Note: Descriptions are shown in the official language in which they were submitted.
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Belt for a lift installation,
production method for such a belt and
lift installation with such a belt
The present invention relates to a belt for a for a lift installation, a
production method for such a
belt and a lift installation with such a belt.
A lift installation comprises a lift cage and usually a counterweight, the
cage and counterweight
being movable in a lift shaft or along free-standing guide devices. For
producing the movement
the lift installation comprises at least one drive unit with at least one
drive pulley, which carry the
lift cage and the counterweight by way of one or more belts and/or transmit
the required drive
forces thereto.
In that case the lift cage and the counterweight can be connected by way of
the same belts,
which are guided over the drive pulley or pulleys and act not only as support
means, but also as
drive means. Alternatively, the lift cage and the counterweight can also be
carried by way of
separate support belts and driven by way of separate drive belts.
A belt according to the present invention can be used for each of the above-
described functions,
thus as a combined drive and support belt, as a support belt which runs over
at least one
deflecting pulley (support roller) and connects the lift cage with the
counterweight and carries
both, or as a drive belt which has exclusively a drive function and runs over
at least one drive
pulley.
Such belts for lift installations usually comprise a belt body consisting of
an elastomer. In order
to transmit the tensile forces, tensile carriers in the from of steel and/or
synthetic material cords
are embedded in the belt body. The cords can be constructed as, for example,
strands or
cables of steel wires or synthetic material fibres. They are advantageously
arranged in the
neutral axis of the belt cross-section in which no tensile or compressive
stresses arise in looping
round of a belt pulley.
A lift installation according to category is known from EP 1 555 234 B1 in
which the belt has on
a traction side facing the drive wheel a rib arrangement with several wedge-
shaped ribs, which
extend in longitudinal direction of the belt and which engage in corresponding
grooves on the
drive wheel. Due to the fact that the contact between the belt and the drive
wheel takes place
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by way of the inclined flanks of the wedge-shaped ribs or grooves, the
pressing forces between
the belt and the drive wheel and thus the traction capability or drive
capability increase for the
same radial force and consequently the same bearing loading and belt tension.
At the same
time the wedge ribs advantageously guide the belt on the drive wheel in
transverse direction.
Since the belts contain tensile carriers with relatively small diameters, it
is possible to use drive
wheels and deflecting wheels with correspondingly small diameters. For
example, the drive
output shaft of the drive unit can itself also be constructed as drive wheel.
In the following there is therefore consistent reference to drive wheels which
comprise
conventional drive pulleys with larger diameters, but also drive pulleys with
relatively small
diameters and, in particular, also drive output shafts of a drive unit of a
lift installation. Where in
the following statements refer not only to drive wheels, but also to
deflecting wheels, these are
designated in common as belt wheels.
The use of belts with thin tensile carriers and of belt wheels with small
diameters has the
consequence of high area pressures between the individual tensile carriers and
the belt bodies
surrounding them, as also high compressive and shear stresses in the belt body
itself. The area
pressure and/or the said stresses in the belt body can attain values at which
the risk of damage
of the belt body is given.
This risk is greater the smaller the diameter of the tensile carriers, since
as a consequence of
the reduction in the force-transmitting surface for the same belt loading the
area pressure as
also the stresses caused by the tensile carriers increase in the belt body. In
addition, the notch
effect on the belt body is amplified with reducing tensile carrier diameter,
which belt body - with
respect to the requisite friction between belt and drive wheel, the requisite
transmission of
tensile forces from the belt body to the tensile carriers and the desired
damping of oscillations or
the absorption of shocks in the belt - is usually made of a relatively soft
elastomer and thus is
particularly susceptible relative to the mentioned loads.
Since the deflection about the belt wheels and the transmission of the tensile
force from a drive
wheel to the individual tensile carriers takes place under shear and/or
tensile deformation of the
belt body there is a possibility, due to the above-illustrated effects, of
damage to the belt body in
the form of abrasion and/or shattering of the elastomer surrounding the
tensile carriers and/or
cutting of tensile carriers into the elastomer.
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This risk also exists with belts according to the introductory part of claim
1, such as are known
from US 7 037 578 B2 and DE 694 01 784 T2. There, too, the tensile carriers
are embedded in
a matrix of the soft elastomer, particularly polyurethane (PU),
polychloroprene (CR) or ethylene-
propylene-diene rubber (EPDM).
Thus, such belts cannot be used, or can be used only conditionally, in safety-
sensitive devices
such as a lift installation, since here the risk potential in the case of belt
breakage due to the
above-described damage is too high. Equally, such belts cannot be used for
transmission of
high forces, since in that case the risk of such damage is increased.
An object of the present invention is therefore to create a lift installation
in which the risk of
failure due to belt breakage is reduced. A further object of the present
invention is to provide a
belt for such a lift installation which can transmit even higher forces. A
further object of the
present invention is to indicate a method for producing such a belt.
For fulfilment of these objects a belt according to the introductory part of
claim 1, a production
method according to the introductory part of claim 7 and a lift installation
according to the
introductory part of claim 7 are developed by the characterising features
thereof.
A belt for a lift installation according to an embodiment of the present
invention comprises a first
part belt of a first material, in which a tensile carrier arrangement with at
least one tensile carrier
of steel wire or of steel wire strands or steel wire cables is arranged, and a
second part belt of a
second material different from the first material.
According to the invention the first material comprises at least one
thermoplastic plastics
material. Preferably this thermoplastic plastics material is polyamide (PA),
polyethylene (PE),
polycarbonate (PC) or polyvinylchloride (PVC). Equally, the first material can
also comprises a
mixture of two or more thermoplastic plastic materials, a so-termed polyblend.
The first material
can, for strengthening, also contain additives, particularly fibres such as,
for example, carbon
fibres or glass fibres. Equally, the first material can comprise a fabric
consisting of a
thermoplastic plastics material.
Through the arrangement of the tensile carrier arrangement in the first part
belt consisting of a
first thermoplastic material this first material, which is particularly
suitable for the purpose,
accepts the forces acting normally and tangentially to the surface of the
tensile carriers and
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transmits these, distributed over substantially the entire connecting area, to
the second part
belt. The area over which the forces from the tensile carriers are introduced
into the second
part belt thereby increases so that the stresses, particularly compressive and
shear stresses,
acting thereon reduce. At the same time the notch effect on the second part
belt reduces.
Advantageously it is thus possible to select the second material of the second
part belt with
respect to the function thereof, particularly the friction-locking contact
with a drive wheel,
damping of oscillations and shocks and/or the elasticity required for looping
around belt wheels.
At the same time, the forces to be transmitted by the tensile carriers and
thus the permissible
belt loading can be increased, since the area pressures and stresses produced
by the tensile
carriers in the belt are initially accepted by the first part belt, the first
material of which can be
selected to be suitable with respect to the load which is present. The loads
transmitted by the
tensile carriers to the belt body can be distributed in the first part belt so
that the maximum area
pressures and compressive stresses acting on the second part belt at the
connecting surface
thereof relative to the first part belt occur only to reduced extent.
Preferably the first part belt is formed to be comparatively thin so that
notwithstanding its greater
hardness it does not significantly impair the elasticity of the belt in
bending. Advantageously the
thickness of the first part belt accordingly amounts to at most 60%,
preferably at most 40% and
particularly preferably at most 30%, of the total thickness of the beR.
In order to ensure that the first material of which the first part belt
consists withstands over the
long term the relatively high local area pressures, compressive stresses and
shear stresses
resulting from the loading of the tensile carriers the first material
preferably has the following
material characteristic values (at room temperature):
- minimum yield stress according to DIN 53455 or ISO 527: 45 N/mm2
- minimum elongation at tear according to DIN 53455 or ISO 527: 45%
- minimum indentation hardness according to DIN 53456 or ISO 2039 (H358/30s):
30 N/mm 2
preferably: 50 N/mmZ
particularly preferably: 70 N/mm2
In materials with these characteristic values the tensile carriers do not cut
in or cut in only
slightly even under high load. They also withstand the compressive and/or
shear stresses,
which occur, without exhibiting impermissibly high deformations, abrasion or
shattering.
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The coefficient of friction of the first material which also forms the belt
back remote from the
traction surface, is preferably also relatively small. The friction force
which arises between the
deflecting wheels and the belt and which has to be overcome for lateral
guidance of the belt on
the deflecting wheel thereby reduces during looping around deflecting wheels
without
longitudinal grooves. As a consequence, the harmful lateral frictional loading
of the belt - for
example by guide flanges of the deflecting wheels - and thus also the required
drive power of
the lift installation are reduced and the service life of the belt increased.
In an advantageous embodiment a belt according to the present invention can
have for this
purpose a coating of the belt rear side from a material which has a lower
coefficient of friction
and/or a higher abrasion resistance than the first material.
The tensile carrier arrangement comprises at least one, but preferably
several, substantially
parallel tensile carriers, which can be arranged, in particular, in the
longitudinal direction of the
belt. The arrangement of the tensile carriers in accordance with the invention
in the stable first
part belt facilitates positionally correct arrangement thereof during the
production process, since
the tensile carriers are already fixed in the first material on application of
the second material.
The tensile carriers can be constructed as a single wire or, preferably, built
up from strands or
cables, wherein the strands or cables are made of steel wires. In a
particularly preferred
construction the tensile carriers of the tensile carrier arrangement are
arranged in or in the
vicinity of the neutral axis of the entire belt, in which axis no tensile or
compressive stresses
occur on deflection around a belt wheel, particularly a drive wheel.
The second part belt of the belt is preferably provided for co-operation with
a drive wheel of the
lift installation. In an advantageous embodiment it has for this purpose a
traction surface in
which at least one wedge rib is formed, which rib engages in a corresponding,
substantially
complementary groove in the running surface of the drive wheel. Preferably
several wedge ribs
can be formed adjacent to one another for increasing the traction capability
or for improving the
lateral guidance of the belt on the belt wheels. These ribs do not necessarily
have to be
connected together. Separate wedge ribs, which are arranged on the first part
belt, of the
second part belt can advantageously provide compensation for positional
deviations of the
individual grooves of a drive wheel relative to one another. On the other
hand, an at least
thinner connecting web, which extends between adjacent ribs on the connecting
surface to the
first part belt, advantageously increases this connecting surface and thus the
strength of the
connection between the first and the second part belt.
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In an advantageous embodiment a wedge rib has a substantially trapezium-shaped
cross-
section with a flank angle, as measured between its two flanks, of 60 to 120
. Other cross-
sectional shapes, for example triangular cross-sections, are also possible.
In an advantageous embodiment the traction surface of the belt has a coating
which has a
defined coefficient of friction with the running surface of a drive wheel of
the lift installation. This
coefficient of friction can be higher than that of the second material so as,
for example, to
improve the traction capability. Alternatively, it can also be lower than that
of the second
material. This reduces, on the one hand, the wear at the traction surface and
can eliminate,
particularly in the case of a traction surface on which one or more wedge ribs
are formed, the
risk of jamming of the wedge ribs in the grooves of a belt wheel.
The second material for the second part belt preferably comprises an
elastomer, particularly
polyurethane, polychloroprene or ethylene-propylene-diene rubber, or a mixture
of two or more
elastomers. An elastomer of that kind of the second part belt is sufficiently
flexible for looping
around belt wheels with smaller diameters. At the same time, such a second
material in known
manner advantageously damps oscillations and shocks in the belt. At the same
time it
withstands, during co-operation with a running surface of a drive wheel, the
shear deformation,
which arises in the belt for transmission of the tensile forces, due to its
elastic characteristics.
It is thus possible to select for the second part belt a relatively soft
second material having a
hardness at room temperature advantageously less than 95 Shore (A), preferably
less than 90
Shore (A) and particularly preferably less than 85 Shore (A), since in
accordance with the
invention the high local area pressures of the individual tensile carriers are
absorbed by the first,
harder material and transmitted to the second material as a more homogeneous
and lesser
area pressure over the connecting surface.
A belt according to one embodiment of the present invention is preferably
produced in the
following steps. Initially the first part belt is made from the first
material. Advantageously this is
carried out by extruding the thermoplastic plastics material, which makes
possible a uniform,
economic and uninterrupted production.
The tensile carriers can be arranged in the first part belt already during
primary forming
(extrusion process) of the first part belt, for which purpose the individual
tensile carriers are fed,
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during the extrusion process, to the first part belt, which arises, in such a
manner that they are
completely encased by the first material at least on the side facing the
second part belt.
The tensile carriers are preferably completely encased by the first material.
For fulfilment of the
object according to the invention it is, however, sufficient if the side of
the tensile carriers facing
the second part belt is separated therefrom by the first material. In a
further form of
embodiment of the present invention the first part belt can therefore be
produced initially and
subsequently the individual tensile carriers arranged on the side thereof
remote from the
connecting surface to the second part belt. For this purpose the first part
belt can
advantageously have, on this remote side, grooves for positionally correct
positioning of the
tensile carriers. The fixing of the tensile carriers in the grooves of the
first part belt can in that
case be carried out by means of thermal subsequent processing of the
thermoplastic material or
through addition of an adhesive. The tensile carriers which are arranged in
the region of the
side of the first part belt remote from the second part belt can, however,
also be fixed at the
second part belt by a third part belt which is connected with the said side of
the first part belt, for
example by gluing and/or extrusion on, in such a manner that the tensile
carriers are fixed
between first and third part belts.
In a further step the second part belt is produced from the second material
and fixedly
connected with the first part belt. This can preferably take place by
extrusion of the second part
belt onto the first part belt. In that case the wedge ribs of the traction
surface of the second part
belt can also be advantageously formed.
Equally, the second part belt can also be glued to the first part belt. In a
particularly preferred
embodiment the second material contains for this purpose an adhesive which at
the time of
extrusion onto the first part belt creates a fixed connection therewith by
thermal adhesion.
The advantageous coating of the traction surface of the second part belt can
be coated thereon
during its production or subsequently. Thus, a synthetic fibre fabric, a layer
of another
elastomer, a flock layer and/or a thermoplastic layer, which, for example,
contains polyamide,
can be arranged on the traction surface of the second part belt during
extrusion thereof, wherein
the coating advantageously fixedly connects with the still formable second
material.
A lift installation according to the present invention comprises a lift cage,
a drive unit with at
least one drive wheel and a belt arrangement with at least one belt according
to an embodiment
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of the present invention. Advantageously the belt arrangement can also
comprise several belts
according to one or various embodiments of the present invention, which can be
fixedly or
releasably connected together in, for example, mechanically positive manner.
This makes it
possible to compose a relatively wide belt arrangement from several narrower
belts, which are
easier to handle, in situ. The drive wheel or the drive wheels has or have in
a preferred
embodiment a wedge rib profile substantially complementary to the traction
surface of the
second belt.
Further objects, features and advantages are evident from the subclaims and
the examples of
embodiment described in the following. For this purpose:
Fig. 1 shows a cross-section through a belt according to an embodiment of the
present
invention; and
Fig. 2 shows a section, which is parallel to a lift cage front, through a lift
installation
according to an embodiment of the present invention.
Fig. I shows a cross-section through a belt 12 according to an embodiment of
the present
invention. This comprises a first part belt 13 of a thermoplastic plastics
material, in the example
of embodiment polyamide. The first part belt 13 is produced by extrusion,
wherein tensile
carriers 14 consisting of multiply stranded steel wires are fed thereto during
its production in
such a manner that these are completely included and fixed in the finished
first part belt 13. A
second part belt 15 of an elastomer, in the example of embodiment
polyurethane, is
subsequently extruded onto the first part belt 13. In that case the side,
which is remote from the
first part belt, of the second part belt 15 is constructed as a traction
surface which is provided for
co-operation with a drive wheel 4.1 (see Fig. 2) having a wedge rib profile on
its running
surface. For this purpose the traction surface of the second part belt 15 has
wedge ribs 15.1,
the flanks of which include an angle y of 900. The wedge ribs 15.1 are
connected together by
relatively thin connecting webs 16 extending between adjacent ribs on the
connecting surface
between the two part belts, whereby the strength of the connection between the
two part belts is
increased.
In an embodiment, which is not illustrated, the traction surface is provided
with a thin coating of
polyamide in order to reduce the coefficient of friction. A sufficient
traction capability
nevertheless results due to the wedge ribs 15.1, wherein the polyamide coating
advantageously
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reduces the wear of the traction surface and decreases the risk of jamming of
the belt 12 in the
drive wheel 4.1.
The size ratios between first and second part belt and the tensile carriers
are illustrated (not to
scale) in Fig. 1 for clarification of the individual elements. The first part
belt 13 is, rather,
actually thinner than the second part belt 15 and has a thickness which is
just sufficient to
completely enclose the tensile carriers 14 and to transmit the stresses, which
are introduced by
this, as homogeneously as possible to the second part belt. The belt 12, which
consists of the
thicker, but more elastic, second part belt 15 and the less elastic, but
thinner, first part belt 13 is
thus overall sufficiently elastic in order to snugly loop around the belt
wheels 4.1, 4.2 and 4.3
(see Fig. 2).
Fig. 2 shows a cross-section through a belt 22 according to a further form of
embodiment of the
present invention. This similarly comprises a first part belt 23 of a
thermoplastic plastics
material and a second part belt 25 of an elastomer, which is extruded onto the
first part belt 13
and forms a traction surface with several wedge ribs 25.1. By contrast to the
belt 12 described
in Fig. I the wedge ribs, in the case of the belt 22 illustrated in Fig. 2,
have between their
trapezium-shaped or wedge-shaped contact sections 28 and the first part belt
23 a substantially
rectangular base section 29 which embraces at least 20% of the height of the
entire second belt
25. The wedge ribs 25.1, i.e. their base sections 29, are completely separated
from one
another by intermediate spaces 26. Such a form of embodiment has the advantage
that the
trapezium-shaped or wedge-shaped contact sections 28 of the wedge ribs 25.1
are resiliently
displaceable relative to one another transversely to the longitudinal
direction of the belt 22 so
that the wedge rib arrangement can overall adapt resiliently to the wedge rib
profile, which is
present, of a corresponding belt wheel in which the shape and/or the mutual
spacings of the
wedge ribs deviate within permissible limits from the shape or the spacings of
the wedge ribs of
the belt. This form of embodiment has advantages with respect to the traction
capability
between a drive wheel and the belt, the service life of the belt and the belt
wheels as well as the
noise output of the entire belt drive.
In Fig. 2 there is in addition shown a form of embodiment of the belt 22 in
which the tensile
carriers 14 are laid in grooves 27 of the first part belt 23, as already
described in the foregoing.
The grooves 27 have been so thermally deformed in the illustrated form of
embodiment after
insertion of the tensile carriers 14 that the tensile carriers are stably
fixed in the first part belt.
CA 02596716 2007-08-09
Fig. 3 schematically shows a section through a lift system, which is installed
in a lift shaft 1, with
the belt 12. The lift system comprises a drive unit 12, which is fixed in a
lift shaft 1, with a drive
wheel 4.1, a lift cage 3, which is guided at cage guide rails 5, with
deflecting wheels mounted
below the cage floor 6 and in the form of cage support rollers 4.2, a
counterweight 8, which is
guided at counterweight guide rails 7, with a further deflecting wheel in the
form of a
counterweight support roller 4.3, and the belt 12 for the lift cage 3 and the
counterweight 8,
which transmits the drive force from the drive wheel 4.1 of the drive unit 2
to the lift cage and the
counterweight.
The belt 12 is fastened at one of its ends below the drive wheel 4.1 at a
first belt fixing point 10.
From this it extends downwardly to the counterweight roller 4.3, loops around
this and extends
from this to the drive wheel 4.1, loops around this and extends downwardly
along the cage wall
at the counterweight side, loops at both sides of the lift cage through 900
around respective
cage support rollers 4.2 mounted below the lift cage 3 and extends upwardly
along the cage
wall remote from the counterweight 8 to a second belt fixing point 11.
The plane of the drive wheel 4.1 can be arranged at right angles to the cage
wall at the
counterweight side and its vertical projection can lie outside the vertical
projection of the lift
cage 3. It is therefore to be preferred that the drive wheel 4.1 has a small
diameter, so that the
spacing between the lefthand cage wall and the wall of the lift shaft 1
opposite thereto can be as
small as possible. Moreover, a small drive wheel diameter enables use of a
gearless drive
motor with relatively small drive torque as drive unit 2.
The drive wheel 4.1 and the counterweight support roller 4.3 are provided at
their periphery with
grooves which are shaped to be substantially complementary to the ribs 15.1 of
the belt 12.
Where the belt 12 loops around one of the belt wheels 4.1 or 4.3 the ribs
present on its traction
surface lie in corresponding grooves of the belt wheel, whereby particularly
good guidance of
the belt on these drive wheels is ensured. Moreover, the traction capability
is improved by the
wedge action arising between the grooves of the belt wheel 4.1 serving as
drive wheel and the
ribs of the belt 12.
In a further form of embodiment (not illustrated) the slide surface of the
belt 12 and the cage
support rollers 4.2 also have corresponding wedge ribs. For this purpose, in
the case of the
further form of embodiment (not illustrated) a third part belt of
polyurethane, which like the
second part belt has wedge ribs, is arranged on the side of the first part
belt 13 remote from the
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second part belt 15. By contrast to conventional lift installations a lateral
guidance between the
cage support rollers 4.2 and the belt 12 is therefore given in the looping
around of the cage
support rollers 4.2 below the lift cage 3, since the belt also has ribs on its
side facing the cage
support rollers 4.2. In order to still further improve the lateral guidance of
the belt, two guide
rollers 4.4 provided with grooves are mounted at the cage floor 6, the grooves
of the rollers co-
operating with the ribs of the belt 12 as lateral guidance.
