IMPROVEMENTS IN Steam Ships, aND SCREW PROPELLERS FOR THE SAME.
Year: 1873

page_text: LETTERS PATENT to Robert Griffiths, of Bayswater, in the County
of Middlesex, Engineer, for the Invention of "IMPROVEMENTS IN
Steam Ships, aND SCREW PROPELLERS FOR THE SAME.
"
STEAM SHIPS, AND SCREW PROPELLERS FOR THE SAME.'
"
PROVISIONAL SPECIFICATION left by the said Robert Griffiths at
the Office of the Commissioners of Patents, with his Petition, on
the 22nd November 1873.
I, ROBERT GRIFFITHS, of Bayswater, in the County of Middlesex,
Engineer, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN STEAM SHIPS, AND SCREW PROPELLERS FOR THE SAME," to be
as follows:-
This Invention relates first to improvements in the construction of
steam ships or vessels of the character described in the Specifications of
Letters Patent granted to me dated 7th November 1871, No. 2991, and
19th April 1872, No. 1164.
MI

page_text: described, consist in forming them with a large extent of propelling
surface at the periphery, and decreasing so as to offer as little resistance
as possible, consistent with strength towards the axis.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Robert Griffiths in the Great Seal Patent Office
on the 22nd May 1874.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ROBERT
GRIFFITHS, of Bayswater, in the County of Middlesex, Engineer, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twenty-second day of November, in the
year of our Lord One thousand eight hundred and seventy-three, in the
thirty-seventh year of Her reign, did, for Herself, Her heirs and suc-
cessors, give and grant unto me, the said Robert Griffiths, Her special
license that I, the said Robert Griffiths, my executors, administrators,
and assigns, or such others as I, the said Robert Griffiths, 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 STEAM SHIPS, AND SCREW PROPELLERS FOR THE SAME," upon the condition
(amongst others) that I, the said Robert Griffiths, 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 Robert Griffiths, 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 :-
This Invention relates first to improvements in the construction of
steam ships or vessels of the character described in the Specifications of

page_text: Letters Patent granted to me dated 7th November 1871, No. 2991, and
19th April 1872, No. 1164.
In practice the effective power of screw propellers in general and also
when arranged to act as described in the Specifications above referred to,
does not propel the ship at a relative speed in proportion to the power
exerted and indicated by the engines employed for driving such pro-
pellers. Now I have discovered that a considerable portion of this loss
of power is due to the deficiency of the supply of water to the screw
propeller in the tunnels or opening in which such propellers are arranged
to revolve in order to propel the vessel..
In order to supply the screw propeller with a sufficient supply of
water to act upon in propelling a ship or vessel, according to the first
part of my present improvements I arrange a lip scoop or projection A¹
(as represented in Figures 1 and 2 Sheet 1 of the Drawings hereunto
annexed) at the mouth or entrance to the stern tunnel A, in order to
gather and conduct the water in a sufficient volume into the tunnel to
supply the screw propeller B which is arranged to revolve therein.
The entrance to the bow tube or tunnel C, as shown in Figures 3 and 4,
sheet 1 of the Drawings, is also formed according to my improvements
with an enlarged funnel mouth C¹ or other suitably shaped enlarged?
entrance of greater area than the circumference of the passage where
the screw propeller D is arranged to revolve, in order to afford an
increased supply of water thrus conducted to the bow propeller than it
can obtain when the mouth or entrance to the tunnel is of the same area
or thereabouts as the circumference of the screw propeller acting
therein.
I would remark that when two screw propellers are arranged to act
simultaneously in tunnels, one at the bow and the other at the stern of
the vessel, there is in that case no advantage in employing the lip scoop
or conductor A¹ to conduct the water to the screw propeller at the stern
of the vessel, as it obtains a sufficient supply of water through the
increased speed of the ship, which will be obtained by using both screws,
thereby causing more water to pass through the tunnels, therefore when
the two screws are in action I either remove or raise the lip or scoop A¹,
out of action up to the level of the mouth or entrace to the tunnel.
For this purpose the lip A' is attached by a hinge or joint to the mouth
of the tunnel, as shown at Figures 9 and 10, Sheet 1, to admit of its being

page_text: raised or lowered from time to time as may be required, the lip or scoop
A' being lowered when the stern screw only is in action to propel the
vessel.
Figures 5 and 6, Sheet 1, represent twin screws B, B, arranged in
accordance with this part of my improvements in tunnels A, A, formed;
by casings applied below the counter on each side of a ship or vessel,
with a lip scoop or projection A¹ for conducting the water to the screws,
as previously described with reference to Figures 1 and 2 of the Drawings,
although in this arrangement the lip A' may be dispensed with owing to
the increased speed given to the vessel by the double or twin screws.
The tunnel or casing for carrying the bow screw and supplying it with
water may if desired be formed partly or wholly in front of the stern
post, and also if desired a similar arrangement may be applied to the
stern screw, thereby avoiding or dispensing with the necessity of
altering or cutting away part of the hull of the vessel but little if at
all.
According to another part of my improvements the lower part of the
tunnels or channels in which the screw propellers are arranged to revolve
either at the bow or at the stern of the vessel may be left open from the
point of entrance to where the water is discharged, provision being made.
by widening the mouth of the opening to the tunnels or channels, so as
to increase the supply of water to the propellers.
Figures 7 and 8 show the stern portion of the hull of a vessel arranged
in accordance with this part of my improvements; A being the tunnel
or channel the under side of which is open to the water, the screw
propeller being arranged to revolve either within the mouth of the
tunnel or channel or just at the back or outer end thereof, as represented
in the Drawing.
In accordance with another part of my improvements, the screw
propeller may if desired be placed and arranged to revolve in a tunnel
about midship of the vessel, the entrance to the tunnel being formed
with a lip scoop or other suitable contrivance for the purpose of con-
ducting and increasing the supply of water to the screw propeller as
previously described, the water being by preference discharged under-
3 neath the vessel.
Figures 9 and 10 show a side view of part of the hull of a vessel

page_text: the vessel, and having a lip or scoop A¹ applied to the mouth or
entrance of the tunnel to conduct the water into it as previously
described.
The second part of my improvements relates to screw propellers which
are arranged to revolve in tunnels or channels formed in the bow or
stern or amidship of a vessel as previously described, by forming such
screws with a large extent of propelling surface at the periphery, and
decreasing so as to offer as little resistance as possible consistent with
strength towards the axis.
Figures 11 and 12 show side and end views of a screw propeller formed in
accordance with this part of my improvements which I prefer to employ
when two screw propellers are employed and acting simultaneously
in tunnels or channels formed one at the bow and the other at the stern
of the vessel. But when the propelling power is applied to a tunnel or
channel formed in the stern of a vessel only, then I prefer to employ in
accordance with this part of my improvements a 'screw propeller of
parallel form and of increasing pitch from end to end, the screw being
mounted so as to revolve in the parallel part of the tunnel A, as
represented in Figures 13 and 14, Sheet 2 of the Drawings hereunto
annexed, the pitch of the screw B increasing from the point of entrance
to the point of exit or discharge of the column of water at the stern of
ship or vessel, by which arrangement the screw propeller is supplied
with a sufficient quantity of water without the necessity of applying a
lip scoop or other contrivance to the mouth of the tunnel, as described
with reference to the first part of my improvements.
Figures 15 and 16 represent a screw propeller B of increasing pitch,
and of taper form arranged to revolve in a tunnel A at the stern of the
vessel, the tunnel A being tapered to correspond with the form of the
screw B in accordance with this part of my improvements. Or the
screw may be of parallel form but corresponding in circumference with
the smaller and outer end of a taper tunnel.
Figures 17 and 18 represent a screw propeller of increasing pitch and
parallel from end to end, the boss of the screw being tapered and
increasing in circumference from the point at which the water enters to
the point at which it is discharged from the stern of the vessel, by which a
arrangement a similar result is obtained to that described with reference
to Figures 15 and 16.in accordance with this part of my improvements.

page_text: A similar result is obtained to that previously described with reference
to Figures 15, 16, 17, and 18, by making the screw propeller of
increasing pitch, and gradually thickening the blade of the screw from
the point where the water enters to the point of exit, as represented in
Figures 19 and 20, Sheet 2 of the Drawings. Or a correspondingly
advantageous result may be obtained by dividing the screw propeller
into two parts B and B', as represented in Figures 21 and 22, Sheet 2 of
the Drawings, the part B¹ of the screw being of faster pitch than the
part B, stationary or fixed reactionary screw blades B³ being placed
between the two parts of the screw in order to take the twist or rotary
movement out of the column of water as it passes from the screw B to
the screw B¹.
I would remark that the outlet end of the stern tunnels in each of the
arrangements previously described may be widened or made bell mouthed
to permit the water to escape freely as it is discharged from the screw
propeller at the stern of the vessel.
Having thus described the nature of my improvements and the
manner of performing or carrying the same into practice, I would have
it clearly understood that I do not intend to confine myself to the exact
details herein-before described so long as the essential and characteristic
features of my Invention are retained, but what I claim is,-
First. The arrangement and application of a lip scoop or other
equivalent contrivance to the mouth or entrance to a tunnel formed at
the stern of a steam ship or vessel for the purpose of conducting a
sufficient quantity of water to supply the screw propeller arranged to
revolve therein, substantially in the manner herein-before described with
reference to Figures 1, 2, 5, 6, 9, and 10 of the Drawings, hereunto
annexed.
Secondly. I claim the improved construction of the bow tunnel in
which the screw propeller revolves by enlarging or forming it funnel or
bell mouthed to increase the supply of water to the screw, substantially
in the manner herein-before described with reference to Figures 3 and 4
of the Drawings hereunto annexed.
Thirdly. I claim the method of arranging the screw propeller in a
channel open on its under side, formed in the stern of a steam ship or
vessel, substantially in the manner herein-before described with reference
to Figures 7 and 8. of the Drawings hereunto annexed.

page_text: Fourthly. I claim the improved construction of screw propellers,
which are arranged to revolve and act in tunnels or channels formed in
the bow or stern of a steam ship or vessel, substantially in the manner
and for the purpose as herein-before described with reference to Figures
11 and 12 of the Drawings hereunto annexed.
I also claim the improved construction of screw propellers and the
method of arranging them so as to act advantageously in tunnels formed
in the stern of a steam ship or vessel, substantially in the manner and for
the purpose herein-before described with reference to Figures 15, 16, 17,
18, 19, 20, 21, and 22 of the Drawings hereunto annexed.
In witness whereof, I, the said Robert Griffiths, have hereunto
set my hand and seal, this Twenty-second day of May, in the
year of our Lord One thousand eight hundred and seventy-four.
Witness,
J. G. TONGUE,
Patent Agent,
ROB™. GRIFFITHS. (L.S.)
34, Southampton Buildings,
Chancery Lane,
. W.C.