Improvements in Steam Generators.
Year: 1897

page_text: Date of Application, 4th Feb., 1897
Complete Specification Left, 4th Nov., 1897-Accepted, 4th Feb., 1898
Improvements in Steam Generators.
I, PAUL DOUDART DE LA GREE, of 95, Boulevard Beaumarchais, Paris, in the
Republic of France, do hereby declare the nature of this invention to be as
follows:-
This invention relates to an improved steam generator, in which circular tubes
arranged in any appropriate manner (in form of coils or otherwise), are practically
utilized.
For the purposes of this invention I provide the interior of the tube with a series
of spirally wound blades, arranged parallel to one another, and a sufficient distance
apart, so that calefaction, or the assumption of the spheroidal state by the water in
the tube, may be avoided: Those blades by reason of their being spirally wound and
their initial width, all have their edges constantly in contact with the walls of the
tube; the lines of the points of contact form elongated curves along the tube,
which wind from and return to points at intervals along a side of the tube. I
thus obtain a series of parallel currents having a helicoidal movement which tends to
throw the denser parts against the sides, in direction of the spirals; the currents
being all heated by the walls of the blades which distribute the heat receives from
the outer tube. The uniformity of pressure between these currents may be ensured
by saw-cuts made in the blade-edges at intervals, so as to establish a communication
between the currents. The uniformity of temperature is obtained by making the
blades of a thickness appropriate to the diameters of the tubes and the widths of the
blades; the thickness of the circular tubes being such as to suit the diameter of
the tube and the heating-system adopted in order to ensure the greatest
conductibility.
When the tubes are of sufficiently small dimensions for the purpose in view, I
replace the spiral blades by one or more solid or hollow rods, having curvilinear or
polygonal sections, wound spirally and arranged either with an equal diameter one
set above the other or with different diameters one set around the other (and in this
latter case the windings may be inclined in opposite directions), the concentrical
windings having the same axis being so arranged that either in the formation of
circular crowns or spaces around spiral windings, or between the different constituent
rods, as the case may be, there always exists only a smaller space than that in which
the calefaction ceases to be produced.
The blades first mentioned, are either in direct contact with the walls of the
tube or placed at an infinitely small distance therefrom. The intermediate spaco
between two of the adjacent blades during and after the twisting operation, is ensured
by small ribs each extending the whole length of a blade, or interrupted at intervals.
Saw-cuts also at intervals ensure the communication of the currents. To obtain
sufficient width at the points of contact of the blades, they may, in proportion to
their thickness, be bevelled, so as to make sufficient surface contact.
I have described this arrangement as having separate superposed blades, but I may
of course employ a set of blades obtained from a single piece by drawing

page_text: The blades may be formed of flattened tubes which have their narrow sides rounded
or not and placed side by side, the walls of two adjacent tubes forming one blade and
the interior of the tubes comprising the intermediate space or distance between the
blades or walls. The intermediate ribs are thus avoided. In order that after the
twisting operation a constant uniformity of the currents may be ensured, all these
tubes may be made to communicate either by means of saw-cuts provided at certain
intervals along their narrow sides, or by ineans of openings in their wider walls.
Thus, supposing that during the twisting operation one, or more of the tube spaces
which form the passages for the current, becoine narrowed; this narrowing can only
take place correlatively to the widening of one or more other tube spaces, the total
section remaining always essentially the same.
In the first example the blades were twisted together upon themselves without a
central core; but I may arrange them in the form of parallel Archimedian screw
blades wound about a central rod. In this case, I ensure the proper intermediate
space between the blades by means of separating wires twisted around the same rod
and when the diameter requires it, I ensure the width of the intermediate spaces
between the blades by turning down flanges or rims. In this example the blades
touch the central rod with their inner edges, and the tube with their outer edges.
When tubes of smaller dimensions are used, I employ spirally wound rods, and I
construct the tubes in the manner hereinafter described.
The circular tube, which, coiled in any suitable way, serves to constitute a
generator of any appropriate form and dimensions, inny enclose a spiral which can
be inserted into the tube before its being wound or coiled. In this example the
spiral is made from a cylindrical rod, but of course, as already herein before
mentioned, the shape and the section of this rod is absolutely indifferent and may
be flattened, or polygonal, oval or other shape.
The tube may enclose a spiral made from a circular rod but in winding this spiral,
I have supposed that the interior space is so large in diameter as not to avoid
calefaction; I have avoided this phenomenon however, by filling up this space with
open tubes having on their part their interior section sufficiently reduced so that
calefaction cannot take place, and kept uniform throughout the system by the
gyratory current produced by the spiral surrounding them.
The tube may contain two spirals having their windings inclined in opposite
directions.
Again the tube may be provided with four spirals and in order to afford at ouce
several examples of solid and hollow spirals; one of these is formed of a solid rod;
a second of a hollow tube with anticalefactric section, a third of a flattened tube
also with anticalefactric section, and finally a fourth of a circular tube, which by
reason of its diameter is itself provided with a spiral, which ensures to this tube an
anticalefactric passage.
As a tube filling I may also employ several rods, each wound spirally, the windings
of which are in contact, and twist them together in the same manner as the strands
of a cord are twisted. Thus a two, three, four, etc. spiral coil can be produced. This
arrangement permits of maintaining each of the spirals in contact with the walls of
the tube, an impossibility when concentrical spirals are employed.
The best received by the tube is thus constantly communicated to the windings of
each spiral and conveyed by conduction to the interior of the section.
In the twisting operation the windings which were in contact with each spiral, will
open and thus permit of a constant communication between each of the channels or
conduits formed by the spirals whereby the equalization of the temperature and of the
pressure is ensured.
In order to utilize this arrangement for larger diameters, I may also take two,
three, four, etc. of these twists each composed of several spirals and twist them
together in the same manner as I do for obtaining a spiral rod or tube.
If for example I take three three-threaded twists and twist them together, I obtain
a nine-threaded twists, each individual spiral of which becomes heated at regular
intervals by contact with the tube.

page_text: I may, finally take compound twists thus obtained and twist them together, for
example, I may take three nine-threaded twists to forin one of 27 threads.
When, by reason of the number of these spirals and of the thickness of the wires
or rods which constitute each of them, the "tiles" (by the term "tilos " I mean the
spaces which are formed between a straight line tangential to the spirals and the
points of contact of the said spirals one with another) have a dimension which no
longer has an auticalefactric effect, I placo in these tiles a wire of appropriate
dimensions which extends throughout their length, and restores to the channel or
conduit, which they form, its anticalefactric quality.
If one wire should not suffice to form an anticalefactric partition, as may happen
whon a twist formed by a large number of threads, is used, I can replace the said wire
either by a simple spiral or by a compound spiral of several threads. In this manner,
irrespective of the number of threads forming the main twist or the enveloping twist,
each individual thread collects at regular intervals, the heat which is communicated
to the tube from the furnace and conveys it inward to a greater or less distance by
its metallic conductive action.
It is sufficient that the wires or rods forming the thread, have a thickness suited
to the distance along which the heat is to be conducted to produce its useful or
working effect (which distance will vary according to the diameter of the tube and
to the number of the constituent threads of the twist) in order to obtain the
vaporization throughout the section of the tube.
The permanent communication of all the channels or conduits, obtained by this
arrangement, ensures the equalization of pressure and temperature; and the
regularity obtained in the relative positions of the constituent spirals and of
the intervals of the heating contact points ensures the minimum of loss of fuel
in working.
Thus an instantaneous vaporization can be obtained in tubes of all dimensions, the
only condition being that the thickness of the rods or wires forming the spirals be
sufficient to carry the heat necessary for the vaporization, to the part farthest from
the point of contact with the tube.
By way of example, a generator, obtained by coiling a tube furnished with any of
the above described anticalefactric devices is composed of two parts: one which
receives radiated heat and the other which is directly subjected to the intense lient
of the flame, the upper portion of which is the striking surface, where the whole jet
is crushed and expanded. These two parts form the limits of the chamber which I
will term the intensity chamber" in which the whole combustion takes place. The
outer periphery of this generator serves moreover to utilize the heat disengaged by
the exhaust current of burnt gases and the principle of my generator consists in
increasing in this part the internal vaporizing surface with a greatly reduced heating
surface. In order to obtain a high output and to collect the total heat still contained
in the exhaust current of the burnt gases after their leaving the intensity chamber,
1 arrange around the boiler the heat abducting feed water pipe, which is connected
with the before mentioned generator. The casing formed by the said abduction feed
pipe is kept tightly closed to the passage of the combined gases by a thin outer casing,
which may be provided with non conducting material.
This casing or jacket forms, so to speak, a third part of the generator for
collecting the residual heat from the burut gases and utilizing them for gradually
heating the liquid before it enters the generator proper, that is to say into the
vaporiser.
As in this third part the heat is not intense, I no longer rely on the inner vaporizing
surface but on the outer heating surface; thus may, according to circumstances
and requirements, give to the feed conduit any diameters and circuits which will
allow it to act as an exterior envelope, while presenting the necessary contact surface
to the exhaust current of burnt gases.
The heat abduction feed pipe for the liquid joins the generator at the lower
extremity in order that the heating, may be progressive, but I may, according to

page_text: circumstances connect the foed conduit to the generator at the upper extremity, in
which case the lower extremity becomes the steam outlet.
Dated this 4th day of February 1897.
Improvements in Dream Generators,
I, l'aul Doudart de la Grée, of 95, Boulyard Beaumarchais, Paris, in the Republic
of France, do hereby declare the nature of this invention and in what manner the
same is to be performed to be particularly described and ascertained in and by
the following statement :-
This invention has for its object improvements in steam generators for instan-
taneous evaporation.
I furnish the interior of the tube with a series of strips twisted in parallel spirals
the said spirals being at a sufficiently small distance apart that calefaction (or the
assumption of the spheroidal state by the water in the tube may be avoided) and
which by their spiral winding and their initial width have their edges constantly in
contact with the walls of the tube. The lines of the points of contact tracing
themselves along the tube in elongated curves which from distance to distance bring
the points of.contact back to the same side of the tube. I obtain thus a series of
parallel currents travelling with a helicoidal movement tending to throw out the dense
portions upon the edges in the direction of the spires. The currents all being heated
by the walls of the strips which distribute to them the heat communicated by the
outer tube. Equality of pressure between these currents may be ensured by saw
cutting the edges of the strips from distance to distance in order to establish
communication between the currents. Equality of temperature is obtained by
making the strips of a thickness suitable to the diameters of the tubes and to
the width of the strips; the round tubes themselves being made of a thickness
suitable to the dinineter of the tube and of the manner in which it is heated in
order to ensure complete conductivity.
When the tubes are sufficiently small to allow of it the spiral strips are replaced by
one or several solid or hollow rods of curvilineal or polygonal section wound in spirala
arranged either with the same diameter the one over the other or of different
diaincters the one around the other (and in this latter caso the spirals may be
inclined in opposite directions) and of which the spirals concentric to the same axis
are arranged in such a manner either in circular crowns around the spirals or between
the different rods of which they are composed that there only exists a separation less
than that at which calefaction ceases to take place.
Figure 1 of the annexed drawings shows au outer view of a tube the wall of which
is supposed to be partly removed to allow the filling to be seen.
Figure 2 shows a transverse section of the same tube.
Figure 2b shows a filling of flat rounded tubes placed back to back.
Figure 3 shows the strips twisted upon themselves with a central core X Y.
Figure 4 is a longitudinal section of a round tube of small diameter in which a
single spiral is placed.
Figure 5 is a transverse section of this tube.
Figures 6 and 7 are longitudinal and transvervo sections of a tube of small diameter
in which is placed a single spiral having an interior spaco filled with two half round
open tubes placed back to back.

page_text: Tigie o
me longituna am transverse sections
Cave of miger ommeter
than those shown in the preceding figures and in which are placed two concentric
spirals with the spires inclined in opposite directions.
Figure 10 is a longitudinal section of a tube of large diameter in which are placod
four spirals the details will be further described.
Figure 11 shows a wire twisted into a close spiral.
Figure 12 shows a twist obtained by twisting three of the spirals shown in
Figure 11.
Figure 13 shows an example of a generator made with these tubes.
As shown in Figure 2 the strips A occupy the section of the tube with which they
are either in absolute or approximate contact. The separation between two consecu-
tive strips during and after torsion is ensured by small projections a each running
the whole length of a strip or interrupted from distance to distance. Saw cuts b
ensure that the currents communicate at intervals. To assure the width of the points
of contact of the strips they may according to their thickness be bevelled at suitable
angles.
I have shown this arrangement obtained by means of several strips superposed but
other fillings obtained from a single piece by drawing may be employed.
The strips may constitute a partly flat tube, with the angles rounded or otherwise,
placed back to back as shown in Figure 2 the walls of the tubes forming two by
two a strip and the separating space the use of distance pieces being thus
avoided.
In order to ensure after twisting constant equality of the currents by their
communication all these tubes may be open either by saw cuts from distance to
distance along their smaller edges or by openings in their flat walls. By this means
supposing even that during twisting one or several of the spaces between the tubes
forming the passages for the current becomes constricted, this can only be produced
correlatively with the enlargement of one or several of the other spaces, the total
section remaining always practically the same.
In the first example the strips were twisted together upon themselves without a
control core; but I may also as shown in Figure 3 arrange these strips A B C as
parallel Archimedean screws round a central rod X Y. In this case I ensure separation
between the strips by means of separating wires twisted around the same rod and
when the diameter requires it I ensure also separation of the wings by cutting away
the edges of the strips.
In this example the strips A B C touch the rod X Y with their inner edges a¹ b' c'
and the tube with their outer edges.
For the case of tubes of smaller dimensions in which I employ spiral rods I give
in Figures 4, 5, 6, 7, 8, 9, 10 examples of carrying out this method.
As shown in Figure 4 the round tube A', which will by any method of winding
form a generator of any shape and size, encloses a spiral S which may be introduced
into the tube before it is rolled up.
In this example the spiral S is made of a round rod but of course as stated above
the section of this rod may be of any shape it may be flat polygonal oval &c.
The tube A shown in Figures 6 and 7 also encloses a spiral S made of a round
rod but in the winding of this spiral I have supposed that the inside space is too
large for calefaction to be avoided. I avoid this phenomenon by filling this space
with open tubes, having themselves an interior section sufficiently reducer for
calefaction not to be produced and which is maintained in regular action by the
gyrating current produced by the spiral which surrounds them.
In Figures 8 and 9 the tube A contains two spirals S S¹ wound in opposite
directions.
Figure 10 represents the section of a tubo having four spirals S S₁ SS. To
give in a single figure different examples of solid or hollow rods, Figure 10 represents
the section of a tube containing four spirals; the spiral S being formed of a solid rod,
the spiral S of a hollow rod of anticalefactory section, the spiral S" of a semi flat
tube of anticalefactory section and lastly the spiral S of a round tube which by

page_text: reason of the diameter of its insido section is itself provided with a spiral 811 which
ensures to this tube an anticalefactory passage section.
As filling for this tube I may again take several rods, each spirally wound with the
spires in contact na shown in Figure 11 and twist them together in the same manner
as threads are twisted for forming a cord. One may thus make twists of two three
four &c. strands. This arrangement allows each of the spires to be maintained in
contact with the walls of the tube which is not the case in the arrangement of
concentric spirals.
The calorie received by the tube is thus constantly communicated to the spires of
each spiral and by conduction to the heart of the section.
On torsion the spires which were in contact in each spiral open, and thus allow
constant communication between each of the channels formed by the spirals between
oze and the other and with the outer passages which ensures unity of temperature
and pressure.
Figure 12 represents a twist of three strands.
In order to utilize this arrangement with tubes of yet larger diameter I may take
two three four &c. of these twists of several strands and twist them together in the
sume manner as I have done for a spiral.
If for example I take three twists of three strands and twist them together I obtain
a twist of nine strands ench unit of which has the same advantage of being reheated
at regular intervals by contact with the tubes.
I inay also successively take each of the twists thus obtained and again twist them
together and may take for example three twists of nine strands to form one of twenty
seven strands.
When by reason of the number of these strands and the thickness of the wires or
rods which for each of them, the recesses (I call recesses the empty spaces a" bl cl
produced between the straight line x-y tangential to the spires and the points of
contact that they may have between them) are of a size which is no longer anti-
calefactory. I placo in these recesses a wire of suitable size which follows them their
whole length and restores to the channel that they forin its anticalefactory quality.
If indeed as may happen with a twist composed of a large number of strands a wire
is not sufficient to again establish the anticalefactory partitioning I may replace this
wire either by a spiml or by a twist of several strands. By this means whatever may
be the number of strands forming the principal twist or the surrounding twist ench
strand forming the unit comes at regular intervals to collect the caloric communi-
cated to the tube by outside heating and conducts it to distances of greater or less
length by metallic conductibility the core of the section is reached.
It is sufficient to give to the wires or rods which form the strand a thickness suit-
able to the distance to which metallic conductivity can produce its useful effect (a
distance which will vary with the diameter of the tube and the number of the strands
constituting the twist) to lead the caloric and obtain vaporisation in all portions of
the section of the Lube.
Permanent communication between all the channels occasioned by this arrange-
ment ensures regularity of action, pressure, and temperature, and the regularity
obtained in the relative positions of the units and the intervals of the heating points
assures the minimum of loss in working.
One may thus obtain instantaneous vaporisation in tubes of all sizes under the
sole condition that the thickness of the rods or wires forming the strands should be
sufficient to conduct to the most distant point of contact with the tube the calorio
necessary for vapourisation.
Figure 13 shows as an example a generator obtained by rolling up a tube fitted in
any one of the ways above described.
The generator is composed of two parts; the surface M which receives the radiated
beat, and the other B B directly submitted to the intense action of the flame, and of
which the upper portion form the striking surface upon which the intense jet is
broken up and dispersed. These two portions limit what I shall call the intense
chamber in which all combustion is effected. The outer casing of this generator also

page_text: serves to utilize the heat given off by the escaping current of gases already burnt and
the principle of my generator consists in increasing in this portion the surface of
internal vaporisation with a very reduced heating surface. In order to give a good
output and recover the totality of the caloric that the escaping current of the burnt
gases still contains after passing out from the intense chamber, 1 arrange around the
boiler the water inlet tube QQ' which makes junction at W with the generator
properly so called. The casing formed of the water inlet tube is kept tight to the
passage of the burnt gases by a thin outer jacket which may also be provided with an
insulator as shown in Figure 13.
This envelope forms in a manner a third portion of the generator collecting the
residues of caloric from the burnt gases and utilizing them to progressively beat
the liquid before its inlet into the generator properly so called that is to say the
vapourizer.
In all this portion the heating no longer being intense I make use of no longer the
internal surface of vapourisation but the external heating surface I may therefore
according to circumstances and the requirements of service give to the inlet pipe any
diameter and circuit arrangement which though preserving to it the function of an
outer casing, will bring into the interior of the escaping current of the burnt gases
the necessary contact surfaces.
I have shown the liquid inlet tube meeting the generator at W so as to heat pro-
gressively but I may according to circumstances cause this inlet tube to meet the
generator by the other extremity P; W then becoming the steam outlet.
At R R¹ a portion is cut away in order to show the spiral.
Having now particularly described and ascertained the nature of my said
invention and in what manner the sume is to be performed I declare that what
I claim is
1. An instantaneous steam generator consisting of tubes containing spirally
arranged partitions dividing the interior of the tube into helical channels
communicating more or less the one with the other.
2. An instantaneous steam generator consisting of tubes containing spirally
arranged partitions substantially as described and illustrated in the drawings hereunto
annexed.
3. An instantaneous steam generator substantially as described and illustrated by
Figure 13 of the annexed drawings.
Dated this 4th day of November 1897.