Patent NZ-333193-A (NZ)
Title: A burst-proof pack comprising inner and outer bands with a pressure dissipation channel in between
Inventor: FENSHAM NOEL CEDRIC
IPC: B65D77/20
Filed: 1998-03-06
Abstract: The specification provides for a burst-proof pack comprising a tray having at least one recess defined therein which houses a fluid, the recess being surrounded by a land, a web extending over and being sealed to the land by a sealing arrangement so as to provide a sealed compartment, the sealing arrangement including at least an inner and an outer peripheral sealing band defining an intermediate pressure dissipation channel for preserving the integrity of the sealed compartment in the event of one of the sealing bands being broached.  Referring first to FIGS. 1, 2 and 2A, a first embodiment of a pack in the form of a swab pack 10 comprises a blister tray 12 which is vacuum formed from a clear polystyrene or PVC material having a thickness of 250 microns to 400 microns. The polystyrene or PVC layer 12A is laminated to an upper low density polyethylene (LDPE) layer 12B having a thickness of approximately 70 microns. The blister tray 12 is formed with five part-spherical swab recesses 14A to 14E within which surgical wound cleansing swabs 16 nest. Each of the surgical swabs 16 is formed from a gauze material using a swab making machine. As is clear from FIG. 2, the absorbent surgical swabs 16 are impregnated with a 0.9% disinfecting saline solution 18. A series of interleading channels 20 facilitates circulation of the non-absorbed saline solution.  The blister tray 12 is formed with an outer peripheral planar land 22 onto which a web 24 is heat sealed along a sealing arrangement 25. The sealing arrangement terminates short of the upper and lower edges of the planar land, thereby defining finger-grippable web flaps 25A which may be gripped to commence the peeling operation. The web is formed with an upper high density, polyethylene (HDPE) layer 24A having a thickness of approximately 40 microns and a lower LDPE layer 24B having a thickness of approximately 30 microns, with the sealing arrangement 25 between the contiguous LDPE layers of the blister tray 12 and the web 24 providing an hermetic seal, whilst at the same time allowing the web to be peeled away from the upper surface of the land 22.  As is clear from the detail in FIG. 2A, the sealing arrangement 25 comprises an inner peripheral heat sealed zone or band 25A, an intermediate continuous heat sealed band or zone 25B and an outer peripheral heat sealed band or zone 25C. An inner peripheral continuous dissipation channel 25D is defined between the sealing bands 25A and 25B, and an outer peripheral continuous dissipation channel 25E is defined between the sealing bands 25B and 25C. The concentric configuration of the bands is clear from FIG. 1. The pressure dissipation channels 25D and 25E serve to dissipate pressure and to increase the burst-proof nature of the pack. By way of explanation, in the event of a broach 26A occurring in the first sealing band 25A, this will cause the scaled compartment lo communicate with the inner dissipation channel 25D, which serves to dissipate the pressurized air and fluid once it has leaked through the broach, thereby acting as a "first line of defence". The dissipation channel 25D thus prevents the broach 26A from migrating through until it broaches the seal arrangement completely, as would be the case with a single broad seal. Similarly, should a further broach 26B subsequently be created between the inner and outer dissipation channels 25D and 25E, the channel 25F will effectively stop the broach 26B from spreading, and will act as a "second line of defence" for preventing the broach from extending through the third outermost sealing zone 25C. The sealing arrangement is created by using a heated die which is recessed along the dissipation zones or channels 25D and 25E, and which non-recessed portions serve to heat seal the zones 25A, 25B and 25C to one another. As the non-sealed zones 25D and 25E effectively reduce the overall area of the contact portion of the die, this results in an effective increase in downward pressure of the die as heat sealing takes place without having to increase the overall force applied to the die.