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CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is filed concurrently with U.S. patent application Ser. No. 12/485,154, entitled “Adjustable Wireline Sheave for Hay Pulley,” which is incorporated herein by reference in its entirety. 
     BACKGROUND 
     Sheaves are used to route a wireline from a reel to a stuffing box at a wellhead. One such sheave mounts onto the stuffing box and has a peripheral groove in which the wireline runs. Conventionally, the sheave&#39;s diameter and the depth of its groove are sized so that the center of the wireline will coincide with the centerline through the stuffing box. Therefore, a different sized sheave must be used to accommodate different sized wirelines so the wirelines can properly line up with the centerline of the stuffing box. 
       FIG. 1  shows one type of sheave assembly  10  according to the prior art for a stuffing box  20 . This sheave assembly  10  and stuffing box  20  are manufactured by Weatherford—the Assignee of the present disclosure. The stuffing box  20  fits atop components of a wellhead (not shown), and the sheave assembly  10  attaches to the stuffing box  20  to guide the wireline in and out of the wellhead. The stuffing box  20  has a body  30  with a collar  32  for fitting onto the wellhead. A cartridge insert  36  has glands and packing and positions in the body  30  to pack off the wireline that passes through the stuffing box  20 . A packing nut  37  affixes the insert  36  on the body  30 , and a hydraulic packing cylinder  34  attaches atop the box  20  and holds a hydraulic packing piston and spring. 
     As for the sheave assembly  10 , side plates  40  connect to a bearing block  38  on the stuffing box&#39;s body  30 , and a sheave  50  mounted between these plates  40  can rotate about a wheel bearing  52  on an axle  55  disposed between the plates  40 . A guard  45  connects by a locking stud  47  to one of the plates  40  so the guard  45  can be removed and adjusted relative to the periphery of the sheave  50 . 
     As best shown in the detail of  FIG. 2A , a bush assembly  60  has a bush  70  that fits onto the axle  55  and the side plate  40  on each side of the sheave  50 . The bush  70  (shown alone in  FIG. 2C ) has an opening  75  for the axle  55  and has a shoulder  72  disposed around the bush  70 . The sheave  50  can be adjusted using the bush assembly  60  so the assembly  10  can accommodate different sized wirelines. In particular, the bush  70  fits in an upright position in the side plate&#39;s opening  42 , as indicated by the arrow on the bush  70 . The bush&#39;s shoulder  72  ( FIG. 2C ) fits into the side plate&#39;s opening  42  ( FIG. 2B ) so the bush  70  can support the axle  55  in the axle opening  75  (See  FIG. 2A ). 
     Depending on how the bush  70  is oriented in the opening  42 , a first bush hole  80 A on the bush  70  can align with one of two plate holes  61 A/ 62 A on the side plate  40 . In this way, the screw  90  in first bush hole  80 A can fit into the plate hole  61 A for 0.187″ wire or can fit into the plate hole  62 A for 0.125″ wire. In addition, a second bush hole  80 B on the bush  70  can align with one of three plate holes  61 B/ 62 B/ 63 B. Here, the screw  90  in second bush hole  80 B can fit into the plate hole  61 B for 0.108″ wire, can fit into the plate hole  62 B for 0.160″ wire, or can fit into the plate hole  63 B for 0.250″ wire. Although effective, adjusting the sheave  50  in this way can be tedious and time consuming. 
     As with the sheave assembly  10  of  FIG. 1  and other conventional sheave assemblies of the prior art, a guard is normally attached above the sheave to prevent the wireline from jumping off of the sheave when being run thereon. When rigging up the wireline, the guard must be moved out of the way by removing studs or screws that hold the guard to the assembly. As expected, this procedure can be tedious and time consuming. 
     In one prior art solution, the assembly supporting the sheave can be entirely hinged out of the way as disclosed in UK Patent Applications GB 2,418,463 and GB 2,433,283 to give access for rigging up the wireline. When such an assembly is hinged out of the way, a cam action lifts the guard clear of the sheave. Because this hinge forms part of the load path of the assembly supporting the sheave, it must be sized in accordance with the safe working load of the stuffing box, which can be disadvantageous. 
     The subject matter of the present disclosure is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above. 
     SUMMARY 
     An assembly for wellhead intervention has a stuffing box and an adjustable sheave assembly. The stuffing box mounts on a wellhead and has a passage for running wireline therethrough. The adjustable sheave assembly mounts onto the stuffing box with a frame having two arms. A sheave fits between these two arms and can rotate on an axle. Instead of having the axle mounted directly to the arms of the frame, the axle connects at each end to hubs that are rotatably mounted on both arms. 
     As the sheave routes wireline to and from the stuffing box, the sheave can rotate about the axle. However, the hubs can be rotated about an eccentric axis of rotation. This rotating of the hubs adjust the location of the axle&#39;s axis of rotation relative to the frame and the stuffing box and can be used to move the sheave away from a guard and the stuffing box. For example, one of the arms of the frame can have the guard affixed thereto. When the hubs are rotated, the sheave is moved away from the guard to provide clearance for rigging up the wireline. To make this adjustment, the hubs are rotated on the arms and move the sheave relative to the guard. 
     Preferably, a lock is used on the hubs to lock them in one of several positions. The lock can uses a spring loaded key attached to one or both of the hubs. To move the sheave, an operator pushes the key toward the center of the hub to disengage the key from a slot in a surrounding housing. Simultaneously, the operator uses handles on the keys to rotate the hubs. As the hubs rotate, the sheave can be moved out of the way of the guard. In addition, rotating the hubs can adjust the alignment of the sheave&#39;s peripheral groove with the centerline through the stuffing box. In this way, the same sheave can be used to accommodate difference sized wirelines. Also, the sheave can be moved by rotating the hubs so removable components on the stuffing box, such as a packing cartridge can be accessed for replacement. 
     Advantageously, the movable keys that can engage and disengage from the lock locations on the housing facilitate the adjustment of the sheave by operators to either move the sheave away from the guard, gain access to the stuffing box, or to adjust what sized wireline the sheave can accommodate. Moreover, the movable keys with handles enable the operators to readily rotate the hubs in the frames and adjust the sheave&#39;s axle location. These adjustments can be made without the tedious and time-consuming handling currently required for sheave assemblies. 
     The foregoing summary is not intended to summarize each potential embodiment or every aspect of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a side view of a stuffing box with a sheave assembly according to the prior art. 
         FIG. 2A  is a detail view of a bush assembly for the sheave assembly of  FIG. 1 . 
         FIG. 2B  is a detail of the side plate showing position holes for the bush assembly of  FIG. 2A . 
         FIG. 2C  is a detail of the bush for the bush assembly of  FIG. 2A . 
         FIGS. 3A-3B  shows side views of a stuffing box with a sheave assembly according to the present disclosure. 
         FIG. 4  is a detail view of a hub assembly for the sheave assembly of  FIGS. 3A-3B . 
         FIG. 5  is a cross-sectional view of the sheave assembly for the stuffing box. 
         FIG. 6  is a side view of the stuffing box with the sheave in a position for fitting and removing a wireline from the sheave. 
         FIG. 7  is a side view of the stuffing box with the sheave in another position for fitting and removing a removable cartridge on the stuffing box. 
         FIGS. 8A-8B  show another hub assembly having multiple adjustment positions. 
         FIGS. 9A-9B  show an alternative hub assembly having multiple adjustment positions. 
     
    
    
     DETAILED DESCRIPTION 
     As shown in  FIGS. 3A-3B , an adjustable sheave assembly  100  according to the present disclosure is used on a stuffing box  20  to run a wireline  50  to and from a wellhead (not shown) during wireline operations. The stuffing box  20  can be similar to that discussed previously. For example, the body  30  of the stuffing box  20  mounts to the wellhead with a collar  30  and houses an insert (not shown) with glands and seals for packing off the wireline  50 . A cartridge  34  at the end of the body  30  passes the wireline  50  therethrough. This cartridge  34  contains a packing chamber for the wireline  50  and is preferably removable from the body  30  for replacement. 
     The sheave assembly  100  has a frame  110  that mounts onto the stuffing box  20  using a bearing assembly or the like. The frame  110  has forked arms  120 - 120 ′ that hold the sheave  130  therebetween. As the wireline  50  is routed from conventional wireline equipment (not shown) to the sheave  130 , the wireline  50  fits into a peripheral channel  132  around the sheave  130 . 
     As shown in  FIG. 3B , a safety guard  140  is affixed to an extended portion  122  of one of the arms  120 ′ and positions at the periphery of the sheave  130 . During operations, the guard  140  can prevent the wireline  50  from jumping out of the sheave  130 . Guided by the sheave  130 , the wireline  50  passes through the centerline of the stuffing box  20  and more particularly into the cartridge  34 . As expected, proper alignment of a tangential line from the sheave&#39;s periphery to the stuffing box&#39;s centerline is important for operation so that the wireline  50  can fed centrally through the stuffing box  20 . 
     Hub assemblies  150 - 150 ′ disposed on both arms  120 - 120 ′ support an axle  172  on which the sheave  130  rotates. The hub assemblies  150 - 150 ′ can be adjusted to move the sheave  130  relative to the arms  120 - 120 ′ and the guard  140  and can be used to provide clearance when rigging up the wireline  50 . As shown in more detail in the side view of  FIG. 4  and the cross-section of  FIG. 5 , the hub assemblies  150 - 150 ′ each have an outer housing  160  attached to the surface of the arm  120 - 120 ′ using bolts  161  or the like. The housings  160  hold hubs  170  that can rotate therein. The center shaft  172  passes through these hubs  170  and the sheave  130  from one hub assembly  150  to the other hub assembly  150 ′, and a bolt  174  affixes the center shaft  172  to one of the hubs  170 . 
     As best shown in  FIG. 4 , the center axis  173  of the shaft  172  is eccentrically located relative to a center axis  171  of the hubs  170  about which the hubs  170  can rotate in the housings  160 . Therefore, rotation of the hubs  170  eccentrically moves the center shaft  172  relative to the arms  120 - 120 ′ and consequently moves the position of the sheave  130  that rotates on the shaft  172 . To rotate the hubs  170 , keys  180  are attached to the hubs  170  and have handles  182  for an operator to turn the hubs  170  in the housings  160 . 
     At least one of these keys  180  on a side of the assembly  100  can engage in any one of several slots on the outer housing  160  to lock the hub  170  in one of the rotated positions. As shown in  FIG. 4 , three such slots  162 ,  164 , and  166  are provided in the housing. In use, an operator uses the handle  188  on the key  180  to push it inward toward the center of the hub  170  against the bias of a spring  186 . In an alternative arrangement, the key  180  may be moved outward from the hub  170  so that portion of the key  180  clears the housing  160 . 
     Regardless, the distal end  182  of the key  180  is movable in a direction perpendicular to the axis of rotation for the hub  170  relative to a proximal end  184  of the key  180  attached to the hub  170 . Shifting the distal end  182  of the key  180  disengages it from the slot  162  in the outer housing  160  so the operator can rotate the hub  170  in the housing  160  using the key&#39;s handle  188 . In turn, the rotation of the hub  170  eccentrically shifts the position of the center shaft  172  and the sheave  130  about the hub&#39;s center  171  and relative to the frame  110 . The key  180  can then be released to engage the distal end  182  in another of the slots  164  or  166  of the housing  160 . 
     Having the key  180  engaged in the first slot  162  shown in  FIGS. 3A &amp; 4  positions the sheave  130  in its operating condition. In this condition, a tangential line running from the sheave&#39;s channel  132  aligns with the stuffing box&#39;s centerline so that the wireline  50  can be properly run into and out of the stuffing box  20 . As shown in  FIG. 3B , the edge of the sheave  130  also fits adjacent the guard  140  affixed to the frame  110 . In this position, the guard  140  can prevent the wireline  50  from jumping out of the peripheral channel  132  of the sheave  132  when running the wireline  50 . 
     As shown in  FIG. 6 , however, rotating the hub assemblies  150 - 150 ′ and fitting the key  180  in the second slot  164  on the outer housing  160  moves the sheave  130  away from the guard  140 . This position provides clearance for rigging up the wireline  50  in the sheave&#39;s channel  132  without having to remove the guard  140 , which can be time consuming. 
     Finally, as shown in  FIG. 7 , rotating the hub assemblies  150 - 150 ′ and fitting the key  180  in the third slot  166  on the outer housing  160  moves the sheave  130  further away from the guard  140  and the stuffing box  20 . With the sheave  130  in this position, an operator can access the hydraulic packing nut and remove and install the cartridge  32  for the stuffing box  20  and perform other maintenance. At any point, the operator can rotate the hub assemblies  150 - 150 ′ and fit the key  180  in the first slot  162  to return the sheave to the operating condition. 
     As indicated above, adjusting the location of the axle&#39;s axis  173  adjusts how the periphery of the sheave  130  aligns with the centerline through the stuffing box  20 . This adjustment can move the sheave  130  from the guard  140  for rigging up the wireline and can permit access to portion of the stuffing box  20 . In addition to these adjustments, adjusting the location of the axle&#39;s axis  173  can shift the sheave  130  to other positions that permit different sizes of wireline  50  to run between the sheave  130  and the stuffing box  20 . For example, although only three positions for the sheave  120  are shown in  FIGS. 3A ,  6  and  7 , additional locations (i.e., slots) can be provided in which to lock the hubs  170  and position the sheave  130 . These additional locations can provide pre-arranged center distances between the sheave  130  and the stuffing box  20  and can be used accommodate different sizes of wireline  50  without needing different sized sheaves and channel depths to match the wire sizes. It should be noted that the position of the guard  140  can be adjusted on the portion  122  of the frame  120  using a locking stud or the like to accommodate the adjustment of the sheave  130 . 
     As shown in  FIGS. 8A-8B , for example, the outer housing  160  of the hub assembly  150  can define a number of more finely spaced slots  165  for engaging portion of the key  180  so that the relative positions of the sheave  130  can be more finely defined. As shown in  FIG. 8B , the key  180  can have a tooth  185  on its underside that fits into the finely spaced slots  165  of the housing  160 . The opposing hub assembly  150 ′ on the other side of the frame can be similarly configured. 
     Using this assembly  100  in  FIGS. 8A-8B  can be similar to that described above, but with an increased amount of adjustment positions available in which the key  180  can engage and lock the assembly  100 . For example, an operator pushes the handle  188  on the key  180  and shifts the distal end  182  of the key  180  inward against the bias of the spring  186 . The tooth  185  on the key  180  disengages from one of the slots  165 , and the operator rotates the hub  170  in the housing  160  using the handle  188 , thereby eccentrically shifting the center axis  173  of the axle  172  about the hub&#39;s center of rotation  171 . The operator can then release the distal end  182  of the key  180  and allow its tooth  185  to engage another of the slots  165  to set the new position of the sheave  130 . This new position can give a different alignment between the sheave&#39;s groove ( 132 ) with the centerline of the stuffing box ( 20 ) that can accommodate a different sized wireline ( 50 ). 
     Rather than using the key  180  that moves perpendicular to the hub&#39;s axis  171  as disclosed previously, other movable mechanisms can be used to lock the hub assemblies  150 - 150 ′ in various rotated positions. For example, in  FIGS. 9A-9B , a key  190  has a stem  192  movable on a plate  194  and biased by a spring  196 . The plate  194  is attached to the hub  170 , and the stem  192  is movably affixed to the plate  194  by the spring  196 . Using a handle  198  on the stem  192 , an operator can pull the stem  192  out of a hole  167  against the bias of the spring  196  to unlock the hub  170  from the housing  160 . The handle  198  can then be used to turn the hub  170  in the housing  160  so that the stem  192  aligns with another hole  167 . At this point, the stem  192  can be released to engage the hole  167  and lock the hub  170  in position. Here, the key  190  moves in a direction parallel to the hub&#39;s axis  171  to engage and disengage from the lock locations of the holes  167 . Again, this arrangement can be used to more finely adjust the position of the sheave  130  relative to the stuffing box ( 20 ) and guard ( 140 ). 
     The foregoing description of preferred and other embodiments is not intended to limit or restrict the scope or applicability of the inventive concepts conceived of by the Applicants. For example, although the number of lock locations are shown only partially around the housing in the Figures, it will be appreciated that lock locations can be positioned entirely around the housing or any suitable portion thereof. In addition, although the disclosed adjustable sheave assembly has been shown for use with a stuffing box on a wellhead, it will be appreciated that the disclosed assembly can be used for other implementations in which wireline is used. For example, the disclosed assembly can be used on a grease injection head or the like. 
     In exchange for disclosing the inventive concepts contained herein, the Applicants desire all patent rights afforded by the appended claims. Therefore, it is intended that the appended claims include all modifications and alterations to the full extent that they come within the scope of the following claims or the equivalents thereof.

Summary:
A stuffing box assembly for a wellhead intervention has a stuffing box and an adjustable sheave. The stuffing box has a body with a collar for connecting to a wellhead and with a passage for running wireline therethrough. A frame connected to the body has side plates and has a hub assembly with hubs rotatable about a first rotational axis. An axle interconnects the two hubs and supports them between the side plates. The sheave can rotate about the second rotational axis of the axel to run the wireline into and out of the stuffing box. The hub assembly can be rotated about its axis of rotation to adjust the location of the axle&#39;s axis of rotation. This can move the sheave away from a fixed guard, can change how the sheave lines up with the stuffing box, and can move the sheave away from the stuffing box.