Abstract:
A valve has a valving element which is rotatably fitted within a valve body. This valving element of the valve is joined by a stem or shaft portion which extends out of the valve body to interact with an actuator and transmit torque to the valving element. In plug valves, pressure needs to be also applied to the valving element to insure a proper closure. The invention relates to a mechanism to adjustably seal the stem/body interface using only one screw that is positioned on the front of the valve cover for easy access. The force generated by the screw is transposed into a vertical force by a rotatable cam. The multiple faces of the cam are used to transmit the force vertically and horizontally and will maintain the mechanism in a straight position.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     The present patent application is a continuation-in-part of commonly assigned U.S. patent application Ser. No. 11/099,651, filed on May 6, 2005 which is itself a continuation in part of commonly assigned U.S. patent application Ser. No. 10/811,497, filed on Mar. 31, 2004. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention generally relates to sealing means for valves, more particularly for plug valves.  
       BACKGROUND OF THE INVENTION  
       [0003]     It is common and usual practice in sealing the top portion of rotary valves to use a top seal that seals against media leakage while simultaneously accommodating rotational movement of the valving element relative to a valve body. The valving element of a rotary valve has a closure portion which is rotatably fitted within a valve body. This closure portion of the valve is joined by a stem or shaft portion which extends out of the valve body to interact with an actuator and transmit torque to the closure portion. This torque is used to rotate the closure portion within the valve body and to open or close a passageway in the valve.  
         [0004]     In plug valves, it is common practice to seal the top of the valve with a centrally apertured diaphragm with the shaft portion of the valve extending through the central aperture of the top seal. The mechanism for the adjustment of plug valves normally turns around the compression of two sealing parts to prevent leakage. These mechanisms involve normally a plurality of tightening bolts or screws (usually three but sometimes two).  
         [0005]     Examples of such valves can be seen in U.S. Pat. Nos. 3,235,272 (Smith); 4,159,818 and 4,475,713 (Reed et al.).  
         [0006]     While all of the above mentioned sealing arrangements have been highly satisfactory, they are not without their attendant disadvantages. For example, the tightening bolts or screws often need to be screwed simultaneously to prevent unwanted side loading on the system. Furthermore, these bolts or screws can be difficult to access with tools, especially in case of toxic leakage. As a result, these screws are rarely adjusted which reduces the effective life of the valve.  
       OBJECTS OF THE INVENTION  
       [0007]     It is thus an object of the present invention to provide an adjustable stem sealing means which uses a single screw that is positioned on the front of the cover for easy access, and eliminating any interference with future automation devices to be installed on the valve.  
         [0008]     It is a further object of the present invention to provide a top valve adjustable seal which provides for ease of adjustment when the valve is serviced in the field and which does not require special tools.  
         [0009]     It is yet another object of the present invention to provide plug valve adjustment means which comprises a rotatable cam and a single actuator.  
         [0010]     Other and further objects and advantages of the present invention will be obvious upon an understanding of the illustrative embodiments about to be described or will be indicated in the appended claims, and various advantages not referred to herein will occur to one skilled in the art upon employment of the invention in practice.  
       SUMMARY OF THE INVENTION  
       [0011]     Our mechanism uses only one actuator that is positioned on the front of the cover for easy access. The force generated by the actuator is transposed into a vertical force and a horizontal force by a rotating cam. The multiple faces of the cam, also referred as the caming faces, are used to transmit the force vertically and will maintain the mechanism in a straight position. The caming faces are adapted to cooperate with their corresponding surfaces disposed on the inside of said cover. The actuator is typically a screw or a bolt but may be any other means allowing the actuator to give a gradual rotatory movement to the cam and to maintain its position when the desired level is obtained. An advantage of this invention is that, as it rotates, the cam transmits a uniformly distributed pressure to the seal, allowing a better performance. More particularly, in comparison to systems where the force or the pressure is applied on only one side of the seal. Indeed, when the pressure is applied on only one side of the seal, the pressure may be non-uniformly distributed and there may be a risk of leakage on the side where the pressure is lower.  
         [0012]     Preferably, the top of the cam is used to indicate its position. As the cam is rotated, an arrow will point its position relative to the graduation on the cover. Also as the cam is rotated it&#39;s vertical motion downward can be used as an indication of the adjustment measured by the part of the cam that is outside the cover, it indicates the amount of compression that is left before the maximum compression is reached (when the top face of the cam mates the top of the cover).  
         [0013]     The base of the cam can be shaped to fit any type of seal or purpose; for example an o-ring or a p-seal. The angle of the compression plate or the like can be varied as needed to redistribute the compression in radial and axial direction on the seal.  
         [0014]     The features of the present invention which are believed to be novel are set forth with particularity in the appended claims.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     The above and other objects, features and advantages of the invention will become more readily apparent from the following description, reference being made to the accompanying drawings in which:  
         [0016]      FIG. 1  is a perspective view of a plug valve made in accordance with the present invention.  
         [0017]      FIG. 2  is a fragmentary perspective view of the plug valve shown in  FIG. 1 .  
         [0018]      FIG. 3  is a top view of the plug valve shown in  FIG. 1 .  
         [0019]      FIG. 4  is a partial top view of the plug valve shown in  FIG. 1 .  
         [0020]      FIG. 5  is a cross sectional view of the plug valve shown in  FIG. 4 .  
         [0021]      FIGS. 6A and 6B  are a perspective views of the cover and of the adjustment cam (unassembled) of the plug valve shown in  FIG. 1 .  
         [0022]      FIG. 7A  is a perspective view of the cam and  FIGS. 7B and 7C  are bottom perspective views of the cover and of the adjustment cam shown in  FIG. 6 .  
         [0023]      FIG. 8  is a bottom perspective view of the cover and of the adjustment cam shown in  FIG. 6  (assembled and in a first position).  
         [0024]      FIG. 9  is a bottom perspective view of the cover and of the adjustment cam shown in  FIG. 6  (assembled and in a second position).  
         [0025]      FIG. 10  is a bottom perspective view of the cover and of the adjustment cam shown in  FIG. 6  (assembled and in a third position).  
         [0026]      FIG. 11  is a fragmentary cross sectional view of the cover and top seal of the plug valve shown in  FIG. 1 .  
         [0027]      FIG. 12  is an exploded perspective view of an adjustable sealing device in accordance with this invention.  
         [0028]      FIG. 13  are top views of the adjustable sealing device shown in  FIG. 12  in its minimum (A), intermediary (B) and maximum (C) compression positions.  
         [0029]      FIG. 14  are cross-sectional views of the adjustable sealing device shown in  FIG. 13  in its minimum (A), intermediary (B) and maximum (C) compression positions.  
         [0030]      FIG. 15  are partial perspective sectional views of the adjustable sealing device shown in  FIG. 13  in its minimum (A), intermediary (B) and maximum (C) compression positions.  
         [0031]      FIG. 16  are top views of the adjustment cam/screw shown in  FIG. 12  in their minimum (A), intermediary (B) and maximum (C) compression positions. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0032]     A novel adjustable sealing means will be described hereinafter. Although the invention is described in terms of specific illustrative embodiment(s), it is to be understood that the embodiment(s) described herein are by way of example only and that the scope of the invention is not intended to be limited thereby.  
         [0033]     Referring now to the drawings and to  FIGS. 1 and 2  in particular, a plug valve  10  constructed in accordance with the present invention is shown. The plug valve  10  includes a valve body  14  having an inlet  16  and an outlet  18  with an internal flow passage  20  extending therebetween. A rotatable valving member  22  extends across the internal flow passage  20  to selectively block fluid flow therethrough. This valving member  22  is rotatably disposed within the valve body  14  of the illustrated embodiment and has a plug portion  24  which extends across the flow passage  20 . A stem portion  26  of the rotatable valving member  22  is attached to the plug portion  24  to extend out of the valve body  14 . Under normal circumstances, the stem portion  26  is interconnected with an actuator (not shown, either manual or automatic) which transmits a torque to the valving member  22  to effectuate relative rotation of the valving member  22  relative to the valve body  14  along a rotational axis  28 . The plug portion  24  of the valving member  22  has a through opening or passageway  30  therein, as is usual, to be placed in and out of registry with the internal flow passage  20  incident to partial rotation of the valving member  22  about the axis  28 . In the illustration of  FIG. 2 , the valving member  22  is shown in an open position. In this open position, the passageway  30  through the plug portion  24  registers with the internal flow passage  20 . As should be readily apparent, the valving member  22  is designed to be rotated about this axis  28  to place its through passageway  30  out of registry with the valve housing&#39;s ( 14 ) internal flow passage  20  and to completely cut off flow through that internal flow passage  20 .  
         [0034]     A first or primary sealing member in the form of a sleeve or liner formed of a fluorinated hydrocarbon polymeric material such as polytetrafluoroethylene, sold under the trademark TEFLON, or equivalent material is preferably fitted about the periphery of the plug portion  24  of the valving member  22  and is apertured in correspondency to that plug portion  24  to permit registry of the plug portions ( 24 ) through passageway  30  with the internal flow passage  20  whenever valving member  22  is in the open position illustrated in  FIG. 2 . The sealing member is snugly fitted on opposite sides of the internal flow passage  20  and provides a seal between the plug portion  24  of the valving member  22  and the valve body  14 .  
         [0035]     As mentioned above, the stem or shaft portion  26  of the valving member  22  extends out of the body  14 . In the illustration of  FIG. 2 , this extension is through an opening in the top of the valve body  14 , and for purposes of the present description, this opening will be referred to as a top opening (although the valve could clearly be oriented differently). This top opening is covered with a top seal in a form of a diaphragm  38  which is apertured to accommodate the stem portion of the valving member  22  which passes through the top seal/diaphragm  38 . The top seal/diaphragm  38  will initially be described as having been formed of a fluorinated hydrocarbon polymer such as polytetrafluoroethylene or equivalent material. However, as will be highlighted below, the design of the top seal  38  is such to permit the use of a wide range of shapes and materials to meet a correspondingly wide range of applications.  
         [0036]     The top seal  38  and the cooperating components of the valve  10  with which it interacts allow movement between the valve body  14  and the plug  22  to occur without interrupting the sealing function provided by the top seal  38 . Plug portion  22  has a taper from the top of the plug (proximal to stem  26 ) to the lower portion of the plug (distal to the stem  26 ). This taper of the plug  26  allows for downward adjustability of the plug by increasing the pressure of the actuator  75 , (a tightening bolt or an adjustment screw in a preferred embodiment) which in turn will apply pressure to the cam  65 . Downward adjustment of plug  22  relative to the body  14  increases the service pressure of the valve  10 , permitting use of higher pressurized content without leakage. Increasing the surface pressure of the valve also increases the torque required to rotate the plug  22  relative to the body  14 .  
         [0037]      FIG. 4  shows where the actuator  75  presses against the contact surface  66  of the cam  65 .  
         [0038]     As shown in  FIGS. 7A and 7B , the cam comprises three caming faces, only two are fully visible on this view which are  91  and  92 , which are adapted to cooperate with their corresponding surfaces  95 ,  96  and  97  disposed on the inside of said cover. These three faces,  91 ,  92  and  93  are fully visible on  FIGS. 16A  to  16 C. There are three caming faces and corresponding surfaces on the inside of the cover in the preferred embodiment but there may be more or less than three. When the actuator is actuated to increase the pressure of the seal, the actuator presses against the contact surface  66  causing the cam to rotate and move downward along stem  26 . When the actuator is released, the cam is free to rotate back with the pressure applied on the seal by the fluid in the adjustable sealing means. The arrow  68  indicates the position of the cam by pointing the graduation  76  on the cover (as seen on  FIG. 6B ).  
         [0039]     In  FIG. 7C , it is possible to see the surface  67  which directly transmits the pressure to the thrust collar (not shown) and to the seal (not shown). The cam  65  is used to transform a rotational movement into a vertical movement. The vertical moment induce a vertical force to the thrust collar and to the seal. The pressure is transmitted by all the surface  67  which is contact with the thrust collar. The pressure is uniformly distributed on the thrust collar and on the seal all around the stem.  
         [0040]     As illustrated in  FIG. 11 , tightening of the seal tightening cam  65  applies a downward force on the thrust collar  50 . This downward force is principally applied to the obliquely oriented bearing surface  54  which, in turn, applies a force to the rotatable valving member  22  in a direction substantially perpendicular to that of the bearing surface  54 . The result in the force applied to the rotating valving member  22  has two components, a first downward component and a second horizontal component. The two resulting components of force urge the top seal  38  in sealing engagement with both the stem portion  26  and the shoulder  80  of the rotatable valving member.  
         [0041]      FIGS. 12-16  show another embodiment of the invention. In this embodiment, a stem sealing device  100  comprises a base  180 , a seal  138 , a thrust collar  150 , a cam  165 , a cover  182  and an actuator  175 . In a preferred embodiment, the actuator  175  is typically a screw, a screw thread or a bolt. The downward force is principally applied to the obliquely oriented bearing surface  154 .  
         [0042]     The base  180  may be replaced by a similarly conFigured portion of the body of the object to be sealed. Bolts  188  are used to securely press the cover  182 , the cam  165 , the thrust collar  150  and the seal  138  to the base  180  and/or body.  
         [0043]     The stem  126  is introduced in the central opening in the stem sealing device  100 . Then the actuator  175  is tightened as needed.  
         [0044]      FIGS. 13-16  show the stem sealing device  100  in its minimum (A), intermediary (B) and maximum (C) compression positions.  
         [0045]     Thus, it is apparent that there has been provided, in accordance with the invention, a top seal that fully satisfies the objects, aims and advantages set forth above. While the invention has been described in conjunction with a specific embodiment thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims.