The invention relates to the technical field of plastic packaging bags, for example bags of the type designed to contain animal feedstuffs.
Advantageously and as well known to those skilled in the art, these types of bags may have, on their lateral edges, gussets capable of increasing the capacity of the bag and improving its stability.
Generally speaking, the gussets are made over the entire height of the bag.
Various manufacturing methods can be envisaged. For example, bags are commonly made from a single plastic film by using a continuous process. The film is subjected to successive folding operations in order to produce lateral gussets between two walls. The external folds of the gussets thus produced are generally assembled by welding operations. The bottom of the bag is also produced by continuous welding and is then turned over and attached to one of the walls of the bag.
Such arrangements are not described in detail here because they are perfectly familiar to those skilled in the art.
In this embodiment, the gussets are therefore made over the entire height of the bag by successive folding. It is therefore apparent that, at the opening of the bag, the ends of said opening are delineated by four walls as a result of the cross section of the gussets.
These arrangements make it necessary to use specific means in order to ensure leaktight closure of the bag. There may also be certain difficulties in fitting the upper part of the bag, where it opens, with means of temporary opening and closing of the ZIP®, ECLAIR®, etc. type.
In order to overcome these drawbacks, there have been proposals to produce plastic bags having lateral gussets which extend over only part of the height of the bag to within a certain distance of the opening of said bag. As a result, above the gussets, the lateral ends of the opening consist of only two wall thicknesses.
This type of bag is disclosed. for example, by Document EP 1.250.999 which describes a method of producing gusseted bags. Nevertheless, the method described in that document relates to a concept for producing bags which is totally different.
In fact, the bag is not formed from a single plastic film subjected to successive folding operations in order to produce gussets but is made of two independent films, the walls of which are joined by independent, separately mounted gussets. It is obvious that, using this solution, it is possible to envisage producing bags with gussets having a height which is less than the total height of the desired bag, given the fact that such gussets are produced independently.
It is, however, apparent that the separate mounting of the gussets reduces production rates significantly.
Patent JP 07100972 relates to a method of producing bags which uses specific means in order to form the gusset over only part of the height of the bag. This technical solution is expensive and does not make it possible to achieve high production rates.
The invention overcomes the above drawbacks simply, reliably, effectively and efficiently.
The problem which the invention aims to solve is to produce a gusseted bag from a plastic film, the gussets being made by successive folding of said film, i.e. they are not separately mounted, and having a height which is less than the total height of the desired bag. This technical solution made it necessary, in particular, to solve the important problem of ensuring leaktight closure of the upper end of the gussets below the free part of the walls resulting from the absence of a gusset.
In order to solve this problem, a production method has been devised whereby:
According to another aspect, the free wall edges are assembled above the 450 closed end of the gussets. The various assembly operations are performed by welding.
Advantageously, the upper part of the bag near its opening is fitted with a closure system.
Given the basic characteristics of the method according to the invention, the bag obtained has lateral gussets over only part of its height so as to leave, over a certain distance from the opening of the bag, wall parts capable of being assembled directly to each other by their lateral edges, the upper end of the gusset being closed by an external area folded at approximately 45° delineating a substantially triangular external shape located between the two folds of the gussets. The external triangular shape may be attached to one of the folds of the corresponding gusset.
The invention is explained below in greater detail, reference being made to the accompanying drawings in which:
a, 1b, 1c and 1d are purely schematic views showing the main phases of the method of producing a bag made of a plastic film;
As indicated and as perfectly familiar to those skilled in the art, the gusseted bag according to the invention is made of a plastic film (1) which is subjected to successive folding operations in order to produce lateral gussets (1a) between two walls (1b) and (1c). (
These arrangements are perfectly familiar to those skilled in the art and are not described in detail. The same applies to producing the bottom (1d) which can be obtained by assembling the lower edge of the two walls (1a) and (1b) by welding and folding over onto one of walls (1a) or (1b).
According to the invention, external folds (1a1), (1a2) of gussets (1a) are assembled over only part of the desired height of the bag, for example to within a certain distance (a) of opening (1e). Classically, the folds (1a1) and (1a2) of each gusset (1a) can be assembled by a welding operation for example (
In another stage of the method according to the invention, the gussets (1a) are detached as far as the area where they are assembled so as to form a free gusset part (1a3) and a free wall part (1b1), (1c1). For example, this detachment of the gussets (1a) as far as the corresponding weld line (S) may be the result of simply cutting each of folds (1a1), (1a2) of each gusset.
Each free gusset part (1a3) is then subjected to an operation capable of ensuring upper transverse closure of the gussets starting from the end of the assembly line (S) of the external folds (1a1), (1a2) of each gusset (1a). These operations to transversely close the upper ends of the gussets are performed after having turned down at least one of the free wall parts (1b1) in order to release the free gusset part (1a3) (
On the basis of this design, various technical solutions can be envisaged.
In the embodiment shown in
The protruding part resulting from said twisting and folding movement (
Given the various stages in the method, the bag obtained has lateral gussets (1a) over only part of the total height of the bag so as to leave, at a certain distance (a) from the opening of the bag, a free wall part (1b1) and (1c1).
These two free wall parts (1b1) and (1c1) can be assembled by their lateral end by welding (S2) for example over two thicknesses only. The upper end of each gusset (2a) is closed by the internal 450 folded area (1a4) delineating a substantially triangular shape.
This triangular shape is located between the two folds (1a1), (1a2) of the corresponding gusset (1a). Note that this triangular shape can be attached (by welding for example) to one of the folds of the corresponding gusset.
After filling, in particular, the bag is closed and made leaktight by the upper horizontal edge of the free wall parts (1b1), (1c1). Also note that one of the walls (1b1) for example, may be fitted with a temporary opening and closing system of the ZIP®, ECLAIR®, etc. type.
The advantages of the invention are apparent from the description, the possibility of making the gussets from a film of plastic over a height which is less than the total height of the bag so that there are only two wall thicknesses in the area where the bag is closed being emphasised and pointed out in particular.
Number | Date | Country | Kind |
---|---|---|---|
0550547 | Mar 2005 | FR | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/FR06/50129 | 2/13/2006 | WO | 00 | 12/6/2007 |