IMPROVE- MENTS IN STEAM ENGINES
Year: 1840

page_text: TO ALL
SILADE
URWIN, of South Shields, in the County of Durham, Engineer, send greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria, by Her
Letters Patent under the Great Seal of Great Britain, bearing date at West-
minster, the Twenty-ninth day of July, in the fourth year of Her reign, did,
for Herself, Her heirs and successors, give and grant unto me, the said Robert
Urwin, my exors, adñiors, and assigns, Her especial licence, full power, sole
privilege and authority, that I, the said Robert Urwin, my exors, adiñiors,
and assigns, and such others as I, the said Robert Urwin, my exors, adñiors,
and assigns, should at any time agree with, and no others, from time to time
and at all times thereafter during the term of years therein expressed, should
and lawfully might make, use, exercise, and vend, within that part of Her
said Majesty's United Kingdom of Great Britain and Ireland called England,
Her Dominion of Wales, Town of Berwick-upon-Tweed, or in any of Her
Majesty's Colonies and Plantations abroad, my Invention of "IMPROVE-
MENTS IN STEAM ENGINES;" in which said Letters Patent is contained a proviso
that, I, the said Robert Urwin, shall cause a particular description of the nature
of my said Invention, and the manner in which the same is to be performed,
to be inrolled in Her said Majesty's High Court of Chancery with six calendar
months next and immediately after the date of the said in part recited Letters
Patent, as in and by the same, reference being thereunto had, will more fully
and at large appear.

page_text: NOW KNOW YE, that in compliance with the said proviso, I, the said
Robert Urwin, do hereby declare that the nature of my said Invention, and the
manner in which the same is to be performed, are particularly described in and
by the following description thereof, reference being had to the explanatory
Drawings hereunto annexed, that is to say :-
Whereas in steam engines, as ordinarily constructed, a certain quantity of
steam is expended in producing each stroke of the piston or pistons up or
down, and produces no more than that one stroke, after which it is either
condensed or allowed to escape into the atmosphere.
Now the nature of my said invented improvements consists in causing each
volume of steam admitted from the boiler into the working cylinder to produce
both the up and down motion of the piston or pistons, whereby a saving of
nearly one half of the steam power is effected. And the Drawings hereunto
annexed exhibit the manner in which the said Improvements are adapted to an
ordinary double acting condensing steam engine. A, Figure 1, is the cylinder,
and B the piston; C and D are the steamways for the admission of the steam
into the cylinder at top and bottom, differing in this only from ordinary
steamways, that the top side of the lower one D is at a height from the
bottom equal to the thickness. of the piston and about three fourths of the
breadth of the said steamway D more. E is the condenser. F, an expanding
receiver, into which the lower steamway D opens. G, G, are two slides
coupled together by means of a stuffing box in the manner represented in the
Drawing, so that any passage of steam from one side of the stuffing box to the
other is prevented, which slides open and close alternately the steamways C
and D in the usual manner, but subject to certain conditions to be herein-after
more particularly explained. Supposing the piston has to make its down-
stroke, steam is let in from the boiler to the top of the cylinder through the
steamway C by the opening of the top slide, and is allowed to flow in unre-
strictedly till the top of the piston is forced just to the top side of the lower
steamway D, on arriving at which point the upper steamway C is closed,
and as the piston descends past the lower steamway D it is opened so as to
allow the steam to pass through it from the upper part of the cylinder A iuto
the expanding receiver F, while a portion of it also rushes beneath the piston
through a vertical groove 9 cut in the cylinder from the points a to b, as repre-
sented in Figure 2; which last portion assists in producing an immediate
reverse action of the piston, and in carrying the top of it past the steamway D,
as soon as it reaches which point a passage is opened by the action of the top
slide for the steam remaining in the upper part of the cylinder to pass into the
condeuser, while at the same time the steam which has escaped into the

page_text: receiver Frushes back into the lower part of the cylinder beneath the piston,
and by its expansive pressure completes the upward stroke of the piston.
When the piston arrives again at the top of the cylinder the lower steamway
D is closed by the action of the slides, and a passage opened for the last used
portion of the steam into the condenser, while at the same time the upper
steamway C is opened for the admission of a new supply of steam to the
top of the cylinder, when the same operation which has been just described
is repeated. And so the engine will continue to work steadily and uninter-
mittingly as long as there is a supply of steam from the boiler. But in order
to the working of an engine on the preceding plan to the greatest useful effect
it will be important to observe the following directions:-Each receiver should
be of a capacity at least one half larger than that of the cylinder, but may be
advantageously even three times larger, where saving of room is not an object;
and where two engines are employed, as on board steam vessels, there must be
a communication between the two receivers, as shewn in the back view,
Figure 4, and longitudinal section Figure 5, in which S represents the steam-
pipe; A, one of the receivers; and T, the connecting pipe. The vertical groove
g, which admits steam beneath the piston, should be of about one third the
area of the steamway D. The slides, again, must be so adjusted that the top
one shall travel as much before the crank as to close the upper steamway C
simultaneously with the opening of the lower steamway D, for which purpose
the top of the upper slide should be about one fifth of the breadth of the
steamway C above that steamway at the time of determining the length of
the slide rod. The face of the top side of the upper slide must also be of
sufficient breadth to shut off any communication with the condenser till the
top of the piston has in its return stroke upwards passed the lower steamway
D. To determine this breadth the following directions will be found of
service-Make the top side of the top slide always three fourth parts broader
than the upper steamway. After this take a radius of half the stroke of the
piston, and describe a circle as represented in the Diagram Figure 3, then
divide this circle into seven equal parts, next draw a cord from one of them
and bisect it, after which draw through the point of bisection the perpendicular
A, C. Now assuming a, a, to represent the space which the crank will travel
through in the same time that the piston is travelling from B to C, and back
again, then the extra breadth allowed on the slide will correspond with the
space which the piston has to travel in the same time, and consequently the
space which the slides have to travel according to the size of the steamways
may be readily ascertained. Care must of course be taken to make the
breadth of the middle bridge of the lower steamway D in proportion to the

page_text: extra space the slide has to travel. It is necessary further to observe, that the
receiver F must have a communication by a stopcock with the steam chest, in
order that, previous to the starting of the engine, when the piston might be at
the bottom of the cylinder, steam may be let into the receiver by the opening
of the said cock, when it will find its way by the passage g beneath the piston,
and by its pressure put it in motion upwards. Instead of a passage g being
cut out of the cylinder to admit the steam from above the piston to beneath it,
an opening of the same area might be made in the piston itself, with a valve
to open and shut it, connected with the same motion which opens and shuts
the lower steamway D.
Instead, moreover, of the piston being allowed to
descend past the steamway D, arrangements might be made so that on its
reaching that point an opening or openings should be made for the passage of
the steam from above to beneath it, and in that case the steamway D need
not be higher up the cylinder than usual.
And lastly, to the bottom of the cylinder and receiver there must be stop-
cocks attached, by the opening of which any condensed steam which may have
accumulated in either may be drawn off previous to the starting of the
engine.
And having now described the nature of my said invented improvements,
and the manner in which the same are to be performed, I declare that what
I claim as of my Invention is, the method or system of working steam herein-
before described, whereby each volume of steam admitted from the boiler into
the cylinder serves to produce both the up and down stroke of the piston, and
whether the expanding receiver employed for the purpose is of the form and
size, and placed in the situation represented in the Drawings hereunto annexed,
or of any other form or size, or placed in any other situation whatever, and
also whether the passage g for the admission of steam from above the piston to
beneath it near to the termination of its downward stroke is cut out of the
cylinder case as represented in Figure 2, or made in the piston itself, with a
regulating valve as herein-before suggested, and also whether one passage of
the area herein-before specified is employed or two or more smaller passages of
the same area in the aggregate, and at whatever point in the descent of the
piston the said passage or passages are opened.
And such my said invented improvements being to the best of my knowledge
and belief entirely new, and never before used within that part of Her Majesty's
United Kingdom of Great Britain and Ireland called England, Her Dominion
of Wales, Town of Berwick-upon-Tweed, or in any of Her Majesty's Colonies
and Plantations abroad, I do hereby declare this to be my Specification of
the same, and that I do verily believe this my said Specification doth comply