IMPROVEMENTS IN GOVERNING APPARATUS FOR SCREW PROPELLER ENGINES
Year: 1871

page_text: LETTERS PATENT to David John Dunlop, of Port Glasgow, in the
County of Renfrew, North Britain, Engineer & Shipbuilder, for
the Invention of "IMPROVEMENTS IN GOVERNING APPARATUS FOR SCREW
PROPELLER ENGINES."
Sealed the 22nd August 1871, and dated the 30th March 1871.
PROVISIONAL SPECIFICATION left by the said David John Dunlop
at the Office of the Commissioners of Patents, with his Petition,
on the 30th March 1871.
I, DAVID JOHN DUNLOP, of Port Glasgow, in the County of Renfrew,
North Britain, Engineer & Shipbuilder, do hereby declare the nature
of the said Invention for "IMPROVEMENTS IN GOVERNING APPARATUS Por
SCREW PROPELLER ENGINES," to be as follows, that is to say :-
This Invention has for its object to prevent screw propeller engines
from "
racing," or acquiring an injurious speed when the propeller is
raised more or less out of the water by the pitching of the ship or
otherwise; and it consists in deriving the desired governing action
in an improved manner from the variation of relative level of the water

page_text: in a well or chamber formed in the stern of the ship. This well has its
bottom open to the sea, whilst from its upper end a pipe, formed
if necessary with a syphon bend to prevent water passing over, is led
to a cylinder or vessel in the engine room. The water when falling
or rising in the well acts on air in the upper part of it, and the action
is transmitted through the pipe to the cylinder, wherein it takes effect
on a diaphragm or piston. A rod is fixed to and moved by the diaphragm
or piston, and acts on the throttle valve or expansion gear of the engines,
either directly or indirectly. Adjustable oppositely acting springs are
applied to the rod to assist its return to a middle point after it has been
moved in either direction. The well at the stern is by preference made
conical, or otherwise varying in cross sectional area, and increasing
downwards so that a lowering of the relative water level due to the
elevation of the stern has a comparatively small effect at first, or if of
small extent, but a rapidly increasing one if the lowering continues
or becomes excessive. The action of the apparatus may be regulated
by pumping air into or out of the cylinder.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said David John Dunlop in the Great Seal Patent
Office on the 29th September 1871.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, DAVID
JOHN DUNLOP, of Port Glasgow, in the County of Renfrew, North
Britain, Engineer and Shipbuilder, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Thirtieth day of March, in the year
of our Lord One thousand eight hundred and seventy-one, in the thirty-
fourth year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said David John Dunlop, Her special
licence that I, the said David John Dunlop, my executors, adminis-
trators, and assigns, or such others as I, the said David Jolin Dunlop,
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

page_text: "IMPROVEMENTS IN GOVERNING APPARATUS FOR SCREW PROPELLER ENGINES,"
upon the condition (amongst others) that I, the said David John
Dunlop, 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 David John Dunlop, do hereby
declare the nature of my said Invention, and in what manner the same
is to be performed, to be particularly described and ascertained in and
by the following statement in writing, reference being had to the
accompanying Drawings, that is to say :-
My said Invention has for its object to prevent screw propeller
engines from "racing," or acquiring an injurious speed, when the
propeller is raised more or less out of the water by the pitching of the
ship or otherwise, and it consists in deriving the desired governing
action in an improved manner from the variation of the pressure or
relative level of the water in a well or chamber formed in the stern of
the ship.
And in order that my said Invention and the manner of performing
the same may be properly understood I hereunto append a Sheet of
explanatory Drawings to be hercin-after referred to and showing my
improved apparatus and the manner of applying it.
Figure 1 is a transverse vertical section of the stern part of a screw
steamer where the well or chamber 1 is fitted; Figure 2 is a longi-
tudinal vertical section, in part corresponding to Figure 1, and in part
showing the engine room 2 or other more forward compartment of the
vessel.
Figures 3 and 4 are enlarged sectional elevations of two slightly
modified forms of the part of the apparatus situated in the engine
room.
The chamber 1 is arranged with its bottom end in communication
with the sea by a pipe 3 provided with a valve 4 for closing it when
5 required, and with a nose cock 5 for drawing off water when it is
desired to get the chamber 1 full of air. From the top of the chamber 1
a pipe 6, commencing with an inverted siphon bend to prevent water

page_text: passing over, is led to a vessel 7 in the engine room 2. The water in
the chamber 1 will tend to rise or fall therein accordingly as the stern
of the steamer is depressed into or clevated out of the sea, and the action
will be transmitted by the air in the upper part of the chamber and in
the pipe 6 and vessel 7 to a diaphragm or piston 8, fitted in the vessel 7.
A rod 9 is fixed to the diaphragm 8 and has jointed to its outer end any
convenient links or other connections for transmitting the movement to
the throttle valve or expansion gear of the engines in such a way that
the supply of steam to the engines may be reduced when the steamer's
stern rises out of the water. The rod 9 is fitted to work in guides
inside of and in connection with the vessel 7, and a spring 10 is applied
to it. In the modification shown in Figure 3 the spring is arranged to
bear against the outside of a cover 11, fixed on the vessel 7, and so as to
tend to draw the diaphragm outwards or upwards; whilst in the modifi-
cation shown in Figure 4 the spring 10 is arranged to bear against the
inside of an elongated cover 12 enclosing it, and so as to tend to press
the diaphragin S inwards or downwards. With the former modification
the chamber 1 is allowed to fill with water when the steamer is in its
normal position, and on the stern rising the tendency of the water to
run out of the chamber 1 causes a sucking action on the diaphragm S.
With the modification shown in Figure 4 the chamber 1 is filled with
air when the steamer is in its normal position, the valve 4 being then
shut, and on this valve being afterwards opened the air becomes com-
pressed in proportion to the column of the external sea water and exerts
an clastic pressure on the diaphragm S in opposition to the spring 10.
This pressure will vary as the stern of the steamer is more or less
immersed, and the desired controlling movement will in consequence be
communicated by the rod 9. A cock is provided at 13 for admitting air
into the vessel 7, and spaces in communication therewith, or it may be
for admitting compressed air from a pump if found desirable. The
spring 10 is made adjustable in both modifications, the rod 9 being
screwed in the one shown in Figure 3, and a nut 14 applied thercon
to act on the disc 15, bearing on the outer end of the spring 10; whilst
in the modification shown in Figure 1 a tubular piece 16 is screwed
through the outer end of the cover 12, and acts on the spring disc 15,
serving also as an outer guide for the rod 9, which passes through
it. Index points and scales 17 may be provided as shown for marking
the adjustment of the spring to suit the draught of the steamer at any
time

page_text: If found desirable a second spring may be applied in each modification
(Figure 3 or 4) in addition to the spring 10 shown, and in order to give
the diaphragm a tendency to return to one position in whichever
direction therefrom it may be moved. I prefer to make the well or
chamber 1 at the stern conical as shown, or otherwise varying in cross
sectional area, and increasing downwards so that a lowering of tho
relative water level due to the elevation of the stern has a compa-
ratively small effect at first, or if of small extent, but a rapidly increasing
one if the lowering continues or becomes excessive. If the action is
found to be too sudden it may be moderated by providing only small
openings 18 in the cover 11 or 12, so as to retard the ingress or egress of
air to or from the enclosed space on the outer side of the diaphragm 8.
It is immaterial whether the apparatus in the engine room be placed
in a vertical, horizontal, or inclined position.
Having thus particularly described my said Invention and the manner
in which the same is to be performed, I have to state that I do not
restrict myself to the precise details herein described or delineated, but
that what I believe to be novel and original, and claim as the Invention
secured to me by the herein-before in part recited Letters Patent is,
the arranging of governing apparatus for screw propeller engines,
substantially in the improved manner herein-before described, that is
to say, so that the action of the sea in a chamber at the stern may
be transmitted by air to a diaphragm or piston, and thence to the
engines.
In witness whereof, I, the said David John Dunlop, have hereunto
set my hand and scal, this Twenty-sixth day of September, in
the year of our Lord One thousand eight hundred and seventy-
ona
) Witness,
EDMUND HUNT,
Patent Agent,
Glasgow.
D. J. DUNLOP. (L.S.)