IMPROVE- MENTS IN AIR ENGINES
Year: 1860

page_text: LETTERS PATENT to Frederic Howorth Edwards, of the Town and County
of Newcastle-upon-Tyne, Civil Engineer, for the Invention of "IMPROVE-
MENTS IN AIR ENGINES."
Sealed the 4th June 1861, and dated the 7th December 1860..
PROVISIONAL SPECIFICATION left by the said Frederic Howorth Edwards
at the Office of the Commissioners of Patents, with bis Petition, on the
7th December 1860.
I, FREDERIC HOWORTH EDWARDS, of the Town and County of Newcastle-
upon-Tyne, Civil Engineer, do hereby declare the nature of the said Invention
of "IMPROVEMENTS IN AIR ENGINES," to be as follows, that is to say:—
This Invention relates to the arrangement and construction of motive power
engines, in which air is used as the impelling fluid in place of steam., Under
one modification or arrangement of these engines it consists of a round
bottomed cylinder, the lower closed end of which is arranged over a furnace
which is formed in brickwork or other suitable material. The cylinder is
arranged in the brickwork, so that its lower half may be heated by the fire,
the products of which pass completely round it, and thence away to the
chimney. The upper portion of the cylinder is cast with a laterally projecting

page_text: part, which forms a cylindrical rectangular chamber or water space surround-
ing the upper portion of the cylinder. The under side of the water space rests
upon the inwardly projecting brick work, so that the lower part is suspended
within the hollow of the furnace. A hollow piston or plunger, corresponding
in figure to the lower part of the cylinder, and occupying about one half of its
internal capacity, is fitted loosely within the cylinder. This piston is fitted
loosely, so that on its being raised or depressed the air contained within the
cylinder will be displaced, and flow past the sides of the plunger into the part
from which the plunger is moving. The plunger is encircled by a belt of fine
wire to absorb the heat of the ascending body of air, and to impart heat to the
descending body of air. The quantity of wire used in this belt is preferred to
be in the proportion of four pounds of wire to each pound of air used in the
engine. The cylinder has fitted to it an ordinary end cover and stuffing box,
through which the rod, which is keyed to the piston or plunger, passes. By
means of suitable self-acting valvular arrangements, the cylinder is supplied
with cold air from a suitable reservoir by preference at a pressure of one
hundred pounds to the square inch when the plunger is down. Upon the
plunger being raised the air flows down the sides of the plunger, and is heated
by coming in contact with the lower part of the cylinder, which-is-kept-at-a-
low red heat. By this means the air is caused to exert double the pressure it
had on its admission to the cylinder; a valve is then opened at the upper part
of the cylinder, and one-fourth of the volume of hot air is allowed to flow off;
but since this quantity of air has to pass through the wire round the plunger,
its heat is thereby absorbed, and its volume is reduced one-half, so that one-
eighth of the contents of the cylinder flows out cold at a pressure of one
hundred and fifty pounds. Upon depressing the plunger again the remainder
of the hot air would ascend through the wire and impart to it its heat, so that
it would have but seven-eighths of its original pressure, so that upon opening
the valve of the reservoir containing the compressed air, one-eighth more air
would flow into the cylinder to be again expelled at the next upstroke of the
plunger by the expansion of heated air, and so on. In practice, the self-acting
valves would be so arranged that the cold air would begin to pass into the
outlet reservoir as soon as a pressure of one hundred and fifty pounds was
obtained. And the air in the supply reservoir would begin to flow into the
cylinder as soon as the pressure in the cylinder fell below one hundred
pounds.

page_text: SPECIFICATION in
pursuance of the conditions of the Letters Patent,.
filed by the said Frederic Howorth Edwards, in the Great Seal Patent
Office on the 7th June 1861.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, FREDERIC
HOWORTH EDWARDS, of the Town and County of Newcastle-upon-Tyne, Civil
Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Seventh day of December, in the year of our Lord
One thousand eight hundred and sixty, in the twenty-fourth year of Her.
reign, did, for Herself, Her heirs and successors, give and grant unto me, the
said Thomas Howorth Edwards, Her special license that I, the said Thomas-
Howorth Edwards, my executors, administrators, and assigns, or such others
as I, the said Thomas Howorth Edwards, my executors, administrators, or
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 law-
fully 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 AIR ENGINES," upon the condition (amongst
others) that I, the said Thomas Howorth Edwards, my executors or adminis-
trators, by an instrument in writing under my hand and seal, or under the
hand and seal of one of them, 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 Howorth Edwards, 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, reference being had to the accompanying Drawings, and
to the letters and figures marked thereon, that is to say :—
My said Invention relates to the arrangement and construction of motive
power engines in which air is used as the impelling fluid; in place of steam.
Under one modification or arrangement of these engines it consists of a round-
bottomed cylinder, the lower closed end of which is arranged over a furnace,
which is formed in brickwork or other suitable material. The cylinder is
arranged in the brick work so that its lower half may be heated by the fire, the
products of which pass completely round it, and thence away to the chimney

page_text: The upper portion of the cylinder is cast with a laterally projecting part, which
forms a cylindrical rectangular chamber or water space surrounding the upper
portion of the cylinder. The under side of the water space rests upon the
inwardly projected brickwork, so that the lower part is suspended within the
hollow of the furnace. A hollow piston or plunger, corresponding in figure to
the lower part of the cylinder, and occupying about one half of its internal
capacity, is fitted loosely within the cylinder. This piston is fitted loosely
so that on its being raised or depressed, the air contained within the cylinder
will be displaced, and flow past the sides of the plunger into the part from
which the plunger is moving. The plunger is encircled by a belt of fine wire
to absorb the heat of the ascending body of air and to impart heat to the
descending body of air. The quantity of wire used in this belt is preferred to
be in the proportion of four pounds of wire to each pound of air used in
the engine. The cylinder has fitted to it an ordinary end cover and stuffing
box, through which the rod which is keyed to the piston or plunger passes. By
means of suitable self-acting valvular arrangements the cylinder is supplied
with cold air from a suitable reservoir, by preference, at a pressure of one
hundred pounds to the square inch when the plunger is down. Upon the
plunger-being-raised-the-air-flows down the sides of the plunger and is heated
by coming in contact with the lower part of the cylinder, which is kept
at a low red heat, or by preference about 700°. By this means the
air is caused to exert double the pressure it had on its admission to the
cylinder. A valve is then opened at the upper part of the cylinder, and one
fourth of the volume of hot air is allowed to flow off. But since this quantity
of air has to pass through the wire round the plunger, its heat is thereby
absorbed and its volume is reduced one half, so that one-eighth of the contents
of the cylinder at a pressure of two hundred pounds to the square inch, or one-
sixth the volume at a pressure of one hundred and fifty pounds per square inch,
flows out cold. Upon depressing the plunger again the remainder of the hot
air would ascend through the wire, and impart to it its heat, so that it would
have but three-quarters of its original pressure, so that upon opening the valve
of the reservoir containing the compressed air one-fourth more air would flow
into the cylinder to be again expelled at the next upstroke of the plunger by
the expansion of heated air, and so on. In practice, the self-acting valves
would be so arranged that the cold air would begin to pass into the outlet
reservoir as soon as a pressure of one hundred and fifty pounds was obtained;
and the air in the supply reservoir would begin to flow into the cylinder as
soon as the pressure in the cylinder fell below one hundred pounds.

page_text: And in order that my said Invention of improvements in air engines may be
properly understood, I shall now proceed to describe the Figure on the expla-
natory Sheet of Drawings, which I have hereunto appended for the purpose of
shewing certain modifications under which my improvements may be judi-
ciously carried out in practice, that is to say, the Figure on the accompanying
Sheet of Drawings is a partially sectional elevation, shewing one arrangement of
the apparatus for obtaining motive power. Upon a suitable foundation or
substructure is laid the sole plate A; on this is built the furnace B, which is
formed of brickwork lined with fire bricks. In this arrangement a moveable
grate C is delineated, as being convenient for experimental purposes, but in
ordinary cases the fire bars would be fitted in the usual way. Above the grate
C is fixed a deflecting plate D, curved on the under side and open at the
central part. This plate serves to deflect the air which rises up round the
grate C, and bring it in contact with the gaseous matters arising from
the burning fuel, so as to facilitate the combustion of the same. Extending
downwards into the furnace B is a long cylinder E, which is supported by
a flange, cast or otherwise formed on its periphery and resting on the upper
part of the furnace B. The products of combustion from the burning fuel
after heating the lower part of the cylinder pass along a flue formed by the
cast-iron plate F. This plate acts as a regulator to the draught; it touches
the side of the cylinder nearest the chimney, or nearly so, and gradually opens
to the side opposite, so as to leave a free passage for the flame around the
cylinder E. This cylinder is formed with a rounded end at the lower part; it
extends some distance above the furnace, and has fitted to it the cover G,
which has two valve chambers H formed in it; the valve chanbers H
open into laterally diverging pipes I, which communicate with the cylin-
drical reservoirs J and K. These reservoirs are by preference formed of
cast iron, and they are supported on the sole plate A. The cylinder J
serves as a reservoir of cold, or nearly cold, high-pressure air, to supply the
cylinder of an ordinary engine, so that this reservoir is put in communi-
cation with, a pipe which conveys the highly-pressed air to the cylinder of
the engine to be actuated. The air after performing its work of actuating
the piston of the engine is conveyed by the exhaust into the lower pressure
reservoir K to be used over again in the cylinder E. The cold air passes into
the cylinder E through an opening in the cover G which is fitted with a valve
L opening inwards, whilst the recompressed air passes off to the higher-pressure
cylinder J through the other opening in the cover, which is closed by the valve
M arranged to open outwards. The higher and lower pressure reservoirs are

page_text: first charged with air compressed to the requisite degrees by a pneumatic
pump worked by hand, by a small steam engine, or other convenient power,
and this compressed air is then transferred from the lower to the higher
pressure reservoir by the reciprocatory movement imparted to a plunger
In this modification the motion of
arranged within the cylinder E.
the plunger is obtained from a small supplementary or donkey engine, but the
required motion may be imparted from the engine which is driven
by the high pressure air. On the upper part of the cylinder E is
fixed the vertical framing N, across which the crank shaft of the donkey
engine extends and gives motion to the cross-head P, to the lower part
of which is keyed the rod Q of the plunger R that passes through a
stuffing box in the cylinder cover. This plunger is formed of iron; it is hollow
and slides easily up and down within the cylinder E, leaving a small annular
space round it free for the passage of the air which it displaces, and thereby
drives past itself from one end of the cylinder E to the other alternately. The
interior of the plunger is filled with charcoal, or other non-conducting
material. The upper part of the plunger is reduced in diameter, and this por-
tion is encased with layers of wire gauze very fine wire in flocks (like
-horse-hair-in-seats), very thin perforated metal, or other good conductor of
heat susceptible of rapid change of temperature, and capable of finely dividing
the air on its passage. When the plunger is put in motion by the crank shaft O,
its downward movement displaces the hot air below it, which rising up the
annular space round its sides encounters the fine wire or gauze S, and yields
its heat to it. The air consequently emerges above the plunger nearly cold,
and with its pressure reduced below that of the lower-pressure reservoir K, a
portion of the air from the reservoir K, flows in consequence through the
valve L into the cylinder E; then by the upward movement of the plunger
the air is caused to flow down its sides, where it again permeates the wire or
gauze S, and from it reabsorbs the heat previously abstracted from the
ascending hot air, and takes a further portion of heat from the hot surface of
the lower part of the cylinder E. The heat imparted from these sources
increases the pressure of the air until the resistance of the valve M being
overcome, a portion of the cold air still remaining above the plunger flows into
the higher-pressure reservoir J. The cold air so expelled being forced out by
the expansion of the portion heated reacting against the bottom of the
cylinder E, for the pressures of the cold air above the plunger and of the hot
air below it, are necessarily always equal, owing to the free communication
existing between them in the annular space between the cylinder E and the

page_text: plunger R, already described. Instead of allowing the air to flow down the
side of the plunger it may, if preferred, be directed through passages in the
plunger, or even outside the cylinder altogether, in which case the fine wire
would be placed in those passages so as to intercept and divide, and thereby
alternately heat and cool the current of air induced by the action of the
plunger, which would then require to be more closely fitted to the cylinder.
The air thus condensed by its expansive force actuates the piston of a motive-
power engine, and after doing this work it escapes by the exhaust pipe to the
lower pressure reservoir K, and in this way, by means of the differential pres-
sure between the two reservoirs, the engine is actuated. In order to keep the
upper part of the cylinder E as cool as possible it is provided with a jacket or
annular water space T, through which cold water is circulated. The water is
supplied from a cistern or reservoir arranged above the air-heating apparatus,
and is conveyed down to the jacket T by the pipe U. From the jacket
T the water ascends up through the pipe V, which enters the jacket W,
arranged on the upper part of the framing, and away by the pipe X to
the cistern of source of supply. If found necessary, the circulation of
the water may be facilitated by means of a force-pump, or other equi-
valent contrivance. The jacket W surrounds the barrel of an air pump
fitted on the upper part of the framing, the plunger of which is keyed to the
cross head P, from which it derives its motion. At the upper part of the air
pump are arranged the inlet valve Z and the outlet valve a, which communi-
cates with the pipe 6 that serves to convey the air down to the lower pressure
reservoir K. The air pump serves to make up for any leakage that may arise
during the working, and the object of surrounding the barrel with a water
jacket is to absorb the heat produced by the compression of the air. The
position as well as the arrangement of the several details may however be
greatly varied and modified to suit the particular purpose for which the appa-
ratus is required.
Engines arranged and actuated according to these improvements are appli-
cable to the driving of machinery, the raising and forcing of water, and other
generally similar purposes to which steam power is ordinarily applied. For
large engines I prefer to increase the number of regenerative cylinders rather
than largely increase their dimensions, in which case it would not be necessary
to increase the number of reservoirs also, since any number of cylinders might
with advantage transfer the contents of one supply reservoir to a single outlet
reservoir, and if acting consecutively, the differential pressure would be subject
to less variation than if one cylinder only were used.

page_text: Having now described and particularly ascertained the nature of my said
Invention, and the manner in which the same is or may be used or carried into
effect, I would observe in conclusion that what I consider to be novel and
original, and therefore claim as the Invention secured to me by the herein-
before in part recited Letters Patent, is,-
First, the system or mode of obtaining a differential pressure between two
air vessels or reservoirs and of applying such differential pressure as a motive
power or means of actuating the piston of an ordinary motive-power engine
as herein-before described.
Second, the combination of air-heating apparatus with differential-pressure
reservoirs for obtaining and applying a differential air pressure to be used for
working motive-power engines and other apparatus in lieu of steam, as herein-
before described and shown in the accompanying Drawings, or any mere
equivalent therefor.
In witness whereof, I, the said Frederic Howorth Edwards, have to this
my Specification hereunto set my hand and seal, this Fifth day of June,
One thousand eight hundred and sixty-one.
FREDERIC HOWORTH EDWARDS. (L.S.)