Abstract:
An anchor features a mandrel with ramps that extent through apertures in slip segments giving the slips a longer ramp to ride out on in a radial direction. The slip segments have ramps adjacent the apertures and in the preferred embodiment ride out on a plurality of spaced ramps on the mandrel.

Description:
FIELD OF THE INVENTION 
   The field of this invention is downhole anchors and more particularly those that are set in larger tubing than they are run through. 
   BACKGROUND OF THE INVENTION 
   Generally speaking anchors are bodies that have a series of slips that are retracted for running into a desired location and then have the slips extended to grip in the wellbore to support a tool or a string of tubulars or other downhole equipment. The objective in anchor design is to allow the tool to have the slimmest profile for insertion and then extend as much as possible for a grip, where the grip will still be strong enough to resist the anticipated loads. 
   U.S. Pat. No. 7,114,559 shows an anchor design in  FIG. 2 . The present invention is an improvement to that design. For completeness in understanding this invention  FIGS. 1 and 2  will illustrate the preferred embodiment in the prior application to better provide a framework to understanding the present invention. 
   Thus, by way of background,  FIGS. 1 and 2  will be reviewed to get an understanding of the present invention that has simply resulted in being able to extend the reach of an anchor for a given run in drift diameter to further than is possible with the design of  FIGS. 1 and 2 .  FIG. 1  is a split view showing a slip in a retracted position for run in on the top half of the drawing and the same slip  10  in an extended position on the bottom half of  FIG. 1 . A jagged section line  2 - 2  in Figure indicates where on  FIG. 1  the section shown in  FIG. 2  is taken. What is shown is a mandrel  12  that has a series of ramps  14 ,  16  and  18 . The mandrel  12  has a passage  20  through which pressure is put on a piston (not shown) that causes relative movement between the mandrel  12  and the slips  10  that are mounted to it. The mandrel  12  is shown to be symmetrical about the center line  22 . 
   Slip  10  has ramps  24 ,  26  and  28  that rest against ramps  14 ,  16  and  18  for run in to create the smaller profile shown in  FIG. 1 . The inserts  30  stick out the most during run in and define the drift diameter necessary for the tool to pass on run in. The mandrel  12  has peaks set apart from each other and two of them  32  and  34  are shown in  FIG. 1  that are disposed above and below ramp  16  for illustrative purposes. The slip  10  is an integral structure that spans over the ramps  14 ,  16  and  18  and is designed to have thin connecting segments such as  36  and  38  that meet design criteria. The Anchor design needs to consider the load to be applied, such as tensile loads through the mandrel  12 , bearing area on slip  10  and ramp  16 , and tensile loads through slip  10 . Also, this should be designed within a small cross section dictated by the amount of travel needed. The segments  36  and  38  need to be thin to allow the tool to get through the smallest drift dimension possible. This is because the slips  10  are mounted fully over the mandrel  12  and the thicker they get in the connecting segments such as  36  and  38  the greater the drift will be required to run the tool downhole. The limiting value on how thin the segments  36  and  38  can get is how much tension load they have to take as the slip  10  rides out on the ramps on the mandrel  12 . If the slip  10  doesn&#39;t move exactly evenly in its radial motion one or more segments get put under a temporary tensile load. Thus the segments must have sufficient cross-section to avoid failure from stressing during setting. The setting occurs when pressure is applied to passage  20  and relative movement of the slip segments  10  occurs with respect to mandrel  12 .  FIG. 2  shows a section view of the slip segment  10  retracted at the top and extended at the bottom. The section view is through the thin segment  36  shown in  FIG. 1 . Looking at the bottom of  FIG. 1 , it is easier to see that the most highly stressed portion of the slip  10  is at the thin segments such as  36  and  38  or the bearing area remaining between ramp  16  and slip  10 . Ideally, the slip  10  has upper and lower ends that move in tandem in a radial direction but in reality due to irregularities in the surrounding tubular some portion of the slip  10  can engage at a different time than another portion to stress the thin segments such as  36  or  38 . 
   Those skilled in the art will appreciate that although only a single slip  10  is shown in two positions in a split view that mandrel  12  supports a series of slips  10  around its circumference that are retained in a retracted position by one or more band springs (not shown). 
   The present invention optimizes the profile of the anchor so that the required drift dimension to run it in is kept to a minimum, while at the same time making it possible to extend the slips further into a larger tubular than the previous design and still get a good bite for support downhole. These and other aspects of the present invention will be more readily apparent to those skilled in the art from reviewing the description of the preferred embodiment and the drawings along with the claims, which are the full measure of the invention. 
   SUMMARY OF THE INVENTION 
   An anchor features a mandrel with ramps that extent through apertures in slip segments giving the slips a longer ramp to ride out on in a radial direction. The slip segments have ramps adjacent the apertures and in the preferred embodiment ride out on a plurality of spaced ramps on the mandrel. 

   
     DETAILED DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a split section view of a prior art design showing a slip in the retracted position at the top and in the extended position at the bottom; 
       FIG. 2  is the view along lines  2 - 2  of  FIG. 1 ; 
       FIG. 3  is a split section view of the present invention showing the slip retracted at the top and extended at the bottom; 
       FIG. 4  is a section view along lines  4 - 4  of  FIG. 3 ; 
       FIG. 5  is a perspective view of the mandrel without the slips; 
       FIG. 6  is a perspective view of the underside of a slip; and 
       FIG. 7  is a perspective view of the gripping side of a slip. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to  FIGS. 3 and 4  mandrel  40  has a series of ramps of which ramps  42  and  44  are shown. In the run in position on the upper part of  FIG. 3  a slip  46  is shown in the run in position. Those skilled in the art will appreciate that a plurality of slips  46  are used around the periphery of the mandrel  40  and they are held to the mandrel by one or more band springs or by other means. All of the structure is not shown to allow a better focus on the interaction between mandrel  40  and a given slip  46 . The actuation occurs by relative movement between the two that, in the preferred embodiment, is initiated with hydraulic pressure in passage  48  but is not limited to just pressure actuation. The actual piston assembly that creates this relative movement has also been omitted to better focus on the layout between a slip  46  and the mandrel  40  that is the present invention. 
   Slip  46  has openings  50  and  52  that can also be seen in  FIGS. 6 and 7 . Ramps  42  and  44  can also be seen in perspective in  FIG. 5 . 
   Mandrel  40  has a series of peaks such as  54  and  56  and as shown in the run position at the top of  FIG. 3  represents the greatest radial dimension of the tool during run in. Stated differently, peaks  54  and  56  extend through openings  50  and  52  in slip  46  during run in to a point further out radially than inserts  58  or equivalent structures to inserts  58 . Referring again to  FIGS. 3 and 6 , the slip  40  has ramps  60  and  62 , for example, and they ride respectively on ramps  42  and  44  of mandrel  40 . Because the slip  46  uses openings  50  and  52  its overall thickness can be greater for the same sized mandrel without increasing the drift diameter required to pass the tool during run in. At the same time, on either side of an opening such as  52 , for example in  FIG. 6 , there are wall segments  64  and  66  that with the greater thickness of slip  40  as compared to the prior design slip  10  have the strength to handle the tensile loads from uneven contact of slip  40  to a surrounding tubular or the wellbore in open hole or to handle tensile loads when the mandrel elongates due to loads applied. 
   In essence, the ramps  16  and  18  of the prior design, for a given angle of inclination, can now be longer, as illustrated in  FIG. 3  with ramps  42  and  44 . Even though the ramps are longer and as a result produce peaks  54  and  56  that are higher than peaks  32  and  34  of the prior tool for a given mandrel size, the drift dimension is not increased because the slip  46  no longer rides on top of peaks  54  and  56  as was done in the prior design. Rather, the openings  50  and  52  let the ramps  42  and  44  get longer for a given thickness of slip  46  to be able to move out further radially by having a longer set of ramps such as  60  and  62  to ride up on similarly longer counterpart mandrel ramps  42  and  44 . Now, the extension of slip  46  is increased for a given mandrel size as best seen by comparing  FIGS. 4 and 2  which are to the same scale. The openings allow making the slip thicker without increasing the drift dimension required for a given mandrel size. The thicker slip with openings allows more material to resist tensile stresses during setting and further radial extension for a given drift requirement than the prior design. 
   It should be noted that ramps  42  and  44  can be equally or unequally spaced. They can be parallel or not with respect to each other. Preferably the ramps on the mandrel  40  are parallel to their counterpart ramp on the slip  46 . 
   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: