IMPROVEMENTS IN STEAM ENGINES
Year: 1877

page_text: LETTERS PATENT to Henry Davey, of Leeds, in the County of York, Engineer,
for the Invention of "IMPROVEMENTS IN STEAM ENGINES."
PROVISIONAL SPECIFICATION left by the said Henry Davey at the Office
of the Commissioners of Patents on the 22nd January 1877.
"IMPROVEMENTS
HENRY DAVEY, of Leeds, in the County of York, Engineer.
IN STEAM ENGINES."
In compound steam engines, as they are usually constructed, the pistons of the
high and the low pressure cylinders are either rigidly connected together or are
connected to one crank shaft, so that the one is compelled to move at a speed
corresponding to that of the other, and thus the acting pressures are determined
independently of the work performed by each piston.
One part of my Invention relates to an arrangement of compound pumping
engines, such that each piston can move independently of the other at a speed
determined by the relation between the pressure acting on it and the work per-
formed by it; and by this arrangement I obtain the additional advantage of dupli-
cation, having two separate engines, either of which can be worked alone while the
other is under repair. For this purpose I construct two complete pumping engines,
each working its own pump or pumps, their steam cylinders being either both of.
the same size, or the one being larger than the other, as circunstances require, and
by preference I place the cylinders near one another, side by side. I provide two
steam reservoirs, preferably the first in the form of an annular cylinder surrounding
and enclosing the second, which is cylindrical, and from the outer to the inner
reservoir I provide a passage fitted with a valve loaded so as to open only when the
pressure within the second reservoir is less than that within the first by an amount
equivalent to the load on the valve. The first or outer reservoir is supplied with
high-pressure steam from a boiler, and supplies the smaller or high-pressure cylinder,
the exhaust from which is led into the second or inner reservoir. From the latter
the larger or low-pressure cylinder is supplied, and the exhaust from this cylinder is
led into a condenser or into the atmosphere. There is also a passage by which the
exhaust from the high-pressure cylinder can be led into the condenser, and the
various pipes and passages are provided with shut-off valves, some of which may be
of compound form, closing one of the communications when they open another.

page_text: Each cylinder may have in line with it an air pump worked direct from its
piston, or there may be a separate air pump worked by an auxiliary engine, or a
pair of air pumps so worked when the duplication of parts is required to be
complete.
When the engines are in their ordinary working condition, both cylinders being
in use, steam at or near boiler pressure flows from the first reservoir to supply the
high-pressure cylinder in which it works, either at full pressure throughout the
stroke or expansively to the extent determined by the adjustment of the valve gear,
the exhaust from this cylinder flows into the second reservoir and thence to supply
the low-pressure cylinder, the exhaust from which flows to the condenser or into the
atmosphere.
Should the load or pressure on either piston vary, its speed will vary indepen-
dently of the other piston, which will nevertheless be influenced by it so as to bring
the two motions nearly to accord. Thus if the high-pressure piston should gain or
lose speed, it will supply more or less exhaust steam to work the low-pressure
piston, and if the latter should gain or lose speed it will accelerate or retard the
high-pressure piston by diminishing or augmenting the back pressure thereon.
By closing the supply and discharge valves of the low-pressure cylinder, and
leading the high-pressure exhaust into the condenser or into the atmosphere, the
high-pressure cylinder can be worked alone. And again by closing the supply and
exhaust valves of the high-pressure cylinder, the low-pressure engine can be worked
alone, being supplied with steam which cannot have higher pressure than that in
the second reservoir as determined by the load on the valve of its supply.
When the boiler is near the engine the first reservoir may be dispensed with, or it
may merely constitute a steam jacket to the second reservoir for the purpose of
sustaining the heat of the steam discharged from the high-pressure cylinder.
Instead of arranging the one.engine to work always as the high-pressure and the
other always as a low-pressure engine, they may be so arranged that both may be
used either as the high-pressure or as the low-pressure engine, as may be required.
For this purpose both steam cylinders may be of the same size, and each engine is
provided with a separate communication with the high-pressure reservoir, provided
with a stop valve.
Between the two engines is a chamber from which lead pipes, communicating
firstly with the low-pressure reservoir, secondly with the valve chest of each engine,
and thirdly with the exhaust port of each engine. The several passages leading to
the two engines are provided with slides or valves that can be moved by hand,
'whereby, according as the one or the other engine is to work as the high-pressure
engine the communication between the said chambers and the valve chest of this
engine is closed (the communication between the latter and the high-pressure
reservoir being opened), and the communication with the exhaust is opened while
the reverse communications are established with regard to the other engine, thus
causing it to work with the exhaust steam of the first-named engine. Or by
establishing the same communications in both engines they may be both worked as
high-pressure or as low-pressure engines.
Engines constructed as above described may directly work pumps in line with the
cylinders, or may work them through the intervention of levers, bell cranks, or other
connections suited to the relative positions of the cylinders and pumps.
The slides or steam and exhaust valves of the two cylinders may be worked
directly by steam pressure according to any of the known arrangements of steam
worked valves; I prefer however to work the valves of each cylinder by differential
gear partly from the motion of its main piston and partly from that of a subsidiary
piston controlled by a cataract in the manner described in the Specification of a
Patent granted to me on the 1st February 1871, No. 277.
In employing such differential gear, I in some cases arrange expansion valves in
connection therewith in the following manner:
According to one arrangement I provide on the back of the main slide which is
worked by the differential gear an expansion slide of any known construction, (
-

page_text: the rod of which is connected by a lever and link to the piston rod of the engine, or
to any convenient part moving in accord therewith, so that while the main slide is
actuated by the differential gear the expansion slide moves with the piston.
According to another arrangement I provide in the steam inlet of the valve box a
double beat valve, the stem of which is connected to the one end of a lever, the
other end of which is connected to the middle of a T lever which can rock upon it
as on a fulcrum. The two opposite arms of this T lever are connected by links to ..
the opposite arms of another T lever, the third arm of which is connected to the
spindle of the slide worked by the differential gear. The third arm of the first-
named lever is connected by a link to the one end of a lever, the other end of
which is either connected to or worked by tappets from the piston rod or a part
moving in accord therewith. Thus the lever that works the double beat expansion
valve receives a motion which is compounded of the movement of the slide valve
spindle and that of the engine piston. The above described arrangements of
expansion valves may be used with any description of engines working with the
differential gear.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Henry Davey in the Great Seal Patent Office on the 21st July
1877.
HENRY DAVEY, of Leeds, in the County of York, Engineer. "IMPROVEMENT'S
IN STEAM ENGINES."
In compound steam engines, as they are usually constructed, the pistons of the
high and the low pressure cylinders are either rigidly connected together or are con-
nected to one crank shaft, so that the one is compelled to move at a speed
corresponding to that of the other, and thus the acting pressures are determined
independently of the work performed by each piston.
One part of my Invention relates to an arrangement of compound pumping
engines, such that each piston can move independently of the other at a speed
determined by the relation between the pressure acting on it and the work per-
formed by it, and by this arrangement I obtain the additional advantage of
duplication, having two separate engines, either of which can be worked alone
while the other is under repair. For this purpose I construct two complete
pumping engines, each working its own pump or pumps, their steam cylinders being
either both of the same size, or the one being larger than the other, as circumstances
require, and by preference I place the cylinders near one another, side by side. I
provide two steam reservoirs, preferably the first in the form of an annular cylinder
surrounding and enclosing the second, which is cylindrical; and from the outer to
the inner reservoir, I provide a passage fitted with a valve loaded so as to open
only when the pressure within the second reservoir is less than that within the
first by an amount equivalent to the load on the valve. The first or outer reservoir
is supplied with high-pressure steam from a boiler, and supplies the smaller or high-
pressure cylinder, the exhaust from which is led into the second or inner reservoir.
From the latter the larger or low-pressure cylinder is supplied, and the exhaust
from this cylinder is led into a condenser or into the atmosphere. There is also a
passage by which the exhaust from the high-pressure cylinder can be led into the
condenser, and the various pipes and passages are provided with shut-off valves,
some of which may be of compound form, closing one of the communications when
they open open another. Each cylinder may have in line with it an air pump worked
direct from its piston, or there may be a separate air pump worked by an auxiliary
engine, or a pair of air pumps so worked when the duplication of parts is required to
be complete.
When the engines are in their ordinary working condition, both cylinders being
in use, steam at or near boiler pressure flows from the first reservoir to sunnly the

page_text: '
:
high-pressure cylinder, in which it works either at full pressure throughout the
stroke or expansively to the extent determined by the adjustment of the valve
gear; the exhaust from this cylinder flows into the second reservoir, and thence to
supply the low-pressure cylinder, the exhaust from which flows to the condenser or
into the atmosphere.
5
Should the load or pressure on either piston vary, its speed will vary independ-
ently of the other piston, which will nevertheless be influenced by it, so as to
bring the two motions nearly to accord. Thus, if the high-pressure piston should
gain or loose speed, it will supply more or less exhaust steam to work the low-
pressure piston; and if the latter should gain or lose speed, it will accelerate or 1
retard the high-pressure piston by diminishing or augmenting the back pressure
thereon.
By closing the supply and discharge valves of the low-pressure cylinder, and
leading the high-pressure exhaust into the condenser or into the atmosphere, the
high-pressure cylinder can be worked alone. And again by closing the supply and
exhaust valves of the high-pressure cylinder, the low-pressure engine can be worked
alone, being supplied with steam which cannot have higher pressure than that in
the second reservoir, as determined by the load on the valve of its supply.
When the boiler is near the engine, the first reservoir may be dispensed with, or
it may merely constitute a steam jacket to the second reservoir for the purpose of
sustaining the heat of the steam discharged from the high-pressure cylinder.
Instead of arranging the one engine to work always as the high-pressure, and the
other always as the low-pressure engine, they may be so arranged that both may be.
used either as the high-pressure or as the low-pressure engine, as may be required.
For this purpose both steam cylinders may be of the same size, and each engine' is
provided with a separate communication with the high-pressure reservoir provided
with a stop valve.
Between the two engines is a chamber from which lead pipes communicating,
firstly, with the low-pressure reservoir; secondly, with the valve chest of each
engine; and, thirdly, with the exhaust port of each engine. The several passages
leading to the two engines are provided with slides or valves that can be moved by
hand, whereby according as the one or the other engine is to work as the high-
pressure engine, the communication between the said chambers and the valve chest
of this engine is closed (the communication between the latter and the high-
pressure reservoir being opened), and the communication with the exhaust is opened
'while the reverse communications are established with regard to the other engine,
thus causing it to work with the exhaust steam of the first named engine. Or by
establishing the same communications in both engines they may be both worked as
high-pressure or as low-pressure engines.
Engines constructed as above described may directly work pumps in line with
"the cylinders, or may work them through the intervention of levers, bell cranks, or
other connections suited to the relative positions of the cylinders and pumps.
The slides or steam and exhaust valves of the two cylinders may be worked
directly by steam pressure according to any of the known arrangements of steam-
worked valves. I prefer however to work the valves of each cylinder by differential
gear, partly from the motion of its main piston, and partly from that of a subsidiary
piston controlled by a cateract in the manner described in the Specification of a
Patent granted to me on the 1st February 1871, No. 277.
In employing such differential gear, I, in some cases, arrange expansion valves in
connection therewith in the following manner :-
According to one arrangement I provide on the back of the main slide, which is
worked by the differential gear, an expansion slide of any known construction, the
rod of which is connected by a lever and link to the piston rod of the engine, or to
'any convenient part moving in accord therewith, so that while the main slide is
actuated by the differential gear, the expansion slide moves with the piston.
According to another arrangement I provide in the steam inlet of the valve box
a double beat valve, the stem of which is connected to the one end of a lever, the

page_text: other end of which is connected to the middle of a T lever, which can rock upon it
as on a fulcrum. The two opposite arms of this T lever. are connected by links to
opposite arms of another T lever, the third arm of which is connected to the spindle
of the slide worked by the differential gear. The third arm of the first named T
lever is connected by a link to one end of a lever, the other end of which is either
connected to or worked by tappets from the piston rod, or a part moving in accord
therewith. Thus the lever that works the double beat expansion valve receives a
motion which is compounded of the movement of the slide valve spindle and that of
the engine piston. The above described arrangements of expansion valves may be
used with any description of engines working with the differential gear.
•
opposite arms of another T lever, the third arm of which is connected to the spindle
of the slide worked by the differential gear. The third arm of the first named T
lever is connected by a link to one end of a lever, the other end of which is either
connected to or worked by tappets from the piston rod, or a part moving in accord
therewith. Thus the lever that works the double beat expansion valve receives a
motion which is compounded of the movement of the slide valve spindle and that of
the engine piston. The above described arrangements of expansion valves may be
used with any description of engines working with the differential gear.
DESCRIPTION OF THE DRAWINGS.
Fig. 1 represents a side view, Fig. 2 an end view, and Fig. 3 a plan of a pair of
direct-acting pumping engines arranged to work according to my Invention. A is
the double reservoir, the interior compartment a¹ being of cylindrical form, enclosed in
a casing which, forms the outer compartment a², of annular form. The outer com-
partment a², being kept supplied with steam from the boiler, supplies the slide casing
of either engine by the pipe B¹ or B2, according as the shut-off valve b¹ or b³ is
opened or closed, and the exhaust from the engine so supplied has communication
by the double valve box C and pipe D with the inner reservoir a¹ as well as with
the slide casing of the other engine. Also each of the engines has a pipe fitted with
a shut-off valve el, e², leading to a condenser and air pump E', E². Fig. 4 represents
a vertical section of the double valve box C arranged so that either engine can be
worked with steam from the reservoir a², whilst the other is worked by the exhaust
of the former, or that both engines can be worked with steam from a³. This valve
box is fitted with two sluice or slide valves F1, F2, worked by screws, each govern-*
ing two ports, which lead respectively, the upper on each side to the slide casing,
and the lower to the exhaust passage of each engine, in the position of the
valves F1, F2, as shewn in Fig. 4; the exhaust from the right-hand engine entering
by the open port f¹ goes by the port f to supply the left-hand engine. The position
of the valves F1, F2, being inverted, the right-hand engine would in like manner be
supplied from the exhaust of the left-hand engine. Engines arranged in this manner
have their slides preferably worked by differential gear of the kind described in the
Specification referred to above, which I have not shewn in the Drawing, indicating
only the positions s¹, s2, and c¹, c³, of the subsidiary steam cylinders and cataract
cylinders employed for gear of that kind.
One form of expansion gear is shewn in Fig. 5, which represents a part longitu-
dinal section of a steam cylinder with a slide and expansion slide worked differen-
tially. The main slide V, which is of the gridiron kind, has two passages v¹, v³,
governed by the expansion slide X, which is worked by its rod x connected to one
end of a lever 1, the other end of which is connected to a lever L worked directly
by the engine in line with the piston thereof. The lever has its fulcrum on the
rod W of the main slide V, which is itself worked by differential gear, the connection
thereof being indicated at w. The expansion slide X thus arranged receives a
differential movement partly direct from the engine through its connection with the
lever L and partly from the differential movement of the main slide V acting at the
fulcrum of the lever l.
Another form of differential expansion gear according to my Invention is shewn
in Fig. 6, which represents a part longitudinal section of a slide casing with a
double beat expansion valve M applied thereto. The valve rod m, which is loaded,
is worked by one end of a lever N, the other end of which is the fulcrum of a
T lever O which receives a certain amount of motion communicated to one of its
arms through a rod p from a lever P worked directly by the engine in time with its
piston. The other arms of the lever O are connected by rods q¹, q2, having slotted
holes to two of the arms of another. T lever Q, the third arm of which is worked by
the main slide rod R that is itself worked by differential gear. The expansion

page_text: valve M thus arranged is necessarily opened by the action of the lever Q and
rods q, q², when the main slide gives steam to either end of the main cylinder, but
it remains open for a variable period, depending on the differential movement
which it receives partly from the said rods q¹, q³, and partly from the lever P. The
amount of stroke given by this lever and the length of the rod p are adjusted as
desired as well as the length of the rods q¹, q², by means of adjusting screws.
Having thus described the nature of my Invention and in what manner the same
is to be performed, I claim,-
First. The combination of a pair of engines with steam and exhaust communi-
cations and valves so arranged that either engine can be worked with steam direct
from the boiler, the other being worked by the exhaust steam of the former, or that
both can be worked with steam from the boiler, substantially as and for the purposes
herein set forth.
.
Second. In engines arranged to work in the manner referred to in the preceding
claim, the use of a compound valve box constructed and operating, substantially as
described with reference to Fig. 4 of the accompanying Drawings.
Third. Combining with a differentially worked steam slide an expansion slide
worked differentially by connecting it to a lever moved partly in accord with the
piston of the engine and partly in accord with the steam slide, substantially as
herein described with reference to Fig. 5 of the accompanying Drawings.
Fourth. In combination with a differentially worked steam slide, the use of an
expansion valve worked differentially by connecting it to levers worked partly in
accord with the engine piston and partly in accord with the steam slide, sub-
.stantially as herein described with reference to Fig. 6 of the accompanying
Drawings.
. In witness whereof, I, the said Henry Davey, have hereunto set my hand
and seal, this Eighteenth day of July, in the year of our Lord One thousand
eight hundred and seventy-seven.
HENRY DAVEY. (L.S.)