Patent Publication Number: US-2023139055-A1

Title: Hydraulic cylinder with a side load sensor retention pin

Description:
TECHNICAL FIELD 
     The present application relates generally to hydraulic systems such as those used on work machines including excavators, trucks, or other heavy equipment for construction, farm implements, and other machines adapted for performing work. More particularly, the present application relates to a securing mechanism for a sensor on a hydraulic cylinder. Still more particularly, the present application relates to a side load retention pin for retaining a position sensor within a hydraulic cylinder. 
     BACKGROUND 
     Position sensors may be arranged in hydraulic cylinders to monitor the position of the piston within the cylinder and, as such, allow for monitoring the extension and retraction of the piston rod extending out of a rod end of a hydraulic cylinder. These sensors may be secured in place using set screws that extend through the cap end of the hydraulic cylinder in an orientation generally perpendicular to an outer surface of the sensor. That is, the set screws may be arranged about a peripheral surface of the cap end of the hydraulic cylinder and may extend radially into and through a housing of the hydraulic cylinder to engage the outer surface sensor. Set screws can suffer from several different problems. In some cases the set screws simply do not get installed. In other cases, they are not torqued enough to maintain a tight grip on the sensor. In still other situations, and where a peripheral groove is provided, the set screw may fail to engage the groove because the sensor may not be fully in position when the set screw is placed. 
     U.S. Pat. No. 9,482,245 relates to a cylinder length sensor mounting/retaining assembly. The assembly includes a casing attachable to a blind end of the cylinder, a sensor retention cap affixable to the casing adjacent the blind end of the cylinder, and a locking pin extendable through the casing and positioned adjacent the sensor retention cap. 
     SUMMARY 
     In one or more embodiments, a hydraulic cylinder may include a housing and a rod extending from a working end positioned outside the housing through a rod end of the housing to a piston end positioned within the housing. The hydraulic cylinder may also include a piston arranged on the piston end of the rod and configured to articulate within the housing. The hydraulic cylinder may also include a cap end secured to the housing and having a pocket for receiving a sensor. The pocket may have a cylindrical sidewall. The cap end may include a bore extending therethrough and arranged generally tangential to the sidewall where the bore extends into the cap end, breaches the sidewall, and extends further passed the pocket. The hydraulic cylinder may also include a retention pin configured for placement in the bore and for an interference fit with the sensor when the sensor is arranged in the pocket. 
     In one or more embodiments, a housing for a hydraulic cylinder may include a cap end comprising a pocket for receiving a sensor. The pocket may have a cylindrical sidewall. The cap end may have a bore extending therethrough and arranged generally tangential to the sidewall. The bore may extend into the cap end, breach the sidewall, and extend further passed the pocket. 
     In one or more embodiments, a retention pin may include a pinhead, a fastening portion distal to the pinhead and comprising a threaded engagement. The retention pin may also include a shaft portion distal to the fastening portion and configured for an interference fit with a retention groove on a sensor of a hydraulic cylinder. The retention pin may also include a positioning tip distal to the shaft portion and configured for free engagement with the retention groove. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective partial breakaway view of a hydraulic cylinder having a sensor and a side load retention pin arranged therein, according to one or more embodiments. 
         FIG.  2    is a perspective view of a sensor, according to one or more embodiments. 
         FIG.  3    is a perspective view of the retention pin, according to one or more embodiments. 
         FIG.  4    is a distal end view of the retention pin and its engagement with a retention groove on a sensor, according to one or more embodiments. 
         FIG.  5    is a side view of the distal end of the retention pin and its engagement with the retention groove on a sensor, according to one or more embodiments. 
         FIG.  6    is a side view of the distal end of the retention pin and its engagement with the retention groove on a sensor, according to one or more embodiments. 
         FIG.  7    is a partial breakaway view of a bore for in the cap end of a cylinder for receiving the retention pin, according to one or more embodiments. 
         FIG.  8    is a block diagram depicting a method of assembling a hydraulic cylinder with a side load retention pin, according to one or more embodiments. 
         FIG.  9    is a perspective view of a cap end of a hydraulic cylinder with a retention pin engaged with a sensor allowing the threads to drive the pin into position. 
         FIG.  10    is a perspective view of a cap end of a hydraulic cylinder with a retention pin stopped short of engagement with a sensor preventing the threads from being used to drive the pin into position. 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    is a perspective and partial breakaway view of a cap end  112  of a hydraulic cylinder  100 . The hydraulic cylinder  100  may be configured to extend and retract and may be present on a work machine, for example. Work machines may include excavators, trucks with articulating truck beds, skid steers, or other work machines having hydraulic systems. The hydraulic cylinder  100  may be adapted, for example, to control the position of one or more articulating elements on the work machine. 
     With continued reference to  FIG.  1   , the hydraulic cylinder  100  may include a housing  102 , a rod  104 , a piston  106 , and one or more ports  108  for delivering and/or receiving hydraulic fluid from the hydraulic cylinder  100 . A sensor  110  may be arranged within the cap end  112  of the cylinder  100  and may be secured with a pin  114 . It is to be appreciated that the location of the breakaway of  FIG.  1    may not reveal the pin  114  if the breakaway is along the centerline of the cylinder  100 . That is, as described in more detail herein, the pin  114  is offset from the centerline so as to tangentially engage the sensor. However, for purposes of general orientation of the parts, the pin  114  is shown in  FIG.  1   . 
     The housing  102  may be configured to contain and withstand relatively high fluid pressures and guide the piston  106  along a pathway allowing the piston  106  to articulate back and forth through a stroke length based on fluid flow on one more sides of the piston  106 . The housing  102  may include a cylinder wall  116  defining a longitudinally extending cylindrical chamber  117 . The housing  102  may also include a cap end  112  and a rod end  120 . The cap end  112  may be a substantially closed end of the cylinder. A port  108  may be provided near the cap end for introduction and ejection of hydraulic fluid. The cap end  112  may include a cap eye  118  for securing the hydraulic cylinder  100  to the work machine. In one or more embodiments, the cap eye  118  may include an eye for receiving a pin or bolt allowing the hydraulic cylinder  100  to pivot relative to its connection to the work machine or implement of the work machine. The rod end  120  may close off of the end of the cylinder with respect to the piston  106  and the hydraulic fluid, but may include a sealed opening  122  for passing through of the rod  104 . Like the cap end  112 , a port  108  may be provided near the rod end  120  for introduction and ejection of hydraulic fluid. 
     The rod  104  may be secured to the piston  106  and may include a longitudinal element having a diameter smaller than the housing  102  and adapted for sleevably articulating within the housing  102  based on articulation of the piston  106 . The rod  104  may be secured to the piston  106  at a piston end, may extend through the rod end  120  of the housing  102  to a working end, and may include an eye or other attachment feature on the working end. The eye or other attachment feature may allow the rod  104  to be secured to the work machine  100  or an implement of the work machine  100  and the eye may provide for pivoting motion of the connection by way of a pinned or bolted connection, for example. 
     The piston  106  may be arranged within the housing  102  and may be adapted to articulate through the housing  102  based on fluid flow into and out of the housing  102  on either side of the piston. In one or more embodiments, the piston  106  may be a cylindrical element having an outer diameter only slightly smaller than the inner diameter of the cylinder wall  116  of the housing  102 . One or more seals  124  may be arranged on the piston  106  to provide the sealing engagement with the inner surface of the housing  102 . The piston  106  may include a through bore for receiving and engaging the rod  104 . For example, the piston  106  may threadably engage the rod  104  and, as such, may include a threaded through bore adapted to threadably secure the piston  106  to the rod  104 . 
     Depending on the nature of the rod/piston connection and whether the rod extends fully through the piston, both the rod and the piston or just the rod may include a bore for receiving a sensing pipe  126  of the sensor  110 . The bore may extend deep into the rod  104  in the form of a gun drilled bore. The bore may allow the piston  106  and the rod  104  to sleevably articulate over the sensing pipe  126 . 
     The port or ports  108  of the hydraulic cylinder  100  may be adapted to deliver and receive hydraulic fluid from the hydraulic cylinder  100  and may be arranged at opposite ends of the housing  102  (i.e., one at the cap end  112  and one at the rod end  120 ). The ports  108  may provide for connection of hydraulic fluid lines and may provide the pathway for hydraulic fluid to enter and exit the hydraulic cylinder  100 . 
     The cap end  112  of the cylinder  100  may be adapted for securing the cylinder  100  to the work machine or an implement thereof, containing cylinder pressure. As shown, the cap end  112  may include a bulkhead casting adapted for securing to the housing  102 . As shown, the bulkhead casting may be welded to the cylinder wall  116  at a circumferentially extending weld  128 . The bulkhead casting may include a piston stop surface  130 . 
     Referring to  FIG.  2   , the sensor  110  may include a puck-shaped housing  132  configured for arrangement in the cap end  112  of the hydraulic cylinder  100 . The sensor  110  may also include a sensing pipe  126  extending from the puck-shaped housing  132  and into and along the length of the cylinder  100 . The puck-shaped housing  132  may enclose and protect sensor elements that energize the sensing pipe  126  and/or receive information or signals from the sensing pipe  126  relating to the position of the piston  106  and/or the rod  104  along the sensing pipe  126 . The puck-shaped housing  132  may include a substantially circular cap side  134  and a substantially circular cylinder side  136 . The cylinder side  136  may have the sensing pipe  126  extending therefrom and a collar or other sensing pipe support or collar may be provided. The cap side  134  may include a wire port for passing wires or other communication lines out of the puck-shaped portion  132  of the sensor  110 . The peripheral portion of the puck-shaped element  132  may include a substantially cylindrical outer wall  140  with a height  142 . The outer wall  140  may include a retention groove  144  and a seal groove  146 , each extending peripherally around the cylindrical outer wall  140  of the puck-shaped element  132 . The seal groove  146  may be adapted to receive an O-ring, for example, and the retention groove  144  may be adapted for engagement by a retention pin  114 . In one or more embodiments, the seal groove  146  may include a substantially rectangular cross-section and the retention groove  144  may include a trapezoidal shape with sloping sidewalls and a flat bottom where the groove  144  is wider at the surface of the outer wall  140  and narrower at the bottom of the groove  144 . 
     As may be appreciated from a review of  FIG.  1   , the articulating motion of the piston  106  and rod  104  within the cylinder housing  102  may occur based on relatively high pressures acting on the piston  106 . As such, maintaining the sensor  110  in a protected position and out of the way of the piston/rod motion may be helpful for the longevity of the sensor  110 . To this end, the cap end  112  of the cylinder may be adapted for accommodating a sensor  110 . That is, the cap end  112  may include a pocket  148  for receiving a sensor  110 . As shown, the pocket  148  may include a substantially cylindrically shaped pocket with a cylindrical sidewall  150  for receiving the sensor  110 . The pocket  148  may have a lateral width or diameter  152  adapted to receive the sensor  110  with limited tolerance around the sensor  110  such that an O-ring or other seal  154  on the sensor  110  may engage the sidewall  150  and create a seal between the piston/rod chamber  117  of the cylinder  100  and the back side of the sensor  110 . The pocket  148  may have a depth for substantially fully seating the puck-shaped portion  132  of the sensor  110  in the pocket  148  to avoid contact with the articulating piston  106 . That is, the longitudinal length  156  (e.g., in the direction of longitudinal articulation of the piston) of the sidewall  150  of the pocket  148  may be the same, similar, or slightly larger than the height  142  of the cylindrical outer wall  140  of the puck-shaped element  132 . An annular surface or shoulder  158  may be provided at the bottom of the pocket  148  against which the sensor  110  may be seated. The annular surface or shoulder  158  may give way to a cavity  160  behind the pocket  148  for routing of wiring or communication lines from the sensor  110  through and out of the cap end  112  of the cylinder  100 . 
     The sensor  110  may be retained in the pocket  148  with a retention pin  114 . The retention pin  114  may extend through the cap end  112  of the cylinder  100  and may engage the retention groove  144  on the outer cylindrical wall  140  of the sensor  110  to retain the sensor  110  in position in the pocket  148 . More particularly, the retention pin  114  may be arranged in a bore  162  that extends through the cap end  112  of the cylinder  100 . The bore  162 , and the pin  114  arranged therein, may be oriented substantially tangentially to the outer cylindrical wall  140  of the sensor  110  so that the side of the pin  114  engages the retention groove  144  of the sensor  110  in a cradling fashion. Moreover, various particular features of the bore  162 , the bore position, the bore size, the pin size, and the pin geometry may provide for several installation and retention advantages. 
     Beginning with the retention pin  114 , and with reference to  FIG.  3   , the pin  114  may include a positioning tip  164 , a shaft portion  166 , a fastening portion  168 , a seal groove  169 , and a pinhead  170 . The positioning tip  164  may be arranged at a distal most end of the retention pin  114 . The positioning tip  164  may have a diameter  172  selected for allowing the positioning tip  164  to slip relatively freely into the retention groove  144  of the sensor  110  when the sensor  110  is fully seated in the pocket  148 , or positioned against the shoulder  158  of the pocket  148 , such that the retention groove  144  of the sensor  110  is aligned with the bore  162 . That is, as shown in  FIG.  4   , the relationship of the center of the bore  162 , the size of the bore  162 , and the size of the positioning tip  164  may be selected to align the positioning tip  164  with the retention groove  144  and allow for generally resistance free motion of the positioning tip  164  into and/or across the groove  144  when the sensor  110  is fully seated. The positioning tip  164  may also be large enough that when the sensor  110  is not fully seated, the positioning tip  164  will not pass into the retention groove  144  and will, instead, contact the outside surface of the sensor housing  132 . That is, as shown in  FIG.  4   , when the positioning tip  164  is in the groove  144 , it may engage the sidewalls of the groove  144  in cradling fashion. That is, the diameter  172  of the positioning tip  164  may be large enough to avoid bottoming out in the groove  144  without also contacting both sidewalls of the groove  144 . In one or more embodiments, the positioning tip  164  may include a diameter  172  ranging from approximately 6 mm to approximately 12 mm, or from approximately 7 mm to approximately 10 mm, or a diameter of approximately 8 mm may be provided. The positioning tip may have a length  174  selected to be long enough to provide a positioning function (e.g., reach into the retention groove  144 ) before the shaft portion  166  engages the sensor  110 . That is, for example, as shown in  FIG.  5   , the length  174  of the positioning tip  164  may be selected to pass into the groove  144  and at least slightly passed the tangent point  176  before the shaft portion  166  with a wider diameter engages the edges of the retention groove  144 . As such, given the tangential nature of the engagement, the positioning tip  164  may have a length  174  ranging from approximately 12 mm to approximately 30 mm or from approximately 16 mm to approximately 24 mm, or a length of approximately 20 mm may be provided. 
     The shaft portion  166  of the retention pin  114  may be adapted to extend from a fastening portion  168  of the retention pin  114 , through the bore  162 , and across the side of the sensor  110  when the retention pin  114  is fully seated in the bore  162 . In contrast to the positioning tip  164 , the shaft portion  166  may be sized and positioned for an interference fit with the retention groove  144 . That is, and with reference to  FIG.  6   , the relationship of the center of the bore  162 , the size of the bore  162 , and the size of the shaft portion  166  may be selected to cause the shaft portion  166  to deflect as it is forced across the tangent point  176  and engages the retention groove  144 . Moreover, and as shown in  FIG.  4   , the diameter  178  of the shaft portion  166  may be selected to engage the sloping surfaces of the trapezoidal-shaped groove  144  without contacting the bottom of the groove  144  (e.g., a cradling engagement). That is, were a smaller diameter to be used, the shaft portion  166  may rest on the bottom of the groove  144  and may allow the sensor  110  to move longitudinally along the cylinder  100  and relative to the pin  114  before the pin  114  would engage the sloping walls of the groove  144 . In one or more embodiments, the shaft portion  166  of the retention pin  114  may have a diameter  178  that is slightly larger than the positioning tip  164  to create the interference fit and a chamfered transition  180  between the positioning tip  164  and the shaft portion  166  may be provided. In one or more embodiments, the shaft portion  166  may have a diameter  178  ranging from approximately 6 mm to approximately 12 mm, or from approximately 7 mm to approximately 10 mm, or a diameter of approximately 8.5 mm may be provided. The shaft portion  166  may have a length  182  selected to allow engagement of threads on a fastening portion  168  of the retention pin  114  to engage threads on a corresponding fastening portion of the bore  162  when the positioning tip  164  is arranged in the retention groove  144  and the distal end of the shaft portion  166  has engaged a side of the sensor  110  as shown in  FIG.  5   . As shown in  FIG.  9   , this may allow the use of the threads to further drive the shaft portion  166  into its interference fit condition with the sensor  110  as shown in  FIG.  6   . However, and as mentioned, when the sensor  110  is not fully seated in the pocket  148 , the positioning tip  164  may not pass into the retention groove  144  and the threads of the fastening portion  168  of the retention pin  114  may not engage the threads on a corresponding fastening portion of the bore  162  as shown in  FIG.  10   . 
     It is to be appreciated that while the shaft portion  166  may deflect to create an interference fit with the retention groove  144 , the deflection may be limited to elastic deflection of the shaft portion  166 . That is, the shaft portion  166  may deflect, but the relative positions and diameters mentioned may be selected to avoid stresses in the shaft portion that exceed the yield strength of the shaft portion material such that any deformations are temporary while the pin is in place and go away as the pin is removed. This may allow for the retention pin  114  to be smoothly removed from the bore  162  without hanging up on or getting caught on the sidewalls of the bore  162  due to more permanent deformations. 
     The fastening portion  168  of the retention pin  114  may include a threaded collar arranged proximal to the shaft portion  166 . The threaded collar may be slightly larger than the shaft portion  166  or the same size as the shaft portion  166 . In one or more embodiments, a larger collar may provide for better control over the alignment of the retention pin  114  with the bore  162  and stronger rotational strength for resisting the bending forces is the shaft portion  166 . Moreover, in one or more embodiments, a larger threaded collar may provide an annular surface on a bottom side thereof that may receive an O-ring where tightening of the pin  114  causes the O-ring to engage an opposing annular surface and create a seal for the connection. In other embodiments, a seal groove  169  between the fastening portion  168  and the pin head  170  may be provided to receive an O-ring that engages a collar on the bore  162  an outboard side of the fastening portion  168 . In one or more embodiments, for example, the connection may be a straight-thread O-ring (STOR) connection. While a threaded engagement between the fastening portions of the retention pin  114  and bore  162  has been described, a push fit connection, laterally extending pin, or other fastening mechanisms adapted to avoid motion of the pin  114  in a lateral direction (e.g., lateral to the cylinder  100  and longitudinal along the retention pin  114 ) may also be provided. 
     The pin head  170  may extend proximally from the fastening portion  168  and may be adapted for manipulating the retention pin  114  when the pin  114  is being inserted or removed from the bore  162 . In one or more embodiments, the pin head  170  may include an internal or external tool engagement feature, such as an internal hex-shaped recess or an external hex-shaped outer surface. Still other tool engagement features may be provided such a square recess, square outer surface, star-shaped recess, straight slot, crossing slot, or other took engagement feature. 
     Turning now to the details of the bore  162  that the retention pin  114  may be inserted into. The bore  162  may extend through the cap end  112  of the cylinder  100  and may include a series of stages adapted for particular types of interfacing with the retention pin  114 . As shown in  FIG.  7   , the bore  162  may include a sleeve portion  184 , a fastening portion  186 , and a pinhead counterbore  188 . 
     The sleeve portion  184  may extend from a fastening portion  186  of the bore  162 , further into the cap end  112  of the cylinder  100  toward the pocket  148 . As mentioned, the bore  162  and, thus, the sleeve portion  184  thereof, may be arranged generally tangential to the cylindrical outer wall  140  of the sensor  110  and, as such, generally tangential to the sidewall  150  of the pocket  148 . As shown in  FIG.  7   , the sleeve portion  184  may breach the sidewall  150  of the pocket exposing the retention pin  114  to the sensor  110  and may further extend beyond the pocket  148 . More particularly, the centerline  190  of the sleeve portion  184  may have an offset distance  199  relative to a tangent point  176  on the sensor  110 . For example, and with reference to  FIG.  4   , the centerline  190  of the sleeve portion  184  may be determined giving consideration to the gap  192  between the bottom of the retention groove  144  and the diameter  172  of the positioning tip  164  of the retention pin  114 . Moreover, the tolerance or gap  194  between the cylindrical outer wall  140  of the sensor  110  and the sidewall  150  of the pocket  148  may be considered to determine the offset distance  196  of the sleeve portion centerline  190  from a tangent point  198  of the sidewall  150 . In one more embodiments, for example, the centerline  190  of the bore  162  may be offset approximately 3.25 mm from a tangent point  198  of the sidewall  150  of the pocket  148  and approximately 4.5 mm from the bottom surface or tangent point  176  of the retention groove  144  on the sensor  110 . Other particular offset distances  196 / 199  of the centerline  190  of the sleeve portion  184  of the bore  162  may be provided giving consideration to the size of the positioning tip  164  of the retention pin  114 , the cradled relationship of the positioning tip  164  in the retention groove  144  and the gap  194  between the sensor  110  and the sidewall  150  of the pocket  148 . 
     The sleeve portion  184  may be adapted to receive the positioning tip  164  and the shaft portion  166  of the retention pin  114 . As such, the sleeve portion  184  may have a diameter or other crossing dimension  200  larger than the diameter or other crossing dimension  178  of the shaft portion  166  of the retention pin  114  and large enough to allow a particular amount of lateral deflection of the shaft portion  166  of the retention pin  114 . That is, as mentioned above, the interference fit of the shaft portion  166  with the sensor  110  may cause the shaft portion  166  to deflect slightly as it engages the sensor  110 . The sleeve portion  184  of the bore  162  may have a diameter or other crossing dimension  200  that is large enough to accommodate this deflection. However, the diameter or other crossing dimension  200  of the sleeve portion  184  may also be selected to limit the deflection of the retention pin  114  such that the pin  114  is unable to move fully out of the retention groove  144  due to contact with an opposing wall of the sleeve portion  184 . In this way dislodgement of the sensor  110  may be avoided. In one or more embodiments, the sleeve portion  184  may have a diameter ranging from approximately 6.5 mm to approximately 12.5 mm, or from approximately 7.5 mm to approximately 10.5 mm, or a diameter of approximately 9 mm may be provided. 
     The fastening portion  186  of the bore  162  may be configured for engagement by the fastening portion  168  of the retention pin  114  and may provide for seated engagement of the fastening portion  168  of the retention pin  114 . In one or more embodiments, as shown, the fastening portion  186  may include a bore having a larger diameter or crossing dimension  202  than the sleeve portion  184  and providing an annular seat at a top of the sleeve portion  184 . This annular seat may be adapted for engagement by an O-ring on a bottom of an opposing annular surface of the retention pin  114 . In other embodiments, the fastening portion  186  may have a collar on an outboard side thereof that is adapted for engagement of an O-ring arranged between the fastening portion  168  and the pinhead  170  of the retention pin  114 . The peripheral wall of the fastening portion  186  of the bore  162  may include a threaded surface for engagement with threads on the retention pin  114  and the fastening portion  186  may have a depth sufficient to accommodate the fastening portion  168  of the retention pin  114 . It is to be appreciated that where fastening mechanisms other than threads are provided on the retention pin  114 , alternative shapes and features may be provided on the fastening portion  186  of the bore  162  that correspond to those features. 
     The pinhead counterbore  188  may include yet a larger portion of the bore having a diameter or other crossing dimension  204  larger than fastening portion  186 . The diameter or crossing dimension  188  of the pinhead counterbore  188  may be selected based on the type of retention pin head  170  that is provided. For example, where an external tool engagement feature is provided on the retention pin  114 , a wider counterbore  188  may be provide to allow sockets or wrenches to access the outer surface of the pinhead  170 . Where internal or recessed tool engagement features are provided on the retention pin  114 , a smaller or narrower counterbore  188  may be provided. 
     INDUSTRIAL APPLICABILITY 
     In operation and use, the present side load retention pin system may provide for retaining sensors within the hydraulic cylinder. The prominent nature of the retention pin may make the pin unlikely to be omitted like set screws. Moreover, the interference fit of the retention pin and the sealing type fastening port may help avoid insufficiently tight retention systems. Finally, the positioning tip of the retention pin may help to make sure the sensor is fully seated in the pocket before the retention pin is advance into position. 
     In one of more embodiments, a method  300  of assembling a cap end of a hydraulic cylinder may be provided as shown in  FIG.  8   . In one or more embodiments, the method may include casting, machining, or casting and machining a cap end of a cylinder  302 . The casting or machining may include creating a pocket in the cap end for receiving a sensor  304  and creating a bore in the cap end for receiving the retention pin  306 . The various feature of the pocket and the bore mentioned above may be incorporated into these elements. The method may also include placing a sensor in the pocket of the cap end  308  such that the sensor is seated against the annular surface or shoulder on a bottom of the pocket. The method may also include inserting a retention pin into the bore from an outside of the cap end of the cylinder  310 . The sensor may be held in its fully seated position such that the positioning tip of the retention pin passes through the sleeve portion of the bore and slides relatively freely into the retention groove along the cylindrical outer surface of the sensor  312 . Where the sensor has become unseated, the positioning tip of the retention pin may engage the cylindrical outer wall of the sensor and the threads on the retention pin may stop short of engaging the threads on the fastening portion of the bore, thereby preventing further forced advancement of the retention pin. Adjustment of the sensor may be performed to allow the positioning tip of the retention pin engage the retention groove thereby allowing the threads of the retention pin to engage the threads of the bore  314 . The retention pin may be further advanced across the sensor by engaging the pinhead with a tool and threading the retention pin into its fully seated position where the O-ring seal on the fastener engages the port on the bore and creates a seal  316 . The advancing of the retention pin may cause engagement of the retention groove by the shaft portion of the retention pin. The shaft portion may engage the sensor in an interference fit and may deflect laterally thereby applying a normal force on the retention groove of the sensor at the tangent point. The shaft portion may engage the retention groove in a cradling fashion, engaging the sloping walls of the retention groove without engaging the bottom of the groove and, as such, preventing or resisting longitudinal movement of the sensor in two directions. The cap end of the cylinder may be welded onto the housing of the hydraulic cylinder to close the cap end of the cylinder  318 . 
     The above detailed description is intended to be illustrative, and not restrictive. The scope of the disclosure should, therefore, be determined with references to the appended claims, along with the full scope of equivalents to which such claims are entitled.