Patent Abstract:
This invention relates to a dual jacking system and method for inserting and extracting tubulars, or the like into and out of a well, such as an oil or gas well, at a relatively high rate of speed.

Full Description:
BACKGROUND  
         [0001]    This invention relates to a dual jacking system and method for inserting and extracting tubulars, or the like, into and out of a well, such as an oil or gas well, at a relatively high rate of speed.  
           [0002]    In oil and gas well operations, long strings of tubulars, such as pipes, are inserted into and removed from wells at various times. When tubulars are inserted into a well, a tubular is attached to the top of a tubular string and the string is lowered into the well. When tubulars are removed from a well, a tubular is removed from the top of a tubular string and the string is raised from the well. Depending on the depth of a well, a string of tubulars may be thousands of feet long and many tubulars will need to be attached to or removed from the string to complete an operation. As a result, operations where a tubular string is inserted into a well and operations where a tubular string is removed from a well may take a relatively long time and require substantial man hours to complete.  
           [0003]    It would be desirable to be able to reduce the amount of time and man hours it takes to insert tubulars into or removal tubulars from an oil or gas well. Accordingly, a dual jacking system and method as described herein is needed. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0004]    [0004]FIG. 1 is an isometric view illustrating an embodiment of a dual jacking system shown in a first operational mode.  
         [0005]    [0005]FIG. 2 is an enlarged isometric view of a portion of the system of FIG. 1.  
         [0006]    [0006]FIG. 3 is an isometric view of the portion of FIG. 2 shown located in the upper section of a tower.  
         [0007]    [0007]FIG. 4 is an enlarged isometric view of another portion of the system of FIG. 1.  
         [0008]    [0008]FIG. 5 is an isometric view of the portion of FIG. 4 shown located in the lower section of the tower.  
         [0009]    [0009]FIG. 6 is an isometric view of the system of FIG. 1 located in the tower.  
         [0010]    [0010]FIG. 7 is an isometric view of the system of FIG. 1 in a second operational mode.  
         [0011]    [0011]FIG. 8 is an isometric view of the system of FIG. 1 in a third operational mode.  
         [0012]    [0012]FIG. 9 is an isometric view of the embodiment of FIG. 1 extending over a wellhead.  
         [0013]    [0013]FIG. 10 is a diagram illustrating an embodiment of a control system associated with the system of FIG. 1. 
     
    
     DETAILED DESCRIPTION  
       [0014]    Referring to FIG. 1 of the drawings, the reference numeral  10  refers, in general, to a dual reciprocating mechanism, also referred to herein as a system, according to an embodiment. The system  10  includes an upper jack  20  including a head  22  to which one end of each of a pair of hydraulic cylinders  24   a  and  24   b  are connected in a manner to be described. The hydraulic cylinders  24   a  and  24   b  operate in a conventional manner to reciprocate the head  22  in a vertical direction, as viewed in FIG. 1. The head  22  includes an engaging and disengaging unit, in the form of a slip bowl  26 , adapted to engage and release a tubular (not shown). Details of the head  22  and the slip bowl  26  will be described later.  
         [0015]    A lower jack  30  extends in a vertically spaced relation to the upper jack  20  and includes a traveling head  32  to which one end of each of a pair of hydraulic cylinders  34   a  and  34   b  are connected, in a manner to be described. The hydraulic cylinders  34   a  and  34   b  operate in a conventional manner to reciprocate the traveling head  32  in a vertical direction, as viewed in FIG. 1. The traveling head  32  includes vertically spaced engaging and disengaging units, in the form of a slip bowl  36   a  and an inverted slip bowl  36   b , for engaging and releasing a tubular (not shown). Each of the slip bowls  26 ,  36   a , and  36   b  is independently operable to engage or release a tubular at a given time and, since conventional, will not be described in additional detail.  
         [0016]    Referring to FIG. 2 of the drawings, the hydraulic cylinders  24   a  and  24   b  of the upper jack  20  extend vertically as viewed in the drawing, and include two rods  40   a  and  40   b , respectively, which move between a retracted and extended position relative to two barrels  42   a  and  42   b , respectively, in a conventional manner. The respective upper ends of the rods  40   a  and  40   b  connect to two pins  44   a  and  44   b , respectively, which are mounted between two sets of flanges  45   a  and  45   b , respectively, on opposing sides of the head  22  to allow rotational movement between the head  22  and the hydraulic cylinders  24   a  and  24   b.    
         [0017]    Linear position transducers  46   a  and  46   b  are attached to the hydraulic cylinders  24   a  and  24   b  , respectively, for detecting and tracking the position of the upper jack  20 . The use of the linear position transducers  46   a  and  46   b  will be described in additional detail below. The head  22  includes guides  48   a  and  48   b  mounted on an upper portion of the head  22  and guides  48   c  and  48   d  mounted on a lower portion of the head  22 . The function of the guides  48   a ,  48   b ,  48   c , and  48   d  will be described in additional detail below.  
         [0018]    [0018]FIG. 3 depicts the upper jack  20  located in an upper tower section  50  which is formed by a plurality of vertical and horizontal structural members in a conventional manner. The upper tower section  50  includes two vertically spaced, opposed rails  52   a  and  52   b  as well as two vertically spaced, opposed rails  54   a  and  54   b  spaced from the rails  52   a  and  52   b . Each of the guides  48   a  and  48   d  of the upper jack  20  extend between the rails  52   a  and  52   b  in engagement therewith; and each of the guides  48   b  and  48   c  extend between the rails  54   a  and  54   b , in engagement therewith to permit vertical movement of the head  22  relative to the upper tower section  50 .  
         [0019]    The hydraulic cylinder  24   a  is mounted between the rails  52   a  and  52   b  and the upper end of the barrel  42   a  attaches to the rail  52   a  at a point  56   a , and to the rail  52   b  at a point  56   b . The hydraulic cylinder  24   b  is mounted between the rails  54   a  and  54   b  and an upper end of the barrel  42   b  is attached to the rail  54   a  at a point  58   a  and attaches to the rail  54   b  at a point  58   b.    
         [0020]    Referring to FIG. 4 of the drawings, the hydraulic cylinders  34   a  and  34   b  of the lower jack  30  also extend vertically as viewed in the drawing, and include two rods  60   a  and  60   b , respectively, which move between a retracted and extended portion relative to two barrels  62   a  and  62   b , respectively, in a conventional manner. The respective lower ends of the barrels  62   a  and  62   b  are connected to two tabs  64   a  and  64   b , respectively, which are mounted between two sets of flanges  65   a  and  65   b , respectively, on opposing sides of the traveling head  32  to allow rotational movement between the traveling head  32  and the hydraulic cylinders  34   a  and  34   b , respectively.  
         [0021]    Linear position transducers  66   a  and  66   b  are attached to the hydraulic cylinders  34   a  and  34   b , respectively, for detecting and tracking the position of the lower jack  30 . The use of the linear position transducers  66   a  and  66   b  will be described in additional detail below. The traveling head  32  includes guides  68   a  and  68   b  mounted on an upper portion of the traveling head  32  and guides  68   c  and  68   d  mounted on a lower portion of the traveling head  32 . The function of the guides  68   a ,  68   b ,  68   c  and  68   d  will be described in additional detail below.  
         [0022]    [0022]FIG. 5 depicts the lower jack  30  located in a lower tower section  70  which is formed by a plurality of vertical and horizontal structural members in a conventional manner. The lower tower section  70  includes two vertically spaced, opposed rails  72   a  and  72   b  as well as two vertically spaced, opposed rails  74   a  and  74   b  spaced from the rails  72   a  and  72   b . Each of the guides  68   a  and  68   d  of the lower jack  30  extend between the rails  72   a  and  72   b  in engagement therewith; and each of the guides  68   b  and  68   c  extend between the rails  74   a  and  74   b , in engagement therewith to permit vertical movement of the traveling head  32  relative to the lower tower section  70 .  
         [0023]    The hydraulic cylinder  34   a  is mounted between the rails  72   a  and  72   b  and is attached between the rails  72   a  and  72   b  at a point  76 , and the hydraulic cylinder  34   b  is mounted between the rails  74   a  and  74   b  and is attached to the rails  74   a  and  74   b  at a point  78  in a conventional manner.  
         [0024]    Referring to FIG. 6, the upper tower section  50  is stacked over, and is connected to, the lower tower section  70  using pins  80   a  and  80   b , thus constructing a tower. The rails  52   a  and  52   b  and the rails  54   a  and  54   b  extend through the lower tower section  70  for guiding the upper jack  20  through the tower and the rails  72   a  and  72   b  and the rails  74   a  and  74   b  extend through the upper tower section  50  for guiding the lower jack  30  through the tower.  
         [0025]    Two tool joint sensors  84   a  and  84   b  are located above and below the upper jack  20  and the lower jack  30 , respectively. The tool joint sensors  84   a  and  84   b  detect the presence of a tool joint attached to a pipe string entering either the upper jack  20  or the lower jack  30 . The function of the tool joints sensors  84   a  and  84   b  will be described in additional detail below.  
         [0026]    Referring to FIG. 7, the hydraulic cylinders  24   a  and  24   b  of the upper jack  20  are shown in a fully extended position, and the hydraulic cylinders  34   a  and  34   b  of the lower jack  30  are shown in a fully retracted position such that the head  22  is at a maximum distance from the traveling head  32 .  
         [0027]    Referring to FIG. 8, the hydraulic cylinders  24   a  and  24   b  of the upper jack  20  are shown in a fully retracted position, and the hydraulic cylinders  34   a  and  34   b  of the lower jack  30  are shown in a fully extended position such that the head  22  is at a minimum distance from the traveling head  32 .  
         [0028]    In operation, the system  10  inserts and extracts jointed tubulars or continuous coiled tubing into and out of a well such as an oil well or a gas well at a relatively high rate of speed. The system  10  may be operated in two modes: a high speed mode and a low speed mode. These modes of operation will be described below with reference to FIG. 1, FIG. 7, and FIG. 8.  
         [0029]    In the high speed mode of operation, the upper jack  20  and the lower jack  30  move in opposing directions. In this mode, the hydraulic cylinders  24   a  and  24   b  of the upper jack  20  move to their full extension at the same time the hydraulic cylinders  34   a  and  34   b  of the lower jack  30  move to their full retraction, as shown in FIG. 7. In this mode, the hydraulic cylinders  24   a  and  24   b  of the upper jack  20  also move to their full retraction at the same time the hydraulic cylinders  34   a  and  34   b  of the lower jack  30  move to their full extension as shown in FIG. 8.  
         [0030]    The operation of the system  10  may vary according to the pressure of a oil or gas well. In particular, the operation may depend on whether the system  10  is operating under pipe heavy conditions or pipe light conditions. Pipe heavy conditions occur where the downward force caused by the weight of the tubulars equals or exceeds the upward force caused by pressure in the well. Pipe light conditions occur where the downward force caused by the weight of the tubulars is less than the upward force caused by pressure in the well. Operation of system  10  in the high and low speed modes of operation will now be described under pipe heavy conditions.  
         [0031]    To insert tubulars into a well in the high speed mode under pipe heavy conditions, the slip bowl  26  of the upper jack  20  engages a tubular in the position shown in FIG. 7. The slip bowls  36   a  and  36   b  of the lower jack  30  remain disengaged in this position. The hydraulic cylinders  24   a  and  24   b  of the upper jack  20  then move to their full retraction at the same time the hydraulic cylinders  34   a  and  34   b  of the lower jack  30  move to their full extension to reach the respective positions shown in FIG. 8. In these positions, the slip bowl  36   a  of the lower jack  30  engages the tubulars and the slip bowl  26  of the upper jack  20  disengages the tubulars. The hydraulic cylinders  24   a  and  24   b  of the upper jack  20  then move to their full extension at the same time the hydraulic cylinders  34   a  and  34   b  of the lower jack  30  move to their full retraction as shown in FIG. 7 to effectively lower the tubulars into the well. The process just described is repeated to continue lowering the tubulars into the well.  
         [0032]    To extract tubulars from a well in the high speed mode under pipe heavy conditions, the slip bowl  36   a  of the lower jack  30  engages the tubulars in the position shown in FIG. 7. The slip bowl  26  of the upper jack  20  remains disengaged in this position. The hydraulic cylinders  24   a  and  24   b  of the upper jack  20  then move to their full retraction at the same time the hydraulic cylinders  34   a  and  34   b  of the lower jack  30  move to their full extension to reach the respective positions shown in FIG. 8. In these positions, the slip bowl  36   a  of the lower jack  30  disengages the tubulars and the slip bowl  26  of the upper jack  20  engages the tubulars. The hydraulic cylinders  24   a  and  24   b  of the upper jack  20  then move to their full extension at the same time the hydraulic cylinders  34   a  and  34   b  of the lower jack  30  move to their full retraction as shown in FIG. 7 to effectively raise the tubulars from the well. The process just described is repeated to continue raising the tubulars from the well.  
         [0033]    In the low speed mode of operation under pipe heavy conditions, the upper jack  20  and the lower jack  30  move in the same direction and each carry a portion of the tubular load. In this mode, the hydraulic cylinders  24   a  and  24   b  of the upperjack  20  move to their full extension at the same time the hydraulic cylinders  34   a  and  34   b  of the lower jack  30  move to their full extension. The upper jack  20  is shown in this position in FIG. 7, and the lower jack  30  is shown in this position in FIG. 8. The hydraulic cylinders  24   a  and  24   b  of the upper jack  20  also move to their full retraction at the same time the hydraulic cylinders  34   a  and  34   b  of the lower jack  30  move to their full retraction. The upper jack  20  and the lower jack  30  are shown in these respective positions in FIG. 1.  
         [0034]    Referring to FIG. 9, a stationary slip bowl  90   a  and an inverted stationary slip bowl  90   b  is mounted over a wellhead  92 . The stationary slip bowl  90   a  is used in the low speed mode of operation under pipe heavy conditions, and it will be assumed that it engages the upper tubular of the tubulars to be extracted from the wellhead.  
         [0035]    To extract tubulars from the well in the low speed mode under pipe heavy conditions, the slip bowl  26  of the upper jack  20  and the slip bowl  36   a  of the lower jack  30  engage the tubulars when the hydraulic cylinders  24   a  and  24   b  of the upper jack  20  and the hydraulic cylinders  34   a  and  34   b  of the lower jack  30  are in the fully retracted position as shown in FIG. 1. The stationary slip bowl  90   a  then disengages the tubulars. The hydraulic cylinders  24   a  and  24   b  of the upper jack  20  and the hydraulic cylinders  34   a  and  34   b  of the lower jack  30  then move to their fully extended position at the same time to effectively raise the tubulars out of the well. Once in these positions, the stationary slip bowl  90   a  engages the tubulars, and the slip bowls  26  and  36   a  disengage the tubulars. The hydraulic cylinders  24   a ,  24   b ,  34   a , and  34   b  then move to their fully retracted position at the same time to repeat the process.  
         [0036]    To insert tubulars into a well in the low speed mode under pipe heavy conditions, the slip bowl  26  of the upper jack  20  and the slip bowl  36   a  of the lower jack  30  engage the tubulars when the hydraulic cylinders  24   a  and  24   b  of the upper jack  20  and the hydraulic cylinders  34   a  and  34   b  of the lower jack  30  are in the fully extended position as shown in FIG. 7 with respect to the cylinders  24   a  and  24   b , and in FIG. 8 with respect to the cylinders  34   a  and  34   b  . The stationary slip bowl  90   a  then disengages the tubulars, and the hydraulic cylinders  24   a  and  24   b  of the upper jack  20  and the hydraulic cylinders  34   a  and  34   b  of the lower jack  30  are moved to their fully retracted position at the same time as shown in FIG. 1 to lower the tubulars into the well. Once in these positions, the stationary slip bowl  90   a  engages the tubulars, and the slip bowls  26  and  36   a  disengage the tubulars. The hydraulic cylinders  24   a ,  24   b ,  34   a , and  34   b  then move to their fully extended position at the same time and the cycle is repeated.  
         [0037]    Although the low speed mode of operation under pipe heavy conditions is described above as using both the upper jack  20  and the lower jack  30 , tubulars may be inserted or extracted in the low speed mode using only one of the upper jack  20  or the lower jack  30 . For example, if only the upper jack  20  is used, system  10  will operate in the low speed mode as described above with the exception that the lower jack  30  will not move and the slip bowl  36   a  of the lower jack  30  will not engage the tubulars. Likewise, if only the lower jack  30  is used, system  10  will operate in the low speed mode as described above with the exception that the upper jack  30  will not move and the slip bowl  26  of the upper jack  20  will not engage the tubulars.  
         [0038]    Operation of system  10  in the high and low speed modes of operation will now be described under pipe light conditions.  
         [0039]    To insert tubulars into a well in the high speed mode under pipe light conditions, the head  22  of the upper jack  20  includes an additional engaging and disengaging unit, in the form of an inverted slip bowl  96  shown in FIG. 9, adapted to engage and release a tubular (not shown). The inverted slip bowl  96  of the upper jack  20  engages a tubular in the position shown in FIG. 7. The slip bowls  36   a  and  36   b  of the lower jack  30  remain disengaged in this position. The hydraulic cylinders  24   a  and  24   b  of the upper jack  20  then move to their full retraction at the same time the hydraulic cylinders  34   a  and  34   b  of the lower jack  30  move to their full extension to reach the respective positions shown in FIG. 8. In these positions, the inverted slip bowl  36   b  of the lower jack  30  engages the tubulars and the inverted slip bowl  96  of the upper jack  20  disengages the tubulars. The hydraulic cylinders  24   a  and  24   b  of the upper jack  20  then move to their full extension at the same time the hydraulic cylinders  34   a  and  34   b  of the lower jack  30  move to their full retraction as shown in FIG. 7 to effectively lower the tubulars into the well. The process just described is repeated to continue lowering the tubulars into the well.  
         [0040]    To extract tubulars from a well in the high speed mode under pipe light conditions, the inverted slip bowl  36   b  of the lower jack  30  engages the tubulars in the position shown in FIG. 7. The inverted slip bowl  96  of the upper jack  20  remains disengaged in this position. The hydraulic cylinders  24   a  and  24   b  of the upper jack  20  then move to their full retraction at the same time the hydraulic cylinders  34   a  and  34   b  of the lower jack  30  move to their full extension to reach the respective positions shown in FIG. 8. In these positions, the inverted slip bowl  36   b  of the lower jack  30  disengages the tubulars and the inverted slip bowl  96  of the upper jack  20  engages the tubulars. The hydraulic cylinders  24   a  and  24   b  of the upper jack  20  then move to their full extension at the same time the hydraulic cylinders  34   a  and  34   b  of the lower jack  30  move to their full retraction as shown in FIG. 7 to effectively raise the tubulars from the well. The process just described is repeated to continue raising the tubulars from the well.  
         [0041]    Referring to FIG. 9, the inverted stationary slip bowl  90   b  is used in the low speed mode of operation under pipe light conditions, and it will be assumed that it engages the upper tubular of the tubulars to be extracted from the wellhead.  
         [0042]    To extract tubulars from the well in the low speed mode under pipe light conditions, the inverted slip bowl  96  of the upper jack  20  and the inverted slip bowl  36   b  of the lower jack  30  engage the tubulars when the hydraulic cylinders  24   a  and  24   b  of the upper jack  20  and the hydraulic cylinders  34   a  and  34   b  of the lower jack  30  are in the fully retracted position as shown in FIG. 1. The inverted stationary slip bowl  90   b  then disengages the tubulars. The hydraulic cylinders  24   a  and  24   b  of the upper jack  20  and the hydraulic cylinders  34   a  and  34   b  of the lower jack  30  then move to their fully extended position at the same time to effectively raise the tubulars out of the well. Once in these positions, the inverted stationary slip bowl  90   b  engages the tubulars, and the inverted slip bowls  96  and  36   b  disengage the tubulars. The hydraulic cylinders  24   a ,  24   b ,  34   a , and  34   b  then move to their fully retracted position at the same time to repeat the process.  
         [0043]    To insert tubulars into a well in the low speed mode under pipe light conditions, the inverted slip bowl  96  of the upper jack  20  and the inverted slip bowl  36   b  of the lower jack  30  engage the tubulars when the hydraulic cylinders  24   a  and  24   b  of the upper jack  20  and the hydraulic cylinders  34   a  and  34   b  of the lower jack  30  are in the fully extended position as shown in FIG. 7 with respect to the cylinders  24   a  and  24   b , and in FIG. 8 with respect to the cylinders  34   a  and  34   b  . The inverted stationary slip bowl  90   b  then disengages the tubulars, and the hydraulic cylinders  24   a  and  24   b  of the upper jack  20  and the hydraulic cylinders  34   a  and  34   b  of the lower jack  30  are moved to their fully retracted position at the same time as shown in FIG. 1 to lower the tubulars into the well. Once in these positions, the inverted stationary slip bowl  90   b  engages the tubulars, and the inverted slip bowls  96  and  36   b  disengage the tubulars. The hydraulic cylinders  24   a ,  24   b ,  34   a , and  34   b  then move to their fully extended position at the same time and the cycle is repeated.  
         [0044]    Although the low speed mode of operation under pipe light conditions is described above as using both the upper jack  20  and the lower jack  30 , tubulars may be inserted or extracted in the low speed mode using only one of the upper jack  20  or the lower jack  30 . For example, if only the upper jack  20  is used, system  10  will operate in the low speed mode as described above with the exception that the lower jack  30  will not move and the inverted slip bowl  36   b  of the lower jack  30  will not engage the tubulars. Likewise, if only the lower jack  30  is used, system  10  will operate in the low speed mode as described above with the exception that the upper jack  30  will not move and the inverted slip bowl  96  of the upper jack  20  will not engage the tubulars.  
         [0045]    Referring to FIG. 10 of the drawings, the operation of the system  10  in the high speed mode and the low speed mode is monitored and controlled by a computerized control system  100 . The control system  100  couples to the upper jack  20 , the lower jack  30 , the transducers  46   a ,  46   b ,  66   a , and  66   b , and the sensors  84   a  and  84   b  using any suitable wired or wireless connection or connections. The control system  100  is also coupled to slip bowls  26 ,  36   a ,  36   b ,  90   a , and  90   b  and causes the slip bowls  26 ,  36   a ,  36   b ,  90   a , and  90   b  to engage or disengage tubulars. The control system  100  may be located on the upper tower section  50  or the lower tower section  70  or another structure that includes the system  10  or may be located remotely from such a tower or structure.  
         [0046]    An operator of the system  10  selects either the high speed mode or the low speed mode and either to raise tubulars from a well or to lower tubulars into a well using the control system  100 . The control system  100  provides signals to the upper jack  20  and the lower jack  30  to control the movement of the upper jack  20  and the lower jack  30  in the manner described above according to the selections by the operator.  
         [0047]    The control system  100  controls and monitors the position and speed of the upper jack  20  and the lower jack  30  according to position information received from the transducers  46   a ,  46   b ,  66   a , and  66   b  shown in FIG. 2 and FIG. 4. The transducers  46   a ,  46   b ,  66   a , and  66   b  provide the control system  100  with position information regarding the positions of the upper jack  20  and the lower jack  30 , respectively. The control system  100  processes the position information to determine the speed and the locations of the upper jack  20  and the lower jack  30 .  
         [0048]    The tool joint sensors  84   a  and  84   b , shown in FIG. 6, detect the presence of a tool joint attached to a pipe string entering either the upper jack  20  or the lower jack  30  and send detection information to the control system  100 . The control system  100  uses the detection information to track the position of a tool joint as the tool joint moves within the system  10 . The control system  100  automatically adjusts the position of the slip bowls  26 ,  36   a , and  36   b  relative to the tool joint to prevent the slip bowls  26 ,  36   a , and  36   b  from engaging and possibly damaging the tool joint.  
       ALTERNATIVE EMBODIMENTS  
       [0049]    In an alternative embodiment not shown, the hydraulic cylinders  34   a  and  34   b  may be inverted such that the rods  60   a  and  60   b  extend in an upward direction from the barrels  62   a  and  62   b . In this example, the rods  60   a  and  60   b  attach to the traveling head  32  similar to the way the rods  40   a  and  40   b  attach to the head  22 .  
         [0050]    In addition, other embodiments are possible by inverting the cylinders and/or changing the mounting of the cylinder barrels and rod ends.  
         [0051]    It is understood that variations may be made in the above without departing from the scope of the invention. For example, mechanisms other than jacks and hydraulic cylinders can be used to reciprocate the slip bowls. Also, the slip bowls may be replaced by other units for engaging and disengaging the tubulars. Further, when the expression “tubular” is used it is meant to cover any type of tubular member such as coiled tubing, conduits, pipes, pipe joints, hoses, etc., and the reference to “tubular” in the singular does not preclude inclusion of a plurality of tubulars in the same string.  
         [0052]    Although only a few exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many other variations and modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the following claims.

Technology Classification (CPC): 4