Improvements in Compound Locomotive Engines
Year: 1898

page_text: Date of Application, 4th July, 1898-Accepted, 3rd Sept., 1898
COMPLETE SPECIFICATION.
Improvements in Compound Locomotive Engines,
I, WALTER MACKERSIE SMITH, of 16, Otterburn Terrace, Jesmond, Newcastle-
on-Tyne, in the County of Northumberland, Engineer, do hereby declare the
nature of this invention and in what manner the same is to be performed to
be particularly described and ascertained in and by the following statement; -
This invention has reference to improvements in compound locomotive engines
of the kind referred to in the Specification of my former Patent No. 20769 of 1890
wherein I have described inter alia improvements whereby such engines are
enabled to start casily and safely and which comprise means for maintaining
in the receiver between the high and low pressure cylinders a suitable pressure
of steam which can be increased at will when it is desired to increase the power
of the engine.
Now my present invention has reference to improved arrangements of
cylinders; an improved arrangement of non-return valves; an improved con-
struction and arrangement of automatic steam regulator with auxiliary valve
for admitting extra steam to the receiver; the combination of such an automatic
steam regulator with non-return valves or their equivalent; an improved arrange-
ment of valve motion; and an improved construction and arrangement of
compound locomotive engine embodying the above indicated features. And
in order that the nature of my improvements and the manner of carrying them
into practical effect may be clearly understood I will now more particularly
describe the same with the aid of the accompanying illustrative drawings,
whereof
Fig. 1 shows a transverse section through the smoke box of a compound
locomotive engine embodying my invention, the engine having three cylinders, viz.
an inside or central high-pressure cylinder and two outside low-pressure
cylinders;
Fig. 2 shows a vertical longitudinal section through the high-pressure
cylinder and valve chest;
Fig. 3 is a part end view partly in section, showing the method of supporting
the back ends of the cylinders on the engine frame;
Fig. 4 is a half front view of the cylinders with their supporting framing, which
shown in cross section;
Fig. 5 shows a half transverse section through the cylinders; and
Fig. 6 shows a vertical longitudinal section through the high-pressure
cylinder and valve chest with one of the ports closed by the valve and the other
in communication with the receiver.
Of these figures, the first is drawn to a smaller scale than the others. Other
figures of the drawings are hereinafter referred to.
1 is the high-pressure cylinder, 2 and 3 are the low-pressure cylinders, and 4
is the receiver which is made up of the exhaust-chamber of the high-pressure
cylinder and the steam-chests of the low-pressure cylinders. 5 and 6 are slide-
valves for the low-pressure cylinders 2 and 3 respectively; in some cases the

page_text: valves 5 and
may be of the piston valve type. 5 and 6" are exhaust pipes
leading therefrom. Between the receiver 4 and the two ends of the high-pressure
cylinder there are communications closed during the working of the engine
(after starting) by non-return valves 7 and 7ª and comprising passages 8 and 8"
formed in the casting of the right-hand cylinder, passages 9 and 9 formed in
the casting of the high-pressure cylinder, and connecting pipes 10 and 10º.
The high-pressure cylinder is by preference cast or made to receive a steam-
distributing valve 11 of the piston type and has one steam-chest 12 at the front
end and another 12" at the back end, these steam-chests being connected together
by a passage 11ª (Fig. 1). The ports 13 and 13" open directly into the pas-
sages 9 and 9 respectively.
On the back end of the high pressure cylinder 1 there is cast a deep plate or
flange 14 (Fig. 3) which fits between the frames 15 and is provided with flanges 14"
and 14 whereby it is attached to the frames 15 by means of bolts 14°, each
made of two diameters and whose parts of larger diameter pass through flanges
of the outside or low-pressure cylinders, so that the central cylinder is secured
to the frames 15 independently of the outside cylinders. A flange may also be
cast on the bottom of the flange 14 so that the cylinder at the back end may be
bolted to the girder 17*.
At the front end the central cylinder 1 is provided with flanges 16 and 16"
(Fig. 4), which correspond to flanges cast or otherwise formed on suitable girders
or stays 17 and 17ª placed above and below the cylinder and fixed to the
frames 15 so as to hold the central cylinder firmly in position at the front end.
It will be seen that by the above arrangements the central cylinder is held
in position between the frames independently of the outside cylinders which are
themselves each bolted to the frames independently of the central cylinder.
Flanges 19 and 19" (Figs. 1 and 5) are cast on the sides of the central cylinder
and correspond to flanges 20 and 20 cast with the outside cylinders. The
parts 19 and 20, and 19 and 20" are respectively bolted together to form a
steam tight joint, but as the cylinders are each fixed to the frames independently
of each other, the strain due to the working of the engine is not borne by the
flanges 19, 19" and 20, 20". In some cases the three cylinders may be cast in
one.
When the engine is at work and running with the regulator closed a vacuum
is formed in the steam chests of the high pressure cylinder. To destroy 'this
vacuum a steam and air valve 1b (Fig. 1) is provided for automatically admitting
steam and air at atmosphere pressure to the steam chests. The admission of air
mixed with steam is preferred to the use of air 'alone, but the admission of air
alone would suffice to destroy the vacuum.
Although I have herein before described an arrangement of three cylinders
it will be obvious that four cylinders may also be employed, in which case two
high pressure cylinders would be arranged centrally with a low pressure cylinder
on each side or vice versa.
In the case of four cylinders the two inside cylinders would be cast in one or
fixed together and secured to the engine frames independently of the outside
cylinders which would themselves be each bolted to the frames independently
of the inside cylinders in the manner bereinbefore described with reference
to three cylinders.
The improved arrangement of non-return valves will be understood from
Figs. 1, 2 and 5. One of the outside cylinders (i.e., the cylinder 2 in Fig. 1)
is provided with passages 8, 8° (one of which 8, is shown best in Fig. 5) which
respectively lead from the steam chest or receiver to the non-return valves 7
and 7 and thereby connect the ends of the high pressure cylinder through
the steam ports 9 and 9°. By my improved arrangement as above described the
non-return valves and passages are rendered easy of access for examination or
repairs.
In lieu of automatic non-return valves, which I prefer, two cocks may be

page_text: provided which will on starting the engine be momentarily opened simul-
taneously by the driver by means of suitable rods and levers to place the piston
of the high pressure cylinder in equilibrium.
For the purpose of admitting extra steam to the receiver at a predetermined
pressure I employ an improved construction of automatic steam regulator of
the kind described in my said former Specification No. 20769 of 1890. One
improved form of such automatic regulator is shown in Figs. 7 to 10 of the
accompanying drawings of which Fig. 7 is a side view partly in section, Fig. 8
a section on the line of Fig. 7, Fig. 9 a section on the line y y of Fig. 7,
and Fig. 10 a section on the line of Fig. 8.
This regulator communicates with the boiler through the pipe 21 and with
the receiver through the pipe 22 (see Fig. 1). The valve 23 is formed with
or carried by a spindle 24 which is formed or provided at the top with a cut-off
valve or piston 25 with grooves and rings, and at the bottom with a valve 26
adapted to bear on a suitable seat so as to prevent any escape of steam from the
boiler into the outer air when it is closed, the valve 23 being kept shut by the
steam in the chamber 22ª pressing on the valve 23 and the pressure of the steam
on the top of the piston 25. In grooves around the piston 27 at the bottom
of the spindle 24 packing rings are arranged to prevent escape of steam even
when the valve 26 is raised from its seat. 28 is a chamber adapted to contain
and which is filled with liquid which may be water or oil that is loaded or is of
itself heavier than water; 28 is a small hole of such a size that a retarding
or cushioning effect is produced when the spindle 24 is raised. 29 is an
auxiliary or controlling valve that is normally pressed to its seat by a spring 30
that can be adjusted so as to exert more or less pressure upon the valve. A
passage 31 leads from the steam chamber 21ª to the valve 29 which admits
steam at the required pressure to the chamber 32 such pressure acting through
the liquid in the chamber 28 upon the piston 25 at the top of the valve stem 24.
When steam is admitted from the boiler to the chamber 21, it acts on the under-
side of the admission valve 23 but as the water or oil in the chamber 28 must
be displaced before the spindle 24 can rise, before this can take
place steam acts on the piston 25 at the top of the spindle 24
and the valve 23, and the blow that would otherwise be given
is prevented. This cushioning may be assisted by means of flexible washers 33
at the bottom of the spindle 24 or, it may be, by a suitable spring. The lift of
the spindle can be regulated by the washer 34 held in position by the nut 35.
The chamber 32 is connected to the chamber 22 by a passage 36 fitted with a
plug through which a small hole 36 is provided, the object of this hole being
to allow a small escape of steam from the chamber 32 to the chamber 22 SO
that when the pressure in the chamber 22 is less than the predetermined pres-
sure and the spring pressed controlling valve 29 is kept open there will be a
steady pressure on the top of the piston 25 at the top of the spindle 24. In
some cases the valve 23 may be a piston fitting into the seat 23 in which case
the spindle 24 would be supported by the valve 26 resting on its seat. The area
of the hole in the valve seat 23ª equal to twice the cross sectional area of either
of the holes in which fit the pistons 25 and 27 which are equal in area.
.
Fig. 11 shows a modification of the automatic regulator wherein the cushion-
ing of the valve 23 is assisted by spring 24 placed above the valve. In this
construction the valve 23 is formed hollow to provide an increased passage for
the steam from the boiler to the receiver. In this case the area of the upper
end 23 of the stem of valve 23 is equal to the area of the space 23° between the
valve and its seating.
Should it be desired at any time to increase the pressure in the receiver and
consequently the pressure in the low-pressure cylinders, it is only necessary to
compress the spring 30 (Fig. 7) in the automatic regulator to obtain any desired
pressure up to the pressure in the boiler, but in order to work the engine most
advantageously I regulate the pressure admitted to the receiver so that the horse

page_text: power developed in each cylinder shall be about equal. To attain this end the
spring 30 which controls the pressure is tested and indexed and the indications
for certain pressures which give certain results are shown on a suitable disc within
reach of the driver.
Figs. 12 and 13 show such a disc in section and side view respectively. The
rod 37 is connected to a screw spindle 38 that passes through a stuffing box (sce
Fig. 7) on the regulator casing. This screw spindle enables the valve 29 to be
closed against any pressure when required. The arrangement is such that
when the hand wheel 39 is turned so that its pointer 39 is opposite a certain
pressure indication on the disc, the spring 30 (Fig. 7) is compressed or relaxed
and a corresponding pressure of steam is admitted to the receiver. Suitable
stops 40 and 40° are provided on the hand wheel and disc respectively. 41 is
a set screw to fix the pointer at the pressure required in the receiver. The pres-
sure of the steam in the receiver may also be indicated by a suitable pressure
gauge. In some cases I provide a steam cock capable of being operated by
hand, independently of the automatic regulator when it is desired to increase the
pressure in the receiver.
Figs. 14 and 15 show the improved arrangement of valve gear in elevation and
plan respectively. The centre line of the valve motion for the outside cylinders
is in the same plane as the centre line of the cylinders and the valves are driven
direct from the axle. The centre or inside cylinder is placed so that the centre
line inclines down to the centre of the crank axle 46 and the centre line of the
valve motion leads up to the centre line of the crank axle, as described in my
previous Specification of Letters Patent, No. 22868A of 1896. In Fig. 15 the centre
line 47 of the high pressure piston valve is shown in the same plane as the centre
line of the cylinder the line of motion 48 being to one side, the valve spindle
being connected to the motion by a crosshead 49. An arrangement of levers
may be employed, but as the crosshead arrangement shown has no joints it is
preferred. It will be seen that the steam distributing valves for the three
cylinders are worked direct by ordinary link motion without the aid of rocking
shafts or swing levers, or other forms of gear that introduce extra joints and
wearing surfaces. The expansion links 50 are all hung from one weigh shaft
by suitable links, the said weigh shaft being by preference placed above the
valve motion. The arm 51 on the weigh-shaft is connected to a reversing screw
of the ordinary type or to a reversing lever by the rod 52. All three sets of
motion are reversed by one operation. Any desired difference between the
points of cut off of the high pressure and the low pressure cylinders can be
arranged for by varying the lengths of the arms 53 on the weigh-shaft from
which hang the swing-links 54 that connect the expansion links, the length of
the expansion links being made to correspond. For example if it be desired
to get a later cut off from the low pressure cylinders, or a greater amount of
expansion, the length of the expansion links would be increased. Or the eccen-
tric rods may be coupled up in front of the link instead of at the ends.
The arrangement of non-return valves enables the engine to be started easily
and safely from any position that the pistons and valves may occupy at starting,
as described in my said former Specification No. 20769 of 1890. For example,
should the distributing valve of the high pressure cylinder be open at starting
to admit steam from the steam chest to one end of the cylinder, the non-return
valve at the other end will open and admit steam at the pressure in the receiver,
hence the pressure acting upon the high pressure piston at starting will be the
pressure of steam in the steam chest minus the pressure of steam in the receiver.
Or, should both ports of the high-pressure cylinder be closed at starting, the
piston will be subjected on both sides to the reduced pressure from the receiver.
Again, should the high pressure distributing valve close one port and open the
other so as to admit steam from the receiver, the non-return valve at the other
end of the cylinder will admit steam at equal pressure. This latter position is
illustrated by way of example in Fig. 6; the engine is then started as follows:-

page_text: Steam is admitted to the receiver 4 and passes therefrom through the steam
port 13 and fills the space between the piston 1" and the back end of the
cylinder 1, and would force the piston to move to the left but as the steam port 13
is closed to the steam chest and the space between the front end of the cylinder
(ie. the left hand end viewing Fig. 6) and the piston is empty of steam, the steam
in the receiver 4 acts on the bottom of the non-return valve 7 and lifts said
valve thereby admitting steam automatically from the receiver to the front end
of the cylinder, thus placing the high pressure piston in equilibrium and conse-
quently free to move in either direction. The engine is thus enabled to make
a start with one or other of the outside cylinders. As the pressure on the top
of the non-return valve after the engine starts is always greater than the pres-
sure on the bottom (that from the receiver) the non-return valve remains closed
after the engine starts and during the time it is working.
The steam passes direct from the boiler through the pipe 21 into the auto-
matic regulator and leaves the latter at a predetermined pressure through the
pipe 22 direct to the low pressure cylinders through the receiver 4. The Ligh
pressure cylinder is formed for the attachment of the steam pipe 45 thereto. The
steam pipes 21 and 45 are both fed from the main 'steam pipe on the opening
of the main steam regulator which regulator is placed in the dome on the boiler
by preference. The steam from the pipe 45 passes direct into the high pressure
steam chests, and the steam from the pipe 21 passes into the low pressure steam
regulator and leaves it again at a previously determined pressure through the
pipe 22 direct to the low pressure cylinders. Thus at about one and the same
time steam at one pressure enters the high pressure cylinder steam chests and
steam at another pressure enters the low pressure steam chest both ready to be
admitted into the cylinders to produce work, when admitted thereto by the action
of the slide valves. After the first exhaust from the high pressure cylinder
has passed into the receiver 4, and if the pressure of the same remains at or above
the predetermined pressure that it is desired to work the low pressure cylinders,
the regulator automatically closes and ceases to draw a supply of steam from
the boiler but should the pressure in the receiver 4 drop below the predetermined
pressure the regulator will open and maintain the desired pressure. Should the
pressure of the steam from the boiler be wire-drawn through the main regulator
down to a pressure less than the predetermined pressure of the steam allowed
to pass the automatic steam regulator that admits steam to the receiver the
valve 29 remains closed the valve 23 will lift and the steam pressure in the
chambers 21 and 22ª will be about equal and the engine will work as a simple
engine.
With low pressure cylinders not much larger than the high pressure cylinder
as herein shown, the latter, when working the engine compound in the ordinary
way developes a higher horse power than either of the low pressure cylinders
and by admitting extra steam to the receiver in order to increase the power of
the lower pressure cylinders the power of the high pressure cylinder is decreased
on account of the back pressure so produced. In this way the horse power
developed by the several cylinders can be made about equal. Or the pressure
in the receiver may be increased to any point up to the boiler pressure the outer
cylinders doing the work while the central piston is practically placed in
equilibrium, the engine then acting as a simple engine. The state of working
between ordinary compound and up to working as a simple engine may be
termed semi-compound, By these means increased power can be obtained when
starting a heavy train, for pulling up inclines, or when extra work is required,
the engine being thus adapted for working with two powers, one as ordinary
compound and the other semi-compound as described.
The power of the engine can thus be increased to any degree within the
maximum limit to suit the work to be done without in any way interfering
with the balance of the engine, the turning effort and stress on the crank and
valve motion being steady and uniform. By the arrangement of cylinders

page_text: herein before described the low pressure pistons never become a drag on the
high and the pressure in the receiver and hence the back pressure on the high
pressure piston is maintained comparatively uniform as one of the two low pres-
sure cylinders is always taking steam and thereby preventing pressure from
accumulating in the receiver. For the same reason the exhausts are frequent
and a uniform draught is obtained.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed I declare that what
I claim in a compound locomotive engine is:-
-
1. The hereinabove described improved construction and arrangement of steam
cylinders wherein one or two inside high pressure cylinders is or are located
between two outside low pressure cylinders arranged one at each side of the
high pressure cylinder or cylinders or the two outside high pressure cylinders
arranged one at each side of two inside low pressure cylinders, the inside cylinder
or cylinders is or are carried by the engine frames independently of the outside
cylinders and vice versa, and the receiver is so formed partly by the exhaust
chamber or chambers of the high pressure cylinder or cylinders and partly by
the steam chests of the two low pressure cylinders that connecting pipes are
dispensed with and steam can pass directly from the said exhaust chamber or
chambers into the said valve chests in the manner set forth with reference to the
drawings.
2. In a compound locomotive engine the combination with three or four
cylinders constructed and arranged as herein before set forth, of an automatic
steam regulator or its equivalent for admitting steam direct to the receiver, and
non-return valves or their equivalent the arrangement being such that the
engine can be easily and safely started in any position and can be worked either
as a compound engine, semi-compound or as a simple engine at will, as set forth.
3. The improved arrangement hereinabove described and illustrated of the
non-return valves and their connecting passages whereby the same are rendered
easy of access.
4. The hereinabove described improved automatic steam regulator with pro-
vision for cushioning the admission valve in its opening_movements whether
such regulator be constructed and arranged according to Figs. 7, 8, 9, 10 12
and 13 or modified according to Fig. 11 of the accompanying drawings.
5. In an automatic steam regulator of the kind hereinbefore referred to, means
for preventing escape of steam from the boiler into the external atmosphero
substantially as described with reference to and shown in Fig. 8.
6. The application and use as hereinabove described of an automatic steam
regulator of the kind referred to in Claim 3 in conjunction with non-return
valves and their passages arranged in the manner set forth and illustrated.
7. The arrangement substantially as described with reference to and shown
in Figs. 14 and 15 of the accompanying drawings of the valve gear cylin:lers
and other parts.
8. A compound locomotive engine embodying the hereinabove described
improvements as set forth.
Dated this 4th day of July 1898