| Method of opening for bags of supple polymeric material subject to interlayer cling -> Monitor Keywords |
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  Method of opening for bags of supple polymeric material subject to interlayer clingRelated Patent Categories: Flexible Bags, With Means To Maintain The Bag Mouth In An Open ConfigurationThe Patent Description & Claims data below is from USPTO Patent Application 20070258664. Brief Patent Description - Full Patent Description - Patent Application Claims
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 opening of bags from the collapsed state. [0004] Bags are considered `difficult` if they are difficult to open from the collapsed state. The contributors to interlayer cling are many, and range from materials composition, to processing speed, to storage conditions, to time in storage, and even to the inter-individual variation in the stickiness of fingers and also variations in the weather either during manufacture or use. Typical polymeric materials as used to make bags are economical to form into products, because they are thermoplastics of which the softening/melting point, or temperature where properties change markedly, is much closer to the ambient temperature in the factory environments than is the case for, say, metals, glass, paper, cotton, etc. The opposite side of the same coin is that their critical temperatures are equally close to the temperatures of the places where the products will be used; the consequence of that is that nearly anything that can happen in seconds during manufacture can also happen at the ambient temperature; it merely happens more slowly. 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. [0005] Many common diseases are transmitted by touching objects and contaminating them, or touching contaminated objects. 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. Clearly there is a ready need awaiting a solution to the problem of bags that are difficult to open, and many patents filed by the industry (e.g. CA 916383 to Walsh and Krein, U.S. Pat. No. 4,911,560 to Hoover et al, U.S. Pat. No. 5,611,627 to Belias et al.) have had the objective of rendering bags more easy to open. [0006] Several approaches have been made for paper packets, which are a different Art. Robert Jack, of Rutherglen, Victoria, Australia, filed patent (Nr. 94831, Klasse 54: Papierzeugnisse, 3 Jan. 1897) in Germany for a paper packet (having reveals or tabs to enable a pushing or pulling, perpendicular to the packet plane, of one stiff semi-rigid sidewall (paper is by nature stiff, until it has been creased, which is a starting point toward disintegration as creasing is exercised) relative to the other. [0007] Shakirov (SU001822842A1) repeated some of Jack's teaching, also for paper packets (references to `packet`, a word clearly restricted to paper in this context, `cemented` etc. in the Derwent translation clearly place the invention in the Art of paper packets and not the Art of polymeric bags). Again the reveals and tabs enable a pushing or pulling, perpendicular to the packet plane, of one stiff semi-rigid sidewall (again employing the natural stiffness of paper) relative to the other. Further confirming the pushing/pulling nature of the operation in Shakirov is his FIG. 1 showing a packet with noncoincident holes which admit of an action pushing the opposing sidewalls, but do not admit of a lateral pulling in the plane of the packet. There is no evidence to suggest that Shakirov was considering anything but paper packets. Both Jack and Shakirov consist of teachings in a different Art. [0008] The approaches of Jack and Shakirov are suited to a non-supple material, and are both in the Art of paper packets composed of elements that are made of pieces separately cut, reoriented, and `cemented` together, as opposed to plastic bags that are formed as a tube of thermoplastic that is then welded and cut without reorientation. I.e. in the blown-film method by which virtually all such bags are currently made, there is no `piecing` together; only a series of layers formed from a flattened and sometimes folded tube in which all layers are cut or welded as needed, without any reorientation, and generally with cut or weld extending through the entire thickness of the multilayer structure. The skills applicable in the Art of paper packets (where skill components include handling of thermally stable materials, cutting them, orienting parts, cementing or gluing, where glues are applied to the material and set by evaporation more than cooling) is not readily transferable to the Art of polymeric bags (where skill components include transformation of cold solid pellets to a hot fluid to a cooled membrane, where bag panels are welded by heat without the need for glue as such, and where bonds and indeed the material itself become solid only through cooling and can become fluid again by heating as in welding, where cutting operations require care to prevent `cold-welding`, etc). In short, paper and thermoplastics are radically different materials and the Arts suitable to one are not readily transferable to the other. [0009] Furthermore, both Jack and Shakirov place their reveals near the centers of their packets' mouths. The amount of movement required to render a flat supple bag open by `peeling` layers apart from a pair of graspable points somewhere along the width of the bag mouth can be algebraically represented. For simplicity, assuming symmetry (lack of which will simply limit the extent of opening possible), consider a flat supple bag having graspable points spaced x units apart and positioned y units from the edge: on tension, the region x will be sheared and then with continued pulling the regions y will be peeled. The total motion required to fully open the bag, i.e. fully disengage the front and rear sidewalls from each other, will be y. Clearly, the highest efficiency for reaching this goal is by minimising y, which Bell does, whereas in contrast neither Jack or Shakirov do that, in fact they seem to maximise y rather than minimise it, which in fact makes sense in a paper packet because the rigidity of the sidewalls enables a separation to propagate rapidly, according to the paper stiffness, so that Jack's and Shakirov's prying action becomes efficient for a paper packet, even though it would not be efficient for a supple polymeric bag. [0010] Those observations at once add confirmation to the difference in the Art addressed by Jack and Shakirov from the Art addressed by Bell, and also show that, even if applied to the latter Art, Jack and Shakirov would be different from Bell (and non-ideal solutions). 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. Confirming the difference between the paper and plastics arts, or the lack of direct transferability of the teachings of Jack and Shakirov to plastics, we do not see the Art of Jack or Shakirov applied to plastic bags, despite that Jack dates from more than a century ago, and Shakirov well over a decade. That is traceable to either the information does not travel between the arts, or Jack and Shakirov are not directly applicable. [0011] Better methods of opening bags would clearly improve hygiene, health, workflow, and economy, and therefore they would clearly be useful. [0012] 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. Like any large handle adapted for the human hand in order to enable a fine tool to address a very small object, the limitations of the human hand in grasping something as thin as a single layer or sidewall of a bag can be overcome if a suitable `handle` is provided. Such `handles` are provided by creating a bag architecture that left regions at or near the bag mouth where only a single sidewall was present or where it was possible to address one sidewall separately from the other by grasping at one such point. A plurality of such points appropriately situated could then allow the first and second sidewalls to be independently grasped or addressed and tensioned in opposing directions to shear them apart while in tension. This method is efficient because it does not increase the normal forces that amplify the sticking forces collectively known as interlayer cling. A presence of three or more such points can further allow for the bag to be both opened and then for the mouth to held in an open polygonal configuration defined by the positions of the devices which grasp such points. [0013] This approach has been applied to side-gusseted bags. [0014] 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. In currently known mechanical bagging systems for bags of supple polymeric materials, applications do not include any means by which a machine can detect that the redundant operation has succeeded so that the machine can stop that step and continue with the next step in opening. [0015] Avoiding the difficulty of opening altogether, one kind of automated bagging employs the form-fill-seal approach whereby a bag is formed in place from a sheet (by definition the bag is already open) and then welded closed around the contents. 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. [0016] 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. Mechanical opening involves either [a] a requirement that either an action must be certain and reliable the first time, and conducted once, or [b] if not reliable the first time the action must be redundantly conducted, i.e. conducted some number of times necessary to result in a near-certainty of effect. Currently, all applications fall into the second group, i.e. the first group has until now no representatives except where humans are involved in a semi-automated system (and even then it could be argued that a redundant-action approach is combined with human sensory capabilities). In a common redundant-operation approach for full automation, bags used are specially made with a front shorter than the back, or the front must be slit open or pre-opened while the back is left intact; then, by holding the bag by the back and blowing compressed air at the top of the front, the front eventually disengages to open the bag. One disadvantage is the constrained architecture of that type of bag. SUMMARY OF THE INVENTION [0017] The present invention is concerned with making plastic bags that can be easily and reliably opened with a predetermined set of motions. A plastic bag as referred to is generally a collapsed bag of unitary construction, made of supple polymeric material such as is commonly and to some extent unpredictably subject to interlayer cling, comprising first and second opposed contiguous flat sidewalls with joined lateral edges defining left and right sides of the bag; a bag mouth defined by upper edges of said sidewalls. The upper edges of the sidewalls may be straight or otherwise. The sidewalls may have apertures cut through them near the top of the bag to create handles. [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. Continue reading... Full patent description for Method of opening for bags of supple polymeric material subject to interlayer cling Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Method of opening for bags of supple polymeric material subject to interlayer cling patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. 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