Method of opening for bags of supple polymeric material subject to interlayer cling

Abstract

Disclosed is a plastic bags that can be easily and reliably opened with a predetermined set of motions. The bags are configured to provide a number of exposed graspable sidewall portions on or near the rim of the bag that can are precisely located so that they can be reliably grasped, manually or by mechanical graspers. These exposed graspable sidewall portions can then be moved in a way that firstly disrupts the interlayer cling, and then secondly holds the bag open for filling. Further steps of automation are possible to seal and remove the bag, and advance the bag.

Description

CROSS-REFERENCE TO RELATED APPLICATION [0001] This application is a continuation in part of U.S. patent application Ser. No. 10 / 450,790 filed Dec. 17, 2001, incorporated by reference herein.FIELD OF THE INVENTION [0002] This invention relates to the art of plastic bags, and in particular to a method of opening bags of supple polymeric material such as is often subject to interlayer cling. The invention also relates to collapsed bags made of supple materials, such as thermoplastic films, which have, integral to their design, features which render them easy to open from the collapsed state so they can be filled with materials. The invention applies to bags of plain (flat) or side-gusseted configurations. BACKGROUND OF THE INVENTION [0003] Bags made of supple polymeric materials are often difficult to open. It has often been observed that cold welding, static, and various forces and frictions which can collectively be called interlayer cling is a major factor in preventing ready openin...

AI Technical Summary

Benefits of technology

[0018] The bags are generally rendered easy to open by providing a reliable and definite means of addressing the panels separately from positions where tension when applied can propagate across the bag mouth causing a shearing of the panels against each other as they move, however slightly, in opposite directions and thus releasing the interlayer cling that otherwise impedes opening.

[0019] The principle of shearing opposing bag panels against each other, as taught here, can be applied to opening of bags either manually, where the bag is opened and then easily handled by any points around its rim by grasping of course only one sidewall at a time (as to grasp both at once would be counterproductive); or mechanically, where handling requires a mechanism to have already gripped and held key points around the rim so that when the interlayer cling is disrupted these same key points can be reoriented by moving the mechanical devices that have gripped them, resulting in the possibility of a machine holding a bag in virtually any degree of openness.

[0020] Key in the manual operation of any bag is eye-hand coordination, and image processing that allows the parts of the bag and the state of openness or closedness at many points around its rim to be instantly evaluated and the hand instructed to exploit the parts that are sufficiently open that a single sidewall can be gripped; this level of intelligence in operation can easily cope with a bag having only one pair of laterally opposed exposed graspable sidewall portions.

[0023] The approach followed here allows bags to be made which can be opened by a precisely arranged set of motions (which may vary according to the embodiment). The bags enable this by providing a number of exposed graspable sidewall portions on or near the rim of the bag that can are precisely located so that they can be reliably grasped, manually or by mechanical graspers. These exposed graspable sidewall portions can then be moved in a way that firstly disrupts the interlayer cling, and then secondly holds the bag open for filling. Given this disclosure, further steps of automation are possible to seal and remove the bag, and advance the bag.

Problems solved by technology

Bags made of supple polymeric materials are often difficult to open.

Bags are considered ‘difficult’ if they are difficult to open from the collapsed state.

Many behaviours are thus possible from articles made of such materials, and there is little that can be done to formulations to alter the fact that, whether occasionally or frequently or typically, problems will occur.

In other words, no matter how careful a manufacturer is, the problem of ‘difficult’ bags is bound to arise.

While a few people know that tricks like rubbing a ‘difficult’ bag between two ripe tomatoes will often cause it to open, and other individuals resort to licking fingers to increase the finger-sidewall coefficient of friction, these approaches are hard on the stock of tomatoes, and also unhygienic.

Any habit involving saliva, such as the finger-licking to which people are driven by ‘difficult’ bags, has a measurable cost in terms of direct expenses in management of patients, indirect costs in terms of lost productivity, and indirect costs in terms of liability when better methods are available.

In short, paper and thermoplastics are radically different materials and the Arts suitable to one are not readily transferable to the other.

Paper bags have long had single reveals to facilitate opening by flexing at those reveals and causing one semi-rigid sidewalls to spring away from the other, but that has never been applied to plastic bags, and indeed it would not work, because plastic film is too supple for one layer to spontaneously and reliably spring away from the other in response to such mild flexing.

While rubbing requires pressure that often increase interlayer cling in proportion to the force applied and often is a relatively fruitless and frustrating exercise, and taught that in principle if the first and second sidewalls were able to be sheared in opposite directions, doing so would disrupt static cling efficiently, i.e. with very little force required, because the method allows the application of lateral tension without increasing the normal force tending to hold the sidewalls together.

Whereas human operators rub and rumple bags, and repeat this redundantly until they detect that an opening has occurred, and then change actions to exploit that opening, the detection part of that has been beyond the state of the art for mechanical devices to open bags.

That approach has several disadvantages, particularly that the cycle of filling and forming needs not only to be synchronised, but also to be performed at a steady pace without interruption.

Thus, when considering mechanical opening of bags from a closed or collapsed state, applications are either human-assisted, or fully automatic; in principle limited to systems which fall into either of two groups, the certain-action group and the redundant-action group.

One disadvantage is the constrained architecture of that type of bag.

Images