A worm
gearing, actuated by a wheel on the upper side of the scaffold, causes
the scaffold to ascend or descend. A railgrip, made to act at the curves
as well as on the straight portions of the rail by being attached to a
radial arm fixed to the under frame, assists the stability of the
scaffold where required, but the gauge of the rails is altered to render
the scaffold more or less stable according to its height. Combined with
the same machine, and traveling up and down one of the same posts used
for the scaffold, is an improved crane. Its action depends upon the
proposition in geometry that if the length of the base of a triangle be
altered, its angles, and therefore its altitude, are altered. A portion
of the vertical post up and down which the crane climbs forms the base
of a triangle, and a portion of the jib, together with the stay, forms
the remaining two sides. Hence, by causing the foot of one or the other
to travel upward, by means of the worm gearing, the upper end of the jib
is either elevated or depressed.
The concrete elevator, which is also combined with the scaffold,
consists of a series of buckets carried upon two parallel endless chains
passing over two pairs of wheels. On the under frame is fixed a hopper,
into which is thrown, either by hand or from a concrete mixer running
upon the rails, the material to be hoisted, and from which it gravitates
into a narrow channel, through which pass the buckets (attached to the
chain) with a shovel-like action.
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