GB2170474A - Tubular packaging film - Google Patents

Abstract

Continuous plastics tubular film has spaced transverse slits each extending around up to one half of the circumference of the tube. The slits may be formed by passing the tube around a support member 12 Figure 1, having two sets of rollers on offset axes one set co-operating with rollers 16a 16b through one wall 10a of the tubing and the other set co-operating with a second pair of rollers via the lower wall 10b of the tubing. The wall 10b is slit by a moving blade at 18 and the wall 10b may be perforated by a wheel at 15. The walls may subsequently be united by a seal adjacent each slit to form a string of bags. Alternatively, as shown in Figure 3, the slit tube is guided around a mandrel 30 which opens each slit in turn thus permitting articles to be inserted into the tube at 31. Beyond the mandrel the tube is sealed at 32 and 34 and cut at 33 to produce separate packages. <IMAGE>

Description

SPECIFICATION Improvements relating to tubular film and to packaging apparatus capable of utilising such film This invention relates to flexible materials in tubular form, such as tubular plastics film. Other materials to which the invention could be applied are wdven materials in tubular form, e.g. polypropylene, for example as used for sacks. Throughout this specification the term "film" embraces any continuous flexible material. This invention also re latest packaging apparatus capable of utilising such film as a packaging material.

Tubular film, particularly of plastics material, has grown in popularity for use in packaging, and predetermined lengths can be cut from the tube as one step in forming either bags, or as an all-round wrapping when pre-packing goods for sale.

Often the tubular film is supplied by the manufacturers in lay-flat form, that is it lies flat such that the tube effectively consists of two superimposed sheets each of width substantially half the circumference of the tube, the sheets being joined at their longitudinal edges.

According to one feature of my invention, I provide tubular lay-flat film and preferably lay-flat film, for use in packaging, with a plurality of axially spaced transverse slits, each of said slits having a transverse length not more than half the tubular circumference.

The two sheets forming the tubular film may be sealed together along transverse lines, each line being adjacent and parallel to each of the slits. The unslit sheet of the lay-flat tubular film may have a transverse line of weakness in alignment with and parallel to the slit in the other sheet. The line of weakness which is to aid rupture of the sheet at that point may comprise a row of perforations.

The slit film according to the invention, and preferably a slit film provided with both seal lines and weakened lines as described above, may be supplied on a roll for use as a packaging material in retail outlets, such as supermarkets, as will be described in more detail hereinafter.

According to another feature of my invention I provide a method of making tubular film slit at spaced axial positions along the tube comprising the steps of feeding tubular film so that it passes around a backing plate and cutting through the film over a transverse width not more than half the circumference of the tube using the backing plate as a support.

According to yet another feature of my invention I provide apparatus for manufacturing tubular film slit at spaced axial positions along the length of the tube comprising film feed means for unslit tubular film, support means for at least part of the inner surface of the film, cutting means operable transversely over not more than half the circumference of the tube, and means to move the cutting means relative to the support means to cut film therebetween.

The support means preferably comprising a flat plate, and in this case preferably includes a first roller rotatably mounted in a cut-out in the plate for location within the film tube, and a plurality of supporting rollers for location outside the tube which contact and support the first roller so that the tube wall passes between the first roller and the support roller. The first roller is preferably divided axially into a plurality of separate sections free to rotate in opposite directions, alternate sections being coaxial and the axes of adjacent sections being offset from one another.

The cutting means itself can be mounted for reciprocating movement towards and away from the support means, or it can be mounted transversely if for instance the film is half against relative axial movement during cutting. The support means may be readily detachable so that it can be replaced by other support means to enable the machine to handle films of differing widths.

According to yet another feature of my invention I provide packaging apparatus comprising supply means for lay-flat tube slit at spaced axial positions along the tube over a transverse width not more than half the circumference of the tube, separating means to space a circumferential portion of the tube adjacent to a slit from the remainder of that circumference so that the slit forms an opening through which a product can be fed into the tube, sealing means to seal said tube at positions adjacent the slits to encapsulate the product within the tube between adjacent seals, and cutting means to separate sections of tube containing a product from the remainder of the tube.

The invention will be further described by way of example with reference to the accompanying drawings, in which: Figure 1 is a schematic section showing apparatus according to the invention for slitting tubular film; Figure 2 is a part view along the line A-A; Figure 3 is a schematic view of a bag-filling apparatus according to the invention and incorporating a film-slitting apparatus essentially as shown in Figure 1; Figure 4 is a cross-sectional view of tubular film being slotted according to the invention, and heat welded; Figure 5 is a schematic view corresponding to a portion of Figure 4 and showing the cut and partially sealed film prior to the filling operation.

Figure 6 is a perspective view of the slitting machine of our invention; and Figure 7 shows in schematic side elevation a roll of slit and sealed tubular plastics film according to the invention, e.g. for use in packaging items in shops or supermarkets.

In the film-slitting apparatus of Figure 1 film 10 is fed from left to right in the direction of the arrow 11. Film 10 is lay-flat form having upper and lower sheets 10a and 10b respectively. Sheets 10a and 10b are integrally connected to their longitudinally extending edges, so that film 10 is tubular.

Located between sheets 10a and 10b is support member 12 carried by guide roller 13. The roller 13 is journalled in a slot provided in a flat separator plate 12 which has forwardly and rearwardly ex tending and generally flat portions 12a and 12b, sheets 10a and 10b pass to either side of the backing plate 12 and guide roller 13 so that they are spaced apart. Transverse slitting of the lower sheet 10b as seen in this view occurs at position 14, the slitting blade reciprocating traverse to the sheet 10b. In more detail the slitting blade (not shown) is mounted on a cable or chain between spaced-apart spools. Simultaneous rotation of the spools in the same direction moves the blade across the sheet to be slit. The next slit is formed by rotating the spools in the opposite direction so that the blade returns across the sheet to its original position.

The blade runs in a groove 18 in the separator plate 12.

Guide roller 13 is positioned by four locating rollers 16, two of the locating rollers 16a, 16b being removably mounted in slots 30 in side plates 31 of the slitting machine, to allow guide roller 13 and separator plate 12 to be introduced between the leading edges of sheets 10a, 10b; the locating rollers 16 can each have a fluted periphery if desired, as seen in Figure 6. The guide rollers 16, other than 16a and 16b are mounted normally nonremovably in side plates 31.

Support rollers 17 resist angular movement of the separator plate 12 to avoid this backing plate swinging and possibly over-stressing sheets 10a and 10b.

Arrow 15 shows the location of an optional perforating wheel which runs back and forth across the sheet parallel to the blade running in the groove 18. The perforating wheel (not shown) runs behind the groove 18 and thus runs on a raised track which preferably has a flat top. Thus the backing plate acts as a support for the film during both the slitting and the optional perforating steps.

Arrow 19 shows the possible direction of approach of a heat sealing or welding mechanism. These mechanisms are provided when a roll of packaging bags are to be made, the heat-seaiing mechanism sealing the sheets 10a and 10b across their full width, to form a closed end for a bag; the perforating mechanism permitting a pre-determined length dependent upon the size of bag required to be detached from the remainder of film 10 as and when required. Clearly the timing and positioning of the various operations will be selected having regard to the forward speed of film 10 and the desired bag size.

In an alternative application, the heat sealing is effected at the axial position and in the approach direction of arrow 20.

As best seen in Figure 2 guide roller 13 has a central shaft 21 to the ends of which support member 12 is attached. Eccentric bushes 22 are non-rotatably secured to shaft 21 at axially-spaced positions, by cross-pins 23. Mounted on shaft 21 and on bushes 22 are rotatable sleeves 24, adjacent sleeves 24 projecting alternatively to a greater and lesser external radius as viewed in Figure 2, so that alternate sleeves contact sheets 10, 10b respectively, and rotate in one angular direction in contact with sheets 10a and in the opposite angular direction in contact with sheet 10b. Adjacent sleeves thus rotate in opposite angular directions when film 10 is moved forwardly.

In the bag-filling apparatus of the invention shown diagrammatically in Figure 3, film 10 is fed upwards, sheets 10a and 10b passing to either side of support member 12 and the associated separator plate 12 and to either side of guide roller 13.

In this embodiment it is sheet 10b which again is slit at arrow 27, conveniently by a slitting mechanism as described above; arrow 28 shows the location of a perforating mechanism. Film 10, slotted and perforated, then passes over stationary guide 29, though in an alternative embodiment a guide having a peripheral velocity equal to the forward movement of film 10 could be used. Sheets 10a and 10b are separated by mandrel 30. As each slit in sheet 10b comes into alignment with mandrel opening 31, the product to be packaged, which may be a singie article or a plurality of individual articles such as sweets, is fed into opening 31 and so between separated sheets 10a and 10b. Because sheets 10a and 10b are sealed at position 32, to form a closed end bag, the product is contained.

The joined sheets 10a and 10b can becut by conventional means at 33 to separate the filled package from the film 10, as an alternative to tearing at the perforations added at 28; cutting at 33 could for instance be used in automatic pre-packaging operations whereas tearing at the perforations would usually be by retail customers.

In alternative embodiments, the package will be further heat-sealed at 34.

Figure 5 shows in more detail film 10 passing the stationary guide 29 of Figure 3, anti-clockwise as seen in this view. Sheets 10a and 10b have been heat-sealed together at 35, and sheet 10b slit at 36.

Figure 6 is a perspective view showing the slitting apparatus depicted in Figure 1.

Figure 7 shows schematically how slot and sealed tubular film according to the invention may be presented in roll form for use as packaging in retail outlets such as supermarkets.

A roll 40 of slit, sealed and perforated lay-flat plastics tubing according to the invention is supported on a hollow cylindrical core 41 and this is mounted on a holder bracket 42 in known manner for free rotation, so that the tubing can be progressively drawn from the top of the roll 40 by rotating the roll in an anticlockwise direction as shown by the arrow 43. The tubing 44 comprises superimposed sheets 10a, 10b as described above, and is separated into individual compartments or bags by spaced transverse heat seals 45 sealing the two sheets together across their width. Adjacent and downstream of each heat-seal in the direction of unrolling, sheet 10b has a transverse slit 46, and opposite each slit at 47, sheet 10a has a transverse row of perforations providing a tear line. In use, a shop assistant or customer who wishes to package an item in a plastics bag first pulls on the free end of the roll to unwind a convenient length of the tubing 44, opens out the slit 46 in the outermost compartment or bag, inserts the item to be packaged as shown by arrow A, and then tears this outermost bag off the roll at the perforation 47a.

The item has therefore been conveniently packaged into a plastics bag.

Claims (13)

1. Tubular film for use in packaging, with a plurality of axially spaced transverse slits, each of said slits having a transverse length not more than half the tubular circumference.

2. Tubular film according to claim 1, which is lay-flat film.

3. Tubular film according to claim 1 or 2, wherein the two sheets are sealed together along transverse lines, each line being adjacent and parallel to a respective slit.

4. Tubular film according to claim 3, wherein the unslit sheet has a transverse line of weakness in alignment with and parallel to the slit in the other sheet.

5. A method of making tubular film slit at spaced axial positions along the tube comprising the steps of feeding tubular film so that it passes around a backing plate and cutting through the film over a transverse width not more than half the circumference of the tube using the backing plate as a support.

6. Apparatus for manufacturing tubular film slit at spaced axial positions along the length of the tube, comprising film feed means for unslit tubular film, support means for at least part of the inner surface of the film, cutting means operable transversely over not more than half the circumference of the tube, and means to move the cutting means relative to the support means to cut film therebetween.

7. Apparatus according to claim 6, wherein the support means comprises a flat plate.

8. Apparatus according to claim 7, wherein the support means also includes a first roller rotatably mounted in a cut-out in the plate for location within the film tube, and a plurality of supporting rollers for location outside the tube which contact and support the first roller so that the tube wall passes between the first roller and the support roller.

9. Apparatus according to claim 8, wherein the first roller is divided axially into a plurality of separate sections free to rotate in opposite directions, alternate sections being coaxial and the axes of adjacent sections being offset from one another.

10. Apparatus according to any of claims 5 to 9, wherein is mounted for reciprocating movement towards and away from the support means.

11. Apparatus according to any of claims 5 to 9, wherein the cutting means is mounted transversely and the film is held against relative axial movement during cutting.

12. Apparatus according to any of claims 5 to 11, wherein the support means is readily detachable so that it can be replaced by other support means to enable the machine to handle films of differing widths.

13. Packaging apparatus comprising supply means for lay-flat tube slit at spaced axial positions along the tube over a transverse width not more than half the circumference of the tube, separating means to space a circumferential portion of the tube adjacent to a slit from the remainder of that circumference so that the slit forms an opening through which a product can be fed into the tube, sealing means to seal said tube at positions adjacent to the slits to encapsulate the product within the tube between adjacent seals, and cutting means to separate sections of the tube containing a product from the remainder of the tube.