Abstract:
A sensor unit for a rotating shaft of a device includes a body having an axial opening and a second opening. The axial opening receives the rotating shaft and contacts an outer surface of the rotating shaft to precisely and repeatedly radially align a sensor to the shaft. The second opening receives the sensor.

Description:
This application is a section 371 of PCT/US02/11056, filed on Apr. 8, 2002 which claims the benefit of provisional application Ser. No. 60/282,038 filed Apr. 7, 2001. 

   FIELD TO WHICH THE INVENTION RELATES 
   This invention relates to speed/direction sensor assembly for consistent inclusion in a device having a rotary shaft. 
   BACKGROUND OF THE INVENTION 
   Hydraulic motors and other units having a rotary output are frequently used with devices for which information as to the positioning and/or speed and/or direction of rotation is useful. Examples include robotic arms, salt spreading units, scissor lifts, winches and power steering units. Some units utilize sensors deep within the housing of the units together with specialized shafts. The Parker hydraulic motor with its slotted shaft and inductive sensor is an example. Other units utilize sensors in specially machined intermediate members between a device and its associated motor. The White Hydraulics motor with cast cap having a screwed in separate sensor is an example. In this motor ( FIG. 11 ) a screw-in sensor  90  is provided with access to, and adjustment of, the clearance  92  through an enlarged dust cap  93  in original and subsequent installations. Typically it is necessary to have a separated power unit to do this. Additional units use specialized housings with multiple sensors. The Ross gear commutation apparatus disclosed in U.S. Pat. No. 4,767,292, Electrical Commutation Apparatus, is such a unit. 
   These units necessitate complicated housings, additional individual manufactured parts and/or additional components. These add to the complexity of the overall device, increasing manufacturing maintenance and other costs relative to the hydraulic units. The units typically require specialized integral design and/or relatively significant individual adjustments. The units also typically have to be removed and rebuilt if there are sensor problems. The units are thus costly to both build and maintain. 
   OBJECTS AND SUMMARY OF THE INVENTION 
   It is an object of this invention to simplify the sensors utilized with hydraulic motors. 
   It is another object of this invention to facilitate the assembly of sensor units. 
   It is still a further object to provide for a self aligning sensor unit. 
   It is a further object to protect the integrity of sensor units. 
   It is yet another object of this invention to facilitate the repair and/or replacement of sensor units. 
   It is another object of this invention to allow for differing types of sensors in a single basic design. 
   It is another object of this invention to allow a single sensor to be utilized in differing units. 
   It is a further object of this invention to simplify the utilization of sensors in rotary devices. 
   Other objects and a further understanding of the invention may be had by referring to the drawings in which: 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a longitudinal cross-sectional view of a hydraulic pressure device incorporating the invention of the application; 
       FIG. 2  is a partial enlargement of  FIG. 1 ; 
       FIG. 3  is a cross-sectional view of the sensor unit of the hydraulic motor of  FIG. 1  taken substantially along the lines  3 — 3  of such FIG.; 
       FIG. 4  is a side view of the sensor of  FIG. 2 ; 
       FIG. 5  is a top view of the sensor of  FIG. 3 ; 
       FIG. 6  is a cross-sectional view of the sensor housing of  FIG. 2 ; 
       FIGS. 7–10  are respective side, front, cross-sectional and back views of an alternate sensor arrangement; and, 
       FIG. 11  is a drawing of a prior art White screw in sensor design. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   This invention relates to an improved sensor unit for a rotary shaft positioned by motor or otherwise. The invention will be described in its preferred embodiment of the sensor unit for a gerotor pressure device having a valve integral with the rotor (White model RE [ FIGS. 1–6 ] and RS [ FIGS. 7–10 ] designs). As understood, a gerotor pressure device will operate as either a motor or a pump, depending on the nature of its fluidic and mechanical connections. They are designed for a specified number of gallons per minute for a given displacement at high pressures up to 4000 psi. Other gerotor devices are spaced separate rotating valved, drive shaft valved, rotating rotor face valved and other such devices made by White, Eaton, Parker, Danfoss and others. 
   The gerotor pressure device  10  exemplified herein includes a power unit  15 , an output shaft  20  and a sensor unit  30 . 
   The power unit  15  serves to interconnect the rotation of the output shaft  20  to and/or from a interconnection to another device (not shown) with a gerotor pressure unit. This other device could be a pump (if the power unit was utilized as a motor), a motor (power unit pump) or another unit utilizing a hydraulic pressure differential. 
   In the particular embodiment disclosed, the power unit is a White model RE hydraulic motor having two ports  16 ,  17  for typical interconnection to a hydraulic pump/source of pressure through a series of valves (FIGS.  1 – 6 —valves not shown). 
   The output shaft  20  serves to physically interconnect the power unit  15  to an object. This interconnection can provide rotary power to the object and/or accept rotary power from the object depending on the particular application involved. An output shaft separate from the power unit may be utilized. 
   In the particular embodiment disclosed, the output shaft  20  is integral with that of the power unit  15 . This shaft is rotatedly interconnected directly to the housing  18  of the power unit by two spaced main bearings  21 ,  22 . These bearings  21 ,  22  thus serve to physically mount the output shaft to the associated device through the power unit by providing the physical support thereof. In that this output shaft  20  is integral with the power unit  15 , a main shaft seal  19  is incorporated in respect to the output shaft  20  so as to fluidically isolate the hydraulic pressure within the housing  18  of the power unit. This shaft seal thus serves to restrict the high pressure within the power unit  15 . A separate thrust bearing  24  between a shoulder of the shaft  20  and the housing  18  of the power unit serves to maintain the output shaft  20  in axial position in respect to the power unit. 
   In the particular embodiment disclosed in  FIGS. 1–6 , the shaft is that of a White Model RE Motor having a shaft diameter of 1.3″ with the cylindrical section extending some 1″ from the front flange of the body  18  of the hydraulic gerotor motor (so as to provide an interactive surface for the later described support section  40  and seal  52 ). In the alternate embodiment of  FIGS. 7–10  the device is a White Model RS Motor having a shaft diameter of approximately 1″ with the cylindrical section extending substantially 0.7″ from the flange to allow for cooperation with the sensor unit  30 . 
   The invention of the present application relates to a sensor unit  30 . This sensor unit  30  is designed to provide for a variety of functions in respect to the output shaft  20 . These include aligning the sensor to the shaft, physically protecting the sensor and any associated seal against rocks and dirt on the outside of the device, providing for the use of differing sensors in a single sensor unit design, reliably orienting the sensor in respect to the output shaft, and allowing for the simplified manufacture/repair of sensor units. Each sensor  30  is chosen in response to the type of motor as well as the device to which it is to be attached. Preferably, this union is optimized to both the sensor as well as motor for example in  FIG. 1–6  one side is utilized to match the RE mounting flange while this outside is designed for strength, maintenance and repair. This also allows existing parts of the RE—its bolt location, its internal lip and other factors this is preferable. 
   The particular sensor unit  30  disclosed has a body  32  with a central opening  34 , a sensor cavity  37  and a mounting surface  45 . 
   The body  32  of the sensor unit is for physically mounting the sensor in respect to the output shaft  20 . The body  32  in addition physically protects the sensor from physical damage and outside contaminants. In the preferred single output shaft design, the body  32  is radially located directly by the shaft  20 . It is held in position after initial operation by its physical connection to the power unit. 
   The central opening  34  of the sensor unit is utilized as the main alignment member for the sensor unit  30 . The central opening provides for this alignment by having an inner support section  40  having an internal diameter  42  substantially the same as the diameter  23  of the output shaft. This inner support section  40  thus physically radially aligns the later described sensor with the shaft and/or anything mounted thereon when first installed. After the power unit  15  is installed, the body  32  of the sensor  30  is tightly captured between the hydraulic unit  15  and the frame  100  with which it is associated. It therefor cannot move in respect to either thereafter. 
   In the preferred embodiment disclosed, the distance between the inner support section  40  and an external mounting surface  45  (for sensor placement) is precisely defined in the manufacture of the sensor unit  30 . This dimension is thus highly controlled providing for a reliable distance between the mounting surface  45  and the output shaft  20  during original manufacture. It is therefore not necessary to compensate for any misalignment within the sensor unit  30  such as by shims, adjustment screws, or other secondary adjustment means on initial installation nor anytime thereafter. After initial installation the sensor unit  30  does not move for it is not subject to any meaningful displacement forces. It therefore retains its initial, and precise, positioning—a positioning that further is common to all other output shafts using the same design power unit. A given sensor can therefor be exchanged with another without concern for any dimensions (as herein explained). 
   In the preferred embodiments disclosed the mounting surface  45  is 1.9″ from the centerline of the shaft  20 . The surface  45  itself is 0.7″ wide and 2″ long. 
   The cavity  37  is located on the inside of the body  32  of the sensor unit for physical mounting of the internal parts of the sensor in addition to any shaft mounted auxiliary components. 
   In the embodiment disclosed, the cavity  37  includes a seal cavity  49 , the inner end  72  of the inside extension of the sensor  60  and a intermediate component  74  utilized between the output shaft  20  and the sensor  60 . 
   The seal cavity is for the physical location of a secondary seal  52 . This seal excludes external contaminants such as water and dirt from the cavity  37 . Note the seal is oriented such that it in addition allows for any grease from the later described grease fitting  54  to exit the cavity  37  if such is pressurized relative to the normal atmosphere. This prevents over pressurization of the cavity (in addition to its previously described elimination of contaminants from the cavity). Note further that the inner support section  40 , being located outside of the seal  52 , serves to protect the seal  19  against dirt, rocks and other physical damage. It also similarly protects the sensor. 
   In the preferred embodiment disclosed in  FIGS. 1–6 , the body  30  of the sensor unit has a central hole 1.3″ in diameter (for the shaft  20 ). The body section itself is substantially 3.6″ high and 5.25″ wide. The mounting surface  45  is substantially 1.9″ from the centerline of the shaft. In the alternate embodiment of  FIGS. 7–10  the support section  40  has an inner diameter of substantially 1″ for its shaft and a width/height of substantially 3″. Again, the mounting surface  45  for the sensor  60  is located 1.9″ from the centerline of the shaft. A small O-ring type seal is located on the sensor surrounding the inside extension  70  so as to seal the sensor unit to the body  32 . 
   The sensor  60  and intermediate component  75  in the embodiment disclosed provide for the actual position/rotation/direction sensing of the output shaft  20 . This is preferred in that the intermediate component  75  increases the relative diameter of the output shaft  20  at the location of the sensor, thus increasing the accuracy of the sensing without requiring a concomitant increase in the diameter of the output shaft. The intermediate component in the preferred embodiment disclosed also provides for a single sensor  60  to be utilized with differing devices (contrast  FIGS. 1–6  with  FIGS. 7–10 ). In the preferred embodiment of  FIG. 1–6  the intermediate component is a 50 pulse magnet ring having an inner diameter of 1.28″ and an outer diameter of 2″. It is substantially 0.25″ wide. In the embodiment of  FIGS. 7–10  the magnet rotor has an inner diameter of 1″ with the same outer diameter and width as the first embodiment. This in combination with the commonality of distance of mounting surface  45  allows a single sensor  60  to be utilized interchangeably with both embodiments. 
   The sensor  60  itself includes a mounting member  64  and an inside extension  70 . 
   The mounting member  64  serves to mount the sensor to the body  32  of the sensor unit  30 . In the preferred embodiment disclosed, the mounting member  64  includes a support surface  67 . This support surface  67  cooperates with the mounting surface  45  of the body of the sensor unit in order to physically interconnect the sensor  60  to such unit. This mounting is preferably removable so as to allow for the installation/replacement of the sensor without disassembly of the sensor unit  30  or the power unit with which it is utilized. This facilitates the initial construction and repair of the unit. 
   In the preferred embodiment disclosed, this removable mounting is provided by a series of mounting holes  65  through the mounting member  64 , which holes allow for the use of screws  68  so as to removably connect the sensor  60  to the body  32  of the sensor unit. 
   It is preferred that some sort of indexing means exist between the sensor  60  and the body  32  of the sensor unit. In the embodiment disclosed this indexing is provided by the mounting holes  65  being offset from the longitudinal axis of the mounting member  64 . This offset ensures that the mounting member  64  can only be assembled with the right orientation between the sensor  60  and the output shaft  20 . Alternate means of providing for a set orientation can be provided by other indexing means such as location pins, orientation slots, or other unidirectional mounting schemes. 
   In the embodiments disclosed the mounting holes  65  are offset some 0.085″ from the centerline of the mounting member  64  of the sensor. 
   The inside extension  70  of the sensor  60  serves to close the distance between the mounting surface  45  and the output shaft  20  (in the preferred embodiment disclosed the diameter of the output shaft expanded by distance  76  via the intermediate component  75 ). 
   The optional inside extension  70  of the sensor  60  has an inner end  72 . The distance between the inner end  72  and the support surface  67  of the mounting member is a set distance  73 , which set distance is selected to precisely locate the inner end  72  in a predetermined relationship in respect to the effective outer surface of the output shaft  20  (in the preferred embodiment as enlarged by the intermediate member). This set distance  73  thus cooperates with the inner support section  40  and its location of the mounting surface  45  so as to reliably and predictably control the critical dimension of the inner end  72  of the sensor to the effective outer diameter of the output shaft  20 . For this reason, the inner end  72  of the sensor can be reliably and uniformly located during initial construction and/or subsequent repair without consideration for secondary adjustment. Further multiple sensors  60  are interchangeable without dimensional concern for a given sensor unit  30  (for shafts of corresponding nature). 
   In the preferred embodiment disclosed, the sensor  60  has an inside extension  70  some 0.88″ long from its surface  67  to the end  72 . The mounting member  64  itself has a width of substantially 0.65″ and a length of substantially 1.7″. It contains a hall-effect sensor with interconnections to ground, input voltage, output and direction. The inner end  72  of the sensor  60  is located within +0.3″ of the ring magnet in both embodiments, this spacing determined by the gauss of the magnet and sensitivity of the hall-effect sensor. 
   Note that due to the use of the cooperation between a support surface  67  of the mounting member  64  and a mounting surface  45  of the body  32  a multiplicity of differing sensors can be utilized in a given design sensor unit. For example, a dual speed Hall sensor, an inductive proximity sensor, an optical sensor, or other sensor could be utilized with a single body  32  to provide for many differing applications while retaining the same construction (albeit in certain instances with a differing intermediate component). This again would be true of initial manufacture as well as subsequent field use. 
   The intermediate component  75  in the preferred embodiment serves to expand the relative diameter of the output shaft  20  as well as providing for a secondary unit for cooperation with the sensor  60  to establish the rotation/angle/direction of the output shaft  20  in respect to the sensor unit  30 . 
   In the preferred embodiment disclosed, the intermediate member is a generally cylindrical magnet  77  located immediately surrounding the output shaft  20  spaced therefrom through a separation member  78 . Preferably the intermediate component  75 , whether the magnet  77  or other component, is fixedly mounted to the output shaft  20  so as to rotate therewith under all conditions. This intermediate component  75  extends off of the shaft  20  so as to expand its relative diameter at this location (by distance  76  disclosed). This allows for an effective shaft diameter differential for sensor location (mounting surface  45  at  40 ) and the set distance  73  of the inner end  72  of the sensor. Note that other intermediate components  75  could be utilized such as a gear having external slots (for use with an induction sensor or optical sensor), a segmented magnet having alternating north and south poles circumferentially about the member, or other expansion means capable of cooperating with a selected operation of sensor  60 . In any event, the intermediate component  75  would be selected to go with the particular sensor to be utilized with the sensor unit  30 . (Note however, that a given intermediate component such as the preferred magnet  77  could be utilized with differing sensors—for example a dual speed hall sensor instead of a single speed hall sensor). 
   Although the body  32  of the sensor unit is radially supported to the output shaft  20  precisely by the inner support section  40 , it is preferred that the sensor unit  30 , once installed, in addition be mounted in a fixed position in respect to the output shaft  20 . In the preferred embodiment disclosed, this is accomplished by a flange  80  extending outwardly off of the body  32  of the sensor unit. The particular flange  80  disclosed has a series of holes therein matching the holes utilized to mount the power unit  15  to its auxiliary component (six holes shown in  FIG. 2 , four holes shown in  FIG. 7 ). Note that the purpose of these holes is primarily to hold the sensor unit  30  in rotational orientation in respect to the housing  18  of the power unit after assembly. To facilitate this, the particular embodiment disclosed has a series of pressed steel sleeves  82  within the mounting holes  81 . These sleeves  82  serve to pass the compression force between the power unit  15  and the component to which it is physically mounted, thus to prevent any compression effect including distortion on the body  32  of the sensor unit  30 . Since the cooperation between the inner support section  40  and the shaft  20  initially locate the sensor  60 , a purpose of the flange  80  is to thereafter retain the sensor unit  30  in respect to such shaft  20 . This reduces considerations of wear from shifting the location of the mounting surface (i.e. once fixed the distance  46  remains constant after installation). Subsequent sensors  60  can therefore be substituted with this knowledge. 
   In the preferred embodiment the body  32  of the sensor unit  30  is made of plastic (Acetal disclosed) having an inner surface diameter  42  some 0.002-4″ over the diameter  23  of the shaft  20 . This precisely locates the mounting surface  45  in respect to the remainder of the device on installation. Once fixed in position on operation any high points/distortions would be removed by the wear by the steel shaft—a wear not compromising the initial relative location of the mounting surface in respect to the shaft  20 . 
   As the distance  73  from the inner end  72  of the sensor  60  to its support surface  67  is set in manufacture, this distance is presubscribed. This distance is preferably within 0.017″ for the set forth hall sensor (with consideration of the extension distance  76 ). 
   Due to the above any sensor  60  used with any sensor body meeting the standards will be properly dimensionally positioned for the shaft utilized therewith. No shimming measurements or other secondary operation is necessary on initial installation, repair or replacement. 
   Although the invention is described in its preferred embodiment with a certain degree of particularity, it is realized that numerous changes may be made without deviating from the invention.