Abstract:
A cartridge seated plug valve includes a hollow body with an inlet, an outlet, and a cylindrical valve chamber. A C-shaped rotor with an elastomeric coating is rotatably held in the valve chamber by a valve cover and a base. A valve facing with an elastomeric gasket is held adjacent to the inlet, with a central aperture of the valve facing aligned with the inlet, and the elastomeric gasket held in compression about an inlet seal surface at a perimeter of the inlet, by facing channels in the cover and base. In a closed position, the rotor is oriented with the elastomeric coating of the plug segment sealing the central aperture. The valve is opened by rotating the main stem, changing an orientation of the rotary plug, and moving the plug segment away from the inlet.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention pertains to the field of hydraulic valves. More particularly, the invention pertains to cartridge seated plug valves. 
       DESCRIPTION OF RELATED ART 
       [0002]    A cartridge plug valve generally includes a hollow valve body with at least one inlet and one outlet each passing through the hollow valve body at opposing sides of a cylindrical valve chamber internal to the hollow valve body. Typically the hollow valve body is constructed of cast iron, but any material that is structurally sound and non-reactive with fluids passing through the cartridge plug valve may be used. A surface of a wall of the cylindrical valve chamber surrounding the inlet forms an inlet seal surface. The cylindrical valve chamber is sealed with a base at a first end of the hollow valve body. The base may be a unitary element of the hollow valve body and part of a single casting, or may be attached to the hollow valve body by welding, bolts, or other types of fasteners, thus closing the first end of the cylindrical valve chamber. 
         [0003]    A cartridge includes a C-shaped rotor and a valve cover. The C-shaped rotor includes a plug segment with a first end and a second end. The first end of the plug segment is connected to the trunnion by a first elbow segment, and the second end of the plug segment is connected to the main stem by a second elbow. The main stem passes through a main stem journal of the valve cover, and the base includes a trunnion journal for accepting the trunnion. Thus, when the cartridge is inserted into the cylindrical valve chamber of the hollow valve body, the valve cover seals the cylindrical valve chamber at the second end of the hollow valve body, and the rotor is free to rotate in the trunnion journal and the main stem journal which share a common axis defined by a center of the trunnion journal and a center of the main stem journal, and henceforth referred to herein as the rotor axis. 
         [0004]    As shown in a prior patent by the present inventor, Kennedy (U.S. Pat. No. 4,697,786, issued 1987), the rotor axis is offset from a central axis of the cylindrical valve chamber so that the rotor turns eccentrically relative to the cylindrical valve chamber. Thus, when the rotor is in a first position, a seal surface of the plug segment is held in contact with the inlet seal surface. When the rotor is turned to a second orientation, generally at a right angle to the first orientation, the plug segment rotates away from the inlet, and due to the eccentricity of the rotor axis relative to the cylindrical valve chamber axis, also moves radially away from the wall of the cylindrical valve chamber. As a result, the plug segment does not contact the surface of the valve chamber or other valve components when in motion, wear on seal surfaces is minimized, and valve operation requires less effort. 
         [0005]    In the prior art, seal integrity at the inlet seal surface has been improved by various constructions. In some constructions, a nickel alloy seat ring is welded into the side of the cylindrical valve chamber surrounding the inlet and forms the inlet seal surface. Additionally, the plug segment of the rotor is coated with an elastomeric layer. Thus, when the plug segment is rotated into the first orientation covering the inlet, the elastomeric coating of the plug segment is compressed against the nickel alloy ring of the inlet seal surface forming a tight seal, and flow of a fluid through the inlet into the cylindrical valve chamber is blocked. 
         [0006]    While this construction is effective, manufacturing costs may be significant. Nickel alloy is a durable metal that is easily welded to, or integrated into, a cast iron hollow valve body. However, nickel alloy is relatively expensive compared to other metals, and integration of the nickel alloy seating ring into the hollow valve body may require significant machining after casting. Further, in the event of damage to the nickel alloy seating ring, the entire hollow valve body may require replacement. 
         [0007]    Also, the prior art Kennedy patent (U.S. Pat. No. 4,697,786, issued 1987) describes a cartridge plug valve having a removable inlet seal surface. In this construction, a metal plate conforms to the wall of the cylindrical valve chamber surrounding the inlet. The metal plate has a central aperture that is the same size of the inlet and aligned with the inlet. An elastomeric coating is applied to both sides of the metal plate and forms a seal surface on both sides of the plate. A channel in the base of the hollow valve body accepts a first end of the metal plate, and a pin in the valve cover mates with a slot cut into a second end of the metal plate. Thus, when the cartridge and hollow valve body are assembled, the metal plate is held firmly against the wall of the valve chamber at the location of the inlet, and is also prevented from rotating within the valve chamber so that alignment with the inlet is maintained. 
         [0008]    A cast iron rotor is cast with an integral nickel alloy ring in the plug segment of the rotor. After machining the plug segment containing the nickel alloy ring to a finished profile, the nickel alloy ring forms a seal surface with the elastomeric coating of the metal plate surrounding the inlet. In the first position of the rotor, the seal surface of the plug segment is held against the central aperture of the metal plate, deforming the elastomeric coating of the metal plate to both the seal surface of the plug segment, and the inlet, thus preventing flow of a fluid from the inlet into the cylindrical valve chamber. When the rotor is moved to a second position, the plug segment rotates away from the metal plate, and also radially away from the metal plate and the wall of the cylindrical valve chamber. Thus, a fluid is permitted to flow from the inlet, through the central aperture of the metal plate, and into the cylindrical valve chamber. 
         [0009]    This construction provides an effective inlet seal, and allows the metal plate forming the inlet seal surface to be easily replaced if necessary. However, the nickel alloy ring cast into the plug segment of the cast iron rotor increases construction materials costs and finishing time to shape the final seal surface of the plug segment. Further, in the event of damage or wear to the seal surface of the plug segment, the entire rotor must be replaced. 
       SUMMARY OF THE INVENTION 
       [0010]    A cartridge seated plug valve of a construction described herein includes a hollow valve body with a cylindrical valve chamber passing between a first end and a second end of the hollow valve body. The cylindrical valve chamber includes a cylindrical wall and a cylindrical valve chamber axis. An inlet passes through the hollow valve body into the cylindrical valve chamber at a first location and an outlet passes through the hollow valve body into the cylindrical valve chamber at a second location. A seal surface surrounds the inlet on the cylindrical valve chamber wall. 
         [0011]    A base is attached to the hollow valve body sealing the cylindrical valve chamber at the first end of the hollow valve body. The base has an inner side including a trunnion journal for receiving a trunnion. The trunnion journal has a center that is radially offset from the cylindrical valve chamber axis. A first facing channel with a radius of curvature having an origin at the cylindrical valve chamber axis is defined in the inner side of the base. 
         [0012]    A valve cover seals the cylindrical valve chamber at the second end of the hollow valve body. The valve cover has an inner side and an outer side, and includes a main stem journal passing from the inner side to the outer side. The main stem journal has a center that is radially offset from the cylindrical valve chamber axis. A second facing channel with a radius of curvature having an origin at the cylindrical valve chamber axis is formed in the inner side of the valve cover. The center of the main stem journal and the center of the trunnion journal define a rotor axis. 
         [0013]    A rotor includes a plug segment with a first end and a second end. The first end of the plug segment is connected to a trunnion by a first elbow segment, and the second end of the plug segment is connected to the main stem by a second elbow segment. The plug segment also has a sealing surface. An elastomeric coating is applied to the first elbow, the second elbow, and the plug segment. The rotor is rotatably held by the main stem being accepted by the main stem journal of the valve cover, and the trunnion being accepted by the trunnion journal of the base. The first elbow segment and the second elbow segment hold the plug segment parallel to the rotor axis with the elastomeric coating of the plug segment adjacent to the seal surface of the inlet of the hollow valve body. 
         [0014]    A valve facing has a body with a first side and a second side opposite the first side. An elastomeric gasket is bonded to the first side of the body. The body of the valve facing has a radius of curvature that is the same as the radius of curvature of the first facing channel and the radius of curvature of the second facing channel. A first end of the valve facing body is held in the first facing channel, and a second end of the valve facing body is held in the second facing channel. A central aperture passing through the valve facing is coincident with the inlet of the valve body. 
         [0015]    When the rotor is in a first orientation with the plug segment adjacent the second side of the body of the valve facing, the eccentric axis of rotation of the rotor forces the elastomeric coating of the plug segment against the second side of the body of the valve facing. The central aperture of the valve facing is thus sealed, blocking flow of a fluid from the inlet into the cylindrical valve chamber. When the rotor is rotated to a second orientation, the plug segment of the rotor moves away from the body of the valve facing. In this orientation, the plug segment of the rotor no longer seals the central aperture of the body of the valve facing, and flow of a fluid from the inlet into the cylindrical valve chamber is permitted. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0016]      FIG. 1  shows a cartridge seated plug valve of a construction described herein. 
           [0017]      FIG. 2A  shows an inner surface of a hollow valve body base. 
           [0018]      FIG. 2B  shows an inner surface of a valve cover. 
           [0019]      FIG. 3  shows a front view of a valve facing with an elastomeric coating. 
           [0020]      FIG. 4  shows a cross-section of a valve facing indicated by  4  in  FIG. 3 . 
           [0021]      FIG. 5  shows a cross-section of a cartridge seated plug valve in a closed position at a location indicated by  5  in  FIG. 1 . 
           [0022]      FIG. 6  shows a cross-section of a cartridge seated plug valve in an open position at a location indicated by  6  in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0023]    A cartridge seated plug valve of a construction described herein provides a replaceable valve facing that effectively seals an inlet of a hollow valve body, and also eliminates the nickel seating ring common in the prior art in either the hollow valve body or the plug segment of the rotor. Thus, material costs are reduced, and extensive machining of an inlet seal surface and/or a plug segment seal surface is significantly reduced or eliminated. Thus, the cartridge seated plug valve reduces overall production costs, and also simplifies maintenance and reduces maintenance costs. 
         [0024]    An embodiment of the cartridge seated plug valve is shown in  FIG. 1 . The cartridge seated plug valve has a hollow valve body  10 . A hollow cylinder internal to the hollow valve body  10  forms a cylindrical valve chamber  40  that allows fluid flow between an inlet  20  and an outlet  30  when the cartridge seated plug valve is opened. A wall  50  of the cylindrical valve chamber  40  has a radius of curvature R w  whose origin defines a valve chamber axis  92 . The inlet  20  is provided with an inlet flange  21 , and the outlet  30  is provided with an outlet flange  31 . Thus the hollow valve body  10  may be assembled in-line with a piping system through, for example, welding or bolting the inlet flange  21  and outlet flange  31  to appropriate mating flanges on pipes. 
         [0025]    A base  60  seals the cylindrical valve chamber  40  at a first end of the hollow valve body  10 , and may be formed as an integral element of the hollow valve body  10  in a single casting. Alternatively, the base  60  may be formed as a separate element and affixed to the hollow valve body  10  with bolts, welds, or other techniques known in the art. As shown in  FIG. 1  and  FIG. 2A , an inner surface of the base  60  is provided with a trunnion journal  91 . In  FIG. 1  and  FIG. 2A , the trunnion journal  91  is shown as a simple cylindrical cup in the base  60  that is open to the cylindrical valve chamber  40 . However, bearings of any suitable type, or other elements that facilitate acceptance of a rotating member, such as a trunnion  90 , may also be used. 
         [0026]    As shown in  FIG. 2A , the trunnion journal  91  has a center that is coincident with a rotor axis  93 , and the rotor axis  93  is slightly offset from the valve chamber axis  92  in a lateral direction relative to the placement of the inlet  20  in the hollow valve body  10 . The inner surface of the base  60  is also provided with a first facing channel  140   a.  The first facing channel  140   a  is arcuate in shape and has a radius of curvature whose origin is coincident with the valve chamber axis  92 . The first facing channel  140   a  follows a circumferential path at a radial distance R c  from the valve chamber axis  92 , generally from a location at a first side of the inlet  20 , past the inlet  20  and to a location at a second side of the inlet  20 . However, the first facing channel  140   a  in  FIG. 2A  is shown as a complete circle for ease of manufacturing. The first facing channel  140   a  is co-axial with an inlet seal surface  22  formed in the wall  50  of the cylindrical valve chamber  40  surrounding the inlet  20 . The inlet seal surface  22  has a radius of curvature R s  with an origin at the valve chamber axis  92   
         [0027]    Referring to  FIG. 1  and  FIG. 2B , a valve cover  70 , being the first element of a cartridge, seals the cylindrical valve chamber  40  at a second end of the hollow valve body  10 , and may be removably attached to the hollow valve body  10  with screws  79 , bolts, or other types of fasteners. The valve cover  70  is provided with a main stem journal  101  that passes through the valve cover  70 . In  FIG. 1  and  FIG. 2B , the main stem journal  101  is shown as a simple cylindrical aperture passing through the valve cover  70 . However, bearings of any suitable type, or other elements that facilitate acceptance of a rotating member, such as a main stem  100 , passing through the valve cover  70  may also be used. 
         [0028]    The main stem journal  101  has a center that is coincident with the rotor axis  93 , and the rotor axis  93  is slightly offset from the valve chamber axis  92  in a lateral direction relative to the placement of the inlet  20  in the hollow valve body  10 . An inner surface of the valve cover  70  is provided with a second facing channel  140   b.  The second facing channel  140   b  is arcuate in shape and has a radius of curvature whose origin is coincident with the valve chamber axis  92 . The second facing channel  140   b  follows a circumferential path, at a radial distance R c  from the valve chamber axis  92 , from a location at a first side of the inlet  20 , past the inlet  20  and to a location at a second side of the inlet  20 . The second facing channel  140   b  is also co-axial with the inlet seal surface  22  formed in the wall  50  of the cylindrical valve chamber  40  surrounding the inlet  20 . 
         [0029]    Comparing  FIG. 2A  and  FIG. 2B , it will be apparent that the offset of the rotor axis  93  on the inner surface of the base  60  and offset of the rotor axis  93  on the inner surface of the valve cover  70  are in opposite directions relative to the valve chamber axis  92 . Thus, when the base  60  and valve cover  70  are in place at opposite ends of the hollow valve body  10 , the trunnion journal  91  and main stem journal  101  will be in alignment on the rotor axis  93 . Similarly, the second facing channel  140   b  will also be aligned with at least an arc length of the first facing channel  140   a  when the valve cover  70  and base  60  are assembled with the hollow valve body  10 . 
         [0030]    The valve cover  70  and/or main stem journal  101  may also be fitted with seals, packing, or other elements known in the art that prevent fluid from passing through the main stem journal  101  from the cylindrical valve chamber  40 . Additionally, a crown with any end play adjustment mechanism known in the art may also be added to the valve cover  70  to ensure proper compression of the rotor  75  against the valve cover  70  as well as proper pressure on packing or other main stem journal  101  elements. Journal seals, packing, and end play adjustment mechanisms are well known in the art, and are omitted here for clarity, as they do not affect the novelty or utility of the cartridge seated plug valve described herein. 
         [0031]    As shown in  FIG. 1 , a rotor  75 , the second element of the cartridge, includes a plug segment  80  that is aligned parallel to the valve chamber axis  92 . A first end of the plug segment  80  is connected to the trunnion  90  by a first elbow segment  81 . A second end of the plug segment  80  is connected to the main stem  100  by a second elbow segment  82 . Thus, the rotor  75 , including the first elbow segment  81 , the plug segment  80 , and the second elbow segment  82 , forms a C-shape. The first elbow segment  81  and second elbow segment  82  are dimensioned to hold a plug seal surface  85  of the plug segment  80  in close proximity to the inlet seal surface  22  surrounding the inlet  20  when the rotor  75  is in a first position with the plug segment  80  aligned with the inlet  20 . As shown in  FIG. 5 , at the first position the plug seal surface has a radius of curvature R p  with an origin in alignment with the valve chamber axis  92 . 
         [0032]    The plug segment  80  of the rotor  75  is also provided with an elastomeric coating  110  that covers at least the plug seal surface  85  of the plug segment  80  of the rotor  75 . In one embodiment, the elastomeric coating covers the entire plug segment  80 , the first elbow  81 , and the second elbow  82 . The elastomeric coating  110  may be bonded to the plug segment  80  by any technique known in the art, and is preferably bonded with a rubber tearing bond. For the purposes of this description, a rubber tearing bond is defined as a destructive bond between an elastomeric material and a second material, wherein the elastomeric material will mechanically fail before the bond fails when forces are applied to the elastomeric material that would otherwise cause the elastomeric material to separate from the second material. The elastomeric coating  110  is preferably ethylene propylene diene monomer (EPDM) rubber. However, any elastomeric material capable of elastic deformation may be used. 
         [0033]      FIG. 3  shows a valve facing  120 . The valve facing  120  is metal plate with a first end E 1  and a second end E 2 , and in preferred embodiments is constructed of stainless steel. However, any other structural material that provides structural rigidity and are non-reactive to fluids passing through the cartridge seated plug valve may also be used, such as carbon fiber, structural plastic, or other metals, for example. The valve facing  120  has a first  120   a  side to which an elastomeric gasket  130  is applied. The elastomeric gasket  130  surrounds a central aperture  125  of the valve facing  120 . The elastomeric gasket  130  may cover the entire first side  120   a  of the valve facing  120 , or may be limited to an area that will mate with the inlet seal surface  22  when the valve facing  120  is positioned in the cylindrical valve chamber  40  at the position of the inlet  20 . 
         [0034]    The elastomeric gasket  130  is preferably made of ethylene propylene diene monomer (EPDM) rubber. However, any elastomeric material capable of elastic deformation may be used. The elastomeric gasket  130  may be bonded to the first side  120   a  of the valve facing  120  by any technique known in the art, and is preferably bonded with a rubber tearing bond.  FIG. 4  shows a cross section of the valve facing of  FIG. 3 . 
         [0035]    Referring again to  FIG. 1 , the cartridge seated plug valve is assembled by first placing the valve facing  120  into the cylindrical valve chamber  40 , with the first end E 1  of the valve facing  120  being accepted by the first facing channel  140   a.  The valve facing  120  is also positioned at the location of the inlet seal surface  22 , with the elastomeric gasket  130  being held in compression against the inlet seal surface  22 . The central aperture  125  of the valve facing  120  coincides with the inlet  20  of the hollow valve body  10 . 
         [0036]    The main stem  100  of the rotor  75  is assembled through the main stem journal  101  of the valve cover  70 , and other elements such as journal seals, packing, and end play adjustment mechanisms are also assembled to complete the cartridge. 
         [0037]    The rotor  75  is then inserted into the cylindrical valve chamber  40  and oriented, as shown in  FIG. 1  and  FIG. 5 , so that the trunnion  90  is received by the trunnion journal  91 . When the cartridge is fully inserted into the cylindrical valve chamber  40 , and the valve cover  70  is bolted to the hollow valve body  10 , the second end E 2  of the valve facing  120  is received by the second facing channel  140   b,  and the elastomeric gasket  130  of the valve facing  120  tightly against the inlet seal surface  22  of the inlet  20 . The first facing channel  140   a  and the second facing channel  140   b,  both being co-axial with, and adjacent to, the inlet seal surface  22  at each end of the cylindrical valve chamber  40 , ensures a tight seal between the valve facing  120  and the inlet seal surface  22 . 
         [0038]    When the cartridge seated plug valve is in a closed state, the elastomeric coating  110  of the plug seal surface  85  of the plug segment  80  of the rotor  75  is held tightly against the second side  120   b  of the valve facing  120 , covering the central aperture  125  of the valve facing  120 , so that flow of a fluid from the inlet through the valve facing  120  is blocked. 
         [0039]    The cartridge seated plug valve is opened by rotating the main stem  100 , generally one-quarter turn relative to the inlet  20 , so that the plug segment  80  rotates away from the position of the inlet  20 . Because the rotor axis  93  is offset relative to the valve chamber axis  92 , and the distance between the plug seal surface  85  and the rotor axis  93  is fixed by the lengths of the first elbow segment  81  and the second elbow segment  82 , as the plug segment  80  rotates away from the inlet  20 , the plug segment  80  also moves radially away from the wall  50  of the cylindrical valve chamber  40 . Thus, frictional forces between the wall  50  of the cylindrical valve chamber  40  are minimized when the plug segment  80  of the rotor  75  is moved to a second position away from the inlet  20 . 
         [0040]    When the rotor  75  is returned to the first position, the plug segment  80  moves radially toward the wall  50  of the cylindrical valve chamber  40  and the inlet seal surface  22 , and compresses the elastomeric coating  110  of the plug seal surface  85  against the second side  120   b  of the valve facing  120 , covering the central aperture  125  of the valve facing  120  to create a fluid-tight seal. 
         [0041]    The cartridge seated plug valve described herein provides a number of advantages over the prior art. Nickel alloy may be significantly more expensive than, for example, stainless steel. Thus, by removing nickel allow seating rings, a significant reduction in manufacturing costs may be achieved. Similarly, whereas incorporation of nickel alloy seating rings into either a hollow valve body  10  or a plug segment  80  of a rotor  75  may require significant machining of seal surfaces after casting to ensure a tight seal during valve operation, the valve facing  120  and elastomeric gasket  130  described herein are easily formed, require lower tolerances at inlet seal surfaces  22 , and may be rapidly replaced in the field. In addition, the elastomeric coating  110  of the rotor  75  may be replaced as necessary by reworking rotors  75  with damaged or worn elastomeric coatings  110 . 
         [0042]    Accordingly, it is to be understood that the embodiments of the invention herein described are merely illustrative of the application of the principles of the invention. Reference herein to details of the illustrated embodiments is not intended to limit the scope of the claims, which themselves recite those features regarded as essential to the invention.