Moisture Detection System for a Sterile Package

This invention relates in general to a sterile package water detection system.

Sterile packages, such as blister packages or surgical kits, generally include a plastic shell having a barrier lid sealed thereto by means of a heat sealable coating on the reverse side of the lid. The package contents and interior are sterilized by passing a gas, such as ethylene oxide, through the pores of the lid and its coating. The pores are small enough to resist bacterial penetration, but may pass moisture. If even a small quantity of water should pass the barrier lid, the sterile condition may be lost.

One problem therefore is to provide an indication that water penetration has occurred.

Another problem is that after a package has been penetrated by water and dried, a memory or record of the prior wetting must be retained to indicate the possible contamination. Still another problem is that such moisture indicating system must be economical and compatible with presently used materials and practices.

Prior art moisture or water indicators using color-change compositions are sometimes ineffective because the operator must be aware of what color designates a moisture condition. Also, the color change may be subtle and not easily differentiated. Further, the operator might be color blind to the color change. Additionally, most moisture or water detection papers do not leave a permanent record. For example, commonly used cobalt chloride detection paper will turn from blue (dry condition) to pink (wet condition). However, upon subsequent drying the paper will return to blue without leaving a record of being wetted.

Accordingly, one object of the present invention is to provide a novel water detection system for a sterile package.

Another object of the present invention is to provide a water detection system for a sterile package which indicates the leak occurrence, after the water has dried.

Still another object of the present invention is to provide a water detection system for a sterile package which is economical and which would readily and immediately indicate a moisture condition.

Other objects and advantages of the invention will become apparent as the description proceeds.

The present invention provides a water detection system for a sterile package by incorporating a water altered pattern in the package behind the barrier lid or on the outside of the barrier lid. The change in appearance in the pattern on contact with a small amount of water provides a permanent record that water has permeated the package.

In the illustrative embodiments, the pattern is provided by printing either the back of the barrier lid or the heat sealable coating thereon with a water soluble pattern of ink or fluorescent dye, which smears or smudges to cover a relatively large area on contact with a small amount of water. Alternatively, a separate material bearing the dye is deposited in the package, but in any event an image indicating the water contamination is provided which is visible through the barrier and through the plastic shell, if transparent, or is visible when the lid is removed from the package.

The pattern is usually formed upon the rear surface of the barrier lid heat sealable coating in a matrix or grid, if a water based heat sealable coating is used, or the pattern is printed directly on the rear surface of the barrier lid if a non-aqueous heat sealable coating is used so that the coating may then be deposited on the printed pattern.

A more detailed explanation of the invention is provided in the following description and claims and is illustrated with accompanying drawings.

FIG. 1 is a front elevational view of a sterile blister package employing the principles of the present invention with a portion of the barrier lid and heat sealable coating peeled away to reveal the pattern greatly enlarged;

FIG. 2 is a rear elevational view of the blister package shown in FIG. 1;

FIG. 3 is a sectional view of the blister package seen in FIG. 1 taken generally along the line 3--3 in FIG. 1 and showing the pattern and heat sealable coating in relatively greatly enlarged cross-section;

FIG. 4 is a fragmentary sectional view illustrating the pattern deposited directly on the rear surface of a barrier lid with the relative cross-section of the pattern and coating greatly enlarged; and

FIG. 5 is a fragmentary sectional view illustrating a paper material bearing the pattern deposited in a sterile blister package.

In FIGS. 1 and 2, a sterile blister package is indicated by the reference character 10. The package 10 includes a transparent plastic shell 12 which may be cup-shaped, box-shaped or have various other shapes, and a barrier lid 14 having a heat sealable coating 16 on the rear surface thereof.

A peripheral flange 18 on the open end of the shell 12 is sealed to lid 14 by means of the heat sealable coating 16, as best seen in FIG. 3, for sealing the contents 20, such as a gauze or packing or any other type of medical device or equipment, in the package 10. The coating 16 is deposited on the rear surface of lid 14 prior to its assembly to the shell 12 and the front surface is printed both with identification of the contents, etc., and a notice to observe the indicia of contamination to be described.

The lid 14 is normally of a paper stock material, such as a 60# surgical kraft paper or a non-woven material made from polyethylene fibers commonly sold under the trademark TYVEK by DuPont. The lid 14, together with the heat sealable coating 16, are permeable to a sterilizing gas, such as ethylene oxide, which sterilizes the contents and interior of the package. The "labyrinth" or "depth" filter formed by lid 14 will not normally pass particles over 0.22 microns, which is smaller than any known bacteria, but does admit moisture (although the coating will retard penetration). The contents 20 of the package can therefore become contaminated.

To indicate water contamination, a pattern 22 of dots 24 formed of a water soluble alcohol, acetone or other water compatible based ink, dye or fluorescent ink or dye is printed on the rear surface of the heat sealable coating, as shown greatly enlarged in FIGS. 1 and 3 wherein the cross-sectional area and size of the dots are shown greatly exaggerated. An example of a type of water soluble dye that may be used is sold by Ink Specialties Company, Arlington Heights, Illinois. The coating 16 extends between the dots on heat sealing.

The pattern is printed on the rear surface of the coating 16 in the form of a matrix of rows and columns of magenta or other color dots, as shown in FIG. 1, with adjacent rows and columns offset or in a grid. As a specific example, although no limitation is intended, a dot pattern with 1/32 inch diameter dots spaced 3/64 inches between centers has been found to be satisfactory. Penetration by water such as a single drop from a fine needle causes the ink or dye to bleed between the dots or through the lid and creates a smudge that is clearly visible on or through the lid 14, or on the underside of a peeled-off lid, or through portions of the transparent shell 12 not blocked by the contents.

As shown in FIG. 4, a pattern 26 of dots or a grid may be printed directly on the paper barrier lid 28, for example, and the pattern 26 covered by a heat sealable coating 30, which flows between the dots to make direct contact with the rear surface of the lid 28. However, it has been found that when the pattern is printed directly on the paper barrier lid 28 (under the coating 30), the lid may become extremely sensitive to moisture applied to the outside thereof. Such extreme sensitivity may be excessive for the purposes desired. For example, a lid having the pattern printed directly thereon in accordance with the FIG. 4 embodiment may demonstrate bleeding of the dot pattern when handled by a person with slightly damp hands, although there is actually no water contamination inside the package. For this reason, the FIG. 3 embodiment is generally preferred.

Alternatively, a sheet of paper 32 or the like, or paper-like material, carrying a pattern 34 of water soluble colored material (as shown in FIG. 5) may simply be deposited in the package or container 36 between the coating 38 on the rear surface of the barrier lid 40 and the plastic shell 42.

It is understood that various modifications and substitutions may be made by those skilled in the art without departing from the novel spirit and scope of the invention.