Patent Application
20070248291
This invention relates generally to heavy duty plastic bags, and more specifically to a vented industrial shipping sack with an attached filter medium for capturing and retaining product, particularly during filling and venting. Vented bags are commonly used for packaging powdery products, such as powdered TiO2, ground gypsum, activated carbon, and the like. Such bags are typically fabricated from LD, HD, or LLD polyolefin sheet or tube stock, such as polyethylene or polypropylene having a thickness in the range of 3 to 12 mils. The sheet or tube stock may be coextruded or monoextruded, and may be a single ply or multi-ply material. The multi-ply material may be multiple thicknesses of the same sheet or tube stock, or different materials to provide particular characteristics, such as strength, flexibility, UV resistance, or color. The sheet stock may also be woven or non-woven synthetic or non-synthetic material. While the invention has particular application to vented bags with a capacity of from 20 to 100 pounds, the present concept can be applied to bags of any size and style.
There exists a present and long-felt need in the industry for a heavy duty industrial shipping sack for packaging powdery products. One primary advantage of traditional paper-like (or fibrous) shipping sacks is their inherent ability to filter product during the filling process. Drawbacks to such bags, however, are substantial. For example, many powdery products cannot tolerate fiber contamination common in a paper environment. Additionally, paper sacks are considerably weaker than plastic, and often cannot withstand the rigors of external, environmental conditions. While use of a plastic bag is generally preferable for increased strength and durability, common fill processes which force powdery product into the bag under pressure require effective ventilation and the ability to retain the product inside the bag during filling, venting, and shipping.
Prior art plastic shipping sacks with perforations have been used to package a variety of products, but have limited use for powdery products due to their inability to properly retain product during filling and ventilation. These bags typically have a rank-and-file arrangement of relatively large perforations. Plastic bags with much smaller perforations have had some success, but often either still allow small particles to exit the package, or worse, the small particles can plug the perforations and not allow the air to evacuate. Other prior art plastic bags comprise multiple layers with off-set perforations. While these type bags have had limited success, excessive powder is often either captured in-between the multiple layers or escapes from the bag altogether.
Outside of re-engineering the plastic bag, some in the industry have invested heavily in equipment designed to remove the air during packaging of powdery products. This equipment is expensive, and still often requires some sort of secondary ventilation.
Therefore, it is an object of the invention to provide a vented industrial shipping bag with an attached filter medium for capturing and retaining powdery product during filling and venting.
It is another object of the invention to provide a vented plastic shipping bag which is fabricated from plastic sheet or tube stock.
It is another object of the invention to provide a vented plastic bag which incorporates a fibrous, air-release filter medium.
It is another object of the invention to provide a vented plastic bag which incorporates a filter medium comprising a random arrangement of variable-size filter openings which resist clogging.
It is another object of the invention to provide a vented plastic bag which can withstand higher packaging temperatures (as compared to standard polyethylene shipping sacks).
It is another object of the invention to provide a vented plastic bag which incorporates a fibrous and absorbent filter medium that acts to draw and trap moisture away from the packaged product, while allowing air release.
It is another object of the invention to provide a vented plastic bag which is applicable for packaging powdery products that can be readily dissolved along with the bag without ever opening the package.
It is another object of the invention to provide a vented plastic bag which is available in a version such that end users could incorporate their own selected micron-rated filter-ply films to custom manufacture, fill and seal their own packaging.
It is another object of the invention to provide a multi-layer packaging composite which is applicable for use with automatic form/fill/seal machines.
It is another object of the invention to provide a method for filling a plastic bag with a powdery product.
These and other objects of the present invention are achieved in the preferred embodiments disclosed below by providing a vented plastic bag adapted for containing a powdery product. The term “powdery product” refers to any loose product composed of or similar to powder and which may contain fines or other small particulate matter. The plastic bag includes a plurality of walls joined together and formed of a flexible plastic material. The term “joined” means either two formerly separate sheets connected together, or integrally formed by, for example, folding over a sheet to form an edge. The walls define a fill opening for receiving the powdery product into the plastic bag. At least one of the plastic bag walls defines a ventilation zone comprising a plurality of spaced-apart perforations. A fibrous filter medium overlies the ventilation zone and covers the plurality of perforations to substantially capture and retain the powdery product within the plastic bag during fill and ventilation. The term “fibrous” is defined broadly herein to mean any material containing, consisting of, or resembling fibers. Alternatively, the filter medium may comprise any non-fibrous material which defines a similar random arrangement of variable-size filtration openings.
Preferably, the filter medium comprises a single-ply filter panel.
According to one preferred embodiment of the invention, the filter panel is affixed to the plastic bag along welded seams (and without needle openings).
Preferably, the filter medium comprises a non-woven material.
According to one preferred embodiment of the invention, the filter medium comprises a fibrous material selected from a group consisting of polyester felt, polypropylene microfiber, nylon monofilament, polyethylene, and PTFE.
Preferably, the micron rating of the filter medium is less than the micron rating of the perforations of the ventilation zone.
According to one preferred embodiment of the invention, the filter medium has a nominal micron rating of less than 100.
According to another preferred embodiment of the invention, the perforations of the ventilation zone have a nominal micron rating greater than 500.
Preferably, the filter medium is positioned to reside between the powdery product and ventilation zone. Alternatively, the filter medium may reside adjacent the ventilation zone on an outside surface of the bag wall.
According to one preferred embodiment of the invention, a product-side surface of said filter medium is glazed to reduce fiber contamination of the powdery product.
In another embodiment, the invention is a method for filling a plastic bag with a powdery product. The method includes the steps of inserting the powdery product into the plastic bag, and venting the plastic bag. During ventilation, air exiting the plastic bag is filtered using a fibrous filter medium to substantially capture and retain the powdery product within the plastic bag.
Some of the objects of the invention have been set forth above. Other objects and advantages of the invention will appear as the description proceeds when taken in conjunction with the following drawings, in which:
The present invention is described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be operative and enabling. Like numbers refer to like elements throughout. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation. Unless otherwise expressly defined herein, such terms are intended to be given their broad ordinary and customary meaning not inconsistent with that applicable in the relevant industry and without restriction to any specific embodiment hereinafter described.
Referring now specifically to the drawings, a plastic vented bag according to a preferred embodiment of the present invention is illustrated in
In the embodiment shown, the vented bag 10 comprises a valve bag which is satchel-style pasted at both ends during its manufacture. The bag 10 is preferably machine-fabricated from heavy duty polyolefin tube stock, and comprises opposing integrally-formed walls 11 and 12 defining a top 14, bottom 15 and sides 16 and 17. When the bag walls 11, 12 are sealed to form the closed ends 14, 15, a tape of plastic is added to create the filling valve (not shown) in one of the corners of the bag 10. A flexible plastic sleeve 18 extends out of the valve and cooperates with a valve packer (e.g., air, auger, impeller, belt) to load product into the bag 10. After filling, the sleeve 18 is typically folded and tucked into the valve. The valve bag 10 may be closed using a self-closing internal valve, ultrasonic sealing, or other suitable means.
As best shown in
Referring to
According to one preferred embodiment, the filter ply 25 comprises a spunbonded, non-woven polypropylene microfiber. Alternatively, the filter ply 25 may comprise other fibrous or fiber-like materials including paper, melt-blown polyethylene, nylon monofilament, polyester felt, or PTFE. The filter ply 25 may also comprise a non-fibrous, mechanically perforated, 2- or 3-dimensional substrate which defines a similar random arrangement of clog-resistant, variable-size openings. Preferably, the filter ply 25 is a self-supported or scrim-supported material. To avoid fiber contamination, the product-side surface 25A of the filter ply 25 may be singed or glazed.
While the micron rating of the filter ply 25 will vary depending on user requirements, the size of the filter openings in all cases will likely be smaller than the wall perforations 21. For most powders, the nominal micron rating will be less than 100. As indicated above, the micron rating selected determines the size of the particles captured as the product is filtered.
A plastic vented bag is described above. Various details of the invention may be changed without departing from its scope. Furthermore, the foregoing description of the preferred embodiment of the invention and the best mode of practicing the invention are provided for the purpose of illustration only and not for the purpose of limitation-the invention being defined by the claims.
