IMPROVEMENTS IN MACHINERY OR APPARATUS FOR COMPRESSING AIR OR GASES
Year: 1874

page_text: LETTERS PATENT to William Johnston, of Lima, Peru, but at present
residing at 47, Lincoln's Inn Fields, in the County of Middlesex,
Engineer, for the Invention of "IMPROVEMENTS IN MACHINERY OR
APPARATUS FOR COMPRESSING AIR OR GASES."
PROVISIONAL SPECIFICATION left by the said William Johnston at
the Office of the Commissioners of Patents, with his Petition, on
the 11th February 1874.
I, WILLIAM JOHNSTON, of Lima, Peru, but at present residing at
47, Lincoln's Inn Fields, in the County of Middlesex, Engineer, do
hereby declare the nature of my said Invention for "IMPROVEMENTS IN
MACHINERY OR APPARATUS FOR COMPRESSING AIR OR GASES," to be as
follows:-
This Invention relates to apparatus for compressing air, and consists
in the employment of any number of cylindrical chambers placed either

page_text: parallel to one another side by side or one within the other con-
centrically, the whole being capable of oscillations on a common axis
supported in bearings, such cylindrical chambers having a regular
decreasing capacity and connected with each other and the largest one
with the atmosphere by means of suitable valves, so that when the
chambers are partially filled with water, mercury, or any other suitable
fluid, and the apparatus caused to oscillate by any available power, the
said fluid operates in each chamber as a piston, thereby driving the air
before it from the receiving or largest chamber in a compressed state
through the valves before mentioned into the second or chamber of lesser ]
capacity, and from that in a still more compressed state into the third
or any number of chambers, decreasing in capacity until it passes into
the last or receiving chamber of the apparatus from which it is carried
off at either or both ends through the axis of the machine, and is applied
to work either machinery, or as blast to furnaces, or for any other
available purpose.
In the case of mercury being used in place of water or other fluid a
half ring of iron cast hollow and filled with lead (having a size trans-
versely somewhat less than the section of the chamber in which it is
placed) is employed, the same floating and oscillating with the mercury
which acts as a packing round it for the purpose of reducing the
quantity of mercury which would otherwise be required.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said William Johnston in the Great Seal Patent Office
on the 7th August 1874.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
JOHNSTON, of Lima, Peru, but at present residing at 47, Lincoln's Inn
Fields, in the County of Middlesex, Engineer, send greeting.
2
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Eleventh day of February, in the year g
of our Lord One thousand eight hundred and seventy-four, in the 37th
year of Her reign, did, for Herself, Her heirs and successors, give and

page_text: valve, while the inner chamber D¹ communicates at each end through
the valved ducts E' with the central portion F of the cylinder A. The
apparatus is now ready for use as follows:-Each chamber D and D' is
filled with water to a point upon a line horizontally with its axis, and
the cylinder A caused to have a semi-rotation in opposite directions until
the partition a reaches a line horizontal with the centre of motion.
The water G maintaining its level will force the air contained between
one end of its column and the downward moving partition through the
duct E into the opposite end of the next inner chamber D', while upon
the opposite side of said partition a partial vacuum will be created by
the recession of said water and air to supply the same will be drawn
through the valved opening d. Upon reversing the motion of the
cylinder a reversal of the currents of air will be effected, the air just
drawn into one end of said chamber being forced into the next inner
chamber, and the exhausted end of said outer chamber again filled from
without. The operations of the inner chambers is precisely the same as
that described, except that each receives the air in a compressed state,
and after further compression forces said air into the next chamber of
the series or of the inner chamber into the central reservoir. The size
of each chamber of the series should be such as to enable it to just
contain the air compressed by the preceding chamber, aud as said air is
still further compressed by its passage through each chamber it follows
that said chambers should decrease in capacity exactly in proportion to
the degree of such compression.
Where great pressure is required and but small space is available for
operating the apparatus it may be expedient to employ some denser
liquid in place of water, but as most available liquids, except mercury,
possess practical objections, and the expense of the latter offers a serious
obstable to its use I employ the following described mechanism for the
purpose of rendering available in part the great specific gravity of the
same. A curved iron shell H having a size transversely somewhat less
than that of a chamber is filled with lead and its ends sealed, and upon
its sides at or near said ends is provided with projecting rollers h, h, that
form rolling bearings for said shell. The length of the loaded shell or
plunger is somewhat less than the length of one half of its chamber, so
that when in place the ends of the former shall be beneath the level of
the fluid, the space between the side of the plunger H and the walls

page_text: of its chamber is now filled with mercury which is permitted to extend
upward nearly to the ends of said plunger, and over the latter, and with
said mercury is placed a sufficient quantity of water G to prevent air
from coming into contact with and causing oxidization of the latter. As
thus arranged the mercury will pack the weighted plunger and cause
the operation to be the same as though the chamber were filled with a
fluid having a density equal to that of lead.
It will be seen that while the pressure of air is constantly increasing
as it passes from one chamber into another the weight of the column of
fluid within the inner chamber operates to precisely the same advantage
as in the outer or first chamber, the pressure in rear of said column
equalizing an equal amount of pressure at its front so as to leave said
column free to increase by its weight the pressure at said latter point in
precisely the same proportion as though the initial pressure was but that
of the external air. It will also be seen that the pressure thrown upon
each valve is only equal to the difference between the air pressure
within the chambers to which it controls communication, so that the
wear of one of the inner valves will be fully equal to that of the outer
valves of the series.

page_text: series, substantially as and for the purpose herein-before described and
illustrated by the accompanying Drawings.
In witness whereof, I, the said William Johnston, have to this my
Specification set my hand and seal, this Sixth day of June, One
thousand eight hundred and seventy-four.
WILLIAM JOHNSTON. (L.S.)