IMPROVEMENTS IN CALORIC MOTOR ENGINES BURNING SOLID FUEL, SOME OF WHICH ARE APPLICABLE TO OTHER MOTOR ENGINES."
Year: 1881

page_text: LETTERS PATENT to Henry Charles Fleeming Jenkin, of No. 3, Great Stuart
Street, in the City of Edinburgh, Professor of Engineering in Edinburgh
University, and Alexander Chalmers Jameson, residing at No. 1, Gillespie
Crescent, Edinburgh, Engineer, for an Invention of "IMPROVEMENTS IN
CALORIC MOTOR ENGINES BURNING SOLID FUEL, SOME OF WHICH ARE
APPLICABLE TO OTHER MOTOR ENGINES."
PROVISIONAL SPECIFICATION left by the said Henry Charles Fleeming
Jenkin and Alexander Chalmers Jameson at the Office of the Commissioners
of Patents on the 12th March 1881.
HENRY CHARLES FLEEMING JENKIN, of No. 3, Great Stuart Street, in the City
of Edinburgh, Professor of Engineering in Edinburgh University, and ALEXANDER
CHALMERS JAMESON, residing at No. 1, Gillespie Crescent, Edinburgh, Engineer.
" IMPROVEMENTS IN CALORIC MOTOR ENGINES BURNING SOLID FUEL, SOME OF
WHICH ARE APPLICABLE TO OTHER MOTOR ENGINES."
The nature and object of this Invention is the construction of a caloric motor
engine, which whilo essentially an engine of the Stirling type differs from the
Stirling engine in using as working fluid instead of air the products of the com-
bustion of solid fuel burnt in a grate directly connected with the interior of what
Stirling calls the air vessel, and we will call the displacer vessel or displacer
chamber, so that the products of combustion are discharged from the grate into the
displacer vessel, partly by expansion under the influence of heat and partly by
flow, the pressure in the grate chamber bearing always such a relation to that in
the displacer vessel that the products of combustion are not driven so far back into
the grate as to impede combustion.
The Invention consists in combining with the ordinary parts of a Stirling engine
the other details hereinafter described or mentioned, that is to say :-
First. A furnace or grate surrounded by non-conducting and refractory material,
in which coke or other suitable solid fuel burns under pressure in a state of vivid
incandescence. As adjuncts of the grate we employ (a) tuyères, through which

page_text: air is driven into the grate and through the fuel; (b) suitable connections between
the grate and the main displacer vessel, the action of these connections being
roughly that of a sieve or strainer, allowing the products of combustion to pass,
and retaining dust and solid materials; (c) suitable openings and arrangements for
clearing out ashes and slag from time to time; (d) an opening or passage in con-
nexion with the fuel feeder, through which the fuel can be introduced; and (e) an
opening through which the fire can be lighted; (c) and (e) may be the same
opening.
Secondly. The Fuel Feeder. This can be made in a great variety of ways. The
essential features of the feeder are that it shall contain a store of solid fuel under
pressure, which can be gradually pressed or fed forwards at varying rates as the
fuel in the furnace is consumed. In all engines intended for continuous running it
is essential that this store can be renewed from time to time without letting down
the pressure in the main displacer vessel. With this object a sort of lock is pro-
vided. The inner chamber (which we shall call A) of this lock is usually in
communication with the outer chamber (which we shall call B); the fuel is fed by
suitable pushing arrangements from chamber A into the furnace, and falls or is
pushed from chamber B'into chamber A. Means are however provided by which
at will B can be shut off from A; the chamber B can then be opened to the outer
air and refilled with fuel. The opening to the open air is then closed, and the
communication between A and B reestablished. The communication between A
and B may either be cut off at each stroke of the engine or it may remain always
open. A second mode of constructing the fuel feeder is to make only one chamber,
which can however be at one point closed at will or divided in two. The outer
half can then be charged and the whole charge of the chamber slowly pushed
forward so as to feed the furnace.
Thirdly. An air pump or pumps by which the air requisite for combustion is
supplied to the grate, either directly through suitable reservoirs and pipes or
indirectly through an adjunct to be described hereafter as the air displacer. There
is some advantage in causing the air from the pumps to pass through a pipe or pipes
led from the cold to the hot end of the regenerator before entering the grate
through the tryères. We by this means obtain a warm blast and slightly cool the
regenerator.
Fourthly. An equilibrating arrangement or equilibrator, by which there is
removed from the engine at each stroke an amount of the working fluid (ie., of
the products of the combustion), which under normal conditions will be equal in
weight to the fuel and air which have been required to do the work during each
stroke, and by which the working fluid is expanded down to about atmospheric
pressure before being ejected into the atmosphere. The equilibrator may consist
of any arrangement which effects this object, but we generally use an ordinary
cylinder and piston. The products of combination in thus expanding will approxi-
mately do the same amount of work as is required to compress the air which is
forced into the hot chamber. Sometimes instead of a separate cylinder and piston,
which we ordinarily use for the equilibrator, we use the same cylinder or cylinders
alternately as air pump or pumps, and equilibrator or equilibrators, the object of
this being that the portion of working fluid withdrawn may be aided in expanding
down to atmospheric pressure by absorbing the heat previously given out to the
walls of the said cylinder or cylinders by the compression of the air. The admission.
of working fluid to the cylinder, which acts alternately as air pump and equi-
librator, is arranged so that, the pump having compressed a charge of air into the
receiver, the working fluid is then admitted to that side of the piston from which
the said charge of air has been immediately before expelled. The working fluid is
at or about the temperature of the cool end of the displacer chamber when in the
working cylinder, but we sometimes draw off the fluid for the equilibrator from
such a point in the regenerator that it is somewhat hotter than the fluid used in
'the cool end of the said chamber. The principle of using our equilibrator or equili-
brating arrangement, as herein described, has already been employed in the
-

page_text: Specification filed in pursuance of Letters Patent, No. 2441, granted to one of us as
of the 11th July, A.D. 1874, the only difference between the application of the
principle in that Specification and the application of it herein described being that
in the said Specification a larger quantity of working fluid was changed at each
stroke than the amount absolutely necessary to produce heat for that stroke, and
in the present case the amount of working fluid changed is limited to that necessary
to produce the heat required for that stroke.
These four parts, viz.:-The solid fuel grate or furnace acting under pressure,
the fuel feeder for solid fuel, the air pump, and the equilibrator are combined with
the ordinary regenerator, refrigerator, and working cylinder of a Stirling engine.
The following are further improvements, all or one or more of which may be
combined with those above mentioned, making a series of combinations, each of
which is novel.
Fifthly. Special arrangements by which we are enabled to use such non-conducting
and refractory materials as fire bricks for lining or constructing the hot end of the
main displacer chamber in order to retain the heat in the said chamber and in the
regenerator, and resist the high temperatures attained without introducing an
injurious cushioning action which would result from the employment of such
materials without these special arrangements. We have found by experiment
that equal sizes of ordinary firebrick or other refractory non-conducting materials
of a similar kind, commonly used for constructing the walls or enclosures of
furnaces and hot chambers absorb of equal volumes of air or other gaseous fluid at
the same temperature and pressure, various per centages ranging according to the
porosity of the material, from about 10 per cent. to 60 per cent., and we have
detected in the use of great continuous thicknesses of such material for the interior
surfaces and walls of the hot portion of the displacer chamber a source of serious
loss of power through the cushioning which arises from the working fluid being
first absorbed by and then given out again from the pores of the material during
the action of the plunger. This cushioning action may be roughly explained by
pointing out that it diminishes the difference of pressure arising from the motion
of the displacer from the hot to the cold end of the displacer vessel, and thereby
diminishes the average working pressure in the cylinder, in that way requiring a
much larger engine to produce the same quantity of power, and this is what we
mean by loss of power arising through the cushioning. It is a loss of power in any
given engine, but not necessarily a loss of efficiency except in so far as the engine
takes more power to drive itself in consequence of its larger size. We obviate, or
to the requisite extent, or at least materially reduce, this cushioning by one or other
or both of two methods, viz. :-(First), we cut off or separate the interior surface
of what is intended to be the hot portion of the displacer chamber, along with a
certain stratum or thickness of the brickwork or other analogous material forming
the walls by interposing between the said interior stratum or thickness and the
remainder a cast- or wrought-iron or other suitable metallic casing or partition,
completely enclosing the said interior stratum, and wo so reduce the thickness
and quantity of the stratum of absorbent material in contact with the working
fluid and liable to be saturated or penetrated by the same. This metal casing
or partition is backed up and supported on the outside by firebrick or other
similar material, and the whole is enclosed in an outer metal covering of sufficient.
strength to resist the internal pressure; or (secondly) we employ for the con-
struction of the said interior stratum inside the inner metal casing or for a portion
of the heat-retaining lining of the hot end of the chamber, refractory non-conducting
substances so constituted or manufactured and prepared as to resist saturation or
penetration by air or gas, such as fireproof glazed bricks or very compact stone, or
bricks made of fine ground well washed and sifted clays, or of other finely divided
material or mixture of materials in use or that may be used for making dense and
compact firebricks, such bricks being subjected in their manufacture to strong
compression by hydraulic or other pressure, or bricks of refractory clay, kaolin, or
other material or mixture of materials such as are in use or may be used for

page_text: making firebricks, furnace hearths, crucibles, and the like, such bricks being
(besides the compression in their original manufacture, and after drying, and either
before or after firing) subjected to immersion in and saturation with a solution of
boracic acid, or of any suitable soluble silicate, or of other suitable soluble
material or mixture of materials which after calcination will form a solid and
non fusible deposit within the pores of the brick; or (thirdly) the two methods
may be combined. The inner casing may be further relieved of strain by placing
the space between the outer and inner metal casing under pressure by allowing
the working fluid to pass into it through a valve which does not allow free
communication between the working fluid and said space.
Sixthly. The Air Displacer. This consists of a cylinder, whereof the one end
(which we may call A) communicates with the twyères leading into the grate, and
the other end (which we may call B) with the cold end of the large or main
displacer chamber already mentioned which contains the working fluid and corre-
sponds to what Stirling called the air vessel. There may or may not be a valve,
not automatic, interposed between the air displacer and the grate. An air reservoir
may be interposed between the air pump and the air displacer. A piston separates
the two ends A and B. The air pump delivers air into the end A during the part
of the cycle of operations, in which the bulk of the working fluid is at the cold end
of the main displacer chamber. At the same time this air may pass in small
quantities through the tuyères or be wholly checked. In either case the main
action of the air is that it drives back the piston of the air displacer and so com-
presses the working fluid while the bulk thereof is in the cold end of the main
displacer chamber. Or the piston may be raised by suitable gearing driven by the
engine. When the working fluid is returned to the hot end the piston of the air
displacer is driven back from the end B by means of a piston rod, and so drives
the air through the twyères, which are then fully open. A very small force is
required for this in-as-much-as the pressure of the two sides of the air displacer
piston is approximately equal. By this device the air pump never requires to raise
the pressure of the air much above that obtaining in the main displacer chamber
when the working fluid is at the cold end. The air displacer may be used in
combination with the constant flow valve described in the Specification filed in
pursuance of Letters Patent, No. 832, granted to one of us on the 28th February,
A.D. 1876. Or in place of the air displacer we may use the said constant flow
valve itself. We interpose the constant flow valve between the supply pumps or
air displacer and the grate with the object of preventing an excess of fuel and air
from being thrown in when the pressure in the main displacer chamber is lowest.
We can diminish the flow at this period or stop it by partially or wholly closing
the orifice which in the constant flow valve regulates the amount of fluid delivered.
The constant flow valve renders it possible to regulate the flow or rate of entrance
of the fluid into the grate independently of the difference of pressures between
the pipes outside the valve and the grate, or makes the flow practically independent
of the pressure in the displacer chamber with which the exit from the grate
communicates. In place of using the constant flow valve alone or with the
air displacer only, we may use the constant flow valve in combination with
a reciprocating valve or with such a valve and the air displacer for the purpose
of wholly or partially cutting off the flow of air; or we may dispense with
both and use a restricted orifice capable of being enlarged or contracted; or
we may use simply a reciprocating valve either with or without the restricted
orifice. The air displacer herein before described may be used in combination
with any of the above alternatives for the constant flow valve or by itself. We
usually cut off the supply of air altogether during the period at which the
working fluid is at the cold end of the cylinder, the fire and grate continuing to
glow not only during this short interval but during comparatively long stoppages
of the engine. The use of the constant flow valve in the manner above described
will be of advantage in combination with any form of engine in which air or air
and gas continue to be supplied while combustion is going on.

page_text: Seventhly. The Circulating Valve or Valves. A valve or suitable arrangement
of valves is provided separating the interior of the main displacer chamber (and
consequently also the grate) from the working cylinder. Å valve or suitable
arrangement of valves is placed between the regenerator on the one hand and the
refrigerator or the passage hereinafter mentioned, avoiding the refrigerator, on the
other, by which valve or valves the working fluid in returning from the working
cylinder and cold end of the displacer chamber is conducted through the refrigerator,
but when on its way to enter the cylinder and refrigerator and the cold end of the
displacer chamber is prevented from passing through the refrigerator, and is
conducted instead through a passage or passages to be provided for the purpose by
which it avoids the refrigerator, the object of this arrangement being to remove
heat from the working fluid and cushion only during the time when compression
is taking place; or this valve or an arrangement of valves performing the same
function may be placed between the refrigerator and the working cylinder, that is
to say, the valve or valves may. be at either end of the refrigerator. We may
arrange the valve or valves so that we may interrupt the communication between
the displacer vessel and the working. cylinder during the time when the change is
taking place in the direction of the current.
Eighthly. A cut off valve interrupting the communication between the displacer
vessel and the working cylinder, this valve being under the direct control of
the governor of the engine, so that the speed of the engine may be regulated
thereby. This valve effects this by controlling the amount of power indicated
during each stroke.
Ninthly. The Pure or Fresh Air Reservoir. We may provide an air reservoir
in which atmospheric air is stored at a sufficiently high pressure to flow into the
grate when the engine is stopped for any considerable period. We then, in order
to keep up combustion, allow a small flow of air from the air reservoir through the
grate and allow a corresponding exit from the main displacer vessel of the products'
of combustion, or this may be effected by means of a donkey pump, or in the case
of long stoppages by a chimney of sufficient height, an air inlet to the furnace and
open to the atmosphere being provided.
Tenthly. The Burnt Air Reservoir. We may provide a reservoir into which the
products of combustion may be taken from the cold end of the displacer vessel.
This reservoir acts as a storer of energy and fluid may be taken from it to start
the engine by being admitted to the equilibrator cylinder.
Eleventhly. The Strainers. At suitable points near the cold end of the
regenerator we place strainers of suitable material to prevent grit or ashes from
being carried into either the working cylinder, the equilibrator, or the air displacer.
Near the hot end of the regenerator we place coarse strainers of refractory material,
such as perforated brick or bundles of rods of pipe clay.
The covering of the grate itself acts as a coarse hot end strainer.
The fuel burned in the furnace or grate may consist of coal, coke, or any other
kind of solid fuel, but we prefer when coals are used that such coals should be
selected as do not produce slags and other products which would tend to clog the
strainers and choke up other passages in the engine.
The action of the engine is as follows:-
The fire is lighted in the furnace through a suitable opening and the products of
combustion pass up through the regenerator and out through a special opening
provided for the purpose. When the refractory material lining the furnace and
main displacer vessel are sufficiently warm the opening by which the fire was lighted
is closed. The combustion is maintained both before and after the closing of the
opening by a small supplementary air pump which may be driven by hand or by a
donkey engine or in any other way, or the air pump may be superseded by a
chimney of sufficient height. After the opening is closed this pump brings the
pressure in the main displacer vessel up to the desired point; or the engine may be
charged with working fluid previously stored in either the fresh air or burnt air
reservoir. The displacer is or may be during this period in the cold chamber. The

page_text: displacer or displacers are temporarily disconnected from the working eylinder. If
this cylinder is double acting, the displacer corresponding with the proper side of
the piston is moved to the warm end. There will then be a difference of pressure
between the two sides of the piston which will start the engine. The action may
be aided by at the same time admitting high pressure working fluid direct from one
displacer vessel to one side of the equilibrator. The action can be still further
assisted by temporarily disconnecting the air pump or pumps, for the glowing
furnace and adjacent part of the displacer chamber will contain a supply of heat
amply sufficient for many strokes. The displacers may require to be worked
several strokes by hand or other extraneous power. When once the engine has
acquired sufficient speed the displacers are thrown into gear by suitable means,
and also the air pump or pumps if these have been disconnected. The course of
events relating to one side of the working piston is (beginning at that period in
which the displacer is at the cold end and the working piston at one end of its
stroke) as follows:-Air is coming through the constant flow valve or other
arrangement for the same purpose to the twyères, and flowing into the furnace
from the air displacer, the piston of which is moving from end B to end A. The
mass of working air has now absorbed the main portion of its heat from the
regenerator and the walls of the hot part of the displacer vessel. Heat is being
generated and transferred into a comparatively small quantity of working fluid
which expands from the grate or furnace through the straining bars to the displacer.
The new heat thus added will be equal to that converted into mechanical effect,
added to that rejected in the refrigerator and that lost by conduction from the
exterior of the working parts. The working fluid will now expand in the hot end,
the displacer during this portion of the action of the engine acting as a barrier or
separator between the hot mass of working air and the cushion which abuts against
the working piston. This whole mass of fluid expands but is directed by the
circulating valves so as not to pass over the refrigerating pipes. Towards the end
of the working stroke the displacer will begin to move rapidly towards the hot
end, and about the time the working cylinder reaches that end will have transferred
the mass of the working fluid to the cold end of the displacer vessel. The circu-
lating valves will still direct this air so that it does not pass over the refrigerating
pipes. The supply of air through the twyeres will now be cut off, and the piston
in the air displacer will move backwards from end A to end B, stowing up air.
The pressure in the main displacer vessel will have fallen, because the regenerator
has cooled a considerable part of the working fluid; the return stroke will begin,
the fluid coming both from the air displacer and working cylinder will be cooled
during compression by the refrigerator. Near the end of the return stroke the
displacer will begin to move rapidly to the cold end, working fluid will then be
forced from the cold end through the regenerator but not past the refrigerating
pipes. This air will be warmed as it descends, and one cycle of changes is complete.
The piston in the air displacer will reverse its motion. During this reverse motion
it will be better that it should not draw the air required for the end B past the
refrigerating pipes. The supplementary action of the equilibrator and the pump
has meanwhile been proceeding, as follows:-
A portion of the working fluid has been admitted to one end of the equilibrator,
has been expanded down approximately to atmospheric pressure and released into
the atmosphere; the pumps also have compressed a corresponding amount of air
which is sufficient when used in the furnace to produce enough of heat for one
cycle of operations which may be stored in the fresh air reservoir before mentioned,
from which it flows into the air displacer. The work done in this cylinder is
nearly equal to that required to drive the air pumps. The cycle of operations is
now complete.
The air compressed may be cooled in the usual way, so as to allow the pumps to
be worked with no injury to the working parts. Sometimes we do not cool this
compressed air in the usual way, but use the same cylinder alternately as
equilibrator and compresser, using the cold developed by the expansion to balance.

page_text: the heat developed during compression. During the cycle a little coal may be fed
either automatically or by hand, or the feeding may only occur every few strokes.
It may occur by short pushes, or be carried out by a continuous motion. The
engine could be made to go with only the four first parts combined with the
ordinary remaining parts of a Stirling engine but it will be less effecient.
The fifth improvement is capable of being introduced into and is valuable in
any analagous form of engine whether it contains any of our special features or
not. The circulating valves, herein before described, in the seventh head or place,
and the cut off valve described in the eighth head or place may for the sake of
simplicity be one or both of them omitted from our combination, in which latter
case the connection between the displacer chamber and the working cylinder is
simply that of the old Stirling engine. By keeping up the combustion constantly.
or continuously we produce heat in the grate in a manner analagous to that in
which heat was supplied continuously to the hot air of Stirling's air vessel by
transmission across the iron casing, but we prefer to check the production of heat
during the period when the displacer occupies the warm end by diminishing the
supply of air, and in some cases we may for a short time wholly discontinue the
supply. Our engine may be double acting, or may by employing an air cushion or
large fly-wheel for the return stroke be made single acting. Communication may
be kept open constantly between the cool chamber and the working cylinder, or
the communication may, as we prefer, be made intermittent by means of any of the
arrangements herein before mentioned as having that effect.
We arrange the pump and equilibrator so that the combination of their turning
moments with the turning moments of the Stirling engine may be such as to avoid
as far as possible the inconvenience of negative moments, in the combination of
which as a whole our engine consists, and to make these moments as constant as
may be practicable. For the purpose of effecting the last mentioned object wo
do not confine ourselves to one single acting engine with its pump and equilibrator,
or to one double acting engine with pump or pumps and equilibrator or equilibrators,
or to any number of engines and any number of pumps and equilibrators in
connection with any engine or number of engines, the variety of possible combina-
tions and arrangements of this nature being infinite.
The displacer vessel and the working cylinder may be combined so as to form
one vessel, according to a well known mode of arrangement as applied in previous
engines.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Henry Charles Fleeming Jenkin and Alexander Chalmers
Jameson in the Great Seal Patent Office on the 12th September 1881.
HENRY CHARLES FLEEMING JENKIN, of No. 3, Great Stuart Street, in the City
of Edinburgh, Professor of Engineering in Edinburgh University, and ALEXANDER
CHALMERS JAMESON, residing at No. 1, Gillespie Crescent, Edinburgh, Engineer.
"IMPROVEMENTS IN CALORIC MOTOR ENGINES BURNING SOLID FUEL, SOME OF
WHICH ARE APPLICABLE TO OTHER MOTOR ENGINES."
The nature and object of this Invention is the construction of a caloric motor
engine, which while essentially an engine of the Stirling type differs from the
Stirling engine in using as working fluid instead of air the products of the
combustion of solid fuel burnt in a grate directly connected with the interior of
what Stirling calls the air vessel, and we will call the displacer vessel or displacer
chamber, so that the products of combustion are discharged from the grate into the
displacer vessel, partly by expansion under the influence of heat and partly by flow, 1
the pressure in the grate chamber bearing always such a relation to that in the
displacer vessel that the products of combustion are not driven so far back into the
grate as to impede combustion.
The Invention consists in combining with the ordinary parts of a Stirling engine
(that is to say, the main displacer vessel with its hot and cold chamber, the s
refrigerator and regenerator, working cylinder, and other ordinary parts of a
Stirling engine, exclusive of its external furnace) the other details or arrangements
hereinafter described or mentioned, that is to say :—
=
First. A furnace or grate surrounded by non-conducting and refractory material
in which coke or other suitable solid fuel burns under pressure in a state of vivid
incandescence. As adjuncts of the grate we employ (a) tuyeres through which air
is driven into the grate and through the fuel; (b) suitable connections between the
grate and the main displacer vessel, the action of these connections being roughly
that of a sieve or strainer, allowing the products of combustion to pass, and
retaining dust and solid materials; this sieve or strainer is not essential, and may¨
in some cases be omitted; (c) suitable openings and arrangements for clearing out
ashes and slag from time to time; (d) an opening or passage in connection with
the fuel feeder, through which the fuel can be introduced, and (e) an opening
through which the fire can be lighted; (c) and (e) may be the same opening.
Secondly. The Fuel Feeder. This can be made in a great variety of ways. The
essential features of the feeder are that it shall contain a store of solid fuel under
pressure, which can be gradually pressed or fed forwards at varying rates as the
fuel in the furnace is consumed. In all engines intended for continuous running it
is essential that this store can be renewed from time to time without letting down
the pressure in the main displacer vessel. With this object a sort of lock is
provided. The inner chamber (which we shall call A) of this lock is usually in
communication with the outer chamber (which we shall call B). The fuel is fed
by suitable pushing arrangements from chamber A into the furnace and falls or is
pushed from chamber B into chamber A. Means are however provided by which
at will B can be shut off from A; the chamber B can then be opened to the outer
air and refilled with fuel.
The opening to the open air is then closed, and the communication between A
and B reestablished.
The communication between A and B may either be cut off at each stroke of the
engine or it may remain always open. A second mode of constructing the fuel
feeder is to make only one chamber, which can however be at one point closed at

page_text: will or divided in two; the outer half can then be charged, and the whole charge
of the chamber slowly pushed forward so as to feed the furnace.
Thirdly. An air pump or pumps by which the air requisite for combustion is
supplied to the grate, either directly through suitable reservoirs and pipes, or
indirectly through an adjunct to be described hereafter as the air displacer.
There is some advantage in causing the air from the pumps to pass through a
pipe or pipes led from the cold to the hot end of the regenerator before entering
the grate through the tuyeres. We by this means obtain a warm blast and slightly
cool the regenerator.
Fourthly. An equilibrating arrangement or equilibrator, by which there is
removed from the engine at each stroke an amount of the working fluid (i.e., of the
products of the combustion), which under normal conditions will be equal in
weight to the fuel and air which have been required to do the work during each
stroke, and by which the working fluid is expanded down to about atmospheric
pressure before being ejected into the atmosphere. The equilibrator may consist
of any arrangement which effects this object, but we generally use. an ordinary
cylinder and piston. The products of combustion in thus expanding will
approximately do the same amount of work as is required to compress the air
which is forced into the hot chamber. Sometimes instead of a separate cylinder
and piston which we ordinarily use for the equilibrator we use the same cylinder
or cylinders alternately as air pump or pumps and equilibrator or equilibrators, the
object of this being that the portion of working fluid withdrawn may be aided in
expanding down to atmospheric pressure by absorbing the heat previously given
out to the walls of the said cylinder or cylinders by the compression of. the air.
The admission of working fluid to the cylinder, which acts alternately as air pump
and equilibrator, is arranged so that the pump having compressed a charge of air
into the receiver, the working fluid is then admitted to that side of the piston from
which the said charge of air has been immediately before expelled. The working
fluid is at or about the temperature of the cool end of the displacer chamber when
in the working cylinder, but we sometimes draw off the fluid from the equilibrator
from such a point in the regenerator that it is somewhat hotter than the fluid used
in the cool end of the said chamber. The principle of using an equilibrator or
equilibrating arrangement, as herein described, has already been employed in the
Specification filed in pursuance of Letters Patent, No. 2441, granted to one of us
as of the 11th July, A.D. 1874, the only difference between the application of the
principle in that Specification and the application of it herein described being
that in the said Specification a larger quantity of working fluid was changed at
each stroke than the amount absolutely necessary to produce heat for that stroke,
and in the present case the amount of working fluid changed is limited to that
necessary to produce the heat required for that stroke.
These four parts, viz., (1) the solid fuel grate or furnace acting under pressure,
(2) the fuel feeder for solid fuel, (3) the air pump, and (4) the equilibrator, are
combined with the ordinary main displacer vessel, regenerator, refrigerator, working
cylinder, and other ordinary parts of a Stirling engine excluding its external
furnace.
The following are further details or arrangements and improvements, all or one
or more of which may be combined with those above mentioned, making a series
of combinations each of which is novel.
Fifthly. A special arrangement by which we are enabled to use such non
conducting and refractory material as fire bricks for lining, or constructing the hot
end of the main displacer chamber in order to retain the heat in the said chamber
and in the regenerator, and to resist the high temperatures attained without
introducing an injurious cushioning action which would result from the employment
of such materials without this special arrangement.
We have found by experiment that equal sizes of ordinary firebrick or other
refractory non conducting materials of a similar kind, commonly used for
constructing the walls or enclosures of furnaces and hot chambers absorb of equal

page_text: volumes of air or other gaseous fluid at the same temperature and pressure, various
per centages, ranging according to the porosity of the material, from about 10. per
cent. to 60 per cent., and we have detected in the use of great continuous thick-
nesses of such material for the interior surfaces and walls of the hot portion of the
displacer chamber a source of serious loss of power through the cushioning which
arises from the working fluid being first absorbed by and then given out again
from the pores of the material during the action of the plunger.
The injury resulting from this cushioning action may be roughly explained by
pointing out that the cushioning diminishes the difference of pressure arising from
the motion of the displacer from the hot to the cold end of the displacer vessel, and
thereby diminishes the average working pressure in the cylinder, in that way
requiring a much larger engine to produce the same quantity of power, and this
is what we mean by loss of power arising through the cushioning. It is a loss of
power in any given engine but not necessarily a loss of efficiency, except in so far
as the engine takes more power to drive itself in consequence of its larger size.
We obviate or to the requisite extent or at least materially reduce this cushioning
by the following method, viz. :-We cut off or separate the interior surface of what
is intended to be the hot portion of the displacer chamber, along with a certain
stratum or thickness of the adjacent brickwork or other analagous material forming
the walls by interposing between the said interior stratum or thickness and the
remainder, a cast or wrought iron or other suitable metallic casing or partition
completely enclosing the said interior stratum, and we thus reduce the thickness
and quantity of the stratum of absorbent material in contact with the working
fluid and liable to be saturated or penetrated by the same, and so diminish the
amount of absorption of the working fluid and the amount of cushioning which
results therefrom, as already explained. This metal casing or partition being itself
liable to be heated, so as to be of insufficient strength, is backed up and supported
on the outside by firebrick or other similar material, and the whole is enclosed in
an outer metal covering of sufficient strength to resist the internal pressure. This
outer casing being cold can be made of moderate dimensions, inasmuch as its
strength can be absolutely calculated and relied upon, which is not the case when
the metal is in a position where it is liable to be heated to high temperatures, the
degree of which cannot be accurately regulated or determined.
We also prefer to employ for the construction of the said interior stratum inside
the inner metal casing refractory non-conducting substances, so constituted or
manufactured and prepared as to resist saturation or penetration by air or gas,
such as fire proof glazed bricks or very compact stone or bricks made of fine
ground, well washed and sifted clays or of other finely divided material or mixture
of materials in use, or that may be used for making dense and compact firebricks,
such bricks being subjected in their manufacture to strong compression by
hydraulic or other pressure, or bricks of refractory clay, kaolin, or other material
or mixture of materials such as are in use or may be used for making firebricks
furnace hearths, crucibles, and the like, such bricks being (besides the compression
in their original manufacture, and after drying and either before or after firing)
subjected to immersion in and saturation with a solution of boracic acid or of any
suitable soluble silicate or of other suitable soluble material or mixture of materials,
which after calcination will form a solid and non fusible deposit within the pores
of the brick.
The inner casing may be further relieved of strain by placing the free space
between the outer and inner metal casing under pressure by allowing the working
fluid to pass into it through a valve, which does not allow free communication
between the displacer chamber and said space, or the re-entry into the working
chamber of the portion of fluid which has passed into said space.
The special objects and purposes of our said arrangement of the materials of
which the walls of the displacer chamber are constructed, may be made clearer by
the following additional explanation.
Our first object is to withdraw the body of metal, which is required to give

page_text: strength to the walls, as far back as is required from the influence of the highly
heated interior of the chamber, by interposing between the said body of metal and
the interior of the chamber a layer or stratum of non conducting material
sufficiently thick to protect the metal from the softening and weakening influence
of the high temperatures which obtain within the chamber. For the resistance to
the pressure from within, we depend wholly or mainly on the said body of metal,
which being kept constantly cool or at a low temperature, can be relied on for not
varying to any appreciable extent in its strength and resistance to pressure fromn
within.
In order to keep it cool we interpose between it and the chamber the said layer
or stratum of non conducting material. But this stratum or layer of non
conducting material will require for the effective protection of the said outer metal
to be so thick that if it were left with its inner surface in immediate contact with
the working fluid, it would absorb and give out alternately large percentages of
the working fluid and give rise to the injurious cushioning action already explained.
To prevent or diminish this action we interpose between the inner surface of said
layer or stratum of non conducting material and the interior of the chamber, a
layer of metal which prevents the working fluid from penetrating into the pores or
interstices of the thickness of non conducting material behind it. This inner layer
of metal, however, if left unprotected would speedily be corroded and destroyed by
the hot gases of the chamber, and therefore we line it on the inside with a layer of
refractory and non conducting material, but this layer is kept so thin as to present
to the working fluid no sufficient bulk or quantity of porous material to allow of
any great quantity of the fluid being absorbed into its pores or interstices. We
cannot, by reason of the thinness of this inner layer of refractory material, rely on
the stratum of metal immediately behind it for any resistance to the pressure from
within, because the inner stratum of metal will always be liable to become softened
and have its strength diminished by the high and irregular temperatures within,
and that to an extent which cannot be made a subject of exact calculation. Wo
use this inner metal therefore only or mainly to prevent the access of the working
fluid into the pores and interstices of the thick layer of non conducting material
behind it. On account of the liability of the inner metal casing to soften and become
incapable by itself of opposing any considerable resistance to the pressure from
within, it must be backed up and supported against that pressure, and that we
effect by making it rest against the thick layer of non conducting material behind
it, which in its turn is supported by the external layer of metal constituting the
cool outer casing or covering, and this outer casing may give its support to
the inner metallic casing or partition either through the solid non conducting
materials between the two metals, or partly or wholly through gas under pressure
as already described.
It is obvious that the same arrangement of the metallic and of the refractory
and non conducting materials may be adopted in any motor engine in constructing
the walls or hot end or hot part of the displacer chamber, working cylinder, or
other vessel in which the working. fluid undergoes variations of pressure in every
case where it is necessary or advisable, on account of the high temperatures
attained therein, to protect the metallic materials of which such chamber or other
vessel is constructed by a lining of such non conducting materials as tend by reason
of their porosity to give rise to the injurious cushioning action above described.
Sixthly. The Air Displacer. This consists of a cylinder, whereof the one end
(which we may call A) communicates with the tuyeres leading into the grate, and
the other end (which we may call B) with the cold end of the large or inain
displacer chamber already mentioned which contains the working fluid and
corresponds to what Stirling called the air vessel. There may or may not be a
valve (automatic or not automatic) interposed between the air displacer and the
grate. An air reservoir may be interposed between the air pump and the air
displacer. A piston separates the two ends A and B. The air pump delivers air
into the end A during that part of the cycle of operations in which the bulk of

page_text: the working fluid is at the cold end of the main displacer chamber. At the same
time this air may pass in small quantities through the tuyeres or be wholly checked;
in either case the main action of the air is that it drives back the piston of the air
displacer and so compresses the working fluid while the bulk thereof is in the cold
end of the main displacer chamber, or the piston may be raised by suitablo gearing
driven by the engine. When the working fluid is returned to the hot end the
piston of the air displacer is driven back from the end B by means of a piston rod
and so drives the air through the tuyeres which are then fully open. A very small
force is required for this, inasmuch as the pressure of the two sides of the air
displacer piston is approximately equal. By this device the air pump never
requires to raise the pressure of the air much above that obtaining in the main
displacer chamber when the working fluid is at the cold end. The air displacer
may be used in combination with the constant flow valve described in the
Specification filed in pursuance of Letters Patent, No. 832, granted to one of us on
the 28th February, A.D. 1876; or in place of the air displacer we may use the
said constant flow valve itself. We interpose the constant flow valve between the
supply pumps or air displacer and the grate with the object of preventing an excess
of air from being thrown in when the pressure in the main displacer chamber is
lowest. We can diminish the flow at this period or stop it by partially or wholly
closing the orifice which in the constant flow valve regulates the amount of fluid
delivered. The constant flow valve renders it possible to regulate the flow or rate
of entrance of the fluid into the grate independently of the difference of pressures
between the pipes outside the valve and the grate, or makes the flow practically
independant of the pressure in the displacer chamber with which the exit from the
grate communicates. In place of using the constant flow valve alone or with the
air displacer only, we may use the constant flow valve in combination with a
reciprocating valve, or with such a valve and the air displacer for the purpose of
wholly or partially cutting off the flow of air, or we may dispense with both and
use a restricted orifice capable of being enlarged or contracted. Or we may use
simply a reciprocating valve, either with or without the restricted orifice. The air
displacer herein before described may be used in combination with any of the above
alternatives for the constant flow valve or by itself. We usually cut off the supply of
air altogether during the period at which the working fluid is at the cold end of tho
cylinder, the fire and grate continuing to glow not only during this short interval, but
during comparatively long stoppages of the engine. The use of the constant flow.
valve in the manner above described will be of advantage in combination with any
form of engine in which air or air and gas continue to be supplied while combustion
is going on.
Seventhly. The Circulating Valve or Valves. A valve or suitable arrangement of
valves is provided separating the interior of the main displacer chamber (and
consequently also the grate) from the working cylinder. A valve or suitable arrange-
ment of valves is placed between the regenerator on the one hand, and the
refrigerator or the passage herein after mentioned, avoiding the refrigerator on the.
other, by which valve or valves the working fluid in returning from the working
cylinder and cold end of the displacer chamber is conducted through the refrigerator,
but when on its way to enter the cylinder and the cold end of the displacer
chamber is prevented from passing through the refrigerator, and is conducted
instead through a passage or passages to be provided for the purpose by which it
avoids the refrigerator, the object of this arrangement, being to remove heat from
the working fluid and cushion only during the time when compression is taking
place; or this valve or an arrangement of valves performing the same function
may be placed between the refrigerator and the working cylinder, that is to say,
the valve or valves may be at either end of the refrigerator. We may arrange
the valve or valves so that we may interrupt the communication between the
displacer vessel and the working cylinder during the time when the change is
taking place in the direction of the current.
Eighthly. A cut off valve interrupting the communication between the displacer

page_text: vessel and the working cylinder, this valve being under the direct control of the
governor of the engine, so that the speed of the engine may be regulated thereby. This
valve effects this by controlling the amount of power indicated during each stroke.
Ninthly. The Pure or Fresh Air Reservoir. We may provide an air reservoir in
which atmospheric air is stored at a sufficiently high pressure to flow into the
grate when the engine is stopped for any considerable period. We then in order
to keep up combustion allow a small flow of air from the air reservoir through the
grate, and allow a corresponding exit from the main displacer vessel of the products
of combustion. Or this may be effected by means of a donkey pump, or in the case.
of long stoppages by a chimney of sufficient height, an air inlet to the furnace
and open to the atmosphere being provided.
Tenthly. The Burnt Air Reservoir. We may provide a reservoir into which the
products of combustion may be taken from the cold end of the displacer vessel.
This reservoir acts as a storer of energy, and fluid may be taken from it to start
the engine by being admitted to the equilibrator cylinder.
Eleventhly. The Strainers. At suitable points near the cold end of the regenerator
we place strainers of suitable material to prevent grit or ashes from being carried
into either the working cylinder, the equilibrator, or the air displacer. Near the
hot end of the regenerator we place coarse strainers of refractory material such as
perforated brick or bundles of rods of pipo clay.
The covering of the grate itself acts as a coarso hot end strainer.
The fuel burned in the furnace or grate may consist of coal, coke, or any other
kind of solid fuel, but we prefer when coals are used that such coals should be
selected as do not produce slags and other products which would tend to clog the
strainers and choke up other passages in the engine, and for this reason also we
avoid the use of comminuted fuel or fuel in the form of dust.
The action of the engine is as follows:-
'
The fire is lighted in the furnace through a suitable opening and the products of
combustion pass up through the regenerator and out through a special opening
provided for the purpose, or they escape by means of a chimney communicating
directly with the hot chamber. When the refractory material lining the furnace
and main displacer vessel are sufficiently warm, the opening by which the fire was
lighted is closed. The combustion is maintained both before and after the closing
of the opening by a small supplementary air pump which may be driven by hand,
or by a donkey engine, or in any other way, or the air pump may be supersedod
by a chimney of sufficient height. After the opening is closed this pump brings
the pressure in the main displacer vessel up to the desired point, or the engine may
be charged with working fluid proviously stored in either the fresh air or burut
air reservoir. The displacer is or may be during this period in the cold chamber.
The displacer or displacers are temporarily disconnected from the working
cylinder. If this cylinder is double acting, the displacer corresponding with
the proper side of the piston is moved to the warm end. There will then
be a difference of pressure between the two sides of the piston which will start
the engine. The action may be aided by at the same time admitting high
pressure working fluid direct from one displacer vessel to one side of the
equilibrator. The action can be still further assisted by temporarily disconnecting
the air pump or pumps for the glowing furnace and adjacent part of the displacer
chamber will contain a supply of heat amply sufficicut for many strokes. The
displacers may require to be worked several strokes by hand or other extraneous
power. When once the engine has acquired sufficient speed the displacers are thrown
into gear by suitable means and also the air pump or pumps if these have been
disconnected. The course of events relating to one side of the working piston is
(beginning at that period in which the displacer is at the cold end and the working
piston at one end of its stroke) as follows:-Air is coming through the constant
How valve or other arrangement for the same purpose to the tuyeres and flowing
into the furnace from the air displacer, the piston of which is moving from end B
to end A. The mass of working air has now absorbed the main portion of its heat

page_text: from the regenerator and the walls of the hot part of the displacer vessel. Heat is
being generated and transferred into a comparatively small quantity of working
fluid which expands from the grate or furnace through the straining bars to the
displacer. The new heat thus added will be equal to that converted into mechanical
effect added to that rejected in the refrigerator and that lost by conduction from
the exterior of the working parts. The working fluid will now expand in the hot
end, the displacer during this portion of the action of the engine acting as a barrier
or separator between the hot mass of working air and the cushion which abuts
against the working piston. This whole mass of fluid expands, but is directed by
the circulating valves so as not to pass over the refrigerating pipes. Towards the
end of the working stroke the displacer. will begin to move rapidly towards the hot
end, and about the time the working piston reaches that end will have transferred
the mass of the working fluid to the cold end of the displacer vessel. The circulating
valves will still direct this air so that it does not pass over the refrigerating pipes.
The supply of air through the tuyeres will now be cut off and the piston in the air
displacer will move backwards from end A to end B storing up air. The pressure
in the main displacer vessel will have fallen because the regenerator has cooled a
considerable part of the working fluid; the return stroke will begin, the fluid
coming both from the air displacer and working cylinder will be cooled during
compression by the refrigerator. Near the end of the return stroke the displacer
will begin to move rapidly to the cold end; working fluid will then be forced from
the cold end through the regenerator but not past the refrigerating pipes. This air
will be warmed as it descends and one cycle of changes is complete. The piston
in the air displacer will reverse its motion. During this reverse motion it will be
better that it should not draw the air required for the end B past the refrigerating
pipes. The supplementary action of the equilibrator and the pump has meanwhile
been proceeding as follows:-
-
A portion of the working fluid has been admitted to one end of the equilibrator,
has been expanded down approximately to atmospheric pressure and released into
the atmosphere; the pumps also have compressed a corresponding amount of air,
which is sufficient when used in the furnace to produce enough of heat for one cyclo
of operations which may be stored in the fresh air reservoir before mentioned from
which it flows into the air displacer. The work done in this cylinder is nearly
equal to that required to drive the air pumps. The cycle of operations is now
complete. The air compressed may be cooled in the usual way so as to allow the
pumps to be worked with no injury to the working parts. Sometimes we do not
cool this compressed air in the usual way, but use the same cylinder alternately as
equilibrator and compressor, using the cold developed by the expansion to balance
the heat developed during compression. During the cycle a little coal may be fed
either automatically or by hand, or the feeding may only occur every few strokes.
It may occur by short pushes or be carried out by a continuous motion. The
engine could be made to go with only the four first parts combined with the
ordinary remaining parts of a Stirling engine, but it will be less efficient.
The fifth improvement is capable of being introduced into and is valuable in any
analagous form of engine whether it contains any of our special features or not. In
particular it is applicable in connection with any motor engine in which any part
of the working cylinder or displacer chamber or other vessel in which the working
fluid undergoes variations of pressure is kept at or exposed to high temperatures
and in which the working cylinder or displacer vessel or any other vessel commu-
nicating with said cylinder or displacer vessel is lined with nonconducting or
refractory materials which would cause injurious cushioning action from the porosity
of said materials in manner bereinbefore mentioned.
The combination of the air displacer described under head 6thly with the
displacer chamber as also the combination of a cylinder alternately used as a pump
and equilibrator so as to save heat in manner described under head 4thly may be
used with advantage in any Stirling engine in which internal combustion is
adopted. The circulating valves hereinbefore described in the seventh head or

page_text: place are useful in any Stirling engine, or any engine the action of which requires
a refrigerator and a cool cushion of air between the working fluid and the piston.
The said circulating valves and the cut off valve, described in the eighth head or
place, may for the sake of simplicity be one or both of them omitted from our
combination, in which latter case the connection between the displacer chamber and
the working cylinder is simply that of the old Stirling engine.
The use of a strainer at or near the cool end of the regenerator, as described
under head 11thly, is applicable and advantageous in any engine which has a cool
cushion of air or gas interposed between the hot working fluid and the working
cylinder. By keeping up the combustion constantly or continuously we produce
heat in the grate in a manner analagous to that in which heat was supplied con-
tinuously to the hot end of Stirling's air vessel. by transmission across the iron
casing, but we prefer to check the production of heat during the period when the
displacer occupies the warm end by diminishing the supply of air, and in some
cases we may for a short time wholly discontinue the supply. Our engine may bo
double acting, or may by employing an air cushion or large fly wheel for the return
stroke be made single acting. Communication may be kept open constantly
between the cool chamber and the working cylinder, or the communication may, as
we prefer, be made intermittent by means of any of the arrangements herein before
mentioned as having that effect.
We arrange the pump and equilibrator so that the combination of their turning
moments with the turning moments of the Stirling engine inay be such as to avoid
as far as possible the inconvenience of negative moments, in the combination of
which as a whole our engine consists, and to make these moments as constant as
may be practicable. For the purpose of effecting the last mentioned object we do
not confine ourselves to one single acting engine with its pump and equilibrator or
other parts, or to one double acting engine with pump or pumps and equilibrator
or equilibrators and other parts, or to any number of engines and any number of
pumps and equilibrators and other parts in connection with any engine or number
of engines, the variety of possible combinations and arrangements of this nature
being infinite.
The displacer vessel and the working cylinder may be combined so as to form
one vessel according to a well known mode of arrangement as applied in provious
engines.
Figures 1º, 2º, 3º, 4º, 5º show one method of constructing the main displacer
vessel and its adjuncts.
In Figure 1° A is the furnace or grate surrounded by the refractory .non-
conducting material a, a, a; B, B, are the tuyeres through which the air enters
the furnace for the purposes of combustion, in the outer end of one of which is
placed an eyepiece, through which the fire may at any time be observed; C is the
hot end strainer or covering of the grate, made of refractory material; this hot end
strainer may however be entirely dispensed with; D is the furnace door, by
which the fire is lit, and ashes, slag, &c., removed; F is a passage which may be
placed in communication with a chimney while the heat in the main displacer
vessel is being raised preparatory to starting the engine; G is the main displacer;
H is the regenerator; I shows the refrigerating tubes, in which is a solid rod J,
leaving an annular space between the inner side of the tube and the solid rod, the
object being to diminish clearance; K, K, are the passages by which the air avoids
passing over the refrigerator tubes at that period of the cycle of operations during
which expansion is going on in the engine; L, L, are the circulating valves; M
shows one of the strainers.
E, Figure 3º, shows one method of constructing the solid fuel feeder. The inner
valved having been pushed inwards, carrying along with it the screw i by the
land wheel e and the lever f, so that the communication between the grate A and
the hopper k is cut off, the outer valve or cover c is then opened, the solid fuel
dropped into the hopper k, and c is again closed. The hand wheel e is then turned
so as to open the valve d; the effect of turning the hand wheel e is at first simply

page_text: to draw back the valve d, but as soon as the shoulder g abuts against the nut h the
valve d ceases to come back, and the valve d, wheel e, and spindle and screw i all
revolve in one piece, screwing the fuel forward and delivering it into the furnace A.
The valve d may then be left open, or it may be closed, which latter is to be
preferred in cases where there is any danger of the heating of the hopper k. A 5
small lever is placed at the side of the hopper k, with which the solid fuel may be
agitated so that it will drop freely into the tube and screw i.
N, Figure 1°, is the inner metallic casing, cutting off from the bulk b, b, b, of the
non-conducting material a thin layer a, a, a, of refractory non-conducting material
sufficient for the protection against oxidation and burning of the surface of the said 1
inner metallic casing, the said exterior refractory nonconducting material being
enclosed in an outer casing o, which may be constructed so that it is capable of
retaining and withstanding pressure from within, or it may be made with a direct
communication between b, b, b, and the atmosphere. It may either be made
continuous or of discontinuous plates or hoops encircling the said exterior non- 1
conducting material. Qis the hot chamber, which is surrounded by refractory
nonconducting material (the main displacer G is shown in Figure 1° as occupying
the hot chamber; P is the cool chamber surrounded by the water casing through
which the refrigerating pipes i, i, pass.
Figure 5° shows a sectional side elevation of the air displacer, also shown in 2
position in Figures 1° and 3°; the end m of the cylinder is constantly in commu-
nication with the cool end of the main displacer vessel by means of a continuation
not shown in this Drawing of the pipe o. The end n alternately draws air from
the air reservoir by the valve g, and delivers it by the valve p into the furnace
through the tuyeres B, B. In the arrangement shown the constant flow valve, the 2
reciprocating valve, and the restricted orifice are all unnecessary. L, Figures 1°,
2º, 3º, and 4°, shows the circulating valves; r, r, are the ports leading to the
passages K, K, by which the refrigerator is avoided; 8, 8, are the ports leading to
the refrigerating tubes by the distributing passage t, t, which run all round the top
of the refrigerating tubes. Suitable ports or openings are placed in the yalve 8
blocks to regulate the period of the flow of air through the passages, as shown in
Figure 4°. These circulating valves are both open or closed, as the case may be, to
corresponding passages at the same time. Two valves are shown in the Drawing,
but there may be any number.
S, S, Figure 8°, are the cut off valves on the connections leading to the working 3
cylinder. They are connected with the governor by any of the usual well known
means; T, Figures 6°, 7°, 8°, is the fresh air reservoir communicating with the
pumps by the pipe h, and with the air displacers by the pipe i.
A burnt air receiver may be provided, placed in any suitable position; it is not
shown in the Drawings.
M, M', are the strainers; M is the equilibrator strainer connected by a passage
with a point near the top of the regenerator; M³ is one of the main strainers.
They are constructed by placing a separator of flannel or cotton wool, or any other
suitable sieve like substance or substances across the passage leading from the main
displacer vessel to the cylinders. The flannel or other substance is supported on
either side by wire gauze, and is made of such area as not to add greatly to the
frictional resistance of the passage.
Figures 6º, 70, 8°, and 9° show one complete form of our engine.
The capital letters apply to corresponding parts in all our Drawings, but the small
letters do not. The small letters refer to corresponding parts on Sheet 1°, and to
other corresponding parts on Sheet 2°.
O, O, are the main displacer vessels; W is the working cylinder with its passages
connecting it with the main displacer vessels and strainers, one of which is shown in
section at M. The main displacer vessels communicate with opposite ends of the
working cylinder. R, R, are the air displacers worked by an eccentric z on the engine
shaft represented by dotted line on Figure 7°. X, X, is the combination of pumps and

page_text: M18 The reeder;
18. Gy nesu ar
equuiorators nereinaiter described;
reservoir.
The action of the engine is as follows :—
The references here being chiefly to Figures 6º, 7°, 8°, and 9°. The furnace
doors D, D, and the outlets to the chimney, not shown in the Drawings, at F, F,
are opened.
The fires are kindled in the grates A, A, Figure 1°, and allowed to burn till the
hot end of the displacer vessel has attained a sufficient temperature. If the engine
is small and the products of combustion from the furnace are so much cooled down
by contact with the sides of the displacer vessel that they have not after entering
the chimney sufficient heat in them to cause a draft, the draft may be assisted by
heating the chimney by means of heat applied directly to it, or the draft or current
of air may be maintained by any of the other means before mentioned. The hot
end having attained a sufficient temperature the fire door and chimney opening are
closed, the fire meanwhile continuing to glow in the grate, and the main displacer
vessels and working cylinder are then filled with working fluid either from the
fresh air receiver or from the burnt air receiver, or by a small supplementary pump
as hereinbefore mentioned. The main displacers are then disconnected from the
engine by means of the rod and handle U, Figure 9°, the pumps are temporarily
thrown out of action, but the equilibrators are allowed to act. The lever V is then
passed back and forward by hand or other power, thereby causing a difference of
pressure on opposite sides of the working piston, which, assisted by the equilibrators,
starts the engine. As soon as the engine is running at sufficient [speed the main
displacers are put in gear, the pumps are thrown into action, and the engine is at
work. The cycle of operations in the main displacer vessels and the working
cylinder is similar to that of the old Stirling engine which has been hereinbefore
described except in so far as the circulating valves may modify, its action. The
circulating valves L, L, are worked by a wyper shaft 6, Figures 8° and 9°, driven
by an eccentric a, Figure 8°, on the rocking shaft which works the main displacers,
and this eccentric is set so that it actuates the valves in such a way that the air on
its way up to the cool end of the main displacer vessels and working cylinder
avoids the refrigerator by passing up the passages K, K, Figure 1º, and on its
return to the hot end passes down through the refrigerating tubos I, I.
While the ordinary cycle of operations of a Stirling engine is going on in tho
working cylinder the following operations are taking place in the pumps and
equilibrators:―The pumping and equilibrating arrangements are carried on in two
cylinders a, a, and the method shown in the Drawing is that in which the two
operations of compressing and expanding are carried on alternately in the same
cylinder. Each end of each cylinder performs in succession, and repeats four
separate operations, viz., 1° draws in air from the atmosphere, 2º compresses and
delivers this air into the fresh air reservoir T, 3° receives a charge of high pressuro
air or fluid from one of the main displacer vessels through the strainors M, M, and
the pipes c, o, and expands this charge down to atmospheric pressure, 4° exhausts
this charge into the atmosphere, and the valve gear Y is so arranged that during
each stroke of the working piston the whole of these four operations are completed,
that is to say, at any time during the working of the engine the four operations
are going on simultaneously, and they take place in the order or succession before
described in each end of each cylinder of the pumps and equilibrators, two
revolutions of the engine being required to complete one cycle of operations in the
pumps and equilibrators. For this purpose the valve gear Y is connected to the
crank shaft of the engine by pinions so adjusted and proportioned that the main
shaft Y of the valve gear shall be driven at half the speed of the crank shaft of the
engine, and each of the small shafts d, d, d, shall be driven at the same speed as
the main shaft of the valve gear. Each end of each cylinder has three valves;
1°, an admission valve e; 2°, an exhaust valve f which also acts as an inlet valve
for fresh air; 3°, a delivery valve g through which fresh air is delivered into the
receiver T through the pipes h, from which it is drawn by the air displacers through

page_text: the pipes i and pass through the grate, returning to the pump and equilibrator
cylinders X, X, by the strainers M, M, and the pipes c, c², being then products of
combustion. The pumps and equilibrators are connected to the crank shaft at such
an angle that they will as far as possible avoid negative moments. The point of
cut off of the valves e regulates the pressure under which the engine is worked.
and the valve.e has suitable gear for varying the point of cut off.
The fuel is fed in by hand from time to time as may be required.
Having now described and specifically ascertained the nature of the said Invention,
and the manner in which the same may be used or carried into effect, we desire to
state that what we claim as novel and original, and as what is secured to us by the
herein before in part recited Letters Patent is,-
First. The caloric motor engine herein before described, that is to say, an engine
the cycle of whose operations is in the main that of the Sterling engine, but which
differs from the Stirling engine primarily in having solid fuel burned, by means
and in manner hereinbefore described, under pressure and internally, and which
engine is a combination of the main displacer vessel, regenerator, refrigerator,
working cylinder, and the ordinary parts of a Stirling engine, other than its external
furnace, with the grate and its adjuncts hereinbefore described under head first,
and (1) the further arrangements, details, or improvements herein before described
in the first place under heads secondly, thirdly, fourthly, fifthly, sixthly, seventhly,
eighthly, ninthly, tenthly, and eleventhly; or (2) in each of the cases wherein for any
detail or arrangement first described under any of said heads one or more alternative
arrangement or arrangements is or are also hereinbefore described, then either with
the said detail or arrangement so first described, or with the alternative or one or
other of the alternatives therefor hereinbefore described, and that whether such
engine be double acting or single acting, and whether it have or have not all or
any of its parts duplicated or otherwise multiplied or repeated, all as herein before
described.
Second. The said caloric motor engine in any of its forms falling under the
preceding claim, but with the omission therefrom of any one or more of the
arrangements or details which it is hereinbefore stated may be omitted.
Third. A caloric motor engine with its cycle of operations in the main that of
the Stirling engine, but which differs from the Stirling engine primarily in the
matter of the internal combustion under pressure of solid fuel, as stated in claim
first, and which consists of a combination with the parts of a Stirling engine
specified in claim first of the arrangements or details hereinbefore first described
under heads firstly, secondly, thirdly, and fourthly, or in place of the arrange-
ment first described under any of those heads of any alternative arrangement
therefor hereinbefore described.
Fourth. A caloric motor engine consisting of the engine in any of its forms
claimed under claim third, with the addition thereto of any one or more of the
arrangements, details, or improvements first described under heads fifthly, sixthly,
seventhly, eighthly, ninthly, tenthly, and eleventhly, or in place of the arrange-
ment first described under any of said heads of any alternative arrangement
therefor hereinbefore described.
Fifth. The use and application in the construction of any part of the displacer
chamber, working cylinder, or other vessel in which the working fluid of any
internal combustion motor engine undergoes variations of pressure, and which part
is kept at or exposed to high temperatures, and requires to be lined with non
conducting or refractory materials, which tend by reason of their porosity to cause
injurious cushioning action, of the arrangement hereinbefore described, whereby,
while the external metal casing is withdrawn from the softening action of the
internal heat by the interposition of a mass of non conducting material, the great
bulk of this non conducting material is, for the purpose of preventing or reducing
the said cushioning action, cut off from contact with the working fluid within the
hot chamber or vessel by a second metal casing or lining, which derives its support
against the internal pressure from the cool outer metallic casing, which may either

page_text: give this support through the solid non conducting materials between the two
casings, or partly or wholly through gas under pressure, all as hereinbefore
described.
Sixth. As a separate Invention the combination of the air displacer described
under head 6 with the displacer chamber of any engine of the Stirling type in
which internal combustion is adopted.
Seventh. As a separate Invention the combination with any engine of the
Stirling type in which internal combustion is adopted of a cylinder alternately
used as an air pump and equilibrator, so as to save heat in the manner described.
under head 4.
Eight. As a separate Invention the use and application in connection with any
engine of the Stirling type or any engine the action of which requires a refrigerator,
and a cool cushion of air between the working fluid and the piston of the
circulating valves hereinbefore described under seventhly.
In witness whereof, I, the said Alexander Chalmers Jameson, have hereunto
set my hand and seal, this Seventh day of September, in the year of
our Lord One thousand eight hundred and eighty one.
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