Improvements in Compressed Air Engines.
Year: 1897

page_text: Date of Application, 17th Apr., 1897-Accepted, 22nd May, 1897
COMPLETE SPECIFICATION.
Improvements in Compressed Air Engines.
I, LUCIUS TUCKERMAN GIBBS of 5 East 27th Street, in the City and State
of New York, United States of America, 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 engines operated by compressed air working expansively it is well known
that as a consequence of such expansion, while performing work, the temperature
of the air becomes reduced, often to such a degree as to cause freezing of moisture
at the exhaust port, and that other disadvantageous results follow.
The invention consists in an engine wherein the working fluid is composed of two
different gases or vapors, one of which enters into the working cylinder at a lower
pressure than the other. One of these gases is inflammable, and this is introduced
at the relatively lower pressure. The other gas is air compressed by external
means to such a degree that the working energy of the motor is chiefly stored
therein and derived therefrom; and, hence, said air is primarily the source of
power in the motor.
Said air, however, is cut off before the piston has completed
its stroke, so that subsequently the expansion of the air supplies motive
energy.
I compensate for the loss of heat due to expansion by igniting and burning in
the working air within the cylinder of the motor a definite quantity of inflammable
gas or vapor, which enters singly into the cylinder when the pressure therein is at
or about that of the atmosphere, so that said air, despite its expansion, is finally
emitted at the exhaust at a temperature considerably above the freezing point
of water.
This results in the following cycle of operations, the motor, for purposes of
illustration, being assumed to be single acting:
1. Gas is admitted into the cylinder when the pressure therein is substantially
that of the atmosphere; hence, in the beginning, and with the engine at rest, the
gas is allowed to enter a chamber opening into the cylinder behind the piston
before compressed air is admitted to the cylinder to start the piston on its
forward stroke, and, subsequently, when the engine is in motion, gas is admitted to
said chamber just before the beginning of the backward or exhaust stroke, or
during the continuance of said exhaust stroke.
2. The working air under pressure then enters behind the piston for a part
of the stroke, and is cut off and permitted to expand over the rest of the
stroke.
3. At or about the time of cut off of said air the gas already in the cylinder,
having become mixed with said air, is ignited, and thus the temperature of the
working fluid in the cylinder is increased, and the pressure thereof incidentally
augmented.
The accompanying drawing is a diagrammatic sectional representation of an
engine constructed and arranged in accordance with my invention.
A is the working cylinder; B the piston, and C the crank shaft. D is the valve
chest, communicating with one end of the cylinder by a passage a, with the
atmosphere by an exhaust port d' and with any suitable source of compressed air
by the opening d. E is a slide valve, operated by a crank or eccentric F on the
shaft C, and arranged to control the admission of compressed air to the cylinder
through the inlet port a, and its discharge from the cylinder through the exhaust

page_text: port d'. The timing of the valve is such that the compressed air is admitted to
the cylinder at the beginning of the working stroke, and cut off at a predetermined
point.
G is the combustion chamber, which communicates through an opening with the
interior of the cylinder. It also communicates by passage g with the chamber of
the valve H, which chamber connects at h with a source of inflammable gas.
The valve stem projects through the case and carries a disk i, between which
and the end of the valve case is a spiral spring I tending to close the valve and
hold it to its seat. On the shaft C is an eccentric or crank K, to which is connected
the valve operating rod J. This rod passes through a bearing; in line with the
stem of valve H, which valve H it is adapted to open and to hold open for a short
interval when the pressure within the cylinder has fallen to or about the atmospheric
pressure.
LL are spark points projecting into the combustion chamber G and connected
by the wires, of an electric circuit, through an induction coil M and a contact
maker N with a source of electricity O. The contact maker N is operated by the
crank shaft C so as to close the circuit and produce a spark at the points L in the
combustion chamber, preferably at or near the instant of cut off of the air in
the working stroke of the engine.
The operation of the engine whereby it performs the cycle before described is
as follows:
The parts being in the position shown in the drawing, the piston B and valve J
moving to the right and the air valve E to the left, as indicated by arrows, com-
pressed air is admitted from the valve chamber D through passage a into the
cylinder to move piston B forward. At the proper point in the working stroke of
the piston the valve E closes the passage a and cuts off the supply of compressed
air to the cylinder, after which the air operates expansively upon the piston during
the remainder of the working stroke. Preferably at or near the point of cut off
the contact maker N closes the electric circuit 11, producing a spark at the
points L L in combustion chamber G. The charge of inflammable gas or vapor
which is contained in said chamber, mingled with sufficient air to render it explosive,
is thereby ignited and exploded, and the heat thus liberated is imparted to the
compressed air in the cylinder at or about the time said air begins to expand and
lose its heat.
At or near the end of the forward or working stroke, or during the return stroke
of the piston, the valve rod J opens the valve H, and a fresh charge of gas or
vapor is admitted into the combustion chamber G. At this time the pressure in
the cylinder behind the piston is reduced to, or nearly to, that of the atmosphere,
and very little extra pressure is required to inject the gas or vapor into the
combustion chamber. As the piston completes its forward stroke the air valve E
brings the passage a into communication with the exhaust port d', and the return
stroke of the piston expels the spent charge of air and gas from the cylinder.
When it reaches the limit of its return movement the valve E again opens the
passage a, admitting air under pressure to the cylinder, and the piston is again
forced forward as above explained.
The heat produced within the cylinder by the admission of gas is directly applied
to and absorbed by the air. Thus the temperature of the air is elevated with the
expenditure of the least possible fuel or energy. The force developed by
the explosion of the gas is also incidentally utilized to aid the air to drive the
piston.
The invention is here shown in a single acting engine; but it is obvious that the
same cycle may be performed by a double acting engine.
Having now particularly ascertained and described 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 motor wherein the working fluid is composed of air and an inflammable

page_text: gas, and wherein the gas is first introduced into the working cylinder at a low
pressure and subsequently the air at a relatively high pressure, and where the air
is cut off and allowed to do work expansively, and the mixture of air and gas
ignited.
:
2. An air pressure engine constructed and operating to perform the following
cycle (1) Gas is admitted into the working cylinder when the pressure therein is
substantially that of the atmosphere. (2) The working air under pressure enters
behind the piston and drives it directly for a part of the stroke and is cut off and
expands over the rest of the stroke. (3) At or about the time of cut off the gas
in the cylinder is ignited, thus increasing the temperature and pressure of the
working fluid.
3. The combination in a compressed air engine of a cylinder provided with an
inlet and an exhaust port for the admission and exit of the working fluid, a valve
controlling said ports, a piston in said cylinder, a gas chamber opening into one end
of said cylinder, and communicating with a source of gas supply, a valve controlling
the admission of gas to said chamber, and an igniter for the gas in said chamber;
the said parts operating to admit air under pressure to actuate the piston over a
part of the working stroke, then to cut off said air to cause said air to work
expansively, then to admit gas into said chamber when the pressure in said chamber
shall have fallen substantially to that of the atmosphere, and subsequently to ignite
said gas, substantially as described.
LUCIUS TUCKERMAN GIBBS.
Haseltine, Lake & Co.,
45 Southampton Buildings, W.C., Agents for the Applicant.