IMPROVEMENTS IN MACHINERY FOR COMPRESSING AIR
Year: 1873

page_text: LETTERS PATENT to John Sturgeon, of Bolton-le-Moors, in the County
of Lancaster, Engineer, for the Invention of "IMPROVEMENTS IN
MACHINERY FOR COMPRESSING AIR."
Sealed the 23rd December 1873, and dated the 1st July 1873.
PROVISIONAL SPECIFICATION left by the said John Sturgeon at the
Office of the Commissioners of Patents, with his Petition, on the
1st July 1873.
I, JOHN STURGEON, of Bolton-le-Moors, in the County of Lancaster,
Engineer, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN MACHINERY FOR COMPRESSING AIR," to be as follows:-
:-
My Invention has for its object "Improvements in Machinery for
Compressing Air," & consists in the first place in certain improvements
in the valves & valve mechanism of pumps used for compressing air.
Heretofore the induction or inlet valves of air compressors have been
generally made to open for the admission of air into the cylinder by the
formation of a vacuum in the cylinder by the receding movement of the

page_text: piston; but this mode of actuating the valves has been found in practice
to be defective & uncertain in its action, more particularly at high speeds,
and is attended with considerable waste of power owing to the com-
pressed air left in the valve passages & the clearance space after cach
stroke of the piston.
Various plans have been from time to time proposed to overcome these
difficultics, but hitherto without success.
According to my Invention I place the inlet valve in the centre of
the cylinder cover of the compressor, having its boss fitting closely
round the piston rod, the latter being free to slide through it, but the
friction between the two being sufficient to draw the valve open as the
piston begins to move away from it, and to push it shut as soon as the
piston begins to move towards it. By this arrangement the valve is
made to open & shut regularly at the commencement of each stroke of
the piston, no matter at what speed the piston may be driven.
In order to enable the friction between the valve & the piston rod to
be adjusted to the requisite degree I place a stuffing box in the boss of
the valve, by means of which the amount of friction may be so regulated
that it cannot draw the valve open until the pressure of the air left in
the cylinder acting against it is relieved by the receding movement of
the piston, while at the same time it is sufficient to close immediately
the valve towards which the piston is moving, there being in that case
no opposing pressure to be overcome. By this means the power which
has been taken up in compressing the air left in the clearance space and
valve passages is not thrown away, as the elastic force of the air so left
is in reality then assisting to propel the piston in its return stroke,
thereby relieving the driving engine. The inlet valves.may however be
actuated on the above described principle, although they may be situated
otherwise than as above described. In such case they may be actuated
by means of suitable frictional mechanism from the rod of the compressor
or driving engine through suitable intermediate gear, the action being
substantially the same as above described; or they may be actuated in a
similar manner by means of a rod or rods moved to & fro by the engine,
& carrying the frictional mechanism for actuating the valves, or acting
direct on the valves substantially as above described. I also place the
delivery valves in the cylinder cover, arranging them in an outer circle
around the central inlet valve, and I make the cylinder cover hollow, so

page_text: .
as to form an air chamber, into which the delivery valves open direct
when the pressure in the cylinder is sufficient to overcome the resistance
against them. The delivery valves being thus placed directly opposite
the direction of movement of the piston offer less resistance to the
passage of the air than in any other position, and I further lessen that
resistance by making the passages into the valves as near as possible of
the form of the " vena contracta." By these means the heating of the
air in compressing will be greatly reduced.
I also arrange the inlet and delivery valves in the cover of the air
cylinder in the following manner:-I make the delivery valve of nearly
the same diameter as the air cylinder, & set concentrically therewith.
This valve may be either a metallic valve, or a circular flap valve; if
the former, I provide it with a boss passing through a stuffing box in the
cylinder cover; if the latter, the stuffing box is not required. The inlet
valve fits round the piston rod, as above described, its boss passing
through the centre of the boss of the delivery valve, leaving a space
between the two for the inlet of the air, & having its seating formed in
front of or on the face of the delivery valve inside the cylinder, so that
one valve, the inlet, is in fact within the other, the delivery, and concentric
therewith, the cylinder cover being made hollow, as above described.
My Invention consists in the next place in making the bed or frame
to which the compressor is attached of a hollow section, so as to serve as
a receiver for the compressed air, thereby dispensing with the necessity.
of a separate receiver and the intermediate piping.
It is usual in machines for compressing air to surround the air cylinder.
with water, in order to prevent the overheating of the metal by the heat
generated in compressing the air. In order that the heat thus imparted
to the water may not be entirely lost I propose to feed the boiler which
drives the compressing engine with the water thus used to cool the air
cylinder, a fresh supply of cold water being regularly fed into the tank
surrounding the air cylinder to supply the place of that drawn out to.
feed the boiler. I thus keep up a continual renewal of cold water round.
the air cylinder, and a large proportion of the heat generated in com-
pressing the air is returned to the boiler.
My Invention consists in the next place in an improved arrangement
of mechanism whereby the driving engine is enabled to regulate its speed
automatically according to the quantity of compressed air required.

page_text: For this purpose I apply to the receiver a piston or other equivalent
contrivance in such a manner that when the pressure in the receiver
rises it imparts a movement in one direction to the piston, which through
suitable intermediate gear acts upon the valve of the driving engine so
as to shorten its stroke, & thereby reduce its speed or stop it altogether,
and as the pressure lowers the contrary action takes place, & the stroke
of the valve increases, giving a greater speed to the engine, so as to keep
the pressure in the receiver.
up
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said John Sturgeon in the Great Scal Patent Office
on the 1st January 1874.
TO ALL TO. WHOM THESE PRESENTS SHALL COME, I, Jo¤ò
STURGEON, of Bolton-le-Moors, in the County, of Lancaster, Engineer,
send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the First day of July in the year of our
Lord One thousand eight hundred and seventy-three, in the thirty-
seventh year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said John Sturgeon, Her special licence
that I, the said John Sturgeon, my executors, administrators, and
assigns, or such others as I, the said John Sturgeon, 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 COMPRESSING AIR," upon the condition (amongst others)
that I, the said John Sturgeon, my 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 Inven-
tion, 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,

page_text: NOW KNOW YE, that I, the said John Sturgeon, do hereby declare
the nature of my said Invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the
following statement:-
My Invention has for its object improvements in machinery for
compressing air, and consists in the first place in certain improvements
in the valves and valve mechanism of pumps used for compressing
air.
Heretofore the induction or inlet valves of air compressors have
been generally made to open for the admission of air into the cylinder,
by the formation of a vacuum in the cylinder by the receding move-
ment of the piston, but this mode of actuating the valves has been
found in practice to be defective and uncertain in its action, more
particularly at high speeds, and is attended with considerable waste of
power, owing to the compressed air left in the valve passages and the
clearance space after cach stroke of the piston.
Various plans have been from time to time proposed to overcome
these difficulties, but hitherto without success.
According to my Invention I place the inlet valve in the centre
of the cylinder cover of the compressor having its boss fitting closely
round the piston rod, the latter being free to slide through it, but the
friction between the two being sufficient to draw the valve open as
the piston begins to move away from it, and to push it shut as soon
as the piston begins to move towards it. By this arrangement the
valve is made to open and shut regularly at the commencement of
cach stroke of the piston, no matter at what speed the piston may be
driven.
In order to enable the friction between the valve and the piston
rod to be adjusted to the requisite degree, I place a stuffing box in
the boss of the valve, by means of which the amount of friction may
be so regulated that it cannot draw the valve open until the pressure
of the air left in the cylinder acting against it is relieved by the
receding movement of the piston, while at the same time it is sufficient
to close immediately the valve towards which the piston is moving,
there being in that case no opposing pressure to be overcome. By
this means the power which has been taken up in compressing the
air left in the clearance space and valve passages is not thrown away,

page_text: as the elastic force of the air so left is in reality then assisting to
propel the piston in its return stroke, thereby relieving the driving
engine. The inlet valves may however be actuated on the above-
described principle, although they may be situated otherwise than as
above described. In such case they may be actuated by means of
suitable frictional, mechanism from the rod of the compressor or
driving engine through suitable intermediate gear, the action being
substantially the same as above described; or they may be actuated
in a similar manner by means of a rod or rods moved to and fro
by the engine, and carrying the frictional mechanism for actuating
the valves, or acting direct on the valves, substantially as above
described. I also place the delivery valves in the cylinder cover,
arranging them in an outer circle around the central inlet valve; and
I make the cylinder cover hollow so as to form an air chamber, into
which the delivery valves open direct when the pressure in the cylinder
is sufficient to overcome the resistance against them. The delivery
valves being thus placed directly opposite the direction of movement
of the piston offer less resistance to the passage of the air than in any
other position; and I further lessen that resistance by making the
passages into the valves as near as possible of the form of the " vena
contracta." By these means the heating of the air in compressing will
be greatly reduced.
I also arrange the inlet and delivery valves in the cover of the air
cylinder in the following manner:-I make the delivery valve of
nearly the same diameter as the air cylinder, and set concentrically
therewith. This valve may be either a metallic valve or a circular
flap valve; if the former I provide it with a boss passing through
a stuffing box in the cylinder cover; if the latter, the stuffing box'
is not required. The inlet valve fits round the piston rod, as above
described; its boss passing through the centre of the boss of the
delivery valve, leaving a space between the two for the inlet of the
air, and having its seating formed in front of or on the face of tho
delivery valve inside the cylinder, so that one valve, the inlet, is in
fact within the other, the delivery, and concentric therewith, the
cylinder cover being made hollow as above described.
My Invention consists in the next place in making the bed or frame
to which the compressor is attached of a hollow section, so as to serve

page_text: as a receiver for the compressed air, thereby dispensing with the necessity
of a separate receiver and the intermediate piping.
It is usual in machines for compressing air to surround the air
cylinder with water in order to prevent the overheating of the metal
by the heat generated in compressing the air. In order that the heat
thus imparted to the water may not be entirely lost, I propose to feed
the boiler which drives the compressing engine with the water thus
used to cool the air cylinder, a fresh supply of cold water being regularly
fed into the tank surrounding the air cylinder to supply the place of
that drawn out to feed the boiler. I thus keep up a continual renewal
of cold water. round the air cylinder, and a large proportion of the heat
generated in compressing the air is returned to the boiler.
My Invention consists in the next place in an improved arrangement
of mechanism, whereby the driving engine is enabled to regulate its
speed automatically according to the quantity of compressed air re-
quired. For this purpose I apply to the receiver a piston or other.
equivalent contrivance in such a manner that when the pressure in the
receiver rises it imparts a movement in one direction to the piston,
which through suitable intermediate gear acts upon the valve of the
driving engine so as to shorten its stroke and thereby reduce its speed or
stop it altogether, and as the pressure lowers the contrary action takes
place, and the stroke of the valve increases, giving a greater speed to
the engine so as to keep up the pressure in the receiver.
DESCRIPTION OF THE DRAWINGS.
Fig. 1 is a side clevation and Fig. 2 a plan of a horizontal double'
acting air compressor constructed according to my Invention and
driven by a steam engine fixed to the same bed as the compressor. a,
Fig. 2, is the cylinder of the steam engine which transmits motion
through the shaft b, fly wheel c, and connecting rod d, to the piston c,
working in the air cylinder e¹, the covers of which f,f', are made hollow
to receive the air as discharged from the air cylinder, and are bolted
direct on to the bed of the machine g, g. This bed is made of a hollow
or box section, so as to serve the purpose of a receiver or air vessel, into
which the air compressed by the movement of the piston passes through
the hollow covers ƒ, ƒ.
The arrangement of the valves is shown on an enlarged scale in
Fig. 3, which is a section through and Fig. 4 which is an end view of

page_text: the air cylinder. e' is the air cylinder; e, the piston; and 7, the piston
rod; the same letters being used to denote the same or corresponding
parts in each Figure. i is the inlet valve, fitting close round the piston
rod h, and carrying the stuffing box and gland 2, and seated on front
of the bush inside the cylinder. This bush contains openings j, j,
through which the outer air passes into the cylinder, as soon as the back-
ward movement of the rod has drawn the valve open, by means of its
frictional hold upon it, the amount of opening being determined by the
position of the collar 3, which serves the purpose of a stop. k, k²,
are a number of small delivery valves which are placed in the hollow
cover f, in a circle surrounding the central inlet valve i, and are closed
in by the covers and guides k², &c., which are screwed in at the front
of the cover. These valves may be held against their scatings by springs
as at k², where needful, but when in a vertical position the springs will not
be required, and are opened by the pressure of air produced in the cylinder
by the forward movement of the piston e. The surfaces of the valves,
& the valve passages on the inside, facing the piston, are curved off
so as to approach as near as possible to the form of the " vena con-
tracta," and thereby lessen the resistance to the passage of the air from
the cylinder to the receiver.
From the above description the modified arrangements shown in
Figs. 5 and 6 will be readily understood. In Fig. 5 is the delivery
valve, of nearly the full diameter of the cylinder and seated in front
thereof, and is provided with a boss passing through the centre of the
cylinder cover and an india-rubber packing ring, of the form shown
at which serves the double purpose of a packing to prevent the escape
of air, and a spring to keep the valve up to its seating; i is the inlet
valve fitting round the rod 7 passing through the boss of the delivery
valve and scated on front thereof. In Fig. 6 k is again the delivery
valve, consisting of an india-rubber ring, or it may consist of a series of
india-rubber or metallic flaps radiating from the centre, and k¹ is the
seating containing a series of openings ² covered by the valves. The
inlet valve i is the same as described in reference to Fig. 5.
In applying that part of my Invention which relates to the actuating
of the inlet valves of air compressors by means of friction upon some
reciprocating part of the machine to air compressors already in
existence or of different constructions to those above described, it is
obvious that the details may be variously modified to suit the required.

page_text: The rising and falling of the air pressure in the receiver is caused to
impart the requisite up and down movement in the slot by acting upon
the piston p through the weighted lever p¹ and the rods q, q', as
shown on an enlarged scale in Fig. 9, in which g, g, shows a portion of
the hollow bed.
.
Instead of the piston or plunger a flexible pipe of india-rubber or
other suitable material may be used, as shown in Figs. 10 & 11. These
pipes lengthen or collapse as the pressure increases or diminishes,
thereby shortening or lengthening the stroke of the valve.
In witness whereof, I, the said John Sturgeon, have hereunto 1
set my hand and scal, this Thirty-first day of December, in the
year of our Lord One thousand eight hundred and seventy-
three.