AN IMPROVED CONSTRUCTION OF AIR ENGINE
Year: 1855

page_text: LETTERS PATENT to Alfred Vincent Newton, of the Office for Patents,
66, Chancery Lane, in the County of Middlesex, Mechanical Draughts-
man, for the Invention of "AN IMPROVED CONSTRUCTION OF AIR ENGINE."-
PROVISIONAL SPECIFICATION left by the said Alfred Vincent Newton at
the Office of the Commissioners of Patents, with his Petition, on the
8th May 1855.
I. ALFRED VINCENT NEWTON. of the Office for Patents, 66. Chancery Lane,
in the County of Middlesex, Mechanical Draughtsman, do hereby declare the
nature of the said Invention for "AN IMPROVED CONSTRUCTION OF AIR ENGINE"
to be as follows:-
This Invention relates to the charging of the tubes of the regenerator and
heater of air engines with fresh compressed atmospheric air at each stroke of
the engine without the employment of a supply pump. For this purpose the
combined movements of two pistons within the same working cylinder (whicli
is closed at one end only) are used. and the introduction of the compressed
air is effected under a state of equilibrium of pressure, so that the supply
piston becomes entirely relieved from resistance during the process of charging
the tubes of the regenerator and heater. whilst at the same time one of these
[Price 8d.l

page_text: pistons performs the oflice of working piston, exerting full force on the engine
without suffering retardation by any unbalanced pressure against the supply
piston.
The engine is constructed with a pair of cylinders, fitted each in like manner
with a working and a supply piston. A coil of pipe set in a furnace supplied
with a blast of heated air is provided for heating the air by which the engine
is driven. The air enters the engine through a valve in the working piston.
and passes (in a compressed state) from the cylinder through a heating chamber
(heated by the air that escapes from the exhaust port of the cylinder), and
thence to the coil of pipe in the furnace, from which pipe it is given off as
required to work the engine.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Alfred Vincent Newton in the Great Seal Patent Office on
the 8th November 1855.
TO ALL TO WHOM THESE PRESENTS SHALL COME. I. ALFRED
VINCENT NEWTON, of the Office for Patents. 66. Chancery Lane, in the County
of Middlesex, Mechanical Draughtsman, send greeting.
WHEREAS er most Excellent Majesty Queen Victoria. by Her Letters
Patent, hearing date the Eighth day of May, in the year of our Lord
One thousand eight hundred and fifty-five. in the eighteenth year of Her
reign, did. for Herself. Her heirs and successors. give and grant unto me.
the said Alfred Vincent Newton. Her special licence that 1. the said
Alfred Vincent Newton, my executors, administrators. and assigns. or such
others as 1. the said Alfred Vincent Newton. 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 "AN IMPROVED CONSTRUCTION OF AIR ENGINE," being a commu-
nication from abroad, upon the condition (amongst others) that I. the said
Alfred Vincent Newton, by an instrument in writing under my hand and seal.
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.

page_text: NOW KNOW YE, that I, the said Alfred Vincent Newton, 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 Drawing hereunto annexed,
and to the letters and figures marked thereon (that is to say)-
The application of the caloric in this engine is identical with that of
air engine, for which the inventor (Captain Ericsson) obtained Patents in
England and other countries in the year One thousand eight hundred and
thirty-three, descriptions and drawings of which have been published in
several works, among which may be mentioned a work called "Dictionary of
the Arts of Life and Civilization," by Sir Richard Philips, published in London.
One thousand eight hundred and thirty-three.
The heated air, after having performed its office in the working cylinder of
the present improved air engine, is made to circulate through a vessel con-
taining a series of tubes, precisely as in the former engine above referred to.
and the current of heated air in passing through the said vessel (called the
regenerator) is met by a current of cold air. circulating in an opposite
direction through the series of tubes on its way to the working cylinder, by
which a transfer of caloric is effected between the two currents of air passing
off from and entering the working cylinder; and the current of cold air on its
way to the working cylinder. after having been thus partially heated by the
described process of transferring the caloric, is afterwards made to pass through
a series of tubes or other vessels exposed to the fire of a furnace also, in the
same manner as in the said former engine.
But although the means for heating and for transferring the caloric from
the escaping to the entering air is similar to that patented by the present
Inventor in the year One thousand eight hundred and thirty-three, yet the
mechanism or engine, which forms the subject of the present Patent, and is
intended to render the heating of the air subservient in producing motive
power, differs altogether from anything heretofore known.
Before. however, describing the Invention, it may be proper first to notice.
in order that its nature may be correctly understood, that in all air engines
working on what is called the differential principle (the improved air engine.
for which the present Inventor obtained Patents in One thousand eight hundred
and fifty. for instance.) the motive energy depends solely on the difference of
areas of the working and supply pistons. Experience has in the meantime
demonstrated, that in order to obtain a suflicient supply of air without resorting
to a dangerously high temperature, the supply pump must be of such large
capacity that the differential active area becomes too small. Unless, therefore, .

page_text: future experience should suggest some improvement, the power of such engines
will always be found insufficient for practical purposes.
I will now proceed to describe the principal feature of the Invention, which
consists in charging the regenerator and heater. or either, with fresh com-
pressed atmospheric air at each stroke of the engine, without the employ-
ment of a supply pump, by the peculiar combined movements of two pistons
within the working cylinder, the introduction of fresh air and its transfer to
the regenerator or heater in a compressed state being effected under a state
of equilibrium of pressure, so that the supply piston becomes entirely relieved
from resistance during the process of charging the regenerator or heater,
whilst at the same time one of these pistons performs the oflice of working
piston, exerting full force on the engine without suffering retardation by any
unbalanced pressure against the supply piston.
In the accompanying Drawing, Fig. 1 is a plan, with the two cylinders, the
pistons, and the air-heating apparatus in section; and Fig. 2 is a side elevation,
with one of the cylinders, the piston, and the air-heating apparatus in section,
to exhibit the internal arrangement. The same letters indicate like parts
in both the Figures. The engine is single acting, and two of them are
connected by a crank shaft, placing the two cranks at an angle of one
hundred and eighty degrees. so that. while the piston of one engine is being
impelled by the tension of heated air, the piston of the other shall be making
its return stroke, and vice versa; and as the two engines are identical in
construction, the .description of one of them will answer for the two. The
manner of connecting the two, and the effects resulting therefrom, will be
subsequently described.
The cylinder a is open at one end, and has a head b at the other, with a
central aperture c; leading to a valve chest d, with an induction port e and an
exhaust port, fitted with valves g. The stem of the valve g passes through
the hollow stem of the valve h, and these valves are to be operated by any
known and suitable valve gear giving the periods of movements, such as will
be presently described. The exhaust port leads by a pipe i to a chamber i
surrounding a series of small tubes k. constituting what has been termed the
regenerator, so that the air passing from the cylinder to the escape pipe l
shall circulate around and among the series of tubes, to impart its heat to the
cold supply air contained within the tubes: and the induction port com-
municates with the tubes m of what is termed the heater. The series of
tubes, constituting the regenerator, are suitably secured to a tube sheet n at
each end, and open into two chambers o and p: the one, o communicating by a
pipe q with a port in the side of the cylinder, governed by a self-acting valve r

page_text: opening outward. and the other, p. communicating with the heater mbes m,
which are to be suitably coiled or otherwise arranged to present a large extent
of surface to the action of the heat evolved from the fire of a furnace x, the
series of tubes m being placed above the fire, so that the products of combustion
in passing to the flue t shall circulate around and among them. The bottom
plate of the flue is a tube sheet, to which are secured a series of flue tubes u,
down which the products of combustion pass to a flue e below, leading to the
chimney.
The fluc tubes u are enclosed in a chamber, having an aperture near the
bottom to receive a current of air from the atmosphere, and another aperture 2
near the top. through which the current of air passes after circulating around
and among the flue tubes, by which it is heated. so that the products of com-
bustion escape into the atmosphere at a very low temperature; for it will be
observed that the two currents travel in opposite directions, the atmospheric
current passing from the coldest towards the hottest ends of the flue tubes,
gradually absorbing the heat from the products of combustion which are passing
through the tubes in the opposite direction.
From the passage x, the partially heated air passes down a vertical flue or
tube y, having two apertures z and a', both governed by dampers or registers,
one leading below the grate in the furnace to supply the fire when more heat
is required, and the other above the fire, to admit the air directly to the heater
tubes m, when it becomes necessary to moderate the heat of the tubes. By
this arrangement a great saving of fuel is effected, and the attendant can
To the
control and regulate the heat of the heater tubes with perfect case.
cylinder are fitted two pistons b' and c'. The one, b, is nearest the open end
of the cylinder, and called the working piston. and is provided with a self-acting
valve d' opening inwards, and the other, c', termed the supply piston. is placed
between the working piston and the head of the cylinder.
The rod of the supply piston passes through a stuffing box e' in the
working piston. This piston rod embraces the end of an arm g', that
vibrates on a fulcrum pin h', and the arm carries two rollers and j', one on
each side of the fulcrum pin ', which rollers, for the purpose of governing
the motions of the supply piston. are alternately acted upon by two cams '
and on the crank shaft m', the cam acting on the roller i. and the
other on the roller j'.
In Figure 1 the arm and the two cams are concealed on one of the engines,
but represented on the other, and in Fig. 2 the arm and its rollers are repre-
sented in the two opposite extreme positions.
The cam operates on the roller to carry the supply piston inwards

page_text: towards the head of the cylinder, and the other cam controls or governs its
motion in the opposite direction when impelled during a part of its movement
by the heated air. The working pision is provided with two wrist pins
m", m", one on each side of the stuffing box e', which are taken hold of by two
connecting rods n', n'. connected with a vibrating arm o' on a rock shaft pl.
which is provided with another arm q' at the angle indicated on the Drawing,
and the arm is in turn connected by a rod with the crank
crank shaft m', before named.
on the
The required motions are to be imparted to the induction and eduction
valves by suitable valve gear taken from the crank shaft, as before stated;
and as the two single-acting engines are connected with one and the same
crank shaft with the cranks on opposite sides. as the pistons of one are im-
pelled by the heated air, any power required to cause the pistons of the other
engine to return will be derived from this source, if the momentum of the
moving parts be not sufficient for this purpose.
Having described the construction of one of the engines with its regenerator
and heater, and stated that the two single-acting engines are alike in every
respect. as indicated by corresponding letters of reference. and having also
described in what manner the two are connected. I will now describe the
mode of operation, assuming that the furnaces of the heaters have been
properly fired up.
By means of a hand air pump applied to the chamber at one end of the
regenerator, or any other part of the regenerator or heater tubes, a supply of
atmospheric air is introduced at about the pressure of the atmosphere, and
then the engine is in a condition to begin its operations. The cranks should
be turned over or beyond the dead point, as usual in steam engines.
Starting with the pistons of one engine in the position represented in
Fig. 2. at the extremity of their outward stroke, as the crank s¹, moving
in the direction indicated by the arrow. is making that part of its circuit near
the outer dead point, and therefore imparting bm little motion to the working
piston, the supply piston is carried from the working piston and towards
the head of the cylinder with a rapid motion by the action of the cam on the
roller of the arm g'. the cam rotating in the direction of the arrow, and its
acting face being formed as represented. that the piston may be gradually
started. rapidly accelerated. and near the end gradually arrested. and there
retained in a state of rest as the extremity of the cam passes the roller.
During this inward motion of the supply piston the working piston makes
but a small portion of its inward stroke. and therefore the valve din
the working piston will be opened by the pressure of the atmosphere to

page_text: permit cold air to enter and fill that part of the cylinder, between the two
pistons.
So soon as the supply piston stops, the exhaust port closes, and the con-
tinued inward motion of the working piston begins to compress the cold air
thus supplied, which of course closes the self-acting valve d, through which
the supply was admitted by atmospheric pressure. This supplied cold air
continues to be compressed by the working piston until the end of its inward
stroke, and as the power for effecting this compression is derived for the time
being from the other engine, it is important to observe the condition of the
connections.
At the time the supply piston of one engine is started and the air is entering
by atmospheric pressure, and when the arm o' on the rock shaft p'. with which
the piston is connected by the rod a'. is at its greatest leverage. the corre
sponding arm of the rock shaft of the opposite engine is at its shortest.
leverage, but as moved inwards, and the supply air, by reason of being gra-
dually compressed, increases the resistance: the arm o gradually shortens in
leverage, and the same arm of the opposite engine gradually and in nearly the
same ratio increases in leverage on the principle of the bent lever. thus apply-
ing the power required to compress the supply air to the best advantage.
should be borne in mind, however. that the power thus applied to compress the
supply air is not actually expended but merely borrowed. for it is so much
added to the elastic force of the air by which when heated the engine is
impelled.
It
Just before the supply piston begins the inward stroke just described, the
eduction valve g is opened, the induction valve having been previously closed,
so that the charge of heated air, by which the previous stroke of the engine
was effected, is permitted to escape freely into the atmosphere, so that the
power required to move the supply piston inward is very sligh, the air escaping
frecly to the atmosphere on one side, and entering by atmospheric pressure on
the other through the valve d'; but as the heated air exhausts or escapes from
the cylinder, it passes around and among the series of small tubes of the
regenerator, thus imparting its heat through the metal of the tubes to the cold
air contained inside of the tubes, which air is this partially heated preparatory
to being finally heated in passing through the heater tubes. In this way much
of the heat which would be otherwise wasted is saved.
The supply of cold air having been introduced and compressed, the engine
is prepared to be impelled by the expansive force of the heated air. The
eduction valve having remained closed during the greater part of the inward
motion of the working piston, the induction valve his now opened, which

page_text: admits the heated air from the heater to the cylinder, by which the supply
piston is forced outwards towards the working piston. The form of the face of
the cam as represented is such as to cause the piston to be carried back
with a rapid accelerated motion until it comes nearly in contact with the
working piston, and at first in this outward motion of the supply piston
the already compressed supply air between the two pistons is still further com-
pressed, not by the power of the engine. but by the elastic force of the heated
air; the supply piston being, as it were. suspended between the heated air
from the heater on one side and the cold air on the other, with the self-acting
valve (in the side of the cylinder) interposed between the two; for it must be
remembered that as the heater and regenerator are in communication, the air,
which is a perfectly elastic fluid. will be under equal pressure in both, notwith-
standing a portion is more highly heated than the other; and as the supply
air in the cylinder is simply separated from the air in the regenerator by the
interposed valve r in the side of the cylinder, the supply piston will be moved
outwards by the heated air until the supply air is compressed to an equal
tension, and then the further motion of the supply piston. effected by the
cam as it approaches the working piston will transfer the supply air from
the cylinder to the regenerator through the valve r. The only power expended
by the engine in this transfer will be the small amount required to move the
supply piston between two equal pressures to give the slight preponderance to
the one necessary to open the valve r, through which the transfer is made.
The moment the supply piston passes this valve and overtakes the working
piston, the preponderance of pressure ceases. and the valve closes by gravity.
If desired, however, a positive motion properly regulated may be imparted to
this valve by a suitable valve gear. The operations just described for the final
compression and transfer of the supply air take place during the time that the
working piston is at rest, or nearly so. It is whilst the crank is passing the
dead point farthest from the arm q'. connected by the rod r' with the crank,
and as the crank and the connecting rod have their centres of motion at the
time of passing the dead point on the same side of their points of connection,
it follows, that during the time the crank moves a given distance each side of
the dead point. the piston will move through a distance comparatively much
shorter than when the crank moves the same distance each side of the opposite
dead point, for in the one case the crank and the connecting rod simply
represent the radii of two excentric circles, whilst in the other they represent
the radii of two opposite circles. By the time the supply piston reaches its
nearest proximity to the working piston, the latter has made but a very small
part of its outward stroke.

page_text: At the time the supply piston passes the valve r, a film of compressed
air remains between the two pistons, to act as an elastic cushion; at this
time the heated air then in the cylinder is cut off by the closing of the
induction valve h. and the working piston is impelled outward by the expan-
sive force of the heated air and the supply piston by the cam movement
described.
The form of the cam P. which acts on the roller to govern the outward
stroke of the supply piston, must be such as represented, that the piston will
move with a rapidly accelerated motion until it approaches the working piston,
then gradually retarded, and from the point 1 to 2 its curvature must be such
that its motion will be in unison with the motion imparted to the working
piston, by reason of its connection with the crank, modified by the interposition
of the arms o' and q' operating on the principle of the bent lever
It has been shewn that the alternating leverage of the arms o' of the two
engines is such as to apply the power for compressing the supply air to the
best advantage, and it remains to show the connection between the two
in furtherance of this economy. It will be seen that the arm o'. connected
with the working piston during the outward stroke, gradually increases in
leverage as the heated air by dilation gradually decreases in tension. Now,
the leverage of this arm gradually increases during the outward stroke of the
working piston of one engine as it gradually decreases in the other engine,
where the working piston is compressing the supply air, and vice versa..
It has been stated that the power exerted on the working piston to compress
the supply air was not an actual consumption, but a mere transfer of power.
This will be apparent from the description of the entire operation, because the
air thus compressed is transferred to the regenerator. and from the regenerator
to the heater, and thence to the cylinder. where it exerts on the piston the
elastic force first impressed upon it by the piston, together with the tensive
force which it has acquired by being heated, so that the compression which it
received at first from the piston when working in one direction it returns to
the piston when working in the opposite direction under the advantages due
to the arrangement of the two engines, as above specified.
By the alternate strokes of each engine the required supply of cold air is
introduced, compressed, and transferred from the cylinder to the regenerator,
carried through the regenerator. thence through the heater, and from the heater
back to the cylinder; and in this circuit it is gradually heated, first by the
heat which it takes up from the escaping heated air, and then by the heat of
the furnace and as atmospheric air is a bad conductor of caloric. the heat will
not be carried back by conduction from the heater to the regenerator, but after

page_text: the heated air has exerted its elastic force in the cylinder, in escaping it trans-
fers its surplus heat to the supply air on its passage through the regenerator.
The object of the regenerator being, however, merely that of economizing fuel,
it is evident that the supply air may be passed directly from the cold end of the
working cylinder by the action of the supply piston to a heater communicating
directly with the other end of the working cylinder.
Having now set forth the nature and object of the Invention of "An
Improved Construction of Air Engine" as communicated to me from abroad,
and explained the manner of carrying the same into effect, I wish it to be
understood, that, under the above in part recited Letters Patent, 1 claim the
method of supplying fresh air to the engine, compressing and transferring it to
the regenerator and heater, or either, by the action of the supply and working
pistons within the one cylinder operating on the principle and in the manner
substantially as herein described, whereby the air is admitted under atmospheric
pressure as the supply piston is moving from the working piston as the previous
charge of heated air is exhausting, so that the said supply piston moves in
equilibria, or nearly so, and by which also the supply air is finally compressed
and then transferred to the regenerator and heater, or either, as the supply
piston moves between the supply air and heated air during the period of the
nearly stationary position of the working piston.
1 also claim, in combination with the double piston movement of each
cylinder, the method of connecting the working pistons of two single-acting
engines to constitute a double-acting engine, by means of two sets of vibrating
arms attached to each other, and vibrating on a common centre connected with
the two working pistons, and with the two cranks on opposite sides of the axis
of the crank shaft, the two sets of arms operating on the principle of the bent
lever, and the crank shaft being so located relatively to the cylinders and the
centres of vibration of the arms, substantially as described. that the working
piston shall be at the end of its inward stroke at the time the crank is passing
the dead point farthest from the point of connection of the connecting rod with
the vibrating arm, as described. by which the power of that working piston
which is being impelled by the heated air is applied to the best advantage to
operate the other working piston during its return stroke, and by which also
the working piston remains nearly at rest duing the time the supply piston is
making that part of its outward stroke, during which the partially compressed
air is finally and fully compressed and transferred to the regenerator and heater,
or either, as described.
And also claim the method herein described of supporting the combustion
and regulating the temperature of the heater by a current of air which is heated

page_text: by passing around and among the series of flue tubes, and thence admitted
either below the fire to excite the combustion, or above the fire and directly to
the heater tubes to reduce the temperature, the admission or exclusion of the
current to or from either being governed by dampers, as set forth.
In witness whereof. 1. the said Alfred Vincent Newton, have hereunto set
my hand and seal. the Eighth day of November. in the year of our
Lord One thousand eight hundred and fifty-five.
Witness.
J. W. MOFFATT,
66 Chancery Lane.
A. V. NEWTON. (L.S.)