IMPROVEMENTS IN HOT-AIR OR CALORIC BVAINES
Year: 1882

page_text: LETTERS PATENT to Matthew Piers Watt Boulton of Tew Park in the
County of Oxford for an invention of IMPROVEMENTS IN HOT-AIR OR CALORIC
BVAINES
PROVISIONAL SPECIFICATION left by the said Matthew Piers Watt
Boulton at the Office of the Commissioners of Patents on the 14th April
1882.
MATTHEW PIERS WATT BOULTON of Tew Park in the County of Oxford
PROVEMENTS IN HOT-AIR OR CALORIC ENGINES
"
"IM-
This Invention relates to engines in which air or elastic fluid is heated in a closed
vessel at high pressure and by its expansion works a piston in a cylinder. I
described a construction of Caloric Engine in the Specifications of the Patents
granted to me A.D. 1879 7th February No. 495 and A.D. 1880 17th Deceinber
No 5299.
In the engines there described there are two cylinders, the piston in one of them
termed the displacer having for its office to take in air and send it into a heater,
while the hot air expands in the other cylinder and by its pressure on the piston
working therein drives the engino
I modify the construction of engine described in those Specifications in the
following manner.
I govern the communication between the heater and the cool end of the displacing
cylinder by a self acting valve. When the displacer is about to commence its stroke
of delivery into the heater, the valvo which governs the communication between
the heater and the hot end of the displacing cylinder is opened by the engine. The
hot air entering the displacing cylinder through this valve urges the displacer
and it compresses the air on its cool side till when the pressure of this air is
sufficiently raised it opens the self acting valve governing the communication between
this air and the heater, and during the remainder of the stroke this air passes into
the heater.
When this construction and mode of working are adopted, the regenerator is no
lanceur needed and is dismenced with

page_text: I consider it desirable to do as little work by means of the cam connected with
the displacer as possible and desire therefore to urge the displacer in both its strokes
by some force not acting through the cam of such amount as is needed to effect its
movement or the greater part of it, the office of the cam being reduced to that of
regulating and timing the movement. For this purpose the following method is
applicable.
Supposing the displacing cylinder to be placed vertically with its hot end lowest
the weight of the displacer is counterbalanced to such an extent as is needed, either
by a weight or by a spring and the displacer is urged through its up-stroke by the
gascous pressure of the hot air entering from the heater, assisted by the action of
this counterbalancing weight or spring.
In the downward stroke it is urged by air admitted from an air vessel in which
suitable pressure is created by means of a pump worked by a crank driven by the
engine. The piston of this pump may make a portion of its stroke during the
downward stroke of the displacer.
If the displacing.cylinder is placed horizontally gaseous pressure may be caused
-to-act on the displacer in both its strokes in the manner above explained but as in
this case its weight-does not act, there is no need to employ a spring to counter-
balance this.
As it is desired to work as little by the-cam-as possible,-it-is-well so to shape
it as to allow the displacer to move freely during a considerable portion-of-it
stroke. And the cam might be dispensed with altogether, the gaseous pressures-
being-so.adjusted as to cause the displacer to move with the requisite velocity.
Another modification-of-construction is as follows:-The displacer is worked by
a crank, so timed that the displacer makes its-upstroke or stroke of delivery into
the heater while the working piston is making its return or exhaust stroke, and
its downstroke-or-stroke of intake while the working piston is making its working
stroke. When this construction is adopted, the working cylinder has to be made
much larger.
Otherwise one cylinder only may be used the piston on its cool side acting-as-a-
pump taking in air from the cooling vessel in one stroke and forcing it into the
heating vessel in the other stroke. On the hot side of the piston it receives hot air
from the heater the admission of which is regulated by a cut off valve and after
this has expanded it is expelled in the next stroke as exhaust. In this construction
the parts are fower, but the introduction of the air into the heater opposes the action
of the engine.
When two cylinders are used, I consider it well to place the cool side of the
working piston in communication with the refrigerator in order to lessen the difference
of pressures acting on the opposite sides of this piston which tends to reduce leakage
and also to equalise the action of the engine.
The constructions which I proceed to describe are applicable whichever of the
constructions previously described are used.
In order to lessen passage of heat from the hot to the cool ends of the cylinders
(or cylinder) they are (or may be) made of two portions flanged together, the flanges
being separated by asbestos or suitable material and the bolts which unite the flanges
being insulated by the same material. As nevertheless a certain amount of heat
passes through the metal of the cylinders from their hot to their cool ends, it is
desirable to utilise this heat or a portion of it, for which purpose the following
methods are applicable.
A narrow annular passage is provided on the exterior of the cooler part of the
cylinder or cylinders and air is forced through this by the engine or drawn by the
chimney draught, which air goes to supply the fire by which the heater is heated.
Otherwise the air which works the engine is caused to pass through a similar
passage on its way from the cylinder in which it is received to the heater.
Both these methods may be used in combination-in which case the air which
supplies the fire passes through the passage nearest the cool end of the cylinder (or

page_text: cylinders) which I shall suppose to be the upper end, and the air going to the
heater passes through a passage immediately below this..
When the engine is constructed as described in my former Specifications,
previously referred to, in which a regenerator is employed, then a small regenerator
is placed between the displacing cylinder and the annular passage provided around
its exterior for the purpose of heating air used to work the engine.
Again a water-casing may be employed round a portion of the cylinder or
cylinders from which steam is generated, this steam passing into the heater and
co-operating with the air in it. In such a case it may be well to provide two
casings, one round a hotter portion of the cylinder or cylinders, the other round a
cooler portion. In the first of these steam is generated, in the second water is
heated, which water serves as supply to the first casing.
This method of utilising the heat may be combined with the former ones. Or
one method may be employed in one cylinder, another in the other.
Although material to obstruct passage of heat is placed within the shield of the
piston yet nevertheless a certain amount of heat passes through it, and if the
engine does not work, while the fires remain alight, the upper part of the piston,
or that side of it which ought to be cool may become heated. It may be desired
therefore to provide means for cooling it, in case it shall have become heated.
This may be done in various ways. A current of cold air may be directed against
it, a pump worked by hand being provided for this purpose. Or a space may be
provided within it through which cold water is caused to pass, which water may
be introduced and taken away through tubes provided within the piston rod.
Means also may be provided for cooling the exterior of the cylinder at its cool end
by a current of cold water or cold air when the engine is not at work, while when
it is at work it is kept cool by air caused to pass through a passage surrounding a
portion of them, as has been previously described, whose motion is caused by the
engine na previously explained.
The hot gases which pass away after heating the under parts of the cylinder or
cylinders have a somewhat high temperature so that in most cases it is desirable
to utilise a portion of their heat. For this purpose the following construction is
applicable. A heating vessel is provided in addition to that on which the fire first
plays and the escaping hot gases whose heat it is desired to utilise act on this. The
air delivered by the engine to the heater passes through this secondary heater to
that on which the fire first plays. The temperature of the air is first raised in the
secondary heater and afterwards still further raised in the primary heater on which
the fire first plays, from which it passes by a short passage to the cylinder in
which it performs work.
Also the secondary heater might consist of two separate parts, in one of which
the air which is used as supply to the engine is heated, while in the other air is
heated which goes to supply the fire.
The air discharged from the cylinder as exhaust is discharged at a somewhat
high temperature, so that it may be desired in many cases to utilise a portion of
its heat. For this purpose the following method is applicablo.
The exhaust in the first instance acts on the tubes or flues of a heating apparatus
through which on the other side air is passed, the air thus heated being conducted
to supply the fire. Or in some cases air passing from the reception cylinder to the
heater might be partly heated in this apparatus. After the exhaust has been
partially cooled by traversing this heating apparatus, it passes to the further
cooling vessel, where it is cooled by water or other agency to the degree desired,
the heat here abstracted from it passing away as waste.
Otherwise this heating apparatus may heat water and generate steam, the steam
so generated passing to the heater and co-operating with it in the cylinder. In
such a case it is well to place the tubes of the heating apparatus in a vertical
position in the water, so that the water gradually diminishes in temperature from
its surface downwards and gives off steam at top.
In heating the air I consider it well so to shape the passage through which it

page_text: flows while being heated, that it shall undergo numerous variations of area; in
order that the air may be disturbed and that successive portions of it may be
brought in contact with the heating surface. In some cases the variation of area
may be caused by employing corrugated metal, in other cases it may be caused in
other ways. All the passages connected with the engine in which air is heated,
may be shaped as above described. The like is also applicable to passages in
which air is cooled.
It may be desirable to use in the engine valves which are balanced or partially
balanced by pistons connected to their stems. In such a case on account of the
heat of the air it is well to make the piston like that of the cylinder that is to say 1
to furnish it with a shield or body which obstructs passage of heat and to cool the
part of the cylinder where the closely fitting part of the piston works by a water-
casing or other suitable means so that liquid or lubricant may be employed to keep
the piston tight.
In the specification of the Patent granted to me A.D. 1880; 17th December,
No. 5299, I described a construction of valve in which a small valve seated on a
large-valve first opened and afterwards opened a large valve.
The-following is another construction for the same purpose. Two small valves
are provided, one on each side of a larger-central valve. The two Binall valves are
first lifted by an arm which afterwards lifts the larger valve-and opens full passage
for the air. The valves may be made flat faced and of square or rectangular-form,
with a view to compactness of arrangement.
The following is a construction of heater suitable for that portion of the heating
apparatus on which the fire-and hot gases first play, which may be termed the
primary heater. Two vessels are provided-of-basin-like form and are united
-together at their edges, so as to leave a narrow passage between then, which
constitutes the space-within which the air is heated. This passage is made to vary-.
in area by means of curvatures, or-curved pieces, which I consider it best-to place
on the upper or inner basin. The air to be heated-is-admitted at the upper part
of the heater and flows downwards in all directions towards the centre, passing
away by a pipe which ascends in the central part of the concavity of the upper
basin and conducts it to the cylinder in which it performs work. The fire plays
first on the bottom of the heater, whence the hot gases flow uniformly over the
surface of the outer or lower basin. They are then conducted into the concave
space over the upper basin, play uniformly over the surface of this basin, and then
ascend by a central flue enclosing the air-pipe above mentioned.
The cylinders (or cylinder) may conveniently be placed immediately above the
heater and their lower portions may occupy part of the central concave space.
The bed-plate to which they are attached may be made hollow, this hollow
communicating with the heating apparatus and forming part of it, so that air
flows through it on its way to the primary heater, or that portion of the heating
apparatus on which the fire first plays.
If a heater is employed having generally the form of that described by me in the
Specification of the Patent granted to me A.D. 1880 17th December No. 5299, the
area of the passages through which the air flows may be made to vary by attaching
numerous projections to the internal diaphragm.
The engine may be provided with a governor of any known kind, which may be
applied to vary the cut off or the draught of the furnace or both. In the above,
for the sake of simplicity of description, I have described only one working
cylinder. But it is obvious that the number of cylinders may be multiplied and
may be worked either from one set of heating and cooling apparatus or from
separate sets of these. And the working cylinders and the connections of their
pistons to cranks on one or more shafts may be arranged in any of the various
ways in which similar parts of steam engines are arranged.

page_text: 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 13th October 1882.
MATTHEW PIERS WATT BOULTON of Tew Park in the County of Oxford
PROVEMENTS IN HOT-AIR OR CALORIC ENGINES
"
" IM-
This invention relates to engines in which air or elastic fluid is heated in a
closed vessel at high pressure and by its expansion works a piston in a cylinder
1 described a construction of Caloric engine in the Specifications of the Patents
granted to me A.D. 1879 7th February No. 495 and A.D. 1880 17th December
No. 5299. In the engines there described there are two cylinders, the piston in
one of them terined the displacer having for its office to take in air and send it
into a heater, while the hot air expands in the other cylinder and by its pressure
on the piston working therein drives the engine.
I modify the construction of engine described in those Specifications in the
following manner :-
I govern the communication between the heater and the cool end of the
displacing cylinder by a self acting valve. When the displacer is about to
commence its stroke of delivery into the heater, the valve which governs the
communication between the hot end of the displacing cylinder is opened by tho
engine. The hot air entering the displacing cylinder through this valve urges the
displacer and it compresses the air on its cool side till when the pressure of this air
is sufficiently raised it opens the self acting valve governing tho communication
between this air and the heater, and during the remainder of the stroke this air
passes into the heater.
When this construction and mode of working are adopted, the regenerator is no
longer needed and is dispensed with.
I consider it desirable to do as little work by means of the cam connected with
the displacer as possible and desire therefore to urge the displacer in both its
strokes by some force not acting through the cam, of such amount as is needed to
effect its inovement or the greater part of it, the office of the cam being reduced to
that of regulating and timing the movement. For this purpose the following
method is applicable.
Supposing the displacing cylinder to be placed vertically with its hot end lowest
the weight of the displacer is counterbalanced. to such an extent as is needed,
either by a weight or by a spring and the displacer is urged through its upstroke
by the gaseous pressure of the hot air entering from the heater, assisted by the
action of this counterbalancing weight or spring.
In the downward stroke it is urged so far as is needed by air admitted from an
air vessel in which suitable pressure is created by means of a pump worked by the
engine.
If the displacing cylinder is placed horizontally it may be driven by gaseous
pressure in both its strokes.
As it is desired to work as little by the cam as possible, it is well so to shape it
as to allow the displacer to move freely during a considerable portion of its stroke.
And the cam night be dispensed with altogether, the gaseous pressures being so
adjusted as to cause the displacer to move with the requisite velocity.
Another modification of construction is as follows:-The displacer is worked
from the engine shaft by a crank or otherwise, its movement being so timed that
it makes its upstroke or stroke of delivery into the heater while the working
piston is making its return or exhaust stroke, and it makes its downstroke or stroke

page_text: of intake while the working piston is making its working stroke. When this
construction is adopted the working cylinder has to be made much larger.
Otherwise one cylinder only may be used the piston on its cool side acting as a
pump taking in air from the cooling vessel in one stroke and forcing it into the
heating vessel in the other stroke. On the hot side of the piston it receives hot
air from the heater the admission of which is regulated by a cut-off valve and after
this has expanded it is expelled in the next stroke as exhaust. In this construction
the parts are fewer, but the introduction of the air into the heater opposes the
action of the engine.
When two cylinders are used, I consider it well to place the cool side of the
working piston in communication with the refrigerator in order to lessen the
difference of pressures acting on the opposite sides of this piston which tends to
reduce leakage and also to equalize the action of the engine.
The constructions which I proceed to describo are applicable whichever of the
constructions previously described herein or in my previous specifications are used.
In order to lessen passage of heat from the hot to the cool ends of the cylinders
(or cylinder) they are (or may be) made of two portions flanged together tho
flanges being separated by asbestos or suitable material, and the bolts which unite
the flange being insulated by the same material-As-nevertheless a certain amount
of heat passes through the metal of the cylinders from their hot to their cool-ends,
it is desirable to utilise this heat or a portion of it, for which purpose the following
methods are applicable.
A narrow annular passage is provided on the exterior of the cooler part of the
cylinder or cylinders and air is forced through this by the engine or drawn by the
chimney draught, which air goes to supply the fire by which the heater is heated.
Otherwise the air which works the engine is caused to pass through a similar
passage-on-its-way from the cylinder in which it is received to the heater.
Both these methods may be used-in-combination, in which case the air which
supplies the fire passes through the passage nearest the cool end of the-cylinder_(or
cylinders) which I shall suppose to be the upper end, and the air going to the heater
passes through a passage immediately below this.
When the engine is constructed as described in my former Specifications
previously referred to, in which a regenerator is employed, then a small regenerator
is placed between the displacing cylinder and the annular passage provided around
its exterior for the purpose of heating air used to work the engine.
Again a water casing may be employed round a portion of the cylinder or
cylinders from which steam is generated, this steam passing into the heater and
co-operating with the air in it. In such a case it may be well to provide two
casings, one round a hotter portion of the cylinder or cylinders, the other round a
cooler portion. In the first of these steam is generated, in the second water is
heated which water serves as supply to the first casing. This method of utilising
the heat may be combined with the former ones. Or one method may be employed
in one cylinder, and another in the other.
Although material to obstruct passage of heat is placed within the shield of the
piston yet nevertheless a certain amount of heat passes through it and if the engine
does not work while the fires remain alight the upper part of the piston, or that
side of it which ought to be cool may become heated. It may be desired therefore
to provide means for cooling it, in case it shall have become heated. This may be
done in various ways. A current of cold air may be directed against it, a pump
worked by hand being provided for this purpose. Or a space may be provided
within it through which cold water is caused to pass, which water may be intro-
duced and taken away through tubes provided within the piston rol.
Means may
also be provided for cooling the exterior of the cylinder at its cool end by a current
of cold water or cold air when the engine is not at work, while when it is at work
it is kept cool by air caused to pass through a passage surrounding a portion of
them, as has been previously described, whose motion is caused by the engine as
previously explained.

page_text: The hot gases which pass away after heating the under parts of the cylinder or
cylinders have a somewhat high temperaturo so that in most cases it is desirable
to utilise a portion of their heat. For this purpose the following construction is
applicable. A heating vessel is provided in addition to that on which the fire first
plays and the escaping hot gases whose heat it is desired to utilise act on this.
The air delivered by the engine to the heater passes through this secondary heater
to that on which the fire first plays. The temperaturo of the air is first raised in
the secondary heater and afterwards still further raised in the primary heater on
which the fire first plays from which it passes by a short passage to the cylinder
in which it performs work.
Also the secondary heater might consist of two separate parts, in one of which
the air which is used as supply to the engine is heated, while in the other air is
heater which goes to supply the fire.
The air discharged from the cylinder as exhaust is discharged at a somewhat
high temperature so that it may be desired in many cases to utilise a portion of its
heat. For this purpose the following method is applicable.
The exhaust in the first instance acts on the tubes or flues of a heating apparatus
through which on the other side air is passed, the air thus heated being conducted
to supply the fire. Or in some cases air passing from the reception cylinder to the
heater, might be partly heated in this apparatus. After the exhaust has been
partially cooled by traversing this heating apparatus it passes to the further
cooling vessel, where it is cooled by water or other agency to the degree desired,
the heat here abstracted from it passing away as waste.
Otherwise this heating apparatus may heat water and generate steam, the steam
so generated passing to the heater and co-operating with it in the cylinder. In
such a case it is well to place the tubes of the heating apparatus in a vertical
position in the water, so that the water gradually diminishes in temperature from
its surface downwards and gives off steam at top.
મ
In heating the air I consider it well so to shape the passage through which it
flows while being heated, that it shall undergo numerous variations of area; in
order that the air may be disturbed and that successive portions of it may bo
brought in contact with the heating surface. In some cases the variation of area
may be caused by employing corrugated metal, in other cases it may be caused in
other ways. All the passages connected with the engine in which air is heated,
may be shaped as above described. The like is also applicable to passages in
which air is cooled. The heater inay be made of steel as being a material suited
to stand heat.
It may be desirable to use in the engine, valves which are balanced or partially
balanced by pistons connected to their stems. In such a case on account of the
heat of the air it is well to make the piston like that of the cylinder, that is to say
to furnish it with a shield or body which obstructs passage of heat and to cool the
part of the cylinder where the closely fitting part of the piston works by a water
casing or other suitable means so that liquid or lubricant may be employed to keep
the piston tight
In the Specification of the Patent granted to me A.D. 1880, 17th December
No 5299 I described a construction of valve in which a small valve seated on a
large valve first opened and afterwards opened a large valve. The following is
another construction for the same purpose. Two small valves are provided, one on
each side of a larger central valve. The two small valves are first lifted by an arm
which afterwards lifts the larger valve and opens full passage for the air. The
valves may be made flat faced and of square or rectangular form, with a view to
compactness of arrangement.
The following is a construction of heater suitable for that portion of the heating
apparatus on which the fire and hot gases first play, which may be termed the
primary heater. Two vessels are provided of basin like form and are united
together at their edges, so as to leave a narrow passage between them, which con-
stitutes the space within which the air is heated. This passage is made to vary in

page_text: area by means of curvatures, or curved pieces, which I consider it best to place on
the upper or inner basin. The air to be heated is admitted at the upper part of the
heater and flows downwards in all directions towards the centre, passing away by
a pipe which ascends in the central part of the concavity of the upper basin and
conducts it to the cylinder in which it performs work. The fire plays first on the
bottom of the heater, whence the hot gases flow uniformly over the surface of the
outer or lower basin. They are then conducted into the concave space over
the upper basin, play uniformly over the surface of this basin and then ascend by a
central flue, enclosing the air pipe above mentioned.
The cylinders (or cylinder) may conveniently be placed immediately above the
heater and their lower portions may occupy part of the central concave space. The
bed plate to which they are attached may be made hollow, this hollow communi-
cating with the heating apparatus and forming part of it, so that air flows through
it on its way to the primary heater, or that portion of the heating apparatus on
which the fire first plays.
If a heater is employed having generally the form of that described by me in the
Specification of the Patent granted to me AD 1880 17th December No 5299 the
area of the passages through-which the air flows may be made to vary by attaching
numerous projections to the internal diaphragm.
The engine may be provided with a governor of any known kind, which-may_be__
applied to vary the cut off or the draught of the furnace or both. In the above,
for the sake of simplicity of description, I have described only one working
cylinder But it is obvious that the number of cylinders may be multiplied and
may be worked either from one--set-of heating and cooling apparatus or from
separate sets of these. And the working cylinders and the connections of their
-pistons to cranks on one or more sliafts may be arranged in any of the various...
ways in which similar-parts-of stent engines are arranged.
In Fig 1, A is the displacing cylinder, D the displacer fitted with shield which
works in it. C is the working cylinder, P the piston fitted with shield which
works in it and drives the engine. c is the valve which governs communication
between A and C. H is the main or primary heater on which the fire maintained
at F first plays. u is the passage within H in which the air passing through H is
heated. is the pipe leading from H to the lower end of A the communication
being governed by the valve . F is the auxiliary heater. This consists in the
main of two chambers a¹ and a² connected by U pipes as shewn in the figure.
m is a pipe leading from the chamber a¹ to the upper or cool end of A the
communication being governed by the valve h. bb are spaces within the hollow
bed plate, which serves as an intermediate heating passage between H and H'.
R is the refrigerator or cooling vessel containing tubes through which water passes.
G is a vessel containing water or liquid, g are coiled tubes passing through this.
A portion of the exhaust from C passes through these tubes, and generates vapour,
which passes through the pipe into the passage in the interior of the primary
heater H. The vapour generated in G is subsequently condensed in R and falls to
the lower part of it. From this it is returned by the pump L to G which it enters
at its lower part. The liquid evaporated in G may be one of low boiling point.
S is a vessel containing U tubes. A portion of the exhaust from the engine passes
through these tubes heating them, and a current of air is caused to pass by a
blower or suitable apparatus on the other side of these tubes, which are after
having been heated by the tubes passes to the fire-place to supply the fire at F.
n is a pipe leading from R to the upper end of A the communication being
governed by the valve 8 which is self acting. hand h² are valves between H
and A, ca valve between A and C, e the exhaust or eduction valve of C. T is a
pump worked by the engine which forces air into the pipe n in order to supply the
loss occasioned by leakage. L' and L² are air vessels which may be employed in

page_text: order to equalise the movement of air through the passages. In practice these may
be considerably larger than the size shewn in the figure. Q is the cam which
governs the movements of the displacer D. 7'99³ are the cams which govern the
movements of the valves 2 c and e. Pumps are provided, by means of which the
pressure can be raised both in the heater and the refrigerator to the extent desired,
but these are not shewn in the drawing.
The general course of operations is as follows:-For starting point I suppose
that P is at the top of C ready to commence its down or discharge stroke. D is
also at the top of A. The space below both pistons is filled with exhaust air
P descends driving out exhaust through e. D also lescends driving exhaust
through cinto C and thence through e. Above D cool air from R enters A
through the self acting valve s. D completes its downstroke while P is performing
the first half or portion of its downstroke. c is then closed. ³ is now opened
and high pressure air from H enters below D urging it upwards. The air above D
is compressed, and when its pressure is sufficiently raised it opens the self acting
valve hand during the remainder of the stroke the air above D is sent through '
into the heating vessels. While D is performing its upstroke, P completes its
downstroke. c is now opened while the other valves are closed. The high
pressure air beneath D expands in C, urging P upwards. The movement of Pin
this stroke drives the engine. The air driven from A through passes first
along the pipe m, then through the tubes in H, in which it receives heat thence
into the hollow space in the bed plate where it is further heated. From this
it passes into the upper part of the passage within H, entering all round this
passage. It flows downwards in all directions to the central aperture and thence
passes through the pipe p and valve h' into the lower part of A. The exhaust
after passing through the eduction valve e divides into two branches, a portion
of it passes through the coiled pipes 9 generating vapour which flows through
the pipe into u the space within the heater, there mixing with the air and
co-operating with it in working the engine. The other portion passes through the
tubes of S heating air which goes to supply the fire in F. Both portions of the
exhaust pass on to R where the first cooling takes place and where the vapour
generated in G is condensed. From R the air passes back by the pipo n and the
valve & to the upper part of A. The liquid converted into vapour in G may either
be water or it may be a liquid of lower boiling point such as ether or volatile
hydrocarbons.
The functions of the heating vessels may be changed in various ways. Thus
the hot gases which have heated the lower parts of the cylinders might be
employed to generate vapour, while the exhaust from C or a portion of it might
be employed to heat air employed as working air in the engine, or in other words
air passing from the refrigerator R to the main or primary heater H. The fire
days first on the lower part of H immediately abovo F. The hot gases spread
out in all directions and rise to the upper part of H. From this they are
conducted to its inner surface and spreading over this pass downwards to its
central part. From this they rise to the central passage u', to the bottoms of the
two cylinders A and C and heat the lower parts of these cylinders and the bed
plate. They then pass to the auxiliary heater H¹ heating the pipes in this and
passing away by M to the chimney or place of discharge. Passages are provider
on the exterior of the two cylinders A and C at their upper parts for the
abstraction of superfluous heat, which heat can be utilised in any of the ways that
have been previously mentioned in this specification. The construction remaining
generally the same, the refrigerator may be dispensed with, the exhaust being
discharged into the air. Instead of a pump to supply loss by leakage to the engine
gas may be generated for this purpose such for instance as carbonic binoxide.
Fig 2 and Fig 3 shew a construction and arrangement of cylinder. Here A is
thic cylinder, the lower part of which is heated by the furnace gases playing within
the firebrick casing or envelope D. The cylinder is carried by the supports N
resting on the bed plate B and attached to its upper part. P is the tight fitting

page_text: part of the piston having on its upper side material such as wood which is a bad
conductor and had absorbent of heat. S is the shield or loosely fitting portion of
the piston. At the bottom of this is a sheet of asbestos held on by a thin sheet of
metal. The cylinder A is formed of two pieces between which are numerous
sheets of metal separated by asbestos or suitable material to obstruct passage of
heat as shewn at . The upper part of A is cooled by air. For this purpose a
passage m is provided on the upper part of A communicating with a lateral
annular passage i. The air first enters m and passes thence to the annular
passage which is shewn formed of varying area and from this it is taken away to
supply the fire or to be used in any other manner that may be desired. The
portion of A between i and l is surrounded by material which obstructs passage of
heat. When two cylinders are employed a similar construction may be applied to
both.
Figs 4 and 5 shew a construction in which the two pistons are so timed that
the displacer piston makes its stroke of delivery into the heater while the other
piston makes its return or exhaust stroke, and its stroke of intake while the other
piston makes its working stroke. In the construction shewn the two cylinders are
placed-horizontally-and-their-piston rods are connected together by crossheads and
side rods as shewn The two-cylinders are placed with their hot ends near
together, enclosed in a hot chamber x or in fire brick-or other suitable-material
which may receive heat from the heater, or may be heated by a separate-fire.as
shewn. The cylinders communicate by a connecting passage governed by a valve e
worked by the engine. A is the charging or displacing cylinder fitted with the
piston P¹, to which is attached-the-shield S. Bis the second cylinder in which
the hot air expands or finishes its expansion. This-cylinder is fitted with the
-piston Pl and shield S. A trunk is attached to P within which is the connecting
rod which is linked-to-the engine crank, but of course an ordinary piston rod
might be employed. The hot air from the heater enters the cylinder A through
the valve 2 (worked by the engine) and drives P₁ from left to right. On the
other side P¹ first compresses the air in A and afterwards drives it into the heater
through the self acting check valve p³. While P is making this stroke Pa moves
from left to right expelling exhaust through the eduction valve e¹ which is
worked by the engine. This exhaust passes to the refrigerator R through the
feed heater G or if no refrigerator is used, it passes to the atmosphere. On its left
side P³ first draws air from the air vessel L reducing the pressure in it and in the
latter part of the stroke takes in air from the refrigerator through the self acting
valve 8. During the stroke above described the valve e between the two cylinders
is kept closed. In the next stroke the valves being opened, P¹ on its left sends
the hot air into cylinder B where it expands urging P², while on its right P¹ takes
in or is followed by the charge of cool air entering through the valve a². On its
left side P² first compresses the air in the air vessel L and afterwards sends air
through the passage m to the cylinder A. T is a pump which supplies loss of air
by leakage when a refrigerator with high pressure is employed. This pump
delivers its charge into the passage m or a vessel connected with it. The supply
of air delivered by the pump T can be varied by varying the clearance space in
the pump, or by throttling the suction by means of a stop cock or valve. A self
acting check valve is provided at u which allows passage of air from B to A but
prevents flow in the reverse direction, when P³ makes its stroke of intake.
The air space within the air vessel L can be adjusted at pleasure by introducing
water or liquid into it, apparatus being provided for this purpose. By varying
this space the preliminary compression given to the air in the cylinder A can be
varied or adjusted as desired. I consider it well to line the interior of L with
some material such as wood which is a bad absorbent and a bad conductor
of heat.
Each of the cylinders A and B is made in two parts with flanges, between which
are placed alternate layers of asbestos and metal as shown at k in order to check
communication of heat from the hot to the cool end of the cylinder. A facing of

page_text: asbestos shown at a is fastened to the hot end of each shield. At the cool end
of A passages ni are provided for abstracting heat from it by air which after-
wards passes on to supply the fire. The passages may be constructed with
varying area as shewn at i in order to disturb the air as it flows through it to
promote the cooling effect.
G is a vessel in which the exhaust on its passage to the refrigerator imparts a
certain amount of heat to the working air previous to its entrance into the main
or principal heater. This apparatus consists of tubes or passages through which
the-exhaust flows, while the air passing from A to the principal heater flows on the
other side of them becoming heated while the exhaust is cooled. This apparatus
is not essential and may be dispensed with. The pipes which convey the warmned
air are covered by some material which obstructs passage of heat. D'and D' are
air vessels the object of which is to equalize the flow of the air. The number of
pairs of cylinders employed may be increased as desired and the position of the
cylinders may be varied as desired.
Also the valves, instead of being worked by cams or eccentrics on a revolving
shaft, might be worked by tappets from the reciprocating parts. If the engine
is employed for compressing air or for pumping, the piston of the pump may be
worked directly from the pistons of the engine either with or without a crank
shaft.
v
Fig 6 shews a construction of equilibrium or balanced valve suitable for
governing the flow or passage of hot air. Here P is a piston which works tightly
in the cylinder shewn. w is a casing through which water is caused to flow to
cool the part of the cylinder in which P works, S is a shield or loosely fitting
piston filled with material which obstructs the passage of heat. This is attached
to the disc which governs communication between the passages a and b. The
seat on which works is shown as an annular groove which may be kept moist
by liquid allowed to drop into it. The balance of the valve may be rendered such
as is desired by suitably proportioning the area of the disc and piston. In order
to prevent leakage of air through the glands, spaces may be provided round the
rods which work in these, into which liquid is supplied in suitable quantities by a
pump, so that this liquid may pass through the space between the rod and the
gland and prevent the passage of air. For the same purpose liquid may be forced
into the space occupied by the packing of the pistons.
Having thus described the nature of my invention and in what manner the same
is to be performed, I claim :-
First. The construction and arrangement of hot air or caloric engine herein
described with reference to Fig 1 of the accompanying drawings.
Second. The construction and arrangement of the heater H and its passages as
herein described.
Third. The construction and arrangement of hot air or caloric engine herein
described with reference Figs 4 and 5
In witness whereof I the said Matthew Piers Watt Boulton have hereunto
set my hand and seal this Tenth day of October in the year of our Lord
One thousand eight hundred and eighty two.