IMPROVEMENTS IN CALORIC ENGINES
Year: 1880

page_text: "
PROVISIONAL SPECIFICATION left by the said Matthew Piers Watt Boulton
at the Office of the Commissioners of Patents on the 17th December 1880.
MATTHEW PIERS WATT BOULTON, of Tew Park, in the County of Oxford.
IMPROVEMENTS IN CALORIC ENGINES."
This Invention relates to caloric engines arranged generally according to the
construction which I have described in the Specification to my Patent, No. 495,
of 1879.
In this construction a vessel is employed fitted with a piston, by means of which
a charge of air is taken in and afterwards introduced into the heater, the piston
which thus introduces it being in equilibrium or nearly so. I shall speak of this
piston as the displacing piston or displacer.
One of my present improvements consists in providing means for urging this
piston in both its strokes by power acting on it directly, so that the cam or other
contrivance by means of which it is connected with the engine does not supply the
power needed to work it, or supplies such power only to a small extent, the
principal office of the cam being thus reduced to that of regulating and timing
the movement of the piston.
In order to supply the power needed to drive the piston when it is sending the
charge of air into the heater, I enlarge the rod by which it is connected with
the engine, so that the gaseous pressure on its hot side exceeds that on its cool side
to such a degree as is desired.
The power needed to drive the piston in the other stroke may be supplied in
various ways. If the cylinder in which it works is placed vertically with its cool
end uppermost, then it may be urged in this stroke by its weight, which weight
may be increased to any extent desired.
If the cylinder is placed horizontally, then it may be urged in this stroke by
means of a weight acting on an arm, or by a spring, or by compressed air.

page_text: I shape the cam which regulates the movement of the displacer in such a way
that the displacer rests for a short time at the hot end of its cylinder, and so that
it moves slowly when near the end of its cylinder in both strokes. The object of
this arrangement is to give time for the proper action of the valves towards and at
the end of the stroke.
Owing to the space occupied by the piston rod and to the clearance, the fresh air
taken in by the displacer is not equal in volume to the space occupied by the
working air on the hot side of the displacer. On this account I work the valves
which govern the passages between the displacing vessel and the heater separately,
shutting off the valve on the hot side a little before the end of the stroke made by
the displacer from the hot to the cool end, so that some expansion of the hot
working air takes place within the displacing vessel.
I place the hot ends of the displacing vessel and the working cylinder in the flue
through which hot gases from the furnace pass, after they have imparted heat to
the heater; my principal object in doing this being to prevent heat from being
abstracted from the air in those vessels by external cooling agency; this arrange-
ment also affords convenient means for heating these vessels before starting the
engine.
I attach an air pump to the passage between the displacing vessel and the
regenerator, and I provide the heater with a passage fitted with a loaded valve, in
order that while the heat of the air within the heater is being raised, cold air may
be occasionally forced through the regenerator, so that its plates may be kept cool.
The following is a construction of heater which I employ :-
The upper part of the heater is cylindrical. The lower part is annular, consisting
of a comparatively narrow space between two cylinders; the fire plays over the
outer surface of the outer cylinder, and the inner surface of the inner cylinder from
the space within which a portion of the hot gases escape through an aperture in the
upper part of the heater. Diaphragms are provided, dividing the annular portion
into two annular passages, and diaphragms in connection with these are also
provided in the upper portion of the heater, so that the air introduced in the upper
part is forced to travel down one of the annular passages, and then up the other,
after which it passes off to the working cylinder.
In order that the air may flow equably through all parts of the annular passages,
I provide guiding diaphragms pierced with apertures in their central portions, so
that the air in its course to the annular passages is first conducted to this central
aperture, whence it spreads out equably in all directions towards the annular
passage. And in like manner after the air has ascended through the other annular
passage, it is conducted to a central aperture before passing off to the cylinder, in
order that its flow through the annular passages may not be favoured in one
direction more than in another.
My caloric engine having the above described improvements may be worked in
combination with a vessel of compressed air and a refrigerator, as set forth in my
Specification before mentioned.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent nied by
the said Matthew Piers Watt Boulton in the Great Seal Patent Office on
the 15th June 1881.
MATTHEW PIERS WATT BOULTON, of Tew Park, in the County of Oxford.
"IMPROVEMENTS IN CALORIC ENGINES."
This Invention relates to caloric engines arranged generally according to the
construction which I have described in the Specification to my Patent, No. 495, of
1879.
In this construction a vessel is employed fitted with a piston, by means of which
a charge of air is taken in and afterwards introduced into the heater, the piston
which thus introduces it being in equilibrium or nearly so. I shall speak of this
piston as the displacing piston or displacer.
One of my present improvements consists in providing means for urging this
piston in both its strokes by power acting on it directly, so that the cam or other
contrivance by means of which it is connected with the engine does not supply the
power needed to work it, or supplies such power only to a small extent, the
principal office of the cam being thus reduced to that of regulating and timing the
movement of the piston.
In order to supply the power needed to drive the piston when it is sending the
charge of air into the heater I enlarge the rod by which it is connected with the
engine, so that the gaseous pressure on its hot side exceeds that on its cool side to
such a degree as is desired.
The power needed to drive the piston in the other stroke may be supplied in
various ways. If the cylinder in which it works is placed vertically with its cool
end uppermost, then it may be urged in this stroke by its weight, which weight
may be increased to any extent desired.
If the cylinder is placed horizontally, then it may be urged in this stroke by
means of a weight acting on an arın, or by a spring, or by compressed air.
I shape the cam which regulates the movement of the displacer in such a way
that the displacer rests for a short time at the hot end of its cylinder, and so that
it moves slowly when near the end of its cylinder in both strokes. The object of
this arrangement is to give time for easy movement of the valves towards and at
the end of each stroke.
Owing to the space occupied by the piston rod and to the clearance, the fresh air
taken in by the displacer is not equal in volume to the space occupied by the
working air on the hot side of the displacer. On this account I work the valves
which govern the passages between the displacing vessel and the heater separately,
shutting off the valve on the hot side a little before the end of the stroke made by
the displacer from the hot to the cool end, so that some expansion of the hot
working air takes place within the displacing vessel.
I place the hot ends of the displacing vessel and the working cylinder in the
flue through which hot gases from the furnace pass, after they have imparted heat
to the heater; my principal object in doing this being to prevent heat from
being abstracted from the air in those vessels by external cooling agency; this
arrangement also affords convenient means for heating these vessels before starting
the engine.
I attach an air pump to the passage between the displacing vessel and the
regenerator in order that while the heat of the air within the heater is being raised,
cold air may be occasionally forced through the regenerator, so that its plates
may be kept cool. I provide in the passage between the heater and the hot end
of the displacing chamber an outlet cock, so that the current of air created by the

page_text: Fig. 1 is a vertical section, partly in elevation, of an engine according to my
Invention. A is the vessel into which the successive charges of air are introduced,
and where they are displaced. D is the displacing piston; S¹ is the shield attached
to it, and W is a water casing for cooling the upper part of the vessel A, which casing
may be extended over its cover; C is the working cylinder which is open at the
top, and P is its piston which drives the engine and has a shield S². The displacing
piston has a trunk rod D', so that when the high pressure air admitted from the
heater acts on both sides of D there is a certain excess of pressure overcoming the
weight of D and its rod and urging D upwards.
H is the heater, a sectional plan of the upper part of which is shewn at Fig. 2;
F is the fire place or furnace. The hot products of combustion issuing from this
pass partly into the interior space B and away by the central flue E, and partly
into the annular space I outside the heater. They then pass into the passage or
flue K, where they heat the lower parts of the vessels A and C, as shewn,
and afterwards they pass away through the flue L to a chimney or place of
discharge.
R is the regenerator; G are plates or bodies within it, in passing through which
the air is alternately cooled and heated. These plates or bodies might be dispensed
with when the passage has considerable length and surface so as to effect the
regenerative action required.
Communication takes place between one side of the heater and the upper or cool
end of the displacing chamber through the pipes M², M², and the regenerator R.
This communication is governed by the valve h³.
V is a valve by which the communication between M¹ and R can be closed and
opened when desired. The object of this valve is to shut off communication
between the heater and regenerator when the engine is not at work, in order to
prevent the heat from rising upwards into the regenerator.
The other side of the heater communicates with the lower or hot end of the
displacing chamber A through the pipe N; this communication is governed by the
valve h².
The operations take place as follows:-
For starting point I suppose that the piston P has just completed its working
stroke and is at the top of its cylinder C ready to commence its down or discharge
stroke. The displacer D is also at the top of its cylinder A, or nearly so.
The

page_text: valves h¹ and h² are closed, u and e are open. The spaces below D and Pare
filled with exhaust air, that is, air which has performed its work on the
piston P.
D descends; below, it expels exhaust through the valve u (which is then open)
into C and out through the eduction valve e which is also open; above, it draws
in or is followed by fresh atmospheric air entering through s, which may either be
a suction valve or may, as shewn in the Drawing, be opened by the engine.
D proceeds in this way to the bottom of A. While D is making this stroke P is
performing the first half or portion of its down stroke, expelling below it exhaust
through e. When D has completed its down stroke it pauses for a short time or
moves very slowly; u and s are closed, and h¹ and h² are opened. High pressure
air from H enters A on both sides of D, and as the area exposed to the action of
this air is larger on the under side of D than on the annular area around the
trunk on its upper side, D is urged upwards and makes its upstroke, governed
by the cam Q, of which Fig. 3 is a front view. The air entering A. on the lower
side of D has the full heat capable of being supplied from the heater; that entering
on its upper side is comparatively cool, having been cooled by passage through the
regenerator R. As D ascends, on its upper side it sends back the air into H through
the regenerator R, while on its lower side it draws in or is followed by hot air
from H. Shortly before D reaches the top of its stroke h³ is closed, and during the
remainder of the stroke the hot air below D expands. When D has completed its
upstroke h¹ also is closed. The space in A below D is now filled with high pressure
hot air ready for performance of work. While D is making its upstroke P performs
the second half or portion of its down stroke, continuing to expel exhaust through e.
When the stroke of P is completed e is closed and u is opened, and the high pressure
hot air with which A is charged below D is admitted to act in C below P.
D now remains stationary, or nearly so, while the hot air beneath it expanding in C
drives P upwards, thus causing it to make its working stroke. While it is doing
this D may be permitted by the cam to move slightly downwards so as to allow
the clearance air above it to expand. The upward stroke of P having been
completed and the proper changes of valves made the point previously taken as
starting point is reached.
Y is a pump worked by hand or by any convenient means, which forces air into
the cool passage connected with the top or cool part of the regenerator and through
the regenerator into the heater. By means of this pump the pressure in the
regenerator and heater can be raised when required. A vessel containing com-
pressed air may be provided for raising the pressure in the heater when it is desired
to start the engine. By opening communication between this vessel and the heater
the pressure needed in the heater can be at once obtained.
pressure regulating
valve may be provided between the vessel containing the compressed air and the
heater. Such an arrangement is particularly applicable when the engine is used for
purposes which require frequent intermission of working.
When it is desired to work with high pressure air instead of with air drawn in
from the atmosphere, then the valves s and e are connected with the two ends of
a refrigerator or cooling vessel containing air at the pressure desired, the former
with its cooler, the latter with its hotter end. The air discharged from the
cylinder C through e is discharged at high pressure, that is to say, a pressure
higher than the atmospheric but lower than that of the hot working air received
from the heater. When this air is discharged through e, though its temperature
has been reduced by performance of work, yet it still retains a considerable
temperature. This temperature is reduced by its passage through the refrigerator
or cooling vessel, and after it has been thus cooled it supplies the vessel A through
the valve s just as atmospheric air does in the case previously described, only at
high pressure.
As any of the various forms of vessels used for boilers and heaters may be used
as cooling vessel or refrigerator, I have not thought it necessary to shew any
construction of refrigerator in the Drawing.

page_text: To supply loss of high pressure air occasioned by leakage a pump worked by the
engine may be employed, as in Stirling's engine, and other cases.
I proceed to describe the form of heater H shewn in Figs. 1 and 2.
The air to be heated enters by the pipe M¹, from which it passes into the
passage o, which passage extends all round the heater, but by means of an eccentric
partition is made of varying area, being widest in the part where the pipe M¹
enters it and growing narrower towards the opposite side, as shewn in Fig. 2.
From o the air passes into the annular passage L, and flows downwards guided by
the diaphragm d. A contraction of passage is made at t, the object of this being
to cause the air to pass equably through 7 and to prevent it from taking its course
principally through one part of it. Having passed downwards through the air
ascends through the inner annular passage r. From this it passes through the
central annular passage x into the eccentric passage p. From this passage the air
passes into the pipe N, which conveys it to the displacing chamber A. A vessel of
form similar to H may be also used for a refrigerator, its external surfaces being
cooled by currents of water or air.
The cams on the engine shaft for effecting the movements of the various parts
are as follows:-X¹ is the cam for working the valve ¹ between the displacing
chamber and the heater; X¹ is the cam which works h², so formed as to close it
somewhat earlier than h¹. These two valves are kept open by the cams during the
upward motion of the displacer, which occupies about one quarter revolution of the
crank shaft, while at other times they are kept closed. X2 is the cam for working the
valve between the displacing chamber and the working cylinder. This cam
keeps the valve u open while the air beneath the displacer is expanding and
performing work in the cylinder C and also during the downstroke of the dis-
placing piston, which periods occupy together about three quarters of a revolution
of the crank shaft. X³ is the cam which works the supply valve s. This cam
keeps the valve open during the downstroke of the displacer, occupying about one
quarter revolution of the crank shaft. X is the cam which works the exhaust
valve e, keeping it open during the downstroke of the piston P, or about half a
revolution of the crank shaft.
The cam which controls the movement of the displacer consists of two plates
fixed on the crank shaft, each having a sunk cam path in which works a roller
mounted on the rod of the displacing piston. The cam paths are so formed that
during half the revolution of the crank shaft the displacer stays at the top of its
cylinder, or moves but slightly near the top, while during the other half revolution
it makes a down and an upstroke, these two strokes being separated by a brief
interval of rest or of very slow movement.
Although I have described and shewn cams as means of effecting the movements
of the displacer and valves, it is to be understood that these movements might be
effected by other known means.
Fig. 4 shews a coustruction for the valves h', h², u, and e. The valve box consists
of a casing, having a division provided with a seating for the main valve. A
smaller valve seats on the main valve, the rod of this valve being worked by one
or other of the cams X1, X2, X³, X. On the valve rod is fixed a stop nut, which
when the smaller valve has been opened a little allowing passage of air to equalise
the pressure on both sides of the main valve, lifts the main valve with little
expenditure of power.
An engine, as above described, may be combined with an air vessel, into which
air is forced by a pump worked by the engine, the supply to the displacing
chamber being received from this air vessel. A construction for this purpose has
been shewn in my Specification No. 495 of 1879 above referred to.
An air vessel thus supplied may be employed for the purpose of driving back
the displacer, when its cylinder is placed horizontally or in such a position that
the weight of the displacer cannot be employed for the purpose. In such a case
air is compressed to the requisite degree in the air vessel by means of the pump
worked by the engine, and the air from this air vessel entering the displacing

page_text: chamber through the supply valve 8 drives or urges the displacer in its stroke from
the cool to the hot end of its cylinder, thus assisting the cam or other apparatus
by means of which the displacer is connected with the engine.
The pressure of air employed for this purpose may be very moderate, and the
pump worked by the engine for compressing it may be of the nature of bellows.
Fig. 5 shews an arrangement for supplying moderately compressed air to the
displacing chamber, in order to drive the displacer from the cool to the hot end of
it; E is an eccentric or crank on the engine shaft working a bellows B¹, which
in its downstroke forces air into the air vessel Z, raising the pressure therein to the
degree desired. The air from this vessel passes by the pipe z to the displacing
chamber, the communication being governed by the supply valve 8, as shewn in
Fig. 1. Apparatus of this kind may be used not only when the supply of cool air
is taken in from the atmosphere, but also when it is taken in from a refrigerator
or cooling vessel containing air at high pressure, as has been above explained. In
such a case the pump or bellows may work within a vessel communicating with
the cooling vessel, and containing air at the same pressure as that within it. The
pump takes in air from this vessel and forces it into the vessel Z at a somewhat
higher pressure, as desired, and from Z it passes to the displacing chamber as
governed by the valve s. On the return stroke, that is to say, from the hot to
the cool end of its cylinder, the displacer may be urged as has been previously
described, namely, by the excess of pressure on its hot side, owing to its area on
that side being greater then the annular area on its cold side around the piston
rod.
Although I have described and shewn the working cylinder as being open at top
to the atmosphere, and its piston as being furnished with a shield, yet this may
be otherwise arranged. The shield may be dispensed with, and the cylinder may
communicate at top with a vessel containing warm air. The warmth of the air
in this vessel may be maintained by passing exhaust air from the engine
through it.
The engine might obviously be made double acting by duplicating the necessary
parts.
Having thus described the nature of my Invention, and in what manner the
same is to be performed, I claim in respect of caloric engines in which a charging
vessel and displacing piston are employed to perform the functions described in
my previous Specification, No. 495 of 1879, above referred to, and in the present
Specification,-
First. The construction and arrangement of caloric engine, substantially as
herein described with reference to the accompanying Drawings.
Second. The construction of heater, substantially as herein described.
Third. Aiding the movement of the displacing piston by making it with an
excess of area on its one side, acted on by the pressure in the charging vessel
so as to urge the piston in the one direction, and by supplying the charging vessel
with air under pressure so as to urge the piston in the other direction, sub-
stantially as herein described.
In witness whereof, I, the said Matthew Piers Watt Boulton, have hereunto
set my hand and seal, this Thirteenth day of June, in the year of our Lord
One thousand eight hundred and eighty one.
M. P. W. BOULTON. (L.S.)