Improvements in Air Pressure Engines Employed for Cooling Purposes.
Year: 1891

page_text: Date of Application, 3rd Jan., 1891-Accepted, 7th Mar., 1891
COMPLETE SPECIFICATION.
Improvements in Air Pressure Engines Employed for Cooling
Purposes.
I, VICTOR POPP, of 54, Rue Etienne Marcel, Paris, in the Republic of France,
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 :-
My invention relates to air-pressure engines.
It is well known that in the expansion of compressed air when work is performed
a lowering of the temperature of the air takes place, which is in definite proportion
to the amount of the work done. This lowering of temperature with the same
initial temperatures is the greater the further the reduction of the tension or the
degree of expansion of the compressed air at work is carried. By using com-
pressed air of various initial tensions or temperatures or by using various degrees
of expansion any desired final temperatures can therefore be obtained within
certain limits after the expansion has taken place. The exhaust air of air-pressure
engines which is cooled in this manner is suitably used for cooling purposes of the
most varying kind. This air is sent through serpentines for the manufacture of
ice, cooling mixtures and the like, or between the double walls of cooling chambers,
or used for the direct cooling of rooms when it passes out freely.
The aforesaid invention has for its subject a rotary air-pressure engine comprising
a cylindrical casing in which a piston is adapted to turn, carrying with it the
eccentric engine shaft. For effecting the permanent working of the engine with
cold air the discharge of the cold exhaust air takes place separately from the
admission of the compressed air in such a manner that when the temperature of the
air is considerably lowered the snow which separates is removed by the piston itself
through the discharge openings, whilst the separate admission opening remains free.
To enable a regulation of the final temperatures desired in each instance for
various initial tensions and temperatures the part shutting off the compressed air is
actuated by a distributing-rod adapted to change its length for causing the adjust-
ment of the necessary degree of expansion.
Figure 1 of the accompanying drawing shows the improved engine in elevation
and the distributing mechanism in vertical section, Figure 2 a vertical section
through the engine, Figure 3 a horizontal section through the engine and distribu-
ting mechanism, and Figure 4 a section through the distributing mechanism on the
line & y, Figure 3.
In the cylindrical casing A is placed the rotary piston B having plane faces
which bear tightly against the bottom and the head a of the casing. I form in
this piston a rectangular slot b which enables the displacement of the piston upon
the tappet c on the engine shaft C. In transverse section the periphery of the
piston constitutes two arcs of a circle having the same radius as the inner periphery
of the casing A, and at the angular points of the piston are blocks D lying in
longitudinal grooves 61, and made tight by means of leather rings d, which blocks
effect the closing at the cylindrical part of the casing under the pressure of the air
itself.
For this purpose the bridge-pieces 62 remaining between the grooves b₁ and the
slot b are bored at 63, and small double valves, having seats formed by pipes 66
secured by means of screw-threads are adapted to move in the bores 6 whilst
bores 66 establish a communication between the casing A and the grooves 6¹³ con-
taining the blocks D.
In Figure 2 the piston B is shown in the position in which it passes the dead
point. When the piston turns in the direction of the arrow the air entering through

page_text: the pipe E passes in front of the piston and causes the same to turn.
At the same
time the air passes from above into the openings 63 forces the valves 6* upon
their lower seats, and is conducted through the bores 6 behind the blocks D
which are thereby forced tightly against the inner periphery of the casing, as
indicated in dotted lines Figure 2. Behind the piston B the compressed air,
mingled with finely divided snow, escapes through the discharge pipe F which
can at times be cleaned through apertures f adapted to be closed. In each
revolution the admission of compressed air takes place twice and the discharge of
exhaust air takes place twice, the use of the latter for the production of cold of any
temperature necessitating a suitable expansion mechanism. For this purpose the
part shutting off the admission of the compressed air is actuated by a distributing
rod, the change of whose length effects the adjustment of the degree of expansion
necessary at the time.
9
To the admission pipe E is secured the box G for the expansion valve H. By
the partition of this box two openings are produced in the slide-valve seat. The
compressed air coming from 'passes through the aperture 92 which is
always open into the valve chest, and when the slide valve is open passes in the
direction of the arrow through the opening g³ and through the admission pipe E
into the cylinder. The slide valve II is provided with two lugs between which is
placed the adjusting ring i held upon the valve rod I.
The movement of the slide valve together with the rod I is effected under the
counterpressure of the spring Figure 3, by the distributing cam L on the shaft C,
which presses upon the roller k' Figure 1, of the distributing rod K guided in a
straight line. To cause the expansion earlier or later an adjustable wedge-shaped
distributing fork M is provided for transmitting the pressure from the rod K to the
rod I, which fork enables these two rods to approach or recede from each other.
A prolongation behind the collar on the rod I extends into the tubular part k
of the distributing rod K and this part is slotted to prevent the turning of the
roller by a pin 4 extending into the slot.
The distributing fork M extending over the flattened part of valve rod and
between and allows by reason of its wedge-shaped form a change in the distance
between the axis of the roller and the centre of the slide valve, by causing the
distributing and valve rods I and K to approach or recede from each other. When
the fork M is raised the distributing cam L, in a certain position of the piston
causes the slide valve H to be displaced by means of the distributing rod and
valve rod to such an extent that the admission g³ is closed and the expansion is
caused. The more the fork M is lowered the more the distributing rod and valve
rod are forced asunder, that is to say the earlier the admission y³ is closed or the
expansion caused. The operation is repeated twice in every revolution. In the
arrangement represented in the drawing the adjustment of the fork M is effected
by the displacement of suspension point m in the slot n of the arm N.
The operation when working for cold air is very simple. The engine is set in
action and its work is led off directly or from the fly wheel or a pulley, either
by applying a brake or by using it for driving a pump or other machine per-
forming work.
The temperature of the exhaust air is ascertained and directly brought to the
desired degree by displacing the distributing fork M so as to adjust the expansion
to the proper degree.
As will be easily understood the fork M may also be controlled by the governor
of the engine in case the same degree of temperature of the exhaust air need not
be exactly maintained and importance is only attached to the regular motion of
the engine. If it is desired to have the temperature of the exhaust air slightly
lowered to say somewhere near zero the air for the sake of economy may be
preliminary heated a little prior to its admission to the engine and then expanded
somewhat more, whereby with a very small consumption of air the same final
temperature as with non-heated air and little expansion is obtained.
All these variations in the working of this engine can be effected without
departing from the principle underlying my invention.

page_text: Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is :-
First. An air-pressure engine for producing cold of any desired degrees of
temperature by its exhaust air, the said engine having a rotary piston and a
separate admission and discharge, in combination with an expansion gear, in which
the valve shutting off the admission of the compressed air is actuated by a
distributing rod the change of the length of which effects the adjustment of the
degree of expansion necessary for obtaining the desired temperature of the cold
exhaust air.
Second. In an air-pressure engine of the kind characterized in the first claiming
clause, for the purpose of causing the surface of the piston before and behind the
admission to bear tightly against the cylindrical wall of the casing by means of the
compressed air used in the engine, the rotary piston B in the grooves of which
the blocks D are adapted to slide and form a tight joint whilst compressed air passes
behind the blocks through the openings 66 and the valves 64 controlled by the
compressed air.
Third. In an air-pressure engine of the kind characterized in the first claiming
clause, for the purpose of causing various degrees of expansion so as to obtain the
desired temperatures of the cold exhaust air, the arrangement of the rods I and K
for actuating the expansion valve these rods being adapted to be moved towards or
away from each other by a wedge-shaped intermediate piece M.
Dated this 3rd day of January 1891.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.