Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
"ANNULAR SEAL GASKET FOR A SHUT-O~'E' BALL V~IVE"
q'hi~ i.nYeIltion relates to a new type of annlll3r ga6ket ~hich
enable~ effective9 reliable an~ la6tirlg herrnetlc ~eal.ing to
be obta~Led in a shut~off ball val~re, even ~hen thls latter
i6 .~itted to large diameter pipe line~ and is thus subjected
to high pre6sure differences.
The se31 in ~ ball valve i.6 knol~m to be provided at the
present t.:i~e by mean6 of an an.nular floating member compris-ing
6uitsb'1e cavitie~ which respectively house the msin annul~r
gasket providing sealing towards the ~al~re b~ll, snd the
annular gasket provi.ding 6ealing towards the valve body~
,Said anrular floating member is urged towards said val~re bali
by a set of springs which keep said main annulsr gasket i~
contsct with the ballS so providi.ng 2 seal even ~rhen the
pressure diEference is zero9 thi6 seal becornin~ hermetic ~s
the operatin6 pressure incresses i.n that this latter gcneratcs
~ progressive additional load on the main gasket by a pi~ton
effect,
It i~ apparcnt that in order to obtain an cffective hermetic
2~ seal~ said main annular ga6ket should ideslly be very soft and
projecting considerably from its housing. In this re6pec-t~
thc softer the gasket and the more it projects, the more it is
~ble to overeome 3XLy deEects on the ball surface due to
constructional imperfectloxLs, scra'cches or incisions c~used by
2~ forei.gn matter entrsined by the operating :Elui~
On the other hand, the fundarlleIltal probl.cm arising in such
valves when subjectf~. to high p:tesa~r:e differellces is the
4~
te~denc~ of the mai~ anrlular gas~et to become extruded~ l~e.
to ~eco~e dra~ged out of its housing during the openi.ng of
such valves ~y fluid which throttlès at h^i~h speed through
said housing~
In the present state of the art1 main annul3r seal ~raskets are
used constructe~ of 3 resilient nlaterial and having a circular
cro 5S- S ectionO
}lowevcr~ such a type of gasket obviously possesses none of the
aforesaid characteristics necessary for provi.ding an effective
hermetic sealO In thi~ respect~ the fact that the ga~ket is
of circu].ar cross-section means that only a s~all proportion
of it can project from the housing if the seal i~ to be
effectively retained within said housingO Again, in order to
prevent said extru&ion9 gasket~ have to be used which instoad
of being soft are on the contrary rather rigid so thak h~rmful
contraction of the gasket cannot occur~
Finally~ a gasket of circular cross-section can rotate in its
seat during the movem~rlt of the b~ resulting in possible
~eformation of the ~asket and a consequent loss of the seal.
The object of the present inventi.on is to obviate the ~fore-
s~id dra~backs by providing a main annular sea'l gasket for a
~hut~off ball valve which does not rotate in its seat during
the nlovement of the bsll~ ~hich is not subject to extrusion
during any thrott'li.n~ of -the operating fluid ~hen the va'lve is
~5 p~rtly open even thou~h it is constructed of so~t ~sterial7
which projects from it.s sest ~ush ~s to en6ure a s~al even
~gr~lnst partly d3~.a~ e(l surfaceF. of the bal,l~ snd finally which
- 3 ~
is of simple and rapid installation.
Accordiny to the present invention there is
provided a main annular seal gasket for a shut-off ball valve
comprising an annular floating seal member which houses said
gasket in a front cavity thereof and keeps it pressed resili-
ently against -the valve ball, wherein said gasket is formed
from an elastomer which has a substantialLy triangular cross-
section with rounded vertices and a curved base, and which
is retained in said front cavity, which is also of t.riangular
cross-section, by means of a metal retention ring supported
by said annular floating member.
Preferably, the triangular cross-.section of the
gasket and the corresponding cross-section of the front cavity
of said annular floating member are s~bstantially in the form
of an isosceles triangle.
The fact of having the annular gasket in a form
other -t:han circular, which is substantially triangular and
which preferably widens rearwards,makes its escape from
its housing impossible.
The invention is descxibed in detail hereinafter
with reference to the accompanying drawings which illustrate a
preferred embodiment thereof gi.ven by way of non-limiting
example in that technical or constructional modifications
can be made thereto without leaving -the scope of the present
invention. In particular, the annular seal gasket according
to the :Lnvention can be fi-tted to a gate valve instead of to
a ball valve.
In said drawings:
.,_
~igure 1 is a partial perspective view of a shut-~o~f ball
valve using the 3nnular seal gasket accordiIlg to the inventioIl;
Figure 2 i.s a front section to an enlarged scale through that
part of Flgure 1 in which the annular ~eal gasket ~c~ording to
the invention is fitted;
~igl~e 3 is a front section through the annul~r 6eal gas~et
according to the invention~ to a further enlarged scale.
In the figures, the reference numeral 1 indicates the valve
body Df a shut-off ball valve, and ~ indicates an annular
floating seal member which i.s dis~osed between the valve body
1 and the valve ball ~9 and is resiliently urged by a circum-
ferential set of springs 4 agairlst said ball 3.
Said.an~ular floating member 2 acts as a support for an
annular gasket 5 providingr a seal tGwards the valve bod~ 1
and for a main annular gasket 6 providin6r a hermetic seal
towards the ball 3~ thiG latte.r gasket being housed in a front
cavity 7 of the flo~ting me~ber 2, ~na being retained therein
by a metal retaining ring ~ which is ~lso supported by the
floatingr mel~ber- 2.
Said main annular g~sket 6 is o~ el.astomcr con6truction, and
is formed sub~tantially by joining~ in a particular mannex,
a normal O~ring of radiu~ r (see I~igure 3) to another 0-ring
having a radius R which i6 much greater than the former, so
as ~o obtain a re~ultant cro6s~secti.0n which wi.dens rearwards.
Xn short~ f;aid anntllar gasket 6 is in practice an elasto]~r of
triaIlgular crosf;~.section wlth rotmaed vertice~ and a cuxved
baf;e 6',
3~
According to a preferled embodiment~ ~aid tri.angul3r cro~
~CC1;ion of the an~ular gasket 6 i5 in the form of an
i~osce~e~ triangle.
