GB2175671A

GB2175671A - Fluid shutoff valve assembly

Info

Publication number: GB2175671A
Application number: GB08513354A
Authority: GB
Inventors: Michael John Vendy
Original assignee: Individual
Current assignee: Individual
Priority date: 1985-05-28
Filing date: 1985-05-28
Publication date: 1986-12-03
Also published as: GB8513354D0

Abstract

In a valve assembly for a ballcock unit for a water cistern, a flexible diaphragm 12 carries an integral rigid moulded male valve member of right circular conical shape. The male valve member is biased by a plunger into contact with a cooperating female surface 16 of a fixed valve seat 14 to effect valve closure. The diaphragm, including the male valve member (122) Fig. 3, (not shown), an annular peripheral sealing rim (124) and a nonplanar connecting web (126), may be injection-moulded in one piece preferably from a polyester elastomer material. <IMAGE>

Description

SPECIFICATION Shutoff valve assembly The invention relates to fluid shutoff valve assemblies. Such valve assemblies are suitable, inter alia, for use in ballcock valves of water cisterns and it is in the context of such ballcock valves that the invention will be described although it must be understood that the invention is of much more general application including use as air valves, gas valves and a variety of on-off valves for liquids.

Ballcock valves are known in which the ball or float actuates a lever arm to urge a plunger against a rubber diaphragm. Flexure of the diaphragm under the bias of the plunger causes a planar central portion of the diaphragm to seat against an annular valve seat rim of a fixed valve seat member, cutting off flow through the valve. The life span of the diaphragms of such ballcock valves is sometimes short. To achieve an efficient valve closure the diaphragm must be made of a relatively soft rubber, so that it is compressed by the annular valve seat and conforms to any surface irregularities of the valve seat. The compression is assisted by forming the valve seat as a narrow upstanding rim so that the pressure per unit area on the diaphragm is as large as possible when the diaphragm is biased against the valve seat rim.One consequence of narrowing the valve seat rim is a tendency for the valve seat rim to cut into the rubber of the diaphragm in use, with a consequent reduction in diaphragm life. Another consequence is that the valve seat rim is made more fragile and liable to damage during assembly and diaphragm changing, so that it is more liable to exhibit undesirable surface irregularities than is a broad rim. Thus at best the existing diaphragm ballcock valves are a compromise between conflicting design criteria.

The invention provides a fluid shutoff valve assembly in which a flexible diaphragm is movable relative to a fixed valve seat, wherein the diaphragm carries a rigid moulded male valve member of right circular conical shape, seatable on a cooperating conical female surface of the valve seat to effect valve closure.

Advantageously the diaphragm, the rigid moulded male valve member of right circular conical shape and an optional annular bead or peripheral sealing rim are injection moulded in one piece, with the conical moulded male valve member forming a central boss portion of the diaphragm.

Rigidity of the male conical valve member portion and flexibility of the diaphragm web can be obtained in the same moulding operation by increasing the wall thickness of the valve member portion and reducing that of the diaphragm web, and by forming the diaphragm web as a nonplanar web. For example, the diaphragm web connecting the conical valve member portion may be conical or convoluted to permit axial movement of the moulded male valve member relative to the outer periphery of the diaphragm.

The entire diaphragm may be injection moulded from a polyester elastomer material such as HYTREL (Trade Mark), made by Du Pont. This material has a low creep in tension or compression. It shows good recovery from deformation, and good flex resistance. Thin sections are flexible and resilient over a broad temperature range, with a good stretch resistance, fatigue resistance and recovery. For example, a sample of HYTREL elastomer with a Shore D hardness of 40 as measured by ASTM No. D2240 had the following properties: Tensile Strength (ASTM No. D638) =26 MPa Bashore Resilience =62% Flexural Modulus (ASTM No. D790) =48 MPa Compression Set (ASTM No. D375A) =27% Shear Strength (ASTM No. D732) =24 MPa Vicat Softening Point (ASTM No. D1525) =112"C Water Absorption/24 hours (ASTM No.D570) =0.6% In the example chosen to illustrate the invention, namely a ballcock valve, the diaphragm is moved by a float lever acting on a plunger. To illustrate the flexibility of the inventive concept, however, it is pointed out that in a valve assembly according to the invention the force acting on the diaphragm to control valve actuation may be mechanical, electromechanical, pneumatic or hydraulic. In each case a precise and controlled on/off action of the valve assembly is obtained by virtue of the ease of accurate register between the conical male valve member and the cooperating conical valve seat.

DRA WINGS: Figure 1 is an axial section through a ballcock valve of a water cistern, incorporating a fluid shutoff valve according to this invention; Figure 2 is an end view of the diaphragm used in the ballcock valve of Fig. 1, as viewed from above in Fig. 3; Figure 3 is an axial section through the diaphragm of Fig. 2; and Figure 4 is an end view of the diaphragm, viewed from below in Fig. 3.

The ballcock valve of Fig. 1 incorporates many components which are standard components in any ballcock valve complying with British Standard No. 1212. An inlet conduit 2 is externally screw threaded both for connection to a mains water supply and for mounting the ballcock assembly in a cistern or tank. At its right-hand end the inlet conduit 2 carries a valve assembly 4 to be described in greater detail hereafter, and pivotally mounted on the valve assembly 4 is a lever arm 6 which carries a ball float (not shown) for controlling the passage of mains water through the valve assembly 4. An adjustable bearing member 8 carried on the lever arm 6 abuts plunger 10 which is axially slidable in the valve assembly 4, bearing on a diaphragm 12.Lifting of the lever arm 6 causes the plunger 10 to move the diaphragm 12 to the left, bringing an integral central boss portion of the diaphragm into contact with a valve seat member 14 so as to interrupt the flow of water past a valve seat 16 and out through an outlet orifice 18.

The valve assembly 4 comprises a valve body 20 which is retained in position on the inlet conduit 2 by means of a retainer screw cap 22 which is threaded onto an external screw thread of the valve body 20, drawing the valve body onto the inlet conduit and entrapping a resilient seal 24 between opposed axial end faces of the inlet conduit 2 and the valve seat member 14 to form a liquid seal therebetween. The valve assembly 4 further comprises an end cap 26 which acts as a guide for the plunger 10 and which is secured to the valve body 20 by means of a retainer screw cap 28 threaded onto an external screw thread of the valve body. A seal is formed between the rim 30 of the end cap 26 and a peripheral portion of the diaphragm 12 as the retainer screw cap 28 draws the end cap 26 axially onto the valve body 20.

The above description is sufficiently general to include all ballcock valves made in accordance with British Standard No. 1212, Sections 1, 2 and 3. The construction of the diaphragm 12 and the valve seat 16 of the valve seat member 14 are, however, of considerable importance according to the invention Figs. 2 to 4 illustrate in greater detail the construction of the diaphragm 12. This diaphragm comprises a central boss portion 122 which is a rigid moulded male valve member of right circular conical shape, connected to an annular peripheral sealing flange 124 by means of a flexible diaphragm web 126. The entire diaphragm 12, comprising the male valve member 122, the web 126 and the sealing flange 124 is injection moulded in one piece from a polyester elastomer material such as HYTREL 40 (Trade Mark).This material has a hardness comparable to that of hard thermoset rubber formulations, but other polyester elastomers are available which are even harder, up to and including the hardness of engineering plastics. Any of these materials can be used for the diaphragm, and the rigidity of the moulded male valve member portion 122 is provided by a combination of the choice of plastics material used and the wall thickness of that portion. In contrast, the flexibility of the flexible web portion 126 is a characteristic of the non-planar shape of that portion (which in the illustrated embodiment is conical) and the relatively thin wall thickness. The construction is such that the overall linear movement of the central male valve member 122 is approximately twice the distance "d" of Fig. 3.

Fig. 3 also illustrates that the angle subtended at the vertex of the cone of the conical male valve member 122 by a diameter at its base is 60 , which is the same angle as the angle of the valve seat 16. Thus there is a particularly efficient seal formed when the male valve member 122 is moved to the left as viewed in Fig. 1 to seat against the valve seat 16.

The ballcock valve of Figs. 1 to 4 has a particularly precise shut-off action, provides a very good seal against leakage, and has been found to be exceptionally durable in use, providing a very significant reduction in the need to change the diaphragm as compared with conventional valve assemblies. The conical shape of the web 126 provides an element of snap-action which has been found to be particlarly attractive for ballcock applications, establishing a reasonably open fluid flow until the cistern is full, followed by a relatively rapid shut-off.

Claims

1. A fluid shutoff valve assembly in which a flexible diaphragm is movable relative to a fixed valve seat, wherein the diaphragm carries a rigid moulded male valve member of right circular conical shape, seatable on a cooperating conical female surface of the valve seat to effect valve closure.

2. A fluid shutoff valve assembly according to claim 1, wherein the rigid moulded male valve member is an integrally moulded central boss portion of the diaphragm.

3. A fluid shutoff valve assembly according to claim 2, wherein an integrally moulded peripheral sealing rim is provided around the diaphragm.

4. A fluid shutoff valve assembly according to claim 3, wherein the diaphragm comprises a non-planar flexible web between the central boss portion and the sealing rim, the flexibility of the web being provided by its non-planar configuration and the thickness of the material from which it is formed.

5. A fluid shutoff valve assembly according to any preceding claim, wherein the diaphragm and rigid moulded male valve member are injection moulded in one piece from a polyester elastomer material.

6. A fluid shutoff valve assembly according to any preceding claim, wherein the angle subtended at the vertex of the cone by a diameter is about 60".

7. A fluid shutoff valve assembly according to any preceding claim, wherein flexure of the diaphragm is controlled by a mechanical movable plunger acting on a rear surface of the male valve member to push it into engagement with the valve seat.

8. A ballcock valve for a water cistern, incorporating a fluid shutoff valve assembly according to any preceding claim.

9. A fluid shutoff valve assembly substantially as described herein with reference to the drawings.