Year: 1885

page_text: The object of my invention is to produce a double-acting steam engine, which
shall work more efficiently, which shall produce and maintain within itself an
improved gradation of temperature extending from each of its two Hot Inlets
to its common central Cold Outlet, which shall cause less condensation of the
entering steam, and which shall work with greater economy than has hitherto
been the case.
DESCRIPTION OF INVENTION.
In the first place-I take a double-acting steam engine cylinder, of that type
which has one or more Outlet openings placed at or near its longitudinal center;
and which also has a piston so proportioned in length, and which piston is also
fitted in some cases with self contained internal escape ports; and which piston is
so worked, that it, by and of itself, forms the release valve, for releasing the waste
steam through the central escape Outlet or outlets near the end of each single
stroke; and which piston also closes the central escape Outlet or outlets at all
other parts of each single stroke.
In such double-acting steam engine cylinders it is therefore the piston itself
which forms the escape valve, and which releases the waste steam automatically
near the end of each single stroke. And as in this class of double-acting steam
engine cylinders, the waste steam can only be released near the ter.nination of
each single stroke, I will herein afterwards, in order to avoid repetition, call
and designate such double-acting steam engine cylinders, "Terminal-exhaust
cylinders.
"

page_text: Now various forms of double-acting "terminal-exhaust" steam engine cylinders
have been known for many years, and yet, after brief existences, have long ago
been abandoned; as they either would not work at all, or would only do so in a
very imperfect manner. For the conditions under which a double-acting" terminal-
exhaust" steam engine cylinder will work satisfactorily, are peculiar, and frequently
widely different from the conditions under which an ordinary double-acting steam
engine will give satisfaction. And as these necessary conditions have not hitherto,
either been ascertained, understood, or put into practice; double-acting "terminal-
exhaust" steam engines have consequently not only remained unsuccessful, but
actually been abandoned.
"
I however, have examined into, and ascertained the conditions necessary to be
observed, so as to ensure success in the working of a double-acting "terminal-
exhaust steam engine cylinder. And have ascertained that any such cylinder
must be specially constructed, proportioned, equipped, and worked, in special
relation to the difference that exists between the Initial pressure, and the Final
pressure of the steam in any such cylinder.
"
Clearance Capacity-For instance, in order to determine the relative capacities of
the Cylinder and Clearance of a double-acting "terminal-exhaust steam engine
cylinder; I take the number of times that the Initial steam pressure exceeds the
Final steam pressure, and then take this number as the greatest number of times
that the Cylinder capacity must exceed the Clearance capacity. And by this
means I prevent, in normal working, the Compression of the unescaped final steam,
from ever exceeding the original initial steam pressure.
Expansion Gear-Again, I take the number of times that the Initial steam
pressure exceeds the Final steam pressure, and then take this number as the
greatest number of times that the expansion gear need be constructed to expand
the steam. And having determined this, I then fit to my improved double-acting
"terminal-exhaust" steam engine cylinder, or to each Hot Inlet end of such
cylinder, any known expansion gear which is capable of expanding the steam up
to this herein before determined greatest number of times. An effective form of
gear for achieving such purpose, consists in the use of two flat superimposed slide
valves, placed near each Hot Inlet end of the cylinder; and with the outermost
flat slide of each pair, containing one or more piston cut-off valves regulated by the
governor.
In some cases, I employ admission steam valves of the "piston" type in
connexion with a double-acting "terminal-exhaust" steam engine cylinder, in
order to prevent any excessive compression, when starting the engine, from raising
these valves from their faces.
Numerical Example-If the Initial pressure exceeds the Final pressure 10 times;
then, the Cylinder capacity must not exceed the Clearance capacity more than this
10 times; and then, the maximum number of times that the Expansion gear will
be required to expand the steam, will also be this 10 times.
Of course, the Initial pressure. may exceed the Final pressure any other desired
number of times than 10, as I do not confine myself to this merely illustrative
difference between these two pressures, herein before. mentioned. And in any
such altered case, the comparative proportions of the cylinder and clearance, and
also the action of the expansion gear, will together be re-arranged in relation to
such altered difference between these two pressures; according to the manner
herein before described.
And when a double-acting "terminal-exhaust" steam engine cylinder, is con-
structed, proportioned, equipped, and worked, according to the manner herein
before described, it will not only work efficiently, but will also, in a vastly
improved manner, produce and maintain within itself an approximately constant
Gradation of Temperature, extending from each Hot Inlet down towards the
common central Cold Outlet. For, during the Advance stroke, the interior skin
of the cylinder becomes graduated from each Hot Inlet, down towards the common
central Cold Outlet, by the falling expansion of the working steam. While again,

page_text: during the Return stroke, the interior skin of the cylinder becoines graduated from
the common central Cold Outlet up towards each Hot Inlet, by the rising com-
pression of the un-escaped waste steam.
And thus my improved double-acting " terminal-exhaust" steam engine cylinder,
possesses the extraordinary advantage of having a Graduated Temperature of the
interior metal skin; which, during Admission, during Expansion, during Release,
and during Compression-that is, during the successive stages of both the
Advance and Return strokes at all times approximately corresponds to the
varying temperatures of the enclosed steam.
And therefore my improved double-acting "terminal-exhaust" steam engine,
works with greater economy than ordinary double-acting steam engines.
DRAWING OF INVENTION.
In order that the herein before stated description of my invention, may be
better and more easily understood, I have caused it to be accompanied by a
drawing, showing a general instance of the application of my invention.
This drawing shows a longitudinal section of a general instance of the application
of my improved double-acting "terminal-exhaust" steam engine cylinder and
valves, constructed according to my invention. It shows each Hot Inlet end of
the cylinder, from which the Temperature is separately Graduated down towards
the common central Cold Outlet. It also shows the proportions of the cylinder,
elongated piston, and waste escape opening or openings; by means of which part
of the Final waste steam escapes, and part is retained to undergo a prolonged com-
pression, extending from the common central Cold Outlet, up towards each Hot
Inlet end. It also shows, as well as can be delineated, the desired proportions of
the cylinder and clearance. And it also shows an expansion gear that will expand
the steam the desired number of times. This consists of two flat superimposed
slide valves placed near each Hot Inlet end of the cylinder; in the outermost valve
of each pair being one or more piston cut-off valves regulated by the governor.
I do not confine myself, however, to the particular form of expansion gear shown
on this drawing, as any other known arrangement of steam. admission valves can
be used; provided always, that such valves will act in accordance with my herein
before stated description, of the means required to produce and maintain the
desired Gradations of Temperature; and will also act in accordance with the
herein before stated general description, of my improved double-acting * terminal-
exhaust" steam engine.

page_text: H
Steam Engines.
I, LEONARD JENNETT TODD, of 67 Walford Road, South Hornsey, in the County
of Middlesex, Engineer do hereby declare the nature of my invention for
IMPROVEMENTS IN AND RELATING TO PRODUCING AND MAINTAINING GRADATIONS
OF TEMPERATURE. IN THE CYLINDERS OF DOUBLE-ACTING STEAM ENGINES," and in
what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement:-
J..
OBJECT OF INVENTION.
The object of my invention is to produce a double acting steam engine, which
shall work more efficiently, which shall produce and maintain within itself an
improved gradation of temperature extending from each of its two Hot Inlets to
its common central Cold Outlet, which shall cause less condensation of the entering
steam, and which shall work with greater economy than has hitherto been the case.
This desired gradation of temperature from the two hot inlets to the cold outlet,
cannot be constantly maintained in ordinary double acting cylinders; as in them
the hot inlet steam enters, and the cold outlet steam escapes, from the same end of
the cylinder. This end of the cylinder is therefore first heated by the inlet steam
of the advance stroke, and then cooled by the outlet steam of the return stroke, with
an endless alternation of beat and cold as long as the engine continues working.
And it is the evil of this alternate heating and cooling, which is the great cause of
waste by "cylinder condensation" in ordinary double acting steam engines, that
I desire to lessen, by maintaining my improved approximately constant gradations
of temperature.
A double acting steam engine cylinder, in which these desired approximately
constant gradations of temperature can be maintained, is one of a special class, and
is described as follows-
A double acting steam engine cylinder, of that type which has one or more
outlet openings placed at or near its longitudinal center; and which has also a
piston so proportioned in length, and which piston is also fitted in some cases with
self contained internal escape ports; and which piston is so worked, that it, by and
of itself, forms the release valve, for releasing the waste steam through the central
escape outlet or outlets near the end of each single stroke; and which piston also
closes the central escape outlet or outlets at all other parts of each single stroke.
In such double acting steam engine cylinders, it is therefore the piston itself
which forms the escape valve, and which releases the waste steam automatically
near the end of each single stroke. And as in this class of double acting steam
engine cylinders, the waste steam can only be released near the end of each single
stroke, I will herein afterwards, in order to avoid repetition, call and designate
such double acting steam engine cylinders, "Terminal-exhaust" cylinders.
I have examined into and ascertained the conditions necessary to be observed, so
as to ensure success in the working of a double acting "terminal-exhaust" steam
engine cylinder. And have ascertained that any such cylinder must be specially

page_text: quipped,
104
difference that exists between the initial pressure and the final pressure of the
steam in any such cylinder.
CYLINDER AND OLEARANCE CAPACITIES.
In double acting “ terminal-exhaust” steam engine cylinders, the compression of
the waste steam is, of course, always very much greater than in ordinary cylinders;
as in the former, the time of "compression" always equals the combined times of
both "admission" and "expansion."
I however have devised an improved method of proportioning, by which this
otherwise excessive compression can not only be prevented, but always kept at
about the best point for economical working. And this, whatever may be the
either great or small difference, between the initial and final pressures of the steam,
in any "terminal-exhaust" cylinder.
This consists in taking the number of times that the initial steam pressure in
the cylinder, exceeds the final steam pressure in the cylinder-and then taking this
number as the greatest number of times, or as the approximate number of times,
that the cylinder capacity must exceed the clearance capacity in any such cylinder.
For instance-If the initial pressure exceeds the final pressure 5 times, then the
cylinder capacity, must approximately exceed the clearance capacity, this same
5 times. Or conversely, the clearance capacity must be approximately * of the
cylinder capacity.
And as with these proportions, the final waste steam can only be compressed
5 times, it follows, of course, that the maximum compression can only just equal
the initial steam pressure. In ordinary work however, this extreme compression
will not be reached, owing to a considerable portion of the heat of the compressed
steam, being transferred to the skin of the enclosing metal. And this limitation of
the extreme compression from this cause, will especially be the case when the
cylinder is worked without the re-heating agency of a steam jacket. And thus
the compression of the waste steam in my improved cylinders, is always kept, in
normal working, a very convenient and economical distance within the initial
steam pressure.
Note. The initial steam pressure may of course exceed the final pressure any
other desired number of times than 5; as I do not confine myself to this merely
illustrative difference between these pressures herein before mentioned. And in
any such altered case, the comparative capacities of the cylinder and clearance, will
be rearranged, in relation to such altered difference between these two pressures;
according to the manner herein before described.
STEAM ADMISSION VALVES.
.I
:
To proportion the action of these, I take the number of times that the initial
steam pressure exceeds the final steam pressure and then take this number as
the greatest number of times, or as the approximate number of times, that
the admission valves need be constructed to expand the steam.
And having
determined this, I then apply to my improved double acting "terminal-exhaust
steam engine cylinder, or to each hot inlet end of such cylinder, any known non-
exhausting steam admission gear which is capable of expanding the steam up to
this desired greatest number of times. The gear however that I prefer for this
purpose, consists of two superimposed non-exhausting slide valves, placed near each

page_text: I will now proceed to give a combined numerical example of initial and final
. pressures; of comparative cylinder and clearance capacities; and of the action of
the steam admission gear.
For instance-If the initial pressure exceeds the final pressure 5 times; then the
cylinder capacity will approximately exceed the clearance capacity 5 times; and
then the maximum number of times that the steam admission gear will be
required to expand the steam will also be this 5 times.
Note. The initial pressure may of course exceed the final pressure, any other
desired number of times than these 5; as I do not confine myself to this merely
illustrative difference of these pressures just mentioned. And in any such altered
the comparative proportions of the cylinder and clearance, and also the action
of the expansion gear, will together be re-arranged in relation to such altered
difference between these two pressures; according to the manner herein before
described.
case,
Having now described the mechanism and its proportions, by which a double
acting steam engine can be made to work successfully, from two constant hot inlets
to a constant cold outlet; and by means of which a double acting "terminal-
exhaust" cylinder, can be made to work successfully, with any desired difference
between its initial and its final pressures. I will now proceed to show how
such cylinders, not only in an improved manner. produce, but also in an
improved manner maintain within themselves, approximately constant gradations
of temperature, extending from each hot inlet temperature, down to the cold outlet
temperatura
In order that these gradations may be clearly understood, I will now proceed to
illustrate the case of a non-condensing cylinder worked with an initial pressure
of 180 lbs. Then, as the initial pressure exceeds the final pressure by 10 times,
the cylinder capacity must not be greater than the clearance capacity, more than
these same 10 times. And as the temperature of steam at 180 lbs. pressure is about
372 degrees, and that of steam at 18 lbs. is about 222 degrees, it follows that the
temperature of the interior skin of the cylinder, is required to maintain an
approximately constant gradation, from this 372 degrees of each hot inlet, down
to the 222 degrees of the cold outlet-that is, through a range in this case of
150 degrees. And in working, this my improved gradation of temperature is
produced and maintained approximately constant as follows.
First advance stroke. When the engine commences working, and the first
advance stroke-from one of the hot inlets to the cold outlet commences, the
working steam of 372 degrees enters until it is cut off. And after that it gradually
descends in temperature until it finally reaches the 222 degrees of the cold outlet.
This action of the steam produces a certain gradation of temperature in the
interior metal skin, which descends from the hot inlet to the cold outlet.
And yet,
owing to the comparative coldness of the enclosing metal, at this first stage of the
working of the engine, this gradation is far from attaining the perfection that it
assumes, after the re-heating effect of the very prolonged compression of my
improved return stroke has taken place.
Release. Then the advance stroke having been nearly completed, the piston
uncovers the cold outlet, and thus allows a portion of the enervated waste steam
to escane

page_text: ་་་
Return Stroke. The' return stroke, from the cold outlet to the hot inlet, then
commences, and the piston soon closes the escape opening. And after that has
taken place, the enervated waste steam that remains confined becomes compressed,
and consequently raised in temperature, until it is eventually forced into my
properly proportioned clearance space. And as this compression always occupies
about 90 per cent, (more or less) of the return stroke, it follows that a very
prolonged and continual rise in temperature is thus produced, extending all the
way from the outlet temperature of 222 degrees, up towards the temperature of
the hot inlet. The extreme compression that could take place, would be of course
to compress the 18 lbs. of final steam, 10 times, or to approximately raise it to
the initial pressure of 180 lbs. But on account of an amount of the heat of
compression, being absorbed by the cooler skin of the enclosing metal, it follows
that this extreme degree of compression will not be reached in normal working;
and this most notably when the cylinder is worked without the heating agency,
of a steam jacket. And thus, for this reason, as well as for others, the rise of
temperature during the return stroke of compression, can never correspond
throughout the stroke with the fall of temperature during the advance stroke
of expansion. But although this is the case, yet still the fact remains that my
improved cylinder maintains an approximately constant gradation of temperature,
extending from its central cold outlet, up towards each of its outer hot inlets.
Succeeding Advance Strokes. Owing to the interior metal skin of the cylinder,
being thus reheated by the very prolonged compression, with a continuous rise of
temperature from its cold outlet up to each hot inlet, it becomes eminently suited
and prepared to favour the action of the working steam during the admission and
expansion of the succeeding advance stroke.. So that when this takes place, it
now produces and maintains a much more perfect gradation of temperature from
the hot inlet down to the cold outlet, than it did when the metal was cold; or
than can be produced in an ordinary double acting cylinder, which has just had
the cold waste steam released from the same end to which the hot steam has now
to be admitted. And thus, in these succeeding advance strokes, as the working
steam now at all times meets with a temperature of the enclosing metal that
considerably approximates to its own; it follows that there is but little con-
densation of the entering and expanding steam, and but little transfer of heat,
either from the steam to the metal, or the reverse, i.e. that is little, in comparison
with the large transfer of heat that takes place between the working steam and
the enclosing metal in ordinary double acting steam engine cylinders. And thus,
in my improved double acting "terminal-exhaust" steam engine cylinder, an
improved and very satisfactory gradation of temperature is produced and also
maintained, from each outer hot inlet down to the common central cold outlet.
Note. This initial pressure of 180 lbs. and this final pressure of 18 lbs. may
either or both be varied in any desired way, from the vacuum of a condenser up
to the highest pressures; as of course I do not confine myself to these merely
illustrative pressures and temperatures herein before mentioned. And in any such
altered case, the temperatures and gradations must always correspond to any
altered conditions of the steam pressure,

page_text: And thus my improved double acting " terminal-exhaust" steam engine cylinder,
possesses the extraordinary advantage of having an approximately constant
graduated temperature of its interior metal skin; which, during Admission, during
Expansion, during Release, and during Compression-that is, during the successive
stages of both the advance and return strokes-at all times approximately. corre-
sponds to the ever varying temperatures of the enclosed steam.
And therefore my improved double acting "terminal-exhaust" steam engine,
works with less condensation of the working steam, and with greater economy,
than ordinary double acting steam engines.
drawings.
Compact specification aro
Sheet 1, is a diagram showing the improved double gradation of temperature
that is produced and maintained in the cylinder by my invention. Each Hot
Inlet where the working steam enters the cylinder is shown by the arrows
marked 1, 1; and the Cold Outlet where part of the waste steam escapes is shown
by the arrow marked 2.
And the shading descending in intensity from each Hot
Inlet at 1, 1, to the Cold Outlet at 2, shows the improved double gradation of
temperature that my improved double acting terminal-exhaust steam engine
cylinder produces and maintains within itself when at work; as herein before
described.
(
Sheet 2, shows my improved cylinder when fitted with my improved non-
exhausting steam admission slide valves and piston cut off valves regulated by
the governor.
The non-exhausting main slides are shown at 3, 3; the expansion
slides at 4, 4; and the piston cut off slides at 5, 5. The two Hot Inlets are
shown at 6, 6; the Cold Outlet at 7; and the properly proportioned clearance
at 8. And this cylinder when at work produces and maintains within itself the
improved double gradation of temperature, illustrated on Sheet 1, and herein
before described.
Sheet 3, shows my improved cylinder when fitted with my improved non-
exhausting steam admission valve of the piston type, which works easily and
cannot be lifted off its face by excessive compression. The non-exhausting piston
valve is shown at 9; the two Hot Inlets at 10, 10; and the Cold Outlet at 11.
And this cylinder when at work produces and maintains within itself the
improved double gradation of temperature, illustrated on Sheet 1, and herein
before described.
And these three Sheets show the action and construction of my improved steam
engine cylinder and its related non-exhausting steam admission valves.
Having now particularly described and ascertained: the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is:-
(1.) A double acting steam engine cylinder having two outer Hot Inlets and
a common central Cold Outlet (or its equivalent) the piston of which uncovers
the cold outlet near the end of each single stroke and covers it during all other
parts of such single stroke: proportioned, equipped with non-exhausting steam
admission gear, and worked as described, so as to produce and maintain within
itself the improved approximately constant double gradation of temperature which
descends from each outer hot inlet end to the common central cold outlet; substan-
tially as described,
(2.) My improvements in and relating to producing and maintaining improved
gradations of temperature in the cylinders of those double acting steam engines
which have two outer Hot Inlets and a common central Cold Outlet (or its
equivalent) the piston of which uncovers the cold outlet near the end of each

page_text: single stroke and covers it during all other parts of such single stroke; substan-
tially as described.
(3.) My improved double acting steam engine cylinders of the type having two
outer Hot Inlets and a common central Cold Outlet (or its equivalent) the piston
of which uncovers the cold outlet near the end of each single stroke and covers it
during all other parts of such single stroke, and my improved non-exhausting
steam admission valves for such cylinders; substantially as illustrated or
described,