Process and apparatus for vacuum packing
AssigneeJ. Sainsbury Limited
InventorTimothy T. Day
Life of this patent
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Abstract
The invention concerns the packaging of commodities into vacuum-sealed packs formed from sheet plastics packaging material. In accordance with this invention, the packaging material is formed from a two-layer laminate the inside layer of which has a much lower softening point than the outside layer. The commodity is sandwiched between two sheets of the packaging material and is passed to a vacuum chamber in which it is sealed between the two sheets under reduced pressure. Simultaneously the material is heated to a temperature at which the inner laminate softens, and when the chamber is aerated, the heated material collapses around the commodity and the inner layers fuse together around the margins to form a highly effective hermetic seal around the commodity.
Claims19
A process for successively packing commodities into vacuum-sealed packs formed from a pair of superposed flexible films each of which comprises a laminate of two flexible layers of plastics material one dominating layer of which has a softening temperature below that of the other layer, comprising thermoforming unstretched depending pockets successively in a lower continuous web of a first film by thermoplastic deformation of but without stressing said film which has the laminate with the lower softening point on its upper surface, said thermoplastic deformation to form pockets taking place above the softening point of said dominating layer, putting a commodity to be packed into each of said unstretched thermoformed pockets, laying an upper continuous web of a second film onto the upper surface of said lower web with lower softening point layer in contact with the upper surface of the lower web in overlying relation to the pockets containing the commodities, impulse sealing said films transversely of the web between the pockets, advancing the superposed webs to a vacuum sealing and continuously heated chamber, enclosing at least one of the pockets in said chamber, hermetically sealing said chamber, heat sealing said films together around the pocket periphery leaving an opening and evacuating the interior of the chamber and the interior of the pocket and simultaneously heating above the softening point of adjacent layers of said two films within the chamber, closing said opening and sealing said pocket under vacuum and aerating the interior of the chamber to cause the heat softened films to collapse without shrinking around the commodity in the pocket, the films in the chamber being heated to a temperature above the softening point of the low melting point layers so as to cause the portions of the inner layers of the films which are in contact with each other to soften sufficiently to fuse together around the commodity on aeration of the chamber.
Apparatus for continuously packing commodities into a succession of vacuum-sealed packs formed from a pair of superposed films each of which comprises a laminate of two layers of flexible plastics material one layer of which has a softening temperature below that of the other layer, comprising heated pocket forming means for successively heat forming in a first, lower continuous web of said film successive rows of pockets across the width of the web and adapted to receive the commodities, means for superposing a second, upper continuous web of said film onto the upper surface of the lower film to overly the pockets containing the commodities, slitting means for slitting the upper web longitudinally thereof along a line which extends intermediate adjacent pockets in the lower web, a vacuum sealing and continuously heatable chamber for receiving successive loaded pockets in the superposed upper and lower webs, heating means within the evacuation and heating chamber for heating at least the upper web therein, sealing means for sealing together the upper and lower webs in the heated chamber along part of the peripheries of the pockets, evacuation means for evacuating the interior of the vacuum chamber and the interior of the partly sealed pockets, and further sealing means for sealing together the upper and lower webs along the remainder of the peripheries of the evacuated pockets, said further sealing means being provided with a passage for communicating said evacuation means with the interior of said pockets in the location of the remainder of pocket peripheries, means being provided for advancing the superposed webs in a step-by-step manner successively through the apparatus.
Dependencies are inferred from the claim text.