IMPROVEMENTS IN STEAM ENGINES
Year: 1882

page_text: LETTERS PATENT to Robert Duncan of Glasgow in the County of Lanark
North Britain for an Invention of "IMPROVEMENTS IN STEAM ENGINES"
"
PROVISIONAL SPECIFICATION left by the said Robert Duncan at the Office
of the Commissioners of Patents on the 23rd June 1882.
ROBERT DUNCAN, of Glasgow, in the county of Lanark, North Britain.
IMPROVEMENTS IN STEAM ENGINES."
This Invention, which relates to improvements in steam engines, has special
reference to a new arrangement of the valves and reversing valve gear of compound
condensing or non-condensing engines.
In carrying out the Invention according to a modification adapted for compound
engines in which the high and low pressure cylinders are arranged side by side, the
pistons are connected to cranks in line, or nearly opposite each other on the crank
shaft, and the valve casing and valves are fitted between the cylinders, being
separated however by a central web or partition.
Ordinary D slide valves or piston valves are used to control the admission of the
steam to the cylinders, and these valves are operated direct from the crank shaft
by a single eccentric without the intervention of a link motion. A pair of piston
valves are provided to act as reversing valves and are operated by a hand lever to
direct the steam for the high and low pressure cylinder, according to the position
of their valves through an upper or lower set of ports which admit the steam to
the admission or to the exhaust side of the ordinary slide or piston valves and thus
enable the engines to be reversed. The reversing piston valves are duplex, having
two pistons connected together with an intermediate steam space, and having
spaces at each end in communication with the slide valve casings. One reversing
valve is provided for each cylinder, but both are connected to the one reversing
hand lever to be operated simultaneously; or one valve with a dividing web or
partition may be used.
Ir operating the engines to rotate the crank shaft in one direction, steam from
the boiler is admitted to the reversing piston valve casing of the high pressure

page_text: cylinder at either end of the duplex piston valve and passes direct into the casing
of the slide or engine valve by which it is admitted to the cylinder. After effecting
a stroke of the piston the steam escapes through the centre of the engine valve
and by a port through the centre of the same reversing valve, thence passes by a
port through the dividing web to the centre of the other reversing valve, from
which it enters by a port to the centre of the slide or engine valve of the low
pressure cylinder and is admitted to that cylinder to effect a stroke of the piston
by expansive working of the steam, thence the exhaust steam escapes through the
valve casing and outside the duplex reversing valve by a discharge outlet to a
condenser or to the atmosphere. To reverse the direction of the crank shaft the
duplex reversing piston valves are traversed in their casing, to a position in which
the steam inlet is between the pistons of the high pressure valve. The steam then
enters from the centre of the reversing valve to the centre of the D slide or
engine valve, and after effecting a stroke of the piston of the high pressure cylinder
passes out to the valve casing, thence to the outside of the low pressure reversing
valve and engine valve casing, and after effecting a stroke of that piston by
expansion, escapes to the condenser or to the atmosphere through the centre of the
engine valve and reversing valve, which in its new or reversed position is in com-
munication through its centre with the exhaust outlet.
By means of the improved arrangements described, the advantage is gained that
a reversing action is obtained without the use of a link motion, while obtaining
expansive working of the steam.
The improvements are also applicable in connection with "tandem" engines, in
which however the reversing valves and slide valves, may be arranged in line or
alongside each other, and at the side of the high and low pressure cylinders instead
of between the cylinders.
When the cranks for the high and low pressure cylinders are arranged at right
angles or at any angle instead of in line, an eccentric is provided to work each
engine valve, and a like provision is made when the engines are arranged as
diagonal engines.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Robert Duncan in the Great Seal Patent Office on the 23rd December
1882.
ROBERT DUNCAN, of Glasgow, in the County of Lanark, North Britain
IMPROVEMENTS IN STEAM-ENGINES"
My said Invention, which relates to improvements in steam engines, has special
reference to a new arrangement of the valves and reversing valve gear of compound
condensing or noncondensing engines.
The improvements consist mainly in combining with the ordinary engine valves
of compound engines, various arrangements of reversing valves or cocks, by means
of which the admission of the steam may be directed through the usual inlet
passages of the engine valves to drive the engines in one direction, or through the
usual exhaust passages of the engine valves to reverse the direction of motion of
the engines. This changing of the direction of the inlet steam to reverso the
engines is effected by simply traversing the reversing valves or cock through which
the steam is first admitted. The use of the ordinary link motion for reversing is
thus dispensed with, and the arrangement and working of the engines is further
simplified, in some cases, by employing a single eccentric to work the valves of
compound engines.
My Invention is illustrated by the accompanying Drawings, in which figure 1
is a longitudinal vertical section of a pair of vertical launch engines of the
compound type to which one modification of my improvements is applied.
Figure 2 is a side elevation, and figure 3 is a horizontal section of the same taken
as at the line 1--1 in figure 1; while figure 4 is a transverse vertical section
taken as at the line 2-2 in figure 3; and figure 5 is a longitudinal vertical
section at the line 3 - 3 in the saine figure. Figure 6 on sheet 2 of the Drawings,
is a longitudinal vertical section of a modified arrangement of my improvements as
applied to compound engines having the high and low pressure cylinders in line,
and which are known as "tandem " engines. Figure 7 is a horizontal section of
the same taken as at the line 4-4 in figure 6. Figure 8 is a front elevation of a
pair of tandem compound engines connected to the same crank shaft, and controlled
by the same valve gear. Figure 9 is a similar view of a compound engine in which
the high and low pressure cylinders are side by side, and in which my
improvements are embodied.
In carrying out my Invention according to the modification shown in the first
sheet of the Drawings, and which is adapted for compound engines in which the
high and low pressure cylinders A A¹, are arranged side by side, the pistons B
and B' are connected by the piston rods B2, B3, and connecting rods B B to
cranks C, C in line, or nearly in line opposite each other on the crank shaft C²;
and the valve chest or casing D D₁ and valves E, E, F, F, are fitted between
the cylinders A, A1, being separated however by a central web or partition D².
Ordinary D-slide valves may be used, but in the Drawings a pair of piston
valves E, E are shown applied to control the admission of the steam to the
cylinders, and these valves reciprocate within open ended cylindrical casings E², E³
fitted with brass liners. The valves E, E¹ are operated direct from the crank
shaft C by a single eccentric G on it, without the intervention of a link motion,
the eccentric rod G' being connected by a cross head G² to the ends of the valve
rods e,
el which pass out through stufling boxes in the valve casing. A pair of
piston valves F, and F are provided to act as reversing valves, and are fitted
in the main valve chests or casings D, D', alongside the corresponding engine

page_text: 0
valves E, E', which in the example shown, are fitted between the cylinders. The
valve rods ff pass out through stuffing boxes in the casing D, and are connected
by a crosshead h to which is attached a hand lever II centred on the standards or
fixed framing I of the engines.
By moving the hand lever H up or down, the reversing valves F F¹ are corre-
spondingly traversed in their casings, and this motion causes the steam for the
high and low pressure cylinders entering by the inlet d, to be directed through an
upper or lower set of ports or passages which admit the steam to the admission, or
to the exhaust side of the ordinary slide or piston valves E, E', and thus enable
the engines to be reversed.
The reversing piston valves F, F' are duplex, having two pistons connected
together, with intermediate steam spaces f, f³ communicating with similar steam
spaces e²e in the engine valves E, E¹ and having their ends open to the chests
D, D', which are in communication with the outer ends of the casings E² of the
engine valves E, E. One reversing valve F or F1 is provided for each cylinder A
or A¹, but both are connected to the one reversing hand lever H to be operated
simultaneously; or a single valve with a dividing web or partition may be used.
In operating the engines to rotate the crank shaft G in one direction, steam from
the boiler is admitted through the inlet d to the reversing piston valve casing F
of the high pressure cylinder A at one end of the duplex piston valve F, and passes
direct therefrom through the chest D into the casing E2 of the slide or engine
valve E, by which it is admitted to the cylinder A through the inlet port a. After
effecting a stroke of the piston B (which in the position of the valves represented
in the drawing would be in the upward direction) the steam escapes through the
centre space of the engine valve E (which has meantime been traversed by the
eccentric C) and by a port e¹ passes into the centre space 2 of the same reversing
valve F. Then the steam passes by a port through the dividing web De between
the valve chests D, D¹ to the centre space f³ of the other reversing valve F¹ from
which it enters by a port cb (similar to e) to the centre space e of the slide or
engine valve E' of the low pressure cylinder A', and is admitted to that cylinder
by the port a¹ to effect an upward stroke of the piston B¹ by expansive working
of the steam. Thence the exhaust steam escapes to the outer end of the piston
valve E (which has again been traversed upwards) and passes through the valve
casing D' to the outer end of the duplex reversing valve F', from which it escapes
finally by a discharge outlet d' to the atmosphere, or to the condenser when such is
provided.
To reverse the direction of the crank shaft, the duplex reversing piston valves F, FI
are traversed in their casing by means of the lever H to a position (corresponding
to the position in which the engine valves E, E, are shown in figure 1) in which
the steam inlet & is opposite the space f° between the pistons of the high pressure
valve F. The steam then enters from the centro space 2 of the reversing valve F
to the centre space e² of the engine valve E, enters the cylinder by the port a² and
after effecting a stroke of the piston B of the high pressure cylinder A (which in
the position of the valves shown, would be in the downward direction) the steam
passes out to the outer end of the valve E, and to the casing D, thence to the outer
end of the low pressure reversing valve F, and of the engine valve casing E3 (which
alike communicate with the easing D') and after entering the port a³ and effecting
a stroke of the piston B¹ by expansion, it escapes to the atmosphere, or to the
condenser, through the centre space e³ of the engine valve E', and by a port through
the corresponding space f³ of the reversing valve F which in its new or reversed
position is in communication through its centre space f³ with the exhaust outlet d'.
The course of the steam through the ports, corresponding to the position of the
valves as shown, is indicated by the arrows. In order to stop the engines, the
reversing valves F, F, are traversed by the hand lever H to a mid-position, in which
the piston F covers the inlet d.
By means of the improved arrangements described, the advantage is gained that
a reversing action is obtained without the use of a link motion, while obtaining

page_text: expansive working of the steam. When the cranks C, C for the high and low
pressure cylinders A, A', are arranged at right angles, or at any other angle instead
of in line, a separate eccentric is provided to work each engine valve; and a like
provision is made when the engines are arranged as diagonal engines.
In applying the present improvements to compound engines of the tandem type,
reversing piston valves similar to those described may be combined with piston
or D-slide engine valves, the valves being arranged either as shown applied to
compound engines in which the high and low pressure cylinders are side by side,
or with the reversing valves and engine valve in line, a single valve only being
required of each kind.
It is preferred however to combine with the engine valve a reversing cock K of
the construction shown in figures 6 and 7. The engine valve L is in this case
quadruplex, that is to say, is formed with four pistons forming four steam
passages . . . 13., the two upper passages l. l., serving as inlet and outlet for the
high pressure cylinder A, and the two lower passages 12. 13. as inlet and outlet for
the low pressure cylinder A¹. Between the casing L¹ of the engine valve, and the
casing K of the cock, are formed four ports m, m³, m³, m³, and opposite those
ports, ports or openings are formed in each side of the cock K, one set k. . ².
being on one side, and another set on the other side. The cock K is
divided by webs or partitions K2. K³. into three passages, one of the outer
passages communicating with the steam inlet N, and the other with the low
pressure exhaust outlet N¹ to the atmosphere or condenser, while the central
passage serves to conduct the exhaust steam from the high pressure cylinder to the
inlet ports for the low pressure cylinder. When the cock K is in the position
represented in figures 6 and 7, the steam entering the inlet N passes through the
port in the cock, and through the corresponding port m of the valve L into the
steain space which in starting would be in a lower position, and would admit the
steam by the cylinder port a to the high pressure cylinder A above the piston, and
effect a stroke. The exhaust steam returning by the port a would then pass into
the valve space l', the valve L having by that time traversed to the position
shown.
Thence the steam passes out by the port m' round the casing of the cock K,
enters the central passage by the port, passes by the port through the valve
port m³ into the valve space P, and by the cylinder port a¹ to the low pressure
cylinder A¹, and effects an upward stroke. The returning exhaust from the low
pressure cylinder passes into the valve space (the valve L having meanwhile
traversed to its lower position) out by the port m² round the casing of the cock
and into the outlet passage of the cock by the port ; thence the exhaust steam
passes by the outlet opening ³, and the exhaust outlet N' to the atmosphere or
condenser.
The direction of rotation of the engine is reversed by turning the cock K to the
extent of half a revolution by means of the hand lever H.
The course of the steam from the inlet is then through the port round the
casing K into the valve space by the valve port m¹, thence into the high
pressure cylinder A. The exhaust from that cylinder returns through the valve
space (the valve L having made a down stroke) through the ports m and to
the central passage of the cock K, thence by the ports / m² into the valve
space, and by the port a' into the low pressure cylinder. Thence the low
pressure exhaust steam passes into the valve space 3 (the valve L having mean-
time made an upstroke) through the ports m³. 7 to the outlet passage of the
cock K, and by the opening to the exhaust outlet N'. The course of the steam
is indicated by the arrows to correspond with the position in which the cock K is
shown in the Drawings.
The arrangement of reversing cock K and engine valve L shown in figures
6 and 7, may be conveniently applied to compound tandem engines in which there
are two high pressure and two low pressure cylinders connected to one crank shaft
as is illustrated by figure 8. In this case two engine valves L. L are used, and

page_text: low pressure cylinders
in the cock being in
If the pistons of the
are placed side by side between the two pairs of high and
A, A. One reversing cock K only is needed, the ports
communication with a set of ports leading to each valve L.
two pairs of cylinders are connected to cranks in line, that is, opposite each other
on the crank shaft, the one engine valve L will be at the upper end of its stroke
when the other is at the lower end of its stroke and vice versa; and if the cranks
are fitted at right angles, the one engine valve will be half its stroke in advance
of the other.
In the arrangement of compound engines shown in the drawings in which the
high and low pressure cylinders are in line, as in tandem engines, the steam is only
represented as acting on one side of each piston. Such compound engines may
however be double acting, that is to say, the high and low pressure cylinders
may be separated, and the steam be admitted to act on both sides of each piston,
while the arrangement of reversing cock or valve remains substantially the same.
The arrangement of reversing cock and engine valve shown in figures 6 and 7,
may also be applied to compound engines in which the high and low pressure
cylinders are fitted side by side, as illustrated by figuro 9. The engine valves
(L. L.) are fitted between the high pressure cylinder A, and the low pressure
cylinder A, and the reversing cock K to one side.
Having thus described my said Invention and the manner of performing the
same, I have to state that I do not restrict myself to the precise details herein
described or delineated but what I consider to be novel and original, and therefore
claim as the Invention secured to me by the hereinbefore in part recited Letters
Patent is,
First. The construction, arrangement, and combination of the parts of compound
steam engines, substantially as and for the purposes herein set forth, and as illus-
trated by the accompanying Drawings.
Second. In compound steam engines the construction and arrangement of a pair
of reversing valves, in combination with a pair of engine valves distributing the
steam to the high and low pressure cylinders, substantially as herein described and
illustrated by figures 1 to 5 of the accompanying Drawings.
Third. The construction and combination in compound steam engines of reversing
valves and engine distributing valves the latter being so arranged as to be operated
by a single eccentric, substantially as herein described and illustrated in figures
1 to 5 of the accompanying Drawings.
Fourth. In compound steam engines the construction and arrangement of a
reversing cock in combination with one or more engine valves distributing the
steam to the high and low pressure cylinders, substantially as herein described and
as illustrated by figures 6 to 9 of the accompanying: Drawings.
In Witness Whereof, I the said Robert Duncan, have hereunto set my hand
and seal, this twentieth day of December, in the year of our Lord One
thousand eight hundred and eighty two.
Witness
WALLACE FAIRWEATHER C.E.
Patent Agent
Glasgow.
RODERI DUNCAN (L.S.)