Abstract:
An apparatus and method for a diaphragm valve includes a valve body having a chamber in fluid communication with a first channel and a second channel. A diaphragm is disposed in the chamber, and a tapered seat member is at least partially disposed in the first channel. A sleeve is compressively disposed in the seat member between the seat member and the first channel to maintain a fluid tight seal between the seat member and the first channel. A valve member is movable to controllably urge the diaphragm into and out of engagement with the seat member to control flow of fluid between the first the first and second channel.

Description:
FIELD OF THE INVENTION 
   The present invention is directed to a valve construction, and more particularly, the present invention is directed to a valve seat construction for diaphragm valves. 
   BACKGROUND OF THE INVENTION 
   Valves are widely used to provide precision flow and/or pressure control of fluids. Diaphragm valves are preferred in many applications due to the valve member being directed into and out of contact with a diaphragm, which likewise directs a valve seat into and out of engagement with the diaphragm to effect the desired fluid flow/pressure control. Other attributes diaphragm valves have are low internal volume, high sealing integrity, compact size and fast actuation/operation. 
   After being subjected to operational use, especially involving caustic or abrasive fluids and/or particulates or condensates, valve components, notably the valve seats, become worn or damaged so that the valve can no longer function properly. One solution is to replace the entire valve, which requires disconnecting the old valve from the connections of the using application or system, and then re-establishing those system connections. In addition to the cost of the replacement valve, care must be taken to ensure the system connections to the replacement valve do not leak. 
   In an attempt to address this problem, replacement valve seats have been developed. For example, U.S. Pat. No. 4,715,578 to Seltzer discloses a valve seat member composed of a synthetic resin that is threadedly engaged with the valve body, including an O-ring disposed between the valve seat member and the valve body. However, for reasons including the difference in thermal coefficients of expansion/contraction between the non-metallic valve seat member and the metallic valve body, the valve seat member is susceptible to working loose from the valve body. 
   Another valve construction is U.S. Pat. No. 6,854,713 to Lin et al., that discloses a valve body having a cylindrical opening formed in a flow channel for receiving a cylindrical non-metal valve base. The opening includes a groove formed in the valve body. Once the cylindrical non-metal valve base has been inserted into the cylindrical opening in the valve body, a tapered ring is directed into the inside diameter of the cylindrical non-metal valve base. Flanges extending outwardly from the ring further compress the valve base between the ring and the valve body, with the groove formed in the valve body opening sized to receive a portion of the valve base, due to expansion of the valve base. However, while being configured to address valve base expansion, U.S. Pat. No. 6,854,713 is not directed to a replaceable valve base. Moreover, the process of press-fitting the tightly fitting ring inside the valve base will necessarily deform the surface of the valve base contacting the diaphragm, which will compromise the quality of the seal between the valve base and the diaphragm. Finally, due to a portion of the valve base flowing into the groove in the opening securing the valve base within the valve body as it is deformed, it is unlikely that the valve base can be removed without damaging the valve body, which would necessitate replacement of the entire valve. 
   What is needed is an improved valve construction that permits replacement of the valve seat without damaging the valve body, which replacement can be accomplished with a manual hand tool. 
   SUMMARY OF THE INVENTION 
   The present invention relates to a diaphragm valve including a valve body including a chamber in fluid communication with a first channel and a second channel. A diaphragm is disposed in the chamber. A tapered seat member is at least partially disposed in the first channel, and a sleeve is compressively disposed in the seat member between the seat member and the first channel to maintain a fluid tight seal between the seat member and the first channel. A valve member is movable to controllably urge the diaphragm into and out of engagement with the seat member to control flow of fluid between the first the first and second channel. 
   The present invention still further relates to a method of constructing a diaphragm valve. The method includes providing a valve body including a chamber in fluid communication with a first channel and a second channel and then inserting a valve member in the valve body. The method further includes inserting a diaphragm in the chamber and inserting a sleeve inside a tapered seat member. The method further includes inserting the seat member at least partially in the first channel, the sleeve being compressively disposed between the seat member and the first channel to provide a fluid tight seal between the seat member and the first channel. The valve member is movable to controllably urge the diaphragm into and out of engagement with the seat member to control flow of fluid between the first the first and second channel. 
   An advantage of the present invention is that it allows for replacement of a valve seat for a diaphragm valve without replacing the valve. 
   Another advantage of the present invention is that it prevents creep of a valve seat for a diaphragm valve. 
   A further advantage of the present invention is that it applies a constant compressive force to retain a valve seat in position in the valve body. 
   Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention. Corresponding reference characters indicate corresponding components throughout the several views of the drawings. Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are typically not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a partial exploded perspective view of an unassembled valve of the present invention. 
       FIG. 2  is a partial exploded cross section of an unassembled valve taken along line  1 - 1  of the present invention. 
       FIG. 3  is a cross section of an assembled valve seat member of the present invention. 
       FIG. 4  is cross section of an assembled valve of the present invention. 
       FIG. 5  is an enlarged partial cross section of an assembled valve of the present invention. 
   

   Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
   DETAILED DESCRIPTION OF THE INVENTION 
   One embodiment of a valve  10  of the present invention is depicted in  FIG. 1 . Preferably, referring to  FIGS. 1-5 , valve  10  includes a valve body  12  having a valve cavity  18  further opening into separate channels  20 ,  24  for directing a fluid through the valve body  12 . A counterbored penetration or bore  22  receives a sleeve  16  and a seat member  14  that are preassembled prior to insertion into the bore  22 . A diaphragm  28  is installed over the seat member  14 , and a collet  34  is then installed in the valve cavity  18  over the diaphragm  28 . Collectively, a lower portion  26  of the valve cavity  18 , including an annular ridge  30  extending outwardly from the valve cavity  18  and the diaphragm  28  define an enclosed region  32  for permitting the selective flow of fluid between the channels  20 ,  24 . To secure the diaphragm  28  between the annular ridge  30  of the valve body  12  and the collet  34 , a nut  36  having a tapered shoulder  62  is threadedly engaged to abut a corresponding tapered surface of the collet  34  in the valve cavity  18 . A valve member  38  is slidably disposed in an aperture  40  formed in the collet  34  for abutting the diaphragm  28 . Collectively, the lower portion  26  of the valve cavity  18 , collet  34  and valve member  38  define a chamber  31  within which the diaphragm  28  moves. 
   To controllably move valve member  38  toward the diaphragm  28 , a stem  42  applies an axial force, such as by a pressurized fluid directed through a passageway  44  formed in the stem  42 . Alternately, or in addition to the pressurized fluid, other means, such as springs (not shown) can also provide the axial forces. Upon application of sufficient axial forces by or through stem  42 , valve member  38  is urged into contact with diaphragm  28  so that diaphragm  28  abuts seat member  14  to interrupt fluid communication between channels  20  and  24 . In other words, when the valve member  38  is urged into contact with diaphragm  28  with sufficient force, a portion of the resilient diaphragm  28  is urged into abutting contact with the seat member  14  to interrupt fluid flow between channels  20 ,  24 . 
   One embodiment of a removable valve seat member  14 , as shown in assembled form in  FIG. 3 , is also shown in unassembled form in  FIG. 2 . Prior to assembly, seat member  14  includes an outer tapered portion  58 , which extends from an end  64  to an annular shoulder  60  that terminates in an opposite end  66 . Preferably, the inner surface of seat member  14  has a substantially uniform inside diameter that receives an end  68  of sleeve  16 . Similarly, sleeve  16  is a hollow cylinder of substantially constant cross section and substantially constant outside diameter. Optionally, the end opposite end  68  of sleeve  16  is flared  52 . Preferably, seat member  14  is composed of a resilient polymeric material such as polychlorotrifluoroethylene, polyetheretherketone or other suitable materials. 
   Sleeve  16  is preferably composed of metal or a material of sufficient structural strength and compatibility with valve applications and materials, and also having a substantially similar thermal coefficient of expansion/contraction as the valve body  12 . The inside diameter of seat member  14  and the outside diameter of seat  16  are sized so that end  68  of seat  16  can be directed inside of end  64  of seat member  14 . Once seat member  14  and sleeve  16  have been preassembled, end  64  of seat  16  is directed into a bore  22  and pressed into position. 
   As shown in  FIG. 2 , from the valve cavity  18 , bore  22  is disposed at the entrance to channel  20 . In one embodiment, bore  22  includes bore portions  70 ,  72 ,  74  that are substantially concentric with respect to axis  76 . Bore portion  70  has the smallest diameter of bore portions  70 ,  72 ,  74  and terminates at a base  50  in channel  20 . Adjacent to bore portion  70  is bore portion  72  which has a slightly larger diameter than bore portion  70  with the juncture between bore portions  70 ,  72  defining a ridge  48 . Similarly, adjacent to bore portion  72  is bore portion  74  which has a slightly larger diameter than bore portion  72  with the juncture between bore portions  72 ,  74  defining a ridge  46 . It is to be understood that bore portions  70 ,  72 ,  74  define a tapered profile, although the circumferential walls of the bore portions  70 ,  72 ,  74  are substantially parallel to each other. Additionally, annular ridges  46 ,  48  preferably are substantially perpendicular to axis  76 . It is also to be understood that bore  22  can include more than three base portions, if desired, and that none of the bore portions are necessarily of the same length. It is also not required that the difference in diameter between adjacent bore portions are equal. 
   It is to be understood that base portions  70 ,  72 ,  74  are not limited to a circular profile, and can include, for example, an ovular profile, nor must annular ridges  46 ,  48  necessarily be planar, that is, for example, the ridge profiles can be curved. However, both the base portions  70 ,  72 ,  74  and ridges  46 ,  48  must each be symmetric about a plane that is coincident with the axis  76  so that resultant forces developed between seat member  14 , base portions  70 ,  72 ,  74 , and sleeve  16 , during installation as well as during operation, i.e., due to pressurized fluid or temperature, are substantially equally applied to each half of the seat member  14  and sleeve  16 . It is also to be understood that sleeve  16  has a matching profile with respect to base portions  70 ,  72 ,  74  so as to ensure the spacing is also symmetric, and thus, the resulting installation and operational forces between the base portions  70 ,  72 ,  74  and the sleeve  16  are also symmetric. That is, if the base portions  70 ,  72 ,  74  are non-circular, sleeve  16  has a similarly configured non-circular profile. 
   To install the preassembled seat member  14  and sleeve  16  in the valve body  12 , end  64  of seat member  14  is directed into bore  22 . However, as shown in  FIG. 3 , a tool, such as tool  54 , is required to maintain the seat member  14  and sleeve  16  in alignment with axis  76  and to additionally urge seat member  14  and sleeve  16  toward an installed or seated position in bore  22 . In the seated position, flared end  52  of sleeve  16  abuts base  50  of bore portion  70  and the juncture of shoulder  60  and tapered portion  58  of seat member  14  abuts ridge  46 . Flared end  52  helps provide a fluid tight seal between the sleeve  16  and base  50  of base  22 . End  66  of seat member  14  extends both upwardly and outwardly from bore  22  a predetermined distance for interacting with the diaphragm  28  to control fluid flow between channels  20 ,  24 . To help provide a substantially fluid tight interface between seal member  14  and bore  22 , the inside diameter of ridge  48  is less than the outside diameter of at least a portion of tapered portion  58 . Stated another way, during installation of the seat member  14  inside of bore  22 , at least a portion of the surface of the tapered portion  58  is plastically deformed by ridge  48  as the tapered portion  58  is further pressed into the bore  22  by the installation tool  54 . Additionally, due to the presence of sleeve  16 , which substantially maintains the inside diameter of the seat member  14  by applying a constant compression force similar to a spring, the seat member  14  is plastically deformed to fit the space provided between sleeve  16  and bore  22 . As further shown in  FIG. 3 , the tapered portion  58  of seat member  14  is forced to conform to the bore portions  70 ,  72 . A small gap  56  in bore portion  50  between end  64  of the seat member  14  and the base  50  of the bore portion  70  can remain, if desired, by sizing the bore  22 , seat member  14  and sleeve  16  to account for thermal expansion of the seat member  14 . 
   The arrangement of the bore  22 , tapered seat member  14  and sleeve  16  provide numerous benefits. In addition to providing a fluid tight seal between the seat member  14  and the bore  22  as originally installed, increased fluid pressure in channel  20  results in sleeve  16  applying additional compressive forces to the seat member  14 , creating an even tighter seal. Further, the arrangement does not allow the polymeric seat member material to expand due to thermal expansion or to swell due to liquid or gas permeability into the polymeric seal material. This expansion prevention is due to the sleeve  16  providing substantially constant compression to the seat member, as well as the sleeve  16  being of sufficient structural strength to react the forces created by the polymeric seat member material during swelling or expansion. Without such expansion prevention, the seat member would otherwise be susceptible to thermal cycling, due to the polymeric seat member having a thermal coefficient of expansion/contraction that is an order of magnitude greater than that of metal, with the risk of the polymeric material “working loose” over time. In other words, during installation, the seat member  14  is sufficiently compressed so that at the extreme operating temperature, i.e., cold temperatures, the seat member  14  doesn&#39;t pull away from the bore  22 . That is, at lower temperatures when the seat member  14  is maximally contracted, the level of compression experienced by the seat member is reduced, but not eliminated, while continuing to maintain contact with the bore  22 . 
   A further advantage is its utility in response to raised valve temperatures. As the valve temperature increases, the polymeric seat member material becomes more flexible, typically lowering its ability to counteract fluid pressure. Due to the arrangement of the bore  22 , tapered seat member  14  and sleeve  16 , in response to rising valve temperature, sleeve  16  expands, tightening the seal with the polymeric material. Tightening this seal provides improved seal integrity at raised temperatures. Additionally, via the arrangement of the present invention, the seat member  14  is not susceptible to permanent plastic deformation due to prolonged exposure to stress or elevated temperature or creep. This is essentially due to the sleeve  16  being constructed of materials not susceptible to creep. 
   Moreover, an additional advantage of the arrangement of the present invention is that removal of the seat member  14  can be achieved using a common manual tool, such as a hand tap (not shown). The tapping tool can be used to engage sleeve  16  to easily and conveniently remove both the sleeve  16  and seat member  14 , requiring only manual force. Ease of removal is possible due to the tapered construction of bore  22 . 
   While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.