Not applicable.
The present invention relates to an improved bag constructed from polymeric film. Particularly, the present invention relates to side gusseted bags commonly referred to as T-shirt bags.
Thermoplastic films are used in a variety of applications. For example, thermoplastic films are used in sheet form for applications such as drop cloths, vapor barriers, and protective covers. Thermoplastic films can also be converted into plastic bags, which may be used in a myriad of applications. The present invention is particularly useful for bags constructed from thermoplastic film.
Polymeric bags are ubiquitous in modern society and are available in countless combinations of varying capacities, thicknesses, dimensions, and colors. The bags are available for numerous applications including typical consumer applications such as long-term storage, food storage, shopping, and trash collection. Like many other consumer products, increased demand and new technology have driven innovations in polymeric bags improving the utility and performance of such bags. The present invention is an innovation of particular relevance to side gusseted bags commonly referred to as T-shirt bags.
Polymeric bags are manufactured from polymeric film produced using one of several manufacturing techniques well-known in the art. The two most common methods for manufacture of polymeric films are blown-film extrusion and cast-film extrusion. In blown-film extrusion, the resulting film is tubular while cast-film extrusion produces a generally planar film. The present invention is generally applicable to bags manufactured from a blown-film extrusion process resulting in tubular film stock.
In blown film extrusion, polymeric resin is fed into an extruder where an extrusion screw pushes the resin through the extruder. The extrusion screw compresses the resin, heating the resin into a molten state under high pressure. The molten, pressurized resin is fed through a blown film extrusion die having an annular opening. As the molten material is pushed into and through the extrusion die, a polymeric film tube emerges from the outlet of the extrusion die.
The polymeric film tube is blown or expanded to a larger diameter by providing a volume of air within the interior of the polymeric film tube. The combination of the volume of air and the polymeric film tube is commonly referred to as a bubble between the extrusion die and a set of nip rollers. As the polymeric film tube cools travelling upward toward the nip rollers, the polymeric film tube solidifies from a molten state to a solid state after it expands to its final diameter and thickness. Once the polymeric film tube is completely solidified, it passes through the set of nip rollers and is collapsed into a collapsed polymeric tube, also referred to as a collapsed bubble.
T-shirt bags are commonly formed by placing partial opposing side gussets in a tubular length of polymeric film. Once the gussets are created, pairs of closely spaced transverse seals are placed on the gusseted tube at predetermined lengths to define bottom seals and top handle seals for each bag. Once the seals are placed on the tube, the tube can be cut between the closely spaced pairs of seals to form a plurality of bag sections. The bag sections can then be stacked. The stacked bag sections then commonly have an opening and opposing side handles die cut out of one side of the stack of bags between the two opposing partial side gussets.
U.S. Pat. No. 6,461,041 (the '041 patent), filed Nov. 7, 2000 and hereby incorporated by reference, is directed to a means of reinforcing the bottom seal of a T-shirt bag. The '041 patent discloses that the weakest area of a common T-shirt bag are the junctions of the bottom seal. Therefore, the '041 patent teaches use of an additional strip of film to reinforce this area of the bag.
It is further known in the art to use a thin strip of material to reinforce the top seals of the bag which define the two opposing side handles. However, use of this strip of film leads to a considerable inefficient use of material because much of the material is cut away from the bag as scrap when the top opening and handles are die cut into the bag. Furthermore, use of the reinforcement strip for the T-shirt bag's handles typically fails to provide any reinforcement to the outer edges of the handle seals, due to the desire to limit material usage.
In consideration of the shortcomings of the above discussed prior art, it would be desirable to provide a T-shirt bag with improved handle strength that more efficiently utilizes material. The present invention represents a novel solution to address this need.
According to one embodiment of the present invention, a bag is formed from a gusseted tube of polymeric film. The bag can comprise a front panel and a rear panel and each panel can have an upper edge and a bottom edge. The front and rear panel can be joined by a bottom seal adjacent to the bottom edge. The bag can further comprise a first side gusset and an opposing second side gusset and each side gusset can be between and on opposing sides of the front and rear panels. Each side gusset can have an inner fold and two outer folds and each side gusset can further comprise two layers between the two outer folds, the two layers defined by the inner fold. The bag can further comprise opposing first and second handles adjacent to the upper edges of the front and rear panels. The first and second handles can be separated from each other by a bag cutout. The first handle can comprise the front panel, the rear panel, the first side gusset, an upper handle seal and a lower handle seal. The upper and lower handle seals can seal together the front panel, the rear panel, and the first side gusset. The upper and lower handle seals can extend from a first side to a second side of the first handle. Additionally, the upper and lower handle seals can be separated by a width of unsealed film.
In certain embodiments of the present invention, the upper and lower handle seals can be generally straight. Additionally, the upper and lower handle seals can be parallel with each other. The upper and lower handle seals can be separated from each other by at least ⅛ of an inch and by no more than one inch. The lower handle seal can be arcuate and have a radius of curvature centered above the upper handle seal. Also, the lower and upper handle seals can comprise heat seals and the lower handle seal can be formed at a lower temperature or at a shorter dwell time than the upper handle seal.
In a further embodiment of the present invention, a bag is formed from a gusseted tube of polymeric film. The bag can comprise a front panel and a rear panel and each panel can have an upper edge and a bottom edge. The front and rear panel can be joined by a bottom seal adjacent to the bottom edge, a first side gusset and a second side gusset. Each side gusset can be between and on opposing sides of the front and rear panels and each side gusset can comprise an inner fold and two outer folds. Each side gusset can further comprise two layers between the two outer folds. The bag can also comprise opposing first and second handles along the upper edge and the first and second handles can be separated from each other by a bag cutout. The first handle can comprise the front panel, the rear panel, and the first side gusset. A first handle seal can seal together the front panel, the rear panel, and the first side gusset. The first handle seal can comprise upper and lower opposing seal edges and the upper seal edge can be generally parallel and proximate to the upper edge. The lower seal edge can have at least one arcuate surface and the first handle seal can extend continuously from the upper seal edge to the lower seal edge.
In at least certain embodiments of the invention, the lower seal edge can curve outward from the upper seal edge such that the lower seal edge is convex. The lower seal edge can also have a single constant radius extending from a first side to an opposing second side of the first handle and the single constant radius can have a length of at least one-half a width of the first handle. Additionally, a seal void can be defined within the first handle seal. The seal void can comprise an area where the front panel, the rear panel, and the first side gusset are not sealed to each other. An upper edge of the seal void can be parallel to the upper seal edge and a lower edge of the seal void can be parallel to the upper seal edge. Furthermore, the first handle seal can comprise a heat seal and the heat seal can be formed at a lower temperature at a location proximate to the lower edge than at a location proximate to the upper edge. Additionally, the entire area defined between the upper and lower seal edges can be a single continuous seal.
It is contemplated that the present invention may be utilized in ways that are not fully described or set forth herein. The present invention is intended to encompass these additional uses to the extent such uses are not contradicted by the appended claims. Therefore, the present invention should be given the broadest reasonable interpretation in view of the present disclosure, the accompanying figures, and the appended claims.
A full and complete understanding of the present invention may be obtained by reference to the detailed description of the present invention and the preferred embodiments when viewed with reference to the accompanying drawings. The drawings can be briefly described as follows.
The present disclosure illustrates one or more preferred embodiments of the present invention. It is not intended to provide an illustration or encompass all embodiments contemplated by the present invention. In view of the disclosure of the present invention contained herein, a person having ordinary skill in the art will recognize that innumerable modifications and insubstantial changes may be incorporated or otherwise included within the present invention without diverging from the spirit of the invention. Therefore, it is understood that the present invention is not limited to those embodiments disclosed herein. The appended claims are intended to more fully and accurately encompass the invention to the fullest extent possible, but it is fully appreciated that certain limitations on the use of particular terms is not intended to conclusively limit the scope of protection.
Prior art T-shirt bag 100 is shown by
Bottom seal reinforcement 602 provides the necessary strength to bottom seal 118 to significantly reduce or eliminate failures at junction points 154 and 156 (as shown in
As shown by
Such an arrangement of dual handle seals provides for redundancy such that if lower handles seals 728b and 730b fail, upper handle seals 728a and 730a can still maintain the integrity of handles 162 and 164. Additionally, having dual seals for each handle seal 728 and 730 allows the two seals at each handle 162 and 164 to share the load so that less stress is imparted to each handle seal and thus the risk of any one of the seals 728a, 728b, 730a and 730b from failing is reduced.
In certain embodiments, seals 728a, 728b, 730a and 730b can be made via heat seals to weld the layers of film together. In further embodiments, upper handle seals 728a and 730a can be formed at a different temperature and/or at a different dwell time than lower handle seals 730a and 730b. For instance, lower seals 730a and 730b can be made at a lower temperature and/or at shorter dwell time.
Such conditions as described above can result in upper handle seals 728a and 730a having a greater seal strength than lower handle seals 728b and 730b. Nonetheless, in certain circumstances, lower seals 728b and 730b being made weaker than the upper seals may be advantageous. For instance, if variations in manufacturing conditions allow for over-sealing on upper seals 728a and 730a, such that the upper seal burns through due to excess sealing temperatures or dwell times, lower seals 728b and 730b can still be in the appropriate temperature range for proper sealing because lower seals 728b and 730b are made at a lower temperature and/or shorter dwell time than upper seals 728a and 730a. Thus, such an arrangement can result in each handles 162 and 164 having at least one proper seal.
In at least certain embodiments, each seal line of each of the handle seals 728a, 728b, 730a, and 730b can have a thickness from about 1/16 to about ⅛ of an inch. Therefore, to ensure that there is separation between each upper and lower seal, upper and lower seals for each handle 162 and 164 can be separated from each other by at least ⅛ of an inch. Furthermore, for at least certain embodiments, the maximum separation between upper and lower seals can be no more than an inch so that user access to bag 700 is not unnecessarily impeded while avoiding excessive usage of material in the construction of bag 700.
Shown in
In at least certain embodiments, the minimum distance between upper and lower handles seals of handle 162 or 164 can be at least 1/16 of the width of the handle. In the same embodiment, the distance between the center of one of the handle's lower seals and the center of one of the handle's upper seals can be about ⅛ of the width of one of the handles 162 or 164 of bag 800. At least for certain sizes of T-shirt bags and as a non-limiting example, the shortest distance between upper and lower handle seals of a handle of bag 800 can be about ⅛ of an inch and the height between the center of the upper and lower handle seals can be at least ¼ of an inch. These distances, however, can vary considerably depending upon the overall size of T-shirt bag 800.
Bag 800 having lower handle seals 828b and 830b as shown is advantageous by relocating the stress concentrations from the inside and/or outside edges of handles 162 and 164 to the center of handles 162 and 164. With such a curvature, a user's hands are likely to make greater contact with the center of seals 828b and 830b; thus the center of each handle 162 and 164 will carry a greater amount of the load of bag 800 than would otherwise. Hence, a tear is less likely to begin at either side of either of the bag handles 162 and 164 with the center of handles 162 and 164 inherently able to carry a greater load without failing. In regards to lower handles seals 828b and 830b having a relatively long radius of curvature, such as shown in
As discussed in regards to bag 700, in certain embodiments, upper handle seals 828a and 830a can be formed at a different temperature and/or at a different dwell time than lower handle seals 830a and 830b. For instance, lower seals 830a and 830b can be made at a lower temperature and/or at shorter dwell time. Such conditions can result in upper handle seals 828a and 830a having a greater seal strength than lower handle seals 828b and 830b. The advantages for such a configuration as discussed above in regards to bag 700 can also be applicable to bag 800.
Now shown in
As shown in
In at least certain embodiments, the minimum distance between upper and lower handles seals of handle 162 or 164 can be at least 1/16 of the width of the handle. In the same embodiment, the distance between the center of one of the handle's lower seals and the center of one of the handle's upper seals can be about ⅛ of the width of one of the handles 162 or 164 of bag 900. At least for certain sizes of T-shirt bags and as a non-limiting example, the shortest distance between upper and lower handle seals of a handle of bag 900 can be about ⅛ of an inch and the height between center of the upper and lower handle seals can be at least ¼ of an inch. These distances, however, can vary considerably depending upon the overall size of T-shirt bag 900.
As discussed above in regards to bag 800, bag 900 with lower handle seals 928b and 930b having a curvature as shown and described is advantageous by relocating the stress concentrations from the inside and outside edges of handles 162 and 164 to the center of handles 162 and 164. Handle seals 928 and 930 having a wide continuous sealed area of bag 900 can be advantageous over the dual seal arrangement of bag 800 by providing a greater seal area to spread the load stress and therefore reduce any stress concentrations.
In a typical manufacturing process, each solid handle seal 928 and 930 will be made by one continuous sealing surface. In certain embodiments, each sealing surface may have a temperature gradient extending on its surface between its upper and lower edges. For instance, a lower side of the sealing surface that defines lower seal edge 928b or 930b can have a lower temperature than an upper side of the sealing surface that defines upper seal edge 928a or 930a. Such a temperature gradient can be advantageous for certain manufacturing conditions where the sealing temperature has a tendency to be inconsistent. Such a temperature gradient provides for a greater likelihood that a proper seal will be made at least at a certain height between the upper and lower sealing edges of handle seals 928 and 930. For at least certain embodiments, this temperature gradient may be between ten and thirty degrees Fahrenheit.
Bag 1000, shown in
Seal pockets 1040 and 1050 in bag 1000 can be advantageous to limit the amount of heat required to form handle seals 1028 and 1030 and to better regulate the temperatures of the seal blocks/sealing surfaces used in a manufacturing process to form handle seals 1028 and 1030. Use of pockets 1040 and 1050 can also assist in eliminating or limiting the formation of bubbles in handle seals 1028 and 1030 by limiting the area of the two seals and providing an additional area for air to evacuate from the various layers of film sealed together by handle seals 1028 and 1030.
As previously noted, the specific embodiments depicted herein are not intended to limit the scope of the present invention. Indeed, it is contemplated that any number of different embodiments may be utilized without diverging from the spirit of the invention. Therefore, the appended claims are intended to more fully encompass the full scope of the present invention.