Patent Publication Number: US-10760359-B2

Title: Wellbore tong

Description:
BACKGROUND 
     Field 
     Embodiments described herein generally relate to a tong for use at a wellbore. 
     Description of the Related Art 
     Wellbore tongs are well known in the art for making and breaking threaded connections between tubulars as strings are assembled or disassembled for use in a wellbore. Typically, a back-up or lower tong holds a tubular extending from the wellbore while an upper tong grasps and then rotates a new tubular into our out of the string. In most cases, the upper tong includes a mechanism to grasp the tubular and then, in a separate step, rotates the tubular to perform threading or unthreading. During the grasping step, one rotating portion of the assembly must be held in place while the gripping assembly operates. Thereafter, both portions are rotated as a unit during the threading operation. There is a need for an improved braking assembly to temporarily hold the rotating portion during the gripping step. 
     SUMMARY 
     The present disclosure generally concerns a wellbore tong. In one embodiment, the tong includes a gear ring powered by a motor assembly, the gear ring having a plurality of ramps formed on an inner surface thereof and a brake plate rotationally independent of the gear ring, the brake plate having a gripping assembly for interacting with the ramps to grip a tubular. In a first position of the gear ring relative to the brake plate, the gripping assembly is open and in a second position the assembly grips the tubular. Also included is a brake assembly for preventing rotation of the brake plate, the brake assembly including an adjustable brake band for applying friction to the brake plate and at least one brake pad made of braking material disposed on an outer surface thereof in the area of contact with the brake band for reducing friction between the brake plate and the brake band. In one embodiment, the braking material is bronze. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments. 
         FIG. 1  is a perspective view of a wellbore tong. 
         FIG. 2  is a perspective view of a portion of the tong including a rotatable brake plate, a gripping assembly rotatable therewith and a separately rotatable gear ring. 
         FIG. 3  is a top view of the assembly of  FIG. 2  showing gripping members that are a part of the gripping assembly. 
         FIG. 4  is a perspective view of the gear ring showing a plurality of ramps formed on an inner surface thereof. 
         FIG. 5  is a perspective view of the gripping assembly illustrating a double pair of wheels on a first side and a single wheel on a second side. 
         FIG. 6  is a top view partially in section, taken through one wheel of the double pair of wheels. 
         FIG. 7  is a top view partially in section, taken through the single wheel. 
         FIG. 8  is a top view partially in section, taken through the single wheel and showing the gripping assembly actuated around a tubular. 
         FIG. 9  is a top view partially in section, taken through the single wheel and showing the tubular member having been rotated in a clockwise direction to make a wellbore connection between tubulars. 
         FIGS. 10 and 11  are top views of a braking member illustrating its operation in conjunction with a brake band to prevent rotation of the brake plate. 
         FIG. 12  is a perspective view of a brake plate illustrating the location of brake pads along an outer perimeter thereof. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a perspective view of a wellbore tong. The tong has two functions: it grasps a tubular (not shown) using a gripping assembly generally shown as  110  and thereafter, it rotates the tubular relative to a tubular therebelow in order to make or break a threaded connection therebetween. A door  120 , shown in a closed position, permits the tubular to be inserted into the gripping assembly  110  of the tong  100 . A hydraulic motor assembly generally shown as  130  rotates a gear ring (not visible) that is responsible for rotation of the tubular when a connection is made. Separately, a “cage” or brake plate  140  is rotatable independent of the gear ring. In the embodiment shown, the gripping assembly  110  is associated with the rotatable brake plate  140  and rotates therewith. Separately, inwardly facing ramps (not visible) are formed on an inner surface of the gear ring. To grip a tubular with the tong  100 , it is necessary to rotationally fix the brake plate  140  with its gripping assembly  110  while rotating the gear ring in order to urge the ramps of the gear ring under a plurality of wheels associated with the gripping assembly  110 . The action of the wheels and ramps acts to close gripping members  112 ,  115  around the tubular. With the tubular gripped, both the gear ring and the brake plate  140  rotate together to make (or break) a connection. 
       FIG. 2  is a perspective view of a portion of the tong  100  including the rotatable brake plate  140 , the gripping assembly  110  rotatable therewith and a separately rotatable gear ring  150 . The gear ring includes teeth formed on a perimeter thereof for engagement with corresponding teeth associated with the motor assembly  130  ( FIG. 1 ). Also shown in  FIG. 2  is a braking assembly for the brake plate in order to stop its rotation during the gripping portion of the operation. The breaking assembly, as will be described in additional detail herein, includes a brake band  160  that can be tightened thereby providing friction between the band  160  and the brake plate  140 . The tightening takes place at each end of the band with piston-actuated braking members  165   a ,  165   b.    
       FIG. 3  is a top view of the assembly of  FIG. 2  showing gripping members  112 ,  115  that are a part of the gripping assembly  110 . As illustrated, the gripping members can be actuated towards or away from the centerline of a tubular. 
       FIG. 4  is a perspective view of the gear ring  150  showing a plurality of ramps  205   a ,  210   a ,  215   b  formed on an inner surface thereof opposite an opening or throat of the ring. The upper and lower ramps  205   a ,  210   a  are constructed and arranged to operate with a set of double wheels  305 ,  310  ( FIG. 5 ) in order to actuate one gripping member  115  of the gripping assembly  110  when a threaded connection is being made. The center ramp  215   b , as is evident by its direction is constructed and arranged to actuate a single wheel  315  associated with gripping member  112  when a connection between tubulars is being broken. An opposite group of ramps, two of which  215   a ,  205   b  are visible in  FIG. 4  are responsible for a reverse arrangement wherein a second set of double ramps (upper ramp  205   b  is visible) operates with the double wheels  305 ,  310  to break a connection and a second single ramp  215   a  operates with the single wheel  315  when a connection is made. 
       FIG. 5  is a perspective view of the gripping assembly  110  illustrating the double pair of wheels  305 ,  310  on a first side and the single wheel  315  on a second side. The gripping assembly  110  is made up of two gripping members  112 ,  115 , each operating like a slip with an inner surface having a concave shape to match the outer surface of the tubular to be grasped by the tong  100 . As illustrated, the gripping assembly  110  utilizes the single wheel  315  associated with one gripping member  112  and the two-wheel set  305 ,  310  operating with a second gripping member  115 . In operation, the wheels (along with the brake plate  140 ) remain rotationally fixed while the gear ring  150  with its various ramps rotates to a position wherein each wheel has ridden up a ramp. The result is a clamping action forcing the gripping members  112 ,  115  into contact with the tubular to be grasped. The make or break nature of the operation determines which set of ramps is utilized by the wheels as the tubular is gripped. 
       FIG. 6  is a top view partially in section, taken through one wheel  305  of the double pair of wheels  305 ,  310  and  FIG. 7  is a top view partially in section, taken through the single wheel  315 . In both Figures, the gripping mechanism is de-activated, meaning that the wheels and ramps are not in contact with one another as indicated by the open position of the gripping members  112 ,  155  in each Figure. For example, in  FIG. 6 , upper wheel  305  of the pair of wheels  305 ,  310  is visible above the ramp  215   a  that is designed to operate in conjunction with single wheel  315  when a connection is being broken. Similarly in  FIG. 7 , on the left side of the Figure, the single wheel  315  is visible with the lower ramp  210   b  below it. 
       FIG. 8  is a top view partially in section, taken through the single wheel  315  and showing the gripping assembly  110  actuated around a tubular  400 . More specifically,  FIG. 8  is a top section view of the assembly shown in  FIGS. 7 and 8  with the view taken through the single wheel  315 . However, in  FIG. 8  the gear ring  150  with its sets of ramps has been rotated clockwise while the brake plate  140  and gripping assembly  110  have been rotationally held in the same orientation as they are in  FIGS. 7 and 8 . The result is that the ramps have changed location relative to the wheels  305 ,  310 ,  315  in a manner whereby the wheels have mounted the ramps  215   a ,  205   a ,  210   a  that are designed to be utilized in actuating the gripping mechanism in order to make a connection. Because the wheels have been actuated by the ramps, the gripping mechanism  110  is actuated and the tubular  400  is gripped. 
       FIG. 9  is a top view partially in section, taken through the single wheel  315  and showing the tubular member  400  having been rotated in a clockwise direction to make a wellbore connection between tubulars. Comparing  FIGS. 8 and 9 , in  FIG. 9  the entire tong unit including gear ring  150  and brake plate  140  has been rotated as a unit. In this manner the tubular  400  retained by the upper portion of the tong  100  is rotated relative to a tubular gripped by a lower portion (not shown) in order to make a threaded connection. It will be appreciated the operation can be reversed, using the same wheels but operating on another set of ramps having reverse formations. In this manner, the tong assembly can be used to make or break a threaded connection between tubulars. 
     As described above, in order to actuate the gripping assembly  110 , the brake plate  140  and gripping assembly must be rotationally fixed or at least rotationally limited relative to the gear ring while the gear ring  150  with its inwardly facing ramps rotates to a location whereby the ramps interact with the wheels of the gripping assembly to close the gripping members  112 ,  115  around a tubular  400 . Thereafter, the gear wheel  150  and brake plate  140  rotate together to make or break a threaded connection. In one embodiment, rotation of the brake plate  140  is prevented with the use of a brake band  160  that is tightened around an outer surface of the plate in order to prevent its rotation. The brake band  160  and braking members  165   a, b  are shown in  FIGS. 2 and 3 . As shown, the band  160  extends around an outer perimeter of the plate  140  and is held at each end by one of the braking members. By holding the band at each end, the brake members can tighten the band  160  by urging each end towards the door  120  of the assembly, essentially removing slack in the band and thereby increasing its friction with the side of the brake plate  140 . In one embodiment, the braking members each include a piston that urges a corresponding end of the brake band  160  in order to tighten it. 
       FIGS. 10 and 11  are top views showing the operation of one of the braking members  165   b  and its relationship with the brake plate  140 . In  FIG. 10  the brake is un-actuated as shown by a gap  146  formed between the band and an outer edge of a brake pad  145  disposed around an outer edge of the plate.  FIG. 11  is a similar view however, in  FIG. 11  the brake band has been tightened as apparent by the absence of gap  146  in the Figure. Arrow  149  illustrates the direction of a force placed upon the band in order to tighten it. 
     One novel aspect of the invention relates to brake pads and their location relative to the brake band and brake plate. In prior art devices, friction and heat generated between the tightened band and brake plate create wear and can cause failure of the entire tong assembly, essentially shutting down operations at a well site. In prior art devices, brake material including non-metallic, semi metallic and ceramic materials has been used on an inner surface of the brake band in order to effect braking between the band and brake plate. In order to extend the life of the brake band and to reduce friction and resulting heat between the surfaces, grease is applied at the intersection of the band and plate. The addition of grease reduces the heat and wear but must be replaced regularly requiring precious time at the working wellsite. Additionally, with or without grease, flexing of the band as it is tightened or loosened can cause the brake material to separate from the band. In one embodiment of the present invention, these problems and others are overcome by placing brake pads made of breaking and friction-reducing material not on the band but on the outer perimeter of the brake plate where it contacts the band. 
       FIG. 12  is a perspective view of the brake plate having apertures  142  around its perimeter for attachment of brake pads. One exemplary brake pad  145  is shown in the Figure. By fastening the brake pads with fasteners around the perimeter, a braking surface is provided in a manner whereby the material is protected from the flexing of the brake band. Additionally, the pieces can be replaced in any area where excessive wear has occurred without replacing the entire band or a large strip of the braking material. In one example, the brake pads are constructed primarily of bronze or sintered bronze. Bronze is an ahoy consisting primarily of copper, commonly with about 12% tin and often with the addition of other metals and sometimes non-metals or metalloids such as arsenic, phosphorus or silicon. 
     While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.