AN IMPROVED STEAM ENGINE
Year: 1831

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, RICHARD
TREVITHICK, of Saint Aith, in the County of Cornwall, Engineer, send
greeting.
WHEREAS His present most Excellent Majesty King William the Fourth,
by His Letters Patent under the Great Seal of Great Britain, bearing
date at Westminster, the Twenty-first February, in the first year of His
reign, did, for Himself, His heirs and successors, give and grant unto me,
the said Richard Trevithick, His especial licence, sole privilege, and autho-
rity, that I, the said Richard Trevithick, my exors, adññiors, and assigns, or
such others as I, the said Richard Trevithick, my exors, adñiors, or assigns,
should at any time agree with, and no others, from time to time and all times
during the term of years therein mentioned, should and lawfully might make,
use, exercise, and vend, within England, Wales, and the Town of Berwick-
upon-Tweed, my Invention of "AN IMPROVED STEAM ENGINE;" in which said
Letters Patent is contained a proviso that I, the said Richard Trevithick, shall
cause a particular description of the nature of my said Invention, and in what
manner the same is to be performed, to be inrolled in His said Majesty's High
Court of Chancery within 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.
NOW KNOW YE, that in compliance with the said proviso, I, the said
Richard Trevithick, do declare that the essential points in my improved steami
engine, for which I claim to be the first and true inventor, arc-

page_text: Firstly, the placing of the boiler within the condenser, in order to obtain
the additional security of the strength of the condenser to prevent mischief in
case the boiler should burst, and also by the same arrangement to con-
veniently make the condenser with a very extensive surface, enabling me to
condense the steam without injecting water into it.
Secondly, the enclosing of the condenser in an air or water vessel, by which
the intention of safety from explosion is further provided for, and my engine
really rendered what I denominate it, a high-pressure safety engine.
Thirdly, the condensing of the steam in the condenser by means of a current
of cold air or cold water forced against the outsides of the condenser.
Fourthly, the returning of the condensed steam from the condenser back
again into the boiler, to the end that sediment and concretion in the boiler
may be prevented; and,
Fifthly, the blowing of the fire with the air after it has been heated by con-
densing the steam.
In forming my improved steam engine I employ several or all of these
points according to convenience, in combination with the other necessary parts
of steam engines in common use.
These, my essential points, will admit of various modifications as to form and
proportions such as must be and are quite familiar to every competent steam
engine manufacturer, and therefore it will be sufficient for the perfect descrip-
tion of my improved steam engine that I explain some of the modes of forming
and combining the essential points of my Invention with the other parts of
steam engines in common use. In my most favorite form of engine in which
I condense by a current of cold air, the fireplace and flue, the boiler, the con-
denser, and the air vessel, are made of six concentric tubes, standing in an
upright position. The inner or first tube forms the fireplace and flue, and at
the same time the inner side of the boiler. This tube is conical, having its
small end upwards. The next or second tube is cylindrical, about six inches
larger in diameter than the lower end of the first tube, and forms the outside of
the boiler, leaving a space all round of about three inches at the bottom, and
so much more at the top, as the flue is taper for holding water and steam
between the two tubes. The third tube is about two inches larger in diameter
than the second, in order to allow a space of about an inch for powdered
charcoal or some other slow conductor of heat. This tube also constitutes the
inner side of the air vessel. The fourth tube is about two inches larger than
the third, and forms the inner side of the condenser. The fifth tube about two
inches larger than the fourth, forms the outside of the condenser; and the sixth
tube about two inches larger than the fifth, forms the outside of the air vessel,

page_text: and at the same time the outside of the whole of the generating and condensing
apparatus, consisting of fireplace. flue, boiler, condenser, and air vessel.
These tubes are made of wrought iron plates rivetted together, and are all
cylindrical, except the first, which is conical, the bottom or fire end being the
largest. The first or inner tube is closed at bottom, but has an opening on
one side near the bottom, through which the fire bars are introduced, and the
ashes and clinkers taken away. To this opening a neck piece about three
inches long is rivetted, having a flanch to fit against the inside of the second
tube, when the two tubes are concentric, through the side of which second tube
is an opening corresponding with that in the first tube, and the flanch is screwed
to the second tube so as to make one opening through the sides of the two tubes.
The second tube extends downwards about five inches below the first tube, and
has a flanch turning inwards, to which a round plate of iron is screwed forming
the bottom of the boiler. The first. tube has an external flanch at the top,
and the second tube an internal flanch, both of the same height, and screwed
to a cast-iron circular plate or cap piece, which extends wide enough around
the boiler to form also. the cover for the air vessel. This plate has a hole in
the middle as large as the flue. The sides of the condenser and air vessel arc
formed of four concentric tubes, each about two inches larger than the one
within it. The inner and outer of these tubes constitute the sides of the air
vessel, and are each furnished with an external flanch at the top by which they
are screwed to the cap piece. The two intermediate tubes constituting
the sides of the condenser are rivetted together at the top, leaving a space of
about an inch between their upper ends and the cap piece, so as to allow of a
free communication over them between the outer and inner parts of the air vessel.
The inner tube of the air vessel extends downwards about an inch below the
boiler, and is closed by a flat plate screwed on to a flanch projecting inwards
from the tube; the two tubes of the condenser descend about three inches lower
than the boiler. The inner tube has an internal flanch to which a flat circular
plate is screwed to close up the tube. The outer tube of the condenser is of
the same length with the inner, and is provided with an external flanch about
three inches broad. The outer tube of the air vessel has an external flanch
two inches broad, and is just long enough to come down upon the broad flanch
of the condenser last described, and these two flanches are together bolted upon
a bottom piece of cast iron, which is a dish of four inches deep, and equal in
diameter with the diameter of the outer tube, and having a flanch the same
breadth as the flanch of the outer tube, and the bottom piece is secured to
the air vessel and outer tube of the condenser by bolts going through all the
three flanches. An opening is made through the sides of all the four tubes of the

page_text: condenser and air vessel opposite to and as wide as the fireplace opening
through the side of the boiler. The upper part of both openings to be of the
same height, but the outer opening is made as low as the bottom of the boiler,
in order to allow room for a pipe to enter that part of the boiler for forcing the
water into it, and also another pipe and cock for drawing off the water or
sediment, in case foul water be used by accident or carelessness. These two
openings through the condenser and air vessel, and through the boiler, constitute
one fire doorway through all the six tubes for access to the fireplace; a ring
is placed between the two tubes of the condenser around the fire doorway, so as
to cut off all communication of the steam in the condenser with the air in the
doorway; another similar ring is placed between the condenser and the outer
tube to prevent the escape of air into the fire doorway, and a half ring is
placed in the lower part of the fire doorway between the condenser and the
inner tube of the air vessel, to prevent ashes from falling into the air vessel,
and yet allow a free passage for the air from the inner part of the air vessel
into the upper part of the fire doorway. Theso two rings and the half ring are
secured in their places by rivets passing through all of them and through the
tubes, and. uniting all firmly together, the interstices being filled with iron
cement. A ring is also placed. between the boiler. and the air vessel around the
fire doorway, against the outside of which ring the charcoal powder is tightly
rammed and will hold the ring in its place, without the necessity of either
rivets or screws. That part of the fire doorway which is above the fire. bars is
supplied with an inner door, to shut the fireplace even with the outside of the
boiler, and exclude all access of air to the fire, except through the grating.
The whole of the fire doorway is enclosed by an outer door even with the
outside of the air vessel, to exclude all air, except that which comes through
the air vessel; a pipe is fixed in the bottom or dish-piece leading to a forcing
pump to draw the water out of the condenser and force it into the bottom of
the boiler through the pipe before described. A blowing cylinder, of about ten
times the content of the main cylinder, is screwed against the outside of the air
vessel, and opposite-to-the-two-outlet-valves-of-the-blowing-cylinder-two aper
tures are made in the air vessel, through which the air is forced in. The main
evlinder of the engine, of the usual dimensions according to power wanted, is
also screwed against the outside of the air vessel high enough above the blowing
cylinder to allow room for the main crank shaft to work between them. The
forcing pump before mentioned is also screwed to the outside of the air vessel,
and thus my improved steam engine becomes more compact and convenient
than any preceding steam engine. For the purpose of supplying the boiler
with distilled water, in case there should be a deficiency in it, a small vessel

page_text: made of two upright tubes, one within the other, is placed on the cap piece.
The inner tube is of the same diameter as the flue, and forms a continuation
of it. The outer tube is about six inches larger than the inner, and the space
at the top and bottom between the two tubes is closed by two ring-shaped
pieces. This vessel may be about eighteen inches high; a cock is fixed in the
top of this vessel, to which a bent pipe is fastened, leading to and united with
a pipe, which arises from the top of the condenser and passes through a hole in
the cap piece, and thus a communicating between the supplying vessel and the
condenser may be opened or shut at pleasure; another pipe, also furnished
with a stopcock, arises from the vessel, and communicates with a water cistern
to receive its supply of water when required; a third pipe, having a cock in it,
opens into the vessel near the bottom to let out the sediment; a small cock to
let the air out is also fixed in the top of the vessel, which cock may also be
used for letting air out of the condenser. In order to supply the boiler with
water by means of this vessel, the stopcock leading to the condenser is shut,
and that leading to the cistern is opened, and at the same time the air-cock is
opened to allow the air to escape that the water may fill the vessel. When
the vessel is nearly full of water, the air-cock and the cock from the cistern are
shut, and that in the pipe leading to the condenser is opened. The water being
then heated by the flue is converted into steam, which, passing into the con-
denser, is there reduced to water again, leaving the sediment or salt in the
supplying vessel, which sediment or salt may be occasionally blown out through
the bottom pipe by filling the vessel with water, shutting the water, steam, and
air cocks, and opening the cock of the outlet pipe at a time when the steam in
the vessel is strong. But the supply of water from the condenser being always
equal to that converted into steam and used in the engine, there is no tendency
to a variation in the height of the water in the boiler, except there be leakage
or waste of steam in some part of the engine. An upright glass tube, having an
iron tube of communication with the lower part of the boiler, and another iron
tube of communication to the upper part of the boiler is conveniently placed
against the outside of the air vessel to indicate at all times the height of the water
in the boiler, as is usual in steam boilers, a valve is placed on the top of the air
vessel to allow of the escape of a portion of the air in case that the quality of the
fuel should not require so much air for perfect combustion as the steam requires
for good condensation. The degree of the condensation of the steam may be
increased at pleasure, by increasing the velocity of the air passing into and
through the air vessel. The other parts of my improved steam engine, such as
the steam pipes, the throttle valve, the safety valve, the vacuum valve, the
working valves, crank, connecting rods, cross heads, pistons, piston rods, and

page_text: various other minor. parts common to engines, in general use may be made in
the usual forms, and placed in the most convenient. situations; they cannot,
therefore, need any description. When it is intended to use water for con-
densing instead of air, my improved steam engine, must be made as before
directed, except that the communication between the air vessel and the fire-
place must be closed, which may be done by a perfect ring of iron surrounding
the opening leading to the fireplace, instead of the half ring before: described,
and a forcing pump. must be employed to draw water from a reservoir, and
force it into the vessel which I have herein-before denominated the air vessel,
but which in this mode of working would more properly bear the name of
water vessel. In this case a blowing cylinder, the dimensions of which must
be.calculated according to the quality of the fuel to be used, may be worked
to blow the fire through, a piperleading into the ash pit. This, however, will
not be necessary where there is a chimney high enough to create a strong draft.
In respect to proportions, my improved steam engine admits of considerable
latitude, and it will be sufficient direction to any practical engineer to say that
for engines working with steam of one hundred and twenty pounds to the inch,
used expansively till it be nearly reduced to atmospheric strength and then
condensed, a ten-horse engine may have a fireplace of twenty inches diameter,
the flue at the top ten inches diameter, and a boiler (of ten feet high;, a sixty-
horse engine a fireplace of thirty-six, inches diameter, a flue of sixteen inches
diameter, and a boiler of twenty feet high. In boat engines, and in other
cases where height cannot be allowed, the diameter must be increased: The
thickness of the-two tubes constituting the boiler sides of a ten-horse engine
may be one eighth of an inch; that of a sixty-horse a quarter of: an inch,
and so in proportion for engines of other power. The tubes constituting the
condenser and inner tube of the air vessel may in all cases be an eighth of an
inch thick. The 'outer tube may be three eighths of an inch thick, to afford
stability to the working cylinder, the blowing cylinder and the forcing. pump
fastened to this tube, and as an ultimate perfect barrier against explosion.
The respective distances of the other tubes constituting the outside of the boiler,
the condenser, and air vessel, will be the same as hercin-before given; and
therefore their diameters will depend upon the diameter of the fireplace.
The cap piece in small engines may be half an inch thick, and in large engines
an inch. The bottom of the ash pit and bottom of the boiler.. must have
about half an inch of thickness for every, foot diameter, or they may be cast
with ribs to afford equivalent strength...The fuel is supplied through a door
in the flue; at the top of the boiler, consisting of coke or coals the least
liable to swell with heat. The fluo may be filled to about one third of the

page_text: height of the boiler, and the water fill about three fourths of the boiler, leaving
one fourth for steam.
Having clearly explained my improved steam engine so that any per-
son competent to make a steam engine can from this description understand
my Invention and carry the same into effect in as beneficial a manner
as myself, I proceed to observe that the extreme safety of my improved
steam engine will be seen, from considering that in case the boiler should
explode inwards into the flue, the power of the steam would be first reduced
by filling the flue and fireplace, and could not escape through the chimney
and fire doorway faster than it would diffuse itself and be condensed by
mixing with the surrounding air, and thus lose all its force. But should
the outside of the boiler burst, part of the force of the steam would be spent
in filling up the interstices between the particles of the charcoal, and would
then probably be too weak to effect a breach through the inner tube of the air
vessel; and should such a second breach be effected the space within the air
vessel would allow the steam to expand and partly condense, and a portion to
escape into and through the fire doorway, where it would divide itself, and pro-
ceed harmlessly up the flue, and out at the doorway; so that the outer case,
being a reserve of strength, would to a certainty withstand the force remaining
in the steam after the before-mentioned successive reductions of power.
In witness whereof, I, the said Richard Trevithick, have hereunto set my
hand and seal, this Nineteenth day of August, in the year of our
Lord One thousand eight hundred and thirty-one.
RICHARD (L.8.)
TREVITHICK.
AND BE IT REMEMBERED, that on the Nineteenth day of August, in
the year of our Lord 1831, the aforesaid Richard Trevithick came before our
said Lord the King in His Chancery, and acknowledged the Specification
aforesaid, and all and every thing therein contained and specified, in form
above written. And also the Specification aforesaid was stamped according
to the tenor of the Statute made for that purpose.
Inrolled the Twentieth day of August, in the year of our Lord One
thousand eight hundred and thirty-one.