AN IMPROVED ROTARY ENGINE TO BE IMPELLED BY STEAM, AND WHICH MAY BE ALSO RENDERED APPLICABLE TO OTHER PURPOSES
Year: 1830

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, Sir THOMAS
COCHRANE, Knight, commonly called Lord Cochrane, of Regent Street, in the
County of Middlesex, 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 Eleventh day of November, in the first year of His reign,
did, for Himself, His heirs and successors, give and grant unto me, the said
Sir Thomas Cochrane, His especial licence, sole privilege and authority, that
I, the said Sir Thomas Cochrane, my exors, aditiors, and assigns, or such
others as I, the said Sir Thomas Cochrane, my exors, adñiors, or assigns, should
at any time agree with (and no others), from time to time and at all times
during the term of years therein mentioned, should and lawfully might make,
usc, exercise, and vend, within England and Wales, and the Town of Berwick-
upon-Tweed, my Invention of "AN IMPROVED ROTARY ENGINE TO BE IMPELLED
BY STEAM, AND WHICH MAY BE ALSO RENDERED APPLICABLE TO OTHER PURPOSES;"
in which said Letters Patent is contained a proviso that I, the said Sir Thomas
Cochrane, 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 Sir
Thomas Cochrane, do hereby declare that the nature of my said Invention, and

page_text: in what manner the same is to be performed, is particularly described and
ascertained by the following description thereof (reference being had to the
three Sheets of Drawing hereunto annexed, and to the figures and letters
marked thereon), that is to say :-
My improved rotary engine consists of a large hollow cylinder or drum,
within which a small cylinder or drum is placed eccentrically; (that is to say,)
the axes or central lines of the two cylinders are placed parallel to each
other, but at such a distance apart that the exterior circumference of the
smaller cylinder touches the internal circumference of the larger cylinder at
one part of each of their respective circumferences; consequently a lunate
or crescent-shaped space or annular channel is formed between the two
cylinders, varying in its width at every part of their circumferences like the
figure of the moon in her least phase or most waning quarter) or like the
Turkish crescent. The ends or sides of the external cylinder are closed by
circular plates, to which the flat ends of the internal or excentric cylinder
apply with a close contact, and they may be received into suitable circular
recesses sunk in the said end plates. The revolving piston, which is to be
impelled by steam, extends all across the said crescent-shaped space or
channel, reaching out from the periphery of the interior small cylinder to the
periphery of the larger cylinder; and the edges of the piston are also closely
fitted to the interior surfaces of the end plates of the large cylinder, in order
that the piston may divide the crescent-shaped channel into two compartments,
within one of which a plenum is always maintained by introducing into it
steam from the boiler; and the other compartment must always be kept
exhausted by connecting it with a condenser, or else (if the engine is to be
impelled by high-pressive steam) the latter compartment must always have an
open communication with the external air. The steam, which is thus
introduced into one compartment whilst the other compartment is left empty,
exerting an unbalanced pressure against one side of the piston, urges the same
round in the crescent-shaped space; and to enable the piston to pass round
in that space (notwithstanding the variable width thereof) the piston is allowed
to retreat into a suitable cavity, which is formed withinside of the internal
excentric cylinder; and the piston is in all cases protruded out from that
cavity just so much as to make its outer edge reach to the inner circumference
of the larger cylinder; for instance, when the revolving piston arrives opposite
to that part of the circumference of the outer cylinder where the said circum-
ference touches the circumference of the internal cylinder, the piston retires
wholly within the cavity formed in the internal cylinder, and does not then
protrude beyond the circumference of the internal cylinder; but after passing

page_text: beyond that position the piston begins to protrude from the cavity in the internal
cylinder, and continues protruding more and more therefrom, according as the
increasing width of the crescent-shaped channel requires the piston to be pro-
truded in order that its outer edge may in every situation reach to the interior
circumference of the larger cylinder; after the piston has made half a revolution,
and passed beyond that part of the crescent-shaped channel where the width
thereof is the greatest, the piston begins to retreat again into the cavity within
the internal cylinder, and it continues retreating more and more into that
cavity according at the diminishing width of the crescent-shaped channel
requires, until the piston has completed a revolution and arrived opposite to
the part where the circumferences of the two cylinders touch each other, after
which the piston begins to protrude again in the manner before mentioned.
The essential conditions on which the operation of my improved rotary
engine depends are the employing of an inclosed lunate space or crescent-
shaped annular channel, which is formed (as above described) by means of
two cylinders of unequal diameters, one placed excentrically within the other,
in such manner as that they shall be in contact at one part of their respective
peripheries, and also the employing of a revolving piston, which is accurately
fitted into the said lunate space or channel, so as to divide the interior capacity
thereof into two compartments, in the manner and for the purposes aforesaid;
but the parts of the improved rotary engine may be combined in different
ways, as
represented in the three Sheets of the Drawings hereunto annexed,
in order to fulfil those conditions; for instance, the piston may be firmly fixed
to a revolving central axis, which passes through the centre of the larger
cylinder, that axis being contained in the internal cavity within the small
excentric cylinder, but not in the centre of that cylinder, as is shewn in
Figures 1, 2, and 3, Sheet 1. From the central position of the main axis the
edge of the outer end of the piston will keep at all times in close contact with
the interior surface of the large cylinder, which cylinder is immoveably fixed,
and also the lateral edges of the piston will keep in close contact with the flat
ends of the large cylinder. The internal cylinder has no central axis of its
own, but it is mounted excentrically within the large one by the ends of the
internal cylinder being lodged on (or within) circular rings (or recesses), which
protrude from (or are excavated in) the two circular end plates of the large
cylinder. The piston passes through an aperture in the circumference of the
small excentric cylinder, into which aperture it fits correctly, with a kind of
compound rolling and sliding joint. As the piston revolves with its axis around
within the large cylinder, it carries the small excentric cylinder round with
it, that cylinder being left at liberty to turn round in its bearings, which are

page_text: formed on the circular rings (or in the circular recesses), whereby its ends are
supported; but in so turning round, the revolving motion of the internal
cylinder being excéntric to the revolving motion of the piston, the said
aperture (or rolling and sliding joint) in the circumference of the small cylinder,
through which the piston passes, will slide along the piston backwards and
forwards alternately; that is to say, the said joint alternately approaches
towards the central axis of the piston, and then recedes from that axis to the
internal circumference of the large cylinder, according as the varying width of
the crescent-shaped channel (between the two cylinders) requires the piston to
protrude more or less from the rolling and sliding joint at the circumference of
the small excentric cylinder. The rolling joint permits the piston to assume
as much obliquity of direction (in sliding through the aperture in the circum-
ference of the small cylinder) as is occasioned by the excentricity of the small
cylinder to the central axis of the piston. The revolving central axis of the
piston passes through the centres of the two circular end plates, and is
surrounded with hemp or other packing, which is retained in suitable stuffing
boxes, to prevent any leakage; and the ends of the axis project out each way
beyond those stuffing boxes, in order to give the means of connecting the axis
with any kind of machinery which is intended to be turned by the power of the
improved rotary engine; and a fly wheel may also be connected with the
revolving axis of the piston, in order to regulate and keep up the rotative
motion of the piston with uniformity and continuance; or otherwise the
circumference or cylindrical rim of the outer cylinder may be made to revolve,
as well as the inner cylinder and piston and central axis. This is shewn in
Figures 4 and 5, and Sheet II. The flat ends of the outer cylinder have each
a larger circular hole in their centres to fit upon circular rims formed in
two end plates or standards, which are immoveably fixed in parallel vertical
planes to sustain the moving parts of the engine between them. The small
internal cylinder has a central axis of its own on which it revolves; and the
ends of that axis pass through stuffing boxes in the fixed end plates, but not in
the centres of the aforesaid circular rims, on which the outer cylinder is
poised. The ends of the axis project out each way, in order to connect the
axis with the fly wheel and other machinery, or the power may be communi-
cated from the external revolving cylinder, either by endless straps or belts
applied on the outside of the cylinder, or by toothed wheelwork actuated by a
ring of teeth fixed around the outside of the cylinder. The outer edge of the
piston is connected with the outer revolving cylinder by a turning joint, which
will allow the piston in all its positions to point to the centre of the interior
cylinder; and the inner part of the piston towards the centre of the engine is

page_text: received into a suitable cavity within the interior of the inner cylinder, and, if
need be, the piston may pass across the centre line of the inner cylinder,
the central axis thereof being made hollow in the middle of its length in order
to admit the piston through it. The lateral edges of the piston apply to the
flat end plates of the large cylinder. When the piston is urged round in the
crescent-shaped channel by the steam, it carries the outer rim of the large
cylinder round with it, and also the internal cylinder, together with its axis;
and in so revolving the piston alternately retreats into and withdraws out
from its cavity within the small cylinder, according as the varying breadth of
the crescent-shaped channel between the two cylinders requires the piston to
protrude more or less beyond the circumstance of the small internal cylinder.
Note. By a slight variation in the construction and combination of parts last
described the piston may be firmly and immoveably fixed to the cylindrical
revolving rim of the outer cylinder, pointing towards the centre thereof, (as is
shewn in Figures 6 and 7, Sheet II.,) and not to the centre of the interior
cylinder, the lateral edges of the piston applying to the flat end plates of the
large cylinder, as before described, of the other Figures, and the inner part of
the piston towards the centre of the engine being received a suitable cavity
within the interior of the small cylinder, the piston passing through an
aperture in the circumference of the small cylinder, into which aperture the
piston fits correctly, with a sort of compound sliding and rolling joint, in a
similar manner to Figure 1st. In order that the piston may be at liberty to
assume as much obliquity of direction (in sliding through the aperture) as is
occasioned by the excentricity of the outer cylinder (and of the piston which is
fixed thereto) to the inner cylinder, and to the central axes with which the latter
revolves, when the piston is urged round in its crescent-shaped chaune! by the
steam, it carries the cylindrical rim of the outer cylinder round with it, and also
the small internal cylinder, together with its axis, and in so revolving the piston
retreats into (and alternately draws out of) its cavity within the interior of
the small cylinder, according as the varying width of the crescent-shaped
channel requires, or otherwise. Instead of the piston being fixed immoveably
to the cylindrical revolving rim of the outer cylinder the piston may be fixed
immoveably to the revolving rim of the inner cylinder and radiating from the
centre thereof, and the outer end of the piston may be received into a cavity
formed at the circumference of the outer (or excentric) cylinder, and pro-
jecting out or radicating beyond that circumference, as is represented in
Figures 8 and 9. When the piston is urged round by the force of the steam
it carries the small inner cylinder round on its axis, and the outer part of the
piston bears against one side of the cavity (which projects out beyond the

page_text: rim of the outer cylinder), and thereby the piston carries that, rim round
with it. In so revolving the piston alternately advances into and retreats
from (or draws out of) its cavity in the rim of the outer cylinder, according
as the varying width of the crescent-shaped channel between the rims of the
inner and outer cylinder requires it to do. Note.-In the three last described
constructions of my improved rotary engine it is most proper to call the cylin-
drical rim of the large external cylinder the outer excentric cylinder, because
it is excentric in respect to the central revolving axis, which axis may
transmit the power of the engine to the work. it is to perform. Note.-Two
of my improved rotary engines may be combined, in order to act in concert
and give a more continuous action than one engine is capable of exerting; the
two engines may be so placed that the revolving central axis of both engines
will stand exactly in a line; this axis may be of one piece, or the adjacent
ends of their respective axes may be connected, so that both axis must turn
round together; or the said axis of the two engines may be so connected by
toothed wheelwork as that they must turn round together; the pistons
of the two engines being in either case so placed in respect of each other that
one piston will be passing through the broadest part of its crescent-shaped
channel (and when it will consequently be deriving the greatest impulse
from the steam) whilst the other piston is passing by the part where
the two cylinders touch, and being then wholly withdrawn into the cavity
within the interior of the inner cylinder (or that beyond the circumference of
the outer cylinder), the piston will consequently derive no force from the
steam; or three or more of my improved rotary engines may be combined, with
their several pistons acting at suitable intervals to keep up a continual action.
My improved rotary engine may be impelled by high-pressure steam, which is
allowed to escape into the open air after it has performed its office, or otherwise
the steam may be condensed in a suitable condenser with an air-pump, in order
to obtain a vacuum, and exhaust the steam from that part of the crescent-
shaped channel toward which the piston is moving when it is impelled by steam,
which is supplied from the boiler to the opposite side of the piston. In the
latter case, low-pressure steam will be sufficient to work the engine; and a
rotary engine of a smaller size than those which are to be impelled by steam,
but on a similar construction, may be applied in lieu of an air pump,. to be
turned forcibly round by the power of the larger engines in order to extract
the condensed vapor, injection water, and air from the condensor for if
mechanical power is applied to the revolving central axis of my improved
rotary engine, and if that axis is thereby forcibly turned round so as to carry
the piston round in its crescent-shaped channel, then the piston of the

page_text: improved rotary engine (by pressing on the fluids contained in one of the com-
partments into which the crescent-shaped channel is divided by the piston)
will operate in the manner of a pump.
Note. When a small rotary engine
is to be employed as aforesaid for an air pump, it may be adviseable to adapt a
discharging valve to the aperture, whereby that compartment into which the
piston is advancing communicates with the atmosphere, and that discharg-
ing valve opening outwards from the said compartment will prevent the
pressure of the atmospheric air from acting against the advancing side of
the piston except during the intervals whilst the water which the piston
drives before it is discharging through that valve into the open air. My
improved rotary engine may thus be rendered applicable to other purposes
than that of deriving mechanical power from the impelling force of steam; for
instance, it may be used for blowing air into furnaces in lieu of bellows,
by turning it round by the power of men or horses, or water or wind mills, or
steam engines, or any other power, a water regulator (or other regulator)
being used to: equalize the blast of air; or it may be used for compressing air
or gas; or my improved rotary engine may be applied to force water
through ducts or channels; or for raising water in lieu of pumps, either
for drawing up water through a suction pipe to raise water from a shallow
well or other place, or else for forcing up water, through an ascending
forcing pipe; or it may act both by suction and by forcing combined.
two of the rotative engines may be combined for a fire engine, to project water
in a jet for extinguishing fires, an air vessel being applied to equalize the eflux
of the jet in the same manner as is used in all other fire engines. And as to
the details of the construction of my improved rotary engine, and the manner
of putting together its various parts, they admit of great variation, according to
the purpose for which it is intended to be used, whether it is to be impelled by
high-pressure steam, or by low-pressure steam with condensation, or to be impelled
by compressed air or other compressed gas, or whether it is to be used for a
locomotive engine, or for navigation in boats or vessels, or for a fixed engine
ou shore; and again, whether it is to be for blowing air or for pumping water,
either by suction or by forcing; and generally, according to the magnitude of
the engine, and the purpose to which it is to be applied, all the requisite
variations and combinations to adapt my improved rotary engine to different
purposes, situations, and occasions, will readily suggest themselves to compe-
tent engineers after the above explanation, together with the descriptive
references hereafter made to the Drawings. The fitting of the edges of the
revolving piston to the interior surface of the crescent-shaped channel within
which it circulates must be accurately made either to work with metal against
Also

page_text: metal, or with packing of hemp or other suitable substance, or with metallic
packing applied in suitable grooves around the edges of the piston. The
means of applying such packing, as well as the mode of adjusting and of
replacing the same as it wears away, will be obvious to those who are conver-
sant with the construction of pistons for steam engines; and when the
improved rotary engine is to be constructed for a pump to impel water, the
revolving piston may be packed round the edges with leather, applied in the
same manner as is usually done for pumps. The arrangements for permitting
the entrance and exit of the steam into and out of the two compartments into
which the crescent-shaped channel is divided by the revolving piston, also
admit of great variation, according to the construction and magnitude of the
engine, and the purpose to which it is to be applied. Thus, the steam entrance
and steam exit pipes may be joined to the fixed circular end plates of the
large cylinder of my improved rotary engine at such part of those plates
as to stand opposite to the ends of the internal receiving cylinder, in suitable
positions to permit the steam to pass freely from the entrance pipe (and into
the exit pipe) through the cavity of the internal small cylinder, which cavity is
divided into two compartments for the purpose of distinct communication with
those two pipes, and by that arrangement (notwithstanding that the internal
cylinder is continually in motion) the communication of each pipe with that
compartment to which it belongs is such as will keep one of those compart-
ments always supplied with steam from the boiler, whilst the other compart-
ment (by its communication with the exit pipe) is always kept exhausted
(if a condenser is used), or always kept in open communication with the
atmospheric air if the engine is to work by high-pressure steam, and suitable
communications must be made from each of the said compartments within the
interior cylinder into the crescent-shaped channel at opposite sides of the
revolving piston; videlicit, the communication with the steam compartment
being at that part of the cresent-shaped channel which is behind the piston
(videlicit, on that side from which the piston is moving away), and the com-
munication with the other compartment being at that part of the crescent-
shaped channel which is before the piston, (videlicit, on that side towards
which the piston is advancing,) the said two compartments into which the
interior capacity of the small cylinder is thus divided may be separated by
a partition at or near to the middle of the length of the cylinder, transversely
to the axis thereof; the cavity, which is provided within the internal revolving
cylinder to allow the revolving piston to retire into, will then be a third com-
partment, distinct from the other two, which third compartment may be
supplied with oil to lubricate the moving parts; or else a partition.. may

page_text: be formed, as shewn in Figure 1, of a circular figure, so as to enclose an
internal central space to form one compartment; the other compartment being
an annular cylindrical space which surrounds the first-mentioned compartment.
In this case the entrance and exit pipes, and their communications through the
fixed circular end plates of the engine, must be situated at suitable distances
from the centre of the internal cylinder, to enable one pipe to communicate
with the interior or central compartment thereof, and the other pipe to
communicate with the aforesaid exterior or annular compartment thereof.
Notc. The said internal central compartment may also serve for the cavity
into which the revolving piston retreats; or else the internal cylinder may be
divided in the manner shewn in Figure 4 and Figure 6, by means of a double
partition extending from the centre towards the circumference, so that each
compartment will be nearly a half cylinder; and the cavity into which the
revolving piston retreats will be a third compartment, distinct from the other
two, or else the internal cylinder may be divided by a partition into two unequal
compartments, the largest of which is adapted to admit the piston, and has
sufficient space to allow the piston all the obliquity of motion which it requires
in order to perform its evolutions in its crescent-shaped channel. Note.-
The steam pipe which communicates with the boiler, and the eduction pipe
which communicates with the atmosphere (or else with the condenser), have
been hitherto mentioned as communicating with the engine by two separate
and unconnected passages, each passage always performing its own office; but
my improved rotary engine is capable of working with equal facility either
forwards or backwards, by making the steam and eduction passages exchange
their offices; for instance, if suitable valves, cocks, or slides are provided, and
having suitable connections with the steam pipe and eduction pipe, the latter may
in a moment be converted into the steam passage, and the steam pipe into the
eduction passage, whereby the revolving motion of the piston will be reversed
in the direction of its motion. This mutual exchange of the characters of the
passages may be performed by employing a four-way cock with suitable
passages and connections, similar to what is used in many reciprocating engines,
and there are many other familiar ways of performing the same exchange.
The internal revolving cylinder will necessarily be exposed to a considerable
pressure of steam acting on one side of it, and in certain positions
of the piston that pressure will be only partly balanced by contrary counter-
acting pressure of steam acting on the opposite side of the cylinder, whereby
at certain periods of every revolution of the piston there will be an unbalanced
pressure on the internal cylinder, tending to move its centre forcibly sideways.
That force must be resisted by the fitting of the axis of the small cylinder into

page_text: it sockets and its stuffing boxes, if it has an axis as in Figures 5, 7, and 9,
or else by the fitting of the ends of the small cylinder upon those projecting
rims (or else into those recesses), in the fixed end plates of the outer cylinder,
which, as before described, constitute the bearings for the internal excentric
cylinder to revolve upon when it has no central axis of its own, as in Figure 2.
The fitting surfaces of those bearings must be made very true and smooth, aud
of suitable materials, with or without packing, and the surfaces must be kept
well supplied with oil introduced through suitable ducts; and in order to
diminish the lateral pressure on the axes or on the bearings of the small
internal revolving cylinder (which lateral pressure is occasioned by the afore-
said pressure of the steam acting partially at one side of its cylindrical surface
more than at other sides) a counteracting pressure of hot water from the
boiler may be applied by the following means:-The internal cylinder may be
made longer in the direction of its axis than the outer cylinder, as is shewn in
Sheet III., and the recesses in the fixed end plates of the outer cylinder must
bo deep enough to receive so much of each end of the small internal cylinder
as will leave only a zone or belt around its exterior cylindrical surface (at the
middle part of the length thereof) exposed in the crescent-shaped channel
within which the revolving piston is to move round; the end parts of the
revolving cylinder which are received into the said cylindrical recesses forming
two other zones of cylindrical surface at each end of the middle zone. By
admitting hot water from the boiler into the cylindrical recesses, so as to press
laterally against one side of each of the said end zones of cylindrical surface
(which end zones are received as aforesaid into the cylindrical recesses of the
end plates), a counter-pressure of water may be exerted laterally on those end
zones, in a suitable direction to greatly diminish (or being duly proportioned to
the central zone) or wholly remove the unbalanced pressure that the steam
must exert against the internal cylinder by acting partially on one side of the
circumference of the middle zone. The hot water from the boiler is conveyed
by small pipes into the said deep cylindrical recesses, and is admitted through
small entrance ducts, which are excavated in the flat surfaces at the bottoms
of the cylindrical recesses (and to which flat surfaces the flat ends of the
revolving cylinder apply with close contact); and the water is admitted from
those entrance ducts into slightly hollowed furrows, which are excavated in
the cylindrical surfaces of the end zones of the revolving cylinder, at suitable
portions of the circumferences thereof, the furrows ranging parallel to the
axis of the cylinder. The hot water being admitted from the boiler into those
furrows, will exert a pressure between the cylindrical exterior of the end zones
of the small cylinder (at that side thereof where the furrows are excavated),

page_text: and the cylindrical interior surfaces of the recesses in the end plates; the
said furrows and the entrance duct being so arranged that the pressure of the
water will force the end zones of the revolving cylinder laterally in a contrary
direction to that in which the steam forces the middle zone thereof laterally.
The said furrows must be made at such parts of the circumference of the end
zones as will enable the water pressure on the end zones to act with the
greatest effect to counteract the steam pressure on the middle zone, and the
number, length, and width of the furrows must be suitably proportioned to the
unbalanced pressure of steam that is required to be counteracted; and in order
to give effect to the said water pressure other exit ducts (corresponding to the
aforesaid entrance ducts which admit the hot water from the boiler into the
furrows) must be excavated in the same flat surfaces at the bottoms of the cylin-
drical recesses but at the opposite side of the centres thereof, and those exit ducts
leading into the open air (or communicating by small pipes with the exhausted.
condenser of the engine) will relieve the cylindrical surfaces of the end zones
from all pressure of water which could counteract the pressure intended to be
exerted on the end zones as aforesaid by the water in the furrows at the
proper times or intervals when the pressure should be operative; for, whilst
the revolving piston and internal cylinder are passing through that part of
their circular course during which the steam does not exert a considerable
unbalanced pressure on the bearings on which the small cylinder revolves, the
said water pressure should be relieved, and accordingly that relief of the water
pressure takes place as the furrows containing water come round in succession
to communicate with the said exit duct. Note.-The aforesaid counteracting
pressure to the unbalanced pressure of the steam may in like manner be obtained
by admitting oil in place of water into the aforesaid cylindrical recesses, to
press laterally against one side of each of the aforesaid end zones of cylindrical
surface; that oil may be conducted by small pipes or channel from a suitable
reservoir or vessel containing oil into the said entrance ducts, which are
excavated as aforesaid in the flat surfaces at the bottom of the deep recesses,
and through those entrance ducts the oil will flow into the furrows that are
formed in the aforesaid zones of cylindrical surface at the two ends of the
revolving cylinder; and in order that the oil so introduced may act with a
suitable pressure between the cylindrical surface of the said end zones (at
that side thereof where the furrows are excavated) and the cylindrical interior
surface of the recesses in the end plates, a small branch from the steam pipe
may be joined to the upper part of the reservoir in which the oil is contained,
and steam from the boiler being thereby admitted to press down upon the
surface of the oil, will force the same into the aforesaid ducts with a pressure

page_text: which (being aided by the relief given, as before explained, by the exit ducts
on the opposite sides of the centre) will be sufficient to diminish or to
counteract the lateral pressure of the steam upon the small cylinder.
Figure 2, are
The internal
Descriptive References to the three Sheets of Drawings hereunto annexed:
Sheet I., Figures 1 and 2, represent that construction of my rotary engine
(herein-before described) wherein the piston is fixed to a central axis D
which passes through the centre of the larger cylinder, tbat axis being con-
tained in the internal cavity within the small excentric cylinder, but not in the
centre thereof; the large cylinder A, A, is closed at the ends by two parallel
circular end plates B, B, which are fixed upright upon feet a, a, and are
united by bolts to the flanges b, b, of the cylinder A, A; the revolving
piston C is firmly fixed on the central axis D, D, which passes through
stuffing boxes d, d, formed in the end plates B, B. E, E, is the small ex-
centric cylinder which has no axis of its own, but it ends e, e,
lodged within circular recesses f, f, in the end plates B, B.
cylinder E, E, has a central cavity F enclosed by a partition, of the shape of a
pear; that cavity receives the piston C. The annular space 1, 1, around the
said partition, is closed at the ends of the cylinder E, E, (see Figure 2), but
the circular part of the pear-shaped cavity F is not closed at the ends except
by the ends B, B, of the cylinder A, A, Figure 2d. The cavity F is filled with
steam from the boiler through the steam pipe G, but the annular space 1, 1, is
kept by the eduction pipe i, either in communication with the condenser or
with the atmosphere, according as the engine is worked by low-pressure steam
with condensation, or by high-pressure steam. The steam passes out from
the annular space 1, 1, through holes in the ends of the-cylinder E, E, and is
received into a circular channel o, o, Figure 2, which is made in one of the
end plates B, opposite to the end of the annular space 1, 1, in order to admit
the steam to the eduction pipe in all positions of the said holes, or otherwise
the annular space 1, 1, may receive steam from the boiler through the pipe i,
and the pear-shaped cavity F may communicate through the pipe G with the
condenser or with the atmosphere, in which case the revolving motion of the
piston will be in a contrary direction to the former case; 4, 4, is the rolling
and sliding joint in the aperture at the circumference of the small cylinder
through which the piston passes. It is two portions of a small cylindrical
roller 4, 4, fitted into the aperture, and the piston passes through the space
between the two portions 4, 4, fitting truly to their adjacent flat sides. The
dotted lines m, m, Fig. 1, are sector-shaped plates which are screwed on
at each end of the internal cylinder E, E, over the aperture through which
the piston passes, see Figure 2a, they complete the circles at the ends of

page_text: the internal cylinder which are lodged in the recesses f, f, Figure 1, in
the end plates B, B, and the lateral edges of the piston apply to insides
of the sectorial plates m, m, also the ends of the small cylindrical roller
4, 4, of the rolling and sliding joint are lodged in circular holes in the
said plates m, m; those ends project beyond the edges of the pistou, and
are complete circles which unite the two portions 4, 4, of the cylindrical
roller together, see Fig. 2 a.
sage
Operation of my improved rotary engine:-Steam from the boiler being
admitted through the steam pipe G into the interior cavity F, when the
engine is in the position of Figure 1, flows from thence through the passage g
in the piston into that compartment 2, 2, of the lunate or crescent-shaped
channel which is bebind the piston. The steam in the other compartment 3,
before the piston, has been previously exhausted and drawn off to the con-
denser, or else allowed to escape into the open air by flowing through the pas-
hinto the annular space 1, 1, and thence through the eduction pipe i to
the condenser or to the open air; and, therefore, the pressure exerted against
the piston by the steam in the compartment before the piston is unbalanced by
any pressure in the compartiment 3, 3, on the opposite side of the piston, and
consequently the piston is urged round in the direction shewn by the arrow, and
it carries round the internal excentric cylinder with it. During that motion
the space 3, 3, in the exhausted compartment before the piston gradually
diminishes, and the space 2, 2, in the steam compartment before the piston
gradually increases, until the piston has made half a turn and arrived at the
dotted position C, Figure 1. Also during that motion the piston gradually
withdraws through its rolling and sliding joint 4, 4, from the crescent-shaped
channel into the interior of the small cylinder until it has retreated quite
within the central cavity F, so that its outer edge conforms with the exterior
circumference of the inner cylinder E, E, in order to pass by the part where
the two cylinders touch. In that position of the piston the steam can exert
no pressure against it to turn it round, and, therefore, its motion must be
continued by the fly wheel, or by two engines being combined together
as herein-before explained. When the piston is thus carried a very little
beyond the point of contact 7, but before it has begun to protrude sensibly out
(through its rolling aud sliding joint) beyond the circumference of the small
cylinder, the passage which communicates with the annular space 1, 1,
and thereby with the condenser or with the atmosphere, becomes opened
to the crescent-shaped channel 2, 2, 3, 3, which is full of the steam which
has performed its office, and then that steam rushes through the aperture
into the space 1, 1, from whence it is exhausted (or it makes its escape)

page_text: through the eduction pipe i, whereby the pressure is relieved throughout all
the lunar space 2, 2, 3, 3, and as soon as the piston by moving forwards
begins to protrude and divide the cressent-shaped channel into two compart-
ments, the aperture 9 in the piston also becomes opened and admits the
steam from the boiler (which flows constantly into the central cavity F, and
keeps the same filled) into the space behind the piston, and the pressure of that
steam (being unbalanced on the opposite side of the piston) will impel the
piston forwards, and it will carry the internal cylinder E round with it until
the piston again arrives at the position shewn by Figure 1, and then the
piston is impelled with its full force, having protruded to its greatest extent.
A packing is applied in a groove which is formed at the lower part of the
cylinder A, A, Figure 1, at the place where the two cylinders touch. The
packing extends all across the space between the ends B, B, Figure 2, of
the large cylinder. The packing may be tightened and forced against the
circumference of the internal cylinder E, E, by screws k, or by springs, or
by interposing any elastic substance. The piston C may have a groove
formed in its edge at its end and sides to receive packing either of metal
or of other fit substance to form a close contact with the interior surface of
the cylinder A, A; B, B, Figure 3, shews a different manner of fitting the
pistón C to the edge of the aperture in the circumference of the internal
cylinder, without the rolling and sliding joint. The aperture is formed
larger than the thickness of the piston, and the steam which presses the
piston forwards makes it bear against the rounded edge of the aperture so
as to be steam-tight, and yet leaving the piston at liberty to slide in and
out, and to accommodate itself to that degree of obliquity of its direction-
-through the aperture which the eccentricity of the two cylinders requires.
Note. When one of my rotary engines is to be used as an air pump a flat
valve may be applied to the aperture h opening inwards from the crescent-
shaped channel 3, 3, into the annular space 1, 1, in order to prevent the
entrance of the atmospheric air into the compartment which is before the
piston; G will be the passage through which the air and water are to be drawn
from the condenser. Figures 4 and 5, Sheet II., exhibit that form of my
improved rotary engine (herein-before described), wherein the outer cylinder
is made to revolve as well as the interior cylinder, which is then mounted on
the central axis D, D, within a fixed frame; A, A is the rim of that outer
cylinder, and B, B, its flat end plates united to the rim A, A, by bolts
through the flanges b, b; a large circular hole a, a, is formed in the centre
of each of the end plates B, B, to fit upon circular rims y, y, which project
out from the fixed standards a, a, of the frame of the engine, and those+-rims

page_text: form the bearings on which the outer cylinder revolves. C is the piston
attached by a turning joint 4 to the circumference A of the exterior cylinder;
its inner end is received into a cavity within the internal cylinder E, E,
which cylinder is mounted and fixed firmly on its central axis D, which is
supported in the fixed framing y, y, a, a, by passing through the stuffing
boxes d, d, which are eccentrical to the rims y, y, wherein the outer cylinder
revolves. The cylinder E, E, is formed of two halves, each forming a
chamber E and E2, which chambers do not communicate with each other,
and the two halves when put together leave a space F between their adjacent
flat surfaces to receive the piston as it slides in and out. The chamber E
is always kept filled with steam brought by the steam pipe G from the boiler,
and that steam passes into the cavity F, and through the passage g which is
formed in the piston, into that compartment of the crescent-shaped channel
which is behind the piston. The chamber E is always kept in open com-
munication with the condenser or with the atmosphere by the eduction
pipe i, and the chamber E cominunicates by the passage h with the other
compartment of the crescent-shaped channel before the piston. But the
arrangement of these passages may be reversed as before directed. The
unbalanced pressure of the steam which is thus caused to act against the
piston urges it round in the crescent-shaped channel, together with the
outer cylinder to which piston is attached, and the inner cylinder is like-
wise turned round by the piston acting within the cavity F; the axis D
of the inner cylinder revolving in its fixed stuffing boxes d, d, and the outer
cylinder turning round exentrically to the axis D on the fixed circular
rims y, y, which project out from the same fixed standards y, a, y, a, in which
the stuffing boxes are formed; 3, 3, are circular channels to receive packings,
which forms tight turning joints between the end plates B, B, and the fixed
standards y, a, y, a.
The steam is admitted from the steam pipe G through
openings n, n, into the chamber E', and the eduction pipe i and openings o, o,
connect the chamber E² with the condenser or with the external air; Figures 6
and 7, Sheet II., shew that form of my improved rotary engine (herein-before
described), wherein the outer cylinder revolves like the last described, but
the piston C is firmly fixed to the outer rim of that cylinder, instead of being
jointed thereto. The same letters of reference being used to denote the
same parts as those last described, it is unnecessary to repeat the descrip-
tion. The internal cylinder E, E, is divided by a double partition into two
chambers, viz, the steam chamber E' and the exhausting chamber E,
leaving a third cavity F between them to admit the piston C, which slides
in and out therefrom through a sliding and rolling joint 4, 4, such as already

page_text: described in Figure 1, and the cavity F is wide enough within to permit the
piston to take as much obliquity of direction in the cavity as the exentricity
of the cylinder requires. Figures 8 and 9, Sheet III., shew that form of my
improved rotary engine (herein-before mentioned), wherein the piston C is
fixed immoveably to the revolving rim of the inner cylinder E, E, and is
received in a cavity F, F, beyond the outside rim of the external revolving
cylinder A, A. The inner cylinder E, E, is divided into two chambers E
and E, Figure 9, by a partition transverse to the axis; one of these
chambers E is kept constantly filled with steam from the boiler, and com-
municates by a passage g to that compartment 2, 2, of the crescent-shaped
channel which is behind the piston, and a constant exhaustion is maintained
in the other chamber E) which communicated through the passage h on
the opposite side of the piston, in order to exhaust the steam from that
compartment 3, 3, of the crescent-shaped channel which is before the
piston; an unbalanced pressure is, therefore, exerted by the steam to turn
the piston and inner cylinder round, and the end of the piston bearing within
one side of cavity F so as to fit close thereto, it turns the outer cylinder round
at the same time. When the piston is in the position drawn in (Figure 8)
the piston is not impelled by the steam, and its motion must be continued by
a fly wheel or by combining two engines. The dotted position F and C,
Figure 8, of the piston, and of its cavity F, shew that the width of the cavity
is sufficient to allow the piston to assume its requisite obliquity of direction in
the cavity. The pressure of the steam always causes the piston to apply with
close contact to one side of the cavity. The other parts of the engine, which
are similar to those in Figures 4 and 5, are are designated in the Drawing by
similar letters.
Sheet III, Figures 10 and 11, represent that form of the improved rotary
engine which is so constructed as to counteract and diminish the unbalanced
pressure which is exerted laterally by the steam against one side of the internal
cylinder by applying a counter-pressure of hot water or oil, as herein-before set
forth. A, A, B, B, is the outer cylinder, and E, E, the inner cylinder, which
is between two and three times longer in the direction of its axis than the
space between the fixed end plates B, B, of the outer cylinder. The end
zones of the internal cylinder E, E, are received into deep cylindrical re-
cesses B', B', which are formed out of the fixed end plates of the outer cylinder.
13, 13, is the middle zone of the internal cylinder E, E. That part is exposed to
the steam contained in the crescent-shaped channel in which the piston moves
round, and the same middle zone is alternately exposed to the exhaustion
which is made in that channel before the piston. 6, 6, are the hot water or

page_text: oil pipes to convey hot water from the boiler or oil from the oil vessel through
entrance ducts 7, 7, which are excavated in the flat surfaces at the bottoms
of the cylindrical recesses B', B', (see Figures 11 and 14,) into the furrows 8,
which are formed along the exterior cylindrical surfaces of the two zones at
the ends of the interior cylinder E, E, which enter into the recesses B', B',
(see Figures 12 and 15). As these furrows arrive successively opposite to
the entrance ducts 7, 7, they are filled with hot water or oil, which water
or oil, being pressed by the steam in the boiler, exerts its pressure in the said
furrows to force the internal cylinder laterally, as shewn by the arrows 8, s,
Fig. 13, in a contrary direction to the lateral pressure which the steam exerts
againsts the middle zone of the internal cylinder.
Figure 12 is an end view of the cylinder E, on which the furrows 8, 8, 8,
are cut only at the side S. In the flat surfaces at the bottom of each of the
cylindrical recesses B' (Figure 14), and at the side R thereof, opposite to the
entrance ducts 7, 7, a channel 9, 9, must be formed, which shall com-
municate with the condenser or with the atmosphere at the end 11, Figure 14.
As the furrows 8 in revolving pass beyond the entrance duct 7, 7, they arrive
successively opposite to the commencements of the exit ducts 9, 9, which,
being open to the condenser or to the atmosphere, they relieve the water
or oil contained in those furrows from the pressure which was previously
transmitted through their communication with the boiler.
When the piston
is in the position of Figures 10 and 13, being then in the middle of its course,
and occupying the widest part of the cresent-shaped channel, all the
furrows 8, 8, at the side S of the end zones of the internal cylinder are brought
into communication with the entrance ducts 7, 7, in order to receive a pressure
of water or oil, which is transmitted, as aforesaid, from the steam in the
boiler. But when the piston has made half a turn more, and come opposite
to the part where the two cylinders touch, then the whole of cresent-shaped
channel will be either filled with vapour or else wholly exhausted; and, at the
same time, the side S of the end zones is relieved from the lateral pressure of
the water or oil, because the furrows 8, 8, which are formed thereon, have all
passed beyond the entrance ducts 7, 7, which introduced water or oil into them,
and have all successively arrived opposite to the exit ducts 9, 9, which is open
to the condenser or to the atmospheric air. It may at times be necessary to
reverse the motion of my improved engine. This can be performed by
turning a four-passaged cock, which changes or reverses the communications
between the engine and the steam or entrance pipe and the exit pipe, so as to
exchange the entrance passage of the steam or fluid by which the engine is
propelled for the exit passage, and vice versa. The steam or fluid will then
B

page_text: press the piston round in an opposite direction to that indicated by the arrows
in the Drawing. Note.-As the direction of the lateral pressure against the
small cylinder is also reversed, a correspondent alteration should be made in
the aforesaid entrance and exit ducts 7, 7, and 9, 9, through which the water or
oil pressure is transmitted, in order to counteract the unbalanced pressure of the
steam against the axis of the interior cylinder. For this purpose another series
of furrows is formed on the two end zones of the cylinder E, E, at the opposite
side thereof to the before-mentioned furrows 8 (see dotted lines 10, 10, at the
side R, Figure 18, and also the perspective Figure 16). These furrows 10, 10,
are not prolonged to the extreme ends of the cylinder (see Figure 16), in order
that they shall not communicate during any part of the revolution of the
'cylinder with the aforesaid entrance ducts 7, 7; but the furrows 10, 10, com-
municate with circular entrance channels. 12, 12, which are formed partly
'round the interior of the deep cylindrical recesses B', B', into which channels
hot water or oil is introduced, through suitable pipes and cocks, from the
boiler or from the oil vessel, by the tubes 14, 14. The channels 12, 12, are
sufficiently far from the ends B', B', not to communicate with the furrows 8
(see 12, 12, Figures 11th and 17th.) Two other corresponding exit channels
(which cannot be shewn in these Figures) are, in like manner, cut out in the
interior circumference of the recesses B', B', at the side thereof opposite to
the before-mentioned entrance channels 12, 12; and the said exit channels
communicate with the open air or with the condenser of the engine. When
the engine is to be worked backwards, or with its motion reversed, the com-
munication between the boiler or oil vessel and the tubes 14, 14, must be
opened, and the communications between the boiler or oil vessel and the
tubes 6, 6, must be shut, and then the entrance ducts 7, 7, will not admit any
water or oil to press into the furrows 8, 8, but the hot water or oil which the
entrance channels 12, 12, will admit into the furrows 10, 10, will exert a
lateral pressure against the two ends zones of the cylinder E in a suitable
direction to resist and counteract the unbalanced lateral pressure which the
steam exerts against the middle zone of that cylinder (which zone is within
the cresent-shaped channel). The furrows 10, 10, (like the furrows 8, 8,
receive the water or oil which exerts the pressure as they revolve, and arrive
in succession opposite to the entrance channels 12, 12, and, in like manner,
they are relieved from pressure as they come in succession opposite to the
corresponding exit channels which communicate with the condenser or are
open to the atmosphere. When the engine is again required to revolve in its
usual course in the direction of the arrows, Figures 10 and 18, the cocks in
the tubes 14, 14, should be shut, so that the water or oil pressure may cease

page_text: to be transmitted through the entrance channels 12, 12, to operate within the
furrows 10, 10. G, Figure 11, is the steam pipe to supply steam from the
boiler to the central cavity F, from whence it flows through a steam channel g
into the cresent-shaped channel. Behind the piston is the eduction pipe;
and o, o, and h are the eduction channels communicating with the condenser
or to the open air, in order to exhaust the steam from the said channel before
the piston, or permit the escape of the steam which has performed its office
into the open air. The interior cylinder E, E, has grooves cut round its
circumference at 18, 18, to receive a circular belt of stuffing, or a ring of
metal, to hinder the escape of steam or other fluid from the cresent-shaped
channel. The edges of the piston are furnished with stuffing in like manner.
The movement of this engine is in effect the same as that before described in
reference to Figures 1 and 2, Sheet I., being produced by an unbalanced
pressure of steam acting against a revolving piston so as to turn the same
round within a lunate or cresent-shaped channel, which is formed by means
of a small cylinder placed excentrically within a larger cylinder, so that the
peripheries of the two cylinders are always in contact at one point.
The axes of the two cylinders being parallel to each other, but excentric, which
essential features or properties of my Invention (as herein-before fully explained)
being adapted to practice by me in the several ways herein-before set forth, I
claim the exclusive privilege of using them, whatever may be the combination
adopted in the arrangement of the parts of my improved rotary engine, for
there are many other ways by which the parts of my improved rotary engine
may be arranged; but as I consider the varieties already described to be the
most important and the best adapted for practical use, it will not be necessary
to enter into any further details, except to state, that whatever may be the com-
binations adapted, the essential features or properties of my improved roto-
tative engine which I claim the exclusive privilege of using are, the employing
of an inclosed lunate or cresent-shaped space or annular channel, which is
formed by means of two cylinders of unequal diameters, the one placed excen-
trically within the other, with their peripheries in contact at one part; and
the employing of a revolving piston in the said lunate or cresent-shaped
space or annular channel, which piston is accurately fitted across the said
channel, and is capable of sliding or protruding outwards from the interior or
small cylinder (or else inwards from the exterior or large cylinder) in such
manner as that during the revolution of the said piston around within the
aforesaid lunate or cresent-shaped space or annular channel, the same shall
be divided by that revolving piston into two separate compartments, answering

page_text: to the two compartments into which the cylinder of the common reciprocating
steam engine is divided by the piston which is moveable therein.
In witness whereof, I, the said Sir Thomas Cochrane, have hereunto set
my hand and seal, this Ninth day of May, in the year of our Lord
One thousand eight hundred and thirty-one.