Abstract:
An improved method and apparatus for a valve assembly features a valve body, a first seat ring mounted in the valve body, a second seat ring mounted in the valve body, and a retractable blade gate slideable in between the first seat ring and the second seat ring. The gate is moveable between open and closed position. A first elastomeric ring is disposed in between the valve body and the first seal ring and projecting towards the gate blade. A second elastomeric ring is disposed in between the second seat ring and the valve body and projecting towards the gate blade.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention pertains generally to fluid control valves, and more particularly, pertains to knife gate valves which use a reciprocating knife gate to selectively close and open a flow passage. More particularly, the invention pertains to a bi-directional knife gate valve. 
       BACKGROUND OF THE INVENTION 
       [0002]    Various valves for fluid control are in wide use in industry. One type of such valve is known as a knife gate valve. In a knife gate valve, a relatively flat knife gate, also referred to as a blade, is translatable back and forth with respect to an aperture in a valve body to open or close a fluid flow passage in the valve body. 
         [0003]    Many such knife gate valves are best adapted only for dealing with pressure in a single direction. That is, in such a single direction valve, when the valve is closed the high pressure side will tend to urge or force the blade in the direction towards the low pressure side so that the blade is forced into a seating arrangement against a valve seat that is part of the body. In such a one-directional arrangement, the seating is accomplished by the low-pressure face of the blade being urged into tight contact with the body the low-pressure side of the seat. These single direction knife gate valves are relatively economical and easily to manufacture, because the pressure of the fluid itself helps assist with seating. 
         [0004]    A disadvantage with these single direction knife gate valves, however, is that they often are not suitable for use as dual direction valves. Typically, if pressures are reversed from the intended orientation, the blade might be urged away from its seat, and positive closure may not be obtained. 
         [0005]    One approach for overcoming this problem has been to form a valve with two seats, one on each side of the blade. However, this can be relatively expensive. 
         [0006]    Another approach to creating bi-directional sealing has been the use of a perimeter seal around the perimeter edge of the blade. However, in some applications the perimeter seal also has disadvantages, as far as exposure, complexity and/or durability. 
         [0007]    Accordingly, it would be desirable to have an improved knife gate valve assembly and method that can accomplish dual directional flow shutoff when desired. It would also be desirable for such a dual directional knife gate valve assembly and method to be convenient and easy to manufacture, assemble, and maintain. 
       SUMMARY OF THE INVENTION 
       [0008]    Some various embodiments of the present invention can provide a knife gate valve apparatus and method that is capable of sealing in dual directions, that is, with the high pressure side on ether side of the blade, and in some embodiments can overcome the disadvantages mentioned above with respect to the prior art. 
         [0009]    In accordance with one embodiment of the present invention, a valve apparatus has a valve body; a first seat ring mounted in the valve body; a second seat ring mounted in the valve body; a retractable blade gate slideable in between the first seat ring and the second seat ring and moveable between open and closed positions; a first elastomeric ring disposed in between the valve body and the first seal ring and projecting towards the gate blade; and a second elastomeric ring disposed in between the second seat ring and the valve body and projecting towards the gate blade. 
         [0010]    In accordance with another embodiment of the present invention, a valve apparatus, has a valve body; a first seat ring mounted in the valve body; a second seat ring mounted in the valve body; a retractable closing means slideable in between the first seat ring and the second seat ring and moveable between open and closed positions; a first elastomeric sealing means disposed in between the valve body and the first seal ring and projecting towards the gate blade; and a second elastomeric sealing means disposed in between the second seat ring and the valve body and projecting towards the gate blade. 
         [0011]    In accordance with yet another embodiment of the present invention, a method of sealing a valve assembly having a valve body, a first and second seat ring mounted in the valve body, and a retractable blade gate slideable in between the first seat ring and the second seat ring and moveable between open and closed positions, includes disposing a first elastomeric ring in between the valve body and the first seal ring and projecting towards the gate blade; and disposing a second elastomeric ring in between the second seat ring and the valve body and projecting towards the gate blade. 
         [0012]    There has thus been outlined, rather broadly, certain embodiments of the invention in order that the detailed description thereof herein may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional embodiments of the invention that will be described below and which will form the subject matter of the claims appended hereto. 
         [0013]    In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of embodiments in addition to those described and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract, are for the purpose of description and should not be regarded as limiting. 
         [0014]    As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a cross-sectional view of a bi-directional knife gate valve assembly according to a first preferred embodiment of the present invention, in a closed position. 
           [0016]      FIG. 2  is a detailed view showing a seat body and blade contact region of the assembly shown in  FIG. 1 . 
           [0017]      FIG. 3  is a detailed view showing an alternative embodiment of the present invention. 
           [0018]      FIG. 4  is a view similar to  FIG. 1  relevant to either embodiment and showing the valve in an open position. 
           [0019]      FIG. 5  is cross-sectional view showing two different elastomeric rings according to the alternative embodiment illustrated in  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION 
       [0020]    Some various embodiments of the present invention can provide a knife gate valve apparatus and method that is capable of sealing in dual directions, that is, with the high pressure side on ether side of the blade, and in some embodiments can overcome the disadvantages mentioned above with respect to the prior art. Some preferred embodiments of the invention will now be described with reference to the drawing figures, in which like reference numerals refer to like parts throughout. 
         [0021]    Turning to  FIG. 1 , a knife gate valve  10  to according to an embodiment of the present invention is illustrated. The knife gate valve  10  can include a valve body  12  that has a flange  14  to which is mounted a packing and stuffing box  16 . A knife gate  18 , also referred to as a blade  18 , has an end  20  protruding from the packing and stuffing box  16 . The end  20  of the blade or knife gate  18  can be connected to a reciprocating actuator to extend the blade  18  into the valve to close it, and to extract or retract the blade or knife gate  18  in the opposite direction to open the valve. The blade or knife gate  18  has another end  22 , also referred to as a tip, which may be slightly beveled as shown. 
         [0022]    The body  12  supports a first metal seat ring  24  and second metal seat ring  26 . The first metal seat ring  24  is press-fit into a corresponding groove in the body  12  and retained therein as shown. The second seat ring  26  is press-fit into a corresponding receiving shape in the body  12  and also retained in place. A first elastomeric sealing ring  30  is provided adjacent the first seating ring  24  and a second elastomeric sealing ring  32  is provided adjacent the second seat ring  26 . 
         [0023]    Turning now to  FIG. 2 , a detailed view is illustrated, including the body  12 , the lower first seat ring  24 , the second seat ring  26 , the first elastomeric ring  30  and the second elastomeric ring  32 . The blade or knife gate  18  is also illustrated in a closed position. 
         [0024]    It will be appreciated that the first and second elastomeric rings  30  and  32  can in fact be similar structures to each other simply having been “flipped” inside out. This provides one advantage of this embodiment of the invention, wherein a single elastomeric ring-type can be manufactured and can be used as both the first and second elastomeric rings  30  and  32  in the preferred embodiment. 
         [0025]    The elastomeric rings  30  and  32  can be made by any suitable method, but in one example are made by extruding elastomeric material, then cutting it to a proper length, and then bonding the two ends to form a ring. 
         [0026]    Turning, for example, to the first elastomeric ring  30 , it will be appreciated that this elastomeric ring  30  has an ear  36 . The second elastomeric ring  32  has a similar ear  38 . The ear  36  fits in a retention groove  40 , and the ear  38  fits in a retention groove  42 , with each of the retention grooves  40  and  42  retaining the respective ring via a mechanical fit. The retention groove  40  is a groove formed in the first seat ring  24 . The retention groove  42  is a groove formed in the body  12 . 
         [0027]    The interaction of the ears  36  and  38  with their respective retention grooves  40  and  42  serves one or more of several functions. In particular, the interaction of the ears  36  and  38  with their retention grooves  40  and  42 , respectively, serves both to provide some sealing and also to retain the elastomeric rings  30   32  mechanically in their location. For example, this interaction prevents the elastomeric rings  30  and  32  from moving axially and sliding out of their mounted orientation when the valve  10  is open. This can provide an improvement compared to bonding via gluing or another adhesive agent of sealing rings in some cases. The mechanical retention shown in this preferred embodiment can, in some cases, be more durable then bonding or gluing. Also replacement of the elastomeric rings can be accomplished without needing to clean off adhesive residue. However, some embodiments of the invention can use bonding instead of mechanical retention. 
         [0028]    The valve  10  also includes a first o-ring  50  and a second o-ring  52 , with each o-ring  50  and  52  providing a seal between the body  12  and one of the upper and lower seat rings  24  and  26 , respectively. For example, o-ring  50  sits in a channel in the body  12  and seals against the side of the first seat ring  24 . O-ring  52  sits in a channel in the body  12  and seals against a face of the second seat ring  26 . 
         [0029]    It will be appreciated that the combination of the two elastomeric rings  30  and  32  as well as the two O-rings  50  and  52  provides adequate sealing without requiring the blade  18  to necessarily have complete sealing contact with both of the sealing rings  30  or  32  at the same time. That is, in an example where the second seat ring  26  is on the high-pressure side, it will be appreciated that the blade  18  will tend to be urged downward in the drawing figure. 
         [0030]    Fluid may tend to leak past the gap between the blade  18  and the seat ring  26 . However, such fluid will tend to be stopped by the sealing between the second elastomeric ring  32  and the blade  18 . Any fluid that does extend past this seal will, if it is directed upwardly, next tend to be stopped by the mating of the ear  38  and the groove  42 , and if any fluid pressure escapes past this seal it will be stopped by the o-ring  52 . 
         [0031]    The other fluid flow escape path direction is around the tip  22  of the blade  18  and will tend to be stopped by the seal between the first elastomeric ring  30  against the blade  18 . Any fluid that does escape past this seal will tend to be stopped by the mating of the ear  36  and groove  40 , and also by the o-ring  50 . 
         [0032]    Therefore, complete sealing by the elastomeric ring against the blade is not required, because secondary sealing is provided by the continuation of the ears and the o-rings. 
         [0033]    In one preferred embodiment, the valve body  12  may be made of any suitably rigid structure including, for example, plastic or metal. The first and second seat rings  24  and  26  are typically made of metal, and the knife gate or blade  18  is also typically made of metal. The elastomeric rings  30  and  32 , as well as the o-rings  50  and  52 , are typically rubber. However, other materials may be utilized as is suitably desired. 
         [0034]      FIG. 3  is a detailed view illustrating a second preferred embodiment of the present invention. The body  112 , blade or knife gate  118 , and seat rings  124  and  126  substantially correspond to those in the first embodiment. The difference relative to the first embodiment is that the elastomeric rings  130  and  132  are different from each other in this embodiment. That is, rather than there being a single elastomeric ring design, which is flipped inside out depending on its installation, in this embodiment, two structurally different and symmetrically opposed elastomeric rings  130  and  132  are utilized. 
         [0035]    In this embodiment, the ears  136  and  138 , respectively, are each directed radially inward. Each sits in a groove in its respective seat ring  124  or  126 . While this embodiment requires the construction of two different elastomeric ring types, it also provides the benefit that the grooves that receive the ears are located on the seat rings  124  and  126  and there is no need for a retaining groove on the body  112 . This permits modification and/or retrofit of existing bodies  112  to have the ear and groove configuration without requiring any changes to the structure of the body  12  itself. Since the seat rings  124  and  126 , as well as the elastomeric rings  130  and  132 , are replaceable components (compared to the body  112 ), this can provide an advantageous future in some situations. 
         [0036]      FIG. 4  is a view showing the valve of either embodiment in an open configuration. In  FIG. 4  the elastomeric rings are shown schematically without detail; in the first embodiment, the ears would face in different directions, and in the second embodiment, they would both face radially inward. 
         [0037]      FIG. 5  shows the two different elastomeric ring cross-sections of the second preferred embodiment, depicting elastomeric rings  130  and  132  as well as their inwardly directed ears  136  and  138 . 
         [0038]    The many features and advantages of the invention are apparent from the detailed specification, and thus, it is intended by the appended claims to cover all such features and advantages of the invention which fall within the true spirit and scope of the invention. Further, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.