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FIELD OF THE INVENTION 
       [0001]    The field of the invention is a modular hydraulic assembly that can be coupled to an otherwise mechanically operated tool and preferably a valve to allow the option of hydraulically opening the tool or valve once or multiple times. More particularly, the assembly further allows the release of a stored force for a boost force upon initial opening of the valve. 
       BACKGROUND OF THE INVENTION 
       [0002]    Different valve styles have been used downhole. One type is a sliding sleeve valve that can selectively cover or open holes in a casing or liner string. These valves are typically shifted with a shifting tool that grabs a recess in the sleeve and pulls or pushes the sleeve to open or close the wall ports in the tubular. Some examples are U.S. Pat. Nos. 5,549,161; 7,556,102 and 7,503,390. 
         [0003]    Formation isolation valves have been used that have a ball that is attached to a sleeve so that movement of the sleeve results in ball rotation between open and closed position. These valves typically included a piston responsive to tubing pressure that worked in conjunction with a j-slot mechanism. The valve was closed mechanically but could be opened once with a predetermined number of pressure cycles on the piston. Eventually, a long slot in the j-slot would be reached to allow a spring or a compressed gas reservoir to move an operating sleeve into another sleeve that was attached to the ball so that the ball could be rotated to the open position. In one design the ball was locked after moving into the open position but that lock could be overcome with another tool run downhole. There was also a provision for an emergency opening with a pressure tool if for some reason the pressure cycles failed to open the ball. This design is illustrated in U.S. Pat. No. 7,210,534. Other formation isolation valves that came as an assembly of a mechanically operated ball that had the option of opening with pressure cycles until a j-slot allowed a pressurized chamber charged to a known specific pressure to move an operating sleeve against another sleeve to get the ball to turn open are illustrated in U.S. Pat. Nos. 5,810,087 and 6,230,807 while U.S. Pat. No. 5,950,733 initiates opening the ball with pressure that breaks a rupture disc to liberate pressure previously stored to move a sleeve to open that valve. 
         [0004]    These combination valves with the hydraulic open feature bundled into a mechanical valve such as a ball valve are very expensive and in many applications represent overkill because a manually operated barrier valve such as with a shifting tool run in on coiled tubing, for example would be sufficient and within the budget for the particular project. On the other hand, the specification for some projects changes where the previously ordered manual barrier valve is determined to be insufficient for the application without a hydraulic opening feature. A hydraulically operated module of the present invention addresses this need for flexibility and further makes it possible for use of the module on a variety of tools when those tools can respond to shifting of an operating rod. The hydraulic module further incorporates either a onetime only configuration which is the simpler variation or another variation that can be re-cocked after an actuation with a tool run in from the surface to move the operating piston back up. The unique configuration of the cycling control assembly allows the ability to re-cock with minimal displacement of the operating rod so that the tool can be shorter because the operating rod does not need to be displaced after the valve opens any further than it takes to land a snap ring back in a groove so that the series of pressure cycles can resume when another hydraulic opening of the valve is required. The above system was described in detail in a commonly assigned application in the U.S. having Ser. No. 12/618,123 and filed on Nov. 13, 2009, entitled Modular Hydraulic Operator for a Subterranean Tool and whose contents are incorporated by reference herein as though fully set forth. 
         [0005]    In another aspect, a backup potential energy source is provided that provides a force assist when trying to crack the valve open against high pressure differentials where an initial force to turn a ball toward open can be in the order of thousands of pounds of force. This auxiliary force is retained isolated during the predetermined pressure cycles that do not release the auxiliary force until the pressure is released on a predetermined cycle so that the boost force is initially applicable as the valve begins to open while the remainder of the movement is accomplished with the indexing spring. Variations that are one time operation or resettable with a tool are described. 
         [0006]    These and other advantages of the present invention will become more apparent to those skilled in the art from a review of the description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is given by the appended claims. 
       SUMMARY OF THE INVENTION 
       [0007]    A modular pressure operated actuator can be coupled with a downhole tool to selectively operate it at least once. In the preferred embodiment the module can be mounted adjacent an isolation valve and after a fixed number of on and off pressure cycles allow a spring to push an actuator to operate the valve to an open position. The actuator, in another embodiment, can be reset with a tool run into the module to move the actuator back against a power spring and hold that spring force until the pressure cycling begins again. The preferred application is for a formation isolation ball valve but other valves, such as sliding sleeves, or other types of downhole tools can be actuated with the module that permits a retrofit of a hydraulic operation to a heretofore purely mechanically actuated tool. The actuation force to initially open is boosted by a secondary potential energy source that is unlocked to give an initial boost force to the indexing spring that is part of a j-slot actuation mechanism. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIGS. 1-6  are a section view of the tool showing it in its position with tubing pressure reduced and against a lower travel stop; 
           [0009]      FIGS. 7-9  correspond to  FIGS. 4-6  with the tool in its position with tubing pressure applied and against an upper travel stop; 
           [0010]      FIGS. 10-12  correspond to  FIGS. 4-6  shown after removal of tubing pressure after a predetermined number of cycles so that the associated tool is operated; 
           [0011]      FIGS. 13-17  correspond to  FIGS. 1-3  showing an alternative embodiment for access of applied tubing pressure against a fluid filled reservoir isolated from well fluids with a floating piston; 
           [0012]      FIGS. 18   a - c  show an alternative embodiment in section in the pressure relieved position before the final controlled element is actuated. 
           [0013]      FIGS. 19 and 20  are rotated sections of  FIG. 18   b  with the tool in the same position. 
           [0014]      FIGS. 21   a - 21   b  are the view of  FIGS. 18   b - 18   c  shown in the pressure applied condition; 
           [0015]      FIGS. 22 and 23  are rotated sections of  FIG. 21   a  shown in the same position; 
           [0016]      FIGS. 24   a - 24   b  are the view of  FIGS. 18   b - 18   c  in the actuated position with the boost force applied; 
           [0017]      FIGS. 25 and 26  are rotated views of  FIG. 24   a  in the same position; and 
           [0018]      FIG. 27  is a rolled flat view of the j-slot that can be used with either embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0019]    Referring to  FIGS. 1-6  the modular tool T starts at a top sub  10  and ends at a bottom sub  12 . The top sub  10  is connected to a tubing string that is not shown. The tool being operated that is also not shown is connected at thread  14  on the bottom sub  12 . In between subs  10  and  12  are spring housing  16 , cylinder sub  18  (shown in full section rather than the half section of the other outer components) and main housing  20 . Interiorly there is a vented spring mandrel  22  connected between the top sub  10  and the cylinder sub  18 . There is also an indexing mandrel  24  between the cylinder sub  18  and the bottom sub  12 . A through passage  26  runs through the tool T from top sub  10  to bottom sub  12 . 
         [0020]    An indexing spring  28  resides in an annular space  30  and bears on shoulder  32  on spring mandrel  22  at a top end and against a spring guide  34  shown in full section in  FIG. 2 . In the position shown in  FIGS. 1-6 , the tool T is under bled off pressure in passage  26  in any one of the first 11 cycles and the indexing spring  28  is shown in its most relaxed condition and the spring guide  34  is at a spaced distance from surface  36  of the cylinder sub  18 . The spring guide moves with compression rods  38  of which there are preferably two at 180 degrees separation although only one is shown in  FIGS. 2-4 . Just like the indexing pistons  42  at thread  44  (only one of which is shown although preferably there are two at 180 degree spacing with a 90 degree offset from the compression rods  38 ) the compression rods  38  are tied to the piston coupler  40  at thread  46 . Note the piston coupler  40  is shown in half section so that its connection to the compression rods  38  at thread  46  is not shown. 
         [0021]    The piston coupler  40  is connected to the indexing sleeve housing  48  for tandem movement. There are four piston couplers  40  at the pistons  42 /compression rods  38 . They are contained in windows cut through the wall of the indexing sleeve housing. Holes through the upper face of the indexing sleeve housing  48  allow the threaded ends of the pistons and compression rods to pass through. At a lower end  50  of the indexing sleeve housing  48  is a thread  52  to secure the collet restraint  54 . The top end  56  of the collet restraint  54  supports an indexing sleeve  60  against surface  58  of the indexing sleeve housing  48 . The indexing sleeve housing  48  moves axially in opposed directions, taking with it the indexing sleeve  60 . Since there is a pin  62  mounted to the indexing sleeve  60  that extends into a j-slot pattern  64  on the indexing mandrel  24 , the axial movement of the indexing sleeve  62  is accompanied by rotation of indexing sleeve on its own axis. The j-slot pattern that is preferred has opposed up and down positions to accommodate preferably 11 cycles of pressure application and removal in passage  26  so that on the 12 th  pressure application followed by removal in passage  26  a longer movement of pistons  42  will be enabled to actuate the tool T as will be explained below. 
         [0022]    The indexing mandrel  24  has a discontinuous shoulder  66  that presents itself upon removal of applied pressure in passage  26  during the first 11 cycles of pressure application and removal in the passage  26 . As shown in  FIG. 4  the indexing sleeve  60  lands on shoulder  66  11 times before a gap in shoulder  66  presents itself on the 12 cycle pressure removal from passage  26  for operation of the tool T. On the first 11 pressurizing cycles of passage  26 , the upward travel limit is defined by shoulder  68  on the collet restraint  54  hitting shoulder  69  on the indexing mandrel  24 . 
         [0023]    The collet restraint  54  holds the lock collet  70  to the indexing mandrel  24  during the 11 pressure application and removal cycles in passage  26  until the 12 th  pressure removal cycle in passage  26 . The lock collet  70  is a tubular member that has a series of collet heads  72  on fingers  74 . On assembly, the heads  72  are in a groove  76  in the indexing mandrel  24  and the presence of the collet restraint  54  in contact with the heads  72  locks them into groove  76 . The lock collet  70  has a protruding or bulbous end  78  that abuts shoulder  80  of the indexing mandrel  24  and has the collet restraint  54  riding on it. Groove  82  is not as wide as end  78  so that movement of the collet restraint  54  past the end  78  will be smooth as the end  78  will simply straddle the groove  82  as the collet restraint  54  moves down. The fingers  74  are made by machining U-shaped slots through the wall of the lock collet. The bulbous end  78  is a solid ring of material that is integrally connected to the main body of the lock collet  70  by means of the webbed area left between the fingers. The width of groove  82  in the collet restraint is not really critical because the end of the lock collet is essentially a tube that always has clearance with the inside diameter of the collet restraint. In the pressure bled from passage  26  position, during the first 11 cycles, the collet restraint  54  has a surface  84  that will ride on end  78 , heads  72  and projection  86 . When moved up during the first 11 pressure cycles the surface  84  will move off projection  86  and still ride on end  78  and heads  72  and the lock collet  70  will be held fixed to the indexing mandrel  24 . 
         [0024]    Preferably a stack of Belleville washers  88  act as a boost force device and push against a spring support  90  that has an upper end  92  that shoulders out against the main housing  20  as shown in  FIG. 4 . At the opposite end the washers  88  bear on surface  96  of coupler sub  94 . Coupler sub  94  has multiple windows  98  through which extend one or more dogs  100  that are initially held in groove  102  in the bottom sub  12  by surface  104  on the lock collet  70 . Groove  106  on lock collet  70  is offset at this time from the dogs  100  so that the coupler sub  94  can hold its position against the bias from the washers  88  acting on surface  96 . 
         [0025]    Connected to the coupler sub  94  is a piston coupler  108  connected to preferably two push rods or actuating pistons  110  spaced at 180 degrees, although only one is shown. The connection here is similar to the one between the pistons and compression rods with the indexing sleeve housing. An adjusting screw  112  can be used with shims  114  to get the proper length to engage the operator of the tool that is not shown and that will be hydraulically operated by the modular tool T. Note that during the 11 cycles of pressure application and removal in the passage  26  the rods  110  do not move. This is mentioned because there can frequently be an accumulation of debris near the lower end of the bottom sub  12  if the barrier valve that is below and not shown in the drawings has been closed for a long time. Reciprocal movement of the rods  110  risks getting them stuck in debris at their lower ends. However, in this design the rods  110  remain locked to the bottom sub  12  until the groove  106  can be presented in alignment with dogs  100  as will be explained below. Also note that cycling of the pistons  42  to compress the indexing spring  28  will not require an applied force to compress the washers  88  that have been pre-compressed on assembly and have that potential energy force on tap when needed on pressure release on the 12 th  cycle. This is advantageous as the number and piston area of the pistons  42  does not need to be altered for the presence of the secondary source of force from the washers  88 . Washers  88  are selected preferably as they deliver a greater force for a short distance than other types of biasing devices. The extra force from the washers  88  is needed to initially move a closed ball, for example, in a barrier valve that is not shown that has to be rotated when subjected to large differential pressures. The applied force of the push rods  110  could be as high as thousands of pounds depending on the differential pressure on the closed ball when trying to open it. 
         [0026]    Referring back to  FIG. 3 , the pistons  42  reciprocate in respective cylinders  116  that are open to the surrounding annulus  118  through a screened opening  120 . Each piston  42  rides on a bushing  122  and has a seal  124  retained to it by a retainer  126 . A wall passage  128  is illustrated schematically that connects annular space  30  to annular space between indexing mandrel  24  and main housing  20 . Applied pressure in passage  26  acts on the lower side of seal  124  and against the pressure in the annulus  118  that communicates to the higher side of seal  124  through the screened opening  120 . Thus, a pressure differential is created across seal  124  with applied pressure. 
         [0027]    Fluid displacement from annular space  30  as the spring guide  34  moves is handled through an opening  130  shown in  FIG. 1  that is preferably a plurality of narrow spaces slots made by wire EDM techniques so that fluid can move while debris is blocked. 
         [0028]      FIGS. 7-9  show the movement of the collet restraint  54  on pressure application to passage  26  until surfaces  68  and  69  engage. What has happened is that the upward movement of the pistons  42  has not only compressed the indexing spring  28  because the compression rods  38  have moved in tandem with the pistons  42  but also the indexing sleeve  48  has come up and taken with it the collet restraint  54 . Now the collet restraint  54  is no longer over projection  86  but it is still over the collet heads  72  and the bulbous end  78  of the lock collet  70 . The force of the washers  88  is still locked as dogs  100  are still held in groove  102  by the lock collet  70  and groove  106  is still offset from the dogs  100 . Push rods  110  have not moved. Thus  FIGS. 1-6  show the positions of the part on removal of pressure in passage  26  for the first 11 times and  FIGS. 7-9  show the par position on application of pressure for each of those 11 cycles as well as the pressurization during the 12 th  cycle. What happens on the 12 th  cycle pressurization is that the gap in the shoulder  66  presents itself in alignment with the indexing sleeve  60  so that on the pressure removal for the 12 th  time, the indexing sleeve  60  and the attached collet restraint can move an extra distance that allows groove  82  to align with heads  72  to effectively unlock the lock collet  70  from the indexing mandrel  24  and connect the lock collet  70  to the advancing collet restraint  54  until groove  106  comes into alignment with dogs  100  and the force of the washers  88  can now be applied to move the coupler sub  94  and the attached push rods  110  so that the initial force to open the barrier valve that is not shown occurs with the tandem force of the indexing spring  28  as well as the washers  88  until an internal travel stop is encountered as will be explained using  FIGS. 10-12  below. 
         [0029]    As shown in  FIGS. 10-12  a gap in ridge  66  has presented itself so that the indexing sleeve  60  can move further than the previous 11 removals of pressure from the passage  26 . As a result the groove  82  on the collet restraint  54  has registered with the heads  72  to trap the lock collet  70  to the collet restraint  54  for tandem movement. That tandem movement has put the groove  106  into alignment with dogs  100  to allow the coupler sub  94  and the push rods  110  to extend from the bottom sub  12  under the initial tandem force of the indexing spring  28  and the washers  88 . Note that spring support  90  has its upper end  92  moved away from a shoulder on the main housing  20 , see  FIG. 4 , by the movement of the collet restraint  54 . At that point the washers  88  are no longer backstopped by the main housing  20  and can no longer provide a force to move the coupler sub  94  and the connected push rods  110 . With a barrier valve or some other tool having an operator in abutment with the push rods  110 , the movement of the parts will cease when the actuation assembly of the tool against which the push rods  110  abut no longer permits further movement. This embodiment of the tool T is not resettable. Once the push rods  110  are extended and the barrier valve below is opened with hydraulic pressure the tool T has served its purpose and its usefulness is done. 
         [0030]    Note that the boost force for initial opening from the washers  88  can be adjusted to last a longer or shorter duration of the push rod  110  movement by reconfiguration of the stack of washers  88  and/or the parts that are unleashed to move with the pressure removal on the 12 th  cycle. Optionally, the boost force from the washers  88  can last for the duration of the movement of the push rods  110 . 
         [0031]    Note that if there is no tool operating mechanism available to stop the push rods  110  such as when the tool T is bench tested then one travel stop for the push rods  110  can be when the piston coupler  108  hits surface  130  in  FIG. 11 . Alternatively some part of the indexing sleeve  60  can be configured to engage the continuous portion of the shoulder  66  at a rotated location from the discontinuous portion of that shoulder  66  using a surface such as  132  on the indexing sleeve  60 . 
         [0032]    It should be noted that the indexing assembly for this embodiment comprises the moving parts between the indexing spring  28  and the piston coupler  108  and outside the passage  26  whose movement causes the actuating piston  110  to actuate the barrier tool. For the subsequent embodiment the indexing assembly comprises the moving parts outside the passage  200  and between and including the indexing spring  210  and the actuating piston coupler  226  whose movement causes actuating pistons  222  to actuate the barrier tool 
         [0033]    Referring to  FIGS. 13-16  it may be desirable to move the pressure entry point to reach the seal  124  through passage  128  as described before to a higher location on the tool T simply to keep the inlet location for pressure application away from the zone where debris can accumulate if the barrier valve below has been closed for a long time. Rather than having the passage  26  access the passage  128  fairly close to the bottom end of the tool T as in  FIGS. 1-6 , the  FIGS. 13-17  disclose an alternate location for applied pressure in passage  26  to reach the passage  128  in the wall of the cylinder sub  18 . The inlet  134  can be in the spring mandrel  22  or it can even be moved higher by extension of the length of the mandrel  22  and the top sub  10 . As with inlet  130  in  FIG. 1  inlet  134  is made with narrow slots using wire EDM to keep debris out of chamber  136  defined by floating piston  138 , spring mandrel  22  and extension mandrel  140 . Chamber  142  is filled with clean incompressible oil or a slightly compressible material such as silicone and extends through extension housing  15  to connector sub  19  and around the indexing spring  28  until terminating at surface  36  in  FIG. 17 . A seal  144  seals the lower end of the passage  142 . By way of the ports in the connector sub and the wall passage in the cylinder sub, the hydraulic fluid extends all the way down to the push rods covering all of the internal mechanism. There is a seal between the bottom sub and indexing mandrel as well as on the push rods to contain the clean oil. Pressure applied at inlet  134  pushes on the floating piston  138  to pressurize passage  142  and  128  to move the pistons  42  in the manner described before. The floating piston  138  is used to allow for compensation for thermal loads from well temperature changes. Extension mandrel  140  has a fill port  146  with a check valve  148  to allow filling the passage  142  with clean oil while venting air through vent  150 . After the filling and air venting is concluded an isolation plug  152  is put into position to close off the fill port  146  and the vent  150 . 
         [0034]    An alternative embodiment that is resettable is shown in  FIGS. 18   a - c  in the 11 positions of relief of pressure in the passage  200 . The tool T′ has a top sub  202  and a bottom sub  204  connected by a spring housing  206 . Indexing mandrel  208  also is connected between the subs  202  and  204  and defines the passage  200  through the tool T′. An indexing spring  210  bears on stop  212  secured to the indexing mandrel  208 . The other end of the indexing spring  210  pushes on the shoulder at the top end  213  of the spring guide extension  214 . A housing  216  has an upper end  218  that is connected to the lower end  220  of spring guide  240  by the spring guide coupler  242  so that when pressure in passage  200  acts on the lower end  224  of actuating piston  222  there is tandem movement from the piston  222  to the top end  213  of the spring guide extension  214  to compress the indexing spring  210 . Piston coupler  226  connects the piston  222  to the housing  216 . Housing  216  translates with indexing sleeve  228  as sleeve  228  turns on its center axis because it has a pin  230  (see  FIGS. 22 and 27 ) that extends into a j-slot pattern  232 . The position  234  of the pin  230  in the j-slot  232  represents its location when pressure is bled off the passage  200  for the 11 th  time. In the next or 12 th  pressure application, the pin  230  will go to position  236  and then when the pressure in passage  200  is bled off, the pin will move to position  238  an extra distance longer that the other 11 cycles so that the piston  222  can extend out of the bottom sub  204  to actuate the connected tool (not shown) at thread  240  as will be explained below. 
         [0035]    The spring guide extension  214  is connected to the spring guide  240 . Lock keys  244  are retained by the spring guide coupler  242  against surface  246  of the indexing mandrel  208  as best seen in  FIG. 19 . The lock keys  244  ride in slots  248  represented by dashed lines  249  in lock key housing  250 . Lock keys  244  can slide between opposed travel stops  252  and  254  as pressure is removed and applied in passage  200  and as pin  230  follows in j-slot  232  between the  232  and the  234  positions during the 11 pressure application and removal cycles. 
         [0036]    One end of a booster force device such as a spring  256  is supported by a stop  258  that is attached to the indexing mandrel  208 . On the other end of booster spring  256  is lock key housing  250  which during the 11 cycles of pressure application and removal cannot move so that the boost force stored in spring  256  is retained during the 11 cycles.  FIG. 20  illustrates that the lock key housing  250  has collet fingers  260  with heads  262  located in groove  264  and held trapped there by surface  266  of spring guide coupler  242 .  FIG. 20  shows the relative part positions with the pressure in passage  200  released and  FIG. 23  shows the pressure applied all cycles. Comparing  FIGS. 20 and 23 , it can be seen that surface  266  has slid along the collet heads  262  so that in  FIG. 23  the groove  268  has moved away from heads  262  that are still trapped by surface  266  in groove  264 . Thus in both the  FIGS. 20 and 23  positions representing respectively removal of pressure in the first 11 cycles and application of pressure in all cycles the stored force of booster spring  256  is retained between the stop  258  and the immobile lock key housing  250 . 
         [0037]    A ramp sleeve  270  moves axially with the indexing sleeve  228  and is configured to release from the movement of the indexing sleeve  228  when the pressure is released for the 12 th  cycle in passage  200 . The ramp sleeve  270  by not moving with the indexing sleeve  228  allows use of its ramped end  272  to push the lock keys  244  radially outwardly enough so the keys  244  will clear the stop  252  that they have hit on the previous 11 occurrences of relief of pressure in the passage  200 . At the same time at the 12 th  relief of pressure in passage  200  the pin is in position  236  in the j-slot  232  and is now able to have extended movement to location  238  in the j-slot  232 , see  FIG. 27 . 
         [0038]    As the longer stroke occurs as described above and as better seen by comparing  FIGS. 23 and 26  the first thing that happens is that groove  268  presents itself opposite heads  262  to allow them to escape groove  264  in the indexing mandrel  208  and stay in a locked position in grove  268  because outer surface of indexing mandrel  208  locks the heads  262  to groove  268 . As a result the force in booster spring  256  can move the lock key housing  250  in tandem with the spring guide coupler  242 , the housing  216  and the piston  222  shown fully extended in  FIG. 24   b . At the same time, the indexing spring  210  pushes on spring guide extension  214  and spring guide  240  and into the spring guide coupler  242  and from there the path to the piston  222  is the same as for the booster spring  256  just described. At the beginning of the stroke of the piston  222  there is a compounding of force from both springs  210  and booster spring  256  to turn for example a ball on a barrier valve (not shown) toward an open position against a large differential pressure in the same manner as described in the previous embodiment of  FIGS. 1. 17 , with the main differences being that the tool T′ is resettable when a mechanically operated valve (not shown) is closed with a tool (not shown) that is inserted in passage  200  to retract the piston  222  to the  FIG. 18   c  position. Another difference between the embodiments is that the piston goes up and down with every application and removal of pressure whereas the previous embodiment locks the pushrods  110  until the dogs  100  are released for the operating of the barrier tool to open or to operate another tool (not shown). 
         [0039]    Those skilled in the art will appreciate that either embodiment allows the provision of a boost force for initial movement of a final controlled element such as a ball on a barrier valve where a hydraulic opening feature is desired. When trying to open a valve against high pressure differential pressure an extra amount of force is frequently needed. A force in the order of thousands of pounds or more may sometimes be required. The high differential pressure can cause some ball distortion and the accumulation of debris near the ball that has been closed for a long period of time can also add to the initial force required to start the ball turning. The large force may only need to be applied until the final controlled element opens slightly to equalize the pressure differential in the tubing. The variations described can be modular to fit against an operator of a mechanically operated valve or they can be integral with the valve assembly and be provided as a unit. 
         [0040]    The number of pressure applications and releases before the final controlled element is operated can be arbitrarily set at fewer or more than 11 cycles, with the recitation of the 11 cycles being arbitrary. The degree of movement of the components in each cycle before operation of the final controlled element can also be varied, with the showing in the two disclosed embodiments of equal movement in each of the 11 cycles also being arbitrary. 
         [0041]    In the embodiment of  FIGS. 1-17  the final controlled element can preferably be in continuous or alternatively in no contact with the push rods  110  during the cycles where the push rods  110  are in a locked position. This can be an adjustment of the adjusting screw  112 . The other embodiment that features one or more pistons  222  that move during the 11 cycles will at times be out of contact with the final controlled element or its actuator by design. However, that design provides a tradeoff of being resettable whereas the design of  FIGS. 1-17  is not resettable. 
         [0042]    While a stack of Belleville washers  88  or a coiled booster spring  256  are illustrated for examples, other types of devices for storing and selectively releasing potential energy force are contemplated included selective release of compressed fluids, wave springs or equivalents. While a boost force is preferably offered for the initial actuation of the final controlled element, the boost force device can be configured for extending the duration of the boost for a greater time of operation of the final controlled element and even for the full stroke length of the tool T or T′. 
         [0043]    The isolation of the boost force delivery device during the cycling of the tool T or T′ until the actuation is desired for the final controlled element removes the need to compress the washers  88  or the spring  256  on each pressure application. This allows the use of a smaller piston area in a tool where space is at a premium and additional pistons also can affect the pressure rating of the housing in which such pistons are disposed. However, in some applications there can be room for more pistons or pushrods to actually move the final controlled element and such alternatives are contemplated as well as the employment of an annular piston instead of one or more rod pistons. 
         [0044]    The above description is illustrative of the preferred embodiment and many modifications may be made by those skilled in the art without departing from the invention whose scope is to be determined from the literal and equivalent scope of the claims below.

Summary:
A housing can be mounted adjacent an isolation valve and after a fixed number of on and off pressure cycles allow a spring to push an actuator to operate the valve to an open position. The actuator, in another embodiment, can be reset with a tool run into the module to move the actuator back against a power spring and hold that spring force until the pressure cycling begins again. The preferred application is for a formation isolation ball valve but other valves, such as sliding sleeves, or other types of downhole tools can be actuated with the module that permits a retrofit of a hydraulic operation to a heretofore purely mechanically actuated tool. The actuation force to initially open is boosted by a secondary potential energy source that is unlocked to give an initial boost force to the indexing spring that is part of a j-slot actuation mechanism.