GB2247937A - Ballcock diaphragm valve - Google Patents

Abstract

A ballcock diaphragm valve comprises a diaphragm valve member 40 and an associated valve seat member 48. The valve member 40 comprises a central valve closure portion 44 which has the shape of a truncated cone, and which projects axially from the centre of a disc-shaped diaphragm which is formed with at least two concentric corrugations 52 and 54. The outermost corrugation 52 is substantially thinner walled and therefore more flexible than the inner corrugation 54. The central valve closure portion 44 may project forwardly from the general plane of the diaphragm on a stem portion 50 that is tapered, but at a lesser angle of taper than that of the valve closure portion 44. <IMAGE>

Description

TITLE: Ballcock Diaphragm Valve DESCRIPT1ON Field of the Invention The invention relates to diaphragm valves and diaphragm assemblies for ballcock valves that are manufactured to British Standard No. 1212 Part 2.

Background Art Diaphragm ballcock valves manufactured to the above British Standard are well-known, and utilise a resilient diaphragm which in use is deflected against the sealing rim of a valve member to interrupt the flow of water through the valve. The water supply is through a central passage through the valve seat, and directed towards the diaphragm. The raising of a float by the water level in a reservoir causes a push rod to deflect the diaphragm until it is seated against the seat to interrupt the flow.

Conventional diaphragm ballcock valve assemblies have utilised a rubber diaphragm with a central bearing pad for pressing against the valve seat to interrupt the flow of water. The bearing pad is provided with a planar face for contacting the valve seat, and when the valve is open or partially open the jet of water passing through the valve orifice is directed normally against the bearing pad of the diaphragm. In use, the rubber diaphragm does perish in water, and this perishing is exacerbated by the very high local pressure of the valve seat on the diaphragm when the valve is closed.

In recent years, there has been a policy of increasing mains water pressures, leading to a greater frequency of pressure surges, particularly at non-peak usage times.

The rubber materials that have been used in ballcock valves for very many years are now proving inadequate and the incidence of leaking valves has greatly increased. In addition the increased pressures worsen the corrosion of the rubber in known valves so that they need to be replaced more frequently. There therefore exists a demand for ballcock valves made of wearresistant materials and capable of withstanding high pressures so as to be essentially maintenance free.

Valves are known (although not diaphragm ballcock valves) in which the valve member and valve seat are both conical surfaces. That shape of valve surface has the advantage that the bearing pressures between the valve member and valve seat can be much less to achieve a given degree of valve sealing in the closed condition, and both mating valve parts can be made from a relatively hard plastics material.

Summary of the Invention The development of the invention began with the initial premise that it might be desirable to replace the flat rubber seating pad of the known diaphragm ballcock valves with a conical valve surface cooperating with a complementary conical surface of the valve seat, thereby to achieve the advantages of reduced wear and increased sealing capacity known from other applications of conical valves. Surprisingly, it was found that no such simple combination was satisfactory in practice. Initially it was found that such conically seating valves were extremely noisy in operation, with the conical valve member vibrating laterally to produce quite an unacceptable degree of noise during the early stages of valve opening or the last stages of valve closing.No such lateral vibration is experienced when the valve member is planar as in the prior art, and it is thought that the adoption of a conical shape imparts radial forces on the valve member which, if positioned at the centre of the flexible diaphragm, is therefore free to undergo rapid and noisy vibratory movement.

The above problem has been solved by adopting a very specific shape of diaphragm valve which resists the lateral vibration and which provides all of the anticipated advantages of a conically seating valve.

The valve member of the invention comprises a central valve closure portion which has the shape of a truncated cone, and which projects axially from the centre of a disc-shaped diaphragm which is formed with at least two concentric corrugations, of which the outermost corrugation is substantially thinner walled and therefore more flexible than the inner corrugation. If there were more than two coaxial rings of corrugations, then it would be desirable for the flexibility to increase progressively from the outside towards the valve element at the centre.

It has further been found that the noise of operation can be reduced by having the frustoconical valve surface project forwardly from the general plane of the diaphragm on a stem portion that is tapered, but at a lesser angle of taper than the valve surface itself.

The new valve construction enables the parts to be made of hard, extremely wear-resistant plastics materials, the preferred materials being polypropylene for the valve seat and HYTREL 4056 NAT (a trade mark of Du Pont) for the diaphragm member.

The invention also provides an improvement in the mounting of the valve seat element, which preferably is formed with a tapered outer rim on which it seats on the metal of the ballcock valve fitting.

Drawings Figure 1 is a side elevation of a diaphragm ballcock valve manufactured to British Standard No. 1212 Part 2.

Figure 2 is an axial section through a valve chamber of the ballcock valve of Figure 1, showing a prior art diaphragm and valve seat member; and Figure 3 is an axial section similar to that of Figure 2, but showing a diaphragm and valve seat according to the invention.

Referring first to Figure 1, the diaphragm ballcock valve assembly comprises a valve chamber 10 for connection to a cold water supply through an externally screw-threaded inlet pipe 12. An exit port 14 leads from the valve chamber 10 to discharge the mains water into a reservoir or tank in which the ballcock valve assembly is fitted, the water level in the reservoir being controlled by a float 16 carried on a float lever 18 pivotally mounted to the outside of the valve chamber 10 by a pivot pin 20.

When the float lever 18 is raised, a heel portion 22 thereon bears against a plunger member 24 which actuates the diaphragm within the valve chamber 10 to interrupt the water supply.

Figure 2 shows the arrangement of diaphragm and valve seat in a known diaphragm ballcock valve according to BS 1212 Part 2. A diaphragm 30 is entrapped between mating parts of the valve chamber 10, with an outer bead 32 of the diaphragm being received in an annular recess in one of those mating parts. The diaphragm 30 comprises a flexible wall formed with a single circular convolutional pleat 34 between the outer bead 32 and a central planar disc portion 36. That disc portion 36 receives the bias of the plunger member 24 to urge it to the right, to the position illustrated in Figure 2, into contact with a valve seat 38 when the float lever 18 is raised. In that condition the flow of water from the mains supply in the direction of the arrow A is interrupted.

The diaphragm 30 is of unitary construction, and made from moulded rubber. Unfortunately the life span of rubber in an aqueous environment is relatively short, and such diaphragms have to be replaced periodically.

The life span of the diaphragm is further reduced by the fact that the zone of contact between the disc portion 36 of the diaphragm and the valve seat 38 is relatively small, producing high pressure loadings.

Figure 3 illustrates how the ballcock valve assembly of Figure 1 can be used with a diaphragm and valve seat according to this invention. The diaphragm valve member 40 comprises an outer bead 42 similar to the bead 32 of Figure 2, for a peripheral anchorage of the diaphragm in the valve chamber 10. The diaphragm valve member 40 further comprises a valve member portion 44 which is formed as a truncated 60 cone for mating precisely with a correspondingly shaped conical mouth 46 of a valve seat 48. The valve member portion 44 is formed at the distal end of a conical projection 50 which extends axially from the diaphragm valve member 40. The cone angle of the conical projection 50 is of the order of 10".

Between the outer bead 42 and the conical projection 50, the diaphragm valve member 40 is formed as a convoluted connecting diaphragm web which is formed as two concentric circular convolutions 52 and 54. The radially outer convolution or corrugation 52 is thinner walled and therefore more flexible than the radially inner convolution or corrugation 54, and it has been found that this has the result that radial vibration of the valve member portion 44 in use is reduced to an acceptable minimum.

The diaphragm valve member 40 of Figure 3 is preferably injection moulded from a hard but flexible plastics material such as that sold under the Trade Mark HYTREL 4056 NAT by E I Du Pont de Namurs, which suffers minimal wear during operation of the valve.

The valve seat 48 is preferably injection moulded from a hard plastics material such as polypropylene, and is shown in Figure 3 as having an outer conical surface 56 to ensure an accurate seating on the brassware of the ballcock valve assembly. The taper of the conical surface 56 is such that the seating is assisted by the mains water pressure.

A test carried out under simulated working conditions produced the result that a typical brass ball valve of the prior art, manufactured according to British Standard 1212 Part 2, began to leak at a hydrostatic pressure of 1.9 MPa (275 p.s.i.). Under the same conditions, a valve according to the present invention did not begin to leak until a hydrostatic pressure of 5.9 MPa (850 p.s.i.) was reached, indicating that the valve of the invention had a sealing capacity 210% above that of the prior art valve.

Claims (8)

1. A ballcock diaphragm valve comprising a central valve closure portion which has the shape of a truncated cone, and which projects axially from the centre of a disc-shaped diaphragm which is formed with at least two concentric corrugations, of which the outer most corrrugation is substantially thinner walled and more flexible than the inner corrugation.

2. A ballcock diaphragm valve according to claim 1, in which the frustoconical surface of the central valve closure portion projects forwardly from the general plane of the diaphragm on a stem portion that is tapered, but at a lesser angle of taper than the valve surface itself.

3. A ballcock diaphragm valve according to claim 1 or claim 2, in which the cone angle over the central valve closure portion is 60".

4. A ballcock diaphragm valve according to any preceding claim that has been injection moulded from a hard but flexible plastics material.

5. A ballcock diaphragm valve substantially as described herein with reference to Figure 3 of the drawings.

6. A diaphragm valve assembly comprising a ballcock diaphragm valve according to any preceding claim, in association with a valve seat member which has a valve seating surface that is conical and complimentary to the truncated conical shape of the central valve closure portion of the ballcock diaphragm valve.

7. A diaphragm valve assembly according to claim 6, in which the valve seat member is formed with an outer conical surface to ensure an accurate and fluid-tight seating on the housing of the ballcock valve assembly.

8. A diaphragm valve assembly substantially as described herein with reference to Figures 1 and 3 of the drawings.