AN IMPROVED SCREW PROPELLER
Year: 1852

page_text: PROVISIONAL SPECIFICATION left by Edmund Hunt at the
Office of the Commissioners of Patents, with his Petition, on
the 9th December 1852.
I, EDMUND HUNT, of Glasgow, in the County of Lanark, North
Britain, Gentleman, do hereby declare the nature of the said Inven-
tion for "AN IMPROVED SCREW PROPELLER" to be as follows: -
This Invention consists in constructing a screw with flexible and
clastic blades, the essential object being that such blades may vary
in obliquity according to circumstances, or may lie in a plane or
planes parallel to the ship's axis when the ship goes by wind alone,
and that such propeller be entirely self acting.
.
With a flexible screw, the direction of the vessel's motion depends
not on the direction in which the shaft revolves, but on whether the
fore or the after part of the blades yields to the twisting or deflecting
action of the water. And whereas, in previous arrangements of
flexible screws, the.necessary reversing adjustment is made by very
complicated contrivances, the blades requiring to be set by means of
some mechanism communicating with the interior of the vessel;
according to the present Invention, the required reversing action is

page_text: produced simply by altering the direction of motion of the shaft,
just as with an ordinary inflexible screw; catches or projections
being fixed on the shaft near the blades, which secure and carry
round the fore or after part of the blades, according as the shaft
revolves in one direction or the other, the opposite end of the blade to
that engaged by the catches being free to yield to the twisting action
of the water. The screw blades are formed of two or more arms
hung on the shaft by their centres, or passing directly through the
centre of an enlarged boss; these arms may be simple rods, or they
may be flattened out (more or less) towards their extremities into
thin flexible plates, sliding on each other as in a fan, and being con-
nected by slots and pins. In the former case, that is, when the arms
are shaped as simple rods, the whole blade is covered with vul-
canized india rubber or other elastic and flexible material, which
forms a web between the rods. In the latter case, when the arms
are flattened out, the india rubber covering is not absolutely neces-
sary, but it may be employed to protect the moving parts, necessarily
minute, from the rusting action of the water.
If the arm at the fore part of the blade be carried round in conse-
quence of a projection on the shaft coming against another on the
arm, the after part of the blade will be twisted round by the resist-
ance of the water, the whole assuming the shape of a screw; this
will stretch the india rubber, or in the case of thin flexible plates,
will twist them and make them slide from over each other, the elas-
ticity of the india rubber, or the spring of the plates, which should
be of steel, bringing the blade to its normal configuration when the
power ceases. Such normal configuration being that of a flat blade
lying in a plane parallel to the ship's axis. If the arms pass through
the centre of an enlarged boss, slots must be provided in the boss to
allow of the twisting round of the rods.