IMPROVEMENTS IN PROPELLERS FOR STEAM SHIPS OR VESSELS
Year: 1878

page_text: PROVISIONAL SPECIFICATION left by John Lorimer Corbett and David
Hosic at the Office of the Commissioners of Patents on the 30th March
1878.
JOHN LORIMER CORBETT and DAVID HOSIE, both of Glasgow, in the County of
Lanark, North Britain. "IMPROVEMENTS IN PROPELLERS FOR STEAM SHIPS OR
VESSELS."
This Invention has reference to certain improvements in the construction and
arrangement of the propelling surfaces, or floats and blades of paddle wheels and
screw propellers for steam ships or other vessels, which it is believed will propel
the vessels faster and steadier for the power and fuel expended than the paddles
and screw propellers as heretofore constructed.
And the nature and novelty of the Invention or improvements consist in setting
the vanes or floats and screw blades at a considerable angle (straight or curved) to
the line of the revolving shaft or wheel and the line of the ship's motion, so that the
water forced or acted upon would glide off the one blade and rush against and
consequently be forced or struck by the next propelling blade or surface coming
round. Each succeeding or alternate blade thus acts on water rushing towards or
in the reverse direction to the propeller's motion, which gives a greater resistance or
reverse action for the propulsion of the ship, and less front and back water in striking
and lifting it while entering and leaving the water than when these acting surfaces,
as heretofore, are made only to act on still water or water moving in the saine
direction as the propelling surfaces.
One construction or arrangement for carrying out these improvements as applied
to a paddle wheel for steam ships is to make each paddle in the form of a curved
Vor W (thus V, W,) in edge view circumferentially, and of sheet iron or boiler
plate, as broad as the depth it is desired to make the paddles radially, and to fix
each radial edge of the plates at the open base of the angles to an arm of the pro-
peller, with the apexes of the angles projecting towards and set to overlap cach
other in the centre of the opposite angular spaces (thus ), the outer and inner
surfaces of the alternate plates or vanes acting and propelling the ship forwards
backwards according to the direction in which the paddle is turned.

page_text: When applied to screw propellers the vanes or blades would all be set on their
boss to the same curvilinear angle or increasing pitch as the blades of screw pro-
pellers are; but by these improvements each alternate blade would project in
advance of and behind each other, that is, each alternate blade would have its
radial axis or stem (passing through the centre of their boss) placed, say, one-third
and two-thirds respectively and alternately from the advanced and rear acting
edges of their blades, so that the alternate blades which acted first on the still water
would deliver the water in a forcible stream off their acting surface at their rear
edge on to the middle of the succeeding intermediate blades of the propeller, which
would thus be re-acting or propelling against a more resisting or reverse acting
current, instead of water flowing in the direction in which the blades are acting,
much similar to the action already described in reference to paddle floats, although
the alternate angles of these are described and set in reverse directions beyond each
other.