Roll top bag constructions

Abstract

A gusseted bag of disposable packaging material has a roll-top closure comprising two releasably engageable fastener components. Each fastener component comprises a plastic base layer carrying either hook or loop elements. In some cases, one component is secured to one face of a rollable top of the bag, and the other component is carried on a flexible flap secured to a lower portion of an opposite face of the bag. In another embodiment, one fastener component extends in a strip from an upper edge of the bag down one face of the bag, and the other fastener component extends in a strip from an upper edge of the bag down an opposite face, such that when the top of the bag is folded downward, one fastener component will engage the other fastener component to hold the top closed.

What is claimed is:  
     
         1 . A gusseted bag of disposable packaging material having a roll-top closure comprising two releasably engageable fastener components, wherein 
 each fastener component comprises a plastic base layer carrying either hook or loop elements,    one fastener component being secured to one face of a rollable top of the bag, and the other fastener component being carried on a flexible flap secured to a lower portion of an opposite face of the bag.    
     
     
         2 . The bag of  claim 1  wherein the flexible flap is secured to the opposite face of the bag along an tipper edge of the flap, with its fastener component facing away from the opposite face of the bag and disposed below the upper edge of the flap, such that the fastener components are engageable by folding the top of the bag down toward the flap, and then folding the flap upward to engage the fastener components and secure the folded top between the opposite face of the bag and the flap.  
     
     
         3 . The bag of  claim 1  wherein the flexible flap is secured to the opposite face of the bag along an upper edge of the flap, with its fastener component facing away from the opposite face of the bag and disposed below an attachment of the flap to the opposite face of the bag, and wherein the top of the bag is folded down over the flap to engage the two fastener components.  
     
     
         4 . The bag of  claim 3  wherein the fastener components are constructed and arranged to redirect at least a significant portion of a peel load applied to the closure into a shear load as the folded top is released and tends to unfold, bending the flap upward to follow the unfolding top.  
     
     
         5 . The bag of  claim 1  wherein the packaging material from which the gusseted bag is formed has an outer layer of thermally weldable plastic in the form of a film or coating, and wherein the plastic base layers of the fastener components are of a compatible thermally weldable material.  
     
     
         6 . The bag of  claim 5  wherein the plastic of the outer layer of the packaging material and the base layers is of substantially the same molecular type.  
     
     
         7 . The bag of  claim 5  wherein the plastic of the outer layer of the packaging material and the base layers each comprise polyethylene.  
     
     
         8 . The bag of  claim 5  wherein the plastic of the outer layer of the packaging material and the base layers each comprise polypropylene.  
     
     
         9 . The bag of  claim 5  wherein the plastic of the outer layer of the packaging material and the base layers each comprise copolymers of EVA and polyethylene.  
     
     
         10 . The bag of  claim 5  wherein the plastic of the outer layer of the packaging material and the base layers each comprise polyester.  
     
     
         11 . The bag of  claim 1  wherein an outer surface of the gusseted bag is defined by paper, and wherein the fastener components carry upon them an adhesive layer securing the fastener components to the paper of the outer bag surface.  
     
     
         12 . The bag of  claim 11  wherein the adhesive layer comprises a pressure-sensitive adhesive.  
     
     
         13 . The bag of  claim 11  wherein the adhesive layer comprises a heat-activatable adhesive.  
     
     
         14 . The bag of  claim 1  wherein the adhesive layer comprises a moisture-sensitive adhesive.  
     
     
         15 . The bag of  claim 1  wherein the loop elements are of a non-woven loop material.  
     
     
         16 . The bag of  claim 1  wherein the hook elements are integrally molded with resin of the plastic base layer of one of the fastener components.  
     
     
         17 . The bag of  claim 1  comprising a closure strip that defines both of the fastener components and a dividing tear strip disposed between the fastener components and adapted to be removed to divide the closure strip into separate fastener components.  
     
     
         18 . The bag of  claim 1  wherein the flexible flap is secured to the opposite face of the bag along a lower edge of the flap, with its fastener component facing toward the opposite face of the bag, such that the fastener components are engageable by moving the flap away from the opposite face of the bag, folding the top of the bag down between the flap and the opposite face of the bag, and then moving the flap back toward the opposite face of the bag to engage the fastener components and secure the folded top between the opposite face of the bag and the flap.  
     
     
         19 . A bag of disposable packaging material having a closure comprising two releasably engageable fastener components, wherein 
 each fastener component comprises a plastic base layer carrying either hook or loop elements,    one fastener component extending in a strip from an upper edge of a foldable top of the bag down one face of the bag, and the other fastener component extending in a strip from the upper edge of the foldable top of the bag down an opposite face of the bag, such that when the top of the bag is folded downward, one fastener component will engage the other fastener component to hold the top closed.    
     
     
         20 . The bag of  claim 19  wherein at least one of the fastener components extends from the top of the bag to a gusseted bottom of the bag.  
     
     
         21 . The bag of  claim 19  wherein both of the fastener components extend from the top of the bag to a gusseted bottom of the bag.  
     
     
         22 . The bag of  claim 19  wherein one of the fastener components covers a fin seal of the bag.  
     
     
         23 . The bag of  claim 19  having gusseted sides formed between the faces along which the fastener components extend.  
     
     
         24 . A method of forming a bag of packaging material having a roll-top closure comprising two releasably engageable fastener components, each fastener component comprising a plastic base layer carrying either hook or loop elements, the method comprising 
 forming a roll-top bag of the packaging material, with the first fastener component disposed on one face of a foldable top of the bag, and a flap extending from a lower portion of an opposite face of the bag and carrying the second fastener component positioned to be engageable with the first component when the top of the bag is rolled downward.    
     
     
         25 . The method of  claim 24  comprising, before forming the roll-top bag, 
 pre-applying the first fastener component to the packaging material; and  
 securing the flap to the packaging material, the flap carrying the second fastener component.  
 
     
     
         26 . The method of  claim 24  comprising 
 introducing the two fastener components to a bag making process as parallel portions of a unitary closure strip;  
 splitting the closure strip into the two fastener components; and then  
 applying the fastener components to the packaging material.