IMPROVEMENTS IN COMBINED GAS AND HEATED AIR ENGINES
Year: 1881

page_text: LETTERS PATENT to Francis Herbert Wenham, of 164, New Bond Street,
London, in the County of Middlesex, Consulting Engineer. for an Invention of
PROVISIONAL SPECIFICATION left by the said Francis Herbert Wenham
at the Office of the Commissioners of Patents on the 1st March 1881.
FRANCIS HERBERT WENHAM, of 164, New Bond Street, London, in the County
of Middlesex, Consulting Engineer. "IMPROVEMENTS IN COMBINED GAS AND
HEATED AIR ENGINES."
The main or air cylinder resembles the cylinder of a steam engine, having a
port at each end which, by the action of a slide valve, admits cold air from the
external atmosphere at the commencement of the stroke, and closes or cuts off after
the piston has travelled some distance, and during the return stroke remains open
so as to allow the contents of the cylinder to be completely discharged. This may
be effected by an excentric on the crank shaft, as in a steam engine.
On both sides of the piston there is a cylindrical trunk or plunger, extending
outwards to a distance of nearly one half of the length of the stroke of the piston.
The trunks pass into gas cylinders bored out in prolongations of the main cylinder
covers. When the piston of the air cylinder is at the end of the stroke or close to
the covers the trunk ends are also close to the bottom of the gas cylinders.
During the up stroke a combustible mixture of gas and air is drawn into the gas
cylinder through a pipe provided at its junction to the cylinder with a clack valve
opening outwards. At the same time the slide valve of the air cylinder admits
external cold air through the open port. Just before the plunger leaves the gas
cylinder the slide valve of the air cylinder closes the port, and the contents of the
gas cylinder is fired, the pressure impels the piston forward, the hot air from the
opened gas cylinder rushes into the air cylinder, expanding the cold air therein,
which actuates the air piston.

page_text: At the return stroke the exhausted hot air is discharged through the port, now
uncovered by the slide valve, and the residual air in the gas cylinder is discharged
by a pipe or passage leading into the air cylinder, which passage is kept permanently
open. If the engine is made double-acting the same action that takes place at one
end of the cylinder is repeated at the other.
The mixture in the gas cylinder may be fired through an orifice or touch bole
by means of an external gas jet. A sliding shutter over the orifice is opened at
the instant the charge requires to be fired, but as the jet is liable to be blown out
by the explosion I surround it with a cage of wire gauze, which being maintained
at a high heat by the flame immediately relights it in the manner patented by me
in A.D. 1864, No. 1173.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Francis Herbert Wenham in the Great Seal Patent Office on
the 26th August 1881.
FRANCIS HERBERT WENHAM, of 164, New Bond Street, London, in the County
of Middlesex, Consulting Engineer. "IMPROVEMENTS IN COMBINED GAS AND
HEATED AIR ENGINES."
In the accompanying Drawings setting forth the mode in which my Invention is
carried into effect Fig. 1 is a longitudinal section and Fig. 2 is a plan of the
cylinders, similar letters of reference applying to the same parts in each.
The main or air cylinder A resembles the cylinder of a steam engine, having a
port B at each end which, by the action of a slide valve C, admits cold air from
the external atmosphere at the commencement of the stroke, and closes or cuts off
after the piston has travelled some distance, and during the return stroke remains
open so as to allow the contents of the cylinder to be completely discharged; this
may be effected by an excentric on the crank shaft, the arrangement being the same
as in a steam engine.
On both sides of the piston there is a cylindrical trunk or plunger D extending
outwards to a distance of nearly one half of the length of the stroke of the piston E;
the trunks pass into gas cylinders F bored out in prolongations of the main cylinder
covers. When the piston of the air cylinder is at either end of the stroke or close
to the covers the trunk ends are also close to the bottom of the gas cylinders.
During the up stroke a combustible mixture of gas and air is drawn into the gas
cylinder through a pipe G, provided at its junction to the cylinders with a valve H
opening outwards by a cam or other movement; at the same time the slide
valve C of the air cylinder admits external cold air through the open port B. Just
before the plunger leaves the gas cylinder the slide valve of the air cylinder closes
the port, and the contents of the gas cylinder is fired, the pressure impels the piston
forward, the hot air from the opened gas cylinder rushes into the air cylinder,
expanding the cold air therein, which combined pressure actuates the air piston.
At the return stroke the exhausted hot air is discharged through the port now
uncovered by the slide valve C, and the residual air in the gas cylinder is discharged
through a clearance round the trunk or by a passage leading into the air cylinder,
which passage is permanently open. If the engine is made double-acting, as
shown in the Drawing, the same action that takes place at one end of the cylinder
is repeated at the other.
The mixture in the gas cylinder may be fired through an orifice or touch hole by
means of an external gas jet. A sliding shutter over the orifice is opened at the
instant the charge requires to be fired, but as the jet is liable to be blown out by
the explosion I surround it with a cage of wire gauze, which is maintained at a
high heat by the flame, and immediately relights it in the manner patented by me
in A.D. 1864, No. 1173.
To prevent conduction of heat from the gas cylinders to the air cylinder a hollow
annular space I is cast in the cover through which the water circulates.
The speed of the engine may be regulated by a centrifugal governor acting on a
throttle valve, which cuts off the gas supply till the excess of speed is reduced; or
on an increase of speed the mixture in the gas cylinder may be cut off or fired at
an earlier portion of the stroke by connecting the sliding shutter of the touch hole
with the governor action.

page_text: Having now described the nature and action of my Invention, I claim,-
The combination of a gas and air cylinder acting substantially in the manner
described and shown by the Drawings.
In witness whereof, I, the said Francis Herbert Wenham, have hereunto set
my hand and seal, this Twenty fourth day of August, in the year of our 5
Lord One thousand eight hundred and eighty one.
FRANCIS HERBERT WENHAM. (L.S.)