IMPROVEMENTS IN STEAM ENGINES
Year: 1878

page_text: PROVISIONAL SPECIFICATION left by the said William Rennie at the Office
of the Commissioners of Patents on the 8th May 1878.
WILLIAM RENNIE, of Newry, Ireland. "IMPROVEMENTS IN STEAM ENGINES."
My Invention relates to a method of arranging the parts of horizontal compound
condensing steam engines, so as to combine in a higher degree than heretofore the
advantages of direct action, durability, accessibility, and compactness.
The three cylinders, formed of a single casting, are of equal length, are parallel
with and abreast of one another, and have their centre lines in one horizontal plane.
The high-pressure cylinder, which is in the centre, exhausts equally and simul-
taneously into the two side ones.
The valve boxes are on the under side, whereby all liability of water accumu-
lating in the cylinders is obviated; and a single plate sorves as cover of all three
cylinders, having flanges upon it to admit of screwing all down to the bed plate.
The valve boxes are also provided with end covers to give ready access to the
valves.
The three piston rods are connected to a single cross head, which works in an
open connecting rod provided with caps and bolts.
The condenser with its air pump and the force pump are screwed upon the bed
plate between the cylinders and the crank shaft, the axes of the air pump and force
pump being respectively in the same lines as those of the two side or low-pressure
cylinders. The piston rods of the latter are prolonged through the cross head, and
serve, one as the piston rod of the air pump, the other as the ram of the force
pump.
The two low-pressure cylinders exhaust into a pocket cast in the bed plate. This
pocket is prolonged, so as to serve as a pipe leading to the condenser, which the

page_text: exhaust steam enters from below, being carried above the water level by a pipe
cast in its interior. The injection water enters the condenser from below by a
stand pipe in its interior, which passes through the bed plate, and which carries in
its upper end the injection valve, the spindle of which passes out through a gland
on the top of the condenser.
A passage for the overflow is cast within the condenser at one side, and com-
municates with a similar passage leading through the bed plate, to the under side
of which the overflow pipe is screwed.
A cast-iron box similar in form to the condenser carries the force pump, and con-
tains within it the valves of the latter.
The suction pipe is led from a tee on the overflow pipe and enters the above-
mentioned box or force pump stand through the bed plate from below, and the
discharge pipe in like manner passes down through the bed plate within the box.
The pipes connected within the condenser and force pump being arranged as
above described, none of them appears above the bed plate. Access is given to
them by a transverse passage left in the foundation through which the injection,
overflow, and feed-water pipes pass out beneath the floor. The steam pipe is also
introduced beneath the floor at the back end of the cylinders, where the steam is
admitted through a combined stop and throttle valve. The screwed spindle of this
valve passes through a nut fitted in the end of a bell-crank lever connected with
the governor, so that it acts as a throttle valve when the engine is at work.
The ends of the cross head travel in slide bars, which extend from the low-
pressure cylinder covers to those of the air pump and force pump respectively.
The three valve spindles are connected to a small cross head, which derives its
motion through two connecting rods from a wiper shaft worked from the eccentric.
The wiper shaft rests in bearings provided for it in the lower pair of the slide bars.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Williain Rennie in the Great Seal Patent Office on the 7th November
1878.
WILLIAM RENNIE, of Newry, Ireland.
"IMPROVEMENTS IN STEAM ENGINES."
My said Invention relates to horizontal compound condensing steam engines, and
consists of an improved arrangement of the parts, so as to combine in a higher
degree than heretofore the advantages of direct action, durability, accessibility, and
compactness.
And in order that my said Invention may be fully understood I shall 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 summe letters of reference
indicating corresponding parts in all the Figures.
Figures 1, 2, and 3, Sheet 1, of my Drawings represent respectively a side
olevation, plan, and transverse section of a compound steam engine constructed
according to my said Invention.
Figure 4 is a longitudinal vertical section (drawn to an enlarged scale) of the
force pump with its stand.
And Figures 5, 6, and 7, Sheet 2, represent respectively (on an enlarged scale)
a longitudinal vertical section, a horizontal section, and a transverse section of tho
condenser detached.
Referring to Figures 1, 2, and 3, Sheet 1, A, B, B¹, are three cylinders formed in
a singlo casting, side by side, and of equal length with their axes in one horizontal
plane. The high-pressure cylinder A, which situate between the two low-pressure
cylinders B, B, exhausts equally and simultaneously into the latter.
The valve boxes a, b, b¹, are arranged beneath the cylinders A, B, B¹, a single
plate serving to cover all three. This plate is provided with flanges, by means
of which the cylinders are bolted down to the bed plate C. The valve boxes are
also provided with end covers c to admit of ready access to the valves.
The three piston rods D, E, E', are connected to a single cross head F, to which
is also attached the forked end d of the connecting rod G jointed to the crank G¹
fast on the crank shaft H.
On the bed plate C, between the cylinders and the crank shaft, are secured the
condenser I and the force pump stand K. The axes of the air pump and the force
pump are respectively in the same lines as those of the two low-pressure cylinders
B, B1, the piston rods E, E¹, of which are prolonged through the cross head F, and
serve the one, E, as the piston rod of the air pump, and the other, E, as the ram
of the force pump.
с
The two low-pressure cylinders exhaust into a pocket M cast in the bed plate
and prolonged, so as to form a pipe N leading to the condenser (see Figures 5, 6,
and 7, Sheet 2). The exhaust steam enters the condenser from below, and is con-
ducted above the water level by a pipe O cast in the interior. The injection water
also enters the condenser from below by a stand pipe P, which passes through the
bed plate C and carries in its upper end the injection valve Q, the spindle e of
which passes out through a stuffing box R on the top of the condenser.
A passage f for the overflow is cast in the interior of the condenser at one side,
and communicates with a passage g leading through the bed plate to the overflow
pipe h.
The air pump S, which is double acting, is situate nearly in the centre of the
condenser, with the steam and water space below on one side, the hot well and the
overflow passage being on the opposite side.
The suction valves T, T¹, with the valve guards U, U¹, are accessible by doors
V, V1; the guards U' being cast on the doors V'.
The force pump is covered by a cast-iron box K, Figure 4, within which are the
pump valves i, i. The suction pipe X leading from the overflow pipe / enters the

page_text: box K from below through the bed plate C, the discharge pipe Y in like manner
passing down through the bed plate.
The pipes connected with the condenser and force pump being arranged as herein-
before described are all situate beneath the bed plate C, and in order to obtain
access to them a transverse passage Z is left in the foundation; the injection, over-
flow, and feed water pipes passing out from beneath the floor into this transverso
passage. Steam is admitted to the cylinder A through a pipe l arranged beneath
the floor behind the cylinder, and provided with a combined stop and throttle
valve m, the screwed spindle n of which passes through a nut o fitted in the end of
a bell-crank lever p, the latter being connected by a rod r with the governor g,
so that the valve acts as a throttle valve when the engine is at work. The
valve m may however be arranged in a well-known manner, so as to act as a
stamper valve by means of a tappet connected by gearing with the crank shaft.
In this case the tappet raises the valve by ineans of a slider on the valve spindle
actuated by the governor, so as to effect a self-acting variable cut-off.
The three valve spindles 8, 81, 82, are connected to a cross head t, which derives
its motion through a pair of connecting rods u from a shaft worked from an
eccentric w on the crank shaft H. The shaft v is mounted on bearings on the lower
pair of slide bars x, on which the cross head F slides.
The engine operates in the following manner:-The steam valve m being opened
by means of a hand wheel 1, steam is admitted into the valve box a of the high-
pressure cylinder A, and the slide valve a' thereof being moved so as to open one of
the ports, say (for example) the port leading to the rear end 2 of the cylinder, the
steam enters the cylinder behind the piston. The piston will then travel towards
the opposite end of the cylinder, and as the piston rod is connected to the cross
head F, the latter will be forced along its guides x, and thereby impart through the
connecting rod G a partial revolution to the crank shaft H. By the time the piston
has completed its forward stroke the slide valve a¹ will have been reversed under
the action of the eccentric wand the port leading to the front end 3 of the cylinder
opened. Steam will then enter the cylinder from the valve box a, and by acting
on the face of the piston cause it to make its return stroke whilst the steam from
behind the piston passes through the ports a², a², from the cylinder A into the valve
boxes b, b, of the two cylinders B, B', entering the latter in front of their pistons
(the rods of which are also connected to the cross head F), and thus acclerates the
back stroke of the engine. Upon the completion of the back stroke the slide valves
a', as, as, of the whole of the cylinders will have been again reversed under the
action of the eccentric w, and live steam from the valve chest a will again enter the
cylinder A behind its piston, causing it to make its forward stroke. The steam in
front of the piston will then pass from the cylinder A through the ports a² and
valve boxes b, 61, into the two low-pressure cylinders B, B', behind their pistons,
whilst the steam from these cylinders in front of their pistons escapes through the
exhaust ports b³ into the pocket M, and travels thence along the pipe N (forming a
continuation of the pocket) into the condenser I. The whole power of the steam is
thus utilized before it is permitted to enter the condenser, whereby considerable
economy in the consumption of steam is effected.
The speed of the engine is regulated by the governor g, which by acting upon the
valve m regulates the admission of steam, as is well understood.
Having now described and particularly ascertained the nature of my said In-
vention, and the manner in which the same is or may be used or carried into effect,
I would observe in conclusion that what I consider to be novel and original, and
therefore claim as the Invention secured to me by the horein-before in part recited
Letters Patent is,―
First. Arranging the condenser and force pump of a horizontal compound engine
between the cylinders and the crank shaft, with their axes in a line with the axes
of two of the cylinders, and utilizing an extension of the piston rods of the latter as
the piston of tho air pump and the rain of the force pump, substantially as herein-
before described, and illustrated by my Drawings.

page_text: Second. Arranging below the bed plate of the engine the whole of the pipes
leading to the condenser and force pump, substantially in the manner and for the
purpose herein-before described, and illustrated by my Drawings.
Third. Placing the valve boxes of horizontal steam engines beneath the cylinders
for the purpose of preventing the accumulation of water in the cylinders, sub-
stantially as herein-before described, and illustrated by my Drawings.
In witness whereof, I, the said William Rennie, have to this my Specification
set my hand and seal, this Fourth day of November, One thousand eight
hundrod and seventy-eight.
WILLIAM RENNIE. (L.S.)