Improvements in Apparatus for Compressing Air or Gases.
Year: 1890

page_text: COMPLETE SPECIFICATION.
Improvements in Apparatus for Compressing Air or Gases.
I ALOIS RIEDLER of 14 Landgrafenstrasse, Berlin in the Empire of Germany,
Professor, 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 :—
When, in compressors of ordinary construction, air or gas is compressed under
high pressure, there occur considerable resistances and losses, partly through the
unfavorable working of the pressure valves, and partly through the relative differences
of temperature. These useless resistances may, for the most part, be avoided.
The cause of these resistances of the pressure valves is that, in compression at high
tension, the pressure valves can only open very late, namely, not until near the change
of the piston's stroke, and at a time at which they must shortly after be closed; for
instance, in the case of compression to 8 atmospheres, the pressure valve can only
open after the piston has made ths of its stroke, and in the last eighth of the piston's
travel, the exit of the compressed air must take place and after this short space of
time has elapsed, corresponding to one eighth of the piston's course, the valve must
be again closed; this is impossible without great resistances and losses, because every
valve, on account of the resistance in the valve rod, and because of its inertia, which
must be first overcome, cannot open suddenly, but only by degrees. In the very
small space of time mentioned, therefore, neither the complete and timely opening of
the valves, nor the timely closing of the same, is possible during the change of
stroke.
These disadvantages may be avoided: 1st by the employment of valves of the
smallest practicable weight, the inertia of which may be overcome by the smallest
excess of pressure. This object is attained by the employment of valves of a material
of considerable strength combined with a small specific gravity, and of vaulted or
dish shape, as represented in Figs. 1 and 2. This vaulted shape permits of the
smallest weight in the valve.
The disadvantages named will be further avoided by the employment of valves
without rigid valve rods, but elastically mounted, as in Figs. 1 & 2, but in such a
manner that the elastic attaching strip (of rubber or steel) possesses no tension when
the valve is open, but receives tension when the valve is closed, so that this tension
assists in the opening of the valves. The tension may be produced by setting the
fastening portion t t at an inclination to the valve seat, and in the direction ta of the
opened valve, so that the tension terminates at the point of fastening at the opening
of the valve. The valves themselves may be constructed either as vaulted plates, or
as rings, or slotted plates.
Valves of this kind, of the smallest possible weight, without rigid guides, and
elastically mounted, with tension in the point of attachment, cannot close auto-
matically, but must be closed compulsorily by means of a special actuating mechanism;
on the other hand, their opening takes place automatically, assisted by the tension in
the elastic attachment.
2nd by the distribution of the pressure between two or more compression cylinders,
so that in each cylinder the opening of the pressure valves does not take place in the
last portion of the piston's stroke only, but in accordance with the divided pressure at
an earlier stage, so that both for the opening of valves, for the passage of the
compressed air, and also for the closing of the valves, a longer period is available.
The details of this will be found below.
In compression to high degrees, moreover, useless resistance occurs by reason of
the heat of compression (which has to be removed by cooling at each moment of the
compression) taking effect upon the further progress of the compression.-In the

page_text: compression of air, the effort should be to effect the change according to the isothermal
law. In reality, however, even when employing the best cooling arrangements, the
result is rather uncertain than isothermal, because the heat of compression cannot be
removed at the right time.
In order to diminish the resistance caused by the compression, raised, as it is, by
the heat, it is found advisable to distribute the compression between two or more
compression cylinders, so that, for example, in the first cylinder (down-pressure
cylinder) C, air or gas is sucked in at d, and is compressed only to, say, one
atmosphere over pressure. In this case, the pressure valve can, however, open in the
middle of the piston's stroke; the one half of the stroke of the piston, therefore,
remains for the exit of the air already compressed by one atmosphere; and for the
timely and gradual closing of the valve, the advantages before mentioned with
reference to the valve will be attained.
Further, all the heat of compression which was not removed in the down-pressure
cylinder C by means of the cooling, may be removed in the following manner, viz. :-
the air already compressed to the extent, say, of 1 atmosphere, before it is led through
the pipe o to the second cylinder C, in which it is compressed to a higher degree, will
be cooled down by special arrangements of apparatus, such as by the adaptation of a
receiver m between the two cylinders C.and C, and cooling of the already com-
pressed air in this receiver m, or by injection of cold water at w; or by the provision
of sufficiently large cooling upper surface in this intermediate receiver. In this
intermediate receiver m, all the heat of compression which arises from the compression
in the first cylinder C, can be removed, and the already compressed air may be led to
the next cylinder C³, with nearly the original temperature which the air had before
the compression in the first cylinder C.
In the cylinder C, the already compressed, and also cooled air, which has been
drawn by suction out of the reservoir m through the tube o, will be further compressed
to a higher degree; and the process described may be repeated between the
cylinder and a further compression cylinder, in which the air is again compressed
to a still higher degree.
When the cooling of the already compressed air in the intermediate receivers m is
effected by means of the injection of water, the air, before being led into the next
compression cylinder, may be deprived of moisture either by suitably diminishing its
velocity, or by the adaptation of special drying arrangements.
The arrangement of the compression cylinder may be of the kind shown in diagram,
at Fig. 3, viz., so that the pressure is distributed over two cylinders only, C & C¹, and
the receiver m inserted between them for the purpose described; or, as represented
diagrammatically at Fig. 4, the pressure is only once divided; but for the preliminary
compression there will not be, as represented in Fig. 3, only one down-pressure
cylinder employed, but there will be two down-pressure cylinders C and C2 employed,
which both draw or suck air together through d, partially compress the same, and
force it into the common receiver m, where the cooling down of the already partially
compressed air takes place.-From this reservoir, the second compressor sucks the
partially compressed air, and compresses it further.
In the above described arrangements, during the compression in the separate
cylinders, the greatest possible cooling of the air compression can be effected by the
cooling of the compression cylinder, or by injection of water into the cylinder, so that
in the intermediate receivers only so much heat remains to be removed as could not
be got rid of at the preliminary compression in the cylinder. The arrangements may,
however, be so disposed, that in the separate compression cylinders a special cooling.
shall take place only by means of upper surface cooling, and not by water injection,
the air compression in that case proceeds without moisture, and all heat of com-
pression will only be removed in the intermediate receivers through the cooling of the
same. If the entire compression is to be carried out dry, that is, without water
injection, then the cooling down of the previously compressed air may be effectedį in
the intermediate receivers only by means of upper surface cooling.

page_text: Having now particularly described and ascertained the nature of my said
Invention and in what manner the same is to be performed, I declare that what
I claim is :-
1. In compressors and blowers with the lightest possible valves and compulsory
closing of the same, the arrangement of the compression cylinders in such a manner
that the compression, distributed over several cylinders, takes place by degrees; for the
purpose of lessening the resistances.
2. In compressors and blowers of the kind referred to in Claim 1, the employment
of intermediate receivers with cooling arrangements, for the purpose of cooling the air
already compressed in the preliminary compression cylinder, before it is led into the
next compression cylinder, for further compression.
3. In compressors and blowers of the kind referred to in Claim 1, the arrangement
of two preliminary compressors, which both draw or suck in air or gas, and compress
the same to a slight extent, and force the same into an intermediate receiver.
4.. In compressors and blowers of the kind referred to in Claim 1, the arrangement
of several compression cylinders for divided compression, in which arrangement the
cooling does not take place by means of an internal injection of water, but in the
intermediate reservoirs between the separate compression cylinders.
Dated this 4th day of February 1890.
NEWTON & SON,
Agents for the Applicant