IMPROVEMENTS IN SAFETY OR RELIEF VALVES
Year: 1867

page_text: PROVISIONAL SPECIFICATION left by John Pasfield at the Office of
the Commissioners of Patents, with his Petition, on the 12th July
1867.
I, JOHN PASFIELD, of Sedgley, in the County of Stafford, Colliery Agent,
do hereby declare the nature of the said Invention for "IMPROVEMENTS IN
SAFETY OR RELIEF VALVES," to be as follows:-
My Invention consists in constructing safety or relief valves in the manner
herein-after described, whereby the said valves are made very sensitive to
variations of pressure, and great facility is afforded for the rapid escape of
surplus steam, air, or gas.
I will describe my Invention in connection with a safety or relief valve for a
steam boiler. I make the valve of the figure of an inverted cup or short hollow
cylinder closed at one end, the open end of the said cylinder being downwards ;
the said cup or cylindrical valve works closely but freely upon the edge or peri-
phery of a circular seat or table carried by the valve box, the said valve box
being secured to the boiler in the ordinary way. Near the bottom and around
the circumference of the valve box is a series of passages or perforations for
the exit of the steam. When the cylindrical valve is in its normal position
these passages or perforations are closed and the escape of steam from the
boiler is prevented. In the axis of the valve seat or table described is a pipe
which passes some distance below the seat of the valve, the top of the said
pipe opening immediately beneath the top or closed end of the inverted cup or
cylindrical valve; steam from the boiler can only therefore act upon the

page_text: valve by passing up the said axial pipe. On the summit of the valve is a
stem working in a frame connected with the valve box; by means of this
stem the valve may be weighted by a weighted lever, or by a spring, or in
any other convenient manner. When the pressure of the steam in the
boiler exceeds that at which the valve is weighted the steam conveyed by
the axial pipe described presses upon the inside of the closed end or top of
the valve and raises the said valve, the latter sliding upon its circular seat or
table at the top of the valve box. By the raising of the valve the lateral
passages or perforations in the valve box are opened, and the surplus steam
may escape without obstruction through the said passages or perforations. By
the construction of the valve described the pressure of the steam under the
valve, and by which the valve is raised, is always the same as that of the
steam in the boiler, and is unaffected by the pressure of the escaping steam.
The steam under the valve is separated from the escaping steam by the circular
seat or table on which the valve slides. By the shape and position of the
valve described a slight increase of pressure beyond that at which it is
weighted tends to slide it upon its seat and open the exit passages, in addition
to which the liability of the valve to slick or get out of order is reduced to a
minimum.
Safety or relief valves constructed according to my Invention besides
being applicable to steam boilers are also applicable to compressed air
engines, blast cylinders, and other apparatus in which steam, compressed air,
or. gas is stored.