IMPROVE- MENTS IN ROTATORY STEAM ENGINES
Year: 1853

page_text: LETTERS PATENT to Alexander Dalgety, of 76, Florence Road,
Deptford, in the County of Kent, for the Invention of "IMPROVE-
MENTS IN ROTATORY STEAM ENGINES."
Sealed the 6th October 1853, and dated the 15th August 1853.
PROVISIONAL SPECIFICATION left by the said Alexander Dalgety
at the Office of the Commissioners of Patents, with his Petition,
on the 15th August 1853.
I, ALEXANDER DALGETY, of 76, Florence Road, Deptford, in the
County of Kent, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN ROTATORY STEAM ENGINES" to be as follows:-
The application of two sliding and one revolving drum, all of exactly
equal diameter, by which method the greatest speed may be acquired
without chance of derangement to the parts, and the immense and
nost destructive pressure on the piston shaft, so fatal to durability
and power (and to which defect all engines of this class have hitherto
been subject) almost entirely removed. There also being but one dead
point, and that of very short duration, in every revolution of the piston.
the economical principle of working expansion may be carried to a very
great extent.
Sp

page_text: The cylinder consists of two chambers of unequal bore, the smaller
being rather more than half the diameter of the larger. On the inner
side of each cylinder cover, and central to the larger chamber, is cast a
hollow circular projection in which the two sliding drums move, the
inner edges of which, when in their places, nearly meet. By this means
a distinct chamber is formed wherein the piston (which is connected
with its shaft by a thin circular plate always running steam-tight
between the edges of the two sliding drums, which press lightly upon
it by means of spiral springs within them) moves. On one side of each
sliding drum a wide channel is cut and fitted with a metallic packing,
having its outer or exposed side concave to fit the convex rim of the
revolving drum which fits and moves within the smaller chamber. The
piston and drum shaft are connected by a pair of spur wheels of the
same size, which causes them to run quickly and at equal speed, and
also presents the cavity in the revolving drum or fulcrum at the right
moment for the piston to pass through. If the steam be now admitted
on either side of the fulcrum the face of the piston (with the exception
of the thin plate before spoken of) will be the only surface capable of
receding, and the force of the steam being concentrated on that one
point must obviously become much more effective.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Alexander Dalgety in the Great Seal Patent
Office on the 15th February 1854.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I,
ALEXANDER DALGETY, of 76, Florence Road, Deptford, in the County
of Kent, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Fifteenth day of August, in the year
of our Lord One thousand eight hundred and fifty-three, in the seven-
teenth year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said Alexander Dalgety, Her special
licence that I, the said Alexander Dalgety, my exccutors, administrators,

page_text: 0
and assigns, or such others as I, the said Alexander Dalgety, my execu-
tors, 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 ROTATORY STEAM ENGINES," upon the condition (amongst others) that
I, the said Alexander Dalgety, 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 Scal Patent Office within
six calendar months next and immediately after the date of the said
Letters Patent.
NOW KNOW YE, that I, the said Alexander Dalgety, 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):
My Invention consists in the arrangement and application of two
sliding drums or cylinders a, a, and of one revolving drum or cylinder b,
each of equal diameter, carried by axes, as hereafter described, by which
arrangement great speed may be acquired without liability of derange-
ment of the parts, and by which arrangement the destructive pressure
on the piston shaft, so injurious to the durability and power of the
apparatus, (and to which defect steam engines of this class have hitherto
been subject,) is almost entirely removed. There being but one dead
point, and that of very short duration, in every revolution of the piston,
the economical principle of working expansively may be carried to a
very great extent.
DESCRIPTION OF THE DRAWINGS.
The nature of each of the views being written thereon, it will not be
And I would here remark that although
necessary to repeat the same.
cylinders or chambers c, c, combined with one
may be varied by employing only one of the
The outer casing or cylinder consists of two
the Drawings show two
central chamber c', this
cylinders or chambers c.

page_text: chambers c, c, of equal bore or diameter, and a small one c', the smaller
being rather more than half the diameter of the larger. On the inner
side of each cylinder cover d, and central to the larger chamber c, is
cast a hollow circular projection d', on which the two sliding drums a, a,
move, to compensate for wear, the inner edges a, of which drums when
in their places nearly meet, and between the outer periphery of the
drum a, and the inner periphery of the chamber c, a distinct chamber
is formed wherein the piston e, (which is connected with its shaft e', by
a thin circular plate e, always running steam-tight between the edges
of the two sliding drums a, a, which press lightly upon it by means of
spiral springs a', acting upon them) moves. On one side of each
sliding drum a, a, a wide channel is cut, as shewn at a*, and fitted
with a metallic packing, having its outer or exposed side concave to
fit the convex surface of the revolving drum b, which fits and moves
within the smaller chamber c'. The piston shafts e', and drum shaft b¹,
are connected by spur wheels ex, 6*, of the same size, which causes the
drum b, to present its cavity 62, in the revolving drum or fulcrum b, at
the right moment for the piston to pass through. If the steam be now
admitted on either side of the drum fulcrum b, the face of the piston
(with the exception of the thin plate before spoken of) will be the
only surface capable of receding, and the force of the steam being con-
centrated on that one point must obviously become much more effective.
ff, show the induction and eduction passages.
In witness whereof, I, the said Alexander Dalgety, have hereunto
set my hand and seal, this Fifteenth day of February, in the
year of our Lord One thousand eight hundred and fifty-four.
Witness,
J. G. TONGUE.
A. DALGETY. (L.S.)