Abstract:
A method and apparatus for detecting the position of a rod member of a cylinder assembly are provided. The cylinder assembly may have a cylinder body with a cylinder chamber therein, a gland member disposed within the cylinder chamber, and a rod member movably arranged within the cylinder chamber and a rod opening of the gland member. The method may include moving the gland member within the cylinder chamber to substantially align a gland aperture of the gland member with a cylinder aperture of the cylinder body; substantially fixing the gland member relative the cylinder body; positioning a position sensor within at least one of the cylinder aperture and the gland aperture; moving the rod member within the rod opening of the gland member and the cylinder chamber of the cylinder body; and operating the position sensor to detect the position of the rod member.

Description:
TECHNICAL FIELD  
       [0001]     The present invention relates generally to a mount for a position sensor and, more particularly, to a cylinder assembly with a position sensor mounted thereto.  
       BACKGROUND  
       [0002]     Expansible chamber hydraulic cylinders having moveable piston-and-rod assemblies therein are widely used on industrial, earthmoving, and material handling machines and vehicles. It may be advantageous for such a machine or vehicle to include an automatic control system for automatically controlling the extension or retraction of a piston-and-rod assembly within a hydraulic cylinder so that partially or totally automatic work operations may be performed. In one type of automatic control system, a position sensor may be attached to a hydraulic cylinder to determine the position of the piston-and-rod assembly within the cylinder. One challenge with using such a position sensor is creating a robust, accurate, and affordable mount and mounting method for coupling the position sensor with the hydraulic cylinder.  
         [0003]     International Patent Application No. PCT/FI93/00285, International Publication No. WO 95/01510, discloses a hydraulic cylinder with means for determining the position of a piston rod relative to a cylinder sleeve. The means consist of (i) optically readable marks provided on the surface of the piston rod and (ii) a reading device for reading the marks. The reading device is supported on the cylinder sleeve and is positioned in a mechanically protected structure, which constitutes part of a sealing/bearing end piece of the cylinder.  
         [0004]     U.S. Pat. No. 5,455,509, issued to Semura et al., discloses a device for mounting a position-detecting sensor to a hydraulic cylinder. Semura discloses a piston rod with a magnetic scale formed on the outer surface thereof and a magnetic sensor mounted on a cylinder head proximate the magnetic scale for detecting the magnetic scale and determining the position of the piston rod. The sensor is mounted on a block, and the block is mounted on the head of the cylinder by a plurality of bolts.  
         [0005]     Prior sensor mounting devices and methods may be improved by providing better arrangements and methods for mounting a sensor in proper alignment with detectable features formed on the rod of a cylinder assembly. For example, if (i) detectable features are disposed along the length of a rod member, (ii) the rod member is assembled in a predetermined rotational orientation within a cylinder body, and (iii) a sensor is mounted in a predetermined orientation on a head or gland member, the gland member must be assembled in a predetermined rotational orientation relative the cylinder body in order for the sensor to be properly rotationally aligned with the detectable features of the rod. However, when a threaded gland member is threaded into a threaded end of a cylinder body, the threaded gland member is typically threaded very tightly into the end of the cylinder body so that a frictional engagement is created between a flange portion of the gland member and the end of the cylinder body. The frictional engagement creates a frictional force sufficient to hold the gland member in position relative the cylinder body during operation of the cylinder assembly. The final rotational position of the gland member relative the cylinder body (and relative the detectable features of the rod) is often difficult to predict or predetermine since (i) the final position of the gland member relative the cylinder body will ultimately depend upon the arrangement of the threads of the gland member relative the flange portion thereof and relative the threads of the cylinder body, and (ii) it is often difficult and/or expensive to manufacture threaded glands and threaded cylinder bodies so that the threads thereof are consistently arranged and engaged exactly as desired.  
         [0006]     Further, prior sensor mounting devices and methods may be improved by providing better arrangements and methods for maintaining the alignment of a sensor with detectable features on a cylinder assembly during operation of the cylinder assembly.  
         [0007]     The present invention is directed at overcoming one or more problems or disadvantages associated with prior sensor-mounting devices and methods.  
       SUMMARY OF THE INVENTION  
       [0008]     In one aspect of the present invention, a cylinder assembly is provided. The cylinder assembly may include a cylinder body having a longitudinally arranged cylinder chamber therein, and having a cylinder aperture in the cylinder body, the cylinder aperture intersecting the cylinder chamber. The cylinder assembly may further include a gland member having a rod opening therein, the gland member being disposed within the cylinder chamber of the cylinder body, the gland member having a gland aperture therein, the gland aperture intersecting the rod opening, and the gland aperture being arranged in substantial alignment with the cylinder aperture. The cylinder assembly may also include a rod member movably arranged within the cylinder chamber and the rod opening and a position sensor disposed within at least one of the cylinder aperture and the gland aperture.  
         [0009]     In another aspect of the present invention, a cylinder assembly is provided. The cylinder assembly may include a cylinder body having a longitudinally arranged cylinder chamber therein, a first threaded area on the cylinder body, and a cylinder aperture in the cylinder body, the cylinder aperture intersecting the cylinder chamber. The cylinder assembly may further include a gland member having a rod opening therein, the gland member being disposed within the cylinder chamber of the cylinder body, the gland member having a second threaded area on the gland member, the second threaded area being threadedly engaged with the first threaded area of the cylinder body. The cylinder assembly may further include a rod member movably arranged within the cylinder chamber of the cylinder body and the rod opening of the gland member, the rod having one or more detectable features disposed along the length of the rod member; a position sensor attached to at least one of the cylinder body and the gland member and arranged in general alignment with a path of the one or more detectable features, the position sensor being operable to detect the one or more detectable features; and a stake member arranged within the cylinder aperture and engaging the gland member, the stake member being operable to substantially rotationally fix the gland member relative the cylinder body.  
         [0010]     In a further aspect of the invention, a method for detecting the position of a rod member of a cylinder assembly may be provided. The cylinder assembly may have (i) a cylinder body with a longitudinally arranged cylinder chamber in the cylinder body and a cylinder aperture in the cylinder body, the cylinder aperture intersecting the cylinder chamber, (ii) a gland member disposed within the cylinder chamber and including a rod opening in the gland member and a gland aperture in the gland member, the gland aperture intersecting the rod opening, and (iii) a rod member movably arranged within the cylinder chamber of the cylinder body and the rod opening of the gland member. The method may include moving the gland member within the cylinder chamber of the cylinder body to substantially align the gland aperture of the gland member with the cylinder aperture of the cylinder body; substantially fixing the gland member relative the cylinder body; positioning a position sensor within at least one of the cylinder aperture and the gland aperture; moving the rod member within the rod opening of the gland member and the cylinder chamber of the cylinder body; and operating the position sensor to detect the position of the rod member.  
         [0011]     In another aspect of the invention, a method for detecting the position of a rod member of a cylinder assembly may be provided. The cylinder assembly may have (i) a cylinder body with a longitudinally arranged cylinder chamber in the cylinder body and a cylinder aperture in the cylinder body, the cylinder aperture intersecting the cylinder chamber, (ii) a gland member disposed within the cylinder chamber and including a rod opening in the gland member, and (iii) a rod member having one or more detectable features thereon, the rod member being movably arranged within the cylinder chamber of the cylinder body and the rod opening of the gland member. The method may include moving the gland member within the cylinder chamber of the cylinder body; positioning a position sensor in an opening of the gland member; substantially aligning the position sensor with a path of the one or more detectable features of the rod member; substantially fixing the gland member relative the cylinder body via a stake member that is (i) disposed within the cylinder aperture of the cylinder body and (ii) arranged in engagement with the gland member; moving the rod member within the rod opening of the gland member and the cylinder chamber of the cylinder body; and operating the position sensor to detect the position of the rod member as a function of the one or more detectable features.  
         [0012]     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate exemplary embodiments or features of the invention and, together with the description, serve to explain the principles of the invention. In the drawings,  
         [0014]      FIG. 1  is a cross-sectional view of a cylinder assembly constructed and operable according to an embodiment of the present invention; and  
         [0015]      FIG. 2  is a cross-sectional view of a cylinder assembly constructed and operable according to another embodiment of the present invention.  
     
    
       [0016]     Although the drawings depict exemplary embodiments or features of the present invention, the drawings are not necessarily to scale, and certain features may be exaggerated in order to better illustrate and explain the present invention. The exemplifications set out herein illustrate exemplary embodiments or features of the invention and such exemplifications are not to be construed as limiting the scope of the invention in any manner.  
       DETAILED DESCRIPTION  
       [0017]     Reference will now be made in detail to embodiments or features of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same or corresponding reference numbers will be used throughout the drawings to refer to the same or corresponding parts.  
         [0018]     Referring to  FIG. 1 , an exemplary embodiment of the present invention includes a cylinder assembly  10  having a cylinder body  14 , a gland member  18 , a rod member  26 , and a position sensor  30 .  
         [0019]     The cylinder body  14  provides a longitudinally arranged cylinder chamber  34  therein for receipt of the rod member  26 . A gland opening  38  is provided at one end  42  of the cylinder chamber  34  and is configured and arranged for receipt of the gland member  18 . The cylinder body  14  includes a radially outer wall  14   a  and a radially inner wall  14   b . Threads  46   a  may be provided on the inner wall  14   b  within the cylinder chamber  34  for engagement with threads  46   b  on the gland member  18 .  
         [0020]     A cylinder aperture  50  may be provided within the cylinder body  14  proximate the end  42  of the cylinder chamber  34 . The cylinder aperture  50  of  FIG. 1  is a throughbore or opening, such as a generally cylindrical throughbore, within the cylinder body  14  and intersects the cylinder chamber  34 . The cylinder aperture  50  shown in  FIG. 1  is generally arranged in a radial direction relative the cylinder chamber  34 . It should be appreciated that the cylinder aperture  50  may be arranged in a substantially predetermined position on the cylinder body  14 . An internal portion of the cylinder aperture  50  may have a threaded area  54   a  thereon for engaging complimentary threads  54   b  on a sensor body or sensor housing  58 , which encloses the sensor  30 . It should be appreciated that, in the absence of a sensor housing  58 , complimentary threads  54   b  may be disposed on the sensor  30  itself.  
         [0021]     Referring again to  FIG. 1 , a generally cylindrical gland member  18  may be disposed within the gland opening  38  and cylinder chamber  34  of the cylinder body  14  and may be sealingly engaged with the inner wall  14   b  of the cylinder body  14 . The gland member  18  has a rod opening therein, such as a longitudinal throughbore  70 , configured for slidable receipt of the rod member  26 . A radially outer surface  74  of the gland member  18  may provide threads  46   b  for engaging the threads  46   a  of the inner wall  14   b  of the cylinder body  14 . A seal groove  78  may also be provided along the outer surface of the gland member  18 , and a seal  82  may be provided therein for ensuring a sealing engagement between the gland member  18  and the inner wall  14   b  of the cylinder body  14 . Grooves  86 ,  90 ,  94 ,  98  may be provided along an internal wall  102  of the gland member  18  for seating a wear ring  106 , a buffer seal  110 , a rod seal  114 , and a wiper seal  118 , respectively. It should be appreciated that seals  114 ,  118  may be configured to engage the outer surface of the rod  26  to keep the area along the rod  26  between the two seals  114 ,  118  free from debris or other substances that may interfere with operation of the sensor  30 . The gland member  18  may have a flange portion  122  disposed outside of the gland opening  38  of the cylinder body  14  and extending radially outward, for example radially beyond the inner wall  14   b  of the cylinder body  14 .  
         [0022]     A gland aperture  126  may be provided within the gland member  18 . The gland aperture  126  of  FIG. 1  forms a sensor opening within the gland member  18  for receiving the sensor  30 . The gland aperture  126  is generally arranged in a radial direction relative the cylinder chamber  34  and intersects the rod opening  70  of the gland member  18 . The gland aperture  126  may be arranged in substantial rotational and longitudinal alignment with the cylinder aperture  50  so that the sensor  30  may be inserted into the cylinder aperture  50  and the gland aperture  126 . In the embodiment of  FIG. 1 , the gland aperture  126  is a generally cylindrical throughbore in the gland member  18  and has a larger cross-sectional area than the cylinder aperture  50 .  
         [0023]     The rod member  26  is slidably arranged within the rod opening  70  of the gland member  18  and is movably arranged within the cylinder chamber  34  of the cylinder body  14 , where the rod member  26  may be operably connected with a piston (not shown), as is known in the art, to form a piston-and-rod assembly. One or more detectable features  174 , such as barcode markings, may be disposed in a substantially predetermined rotational orientation along the length of the rod  26 . It should be appreciated that the rod member  26 , and therefore the detectable features  174 , may be arranged in a substantially predetermined rotational orientation relative the cylinder body  14 , and more specifically relative the cylinder aperture  50 , so that the path of the detectable features  174  will be substantially rotationally aligned with the cylinder aperture  50 . It should further be appreciated that, in one embodiment, even though the rod member  26  may be arranged in a substantially predetermined rotational orientation relative the cylinder body  14 , a generally small or otherwise insignificant rotation of the rod member  26  relative the cylinder body  14  may be permissible so long as a path of the detectable features  174  remains substantially rotationally aligned with the cylinder aperture  50 .  
         [0024]     As shown in  FIG. 1 , the position sensor  30  is mounted to the cylinder body  14  in general alignment with the path of the one or more detectable features  174 . The sensor  30  may be operable to detect the one or more detectable features  174  and responsively generate a signal indicative of the position of the rod  26  as a function of the one or more detectable features  174 . In the embodiment of  FIG. 1 , the sensor  30  is enclosed within a sensor housing  58 , is arranged within the cylinder aperture  50  and the gland aperture  126 , and is therefore arranged in substantial alignment with the cylinder aperture  50  and the gland aperture  126 .  
         [0025]     Referring to  FIG. 2 , an alternative embodiment of the present invention includes a cylinder assembly  10 ′ having a cylinder body  14 ′, a gland member  18 ′, a rod member  26 , and a position sensor  30 . The elements of the embodiment of  FIG. 2  are generally like the elements described above with respect to  FIG. 1  with the general exceptions described below.  
         [0026]     The cylinder aperture  50 ′ shown in  FIG. 2  is configured to hold a set screw  194 . For example, threads  54   a′  may be provided within the cylinder aperture  50 ′ for engagement with complimentary threads  54   b′  formed on the outer surface of the set screw  194 , which is arranged within the cylinder aperture  50 ′ to act as a stake member with respect to the cylinder body  14 ′ and the gland member  18 ′.  
         [0027]     The gland member  18 ′ shown in  FIG. 2  includes a stake slot  182  therein. The stake slot  182  is arranged in substantial rotational and longitudinal alignment with the cylinder aperture  50 ′ so that the set screw  194  may be inserted into the cylinder aperture  50 ′ to engage the stake slot  182 . In the embodiment of  FIG. 2 , the stake slot  182  is a longitudinally arranged groove on the gland member  18 ′ and is longitudinally longer than the diameter of the cylinder aperture  50 ′.  
         [0028]     A gland aperture, such as a generally cylindrical throughbore  126 ′, may be formed within the flange portion  122 ′ of the gland member  18 ′ to form a sensor opening for receiving a sensor  30 . The gland aperture  126 ′ of  FIG. 2  is generally arranged in a radial direction relative the cylinder chamber  34  and intersects the rod opening  70  of the gland member  18 ′. The gland aperture  126 ′ may be arranged in substantial rotational alignment with the cylinder aperture  50 ′. It should be appreciated that the gland aperture  126 ′ may be arranged in a substantially predetermined position on the gland member  18 ′ with respect to the stake slot  182 . An internal portion of the gland aperture  126 ′ may have a threaded area  204   a  thereon for engaging complimentary threads  54   b  on the sensor body or sensor housing  58 , which encloses the sensor  30 . It should be appreciated that, in the absence of a sensor housing  58 , complimentary threads  54   b  may be disposed on the sensor  30  itself.  
         [0029]     A groove  98 ′ may be provided along the internal wall  102  of the gland member  18 ′ for seating a wiper seal  118 ′ therein. It should be appreciated that seals  114 ,  118 ′ may be configured to engage the outer surface of the rod  26  to keep the area along the rod  26  between the two seals  114 ,  118 ′ free from debris or other substances that may interfere with operation of the sensor  30 .  
       INDUSTRIAL APPLICABILITY  
       [0030]     The present invention provides an affordable and robust sensor mount operable to accurately mount a position sensor to a hydraulic cylinder.  
         [0031]     With specific reference to  FIG. 1 , the cylinder assemblies  10 ,  10 ′ of  FIGS. 1 and 2  may be assembled by placing the rod member  26  through the rod opening  70  of the gland member  18  so that the buffer seal  110  and rod seal  114  provide a sealing engagement between the rod member  26  and the gland member  18 . The rod member  26  may be inserted into the cylinder chamber  34  of the cylinder body  14  and rotated into a substantially predetermined rotational orientation relative the cylinder body  14 . The gland member  18  may be moved longitudinally into the gland opening  38  and cylinder chamber  34  of the cylinder body  14 , via rotation of the gland member  18  relative the cylinder body  14  and via engagement of the threads  46   a ,  46   b , so that the seal  82  is held in sealing engagement between the outer surface  74  of the gland member  18  and the inner wall  14   b  of the cylinder body  14 . After the gland member  18  is sufficiently threaded within the cylinder body  14  to create a sealing engagement between the gland member  18  and the inner wall  14   b  of the cylinder body  14  (via the seal  82 ), the gland member  18  may be further rotated with respect to the cylinder body  14  until the gland aperture  126  is substantially rotationally aligned (and longitudinally aligned, in the embodiment of  FIG. 1 ) with the cylinder aperture  50 . Since the gland aperture  126  of  FIG. 1  has a larger cross-sectional area than the cylinder aperture  50 , the gland member  18  of  FIG. 1  can be threaded into the cylinder body  14  so that the gland aperture  126  and cylinder aperture  50  may be substantially both rotationally and longitudinally aligned even if the complimentary threads  46   a ,  46   b  are not machined according to an extreme tolerance.  
         [0032]     Referring again to the embodiment of  FIG. 1 , the sensor  30  and sensor housing  58  may be threaded into the cylinder aperture  50 , via the threads  54   a  on the cylinder aperture  50  and the threads  54   b  on the sensor housing  58 , until the sensor  30  and sensor housing  58  extend into the gland aperture  126  in sufficient proximity to the rod member  26  so that the sensor  30  may be operable to detect the one or more detectable features  174  on the rod member  26 . It should be appreciated that the sensor housing  58  (or in the absence of the housing  58 , then the sensor  30 ) of  FIG. 1  acts as a stake member through engagement with the cylinder aperture  50  and the gland aperture  126  to prevent or significantly inhibit rotation of the gland member  18  relative the cylinder body  14 . Thus, the gland member  18  shown in  FIG. 1  is substantially rotationally and longitudinally fixed relative the cylinder body  14  via the sensor housing  58  (or the sensor  30 ) (and the threads  46   a ,  46   b ). It should be appreciated that since the sensor housing  58  acts as a stake member to hold the gland member  18  in position relative the cylinder body  14 , the flange portion  122  of the gland member  18  need not be fully tightened against the end  178  of the cylinder body  14 . This feature of the embodiment shown in  FIG. 1  allows the gland member  18  to be held in its desired position relative the cylinder body  14  without relying on a tight frictional engagement between the flange portion  122  of the gland member  18  and the end  178  of the cylinder body  14 , thereby reducing or eliminating a substantial reliance upon extreme accuracy in positioning/machining the threads  46   a ,  46   b  to ensure proper alignment of the gland aperture  126  with the cylinder aperture  50 .  
         [0033]     Referring more specifically now to  FIG. 2 , during assembly after the gland member  18 ′ is sufficiently threaded within the cylinder body  14 ′ to create a sealing engagement between the gland member  18 ′ and the inner wall  14   b  of the cylinder body  14 ′ (via the seal  82 ), the gland member  18 ′ may be further rotated with respect to the cylinder body  14 ′ until the stake slot  182  of the gland member  18 ′ is substantially rotationally and longitudinally aligned with the cylinder aperture  50 ′. Since stake slot  182  is longitudinally longer than the cylinder aperture  50 ′, the gland member  18 ′ can be threaded into the cylinder body  14 ′ so that the stake slot  182  and cylinder aperture  50 ′ maybe substantially both rotationally and longitudinally aligned even if the complimentary threads  46   a ,  46   b  are not machined according to an extreme tolerance.  
         [0034]     The set screw  194  may be threaded into the cylinder aperture  50 ′, via the threads  54   a′  on the cylinder aperture  50 ′ and the threads  54   b′  on the set screw  194 , until the set screw  194  extends into and engages the stake slot  182 . It should be appreciated that the set screw  194  acts as a stake member through engagement with the cylinder aperture  50 ′ and the stake slot  182  to prevent or significantly inhibit rotation of the gland member  18 ′ relative the cylinder body  14 ′. Thus, the gland member  18 ′ shown in  FIG. 2  is substantially rotationally and longitudinally fixed relative the cylinder body  14 ′ via the set screw  194  (and the threads  46   a ,  46   b ). It should be appreciated that since the set screw  194  acts as a stake member to hold the gland member  18 ′ in position relative the cylinder body  14 ′, the flange portion  122 ′ of the gland member  18 ′ need not be fully tightened against the end  178 ′ of the cylinder body  14 ′.  
         [0035]     In the embodiment shown in  FIG. 1  (and  FIG. 2 ), the one or more detectable features  174  are arranged in a substantially predetermined orientation on the rod member  26 ; the rod member  26  is assembled in a substantially predetermined rotational orientation relative the cylinder body  14  ( 14 ′ in  FIG. 2 ) and the cylinder aperture  50  ( 50 ′ in  FIG. 2 ); the gland aperture  126  (or stake slot  182  in  FIG. 2 ) is assembled in a substantially predetermined orientation relative the cylinder aperture  50  ( 50 ′); and the sensor  30  is arranged in a substantially predetermined orientation relative the gland aperture  126  (or stake slot  182 ) and therefore the cylinder aperture  50  ( 50 ′). As a result, the position sensor  30  will be substantially rotationally aligned with a path of the one or more detectable features  174 , and the position sensor  30  may function properly by detecting the one or more detectable features  174  and responsively generating a signal indicative of the position of the rod  26  as a function of the one or more detectable features  174 .  
         [0036]     With specific reference again to  FIG. 2 , it should be appreciated that, during assembly when the gland member  18 ′ of  FIG. 2  is sufficiently threaded within the cylinder body  14 ′ to create a sealing engagement between the gland member  18 ′ and the inner wall  14   b  of the cylinder body  14 ′ (via the seal  82 ), the gland member  18 ′ may be further rotated, if necessary, with respect to the cylinder body  14 ′ until the sensor  30  is substantially rotationally aligned with the path of the detectable features  174  on the rod member  26 . After such alignment of the sensor  30  with the detectable features  174  of the rod member  26 , the set screw  194  may be applied to the gland member  18 ′ to substantially fix the gland member  18 ′ relative the cylinder body  14 ′.  
         [0037]     From the foregoing it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit or scope of the invention. Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and figures and practice of the invention disclosed herein. It is intended that the specification and disclosed examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims and their equivalents. Accordingly, the invention is not limited except as by the appended claims.