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 outer surface of the inner tube and/or the inner surface of the outer tube are provided with a matte finish that forms an array of peaks and valleys. The valleys form circuitous paths that accommodate a flow of air to facilitate insertion of the inner tube into the outer tube. The circuitous paths also allow air to vent during processing to low pressure.

Description:
RELATED APPLICATIONS 
     This application is a continuation-in-part of appl. Ser. No. 09/933,653 filed on Aug. 21, 2001 now U.S. Pat. No. 6,651,835, which in turn was a continuation-in-part of appl. Ser. No. 09/625,287 filed on Jul. 25, 2000now U.S. Pat. No. 6,354,452. 
    
    
     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 barrier against water and gas permeability and for extending the shelf-life of assembly especially when used for blood collection. 
     2. Description of the 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. 
     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. 
     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 
     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 gas 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 surface for the specified clinical performance of the material being stored in the container assembly. Materials that exhibit good gas barrier characteristics may include: acrylic polymers and copolymers, including ABS, SAN; ethylene vinyl alcohol; polyesters; PET; PETG; PETN; PEN and engineered thermoplastics, including polycarbonate and blends thereof. Materials that exhibit good moisture or vapor barrier characteristics may include: polyolefins, including polyethylene, polypropylene and copolymers thereof, cyclic olefin copolymers and chloro-and fluoro-polymers, including PVDC, PVDF, PVF, EPF and ACLAR. 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 outer surface of the inner tube and the inner surface of the outer tube are dimensioned to substantially nest with one another as explained further herein. 
     The cylindrically generated outer surface of the inner tube and/or the cylindrically generated inner surface of the outer tube have a matte finish or are roughened to define an array of small peaks and valleys. The maximum diameter defined by the peaks on the outer surface of the inner tube may be equal to or slightly greater than the inside diameter of the outer tube. Similarly, the minimum diameter defined by peaks on the inner surface of the outer tube may be equal to or slightly less than the outside diameter of the inner tube. Hence, the peaks defined by the matte-finish or by the roughening will provide secure engagement between the inner and outer tubes. However, the valleys between the peaks defined by the matte-finished or roughening will define circuitous paths for venting air trapped between the inner and outer tubes as the tubes are being assembled and after the tubes have been assembled. Liquid is prevented from entering the space between the inner and outer tubes because due to the pore size created by the matte finish and due to the 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 
     FIG. 1 is an exploded perspective view of the container assembly of the present invention. 
     FIG. 2 is a perspective view of the inner and outer containers at a first stage during their assembly. 
     FIG. 3 is a cross-sectional view taken along line  3 — 3  in FIG.  2 . 
     FIG. 4 is a cross-sectional view similar to FIG. 3, but showing an alternate embodiment. 
     FIG. 5 is a side elevational view of the container assembly of FIG. 1 in its assembled condition. 
     FIG. 6 is a cross-sectional view taken along line  6 — 6  of FIG.  5 . 
    
    
     DETAILED DESCRIPTION 
     As shown in FIGS. 1-6, an assembly  10  includes an outer tube  12 , an inner 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  substantially extending there between. However, 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 formed unitarily from polypropylene and includes a spherically generated closed bottom wall  26 , an open top  28  and a substantially cylindrical side wall  30  extending therebetween. However, 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 . 
     Cylindrical side wall  30  of inner tube  14  has an outer surface  32  with an outside diameter “d” hat is substantially equal to or slightly less than inside diameter “b” of side wall  22  on outer tube  12 . Cylindrical outer surface  32  of side wall  30  is provided with a matte finish or is roughened to define an array of peaks and valleys. Preferably, the roughened side wall is formed by injection molding within tooling that has been machined by an electrical discharge machining (EDM) 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, the matte-finished or roughened cylindrical outer surface  32  of side wall  30  defines a surface finish of 1.6 to 12.5 microns and more preferably a surface finish of 4.5 to 12.5 microns. Additionally, the roughened cylindrical outer surface  32  should be cross-referenced visually to a Charmilles finish number between 24 and 42 and more preferably between 30 and 42. 
     The peaks on roughened cylindrical outer surface  32  of 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  32  of cylindrical side wall  30  will telescope tightly against cylindrical inner surface  24  of side wall  22  of outer tube  12  as shown in FIGS. 3 and 6. 
     As an alternate to the roughening of the outer surface on inner tube  14 , cylindrical wall  22  of outer tube  12  may have a matte finish or roughening on inner surface  24  of cylindrical wall  12  as shown in FIG.  4 . The extent of roughening inner surface  24  may be identical to the roughening on the outer surface described with respect to a first embodiment. 
     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 dimensioned cross-sectionally 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 , as shown in FIGS. 2-4. Air in outer tube  12  will escape through the valleys between the peaks defined by the matte finish or roughening provided on outer surface  32  of inner tube  14 , as shown by the arrow “A” in FIG. 3 or through the valleys between the peaks of the matte finish or roughening on inner surface  24  of outer tube  12 , as shown by the arrow “A” in the FIG. 4 embodiment. This relatively easy insertion of inner tube  14  into outer tube  12  is achieved without an axial groove in either of the tubes. However the roughening provided on cylindrical outer surface  32  of side wall  30  of inner tube  14  defines an array of peaks and valleys. The peaks define the outside diameter “f” and hence define portions of cylindrical outer surface  32  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 the opposed cylindrical inner surface  24 . The valleys between the peaks of roughened cylindrical outer surface  32  are spaced from cylindrical inner surface  24  of side wall  22  of outer tube  12 . Similarly, the roughened cylindrical inner surface  24  of outer tube  12  on the alternate embodiment of FIG. 4 would be spaced from outer cylindrical surface  32  of side wall  30  on inner tube  14  as shown on FIG.  4 . Hence, the valleys between the peaks on roughened cylindrical outer surface  32  or roughened cylindrical inner surface  24  define circuitous passages that permit an escape of air between inner tube  14  and outer tube  12 , as indicated by arrow “A” in FIGS. 3 and 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 nested relationship. In this condition, as shown most clearly in FIGS. 5 and 6, inner tube  14  is supported by the internally nested relationship of bottom wall  26  of inner tube  14  with bottom wall  18  of outer tube  12 . Additionally, inner tube  14  is supported further by the circumferential engagement of the peaks on outer circumferential surface  32  with inner circumferential surface  24  of side wall  22  on outer tube  12  or with the reverse engagement of peaks on inner circumferential surface  24  of outer tube  12  with outer circumferential surface  32  of inner tube  14 . Hence, inner tube  14  is maintained stably 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 due to the ability of the peaks to yield and deform slightly. 
     Air will exist in the space defined by the valleys between the peaks. However, the volume of air will not be great, and the air will not be in a compressed high pressure state. Accordingly, there will not be a great pressure differential between valleys defined by the matte finish or roughening and the outer surface  32  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 the space defined by the valleys between the peaks generated by the matte finish or roughening. 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 valleys defined by the matte finish or roughening to traverse the circuitous path of valleys between the peaks to the lower pressure ambient surroundings. 
     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 the internal surface of inner tube  14  adjacent open top  28 . Hence, closure  16  securely seals the interior of inner tube  14  and the valleys between the peaks formed by the matte finish or roughening between inner tube  14  and outer tube  12 . 
     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.