AU1011899A

AU1011899A - A multi-wall sack

Info

Publication number: AU1011899A
Application number: AU10118/99A
Authority: AU
Inventors: Larry Thomas Challis
Original assignee: Amcor Packaging Australia Pty Ltd
Current assignee: Orora Ltd
Priority date: 1997-11-03
Filing date: 1998-11-02
Publication date: 1999-05-24
Anticipated expiration: 2018-11-02
Also published as: AU760523B2

Description

WO99/23000 PCT/AU98/00908 A MULTI-WALL SACK 5 The present invention relates to a multi-wall sack. The term "multi-wall" sack is understood to mean a sack that has: 10 (i) two or more walls; (ii) each wall is formed from paper, polymeric, or any other suitable material; and 15 (iii)the walls may be adhered together so that the sack is a single multi-wall bag or may be separate (or partly adhered together and partly separate) so that the sack includes an outer bag and one or more inner bags 20 positioned in the outer bag. The present invention relates particularly, although by no means exclusively, to a multi-wall sack which includes a single or multi-wall outer bag, typically 25 formed from paper, and an inner pouch, typically formed from a polymeric material. These sacks are suitable for storing a wide range of products including dry food products, such as powdered 30 milk products. In the storage of such products it is important to ensure that the dry food product is completely sealed in a pouch made from a polymeric material to maximise the 35 product life. A strong outer bag (usually having two or more walls of paper) is also necessary to protect the inner pouch and to facilitate handling and identification of the WO99/23000 PCT/AU98/00908 - 2 enclosed goods. Known multi-wall paper/polymeric material sacks for dry food products comprise an inner polyethylene pouch 5 and an outer paper bag having either a block (ie, rectangular) bottom end or a "pinch" (ie. flat, folded over) bottom end. Some known multi-wall paper/polymeric material 10 sacks are manufactured with an "easy-open" tearing feature at their bottom end to facilitate the easy opening of the outer paper bags of the sacks, without the use of a sharp instrument, so as to enable the inner polymeric pouches to be removed from the bags. These easy-open tearing features 15 are incorporated into cover sheets (often referred to as patches) that are glued onto and thereby cover the folded bottom ends of the outer paper bags during manufacture of the sacks. Such sacks are sold to manufacturers of the food products with an open-top ready for filling with the 20 food products and then closing by the "pinching" method to form a pinch-top end or by stitching to make a stitched top end. These last closure steps are completed by the food products manufacturer. 25 The production steps required to manufacture multi-wall paper/polymeric material sacks with this easy open feature at the bottom ends must be conducted with a high level of accuracy. 30 Specifically, in the case of the block-bottom sack, the cover sheet incorporating the easy-open tear feature on the base of the block-bottom sack must be carefully positioned to ensure that the tear-strip is correctly aligned with the underlying edge of the folded 35 bag end. If not correctly aligned, it is not possible to open the bottom of the outer paper bag without the use of a sharp instrument.

WO99/23000 PCT/AU98/00908 - 3 The control of the sack manufacturing operation required to ensure correct positioning of the easy-open cover sheets adds significantly to the cost of manufacture 5 of the sacks. It is a specific object of the present invention to alleviate the problems associated with these known paper/polymeric material multi-wall sacks. 10 It is a general object of the present invention to provide an improved multi-wall sack with easy open capability. This object extends not only to known paper/polymeric material multi-wall sacks discussed above 15 but also extends to other sacks, including single multi wall bags that are within the above definition of "multi wall" sack. According to the present invention there is 20 provided a multi-wall sack which includes: (a) a closed bottom end; and (b) an open top end that, when closed, forms a 25 closed top end with a tearing means which facilitates easy opening of the sack. The above-described easy-open sack is less complex to manufacture than the known easy-open 30 paper/polymeric material multi-wall sacks described above, is more effective in opening the sack, and is less costly to manufacture. The closed top end may be of any suitable 35 configuration. By way of example, the closed top end may be a pinch-top end. By way of further example, the closed top end may be a stitched top end, a stitched/folded top WO99/23000 PCT/AU98/00908 -4 end or a folded/stitched top end that are used for flour sacks. As used herein, the term "tearing means" is to 5 be construed as referring to any flexible elongate element suitable for tearing the sack, such as a string, strip, ribbon or rope. The tearing means may be integrally formed as part of an outer wall of the sack or may be affixed to or otherwise positioned in relation to the outer wall and 10 become part of the closed top end when that end is formed. The tearing means may form part of a cover sheet formed from paper or other suitable material. 15 Preferably the cover sheet is affixed to the sack in a location that is selected so that the tearing means becomes part of the closed top end as sections of the sack at the open top end are folded to form the closed end. 20 More preferably, the sack is pre-cut and folded with a predetermined design at the open top end and the cover sheet is glued to an outer wall of the sack in a location that is selected so that the tearing means can be part of the closed top end of the sack. 25 It is particularly preferred that the tearing means form part of a cover sheet that has a first cover sheet section on one side of the tearing means and a second cover sheet section on the other side of the tearing means. 30 It is more particularly preferred that the first section of the cover sheet be affixed, typically glued, to an outer wall of the sack in a position that is selected so that the top end of the sack can be folded over onto the 35 second section of the cover sheet and affixed, typically by gluing and/or stitching and/or by any other suitable means to the second section in the process of forming the closed WO99/23000 PCT/AU98/00908 top end. With this arrangement, it is possible to open a closed top end by detaching the tearing means from the sack and pulling back the second section of the cover sheet. Since the second section of the cover sheet is adhered to 5 the folded over top end of the sack, the action of pulling back the second section unfolds the top end of the sack to allow access to the sack. It is preferred that the sack includes; 10 (i) an outer bag having the above described closed bottom end, open top end, and tearing means; and 15 (ii) an inner pouch that is adapted to be filled with product and sealed. The inner pouch and the outer bag may be formed from any suitable material. 20 Preferably, the inner pouch is formed from a polymeric material. Preferably, the outer bag is formed from paper. 25 More preferably, the outer bag comprises a plurality of layers of paper. Preferably, the outer bag is formed with a block 30 end. According to the present invention, there is also provided a method for forming a closed multi-wall sack which includes the steps of: 35 (i) filling a product into the sack via an open end of the sack; and WO99/23000 PCT/AU98/00908 -6 (ii) folding the sack at the open end to form a closed top end with a tearing means which facilitates easy opening of the sack. 5 The above-described method may include stitching closed the open end of the filled sack prior to step (ii). According to the present invention, there is also 10 provided a method for manufacturing a multi-wall sack which includes the steps of: (i) forming a sack having a closed bottom end and an open top end; and 15 (ii) adhering or otherwise attaching a tearing means to the sack in a manner such that, when the sack is filled and a closed top end is formed at the open top end, pulling the 20 tearing means facilitates the easy-opening of the outer bag. Preferably the closed top end is formed in step (ii) by folding the sack at the open top end. 25 Preferably, the open top end formed in step (i) is pre-cut and folded to permit the formation of the closed top end. 30 As indicated above, the closed top end may be of any suitable configuration, such as a pinched top end, a stitched top end, a stitched/folded top end, or a folded/stitched top end. 35 Preferably, the tearing means is attached to the sack by adhering the tearing means to an outer wall of the sack at the open top end so that it extends laterally of WO99/23000 PCT/AU98/00908 - 7 the open top end. Preferably the tearing means forms part of a cover sheet which includes a first cover sheet section on 5 one side on the tearing means and a second cover sheet section on the other side of the tearing means and the tearing means is affixed to the sack by adhering the first section to the outer wall of the sack. 10 According to the present invention there is provided a multi-wall sack filled with product, which sack includes a closed bottom end and a closed top end with a tearing means that facilitates easy opening of the sack at the top end. 15 The present invention is described in further detail with reference to the accompanying drawings, in which: 20 Figure 1 is a perspective view of a multi-wall sack in accordance with one embodiment of the invention in the as-manufactured form; Figure la is an enlarged view of the circled 25 region in Figure 1; Figure lb is a cross-section along the line lb-lb in Figure la; 30 Figure ic is a cross-section similar to Figure lb but showing the sack after it has been filled with product and closed with a pinch-top end; Figure 2 is a perspective view of the sack shown 35 in Figure 1 after the sack has been filled with a product, such as flour, and the open top end has been closed by folding the sack to form a pinch-top end; WO99/23000 PCT/AU98/00908 - 8 Figure 3 is a side elevation of a multi-wall sack in accordance with another embodiment of the invention; 5 Figure 4 is a perspective view of the sack shown in Figure 3 after the sack has been filled with a product and before the sack is folded at the open top end to form a pinched-top end; 10 Figure 5 is a perspective view of the sack shown in Figure 4 after the pinch-top end has been formed; Figures 6 to 9 are side elevations which illustrate the manufacture of a sack of a second embodiment 15 of the invention; and Figures 8 to 12 are side elevations of the sack shown in Figure 9 which illustrate the sequence of steps to open the outer bag and remove the inner sack. 20 Figures 1 and 2 show an embodiment of a multi wall sack 1 in an as-manufactured form. In this form the sack is essentially pressed flat. 25 With reference to Figures 1 and 2, the sack has inner and outer paper walls 21a, 21b that are adhered together, a block bottom end 2, and an open top end. The open top end is designed to form a pinch-top 30 end 28(Figure 2) which closes the sack 1. In this connection, the sack 1 includes a line of melt adhesive 26 on the inner faces of the walls 21a, 21b which extends across one side of the flattened sack 1 at the open top end. 35 It is noted that the present invention is not limited to forming a pinch-top end and extends to any WO99/23000 PCT/AU98/00908 -9 suitable closed top end. By way of example, the present invention extends to stitched/folded and folded/stitched top ends that are used on flour sacks. 5 As can best be seen in Figure lb, the as manufactured form of the sack 1 further includes a paper cover sheet 22 that is glued to the outer face of the wall 21a on the other side of the flattened sack 1 to the side on which the melt adhesive 26 is applied. The cover sheet 10 includes a tear strip 24 which divides the cover sheet into a lower cover sheet section 22a and an upper cover sheet section 22b. The lower section 22a is glued to the sack 1. The position of the cover sheet 22 is selected so 15 that in use, when the pinch-top end is formed by folding over the sections of the walls 21a, 21b at the open end of the sack 1 in the direction of the arrows shown in Figures 1 and lb, the line of melt adhesive 26 is brought into contact with and can adhere to the outer face of the upper 20 section 22b of the cover sheet 22 above the tear strip 24. Specifically, in use the sack 1 is closed by the steps of: 25 (i) filling the sack 1 with product so that the product pushes against the base of the sack and causes it to open flatten out and form a filled open sack with a block bottom as shown in Figure 1; 30 (ii) pressing flat the open end of the sack and folding over the sections of the walls 21a, 21b at the open end to bring the line of melt adhesive 26 into contact with the upper 35 section 22b of the cover sheet; and (iii)applying heat/pressure to the folded over WO99/23000 PCT/AU98/00908 - 10 area to activate the melt adhesive and adhere the inner faces of the walls 21a, 21b on that side of the flattened open end to the cover sheet. 5 As a consequence, as is shown in Figure 1c, the pinch-top end is formed and securely closes the open top end of the sack 1. 10 With this arrangement, the pinch-top may be opened by removing the tear strip 24 and pulling upwardly (as viewed in Figure ic) the upper section 22b of the cover sheet. This action unfolds the pinch-top end and allows direct access to the contents of the sack 1. 15 The embodiments of a multi-wall sack 1 shown in Figures 3 to 12 are formed with an inner pouch of polymeric material and an outer multi-layer bag formed from paper. The outer bag of the sack 1 may include either a block 20 bottom end 1, as illustrated in Figures 3-5, or a pinch bottom end 2, as illustrated in Figures 6-12. The embodiment of the sack 1 shown in Figures 3 to 5 is manufactured by: 25 (i) forming a sack having an internal pouch (not shown) and an outer bag, generally identified by the numeral 32, with a closed block bottom end 2 and an open top end 3 30 that is cut and folded to permit the formation of a pinch-top end; and (ii) adhering a tearing means that is in the form of a plastic ribbon 4 to the outer bag 32 at 35 the open upper end 3 so that the plastic ribbon 4 extends laterally of the open upper end of the outer bag to form the as- WO99/23000 PCT/AU98/00908 - 11 manufactured embodiment of the sack illustrated in Figure 3. In use, the embodiment of the sack 1 shown in 5 Figures 3 to 5 is closed by the steps of: (i) filling the inner bag of the sack 1 with product so that the product pushes against the base of the sack and causes it to open 10 out and form a filled open sack with a block bottom as illustrated in Figure 4; (ii) sealing the product in the inner bag by pressing together each inner bag along a 15 line extending across a section of the inner bag in the region of the open upper end of the sack and heat sealing the inner bag along the line; and 20 (iii)folding over the outer bag 32 at the open top end in the direction of the arrow in Figure 4 to form a pinch-top end over the plastic ribbon 4 and adhering the pinch-top end closed. 25 The embodiments of the closed sack, shown in Figures 2 and 5 have easy-open features at the top ends, which are simple to access, simple to operate, and simple to position during manufacture compared with the known 30 block-base tearing strip. Furthermore, the sacks in accordance with these embodiments are less costly to manufacture than known sacks with block-base tearing strips. 35 An alternative method of manufacturing a multi wall sack having an easy-open tearing feature in the top end of the sack as illustrated in Figures 6 to 9.

WO99/23000 PCT/AU98/00908 - 12 In accordance with this embodiment of the invention, the sack (a pinch-bottom sack) is filled with product to form a filled sack. The plastic ribbon 4 is 5 inserted during the closing step into the fold so that it will be retained in the pinch-top end when the pinch-top end is adhered closed. The inner pouch of product can be removed from 10 either of the bags by pulling on the plastic ribbon 4 to tear open the overlying layers of paper. The sack is then inverted to allow the inner pouch 5 to be removed. Many modifications can be made to the preferred 15 embodiments without departing from the spirit and scope of the invention.

Claims

1. A multi-wall sack which includes: 5 (a) a closed bottom end; and (b) an open top end that, when closed, forms a closed top end with a tearing means which facilitates easy opening of the sack. 10

2. The sack defined in claim 1 wherein the tearing means forms part of a cover sheet formed from paper or other suitable material. 15

3. The sack defined in claim 2 wherein the cover sheet is affixed to the sack in a location that is selected so that the tearing means becomes part of the closed top end as sections of the sack at the open top end are folded to form the closed end. 20

4. The sack defined in claim 3 wherein the sack is pre-cut and folded with a predetermined design at the open top end and the cover sheet is glued to an outer wall of the sack in a location that is selected so that the 25 tearing means can be part of the closed top end of the sack.

5. The sack defined in claim 1 wherein the tearing means forms part of a cover sheet that has a first 30 cover sheet section on one side of the tearing means and a second cover sheet section on the other side of the tearing means.

6. The sack defined in claim 5 wherein the 35 first section of the cover sheet is affixed, typically glued, to an outer wall of the sack in a position that is selected so that the top end of the sack can be folded over WO99/23000 PCT/AU98/00908 - 14 onto the second section of the cover sheet and affixed, typically by gluing and/or stitching and/or by any other suitable means to the second section in the process of forming the closed top end. 5

7. The sack defined in any one of the preceding claims includes: (i) an outer bag having the closed bottom end, 10 the open top end, and the tearing means; and (ii) an inner pouch that is adapted to be filled with product and sealed. 15

8. A method for forming a closed multi-wall sack which includes the steps of: (i) filling a product into the sack defined in any one of the preceding claims via the open 20 end of the sack; and (ii) folding the sack at the open end to form the closed top end with the tearing means which facilitates easy opening of the sack. 25

9 A method for manufacturing a multi-wall sack which includes the steps of: (i) forming a sack having a closed bottom end 30 and an open top end; and (ii) adhering or otherwise attaching a tearing means to the sack in a manner such that, when the sack is filled and a closed top end 35 is formed at the open top end, pulling the tearing means facilitates the easy-opening of the outer bag. WO99/23000 PCT/AU98/00908 - 15

10. The method defined in claim 9 wherein the closed top end is formed in step (ii) by folding the sack at the open top end. 5

11. The method defined in claim 9 or claim 10 wherein the open top end formed in step (i) is pre-cut and folded to permit the formation of the closed top end. 10

12. The method defined in any one of claims 9 to 11 wherein the tearing means is attached to the sack by adhering the tearing means to an outer wall of the sack at the open top end so that it extends laterally of the open top end. 15

13. The method defined in any one of claims 9 to 12 wherein the tearing means forms part of a cover sheet which includes a first cover sheet section on one side on the tearing means and a second cover sheet section on the 20 other side of the tearing means and the tearing means is affixed to the sack by adhering the first section to the outer wall of the sack.

14. A multi-wall sack filled with product, which 25 sack includes a closed bottom end and a closed top end with a tearing means that facilitates easy opening of the sack at the top end.