IMPROVEMENTS IN STEAM ENGINES
Year: 1881

page_text: PROVISIONAL SPECIFICATION left by the said Joseph Hunter MoFerran
and William Rennie at the Office of the Commissioners of Patents on the
12th May 1881..
JOSEPH HUNTER MCFERRAN and WILLIAM RENNIE, of Newry, Ireland.
"IMPROVEMENTS IN STEAM ENGINES."
Our Invention relates to compound engines, and has reference to a less expensive
and more effective method of making new engines, and especially for compounding
existing single cylinder engines, either marine, stationary, or locomotive.
In carrying out our Invention we use two cylinders to each engine, one placed
within the other, that is the high pressure cylinder is placed within the low
pressure or condensing cylinder; this enables us to have passages so short that we
can dispense with two of the valves required in common compound engines, that is,
we make the steam valves of the condensing cylinder serve as exhaust valves for
the high pressure cylinder; either slide or stamper valves are applicable to our
plan; we have one rod to the high pressure cylinder and two to the low pressure
cylinder, we connect all three rods to one crosshead when driving a single crank,
but when working two cranks we, of course, connect each cylinder to separate
crossheads; in the case of condensing engines we extend one of the low pressure
piston rods to form the air pump rod, and the second part of the same Invention
to form the force pump rod.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Joseph Hunter McFerran and William Rennie in the Great Seal
Patent Office on the 12th November 1881.
JOSEPH HUNTER MCFERRAN and WILLIAM RENNIE, of Newry, Ireland.
"IMPROVEMENTS IN STEAM ENGINES."
Our said Invention relates to compound engines, and has reference to a less
expensive and more effective method of making new engines, and especially for
compounding existing single cylinder engines, either marine, stationary, or
locomotive.
In carrying out our said Invention we employ two cylinders to each engine, one
placed within the other, that is to say, the high pressure cylinder is placed within
the low pressure or condensing cylinder, whereby we are enabled to reduce the
length of the passages so that we can dispense with two of the valves required in
ordinary compound engines, the steam valves of the condensing cylinder serving,
according to our arrangement, as the exhaust valves for the high pressure cylinder.
Our said Invention is equally applicable whether slide or stamper valves are
employed. We have one rod to the high pressure cylinder and two to the low
pressure cylinder, we connect all three rods to one cross head when driving a single
crank, but when working two cranks we necessarily connect each cylinder to
separate crossheads; in the case of condensing engines we extend one of the low
pressure piston rods to form the air pump rod, and the second rod of the same
piston to form the force pump rod.
And in order that our said Invention may be fully understood, we will now
proceed more particularly to describe the same, and for that purpose shall refer to
the several Figures on the annexed Sheets of Drawings, the same letters of reference
indicating corresponding parts in all the corresponding Figures.
Figures 1 and 2 (Sheet 1) of the accompanying Drawings represent a sectional
plan and sectional elevation respectively of a compound stationary condensing
engine constructed and arranged according to one part of our said Invention ;
Figures 3 and 4 shew modifications for compounding existing engines.
In the arrangement illustrated in Figures 1 and 2 (Sheet 1) A represents the
high pressure cylinder which is contained within that of the low pressuro
cylinder B. The high pressure cylinder is fitted with an ordinary piston a of
suitable area, and a piston rod a² (passing through a stuffing box) for transmitting
the motion of the piston. The low pressure cylinder B is provided with an annular
piston b which works against the outside of the high pressure cylinder and the
inner surface of its own cylinder, and is fitted with two rods b¹ and 62 which are
carried through stuffing boxes in the cylinder covers in the ordinary way, as
shewn.
C is a slide valve (which may be of any suitable form) working within the valve
box c by an eccentric or other similar convenient means, and so arranged as to
work in common relation to both cylinders.
D is a stamper valve placed within the steam supply pipe d and arranged under
the control of a governor so as to vary the cut off according to the fluctuations of
the work or load placed upon the engine.
E is the condensor of any known construction carried by suitable framing and
having its air pump e actuating by the rod b connected to the one side of the low
presser piston b.
F is the force pump, likewise of any known construction, which is similarly
worked by means of the second corresponding piston in rod b¹.
Any ordinary communication or passage G is provided for establishing connection

page_text: between the condenser E and the low pressure exhaust n, by which means a
vacuum is produced for assisting the economical action of the low pressure
cylinder.
It will now be understood that according to this construction and arrangement
of compound engine in which one cylinder is placed within the other we are
enabled to so reduce the length of the communicating passages that we can
dispense with two of the valves ordinarily required in such class of engines. That
is to say, according to our method, the steam supply valves of the condensing or
low pressure cylinder are arranged to serve also as the exhaust valves for the high
pressure cylinder.
On referring to Figure 1 of the Drawings it will be seen that the slide valve is
so situated as to be admitting steam from the boiler to the rear side of the high
pressure piston by means of the passage h, and thus causing it to make its forward.
stroke. At the same time the low pressure piston b is making a similar forward
movement by means of the utilized steam passing from the top end of the high
pressure cylinder by the passages i, j, and k to the back end of the low pressure
cylinder as indicated by the direction of the arrows. The steam on the opposite
side of the low pressure piston having been finally utilized, it is exhausted by
means of the previously mentioned air pump e, through the passages l, m, n, and G,
in communication with the condenser. The steam thus condensed may be
subsequently forced to a hot well or other similar accumulator for feeding the
boiler.
In engines where it is only required to drive a single crank with a fly wheel
provided for carrying it over its dead centres the three piston rods, videlicet, one high
and two low pressure, may all be connected to one cross head working in suitable
guides, and to which the connecting rod is attached. But it is obvious that when
the piston rods are required to actuate two cranks fixed at different angular
relations upon the shaft in lieu of a fly wheel, the rods from the two cylinders
must be connected to separate crossheads or other similar devices, whereby
independent motion is conveyed to such driving shaft.
It has already been explained that in the cases of condensing engines one low
pressure piston rod is extended to work the air pump while the other one is
employed for actuating the force pump.
In Figure 3 (Sheet 2) is shewn a part sectional plan of a simple method of
compounding existing engines according to a modification of our said Invention.
By this arrangement it will be understood that the main portion of a common
or single existing cylinder B may be utilized, while an additional cylinder A is
inserted in the interior thereof, the annular area of the former serving for low
pressure, and the latter for high pressure purposes, similar to the arrangement first
herein before described, while in the Drawings the corresponding letters indicate
similar parts.
One existing cylinder cover A' may be tapped to receive the steam pipe o, while
the other one A is conveniently formed by a fresh casting so as to carry the three
stuffing boxes and interior cylinder in one piece as shewn in the Drawings.
According to this modification stamper valves are employed for controlling the
steam supply and exhaust to and from the said cylinders.
Assuming the high pressure steam from the boiler to be entering the valve
chamber by the pipe d and thence passing through the stamper valve C and pipe p
to the interior of the high pressure cylinder A, the piston a is making its forward
stroke as indicated by the arrow. Simultaneously with this forward motion the
previously used steam on the opposite side of the piston is expelled' and exhausted
into the low pressure cylinder B by means of the pipe o, and diagonal passage to
the stamper valve D, whence it passes by the valve F and pipe q to the back of
the annular piston b. The low pressure piston is thus caused to travel in
the same direction as the high pressure piston at a certain time and for a definite
relative distance, but the timing of the pistons may be modified as desired in any
known manner according to requirements. The expanded steam from the high

page_text: pressure steam being finally enclosed on the one side of the low pressure piston, it
is exhausted to the condenser through the piper controlled by the stamper
valve G. The opposite or return stroke of the pistons is effected in an exactly
similar manner, only the steam is admitted at the other end of the cylinders by
the counter passages and valves of corresponding construction and arrangement.
According to another modification illustrated at Figure 4 of the Drawings, we
provide supplementary stamper valves in the covers of existing cylinders which
have been previously fitted with ordinary slide valves so as to convert them into
compound cylinders at as little expense and labour as possible. In this arrange-
ment it will be unnecessary to repeat the description of the various elements of
construction as they are precisely similar to those already explained, and are
marked with similar letters of reference to the preceding Figures. But in this
modification, for certain economical purposes above stated, the two steam stamper
valves C and D, with a similar pair of valves E and F for respectively supplying
and exhausting the high pressure cylinder are separately located in the covers of
the cylinders as represented, whilst the ordinary existing slide valve G is caused
to serve as the steam and exhaust valve for the low pressure cylinder.
It will be readily understood that according to our method of compounding
engines the cylinders may be connected and controlled in various equivalent ways
without departing from the essence of our Invention.
Having now described and particularly ascertained the nature of our said
Invention, and the manner in which the same is or may be used or carried into
effect, we would observe in conclusion that what we consider to be novel and
original, and therefore claim as the Invention secured to us by the herein before
in part recited Letters Patent is,―
First. A compound steam engine in which the high pressure cylinder is arranged
within the low pressure cylinder, the steam valves to the low pressure or condensing
cylinder being also utilized as the exhaust valves to the high pressure cylinder,
substantially as hereinbefore described, and illustrated in the accompanying
Drawings.
Second. The peculiar construction and arrangement of compound steam cylinders
and valves adapted for compounding existing single cylinder engines, substantially
as hereinbefore described, and illustrated in Figures 3 and 4 of the accompanying
Drawings.
In witness whereof, we, the said Joseph Hunter McFerran and William
Rennie, have to this our Specification set our hands and seals, this Eleventh