art to be useful for elevator belt assemblies. Given
this description, those skilled in the art will be able to select a proper jacket
material to suit the needs of their particular situation.
The jacket 24 establishes an exterior length, L, width,
W, and a thickness, t, of the belt assembly 20. In one example, the width W of the
belt assembly is 30 millimeters, the thickness t is 3 millimeters and the depth
of each groove is 0.7 millimeters. In the same example, the cords 22 have a diameter
of 1.65 millimeters. The cords 22 preferably extend along the entire length L of
The jacket 24 includes a plurality of grooves 30, 32, 34,
36, 38, 40 and 42 on at least one side of the jacket 24. In the illustrated example,
the grooves extend across the entire width of the belt assembly.
The grooves result from some manufacturing processes, many
of which are well known in the art, that are suitable for formation of the belt
assembly 20. In the example embodiment of Figures 1 and 2, the grooves are spaced
apart different distances so that there are different spacings between various grooves.
For example, a first spacing 44 separates the groove 30 from the adjacent groove
32. A different spacing 46 separates the groove 32 from the adjacent groove 34.
Similarly, the spacings 48, 50, 52 and 54 vary in size.
It is not necessary that all of the illustrated spacings
are different, however, it is preferred to provide as many different spacings along
the length of the belt assembly as possible. As a practical matter, a repeated pattern
of the varying spacings will typically extend along the entire length of the belt
assembly 20. Depending on the particulars of the belt assembly and the equipment
used to form and apply the jacket 24, the pattern of different spacings will repeat
at different intervals. Preferably, the interval of pattern repetition will be as
large as the manufacturing equipment allows. In one example, there is a pattern
of different spacings that repeats about every two meters. Within each two meter
section, the spacings between adjacent grooves are selected to be varying and non-periodic.
By altering spacings between adjacent grooves, the noise
component, caused by contact of the belt assembly with other elevator system components,
such as the sheaves, during system operation, is spread over a broader range of
frequencies. Thus, steady state frequencies of noise are avoided which eliminates
the potential for an audible, annoying tone.
In addition to varying the spacing between the grooves,
the inventive arrangement provides the ability to vary the lengths of cord "segments,"
which result from certain manufacturing techniques (but are not necessarily included
in the inventive arrangement). A belt assembly designed according to this invention
may include a series of cord segments along which the distance between the cord
and the jacket outer surfaces varies. The ends of such cord "segments" coincide
with the location of the grooves. Varying the spacing of the grooves also varies
the length of the segments and therefore varies the pattern of the cord geometry
relative to the jacket outer surfaces. With the inventive arrangement, the length
of the cord segments varies along the length of the belt.
Because the segments are of various lengths, there is no
periodic, repeated geometric pattern of the cords relative to the jacket outer surfaces.
By varying the length of the cord segments (i.e., changing spacing between similar
distortions in the position of the cord relative to the jacket outer surfaces) any
contribution to noise or vibration caused by the cord geometry, is reduced or eliminated.
By eliminating the periodic feature of the cord geometry,
this invention provides a significant advantage for reducing vibration and noise
generation during elevator system operation.
Figures 3 through 6 illustrate various strategies according
to this invention for avoiding noise levels caused by belt movement during elevator
operation. The example of Figure 3 includes a jacket 24a having a plurality of grooves
56. In this example, an equal spacing 58 separates adjacent grooves 56. The grooves
56 comprise straight lines extending across the width of the belt assembly. Each
groove 56 is at an acute angle 60 relative to the longitudinal axis of the belt.
Whether the angle of groove alignment is acute or obtuse depends only on a frame
of reference. Arranging at least a portion of the grooves 56 to be non-perpendicular
to the longitudinal axis of the belt avoids the steady state frequency of noise
generation, that otherwise occurs when perpendicularly aligned grooves (and associated
cord distortions) are equally spaced along the length of the belt.
The example of Figure 4 includes a jacket 24b having a
plurality of grooves 56'. The grooves 56' are spaced apart using different spacings
62, 64 and 66, for example. The grooves 56' are aligned at an acute angle 60 relative
to the longitudinal axis of the belt. The example of Figure 4 combines the inventive
angular alignment of the grooves with the inventive varying spacing strategy, either
or both of which can be employed in the present invention.
Figure 5 illustrates another example belt assembly having
a jacket 24c. In this example, a plurality of grooves 70 each have a plurality of
line segments 72 and 74. In the example of Figure 5, the grooves 70 are equally
spaced using a spacing 76. Because the line segments 72 and 74 are not perpendicular
to the longitudinal axis of the belt, the equal spacing does not present the noise
generation difficulties provided if the grooves 70 were straight lines that were
perpendicular to the longitudinal axis of the belt.
The example of Figure 6 includes a jacket 24d that has
a plurality of grooves 70', each of which includes line segments 72' and 74'. In
this example, different spacings 78 and 80, for example, separate each of the grooves
from an adjacent groove.
With reference to Figure 7, the process of making an elevator
belt assembly designed according to this invention is schematically illustrated
by machinery 100. The cords 22 move through the machinery 100 which provides a mold
for forming the jacket 24.
The machinery 100 includes a plurality of cord supports
110. In the case of forming the belt assemblies of Figures 1, 4 and 6, the spacing
between the cord supports is variable. Although the spacing between two adjacent
cord supports 110 may be the same, it is preferred that the spacing between the
cord supports 110 not be arranged in a repeating pattern. Preferably, the spacing
should be randomized within an acceptable range that will depend on the machinery.
As the cords 22 are fed through the machinery 100 they
are supported on each of the cord supports. In examples where the cords 22 are fed
continuously, the cord supports 110 move as the cords 22 are fed through the machinery
100. A polyurethane-based jacket material is fed into the machinery from a reservoir
122 in a conventional manner. As the jacket material envelopes the cords 22, the
cord supports cause grooves to be formed in the jacket. The machinery preferably
causes an opposite side of the jacket 24 to be flat. The machinery 100 operates
in a known manner to extrude, mold or otherwise form the jacket 24 around the cords
Providing different spacing between the cord supports yields
different spacing between the grooves along the length of the belt.
In another example, as in forming the belt assemblies of
Figures 3-6, the cord supports have a configuration that provides a desired groove
alignment on the exterior surface of the jacket 24. Example groove configurations
and alignments are shown in Figures 3-6, but this invention is not limited to those
By placing the grooves in a desired alignment, the difficulties
of audible noise generation experienced with conventional coated belt assemblies
can be at least greatly reduced and usually eliminated. Providing different spacings
between grooves or a properly selected angular alignment of at least a part of each
groove, or a combination of both results in a much quieter arrangement.
The preceding description is exemplary rather than limiting
in nature. Variations and modifications to the disclosed examples may become apparent
to those skilled in the art that do not necessarily depart from the essence of this
invention. The scope of legal protection given to this invention can only be determined
by studying the following claims.