IMPROVEMENTS IN APPARATUS FOR COMPRESSED AIR MOTORS
Year: 1883

page_text: LETTERS PATENT to Reginald Bolton of 39 Moorgate Street City of London
Consulting Engineer for an Invention of "IMPROVEMENTS IN APPARATUS
FOR COMPRESSED AIR MOTORS "
communicated to him from abroad by
Charles William Potter of New York United States of America Engineer
PROVISIONAL SPECIFICATION left by the said Reginald Bolton at the
Office of the Commissioners of Patents on the 15th February 1883.
REGINALD BOLTON of 39 Moorgate Street City of London Consulting Engineer.-
"IMPROVEMENTS IN APPARATUS FOR COMPRESSED AIR-MOTORS" [A communication
to him from abroad by Charles William Potter of New York United States of
America Engineer]
Engines using compressed air as a motive power, are frequently obliged to store
the air at a very high pressure so that the supply of air in the storage reservoir is
at a pressure considerably above the working pressure, for example, in the case of
a locomotive engine propelled by means of compressed air, it is necessary for the
sake of portability to store the air at a pressure eight or ten times as great as is
required for use in the Cylinder.
Patents have been taken out for compounding the cylinders in air motors, in
order to use the air at its high initial pressure, and by so doing avoid the loss
which has hitherto always occurred when the air has to be lowered to a convenient
working pressure by means of a reducing valve.
This however entails complications and moreover has not been found to achieve
the desired result. By this invention which is applicable to any compressed air
engine carrying its supply of air stored at a higher pressure than the actual
working pressure it is proposed to obviate this loss at the same time using the air
at any convenient working pressure which may be decided on, and storing it
originally at any higher pressure which may be necessary in order to carry a
sufficient quantity in a limited space.
The principle of this invention consists in so controlling the expansion of the
air from the storage to the working pressure which now takes place uselessly so as
to make it do useful and valuable work, which must evidently be a clear gain, and
[Prins GJI

page_text: this is accomplished by causing the expansion of the storage air down to working
pressure, to take place in a suitably constructed injector, through which the
expanding air draws along with it into the cylinder (or a second low pressure
storage tank) an additional volume of air from the atmosphere, thus supplying to
the engine a larger amount of air at working pressure, than would have been
produced merely by the expansion of the storage air.
In one application a pipe leads from the high pressure storage reservoir, to a low
pressure chamber into which the reduced air discharged and from which it is
conducted to the cylinders of the machine. In the injector there is a discharging
and a receiving nozzle, and a chamber in which a vacuum is formed by the velocity
of the high pressure-air-rushing through the nozzles. There is a check valve for
the admission of atmospheric air to the chamber.
In applying the invention a cylinder of a compressed air locomotive, has
attached a high pressure and a lower pressure reservoir, the injector being placed
-between them, and a reducing valve which is operated by a loaded piston carried
in a cylinder so weighted as to shut the valve when the pressure in the low
pressure chamber shall reach any required height. There is a flange secured to the
pipe of the discharging nozzle, by means of which the position of the latter can be
adjusted, but this adjustment may also be performed automatically if convenient.
The mode of working is as follows:-When the reducing valve is opened, the high
pressure air from the storage reservoir rushes with intense velocity through the
nozzles contained in the chamber and expands freely to any required working
pressure in the low pressure reservoir. The great velocity of the jet of air, creates
a vacuum in the chamber, and air from the atmosphere enters through the check
valve is carried by the jet into the low pressure reservoir. It will thus be seen
that while the high pressure air is being reduced to a working pressure, a
-constant additional supply of air. is being carried with it into the low pressure
chamber, and this gain in volume of low pressure air, is due to the surplus energy.
of the high pressure air which in this case instead of being uselessly expended by
free expansion is transformed into velocity, and made to perform work. The
nozzles of the injector as to shapes and the distance between them may be varied
either automatically or by hand, to suit the varying pressure in the high pressure
reservoir.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Reginald Bolton in the Great Seal Patent Office on the
14th August 1883.
REGINALD BOLTON of 39 Moorgate Street City of London, Consulting Engineer
"IMPROVEMENTS IN APPARATUS FOR COMPRESSED AIR MOTORS" (A communication
to me from Abroad by Charles William Potter of New York United States of
America Engineer.)
Engines using air under compression as a motive power are frequently obliged
to store the air at a very high pressure so that the supply of air in the storage
reservoir is at a pressure considerably above the working pressure for example in
the case of a Locomotive Engine propelled by means of compressed air it is
necessary for the sake of portability to store the air at a pressure eight or ten
times as great as is required for use in the cylinders. Although I do not confine
my Invention entirely to its applicability to Locomotives yet for purposes of
reference and description I will refer to it as applied to any Locomotive which
uses compressed Air as its motive power
I am aware that Patents have been taken out for compounding the Cylinders in
Air Motors in order to use the air at its high initial pressure and by so doing avoid
the loss which has hitherto always occurred when the air has to be lowered to a
convenient working pressure by means of a reducing valve. This however entails
complication and moreover has not been found to achieve the desired result. This
invention which is applicable generally to compressed Air Engines carrying their
supply of air stored at a higher pressure than the actual working pressure obviates
this loss, at the same time using the air at any convenient working pressure which
may be decided on and storing it originally at any higher pressure which may be
necessary in order to carry a sufficient quantity in a limited space.
Before describing my apparatus I will illustrate by the diagram Figure 4 the
extent of the loss which exists in all cases where high pressure air is reduced to a
lower pressure before being used. The rectangle W. X. Y. Z. (Figure 4) represents
any volume of air at atmospheric pressure. In order to compress this air say for
example 68 times or to a pressure of 1020 lbs per square inch above a vacuum an
amount of power is required represented approximately by the curved line I. V. J.
Now suppose this volume to be reduced to a working pressure of say 115 lbs the
power developed by its expansion is represented by the curved line I V
As however the volume and pressure now contained in the rectangle U. V. Y. S
represent the total efficiency of the air after its expansion it follows that the
amount of power enclosed by the shaded part of the diagram L. U. V. has been
lost by free expansion and this loss is in the particular case I have selected for my
illustration, equal to about 68% of the total efficiency of the air stored.
This can also be demonstrated as follows:-
The horsepower contained in one Oubic foot of air at 1000 lbs pressure is 14.23;
the horsepower contained in 10 Cubic feet of air at 100 lbs pressure (though equal
in volume of free air to one Cubic foot at 1000 lbs) in only 4.53. showing a loss in
power by free expansion from 1000 lbs of 9.7 horse power or 68% of the total
power. In other words if a certain volume of air at a certain high pressure be
applied directly to do work upon the piston of an Engine it will develop a certain
power proportional to the power spent in compressing it but if this same volume of
air be allowed to expand freely to a lower pressure before being allowed to do its
work in the piston the power developed on the piston will in this case be con-
siderably reduced in fact it will only be proportional to the power which would

page_text: have been required to compress the air originally to this lower pressure. A loss is
incurred, therefore, directly proportional to the amount of power which was actually
expended in compressing it originally from the lower pressure to the higher, and
to continue the illustration of the case if the same volume of air be allowed to
freely expand still further say down to atmospheric pressure it would then exert
no power at all upon the piston and the whole original work of compression would
be entirely lost
It will therefore easily be seen that in all compressed air motors in which the
pressure of the air before being admitted to the cylinders is reduced by free
expansion to a lower pressure than that to which it was necessary to compress it
originally in order to carry a sufficient quantity a loss is incurred proportional
to the amount of reduction or in other words to the difference between the
storage and the working pressures. Having now shown the nature and extent of
- the loss incurred in lowering the pressure of the air by-passing it through an
ordinary reducing valve (commonly called wire-drawing it) I will explain the
invention by which I am able to reduce this loss to a minimum. The principle of
-this Invention consists in so controlling the expansion of the air from the storage
to the working pressure, which now takes place uselessly, so as to make it do useful
and valuable work which must evidently be a clear gain and this is accomplished
by causing the expansion of the storage air down to working pressure to take place
in a suitably constructed Injector through which the expanding air draws along
with it into the cylinder (or a second low pressure storage tank) an additional
-volume-of air from the atmosphere thus supplying to the engine a larger amount
of air at working pressure than would have been produced merely by the expansion
of the storage air
Referring to the Drawings
Figure 1 is a section of my-Injector-in-which-D-is-a-pipe leading from the high
pressure storage reservoir A to a low pressure chamber B into which the reduced
air is discharged and from which it is conducted to the cylinder of the Machine-
In the Injector there is a discharging nozzle E and a receiving nozzle F and a
chamber G in which a vacuum is formed by the velocity of the high pressure air
rushing through the nozzles. H. is a check valve for the admission of atmospheric
air to the chamber G. In some cases I place this check valve H above instead of
below as shown in Figure 3 and I carry up a tube Q therefrom furnished with
a trumpet mouthpiece O, capable of being turned to meet the air in the direction
of motion of the Engine or opposing the direction of the wind.
Figure 2 shows the invention applied-K is a cylinder and L L the wheels of a
compressed Air Locomotive A. is the high pressure and B the low pressure reservoir.
C is the injector placed between them. M is a reducing valve which is operated by
a loaded piston carried in a cylinder P so weighted as to shut the valve M when
the pressure in the low pressure chamber B shall reach any required height-R. is
a flange secured to the pipe D of the discharging nozzle by means of which the
position of the latter can be adjusted but this adjustment may also be performed
automatically if convenient or by hand as in Figure 3 in which the flange R is
carried down to and embraces a hand wheel T screwed with a thread running in
the screw V. The mode of working is as follows:-
When the reducing valve M is opened the high pressure air from the storage
reservoir A rushes with intense velocity through the nozzle contained in the
chamber G and expands freely to any required working pressure in the low
pressure reservoir B The great velocity of the jet of air creates a vacuum in the
chamber G and air from the atmosphere enters through the check valve H (Figure 1)
and is carried by the jet into the low pressure [reservoir B. It will then be seen
that while the high pressure air is being reduced to a working pressure a constant
additional supply of air is being carried with it into the low pressure chamber B
and this gain in volume of low pressure air is due to the surplus energy of the
high pressure air which in this case instead of being uselessly expanded by free
expansion is transformed into velocity and made to perform work. The nozzles

page_text: of the Injector are so shaped as to give the best results and the distance between
them may be varied either automatically or by band to suit the varying pressure
in the high pressure reservoir.
In some cases to provide for working the motor according to this Invention
when the pressure of the storage reservoir gets down to less than is sufficient for
the effective working of the injector (Say less than six to 1 or 600 lbs storage
pressure to 100 lbs working pressure) I find it convenient to employ an inter-
mediate tank or reservoir in which a suitable pressure of say (50 lbs) may be
maintained by an injector hereinafter called the first or supplemental injector as
previously described, which intermediate reservoir communicates by a pipe with
and forms the atmospheric inlet of another injector called the second or working
injector having like the former one communication with the high pressure storage
reservoir for its supply of air and with the motor to inject such air or the number
of the supplemental injectors and their intermediate reservoirs may be increased.
By the use of such supplemental injector the air under pressure for instance of
700 lbs in the main reservoir passes by the first or supplemental injector drawing
with it the atmospheric air into the intermediate tank where a pressure of say
(50 lbs) is maintained, thence it passes by a channel to the atmospheric air duct of
the second or direct supply injector and is by this second injector which communi-
cates with the storage reservoir (having as already mentioned say 700 lbs pressure)
carried into the working pressure-reservoir (at say 100 lbs pressure) check valves
being provided to each injector. The second or working injector has obviously
less duty to perform, as it has only to reduce the air in the intermediate chamber
to less than 50 lbs pressure to enable it to lift the check valve, the gain of air
taking place from the atmosphere at the first injector.
What I claim as my Invention and desire to secure by Letters Patent is :-
1 In compressed Air Motors the improved construction and arrangement of
apparatus whereby with an air storage of higher pressure than the initial working
pressure in the Cylinders the energy of the stored air above such initial working
pressure usually lost by free expansion is enabled to be utilised by causing the
expansion to produce useful work in the shape of an additional supply of
atmospheric air to the cylinders (or low pressure chamber) substantially as set
forth.
2nd In apparatus for compressed Air Motor with an air storage of higher
pressure than the initial working pressure in the cylinders the combination with
the high pressure storage reservoir of an Injector supplied therefrom and forcing
an additional amount of atmospheric air into the intermediate low pressure
chamber which supplies the valve chests of the working Cylinders) substantially
as described
3rd. In an Injector operating as described above in connection with a compressed
Air Motor means for adjusting either by hand or automatically the relative
distances of the nozzles thereby regulating the work of the Injector in proportion
to the pressure in the Storage reservoir in combination with a check valve opening
inwards substantially as described.
In witness whereof I the said Reginald Bolton have hereunto set my hand
and seal this thirteenth day of August in the year of our Lord One thousand eight
hundred and eighty three