IMPROVEMENTS IN MODES OF AND APPARATUS FOR REGULATING PRESSURE IN PIPES OR OTHER CONDUITS
Year: 1875

page_text: PROVISIONAL SPECIFICATION left by Thomas Melling at the Office
of the Commissioners of Patents, with his Petition, on the 20th
November 1875.
I, THOMAS MELLING, of Grassendale Park, Aigburth, in the County
of Lancaster, Civil Engineer, do hereby declare the nature of the said
Invention for "IMPROVEMENTS IN MODES OF AND APPARATUS FOR REGULATING
PRESSURE IN PIPES OR OTHER CONDUITS," to be as follows:-
It frequently happens that waterworks have to supply water to a
district at different levels, and that, consequently, when the pressure in
the mains or pipes is right for a higher level it will by gravitation be too
great for a lower level, and thereby render the mains liable to breakage
and leakage to a dangerous extent. The same evil of excessive pressure
in the mains is also often experienced from pumping into them. Now,
my valve is designed to diminish the pressure (where required) to a
regulated head; and in order that it may do this effectually, it is of the
greatest importance that it should when closed or "shut" be perfectly.
tight, otherwise when no drawing off from the mains is taking place (as,
in the night time for instance) the water would work its way, slowly
perhaps, but surely, through the valve and all the damage occur which

page_text: it is intended to prevent. My apparatus for diminishing the pressure
at any desirable points in mains or pipes containing water or other fluids,
consists as follows:-
Istly. In a chamber, out of one side of which the exit pipe proceeds,
the said exit pipe being in free communication with the said chamber.
2ndly. The said chamber has a valve seat above and below, and in each
of these is a valve. I usually make the lower valve smaller than the
upper one.
3rdly. Both valves are usually turned or fixed on the same spindle,
which projects upward through an outer stuffing box to a lever to be
afterwards described. By lifting the spindle both valves are raised
simultaneously. The water from the delivery pipe presses upon the
upper surface of the upper valve and on the lower surface of the lower
valve; and as the area of the former is greater than that of the latter,.
the pressure of the water or other fluid on the back of it (when it is
released from the lever) closes it and keeps it closed.
4thly. Connected with the exit pipe is another cylinder, the axis of
which is parallel to the axis of the valve spindle before mentioned.
This cylinder is fitted with a water-tight piston having a rod projecting
outwards.
5thly. Both the piston rod and the valve spindle already described are
jointed to a lever weighted by a moveable weight at one end. Their
junction points with the lever are on opposite sides of the fulcrum, and
as near as may be convenient to it.
6thly. The manner of working is as follows:-Pressure being exerted
on the valves by the head of water in the main, the said valves remain
closed as long as the water in the exit pipe is at or above its normal or
required pressure, as regulated by the weight on the weighted lever.
The instant however water is drawn from the exit pipe the pressure falls
slightly and is no longer able by its pressure on the under surface of the
piston, together with the unbalanced pressure of the head of water on
the upper valve (after deducting the pressure on the lower valve) to
counteract the effect of the weight on the weighted lever. The valves
consequently open a little and continue to admit water so as to keep the
pressure in the exit pipe (acting under the piston) at the required
pressure. The moment however the water ceases to be drawn from the

page_text: exit pipe, and the pressure therein rises ever so slightly above the
normal pressure, the piston is raised and the valves being thereby released
from the upward pull of the lever, are closed by the excess of pressure
upon the upper over that under the lower valve assisted by their own
gravity, and any further rise of pressure in the main exit pipe is thereby
presented.