Patent Publication Number: US-8109338-B2

Title: Pipe section guide system with flexible member

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is the U.S. National Stage under 35 U.S.C. §371 of International Patent Application No. PCT/US2009/058995 filed Sep. 30, 2009, which claims the benefit of U.S. Provisional Patent Application No. 61/101,474 filed Sep. 30, 2008, entitled “Guide System For Pipe Section.” 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     BACKGROUND 
     The present disclosure relates generally to methods and apparatus for drilling earthen wells. More specifically, the present disclosure relates to systems for drilling earthen wells using joints of connectable pipe. 
     Drilling rigs require tubular members, such as drill pipe, drill collars, and casing, to be added or removed from the downhole tubular string in sections. The sections of tubular members may be stored in a setback area on or near the drilling rig. The sections of tubular members comprise three joints of pipe coupled together, for example, and the drilling rig is called a triple rig. In other examples, the pipe sections may comprise more or less pipe joints and the corresponding drilling rig may be called a quadruple rig, a double rig or a single rig. The tubular members may be stored vertically adjacent the rig, or horizontally away from the rig where they are transported to the rig and inclined toward the vertical position. 
     As the different tubular members are needed, they are brought to the drill floor one at a time and added to the string. Handling these tubular members has historically been a highly manual job using winches or other lifting appliances within the rig. Automated systems for use in drilling rigs must be able to safely handle a variety of tubular members while not slowing down drilling or tripping processes. 
     Thus, there remains a need to develop methods and apparatus for pipe handling and drilling systems, which overcome some of the foregoing difficulties while providing more advantageous overall results. 
     SUMMARY 
     A pipe handling system includes a pipe guide system with a flexible pipe guide that is operable to engage a pipe and control lateral movement of the pipe as it is moved between a storage position and a well center position. In some embodiments, the system includes a lifting mechanism coupled to an upper end of the pipe and the guide system includes a pair of support members including extendable end portions and a flexible pipe guide coupled between the extendable end portions. The flexible pipe guide may be expandable between the extendable end portions. The flexible pipe guide may include an expanded position engaging the pipe between extended positions of the end portions. The flexible pipe guide may include a contracted position releasing the pipe when the end portions are fully retracted. Support ends of the support members opposite the extendable end portions may be rotated about pivot points having multiple axes of rotation. The support members may be rotatable arms having offset axes of rotation. 
     In further embodiments, the system includes a rig structure to which the lifting mechanism and the guide system are coupled. The system may further include an elevated drill floor of the rig structure, a pipe erector operable to move a pipe from a horizontal storage position to an inclined position where an upper end of the pipe is adjacent to the elevated drill floor, wherein in the inclined position, the pipe is at an angle between horizontal and vertical and the upper end of the pipe is offset from well center, and wherein the guide system is operable to engage the pipe and control lateral movement of the pipe toward well center as the pipe is moved from being supported in the inclined position by the pipe erector to a vertical position supported by the rig, the support members extending to expand the flexible guide and engage the pipe between the inclined position and the vertical position, and the support members retracting to contract the flexible guide and release the pipe in the vertical position. 
     In additional embodiments, a pipe handling system includes a lifting mechanism coupled to an upper end of a pipe above a free end of the pipe, and a guide system operable to engage the pipe and control lateral movement of the pipe as it is moved between a storage position and a well center position, the guide system including a pair of rotatable support arms having first pivot ends and second ends and an expandable pipe guide connecting the second ends. The pivot ends may each include a pivot point having an axis of rotation. The axes of rotation may be different. The axes of rotation may be angled relative to each other. The axes of rotation may be offset. The expandable pipe guide may include a cable including a roller assembly. A drive mechanism may be included to rotate the pair of arms about the pivot ends. A frame may be included to support the pivot ends. The frame may include bend plates supporting the pivot ends at offset angles. The arms may include angled levers and intermediate bends. 
     In some embodiments, a pipe handling method includes supporting an upper end of a pipe with a lifting mechanism, extending a flexible pipe guide, and engaging the pipe with the extended flexible pipe guide to control lateral movement of the pipe. The method may include expanding the flexible pipe guide to engage the pipe and contracting the flexible pipe guide to release the pipe. The method may include moving the pipe from a storage position toward a well center position by retracting pipe guide support arms and contracting the flexible pipe guide between the support arms. The method may include moving the pipe from a well center position toward a storage position by extending pipe guide support arms and expanding the flexible guide between the support arms. The method may include retracting and contracting the flexible pipe guide, aligning the pipe with a drill string supported by a drilling rig, disengaging the pipe from the flexible pipe guide, and engaging the pipe with the drill string. 
     Thus, the embodiments herein include a combination of features and advantages that enable substantial enhancement of moving pipe and other tubular members to and from a drilling rig. These and various other characteristics and advantages of the present disclosure will be readily apparent to those skilled in the art upon reading the following detailed description of the embodiments and by referring to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more detailed description of the embodiments of the disclosure, reference will now be made to the accompanying drawings, wherein: 
         FIG. 1  is an elevation view of a drilling system including an embodiment of a pipe guide system in accordance with principles set forth herein; 
         FIG. 2A  is an enlarged side view of the pipe guide system of  FIG. 1 ; 
         FIG. 2B  is a front view of the pipe guide system of  FIG. 2A ; 
         FIG. 3A  is an enlarged view of a drive mechanism of the pipe guide system of  FIG. 2A ; 
         FIG. 3B  is a front view of the drive mechanism of  FIG. 3A ; 
         FIG. 3C  is a top view of the drive mechanism of  FIG. 3A ; 
         FIG. 4A  is a side view of an alternative embodiment of a drive mechanism; 
         FIG. 4B  is a front view of the drive mechanism of  FIG. 4A ; 
         FIG. 5A  is an elevation view of a pair of guide arms of the pipe guide system of  FIG. 1 ; 
         FIG. 5B  is an enlarged top view of one of the guide arms of  FIG. 5A ; 
         FIG. 5C  is a side view of the guide arm of  FIG. 5B ; 
         FIG. 6  is an elevation view of a flexible guide member and roller assembly of the pipe guide system of  FIG. 1 ; 
         FIGS. 7A-7H  illustrate an operating process using the drilling system of  FIG. 1 ; 
         FIG. 8A  is an enlarged view of  FIG. 7D  showing the range of motion of the pipe guide system; 
         FIG. 8B  is a top view of  FIG. 8A ; 
         FIG. 8C  is a top view of the drilling system of  FIGS. 8A and 8B  disposed on a fully equipped drill floor; 
         FIG. 9  is an elevation view of an exemplary drilling system with a pipe erector; and 
         FIGS. 10-12  are enlarged views of the pipe erector moving a pipe section from a horizontal position to an inclined position toward the rig structure. 
     
    
    
     DETAILED DESCRIPTION 
     In the drawings and description that follow, like parts are typically marked throughout the specification and drawings with the same reference numerals. The drawing figures are not necessarily to scale. Certain features of the disclosure may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in the interest of clarity and conciseness. The present disclosure is susceptible to embodiments of different forms. Specific embodiments are described in detail and are shown in the drawings, with the understanding that the present disclosure is to be considered an exemplification of the principles of the invention, and is not intended to limit the invention to that illustrated and described herein. It is to be fully recognized that the different teachings of the embodiments discussed below may be employed separately or in any suitable combination to produce desired results. 
     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 interaction between the elements and may also include indirect interaction between the elements described. The use of pipe or drill pipe herein is understood to include casing, drill collar, and other oilfield and downhole tubulars. In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . ”. The various characteristics mentioned above, as well as other features and characteristics described in more detail below, will be readily apparent to those skilled in the art upon reading the following detailed description of the embodiments, and by referring to the accompanying drawings. 
     Referring initially to  FIG. 1 , a drilling system  10  includes a rig structure  12  having a drill floor  14  and a mast or derrick  16 . A drill string  18  extends through the drill floor  14 . A series of pipe joint sections  20  or other tubular members is set back from the drill string on the drill floor  14 , waiting to be added to the drill string  18 . In exemplary embodiments, the triple pipe joint sections  20  include three connected pipe joints. In other exemplary embodiments, the pipe joint sections include two or four pipe joints. A stabbing system  22  is disposed on the drill floor  14  adjacent the drill string  18 . In exemplary embodiments, the stabbing system  22  may be a combination unit including slips, a pipe lubricator, a mud bucket and other systems used in making up or breaking out pipe joints. A torque tube  24  or other support structure extends downward from a top drive system (shown elsewhere herein). A pipe guide system  30  is coupled to the tube  24 , and includes an arm  32 , or pair of arms  32 , a drive mechanism  34 , a flexible line or cable  36 , and a roller assembly  38 . In exemplary embodiments, the pipe guide system is coupled to the mast or derrick  16 . 
     Referring now to  FIG. 2A , a side view of the pipe guide system  30  is shown. The drive mechanism  34  includes a support frame  40  coupled to the tube  24 . The frame  40  couples to the arm  32  at a pivot point  42 . The frame  40  supports a hydraulic cylinder  44  that couples to a pivot point  46  at the end of an arm lever  48  attached at the end of the arm  32 . The other end of the arm  32  is coupled to the cable  36  and roller assembly  38 . 
     Referring next to  FIG. 2B , a front view of the pipe guide system  30  is shown. Each of the pair of arms  32  includes an intermediate bend  50  separating an upper arm  52  from a lower arm  54 . An arm hub  56  at the upper ends of the arms  32  provides the pivot point  42  for moveably coupling the arms  32  to the frame  40 . Cable eyes  55  at the lower end of the arms  32  receive the cable  36 , which also attaches to the roller assembly  38  at cable eyes  62 . The roller assembly  38  also includes a bent or V-shaped axle  60  rotatably supporting rollers  58 . 
     Referring to  FIGS. 3A-3C , enlarged views of the drive and pivotal arm support mechanism  34  are shown. In  FIG. 3A , a side view shows that the arm  32  pivotally couples to the frame  40  via a pin  43  inserted through a frame plate at pivot point  42 . The arm lever  48  pivotally couples to a piston rod  49  at pivot point  46 , and the hydraulic cylinder  44  provides the actuation forces to move the piston rod  49  up and down to create a lever action in the arm  32 . As shown in  FIG. 3B , the frame  40  having top plate  41  pivotally supports the arms  32  at the pivot points  42  by running a pin  43  through the frame  40  and the arm hubs  56 . 
     Referring now to  FIG. 3C , a top view of the mechanism  34  is shown. The frame  40  includes an intermediate straight plate  64  and a pair of bend plates  66  extending at an angle from opposite sides of the plate  64 . The bend plates couple to and support the arms  32  via the pivotal couplings  42  and the hubs  56 . Further, the arm levers  48  extending from the hubs  56  and connecting to the pivotal couplings  46  also include bends, as shown. The angled or bent plates  66  and arm levers  48  assist in providing the extension or tightening action of the cable  36  for receiving pipe sections, as will be explained more fully herein. 
     In exemplary embodiments, the mechanism  34  is replaced with a mechanism  134 , shown in  FIGS. 4A and 4B . In  FIG. 4A , a side view of the mechanism  134  shows that a hydraulic cylinder  144  provides actuation forces to a piston rod  149  coupled to a linkage assembly  118 . The linkage assembly  118  pivotally and rotatably couples to a ball end  112  of a rod  114 . The opposite end  116  of the rod  114  also includes a ball member for pivotally and rotatably coupling to an arm lever  148  (equivalent to the lever  48  of  FIGS. 3A and 3C ) at pivot point  146  (equivalent to the pivot  46  of  FIGS. 3A and 3C ). The ball couplings at the ends of the rod  114  provide additional degrees of freedom in movement between the drive mechanism and the extendable guide arms, thereby further facilitating the relative separation of the lower ends of the two guide arms as they extend toward the pipe joints  20 . The movement of the lower ends of the guide arms away from each other causes the cable to extend lengthwise, or tighten, such that the roller assembly will receive a pipe section, as will be further described herein. 
     Referring next to  FIGS. 5A-5C , different views of the guide arms  32  are shown. In  FIG. 5A , the pair of arms  32  include upper arms  52  and lower arms  54  separated by the bends  50 . In  FIGS. 5B  (top view) and  5 C (side view), the arm  32  also includes a lowermost end having the cable eye  55  and an uppermost end including the hub  56  and the arm lever  48 . 
     Referring to  FIG. 6 , the roller assembly  38  includes the bent support axle  60 , the rollers  58 , and the cable eyes  62  for coupling to the cable  36 . 
     In operation, the pipe guide system  30  provides an automated means for handling and guiding pipe joint sections and other oilfield tubulars while they are moved about the drill floor. Referring now to FIGS.  1  and  7 A- 8 D, the different stages of operation are illustrated. In  FIGS. 1 and 7A , a group of triple joint sections  20  is stored in a setback or storage area  23  waiting to be made up with the drill string  18 . The sections  20  include first pipe joints  27 , second pipe joints  29  and third pipe joints  31 . The stabbing system  22  and the pipe guide system  30  are in retracted positions. As previously noted, the stabbing system  22  may be a combination unit including slips, a pipe thread lubricator, a mud bucket and other systems used in making up or breaking out pipe joints. The drive mechanism  34  of the pipe guide system  30  is disengaged to allow the arms  32 , the cable  36 , and the roller assembly  38  to hang in a downward position. As shown in  FIG. 2B , the arms  32  hang downward causing the cable  36  to be in a relaxed or contracted position about the roller assembly  38 . The upper portion of the rig structure  16  supports a top drive system  82  including a pipe elevator  82 . 
     Referring next to  FIG. 7B , the stabbing system  22  is extended to a position above the drill string  18  by actuating the hydraulic cylinders  74 , or other drive mechanism, and pivoting the supports arms  70 ,  72 . Additionally, the drive mechanism  34  is actuated and the hydraulic cylinder  44  pivots the arms  32  about the pivot point  42 . Referring back to  FIGS. 3A-3C , the hydraulic cylinder  44  is actuated to retract the piston rod  49  and exert a downward force on the pivotal couplings  46  and the ends of the arm levers  48 . The arm levers  48  rotate about the pins  43  at the pivot points  42 , thereby transferring a rotational force to the arms  32  and extending them to the position shown in  FIG. 7B . 
     Referring now to  FIGS. 8A and 8B , the extended position of  FIG. 7B  also corresponds to the position  57   a  wherein the rotation of the arms  32  extends and tightens the cables  36  as the ends  55  of the arms  32  move away from each other. The ends  55  move away from each other while the arms  32  move from the position of  FIG. 7A  to the position of  FIG. 7B  by virtue of the angled plates  66  of the support frame  40 . The angled support plates, along with the angled lever arms  48  and the bends  50  (see also  FIGS. 5A and 5B ), cause the ends  55  to move away from each other as the arms  32  extend outwardly, and move back toward each other as the arms  32  are brought back toward vertical alignment. The extension of the cable  36  may also be facilitated by a ball coupling assembly as shown in  FIGS. 4A and 4B . 
     Referring now to  FIG. 7C , the single pipe section  21  is picked up by a pipe elevator of a top drive assembly. As the pipe section  21  is moved toward well center at the drill string  18  and the extended stabbing system  22 , it will tend to swing, often times uncontrollably, and be a danger to rig personnel and equipment. As shown, the pipe guide system  30  engages or catches the pipe section  21  as it begins moving toward well center. The pipe section  21  is gathered and stabilized by the roller assembly  38 . If the pipe section  21  is misaligned from the roller assembly  38  as it engages the guide system  30 , the cable  36  will direct the moving pipe section  21  toward the roller assembly  38 . In some embodiments, slack in the cable  36  and flex in the arms  32  provide cushion for the pipe section  21  as it swings into the guide system  30 . However, spring-back reaction forces may be created in the guide system  30 . As the pipe section  21  impacts the guide system  30 , a hydraulic pressure spike is created in the hydraulic fluid system coupled to the hydraulic cylinder  44 , resulting in spring-back. In an exemplary embodiment, a relief valve is provided in the drive mechanism  34  and coupled to the hydraulic cylinder  44  to relieve hydraulic pressure and absorb the impact of the swinging pipe section  21 . 
     Referring now to  FIG. 7D , the drive mechanism  34  is actuated to provide a controlled retraction of the guide system  30  such that the arms  32  travel through a range  57  of positions, from the extended and receiving position  57   a  to the fully retracted position  57   j . The controlled retraction of the guide system  30  brings the pipe section  21  to well center above the drill string  18  and into the grasp of the stabbing system  22 . 
     Briefly referring to  FIGS. 8A-8C , the range  57  of positions of the guide system  30  is shown in more detail. At position  57   a , the drive mechanism  34  has extended the arms  32  and the ends of the arms  32  have moved apart to pull the cable  36  tight on either side of the roller assembly  38 . As previously described, the ends of the arms  32  move away from each other as the arms extend because the pivot points of the arms  32  do not share the same axis or have parallel axes, instead having rotational axes which are angled relative to one another. Referring back to  FIG. 3C , the plates  66  of the frame  40  support a pair of pins  43  that are angled relative to the center plate  64  and angled relative to each other. The offset longitudinal axes of the pins  43  provide the offset rotational axes of the pivot points  42 , about which the arms  32  rotate. Thus, as the hydraulic cylinder  44  and the piston rod  49  pull on the levers  48 , the arms  32  rotate about offset or angled axes such that the ends of the arms  32  move from proximate positions while the arms  32  are vertically disposed to displaced positions as the arms  32  extend outwardly toward horizontal. The angled lever arms  48  and the bends  50  also facilitate relative movement of the ends of the arms  32 . Furthermore, other means for providing relative movement of the arm ends are also contemplated, such as the drive mechanism  134  of  FIGS. 4A and 4B . 
     Also at position  57   a , the pipe section  21  is moved by a pipe elevator and top drive system, such as those shown in  FIG. 7H , from a storage position in the setback area to the cable  36  and the roller assembly  38 . The swinging pipe section  21  will be received and guided to the roller assembly  38  as previously described, while also absorbing the impact of the pipe section  21 . Next, the arms  32  are retracted by the drive mechanism  34  to a position  57   b . The lines  57  track the motion of the ends  55  of the arms  32  as they travel through the positions described. At a position  57   b , the ends  55  have begun to move back toward each other and the cable  36  has slackened. As this occurs, the rollers  58  allow the roller assembly to roll down vertically along the pipe section  21 . At positions  57   c  and  57   d , the ends  55  continue to move toward each other, causing the cable  36  to further slacken and the roller assembly  38  to move further down the pipe section  21  as the pipe section moves laterally toward a well center position  59 . At a position  57   e , the pipe section  21  is located at the well center position  59  and is stabilized there by the controlled retraction of the pipe guide system  30 . At positions  57   f  and  57   g , the roller assembly  38  disengages from the vertically disposed and substantially still pipe section  21 . The cable  36  continues to slacken due to the relative movement of the ends  55  toward each other. At positions  57   h  and  57   i , the arms  32  continue to retract and move the roller assembly  38  and the cable  36  laterally toward the original retracted position  57   j.    
     In exemplary embodiments, the cable  36  is a steel cable. In other embodiments, the cable  36  is a length of an elastomeric material that stretches over the expanding and contracting distance between the ends  55  of the extendable support arms  32 . The elastomeric line  36  may or may not include the roller assembly  38 . In some embodiments, the elastomeric line  36  includes a receiving member for capturing the pipe section  21  rather than the roller assembly  38 . In still other embodiments, the cable  36  includes rigid members. A first rigid member is coupled between the first arm end  55  and the first roller assembly eye  62 , and a second rigid member is coupled between the second arm end  55  and the second roller assembly eye  62 . The couplings at  55 ,  62  are rotatable to allow the expansion and contraction of the overall expandable guide member  36 . In the various embodiments, the flexibility of the guide member  36 ,  38  allows for expansion and contraction between the ends  55  of the extendable support arms  32 . The retracted arms  32  and contracted guide member  36 ,  38  provide a space efficient, stored pipe guide system. When extended and expanded, the arms  32  and the guide member  36 ,  38  are flexible to laterally transport pipe sections in a safe manner. 
     Referring to  FIG. 8C , the pipe guide system  30  is disposed on a fully equipped drill floor  14  including the setback area  23 , a mousehole  25 , the pipe section  21  engaged with and placed by the guide system  30  to the well center position  59 , and an iron roughneck  80  for applying torque to the pipe section  21 . 
     Now, referring back to the drill floor operation incorporating the pipe guide system  30 ,  FIG. 7E  illustrates centralizing the pipe section  21  by the elevator and stabbing of the lower end of the pipe section  21  by the stabbing system  22 . In some embodiments, wherein the stabbing system  22  is a combination unit, a lubricator operably coupled thereto may be actuated to lubricate the pipe threads on the pipe section  21  and/or the drill string  18 . In  FIG. 7F , the stabbing system or combination unit  22  is retracted to leave the connected pipe section  21  available to receive the iron roughneck  80 . In  FIG. 7G , the iron roughneck  80  is moved adjacent the connection between the pipe section  21  and the drill string  18 . The iron roughneck  80  engages the pipe section  21  and spins it to torque it up with the drill string  18 . The pipe section  21  is now part of the drill string  18 . As illustrated in  FIG. 7H , the top drive  82  with elevator  84  moves the drill string  18  down to a position where it can receive another pipe section. In an exemplary embodiment, the combination unit  22  may include a slip system  86  for engaging the drill string  18  at this time. In exemplary embodiments, the combination unit  22  may also include a mud bucket for surrounding the connection and receiving mud as a pipe section is broken out from the drill string  18 . 
     Various combinations of the steps just described are also used to perform additional operations. For example, a reverse order of the steps generally described with reference to  FIGS. 7A-7H  may be executed during a tripping out process. The extension of the pipe guide system  30  may be used to push a tripped out pipe section  21  back toward the storage setback area  23 . 
     Referring now to  FIG. 9 , some embodiments of the drilling system with the pipe guide system  30  may include a pipe erector and other components. A drilling system  100  comprises a rig structure  112 , a hoisting system  114 , a pipe erector system  400 , a top drive system  118 , and drill floor equipment  120 . The rig structure  112  comprises a mast  122 , an elevated drill floor  124 , and a sub-structure  126 . The hoisting system  114  comprises drawworks  128 , a crown block  130 , and a traveling block  132 . The top drive system  118  comprises a top drive  134 , bails  136 , and an elevator  138 . The drill floor equipment  120  comprises an iron roughneck system  148  and slips  150  that are located on well center  152 . The pipe erector system  400  moves the drill pipe  160  from a horizontal storage position  162  to an inclined position  164  where the upper end  166  of the drill pipe is substantially adjacent to the elevated drill floor  124 . 
     Referring to  FIGS. 10-12 , the erector system  400  comprises an erector frame  402 , pipe guides  404 , a pivot  406 , an elevating cylinder  408 , and a rail  410 . The erector system  400  is utilized to elevate a pipe  412  from horizontal, as in  FIG. 1 , and move the pipe to a ramp  414  of the rig  416 . The pipe  412  is received by pipe guides  404  mounted on the frame  402 . The elevating cylinder  408  elevates the frame  402  to an angle so that the axis of the pipe  412  is substantially parallel to the ramp  414 . The frame  402  is then moved along the rail  410  until the pipe  412  is adjacent to the ramp  414 . Once on the ramp  414 , the elevator  84 ,  138 , or some other lifting mechanism can engage the pipe  412  and lift the pipe into the rig  416 . 
     When the pipe  412  is lifted into the rig  416  from the angled ramp  414 , as previously noted, it may be desirable to control the lateral movement of the lower end of the pipe  412  so that the pipe does not swing dangerously once lifted from the ramp  414 . Thus, the various embodiments of a pipe guide system as disclosed herein may be attached to the mast  122 , or other drill floor equipment, and operated as described herein to control and guide the pipe  412  to well center  152 . In the pipe guide system  30 , the rotating arms are moveable support members, and the cable coupled therebetween is an expandable guide member adapted to receive and guide the pipe. The cable may also include a roller assembly to facilitate movement and release of the expandable guide member from the pipe. 
     While certain embodiments of the disclosed principles have been shown and described, modifications thereof can be made by one skilled in the art without departing from the scope or teaching of this disclosure. The embodiments described herein are exemplary only and are not limiting. Accordingly, the scope of protection is not limited to the embodiments described herein, but is only limited by the claims that follow, the scope of which shall include all equivalents of the subject matter of the claims.