[MPROVEMENTS IN STEAM ENGINES
Year: 1876

page_text: LETTERS PATENT to John Mills, of Oldham, in the County of Lancaster,
Engineer, for the Invention of "[MPROVEMENTS IN STEAM ENGINES."
led tho 22nd June 1877, and dated the 30th December 1876.
PROVISIONAL SPECIFICATION left by the said John Mills at the Office of
the Commissioners of Patents on the 30th December 1876.
JOHN MILLS, of Oldham, in the County of Lancaster, Engineer.
IN STEAM ENGINES."
"IMPROVEMENTS
My Invention relates to the class of steam engines styled compound engines. In
such engines the steam which has acted within one cylinder is exhausted into a
second cylinder or set of cylinders wherein it acts expansively upon a greater piston
arca, as is well understood.
In some cases the steam is further expanded and permitted to act within other
cylinders before being passed into the condensers.
In such engines as constructed previously to my said Invention it has been usual
when employing cut-off valves to apply such valves only to the high-pressure
cylinders.
According to iny Invention I apply such cut-off valves to the low-pressure cylinder
or cylinders as well as to the high-pressure cylinders, or I apply cut-off valves
to the low-pressure cylinders only, or I so suitably form and arrange the valves of
the low-pressure cylinders as that the steam shall be purposely cut off at compara-
tively carly points in the strokes of the pistons, so as to cause back pressure within
the high-pressure cylinders. I so form and arrange the valves of the said low-
pressure cylinders as that the point of cut-off is fixed, or I provide ordinary or
suitable arrangements for effecting the cut-off by hand, or for controlling the cut-off
by means of the governor.
I consider my said Invention to be applicable more particularly to condensing
engines, but I do not confine myself to such application, as I may apply my Inven-
tion to engines not fitted with condensers.
1 believe that the application of my said Invention is productive of economical
advantages in the working of the engines.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said John Mills in the Great Seal Patent Office on the 29th June 1877.
JOHN MILLS, of Oldham, in the County of Lancaster.
ENGINES."
"IMPROVEMENTS IN STEAM
My Invention relates to that class of steam engines styled compound engines. In
such engines the steam which has acted within one cylinder is exhausted into a
second cylinder or set of cylinders wherein it acts expansively upon a greater piston
area in manner as is now well understood.
In some cases the steam is further expanded and is permitted to act within other
cylinders upon pistons having collectively a still greater area or within a single
cylinder having a piston still greater in area before the said steam is finally passed
into the condenser or condensers.
In the said compound engines as constructed previously to my said Invention it
has been usual when employing cut-off valves to apply such valves only to the
high-pressure cylinders, the steam being freely admitted into the low-pressure
cylinders when discharged from the said high-pressure cylinders.
According to my Invention I apply cut-off valves to the low-pressure cylinders
as well as to the high-pressure cylinders, or I apply cut-off valves to the low-pressure
cylinders only, that is to say, I so suitably form and arrange the valves of emission
from the high-pressure cylinders or of admission to the low-pressure cylinders as
that the steam shall be purposely cut off at comparatively early periods in the
strokes of the pistons, so as to have the effect of creating "back pressure" within
the high-pressure cylinders. I may so form and arrange the valves which control
the admission of steam to the low-pressure cylinders as that the point or period of
"cut-off" is fixed, as, for example, I may form the exhaust passage within a slide
valve fitted to a high-pressure cylinder with an amount of lap so that the exhaust
port is covered before the said cylinder is fully exhausted, or I may provide ordinary
or suitable arrangements for regulating the period of cut-off by hand or by the action
of the governor.
Arrangements now in use for regulating or controlling the period of cut-off of the
steam admitted to the high-pressure cylinders or to the cylinders of engines which
are not compound engines are suitable for application to the valves which adınit
the steam to the low-pressure cylinders, and may be adapted to such valves to
answer my intended purpose, and therefore I have not considered it to be necessary
to illustrate or describe any special arrangement.
I consider my Invention to be applicable more particularly to condensing engines,
but I do not confine myself to such application, as I may apply my Invention to
engines not fitted with condensers.
I believe that the application of my said Invention to the said compound engines,
that is to say, the application of cut-off valves to the low-pressure cylinders of
compound engines, or the cutting off of the admission of steam from the high-
pressure to the low-pressure cylinder before the high-pressure cylinder is completely
exhausted is productive of economical advantage in the working of engines.
Having now fully set forth and indicated the nature of my said Invention, and
means whereby the same may be carried into effect, I would have it understood in
conclusion that I claim,-
First. The application of cut-off valves to the low-pressure cylinders of compound
engines, that is to say, to the cylinders into which steam is expanded from the high-
pressure cylinders.
And, lastly. So forming, arranging, and actuating the valves which control the
passage of steam from the high-pressure cylinders to the low-pressure cylinders of
compound engines as that the passage of steam from one cylinder to the other is
cut off or stopped before the terminations of the strokes of the high-pressure

page_text: pistons, whereby back pressure is purposely created within the said high-pressure
cylinders.
In witness whereof, I, the said John Mills, have hereunto set my hand and
seal, this Twenty-seventh day of June, in the year of our Lord One
thousand eight hundred and seventy-seven.
Signed and sealed by the said John
Mills, in the presence of
EDWARD K. DUTTON,
Agent to the Patentee,
3, Princess Street,
Manchester.
JOHN MILLS. (L.S.)