AND RELATING TO AIR COMPRESSING MACHINERY."
Year: 1880

page_text: PROVISIONAL SPECIFICATION left by Peter Evans at the Office of the
Commissioners of Patents on the 1st September 1880.
PETER EVANS, of Liverpool, in the County of Lancaster.
AND RELATING TO AIR COMPRESSING MACHINERY."
"IMPROVEMENTS IN
My Invention has for its object the efficient filling of the cylinders of air
compressing machinery with full bodies of air at atmospheric and low temperatures,
and the maintenance of such low temperatures during the process of compression ;
also the utilization of the heat liberated in compressing air for increasing the
effective force of such air after compression; also the production of compressed air
in such a state that it can be worked expansively, with efficiency, and economy.
According to my Invention I construct an air compressing cylinder so as to
receive two pistons on the same piston rod, the air being compressed between each
piston and its respective end of the cylinder. The space between the pistons forms
an air or water chamber, which serves to keep the cylinder cool. I admit the air
into the cylinder ends through valves at the ends of the cylinder or in the cylinder
covers, and also through ports or passages in the centre of the cylinder, past which
each piston travels. By this means I ensure each end of the cylinder being filled
to its entire capacity with air at atmospheric or low temperature for compressing.
The compressed air is delivered from the ends of the cylinder through suitable
valves to a receiver or otherwise.
For the purpose of abstracting the heat concentrated and liberated by the com-
pression of the air I surround, or partly surround, the compressing cylinder with
an annular space between the cylinder and the usual water jacket, and through
this annular chamber I keep a current of cold air constantly passing, induced either
by the suction of the compressor itself or by other means, so that the heat liberated
from the air under compression is absorbed by the current of cold air passing round
the compressor.
I abstract or utilize as far as possible the heat taken up by the air current in
its passage around the cylinder by passing such current through a receiver by
surface piping, or by its circulation through air distributors or other suitable
apparatus. By this means I increase the efficiency of the air in the receiver or
distributor, and produce it in such a state that it can be worked expansively.
[Duins 21

page_text: By my Invention I am enabled to work air compressing machinery at high
velocities, as I ensure a perfect filling of the cylinder with fresh air at low
temperature at each stroke of the piston, and by the use of the air jacket, which
also acts as a non conductor, the liberated heat is absorbed, and I can dispense
with the ordinary means of keeping the air cool during compression by water
conduction or radiation, such as water in actual contact with the air in the com-
pressing cylinders, either in continuous streams or by injecting sprays of water,
and I deliver into the receivers, air distributors, or otherwise compressed air that
can be used expansively without the annoyance, inconvenience, and waste resulting
from the formation of ice or snow in the passages, pipes, cylinders, or parts, which
prevent its more general adoption as a motive power.
By thus maintaining a low atmospheric temperature during compression I
compress the air in as dense a state as possible, and require only a minimum
pressure to be exerted by the prime motor, whether steam, water, or by any other
suitable arrangement, and thereby effect a saving of initial pressure by obviating
the necessity of carrying a higher pressure in the compressing cylinder in order
that finally a given volume of air inay be produced at a given pressure, and at
atmospheric or low temperature.
By means of keeping up a current of cold air around the compressing cylinders,
and passing the same after it has abstracted the heat liberated during compression
through the receiver or air distributors, I overcome the great difficulty of utilizing
air economically by working it expansively at great initial pressure; or the applica-
tion of the air jacket and double piston with the necessary accessories may
be applied to existing compressors so long as the principle of my Invention is
maintained.
A compressor and accessories constructed according to my Invention may be
driven by any suitable driving engine, or by straps, or gearing, as desired.