Abstract:
A knuckle-swivel ( 10 ) is used with well drilling equipment for protecting helical wound line  62 , which may be wire rope, cable and/or strand, against torsional forces and also providing for angular displacement of sinker bars or other tools during wireline strip over operations to minimize interference with rig equipment ( 80 ) when pulling pipe or tools  64  from a well head.

Description:
BACKGROUND OF THE INVENTION 
   Many conventional drilling rigs use a top-drive for pulling pipe and/or tools from a well bore. Powerful motors are used to pull and wind wire rope, cable or strand about a drum located above the derrick floor. Swivels are used in-line with helical wound members such as rope, cable or strand for allowing rotation about a longitudinal axis thereof under tension for minimizing or avoiding straightening of the helical windings in order to protect the strength and integrity of the rope, cable or strand by compensating for the torsional force induced by large axial forces on the helical member. Typical forces can be on the order of several tons, or more. 
   In one typical operation referred to as a “wireline strip over operation”, a sinker bar is used in-line with the wire rope. Sinker bars have in the past been comprised of a rigid member which may be in the form of a solid bar on the order of 15 to 20 feet in length. Use of such a sinker bar with a top drive creates interference between the sinker bar and rig equipment located vertically above the drill pipe; heretofore, it has been necessary to move and relocate the top drive unit out of the way. This is a time consuming operation that is best to be avoided. 
   SUMMARY OF THE INVENTION 
   The invention relates to the use of a unique implement which is now referred to as a “knuckle=swivel” and which provides for the multiple function of introducing a 360 degree swivel capability for minimizing and/or precluding the above referred torsional forces on the rope, cable or strand and, in addition, provides for a knuckle function to allow angular displacement for minimizing or precluding bending loads transmitted into the swivel during withdrawal of sinker bars from the well bore or other tools and the like being pulled around an obstacle. 
   The present invention is particularly useful for well drilling operations including but not limited to those utilizing a top drive winding drum for pulling items from the well bore and, more particularly, the invention is intended to be used with “Flexible Sinker Bar Assemblies” which are the subject of my U.S. Pat. No. 6,227,292 B1, granted on May 8, 2001; the disclosure of my earlier patent is incorporated herein by reference. An important feature of the present invention resides in the combination of the instant knuckle-swivel and a sinker bar, either a rigid sinker bar or ideally a flexible sinker bar, in order to minimize or preclude the heretofore requirement of moving the top drive unit during pulling operations. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a longitudinal, sectional view of a knuckle-swivel in accordance with the invention. 
       FIG. 2  is a side elevational view of the knuckle-swivel showing the extent of side rotation. 
       FIG. 3  is a schematic representation of the knuckle-swivel connected to a helical wound wire rope, cable or strand which comprises part of a sinker bar. 
       FIG. 4  is a schematic view showing a helical wound rope, cable or strand being diverted around rig equipment with the knuckle-swivel located at the mouth of the well. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   A knuckle-swivel body member, generally indicated by the numeral  10 , includes a bottom sub  14  having threads  16  at one end thereof and receiving a bearing pin  18  in its opposite hollow end  20  and being connected thereto by a slotted spring pin  22 . 
   An upper sub  24  includes a first threaded end  26  and a second threaded end  28 , the latter being connected to the knuckle-swivel body member  10  in alignment with bottom sub  14 . Body member  10  contains a pair of bearing cones  30 ,  30 , a pair of bearings cups  32 ,  32  and a pair of bearing races  34 ,  34  which are mounted upon cylindrical posts  36 ,  36  disposed on opposite sides of bearing pin  18 . A flat wire compression spring  40 , of a type known as a crest-to-crest spring, is located between one bearing cup  32  and the adjacent end of upper sub  24  for applying a constant force against the cup  32  for stabilizing a plurality of ball bearings  42  between the bearing cones  30 ,  30  and the bearing races  34 ,  34 . A grease fitting  44  is provided for passing lubricant through a passage  46 , it being understood that the lubricant can pass through spring  40  and protect the various bearing components. 
   As is best shown in  FIG. 1 , body member  12  is provided with a frusto-conical surface  50  which limits bearing pin  20  to approximately 20 degrees of side-to-side rotation, the extent of rotation being best shown in  FIG. 2 . Thus, bearing pin  18  is capable of rotating 360 degrees about its longitudinal axis within body member  12  in addition to a side-to-side conical movement of 20 degrees. 
   Referring to  FIGS. 3 and 4 , it will be seen that the knuckle-swivel  10  is secured by a swaged end connector  60  to a line  62 , which may be a helical wound wire rope, or cable, or strand member. It is to be understood that helical wound line  62  is protected by knuckle-swivel  10  because of the capability of 360 degrees of axial rotation of bearing pin  18  minimizes or precludes torsional forces upon the line  62 . In the absence of such protection, large axial loads would tend to straighten the helical windings and thereby severely weaken the strength of the line  62 . End connector  60  is threaded onto sub  14 , and sub  24  can be threadedly connected to a pipe or tool  64 . 
   It is to be understood that it is conventional in the well drilling industry to provide a top drive (not shown) in the form of a winding drum located at or near the top of a derrick or rig, for pulling pipe or tools from the well. It is not unusual for portions of the derrick or rig to be interposed between the well head and the winding drum. As a result, it has heretofore been necessary to mount the top drive so that it may be adjustably moved laterally to prevent interference between the pulling line and rig. As is best shown in  FIG. 4 , line  62 , which may be a component of a flexible sinker bar as described in U.S. Pat. No. 6,227,292, can be angularly displaced while under load because of the provision of knuckle-swivel  10 . As a result, interference with rig equipment, generally indicated by the numeral  80 , is avoided and it is unnecessary to move or relocate the top drive member. Line  62  can be trained over a guide roller (not shown) upwardly of or adjacent the rig equipment  80  for preventing contact during a wireline strip over operation, or the like. 
   From the foregoing, the preferred construction of the invention will be obvious to those skilled in this art but it is to be understood that some changes in construction and operation are possible without departing from the spirit and scope of the invention as defined in the claimed subject matter appended hereto.