IMPROVEMENTS IN THE CONSTRUCTION AND WORKING OF CAISSONS, WHICH IMPROVEMENTS ARE ALSO APPLICABLE TO MOVABLE BRIDGES AND THE GATES OF DOCKS AND CANAL Locks
Year: 1872

page_text: PROVISIONAL SPECIFICATION left by David Cunningham at the
Office of the Commissioners of Patents, with his Petition, on the
18th May 1872.
I, DAVID CUNNINGHAM, of Dundee, in the County of Forfar, North
Britain, Civil Engineer, do hereby declare the nature of the said Inven-
tion of "IMPROVEMENTS IN THE CONSTRUCTION AND WORKING OF CAISSONS, WHICH
IMPROVEMENTS ARE ALSO APPLICABLE TO MOVABLE BRIDGES AND THE GATES OF
DOCKS AND CANAL Locks," to be as follows, that is to say :-
This Invention which relates to improvements in caissons employed
for closing dock entrances, canal locks, and other spaces within which
it is required to confine water, and which improvements may also be
applied to movable bridges, consists in so constructing these caissons that
their descent and ascent in the water may be effected without the
employment of sluices, valves, or pumps as hitherto used to admit water
to, and run it off from them in order to alter the amount of ballast,
accordingly as it is desired to sink or raise the caissions. Under this
Invention the caissons are provided with floats at the sides which are
raised or lowered by screws or other suitable mechanism. By actuating the
screw or other mechanism so as to raise the floats in the water, the caisson

page_text: is sunk, and vice versa, by lowering them it is raised, and by raising the
floats clear out of the water they act as weights by which the caisson
is forced down to its lowest level, thereby keeping tight the entrance
to the dock, canal lock, or other water space. It is preferred to arrange
the floats on both sides of the caisson, as in such a position they act as
fenders besides materially contributing to the strength of the caisson,
the screws by which the said floats are operated being supported in
brackets fixed to the caisson at its upper and lower parts, and it is also
preferred to employ in combination with the floats in cases where the
situation is exposed, and where the level of water is the same on both
sides of the caisson shoulders projecting from the sides or ends of the
caisson which rest in the side walls when the caisson is at its lowest
position, by which means the weight on the caisson, caused by raising
the floats clear of the water, is sustained and the bottom of the caisson
is free to move and press tightly on its sill and thereby become water-
tight. Towards the lower extremity of the caisson one or more buoyant
chambers is or are situated by which the floats are assisted in raising
the caisson when necessary and an open space is formed at its upper
part in which the outside water may flow freely and over which the
usual deck or bridge for traffic is situate. In lieu of employing floating
bodies in conjunction with the caissons as herein-before set forth, other
bodies which are capable of displacing water and whose specific gravity
is greater than the water may be used for effecting the objects herein-
before described, such for example as boxes laden with pig iron, stones,
gravel, or other heavy materials.