IMPROVEMENTS IN SAFETY VALVES.
Year: 1874

page_text: LETTERS PATENT to Frederick William Colls, of Erith, in the
County of Kent, for the Invention of "IMPROVEMENTS IN SAFETY
VALVES.".
Sealed the 29th December 1874, and dated the 3rd July 1874.
PROVISIONAL SPECIFICATION left by the said Frederick William Colls
at the Office of the Commissioners of Patents, with his Petition,
on the 3rd July 1874.
1
I, FREDERICK WILLIAM COLLS, of Erith, in the County of Kent, do
દ IMPROVEMENTS IN
hereby declare the nature of the said Invention for
SAFETY VALVES," to be as follows:-
The object of this Invention is to construct safety valves for steam
boilers in such manner that if the valve be slightly raised by an excess
of pressure it shall at once open fully, and allow a free escape of steam'
until the pressure has been sufficiently reduced in the boiler, and so

page_text: that the valve shall then close quickly. To effect this I form the
weighted lever arm by which the valve is held down on to its seat of a
metal tube having at each end a closed chamber, and the valve is set so
that when the valve is held down on to its seat this arm is horizontal or
nearly so. Into the chamber which is at the weighted end of the arm
is placed a quantity of mercury until the upper surface of the mercury
is level with or somewhat above the bottom of the tubular arm. When
the valve is raised the mercury in the vessel flows along the arm and
into the vessel at its opposite end behind the fulcrum, the load upon
the valve is thus slightly reduced, and the valve opens to its full extent
and remains open until the pressure has been sufficiently reduced,
when the valve again quickly closes as the load upon it continues to
increase during the return of the tubular arm to its former horizontal
position.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Frederick William Colls in the Great Seal Patent
Office on the 1st January 1875.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, FREDERICK
WILLIAM COLLS, of Erith, in the County of Kent, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Third day of July, in the year of our
Lord One thousand eight hundred and seventy-four, in the thirty-eighth
year of Her reign, did, for Herself, Her heirs and successors, give and
grant unto me, the said Frederick William Colls, Her special license
that I, the said Frederick William Colls, my executors, adminis-
trators, and assigns, or such others as I, the said Frederick William
Colls, my executors, administrators, and assigns, should at any time
agree with, and no others, from time to time and at all times there-
after 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 Inven-
tion for "IMPROVEMENTS IN SAFETY VALVES," upon the condition (amongst
others) that I, the said Frederick William Colls, my executors or

page_text: administrators, by an instrument in writing under my, or their, or
one of their hands and seals, 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 Frederick William Colls, 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 :-
The object of this Invention is to construct safety valves for steam
boilers in such manner that if the valve be slightly raised by an excess
of pressure it shall at once open fully, and allow a free escape of steam
until the pressure has been sufficiently reduced in the boiler, and so
that the valve shall then close quickly. To effect this I form the
weighted lever arm by which the valve is held down on to its seat of -a
metal tube having at each end a closed chamber, and the valve is set so
that when the valve is held down on to its seat this arm is horizontal or
nearly so. Into the chamber which is at the weighted end of the arm
is placed a quantity of mercury until the upper surface of the mercury
is level with or somewhat above the bottom of the tubular arm. When
the valve is raised the mercury in the vessel flows along the arm and
into the vessel at its opposite end behind the fulcrum, the load upon
the valve is thus slightly reduced and the valve opens to its full extent
and remains open until the pressure has been sufficiently reduced,
when the valve again quickly closes as the load upon it continues to
increase during the return of the tubular arm to its former horizontal
position.

page_text: position by set screws C passing through them at the top, and pressing
upon and holding the lever A. To the end of the lever A behind. the
fulcrum is secured a cast-iron box D, the inside of the bottom of which
is level with the inside of the lever tube. At the opposite end of the
lever is a similar box of cast iron, but much deeper, the bottom being of
thick cast iron to give weight, and a space being left below the bottom
of the lever tube to contain mercury, as shewn. The pressure upon the
valve is regulated by setting this weighted end of the lever at any
desired distance from the fulcrum, and the lever is then retained by the
set screws C; when once it has been adjusted by the engineer or other
responsible person it may be secured from being altered by the man in
charge of the boiler by sliding over the heads of the screw bolts C a
tubular cap
E having a slot formed along it at the bottom for the stems.
of the screws to pass through. The cap is closed at one end and at the
other is provided with a cover which is applied to it when the cap has
been slidden over the heads of the bolts, and the cap is-then secured
by a padlock or other lock, and all access to the set screws in thus
prevented.
When the maximum pressure of steam at which the valve is set is
attained in the boiler the valve slightly lifts like any ordinary one, but
in so lifting the lever is thrown slightly out of its horizontal position,
and the mercury from the weight box flows through the tube into the
box behind the fulcrum. By so doing the weight of mercury is not
only displaced from the end of the lever, but a corresponding weight is
given behind the fulcrum. This relief being given allows the valve to
open a considerable area, and while in this position no further pressure
can be obtained. When the boiler has been relieved of some few
pounds pressure the lever weight is sufficiently heavy to close the
valve, and the mercury returning to its original position prevents the
valve opening again until the same maximum pressure is attained.
Having thus described the nature of my Invention and the manner
of performing the same, I would have it understood that I claim as my
improvements in safety valves, the construction of safety valves, as
herein described, with a horizontal tubular lever arm provided with
chambers at either end to contain mercury, so that when the valve is.
raised mercury may flow from the chamber at the weighted end of the

page_text: lever to the chamber at the opposite end, thereby reducing the load upon
the valve, and allowing it to at once open to a considerable area.
In witness whereof, I, the said Frederick William Colls, have
hereunto set my hand and seal, this Thirty-first day of December,
in the year of our Lord One thousand eight hundred and seventy-
four.
FREDERICK WILLIAM COLLS. (L.S.)