Note: Descriptions are shown in the official language in which they were submitted.
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Elevator Door System
The invention relates to elevator doors systems and, in particular, to an
elevator door
system comprising a door that is wound upon a vertical axis during an opening
operation.
Such elevator door systems are well known from the prior art and are
described, for
example, in WO-A2-2005/070807 and WO-A2-2005/070808. Each elevator door is
generally formed from a stainless steel sheet or interconnected vertical rigid
panels,
typically manufactured from a metal. In operation, as the elevator door is
opened and
~o closed, the plurality of panels or sheet is wound onto and unwound from a
vertical axis in
the form of a motorised reel whereby the driving force from the motor is
transmitted
through the reel and onto the door to provide lateral movement thereof.
Normally, the door
is biased to its closed position by a weight or spring. Accordingly, to open
the door, the
motor must develop a force which must overcome the inherent friction and also
the
~s counteracting biasing force of the weight or spring to provide the
necessary acceleration.
The objective of the present invention is to make more efficient use of the
motor, thereby
enabling savings in both cost and space requirement.
2o This objective is achieved by an elevator door system comprising, a motor,
a vertical axis,
a door attached at a first end to the vertical axis for winding and unwinding
thereupon
CHARACTERISED IN further comprising force transmission means interconnecting a
second end of the door and compensation means whereby the motor simultaneously
drives the vertical axis and the compensation means and wherein the
compensation
25 means has a variable diameter.
In use, as the door is unwound from the vertical axis, the force transmission
means is
simultaneously wound upon the compensation means. Hence, not only is a thrust
exerted
on the door by the vertical axis but a drag is exerted thereupon by the force
transmission
3o means. Furthermore, the compensation means has a variable diameter to
compensate
for, amongst other things, the changes in the diameter the door wound on the
vertical axis.
Hence, the tension in the force transmission means and the door can be kept
substantially
constant during operation.
35 Preferably, the compensation means is a cone whereby the force transmission
means is
attached to a large diameter portion thereof and, in use, is wound
successively in
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decreasing diameter thereupon. Advantageously, at any time during operation,
the current
diameter at which the force transmission means is being wound around the cone
corresponds with the diameter that the outermost layer of the door is wound
around the
vertical axis. Hence, as a given length of the door is unwound from the
vertical axis, the
s same length of force transmission means is taken up on the cone. Therefore
the tension in
the force transmission means and the door is kept relatively constant during
operation.
Preferably, the pitch between successive windings of the force transmission
means on the
cone is substantially equal to the depth of the door. Accordingly, the tension
in the force
~o transmission means and the door can be kept relatively constant during
operation even
though the depth dimension of the force transmission means is considerably
smaller than
that of the door. In this instance, a wire, a rope or a cable is suitable for
use as the force
transmission means.
15 In one embodiment, the compensation means is mounted on the vertical axis.
According.
the motor need only drive one of the compensation means and the vertical axis
to ensure
simultaneous rotation of the other. Preferably, resilient means interconnects
the cone and
the vertical axis. It is beneficial to provide some resilience in the system
to absorb energy
therefrom if, for example, the door engages with an obstruction during a
closing operation.
To make most efficient use of the available space, preferably the vertical
axis and the
compensation means are disposed on one side of the doorway and the force
transmission
means is deflected by a pulley disposed on an opposite side of the doorway.
A door system according to any preceding claim wherein the tension in the
force
transmission means is greater than or equal to a combination of the
acceleration and
friction forces acting on the door. Accordingly, the force transmission means
will never go
slack during operation of the door system.
3o Preferably, a first force transmission means is provided at an upper part
of the door and
coupled to a first compensation means, and a second force transmission means
is
provided at a lower part of the door and coupled to a second compensation
means. To
counteract the door's tendency to tilt, the tension of the second force
transmission means
should be at least mgs/h greater than the tension of the first force
transmission where m is
the mass of the door panel, g is the gravitational force, s is horizontal
displacement of the
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upper end of the panel relative to the lower end of the panel and h is the
height of the
panel.
The present invention is hereinafter described by way of a specific example
with reference
to the accompanying drawings in which:
Figure 1 is an exploded perspective view an elevator door system according to
the
present invention;
Figure 2 is a partial cross-section showing in greater detail the compensation
means and
vertical axis of the embodiment of Fig. 1; and
~o Figure 3 is an illustration of the forces acting on the leading panel of
the door.
Fig. 1 is a general perspective view of an elevator door system 1 according to
the present
invention incorporating a car door 2 which, in use, is used to control access
to an elevator
car (not shown) through a doorway from a landing within a building. The door 2
is
5 composed of a plurality of vertically aligned panels 4 each of which is
preferably extruded
from aluminium for its superior strength to weight ratio. The panels 4 are
bound at their
upper and lower extremities by flexible belts 6 and guided in upper and lower
guide
channels (not shown). The belts 6 are attached at one end to a reel 10 mounted
at one
side of the doorway, rotation of which is controlled by a motor 12 to open and
close the
2o door 2. The opposing ends of the belts 6 are attached to cables 14 which
are deflected by
diverting pulleys 16 mounted at the other side of the doorway and connected to
conical
spools 20 which are also rotated by the motor 12. In a closing operation, the
door 2 is
unwound or paid-out from the reel 10 whereas the cables 14 are simultaneously
wound or
drawn upon the conical spools 20. Conversely, in an opening operation, the
door 2 is
2s wound onto the reel 10 while the cables 14 are unwound from the conical
spools 20.
Fig. 2 is a cross-section through an upper portion of the reel 10 of Fig. 1.
It will be readily
appreciated that the lower portion of the reel 10 corresponds. The reel 10 is
provided with
a central axle 18 which, in use, is driven by the motor 12. The reel 10 and
central axle 18
so are rotatably supported by bearings 32 on a fixation bracket 30 which is
securely mounted
to the elevator car. The conical spool 20 is rotatably mounted on the central
axle 18 and
connected thereto by a helical spring 24.
The cable 14 is attached to the conical spool 20 at a point 14a on the widest
diameter of
35 the spool 20. In the diagram, both the cable 14 and the door 2 extend from
the plane of
the page.
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In the fully open position, the door 2 is completely wound in layers on the
reel 10 while the
cable 14 is completely unwound from the conical spool 20 and attached thereto
only at
point 14a. Preferably the diameter of the spool 20 at point 14a corresponds to
the
diameter the outer layer of the door 2 makes on the reel 10. In a closing
operation,
indicated by arrow C in Fig. 2, the door 2 is sequentially unwound from the
reel 10,
whereas the cable 14 is sequentially wound onto a spiral groove 22 on the
conical spool
20. The spiral groove 22 has decreasing diameter and preferably its pitch P
corresponds
to the depth D of the door 2. With this arrangement, for every rotation of the
central axle
18, the same amount of door 2 is unwound from the reel 10 as the amount of
cable 14
wound onto the conical spool 20. Hence, the tension in the door 2 and cable 14
can be
kept relatively constant during operation. In the specific situation shown in
Fig. 2, the door
2 has almost been completely unwound from the reel 10 while the cable 14 has
almost
been completely wound onto the conical spool 20.
Although in the preferred embodiment, the instantaneous diameter the cable 14
makes on
the conical spool 20 is substantially the same as the diameter of the outer
layer door 2 on
the reel 10 and the pitch P of the spiral groove 22 corresponds to the depth D
of the door
2, it will be readily understood that the same effect of constant tension can
be achieved
2o using differing diameters and pitches.
Fig. 3 shows an analysis of the tensioning forces required in the door system
1. Due to
the inherent nature of the panels 4 which make up the door 2, there is a
tendency for the
panels 4 to tilt under the force of gravity. To counteract this tendency, the
tension Fi2 in the
lower cable 14 is mgs/h greater than the tension F" in the upper cable 14;
where m is the
mass of the door panel 4, g is the gravitational force, s is horizontal
displacement of the
upper end of the panel 4 relative to the lower end of the panel 4 due to tilt
and h is the
height of the panel 4.
so Furthermore, to ensure that the cables 14 are always tensioned during
operation of the
door system 1, the tension Ft in both of the cables 14 should be at least
equal to the
acceleration and friction forces acting on the door 2: Ft >_ m (a + pg), where
N is the
coefficient of friction.
Although the invention has been described with specific reference to a door 2
comprising
a plurality of vertically aligned panels 4, it will be appreciated that the
invention is equally
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applicable for any door which is capable of being wound upon and unwound from
the reel
10. In particular, the door can be in the form of sheet material as disclosed
in WO-A2-
2005/070807.
