WO2000071420A1

WO2000071420A1 - Web structure and the production of a web structure

Info

Publication number: WO2000071420A1
Application number: PCT/ZA1999/000036
Authority: WO
Inventors: Nigel Ervine Claxton
Original assignee: Nigel Ervine Claxton
Priority date: 1999-05-24
Filing date: 1999-05-24
Publication date: 2000-11-30
Also published as: AU4103399A

Abstract

A method of producing a web (10) construction from which individual bags can be made is disclosed. A web (10) of synthetic platics material, which can be single ply or mult-ply, has a male rib (14) and a female rib (16) attached thereto, the ribs being spaced apart in the direction of the length of the web and running the full length of the web. The web is folded between the ribs so that the ribs are interengaged. At spaced locations along their length the ribs are heated, flattened and slit. This procedure results in a web structure that can subsequently be used on a form, fill and seal machine.

Description

WEB STRUCTURE AND THE PRODUCTION OF A WEB STRUCTURE

FIELD OF THE INVENTION

THIS INVENTION relates to a web structure, and to the production of a

web structure, for use on form-fill-seal machines in the packaging of products.

BACKGROUND TO THE INVENTION

Products such as vegetables, including cauliflower and broccoli florets,

peas and beans, grated cheese, bread-crumbs, prepared fish, chicken portions and

the like are commonly offered to the market in bags of synthetic plastics material.

The products may be pre-frozen before packaging, or frozen within the bags.

Automatic machines, known as form-fill-seal machines, are commonly

used for the task of forming a web of synthetic plastics material film into bags. Such

webs are commonly printed with graphics, pictures of the product, cooking

instructions and so on. The printed matter is repeated along the web at discrete

intervals. The machine feeds the product to be packed into the interior of each bag

after the bag has been partially formed, and thereafter seals the last border of the bag, generally the open mouth. By this action the machine closes the bag and parts

it off from the web of film. The machine positions the web so that the printed area is

properly positioned on the bag being formed.

For many products it is desired to provide the mouth of the bag with complementary releasably engageable ribs, thus permitting the user of the product

to access the interior of the bag, to remove some of the product, to re-close the bag

and render it substantially airtight, and return it to a refrigerator for storing before use

of the remainder of the product at a later date. The use of a re-closable bag is also

of advantage for packing other particulate material and dry products, such as

biscuits, breakfast foods, tablets or capsules, or wet products such as jams,

chutneys, spreads, dairy products, or liquid medicines and ointments.

In order to achieve this re-closable form of packaging, it is conventional

to provide the form-fill-seal machines with special apparatus or adaptations for

introducing strings, tapes or strips, which constitute releasable engagement means.

The apparatus guides and places the continuous ribs in the desired position and

provides the means of heat welding them to the bags shortly before or during their

formation. The technical complexity of this apparatus generally significantly

increases the cost of and the difficulty of running the form-fill-seal machines. It

should be noted that these machines are commonly used in a food factories,

bakeries and freezer or pharmaceutical plants, where the level of technical expertise

available is directed towards cooking, processing, blending and freezing, rather than

to the operation of machinery for handling the synthetic plastics material packaging

film. BRIEF DESCRIPTION OF THE INVENTION

According to one aspect of the present invention there is provided an

elongate web structure that can be used on a form, fill and seal machine, the web

structure including an elongate web of synthetic plastics material carrying elongate

complementary male and female ribs extending in the direction of the length of the

web, the web structure being folded longitudinally and the ribs being interengaged,

said ribs being flattened at spaced locations along their length.

If a printed web is used, the ribs are flattened at spaced locations

between the repeated print areas.

According to a further aspect of the present invention there is provided

a method of producing a web structure that can be used on a form, fill and seal

machine, the method comprising providing, on one surface of a web of synthetic

plastics material, complementary releasably engageable ribs which are elongate in

the direction of the length of the web, folding the web longitudinally and

interengaging the complementary ribs, and flattening the ribs at spaced locations

along their length to produce said web structure.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, and to show how

the same may be carried into effect, reference will now be made, by way of example,

to the accompanying drawings in which:- Figure 1 diagrammatically illustrates a web structure forming method

according to the present invention; and

Figure 2 diagrammatically illustrates bag forming, filling and sealing using the

web structure of Figure 1

DETAILED DESCRIPTION OF THE DRAWINGS

Referring firstly to Figure 1 , a web 10 of synthetic plastics material is

unreeled from a roll 12. A male rib 14 and a female rib 16 are extruded at zone A

through dies (not shown) located in juxtaposition to the web 10. The ribs 14 and 16

and the web 10 are of compatible material and hence the hot ribs melt the web 10

and bond to the web 10. The ribs are located on the web in asymmetrical off-medial

positions. In a simple form the female rib, in section, has a groove bounded by a

wall that is substantially more than 180 degrees in peripheral extent. The male rib,

in section, has an arrow head. When pressed against the female rib, the arrow head

opens up the entrance to the groove in the female rib and enters the groove, the

bounding walls of the groove snapping back to their undeformed condition behind

the arrow head and hence holding the rib in the groove.

The web is then folded longitudinally at zone B along the lines

designated 18J and 18.2. The line 18J is between the ribs so that the male rib 14

enters the groove of the female rib 16 thereby securing the juxtaposed parts of the

folded web to one another. The greater part of the width of the web 10 is folded

about the line 18.2 thus positioning the web edge 20J in register with, or approximately in register with, the other edge 20.2.

Pressure can be exerted to cause the male rib to enter the

complementary groove of the female rib.

At zone C, at intervals equal to one of the eventual dimensions of a

bag, the interengaged ribs 14, 16 are heated and then flattened as shown at 22.

Once the flattened areas have cooled, slits are provided to weaken the flattened

areas so that the folded web can then be fan folded into a box (not shown) for

storage.

The web is used by advancing it step wise over a cylindrical filling

mandrel 24 (Figure 2) down which the product to be packaged falls. The edges

20J , 20.2 of the web are welded to one another to form a vertical seal 26 thereby to

form the web into a tube.

The mandrel 24 terminates at zone D and, immediately below the

lower end of the mandrel, there is a pair of horizontally extending sealer bars which,

when temporarily clamped onto the tube, form upper and lower transverse seals S1

and S2. The upper seal S1 of the pair forms the lower closure of an upper bag B1

which has yet to be filled and the lower seal S2 of the pair closes off the upper end

of an already filled bag B2. Between the upper and lower seals S1 and S2 the tube

is cut through thereby to part-off the lower bag B2 from the lower end of the tube. Once the seals have been formed and the sealer bars have been moved apart, the

tube is advanced downwards, a measured quantity of product is fed into the partially

formed bag B1 which is now just below the lower end of the mandrel 24, and the

bars are moved together to form further upper and lower seals and to part-off the

now filled bag.

The web 10 can be a single ply film formed by extrusion or casting or a

multi-ply film produced by casting and laminating. The film can be opaque or

transparent, and can be printed on the outer face. Where the film is multi-plied, it

can be printed on one of its faces prior to lamination so that the printing is not on an

exposed face.

The ribs can, as described, be extruded directly onto the web so that

they melt the web and bond with it. Alternately the ribs may be extruded, stored by

reeling them up, and then used by feeding them into juxtaposition with the web with

the application of heat and pressure or the interposition of an adhesive.

A preferred form of the invention utilizes a single ply film of low density

polyethylene extruded with integral complementary ribs.

Instead of fan folding the web and packaging it in a box, the web can

be reeled e.g. on a spool or on a collapsible mandrel. A rib or line of weakness can be provided at 28 to facilitate opening of

the bag between the folded edge 18J and the inter-engaged ribs 14 and 16.

Depending on the type of bag required, the ribs 14, 16 can be

diametrically opposed to the seal 26 or in any other position between relatively close

to the seal 26 (as illustrated) and diametrically opposed to the seal.

Claims

CLAIMS:

1. An elongate web structure that can be used on a form, fill and seal

machine, the web structure including an elongate web (10) of synthetic plastics

material carrying elongate complementary releasably engageable ribs (14, 16)

extending in the direction of the length of the web, the web structure being folded

longitudinally and the ribs (14, 16) being interengaged, said ribs being flattened at spaced locations (22) along their length.

2. A web as claimed in claim 1 , wherein said ribs (14, 16), where they are

flattened, are slit along lines extending transverse to the direction in which the ribs

(14, 16) are elongate.

3. A method of producing a web structure that can be used on a form, fill

and seal machine, the method comprising providing, on one surface of a web of

synthetic plastics material, complementary male and female ribs (14, 16) which are

elongate in the direction of the length of the web, folding the web longitudinally and

interengaging the complementary ribs (14, 16), and flattening the ribs (14, 16) at

spaced locations (22) along their length to produce said web structure.

4. A method as claimed in claim 3 and including a step of heating the ribs

(14, 16) prior to flattening them.

5. A method as claimed in claim 3 or 4, and including slitting the flattened

ribs, the slits extending transversely to the direction in which the ribs are elongate.

6. A method as claimed in claim 5, wherein the flattened areas are slit so

that the slits extend across the web.