A SACK AND A PACKAGING METHOD FOR THE SACK

Abstract: The invention relates to a sack (1) or a similar flexible package and a packing method based on the use of such a sack. The sack (1), which is intended for packing fine-ground material, is provided with a filling duct (3) leading inside the sack and made of flexible material and a bendable covering patch (12) protruding from the sack with the aid of which the end (11) of the filling duct can be closed after the filling of the sack. It is essential to the invention that the filing duct (3) extends at least to the bending line (13) of the covering patch (12) and preferably past it and that the filling duct (3) is, at least at the end thereof, narrower than the covering patch (12). Thus the covering patch (12) can be bent against the surface of the sack and attached thereto in such a way that it forms a uniform closing zone closing the end (11) of the filling duct in a cross-direction and extending to each side thereof.

Description: A sack and a packaging method for the sack The object of this invention is a sack or a similar flexible package, intended for packing powdery material, which is provided with a filling duct of flexible material leading inside the sack and with a flexible covering patch protruding from the sack with the aid of which the end of the filling duct can be closed after the filling of the sack. In the sack according to the invention, the flexible filling duct acts as a valve which in the filling process lets the material to be packed flow into the sack and flatten out after the filling, in such a way that the path of flow is closed. An advantage of the sack provided with a valve compared to open sacks has been, amongst other things, that it allows for a fast mechanical filling process. When the valve of the sack is self-closing, it does not require other closing procedures. A drawback of a simple valve like this is, however, that some of the packed material tends to leak out of the filled sack through the valve. When the nature of the material to be packed is such that it is not desirable or permitted to let it come out of the sack in the form of a leak through the valve, a valve such as a so-called pocket valve must be selected enabling absolute tightness. It is only possible to partly mechanize the filling of such a sack and the valve usually must be closed by manually bending it which on the other hand is slow and requires man-power. It is known in the art that a duct acting as a valve can be closed after the filling of the sack by adhering a covering patch on top of it. It is also known that an extra patch can be attached, in conjunction with the manufacture of the sack, on the upper or lower sides of the valve. The extra patch is folded over the valve and attached by glue after the filling of the sack. It is further known that the inner surface of the valve can be of a material which can be glued or heat-sealed shut after the filling. All the said known packages have drawbacks when a tight package is required for a product which is difficult to control, moves very easily and is very powdery and which, because of its nature, has to be packed on a fully automated packing line and which is not allowed to leak from the package even during very difficult transportation conditions. The purpose of this invention is to form a sack or a similar flexible package in which the above problems of known sacks are avoided. The sack according to the invention is characterized in that the filling duct extends at least to the bending line of the covering patch and that the end of the filling duct is narrower than the covering patch, whereby the covering patch can be bent against the surface of the sack and attached thereto in such a way that it forms a uniform closing zone which closes the end of the filling duct in a cross-direction and extends on each side thereof. The solution according to the invention prevents leakage through the fringes of the filling duct serving as a valve which is a problem of the known sacks in which the filling duct and the covering patch are of the same width. The invention thus prevents the material possibly remaining in the filling duct from leaking out of the package, as well as leakage through channels caused by the corrugations of the filling duct, which so far have been very common occurences in the case of under-filled sacks. When using the sacks according to the invention, the packing process can be carried out fully-automated without manual procedures. The sack or a similar flexible package according to the invention is particularly suitable for such fine-ground, powdery products which, because of leakage, would cause contamination of their surroundings or other damage or risks or which themselves would suffer from environmental effects, such as air humidity. As a result of the prevention of the leakage, the advantage is achieved that loss of the product caused by leakage is avoided. As for the material of the sack according to the invention, different flexible materials are well adapted, such as paper, plastic and textiles or combinations thereof which can be provided in the sack as one or more layers. In addition to sacks, other flexible packages such as bags, can be considered in which the application of a similar filling technique is possible. According to a preferred embodiment of the invention, the filling duct of the sack extends past the bending line of the covering patch in such a way that while closing the sack, the end of the duct is turned, along with the covering patch, against the surface of the sack. An extremely safe closure is obtained by this solution in which the covering patch engages the surface of the sack on the uniform closing zone, closing the end of the filling duct in a cross- direction and extending axially between the end of the duct and the bending line on each side of the duct. With respect to the other embodiments of the sack according to the invention, a reference is made to the appended Claims. The object of the invention is also to provide a packing method in which fine-ground material is packed into the sack or a similar flexible package through an associated filling duct of flexible material and in which the sack is closed, after the filling, with a covering patch protruding from the sack. The covering patch is folded against the surface of the sack against the end of the filling duct and is attached thereto. The method is characterized in that the filling duct is extended at least to the bending line of the covering patch and is formed, at least at the end thereof, to a width smaller than the covering patch, whereby when closing the sack with the covering patch, a uniform closing zone is obtained closing the end of the filling duct in a cross-direction and extending on each side thereof. In addition, different applications of the method according to the invention are disclosed in the Claims. In the following the invention is described in more detail with the aid of examples by reference to the appended drawings, where: Fig. 1 shows a sack according to the invention before the filling, Fig. 2 shows a corner of the sack in Fig. 1 which is provided with a filling duct leading inside the sack and serving as a valve, and a covering patch, Fig. 3 shows the corner of the unfilled sack in Fig. 2 as viewed from the side. Fig. 4 shows the corner of the sack corresponding to Fig. 2 after its filling and the application of the glue, Fig. 5 shows the corner of the sack which is closed by gluing a covering patch on the end surface of the sack. Fig. 6 shows the corner of the filLed and closed sack according to Fig. 5, as viewed from the side. Fig. 7 shows another sack or bag according to the invention, as viewed from the side. Fig. 8 shows the filling duct and the covering patch on the side of the sack according to Fig. 7 before the closing of the sack. Fig. 9 shows the parts of the sack according to Fig. 8 after the sack has been closed. Fig. 10 shows, corresponding to Fig. 8, the filling duct and the covering patch on the side of the sack such as they are according to an alternative embodiment of the invention, and Fig. 11 shows the parts of the sack according to Fig. 10 after the sack has been closed. Fig. 1 shows unfilled, glued sack 1 according to the invention which is suitable for a package of fine-ground materials, such as PVC plastic, diatomaceous earth or food stuffs such as flour. The sack is a flexible package which is closed except for a filler opening in one corner 2 of the sack which has filling duct 3 fitted to serve as a valve. The material of sack 1 can be, for instance, strong paper and filling duct 3 is of flexible material, such as plastic. Ends 4, 5 of sack 1 are formed by bending the ends of a tubular sack blank so as to overlap and by joining them, for instance, by gluing. According to the figure, other end 4 is further provided with end or botton patch 6 glued thereto. (In practice the bottom patches, when used, are usually provided on both ends of the sack.) The construction of the filler opening in corner 2 of the sack according to Fig. 1 is shown more closely in Figs. 2 and 3. Strip 8 is attached by plain joint 7 on top of the corner of the sack at the end thereof, on which strip filling duct 3 is attached by plain joint 9, which duct has end 4 of the sack attached thereon by plain joint 10, which end is provided with glued bottom patch 6. Figs. 2 and 3 show that said strip 8 extends in the direction of filling duct 3 past end 11 of the duct forming covering patch 12 protruding from the sack with the aid of which the sack can be closed after the filling. Covering patch 12 is thus bent 180° along bending line 13 which is situated at the edge formed by the base of the patch in the corner of the sack. In the application of the invention according to Figs. 2 and 3 it is essential that filling duct 3 extends slightly past bending line 13 of covering patch 12 and that end 11 of the filling duct (the whole filling duct in the illustrated application) is narrower than the covering patch. In corresponding sacks which are already known, the filling duct has been of the same length as the end of the sack and the covering patch protruding from it, whereas according to the invention, filling duct 3 has been so tapered that on each side of its end 11 there remains a strip of covering patch 12 which is at least a few millimeters and preferably at least about 1 cm in width and forms a part of the closing zone which is formed when the sack is closed and which is better shown in Figs. 4 and 5. When the sack is filled with material which is packed through filling duct 3, the surroundings of end 11 of the duct are cleaned of the dust left by the material. After that, glue is applied on covering patch 12 on area 14 marked in Fig. 4, or at the end of the sack on area 15 or possibly on both areas. It is also possible that the adhesive has already been applied to these areas 14, 15 in conjunction with the manufacture of the sack. Covering patch 12 is then bent 180° along bending line 13, whereby the patch and the end of the filling duct turning therewith are pressed against end 4 of the sack according to Fig. 5. The glue or the adhesive adhered by heat sealing thus forms closing zone 16 shown in Fig. 5 on which covering patch 12 has engaged end 4 of the sack. It can be seen that closing zone 16 closes end 11 of the duct in the cross-direction of the filling duct and extends to each side of the end of the duct and further axially on each side of the duct until bending line 13 remaining in the corner of the closed sack. Closing zone 16 has thus been achieved surrounding tightly end 11 of the filling duct in three directions thereof and preventing leakage from the sack even in difficult transportation conditions. Due to the techinques of manufacture, the position of covering patch 12 with respect to filling duct 3 and its end 11 tends to move in a transverse direction and when closing the sack after the filling, the covering patch does not in practice always bend accurately along designed bending line 13, whereby a certain inaccuracy results. This inaccuracy has so far resulted in that the end of the filling duct serving as a valve has remained open on either corner thereof and exposed to leakage. In the disclosed solution according to the invention, this drawback is eliminated because the solution enables a tight closure even when bending line 13 of covering patch 12 does not settle accurately in the desired spot. Fig. 7 shows sack 1 according to the invention, in which the filling duct and the covering patch are situated on the side of the sack in a spot indicated by line 17. Filling duct 3 and covering patch 12 are shown in Fig. 8 in which the construction, with respect to the essential parts, corresponds to the one illustrated in Figs. 2 to 6. Filling duct 3 thus extends past bending line 13 of covering patch 12 in such a way that when closing the sack, end 11 of the duct turns along with the covering patch against the side of the sack. The closed sack with closing zones 16 obtained with the aid of glue or adhesive is shown in Fig. 9. Figs. 10 and 11 show an alternative application of the invention corresponding to Figs. 8 and 9 in which end 11 of filling duct 13 is situated on bending line 13 of covering patch 12. When attaching bent covering patch 12 on the surface of the sack, the glue or the adhesive forms closing zone 18 covering the major area of the covering patch and extending past end 11 of the filling duct to each side thereof. It is clear to those skilled in the art that different applications of the invention are not limited by the disclosed examples but can vary within the appended Claims. The material of covering patch 12 and end patch 6 can be preferably, instead of paper, for instance a plastic film or other plastic-coated or laminated material. Thus the attachment of the covering patch to the end patch forming the surface of the sack can be effected by heat sealing. Plastic which is processed to be antistatic can thus preferably be used as the adhesive, whereby the cleaning of the surfaces attached together is easier.

Claims: Claims 1. A sack (1) or a similar flexible package intended for the packing of fine-ground material and provided with a filling duct (3) leading inside the sack and made of flexible material and a flexible covering patch (12) protruding from the sack with the aid of which the end (11) of the filling duct can be closed after the filling of the sack, c h a r a c t e r i z e d in that the filling duct (3) extends at least to the bending line (13) of the covering patch (12) and that the end (11) of the filling duct is narrower than the covering patch, whereby the covering patch can be bent against the surface of the sack (1) and attached thereto in such a way that it forms a uniform closing zone (16, 18) closing the end __ the filling duct in an axial direction and extending to each side thereof. 2. A sack or a similar package according to Claim 1, c h a r a c t e r i z e d in that the filling duct (3) extends past the bending line (13) of the covering patch (12) in such a way that when closing the sack (1) the end (11) of the duct turns along with the covering patch against the surface of the sack. 3. A sack or a similar package according to Claim 1 or 2, c h a r a c t e r i z e d in that the sack (1) comprises a strip-like part (8) which is attached under the filling duct (3) and extends in the direction of the filling duct as a projection forming the covering patch (12), whereby the sack can be closed by bending the covering patch 180° along the bending line (13) formed by its base. 4. A sack according to any of the preceding Claims c h a r a c t e r i z e d in that the end (11) of the filling duct (3) and the covering patch (12) are situated in the corner (2) of the sack (1) which has a shape of an essentially rectangular prism in such a way that the covering patch can be bent along the corner against the end (4) of the sack and attached thereto. 5. A sack or a similar package according to any of Claims 1 to 3, c h a r a c t e r i z e d in that the end (11) of the filling duct (3) and the covering patch (12) are situated on the side of the essentially flat-shaped sack (1) or a similar package. 6. A Sack or a similar package according to any of the preceding Claims, c h a r a c t er i z e d in that the covering patch (12) and/or the surface of the sack (1) comprises adhesive, whereby the covering patch can be attached to the surface of the sack by heat sealing. 7. A packing method in which fine-ground material is packed into a sack (1) or a similar flexible package through an associated filling duct (3) of flexible material and in which the sack is closed after the filling by the covering patch (12) protruding from the sack which is bent along the end (11) of the filling duct against the surface of the sack and attached thereto, c h a r a c t e r i z e d in that the filling duct (3) is extended at least to the bending line (13) of the covering patch (12) and formed, at least at the end (11) thereof, so as to be narrower than the covering patch, whereby when closing the sack (1) with the covering patch, a uniform closing zone (16, 18) is obtained which closes the end of the filling duct in a cross-direction and extends to each side thereof. 8. A method according to Claim 1 , c h a r a c t e r i z e d in that the filling duct (3) is extended past the bending line (13) of the covering patch (12), whereby when bending the covering patch, the end (11) of the duct turns along with the patch against the surface of the sack (1) and in that the sack is closed by attaching the covering patch on the surface of the sack on a uniform closing zone (16) which closes the end of the filling duct in a cross-direction and extends axially between the end of the duct and the bending line to each side of the duct. 9. A method according to Claim 7 or 8, c h a r a c t e r i z e d in that the attachment of the covering patch (12) to the surface of the sack (1) is effected by gluing. 10. A method according to Claim 7 or 8, c h a r a c t e r i z e d in that the covering patch (12) and/or the surface of the sack (1) is provided with adhesive and that the sack is closed by heat sealing the covering patch shut to the surface of the sack.

Inventors: NISKALA OLAVI, NISKALA, OLAVI
Applicants: WISAFOREST OY AB
Application year: 1991
Main classification: B65D30
IPC codes: B65D30