Abstract:
The invention is generally directed towards diaphragms and diaphragm valves with geometries that decrease stress and wear on diaphragms and increase the cycle life of diaphragms. Stresses and wear can be decreased by reducing the amount of diaphragm deflection needed to open and close a valve, or by reduce or eliminate contact between a diaphragm and other diaphragms or components.

Description:
RELATED APPLICATIONS  
       [0001]     This application claims the benefit of U.S. Provisional Applications Nos. 60/524063 filed on Nov. 21, 2003 and 60/521334 filed on Apr. 2, 2004, the entire disclosures of which are fully incorporated herein by reference. 
     
    
     FIELD OF INVENTION  
       [0002]     The present application is directed to diaphragms and diaphragm valves. More specifically, the application is directed to diaphragm valve configurations and methods of fabricating diaphragm valves which reduce wear and stress on diaphragms.  
       BACKGROUND  
       [0003]     Diaphragm valves are well known, such as those that are described in U.S. Pat. Nos. 6,092,550, 4,606,374, 5,131,627, and 6,189,861, the entire disclosures of which are fully incorporated herein by reference.  FIG. 1A  illustrates a conventional diaphragm valve A, wherein  FIG. 1B  is an enlarged illustration of the area B shown in  FIG. 1A .  
         [0004]     The valve A includes an inlet C and an outlet D formed in a valve body E. The inlet C is in fluid communication with an inlet flow passage F and the outlet D is in fluid communication with an outlet flow passage G. Inlet and outlet as used herein are for convenience as flow can be reversed in some applications through the valve A. Also formed in the valve body is a valve cavity or chamber H. The inlet flow passage F opens to the valve cavity H at a first orifice I and the outlet flow passage G opens to the valve cavity H at an orifice J. An annular valve seat K surrounds the first orifice I, and a circular domed diaphragm L is used to open and close communication between the first orifice I and the valve cavity H to thus open and close flow between the two orifices I and J as is known. When the diaphragm L is pushed downward (as viewed in  FIGS. 1A and 1B ) into contact with the valve seat K, the valve is closed. An actuator assembly M is used to control the position of the diaphragm L. The actuator assemble M may be pneumatic, hydraulic, manual or electromechanical. The actuator system M typically includes an actuator stem (not shown) that pushes on a button N in a central region of the diaphragm L. The diaphragm L typically is clamped about its periphery against the valve body E by a bonnet P to form a body seal to prevent leakage. The bonnet P is secured to the valve body E by a bonnet nut R. The diaphragm L may be plastic or metal, and the valve seat may be plastic or metal depending on the specific application of the valve A.  
         [0005]     Referring to  FIG. 2 , flow capacity through the valve from inlet to outlet is largely influenced by the flow gap S that exists between the domed diaphragm L and the valve seat K.  FIG. 2  illustrates in simplified schematic form this flow gap S. Increasing the gap S between the diaphragm L and the seat K will generally increase the flow capacity of the valve A.  
         [0006]     In the prior art example of  FIG. 2 , the diaphragm is a multi-layered diaphragm (i.e.—an upper diaphragm U is disposed over a lower diaphragm V), and is a generally hemispherical dome that has a slightly flattened profile (due to manufacturing processes rather than by design). This diaphragm L is also supported in the open position by a diaphragm backing surface T, which deforms the diaphragm L and results in a flatter profile. The surface T may be formed as part of the bonnet P. In the open position illustrated in  FIG. 2 , the multi-layer diaphragm L is subjected to stress (in the regions indicated by the lines AA) due to its generally hemispherical slightly flattened profile interfering with the diaphragm backing surface T. The rated cycle life of the diaphragm L is a function of not only the geometry, but also wear caused by direct contact with the diaphragm backing surface T. The wear can also be caused in part by the diaphragm L rubbing against the backing surface T (e.g. micro-abrasions). Such wear is cause when fluid pressure in the open position pushing the diaphragm L against the surface T and button N.  
       SUMMARY OF THE INVENTION  
       [0007]     The invention is generally directed towards diaphragms and diaphragm valves with geometries that decrease stress and wear on diaphragms and increase the cycle life of diaphragms. Stresses and wear can be decreased by reducing the amount of diaphragm deflection or by reducing or eliminating contact between two diaphragms or a diaphragm and valve components.  
         [0008]     One embodiment of the invention is a diaphragm for sealing an orifice of a valve that includes a bonnet. The diaphragm includes a diaphragm peripheral mounting portion and a sealing portion. The sealing portion includes an inner portion having a contour defined by a first radius and an outer portion having a contour defined by a second radius and extending from the diaphragm peripheral mounting portion to the inner portion. The first radius and the second radius are selected to prevent an interference with the bonnet.  
         [0009]     Another embodiment of the invention is a diaphragm assembly for sealing an orifice of a valve. The diaphragm assembly includes a first diaphragm and a second diaphragm. The first diaphragm includes a first diaphragm peripheral mounting portion and a first diaphragm deflectable portion extending inward of the first diaphragm peripheral mounting portion. The first diaphragm deflectable portion includes a first concave surface, having a first radius, and a first convex surface. The second diaphragm is disposed over the first diaphragm. The second diaphragm includes a second diaphragm peripheral mounting portion and a second diaphragm deflectable portion extending inward from the second diaphragm peripheral mounting portion. The second deflectable portion includes a second concave surface, having a second radius, and a second convex surface. The second radius is greater than the first radius when the first and second diaphragms are in a non-deformed state.  
         [0010]     Another embodiment of the invention is a diaphragm assembly for sealing an orifice of a valve that includes a first diaphragm and a second diaphragm. The first diaphragm includes a first diaphragm peripheral mounting portion and a first diaphragm deflectable portion extending inward from the first diaphragm peripheral mounting portion. The second diaphragm is disposed over the first diaphragm and includes a second diaphragm peripheral mounting portion and a second diaphragm deflectable portion. The second deflection portion includes an inner portion having a contour defined by a first radius and an outer portion having a contour defined by an second radius and extending from the second diaphragm peripheral mounting portion to the inner portion. The first radius is different than the second radius.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1A  is a cross-sectional view of a prior art valve;  
         [0012]      FIG. 1B  is an enlarged cross-sectional view of a portion of the prior art valve, indicated by reference character B in  FIG. 1A ;  
         [0013]      FIG. 2  is a cross-sectional view of a prior art multi-layered diaphragm assembled in a valve;  
         [0014]      FIG. 3  is a cross-sectional view of a diaphragm assembled into a valve, showing the valve in an open position;  
         [0015]      FIG. 4  is a cross-sectional view of a diaphragm assembled into a valve, showing the valve in a closed position;  
         [0016]      FIG. 5  is a geometric illustration of a diaphragm cross-section;  
         [0017]      FIG. 6  is a cross-sectional view of a diaphragm assembly with diaphragms of different dimensions; and  
         [0018]      FIG. 7  is a cross-sectional view of a diaphragm assembly with diaphragms of different dimensions. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]     While the described embodiments herein are presented in the context of utilizing geometries to reduce stresses and wear of diaphragms deflected to open and close valves, those skilled in the art will readily appreciate that the present invention may be used in cooperation with many different diaphragm and valve configurations and with any system in which a diaphragm is repeatedly deflected, including but not limited in any manner to: diaphragms of complex material composition, such as diaphragms formed of multiple materials pressed or welded together; multilayered diaphragm assemblies or stacks that comprise numerous diaphragms, such as five or six; valves with metal or plastic valve seats; diaphragm pumps; and acoustic devices which modulate a diaphragm to create sound. These examples are intended to illustrate the broad application of the invention for utilizing geometry to reduce stresses and wear in diaphragms. The specific design and operation of the diaphragm valves provides no limitation on the present invention except as otherwise expressly noted herein.  
         [0020]     One embodiment of a diaphragm  10  is illustrated in  FIGS. 3 and 4 .  FIG. 3  shows the diaphragm  10  assembled in a valve A in an open position.  FIG. 4  shows the diaphragm  10  in the valve A in a closed position. The diaphragm  10  is a single diaphragm. The diaphragm  10  includes a mounting portion  18  and a sealing portion  30 . When the valve A is in the open position the diaphragm  10  is in a free or relaxed state. In the free or relaxed state, the actuator system is not actively working to close the valve A and the shape of the sealing portion  30  of the diaphragm  10  is in a natural state. In the free and relaxed state, the sealing portion  30  is not hemispherical with a single radius of curvature, but rather has a variable radius of curvature with at least two different radii of curvature. The sealing portion includes an inner portion  14  and an outer portion  16 . The inner portion  14  is defined by a first radius of curvature R 1  and the outer portion  16  is defined by a second radius of curvature R 2 . The sealing portion  30  can be deflected to seal an orifice I in the valve A. The mounting portion  18  is disposed around the periphery of the sealing portion  30 . Although the sealing portion  30  is described as having first and second radii of curvature R 1 , R 2 , in practice, the sealing portion  30  may have a complex set of radii of curvature. For example, the outer portion  16  may be defined by multiple radii and deviate from a hemispheric contour. Moreover, near the clamped periphery the radii of curvature may becomes quite varied. The inner portion  14  can also have an equally complex set of radii defining its contour. Thus, as to the sealing portion  30 , the radii of curvatures of the inner and outer portions  14 ,  16  may be defined as an average radius of curvature as opposed to a single radius of curvature, particularly in the region close to the clamped periphery. In the exemplary embodiment, the average radius of the inner portion  14  is different than the average radius of the outer portion  16 .  
         [0021]     In accordance with an aspect of the invention, a radius of the inner portion  14  or the outer portion  16 , varies by location on the inner portion  14  or outer portion  16 . Referring to  FIG. 3 , the radii defining the outer portion increase as the distance away from (direction indicated by arrow W) the diaphragm mounting portion  18  increases. The radii defining the inner portion increase as the distance away from (direction indicated by arrow X) the outer portion  16  increases.  
         [0022]     In the exemplary embodiment, the diaphragm  10  is configured to avoid or minimize contact with the bonnet P when in the relaxed or free state of  FIG. 3 . By increasing the average radius of the inner portion  14 , the inner portion is flattened and the profile and dome height of the diaphragm  10  are lowered. The diaphragm  10  in  FIG. 3 , with a flattened inner portion  14 , avoids the contact or interference with the bonnet P that is seen in  FIG. 2 , where the diaphragm L has a conventional profile. In addition to avoiding contact with the bonnet P when the diaphragm  10  is in a free and relaxed state, the lower profile and dome height allow the sealing portion  30  to experience some movement or expansion, due to pressure from fluid flow through the valve in the open position, and avoid or minimize interference or contact with the bonnet P.  
         [0023]     In accordance with an aspect of the invention, the radius of curvature R 1  is significantly greater than the radius of curvature R 2 , so that the inner portion  14  of the diaphragm  10  is significantly flattened as viewed in profile. Such a flattening of the diaphragm  10  maintains a substantial flow gap S′, but with significantly reduced stress in the deflected diaphragm  10 , as shown in  FIG. 4 . In conventional diaphragms, large flow gaps require greater diaphragm deflection to achieve valve closure. As the necessary deflection increases, the stress on the diaphragm material also increases. The magnitude of the stress experienced by the diaphragm with each valve cycle (on/off cycle) has a significant influence on the cyclic lifetime of the diaphragm, with greater stress leading to fewer cycles and thus a lower rated cycle life. The flattened profile resulting from a radius of curvature R 1  significantly greater than the radius of curvature R 2  provides for less diaphragm deflection to achieve valve closure, which leads to reduced stress in the diaphragm  10  and a longer cycle life as compared to traditional diaphragms.  
         [0024]     As described above, the radius of curvature R 1  of the inner portion  14  and the radius of curvature R 2  of the outer portion  16  can be selected in a manner that avoids or minimizes interference between the diaphragm  10  and the bonnet P. For example, the radius of curvature R 1  of the inner portion  16  may be at least two ( 2 ) times as great as the radius of curvature R 2  of the outer portion  14 , and particularly about twice as great as the average radius of curvature near the diaphragm periphery. The general appearance of the diaphragm is that of a dome with the inner portion significantly flattened, which provides an increased flow gap at a given dome height and reduced diaphragm stress at a given deflection. When the inner portion  14  radius of curvature R 1  is at least twice the outer portion  16  radius of curvature P 2  the bonnet P does not interfere with the diaphragm when the valve A is in an open position and the diaphragm  10  is in a relaxed or free state. An example of such an embodiment is a diaphragm with an inner portion  14  radius of curvature R 1  equal to 4.718 inches and an outer portion  16  radius of curvature R 2  equal to 1.978 inches. This example produces a dome height of 0.0290 inches. A conventional diaphragm with a single radius of curvature equal to 2.356 inches produces a dome height of 0.0340 inches.  
         [0025]     Selecting radii to avoid or minimize contact between the diaphragm  10  and the bonnet P can also be achieved by R 1  to R 2  ratios that are less than 2 to 1. In addition, R 2  can be larger than R 1 . Increasing the radius of either the inner portion  14  or the outer portion  16  will reduce the dome height of the diaphragm  10  and reduce the likelihood of the diaphragm  10  interfering with the bonnet P. In another aspect of this embodiment, either R 1  or R 2  can approach infinity, which would produce an inner or outer portion that is substantially flat. An inner portion  14  radius of curvature R 1  approaching infinity produces a substantially flat inner portion  14 , resulting in a lower dome height than conventional diaphragms.  
         [0026]      FIG. 3  shows the actuator system M in contact with the diaphragm  10 , through the button N, in the free or relaxed state. In this state, the button N merely “sits” on the diaphragm  10  under the force of gravity, as the button is loosely retained within the bonnet. Thus, there are no large stresses applied to the diaphragm  10  by the actuator system M when the diaphragm  10  is in a free or relaxed state.  
         [0027]      FIG. 4  illustrates the diaphragm  10  deflected into the closed position by the actuator system exerting a force F 1  on the diaphragm  10  though the button N.  FIG. 5  illustrates geometrically how the flattened profile is provided by an inner portion  14  radius of curvature R 1  that is about twice the radius of curvature R 2  of outer portions  16  of the diaphragm  10 . As is shown in  FIG. 5 , the contour of the inner portion  14  is generally defined by the radius of curvature R 1  and the outer portion  16  is generally defined by the radius of curvature R 2 .  
         [0028]     One embodiment of a diaphragm assembly or diaphragm stack  40  is illustrated in  FIG. 6 . The diaphragm assembly  40  is shown in cross-section and includes two diaphragms  11 ,  12 . The diaphragm assembly  40  can be used in place of the single diaphragm  10  used in the valve A illustrated in  FIGS. 3 and 4 .  
         [0029]     In the example of  FIG. 6 , the diaphragm assembly  40  includes a lower diaphragm  11  and an upper diaphragm  12 , with the upper diaphragm  12  overlaying or disposed over the lower diaphragm  11 . The illustrated diaphragms  11 ,  12  each include an outer peripheral mounting portion  18 A,  18 B respectively. The peripheral mounting portions  18 A,  18 B are sealingly clamped between the valve body E and the bonnet P. The diaphragms  11 ,  12  thus provide a body seal for the valve assembly. The diaphragms  11 ,  12  also include deflectable portions  20 ,  22  that extend inward from the outer peripheral mounting portions  18 A,  18 B respectively. The deflectable portions  20 ,  22  are generally, although not exclusively, arcuate or dome shaped. The deflectable portion  20  of the lower diaphragm  11  includes a concave surface  28 , with a radius of curvature R 3 , and a convex surface  26  with a dome height H 2 . The deflectable portion  22  of the upper diaphragm  12  includes a concave surface  24 , with a radius of curvature R 4 , an inner dome height Hi, and a convex surface  29 .  
         [0030]     Conventionally, diaphragms that comprise multi-layer diaphragms are manufactured to have substantially the same dimensions and geometry. When such conventional diaphragms are assembled as a multi-layered diaphragm into a valve, the upper diaphragm is forced over the lower diaphragm with an end result of both diaphragms undergoing deformation. This deformation causes stresses in both diaphragms. In addition, this deformation results in the lower surface of the upper diaphragm being forced into contact with the upper surface of the lower diaphragm. This contact causes additional wear as the upper and lower diaphragms rub against each other as the multi-layered diaphragm is moved into position to close or open the valve. Elimination or reduction of the stresses due to deforming diaphragms during assembly and the elimination or reduction of wear due to diaphragms rubbing against one another when the valve is opened and closed can lengthen the cycle life of multi-layered diaphragms.  
         [0031]     In accordance with the embodiment illustrated in  FIG. 6 , the two diaphragms  11 ,  12  do not have the same dimensions and geometry. The upper diaphragm  12  is generally larger than the lower diaphragm  11 . This allows the upper diaphragm  12  to be disposed over the lower diaphragm  11  with either an elimination of dimensional interference or a lessening of demensional interference. Either the elimination of interference or a lessening of interference will have the result of lessening the stress on the diaphragms  11 ,  12  when the diaphragms  11 ,  12  are assembled into a diaphragm assembly  40 , as compared to conventional diaphragms assemblies.  
         [0032]     The diaphragms  11 ,  12  have generally congruent outer diameters D and closely overlay each other along their peripheries. The inner dome height Hi, arc length, and surface area of the lower surface  24  of the upper diaphragm  12  are about equal to or greater than the dome height H 2 , arc length, and surface area of the upper surface  26  of the lower diaphragm  11 . These dimensional relationships improve the nesting or stacking of the two diaphragms  11 ,  12  and reduce interference, as compared to conventional diaphragms. The reduced interference lessens the deformation of the diaphragms  11 ,  12  in the diaphragm assembly  40 , thus reducing the stress as well as wear.  
         [0033]     In the embodiment illustrated by  FIG. 6 , the upper diaphragm  12  is larger than the lower diaphragm  11  when comparing the concave surfaces  28 ,  24  of the diaphragms  11 ,  12 . Configuring radius R 4  to be larger than radius R 3  improves the nesting or stacking of the diaphragms  11 ,  12 . In an exemplary embodiment, the radius R 4  defining the concave surface  24  of the upper diaphragm  12  is larger than the radius R 3  defining the concave surface  28  of the lower diaphragm  11 , where the radii R 3 , R 4  are measured prior to disposing the upper diaphragm  12  over the lower diaphragm  11 , when the diaphragms  11 ,  12  are in a non-deformed state. A radius R 4  that is larger than radius R 3  results in a surface area of the concave surface  24  of the upper diaphragm  12  that is larger than the surface area of the concave surface  28  of the lower diaphragm  11 .  
         [0034]     In one embodiment the difference in the geometry and dimensions of the diaphragms  11 ,  12  is large enough to create a gap between the upper  12  and lower  11  diaphragms when the diaphragms  11 ,  12  are assembled. In another embodiment the difference in the geometry and dimensions are small enough to allow the diaphragms  11 ,  12  to touch along the lower surface  24  of the upper diaphragm  12  and the upper surface  26  of the lower diaphragm  11 . Provided there are differences that make the upper diaphragm  12  larger than the lower diaphragm  11  in the non-deformed state, the stresses on the diaphragms  11 ,  12 , once they are assembled, will be less than the stresses on assembled diaphragms that are substantially similar in geometry and dimensions.  
         [0035]     In the example of  FIG. 6  the diaphragms  11 ,  12  have a general dome or arcuate shape. The example of  FIG. 7  illustrates diaphragms with more complex geometries, of the type shown in  FIGS. 3 and 5 . If the dimension of an upper diaphragm make the upper diaphragm larger than the lower diaphragm, diaphragms of any geometry are more easily assembled or stacked and are subject to less stress when assembled. Referring to  FIG. 7 , the surface area of the inner surface  24  of the upper diaphragm  12  is larger than the surface area of the inner surface  28  of the lower diaphragm  11 . This allows the diaphragms  11 ,  12  to be dimensioned in a manner to allow a gap between the upper and lower diaphragms  11 ,  12  or allows the inner surface  24  of the upper diaphragm to be in contact with the outer surface  26  of the lower diaphragm and still result in lower stresses on the assembled diaphragms  11 ,  12  than if the diaphragms  11 ,  12  were substantially similar in dimensions.  
         [0036]     Additional aspects of the invention directed to a multi-layered assembled diaphragm of different dimensions are: utilizing diaphragms of different thicknesses within the same assembly; utilizing diaphragms made of different material within the same assembly; and placing lubricant between the upper and lower diaphragms. Diaphragms of differing thicknesses or differing materials may offer different resistances to forces. Such forces may be applied to diaphragms by the actuator system or from the pressure of fluid flowing through the valve. Combining diaphragms of different thicknesses or materials allows for greater flexibility in providing the proper resistance to such forces in valves that serve different purposes. Examples of materials that may be used for manufacturing diaphragms are elgiloy, hastelloy, MP35N alloy, and 316 stainless steel. Placing lubricant between the upper and lower diaphragms in a multi-layer diaphragm assembly can reduce stresses and wear on the diaphragms. As a diaphragm assembly is deflected to seal a valve, the upper diaphragm may rub against the lower diaphragm. A lubricant may reduce the stresses and wear experience by the diaphragms by reducing the coefficient of friction between the upper and lower diaphragms. Examples of lubricants that may be applied to diaphragms are krytox, polytetrafluoroethylene (PTFE), and tungsten disulphide (WS 2 ).  
         [0037]     While various aspects of the invention are described and illustrated herein as embodied in combination in the exemplary embodiments, these various aspects may be realized in many alternative embodiments, either individually or in various combinations and sub-combinations thereof. Unless expressly excluded herein all such combinations and sub-combinations are intended to be within the scope of the present invention. Still further, while various alternative embodiments as to the various aspects and features of the invention, such as alternative materials, structures, configurations, methods, devices, and so on may be described herein, such descriptions are not intended to be a complete or exhaustive list of available alternative embodiments, whether presently known or later developed. Those skilled in the art may readily adopt one or more of the aspects, concepts or features of the invention into additional embodiments within the scope of the present invention even if such embodiments are not expressly disclosed herein. Additionally, even though some features, concepts or aspects of the invention may be described herein as being a preferred arrangement or method, such description is not intended to suggest that such feature is required or necessary unless expressly so stated. Still further, exemplary or representative values and ranges may be included to assist in understanding the present invention however, such values and ranges are not to be construed in a limiting sense and are intended to be critical values or ranges only if so expressly stated.