IMPROVEMENTS IN ENGINES FOR DEVELOPING MECHANICAL POWER BY THE ACTION OF HEAT A PROVISIONAL SPECIFICATION
Year: 1853

page_text: LETTERS PATENT to James Robert Napier, of Lancefield House,
Glasgow, in the County of Lanark, Mechanical Engineer and
Iron Ship Builder, and William John Macquorn Rankine, of
Rosebank House, in the Parish of Rutherglen, and County
aforesaid, Civil Engineer, for the Invention of "IMPROVEMENTS IN
ENGINES FOR DEVELOPING MECHANICAL POWER BY THE ACTION OF HEAT
A
PROVISIONAL SPECIFICATION left by the said James Robert
Napier and William John Macquorn Rankine at the Office of
the Commissioners of Patents, with their Petition, on the 9th
June 1853.
We, JAMES ROBERT NAPIER, of Lancefield House, Glasgow, in the
County of Lanark, Mechanical Engineer and Iron Ship Builder, and
WILLIAM JOHN MACQUORN RANKINE, of Rosebank House, in the Parish
A

page_text: of Rutherglen, and County aforesaid, Civil Engineer, do hereby jointly
& severally declare the nature of the said Invention for "IMPROVE-
MENTS IN ENGINES FOR DEVELOPING MECHANICAL POWER BY THE ACTION OF
HEAT ON AIR AND OTHER ELASTIC FLUIDS to be as follows, that is to
say:
The engines which this Invention is calculated to improve are those
which develope mechanical power applicable to the moving of any kind
of machinery by successively heating, dilating, cooling, & condensing
a portion or portions of air or any other elastic fluid in such a manner
that the dilatation takes place at a higher temperature, and the con-
lensation at a lower temperature, and which are known by the names
of air engines and caloric engines.
The engine which we will now describe for the purpose of showing
the nature of the improvements proposed by us, and which is repre-
sented in the annexed Drawing, consists partly of parts and combina-
tions of parts resembling those which have heretofore been used in
engines of the class referred to, and in steam engines, and partly of
parts and combinations of parts which we claim as our Invention
for the improvement of such engines, and which we shall herein-after
specify and claim in detail.
The arrangement of the different portions of the engine shewn in
the Drawing is one of many practicable arrangements which we select
as being well adapted to display all the essential parts of the engine
at one view. It is obvious that the essential parts of the engine being
properly connected with each other may be arranged in any other way
which may be found best suited to the situation in which it is to be used,
and the work which it is to perform. The framework by which the
working parts of the engine are to be supported is omitted from the
Drawing because it involves nothing new or peculiar, and would
interfere with the distinct representation of the working parts.
A, is a vertical section of a cylinder containing a piston B, fixed on
a piston rod C, which traverses a stuffing box b, and is connected by
means of a connecting rod D, with a crank E, and gives motion to a
shaft F, which may be used to drive any machinery, and on which is a
fly wheel not shown in the Drawing.

page_text: G, G, are guide rollers for the cross head of the piston rod.
Besides the mode here shewn of connecting the piston with the
crank, any of the other modes used in steam engines and air engines
might be employed.
H₁, is a passage connecting the top of the cylinder with a strong air-
tight receiver K, the body or central part of which is cylindrical, and is
shewn in section in the Drawing.
These
The uppermost part of this receiver consists of a number of brass or
other metal tubes i, i, i, i, i, of which five are shewn closed at the top,
open at the bottom, where they are strongly fixed in a plate j₁.
tubes are to be surrounded by water circulating in a tank O₁.
intended that the air or other gas should be cooled in them.
It is
The lowest part of the receiver K₁, consists of a number of brass
or other metal tubes k, k, h, k, l, five of which are shown in the
Drawing closed at the bottom, and open at the top, where they are
strongly fixed in a plate . It is intended that the air or other gas
should receive heat through them by conduction from the flame from a
furnace circulating in a flue I, round the tubes.
The plate , is protected from the action of the flame by a fire clay
shield 01-
M, is a main flue conducting the flame from a furnace; m, a branch
flue leading into the flue or chamber L; ₁, a branch flue leading from
this chamber to a main fluc N, which conducts the products of com-
bustion to the chimney.
P₁, is a plunger of sheet iron or other metal divided into compart--
ments so as to be at once light and strong. Some of these compart-
ments are to be air-tight, and to be filled with brick dust, fire clay, or
some other substance which conducts heat slowly; but one or more
compartments are to extend through the plunger, so as to form a
passage for air or gas, and are to be filled with a series of layers of
wire gauze, or thin perforated metal plates, or wires, or of some
substance capable of conducting heat rapidly, and so formed and
arranged as to expose a large surface for the communication of heat to
and from the air which may pass through. One such passage, occupied
as described, is represented by P₁, in the Drawing.

page_text: The plunger P, is to be made to fit the body of the receiver K₁, as
closely as is consistent with its moving up and down without friction
against the sides of the receiver. It is to be suspended by one or more
rods from a beam R, which turns on a pivot 7. In the engine shewn
in the Drawing there are two such rods for this plunger marked Q₁, Q.
They traverse stuffing boxes at the top of two of the tubes i, i, and are
attached to a cross bar which is hung from the beam R, and is so
formed as to allow a third rod T₁, to pass freely through it for a
purpose to be afterwards stated. Another of the tubes i, is traversed
by this rod. The remainder of those tubes, two of which are shown
in the section, are occupied by cylindrical metal rods ₁, fixed to the
top of the plunger P₁, forming part of it, and moving along with it,
and fitting the tubes loosely, so as to leave a passage for air or gas all
round each tube about an eighth of an inch wide.
The rod T, suspended from the beam U₁, traverses a stuffing box at
the top of one of the tubes i, and descending through that tube
traverses also the centre of the plunger P, by a hole wide enough to
Ict it work without friction, and is attached to the heat screen S,.
This heat screen consists of a circular plate s, of iron, brass, or other
metal, pierced with holes, fitting the cylindrical part of the receiver K',
but not so tight as to produce friction, and of a series of rods t₁, of
brass, copper, or other metal, fixed to this plate, and moving with it,
and capable of filling the tubes , completely, except a passage of
about an eighth of an inch all round each tube.
The object of this heat screen is to regulate the transmission of heat
from the flame in the chamber I, to the air or other gas in the
lower part of the receiver K, so that it shall take place wholly or chicfly
during the expansion of this air or other gas, which is the period most
favorable for the developement of mechanical power, and shall be
wholly or almost wholly cut off at other times when it would be wasted
or impede the action of the engine.
The rods, and t₁, may be made hollow for the sake of lightness,
but the hollows should be air-tight.
The peculiar form of the heat screen shewn in the Drawing is a
result of the tubular form of the bottom of the receiver, with which it is

page_text: In like
made to correspond. Should the bottom of the receiver be made of
any other shape, the heat screen must be made to fit it.
manner the top of the plunger P₁, is to be made to fit the top of the
receiver.
The beam U,, from which the heat screen hangs by the rod T₁,
turns on the axis ₁. V₁, is a counterpoise to balance wholly or partially
the weight of the heat screen. In stationary engines a preponderance
may be allowed to the heat screen suflicient to make it descend to the
bottom of the receiver from the top of its stroke with rapidity, but
not with violence. In marine and locomotive engines the balance
of weight should be exact, and the descent of the heat screen should be
produced by means of a spring.
1
W₁, is a catch turning on a pivot w₁, in the beam U₁, resting against
the stud v and kept in its place by a spring a. The roller X,
at the end of the beam R, acting on this catch, raises the beam U
and heat screen S', during the latter part of the up stroke of the
plunger P. When this plunger is near the top of its stroke, the catch
escapes from the roller, and the heat screen descends. During the
down stroke of the plunger P₁, the roller pushes the catch down into
the position shewn by the dotted lines at W., and passes it, when the
catch springs back to its original position. The counterpoise end of
the lever U, is omitted, the better to display some other parts of the
engine.
At the side of the Drawing towards the left hand the catch is
supposed to have just escaped from the roller, and the heat screen to
be in the act of falling. At the side towards the right hand the heat
screen is supposed to be in its lowest position.
Y, is an eccentric wheel for working the plungers and heat screens.
By means of the rod Z, it gives a reciprocating motion to the link A, a,
which turns on a pivot at a, a. In this link is fitted a slide b, b,
furnished with a spring catch for fixing it at various notches on the
link. This slide is connected by the rod B, b, with the end of the
lever C, c, which is either part of the beam R, or fixed to the same
axis. Thus a reciprocating motion is communicated from the eccentric
to this beam.

page_text: The handle D, d, serves to shift the slide b, b, to various positions in
the link. When the slide is in the position shewn in the Drawing
the shaft , will revolve in the direction shewn by the arrow; when
at the centre of the link the engine will stop; when at the opposite end
the motion will be reversed; when in intermediate portions the speed
will be moderated.
The most economical mode, however, of working at a reduced
speed will be to close partially the dampers with which the flues are to
be provided, and thus to moderate the combustion in the furnace.
The passage H, leads from the lower end of the cylinder to the
receiver K, which, with its tubes, water tank, flues, plunger, heat
screen, rods, beams, and other appurtenances, is to be similar to that
already described. It is shewn in elevation only. The visible parts
of the engine specially belonging to the lower end of the cylinder are
marked with the same letters with the corresponding parts belonging
to the upper end, and distinguished by having the Figure 2, affixed
instead of 1.
E, e, is a rod attached to the eccentric ring for working a forcing
pump F, f, by which air or the other gas employed is to be com-
pressed into the magazine K, k, both to obtain a sufficient pressure
and to supply the loss by leakage. This forcing pump being behind
the cylinder, its position is shown by dotted lines. H, h, is an adjusting
screw by which the rod E, e, can be lengthened or shortened so as to
increase or diminish or altogether to stop the supply of compressed air
or gas forced into the magazine at each stroke of the pump.
L, L, are pipes leading from the magazine to the passages
communicating with the two ends of the cylinder respectively, and
furnished with valves opening upwards, so that whenever the pressure
in either end of the cylinder falls below that in the magazine a supply
of air or gas may pass to the end of the cylinder which requires it.
M, m, M, ma, M, ma, are safety valves for the two ends of the
cylinder and for the magazine respectively.
Another forcing pump, which needs not be shewn, as it presents
nothing peculiar, is concealed behind the magazine, and worked by
another rod from the eccentric ring. Its function is to supply a stream

page_text: of cold water to each of the tanks O₁, O., which gradually rising amongst
the tubes escapes finally by the waste pipes 0, 0, 0, 0, which should be
conducted to some convenient outlet. In locomotive and marine
engines these tanks should be subdivided by thin perforated partitions,
to check agitation of the water. Another mode of cooling the tubes i,
is to sprinkle them with water from a number of jets.
Near the three safety valves are fixed three pressure guages Q,
QQ They should be capable of indicating pressures up to
200 lbs. on the square inch.
PP PP, are outer casings for the lower part of the cylindrical body
of the receivers K₁, K, filled with brick dust, engine ashes, or some
other slow conductor of heat.
R,, R,, R,, R, 7, are dampers for the flues.
In the engines shewn in the Drawing the receivers are vertical, but
it is obvious that they might be placed horizontally, the plungers and
heat screens being supported on rollers, and the motion of the heat
screens towards the hot ends of the receivers being produced by
springs.
Having thus described the parts of the proposed engine, and their
connection with each other, we shall now describe how it is to be set
in motion and worked.
When the engine is at rest the pressures on the top and bottom
of the piston will be equal, and it will place itself nearly in the middle
of the cylinder, being the position shewn in the Drawing. The slide b, b,
being at the middle of the link A, a, the beams R, U,, and U, will all
be horizontal, the plungers will be in the middle of their respective
receivers, and the heat screens at the bottom.
If the fire be now lighted, the flame circulating in the chamber L,
and the corresponding chamber for the other receiver, will heat the
tubes, the rods of the heat screen t₁, and the film of air between them.
At first the greater part of the heat will be accumulated in these bodies,
The effect
a small portion only reaching the air above the heat screen.
in each receiver being the same, the piston will still be pressed equally
on both sides, and will continue at rest.
Let us suppose that the crank stands as shewn in the Drawing, and

page_text: that it is required to set the engine in motion in the direction indicated
by the arrow. The engine man, by looking through a hole made for
the purpose, must watch the instant when the soot which has accumu-
lated on the outside of the tubes k, begins to burn off. He must then
loosen the spring catch of the slide b, b, and by means of the handle D, d,
move it to the upper end of the link. This motion will throw the
beam R, into the position shewn in the Drawing. It will lower the
plunger of the receiver K., sending the air through the passage in that
plunger to the top of the receiver, and into the tubes contained in the
tank O, so that such heat as may have reached it from the flame will
be abstracted. At the same time the plunger P₁, will be lifted to the
top of the receiver K, sending the air out of the tubes i, and the
upper portion of the body of the receiver down through the passage P
The heat screen S₁, will also be lifted and allowed to drop again, the
effect of which will be, that the air in the lower part of the receiver
will be made to circulate rapidly over the surface of the hot rods t
and through the hot tubes k, and will receive a certain quantity of heat.
This heated air expanding will transmit its pressure and its motion
through the passage II, to the air in the cylinder A, and finally to the
piston B, and the engine will begin to move.
During the working of the engine the following is the succession of
changes undergone by the air in the receiver K,
During the end of the down stroke and beginning of the up stroke
of the piston the heat screen lies at the bottom of the receiver. The
plunger P, descends, and the air, with the exception of a trifling
quantity, passes through the passage p₁, and gives out a large portion
of its sensible heat to the layers of wires or sheet metal contained in
that passage. The remainder of the excess of its heat above that of
the water in the tank O₁, is abstracted by the surface of the tubes i
and rods The up stroke of the piston causes the air to be com-
pressed this compression produces heat, which is also abstracted by
these rods and tubes. This heat, were it not so abstracted, would
increase the elasticity of the air, and oppose the motion of the piston.
During the end of the up stroke and beginning of the down stroke
the plunger P, rises, the air descends through the passage p₁, and

page_text: recovers the greater part of the sensible heat formerly lost from the
layers of wire or sheet metal. During the first half of the down
stroke the heat screen S₁, is raised and dropped, and the air, by cir-
culating over its rods and through the hot tubes, acquires the
remainder of the sensible heat necessary to elevate its temperature, and
also the latent heat necessary to expand it. This completes the cycle
of operations in the receiver connected with the upper end of the
cylinder.
In the other receiver the same operations take place, substituting
only the up stroke for the down stroke, and vice versa.
The effect of these operations is of a similar nature to that which
takes place in all engines driven by the action of heat on an elastic sub-
stance, viz., that the substance is alternately expanded at a higher
temperature, and compressed at a lower, so that the power developed
by the expansion is greater than the power consumed by the com-
pression, and a surplus of power remains to drive machinery.
When the proposed engine begins to work, should the cylinder and
receivers be filled with air or other gas at a pressure not sufficiently
great to perform the required work, the engine must be disconnected
from the machinery it is intended to drive, and the pump rod E, e, being
adjusted by the screw H, h, so that the piston of the pump shall nearly
touch the bottom of the barrel at each stroke; the whole surplus power
of the engine will be employed for some minutes in filling the magazine,
the receivers, and the cylinder with compressed air.
When the gauges
indicate that the required pressure has been attained, the engine may be
connected with the machinery to be driven, and the pump rod E, e
shortened by means of the screw II, h, so as to supply enough of air
only to make up for leakage, which condition will be indicated by the
pressure gauges.
The motion of the engine is stopped by moving the slide b, b, to the
centre of the link, and reversed by moving it to the opposite end of the
link.
The steadiness of motion may be increased, as in the case of steam
engines, by using a pair of engines to drive the same shaft, one being
a quarter of a revolution in advance of the other.

page_text: We claim, as the improvements which constitute the peculiarity of
the engine proposed by us, and its advantage over other engines driven
by the action of heat or air or other elastic fluids.
In the first place, the Invention and adaptation of the thing which we
have called a heat screen, being a species of plunger, separate from the
plunger, whereby the air or other gas is driven from the hot to the cold
end of the receiver, and vice versa, and serving the following purposes:
1. To screen the principal portions of the air or other gas from the
communication of heat from the furnace at those times when that heat
would be wasted, or would impede the motion of the engine, that is to
say, when the air or other gas is being passed towards the cold end of
the receiver to be cooled, when it is not being expanded, and when it is
being compressed.
2. To receive and store up at such times the heat communicated
from the furnace.
3. To permit and accelerate, by its motion at the proper period, the
communication of heat to the air or other gas at the time when it
is most effective in developing mechanical power; that is to say, when
the air or other gas is being expanded.
.
In the second place, we claim the adaptation of tubular receivers, for
the purpose of heating and cooling the air or other gas, in the manner
described in this Specification, that is to say, by the aid of rod-shaped
plungers or heat screens, nearly filling the tubes and serving, by being
moved out and in, to admit and expel the air or other gas, and promote
its circulation over the heated or cooled surface.
We do not, however, claim the Invention of tubes as a means of
increasing heat-conducting surface, but simply the adaptation of tubes
to engines worked by the action of heat or air or other gases by the
aid of the plungers or heat screens before described.
We claim the above-mentioned improvements in whatsoever manner
the parts of the engine may be arranged; many different arrangements
being practicable in combination with our improvements.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said James Robert Napier and William John Mac-
quorn Rankine in the Great Scal Patent Office, on the 8th
December 1853.
TO ALL TO WHOM THESE PRESENTS SHALL COME, we,
JAMES ROBERT NAPIER, of Lancefield House, Glasgow, in the County
of Lanark, Mechanical Engineer and Iron Shipbuilder, and WILLIAM
JOHN MACQUORN RANKINE, of Rosebank House, in the Parish of
Rutherglen, and County aforesaid, Civil Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Ninth day of June, in the year of
our Lord One thousand eight hundred and fifty-three, in the sixteenth
year of Her reign, did, for Herself, Her heirs and successors, give and
grant unto us, the said James Robert Napier and William John
Macquorn Rankine, Her special license that we, the said James
Robert Napier and William John Macquorn Rankine, our executors,
administrators, and assigns, or such others as we, the said James
Robert Napier and William John Macquorn Rankine, our executors,
administrators, and assigns, should at any time agree with, and no
others, from time to time and at all times thereafter during the term
therein expressed, should and lawfully might make, use, exercise, and
vend, within the United Kingdom of Great Britain and Ireland, the
Channel Islands, and Isle of Man, an Invention for "IMPROVEMENTS
IN ENGINES FOR DEVELOPING MECHANICAL POWER BY THE ACTION OF HEAT
ON AIR AND OTHER ELASTIC FLUIDS," upon the condition (amongst others).
that we, the said James Robert Napier and William John Macquorn
Rankine, by an instrument in writing under our hands and seals, or
under the hand and seal of one of us, should particularly describe and
ascertain the nature of the said Invention, and in what manner the
same was to be performed, and cause the same to be filed in the
Great Seal Patent Office within six calendar months next and imme-
diately after the date of the said Letters Patent.
NOW KNOW YE, that we, the said James Robert Napier and
William John Macquorn Rankine, do hereby declare the nature of our

page_text: said Invention, and in what manner the same is to be performed, to
be particularly described and ascertained in and by the following
statement, that is to say:
The engines which this Invention is calculated to improve are those
which develope mechanical power applicable to the moving of any kind
of machinery by successively heating, dilating, cooling, and condensing
a portion or portions of air or any other clastic fluid in such a manner
that the dilatation takes place at a higher temperature, and the con-
densation at a lower temperature, and which are known by the names
of air engines and caloric engines.
The engine which we will now describe for the purpose of showing
the nature of the improvements proposed by us, and which is repre-
sented in the annexed Drawing, consists partly of parts and combina-
tions of parts resembling those which have heretofore been used in
engines of the class referred to, and in steam engines, and partly
of parts and combinations of parts which we claim as our Invention
for the improvement of such engines, and which we shall herein-after
specify and claim in detail.
The arrangement of the different portions of the engine shewn in the
Drawing is one of many practicable arrangements which we select as
being well adapted to display all the essential parts of the engine at one
view. It is obvious that the essential parts of the engine being
properly connected with each other may be arranged in any other way
which may be found best suited to the situation in which it is to
be used and the work which it is to perform. The framework by
which the working parts of the engine are to be supported is omitted
from the Drawing, because it involves nothing new or peculiar, and
would interfere with the distinct representation of the working parts.
Figure 1, represents a vertical section of some portions of the engine,
and an elevation of others.
Figures 2, 3, 4, and 5, are plans upon a larger scale of detached
portions, to be afterwards more particularly specified.
In Figure 1, A, is a vertical section of a cylinder containing a
piston B, fixed on a piston rod C, which traverses a stuffing box 6, and
is connected by means of a connecting rod D, with a crank E, and

page_text: gives motion to a shaft F, which may be used to drive any machinery,
and on which is a fly wheel not shewn in the Drawing.
G, G, are guide rollers for the cross head of the piston rod.
Besides the mode here shewn of connecting the piston with the
crank, any of the other modes used in steam engines and air engines
might be employed.
H₁, is a passage connectingthe top of the cylinder with a strong
air-tight receiver K₁, the body or central part of which is cylindrical,
and is shewn in section in Figure 1.
The uppermost part of this receiver consists of a number of tubes of
brass or other suitable metal, open at the bottom, where they are
strongly fixed in a plate. These tubes are to be surrounded by
water circulating in a tank O₁. Their arrangement is shewn on an
enlarged scale in the plan, Figure 2. Three of those tubes marked I₁,
are provided with stuffing boxes at the top, being intended for the
passage of rods to be afterwards described. The remainder, marked i₁,
are closed at the top, and it is intended that the air or other gas should
be cooled in them.
The lowest part of the receiver K₁, consists of a number of tubes of
brass or other suitable metal marked k₁, arranged in the manner shewn
on an enlarged scale in the plan, Figure 3, closed at the bottom and
open at the top, where they are strongly fixed in a plate 4. It is
intended that the air or other gas should receive heat through them by
conduction from the flame from a furnace circulating in a flue L₁,
around and between the tubes.
The plate, is protected from the action of the flame by a fire clay
shield 01.
M, is a main fluc conducting the flame from a furnace; m₁, a branch
flue leading into the flue or chamber L₁₁, a branch flue leading
from this chamber to a main flue N, which conducts the products of
combustion to the chimney.
P₁, is a plunger of sheet iron or other metal divided into compart-
ments, so as to be at once light and strong, as shewn on an enlarged
scale in the plan, Figure 4. Some of these compartments are to be air-
tight, and to be filled with brick dust, fire clay, or some other substance

page_text: which conducts heat slowly; but one or more compartments are to
extend through the plunger so as to form a passage for air or gas, and
are to be filled with a series of layers of wire gauze or thin perforated
metal plates, strips, or wires, or of some substance capable of conduct-
ing heat rapidly, and so formed and arranged as to expose a large sur-
face for the communication of heat to and from the air which may pass
through. One such passage, occupied as described, is represented by Pi
in the section and plan.
The plunger P₁, is to be made to fit the body of the receiver K₁, as
closely as is consistent with its moving up and down with as little
friction as may be against the sides of the receiver. It is to be sus-
pended by one or more rods from a beam R, which moves on a pivot 2.
In the engine shewn in the Drawing there are two such rods for this
plunger, marked Q₁, Q. They work through stuffing boxes at the
top of two of the tubes I₁, and are attached to a cross bar, which
is hung from the beam R, by a rod J₁, and is so formed as to allow
a third rod T₁, to pass freely through it for a purpose to be afterwards
stated. This rod is partly concealed by the rod J. Another of
the tubes I, is traversed by this rod. The tubes ₁, two of which
only are shewn in section, are occupied by cylindrical rod-shaped
metal plungers, which, being arranged as shewn in the plan,
Figure 4, are fixed to the top of the plunger P₁, forming part of it, and
moving along with it, and fitting the tubes ₁, loosely, so as to leave
a passage for air or gas all round each tube about an eighth of an
inch wide.
The rod T₁, suspended from the beam U₁, works through a stuffing
box at the top of one of the tubes I₁, and descending through that
tube traverses also the centre of the plunger P₁, by a passage wide
enough to let it work without friction, and is attached to the heat
screen S₁.
This heat screen consists of a circular plate s₁. of iron, brass, or other
suitable metal, pierced with holes, fitting the cylindrical part of the
receiver K, but not so tight as to produce friction, and of a series
of rod-shaped plungers t₁, of brass, copper, or other suitable metal.
fixed to this plate, and moving with it, and capable of filling the

page_text: tubes, except a passage of about an eighth of an inch all round each
tube. This heat screen is shewn in plan on an enlarged scale in Figure
5, where the holes in the plate s₁, are indicated by small full circles, the
rod-shaped plungers t₁, by dotted circles, and the rod T₁, by which
the heat screen is suspended, by a dark spot.
The object of the heat screen is to regulate the transmission of heat
from the flame in the chamber L₁, to the air or other gas in the
lower part of the receiver K₁, so that it shall take place wholly
or chiefly during the expansion of this air or other gas, which
is the period most favorable for the developement of mechanical
power, and shall be wholly or almost wholly cut off at other times,
when the heat would be wasted, or would impede the action of the
engine.
The rods, and 4, may be made hollow for the sake of lightness,
but the hollows should be air-tight.
The form of the heat screen shown in the Drawing is a result
of the tubular form of the bottom of the receiver, with which it is
made to correspond. Should the bottom of the receiver be made of
any other shape the heat screen must be made to fit it. In like
manner the top of the plunger P₁, is to be made to fit the top of
the receiver.
The beam U₁, from which the heat screen hangs by the rod T₁,
moves on the axis u₁. V₁, is a counterpoise to balance wholly or
partially the weight of the heat screen. In stationary engines a pre-
ponderance may be allowed to the heat screen sufficient to make it
descend to the bottom of the receiver from the top of its stroke with
rapidity, but not with violence. In marine and locomotive engines
the balance of weight should be exact, and the descent of the heat
screen should be produced by means of a spring or some other suitable
mechanical contrivance.
W₁, is a catch turning on a pivot w₁, in the beam U₁, resting
against a stud v₁, and kept in its place by a spring a₁. The roller X₁,
at the end of the beam R, acting on this catch, raises the beam U₁,
and heat screen S₁, during the latter part of the up stroke of the
plunger P. When the plunger is near the top of its stroke the catch

page_text: escapes from the roller, and the heat screen descends. During the
down stroke of the plunger P₁, the roller pushes the catch down into
a position similar to that shewn by dotted lines at W., and passes it,
when the catch springs back to its original position. The counterpoise
end of the lever U, is omitted, the better to display some other parts
of the engine.
At the side of Figure 1, towards the left hand, the catch is sup-
posed to have just escaped from the roller, and the heat screen to be
in the act of falling. At the side towards the right hand the heat
screen is supposed to be in its lowest position.
Y, is an eccentric wheel for working the plungers and heat screens.
By means of the rod Z, it gives a reciprocating motion to the link A, a,
which turns on a pivot at a, a. In this link is fitted a slide b, b, fur-
nished with a spring catch for fixing it at various notches on the link.
This slide is connected by the rod B, b, with the end of the lever C, c,
which is either part of the beam R, or fixed to the same axis. Thus
a reciprocating motion is communicated from the eccentric to this
beam.
The handle D, d, serves to shift the slide b, b, to various positions in
the link. When the slide is in the position shewn in the Drawing the
shaft F, will revolve in the direction shewn by the arrow; when at
the centre of the link the engine will stop; when at the opposite end
the motion will be reversed; when in intermediate positions the speed
will be moderated.
The most economical mode, however, of working at a reduced speed
will be to close partially the dampers with which the flues are to be
provided, and thus to moderate the combustion in the furnace.
The passage E, leads from the lower end of the cylinder to the
receiver K, which, with its tubes, water tank, flues, plunger, heat
screen, rods, beams, and other appurtenances, is to be similar to that
already described. It is shewn in elevation only. The visible parts of
the engine specially belonging to the lower end of the cylinder arc
marked with the same letters with the corresponding parts belonging to
the upper end, and distinguished by having the Figure 2, affixed instead
of 1.

page_text: E, e, is a rod attached to the eccentric ring for working a forcing
pump F, f, by which air or the other gas employed is to be compressed
into the magazine K, k, behind the cylinder, both to obtain a sufficient
pressure, and to supply the loss by leakage. This forcing pump being
behind the cylinder, its position is shewn by dotted lines. H, h, is an
adjusting screw, by which the rod E, e, can be lengthened or shortened.
so as to increase or diminish or altogether to stop the supply of com-
pressed air or gas forced into the magazine at each stroke of the pump.
L, L,, are pipes leading from the magazine to the passages,
communicating with the two ends of the cylinder respectively, and
furnished with valves opening upwards, so that whenever the pressure
in either end of the cylinder falls below that in the magazine a supply
of air or gas may pass to the end of the cylinder which requires it.
M, m, M, m, M, ma, are safety valves for the two ends of the
cylinder and for the magazine respectively.
Another forcing pump, which needs not be shewn, as it presents.
nothing peculiar, is concealed behind the magazine, and worked by
another rod from the eccentric ring. Its function is to supply a stream
of cold water to each of the tanks O₁, O, which, gradually rising
amongst the tubes contained in those tanks, escapes finally by the waste
pipes 0, 0, 0, 0, which should be conducted to some convenient outlet.
In locomotive and marine engines those tanks should be subdivided by
thin perforated partitions to check agitation of the water. Another
mode of cooling the tubes is to sprinkle them with water from a
number of jets.
Communicating with the two ends of the cylinders and with the air
magazine respectively are fixed three pressure guages Q, 21. Q. 927 13.
They should be capable of indicating pressures up to 200 lbs. on the
square inch.
P, P₁ P, Ps, are outer casings for the lower part of the cylindrical
body of the receivers K. K., filled with brick dust, engine ashes, or
some other slow conductor of heat.
R, r, R, r, R, r, R, r, are dampers for the flues.
In the engine shewn in the Drawing the receivers are vertical, but
it is obvious that they might be placed horizontally, the plungers and
B

page_text: heat screens being supported on rollers, and the motion of the heat
screens towards the hot sides of the receivers being produced by springs
or other mechanical contrivances.
Having thus described the parts of the engine, and their connection
with each other, we shall now describe how it is to be set in motion
and worked.
When the engine is at rest the pressures on the top and bottom of
the piston will be equal, and it will place itself nearly in the middle
of the cylinder, being the position shewn in the Drawing. The slide
b, b, being at the middle of the link A, a, the beams R, U₁, and U
will all be horizontal, the plungers will be in the middle of their
respective receivers, and the heat screens at the bottom.
If the fire be now lighted, the flame circulating in the chamber L₁,
and the corresponding chamber for the other receiver, will heat the
tubes k₁, the rods of the heat screen t₁, and the film of air between
them; also the corresponding parts and film of air belonging to the
other receiver. At first the greater part of the heat will be accumu-
lated in these bodies, a very small portion only reaching the air above
the heat screens. The effect in each receiver being the same, the piston
will still be pressed equally on both sides, and will continue at rest.
Suppose the crank to stand as shewn in the Drawing, and that it is
required to set the engine in motion in the direction indicated by the
arrow. The engine man must loosen the spring catch of the slide b, b,
and by means of the handle D, d, move it to the upper end of the link.
This motion will throw the beam R, into the position shewn in the
Drawing. It will lower the plunger of the receiver K., sending the
air through the passage in that plunger to the top of the receiver, and
into the tubes contained in the tank O., so that such heat as may have
reached it from the flame will be abstracted. At the same time the
plunger P, will be lifted to the top of the receiver K₁, sending the air
out of the tubes ₁, and the upper portion of the body of the receiver
down through the passage P₁. The heat screen S₁, will also be lifted
and dropped, the effect of which will be, that the air in the lower part
of the receiver will be made to circulate rapidly over the surface of the
hot rods t₁, and through the hot tubes k₁, and will receive a certain

page_text: quantity of heat. This heated air expanding will transmit its pressure
and its motion through the passage H₁, to the air in the cylinder A,
and finally to the piston B, and the engine will begin to move.
During the working of the engine the following is the succession of
changes undergone by the air in the receiver K₁:
During the end of the down stroke and beginning of the up stroke of
the piston the heat screen lies at the bottom of the receiver. The plunger
P₁, descends, and the air, with the exception of a trifling quantity,
passes through the passage p₁, and gives out a large portion of its sensible
heat to the wires, strips, or sheets of metal or other conducting bodies
contained in that passage. The remainder of the excess of the heat of
the air above that of the water in the tank O₁, is abstracted by the
surface of the tubes ₁, and rods 1. The up stroke of the piston causes
this air to be compressed; this compression produces heat, which is
also abstracted by these rods and tubes. This heat, were it not so
abstracted, would increase the clasticity of the air, and oppose the
motion of the piston.
During the end of the up stroke and beginning of the down stroke
the plunger P, rises, the air descends through the passage p₁, and
recovers the greater part of the sensible heat formerly lost from the
wires, or metal sheets, or strips, or other conducting substances.
During the first half of the down stroke the heat screen S₁, is raised
and dropped, and the air, by circulating over its rods t₁, and through the
hot tubes k₁, acquires the remainder of the sensible heat necessary to
elevate its temperature, and also the latent heat necessary to expand it.
This completes the cycle of operations in the receiver connected with
the upper end of the cylinder.
In the other receiver like operations take place, substituting only the
up stroke for the down stroke, and vice versa.
The effect of these operations is of a similar nature to that which
takes place in all engines driven by the action of heat on an elastic
substance, viz., that the substance is alternately expanded at a higher
temperature and contracted at a lower, so that the power developed by
the expansion is greater than the power consumed by the contraction,
and a surplus of power remains to drive machinery.
B2

page_text: When the engine begins to work, should the cylinder and receivers
be filled with air or other gas at a pressure not sufficiently great to
perform the required work, the engine must be disconnected from the
machinery it is intended to drive, and the pump rod E, c, being adjusted
by the screw E, h, so that the piston of the pump shall nearly touch
the bottom of the barrel at each stroke; the whole surplus power of the
engine will be employed for some minutes in filling the magazine, the
receivers, and the cylinder with compressed air. When the guages
indicate that the required pressure has been attained, the engine may
be connected with the machinery to be driven, and the pump rod E, e,
shortened by means of the screw II, h, so as to supply enough of air
only to make up for leakage, which condition will be indicated by the
pressure guages.
The motion of the engine is stopped by moving the slide b, b, to the
centre of the link, and reversed by moving it to the opposite end of the
link.
The steadiness of motion may be increased, as in the case of steam
engines, by using two or more engines to drive the same shaft, their
motion being so adjusted as to produce the nearest possible approach
to uniformity of action on the shaft.
We would remark, that it will be evident that many of the details
may be varied without departing from the peculiar character of our
invention as herein described, and it is obvious that the principles and
mode of construction and action described in this Specification as
applied to a double acting engine for driving a revolving shaft may also
be applied to a single acting engine, by causing the air to act upon,
and employing the parts belonging to, one side of the piston only.
Having thus described the nature of our invention, we would have it
understood that we make no claim to any of the mechanical parts
separately. But we claim as the improvements which constitute the
peculiarity of the engine,-
In the first place, the invention and adaptation of what we have
called a heat screen, the form of which may be varied, and the means
of giving motion thereto may be also varied; the said heat screen-being
separate and distinct from the plunger, which drives the air or other gas

page_text: from the hot to the cold end of the receiver, and vice versâ, and being
adapted to the following purposes:
1. To screen the principal portions of the air or other gas from the
communication of heat from the furnace or source of heat at those
times when that heat would impede the motion of the engine, that is to
say, when the air or other gas is being passed towards the cold end of
the receiver to be cooled, when it is not being expanded, and when it is
being compressed.
2. To receive and store up in its own material at such times the
heat communicated from the furnace.
3. To permit and accelerate the communication of heat to the air or
other gas at the time when it is most effective in developing mechanical
power, that is to say, when the air or other gas is being expanded.
In the second place, we claim the adaptation of tubular receivers for
the purpose of heating and cooling the air or other gas in the manner
described in this Specification, that is to say, by the aid of rod-shaped
heat screens or plungers, nearly filling the tubes, and serving, by being
moved out and in, whether by the mechanism shewn in the Drawing or
by any other suitable mechanism, to admit and expel the air or other
gas, and promote its circulation over the heated or cooled surface.
We do not, however, claim the Invention of tubes as a means of
increasing heat-conducting surface, but simply the adaptation of tubes
to engines worked by the action of heat on air or other gas by the aid
of the rod-shaped heat screens or plungers before described.
In witness whereof, we, the said James Robert Napier and
William John Macquorn Rankine, have hereto set
respective hands and seals, this Fifth day of December, One
thousand eight hundred and fifty-three.
JAMES R. NAPIER.
(L.S.)
W. J. MACQUORN RANKINE. (L.S.)