IMPROVEMENTS IN MOTIVE-POWER ENGINES
Year: 1878

page_text: LETTERS PATENT to Peter Ferguson and Wiliam Henderson, both of Glasgow,
in the County of Lanark, North Britain, Engineers, for the Invention of
"IMPROVEMENTS IN MOTIVE-POWER ENGINES."
Sealed the 10th April 1879, and dated the 10th December 1878.
PROVISIONAL SPECIFICATION left by the said Peter Ferguson and William
Henderson at the Office of the Commissioners of Patents on the 10th
December 1878.
PETER FERGUSON and WILLIAM HENDERSON, both of Glasgow, in the County of
Lanark, North Britain, Engineers. "IMPROVEMENTS IN MOTIVE-POWER ENGINES."
This Invention relates to motive-power engines to be operated by the expansive
force of steam or other elastic fluid, and has for its object to construct such engines
in a novel, simple, and inexpensive manner, and so as to obtain in most cases by
the use of a single cylinder the advantages which have hitherto been only obtainable
from two or more separate cylinders working in combination.
In carrying out the Invention, according to one modification, mainly applicable
to high-pressure or non-condensing engines, a cylinder, having a central steam inlet
or port and an exhaust port or outlet at or near each end, is fitted with two pistons
which are connected each by separate piston and connecting rods to two cranks
held by a connecting link at right angles or any other fixed angle to each other on
one shaft or line of shafting. The pistons are placed one within the other in the
cylinder, the outer piston being hollow, and to admit of the connection between
the inner piston and the corresponding crank, its piston rod passes through the end
of the hollow piston nearest the crankshaft and through the other piston rod, which
is made tubular or open for that purpose. On the admission of steam or other
high pressure fluid into the cylinder between the pistons they are moved apart to
an extent depending on the positions of the cranks and the length of the link con-
necting them, one piston advancing or receding to the end of its stroke whilst the
other moves to an intermediate position, and only attains the corresponding end of

page_text: its stroke during the return stroke of the first piston. The steam may be cut off
by a valve at the admission port at any given part of the stroke, and after effective
expansion it is allowed to escape on either piston arriving at and uncovering its
exhaust port at that end of the cylinder. By the arrangements described the
effective pressure of the steam on the advancing or receding pistons is greatest at
the time when the corresponding cranks are nearly midway between their dead
centres, and the wear and tear of the bearings is reduced to a minimum.
According to a second modification particularly adapted as a condensing engine
of the compound or combined high- and low-pressure type, two pistons are fitted in
a cylinder of comparatively large diameter, and these pistons are rigidly held at a
given distance apart by a cylinder of small diameter placed centrally in the interior
of the larger cylinder. A piston rod attached to a single piston fitted into the inner
cylinder passes through one of the larger pistons, and by means of a connecting rod
actuates a crank on the main shaft, whilst the large piston nearest the crank-shaft
is connected to a separate crank on the same shaft by means of a large tubular
piston rod enveloping the other and a connecting rod, or instead of a tubular piston
rod by, two or more piston rods provided with a crosshead, the cranks being linked
together as in the example already described. Steam is admitted to the space
between the inner and outer cylinders which is enclosed by the large pistons at
either end, and whilst the engines are at work forms a steam jacket to the inner or
high-pressure cylinder. The steam direct from the boiler passes through one of
two admission ports provided near the ends in the smaller cylinder, and effecting
a stroke of the piston in that cylinder it escapes through an exhaust outlet in one
of the large pistons into that end of the outer large cylinder, is then used expan-
sively as in the ordinary compound engine, and finally passes into a condenser. A
similar admission of steam at the opposite end of the inner cylinder takes place for
the return stroke, and the outer cylinder also receives the exhaust in like manner
at that end, no slide valves with their eccentrics and other connections being
required excepting when the engines have a reversing motion.
In another modification of compound engine the inner cylinder between the two
large pistons is dispensed with, the small piston in that case being replaced by a.
third piston equal in diameter to the others. The two outer pistons are rigidly
connected by rods or bars passing freely through the central or intermediate piston,
and the piston rods are connected to their respective cranks in the manner
previously described. The steam is admitted alternately on either side of the
central piston, and thence passes through suitable ports formed in the other pistons
to the outer divisions of the cylinder where its expansive force is used in completing
the stroke of the outer pistons, and finally it exhausts into a condenser. In order
to retain the requisite proportional area between the high-pressure and the low-
pressure spaces in the cylinder the outer pistons are fixed closer together, and the
link connecting the two cranks is shortened to reduce the stroke of the central
piston. Instead of employing three pistons two only may be used, but without
bars or rods rigidly connecting them, and the steam may be admitted between the
two pistons and be expanded in the ends of the cylinder; or the three spaces in the
cylinder may each be supplied direct with steam and freely exhausted.
The reversing of such engines may be effected in the usual way by means of
eccentrics, links, and valves; but in cases where only an occasional reversal of the
motion is required the direction of rotation may be changed by removing the link
connecting the separate cranks, turning one crank through half a revolution when
the cranks are at right angles, or through a corresponding part of a revolution for
any other angle of the cranks, and again fixing the link to retain their new relative
positions.
Instead of one piston rod passing through the other as described in the foregoing
examples the rods may pass out at opposite ends of the cylinder or cylinders and
be connected by connecting rods to a crank or crauks on a shaft situated above,
below, or on either side of the cylinder.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Peter Ferguson and William Henderson in the Great Seal Patent
Office on the 6th June 1879.
PETER FERGUSON and WILLIAM HENDERSON, both of Glasgow, in the County of
Lanark, North Britain, Engineers. "IMPROVEMENTS IN MOTIVE-POWER ENGINES."
Our said Invention relates to motive-power engines to be operated by the expan-
sive force of steam or other fluid, and has for its object to construct such engines in
a novel, simple, and inexpensive manner, and so as to obtain in most cases by the
use of a single fixed cylinder the advantages which have hitherto been only obtain-
able from two or more separate cylinders working in combination.
And in order that our said Invention, and the manner of performing the same,
may be properly understood, we hereunto append four Sheets of explanatory
Drawings, to be hereinafter referred to, and representing various modifications of
our improvements. In these Drawings the same reference letters are used to mark
the same or like parts wherever they are repeated.
Figure 1 on Sheet 1 of the Drawings is a vertical section of a high-pressure or
non-condensing engine of our improved construction of a type mainly adapted for
small sizes. The cylinder A, which is open at both ends, has a central inlet or
port a in direct communication with a steam boiler or a receiver containing air or
other fluid at high-pressure,-and-is-provided-with-exhaust ports or outlets a¹, a²,
near each end. In this cylinder A are placed two pistons B, B¹, which are connected
cach by separate piston rods b, b', and connecting rods c, c', (the centre lines only
of which are shown,) to two cranks C, Ct, held by a connecting link d at right
angles, or it might be at any other fixed angle, to each other on a single shaft or line
of shafting D. The pistons are placed one within the other in the cylinder A, the
outer piston B¹, being in the form of a hollow cylinder, and to admit of the connec-
tion between the inner piston B, and the corresponding crank C, its piston rod b
passes through the end of the outer piston B¹ nearest the crankshaft, and between
the other piston rods 61, 61, which form guides for the piston rod head E. The outer
cylindrical piston B₁ is provided, with ports a³, a³, which when opposite the inlet a
serve.as admission ports to the inner piston, and corresponding ports a, a, are
provided, from which the steam after effective expansion is exhausted when the
piston B' arrives at a position at which they are opposite the exhaust ports a¹, a²,
of the cylinder. The pistons B, B', on the admission of steam or other high-pressure
fluid, move to an extent depending on the positions of the cranks C, C₁, and the
length of the link & connecting them, one piston advancing or receding to the end
of its stroke, whilst the motion of the other being constrained, it only reaches the
corresponding end of its stroke during the return stroke of the first piston. In this
example of engine, the outer piston acting as a valve, no separate slide valve is
required, but when preferred an expansion valve can be readily fitted for cutting off
steam at any part of the stroke.
Figures 2 and 3 on Sheet 2 of the Drawings are vertical sections taken as at
right angles to each other; and Figures 4 and 5 are horizontal sections of a con-
densing engine of the compound or combined high and low pressure type of our
improved construction, in which two pistons B1, B₁, are fitted in a cylinder A of
comparatively large diameter, and these pistons are rigidly held at a given distance
apart by a cylinder A¹ of small diameter placed centrally in the interior of the
larger cylinder. A piston rod b, attached to a single piston B fitted into the inner
cylinder A', passes through the lower large piston B', and by means of a connecting
rod c actuates a crank C on the main shaft D, whilst the large piston B' nearest the
crank shaft is connected to a separate crank C on the same shaft or line of shafting
by two piston rods b', b', provided with a crosshead E and connecting rod c', the
cranks being firmly held together by a link d, as described with reference to
Figure 1, or they may be forged in one piece. Steam may be admitted to the

page_text: space F between the inner and outer cylinders, which is enclosed by the large
pistons B, B', at either end, and whilst the engines are at work will form a steam
jacket to the inner or high pressure cylinder A³. The steam direct from the boiler,
entering an inlet a, passes through one of two admission ports a³, a³, provided near
the ends in the small cylinder A³, is cut off at any desired part of the stroke by a
valve G, and after effecting a stroke of the piston B, escapes through an exhaust
outlet into a receiver H, whence it passes through an admission port a³ into one end
of the outer or low pressure cylinder, is there used expansively as in an ordinary com-
pound engine, and finally passes through an exhaust port a into a condenser I. A
similar admission of steam at the opposite end of the inner cylinder A¹³ takes place
for the return stroke, and the outer cylinder also receives the exhaust in like
manner at the corresponding end. Slide valves G, G¹, are shown applied for regu-
lating the admission and exhaust of the steam, but rotatory valves or suitable
valves of any other known construction may be used; and instead of the inner
cylinder being placed centrally it may be in a position which is not concentric with
the larger cylinder A, and which may be such that one piston rod only will be
required for the larger pistons.
In another modification of compound engine the inner cylinder between the two
large pistons is dispensed with, the small piston in that case being replaced by a
third piston equal in diameter to the others, as seen in Figure 14 on Sheet 3 of the
Drawings. The two outer pistons are rigidly connected by rods or bars k passing
freely through the central or intermediate piston, and the piston rods are connected
to their respective cranks as previously explained, or in the manner hereinafter
described with reference to Figures 12, 13, 14, and 15. The steam is admitted
alternately on either side of the central pistou, and thence passes through suitable
ports formed in the other pistons to the outer divisions of the cylinder, where its
expansive force is used in completing the stroke of the outer pistons, and finally it
exhausts into a condenser. In order to retain the requisite proportional area
between the high pressure and low pressure spaces in the cylinder, which the
removal of the inner cylinder destroys the outer pistons are fixed closer together,
and in the case where the rods of both sets of pistons pass from one end of the
cylinder, the angle of the cranks is altered to correspond, but when the rods pass
out at opposite ends, as shown in Figure 14, the. position of the crank shaft in
relation to the centre of the cylinder, and consequently the angle of the con-
necting rods, must be adjusted to reduce the stroke of the central piston.
Instead of employing three pistons, two only may be used, as shown in Figures 6
and 7, on Sheet 1, without bars or rods rigidly connecting them, and the steam may
be admitted between the two pistons and be expanded in the ends of the cylinder;
or the three spaces in the cylinder may each be supplied direct with steam and
freely exhausted. Figures 8, 9, 10, and 11 show the relative positions which the
pistons and cranks assume at various parts of the stroke.
Instead of one piston rod passing through or between the others, as described in
the foregoing examples, the rods may pass out at opposite ends of the cylinder or
cylinders and be connected by connecting rods to a crank or cranks on a shaft
situated above, below, or on either side of the cylinder. Figure 12, on Sheet 3 of
the Drawings, is a vertical section, showing one modification of a high pressure
engine constructed in this manner. Two pistons B, B', are placed in the cylinder A,
and each piston rod b, b¹, is connected to a block or cross head E, sliding on a guide
piece A2 cast on or fitted to each cylinder cover; and to these blocks E are attached
the connecting rods c, c', connecting each to the crank or disc pin C on the shaft D.
Steam is admitted through the ports a³ by a rotatory valve in turn between the
pistons B, B, and at either end of the cylinder, the resultant reciprocation of the
pistons being similar to that occurring in all the previous examples, and more par-
ticularly described with reference to Figure 1. Figure 13 shows a compound or
combined high and low pressure engine, in construction similar to that just
described, but having one piston B within the other B'; and Figures 14 and 15 are
a vertical section and end elevation respectively of a modification in which three

page_text: pistons are fitted into one cylinder, the action of which has been already herein-
before described, but which may be more readily understood by reference. to the
diagrams Figures 16, 17, 18, 19, and 20, on Sheet 1, showing various positions of
the pistons B, B', and corresponding positions of the cranks C, C¹. Instead of con-
necting the piston rods b, b', to the slide blocks or cross heads E each piston rod
may be connected by a pin to a lever / forming part of a parallel motion, to which
the connecting rod c¹ is also attached, as shown by Figure 21. Figure 22 also shows
a mode of connecting the piston rod 6₁ to the connecting rod c' by means of a
forked lever centred on the engine sole plate, a pin in which lever works in a slot
in the end of the piston rod and admits of the free reciprocation of the piston. The
valves for the type of engines shown in Figures 12, 13, 14, and 15 may be of any
suitable known construction, rotatory or reciprocating, and may be operated by
eccentrics M, as shown in Figure 15; but in cases where the rate of travel of the
valve is not intended to be uniform throughout a complete revolution or recipro-
cation of the valve, as in Figure 13, a device similar to that shown by Figure 23
may be employed. In this arrangement a crank C³ fitted on the engine crank
shaft D is connected to a second crank C on the valve spindle D' by a link N,
which passes through a slotted guide block O oscillating freely on a fixed centre,
and the variation of the length of one arm of the lever N from the crank pin C³ to
the centre O during a revolution of the crank shaft D gives a corresponding
variation of speed of travel to the other end of the lever or link and to the crank C+,
the amount of which variation is dependent on the throw of the cranks.
Figure 24, on Sheet 4 of the Drawings, is-a-plan,-and-Figure-25-is-a-horizontal-
section, of an engine of our improved construction applied in combination with a
pump. The steam cylinder A is cast in one piece with the pump barrel A³, and is
fitted with two pistons B, B', with piston rods b, b', passing out at opposite ends
and connected to crossheads E, to which the rods 62, 63, of the pump plungers B², B³,
are also attached. Connecting rods c, c¹, link the crosshead E to the crank or disc
pin C on the valve spindle D, by which means the valves for the admission of
steam are actuated; and the valves for the admission and eduction of the water are
operated in a similar way by the rods c², c³, connected to the disc C2. The valves
for the steam and water are similar in construction, and the water being admitted
and ejected alternately in turn between the pistons and at either end of the
cylinder or barrel A³ in the same manner as the admission and exhaust of the
steam in the cylinder A, the pump is thus triple in action, but three pistons may be
fitted both in the steam cylinder and pump barrel to give a quadruple action.
In the various arrangements of our improved engines herein described it will be
observed that in nearly all cases the effective pressure of the steam on the advancing
or receding piston in the cylinder is greatest at the time when the position of
the corresponding crank is between the ordinary dead centres, and there is no actual
dead centre, an advantage which is not however gained when the engines are placed
in line or directly opposite each other, and is only even imperfectly obtainable in
ordinary engines by combining two or more separate cylinders and the accom-
panying engine details. The strain or stress on the crank shaft bearings, and the
consequent wear and tear, is also in this way reduced to a minimum.
Having thus particularly described our said Invention, and the manner in which
the same is performed, we have to state that we do not restrict ourselves to the
precise details herein described or delineated; but that what we believe to be novel
and original, and claim as the Invention secured to us by the herein before in part
recited Letters Patent is,-
1. The arrangement and construction of motive power engines in which two or
more pistons are actuated by steam or other fluid in a single fixed cylinder, sub-
stantially in the manner herein described and delineated.
2. The disposition of two working pistons in a steam cylinder, one within the
other, and operated without the intervention of separate valves, substantially in
the manner herein described and delineated.
3. The using of the adjustment of a connecting link between two cranks or the

page_text: variation of the angle of the connecting rods of a steam engine to obtain a
differential motion between two or more pistons in one cylinder, and to vary the
amount of stroke of the pistons in compound engines, substantially as herein
described.
4. The arrangement of the relative positions of the cranks and pistons in an
engine, as herein described, so that the effective pressure of the steam or other fluid
on the pistons at admission is highest when the cranks are at other and more
effective positions than the ordinary dead centres.
In witness whereof, I, the said William Henderson, on behalf of the said
Peter Ferguson and myself, have hereunto set my hand and seal, this Fifth
day of June, in the year of our Lord One thousand eight hundred and
seventy nine.
Witness,
WALLACE FAIRWEATHER, C.E.,
Patent Agent,
Glasgow.
W. HENDERSON. (L.S.)