Abstract:
A method of loading a tape from a single reel tape cartridge into a take-up reel. Position sensors detect position of a guide arm as a tape loading mechanism loads and unloads tapes from a single reel tape cartridge. The position sensors are accurate and eliminate problems that occur from small misalignments of hub filler access with the access of the take-up reel. Further, the position sensors enable the hub filler to consistently attach to a leader pin at the end of the tape of the single reel tape cartridge without frequent malfunctions.

Description:
RELATED APPLICATIONS 
     This application claims priority from U.S. provisional patent application Ser. No. 60/200,714, filed Apr. 27, 2000, which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a method and apparatus for sensing the position of a hub filler of a tape drive between a single reel tape cartridge and a take-up reel. 
     DESCRIPTION OF RELATED ART 
     Single reel tape cartridges are used to transport and store tape for reel-to-reel tape drives. A single reel tape cartridge is inserted into a tape drive and a mechanism is used to load the end of the tape into a take-up reel from the tape cartridge. Once the end of the tape is loaded into the take-up reel, the tape drive operates as a reel-to-reel tape drive. A motor is coupled to the take-up reel to rotate the take-up reel about the take-up reel axis and another motor is coupled to the single reel tape cartridge to rotate the reel of the tape cartridge about its axis. 
     The tape drive loading mechanism attaches to a tape leader pin. The tape leader pin is located at the end of the tape which is contained in the single reel tape cartridge. A slot in the hub filler is used for receiving the tape leader pin. The hub filler is driven by a guide arm between the single reel tape cartridge and the take-up reel. An example of a mechanism for driving the hub filler between the tape cartridge and the take-up reel is disclosed in U.S. Pat. No. 6,034,839. 
     FIG. 1 is a view of the tape drive loading mechanism disclosed in U.S. Pat. No. 6,034,839. The hub filler  300  enters into the cartridge  210  and attaches to the end of the tape. The hub filler  300  then moves along a guide rail  247 , driven by the guide arm  250 . Typically, the hub filler  300  attaches to the end of a tape in the tape cartridge  210  and the guide arm  250  moves the hub filler  300  along the guide rail  247 , trailing the tape across the read/write head  222  and into the take-up reel  242 . The hub filler  300  enters the take-up reel  242  through a channel  244  and into the hub  245  of the take-up reel  242 . 
     FIG. 2 is a top view of the tape drive, depicting the hub filler  300  in the take-up reel  242  with the tape  216  attached. The tape  216  passes across the read/write head  222  and the end of the tape  216  is secured to the take-up reel  242 . The tape drive is then operated by rotation of the take-up reel  242  and the single reel of the cartridge  210  about their respective axes to move the tape  216  across the read/write head  222 . Motors are used to rotate the take-up reel  242  and the single reel of the cartridge  210 , controlling the speed of the tape  216  as it moves across the read/write head  222 . The hub filler  300  pivots on an axle  252  that is coupled to the guide arm  250 . This pivoting is necessary for the hub filler  300  to be guided on the guide rail  247  into the take-up reel  242 . Once the hub filler  300  is in the take-up reel  242 , with the tape  216  attached, the take-up reel  242  rotates to thereby unload the tape from the cartridge  210 . The hub filler  300  rotates with the take-up reel  242  on the axle  252 . The loading mechanism attempts to align the axle  252  axis and the take-up reel  242  axis perfectly. 
     There are some concerns regarding the tape drive loading mechanism described above. Perfectly aligning the hub filler&#39;s axle axis and the take-up reel axis is very difficult to do, due to mechanical tolerances. Misalignment can cause minor imbalances during rotation of the take-up reel; these minor imbalances can create small speed variations in the tape wind and unwind speeds. These variations in speed are difficult for the motors of the take-up reel and cartridge reel to compensate for. Hence, the variations in speed deter from the quality of the reading and writing of the tape at the read/write head. Additionally, misalignment of the hub filler axis and the take-up reel axis reduce the life of the bearings in the take-up reel. Worn bearings will produce vibrations and result in noise during recording and reading at the read/write head. 
     Controlling the hub filler at the single reel tape cartridge to attach to a tape leader pin is somewhat difficult to consistently accomplish. This difficulty arises from the circumstance that the tape leader pin is very small and the slot in the hub filler for receiving the tape leader pin is very small. Small misalignments or miscalibrations of the movement of the hub filler at the single reel tape cartridge may cause a failure of the hub filler to pick up the tape leader pin and thereafter load the tape from the tape cartridge onto the take-up reel. Hence, misalignment of the hub filler at the single reel cartridge can cause a malfunction in the tape drive loading mechanism and therefore make the tape drive loading mechanism unreliable. 
     SUMMARY OF THE INVENTION 
     There is a need for a tape drive loading mechanism with the ability to sense the precise position of the hub filler during loading and unloading of tape from a removable tape cartridge. 
     These and other needs are met by embodiments of the present invention, which provide sensors for sensing the precise position of a guide arm. More specifically, the present invention relates to an apparatus for loading a take-up reel with tape from a removable tape cartridge. The apparatus comprises a hub filler for transporting an end of the tape from the tape cartridge to the take-up reel. The hub filler is driven by a guide arm along a guide rail from the removable tape cartridge into the take-up reel. The apparatus also comprises at least one sensor for detecting the position of the hub filler. The tape loading mechanism of the present invention uses feedback from the at least one sensor to control the motor that drives the guide arm that drives the hub filler. The present invention has the advantage of utilizing the feedback from at least one of the sensors in a precise manner to detect and utilize the exact position of the hub filler to reliably attach and detach the hub filler to the tape leader pin at the removable tape cartridge and to precisely align the axle of the hub filler in the take-up reel. The present invention also eliminates the need for the tape loading device to rely on encoded motor positions, which can be miscalibrated, to position the hub filler. 
     There are several advantages of the present invention. The present invention enables the hub filler axis and the take-up reel axis to be precisely aligned as the hub filler attaches to the take-up reel. The present invention mitigates imbalances during rotation of the take-up reel. These imbalances create small speed variations in the tape wind and unwind speeds as a result of the misalignment of the hub filler axis and the take-up reel axis. Another related advantage of the present invention is that the bearings are not damaged due to the misalignment of the hub filler axis and the take-up reel axis. Worn bearings produce vibrations that cause noise in the read/write head during reading and writing of the tape. Yet another advantage of the present invention is that the hub filler can attach to the leader pin consistently and reliably, as the position of the hub filler and the timing of the gearing mechanisms can act cooperatively to efficiently and effectively enable the attachment of the leader pin to the hub filler. The above-listed advantages are examples and not exclusive. 
     The foregoing and other features, aspects, and advantages of the present invention will become more apparent from the following detailed description of the present invention, taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a view of a tape drive loading mechanism. 
     FIG. 2 is a top view of the tape drive loading mechanism of FIG.  1 . 
     FIG. 3 is a perspective view of the tape drive loading mechanism of the present invention. 
     FIG. 4 is a perspective view of the hub filler on the guide rail. 
     FIG. 5 is a top view of the tape drive loading mechanism of the present invention. 
     FIG. 6 is a side view of the hub filler entering the take-up reel. 
     FIG. 7 is a side view of the hub filler entering the take-up reel and decoupling from the guide arm. 
     FIG. 8 is a side view of the hub filler completely lodged in the take-up reel. 
     FIG. 9 is a side view of the hub filler in the take-up reel and decoupled from the guide arm. 
     FIG. 10 is a side view of the axle. 
     FIG. 11 is a side view of the shaft in the hub filler for receiving the axle. 
     FIG. 12 is a view of the ramp. 
     FIG. 13 is an oblique view of the tape loading mechanism comprising two position sensors. 
     FIG. 14 is a top view of the tape loading mechanism with the hub filler in position for attachment to a tape leader pin and its position being detected by a sensor. 
     FIG. 15 is a top view of the tape loading mechanism with the hub filler attached to the take-up reel with its position being detected by a sensor. 
     FIGS. 16A-16G show cross-sectional diagrams of a tab interacting with a sensor. 
     FIG. 17 is a block diagram of a guide arm motor controller coupled to both a position sensor and a guide arm motor. 
     FIG. 18 depicts an exemplary feed back signal. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention relates to an apparatus for sensing the position of a hub filler at a cartridge and a take-up reel of a tape drive. The cartridge of the present invention is a removable single reel cartridge and it is necessary for the tape drive to load the end of a tape from the cartridge to the take-up reel. A hub filler, which is part of the tape drive, receives the end of the tape from the cartridge. A sensor located proximate to the cartridge detects the precise position of the hub filler and serves to calibrate the hub filler as it receives the end of the tape from the cartridge. After the hub filler has attached to the end of the tape in the cartridge, usually by attaching to a leader pin that is connected to the end of the tape, the hub filler moves along a guide rail pulling the tape out of the cartridge, across the read/write head, and into the take-up reel. The hub filler enters the take-up reel, with the tape attached, bringing the hub filler to the hub of the take-up reel. Upon the hub filler attaching to the take-up reel, the tape is connected to both the single reel of the cartridge and the take-up reel. A sensor located proximate to the take-up reel detects the position of the hub filler serving to calibrate the attachment of the hub filler to the take-up reel in a precise manner. The rotation of the reel of the tape cartridge and the take-up reel controls the movement of the tape across the read/write head and consequently the reading of the tape. A guide arm drives the hub filler between the cartridge to the take-up reel. 
     FIG. 3 is a perspective view of the tape drive loading mechanism of the present invention. A removable single reel tape cartridge  610  is shown positioned in the tape drive. The tape  613  is wound on a reel inside the cartridge  610  and the end of the tape  613  is attached to a leader pin  618 . A hub filler  616  moves along a guide rail  624 , driven by a guide arm  626 , between the cartridge  610  and a take-up reel  614 . The hub filler  616  pivots on an axle  620 . The hub filler  616  is held to the guide rail  624  by pressure from a spring  622  as the hub filler  616  moves along the guide rail  624  to and from the tape cartridge  610  and the take-up reel  614 . The hub filler  616  also includes a slot  617  that attaches to the leader pin  618  when entering the cartridge  610 . As the hub filler  616  enters the take-up reel  614 , the axle  620  is lifted from the hub filler  616  by a ramp  612  that de-couples the axle  620  from the hub filler  616 . 
     Other mechanisms can be used to de-couple the axle  620  from the hub filler  616  within the scope of the invention. For example, one embodiment that may be used to de-couple the axle  620  from the hub filler  616  is a spring mechanism that manipulates spring tension at the take-up reel  614  to lift the axle  620  out of the hub filler  616 . Other embodiments include a snap coupling arrangement, and a latch and release arrangement. Still another embodiment that may be used to de-couple the axle  620  is a motor lifting the axle  620  out of the hub filler  616 . The above-described embodiments for lifting the axle  620  out of the hub filler  616  are not exclusive. 
     FIG. 4 is a perspective, enlarged view of the hub filler  616  on the guide rail  624  between the tape cartridge  610  and the take-up reel  614 . The hub filler  616  is held to the guide rail  624  by the spring  622  disposed around the axle  620 . The spring  622  creates tension between the hub filler  616  and the guide arm  626 . The axle  620  is moveable in the vertical direction and rotatable in a bore of the guide arm  626 . The top of the axle  620  has a portion that is larger than the bore of the guide arm  626 . The guide arm  626  moves in a horizontal plane during travel between the cartridge  610  and the take-up reel  614 . The spring  622  between the guide arm  626  and the hub filler  616  exerts downward pressure (as viewed in FIG. 4) on the hub filler  616 , pressing the hub filler  616  against the guide rail  624 . This ensures that the hub filler  616  stays on the guide rail  624  during travel from the cartridge  610  to the take-up reel  614 . The spring  622  is attached to a notch in the axle  620  and pushes the axle  620  into the hub filler  616 . When the axle  620  is pulled out of the hub filler  616 , the tension of the spring  622  is increased. 
     FIG. 5 is a top view of the tape drive loading mechanism of the present invention. The single reel tape cartridge  610  is shown inserted in the tape drive. The hub filler  616  is shown entering the take-up reel  614 , but not yet fully inserted. The axle  620  is shown at the entering position of the ramp  612 . The hub filler  616  travels from the cartridge  610  to the take-up reel  614  along the guide rail  624 , pulling tape from the cartridge  610  across a read/write head  619 . 
     FIG. 6 is a side view of the hub filler  616  just entering the take-up reel  614 . The side view of the hub filler  616  shows the axle  620  in a sheath  628  of the hub filler  616 . Since the sheath  628  and the axle  620  are cylindrical, the hub filler  616  is able to pivot about the axle  620  as the hub filler  616  travels along the bends of the guide rail  624 . A small shaft  621  of the axle  620  and a small bore  623  of the sheath  628  fit snugly together, such that the hub filler  616  pivots about the axle  620  and is tightly controlled by the movement of the guide arm  626 . The spring  622  is attached to the axle  620  at a notch  625  in the axle  620 . The other end of the spring  622  presses against the guide arm  626 , creating tension and pushing the axle  620  into the sheath  628  of the hub filler  616 . The axle axis  630  is the axis about which the hub filler  616  pivots during travel along the guide rail  624 . 
     As will be explained in more detail with respect to FIGS. 7-9, the axle  620  is de-coupled from the hub filler  616  by the ramp  612 , so that the hub filler  616  can rotate freely on the axis of the take-up reel  614  during winding and unwinding of the tape. The large shaft  627  of the axle  620  is rotatable inside the bore  613  of the guide arm  626 . Above the large shaft  627  of the axle  620  is a top section  629  of the axle  620 . As the hub filler  616  enters the take-up reel  614 , the axle top section  629  contacts the ramp  612  and the axle  620  is lifted out of the hub filler  616 . When the hub filler  616  is not in the take-up reel  614 , the axle  620  is in the hub filler  616  and the hub filler  616  is tightly pivoting on the axle  620 . A small spherical stop  631  interacts with the top of a large bore  635  to limit movement of the axle  620  into the sheath  628 . 
     FIG. 7 is a side view of the hub filler  616  entering the take-up reel  614 . The axle top section  629  and the axle  620  are lifted up the ramp  612  as the hub filler  616  moves into the take-up reel  614  driven by the guide arm  626 . This causes the axle  620  to partially lift out of the hub filler  616 . The small shaft  621  is almost, but not completely, removed from the small bore  623 . The axis  630  of the axle  620  is now closer to the axis  632  of take-up reel  614  than shown in FIG.  6 . 
     FIG. 8 is a side view of the hub filler  616  in the take-up reel  614 . The hub filler  616  is fully inserted in the take-up reel  614  due to the continued movement of the arrangement by the motor and linkage. In the illustrated embodiment, the axle  620  is lifted up by the ramp  612  and a main shaft portion  633 , of larger diameter than small shaft  621 , pushes the hub filler  616  completely into the take-up reel  614  by pushing against one side of the large bore  635 . The small shaft  621  has been completely lifted out of the small bore  623  to de-couple the small shaft  621  from the small bore  623 . This allows some freedom of movement of the axle  620  in the hub filler  616 . The main shaft portion  633  is only able to push the hub filler  616  through contact with the large bore  635 , when the small shaft  621  is not de-coupled from the small bore  623 . At this point, the guide arm  626  has pushed the hub filler  616  to the extreme end of the channel in the take-up reel  614 . The axle  620  is still in contact with the hub filler  616  and not de-coupled from the hub filler  616 . The axis  630  of the axle  620  is not aligned with the axis  632  of the take-up reel  614 . In certain embodiments of the invention, the take-up reel  614  will rotate several times while the main shaft portion  633  is still in contact with the large bore  635 . 
     FIG. 9 is a side view of the hub filler  616  in the take-up reel  614  when it is fully decoupled from the guide arm  626 . The axle  620  is now centered in the sheath  628  such that the axis  630  of the axle  620  and the axis  632  of the take-up reel  614  are aligned. Since the guide arm  626  is fully de-coupled from the hub filler  616 , the take-up reel  614  is able to rotate freely around the axis  632 , immune from any small misalignments between the axle axis  630  and the take-up reel axis  632 . This relative immunity helps prevent small speed variations and wearing down of the bearings. 
     In certain embodiments of the invention, the guide arm  626  is driven by a motor (not shown) with an encoder. The motor has encoded positions for positioning of the guide arm  626  throughout the loading and unloading of the tape; such positioning can include attachment of the tape  613  at the cartridge  610 , movement along the guide rail  624  into the take-up reel  614 , the de-coupling movements in the take-up reel  614 , recoupling movements of the guide arm  626  with the hub filler  616 , return of the tape to the cartridge  610 , and detachment movements of the tape from the hub filler  616 . Small misalignments due to the encoded motor position or other mechanical tolerations are immune in the take-up reel  614 , as the axle  620  is de-coupled from the hub filler  616  during rotation of the take-up reel  614  during the reading and writing of the tape  613  in the tape drive. 
     FIG. 10 is a side view of the axle  620 . The axle top section  629  is above the large shaft  627  which is above the notch  625  for the spring. The notch  625  for the spring is above the small spherical stop  631 . The small spherical stop  631  is above the main shaft  633 . The medium shaft  633  is above the small shaft  621 . The small shaft  621  is above the axle point  637 . 
     FIG. 11 is a side view of the shaft  628  of the hub filler  616 . The large bore  635  is above the small bore  623 . The small bore  623  is above the axle&#39;s point receiver  639 . 
     FIG. 12 is a top perspective view of the ramp  612 . The ramp  612  has a first bore  640  and a second bore  642  for attachment of the ramp  612  above the take-up reel  614 . The ramp  612  has diagonal regions  646  and a plateau region  644 . A channel  648  in the ramp  612  is disposed in the plateau region  644  and between the diagonal regions  646 . As the axle  620  enters the channel  648  of the ramp  612 , the top section  629  of the axle  620  is positioned between the diagonal regions  646  to catch on the ramp  612 . The large shaft  635  travels inside the channel  648  as the axle  620  is lifted out of the hub filler  616  by the ramp  612 . 
     FIG. 13 is an oblique perspective of embodiments of the present invention utilizing position sensors to detect the position of a hub filler during loading and unloading of tape from a removable tape cartridge to a take-up reel. These embodiments of the present invention include position sensors  702 ,  704  and tabs  706 ,  710 . The tabs  706 ,  710  interfere with the position sensors  702 ,  704  to produce a feedback signal indicative of the precise position of the hub filler  616 . In some of the embodiments, the tape loading mechanism includes one position sensor  702  for detecting the exact position of the hub filler  616  as the hub filler  616  is inserted into a removable tape cartridge (not shown) and another position sensor  704  for sensing the exact position of the hub filler  616  when the hub filler  616  is inside the take-up reel  705 . The sensors  702 ,  704  cooperate with tabs  706 ,  710  in the respective positions. The tabs  706 ,  710  are attached to the guide arm  626  which drives the hub filler  616  along the guide rail  624 . One sensor  702  is positioned proximate to the location along the guide rail  624  where the hub filler  616  attaches to a tape leader pin (not shown). The tab  710  is attached to the guide arm  626  and aligned such that the tab  710  enters the position sensor  702  when the hub filler  616  is in position to attach or detach a leader pin. Likewise, position sensor  704  is attached to the tape loading mechanism proximate to the take-up reel  705 . When the hub filler  616  is positioned inside the take-up reel, tab  706  is aligned such that tab  706  is inserted into the position sensor  704 . 
     FIG. 14 is a top view of the tape loading mechanism of the present invention. FIG. 14 depicts the hub filler  616  in position to attach or detach from a leader pin. Accordingly, tab  710  is inside position sensor  704 . 
     FIG. 15 is a top view of the tape loading mechanism of the present invention. FIG. 15 depicts the hub filler  616  aligned inside the take-up reel  705 . Accordingly, the tab  706  is inside the position sensor  702 . 
     In embodiments of the present invention, the position sensors  702 ,  704  are optical sensors and the tabs  706 ,  710  have apertures that interact with the position sensors. In some embodiments, the position sensors  702  and  704  are differential hall effect sensors and the tabs  706 ,  710  are metallic veins. 
     One of ordinary skill in the art will appreciate other types of position sensors and tabs that can be used to accurately detect the position of the hub filler during loading and unloading of tape from a tape cartridge to a take-up reel. Such sensors would include a sensing element that would detect the position of the hub filler, preferably without physical contact. Preferably, the position sensors manipulate electromagnetic phenomena (i.e. light or magnetic fields) such that the tabs interact with the position sensors without friction to indicate the position of the hub filler  616 . Further, one of ordinary skill in the art would appreciate the use of other forms of electro-magnetic fields to detect the position of the hub filler of the tape loading mechanism of the present invention. 
     FIGS. 16A-16G depict an exemplary embodiment of the present invention, wherein the position sensor is an optical sensor and the tab includes an aperture. FIGS. 16A-16G are cross-sectional views of the optical sensor and the aperture in different stages of the aperture passing through the optical sensor. The optical sensor is a bi-cell arrangement comprising a light emitting element  724  and two photocells  720 ,  722 . The first photocell  720  is adjacent to the second photocell  722  and are opposite from a light emitting element  724 . The tab comprises two parts; a first leading edge  718  and a trailing edge  716 . The aperture  717  is between the leading edge  718  and the trailing edge  716 . As the aperture  717  moves through the optical sensor, the leading edge  718  and the trailing edge  716  sequentially block light emitted by the light emitting element  724  from being received at the first photocell  720  and second photocell  722 . Each photocell  720 ,  722  outputs a voltage according to the intensity of light received by each photocell  720 ,  722  from the light emitting element  724 . The voltages output from the photocells  720 ,  722  are electrically connected to a guide arm controller (not shown). 
     FIG. 17 is a block diagram of a guide arm controller  745 . FIG. 17 depicts the relationship between the guide arm controller  745 , the position sensor  741 , and the guide arm motor  747 . The guide arm motor  747  drives a guide arm which drives a hub filler  616 . The guide arm controller  745  is electrically coupled to position sensor  741 . The controller  745  receives information from the position sensor  741  and uses this information to control the guide arm motor  747 . The sensor output  743  is a feedback signal that the guide arm controller  745  utilizes to determine the appropriate guide arm motor input  744  to control the guide arm motor  747  such that the position of a hub filler  616  can be accurately controlled. The guide arm controller  745  also controls the guide arm motor  747 , according to the particular function of the hub filler  616 . For instance, when a hub filler  616  attaches to a leader pin at a removable tape cartridge, the guide arm controller  745  will utilize the position sensor output  743  to accurately pick up the leader pin at a predetermined position. After the leader pin has been picked up at the predetermined position, the guide arm controller  745  will control the guide arm motor through the guide arm motor input  744  to deliver the end of the tape from a removable tape cartridge to a take-up reel. This operation will not require feedback from the position sensor  741 . In embodiments of the present invention, a plurality of position sensors will be located throughout the tape drive at points where accurate positioning of a hub filler  616  is required. Each one of the plurality of position sensors will be individually coupled to the guide arm controller  745 , each providing separate feedback. Accordingly, position sensor  741  and position sensor output  743  are exemplary of only one of the plurality of position sensors. 
     In the bi-cell sensor arrangement, the guide arm controller  745  applies an algorithm for determining the exact position of the hub filler by processing the voltage output from the first photocell  720  and the second photocell  722 . In one embodiment, the algorithm uses a ratio that is the difference of the voltage continuously read from photocell  720  and photocell  722  divided by the constantly held sum of the voltage of photocell  720  and photocell  722  when an aperture is not obstructing light from being received from the light emitting element  724  into photocells  720 ,  722 . The following is an equation representative of the algorithm, wherein A is the continuous output from photocell  720  and B is the continuous output of photocell  722 .          Sensor                 Output     =       A   -   B       A   +   B                              
     FIG. 18 is an output signal from a bi-cell arrangement. Each of the points  746 ,  750 ,  752  on the graph of the output signal represent a precise position of the hub filler. The guide arm controller  745  interprets the signal from the bi-cell arrangement to control the position of the hub filler. 
     The use of the sensors in the embodiments of the present invention provides more precise control of the movements employed in loading a tape in a tape drive. This precise control permits minor adjustments of the alignment of a hub filler axle with a hub filler, as seen in FIGS. 6-9, without placing total reliance on an encoder. 
     The present invention provides an improved method of loading a tape from a single reel tape cartridge into a take-up reel. This is accomplished, in part, by sensing the position of a hub filler as it enters a take-up reel and when the hub filler attaches to a tape leader pin. The sensing of the position of the hub filler mitigates problems of conventional tape drive mechanisms that result from small misalignments of the axis of the hub filler axle with the axis of the take-up reel. Also, small misalignments of the hub filler at the tape cartridge result in inconsistencies of the hub filler attaching the tape and the tape cartridge. 
     Although the present invention has been described and illustrated in detail, it is to be clearly understood that the same is by way of illustration and example only, and is not to be taken by way of limitation. The scope of the present invention being limited only by the terms of the appended claims.