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.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a collection container assembly that includes a plurality of nested containers formed from different respective materials and provides an effective is barrier against water and gas permeability and for extending the shelf-life of assembly especially when used for blood collection. 
     2. Description of Related Art 
     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. 
     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. 
     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. 
     SUMMARY OF THE INVENTION 
     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). 
     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 abut the bottom wall of the outer tube. Additionally, portions of the inner tube near the open top are configured to nest closely 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 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 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. 
     The container assembly of the present invention achieves the required shelf life for medical applications. Furthermore, the inner container can be formed from a material that will exhibit appropriate clinical performance in the presence of the specimen and/or additives in the container assembly. 
     The container of the present invention substantially eliminates the complications of maintaining the shelf-life of plastic containers that contain liquid additives. In addition, the container of the present invention minimizes the rate of moisture loss from plastic containers that contain liquid additives. 
     The container of the present invention provides the means to deliver a higher quality plastic container product to the customer because liquid additive concentration, additive volume and additive solubility are better controlled. 
     Another notable attribute of the container of the present invention is that it will not interfere with testing and analysis that is typically performed on blood in a tube. Such tests include but are not limited to, routine chemical analysis, biological inertness, hematology, blood chemistry, blood typing, toxicology analysis or therapeutic drug monitoring and other clinical tests involving body fluids. Further, the container of the present invention may be subjected to automated machinery such as centrifuges and may be exposed to certain levels of radiation in the sterilization process with substantially no change in optical, mechanical or functional properties. 
     Most notably, is that the container of the present invention impedes the rate of water vapor transport from within the container interior and thus controls additive solution concentration and volume for containers containing a liquid additive. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded perspective view of the container assembly of the present invention. 
     FIG. 2 is a side elevational view of the container assembly of FIG. 1 in its assembled condition. 
     FIG. 3 is a cross-sectional view taken along line  3 — 3  of FIG.  2 . 
    
    
     DETAILED DESCRIPTION 
     As shown in FIGS. 1-3, an assembly  10  includes an outer tube  12 , an inner tube  14  and a closure  16 . 
     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”. 
     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 circumfercntially 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 . 
     Cylindrical portion  32  of side wall  30  of inner tube  14  has a 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 0.12″ less than inside diameter “b” of side wall  22  on outer tube  12 . As a result, an annular clearance “e” of approximately 0.006″ 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 . 
     Cylindrical outer surface  38  of enlarged top section  34  on side wall  30  defines an outside diameter “f” which is approximately equal to inside diameter “b” of side wall  22  of outer tube  12 . Hence, cylindrical outer surface  38  of enlarged section top  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″ has been found to provide acceptable stability. 
     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 . 
     Assembly  10  is assembled by slidably inserting inner tube  14  into open top  20  of outer tube  12 . 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 circumferential space between cylindrical portion  32  of side wall  30  of inner tube  14  and cylindrical inner surface  24  of outer tube  12 . 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 is impeded when enlarged top section  34  of inner tube  14  engages side wall  22  of outer tube  12 . However, insertion of inner tube  14  into outer tube  12  is nearly complete at that stage of insertion, and hence only a minor compression of air is required to complete insertion of inner tube  14  into outer tube  12 . Insertion of inner tube  14  into outer tube  12  continues 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. 2 and 3, 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. 
     A substantially cylindrical space  54  is defined between inner tube  14  and outer tube  12  along most of their respective lengths. However, space  54  is sealed by outer cylindrical surface  38  of enlarged top section  34 . Consequently, there is no capillary action that could draw liquid, such as citrate, into cylindrical space  54 , and accordingly there is no perception of contamination. 
     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 internal top regions of both inner tube  14  and outer tube  12 . Furthermore, engagement between closure  16  and tapered internal surface  40  of enlarged section  34  contributes to the sealing engagement between cylindrical external surface  38  of enlarged section  34  and cylindrical internal surface  24  of outer tube  14 . 
     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.