You are an expert at summarizing long articles. Proceed to summarize the following text:

You are an expert at summarizing long articles. Proceed to summarize the following text: 
FIELD OF INVENTION 
       [0001]    The invention relates generally to planetary gears, and more particularly to reels carrying coiled tubing for coiled tubing injectors and similar mechanisms driven by a planetary gearing system. 
       BACKGROUND 
       [0002]    Coiled tubing well intervention has been known in the oil production industry for many years. A great length, often exceeding 15,000 feet of steel tubing, is handled by coiling it on a large reel, which explains the name of coiled tubing. The tubing reel cannot be used as a winch drum. The stresses involved in using it as a winch would destroy the tubing. The accepted solution in the oil industry is to pull tubing from the reel as it is required and pass it around a curved guide arch so that it lies on a common vertical axis with the well bore. To move the tubing into and out of the well bore, a device called a coiled tubing injector is temporarily mounted on the wellhead, beneath the guide arch. Examples of coiled tubing injectors include those shown and described in U.S. Pat. Nos. 5,309,990, 6,059,029, and 6,173,769, all of which are incorporated herein by reference. 
         [0003]    Coiling tension is controlled by a tubing reel drive system and remains approximately constant no matter if the injector head is running tubing into or out of the well, or if it is pulling or snubbing. The coiling tension is insignificant by comparison to tubing weight and payload carried by the tubing in the well bore and therefore is no danger to the integrity of the tubing. 
         [0004]    Although other methods of achieving this aim are known, injector heads used for well intervention and drilling utilize a plurality of chain loops, on which are mounted grippers for gripping the tubing. There are many examples of such injector heads. Most rely on roller chains and matching sprocket forms as a means of transmitting drive from the driving shafts to the chain loop assemblies. For the injector head to manipulate tubing, it pushes, from opposite sides, the grippers against the tubing and then concurrently moves the grippers by rotating to move the tubing in and out of the well bore. 
         [0005]    A coiled tubing reel assembly includes a stand for supporting a spool on which tubing is stored, a drive system for rotating the reel and creating back-tension during operation of the reel, and a “level winding” system that guides the tubing as it is being unwound from and wound onto the spool. The level winding system moves the tubing laterally across the reel so that the tubing is laid across the reel in a neat and organized fashion. The coiled tubing reel assembly must rotate the spool to feed tubing to and from the injector and well bore. The tubing reel assembly must also tension the tubing by always pulling against the injector during normal operation. The injector must pull against the tension to take the tubing from the tubing reel, and the reel must have sufficient pulling force and speed to keep up with the injector and maintain tension on the tubing as the tubing is being pulled out of the well bore by the injector. The tension on the tubing is always being maintained in an amount sufficient to wind properly the tubing on the spool and to keep the tubing wound on the spool. 
         [0006]    Although a spool can be rotated by means of a chain and a sprocket mounted on the axle of the coiled tubing spool, planetary gear drives are typically used to rotate the spool. A planetary gear drive is capable of delivering high torque at low speeds without the heaviness and expense of a chain and sprocket. Closed center planetary gear drives are usually preferred. Such drives have all of their components mounted symmetrically about the center of rotation, including the drive motor, which may be electric or hydraulic. 
         [0007]    In a typical arrangement, the output of a planetary gear drive supports one end of the reel, connecting directly to the axle of the reel. Integral brakes are usually fitted to the planetary drive to provide a parking brake for preventing unwinding of the stored tubing when the drive motor is not powered. Planetary gearing is also referred to as epicyclic gearing. Planetary gearing comprises one or more gears, called planet gears, that revolve around a central gear called a sun gear. The planet gears are mounted to a carrier, which may rotate relative to the sun gear. An outer gearing, called an annulus, meshes with the planet gear. Planetary gearing may be either simple or compound. A simple planetary gear has one sun, one ring, one carrier and one set of planet gears. A compound planetary gearing has a more complex structure. There exist many examples of compound structures too numerous to list. In a coiled tubing reel application, the planetary gear drive functions as reduction gearing that takes a relatively high speed, low-torque input, such as from a hydraulic motor, and provides a relatively low speed, high-torque output that is coupled with the hub of the reel, with the input to the planetary gearing rotating about the same axis as its output and the spool. 
         [0008]    A fluid swivel connects to the other end of the axle of the reel for coupling a fluid source to the coiled tubing wound on the reel. Because the planetary gear drive is connected to one end of the spool&#39;s central axle, and the fluid axle is connected to the other end, a concentric rotary union or a slip ring assembly is used to run electrical and other wires into the coiled tubing for transmitting electrical signals to and from sensors and other equipment connected to the end of the coiled tubing. The concentric rotary union must have a sufficiently large internal hub that can be bored out to pass over the axle of the reel. Alternately, to avoid having to incorporate concentric rotary ring, a chain and sprocket is used. 
       SUMMARY 
       [0009]    The invention pertains generally to a modified planetary gear box or drive and arrangement of the gear box with a drive motor that permits electrical, optical, hydraulic or other types of cabling, wiring, or lines to be passed through the planetary gear box. When the planetary gear is connected to one end of a reel of coiled tubing, cabling is able to be passed through the planetary gear box directly into one end of a hub of the reel, and then into the end of the coiled tubing that is being injected into a wellbore, while the other end of the reel&#39;s hub is connected to a swivel joint that can be connected to a pump for pumping fluid into the coiled tubing. 
         [0010]    In one representative embodiment, a conduit extends through the center of the planetary gear box housing and its sun gear, the axis of the conduit being aligned with the axis of rotation of the input to the planetary gear box and to its output, the output being coupled to the axle of, for example, a coiled tubing reel. An output shaft of a drive motor that is offset from the central axis of the planetary gear is coupled to the rotary input of the planetary gear box through, for example, one or more gears, chains, or other means for coupling the output shaft of the drive motor to the input of the planetary gear box. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a side view of a representative example of a coiled tubing unit deployed at a well site, with a cooled tubing reel assembly mounted on a trailer feeding coiled tubing into a coiled tubing injector connected to a riser on top of a well head. 
           [0012]      FIG. 2  is a side view, partially section, of a coiled tubing reel comprising a stand and spool. 
           [0013]      FIG. 3  is an enlarged portion of the side view of  FIG. 2  showing the details of a planetary gear drive. 
       
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0014]    In the following detailed description of the illustrative embodiments, reference is made to the accompanying drawings that form a part hereof. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is understood that other embodiments may be utilized and that logical structural, mechanical, electrical, and chemical changes may be made without departing from the invention. In the drawings and description that follow, like parts are typically marked throughout the specification and drawings with the same reference numerals, respectively. The drawing figures may not be to scale. Certain features of the invention may be shown exaggerated in scale or in a schematic form, and details of conventional elements may be omitted in the interest of clarity and conciseness. The terms “including” and “comprising” are meant to be inclusive or open-ended, and not exclusive. Unless otherwise indicated, as used throughout this document, “or” does not require mutual exclusivity. 
         [0015]    Unless otherwise specified, any use of any form of the terms “connect,” “engage,” “couple,” “attach,” or any other term describing an interaction between elements is not meant to limit the interaction to direct contact between the elements unless the context plainly states otherwise. It may include indirect interaction between the elements. The phrases “hydraulically coupled,” “hydraulically connected,” “in hydraulic communication,” “fluidly coupled,” “fluidly connected,” and “in fluid communication” refer to a form of coupling, connection, or communication related to fluids, and the corresponding flows or pressures associated with these fluids. Reference to a fluid coupling, connection, or communication between two components describes an arrangement that allows fluid to flow between or among the components. Hydraulically coupled, connected, or communicating components may include certain arrangements where fluid does not flow between the components, but in which fluid pressure may be transmitted such as via a diaphragm or piston. Similarly, electrical coupling, connection, or communication between two or more components describes an arrangement that allows for transmission of information between the components by one or more electrical circuits or electro-magnetic waves. The terms “seal”, “sealing”, “sealing engagement,” and “sealingly-coupled” are not intended to imply, unless the context otherwise states, formation of a perfect seal or a seal that works under all circumstances. 
         [0016]      FIG. 1  illustrates one example of a coiled tubing injector unit. The example is not intended to be limiting. It is intended to be representative generally of coiled tubing injector units and their components. A reel  10  of coiled tubing is mounted on a trailer  11  for transport to the site. A coiled tubing injector, control cabin and other equipment for operating the injector is sometimes referred to collectively as a “coiled tubing unit,” and is generally designated in the figures by the reference number  12 . As coiled tubing  14  is unspooled from the reel, or is spooled back onto the reel, it is guided into alignment with the chains of the coiled tubing injector by a tubing support guide  16 . Because such guides are typically arched, they are sometimes referred to as “gooseneck” supports. When the coiled tubing injector is deployed, the guide is connected to the frame of the coiled tubing injector so that it has a fixed relationship with the coiled tubing injector while the injector is being operated. Generally, the guidance arch is positioned or oriented so that the coiled tubing is threaded into the top of the head of the injector, between its rotating chains or, optionally, into a straightener mounted to the frame, on top of the injector head, for removing the bend in the tubing before it enters the injector head. (As used in this description, “coiled tubing injector” refers to the injector head with or without the straightener, unless the context indicates otherwise.) The reel must maintain tension on the coiled tubing in order to wind the tubing coiled on the reel and to keep it wound on the reel, as it is being unspooled or spooled. The guidance arch prevents the coiled tubing from kinking or otherwise being damaged by the tension the reel is applying to the tubing. However, a guidance arch is typically attached to the frame of the coiled tubing injector in a manner that allows it to be attached or connected in different positions or orientations. For example, the best positioning or orientation may depend on the diameter of tubing being used and whether the tubing is being lowered or pushed into the well bore or pulled out of the well bore. When the pipe is coming off a reel, it has relatively more curve than when it is pulled from the well, which may affect how the guidance arch is fixed to the injector. Thus, “fixed relationship” does not imply one that cannot allow for adjustment. 
         [0017]    When being used, the coiled tubing injector is positioned over the well head, high enough to accommodate one or more blow out preventers  20 , a riser  22 , and other equipment that might be connected to the wellhead through which the coiled tubing must pass before entering the well bore. The riser is made up from one or more sections of straight pipe that extends from the blow out preventers attached to the wellhead. The riser is used to accommodate elongated, rigid tools that are attached to the end of the coiled tubing prior to being lowered into the well bore. The coiled tubing injector is connected to the riser with a stripper, through which the coiled tubing is pushed or pulled. Because there is no derrick or platform, a temporary structure erected above the wellhead, or a mobile crane driven to the site, is used to position and hold the injector in place. 
         [0018]    A coiled tubing reel assembly includes a stand for supporting a spool on which tubing is stored, a drive system for rotating the reel and creating back-tension during operation of the reel, and a “level winding” system that guides the tubing as it is being unwound from and wound onto the spool. The level winding system moves the tubing laterally across the reel so that the tubing is laid across the reel in a neat and organized fashion. The coiled tubing reel assembly must rotate the spool to feed tubing to and from the injector and well bore. The tubing reel assembly must also tension the tubing by always pulling against the injector during normal operation. The injector must pull against the tension to take the tubing from the tubing reel, and the reel must have sufficient pulling force and speed to keep up with the injector and maintain tension on the tubing as the tubing is being pulled out of the well bore by the injector. The tension on the tubing must always be maintained. The tension must also be sufficient to wind properly the tubing on the spool and to keep the tubing wound on the spool. Consequently, a coiled tubing reel assembly is subject to substantial forces and loads. Historically, tubing reel assemblies have been shipped to wells with the required coiled tubing wound on the spool, and the spool installed in a reel assembly. Such spools are specially designed for the particular reel assembly and typically not meant to be disconnected or removed from the reel assembly during normal operation. However, systems exist that permit spools from being removed from reel assemblies, such as the ones shown in U.S. Pat. No. 6,672,529, which is incorporated herein by reference. 
         [0019]    A high capacity, self-propelled crane  26  is used to lift and hold the coiled tubing injector  18  and guidance arch in the proper position during the well servicing job. The crane is generally placed opposite the wellhead of the coiled tubing reel  10  or, if necessary, to one side. Some or all of the weight of the injector and the tubing is transferred to the boom of the crane. 
         [0020]      FIGS. 2 &amp; 3  are partially-sectioned side views of a representative example of a coiled tubing reel assembly with a planetary gear drive. No coiled tubing is shown wrapped around the reel in this figure. It has been omitted to show details of the hub of the reel. The reel assembly  30  includes a spool  32  mounted on a stand that is generally indicated by reference number  34 . The spool is comprised of central section, or drum  36 , a left flange or rim  38  and a right flange or rim  40 . The stand is comprised of a frame  42  (partially illustrated). The drum is connected to a central hub by a framework  46  of struts. The hub  44  has a hollow, cylindrical shape in this example. It rotates with the spool. The hub  44  is supported on the frame  42  of the stand at opposite ends so that it may rotate on the stand when turned. 
         [0021]    A planetary gearing drive, which is generally designated by reference number  48 , is mounted directly within one end of hub  44 . An outer housing  50  of the planetary gear drive, functioning as its output, is connected with the hub  44  in this example by fitting it inside an open end of the hub and connecting it to an end flange  52 . The planetary gear drive  48  is connected to the stand at flange  54 , which is part of frame  42 . The input to the planetary drive is a shaft  56  that is connected to a sun gear  58 . The shaft  56  rotates the sun gear. It is supported by front radial bearing  60  and rear radial bearing  62 . The shaft extends from one side of the planetary gear box drive to the other. Through the center of the shaft is formed a hollow passageway or conduit  64 , with an outside or front opening  66  and an inside or rear opening  68 . Although indicated as a single piece, the drive shaft may be comprised of multiple, co-axial elements that rotate together and collectively form a conduit that defines a single passageway that extends along the axis of rotation of the planetary gear drive, which is adapted or otherwise suitable for passing an electrical or optical cable from the one side the planetary gear to the other side of the planetary gear along its central axis of rotation. The central axis of rotation of the planetary gear is coincident with the central axis of rotation the spool  32  (and hub  44 ), which is indicated by dashed line  69 . A conduit may, therefore, be comprised of one or more structural pieces or segments. The term “conduit” is not intended to imply a single length of pipe. Although not shown, an electrical cable, hydraulic control line, or optical cable (collectively, each a “line”) used for powering or controlling a downhole tool, or transmitting signals from a sensor can be fed through conduit  64  for insertion into one end of coiled tubing (not shown) wrapped around the spool  32 . A conduit  70  may be used to direct the line toward the opposite side of the hub, at which point the line would exit and be fed into the open end of the coiled tubing, which would not be attached to outlet  74 . Alternately, the line can be threaded or inserted through an arrangement (not shown) that attaches to outlet  74  of fluid axle  72  and permits either the line to be fed into, or fluid to be pumped through, the coiled tubing, or both. The line could also be used to power or control devices on the spool  32  such as a valve for closing the connection between the coiled tubing and the fluid axle  72 . 
         [0022]    The other end of hub  44  is attached to fluid axle  72 . The fluid axle is mounted to frame  42  of the stand on flange  73 . Coiled tubing may be attached to outlet  74  of pipe  76  to allow for fluid to be pumped through the coiled tubing. Pipe  76  couples to a swivel joint  78  so that it may rotate with respect to the joint. A source of high pressure fluid outside of the reel is connected to the stationary side of the swivel joint  78 . 
         [0023]    Drive motor  80  is coupled to the input shaft  56 . The drive motor is offset to form the axis of the input shaft  56 , allowing access to opening  66  of conduit  64 . The drive motor is, in this example, coupled to the input shaft by a gear train comprised of gears  82  and  84 . Gear  82  is connected to an output shaft of drive motor  80 , and gear  84  is connected to the input shaft  56 . In this example, the gears form a reduction gear train that reduces speed and increases torque on the input shaft  56 . Optionally, more than one drive motor may be utilized by arranging the drive motors around the input shaft  56 , each placed to one side of the axis of rotation of the input shaft in an arrayed fashion, with each of them coupled to the input shaft through a gear train. The drive motors may be hydraulic and/or electric. 
         [0024]    Rotation of the drive motor turns input shaft  56 , which turns sun gear  58 . Sun gear  58  rotates planetary gears  86  and  88 . The planetary drive may have, optionally, have just one planet gear. It may also have more than two planet gears. In this example, the planetary gears are rotationally mounted on arms of a carrier  90 , which is connected to flange  54  of the frame  42 . Connected, or integrally formed with, sun gear  58  is a carrier with at least two arms  92  and  94 . Planet gears  96  and  98  are mounted, respectively, on the arms  92  and  94 . The planetary gears  86 ,  88 ,  96  and  98  mesh with an annulus or outer gearing formed on the side of housing  50 , causing it to rotate when the input shaft is rotated. Integrated into the planetary gear drive  48  is a brake  102 . One part of the brake is mounted to input shaft  56  and the other to the stationary carrier  90 . 
         [0025]    The drawing of planetary gear drive  48  is a simplified to show representative elements of a planetary drive. It is just one example of compound planetary gearing. It is intended to be merely representative, and not an limiting example, of planetary gear drives or boxes generally for purposes of illustrating basic principles of operation and a conduit  66  extending through the center of the planetary gearing arrangement to allow passage of a cable or wiring. 
         [0026]    In an alternate embodiment, the reel stand assembly is modified to include a coupling between the spool and the stand to allow for the spool to be removed relatively more quickly from the stand. In such an embodiment, the planetary drive is connected to an outer coupling member (such as an axle) and the hub of the spool being connected to an interior coupling member. An extension of conduit or passageway  66 , which is coaxial with the planetary gearing, extends through both parts of the coupling, along their respective axes of rotation, and into the hub of the spool. 
         [0027]    The foregoing description is of exemplary and preferred embodiments. The invention, as defined by the appended claims, is not limited to the described embodiments. Alterations and modifications to the disclosed embodiments may be made without departing from the invention. The meaning of the terms used in this specification are, unless expressly stated otherwise, intended to have ordinary and customary meaning and are not intended to be limited to the details of the illustrated structures or embodiments.

Summary:
A modified planetary gear box and arrangement of the gear box with a drive motor permits electrical, optical or other types of cabling or wiring to be passed through the planetary gear box along its axis of rotation. The planetary gear box drives or rotates a reel of coiled tubing. Electrical, hydraulic, optical and other types of line for lowering into a well bore through the coiled tubing is passed through a passageway through the center of the planetary gear box, into one end of a hub of the reel, and then into the coiled tubing, which is injected into the wellbore. The other end of the hub of the reel is able to be connected to a swivel joint that can be connected to a pump for pumping fluid into the coiled tubing.