RELATED APPLICATIONS 
     This application is a continuation in part of U.S. application Ser. No. 11/595,596 filed on Nov. 9, 2006 and having the title Downhole Lubricator Valve. 
    
    
     FIELD OF THE INVENTION 
     The field of the invention relates to downhole barrier valves such as, among other applications, a valve for forming a downhole lubricator that allow a string to be made up in a live well by isolation of a lower portion of it and more particularly to features regarding such valves relating to locking them, assembling them and component fabrication techniques. 
     BACKGROUND OF THE INVENTION 
     Lubricator valves are valves used downhole to allow long assemblies to be put together in the well above the closed lubricator valve with well pressure further below the closed lubricator valve. These valves are frequently used in tandem with sub-surface safety valves to have redundancy of closures against well pressures below. Valves are also used downhole for other isolation purposes. 
     Lubricator assemblies are used at the surface of a well and comprise a compartment above the wellhead through which a bottom hole assembly is put together with the bottom valve closing off well pressure. These surface lubricators have limited lengths determined by the scale of the available rig equipment. Downhole lubricators simply get around length limitations of surface lubricators by using a lubricator valve downhole to allow as much as thousands of feet of length in the wellbore to assemble a bottom hole assembly. 
     In the past ball valves have been used as lubricator valves. They generally featured a pair of control lines to opposed sides of a piston whose movement back and forth registered with a ball to rotate it 90 between an open and a closed position. Collets could be used to hold the ball in both positions and would release in response to control pressure in one of the control lines. An example of such a design can be seen in U.S. Pat. Nos. 4,368,871; 4,197,879 and 4,130,166. In these patents, the ball turns on its own axis on trunnions. Other designs translate the ball while rotating it 90 degrees between and open and a closed position. One example of this is the 15K Enhanced Landing String Assembly offered by the Expro Group that includes such a lubricator valve. Other designs combine rotation and translation of the ball with a separate locking sleeve that is hydraulically driven to lock the ball turning and shifting sleeve in a ball closed position as shown in U.S. Pat. No. 4,522,370. Some valves are of a tubing retrievable style such as Halliburton&#39;s PES® LV4 Lubricator Valve. Lock open sleeves that go through a ball have been proposed in U.S. Pat. No. 4,449,587. Other designs, such as U.S. Pat. No. 6,109,352 used in subsea trees have a rack and pinion drive for a ball and use a remotely operated vehicle (ROV) to power the valve between open and closed positions claiming that either end positioned is a locked position but going on to state that the same ROV simply reverses direction and the valve can reverse direction. 
     What is lacking and addressed by the present invention is a more elegant solution to a downhole ball type lubricator valve. One of the features is the ability to translate the ball for the purpose of locking open a ball that normally rotates between open and closed on its own axis. Another feature is a method of manufacturing parts that must be longitudinally split so that they retain the original bore dimension despite the wall removal occasioned by longitudinally splitting the part. Yet another feature is the ability to assemble components to a given overall dimension so as to accurately set preload on biased seats that engage the ball. 
     In one embodiment, the annular piston that actuates the valve is replaced with at least one rod piston and the space made available with this change allows the addition of a seal to prevent leakage under high differential pressure conditions from the uphole to the downhole direction. 
     These and other features of the present invention will be more readily apparent to those skilled in the art from a review of the preferred embodiment and associated drawings that are described below while recognizing that the full scope of the invention is determined by the claims. 
     SUMMARY OF THE INVENTION 
     A ball type downhole barrier valve capable of bidirectional sealing features a ball rotating on its axis to open or close with control line pressure to an actuating rod piston assembly. The ball is also shiftable to a locked open position. A cage surrounds the ball and retains opposed seats to it. The cage is made from one piece and tangential holes are drilled and tapped before the piece is longitudinally split with a wire EDM cutting technique. Fasteners to rejoin the cut halves properly space them to the original one piece internal dimension. Auxiliary tools allow determination of spacing of internal components so that a desired spring preload on the seats against the ball can be achieved. Seals on the sleeves that form ball seats help prevent leakage due to ball distortion at high differential pressures when the valve is closed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a section view of the entire lubricator valve; 
         FIG. 2  is a larger view of the top end of the valve of  FIG. 1 ; 
         FIG. 3  is a larger view of the middle of the valve from  FIG. 1  showing the ball open; 
         FIG. 4  is an alternate view to  FIG. 3  showing the ball closed; 
         FIG. 5  is a larger view of the lower end of the valve of  FIG. 1 ; 
         FIG. 6  is a perspective view of the section views shown in  FIGS. 4 and 5 ; 
         FIG. 7  shows the top end of the valve in  FIG. 1  during assembly to get proper spacing of internal components; 
         FIG. 8  shows the lower end of the valve in  FIG. 1  during assembly to get proper spacing of internal components; 
         FIG. 9  is a perspective of the cage that surrounds the ball and is longitudinally split. 
         FIG. 10  is a section view of the embodiment showing the use of rod pistons and an additional lower seal to deal with issues of ball distortion under high differential pressures; 
         FIG. 11  is an enlarged view of an upper seal around a sleeve that support the upper ball seat; 
         FIG. 12  is a force diagram of the  FIG. 1  design showing a condition of a differential force in an uphole direction; 
         FIG. 13  is the view of  FIG. 12  with a differential force in a downhole direction and leakage from ball distortion under high differential pressures; 
         FIG. 14  shows a differential in the uphole direction using a seal on the sleeve above the ball; 
         FIG. 15  is the view of  FIG. 14  with a differential in a downhole direction showing how leakage is reduced or eliminated under high differentials in a downhole direction and showing an additional seal on the OD of the lower sleeve to assist with sealing. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  illustrates the layout of the main components in housing  9  to show their position relative to each other with the ball  10  in the center and in the closed position. Sleeve  12  is above ball  10  and sleeve  14  is below ball  10 . These sleeves respectively form seats  16  and  18  that are held against ball  10  by a cage  20 . Cage  20  is shown in perspective in  FIG. 9 . A slide  22  extends through cage  20  and registers with ball  10  to rotate it between the open and closed position on trunnions  24 . A piston  26  is responsive to control line pressure to reciprocate the slide  22  to operate ball  10 . A lock open assembly  28  is disposed near the top of the tool while the preload adjustment mechanism  30  is located near the opposite end. Using this basic locating of the major components of the valve, the other FIGS. will now be used to bring out additional details and explain the basic operation. 
       FIG. 6  can be used to appreciate how the ball  10  is rotated 90 degrees between the closed position shown in  FIG. 6  and the open position shown in section in  FIG. 3 . Piston  26  operates like many pistons known in the art and used in downhole valves. A pair of control lines (not shown) are run from the surface to opposing piston face areas on piston  26  to urge it to move in opposed directions. The piston  26  is secured to the slide  22  for tandem movement. Slide  22  has an upper ring  32  and a lower ring  34  connected by arms  36 , one of which is visible in  FIG. 6 . Looking at  FIG. 9  it can be seen that the cage has longitudinal slots  38  and  40  that accept the arms  36  of slide  22 . Referring to  FIGS. 1 and 6  it can be seen that slide  22  is at the end of its uphole stroke as it has contacted the mandrel  42 . Ball  10  has opposed angled exterior slots  44  one of which is partially in view in  FIG. 6 . The slots  44  are parallel to each other on opposed flats  46  better seen in  FIG. 1 . Flats  46  on ball  10  abut arms  48  and  50  of cage  20  as best seen in  FIGS. 6 and 9 . Holes  52  and  54  accept trunnions  24  that extend into ball  10  to allow it to rotate on its own axis. Cage  22  does not move but when slide  22  is moved by piston  26  the result is rotation of ball  10  on its own axis. This happens because arms  36  have inwardly facing pins (not shown) that register with slots  44  in ball  10  off center from trunnions  24  to induce rotation of ball  10 . 
     To better see this movement,  FIGS. 3 and 4  need to be compared.  FIG. 4  shows the ball  10  in a closed position and upper ring  32  close to mandrel  42  but not in contact. This is because, optionally, a snap ring  56  registers with slot  58  on sleeve  12  to hold the ball  10  in a closed position until enough pressure is exerted on piston  26  to pop the snap ring  56  out of groove  58  until it registers with groove  60  to define the open position of  FIG. 3 . Again, in  FIG. 4  during normal opening and closing of the ball  10 , the only moving part except ball  10  shown in that FIG. is slide  22  with ring  56 .  FIG. 3  shows the fully open position of ball  10  with ring  56  registering with groove  60 . Slide  22  may optionally contact cage  20  at this time.  FIG. 3  also shows piston  26  attached to slide  22  with an anti-rotation pin  62 . One of the control line connections  65  to operate piston  26  is also shown in  FIG. 3 .  FIG. 3  also shows that sleeves  12  and  14  respectively form flanges  64  and  66  and how the cage  20  retains those flanges together against ball  10 . Seals  16  and  18  respectively are disposed in flanges  64  and  66  for circumferential sealing contact with ball  10  as it rotates between the open and the closed positions of  FIGS. 3 and 4 . 
     Looking now at  FIG. 5 , the lower end of the sleeve  14  can be seen as well as another control line connection  68  that is used to urge piston  26  in an opposite direction from pressure applied to connection  65  shown in  FIG. 3 . A bottom sub  70  has a shoulder  72  on which a spring  74  is supported. Spring  74  pushes on ring  76  that is attached to sleeve  14  with a thread  78 . A screw  80  locks the position of ring  76  after that position is initially determined in a procedure that will be explained below. In essence, spring  74  is a preload spring on an assembly that begins with ring  76  and extends to the upper end of the valve shown in  FIG. 2 . 
     Referring to  FIG. 2  a spring  114  is used to push on ring  86  and through the other parts described before downwardly on sleeve  12  to insure engagement of seat  16  with respect to the ball when pressure above the ball  10  is applied. Conversely, sleeve  14  is biased uphole by spring  74  to ensure a similar engagement of the ball and seat when pressure below the ball is applied. As those skilled in the art will appreciate the assembly of parts from shoulder  84  at the upper end to shoulder  118  at the lower end each have their own tolerance and the adjustment available for the position of ring  76  on thread  78  is fairly minimal. As a result, the total dimension of the parts between shoulders  84  and  118  can be determined and the position of ring  76  necessary to give the right preload to the assembled parts also determined before final assembly of top sub  82  and bottom sub  70 .  FIGS. 7 and 8  show this technique. 
     Instead of assembling top sub  82  and spring  114  to mandrel  42  an upper gauge  122  is assembled to mandrel  42 . When fully threaded on, a shoulder  124  hits ring  86  in nearly the exact spot that shoulder  84  from top sub  82  would normally engage it. At the same time at the lower end in  FIG. 8  instead of putting on bottom sub  70 , spring  74  or screw  80 , a lower gauge  124  is threaded on to mandrel  42 . Lower gauge  124  has a pair of arms  126  and  128  that respectively have shoulders  130  and  132  that wind up exactly where shoulder  118  would be when bottom sub  70  is screwed on. Because of the open gaps between arms  126  and  128  there is access to adjustment ring  76  and it can be moved up or down on thread  78  as long as screw  80  is not assembled. Ring  76  is turned to bottom on shoulders  130  and  132  and then the rotation is reversed to allow installation of screw  80  in recess  136  (see  FIG. 5 ) so that ring  76  has its position fixed as close as possible to shoulder  118  when the bottom sub  70  is assembled with spring  74 . Similarly, the upper gauge  122  ( FIG. 7 ) is first removed and replaced with top sub  82  and spring  114  ( FIG. 2 ). When the bottom sub  70  and spring  74  get screwed on, spring  74  will have the needed preload since despite the accumulation of tolerances of all the assembled parts the actual surface of ring  76  is determined as it related to spring  74  for the desired preload. 
     Referring now to  FIG. 9  the cage  20  is illustrated as fully assembled. Since it needs to straddle ball  10  and flanges  64  and  66  ( FIG. 3 ) it needs to be made into two pieces. The technique for making this piece or, for that matter, other pieces that need to be made in two pieces to be assembled over yet other pieces, is to make a longitudinal cut  140 . Before doing that, all the machining shown in  FIG. 9  is done including bores  142  and  144  on one side and similar bores on the other side (not visible) that go though where longitudinal cut  140  will be made. Again, before the cut is made, the bores  142  and  144  are tapped. Thereafter the cut  140  is made by a wire EDM technique. This known technique removes a part of the wall away where the cut is made. Thus, after the cut halves are pushed together, their inside diameter  146  will be smaller than it was before the cut. However, the pitch of the tapped thread and the matching thread on the studs  148  and  150  when screwed in to bridge the cut  140  will, because of the thread pitch separate the halves at cut  140  just enough to compensate for the amount of wall removed during the cut so that when fully assembled the original one piece diameter  146  that was there before the cut is again present. While the wire EDM removes only a few thousandths of an inch out of the wall to make the longitudinal cut the result is still a change in the internal bore dimension. This technique of drilling and tapping before a longitudinal cut with wire EDM allows the original bore dimension to be regained while holding the cut halves together. 
     Referring to  FIG. 2  the lock open feature will be described. Sleeve  12  is ultimately selectively retained by top sub  82 . Shoulder  84  contains fixed ratchet ring  86  to prevent upward movement of the ratchet ring  86 . Ring  86  has an undercut  88  defining taper  90 . Ring  92  initially sits in undercut  88 . It has ratchet teeth  94  that, in the position of  FIG. 2  are offset from ratchet teeth  96  on ring  86 . Ring  92  bears on retainer ring  98  which, in turn, captures split ring  100  in groove  102  of sleeve  12 . Due to urging of spring  114 , sleeve  12  is held down against ball  10  and against the uphole force on sleeve  14  from spring  74  (see  FIG. 5 ). Locking collar  104  has one or more internal grooves  106  for engagement with a tool (not shown) that will ultimately pull the collar  104  uphole. A shear screw  108  initially secures the collar  104  to the sleeve  12 . Sleeve  12  has a groove  110  that eventually registers with tangential pins  112  extending from collar  104 . Collar  104  initially retains ring  92  in undercut  88 . In operation, the collar  104  is pulled up with a tool (not shown) to break the shear screw  108 . As the collar then moves up, tangential pins  112  ride in groove  110  until hitting the top of it at which time the collar  104  moves in tandem with sleeve  12 . In the meantime, collar  104  moves uphole from ring  92  allowing it to collapse inwardly to clear taper  90 . When pins  112  register with the top of groove  110  and the sleeve  12  is moving with collar  104 , ring  100  in groove  102  of sleeve  12  takes with it ring  98  which, in turn now can push ring  92  beyond taper  90  so that ratchet teeth  94  move into engagement with ratchet teeth  96  on ratchet ring  86 . The uphole movement described above continues until sleeve  12  hits a travel stop. This happens in two ways depending on the position of ball  10  when sleeve  12  is being pulled up. If the ball  10  is open, as shown in  FIG. 3 , flange  64  pulls up cage  20  as well as slide  22  which was registered with sleeve  12  at groove  60 . The ball  10  comes up with cage  20  because they are connected at trunnions  24 . The ball  10  does not rotate because there is no relative movement between the slide  22  and the cage  20 . Motion of sleeve  12  stops when ring  32  hits mandrel  42  and that position is held locked by the ratchet teeth engagement of teeth  94  and  96 . On the other hand, if ball  10  is in the closed position of  FIG. 4 , the sleeve  12  will bring up the cage  20  and move it relatively to slide  22 . This happens because at the onset of movement of sleeve  12  the upper ring  32  of slide  22  is already close to mandrel  42  and fairly quickly hits it as the sleeve  12  comes up. Further uphole movement of sleeve  12  pulls the cage  20  relative to the slide  22  which causes the pins in slide  22  to rotate ball  10  to open as they register with slots  44  in ball  10 . When the cage  20  comes against already stopped ring  32  of the slide  22  uphole motion stops and the position is again locked in by engaging teeth  94  and  96 . 
     Those skilled in the art will recognize that the ball type lubricator valve can be normally operated with control line pressure that moves piston  26  in opposed directions to rotate ball  10  on its own axis for 90 degrees to the open and closed positions. An optional indexing feature holds the open and closed positions when they are attained. The valve can be locked open from either the open position or the closed position by freeing the upper sleeve  12  to move and lifting it until it ratchet locks with the ball  10  in the open position while maintaining a full bore through the valve. While a ratchet lock is illustrated other locking devices such as dog through windows, collets or other equivalent devices are also contemplated. It should be noted that translation of ball  10  is only employed when attempting to lock it open. It should be noted that parts can be reconfigured to alternatively allow the ball  10  to be locked closed as an alternative. 
     Yet another feature of the barrier valve is the preloading of the internal components and the ability to gauge the dimension of the internal components before mounting the top and bottom subs with the spring or springs that provide the preload so the proper amount of preload can be applied. Yet another feature is a way of making longitudinally split parts so that they retain their original internal dimension despite removal of a part of the wall for a cutting operation using the drill and tap technique before longitudinal cutting by wire EDM and then regaining near the original spacing in the joined halves relying on the pitch of the tapped thread and the fastener inserted in the bore and spanning the longitudinal cut. In this particular tool the cage  20  and slide  22  can be made with this technique. The technique has many other applications for longitudinally split parts with internal bores that must be maintained despite wall removal from a cutting process like wire EDM. 
       FIGS. 12 and 13  illustrate what happens under high differential loading conditions in the uphole and downhole directions respectively in the design discussed above and illustrated in  FIGS. 1 and 4 . In  FIG. 12  the ball  10  is in the closed position and holding pressure from below. Upper ball seal  16  is on sleeve  12  and there is an external seal  200  to isolate the annular space  202  which is not sealed from the interior passage  204  of the ball  10  because the pivots  24  are not sealed. Pressure from downhole can come to the ball  10  through the annular space  204  as well as tube  14  since there is no outer seal on tube  14  to isolate the annular space  202 . Lower seal  18  that is below the ball  10  is mainly a dust seal as seal  16  is the seal that is intended to hold pressure differential in either direction. When the pressure differential is in an uphole direction as illustrated in  FIG. 12  the pressure reaches annular space  202  because there is no exterior seal on tube  14 . The uphole directed differential pressure is stopped at seal  200  and seal  16 . The downhole pressure enters the passage  204  in the ball to uniformly load the ball  10  from its interior as illustrated by arrows  208 . This uniform loading from within the ball  10  helps the ball  10  maintain its shape and contact continues all along the seat  16  for a seal against uphole differential pressure against high differentials of over 10,000 PSI. 
     In a high downhole oriented differential pressure situation as shown in  FIG. 13 , something different happens. Here seal  200  isolates such pressure from uphole from getting to the annular space  202  so that the entire differential loading on the ball  10  is from within passage  210  as long as seal  16  is holding. However, at this time the pressure inside the ball  10  at  204  is substantially less so that the pressure in passage  210  represented by arrows  212  can distort ball  10  to an oblong shape as illustrated schematically by dashed line  214 . When that happens the seal between the ball  10  and its seat  16  no longer holds and pressure get beyond the ball  10  into the annular space  202  and beyond seat  18  that is meant only to serve as a dust seal as well as down the outside of sleeve  14  because in this embodiment it has no external seal. While the assembly in  FIG. 13  has been shown to be perfectly serviceable at lower pressure differentials, testing has indicated the potential for leakage in the manner described above at differentials in the downhole direction in excess of 10.00 PSI. 
     In  FIG. 14  an additional seal  216  has been added. It blocks pressure from downhole from getting around tube  14  and into annular space  202 . Seal  200  is still there on the outside of tube  12 . Arrows  218  reflect the initial loading on ball  10  that until a predetermined differential pressure exists can hold the pressure in passage  206  at seal  18 . After the differential gets higher the pressure will get by seal  18  by either distorting ball  10  or displacing sleeve  14  away from ball  10 . At that time the downhole pressure will get into the annular space  202  as well as within ball  10  at  204 . This effect is demonstrated schematically by arrows  220 . At this point seal  16  holds the high uphole oriented pressure differential in the manner described before for  FIG. 12 . Again, even if temporary distortion of ball  10  occurs to let pressure into annular space  202  the deformation is elastic rather than plastic and the ultimate job of sealing against uphole oriented differential pressures falls to seal  16 . Once the internal space  204  of the ball  10  is equalized with the pressure from downhole, regardless of the mechanism by which that occurs, the ball  10  is uniformly loaded against seat  16  and as a result even with high uphole differential pressures, there is no leakage uphole past seal  16 . 
       FIG. 15  is now contrasted with the same situation as shown in  FIG. 13 . Only this time there is a seal  216  outside of tube  14  and seal  200  is still there above ball  10  and outside sleeve  12  although it is not shown in  FIG. 15 . A buildup of downhole oriented differential pressure is shown by arrows  220 . This differential pressure force at a predetermined level gets past seal  16  temporarily and into annular space  202  and into the ball  10  in space  204 . Now the annular space is sealed with seal  216  so pressure in space  204  represented by arrows  222  equalizes with the pressure on ball  10  represented by arrows  220  so that ball  10  is uniformly loaded on seat  18  and seat  18  holds the downhole oriented differential pressure from getting in passage  206 . In essence the performance of the assembly under a differential pressure from downhole in  FIG. 14  is the same as when the differential is in the opposite direction as shown in  FIG. 15 . The only difference is which seal holds the differential. In both cases the ball  10  elastically deforms to equalize ball pressure through the annular space  202  and the ball goes right back to its spherical shape once equalization of pressure takes place. This is to be contrasted with the downhole oriented pressure differential situation of  FIG. 13  where leakage continued as equalization did not happen and the ball  10  distorted under the differential as indicated by lines  214  and leakage continued as long as the differential pressure on ball  10  existed. 
     In another aspect of the present invention, it was noticed that in very deep settings of the valve assembly shown in  FIGS. 1-9  the annular piston  26  was subject to such high differential forces that its shape distorted in the annular passage that surrounded it and what resulted were wear locations on the surrounding wall that defeated the seals that surrounded annular piston  26  or in extreme cases could distort the piston shape to a sufficient extent to cause it to seize in its bore and become immovable. To counteract this effect noticed when the valve assembly depicted is in very deep applications that involve very high hydrostatic pressures on an annular piston  26 , the design was changed to use rod pistons  224  which is in pieces and is exposed to connections  68  and  64  to which a control line (not shown) is connected. Preferably the rod pistons are arrayed symmetrically about the central axis of the valve assembly so that any moment that one such rod piston created can be canceled by another rod piston disposed 180 degrees from it. Any number of rod pistons can be used although an even pairing for symmetry is preferred. The use of rod pistons eliminates the distortion issues at high differential pressures such as existed with annular piston  26 . It also makes room to add the seal  216  whose purpose was discussed above. It marks a first for downhole ball valves that are actuated with a rod piston assembly and makes the design useful for very high differential pressure installations where annular pistons can fail under differentials that can exist at differentials above 10,000 PSI. Of course the rod piston design can also be used at lower differentials instead of the annular design with good results. 
     While the preferred embodiment has been set forth above, those skilled in art will appreciate that the scope of the invention is significantly broader and as outlined in the claims which appear below.
A ball type downhole barrier valve capable of bidirectional sealing features a ball rotating on its axis to open or close with control line pressure to an actuating rod piston assembly. The ball is also shiftable to a locked open position. A cage surrounds the ball and retains opposed seats to it. The cage is made from one piece and tangential holes are drilled and tapped before the piece is longitudinally split with a wire EDM cutting technique. Fasteners to rejoin the cut halves properly space them to the original one piece internal dimension. Auxiliary tools allow determination of spacing of internal components so that a desired spring preload on the seats against the ball can be achieved. Seals on the sleeves that form ball seats help prevent leakage due to ball distortion at high differential pressures when the valve is closed.