IMPROVE- MENTS IN HIGH PRESSURE HOT AIR ENGINES
Year: 1880

page_text: LETTERS PATENT to Hugh Gearing Grant, of the Firm of Messrs. Bosshardt
and Grant, Patent Solicitors, of 24, Bull's Head Exchange Chambers, Market
Place, Manchester, in the County of Lancaster, for an Invention of "IMPROVE-
MENTS IN HIGH PRESSURE HOT AIR ENGINES." A communication from abroad
by Le Comte Paul Edward de Massia de Ranchin, of Paris, in the Republic of
France
PROVISIONAL SPECIFICATION left by the said Hugh Gearing Grant at the
Office of the Commissioners of Patents on the 21st June 1880.
HUGH GEARING GRANT, of the Firm of Messrs. Bosshardt and Grant, Patent
Solicitors, of 24, Bull's Head Exchange Chambers, Market Place, Manchester, in
the County of Lancaster. "IMPROVEMENTS IN HIGH PRESSURE HOT AIR ENGINES."
A communication from abroad by Le Comte Paul Edward de Massia de Ranchin,
of Paris, in the Republic of France.
If air of 0° be enclosed in a vessel and heat applied thereto, then as the
temperature rises to about 272° there will be an internal pressure of upwards of
is
2 kilogs. per square inch, and by the well known law of Mariotte, when pressure
applied its volume is diminished. If the enclosed air is at 0° and the pressure
five atmospheres, this pressure will be increased to ten atmospheres when the
temperature is raised to 272°, and as the volume remains constant the pressure
will be double. The vessel containing heated air is connected by means of a
suitable pipe provided with cocks to a cylinder and is fitted with a piston. The
piston will be put in motion by a pressure in the cylinder of ten atmospheres, but
as the air in the boiler will be diminished until it arrives at the atmospheric
pressure when the engine would stop. To prevent this, the piston is made to drive
a pump, which carries or pumps the hot air back to the heating vessel. By these
means the air enclosed below one-piston, when it arrives at four fifths of its stroke,
is compressed to five atmospheres pressure in a volume equal to that in the other

page_text: of two cylinders placed in juxa position. If it be then pumped back into the
heating vessel its elastic force would double, and it will then exactly make up the
loss caused by the working of the engine. It will be required to have a pressure
equal to the pressure in the boiler. In order to attain this the piston is moved on
further, when the pressure of the air will lift a valve in the piston and the air will 5
be returned into the boiler. To prevent the action of the piston being retarded by
the air an arrangement of levers is employed, known as the knee joint arrangement.
To avoid loss of heat by radiation the parts are preferably jacketted.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by the
said Hugh Gearing Grant in the Great Seal Patent Office on the 21st December
1880.
HUGH GEARING GRANT, of the Firm of Messrs. Bosshardt and Grant, Patent
Solicitors, of 24, Bull's Head Exchange Chambers, Market Place, Manchester, in
the County, of Lancaster. ¨“IMPROVEMENTS IN HIGH PRESSURE HOT AIR ENGINES."
A communication from abroad by Le Comto Paul Edward Massia de Ranchin,
of Paris, in the Republic of France.
If air of 0° be enclosed in a vessel and heat applied thereto, then as the
temperature rises to 272° there will be an internal pressure of upwards of
2 kilogs. per square inch. On the other hand, when pressure is applied to a gas
its volume diminishes, as, for example, if the pressure be doubled its volume is
diminished one half. If the enclosed air is at 0° and the pressure five atmospheres,
this pressure will increase to ten atmospheres; if the temperaturo be raised to
272°, for at this temperature the volume would be double that of before; now as the
volume remains constant the pressure will be double. The receptacle is put into
communication with a cylinder, as, for example, the cylinder of an engine, the
piston will be put in motion by a pressure of ten atmospheres; but as the air is
carried away by this process the boiler pressure diminishes until it arrives at atmo-
spheric pressure when the engine will stop. To prevent this the piston is arranged
to drive a pump which pumps the air back into the receptacle.
And in order that the Invention may be better understood I have caused to bo
appended hereunto a Sheet of Drawings marked with letters of reference.
Referring in this place to the said Drawings, Fig. 1, R is a receptacle for heating
the air, coals being placed on the grate g. The air is heated to 272°. Now if the
cock a be opened the air will flow into the cylinders M, N. The pistons p and p¹
are in the same position and work together. The hot air enters from the boiler
by the tube T and cock a, and presses upwards the piston p. In the same time
the air which is below presses on the piston P' in the cylinder N. This piston
having made its stroke the space is filled with air of ten atmospheres pressure. The
air which is enclosed between the two pistons acts to prevent p to descend, and if
the surfaces of p and p' wero equal there would be no movement of the pistons,
but the surface of p¹ is larger, the total effect produced is equal to what acts from
up to down on p equal to the difference of pressure on the two unequal surfaces.
In the same time the hot air which is below p' passes into the atmosphere through
All; by closing the cocks A, A', A", and opening the cocks B, B, B", the same
effect is produced. The air coming by B from the boiler and escaping by B³ being
continued, the pressure in the boiler would diminish, and at last the engine would
stop. In order to prevent this the engine works a pump, the piston of which acts
in concert with the pistons p, p'. This piston moves in a cylinder of the same
height but having five times the capacity of the cylinder M. By these means air
enclosed below when the latter arrives at four fifths of its stroke, is compressed
to five atmospheres pressure in a volume equal to the cylinder M. If it then be
carried into the boiler R its elastic forco would double, and it will exactly make up
the loss caused by the working of the engine. The air is admitted into the cylinder
through the cock a or b, according to the position of the piston p; it then escapes
by the valve b, c, and goes into the boiler by the tube e, F, F; A, A¹, represents
the large and small cylinders of the engine motor; B, B', piston rods; C, connecting
rods; D, excentrics; E, E, rods fastened directly to the crank of the engine shaft,
and by which the motion is communicated to the knee lever arrangement H, H',
H, H, which set in motion the piston of the air compressing pump. These

page_text: levers have to equalise the force produced by the engine at the beginning of the
stroke of the pistons; I is the pump rod guide; J, the pump piston rod; K, K',
air compressing pump; in practice these pumps are constantly cooled by a flow of
water; L, L, L, tube conducting the compressed air from the pumps to the boiler;
m, m, cast iron standard; n, n, cast iron engine standard; o, bracket guiding
the rod P, P, when the large and the small engine cylinders are fixed to Q excentric
for working the compressed air from the boiler Q', escape tube R, R, Alue for the
products of combustion.
Having now described the nature of the Invention, and the manner of carrying
the same into effect, I would have it to be understood that I claim the manner of 1
constructing apparatus worked by high pressure hot air in the manner described
and illustrated in the Drawings.
In witness whereof, I, the said Hugh Gearing Grant, have hereunto set my
hand and seal, this Twentieth day of December, in the year of our Lord One
thousand eight hundred and eighty.
HUGH G. GRANT. (L.S.)