LMPROVEMENTS IN THE CONSTRUCTION OF ENGINES OR OTHER PRIME MOVERS USING COMPRESSED AIR FOR THEIR MOTIVE POWER
Year: 1880

page_text: LETTERS PATENT to William Dredge, of 10, Buckingham Streot, Adelphi, in
the County of Middlesex, Civil Engineer, for an Invention of "LMPROVEMENTS
IN THE CONSTRUCTION OF ENGINES OR OTHER PRIME MOVERS USING
COMPRESSED AIR FOR THEIR MOTIVE POWER."
PROVISIONAL SPECIFICATION left by the said William Dredge at the
Office of the Commissioners of Patents on the 15th October 1880.
WILLIAM DREDGE, of 10, Buckingham Street, Adelphi, in the County of
Middlesex, Civil Engineer. "IMPROVEMENTS IN THE CONSTRUCTION OF ENGINES
OR OTHER PRIME MOVERS USING COMPRESSED AIR FOR THEIR MOTIVE POWER."
Inside a tank I construct a reservoir in form and capacity proportioned to the
work required to be done, into which I compress my pump or pumps worked by
steam, wind, or water, according to which of these motive powers. is best adapted to
the locality and the purpose to which my Invention is to be applied. The heat
developed by the compression is removed by the action of cold water flowing over
and around the pumps and pipes through which the air passes on its way to the
reservoir, but the temperature finally developed at which it is delivered is
maintained in the reservoir, and for this purpose the tank is filled or partly filled
with water kept warm by flues from the engine furnace (if steam power for
compression is used), passing through and around the tank, or, where other than
steam power for compressing is applied, by a small fire within the tank.
For stationary engines I conduct or convey the air to the spot where it is to be
used, but for tramways the locomotive engine would stand alongside the fixed
reservoir and charge its receiver.
From the locomotive receiver the compressed air flows along pipes through two
valves into a vessel or tube, which I call the regulator. The first of these valves
through which the air flows is under the control of the attendant, who by it
regulates and maintains the density of the air in the regulator, proportional to the
work that is at the time being done by the engine. The other valve opens inwards
towards the regulator and stops any back-flow, should the pressure at any time
within the regulator be in excess of the pressure outside it, which under certain
conditions, as presently described, it may sometimes be.

page_text: From the regulator, when the engine is in motion, the air flows past the starting
and stopping valves into a small cylinder which I call No. 1 (Nos. 2, 3, 4, &c.,
follow), within which it expands and the exhaust flows through a tube or tubes into
cylinder No. 2, when it again works expansively and passes on from the eduction
side into the induction of No. 3, where it is still further expanded and discharged
through a tube or tubes into cylinder No. 4, within which the attenuation is
continued, and from which the air would probably be finally discharged. But the
process may be continued to cylinders 5 and 6, indeed until there were no further
available energy left in the air.
I prefer arranging the cylinders in two parallel lines, so that two piston rods only
may be required. On one piston rod I would probably attach the pistons of No. 1
and 4 cylinders, and on the other piston rod the pistons of Nos. 2 and 3 cylinders,
thus working direct on the driving shaft or axle in the usual way at right angles
to each other without alteration of the gearing and motion now in use. I do not
however confine myself to this arrangement of the cylinders should circumstances
make it desirable to modify it.
The whole of the apparatus or machinery as above described is fixed to the
bottom of a tank carried by the frame of the engine, the ends of which are
removable, so that the piston rods, valve spindles, and all the motions for working
and controlling the engine are carried through glands in one or both ends
as required.
The tank is filled or partly filled with water, kept as nearly as practicable to a
boiling point by means of a small furnace within it supplied from the exhaust air
from the last cylinder, the products of combustion flowing through a tube lying on
the bottom of the tank.
A sinall donkey engine is fixed on the foot plate to be driven by air from the
receiver, for the purpose of increasing when required the density of the air
in the regulator.
My Invention is substantially the same as above described when applied to
stationary engines, the difference being that the stationary engine is driven either
direct from the reservoir or from a portable reservoir in lieu of a receiver.
The advantages I claim are that I can, by the means I have above generally
described, maintain an uniform or nearly uniform temperature of the compressed air
from the time of its leaving the compressors until it is finally discharged, as well as
regulate the pressure on the piston in proportion to the work the engine has to
overcome, and also to utilize the air until all potential energy is removed more
effectually and economically than it is at present done, and the machinery and
arrangements to effect this as above described substantially constitute my
Invention.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said William Dredge in the Great Seal Patent Office on the 28th
February 1881.
WILLIAM DREDGE, of 10, Buckingham Street, Adelphi, in the County of
Middlesex, Civil Engineor. "IMPROVEMENTS IN THE CONSTRUCTION OF ENGINES
OR OTHER PRIME MOVERS USING COMPRESSED AIR FOR THEIR MOTIVE POWER."
Inside a tank I construct a reservoir, in form and capacity proportioned to the
work required to be done, into which I compress air by pump or pumps worked by
steam, wind, or water, according to which of these motive powers is best adapted
to the locality and purpose to which my Invention is to be applied. The heat
developed by the compression is removed by the action of cold water flowing over
and around the pumps and pipes through which the air passes on its way to the
reservoir, but the temperature finally developed at which it is delivered is main-
tained in the reservoir, and for this purpose the tank is filled or partly filled with
water kept warm by flues from the engine furnace (if steam power for compression
is used) passing through and around the tank; or, where other than steam power
for compressing is applied, by a small fire within the tank.
For stationary engines I conduct or convey the air to the spot where it is to be
used, but for tramways the locomotive engine would stand alongside the fixed
reservoir and charge its receiver.
.
From the locomotive receiver the compressed air flows along pipes through two
valves into a vessel or tube which I call the regulator. The first of these valves
through which the air flows is under the control of the attendant, who, by it,
regulates and maintains the density of the air in the regulator proportioned to the
work that is at the time being done by the engine. The other valve opens inwards
towards the regulator, and stops any back flow, should the pressure at any time
within the regulator be in excess of the pressure outside it, which, under certain
conditions, as presently described, it may sometimes be.
From the regulator, when the engine is in motion, the air flows past the starting
and stopping valves into a small cylinder, which I call No. 1 (Nos. 2, 3, 4, &c.,
follow), within which it expands, and the exhaust flows through a tube or tubes
into cylinder No. 2, where it again works expansively, and passes on from the
eduction side into the induction of No. 3, where it is still further expanded and
discharged through a tube or tubes into cylinder No. 4, within which the.
attenuation is continued, and from which the air would probably be finally
discharged. But the process may be continued to cylinders 5 and 6; indeed, until
there were no further available energy left in the air.
I prefer arranging the cylinders in two parallel lines, so that two piston rods only
may be required. On one piston rod I would probably attach the piston of Nos. 1
and 4 cylinders, and on the other piston rod the pistons of Nos. 2 and 3 cylinders,
thus working direct on the driving shaft or axle in the usual way at right angles to
each other, without alteration of the gearing and motion now in use.
I do not however confine myself to this arrangement of the cylinders, should
circumstances make it desirable to modify it.
The whole of the apparatus or machinery, as above described, is fixed to the
bottom of a tank carried by the frame of the engine, the ends of which are
removable, so that the piston rods, valves, spindles, and all the motions for working
and controlling the engine are carried through glands in one or both ends as
required.
The tank is filled or partly filled with water kept as nearly as practicable to a
boiling point by means of a small furnace within it, supplied from the exhaust air
"

page_text: from the last cylinder, the products of combustion flowing through a tube lying on
the bottom of the tank.
A small donkey engine is fixed on the foot plate to be driven by air from the
receiver, for the purpose of increasing when required the density of the air in the
regulator.
My Invention is substantially the same as above described when applied to
stationary engines, the difference being that the stationary engine is driven either
direct from the reservoir or from a portable reservoir in lieu of a receiver.
The advantages I claim are that I can, by the means I have above generally
described, maintain an uniform, or nearly uniform, temperature of the compressed
air from the time of its leaving the compressors until it is finally discharged, as
well as regulate the pressure on the piston in proportion to the work the engine
has to overcome, and also to utilize the air until all potential energy is removed,
more effectually and economically than it is at present done. And the machinery
and arrangements to effect this, as above described, substantially constitute my
Invention.
I will now proceed, with the assistance of the accompanying Drawings, to describe
the manner in which my Invention is to be carried into effect.
The compression of the air, either by steam or water power, and the cooling or
abstracting the heat between each successive stage of the compression, is in common
use, but the application of wind power for this purpose is new, and my method of
applying it is as follows:-
Fig. I represents a number of windmills W, W, &c., W, built at some distance
1
1
2
1
1
apart and in such positions as are most suitable and convenient. Fig. 2 shews the
internal arrrangement of the machinery employed; is the crown wheel as in an 2
ordinary windmill, receiving power and motion direct from the sails; S. and S are
conical drums arranged as shewn; the first is driven from off the crown wheel
shaft through gearing, the other S is driven off S by means of the belt T,
regulated by governor x. From off a pulley on the drum S the pump or pumps
V and V are worked. When more than one is used they are differential pumps.
The air passes from the pump V through the pipe c, which is surrounded by water
in an outside pipe b, as shewn, to the pumps in windmill W, when it is further
compressed, and the same process takes place as in windmill W, after which it is
passed on to windmill W, and so on to windmill W; or, as I do not confine myself
to the use of any fixed number of compressions, to W.
1
I
8
1
Б
11
1
When the air has received its final compression it is forced from the last pump
into the reservoir 0¹, Fig. 1.
I
2
3
Between each windmill there is a subsidiary reservoir 0¹, 01, 0', &c., with
pressure valves to regulate the supply to each windmill in proportion to the work
it can do.
Whatever means of compression are used the store reservoir O' would be the
same, and would most probably be composed of tubes, or coils of tubes, and from
which the air would be supplied through a pipe P¹ either to charge the receiver of
the locomotive, or to supply power to work the stationary engine.
1
1
For locomotive purposes I should fix the tubes forming the reservoir into a tank
partly filled with water, which, when steam is used as the compressing power, I
should keep warm by passing the waste steam from the engine furnace into and
through it, but when water or wind is used for compressing, I would keep the
water in the tank warm by a small furnace, similar to that presently described,

page_text: the reservoir.
Fig. 3 is an outline elevation of a locomotive engine built according to my
Invention.
Fig. 4, a section on the line A, A.
Fig. 5, a section on the line B, B.
Fig. 6, a section on the 'line C, C.
Fig. 7, a section on the line D, D, D, D.
Fig. 8, a section on the lino E, E.
Fig. 9, a section on the line F, F.
Fig. 10, a section on the line G, G, and
Fig. 11. a section on the line H, H.
The same letters of reference indicate the same parts in each of the above
Figures.
I is the frame of the locomotive engine; J, a cast iron tank fitted with removable
ends K, K. It is fastened to the engine frame and contains the motive machinery;
it is filled with water to the level a, a. L is the receiver or subsidiary locomotive
reservoir, which is here shewn as formed of tubes. This receiver is charged through
the pipe P¹ from the reservoir O', Fig. 1.
1
I
Mis the regulator tube, into which, just before the engine starts, and whilst it
is working, air flows from the receiver L through the valve b, pipe N, and valve c,
entering into the regulator M in the direction of the arrow. The valve b is under the
control of the attendant, so that he can regulate the opening and admit just as
much air, and no more, than is consumed by the engine, and maintaining in the
regulator tube M the required density; e is a pipe communicating with the donkey
engine, which is presently specified; f, a pipe leading from the regulator M to the
valve box of the starting or stopping valvo g, which corresponds to the regulator
or throttle valve in the ordinary engine. This valve is also controlled by the
attendant.
1
The air, after passing the valve g, enters in the ordinary way through the slide
valve box into cylinder O where it works expansively, and the exhaust is discharged
through the tubes Q into the slide valve box of cylinder O, in which cylinder it is
again expanded and escapes in the same way into cylinder O, and, after doing the
work in that cylinder, the exhaust is again discharged through the tubes Q into
Qi
cylinder O, from which it is here shewn to flow away through the pipe n into the
small furnace R.
3
Figs. 5, 6, and 9 shew the arrangement of pistons and cylinders with reference
to the action on the driving axle.
The whole machinery and motion with the tubes Q, Q, &c., is fixed to the bottom
of the tank J, the ends K, K, fastened on, and glands i, i, 1, 1, 1, &c., formed, through
1 2
which the piston rods and spindles of slide valves work. The tank, when the
ends K, K, are bolted on, is water tight, and is filled with water to the level a, a,
covering by a few inches the crown of the small furnace R.
The products arising from the combustion pass off through the tube S lying at
the bottom of the tank.
:
A cover T made of some imperfect conducting material, as wood, and lined with
iron, and easily removable, covers the receiver and prevents the escape and waste
of heat and steam.
The starting and stopping valves are marked m, m, m, and are worked by the
I
2
spindles and n through the glands and l. The handle O is.keyed to one of
these spindles, and controls its action and the travel of the valves.
1

page_text: The spindles work simultaneously, being connected by bevelled gearing as
shewn.
The starting and stopping valves are represented in the Figures as they would
be when the engine was in motion, and the valve ? through which the air passes
from the regulator M to the cylinder is open.
After the action of the air on the piston P it flows through the exhausts and the
2
2
1
2
1
tube to the valve box of the cylinder O, and passing the slide valve works the
piston P, after which it flows along passages and ports p and to the valve box
of cylinder O along the passage indicated by the dotted lines, where, after acting
on piston P it passes through the channel s to pipe Q and through to valve box of 1
cylinder O, where it drives the piston P, and then flows to exhaust through
+
8
3
4
3
ports p and p to pipe n which carries it away.
a
1
1
To stop the engine reverse the handle O acting on the spindles n and n, which
will move the valves m, m, and m, from the position in which they are now
shewn to that in which they will cover the ports P, P, and P,
leaving the ports
and
P open.
1
1
2
2
B
?
When, as in this position, p is closed, all communication with the regulator M is
cut off, and the piston P would be moving against the pressure of air in the tube Q.
The air in tube would still continue to flow into the valve box O, and afterwards
through the ports p and
P
back to pipe Q. The connection with cylinder O is cut 2
off by closing the port 2, and the piston is working against the pressure of the air
in Q, but as before with reference to cylinder O, so here the air in the tube Q
presses on the piston P, but instead of the exhaust flowing away to waste it flows
back through the ports p and p to the tube Q from which it came.
0
G
I
-y
1
U is a donkey engine driven by air from receiver L through the pipe q. On one 2
side the piston is worked by the air, the exhaust flowing away; on the other side
the air is compressed and forced back through the pipe e into the regulator M,
thereby obtaining any pressure in the regulator M. for any special occasion which
may be required to work the engine U.
Fig. 13 is the section of a stationary engine constructed according to my Invention 3
on the line 3-3.
Fig. 14, a section on the line 2-2. 2, 2.
Fig. 15, a section on the line 1-1.
1
1
P is a pipe conducting compressed air from the reservoir 01, Fig. 1, to the
stationary engine, which in Figs. 13, 14, and 15 is drawn to a larger scale.
Within a tank B' having a movable cover the engine here represented has three
1
cylinders F¹, F, and F, ascending in capacity in the ratio required. The first
cylinder F, into which the air flows, has its valves worked by automatically
expanding gear. The expansion in the cylinders F and F is fixed by the ratio
of their sizes, and the cut off is constant.
The tank is filled with water to the level al, a", which a small furnace G' keeps
boiling or nearly boiling, the products of combustion flowing along the tube M, M²,
and out at the uptake T¹.
The air, entering by the pipe P¹ passes along the tubes C¹ to the valve box in
through the port p¹ to the cylinder F in the way as before described. From this
1

page_text: where
the air, which is chilled by expanding, passes along the channel n¹, shewn, to
tube D¹, and is here again warmed to the temperature of the water before it enters
the valve, box m³, and flowing through the port p¹ into the cylinder F¹¹,
working the piston it is again expanded, and passing along the channels n¹ to E¹
into cylinder F, the temperature being raised before entering F" when passing
through the tube E¹. From this last it goes into the uptake T¹ or else in the
furnace G¹.
I
S
The piston rods and valve spindles are taken through the glands 1, 1, 1, &c.
The regulator valves m², m³, and m² are worked by the spindle n', which passes
1
2
8
1
through the glands S¹ on the side of the tank, and is under the control of the
1
attendant, by the wheel R', which works a screw and regulates the flow.
The tubes D' and E' can be placed in communication with the tube C¹; a pipe
connects them, but the communication is controlled and can be stopped by the
attendant, who commands the valves in the pipes of connection; and, similarly, the
same may be said of the locomotive previously described.
Although in Fig. 12 I shew a section (greater than full size) of the kind of valve
I intend to use for controlling or stopping the flow of air from the receiver or
reservoir to the working parts of the engine, and have also in the other Figures
shewn all the valves of transmission as ordinary slide valves, I do not limit my
action to the use of these or any other kind of valves.
Having thus described the nature of my Invention and. the manner in which I
carry it into practice, I claim,—
1st. Compressing the air by the use of windmills, substantially as shewn,
2nd. The use of a reservoir holding compressed air within a tank containing
water, and maintained at a high temperature by means of waste steam or furnace,
as described.
3rd. The use of a tank holding water, within which the working parts of the
engine are fixed.
4th. The mode of heating the water by means of a furnace within the tank con-
taining the machinery, and passing the products of combustion through the water,
substantially as described.
5th. For locomotives the arrangement of the cylinders for the purpose of working
then expansively two or more on the same axis.
6th. The use in the locomotive of the regulator tube M and the means, sub-
stantially as shewn, for regulating the flow into and the pressure of the air in the
said regulator.
7th. The stopping and starting gear and valve arrangement, as described.
8th. The mode of heating the air between the cylinders within the tank,
substantially as described.
9th. The application of a donkey engine with pump to be employed when the
pressure of the air in the regulator renders it advantageous to do so.
In witness whereof, I, the said William Dredge, have hereunto set my hand
and seal, this 28th day of February, in the year of our Lord One
thousand eight hundred and eighty one..
WILLIAM DREDGE. (L.S.)