Patent Abstract:
A plurality of rows of locking dogs are provided with housing flexibility between rows to allow them to share a shear loading while leaving enough structural integrity in the housing to define the windows through which the dogs emerge. The dogs can also have extensions with a surface that grippingly engages the housing adjacent the window on extension of the dogs such that loads can transfer from the housing into the extension and into the profile in which the dog is disposed rather than passing the shear stress through the window edge into the dog that is in the profile. The dog configuration can also share the load on multiple contact surfaces of the housing to reduce stress at each contact location.

Full Description:
FIELD OF THE INVENTION 
     The field of the invention is lock mandrels that engage a mating profile in a tubular with dogs and more particularly design features that distribute shear loads on the dogs when stacked or that transfer loads on the housing between dog windows to the dogs from the adjacent body portion to reduce stress otherwise passing to the housing portions between dog windows. 
     BACKGROUND OF THE INVENTION 
       FIGS. 1-3  show an existing design for a lock mandrel tool  10  that has an outer housing  14  with openings  16  for extendable dogs  18  shown retracted in  FIG. 1 . One or more seals  20  engage a seal bore in a surrounding tubular that is not shown when the tool  10  hits a no-go also not shown in the surrounding tubular. A setting sleeve  22  has a thin lower end  24  that is under the dogs  18  for run in so that dogs  18  will be retracted inside windows  16 . A ramp  26  leads to a larger diameter portion  28 . As seen in  FIG. 2  when the ramp  26  is pushed against the dogs  18  the dogs  18  get pushed out through the windows  16  to the point where portion  28  underlies the dogs  18  and the dogs  18  are extended into a surrounding profile that is not shown. The extension of the dogs  10  raises the tool  10  off the no-go that is not shown. 
     Housing  14  has elongated segments  30  that define the windows  16  between them. There needs to be sufficient wall in segments  30  so that when there is a pressure differential from uphole and the dogs  18  are extended into a surrounding profile and the tool  10  as a result of dog extension is no longer supported on the no-go, that the tensile stress in the segments  30  is not exceeded. There is normally a tradeoff between making the dogs  18  wider and the need for sufficient wall thickness to tolerate the stresses administered from pressure differential. Wider dogs  18  can hold more shear load but the strength of the body is reduced when the width of segments  30  is reduced to make the dogs  18  wider. 
     The present invention addresses this issue in at least two ways that can be used separately or together. In one aspect the load is transferred to the dogs from the housing while avoiding or minimizing loading the window periphery and the sections of the housing that are among the windows. In another approach multiple rows of dogs are presented to share the shear loading and flexibility in the housing between rows of dogs allows the sharing of shear loading. This addresses an issue of manufacturing tolerances being high enough so that engagement of a first row of dogs can move another row of dogs into a position where they do not take the shear loading at all because they are displaced from the profile end. These and other aspects of the present invention will be more readily 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 to be determined from the appended claims. 
     SUMMARY OF THE INVENTION 
     A plurality of rows of locking dogs are provided with housing flexibility between rows to allow them to share a shear loading while leaving enough structural integrity in the housing to define the windows through which the dogs emerge. The dogs can also have extensions with a surface that grippingly engages the housing adjacent the window on extension of the dogs such that loads can transfer from the housing into the extension and into the profile in which the dog is disposed rather than passing the shear stress through the window edge into the dog that is in the profile. The dog configuration can also share the load on multiple contact surfaces of the housing to reduce stress at each contact location. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a run in configuration of a prior art lock mandrel tool; 
         FIG. 2  is the view of  FIG. 1  during the extension of the dogs; 
         FIG. 3  is the view of  FIG. 2  with the dogs fully extended; 
         FIG. 4  shows the multi-row version of the lock mandrel tool in the dogs extended position. 
         FIG. 5  is a view along lines  5 - 5  of  FIG. 4   
         FIG. 6  shows the dogs having extensions that engage the housing on radial extension of the dogs to transfer stress from the housing to the extension and into a surrounding profile; 
         FIG. 7  is a view along lines  7 - 7  of  FIG. 6 ; 
         FIG. 8  is a view of an alternative embodiment of a load distributing dog design; 
         FIG. 9  is a section view showing the dog of  FIG. 8  in a nipple profile; 
         FIG. 10  is a top view of the dog of  FIG. 8  extending through a matching pattern in the dog housing; and 
         FIG. 11  is an alternative view of the dog of  FIG. 8 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 4  shows the tool  40  with a nose  42  and a flow port  44  to allow fluid movement through the tool  40  during run in. A housing  46  has an upper row of openings or windows  48  disposed circumferentially in a predetermined pattern and in a quantity that space will allow.  FIG. 5  shows four dogs circumferentially spaced at 90 degrees but other even or uneven spacing or number of windows  48  and dogs  50  can be used. A second row of windows  52  each having a radially extendable dog  54  is illustrated below windows  48  and dogs  50 . More than two rows can be used and the windows  48  and  52  can be aligned or misaligned in the axial direction. The windows  48  and  52  and their corresponding dogs  50  and  54  can be identical in shape or volume or they can be different. A surrounding tubular  56  has profiles  58  and  60  to match the shape and size of the dogs  50  and  54 . The spacing of the rows of dogs or the shape of the dogs and their mating profiles can be unique so that of more than one tool is to be located in a given tubular  56  at different locations each location can have a unique profile location using profiles such as  58  or  60 . 
     The housing  46  also has seals  62  and  64  to align with a seal bore  66  that is just above the no-go  68  on the tubular  56 . When the housing  46  hits the no go  68  the seals  62  and  64  line up with the seal bore  66  while the dogs  50  and  54  line up with the profiles  58  and  60 . For initial run in the actuation sleeve  70  is supported by a running string that is not shown in  FIG. 4 .  FIG. 4  shows a plug  72  that is later delivered in a separate trip as will be later explained. With the housing  46  landed on the no-go  68 , setting down weight will first ramp out dogs  50  as they are engaged by taper  74  on the actuation sleeve  70  as a result of setting down weight on the running string that is not shown. The dogs  50  cam against the profile as they are extended picking the tool up off the no-go profile. Further setting down weight advances the taper  74  into contact with dogs  54  to radially extend them into their profile  60 . A snap ring  76  jumps into groove  78  in the housing  46  after all the dogs  50  and  54  are forced radially out to hold the position of sleeve  70  with respect to the housing  46 . Drill hole  80  allows attachment of the running tool, not shown, to the housing  46  via a shear wire, not shown. A port  44  allows for by-pass fluid to flow through the tool during run-in. 
     The objective of multiple rows is to reduce the stress on a given dog by having more dogs share the same loading. The issue when doing this in axially offset rows is that the machining tolerances of the windows  48  and  52  and the associated dogs  50  and  54  is such that advancing of the dogs  54  into profiles  60  can lift the dogs  50  in their profiles  58  because of the way the clearances play out to the point that dogs  50  carry no load or minimal load. This would defeat the purpose of the rows of dogs sharing the load. Accordingly, the present invention addresses this issue by providing axial flexibility between the rows of dogs. One way this is done is to take a section  83  between the rows of windows  48  and  52  and make it axially elastically flexible or/and elastically flexible in other planes or in torsion. What is illustrated is a series of circumferentially oriented elongated narrow openings that have opposed ends that are offset circumferentially from slots in an adjacent row. The rows can be equally or unequally spaced or the pattern can a spiral slot pattern as opposed to slots in a plane perpendicular to the longitudinal axis of the housing  46 . Rather than slots, scores can be used in conjunction with slots or by themselves. A series of identical or differing openings can be used. 
     Section  83  in whole or in part can be made from a shape memory alloy (SMA) such as Nitinol®. SMAs will tolerate stretch for a predetermined distance at low modulus so that the load can be shared by the rows of dogs  50  and  54  without a failure of the part and with the ability to revert to the original dimension when the dogs are retracted. The section  83  can be a solid annular shape and its inherent properties will give it a spring-like quality within the anticipated amount of stretch envisioned when the dogs are extended so that they can share the load between or among rows. 
     Another concern is that the no-go  68  can receive a large load and fail if differential pressure loading puts the taper on the tool  40  against the no-go  68 . One way to minimize or eliminate this risk is to use an SMA on the body in the region between the taper that is designed to initially land on the no-go  68  for extending the dogs  50  and  54 . The run in dimension will properly position the dogs  50  and  54  to enter recesses  58  and  60 . However after setting the tool  40  well fluids or another heat source can make that lower end of the tool  40  get shorter as it reverts to that length when the transition temperature for the SMA is crossed. This feature can be used regardless of whether there is a single row or multiple rows in the tool of  FIG. 4  or  FIG. 6 . 
     Regardless of the approach the goal is to increase flexibility of the housing  46  between the rows of windows such as  48  and  52  so that radially extending one row of dogs will not cause the other row or rows of dogs to not take their share of the load. As previously explained this can happen when the spacing of the dogs  50  and  54  is axially off the spacing of the profiles  58  and  60  due to the various tolerances in the assembled tool  40 . By providing the flexibility in the alignment process the result of sharing the load among multiple rows of dogs is achieved and each dog can then be designed for a smaller loading without reduction of the overall ability of the tool  40  to resist the targeted load. 
     The plug  72  with its seals  82  and  84  lands in the nose  42  on a separate trip. It has passages  85  to allow fluid flow during run in. Its upper end  86  is secured to the sleeve  70  by rotation or another way. 
       FIGS. 6 and 7  show a single row of openings  100  through which a dog assembly  102  extends. Rather than having an internal flange to prevent overextension from housing  46  as is the case with the dogs  50  and  54 , the dog assembly  102  in each window or at least some windows has an extension  104  that has a surface gripping profile  106  that matches a similar profile  108  on the housing  110 . When the dog assemblies are pushed out radially in the same manner as in  FIG. 5 , the radial movement brings profiles  106  and  108  into an interlocking relationship when a shear load is applied due to differential pressure acting on seals when the housing  110  is no longer supported on a no-go of a surrounding tubular that is not shown for clarity in  FIG. 6  but is the same as illustrated in  FIG. 4 . For example when there is a net pressure differential from above the dog assemblies  102  the result is a tensile force on the housing between the dogs  102  and the seals  112  and  114 . Was it not for the engagement of the gripping profiles  106  and  108 , which could be a series of ridges parallel to each other or a spiral thread form to name a few options, the stress can be communicated to the portions of the housing between the windows  100 . This phenomenon was discussed earlier with regard to the  FIGS. 1-3  embodiment with regard to segments  30  that have to be designed to take stress from differential pressure stresses. As previously explained this limited the size of the dogs  18  as there had to be enough body material left to take the stress communicated through it with the dogs  18  extending into their respective profiles. 
     However, in the  FIG. 6  design the extensions  104  transfer the stress from a location on the housing  110  where there are no windows and through the dogs  102  and into the surrounding profile that is not shown in  FIG. 6 . Thus, the portion of the housing  110  that is between the windows  100 , best seen as  116  in  FIG. 7 , is minimally stressed. This allows for windows  100  and their respective dogs  102  to be made larger for a greater capacity for stress while still reducing the extent of the wall areas at  116  as compared to the design of  FIGS. 1-3  where the portions  30  are more severely stressed. 
     While  FIG. 7  shows a single row, multiple rows as shown in  FIG. 4  can be used with the feature of the extensions  104  also shown in  FIG. 7 . The flexible segment  82  would be located between rows as shown in  FIG. 4 . Combining the features allows the use of larger dogs and smaller spaces between windows in a given row with the feature of load sharing that is achieved from using multiple rows without the concern that one row will not adequately share the loading with dogs in another row. 
     In another embodiment, shown in  FIGS. 8-10  the dogs  220  extend into a nipple profile  290 . Dogs  220  extend through a dog housing  200  and are driven out radially into the profile  290  by a ramped sleeve  210 . The dogs  220  extend through a similarly shaped opening  230  in the dog housing  200  as seen in  FIG. 10 . As shown in  FIG. 8  there are multiple generally parallel rows  204 ,  206  and  208  that are spaced apart using connecting segments  212  connecting  204  and  206  and  214  connecting  206  and  208 . The end contact surfaces  310  and  300  are tapered to the angle of end surfaces  216  and  218  in the profile  290 . Row  206  does not contact the profile  290  and has opposed parallel sides  222  and  224 . Segments  204  and  208  have interior surfaces  226  and  228  respectively. Surface  226  is substantially parallel to surface  222  and surface  228  is substantially parallel to surface  224 . Surface  232  on dogs  220  faces surface  240  on the opening  230  in housing  200 . On the other end of the dogs  220 , surface  234  faces surface  236  of opening  230  in housing  200 . 
     The shape of the opening  230  is shown in more detail in  FIG. 10 . In the position shown there is differential loading on the housing  200  with the dogs  220  extended into the profile  290 . As a result there are three loading surfaces on the housing  200  that are loaded by each dog  220  and those surfaces are  240 ,  250  and  252 . Those surfaces are stressed by the following surfaces, respectively on each dog  220 , when there is differential loading in the downhole direction on the housing  200  as represented by arrow  243 :  232 ,  222  and  228 . The dogs  220  are loaded in compression. Tension loading can result in necking that can lead to dog failure and possible loss of well control if the dogs  220  were retaining a well plug for example. 
     Note that the segments  204 ,  206  and  208  progressively reduce in length from  204  to  208 . The sections  286 ,  284  and  282  of the housing  200  between the openings  230  correspondingly increase in width. Load  243  is applied to the housing below the dogs  220  at seal  292  so the full load is transmitted in tension through section  282  and all other sections between  282  and the seals  292 . A portion of the load is transmitted through surface  252  into the dog  220 , thus the amount of load that goes through housing section  284  is the remainder of the portion transmitted through surface  252  and total load  243 . Likewise a portion of the load is transmitted to the dog  220  through surfaces  240  and  250  and thus housing section  286  carries the least load out of sections  282 ,  284  and  286 . This apportions the load so the strongest of housing sections  282 ,  284  and  286  takes the most load. It should be noted that surface  232  has two disparate segments  235  and  237  separated by the recess  239  with the purpose being to bring the stressed areas on the dog closer to equivalence so as to more equally distribute stress among the three loaded surfaces  240 ,  250  and  252 . 
     Load  243  transmitted to the dog  220  from the housing  200  occurs at surfaces  232 ,  222 , and  228  and each portion is transmitted through the length of the dog between said surfaces and surface  300  where the load is transmitted to profile  290 . Thus the portions of the dog  220  closer to surface  300  carry more load. 
     When the differential loading is in the uphole direction opposite arrow  202 , surfaces  260 ,  270  and  280  are loaded by surfaces  233 ,  241  and  236 . Section  282  and all other sections between section  282  and the seal  292  again transmit the load but in this case it is a compressive load. 
     The spacing of the loading surfaces  240 ,  250  and  252  can be even or uneven and the same is true for the load surfaces  232 ,  222  and  228  on the dogs  220 . While three locations of load distribution are shown for each dog extending through a respective opening, other numbers of load distributing surface pairs can be employed within the scope of the invention. 
     Those skilled in the art will appreciate that multiple rows or other orientations of dogs can be provided and the issue of cumulative tolerances causing the insertion of one dog into its profile to move another dog out of a load carrying placement in its profile will be addressed with a flexibility feature in the housing among axially spaced dogs. The housing flexibility can be provided by selective weakening of the housing with slots or scores of a variety of shapes and regular or random patterns. Alternatively the material itself can change properties to provide the flexibility when extending the dogs in response to a stimulus such as well fluids, heat, pressure or various applied fields, to mention a few flexibility providing features. The housing material itself between the rows of dogs can be flexible as long as it can tolerate the stress imposed on dog extension and subsequent pressure differential loading when latched. 
     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:

Technology Classification (CPC): 4