IMPROVEMENTS IN SAFETY VALVES
Year: 1875

page_text: LETTERS PATENT to Thomas Gilmour, of Kilcattan Tile Works, in the
County of Bute, North Britain, for the Invention of "IMPROVEMENTS
IN SAFETY VALVES."
Sealed the 13tli July 1875, and dated the 15th January 1875.
PROVISIONAL SPECIFICATION left by the said Thomas Gilmour at the
Office of the Commissioners of Patents, with his Petition, on the
15th January 1875.
I, THOMAS GILMOUR, of Kilcattan Tile Works, in the County of Bute,
North Britain, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN SAFETY VALVES," to be as follows, that is to say :—
This Invention has for its object to increase the efficiency and security
of safety valves, and to arrange them so as whilst providing full and
immediate relief for an excess of pressure to close again on the pressure
becoming very slightly lower than that to which the valves are loaded in
order that the steam or other fluid under pressure may not be wasted.

page_text: The improvements are effected by means of what may be termed
automatic easing apparatus, consisting of a small additional valve loaded
to the pressure at which the main valve or valves are to open, and
having over it a cover fitted to work freely on the spindle of a small
valve, and on the outside of the valve seat. This cover is connected to
the lever of the main valve, or to a lever by which the main valve or
valves can be eased. On the steam or other pressure exceeding the
limit, the small valve opens and allows some steam or fluid to act inside
its cover, and the pressure thereby produced on the cover raises it and
causes it to ease or reduce the load on the main valve or valves so that
these open freely to relieve the pressure. The steam is however con-
tinually escaping from under the cover of the small valve, and on the
pressure in the boiler or vessel to which the valve is fitted becoming
reduced the small valve at once closes, and the pressure ceasing to be
maintained under the cover this cover immediately descends and allows
the main valve or valves to close. The cover is made smaller or larger
in area accordingly as in each case it requires to exert less or morc
lifting force for casing the main valve or valves; the additional valve
may be made of a very small size, and can be very conveniently secured
by lock and key, and so as to render ineffective any tampering with the
main valve or valves.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Thomas Gilmour in the Great Seal Patent Office
on the 14th July 1875.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, THOMAS
GILMOUR, of Kilcattan Tile Works, in the County of Bute, North
Britain, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Fifteenth day of January, in the
year of our Lord One thousand eight hundred and seventy-five, in the
thirty-eighth year of Her reign, did, for Herself, Her heirs, and suc-
cessors, give and grant unto me, the said Thomas Gilmour, Her special
licence that I, the said Thomas Gilmour, my executors, administrators,

page_text: and assigns, or such others as I, the said Thomas Gilmour, 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 SAFETY VALVES," upon the condition (amongst others) that I,
the said Thomas Gilmour, my executors or administrators, by an instru-
ment in writing under my, or their, or one of their hands and seals,
should particularly describe and ascertain the nature of the said In-
vention, 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 Thomas Gilmour, do hereby declare.
the nature of my said Invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the
following statement in writing, reference being had to the accompanying
Drawings, that is to say :-
My said Invention has for its object to increase the efficiency and security
of safety valves, and to arrange them so as whilst providing full and
immediate relief for any excess of pressure to close again on the pressuro
becoming very slightly lower than that to which the valves are loaded,
in order that the steam or other fluid under pressure may not be
wasted.
My improvements are effected by means of what may be termed
automatic easing apparatus, consisting of a small additional valve loaded
to the pressure at which the main valve or valves are to open, and having
over it or over the outlet from it a cover fitted to work freely on the
outside of the valve seat, or on the outside of a disc in which the outlet.
is formed. This cover is connected to the lever of the main valve, or to
a lever by which the main valve or valves can be eased. On the steam
or other pressure exceeding the proper limit, the small valve opens and
allows some steam or fluid to act inside the cover, and the pressure
thereby produced on the cover raises it and causes it to ease or reduce
the load on the main valve or valves, so that these open freely to relieve.

page_text: the pressure. The steam is however continually escaping from under
the cover, and on the pressure in the boiler or vessel to which the valve
is fitted becoming reduced the small valve at once closes, and the
pressure ceasing to be maintained under the cover, this cover imme.
diately descends and allows the main valve or valves to close.
And in order that my said Invention and the manner of performing
the same may be properly understood, I hereunto append a Sheet of
explanatory Drawings to be herein-after referred to, and representing
two modifications of my improved apparatus.
In these Drawings the same reference numerals are used to mark the
same or like parts wherever they are repeated.
by a cross
Figure 1 is a vertical section showing a modification of my improved
automatic casing apparatus as applied in connection with an ordinary
steam boiler safety valve 4 loaded by a weighted lever 5; Figure 2 is a
plan showing the cap 6. In a tubular casting 7 bolted to the boiler a
brass seating 8 is fitted for the small easing valve 9. This valve 9 is
loaded by a direct weight 10, the spindle of which is guided
head 11 carried by a pair of rods 12 fixed to the casting 7. The brass
cap 6 is fitted to work frecly on a cylindrical ring 13 fixed on the
enlarged top of the tubular casting 7, and the cap also works freely on
the cup-like centre of the valve 9. The main valve lever 5 is made with
a fork 14 at its outer end, the two points of the fork being bent down
and situated upon the cap 6, one on each side of its centre. The valve 9
must be loaded accurately to the pressure which it is desired shall not
be exceeded, but the load on the main valve 4 may be a little in excess
of what corresponds to that pressure without injury. On the pressure in the
boiler rising, so as to open the small valve 9, the steam gets access to the
inside of the cap 6, and although it escapes gradually between the cap
and the ring 13, and between the cap and the top of the valve 9, a
sufficient pressure is produced and maintained on the inside of the cap 6
to cause it to bear up the lever 5, and thereby ease the main valve 4,
and allow of the free escape of surplus steam. On the pressure becoming
reduced again the small valve closes before the pressure gets much
below the proper point, and then the supply to the cap 6 being stopped
the pressure in the cap at once diminishes, and allows the full load to
take effect in closing the main valve 4.

page_text: substantially as herein-before described.
In witness whereof, I, the said Thomas Gilmour, have hereunto
set my hand and seal, this Thirteenth day of July, in the year of 5
our Lord One thousand eight hundred and seventy-five.
Witness,
EDMUND HUNT,
Patent Agent,
Glasgow..
THOMAS GILMOUR. (L.S.)