IMPROVEMENTS IN MOTIVE-POWER ENGINES
Year: 1878

page_text: LETTERS PATENT to John Clayton Mewburn, of 169, Fleet Street, in the City
of London, Patent Agent and Consulting Engineer, for the Invention of
"IMPROVEMENTS IN MOTIVE-POWER ENGINES." A communication from abroad
by Edouard de Morsier, of Bologna, Italy.
Sealed the 18th February 1879, and dated the 21st August 1878.
PROVISIONAL SPECIFICATION left by the said John Clayton Mewburn at
the Office of the Commissioners of Patents on the 21st August 1878..
"
JOHN CLAYTON MEWBURN, of 169, Fleet Street, in the City of London, Patent
Agent and Consulting Engineer. IMPROVEMENTS IN MOTIVE-POWER ENGINES."
[A communication from abroad by Edouard de Morsier, of Bologna, Italy.]
The object of this Invention is to construct steam or motive-power engines at a
comparatively small cost, and which shall lead to a great economy of steam, and
therefore of fuel.
The characteristic features of the improved engine are,―
First. That there are two driving cylinders, a smaller one, in which the steam
acts directly and by expansion, and a larger one in which the expansion is
completed.
Secondly. That these two cylinders fitted with their pistons are open at one end,
and both placed at the same side of the main shaft, which they actuate by two con-
necting rods acting upon two opposite cranks.
Thirdly. That the steam is single acting, not reaching the end of the cylinders;
it alternately drives the pistons forward, and the action of one piston by means of
the opposite cranks drives the other piston to the end of its cylinder.
Fourthly. The distributing apparatus placed between the two cylinders is cylin-
drical, adjustable, without friction, dependent on the pressure of the steam, and its
piston valve is pushed by the steam continually in the same direction, while the
excentric which regulates the distribution retains it and pushes it back..

page_text: Having stated the characteristic features I will now proceed to describe an engine
constructed in accordance therewith.
As already mentioned, there are two driving cylinders; they are, according to the
size of the engine, either cast in one piece with the intermediate distributing box
and the rest of the frame of the engine, or in several pieces united by bolts, but
always so as to be rigid and invariable. In the small cylinder the steam acts partly
at full pressure, partly by expansion. In the large cylinder when the engine is
working normally the steam acts only by expansion on escaping from the small
cylinder.
In each of the cylinders is a double piston, that is to say, that it is composed of
the piston properly so called provided with its elastic rings, and which I will call
the driving piston, and of a guide piston recessed to receive the joint of the con-
necting rod. These guide pistons are, according to the size of the cylinder, either
of the same diameter as the driving pistons or of different diameter. In the former
case the cylinder itself acts as a guide at its end (and the distance between the two
pistons is sufficient to prevent the rings of the driving piston ever working in the
portion which serves as a guide, and is more subject to wear). In the latter case
the guide is formed by a smaller cylinder fixed concentrically in the end of the
driving cylinder by means of a flange, but without closing it; for this purpose
openings are formed in the said flange. In this guide cylinder works the guide
piston, which may be made in a piece with the driving piston. The two cylinders
are provided with double covers, and are surrounded either simply with an insu-
lating material, or also with a steam jacket for the working portion only. This steam
jacket also surrounds a great part of the distributing apparatus and the steam
passages.
The distributing apparatus is composed of a double piston made either for engines
without variable expansion or with variable expansion, as herein-after explained.
The steam, which enters the distributing apparatus by a valve, acts continually at
full pressure behind this piston valve, which, prolonged by a rod whose length can
be exactly regulated by means of a threaded part receiving a screw, bears constantly
(without having need to be fixed thereto) against an annular guide, to which is
jointed the rod of the excentric which communicates to it, and regulates the motion
necessary for the distribution of the steam. For valves with variable expansion the
said rod is square and engages between two lugs of the annular guide in order to
prevent the valve turning.
In order to always ensure the tight fitting of the piston valve it is made
adjustable, and for this purpose it works in a sort of sheath, which carries the ports;
this sheath, cylindrical internally, is conical externally, and exactly fits against the
partitions of the steam passages, but the ports for the passage of the steam distri-
buted all round the sheath are shorter in the direction of the axis than the steam
passages communicating with the driving cylinders. In this manner, by means of a
screw or screws bearing against the sheath through the intermediation of a cap
or a solid ring, it is easy to force it more or less forward without narrowing the
steam passages, and thus contracting its internal cylindrical space either by the com-
pression of the sheath or by making a slit therein, which is completely closed by
forcing it; thus the desired tight fitting of the piston valve can always be obtained
without having sensible friction.
The exact mean position which the piston valve should have in the direction of
the axis. with regard to the sheath which carries the ports can always be rigorously
obtained by means of the screw let into the valve rod, as above explained.
The distribution of the steam is effected very simply, as with an ordinary slide
valve. According to the position of the piston valve, regulated by the excentric,
the steam enters first by a passage into the small driving cylinder, and drives its
piston forward. When it has reached the end of its stroke the excentric has brought
the valve into a position to allow the steam to pass from the small cylinder back
through the passage by which it entered, through the space between the pistons of
the valve, and through another passage into the large cylinder. The large piston is

page_text: then driven forward, and having reached the end of its stroke it has driven the
small piston to the end of its cylinder, and the piston valve has returned to its first
position, that is to say, the direct steam enters from the supply, and the expanded
steam issues either into the open air or into a condenser.
The movement of the pistons, as above explained, is communicated to the driving
shaft by means of the two connecting rods actuating the two opposite cranks. As
the connecting rods act only by compression, they have no need of parts for
tightening joints, and have not a cap, which is replaced, as in the ring of the
excentric, by a small piece fixed by a screw, and which simply prevents the rods
leaving their place when the engine is made to turn without steam. The excentric
is fixed in two pieces on the journal of the shaft between the two cranks, and if the
journal be turned excentrically it can itself serve directly as the excentric. The
shaft rests on two bearings with half packing of bronze, and without a cap. This
shaft can be extended at both ends if necessary, or at one only. Where it extends
beyond the frame of the engine it is well to put a stuffing box, and this is necessary
when the waste steam is condensed, because the internal space of the frame should
be put in communication with the condenser, and for this purpose be closed at every
part.
In order to allow the shaft to be inserted into the frame a longitudinal opening is
made fitted with a cover which carries a stuffing box, and the man-holes strictly
necessary for erecting and watching the engine are also made.
To complete the engine and satisfy all requirements a variable expansion gear
operated by the governor has been designed, which can be applied thereto at will.
It is arranged as follows:-The driving shaft carries outside the frame bevel
gearing which actuates the governor, the shaft of which carries at its upper part a
toothed wheel gearing, with another wheel fixed on a small vertical shaft. The
proportions of the geared wheels should be such that this small shaft makes the
same number of revolutions as the main shaft of the engine, while permitting
the governor to possess
the speed for which it is constructed. On this small shaft
is keyed so as to slide freely a cam connected to the governor by levers in such
manner that while turning with its shaft it participates in the vertical move-
ment of the governor, descending when it rises by an increase of speed, and
inversely.
One of the levers which connect the cam and the governor works an oil pump, so
as to avoid sudden oscillations, and its end indicates on a dial the degree of
expansion.
The cam has a portion of a helix at the end of its acting surface. Against this
cam a lever constantly bears, which receives an oscillating movement and actuates
the expansion in the following manner :-The piston valve is prolonged at the steam
supply end by a recessed piece forming a body with one of the valve pistons, and
having ports whose position on the circumference corresponds with those of the
sheath before described, so that the steam should pass through them to enter at the
desired moment the small cylinder. In the interior of this prolongation of the piston
valve, and fitted with slight friction, is another piece having equal ports. When the
openings correspond the steam passes, but if the internal piece turns to a very small
extent, say 30°, the passages are closed. Now the oscillation of the lever precisely
causes the opening and closing of these ports, and consequently stops the introduc-
tion of the steam at different moments of the travel, and this as follows:-The
internal piece is mounted on a small rod fitted in the valve so as to turn freely.
This rod passes through a stuffing box, and outside carries a lever keyed thereto
with slight friction, and held in place in a longitudinal sense by a support, while
the internal rod participates in the reciprocating movement of the valve. This lever
is held in a certain position by a spring, which makes it bear against its support;
in this position the ports are closed, and the passage of steam prevented. Against
this lever acts one end of the main lever, whose other end bears on the cam. It
therefore follows that every time the main lever reaches the commencement of the
cam surface, this forces the other lever to turn a certain angle, and to cause the

page_text: 'ports to open; and when the main lever reaches the end of the cam surface,
the spring before named causes the other lever to take up its first position, drawing
with it the internal piece, which closes the ports and shuts off the steam. Now, as
has been before stated, the end of the cam surface is a portion of a helix, and it
follows that the more it is lowered, that is to say, the higher the governor is, the
quicker will the closing be effected and the expansion commence, and vice versa.
The commencement of the cam surface is, on the contrary, rectilinear, and in such a
position that the play of the lever always causes the entire opening of the ports
before the small piston commences its stroke.
In order to facilitate the starting of the engine I fit a valve to allow of the intro-
duction of the steam directly into the large cylinder in the position in which it
would normally only receive the escape steam from the small cylinder:

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said John Clayton Mewburn in the Great Seal Patent Office on the 19th
February 1879.
JOHN CLAYTON MEWBURN, of 169, Fleet Street, in the City of London, Patent
Agent and Consulting Engineer. IMPROVEMENTS IN MOTIVE-POWER ENGINES,"
"
(A communication from abroad by Edouard de Morsier, of Bologna, Italy.)
The object of this Invention is to construct steam or motive-power engines at a
comparatively small cost, and which shall lead to a great economy of steam, and
therefore of fuel.
The characteristic features of the improved engine are,―
First. That there are two driving cylinders, namely, a smaller one in which the
steam acts directly and by expansion, and a larger one in which the expansion is
completed.
Secondly. That these two cylinders fitted with their pistons are open at one end,
and both placed at the same side of the main shaft, which they actuate by two con-
necting rods acting upon two opposite cranks.
Thirdly. That the steam is single acting, it drives the pistons forward alternately,
and the action of one piston by means of the opposite cranks drives the other piston
to the end of its cylinder.
Fourthly. That the distributing apparatus placed between the two cylinders is
cylindrical, adjustable with or without friction due to the pressure of the steam,
and its double piston valve receiving steam at only one end is pushed by the steam
continually in the same direction, while the excentric which regulates the distri-
bution retains it and pushes it back.
Having stated the characteristic features I will now proceed to describe with
the aid of the annexed Drawings an engine constructed in accordance with this
Invention.
Figure 1 is a longitudinal vertical section of the engine through the centre of
the cylinders, that is to say, through the line Y, Y, Figure 3.
Figure 2 is a vertical section through the centre of the piston valve.
Figure 3 is a plan of the engine with the governor removed.
Figure 4 is a horizontal section through the line X, X, of Figure 1, all the outer
parts, the governor, &c., as well as the shaft, the covers, and pistons being removed.
Figure 5 is a section through the centre of the steam supply pipe, the valve
being removed, and shewing the internal arrangement for the variable expansion.
Figure 6 is a longitudinal section of the distributing apparatus, and Figure 7 a
plan of the cam and of the end of the lever which controls the expansion.
Figures 5, 6, and 7 are drawn to double the scale of Figures 1 to 4.
The Figures represent a vertical engine, but it is evident that the Invention can
be adapted to an inclined or a horizontal engine.
As has already been mentioned there are two driving cylinders A and B.
According to the size of the engine they are either cast in one piece with the inter-
mediate distributing box C and the rest of the frame of the engine, or in several
pieces united by bolts, but always so as to be rigid and invariable. The two
cylinders are provided with double covers, and are surrounded either simply with
an insulating material, or also, as shewn in the Drawing, with a steam jacket d,
which also surrounds a great part of the distributing apparatus and the steam
passages. In the small cylinder A the steam acts partly at full pressure; partly by
expansion. In the large cylinder B when the engine is working normally the
steam acts only by expansion on escaping from the sinall cylinder.
In each of the cylinders is a double piston, that is to say, that it is composed of
the piston, properly so called, p and P, provided with its elastic rings, and which I
will call the driving piston, and of a guide piston p' and P¹ recessed to receive the
joint of the connecting rod. These guide pistons are, according to the size of the

page_text: .
cylinder, either of the same diameter as the driving pistons as p' (and can even be
in one with it without intermediate diminution of diameter, and this especially
for small engines) or of different diameter, as P¹; in the former case the cylinder
acts as a guide to one of its parts; in the latter case the guide is formed by a
smaller cylinder G fixed concentrically in the end of the driving cylinder by means
of a flange g, but without closing it; for this purpose openings t, t, are formed in
the said flange. In this guide cylinder works the guide piston P', which may be
made in a piece with the driving piston or separately.
The distributing apparatus is composed of a double piston c, c¹, working in a
sort of sheath e, which has the ports arranged round it. The steam which enters
the engine by the pipe Z passes into the jacket, and thence by the valve Y to the
distributing apparatus, and acting continually behind the piston valve bears
against the cylindrical guide c², to which is jointed the rod of the excentric, which
communicates to it and regulates the motion necessary for the distribution of the
steam.
The piston valve participates in the general property of the engine, which is to
draw the connecting rods, &c., only in one direction. For this reason the piston
valve need not be connected to the guide or to the excentric rod, but need only
bear against the former. This bearing can be produced or not at will by means of
a threaded part, which permits of always exactly regulating the position of the
valve relatively to the orifices, and of modifying to a certain degree the covering
and the lap, the expansion and the compression. This arrangement also allows of
more or less advancing the sheath e in which the ports are formed. As this piece
is conical externally its advance draws closer its internal cylindrical part, whereby
perfect tightness of the valve itself is obtained without the necessity for the elastic
rings referred to below. Under these conditions the valve acts without friction due
to the pressure of the steam.
In order to always ensure this tightness without much trouble the piston
valves c, c¹, are constructed as follows:-Each piston has a set of rings i, either
elastic, slit, or in several pieces or segments, like those ordinarily employed in
pistons; these rings form the rubbing and obturating part; over these rings others
may be fitted, so that the arrangement may be as uniformly elastic as possible;
lastly, either internally or between two metallic rings there is at least one caout-
chouc ring f, which ensures a hermetic joint; it prevents the passage of the steam
which enters by the channels h the interior of the last ring, and tending to dilate
the whole ensures its perfect action. To get this steam pressure as equal as possible
in the two piston valves c, c¹, I take for c the direct pressure, and for c¹ the exhaust
pressure from the small cylinder, as is clearly seen in Figure 6.
The distribution of the steam is effected very simply. According to the position
of the piston valve c, c', regulated by the eccentric, the steam enters first by the
passage a (Figure 6) into the small cylinder A and drives its piston forward; when
it has reached the end of its stroke the eccentric has brought the valve into the
position shewn in Figures 1 and 2, and the steam passes from the small cylinder
back through the passage a, through the annular space between the pistons c, c¹,
and through the passage b into the large cylinder. The large piston is then driven
forward, and having reached the end of its stroke it has driven the small piston to
the end of its cylinder, and the piston valve has returned to a position such that
the steam passes through a into the small cylinder, and that the steam which has
done its work in the large cylinder issues by k, k³, either into the open air, as in
the Drawing, or into a condenser, which can easily be fitted with a vertical or
horizontal air pump.
The movement of the pistons, as above explained, is communicated to the driving
shaft by means of the two connecting rods p², P2, actuating the two opposite cranks.
As the connecting rods act only by compression they have no need of parts for
tightening joints, and have not a cap, which is replaced, as in the ring of the
eccentric, by a piece 7 fixed by a screw, and which simply prevents the rods leaving

page_text: their place when the engine is made to turn without steam. The circular or cam
excentric is fixed on the journal of the shaft between the two cranks. The shaft
rests on two bearings, which can be without caps for vertical and much inclined
engines. This shaft can be extended at both ends if necessary, or at only one, as
shown in the Drawings. Where it extends beyond the frame of the engine it is
well to put a stuffing box, and this is necessary when the waste steam is condensed,
because the internal space of the frame should be put in communication with the
condenser, and for this purpose be closed at every part.
In order to allow the shaft to be inserted into the frame one or two longitudinal
openings are made, fitted with a cover m, which carries a stuffing box; and the
man-holes necessary for erecting and watching the engine are also made, and sight
holes fitted with glass may also be formed for this purpose.
To complete the engine and satisfy all requirements a variable expansion gear
operated by the governor has been designed, which can be applied thereto at will;
it is arranged as follows:-The driving shaft carries outside the frame bevel
gearing N, which directly actuates the governor, the shaft of which carries at its
upper part a toothed wheel gearing with another wheel n fixed on a small vertical
shaft o. The proportions of the geared wheels should be such that this small shaft o
makes the same number of revolutions as the main shaft of the engine, while per-
mitting the governor to possess the speed for which it is constructed. On this
small shaft o is keyed, so as to slide freely, a cam q (Figures 1, 3, and 7), connected
to the governor by the lever r, the rod r¹, and the lever 2, in such manner that
while turning with its shaft it participates in the vertical movement of the governor,
descending when it rises by an increase of speed, and inversely.
The lever works an oil pump (Figure 1) so as to avoid sudden oscillations,
and its end indicates on a dial the degree of expansion.
The cam q has a portion of a helix at the end of its acting surface. Against this
cam a lever S constantly bears, which receives an oscillating movement and
actuates the expansion in the following manner:-The sheath e in which the
valve c, c', acts is closed at its upper part by a fixed disc c³, having orifices separated
by larger intervals; upon this bears a movable disc c, having similar orifices, in
such manner that when the orifices coincide the steam passes, but by turning a
portion of a circle (/eth in the Drawing) the full parts of the movable disc coincide
with the orifices of the fixed disc, and the steam is cut off. Now the oscillation of
the lever S precisely causes the opening and closing of these ports, and consequently
stops the introduction of the steam at different moments of the travel, and this is as
follows: The movable disc c is mounted on a rod u capable of turning freely. This
rod passes through a stuffing box, and outside carries a lever S¹. This lever is held
in a certain position by a spring W, which makes it bear against the support V ;
in this position the ports are closed, and the passage of steam prevented. Against
the lever S¹ acts one end of the main lever S, whose other end bears on the cam q.
It therefore follows that every time the end of the lever S reaches the commence-
ment of the cam surface it forces the lever S' to turn a certain angle and to cause
the ports to open, and when the end of the main lever reaches the end of the cam
surface the spring causes the lever S¹ to take up its first position, drawing with it
the piece c, which closes the ports c³ and shuts off the steam. Now, as has been
before stated, the end of the cam surface is a portion of a helix, and it follows that
the more it is lowered, that is to say, the higher the governor is, the quicker will
the closing be effected and the expansion commence, and vice versa. The com-
mencement of the cam surface is on the contrary rectilinear, and in such a position
that the play of the lever always causes the entire opening of the ports before the
small piston commences its stroke.
α,
In order to facilitate the starting of the engine I fit the valve X, Figures 2
and 4, to allow of the introduction of the steam directly into the channel and
consequently into the large cylinder, in the position in which it would normally
only receive the escape steam from the small cylinder.

page_text: .
And having now described the nature of the said Invention, and in what manner
..the same is to be performed, I declare that I claim,―
First. Constructing motive-power engines with two cylinders placed at the same
side of the driving shaft and receiving their steam at only one end, the other end
being open, and their pistons working two opposite cranks, substantially as herein-
before described, and represented in the annexed Drawings.
Second. The improved distributing apparatus, with its cylindrical valve of
special construction, and situated between the two cylinders, the steam entering at
one end and exhausting at the other after having done its work, substantially as
herein-before described, and represented in the annexed Drawings.
Third. Constructing motive-power engines, arranged and acting substantially
as herein-before described, and represented in the annexed Drawings.
In witness whereof, I, the said John Clayton Mewburn, have hereunto set
my hand and seal, this Nineteenth day of February, One thousand eight
hundred and seventy-nine.
J. C. MEWBURN. (L.S.)