Patent Application
20090022430
The present invention relates to a bag having a carrying handle and extends to a method of manufacturing such a bag. The invention has particular application to plastic bags.
Plastic bags are a ubiquitous and highly practical mode of carrying things and there is a whole panoply of shapes and structures of such bags depending on the particular function of the bag. Many bags have handles of some kind or other. These may be merely formations in the material of the bag or may include additional elements which are attached to the main carcase of the bag and which provide added strength and convenience.
United States patent application 20060188178 describes a packaging container made of plastic film having a strap handle fixed into the container wall. The container wall has an inner side and the strap handle is arranged on the inner side. The container wall has an access opening through which the strap handle is accessible from the exterior of the container. A support patch made of plastic film is connected to the container wall and closes off the access opening relative to the interior of the container.
While this arrangement offers value, further improvements are possible to improve the performance and manufacturability of bags having associated handles. Limitations and disadvantages of conventional and traditional approaches to bag-with-handle designs and manufacture thereof will become apparent to one of ordinary skill in the art through comparison of such bag and handle arrangements with the present invention.
For simplicity and clarity of illustration, elements illustrated in the following figures are not drawn to common scale. For example, the dimensions of some of the elements are exaggerated relative to other elements for clarity. Advantages, features and characteristics of the present invention, as well as methods, operation and functions of related elements of structure, and the combinations of parts and economies of manufacture, will become apparent upon consideration of the following description and claims with reference to the accompanying drawings, all of which form a part of the specification, wherein like reference numerals designate corresponding parts in the various figures, and wherein:
Referring to
The side panel 20 has a handle 28 attached to it to allow the bag to be carried in one hand like a briefcase or suitcase. As shown in longitudinal section in
Referring to
Referring to
In each of the embodiments of the invention described, the bag, the handle strip and the reinforcing strip are formed from heat-sealable thermoplastics film materials and sealing is effected by heat sealing. Such materials include, by way of example and not limitation, polyolefins such as polyethylene and polypropylene, polyesters, vinyl polymers, and the like. The materials may be low-, medium- or high-density polymers and may be single or multi-layer composite material. Composite laminated materials may include adhesive layers. Suitable materials for adhesive or tie layers are adhesive resins such as Mitsui Petrochemical's ADMER®). Sealing resins such as ethylene vinyl acetate may be used to improve sealing of certain polymer layers and the use of such sealing resins may obviate the use of adhesive tie layers. The invention contemplates the use of thermoplastics films which are made of, or which include, a barrier sheet material such as, for example, EVOH which provides a barrier generally preventing the transmission of gases.
The thickness of the film material is selected mainly on the basis of the intended weight the bag must carry and generally ranges from about 2 to 20 mils.
While thermoplastics film is preferred as a construction material, the invention is also applicable to bags formed of other sheet materials such as stiff paper or card and to other sheet or foil materials. The type of thermoplastics or other sheet material used will depend on the purposes to which the bag is to be put, whether it is easy to handle in manufacturing, whether it can be readily printed upon, whether it is waterproof, whether it is strong enough to resist tearing or bulging, etc.
In one example, the film material of the handle strip and the reinforcing strip are formed from two layers of a composite sheet of coextruded, alternating layers of thermoplastics and adhesive in the following order: 1.75-1.9 mils polyethylene, 0.35-0.5 mils adhesive polymer, 0.5 mils nylon, 0.35-0.5 mils adhesive polymer, 1.75-1.9 mils polyethylene. This composite sheet can be bought from a number of extrusion companies, including the Pliant Corporation. The handle can be made by laminating together two layers of the composite sheet described above using an adhesive that may be solvent based or solvent-less (i.e. 100% solids). The strips can be formed from other film material depending on the particular properties required of the handle and the reinforcement from the viewpoint of the bag function and its manufacturability. An alternative composite structure thermoplastics has a multi-ply layered material with outer layers of polyethylene and a core layer of nylon. The particular selection of ply materials and the number of layers of each material is chosen for the particular properties desired in the bag. Thus, polyethylene has good heat sealing properties and relatively high strength. A copolymer polyethylene with high elastomeric content can be used where a soft handle is required. The material of both the handle strip and the reinforcing strip is selected to achieve required reinforcing action where the handle strip is anchored to a bag panel. For example, thermoplastic films can be used which have been oriented during manufacture to impart particular mechanical strength along the line of the handle or at other critical stress sites. Such oriented strength can be imparted, as is known, by for example stretching at ambient temperatures, melt orienting during extrusion, etc.
Heat sealing and bonding of layers of sheet material is effected by the application of temperature and pressure for a predetermined time at locations where the layers are to be heat sealed. The particular temperature, pressure and time are selected based on the particular nature of the sheet materials being bonded together. Bonding is typically effected at multiple bonding stations, with the bonded material subsequently being cooled. For materials such as stiff paper or card which cannot be heat sealed, an adhesive is used at the contact zones between the handle strip and the reinforcing strip, with adhesive being used also where the reinforcing strip and the handle strip, other than the handle part, contact the surfaces of the panel within which the handle is anchored.
It will be appreciated that many variations are possible in the design of a bag and handle arrangement using the principles of the invention. For example, a circular shape is used for the holes 34 because this shape acts to distributes forces around the edge of the holes when the bag is lifted by the handle and so reduces the chance of the bag or handle material tearing. However, other shapes can be utilized depending on the properties required at the joint between the handle strip 30 and the reinforcing strip and the relationship of that joint with the bag panel in which the joint is located. Thus, the holes can be of oval, slot, D or other suitable form.
In addition, although the preferred embodiments have two spaced holes, more that two holes can be used with the handle strip and the reinforcing strip sealed together at some or all of the holes. In a further alternative, a multiplicity of small perforations is made in the bag panel so that the handle strip and the reinforcing strip at each contact site are sealed together effectively through a grid or lattice portion of the bag panel.
A method of manufacturing a bag and handle arrangement according to one embodiment of the invention will now be described, the manufacturing method having particular application to the embodiment of bag illustrated in
The bag web 60 shown is suitable for forming a pouch bag of the form shown in
In the preparation of a bag with handle arrangement according to one embodiment of the invention, and as illustrated in
Referring to
The bag web 60 and the handle strip web 62 are then fed to a threading station where the webs are momentarily halted to allow a handle strip 30 to be separated from the handle strip web 62 and to be attached to a suspended part of the bag web 60. In one embodiment, a separated handle strip is delivered from the side as shown in
In a variation of the transfer head, instead of, or in addition to, the vacuum, retractable contact claws are used at the transfer head to temporarily clamp the handle strip against finger-shaped parts of the transfer head prior to the transfer head being brought close to the bag web to thread the handle strip end regions into the holes. The contact claws are released after the threading action is completed. In an alternative embodiment of the threading station, the handle strip web is end-delivered as shown in
The bag web with the handle strip in place is then fed to a first heat sealing station. At the first heat sealing station, the end regions 74 which project through and lie adjacent the lower surface of the bag web 60 are tack sealed to the bag web. The tack seal serves to fix the bag web and handle strip in a proper disposition for subsequent processing. It also initiates a folding action in each part of the handle strip projecting through the spaced holes 70 to form folded portions. These folded portions are shown in finished form as elements 36 and 44 in
In the heat sealing operation, the heat sealing zone is made to extend over the full area of the folded material so that no part of the folded material is free. Any free part of the handle strip or reinforcing strip material is undesirable because it can be a source of weakness and a source of air and contaminant entry. It can also contribute to an overly bulky material which is undesirable especially if, at a later stage of bag formation, the panel containing the handle is to be folded to form a gusset area.
It is important in all bonding operations, whether by heat sealing or adhesive, to avoid channel leaks since these can be a source of entry of insects, air and moisture which can later attack and adulterate the contents of the bag if the contents are edible materials such as pet food. One source of channel leaks is wrinkling of the materials being bonded. In the case of thermoplastics, wrinkling and channel leaks are minimized by ensuring that a thermoplastics material is used which has good heat flow properties. For example, high heat flow can be obtained by increasing the elastomeric polythethylene content of a polyethylene layer, the regular polyethylene and elastomeric polyethylene forming a tailored co-polymer. However, the elastomeric content is not made so high as to adversely affect the machinability of the finish material or to render it unpleasantly tacky. A suitable percentage of elastomeric polyethylene is 23%.
The bag and handle embodiments of
The embodiments of the invention illustrated and described all relate to a bag in which the panel to which the handle is attached also functions as a gusset. It will be understood that the handle can be attached to any panel of the bag. The handle can, for example, be located in either side panel, either end panel or in a bottom panel at end 12 of the exemplary bag shown in
There have been described herein various embodiments of a bag and handle arrangement and manufacturing processes therefor, such arrangements and processes having features that distinguish the present invention from the prior art. It will be apparent to those skilled in the art that the bag and manufacture of the disclosed invention may be modified in numerous ways and may assume many embodiments other than the preferred forms specifically set out and described above. Accordingly, it is intended by the appended claims to cover all modifications of the invention which fall within the true spirit and scope of the invention.
