Patent Publication Number: US-2005124446-A1

Title: Positioning structure for power transmission mechanism

Description:
BACKGROUND OF THE INVENTION  
      The present invention relates to a power transmission mechanism that is connected to a housing of a rotary machine for inputting power to a rotary shaft of the rotary machine and more particularly to a positioning structure for positioning the power transmission mechanism on the housing of the rotary machine.  
      A power transmission mechanism of such type is, for example, shown in  FIG. 4  in which the power transmission mechanism is arranged in a power transmission path between a refrigerant compressor  101  of a vehicle air conditioner and an engine (not shown) for traveling a vehicle.  
      Namely, a boss  102   a  for a rotary shaft  104  extends from a housing  102  of the compressor  101 . A pulley  105  is rotatably supported by the boss  102   a  through a bearing  113  for inputting power from the engine to the rotary shaft  104 . A rotor  106   a  is supported by the rotary shaft  104  inside the pulley  105  so as to rotate integrally with the rotary shaft  104 . A stator  106   b  is supported by the boss  102   a  inside the pulley  105  through a stator bracket  109 . The rotor  106   a  and the stator  106   b  constitute the electric motor  106 .  
      The bearing  113  is positioned in its axial direction by a first rear positioning surface  114  and a first front positioning surface  116   a . The first rear positioning surface  114  is a wall surface of a step that is formed at the boss  102   a  on the rear side relative to the bearing  113  in the axial direction. The first front positioning surface  116   a  is a part of circular clip  16  that is fixedly fitted on the boss  102   a  on the front side relative to the bearing  113  in the axial direction.  
      The stator bracket  109  is positioned in its axial direction by a second rear positioning surface  110  and a second front positioning surface  112   a . The second rear positioning surface  110  is a wall surface of another step that is also formed at the boss  102   a  on the rear side relative to the stator bracket  109  in the axial direction. The second front positioning surface  112   a  is another part of the circular clip  112  that is also fixedly fitted on the boss  102   a  on the front side relative to the stator bracket  109  in the axial direction. In summary, the bearing  113  and the stator bracket  109  are positioned in their axial direction by exclusive positioning means, respectively.  
      The positioning means for positioning the bearing  113  and the stator bracket  109  exclusively include the front positioning surfaces  112   a ,  116   a  and the rear positioning surfaces  110 ,  114  in the axial direction, respectively. Accordingly, the positioning structure (a mounting structure) for positioning the power transmission mechanism on the housing  102  of the compressor  101  becomes complicated so that various problems may occur.  
      Namely, for example, the positioning means for positioning the bearing  113  and the stator bracket  109  respectively need the circular clips  112 ,  116  so that the number of components and assembling processes increase for the compressor  101  with the power transmission mechanism. Also, the positioning means respectively require annular grooves  111 ,  115  for fitting the circular clips  112 ,  116  so that it is complicated to recess the annular grooves  111 ,  115  in the housing  102 . Furthermore, the positioning means respectively require the steps (the rear positioning surfaces  110 ,  114 ) for positioning so that it is also complicated to form the steps in the housing  102 .  
      Additionally, the exclusive positioning means for positioning the bearing  113  and the stator bracket  109  require relatively large displacement of the bearing is  113  and the stator bracket  109  in the axial direction, in view of a space for arranging the positioning means in the housing  102 . Accordingly, there occurs a problem that the power transmission mechanism becomes large in size in its axial direction. Therefore, there is a need for simplifying a positioning structure for positioning a power transmission mechanism on a housing of a rotary machine.  
     SUMMARY OF THE INVENTION  
      In accordance with the present invention, in a power transmission mechanism that is attached to a housing of a rotary machine for inputting power to a rotary shaft of the rotary machine, the power transmission mechanism includes a rotary body and an electric motor. The rotary body is rotatably supported by the housing through a rotary body bearing for transmitting power from an external drive source to the rotary shaft. A stator of the electric motor is supported by the housing through a stator bracket. The rotary shaft is optionally driven by the electric motor during stop of the external drive source. A positioning structure has a bearing positioning means and a bracket positioning means. The bearing positioning means positions the rotary body bearing forward and rearward in an axial direction of the rotary shaft relative to the housing of the rotary machine and has front and rear positioning surfaces. The bracket positioning means positions the stator bracket forward and rearward in the axial direction and has front and rear positioning surfaces. At least one of the front and rear positioning surfaces of the respective bearing positioning means and bracket positioning means is shared with each other.  
      Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The features of the present invention that are believed to be novel are set forth with particularity in the appended claims. The invention together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:  
       FIG. 1  is a longitudinal cross-sectional view of a compressor with a power transmission mechanism according to a preferred embodiment of the present invention;  
       FIG. 2  is a partially enlarged view of  FIG. 1 ;  
       FIG. 3  is a cross-sectional view that is taken along the line I-I in  FIG. 2 ; and  
       FIG. 4  is a partially enlarged cross-sectional view of a compressor with a conventional power transmission mechanism according to a prior art.  
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      A preferred embodiment of the present invention will now be described with reference to  FIGS. 1 through 3 . The left side and the right side in  FIGS. 1 and 2  respectively correspond to the front side and the rear side of a compressor C.  
      Now referring to  FIG. 1 ,  FIG. 1  illustrates a longitudinal cross-sectional view of the compressor C with a power transmission mechanism PT according to the preferred embodiment of the present invention. The refrigerant compressor C is a rotary machine for partially constituting a refrigeration cycle of a vehicle air conditioner. A housing  11  of the compressor C accommodates a piston type compression mechanism  12 . The piston type compression mechanism  12  has a well-know structure in which the rotation of a swash plate  14  in accordance with the rotation of a rotary shaft  13  is converted to the reciprocation of a piston  16  is through a pair of shoes  15 . Thus, refrigerant gas is compressed.  
      With respect to the compressor C, the power transmission mechanism PT is arranged coaxially with the rotary shaft  13  on the outside of the housing  11  for inputting power to the rotary shaft  13 . The power transmission mechanism PT includes a pulley or a rotary body  17  and an electric motor  38  and is coupled to an engine or an external drive source E for traveling a vehicle. The pulley  17  is rotatably supported by the housing  11  and transmits power from the engine E to the rotary shaft  13 . The electric motor  38  is, for example, utilized for driving the rotary shaft  13  when the engine E is stopped. The compressor C with the electric motor  38  is capable of air-conditioning (cooling) during the stop of the engine E.  
      The power transmission mechanism PT and a mounting structure for the power transmission mechanism PT to the compressor C will now be described.  
      Now referring to  FIGS. 1 and 2 ,  FIG. 2  illustrates a partially enlarged view of  FIG. 1 . The rotary shaft  13  of the compression mechanism  12  is rotatably supported by the housing  11 . The front end of the rotary shaft  13  extends through the front end wall of the housing  11  and protrudes outside from the housing  11 . A boss  35  for the rotary shaft  13  is integrally formed with the housing  11  and extends from the front end wall of the housing  11 . The boss  35  forms a relatively large diameter portion  35   a  and a relatively small diameter portion  35   b . The large diameter portion  35   a  is formed on the rear side (the proximal end of the boss  35 ), while the small diameter portion  35   b  is formed on the front side (the distal end of the boss  35 ).  
      A cylindrical brush unit holder  37  is fixedly fitted around the large diameter portion  35   a  of the boss  35 . A power supply ring  41  is fixed to the radially outer side on the front wall surface of the housing  11  so as to surround the rear end of the brush unit holder  37 . A first seal member  43  is interposed at an annular contact region between the front wall surface of the housing  11  and the power supply ring  41 .  
      The pulley  17  includes an upstream pulley member  18  and a downstream pulley member  19 . The upstream pulley member  18  forms a groove  18   a  at its outer circumferential surface for winding a belt  20  to be coupled with the engine E. The upstream pulley member  18  is rotatably supported by the brush unit holder  37  on the housing  11  through a pulley bearing or a rotary body bearing  57 . The pulley bearing  57  is a ball bearing that includes an outside movable race  59  on the side of the upstream pulley member  18 , an inside fixed race  58  on the side of the brush unit holder  37  and a rolling ball  60  (which is interposed between the inside fixed race  58  and the outside movable race  59 ).  
      The downstream pulley member  19  is supported by a hub  30  through a first one-way clutch  31 . The hub  30  is fixedly connected to the front end of the rotary shaft  13 . The upstream pulley member  18  is connected to the downstream pulley member  19  by a power transmission pin  28  and a rubber damper  29 . The power transmission pin  28  functions as a breaking-type torque limiter. The rubber damper  29  moderates the variation of torque transmitted between the pulley members  18 ,  19 .  
      The first one-way clutch  31  provides a clutch mechanism  31   a  and a bearing mechanism  31   b . The clutch mechanism  31   a  permits power transmitted from the downstream pulley member  19  to the hub  30 , while the clutch mechanism  31   a  disrupts power transmitted from the hub  30  to the downstream pulley member  19 . Accordingly, as the upstream pulley member  18  is rotated in one direction by the operation of the engine E, the downstream pulley member  19  is also rotated in the same direction as the upstream pulley member  18  through the power transmission pin  28  and the rubber damper  29 . This rotational power is input to the rotary shaft  13  through the first one-way clutch  31  and the hub  30 .  
      On the contrary, as the rotary shaft  13  is rotated in the same direction by the electric motor  38  when the engine E is stopped, this rotational power is transmitted to the first one-way clutch  31  through the hub  30 . However, the clutch mechanism  31   a  of the first one-way clutch  31  does not permit the power transmitted from the hub  30  to the downstream pulley member  19  so that the power of the electric motor  38  is prevented from being transmitted to the engine E, that is, the power generated by the electric motor  38  is prevented from being consumed by another operation other than the operation of the compression mechanism  12 .  
      A sealed space  88  is defined inside the pulley  17  by connecting the upstream pulley member  18  and the downstream pulley member  19 . The electric motor  38  is arranged coaxially with the pulley  17  in the sealed space  88 .  
      Namely, a rotor  45  is connected to the rotary shaft  13  through a second one-way clutch  44  in the sealed space  88  of the pulley  17 . The rotor  45  includes an iron core  45   a  and a coil  45   b  that is wound around the iron core  45   a . A commutator  50  is fixedly connected to the rear end of the rotor  45 . A stator  49  made of a magnet is arranged outside the rotor  45  in the sealed space  88 . The stator  49  is supported by the housing  11  through a stator bracket  48 .  
      A plurality of recesses  37   a  is formed on the front end of the brush unit holder  37  in the sealed space  88  of the pulley  17 . The recesses  37   a  (only one of them shown in  FIGS. 1 and 2 ) are formed around the axis of the pulley  17  at equiangular positions. Each of the recesses  37   a  holds a power supply brush unit  39 . A brush  39   a  of the power supply brush unit  39  is pressed to contact the commutator  50 . A wiring (not shown) is buried in the power supply ring  41  for externally supplying the brush  39   a  with electric power. Accordingly, the electric power is externally supplied to the coil  45   b  through the power supply ring  41  (the buried wiring), the power supply brush unit  39  and the commutator  50  so that the rotor  45  is rotated.  
      The second one-way clutch  44  includes a clutch mechanism  44   a  and a bearing mechanism  44   b  as well as the first one-way clutch  31 . With respect to the rotation in one direction described for the first one-way clutch  31 , the clutch mechanism  44   a  permits power transmitted from the rotor  45  to the rotary shaft  13 , while the clutch mechanism  44   a  disrupts power transmitted from the rotary shaft  13  to the rotor  45 . Accordingly, as the electric motor  38  is started during the stop of the engine E, the rotational power of the electric motor  38  is transmitted to the rotary shaft  13  through the second one-way clutch  44 . On the contrary, even if the rotary shaft  13  is rotated by the operation of the engine E when the engine E is running, this rotational power is not input to the rotor  45 . Thus, load for driving the rotor  45  by the engine E is reduced.  
      The positioning structure for positioning the pulley bearing  57  and the stator bracket  48  in the housing  11  will now be described.  
      As shown in  FIG. 2 , the radially outer surface of the front end of the brush unit holder  37  forms the recesses  37   a  so that the annular shape of the brush unit holder  37  is split. The power supply brush unit  39  is accommodated in each recess  37   a  to occupy the split spaces of the brush unit holder  37 . A collar  51  is loosely fitted to cover a cylindrical surface, which is formed by the outer surface of the front end of the brush unit holder  37  and the outer surface of the power supply brush unit  39 .  
      The collar  51  includes a cylindrical portion  52  and a flange  53 . The cylindrical portion  52  is fitted around the brush unit holder  37  and the power supply brush unit  39 . The flange  53  is provided at the rear end periphery of the cylindrical portion  52 . The fixed race  58  of the pulley bearing  57  is press-fitted around the cylindrical portion  52  of the collar  51  and is pressed into in such a manner that the rear end surface of the fixed race  58  contacts the flange  53 . A second seal member  61  is interposed at an annular contact region between the fixed race  58  and the cylindrical portion  52 .  
      A rear surface  53   a  of the flange  53  of the collar  51  contacts an annular region of a front surface  41   a  of the power supply ring  41  through a third seal lo member  56 . Namely, the front surface  41   a  of the power supply ring  41  contacts; the collar  51  to restrict the collar  51  from moving rearward in the axial direction of the rotary shaft  13 . Thus, the front surface  41  a of the power supply ring  41  serves as a rear positioning surface  41   a  for positioning the pulley bearing  57  (the fixed race  58 ) in the axial direction.  
      The stator bracket  48  includes an annular proximal portion  67 , an annular disc-shaped portion  68  and a cylindrical stator fixing portion  69  for fixing the stator  49 . The disc-shaped portion  68  radially extends outward from the proximal portion  67 . The stator fixing portion  69  extends forward from the outer periphery of the disc-shaped portion  68 . The stator  49  is fixedly connected to the inner surface of the stator fixing portion  69 . The proximal portion  67  of the stator bracket  48  is loosely fitted around the small diameter portion  35   b  of the boss  35 . A pin  76  is interposed between the proximal -portion  67 Sand the brush unit holder  37 . The rotation of the stator bracket  48  is blocked by the pin  76  relative to the brush unit holder  37 , that is, the housing  11 .  
      An annular groove  77  is recessed in an outer circumferential surface of the small diameter portion  35   b  of the boss  35  on the front side relative to the proximal portion  67  of the stator bracket  48 . A circular clip  78  is fitted in the annular groove  77 . A front surface  67   a  of the proximal portion  67  of the stator bracket  48  contacts a rear surface  78   a  of the circular clip  78  at an annular contact region. In other words, the rear surface  78   a  of the circular clip  78  serves as a front positioning surface  78   a  that contacts the stator bracket  48  for restricting the forward movement of the stator bracket  48  in the axial direction of the rotary shaft  13 .  
      A front end surface  52   a  of the cylindrical portion  52  of the collar  51  contacts the rear surface  68   a  of the disc-shaped portion  68  of the stator bracket  48 . Accordingly, the forward movement of the collar  51  in the axial direction is directly restricted in such a manner that the front end surface  52   a  of the cylindrical portion  52  contacts the rear surface  68   a  of the disc-shaped portion  68  of the stator bracket  48 . As a result, the front surface  67   a  of the proximal portion  67  of the stator bracket  48  is restricted by contacting the front positioning surface  78   a  of the circular clip  78 . On the other hand, the rearward movement of the stator bracket  48  in the axial direction is directly restricted in such a manner that the rear surface  68   a  of the disc-shaped portion  68  contacts the front end surface  52   a  of the cylindrical portion  52  of the collar  51 . As a result, the rear surface  53   a  of the flange  53  of the collar  51  is restricted by contacting the rear positioning surface  41   a  of the power supply ring  41  through the third seal member  56 .  
      The circular clip  78  is a tapered circular clip and presses the proximal portion  67  of the stator bracket  48  rearward in the axial direction by being fitted in the annular groove  77 . Accordingly, this pressing force is applied to the cylindrical portion  52  of the collar  51  through the disc-shaped portion  68  of the stator bracket  48 , and the flange  53  of the collar  51  is pressed against the rear positioning surface  41   a  of the power supply ring  41  through the third seal member  56 .  
      In the preferred embodiment, a means for positioning the pulley bearing  57  in the axial direction and a means for positioning the stator bracket  48  in the axial direction share both the front positioning surface  78   a  and the rear positioning surface  41   a , which are components of the respective positioning means.  
      Incidentally, in the preferred embodiment, the collar  51  (the front end surface  52   a ), the stator bracket  48  (the rear surface  68   a , the front surface  67   a ) and the circular clip  78  (the rear surface  78   a ) constitute a front bearing positioning means for positioning the pulley bearing  57  forward. The power supply ring  41  (the front surface  41   a ), the third seal member  56  and the collar  51  (the rear surface  53   a ) constitute a rear bearing positioning means for positioning the pulley bearing  57  rearward. The circular clip  78  (the rear surface  78   a ) is a front bracket positioning means for positioning the stator bracket  48  forward. Then, the power supply ring  41  (the front surface  41   a ), the third seal member  56  and the collar  51  (the rear surface  53   a , the front end surface  52   a ) constitute a rear bracket positioning means for positioning the stator bracket  48  rearward.  
      Now referring to  FIGS. 2 and 3 ,  FIG. 3  illustrates a cross-sectional view that is taken along the line I-I in  FIG. 2 . A plurality of engaging protrusions  54  extends forward from the front end surface  52   a  of the cylindrical portion  52 . The engaging protrusions  54  are provided at equiangular positions along the circumferential direction of the cylindrical portion  52 . Only one of the engaging protrusions  54  is shown in  FIG. 2 . Engaging holes or engaging recesses  68   b  are formed in the disc-shaped portion  68  of the stator bracket  48  so as to correspond with the engaging protrusions  54  of the collar  51 .  
      The engaging protrusions  54  engage the engaging recesses  68   b  in such a manner that the pulley bearing  57  and the stator bracket  48  are positioned in their axial direction. Thereby, the collar  51  and the stator bracket  48 , that is, the fixed race  58  and the housing  11 , do not rotate around the axis of the pulley  17  relative to-each other. Namely, the engaging protrusions- 54  and the engaging recess  68   b  constitute a rotation blocking means.  
      The following advantageous effects are obtained from the preferred embodiment.  
      (1) The positioning means for positioning the pulley bearing  57  and the positioning means for positioning the stator bracket  48  share the positioning surfaces  41   a ,  78   a . Accordingly, the positioning structure (the mounting structure)  10  for the power transmission mechanism PT in the housing  11  of the compressor C becomes simple. As a result, the various problems due to the complicated positioning structure, such as the complicated machining, the increased number of components and the enlarged size of the power transmission mechanism PT in the axial direction, are solved.  
      (2) The positioning means for positioning the pulley bearing  57  and the positioning means for positioning the stator bracket  48  share both the front positioning surface  78   a  and the rear positioning surface  41   a  in the axial direction. This leads to a further simple positioning structure for the power transmission mechanism PT in the housing  11  of the compressor C.  
      (3) The circular clip  78 , which exclusively serves as a positioning member, not only serves as the positioning means for positioning the pulley bearing  57  but also serves as the positioning means for positioning the stator bracket  48 . The shared circular clip  78  for exclusively positioning results in reducing the number of components for the positioning structure so that the shared circular clip  78  largely contributes to providing the low-cost compressor C with the power transmission mechanism PT.  
      (4) The electric motor  38  is accommodated in the sealed space  88  that is defined inside the pulley  17 . The pulley bearing  57  is arranged at a boundary between the sealed space  88  and the outside space. Water may be involved from the outside space into the sealed space  88  through a clearance between the collar  51  integrated with the pulley bearing  57  (the rear surface  53   a  of the flange  53 ) and the power supply ring  41  on the side of the housing  11  (the rear positioning surface  41   a ).  
      Then, in the preferred embodiment, the pulley bearing  57  contacts the rear positioning surface  41   a  through the third seal member  56 , which shuts the water immersion path. Accordingly, the sealed space  88  has relatively high water resistance and protects the electric motor  38  from being immersed in water. Thus, as the third seal member  56  is arranged at the positioning portion of the pulley bearing  57 , sealing pressure of the third seal member  56  is ensured by utilizing pressing force that acts at the positioning portion between the members  41  and  51  in comparison to a state where the third seal member  56  is separately arranged from the positioning portion, there is no need for assembling an additional exclusive member for ensuring sealing pressure of the third seal member  56  in the preferred embodiment.  
      (5) The rotation blocking means  54 ,  68   b  are arranged between the fixed race  58  of the pulley bearing  57  and the housing  11  for blocking the relative rotation between the members  11  and  58  around the axis of the pulley  17 . Accordingly, the fixed race  58  is prevented from being rotated with the rotation of the pulley  17  so that, for example, the pulley bearing  57  is prevented from rattling due to the slide abrasion by the relative rotation between the fixed race  58  and the housing  11 .  
      (6) The rotation blocking means  54 ,  68   b  is formed with the collar  51  and the engaging holes  68   b . The collar  51  is fixedly fitted to the fixed race  58  of the pulley bearing  57  and forms the engaging protrusions  54  around the axis of the pulley  17 . The engaging holes  68   b  are formed around the axis of the pulley  11  on the side of the housing  11 . The collar  51  engages the side of the housing  11  with recess-protrusion engagement so as to block the relative rotation between the fixed race  58  and the housing  11 . Thus, the collar  51  for forming the engaging protrusions or the rotation blocking means  54  is interposed between the pulley bearing  57  and the housing  11 . Thereby, the pulley bearing  57  is not especially formed by, for example, directly forming the engaging protrusions  54  with the fixed race  58 , but a general purpose bearing may still be used. This leads to providing the low-cost compressor C with the power transmission mechanism PT.  
      (7) With respect to the rotation blocking means  54 ,  68   b , the engaging holes  68   b  on the side of the housing  11  are formed in the stator bracket  48 . As described above, the pulley bearing  57  and the stator bracket  48  are positioned on the housing  11  so as to correspond with each other. Accordingly, while the pulley bearing  57  and the stator bracket  48  are positioned, the engaging protrusions  54  and the engaging holes  68 b may be engaged with each other. As a result, the power transmission mechanism PT is easily assembled to the compressor C.  
      The present invention is not limited to the embodiment described above but may be modified into the following alternative embodiments.  
      In alternative embodiments to those of the above preferred embodiment, the positioning means for positioning the pulley bearing  57  and the positioning means for positioning the stator bracket  48  share only one of the front positioning surface  78   a  and the rear positioning surface  41   a  in the axial direction. For example, the stator bracket  48  is positioned rearward in the axial direction by a stepped wall surface at a boundary between the large diameter portion  35   a  and the small diameter portion  35   b  in the boss  35 .  
      In alternative embodiments to those of the above preferred embodiment, the exclusive positioning member is not limited to the circular clip  78 . For example, a screw recess is formed on the outer circumferential surface of the small diameter portion  35   b  in the boss  35 , and a nut is screwed to this screw recess to provide a front positioning surface.  
      In alternative embodiments to those of the above preferred embodiment, the engaging recess is formed in the collar  51 , while the engaging protrusion is formed on the stator bracket  48 .  
      In alternative embodiments to those of the above preferred embodiment, the collar  51  and the brush unit holder  37 , or the collar  51  and the power supply ring  41 , are engaged with each other with recess-protrusion engagement to serve as the rotation blocking means.  
      In alternative embodiments to those of the above preferred embodiment, the engaging protrusion  54  is directly provided on the fixed race  58  of the pulley bearing  57 .  
      In alternative embodiments to those of the above preferred embodiment, the collar  51  is fixedly press-fitted to the brush unit holder  37  and the power supply brush unit  39  to be integrated with these members  37 ,  39 . This integration blocks the pulley bearing  57  (the fixed race  58 ) from rotating relative to the housing  11 . In this state, the press-fit structure of the collar  51  relative to the brush unit holder  37  and the power supply brush unit  39  serves as the rotation blocking means.  
      In alternative embodiments to those of the above preferred embodiment, the collar  51  is omitted, and the pulley bearing  57  is directly fitted around the brush unit holder  37  and the power supply brush unit  39 . In this state, the engaging protrusion  54  (the rotation blocking means) is directly provided on the fixed race  58  of the pulley bearing  57 .  
      In the above preferred embodiment, the electric motor  38  is an inner rotor type, which arranges the rotor  45  inside the stator  49 . In alternative embodiments to those of the above preferred embodiment, an electric motor is not limited to the inner rotor type but may employ an outer rotor type, which arranges a rotor outside a stator, or may employ a flat rotor type, which arranges a flat-shaped stator and a flat-shaped rotor in series in the axial direction.  
      Therefore, the present examples and embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein but may be modified within the scope of the appended claims.