Blister assembly
A blister assembly comprises at least one collapsible blister adapted, as it is collapsed, to eject a liquid contained therein. The blister assembly comprises a first layer ( 130 ) having at least one blister chamber ( 150 ) and a second layer ( 131 ) sealed to the first layer at least around a periphery of the at least one blister chamber such that a liquid is contained between the first layer and the second layer. The seal between the first and second layers comprises a first planar portion having a first peel strength and a second planar portion having a second peel strength, wherein the first peel strength is greater than the second peel strength, such that when pressure is applied to the blister, the second portion of the seal breaks to release the liquid contained within the chamber into the liquid inlet. The blister assembly further comprises at least one discontinuity ( 142 ) formed in the first and second layers in the region of the first portion of the seal, such that a shear force is required to delaminate the first and second layers in that region.
1 . A method of manufacturing a blister assembly, the method comprising:
forming at least one collapsible blister between a first layer and a second layer, wherein the blister assembly comprises a first seal having a first peel strength between the first layer and the second layer over a first portion of the blister assembly and a second seal having a second peel strength between the first layer and the second layer over a second portion of the blister assembly, wherein the first peel strength is greater than the second peel strength, such that when pressure is applied to the blister, the second portion of the seal breaks to release contents from the blister;
deforming the first and second layers to form at least one discontinuity comprising a pimple formed in the first and second layers in a region of the second portion of the seal.
2 . The method of claim 1 , wherein the step of forming at least one collapsible blister comprises:
forming at least one blister chamber in the first layer;
applying the second layer over the first layer and applying the second seal between the first layer and the second layer over the second portion of the blister assembly such that the blister chamber is defined between the first layer and the second layer;
applying the first seal between the first layer and the second layer over the first portion of the blister assembly.
3 . The method of claim 1 , further comprising:
forming at least one fill tube in the first layer wherein the at least one fill tube is in fluid communication with the blister chamber;
introducing a liquid into the blister chamber through the fill tube;
applying a third seal between the first layer and the second layer across the fill tube, thereby sealing the liquid within the collapsible blister.
4 . The method of claim 1 , wherein the first portion and the second portion at least partially overlap.
5 . The method of claim 1 , wherein the first and second layers remain sealed to each other throughout the at least one discontinuity such that a shear force is required to delaminate the first and second layers in said region of the second portion of the seal, causing the second peel strength to be greater than the first peel strength.
6 . The method of claim 1 , wherein the at least one discontinuity is formed around the periphery of the collapsible blister.
7 . The method of claim 1 , wherein the at least one discontinuity protrudes from the blister assembly in the same direction as the collapsible blister.
8 . The method of claim 1 , wherein the at least one discontinuity is hot formed in the same step as the second seal.
9 . The method of claim 1 , wherein at least a portion of first and/or second side portions of the at least one discontinuity is aligned radially to the blister.
10 . The method of claim 1 , wherein profile of the at least one discontinuity is approximately hemispherical.
11 . The method of claim 1 , wherein the first layer and the second layer are heated to 150° C. to form the second seal.
12 . The method of claim 3 , wherein the at least one discontinuity is formed before filling the liquid in the blister by cold-forming.
13 . The method of claim 1 , wherein the first layer comprises a deformable polymeric layer, and a blister cavity may be cold formed in the deformable polymeric layer.
14 . The method of claim 1 , wherein the first layer is heat-sealed to the second layer at a temperature of about 100° C.