Note: Descriptions are shown in the official language in which they were submitted.
g~
The invention refers to a butterfly valve embodying
a valve housing with a valve seat and a throttle arranged so
as to revolve around a shaft going through the valve housing,
between an open position and a shut-off position in which a
seal face of the throttle is pressed against the seat in the
valve housing.
The buttexfly valves in existence today are usually
built on the principle of soft gaskets. A very frequent valve
type is illustrated in e.g. the Swedish paten-t specification
199 078. With this valve type -the whole of the valve housing
is lined with a soft material, e.g. rubber or other polymer.
A frequent thing is also to manu.~acture just the valve sea-t
itself from a soft material. Examples of this valve type are
illustrated in the Swedish patent specifications 175 149 and
178 131. I'here are also cases of the soft sealing element bein~
instead placed on the sealing face of the throttle. Examples
of -this principle are shown in the Swedish patent specification
195 072 and the German patent specifications 1 011 683 and
*
1 232 42~.
A ~isadvantage of soft sealing elements in butterfly
valves is that their resistance to high~temperature media is
often low. It is true that the insensitiveness of synthetic
rubber and certain other polymers to high temperatures has
gradually improved, but still these kinds of ma-terial cannot in
any way compare favourably with the resistance to high tempera-
tures 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 qu.ite superior to those
of soft materials of rubber type. These circumstances are
of course well-known, and many a trial has been made with
replacing the soft sealing elements by metallic ones. In
* see page 7 for publication dates `
B~
these cases, however, the sealing has not been to satisfaction
or has the sealing device and/or the equlpment part~ belonging
to it become so complicated that this valve type has not got
any practical importance so far. An example of a valve
belonging to this category is shown in the Swedish patent
speci~ication 193 923.
The main object of the present invention is to provide
a butterfly valve having good sealing capacity and not implying
soft sealing element made of rubber, plastic or similar
materials. More specifically an object is to produce a valve
having good sealing capacity and which can be entirely manu-
factured of metal. An object of 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 such materials will also have to be
used, e.g. in valve seats, 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 for the medium which the valve is
intended to operate with.
Another object is to provide a valve the throttle
of which when being turned from its shut-off to its open
position and vice versa is not principally in contact with the
valve seat, which is favourable from a wear point of view~
An object of this invention is also to provide a
butterfly valve being sturdy and reliable, simple to operate
and having a long life.
These and other objects can be attained by the seal
face of the swivel throttle having two opposite, essentially
spherical sections intersected by a symmetry plane through
the throttle, which plane coincides with the swivel stem of
-- 2 --
* published January 12/ 1965
~88~3~
the throttle and two opposite, essentially conically shaped --
sections on both sides of the aforementioned symmetry plane
between the two essentially spherically shaped sections, and
by the fact that the essentially spherically and the essentially
conically shaped sections successively mer~e into each other.
Moreover, according to the lnvention, the pivot shaft
of the conically shaped faces is placed at a slight angle to a
shaft coinciding with the above-rnentioned symmetry plane and
is perpendicular to the pivot shaft of the damper. The angle
may vary according to the angle between -the pivot shaft and
-the generating line and is also determined by the dimensions
of the throttle, like its diameter and the width of the seal
face. In the normal case the angle should be between 5 and
8. At the sam~ time it is suitable that the angle between
the conical sections, i.e. the top ra~e of the cone, amounts
to between 10 and 40, at which the optimal angle is determined.
According to the invention the seat is arranged to be
flexible in its plane so that, when the essentially conically
shaped faces are being pressed against it, the seat can concur
with the shape of the curve going around -the circumference of
the seal face at the level determined by the contact points
between seal face and valve seat. According to the invention
the curve m~n-tioned befoxe essentially consists of an elliptic
curve, the major axis of which coindices with the symmetry
plane of the throttle. In the open position of the valve
the seat has furthermore a preferably circular shape. This
implies that the seat is fle~ible at the level of the sea-t so
that it can be drawn out by the conical faces in the direction
of the major axis and at the same time be compressed in the
direction of the minor axis maintaining an essentially constant
circumference. The valve seat is then suitably arranged
displaceable in an annular groove in the valve housing.
- ~ 3 --
~ccording to the best mode of carrying out the invention the
annular groove is formed by a couple of spring washers which
are for sealing reasons pressed to both sides of the valve seat
ring.
Further objects and advantages as well as character-
istics of the invention will appear from the following descrip-
tion of the best mode of carrying out the invention.
In the following description of the best mode of
carrying out the invention reference will be made to the
drawing figures.
FigO 1 illustrates the geometrical conditions at the
throttle containéd ln the valve.
Fig. 2 shows a planar view of the butterfly valve
according to the best mode of carrying out the invention.
.
Fig. 3 constitutes a section III-III of Fig. 2, and
Fig. 4 constitutes a section IV-IV of Fig. 2.
Reference is first being made to Fig. 1 that shows
a lateral view of the throt-tle according to the best mode of
carrying out the invention, the throttle in general shown as
1. The throttle 1 consists of a throttle disk 2 with an
annular seal face 4 and a bearing 3. The mean llne a going
all around the seal face 4 has an elliptic shap3. More
specifically the mean line a forms an ellipse obtained as a
taper section through an imaginary cone having the top rake ~,
with the perpendicular b to the taper section level forming
the angle ~ to the axis c of the cone.
The torsional axis i f the throttle 1, which axis i
is parallel to the level of the mean line a, is dislo-ated the
distance X from said level More specifically the distance X
is chosen so that the straight lines d and e between said
torsional axis i (at the symmetry level of the -throttle as per
Fig. 1) and the points of intersection f and ~ of the mean
-- 4 --
line form the angles 90 ~ ~ and 90 ~ ~ , resp., to the major
axis of the ellipse, to the generating line of the envelope
surface 4 which in the area of points f and q has a conical
shapeO More specifically the distance X is chosen so that the
ang e ~ lS - ~.
These geometrical conditions imply that the point
called f1 in Fig. 1 will describe an arc havin~ a radius which
is larger thall the radius o-f the arc described by a point f2
when the throttle is turned around its torsional centre i.
On the opposite side of the seal face 4, i.e. in the conical
area of point q, the conditions are contrary. Thus the arc
generated by point q, has a smaller radius than the circle
generated by point q2. These conditions may also be expressed
as if2~ if >i~ and ~ q >lq2 P
In the areas of points f and ~, i.e. in the areas of
the intersecting points between mean line a and its major
axis, the seal face 4 has a conical shape. In the areas of
the intersecting points h and i of the minor axis with the
mean line a the seal face 4 has, however, been given a spherical
shape, with the radius R of the sphere co.rresponds to the
distance from points h and 1 to the centre of the ellipse
formed by the mean line a. In the areas between the conic~l
and spherical sections of seal face 4, the conical and
spherical shapes successively merge into each other. The shapes
of the throttle 1 may be produced by copying a cast workpiece.
In Figs. 2-4 a valve housing is generally marked
with the digital 5. The valve housing 5 forms a circular
opening 6 for the medium to be led through the valve, the
opening 6 having a somewhat larger diameter than the major
axis of the ellipse created by the mean line a on the seal
face 4 of the throttle 1. The valve housing 5 is provided with
a flange 7 for the connection of an adjustin~ appliance and
-- 5 --
with a gland ~ mounted by means of stud bolts. A couple of
lugs 10 are provided with holes 11 to make fitting into a
piping easier.
A stem 12 carried in a bearing in the valve housing
5 goes through the housing and is tightened on the contxol side
by a stuffing box 13 and on the opposite side ~y a plug 14.
Furthermore, the stem 12 goes through the bearing 3 of the
throttle 1. The throttle 1 is fixed to the s-tem 12 by means
of conical rivets 15. The axis of spindl~ coincides with the
torsional axis i f the throttle.
A covering plate 16 is fixed to the valve housing
5 by means of screws 17. Be-tween covering plate 1~ and valve
housing 5 is arranged for a valve seat 18. The valve seat 18
consists of a comparatively flat ring having a rounded inner
edge. By "comparatively flat" is understood that the thickness
is considerably smaller than the radial extension. The material
of the valve'seat ring 18 is normally steel or some other alloy,
'but other comparatively stiff though to a certain extent elastic
materials are thinkable, such as certain rigid plastics type
PTFE. The valve seat ring 18 is carrLed in a bearin~ between a
couple of opposite spring washers 19 and 20 which form a groove
21 in which the valve seat is displaceable in the radial
direction. Two gaskets have been marked 22 and 23 resp.
The flat ring constituting the valve seat 18 has in
its resting position, ie.e -when -the valve is open, a quite
circular shape. When the valve is shut by turning the stem in
an anti-clockwise direction around the torsinal axis 1, Fig. 2
and Fig. 4, the conical parts of the seal face 4 in the areas
of points f and ~ will slide towards the valve seat 18. Since
the distance between -the torsional axis i and the contact
points of the conical parts continuously grow bigger as the
throttle is turned in an anti~clockwise direction (cf.
if ~ifl and 1~1 <~ ~it~2 ), the conical parts of the seal
face 4 will draw out the valve seat ring 18 in the direction
of the major axis of the mean line a. At the same time the
valve seat ring 18 yields inwards in the direction of the minor
axis so that the circumference of the valve seat will principally
reamin constant. Finally the valve seat is pressed again~t the
seal face 4 around the whole of its circumference which occurs
when the valve seat 18 concurs with the elliptical shape of
the mean line a, which implies that in this position the valve
seat 18 is also pressed against the spherical parts of the seal
face. Those latter in this position act as spherical slide
bearings towards valve seat 18, minimizing the wear and maintain-
ing the flatness of the valve seat~ The deformation of the
valve seat 18 at the level of the seat is furthermore so in-
considerable that it is well inside the area of elasticity of
the material. When the throttle is opened by turning it in a
clockwise directionl Figs. 2 and ~, from the closed position,
the valve seat will then recover its circular shape. At the~
same time the surface contact between the throttle 1 and the
seat is released by the valve seat yielding out in the direction
of the minor axis and recovers its larger, entirely circular
extension in said direction. During the main part of the
turning of the throttle from its closed to its open position,
and vice versa, the throttle thus is not in co~tact with the
valve seat 18 which is of course very advantageous from a wear
point of view.
* Publication dates (from pa~e 1)
SE 199 078 - Ot~tober 19, 1965 - S~ 195 072 - March 16, 1965
SE 175 149 - April 25, 1961 - DE 1 011 683 - July 4, 1957
SE 178 131 - February 6, 19~2 - DE 1 232 422 - January 12, 1967
~`'''' .
