Abstract:
An expanding disk gate valve assembly comprises two gate disks and an elastomeric disk. A first flange on a first gate disk mates to a second flange on a second gate disk forming an internal volume surrounding the elastomeric disk. An elastomeric sheath covers the mated disks with the first gate disk being radially offset from, and radially movable relative to, the second gate disk. A width of the gate disk assembly is less than a width between two valve seats when the gate disk assembly is in an open position. In a closed position, the first flange moves radially toward the second flange, compressing elastomeric disk, and causes the elastomeric disk to expand axially against the two gate disks, forcing them apart, and increasing the gate disk assembly width so that the gate disk assembly actively seals against the valve seats.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention pertains to the field of gate valves. More particularly, the invention pertains to expanding double disk gate valves. 
     2. Description of Related Art 
     Industrial valves provide accurate control of high-pressure fluid or gas flow. Gate valves are often used where fluid flow or gas flow is seldom interrupted, and accurate regulation of flow quantity is a prime consideration. Gate valves allow maximum flow while exercising flow control through the closure of a sliding gate transverse to the direction of flow in a flow channel. 
     The gate is user controlled through an operating stem such as a spindle screw or other types of operating stems and mechanisms. These operating stem mechanisms open and close the gate and also allow adjustments in flow rate by positioning the gate in intermediate positions in a flow channel. The primary advantage of a gate valve is that the nominal working flow rate of the fluid or gas is not reduced by installing the hollow valve body. 
     Various types of gate valve assemblies are known for opening and closing pipelines to control the flow of fluid or gas. The traditional gate valve employs a single metallic disk that is movable between an open position and a closed position transverse to a flow channel to stop or allow flow of a liquid or gas from an inlet through the gate valve and out through an outlet. 
     Single disk gates are typically mounted in valve bodies and seating channels with a small amount of play, so that pressure on an inlet side of the disk biases the gate toward a valve seat in the hollow valve body when the gate is in a closed position. This play may, however, allow leakage around the gate and the valve seat, and over time may result in wear that may require repair or replacement of the gate valve or the gate disk assembly. 
     Alternatively, single metal disks with close tolerances that more effectively seal flow when the gate is in a closed position can be subject to friction between the gate disk and the valve seat surfaces of the hollow valve body. Friction between the gate disk and the valve seat may hinder movement of the gate disk, and over time cause wear on the gate disk and/or valve seat that similarly degrades the sealing capacity of the valve seal and necessitates repair or replacement of the gate valve body or gate disk. 
     In the prior art, Kennedy (U.S. Pat. No. 4,483,514, “Gate Valve Member For Resilient-Seated Gate Valve”) describes a valve gate disk assembly with two disks that reduces leakage and valve gate play. The two disks are positioned between two opposing valve seat surfaces in the hollow valve body. One disk is adjacent an inlet and the other disk is adjacent an outlet of a gate valve body. When closing the gate valve, the gate disk moves into the gate valve body, and the double disk construction sealingly engages the respective valve seat surfaces as the gate disk assembly moves into a fully closed position. The gate disks may be pressed outwards against the valve seats by a spring assembly, or by fluid pressure introduced between the gate disks. 
     Tiefenthaler (U.S. Pat. No. 4,913,400, “Double Disk Gate Valve”, issued in 1990) describes a prior art double disk gate valve in which two disks are biased outwardly toward valve seat surfaces by fluid pressure. In this construction, a fluid medium is used to force the two gate disks apart through the use of pistons, cylinders, valves, and channels or piping that regulate the flow and pressure of the fluid between the two gate disks at open and closed positions. 
     Kennedy (U.S. Pat. No. 6,254,060, “Gate Assembly for a Double Disk Gate Valve”, issued in 2001) describes another prior art dual disk gate valve in which an elastomeric material is positioned between two gate disks. In this construction, a cross member is included between the two gate disks, comprising a gate assembly attached to an operating stem, and in contact with the elastomeric material between the two gate disks. When the gate assembly is moved into a closed position, and when the gate disk assembly reaches a closed position pressing against the hollow valve body, the cross member is forced toward an opposing position of the hollow valve body. The cross member thus compresses the elastomeric material between the two gate disks, and this compressive force is translated outwardly against the two gate disks forcing them to positively seal against valve seats in the hollow valve body. 
     Gate valve assemblies employing double disk closure gates have been improved upon through the incorporation of elastomeric sealing material around the periphery of the gate disks. When the gate assembly is moved into a closed position in the hollow valve body, the elastomeric material located on the peripheral surfaces of the gate assembly are deformed at the valve seat surfaces through the application of pressure to the gate assembly, thereby helping to provide a tighter seal between the valve seat surfaces and the gate assembly than can be accomplished by bare metal disks alone. 
     Prior art configurations employing elastomeric sealing members around the periphery of a gate assembly must be constructed with narrow tolerances to ensure positive sealing characteristics. These tolerances must be even more precise when side wall portions of the valve seat surface perpendicular to the direction of gate travel are considered. The prior art typically mounts these elastomeric sealing members on the periphery of the gate assembly, making the dimensional tolerances of the elastomeric sealing member very narrow, to prevent compression of the elastomeric sealing member beyond its elastic limit. Maintaining narrow tolerances of elastomeric sealing members and valve seats requires significant manufacturing oversight, is time consuming, and is a cost factor limiting the application of double disk gate valves. 
     Further, in some prior art configurations, the pressure available for forcing gate disks outwardly against valve seating surfaces may be limited, delivered by complex structures, and/or unevenly applied about the circumference of the gate valve. These factors may negatively impact the reliability of these constructions, further increase costs, and may limit the diameter of flow channels in which they can be employed, as well as the maximum operating pressures of fluid flow they may effectively control. 
     For example, when an elastomeric material is located between two gate disks and compressed by a cross member, compression of the elastomeric material may not be uniformly distributed throughout the elastomeric material. Portions of the elastomeric material closest to the cross member may experience greater compression than portions of the elastomeric material that are farthest from the cross member. As a result, the outward pressure on the two gate disks may be greater near the cross member than at a location diametrically opposed to the cross member. This condition may limit the maximum diameter valve in which such a solution may be implemented. 
     SUMMARY OF THE INVENTION 
     An expanding disk gate valve of a construction described herein includes a valve assembly with two gate disks. A first gate disk has a flange extending perpendicularly from a back side of the first gate disk and encompassing slightly more than half the circumference of the first gate disk. A second gate disk similarly has a flange extending perpendicularly from a back side of the second gate disk and encompassing slightly more than half the circumference of the second gate disk. Each flange has two ends that are each mortised, with the mortises on one gate disk flange arranged to mate with the mortises on the other gate disk flange. Thus, when the two gate disks are assembled, a gate disk assembly is formed that defines a hollow internal volume, with the two disks being translatable from a coaxial relationship, to a slightly offset non-coaxial relationship in which one disk is radially offset from the other gate disk. 
     The hollow internal volume defined by the two gate disks is filled with a disk of an elastomeric material that fills the hollow internal volume when the two gate disks are slightly offset relative to each other in a non-coaxial relationship. The gate disk thus constructed may be covered in a sheath that is also formed of an elastomeric material, and completes the gate disk assembly. An operating stem may be coupled to the flange of one gate disk to control movement of the gate disk assembly. 
     When the gate disk assembly is in an “open” position, the first gate disk is slightly offset radially relative to the second gate disk, and the gate disk assembly has a minimum width between an inlet side and an outlet side of the gate disk assembly. 
     When the gate assembly is moved into a hollow valve body between two valve seats, the gate disk assembly is free to move with little friction, as the minimum width of the gate disk assembly is less than the distance between the two valve seats. When the gate disk assembly contacts a wall of the hollow valve body, opposite the operating stem coupled to the first gate disk, further motion of the second gate disk is prevented by the wall of the hollow valve body. The first gate disk, having been offset from the second gate disk, may continue to move with continued movement of the operating stem until the first gate disk comes into coaxial alignment with the second gate disk. 
     The elastomeric disk between the two gate disks is thereby compressed between the flange of the first gate disk and the flange of the second gate disk along a common radius of the two disks. Radial compression of the elastomeric disk translates into a lateral expansion of the elastomeric disk toward the back side of each of the two gate disks, and forces the two gate disks apart. This force is relatively uniform about the circumference of the gate disk assembly, and results in a positive engagement between the elastomeric sheath covering the gate disk assembly and the valve seats on either side of the gate disk assembly. 
     Pressure of the operating stem on the gate disk assembly also forces the gate disk assembly against a wall of the hollow valve body opposing the location of the operating stem, and also provides for positive engagement of the gate disk assembly against the hollow valve body between the two valve seats. These forces together provide a positively engaging seal about the circumference of the gate disk assembly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  shows a gate valve with an expandable dual disk gate in an interim position between a gate housing and a gate chamber in a non-rising operating stem configuration. 
         FIG. 1B  shows a gate valve with an expandable dual disk gate in an interim position between a gate housing and a gate chamber in a rising operating stem configuration. 
         FIG. 2  shows a perspective of an expanding dual disk gate disk assembly. 
         FIG. 3  shows an exploded view of an expanding dual disk gate disk assembly. 
         FIG. 4  shows an expanding dual disk gate disk assembly in an interim position between a gate housing and a gate chamber. 
         FIG. 5  shows an expanding dual disk gate disk assembly forced against a wall of a gate chamber and expanded laterally against valve seats by compression of an elastomeric material between two gate disks. 
         FIG. 6  shows a cross-section of overlapping mortises on flanges of two gate disks allowing radial motion of one gate disk relative to the other gate disk. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A double disk gate valve assembly of a construction described herein eliminates complex expansion mechanisms between two gate disks of a gate disk assembly, reduces material and manufacturing costs, improves reliability, reduces servicing costs and frequency, and may provide improved seal integrity about the circumference of the gate disk assembly over a larger range of gate valve diameters and flow pressures. 
     Referring to  FIGS. 1A-1B , a hollow valve body  10  is mounted in a pipe by conventional connections, such as, for example, flanges, threads, solder joint, welding, or other connections known in the art (not shown in this figure). Fluid flows from an inlet  20 , through a gate chamber  25 , and out an outlet  30 . The ends of the gate chamber  25  form valve seats  24  on the inlet  20  side and outlet  30  side of the gate chamber  25 . For ease of assembly, the hollow valve body  10  may be formed in multiple parts, for example, being split into a first gate housing  40  and a second gate housing  45 , together defining a gate receiving area  50  adjacent the gate chamber  25 , and attached together by any means known in the art, for example by bolts  43  in these figures. 
     The gate chamber  25  is shown as a simple notch in an inner surface of the hollow valve body  10 , and extends upwardly through the hollow valve body  10  into the first gate housing  40 , where the first gate housing  40  also forms valve seats  24 . However, the gate chamber  25  may have any cross sectional profile that is advantageous to manufacturing of the hollow valve body  10 , and capable of forming valve seats  24  at the inlet  20  and outlet  30  sides of the gate chamber  25 . 
     The gate chamber  25  also includes two surface features  26  that extend radially around a surface of the gate chamber  25  opposite the first gate housing  40  and inwardly toward the hollow valve body  10 . These surface features  26  allow small debris, for example, sand, pebbles, razor muscles and other types of shells, to rest in the gate chamber  25  while the surface features  26  restrict further movement of the a gate disk assembly  70  into the gate chamber  25 . 
     Thus, the effect of debris on restricting closure of the gate disk assembly  70  is reduced, and damage to elastic components, such as an elastomeric sheath  90  that is part of and surrounding the gate disk assembly, as shown in  FIGS. 2-5 , is also reduced.  FIG. 5  illustrates the operational relationship between the surface features  26  of the gate chamber  25  and the elastomeric sheath  90  of the gate disk assembly  70  when the gate disk assembly  70  is in a closed position inside the hollow valve body  10  and gate chamber  25  against the surface features  26  of the gate chamber  25 . 
     The gate disk assembly  70  is free to move between the gate receiving area  50  and the gate chamber  25  to regulate flow between the inlet  20  and the outlet  30  of the hollow valve body  10 . An operating stem  60  is be coupled to the gate disk assembly  70  to move the gate disk assembly  70  between an open position in which the gate disk assembly  70  is within the gate receiving area  50 , and a closed position in which the gate disk assembly  70  is within the gate chamber  25 . 
     Any operating stem  60  arrangement of any type known in the art may be employed with the gate disk assembly  70 . In one embodiment, an operating stem  60  having threads is used to move the gate disk assembly  70  laterally into and out of the gate chamber  25 . In a non-rising stem configuration, shown in  FIG. 1A , an operating stem coupling  78  between the operating stem  60  and the gate disk assembly  70  is of the stationary threaded type, with a threaded end  78   a  of the operating stem  60  passing through a threaded operating stem coupling  78  into and out of the gate disk assembly  70  when the operating stem  60  is rotated. In this embodiment, a gate housing coupling  47  may comprise a thrust bearing retainer and the operating stem  60  may comprise a thrust bearing  47   a,  for example, and allows free rotation of the operating stem  60  passing through the second gate housing  45 , while holding the operating stem  60  at a fixed location along a length of the operating stem  60 . 
     The gate disk assembly  70  thus translates along the operating stem  60  when the operating stem  60  is turned, and the threaded end  78   a  of the operating stem  60  moves into and out of the gate disk assembly  70 . A seal or sealed bearing may be provided at the gate housing coupling  47  and thrust bearing  47   a  to prevent leakage around the operating stem  60  from the gate receiving area  50 . A tube  97  is provided so that the operating stem  60  may move into and out of the gate disk assembly  70  as the gate disk assembly  70  moves along the operating stem  60 . 
     Alternatively, as shown in  FIG. 1B , a rising stem configuration may be used. In this figure, a threaded length  48   a  of the operating stem  60  passes through a threaded gate housing coupling  48 , for example, a threaded stem nut. An end of the operating stem  60  may be rotatably coupled to the gate disk assembly  70  by an operating stem coupling  79  comprising a thrust bearing retainer receiving a thrust bearing  79   a  affixed to an end of the operating stem  60 , or similar coupling. Thus, when the operating stem  60  is rotated, the operating stem  60  moves into and out of the gate receiving area  50 , and also moves the gate disk assembly  70  accordingly. In other embodiments, the gate disk assembly  70  may be driven by a linear actuator, hydraulic mechanism, or other actuator capable of moving the gate disk assembly  70  between the gate chamber  25  and the gate receiving area  50 . 
     Referring now to  FIGS. 2-3 , the gate disk assembly  70  is shown separated from the hollow valve body  10  and the operating stem  60 .  FIG. 2  shows the gate disk assembly  70  with a first gate disk  72  and second gate disk  74  in solid lines, and the elastic sheath  90  surrounding the first gate disk  72  and second gate disk  74  in dashed lines.  FIG. 2  shows the elastic sheath  90 , first gate disk  72 , second gate disk  74 , and an elastomeric disk  95  in an exploded view. 
     The gate disk assembly  70  includes a first gate disk  72  with a face  72   a  forming an outlet side of the gate disk assembly  70 , and a second gate disk  74  with a face  74   a  forming an inlet side of the gate disk assembly  70 . 
     The first gate disk  72  has a flange  73  extending perpendicularly from a back surface of the first gate disk  72 . The flange  73  has an extent of more than one half of the circumference of the first gate disk  72 . Similarly, the second gate disk  74  also has a flange  75  extending perpendicularly from a back surface of the second gate disk  74 . The flange  75  also extends more than one half of the circumference of the second gate disk  74 . 
     The ends of flange  73  are mortised (not visible in this view, see ref.  77  in  FIG. 6 ) on an inner surface of flange  73 , while the ends of flange  75  are mortised  76  on an outside of flange  75 . As a result, when the first gate disk  72  and second gate disk  74  are assembled with flange  73  and flange  75  diametrically opposed, the mortise  76  and the mortise  77  overlap. In this orientation, the first gate disk  72  and the second gate disk  74  form a face  72   a  at an outlet side of the gate disk assembly  70 , and a face  74   a  forming an inlet side of the gate disk assembly  70 , and flange  73  of the first gate disk  72  and flange  75  of the second gate disk  74  together form the circumference of the gate disk assembly  70 . The first gate disk  72  and the second gate disk  74 , and flange  73  and flange  75 , also define a hollow volume within the gate disk assembly  70 . 
     The gate disk assembly  70  shown in  FIG. 2  is presented in a resting, un-expanded state, as would be the case when the gate disk assembly  70  is in an open position. In this state, the first gate disk  72  and second gate disk  74  are not coaxial, with a central axis of the first gate disk  72  being radially offset slightly relative to a central axis of the second gate disk  74  along a diameter that is co-linear with the operating stem  60 . The combination of the first gate disk  72  and second gate disk  74  in this state forms a gate disk assembly  70  that, together with an elastomeric sheath  90  covering the gate disk assembly  70  has a minimum nominal width. 
     The elastomeric sheath  90  may act to hold the first gate disk  72  and second gate disk  74  together as an assembly when the gate disk assembly  70  is in an open position. The elasticity of the elastomeric sheath  90  holds the face  72   a  of the first gate disk  72  and the face  74   a  of the second gate disk  74  toward each other when the gate disk assembly  70  is in the open position. Thus, the gate disk assembly  70 , including the thickness of the elastomeric sheath  90 , has a minimum nominal thickness and may move freely between the gate receiving area  50  and gate chamber  25  without binding or excessive frictional wear. 
     The elastomeric sheath  90  may also act as a resilient seal that deforms to the valve seats  24  in the hollow valve body  10  when the gate disk assembly  70  is in a fully closed and expanded position, improving the sealing of the valve seats  24 . The elastomeric sheath  90  also includes an aperture  100  through which an operating stem coupling  78  passes. 
     Referring now to  FIG. 3 , in addition to the first gate disk  72 , the second gate disk  74 , and the elastomeric sheath  90 , an elastomeric disk  95  is placed within the hollow volume defined between the first gate disk  72  and the second gate disk  74 . The elastomeric disk  95 , in an uncompressed state, holds the first gate disk  72  and second gate disk  74  in a radially offset, non-coaxial, alignment, as shown in  FIG. 4 , indicated by the dashed arrows, A 1  and A 2  representing a central axis of the first gate disk  72  and a central axis of the second gate disk  74 , respectively. 
     Referring still to  FIG. 3 , the first gate disk  72  is shown with a tube  97  for receiving the operating stem  60  when an operating stem  60  of the non-rising type is employed, and the gate disk assembly  70  moves along a length of the operating stem  60 . The tube  97 , shown as a projection through the face  72   a  of the first gate disk  72  with dashed lines, or similar structure formed within the hollow volume between the first gate disk  72  and second gate disk  74 , may act as a central spine against which compression of the elastomeric disk  95  may deflect radial compressive forces axially toward the face  72   a  and the face  74   a  of the first gate disk  72  and the second gate disk  74 . In some embodiments, the tube  97  may be included regardless of the operating stem  60  configuration, and may be a surface feature on the inner side of one or both the first gate disk  72  and the second gate disk  74  that may favorably bias radial compression of the elastomeric disk  95  by the flange  73  and the flange  75  toward axial expansion of the elastomeric disk  95 . 
     As shown in  FIGS. 2-3 , a pin  80  and groove  85  are included to limit maximum radial and axial movement of the first gate disk  72  relative to the second gate disk  74  and also improve structural integrity of the gate disk assembly  70 . The pin  80  is shown extending radially from the mortise  76  of the flange  75  of the second gate disk  74 , and the groove  85  is shown passing through the flange  73  of the first gate disk  72 . It will be understood that the locations of the pin  80  and groove  85  may be reversed so that the groove  85  passes through the mortise  76  of the flange  75  of the second gate disk  74 , and the pin  80  extends radially from the mortise (not shown in this view, see ref.  77  in  FIG. 6 ) of the flange  73  of the first gate disk  72 . Similarly, while the mortise  76  of the flange  75  of the second gate disk  74  is shown underlapping the mortise (not shown, see ref.  77  in  FIG. 6 ) of the flange  73  of the first gate disk  72 , these orientations may also be reversed so that the mortise  76  of the flange  75  overlaps the mortise of the flange  73 . 
     The expansion and improved sealing capability of the gate disk assembly  70  is illustrated beginning with  FIG. 4 . The gate disk assembly  70  is shown within the hollow valve body  10 . In this figure, the gate disk assembly  70  is shown in an interim position in the hollow valve body  10  in which there is no pressure applied to the first gate disk  72  by the operating stem  60 , and the second gate disk  74  is not in contact with the side of the gate chamber  25  opposing the gate receiving area  50 . The elastomeric disk  95  between the first gate disk  72  and the second gate disk  74  is in a non-compressed state and holds the face  72   a  and the face  74   a  of the first gate disk  72  and the second gate disk  74  apart. At the same time, the elastomeric sheath  90  holds the first gate disk  72  and the second gate disk  74  against the elastomeric disk  95 . The gate disk assembly  70  has a minimum thickness d 1  in this open state. In the open state, the central axis A 1  of the first gate disk  72  is also slightly offset radially relative to the central axis A 2  of the second gate disk  74 . 
     Referring now to  FIG. 5 , when the gate disk assembly  70  is moved to a closed position in the gate chamber  25  between the valve seats  24 , the gate disk assembly  70  contacts the surface features  26  of the gate chamber  25  opposite the gate receiving area  50 . Further movement of the second gate disk  74  is stopped, and the elastic sheath  90  is pressed against the surface features  26  of the gate chamber  25  by the flange  75  of second gate disk  74 . The first gate disk  72 , being offset radially from the second gate disk  74  in an open state, remains free to move into the gate chamber  25  under the pressure of the operating stem  60  through the coupling  78 . 
     As the first gate disk  72  moves further into the gate chamber  25 , the central axis A 1  of the first gate disk  72  comes into coaxial alignment with the central axis A 2  of the second gate disk  74 . The elastomeric disk  95  is compressed radially inwardly by the flange  73  of the first gate disk  72  in one direction, and radially inwardly by the flange  75  of the second gate disk  74  in an opposing direction. As the elastomeric disk  95  deforms in compression between the flange  73  and the flange  75 , the elastomeric disk  95  translates inward radial pressure from the flange  73  and the flange  75  into axial pressure, expanding against the first gate disk  72  and the second gate disk  74 . Thus, the first gate disk  72  and the second gate disk  74  are forced away from each other, and are separated so that the gate disk assembly  70  increases in width, from d 1  to d 2 . 
     The elastomeric sheath  90  deforms to allow expansion of the gate disk assembly  70 , and is also forced against the valve seats  24  about the circumference of the gate disk assembly  70  and the circumference of the valve seats  24 . Seal integrity is therefore provided by the pressure of the gate disk assembly  70  expanding longitudinally against the valve seats  24  about the circumference of the gate disk assembly  70 , as well as the force of the gate disk assembly  70  being pressed into the gate chamber  25  by the operating stem  60 . These forces cause the elastomeric sheath  90  to conform to sides of the gate chamber  25  and the valve seats  24 , and form a positive seal with the valve seats  24  and the gate chamber  25 . 
       FIG. 6  illustrates the mortise  76  on the flange  75  of the second gate disk  74  and the mortise  77  on the flange  73  of the first gate disk  72 . This figure is a cross-section of the gate disk assembly  70  through a plane between the face  72   a  and the face  74   a  of the first gate disk  72  and second gate disk  74 , and through the groove  85  and the pin  80 . The gate disk assembly  70  is shown in an open state where the first gate disk  72  is offset radially from the second gate disk  74 . As shown by the arrows in this figure, when pressure is applied to the flange  73  of first gate disk  72  in a first direction, and pressure is also applied to the flange  75  of the second gate disk  74  in an opposing direction, the extent of the mortise  76  and the mortise  77  and the overlap between the flange  73  and the flange  75  created by the mortise  76  and the mortise  77 , allows the first gate disk  72  and the second gate disk  74  to move radially relative to each other. 
     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.