CA1120907A - Disc valve - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A circular seal ring for co-operation with a conically shaped seating surface of a disc valve that is concentric with respect to a valve axis. The seal ring comprises, in cross-section, a base having a width in a radial direction and a thickness in an axial direction. A
slanted web protrudes in a generally radial direction from the base having substantially parallel, generally axially oriented faces. A slanted web center line intersects a radially oriented surface of the base at a first point. The web has a thickness substantially less than the thickness of the base to render it relatively flexible. A sealing member protrudes in a generally radial direction from an end of the web remote from the base. The sealing member terminates in a convex, arcuately shaped sealing surface extending in a generally axial direction and has a center of curvature which lies on the slanted web center line. The distance from the sealing surface to the first point is less than from the sealing surface to the center of curvature. The base, the web and the sealing member are constructed of a resilient material. The ring permits a disc valve that is easy and relatively cheap to make yet effective at widely varying pressures.

Description

The present invention relates to a sealing ring for a disc or butterfly type valve in which a disc is pivotally disposed within a conduit of the valve defined by a generally cylindrlcal housing for pivotal movement of -the disc between an open position, in which it is generally parallel to an axis of the valve, and a closed position in which the disc is generally perpendicular to the valve axis.
The present application is divided from our Canadian patent application 320,974, filed ~ebruary 6th, 1979, the parent application.
Disc valves as such are presently in wide use. The specific construction of such valves differs widely. One advantageous construction is disclosed and claimed in U.S.
Patent No. 3,442,488, issued May 6, 1969 to Adams. The valve disclosed in -that patent includes a disc fitted with a peripheral seal ring and rotatable about an eccentric axis for moving the seal ring into and away from sealing en-gagement with an internal sealing surface of an annular valve seat defined by the housing of the valve. The sealing surface is a conical surface whose axis forms an acute angle with the axis of the valve housing. An improvement to such a valve and in particular to the construction, alignment and operation of the sealing ring carried by its disc is disclosed to U.S. Patent No. 4,003,394, issued January 18, 1~77 to Adams.
The valves disclosed in the above-referenced U.S.
patents have yielded excellent operating results, that is they assure air right seals under the most adverse operating conditions such as high fluid pressures and/or temperatures, ~lZ~ 7 high flow rates, the handling of chemically or mechanically abrasive fluids, etc., and they have enjoyed a corresponding commercial success. It is believed that the technological efficiency of such valves ls at least in part the result of the particular sealing arrangement employed by them especially the provision of an angularly offset (with respect to the valve axis) but otherwise conical seating surface in the valve housing and a correspondingly arranged seal ring in the disc which assured that the latter is wedged in~o sealing engagement with the former when the disc is titled into its closed positlon. The wear of the seating surface and/or of the seal ring from predominantly sliding engage-ment is thereby reduced or eliminated.
This advantageous operating characteristic of the val~e, however, complicated its manufacture and required, ~` for example, special jigs, tools, and machinery to accurately machine the angularly offset, conically shaped seating surface in the housing. This is particularly true for valves of relatively large diameter, say in the order of 24 inches or more where the cost of such jigs, tools, etc, can be a significant factor in the overall cost of the finished valve. Similar care had to be exercised in manufacturing the disc and the seal ring mounted therein. Thus such valves are not always as economical to manufacture as may be desired.
On the other hand, attempts to build disc valves with conical seal rings and seats that are coaxial with the valve axis have met only limited success. Although such constructions can sometimes be effective for low pressure, particularly in instances in which a perfect seal is not --2~

required/ they have generally been ineffective for establi-shing air tight seals under adverse operating conditions since even the slightest degree of eccentricity can cause the loss of the seal. Further, such arrangements are effectively limited to disc valves in which the disc acts as a flap e.g., in which the disc is pivoted about a pivot axis that is located outside the seal ring diameter. Since such arrangements require a high operating torque for opening the disc against fluid pressure, they are only feasible for low pressure applications.
The present application describes and claims a disc valve of the type described above, that is one which comprises a valve housing including a conduit through the valve and an eccentrically mounted, pivotal disc that is movable between an open and a closed position. Mounted to the housing is a seal ring which defines a sealing surface at least a portion of which lies in a plane that is per-pendicular to the valve axis. Further, at least that portion has a conical shape which is coaxial with the valve axis (as defined by the properly centered seal ring).
A co-operating seating surface on the disc has a portion which has the same conical shape as the portion of the sealing surface at the sealing plane. The disc is sufficiently wide so that it can be moved beyond its closed position (in which the seating surface contacts the sealing surface at the intersection between the latter and the sealing plane), and in which the two portions of the sealing surface and the seating surface are in mutual alignment, to thereby increase the sealing pressure generated between the t~o surfaces and thus enhance the seal formed by the valve.

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To avoid a premature contact between the sealing surface of the seal ring in the housing and the seating surface of the disc, faces of the disc are slanted relative to the axis of the conically shaped portion of the seating surface.
A valve constructed as broadly outlined in the preceding paragraphs has the advantage that the housing is of an entirely concentric construction. Thus, the valve housing can be more readily manufactured with relatively simple machinery without requiring special jigs and tooling which take into account angular offsets as was the case with some of the earlier discussed prior art valves. The manu-facture of the valve disc and seal ring is similarly simpli-fied. Preferably, a simple jig is provided for machining the disc while taking into account the slight slanting of the disc face. The seal ring is entirely perpendicular to its axis and therefore requires no jigs or its manufacture.
As a consequence a valve constructed in accordance with the present invention can be made at a relatively lesser cost.
The invention of the parent application provides significant economies in the manufacture of the valve and the operating characteristics of the valve are excellent.
The operating characteristic are further enhanced by con-structing the seal ring so that a member thereof which defines the sealing surface can be resiliently deflected when the disc is moved beyond its closed position to in-crease sealing pressures and assure an air tight seal even under the adverse operating conditions such as high pressures, temperatures and difficul-t to handle fluid media.
Accordingly the present invention is a circular 3~ s~al ring for co-operation with a conically shaped seating surface of a disc valve that is concentric with respect to a valve axis, the seal ring comprising in cross-section, a base having a width in a radial direction and a thickness in an axial direction; a slanted web protruding in a generally radial direction from the base having substantially para-llel, generally axially oriented faces, and defining there-between a slanted web center line which intersects a radially oriented surface of the base at a first point, the web further having a thickness which is substantially less than the thickness of the base so as to render it relatively ~ flexible; and a sealing member protruding in a generally : radial direction from an end of the web remote from the base, the sealing member terminating in a convex, arcuately shaped sealing surface extending in a generally axial direction and having a center of curvature which lies on the slanted web center line, the distance from the sealing surface to the first point being less than from.the sealing surface to the center of curvature, the base, the web and the sealing member being constructed of a resilient material.
Preferably, the cross-section of the sealing surface of the seal ring is curved, preferably arcuately curved (meaning circularly arcuate) having a radius of curvature which is greater, for example by a factor of 1.5:1, than the distance between the intersection of the seal.ing surface and the sealing plane and the intersection of the center of the web and the base of the seal ring.
When so constructed, movement of the disc beyond the closed position causes the deflection of the seal ring along a circular path having its center at the intersection between the seal ring base and the web. Since the radius of cur-.

)907 vature of the sealing surface exceeds the radius about whichthe sealing surface is deflected, the closure of the disc beyond the closed position result in an increased contact pressure between the sealing surface of the seal ring and the seating surface of the disc.
The effectiveness of the seal provided by a valve constructed in accordance with the invention of the parent application including a sealing ring, according to the present invention is further enhanced by an increase in the contact pressure between the seating surface and the sealing surface when the disc is in its closed position and the fluid pLessure on either side of the disc is increased. The resulting pressure differential slightly deflects the sealing member of the seal ring, together with the web, in one or the other direction, again about the intersection between the web and the ~ase (which is rigidly clamped to the housing). Such deflection of the sealing member, however, increases the surface contact and the contact pressure between the sealing surface and the seating surface of the disc thereby enhancing the seal and thus rendering the valve effective for establishing an air tight seal even when it is subjected to high pressure differentials.
The contact pressure obtained with the valve is thus not onlv a function of the force with which the disc is closed, that is with which the seating surface presses ; against the sealing surface due to their relative positions and dimensions, but is further a function of the pressure differential hetween the two sides of the closed disc. In ; other words, if the pressure differential increases the 3~

. , ~Z~907 sealing force between the seal ring and the disc also increases, thereby assuring an air tight seal even at very high pressures without requiring the application of corres-pondingly larger forces to the disc when it is closed to mechanically generate the required contact pressure.
Thus, since it is not necessary to generate high contact pressure with the closed disc and the associated actuating mechanism therefor, the pivot axis for the disc can be brought closer to the valve axis, thereby reducing the torque that is required for openlng the disc against fluid pressure applied to one side thereof. In the past, it ~::
was frequently necessary to provide relatively large eccen-tricities for the disc pivot axis to facilitate the gene-: ~
ration of the required, relatively high contact pressure lS between the disc and the seal ring. This had the adverse consequence, however, of correspondingly inoreasing the ;~
torque for operating the disc under pressure conditions.
Since the present invention eliminates such requirements, it , is now possible to operate the disc with pivot axis eccen-~ 20~ tricities of as little as~l to 5~;mm and normally no more than about 10 mm.~ This, ln turn, enables one to provide smaller valve actuators which correspondingly reduces the -~
- : ~
overall costs of the valve.
To further reduce manufac-turing costs, the require-ment to maintain close tolerances, etc the seal ring is desirably mounted in an inwardly opening groove defined by the valve housing which is dimensioned so that the seal ring can be adjusted, e.g. moved in a radial direction and by providing means such as a clamping ring for locking the seal rlng in any desired relative position in the groove. The _7-Q~)7 seal ring can be centered relative to the seating surface of the disc by loosening the clamping ring, closing the disc so that the seating surface engages the seal ring surface, whereby the seal ring is centered relative to the disc, and, thereafter, while the disc is in its closed position, tightening the clamping ring so as to lock the seal ring in its centered position. In this manner, the valve housing as well as the seal ring can be manufactured with relatively loose tolerances and manufacturing costs can be reduced while a perfect alignment between ths seal ring and the co-operating seating surface of the disc is assured.
It is apparent that the presen-t invention permits a disc valve which has operating characteristics and capa-bilities at least as good if not better than those exhibited by the highest quality prior art valves. In addition, a disc valve having the seal ring of the present invention exhibits the same sealing characteristics irrespective of whether the upstream or the downstream side of the valve disc only is pressurized. Yet, by virtue of the present invention, such as a valve can be manufactured at a re-latively low cost.
The invention, is illus-trated by way of example, in the drawings, in which:
Figure 1 is a side elevational view, in section, of a valve constructed in accordance with the present invention and shows, in dotted lines, the disc of the valve in its open position;
Figure 2 is a fragmentary, simplified side ele-vational view, in section, and illustrates the geometxic relationships of the valve housing, the seal ring and the ~ 7 valve disc;
Figure 3 is an enlarged, fragmentary, side ele-vational view which illustrates the sealing arrangement of the present invention in greater detail; and Figure 4 is an enlarged, side elevational view, in section, illustrating in detail the seal ring cross-section and the deflection of the seal ring under axially acting forces.
Referring first to Figure 1, a valve 2 constructed in accordance with the invention of the parent application generally comprises a valve housing 4 which includes a conduit 6 that extends through the housing. A valve disc 8 is disposed within the conduit and pivotally mounted -thereto with a shaft 10 that is suitably journalled in the valve housing and that defines a pivot axis 12 for the disc for pivotally moving the disc between its open position, shown in dotted lines, in which the disc is generally parallel to a valve axis 14 and a closed positlon in which the disc is generally perpendicular to the valve axis as is more fully 20 described hereinafter. ~ ;
The conduit 6 includes a cylindrical section 16 which extends from a first end 18 of the housing towards a second end 20, an inwardly protruding, tapered section 22 which is disposed intermediate the housing ends, and a 25 second cylindrical conduit section 24 of an enlarged outer ;
diameter that terminates at the second housing end.
An annular recess is formed in the inwardly protruding section 22 of the housing, its radially outermost extent is defined by a cylindrical wall 28. A clamping ring _g_ ~ 07 30 is positioned within the second cylindrical conduit section 24 and it is secured to the housing with a plurality of axially oriented bolts 32. Preferably, the clamping ring has a slanted inner wall 34 which slopes from the second housing end towards the annular recess 2~ and which has an innermost diameter approximately equal to the innermost diameter of the protruding housing section 22. Thus, annular recess toyether with the portion of clamping ring 30 that extends beyond the cylindrical wall 28 define a radially inwardly open, annular groove 36 in the housing.
Disposed within groove 36 is a seal ring 38 which is constructed as is further described below. It has a base 40 that terminates in a radially outermost, cylindrical wall 42 of a diameter less than the diameter of groove wall 28 so that the seal ring can be adjusted in radial directions within the confines of the groove. For instances in which the seal ring is constructed of a metal or similar material, a gasket ring 44 may be placed between the seal ring base and the inwardly protruding section 22 of the housing so as to prevent the leakage of fluid therebetween when the disc is in its closed position and one or the other side of the disc is pressurized.
The operation of valve 2 illustrated in Figure l can now be briefly summarized. When the valve is to be closed, a valve actuator (not separately shown) coupled to shaft lO is energized to pivotally move disc 8 about pivot axis l2 in a counterclockwise direction, as indicated by corresponding arrows in Fi~ure l, from the open position (shown in dotted lines) into the closed position in which the disc is oriented transverse to the valve axis 14. In ~ )7 the closed position a sealing plane 46 defined by the theoretical line of contact between a seating surface ~8 of the disc and a sealing surface 50 of the seal ring is perpendicular to the valve axis. To open the valve, the actuator is energized to pivot the disc in Figure 1, in the opposite direction until it is again substantially parallel to the valve axis.
Referring now to Figure 2, the detailed construc-tion, position and co-operation of seating surface 48 of disc 8 and sealing surface 50 of seal ring 38 are described.
The seating surface 48 of disc 8 has a c~nical shape and it is selected so that when the disc is in the closed position, the apex "A" of the (seating surface) cone 52 (shown in dotted lines) is on valve axis 14 and ~he axis "X" of the cone is coaxial, that is coincides with valve axis 14.
Further, the disc is given an excess thickness "T" (measured parallel to cone axis "X") and disc end faces 54, 56 are slanted by an angle "a" of between 1 to 10 and preferably of no more than about 5 relative to a plane which is perpendicular to the housing axis "X"~
The end faces 54, 56 of the disc are normally substantially parallel with respect to each other and they are slanted so that slant angle "a" lies in a plane that includes cone axis "X" and is perpendicular to pivot axis 12. Further, the slant angle is chosen so that the end faces slope away from the (counterclockwise) pivotal closing movement of the disc as is clearly illustrated in Figure 2 to avoid a premature contact between the disc and the seal ring. Such premature contact would take place if 'che end faces were perpendicular to cone axis "X" as is indicated in ~o~

Figure 2 in dotted lines and identified with reference numerals 54' and 56', respectively.
If the end faces were not so slanted, the end faces and the seating surfaces 48 would meet at ~imaginary) leading edges 58 and 60 ~during movement of the disc from the open to the closed position in a counterclockwise direction). Since the distance from disc pivot axis 12 to imaginary leading edges 58, 60 is greater than the distance from the pivot axis to the intersection points 62 between sealing plane 46 and seating surface 48 (or sealing surface 50), the leading edges would contact the sealing surface before the disc is in its closed position. To avoid such contact and potential damage to the seal ring, the disc faces 54, 55 are slanted as above described to thereby in effect form recesses in perpendicular disc faces 54', 56' which avoid such premature contact. Moreover, the trans-ition between the end faces and the seating surface is curved as is illustrated as a further precaution against such premature contact.
To facilitate and simplify the further discussion of the application herein, and to simplify claim termi-nology, the orientation of the slant angle "a" as above described will hereinafter be sometimes referred as a slant "angle trailing the closing motion of the disc" or as a "trailing slant angle".

; The detailed construction of seal ring 38 is set forth later on. In its broadest form, however, it may have any cross-sectional profile so long as at least a portion of its sealing surface 50 at the intersection 62 between the sealing surface and the sealing plane 46 has the same conical shape as the conical shape of seating surface 48 of disc 8 at these points. In a preferred embodiment of the invention, such conically shaped portion is defined by a curved sealing surface which, at point 62, has a tangent that defines over the full circular extent of the seal ring a tangent cone. The tangent cone is the same cone as the cone of which seating surface 48 is a part. Further, the tangent cone has the same orientation as the cone of the seatlng surface when the disc is in its closed position.
Thus, the tangent cone, like the cone defined by the seating surface has an apex "Al' on valve axis 14 and a cone axis "X"
which i5 coaxial with the valve axis.
It should also be noted that the seating surEace 48 of disc 8 and the sealing surface 50 of seal ring 38 are constructed and arranged so when the disc is in its closed position sealing plane 46 intersects the conical seating surface but is otherwise immediately adjacent the ~pro-ximate) end face 54 (upper half of disc in ~igure 2) and 56 (lower disc half~ and the curved transition between the respectlve end faces and the seating surface. Thus, there is an additional width of seating surface, identified with reference numeral 64, which is available for contacting the sealing surface of the seal ring. In other words, the seating surface is given an additional width thickness over what is theoretically necessary to establish a seal. By slanting the end faces in the above-discussed manner the additional width is provided without correspondingly in-creasing the thickness of the disc (to "T"). The additional sea-ting surface width 64 allows one to increase the contact pressure between the disc and the seal ring as is more fully ~L~Z~9~7~

described below.
Referrlng now to Figures 3 and 4, the construction of seal ring 38 and its co-operation with valve disc 8 are described in detail. Generally speaking, the seal ring may have a variety of cross-sections, for example, it may have the cross-section shown in Figure 2, and its seal rings surface 50 may ha~e varying configurations so long as it defines the above-described conically shaped sealin~ surface at least at the intersection between the sealing surface and sealing plane 46. Therefore, the sealing surace may, for example, have a conical shape complementary to that of seating surface 48. One aspect of the present invention, however, contemplates to give the sealing surface in cross-section, a convex, arcuately curved shape. Furthermore, the sealing surface is defined by a sealing member 66 of the seal ring which is deflectable under axially acting pre~
ssureO
Structurally, the cross-section of the seal ring comprises the above mentioned generally rectangular seal ring base 40 which has a width and a thickness so that the base is compressed in seal ring groove 36 when clamping ring ; 30 is tightened to prevent the leakage of ~luid between the :
seal ring base and the valve housing 4. If a gasket 44 is used the thickness of the base is such that it slightly exceeds the distance between the opposing fac~s of the gasket and the clamping ring.
Joined to the base ls a generally radially in-wardly extending web 70 which has a thickness (in the axial direction) substantially less than the thickness o~ the base so as to render the web relatively flexible. Further, the ~Z~9~7 web is slanted so that it is generally perpendicular to the tangent at the intersection between seal ring surface 50 and sealing plane 46. Expressed in other words, the web is perpendicular to seating surface 48 of the disc when the disc is in its closed position. Lastly, in cross-section the sealing member 66 extends generally perpendicular to the web to either side thereof, somewhat akin to the flange of an I-beam, for example.
Particularly for high temperature applications the seal ring is constructed of a resiliently deformable metal such as steel, stainless steel, berylium, copper or the like. For such applications it is necessary to provide gasket 44 to prevent fluid leakage past the base. For low temperature applications, say for applications in which the maximum temperature does not exceed 150C the seal ring may also be constructed of an elastomeric material such as plastic, rubber or the like of the desired hardness. In such instances, it is normally not necessary to provide a sepa-rate gasket 44 since the tightened clamping ring 30 provides sufficient pressure between the seal ring base and the housing to prévent fluid leakage past them. In both instances the base, the web and the sealing member are preferably integrally constructed.
The radial width of base 40 is selected so that the intersection between the (imaginary) extension of its radially inwardly facing, cylindrical surface 72 with a center line 74 of the web (which is perpendicular to the conical seating surface at point 62) defines a center of deflection 76 for sealing member 66 and web 70 that is spaced from sealing point 62 a distance "r". Further, ~L~Z~07 sealing surface 50 is convexly arcuately shaped about a center point 78 which lies on a straight line extension of web center line 74 and which is spaced from sealing point 62 a distance "R" which is greater than "r", preferably by a factor of at least about 1.5:1.
The seat ring 38 constructed as above described assures that the contact pressure generated at sealing point 62 between disc seating surfaces 48 and ring sealing surface 50 can be increased by moving the disc beyond its closed position. The contact pressure further increases as a function of the pressure differential that may act on the seal ring when the disc is closed whether the pressure differential acts from one side or the other of the seal ring. This results from the fact that the relatively thin 15 and, therefore, flexible web is connected to the rigidly .
~ cla~ped seal ring base 40 so that an axial force component -~ will swing the web and, therewith, the s~ealing member 66 approximately above a circular path which is centered at point 76.
~ 20 Thus,~if pressure Pl acts from the left, as illus- -;~ trated in Figure~4, disc 8 is closed and the opposite side ~ , is at a lower pressure, say at atmospheric pressure, the forces applied a.gainst the left hand side of sealing member 66 and web 70 force the two to the right along a generally ci.rcular path having its center at point 76 and into the position shown in Figure 4 in dotted lines and identified with the reference numeral 80. Since the radius of curva-ture "R" of sealing surface 50 is greater than the swing radius "r" of the sealing member, a left-hand portion 82 (as seen in Figure 4) of sealing surface 50 moves radially ~2~07 inward as is indicated by the dotted lines in Figure 4. In actuality such a radial movement of the sealing member is prevented by the closed disc 8; instead, the sealing member and the web are moved slightly to the right and resiliently compressed, thereby correspondingly increasing the contact pressure between seatlng surface 48 and sealing surface 50 as a function of the magnitude of the pressure differential sides generated by Pl.
Accordingly, the greater the pressure differen- -~
tialj which normally increases the danger of a resulting leak between the seal ring and the valve disc, the greater is the contact pressure between the two, thereby preventing such leaks and assuring that the valve of the present invention maintains a complete seal irrespective of the pressure which it must seal off.
If the pressure differential acts from the right ~ of the seal ring as seen in Figure 4 by virtue of a fluid ;`~ pressure P2 which exceeds the pressure on the left-hand side of the rlng, the same result is obtained. The pressure ~20 differential causes sealing member 66 and web 70 to swing to the le~t about point 76 into the position indicated by reference numeral 84. By virtue of the above described relationship between "R" and "r" the right-hand portion of sealing surface 50 is theoretically moved radially inward as is indicated at 86. Since the disc blocks a radially inward motion, the contact pressure between the seal ring and the disc is again increased in the above described manner.
Lastly, the contact pressure between the disc and the seal ring can be increased by pivotally moving disc 8 about pivot axis 12 beyond its closed position, that is llZ0~7 beyond the position in which cone axis "X" of the conically shaped sealing surface 48 is coaxial with valve axis 14, so that the apex "A" of the cone would fall below the valve axis and below point "A" as viewed in Figure 2. This is accomplished by selecting the conical shape of seating surface 48 relative to the position o~ pivot axis 12 so that the distance from the pivot axis to the sealing point 62 (when the valve is ln its normal, theoretically closed position) is less than the distance from the pivot axis to 10 any of the points of the remaining width 64 of the seating ;~
surface, such as points 88 (Figures 2-4) and 90 (Figure 2).
~;; If this condition is met, movement of the disc beyond its closed position will resiliently compress sealing member 66 and web 70, thereby increasing the contact pressure. Such ~: .
movement of the disc beyond its closed position may be accompanied by a slight resilient deflection of the sealing member and the web in the direction~in which the disc moves, thereby swinging~;the two about~point 76 to the right (as seen in Figure 4) which causes àn additional increase in the ; 20 contact pressure.
In the presently preferred embodiments of the invention with an offset between pivot axis 12 and valve axis 14 of between 1 to 5 mm, a cone angle "b" (Figure 2) in the range of between about 20 to 70 has yielded good results although under given circumstances the angle may exceed the stated range so long as the above condition is satisfied. For many applicatlons the optimal angle is in the vicinity of about 40 and generally it can be observed , that smaller diameter valves will have larger cone angles `~

30 and vice versa because of the relative position of shaft `~

axis 12 and, in the case of larger diameter valves, the need for limiting the thickness of the valve disc. Thus, in one example, a valve of a nominal valve diameter of 300 mm may have a cone angle "b" of approximately 34~ while a valve of a nominal valve diameter of 600 mm may have a cone angle "b"
of approximately 25, the valves having an eccentricity between the valve axis and the pivot axis of 2 and 3 mm, respectively.

Claims (8)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:-

1. A circular seal ring for co-operation with a conically shaped seating surface of a disc valve that is concentric with respect to a valve axis, the seal ring comprising in cross-section, a base having a width in a radial direction and a thickness in an axial direction; a slanted web protruding in a generally radial direction from the base having substantially parallel, generally axially oriented faces, and defining therebetween a slanted web center line which intersects a radially oriented surface of the base at a first point, the web further having a thick-ness which is substantially less than the thickness of the base so as to render it relatively flexible; and a sealing member protruding in a generally radial direction from an end of the web remote from the base, the sealing member terminating in a convex, arcuately shaped sealing surface extending in a generally axial direction and having a center of curvature which lies on the slanted web center line, the distance from the sealing surface to the first point being less than from the sealing surface to the center of curva-ture, the base, the web and the sealing member being con-structed of a resilient material.

2. A seal ring according to claim 1 wherein the radius of curvature of the arcuate profile is at least about 1.5 times the radius of curvature of the circular path.

3. A seal ring according to claim 1 wherein the web center line is perpendicular to the tangent of the arcuate sealing surface at the intersection between the center line and the sealing surface.

4. A seal ring according to claim 1 wherein the base forms the radially outermost portion of the seal ring.

5. A seal ring according to claim 1 wherein the sealing surface faces in a generally radially inward direc-tion.

6. A seal ring according to claim 1 wherein the center line of the web is perpendicular to the tangent to the sealing surface at the intersection between the sealing surface and the center line.

7. A seal ring according to claim 1 wherein the base, the web and the sealing member are integrally con-structed.

8. A seal ring for use with disc valves having a valve housing including means for positioning the seal ring within the housing, a valve disc including a seating surface for sealingly engaging a sealing surface of the ring, and means for pivotally moving the disc between an open position and a closed position in which the disc is substantially perpendicular to the valve axis and in engagement with the seal ring, the seal ring comprising: an annular base having a width in a radial direction and a thickness in an axial direction; a sealing member spaced radially inward of the base and defining a generally radially inwardly facing sealing surface having, in cross-section, a convexly arcuate profile a radius "R" for engaging the seating surface of the disc; web means constructed of a resilient material and interconnecting the base with the member, the web means extending generally radially inward of the base and having a thickness in the direction of the valve axis which is substantially less than the thickness of thd base; and means for causing the deformation of the member and the web means relative to the base along a generally circular path of a radius "r" when an axially acting force is applied to at least one of the members at the web means; and wherein "R"
is greater than "r" and the circular path is arranged so that the force with which the sealing surface is biased against the seating surface is enhanced when the axially acting force is applied.