Patent Publication Number: US-2022213743-A1

Title: Indexing mechanisms

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of, and priority to, U.S. Patent Application No. 62/842,562 filed on May 3, 2019, which is incorporated herein by this reference in its entirety. 
    
    
     BACKGROUND OF THE DISCLOSURE 
     A wellbore may include sections uphole from the wellbore bottom that may need to be expanded, or structures that may need to be removed after installed. These sections and structures may include plugs, casings, drill pipe, formation, and so forth. A downhole tool may include radially expandable cutting structures that may remove material from a wellbore wall. The radially expandable cutting structures may be actuated after the downhole tool has been tripped to a desired hole depth. The radially expandable cutting structures may be hydraulically actuated by changing the hydraulic pressure or a fluid flow rate from the surface. 
     SUMMARY 
     In some embodiments, an indexing mechanism includes a piston. An indexing sleeve encases a portion of the piston. The indexing mechanism is longitudinally fixed to the piston, and is rotatable relative to the piston. The indexing sleeve includes an indexing track. An indexing ring surrounds less than an entirety of the indexing sleeve. The indexing ring is rotatable relative to the piston. The indexing ring includes one or more indexing pins that extend into the indexing track. 
     In other embodiments, an indexing mechanism includes a piston. An indexing sleeve encases a portion of the piston. An indexing ring surrounds a portion of the indexing sleeve. The indexing ring includes a ring stop and one or more indexing pins. The indexing pin or pins extend into the indexing track. The indexing ring is rotatable relative to the piston. 
     In yet other embodiments, a method for operating an indexing mechanism includes moving a piston from a first longitudinal piston position to a second longitudinal piston position. The method includes rotating at least one of an indexing sleeve or an indexing ring relative to the piston into a first indexing alignment. The indexing ring encases less than an entirety of the piston. The indexing ring surrounds a portion of the indexing sleeve. The first indexing alignment aligns a ring stop on the indexing ring with a first sleeve stop on the indexing sleeve such that the first sleeve stop contacts the ring stop in the second longitudinal piston position. 
     This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter. 
     Additional features and advantages of embodiments of the disclosure will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of such embodiments. The features and advantages of such embodiments may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims. These and other features will become more fully apparent from the following description and appended claims, or may be learned by the practice of such embodiments as set forth hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to describe the manner in which the above-recited and other features of the disclosure can be obtained, a more particular description will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. For better understanding, the like elements have been designated by like reference numbers throughout the various accompanying figures. While some of the drawings may be schematic or exaggerated representations of concepts, at least some of the drawings may be drawn to scale. Understanding that the drawings depict some example embodiments, the embodiments will be described and explained with additional specificity and detail through the use of the accompanying drawings in which: 
         FIG. 1  is a partial cut-away view of a drilling system, according to at least one embodiment of the present disclosure; 
         FIG. 2-1  is a perspective view of an indexing mechanism, according to at least one embodiment of the present disclosure; 
         FIG. 2-2  is a cross-sectional view of a downhole tool including the indexing mechanism of  FIG. 2-1 , according to at least one embodiment of the present disclosure; 
         FIG. 3  is a cross-sectional view of an indexing mechanism, according to at least one embodiment of the present disclosure; 
         FIG. 4-1  is a view of an indexing track, according to at least one embodiment of the present disclosure; 
         FIG. 4-2  is another view of an indexing track, according to at least one embodiment of the present disclosure; 
         FIG. 5-1  is a perspective view of an indexing mechanism, according to at least one embodiment of the present disclosure; 
         FIG. 5-2  is a cross-sectional view of a downhole tool including the indexing mechanism of  FIG. 2-2 , according to at least one embodiment of the present disclosure; 
         FIG. 6  is a perspective view of an indexing mechanism, according to at least one embodiment of the present disclosure; 
         FIG. 7-1  is a perspective view of another indexing mechanism, according to at least one embodiment of the present disclosure; 
         FIG. 7-2  is a cross sectional view of a downhole tool including the indexing mechanism of  FIG. 7-1 , according to at least one embodiment of the present disclosure; 
         FIG. 8  is a cross-sectional view of another indexing mechanism, according to at least one embodiment of the present disclosure; and 
         FIG. 9  is a method chart of a method for operating an indexing mechanism, according to at least one embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     This disclosure generally relates to devices, systems, and methods for actuating a downhole tool using an indexing mechanism.  FIG. 1  shows one example of a drilling system  100  for drilling an earth formation  101  to form a wellbore  102 . The drilling system  100  includes a drill rig  103  used to turn a drilling tool assembly  104  which extends downward into the wellbore  102 . The drilling tool assembly  104  may include a drill string  105 , a bottom hole assembly (“BHA”)  106 , and a bit  110 , attached to the downhole end of drill string  105 . 
     The drill string  105  may include several joints of drill pipe  108  connected end-to-end through tool joints  109 . The drill string  105  transmits drilling fluid through a central bore and transmits rotational power from the drill rig  103  to the BHA  106 . In some embodiments, the drill string  105  may further include additional components such as subs, pup joints, etc. The drill pipe  108  provides a hydraulic passage through which drilling fluid is pumped from the surface. The drilling fluid discharges through selected-size nozzles, jets, or other orifices in the bit  110  for the purposes of cooling the bit  110  and cutting structures thereon, and for lifting cuttings out of the wellbore  102  as it is being drilled. 
     The BHA  106  may include the bit  110  or other components. An example BHA  106  may include additional or other components (e.g., coupled between to the drill string  105  and the bit  110 ). Examples of additional BHA components include drill collars, stabilizers, measurement-while-drilling (“MWD”) tools, logging-while-drilling (“LWD”) tools, downhole motors, underreamers, section mills, hydraulic disconnects, jars, vibration or dampening tools, other components, or combinations of the foregoing. 
     In general, the drilling system  100  may include other drilling components and accessories, such as special valves (e.g., kelly cocks, blowout preventers, and safety valves). Additional components included in the drilling system  100  may be considered a part of the drilling tool assembly  104 , the drill string  105 , or a part of the BHA  106  depending on their locations in the drilling system  100 . 
     The bit  110  in the BHA  106  may be any type of bit suitable for degrading downhole materials. For instance, the bit  110  may be a drill bit suitable for drilling the earth formation  101 . Example types of drill bits used for drilling earth formations are fixed-cutter or drag bits. In other embodiments, the bit  110  may be a mill used for removing metal, composite, elastomer, other materials downhole, or combinations thereof. For instance, the bit  110  may be used with a whipstock to mill into casing  107  lining the wellbore  102 . The bit  110  may also be a junk mill used to mill away tools, plugs, cement, other materials within the wellbore  102 , or combinations thereof. Swarf or other cuttings formed by use of a mill may be lifted to surface, or may be allowed to fall downhole. 
       FIG. 2-1  is a perspective view of a representation of a indexing mechanism  212 , according to at least one embodiment of the present disclosure. The indexing mechanism  212  may include a piston  214 . An indexing sleeve  216  may encase a portion of the piston  214 . In other words, the indexing sleeve  216  may surround at least a portion of the piston  214 . In some embodiments, the indexing sleeve  216  may encase less than an entirety of the piston  214 . In at least one embodiment, the indexing sleeve  216  may be coaxial with the piston  214  about a longitudinal axis  217 . The indexing sleeve  216  may include an indexing track  218 . The indexing track  218  may include a series of walls and/or tracks on the indexing sleeve  216 . 
     The indexing mechanism  212  may include an indexing ring  220 . The indexing ring  220  may surround at least a portion of the indexing sleeve  216 , and therefore, the indexing ring  220  may surround at least a portion of the piston  214 . In at least one embodiment, the indexing ring  220  may surround less than an entirety of the indexing sleeve  216 . The indexing ring  220  may be coaxial with the piston  214  and the indexing sleeve  216  about the longitudinal axis  217 . The indexing ring  220  may include an indexing pin  222 . The indexing pin  222  may be inserted into the indexing track  218 . 
     The indexing sleeve  216  may be rotatable relative to the piston  214  about the longitudinal axis  217 . Furthermore, the indexing sleeve  216  may be rotatable relative to the piston  214  and the indexing ring  220  about the longitudinal axis  217 . The indexing ring  220  may be rotatable relative to the piston  214  about the longitudinal axis  217 . Furthermore, in at least one embodiment, the indexing ring  220  may be rotatable relative to the piston  214  and the indexing sleeve  216  about the longitudinal axis  217 . 
     In some embodiments, the indexing sleeve  216  may be longitudinally fixed to the piston  214 . In other words, when the piston  214  moves along the longitudinal axis  217 , the indexing sleeve  216  may move along the longitudinal axis  217  with the piston  214 . In at least one embodiment, the piston  214  and the indexing sleeve  216  may be longitudinally movable along the longitudinal axis  217  relative to the indexing ring  220 . As the indexing sleeve  216  moves longitudinally relative to the indexing ring  220 , the indexing pin  222  may contact a wall  224  of the indexing track  218 . Contacting the wall  224  of the indexing track  218  may cause the wall  224  to push on the indexing pin  222  and the indexing pin  222  to push on the wall  224 . This pushing may result in a torque about the longitudinal axis  217  that acts on both the indexing sleeve  216  and the indexing ring  220 . When the torque exceeds a breakout torque of at least one of the indexing sleeve  216  and/or the indexing ring  220 , one or both of the indexing sleeve  216  and/or the indexing ring  220  may rotate relative to the piston  214  about the longitudinal axis  217 . Thus, the indexing sleeve  216  and the indexing ring  220  may rotate relative to the piston  214  in response to the longitudinal motion of the piston  214 . In other words, the indexing sleeve  216  and the indexing ring  220  may rotate relative to the piston  214  in response to the indexing pin  222  engaging the wall  224  of the indexing track  218 . 
     For example, when the torque exceeds the sleeve breakout torque of the indexing sleeve  216  but not the ring breakout torque of the indexing ring  220 , the indexing sleeve  216  may rotate relative to the piston  214  and the indexing ring  220 . In this manner, the sleeve breakout torque may be less than the ring breakout torque. In other examples, when the torque exceeds the ring breakout torque but not the sleeve breakout torque, the indexing ring  220  may rotate relative to the piston  214  and the indexing sleeve  216 . In still other examples, the torque may exceed both the ring breakout torque and the sleeve breakout torque, and both the indexing sleeve  216  and the indexing ring  220  may rotate relative to each other and the piston  214 . 
     The torque exerted on the indexing sleeve  216  may be opposite the torque exerted on the indexing ring  220 . Thus, the torque may cause the indexing sleeve  216  to rotate in a first direction, and the indexing ring  220  to rotate in a second direction, the first direction being different than the second direction. For example, in the embodiment shown in  FIG. 2-1 , if the indexing sleeve  216  were moved along the longitudinal axis  217  in a downhole direction (i.e., such that an uphole end  226  of the indexing sleeve  216  moves toward the indexing ring  220 ), the indexing pin  222  may engage a portion of the wall  224  that is curved clockwise. This engagement may cause the indexing sleeve  216  to rotate counter-clockwise as viewed from the uphole end  226 , and the indexing ring  220  to rotate clockwise as viewed from the uphole end  226 . In other examples, the wall  224  may be oriented in a different direction, thereby causing the indexing sleeve  216  to rotate clockwise and the indexing ring  220  to rotate counter-clockwise. 
     Including an indexing sleeve  216  and an indexing ring  220  that both rotate may increase the reliability of the indexing mechanism  212 . For example, if the indexing sleeve  216  jams, then the indexing ring  220  may still be able to rotate, and the indexing mechanism  212  may be able to cycle. Similarly, if the indexing ring  220  jams, then the indexing sleeve  216  may still be able to rotate, and the indexing mechanism  212  may be able to cycle. Thus, the indexing mechanism  212  may cycle more reliably, or may have a longer operational life between servicing. This may decrease the amount of times that the drill string needs to be tripped out of the hole, thereby potentially decreasing costs. 
     Furthermore, including the indexing track  218  on the indexing sleeve  216  may reduce the overall manufacturing complexity of a downhole tool. For example, machining the indexing track  218  may be one of the last manufacturing steps taken in the fabrication of a downhole tool. If a mistake is made during machining of an indexing track  218  located directly on a piston  214 , then the entire piston  214  must be discarded, which may represent a loss of a significant investment in materials, consumables, labor, and so forth. By including the indexing track  218  on the indexing sleeve  216 , if a mistake is made during machining of the indexing track  218 , then only the indexing sleeve  216  must be discarded, which may represent significantly less of an investment in materials, consumables, labor, and so forth than the piston. Thus, the indexing sleeve  216  reduces the complexity of the manufacturing process, and also reduces the risk of having to re-manufacture an entire piston  214 . 
     Furthermore, including an indexing sleeve  216  that is separate from the piston  214  may reduce the mass that is rotated when the indexing mechanism  212  is cycled. A lower mass may reduce the amount of torque required to rotate the indexing sleeve  216 . This may reduce the forces experienced by the indexing pin  222  and/or the wall  224 . Reducing the torque and the forces on the indexing pin  222  and/or the wall  224  may reduce the chance of the indexing pin  222  failing by fracturing, shearing, and so forth. In at least one embodiment, an indexing ring  220  may have a lower mass than the indexing sleeve  216 . This means that the indexing ring  220  may require a lower torque to rotate than the indexing sleeve, thereby further reducing forces on the indexing pin  222  and/or the wall  224 . 
     The indexing sleeve  216  has a sleeve mass. In some embodiments, the sleeve mass may be in a range having an upper value, a lower value, or upper and lower values including any of 1 kg, 2 kg, 3 kg, 4 kg, 5 kg, 6 kg, 7 kg, 8 kg, 9 kg, 10 kg, 15 kg, 20 kg, or any value therebetween. For example, the sleeve mass may be greater than 1 kg. In another example, the sleeve mass may be less than 20 kg. In yet other examples, the sleeve mass may be any value in a range between 1 kg and 20 kg. In some embodiments it may be critical that the sleeve mass is 8 kg or less to reduce the chance of failure of the indexing pin  222 . 
     The indexing ring  218  has a ring mass. In some embodiments, the ring mass may be in a range having an upper value, a lower value, or upper and lower values including any of 0.25 kg, 0.5 kg, 0.75 kg, 1 kg, 2 kg, 3 kg, 4 kg, 5 kg, 6 kg, 7 kg, 8 kg, 9 kg, 10 kg, or any value therebetween. For example, the ring mass may be greater than 0.25 kg. In another example, the ring mass may be less than 10 kg. In yet other examples, the ring mass may be any value in a range between 0.25 kg and 10 kg. In some embodiments it may be critical that the ring mass is 2 kg or less to reduce the chance of failure of the indexing pin  222 . 
     The indexing sleeve  216  and the indexing ring  220  have a mass ratio that is the ratio of the ring mass to the sleeve mass. In some embodiments, the mass ratio may be in a range having an upper value, a lower value, or upper and lower values including any of 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, or any value therebetween. For example, the mass ratio may be greater than 1:1. In another example, the mass ratio may be less than 1:10. In yet other examples, the mass ratio may be any value in a range between 1:1 and 1:10. In some embodiments it may be critical that the mass ratio less than 1:4 to improve the reliability of the indexing mechanism  212 . 
       FIG. 2-2  is a cross-sectional view of a downhole tool  213 , including a cross-sectional view of the indexing mechanism  212  of  FIG. 2-1 . The downhole tool  213  includes a housing  228 . A piston  214  may be located inside a central bore  230  of the housing  228 . An indexing sleeve  216  may encompass less than an entirety of the piston  214 . In other words, an inner surface  232  of the indexing sleeve  216  may abut an outer surface  234  of the piston  214 . 
     An indexing ring  220  may surround at least a portion of the indexing sleeve  216 . For example, the indexing ring  220  has an indexing ring width  236  and the indexing sleeve  216  has an indexing sleeve width  238 . The indexing ring width  236  and the indexing sleeve width  238  affect the mass of the indexing ring  220  and the indexing sleeve  216 , respectively. For example, a larger indexing ring width  236  results in a heavier indexing ring  220 , and a smaller indexing ring width  236  results in a lighter indexing ring  220 . 
     As described herein, the indexing ring may surround less than an entirety of the indexing sleeve. For example, the indexing ring width  236  is a ring percentage of the indexing sleeve width  238 . In some embodiments, the ring percentage may be in a range having an upper value, a lower value, or upper and lower values including any of 5%, 10%, 12%, 14%, 15%, 16%, 18%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or any value therebetween. For example, the ring percentage may be greater than 5%. In another example, the ring percentage may be less than 50%. In yet other examples, the ring percentage may be any value in a range between 5% and 50%. In some embodiments it may be critical that the ring percentage is less than 10% to improve the reliability of the indexing mechanism  212 . 
     The housing  228  may include a fluid path  240 . The fluid path  240  may be sealed by a sealing member  241  between the fluid path  240  and the piston  214 . The piston  214  may pass through a channel wall  242  such that the channel wall  242  separates the central bore  230  from the fluid path  240 . The channel wall  242  may include a channel opening  243 . In the position shown in  FIG. 2-2 , the channel opening  243  is sealed from the central bore  230  by the piston  214 . 
     A fluid flow  244  may pass through the central bore  230  with a volumetric flow rate that is related to a fluid pressure. The fluid pressure may push on an uphole end  246  of the piston  214 . As the volumetric flow rate increases, the fluid pressure may urge the uphole end  246  of the piston  214  downhole. A biasing member (not shown) located past a downhole end  248  of the indexing mechanism  212  may urge the piston  214  uphole. The biasing member may be any biasing member, such as a coil spring, a Bellville washer, a leaf spring, a wave spring, a hydraulic or pneumatic piston, or other biasing member. When the fluid pressure exerts a force on the piston  214  that is greater than the opposing force from the biasing member, the piston  214  may move downhole. In at least one embodiment, the piston  214  may move downhole enough that the fluid flow  244  may pass into the fluid path  240 . The fluid path  240  may be directed to hydraulically actuate a downhole tool, including an expandable tool such as a reamer, a section mill, other expandable tool, an expandable stabilizer, an anchor, a bypass valve, a packing element, another downhole tool, or combinations of the foregoing. 
     In the embodiment shown in  FIG. 2-2 , the indexing mechanism  212  is in a low-flow state. In other words, the fluid pressure from the fluid flow  244  is insufficient to overcome the opposing force from the biasing member. In this state, the fluid path  240  is blocked, and the downhole tool is not actuated. As the fluid flow  244  increases, the piston  214  moves downhole, the indexing sleeve  216  may move downhole with the piston  214 . An indexing pin  222  may be inserted into a track  250  of an indexing track  218 . When the indexing pin  222  engages a wall  224  of the indexing track  218 , one or both of the indexing sleeve  216  and the indexing ring  220  may rotate to allow the piston  214  and the indexing sleeve  216  to continue to move longitudinally downhole as the fluid flow is increased. 
       FIG. 3  is a close-up cross-sectional view of an indexing mechanism  312 , according to at least one embodiment of the present disclosure. The indexing mechanism  312  may include a housing  328 . A piston  314  may be located in a central bore  330  of the housing  328 . An indexing sleeve  316  may encompass at least less than an entirety of the piston  314 . In other words, the indexing sleeve  316  may surround a portion of the piston  314 . The indexing sleeve may be longitudinally fixed to the piston  314  by an upper sleeve block  352 - 1  and a lower sleeve block  352 - 2 . The upper sleeve block  352 - 1  and the lower sleeve block  352 - 2  may prevent the indexing sleeve  316  from moving longitudinally relative to the piston  314 . For example, when the piston  314  moves downhole (i.e., toward the lower sleeve block  352 - 2 ), the indexing sleeve  316  may push against the upper sleeve block  352 - 1 . Similarly, when the piston  314  moves uphole (i.e., toward the upper sleeve block  352 - 1 ), the indexing sleeve  316  may push against the lower sleeve block  352 - 2 . 
     The indexing sleeve  316  may be rotatable relative to the piston  314 . In at least one embodiment, the indexing sleeve  316  may rotate directly against the piston  314 , without any bearings. In other embodiments, the indexing sleeve  316  may rotate against a radial bearing  354  between the indexing sleeve  316  and the piston  314 . In at least one embodiment, including a radial bearing  354  may decrease the torque required to rotate the indexing sleeve  316 . Furthermore, in the same or other embodiments, the radial bearings  354  may help to centralize the indexing sleeve  316  with respect to the piston  314 . Rotating against the piston  314  without any bearings may reduce the cost and complexity of the indexing mechanism  312 . 
     The indexing mechanism  312  may include an indexing ring  320 . The indexing ring  320  may include an indexing pin  322  fixed to the indexing ring  320 . The indexing pin  322  may be located in a ring stop  356  located in the indexing ring  320 . For example, the indexing pin  322  may be inserted into a bore in the ring stop  356 . In some embodiments, the indexing pin  322  may be connected to the ring stop  356  with a mechanical connection, such as a threaded connection, a press-fit, an interference fit, a snap ring, a locking pin, a cotter pin, a shear pin, or other mechanical connection. In other embodiments, the indexing pin  322  may be connected to the ring stop  356  with a weld, braze, or other joining process. In some embodiments, the indexing pin  322  and the ring stop  356  may be formed of a single unitary piece. For example, a blank may be machined to form the ring stop  356  and the indexing pin. Including the indexing pin  322  in the ring stop  356  may strengthen the indexing pin  322  for the contact between the indexing pin  322  and a wall  324  of the indexing track  318 . Furthermore, including the indexing pin  322  with the ring stop  356  may shorten the indexing mechanism  312  and allow a sleeve stop  362  on the indexing sleeve  316  to be located uphole of the indexing ring  320  and the ring stop  356 . 
     In some embodiments, the indexing pin  322  may be rotatable relative to the ring stop  356 . For example, as the indexing pin  322  engages the wall  324  and one or both of the indexing sleeve  316  and the indexing ring  320  rotate, the indexing pin  322  may slide along the wall  324 . A rotating indexing pin  322  may roll along the wall  324  rather than slide along the wall. This may reduce wear on the wall  324  and/or the indexing pin  322  during repeated cycling of the indexing mechanism  312 . 
     In some embodiments, the indexing ring  320  may include a plurality of indexing pins  322  connected to a plurality of ring stops  356 . For example, the indexing ring  320  may include two, three, four, or more indexing pins  322  and ring stops  356 . 
     The indexing pin may extend into a track  350  of an indexing track  318  of the indexing sleeve  316 . The indexing ring  320  may be secured to the housing  328  with a ring support  358 . The ring support  358  may be longitudinally and rotationally fixed to the housing  328  with any type of connection, such as a threaded connection, a bolted connection, a weld, braze, or any other type of connection. The indexing ring  320  may rotate relative to the ring support  358 . In at least one embodiment, the indexing ring  320  may rotate directly against the ring support  358 , or without any bearings. In other embodiments, the indexing ring  320  may rotate against the ring support  358  against a bearing, such as an axial or a radial bearing. In some embodiments, the indexing ring  320  may be directly secured to the housing  328 . For example, the indexing ring  320  may be inserted into a annular channel machined or cast into the inner wall of the housing  328 . 
     As the piston  314  and the indexing sleeve  316  move longitudinally downhole, a wall  324  of the indexing track  318  may engage the indexing pin  322 . Thus, the indexing pin  322  may be inserted far enough into the indexing track  318  and the track  350  to contact the wall  324 . In at least one embodiment, the indexing pin  322  may contact a bottom surface  360  of the track  350 . When the indexing pin  322  contacts the wall  324 , the indexing sleeve  316  may be pushed toward the upper sleeve block  352 - 1 . Uphole movement of the indexing sleeve  316  may be stopped by the upper sleeve block  352 - 1 , and a torque may be applied to the indexing sleeve  316  and the indexing ring  320 . 
     The torque may be greater than a sleeve breakout torque of the indexing sleeve  316 , and the indexing sleeve  316  may rotate relative to the piston  314 . In at least one embodiment, the upper sleeve block  352 - 1  may be rotationally fixed to the piston  314 , and the indexing sleeve  316  may rotate directly against the upper sleeve block  352 - 1 , without any bearings. In other embodiments, the upper sleeve block  352 - 1  may be a bearing, such as a thrust bearing or a ball bearing. 
     As the piston  314  and the indexing sleeve  316  move further downhole, a sleeve stop  362  on the indexing sleeve  316  may contact or engage the ring stop  356 . This may cause the piston  314  and the indexing sleeve  316  to stop moving downhole. In some embodiments, the sleeve stop  362  may directly engage the ring stop  356 . The ring stop  356  may be sized to stop the motion of the piston  314  and the indexing sleeve  316  without damage. In other embodiments, the sleeve stop  362  may engage the indexing pin  322 , and the indexing pin  322  may be sized to stop the motion of the piston  314  and the indexing sleeve  316  without damage. Thus, in some embodiments, the sleeve stop  362  may be located uphole of the ring stop  356 . Locating the sleeve stop  362  uphole of the ring stop  356  may reduce the number of parts of the system, which may reduce the manufacturing cost. Furthermore, locating the indexing pin  322  in the indexing ring  320  may shorten the length of the indexing sleeve  316 , which may reduce manufacturing costs and reduce the length the indexing sleeve  316  has to move to cycle the indexing mechanism  312 . 
       FIG. 4-1  is a representation of an indexing track  418 , according to at least one embodiment of the present disclosure. The indexing track  418  may include a track  450  located between walls  424  in the indexing track  418 . An indexing pin  422  may be installed in a ring stop (e.g., the ring stop  356  of  FIG. 3 ) of an indexing ring (e.g., indexing ring  220  of  FIG. 2-1 ). The indexing pin may extend into the track  450  at a first longitudinal piston position  464 - 1  (e.g., the position shown in  FIG. 2-1  and  FIG. 2-2 ). As an indexing sleeve (e.g., the indexing sleeve  216  of  FIG. 2-1 ), in which the indexing track  418  is located, is moved downhole, the indexing pin  422  may follow a first indexing pin path  466 - 1 . The walls  424  may direct the indexing pin  422  until the piston (e.g., piston  214  of  FIG. 2-2 ) and the indexing sleeve are stopped a second longitudinal piston position  464 - 2 . This may occur, for instance, when the fluid flow (e.g., the fluid flow  244  of  FIG. 2-2 ) is increased to a high flow state. A first sleeve stop  462 - 1  may engage a ring stop and stop downhole movement of the piston and the indexing sleeve at the second longitudinal piston position  464 - 2 . 
     In the second longitudinal piston position  464 - 2 , fluid flow to a fluid path (e.g., fluid path  240  of  FIG. 2-2 ) may be blocked by the piston. When the fluid flow is decreased to a low flow state, then the piston and the indexing sleeve may move uphole, and the walls  424  may direct the indexing pin  422  until the piston and the indexing sleeve are back to the first longitudinal piston position. In this manner, the cycling of the indexing mechanism may be repeated indefinitely without allowing fluid flow into the fluid path. In other words, the cycling of the indexing mechanism may be repeated indefinitely without actuating a downhole tool. 
     In the second longitudinal piston position  464 - 2 , the indexing ring and the indexing sleeve may be in a first indexing alignment. In the first indexing alignment, the indexing ring may be in one of a first lower straight section  465 - 1  of the indexing track  418  and a first upper straight section  467 - 1  of the indexing track  218 , the first lower straight section  465 - 1  and the first upper straight section  467 - 1  being in line in the indexing track  418 . For instance, the first lower straight section  465 - 1  and the first upper straight section  467 - 1  may be in the same circumferential position on the indexing sleeve. Furthermore, in the first indexing alignment, the ring stop may be aligned to contact a first sleeve stop  462 - 1  on the indexing sleeve such that the first sleeve stop  462 - 1  contacts the ring stop in the second longitudinal piston position  464 - 2 . 
       FIG. 4-2  is a representation of the indexing track  418  of  FIG. 4-1 , according to at least one embodiment of the present disclosure. The indexing track  418  may include a track  450  located between walls  424  in the indexing track  418 . An indexing pin  422  may extend into the track  450  at a first longitudinal piston position  464 - 1 . As the flow is increased from the low flow state to the high flow state, the piston and the indexing sleeve are moved downhole, the indexing pin  422  may follow a second indexing pin path  466 - 2 . The second indexing pin path  466 - 2  may follow the same initial path as the first indexing pin path  466 - 1  shown in  FIG. 4-1  until the piston and the indexing sleeve are in the second longitudinal piston position  464 - 2 . 
     To actuate a downhole tool, fluid flow may be reduced to an indexing flow between the high flow state and the low flow state. At the indexing flow, the piston and indexing sleeve may be moved to a third longitudinal piston position  464 - 3 . The third longitudinal piston position  464 - 3  may be between the first longitudinal piston position  464 - 1  and the second longitudinal piston position  464 - 2 . In the third longitudinal piston position  464 - 3 , the indexing ring and the indexing sleeve may be in a second indexing alignment. In the second indexing alignment, the indexing pin  422  may be in middle section  468  of the indexing track, and not aligned with the first lower straight section  465 - 1 , a second lower straight section  465 - 2 , a first upper straight section  467 - 1 , or a second upper straight section  475 - 2 . Thus, the ring stop may not be aligned with either the first sleeve stop  462 - 1  or the second sleeve stop  462 - 2 . 
     The fluid flow may then be increased from the indexing flow to the high flow. This may cause the indexing pin  422  to direct the piston and the indexing sleeve to a fourth longitudinal piston position  464 - 4 . In at least one embodiment, the first sleeve stop  462 - 1  may engage a ring support in the fourth longitudinal piston position and halt downhole movement of the piston and the indexing sleeve. The ring support may include a surface downhole of the indexing ring against which the first sleeve stop  462 - 1  may contact, thereby preventing further longitudinal movement of the piston and the indexing sleeve. 
     In the same or other embodiments, a second sleeve stop  462 - 2  may engage the ring stop and halt downhole movement of the piston and the indexing sleeve. In some embodiments, the indexing sleeve may both contact the ring stop and the second sleeve stop  462 - 2  may engage the ring stop in the fourth longitudinal piston position. In the fourth longitudinal piston position  464 - 4 , the indexing ring and the indexing sleeve may be in a third indexing alignment. In the third indexing alignment, the indexing ring may be in one of the second lower straight section  465 - 2  and the second upper straight section  467 - 2 , the second lower straight section  465 - 2  and the second upper straight section  467 - 2  being in line in the indexing track  418 . For instance, the second lower straight section  465 - 2  and the second upper straight section  467 - 2  may be in the same circumferential position on the indexing sleeve. Furthermore, in the third indexing alignment, the first sleeve stop  462 - 1  may be aligned to contact the ring support between two ring stops, and/or the ring stop may be aligned to contact the second sleeve stop  462 - 2  on the indexing sleeve such that the first sleeve stop  462 - 1  contacts the ring support and/or the second sleeve stop  462 - 2  contacts the ring stop in the fourth longitudinal piston position  464 - 4 . In other words, in the third indexing alignment, the ring stop may be longitudinally offset from the first sleeve stop  462 - 1  in the fourth longitudinal piston position and the third indexing alignment. 
     In the fourth longitudinal piston position  464 - 4 , the fluid path may be open to the fluid flow. In this manner, the fluid flow may actuate a downhole tool. When the fluid flow is reduced to the low flow state, then the indexing pin  422  may direct the piston and the indexing sleeve back to the first longitudinal piston position  464 - 1 . When the fluid flow is increased back to the high flow state, then the indexing pin  422  may direct the piston and the indexing sleeve back to the fourth longitudinal piston position  464 - 4 . In this manner, the downhole tool may be indefinitely cycled between actuating a downhole tool and deactivating a downhole tool by changing the fluid flow from the low flow state to the high flow state and back again. 
       FIG. 5-1  is a representation of an indexing mechanism  512 , according to at least one embodiment of the present disclosure. The indexing mechanism  512  may be in the second longitudinal piston position (e.g., second longitudinal piston position  464 - 2  of  FIG. 4-1 ). As a piston  514  and an indexing sleeve  516  are moved into the second longitudinal position, one or both of the indexing sleeve  516  and an indexing ring  520  may be rotated to place the indexing sleeve  516  and the indexing ring  520  in a first indexing alignment. In the first indexing alignment (and the second longitudinal piston position) a first sleeve stop  562 - 1  may be aligned to contact a ring stop  536  on the indexing ring  520 . An indexing pin inserted into a track  550  of an indexing track  518 . Thus, the first sleeve stop  562 - 1  may be located uphole of the ring stop  536 . 
     In some embodiments, the first sleeve stop  562 - 1  may be fixed to the indexing sleeve  516 . For example, the first sleeve stop  562 - 1  may be rotationally and longitudinally fixed to the indexing sleeve  516 . The first sleeve stop  562 - 1  may be integrally formed with the indexing sleeve  516 . For example, the first sleeve stop  562 - 1  may be machined, cast, chemically etched, or otherwise formed from a single unitary piece of the indexing sleeve  516 . In other embodiments, the first sleeve stop  562 - 1  may be attached to the indexing sleeve  516 . For example, the first sleeve stop  562 - 1  may be welded, brazed, attached with a mechanical fastener, press-fit, interference fit, or otherwise attached to the indexing sleeve  516 . In still other embodiments, the first sleeve stop  562 - 1  may be attached to the piston  514  and overlap the indexing sleeve  516 . 
       FIG. 5-2  is a cross-sectional view of a downhole tool  513 , including a cross-sectional view of the indexing mechanism  512  of  FIG. 5-1 . In the embodiment shown, the indexing mechanism  512  is in the second longitudinal piston position and the first indexing alignment. Thus, the ring stop  536  may be contacting the first sleeve stop  562 - 1 , thereby blocking downhole movement of the piston  514  and the indexing sleeve  516 . While the fluid flow  544  is in a high flow state, the piston  514  may be blocking a channel opening  543  to a fluid path  540 . This may prevent the downhole tool  513  from actuating (i.e., prevent an expandable member from expanding.) 
       FIG. 6  is a perspective view of an indexing mechanism  612  in a third longitudinal piston position, according to at least one embodiment of the present disclosure. As a piston  614  and an indexing sleeve  616  are moved into the third longitudinal piston position, the indexing ring  620  and the indexing sleeve  616  are rotated into a second indexing alignment. An indexing pin  622  connected to a ring stop  636  on the indexing ring  620  may be inserted into a track  650  of an indexing track  618 . In the second indexing alignment, the ring stop  650  may be misaligned with either a first sleeve stop  662 - 1  or a second sleeve stop  662 - 2 . 
     In some embodiments, the second sleeve stop  662 - 2  may be fixed to the indexing sleeve  616 . For example, the second sleeve stop  662 - 2  may be rotationally and longitudinally fixed to the indexing sleeve  616 . The second sleeve stop  662 - 2  may be integrally formed with the indexing sleeve  616 . For example, the second sleeve stop  662 - 2  may be machined, cast, chemically etched, or otherwise formed from a single unitary piece of the indexing sleeve  616 . In other embodiments, the second sleeve stop  662 - 2  may be attached to the indexing sleeve  616 . For example, the second sleeve stop  662 - 2  may be welded, brazed, attached with a mechanical fastener, press-fit, interference fit, or otherwise attached to the indexing sleeve  616 . In still other embodiments, the second sleeve stop  662 - 2  may be attached to the piston  614  and overlap the indexing sleeve  16 . 
     In some embodiments, the first sleeve stop  662 - 1  and the second sleeve stop  662 - 2  may be integrally formed. In other embodiments, the first sleeve stop  662 - 1  and the second sleeve stop  662 - 2  may be separate pieces, and individually attached to or formed with the indexing sleeve  616 . 
       FIG. 7-1  is a perspective view of an indexing mechanism  712  in a fourth longitudinal piston position, according to at least one embodiment of the present disclosure. As a piston  714  and an indexing sleeve  716  are moved into the fourth longitudinal piston position, at least one of an indexing ring  720  and/or the indexing sleeve are rotated into a third indexing alignment. An indexing pin  722  connected to a ring stop  736  on the indexing ring  720  may be inserted into a track  750  of an indexing track  718 . In the fourth longitudinal piston position and the third indexing alignment, the first ring stop (e.g., first ring stop  562 - 1  of  FIG. 5-2 ) may engage a ring support between two ring stops  736  on the indexing ring. In the same or other embodiments, a second sleeve stop  762 - 2  may engage the ring stop  736 . The ring stop  736  may prevent further downhole movement of the piston  714  and the indexing sleeve  716 . 
       FIG. 7-2  is a cross-sectional view of a downhole tool  713 , including a cross-sectional view of the indexing mechanism  712  of  FIG. 7-1 , according to at least one embodiment of the present disclosure. In the embodiment shown, the piston  714  and the indexing sleeve  716  are in the fourth longitudinal piston position. As may be seen, the piston  714  has uncovered the channel opening  743 , thereby allowing a portion  770  of fluid from the fluid flow  744  to enter the fluid path  740 . The portion  770  of fluid may be directed to actuate a downhole tool, such as an expandable tool. In the fourth longitudinal piston position, the first ring stop may engage a ring support between two ring stops  736  on the indexing ring. In the same or other embodiments, a ring stop  736  on the indexing ring  720  may engage the second sleeve stop  762 - 2  on the indexing sleeve  716 , thereby preventing further downhole movement of the piston  714  and the indexing sleeve  716 . 
       FIG. 8  is a cross-sectional view of a downhole tool  813 , according to at least one embodiment of the present disclosure. The downhole tool  813  may include an indexing mechanism  812 . The indexing mechanism  812  may include a piston  814 . An indexing ring  820  may surround at least a portion of the piston  814  and be rotatable relative to the piston  814 . The indexing ring  820  may be secured to a ring support  858  secured to the piston  814 . The ring support  858  may be longitudinally secured to the piston  814  such that as the piston  814  moves longitudinally, the indexing ring  820  may move longitudinally. Thus, the indexing ring  820  may be longitudinally fixed to the piston  814 . 
     An indexing sleeve  816  may be located radially outward from the indexing ring  820  and the piston  814 . The indexing sleeve  816  may abut a housing  828  of the downhole tool  813 . The indexing sleeve  816  may be rotatable relative to the housing  828 . The indexing sleeve may be longitudinally fixed to the housing  828  with an upper sleeve block  852 - 1  and a lower sleeve block  852 - 2 . As the piston  814  moves longitudinally relative to the indexing sleeve  816 , the indexing ring  820  may move longitudinally along the indexing sleeve  816 . 
     The indexing pin  822  may engage a wall  824  of an indexing track  818  of the indexing sleeve  816 . This may cause one or both of the indexing sleeve  816  and the indexing ring  820  to rotate relative to each other and the piston  814 . In this manner, the indexing track  818  may be located in an inner surface of the indexing sleeve. 
       FIG. 9  is a method chart of a method  976  for operating an indexing mechanism. The method  976  may include moving a piston from a first longitudinal piston position to a second longitudinal piston position at  978 . Moving the piston may include moving an indexing sleeve from the first longitudinal piston position to the second longitudinal piston position, the indexing sleeve encasing at least a portion of the piston. Moving the piston may include increasing a fluid flow from a first flow rate to a second flow rate, the second flow rate being higher than the first flow rate. 
     The method  976  may include rotating at least one of an indexing sleeve and/or an indexing ring relative to the piston at  980  to an alignment. Rotating the indexing sleeve and/or the indexing ring may be in response to the longitudinal movement of the piston and/or the indexing sleeve. For example, moving the piston and the indexing sleeve longitudinally may cause an indexing pin located in a ring stop of the indexing ring to engage an indexing track of the indexing piston. This may apply a torque to the indexing ring and the indexing sleeve, thereby causing one or both of the indexing ring and the indexing sleeve to rotate. The indexing track of the indexing piston may be shaped such that at least one of the indexing sleeve and/or the indexing track may rotate to self-align or automatically align stopping or positioning features on the indexing mechanism. For example, the indexing sleeve may include a sleeve stop and the indexing ring may include a ring stop, and the indexing track may be shaped to align the sleeve stop with the ring stop such that the sleeve stop may contact the ring stop. In other examples, the indexing sleeve may include the sleeve stop and the indexing ring may include a gap between two ring stops, and the sleeve stop may be aligned to pass through the gap between the ring stops and contact a ring support, the ring support holding the indexing ring in place. 
     In at least one embodiment, rotating at least one of the indexing sleeve and/or the indexing ring may include rotating the indexing sleeve and the indexing ring relative to each other. In the same or other embodiments, rotating at least one of the indexing sleeve and/or the indexing ring may include rotating the indexing sleeve in a first direction and the indexing ring in a second direction, the first direction being different from the second direction. Rotating at least one of the indexing sleeve and/or the indexing ring may include aligning the indexing sleeve and the indexing piston into a first indexing alignment, the first indexing alignment aligning a ring stop on the indexing ring with a first sleeve stop on the indexing sleeve such that a first sleeve stop on the indexing sleeve contacts a ring stop on the indexing ring in the second longitudinal piston position. 
     The method  976  may include engaging the aligned stopping or positioning features at  982 , which may result in the indexing sleeve being stopped in a terminal longitudinal piston position. In other words, the method  976  may include engaging the sleeve stop with the ring stop or the ring support. For example, the sleeve stop of the indexing sleeve may be aligned to engage or contact the ring stop of the indexing ring, thereby stopping the indexing sleeve in a terminal longitudinal piston position, or the second longitudinal piston position. In another example, the sleeve stop of the indexing sleeve may be aligned to engage or contact the ring support that supports the indexing ring, thereby stopping the indexing sleeve in a terminal longitudinal position, or the fourth longitudinal piston position. 
     The method  976  may further include moving the piston from the second longitudinal piston position to a third longitudinal piston position, the third longitudinal piston position being between the first longitudinal piston position and the second longitudinal position. Moving the piston may include changing the fluid flow from the second flow rate to a third flow rate, the third flow rate being between the first flow rate and the second flow rate. Moving the piston to the third longitudinal position may include rotating at least one of the indexing sleeve and/or the indexing ring relative to the piston to a second indexing alignment. 
     The method  976  may further include moving the piston from the third longitudinal piston position to a fourth longitudinal piston position, the fourth longitudinal piston position being further from the first longitudinal piston position than the second longitudinal piston position. Moving the piston may include rotating at least one of the indexing sleeve and/or the indexing ring relative to the piston to a third indexing alignment. The third indexing alignment may align the ring stop with a second sleeve stop such that the second sleeve stop contacts the ring stop in the fourth longitudinal piston position. 
     In some embodiments, a downhole tool includes a piston, an indexing sleeve encasing a portion of the piston, and an indexing ring surrounding less than an entirety of the indexing sleeve. The indexing sleeve is rotatable relative to the piston. The indexing ring includes an indexing pin extending into the indexing track. The indexing ring may be rotatable relative to the indexing sleeve. The indexing sleeve may be longitudinally fixed to the piston. The indexing sleeve and the indexing ring may rotate relative to the piston in response to a longitudinal motion of the piston. The indexing sleeve and the indexing ring may rotate relative to the piston in response to the indexing pin engaging the indexing track. The indexing ring may have a mass of 2 kg or less, and the indexing sleeve may have a mass of 8 kg or less. The indexing ring and the indexing sleeve may have a mass ratio of less than 1:4. The indexing track may include a first sleeve stop and a second sleeve stop. The first sleeve stop may engage a ring stop in a first longitudinal piston position, and may engage a ring support in a second longitudinal piston position. The second longitudinal piston position may be further uphole than the first longitudinal piston position. 
     In some embodiments, a downhole tool includes a piston, an indexing sleeve with an indexing track, and an indexing ring surrounding a portion of the indexing sleeve. The indexing sleeve encases a portion of the piston. The indexing ring includes a ring stop and an indexing pin extending into the indexing track. The indexing ring is rotatable relative to the piston. The indexing pin may be located in the ring stop. The indexing sleeve may include a sleeve stop located uphole of the ring stop. The sleeve stop may engage the ring stop in a high flow state. The indexing ring may extend less than 10% of length of the piston. 
     In some embodiments, a method for operating an indexing mechanism includes moving a piston from a first longitudinal piston position to a second longitudinal piston position, and rotating at least one of an indexing sleeve or an indexing ring relative to the piston to a first indexing alignment. The indexing sleeve encases less than an entirety of the piston and the indexing ring surrounds a portion of the indexing sleeve. The first indexing alignment aligns a ring stop on the indexing ring with a first sleeve stop on the indexing sleeve such that the first sleeve stop engages the ring stop in the second longitudinal piston position. The method may include moving the piston from the second longitudinal piston position to a third longitudinal piston position that is between the first longitudinal piston position and the second longitudinal piston position. The method may include rotating at least one of the indexing sleeve or the indexing ring relative to the piston to a second indexing alignment. The method may also include moving the piston from the third longitudinal piston position to a fourth longitudinal piston position that is further from the first longitudinal piston position than the second longitudinal piston position. The method may include rotating at least one of the indexing sleeve or the indexing ring relative to the piston to a third indexing alignment, the third indexing alignment aligns the ring stop with a second sleeve stop such that the second sleeve stop contacts the ring stop in the fourth longitudinal piston position. The method may include rotating at least one of the indexing sleeve or the indexing ring by rotating the indexing ring relative to the indexing sleeve. The method may include rotating at least one of the indexing sleeve or the indexing ring by rotating the indexing sleeve in a first direction and rotating the indexing ring in a second direction that is different than the first direction. 
     The embodiments of the indexing mechanism have been primarily described with reference to wellbore drilling operations; the indexing mechanisms described herein may be used in applications other than the drilling of a wellbore. In other embodiments, indexing mechanisms according to the present disclosure may be used outside a wellbore or other downhole environment used for the exploration or production of natural resources. For instance, indexing mechanisms of the present disclosure may be used in a borehole used for placement of utility lines. Accordingly, the terms “wellbore,” “borehole” and the like should not be interpreted to limit tools, systems, assemblies, or methods of the present disclosure to any particular industry, field, or environment. 
     One or more specific embodiments of the present disclosure are described herein. These described embodiments are examples of the presently disclosed techniques. Additionally, in an effort to provide a concise description of these embodiments, not all features of an actual embodiment may be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous embodiment-specific decisions will be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which may vary from one embodiment to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure. 
     The articles “a,” “an,” and “the” are intended to mean that there are one or more of the elements in the preceding descriptions. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Additionally, it should be understood that references to “one embodiment” or “an embodiment” of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. For example, any element described in relation to an embodiment herein may be combinable with any element of any other embodiment described herein. Numbers, percentages, ratios, or other values stated herein are intended to include that value, and also other values that are “about” or “approximately” the stated value, as would be appreciated by one of ordinary skill in the art encompassed by embodiments of the present disclosure. A stated value should therefore be interpreted broadly enough to encompass values that are at least close enough to the stated value to perform a desired function or achieve a desired result. The stated values include at least the variation to be expected in a suitable manufacturing or production process, and may include values that are within 5%, within 1%, within 0.1%, or within 0.01% of a stated value. 
     A person having ordinary skill in the art should realize in view of the present disclosure that equivalent constructions do not depart from the spirit and scope of the present disclosure, and that various changes, substitutions, and alterations may be made to embodiments disclosed herein without departing from the spirit and scope of the present disclosure. Equivalent constructions, including functional “means-plus-function” clauses are intended to cover the structures described herein as performing the recited function, including both structural equivalents that operate in the same manner, and equivalent structures that provide the same function. It is the express intention of the applicant not to invoke means-plus-function or other functional claiming for any claim except for those in which the words ‘means for’ appear together with an associated function. Each addition, deletion, and modification to the embodiments that falls within the meaning and scope of the claims is to be embraced by the claims. 
     The terms “approximately,” “about,” and “substantially” as used herein represent an amount close to the stated amount that still performs a desired function or achieves a desired result. For example, the terms “approximately,” “about,” and “substantially” may refer to an amount that is within less than 5% of, within less than 1% of, within less than 0.1% of, and within less than 0.01% of a stated amount. Further, it should be understood that any directions or reference frames in the preceding description are merely relative directions or movements. For example, any references to “up” and “down” or “above” or “below” are merely descriptive of the relative position or movement of the related elements. 
     The present disclosure may be embodied in other specific forms without departing from its spirit or characteristics. The described embodiments are to be considered as illustrative and not restrictive. The scope of the disclosure is, therefore, indicated by the appended claims rather than by the foregoing description. Changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.