IMPROVEMENTS IN ROTARY STEAM ENGINES
Year: 1852

page_text: LETTERS PATENT to Duncan Bruce, of Canada, North America,
Gentleman, for the Invention of "IMPROVEMENTS IN ROTARY STEAM
ENGINES."
Sealed the 13th January 1853, and dated the 1st October 1852.
PROVISIONAL SPECIFICATION left by the said Duncan Bruce at
the Office of the Commissioners of Patents, with his Petition, on
the 1st October 1852.
I, DUNCAN BRUCE, of Canada, North America, Gentleman, do
hereby declare the nature. of the said Invention for
IN ROTARY STEAM ENGINES" to be as follows:-
IMPROVEMENTS
This Invention consists of making the piston of three or more sections
of a larger circle than the cylinder within which such piston rotates,
and causing the slides to be connected together and guided in their
action by guides corresponding with the piston, and acted on by a small
steam piston and cylinder to relieve the working piston from the pres-
sure and friction of the slides.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Duncan Bruce in the Great Seal Patent Office
on the 30th March 1853.
year of
TO ALL TO WHOM THESE PRESENTS SHALL COME, I,
DUNCAN BRUCE, of Canada, North America, Gentleman, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the First day of October, in the
our Lord One thousand eight hundred and fifty-two, in the sixteenth
year of Her reign, did, for Herself, Her heirs and successors, give and
grant nuto ne, the said Duncan Bruce, Her especial license that I,
the said Duncan Bruce, my executors, administrators, and assigns, or
such others as I, the said Duncan Bruce, my executors, administra-
tors, 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 Chan-
nel Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN
ROTATORY STEAM ENGINES," upon the condition (amongst others) that
I, the said Duncan Bruce, 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 per-
formed, 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, in compliance with the said proviso, I, the
said Duncan Bruce, do hereby declare that the nature of my said In-
vention, and in the manner of performing the same, are fully described
and ascertained in and by the following statement thereof, reference
being had to the Drawings hereunto annexed, and to the figures and
letters marked thereon, that is to say:
This Invention consists in making the piston of three or more sections
(of a larger circle than the cylinder within which such piston rotates),
and causing the slides to be connected together and guided in their
action by a guide corresponding with the form of the piston, and acted

page_text: on by a small steam piston and cylinder to relieve the working piston
from the pressure and friction of the slides.
DESCRIPTION OF THE DRAWINGS..
Figure 1, shews an elevation of an engine constructed according to
my Invention; Figure 2, shows a plan thereof; Figure 3, a longitu-
dinal section; and Figure 4, a horizontal section thereof. In each of
these Figures the same letters are used to indicate the same parts.
, a, is a cylinder having steam ways b, b', and c; the steam passages
6, 61, being those ordinarily used. The steam passages e, c, are those by
which steam is admitted when the engine is to be reversed, and which
ordinarily are the eduction ways for the steam to get away to the con-
denser or to the open air, as the case may be. d, is a valve box com-
municating with the steam passages b, b', there being a slide valve with
ports through it by which the steam can be cut off at any part of the
stroke, such valve being moved by means of a 'pinion on the axis e,
which passes through a stuffing box, and may be moved by suitable
apparatus put in motion by the working of the engine. ; is a pipe
connected to the steam pipe from the boiler; on the pipe f, there is a
cock f', which is kept open when the engine is at work, but is closed
when the engine is to be reversed, and during the time the engine is
working in the reversed direction. g, is a cock on a pipe communicating
with the condenser or the open air and with the valve box; this cock
is kept shut when the engine is at work in its ordinary direction, but is
opened when the engine is to be reversed in its action, and then the
passages b, b, become for a time the eduction ways. The steam ways
c, open into the cylinder at the backs of the gates, and the other end
opens into a box h, which at one end has a pipe leading to the steam
supply pipe from the boiler, and at the other end a pipe leading to the
condenser or to the open air. i, is a cock, which is kept closed during
the time that the engine is at work in the ordinary direction; and the
cock j, is kept open during the same time and it is not necessary to
have any slide valve in the box h. I would state that, although I prefer
this mode of admitting and emitting steam, I do not confine myself
thereto, nor do I claim the same. a, is a cylinder within which a piston
works, such piston, as shewn, being composed of three parts or sections

page_text: kkk, (of a larger circle than the cynder a within which stien
piston rotates), but the piston may be composed of more parts than three,
though I believe three to be the most convenient. The piston, by reason
of its being composed of three sections, touches the cylinder within which
it works at three points;; or, as before, stated, it may be of more sections
than three, and consequently touch at more points within the cylinder,
Feare being, observed that the diameter of the piston constantly offered
to the two slides or gates which are to be connected together shall be
equal or nearly so, that the difference will be compensated by the
yielding of the packing. 1, 1, are two gates or slides which constantly
work up to the surfaces of the piston. The slides 7, 1, move into 'and
out of recesses or. boxes m, m, there being to such gates rods 1, 1,
which work through stuffing boxes; and the two gates 7, 1, are connected
together by means of the frames 1, 1, the nature of which is clearly
shewn in the Drawings. The rods 1, 1, have cross heads, , and
these cross heads by side rods 1, 1, are connected to the frames . To
make the sections h, k, so that the diameter. of the piston acted on
by the two gates shall at all times be equal, the surfaces between the
points of bearing of the gates thercon must be irregular, as indicated
by the green lines in Figure 3, the mean lines of which are indicated by
red lines; and although each surface or section of the piston between
the points of contact with the cylinder may be made according to such
mean lines, I prefer such an arrangement that the diameter of the
piston will be more nearly alike in all parts; and sufficient adjustnient
will be found in the use of metallic packings to compensate for any
slight inequality of diameter of the piston. m, n, are two hollow tracks
for guides, similar in form to the surfaces of the piston, and these tracks
or guides control the movements of the slides or gates by reason of the
rollers or wheels, o, o, which are on axes fixed to the side rods, as
shown, and move within the tracks or guides n. n. These tracks or
guides n, n, are fixed to the axis of the piston, and consequently revolve
with it, hence the gates will be moved so as to remain in contact with
-the surfaces of the piston. The gates are packed on either side, as,
shewn, or in any other. convenient manner. The ends of the piston
are also to be provided with packing where they come in contact with
the ends of the cylinder.

page_text: In order to relieve the piston and guides from the pressure of the
gates, particularly in large engines, I prefer to employ a small steam
cylinder and piston, which, by its piston rod p, is connected to one of the
gates, as shewn, such cylinder having a slide valve put in motion by
suitable apparatus worked by the engine, as is well understood. By this
arrangement the small engine will constantly be tending to move
one of the gates towards and the other away from the surfaces of the
piston, and thus relieve the piston and guides or tracks from the pres-
sure of the gates; or a like result may be obtained by admitting steam
alternately into the two boxes or cases of the slides or gates, and
packing such gates as pistons; or when, in lieu of the straight slides or
gates, curved gates or flaps hinged to the cylinder and connected in
the aforesaid manner are used (one modification of which is shewn in
Figure 5), the external coupling gear and connection with the cross
heads of the gates may be constructed, as shewn by the red lines.
Having thus described the nature of my Invention, and the manner
of performing the same, I would state that variations may be made in
the details so long as the peculiar character of my Invention be re-
tained. But what I claim is, the constructing rotatory steam engines
each with a piston of three or more sections or surfaces, and conse-
quently having three or more points in contact with the cylinder within
which such piston rotates, and causing the slides or gates to be con-
nected together and guided in their action by a guide corresponding
with the form of the piston, and also having a small steam piston and
cylinder to relieve the working piston from the pressure and friction of
the slides or gates.
In witness whereof, I, the said Duncan Bruce, have hereunto set
my hand and seal, this Twenty-sixth day of February, in the
year of our Lord One thousand eight hundred and fifty-three.
0
Witness,
JNO. ALCOCK,
Lincoln's Inn.
DUNCAN BRUCE. (L.S.)