IMPROVEMENTS IN STEAM ENGINES
Year: 1865

page_text: LETTERS PATENT to William Brookes, of 62, Chancery Lane, in the
County of Middlesex, Civil Engineer and Patent Agent, for the Inven-
tion of "IMPROVEMENTS IN STEAM ENGINES."-A communication from
abroad by Philibert Vabe, of Paris, in the Empire of France.
Sealed the 4th July 1865, and dated the 13th January 1865.
PROVISIONAL SPECIFICATION left by the said William Brookes at the
Office of the Commissioners of Patents, with his Petition, on the 13th
January 1865.
I, WILLIAM BROOKES, of 62, Chancery Lane, in the County of Middlesex,
Civil Engineer and Patent Agent, do hereby declare the nature of the said
Invention for "IMPROVEMENTS IN STEAM ENGINES" (communicated to me from
abroad by Philibert Vabe, of Paris, in the Empire of France), to be as
follows:-
The improvements relate to using steam which has acted on one side of
the piston of a steam engine to act thence equally on the piston of a second
cylinder. In carrying out the improvements steam is admitted but once each
revolution of the crank, by which great economy is obtained over the ordinary

page_text: system of working steam engines. One piston rod is connected to two pistons,
each in a different cylinder, and one cylinder has an area double that of the
other. The slide valve directing the course of the steam is arranged in such
manner that the steam acts on one of the faces of the smaller piston, whilst
the other face thereof, and one face of the piston of the larger cylinder, are
open to the atmosphere. At the end of the course of the smaller piston the
communication thereof with the atmosphere is closed, and the steam on one
side of this piston is then allowed to communicate with the other side thereof
and with the corresponding side of the larger cylinder, by which equal pressure
is obtained on both sides of the smaller piston, and the steam effects the return
motion by its action on the larger area of the larger piston, the other side of
which is in constant communication with the atmosphere. The same steam
consequently produces a to-and-fro motion of the piston without its escape
until it has produced these two effects.
The improvements are applicable when steam is used expansively, in which
case a valve may be used with four orifices, two of which (one larger than
the other) communicate with one side of the smaller piston. When low or
mean pressure steam and condensing apparatus are employed other escape
passages will be required, and the side of the piston of the larger cylinder now
open to the atmosphere will be enclosed and used.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said William Brookes in the Great Seal Patent Office on the
13th July 1865.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
BROOKES, of 62, Chancery Lane, in the County of Middlesex, Civil Engineer
and Patent Agent, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Thirteenth day of January, in the year of our Lord
One thousand eight hundred and sixty-five, in the twenty-eighth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me, the
said William Brookes, Her special licence that I, the said William Brookes, my
executors, administrators, and assigns, or such others as I, the said William
Brookes, 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,

page_text: and vend, within the United Kingdom of Great Britain and Ireland, the
Channel Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN
STEAM ENGINES," communicated to me from abroad by Philibert Vabe; of
Paris, in the Empire of France, upon the condition (amongst others) that I,
the said William Brookes, 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 William Brookes, do hereby declare
the nature of the said Invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement thereof, that is to say:
The improvements relate to using steam which has acted on one side of
the piston of a steam engine to act thence equally on the piston of a second
cylinder. In carrying out the improvements steam is admitted but once
during each revolution of the crank, by which great economy is obtained over
the ordinary system of working steam engines. One piston rod may be con-
nected' to two pistons, each in a different cylinder, and one cylinder has an
area double that of the other. This effect is produced by the following means:
-Two cylinders A and B, of different diameters, are provided with two pistons
P and P' mounted on the rod E. The two cylinders instead of being a pro-
longation one of the other may be placed side by side, when their rods will
work parallelly. The first cylinder A communicates by the face c of its
piston P through the orifice a with the slide valve, and by its face c' through
the orifice a¹ of the same valve. The second cylinder B communicates by the
face d of its piston P¹ through the orifice a', and by its face d' with the
atmosphere through the tube t, or in other suitable manner. The surface
of the piston P¹ is double that of the piston P. The valve seat has also
another opening a communicating with the atmosphere. A valve T, of
which one face b' has twice as much overlap as the other face b, opens' and
closes these orifices. This valve is set in motion by an ordinary eccentric, or
may be by a crank or otherwise. The working of the engine is simple and
economical; and supposing the piston P to be at the commencement of its
stroke, the orifice a is slightly open at the same time the orifice a¹¹ com-
municates with the interior of the slide valve, and therefore with the orifice a¹
and with the face of the piston P. At this moment the face c' of the
it

page_text: piston P and the face d of the piston P¹ communicate with the atmosphere.
As the orifice a opens, the steam acts on the face c of the piston, which moves
under the action. At half stroke, which is that shown by the Drawing, the
orifice a is fully open, and the slide valve returns during the other half of the
stroke. At the end of the stroke the angle of motion of the eccentric acting
on the slide valve has just closed the orifice all at the same time that it has
opened a communication between the orifice a¹ and the face d of the piston P¹.
The steam acting then equally on the two faces of the piston P produces
an equilibrium in the cylinder A, but this same steam pressing also on the
face d of the piston P¹ that piston moves under its pressure because its face d¹
is in communication with the atmosphere by means of the pipe t¹, and the
cylinder A acts simply during that return stroke as a box from which the
steam expands into the cylinder B without having contra-pressure on the face c
of the piston P. The face of the slide T having an overlap double that of
the face 6 stops the communication with the orifice a", and consequently with
the atmosphere during the return stroke. When the piston P¹ passes the
middle of the stroke the eccentric forces back the face b¹ of the valve T, and
when it has arrived at the end of the stroke the slide valve begins to admit
steam through the orifice a at the same time the steam contained in the
cylinder A on the side c¹ of the piston P, and that contained on the side d of
the piston P¹ in the cylinder B escapes into the atmosphere through the
orifice a¹. The piston P now makes its forward stroke, and the same move-
ments are reproduced. There is, therefore, admission of steam but once each
revolution of the crank, and therefore only one escape. It is well to remark
that at the time when expansion commences the power of the engine far from
being diminished is rather augmented, for the steam acts at this moment on a
surface twice as great as that on which it began to act. At the middle of the
return stroke the motive power is equal to that at starting, for the steam
being half expanded the pressure is half that at starting, this pressure acting
on a surface twice as great, then at this moment the motive power is equal to
that at starting. It is true that in the last half of the stroke the power is less,
but the increase of power during the first half of the stroke, as well as the
increase of initial velocity, compensates for it. If may therefore be practically
considered that the power of the return stroke equals the forward one. It
should be remarked that at the end of this return stroke the piston does
not compress the air in the cylinder during the return of the overlap of the
valve over the orifice communicating with the escape compression which is
felt at the end of the forward motion, and in both strokes of ordinary engines.

page_text: R is a moveable cover to facilitate inspection and tightening of the stuffing
box C and the cover D. The cover D is held in position by means of screws.
e, e, passed through the flange f, which is held in position by the heads of the
screw bolts g, and by the screw bolt h. This system combines the advantages
of medium and high pressure. In order to diminish the force according to
need, there may be provided a variable expansion based within limits upon
the pressure in the boiler and on that in the cylinder B at the end of the
stroke. If a condenser be applied to this engine it must be beyond the escape
that the face d' of the piston P¹ may communicate with the condenser. This
engine provided with a condenser, and working at low pressure, will be found
of great advantage by employing only half the usual quantity of water for con-
densation. For the sake of conforming to the practical rules with regard to
the section of the orifices, and to facilitate expansion upon the larger piston,
there may be employed a slide valve T having four orifices, of which two, a and q,
communicate with the face c of the piston P, the orifice q having a section
double that of the orifice a, all maintaining the same breadth. The orifice a²
must then have a section equal to that of a and 7 united, and the escape
orifice a section so great as not to impede the engine. It is desirable in
the use of this system to have a second passage for steam to enter adjoining
the plate p of the cylinder B in the event of the engine stopping in the
return stroke to avoid the necessity of having to bring back the parts to the
position for the regular admission of steam. This arrangement is exempt
from defects which are experienced in engines on the ordinary system. The
advantage of this system arises from this, that the escape of steam is effected
only once a revolution, and at the moment when this escape commences the
steam of the cylinder B has a pressure much less than that which issues from
the boiler on to the face c of the piston P, consequently the engine does not
experience great back pressure during the escape. The surface of the large
piston can be augmented in proportion to the pressure to give greater force
to the expansion that effects the return stroke. It is evident that the setting
up of an engine of this kind is based on ordinary practical rules, because the
superficial area of the large piston is determined by that of the small one.
There should be taken as a minimum, for a base of calculation, a pressure in
the boiler that at the end of the expansion the motive power should be
greater than atmospheric pressure, the amount employed in ordinary expansive
engines.
The improvements are applicable to all classes of engines, stationary,

page_text: Having thus described the improvements as communicated to me, I would
have it understood that what I claim is, the adaptation or combination of means,
and the mode or system of working applied to steam engines, substantially as
described!.
In' witness whereof, I, the said William Brookes, have hereunto set my
hand and seal, this Thirteenth day of July, in the year of our Lord
One thousand¹ eight hundred and sixty-five.
WILLIAM BROOKES. (L.B.)