Abstract:
Apparatus and methods for dispensing sheet material from a sheet material dispenser are described. A drive mechanism powered at least in part by one or more springs discharges sheet material from the dispenser. A diverter redirects at least one of the springs enabling use of a relatively longer spring in a more compact and space-efficient dispenser housing. The dispenser may include a cutting mechanism powered at least in part by the one or more springs.

Description:
RELATED APPLICATION  
       [0001]     This application claims the benefit of provisional U.S. patent application Ser. No. 60/681,241 filed May 13, 2005 the entire contents of which are incorporated herein by reference. 
     
    
     FIELD  
       [0002]     The field relates to dispenser apparatus and, more particularly, to sheet material dispensers and drive mechanisms for use therewith.  
       BACKGROUND  
       [0003]     Dispensers for flexible sheet material, such as paper towel, cloth towel, tissue and the like, are well known in the art. Certain types of sheet material dispensers are powered through some or all of a dispense cycle by a drive mechanism including one or more springs. For example, in a dispenser type known as a hands-free dispenser, a drive mechanism is utilized to discharge sheet material from the dispenser and to power a cutting mechanism which provides a single sheet of material to the user. More specifically, a dispense cycle is initiated when a user pulls on the sheet material tail which extends from the dispenser. Pulling of the tail initiates operation of the dispenser drive mechanism by rotating a dispenser drive roller and by energizing one or more springs associated with the drive roller. The spring or springs then power the drive roller to rotate through the dispense cycle and may further power the cutting mechanism to fully or partially sever the sheet material resulting in the user being provided with a single sheet of material.  
         [0004]     Dispensers of the type described above must be robust and must be capable of dispensing a separate sheet of material to a user reliably over many dispense cycles. And, because space in a washroom or other intended dispenser location may be limited, the dispenser should include components enabling the dispenser to be manufactured with a compact housing.  
       SUMMARY  
       [0005]     Apparatus and methods for dispensing sheet material from a sheet material dispenser are described. In preferred embodiments, the apparatus comprises a housing and a drive mechanism for discharging sheet material from the dispenser. Preferably, the drive mechanism comprises a drive roller rotatably mounted with respect to the housing and at least one spring powering rotational displacement of the drive roller during at least a portion of a drive roller rotational cycle.  
         [0006]     The drive mechanism includes diverter apparatus adapted to bend at least one of the springs along at least one spring position, preferably intermediate the spring ends. Such diverter apparatus enables use of one or more springs each having a length greater than that of a spring arranged in a traditional axial orientation. Elongation of each diverted spring enables each such spring to better power the drive mechanism in a more compact dispenser housing. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]     The foregoing and other objects, features and advantages of the invention will be apparent from the following description of preferred embodiments, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. In the drawings:  
         [0008]      FIG. 1  is a perspective view of an exemplary dispenser.  
         [0009]      FIG. 2  is a perspective view of the dispenser of  FIG. 1  with the front cover removed.  
         [0010]      FIG. 3  is a further perspective view of the dispenser of  FIG. 1  with the front cover removed.  
         [0011]      FIG. 4  is a perspective view of a dispenser frame removed from the dispenser.  
         [0012]      FIG. 5  is a further perspective view of the dispenser frame of  FIG. 4 .  
         [0013]      FIG. 6  is an exploded view of the dispenser frame and other dispenser parts.  
         [0014]      FIG. 7  is a perspective view of a drive roller portion.  
         [0015]      FIG. 8  is a further perspective view of the drive roller portion of  FIG. 7 .  
         [0016]      FIG. 9  is a perspective view of a cam.  
         [0017]      FIGS. 10-15  are schematic side elevation views of the exemplary dispenser of  FIGS. 1-9  showing the position of certain drive mechanism, cutting mechanism and other components during different stages of a dispense cycle. Certain parts are shown in phantom line or are omitted to facilitate understanding of the apparatus and methods of operation.  
         [0018]      FIG. 10A  is a partial sectional view taken along section lines  10 A- 10 A of  FIG. 10  showing portions of a diverter and spring.  
         [0019]      FIG. 10B  is a partial side sectional view taken along section lines  10 B- 10 B of  FIG. 10A  showing portions of a diverter and spring.  
         [0020]      FIG. 10C  is the partial sectional view of  FIG. 10A  but showing only portions of the diverter and frame. 
     
    
     DETAILED DESCRIPTION  
       [0021]     The mechanical components comprising preferred embodiments of an exemplary dispenser  10  will first be described. Referring first to  FIGS. 1-3 , dispenser  10  preferably includes housing  11  and removable front cover  13 . In the embodiment, dispenser  10  is configured for mounting on a vertical wall surface (not shown) permitting a user to easily access dispenser  10 . Housing and cover  11 ,  13  may be made of any suitable material or materials such as formed sheet metal, plastic and the like.  
         [0022]     Frame  15  is mounted within housing  11  as shown in  FIGS. 2-3 . Frame  15  may be a unitary part made of plastic or other suitable material and secured with respect to housing  11  in any suitable manner. Frame  15  supports drive roller  17 , springs  19 ,  21  and diverter  23 . Drive roller  17  may also be referred to by some in the industry as a “drum.” 
         [0023]     Preferably, dispenser  10  is adapted to dispense sheet material in the form of a sheet material roll (not shown). As is well known, sheet material in roll form comprises a hollow cylindrically-shaped tubular core (not shown) and sheet material in the form of a web  25  of sheet material ( FIGS. 10-15 ) wrapped around the core. The core is typically a hollow tube made of cardboard, plastic or the like.  
         [0024]     The dispenser shown can accommodate a stub roll (not shown) and a reserve roll (not shown) of the sheet material. The stub roll may be supported within frame  15  on stub roll holders  27 ,  29  mounted on frame  15 . Each end of the tubular core of the stub roll is mounted on a respective roll holder  27 ,  29  with the respective roll holder inserted into the hollow core. Holders  27 ,  29  are preferably made of a resilient material so that they may be spread apart to receive the stub roll between them. The stub roll is free to rotate when mounted on holders  27 ,  29 .  
         [0025]     The reserve roll is supported by support arms  31 ,  33  and web roll support cups  35 ,  37  mounted on respective arms  31 ,  33 . Each end of the tubular core of the reserve roll is mounted on a respective cup  35 ,  37  with the respective cup inserted into the hollow core. Arms  31 ,  33  are preferably made of a resilient material so that they may be spread apart to receive the reserve roll core between them.  
         [0026]     As will be appreciated, any type of support structure may be utilized to support the stub and reserve rolls. For example, the stub roll may simply rest on bottom wall  39  of frame  15  without holders  27 ,  29 . By way of further example, holders  27 ,  29  and support arms and cups  31 ,  33 ,  35 ,  37  could be replaced with a rod inserted through the hollow roll core. Such a rod may be supported at its ends by housing  11 .  
         [0027]     There is no particular requirement with respect to the number of sheet material sources which may be dispensed from dispenser  10 . Dispenser  10  could dispense, for example, from single or plural rolls of material depending on the intended use of dispenser  10 .  
         [0028]     A drive mechanism  41  is provided for discharging web  25  from dispenser  10 . Drive mechanism  41  comprises drive roller  17 , tension roller  43 , tension springs  19 ,  21 , diverter  23  and the related components as hereinafter described and as shown particularly in  FIGS. 2-15 .  
         [0029]     Preferred drive roller  17  may be a drum-shaped member which is generally-cylindrical in appearance. Drive roller  17  may comprise first and second sections  45 ,  47 , first and second ends  49 ,  51  and outer surface  53 . Sections  45 ,  47  may be made of plastic or any other suitable material and may be joined by use of adhesives or fasteners  55  ( FIG. 6 ).  
         [0030]     Drive roller  17  is preferably mounted on frame  15  along axis  56 . Drive roller  17  is preferably mounted for bidirectional rotatable movement by stub shafts  57 ,  59  which extend axially outward from a respective drive roller end  49 ,  51 . Stub shafts  57 ,  59  are received in a respective bearing  61 ,  63 . Bearing  61  is seated in opening  65  of cam  67  and bearing  63  is seated in opening  68  of frame  15 . Bearings  61 ,  63  are preferably made of nylon or a similar low-friction material.  
         [0031]     Referring to  FIGS. 3-4 ,  6 , and  10 - 15 , eccentric arm  69  is seated on stub shaft  57  and is secured to stub shaft by fastener  71 . Arm  69  co-rotates with drive roller  17 . A spring-attachment member  73  is rotatably mounted to end  75  of arm  69  by fastener  77 . Member  73  includes arms  79 ,  81  for attachment to a respective spring  19 ,  21  as described herein.  
         [0032]     Referring to  FIGS. 1-2  and  5 - 6 , a hand wheel  83  linked to drive roller  17  may optionally be provided. Hand wheel  83  is provided to permit manual rotation of drive roller  17 , such as to feed web  25  out from dispenser  10  through discharge opening  85  at the time web  25  is loaded into dispenser  10 . Hand wheel  83  is linked to drive roller  17  at end  51  by means of a hand wheel post  87  keyed to fit into corresponding female opening (not shown) in stub shaft  59  and secured by fastener  89 .  
         [0033]     As shown in  FIGS. 2-8 , drive roller outer surface  53  preferably includes one or more friction surfaces  91  for engaging and gripping web  25 . Friction surfaces  91  are provided to ensure that the drive roller outer surface  53  has sufficient frictional contact with the web  25  so that drive roller  17  will rotate as web  25  positioned across drive roller  17  is pulled from dispenser  10  by a user.  
         [0034]     The plural friction surfaces  91  ( FIGS. 2-6 ) may be in the form of sheet-like strips adhered to drive roller outer surface  53  with a suitable adhesive (not shown). However, such friction surfaces  91  could be provided in other manners, such as by forming such friction surfaces directly in outer surface  53 . Further, the friction surfaces  91  need not be limited to the plural strip-like material shown and could comprise any appropriate configuration, such as a single sheet of material (not shown). Friction surfaces  91  may consist of any suitable high-friction material, such as grit or rubberized material. An over molded thermoplastic elastomer may also be applied to drive roller  17  out surface  53 . Such an elastomer is applied directly to the surface  53  and sets to form a gripping surface similar to friction surfaces  91 .  
         [0035]     Fingers  92  of guard  94  extend into corresponding annular grooves  96  in drive roller  17  to separate web  25  from drive roller  17  so that web  25  does not become adhered to the drive roller  17  (such as by static electricity) and to ensure that web  25  is properly directed out of dispenser  10  through discharge opening  85 . Guard  94  may be attached across frame  15  by any suitable means well known in the art.  
         [0036]     Drive roller  17  preferably further includes a longitudinal opening  93  through which a cutting blade  95  of a cutting mechanism  97  extends to perforate the web  25  as hereinafter described.  
         [0037]     Tension roller  43  urges web  25  against outer surface  53  of drive roller  17 . Tension roller  43  preferably is a generally cylindrically-shaped member having first and second axial stub ends  101 ,  103 . Roller axial stub ends  101 ,  103  fit rotatably in respective slots  109 ,  111  provided in frame  15 . As shown in  FIGS. 3-6 , torsion springs  113 ,  115  urge tension roller  43  against drive roller  17 . Tension roller  43  is generally coextensive with drive roller  17  and is mounted along an axis  117  parallel to axis  56 .  
         [0038]     Tension roller  43  may be provided with annular gripping surfaces  119  seated in a respective annular seat  121  and positioned to abut a respective drive roller friction surface  91 . Such gripping surfaces  119  are preferably made of a tactile material such as rubber, or the like.  
         [0039]     Drive roller  17  and tension roller  43  form a nip  123  at the interface of drive roller  17  and tension roller  43 . Web material  25  is drawn from a respective stub or reserve roll through nip  123 , against outer surface  53  of drive roller  17  and out of dispenser via discharge opening  85  as described in detail below.  
         [0040]     Drive mechanism  41  further includes springs  19 ,  21  and diverter  23 . Each spring  19 ,  21  is preferably a tension spring. Each spring  19 ,  21  may be identical to each other, but this is not required. Springs  19 ,  21  are loaded, or energized, by rotation of drive roller  17  resulting from user web pulling. Loaded springs  19 ,  21  then power further rotation of drive roller  17  and operation of the cutting mechanism  97  (as the springs are unloaded) to complete a dispense cycle.  
         [0041]     As is well illustrated in  FIGS. 3-5 ,  6 ,  10 ,  10 A- 10 C and  11 - 15 , spring  19  has ends  127 ,  129 . End  127  is secured to frame  15  at post  131  and may be secured to post  131  by fastener  133 . The other spring  19  end  129  is attached to arm  79  of spring-attachment member  73 . Spring  21  had ends  135 ,  137 . Spring end  135  is secured to frame  15  at post  139  and may be secured to post  139  by fastener  141 . The second spring  21  end  137  is attached to arm  81  of spring-attachment member  73 .  
         [0042]     Referring further to  FIGS. 3-5 ,  6 ,  10 ,  10 A- 10 C and  11 - 15 , diverter  23  is provided to contact spring  21  and to bend spring  21  when spring  21  is in the rest position of  FIG. 10 . Preferably, diverter  23  contacts spring  21  between ends  135 ,  137 . Diverter  23  is secured to frame  15  by adhesive or other suitable fastener  181  ( FIG. 10B ). Referring again to FIGS.  10 ,  10 A- 10 C and  11 - 15 , diverter  23  may include a guide surface  143 . Guide surface  143  preferably includes a groove, or recess, in which spring  21  is fully or partially seated when in the rest position of  FIG. 10 . Guide surface  143  groove serves as a guide to keep spring  21  in place during the dispense cycle. Diverter  23  may be made of materials such as plastics. Diverter  23  could be an integral component of frame  15 .  
         [0043]     In the preferred rest position of  FIG. 10 , spring  19  has a generally axial orientation which is retained generally throughout a dispense cycle. Spring  21  has a generally axial segment  145  between end  135  and diverter  23  and a generally axial segment  147  between diverter  23  and end  137 . Axes  146 ,  148  are shown on  FIG. 10B . Spring  21  has a segment  149  therebetween which is bent as it contacts diverter  23 . Segments  145 ,  147  are axial only in the sense that they represent generally straight spring portions about diverter  23  when at rest as in  FIG. 10 . Put another way, spring  21  is bent by the diverter. The bend preferably includes a radius as shown in  FIGS. 4, 10A ,  10 B and  10 - 15 . The position and orientation of segment  147 , in particular, will change as spring  21  bends and is moved during a dispense cycle as is well-illustrated in  FIGS. 10-15 . Thus, diverter  23  acts on spring  21  such that segments  145 ,  147  are not co-axial when in the rest position of  FIG. 10 . It is preferred but not required that springs  19 ,  21  are essentially co-planar along plane  146 . By way of further example, spring  21  segment  147  could be arranged such that it lies outside of plane  146  in which springs  19 ,  21  are arranged ( FIG. 10 ).  
         [0044]     Diverter  23  advantageously permits use of a spring  21  which may be identical to spring  19 , particularly in length and spring force. And, diverter  23  enables this result in a housing  11  which is more compact than if diverter  23  were not present. More specifically, if diverter  23  were not present, it would be necessary to use a spring which would be relatively shorter than spring  21  with the spring end  135  secured to frame  15  at a location proximate the point where diverter  23  contacts spring  21  in  FIG. 10 . Such a point is identified by reference number  163  in  FIG. 10 .  
         [0045]     It is desirable, however, that the spring selected for use as spring  21  is a relatively longer spring because the relative extension of such a longer spring is less than that of a relatively shorter spring. As a result, the spring rate of the longer spring is more moderate and consistent throughout the full range of spring movement than that of a relatively shorter spring having a relatively more rapid rebound and more powerful spring force. Use of a relatively longer spring  21 , therefore, desirably provides for more consistent and smooth operation of drive roller  17 . A relatively shorter spring may be more likely to fail because of the tensile forces applied to it thereby requiring the use of more costly high tensile springs. Use of a relatively longer spring provides the manufacturer with the option to use springs made with less costly materials thereby minimizing cost while extending service life of the dispenser.  
         [0046]     While a relatively longer spring  21  could be used in dispenser  10  without a diverter  23 , such spring  21  end  135  would be required to be mounted below bottom wall  39  of frame  15  (at approximately point  164 ) to power rotational displacement of drive roller  17  in the same manner as shown in  FIGS. 10-15 . A larger housing  11  would be required to accommodate this mounting location and such a larger housing  11  may be unacceptable for some applications where space is at a premium or a more compact housing  11  and dispenser  10  appearance is desired.  
         [0047]     Referring to  FIGS. 2-15 , a preferred cutting mechanism  97  for cutting web  25  is illustrated. The cutting mechanism  97  is preferably provided to cut fully through web  25  positioned against drive roller  17  outer surface  53  as drive roller  17  rotates under the force applied by user web pulling and springs  19 ,  21 . The exemplary cutting mechanism  97  comprises blade  95 , blade carrier  151 , arm  162 , follower  165 , cam  67  and the related components. As shown in  FIGS. 6-8 , blade  95  may be provided with serrated teeth  150  secured to blade carrier  151  by fasteners  153 . Blade carrier  151  is pivotally mounted to respective ends  49 ,  51  of drive roller section  45  by means of pin  155  seated in bearing  157  and stub shaft  159  seated in bearing  161 . Bearings  157 ,  161  are seated in respective drive roller ends  49 ,  51 . Pivoting action of carrier  151  enables blade  95  to extend outward from drive roller  17  to cut web  25  and further enables blade  95  to retract inward to drive roller  17  following cutting. In the embodiment, serrated teeth  150  cut completely through web  25  so that a single sheet  179  of web  25  is provided during user web pulling.  
         [0048]     Arm  69  is attached at one end to blade carrier  151  and supports rotatable cam follower  165  at its other end. Arm  69  and cam follower  165  are positioned for mounting outside of first drive roller section  45  end  49  so that cam follower  165  may be positioned in cam track  167  of stationary cam  67  as is well shown in  FIGS. 9 and 10 - 15 .  
         [0049]      FIGS. 6, 9  and  10 - 15  illustrate exemplary cam  67 . Cam  67  is preferably mounted to frame  15  with fasteners  168  so that cam track  167  extends through frame opening  170  and faces drive roller  17  and cam follower  165 . Cam track  167  provided in cam  67  includes inwardly arcuate portion  169  and outwardly arcuate portion  171 . Cam follower  165  follows cam track  167  as the drive roller  17  rotates during a dispense cycle. Cam track  167  is eccentric relative to stub shaft  57  and axis  56  and is structured and arranged such that the action of cam track  167  on cam follower  165  and arm  162 , urges carrier  151  to pivot such that blade  95  extends to cut web  25  and retracts during each revolution of drive roller  17  as described more fully below.  
         [0050]     Tail  172  of web  25  of the reserve roll may be manually loaded into nip  123  when the stub roll is fully depleted. Alternatively, an automatic transfer mechanism may be incorporated into dispenser  10  to automatically transfer tail  172  of web  25  of reserve roll to the nip  123  when the stub roll is fully depleted or very near full depletion., Such an automatic transfer mechanism is the subject of commonly owned U.S. Pat. No. 6,460,798, the entire contents of which are incorporated herein by reference. To provide a frame of reference for location of transfer mechanism, a transfer arm  173  as described in U.S. Pat. No. 6,460,798 and which urges web  25  of reserve roll into nip  123  is shown in  FIGS. 2-6 . Other transfer mechanism structure is not shown.  
         [0051]     Operation of exemplary dispenser  10  will now be described particularly with respect to  FIGS. 10-15 . It will be understood that  FIGS. 10-15  illustrate representative positions of drive roller  17  and other dispenser  10  components during a dispense cycle. The operational description will center on drive mechanism  41  and cutting mechanism  97 . Web  25  may be supplied by a single roll, a stub roll or a reserve roll. The reader is again referred to U.S. Pat. No. 6,460,798, incorporated herein by reference, for a description of the structure and operation of exemplary transfer mechanisms suitable for use in supplying web  25  to nip  123  upon depletion of the stub roll.  
         [0052]      FIG. 10  represents dispenser  10  in a rest, or ready, position prior to commencement of a dispense cycle. Web  25  is positioned between drive roller  17  and tension roller  43  through nip  123 . (Tension roller  43  is not shown in  FIGS. 10-15 .) To facilitate threading of web  25  into nip  123  during loading of web  25 , drive roller  17  may be manually rotated in the direction of arrow  175  (i.e. counterclockwise in the example shown) by means of hand wheel  83 . As drive roller  17  is rotated, friction surfaces  91  engage web  25  which is urged against such friction surfaces by tension roller  43  and, potentially, by the action of user web pulling. Web  25  is drawn through nip  123  as drive roller  17  rotates in the direction of arrow  175  and tension roller  43  rotates in the opposite direction.  
         [0053]     After exiting nip  123 , web  25  is guided toward discharge opening  84  by arcuate guide wall  177 . Web  25  is positioned over a portion of drive roller  17  outer surface  53  friction surfaces  91 . Pulling of web  25  by a user draws web  25  tightly across the portion of friction surfaces  91 , as shown in  FIGS. 10-15 . Guard  94  fingers  92  extend into corresponding annular grooves  96  of drive roller  17  to separate web  25  from drive roller  17  to facilitate movement of web  25  out of dispenser  10  through discharge opening  85 . Web tail  172  is then extended from discharge opening  85  by rotation of hand wheel  83  to an appropriate length for gripping by a user. Web  25  is now positioned for dispensing from dispenser  10 .  
         [0054]     In the rest, or ready, position of  FIG. 10 , springs  19 ,  21  are partially loaded, or energized, and springs  19 ,  21  bias drive roller  17  and arm  69  to the position shown in  FIG. 10 . At the beginning of a dispense cycle, blade  95  is preferably retracted within drive roller  17  also as shown in  FIG. 10 . Dispenser  10  is now ready for use.  
         [0055]      FIG. 11  represents dispenser  10  shortly after commencement of a dispense cycle. The dispense cycle is initiated by user web pulling of web  25  tail  172 . The tension, or pulling, force of web  25  against drive roller  17  outer surface  53  friction surfaces  91  causes drive roller  17  to rotate in the direction of arrow  175 . Springs  19 ,  21  are partially extended and are loaded (i.e., energized) as drive roller  17  rotates under the influence of web  25 .  
         [0056]      FIG. 12  represents a further position of dispenser  10  after commencement of a dispense cycle. Spring  19  is near fully extended and loaded (i.e., energized) at a centered position. Spring  21  is further partially extended and is being loaded (i.e., energized) as drive roller  17  rotates further under the influence of web  25 . Blade  95  begins to move toward web  25  to perforate web  25  as cam  67  cam track  167  urges follower  165  and arm  162  to pivot blade carrier  151 .  
         [0057]      FIG. 13  represents yet a further position of dispenser  10  after commencement of a dispense cycle. Spring  19  is past the near centered position of  FIG. 13  and powers rotation of drive roller  17  as the spring is unloaded by release of stored energy. Spring  21  segment  147  is now in approximately a centered position and spring  21  is fully loaded (i.e., energized) as shown. Spring  21  is just starting to power drive roller  17  rotation at this point in the dispense cycle. Blade  95  moves further toward web  25  to perforate the web as cam  67  cam track  167  urges follower  165  and arm  162  to pivot blade carrier  151 . Spring  19  provides energy required to extend blade  95 .  
         [0058]      FIG. 14  represents yet another position of dispenser  10  after commencement of a dispense cycle. Springs  19 ,  21  are both past their centered positions and combine to power rotation of drive roller  17  as the springs are unloaded and stored energy is released. Blade  95  moves fully toward web  25  to completely cut web  25  as follower  165  enters inward portion  169  of cam track  167 . Springs  19 ,  21  provide energy required to fully extend blade  95  to completely cut web  25 . The result is a single sheet  179  of web  25  being provided to the user.  
         [0059]      FIG. 15  illustrates a further position of dispenser  10  near completion of a dispense cycle. Springs  19 ,  21  are both past their centered positions and combine to power rotation of drive roller  17  as stored energy is released. Blade  95  begins to retract as follower  165  exits inward portion  169  of cam track  167 . Spring  21  is the primary provider of energy required to retract blade  95  and return drive roller  17  to the resting position following web  25  cutting.  
         [0060]     Finally, drive roller  17  is returned to the rest, or ready, position of  FIG. 10 . Tail  172  of web  25  is extended from discharge opening  85  and is ready to be grasped and pulled by a user. The dispenser  10  is now ready to initiate a new dispense cycle.  
         [0061]     Dispenser  10  and its component parts may be made of any suitable material or combination of materials as stated above. Selection of the materials will be made based on many factors including, for example, specific purchaser requirements, price, aesthetics, the intended use of the dispenser and the environment in which the dispenser will be used.  
         [0062]     While the principles of this invention have been described in connection with specific embodiments, it should be understood clearly that these descriptions are made only by way of example and are not intended to limit the scope of the invention.