IMPROVEMENTS IN HOT AIR ENGINES
Year: 1868

page_text: LETTERS PATENT to James Dixon Churchill, of Oxford Street, in the
County of Middlesex, for the Invention of "IMPROVEMENTS IN HOT
AIR ENGINES."
Sealed the 8th January 1869, and dated the 10th July 1868.
PROVISIONAL SPECIFICATION left by the said James Dixon Churchill
at the Office of the Commissioners of Patents, with his Petition, on
the 10th July 1868.
I, JAMES DIXON CHURCHILL, of Oxford Street, in the County of
Middlesex, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN HOT AIR ENGINES," to be as follows:-
This Invention relates to various improvements in the construction
and arrangement of the parts of hot air engines, whereby these motive-
power engines may be rendered more effective than heretofore.
The first improvement relates more particularly to the formation of
the bed plate in which the air passage is cast on or attached to its under
side; this passage turns upwards and communicates with a vertical air
passage cast on or attached to the receiver or main casting which
contains the fire-box; these air passages are provided with an arrange-

page_text: ment of dampers, the lower one of which is horizontal in position
and closes against the receiver, and the top one is vertical, and is
provided with a stop so that it cannot be wholly closed.
The next improvement relates to the working cylinder. The hollow
drum attached to the piston is made perfectly air-tight, so that there
can be no influx of heated air into it from the cylinder. I adapt to the
upper part of this drum two pipes, one of which is provided with a bell-
mouth, and the other is bent at right angles so as to admit cold air by
the bell-mouth tube and throw off hot air by the bent tube. By thus
causing a current of air to pass through the drum, the piston drum,
diaphragm, and packings of the piston will be kept cool, and therefore
not so liable to destruction and derangement as heretofore. The packing
of the piston is metallic, and is held in what is called a junk ring, that
is a cast or wrought iron ring turned on its edge, and accurately fitted
to the cylinder, and having a groove turned therein to receive the
metallic packing rings which are of cast iron. The junk ring which
carries the metallic packings is detachable from the piston body to
which it is temporarily secured by bolts to facilitate its removal for the
purpose of renewing, cleaning, or examining the packings without the
necessity of disconnecting the piston links or taking the piston out.
There is also a metallic spring lubricator ring, which is lapped round with
lamp wick or other substance, and is secured to the junk ring by clips.
This lubricating ring is supplied with oil for the purpose of lubricating
the cylinder throughout the whole of the stroke. The ash-pit is lined
with fire-clay, and the fire-place is made in the form of an inverted
truncated cone with a small grate surface at the bottom, and with the
top expanding out to the same or a larger area than the cylinder, so that
the air. (in passing through the fire-place) shall be exposed to a large
area of fire. The fire-place and ash-pit are closed by doors, which are
secured by levers provided with wedges, which enter notches in a fixed
stud, so as to keep the doors close. The fire-place is lined with a thick
lining of fire-clay where the greatest heat comes, and the slab which
forms the top of the fire-place is formed either of fire-clay or cast iron,
or the two materials combined, and has a piece projecting downwards
over the fire and opposite to the inlet or cold air port, so as to deflect
the air and throw as thin a film of cold air as possible down on to the
fire and to prevent its direct passage to the outlet port leading to the
valves. Horizontal circuitous air passages are formed in the fire-clay

page_text: lining and slab of the fire-place immediately under and in contact with
the bottom of the cylinder, so that the air shall pass through a con-
siderable length of an intensely heated air passage, and thus become
thoroughly heated and rarified. By the circuitous nature of the air
passage the flame from the fire will be cut off from the valves, and the
bottom of the cylinder will be kept hot. The air passage will also be
more immediately connected with the valve box, which is attached
immediately on the outside of the receiver, and this connection may be
effected either with or without the intervention of any exterior pipes
or passages. The valve box is provided with two valves, one opening
upwards and the other downwards. The stems of these valves are
jointed to a rocking lever provided with a handle, whereby they may be
worked, and whereby the engine may be stopped by opening both valves,
so that the heated air may pass direct into the outlet without passing
into the working cylinder. The throttle valve for regulating the supply
of air is acted upon and controlled by a governor, the central stem or
spindle of which carries a series of weights whereby the operations of the
governor may be accurately adjusted. This central stem or spindle
passes down through a hollow or sleeve shaft, to which the expanding
balls are connected by two pairs of arms. Another pair of arms connect
the expanding or centrifugal arms to a collar, in which works one end
of a bell-crank lever, whereby the throttle valve is controlled. Motion
is imparted by bevil gear to the sleeve shaft, in which is made a vertical
alot to receive a pin which passes through the inner central spindle, so
that the weights above will always have a tendency to keep down the
collar which is being raised by the centrifugal action of the balls.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said James Dixon Churchill in the Great Seal Patent
Office on the 9th January 1869.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JAMES
DIXON CHURCHILL, of Oxford Street, in the County of Middlesex, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Tenth day of July, in the year
of our Lord. One thousand eight hundred and sixty-eight, in the thirty-

page_text: second year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said James Dixon Churchill, Her special
licence that I, the said James Dixon Churchill, my executors, adminis
trators, and assigns, or such others as I, the said James Dixon Churchill,
my executora, 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 Ohannel Islands, and Isle of Man, an Invention for
"IMPROVEMENTS IN HOT AIR ENGINES," upon the condition (amongst others)
that I, the said James Dixon Churchill, my executors or administrators,
by an instrument in writing under my, or their, or one of their hands and
seals, 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 immediately after the date of the said Letters
Patent.
NOW KNOW YE, that I, the said James Dixon Churchill, do hereby
declare the nature of my said Invention, and in what manner the same
is to be performed, to be particularly described and ascertained in and by
the following statement :-
My Invention relates to and consists in the construction and arrange-
ment of the parts of hot air engines, whereby these motive-power engines
may be rendered more effective than heretofore. The said improvements
are as follows:-
The first improvement relates more particularly to the formation of the
bed plate in which the air passage is cast on or attached to its under side.
This passage turns upwards and communicates with a vertical air passage
cast on or attached to the receiver or main casting which contains the
fire-box. These air passages are provided with an arrangement of
dampers, the lower one of which is horizontal in position and closes
against the receiver, and the top one is vertical and is provided with a
stop so that it cannot be wholly closed. Or, as I generally prefer, a
single valve damper hereafter described with reference to the Drawings
may be used.
The next improvement relates to the working cylinder. The hollow
drum attached to the piston is made perfectly air-tight, so that there can
be no influx of heated air into it from the cylinder; I adapt to the upper

page_text: part of this drum two pipes, one of which is provided with à bell-mouth,
and the other is bent at right angles so as to admit cold air by the bell-
mouth tube and throw off hot air by the bent tube. By thus causing a
current of air to pass through the drum the piston drum, diaphragm, and
packings of the piston will be kept cool, and therefore not so liable to
destruction and derangement as heretofore. The packing of the piston
is metallic, and is held in what is called a junk ring, that is, a cast or
wrought iron ring turned on its edge and accurately fitted to the cylinder,
and having a groove turned thereon to receive the metallic packing rings
which are of cast iron. The junk ring which carries the metallic
packings is detachable from the piston body, to which it is temporarily
secured by bolts to facilitate its removal for the purpose of renewing,
cleaning, or examining the packings without the necessity of discon
necting the piston links or taking the piston out. There is also a
metallic spring lubricator ring which is lapped round with lamp wick
or other substance, and is secured to the junk ring by clips. This
lubricating ring is supplied with oil for the purpose of lubricating the
cylinder throughout the whole of the stroke. The ash-pit is lined with
fire-clay, and the fire-place is made in the form of an inverted truncated
cone with a small grate surface at the bottom and with the top
expanding out to the same or a larger area than the cylinder, so that
the air in passing through the fire-place shall be exposed to a larger area
of fire. The fire-place and ash-pit are closed by doors which are secured
by levers provided with wedges which enter notches in a thick stud so as
to keep the doors close. The fire-place is lined with a thick lining of
fire-clay where the greatest heat comes, and the slab which forms the
top of the fire-place is formed either of fire-clay, or cast iron, or the two
materials combined, and has a piece projecting downwards over the fire
and opposite to the inlet or cold air port, so as to deflect the air and
throw as thin a film of cold air as possible down on to the fire, and to
prevent its direct passage to the outlet port leading to the valves. Hori
zontal circuitous air passages are formed in the fire-clay lining and slab
of the fire-place immediately under and in contact with the bottom of the
cylinder, so that the air shall pass through a considerable length of an
intensely heated air passage and thus become thoroughly heated and
rarified; by the circuitous nature of the air passage the flame from the
fire will be cut off from the valves, and the bottom of the cylinder will
be kept hot. The air passage will also be more immediately connected
with the valve box, which is attached immediately on the outside of the

page_text: receiver; and this connection may be effected either with or without the
intervention of any exterior pipes or passages. The valve box is provided
with two valves, one opening upwards and the other downwards; the
stems of these valves are jointed to a rocking lever provided with a
handle, whereby they may be worked, and whereby the engine may be
stopped by opening both valves, so that the heated air may pass direct
into the outlet without passing into the working cylinder. The throttle
valve for regulating the supply of air is acted upon and controlled by a
governor, the central stem or spindle of which carries a series of weights
whereby the operation of the governor may be accurately adjusted.
This central stem or spindle passes down through a hollow or sleeve
shaft to which the expanding balls are connected by two pairs of arms.
Another pair of arms connects the expanding or centrifugal arms to
a collar, in which works one end of a bell-crank lever whereby the
throttle valve is controlled. Motion is imparted by bevil gear to the
sleeve shaft, in which is made a vertical slot to receive a pin which passes
through the inner central spindle, so that the weights above will always
have a tendency to keep down the collar which is being raised by the
centrifugal action of the halls.

page_text: the dotted line at will open d³ and close d. The valve can be actuated
by an external lever not shewn on the Drawing, or each of the
passages d', d, can be provided with a valve by which the proportions
of the air passing through and over the fire may be adjusted at pleasure.
dis a deflecting plate placed in front of the passage d so as to cause
the air entering by that passage to spread out into a sheet, and thus play
over a greater extent of heated surface and burning fuel, and become
more uniformly diffused among the products of combustion. I prefer
to attach this deflecting plate to a rod passing through a hole in the
casing as shewn. The fire-box e is lined with and covered by fire-brick
or such like refractory material, and is provided with a fire-door e¹ and
ash-pit door e; these doors are opened occasionally for supplying fuel
and removing ash, but during the working of the engine are closed
air-tight. In order to open them quickly and close them rapidly and
tightly I prefer to secure them by a notched lever in the manner shewn
in Fig. 3, which represents an elevation of one of these doors. e³ is the
door; e, e, are collar studs fixed in the casing on either side of the door,
and e' is a lever which may be of any convenient length, having notches
into which the studs e, e, enter when the lever is put in place. The
face of the notch e* is somewhat inclined, so that when the lever having
its notched end entered under the collar of is pressed down
the inclined face of the other notch bearing against the collar of e
causes the lever to bear against the door and thus to price it tightly
against the casing. The air heated and mingled with products of com-
bustion in the fire-box e passes through a tortuous channel f formed in
the refractory material which serves as covering to the fire-box and
reaches the valve box g, which communicates by a passage with the
working cylinder k at or near the centre of its bottom. The valve box g
contains two valves g¹ for admitting the heated fluid to the cylinder,
and g for its discharge after it has acted on the piston therein. Both these
valves are worked by rods passing upwards through tubes and stuffing
boxes to holes in a guide frame in which they are free to slide. Each
valve rod is fitted with a spiral spring, that for g¹ bearing it upwards,
and that for g³ bearing it downwards, and the rods are caused to move
respectively downwards and upwards in opposition to their springs by
means of tappets upon a rocking shaft which is worked by a crank
and rod m from a cam or eccentric on the shaft of the engine, so set as
to time the opening and closing of the valves g', g², respectively to the
strokes of the piston. n is a lever mounted on a pin supported by the

page_text: guide framing of the valve rods, and bearing upwards against a pin on
the one of these rods, and downwards against a pin on the other of these
rods. The lever n is worked by a connecting rod and cross lever n¹
projecting sideways so as to be conveniently within reach of the hand.
When it is desired to stop the engine or to relieve the pressure of the
fluid within the fire-box, this hand lever is borne down and the lever n
then simultaneously opens the two valves g', g, and permits the fluid
to escape by the eduction passage g³. The working cylinder / consists
of a lower portion which may be rough inside set in the upper part of
the fire-box casing and surrounded by non-conducting material k¹. The
upper part of the cylinder is bored smooth inside for the working of
the piston. The piston consists also of two parts, the lower part being
a hollow drum made air-tight in itself and rather smaller than the bore
of the cylinder so as not to bear against its interior in working. is a
pipe with a funnel-shaped mouth, and is a bent pipe both making a com-
munication between the interior of the drum 1, and the outer air for
the purpose of keeping it cool by ventilation in the following manner:-
When the piston makes its upward stroke air enters by the pipe which
presents its funnel mouth to the outer atmosphere and issues by the
bent pipe . Thus at every stroke of the piston there is a certain change
of the air within the drum which is thus prevented from attaining too
high a temperature; the upper part of the piston is made to fit the
cylinder so as to work smoothly therein; it is fitted with metallic packing
kept in place by a junk ring. The upper surface of this junk ring is
made to slope downwards towards the outer periphery, and a ring of
cotton, wool, or other fibrous or spongy material is placed upon this
sloping surface, and kept charged with oil or grease for lubricating the
interior surface of the cylinder; clamps secured to the junk ring
Berve as a guard or fence to keep the lubricating ring in place during the
movements of the piston.
The construction represented in the Drawings and described above
gives facilities for removing the junk ring, metallic packing, and
lubricating apparatus for purposes of cleansing, adjustment, or repair
without the necessity for disconnecting and removing the whole piston
ofrom the cylinder. The piston is guided by a rod passing through a hole
in the upper framing, and is connected by two side rods to the working
beam 6 in the ordinary way.
The mode which I adopt of mounting the beam and the crank shaft,

page_text: and the general form and construction of the casing and framing, are
sufficiently indicated on the Drawings.
Fig, 4 represents a form of governor which I apply to these engines,
and which affords facilities of adjusting the speed. The upright shaft
of the governor o, which may be driven by bevil gearing or otherwise, is
tubular, and a spindle o¹ passes through it, carrying weights wo at the top;
this spindle o' is connected to the sliding collar p by means of a pin or
feather which works freely in a slot formed in the sides of the tube o,
and the sliding collar P works a lever connected with a throttle or other
suitable regulating valve in the ordinary way. When it is desired that the
engine should go faster, more weights w are put upon the spindle so as to
counterbalance the increased centrifugal force of the governor balls due
to increased speed of rotation. Conversely when it is desired to work the
engine more slowly some of the weights wo are removed. Instead of
applying the governor to the opening or closing a valve so as to regulate
the quantity of fluid passing to or from the fire-box or working cylinder,
I sometimes find it convenient to adapt it to a break applied to the
periphery of a fly wheel,
Fig. 5 represents a plan of an arrangement which I adopt. for this
purpose. o is the governor, and q is a forked lever actuated by the
sliding collar p; the lever q is mounted on a pin or fulcrum q', and
supports a shoe or break placed under the rim of the fly wheel which
is turned true and smooth. When the velocity of the engine increases
the lever is raised and bears the shoe r against the rim of the fly wheel,
causing a friction there which reduces the excess of velocity; when the
velocity is so reduced, the lever q sinking down relieves the fly wheel
from the pressure of the shoe. The object I attain by this mode of
applying the governor for regulating speed is that the intensity of the
combustion, and the pressure of the working fluid are kept up as much
while the brake is in action as when the engine is doing useful work,
whereas when the governor regulates the speed by acting on a valve
for the supply of air, the opening or partial opening of such valve reduces
the intensity of the combustion and the working pressure, so that when
work is suddenly thrown on the engine it takes some time to recover its
force, and thus has its speed too much reduced or its movement
altogether arrested by the extra load. When the regulation of speed
is effected by a brake, as above described, such a result cannot occur, for
on work being suddenly thrown on the engine the break is immediately

page_text: relieved, and the intensity of combustion and pressure of working fluid
being in their usual condition the engine is ready to sustain the
load, which indeed in this case merely replaces the friction of the
break.
Having thus described the nature of my Invention, and in what
manner the same is to be performed, I would have it understood that I do
not limit myself to the precise details and proportions represented on
the Drawings, as these, except as constituent parts of my engines, are
not my Invention, and may be varied without departing from the
general principles of form, arrangement, and construction herein-before
described.
In witness whereof, I, the said James Dixon Churchill, have
hereunto set my hand and seal, the Eighth day of January,
in the year of our Lord One thousand eight hundred and
sixty-nine.
JAMES D. CHURCHILL. (L.S.)
Witness,
THOMAS MORGAN,
Clerk to the Inventors' Patent Right Association, Limited,
21, Cockspur Street, Charing Cross,
London.