IMPROVEMENTS IN SAFETY VALVES
Year: 1882

page_text: PROVISIONAL SPECIFICATION left by Charles William Collins at the Office
of the Commissioners of Patents on the 30th June 1882.
CHARLES WILLIAM COLLINS of Moss Side Manchester in the County of
Lancaster Engineer "IMPROVEMENTS IN SAFETY VALVES."
This Invention is a continuation and improvement on an Invention for which
Provisional Protection was granted to me bearing date the 30th of December
1881 No. 5729 and relates, First to Single beat valves in which the pressure is
applied by means of springs and consists in various improved modes of compensating
or counteracting the additional load upon the valve from the increased resistance
of the spring when the valve rises.
For each valve I use a lever working in or on a bearing fixed to the valve box,
the lever in one arrangement being in contact with a segment cast or fixed to a
swing rod jointed to a standard cast or fixed to the valve there being a radius rod
for regulating the movement of the swing rod, "and on the lever there is an arm
connected by a bolt to the spring which is coiled like a volute, or the mainspring
of a timepiece. When the valve is shut, the segment is at its shortest distance from
the bearing or fulcrum of the lever; but when the valve rises for the escape of
steam the radius rod moves the segment further from the fulcrum thereby enabling
the valve to act upon increased leverage and counteract the increasing power of the
spring. In other arrangements I use for each valve a spindle communicating with
the lever and valve, there being on the lever an upright either directly over the
valve spindle, or nearer the fulcrum as may be required and the top of the upright
is in communication with one end of an expanding or contracting spring. When
the valve is shut, the top of the upright is at its greatest distance from the fulcrum
of the lever, but when the valve rises, it gradually moves towards the fulcrum, and
lessens the leverage between the spring and the fulcrum and increases the
leverage between the valve and the spring, thereby counteracting the increasing
power of the spring, and one end of the spring is held in a stationary or swing frame.
In a modification of these arrangements I connect the top of the upright on the
lever to one end of a spiral or volute spring, held at its other end to an arm or
standard jointed or fixed to a bracket cast or fixed to the valve box and in this
case when the valve rises the top of the upright moves towards the fulcrum of the

page_text: lever, and so lessens the leverage between the spring and the fulcrum as to
effectually counteract the increasing power of the spring and when desired two
springs may be used instead of one, and also one spring for two or more valves.
These compensating or counteracting movements are used with ordinary
valves having no overlapping flanges, or used in combination with valves having
overlapping flanges, and for the helical springs, I prefer the cross section of the
metal to taper to the centre of the spring so that the inner surface shall be less
than the outer thereby equalizing the tension and for overlap valves without any
of the before-mentioned compensating motions I use a spring of this description
so coiled as to exert its force when pulled or expanded and also lessen the action
of the spring by causing a rod which acts upon it to be moved on one side by a
radial arm.
Another part of my Invention relates to double-beat valves of the
differential and equilibrium class each valve having two rims or sealing surfaces,
one above the other corresponding with two seatings also one above the other and
cast to the valve box the valves being made with the object of employing much
lighter weights or spring pressures than are required for the ordinary single-beat
valves. Hitherto valves of this description have invariably failed in consequence
of the inability of keeping them tight on account of unequal expansion and con-
traction of the parts, and also in not providing for dead weight valves a simple
and safe counterpoise to counteract the additional pressure of the steam on the
rims or edges of the valves when they have been lifted from their seatings.
Instead of making the valve with its two rims or edges of one piece of metal I
make it of two pieces, one piece having a plate which is rivetted or brazed to the
other piece. Or, I make each piece with a flange and rivet to them a plate of metal
the plates in both cases being thin to enable them to yield to any inequalities arising
from unequal expansion and contraction thereby keeping the rims or edges tight
upon their seatings and it is the small area between the two pieces against which
the steam acts. In another arrangement I cause the tops of the two pieces of the
valve to be fitted loosely to each other, but leave a space below for the entry of the
steam, and over the joint I place one or more thin flat rings or washers of metal,
carbonized card-board, silicated cloth, asbestos paper or any other material suitable
for sealing the parts and on these washers and the before mentioned thin plates I
place two loosely fitting rings or cylinders for carrying the frames in connection
with the springs or weights used for exerting the required pressure on the valves.
For weighting these differential double rimmed valves I use constant lever weights,
the leverage being increased to balance or counteract the increased pressure when
the valve is lifted, and the steam acting with all its force on the double rims but
after the valve has risen to a certain height and the steam lost power by expansion
the leverage is decreased the movements being regulated by a radius rod or by
arms formed on or connected to the levers and when springs are used for exerting
pressure on these differential double-rimmed valves 1 use when required
compensating or counteracting motions.