IMPROVEMENTS IN ENGINES WORKED BY THE COMBUSTION AND EXPANSIVE FORCE OF AN INFLAMMABLE FLUID MIXTURE
Year: 1876

page_text: LETTERS PATENT to Matthew Piers Watt Boulton, of Tew Park, Oxfordshire,
Esquire, for the Invention of "IMPROVEMENTS IN ENGINES WORKED BY THE
COMBUSTION AND EXPANSIVE FORCE OF AN INFLAMMABLE FLUID MIXTURE."
PROVISIONAL SPECIFICATION left by the said Matthew Piers Watt Boulton
at the Office of the Commissioners of Patents on the 15th September 1870.
MATTHEW PIERS WATT BOULTON, of Tew Park, Oxfordshire, Esquire. "IM-
PROVEMENTS IN ENGINES WORKED BY THE COMBUSTION AND EXPANSIVE FORCE
OF AN INFLAMMABLE FLUID MIXTURE."
This Invention relates to engines which are worked by the elastic pressure caused
by the combustion of an inflammable fluid mixture, such as gas or inflammable
vapour with air.
I proceed to describe one construction and mode of working which I employ,
modifications of which will be mentioned afterwards. An inflammable mixture of
elastic fluids is introduced into a cylinder or chamber connected with it and is
ignited so as to produce pressure or clastic force acting on the piston. This opera-
tion may be performed by any of the various known methods used in engines in
which a piston is actuated by force thus produced.
While the products of combustion are acting on the piston, and while they are
still at high pressure, a valve is opened and air or elastic fluid which has been
raised to high pressure by a pump or forcing apparatus worked by the engine
enters the cylinder, mixes with the hot products within it, and acts conjointly
with them in propelling the piston. This air or clastic fluid enters the cylinder
from the pump or high-pressure chamber which supplies it without passing through
a regenerator, and without having its temperature raised otherwise than by the
compression to which it has been subjected. After a certain determinate quantity
of this fluid at high pressure has been adinitted into the cylinder the valve by
which it entered is closed. The clastic fluid in the cylinder continues to expand,
its temperature being reduced by the expansion, but no cooling agent is applied to
the cylinder in order to reduce its temperature. When the pressure has been
reduced so low as is thought desirable the piston completes its stroke. In the
Prins 1021

page_text: return stroke the waste fluid may be discharged either into the atmosphere or into
a refrigerator or cooling chamber maintained at low pressure from which it is
extraxted by an air pump. If such a refrigerator is employed the expansion of the
fluid in the working stroke is continued to a point at which its pressure falls below
that of the atmosphere.
After the extraction of the exhaust fluid from the cooling chamber the whole of
it may be discharged as waste, but otherwise a portion of it may be used to supply
the pump or forcing instrument which compresses the elastic fluid supplied to the
cylinder to work on the piston as previously explained, and with respect to thermal
efficiency I consider this latter course preferable. Similar operations are performed
on each side of the piston, or in other words the engine is double acting.
The degree of compression given to the air or elastic fluid which is introduced
into the cylinder in order to perform work in it may be much varied. I consider
that the best result is obtained with respect to thermal efficiency when it is raised
to a pressure not far short of the highest pressure produced in the cylinder by the
combustion of the inflammable mixture. But in order to diminish the opposing
action of the compressing pump and reduce the bulk of the engine, it may frequently
be desirable in practice to give to it a less degree of compression.
The compression of the clastic fluid used in the cylinder, and the extraction of
the elastic fluid from the refrigerator or cold chamber may be performed by means
of ordinary pumps, in which pistons work in cylinders. I prefer however in both
cases to work by rotary pumps. In order that the action may be continuous, and
that the revolving parts may perform the office of a fly wheel in equalizing the
action of the engine, succession of pumps or forcing instruments may be used.
The rotary pump or apparatus which compresses the fluid used in the cylinder
forces the air or fluid into a chamber of considerable capacity, in which it is con-
tained at high pressure, and from which a certain determinate quantity is admitted
into the cylinder, while the valve for its admission is opened. The regulation of
the quantity of fluid thus admitted into the cylinder is effected nearly to the point
desired by the size of passage governed by the valve, and the time during which it
is open; but it is adjusted to greater nicety by means of a regulator provided for
the purpose.
In order to lessen the shock produced by the ignition of the inflammable mixture,
and the consequent sudden rise of pressure on the piston, I employ a secondary
piston between the charge of inflammable mixture and the working piston. This
piston is furnished with a valve which allows passage of the fluid from the space
between the pistons into the cylinder behind, but prevents passage of fluid in the
contrary direction. A spring is also placed between the two pistons. At each
stroke air or elastic fluid is supplied to the space between the pistons by a valve
After this has been done, the
provided for the purpose, worked by the engine.
charge of inflammable mixture is introduced behind the secondary piston.
When the inflammable mixture is ignited, and the sudden rise of pressure
consequent on the ignition takes place, the ignited fluid drives the secondary piston
towards the main or working piston, compressing the air or elastic fluid between
them, and as the pistons approach compressing the spring. Under these circum-
stances the force produced by the sudden rise of pressure of the clastic fluid is
communicated gradually to the working piston.
As the pressure of the products of combustion falls the valve in the secondary
piston opens, and the compressed fluid within escapes into the space containing the
hot products of combustion, with which it mixes, and performs work along with
them.
At the end of the exhaust stroke the two pistons are brought close together;
at the commencement of the succeeding stroke they separate while the air or
fluid is introduced between then through the valve provided for the purpose.
All the air or fluid employed to co-operate with the products of combustion
might be introduced in this manner between the pistons, in which case the com-
pressing pumps or instruments previously mentioned might be dispensed with

page_text: but I prefer to employ them as previously described, since by their use tho
length of the working cylinder is shortened, and the action of the engine rendered
more uniform.
In the arrangement of the two pistons, other things remaining as above described,
the valve in the secondary piston may be dispensed with. In this case the fluid
compressed between the two pistons escapes between the secondary piston and the
cylinder, or between this and the piston rod, or through a small aperture provided
for its passage.
Either gas or inflammable vapour may be used as one of the ingredients of the
inflammable mixture. The other ingredient may be air drawn in from the atmosphere,
as in ordinary gas engines; but otherwise the gas or vapour and the air may be
compressed by the action of the engine, and delivered into the cylinder at high
pressure. In such a case the pressure imparted to the air or clastic fluid by the
compressing pumps or instruments previously mentioned is raised in a corresponding
degree, that is to say, it is raised to a pressure higher than that at which the
inflammable mixture is introduced into the cylinder, and it may be to a pressure
equal to the highest pressure produced in the cylinder by the combustion of the
inflammable mixture within it.
When the ingredients composing the inflammable mixture are thus subjected to
compression before their introduction into the cylinder I prefer to effect their com-
pression by means of rotary pumps or forcing instruments working continuously,
and delivering the fluids which they compress into chambers of considerable capacity
from which a certain determinate quantity is admitted into a mixing chamber, and
thence into the cylinder while the valve provided for its issue from the chamber is
open. In this case, as in that previously mentioned, the more accurate adjustment
of the quantities allowed to pass while the valves are open is effected by a
regulator.
I prefer that each ingredient of the fluid should be compressed into a separate
chamber, the mixture of the fluids being effected as they pass from the chambers
containing them at high pressure towards the cylinder.
When the ingredients of the inflammable fluid mixture are thus compressed
before introduction into the cylinder I consider it, on some accounts, preferable to
employ oxygen instead of air as one of the ingredients of the mixture. The oxygen
in this case is not supplied gratis, as it is when atmospheric air is employed, but
its use reduces the work to be done by the compressing pumps, and renders the
action of the engine more efficient, so that the cost of the oxygen may be repaid by
saving in the cost of the gas or inflammable vapour.
In engines operating as above described there is great variation of pressure on
the piston. Inconvenience from this cause may be obviated by employing numerous
cylinders, as is sometimes done with steam engines so disposed as to render the
total action of the engine more uniform.
DESCRIPTION OF DRAWINGS.
Figure 1 and Figure 2 are a longitudinal and cross section; and Figure 3, a plan
showing a form of apparatus constructed according to my Invention.
A, A, is the working cylinder within which the heated elastic fluid acts on a
piston, and performs work; B, B, is a cooling chamber cooled by cold water pressing
through the chambers i, i, and the tubes k, k. In place of the form of cooling
chamber shewn any of the known form of surface condensors and refrigerators may
be employed. The pressure within this chamber is maintained below that of the
atmosphere by means of the rotary pump E worked by the engine, as shewn,
which continually extracts from it the elastic fluid which passes into it from the
cylinder. c, c, is a chamber containing air or elastic fluid at high pressure, which
s forced into it by means of the rotary pump F also worked by the engine.

page_text: the cylinder communicates alternately with the migh-press
chambers; v and v² are the valves or slides which govern the admission and cut-off
of the inflammable fluid mixture into the cylinder. I represent these as having
the construction used in Otto and Langen's gas engine, but 1 do not show the whole
of the construction as it is well known.
Supposing the piston P to be at the left end of the cylinder the operations take
place as follows:-The slide v opens the passage for the admission of the inflam-
mable fluid from S to the space between the left end of the cylinder and the piston
P, while simultaneously the slide V opens the passage between the right-hand end
of the cylinder and the low-pressure chamber or refrigerator B. The piston P
moves from left to right; the inflammable mixture enters behind it on the left,
while in front of it fluid passes from the right-hand end of the cylinder to the refri-
gerator. As soon as the charge of inflammable fluid has been admitted into
the cylinder the valve v¹ closes the passage for its admission, and the mixture is
ignited. Soon afterwards at a period determined by the degree of compression
employed the slide V opens the passage between the cylinder and the high-pressure
chamber, and air or elastic fluid passes from that chamber into the cylinder, where
it mixes with the hot products of combustion. Shortly afterwards the slide V
cuts off the admission of air or fluid from the high-pressure chamber to the
cylinder.
The mixed elastic fluid expands and urges forward the piston P until it reaches
the end of its stroke at the right-hand end of the cylinder. The slide V then closes
the passage between the right-hand end of the cylinder and the low-pressure
chamber, and the series of operations previously described is repeated for the return
stroke.
When the refrigerator is dispensed with the operations are the same, except that
the discharge of waste fluid from the cylinder takes place into the air instead of
taking place into a chamber wherein the pressure is below the atmospheric, and the
exhausting or extracting pump E is dispensed with.
In Figure 2 g, g, shews the regulator by means of which the quantity of air
or fluid admitted into the cylinder from the high-pressure chamber c is
regulated.
The rotary pumps which I prefer to employ for the extraction and compression
of the elastic fluid are of the form known as Sudlow's.
A hand pump is provided in connexion with the high-pressure chamber by means
of which its pressure can be raised to the degree desired before starting. Issue of
air from this chamber into the working cylinder may be made use of for starting
the engine.
In the Drawings above described a plain piston P is represented for the sake of
simplicity, but I prefer to employ a compound piston with other parts working in
connection with it, as is shown at Figure 4.
In Figure 4 P is the main or working piston; p, the secondary piston.
As the engine is double working there are two secondary pistons, one on either
side of the main piston. The rods 7, 7, working in the passages t, t, allow the pistons
to approach, but prevent them from separating further than as shewn in the Figure.
The valve v allows air or elastic fluid to pass from between the pistons into the
space 8, but prevents its passage in the contrary direction.
When the inflammable mixture is ignited, and high pressure is suddenly pro-
duced, the pressure of the ignited elastic fluid drives the two pistons together,
After-
compressing the air or fluid between them, and conpressing the spring e, e.
wards as the pressure behind the piston becomes reduced by expansion the com-
pressed fluid between the pistons escapes through the valve v into the space 8, or
the portion of the cylinder in which are the hot products of combustion.
The spring e may if preferred be omitted.
At the end of the stroke the pistons are forced together. At the commencement
of the next stroke a valve W worked by the engine is opened, which allows air
from the atmosphere to enter between the pistons. The air enters and the pistons

page_text: separate so far as the rods r, r, allow, after which the valve W closes, and the
pistons P and p move together. As soon as the movement of the second piston p
commences the valve G for the admission of the inflammable fluid mixture is
opened, and it enters behind the secondary piston p, p.
As soon as the proper
quantity of it is admitted its admission is cut off, and it is ignited. p', pl, repre-
sents the secondary piston on the other side of the main piston. Instead of air a
portion of the exhaust fluid which has been discharged from the cylinder may be
introduced into the space between the pistons.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Matthew Piers Watt Boulton in the Great Seal Patent Office on the
14th March 1877.
MATTHEW PIERS WATT BOULTON, of Tew Park, Oxfordshire, Esquire.
"IM-
PROVEMENTS IN ENGINES WORKED BY THE COMBUSTION AND EXPANSIVE FORCE
OF AN INFLAMMABLE FLUID MIXTURE."
This Invention relates to engines which are worked by the elastic pressure caused
by the combustion of an inflammable fluid mixture such as gas or inflammable
vapour with air.
I proceed to describe one construction and mode of working which I employ,
modifications of which will be mentioned afterwards. An inflammable mixture of
elastic fluids is introduced into a cylinder or chamber connected with it, and is
ignited, so as to produce pressure or elastic force acting on the piston. This opera-
tion may be performed by any of the various known methods used in engines in
which a piston is actuated by force thus produced.
While the products of combustion are acting on the piston, and while they are
still at high pressure, a valve is opened and air or elastic fluid which has been
raised to high pressure by a pump or forcing apparatus worked by the engine enters.
the cylinder, mixes with the hot products within it, and acts conjointly with them
in propelling the piston. This air or clastic fluid enters the cylinder from the pump
or high-pressure chamber which supplies it, without passing through a regenerator, and
without having its temperature raised otherwise than by the compression to which
it has been subjected. After a certain determinate quantity of this fluid at high
pressure has been admitted into the cylinder, the valve by which it entered is closed.
The elastic fluid in the cylinder continues to expand, its temperature being reduced
by the expansion, but no cooling agent is applied to the cylinder in order to reduce
its temperature. When the pressure has been reduced so low as is thought desirable
the piston completes its stroke. In the return stroke the waste fluid may be dis-
charged either into the atmosphere or into a refrigerator or cooling chamber main-
tained at low pressure, from which it is extracted by an air pump. If such a
refrigerator is employed the expansion of the fluid in the working stroke is con-
tinued to a point at which its pressure falls below that of the atmosphere.
After the extraction of the exhaust fluid from the cooling chamber the whole of
it may be discharged as waste; but otherwise a portion of it may be used to supply
the pump or forcing instrument which compresses the elastic fluid supplied to the
cylinder to work on the piston, as previously explained; and with respect to thermal
efficiency I consider this latter course preferable. Similar operations are performed.
on each side of the piston, or in other words, the engine is double acting.
The degree of compression given to the air or clastic fluid which is introduced
into the cylinder in order to perform work in it may be much varied. I consider
that the best result is obtained with respect to thermal efficiency when it is raised
to a pressure not far short of the highest pressure produced in the cylinder by the

page_text: combustion of the inflammable mixture. But in order to diminish the opposing
action of the compressing pump and reduce the bulk of the engine, it may frequently
be desirable in practice to give to it a less degree of compression.
The compression of the elastic fluid used in the cylinder and the extraction of
the elastic fluid from the refrigerator or cold chamber may be performed by means
of ordinary pumps, in which pistons work in cylinders. I prefer however in both
cases to work by rotary pumps, in order that the action may be continuous, and
that the revolving parts may perform the office of a fly wheel in equalising the
action of the engine. Succession of pumps or forcing instruments may be used.
The rotary pump or apparatus which compresses the fluid used in the cylinder
forces the air or fluid into a chamber of considerable capacity in which it is con-
tained at high pressure, and from which a certain determinate quantity is admitted
into the cylinder, while the valve for its admission is opened. The regulation of
the quantity of fluid thus admitted into the cylinder is effected nearly to the point
desired by the size of passage governed by the valve, and the time during which it
is open; but it is adjusted to greater nicety by means of a regulator provided for
the purpose.
In order to lessen the shock produced by the ignition of the inflammable mixture
and the consequent sudden rise of pressure on the piston, I employ a secondary
piston between the charge of inflammable mixture and the working piston. This
piston is furnished with a valve which allows passage of the fluid from the
space between the pistons into the cylinder behind, but prevents passage of fluid
in the contrary direction. A spring is also placed between the two pistons. At
each stroke air or clastic fluid is supplied to the space between the pistons by
a valve provided for the purpose worked by the engine. After this has been
done the charge of inflammable mixture is introduced behind the secondary piston.
When the inflammable mixture is ignited and the sudden rise of pressure con-
sequent on the ignition takes place, the ignited fluid drives the secondary piston
towards the main or working piston, compressing the air or clastic fluid between
them, and as the pistons approach compressing the spring. Under these circum-
stances the force produced by the sudden rise of pressure of the elastic fluid is com-
municated gradually to the working piston.
As the pressure of the products of combustion falls the valve in the secondary
piston opens, and the compressed fluid within escapes into the space containing the
hot products of combustion with which it mixes, and performs work along with them.
At the end of the exhaust stroke the two pistons are brought close together; at
the commencement of the succeeding stroke they separate, while the air or fluid is
introduced between them through the valve provided for the purpose.
All the air or fluid employed to co-operate with the products of combustion might
be introduced in this manner between the pistons, in which case the compressing
pumps or instruments previously mentioned might be dispensed with; but I prefer
to employ them as previously described, since by their use the length of the
working cylinder is shortened and the action of the engine rendered more uniform.
In the arrangement of the two pistons, other things remaining as above described,
the valve in the secondary piston may be dispensed with. In this case the fluid
compressed between the two pistons escapes between the secondary piston and the
cylinder, or between this and the piston rod, or through a small aperture provided
for its passage.
Either gas or inflammable vapour may be used as one of the ingredients of the in-
flammable mixture. The other ingredient may be air drawn in from the atmosphere,
as in ordinary gas engines, but otherwise the gas or vapour, and the air may be com-
pressed by the action of the engine, and delivered into the cylinder at high pressure.
In such a case the pressure imparted to the air or elastic fluid by the compressing
pumps or instruments previously mentioned is raised in a corresponding degree, that
is to say, it is raised to a pressure higher than that at which the inflammable mixture
is introduced into the cylinder, and it may be to pressure equal to the highest

page_text: Figure 1 and Figure 2 are a longitudinal and cross section, and Figure 3, a plan
shewing a form of apparatus constructed according to my Invention.
A, A, is the working cylinder within which the heated elastic fluid acts on a
piston and performs work; B, B, is a cooling chamber cooled by cold water passing
through the chambers i, i, and the tubes k, k. In place of the form of cooling
chamber shown any of the known forms of surface condensors and refrigerators may
be employed. The pressure within this chamber is maintained below that of the
atmosphere by means of the rotary pump E worked by the engine, as shewn which
continually extracts from it the elastic fluid which passes into it from the cylinder.
c, c, is a chamber containing air or elastic fluid at high pressure which is forced into
it by means of the rotary pump F also worked by the engine, as shewn. This
pump may be supplied either from the atmosphere or from the exhaust fluid;
V is the valve or slide which governs the passages by which the cylinder com-
inunicates alternately with the high-pressure and low-pressure chambers;' v¹ and
are the valves or slides which govern the admission and cut off of the inflam-
mable fluid mixture into the cylinder; I represent these as having the construction
used in Otto and Langen's gas engine, but I do not shew the whole of the
construction as it is well known.
Supposing the piston P to be at the left end of the cylinder the operations take
place as follows:-The slide v opens the passage for the admission of the inflam-
inable fluid from S to the space between the left end of the cylinder and the
piston P, while simultaneously the slide V opens the passage between the right-hand
end of the cylinder and the low-pressure chamber or refrigerator B. The piston P
moves from left to right, the inflammable mixture enters behind it on the left, while
in front of it fluid passes from the right-hand end of the cylinder to the refrigerator.
As soon as the charge of inflammable fluid has been admitted into the cylinder the
valve v closes the passage for its admission, and the mixture is ignited. Soon
afterwards at a period determined by the degree of compression employed the.

page_text: slide V opens the passage between the cylinder and the high-pressure chamber, and
air or elastic fluid passes from that chamber into the cylinder where it mixes
with the hot products of combustion. Shortly afterwards the slido V cuts off the
admission of air or fluid from the high-pressure chamber to the cylinder.
The mixed elastic fluid expands and urges forward the piston P until it reaches
the end of its stroke at the right-hand end of the cylinder, the slide V then closes
the passage between the righ-hand end of the cylinder and the low pressure
chamber, and the series of operations previously described is repeated for the return
stroke.
When the refrigerator is dispensed with the operations are the same, except that
the discharge of waste fluid from the cylinder takes place into the air instead of
taking place into a chamber wherein the pressure is below the atmospheric, and the
exhausting or extracting pump E is dispensed with.
In Figure 2, 9, g, shews the regulator by means of which the quantity of air or
fluid admitted into the cylinder from the high-pressure chamber c is regulated.
The rotary pumps which I prefer to employ for the extraction and compression of
the elastic fluid are of the form known as Sudlow's.
A hand pump is provided in connection with the high-pressure chamber, by
means of which its pressure can be raised to the degree desired before starting.
Issue of air from this chamber into the working cylinder may be made use of for
starting the engine.
In the Drawings above described a plain piston P is represented for the sake of
simplicity, but I prefer to employ a compound piston with other parts working in
connection with it, as is shown at Figure 4.
In Figure 4, P is the main or working piston; p, the secondary piston.
As the engine is double working there are two secondary pistons, one on either
side of the main piston. The rods, r, working in the passages t, t, allow the
pistons to approach, but prevent them from separating further than as shown in the
Figure. The valve v allows air or elastic fluid to pass from between the pistons
into the space 8, but prevents its passage in the contrary direction.
When the inflammable mixture is ignited and high pressure is suddenly produced,
the pressure of the ignited elastic fluid drives the two pistons together, compressing
the air or fluid between them, and compressing the spring e, e. Afterwards as the
pressure behind the piston p becomes reduced by expansion, the compressed fluid
between the pistons escapes through the valve v into the space s, or the portion of
the cylinder in which are the hot production of combustion.
The spring e may if preferred be omitted.
At the end of the stroke the pistons are forced together. At the commencement
of the next stroke a valve W worked by the engine is opened, which allows air from
the atmosphere to enter between the pistons. The air enters and the pistons
separate so far as the rods r, r, allow, after which the valve W closes and the
pistons P and p move together. As soon as the movement of the second piston p
commences, the valve G for the admission of the inflammable fluid mixture is
opened and it enters behind the secondary piston p, p.
As soon as the proper
quantity of it is admitted its admission is cut off and it is ignited. p¹, p', represents
the secondary piston on the other side of the main piston.
Instead of air a portion of the exhaust fluid which has been discharged from the
cylinder may be introduced into the space between the pistons.
Having thus described the nature of my said Invention, and the manner of per-
forming the same, I would have it understood that in respect to the apparatus and
operations above described, I do not claim the use of a refrigerator or cooling
chamber at low pressure into which the exhaust fluid is discharged, and from which
it is subsequently extracted by a pump, since I do not regard this mode of treating
the exhaust fluid of a hot air engine as novel; but I claim in respect to engines
worked by the elastic force produced by the combustion of inflammable elastic fluid
acting on a piston in a cylinder, the introduction into the hot products of combustion

page_text: while they are working at high pressure, of air or elastic fluid which has been raised
to high pressure by a pump or forcing instrument separated from the working
cylinder by valves which are only opened at certain periods.
Also I claim the construction of pistons to reduce violence of shock and utilise
the compression of fluid between them, substantially as I have described.
Also I claim the construction of apparatus for carrying out the various operations
explained, substantially as I have described.
In witness whereof, I, the said Matthew Piers Watt Boulton, have hereunto
set my hand and seal, this Tenth day of March, in the year of our Lord,
One thousand eight hundred and seventy-seven.
M. P. W. BOULTON. (L.S.)