CERTAIN IMPROVEMENTS IN COMPOUND STEAM ENGINES
Year: 1876

page_text: LETTERS PATENT to William Pratchitt and John Pratchitt, both of the Denton
Iron Works, Carlisle, in the County of Cumberland, Engineers, for the Invention
of "CERTAIN IMPROVEMENTS IN COMPOUND STEAM ENGINES."
Sealed the 13th February 1877, and dated the 5th September 1876.
PROVISIONAL SPECIFICATION left by the said William Pratchitt and John
Pratchitt at the Office of the Commissioners of Patents on the 5th September
1870.
WILLIAM PRATCHITT and JOHN PRATCHITT, both of the Denton Iron Works,
Carlisle, in the County of Cumberland, Engineers. "CERTAIN IMPROVEMENTS IN
COMPOUND STEAM ENGINES."
This improvement consists in placing the high-pressure cylinder of compound
horizontal engines above the low-pressure cylinder in an inclined position, so that
its connecting rod may be attached to and work upon the same crank as that of
the low-pressure cylinder, a receiver being placed between the two cylinders, which
we prefer to provide with an apparatus of the ordinary construction for reheating
the steam from the high-pressure cylinder before it enters the low-pressure one.
The valves of these cylinders we prefer to make of the usual Corliss description,
regulated from the governor, and where circumstances admit of doing so we place
the air pump and condenser under the low-pressure cylinder in such a way as to
form a base for its support.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said William Pratchitt and John Pratchitt in the Great Seal Patent Office
on the 22nd February 1877.
WILLIAM PRATCHITT and JOHN PRATCHITT, both of the Denton Iron Works,
Carlisle, in the County of Cumberland, Engineers. " CERTAIN IMPROVEMENTS IN
COMPOUND STEAM ENGINES."
This improvement consists in placing the high-pressure cylinder of compound
horizontal engines above the low-pressure cylinder in an inclined position, so that
Drine A77

page_text: its connecting rod may be attached to and work upon the same crank as that of
the low-pressure cylinder, a receiver being placed between the two cylinders,
which we prefer to provide with a steam jacket or an apparatus of the ordinary
.construction, for reheating the steam from the high-pressure cylinder before it enters
the low-pressure one.
The valves of these cylinders we prefer to make of the Corliss description,
regulated from the governor, and where circumstances admit of doing so we place
the air pump and condenser under the low-pressure cylinder, in such a way as to
form a base for its support.
And in order that our Invention may be fully understood and readily carried into
operation, we will proceed to describe the accompanying Sheet of Drawings, in
which Fig. 1 is a side elevation, and Fig. 2 an end view, both partly in section, of
our improved compound steam engine.
a is the high-pressure cylinder placed in an inclined position above the low-
pressure cylinder b, which is placed horizontally or nearly so. The piston rods of
the two cylinders are connected to the same crank on the crank shaft c, as in some
other compound steam engines. d is the receiver between the high-pressure and the
low-pressure cylinders, in which may be placed an apparatus of the ordinary
construction for reheating the steam from the cylinder a before it enters the
cylinder b.
In condensing engines we prefer to place the
cylinder b. The bucket of the air pump is
cross head of the piston rod of the cylinder b.
commonly used for Corliss engines.
air pump e under the low-pressure
worked by the arm e¹ fixed-to the
The framing is of the girder form
In non-condensing engines the air pump e is not required. The high-pressure
steam for the cylinder a is supplied to the admission valves f.f, and the exhaust
steam is discharged through the valves g, g, all the valves being united to the wrist
plate h, as in Corliss engines of the ordinary. construction.
The cut-off is regulated from the governor i in the following manner-The rods
jj, for working the admission valves f, f, are hung upon the pendant links k, l, the
rods having steel catches upon them, which engage with the jointed points of the
valve levers l, l. The fulcra of the links k, k, are free to move by the action of the
governor nearly in the arc of a circle, having the point of the valve lever (when the
valve is closed) for its centre, and when the governer pushes the fulcra of the
links further from the centres of the valves the valve levers are released from the
catches on the rods j, j, earlier than when the fulcra are nearer to the centies of the
valves. The cylinder 6 is also shewn with Corliss valves, as we prefer them, but
any other description of valve may be used.
•
The improved compound expansion steam engines above described are compact,
strong, and can be worked with great economy of steam.
Having thus stated the nature of our Invention and described the manner of
performing the same, we declare that we claim,-
The improved compound steam engine shewn and described, in which the high-
pressure cylinder is provided with Corliss valves, and the low-pressure cylinder with
Corliss or other valves.
We also claim the particular valve releasing motion shewn on the plan, although
other descriptions may be applied, and the combination of cylinders with a framing
of the form shewn on the Drawing.
In witness whereof, we, the said William Pratchitt and John Pratchitt, have
hereto set our hands and seals, this Twentieth day of February, One
thousand eight hundred and seventy-seven.