IMPROVEMENTS IN MOTIVE POWER ENGINES TO BE WORKED BY STEAM OR OTHER ELASTIC FLUID
Year: 1878

page_text: LETTERS PATENT to Peter William Willans, of Bow, in the County of
"
Middlesex, for the Invention of IMPROVEMENTS IN MOTIVE POWER ENGINES
TO BE WORKED BY STEAM OR OTHER ELASTIC FLUID."
Sealed the 20th June 1879, and dated the 31st December 1878.
PROVISIONAL SPECIFICATION left by the said Peter William Willans at
the Office of the Commissioners of Patents on the 31st December 1878.
PETER WILLIAM WILLANS, of Bow, in the County of Middlesex. 'IMPROVE-
MENTS IN MOTIVE POWER ENGINES TO BE WORKED BY STEAM OR OTHER ELASTIC
FLUID."
"
This Invention has for its object improvements in motive power engines to be
worked by steam or other elastic fluid.
The engine consists of a high and a low pressure cylinder parallel the one to the
other, and with a valve chamber between or at the side of them in which a piston
valve works. The cylinders are single acting, and they contain pistons from which
connecting rods pass direct to opposite cranks on the engine shaft. The valve
chamber is cylindrical, and has in its sides three ports, one by which the steam (or
fluid) is admitted, and others by which it passes into and from the cylinders.
The valve consists of two pistons rigidly connected by a stem, so that they
enclose between them a small cavity within the valve chamber. The action is as
follows-When the valve is at one end of its stroke the inlet port is uncovered,
and steam (or fluid) passes into the cavity between the two pistons of which the
valve is composed, and thence into the high pressure cylinder by the port communi-
cating therewith. At a suitable part of the stroke of the engine the inlet port is
covered by the piston valve, and the supply of steam (or fluid) to the high pressure
cylinder is cut off. As the effective stroke of the high pressure piston is completed
the further movement of the valve causes the port of the low pressure cylinder to
become uncovered; the steam (or fluid) then returns from the high pressure
cylinder, and, passing through the cavity of the valve, enters the low pressure

page_text: cylinder and exerts a pressure on the piston within this cylinder. The valve then
returns, and towards the completion of the effective stroke of the low pressure
piston the port in the low pressure cylinder becomes uncovered, and the cylinder is
then able to exhaust its contents by the open end of the valve chamber. The inlet
port now also becomes again open to the cavity between the pistons of the valve
and to the high pressure cylinder, as at the commencement, and ready for another
stroke.
In some cases I reverse the positions of the inlet port and of the exit passage at
the end of the valve chamber, making the latter the inlet and the former the
exhaust.
I do this in cases where I wish it to be able to vary the cut off. I then provide
an additional port to admit the steam (or fluid) to the high pressure cylinder. The
steam (or fluid) does not pass directly from the port into the cylinder, but into a
chamber containing a cut off valve which is attached by a rod to the high pressure
piston. This cut off valve is readily accessible, and can be turned or set to give
any degree of expansion which may be desired.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Peter William Willans in the Great Seal Patent Office on the 28th
June 1879.
PETER WILLIAM WILLANS, of Bow, in the County of Middlesex. " IMPROVE-
MENTS IN MOTIVE POWER ENGINES TO BE WORKED BY STEAM OR OTHER ELASTIC
FLUID."
This Invention has for its object improvements in motive power engines. to be
worked by steam or other elastic fluid.
The engine consists of a high and a low pressure cylinder parallel the one to the
other, and with a valve chamber between or at the side of them in which a piston
valve works. The cylinders are single acting, and they contain pistons from which
connecting rods pass direct to opposite cranks on the engine shaft. The valve
chamber is cylindrical, and has in its sides three ports, one by which the steam (or
fluid) is admitted, and others by which it passes into and from the cylinders.
The valve consists of two pistons rigidly connected by a stem, so that they
enclose between them a small cavity within the valve chamber. The action is as
follows: When the valve is at one end of its stroke the inlet port is uncovered
and steam (or fluid) passes into the cavity between the two pistons of which the
valve is composed, and thence into the high pressure cylinder by the port communi-
cating therewith. At a suitable part of the stroke of the engine the inlet port is
covered by the piston valve and the supply of steam (or fluid) to the high pressure
cylinder is cut off. As the effective stroke of the high pressure piston is completed
the further movement of the valve causes the port of the low pressure cylinder to
become uncovered; the steam (or fluid) then returns from the high pressure

page_text: cylinder, and, passing through the cavity of the valve, enters the low pressure
cylinder and exerts a pressure on the piston within this cylinder. The valve then
returns, and towards the completion of the effective stroke of the low pressure
piston the port in the low pressure cylinder becomes uncovered, and the cylinder is
then able to exhaust its contents by the open end of the valve chamber. The inlet
port now also becomes again open to the cavity between the pistons of the valve
and to the high pressure cylinder, as at the commencement, and ready for another
stroke.
In some cases I reverse the positions of the inlet port and of the exit passage at
the end of the valve chamber, making the latter the inlet and the former the
exhaust.
I do this in cases where I wish to be able to vary the cut off. I then provide
an additional port to admit the steam (or fluid) to the high pressure cylinder. The
steam (or fluid) does not pass directly from the port into the cylinder, but into a
chamber containing a cut off valve which is attached by a rod to the high pressure
piston. This cut off valve is readily accessible, and can be turned or set to give
any degree of expansion which may be desired.
In order that my said Invention may be most fully understood and readily carried
into effect, I will proceed to describe the Drawings hereunto annexed.
DESCRIPTION OF THE DRAWINGS.
Figure 1 is a longitudinal section of an engine constructed according to my
Invention.
a and b are the cylinders, and c the valve chamber between them; d and e are
the pistons in the cylinders a and b. These pistons are hollow, and within each of
them is the joint for attaching the connecting rod; ƒ and g are the connecting rods
coupling the pistons with the opposite cranks upon the crank shaft h. The crank
shaft has also an intermediate throw, or it may be an eccentric, from which motion
is transmitted to the valve by the connecting rod i. The valve consists of two
pistons and k³ connected by the stem. When the valve is in its lower position
the space around the stem is in communication with the steam supply passage 1,
and the steam is able to pass into the high pressure cylinder by the port a'. As
the valve rises the lower valve piston 2 covers the mouth of the steam passage 1,
stopping the flow of steam to the high pressure cylinder, and then the stroke of
the piston d is continued by the partial expansion of the steam in the cylinder a.
By the time that the stroke is completed the valve has risen to such a position
that the port b' of the low pressure cylinder also communicates with the space
around the stem of the valve; and then during the return stroke of the piston d
and the effective stroke of the piston e the steam passes from the cylinder a into
the cylinder b and a further expansion takes place. When the piston e reaches the
bottom of the cylinder b, the valve having passed, the top of its stroke has again
descended so far that the port 61 is uncovering at the top of the valve, and the
spent steam thus passes out from the low pressure cylinder 6 during the return of
its piston e.
As already mentioned, when I wish to vary the cut off I reverse the arrangement,
making the passage the outlet for the spent steam and supplying the steam at the
top of the valve chamber. This form of engine is illustrated by Figure 2. The
expansion valve consists of a piston m of suitable length attached by a rod to the
piston of the high pressure cylinder; it works in a valve chamber n, in the side of
which there is the steam passage n'; and when the valve m rises high enough to
uncover the mouth of the passage n' steam passes by it into the high pressure
cylinder; the cut off takes place when the valve descends so far as to cover the
inner end of the passage n¹. The steam is caused to pass from the high into the
low pressure cylinder in the manner already described.
Figure 3 shows a modification of the arrangement in which the cut off valve is
placed upon the low pressure piston. The cut off also is so arranged that the

page_text: degree of expansion can be varied whilst the engine is at work. The cut off valve
in this Figure is marked o. It is attached to the low pressure cylinder by a hook
which admits of its being turned round by means of a square stem p entering a
hole of corresponding form within the valve. The valve o works in a valve
chamber to which the boiler steam is supplied. The stem p passes out through
the top of the valve chamber q by a stuffing box, and is fitted with a hand lever;
it may be also worked by the governor. The upper end of the expansion valve is
inclined, so that by turning it the time at which it uncovers the mouth of the
passager by which the steam passes to the valve chamber c, and so to the high
pressure cylinder, can be varied at pleasure, even when the engine is in motion.
The valve o being constantly exposed to steam pressure also acts as a ram, and by
it a constant downward thrust is maintained even when the steam is expanded in
the low pressure cylinder below the atmospheric pressure. The ram also tends to
equalize the power given out by the engine during the effective strokes of the two
cylinders. In Figures 1 and 2 a ram 8 is also shown mounted on the top of the
low pressure piston.
Figure 4 is a vertical transverse section taken on the line 1, 1, in Figure 3.
Having thus described the nature of my said Invention, and the manner of
performing the same, I would have it understood that I claim,-
First. In the construction of motive power engines the combination, substantially
as described, of a high pressure and low pressure cylinder with a piston valve for
distributing the steam or elastic fluid.
Second. The means for regulating the admission and cut off of the steam or
fluid in its passage to the high pressure cylinder of single acting compound engines,
such as herein described.
Third. In connection with the regulation of the admission and cut-off as described,
or it may be separately therefrom, the means for maintaining a constant pressure in
the direction of the crank shaft upon the low pressure piston.
Fourth. The construction of motive power engines to be worked by steam or
other elastic fluid, substantially as described, and represented in the annexed
Drawings.
In witness whereof, I, the said Peter William Willans, have hereunto set my
hand and seal, this 25th day of June, in the year of our Lord One thousand
eight hundred and seventy nine.