Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~07609Z
The invention relates to butterfly valves of the
usual kind comprising a body surrounding a substantially
cylindrical tubular passageway and containing a closure
flap which swings between an open position within the
passageway and a closed position in which the periphery
of the flap seals against the surrounding body.
secure seal between the periphery of the closure
flap and the surrounding body is sometimes provided by
forming the periphery of the closure flap of resilient
material, or lining the inner surface of the body with a
resilient lining, or by mounting in the body a resilient
seal which projects radially inwardly into the passageway.
The use of an inwardly proJecting seal has the advantages
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~ that it can be shaped to make a good seal against the closure
- 15 flap but the disadvantage that the projecting seal inter-
feres with the smooth flow through the passageway when the
valve is open. It has been proposed to overcome this latter
disadvantage by providing a separate lining substantially
flush with the radially inner part of the seal and butting
against the projecting seal but this involves the use of
- additional parts and can interfere with the seal function.
` In accordance with the present invention, a butterfly
valve has a body surrounding a substantially cylindrical
passageway and a closure flap which swivels within the
passageway, the body being provided with an annular resilient
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sealing portion against which the periphery of the flap
engages in the closed position, the sealing portion
sprouting from the base of an annular recess in the inner
surface of the body and projecting radially inwardly to a
position substantially flush with the surface defining
the passageway, and being provided on each side with an
axially projecting undercut lip which is spaced from the
adjacent side of the recess.
With this construction the sealing portion does not
project significantly into the passageway, although in
practice the annular tips o~ the lips may project slightly
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into the passageway. However, when the closure flap is
in a closed position, a good seal is made against the flap
as the fluid pressure on the high pressure side of the flap
acts under the lip and urges it towards the closure flap.
- ~ - The radially innermost surface of the sealing portion
between the axial extremities of the sealing lips may be
slightly recessed so that the lips project radially inwardly
as well as axially.
Although the sealing portion may be made of one material,
such as rubber, mounted in a recess in a body lining made of
material such as cast iron, the sealing portion is
preferably formed integrally with a lining which lines the
body internally and defines the fluid passageway. At each
axial end the lining may have a radially outwardly projecting
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integral flange which is wrapped around the body to locate
the lining in position.
me sealing portion, or integral lining and sealing
portion, may be made of a material such as rubber, or a
resilient synthetic plastics material such as nitrile rubber,
PTFE, or PCTFE. PCTFE is preferred to PTFE for cryogenic
applications as it retains its flexibility bet-ter at subambient
temperatures.
One example of a butterfly valve constructed in
accordance with the present invention is illustrated in the
accompanying drawings, in which:-
Figure 1 is a side elevation as seen from the left
in Figure 2;
`~. Figure 2 is an end elevation with parts in section;
Figure 3 is a section taken on the line III-III in
Figure 2 with the valve closed; and,
Figure 4 is a section corresponding to part of Figure 3
with the valve open.
The illustrated valve has an annular cylindrical metal
body 4 provided on one side with a radially outwardly projecting
~; spindle housing 5. Two webs 6 provided with bolt holes 7 extend
between an annular flange 8 at the outer end of the housing 5 and
the main part of the body 4.
The body 4 is lined with an annular cylindrica] replaceable
lining 9 made of nitrile rubber and provided at its axial ends
with integral radially outwardly extending flanges 10 which are
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wrapped around the ends of the body 4 and seat in re~esses
11 in the body end walls. Midway along its length the lining
9 is formed with an annular recess 12 from the base of which
there sprouts an integral annular sealing portion 13 with
two oppositely axially projecting undercut sealing lips 14.
As shown in Figure 4, the radially inwardly facing surfaces
of the lips 14 are inclined in a shallow V shape towards one
another and are separated by a groove 15.
The valve has a circular closure flap 16 which is
, 10 fixed by two screws 17 on a spindle 18 which is rotatably
; - mounted in PFTE coated brass bearings 19 in the spindle housing
5 and in the diametrically opposite portion 20 of the body 4.
m e lining 9 closely surrounds the spindle where it passes
1- through the lining to seal the spindle to the body. The spindle
18 is fixed ~o an operating handle 21, although it may be rotated
mechanically in other applications, such that rotation of the
handle 21 through 90 rotates the spindle 18 and the closure
- flap 16 between the fully closed position shown in Figure 3 and
a fully open position. me position of the closure flap at any
~ime is indicated by a pointer 22 which is fixed to the handle
21 and is aligned with a mark C on a plate 2~ fixed to the flange
8 in the fully closed position, and with a mark 0 in the fully
open position. me handle may be located in one of a number of
selected positions by a wing head screw 24 which screws through
a portion 25 of the handle 21 and engages in a selected one of
' a number of recesses in a rack portion 26 on the flange 8.
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In use the flap is used as a wafer valve and the
body 4 is sandwiched between adjacent conduit modules which
are drawn up together by a ring of bolts which extend radially
outwardly of the body 4 between the adjacen-t modules, two of
the bolts passing through the holes 7 in the webs 6. A seal
is made between each end of the valve and the adjacent conduit
module.by compression of the respective flange 10 of the
. lining 9. During this compression some of the resilient material
from which the lining is made will be forced into a pair of
~ 10 machined grooves 27 in the bottom of the respective recess 11
to assist in keying the lining in position. The inner cylindrical
peripheral surface of the lining 9 will be aligned with the
~ fluid passageway through the adjacent conduit modules.
: Since the valve is symmetrical, it can be used equally
~ 15 efficiently irrespective of the direction of flow through the
;~ valve. When the valve is closed as shown in Figure 3, the
ed~e of the flap 16 seals against both the lips 14 of the
sealing portion 13, the sealing engagement being enhanced by
the fluid pressure on the high pressure side acting on the under-
cut of a respective one of the lips 14 thereby urging the lip
more firmly into engagement with the periphery of the flap 16.
When the. valve is opened, the sealing portion 1~ adopts the
configuration shown in Figure 4 in which the extreme tips of the lips 14 are substantially in alignment with the inner
cylindrical peripheral surface of the lining 9 so as not to
- provide any significant obstruction to fluid flow through the
valve.
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