Abstract:
A down hole vibration dampener is disclosed that uses a set of polyurethane rings and steel support rings to create a shock absorber within the drill string to reduce the amount of vibration in the drill string. A splined mandrel extends longitudinally within a hollow cylindrical housing. A seal structure present between the exterior of the mandrel and the interior of the housing forms a lubricant receiving chamber. The series of polyurethane and steel rings are located in the lubricant chamber and are compressible longitudinally to absorb vibration and shock loads.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority from a previously filed provisional application Ser. No. 61/145,863, filed Jan. 20, 2009, entitled “Down Hole Vibration Dampener”, by the same inventors. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This invention relates to a tool positionable in a drill string or stem which is useful for absorbing shock, vibration and impact loading otherwise imparted to the drill string during drilling operations. 
         [0004]    2. Description of the Prior Art 
         [0005]    When a well is being drilled, the vibration caused by the drill bit is substantial. In some cases, the vibration frequency caused by the drilling can reach the harmonic frequency of the drill string, which causes the drill bit to begin bouncing off of the bottom of the hole. This condition is called slip-stick. This condition is completely undesirable, and is harmful to the drill bit and the other tools of the drill string. These tools include such equipment as the mud motor, the MWD Tools (Measurement While Drilling), and the LWD Tools (Logging While Drilling), just to mention a few. Slip-stick can also reduce penetration rates, which adds to the over all cost of drilling a borehole. 
         [0006]    Because of the above noted problems, a number of prior art references exist which show various forms of vibration dampening and shock absorbing devices for incorporation into the drill string. By way of example, U.S. Pat. No. 4,162,619, issued Jul. 31, 1979, to Nixon et al., shows a shock sub for a well drilling string having a tubular housing adapted to be connected to one part of a drill string and a mandrel extending longitudinally into the housing and having an end portion adapted for connection to another part of the drill string. The mandrel and housing are shaped to define a non-circular annular cavity there between when assembled together. A compressible elastic metallic spring means is positioned in and substantially fills the non-circular annular cavity and is compressible longitudinally, radially and circumferentially to absorb longitudinal, radial and torsional vibration and impact loads and to transmit rotary movement between said housing and mandrel for imparting rotation from one part of the drill string to the other part connected by the drill sub. The spring means is preferably a knitted wire fabric or rope compressed into a compact mass capable of spring deflection in longitudinal, radial and circumferential directions relative to said shock sub assembly. 
         [0007]    U.S. Pat. No. 4,211,290, issued Jul. 8, 1980, to Mason et al., shows a drill string tool having a low spring rate deformable element and a relatively long stroke. The deformable element comprises a stack of alternating non-deformable washers and deformable elastomer rings extending throughout the length of the element chamber. The element washers and rings are substantially out of contact with the side walls of the mandrel and barrel, so that each segment of the element experiences the total shock load. The spline and deformable element are in an oil bath. The annular space between mandrel and barrel is sealed at the upper end by a fixed seal and at the lower end by a floating seal. 
         [0008]    The several forms of vibration dampeners and shock absorbers known in the prior art all suffer from one or more deficiencies. 
         [0009]    The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings. 
       SUMMARY OF THE INVENTION 
       [0010]    The primary aspect of the present invention is to dampen vibrations caused by the act of drilling a well bore. 
         [0011]    The following embodiments and aspects thereof are described and illustrated in conjunction with systems, tools, and methods which are meant to be exemplary and illustrative, not limiting in scope. In various embodiments, one or more of the above described problems have been reduced or eliminated, while other embodiments are directed to other improvements. 
         [0012]    In accordance with the principles of the present invention, a down hole vibration dampener is disclosed that uses a set of polyurethane rings and specially designed steel support rings to create a shock absorber within the drill string to reduce the amount of vibration in the drill string and dampen the vibrations caused by drilling a well bore. The down hole vibration dampener of the invention includes a hollow cylindrical housing having an interior and an exterior and having a lower connecting extent for connection to one part of a drill string. A splined mandrel extends longitudinally into the interior of the cylindrical housing and has an upper connecting extent for connection to another part of a drill string. The splined mandrel also has a through bore for the passage of fluids. A seal structure is present in longitudinally spaced relation between the interior of the cylindrical housing and the splined mandrel and forms a liquid receiving chamber. A vibration dampening structure is located in the liquid receiving chamber, the vibration dampening structure being compressible longitudinally to absorb vibration and shock loads. The preferred vibration dampening structure is made up of a series of resilient rings formed of a polymeric material which are separated by a series of interspersed metal rings which give the resilient rings support and definition while being subjected to a load. 
         [0013]    In a preferred embodiment of the invention, the resilient rings are formed of polyurethane and the metal rings are formed of steel. The polyurethane rings are shaped and engineered in such a manner that when the set of polyurethane rings are subjected to a shock load, the metal rings will not touch one another except under maximum load circumstances. As a result, the polyurethane rings and interspersed steel rings form a vibration dampening column, the column being encased on either of opposite ends thereof by metallic end rings. Preferably, the polyurethane rings each have an upper circumferential surface and a lower circumferential surface at least a selected one of which is provided with machined ridges which act as further shock absorbers and to improve the deformation properties of the polyurethane rings. The ridges which are present on the selected circumferential surface of the polyurethane rings are on the order of about 0.050 inch in height. The interspersed steel rings have chamfered outer edges in order that the edges not gouge the inner surface of the cylindrical outer housing nor gouge the outer surface of the spline mandrel. 
         [0014]    In addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent by reference to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a longitudinal view of the vibration damper. 
           [0016]      FIG. 2  is a cross section of  FIG. 1  along line  2 - 2 . 
           [0017]      FIG. 3  is a cross section of  FIG. 1  along line  3 - 3 . 
           [0018]      FIG. 4  is a cross section of  FIG. 1  along line  4 - 4 . 
           [0019]      FIG. 5  is a cross section of  FIG. 1  along line  5 - 5 . 
           [0020]      FIG. 6  is as detail view of a portion of  FIG. 3 . 
           [0021]      FIG. 7  is an exploded view of a single set of metal and polymeric rings. 
           [0022]      FIG. 8  is a cross section along line  8 - 8  of  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0023]    Before explaining the disclosed embodiment of the present invention in detail, it is to be understood that the invention is not limited in its application to the details of the particular arrangement shown, since the invention is capable of other embodiments. Exemplary embodiments are illustrated in referenced figures of the drawings. It is intended that the embodiments and figures disclosed herein are to be considered illustrative rather than limiting. Also, the terminology used herein is for the purpose of description and not of limitation. 
         [0024]    Parts, shown in the following drawings, toward the left of the drawings are referred to as down hole or forward parts as relating to the drilling direction. The back or up hole end of such parts is to the right. 
         [0025]    Referring first to  FIG. 1 , the vibration dampener  100  has a hollow generally cylindrical housing  200  made up of a bottom sub  101 , a bowl  102 , female hex housing  103 , a seal carrier  104 . The housing  200  is supported around a spline mandrel  105  and second mandrel  128 . In the course of building a Bottom Hole Assembly, or the BHA, the bottom sub  101  of the vibration dampener  100  could be screwed into the top of a mud motor (not shown) and the top of the spline mandrel  105  of the vibration dampener  100  would then be screwed into the drill collars. Another BHA may have the vibration dampener farther up the hole and place it in the middle of the drill collars. In this case the vibration dampener  100  would be located several joints above the mud motor and both the down-hole and up hole ends of the vibration dampener would be screwed into the drill collars. The vibration dampener  100  has a through bore for flow with a center line show by dotted line C in  FIGS. 2-5  and  7 . 
         [0026]    Referring next to  FIGS. 2 and 3 , the bottom sub  101  has two threaded male ends  106  on the down-hole end and  107  on the up hole end. The up hole end male thread  107  is attached to bowl  102  at down-hole threaded female end  108 . The bowl  102 , has threaded male end  109  at the up hole end, as seen in  FIG. 4 . The threaded male end  109  of bowl  102  attaches to the female hex housing  103  at the female threads  110 . The female hex housing  103  has two female ends, down-hole end  110  and up hole end  111 . The up hole end  111  female threads attaches to the seal carrier  104  at the down-hole male end  112 , as seen in  FIG. 5 . At each of the threaded connections between the pieces of the housing  200  the male end has a circumferential shoulder E that the end S of the female threaded connection rests against, as seen in FIGS.,  3 ,  4  and  5 . These connections allow the housing  200  to act as a single piece with regard to weight transfer of the drilling string. 
         [0027]    The spline mandrel  105  is supported within the housings  102 ,  103 , and  104 , and extends from the bowl  102  through the female hex housing  103  to the seal carrier  104  and extends beyond the seal carrier  104 , as seen in  FIG. 5 . The spline mandrel  105  has an outer surface  114  and an inner bore  115 . The seal carrier  104  has seals (not shown) in grooves  117 . Seals are standard seals used for mud motors and similar devices, known in the art and therefore not further described. Threaded hole  113  is a fill port to fill the entire body of the tool with oil to act as a lubricant and shock absorber. The seals at the seal carrier  104  forms one end of a sealed chamber and the piston  118  ( FIG. 2 ) is the other end. The seal carrier  104  functions to form a sealed area on the inside of the vibration damper  100  from the seal carrier  104  to the piston  118 , seen in  FIG. 2 . The floating movable piston  118  is capable of moving up hole or down hole to compensate for the expansion and contraction of the oil placed inside. 
         [0028]    The spline mandrel  105  extends through the female hex housing  103 . As see in  FIG. 4 , in the area  119  of the female hex housing  103  the spline mandrel  105  has a non-circular outer surface  120 , which corresponds to the non-circular inner bore  121  of the female hex housing  103 , as seen in  FIG. 8 , which functions to lock the spline mandrel  105  into engagement with the female hex housing  103 , and thereby in to engagement with the housing  200  in torque only, but allows spline mandrel  105  to move axially within housing  103 . In the disclosed embodiment the spline mandrel  105  has a hexagonal outer surface  120 , in the area  119 . In the other areas of the spline mandrel  105  the outer surface is generally circular. The hexagonal section of the spline mandrel transfers any torque applied to the spline mandrel  105  to the female hex housing  103  and then this torque is transferred via the threaded connection down to the bottom sub  101 . This allows the torque to continue down hole to the bit, while at the same time it allows the inner part of the tool to move up and down hole relative to the outer housing  200  so that vibration is transferred to the polyurethane rings  137 , as discussed below. The edges of the hexagon are shown in dotted lines  122  on  FIG. 4 . The outside of the female hex housing  103  has a portion surface that is undercut from the outer diameter, shown in the slight waviness of the surface in  FIG. 4 . This is an identification band where a user can stamp information about the tool such as a serial number. This undercut of the OD of the housing allows a person to stamp a number on the outside surface but keep it under the original OD so that it is not so easily worn off. 
         [0029]    The spline mandrel  105  extends from the female hex housing  103  down to the bowl  102  in  FIG. 3 . The outer surface of the spline mandrel  105  has a shoulder  123 , which in the relaxed position of the tool, lines up directly across from the shoulder  124  of the bowl  102  forming a space  125  between the inner surface  126  of the bowl  102  and the outer surface  114  of the spline mandrel  105 . Space  125  extends for a substantial portion of the length of bowl  102 . This space  125  is taken up with a saplurative number of polyurethane rings  137  incased by steel rings  138 . In the depicted embodiment there are 36 rings of each type. More or less could be used depending on the application. The steel rings  138  give the polyurethane rings  137  support and definition while being subjected to a load. The polyurethane rings  137  are shaped and engineered in such a manner that when the set of rings are subjected to a shock load, the steel rings  138  will not touch one another except under the maximum load circumstances. Therefore just the polyurethane rings  137  bear the vibrations or shock loads and not the steel rings  138 . The ridges  139  as found in  FIG. 6  are 0.050 inches high in the depicted embodiment and act as further shock absorbers and to improve the deformation properties of the rings  137 . This height of about 0.050 of an inch has been determined to be at the most desirable height in terms of function, any shorter and these ridges did not deform as desired and any taller these ridges tended to bend over instead of squishing flat in the desired configuration. In the depicted embodiment there are 5 ridges, however, other numbers of ridges could be used as well, depending on the application. The edges of steel rings  138  (see in  FIG. 6 ) are chamfered in order that the sharp edges do not gouge into the inner surface  126  of the bowl housing  102  nor gouge into the outer surface  114  of the spline mandrel  105 , which would impair there functionality or ability to slide along these surfaces without restrictions. 
         [0030]    The down-hole end of the spline mandrel  105  is a male thread  129  which is screwed into the female threaded end  130  of the second mandrel  128  in  FIG. 3 . The second mandrel  128  has holes  131 , shown in dotted lines, extending from threaded female end  130  to shoulder  132 . The down hole end  133  of second mandrel  128  bears piston  118  and piston nut  134 . 
         [0031]    End rings  135 ,  136  are placed at each end of space  125 . The down hole end ring  135  abuts against both the female threaded end  130  of the second mandrel  128  and the male threaded end  107  of the bottom sub  101 . The up hole end ring  136  abuts against the shoulder  124  of the bowl  102  and the shoulder  123  of the spline mandrel  105 . This allows the transfer of force from the drill string to the shock absorber portion of the invention . . . ie the polyurethane rings. This also limits the amount of movement the inner and outer sections can have in the down hole/up hole directions relative to each other. They can only move until maximum compression of the polyurethane rings  137  is reached, and the polyurethane rings no longer posses the ability to act as a shock absorber or vibration dampener due to the fact that the elastic point for the polyurethane rings  137  has been exceeded, thus the total compression forces are now so large that the steel rings  138  are now against each other. 
         [0032]    While a number of exemplary aspects and embodiments have been discussed above, those of skill in the art will recognize certain modifications, permutations, additions and sub-combinations therefore. It is therefore intended that the following appended claims hereinafter introduced are interpreted to include all such modifications, permutations, additions and sub-combinations are within their true sprit and scope. Each apparatus embodiment described herein has numerous equivalents. 
         [0033]    The terms and expressions which have been employed are used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed. Thus, it should be understood that although the present invention has been specifically disclosed by preferred embodiments and optional features, modification and variation of the concepts herein disclosed may be resorted to by those skilled in the art, and that such modifications and variations are considered to be within the scope of this invention as defined by the appended claims. Whenever a range is given in the specification, all intermediate ranges and subranges, as well as all individual values included in the ranges given are intended to be included in the disclosure. 
         [0034]    In general the terms and phrases used herein have their art-recognized meaning, which can be found by reference to standard texts, journal references and contexts known to those skilled in the art. The above definitions are provided to clarify their specific use in the context of the invention. 
         [0035]    All patents and publications mentioned in the specification are indicative of the levels of skill of those skilled in the art to which the invention pertains. All references cited herein are hereby incorporated by reference to the extent that there is no inconsistency with the disclosure of this specification. 
         [0036]    While the invention has been shown in only one of its forms, it is not thus limited but is susceptible to various changes and modifications without departing from the spirit thereof.