IMPROVEMENTS IN APPARATUS FOR REGULATING THE ACTION OF SAFETY VALVES
Year: 1872

page_text: PROVISIONAL SPECIFICATION left by Henry William Wilcke at the
Office of the Commissioners of Patents, with his Petition, on the
30th October 1872.
I, HENRY WILLIAM WILCKE, of Crown Villas, Greengate Street,
Plaistow, in the County of Essex, do hereby declare the nature of
the said Invention for "IMPROVEMENTS IN APPARATUS FOR REGULATING THE
ACTION OF SAFETY VALVES," to be as follows:-
-
This Invention relates to the construction and working of apparatus
whereby the action of a safety valve is rendered more effective by
'causing it to open freely when the pressure in the boiler is in excess,
and to close readily when the pressure has been sufficiently relieved, and
whereby the load which determines the pressure can be easily adjusted,
and the danger arising from the sticking of the safety valve or neglect-
ing to work the lifting gear is to a great extent avoided. For this
purpose I provide a piston which works in a cylinder communicating
with the boiler and which is connected to the stem of the safety valve.
This piston is loaded by a weight or spring which can readily be adjusted
to suit the desired working pressure in the boiler. When the pressure in

page_text: the boiler is in excess, the piston is forced along the cylinder, and the
safety valve is thereby opened and kept open until the pressure in
the boiler becomes so far reduced that the piston is forced back, whereby
the safety valve is permitted to close. It will be seen that by this
arrangement the load on the safefy valve itself may be in excess of that
due to the maximum working pressure; the load on the piston or
its leverage being adjusted so that the safety valve is opened by it
whenever the working pressure is exceeded.
The cylinder in which the piston works may be in direct communica-
tion with either the steam or the water in the boiler, and it may be so
placed, and its load or leverage so arranged as to be readily accessible to
the engineer or to an official; also instead of locking the load on the safety
valve itself, or providing a separate locked valve, the load on the piston
may be locked and the working pressure may be thus controlled.
Instead of placing the cylinder in direct communication with the
boiler it is preferred to make the cylinder communicate with the boiler
by a passage having an opening to the atmosphere. In this passage is
fitted a double faced valve so that it can close either the opening to the
boiler or the opening to the atmosphere, this valve is loaded with a
weight or spring adjusted to the desired working pressure. When the
pressure in the boiler is under the working pressure the valve closes the
opening to the boiler but leaves open that to the atmosphere, the piston
being in that case relieved entirely from the boiler pressure takes such
a position as to allow the safety valve to be closed; but when the
pressure in the boiler exceeds the working pressure the valve in the
passage opens a way from the boiler to the cylinder, and closes the
opening to the atmosphere. The piston being then subjected to the boiler
pressure is forced along the cylinder and causes the safety valve to open.
As soon as the boiler pressure is reduced to the working pressure, the
valve in the passage again cuts off communication between the boiler
and the cylinder, and opens the commmunication from the cylinder to
the atmosphere, whereupon the piston makes its return stroke and
permits the safety valve to close. By this means the safety valve is
rendered very sensitive, opening fully when the pressure becomes too
great, and closing quickly when the pressure is reduced. Also as the
valve in the passage may be of small dimensions, while the safety valve
itself or the piston is large, the working pressure is thus made to depend
upon the adjustment of the comparatively small load on the valve in th

page_text: passage, which is more easily dealt with than the great weight or
powerful spring required for the supply valve or piston; and moreover as
the force of the piston is applied to open the safety valve besides the
pressure on the valve itself the danger arising from the sticking of the
valve to its seat or from neglecting to work, the lifting gear is to a great
extent avoided by the use of the apparatus described above, which thus
forms an additional precaution against danger of explosion.
The said apparatus is applicable with particular advantage to those
safety valves of marine and other boilers that are acted on by a powerful
spring, as the pressure of such spring increases considerably on the
opening of the valve and thus prevents it from opening freely.