BALL-VALVE SEAL

ETANCHEITE D'UN ROBINET A BILLE

English Abstract

ABSTRACT OF THE DISCLOSURE
In a ball-valve having a rotatable ball and a sealing ring
contacting the surface of the ball, a radial seal includes
a backing ring to contact the rear face of the sealing ring
and a spring between the backing ring and an abutment on
the valve body, the sealing ring having a radial step
which contacts a similar radial step on the valve body
when the ball is under fluid pressure.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN
EXCLUSIVE PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A ball-valve assembly including a valve body,
said body including an annular abutment and an annular radial
step formed axially inwardly of said abutment, a backing ring
of rigid material and a spring element between the rear of
said backing ring and said abutment, a sealing ring of deformable
material, the outer peripheral surface of said sealing ring
having a radial step conforming in dimension to said annular
radial step formed on said valve body and spaced therefrom when
the hall is not displaced by fluid pressure; the ball when
displaced by fluid pressure, causing said annular radial step
on said sealing ring to contact said annular radial step on
said body thereby to improved the sealing contact with said body
and to increase the area of contact of said ring with said ball,
2. A ball-valve sealing assembly as claimed in claim
1, further characterized in that the rear face of the sealing
ring is of wedge-section and mates with n similar wedge-section
formed on the bottom front face of said backing ring.
3. A ball-valve sealing assembly as claimed in claim
2, further characterized in that both the rear face of the
sealing ring and the bottom front face of the backing ring are
provided with mating steps at their adjoining surfaces.

Description

THIS INVENTION relates to ball-valves, that is, valves
in which a rotary ball having a dia~netral hole acts to block or
open the way between inlet and outlet passages in the valve
body~
In particular~ this invention relates to the
construction o-f a peripheral seal between the ball and th~
periphery of said passagesO
Such peripheral seals have been formed with a resilient
sealing ring in contact with the surface of the ball, a rigid
backing ring behind the sealing ring and a spring element
between the rear of the backing ring and an abutment on the
valve body.
In high-pressure valves where the ball is "floating"
(i.e. is not trunnion-mounted) the ball in "off" position is
forced by fluid pressure against the downstream sealing
assembly. This may tend to extrude the sealing ring out of its
position or make it "cold-flow", particularly in large-di~meter
valves, and 90 make the seal assembly ineffective~
In Australian Patent No~ 439,927 it is proposed to form
corresponding steps in the rear face of the sealing ring and
~` the front face of the backing-ring, to hinder this extrusion of
the sealing ring under pressure.
SUMMARY OF_THE PRESENT INVENTION
; 25 It is an object of this invention to provide further
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means in the seal asse ~ ly to prevent such extrusion.
¦ The invention also enables large-valve sealing assem-
blies to be made o~ less longitudinal width, and of greater
radial thickness at the ball contact.
The invention comprises a ball-valve assembly including
a valve body, said body including an annular abutment and an
annular radial step formed axially inwardly of said a~utment, a
backing ring of rigid material and a spring element between the
rear of said backing ring and said abutment, a sealing ring of
deformable material, the outer peripheral surface of said sealing
riny having a radial step conforming in dimension to said annular
radial step formed on said valve body and s~aced therefrom when
the ball is not displaced by fluid pressure, the ball, when dis-
placed by fluid pressure, causing said annular radial step on
said sealing ring to con-tact said annular radial step on said
body thereby to improve the sealing contact with said body and
to increase the area of contact of said ring with said ball.
The present invention will be further illustrated by
way of the accompanying drawings in which:
Fig. 1 shows in section part of a ball and sealing
assembly not under pressure; and
Fig. 2 shows the same view with pressure applied to
the ball.
Referring to the drawings a valve body 10 has an outlet
passage 11, flow through which is controlled by a rotary ball 12.
A sealing assembly between ball 12 and body 10 includes
a sealing ring 13 of deformable material such as P.T.F.E.,
contacting and sealing to ball 12, a rigid backing ring 14
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behind ring 13 and a ~lat spring ring 15 between the rear face
16 of ring 14 and a radial abutment 17 on body 10.
The rear face 18 of ring 13 is of wedge-section and
mates with the ~ront face of ring 14 with a "step" 19 in both
(as is described in Australian Patent 439~927)o
The outer periphery of ring 13 has a radial step 20 and
the body 10 a corresponding step 21, As shown in FIG. 1, with
spring 15 not fully compressed steps 20~ 21 are not in contact
: but when spring 15 is flattened by moven1ent of ball 12 to the
right the steps do contact (FIGo 2) ~
The area of contact of steps 20~ 21 greatly increases
the area taking longitudinal thrust, so that thrust per unit
area is reducedO
Sealing ring 13 is held in position both by step 19
and steps 20, 21 and is prevented from being extruded. Also
the sealing of ring 13 to the body 10 is impro~ed by the
contact of steps 20, 21.
It will be seen that the provision of step 20 on ring
13 also pro~ides greater radial thickness of ring 13 at the
end contacting ball 12. The area of ball contact therefore is
increased, with less likelihood of cold flow or extrusion of
. the ring 13 in this region.
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`~,. While the invention has been described in relation to
the 'Iwedge-seal" type of assembly of Australian Patent
No. 439,927 it can be applied to other assemblies of sealing
ring, backing ring and spring.
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