IMPROVEMENTS IN APPARATUS FOR GENERATING STEAM, AND FOR APPLYING THE SAME TO MOTIVE POWER PURPOSES
Year: 1855

page_text: LETTERS PATENT to Mathieu François Isoard, of Paris, in the Empire of
France, Engineer, of the firm of Isoard and Company, for the Invention
of "IMPROVEMENTS IN APPARATUS FOR GENERATING STEAM, AND FOR APPLYING
THE SAME TO MOTIVE POWER PURPOSES."
Sealed the 26th November 1855, and dated the 19th July 1855.
PROVISIONAL SPECIFICATION left by the said Mathieu François Isoard
at the Office of the Commissioners of Patents, with his Petition, on the
19th July 1855.
I, MATHIEU FRANÇOIS ISOARD, of Paris, in the Empire of France, Engineer,
of the firm of Isoard and Company, do hereby declare the nature of the said
Invention for "IMPROVEMENTS IN APPARATUS FOR GENERATING STEAM, AND FOR
APPLYING THE SAME TO MOTIVE POWER PURPOSES," to be as follows:-
My improved generator consists of conical coils of pipe set upright one
within the other, a space being left between them for the circulation of the
heated gases from the fire-place. A dome of fire brick surrounds the outer
cone, and deflects the ascending flame, and causes it to traverse between the
outer and inner cone, and it eventually makes its escape into the chimney
after passing between the outer cone and the casing which encloses it.

page_text: Two conical tubes are usually found sufficient, but in large engines a third
may be employed. The water is fed into the lower part of these tubes, and
the steam escapes from the upper part into the steam chest.
As a modification of this arrangement, I propose to form the cones of a
serpentine arrangement of pipes, and at the apex of each turn to provide
apertures, which I close by screw plugs; these being easily removeable will
facilitate the cleaning out of the pipes.
The water I supply to my improved generators in pulsations by an ordinary
feed pump, in such manner that the several tubes composing the generator
shall successively receive a small and equal supply. For this purpose the
tubes are brought successively and momentarily into communication with the
water reservoir by means of a rotating supply cock, provided with a single
aperture or water way. This cock is operated by the pressure of the water
on the under side of a valve, which at every stroke is caused to rise, and is
again forced down to its seat by means of a counteracting spring.
In order to diminish the friction of the working parts of steam engines, I
construct the pistons in such a manner as to allow of their playing freely in
their cylinder. This I effect by making their diameter somewhat less than
the internal diameter of the cylinder. I also construct the piston and valve
rods in the same manner, as regards their stuffing boxes; by this means a
thin stratum of steam will be allowed to introduce itself between the moving
parts, and thus diminish the friction of the parts. I adapt the same principle
to the steam or slide valve, steam being allowed to enter between the moving
and stationary parts. For this purpose, I make this valve of a hollow
cylindrical form, by which means it is allowed to work freely in the cylindrical
steam chest; it is provided at each extremity with a flange, which as it
reciprocates alternately opens the induction steam passages, the steam escaping
by a third passage, corresponding to the interval between the two flanges.
As a packing for the stuffing boxes, I employ a helical spring formed of flat
or square wire.
In order to regulate the working of the steam supply valve, I connect this
valve with a ball or other governor in the following manner:-To the sliding
tube of the governor I attach a saddle piece, which is capable of slipping
round the tube; this saddle piece carries a fulcrum pin, on which a double
armed rocking lever is mounted. Both arms of this lever are slotted. In
the slot of the lower arm plays a pin that projects from a slide rod, which is
kept in motion by the throw of a crank on the fly wheel shaft, and into the
slot of the upper arm a pin on the slide valve rod projects. The rise and fall

page_text: therefore of the sliding tube will raise or depress the slotted lever, and thereby
increase or diminish the arc of its vibrations, according to the speed the
engine has attained.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Mathieu François Isoard in the Great Seal Patent Office on
the 19th January 1856.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, MATHIEU
FRANÇOIS ISOARD, of Paris, in the Empire of France, Engineer, of the firm
of Isoard and Company, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Nineteenth day of July, in the year of our Lord One
thousand eight hundred and fifty-five, in the nineteenth year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the
said Mathieu François Isoard. Her special licence that I, the said Mathieu
François Isoard, my executors, administrators, and assigns, or such others as
I, the said Mathieu François Isoard, 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 "Iм-
PROVEMENTS IN APPARATUS FOR GENERATING STEAM, AND FOR APPLYING THE SAME
TO MOTIVE POWER PURPOSES," upon the condition (amongst others) that I, the
said Mathieu François Isoard, by an instrument in writing under my band
and seal, 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 Mathieu François Isoard, 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, reference being had to the Drawings hereunto annexed, and to the
letters and figures marked thereon (that is to say) :-
--
The object of my Invention is to obtain the following advantages, viz*,
diminution in the space, weight, and size of steam engines, and multiplication
of their power, without danger of breakage of the parts intended to produce

page_text: On the Twenty-eighth August, One thousand eight hundred and forty-five, I
obtained a Patent for the instantaneous production of steam and the utilization
of the same. For this purpose I caused water to pass through a helical coil
of pipe, which was raised to a high temperature, the water being converted
into steam by coming into contact with the sides of the tube, which was
always maintained at the same degree of heat, this being regulated by the
movement of the generating apparatus, which was caused to turn together
with its furnace, by reason of the reaction produced by the free escape of the
steam.
In this my first system I discovered that the most important point was the
instantaneous production of the steam. The advantages of this mode of
generation are incontestable; they are as follows: first, economy in the cost
of construction; second, economy of space; third, economy of fuel, especially
as the steam may be raised to a pressure of forty atmospheres; fourth, perfect
freedom from any danger of explosion, the acknowledged cause of explosion
being rendered available for the production of a useful result, under conditions
well considered and established.
Having obtained this steam under these conditions, and which will be
presently described, I wished to render my receiver as simple as my generator.
It being indicated by theory that action is equal to reaction, it became
important to demonstrate this principle by reducing it to practice. The
engine which I patented in One thousand eight hundred and forty-five did
not produce a satisfactory result, inasmuch as not more than one quarter of
the-power-which the steam was capable of yielding was obtained. I therefore
decided upon causing the steam to act by expansion upon a piston working in
a cylinder in the ordinary way.
As I obtained a constant and regular supply of steam at a pressure of from
twenty-five to forty atmospheres, and that from this principally resulted the
economy of fuel effected by my improved system, I was obliged to employ

page_text: the steam at this high degree of pressure, and this I did successfully in several
engines of fifteen horse power.
In one of my improved generators, which I will now describe, I also suc-
ceeded in utilizing nearly the whole of the calorific power of the fuel, the
heating surface of my generator being increased by causing the flame and
products of combustion to traverse a greater space before passing into the
chimney, loss of caloric by radiation being prevented by surrounding the gene-
rator and furnace with an air jacket.
In Sheet I. of the accompanying Drawings, Fig. 1 represents this improved
generator in vertical section. It consists mainly of two conical coils of pipes
A, A, and B, B; the lower extremities F, F, and F, F, of the coils A and B,
which project outside the casing of the generator, receive the water to be con-
verted into steam. The steam makes its exit at the upper extremities of these
pipes into the steam chest Q. C is the ash pit, which is rendered larger by
an opening D, made in the bed of the furnace for that purpose. E, E, are
openings made in the outer casing for the reception of a current of cold air.
The injection pipes and the steam-generating pipes are united at G. H is the
fire-place; I, the fire bars, mounted on brackets or supports J; K, K, is
the masonry for supporting the boiler; and L, L, is a dome of fire brick,
resting upon the last turn of the outer coil of pipes B; M, M, is a second or
inner casing, which is maintained at the required distance from the first by
filling pieces N, N, and bolts O, O. The three parts which constitute the
entire casing of the generator are provided with flanges, which are bolted
together at P, P, P". R is a damper in the flue T; and S, the pipe for con-
veying the steam from the steam chest Q to the engine.
This generator, it will be seen, consists, as in my first Patent, of a coil of
pipes. The first modification which I have made therein consists in rendering
the furnace stationary, the necessary draught being caused by the escape of
steam into the chimney. In order to obtain increased effect from the furnace
I have made the coil of pipes conical; and I would here remark that I propose
to use either a single coil of pipe or several, two or more coils united. In
Fig. 1 a second conical coil of pipes, of larger diameter than the first, is shewn
as enclosing the same in such manner as to leave an annular space between
them. The dome of fire brick carried by the outer cone is for the purpose of
deflecting the flame and heated gases, which pass up the middle of the small
cone back between the two cones; the heated gases thence pass outside the
larger cone and escape at the chimney. Two sets of conical pipes will in
general be found sufficient, but for large engines a third may be added. This
large number of steam pipes is advantageous; firstly, as regards the supply of

page_text: water,
which is effected in small continuous quantities; and, secondly, in that it
facilitates the regulation of the distance to be traversed by the steam, and thus
allows of the production of steam at a nearly uniform pressure in all the pipes
of the generator, although the action of the fire may be greater upon the first
cone than the others. Thus, if three cones be employed, there will be in the
first three tubes, in the second two, and in the third, where the heat is least,
there should be two or one, so as to prolong considerably the distance to be
traversed by the steam in the pipes in contact with the flame, and thus to
obtain steam of equal pressure in all the coils. By means of this arrangement
the working of the engine is rendered more regular, and consequently more
economical, than heretofore. The tubes which I employ for this purpose have
an internal diameter of about an inch, and are constructed of iron about one-
third of an inch in thickness, which will be found to present perfect security
against explosion.
The generator above described possesses, however, several disadvantages,
such as difficulty of construction and of cleaning, it being necessary for this
latter purpose to blow through the pipes before and after working; if, therefore,
one of the pipes should become choked up by accident, the whole must be
taken to pieces, and this might even render the whole coil useless.
In order to obviate these inconveniences and effect greater economy, I prefer
to employ the arrangement represented in vertical section at Fig. 2, Sheet J.,
and in sectional plan at Fig. 3. It will be observed that the general construc-
tion is the same, only instead of using a conical coil of pipe I make a cone
generator with pipes arranged in a serpentine or zig-zag form, as represented
by dots apertures are provided at each turn of the pipes and closed by means
of screw plugs, which may be removed when it is required to clean out the
pipes. In case the turn or elbow of the pipes should be found to be two sharp
for the dimensions of the apparatus, I cast them according to a fixed model,
and connect their ends by means of small sections of pipe, surrounding the
whole by one or more casings of sheet iron, in order to guide the flame in its
course. This generator is shewn in the Figures as cast in one piece, the
arrangement being the same. By adopting this construction, the apparatus
will be much less costly than the first-described arrangement, and equally
efficient.
It will be understood that in this arrangement the operation of cleaning will
not be so easily performed by blowing through, as in that first described; but
that by removing the screw plugs the sections of pipe may be readily cleaned
by means of rods, as will be seen on reference to the Drawings.
The dimensions of the fire-place will vary according to the nature of the

page_text: fuel employed, as in other kinds of steam generators. The apertures below for
the admission of a current or jacket of air, which serves to prevent radiation of
heat from the boiler, may be closed at pleasure, according to circumstances;
other apertures above are provided, which, by also opening those below, cause
a continuous current of air, by which means the casing will be maintained at
the temperature of the surrounding atmosphere. This current of air would,
however, carry off a certain amount of heat, which it is nearly always advisable
to retain; the apertures above are therefore very seldom employed, the air
escaping into the chimney in order to create the necessary draught.
This improved generator when applied to a steam engine constructed accord-
ing to my plan (constituting the second head of my present Invention) possesses
the advantage, when regulated for a given speed, of working continuously at
that speed, whatever may be the amount of work required to be performed.
This is effected by means of the regulator, which, acting directly upon the
steam valve, causes a variation in the supply of stean, and consequently in
the working power of the engine.
The feed pump is caused to supply water to the generator in proportion to
the quantity of steam expended, the supply of water never exceeding in quan-
tity that required for a given pressure; it is therefore the work required to be
performed which regulates the working of the engine, and not the feeding of
the furnace, the stoker only being required to keep up the heat of his furnace
according to the indications of the manometer.
In Sheet II. of the accompanying Drawings, Fig. 1 shews, in sectional
elevation, my improved water-feeding apparatus.
Au ordinary pump, similar to those employed by boiler-makers, feeds the
water periodically to a reservoir, upon which rest the extremities of a series of
pipes T, T, T, T, leading to the generator. The water passes from the reservoir
through these pipes to the generator to be converted into steam: but here a
difficulty occurs; the different pipes not being always equally heated, the water
will be supplied to those which generate the least steam, and will soon cool
them. In order to obviate this, and supply the water equably to all the pipes,
I cause it to be supplied in small quantities to each pipe in succession, and for
this purpose I arrange the apparatus so that one only of the pipes shall be
momentarily in communication with the water reservoir, and after having been
supplied with water, communication shall be cut off from the first and opened
with the second, and so on. This is effected by arranging the orifices of the
pipes T in a circle, and causing an opening O in the water supply cock P to
be presented to these pipes in succession as it travels round.
The manner of working this feed apparatus is as follows:-The water is

page_text: supplied from the pump to the receiver through the water way a, b. In the
vertical part of the water way is a cylindrical tube d, closed at its upper end,
and having a lateral exit opening f. The periphery of this tube is provided
with a helical groove, into which projects a stationary stud fixed in the side of
the water passage. On a pulsation of the pump taking place, the water rising
in the tube will force it up until the exit aperture has arrived at the largest
cavity of the reservoir, into which a certain quantity of water will enter, and
simultaneously with this upward movement an axial motion will have been
imparted to the closed tube, the extent of which will be determined, as will
be well understood, by the number of generators employed. Whilst the tube
rises and turns, a clutch at its upper part comes into contact with a clutch
box upon the cock p, p, and causes it to turn until its orifice is presented to
the next pipe. Another helical spring above acts between two successive
pulsations, and forces back the different parts into their former position, and
prepares them for producing the same effect during the next pulsation.
In order to regulate the quantity of water to be supplied, I employ a
Bourdon's, or any other suitable manometer, one of its extremities being in
contact with the steam and the other acting upon a cock.
I will now describe the second head of my Invention, relating to improve-
ments in the steam engine proper, reference being had to Sheets II., III., and
IV. of the accompanying Drawings; in which, Fig. 2, Sheet II., represents
my improved engine in end view; Fig. 3 is a longitudinal section, taken
through the middle of the cylinder slide valves and piston; and Fig. 4 is a
back view of the regulator and cranks, for regulating the admission of the
steam. The Figure in Sheet III. represents the engine in side elevation, and
in Sheet IV. the same is shewn in partial plan view.
The two principal acting parts in steam engines consume by their friction a
large portion of the motive force. One of these is the piston, which has to
overcome, on the one hand, the friction of its curved surface against the sides
of the cylinder; and on the other, that of the piston rod in its stuffing box.
This friction is the more considerable in proportion as the speed of the engine
and the temperature are increased. The other principal part is that for
effecting the supply of the steam, in which the slide valve acted upon by the
steam rubs against the fixed parts of the box. Here, as in the former
instance, the resistance becomes greater as the temperature of the steam
is raised.
The modifications which I propose to effect in the arrangement of these
parts have for their object to overcome the resistance above mentioned, and
thus to diminish the necessity for the frequent repairs occasioned thereby.

page_text: First, as regards the piston; I construct it in such a manner that it may
work freely in the cylinder, for which purpose I give it a diameter a little
smaller than the internal diameter of the cylinder. I construct the piston rods
in the same manner with respect to the boxes through which they work. By
this arrangement it will be seen that the steam will introduce itself between
the friction surfaces, and prevent their coming into contact and rubbing
against each other, thus avoiding the wear resulting from the friction. I con-
struct the supply valves on the same principle, causing a jacket of steam to
be introduced between the stationary and working parts. I effect this by
making the slide valve cylindrical (as shewn at B, Fig. 6). This valve works
freely in the cylindrical portion of the steam chest, and is provided with pro-
jecting rings C, which, by the reciprocating motion of the cylindrical slide
valve, alternately opens and closes one of the circular steam supply passages in
the steam chest. The exit steam escapes through a steam way intermediate
between the two supply passages. The slide valve is worked by means of a
rod, which works like that of the piston without friction in the end of the
steam chest.
As regards the packing of piston rods, experience having taught me that in
order to obtain the greatest possible power from steam engines it was neces-
sary to close the cylinders as hermetically as possible, I propose to employ
for this purpose metallic packing, as shewn in section at Fig. 5, Sheet II.
This packing consists of a coil of flat wire a, made of steel or any other metal
of sufficient temper to give it the necessary elasticity, and fitted into the
stuffing box through which the rod works, in the manner of ordinary packing.
It must, however, be understood that I make no claim to this construction
of packing.
It will be observed from the preceding, that one of the advantages resulting
from the employment of my improved engine is, that it admits of steam being
employed at a high pressure and elevated temperature, so that the steam, instead
of wetting the surfaces with which it comes in contact, will, on the contrary,
have a tendency to dry them.
For regulating the working of the slide valve, and consequently the supply
of steam, I adopt the arrangement represented in end view at Fig. 2, and
in elevation at Fig. 4, Sheet 1I., and shewn also in the elevation and partial
plan views, Sheets III. and IV. I employ for this purpose the ordinary ball
governor this part of my Invention consisting in the following means of
transmitting the action of this governor to the valve rod:-A sliding tube A,
mounted upon the shaft of the governor, carries a horizontal bracket piece B,
which is provided with bearings C to receive a rocking shaft D. To the two

page_text: extremities of this shaft are fixed the slotted arins E, E', which extend in
opposite directions, the one above and the other below. In the slot of the
arm E¹ works a pin or stud F, set at the extremity of the connecting rod,
which is caused to work backwards and forwards by a crank on the fly wheel
shaft, aud in the slot of the second arm E works a stud set on the valve rod.
When by reason of the increased speed of the engine the balls of the
governor are caused to rise and carry the shaft D with them, the stud F on
the connecting rod which remains at the same height will act upon a point
of the slotted arm further removed from the centre of the shaft D, and as the
horizontal course of this stud is always of the same extent, it will now traverse
the cord of an arc of less degree than before, and consequently the cord of the
are traversed by the stud of the valve rod will be smaller than before, thus
shortening the stroke of the valve, and consequently diminishing the supply of
steam to the cylinder. The contrary will be the case when, on the diminution
of the speed, the balls of the governor fall and cause the horizontal shaft to
descend. The position of this shaft is adjusted at starting (according to the
speed required) by means of adjusting screws V.
In conclusion, I desire it to be understood that what I claim as my Inven-
tion, and desire to secure under the above in part recited Letters Patent, is,
the construction of steam generators as described with reference to Sheet I.
of the Drawings, whereby I am enabled to obtain high-pressure steam both
economically and with great expedition.
I also claim for the purpose of effecting the same objects, firstly, the general
arrangement of the apparatus above shewn and described for supplying water
to the steam generator; and, secondly, the general construction and arrange-
ment of slido valve and its accessories; also the manner of working and
regulating the action of the same.
In witness whereof, I, the said Mathieu François Isoard, have hereunto
set my hand and seal, the Fifteenth day of January, in the year of
our Lord One thousand eight hundred and fifty-six.
Witness,
AE PERPIGNA,
46, R. Sto Ann, Paris.
M. F. ISOARD. (L.S.)