AU2005202091A1 - Improvements To Packages And Packaging Methods - Google Patents

Description

17-MRY-2005 15:43 A J PARK 64 4 472 3358 P.05/31 -1 Regulation 3.2

AUSTRALIA

PATENTS ACT, 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

Name of Applicant: Actual Inventor: Address for service in Australia: Invention Title: SEALED AIR (NEW ZEALAND) BARRY MULDER a New Zealand citizen of Cnr Avalon Drive and Foreman Road, Hamilton, New Zealand A J PARK, Level 11, 60 Marcus Clarke Street, Canberra ACT 2601, Australia Improvements To Packages And Packaging Methods The following statement is a full description of this invention, including the best method of performing it known to us.

387684.1DOC COMS ID No: SBMI-01249820 Received by IP Australia: Time 13:54 Date 2005-05-17 17-MAY-2005 15:44 A J PARK 17-PY-200 1544 3 PRK64 4 472 3358 P.06/31 In 2 FIELD OF THE INVENTION The invention relates to a package which is formed by joining together parts of a tearable sheet material along one or more join lines and which is openable by tearing the sheet material along one or more tear lines each starting at a line of weakness and extending across one or more of the join lines. The invention also relates to blank for fanning such a package, and a method of o forming such a blank.

BAKRON

It is known to form packages or bags from a tearable sheet material and particularly from flat tubular plastics film material, by heat sealing across the end(s) of the tubular material. The packages are opened subsequently by cutting or tearing the package walls. To facilitate the start of the tearing, a line of weakness may be provided in the sheet material during manufiloture of the package, or an initial cut may be made using a cuffing tool, such as a knife or scissors, for example by an end user when about to open the package.

SUMMARY OF INVENT[ON In broad terms in one aspect the invention may be said to be a package having a wall made from a tearable sheet material the wall having two wall portions which are joined together along a boundary line between the package wall and a peripheral marginal portion of the sheet material, two portions of the boundary line forming an acute angle which embraces a part of the marginal portion, the marginal portion being at least partially severed along a sever line which does not 2$ intersect the boundary line, and one end of the sever line lying between the two boundary tine portions forming the acute angle.

The sever line preferably extends to an external peripheral edge of the marginal portion, and may be a series of separate perforations or a single cut line, and each perforation or cut may extend either partially or completely through the thickness of the marginal portion.

233310-1 COMS ID No: SBMI-01249820 Received by IP Australia: Time 13:54 Date 2005-05-17 17-MAY-2005 15:44 A J PARK 17-RY-00515:4 P 5 PRK64 4 472 3358 P.07/31 3 The wall portions may be sealed together along the boundary line, and the sheet material may be Ct a plastics filmn in which case the wall portions may be heat sealed together along the boundary line.

In one preferred option the package is formed from a flattened tubular blank of material such as plastics film material the tubular blank providing two panels joined together at opposed edges o by a pair of respective inwardly folded gussets, one end of the package being formed by sealing N each panel to each gusset along a respective sealing line extending inwardly from a respective N one of the opposed panel edges, at least one of the sealing lines having an approximate z-form to o 10 define the acute angle which embraces the sever line in the marginal portion of the sheet Ci material.

Preferably each of the two sealing lines sealing one of the two panels to the two gussets has an approximate z-orm defining an acute angle embracing a sever line in the marginal portion of the sheet material. Alternatively, each of the two scaling lines sealing one of the two gussets to the two panels has an approximate z-form defining an acute angle embracing a sever line in the marginal portion of the sheet material.

In broad terms in another aspect the invention may be said to be a tubular blank for forming a package, the blank being made of a tearable sheet material and having two panel portions joined together at opposed edges by a pair of respective inwardly folded gusset portions, each panel portion being sealed to each gusset along a respective line extending inwardly from a respective one of the opposed edges to define a marginal portion at one end of the blank, at least one of the sealing lines having an approximate z-form defining an acute angle which embraces a sever line in the marginal end portion of the blank.

In broad terms in another aspect the invention may be said to be a method of forming a blank for a package, the method including the steps of forming a flattened elongate tube of a sheet material, the tube having two fiat outer panel portions joined together at opposed side edges by an intermediate pair of respective inwardly folded gusset portions, each panel portion being sealed to each gusset along a respective sealing line extending inwardly froma a respective one of the opposed side edges, each sealing line defining part of a boundary between a respective panel 203310-1 COMS ID No: SBMI-01 249820 Received by IP Australia: Time 13:54 Date 2005-05-17 17-MAY-2005 15:45 A J PARK 17-Y-205 5:4 flJ PRK64 4 472 3358 P.09/31 Ic) 4 portion and a marginal end portion of the blank, at least one of the sealing lines having an approximate z-formn defining an acute angle which embraces a sever line in the marginal end portion of the blank.

Preferably each of the two sealing lines sealing one of the two panels to the two gussets is in an approximate z-form including an acute angle embracing a sever line in the marginal portion of o the sheet material. Alternatively, each of the two sealing lines sealing one of the two gussets to o the two panels is in an approximate z-fonn including an acute angle embracing a sever line in the marginal portion of the sheet material.

00 The term 'comprising' as used in this specification and claims means 'consisting at least in part of', that is to say when interpreting statements in this specification and claims which include that term, the features, prefaced by that ternm in each statement, all need to be present but other features can also be present.

The invention may fur-ther be said to consist in any alternative combination of parts or features mentioned herein or shown in the accompanying drawings. Known equivalents of these parts or features which are not expressly set out are nevertheless deemed to be included.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is fur-ther described with reference to the accompanying drawings, by way of example and without intending to be limiting, wherein: Figure 1 shows an isometric view of an end portion of a flattened tubular blank for forming into a package, Figure 2 shows an isomnetric view of an end portion of a package formed by expanding the blank shown in part in Figure 1, Figure 3 shows one corner of a package of the invention in more detail, Figures 4-6 show sequential steps in tearing open a package of the invention such as the pac;kage of Figures 1& 2, after use of the package to contain a product, to open the package, Figure 7 shows an isometric view of an end portion of an alternative flattened tubular blank for forming into a package, 283310-1 COMS ID No: SBMI-01249820 Received by IP Australia: Time 13:54 Date 2005-05-17 1?-MAY-2005 15:45 A J PARK 17-PY-00515:5 P3 PRK64 4 472 3358 P.09/31 Figure 8 shows an isometric view of an end portion of a package Contned by expanding the blank shown in part in Figure 3, and Figure 9 shows an isometric view of an end portion of a package formed by expanding another embodiment of a tubular blank.

DETAILED DESCRIPTION OF PREFERRED FORM o Referring to Figure 1, a flattened tubular blank is made from a flexible and tearable sheet material. Typically the sheet material is a tubular plastics film material. The blank may be o 0 expanded into a package as will be described in futher deail below.

The blank has two wall panels 1, 2 each having two opposed side edges 3, 4, 5 and 6.

Respective pairs of these opposed side edges are joined together by two respective inwardly folded gussets 7 and 8.

In the flattened form of the blank, as shown in Figure 1, the gussets are intermediate, ic they lie between, the two wall panels. One gusset 7 has two folds 11, 12 which lie respectively adjacent the two panels 1, 2. The other gusset 8 has two folds 13, 14 which lie respectively adjacent the two panels 1, 2. It is to be noted that in Figure 1 the blank is shown with an exaggerated separation between the panels and folds which are shown as slightly expanded for the purposes of explanation.

A seal line 15 extends transversely across the blank to sea], the two panels 1, 2 together, at least at a mid-portion 16 of the blank between the two gussets 7, 8. The seal line 15 preferably extends right across the blank from one of the outer side edges 3, 5 to the opposite outer side edges 4, 6 of the two panels, as shown in Figure 1. Where the seal line 15 crosses the two gussets, both folds of each gusset are preferably sealed together and to each of the two panels.

One wall panel 1 is sealed along respective generally diagonal seal lines 17, 18 to the adjacent folds 11, 13 of the two gussets. The other wall panel 2 is similarly staled along respective generally diagonal seal lines 17A, I18A (seen in Figure 2 but largely hidden from view in Figure 1) to the adjacent folds 12, 14 of the gussets. 'These generally diagonal seal lines 17, 18, 17A, 283310-1 COMS ID No: SBMI-01249820 Received by IP Australia: Time 13:54 Date 2005-05-17 17-MAY-2005 15:45 A J PARK 17-m-205 j:45 J PRK64 4 472 3358 P.1I0/31 6 18SA, extend from respective outer side edges 3, 4, 5 and 6 of the panels 1, 2 to intersect with the Ct inner edge of the gussets 7, 8 and are preferably set at about 45 degrees to these edges which are parallel to the axis of the tubular form.

The generally diagonal seal lines 17, 17A, 18, 18A and the mid-portion of the transverse seal line together seal the end of the blank and define boundary lines between, on one hand, respective o substantially triangular corner parts 19, 19A, 20, 20A and an end strip 21 of a marginal end o portion of the blank and, on the other hand, major portions of the panels and gussets which form N the package walls when the blank is expanded, o 1 00 NA Although in preferred embodiments, the blank and package are made from a flexible plastics film or sheet material and the seal lines are seals made by heat sealing the plastics material, the seal lines can be replaced by other sealing methods, for example by glue lines, and the blank and package may be formed from paper alternatively, or alternatively again layers of paper and plastics film material.

One embodiment of the package is shown in Figure 2 in an expanded configuration. Two sever lines 22, 23 are respectively formed in the corner parts 19, 20 of the marginal end portion and extend inwardly from near respective outer side edges 3, 4 of one panel 1. The generally diagonal seal lines 17, 18S follow respective z-forxns 24, 25, each z-form path having two sharp turns in opposite directions, just inboard of the outer side edges 3, 4 of the panel. Each z-form 24, 25 in the seal lines 17, 18 forms an acute angle that opens toward the respective panel edge 3, 4. Each sever line 22, 23 is formed in the part of the marginal end portion embraced by the respective acute angle. The sever lines 22, 23 do not cross the seal lines. Figure 3 shows one corner of the package in more detail.

The sever lines 22, 23 are provided as lines of weakness for facilitating the initiation of a tear line in the sheet material when opening the package. The sever lines may be made completely or partially through the thickness of the combined layers of panels and gusset folds. Each sever line may be a single cut, or a row of multiple cuts or perforations. As shown in the figures, the sever lines may not extend right to the outer edge of the panel. However, in an alternative embodiment (not shown), the sever lines may extend right to the outer edge of the panel.

283310-1 COMS ID No: SBMI-01249820 Received by IP Australia: Time (I-tm) 13:54 Date 2005-05-17 17-MAY-2005 15:46 A J PARK 17-PY-00515:6 PJ PRK64 4 472 3358 P.11/31 CA Figure 2 shows one end of a package formed when the blank, shown in part in Figure 1, is expanded- Corresponding features in Figure 1 and 2 are labelled alike. The blank is expanded by drawing the two panels 1, 2 apart while simultaneously unfolding the two gussets 7, 8 to form a substantially euboid package. Parts of the panels and gussets, between the diagonal seal lines 17, 17A, 18, 1iSA and imaginary lines joining the outer ends 26, 26A, 27, 27A of the generally diagonal seal lines, form an end wall 28 of the package. The remaining parts of the panels 1, 2, shown ini Figure 1 beyond, ic above, the imaginary line joining the outer ends 26, 27 of the N generally diagonal seal lines 17, 18, form a first pair of opposite side walls of the package. The NA remaining parts of the gussets 7, 8, beyond, ie above, the imaginary line joining the outer ends o 10 26, 27 of the generally diagonal seal lines 17, 18 in Figure 1, form a second pair of opposite side walls of the package, the second pair of opposite side walls being generally perpendicular to the first pair of opposed side walls when the package is in the expanded configuration.

The corner parts 19, 19A, 20, 20A of the marginal end portion lie flat against the end wall 28 of the expanded package. The end strip 21 is shown in Figure 2 as outstanding from the end wall 28 of the package, but may lie flat against the end wall 28.

The end wall 28 closes and seals the end of the package. This end wall may be manually opened, without the intervention of tools, 'by grasping an outer corner of each one of the triangular corner parts 19, 20, defined by the z-lines 17, 18, and pulling the outer corners away from the remainder of the package to open the sever lines 22. 23 as shown in Figure 4 and, by tearing the sheet material, to extend each opened sever line into a tear line. Further pulling of the corner extends the tear lines into the acute angles of the z-forms 24, 25 and across the seal lines 17, 18. The acute angles steer the tear lines into the intersection of the z-lines at the acute angles to ensure that the sever lines, which are initially provided outside the seal lines, cut across the seal lines and continue inside the seal lines to rupture the sealed end wall 28 of the package. In this way the triangular corner parts 19, 20 and the associated generally diagonal seal lines 17, 18 are parted from the major remaining portion of the package end wall 28, as shown for one corner part in Figure By pulling further on the triangular corner parts, the resulting tear lines can be extended toward one another, across the package end wall 28, to be joined up to one another and thereby to 293310-1 COMS ID No: SBMI-01249820 Received by IP Australia: Time 13:54 Date 2005-05-17 17-MAY-2005 15:46 A J PARK 17-PY-200 1:46Fl PFRK64 4 472 3358 P.12/31 8 Cl separate the marginal end portion and the associated seal lines 15, 17, 18, from an end panel Ct of the package end wall 28. The end panel 30 can then be stripped back toward the opposite end of the package to progressively tear open the wall panel 1, as shown in Figure 6.

A second embodiment of the current invention is shown in Figure 7 in a flattened configuration and in Figure 8 in an expanded configuration. Features corresponding to those already described are given corresponding labels. As in the previously-described embodiment shown in Figures 1 Cl and 2, the flattened tubular blank is made from a flexible and tearable sheet material and has two Nl wall panels 1, 2 each having two opposed side edges 3, 4, 5, 6, respective pairs of which are O) 10 joined together by two inwardly folded gussets 7 and 8.

Figure 8 shows one end of a package formed when the blank, shown in part in Figure 3, is expanded. Corresponding features in Figure 3 and 4 are labelled alike. Two sever lines 23, 23A are respectively formed in the corner parts 20, 20A of the marginal end portion and extend inwardly from near respective outer side edges 4, 6 at the junctions between one of the gussets S and the two panels 1, 2. The generally diagonal seal lines 18, I SA follow respective z-form each z-form having two shar turns in opposite directions, just inboard of the outer side edges 4, 6. Each z-forsn 25, 25A in the seal lines 18, 18A formas an acute angle that opens toward the respective panel edge 4, 6. Each sever line 23, 23A is formed in the part of7 the marginal end portion embraced by the respective acute angle. The sever-lines 23, 23A do not cross the seal lines.

As in the previously-described embodiment the end wall 28 closes and seals the end of the package. This end wall may be manually opened, without the intervention of tools, by grasping an outer corner of each one of the two triangular corner parts 20, 20A formed respectively by the two side panels 1, 2 and the one gusset 8, and pulling the outer corners away from the remainder of the package to open the sever lines 23, 23A and, by tearing the sheet material, to extend each opened sever line into a tear line.

301 Further pulling of the corners extends the tear lines into the acute angles of the z-forms 25, and across the seal lines 18, ISA. The acute angles steer the tear lines into the intersection of the z-forms at the acute angles to ensure that the sever lines, which are initially provided outside the 283310-1 COMS ID No: SBMI-01249820 Received by IP Australia: lime 13:54 Date 2005-05-17 17-MAY-2005 15:47 A J PARK 17-RY-005 j5:7 R 5 RRK64 4 472 3358 P.13/31 seal lines, cut across the seal lines and continue inside the seal lines to rupture the sealed end wall 28 of the package. In this way the triangular corner parts 20, 20A and the associated generally diagonal seal limes 18, 18A are parted from the major remaining portion of the package end wall 28.

By pulling further on the triangular corner parts, the resulting tear lines can be extended toward o one another, across the package end wall 28, to be joined up to one another and thereby to o separate the marginal end portion and the associated seal lines 18, ISA, from a generally N triangular end panel 32 (seen largely obscured in Figure 8) of the package end wall 28. The end o 10 panel 32 can then be stripped back toward the opposite end of the package to progressively tear Ni open the side gusset 8.

A third embodiment of the current invention is shown in Figure 9 in an expanded configuration.

Features corresponding to those already described above are indicated by the same reference numerals. As in the previously-described embodiments, the flattened tubular blank is made from a flexible and tearable sheet material and has two wall panels 1, 2 each having two opposed side edges 3, 4, 5, 6, respective pairs of which are joined together by two inwardly folded gussets 7 and s.

Figure 9 shows one end of a package formed when a blank, similar to that shown in Figure 1, is expanded. Four sever lines 22, 22A, 23, 23A are respectively formed in the four corner parts 19, 19A, 20, 20A of the marginal end portion and exend inwardly from near respective outer side edges 3, 5, 4, 6 at the junctions between the two gussets 7, 8 and the two panels 1, 2. The generally diagonal seal lines 17, 17A4, 18, ISA follow respective z-paths 24, 24Ak 25, 25A, each z-patb having two sharp turns in opposite directions, just inboard of the respective outer side edges 3, 5, 4, 6. Each zigzag 24, 24A, 25, 25A in the seal lines 17, 1 7A, 18, I SA forms an acute angle that opens toward the respective panel edge 3, 5, 4, 6. Each sever line 22, 22A, 23, 23A is formed in the part of the marginal end portion embraced by the respective acute angle. The sever lines 22, 22A, 23, 23A4 do not cross the scat lines.

The end wall 28 closes and seals the end of the package. This end wall may be manually opened, without the intervention of tools, by grasping an outer corner of one of the triangular 283310-1 COMS ID No: SBMI-01249820 Received by IP Australia: Time 13:54 Date 2005-05-17 17-MAY-2005 15:47 A J PARK 17-Y-205 5:4 FtJ PPK64 4 472 3358 P.14/31 corner parts 19, 19A, 20, 20A and pulling the outer corner away from the remainder of the package to open the respective sever line 22, 22A, 23, 23A and, by tearing the sheet material, to extend the opened sever line into a tear line.

Further pulling of the corner extends the tear line into the acute angle of the z-fonn, 24, 24A, and across the seal line. The acute angle steers the tear line into the intersection of the zlines at the acute angle to ensure that the sever line, which is initially provided outside the seal o line, cuts across the seal line and continues inside the seal line to rupture the sealed end wall 28 of the package. In this way the triangular corner part 19, 1 9A, 20, 20A and the associated o 10 generally diagonal seal line 17, 17A, 18, 18A is parted from the major remaining portion of the Ci package end wall 28.

This operation may be repeated for each of the remaining three corner parts and the resulting tears joined up to one another to separate the marginal end portion and all associated seal lines from the remainder of the package. Upon completion of this opening operation the end wall 28 of the package is reduced to four separate flaps each of which can be readily folded outward to provide a completely open end allowing easy access to, or removal of, the package contents.

Where the bottom of the package is fully opened as described above, the package may be simply lifted clear away from the package contents. This ability to fully open the package end wall and easily separate the package from its contents without the use of tools is particularly useful where the package contains a single solid block that has substantially the same overall dimensions as the expanded package.

The flaps can be stripped back toward the opposite end of the package to progressively tear open the wall panels 1, 2 or the side gussets 7, 8.

The preferred embodiments of packages described above are packages with gusseted sides but the invention may also be applied to non-gusseted packages such as bags formed by sealing across a tubular material by providing a z-forni boundary line or seal at one or more corners of such a bag adjacent a sealed end of the bag.

283310-1 COMS ID No: SBMI-01249820 Received by IP Australia: Time 13:54 Date 2005-05-17 17-MY-2005 15:48 A J PARK 64 4 472 3358 P.15/31 11

C

The foregoing describes the invention including a preferred thereof so alterations and t modifications as will be obvious to those skilled in the art are intended to be incorporated within the scope hereof as defined in the accompanying claims.

-2833 -i 283310-1 COMS ID No: SBMI-01249820 Received by IP Australia: Time 13:54 Date 2005-05-17

Claims (2)

17-MAY-2005 15:48 A J PARK 17-Y-205 5:4 flJ PRK64 4 472 3358 P.16/31 Ic) 12 c~KI CLAIMS 1. A package having a wall made from a tearable sheet material, the wall having two wall portions which are joined together along a boundary line between the package wall and a peripheral marginal portion of the sheet material, two portions of the boundary line fonming an acute angle which embraces a part of the marginal portion, the marginal portion being at least partially severed along a sever line which does not intersect the boundary line, and one end of NA the sever line lying between the two boundary line portions forming the acute angle. o 10 2. A package according claim I wherein said package wall comprises two opposing panels N- joined on either side of said panels at opposed edges by inwardly folded gussets, and wherein said boundary line extends inwardly from a said opposed panel edge. 3. A package according to claim 1 wherein said package wall comprises two opposing panels joined on either side of said panels at opposed edges by inwardly folded gussets, and wherein a said boundary line extends inwardly from two of said opposed panel edgcs. 4. A package according claim 1 wherein said package wall comprises two opposing panels joined on either side of said panels at opposed edges by inwardly folded gussets, and wherein a said boundary line extends inrwardly from each of said opposed panel edges. A package according to any one of claims 2 to 4 wherein said package is closed at least at one end and said boundary line(s) extend(s) inwardly from said opposed panel edge(s) adjacent said closed end of the package. 6. A package according to any one of claims I to 4 wherein said two opposing panels and inwardly folded gussets are parts of a tube of a sheet material forming said package. 7. A package according to any one of claims 1 to 6 wherein the wall portions are sealed together along the boundary line(s).

293310-1 COMS ID No: SBMI-01 249820 Received by IP Australia: Time (I-tm) 13:54 Date 2005-05-17 17-MAY-2005 15:48 A J PPIRK 17-MY-205 5:4 fl5 PlRK64 4 472 3358 P.17/31 13 8. A package according to any one of claims i to 6 wherein said sheet material is a plastics sheet Ct material and the wall portions are heat sealed together along the boundary line(s). 9. A package according to any one of claims I to 8 wherein the boundary line(s) follow(s) a respective z-form. including said acute angle embracing a sever line in the marginal portion(s) of the sheet material. A package according to any one of claims 1 to 9 wherein each sever line comprise(s) a series (N of separate perforations or a single cut line which extends to an external peripheral edge of a o 10 respective marginal portion. 11, A package according to any one of claims 1 to 10 wherein each sever line extents fully through the thickness of a respective marginal portion. 12. A package having a wall made from a tearable sheet material, the wall having two wall portions which are joined together along a boundary line between the package wall and a peripheral marginal portion of the sheet material, two portions of the boundary line forming an angle which embraces a part of the marginal portion, the marginal portion including a line of weakness which does not intersect the boundary line, and one end of the sever line lying between the two boundary line portions forming the said angle. 13. A package according to claim 12 wherein said package wail comprises two opposing panels joined on either side of said panels at opposed edges by inwardly folded gussets, and wherein a said boundary line extends inwardly from at least two of said opposed panel edges. 14. A package according to any one of claims I to 13 wherein said sheet material is a plastics sheet material and the wall portions are heat sealed together along the boundary line(s). A blank for a package having a wall made from a tearable sheet material, the wall having two wall portions which are joined together along a boundary line between the package wall and a peripheral marginal portion of the sheet material, two portions of the boundary line forming an acute angle which embraces a part of the marginal portion, the marginal portion being at least 283310-I COMS ID No: SBMI-01249820 Received by IP Australia: Time 13:54 Date 2005-05-17 17-MAY-2005 15:49 A J PARK 17-RY-005 15:9 f 3 PRK64 4 472 3358 P.183/31 14 partially severed along a sever line which does not intersect the boundary line, and one end of the sever line lying between the two boundary line portions forming the acute angle. 16. A blank according claim iS comprising two opposing panels joined at least at one end and joined on either side of said panels at opposed edges by inwardly folded gussets, and wherein said boundary line extends inwardly from a said opposed panel edge. 17. A blank according to claimi 5 comprising two opposing panels joined on either side of said panels at opposed edges by inwardly folded gussets, and wherein a said boundary line extends o 10 inwardly from two of said opposed panel edges. 18. A blank according claim 15 comprising two opposing panels joined on either side of said panels at opposed edges by inwardly folded gussets, and wherein a said boundary line extends inwardly from each of said opposed panel edges. 19. A blank according to any one of claims 15 to 18 wherein said blank is closed at least at one end and said boundary line(s) extend(s) inwardly from said opposed panel edge(s) adjacent said closed end. 20, A blank according to any one of claims 15 to 19 wherein the wall portions are sealed together along the boundary line(s). 21. A blank according to any one of claims 15 to 19 wherein said sheet material is a plastics sheet material and the wall portions are heat sealed together along the boundary line(s). 22. A blank according to any one of claims 15 to 21 wherein the boundary line(s) follow(s) a respective z-form including said acute angle embracing a sever line in the marginal portion(s) of the sheet material. 23. A blank according to any one of claims 15 to 22 wherein each sever line comprises a series of separate perforations or a single cut line which extends to an external peripheral edge of a respective marginal portion. 283310-1 COMS ID No: SBMI-01249820 Received by IP Australia: Time 13:54 Date 2005-05-17 i7-MAY-2005 15:49 A J PARK 17-MY-205 5:4 RIJ PIRK64 4 472 3358 P.19/31 Ct 24. A blank according to any one of claims 15 to 23 wherein each sever line extends fully through the thickness of a respective marginal portion. 25. A tubular blank for forming a package, the blank being made -of a tearable plastics fim material and having two panel portions joined together at opposed edges by a pair of respective o inwardly folded gusset portions, each panel portion being sealed to each gusset along a o respective line extending inwardly from a respective one of the opposed edges to define a ~fl marginal portion at one end of the blank, at least one of the sealing lines having a z-form o 10 including an acute angle which embraces a sever line in the marginal end portion of the blank. 26. A blank according to claim 25 wherein a said boundary line extends inwardly frm two of said opposed panel edges. 27. A blank according claim 25 wherein a said boundary line extends inwardly from each of said opposed panel edges. 28. A method of forming a blank for a package, the method including the steps of forming a flattened elongate tube of plastics film, the tube having two flat outer panel portions joined together at opposed side edges by an intermediate pair of respective inwardly folded gusset portions, each panel portion being heat sealed to each gusset along a respective sealing line extending inwardly from a respective one of the opposed side edges. each sealing line defining part of a boundary between a respective panel portion and a marginal end portion of the blank, at least one of the sealing lines having an approximate z-fonn including an acute angle which embraces a sever line in the marginal end portion of the blank. 29. A method according to claim 28 including forming a said sealing line extending inwardly from two of said opposed panel edges. 30. A method according claim 28 including forming a said sealing line extending inwardly from each of said opposed panel edges. 293310-1 COMS ID No: SBMI-O1 249820 Received by IP Australia: Time 13:54 Date 2005-05-17 17-MAY-2005 15:49 A J PARK 17-Y-205 5:4 I PRK64 4 472 3358 P.20/31 16 3 1. A method according to any one of claims 28 to 30 including forming the package so that the package is closed at least at one end and said sealing line(s) extend(s) inwardly from said opposed panel edge(s) adjacent said closed end of the package. 32. A method according to any one of claims 28 to 31 including forming each sever line(s) as a series of separate perforations or a single cut line which extends to an external peripheral edge of o a respective marginal portion. Cl 33. A method according to any one of claims 28 to 31 including forming each sever line(s) fully 0 10 trough the thickness of a respective marginal portion. 2&3310-1 COMS ID No: SBMI-O1 249820 Received by IP Australia: lime 13:54 Date 2005-05-17