Improvements in or connected with Screw Propellers.
Year: 1892

page_text: Date of Application, 5th Jan., 1892
Complete Specification Left, 5th Oct., 1892-Accepted. 5th Nov.
1802
PROVISIONAL SPECIFICATION.
Improvements in or connected with Screw Propellers.
I, GEORGE FREDERICK ASKEW of 14 Cromwell Terrace Galbraith Street
Poplar in the County of Middlesex Engine Fitter do hereby declare the nature
of this invention to be as follows:-
.
My invention relates to improvements upon an invention for which Letters Patent
were granted to me dated the 8th day of December 1884 No. 16122 entitled
"Improvements in or applicable to Screw Propellers" and which had for its
object to reduce or counteract the skin friction of the propeller blades in passing
through the water and my present invention has for its object primarily to improve
various details of construction of the apparatus employed for that purpose.
In carrying my present invention into effect I employ a channel in the leading
edge of each of the propeller blades which communicates with a longitudinal passage
formed through the propeller shaft which communicates with radial passages formed
between the faces of the shaft couplings thus putting the channels in the leading
edge of the propeller blades in communication with the chamber that surrounds the
shaft couplings as described in my former Specification filed in pursuance of the
said former Letters Patent.
One of my present improvements however consists of forming the channel near
the leading edge of the propeller blade but in the driving face thereof and with its
side open and I form the narrow opening in the propeller blade by means of a
fitting piece that projects across and beyond the channel and with its leading part
securely rivetted or screwed to the leading part of the propeller blade and I form
this fitting piece with its after edge square so that as the water rushes by the over-
lapping square edge of the fitting piece it will leave a cavity into which the air will
be drawn, and from this cavity it will be drawn and distributed by the passing
water in a thin film over the entire driving faces of the propeller blades.
As it is most important to obtain a very nice adjustment of the narrow openings
in the blades of the propeller I can by means of the above described fitting piece
arrive at the desired exactness and by forming the channels in the leading edge of
the propeller blade open on the driving face they are easy to cast or forge or machine
out of the solid.
In some cases I form the before mentioned cavity by bevelling the overlapped
portion of the blade and making the after edge of the fitting piece square as before
described.
Another improvement consists in employing a half cup or air catcher behind each
of the radial passages that is to say the radial passages drilled in between the faces
of the couplings these half cups gather the air as the shaft revolves and direct it
nto the radial passages and so to the propeller.
Another improvement consists in conducting the pipe that supplies the chamber
hat surrounds the shaft coupling up to a cowl placed on deck so that it is open to
he atmosphere, and as it is very important that the supply of air to the propeller
hould be under control I place a cock or valve at some part of this pipe between
he cowl and the chamber by which means the supply of air to the propeller can be
gulated at will.
I use air under pressure to clear the chamber and channels of water when the ship
st starts and after she has got up her speed I simultaneously cut off the pressure
id open the chamber to the atmosphere so that as the propeller revolves it will.
aw the air in between the blades and the water as before described.
By the arrangement of parts hereinbefore described I obtain a nunatical

page_text: applying a film of air to the blades of a screw propeller and thus reducing the
friction thereof in passing through the water.
Dated this 5th day of January 1892.
WHITE & WOODINGTON.
27, Southampton Buildings, London, Agents.
COMPLETE SPECIFICATION.
Improvements in or connected with Screw Propellers.
I, GEORGE FREDERICK ASKEW of 14 Cromwell Terrace Galbraith Street;
Poplar in the County of Middlesex Engine Fitter do hereby declare the nature of
this invention and in what manner the same is to be performed to be. particularly
described and ascertained in and by the following statement :-
My invention relates to improvements upon an invention for which Letters
Patent were granted to me dated the 8th day of December 1884 No. 16122, entitled
Improvements in or applicable to Screw Propellers" and which had for its object
to reduce or counteract the skin friction of the propeller blades in passing through
the water, and my present invention has for its object primarily to improve various
details of construction of the apparatus employed for that purpose.
In carrying my present invention into effect I employ a channel in the leading
edge of each of the propeller blades which communicates with a longitudinal passage
formed through the propeller shaft which communicates with radial passages formed
between the faces of the shaft couplings, thus putting the channels in the leading
edge of the propeller blades in communication with the chamber that surrounds the
shaft couplings as described in my former Specification filed in pursuance of the said
former Letters Patent.
One of my present improvements however, consists in forming the channel near
the leading edge of the propeller blade but in the driving face thereof, and with its
side open, and I form the narrow opening in the propeller blade by means of a
fitting piece that projects across and beyond the channel and with its leading part
securely rivetted or screwed to the leading part of the propeller blade, and I form
this fitting piece with its after edge square so that, as the water rushes by the over-
lapping square edge of the fitting piece, it will leave a cavity into which the air will
be drawn, and from this cavity it will be drawn and distributed by the water in a
thin film over the entire driving faces of the propeller blades.
As it is most important to obtain a very nice adjustment of the narrow openings
in the blades of the propeller, I can, by means of the above described fitting piece
arrive at the desired exactness, and by forming the channels in the leading edge of
the propeller blade open on the driving face, they are easy to cast or forge or
machine out of the solid.
In some cases I form the before mentioned cavity by bevelling the overlapped
portion of the blade, and making the after edge of the fitting piece square, as before
described.
Another improvement consists in employing a half cup or air catcher behind each
of the radial passages, that is to say the radial passages drilled in between the faces
of the couplings, these half cups gather the air as the shaft revolves and direct it
"into the radial passages, und so to the propeller.
Another improvement consists in conducting the pipe that supplies the chamber
that surrounds the shaft coupling up to a cowl placed on deck so that it is open to
the atmosphere, and as it is very important that the supply of air to the propeller
should be under control, I place a cock or valve at some part of this pipe between
the cowl and the chamber, by which means the supply of air to the propeller can
be regulated at will.
I use air under pressure to clear the chamber and channels of water when the ship
fi st starts, and after she has got up her speed, I simultaneously cut off the pressure

page_text: and open the chamber to the atmosphere, so that as the propeller revolves it will
draw the air in between the blades and the water as before described.
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.
To describe the same.
DESCRIPTION OF THE DRAWINGS.
Figure 1 is a side elevation partly in section of part of a ship or vessel having my
improvements applied thereto.
Figure 2 is a transverse section drawn to an enlarged scale, of one of the blades
of the screw propeller illustrating more clearly the application thereto of my fitting
piece.
Figure 3 is a similar view to Figure 2, but with the fitting piece removed.
Figure 4 is a similar view to Figure 2, but representing a slight modification.
Figure 5 is a side view drawn to an enlarged scale of the shaft coupling and con-.
nected parts, and
Figure 6 is an end view thereof.
In the several figures like parts are indicated by similar letters of reference.
a represents the hull of the vessel, represents the screw propeller, c represents
the propeller shaft and d represents a chamber surrounding the shaft coupling.
C
In the driving face of each blade 6 of the propeller near the leading edge thereof
and with its side completely open is formed a channel which connects with a
conduit c' formed in the propeller shaft c for the purpose hereinafter described.
In connection with the channel in order to form the narrow opening 1 employ
a fitting piece 62 which at its leading part is securely fixed by rivetting or screwing
to the propeller blade, and which at its rear part projects across and beyond the
channel so as to form the narrow opening between the inner face of the fitting
piece and the driving face of the blade b.
The after edge of the fitting piece is formed square so that as the water rushes
by, or the blade passes through the water the square edge of the fitting piece will
leave a cavity into which the air will be drawn and distributed by the water in a
thin film over the entire driving face of the propeller blade.
of
It is most important to obtain a very nice adjustment of the narrow opening
the blade band it will be seen that by means of the above described fitting piece
I can arrive at the desired exactness and by forming the channel in the leading
edge of the propeller blade & completely open on the driving face of the blade it
is easy to cast or forge or machine out of the solid.
In the example given at Figure 4 I have shown a modified method of construc-
tion in which the fitting piece 62 is countersunk in the face of the propeller blade b
whilst the required narrow opening is formed by bevelling the overlapped portion
of the blade the after edge of the fitting piece being formed square as herein-
before described but this arrangement in my opinion is inferior to that represented
in the previous figures in which the narrow opening is parallel with the face of
the .blade b.
The faces of the half couplings of the shaft c are formed with radial passages c
therein which communicate with the longitudinal passage or conduit in the
shaft c as described in the Specification of the herein before recited Letters Patent
but according to my present invention I arrange a half cup or air catcher c upon
the coupling behind each of the radial passages and these half cups c* gather the
air as the shaft c revolves and direct it into the radial passages c² and so through
the longitudinal passage or conduit c' to the propeller blades b.
The shaft coupling is enclosed within an air chamber d as heretofore proposed
by me but I now conduct the necessary supply of air to the chamber d by means of
a cowl or windsail d' which is connected with the chamber d my means of a pipe d'
and as the vessel steams ahead catches the air and carries it to the chamber d.
As it is very important that the supply of air to the propeller blades & should be
1

page_text: under control I place a cock or valve d³ in the pipe d' by which means the supply
of air to the propeller 6 can be regulated at will.
In order to clear the chamber d and channels c¹ of water when the ship first
starts I provide a pipe e which connects with the pipe d' below the cock or
valve d and I close the cock or valve and force air through the pipe e until
the ship has got up her speed when I simultaneously cut off the air pressure
and open the cock or valve d³ thus opening the chamber d to the outer atmo-
sphere so that as the propeller revolves a film of air will be drawn in between
the blades b thereof and the water in the manner herein before described.
By the arrangement of parts herein before described I obtain a practical means
of applying a film of air to the blades of a screw propeller and thus reducing the
friction thereof in passing through the water.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is
1. In combination with a screw propeller of the character hereinbefore referred
to, an open sided channel formed in the driving face of the propeller blade, and
a separate fitting piece fixed to the blade and so proportioned as to overlap the face
of the blade for some distance beyond the channel, and together therewith form
a long narrow opening parallel with the face of the blade and means for con-
ducting air to the channel substantially as herein shown and described and for
the purpose stated.
2. In combination with a screw propeller of the character hereinbefore referred
to, a fitting piece formed with a square after edge and forming a long narrow
opening parallel with the face of the blade and near to the leading edge thereof,
and means for conducting air to such narrow opening substantially as herein
shown and described and for the purpose stated.
3. In combination with a screw propeller of the character herein before referred
to, a shaft formed with a longitudinal passage therein, a coupling provided with
several radial passages communicating with the longitudinal passage and a half
cup or air catcher fixed to the coupling at the rear of each radial passage sub-
stantially as herein shown and described and for the purpose stated.
4. In combination with a screw propeller of the character hereinbefore referred
to, a shaft formed with a longitudinal passage therein, a coupling provided with
several radial passages communicating with the longitudinal passage, a half cup
or air catcher fixed to the coupling at the rear of each radial passage, a case or
chamber surrounding the coupling and an air supply pipe leading into the chamber
and provided with a regulating cock or valve substantially as herein shown and
described and for the purpose stated.
Dated this 5th day of October 1892.
WHITE & WOODINGTON,
27, Southampton Buildings, London, Agents.