IMPROVEMENTS IN SAFETY VALVES, WHICH IMPROVEMENTS ARE ALSO APPLICABLE TO STEAM ENGINE AND OTHER VALVES
Year: 1865

page_text: PROVISIONAL SPECIFICATION left by Charles Vernon and William
Hodgkins, at the Office of the Commissioners of Patents, with their
Petition, on the 9th June 1865.
We, CHARLES VERNON, of West Bromwich, in the County of Stafford,
Engine Fitter, and WILLIAM HODGKINS, of West Bromwich, aforesaid, Engine
Fitter, do hereby declare the nature of the said Invention for "IMPROVEMENTS
IN SAFETY VALVES, WHICH IMPROVEMENTS ARE ALSO APPLICABLE TO STEAM ENGINE
AND OTHER VALVES," to be as follows:-
In making a safety valve according to our Invention we make two valve
seats in a vertical pipe the said two valve seats being situated the one directly
over the other. Upon the said valve seats two conical valves are fitted, the
said valves being connected together by a vertical stem or stalk. The said
valves are made of different areas, the upper one being of greater area than
the lower one. The stem or stalk of the double valve is prolonged beyond
the lower valve and upon the said prolonged end the weight with which the
double valve is to be weighted is hung, the said valves are so arranged in
the vertical tube that the steam from the boiler or vessel is made to press
upon the inner sides of both valves, the said steam pressing the top valve
upwards and the bottom valve downwards. The upward pressure upon the top
valve, in consequence of its greater area, being greater than the downward
pressure upon the lower valve it is necessary to weight the valve more or
less according to the pressure at which it is required that the steam shall

page_text: blow off. For example, if the area of the top valve be half an inch greater
than that of the bottom valve, and the pressure of the steam in the boiler is
to be maintained at thirty pounds on the square inch, then the valve stem
must be loaded with a weight which with that of the valves themselves
amounts to fifteen pounds. The pressures on the two valves being thus
equalized the pressure of the steam in the boiler is balanced and the valves
kept to their seats. When the pressure of the steam exceeds that described
its action on the greater area of the upper valve lifts the two valves from
their seats and permits steam to escape. The stem or stalk connecting the
two valves may either be made solid or hollow. When the stem or stalk is
made solid the steam escapes above the top valve and below the bottom valve.
We prefer, however, to make the stem hollow so as to permit of the steam
escaping upwards from both valves, in this case the stem has a central
passage in it open at top. In the valve stem below the bottom valve a
series of holes is made, the side holes opening into the central passage of the
stem; on the lifting of the valves the steam escaping at the lower valve
passes through the holes described to the central passage and from thence to
the atmosphere.
In this arrangement the bottom of the tube in which the valve seats are
made is closed excepting for the passage of the prolonged end of the stem
upon which the weight is placed. Instead of prolonging the stem or stalk
of the valve for carrying the weight, as already described, the lower valve
itself may be made of a hollow globular figure, in the hollow of which the
Decessary weight is put. A portion only of the circumference of this globular
valve is shaped to fit the valve seat, holes are made in the hollow valve
below its acting part through which the steam escapes to the hollow stem.
In the last described arrangement the bottom of the tube containing the
valve seats is completely closed. By constructing safety valves in the manner
described the adjustment of the weight of the valve to the pressure of the
steam can be effected with the greatest nicety, and the rapid escape of steam
permitted when the valves are lifted, also by the absence of levers and guiding
stalks the valves work with little or no friction. The improvements described
in safety valves may also be applied to steam and exhaust valves of steam
engines, to valves for proving machines and blast engines, and to valves for
various other purposes.