VALVES

Abstract: A gas isolation valve which is capable of maintaining a reliable seal even if exposed to a fire. In one arrangement a ball valve is sealed by O-rings (5, 7), the ball valve being in the form of a housing, a ball (3) located within the housing, and a spindle (4) engaging the ball through an opening in the housing wall. The spindle (4) and ball (3) are interengaged by mating dovetail formations. One of the sealing O-rings may be associated with an annular member (12) which is spring (14) biased towards the ball (3), the annular member (3) being arranged such that in the absence of the O-ring it is biased against the ball (3) and forms a seal between the ball and the valve housing. The ball valve may be used in association with a heat activated isolation valve in which a valve member is mounted on a spring biased over centre mechanism extending across the interior of the valve housing. A bimetallic strip (26, 27) extends adjacent the over centre mechanism, the bimetallic strip being arranged to move the valve member to a valve closed position if the temperature exceeds a predetermined limit.

Description: VALVES The present invention relates to valves, and in particular to valves which may be used in fuel gas distribution. There is a demand for large volumes of isolation valves which may be manually operated to isolate a fuel gas supply main from a gas distribution network within for example domestic premises. Such valves are used to isolate premises from the gas main for example when the premises are unoccupied, or when a leak has been detected within the premises. Given the large number of valves required and the importance of their function from the point of view of safety it is essential that such valves are both cheap to produce and highly reliable. Conventional gas isolation valves have a metal body defining a tapered bore into which a tapered spindle is inserted, a transverse bore being formed through the spindle. When the bore is aligned with inlet and outlet ports in the body the valve is open, rotation of the spindle through 90° moving the bore to a position in which it is isolated from both the inlet and outlets. Grease is applied to the mating faces of the spindle and valve body and as a result a substantially gas-tight seal is formed between them. Such a valve design has been used satisfactorily for many years, but the design demands accurate machining of the component parts and this is difficult to achieve economically. Furthermore, given that isolation valves are rarely operated, such that years may elapse during which the spindle and body do not move relative to each other, and given the interference fit between the spindle and body, considerable force may be needed to move the spindle relative to the body on those rare occasions when the valve has to be opened or closed. This means that the shaft and body must be relatively robust components, and hence relatively expensive in terms of materials. Ball valves sealed with O-rings can be manufactured relatively cheaply. Many designs of such valves are available, for example that described in British Patent No. 2242963. A common feature of most such designs is a body defining a through bore, an aperture extending through a wall of the body and receiving a valve spindle, and a ball located within the passageway and coupled to the spindle. The ball defines a through bore which may be positioned so that it is either aligned with the passageway or transverse to the passageway. At least one O-ring is located within the passageway so as to define a seal with the ball, and an O-ring is located between the spindle and the body to prevent leakage from the passageway. Such valves are cheap to produce, and relatively small versions of such valves have been widely used to control the supply of gas to individual appliances. There has been a reluctance to use such valves for mains isolation however, primarily because they are not fire proof. In the event of a ball valve of the above design being exposed to heat from a fire, the O-rings are destroyed. The valve then leaks, even when the valve is closed, making it impossible for premises in which a fire is burning to be reliably isolated from the gas main. Thus gas distributors are reluctant to use simple ball valves for mains isolation unless they are associated with back-up valves which automatically and reliably isolate the main in the event of a fire. A feature of ball valves used for gas mains isolation is that they must be robust so as to be able to survive mechanical abuse, for example as a result of being closed in haste with an inappropriate tool. There must be little risk of the spindle shearing, or of the spindle being decoupled from the ball. The objectives of achieving a design which is cheap to produce and yet is sufficiently strong that the spindle and ball cannot be accidentally decoupled are difficult to reconcile. The present invention has the objective of providing valves which are suitable for use as gas main isolators and in particular such valves which perform in a safe manner even if exposed to high temperatures. According to a first aspect of the present invention, there is provided a ball valve comprising a housing formed by a main body and a separable insert which together define a passageway, a ball valve member located within the passageway between the main body and the insert, a spindle extending through an opening in the housing to engage the valve member, and at least one resilient seal arranged between the valve member and the housing, the valve member defining a bore therethrough and being rotatable by the spindle between a valve open position in which the bore communicates with the passageway on opposite sides of the valve member and a valve closed position in which the bore is isolated from the passageway on at least one side of the valve member, wherein the valve member and spindle are interengaged by a dovetail joint such that the joint may be disengaged by separating the main body and insert and moving the valve member out of the main body through the passageway. Any convenient form of dovetail interengagement may be provided. For example a conventional tapered dovetail may be used in which the ball defines a slot which is of uniform cross-section along its length and which increases in width with depth, and the spindle may define a projection which is a sliding fit in the tapered slot. According to a second aspect of the present invention, there is provided a ball valve comprising a housing which defines a passageway, a ball valve member located within the passageway, a spindle extending through an opening in the housing from the valve member, and at least one resilient seal arranged between the valve member and the housing, the valve member defining a bore therethrough and being rotatable by the spindle between a valve open position in which the bore communicates with the passageway on opposite sides of the valve member and a valve closed position in which the bore is isolated from the passageway on at least one side of the valve member, wherein said at least one seal comprises a resilient O-ring interposed between the valve member and an annular member which is spring biased towards the valve member, the annular member being arranged such that in the absence of the O-ring it is biased against the valve member and forms a seal between the housing and the valve member. The annular member may comprise a tubular portion projecting from a flange, the free end of the tubular portion being chamfered to define an annular sealing surface adjacent the ball, and the O-ring being arranged around the tubular portion of the annular member. The body may support a further O-ring arranged to contact the ball on the side of the ball remote from the annular member, the further O-ring being located adjacent a further annular sealing surface such that in the event of the O-rings being destroyed the ball is displaced into contact with the further annular sealing surface by the spring bias applied to the annular member. The spring bias may be generated by a deformable spring washer located between the valve housing and the annular member. According to a third aspect of the present invention, there is provided a heat-activated isolation valve comprising a body defining a passageway between an inlet and an outlet, a sealing surface defined by the body, a valve member supported within the passageway adjacent the sealing surface and moveable between a first valve open position spaced from the sealing surface and a second valve closed position in contact with the sealing surface, a spring-biased over centre mechanism extending across the passageway and arranged to bias the valve member to either the first or the second position, and a bimetallic strip extending across the passageway adjacent the over centre mechanism, the bimetallic strip being arranged to move the valve member to the second position if the temperature exceeds a predetermined limit. The over centre mechanism may comprise a two part leaf spring, each part engaging a groove in the housing wall at one end and a slot in the valve member at the other end. The Bimetallic strip may extend alongside the leaf spring such that the leaf spring is deformed by an increase in temperature to a shape in which the valve member is forced to the second position. Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a sectional view of a first embodiment ofthe present invention; Figure 2 is a view on the line 2-2 of Figure 1, Figure 2 indicating the section shown in Figure 1 on the line 1-1; Figure 3 is an exploded view of components shown in Figure 1; Figure 4 schematically illustrates the interrelationship between a valve housing and a ball valve and spindle structure of the embodiment of Figures 1 and 2; Figure 5 is a view on the line 5-5 of Figure 4; Figure 6 is a view on the line 6-6 of Figure 5; Figure 7 is a view on the line 7-7 of Figure 6; Figure 8 illustrates an alternative component which may be introduced into the embodiment of Figure 1 in place of the components shown in Figure 3; Fig. 9 illustrates an alternative housing structure to that shown in Fig. 1; Figures 10, 11 and 12 illustrate a thermally activated isolation valve structure which may be used in association with the ball valve of Figures 1 and 2, Figure 10 showing the valve open and Figure 11 showing the valve closed; and Figure 13 shows a thermally activated isolation valve of the same general type as that shown in Figures 10 to 12 but intended for independent use rather than incorporation in the ball valve structure of Figures 1 and 2. Referring to Figures 1 to 7, the illustrated structure comprises a housing formed by a main body 1 and an insert 2. The housing defines a passageway in which a ball valve member 3 is located, the ball valve member being retained between the main body and the insert. A spindle 4 extends through an opening in a side wall of the main body and engages the ball 3. A first O-ring 5 is located between the ball and the main body 1, a second O-ring 6 is arranged around the spindle 4, and the third O-ring 7 is arranged between the ball and the insert 2. A cupped washer 6a is also arranged around the spindle, the cupped washer being an interference fit on the spindle 4 and an interference fit within the bore in the main body through which the spindle 4 extends. The upper portion of the main body defines a projection 8 which co-operates with a cut out 9 on the spindle to limit rotational movement of the spindle to 90°, positioning the spindle at one extreme of its freedom of movement resulting in the ball adopting the position shown in Figure 1 in which a through bore 10 defined by the ball is aligned with the passageway through the main body. Rotating the ball through 90° from the position shown in Figure 1 results in the bore being wholly located between the seals 5 and 7. The O-ring 5 is received in an annular recess defined around a tubular extension of the main body extending towards the ball. This tubular extension terminates in a frustoconical sealing surface 11. The O-ring 5 ensures that the ball is held in a position in which it does not contact the sealing surface 11. In a similar manner, the O-ring 7 is supported on an annular member 12 which defines a flange from which a tubular chamfered extension projects, the tubular extension defining a frustoconical annular sealing surface 13. The O-ring 7 ensures that the surface 13 is held a short distance away from the surface of the ball 3. The annular member 12 is received within the insert 2 so as to be a reasonably tight sliding fit therein, a spring washer 14 being located between the insert 2 and the annular member 12. Thus the spring washer applies a force to the annular member 12 which causes it to move towards the ball as far as it is able to given the interposition of the O-ring 7 between the annular member 12 and the ball. In the event of the illustrated valve being exposed to a fire, the resilient O- rings 5, 6 and 7 will be destroyed. When this occurs the biasing force generated by the spring washer 14 pushes the annular member 12 against the surface of the ball 3 and in turn pushes the ball against the sealing surface 11. The cupped washer 6a remains in position between the spindle 4 and the main body. Thus even though the O-rings have been destroyed and therefore provide no sealing function gas cannot escape from the valve assembly except for very limited leakage which may occur between the metal-to-metal seals defined by the ball 3 and the sealing surfaces 11 and 13 with which it is in contact, and the metal-to- metal seals defined between the washer 6a and the spindle and main body. Thus the valve will have a minimal leakage rate in the event of its exposure to very high temperatures. The spring washer 14 may be of any suitable type. For example, as shown in Figure 1, the spring washer may be corrugated in the circumferential direction such that when compressed the height of the corrugations is reduced. Alternatively, the spring washer may be frustoconical for example. It is important that the spindle 4 and ball 3 are securely interengaged. This is achieved by arranging for the ball 3 to have a slot 15 formed therein into which a dovetailed tongue 16 is inserted. The slot 15 is of substantially uniform cross-section but of increasing width with depth and the tapered tongue 16 is shaped to be a close sliding fit in that slot. The valve can be simply assembled by removing the insert 2 from the main body 1, inserting the spindle through the aperture in the side wall of the main body and arranging the tongue 16 so that it extends axially, pushing the ball 3 into the open end of the main body so that the slot 15 is aligned with and slides over the tongue 16, and then replacing the insert in the main body. Thus it will be appreciated that the various components can be easily interconnected and yet an extremely strong interengagement between the spindle and ball is achieved. The insert 2 of Figures 1 and 2 may be replaced by a more conventional component as shown in Figure 8 which does not incorporate an axially biased annular member 12. As shown in Figure 8, the alternative insert 17 defines an annular groove 18 which receives an O-ring 19, the annular groove 18 being limited on its inner side by a sealing surface 20 which extends parallel to the adjacent surface of the ball 3 when the insert 17 is inserted in the main body 1. It will be appreciated however that with such an arrangement some leakage will occur in the event of the O-rings 19 and 5 being burnt out. In some applications this will not be a problem however and therefore there is benefit to being able to use the simpler and cheaper assembly shown in Figure 8 rather than the assembly shown in Figure 3. Fig. 9 illustrates an alternative housing to that of the embodiment of Fig. 1. In the arrangement of Fig. 9, the O-ring 5 is retained on a carrier 5a rather than being supported on a groove machined into the housing, and the O-ring 7, annular member 12 and spring washer 14 are retained on a carrier ring 7a rather than being retained in an insert 2. The carrier ring 7a is retained in the one-piece housing by a circlip 7b, and an additional O-ring 7c may be provided to prevent any slight leakage around the carrier ring 7a bypassing the O-ring 7. The structure of Fig. 9 is easier to manufacture cheaply than that of Fig. 1. In some applications it will be desirable to provide a heat-activated isolation valve in association with the ball valve which will not only enable the isolation valve to be closed in a gas-tight manner if the valve is exposed to high temperatures but will in addition automatically close the valve even if the ball 3 remains in the open position as shown in Figure 1. A suitable heat-activated isolation valve is illustrated in Figures 10, 11 and 12 and comprises a body 21 a threaded end 22 of which is intended to be screwed into the main body 1 shown in Figure 1 in place of the insert 2. A heat-activated valve assembly is supported within the body, that assembly comprising a valve member 23 supporting a cylindrical on-axis post in which an axial slot 24 and a circumferential slot 25 have been formed, two bimetallic strips 26 and 27 each of which has a central portion of reduced width to enable it to be inserted in the axial slot 24, and two leaf springs 28 and 29 the abutting ends of which are of reduced width to enable them to be positioned within the axial slot 24. Shoulders 30 are defined as a result of the reduced width of the end portions of the leaf springs and those shoulders engage in the circumferential slot 25. Figure 10 shows the assembly in the valve open position. It will be seen that the radially outer ends of the springs 28 and 29 are received in a groove 31 formed in the inner wall of the body 21, the lengths of the springs 28 and 29 in their unstressed condition being slightly greater than the radius of the base of the groove 31. Thus the springs 28 and 29 act as an over-centre mechanism such that the valve member 23 is either biased to the position shown in Figure 10 or biased to the closed position as shown in Figure 11. The bimetallic strips in the valve open configuration shown in Figure 10 bear against the undersides of the springs 28 and 29 and thus prevent the valve member becoming detached from the body 21. When the bimetallic strips 26 and 27 are heated however they bend to the configuration shown in Figure 11 and in so doing push the valve member towards the sealing surface 32 defined by the body 21 until the springs 28 and 29 are just beyond the position in which the radially inner ends of the springs are located in the same plane as the radially outer ends of the springs. The mechanism then snaps to the closed configuration as shown in Figure 11. One advantage of the illustrated heat-activated isolation valve as described in Figures 10 to 12 is that the valve can be readily tested and thereafter simply reset by pushing the valve member 23 away from the sealing surface 32. In the structure illustrated in Figures 10 to 12, two bimetallic strips are used. It will of course be appreciated that if appropriate bimetallic materials are available it would be preferable to use a single bimetallic strip. The heat-activated isolation valve structure of Figures 10 to 12 is intended for fitting into an associated component such as the ball valve of Figures 1 and 2. It will be appreciated however that the same assembly of components could be used in a stand-alone valve assembly which could be fitted at any convenient point in a gas supply pipe. Such an arrangement is illustrated in Figure 13. The same components as those illustrated in Figure 12 are used in the embodiment of Figure 13 and therefore both components will not be further described.

Claims: CLAIMS 1. A ball valve comprising a housing which defines a passageway, a ball valve member located within the passageway, a spindle extending through an opening in the housing from the valve member, and at least one resilient seal arranged between the valve member and the housing, the valve member defining a bore therethrough and being rotatable by the spindle between a valve open position in which the bore communicates with the passageway on opposite sides of the valve member and a valve closed position in which the bore is isolated from the passageway on at least one side of the valve member, wherein said at least one seal comprises a resilient O-ring interposed between the valve member and an annular member which is spring biased towards the valve member, the annular member being arranged such that in the absence of the O-ring it is biased against the valve member to cause a seal to be formed between the housing and the valve member. 2. A ball valve according to claim 1, wherein the annular member comprises a tubular portion projecting from a flange, the free end of the tubular portion being chamfered to define an annular sealing surface adapted to form a seal with the ball, and the O-ring being arranged around the tubular portion of the annular member. 3. A ball valve according to claim 1 or 2, wherein the housing supports a further O-ring arranged to contact the ball on the side of the ball remote from the annular member, the further O-ring being associated with a sealing surface against which the ball is pressed by the spring bias supplied to the annular member in the event of the O-rings being destroyed. 4. A ball valve according to claim 1,2 or 3, wherein the spring bias is applied to the annular member by a deformable spring washer located between the housing and the annular member. 5. A ball valve according to any preceding claim, wherein the spindle has a portion of square section, and the housing defines an abutment surface which co¬ operates with a cut-out in the square section spindle to limit the rotational movement of the spindle. 6. A ball valve comprising a housing formed by a main body and a separable insert which together define a passageway, a ball valve member located within the passageway between the main body and the insert, a spindle extending through an opening in the housing to engage the valve member, and at least one resilient seal arranged between the valve member and the housing, the valve member defining a bore therethrough and being rotatable by the spindle between a valve open position in which the bore communicates with the passageway on opposite sides of the valve member and a valve closed position in which the bore is isolated from the passageway on at least one side of the valve member, wherein the valve member and spindle are interengaged by a dovetail joint such that the joint may be disengaged by separating the main body and insert and moving the valve member out of the main body through the passageway. 7. A ball valve according to claim 6, wherein the ball defines a slot which is of uniform cross-section along its length and which increases in width with depth, and the spindle defines a projection which is a sliding fit in the slot. 8. A heat-activated isolation valve comprising a body defining a passageway between an inlet and an outlet, a sealing surface defined by the body, a valve member supported within the passageway adjacent the sealing surface and moveable between a first valve open position spaced from the sealing surface and a second valve closed position in contact with the sealing surface, a spring-biased over centre mechanism extending across the passageway and arranged to bias the valve member to either the first or the second position, and a bimetallic strip extending across the passageway adjacent the over centre mechanism, the bimetallic strip being arranged to move the valve member to the second position if the temperature exceeds a predetermined limit. 9. An isolation valve according to claim 8, wherein the over centre mechanism comprises a leaf spring engaging a groove at opposite sides of the passageway, the bimetallic strip extending alongside the leaf spring such that the leaf spring is deformed to a configuration in which the valve member is forced to the second position when the bimetallic strip is heated to the said predetermined temperature. 10. An isolation valve according to claim 9, wherein the leaf spring is in two halves, each half engaging the groove at one end and a slot in the valve member at the other end. 11. A valve substantially as hereinbefore described with reference to any one or more of the accompanying drawings.

Inventors: BROOKES GEORGE, BROOKES, GEORGE
Applicants: BROOKES GEORGE, BROOKES, GEORGE
Application year: 1996
Main classification: F16K5
IPC codes: F16K5