IMPROVEMENTS IN CALORIC OR HEATED AIR ENGINES
Year: 1865

page_text: LETTERS PATENT to Samuel Blatchford Tucker, of Threadneedle Street,
in the City of London, Merchant, for the Invention of "IMPROVEMENTS IN
CALORIC OR HEATED AIR ENGINES."-A communication from abroad by
Cyrus W. Baldwin and Walter Davis Richards, both of Boston, in the
United States of America.
Sealed the 1st December 1865, and dated the 8th June 1865.
PROVISIONAL SPECIFICATION left by the said Samuel Blatchford Tucker
at the Office of the Commissioners of Patents, with his Petition, on
the 8th June 1865.
I, SAMUEL BLATCHFORD TUCKER, of Threadneedle Street, in the City of
London, Merchant, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN CALORIC OR HEATED AIR ENGINES," communicated to me
abroad by Cyrus W. Baldwin and Walter Davis Richards, both of Boston, in
from the United States of America, to be as follows:
These improvements relate to caloric or hot air engines, and have for object
to render their operation certain and powerful, reduce cost and liability to rapid
deterioration, and afford facility for replacement of parts which wear or burn
ont

page_text: According to these improvements the furnace is isolated from the rest of
the engine, so that the cylinder and parts therein, and the valves may be less
liable to injury from heat from the furnace. The air pump has its axis in a
vertical plane, passing through the centre of the main shaft, so that it can be
used to support the bearings and worked directly from the main crank. A disc
valve is employed, guided at its periphery in connection with the casing and
valve passages. The exhaust valve seat is detachable from the valve chest, so
that the seat can be removed for inspection, repairs, or change without
removing the valve chest, cover, or other part appertaining to the valve chest.
The exhaust valve seat is on the end of a flanged tube or thimble, inserted in.
and jointed to the valve case from without. A secondary fire-box is introduced
into the passage between the main fire-box and the valve chamber, so that the
unconsumed gases escaping from the primary fire-box may be burned by
coming in contact with a flame produced in the secondary fire-box by gas jets,
oil, petroleum, or other combustible matter. Between the upper and lower
parts of the engine cylinder is a water passage, provided with circulation pipes,
so that cool water flows through one pipe into the passage, and as fast as
heated escapes therefrom by the other pipe, thus intercepting and carrying off
much of the heat which would have been communicated from the lower to
the upper part of the cylinder and have injured the piston packing. The
furnace lining may be made in separate rings and segments. The lining and
the air passage, through which air is supplied to the fuel above the grate, are
removeable, and such passage can be interchanged with the lining rings and
pass air into the fuel at a bigher or lower point, or entirely above it; the air
passage may be next above the grate and below all the lining rings, or between
any. The engine cylinder is as usual divided into an upper and a lower part;
between these parts is a water passage, which may extend entirely around the
cylinder as a ring between the two parts, and have in its middle or connecting
piece holes for free circulation of water, cold water being fed through one
pipe and the heated water removed through another pipe. To prevent loss
of heat from the lower part of the cylinder it is surrounded with a casing, the
space between which and the cylinder, and between the cylinder and bed
plate is filled with fire brick or other non-conductor; the furnace being
isolated from the cylinder and valve chest, the bed plate being the only
means of conducting heat between the cylinder and furnace, and a pipe the
only means of communicating between the furnace and valve chamber. To
allow of expansion and contraction, the pipe is of great length, with crooks or
curves and of thin metal. In the pipe between the furnace and valve chest
is an auxiliary furnace or chamber, which may be supplied with means of

page_text: consuming gas or other combustible to form a flame to come in contact with
and burn the gases resulting from the fuel in the large furnace, which do not
burn when generated. In order that the exhaust valve may fit its seat truly,
provision is made for examining the joint and repairing deterioration; by
forming the seat on the end of a tube or thimble, provided with a flange which
when inserted into the valve chest makes the joint therewith, and the exhaust
pipe is connected with that end of the tube or thimble outside the valve chest,
so that it can be readily removed and refaced.
The air-pump valves are flexible discs, which have no binges and are not
guided by central rods; the eduction valve rests freely on a flat seat and is
prevented by a grating from being forced through the aperture; the valve is
guided at the periphery by pins or rods standing up vertically around the seat
in contact or nearly so with the edge of the valve, which in its rise and fall is
kept in proper place. These guides may be wings or ridges extending from
the cap inward towards the valve, such cap being excentric over and with
respect to the valve which gives room for the crescent-shaped eduction pipe
beyond the valve and between it and the inner boundary of the cap or
chamber.
According to this Invention also two or more fire-boxes are provided for
each cylinder, the aggregate capacity of such fire-boxes being equal to the
required supply of heated air; thus the air for a single cylinder is heated in
two or more furnaces separate from each other as to the means for supply of
fuel and air, but discharging their gaseous products of combustion into a
common valve chamber. The delivery pipe affords free communication
between the furnaces, so as to equalize pressure, and it may be fitted with
valves so that any one furnace can be shut off from the others. To cut off
from the engine supply valve the blaze or flame from the fuel and to intercept
ashes and other solids from being conveyed to the valves and cylinder, a tortuous
passage is used, which carries off the volatile products of combustion and the
heated air. Above the furnace lining and resting thereon in the outer casing
is a hollow head, in which is a passage, through which the current from the
furnace passes into a pipe. A coiled pipe, protected by a plate or diaphragm,
may be used instead of the head; or the air, both that which is, or is to be
beated and expanded, and that which supports combustion, may be introduced
into the fire-box or furnace wholely above the fuel, but not through it, so that
upward blast through it is avoided. The air supply passages may debouch
into openings in the vertical furnace walls, through which fuel may be introduced
also through another opening, which openings, as also that through which the
ashes are removed, are closed to the atmosphere when the engine is at work.
:

page_text: The top of the furnace is provided with a hollow cap or cavity supplied with
water, so that heat escaping from the furnace top is 'utilized by its 'vaporizing
the water.
To prevent the evils of oxydation and wear of valves and valve iseats
by 'excessive heating they and the pipe leading to them are encased from the
furnaces, and cold air is forced or pumped into the space surrounding the
valve chest and supply pipe, such air as it travels to and into the furnaces
surrounds the valve chest and supply pipe and absorbs heat radiated there-
from, which passes with the air into the furnace. To supply the impelling
medium so that it shall act squarely and centrally, or directly and vertically
on the piston, the entrance port is placed directly under the centre of the
piston. Air engine cylinders are usually made in two parts, an upper and a
lower. Hitherto the lower part has been formed of iron, encompassed by an
iron casing, the space between the 'two parts being filled with air or with solid
non-conductors. According to these improvements the inner iron cylinder is
dispensed with, and the space between the casing' and the piston, when at its
lowest stroke, is filled with a solid non-conductor, or the lower part of the
cylinder has no metallic inner boundary, the fire-brick or other non-conductor
being supported by a metallic casing. The lower boundary may be of masonry
resting on the bed plate.
Improved packing is formed of a plain strip or belt of leather of 'width
sufficient to lap over the top of the piston, and to be secured thereupon under
and by the follower, and make a right angled turn and encompass the working
face of the piston like cup-leather packing. The strip is moistened and
crimped or bent to a flat ring, and secured to the piston by the follower, and
the projecting edge of the leather ring is then bent downward by forcing upon
the piston from above and over the leather a ring or band, which remains
until the leather dries, when it will retain the form imparted to it. Instead
of using the piston and follower to prepare the packing, a block and ring may
be used.
'SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Samuel Blatchford Tucker in the 'Great Seal Patent Office
on the 8th December 1865.
TO ALL TO WHOM THESE PRESENTS SHALL 'COME, I, SAMUEL
'BLATCHFORD TUCKER, of Threadneedle Street, in the City of London, Mer-
chant, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters

page_text: Patent, bearing date the Eighth day of June, in the year of our Lord
One thousand eight hundred and sixty-five, in the twenty-eighth year
of Her reign, did, for Herself, Her heirs and successors, give and grant unto
me, the said Samuel Blatchford Tucker, Her special licence that I, the said
Samuel Blatchford Tucker, my executors, administrators, and assigns, or such
others as I, the said Samuel Blatchford Tucker, my 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 CALORIC OR HEATED AIR ENGINES," com-
municated to me from abroad by Cyrus W. Baldwin and Walter Davis
Richards, both of Boston, in the United States of America, upon the condition
(amongst others) that I, the said Samuel Blatchford Tucker, 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 Samuel Blatchford Tucker, do
hereby declare the nature of the said Invention, and in what manner the
same is to be performed, to be particularly described and ascertained in and
by the following statement thereof, reference being had to the accompanying
Drawings, that is to say :-
These improvements relate to caloric or hot air engines, and have for
object to render their operation more certain and powerful, to reduce cost and
liability to rapid deterioration, and to afford facility for replacement of parts
which wear or burn out.
According to the first improvement the furnace is isolated from the rest of
the engine, so that the cylinder and parts therein and the valves may be less
liable to injury from heat conducted from the furnace.
The next improvement consists in arranging the air pump so that it shall
have its axis in a vertical plane passing through the centre of the main shaft,
so that such axis can be utilized as a support for the shaft bearings, and be
worked directly from the main crank.
The third improvement consists in arranging a dise valve, so as to be guided
at its periphery in connection with the casing, and valve passages or passages
making the valvular system.
The fourth improvement consists of the detached arrangement of the ex-.

page_text: haust valve seat from the valve chest, that is to say, the exhaust valve seat
is detachable from the valve chest, so that the seat can be removed for in-
spection, repairs, or change, without removing the valve chest, cover, or other
part appertaining to the valve chest. I herein-after describe an exhaust
valve seat on the end of a flanged tube or thimble, inserted in and joined to
the valve case from without..
The next improvement consists in introducing a secondary fire-box into the
passage between the main fire-box and the valve chamber, so that the un--
consumed gases escaping from the primary fire-box may be burned by coming
in contact with a flame produced in the secondary fire-box by gas jets, oil,
petroleum, or other combustible matter.
The next improvement consists in introducing a water passage between the
upper and lower parts of the engine cylinder, such water passage being pro-
vided with circulation pipes, so that cool water flows through one of the pipes
into the passage, and as fast as heated it escapes therefrom by the other pipe,
thus intercepting and carrying off much of the beat which would otherwise
have been communicated from the lower to the upper part of the cylinder,
and would have injured the piston packing.
In the next improvement the air passage, through which air is supplied
above the grate to the fuel, is so arranged that the air passage can be inter-
changed with the rings of the furnace lining and thus pass air into the fuel at
a higher or lower point or entirely above it. The air passage may be next
above the grate and below all the lining rings or between any.
The foregoing constitute the first series of improvements in the present
Invention, Sheets 1, 2, and 3, the Figures on which are herein-after described,
illustrate the foregoing parts of the Invention, and shew an engine embodying.
and constructed according to these improvements in order that the mode of
carrying the same into practical effect may be well understood.
Figure 1 represents a side elevation of an engine embodying these
improvements; Figure 2 is a vertical longitudinal section of the same on the
line x, a, seen on Sheets 3 and 4. Figure 3 is a vertical cross section of the
same through the axes of the cylinder and of the induction valve stem; and
Figure 4 is an end elevation of the same at the air pump end of the engine.
Figure 5 is a reversed plan of the engine bed plate; and Figure 6 a hori-
zontal section through the bed plate in its reversed position. Figure 7 is a
plan of the bed plate without the air pump, engine, cylinder, and furnace,
illustrating the valvular system and the passages appertaining to the air pump.
Figure 8, vertical section on the line a, b, of Figure 7. Figure 9, vertical
section through the engine valves and valve cliest on the line y, y, Figure 4.

page_text: As the general arrangements and method of operation of hot air engines
are well known, the following description will be confined as nearly as possible
to the exemplification of this Invention.
c is the outer casing of the furnace; d is the lining thereof, made in separate
rings and segments; e, passage by which air is supplied to the fuel above the
grates. The passage e and the lining d are removeable, and the passage e
may be placed next above the grate and below all of the lining rings d, or
between any of the lining rings d, as desired. The engine cylinder, as is
usual, is divided into two parts, an upper and a lower one, the upper part of
the piston being packed in the upper part of the cylinder as usual, and the
lower part of the piston works loosely in the lower part of the cylinder as
usual. Between these two parts of the cylinder is a water passage f, which is
in section of H form, and extends entirely around the cylinder, as a ring
between the two parts. In the middle or connecting piece of this passage f
are holes, Figures 2 and 3, which permit free circulation of water therein
supplied to f in a cold state by one of the pipes g, and taken therefrom when
heated by the other pipe 9; these pipes are arranged as usual in heated
water circulation systems. Thus the heat, which would without intervention
of the water passage f be conducted from the lower to the upper part of the
engine cylinder, is intercepted and carried off by the water passing through the
passage f, and the heat which the upper part of the cylinder receives from
direct contact with the hot products of combustion from the furnace is kept
down by radiation so as to prevent the burning of the piston packing. To
prevent loss of heat from the lower part of the cylinder it is surrounded with
a casing h; the space between this casing and the cylinder, and between the
cylinder and the bed plate, is filled or partially filled with fire-brick or other
non-conductor. Hitherto hot air engines have had their furnace directly in
the lower part of the cylinder; or beneath it or encased with it, in such
manner that by the unequal expansion and conducted heat the deterioration
of the engines has been rapid, owing to the burning out of the working parts,
and the breakage and leakage consequent upon unequal expansion. To
remedy this the furnace is isolated from the cylinder and the engine valve
chest, the bed plate being the only means of conducting heat between the
cylinder and furnace, and the pipe i is the only means of communication
between the furnace and the valve chamber j. As heat tends upward, and
the space in the furnace below the grates is supplied with cold air from the
air pump, no heat will be communicated to the cylinder from the furnace by
the connection of the bed plate. To allow of expansion and contraction this

page_text: pipe i is made of considerable length with crooks or curves therein, and of
thin metal, so that it conducts very little beat; though it conveys the heated
volatile products of combustion. In the pipé i; between the furnace and the
valve chest, is an auxiliary furnace or chamber k, which may be supplied
with means for consuming therein with a flame gas oil, petroleum, or other
similar combustible substance. Part of the fuel in the large furnace is changed
by the heat into volatile gases, which do not burn when generated, but which
will burn if while hot they are brought directly into contact with flame. To
supply such a flame, through which all the volatile products of combustion
from the large furnace must pass, the small furnace k is supplied as stated,
and it is found in practice that its application is attended with very beneficial
results. In hot air engines it is of special importance that the exhaust valve
should fit its seat perfectly, for if at the time when the induction valve is open
the eduction valve leaks, there is nothing to prevent the gaseous contents of
the cylinder and furnace from escaping past the leak. Hence it is important
that provision should be made for examining the condition of the joint made
by the exhaust valve with its seat, and for repairing deterioration therein as
soon as it becomes sensible. In Figure 9 the exhaust valve 7 is seen as closed
upon its seat, which is formed on the end of a tube or thimble m, provided
with a flange, so that when the tube or thimble m is inserted into the valve
chest j, the flange on m will make a joint with the valve chest, and the
exhaust pipe can be connected with that end of mi which is outside the valve
chest. This piece in can be readily removed from the valve chest and faced
anew in the lathe readily where the valvė rests upon it, so that this valve seat
may be easily kept in working order. The air pump is so arranged that a
vertical plane passing through its axis shall intersect the axis of the main
shaft, so that the pump affords a suitable stand to support the main shaft
boxes n, and simplifies the construction of the engine. The air pump valves,
which are of the flexible disc variety, are peculiar in this, that they have no
hinges and are not guided by a central rod. By reference to Figure 8,
Sheet 4, it will be seen that the eduction valve o rests freely on a flat seat,
and is prevented by a grating from being forced through the aperture which
it closes. The valve is guided at its periphery by pins or rods standing up
vertically around the valve seat, and in contact or nearly so with the edge of
the valve, which in its rising and falling is kept in place. These guides may be
formed as wings or ridges; extending from the cap p inward towards the valve.
This cap is arranged excentrically over and with respect to the valve, which
gives room for the crescent-slinped eduction pipe, Figures 6 and 7, which is

page_text: formed beyond the valve and between it and the inner boundary of the cap or
chamber. The arrows indicate the direction of the currents in the operation
of the engine.
I now proceed to describe a second series of improvements, which are
illustrated by the Figures on Sheets 4 and 5, herein-after described.
According to the first of these improvements two or more fire-boxes are pro-
vided for each cylinder, their aggregate capacity being equal to the required
supply of heated air; thus the air for a single cylinder is heated in two or
more furnaces, separate from each other as to the means for the supply of
fuel and air, but discharging their gaseous products of combustion into a
common valve chamber. The delivery pipe affords free communication
between the furnaces so as to equalize the pressure, and it may be so fitted
with valves that any one furnace can be shut off from the others.
In my next improvement the blaze or flame from the fuel is cut off from
the engine supply valve, and ashes and other solids are intercepted and pré-
vented froni being conveyed to the valves and cylinder by means of a tortuous
passage, which carries off the volatile products of combustion and the heated
air. Above the furnace lining and resting thereon in the outer casing is a
hollow head, in which is a passage, through which the current from the
furnace passes into a discharge pipe, a coiled pipe protected by a plate or
diaphragm may be used instead of the head.
In my next improvement all the air, both that which is or is to be heated
and expanded and that which supports combustion, is introduced into the fire-
box or furnace wholely above the fuel but not through it, so that upward blast
through it is avoided. The air supply passages debouch into openings in the
vertical furnace walls, through which fuel may be introduced; also through
another opening, which opening, as also that through which the ashes are
removed, are closed to the atmosphere when the engine is at work.
In the next improvement the top of the furnace is provided with a hollow
cap or cavity supplied with water, so that heat escaping from the furnace top
is utilized by its vaporizing the water.
In my next improvement, which is to prevent the evils of oxydation and
wear of valves and valve seats by excessive heating, they and the pipe leading
to them are encased from the furnaces, and cold air is forced or pumped into
the space surrounding the valve chest and supply pipe; such air as it travels
to and into the furnaces surrounds the valve chest and supply pipe, and absorbs
heat radiated therefrom, which passes with the air into the furnace.
In my next improvement I supply the air or impelling medium so that it
shall act squarely and centrally, or directly and vertically on the piston, the

page_text: entrance port is placed directly under the centre of the piston. Air engine
cylinders are usually made in two parts, an upper and a lower. Hitherto
the lower part has been formed of iron encompassed by an iron casing, the
space between the two parts being filled with air or with solid non-conductors.
Now, according to my next improvement: the inner iron cylinder is dispensed
with, and the space between. the casing and the piston when at its lowest
stroke is filled with a solid non-conductor; thus the lower part of the.cylinder
has no metallic inner boundary, the fire-brick or other non-conductor being
supported by a metallic casing. The lower boundary may be of masonry
resting on the bed plate.
The last improvement consists of improved packing formed of a plain strip
or belt of leather of width sufficient to lap over the top of the piston, and to
be secured thereupon under and by the follower, and to make a right angle
turn.and encompass the working face. of the piston like cup leather packing.
The strip is moistened and crimped or bent to a flat ring, and secured to the
piston by the follower, and the projecting edge of the leather ring is then bent
downward. by forcing upon the piston from above and over the leather a ring
or band, which remains until the leather dries, when it will retain the form
imparted. to it. Instead of using the, piston and follower to prepare the
packing a block and ring may be used..
This series of improvements are exemplified by the following Figures on
Sheets 4 and 5, which represent in what manner [the same may be carried
into practical effect, so that the same may be well understood.
Figure 10 is a side elevation of the main parts of an engine constructed
-according to these improvements; Figure 11 is a vertical sectional view on
the line a, b; Figure 12 showing the piston packing exhaust valve, and
passage, air pump, and delivery passages, etc.; Figure 12 is a plan, and a
partial horizontal section on the line c, c (Figures 10, 11, and 13), showing
the system of air passages; Figure 13, vertical section on the line a, d,
(Figure 12), showing in connection with Figure 14 the construction of the
top of fire-box; Figure 14 is a horizontal section on the line e, f, Figure 13;
Figure 15 is a perspective view showing the leather piston packing.
:
Experience has shown that for heating large quantities of air, such as are
required for the supply of hot air engines, the purpose is better accomplished
in small furnaces than in one large one of the same cubic capacity with two
or more small ones. The reason for this is that air being a poor conductor of
heat prevents the heating of a large body uniformly throughout, while in a
number of smaller furnaces all portions of the air therein would be nearer the
fuel or the heated furnace boundary than some of them would be if the body of

page_text: air was not subdivided, and consequently the air will thus be more uniformly
heated throughout. Now one of my improvements consists in providing each
cylinder with a hot air engine with two or more fire-boxes, the aggregate
capacity of which is equal to the supply of heated air for the requirements.
thereof; g, g, is a non-conducting lining of the furnaces, two being shown.
These furnaces deliver their heated air into a pipe h, which is common to both:
furnaces and supplies one engine cylinder. This pipe affords means for free
communication between both furnaces, and the pressure in one will be obtained.
in the other. In the pipe may be stop valves, so arranged that one furnace
could be shut off from the other or others while replenishing the fuel in the
furnace thus detached, or while it undergoes repairs, the engine in the mean-
time being supplied from the furnace or furnaces not shut off. To cut off the
blaze proceeding from the fuel from the engine supply valve, and to intercept
ashes and other solid matters, so as to prevent them from being carried to the
valves and cylinder, a tortuous passage for the volatile products of combustion.
and the heated air is made, and in this consists another part of the Invention..
Above the furnace lining g, and resting thereupon in the outer casing i, is a
hollow bead (Figures 13 and 14), in which is a passage into: which the
current from the furnace enters through the opening k, and moving through
the passage in the head j in the direction shown by the arrows (Figure 14),.
discharges through the opening. into pipe h. A coiled iron pipe protected by
a plate or diaphragm from the direct action of the heat might be employed in:
lieu of the head j. Further, to keep ashes and solid matter from being carried
into the cylinder and the valve seats, all of the air, both that which is heated
and expanded merely and that which supports combustion, is introduced wholly
above the fuel, so that the upward blast of air through the fuel, which carries,
solids with it into the supply passages of the cylinder is avoided, and at the same.
time no difficulty is found in maintaining combustion. In this introduction of all
of the air which leaves the fire-box above the fuel consists a part of this Inven-.
tion, to practice which it matters little how the air is introduced, provided it.
does not pass amongst the fuel in entering the furnace. In Figure 12. the
air supply passages for the furnace, marked m, debouch into the openings n in.
the vertical walls of the furnaces, through which fuel may be introduced to
rest upon the grate o.. Beside this opening n into the furnace there is another
shewn at p, through which fuel. can be supplied, but these openings; as also
that seen at 9 through which the ashes are removed, are closed to the atmo-,
sphere when the engine is at work. To utilize the heat radiating from the
top of the furnace it is provided with a hollow cap r, kept supplied with water,
so that the escaping heat shall be utilized by vaporizing the water, which

page_text: may be employed as is needed, by introduction into the furnace to aid and
support combustion or otherwise, as deemed desirable. In this construction
of the top of a furnace of a hot air engine to contain water consists another
part of the Invention.
To avoid the evils of overheating and wear of valves and valve seats, they,
and the pipe leading thereunto are, according to these improvements, encased
from the furnaces admitting into the space surrounding the valve chest and
supply pipe cold air supplied by a force pump, so that the air as it moves
toward and into the furnaces shall surround the valve chest and supply pipe
and absorb the heat radiated therefrom, thus keeping down the temperature,
the heat so abstracted not being lost as it passes with the air into the furnace;
a is the passage from the force pump to the casing about the valve chest
(Figures 11 and 12); t is the valve chest; u is the casing surrounding it. It
is in thus encasing the valve chest, and causing the air from the force pump
to surround the chest on its passage to the furnace, that another portion of the
Invention consists.
The pistons of hot air engines are guided less perfectly than those of steam
engines, on account of yielding packings of leather instead of metallic
packings being used; thus they are more apt to be deflected and wear
sidewise from slight causes than are metal packed pistons. Heretofore it has
been considered sufficient to introduce the impelling medium anywhere into
the cylinder below the bottom of the engine piston, and hence the port has
been made to open into the cylinder on the side nearest the source of supply.
Now, according to this Invention the impelling medium is so supplied that it
will act squarely and centrally upon the piston, and this part of the Invention
consists in placing the entrance port for this purpose directly under the centre
of the piston v. Figures 11 and 13 is the entrance port. By this improve-
ment a material improvement is found in the working of the engine, and a
saving in the wear of the piston packing is effected. Hitherto cylinders of
hot air engines are made in two parts, an upper one, which is bored smooth
for a packed piston to work in, and a lower one, which is left larger in
diameter and into which the extension part of the piston descends without
touching. The lower part or cylinder of hot air engines has 'been hitherto
formed of iron and encompassed by an iron casing, the space between the two
iron parts bas been in some cases left vacant, or filled with air as a non-
conductor of heat, and in other instances with solid non-conductors, such as
fire-brick. Now this part of the Invention consists in dispensing, with the
inner iron cylinder, and in filling the space between the casing and the piston
when at its lowest stroke with soapstone, fire-brick, or other solid non-

page_text: conductor, care being taken that the interior diameter of the lower part of the
cylinder is such as to give a clearance to that part of the piston which enters
therein, w is the outer casing of the lower part of the cylinder, and the
filling which makes the lower cylinder. The lower boundary of the cylinder
may be advantageously made, including the port v of masonry resting on the
iron bed plate, tlius rendering the use of iron plates and a cellular structure
unnecessary.
Leather piston packings of hot air engines' require to be renewed frequently,
and as the pistons are of considerable size for the power obtained, as comi-
pared with steam engine pistons, such leather packings have hitherto been cut
out of large discs, involving waste and cost. Now to obtain less costly.leather
packings is a desideratum, and the mode in which this is effected constitutes
another part of the Invention. Improved leather packings are formed
according to this Invention of a plain strip of leather like a piece of
belting, and of width sufficient to lap over the top of the piston andito .be
secured thereupon under and by the follower (Figure 11), and a right angle
turn is made to encompass the working face of the piston like a common cup
leather packing. This strip, which in the plain form is shewn in Figure 17,
is moistened and crimped or bent to a flat ring of the right diameter, care
being taken to make the ends meet with a good joint. In this condition it is
secured to the piston by the follower, and the projecting edge of the leather
ring is then bent downwards, by forcing upon the piston from aboveland over
the leather a ring or band, which is allowed to remain until the 'leather dries,
when it will retain its form. Instead of using the piston and follower to
prepare the packing, a block and ring of the diameter of the piston and
follower may be used.
Having now described the nature of the said Invention, and in what manner
the same may be performed, I declare that I claim,-.
First, the isolated arrangement of the furnace, with respect to the cylinder
and valve chest.
Second, the arrangement and employment of the air pump, substantially as
set forth.
Third, guiding a flexible disc valve, substantially as described.
Fourth, the construction of the exhaust valve seat on the end of a flanged
tube or a thimble inserted in and joined-to the valve case from without, sub-
stantially as described.
Fifth, the employment substantially as and for the purpose specified of a
secondary furnace.
Sixth, the introduction between the upper and lower parts of the cylinder

page_text: of a water passage, provided with means for circulation of water, arranged and
operating substantially as specified.
Seventh, arranging the air passage so that it can be interchanged with the
rings of the furnace lining, and thus pass air into the furnace at a higher or
lower point, substantially as described.
Eighth, heating the air for the supply of a single cylinder in two or more
furnaces separate from each other, as to the means for the supply thereunto
of fuel and air, but arranged to discharge their gaseous products of combustion
into a common valve chamber, substantially as and for the purpose specified.
Ninth, the employment at the top of the fire-box (of a hot air engine) of a
tortuous passage for conducting the gaseous products of combustion to the
cylinder, so as to cut off therefrom and from the valve chamber actual flame,
and to cause deposit of solid matter, substantially as described.
Tenth, supplying the air for the support of combustion, and to be heated to
fill the cylinder by passing the whole of it into the fire-box above the fuel,
instead of passing the whole or a portion thereof through the fuel.
Eleventh, constructing the top of a hot air engine fire-box with a cavity
suited for being supplied with water, so that the escaping heat shall be utilized
by the vaporization of the water, substantially as described.
.
Twelfth, cooling the valve chest, by encasing it and passing the cold air
from the force pump on its way to the cylinder into the said casing and
around the chest, substantially as set forth.
Thirteenth, making the entrance port into the cylinder so as to discharge
the impelling medium therein directly under the centre of the piston,
and in a vertical direction, substantially as set forth..
Fourteenth, constructing the lower part of the cylinder without any metallic
inner boundary, but.of fire-brick or other non-conductor supported by a metallic
casing, substantially as described.
Fifteenth, the construction of the improved leather packing, substantially
as described.
In witness whereof, I, the said Samuel Blatchford Tucker, have hereunto
set my hand and seal, this Twenty-ninth day of November, in the year
of our Lord One thousand eight hundred and sixty-five.
Witness,
M. HENBY, 68, Fleet Street, London.
S. B. TUCKER. (LS.)