Abstract:
The present invention is a container assembly that includes an inner tube formed from a plastic that is substantially inert to bodily fluids and an outer tube that is formed from a different plastic. Collectively, the container assembly is useful for providing an effective barrier against gas and water permeability in the assembly and for extending the shelf-life of the container assembly, especially when used for blood collection. The inner container is spaced from the outer container at most locations. However, the inner container includes an enlarged top configured to engage the outer container. The enlarged top has a roughened outer surface to permit an escape of air from the space between the containers.

Description:
RELATED APPLICATIONS  
       [0001]    This application is a continuation-in-part of pending appl. Ser. No. 09/625,287 filed on Jul. 25, 2000. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The invention relates to a collection container assembly that includes a plurality of nested containers formed from different respective materials and provides an effective barrier against water and gas permeability and for extending the shelf-life of assembly especially when used for blood collection.  
           [0004]    2. Description of the Related Art  
           [0005]    Plastic tubes contain an inherent permeability to water transport due to the physical properties of the plastic materials used in manufacturing tubes. Therefore, it is difficult to maintain the shelf-life of plastic tubes that contain a liquid additive. It is also appreciated that deterioration of the volume and concentration of the liquid additive may interfere with the intended use of the tube.  
           [0006]    In addition, plastic tubes that are used for blood collection require certain performance standards to be acceptable for use in medical applications. Such performance standards include the ability to maintain greater than about  90 % original draw volume over a one-year period, to be radiation sterilizable and to be non-interfering in tests and analysis.  
           [0007]    Therefore, a need exists to improve the barrier properties of articles made of polymers and in particular plastic blood collection tubes wherein certain performance standards would be met and the article would be effective and usable in medical applications. In addition, a need exists to preserve the shelf-life of containers that contain liquid additives. The time period for maintaining the shelf-life is from manufacturing, through transport and until the container is actually used.  
           [0008]    Some prior art containers are formed as an assembly of two or more nested containers. The nested containers are formed from different respective materials, each of which is selected in view of its own unique characteristics. Some nestable containers are dimensioned to fit closely with one another. Containers intended for such assemblies necessarily require close dimensional tolerances. Furthermore, air trapped between the two closely fitting nestable containers can complicate or prevent complete nesting. Some prior art container assemblies have longitudinal grooves along the length of the outer surface of the inner container and/or along the length of inner surface of the outer container. The grooves permit air to escape during assembly of the containers. However, the grooves complicate the respective structures and the grooved containers still require close dimensional tolerances.  
           [0009]    Other container assemblies are dimensioned to provide a substantially uniform space at all locations between nested inner and outer containers. Air can escape from the space between the dimensionally different containers as the containers are being nested. Thus, assembly of the nestable containers is greatly facilitated. Additionally, the nestable containers do not require close dimensional tolerances. However, the space between the inner and outer containers retains a small amount of air and the air may be compressed slightly during final stages of nesting. Some such container assemblies are intended to be evacuated specimen collection containers. These container assemblies are required to maintain a vacuum after extended periods in storage. However, air in the space between the inner and outer containers is at a higher pressure than the substantial vacuum in the evacuated container assembly. This pressure differential will cause the air in the space between the inner and outer containers to migrate through the plastic wall of the inner container and into the initially evacuated space of the inner container. Hence, the effectiveness of the vacuum in the container assembly will be decreased significantly. These problems can be overcome by creating a pressure differential between the annular space and the inside of the inner container to cause a migration of air through the walls of the inner container. The inner container then is evacuated and sealed. This approach, however, complicates and lengthens an otherwise efficient manufacturing cycle.  
         SUMMARY OF THE INVENTION  
         [0010]    The present invention is a container assembly comprising inner and outer containers that are nested with one another. The inner and outer containers both are formed from plastic materials, but preferably are formed from different plastic materials. Neither plastic material is required to meet all of the sealing requirements for the container. However, the respective plastic materials cooperate to ensure that the assembly achieves the necessary sealing, adequate shelf life and acceptable clinical performance. One of the nested containers may be formed from a material that exhibits acceptable vapor barrier characteristics, and the other of the containers may be formed from a material that provides a moisture barrier. The inner container also must be formed from a material that has a proper clinical surface for the material being stored in the container assembly. Preferably, the inner container is formed from polypropylene (PP), and the outer container is formed from polyethylene terephthalate (PET).  
           [0011]    The inner and outer containers of the container assembly preferably are tubes, each of which has a closed bottom wall and an open top. The outer tube has a substantially cylindrical side wall with a selected inside diameter and a substantially spherically generated bottom wall. The inner tube has an axial length that is less than the outer tube. As a result, a closure can be inserted into the tops of the container assembly for secure sealing engagement with portions of both the inner and outer tubes. The bottom wall of the inner tube is dimensioned and configured to nest with or about the bottom wall of the outer tube. Additionally, portions of the inner tube near the open top are configured to nest closely or have an interference fit with the outer tube. However, portions of the inner tube between the closed bottom and the open top are dimensioned to provide a continuous circumferential clearance between the tubes. The close nesting or interference fit of the inner tube with the outer tube adjacent the open top may be achieved by an outward flare of the inner tube adjacent the open top. The flare may include a cylindrically generated outer surface with an outside diameter approximately equal to or greater than the inside diameter of the side wall of the outer tube. The flare further includes a generally conically tapered inner surface configured for tight sealing engagement with a rubber closure.  
           [0012]    The cylindrically generated outer surface of the inner tube may be roughened to define an array of peaks and valleys. The maximum diameter defined by the peaks may be equal to or slightly greater than the inside diameter of the outer tube. Hence, the peaks on the roughened cylindrically generated outer surface of the flared top on the inner tube will provide secure engagement between the inner and outer tubes. However, the valleys between the peaks on the roughened cylindrically generated outer surface at the top of the inner tube will define circuitous paths for venting air trapped in the circumferential space between the inner and outer tubes at locations between the flared top of the inner tube and the closed bottom of the outer tube and to prevent liquid from entering the circumferential space between the inner and outer tubes. Liquid is prevented from entering the space between the inner and outer tubes because due to the pore size, viscosity and surface tension of the liquid. As a result, the container assembly achieves efficient nesting without longitudinal grooves and close dimensional tolerances and simultaneously enables evacuation of air from the space between the inner and outer tubes so that a vacuum condition can be maintained within the inner tube for an acceptably long time and prevents liquid from entering the space between the inner and outer tubes. 
       
    
    
     DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 is an exploded perspective view of the container assembly of the present invention.  
         [0014]    [0014]FIG. 2 is a perspective view of the inner and outer containers at a first stage during their assembly.  
         [0015]    [0015]FIG. 3 is a cross-sectional view taken along line  3 - 3  in FIG. 2.  
         [0016]    [0016]FIG. 4 is a cross-sectional view similar to FIG. 3, but showing a later stage during assembly of the inner and outer containers.  
         [0017]    [0017]FIG. 5 is a side elevational view of the container assembly of FIG. 1 in its assembled condition.  
         [0018]    [0018]FIG. 6 is a cross-sectional view taken along line  6 - 6  of FIG. 5. 
     
    
     DETAILED DESCRIPTION  
       [0019]    As shown in FIGS.  1 - 6 , an assembly  10  includes an outer tube  12 , an inner tube  14  and a closure  16 .  
         [0020]    Outer tube  12  is unitarily formed from PET and includes a spherically generated closed bottom wall  18 , an open top  20  and a cylindrical wall  22  extending therebetween whereby side wall  22  slightly tapers from open top  20  to closed bottom wall  18 . Outer tube  12  defines a length “a” from the interior of the bottom wall  18  to the open top  20 . Side wall  22  of outer tube  12  includes a cylindrically generated inner surface  24  with an inside diameter “b”.  
         [0021]    Inner tube  14  is unitarily formed from polypropylene and includes a spherically generated closed bottom wall  26 , an open top  28  and a cylindrical side wall  30  extending therebetween whereby side wall  30  slightly tapers from open top  28  to closed bottom wall  26 . Inner tube  14  defines an external length “c” that is less than internal length “a” of outer tube  12 . Side wall  30  of outer tube  14  includes a cylindrical section  32  extending from bottom wall  26  most of the distance to open top  28  of inner tube  14 . However, side wall  30  is characterized by a circumferentially enlarged section  34  adjacent open top  28 . Enlarged top section  34  of side wall  30  includes an outwardly flared outer surface  36  adjacent cylindrical portions  32  of side wall  30  and a cylindrical outer surface  38  adjacent open top  28  of inner tube  14 . Additionally, enlarged top section  34  of side wall  30  includes a conically flared inner surface  40  adjacent open top  28 .  
         [0022]    Cylindrical portion  32  of side wall  30  of inner tube  14  has an outside diameter “d” that is less than inside diameter “b” of side wall  22  on outer tube  12 . In particular, outside diameter “d” of cylindrical portion  32  of side wall  30  is approximately 0.012 inches less than inside diameter “b” of side wall  22  on outer tube  12 . As a result, an annular clearance “e” of approximately 0.006 inches will exist between cylindrical portion  32  of side wall  30  of inner tube  14  and side wall  22  of outer tube  12  as shown most clearly in FIG. 3.  
         [0023]    Cylindrical outer surface  38  of enlarged top section  34  on side wall  30  is roughened to define an array of peaks and valleys. Preferably, the roughened side wall is formed by an electrical discharge machining process so as to form an electrical discharge machining finish. The finished part then is compared visually with a visual standard, such as the Charmilles Technologies Company visual surface standard (Charmilles Technology Company, Lincolnshire, Ill.). Using this standard practice, roughened cylindrical outer surface  38  of enlarged top section  34  on side wall defines a finish of 1.6 to 12.5 microns and more preferably a finish of 4.5 to 12.5 microns. Additionally, the roughened cylindrical outer surface  38  should be cross-referenced visually to a Charmilles finish number between  24  and  42  and more preferably between  30  and  42 .  
         [0024]    The peaks on roughened cylindrical outer surface  38  of enlarged top section  34  on side wall  30  define an outside diameter “f” which is approximately equal to or slightly greater than inside diameter “b” of side wall  22  of outer tube  12 . Hence, roughened cylindrical outer surface  38  of enlarged top section  34  will telescope tightly against cylindrical inner surface  24  of side wall  22  of outer tube  12  as shown in FIG. 3. Enlarged top section  34  of inner tube  12  preferably defines a length “g” that is sufficient to provide a stable gripping between outer tube  12  and inner tube  14  at enlarged top section  34 . In particular, a length “g” of about 0.103 inches has been found to provide acceptable stability.  
         [0025]    Closure  16  preferably is formed from rubber and includes a bottom end  42  and a top end  44 . Closure  16  includes an external section  46  extending downwardly from top end  44 . External section  46  is cross-sectionally larger than outer tube  12 , and hence will sealingly engage against open top end  20  of outer tube  12 . Closure  16  further includes an internal section  48  extending upwardly from bottom end  42 . Internal section  48  includes a conically tapered lower portion  50  and a cylindrical section  52  adjacent tapered section  50 . Internal section  48  defines an axial length “h” that exceeds the difference between internal length “a” of outer tube  12  and external length “c” of inner tube  14 . Hence, internal section  48  of closure  16  will engage portions of outer tube  12  and inner tube  14  adjacent the respective open tops  20  and  28  thereof, as explained further below. Internal section  52  of closure  16  is cross-sectionally dimensioned to ensure secure sealing adjacent open tops  22  and  28  respectively of outer tube  12  and inner tube  14 .  
         [0026]    Assembly  10  is assembled by slidably inserting inner tube  14  into open top  20  of outer tube  12 , as shown in FIGS.  2 - 4 . The relatively small outside diameter “d” of cylindrical portion  32  of side wall  30  permits insertion of inner tube  14  into outer tube  12  without significant air resistance. Specifically, air in outer tube  12  will escape through the cylindrical space  54  between cylindrical portion  32  of side wall  30  of inner tube  14  and cylindrical inner surface  24  of outer tube  12 , as shown by the arrow “A” in FIG. 3. This relatively easy insertion of inner tube  14  into outer tube  12  is achieved without an axial groove in either of the tubes. The escape of air through the cylindrical space  54  is impeded when enlarged top section  34  of inner tube  14  engages side wall  22  of outer tube  12 . However the roughening provided on cylindrical outer surface  38  of enlarged top section  34  defines an array of peaks and valleys. The peaks define the outside diameter “f” and hence define portions of cylindrical outer surface  38  that will engage cylindrical inner surface  24  of side wall  22  of outer tube  12 . Roughening to a Charmilles finish number between  30  and  42  provides a sufficient density of peaks to grip cylindrical inner surface  24  of outer tube  12 . The valleys between the peaks of roughened cylindrical outer surface  38  are spaced from cylindrical inner surface  24  of side wall  22  of outer tube  12 . Hence, the valleys between the peaks on roughened cylindrical outer surface  38  define circuitous passages that permit an escape of air from the circumferential space as indicated by arrow “A” in FIG. 4. Insertion of inner tube  14  into outer tube  12  continues with little air resistance until the outer surface of spherically generated bottom wall  26  of inner tube  12  abuts the inner surface of bottom wall  18  on outer tube  12  in an internally tangent relationship. In this condition, as shown most clearly in FIGS. 5 and 6, inner tube  14  is supported by the internally tangent abutting relationship of bottom wall  26  of inner tube  14  with bottom wall  18  of outer tube  12 . Additionally, inner tube  14  is further supported by the circumferential engagement of outer circumferential surface  38  of enlarged top section  34  with inner circumferential surface  24  of side wall  22  on outer tube  12 . Hence, inner tube  14  is stably maintained within outer tube  12  with little or no internal movement that could be perceived as a sloppy fit. This secure mounting of inner tube  14  within outer tube  12  is achieved without a requirement for close dimensional tolerances along most of the length of the respective inner and outer tubes  14  and  12  respectively.  
         [0027]    Cylindrical space  54  is defined between inner tube  14  and outer tube  12  along most of their respective lengths. Air will exist in cylindrical space  54 . However, the air will not be in a compressed high pressure state. Accordingly, there will not be a great pressure differential between cylindrical space  54  and the inside of inner tube  14 , and migration of air through the plastic material of side wall  30  of inner tube  14  will not be great. Migration of air through side wall  30  of inner tube  14  can be reduced further by evacuating cylindrical space  54 . More particularly, the assembly of outer and inner tubes  12  and  14  can be placed in a low pressure environment. The pressure differential will cause air in cylindrical space  54  to traverse the circuitous path of valleys between the peaks of roughened outer cylindrical surface  38  to the lower pressure ambient surroundings.  
         [0028]    The assembly of inner tube  14  with outer tube  12  can be sealed by stopper  16 . In particular, tapered portion  50  of internal section  48  facilitates initial insertion of stopper  16  into open top  20  of outer tube  12 . Sufficient axial advancement of stopper  16  into open top  20  will cause cylindrical outer surface  52  of internal section  48  to sealingly engage internal surface  24  of outer tube  12 . Further insertion will cause tapered surface  50  of internal section  48  to sealingly engage tapered internal surface  40  of enlarged section  34  of inner tube  14 . Hence, closure  16  securely seals the interior of inner tube  14  and cylindrical space  54  between inner tube  14  and outer tube  12 .  
         [0029]    While the invention has been defined with respect to a preferred embodiment, it is apparent that changes can be made without departing from the scope of the invention as defined by the appended claims.