IMPROVEMENTS IN STEAM ENGINES
Year: 1855

page_text: Sealed the 18th September 1855, and dated the 30th March 1855.
PROVISIONAL SPECIFICATION left by the said Theophilus Wood Bunning
at the Office of the Commissioners of Patents, with his Petition, on the
30th March 1855.
I, THEOPHILUS WOOD BUNNING, of Newcastle-upon-Tyne, Engineer, do
hereby declare the nature of the said Invention for "IMPROVEMENTS IN STEAM
ENGINES" to be as follows:-
My Invention refers to that class of steam engines in which the steam,
after being used at its maximum pressure on one side of a piston, is made to
work expansively on the other side thereof, and so produce the up and down
strokes. My Invention consists in a new arrangement of trunk engine,
wherein the steam from the boiler is only admitted under the piston to perform
the up stroke, while it is made to enter through a slide of the particular con-
struction herein-after described into the upper part of the cylinder, there to
work expansively, and perform the down stroke. The particular construction
of slide is such that while it admits of bigh pressure steam entering the

page_text: bottom of the cylinder, it opens a passage for the escape of the steam which
has expanded and done its work on the upper part of the piston into the
condenser, while on the down stroke of the piston the slide admits steam
from under the piston into the expansion chamber, to perform its work on the
upper side of the piston.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Theophilus Wood Bunning in the Great Seal Patent Office
on the 27th September 1855.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, THEOPHILUS
WOOD BUNNING, of Newcastle-upon-Tyne,. Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Thirtieth day of March, in the year of our Lord
One thousand eight hundred and fifty-five, in the eighteenth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me,
the said Theophilus Wood Bunning, Her special licence that I, the said
Theophilus Wood Bunning, my executors, administrators, and assigns, or such
others as I, the said Theophilus Wood Bunning, my 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, exercise, 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 I, the said Theophilus Wood Bunning, by an instrument in writing under
my hand and seal, should particularly describe and ascertain the nature of
the said Invention, and in what manner the same was to be performed,
and cause the same to be filed in the Great Seal Patent Office within six
calendar months next and immediately after the date of the said Letters
Patent.
NOW KNOW YE, that I, the said Theophilus Wood Bunning, do hereby
declare the nature of my 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, reference being had to the Drawings hereunto
annexed, that is to say:-
My Invention refers to that class of steam engines in which the steam, after

page_text: being used at its maximum pressure on one side of a piston, is made to work
expansively on the other side thereof, and so produce the up and down strokes.
My Invention consists in a new arrangement of trunk engine, wherein-the
steam from the boiler is only admitted under the piston' to perform the up
stroke, while it is made to enter through a slide of the particular construction'
herein-after described into the upper part of the cylinder, there to work
expansively and perform the down stroke. The particular construction of
slide is such, that while it admits of high-pressure steam entering the bottom
of the cylinder, it opens a passage for the escape of the steam which has
expanded and done its work on the upper part of the piston into the condenser,
while on the down stroke of the piston the slide admits steam from under the
piston into the expansion chamber, to perform its work on the upper side of
the piston.
:
Figures 1, 2, 3, 4, 4, and 5, of the Drawings annexed, represent different'
views of a trunk engine constructed according to my Invention; Figure 6*
represents a modification of the same; and Figures 7, 8, and 9 shew the form
of slide valve which I propose to employ with this 'description of engine; in
the three different positions of top, half, and bottom" stroke. In describing
these Figures I shall refer only to those, parts which are necessary to enable
me to explain the peculiarity of my improvements. A is the cylinder; B, the
piston; C; the trunk, and D, the connecting rod. The cylinder A is in an
inverted position; and the trunk C passes out through the bottom of the
cylinder; for. the "purpose" of diminishing the area of the underside of the
piston in the requisite proportion to that of the upper side thereof, and at
the same time forming a guide for the connecting rod. In the first of these
arrangements a small trunk Cis employed at the upper side of the piston,
for the purpose of allowing a large space above the piston for 'the steam to
expand in; and of giving access to the connecting rod: The slide which I
employ for the admission of steam-under the piston, for its free communication
between the bottom and top of the cylinder; and for its final exit to the con-
denser, is shewn in Figures 7; 8, and 9;-a is the slide casing which is in
communication with the boiler; 6 is the slide; c'is the bottom "port; d; the
top port; and e, the passage leading to-the condenser. When the slide is, at
top stroke, as in Figure 7, the high-pressure steam enters the lower port c
and acts against the under side of the piston; whilst the steam which had
before been pressing the piston down, and -had become duly expanded, escapes
through the passage e into the condenser. Again, when the slide is down, as in
Figure 9, no steam is either admitted or allowed to escape, there being, then

page_text: merely a free communication between the bottom and top of the cylinder.
The valve is worked by an excentric in the ordinary manner, and can be
adjusted so as to cut off the steam at any portion of the up stroke of the
engine. The excentric is loose on the shaft; and is provided with stops for
forward and backward motion. For the purpose of starting the engine, I
do not move the large slide, but isolate it, on the contrary, from both boiler
and condenser, and employ a separate slide of smaller dimensions, which acts
in the ordinary way, admitting steam above or below the piston, and putting
either side in communication with the condenser, as may be required. This
arrangement is the subject of other Letters Patent granted to me of even date
herewith, and need not therefore be further described here. X, X, shew the
starting valves, and the rods for working them; Y, Y, the throttle valve, and
the rods and levers for working it; and Z, Z, the eduction throttle valves, and
the rods and levers by which they are worked. The air pumps are worked
from the trunks, by which arrangement the weights of the moving parts can
-be made to equalize the upward and downward pressure of the steam.
will be seen that the average force of the high-pressure steam on the annular
surface of the lower side of the piston, combined with the pressure of the
atmosphere on the trunk C, is greatly in excess of the average force of the
expanded steam on the upper side of the piston, reduced as it is by its free
communication with the annular space between the cylinder and the trunk,
and by the upward atmospheric pressure on the trunk; a judicious adaptation
of the weights of the moving parts to this excess will, therefore, balance the
whole, and make the action of the engine uniform both in its up and down
stroke.
It
And having now described the nature of my said Invention, and in what
manner the same is to be performed, I declare that what I claim is,―
First, the mode of constructing trunk engines, wherein the cylinder is
placed in an inverted position with the trunk, passing out at the lower end
thereof; and the several parts are so arranged as to allow of the up stroke
being performed by means of high-pressure steam admitted at the under side of
the piston, and the down stroke by means of the same steam conducted to the
upper side of the piston, and working expansively, as herein-before exemplified
and described.
Second, the constructing of the trunk of steam engines in such manner
that the diameter thereof is diminished on that side of the piston in which the
steam is to work expansively, as herein-before described, and particularly shewn
at Figure 2 of the Drawings annexed.

page_text: And, third, the mode of constructing the slides of trunk engines, for the
admission of high-pressure steam at the under side of the piston to perform
the up stroke, and for the transmission of the same steam to the upper side
of the piston, to perform the down stroke, by its expansion, as herein-before
exemplified and described.
In witness whereof, I, the said Theophilus Wood Bunning, have here-
unto set my hand and seal, this Twenty-first day of September, One
thousand eight hundred and fifty-five.
THEO. W. BUNNING.
(L.B.)