Belt-driven elevator without counterweight
Field of the invention
The present invention relates to an elevator without counterweight and related
drive assembly. The invention relates in particular to the tensioning system for
the traction member of such elevator.
Prior art
Elevators without counterweight have a self-supporting construction separated
from the structure of the building, providing a significant cost reduction and
making them attractive for installation in small or old buildings The hoisting
system can be arranged on one side or both sides of the cabin. For example,
the elevator comprises a cabin, a frame structure with two vertical guide
elements, and a drive system comprising a motor and a traction member such
as a hoisting rope.
A problem of this kind of elevators is to maintain a suitable tension of the
traction member, due to lack of the counterweight. There is the need of a
tensioning and compensation system to maintain the suitable tension of the
traction member, e.g. taking into account the thermal expansion.
WO 2008/056026 discloses an elevator without counterweight wherein an
elevator car is suspended on hoisting ropes, and comprising rope pulley
modules, each pulley modules comprising a plurality of diverting pulleys.
Basically, the plurality of diverting pulleys serves to reduce - according to the
well known principle of multiple pulleys or sheaves - the power required to
operate the elevator. To provide the tensioning of the hoisting ropes, a bottom
pulley module comprises a rope compensation mechanism.
This prior art has the following disadvantages: the compensation system is not
able to provide accurate adjustment of the tension; the disclosed system is not
suitable to use of a belt as the traction member, due to the fact that the pulleys
are coaxial and require a lateral deviation of the traction member, which
however is not permitted by belts unless specific guide elements are provided,
leading to a more complicated arrangement; moreover, the coaxially arranged
pulleys generate an overturning momentum on the cabin, which results in
major abrasion on the guide elements and increase of the need of traction
power.
Summary of the invention
The aim of the invention is to overcome the above drawbacks of the prior art.
An object of the invention, in particular, is a drive arrangement suitable for a
belt-driven elevator without counterweight, and a related tensioning and
compensation device.
The underlying idea of the invention is to provide a drive system with at least
one belt, running over stationary pulleys fixed to the frame structure of the
elevator, and moving pulleys associated with the cabin, said moving pulleys
being arranged in at least a first assembly fixed to the cabin, and a second
assembly connected to the first assembly by a compensation device of the
tension of said drive belt.
For example, moving pulleys comprises a set of pulleys associated with a
support firmly fixed to the cabin, and a further set of pulleys associated with a
floating support, elastically suspended t o t he fixed s u p po r t by t he
compensation device. The second assembly is suitably distanced from the first
assembly, by tensioning the compensation device, e.g. compressing one or
more spring(s).
Hence, an object of the invention is an elevator without counterweight
comprising: a cabin and a frame structure, the cabin being movable relative to
the frame structure in a vertical direction; a drive system comprising at least
one drive belt running over a respective plurality of pulleys; the pulleys of said
drive belt being grouped in at least one group of stationary pulleys associated
with the frame structure, and at least one group of moving pulleys associated
with the cabin; wherein said moving pulleys are arranged in at least a first
assembly fixed to the cabin, and a second assembly distanced from said first
assembly in the vertical direction, the second assembly being connected to the
first assembly by a compensation device of the tension of said drive belt.
According to one aspect of the invention, the pulleys are coplanar. In a
preferred embodiment, the pulleys are substantially aligned on the vertical
direction so that also their axes lie on a same plane.
For example, each group of pulleys comprises a plurality of substantially
coplanar pulleys, the pulleys of each group being arranged vertically one
above the other and having a diameter progressively decreasing from a first
pulley of the group having a maximum diameter, to a last pulley of the group
having a minimum diameter. Each of the groups of pulleys can be composed
of any number of vertically aligned pulleys, with a diameter progressively
decreasing from a first larger pulley to a last and smaller pulley. In common
embodiments of the invention, each group is composed of two or three pulleys.
At least one of the pulleys is driven by a suitable motor. In some embodiments,
a disc-like motor can be used to save space.
In a preferred embodiment, the first assembly of moving pulleys comprises a
first plurality of pulleys associated to a first support fixed to the cabin, and the
second assembly of moving pulleys comprises a second plurality of pulleys
associated to a floating support, the floating support being elastically
connected to the fixed support by said compensation device. Preferably, the
compensation device comprises at least a spring which, in use, is compressed.
A preferred embodiment of the compensation device provides that a spring or
a plurality of springs act(s) on corresponding pin(s) passing through guide
elements of the fixed support and the floating support. For example, the
compensation device comprises a left pin and a right pin passing through a
first and a second coaxial sleeves of the fixed support and of the floating
support respectively, each of said left and right pin having a spring
compressed between the head of the pin and one of said first and second
coaxial sleeves, and having an end opposite to said head abutting against the
other coaxial sleeve.
In one embodiment, a first group of stationary pulleys are fixed to the top of the
frame structure of the elevator, a second group of stationary pulleys are fixed
to the bottom of said frame structure, and moving pulleys are associated with
the cabin, the drive belt having opposite fixed ends located in correspondence
of said first and second groups of stationary pulleys.
The drive belt is a belt comprising a coating e.g . of a plastic material,
enveloping suitable tension members, according to known art. For example the
tension members are steel wires. The drive belt may have an arcuate shape
with a convex or concave surface, matching a corresponding concave or
convex surface of the pulleys, with a self-centering capability.
According to different embodiments of the invention, the elevator may have
one drive belts or multiple drive belts. The drive belt or drive belts may be
arranged at the sides of the cabin or behind the cabin, for example.
In embodiments with a single drive belt, said compensation device may act
also as a tensioning device.
In embodiments with multiple drive belts, i.e. two or more drive belts, the
above described compensation device is preferably in common for all belts,
and each drive belt has preferably its own tensioning device. The common
compensation device also cooperates to tension the belts.
Each belt has two opposite terminations, where the belts is fixed e.g. to a
suitable termination assembly. The termination assembly preferably provides
adjustment of the tension of the respective belt. In those embodiments with
multiple drive belts, it is preferred that the drive belts have first terminations
fixed to a common termination assembly, and second terminations fixed to a
respective termination assembly associated with a respective tensioning
device. Hence, each belt has a first termination fixed to the common
termination assembly, and a second, opposite termination fixed to a specific
termination assembly of that belt, with a suitable tensioning device. The
tensioning device of each belt preferably comprises a resilient member such
as a spring.
In a particularly preferred embodiment, the termination of the belt is secured to
an anchor bolt that can be rotated in order to adjust the tension of the belt. The
head of said anchor bolt is fixed to a lever; a distal end of said lever is acting
on a pin; the pin is movable axially in a slot, and is biased by a resilient
member.
An advantage of the invention is that the compensation device is integrated
with the moving cabin. Another advantage is that the adjustment of the tension
of the drive belt is more accurate and stable during operation. For example the
tension can be regulated by acting on one of the fixed ends of the belt, and the
reduction factor between the end of the belt and the tensioning device allows a
fine adjustment of the tension.
The invention permits application of pulleys of minimum diameter, requiring
less lateral space and keeping all the functional advantages of belts over steel
cords, in particular if applied in elevators without counterweight, which in the
known art depend on the friction exerted onto the rope of the driving pulley for
correct movement.
The coplanar pulleys placed on mutually parallel axes, located one above the
other vertically, and of decreasing diameters, allow to obtain a course of the
belt adapted to reduce the power requirements by a factor of four, six or more.
The reduction of power requirements is obtained with the adoption of two,
three pulleys per group, etc. in such manner that the single parallel vertical
tracts of the belt are not contacting each other, and that the belt does not
undergo any lateral deviation. The invention provides a higher coefficient of
friction and the possibility of applying smaller pulleys without requiring lateral
guide elements for the belt, which moves always in the same plane and do not
induce any lateral excursion of the cabin. Further advantages are the silent
and vibration-free operation.
The advantages of the invention, thanks to the fact that the belts are applied in
arrangements requiring a minimum of space, and with a higher factor of
reduction of the drive power required, allow realisation of elevators with or
without counterweight under conditions of scarce availability of space, at
limited cost, and securing efficient and reliable operation.
These and other advantages of the invention will be elucidated hereinbelow
with reference to preferred and non-limiting embodiments.
Description of the figures
Fig. 1 is a view of an elevator according to a first embodiment of the invention
with a single drive belt.
Figs. 2 and 3 are details of Fig. 1 showing the top and bottom groups of
pulleys.
Fig. 4 is a detail of Fig. 1, showing the pulleys associated with the cabin and
the tensioning device.
Fig. 5 is a scheme of the arrangement of the drive belt and pulleys of the drive
system of the elevator of Fig. 1.
Fig. 6 relates to a second embodiment of the invention wherein the elevator
comprises two drive belts, and is a detail of pulleys associated with the cabin
and the tensioning device.
Fig. 7 is a detail of the top groups of pulleys of an elevator according to the
second embodiment of Fig. 6 .
Fig. 8 is a detail of the bottom groups of pulleys of an elevator according to the
second embodiment of Figs. 6 and 7 .
Detailed description of preferred embodiments
First embodiment
Figs. 1 to 5 relate to an embodiment of the invention, wherein an elevator
without counterweight comprises a cabin 1 and a frame structure 2 with guide
rails 2a, 2b for said cabin 1. The cabin 1 is moved relative to the frame
structure 2 in a vertical direction when a drive system is operated. In this
embodiment, the drive system comprises a single drive belt 3 which is
arranged behind the cabin 1.
The drive system comprises a number of stationary pulleys arranged in a
group 4 fixed to a top element 5 of the frame structure (Fig. 2), and a group 6
fixed to a bottom element 7 of the frame structure (Fig. 3). The drive system
also comprises moving pulleys arranged in groups 8, 9 associated with the
cabin 1.
The arrangement of the pulleys and the belt can be readily appreciated in Fig.
5 . From a fixed termination around a first anchor bolt Pi, the belt 3 runs over
pulleys 101 to 112 respectively, up to an opposite fixed termination of anchor
bolt P2. A drive motor 10 is also shown. The anchoring of the terminations of
belt 3 at the anchor bolts Pi and P2 is realized according to a known technique.
At least one of said anchor bolts allows to wrap around the belt 3 in order to
regulate the overall tension of the belt itself.
Each group of pulleys comprises a plurality of coplanar pulleys, in the example
there are three pulleys each group. The pulleys of each group have a diameter
decreasing, from a larger pulley to a smaller one. Referring for example to
group 4 of Fig. 2, the upper pulley 106 is larger than the intermediate pulley
104, and the intermediate pulley 104 is larger than the bottom pulley 102.
Pulleys 102, 104 and 106 are part of the group 4 of stationary pulleys and are
rotatably supported on a plate 4a firmly screwed to the frame elements 5 . The
pulleys 107, 109 and 111 are part of the stationary group 6 and are rotatably
supported on a plate 6a firmly screwed to the frame element 7 . The pulleys
10 1, 103 and 105 are part of the group 8 of moving pulleys; the pulleys 108,
110 and 112 are part of the group 9 of moving pulleys. It can be demonstrated
that this arrangement of the belt 3 has a power factor of six, i.e. the lifting force
is six times the tension of the belt.
The moving pulleys 10 1, 103, 105 and 108, 110, 112 are associated to
respective assemblies. One assembly is firmly fixed to the cabin 1, while the
other assembly is "floating", being elastically suspended to the fixed assembly
by a tensioning device. In the example, the group 8 is associated to the fixed
assembly and the group 9 is associated with the suspended (floating)
assembly.
A compensation device 30 is provided between said fixed assembly and said
suspended assembly.
A preferred arrangement of the compensation device 30 is shown in Fig. 4 .
The three pulleys 10 1, 103 and 105 are supported by a plate 20 which is
screwed to the rear wall of the cabin 1, while the three pulleys 108, 110 and
112 are supported by a plate 2 1 which is separate from the cabin 1. The plate
2 1 is connected to the plate 20 by a left pin 22 and a right pin 23. Each of the
left pin 22 and right pin 23 passes through a first guide sleeve 24 fixed to the
plate 20, and a second guide sleeve 25 fixed to the plate 2 1.
Said sleeves 24 and 25 may be realized with tubes welded to the plates 20
and 2 1, respectively.
Springs 26 and 27 are mounted coaxially on each of said pins 22, 23, the
spring 26 or 27 being then compressed between an end of the pin 22 or 23,
and a guide sleeve. The connection between the plates 20 and 2 1, by means
of said pins 22, 23 and springs 26, 27 form said tensioning device 30 of the
belt 3 .
More preferably, the spring 26 or 27 is compressed between a head portion of
the pin and the guide sleeve of one of the fixed and floating supports. In the
example of Fig. 4, the spring 26 is compressed between the head 22a of the
pin 22, and the guide sleeve 24 fixed to the plate 20. The opposite end of the
pin is abutting against the sleeve 25 of the plate 2 1 . In the shown embodiment,
the pins have a threaded end and a nut is provided at the end of the pin. Fig. 4
shows the nut 22b at the end of the pin 22.
The system is adjusted so that the compensation device 30 induces a pre
tension of the belt 3 . For example the distance y between the fixed plate 20
and the floating plate 2 1 is chosen to provide a given compression of the
springs 26, 27 and a related pre-tension of the belt 3 . Hence the device 30 acts
also as a tensioning device of the belt 3 in a single-belt elevator.
In operation, the compensation device 30 reacts to change in length and/or
tension of the belt 3, e.g. due to temperature, thermal expansion, maintaining
the tension of the belt. Adjustment is possible by wrapping the belt around one
of the anchor bolts. The system is designed so that the springs 26 and 27
operate always by compression.
Second embodiment
Figs. 6 to 8 relate to an embodiment with multiple drive belts. The items
corresponding to those of the Figs. 1 to 5 are indicated with the same
numerals.
In the example, the elevator has two drive belts 3a and 3b. Embodiments with
more than two belts are also possible.
The compensation device 30 is in common between the two belts 3a and 3b,
as seen in Fig. 6 . Said belts 3a and 3b are wrapped around the moving groups
of pulleys 8 and 9 associated to the cabin 1 (Fig. 6), having the compensation
device 30 in common.
The pulleys of first group 8 are rotatably supported on the plate 20, fixed
behind the cabin 1, and the pulleys of second group 9 are rotatably supported
on the plate 2 1, suspended to the plate 20 by means of pins 22, 23 and related
springs 26, 27. Fig. 6 shows a different arrangement of the springs than that of
Fig. 4, wherein the spring is abutting against the sleeve fixed to the floating
plate. The arrangement of the springs of Fig. 4 or 6 are substantially
equivalent.
Each drive belt 3a and 3b has two opposite fixed terminations connected to a
respective termination assembly. One termination assembly is common to both
the drive belts 3a and 3b; the other termination assembly is separate for belts
3a and 3b, and is associated to a respective tensioning device 30a, 30b.
Fig. 8 shows a common anchor belt P3, which is common to a first termination
of drive belt 3a and a first termination of drive belt 3b. In this example, the
common termination assembly is at the lower stationary group of pulleys 6,
where pulleys are supported by the plate 6a.
Fig. 7 shows that belts 3a and 3b have second terminations, opposite to said
first terminations at the upper stationary group of pulleys 4, supported on the
plate 4a. Said second terminations are fixed to separate anchor bolts P4a and
P4b. The second termination of belt 3a is fixed to the anchor bolt P a and the
second termination of belt 3b is fixed to the anchor bolt P b.
Each of said anchor bolts P4a and P4b is associated to a respective tensioning
device 30a, 30b, comprising a lever 40, 4 1 fixed on the head of the anchor
bolt, and having a distal end acting on a pin 42, 43; the pin 42, 43 is movable
axially in a slot of a fixed member 46, 47, which in the example is a metal plate
welded to the plate 4a; the displacement of the pin 42, 43 relative to said fixed
member 46, 47 is biased by a spring 44, 45 coaxially mounted on the pin and
compressed between the pin and the fixed member.
This arrangement provides separate regulation for the belts 3a and 3b, acting
on the respective anchor bolt. The termination assemblies are preferably
arranged in such a way that the belts 3a and 3b have the same tension when
the levers 40 and 4 1 are parallel each other. Hence the levers 40, 4 1 give an
immediate visual help for adjustment of the tension of the belts.
CLAIMS
1. An elevator without counterweight comprising:
a cabin ( 1 ) and a frame structure (2), the cabin being movable relative
to the frame structure in a vertical direction;
a drive system comprising at least one drive belt (3) running over a
respective plurality of pulleys;
said plurality of pulleys comprising stationary pulleys associated with
the frame structure, and moving pulleys associated with the cabin, so
that the moving pulleys move together with the cabin when the
elevator is in use;
characterized by:
said moving pulleys being arranged in at least a first assembly fixed to
the cabin, and a second assembly which is elastically connected to the
first assembly by a compensation device (30) of the tension of said
drive belt.
2 . Elevator according to claim 1, characterized in that the first assembly of
moving pulleys comprises a first plurality of pulleys (8) associated to a first
support (20) fixed to the cabin ( 1 ) , and the second assembly of moving
pulleys comprises a second plurality of pulleys (9) associated to a floating
support (21 ) , the floating support being elastically connected to the fixed
support by said compensation device (30).
3 . Elevator according to claim 2, the compensation device (30) comprising at
least a pin (22, 23) passing through guide means (24, 25) of the fixed
support and guide means of the floating support, and at least a resilient
member (26, 27) acting on said pin.
4 . Elevator according to claim 3, the resilient member (26, 27) being a
compressed spring.
5 . Elevator according to claim 4, the compensation device (30) comprising a
left pin (22) and a right pin (23) passing through a first and a second
coaxial sleeves (24, 25) of the fixed support and of the floating support
respectively, each of said left and right pin having a spring (26, 27)
compressed between the head (22a) of the pin and one of said first and
second coaxial sleeves, and having an end (22b) opposite to said head
abutting against the other coaxial sleeve.
6 . Elevator according to any of claims 1 to 5, characterized in that the first
assembly and the second assembly of moving pulleys are distanced each
other, so that the compensation device (30) induces a pre-tensioning of
the belt.
7 . Elevator according to any of the preceding claims, characterised in that the
stationary pulleys and the moving pulleys of said drive system are
coplanar.
8 . Elevator according to claim 7, characterized in that the pulleys are
arranged in groups of pulleys, each group of pulleys comprising a plurality
of coplanar pulleys disposed vertically one above the other and having a
diameter progressively decreasing from a first pulley of the group having a
maximum diameter, to a last pulley of the group having a minimum
diameter.
9 . Elevator according to claim 8, comprising a first group of stationary pulleys
fixed to the top of the frame structure of the elevator, a second group of
stationary pulleys fixed to the bottom of said frame structure, and moving
pulleys associated with the cabin, the drive belt having opposite fixed ends
located in correspondence of said first and second groups of stationary
pulleys.
10 . Elevator according to any of the previous claims, the drive belt (3) being a
flat belt, or a belt with at least one convex or concave surface in contact
with the pulleys.
Elevator according to any of the previous claims, the drive system
comprising a plurality of drive belts (3a, 3b), said belts running over pulleys
of said first and second assemblies (9) which is elastically connected to the
first assembly by said compensation device (30).
Elevator according to claim 11, each of said belts (3a, 3b) of the drive
systems having a first termination and a second termination, the first
terminations of the belts being fixed to a common termination assembly
(p3); the second termination of each belt (3a, 3b) being fixed to a
respective termination assembly (P4a; P4b) with a respective belt tensioning
device (30a, 30b).
Elevator according to claim 12, said tensioning devices (30a, 30b)
comprising an anchor bolt (P a; P4b), the respective belt (3a, 3b) being
secured to said anchor bolt, the bolt being rotatable to adjust the tension of
the belt, a head of the anchor bolt being fixed to a lever (41 , 42); a distal
end of said lever acting on a pin (42, 43); the pin being movable axially in a
slot, and biased by a resilient member (44, 45).