Improvements in the Construction of Compound Steam Engines.
Year: 1885

page_text: Improvements in the Construction of Compound Steam Engines.
I GEORGE DOWNING, of 8 Quality Court, Chancery Lane, in the County of
Middlesex, Patent Agent, do hereby declare the nature of my invention for
"IMPROVEMENTS IN THE CONSTRUCTION OF COMPOUND STEAM ENGINES," a com-
munication from Auguste Queruel, of 7 Boulevard de Strasbourg, Paria, France,
Engineer, and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement :-
The object of my invention is to effect improvements in three-cylinder compound
steam engines, for compressing gases and other analogous purposes.
My improved steam engine consists, essentially, of a high pressure steam cylinder,
compounded with two low pressure steam cylinders, one on each side of the high
pressure cylinder, with the usual pistons, piston rods, and connecting rods; the
crank of the high pressure cylinder being placed 180° from those of the low
pressure cylinders, by which arrangement the steam passages from the high to the
low pressure cylinders are made very short and direct, thereby saving steam and
rendering the expansion more perfect, than with engines having long steam
passages.
And in order that my said invention may be particularly described and ascer-
tained reference is hereby made to the accompanying drawings, in which similar
letters of reference indicate corresponding parts.
Fig. 1 is a sectional elevation shewing the principal parts of my improved steam
engine; Fig. 2 is a sectional elevation shewing the central high pressure cylinder
and valves. Figs. 4 5, 6, 7 8 9, 10, and 11, are enlarged details of the valves, and
valve gear.
The drawings represent the engine as of the vertical type, but the cylinders may
be arranged horizontally or diagonally, if necessary, the framing being modified to
suit such positions.
a a is the foundation plate, of a cellular construction, the parts being bolted
together. The bearings for the crank shaft are cast on the plate a a. b b. are the
cellular frames for carrying the cylinders.
c is the high pressure cylinder, placed between the two low pressure
cylinders c¹ c.
•
The three cylinders are solidly united and bolted upon the cellular frames.
All the cylinders are completely steam jacketed, and one of their special features
is that they have their steam ports in a straight line, communicating at the
cylinder ends.
The cylinders may be lagged, to prevent conduction of heat from their frames,
by means of any suitable nonconducting material, such as vitreous or silicious

page_text: materials, asbestos or wood. For this purpose it is advantageous to connect the
· frames by metal plates, or by other means so as to maintain them always at the
same distance apart.
:
The shaft d has three cranks e e e. The two outer cranks, are connected to the
piston rods of the large cylinders, and the centre crank to the piston rod of the
small piston and at an angle of 180° from those of the large cylinders.
The framing is sometimes used as an injection condenser, and the air pump is
then fitted as shewn at f in dotted lines in Fig. 2; but surface condensers may be
used, if preferred.
The various arrangements herein mentioned are applicable to large and small
engines, with vertical, horizontal, or inclined cylinders, and having a small cylinder,
and a large cylinder, or large cylinders, into which the steam passes.
The valve gear consists of a modification of the "Farcot" slide valve gear.
The drawings represent my arrangements, with a novel method of regulating the
distribution of the steam.
I
The main slide valves are driven by connecting rods, actuated by excentrics, as
shewn in Figs. 1 and 2. g g are the two slide valves to the high pressure
cylinder c. Between the two valves a cataract cylinder h is fitted for controlling
the "cut-off" valves; aided by springs i i.
The exhaust is by this slide valve rendered independent of the admission, the
excentric by which it is actuated may therefore be arranged to work in the usual
manner; but the action of the cataract pistons upon the "cut off" valves may bo
⚫ effected in the manner herein after described.
The cataract cylinders h (Figs. 2 and 3) have inlet & outlet ports k k so arranged
at various heights that the enclosed steam arrests the pistons h¹ h¹ and the cut off
valve, and cuts off steam at the required moment.
The two main valves g g are connected together by the union rod g¹, and there-
fore move simultaneously; and, when moved by the excentric they have a tendency
to carry the cut-off valves with them; but the connection between the pistons of
the cataract and the cut-off valves retards the motions of the cut-off valves, and
allows the steam to enter the cylinder, by ports c³ for the desired proportion of the
stroke.
By throttling the exit of the steam from the cataract cylinder h, through the
ports kk, or entirely closing some of those ports, the admission of steam to the
cylinder c is increased, and vice versâ ; and the period of admitting full steam can
be regulated, as desired.
In order that the cataract pistons may freely leave the ends of the cylinders,
valves (opening inwards) are arranged which re-admit the steam by reason of the
suction of the pistons. The valves are again closed by the cushioning which
takes place on the return of the pistons.
Another arrangement is shown in figure 4, in which the cataract cylinder is
fitted with two pistons m m, which move in opposite directions. The rods n n of
these small pistons govern the cut off plates. To insure equal action they are
connected by connecting rods o o and cranks p p to a shaft p¹ common to both.-
It will be observed that the cranks are dissimilar as to the length of radius, and
the manner in which they are keyed, so that the disturbing effect caused by the
obliquity of the connecting rods may be corrected..
The cut-off plates may be suitably supported by springs of any kind, preferably
however by the arrangement of springs ii shown in Figure 2. The coiled springs
i i support the rods n, of the cut off valves 9 9. Two arms rr fixed on the main
valve rod g', carry stuffing boxes through which the rods n n pass, working “stiff”
therein. The movements of the arms carry the rods n n with them.
The admission or passage of the steam from the high pressure cylinder, into the
expansion cylinder or cylinders, takes place in a straight line, and with the minimum
of clearance, by means of slide valves with two parallel faces. Each slide valve is-
divided into two equal and similar parts, each part fitting valve face at the end of
the cylinder, as shown in Fig, 8.

page_text: Each half of the slide valve consists of two distinct parts, one part t sliding on
the valve face on the small cylinder, and t¹ sliding on the valve face on the large
cylinder. 88 are thin metal plates which afford sufficient elasticity to compensate
for wear & prevent leakage.
In this manner the steam at the moment of its passage passes between the two
movable portions, and forcibly and simultaneously presses the two parts of the slides
upon the seats of the two cylinders, and ensures contact of the surfaces.
Modifications of these compensating plates 8 are shewn in Figs. 7, 9, 10 and 11,
which will be readily understood from the drawings.
It will be seen on reference to Fig. 1, that the movement of one slide valve for
leading the steam from one cylinder to the other is transmitted to the other slide
valve by a beam, w, which places them in equilibrium, and very much simplifies
the motion.
To obtain as perfect an action as is attainable, and without rejecting the use
of the Stephenson link, and excentric arrangement, which may with advantage
be employed, it is generally desirable to adopt a more solid and simple arrangement,
specially for high powers.
In operating the valves I prefer to use the spur wheels shown in Figs. 1 and 2,
consisting of a toothed wheel u, so mounted on the crank shaft as to be capable of
rotating a certain number of degrees on the shaft, as a shifting exentric is usually
mounted.
This wheel, u, drives a second toothed wheel u¹, likewise capable of shifting
between stops on the counter shaft v.
The wheel u' by its crank pin u² imparts movement to a connecting rod as shewn,
this rod is jointed to a Beam The latter at the same time transmits motion in an
opposite direction to the slide valves on the large Cylinder on the opposite side.
It may be added that, to meet the inversion of the motion, the slide valves are
also inverted with relation to the other.
When power is required for reversing the motion of the engine, I fit the same as
shewn at x, in Fig. 2.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is :-
1. In compound steam engines of the description aforesaid, the application and
use of expansion valves controlled by cataract cylinders and pistons, arranged for
variable expansion, substantially as herein before described and shewa on the
drawings.
2. In compound steam engines, constructed as aforesaid, the application and use
of the springs i i to support the cut-off valves and rods and assist the cut-off,
substantially as herein before described or referred to and shewn on the drawings.
3. In compound steam engines constructed as aforesaid the application and use
of double faced valves having through passages and provisions for taking up wear,
substantially as herein before described and shewn on the drawings.
4. The general combination and arrangement of the several and respective parts,
together forming my improvements in compound steam engines, substantially as
herein before described and shewn on the drawings.