Note: Descriptions are shown in the official language in which they were submitted.
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The present invention rela-tes to a valve seat in a
valve housing. More particularly does.the i~vention relate in
the first place to a.valve seat intended for.butterfly.valves.
The butterfly.valves in existence-today are usually
built on the princlple of soft gaskets. 'A.'very frequent.valve
type is illustrated in e.g. the Swedish patent specification
199,078. With this,valve type the whole oE.the.valve housing
i5 lined with a soft material, e.g. rubber or other polymer.
A frequent thing is also.to manufacture just the.valve seat
ltself from a soft material. Examples of this.valve,.type.are
. illustrated in the Swedish patents 1,75,149 of April 25, 1961,:
- '. and 178,131 of February 6, 1962. There are also cases of the '-
soft sealing element being instead placed on the sealing face~.
of the throttle. Examples of this principle are.shown in thç
Swedish patent 195,072 of ~arch 16, 1965 and'the German patents
1,011,683 o.f July 4~ 1957 and 1,232,422 of Januar.y 12,,1967.;~
A disadvantage of soft sealing elements in,butterfly~valves.is
that their resistance to hlgh-temperature'media is often low.
It is true that the insensitiveness of-synthetic rubber..and-
certain other polymers~to hlgh~temperatures has gradually impro,ved,
,but still these klnds of~material cannot:~in any way,compare',,
favourably with the resistance to hLgh templeratures of`,steels.':
and other metals and alloys~ The same thing also applies~to the-
resistance to certain chemically aggressive media. In these' -:
cases,,too, the properties of high-alloyed stainless~steels and
other alloys are quite ..... ~A_... .__._.. _ '''.~. -,''' '-'~
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superior to those of soft-materials of rubber type. These
circumstances are, of course, well known, and man~ a trial has
been made wi-th replacing the soft sealing elements by metallic
ones. An example of this type of valve is disclosed in U.S.
patent specification 4,058,290. A drawbac~ oE this valve,
however is the wear between the throttle and the seat which has
the form of a resilient ring, and also between the seat ring
and the housing of the seat ring as the seat ring is displaced
relative to the housing each time the throttle is opened or shut.
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DISCLOSURE_OF INVENTION
A first object of the present invention is to provid-e
a valve seat having a good sealing capacity and not employing
soft sealing elements made of rubber, plastics or similar
materials. More specifically an object is to produce a valve
seat having good sealing capacity and which can be entirely
manufactured of metal. An object oE the present invention is,
however, that the principles of the invention shall not exclude
the use of such soft materials as e.g~ PTFE and nylon. There is
rather an object that also such materials may be used for the
manufacturing of the valve seat, if for some reason or other
these are more suitable or otherwise more desirable than
metallic materials. In other words, a purpose of the present
invention is to create liberty of choice between different
materials in regard to their convenience to the medium which
the valve is intended to operate with. Further, there is an
important object of the invention to provide a valve seat which
can be used for throttles of different shapes, e.g. throttles
having cylindrical, spherical or conical seal faces, or combina-
tions of these or other shapes. An object of this invention is
also to provide a butterfly valve being sturdy and reliable,
simple to operate and having a long life because of i.a. a
minimum of wear between the sealing members.
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In accordance witil the broad concept of the invention,
there is provided and claimed herein an improvement in a
throttle valve comprising a valve housing having an annular
recess therein, a throttle member,pivotally movable in the
valve housing and having an annular seal face, and a valve seat
in said annular recess and engageable b~ said throttle member
seal face, the i~provement comprising said valve seat including
resilient means located in said annular recess and defining an
annular groove, and a radially movable seat ring located in said
annular groove, said seat ring being made of a stiff material
but with sufficient radial direction resiliency such that when
subject to a radial load from contact with the throttle member
seal face, said seat ring may be displaced in the radial
dire~ction, said resilient means and said seat ring cooperating
so that when sai~ seat ring maves in a radial direction under
said radial load said resilient means sealingly engages said
seat ring and when said radial load is removed from said seat
ring said resilient means maintains said seat ring substantially
in the displaced shape and position,-so that wear between said
seat ring and said seal face is minimized, in that when said
seat ring is circular and said seal face is circular, the seat
ring is displaceable into alignment with said seal face and is
maintained in the aligned position when said radial load is
removed therefrom, and when said seat ring is circular and said
seal face is elliptical, said seat ring is de~ormed into an
elliptical shape and is maintained in said elliptical shape when
said load is removed therefrom.
Further objects and advantages as well as
characteristics of the invention will appear from the following
description of the best mode of carrying out the invention.
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BRIEF DES~RIPTION OF DRAWINGS_
In the following description of the best mode of
carrying out the invention reference will be made to the
drawings.
Fig. 1 is a section through a valve housing provided
with a valve seat according to the preferred embodiment of the
invention. The figure also shows a throttle which is in sealing
contact with the valve seat.
Fig. 2 shows the valve seat more in detail and how
the valve seat can cooperate with the throttle shown in Fig. 1.
BEST MODE OF CARRYING OUT THE INVENTION
Reference is first being made to Fig. 1 that shows
a throttle generally shown as 1. The throttle can be turned
clockwise from the sealing position according to Fig. 1 to an
open position and vice versa by means of a stem 2 carried in
a bearing 3 on tho throttle.
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A seal face on the throttle 1 is shown as 4. The seal face 4 is annular
and its mean line 5 has an elliptic shape with the major axis coinciding
with a vertical plane to Fig. 1. As an alternative the mean line 5 has
a circular shape. The throttle 1 is eccentrically mounted in bearings
in a valve house, a.i. the centre axis oE the stem 2 doesnot intersect
the axis oE symmetry through a valve opening in the valve house 6.
The valve house 6 consists of a main portion 7 and a covering plate 8
which is fixed to the main portion by means of screws which are not
shown in the drawing. On the side which is turned to the coYering plate
8 the main portion 7 of the valve house is provided with an annular
recess 9. In the recess 9 there are provided two spring washers 10 and
11 which constitute carriers and bearing for a valve seat in the form
of a seat ring 12. A pair of gaskets has been designated 13 and 14,
respectively.
Fig. 2 shows more in detail how the valve seat ring 12 and the carriers
and bearings 10 and 11 of the seat ring are designed. The latter members,
as above mentioned, consist of a pair of spring washers, usually of -
sta~nless steel. The two washers 10 eeh ll are reversedly designed.
In a radial section they comprise a rib portion 15a ~ 15b, respectively,
and a leg portion 16a and 17a as well as 16b and 17b respectively, in
the outer and the inner end of the rib portion, respectively. The legs of
each washer form right angles to the rib portion and are turned in the
same direction. Further the inner legs 17a and 17b are shorter than the
outer legs 16a and 16b, respectively. The annular groove between the
washers 10 and 11 is shown as 18.
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The valve seat, i.e. the ring 12, is comparatively flat and is provided
with two parallel flat side surfaces 19 and~20 and has a rounded seat
face 21. According to the embodiment the seat ring 12 consists of steel.
Its extension in the radial direction is about four times~ as large as
its thickness.
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Further the spring washers 10 and 11 are worked such that they in the
unloaded condition are slightly conic. More particularly the conicity
implies that the legs 17a and 17b tend to approach each other. I~hen
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mounting the assembly the seat ring 12 is arranged between the legs
17a and 17b whereupon the assembly consisting of the spring washers
10 and 11 and the intermediate seat ring 12 are brought together by
means of the covering plate 8. ~lerein the legs 17a and 17b~are forced
out to a maximum which is cleterminecl on one hand by a space 22 between
the main part of the valve house and the spring washer LU, and on the
other hand a space bet~een the covering plate 8 and the second spring
washer 11. The forces deveLoped by the spring washers 10, 11 are
dimensioned such that they are not greater than the seat ring 12 may
move in its plane in the groove 18 when subjected to a radial load from
the throttle 1 when the throttle is being shut, while the flat, parallel
end faces 24a and 24b of the legs 17a and 17b, respectively, sealingly
engage the side faces 19 and 20 of the seat rings. However, at the same
time the spring forces of the washers 10 and 11 are dimensioned such that
they are sufficiently great to maintain the seat ring 12 in its possibly
new position and with its possibly changed shape when the ring is released
from the radial load when the throttle is opened again. Therefore, through
the spring action by the washers 10 and lI there is obtained a tight
joining without jamming the seat ring 12 harder than the seat ring being
able to adapt its form and position after the shape and position of the
~throttle and thereafter maintaining its form and position when the valve
is re-opened. Next time the throttle is shut the seat ring therefore
. normally will not be changed neither as ~3~ as its position or its form
is concerned. This offers the advantage that the seat ring normally does
not move when the valve is being shut or opened which means that wear
-can be avoided.
In the starting position the seat ring has a completely circular shape~
which has been indicated by dashed lines in Fig. 2 illustrating the case
when the mean line~5 of the throttle has an elliptic~al shape. When the
valve is being shut the sealing face 4~on the throttle l~ however, will
force the seat ring 12 to be more-and more oval but with constant
circumference. Finally when the throttle is completely shut the seat
ring will concur with the elliptical shape of the mean ring 5. During
these shape changes of the seat ring, the seat ring hence will be dis-
placed in the groove 18 with maintained sealing action between the seatring 12 and the flat end faces of the spring washers 17a and 17b, and 24a
and 24b respectively. When the throttle is re-opened and the seat ring is
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released ~rom the radial loacl from the throttle, the elliptical shape
o~ Lhe seat ring will be mclirltailled by means of the spring washers 10,
Il whictl press ag.li[lst the ;;de [aces L9, 20 with forces which are
sufficienL to prevent ring L2 Erom re-aclopting its circular~ resting
position. In the case whell ~he mean Line 5 in~stead is circuIar, the
shape of the seat r;ng will not change during the "prime~ry" shutting
action, but its position in the groove 18 can be changed, which position
thereafter normally is maintained by means of the spring washers during
subsequent shuttillg and opening actions.
The spring washers 10, 11 also have another function. They may namely
absorb thermal expansions, variations of pressures and the like with-
out impairing the sealing action. To the contrary the sealing action
may be improved when a pressure of the fluid in the conduit is exerted
upon each or both of the spring washers in the space 22 and/or 23, which
pressure is transferred via the inner portions 17a and/or 17b of the
spring washers.
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