IMPROVEMENTS IN CRANES
Year: 1880

page_text: PROVISIONAL SPECIFICATION left by Richard Christopher Rapier at the
Office of the Commissioners of Patents on the 7th October 1880.
RICHARD CHRISTOPHER RAPIER, of 5, Westminster Chambers, in the City of
Westminster. "IMPROVEMENTS IN CRANES."
My improvements in cranes have reference to the class of cranes known as
derrick cranes, having jibs of variable radius. In such cranes the radius of the jib
is raised by lifting or lowering the jib by means of a chain which is wound on to
or unwound from a barrel provided for that purpose.
When the jib is in its lowest position the strain on such chain is much greater
than in its highest position, and the strain so caused on the machinery of the crane
is sometimes partially equalised by the use of a fusee barrel, so arranged that when
the jib is in its lowest position, the chain is wound on to the smaller part of the
barrel, and the diameter of the barrel increases as the strain on the chain
diminishes.
As the jib is raised the load is also raised, and this is sometimes very incon-
venient.
To obviate this inconvenience to some extent, improvements were made by
D. Henderson, and Letters Patent were granted to him in 1845 (No. 10,713) for
such improvements. Under that Invention, a fusee barrel was used for winding up
the jib, and this fusee barrel was geared by spur wheels to the barrel on which the
load chain was wound, and these two barrels were so geared together by cog wheels
that as the jib was lifted, the load chain was paid out in proportion so as to keep
the load at or about the same height. This Invention was of great use and merit,
although the strain of lifting and lowering the load, and the consequent friction,
always had to pass through the gear.
Now my present Invention accomplishes the same object in a simpler way with
fewer parts and without passing the strains through the gear.
I use a fusee barrel properly proportioned in its variations of diameter, and I
attach the jib chain to one end of the barrel and wind it up as many turns as may
be necessary to lift the jib to its full height. I then take the dead end of the load
chain (which for cranes of this class is nearly always double), and instead of
attaching it to the jib head I pass it over a pulley on the jib head and lead it
down and attach it to the other end of the fusee barrel, so that it may be wound
up turn for turn as the jib chain unwinds, and in such proportion, that the one
neutralises the other, and the load remains at the same level in all positions of the
jib.

page_text: It will be seen that under these circumstances the one chain is helping to pull
the barrel round just as much as the other chain is resisting, and thus the barrel is
in a neutral state, and the friction on the gear for driving it is reduced to a
minimum. In short the gear has no longer to lift the load by one set of appliances
and lower it by another, but the one appliance of the single fusee barrel raises the
position of the jib without lifting or lowering the load at all.
The advantage of this improvement lies in reduction of friction and power to be
applied, the reduction of parts, and consequent greater accuracy obtainable as to
the maintenance of level of the load.
The fusee barrel may be constructed on the plan of increasing the diameter as
the strain diminishes, but this is not necessary, and there are some practical
advantages in arranging that the jib chain begins to wind up on the big part of
the fusee, as by that means the maximum diameter of the fusee is diminished.
When it is desired to raise or lower the load this is done by the other end of the
load chain to that before mentioned being wound on to or unwound from the load
barrel in the ordinary manner.