Patent Publication Number: US-9840881-B2

Title: Injector head for coiled tubing systems

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 13/439,320, which was filed in the U.S. Patent and Trademark Office on Apr. 4, 2012 and issued as U.S. Pat. No. 9,091,129, and claims priority to U.S. Provisional Patent Application No. 61/471,391, which was filed in the U.S. Patent and Trademark Office on Apr. 4, 2011, the entire disclosures of which are both herein incorporated by reference for all purposes in their entirety. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     This application is not the subject of any federally sponsored research or development. 
     THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT 
     There has been no joint research agreements entered into with any third parties. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The embodiments of the present invention relate generally to a coiled tubing injector head utilizing a tension cylinder that automatically adjusts a tension of the chain or conveyor member. 
     Description of the Related Art 
     In the development and production of an oil or gas well, elongated tubing may be inserted into the well from the surface for such purposes as the injection of certain types of fluids for stimulation of the production, displacing fluids in the well, for performing cleaning operations on the production tubing, as well as various other purposes. A continuous length of tubing is inserted into the well from a large reel at the surface. In the oil and gas industries, this process is known as coiled tubing. An example of an apparatus for inserting and withdrawing coiled tubing into a well can be found in U.S. Pat. No. 5,188,174 to Anderson, Jr. et al., which is hereby incorporated by reference in its entirety. 
     Coiled tubing units are used for interventions in oil and gas wells, and sometimes the tubing, which comes spooled on a large reel, is used as production tubing in depleted gas wells. The injector head is the heart of a coiled tubing system. Coiled tubing injector heads inject coiled tubing into an oil or gas well to facilitate the servicing of the well. 
     Coiled tubing injector heads are well known in the art. Coiled tubing injector heads typically have two opposed counter-rotating vertical chains loops with a fixed drive sprocket at the top and a floating sprocket at the bottom. The two opposed counter-rotating chains provide the injector head with the capability to snub coil tubing into a well with pressure. To snub the coiled tubing into a high-pressure well, the injector head must exert a significant amount of compression to overcome the resistance from the wellhead pressure. In other words, the well pressure exerts a force to eject the coil tubing from the well which must be opposed by a force applied to the bottom sprockets to keep the chain loops tight. This is known by a person skilled in the art as chain tension. 
     The majority of injector head chain and skate bearing failures are caused by applying an improper chain tension when operating the injector head. In the prior art, chain tension is controlled by an operator adjusting hydraulic pressure at a control panel in tension cylinders attached to lower sprocket shafts. The operator must determine the proper chain tension pressure based on the coil tubing&#39;s outside diameter and the well pressure (and in horizontal wells, the friction force acting on the coil tubing). These factors can change during the course of a drilling project, requiring the operator to monitor the snub load and chain tension pressure. It is sometimes difficult for an operator to continuously monitor the snub load. As a result, mechanical stops were added at the lower sprocket shafts in the prior art. The mechanical stops prevent the lower sprocket from moving past a predetermined setting, and must be manually adjusted as the chain wears. The chain wear (chain length elongation) is caused by pin-bushing wear (when a chain is operating, the outer surface of the pin and inner surface of the bushing rub against one another, wearing little by little). Another consideration is the position in which the chain and the sprocket engage, which fluctuates, causing the chain to vibrate along with this fluctuation. The vibration occurs because there is a pitch length in the chains, where they can only bend at the pitch point. The height of engagement (the radius from the center of the sprocket) differs when the chain engages in a tangent position and when it engages in a chord. A chain tension pressure that will keep the chains tight against a high snub force results in load spikes from the chain chordal action. At least for the reasons provided above, there is a need for an injector head used in coiled tubing systems that automatically adjusts the tension of the chain. 
     SUMMARY OF THE INVENTION 
     For the reasons included above, it is therefore an object of embodiments of the present invention to provide an injector head that automatically adjusts the tension of the chain or conveyor member. 
     The embodiments of the present invention allow the operator to set a proper chain tension pressure that prolongs the useful life of the chains, and provide a mechanical stop to prevent the bottom sprockets from being pushed up from the well pressure on the coil tubing. The embodiments of the present invention automatically adjust to compensate for an increase in chain length due to wear. 
     The embodiments of the present invention include an injector head used in coiled tubing systems including at least two opposed counter-rotating chain loops having a first end and a second end, the chain loops having a chain. The injector head of the embodiments of the present invention further includes a fixed drive sprocket disposed at the first end of a chain loop and a floating sprocket disposed at the second end of the chain loop. In the injector head of the embodiments of the present invention, there is a force applied to the floating bottom sprocket to maintain the chain loop at a desired chain tension. Additionally, the injector head of the embodiments of the present invention includes a tension cylinder that automatically maintains the chain loop at the desired chain tension. 
     Yet another embodiment of the present invention is directed to a tension cylinder, where the tension cylinder includes: a cylinder head and a cylinder head seal; a rod and a rod seal; a rod wiper; a cylinder barrel; a retainer; a piston seal; and a piston and a cylinder, where the piston divides the cylinder into two chambers, a first chamber and a second chamber, and each chamber includes a piston area, where the piston area is substantially the same in the first and second chambers. The tension cylinder further includes a check valve connecting the first and second chambers, where the check valve allows fluid and pressure to pass from the first chamber to the second chamber. 
     The embodiments of the present invention further include a method of automatically adjusting the tension of a chain in an injector head used in coiled tubing systems including applying a force to a floating sprocket to maintain a chain loop at a desired chain tension. The injector head includes: at least two opposed counter-rotating chain loops having a first end and a second end, the chain loops having a chain; and a fixed drive sprocket disposed at the first end of the chain loop, where the floating sprocket is disposed at the second end of the chain loop. The method of automatically adjusting the tension of a chain in an injector head used in coiled tubing systems further includes: preventing the floating bottom sprocket from moving toward the first end of the chain loop using a mechanical stop; and automatically maintaining the chain loop at the desired chain tension using a tension cylinder. 
     Yet another embodiment of the present invention is directed to an injector head used in coiled tubing systems including: at least two opposed counter-rotating vertical chain loops having a top and a bottom, the chain loops having a chain; a fixed drive sprocket at the top of a vertical chain loop and a floating sprocket at the bottom of the vertical chain loop; a force applied to the floating bottom sprocket to keep the chain loop tight thereby creating a desired chain tension; a mechanical stop to prevent the floating bottom sprocket from moving toward the top of the vertical chain loop; and a tension cylinder that automatically maintains the chain loop at the desired chain tension. The tension cylinder includes: a cylinder barrel; a cylinder head and a cylinder head seal; a rod and a rod seal; a rod wiper; a retainer ring; and a floating piston and a cylinder, where the piston divides the cylinder into two chambers, a first chamber and a second chamber, each chamber having a piston area, and where the piston area is substantially the same in the first and second chambers. The tension cylinder further includes: a spring mounted between the piston and the rod, where the spring maintains a distance substantially equivalent to chordal movement of the chain on the sprockets; a piston seal; a check valve connecting the first and second chambers, where the check valve allows fluid and pressure to pass from the first chamber to the second chamber, but the check valve does not allow fluid and pressure to pass from the second chamber to the first chamber; and two ports, a first port and a second port, where the first port is connected to a chain tension pressure control valve, and where the first port bleeds air from the cylinder, and the second port is plugged during operation of the injector head. The injector head further includes: sprocket shafts engaged with the floating bottom sprocket, where the rod includes slots that are cut into an end of the rod, the rod is connected to the sprocket shafts, and the rod is connected to the piston with the retainer ring. Additionally, the injector head includes: rollers that are engaged with the chain and move with the chain; and floating/moving traction cylinders, where forces from the chain push the rod against the floating sprocket in the chain loop. If forces push the floating sprocket toward the top of the chain loop, the rod will travel a distance substantially equal to the distance maintained by the biasing member, and the floating sprocket is prevented from moving past a location of the piston in the cylinder. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred features of the embodiments of the present invention are disclosed in the accompanying drawings, wherein similar reference characters denote similar elements throughout the several views, and wherein: 
         FIG. 1  is a front/side perspective view of an injector head according to an embodiment of the present invention; 
         FIG. 2  is a front view of an injector head according to an embodiment of the present invention; 
         FIG. 3  is a right side view of an injector head according to an embodiment of the present invention; 
         FIG. 4  is a left side view of an injector head according to an embodiment of the present invention; 
         FIG. 5  is a rear view of an injector head according to an embodiment of the present invention; 
         FIG. 6  is a front/side perspective view of an injector head according to an embodiment of the present invention 
         FIG. 7  is a front view of an injector head according to an embodiment of the present invention; 
         FIG. 8  is a right side view of an injector head according to an embodiment of the present invention; 
         FIG. 9  is a cross-sectional view through line D-D of  FIG. 7 ; 
         FIG. 10  is a top perspective view of an injector head according to an embodiment of the present invention; 
         FIG. 11  is a bottom perspective view of an injector head according to an embodiment of the present invention; 
         FIG. 12  is a bottom perspective view of an injector head according to an embodiment of the present invention; 
         FIG. 13  is a side perspective view of an injector head lower shaft according to an embodiment of the present invention; 
         FIG. 14  is a rear-side perspective view of a tension cylinder according to an embodiment of the present invention; 
         FIG. 15  is a side sectional view showing the inner workings of a tension cylinder according to an embodiment of the present invention; 
         FIG. 16  is a cross-sectional side view of a tension cylinder according to an embodiment of the present invention; 
         FIG. 17A  is a top sectional view showing the inner workings of a tension cylinder according to an embodiment of the present invention; and 
         FIG. 17B  is a bottom view of a tension cylinder according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The embodiments of the present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the illustrated embodiments set forth herein. Rather, these illustrated embodiments are provided so that this disclosure will be thorough and complete and will convey the scope of the invention to those skilled in the art. 
     In the following description, like reference characters designate like or corresponding parts throughout the figures. Additionally, in the following description, it is understood that terms such as “top,” “bottom,” “upper,” “lower,” “left,” “right,” and the like, are words of convenience and are not to be construed as limiting terms. 
     The embodiments of the present invention include coiled tubing injector heads  1  that have two opposed counter-rotating vertical chains loops  2  with a fixed drive sprocket  4  at the top and a floating sprocket  6  at the bottom. As understood by a person of ordinary skill in the art, a floating sprocket  6  is a sprocket that has provisions to move up or down in a slot  8  but it is not able to move sideways. The slot length is equal to the distance the floating sprocket  6  can move for an acceptable amount of chain wear. The two opposed counter-rotating chains  2  provide the injector head  1  with the capability to snub coil tubing  10  into a well with pressure. The well pressure exerts a force to eject the coil tubing  10  from the well which must be opposed by a force applied to the bottom floating sprockets  6  to keep the chain loops  2  tight (the chain tension). The tension in an embodiment of the present invention has been determined empirically. In an embodiment of the present invention, 500 psi is the minimum pressure applied to the tension cylinders  12  to provide quiet and smooth operation of the chain  2 . However, in other embodiments of the present invention, the tension pressure may be different because of factors such as the tension cylinder diameter and chain pitch. 
     The embodiments of the present invention include a tension cylinder  12  including a cylinder barrel  14 , cylinder head  16 , and a rod  18 . Additionally, the embodiments of the present invention include a floating piston  20 , a spring  22 , and a manner in which the piston  20  and rod  18  connect. 
     The embodiments of the present invention further include a tension cylinder  12  that allows an operator to set a proper chain tension pressure that prolongs the useful life of the chains  2  and provides a mechanical stop to prevent the bottom floating sprockets  6  from being pushed up by the well pressure on the coil tubing  10 . The tension cylinder  12  included in the embodiments of the present invention automatically adjusts for an increase in chain length due to wear. The chain wear (chain length elongation) is caused by pin-bushing wear (when a chain  2  is operating, the outer surface of the pin  24  and inner surface of the bushing  26  rub against one another, wearing little by little). The chain tension pressure must therefore be consistently maintained to provide smooth and quiet operation with optimum life of the chains  2 . The operator of the coil tubing unit system is not required to monitor snub loads to determine chain tension during operation and the chain  2  is not subject to high loads resulting from high chain tension pressure. 
     As shown in the figures submitted herewith, the tension cylinder  12  included in the embodiments of the present invention includes a piston  20  and a cylinder  14 , where the piston  20  divides the cylinder  14  into two chambers—a first chamber  28  and a second chamber  30 . The piston area is substantially the same in the first and second chambers  28 ,  30 . A check valve  32  connects the first chamber  28  to the second chamber  30  allowing fluid and pressure to pass from the first chamber  28  into the second chamber  30 , but not from second chamber  30  into the first chamber  28 . 
     The tension cylinder  12  also includes a cylinder head  16 , a cylinder head seal  36 , a rod seal  38 , a rod wiper  40 , a cylinder barrel  14 , a retainer  34 , and a piston seal  42 . 
     Elements of the tension cylinder  12  included in an embodiment of the present invention will now be described. 
     The cylinder barrel  14  is typically made of steel and is a seamless thick walled tube, with a cylinder shaped component, also typically made of steel, welded at one end where the inner diameter is machined. However, one skilled in the art will understand that the cylinder barrel, and other components of the tension cylinder  12  may be constructed of additional materials other than those described herein. 
     The cylinder head  16  is a cylinder shaped component, typically made of steel, that attaches to the open end of the cylinder barrel  14  and contains a cylinder head seal  36 , a rod seal  38  and a rod wiper  40 . 
     The cylinder head seal  36  is typically made of an elastomeric material and is the component that seals the clearance between the cylinder head  16  and cylinder barrel  14 . 
     The rod seal  38  is typically made of an elastomeric material and is the component that seals the clearance between the cylinder head  16  and the cylinder rod  18 . 
     The rod wiper  40  is typically made of a hard elastomeric material and is the component that scrapes contaminates from the exposed portion of the rod  18  before it moves through the rod seal  38 . 
     The rod  18  is a cylinder shaped component, typically made of steel, that extends from the cylinder  14  and has one end machined to attach to the injector head lower shaft  44  and the opposite end machined to contain the biasing member  22  (typically a spring) and attach to the piston  20 . The injector head lower shaft  44  may include the floating sprockets  6  in an embodiment of the present invention. 
     The piston  20  is a cylinder shaped component, typically made of steel, that separates the two chambers  28 ,  30  of the cylinder barrel  14  internally. 
     The piston seal  42  is typically made of an elastomeric material and is the component that seals the clearance between the piston  20  and cylinder barrel  14 . 
     The biasing member  22  is a spring in the preferred embodiment of the present invention. The biasing member  22  is an elastic device that stores energy used to maintain a predetermined distance between the rod  18  and piston  20 . One skilled in the art would readily understand that the biasing member  22  may be in the form of any elastic device that stores energy. For example, the biasing member  22  may be leaf springs, coil springs, torsion bars, or a combination of these, or the like. The biasing member  22  may also be an elastic material. 
     The retainer  34  is a device that attaches the rod  18  to the piston  20 . 
     The check valve  32  is a mechanical device that allows fluid to flow through it in only one direction. 
     The tension cylinder  12  further includes two ports—a first port  46  and a second port  48 . The first port  46  is connected to a chain tension pressure control valve  50 . 
     A rod  18  is connected to the lower sprocket shafts  44 , and the rod  18  includes slots  52  that are cut into the end  54  of rod  18 . The rod  18  is connected to the piston  20  with a retainer  34 . The retainer  34  may be a retainer ring as depicted in the figures. One skilled in the art would readily understand that different means may be used to connect the rod  18  and the piston  20  including, but not limited to, a clip or a pin. 
     Chordal movement is the difference between the pitch radius and the distance from the center of the sprocket  6  to the chord (when a chain engages a sprocket, the centers of the chain joints lie on the pitch circle of the sprocket and the center line of each link forms a chord of this circle). A spring  22  is mounted between the piston  20  and the rod  18  and the spring  22  maintains a distance equivalent to the chordal movement of the chain  2  on the sprocket  6 . This distance needs to be at a minimum to restrict slack in the chain  2  at a high snub load. 
     In an embodiment of the present invention, the second port  48  bleeds air from the cylinder  14 , and second port  48  is plugged during operation. 
     In the embodiments of the present invention, the chain tension pressure pushes the rod  18  against the lower floating sprocket  6  in the chain  2 . The pressure is substantially equal in first and second chambers  28 ,  30 , and because the piston area is substantially the same in both chambers, the piston  20  is not forced to move in either direction. The spring  22  between the rod  18  and the piston  20  maintains clearance for the rod  18  to move as the lower sprocket shaft  44  fluctuates from chordal action. As the chain  2  wears and increases in length, the check valve  32  in the piston  20  allows fluid to flow from the first chamber  28  into the second chamber  30  as the tension pressure extends the rod  18  moving the lower sprockets  6  down until the lower sprocket  6  is supported by the chain  2 . If the snub force on the coil tubing  10  pushes the lower sprockets  6  up, the rod  18  will travel a distance equal to the clearance maintained by the spring  22  between the rod  18  and the piston  20 . In the embodiments of the present invention, the hydraulic fluid is incompressible and the check valve  32  prevents the fluid from flowing from the second chamber  30  to the first chamber  28 . Additionally, the lower sprockets  6  are prevented from moving past the piston location in the cylinder  14 . 
     It should be appreciated that automatic adjustment of the tension of the chain  2  is thus provided due to the internal structure of the tension cylinder  12  in combination with the aspect of a floating sprocket  6  that is free to move within the slot  8 . To automatically maintain tension of the chain  2 , as used herein and in the claims, means adjustment of the chain tension without an operator and without manual control in response to a change in chain tension. Referring to  FIG. 12 , initially, the floating sprocket  6  is kept biased against the tension cylinder  12  due to the initial tension of the chain  2 . In response to the loss of tension and loosening of the chain  2 , the floating sprocket  6  will no longer be held tightly by the chain  2 . Accordingly, the floating sprocket  6  will drop down to the position of the loosened chain  2 . 
     Referring to  FIG. 16 , the rod  18  and the piston  20  of the tension cylinder  12  are also initially held in place by the upward force of the chain  2  on the floating sprocket  6 . As discussed above, the floating sprocket  6  drops to a new position as the chain  2  loosens. Accordingly, the rod  18  and the piston  20  also drop to a new position due to fluid flowing from the first chamber  28  into the second chamber  20  through the one way check valve  32 . Because fluid can only flow in a single direction, from the first chamber  28  to the second chamber  30 , the chain  2  is again in a tensioned condition and automatic tensioning is achieved. 
     It is noted that the hydraulic fluid may be incompressible such that any upward pressure applied to the chain  2  would not substantially change the position of the floating sprocket  6 . However, upward pressure may be absorbed by a spring  22  attached between the rod  18  and the piston  20  of the tension cylinder  12 , as illustrated in  FIG. 15 . It should be appreciated that the degree of absorbing upward pressure will depend upon the elasticity modulus of the spring  22  that is used in the tension cylinder  12 , and a wide range of elasticity may be chosen. 
     An embodiment of the present invention could be used in any chain drive that requires hydraulic tensioning. Another embodiment of the present invention includes a relief valve  56  installed at the second port  48  which can be used in, for example, a tension system that requires a maximum limit. 
     The embodiments of the present invention remove the manual maintenance of the lower sprocket stops which an operator sometimes has difficulty in maintaining. Additionally, the embodiments of the present invention provide the optimum distance in which the lower sprocket shaft  44  travels before contacting the stop. 
     As depicted in  FIG. 12 , in an embodiment of the present invention, the self-adjusting chain tensioning mechanism with a check valve in a cylinder as described above is used in an injector head that includes rollers  58  that are moving and installed with the chain  2 . Conversely, in another embodiment of the present invention, the self-adjusting chain tensioning mechanism with a check valve in a cylinder as described above is used within an injector head that includes stationary rollers that are installed in the skates  61 . The skates  61  are the elements that include the rollers in this embodiment. Additionally, the skates  61  are the members that are adapted to engage the ram  64  of the piston  60  of the traction cylinders  62  in an embodiment of the present invention. In an embodiment of the present invention, the gripping force on the coiled tubing  10  may be controlled by the amount of force applied by the traction cylinders  62 . 
     Additionally, as depicted in the Figures, in an embodiment of the present invention, the self-adjusting chain tensioning mechanism with a check valve in a cylinder as described above is used within an injector head that includes floating/moving traction cylinders  62 . Conversely, in another embodiment of the present invention, the self-adjusting chain tensioning mechanism with a check valve in a cylinder as described above is used within an injector head that includes stationary traction cylinders. 
     In the embodiment of the present invention shown in  FIG. 1 , the coiled tubing injector head  1  includes an inner frame  66 , an outer frame  68 , and a base frame  70 . As is known to those skilled in the art, the various structural members of the frames  66 ,  68 ,  70  may include a variety of commonly used structural components, such as plates, I-beams, channel beams, structural tubing, and the like, that are sized and configured in a manner sufficient to withstand all of the forces encountered in normal coiled tubing operations. The design, selection, and sizing of these various components are matters of design choice that are well within the level of ordinary skill in the present art. The coiled tubing injector head  1  further includes drive assemblies  72  that include drive motors that are typically used in the art, for example, hydraulic motors. A person of ordinary skill will understand that various drive means may be used with the coiled tubing injector head  1  according to the embodiments of the present invention. The drive assemblies  72  are connected to drive shafts, which include the drive sprockets  4  that drive the chains  2 . The coiled tubing injector head  1  depicted in  FIG. 1  includes many accessories and represents a typical complete coiled tubing injector head  1  in the art with the enhanced and novel features described herein. 
     As depicted in  FIG. 2 , various piping may be connected to the first and second ports  46 ,  48  of the tension cylinder  12 . The piping may include gauges  74  such as pressure gauges for obtaining relevant measurements that would be helpful to an operator of the coiled tubing injector head  1  according to an embodiment of the present invention. In an embodiment of the present invention, a chain tension pressure control valve  50  is connected to the first port  46  and a relief valve  56  is connected to the second port  48 . 
     As is known to a person of ordinary skill in the art, the chains  2  comprise endless chains that rotate (one clockwise and the other counter-clockwise) via the drive assemblies  72  coupled to the drive sprockets  4 . However, one skilled in the art will understand that the embodiments of the present invention need not include a chain—for example, a conveyor member may be used in lieu of a chain. The particular types of sprockets, fraction cylinders, motors, chains, and other components used in the coiled tubing injector head  1  according to embodiments of the present invention are all matters of design choice, and the selection and sizing of which may vary depending upon a particular application. These features are matters within the level of those of ordinary skill in the art, and should not be considered a limitation of the embodiments of the present invention. 
       FIG. 6  depicts a coiled tubing injector head  1  according to an embodiment of the present invention without the outer and base fames  66 ,  68 , and most of the other piping and additional mechanical elements common in injector heads removed for clarity. The inner frame  66  of the coiled tubing injector head  1  is clearly shown in this figure, as well as in  FIGS. 7 and 8 . In an embodiment of the present invention, the chains  2  include gripper blocks  76  for gripping the coiled tubing  10 . 
       FIG. 9  is a cross-sectional view through line D-D of  FIG. 7 . In  FIG. 9 , the inner workings of the traction cylinder  62  are visible including the piston  60  and rod  78 , as well as the traction cylinder ram  64 . In the embodiment shown in  FIG. 9 , the skates  61  engage the ram  64  of the piston  60  of the traction cylinders  62  in an embodiment of the present invention. As stated above, in an embodiment of the present invention, the gripping force on the coiled tubing  10  may be controlled by the amount of force applied by the traction cylinders  62 . 
       FIG. 12  is a close-up view of the bottom of an injector head  1  according to an embodiment of the present invention, where a portion of the inner frame  66  has been removed to clearly display the components of the injector head  1 . 
     During operation, coiled tubing  10  is inserted through the top of the coiled tubing injector head  1  where it engages with the plurality of gripper block assemblies  76  as the chains  2  are rotated by the drive assemblies  72 . An operator of the coiled tubing injector head  1  according to the embodiments of the present invention sets a proper chain tension pressure that prolongs the useful life of the chains  2 . Then, in operation, the coiled tubing injector head  1  according to embodiments of the present invention automatically adjusts to compensate for an increase in chain length due to wear through the use of the tension cylinder  12 . 
     It will be obvious to a person of ordinary skill that the coiled tubing injector heads according to the embodiments of the present invention are able to accommodate coiled tubing of different sizes. Additionally, one skilled in the art would readily understand that an embodiment of the present invention includes an injector head in a vertical configuration as depicted in the figures. However, one skilled in the art would also readily understand that the embodiments of the present invention also include injector heads that may be configured in different alignments and configurations, for example horizontal or diagonal. 
     LIST OF REFERENCE NUMBERS INCLUDED IN FIGURES 
     The following is a list of reference numbers used in the attached figures for embodiments of the present invention:
     ( 1 ) Coiled Tubing Injector Head ( 44 ) Injector Head Lower Shaft   ( 2 ) Chain ( 46 ) First Port   ( 4 ) Drive Sprocket ( 48 ) Second Port   ( 6 ) Floating Sprocket ( 50 ) Chain Tension Pressure Control Valve   ( 8 ) Slot ( 52 ) Slot   ( 10 ) Coiled Tubing ( 54 ) End of the Rod   ( 12 ) Tension Cylinder ( 56 ) Relief Valve   ( 14 ) Cylinder Barrel/Cylinder ( 58 ) Roller (Moving)   ( 16 ) Cylinder Head ( 60 ) Piston (Traction Cylinder)   ( 18 ) Rod ( 61 ) Skate   ( 20 ) Piston ( 62 ) Moving Traction Cylinder   ( 21 ) Ram ( 64 ) Ram (Traction Cylinder)   ( 22 ) Spring ( 66 ) Inner Frame   ( 24 ) Pin ( 68 ) Outer Frame   ( 26 ) Bushing ( 70 ) Base Frame   ( 28 ) First Chamber ( 72 ) Drive Assembly   ( 30 ) Second Chamber ( 74 ) Guages   ( 32 ) Check Valve ( 76 ) Gripper Block Assembly   ( 34 ) Retainer ( 44 ) Injector Head Lower Shaft   ( 36 ) Cylinder Head Seal ( 46 ) First Port   ( 38 ) Rod Seal ( 48 ) Second Port   ( 40 ) Rod Wiper ( 50 ) Chain Tension Pressure Control Valve   ( 42 ) Piston Seal ( 52 ) Slot