GB2033058A

GB2033058A - A butterfly valve

Info

Publication number: GB2033058A
Application number: GB7934651A
Authority: GB
Original assignee: Klein Schanzlin and Becker AG
Current assignee: Klein Schanzlin and Becker AG
Priority date: 1978-10-07
Filing date: 1979-10-05
Publication date: 1980-05-14
Also published as: SE7907971L; GB2033058B; SE438540B; AT381773B; ATA632279A; FR2438216A1; CH639467A5; DE2843860A1; FR2438216B1; IT7925926A0; IT1123283B

Abstract

In a butterfly valve having a valve casing 1, a valve member 2 centrally mounted in the valve casing, within an elastomeric lining 5 co-operating with the valve member 2 to provide sealing tightness, the peripheral sealing surface 6 of the valve member 2 has the form of part of the surface of a sphere and co-operates with a sealing bead 9 formed on the inside of the lining 5, the bead being narrower than the sealing surface 6 of the valve member 2 and dividing, to extend with clearance around either side of each pivot shaft 3, 4 of the valve member, the bead 9, in the closed position of the valve, lying everywhere within the limits, in the direction of flow through the valve, of the part-spherical surface 6. <IMAGE>

Description

SPECIFICATION A butterfly valve This invention relates to a butterfly valve having a valve casing with a centrally mounted valve member, disposed in the valve casing, the casing having therein an elastomeric lining co-operating with the valve to provide sealing tightness in the closed position of the valve.

In a butterfly valve having such an elastomeric lining, such as are known e.g. from German Patent Specifications 1,251,117, 1,290,395 and 1,550,499, the valve member, whose outer diameter is greater than the inner diameter of the resilient lining, engages fairly deeply therein to provide sealing tightness; some of the lining material is displaced when the valve is closed and takes up a position around the valve member. During the opening of the valve, the displaced or compressed elastomer is responsible for a holding torque greater than the closing torque.

In butterfly valves having centrally mounted valve members there are difficulties in sealing the regions near the shaft leadthroughs, i.e.

near the regions where a pivot shaft, or aligned pivot shafts, by means of which the valve member is pivotally mounted in the valve casing, extends or extend between the valve member and the valve casing. A popular solution of the problem of preventing leakages in these areas when the valve is closed is to displace an even greater volume of elastomer in these regions, to which end the lining and the valve member are formed with flattened parts near the shaft.

Since the compressed elastomeric lining could not on its own seal the shafts, it was often necessary for the shafts to have a separate seal; unfortunately, the medium flowing through the valve inevitably contacted the shafts and to some extent the casing. Where the flow medium was corrosive, therefore, the shafts and the casing had to be made of a noble material to prevent possible corrosion.

It is an object of the invention to provide a butterfly valve of the kind described which requires reduced opening and closing torques as compared with known valves and which provides satisfactory and uniform sealing around its entire periphery.

According to the invention, therefore, proceeding from the fact that uniform sealingtightness of the lead-through seal calls for a uniform sealing force between the valve member and the elastomeric lining right around the periphery, the sealing surface of the valve member in shape resembles a portion from a spherical surface and co-operates with a seal ing bead on the inside of the lining, the bead being narrower than the sealing surface of the valve member and extending with clearance around the shaft lead-throughs, the sealing surface of the valve member being larger than the annular bead near the shaft lead-throughs.

The effect of the sealing surface of the valve member having a spherical shape is that the bead engages with the same specific sealing force right around the periphery, while since it extends like a ring around the shaft lead-throughs, the sealing bead also serves as a preliminary seal for the shafts. Since the sealing surface of the valve member deforms the sealing bead but does not engage in the elastomeric lining, there is no need to increase the torque required to open or close the butterfly valve.

An embodiment of the invention is described below, by way of example, with reference to the accompanying drawings in which Figure 1 is a view in section along the pivotal axis of the valve member and along the longitudinal axis of the flow passage through the valve casing, of a butterfly valve according to the invention; Figure 2 is a view of the valve of Fig. 1, in section at right-angles to the pivotal axis of the valve member, Figure 3 is a sectional view similar to Fig. 1 but showing an elastomeric lining, forming part of the valve of Fig. 1, in isolation, and Figure 4 is a sectional view, similar to Fig.

2, but showing the elastomeric lining of Fig.

3 in isolation.

Referring to the drawings, a butterfly valve comprises a valve casing 1, which, in the embodiment shown, is in the form of an annulus, of an axial length small in relation to its diameter, adapted to be secured between two axially aligned pipe parts, for example equipped with mounting flanges or the like for the casing 1, in a pipe-line. Alternatively, the part indicated at 1 may simply form a central part of a valve casing to be mounted between tubular spigot parts, not shown, adapted for connection in turn to adjoining pipe parts in a pipe line or the like. In either event, the valve casing defines a flow passage therethrough, which is of circular cross-section and of which the longitudinal axis corresponds with the axis of said annulus 1.

A valve member 2 is mounted in casing 1 by means of two aligned shafts 3, 4, for pivoting about an axis extending diametrally with respect to the annular casing 1. The interior of the annular casing 1 has an elastomeric lining 5 fitted therein and encircling the valve member 2, so that as shown in Figs.

1 and 2, in the closed position of the valve the lining 5 lies between the peripheral surface 6 of the valve member 2 and the interior of the valve casing. The shaft 3, which is nonrotatably engaged in valve member 2 and extends rotatably through a collar in casing 1 to project therefrom for engagement by an operating member (not shown) and the shaft 4, which is fixed in the valve casing and enters a bearing provided in the valve member 2, both extend through respective apertures formed in the lining 5.

The peripheral surface 6 of the valve member 2 has the form of part of the surface of a sphere having its centre lying at the intersection of the axis of shafts 3, 4, with the axis of the flow passage through the valve casing.

The surface 6, in the closed position of the valve cooperates with a peripheral sealing bead 7 which is disposed on the inner side of lining 5. The bead 7, in the closed position of the valve, extends continuously, without a break, around the valve member 2, in engagement with surface 6, to seal the valve member 2 with respect to the casing 1.

The shafts 3 and 4 extend through leadthrough apertures 8 provided in the lining 5 and, as shown in Figs. 1 and 4, the bead 7, which in its other regions lies substantially in a plane containing the pivotal axis of valve member 2 and extending perpendicular to the axis of the flow passage, divides on either side of each aperture 8, and thus, in the assembled valve, on either side of each shaft 3, 4, to pass with clearance on both sides of each shaft 3, 4. Each said divided portion of the bead 7 forms an annular bead portion 9, substantially co-axial with shafts 3, 4 and spaced radially outwardly, with respect to the axis of shafts 3, 4, from the apertures 8.

It will be noted that the bead 7, between the head portions 9, is substantially narrower, as measured in the direction of the axis of the flow passage through the valve casing, than the surface 6 of the valve member, measured in the same direction when the valve is closed, and that in the closed position of the valve, the sealing bead, at every position around the periphery of the valve member, lies entirely between the limits, in the direction of the axis of the flow passage through casing 1, of the peripheral surface 6 of the valve member.

It will also be appreciated that in the unstressed state of the lining 5, the internal diameter of the space defined within bead 7 is somewhat less than the diameter of the sphere of which the surface 6 forms part, so that the bead 7, where engaged by the surface 6 is slightly deformed resiliently, ensuring adequate sealing between the bead 7 and the valve member 2. Nevertheless, because of the small width of the bead 7, the torque required to overcome friction between the bead 7 and member 2 in opening and closing the valve is small. Furthermore, the bead portions 9 extending around the shafts 3, 4, seal the same off from the interior of the valve casing, while being spaced from the shaft portions 9 are not subject to damage by the shafts, nor is there friction between the portions 9 and the shafts.

Claims

1. A butterfly valve having a valve casing with a flow passage therethrough, a valve member centrally mounted in the flow passage, via aligned shaft portions supported in the casing and extending into said flow passage, for pivoting, about a pivotal axis corresponding to the longitudinal axis of said shaft portions, between a closed position and an open position, the valve including an elastomeric lining so disposed in said casing as to lie between a peripheral surface of the valve member and the wall of said flow passage in the closed position of the valve, said peripheral surface of the valve member having the form of part of the surface of a sphere, said elastomeric lining including a sealing bead which, in said closed position of the valve member, extends continuously around said part-spherical surface in engagement with said part-spherical surface to seal the valve member with respect to the valve casing, said bead dividing on either side of each said shaft to pass, with clearance, on both sides of each said shaft, so that in the closed position of the valve said bead seals off each said shaft with respect to the portions of said flow passage upstream and downstream of the valve member, the forms and relative dimensions of the sealing bead and the valve member being such that in the closed position of the valve, at any circumferential position around the valve member the sealing bead lies entirely between the limits, in the direction of flow through the flow passage, of the part-spherical peripheral surface of the valve member.

2. A butterfly valve substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.

3. Any novel feature or combination of features described herein.