WO2004083694A1

WO2004083694A1 - Diaphragm valves and diaphragms therefor

Info

Publication number: WO2004083694A1
Application number: PCT/GB2004/001175
Authority: WO
Inventors: Vicki Jane Johansen
Original assignee: Crane Process Flow Technologies Ltd
Current assignee: Crane Process Flow Technologies Ltd
Priority date: 2003-03-19
Filing date: 2004-03-19
Publication date: 2004-09-30
Anticipated expiration: 2005-09-19
Also published as: GB0306302D0; GB2399616A

Abstract

A diaphragm (1) for a diaphragm valve includes a peripheral zone (2) which in use is compressed between a flange provided on a valve body and a flange provided on an operating mechanism. The diaphragm (1) includes a relatively flexible inner region (6) and a relatively rigid outer peripheral region (7). The outer peripheral region incorporates a reinforcing element (8) which is substantially completely moulded into the material of the diaphragm so that it is not visible from the exterior of the diaphragm. The reinforcing element (8) may be in the form of a perforated plate (9) of suitable metal. The reinforcing element reduces compression set of the diaphragm periphery to the extent that relatively compressible material such as butyl rubber may be used without the need for periodically re-tightening the diaphragm fixing members.

Description

DIAPHRAGMVALVESAND DIAPHRAGMS THEREFOR

This invention relates to a diaphragm valve, and to a diaphragm for a diaphragm valve.

A diaphragm valve is a type of valve which includes a valve body which defines an inlet port, an outlet port, and a diaphragm opening. A diaphragm is secured to the diaphragm opening in a fluid-tight manner to define with the valve body a flow passage which extends from the inlet port to the outlet port. An operating mechanism is provided for controlling the configuration of the diaphragm. In one extreme configuration of the diaphragm the diaphragm is pressed into engagement with a weir defined on the valve body to close the passage to fluid flow. In the opposite extreme position of the diaphragm, the diaphragm is at a maximum spacing from the weir to open the valve fully to fluid flow. In intermediate configurations a limited space is defined between the weir and the opposing surface of the diaphragm to control the flow area of the flow passage.

Diaphragm valves are a common industrial product and are available from many sources. The materials of the valve body and of the diaphragm are chosen in light of the line media to be controlled. In many applications the known characteristics of isoprene isobutylene rubber (also known as HR or butyl rubber) would render it highly suitable for the construction of diaphragm valve diaphragms. Butyl rubber is a highly saturated hydrocarbon and the polymer chain structure results in physical properties which are well known for good vibration and shock damping characteristics. However, when compounded for use as a diaphragm to provide good flex, temperature and chemical resistance properties heretofore the application of butyl rubber in the construction of diaphragms has been limited (subject to re-tightening) by the compression set characteristics of the material. The manner in which the diaphragm is secured to the diaphragm valve body is by providing a flange on the diaphragm valve body and a flange on the cover of the valve operating mechanism. The two flanges are secured to each other with suitable releasable fastenings with a peripheral portion of the diaphragm trapped between the flanges. Because of the compression set characteristics of butyl rubber some re-tightening of the releasable fastenings is necessary especially after thermal cycling if an adequate seal between the diaphragm periphery and the diaphragm body flange is to be maintained. Re-tightening or checking of the fastenings torque is a time-consuming requirement in the context of industrial processing.

We have now devised a system whereby the stiffness of the peripheral region of a diaphragm may be increased and the tendency of the peripheral region to suffer from compression set may be reduced. Accordingly, the present invention makes it practicable to utilize butyl rubber as a construction material for the diaphragm of a diaphragm valve. It is to be noted, however, that the present invention may be applied to a wide range of materials and is not limited to diaphragms constructed exclusively or even partly from butyl rubber.

According to one aspect of the present invention a diaphragm valve comprises: a valve body which defines an inlet port, an outlet port, and a diaphragm opening; a diaphragm secured to the diaphragm opening in a fluid-tight manner to define with the valve body a flow passage which extends from the inlet port to the outlet port; an operating mechanism for controlling the configuration of the diaphragm between a first extreme configuration in which the diaphragm is pressed into engagement with a weir defined on the valve body to close the passage to fluid flow and a second extreme configuration in which the diaphragm is at a maximum spacing from the weir to open the valve fully to fluid flow; wherein the diaphragm incorporates a substantially rigid reinforcing element extending around substantially the entire periphery of the diaphragm, the reinforcing element being substantially completely encapsulated within the material of the diaphragm for resisting compression setting of the material of the diaphragm.

In the preferred embodiment of the invention the reinforcing element includes a first region which extends to a location adjacent one major surface of the diaphragm and a second region which extends to a location adjacently the opposite major surface of the diaphragm, the first and second regions being radially offset from each other. In the preferred embodiment of the invention the first region is adjacent the outer surface of the diaphragm and the second region is adjacent the inner surface of the diaphragm, the second region being located radially outwardly of the first region. Preferably, the first and second regions are interconnected by a portion of the reinforcing element which extends substantially parallel to the first and second major surfaces of the diaphragm. Preferably, one of the first and second regions is located immediately adjacent the radial extremity of the diaphragm and the second region is located adjacent a sealing bead provided on the diaphragm spaced radially inwardly from the radially outer extremity of the diaphragm. Preferably, when viewed in transverse cross-section the reinforcing element comprises a substantially horizontal central region, a first leg extending upwardly from one extremity of the horizontal region, and a second leg extending downwardly from the opposite extremity of the horizontal region. Such a reinforcing element can readily be formed from suitable perforated material by a stamping process.

Preferably the reinforcing element is in the form of a perforated plate to enhance the mechanical connection between the material of the plate and the material of the diaphragm. In the preferred embodiment of the invention the diaphragm is a perforated steel plate.

In the preferred embodiment of the invention the reinforcing element at least partially surrounds any holes provided in the diaphragm for the passage of releasable fastenings used to secure the operating mechanism flange to the body flange of the valve.

The invention will be better understood from the following description of a preferred embodiment thereof, given by way of example only, reference being had to the accompanying drawings wherein:

Figure 1 is a partly broken away side view of an embodiment diaphragm in accordance with the present invention;

Figure 2 is a schematic isometric view showing a portion of a diaphragm in accordance with the present invention;

Figure 3 is a bottom plan view of the diaphragm of Figures 1 and 2;

Figure 4 is a side view of the reinforcing element of the diaphragm of Figures 1-3;

Figure 5 is an isometric view of the reinforcing element of Figure 4; and

Figure 6 is a cross-sectional view of a peripheral region of the diaphragm of Figures 1-3.

The drawings illustrate a diaphragm 1 for use in a diaphragm valve. As will be understood by those skilled in the art, in use the diaphragm 1 will be secured to a valve body by compressing the peripheral zone 2 of the diaphragm between a flange provided on the valve body (which engages the underside 3 of the diaphragm) and a flange provided on an operating mechanism, for example a bonnet assembly, which engages the upper surface 4 of the peripheral region 2. The respective flanges are secured together using appropriate fastenings, typically releasable fastenings. The releasable fastenings may, for example, be in the form of screws which engage threaded openings in the body flange. A boss 5 is provided in the central region of the diaphragm for connection to the operating mechanism.

Referring now to Figure 2 the diaphragm 1 includes a relatively flexible inner region 6 and a relatively rigid outer peripheral region 7. The region 6 is typically formed of a suitable rubber compound, for example butyl rubber and may be provided with reinforcing material, for example layers of woven or non- woven fabric. The outer peripheral region incorporates a reinforcing element 8 which is substantially completely moulded into the material of the diaphragm so that it is not visible from the exterior of the diaphragm. Reinforcing material provided in the inner region 6 may extend to overlap the reinforcing element 8 or may stop short of the reinforcing element 8 so that a narrow un-reinforced area of the diapliragm exists between the flexible reinforcing material and the substantially rigid reinforcing element 8.

The reinforcing element 8 is shown in greater detail in Figures 4 and 5. It is in the form of a perforated plate 9 of suitable material, for example steel. As viewed in the drawings, the reinforcing element includes a substantially horizontal central region 10 which, as illustrated in Figure 6, extends substantially parallel to the adjacent upper surface 11 and lower surface 12 of the diaphragm. At the radially inner end of the surface 10 a first leg 13 extends upwardly to terminate in a region 14 located adjacent the upper surface 11 of the diaphragm. At the radially outer extremity of the surface 10 a second leg 15 extends downwardly to a region 16 located adjacent the lower surface 12 of the diaphragm. Preferably, the lower surface 12 of the diaphragm incorporates a raised sealing bead 17 which has a radial location substantially corresponding to the radial location of the first leg 13 of the reinforcing element. It will be noted from Figure 5 that the reinforcing element has cut-out regions 18 which correspond to through holes 19 provided in the diaphragm for the passage of bolts or screws.

It has been found that the provision of a reinforcing element in accordance with the present invention substantially enhances the mechanical properties of the peripheral region of the diaphragm. The peripheral region is considerably stiffened by the presence of the reinforcing element and compression set is reduced to such an extent that diaphragm materials for general engineering applications, for example butyl rubber, may now be utilized without the need for periodical re- tightening of the diaphragm fixing element under certain conditions. It will be noted that in the illustrated embodiment of the invention the reinforcing element is completely encapsulated within the material of the diaphragm. Whilst this arrangement is preferred there may be applications in which the outer radial surface 20 of the reinforcing element may be exposed to show the presence of the reinforcing element. Additionally or alternatively the reinforcing element preferably has a tab 21 which is over-moulded with the material of the diaphragm to provide a radial projection 22 which can carry information such as the material of the diaphragm and the fact that the diaphragm is reinforced. The stiffening of the projection 22 provided by the tab 21 will of itself provide a physical indication that the diaphragm periphery is reinforced.

Claims

CLAIMS:

1. A diaphragm valve comprising a valve body which defines an inlet port, an outlet port, and a diaphragm opening; a diaphragm secured to the diaphragm opening in a fluid-tight manner to define with the valve body a flow passage which extends from the inlet port to the outlet port; an operating mechanism for controlling the configuration of the diaphragm between a first extreme configuration in which the diaphragm is pressed into engagement with a seat defined on the valve body to close the passage to fluid flow and a second extreme configuration in which the diaphragm is at a maximum spacing from the seat to open the valve fully to fluid flow; wherein the diaphragm incorporates a substantially rigid reinforcing element extending around substantially the entire periphery of the diaphragm, the reinforcing element being substantially completely encapsulated within the material of the diaphragm for resisting compression setting of the material of the diaphragm.

2. A diaphragm valve according to Claim 1 wherein the reinforcing element includes a first region which extends to a location adjacent one major surface of the diaphragm and a second region which extends to a location adjacently the opposite major surface of the diaphragm, the first and second regions being radially offset from each other.

3. A diaphragm valve according to Claim 2 wherein the first region is ad acent the outer surface of the uiapiiragni and the second region is adjacent the inner surface of the diaphragm, the second region being located radially outwardly of the first region.

4. A diaphragm valve according to Claim 2 or Claim 3 wherein the first and second regions are interconnected by a portion of the reinforcing element which extends substantially parallel to the first and second major surfaces of the diaphragm.

5. A diaphragm valve according to any of Claims 2 - 4 wherein one of the first and second regions is located immediately adjacent the radial extremity of the diaphragm and the other of the first and second regions is located adjacent a sealing bead provided on the diaphragm spaced radially inwardly from the radially outer extremity of the diaphragm.

6. A diaphragm valve according to any preceding claim wherein when viewed in transverse cross-section the reinforcing element comprises a substantially horizontal central region, a first leg extending upwardly from one extremity of the horizontal region, and a second leg extending downwardly from the opposite extremity of the horizontal region.

7. A diaphragm valve according to any preceding claim wherein the reinforcing element is formed from perforated material by a stamping process.

8. A diaphragm valve according any preceding claim wherein the reinforcing element is in the form of a perforated plate to enhance the mechanical connection between the material of the plate and the material of the diaphragm.

9. A diaphragm valve according to Claim 8 wherein the reinforcing element is a perioratcu steei piate.

10. A diaphragm valve according any preceding claim wherein the reinforcing element at least partially surrounds the holes provided in the diaphragm for the passage of releasable fastenings used to secure the operating mechanism flange to the body flange of the valve.

11. A diaphragm valve substantially as hereinbefore described with reference to the accompanying drawings.