Improvements in Hot Air Engines.
Year: 1898

page_text: Date of Application, 23rd Sept., 1898-Accepted, 15th July, 1899
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COMPLETE SPECIFICATION.
Improvements in Hot Air Engines.
I, RICHARD BOCK, of Augustastrasse 18, Magdeburg, Prussia, in the German
Empire, Engineer, 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:-
In the open hot-air engines hitherto, used, the efficiency of the heat utilized has
been so low because the temperature of the furnace gases has not been accompanied
by a correspondingly high pressure, so as to obtain by its expansion and the cooling
thus produced, a conversion of heat into work. The furnace gases thus reached
the exhaust at a very high temperature. Further, the loss of heat by radiation
was considerable. It was also impossible to regulate the fire according to the
power required, so that when little power was being used the combustion of the
fuel was imperfect owing to the insufficient supply of air, and in addition to
the useless waste of fuel, the cylinders became dirty.
The present invention is intended to remedy these defects.
For this purpose two or more double-acting cylinders are employed which act
upon cranks at a suitable distance apart, so that the highly compressed and heated
air has a short period of admission and a longer one for expansion, without
requiring the current of air through the furnace to be interrupted.
The cylinder jackets serve as air chambers and help to cool the cylinders at the
same time as to warm the compressed air beforehand.
The desired high pressure is constantly maintained in the air-chamber by a
suitably loaded piston communicating with it, which regulates the supply to the
cylinder according to the position of the valves. A speed-governor regulates the
supply of fuel. In regular working the supply of air to the cylinder remains
always the same, whilst the admission of fuel is regulated according to the power
required.
In Fig. 2 of the drawing the arrangement of the engine is shown dia-
grammatically; engine-frame, crank-shaft and valve-arrangement are omitted. as
being unnecessary for illustration. m¹ is the fuel filling screw, n connection with
air-chamber of the engine, o connection with governor and p the combustion
chamber.
In the compressing cylinder a provided with the suction valves b and c and the
pressure valves d and e the air is brought to the highest pressure possible, which
adjusts itself according to the construction of the engine. This compression ought.
however, not to be carried so far that the heat thus produced raises it to the temper-
ature attained in the furnace, but the compressed air is able to take in more heat
from the furnace. The compressed air enters through the tubes f and g into the
jackets of the working-cylinders h and i, and thence through the tube k and furnace
jacket to the furnace m, and is there heated. From here it passes through the.
regulated valves no qr into the working cylinders s and t, where it expands and
then escapes by the regulated outlet valves u v w x. The two working cylinders s

page_text: and actuate cranks which are set at 90° apart, so that the current of air through
the furnace suffers almost no interruption, and the latter is not extinguished.
The cylinder jackets and i, as well as the furnace jacket 7 serve as air-
chambers, the air which is in or streaming through them helps to cool the cylinder
and is itself heated by the heat of the cylinder. A part of the heat thus passing
through the walls of the cylinder performs a complete cycle.
-
The regulating of the engine is effected by the speed-governor suspending the
supply of fuel, which is gaseous or liquid, according to the power required. With
small engines with liquid fuel, a wick may be used which is pushed through a
burner. With a very large engines solid fuel may be also used for the production
of the smallest amount of power required, and that which is required owing to
deviations from this amount may be supplied by gas or liquid fuel.
In order that the intended pressure may be constantly maintained in the air-
chamber, a suitably loaded plunger (not in the drawing) put in connection
with the air-chamber, and acts upon the valve-gear so as to increase or diminish
the supply of air to the working cylinder. The regulating may also be effected by
throttling the admission of air to the compressing cylinder.
Before setting the engine to work there is no pressure in the air-chambers.
The valve-gear is, therefore, set for the smallest supply of air to the cylinder.
After the fire (or flame) has been lighted the engine commences to work.on turning
the fly-wheel the pressure of the air in the air-chamber rises to that which is
desired in accordance with the load on the plunger then the plunger will rise and
adjust the valve-gear for a larger supply of air. The engine will in consequence
increase its speed, and now the speed-governor reduces the intensity of the fire by
decreasing the supply of fuel, and .continues to regulate the flame according to
the power required. The maximum power of the engine occurs when the supply
of fuel is adjusted to the quantity of air present, so that .complete combustion takes
place. With a less power the engine works with an excess of air and so
proportionally.
For short intervals, when -no.power is required, the engine may continue to
run by the pressure of air in the air-chamber without turning on the .supply
of fuel.
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. An open-hot-air engine characterised by the use of two or more cylinders,
which actuate cranks at proper distances apart, driven by thot air that has a short
period of admission and much expansion, without the current of air through the
furnace being interrupted.
2. The surrounding of the working cylinder with a jacket which serves as an
air chamber, so that the cylinder is thereby cooled and the compressed air warmed,
and thus, a subsidiary circulation of heat itakes place through the cylinder walls.
3. The governing of the engine by regulating the supply of fuel, whilst a loaded
plunger in communication with the air chamber controls the supply of air to the
cylinder by valves.
5. In engines of larger size the regulation of the fuel supply by allowing the
liquid fuel to fall by gravity from a cistern placed at a higher level and under the
working pressure, down to the combustion chamber of the engine, and at the same
..time adjusting the supply cock by means of a speed-governor.
Dated this 21st day of Sen ember 1898.
ember 1898.
AVM. P. THOMPSON & 1Co.,.
6. Bank Street, Manchester, Patent Agents.