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You are an expert at summarizing long articles. Proceed to summarize the following text: 
FIELD 
     The present embodiments generally relate to a top drive with an airlift thread compensator without the need for an additional traveling block. 
     BACKGROUND 
     Top drives need secure arrangements to allow load to transfer during drilling. 
     A need exists for a top drive with airlift compensator that provides a more secure load transfer than a top drive supported by a hook and avoids the need for a traveling block. 
     The present embodiments meet these needs. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The detailed description will be better understood in conjunction with the accompanying drawings as follows: 
         FIG. 1  depicts a front detailed view of a top drive with an airlift thread compensator with the airlift thread compensator in an extended, non-compressed position. 
         FIG. 2  depicts a front detailed view of the top drive of  FIG. 1  with the airlift thread compensator in a compressed position. 
         FIG. 3  depicts a top view of the traveling block housing of  FIG. 1 . 
         FIG. 4  depicts a side view of the top drive housing of  FIG. 1  with the airlift thread compensator in an extended position, not compressed. 
         FIG. 5  depicts a side view of the top drive housing of  FIG. 1  with the airlift thread compensator in a compressed position. 
         FIG. 6  depicts a drilling rig positioned over a wellbore with a top drive assembly. 
         FIG. 7  depicts a sequence of steps to operate the top drive assembly according to one or more embodiments. 
     
    
    
     The present embodiments are detailed below with reference to the listed Figures. 
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Before explaining the present apparatus in detail, it is to be understood that the apparatus is not limited to the particular embodiments and that it can be practiced or carried out in various ways. 
     The present embodiments generally relate to a top drive with an airlift thread compensator without the need for an additional traveling block. 
     The present embodiments relate to a top drive with an airlift thread compensator that provides a more secure load distribution when the top drive is operating. 
     In one or more embodiments, a top drive having an airlift thread compensator can have an airbag with a valve for supporting weight of the top drive during threadable engagement and disengagement of tubulars using the top drive, thereby reducing or eliminating the need for high pressure gas and reducing the number of points of failure of the overall system. 
     The top drive assembly can be used on a drilling rig, which can be used for drilling a wellbore. 
     The term “top drive assembly” as used herein can refer to a traveling block housing with sheaves, an airbag, pins, an air valve and links installed, and a top drive. 
     In an embodiment, the sheaves can be wire rope sheaves used for suspending the top drive assembly in a drilling rig derrick. 
     When the top drive assembly is first hung in the drilling rig derrick, no drill pipe is attached to the top drive. 
     Turning now to the Figures,  FIG. 1  depicts a front detailed view of a top drive with an airlift thread compensator with the airlift thread compensator in an extended, non-compressed position. 
     A top drive assembly  7  can include a top drive  11  and can engage a tubular  116   a.    
     The top drive  11  can be connected to a first link first end  17  of a first link  13 . The top drive  11  can be connected to a second link first end  19  of a second link  15 . 
     The first link  13  can be connected at a first link second end  22  to an upper airbag plate  23 . The second link  15  can be connected at a second link second end  24  to the upper airbag plate  23 . In one or more embodiments, the links can be made of steel. 
     The upper airbag plate  23  can be made of steel with a thickness sufficient to resist deformation when a load is supplied. 
     In one or more embodiments, a first pin  28   a  and a second pin  28   b  can function as both load carrying pins and as axles for at least one sheave. 
     The first link second end  22  and the second link second end  24  can be attached to the upper airbag plate  23  in a floating manner, in a loose slot. 
     The first link second end  22  and the second link second end  24  can be contained within a traveling block housing  10 . The traveling block housing can be made of steel. 
     The traveling block housing  10  can have an upper plate  90 . A first outside plate  89  can extend from the upper plate  90 . A first lower plate  93   a  can be connected to the first outside plate  89 , such as at a right angle. 
     A first inside plate  33  can be connected to but spaced apart from the first lower plate  93   a . The first inside plate  33  can be parallel to the first outside plate  89 . 
     The first pin  28   a  extends through a hole in the first inside plate  33 . 
     A first sheave  80   a  can be contained between the first outside plate  89  and the first inside plate  33  using the first pin  28   a  as an axle. The first sheave can freely rotate on the first pin  28   a.    
     A third sheave  82   a  can also be positioned between the first outside plate  89  and the first inside plate  33  adjacent the first sheave  80   a  to provide two sheaves working in tandem. 
     In one or more embodiments, a first middle plate  95   a  can be used to separate the first sheave  80   a  from the third sheave  82   a  and provide additional support between the upper plate  90  and the first lower plate  93   a  when a pair of sheaves is used. When a pair of sheaves is used, the first pin  28   a  can extend through both sheaves, acting as an axle for both sheaves. 
     A second outside plate  92  can extend from the upper plate  90 . A second lower plate  93   b  can be connected to the second outside plate  92 , such as at a right angle. 
     In one or more embodiments, both the first outside plate  89  and the second outside plate  92  can have a thickness from 2 percent to 50 percent greater than the first and second lower plates  93   a  and  93   b.    
     A second inside plate  34  can be connected to but spaced apart from the second lower plate  93   b . The second inside plate  34  can be parallel to the second outside plate  92   
     The second pin  28   b  can extend through a hole in the second inside plate  34 . 
     A second sheave  80   b  can be contained between the second outside plate  92  and the second inside plate  34  using the second pin  28   b  as an axle. The second sheave can freely rotate on the second pin  28   b.    
     A fourth sheave  82   b  can also be positioned between the second outside plate  92  and the second inside plate  34  adjacent the second sheave  80   b.    
     The second pin  28   b  can serve as an axle for both the second and fourth sheave simultaneously. 
     In one or more embodiments, a second middle plate  95   b  can be used to separate the second sheave  80   b  from the fourth sheave  82   b  when the pair of sheaves is used. 
     A lower airbag plate  21  can be connected between the first inside plate  33  and the second inside plate  34 . The lower airbag plate  21  can be parallel to the upper airbag plate  23 . 
     A lower center housing plate  30  can be connected parallel to but spaced apart from the lower airbag plate  21  and connected between first inside plate  33  and the second inside plate  34 . 
     The first pin  28   a  can extend through a slot into a second load carrying plate  32  for load transfer. The second pin  28   b  can extend through a slot into a first load carrying plate  31  for load transfer. In one or more embodiments, each pin can extend from the first and the second load carrying plates though one of the links and the sheaves. 
     The first load carrying plate  31  and the second load carrying plate  32  can be connected at right angles to and between the lower airbag plate  21  and the lower center housing plate  30  as well as and between the first link  13  and the second link  15 . 
     The first link  13  and the second link  15  can pass through the lower airbag plate  21 . 
     An airbag  35  can be located between the upper airbag plate  23  and the lower airbag plate  21 . 
     The airbag  35  can be inflated to raise the weight of the top drive or allowed to compress using an air valve  100 , which can be connected to a low pressure compressed gas source, such as an air source with less than 300 psi. The air valve  100  can be operable using an inflator, such as a Schrader valve. The inflator can be used to inflate the airbag  35 , raising the links supporting the top drive from a first position to a second position. The air valve  100  can be used to deflate, at least partially, the airbag  35 , enabling the links supporting the top drive to move from the second position to another position, such as the first position. 
     The airbag  35  can be used to support and/or suspend weight of the entire top drive, such as during any making or breaking of tubulars or stands of tubulars using the top drive. 
     The airbag can replace hydraulically operable systems that are currently used in the art to support and/or suspend the weight of top drives. 
     The airbag can operate more reliably than hydraulic cylinders connected to high pressure gas accumulators, such as nitrogen accumulators, which can require pressures of over 500 psi and up to 2000 psi. The airbag can operate at substantially lower pressures, making it much safer for operators, and less prone to explosions. 
     Many currently used systems require the use of complicated, leak prone, hydraulically operated systems that require numerous hoses and fittings, hydraulic parts, piston seals, rod seals, accumulator seals, fittings, connectors, valves, hydraulic cylinders, and high pressure gas accumulators. 
     High pressure gas is not normally available on drilling rigs; whereas the present system with a low psi airbag can utilize standard compressed air sources which provide little pressure, such as 120 psi, to provide pressurization to the airbag. 
     In one or more embodiments, air provided from the compressed air source can be at a pressure from about 60 psi to about 70 psi, depending upon the weight of the top drive. Use of high pressure gas and high pressure gas accumulators can require trained operators due to the dangers involved. The unique use of the airbag described herein can thereby eliminate the need for costly, dangerous, and otherwise unnecessary equipment and training. 
     The top drive assembly with airbag provides fewer points of failure, such as leaks, compared to hydraulic systems. In the event of a failure of a hydraulic system, an operator has to shut the entire system down and check every single potential point of failure and make repairs before resuming operation of the system. The airbag described herein can include a simple single inflator valve, depicted as air valve  100 , which can be the sole leak path. 
     This single inflator valve or air valve can be the only connection point of the airbag that can be a potential point of failure. Therefore, upon occurrence of a failure of the system with the airbag, an operator only needs to check the inflator valve for repairs, and the airbag itself for damage, before resuming operation of the system. Therefore, the airbag reduces the amount of system shut down time and the number of points of failure of the system. 
     The airbag can have a toroidal shape, a double toroidal, or another shape. 
     In operation, the inflator valve or air valve  100  can be a valve stem configured to receive compressed air from a compressed air source for inflating the airbag. 
     The inflator valve can be used with low pressure air, also called “rig air,” from a compressed air source, such as an air compressor. 
     The inflator valve can be the same type of valve used in vehicle tires, therefore providing an equivalent level of safety and reliability. 
     The airbag can be inflated by transmitting pressurized air into the airbag through the inflator valve or air valve  100 . The airbag can be inflated until an assembled weight of the top drive is lifted and supported. 
       FIG. 2  depicts a front detailed view of the top drive of  FIG. 1  with the airlift thread compensator in a compressed position. 
     The first sheave  80   a , second sheave  80   b , third sheave  82   a , and fourth sheave  82   b  are shown in the traveling block housing  10 . 
     When the sheaves  80   a ,  80   b ,  82   a , and  82   b  are hoisted by a drilling rig wire rope to raise the drill pipe or tubular load secured to the top drive  11 , the airbag  35  compresses. 
     The first sheave  80   a  and the third sheave  82   a  can use the first pin  28   a  as an axle. The second sheave  80   b  and the fourth sheave  82   b  can use the second pin  28   b  as an axle. 
     The airbag  35  is depicted between the upper airbag plate  23  and the lower airbag plate  21 . 
       FIG. 3  depicts a top view of the traveling block housing of  FIG. 1 . 
     The first sheave  80   a  and the third sheave  82   a  can form a first pair of sheaves and can be adjacent the second link  15 . The second sheave  80   b  and the fourth sheave  82   b  can form a second pair of sheaves and can be adjacent the first link  13 . 
     The traveling block housing  10  and the airbag  35  are shown. The airbag  35  can be disposed beneath the upper airbag plate  23 . 
       FIG. 4  depicts a side view of the top drive housing of  FIG. 1  with the airlift thread compensator in an extended position, not compressed. 
     A second slot  25   b  can be formed on the first link  13  at the first link second end. 
     The second pin  28   b  can extend through the second slot  25   b  at a first position while the airbag  35  is in the non-compressed position or extended position. 
     The upper airbag plate  23  can be attached to the airbag  35  opposite the lower airbag plate  21 . 
     When the airbag is inflated though the air valve, the first pin and the second pin can both be in a lower position in the slots of the links simultaneously and can be used to raise the top drive to a first raised position. 
       FIG. 5  depicts a side view of the top drive housing of  FIG. 1  with the airlift thread compensator in a compressed position. 
     A first slot  25   a  can be formed on the second link  15  at the second link second end. 
     The first pin  28   a  can extend through the first slot  25   a  at a second position while the airbag  35  is in a compressed position. 
     The upper airbag plate  23  can be attached to the airbag  35  opposite the lower airbag plate  21 . 
     In operation, each link can slidably engage a pin within each respective slot, and move simultaneously from a first position to a second position and back to a first position as the airbag is expanded and compressed, by the insertion or removal of air or another gas into the airbag through the air valve. 
     The airbag can receive and support at least a portion of the weight of the links and anything connected to the links. In one or more embodiments, the airbag can be used to support and/or raise ten thousand pounds or more. 
     When the airbag is compressed, the first pin and the second pin can both be in a second location. 
     The airbag can be inflated sufficiently to raise the top drive to a floating position, to a location that is greater than the length of the drill pipe thread. The pins do not necessarily need to move all the way to the top of the slots. Without the floating function, the weight of the top drive can damage the threads as it is unscrewed past the first thread. 
     The top drive assembly in drilling can enable a drilling rig to add lengths of drill pipe, making up drill pipe together. The top drive assembly can be lowered using the sheaves to the drill pipe stand. Because the top drive is floating on the airbag and the links are floating on the pins, the thread of the drill pipe cannot be damaged. 
       FIG. 6  depicts a drilling rig positioned over a wellbore with a top drive assembly. 
     The drilling rig  9  can support a derrick  73  and can be positioned over a wellbore  8 . The derrick  73  can include a crown block  160  for supporting the top drive assembly  7 . 
     The derrick  73  can be used to install a tubular  116   a  into the wellbore  8 . A drill bit  119  can be attached to the tubular  116   a . Additional tubulars  116   b  and  116   c  can be threaded to the tubular  116   a  in the wellbore  8  using the top drive assembly  7 . 
     The top drive assembly  7  can be used for engaging a tubular or a stand of tubulars, such as tubular  116   a , which can be a drill pipe extending from the rig floor  94 , through the substructure  91 , and into a wellbore  8 . 
     Engines  164  and  166  can be located beneath the substructure  91  and the rig floor  94  for use in drilling operations. 
     Wire rope  158  can be used to raise and lower the top drive assembly  7 . Drawworks  162  can be used to operate the wire rope  158 , which can be connected to the sheaves in the top drive assembly  7 . 
     Additionally, the drilling rig  9  can include a fluidly connected mud pump  71  with a mud tank  70  for pumping drilling mud into the wellbore  8 . 
     A racking board  350  for holding the tubulars prior to being formed into a drill string with the tubulars is shown, as well as slips  352 . 
     In an embodiment, the top drive assembly includes a rotatable stem and a motor spinably connected to the rotatable stem. In one or more embodiments, a heavy thrust bearing can be disposed about the rotatable stem. 
       FIG. 7  depicts a sequence of steps to operate the top drive assembly according to one or more embodiments. 
     The method of operation can include inflating the airbag to a preselected pressure sufficient to lift and support the top drive over a tubular, as illustrated by box  702 . 
     The method can include using the airbag to suspend the weight of the top drive during: threadable engagement to a tubular or to a stand of tubulars; threadable disengagement to a tubular or to a stand of tubulars; threadable engagement of a tubular to another tubular; threadable disengagement of a tubular to another tubular; threadable engagement of a stand tubulars to another stand of tubulars; threadable disengagement of a stand of tubulars to another stand of tubulars; or combinations thereof; as illustrated by box  704 . 
     The method can include using the airbag to suspend weight of the top drive to prevent damage to the threads during threadable engagement of the first tubular, as illustrated by box  714 . 
     The method can include threadably connecting the first tubular using a torque wrench head while simultaneously suspending the weight of the top drive using the airbag, as illustrated by box  716 . 
     The method can include using the airbag to suspend the weight of the top drive to prevent damage to the threads during threadable disengagement of the first tubular, as illustrated by box  718 . 
     The method can include threadably disengaging the first tubular using the torque wrench head while simultaneously suspending the weight of the top drive using the airbag, as illustrated by box  720 . 
     The method can include releasing the torque wrench head from the first tubular, as illustrated by box  722 . 
     While these embodiments have been described with emphasis on the embodiments, it should be understood that within the scope of the appended claims, the embodiments might be practiced other than as specifically described herein.

Summary:
A top drive assembly arranged to travel in a derrick. An important use of this assembly is to manipulate tubulars in a wellbore, so it includes a traveling block housing and sheaves disposed about a compensating airbag. The airbag is arranged to prevent damage to the threads during screwing and unscrewing operations of tubulars in a wellbore. The arrangement of the airbag requires only a single air valve thus having only a single leak path.