AN IMPROVED DOUBLE CYLINDER CONDENSING ENGINE
Year: 1845

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, EDWARD
ALL, of Dartford, in the County of Kent, Civil Engineer, send greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria, by Her
Letters Patent under the Great Seal of Great Britain, bearing date at West-
Ininster, the Fifteenth day of November, in the ninth year of Her reign, did,
for Ilerself, Her heirs and successors, give and grant unto me, the said
Edward Hall, Her especial licence, that I, the said Edward Hall, my
exors, adors, and assigns, or such others as I, the said Edward Hall, my
exors, admors, or assigns, should at any time agree with, and no others,
from time to time and at all times during the term of years therein
expressed, should and lawfully might make, use, exercise, and vend, within
England, Wales, and the Town of Berwick-upon-Tweed, my Invention
of "AN IMPROVED DOUBLE CYLINDER CONDENSING ENGINE;" in which said
Letters Patent is contained a proviso obliging me, the said Edward Hall,
by an instrument in writing under my hand and seal, particularly to describe
and ascertain the nature of my said Invention, and in what manner the same
is to be performed, and to cause the same to be enrolled in Her said Majesty's
High Court of Chancery within six calendar months next and immediately
after the date of the said in part recited Letters Patent, as in and by the same,
reference being thereunto had, will more fully and at large appear.
NOW KNOW YE, that in compliance with the said proviso, I, the said
Edward Hall, do hereby declare that the nature of my said Invention consists

page_text: in the application of an expansion slide valve to the back of the ordinary slide
valve of the steam nozle of a double cylinder condensing steam engine, which
expansion slide valve is provided with a separate tumbler for its motion, which
motion should be half the throw of the tumbler of the other valve, and has for
its object the regulation of the supply of steam to the cylinders of the engine
by admitting it during such part only of the stroke of the small piston as may
be necessary to expand it to the extent desired. I prefer the action of the
valves to be so adjusted as to admit the steam to the small piston during two
thirds or three fourths only of its stroke. The capacity of the two steam
cylinders have hitherto been generally in the ratio of one to four, and by
means of this arrangement of the expansion slide valve for cutting off the supply
of steam to the small cylinder at any part of the stroke, the steam may be
expanded to four, six, or more times its original yolume previous to its being
condensed, or, in other words, the expansion of the steam may be carried to a
much greater extent by this combination than without it; beside this, an
increase of power and a saving of fuel is obtained. The action of the steam
on the pistons is better regulated, and the sudden shock from the admission
of very dense steam on the large piston at the commencement of every stroke
in ordinary double cylinder engines, and while the position of the crank is
unfavorable for receiving the greatest impulse, is obviated; a less weighty fly
wheel than usual is capable of governing the reciprocating action of the piston,
and the lesser quantity of steam required for the engine enables a smaller
boiler to be used for its supply. And in further compliance with the said
proviso, I, the said Edward Hall, do hereby describe the manner in which my
said Invention is to be performed by the following statement thereof, reference
being had to the Drawing annexed and to the figures and letters marked

page_text: through the cylinder casing F, and the pipe G to the valve box C, through the
slide valve D, and by means of its tumbler mction is admitted alternately to
the top of the piston B by the passage I, I, or to the bottom of the piston by
the passage J; at the same time this valve conveys the steam on its exit from
the top or bottom of the piston B, by the passage K, to the valve box L or
nozle of the larger cylinder A¹, and is there distributed above and below the
large piston in the usual manner, and thence escapes by the eduction pipe Q to
the condenser,; but the expansion slide E receives its motion from a separate
tumbler N (worked by the tumbler shaft H, and by the cog wheels M, M, and
of only half the throw of the other tumbler P, which moves the slide D), and
is adjusted in such a manner as alternately to close the two apertures I and J of
the slide D. When the piston 13 has travelled through such part of its stroke as
may have been determined upon, so that the admission of the dense steam from the
boiler to the small cylinder being interrupted by this expansion slide, the steam
inside the cylinder expands during the completion of the stroke of the piston B,
both in ascending and descending, and in proportion to the degree of expansion
obtained in the small cylinder is the whole expansion of the steam in the two
cylinders determined; that is, if the capacity of the two working cylinders A, A¹,
of the engine are as one to four, and the steam is cut off at half the stroke in
the small cylinder, then the expansion of the steam, which by the two cylinders
only would be four times, is doubled, and becomes eight times the volume of
the dense steam admitted at each stroke to the small cylinder, and so in
proportion for any other limitation of the supply by the expansion valve.
Now, whereas I do not claim the application of expansion valves to steam
engines which have been used heretofore to intercept the passage of steam in
the steam pipes of engines, nor do I claim as my Invention any part of the
double cylinder steam engine to which the said valves are applicable; but I do
claim the application to the double cylinder condensing steam engine, the
peculiar arrangement of the said two valves herein-before described, combined
with their two separate tumbler motions as the most efficient mode of expand-
ing steam in the small cylinder of a double cylinder steam engine, which
application is fully shewn and described in the Drawing annexed; and such
my Invention being, to the best of my knowledge and belief, entirely new, and
never before used within that part of Her said Majesty's United Kingdom of
Great Britain and Ireland called England, Her said Dominion of Wales, or 'Town
of Berwick-upon-Tweed, I do hereby declare this to be my Specification of the
same, and that I do verily believe this my said Specification doth comply in all
respects, fully and without reserve or disguise, with the proviso in the said

page_text: herein-before in part recited Letters Patent contained, wherefore I hereby
claim to maintain exclusive right and privilege to my said Invention.
In witness whereof, I, the said Edward Hall have hereunto set my
hand and seal, this Fifteenth day of May, in the year of our Lord
One thousand eight hundred and forty-six.
AND BE IT REMEMBERED, that on the Fifteenth day of May, in the year
of our Lord 1846, the aforesaid Edward Hall came before our said Lady
the Queen in Her Chancery, and acknowledged the Specification aforesaid,
and all and every thing therein contained and specified, in form above
written. And also the Specification aforesaid was stamped according to the
tenor of the Statute made for that purpose.