Patent Publication Number: US-6709549-B2

Title: Multi-reel apparatus in a paper machine

Description:
FIELD OF THE INVENTION 
     The present invention relates to papermaking machines, and more particularly relates to a method and apparatus for achieving a continuous paper winding process using a number of reel-up stations at different locations along a travelling paper web path wherein one station is always prepared to commence winding upon completion of the paper roll at another station. 
     BACKGROUND OF THE INVENTION 
     In the manufacture of various types of tissue products, such as facial tissue, bath tissue, paper towels and the like, the dried tissue web or sheet coming off of the tissue machine is initially wound into a parent roll and temporarily stored for further processing. Sometime thereafter, the parent roll is unwound and the sheet is converted into a final product form. 
     In a conventional dry end of a papermaking machine, the dried web is wound into rolls by the reel-up. The conventional reel-up includes a rotating reel shaft held by a pair of primary arms against a reeling drum to form a nip. The free end of the continuous paper web, in the form of a leader, is introduced into the nip. The paper web is adhered to the reel shaft by a vacuum tape or glue and winds onto the reel shaft as it is advanced into the nip to form a roll. Once partially wound, the primary arms transfer the roll to a set of secondary arms which complete the winding process. After the roll is completed, the continuous paper web is severed, the downstream portion of the web becoming the tail end that is wound onto the completed roll and the upstream portion becoming the new leader. 
     Completion of the roll frees the apparatus to receive a new reel shaft. A pair of lowering arms, positioned above the primary arms and the reeling drum, retrieve a new reel shaft from a stock of reel shafts and lower the new reel shaft into the primary arms. The primary arms grippingly receive the new reel shaft and hold the new reel shaft against the reeling drum to form the nip. The new leader is advanced into the nip to begin a new roll. 
     Reel changing methods are commonly assisted by balloon blowing. Balloon blowing entails creating slack across the full width of the paper by somewhat retarding the finished roll. With the aid of compressed air, the fold thus formed is then forced into the nip between the new reel shaft and the reel drum, after which the paper web is cut off. The degree of control over the paper web in the balloon blowing procedure is relatively low because the web is not supported on any support in the ballooned portion of the web. This lack of control can lead to problems. 
     U.S. Pat. No. 5,901,918 to Klerelid et al. (&#39;918) addresses this lack of control by providing support for the paper web during reel switching. The apparatus disclosed by the &#39;918 patent includes a reel-up having a fabric run defined by a flexible transfer belt spanning two support rolls. The flexible transfer belt supports and advances the paper web. The web is transferred from the transfer belt to a parent roll as the parent roll is urged against one portion of the flexible belt. Reel switching occurs when a new reel spool is lowered into an initial winding position against the web on another portion of the belt. No balloon blowing is used and the paper web is continuously supported. However, arms are required to lower the new reel spool into the initial winding position, and the new reel spool must be moved along the transfer belt from the initial winding position into a final winding position as winding proceeds. This movement of the building paper roll complicates the control of the nip load. 
     Another disadvantage of reel switching is the production down time associated with the reel switching process. The production of large jumbo rolls minimizes the frequency of reel switching. However, jumbo rolls are even more difficult to wind and handle due to their size and weight. The winding process typically starts when a core is brought into contact with a reel drum supporting the paper web. Controlling the linear load in the paper web at the nip during initiation of the winding process is made more difficult by the heavy core shafts of the jumbo rolls. These difficulties continue as the roll is wound and its weight increases, because the tissue paper web is fragile and sensitive to the nip pressure. Conventional reel-ups require a complicated control system to control the linear load and meet requirements for tissue web quality when winding jumbo rolls. Manufacturing losses from these difficulties occur because the failure to control linear load often results in 200 to 300 meters of tissue paper web at the beginning of the jumbo roll not being of commercial quality. 
     Therefore, it would be advantageous to have a reeling apparatus that always supports the paper web and that minimizes any delay caused by the reel switching process. It would be further advantageous to have a reeling apparatus that produced smaller rolls without additional production down time. 
     SUMMARY OF THE INVENTION 
     These and other needs are met by the multi-reel apparatus according to the present invention. The present invention avoids problems with web instability by supporting the paper web along its entire path through the apparatus. Delays in parent roll production are reduced by alternating between multiple reeling apparatuses so that any one apparatus is winding paper web onto a parent roll while the others are swapping a completed parent roll for a new empty reel shaft. The reduction in down time due to reel switching allows for the production of small rolls which are easier to wind and handle. 
     A paper web manufacturing machine includes a wet section having a former for forming a wet web, a drying section for drying the wet web, and the multi-reel apparatus for winding the dried web into completed rolls. The multi-reel apparatus includes a web support which supports the travelling web along a path of travel that extends from a first vertical level to a second vertical level, wherein the two levels are vertically spaced. First and second reeling stations are located, respectively, at the first and second vertical levels. Each reeling station has a reeling device operable to hold and rotatably drive a core onto which the web is wound to form a roll. The reeling devices are further operable to move the core into engagement with the web on the web support thereby initiating winding of the web onto the core. The reeling devices are also operable to move the core away from the web support when the roll is fully wound so that the web can begin winding onto the core held in the reeling device of the other reeling station. In this manner, the web is continuously wound alternately in one reeling station and then in the other reeling station. This increases the efficiency of the papermaking process by eliminating the down-time during reel switching. 
     In another embodiment, the continuous web prior to winding is divided into two partial-width web portions. Each reeling station includes two reeling devices spaced in the width direction of the web for the simultaneous winding of the two web portions. The continuous web is alternately wound in the two reeling devices of the first reeling station and then in the second reeling station. The partial-width web portions are advantageously wound onto separate cores and shafts at each station to form small rolls that are easily manipulated in additional downstream processing. The small rolls generally have lighter cores and shafts, and can even use composite based shaftless cores for an additional reduction in weight and an increase in reeling speed. 
     In yet another embodiment, the partial-width web portions are simultaneously wound in the first and second reeling stations into small rolls. Each reeling station includes first and second reeling devices that are vertically stacked whereby each web portion is continuously wound alternately in the first and then the second reeling devices of each reeling station. 
     Initiation of a new roll preferably is aided by a cutting device operable to sever the web when the roll in one of the reeling stations is completed so that the other reeling station can begin to wind the web onto its core. The cutting device may be combined with an adhesive applicator positioned adjacent to the path of travel of the web and upstream of the reeling stations. A signal triggers the adhesive applicator to apply adhesive to the web and the cutting device cuts the web so that the cut is downstream of the applied adhesive. 
     The web support in some embodiments comprises an endless carrying clothing guided along the path of travel by a plurality of rolls about which the clothing is looped. This clothing may be a through-air drying fabric on which the web is dried in the drying section, or it may be a separate clothing that receives the web from the drying section. Alternatively, the web support may comprise a foil or plurality of foils for supporting the web thereon. 
     The multi-reel apparatus has several advantages. The elimination of down time for reel switching allows for continuous paper web production and the cost-effective production of small rolls in place of jumbo rolls. Small, relatively light rolls reduce winding and downstream handling problems associated with heavy jumbo rolls. Lighter reel shafts used in smaller rolls are more easily controlled by the reeling device to maintain proper web tension and nip load for high quality tissue paper web production. In addition, the multi-reel apparatus does not require lowering arms or any mechanisms for moving a new reel shaft on which winding is commencing from an initial winding position into a final winding position previously occupied by the prior-wound roll. This further improves the simplicity of operation as well as the control of the nip load. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein: 
     FIG. 1 is a schematic diagram that depicts a paper machine including a multi-reel apparatus in accordance with the present invention; 
     FIG. 2 is a schematic diagram of the multi-reel apparatus shown in FIG. 1 that depicts core replacement at the first reeling station; 
     FIG. 3 is a schematic diagram of the multi-reel apparatus shown in FIG. 1 that depicts the completed parent roll positioned for lift-off at the first reeling station; 
     FIG. 4 is a schematic diagram of the multi-reel apparatus shown in FIG. 1 that depicts the initial winding of a new roll at the first reeling station during removal of a completed parent roll at the second reeling station; 
     FIG. 5 is a schematic diagram of the multi-reel apparatus shown in FIG. 1 that depicts core replacement at the second reeling station; 
     FIG. 6 is a schematic diagram of a multi-reel apparatus that depicts switching between winding at a second reeling station to winding at a first reeling station; 
     FIG. 7 is a schematic diagram of the multi-reel apparatus shown in FIG. 6 that depicts placement of a new core at the second reeling station during winding of the parent roll at the first reeling station; 
     FIG. 8 is a schematic diagram of the multi-reel apparatus shown in FIG. 6 that depicts switching between winding at the first reeling station to winding at the second reeling station; 
     FIG. 9 is a schematic diagram that depicts a backward leaning multi-reel apparatus; 
     FIG. 10 is a schematic diagram that depicts a multi-reel apparatus with three reeling stations; 
     FIG. 11 is a schematic diagram that depicts a multi-reel apparatus wherein the direction of travel of the paper web has been reversed relative to that in FIGS. 1-10; 
     FIG. 12 is a schematic diagram that depicts a paper web drying section including a Yankee dryer which has been bypassed for rebuilding; 
     FIG. 13 is a schematic diagram that depicts a paper web drying section including a pair of stacked through-air dryers (TADs); 
     FIG. 14 is a schematic diagram that depicts a paper web drying section with a shortened layout; 
     FIG. 15 is a schematic diagram that depicts a paper web drying section with a flat layout; 
     FIG. 16 is a schematic diagram that depicts a paper web drying section including the combination of a pair of TADs with a Yankee dryer; 
     FIG. 17 is a schematic diagram that depicts a paper web drying section including a Yankee pre-dryer and a final TAD dryer; 
     FIG. 18 is a schematic diagram that depicts a paper web drying section including a conventional Yankee dryer and a plurality of foils supporting the paper web; 
     FIG. 19 is a schematic diagram that depicts a paper web drying section including a Yankee dryer with a dry-end wire for carrying the web from the Yankee to the multi-reel apparatus; 
     FIG. 20A is a schematic diagram that depicts a multi-reel apparatus wherein each reeling station has a pair of adjacent reeling devices for reeling small rolls; 
     FIG. 20B is an elevation view of the multi-reel apparatus of FIG. 20A; 
     FIG. 21A is a schematic diagram that depicts a multi-reel apparatus wherein each reeling station has a pair of vertically stacked reeling devices for reeling small rolls; and 
     FIG. 21B is an elevation view of the multi-reel apparatus of FIG.  21 A. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout. 
     A first embodiment of a multi-reel apparatus  101  is shown in FIG. 1 as part of a paper machine having a forming section  132  and a drying section  102 . FIGS. 2 through 8 depict two embodiments of the multi-reel apparatus  101  during different phases of operation. The forming section  132  includes an inner forming fabric  112 , an outer forming fabric  125 , a headbox  103 , and a forming roll  115 . The headbox  103  deposits an aqueous suspension of papermaking fibers between the inner fabric  112  and the outer fabric  125  as they traverse the forming roll  115 . The outer forming fabric  125  diverges from the inner forming fabric after the fabrics depart from the forming roll  115 . The paper web  108  is then carried on an underside of the inner forming fabric  112 . 
     The inner forming fabric  112  also comprises a drying fabric carrying the web  108  through the drying section  102 . More particularly, the paper web  108  is carried on the forming and drying fabric  112  through a pair of through-air dryers (TADs). The TADs  104  each include a drying cylinder  118  partially surrounded by a hood  119  which is connected to a blower (not shown). The fabric  112  with the paper web  108  supported thereon is guided around the pair of drying cylinders  118 . The drying cylinders  118  have outer surfaces that are air permeable and allow the passage of air, as shown by arrows  120 , through the paper web  108 , the fabric  112  and through the drying cylinder&#39;s permeable outer surface. The pressure of the air on the paper web  108  secures it against the fabric  112  in opposition to centrifugal forces. The choice of two TADs  104  is not meant to be restrictive, as a single TAD, several TADs, or other drying devices could be used to dry the paper web  108 . 
     The fabric  112  in the current embodiment also supports the web  108  through the multi-reel apparatus  101 . Thus, downstream of the TAD units a portion of the loop of fabric  112  travels upwards past a first reeling station having a first reeling device  110  at a first elevation and then past a second reeling station having a second reeling device  110 ′, at a second, higher elevation. The paper web  108  is transferred from the fabric  112  to whichever reeling device  110  or  110 ′ is currently winding the web onto a core  109 . A more detailed description of the multi-reeling apparatus  101  appears below. 
     Many advantages of the current invention will be apparent from a detailed description of the multi-reel apparatus  101 . The multi-reel apparatus includes the first reeling device  110  and the second reeling device  110 ′ positioned at different vertical levels along a portion of the loop of the forming and drying fabric  112 , allowing continuous winding of the paper web  108  because one of the pair of reeling devices is engaged with the web support assembly at all times. The pair of reeling devices  110  and  110 ′ alternate between winding and core switching roles, as shown in FIGS. 2 through 5, to prevent interruption of the winding process. 
     Each reeling device  110 ,  110 ′ includes a pair of carriages  122  each of which slides along one or more carriage rails  123  toward and away from the fabric  112  and is configured to support one of the cores  109  in a position proximate a pair of paper roll support rails  123 . The pair of rails  123  for the second reeling device  110 ′ are mounted at a greater height than those for the first reeling device  110 . The difference in vertical height places the carriage  122  of the first reeling device  110  further upstream along the fabric  112  than the carriage  122  of the second reeling device  110 ′. Each carriage  122  is driven toward and away from the fabric  112  along the rails  133  by a hydraulic actuator (not shown). Two guide rolls  126  and  127  bracket a fabric run  128  of the fabric  112  that extends above and below the first and second reeling devices. 
     The web  108  is supported by the fabric  112  along the fabric run  128  between the two support rolls  126  and  127  and is wound onto a roll  111  rotatably supported by one of the reeling devices. The core  109  can be moved toward and away from the fabric  112  by the carriage  122 . As the parent roll  111  builds, the core  109  is continually moved away from the fabric to compensate for the increasing diameter of the roll. Movement of the carriage  122  can also be controlled to control a nip load between the paper roll and the fabric  112 . One suitable method for controlling nip load in this fashion is described in U.S. Pat. No. 5,901,918, hereby incorporated herein by reference. 
     Continuous winding is achieved by alternating reel-up operation between the first and second reeling devices  110  and  110 ′. FIGS. 2 and 3 show the second reeling device  110 ′ having completed a parent roll  111  and ready for switching. The switching process is aided by the tail cutter  106  which includes two nozzles, one to spray a water jet, and another to spray a glue jet, across a transverse section of the traveling web  108 . Once the parent roll  111  is near completion, the controller signals the tail cutter  106  to cut a section of the paper web  108  transverse to its direction of travel using the water jet. Simultaneously, or shortly thereafter, the glue nozzle sprays a glue jet slightly upstream from the severed edge of the paper web  108 . Advantageously, the water and glue nozzles are mounted for traversal in a cross-machine direction along the width of the paper web  108  and preferably can be mounted in the same traversing mechanism (not shown). 
     The first reeling device  110  advances a new core  109  into contact with the paper web  108  on the fabric  112  before the glue line is applied to the paper web  108  or before the glue line reaches the first reeling device. At the same general time, the second reeling device  110 ′ moves the nearly completed parent roll  111  away from the fabric  112 . As the paper web  108  continues to advance, the portion of the paper web downstream of the cut becomes the tail end of the current parent roll  111 . This downstream portion continues to be wound to completion on that parent roll by the second reeling device  110 ′. The portion of the paper web upstream of the cut, containing the glue line, advances along the fabric  112  until it encounters the outside surface of the core  109  that is currently held by the first reeling device  110 . The glue line causes the upstream portion of the paper web to adhere to the core  109  of the second reeling device  110 ′, thereby beginning a new parent roll  111 ′, as shown in FIG.  4 . 
     The completed parent roll  111  at the second reeling device  110 ′ is preferably rolled along the guide rails  123  by the carriage  122  to a pick-up location, keeping the movement and position of the roll under control. Alternatively, the roll  111  could be kicked off the carriage to roll along the guide rails  123 . The completed parent roll  111  can be lifted from the rails  123  in any suitable manner (e.g., by using a traversing crane) for further distribution. 
     As shown in FIG. 5, the situation has reversed itself in that a new core  109  is being advanced into a position in contact with the fabric  112  at the second reeling device  110 ′. The new core  109  is loaded onto the carriage  122  of the second reeling device  110 ′ and advanced toward the fabric  112 . Meanwhile, the first reeling device  110  continues winding of the core  109  into a parent roll  111  using the first reeling device  110 . Once the parent roll  111  approaches completion on the first reeling device  110 , the tail cutter  106  is triggered (as shown for another embodiment in FIG.  8 ). The paper web  108  is cut and glued by the tail cutter  106  with the downstream portion becoming the tail end of the parent roll  111  at the first reeling device  110  and the upstream portion (with the glue line) adhering to the core  109  held by the second reeling device  110 ′. Before wind-up at the second reeling device  110 ′ commences, the first reeling device  110  has performed its kick-off operation. In this manner, the multi-reel apparatus  101  can continue the winding process indefinitely and without interruption. No delay is encountered while switching out completed rolls for new cores. Furthermore, the paper web at all times is supported on the fabric  112  during winding. 
     Note that variations are possible for the commencement of a new roll  111 ′ beyond the use of the tail cutter  106 . In one embodiment, the web  108  is severed by kicking the fully wound roll away from the fabric  112  to cause a rapidly imposed tensile force on the web. One or more air jets serve to blow the paper web back toward the new core after it has been severed by the kick-out procedure. The paper web is then captured by vacuum suction from within the core. In another embodiment, glue could be applied directly to the new core so that contact with the paper web commences reel-up and simultaneously tears the web thereby allowing completion of the old parent roll. 
     A range of other embodiments of the multi-reel apparatus  101  are also possible. The flexibility inherent in the multi-reel  101  invention is important due to the fact that in many situations it may be retrofit to a preexisting paper machine. Paper machines are often custom built to meet the user&#39;s desired paper type and quality. In addition, each user is operating under unique space and cost constraints that will, in part, dictate the layout of the paper machine (such as whether portions of the machine are above or below a main floor  200 ). Existing machines can have any number of dryers in varying arrangements and still benefit from continuous winding as performed by the multi-reel  101 . The following description of alternative embodiments is only intended to be demonstrative of the flexibility of this invention and not limiting in any way. 
     FIGS. 6 through 8 show another embodiment of the multi-reel apparatus  101  wherein the fabric  112  extends horizontally out from the top guide roll  127 . FIG. 6 depicts completion of the parent roll  111  at the second reeling device  110 ′. FIG. 7 depicts kick-out of the completed parent roll  111  and core  109  replacement at the second reeling device  110 ′ while winding of the new roll  111 ′ continues at the first reeling device  110 . FIG. 8 depicts engagement of the core  109  with the fabric  112  at the second reeling device  110 ′ as winding of the parent roll  111  is completed at the first reeling device  110 . 
     FIG. 9 shows an embodiment of the multi-reel apparatus  101  wherein the fabric run  128  is backward leaning. In this embodiment, the first and second reeling devices  110  and  110 ′ are nearly vertically aligned. This cuts down on the horizontal space needed for the multi-reel apparatus  101 . Note that the fabric run  128  could also be vertical or slightly forward leaning and still achieve near vertical alignment. 
     FIG. 10 presents an embodiment wherein the multi-reel  101  comprises an additional third reeling device  110 ″. The first reeling device  110 , the second reeling device  110 ′ and the third reeling device  110 ″ are all vertically stacked at different vertical levels. One advantage is that this allows greater cycle times for a given reeling device which allows more time for the kick-out and removal of parent rolls  111  and/or the placement of new cores  109 . Another advantage is that maintenance could be performed on any one of the reeling devices  110 ,  110 ′ and  110 ″ while the others continue normal operation. 
     FIG. 11 schematically depicts another embodiment wherein the direction of travel of fabric  112  and paper web  108  has been reversed. In this embodiment, the upper or second reeling device  110 ′ is upstream of the lower or first reeling device  110 . FIG. 12 depicts another embodiment wherein a pre-existing drying section  102  has been retrofit to bypass a Yankee dryer  129  and substitute through-air drying. Note also that this embodiment includes a separate inner forming fabric  130  from which the web  108  is transferred onto the drying fabric  112 . 
     FIG. 13 schematically depicts an embodiment wherein the TADs  104  are stacked instead of adjacent which reduces the footprint of the drying section  102 . The top TAD  104  is an outward-flow unit indicated by the arrows  120 . The paper web  108  through the top TAD is on the inside of the fabric  112 , against the drying cylinder  118 . The bottom TAD is an inward flow unit having the fabric  112  between the web and the drying cylinder  118 . 
     FIG. 14 depicts an embodiment with a layout shortened by use of the backward leaning fabric run  128  for the multi-reel  101  similar to FIG. 9, but at a steeper angle, such that a part of the multi-reel is directly above the drying section  102 . In this embodiment, the multi-reel apparatus  101  is located above and supported by the main floor  200 . The TADs  104  are located below the main floor  200 . 
     FIG. 15 depicts an embodiment using two outward flow TADs  104  that have their hoods  119  above, rather than below, the drying cylinders  118 . This embodiment advantageously eliminates the requirement of space below the main floor  200 . The forming section  132 , the TADs  104  and the multi-reel apparatus  101  are all located above and supported by the main floor  200 . 
     FIG. 16 depicts an embodiment with a combination of TADs  104  located below the main floor  200  and a Yankee dryer  129  located above the main floor. After being creped from the Yankee dryer  129 , the web  108  is received by a support clothing  112 ′ that carries the web through the multi-reel apparatus  101  which is located below the main floor  200 . 
     FIG. 17 depicts a machine having two TADs  104  located below the main floor  200  and a Yankee dryer  129  located above the main floor performing a pre-drying operation. The final drying is performed by an additional TAD  104  whose drying fabric  112  carries the web through the multi-reel apparatus. The second reeling device  110 ′ is also located above the main floor  200 , while the first reeling device  110  is located below the main floor. 
     FIG. 18 depicts an embodiment wherein the web  10  is supported through the multi-reel apparatus  101  by a plurality of foils  131 . FIG. 19 depicts an embodiment similar to that of FIG. 16 but having only a Yankee dryer for drying the web. 
     In another embodiment, the tissue paper web  108 , which in many cases may be 5 to 6 meters in width, is cut in the middle prior to reel-up to create two small rolls  111 A and  111 B that are approximately half the original width of the paper web. Two separate, partial-width web portions  108 A and  108 B are simultaneously wound onto separate cores  109 A and  109 B, respectively, to form the small rolls  111 A and  111 B. In one embodiment, as shown in FIGS. 20A and 20B, the first reeling station includes a pair of small roll reeling devices  210  positioned at different vertical levels, and spaced in the cross-machine direction. The second reeling station includes another pair of small roll reeling devices  210 ′ positioned in an arrangement similar to that of the first reeling station. The adjacent arrangement allows the simultaneous winding of the split web portions  108 A and  108 B in the same reeling station. Continuous winding is achieved by alternating between each pair of small roll reeling devices  210  and  210 ′. 
     In another split web embodiment, as shown in FIGS. 21A and 21B, the first reeling station includes two alternately operable reeling devices  210  for winding one of the partial-width web portions, and the second reeling station includes two alternately operable reeling devices  210 ′ for winding the other web portion. The vertical stacking arrangement allows the simultaneous winding of the split web portions  108 A and  108 B in different reeling stations. Continuous winding is achieved by alternating between the small roll reeling devices of each pair of reeling devices  210 ,  210 ′. In general, smaller rolls are easier to handle in downstream operations than the heavier jumbo rolls. Nip loads are easier to handle with small rolls, contributing to the production of high-quality tissue paper. The smaller rolls also allow the use of composite based shaftless cores such as those described in commonly owned U.S. patent application Ser. No. 60/214,504 filed Jun. 28, 2000. 
     Note that additional embodiments of the present invention where the layout of the above-listed embodiments are inverted or in mirror image, are also possible. Although preferred for the manufacture of tissue paper webs, the multi-reel apparatus of the present invention could also be used with other paper grades. 
     Many modifications and other embodiments of the invention will come to mind to one skilled in the art to which this invention pertains having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.