Improve- MENTS IN MACHINERY FOR COMPRESSING AIR
Year: 1870

page_text: LETTERS PATENT to Thomas Brown, of Newgate Street, in the
City of London, Civil. Engineer, for the Invention of "Improve-
MENTS IN MACHINERY FOR COMPRESSING AIR." -A communication from
abroad, by Charles Burleigh, of Fitchburg, Massachusetts, United
States of America.
Sealed the 10th February 1871, and dated the 13th August 1870.
..
PROVISIONAL SPECIFICATION left by the said Thomas Brown at the
Office of the Commissioners of Patents, with his Petition, on the
13th August 1870. .
'
I, THOMAS BROWN, of Newgate Street, in the City of London, Civil
Engineer, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN MACHINERY FOR COMPRESSING AIR," a communication, to
be as follows:-
The said Invention relates to machinery for compressing air to serve
as a medium whereby motive power generated in one situation may be
transmitted in a convenient and economical manner to operate engines
or machines in other situations.

page_text: The said Invention is chiefly designed to be used in connection with
rock drilling machines, when the same are employed in the formation of
shafts, tunnels and deep cuttings, and other like operations where the
use of steam would be very disadvantageous in consequence of the loss
arising from condensation, and the inconvenience to the workmen
employed occasioned by the exhaust steam.
In forcing air under compression into a reservoir or air vessel, the
working of the air compressing pumps has hitherto been attended
with certain difficulties, amongst the most important of which is that
arising from the varying resistance offered by the compressed air to the
pistons of the pumps, which resistance increases from the commencement
to the termination of each stroke of the pump, from nothing to the
full pressure in the air reservoir. Another very important difficulty
has arisen from the fact that in the compression of air the latent heat
therein becomes sensible and heats the working parts of the pumps, the
consequent unequal expansion of these heated parts causing great
unnecessary friction, leakage of the valves and other difficulties which it
has been attempted to obviate by causing a current of cold water to
flow around the heated parts.
.
By my present Invention I am enabled to construct a machine which
is entirely free from the above enumerated objectionable features and
which is moreover greatly more compact and therefore more economical
of construction, and more convenient in use than the air compressing
machinery heretofore used.
For compressing air according to my Invention I arrange the pumps
and a steam engine for working them upon one frame. The said pumps
are single acting, the pumps and engine are placed vertically on the
frame, and their pistons are connected to one crank shaft, supported
to rotate in suitable bearings below the pumps on the bed or foundation
plate of the machine. These pumps admit the air at the downward
stroke of the piston, and compress it in the upward stroke. I prefer to
use two pumps with a common top chest, or receiver, into which the air
is discharged by both pumps, its return being prevented by valves, which
are forced open by the pressure at the upward stroke of the piston, and
which close at the termination of the up stroke. This top chest or
receiver by means of a pipe or pipes may communicate with an air
receiver or reservoir of any suitable construction. By having the pumps
arranged vertically the closing of the said valves at each stoke is effected

page_text: by their own gravity without the aid of springs. On the top flange of.
the pump cylinders is a plate, wherein are formed circular openings
which are covered by the aforesaid eduction valves. These valves are
of the poppet form, and their spindles or stems are guided in sleeves
formed on the covers of the air chest. This chest which extends across
both pump cylinders, not only serves as a recipient of the compressed -
air, but also braces and strengthens the top of the machine, and this
peculiar construction and arrangement of the chest and valves in com-
bination with the pump cylinders is an important feature of my..
Invention.
The air pump pistons are of the trunk form, that is to say, they are
extended to work through the bottom of the pumps, and are open at
their lower end to admit the connecting rod which is fitted upon a
wrist pin secured inside the piston near the upper end thereof. This
arrangement obviates any necessity for cross heads or guide ways for
the piston. Each piston has at its inner or upper end an induction valve;
whereby the air is admitted into the pump at each downward stroke of
the piston. The said valve is a flat disc with a spindle or stem which
is guided in a hole formed in the end of the piston. The connecting
rod wrist pin is placed as near as practicable to the valve.
To obviate the difficulty arising from the varying resistence to the
pump pistons, I arrange the cranks as follows:- As before stated the
engine and pumps are both connected directly to one crank shaft, which
is driven by the engine and imparts the required reciprocating motion
to the pump pistons. The said shaft is cranked for the pumps, while for
the engine a crank pin may be fixed at the side of the fly wheel, the
pump crank pins are set at an angular distance apart of one hundred and
eighty degrees, and the engine crank pin has about forty-five degrees
"lead," that is to say it is set so much in advance of one of the pump
cranks in the direction of rotation.
My Invention partly consists in the compact arrangement of my
improved pumps and the engine vertically upon the frame and in
connection with one crank shaft, but if desired I may construct a
machine in which my improved pumps with the aforesaid peculiar
arrangement of the cranks may be combined with a horizontal or
inclined engine cylinder.
To prevent the heating of the parts and the ill effect thereof upon the
I intendues gold water into the said numn's*
C 11.

page_text: between the induction valve on the top of the piston and the eduction
valve, the water will as the piston ascends lubricate the surface of the
cylinder, and will also make the packing at the working surfaces more
perfectly air-tight. The water also forms a cushion for the valves
whereby they are lowered gently upon their seats, instead of striking the
same violently at each descent of the piston.
The main object however of the introduction of this water is the
one first stated, namely, the abstraction from the pumps of the heat
developed in compressing the air. The water may be supplied to the
pumps from a head or reservoir, or by the feed pump which supplies
the steam boiler, the supply pipe being furnished with a check valve to
prevent the escape of the air and the return of the water from the pumps,
or if desired a separate pump may be used, arranged and timed to
deliver only the required quantity to the air pumps. The excess of water
in the pumps with any vapor generated therein is carried away with the
compressed air to the receiver and naturally falls and accumulates in the
bottom of the same,
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Thomas Brown in the Great Seal Patent Office on
the 13th February 1871.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, THOMAS
BROWN, of Newgate Street, in the City of London, Civil Engineer,
send' greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Hor
Letters Patent, bearing date the Thirteenth day of August, in the year of
our Lord One thousand eight hundred and seventy, in the thirty-fourth
year of Her reign, did, for Herself, Her heirs and successors, give and
“grant unto me, the said Thomas Brown, Her special licenge that I,
the said Thomas Brown, my executors, administrators, and assigns, or
such others as I, the said Thomas Brown, my executors, administrators,
and assigns, should at any time agree with, and no others, from time
to time and at all times thereafter during the term therein expressed,
should and lawfully might make, use, exercise, and vend, within the
United Kingdom of Great Britain and Ireland, the Channel Islands,
and Isle of Man, an Invention for "IMPROVEMENTS IN MACHINERY FOR

page_text: COMPRESSING AIR," a communication to me from abroad by Charles
Burleigh, of Fitchburg, Massachusetts, United States of America, upon
the condition (amongst others) that I, the said Thomas Brown, mý
executors or administrators, by an instrument in writing under my, or
their, or one of their hands and seals, should particularly describe and
ascertain the nature of the said Invention, and in what manner the
same was to be performed and cause the same to be filed in the Great
Seal Patent Office within six calendar months next and immediately
after the date of the said Letters Patent.
NOW KNOW YE, that I, the said Thomas Brown, do hereby declare
the nature of the said Invention, and in what manner the same is to
be performed, to be particularly described and ascertained in and by
the following statement, reference being had to the accompanying
Drawing forming a part of this Specification.
The said Invention relates to machinery for compressing air to serve
as a medium whereby motive power generated in one situation may
be transmitted in a convenient and economical manner to operate engines
or machines in other situations.
The said Invention is chiefly designed to be used in connection with
rock drilling machines, when the same are employed in the formation of
shafts, tunnels, and deep cuttings, and in other like operations where
the use of steam would be very disadvantageous in consequence of the
loss arising from condensation and the inconvenience occasioned to the
workmen employed by the exhaust steam.
In forcing air under compression into a reservoir or air vessel the
working of the air compressing pumps has hitherto been attended with
certain difficulties, among the most important of which is that arising
from the varying resistance offered by the compressed air to the pistons
of the pumps, which resistance increases between the commencement
and the termination of each stroke of the pump from none or zero to the
full pressure in the air reservoir. Moreover, in the compression of air
the latent heat therein becomes sensible and heats the working parts of
the pumps, the consequent unequal expansion of these heated parts
causing great unnecessary friction, leakage of the valves, and other
difficulties which it has been attempted to obviate by causing a current
of cold water to flow around the heated parts.
By my present Invention I am enabled to construct a machine which
is entirely free from the above enumerated objectionable features, and

page_text: which is also much more compact, and therefore more economical of
construction, and more convenient in use than the air compressing
machinery heretofore employed.
For compressing air according to my Invention I arrange the pumps
and a steam engine for working them upon one frame. The said pumps
are single acting; the pumps and engines are placed vertically on the
frame, and their pistons are connected to one crank shaft supported to
rotate in suitable bearings below the pump on the bed or foundation
plate of the machine. These pumps admit the air at the downward strokė
of the piston and compress it in their upward stroke. I prefer to use two
pumps with a common top chest or receiver into which the air is
discharged by both pumps, its return being prevented by valves which
are forced open by the pressure at the upward stroke of the piston and
close at the termination of the up stroke. This top chest or receiver bý
means of a pipe or pipes may communicate with an air receiver or
reservoir of any suitable construction. By having the pumps arranged
vertically the closing of the said valves at each stroke is effected by their
own gravity without the aid of springs. On the top flange of the pump
cylinders is a plate, wherein are formed circular openings, which are
covered by the aforesaid eduction valves. These valves are of the
poppet form and their spindles or stems are guided in sleeves formed on
the covers of the air chest. This chest, which extends across both pump
cylinders, not only serves as a recipient of the compressed air, but also
braces and strengthens the top of the machine, and this peculiar
construction and arrangement of the chest and valves in combination
with the pump cylinders is an important feature of my Invention.
The air pump pistons are of the trunk form, that is to say, they are
extended to work through the bottom of the pumps and are open at
their lower end to admit the connecting rod which is fitted upon a
wrist pin secured inside the piston near the upper end thereof. This
arrangement obviates any necessity for cross heads or guideways for the
piston. Each piston has at its inner or upper end an induction valve,
whereby the air is admitted into the pump at each downward stroke of
the piston. The said valve is a flat disc with a spindle or stem which is
guided in a hole formed in the end of the piston. The connecting rod a
wrist pin is placed as near as practicable to the valve.
To obviate the difficulty arising from the varying resistance to the
pump pistons, I arrange the cranks as follows:-As before stated the

page_text: engine and pumps are both connected directly to one crank shaft, which
is driven by the engine and imparts the required reciprocating motion to
the pump pistons. The said shaft is cranked for the pumps, while for
the engine a crank pin may be fixed in the side of the fly wheel, the
pump crank pins are set at an angular distance apart of one hundred and
eighty degrees, and the engine crank pin has about forty-five degrees
"lead," that is to say, it is set so much in advance of one of the pump
cranks in the direction of rotation.
This Invention partly consists in the compact arrangement of my
improved pumps, and the engine vertically upon one bed or frame and in
connection with one crank shaft; but if desired I may construct a machine
in which my improved pumps with the aforesaid peculiar arrangement
of the cranks may be combined with a horizontal or inclined engine
cylinder.
To prevent the heating of the parts and the ill effect thereof upon the
working of the pumps, I introduce cold water into the said pumps
between the induction valve on the top of the piston and the eduction
valve, the water will as the piston ascends lubricate the surface of the
cylinder, and will also make the packing at the working surfaces more
perfectly air-tight. The water also forms a cushion for the valves,
whereby they are lowered gently upon their seats, instead of striking the
same violently at each descent of the piston.
The main object however of the introduction of this water is the one
first stated, namely the abstraction from the pumps of the heat developed
in compressing the air. The water may be supplied to the pumps from a
head or reservoir or by the feed pump which supplies the steam boiler,
the supply pipe being furnished with a check valve to prevent the.
escape of the air and the return of the water from the air pumps, or if
desired a separate pump may be used, arranged and timed to deliver
only the required quantity to the air pumps. The excess of water in the
pumps with any vapor generated therein is carried away with the
compressed air to the receiver and naturally falls and accumulates in the
bottom of the same.

page_text: section af the aforesaid top piece or chest and pump cylinders. Like
letters indicate the same parts in both of the Figures.
a is the bed plate having cast on it the bearings for the crank shaft b;
c, d, are the pump crank wrists, and e is the steam engine crank wrist
on which is fitted the connecting rod e¹ of the steam engine a²; f, g, are
the pump cylinders which are firmly supported upon the frames or
standards a¹; h is a plate fitted on the top flanges of the cylinders f; g;
the said plate having two circular openings concentric with the bore
of the said pumps. This plate forms the seat for the eduction valves i,
whose stems fit and are guided in the sleeves ¹ of the covers; of the
top piece or chest k.
The construction of the pump pistons / is clearly illustrated in Figure 1,
the piston of one pump being shewn in section, and that of the other in
dotted lines; is the slight inwardly projecting flange, which forms the
seat of the induction or inlet valve m, and m¹ is the check spindle of the
said valve, which is fitted in the guide piece or bridge n fixed or formed
in the hollow piston. In Figure. 2 the cylinder f is shown partly in
section on the line x, x, and the cylinder g on the line y, y. Below
these guide pieces are the wrist pins o which are connected to the crank
wrists or pins c, d, by the rods o¹. The direction of rotation of the
shaft is indicated by the arrow, Figure 1. The revolution of these
cranks imparts to the air pump pistons the required reciprocating
motion, the valves m lift as the pistons descend admitting air through
the top of the said pistons into the air pump cylinders f, g, when the
pistons begin to rise in the said cylinders, the valves me immediately
close, and the air above them in the cylinders is compressed until its
elastic force is sufficient to overcome the weight of the valve i and the
pressure of the air in the reservoir with which the chest k communicates
through the pipe p. The pipes q which enter the cylinders near the top
of the same, as shewn in Figure 1, serve to convey the water to the said
pumps, and these pipes if required may have a check valve as herein-
before described to prevent the back flow of the water.
Having thus fully described the said Invention as communicated to me
by my foreign correspondent, I claim,-
First. An air compressing machine or engine with the air cylinders
connected to a common top chest and with the air and steam cylinders
supported on one bed or frame, and connected to a single-rotating crank

page_text: shaft whereon the crank are arranged in the relative positions shewn, all
substantially as herein set forth for the purposes specified.
Second. In an air compressing machine or engine, with the cylinders
and other parts constructed and arranged as herein described, the means
for introducing water into the air pumps between the top of the pump
pistons, and the eduction or delivery valves, substantially as set forth for
the purposes specified.
In witness whereof, I, the said Thomas Brown, have hereunto set
my hand and seal this Eleventh day of February in the year of
THOMAS BROWN. (L.S.)
Witness,
W. ROBT. LAKE.