Improvements in Steam Engines.
Year: 1889

page_text: Date of Application, 13th June, 1889
mpre e Specification Left, 13th Mar., 1890-Accepted, 19th Apr., 1890
PROVISIONAL SPECIFICATION.
Improvements in Steam Engines.
I WILLIAM ROBERT RENSHAW of Union Foundry Kidsgrove in the County of
Stafford Engineer and Ironfounder do hereby declare the nature of this Invention to
be as follows:-
This Invention has for its object improvements in steam engines.
I construct a triple expansion engine in the following manner:
I employ two sets of cylinders with three cylinders in each set. The cylinders in
each set are arranged one above the other and a single piston-rod serves for the three
cylindere. A connecting rod transmits the movement from the lowest piston to a
crank on a crank shaft. There are two cranks on the shaft, one for each set of
cylinders, and these cranks are diametrically opposite the one to the other. The
cylinders are single acting and the connecting rods are always in compression. The
centre of the crank shaft I do not place in the same plane with the piston-rods but to
one side of them, by which means I obtain a more favorable angle for the connecting
rod when exerting its effective pressure and this I do at the expense only of having
a somewhat worse angle during the upward or return stroke when there is but little
pressure upon the crank.
The high pressure cylinder first receives the steam on the upper side of the
piston and at the end of the stroke this steam passes to the upper side of the inter-
mediate cylinder, not the intermediate cylinder in the same set, but that in the other
set which makes its effective or downward stroke whilst the first mentioned high
pressure piston is ascending. From the intermediate cylinder at the end of its stroke
the steam passes to the low pressure cylinder and there it acts on the underside of the
piston tending to lift the pistons and piston-rod but without wholly overcoming the
resistance offered by back pressure gravity, inertia and friction to the upward
movement of the parts. In each set of cylinders the intermediate cylinder is the
lowest and the piston in this cylinder is coupled by the connecting rod with the crank
shaft. The high pressure cylinder is immediately over the intermediate cylinder, and
above the high pressure cylinder is the low pressure cylinder.
The high pressure and low pressure cylinders are cast in one piece and are bored
out together. The cover of the high pressure cylinder is passed down into its place
through the low pressure cylinder. The intermediate cylinder forms part of another
casting; it receives a cover and the high pressure cylinder stands upon this cover.
The piston-rod passes through glands in the cylinder covers, and these glands are
rendered steam-tight by rings inserted into grooves formed in the glands. The
piston-rod at its lower end has a head of larger diameter than the rod and this is
received into a recess in the intermediate piston. The recess is somewhat larger than
the head of the rod and there is a slight freedom which allows the piston to adjust
itself in its position on the rod to compensate any slight want of truth there may be
in the centreing of the cylinders. There is a cover plate upon the piston which is
tightened down upon the head of the rod by bolts, so that there is no looseness when
the engine is at work. The piston-rod is perforated from end to end with a lubricating
passage leading to the joint of the connecting rod; and the connecting rod may be
similarly perforated to conduct oil to the crank pin.
The pistons are rendered steam-tight by means of rings of angular section. These
rings may be of cast iron and the part of the ring which bears against the interior of
the cylinder is made sufficiently thin to yield to the steam pressure to the extent
necessary to keep the edge of the ring in steam-tight contact with the interior of the
cylinder.

page_text: The steam is admitted to the high pressure cylinders by means of a cylindrical
valve contained in a casing of like form. The axis of the valve is horizontal and it
receives a partial rotary motion to and fro by connection with an eccentric upon the
crank shaft.
The cylindrical valve is open at the back and the steam pressure is constantly apon
it. A port through the valve, parallel to the axis allows steam to pass alternately to
the two high pressure cylinders. There is a cavity formed in the valve on either side
of the steam port and this cavity in the to and fro rotation of the valve forms a
communication between the steam passage leading to the cylinder and the exhaust or
outlet passage.
At each movement of the valve the steam port in it passes from the
passage leading to the one high pressure cylinder to that leading to the other high
pressure cylinder, and during the same motion, the cylinder which at first is supplied
with steam, is opened to the exhaust as the valve approaches the end of its course.
The admission of the steam to the high pressure cylinders is further regulated by
a cut off valve which fits into a concentric cylindrical cavity formed in the main valve.
This cut off valve is so formed at the periphery that its acting portion consists only
of two bars parallel to the axis of the valve and to the steam port. These are stiffened
by cross bars passing from one longitudinal bar to the other. This cut off valve is
independently rotated through a constant angle first in one direction and then in the
other by an auxiliary eccentric. By this means one or other of the bars is brought
to cover the steam port in the main valve at the time when the cut off is required to
take place. The anxiliary eccentric is controlled by a governor which alters the lead
of the eccentric, so that when the speed increases the auxiliary valve cuts off the
steam earlier.
The fly wheel of the engine is hollow and the governor is enclosed within it. The
governor weights are moveable radially or nearly so within the wheel and they are
coupled in such manner that by their movement they turn the auxiliary eccentric on
the crank shaft; in one direction when the weights move outwards from the centre
and in the other direction when the weights fall in again towards the centre under the
influence of springs which operate in opposition to the centrifugal force.
The engine has three valves, one serving for the high pressure cylinders, as already
explained, another for the intermediate cylinders and a third for the low pressure
cylinders. The valves belonging to the intermediate and low cylinders may or may
not be provided with an auxiliary or cut off valve as explained above.
The cavities in the cylinders to which steam is not admitted are all enclosed and
are connected the one with the other in such manner as to maintain a uniformity of
pressure. The cranks also are enclosed in a chamber and this also may be connected
with the cavities in the cylinders. Or the cylinders of one set may each be connected
with the corresponding cylinder in the other set to maintain a uniformity of pressure
in the cavities. Parts of this invention are applicable to engines other than triple
expansion engines.
Doted this 12th dow of In 1990
CARPMAEL & Co.,
Agents.
COMPLETE SPECIFICATION.
Improvements in Steam Engines,
1, WILLIAM ROBERT RENSHAW of Union Foundry, Kidsgrove in the County of
Stafford, Engineer and Ironfounder, 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 for its object improvements in steam engines.
I construct a triple expansion engine in the manner shown in the drawings
Figure 1 being a vertical transverse section and Figure 2 a side elevation.

page_text: set.
I employ two sets of cylinders with three cylinders A B C and A¹ B' C' in each
The cylinders in each set aro arranged one above the other and a single piston
rod D serves for the three cylinders. A connecting rod E transmits the movement
from the lowest piston to a crank F on a crank shaft G. There are two cranks F
on the shaft, one for each set of cylinders, and these cranks are diametrically opposite
the one to the other. The cylinders are single acting and the connecting rods are
always in compression. The centre of the crank shaft I do not place in the same
plane with the piston rods but as shown in Figure 1 to one side of them, by which
means I obtain a more favorable angle for the connecting rod when exerting its
effective pressure and this I do at the expense only of having a somewhat worse angle
during the upward or return stroke when there is but little pressure upon the crank.
The high pressure cylinder say A first receives the steam on the upper side of the
piston and at the end of the stroke this steam passes to the upper side of the inter-
mediate cylinder B' that is to say not the intermediate cylinder in the same set,
but that in the other set which makes its effective or downward stroke whilst the
first mentioned high pressure piston is ascending. From the intermediate cylinder Bl
at the end of its stroke the steam passes to the low pressure cylinder C' and there it
acts on the underside of the piston tending to lift the pistons and piston rod but
without wholly overcoming the resistance offered by back pressure gravity, inertia
and friction to the upward movement of the parts. In each set of cylinders the
intermediate cylinder is the lowest and the piston in this cylinder is coupled by the
connecting rod E with the crank shaft G. The high pressure cylinder is immediately
over the intermediate cylinder, and above the high pressure cylinder is the low
pressure cylinder.
The
The high pressure and low pressure cylinders A A¹ C C¹ are cast in one piece
and are bored out together. The covers of the high pressure cylinders A A¹ are
passed down into their places through the low pressure cylinders. The intermediate
cylinders B B' form part of another casting; they receive covers b and the high
pressure cylinders A A¹ stand upon these covers. The piston rods D pass through
giands J K in the cylinder covers, and the glands J are rendered steam tight as shown
in Figures 1 and 3 by rings inserted into grooves formed in the glands. The
piston rods at their lower ends have as shown in Figure 1 heads of larger diameter
than the rods and these are received into recesses in the intermediate pistons.
recesses are somewhat larger than the heads of the rods and there is a slight freedom
which allows the pistons to adjust themselves in their positions on the rods to
compensate any slight want of truth there may be in the centreing of the cylinders.
There are cover plates L upon the pistons which are tightened down upon the heads
of the rods by bolts M so that there is no looseness when the engine is at work.
piston-rods are perforated from end to end as shown in Figure 1 with a lubricating
passage leading to the joints of the connecting rods E and the connecting rods may
be similarly perforated to conduct oil to the crank pin.
The
The pistons are rendered steam-tight by means of rings N of angular section.
These rings may be of cast iron and the part of the ring which bears against the
interior of the cylinder is made sufficiently thin to yield to the steam pressure to
the extent necessary to keep the edge of the ring in steam-tight contact with the
interior of the cylinder.
The steam is admitted from the steam pipe O to the high pressure cylinders A A¹
by means of a cylindrical valve P contained in a casing of like form. The axis of
the valve is horizontal and it receives a partial rotary motion to and fro by connection
with an eccentric Q upon the crank shaft.
The cylindrical valve P is open at the back and the steam pressure is constantly
upon it. A port p through the valve, parallel to the axis allows steam to pass
alternately to the two high pressure cylinders A A'. There is a cavity p' formed in
the valve on either side of the steam port and this cavity in the to and fro rotation
of the valve forms a communication between the steam passage leading to the
cylinder aud the exhaust or outlet passage R. At each movement of the valve the
steam port in it passes from the passage leading to the one high pressure cylinder to

page_text: that leading to the other high pressure cylinder, and during the same motion, the
cylinder which at first is supplied with steam, is opened to the exhaust as the valve
approaches the end of its course.
A small quantity of steam for cushioning is admitted to the top of the cylinders CC'
by means of the pipe Y and adjustable reducing valve Z.
The admission of the steam to the high pressure cylinders is further regulated
by a cut off valve S which fits into a concentric cylindrical cavity formed in the
main valve P. This cut off valve is so formed at the periphery that its acting portion
consists only of two bars parallel to the axis of the valve and to the steam port.
These are stiffened by cross bars passing from one longitudinal bar to the other. This
.cut off valve is independently rotated through a constant angle first in one direction
and then in the other by an auxiliary eccentrics. By this means one or other of the
-bars is brought to cover the steam port in the main valve at the time when the cut off
is required to take place. The auxiliary eccentric 8 is controlled by a governor which
alters the lead of the eccentric so that when the speed increases the auxiliary valve
'cuts off the steam earlier.
As shown in Figure 4 the fly wheel T of the engine is hollow and the governor
is enclosed within it. The governor weights U are moveable radially or nearly so
within the wheel and their arms u are coupled at u to rods whose other ends are
connected by stud w to the eccentrics 8 in such manner that by their movement
they turn the auxiliary eccentric 8 on the crank shaft; in one direction when
the weights move outwards from the centre and in the other direction when the
weights fall in again towards the centre under the influence of springs which
operate in opposition to the centrifugal force.
The engine has three valves P P P one namely P serving for the high
pressure cylinders as already explained, another PI for the intermediate cylinders
and a third Pu for the low pressure cylinders. The valves belonging to the
intermediate and low cylinders may as shown or may not be provided with an
auxiliary or cut off valve as explained above.
Figures 5 and 6 are end views showing the valve gear-Q is the eccentric and
Qits rod for working the valve P and it also by means of the rod Q works
the valve P¹. V is the eccentric for the valve P. On the other side is the
eccentric 8 and its rod s¹ for working the cut off S of the valve P and X the
eccentric and X¹ its rod for working the cut offs S¹ S" of the valves P¹ P".
O is the steam pipe 0) the pipe connecting the cylinders A A¹ to the
.cylinders B B₁-O the pipe connecting the cylinders B B¹ to the cylinders C C¹
and O is the exhanet pipe from the latter.
The cavities in the cylinders to which steam is not admitted are all enclosed
and are connected the one with the other in such manner as to maintain a
uniformity of pressure. The cranks also are enclosed in a chamber and this also
may be connected with the cavities in the cylinders. Or the cylinders of one set may
each be connected with the corresponding cylinder in the other set to maintain a
uniformity of pressure in the cavities. Parts of this invention are applicable to
engines other than triple expansion engines.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. A triple expansion engine with two sets of three cylinders each set having a
common piston rod substantially as described.
2. A triple expansion engine with three single acting cylinders whose pistons
have a common rod and valves so arranged that steam is admitted to the same end of
the two higher pressure cylinders and to the other end of the lowest pressure cylinder
substantially as described.
3. A triple expansion engine with two sets of three cylinders each set having a
common piston rod and valves such that steam is first admitted to one end of the high
pressure cylinder of one set then to the same end of the intermediate pressure

page_text: cylinder of the other set and lastly to the other end of the low pressure cylinder of
the last mentioned set substantially as described.
4. In engines such as are referred to in claims 1 and 3 admitting and exhausting
steam to and from the cylinders by means of three valves one for each pair of similar
cylinders substantially as described.
5. The valves and gear for working the same substantially as described.
6. The pistons substantially as described.
7. Engines substantially as described and shown in the drawings.