GB2033057A - Butterfly valve - Google Patents

Abstract

A butterfly valve has a valve casing 1, an elastomeric lining 2 within the casing and a valve member 4 centrally mounted in the casing, within the lining 2 by means of shafts 3 extending through apertures in the wall of lining 2. The lining is formed with sealing lips 8 which encircle the shafts 3 and sealing engage the same, each lip 8 being surrounded by a respective sealing bead 6, spaced from the lip 8 outwardly away from the axis of shafts 3, which bead 6 sealingly engages the peripheral surface 7 of the valve member. The beads 6 are formed as portions of a continuous sealing bead extending around the interior of the lining and adapted to engage the peripheral surface sealingly when the valve is closed to seal the part of the flow passage upstream of the valve with respect to the part downstream. <IMAGE>

Description

SPECIFICATION Butterfly valve THIS INVENTION relates to a butterfly valve of the kind having a valve casing defining a flow passage therethrough, an elastomeric lining within said flow passage, a valve member centrally mounted in the flow passage, via aligned shaft portions supported in the casing for pivoting about the common axis of said shaft portions between an open position and a closed position, the valve member being mounted within said lining and said shaft portions extending through said lining to the valve member. A butterfly valve of the abovenoted kind is herein referred to as being "of the kind, specified".

In known valves of this kind, the usual way in which the valve is sealed in the closed position is for the valve member to be forced into the lining proper, resiliently, deforming the same. Seals of this kind give rise to special problems in the regions where the aligned shaft portions mounting the valve member extend through the lining. As a rule, the shaft-receiving apertures in the lining are expanded resiliently by the shafts, when the valve is assembled to such an extent as to provide some sealing effect.

In constructions of this kind the lining is deformed not only near the openings for the shafts but also in the sealing zone co-operating with the valve member, and so the valve member displaces material, principally near the shaft. Consequently, when the valve member is moved a torque is produced near the shaft in the layers of elastomer which extend around the shafts, with the possible result of distortions of the lining and therefore of leaks between the shaft and the lining. Previous endeavours to solve the problem have mainly been directed to providing adequate seals around the shaft portions themselves, for instance, by providing separate shaft seals, for instance, using O-rings, in the shaft-receiving bores of the valve casing.Unfortunately, in constructions of this kind the flow medium may issue between the shaft and the lining and contact the casing in the region on the side of the or each shaft seal which is exposed to the interior of the valve casing thus partly sacrificing an advantage provided by the elastomeric lining of the casing, namely, the fact that the lining protects the casing against corrosive media as well as providing sealing tightness, so that metals relatively susceptible to corrosion could be used for the casing, ceased to hold good for the region between the lining and the shaft seal or seals.

Consequently, in the region of said shaft portions of butterfly valves of the kind specified, there are two sealing problems which, if they are both to be solved satisfactorily, must be dealt with separately. However, the separation must not be physical to the extent that the flow medium can pass between the two distinct sets of seals provided for the shaft portions and for the valve member.

It is an object of the invention to provide an improved lining for a butterfly valve of the kind specified by means of which the abovementioned sealing problems may be met in a simpler and less expensive way than hitherto.

According to one aspect of the invention, there is provided an elastomeric lining for a valve member of the kind specified, the lining comprising an annular body for fitting within a said valve casing, opposing apertures, to receive said shaft portions, formed in the wall of the lining, said apertures being aligned along a common axis and the lining having, on its inner side, extending around each said aperture, a respective sealing lip extending in the direction towards the other said aperture.

According to another aspect of the invention there is provided a valve of the kind specified in which said elastomeric lining is formed in accordance with the first-mentioned aspect of the invention.

It is very little dearer to produce an elastomeric lining embodying the invention than to produce a known elastomeric lining. The sealing lips formed on the lining call for only a relatively minor alteration of the previous shape. However, this minor alteration has a considerable effect, as will be apparent more particularly from the wide variety of possible constructions for the sealing lip. For instance, the same can each have one or more O-ringsection sealing beads extending towards the shaft portions. Also, the sealing lips can be arranged to bear on the shaft portions at a presure boosted by the pressure of the flow medium.

In another advantageous development of the invention, each of the sealing lips extends into a respective annular chamber formed in the valve member and engage, in each case by way of a respective sealing edge, with a sidewall and the base of the annular chamber.

Integrating the shaft seal in the elastomeric lining makes possible an advantageous cooperation with the valve member seal. For instance, the sealing lips can have extending around them annular sealing beads disposed on the elastomeric lining, the beads being the continuation of a peripheral sealing bead which cooperates with the valve member.

Gaps which can receive lubricant are therefore left between these annular beads and the sealing lips.

An embodiment of the invention is described below with reference to the accompanying drawings in which: Figure 1 is a fragmentary view, showing part of a butterfly valve embodying the invention, in section in a plane containing the axis of a flow passage through the valve and the perpendicular pivotal axis of the valve mem ber, and Figure 2 is a,fragmentary view, showing only a fragment of the elastomeric lining of the valve of Fig. 1, and as viewed from the inside of the lining, along the axis of holes in the lining which, in the assembled valve, receive the shaft portions which pivotally support the valve member, the Figure showing the part of the lining in the region of one of said holes.

Referring to Fig. 1, a butterfly valve of the kind specified comprises a tubular casing 1 (shown only fragmentarily) which defines a flow passage for fluid, the casing 1 being short in the axial direction of said flow passage (which direction is the horizontal in Fig.

1). Fitted around the interior of the valve casing 1 is an annular elastomeric lining 2 (also shown only fragmentarily). A valve member 4 (shown only fragmentarily) is mounted in the valve casing, within the lining 2, for pivoting, between an open and closed position, the valve member being so mounted via two shafts (one of which is indicated at 3 in Fig. 1), which are aligned along a common axis, corresponding to the pivotal axis of the valve member, which axis intersects the axis of the flow passage through the valve member 4 and extends vertically in Fig. 1. These two shafts, mounted in the valve casing in respective bores extend into the casing at diametrally opposed positions, through respective apertures in the wall of the lining 2, and into the valve member 4.

Extending around the inner surface of the lining 2, and thus encircling the axis of the flow passage, is a sealing bead 5 which, in the closed position of the valve cooperates sealingly with the peripheral surface of the valve member 4 to seal off the portion of the flow passage upstream of the valve member from the portion of the flow passage downstream of the valve member.

As will be appreciated from Fig. 2, in the region of each of said shafts, the bead 5 divides into two parts which pass on opposite sides of the respective shaft to unite once more beyond the shaft, so that the portion of the bead 5 in the region of the hole for each shaft forms, as viewed radially outwards with respect to the axis of the flow passage, a respective annular sealing bead portion 6 which, as shown, is spaced outwardly from the axis of said shafts, relative to the shaft surfaces and to the edges of the apertures through which the shafts pass as a close fit.

Each said sealing bead 6 cooperates with the peripheral surface of the valve member 4, which valve member has a rounded shoulder 7 in the region of each said bead 6, so that not only is the valve member sealed with respect to the valve casing as regards fluid flow along the flow passage when the valve is closed, but each bead 6 forms a first sealing zone encircling the respective shaft and sealing the shaft with respect to the part of the flow passage in the interior of the lining 2.

Furthermore, around each said shaft portion, the lining 2 is formed with a sealing lip 8 which is annular in form and is spaced radially inwardly of the respective sealing bead 6 relative to the axis of shafts 3, the lip 8 and seal 6 both extending radially inwardly relative to the axis of the flow passage through the valve, i.e. towards the other aperture.

Each sealing lip 8 sealingly engages the periphery of the respective shaft 3 via a plurality of annular sealing ribs 9 which are rounded in section as viewed in Fig. 1 and act like O-rings. Furthermore, each sealing lip 8 extends into an annular chamber 10 defined in the valve member 4 between the periphery of the shaft 3, which fits in a bore in the member 4, and an enlarged counter-bore formed in the valve member co-axial with the last-mentioned bore.

Each lip 8 has an annular sealing rib on its peripheral surface which faces away from the axis of shafts 3, and which rib engages the outer side wall 11 of the respective annular chamber and has a further annular sealing rib or sealing edge which engages the end wall 1 2 of the respective annular chamber 1 0.

Between each lip 8 and the adjoining bead 6 there is a gap 1 3 serving to store lubricant to supply the sealing zone embodied by the shoulder 7 and bead 6. The form of lip 8 is such that, in the event of the bead 6 leaking, the lip 8 will be pressed more firmly on the shaft 3 by the pressure of the medium flowing through the valve.

Claims (10)

1. An elastomeric lining for a valve member of the kind specified, the lining comprising an annular body for fitting within a said valve casing, opposing apertures, to receive said shaft portions, formed in the wall of the lining, said apertures being aligned along a common axis and the lining having, on its inner side, extending around each said aperture, a respective sealing lip extending in the direction towards the other said aperture.

2. An elastomeric lining according to claim 1 in which the sealing lips each have one or more sealing beads encircling said common axis of the aligned apertures and extending towards said axis.

3. An elastomeric lining according to claim 1 or claim 2 including, on the inner side of the lining, around each of said sealing lips, and encircling said common axis, annular sealing beads, each formed by a longitudinally divided portion of a peripheral sealing bead extending continuously around the interior of the annular body of the lining, for engagement with the periphery of the valve member when the lining is fitted in a valve of the kind specified.

4. A lining according to claim 3 wherein an annular gap is defined between each said sealing lip and the respective said annular sealing bead, for receipt of a lubricant.

5. A butterfly valve of kind specified, wherein said elastomeric lining is a lining according to any of claims 1 to 4, said shaft portions extending through said apertures and being encircled by respective said sealing lips.

6. A butterfly valve according to claim 5 wherein said sealing lips bear sealingly on the respective said shaft portions which they encircle and wherein the arrangement is such that in operation, when the interior of the valve casing is occupied by a fluid under pressure, the fluid pressure acts on said sealing lips to increase the pressure with which the sealing lips bear on the respective said shaft portions.

7. A butterfly valve according to claim 5 or claim 6 wherein the valve member is formed, around each of said shaft portions, with a respective annular chamber coaxial with the shaft portions and open towards said elastomeric lining, and wherein each said sealing lip extends into a respective said annular chamber and has one sealing edge sealingly engaging a peripheral wall of the respective annular chamber, and another sealing edge sealingly engaging an end wall of the respective annular chamber.

8. An elastomeric lining for a butterfly valve of the kind specified, substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.

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

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