IMPROVEMENTS IN SCREW PROPELLERS
Year: 1876

page_text: PROVISIONAL SPECIFICATION left by Henry Samuel Eyre at the Office of
the Commissioners of Patents on the 25th February 1876.
HENRY SAMUEL EYRE, of No. 9, Circus Road, Saint John's Wood, in the County
of Middlesex. "IMPROVEMENTS IN SCREW PROPELLERS."
This Invention of improvements in screw propellers relates to screw propellers of
the class in which the blades are arranged in conjunction with suitable actuating
apparatus for turning the blades upon their own axes by means of racks taking
into teeth formed at the roots of the blades, so that the pitch of the blades may be
altered or the blades reversed without stopping or reversing the engines, whereby
the propeller shaft is driven.
My improvements in screw propellers of the class above referred to consist in
certain arrangements for actuating the racks from the deck or other part of the
vessel as required for altering the pitch or direction of the blades; also in methods
of locking the blades in the positions to which they are so moved.
For moving the racks backward and forward in a line parallel with the axis
of the propeller shaft so that the teeth of the racks acting against teeth on the
roots of the blades shall turn the latter, I employ the following arrangement:-1
connect the racks together by a frame or plate, a central opening through which is
of circular form. The inner periphery of this plate takes into a circular groove
formed in and around the periphery of a compound ring composed of suitable plates
or parts bolted or secured together. At the inner periphery of this compound ring
I form recesses to receive the ends of two or more trunnion-shaped projections of a
nut, which fits on a screwed shaft capable of being rotated from the deck or other
part of the vessel by a worm and wheel or otherwise, but this screwed shaft is
arranged to be incapable of longitudinal or end movement. The racks with their
connecting frame, compound ring, and nut, are arranged within the hollow boss of
the propeller, and the screwed shaft passes into the boss through a stuffing box, one
part of which projects into the hollow boss in the form of a tube, having formed in
it longitudinal slots through which the projections of the nut pass, so that by
turning the screwed shaft the nut and with it the compound ring, frame, and racks
may be moved in either direction longitudinally, but the nut cannot be rotated by
the screwed shaft.
One method of locking the blades in either of their two extreme positions
according to my Invention is as follows:-Only a portion of the periphery of each

page_text: blado root is formed with teeth; the outer extremities of these teeth are of the same
radius from the axis of the blade root as is the plain circular part of the root. On
this plain circular part I form at each side of the series of teeth flat portions so
arranged that when the racks have been moved right home in either the forward
or backward direction, one of the flat parts of the boss will bear against a corre-
sponding part of the neighbouring rack, thus the root will be as it were jammed up,
and the blade will be held in the position to which it has been moved. The blade
root with its flat or plane parts may be made in various forms; the flat parts may
be tangential to the periphery of the blade root, and the racks may be made with
inclined surfaces, so that the flat parts of the roots may have a wedge-like
action.
According to another method of locking the blades each blade root is made with
a circular flange formed on a part of its circumference with ratchet teeth to receive
a pawl having its axis in the body of the boss; the pawl is pressed towards the
flange of the blade root by a spring, and is moved out of gear by the movement of
the free end of a small lever having its fulcrum on the boss, and provided with a
projection which acts upon a cam-shaped part of the pawl, the free end of the lever
being moved as required by pins or projections on the flange.
It will be evident that my improvements may be carried out in various forms
without departing from their distinctive character.