IMPROVEMENTS IN PROPELLERS FOR SHIPS AND OTHER VESSELS
Year: 1873

page_text: LETTERS PATENT to Frederick Harris, of the Firm of Harris and
Mills, of 85, Southampton Buildings, in the County of Middlesex,
Patent Agent, for the Invention of "IMPROVEMENTS IN PROPELLERS FOR
SHIPS AND OTHER VESSELS."-A communication from abroad by
Newton Alexander Patterson, of Cleveland, in the County of
Bradley, and State of Tennessee, United States of America.
PROVISIONAL SPECIFICATION left by the said Frederick Harris at the
Office of the Commissioners of Patents, with his Petition, on the
7th August 1878.
I, FREDERICK HARRIS, of the Firm of Harris and Mills, of 85, South-
ampton Buildings, in the County of Middlesex, Patent Agent, do hereby
- declare the nature of the said Invention for "IMPROVEMENTS IN PROPELLERS
*FOR SHIPS AND OTHER VESSELS," a communication to me from abroad by
Newton Alexander Patterson, of Cleveland, in the County of Bradley,
and State of Tennessee, United States of America, to be as follows:―
The primary object of this Invention is to produce a propellor adapted

page_text: by the peculiar formation of its blades to impart to the water in which
it turns a longitudinal motion in a direction coincident or parallel with
the axis of the screw, avoiding lateral or tangential motion; to this
end the blades are constructed of concavo-convex form.
To render the concavo-convex blades more effective it is preferred to
form them with a helicoidal curvature, and to mount them upon the
ends of arms to increase their radius.
A rearward projection may also be formed upon each of the blades,
which under some modifications of the Invention is found to aid in
restricting the impulse imparted to the water to a longitudinal direction
coincident with the line of motion of the vessel.
•
It is believed that the most effective shape of propelling blade is
produced by forming it with a centre of concavity at or near the forward
or cutting edge and at about the centre of the said edge; from this
point the surface has a curvature of about equal radius in each direction,
inward, outward, and rearward for a certain distance, beyond which the
curvature varies in blades of different outline.
Blades designed for rapid motion have their greatest length in a
direction radial to the shaft.
Blades designed to exert great power with comparatively slow move-
C
SPECIFICATION in pursuance of the conditions of the Letters Paten
filed by the said Frederick Harris in the Great Seal Patent Office
on the 7th February 1874.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, FREDERICK 2
HARRIS, of the Firm of Harris and Mills, of 35, Southampton Buildings,
in the County of Middlesex, Patent Agent, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Seventh day of August, in the year
of our Lord One thousand eight hundred and seventy-three, in the 3
thirty-seventh year of Her reign, did, for Herself, Her heirs and
successors, give and grant unto me," the said Frederick Harris, Her

page_text: .
-
special license that I, the said Frederick Harris, my executors, admi
nistrators, and assigns, or such others as I, the said Frederick Harris,;
my executors, administrators, and assigns, should at any time agree
with, and no others, from time to time, and at all times thereafter
during the term therein expressed, should and. lawfully might make,
use, exercise, and vend, within the United Kingdom of Great Britain
and Ireland, the Channel Islands, and Isle of Man, an Invention for
"IMPROVEMENTS IN PROPELLERS FOR SHIFS AND OTHER VESSELS," (a communica-
tion to me from abroad by Newton Alexander Patterson, of Cleveland;
in the County of Bradley, and State of Tennessee, United States of
America, upon the condition (amongst others) that I, the said Frederick
Harris, my executors or administrators, by an instrument in writing
under my, or their, or one of their hands and seals, should particularly
describe and ascertain the nature of the said Invention, and in what
manner the same was to be performed, and cause the same to be filed
in the Great Seal Patent Office within six calendar months next and
immediately after the date of the said Letters Patent.
. NOW KNOW YE, that I, the said Frederick Harris, do hereby
declare the nature of the said Invention, and in what manner. the
same is to be performed, to be particularly described and ascertained
in and by the following statement thereof, that is to say :--
The primary object of this Invention is to produce a propellor adapted
by the peculiar formation of its blades to impart to the water in which
it turns a longitudinal motion in a direction coincident or parallel with
the axis of the screw, avoiding lateral or tangential motion; to this.end
the blades are constructed of concavo-convex form.
To render the concavo-convex blades more effective. it is preferred to
form them with a helicoidal curvature, and to mount them upon the
ends of arms to increase their radius.
፡
À rearward projection may also be formed upon each of the blades,
which under some modifications of the Invention is found to aid in
restricting the impulse imparted to the water to a longitudinal direction
coincident with the line of motion of the vessel.
..It is believed that the most effective shape of propelling blade is pro-
3 duced by forming it with a centre of concavity at or near the forward or
cutting edge, and at about the centre of the said edge; from this point
:

page_text: the surface has a curvature of about equal radius in each direction,
inward, outward, and rearward, for a certain distance, beyond which the
curvature varies in blades of different outline.
Blades designed for rapid motion have their greatest length in a
direction radial to the shaft.
Blades designed to exert great power with comparatively slow move-
ment are longer in a direction perpendicular to the radius.
The helicoidal bladed screw and blades of simple spiral form lose much
of their effectiveness by reason of lateral displacement of the water.
This fact is demonstrated by the extent by which the water is moved by
such screws in lines divergent from that of the vessel's motion. By
constructing the blades in concavo-convex form it is found that the
screw is adapted to impel the water in a line coincident with that of the
motion of the vessel, and it has been found practicable to combine this
concavo-convexity with a helicoidal curvature so as to avail the well
known effective and easy rotation of the helicoidal bladed screw.
The Invention admits of embodiment under a variety of modified
forms, some of which will be described for the purpose of illustration.
And in order that the said Invention may be more clearly understood
and readily carried into effect I will proceed, aided by the accompanying
Drawings, more fully to describe the same.

page_text: Figures 9 and 10 are respectively a face view and a section of another
modification.
In all the Figures a is the front or cutting edge of the blade, and o
the back edge, considered in respect to its forward rotation; c is the
point of central concavity on the face of the blade, which it will:be
observed is in most of the modifications located at or near the cutting
edge. The term centre of concavity may be defined as a point from
which the surface has a curvature of equal pitch or radius in each
direction, inward, outward, and rearward (as illustrated by radial lines f
in Figure 1), for some distance, as for example to the line g, Figure 1.
Locating this point o at or near the cutting edge of the blade prevents
pressure being produced on the back of the blade either by the rotary
movement of the screw or by the forward movement of the vessel
through the water.
The Invention also admits of combining the advantages of a concavo-
convex form which perfectly prevents the imparting of lateral or
tangential motion to the water with a helicoidal form in the entire
blade which is the most effective for propulsion.
The concavo-convex blades may be connected directly to the hub d,
but it is preferred to form them with arms e of any desired length.
The propellor may consist of two, three, or four blades, and may
cast in one piece or separately, as preferred.
be
The most advantageous angle of the blade with the plane of motion
will vary according to speed, and will be determined by experiment.
5 The circumferential width of the blades or the extent of their pro-
jecting lobes will vary with the number of blades on a shaft and with
the size of the wheel and the rapidity of its intended rotation.
In wheels of small size having a rapid rotation the curvature of the
blades toward the periphery is. more abrupt or rapid than in larger
O wheels having a slower movement.
5
The blades are to be arranged spirally on the shaft, if preferred,
instead of in one plane. The spaces between the arms of the blades
directly around the shaft form throats to permit the free escape of the
water longitudinally without injurious reaction.
In Figure 1 the periphery or outer edge of each blade is concentric
(or nearly so) with the axis of rotation.