Abstract:
An adjustable moment arm flapper including a flapper defining a cavity there within and a moveable mass system disposed within the cavity, a center of mass of the flapper changeable based upon position of the movable mass and a method for dynamically controlling a flapper.

Description:
BACKGROUND 
       [0001]    In the drilling and completion arts, many different uses of flapper valves are made. These valves are failsafe and robust and hence have been adopted by individual operators and regulatory agencies alike for use in downhole industries. Flappers of flapper valves are generally articulated to a housing in one portion thereof and allowed to swing relatively freely otherwise. Such flappers may be of a number of shapes including square, round, etc. and in the downhole industry are often rounded as tubing strings used in this industry tend to be at least substantially cylindrical. 
         [0002]    Flappers are commonly openable hydraulically either by the application of hydraulic pressure through a control line forcing a flow tube to push the flapper open or in the case of an injection valve, applied fluid pressure acting directly upon the flapper. While these configurations work well for their intended purposes, improvements in functionality and/or cost reduction are always welcomed by the art. 
       SUMMARY 
       [0003]    An adjustable moment arm flapper including a flapper defining a cavity there within; and a moveable mass system disposed within the cavity, a center of mass of the flapper changeable based upon position of the movable mass. 
         [0004]    A method for dynamically controlling a flapper including employing the flapper An adjustable moment arm flapper including a flapper defining a cavity there within; and a moveable mass system disposed within the cavity, a center of mass of the flapper changeable based upon position of the movable mass; urging the flapper to an open position; and positioning a moveable mass system to shift a center of mass of the flapper away from a pivot point of the flapper. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    Referring now to the drawings wherein like elements are numbered alike in the several Figures: 
           [0006]      FIG. 1  is a schematic partially broken away representation of a flapper in a closed position; 
           [0007]      FIG. 2  is a schematic partially broken away representation of the flapper of  FIG. 1  in an open position; 
           [0008]      FIG. 3  is a schematic partially broken away representation of an alternate flapper in a closed position; 
           [0009]      FIG. 4  is a schematic partially broken away representation of the flapper of  FIG. 3  in an open position; 
           [0010]      FIG. 5  is a schematic plan view of the flapper illustrated in  FIGS. 4 and 5 ; 
           [0011]      FIG. 6  is a cross sectional view taken along section line  6 - 6  in  FIG. 5 ; 
           [0012]      FIG. 7  is a cross sectional view taken along section line  7 - 7  in  FIG. 5 ; 
           [0013]      FIG. 8  is a cross sectional view of an alternate embodiment taken along the section line  7 - 7 . 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    Referring to  FIG. 1 , a schematic view of a flapper valve  10  is illustrated. The valve  10  includes a flapper  12  and a housing  14 . The valve  10  is similar to existing flapper valves of the art except for the particular construction of the flapper  12 . For this reason and to make plain the concept disclosed herein, it will be appreciated that the flapper  12  has been partially broken away to allow visual inspection of its interior. The flapper  12  is configured with a cavity  16  that may have a number of geometrical shapes but will extend substantially diametrically from a pivot pin  18  of the flapper  12 . It is to be appreciated that the cavity  16  extending as stated provides for translation of other components discussed hereunder in a direction most effective for the purpose of the invention. It is also to be appreciated that although it is important to provide for extension of the cavity  16  diametrically from the pivot pin, there is no reason that the entirety of the flapper  12  cannot define a cavity (being for example, completely hollow) or some other proportion thereof providing that the translatory motion discussed below is accommodated. Further, it is noted that the cavity will in each embodiment have matter therewithin in at least two phases. For example, there may be solid components and liquid components within the cavity; there may be liquid and gaseous components within the cavity; there may be solid and gaseous components within the cavity; and there may be all three phases of matter within the cavity. 
         [0015]    Within the flapper  12  and seen through the broken away portion of the flapper  12 , is a movable mass system  19  comprising a biasing member  20  and a weight  22 . The weight  22  is connected to the biasing member  20  and the biasing member  20  is connected to a nonmovable portion  24  of the flapper  12  near the pivot pin  18  such as simply an anchor point in the flapper  12 . The biasing member  20  is, in one embodiment, a coil spring configured to work primarily in tension. Other equivalently functioning configurations are also contemplated. The purpose of the spring is to move the weight  22  toward the pivot pin  18 . The spring  20  is selected to have sufficient tensile force to move the weight  22  toward the pivot pin  18  when the flapper is pivoted to a position that is not vertical. Stated alternatively, when the flapper  12  is pivoted to the fully open position the weight  22  is suspended by the biasing member  20  at a particular position within the flapper  12 . The position is ideally close to an end of the cavity  16  opposed to the pivot pin  18 . Then as the flapper begins to pivot towards the closed position, the member  20  will begin to be capable of moving the weight toward the pivot pin  18 . The more the flapper pivots toward the closed position the more the spring  20  is able to move the weight  22  because the weight is increasingly supported by the flapper so that the spring must overcome less and less of the weight  22  due to gravity. As the flapper gets closer to close then it becomes easier to close since the weight presents a lesser moment arm on the flapper. When the flapper is closer to the open position, shown in  FIG. 2 , the weight  22  extends the member  20  under the force of gravity and positions itself such that the flapper stays substantially open with less input than prior art flappers need. The member  20  must be carefully configured to provide the correct amount of resistance to the weight  22  during moving and enough resilience to pull the weight back toward the pin  18  once the flapper  12  begins to move toward the closed position. More specifically, and related to each embodiment disclosed herein, the flapper exhibits less resistance to pivotal movement when the flapper is internally in one configuration (internal mass centered closer to the pivot pin  18 ) than it does when it is internally in another configuration (internal mass centered farther from the pivot pin  18 ), the configurations being changeable based upon the position of the flapper. Stated alternatively, each embodiment hereof is configured in various ways to increase the mass of the flapper at a point diametrically opposed to the pivot pin  18  as the flapper is opening. The shifting of mass is due to gravitational forces and has the effect of keeping the flapper in the open position and out of the flow there past due to the reduced impetus to move about the pivot pin. This is due to a changing moment arm of the flapper itself. As the weight  22  moves to the largest diametrical position relative to the pivot pin  18  the moment arm increases and as the weight is moved toward the pivot pin  18  by the member  20  the moment arm decreases. The changing moment arm allows the flapper to experience more or less resistance to pivotal movement as noted above. 
         [0016]    In various embodiments of the movable mass system, the weight  22  includes a low friction coating or is of a low friction material; the cavity  16  is coated with a low friction material; the weight is endowed with one or more rollers  23  disposed in contact with the flapper to reduce friction between the flapper  12  and the weight  22 . 
         [0017]    In an alternative embodiment, referring to  FIGS. 3-8  the movable mass system is altered by replacing the weight  22  and biasing member  20  with a fluid system comprising a liquid component and a gaseous component. As noted above, the functionality of the invention comes from the capability of the flapper to move its center of mass closer to or farther from the pivot pin  18 . The fluid system functions similarly in that the gaseous component will automatically find a higher point elevationally whereas the liquid component will find a lower point elevationally. Since the density of the gaseous fluid is distinctly different than the density of the liquid fluid, the center of mass shifts as the liquid component moves relative to the gaseous component. Referring to  FIG. 3 , it will be appreciated that a flapper  112  is illustrated having a cavity  116  partially occupied by a liquid component  130  and partially occupied with a gaseous component  132 . The gaseous component  132  naturally migrates to the elevationally higher position whether the flapper  112  is closed ( FIG. 3 ) or open ( FIG. 4 ). The gas and liquid will move smoothly between these two positions as the flapper  112  moves. As the flapper  112  moves toward the open position and the liquid naturally follows that movement to reposition itself and hence the center of mass of the flapper  112  farther from the pivot pin  18 , the functionality of the invention as noted above is effected. The flapper  112  will stay in the open position with the benefit of a longer moment arm at the pivot pin  18  and since the liquid and gaseous components will again reposition upon a closing moment put on the flapper  112  from another input, such as a torsion spring or a flow tube moving out of the way, thus reducing the moment arm acting to hold the flapper  112  open. 
         [0018]    In addition to the mere weight of the liquid component versus the gaseous component, it is also possible depending upon fluid selected and environment in which the device is used for buoyancy of the gaseous component to assist in closing the flapper  112  as it nears the closed position because at that point a buoyancy of the gaseous “bubble” will be urging the flapper  112  closed. 
         [0019]    Referring to  FIGS. 5 ,  7  and  8  it will be appreciated that the cavity  116  may comprise substantially a smaller cylindrical or semispherical void  134  atop a larger cylindrical or semispherical void  136  and the smaller void may be entirely joined to the larger void  136  or may only be joined thereto by a channel  138 . 
         [0020]    While one or more embodiments have been shown and described, modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustrations and not limitation.