GB2311246A - A stack of bags formed by heat welding - Google Patents

Abstract

A stack of flexible plastic bags 1, the bags being suitable for storing organic produce such as lettuce, is formed by perforating an area of each bag to define at least one tear-off region 5,6 on the bags, aligning the perforated areas of all the bags in the stack, making a through-hole 7.8 within the/each perforated area and heat welding the bags together at the through-holes. Preferably a heated rod (23, Fig 4) is applied to the stack thus forming the through-holes and welding the bags together simultaneously. The tear-off region(s) may be semi-circular and extend to the top edge of each bag. Preferably a bag is dispensed by inserting a hand (13, Fig 3) between the back sheet 2 and the front sheet 4, and causing the bag both to open and be torn away from the stack at the perforated areas 5,6.

Description

PACKAGING This invention relates to packaging, for example to packaging for fresh produce. In particular, but not exclusively, it relates to packaging such as bags into which an individual item such as a lettuce is placed during harvesting and in which the lettuce is subsequently transported and sold. The invention is applicable to many other types of produce, however, in addition to lettuces.

The harvesting of vegetables such as iceberg lettuces is labour intensive. The process is still generally done by hand. In a common method, a lettuce picker carries with him a stack of thin, flexible, transparent plastics bags which are mounted on a metal wicket. The wicket comprises a pair of metal prongs which are mounted through holes in the stack of bags.

The wicket is fixed to the user's belt or clothing. As the user approaches a lettuce in the field, he inserts his hand into the first bag in the stack and pulls it off the wicket. The hand, inside the bag, is then placed over a lettuce and the lettuce is manually cut at its stalk.

The user then pulls the lettuce into the bag by inverting the bag so that the lettuce ends up inside the 'insideout' bag. The lettuce can then be transported and sold in the same bag. The bags may be microperforated to prolong the shelf life of the lettuce.

In order to keep a stack of bags on the wicket, it is necessary to insert grommets over the end of the wickets after the bags have been placed in position and the bags are then, in turn, torn off the wicket in use.

After use, the grommets are removed and are generally discarded into the fields. There is also a problem that the wickets themselves, comprising two prongs, usually of metal, are also often discarded into the field. Here, they pose a great problem for tractors and other vehicles and also represent a safety hazard.

The present invention arose in an attempt to provide an improved wicketted bag and method of manufacturing a wicketted bag.

According to the present invention there is provided apparatus for collecting and storing organic produce, comprising a portable stack of flexible bags of plastics material, each bag having at least one individually perforated area defining a tear-off region, the perforated areas of all the bags in the stack lying generally in register and a through-hole being provided through the stack within the or each tear-off region, the bags being heat-welded together at the through-hole.

Preferably, two through-holes are provided and tear-off regions and the bags are heat welded together at each of these through-holes.

The perforations in each individual bag are preferably arranged in a generally arcuate manner and may be in a semi-circular disposition extending around the through-hole, and portions perpendicular to the side edges of the bag extending from the ends of the semi-circular portion to the top of the bag.

By arranging for a stack of bags to be welded together, it may be stored and transported without the need for a separate wicket. A semi-permanent wicket arrangement may then be attached to a user's belt and a stack affixed when desired to this wicket. If the prongs of the wicket extend generally upwardly, or have an upwardly pointing end portion, then there will be no need for a separate grommet to retain the stack upon the wicket and thereby the problem of discarded grommets and wickets is overcome.

The perforations enable each bag in turn to be easily removed from the stack. The spacing of the perforations from the edge of the holes may be chosen to best facilitate this tearing. Typically, it may be 0.5 to 2cm, preferably about 1cam, but spacings less or greater than this may be used. The spacing may vary for different types of plastics materials.

According to the present invention in a further aspect there is provided a method of forming a stack of bags for use in collecting and storing fresh produce, comprising; forming a plurality of individual bags from a flexible plastics material, each having at least one perforated region defining a tear-off region; arranging the bags in a stack with the tear-off regions generally in register; forming a through-hole through the or each set of tear-off regions, the or each through-hole extending through the stack; and heat-welding the stack at the or each throughhole to secure the bags together at the or each tear-off region.

Preferably, the welding is done at the same time as forming the through-hole, by the use of a heated rod which is applied to the stack to form the holes and to heat the inner surface of the holes to weld the bags together.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which; Figure 1 shows a plastics bag according to the present invention; Figure 2 shows part of a stack of bags; Figure 3 shows a stack of bags in use with one being dispensed; and Figure 4 shows schematically an apparatus for producing a stack of bags.

Referring to Figure 1, each bag in a stack of bags for collecting, transporting and storing fresh produce is of thin flexible plastics material and is generally transparent so that the produce can be seen through it. Preferred plastics materials forming the bag are polyethylene and polypropylene. Other plastics materials may be used. Each bag 1 is formed from a continuous sheet of material and is folded to produce a back sheet 2, a gusset 3, and a front sheet 4. The front sheet 4 is shorter than the back sheet to enable the user to gain easy access to the bag with his hand and also to enable perforations and through-holes to be made in the back sheets of the bags as described below. The edges of the front and back sheets are welded together by heat.

Each individual bag is provided with two perforated sections 5, 6 forming tear-off regions which are desirably in semi-circular form but may be shaped otherwise as desired. Each bag is individually formed with the perforations and is then, during manufacture, placed on a stack with other bags in which all the tear-off regions are generally in register. Two through-holes 7, 8 are then made within the stack, generally within the tear-off regions and these through-holes are heated so as to heat weld the individual bags together at these through holes.

An additional hole 9 is shown in each bag, not within the area defined by the perforations. This hole is formed individually in each bag and is used solely for transporting the bags on a forming apparatus. After a stack has been manufactured, this hole is generally redundant.

Figure 2 shows part of a stack of bags and illustrates how the perforated areas 5 are arranged in register in the bags before a welded through-hole is made.

A heating element, being part of the hole forming means, or applied separately, causes the plastics material to melt around the hole and to solidify again after the heat is removed, causing fusing of the adjacent plastic bags at the hole and thus welding them together. The bags are not welded together at their topmost edge and the perforations extend to this edge. Thus, the frontmost bag in the stack may easily be removed from the stack by tearing it at the weakened regions (the "tear-off" region) defined by perforations 5 and 6 and this removes the bag, leaving only the tear-off region 5 still in contact with the adjacent bag of the stack.

Figure 3 shows a stack of bags, according to the present invention, in use. The welded through-holes 7 and 8 are used to locate the stack upon a wicket comprising two rods 11 which are connected at one end to a belt 12 or other article of clothing of a user. At their other end, the rods extend upwards so as to keep a stack of bags in place without requiring additional grommets.

Since the rods 11 are permanently or semi-permanently attached to a belt 12, then, when a stack of bags has run out, it is not necessary to discard a wicket but, instead, a new stack may be placed upon the same wicket. The user loads a stack of bags onto his wicket and goes to the field to pick lettuces or whatever produce is to be contained within the bags. To dispense a bag, he inserts a hand 13 into the gap between the front 4 and rear 2 of the frontmost bag. This serves to open the bag and also to pull the bag away from the stack by tearing it at the weakened portion defined by the perforations. The frontmost bag of Figure 3 is shown removed from the stack.

Note that the portions of the bag directly adjacent the through holes 7 and within the area defined by the perforated portions 5 and 6 remain on the stack. The bag may then be used as desired and the stack is ready for the next bag to be dispensed.

The number of bags in a stack is not crucial and may be determined by the capacity of the user, or the wicket. A stack may comprise, say 200 bags in one embodiment.

In some embodiments, it may only be necessary to provide one through-hole and tear-off region in each bag.

Alternatively, more than two through-holes and tear-off regions may be present.

Figure 4 shows schematically an apparatus for producing stacks of bags. In the process, flexible film, generally either polyethylene or polypropylene, is loaded from a reel 14. The film is pulled off the reel by a driven nip roller via a film accumulator/tensioner (not shown). It is pulled by pull to length feed rollers 15 which work in conjunction with a cut and weld sealing head 16 in conventional manner. The process is an intermittent one. During the "stop" part of the pull to length operation a hole is punched in the film by a stacking hole punch cylinder 17. This hole is to enable a bag to be stacked upon a stacking pin, and is redundant after manufacture of the bag. A shaped, serrated, blade 22 is then used to punch through the film in desired places, or two serrated blades may be applied simultaneously, to provide the serrated portions 5 and 6.

After the film has been drawn to length and formed in the shape of the bag it is cut and welded by the sealing head 16 and is then removed via one of a plurality of windmill vacuum take off and stacking arms 18. These are provided radially on a rotating body and a vacuum is applied so that a bag is attached to a respective arm by the vacuum. The bag is carried by the arm to a stacking pin 19 on an indexed conveying system 20. The indexed conveying system 20 remains static until a desired number of bags have been placed upon stacking pin 19 to form a stack of required size. The conveyor then indexes to a new position where an empty stacking pin is ready to accept bags. The stack of bags then proceeds to a "hot blocking" station 21. This comprises two high pressure air cylinders 22, each having a heated rod 23 at their tip and adapted to be pressed into the stack of bags. The rods 23 are heated (e.g. electrically heated) to a temperature sufficient to melt the plastics material of the bags and weld them together and are then pushed through the film in the centre of the serrated half circles to produce welded through-holes 7 and 8. The rods 23 are then raised and, when the next index of conveyor 20 occurs, the through-hole welded bags are ready to be removed from the stacking pin for use.

Preferably, more than one row of bags are prepared at the same time for ease of manufacture.

Usually, the bags will be micro-perforated.

That is, a plurality of small perforations are provided over substantially the entire surface of the bag which helps to prolong the shelf life of the product within the bag by allowing air to circulate. The step of microperforation is a well-known one and may be done either before or during the bag forming process.

Claims (13)

1. Apparatus for collecting and storing organic produce, comprising a portable stack of flexible bags of plastics material, each bag having at least one individually perforated area defining a tear-off region, the perforated areas of all the bags in the stack lying generally in register and a through-hole being provided through the stack within the or each tear-off portion, the bags being heat-welded together at the through-hole.

2. Apparatus as claimed in Claim 1, wherein two through-holes and tear-off regions are provided.

3. Apparatus as claimed in Claim 1 or Claim 2, wherein the perforations define at least a semi-circular tear-off region.

4. Apparatus as claimed in any one of the preceding claims, wherein the or each tear-off region extends to the top edge of the bag.

5. A method of forming a stack of bags for use in collecting and storing fresh produce, comprising; forming a plurality of individual bags from a flexible plastics material, each having at least one perforated region defining a tear-off region; arranging the bags in a stack with the tear-off regions generally in register; forming a through-hole through the or each set of tear-off regions, the or each through-hole extending through the stack; and heat-welding the stack at the or each throughhole to secure the bags together at the or each tear-off region.

6. A method as claimed in Claim 5, wherein two tear-off regions are formed in each bag.

7. A method as claimed in Claim 5 or Claim 6, wherein the or each tear-off region extends to the top edge of each bag.

8. A method as claimed in any one of Claims 5 to 7, wherein the heat welding and through-hole forming are done simultaneously.

9. A method as claimed in Claim 8, wherein a heated rod is used to form, and hot-weld, the or each throughhole.

10. A stack of plastics bags, when formed by a method as claimed in any of Claims 5 to 9.

11. A plastics bag substantially as hereinbefore described with reference to, and as illustrated by, the accompanying drawings.

12. A stack of plastics bags substantially as hereinbefore described with reference to, and as illustrated by, the accompanying drawings.

13. A method of forming plastics bags substantially as hereinbefore described with reference to, and as illustrated by, the accompanying drawings.