Improvements in Relief or Back Pressure Valves.
Year: 1899

page_text: Date of Application, 20th June, 1899-Accepted, 29th July, 1899
COMPLETE SPECIFICATION.
Improvements in Relief or Back Pressure Valves.
I, WILLIAM PHILLIPS THOMPSON, F.C.S., M.I.M.E., of the Agency for Foreign
Patent Solicitors, 6, Lord Street, Liverpool, and 6, Bank Street, Manchester,
both in the County of Lancaster, 118, New Street, Birmingham, in the County
of Warwick, and 322, High Holborn, in the County of Middlesex, Civil Engineer,
do hereby declare the nature of this invention (which has been communicated
to me by The Foster Engineering Company, of 21 and 23, Prospect Street, Newark,
in the State of New Jersey, United States of America) and in what manner
the same is to be performed, to be particularly described and ascertained in and
by the following statement:-
This invention relates to relief or back pressure valves used for maintaining
any desired pressure in a receptacle or system of pipes and dealing with any
excess of pressure which may at any time arise within the receptacle or system.
In most valves of this class it has heretofore been the practice to employ some
arrangement of weighted levers to resist the fluid pressure to which the valve is
adjusted, and as such weighted valves are liable to operate in an irregular
manner, iz; with a chattering, jumping or hammering movement, the weight
has been sometimes replaced by a spring to overcome the said hammering or
jumping. But in the ordinary application of such spring to a clapper valve there
is incurred the disadvantage of requiring a greater volume of fluid pressure to
hold the valve open sufficiently to pass a large volume than when open to pass
a small volume, thus making a material difference in the pressure with variable
volume of delivery. To overcome this disadvantage of the spring as ordinarily
applied I have provided what may be termed a compensating arrangement of
valve-controlling devices whereby the resisting power of the spring as applied
to a clapper valve is made practically constant, with a result that a constantly
uniform pressure can be maintained in the lower part of the valve casing, because
the valve will freely rise any distance sufficient to allow the escape of any pressure
in excess of that desired.
My invention consists in features of construction and novel combinations of
parts in a relief or safety valve, or back pressure valve, as hereinafter described
and claimed.
In the annexed drawings which illustrate the invention Fig. 1 is a vertical
section of my improved relief valve and Fig. 2 a horizontal section of the same.
The valve comprises a lower circular casing, 1, and an upper circular casing 2,
each made from some hard metal of moderate cost, such for instance as cast iron:
Between the adjacent edges of these casings there is clamped an annular web 3,
which is preferably made of brass, bronze composition or other soft non-corrosive
material. A dash pot 4 is supported in a vertically depending position in the
lower valve casing 1 by means of radial arms 5, connecting with the web 3.
The boundary of the latter rests in a slight annular recess in the inner rim of
the lower casing and is tightly clapped and held in position between the said
lower casing and the upper casing by means of bolts 6 inserted through
annular flanges 7 on said casings. This construction serves the double purpose

page_text: of holding the web 3 and central dash pot 4 in proper position, and forming a
tight joint between the lower and upper casings of the valve so as to prevent
escape of steam or other fluid pressure at the joints of the said clamped together
web and casings.
The valve proper consists of an inverted dish-shaped clapper 8, having a
central depending hollow stem 9, which is open at the top and closed at its
lower end, except for a vertical passage 10 at one side. This hollow valve stem 9
is fitted to slide freely in the vertically arranged dash pot 4, and is provided with
circumferential packing 11 at each end. On the under side of the clapper 8
there is a strengthening ring 12 and a number of radially arranged ribs 13 that
further strengthen the device. The peripheral portion of the clapper 8 is
turned downward and normally rests upon an annular valve seat 14 that is
provided on the annular web 3. The length of the hollow valve stem 9 is such
that it does not reach the bottom of the dash pot and so, when the valve is
seated, there is left below the stem 9 a shallow space 15 which will ordinarily
be filled, through the small passage 10, with water of condensation from the
hollow valve stem 9, it being understood that this valve is to be arranged and
operated in a vertical position.
The valve S is normally held down on its seat 14, as against fluid pressure on
its under surface, by means of a vertically arranged stud or post 16 having its
enlarged rounded lower end resting centrally in the bottom of the hollow valve
stem 9 and its upper rounded end in contact with the concaved or inverted cup
shaped end of a yoke-shaped lever 17, the outer end of which is fulcrummed on
a pivot pin or rod 18 that is supported longitudinally at one side of the upper
valve casing. This yoke or lever 17 is forced downward at all times by a
diagonally arranged spring 19 having at one end a widened scale bearing
washer 20 resting in a pocket or bearing 21 on the yoke or lever. The outer
or upper end of the spring 19 is provided with a washer 22, having a central
hole or recess into which fits the end of an adjusting screw 23, that is threaded
into and projects from the upper casing of the valve. By means of this adjusting
screw 23 there can be given to the spring 19 the required compression to resist,
through the yoke 17 and post 16, any predetermined pressure against the valve
or clapper.
In order to hold 'the valve 8 open or lifted, when no back pressure is required,
it is preferable to connect the lever or yoke 17 with the valve 8, through a
yoke piece 24 that is bolted to the valve in a horizontal position above the same.
The bifurcation of the yoke 24 is arranged toward the end of the lever 17 and
the ends of said yoke, 24 are extended downward to form lugs 25 that rest on
the top of the valve 8, and through which the vertical attaching bolts 26 are
passed. The end of the yoke lever 17 is provided on opposite sides with trun-
nions 27, that are engaged under the ends of the yoke-piece 24 so as to have a
lifting action thereon when the valve 8 is to be held open regardless of the
pressure or absence of pressure at its under side. For the purpose of acting on
the lever 17 so as to cause it to lift the valve 8 and hold it at any required
elevation, the pivotted end of said lever is provided with a downward extension 28
arranged to afford a bearing for the end of an adjusting screw 29 that is
threaded through an adjacent portion of the valve casing. By causing the inner
end of this screw 29 to bear forcibly against the lever extension 28 and adjusting
the screw inward a sufficient distance, the lever 17 may be made to lift the valve S
and hold it at any elevation desired; when no back pressure is to be regulated
or controlled. The inward adjustment of the screw 29 to a sufficient distance,
not only overcomes the compression of the valve-closing spring 19, but lifts the
valve from its seat, holds it open and thus permits the passage of any pressure
that might be insufficient to raise the valve against the action of the spring.
The valve is secured to a suitable receiver, or to a system of piping, by means
of bolts passed through the flange 30 on the lower end of the lower casing 1, so
that the steam or other fluid pressure will enter at the inlet port 31, and fill

page_text: the space below the valve 8, remaining confined there until a sufficient pressure
is accumulated to overcome the resistance or compression to which the spring 19
has been adjusted and which is acting through the lever 17 to hold the valve
normally closed. Any excess of pressure, above a predetermined amount, will
lift the valve 8, against the resistance of the lever 17 and spring 19, and will
then pass freely to the atmosphere through the exit port 32 of the upper casing 2
around which port there is an annular flange 33, to which a suitable escape pipe
may be bolted.
It will be observed that the lever 17 and spring 19 are so arranged that when
the valve or clapper 8 is closed down onto its seat 14, as represented by full
lines in Fig. 1, the leverage of the compression spring 19 on the lever 17 is about
equal to the distance from a to a; and when the valve is in its highest position,
or open to the fullest extent required, as indicated by the contour line b, the
spring 19 will have been compressed an amount equal to distance cc, which will
'have considerably increased its stored power, but in the meantime its leverage
has been decreased from distance a to distance d d and, thus, its actual resistance
through lever 17 and post 16 to valve 8 will have been maintained practically
constant, the relative arrangement of the lever 17 intermediate the valve and
its spring being stich as to compensate for varying degrees of compression in the
spring through varying positions of the opening and closing valve. Thus, by
means of the compensating lever 17, the resisting power of the spring 19 as
indirectly applied to the valve 8 is equalized or made practically constant, with
the result that no greater fluid pressure is required to hold the valve open
sufficiently to pass a large volume than when open to pass a small volume, and
as the valve will freely rise any height required to permit escape of any pressure
in excess of that desired, there is easily maintained a constantly uniform pressure
in the lower valve casing.
The valve operates readily, without hammering, jumping. or any irregular
movement and by means of the communication afforded by the passage 10
between the dash pot 4 and hollow valve stem 9 the water of condensation collected
in these parts, or any suitable fluid therein, will cushion the valve against shock
or jar in closing down onto its seat.
If it is desired to hold the valve S, open, for any purpose or when no back
pressure is to be maintained, the screw 29 affords a convenient means for causing
the lever 17 to exert the required lifting power.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
1. claim is
First. A relief or back pressure valve characterised by lower and upper casings,
an annular web'forming a valve seating clamped between said casings fluid-tight,
a centrally supported vertically depending dash-pot connected with said annular
web, a vertically movable valve having a depending stem arranged to fit and
slide in said dash pot, a spring, and a compensating lever intermediate of said
spring and valve.
Second. A relief or back pressure valve comprising lower and upper casings,
an annular web forming a valve seating clamped between said casings fluid-tight,
a central vertically depending dash-pot supported by said annular web, and a
vertically movable valve having a depending hollow stem arranged to fit and
slide in said dash pot for the purpose of guiding the valve onto its seat, the
said stem being open at the top and having its enclosed lower end provided with
a passage communicating with the dash pot, for the purpose substantially as
described.
Third. A relief or back pressure valve comprising lower and upper casings, an
interposed annular web forming a valve seating and provided with a central
vertically depending dash pot, a vertically movable valve having a central depend-
ing hollow stem open at the top and fitted to slide freely in said dash-pot, a

page_text: lever fulcrummed within the valve casing above the valve, a post interposed
between the said lever and the bottom of the hollow valve stem, and a spring
arranged to bear downward on said lever and post to resist pressure against the
underside of the valve, substantially as described.
Fourth. A relief or back pressure valve comprising a lower casing and an
upper casing, an annular web interposed between said casings to form a valve
seating and a carrier for a central vertically depending dash pot connected to
it, a vertically movable valve having a central depending hollow stem open at
the top and fitted to slide freely in said dash pot, a lever fulcrummed at one
end within the valve casing, a post interposed between the other end of the said
lever and the bottom of the hollow valve stem, a spring having one end bearing
against said lever, and an adjusting screw bearing against the other end of said
spring to give different degrees of compression to the spring for resisting any
predetermined pressure on the under side of the valve, substantially as described.
Fifth. A relief or back pressure valve comprising a lower casing, an upper
casing, an annular web forming a valve seating clamped between said casings
and provided with radial arms and a central vertically depending dash pot
supported by said arms, a vertically movable valve having a central depending
stem fitted to slide freely in said dash pot, a yoke-shaped lever fulcrummed at
one end within the valve casing and having its other end extended above the
valve, a diagonally arranged spring having one end bearing against said lever,
and an adjusting screw bearing against the other end of said spring, the relative
arrangement of said lever and spring being such as to compensate for varying
degrees of compression in the spring through the opening and closing movements
of the valve, substantially as described and set forth.
Sixth. A relief or back pressure valve comprising a lower casing, an upper
casing, an annular web, forming a valve seating, provided with radial arms
and a central vertically depending dash pot, a vertically moving valve having a
central stem fitted to slide freely in said dash pot, a yoke-shaped lever fulcrummed
within the valve casing and having one end connected with the valve and its
other end provided with a downward extension, an adjusting screw inserted through
the valve casing and capable of adjustment to bear against said lever extension
for causing the lever to lift the valve and hold it open, a diagonally arranged
spring having one end resting against said lever, and an adjusting screw having
a bearing against the other end of said spring, substantially as described and
set forth.
Dated this 19th day of June 1899.
W. P. THOMPSON & Co.,
11, Burlington Chambers, New Street, Birmingham,
Also of Liverpool, London and Manchester,
Patent Agents for the Applicants.