Flexible bags – End structure
Reexamination Certificate
1999-10-18
2002-02-19
Pascua, Jes F. (Department: 3727)
Flexible bags
End structure
C383S011000, C220S495110
Reexamination Certificate
active
06347886
ABSTRACT:
The present invention relates to a contoured tank liner and a method of production of such a liner, and more particularly, it relates to such tank liner and method of production where the base of the tank liner presents a substantially flat surface of approximately circular configuration when the liner is disposed in a tank and contains a fluid. The tank liners of the invention are particularly useful for mixing biologics, since they may be sterilized.
BACKGROUND OF THE INVENTION
Tank liners are well known in the art and are used in many applications. Generally speaking, tank liners are used for lining tanks in which a fluid is disposed and where it is desired that the fluid not contaminate the tank. For example, if a biologic liquid, such as blood, plasma, etc., or a saline solution, which for present purposes is considered as a biologic liquid, is processed in a tank without a liner, after that liquid has been processed and discharged from the tank, the tank must be thoroughly cleaned, under biological standards, before that tank can be reused for processing a further batch of the liquid. However, when a tank liner is used in such a tank, and when that tank liner has been previously sterilized, the liquid can be processed within the tank and tank liner, and after a discharge of the liquid, the tank liner is simply disposed of and a new sterilized tank liner is placed into the tank for subsequent processing of additional liquid.
Thus, tank liners are used in applications where it is less expensive to use a tank liner and avoid the necessary thorough cleaning of the tank, as well as the extensive biological and analytical studies required to prove to regulatory agencies that the tank is clean. As can therefore be easily appreciated, in view of that economic consideration, in order for such disposable tank liner to be commercially acceptable, it must be manufactured at a relatively low cost. Otherwise, it would be more economical to clean the tank after each use.
Accordingly, prior art tank liners, in order to be manufactured at a low cost, are, generally, relatively uncomplicated structures, so as to promote ease of manufacture and, hence, production at a low cost. Typically, such disposable tank liners are made from tubular thermoplastic film.
In one prior art liner, a weld seam is made transverse to the longitudinal direction of the tubular film to form a closed bottom of the film and produce a liner. However, when such liners are disposed in a conventional processing tank, which typically is generally cylindrical and has a generally flat bottom, the welded base bunches against the flat bottom of the tank when the liner contains a fluid, and the base, thus presented, is not flat but exceedingly rough. This rough base causes difficulties in processing and especially in mixing, and most especially in mixing biologics, since it is necessary, for example, that a solid solute be completely dissolved in a solvent to ensure that the concentration of the solute in the solvent is as required. With the rough bottom of such conventional tank liners, as described above, for example, solid solute, such as a saline solute, can settle to the bottom of the liner disposed in the tank before being solubilized, and the rough surface on the base of the liner tends to trap that undissolved solute and prevent that solute from being solubilized by the solvent. When this occurs, either prolonged mixing is required, which is uneconomical, or the solution will not have the desired concentration of solubilized solute therein and is, generally, therefore not acceptable for use.
In addition, the conventional tank liner, as described above, when disposed in a generally cylindrical tank and containing a liquid, not only presents the rough base, due to bunching of the liner at the base, but, in addition, bunches around the side walls of the tank near its base because the base of the liner, being simply welded along its traverse, cannot form a configuration in the tank which approximates a circular configuration of a generally cylindrical tank. This bunching of the liner at the side walls near the base, again, causes a rough surface against which, for example, the solvent must flow during mixing. That rough surface can produce stagnant pockets of the solvent, which can result in inadequate mixing of the solute in the solvent and can produce variations in the concentration of the solute throughout the bulk of the solution. If, for example, the solution is removed from the tank and serially loaded into separate containers, for example, sterile saline bags, then it is possible that the concentration of the solute in those serially filled saline bags will be different, which is quite unacceptable.
In another prior art liner, efforts have been made to avoid the above-described difficulties. This other prior art liner uses, again, a tubular thermoplastic film, but seam welds to an end thereof a circular disc so as to provide a circular bottom to the tank liner. Basically, the disc has a greater diameter than the diameter of the tubular film. A lower edge of the tubular film is bent inwardly to form an inwardly directed “flange” and the disc, with edges extending over the flange and beyond the diameter of the tubular film, is welded, along its circumference, thereto.
However, this approach has a number of disadvantages. Aside from the high cost of tooling and difficulty of manufacture, the inwardly bent flange remains along the inside circumference of the bottom of the finished liner and presents not only a rough surface, as described above, but also presents areas along the circumference which can, for example, trap solute during mixing.
Further, the thermoplastic of choice of the tank liner is a polyolefin, e.g. polyethylene, since that thermoplastic has excellent welding properties. Thus, to make the circular weld, described above, the weld must be between polyolefin surfaces, which means that an outside surface of the liner cannot have a barrier layer film thereon. Normally, tank liners for processing biologics have a polyolefin film bonded to an outside barrier layer film, e.g. a nylon film. This is because polyolefins are permeable, which is most undesirable for biologics since tank contamination can occur. Thus, an impermeable barrier layer film, e.g. nylon film, is required as an outside layer of the thermoplastic film for most biologics processing liners. This nylon outside barrier layer film also greatly increases tear resistance of the liner.
Also, in both of the above-described prior art approaches using tubular thermoplastic film, the diameter, and hence size, of the tank liner is dictated by commercially available diameters of tubular film. This means that the liners cannot be manufactured to snugly fit all usual tanks.
Thus, neither of these prior art tank liners is fully acceptable and, hence, have not been widely used.
As a result of the foregoing, when critical processing is required, e.g. mixing of a solute in a solvent, in biologics, it is not uncommon for manufacturers to dispense with the use of a tank liner, because of the above-described difficulties, and accept the increased cost of production associated with a thorough cleaning and inspection of a tank, accordingly to biologic standards, after each use.
From the above, it can easily be seen that it would be a substantial advantage in the art to provide a disposable tank liner, where the base presents a substantially flat surface, so as to avoid the rough base surface of the prior art and the possibility of difficulties, as described above. It would also be a substantial advantage in the art to provide such a liner with a base which approximates a circular configuration when the liner is disposed in the tank and contains a liquid, so as to avoid the bunching of the liner at the side walls near the base, and the difficulties associated therewith, as described above.
It would also be an advantage to provide such liner which can be made of thermoplastic film having a barrier layer film on all parts thereof and one which does not have a circu
Birch & Stewart Kolasch & Birch, LLP
Charter Medical, Ltd.
Pascua Jes F.
LandOfFree
Disposable contoured tank liner and method of production does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Disposable contoured tank liner and method of production, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Disposable contoured tank liner and method of production will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2980968