Abstract:
A heat exchanger has a multi-lumen tubing having one end connected to a supply fitting and another end connected to a return fitting. The tubing has a central lumen, a middle lumen that surrounds the central lumen and an outer lumen that surrounds the middle lumen. The supply fitting has an inlet, an outlet and a proximal port wherethrough an infusate is input to the heat exchanger. The supply fitting is configured such that its inlet is connected to the central lumen, its outlet connected to the outer lumen, and its proximal port connected to the middle lumen of the tubing. The return fitting is configured to establish a through passage between the central lumen and the outer lumen of the tubing so that a heating fluid fed through the supply fitting to the central lumen is returned to the supply fitting by way of the outer lumen. The return fitting further has a distal port configured to connect to the central lumen of the tubing, so that the infusate fed to the proximal port of the supply fitting may be output from the distal port of the return fitting, after passing through the central lumen of the tubing. As the infusate traverses along the heat exchanger, it is heated by the heating fluid that flows along the central lumen, and also by the rerouted heating fluid that flows along the outer lumen of the tubing. The heat exchanger is fluidly coupled to a heater by its inlet and outlet so that the temperature of the heating fluid for warming the infusate is maintained at a predetermined temperature.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to the art of heat exchangers, and particularly to heat exchangers that are used for heating physiological infusate or solutions. 
       BACKGROUND OF THE INVENTION 
       [0002]    Heat exchangers for warming physiological solutions are known. One such heat exchanger is disclosed in U.S. Pat. Nos. 4,759,749 and 4,878,537, both assigned to the assignee of the instant invention. The heat exchanger disclosed in the &#39;749 and &#39;537 patents has an outer conduit covering an inner conduit that is made of aluminum. End caps seal the outer conduit. A through channel is provided by the inner conduit and another flow channel is provided between the outer wall of the inner conduit and the inner wall of the outer conduit. The outer wall of the inner conduit has a spiral configuration so that the infusate that is to be heated would follow the spiral path established between the outer wall of the inner conduit and the inner wall of the outer conduit. The infusate is therefore heated by convection from the wall of the inner conduit. This heat exchanger works well. However, due to the fact that the inner conduit is made of aluminum, the cost of manufacturing the heat exchanger is relatively high. Moreover, a multi-step manufacturing process is required to effect a spiraled path at the outer wall of the inner conduit and the fitting of the inner conduit to the outer conduit, and to ensure that there is a flow channel established between the outer spiraled wall of the inner conduit and the inner wall of the outer conduit. Furthermore, given that only the inner conduit is heated by the heated water from the heater, the infusate is only convectively heated by the heat at the outer wall of the inner conduit, while at the same time heat loss occurs due to the infusate contacting the inner wall of the outer conduit which is exposed to atmosphere. 
       SUMMARY OF THE PRESENT INVENTION 
       [0003]    The present invention heat exchanger has a one piece tubing that is configured to have a central lumen, a middle lumen that surrounds the central lumen, and an outer lumen that surrounds the middle lumen. The tubing is made of medical grade plastics material, such as for example PVC, urethane and Pebax, and can be manufactured by a conventional extrusion method whereby the tubing is extruded from a mold to include the central and concentric middle and outer lumens. A supply fitting is connected to one end of the tubing. This supply fitting has a proximal port, an inlet and an outlet, and is configured to connect the proximal port to the middle lumen, the inlet to the central lumen and the outlet to the outer lumen. A return fitting is connected to the other end of the tubing. The return fitting has a distal port and an internal orifice that establishes a through passageway between the central lumen and the outer lumen of the tubing. The return fitting is further configured to connect the middle lumen to the distal port, so that a through passage extends from the proximal port at the supply fitting to the distal port at the return tubing. 
         [0004]    The proximal port is connected to an infusate line so that infusate or physiological solution may be input to the heat exchanger. The inlet and the outlet of the supply fitting are mated to an output port and input port, respectively, of a heater device that is adaptable to heat a fluid to a predetermined temperature and output the temperature regulated fluid through its output port to the inlet of the heat exchanger, and to receive from the outlet of the heat exchanger, via its inlet port, the fluid that has circulated through the heat exchanger for reheating. The distal port at the return fitting outputs the infusate to a patient or a patient line. 
         [0005]    With the construction of the heat exchanger of the instant invention, a heated or heating fluid, such as for example heated water, is provided from the heater device to the supply fitting of the heat exchanger. This heated fluid is then fed by the supply fitting to the central lumen of the tubing where, by means of the internal orifice at its distal end, which is at the return fitting, the heated fluid is routed to the outer lumen of the tubing. As the heated fluid from the heater traverses through the central lumen, the central lumen is heated; and as the heated fluid is rerouted to the outer lumen, the outer lumen is heated, albeit the temperature of the heated fluid returned by the outer lumen to the supply fitting is at a lower temperature, due to heat loss, than that fed by the heater device to the supply fitting. The cooler heating fluid is returned to the heater device where it is once more heated to the predetermined temperature and re-circulated back to the heater exchanger. In the meantime, the infusate input to the heat exchanger at the proximal port, which is traversing through the heat exchanger by way of the latter&#39;s middle lumen, is heated convectively by the heat being conducted from both the central lumen and the outer lumen. In other words, the infusate that flows through the middle lumen of the heat exchanger tubing is enveloped by heat from the heating fluid with no heat loss to the ambient environment. The infusate thus warmed by the heated fluid is output from the distal port of the returned fitting. 
         [0006]    The present invention therefore is directed to a heat exchanger that comprises a tubing having a central lumen, a middle lumen surrounding the central lumen and an outer lumen surrounding the middle lumen. The heat exchanger further includes a supply fitting connected to one end of the tubing. The supply fitting has a proximal port, an inlet and an outlet, and is configured to connect the proximal port to the middle lumen, the inlet to the central lumen and the outlet to the outer lumen. Also included in the heat exchanger is a return fitting connected to the other end of the tubing. The return fitting has a distal port and an internal orifice, and is configured to connect the middle lumen of the tubing to the distal port so that a through path is established between the proximal port of the supply fitting and the distal port of the return fitting. The return fitting further is configured to establish a through passage between the central lumen and the outer lumen via the internal orifice, such that a fluid input to the inlet at the supply fitting would flow from the supply fitting to the central lumen and then be rerouted to the outer lumen and thereafter the outlet at the supply fitting. 
         [0007]    The present invention is further directed to a heat exchanger that comprises a tubing having one end fixedly connected to its supply fitting and an other end fixedly connected to a return fitting. The tubing has a central lumen, a middle lumen surrounding the central lumen and an outer lumen surrounding the middle lumen. The supply fitting has an inlet in fluid communication with the central lumen and an outlet in fluid communication with the outer lumen. The return fitting is configured to have an internal orifice for establishing a fluid communication passage between the central lumen and the outer lumen. A proximal port is provided at the supply fitting and a distal port is provided at the return fitting. The proximal and distal ports are connected by the middle lumen, with the proximal port connectable to an infusate line and the distal port connectable to a patient line. The inlet and the outlet at the supply fitting are mateable to an output port and an input port, respectively, of a heater device so that a heated fluid may be output from the heater device to circulate from the central lumen to the outer lumen and then back to the heater device via the input port, so that an infusate that flows through the proximal port, the middle lumen and the distal port is heated by the heated fluid that circulates through the central and outer lumens. 
         [0008]    The instant invention is further related to a heat exchanger tube that comprises an elongate tube extruded from a plastics material to have a central lumen, a middle lumen surrounding the central lumen and an outer lumen surrounding the middle lumen. Each of the lumens has a plurality of sections separated by the plastics material, with each of the sections of each of the lumens extending along the length of each of the lumens. One end of the tube is fixedly connected to a supply fitting and the other end of the tube is fixedly connected to a return fitting. A passageway is provided between the central and outer lumen at the return fitting to enable a first fluid to circulate between the central and outer lumens. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0009]    The present invention will become more apparent and the invention itself will be best understood by reference to the following description of the invention taken in conjunction with the following drawings, wherein: 
           [0010]      FIG. 1  is a disassembled view of the various components of the instant invention heat exchanger, shown relative to a mount to which the supply fitting of the heat exchanger is coupled; 
           [0011]      FIGS. 2A and 2B  are side views of the assembled  FIG. 1  heat exchanger coupled to the mount of a heater device; 
           [0012]      FIG. 3A  is a sectional view along section A-A of  FIG. 2A ; 
           [0013]      FIG. 3B  is a cross-sectional view along section B-B of  FIG. 2A ; 
           [0014]      FIG. 3C  is an enlarged view of detail C shown in  FIG. 3A ; 
           [0015]      FIG. 3D  is an enlarged view of detail D shown in  FIG. 3A ; 
           [0016]      FIG. 3E  is a cross-sectional along section E-E shown in  FIG. 2B ; 
           [0017]      FIG. 3F  is an enlarged view of detail F of  FIG. 3E ; 
           [0018]      FIG. 3G  is an enlarged view of detail G shown in  FIG. 3E ; 
           [0019]      FIG. 4  is a cross-sectional view of the tubing of the instant invention heat exchanger; 
           [0020]      FIG. 5A  is a perspective view of the core of the supply fitting of the heat exchanger of the instant invention; 
           [0021]      FIG. 5B  is a cross-sectional view of the core of the supply fitting; 
           [0022]      FIG. 6A  is a perspective view of the core of the return fitting of the inventive heat exchanger; 
           [0023]      FIG. 6B  is a cross-sectional view of the core of the return fitting; 
           [0024]      FIG. 7A  shows in perspective view the fluid paths at the distal end of the heat exchanger sans the physical components; 
           [0025]      FIG. 7B  is a cross-sectional view of the fluid paths of  FIG. 7A ; 
           [0026]      FIG. 8  is a view showing the fluid paths of the various fluids at the proximal end of the heat exchanger sans the physical components; and 
           [0027]      FIG. 9  is a simplified schematic illustrating the heat exchanger of the instant invention coupled to a heater device. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0028]    With reference to  FIG. 1 , the heat exchanger  2  of the instant invention is shown to include a tubing  4 , a supply fitting  6  and a return fitting  8 . Supply fitting  6  is shown to include a core  10 , a housing  12  to which the core is fitted, and a cap  14  that fixedly attaches to the top end of core  10  for providing a sealed environment for the supply fitting. As shown, housing  12  has two hollow arms  12   a  and  12   b  each fitted with a corresponding gasket  16 , so that arms  12   a  and  12   b  may be mated to ports  18   a  and  18   b , respectively, of a mount  20  that is a part of a heater device  22 , per shown in  FIG. 9 . The main part of core  10  is fitted to the inside of housing  12 , and the base  14   b  of cap  14  is fixedly secured, for example by bonding, to the proximal end  10   a  of core  10 , per shown in  FIG. 3A  for example. The distal end  12   d  of housing  12  is connected to the distal end  4   a  of tubing  4 . 
         [0029]    Return fitting  8  has a housing  22 , a core  24  fitted in the housing and a cap  26 . Housing  22  has a proximal end  22   a  that fixedly attaches to distal end  4   b  of tubing  4 . Core  24  is fitted inside housing  22 , and the base  26   b  of cap  26  is securely bonded to a base  24   a  of core  24  so as to form a sealed environment for return fitting  8 . Given that tubing  4  is sealingly attached to supply fitting  6  per its proximal end  4   a  and to return fitting  24  per its distal end  4   b , by capping its proximal port  14   c  at cap of  14  and the distal port  26   c  at cap  16 , the heat exchanger  2  is sealed against the environment and remains sterile before use. 
         [0030]      FIGS. 2A and 2B  show the coupling of heat exchanger  2  to mount  20  of a heater device. As shown, cap  14  of supply fitting  6  has a bore for its distal port  14   c . It is at this port that an infusate line  28 , shown in  FIG. 9 , is connected to enable an infusate, such as for example an intravenous (IV) fluid or other physiological fluids, to be introduced to the heat exchanger  2 . The infusate is conveyed along the heat exchanger  2  and exits at a bore that forms the distal port  26   c  at cap  26  of the return fitting  8 . A patient line, such as  30  shown in  FIG. 9 , may be connected to distal port  26   c  for conveying the infusate to a patient. 
         [0031]    With reference to the cross-sectional view of section A-A in  FIG. 3A  and the cross-sectional view of  FIG. 4 , tubing  4  is shown to have a central lumen  4   a , a middle lumen  4   b  that surrounds the central lumen  4   a , and an outer lumen  4   c  that surrounds the middle lumen  4   b . The diameter of the central lumen  4   a  is much larger than the respective widths of the middle and outer lumens. Note that the concentric middle lumen  4   b  and outer lumen  4   c  each comprise a plurality of sections, for example  4   b   1 ,  4   b   2  and  4   b   3  for the middle lumen  4   b , and  4   c   1 ,  4   c   2  and  4   c   3  for the outer lumen  4   c . The various sections of lumens  4   b  and  4   c  extend along the length of each of the lumens. The multiple sections of lumens  4   b  and  4   c  are separated by the plastics material in a spoke wheel fashion, which is effected when tubing  4  is extruded from a medical plastics material such as PVC, urethane and Pebax by a conventional extrusion method. To enable tubing  4  to be fixedly connected to housing  12  of supply fitting  6  and housing  22  of return fitting  8  in a manner that allows the warming of the infusate, the central portion of tubing  4  is extended at its proximal end  4   a  and its distal end  4   b , per shown in  FIG. 1  and the cross-sectional views of  FIGS. 3A and 3E . 
         [0032]    With reference to  FIGS. 3C and 3F  illustrating the enlarged details C and F, respectively, the proximal end of the heat exchanger is shown to include cap  14 , housing  12  and core  10  of supply fitting  6 . Base  10   a  of core  10  is shown to form an upside down well  10   i  that is fixedly attached to base  14   b  of cap  14 . Well  10   i  of core  10  extends to a passageway  10   c  that is connected to the middle lumen  4   b  of tubing  4 . The central lumen  4   a  of tubing  4  is shown to be connected to core  10  and exits to a space  28 , which leads to the inlet of supply fitting  6  represented by the hollow arm  12   a  shown in  FIG. 1 . Outer lumen  4   c  is shown to extend into a passageway  30  defined by the external wall of a tubular extension  10   b  of core  10  and the inside wall of housing  12 . Supply fitting  6  is also shown to be grasped by arms  20   a  and  20   b  of mount  20  in  FIG. 3C . 
         [0033]    The cross-sectional view of enlarged detail F of  FIG. 3F  shows the mating of outlet  12   b  of supply fitting  6  to mount  20 . As shown, the infusate is fed through bore  14   c  of cap  14  into the cavity formed by well  10   i , per directional arrow  32 . The infusate is then directed to the passageway  10   c  at tubular extension  10   b  of core  10 , and from there to the middle lumen  4   b.    
         [0034]    With reference to  FIGS. 3D and 3G , which are the enlarged details D and G, respectively, of  FIGS. 3A and 3E , the distal end of the heat exchanger where the return fitting  8  is connected to tubing  4  is illustrated. As shown, base  24   a  of core  24  is fixedly bonded to base  26   b  of cap  26 . The well area formed by base  24   a  of core  24  is designated  24   c . It is there that the infusate input from proximal port  14   c  of cap  14  at supply fitting  6  is fed, by means of middle lumen  4   b . The infusate collected at cap  24   b  is output from distal port  26   c  to the patient line  30  ( FIG. 9 ), per directional arrow  34 . 
         [0035]    As further shown in  FIG. 3D , and also  FIGS. 8   a  and  8   b , between the inner wall of housing  22  and the outer wall of tubular extension  24   b  there is a circular space  36  that connects to outer lumen  4   c  of tubing  4 . This circular space is where the heated fluid that flows through central lumen  4   a  is being rerouted to outer lumen  4   c  for return to the supply fitting, and from there returned to the heater device for reheating. The space at supply fitting  6  to which the cooler heating fluid is returned had previously been designated as space  30 . Thus, the hot recirculating fluid, i.e., the heated water for example, is fed by heater device  22  from its output port  18   a  to supply fitting  6 , which routes it to central lumen  4   a  of tubing  4 . The heated fluid is then returned to heater device  22  by means of outer lumen  4   c.    
         [0036]    A cross-sectional view illustrating the flow of the heated fluid from the heater device to the heat exchanger, and the return of the heated fluid back to the heater device at supply fitting  6  is shown in  FIG. 3B . The feeding of the heated fluid from the heater device to the supply fitting, and the routing of the heated fluid and the infusate to tubing  4  are best discussed with reference to core  10  for the supply fitting shown in  FIGS. 5A and 5B . 
         [0037]    As shown, core  10  for supply fitting  6  has a base portion  10   a  and a tubular extension  10   b . Base  10   a  has a well area  10   i  that, together with cap  14  shown in  FIG. 3C , provide a cavity whereto the infusate from an infusate line is fed. Well  10   i  extends to a passageway  10   c  at tubular extension  10   b . Passageway  10   c  in turn is connected to middle lumen  4   b , so that the infusate can be conveyed from proximal port  14   c , shown in  FIG. 3   c , to middle lumen  4   b.    
         [0038]    Core  10  also has a space  10   d  that forms a part of the inlet that connects to output port  18   a  of mount  20  of the heater device. Space  10   d  is aligned with hollow arm  12   a  of housing  12 , when core  10  is fitted within housing  12 . Thus, the heated fluid output from output port  18   a  of the heater device is fed through inlet  12   a  into space  10   d , and from there flows to a passageway  10   e  that is connected to central lumen  4   a  of tubing  4 . The flow of the heated fluid from the heater device is shown per directional arrow  38 . Space  10   d  is defined by the back wall  10   f  of base  10   a  and a flange  10   g , and of course also the inside wall of housing  12  when core  10  is fitted therein. 
         [0039]    Core  10  for supply fitting  6  further has a space  10   h , when core  10  is fitted within housing  12 , that is defined by the back wall  10   f  of base  10   d , the underside  10   g ′ of flange  10   g , the outer wall of tubular extension  10   b , designated  10   b ′, and the inside wall, designated by the dotted lines  12   e  in  FIG. 5   a , of housing  12 . This space  10   h  is communicatively connected to outer lumen  4   c  of tubing  4  so that it in effect, along with hollow arm  12   b , provide the outlet for supply fitting  6  to mate to inlet port  18   b  of mount  20 . It is therefore through this outlet that the heated fluid, now having been cooled due to heat dissipation as it flows through the heat exchanger, is returned to heater device  22  for reheating, and subsequent re-circulation through the heat exchanger. 
         [0040]    With reference to  FIGS. 6A and 6B , core  24  for the return fitting has a base  24   a  and a tubular extension  24   b . As was the case with supply fitting core  10 , base  24   a  of return fitting core  24  provides a well area  24   c  that is fixedly coupled to base  26   b  of cap  26 , which is connected to patient line  30  for outputting the infusate to the patient. As shown, cavity  24   c  extends into a circumferential passageway  24   d , that in turn is connected to the middle lumen  4   b  of tubing  4 . A fluid communication path is thereby established between cavity  24   c  and passageway  24   d  of return fitting  8 , middle lumen  4   b , and passageway  10   c  and cavity  10   i  of supply fitting core  10 . 
         [0041]    There is formed at return fitting core  24   a  central passage  24   e  that ends at the back wall  24   f  of base  24   a . An internal orifice  24   g  is formed at the lowermost portion of passageway  24   e  that connects passageway  24   e  to a space  24   h  that is defined by the back wall  24   f  of base  24   a , the outside wall  24   b ′ of tubular extension  24   b  and the inside wall of housing  22 , designated by the dotted line  22   c  in  FIG. 6A . Space  24   h  in turn is connected to outside lumen  4   c , so that a through passage extends from space  24   h  to lumen  4   c , and from there to defined space  10   h  at supply fitting  6 , per shown in  FIG. 5A , so that the heated fluid from central lumen  4   a  that flows through passage  24   e , per shown by directional arrow  40 , would pass through orifice  24   g , and be rerouted into defined space  24   h , per shown by directional arrow  42 . The rerouted heated fluid is then directed to outer lumen  4   c  of tubing  4 , and from there to defined space  10   h  of supply fitting  6  for return to the input port  18   b  of the heater device. 
         [0042]    The respective flows of the infusate and the heated recirculating fluid are shown in  FIGS. 7A ,  7 B and  8 . For the sake of clarity, only the fluids are shown. 
         [0043]    With reference to the distal end of the heat exchanger shown in  FIGS. 7A and 7B , note that the infusate (IV)  44  flows from the middle lumen, designated  44   a , to the tubular extension of the return fitting, identified as  44   b , and from there to the base of the return fitting, designated  44   c . The infusate next is output to the cavity formed by the return fitting cap and the base of the return fitting core, designated  44   d , and then out to the patient line. 
         [0044]    In the meanwhile, the heated fluid, for example heated water, flows through the central lumen, designated  46  in  FIGS. 7A and 7B . As best shown in  FIG. 7A , the hot fluid traverses down the central lumen. Due to internal orifice  24   g  provided at return fitting core  24  ( FIGS. 6A and 6B ) that creates a passageway between the central lumen and the outer lumen, the hot fluid is rerouted, per indicated by directional arrow  48 , from the central lumen to the outer lumen. By the time that the heated fluid gets to the distal end of the heat exchanger, it has lost a measurable amount of heat due to heat dissipation. Therefore, the return fluid, designated  50 , has a cooler temperature than heated fluid  46  flowing along the central lumen of the heat exchanger. Nonetheless, there continues to be heat in the cooler heating fluid as it traverses to the proximal end of the heat exchanger where the supply fitting is. 
         [0045]    With reference to  FIG. 8 , it can be seen that hot fluid  46  from the heater is fed to the heat exchanger at the latter&#39;s inlet. Being guided by space  10   d  of the supply fitting ( FIGS. 5A and 5B ), hot fluid  46  is fed to the tubular extension of the supply fitting core, and then the central lumen of the tubing, per shown by the directional arrow  52 . The being returned cooler heating fluid  50  is shown to flow along the outer lumen of the tubing and also space  10   h  defined by the supply fitting core and the supply fitting housing, so that the cooler heating fluid is returned to the outlet of the heat exchanger and the input port of the heater device, per shown by the direction arrow  54 . In the meanwhile, infusate  44  is fed from an infusate line to the proximal port of the supply fitting, designated  44   e , flows into the cavity defined by the supply fitting cap and the supply fitting core base, designated  44   f , and from there through the tubular extension of the supply fitting core, designated  44   g , and finally to the central lumen, previously designated  44   a  in  FIGS. 7A and 7B . 
         [0046]    As the middle lumen of the heat exchanger tube concentrically bounds the central lumen and is in turn concentrically bounded by the outer lumen, when the infusate flows through the central lumen, heat exchange is provided thereto from both directions at both its inside and outside perimeters due to the recirculating heating fluid flowing along the central lumen and the outer lumen. The effective heat exchange to the infusate by the instant invention tubing is maximized due to the narrow annular shape of the central lumen, which provides a large effective perimeter for heat exchange from the recirculating fluid to take place. Further, the temperature gradient of the hot recirculated fluid in the central lumen radiates outwards toward the infusate for maximally warming the infusate. The heating of the heat exchanger of the instant invention is therefore quite efficient in that there is no direct heat loss by the hot fluid flowing through the central lumen, as it is surrounded by the infusate flowing through the central lumen. 
         [0047]      FIG. 9  shows the coupling of the heat exchanger to a heater device  22 . As shown, outlet  12   b  and inlet  12   a  of supply fitting  6  are mated to inlet port  18   b  and output port  18   a , respectively, of mount  20  of heater device  22 . The heater device  22  may be a Level 1 H-1200 Fast Flow Fluid Warmer. The returned fluid from the heat exchanger is first routed to a reservoir  56 , and from there to a heater  58 . A pump  60  pumps the heated fluid to output port  18   a , and from there to inlet  12   a  of the heat exchanger for circulation as discussed above. Pump  60 , instead of being placed at the output line of the heater device, may also be placed at the input line to enhance the inflow of the cooler heating fluid being returned to heater device  22 . 
         [0048]    An infusate line  28  is connected to proximal port  14   c  of supply fitting  6 , while a patient line  30  is connected to distal port  26   c  at return fitting  8  of the heat exchanger. As discussed above, the infusate, as it flows from the proximal end to the distal end of the heat exchanger via the central lumen, is heated both by the central lumen through which the hot fluid flows and the outer lumen through which the now cooler heating fluid is being returned to the heater device. As the heating fluid is continuously circulated through the heat exchanger, the temperature of the fluid is kept to a predetermined temperature so that the amount of heat for warming the infusate or other physiological fluids fed to the heat exchanger can be readily regulated. 
         [0049]    Inasmuch as the present invention is subject to many variations, modifications and changes in detail, it is intended that all matters described throughout this specification and shown in the accompanying drawings be interpreted as illustrative only and not in a limiting sense. Accordingly, it is intended that the invention be limited only the spirit and scope of the hereto appended claims.