Page 170 - ELEMENTS EUROPA (EN)

166
it needs to tie in with the general impression of peacefulness
emanating from the design.
1.10 m wide, 1.99 m high and 8.03 m long, the elevator can
easily pass through the atrium’s double entrance doors and
can similarly travel down the circular ramp to the underground
car-park where it is normally parked.
The upper part of the lantern cannot be accessed from
the ground. This means that to clean it a suspended cradle is
needed. But the natural vertical nature of the suspension cables
does not harmonise with the curved shape of the surface to be
cleaned. The system installed (System E) thus involves a mobile
base (trolley) with a cradle suspended – via a pivoting bracket
– from the end of a telescopic arm fixed to the base. An access
platform fitted with a perforated steel surround hangs under
the telescopic arm. In front of the cradle, a small jointed arm
allows a winch to be attached, should it be necessary to replace
any glazing. The system’s total weight is 5,793.70 kg, including a
240 kg payload for two operators and 375 kg for a replacement
window pane.
The base and the attached cradle can manoeuvre five ways:
1. Travelling along the two parallel rails fixed to the atrium’s
ceiling and circumventing the whole lantern,
2. Rotating the base to bring the cradle up to the glass surface,
3. Extending the telescopic arm to detach the cradle from the
platform,
4. Pivoting the bracket to position the cradle parallel to the glass been installed, a large-scale mock-up was built to check the
to be cleaned,
5. Moving the cradle up and down to reach each pane.
The cradle’s positioning is determined by a combination
of these five manoeuvres. An on-board computer constantly
monitors the different parameters, so the cradle’s exact
position is known at all times. The computer also has a three-
dimensional model of the lantern in which all possible working
positions of the cradle are stored. There are some 800 of these,
divided into 36 columns, each corresponding to a vertical
descent of the cradle from its top starting position. To access
any one of these positions, all an operator in the cradle has
to do is to select the required position via a touch screen.
The computer then automatically carries out all manoeuvres
necessary to position the cradle. It then descends in steps
of one metre down the facade, with the system in charge of
adapting the system’s geometry so that the cradle skims over
the glazed surface and so that its angle never exceeds 5°. The
cradle’s positioning tolerance is 30 mm and its repeatability
tolerance 20 mm, ensuring that the edge of the cradle guardrail
is always 45 - 55 cm away from the glass surface.
Access to the platform is from above, via the grated ceiling
forming the underside of the atrium’s roof. The normal parking
position of the base/cradle is at the end of the rails, just a short
distance away from the access to the grated ceiling and in line
with the roof’s structure. To avoid any risk of falling, the access
trapdoor on the grating is protected by a surround made of
perforated steel sheeting. The door can be opened only when
the machine is in its parking position.
An emergency parking position is also available towards the
centre of the atrium, equipped with the same protection. In the
event of any problem, the position of the rails and the machine’s
orientation are such that it is possible to have the cradle
descend right down to the ground without it actually touching
the lantern. Even in the case of a power failure, access to this
emergency position is always guaranteed, as the motors are
powered by two separate high-reliability power circuits.
The system was completely designed, calculated and drawn in
three dimensions before being built. However, as it would have
been virtually impossible to make any corrections once it had
system’s full functionality.
This saw the machine’s Spanish manufacturer building a
partial mock lantern and atrium ceiling in his Madrid workshop,
from which the machine was suspended. Two whole days were
necessary to complete all the planned tests.