An Improved Thermo-pneumatic Engine.
Year: 1898

page_text: Complete Specification Left, 20th Feb., 1899-Accepted, 25th Mar., 1899
An Improved Thermo-pneumatic Engine.
I, ANTOINE GEORGES MARIE DUTHEIL, of 2, Rue Briquet, Paris, France,
Mechanician, do hereby declare the nature of this invention to be as follows;-
This invention relates to a hot air engine operated by highly compressed and
heated air or gas such as carbonic acid, hydrogen, nitrogen, etc.
The fluid employed which is alternately heated and cooled actuates a piston by
which the motion is transmitted to a vehicle or machine according to the pur-
pose for which it is intended.
My invention is illustrated in the accompanying drawings wherein Figure 1
represents, in an elementary manner, an elevation of the general arrangement of
the engine and Figure 2 a plan of the same. The same letters denote like
parts in both figures.
The apparatus consists essentially of two generating cylinders a whose
opposite ends communicate with a working cylinder b. Each of the generators a
is provided with what I term a displacer piston, the purpose of which is to pass,
at a given moment, the gases from the upper to the lower end of the generator
as will hereinafter appear. The upper end of each of the cylinders a is provided
with a jacket c for the circulation of water for cooling and at the lower end is
surrounded by a casing d for confining the heat from any suitable source e for
raising the gases to the required temperature. When the displacer piston is at
the lower end of the generator the gases are at the upper end and consequently
at their lowest temperature corresponding to their lowest pressure and when the
piston is at the upper end of the generator the gases are at the lower heated part
of the generator cylinder and are raised to their highest pressure. The alterna-
tions of one piston are opposed to those of the other, so that when the gas in
the one generator is at the minimum the other is at the maximum pressure,
these alternations being timed by the shaft f to the crank gl of which the engine
piston g
is coupled and which has a second crank f' coupled by a rod h to an
oscillating beam to whose opposite ends the two displacer pistons are coupled,
the two cranks being at 90° to one another so that the face of the engine piston
which is opposed to the direction of its movement will always be under the

page_text: maximum pressure for the moment, whilst the other face is under the minimum
pressure.
In order to obtain rapid changes of temperature the generators are so con-
structed as to expose large areas of surface to the gases in order that the latter
may be heated and cooled almost instantaneously, these conditions being essential
to the rapid development of power. With this object each end of the generators
is provided with internally projecting concentric circular gills k whose depth is
equal to the stroke of the displacer piston and the two faces of the piston are
also provided with concentric circular gills which enter between those of the
generator and vice-versa. By this means it is possible to obtain within a capacity
of a cubic decimetre, for example, forty square decimetres of heating surface.
The two faces of each piston are separated by a sleeve m of material which is
refractory and non-conductive of heat, such as porcelain, compressed asbestos
mica, and the like, centrally within which is arranged a regenerator n consisting
of a network of metallic gauze which the gases must traverse in order to pass
from the lower to the upper part of the generator and to which they give up a
great portion of their heat which is again absorbed in passing in the opposite
direction, this arrangement enabling great economy to be effected.
If now a gas be compressed in the generators to a pressure of twenty kilo-
grammes per square centimetre, for example, and if one of the generators be
heated to a temperature of 300° C., for example, the contained gas will tend to
expand and occupy double its original volume, but being in a closed vessel the
pressure will rise from twenty to forty kilogrammes, the pressure of the second
receiver not having been altered, the amount of the difference will therefore be
twenty kilogrammes. Now if there be interposed between these generators a
working cylinder b provided with a piston 9 the latter will be driven from the
first towards the second generator under this difference of pressure and by then
cooling the first, and heating the second, generator the pressure will be trans-
mitted in the opposite direction. The working piston drives shaft f on which
may be keyed a fly wheel or a running wheel the motion being transmitted
through rod to the beam i and so actuating the generator pistons.
It will thus be seen that the engine works at high pressure without compression
and without exhaust the same gases being constantly utilized.
It is to be understood that the heating and cooling surfaces on the covers of
the generators and the faces of the pistons may be constituted in any suitable
manner, for example they may consist of metal perforated blocks through which
rods would be made to slide; or of transverse or radial partitions or of other
suitable form so as to mutually slide and fit in the cavities each of the other at
the proper moment.
111
.
An Improved Thermo-pneumatic Engine.
I, ANTOINE GEORGES MARIE DUTHEIL, of 2, Rue Briquet, Paris, France,
Mechanician, 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 relates to a hot air engine operated by highly compressed and
heated air or gas such as carbonic acid, hydrogen, nitrogen, etc.

page_text: The fluid employed which is alternately heated and cooled actuates a piston by
which the motion is transmitted to a vehicle or machine according to the pur-
pose for which it is intended.
My invention is illustrated in the drawings accompanying my Provisional
Specification wherein Figure 1 represents in an elementary manner a part sec-
tional elevation of the general arrangement of the engine and Figure 2 a plan
of the same. The same letters denote like parts in both figures.
The apparatus consists essentially of two generating cylinders a which com-
municate with the opposite ends of a working cylinder b. Each of the generators a
is provided with what I term a displacer piston, the purpose of which is to pass,
at a given moment, the gases from the upper to the lower end of the generator
as will hereinafter appear. The upper end of each of the cylinders a is provided
with a jacket c for the circulation of water for cooling and at the lower end is
surrounded by a casing & for confining the heat from any suitable source e for
raising the gases to the required temperature. When the displacer piston is at
the lower end of the generator the gases are at the upper end and consequently
at their lowest temperature corresponding to their lowest pressure and when the
piston is at the upper end of the generator the gases are at the lower heated part
of the generator cylinder and are raised to their highest pressure. The alterna-
tions of one piston are opposed to those of the other so that when the gas in
the one generator is at the minimum the other is at the maximum pressure,
these alternations being timed by the shaft f, to the crank g of which the engine
piston g is coupled and which has a second crank f' coupled by a rod h to an
oscillating beam i to whose opposite ends the two displacer pistons are coupled,
the two cranks being at 90° to one another so that the face of the engine piston
which is opposed to the direction of its movement will always be under the
maximum pressure for the moment, whilst the other face is under the minimum
pressure.
In order to obtain rapid changes of temperature the generators are EO con-
structed as to expose large areas of surface to the gases in order that the latter
may be heated and cooled almost instantaneously, these conditions being essential
to the rapid development of power. With this object each end of the generators
provided with internally projecting concentric circular gills whose depth is
equal to the stroke of the displacer piston and the two faces of the piston are
also provided with concentric circular gills which enter between those of the
generator and vice-versa. By this means it is possible to obtain within a capacity
of a cubic decimetre, for example, forty square decimetres of heating surface.
The two faces of each piston are separated by a sleeve m of material which is
refractory and non-conductive of heat, such as porcelain, compressed asbestos
mica, and the like, centrally within which is arranged a regenerator n consisting
of a network of metallic gauze which the gases must traverse in order to pass
from the lower to the upper part of the generator and to which they give up a
great portion of their heat which is again absorbed in passing in the opposite
direction, this arrangement enabling great economy to be effected.
If now a gas be compressed in the generators to a pressure of twenty kilo-
grammes per square centimetre, for example, and if one of the generators be
heated to a temperature of 300° C. for example, the contained gas will tend to
expand and occupy double its original volume, but being in a closed vessel the
pressure will rise from twenty to forty kilogrammes, the pressure of the second
receiver not having been altered, the amount of the difference will therefore be
twenty kilogrammes per square centimetre. Now if there be interposed between
these generators a working cylinder b provided with a piston g the latter will be
driven from the first towards the second generator under this difference of pressure
and by then cooling the first and heating the second generator, the pressure will be
transmitted in the opposite direction. The working piston drives shaft f on which
may be keyed a fly wheel or a running wheel o the motion being transmitted
through rod h to the beam i and so actuating the generator pistons.

page_text: It will thus be seen that the engine works at high pressure without exhaust,
the same gases being constantly utilized.
It is to be understood that the heating and cooling surfaces on the covers of
the generators and the faces of the pistons may be constituted in any suitable
manner, for example they may consist of metal perforated blocks through which
rods would be made to slide; or of transverse or radial partitions or of other
suitable form so as to mutually slide and fit in the cavities each of the other at
the proper moment.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed I-declare that what
I claim is;
-
1. A thermo-pneumatic engine comprising generators a each enclosed at the
upper end in a cooling jacket c and at the lower end in a casing d collecting the
heat emitted from a suitable source for raising the contained gases to the
required temperature, the ends of the generator being provided with internally
projecting concentric circular gills & between which enter corresponding gills
on the opposite faces of a displacer piston working in the generator, said piston
being constructed of a sleeve m of refractory material surrounding a regenerator n
formed of wire gauze and giving passage through it to the gases from one end
of the generator to the other as described.
2. A thermo-pneumatic engine consisting of a pair of generators cooled at
their upper and heated at their lower ends as described, containing displacer
pistons constructed of refractory material enclosing a regenerator giving passage
to the gases from one side to the other and provided on their opposite faces with
gills adapted to enter between corresponding gills within the ends of the
generators, the pistons being coupled by a rocking beam so as to produce their
alternation of motion as described, in combination with a working cylinder whose
opposite ends are connected respectively to the two generators and whose working
piston is coupled to a crank shaft which is coupled in turn to the rocking beam
so as to produce oscillating motion thereof substantially as described.
UMID NVVLEUT
.........
A. M. & WM. CLARK,
Chartered Patent Agents. 53, Chancery Lane, London.