GB2034278A

GB2034278A - Closing Large Sacks

Info

Publication number: GB2034278A
Application number: GB7936575A
Authority: GB
Original assignee: Windmoeller and Hoelscher KG
Current assignee: Windmoeller and Hoelscher KG
Priority date: 1978-11-15
Filing date: 1979-10-22
Publication date: 1980-06-04
Also published as: SU816395A3; FI792695A; JPS55109617A; ES253552Y; AT383324B; ATA559779A; IT7926226A0; FR2441546A1; IT1123438B; FR2441546B1; ES253552U; BR7907364A; GB2034278B

Abstract

After filling, the open end of a thermoplastic sack is closed by gathering it into zig-zag folding (1) which is compressed between apertured jaws (3, 4). Heated needles (7) insertable through the jaw apertures (5) pierce the compressed zig-zag folding and cause the individual folds to be welded to each other adjacent the piercings to secure the closure against springing open after the jaws (3, 4) are removed. <IMAGE>

Description

SPECIFICATION Method and Apparatus for Closing Large Sacks The invention relates to a method of closing large sacks of thermoplastic material, wherein the upper empty end of the sack is erected substantially vertically, laid into a zig-zag fold, pulled together and secured against springing open, as well as to an apparatus for performing this method.

In a method of this kind known from DE-OS 26 52 010, the end of the sack that has been laid into a zig-zag fold and pulled together into a frill is held together by a closure member, for example a ring clip. The application of special closure members for closing the large sacks complicates the method of closing and, for automatic execution of the method, gives rise to additional mechanical expenditure.

It is therefore the problem of the present invention to provide a closure for large sacks, with which the sack end that has been pulled together to a frill in zig-zag fashion can be fixed in the pulled-together condition in a simple manner and without special closure members and secured aginst springing open.

According to the invention, this problem is solved in a method of the aforementioned kind in that a pulled-together zig-zag fold of the sack end is fixed by piercing with warm needles.

From US-PS 29 73 797 and 30 21 947, it is for example known to form blocks of bags by connecting stacks of superposed bags of plastics film in a manner such that one margin of the stack is pierced with warm needles and cause them to be welded together in the pierced zone.

Large sacks of the kind here in question are usually made from a circular weave of stretched plastics tapes or strips that have been coated with plastics material on the outside or laminated with plastics film and they have a capacity of 1 ton and more. Such large sacks can be lifted and transported in a simple manner in that the sack end which has been gathered into a zig-zag fold and flattened is flung about the clamping bars of lifting tackle. The large sacks closed by the method of the invention have a cleanly folded flattened end so that manipulation of the sacks is facilitated when they are transported and rearranged.

Another requirement of a good sack closure is that no moisture can penetrate into the sack. A development of the invention therefore provides that the pierced holes are axially compressed between jaws which are movable towards each other until the plastics material plasticized by the needles has solidified sufficiently. By reason of this compression, the as yet plastic plastics material enters the holes produced by the needles so that these become completely filled and closed by the plastics material.

The upper margin of the sack end can, before the zig-zag folding, be sealed against moisture or folded over one or more times.

A sealed closure for the sack end can also be achieved in that the pulled-together zig-zag fold is folded over one or more times before it is fixed or the end edges of the sack pulled together into a zig-zag fold are fused together under heat.

According to another embodiment of the invention, it is provided that, for the purpose of fixing, a transverse weld seam is applied through all layers of the sack end which has been pulled together and possibly folded over one or more times.

An apparatus for performing the method according to the invention is characterised according to the invention in that provision is made for clamping jaws which compress the pulled-together zig-zag fold between each other and comprise aligned holes, and a bar provided in comb-like manner with a row of needles which are insertable in the holes.

One example of the invention will now be described in more detail with reference to the drawing, wherein.~ Figs. 1.1 to 1.6 are diagrammatic representations of the as yet flat end of the sack; Figs. 2.1 to 2.6 are perspective views of the sack ends of Figs. 1.1 to 1.6 pulled together into a zig-zag fold; Figs. 3.1 to 3.6 are perspective views of the sack ends of Figs. 2.1 to 2.6 pulled together by zig-zag folding after they have been fixed by welding, and Fig. 4 is a horizontal section through the welding apparatus for the sack end that has been gathered in zig-zag fashion.

The sack end which has been pulled flat and is shown in Fig. 1.1 has been closed in that the upper margin 1 1 of the sack end 10 is folded onto an adjoining side wall. The sack end prepared in this manner is, as shown in Fig. 2.1, laid into a zig-zag fold 1.1. This zig-zag fold 1.1 is secured against springing open and fixed by rod-like welds 12 in a manner shown in Fig. 3.1. The rod-like welds 12 are produced in that the holes pierced with warm needles are pressed together between jaws before solidification of the plastics material that has been plasticized by the needles.

The sack closure shown in Figs. 1.2, 2.2 and 3.2 differs from the sack closure of Figs. 1.1,2.1 and 3.1 in that the upper margin 13 of the sack end 10 has been folded over twice before formation of the zig-zag fold 1.2.

In the sack closure according to Figs. 1.3, 2.3 and 3.3, the sack end 10 which has been pulled flat is first laid into a zig-zag fold 1.3 and fixing of the zig-zag fold by welds 15 passing therethrough in rod form is effected only after the upper margin 14 of the zig-zag fold 1.3 has been folded over onto an adjoining sack wall.

The sack closure according to Figs. 1.4, 2.4 and 3.4 differs from the one just described only in that the upper margin 1 6 of the zig-zag fold 1.4 is folded over twice before welding.

In the sack closure illustrated in Figs. 1.5, 2.5 and 3.5, the sack end 10 which has been pulled flat is laid into a zig-zag fold 1.5 and the end edges of the zig-zag fold are fused together by radiated heat. The fusing 17 provides a sack closure which is sealed against moisture.

The sack closure shown in Figs. 1.6, 2.6 and 3.6 corresponds to that of Figs. 1.3, 2.3 and 3.3 and differs therefrom only in that fixing of the folded-over margin of the zig-zag fold 1.6 is effected by a transverse weld seam 18 instead of rod-like welds 15.

Fig. 4 diagrammatically illustrates an apparatus with which the rod-like welding of the zig-zag folding can be performed. The end of the large sack that has been pulled flat is laid into a zig-zag fold 1 in known manner and compressed between pressure jaws 3, 4 of flat steel.

The pressure jaws 3, 4 are provided with aligned bores 5. Three needles 7 arranged on a horizontally displaceable guided bar 6 are horizontally insertable in the aligned bores 5 of the pressure jaws 3, 4 to pierce the zig-zag fold 1 clamped between the pressure jaws. For the purpose of fixing the zig-zag fold in the clamped position, the needles are heated before insertion in the bores 5 so that they weld the zig-zag fold together in the piercing zone.

Claims

1. A method of closing large sacks of thermoplastic material, wherein the upper empty end of the sack is erected substantially vertically, laid into a zig-zag fold, pulled together and secured against springing open, characterised in that the pulled-together zig-zag fold (1) of the sack end is fixed by piercing with warm needles (7).

2. A method according to claim 1, characterised in that the pierced holes are axially compressed between jaws which are movable towards each other until the plastics material plasticized by the needles (7) has solidifed sufficiently.

3. A method according to claim 1 or claim 2, characterised in that the upper margin (10) of the sack end is folded over one or more times before zig-zag folding (1.1,1.2).

4. A method according to claim 1 or claim 2, characterised in that the pulled-together zig-zag fold (1.3, 1.4, 1.6) is folded over one or more times before it is fixed.

5. A method according to one of claims 1 or 2 to 4, characterised in that the end edges of the sack pulled together into a zig-zag fold are fused together under heat.

6. A method according to one of claims 1 or 3 to 5, characterised in that, for the purpose of fixing, a transverse weld seam (18) is applied through all layers of the sack end which has been pulled together and possibly folded over one or more times.

7. Apparatus for performing the method of one of claims 1 to 5, characterised by the provision of clamping jaws (3, 4) which compress the pulledtogether zig-zag fold (1) between each other and comprise aligned holes (5), and a bar (6) provided in comb-like manner with a row of needles (7) which are insertable in the holes (5).

8. Apparatus according to claim 7, characterised in that the bar (6) has three needles (7).

9. A large sack having one end laid into a zigzag fold and pulled together to form a frill, characterised in that the zig-zag fold is held together by welds passing therethrough in rodlike manner.

10. A method of closing sacks of thermoplastics material substantially as hereinbefore described with reference to the accompanying drawings.

11. Apparatus for closing sacks of thermoplastics material constructed and arranged substantially as hereinbefore described and shown in Figure 4 of the accompanying drawings.