Abstract:
A method of making a hose is provided that includes providing a fitting configured to receive a hose liner therethrough and configured to receive a material configured to be bonded to the hose liner. The method includes receiving the material in the fitting, drawing the hose liner through the fitting, and bonding the material to the hose liner such that the hose liner and material are secured to an outer face of the fitting.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of priority under 35 U.S.C. §119(e) to U.S. Provisional Application No. 61/223,957, filed on Jul. 8, 2009, the entire contents of which are incorporated by reference herein. 
     
    
     BACKGROUND 
     Field 
       [0002]    The present disclosure relates to an arrangement of a hose liner and hose fitting which can reduce the potential for contamination between the hose liner and the hose fitting. More particularly, one aspect is related to an arrangement of an interface between a fluoropolymer lined hose and a sealing flange of a hose fitting which reduces the potential for entry of contamination therebetween. 
         [0003]    Within industries concerned with conveying chemical and pharmaceutical media under conditions of very high purity hose and piping end fitting connections are commonly arranged in accordance with the American Society of Mechanical Engineers Bio-Pharmaceutical Equipment (ASME BPE 2009) standard, which is incorporated by reference herein in its entirety. These fitting designs are generally robust and trouble-free for users. For example, one commonly used type of hose fitting is a “sanitary flange fitting”  101  shown in the section view in  FIG. 1 . The hose fitting  101  is attached to the end of the hose  102  which is comprised of a liner  104  in a carcass  106 . However, within the specific arena of hoses, the hose-to-end fitting connection has been identified as a potential source of media entrapment. As pointed out in  FIG. 1 , an area between the inner end  103  of the fitting  101  and a liner  104  is a potential area for the accumulation of contamination, such as in the form of diluents and bacterial blooms. The areas of accumulation are largely the result of elevation changes at the hose liner/fitting interface, and a microscopic gap that can exist between the hose liner and the outer surface of the fitting near its inner end  103 . 
         [0004]    Sanitary fittings configured in accordance with ASME BPE 2009 also include a concave annular groove  107  formed in the face  105 , which facilitates alignment of a sanitary sealing gasket having a mating convex annular surface. Such a gasket is disposed between two mating sanitary fittings  101  and held in position by the application of compressive forces from the sanitary fittings using a clamp, as is known in the art. 
         [0005]    In response to the problem of contamination accumulation between the inner end  103  and the liner  104 , hoses with flared-through liner were developed, an example of which is shown in  FIG. 2 . The flared-through hose and fitting designs can mitigate the problem of entrapment of contaminants at the area identified in  FIG. 1  by extending a hose liner  204  through an end fitting  201 , eliminating the discontinuity at the hose liner  204 /fitting  201  interface, and subsequently expanding (“flaring”) an exposed outer end of the liner  204  radially outward onto the flanged face  205  of the fitting  201 , forming a sealing surface  208  over the face  205 . Upon flaring the hose liner  204 , a sealing gasket groove  207 , is then imparted to the sealing surface  208  of the liner  204  conforming to a concave groove  206  formed in the face  205  of the fitting  201 , such that the sealing surface  208  and the sealing gasket groove  207  can receive sanitary gaskets. 
         [0006]    While flare-through hose liner  204  and fitting  201  designs are considered a solution to the foregoing problem of entrapment of contamination in conventional sanitary hose assemblies, contamination problems remain with flare-through designs. Specifically, the sealing surface  208  tends to warp in a wavy pattern, allowing contaminants to be introduced between gaps formed between an inner side of the sealing surface  208  and the flanged face  205  of the fitting  201 . Although this area is not part of the normal fluid stream, it is known to be resistant to normal cleaning methods, and subsequent bacterial migration or leaching can contaminate the fluid stream. The existing flare-through designs (e.g.,  FIG. 2 ) rely on one of two solutions to ensure that the flared sealing surface  208  remains flat and in intimate contact with the metallic substrate  205  of the fitting  201 , especially against the face of the fitting. One solution to this problem is to use liner materials that possess an inherent moldability, which enables the flare, when formed under proper conditions of time, temperature, and pressure, to remain relatively flat and stable during normal handling, installation and cleaning operations. A second solution to this problem is to use an adhesive to bond the flared sealing surface  208  to the face  205  of the fitting  201 . 
         [0007]    However, both of these conventional solutions have drawbacks. First, designs which rely on the moldability and stability of the plastic liner to achieve a flat flare surface still suffer from the problem of contaminants entering behind the flare  208  due to wicking. The flare-through hose can suffer from wicking (i.e., capillary) action of liquid that causes the liquid to migrate into and remain in any small clearances between the flared liner  208  and the face  205  of the fitting  201 . 
         [0008]    Moreover, designs which rely on adhesive(s) to bond the flared sealing surface  208  to the face  205  are also problematic. The commonly used liner  204  materials are a class of plastics known as fluoroplastics. The very qualities which make these materials desirable for high purity applications, including chemical resistance and low affinity for liquid media, make them very difficult to bond with traditional adhesives. Accordingly, the surface of these plastics must be etched or otherwise treated by one of several techniques to form a surface which can be bonded with adhesives. A problem with etching or treating the liner is that neither the etched surface, nor the adhesive are safe for environments requiring high purity. Firstly, the adhesives are toxic chemicals. Secondly, the etching or treatment process works by stripping sub-atomic particles and otherwise modifying the plastic on a molecular level, effectively creating a surface of unknown chemical make-up. As the etching and adhesive are not in the fluid stream, the design can be functional, but the presence of these materials adds a level of risk to the hose design. In the event of a breach of the liner  204 , a potentially highly toxic substance can be introduced to the process media. 
       SUMMARY 
       [0009]    Accordingly, solutions are set forth below for the problems associated with flared through hoses discussed above. 
         [0010]    In a first aspect a method of making a hose is provided that includes providing a fitting configured to receive a hose liner therethrough and configured to receive a material configured to be bonded to the hose liner. The method includes receiving the material in the fitting, drawing the hose liner through the fitting, and bonding the material to the hose liner such that the hose liner and material are secured to an outer face of the fitting. 
         [0011]    In another aspect, a hose is provided that includes a hose liner, a retaining member extending from the hose liner, at least one fitting having an outer sealing face. The fitting is configured to receive the hose liner therethrough and is also configured to engage at least a portion of the retaining member to retain at least a portion of the hose liner against the sealing face of the fitting. 
         [0012]    In yet another aspect, a fitting for a hose is provided. The fitting includes a body portion configured to received a hose liner therethrough, and a flanged portion extending from the body portion including an outwardly directed sealing flange. The flanged portion is configured to receive a hose liner therethrough. The sealing flange is configured to receive a portion of the hose liner and is configured to receive and retain at least a portion of a retaining member when the retaining member is in a melt-processable state and when the retaining member is in a bonded state when bonded to the portion of the hose liner. 
         [0013]    Also, in another aspect a hose produced according to a method is provided. The method includes providing a fitting configured to receive a hose liner therethrough and configured to receive a material configured to be bonded to the hose liner. The method includes receiving the material in the fitting, drawing the hose liner through the fitting, and bonding the material to the hose liner such that the hose liner and material are secured to an outer face of the fitting. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The attached drawing figures provide additional disclosure: 
           [0015]      FIG. 1  shows a sectional view of a hose assembly that does not employ a flare-through arrangement. 
           [0016]      FIG. 2  shows a sectional view of a flare-through hose assembly. 
           [0017]      FIG. 3A  shows various details of an exemplary embodiment. This figure should be read as being to scale, and the proportions shown therein constitute part of the disclosure. 
           [0018]      FIG. 3B  shows an exploded sectional view of a portion of the end fitting shown in  FIG. 3A . 
           [0019]      FIG. 3C  shows another exemplary embodiment of an end fitting. 
           [0020]      FIG. 4  shows an exploded sectional view of a portion of a hose in accordance with an embodiment. 
           [0021]      FIG. 5  shows an exploded cutaway view of a portion of another embodiment of an end fitting. 
           [0022]      FIG. 6  shows an exploded cutaway view of a portion of another embodiment of an end fitting. 
           [0023]      FIG. 7  shows an embodiment of a grooving tool used in conjunction with another embodiment of an end fitting. 
           [0024]      FIG. 8  shows an embodiment of a forming head. 
           [0025]      FIG. 9  shows an embodiment of a grooving tool used in conjunction with another embodiment of an end fitting. 
       
    
    
     DETAILED DESCRIPTION 
       [0026]      FIG. 3A  shows, in detail A, a section view of an embodiment of an end fitting  301 . The fitting  301  includes a body portion  300   a  formed generally as a hollow cylinder having a serrated or barbed outer surface extending from a first, open end  308  toward a second end  309  in communication with a flanged portion  300   b . The flanged portion  300   b  extends from the second end  309  toward an open, flanged face  303  of a sealing flange  306 . As shown in detail A, the body portion  300   a  and the flanged portion  300   b  are coaxial with respect to a longitudinal axis A-A through the center of portion  300   a  and  300   b , and are configured to be coaxial with a hose (not shown) in which the body portion  300   a  is configured to be inserted. 
         [0027]    As shown in detail B, the face  303  of the end fitting  301  includes a concave sealing gasket groove  307  formed therein.  FIG. 3B  shows an enlarged partial section view of the flange  306  shown in details A and B, including detail of the groove  307 . The groove  307  is generally hemispherical having a radius r centered at a radius R with respect to the axis A-A. In one embodiment where the end fitting  301  has a nominal diameter of 1 inch, the radius r is about 0.092 inches and the radius R is about 1.718 inches. 
         [0028]    Groove  302  is formed in groove  307 . The groove  302  is shown having a lower edge at the surface of groove  307  that is a predetermined radial distance R 1  from axis A-A. In one embodiment where the end fitting  301  has a nominal diameter of 1 inch, the radius R 1  is about 1.538 inches. The groove  302  is configured to retain a ring  304  of melt-processable material therein. In at least one embodiment, the end fitting  301  can be formed from a metal, such as stainless steel, and the grooves  307  and  302  may be formed in the face  303 , such as by machining, casting, and the like. Of course, in other embodiments, other materials may be used to form the end fitting  301 . Moreover, while the groove  302  is shown in  FIG. 3B  as being formed in groove  307 , in other embodiments, the groove  302  may be formed in another portion of the face  303  which, for example, can accommodate the groove  302 . 
         [0029]    The groove  302  is shown formed having a generally square or rectangular shape extending in a direction at a predetermined angle θ with respect to axis A-A. The groove  302  is formed having a predetermined width w and depth D. The dimensions of the groove  302  are configured to retain the ring  304  therein, such as by friction or compression fit, such that the ring  304  will not tend to fall out of the groove  302  prior to or during processing of the fitting  301  and hose, described herein. For example, in one embodiment, the ring  304  is constructed so that the inner radius of the ring  304  is less than the dimension R 1  of the fitting  301 . Once stretched beyond the edge of the groove  304  at dimension R 1 , the ring  304  can be inserted into the groove  302 . The resiliency of the ring  304  will tend to keep the ring  304  in the groove  302  and, therefore, the ring  304  will not tend to fall out of the groove  302  prior to or during processing of the fitting  301  and hose, described earlier. 
         [0030]    The angle θ of the groove  302  with respect to axis A-A can be an acute angle and is preferably between 30 and 45 degrees. In one embodiment, the groove  302  is configured to at least partially receive an o-ring  304  having a predetermined cross-sectional diameter which can vary, for example, between 0.035 and 0.060 inches, depending on the nominal size and configuration of the end fitting  301 . In one embodiment where the end fitting  301  has a nominal diameter of 1 inch, the o-ring has an annular diameter of 1.5 inches and has a cross-sectional diameter of about 0.060 inches. The inside radius of the ring  304  is made smaller than the dimension R 1  of the fitting  301 . Once snapped into groove, the ring  304  will not tend to fall out of the groove  302  prior to or during processing of the fitting  301  and hose, described earlier. 
         [0031]    The annular width W a  ( FIG. 3B ), the depth of the flange  306  ( FIG. 3C ), and the configuration and placement of the groove  307  may vary based on the nominal diameter size of the end fitting  301 . For example, a nominal 1 inch diameter sanitary fitting has a larger annular width W a  than a nominal 2 inch sanitary fitting and, therefore, additional surface area to accommodate the groove  302 . Accordingly, for the various sized sanitary fittings, the dimensions and location of the groove  302  (and therefore the ring  304 ), are configured based at least upon the nominal size of the sanitary fitting  301 . 
         [0032]    In the case of sanitary fittings constructed in compliance with ASME BPE 2009, the shapes of the groove  302 , as well as their location on the face  303 , may be selected based upon the nominal inner diameter of the hose assembly, and the arrangement of standard sized sanitary style fittings corresponding to the nominal inner hose diameter. For example, arrangement of the groove  302  shown in  FIGS. 3A-3C  can be used for a hose assembly having nominal inner diameter of 1 inch by forming the groove  302  into a standard 1 inch sanitary fitting. Moreover, the arrangement shown in  FIG. 5  can be used for a nominal inner diameter of ¾ inch by forming the groove  302  into a standard ¾ inch sanitary fitting. The arrangement shown in  FIG. 6  can be used for a nominal inner diameter of 1½ inches and 2 inches by forming the groove  302  into a standard 1 ½ inch and 2 inch sanitary fitting. 
         [0033]    As shown in  FIG. 3B , the groove  302  is configured to receive the aforementioned ring  304 , which, in at least one exemplary embodiment, is a pre-formed melt-processable material, and more preferably, a material which, when heated to a predetermined temperature, will flow in the groove  302  and contact another material that is disposed in groove  307 , such as a portion of a hose liner  401  ( FIG. 4 ) that is flared over the face  303  of the end fitting  301 . Accordingly, in at least one embodiment, the groove  302  acts as a mold in forming a net-shape of the ring  304 , upon processing. 
         [0034]    In one embodiment, the ring  304  is formed of a material which can be molded to the shape of the groove  302  while also being bonded to a material used for the hose liner  401  ( FIG. 4 ). In one embodiment the hose liner  401  is formed from polytetrafluoroethylene (PTFE), and the ring  304  can be formed from at least one of perfluoroalkoxy (PFA) and tetrafluorethylene-perfluorpropylene (FEP). The melting point at atmospheric pressure of PTFE is about 621 degrees Fahrenheit while the melting point of PFA is about 582 degrees Fahrenheit and the melting point of FEP is about 500 degrees Fahrenheit. 
         [0035]    As shown in  FIG. 4 , the face  303  of the fitting  301  is configured to be covered by a flared sealing surface  402  of the liner  401 . The flared liner sealing surface  402  is processed such that a portion of the liner  401  covering the groove  307  will be pressed into the groove  307  and will come into contact with the melt-processable ring  304  and become bonded to the liner  401  during a forming process which applies heat and pressure to the liner against the fitting  301 . By virtue of the angle θ ( FIG. 3B ) of the groove  302 , and the combined structure composed of the molded ring  304  and the sealing surface  402  of the liner  401 , becomes interlocked with the face  303  of the end fitting  301 . The molded ring  304  forms a lip around the opening in the end fitting  301  at a radius R 1  ( FIG. 3B ). This lip interlocks the sealing surface  402  with the sealing face  303  and can prevent warping of the sealing surface  402  away from the sealing face  303 . Moreover, because the molded ring  304  forms a lip that extends beneath the sealing face  303 , the lip can act as a barrier to limit the migration of contaminants radially inwardly at the interface between the sealing face  303  and the liner  401 . 
         [0036]    In other alternative embodiments the groove  302  may also have a curved shape, including teardrop ( FIG. 5 ) and hemispherical shapes ( FIG. 6 ), as well as other rectilinear shapes including but not limited to, T-shape, trapezoidal, triangular, square, rectangular, and dovetail ( FIG. 7 ) shapes. In an alternate embodiment shown in  FIG. 3C , the o-ring  304  shown in  FIG. 3B  is replaced with a ring having a generally square cross section, which is seated in groove  302  having a generally square cross section. 
         [0037]    Another embodiment of an end fitting  301  is shown in  FIG. 5 . The end fitting  301  is constructed to receive a ring  304  having a teardrop shaped cross section. The fitting  301  has a corresponding teardrop shaped groove  302 . At least a portion of the teardrop shaped cross section of the ring  304  conforms to the surface of the teardrop shaped groove  302 . In its unprocessed state, the teardrop shaped ring  304  is seated and positioned in the groove  302  such that the outer exposed surface of the ring  304  substantially conforms to the curvature of the groove  307 . In one embodiment, the teardrop shaped groove  302  and ring  304  are formed in a modified ¾ inch standard sanitary fitting so that the resulting fitting can be used to connect to ¾ inch standard sanitary fittings and gaskets. 
         [0038]    Also, as shown in  FIG. 6 , another embodiment of an end fitting  301  is shown that is constructed to receive a ring  304  having a circular shaped cross section. Such circular shaped ring  304  can be of similar construction to the o-ring described with respect to  FIGS. 3A-3C . The fitting  301  has a corresponding curved groove  302 , which is shown as being generally semicircular and conforms to the surface of the ring  304 . In one embodiment, the circular groove  302  and ring  304  are formed in a modified ¾ inch standard sanitary fitting so that the resulting fitting can be used to connect to ¾ inch standard sanitary fittings and gaskets. 
         [0039]    As shown in  FIG. 7 , another embodiment of an end fitting  301  is shown that is constructed to receive a ring  304  having a circular shaped cross section. In  FIG. 7 , the groove  302  has a dovetail shape. That is, the two sides of the groove  302  extend at an acute angle with respect to the base of the groove  302  so that the outer edges of the groove  302  at the surface of groove  307  pinch and retain the unprocessed ring  304 , at least partially, in the groove  302 . In one embodiment, the dovetail shaped groove  302  and circular ring  304  are formed in a modified ¾ inch standard sanitary fitting so that the resulting fitting can be used to connect to ¾ inch standard sanitary fittings and gaskets. 
         [0040]    A method of manufacturing a lined hose will now be described. In one embodiment of the method, an end fitting  301 , constructed in accordance with the first aspect, is provided and a hose liner  401  is drawn through the end fitting  301 . In one embodiment, the hose liner  401  is drawn concurrently through a hose carcass (not shown) and the end fitting  301 . The method also includes introducing the melt-processable ring  304  into the groove  302 . The hose liner  401  is drawn through the end fitting  301  outwardly from the face  303  a certain distance sufficient to flare the drawn end of the liner  401  over the face  303  of the end fitting  301 . The drawn end of the liner  401  is heated to a gel state and is flared radially outwardly onto the face  303 , preferably using a hydraulic operated balloon which inflates from within the end of the hose liner  401  to spread the liner  401  toward the sealing face  303  of the end fitting  301 . 
         [0041]    While the sealing face  303  is in the gel state, a grooving tool  701  ( FIG. 7 ), shown in one embodiment in  FIG. 7 , is pressed onto the flared liner  401  at a predetermined pressure sufficient to press the flared liner  401  into the groove  307  and impart a sealing gasket groove  403  ( FIGS. 4 ,  7 , and  9 ) which is configured to receive a complimentary surface of a sanitary gasket (not shown). The grooving tool includes a protruding surface  707  which, when aligned with the sealing surface  402 , imparts the formed sealing gasket groove  403  into the sealing surface  402 . Moreover, the grooving tool compresses the liner  401  into contact with and around a portion of the ring  304  that protrudes from the groove  302  above the surface of groove  307 . 
         [0042]      FIG. 9  shows a similar arrangement of the grooving tool and end fitting shown in  FIG. 7 , except that the fitting  301  and ring  304  are shown corresponding to the embodiment shown in  FIG. 5 , described above. Also shown in  FIG. 9  is a grooving tool  901  which has a protruding surface  907  which is similar in shape to the protruding surface  707  shown in  FIG. 7 . The forming tool  901  is used in the same manner as forming tool  707  to form sealing gasket groove  403 . 
         [0043]    A forming head  801 , an example of which is shown in  FIG. 8 , is pressed onto the sealing surface face  402  of the end fitting  301 , and is pressed in contact to apply a predetermined pressure to the sealing surface face  402  especially in the area of the grooves  403 ,  302 , and  307 . In one embodiment, the forming head  801  can be retained against the sealing surface  402  with a sanitary clamp (not shown). Such a sanitary clamp can compress a flange  806  of the forming head  801  against the sealing flange  306  of the end fitting  301 . Preferably, the forming head  801  has a sealing face  802  that is configured to engage and align with the grooved flared face  402  in a similar fashion to a sanitary gasket. For example, as shown in  FIG. 8 , a forming head is shown in section view showing an annular raised hemispherical ridge  803  extending from the face  802  configured to engage and seal with the mating sealing gasket groove  403  and sealing surface  402 . 
         [0044]    While retained against the surface  402 , forming head  801  and at least a portion of the end fitting  301  are inserted into a salt bath that is maintained at a predetermined temperature for a predetermined duration up to a depth covering the sanitary clamp holding the forming head  801  to the end fitting  301 . In an exemplary embodiment, where a flared 1 inch stainless steel end fitting  301  is configured as shown in  FIGS. 3A-3C , is attached to a 1 inch forming head  801 , and the hose liner is made from PTFE and the ring is made from PFA, the temperature of the salt bath is preferably about 720 degrees Fahrenheit and the forming head  801  and the end fitting  301  are inserted in the salt bath for about 4 minutes. 
         [0045]    While still compressed together, the end fitting  301  and the forming head  801  of the hose assembly are inserted into a cooling bath, comprised of, for example, water, to a predetermined depth, measured inwardly from the sealing surface  402 , for a predetermined amount of time. At the end of that predetermined amount of time, the end fitting  301  and forming head  801  are immersed to a greater depth in the cooling bath, such as down to the second end  309  ( FIG. 3A ) of the body portion  300   a  of the end fitting  301 , for another predetermined duration to rapidly cool the end fitting  301 . For example, in the exemplary embodiment discussed above for the 1 inch sanitary fitting in accordance with  FIGS. 3A-3C , the end fitting  301  is inserted in the cooling bath to a depth of about ½ inch inward of the sealing surface  402  for 1 minute prior to fully immersing the remainder of the flanged portion  300   b  of the fitting  301  in the cooling bath. Upon cooling of the sealing surface  402  and the ring  304  to a certain temperature, the forming head  801  can be released from the sealing face  303 . 
         [0046]    In one embodiment, the forming head  801  can be configured with a thermal mass at a longitudinally outward end of the forming head  801  which is sufficient to act as a heat sink that can keep the longitudinally inner portions of hose liner  401 , which are surrounded by the body portion  300   a  of the end fitting  301 , from being heated above a certain temperature, while concentrating the heat transferred from the salt bath at the sealing surface  402  and the sealing flange  306 , in order to melt the ring  304  and the flared liner  402  and bond the them together, as shown in  FIG. 4 . In at least one embodiment, by virtue of heat transfer to the sealing surface  402  from the forming head  801 , the ring  304  and flared liner  402  are heated at least to the higher of the melting points of the ring  304  and the liner  401  while the sealing surface  402  is compressed onto the face  303  and in the groove  307  at a predetermined pressure. In cooling the end fittings  301 , the temperature of the sealing surface  402  and the ring  304  are decreased below a predetermined temperature to a state where the ring  304  is sufficiently solidified in the shape of the groove  302  and is strong enough to hold a formed shape of the groove  302  prior to removing the restraining pressure holding the forming head  801  against the sealing surface  402 . 
         [0047]    A comparison was made between two different hose/end fitting connections using a nominal 1 inch diameter hose of a type available under the trademark Stratus from Crane Co. (smooth PTFE inner core, and platinum-cured silicone with stainless-steel wire and fabric reinforcement) after soaking each end fitting connection for 15 seconds in dye penetrant (Kingscote fluorescent red tracer dye item #106023 FWT 25). One end fitting  301  was configured in accordance with an embodiment described above using a dual-grooved fitting  301 , the PTFE liner bonded to a melt-processable PFA o-ring molded in the groove  302  of the fitting  301 . A second end fitting did not include a PFA O-ring at all. The end fitting face  303 /sealing surface  402  interface at the first end fitting showed a flatter sealing surface  402  than compared to the second end fitting. In the latter instance, the flared face which did not have a PFA o-ring bonded thereto consequently displayed a characteristic wavy appearance and separation from the sealing face  303  of the end fitting  301 . In the case of the first tested configuration, it was found that in between the sealing surface  402  and the face  303  penetrant did not move moved radially inward past the PFA o-ring. In the case of the second configuration without the ring  304  bonded to the sealing flange  402 , it was found that in between the sealing surface  402  and the face  303  penetrant was detected radially inwardly past the radial distance of the ring  302  in the first configuration. In this latter case, close clearances between the sealing surface  402  and the face  303  captured and restrained the penetrant from draining when the flared end fitting was removed from the soaking solution. 
         [0048]    While the present invention has been described with respect to various embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, the invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.