Flexible bags – With closure – Closure within bag
Reexamination Certificate
2000-10-13
2002-08-06
Pascua, Jes F. (Department: 3727)
Flexible bags
With closure
Closure within bag
C383S107000, C383S113000
Reexamination Certificate
active
06428209
ABSTRACT:
The invention relates to a sack from a flexible material, such as paper and/or plastic material, which sack is provided with a longitudinal closing seam and/or a transverse closing seam, which connects to each other layers of material that lie on each other. The invention also relates to a method for forming such a sack.
Such sacks are generally known. An example is a sack from a plastic material in the shape of a part of a plastic tube, of which first the transverse seam at one end is formed by sealing, and after filling the sack the transverse seam near the other end is formed by sealing in order to close the sack. The closing off can also take place by gluing or sewing, but this is less common. Another example is a paper sack, of which the longitudinal seam and the bottom are usually closed off by gluing. After filling the paper sack the open upper side is usually sewn closed or closed by gluing. When the product packed in the sack may not leak into the surroundings, such as a crop protection agent, or when the product has to be protected from for instance moist, the paper sack is provided with a plastic inner sack. Its closing off usually takes place by sealing.
A drawback of closing off a plastic sack with the help of sealing is that heat has to be supplied, as a result of which the product may be affected. Moreover some products and product surroundings may not be exposed to heat, for instance because of danger of explosion. Another drawback is that the adjustment of the sealing temperature is difficult to measure and hard to control, as a result of which the sealing seam might not seal well. With paper sacks it is a drawback that the glue or hotmelt has to be supplied to the seams, which requires time to let the glue or hotmelt stick or to activate it. For making a sewing seam it is disadvantageous among other things that the sack has to be placed accurately in a certain position and the sack can be recycled less well.
It is an object of the invention to provide an improved sack from a flexible material. It is another object of the invention to provide a plastic sack to which no heat has to be supplied after filling. It is yet another object to provide a paper sack which can be recycled well. Yet another object is to provide a sack of which the seam is reliably closed off. Yet another object is to provide a sack of which the seam can relatively easily be made.
According to a first aspect of the invention at least one of these objects is achieved with a sack of the kind described in the preamble, in which the closing seam is formed by attaching to each other the layers of material that lie on each other by plastic deformation of a part of said layers, without adding an adhesive such as glue and without adding heating energy.
Surprisingly it appeared that such a seam obtained by plastic deformation offers a sufficiently strong attachment to resist the shearing forces on the longitudinal seam or the peeling forces on the transverse seam of for instance the filling opening. The attachment between the layers of material is obtained without it being necessary to supply heat to seal (with plastic) and without it being necessary to apply glue or hotmelt (with paper), and without it being necessary to make a sewing seam (both with paper and with plastic). As a result the product in the sack is not affected by the heat or the glue and a paper sack can be recycled well. Also sacks from other materials, such as paper lined with aluminium or plastic, can be made by plastic deformation of the seams.
It is noted that in the older not pre-published Dutch patent application 1004420 of applicant's a valve sack is described of which the filling opening is closed by mechanical deformation. On such an filling opening, however, hardly any forces which could open the filling opening are active. The mechanical deformation was meant to prevent the streaming out of the product in the sack, such as cement. Making a longitudinal or transverse seam in the sack by plastic deformation is not described in said document.
Preferably the plastic deformation extends band-shaped over the length of the closing seam. Such a band-shape is easy to make with the help of two rotatable wheels or two clamping jaws at the location of both sides of the seam to be formed.
Preferably the plastic deformation has been accomplished by corrugating the layers of material. By corrugation a strong plastic deformation is created, which can easily be made.
Preferably the plastic deformation has been accomplished by knurling the layers of material that lie on each other. When knurling (German: prägen) a relief is pressed into the material, as a result of which the layers of material that lie on each other undergo a strong plastic deformation and adhere to each other.
According to an advantageous embodiment the sack consists of one single layer of paper, the closing seam being formed by attaching to each other the layers of paper that lie on each other by plastic deformation at the location of the closing seam. The sack is then formed from one single strip of paper. If so desired all seams could be obtained by means of plastic deformation; in any case it is profitable to make the closing seam of the open upper side by plastic deformation. Possible residues of the product at the location of the closing seam are either pushed away or integrated into the deformed layers of paper.
According to another advantageous embodiment the sack comprises two or more layers of paper, all layers of paper being attached to each other by plastic deformation at the location of the closing seam. Because all layers of paper are attached to each other the sack obtains an extra strength. When using glue this is only possible by applying extra glue between the layers.
According to yet another advantageous embodiment the sack consists of an inner sack of plastic material and an outer sack of one or more layers of paper, the transverse closing seam being formed by attaching all layers to each other by plastic deformation. As a result of the plastic deformation both sides of the plastic inner sack adhere to each other as well as the paper layers to the plastic inner sack and, if more than one layer of paper is present, to each other.
According to yet another advantageous embodiment the sack consists of plastic material, the closing seam being formed by attaching the plastic walls to each other by plastic deformation at the location of the closing seam. As a result of plastic deformation both the plastic sides of the sack adhere to each other without sealing being necessary. The plastic deformation can be performed quickly and easily. No time is needed to heat up the plastic to the softening temperature.
The sack for instance is a hexagonal bottom sack, of which the open upper side is closed after filling by attaching to each other the walls of the upper side that lie on each other by plastic deformation. A standard hexagonal bottom sack too can therefore be provided with a closing seam to be obtained by plastic deformation.
Preferably the sack is meant for accommodating approximately 1 kg or more of a product, and more preferably 2.5 kg or more.
According to another aspect the invention relates to a method for forming, filling and closing a sack from flexible material such as paper and/or plastic material, a tubular material being taken as starting point, which can be formed from a flat strip by making a longitudinal seam, after which a part of the tube is provided with a bottom sealing to form an open sack, and in which the sack after filling is provided with a top sealing. According to the invention the longitudinal seam and/or the bottom sealing and/or the top sealing is obtained by attaching to each other the layers of material that lie there on each other by plastic deformation, without an adhesive such as glue being added and without heating energy being supplied. With this method a sack with the above-mentioned advantages is obtained with the known forming, filling and closing technique, the longitudinal seam and/or sealing(s) being made by pl
Frantschach Industrial Packaging Netherlands N.V.
Long William C.
Pascua Jes F.
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