IMPROVEMENTS IN HOT AIR AND SIMILAR HEAT ENGINES
Year: 1884

page_text: I WILHELM SCHMIDT Engineer of Brunswick; Germany, do hereby declare the
nature of said Invention for "IMPROVEMENTS IN HOT AIR AND SIMILAR HEAT
ENGINES," to be as follows:--
My invention relates to engines driven by hot atmospheric air or other highly
heated gases.
It consists chiefly. in improved methods of cooling and lubricating the power
cylinder.
Instead of surrounding the cylinder with a water jacket or injecting water into
the working part of the cylinder, (namely that part which contains the gases
propelling the pistons) I admit water to the discharge side of the cylinder or to the
gases which have almost or entirely completed their expansion.
For heating the air before admission to the cylinder I employ a pipe coil
composed of several superposed spiral pipes, the ends of which are turned out of
their respective planes (the plane of the individual spiral) and connected with the
ends of the contiguous spirals so as to form a continuous conduit of great length in
a small space.
The inlet port for the hot air and the outlet for the expanded air are separate
from each other, but in single acting engines they are situated on the same side of
the cylinder, so that the inlet and the outlet valve may be set in motion by one
valve spindle.
In single acting engines the working side of the cylinder is supplied with hot
gases through a lift valve coupled with the rod of the slide valve which controls
the compression side of the cylinder, by means of a slotted sleeve and a pin, the
slots allowing the hot air supply valve to be closed by a spring without affecting
the motion of the slide valve.
The outlet of the gases from the working side of the cylinder is controlled by an
extension of the slide valve which controls the compression side, said valve having
on its face a recess which periodically puts the outlet port of the working side of
the cylinder in communication with a discharge pipe leading to the atmosphere.
In closed hot air engines, namely engines. which repeatedly use the same air, the
air discharged from the working side of the cylinder is conducted through the slide
valve situated in the compression valve chest to the compression side of the
cylinder, for which purpose the slide valve has a special recess adapted to com-
municate periodically with an auxiliary port situated between the two main ports
(of the compression valve chest).

page_text: Instead of using a separate valve for controlling the admission of hot air to the
working side of the cylinder, the slide valve situated on the compression side of
the cylinder may have an extension and an additional recess adapted to commu-
nicate periodically with a channel leading to the hot air space, so that the hot air
passes from the latter through the slide valve, which is continually cooled, to the
port which leads to the working side of the cylinder, this port thus serving
alternately for the inlet and outlet of the hot gases.
In order to control the combustion of fuel on the grate, the air is supplied to the
fire-place by a pipe provided with a throttle valve, the axle of which is connected
by a rod and levers with a flexible membrane placed over the valve chest and
exposed to the hot air contained in the latter.
The membrane will expand in proportion to the heat of the gases entering the
valve chest, and will communicate its motion to the valve spindle, so that the
position of the throttle valve always depends on. the heat of the working gases.
The admission of cooling water to the cylinder may take place before the
expansion of the working gases is completed, or immediately on the completion,
or after the same.
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The water inlet may be controlled by cocks connected with the slide valve
spindle..

page_text: I, WILHELM SCHMIDT, Engineer, of Brunswick, Germany, do hereby declare the
nature of my invention for IMPROVEMENTS IN HOT-AIR AND SIMILAR HEAT
ENGINES, and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement:-
My invention relates to engines driven by hot atmospheric air or other highly
heated gases.
The invention may be applied to all existing hot air engines, as well as to gas
engines, and chiefly consists in improved methods of cooling and lubricating the
power cylinder.
In further describing the invention reference will be made to the accompanying
drawing, in which Fig. I is a partial side view of an engine, with vertical-section
of the heating, apparatus, Fig. II an end view of the same, Fig. III a horizontal
section of the cylinder and valve chest. The remaining figures illustrate details
and modifications.
For the sake of clearness that part of the power cylinder in which the expansion
takes place (namely that part which contains the gases propelling the piston) will
be hereinafter called the working side.
The improvement consists in admitting water to the discharge side of the
cylinder, (that is to say to that part which for the moment is not at work), and
has for its object to cool the walls of the cylinder which have just been in contact
with and heated by the gases propelling the piston.
The cylinder is thus cooled internally and directly, instead of having a water
jacket.
The introduction of water and steam into the working side of the power
cylinder for the formation of steam and increase of power is well known, not so
the introduction of steam into the exhaust side, namely that side of the cylinder
which is not at work at that moment.
This method of introducing water is applicable to open and closed, single and
double acting hot-air engines, to combined, hot-air and steam engines, and to gás
engines.
The quantity of cooling water may be controlled as desired, and thereby the
temperature of the cylinder wall maintained conveniently low.
In single acting engines the cooling water is always introduced on the same side
of the piston, in double acting engines, however, the water is introduced into that
side which has just been used as the working side, but only after the gases therein
have almost or entirely completed their work, or expansion.
Figs. I and II represent by way of example the arrangement applied to single
acting, open hot air engines.
1, 2, is the cylinder, part 1 of which works as power cylinder and part 2 as
compression cylinder.
The hot working gases are, adınitted through valve 3, valve chest 4, and pipe 5
fed with hot gases from the pipe coil 6, the special arrangement of which will be
hereinafter described.

page_text: The hot gases, introduced through valve 3, expand in part 1 of the cylinder, and
drive the piston towards the right; during the return stroke of the piston (the
valve 3 having been closed in the mean time) the expanded hot gases are conducted
through port 7 under the slide valve 8, into the compression valve chest 9, and
thence through pipe 10 into the atmosphere.
During the discharge of the spent gases on the left side of the piston, air and
water are sucked in on the right side of the piston, through recess' 13 from pipe 11,
which contains the water injecting pipe 12; the air and water thus sucked in
serving to cool and lubricate the cylinder walls which have previously been in
contact with and heated by the working gases.
. During the return stroke of the piston towards the right, the cold air which has
been sucked in, is compressed and passes, together with tlie water driven along in
front of the returning piston, through cylinder port 14, valve port 15 and valve 16
into the valve chest 9, from where the cold compressed air and the water pass into
the pipe coil 6 to be heated, and thence through pipe 17 again into the valve
chest 4, and through valve 3 into the working cylinder 1, to be again utilized.
For this type of engine (Figs. I to III) I have also devised some improvements
in the construction of details, hereinafter described and claimed.
1, The pipe coil 6, Fig IV is composed of several superposed spiral pipes the
inner and outer ends, a, b, of which are somewhat turned out of their plane (the
plane of the individual spiral) so that alternately the inner ends and the outer ends
are connected with each other, namely a with a, and b with b, by means of screw-
muffs m, or by welding or by flanges.
In this manner these spirals form together a specially compact continuous system
of pipes into which the cold compressed gases enter at p, and in which they are
heated by the surrounding hot gases of combustion generated in the fire place f;
the heated gases subsequently pass out at q and are conducted into the slide valve
box 4 of the working cylinder.
2, The feed valve 3, serving to control the admission of hot gases into the
cylinder, is pressed on its seat and closed by means of the spring 18, and connected
with the valve rod 19 of the compression slide valve 8 by means of a key passing
through slot 20, so that the lifting of the valve 3 and consequently the
introduction of the working gases can take place at the proper moment, without
requiring a special eccentric for this valve. This connection allowing a dead
motion (through slot 20) is sufficient in the present case, the discharge of the
working gases being controlled by the compression slide valve 8 and effected
directly through port 7. The outlet is thus situated in the cold compression slide
valve box, so as to prevent any damage to the packing surfaces through heat,
the water entering the compression slide valve box continually cooling the slide
valve surfaces.
As the valve 3 itself requires no lubrication and cooling, the packing surface,
indispensable for the valve gear of the power cylinder, is removed from the hot
slide valve box of the power cylinder and arranged in the automatically cooled and
lubricated compression slide valve box.
Fig. V illustrates the arrangement of the ports in a closed single acting hot air
engine. The hot air enters the cylinder through valve 3 and drives the piston to
the right; when the piston returns to the left; the spent gases are forced through
port 21, recess 22 and port 23 into the right or compression side, into which water
is introduced.
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The spent gases are therefore cooled directly in the cylinder, then compressed by
the piston moving to the right, and discharged through valve port 15 and valve 16
into the compression slide valve box 9, in order to enter again into the circulation
after having been relieved of a portion of the water.
Fig. VI illustrates a modified construction in which the inlet valve for the hot
air is completely removed from the slide valve box of the hot power cylinder.
This engine has a port 24, recess 25, port 26, recess 27, and exhaust port 28, the
latter leading to the atmosphere or, in closed hot-air engines, to the coil 6. The

page_text: hot gases pass through port 24 into the recess 25 and then through port 26 into
the power cylinder where they drive the piston. After having been thus utilized
the gases pass from port 26 through recess 27 into the exhaust port 28.
3, A third improvement, represented by Figs. I to III, consists in the means for
controlling the water supply.
The air supply pipe 29 of the fire place f contains a throttle valve 30 adapted to
be turned by lever 31.
The lever 31 is moved automatically by the diaphragm 32, which is placed over
a space 33, filled with fluid exposed to the heat of the gases working the engine.
When the temperature of the hot air is too high, the fluid in the space 33
expands and closes the valve 30 in the air supply pipe 29, so as to diminish the fire.
This diaphragm (or a piston) therefore serves to control the temperature of the
liot air.
The diaphragm 34 secured in the cover of the compression slide valve box 9
(which diaphragm may, however, also be situated at another part of the conduit for
compressed fluid) is directly-influenced by the expansion of the gases in the
compression slide valve box, and the motions of this diaphragm 34 operate
a lever 35 which controls the valve 36 of the water supply pipe 12.
If the pressure in the engine is too high, the water supply is diminished, so that
less water is sucked in by the compression cylinder 2 and the expansion immediately
decreases in consequence of a diminution in the generation of steam.
In double acting engines working with highly heated air, the water for cooling
and lubricating the cylinder is introduced, as already mentioned above, to the gases
which have almost or entirely completed their expansion.
Fig. VII represents the valve gear in a closed hot air engine; 1, 2, is the double
acting combined power and compression cylinder, 37 the pipe leading to the heating
coil, 9 the compression slide valve box, 38 and 39 are the valves serving to admit
the hot air, 4 is the valve box on the inlet side of the cylinder, 40 and 41 are
valves for controlling the injection of cooling water, set in motion by the valve
rod 42.
The functions are as follows:
The hot air coming from the left forces the piston towards the right (at the
beginning of which period the valve 38 is opened by means of the valve rod 43)
the right injecting cock 41 opens, and injects water into the gases which have just
been expanded on the right side of the piston. The introduction of the cooling
water takes place shortly before the reversal of the piston stroke, (towards the end
of the expansion period) whereby the cylinder is simultaneously cooled and
lubricated. During the return stroke of the piston the cooling is continued, and
the spent gases are compressed.
The compressed gases pass through valve 44 into the compression valve box 9,
and from the latter, after having been partially relieved of water, through pipe 6
into the heating coil.
If the piston is on the right, the opposite takes place; the gases on the left side
have been expanded, the water is introduced from the left through cock 40, the
admission valve 39 on the right opens and permits the hot working gases to act
against the right side of the piston, while cooling, lubricating and compression
take place on the left.
In open engines, the cooling water and the spent working gases are discharged
into the atmosphere through pipe 6.
The introduction of the cooling water may take place, when the working gases
have almost completed their expansion, or at the close of the expansion, or after
the same.
Having now particularly described and ascertained the nature of my said
nvention and in what manner the same is to be performed I declare that what
I claim is
1. In engines actuated by the pressure of hot fluids, the method of cooling and
ubricating, the power cylinder, which consists in admitting water to the exhaust-

page_text: side of the cylinder or to the working gases when their expansion has been almost
or entirely completed, substantially as described.
2. In hot-air engines and combined hot-air and steam engines, a pipe coil
composed of superposed spiral shaped sections connected with each other alternately
at their inner and outer ends, substantially as described.
3. In hot-air and combined hot-air and steam engines, an admission valve for
the power cylinder, connected with the compression valve by a joint adapted to
allow a dead motion, substantially as described.
4. In hot-air and combined hot air and steam engines, a port 7, leading from the
working side of the cylinder to the compression slide valve, in combination with
a recess in the face of the compression slide-valve, for the purpose of exhausting
the spent gases through the cooled compression valves, substantially as described.
5. In hot-air and combined hot air and steam engines, the combination of a port 7
leading from the working side of the cylinder to the compression slide valve, with
a recess in the face of the compression slide valve, and canal 23 (shown in Fig. 5)
adapted to lead from the said recess to the port for compressed gases, for the
purpose of leading the spent working gases of closed engines directly into the
compression space of the cylinder and thereby cooling the same, substantially as
described.
6. In hot-air and combined hot air and steam engines, the combination of canal 26
leading from the working side of the cylinder to the compression slide valve, with
a recess in the face of the said valve, a canal 24 leading from the face of the said
valve, to the valve chest for hot air, and with a second recess in the valve face
adapted to set canal 26 in communication with canal 24, for the purpose of
controlling the admission of hot gases to the cylinder by the compression slide
valve, substantially as described.
7. In hot-air and combined hot air and steam engines, the combination of a valve
for controlling the admission of air to the fire-place with mechanism adapted to
control the position of the said valve according to the temperature of the .hot
working gases; substantially as described.