IMPROVEMENTS IN STEAM ENGINES
Year: 1869

page_text: LETTERS PATENT to Herbert Thomas Jennings and Thomas Jennings,
both of 20, Sidney Street, City Road, in the County of Middlesex,
for the Invention of "IMPROVEMENTS IN STEAM ENGINES."
Sealed the 13th July 1869, and dated the 19th February 1869.
PROVISIONAL SPECIFICATION left by the said Herbert Thomas
Jennings and Thomas Jennings at the Office of the Commissioners
of Patents, with their Petition, on the 19th February 1869.
We, HERBERT THOMAS JENNINGS and THOMAS JENNINGS, both of 20,
Sidney Street, City Road, in the County of Middlesex, do hereby declare
the nature of the said Invention for "IMPROVEMENTS IN STEAM ENGINES,"
to be as follows:-
This Invention has for its object to construct high-pressure steam
engines in such manner as to afford a free escape for the steam from the
cylinder of the engine after it has done its work therein in order that
there may be no back pressure upon the piston. For this purpose in
addition to forming the cylinder with two passages leading into it, one to
cach of its ends, through which steam is alternately admitted to and

page_text: allowed to escape from the ends of the cylinder by means of a slide
valve worked by an eccentric, as heretofore usual, I also form another
opening at each end of the cylinder, which opening or passage is only
employed for allowing steam to escape from the cylinder. The opening
and closing of these passages I effect by means of a slide valve worked
by preference by tappets from the piston of the engine, so that as the
piston is moving towards one end of the cylinder not only will the
ordinary exhaust passage be open to allow steam to escape from that end
of the cylinder, but in addition there will be a second outlet for the
steam, and this second outlet will be kept full open until the piston
has all but completed its stroke. The valve governing the opening and
closing of the additional exhaust outlets is then suddenly shifted, so that
this outlet is closed, and the additional exhaust outlet from the opposito
end of the cylinder is at the same time opened. The cylinders of
condensing engines might similarly be fitted with two exhaust passages.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Herbert Thomas Jennings and Thomas Jennings
in the Great Seal Patent Office on the 19th August 1869.
HERBERT
TO ALL TO WHOM THESE PRESENTS SHALL COME,
THOMAS JENNINGS and THOMAS JENNINGS, both of 20, Sydney Street,
City Road, in the County of Middlesex, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Nineteenth day of February, in the year
of our Lord One thousand eight hundred and sixty-nine, in the thirty-
second year of Her reign, did, for Herself, Her heirs and successors, give
and grant unto us, the said Herbert Thomas Jennings and Thomas
Jennings, Her special licence that we, the said Herbert Thomas Jennings
and Thomas Jennings, our executors, administrators, and assigns, or such
others as we, the said Herbert Thomas Jennings and Thomas Jennings,
our executors, administrators, and assigns, should at any time agree with,
and no others, from time to time and at all times thereafter during the
term therein expressed, should and lawfully might make, use, excrcise,
and vend, within the United Kingdom of Great Britain and Ireland, the
Channel Islands, and Isle of Man, an Invention for "IMPROVEMENTS
IN STEAM ENGINES," upon the condition (amongst others) that we, the

page_text: said Herbert Thomas Jennings and Thomas Jennings, our exccutors
or administrators, by an instrument in writing under our or their
hands and seals, or under the hand and seal of one of us or them,
should particularly describe and ascertain the nature of the said Invea-
tion, and in what manner the same was to be performed, and cause the
same to be filed in the Great Scal Patent Office within six calendar
months next and immediately after the date of the said Letters Patent.
NOW KNOW YE, that we, the said Herbert Thomas Jennings and
Thomas Jennings, do hereby declare the nature of the said Invention,
and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement thereof,
that is to say :-
This Invention has for its object to construct high-pressure steam.
engines in such manner as to afford a free escape for the steam from the
cylinder of the engine after it has done its work therein in order that.
there may be no back pressure upon the piston. For this purpose in
addition to forming the cylinder with two passages leading into it, one
to each of its ends, through which steam is alternately admitted to and
allowed to escape from the ends of the cylinder by means of a slide valve
worked by an eccentric, as heretofore usual, I also form another
opening at each end of the cylinder, which opening or passage is only
employed for allowing steam to escape from the cylinder. The opening.
and closing of these passages I effect by means of a slide valve worked
by preference by cams on the crank shaft or by tappets from the piston
of the engine, so that as the piston is moving towards one end of the
cylinder not only will the ordinary exhaust passage be open to allow
steam to escape from that end of the cylinder, but in addition there will.
be a second outlet for the steam, and this second outlet will be kept
full open until the piston has all but completed its stroke. The valve,
governing the opening and closing of the additional exhaust outlets is
then suddenly shifted so that this outlet is closed, and the additional
exhaust outlet from the opposite end of the cylinder is at the same time,
opened. The cylinders of condensing engines might similarly be fitted.
with two exhaust passages.
And in order that my said Invention may be fully understood and
readily carried into effect, I have in the Drawings hereunto annexed-
shewn the cylinder of a steam engine thus fitted with additional outlet
or exhaust passages.

page_text: Figure 1 shews a plan view of the cylinder; Figure 2, a vertical
section taken through the additional outlet or exhaust passages, which,
are marked a, a; and Figure 3, a vertical section taken through the
passages, which are, as is usual, used alternately as outlet or exhaust.
passages and inlet passages to admit steam to the cylinder; these
1-assages are marked b, b. The admission of steam to these passages.
from the valve box c, which is, as usual, kept supplied with steam from
a steam boiler, is shewn to be regulated by an ordinary, D slide, valve,
which is worked by an excentric on the crank shaft, but in place of this.
the admission of steam to these passages may be governed by other form
of valve so long as the passages are caused to act alternately as inlet and
outlet passages for the steam or gaseous fluid by which the engine is
worked. The alternate opening and closing of the additional exhaust
passages a, a, is effected in the arrangement shewn in the Drawing by a
slide valve d kept up to the valve face, against which it works by means
of air, steam, or other fluid under pressure being caused' to act against it
at the back. For this purpose the valve is enclosed in a valve box e, the
interior of which is kept supplied with air, steam, or fluid under pressure,
by preference with steam from the boiler. Any water condensing in the
valve box can be drawn off therefrom by a steam trap, as is well under-
stood, or by a stop-cock, opened from time to time when necessary; or
the valve might be kept up to its seat by a spring or springs. The slide
valve d is so formed and actuated that at each end of its stroke it closes
one of the outlet or exhaust passages a, whilst at the same time it puts
the other passage a in communication with an outlet or exhaust pipe f
to which the outlet or exhaust passage from the valve c is also led; or
it might lead to a separate outlet or exhaust pipe. I prefer to give
motion to the valve rod of the slide valve d by a cam on the crank shaft
of the engine, the valve rod being drawn endwise up to such cam by a
spring or otherwise. The cam is so formed that the valve shall be
caused to move suddenly from one extremity of its stroke to the other
just previously to the piston of the engine completing its stroke, so that
as the piston is moving towards one end of the cylinder the exhaust
passage a from this end of the cylinder shall be kept fully opened until
the piston has all but finished its stroke, as before explained. In place
of employing a slide valve to regulate the opening, and closing of the
additional outlet passages a, a; other forms of valve may be employed;.
and they may be opened or closed: by any suitable arrangement. of
mechanism.

page_text: Having thus described the nature of our Invention, and the manner
of performing the same, we would have it understood that what we
claim is, the constructing steam engines substantially as herein
described, that is to say, with the cylinder (or cylinders) of the engine
formed with an outlet or exhaust passage at each end in addition to
the ordinary passage which is employed alternately to admit steam to
and allow steam to escape from the cylinder.
In witness whereof, we, the said Herbert Thomas Jennings and
Thomas Jennings, have hereunto set our hands and seals, this
Thirteenth day of August, in the year of our Lord One thousand
eight hundred and sixty-nine.
H. T. JENNINGS.
(L.S.)
THOMAS JENNINGS. (L.S.)