Compressing Air.
Year: 1885

page_text: Compressing Air.
We ISAAC SHONE and EDWIN AULT, both of Pentrefelin House, Wrexham in
the County of Denbigh, North Wales, Civil and Mining Engineers do hereby
declare the nature of the said Invention for IMPROVEMENTS IN AND IN CONNECTION
WITH APPARATUS FOR COMPRESSING AIR to be as follows:-
Our Invention consists of certain improvements hereinafter particularly described
in and in connection with apparatus for compressing air, which are as follows. A
particular mode of arranging the air compressing cylinder, or cylinders in relation
to the steam cylinder, or cylinders for operating the air cylinder, or cylinders. A
mode of and apparatus for connecting and controlling the air inlet valves of the air
cylinder, or cylinders and a mode of and apparatus for regulating, or controlling
the action of the steam cylinder.
The following is a description of an apparatus for compressing air with our
improvements applied thereto. Upon a suitable bed plate, frame, or entablature,
there is, or are mounted one, or more horizontal steam cylinders, a convenient
arrangement being two horizontal cylinders, namely a high and a low pressure
cylinder forming a compound steam engine; or two high pressure steam cylinders
forining a twin engine, the connecting rods of which work two cranks set at right
angles to each other, on a horizontal shaft. The steam cylinders are arranged
sufficiently far apart to allow the air cylinders to be placed intermediate between
them in such a manner that the centre line of the air cylinders is vertically over
the centre line of the above mentioned crank shaft, which is provided with one
crank, or two parallel cranks to actuate the connecting rod, or rods of the air
compressing cylinders. When high and low pressure cylinders are used we prefer
to let the air compressing crank, or cranks be parallel to the crank of the low
pressure cylinder and at a right angle to the crank of the high pressure cylinder.
The two single acting air cylinders are supported by what is commonly termed
steam hammer standards, the top of these said standards forming a distance piece
with guides for the cross head, and the air cylinders are bolted to the upper and
lower end of the distance piece by suitable flanges, or lugs. The cylinders are
water jacketted and the bottom end of the lower cylinder and the top end of the
upper cylinder are provided with cylindrical valve boxes and delivery valves, the
valves being disc valves having their seat on the circumference or edge of the metal
ID 1071

page_text: of the cylinder, so that the valve opens round the whole of the said circumference.
The valves are held to their seats by springs and open into the cylindrical valve
box on the end of each cylinder respectively, to which valve box, the cover of the
cylinder is in each case bolted, or secured. The valve boxes of both cylinders are
connected by a pipe having an intermediate branch to which the compressed air
delivery pipe is attached. The pistons of the air cylinders are of ordinary type
with spring packing and have a central. valve in each piston opening into each
cylinder and being the air inlet valves. Each piston is rigidly connected by one, or
more parallel piston rods to a cross head guided by guide blocks in the above
mentioned guides of the distance piece and actuated by one, or two connecting rods
from the above mentioned air compressing cranks. The air inlet valves in the
above pistons are connected by a valve rod which passes and works through the
centre of the cross head. Above the cross head and on this valve rod, there is a
spiral spring, the object of which is to balance the two valves as much as possible.
The valves and valve rod are controlled by a friction clutch which may consist of
a block of lignum vitae, or equivalent material, which may be divided, or split in
line with the rod. This block is carried by brackets from the frame which supports
the air cylinders and a lever jaw, or cramping device worked by a screw rod is
provided for bringing the wooden blocks to bear upon the valve rod, so as to
control the working of the rod by friction. A toothed wheel and pawl is provided
in connection with the screwed rod, so that the amount of friction of the wooden
block on the valve rod can be regulated, or set. The action of the steam cylinder
is controlled by a regulating valve, which may be inserted at any convenient point
in the steam pipe. This regulating valve may take the form of a box, or.cylinder,
which contains a flexible diaphragm, or a small piston with a spiral, or helical
spring, either of which is connected with and actuates an equilibrium steam supply
valve. The box, or cylinder is in communication with the compressed air supply so
that the pressure of such air presses upon the piston, or diaphragm and thus
controls the steam supply. The connections may be through levers and rods and
the regulator is provided with a spring whereby the action of the flexible
diaphragm, or piston can be controlled so as to more, or less open, or close the
equilibrium steam valve. The effect of this device is that the pressure of the com-
pressed air is employed to govern the supply of steam to the steam engine and so
adjusts the speed of the steam engine and thereby keeps the pressure of the air in
the air main constant.

page_text: Figure 12 is a plan shown partly in section of a modified arrangement of the
friction clutch.
Figure 12 is a part of Figure 12 shown detached for convenience of space.
Figure 13 is a sectional elevation taken through X¹ X' Figure 12.
Figure 14 is a sectional elevation showing arrangement of inlet and outlet valves
of an air compressing engine according to our Invention when only one single
acting cylinder is used.
Figure 14 is a sectional elevation showing the arrangement of valve rods and
friction clutch in connection with the apparatus shown in Figure 14.
Figure 15 is a sectional elevation of the regulating valve according to our Inven-
tion. This Figure 15 is shown for convenience of space upon two sheets the dotted
line indicating the point of junction. Figure 154 is a part side view in section of
Fig. 15.
The more particular object of our Invention is the construction of a suitable
apparatus for supplying variable qualities of compressed air at variable pressures,
chiefly for use in connection with air injector apparatus for removing sewage, such
as that patented to Isaac Shone under Patent No 3524 A.D. 1878, but at the same
time, it will be obvious that the apparatus the subject of our present Invention can
be used for compressing air for other purposes.
Air compressing machinery has previous to our present Invention been mainly
designed much on the same principles as pumps for lifting water; the inlet and
outlet valves of most air compressors are nearly the same as valves used in water
pumps and air compressors have hitherto been designed to work at a uniform speed
and to compress the air that is not immediately used into air vessels, or receivers
exactly as water pumps lift water into reservoirs during those periods when little
water is used and such water is drawn from the reservoirs during those periods
when the consumption of water is greater than the supply from the pump.
We have found from practical experience that in the employment of compressed
air the valves of the air compressors must be arranged very differently to the valves
of water pumps in order to obtain economical results and also that neither sewage,
nor compressed air should be stored in receivers because sewage decomposes by
storage and should be carried off as quickly as it is emitted from its source, and
because compressed air can only be stored by compressing it to a higher pressure
than actually required and this involves a real and considerable loss of motive
power.
The essential features of our Invention are therefore as follows. The arrange-
ment of the inlet valves of air compressors in such a manner that they are not
dependant on the motion of the fluid for being opened and shut: neither are they
dependant on the friction of an elastic packing in the valves themselves, which
cannot easily be adjusted while the compressor is running, or dependant on the
momentum of working parts as the momentum varies as the square of the speed
and therefore can only be correct for one particular piston speed of the compressor.
The arrangement of the compressing cylinder in such a manner relatively to the
prime mover that they can be run at any speed namely five, or ten feet per minute
up to six hundred, or seven hundred feet piston speed per minute, so that we are
always able to supply exactly the quantity of compressed air required and are not
obliged to waste power in storing compressed air.
The regulation of the speed of the air compressor according to the pressure in
the air receiver, or air main so that when much air is required and the pressure
falls the compressor works quickly and conversely when little air is required the
pressure rises and the compressor works slowly.
The following is a description of an apparatus for compressing air with our
improvements applied thereto and embracing the features above set forth.
The example shown in reference to Figures 1. 2 and 3. is that of two single
acting air compressing cylinders driven by a horizontal high and low pressure
steam engine and arranged as follows. On the bed plate, or frame A there is
mounted a high pressure steam cylinder B and a low pressure steam cylinder B¹

page_text: together forming a compound steam engine the connecting rods of which work two
cranks C set at right angles to each other on a horizontal shaft D. The steam
cylinders B B are arranged sufficiently far apart to allow the air compressing
cylinders E to be placed intermediately between them in such a manner that the
centre line of the air cylinders E is vertically over the centre line of the crank
shaft D, which is also provided with two parallel cranks C₁ C₁ to actuate the
connecting rods F of the air compressing cylinders E. In using high and low
pressure cylinders, the air compressing cranks C¹ may be parallel to the crank of
the high pressure steam cylinder and at a right angle to the crank of the low
pressure cylinder. The air compressing cylinders E are supported by what are
commonly known as steam hammer standards G the top of which form a distance
piece G with guides G' for the cross head H bereafter spoken of. The two air
cylinders E E are respectively bolted to the upper and lower end of the distance
piece G¹ by flanges as shown. The air compressing cylinders are water jacketted
as shown in the Drawings. The bottom end of the lower cylinder E and the top
end of the upper cylinder E are provided with cylindrical valve boxes a and
delivery valves e, which are shown in detail at and hereinafter more particularly
described in reference to Figure 8 of the Drawings. The delivery valves e being
disc valves having their seat at e¹ on the circumference, or edge of the metal of the
cylinder E so that the valve e opens round the whole of the said circumference.
The construction will be understood on reference to Figure 8. The valve box a is
circular with an air delivery pipe a¹ and valve box cover a³. The valve e is circular
and has a cylindrical guide e¹ which slides in a corresponding cylindrical recess in
the valve box cover a². Small openings e³ are provided in the guide e¹ corre-
sponding openings a³ being provided from the valve box a so as to admit the
compressed air over the whole surface of the valve e so that the valve e is in
equilibrium even when the air to be compressed in the cylinder E reaches its
maximum tension. To overcome the weight of the valve e of the bottom cylinder E
and also to give a slight additional closing force to both the valves e of the bottom
and top cylinders E a spiral spring e' is provided. The tension of this spring e* can
be regulated by means of a screw e and a nut es which latter slides in two grooves
in the cover a³ to prevent it from revolving when the screw e is turned as shown
in Figure 7. By raising, or lowering the nut e the tension of the spring e* can be
regulated while the compressor is working. To prevent the escape of compressed
air, the screw e is provided with a conical plug e' ground to fit its seating in the
valve box cover a. The lift of the valve e is adjusted by a ring ea of india rubber,
or other suitable material laid round the guide e. The valve boxes a of the two
cylinders E are connected by a pipe a³, the ends of which join the delivery pipes a¹
the pipe a³ having an intermediate branch at and a cock as to which the compressed
air delivery pipe a is attached. The pistons d of the air cylinders E are of
ordinary type with spring packing rings and are shown in detail in Figures 4.
5 and 6. There are two pistons one for each cylinder E and they are firmly con-
nected together and to the cross head H by the rods d¹ so as to form a rigid
connection with the cross head H and with one another. The air inlet valve f is
arranged in the centre of each piston d in manner such as shown in the Drawings
so as to get the greatest free area of opening with the smallest lift. The air
inlet valves of the two pistons d are connected together by the valve rod h, the
length of which can be adjusted to give the required lift and so that when one
valve f is open the other valve f is closed. The valve rod h works freely through
a hole in the centre of the cross head H a spring h¹ being provided to balance the
weight of the valves f and their rod h. The valve spindle h allows the lift of
about half an inch to the valves f, but otherwise the valves f move with the
pistons d. The crosshead H and thereby the pistons d are actuated by the
connecting rods F from the cranks C¹.
The air inlet valves d and their valve rods h are controlled by a friction clutch i
shown in detail in Figures 9. 10 and 11. This clutch i is fitted on the valve rod h
below the cross head H and inside the distance piece G₁ and consists as follows: the

page_text: The
valve rod h is provided with and works through a longitudinally divided bearing i¹
preferably of hard wood. The two parts of this bearing i are firmly pressed against
the rod h by means of the clutch i which is formed of two parts, or jaws hinged
together at one end and adjustably brought together at the other end by means of
the screwed rod which screwed rod is adjustable from the outside of the
distance piece G¹ through which it passes as shown in Figure 9, and is adjusted
and held in its position by a cog wheel and pawl as shown in Figure 11.
friction clutch i is supported inside the distance piece G₁ by the brackets
shown in Figures 9 and 10 and is thus prevented from having vertical motion, but
at the same time it is free to have lateral motion in order that the tightening of the
jaws by the screw f* shall not exert lateral strain on the valve rod h and thus hinder
the free action of the inlet valves d, at the same time the device permits of the
wooden blocks i¹ being cramped upon the valve rod h so as to control the working
of the rod h by their friction.
as
The action of the steam cylinders B B¹ is controlled by a regulating valve which
may be inserted at any convenient point in the steam pipe. This regulating valve
is shown in detail in Figure 15. As we have explained above it is essential to the
economical working of air compressing machinery that the air should not be
compressed to a higher tension than actually required, because the work done in
raising the air to the required pressure is completely lost and only the work done
in forcing the compressed air out of the compressing cylinder is available for doing
useful work in non expansion engines. One of the objects of our Invention is
therefore to keep the air pressure as nearly constant as possible and to regulate the
speed of the engine by the pressure of the air in the receiver or the air mains.
Previous to our Invention this object has been sought by using automatic variable
expansion gear, but as such gear is always complicated and to some extent
unreliable and as our object is that the resistance should vary as little as possible
and consequently the range of expansion required would be very small, we prefer
to use on the steam cylinders slide valves of the plainest and most reliable
construction and to regulate the speed of the engine by the arrangement of
regulating valves shown at Figure 15 and of which the following is a description.
k is a valve box with flanges for the steam pipe k k through which the steam
travels in the direction indicated by the arrows. Z is an equilibrium bell valve of
any well known approved construction, having a valve spindle passing through
stuffing boxes on both sides of the valve box / to ensure perfect equilibrium. The
amount of opening of this valve is regulated by the pressure of the compressed
air in the receiver, or air main which is led into the cylinder m (which is fitted
onto the valve box k as shown) and under the piston p and against the action of
the spring n.
This spring n is shown detached in Figure 15 relieved from all
pressure and extended to its natural length and in Figure 15 it is shown in its
actual position during the working of the air compressor when the tension of the
air increases to its maximum value and the equilibrium valve l is shut.
It is evident that if for instance the normal working air pressure required be
say, forty pounds per square inch and the maximum pressure to be allowed is say
forty two pounds per square inch, the extra two pounds of pressure per square
inch will only give a very small contraction per coil to a spring strong enough to
sustain a normal pressure of forty pounds per square inch, we therefore to avoid
using a very long spring employ the compound multiplying lever o o¹ o³; the
lever o is moved directly by the piston p through the piston rod p¹ and the
movement imparted to it is increased any suitable number of times through
the link o actuating a second lever o².
As it may be desirable to increase, or diminish the normal working pressure of
the air in the receiver, or main, we provide a nut q with a hand wheel q'; by
turning this hand wheel q we can increase, or diminish the tension of the spring n
so that it takes a greater, or smaller pressure of air to close the valve land
diminish the speed of the engine. The rim of the hand wheel q¹ is provided with
notches q into which a pawl q³ falls so as to fix the hand wheel q¹ in any required

page_text: position. We provide this pawl q³ with an index q* showing the pressure to which
the valve is set either in pounds per square inch, or any other standard measure,
and we arrange the pitch on the screw 9 and the notches q' on the hand wheel q¹
so that each notch represents a pound per square inch, or a convenient fraction
of a pound per square inch, or any other suitable standard measure such as a
kilogramme per square centimetre.
To avoid stopping the engine, we provide the regulating valve with a by-pass
cock that can be adjusted, so that steam can be admitted in quantities just
sufficient to turn the engine round at the slowest possible speed when the valve
is closed. Instead of employing the small piston p above described a flexible
diaphragm can be used as an alternative, the other fittings of the regulating valve
being the same as those above described.
In Figures 12. 12 and 13 we have shown a modified arrangement of the
friction clutch above described in reference to Figure 9. In this modification the
divided bearings i¹ are pressed against the valve rod h by means of pivotted bars i
brought together by a screw with a nut provided with teeth and a pawl as
shown at Figure 13. This arrangement also prevents vertical motion of the bars i
and allows horizontal motion to prevent any lateral strain of the rod d.
In Figures 14 and 14* we show our Invention as applied to an air compressor
having one single acting cylinder, instead of two as in the example shown in
Figures 1. 2 and 3. In this case the air inlet valve rod h passes through an
opening in the delivery valve e. The air inlet valve and the delivery valves are
practically the same as those above described. The friction clutch, or bearing it
consists of a hollow cylinder preferably of hard wood, which is cloven at one end
(see Figure 144) so that it can be pressed against the sides of the rod h by being
forced into the conical recess in the delivery valve spindle. The delivery valve e
is pressed towards its seating in the same manner as before described by a spring e
the tension of which can be regulated by means of a screwed nut e which can be
turned from the outside while the compressor is working by turning the tube, or
spindle e which again turns through the valve the nut 6 by means of the studs e³.
The example of an air compressor according to our Invention which we have
shown in Figures 1. 2 and 3 is a very suitable type for air compressors indicating
thirty horse power and upwards, but for smaller sizes one, or more high pressure
cylinders can be substituted for the high and low pressure cylinders, arranged as
shown, or otherwise. For very large air compressors triple, or other multiple
expansion steam engines may be used to work the air compressing cylinders the
cranks being set at such angles as to ensure the greatest regularity of motion.
In further reference to Figures 1. 2 and 3 and in explanation of the working of
the air compressing engine therein shown, the compound steam engine, namely the
high and low pressure steam cylinders B B₁, the shaft D the cranks C the
standards G and distance piece G₁ being arranged as before described and shown in
the Drawings and the air compressing cylinders E, which are both of the same
construction being fixed respectively to the top and bottom ends of the distance
piece G¹ and the pistons d which are of the same construction, but reversed in
position being connected together and to the crosshead H by the rods d¹ the air
inlet valves of the pistons d are connected together by the valve rod h (which is
common to both valves f) and adjusted so that the combination of the valve rod h
and the two valves ff works freely giving the requisite lift for one of the inlet
valves so that in action when the valve f of one piston d is closed, the valve f of
the other piston d is opened. The valve rod h is then gripped by cramping the
friction clutch i, the tension being regulated as required in the following manner.
Presume the combined pistons move upwards the valve f of the upper piston will
be on its seating and the valve f of the lower piston be open and the combined
valves ff and the rod h will be moved upwards with the pistons in spite of the
retarding action of the friction clutch i. This retarding action of the friction
clutch is however sufficient to support the weight of the combined valves ff and
the rod / during the downstroke of the piston so that the valve ƒ of the upper piston

page_text: remains open during the downstroke of the piston so that when the upstroke is
completed the combined valves ff and the rod h are held in their highest position
by the friction clutch until the pistons d d have travelled the portion of the
downstroke equal to the lift of the valves f. During the remainder of the down-
stroke the valve f of the lower piston d is closed on its seat and the valve f of the
upper piston is opened and the piston d drags the combined valves ffand rod h
downwards through the friction clutch i. To render the action of the friction
clutch equal in vertical compressors the weight of the combined valves f and rod h
is preferably balanced by the spring h¹, but the use of this spring h¹ is not essential,
but it is desirable because it enables us to work with less pressure on the friction
clutch i.
Having now particularly described and ascertained the nature of our said
Invention and in what manner the same is to be performed we declare that what
we claim is:
First. The construction of apparatus for compressing air substantially as herein
described and shown in reference to Figures 1. 2 and 3 of the Drawings, which
construction consists in the particular arrangement of horizontal steam cylinders,
and vertical air compressing cylinders, having their cranks so arranged as to avoid
dead centres, as set forth.
Second. The arrangement of parts of the apparatus for compressing air as herein
described and shown in reference to Figures 1. 2 and 3 of the Drawings.
Third. In connection with air compressing apparatus of the type herein described
the use of a friction clutch in connection with and for actuating the air inlet valves
as set forth.
Fourth. The construction of adjustable friction clutch for actuating the air inlet
valves of air compressing apparatus substantially as herein described and shown in
reference to Figures 9. 10 and 11 of the Drawings hereto annexed.
Fifth. The construction of adjustable friction clutch for actuating the air inlet
valves of air compressing apparatus, substantially as herein described and shown in
reference to Figures 12. 12 and 13 of the Drawings hereto annexed.
Sixth. The construction of adjustable friction clutch for actuating the air inlet
valves of air compressing apparatus substantially as herein described and shown in
reference to Figures 14 and 14° of the Drawings hereto annexed.
Seventh. The construction of parts of the delivery valve substantially as herein
described and shown in reference to Figures 7 and 8 of the Drawings hereto
annexed.
Eighth. The means substantially herein described and shown in reference to
Figures 7 and 8 for adjusting the tension of the closing spring of the delivery valve
as set forth.
Ninth. The construction of parts of the delivery valve substantially as herein
described and shown in reference to Figures 14 and 144 of the Drawings hereto
annexed.
Tenth. The means substantially herein described and shown in reference to
Figures 14 and 14 of the Drawings for adjusting the tension of the closing spring
of the delivery valve as set forth.
Eleventh. The construction and arrangement of parts of the apparatus for
compressing air as herein described and shown in reference to Figures 14 and 14^
of the Drawings hereto annexed.
Twelfth. In air compressors of the type herein described and shown in reference
to Figures 1. 2 and 3 of the Drawings connecting the pistons of the air compressing
cylinders and their inlet valves to each other as herein described as and for the
purposes and operating as set forth.
Thirteenth. In air compressors of the type herein described and shown in
reference to Figures 1. 2 and 3 of the Drawings, the use of a spring to balance the
weight of the air inlet valves and their valve rod, as set forth.

page_text: Fourteenth. In connection with air compressing apparatus of the type herein
described the means substantially herein described of regulating the speed of the
compressor according to the tension of the compressed air in the receiver which means
consist in the employment of a piston, a flexible diaphragm or equivalent device
actuated by compressed air from the receiver to control the throttle, or equivalent
supply valve as set forth.
Fifteenth. The construction and arrangement of parts of the equilibrium throttle
valve for regulating the speed of air compressing apparatus according to the
tension of the compressed air in the air receiver or main and according to the
quantity of compressed air required at each moment, substantially as herein
described and shown in reference to Figures 15 and 15ª of the Drawings hereto
annexed.
Sixteenth. The use in combination with regulating valves for air compressors of
a by-pass and cock such as r, as and operating as herein described in reference to
Figure 15 of the Drawings hereto annexed.
Seventeenth. The combination of an air compressor, or compressors constructed
as herein described and shown in reference either to Figures 1. 2, and 3, or to
Figures 14 and 14ª of the Drawings with one, or more steam cylinders which may
be of high pressure, condensing, compound, triple expansion, or other known type.
Dated this ninteenth day of February 1886.