Plastic film hinging and pre-creasing process

Details Plastic film hinging and pre-creasing process Plastic film hinging and pre-creasing process

2001-09-27

2003-12-30

Kim, Eugene (Department: 3721)

Manufacturing container or tube from paper; or other manufacturi

Container making

Pliable container

C493S142000, C493S197000, C493S215000

Reexamination Certificate

active

06669615

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to plastic bag and film bag products that may be used for a multitude of purposes such as, but not limited to, fast foods, supermarkets, retail merchandise and point-of-purchase bags.
Common plastic bag styles used by retailers in fast food chains, supermarkets, and general merchandise, as well as in point-of-purchase applications, are typically of the bottom seal or sideweld variety. These bags are usually gusseted along their sides or along the bottom with the open bag mouth at the top. Many of these common bags have carrying handles, usually of the strap variety or die-cut holes. Typical plastic bags used in supermarket applications are about 0.0005 to 0.00065 in gauge; those used in retail merchandise bags are from 0.0005 to 0.0001; fast food bags are usually from 0.0007 to 0.00125, and; those used in point of purchase applications are typically from 0.001 to 0.004 mil thick. Retailers that desire to have a bag stand up on its own usually use square bottom paper bags instead of plastic bags due to their ability to stand up.
Common plastic bags when manually put into use usually follow a certain sequence. First, the user's fingers open the bag mouth. Second, the user at one hand grasps one side of the open mouth at the top. Third, the other hand grasps the opposing side of the bag mouth at the top. Fourth, the bag is pulled upward to capture air and billow open. Fifth, a hand is inserted in the bag to “find the bottom” as the bag is placed on the packing surface. Sixth, once the bottom is found, the hand is withdrawn, and; seventh, the user grasps the merchandise and begins loading the bag. Variations on this theme may include the shaking of bags to get them open and then the placement of a hand to find the bottom, or the insertion of a hand directly into the bottom to push the gussets down and out. Similar bag opening operations take place when paper bags are used.
Paper bags when opened are usually set upright and allow the user to place merchandise inside the bag at the bottom. On the other hand, most common plastic bags do not allow the bag to stand up without substantial difficulty. It would take a user several seconds to open up and put a common plastic bag in the right shape to make it stand up. It is impractical for a user in a high volume retail outlet to do this, as the cost of labor is substantial. This is one key reason most fast food restaurants still use paper bags.
Many attempts have been made to overcome the inability of plastic bags to stand up like paper bags. In a bottom seal bag variety, Hansen et al, U.S. Pat. Nos. 3,988,870 and 4,929,224, have created a square bottom bag by using a complex means of placing a mandrel inside the plastic tube which forms the bags. Others have accomplished this with a means of folding up the gussets after the bag has been made such as in Ross, U.S. Pat. No. 5,102,384 and Cole U.S. Pat. No. 3,886,850. Other approaches include the folding of bag bottoms as illustrated in Platz, U.S. Pat. No. 3,917,159, and angular heat seals as in LaFleur U.S. Pat. No. 3,915,077 and Brinkmeier, U.S. Pat. No. 3,896,709. Roen reveals a means of using angular seals in a sideweld bag in U.S. Pat. No. 4,717,262. As this disclosure points out, side weld bags are not satisfactory in the square bottom bag disclosure herein set forth.
With the exception of Roen, '262, all of these processes are relatively complex and require cumbersome processes of grasping, clamping, folding and/or heat sealing, most of which operations are conducted after the basic bag size and configuration has been cut and sealed from the plastic tube stock. Furthermore, the objective in all of the previously related patents reveals the means to fold or crease the bag material a specific, pre-determined direction, thereby creating a square bottom. The bag is not manufactured in a planar disposition and pre-configured so that upon first being opened it naturally squares out and forms a so-called square bottom.
In the high-speed bag manufacturing process used throughout the world, plastic bags are typically made from tube stock. This tube stock is cut and sealed—either bottom sealed or sidewelded—as the last step before being packed in a carton. These bags are conventional and do not have square bottoms.
Where square bottoms have been imparted to a bag after it has been formed, such imparting of square bottoms has been proven to be costly. Simply stated, to try to clamp and fold over and/or seal gussets together after a bag has already been cut and sealed from its tube stock is not economical. As illustrated in the above patents, Ross '384 and Platz '159, this bag forming requires a costly secondary operation after the bottom sealing process is completed and the bag has been cut free from the tube stock. These processes use a relatively sophisticated grasping and clamping to accomplish the folding process. For example in Hansen '224, the making of these square bottom bags requires placing a mandrel inside the tube prior to cutting and sealing. This too is unreliable and costly. Key reasons include the fact that tube widths vary greatly—a narrow tube will cause the mandrel to lock up inside the tube and then break the tube, a slightly wider tube will result in not having a properly formed bag. Second, this process requires narrow plastic tubes instead of the wider, more efficient ones used on 3-5 lanes machines and; three, the bag machine speeds are slow. These three factors would drive up the price of the bags making them impractical when compared to paper or other alternative technologies.
La Fleur, '077, reveals a means of angle sealing that is more cost effective than the three others listed above, but is still costly for bags made on modern, high-speed bag equipment that typically runs 3-5 lanes across and in speeds in excess of 125 cycles per minute. Trying to simultaneously control the heat sealing (or the folding, for that matter) of 12 to 24 side gussets pairs per cycle would result in either substantially reducing the machine's speed or it would have a highly unreliable outcome at best. It is important to note that this angle seal technology can produce uneven seals, which then results in irregular bag bottoms once they are opened and placed into use.
All of the above bag styles will cost substantially more to produce than common plastic bag styles, generally as much as 20-80% or more depending upon size. Only the Roen '262 bag product can produce an economically cost-effective bag but is limited to sideweld bag production and is not practical on smaller bags running 3-5 lanes across.
In what follows, we disclose a method that can be adapted to existing, modern high-speed bag making machinery and technology that can simultaneously produce bags 3-5 lanes across. At the same time, the disclosed method will not substantially reduce the manufacturing speed and produces a reliable quality product.
SUMMARY OF THE INVENTION
A hinge is disclosed for a plastic film. This film has a predetermined thickness sufficient for the plastic film to remain planar in an absence of a first bending moment applied across the plastic film. The hinge includes at least one linear groove configured in the plastic film to reduce the predetermined thickness of the plastic film at the linear groove. The hinge permits preferential hinging of the plastic film at the linear groove responsive to a bending moment at the linear groove across the plastic film less than the first bending moment. The linear groove has insufficient depth to sever the plastic film and enables the hinge film to retain sufficient remaining thickness at the linear groove to permit hinging and not tearing of the plastic film at the linear groove. When the hinge is placed across a plastic film, and the film bent at the hinge, the film defines a first panel and a second panel with each panel disposed at an angle to one another at the hinge. This allows the first panel and the second panel to form a three dimensional structure to maintain the pla

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