IMPROVEMENTS IN SELF-ACTING DIFFERENTIAL VALVES
Year: 1857

page_text: LETTERS PATENT to Charles Renshaw, of Dukinfield, in the County of
Chester, Engineer and Millwright, for the Invention of "IMPROVEMENTS IN
SELF-ACTING DIFFERENTIAL VALVES."
Scaled the 29th September 1857, and dated the 4th April 1857.
PROVISIONAL SPECIFICATION left by the said Charles Renshaw at the
Office of the Commissioners of Patents, with his Petition, on the
4th April 1857.
I, CHARLES RENSHAW, of Dukinfield, in the County of Chester, Engineer
and Millwright, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN SELF-ACTING DIFFERENTIAL VALVES," to be as follows:-
I employ a column of mercury as a self-acting medium for the purpose of
regulating the spaces between the valve discs and their seatings, so that as
steam at a high pressure enters the valve box it escapes at any reduced
pressure from the exit pipe with correctness and certainty, the weight of a
column of mercury forming a balance or equilibrium with the pressure of the
steam in the boiler and the exit, so that when the pressure of the steam

page_text: entering the valve box is low, the discs rise and give more space, allowing
more steam to pass through; and when the steam is high, the discs are
depressed, contracting the space and wire-drawing the steam, thereby main-
taining an uniform pressure in the delivery, although the pressure in the boiler
may vary.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Charles Renshaw in the Great Seal Patent Office on the
3rd October 1857.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, CHARLES
RENSHAW, of Dukinfield, in the County of Chester, Engineer and Millwright,
send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Fourth day of April, in the year of our Lord
One thousand eight hundred and fifty-seven, in the twentieth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me,
the said Charles Renshaw, Her special licence that I, the said Charles
Renshaw, my executors, administrators, and assigns, or such others as I,
the said Charles Renshaw, 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 "IMPROVE-
MENTS IN SELF-ACTING DIFFERENTIAL VALVES," upon the condition (amongst
others) that I, the said Charles Renshaw, 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 Charles Renshaw, do hereby declare the
nature of the said Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement (that is to say):-
I employ mercury placed in a vessel or cistern in connection with a tube, at
the top of which is an air-tight air vessel or receiver. In the cistern I place a

page_text: float, to which the valves are connected by means of a rod, which valves rise
up and down or off or upon their seatings, according to the level of the
mercury, which rises when the diminished pressure is lower than required, at
the same time raising the valves and permitting the passage of steam-until the
desired equilibrium is obtained; but when the diminished pressure is too high
the mercury in the cistern is depressed, the surplus rising into the interior of
the aforesaid tube, which maintains the balance or equilibrium, according to
the length of the tube, so that as steam at a high pressure enters the valve
box it escapes at any reduced pressure from the exit pipe with correctness and
certainty.
The manner in which my said Invention is to be performed will be clearly
understood by reference to the accompanying Sheets of Drawings, and the
letters of reference thereon, in which Fig. 1 is a vertical and longitudinal
section of a diminishing valve placed in the valve box, having the mercury
cistern and tube attached; Fig. 2 is an end elevation of the same. a repre-
sents the passage from the boiler into the valve box; b, the valves; c, the
spindle; d, the seatings; e, the passage from the valves for the steam at a
diminished pressure; f, apertures or spaces affording communication with the
steam and mercury; g, the cistern for containing the mercury; h, the float;
and i, the horizontal tube which connects the cistern with the vertical tube k,
at the top of which is the air vessel or receiver l, employed for the double
purpose of acting as an air vessel and receiver of the mercury. If any water
or condensed steam shall accumulate in the tube or air vessel, the mercury,
being the heavier body, will descend and displace the water, which will escape
by a valve, if found desirable, placed on the top of the receiver; the said valve
is not shewn in the Drawings. In the bonnet or cover m of the valve box
I place an ordinary stop valve spindle n, working in a stuffing box in the.
usual manner; the end of the spindle is screwed and works in the nut o, the
spindle being acted upon by a handle or fly wheel p. The stop valve spindle
at its lower part can be pressed upon the top of the spindle of the diminishing
valve, so as to press the valves to their seatings, thereby causing the valve to
become an efficient shut-off or stop valve.
Having thus fully described the nature of my said Invention, and the.
manner in which the same is to be performed, I desire it to be distinctly
understood that I do not confine myself to the exact details herein set forth,
as such may be varied or modified without departing from the principle
thereof; but I claim as my Invention, and which, to the best of my knowledge

page_text: and belief, has not been hitherto used within the realm, the general arrange-
ment and construction of self-acting differential valves, as herein described, and
illustrated in the accompanying two Sheets of Drawings.
In witness whereof, I, the said Charles Renshaw, have hereunto set my
hand and seal, this Second day of October, in the year of our Lord One
thousand eight hundred and fifty-seven.
Signed, sealed, and delivered by the
within-named Charles Renshaw,
in the presence of
E. J. HUGHES, Patent Agent,
Manchester.
CHAS. RENSHAW. (L.S.)