Material having a thermally expandable passage
AssigneeBritish Technology Group Limited
InventorsAnthony Arthur Leonard Challis, Michael John Bevis
Life of this patent
Estimating the term…
Abstract
A bilayer laminated material has a gas permeability increasing greatly with temperature, achieved by cutting a star-shaped hole in it when it is relaxed and flat. On warming, the leaves between the radial cuts curl and disproportionately increase the hole size. Such a material, if flat at 5.degree. C. and wide open at 20.degree. C., is useful for packaging vegetable produce.
Claims25
A wrappable packaging material sufficiently flexible for use as a wrapping and asymmetrically laminated from at least two plastic layers disposed adjacent to each other and having different coefficients of thermal expansion, the material having a non-straight slit, wherein the slit forms a passage through the plastic layers, which passage varies in size with temperature, at least over a certain temperature range, at a range greater than the thermal coefficient of expansion of the plastic layers.
A packaging material asymmetrically laminated from at least two plastic layers disposed adjacent to each other and having different coefficients of thermal expansion, the material having a non-straight slit, wherein thicknesses of the layers are in at least approximate proportion to an inverse cube root of their respective Young's moduli, and wherein the slit forms a passage through the plastic layers, which passage varies in size with temperature, at least over a certain temperature range, at a rate greater than the thermal coefficients of expansion of the plastic layers.
Dependencies are inferred from the claim text.