AN IMPROVED METHOD OF COMPRESSING AIR
Year: 1881

page_text: LETTERS PATENT to Frank Wirth, of the Firm of Wirth and Company, Patent
Solicitors, at Frankfort on the Main, in the Empire of Germany, for an
Invention of "AN IMPROVED METHOD OF COMPRESSING AIR." A com-
munication from Friedrich Honigmann, Director of Mines, of Aix-la-Chapelle,
in the Empire of Germany.
PROVISIONAL SPECIFICATION left by the said Frank Wirth at the Office
of the Commissioners of Patents on the 1st January 1881.
FRANK WIRTH, of the Firm of Wirth and Company, Patent Solicitors, at Frankfort
on the Main, in the Empire of Germany. "AN IMPROVED METHOD OF
COMPRESSING AIR." [A communication from Friedrich Honigmann, Director of
Mines, of Aix-la-Chapelle, in the Empire of Germany.]
The Invention communicated to me relates to an improved method of compressing
air up to ten atmospheres to be used for working engines and other purposes, and
consists in using an air compressor which draws in air at one side of the piston
and compresses it up to the pressure of the air contained in the reservoir, into
which it then forces it. On the other side of the piston, in place of using water or
steam as a motive power to work the same, I use compressed air of the same
pressure as that contained in the reservoir. This air serving as a motive power
has a much greater volume than the air being compressed on the other side, and
works by expansion down to the normal pressure of the atmosphere; this air is
highly heated on its way from the reservoir to the working cylinder.
The object of heating the air, as hereinbefore described, is to greatly increase the
quantity of air introduced into the cylinder at the same pressure, and thus to
render it possible to have an equally large volume of expanded air to work on the
piston, with sufficient extra power to give the motion. In this manner a surplus
of air is obtained in the reservoir, which is passed off into another reservoir in
order to avoid an increase of pressure in the first. The compressed air for use is
taken from the second reservoir.

page_text: When air is heated to two hundred and seventy three degrees centigrade it
expands to twice its volume, at four hundred and ten degrees centigrade three
times its volume, at five hundred and forty six degrees centigrade four times its
volume, all at the same pressure; thus the surplus of compressed air, taking no loss
into account, and considering that the same force taken for compression at one
side of the piston is derived from the expansion at the other, would be, when
heated to two hundred and seventy three degrees centigrade, the half, at four
hundred and ten degrees centigrade two thirds, at five hundred and forty six
degrees centigrade three fourths, and so on.
In order to obtain the above results, together with as large a surplus of compressed
air as possible, the air pumps must be properly constructed and well carried out;
any system however can be employed.
To construct a properly working air pump the following should be observed:-
The packed part of the piston should work in a part of the cylinder which is
cooled; this can be effected by making the piston longer than the stroke. The
machine can be constructed in such a manner that the hot air and the air to be
compressed are both in one cylinder, and operating against one piston, or they
may each work in a separate cylinder.
It is to be further observed that the pressure in the reservoir should be as equal
as possible, and should correspond to the working pressure of the hot air, in order
to obtain the proper expansion.
The heating of the compressed air for the working is best accomplished in a
system of tubes.
The air is best kept cool during compression by injecting water or oil into the
cylinder in the form of spray, this serving at the same time as a lubricant. When
these substances collect at the bottom of the reservoir they can be cooled and used
again for the same purpose.
The valves are best situated in the heads of the cylinder in order to avoid
dead space as much as possible. They should be constructed large so as to ease
the working.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Frank Wirth in the Great Seal Patent Office on the 17th June
1881.
FRANK WIRTH, of the Firm of Wirth and Company, Patent Solicitors, at Frankfort-.
on-the-Main, in the Empire of Germany. "AN IMPROVED METHOD OF
COMPRESSING AIR." A communication from Friedrich Honigmann, Director of
Mines, of Aix-la-Chapelle, in the Empire of Germany.
The Invention communicated to me relates to an improved method of com-
pressing air up to ten atmospheres to be used for working engines and for other
purposes, and consists in using an air compressor which draws in air at one side of
the piston, and compresses it up to the pressure of the air contained in the receiver
or reservoir into which it then forces it. On the other side of the piston in place
of using water or steam as a motive power to work the same, I use compressed air
of the same pressure as that contained in the receiver or reservoir. This air serving
as a motive power has a much greater volume than the air being compressed on
the other side, and works by expansion down to the normal pressure of the
atmosphere; this air is highly heated on its way from the reservoir to the working
cylinder.
The object of heating the air as hereinbefore described is to greatly increase the
quantity of air introduced into the cylinder at the same pressure, and thus to
render it possible to have an equally large volume of expanded air to work
on the piston with sufficient extra power. to give the motion. In this manner a
surplus of air is obtained in the reservoir, which is passed off into another reservoir
in order to avoid an increase of pressure in the first. The compressed air for use is
taken from the second reservoir.
When air is heated to two hundred and seventy three degrees centigrade, it
expands to twice its volume, at four hundred and ten degrees centigrade to three
times its volume, at five hundred and forty six degrees centigrade to four times its
volume, all at the same pressure; thus the surplus of compressed air, taking no loss
into account, and considering that the same force taken for compression at one side
of the piston is derived from the expansion at the other, would be, when heated to
two hundred and seventy three degrees centigrade, the half, at four hundred and
ten degrees centigrade two thirds, at five hundred and forty six degrees centigrade
three fourths, and so on.
In order to obtain the above results, together with as large a surplus of
compressed air as possible, the air pumps must be properly constructed and well
carried out; any system however can be employed.
To construct a properly working air pump the following should be observed :-
The packed part of the piston should work in a part of the cylinder which is cooled;
this can be effected by making the piston longer than the stroke. The machine
can be constructed in such a manner that the hot air and the air to be compressed
are both in one cylinder and operating against one piston, or they may each work
in a separate cylinder.
It is to be further observed that the pressure in the reservoir should be as equal
as possible, and should correspond to the working pressure of the hot air in order
to obtain the proper expansion.
The heating of the compressed air for the working is best accomplished in a
system of tubes.
The air is best kept cool during compression by injecting water or oil into the
cylinder in the form of spray, this serving at the same time as a lubricant. When
these substances collect at the bottom of the reservoir, they can be cooled and used
over again for the same purpose.

page_text: The best position for the valves is in the heads of the cylinder in order to avoid
dead space as much as possible. They should be constructed relatively large so as
to ease the working.
Having thus described the nature of the Invention communicated to me, and the
best means with which I am acquainted for carrying the same into effect,
I would have it understood that what is claimed and intended to be protected by
the herein-in-part recited Letters Patent is,-
The method herein described of producing compressed air by using a portion of
this same compressed air after heating the same.
In witness whereof, I, the said Frank Wirth, have hereunto set my hand and
seal, this Fourteenth day of June, in the year of our Lord One thousand
eight hundred and eighty one.
FRANK WIRTH. (L.S.)