IMPROVEMENTS IN HYDRAULIC LIFT APPARATUS FOR DRY DOCKING VESSELS
Year: 1872

page_text: PROVISIONAL SPECIFICATION left by Edwin Clark at the Office
of the Commissioners of Patents, with his Petition, on the 9th
January 1872.
I, EDWIN CLARK, of Westminster Chambers, Victoria Street, in the
City of Westminster, Civil Engineer, do hereby declare the nature of
the said Invention for "IMPROVEMENTS IN HYDRAULIC LIFT APPARATUS FOR
DRY DOCKING VESSELS,” to be as follows :---
The object of this Invention is to improve the construction of the
hydraulic lift for raising ships out of the water for inspection and repair,
for which I obtained Letters Patent bearing date the 19th January 1857,
No. 159. This lift consisted of two rows of presses so arranged as to
lift simultaneously a series of transverse girders, over which was floated
when in a depressed position a pontoon carrying the vessel intended
to be raised out of the water.
I now propose so to arrange the apparatus as to render the cost of the
pontoon unnecessary, and also to provide an efficient means for sus-
taining the ship when raised in an elevated position.

page_text: The manner in which I carry out the first named object will vary
somewhat according to the requirements of the locality where the
hoisting apparatus is to be erected, but in all cases I so utilize the
transverse girders as to make them form a portion of the stageing,
whether it be a floating stageing or otherwise. To this end I propose
to join together the whole of the transverse girders that are continued
across the dock between the opposite columns or lines of presses by
longitudinal wrought-iron girders firmly secured to each transverse
girder and of sufficient depth and strength to form with them a rigid
table or grid. This grid when fitted with the necessary bilge and keel
blocks will carry the vessel intended to be docked without yielding at
any part, and will thereby distribute the weight of the vessel over the
hydraulic presses. The upper side of this table or grid can be covered
over with iron or wood, and provided with the necessary facilities for
the examination or repair of vessels when raised, and thus the separate
pontoon hitherto used can be dispensed with.
In place of using the girders only with or without a covered top over
the whole grid or table, I purpose occasionally to make all the outer
girders of solid wrought-iron, and to cover the bottom with iron plates
or timber, and thus make a water-tight grid or pontoon which would be
provided with valves as in the ordinary pontoon. By thus combining
the transverse girders of the lift and the pontoon I obtain most of the
advantages of the separate apparatus and at a greatly reduced cost.
When this arrangement is used, I make a new and special connection
of the lifting chains to the floating grid to allow of the ram, crosshead,
and chains being entirely disconnected from the grid, which would then
float freely; this I may do by suspending a strong wrought-iron or steel
pin between the lower extremity of cach set of the suspension bars,
which pin shall fit into a semi-cylindrical casting secured to the end of
the transverse girder, or some other suitable detachable contrivance
may be adopted.
The grid or table may be covered over both at top and bottom with
iron plates or timber, and thus made both water and air tight. In this
case it should be provided with air pipes and valves as usual, and it
may be worked in connection with the hydraulic lift as explained.
The hydraulic press or pair of presses to cach column, I purpose to
provide with two outside presses, one under either end of each cross
head, which outside presses would not be used for lifting but simply as a

page_text: blocking apparatus to the cross head, to retain it in place and assist in
supporting the vessel at any level in case the main press should from
any cause fail. These auxiliary presses will be contained in the main
cylinders or columns and provided with valves by which as the ram
ascended water would enter and fill the press through a self-acting
valve opening inward. The water thus admitted would be retained and
keep the ram elevated until discharged by the opening of a specially
constructed discharge valve or valves.
.