Packaging Apparatus and Method of Making Packages

Abstract

A packaging apparatus including a cutting device, the cutting device comprising an elongate holder, an elongate knife having an elongate cutting edge, and a heat seal device located on the elongate holder on opposed sides of the knife, the heat seal device comprising a pair of elongate pressure strips projecting outwardly from the elongate holder, each pressure strip extending along a respective side of the knife, wherein each pressure strip comprises an elongate bar mounted for sliding movement in a respective slot in the elongate holder, the sliding movement varying the distance an outer edge of the elongate bar projects from the elongate holder, and a biasing element within the respective slot, the biasing element engaging an inner edge of the elongate bar and arranged to bias the elongate bar outwardly of the slot. A packaging method is also disclosed.

Description

The present invention relates to packaging apparatus and to a method of making packages.

It is known to employ vertical form, fill, and seal (VFFS) packaging apparatus to produce packages, in the form of bags, pillow packs or pouches of products, such as snack foods. A tubular film, having been formed from a roll of packaging film of heat sealable plastic material which has been longitudinally sealed, is fed intermittently through a jaw device. The film forms a flattened tube at the jaw device. The jaw device forms a pair of vertically spaced hermetic heat seals extending transversely across the tube, the seals being located between vertically adjacent packages. The jaw device also cuts through a middle portion, located between the hermetic seals, extending across the tube which separates a lower sealed package containing the packaged product from an upper unsealed package.

In this way, a lower hermetic seal forms the upper seal of the lower package, and an upper hermetic seal forms the lower seal of the upper package. The upper package is then filled with product, the tube is advanced downwardly through the jaw device, and then the cycle is repeated when the upper edge of the upper package, and the lower edge of the following package, is disposed between the jaws of the jaw device.

There are several known principles of operation of such jaws of a vertical, form, fill, and seal (VFFS) packaging apparatus. One class of jaw devices utilises a continuous rotary jaw motion, which is illustrated with reference to FIG. 1.

Referring to FIG. 1, in such a jaw device 10, a knife 12 is disposed on one side of the flattened, longitudinally sealed tube 14, and a hardened reaction pad or anvil 16 is disposed on the opposite side of the tube 14, with the tube located between the knife 12 and anvil 16. The knife 12 is urged under pressure against the anvil 16 to cut through the film of the tube 14, trapped between the knife blade 18 and the anvil 16, by a pressured crush-cutting action.

The knife 12 and the anvil 16 both rotate in phase and in opposite rotational directions as shown by the arrows in FIG. 1 so that the knife 12 and the anvil 16 engage so as to cut packaging film material, in the form of a flattened tube as described below, centrally located therebetween.

The knife 12 is rotated about an axis X orthogonal to the longitudinal direction L of the tube 14 and parallel to the surface of the anvil 16 and the cutting edge 20 of the blade 18. Although not illustrated, plural knives 12 may be mounted about a common shaft disposed along axis X and mutually angularly separated, so that for each cycle of rotation of the common shaft, plural cuts are made by respective knives 12. Plural anvils 16 would be correspondingly provided.

The elongate knife 12 is mounted in an elongate holder 21 in the form of a mounting block. The lower portion of the knife 12 is received in an elongate recess 30 in the elongate holder 21 and securely fixed therein. The cutting action of the knife 12 is progressive, so that during the continuous rotation of the knife 12 in holder 21, initially one longitudinal end of the knife 12 first contacts the anvil 16 and subsequently the contact point therebetween progresses along the cutting edge 20 of the blade 18 towards the other longitudinal end of the knife 12. To achieve such progressive cutting action, the cutting edge 20 of the blade 18 is ground at an angle α to the plane of the knife 12. Typically, the angle α is 2 degrees. Accordingly, as the rotary contact progresses, the whole width of the flattened tube 14 is not cut through simultaneously, but instead point contact of the knife blade 18 transitions across the tube 14 as the rotary action progresses. The progressive cutting action is similar to that of a rotary blade of a cylinder lawnmower.

Elongate heat seal devices 26, 28 are disposed either in the anvil 16 and/or in the elongate holder 21 for the knife so that transverse hermetic seals 32, 34 are formed in the flattened tube 14 on opposite sides of the transverse cut 36 made by the knife 12. The heat seal devices 26, 28 may take a number of forms, typically transversely extending mating ridges and grooves formed in the opposed surfaces of the anvil 16 and the elongate holder 21.

The knife 12 and the heat seal devices 26, 28 are mutually parallel and also parallel to the sides 40, 42 of the elongate holder 21 which is orthogonal to the longitudinal direction L. Thus, when the longitudinal direction is conventionally oriented vertically, the knife 12 and the heat seal devices 26, 28 are horizontal.

The known rotary jaw device provides an effective heat sealing and cutting mechanism, which reliably forms hermetic seals at the opposite ends of a package and with adjacent packages being reliably separated by the action of the knife.

However, there is an increasing need for product manufacturers to reduce the amount of packaging material associated with their products, and in particular not only to reduce packaging costs but also to reduce the carbon footprint, expressed in tonnes of carbon dioxide emissions, of the packaging material and/or the packaging operation.

The known rotary jaw device forms hermetic seals which are rather wide, in the longitudinal direction of the tube, and also there is material wastage between adjacent hermetic seals, because a portion of the film material of the tube which is cut through by the rotary cutting action of the knife must be provided between the adjacent hermetic seals.

Accordingly, there is a need in the art for a rotary jaw device for a packaging apparatus, and to a method of making packages, which can permit the amount of packaging material to be reduced, together with the associated packaging costs and carbon footprint, i.e. carbon dioxide emissions, while still achieving effective hermetic seals at the opposite ends of a package.

The present invention aims at least partially to meet this need.

The present invention accordingly provides a packaging apparatus adapted for forming pillow packs of film material, the apparatus including a cutting device, the cutting device comprising an elongate holder, an elongate knife having an elongate cutting edge, and a heat seal device located on the elongate holder on opposed sides of the knife, the heat seal device comprising a pair of elongate pressure strips projecting outwardly from the elongate holder, each pressure strip extending along a respective side of the knife, wherein each pressure strip comprises an elongate bar mounted for sliding movement in a respective slot in the elongate holder, the sliding movement varying the distance an outer edge of the elongate bar projects from the elongate holder, and a biasing element within the respective slot, the biasing element engaging an inner edge of the elongate bar and arranged to bias the elongate bar outwardly of the slot, wherein the elongate bar is rigid and has a thickness of from 1.5 to 2.5 mm, and wherein the biasing element comprises an elongate strip of elastic resilient material which has an upper surface which mates with the inner edge of the elongate bar, and an anvil mounted in opposition to the elongate holder, so that the elongate holder and the anvil comprise opposed jaws of a jaw device, the anvil having a reaction surface for the cutting action of the knife and for the pressure strips.

Preferably, the elongate bar is composed of a metal, such as stainless steel.

Optionally, the outer edge of the elongate bar has a convex cross-section. Typically, the convex cross-section is arcuate, and optionally the arcuate cross-section has a radius of from 0.75 to 1.25 mm.

Preferably, the elongate bar is captive in the elongate holder. Optionally, the elongate bar has a first coupling element located at each longitudinal end of the elongate bar which couples with a second coupling element located at each longitudinal end of the slot, the first and second coupling elements retaining the elongate bar captive in the elongate holder. Preferably, the first coupling element comprises a male element and the second coupling element comprises a channel extending along the sliding direction of the elongate bar.

The elastic resilient material preferably comprises an elastomeric polymer. Typically, the elongate strip of elastic resilient material has a circular cross-section.

In one embodiment, the elongate knife is mounted on and projects outwardly from the elongate holder.

In one preferred embodiment, the holder is mounted on a mounting support adapted to rotate about a rotational axis, the knife is planar, the elongate cutting edge is parallel to the plane of the knife and the plane of the knife is inclined to the rotational axis. Preferably, the cutting edge extends along a centre of the knife. Typically, the knife has a thickness of from 1 to 3 mm.

Preferably, the holder is mounted on a mounting support adapted to rotate about a rotational axis, the elongate cutting edge is parallel to the plane of the knife and the plane of the knife is inclined to the rotational axis and the knife and anvil are mutually arranged so that as the knife rotates by rotation of the elongate holder, the cutting edge of the knife progressively contacts the reaction surface with a contact point therebetween moving longitudinally along the cutting edge.

Preferably, the anvil comprises a heater for heating the reaction surface.

The packaging apparatus of the invention may be particularly adapted for forming pillow packs of film material.

The present invention further provides a method of making packages, wherein the packages are pillow packs of film material, the method comprising the steps of:

• • a. providing a flattened tube of packaging film;
  • b. providing a cutting device mounted in opposition to an anvil so that the cutting device and the anvil comprise opposed jaws of a jaw device, the cutting device having an elongate knife with an elongate cutting edge, a pair of elongate pressure strips projecting outwardly from an elongate holder, each pressure strip extending along a respective side of the knife, wherein each pressure strip comprises an elongate bar mounted for sliding movement in a respective slot in the elongate holder, the sliding movement varying the distance an outer edge of the elongate bar projects from the elongate holder, and a respective biasing element within the slot, the biasing element engaging an inner edge of the elongate bar and arranged to bias the elongate bar outwardly of the slot, wherein the biasing element comprises an elongate strip of elastic resilient material, wherein the elongate bar is rigid and has a thickness of from 1.5 to 2.5 mm, and the anvil having a reaction surface for the cutting action of the knife and for the pressure strips, at least the reaction surface for the pressure strips being heated;
  • c. locating a portion of the flattened tube between the cutting device and the anvil;
  • d. relatively moving the cutting device and the anvil together;
  • e. cutting through the portion of the flattened tube between the cutting device and the reaction surface of the anvil by the cutting action of the knife; and
  • f. pressing the pressure strips against the heated reaction surface thereby simultaneously heat sealing together opposed sides of the flattened tube to form an elongate transverse hermetic seal in the vicinity of each cut end of the flattened tube, during the pressing action each elongate bar sliding rearwardly in the respective slot against the bias of the biasing element within the slot.

Typically, the cut edge of each package is 0.5 to 1.5 mm from the hermetic seal, more typically about 1 mm from the hermetic seal. Typically, the hermetic seal has a width of from 1 to 4 mm, more typically from 1 to 2 mm.

Preferably, the packages are pillow packs of film material, and typically the packages contain snack food.

Embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings, in which:

FIG. 1 is a schematic side view of known rotary jaw device for a packaging apparatus;

FIG. 2 is a schematic section through a side of a rotary jaw device for a packaging apparatus in accordance with an embodiment of the present invention;

FIG. 3 is an enlarged schematic section through the cutting and heat sealing assembly and opposed anvil used in the rotary jaw device of FIG. 2;

FIG. 4 is a schematic section on line A-A through the cutting and heat sealing assembly of FIG. 3;

FIG. 5 is a schematic plan view of the cutting and heat sealing assembly of FIG. 3; and

FIG. 6 is a schematic side view of a pair of packages produced by the rotary jaw device of FIG. 2.

FIGS. 2 to 5 illustrate a preferred embodiment of a rotary jaw device for a packaging apparatus according to the present invention, which has a continuous rotary jaw motion. The device is structured and operates in a manner similar to that of the known device of FIG. 1 except that the structure of the mounting block, the knife and the heat sealing devices is significantly modified to achieve the desired reduction in the amount of packaging material required to form packages. The cutting and heat sealing assembly and the anvil both rotate in phase and in opposite rotational directions as shown by the arrows in FIG. 2 so that the knife and the anvil engage so as to cut the film material centrally located therebetween. The film material is intermittently advanced in the longitudinal direction L.

In the jaw device 110 of FIG. 2, a knife 112 is disposed in a cutting and heat sealing assembly 111 on one side of a flattened, longitudinally sealed tube 114 of packaging film to form packages 115, similar to the known device of FIG. 1. One package 115 is shown in FIG. 2. A hardened reaction pad or anvil 116 is disposed on the opposite side of the tube 114, with the tube 114 located between the knife 112 and anvil 116. The knife 112 is urged under pressure against the anvil 116 to cut through the film of the tube 114, trapped between the knife blade 118 and the anvil 116, by a pressured crush-cutting action.

In the illustrated embodiment, the elongate knife 112 is mounted on and projects outwardly from the elongate holder.

The knife 112 is rotated about an axis X orthogonal to the longitudinal direction L of the tube 114 and parallel to the surface of the anvil 116 and the cutting edge 120 of the blade 118. The cutting and heat sealing assembly 111 holding the knife 112 is mounted about the axis, for example to a shaft disposed along the axis, by a mounting support 111. The anvil 116 is similarly is rotated about an axis Y.

As shown particularly in FIGS. 3 and 5, the elongate knife 112 is mounted in an elongate holder 121 in the form of a mounting block. For clarity of illustration, some dimensions and angles are exaggerated in FIGS. 3 and 4. Typically, the width of the knife (dimension a in FIGS. 3 and 5) is from 1 to 3 mm, most typically 2 mm, and the cutting edge 120 is centrally located along the entire length of the blade 118 of the knife 112.

In the illustrated embodiment, the elongate knife 112 is mounted on and projects outwardly from the elongate holder 121. However, in alternative embodiments other knife mounting and cutting arrangements may be used. For example, the knife may be disposed in a gap between two holder parts and reciprocally slidable, forwardly and rearwardly, in the gap, the sliding motion being between a forward projecting cutting position and a rearward recessed non-cutting position. Known form, fill and seal machines have a variety of different cutter arrangements and the heat seal device employed in the present invention has utility with these various machines.

The lower portion of the knife 112 is received in an elongate recess 130 in the elongate holder 121 and securely fixed therein. The cutting action of the knife 112 is progressive, so that initially one longitudinal end 122 of the knife 112 first contacts the anvil 116 and subsequently the contact point progresses along the cutting edge 120 of the blade 118 towards the other longitudinal end 124 of the knife 112.

To achieve such progressive cutting action, as shown in FIGS. 3 and 5, the knife 112 is mounted at an angle β to the longitudinal direction of the elongate holder 121. The cutting edge 120 of the blade 118 is ground so as to be parallel to the plane of the knife 112. Typically, the angle β is 2 degrees.

A heat seal device is located on the elongate holder 121 on opposed sides of the knife 112. The heat seal device comprises a pair of elongate pressure strips 126, 128.

The elongate pressure strips 126, 128 are parallel to the knife 112, and accordingly the elongate pressure strips 126, 128 are also mounted at an angle β to the longitudinal direction of the elongate holder 121. The knife 112 and the pressure strips 126, 128 are therefore inclined at the angle β to the longitudinal sides of the elongate holder 121 which is orthogonal to the longitudinal direction L. Thus, when the longitudinal direction is oriented vertically, knife 112 and the pressure strips 126, 128 inclined at the angle β to the horizontal.

The knife 112 and the pressure strips 126, 128 stand proud of the mounting surface 138 of the elongate holder 121. Each pressure strip 126, 128 extends along a respective side of the knife 112. Each pressure strip 126, 128 comprises an elongate bar mounted for outward or inward sliding movement in a slot 127, 129 in the elongate holder 121. The outward (indicated by the direction O in FIG. 4) or inward (indicated by the direction I in FIG. 4) sliding movement can vary the distance an outer edge 131 of the elongate bar 126, 128 projects from the elongate holder 121. Each elongate bar 126, 128 is rigid, and typically is composed of a metal such as stainless steel. The elongate bar 126, 128 has a thickness of from 1.5 to 2.5 mm. The outer edge 131 of the elongate bar 126, 128 has a convex cross-section, which is typically arcuate, for example the arcuate cross-section having a radius of from 0.75 to 1.25 mm.

In the illustrated embodiment, the anvil 116 has a front surface 160 formed with a pair of recessed channels 162, 164. Each channel 162, 164 is aligned with and complementarily shaped with the outer edge 131 of a respective elongate bar 126, 128. Accordingly, as described below, during the heat sealing action the plural layers of the film material to be sealed are pushed into the channels 162, 164 by the respective elongate bars 126, 128, which are at least partly received in the channels 162, 164, to form an arcuate hermetic seal.

Alternatively, the front surface 160 of the anvil 116 may be planar.

A biasing element 133, 135 is located within the slot 127, 129 and engages an inner edge 137, 139 of the elongate bar 126, 128. The biasing element 133, 135 comprises an elongate strip of elastic resilient material, such as an elastomeric polymer. The elongate strip 133, 135 of elastic resilient material has an upper surface 147, 149 which mates with the inner edge 137, 139 of the elongate bar 126, 128. Preferably, the elongate strip 133, 135 of elastic resilient material has a circular cross-section.

The biasing element 133, 135 biases the elongate bar 126, 128 outwardly of the slot 127, 129. However, additionally each elongate bar 126, 128 is captive in the respective slot 127, 129 in the elongate holder 121. The elongate bar 126, 128 has a first coupling element 141, 142 located at each longitudinal end 143, 145 of the elongate bar 126, 128 which couples with a respective second coupling element 146, 148 located at each longitudinal end 150, 152 of the slot 127, 129. The first and second coupling elements 141, 146; 142, 148 retain the elongate bar 126, 128 captive in the elongate holder 121. In the illustrated embodiment, the first coupling element 141, 142 comprises a male element and the second coupling element 146, 148 comprises a channel extending along the sliding direction, indicated by the arrows O-I) of the elongate bar 126, 128.

As the rotary contact progresses, the whole width of the flattened tube 114 is not cut through simultaneously, but instead point contact of the knife blade 118 transitions across the tube 114 as the rotary action progresses.

The anvil 116 is a heated block incorporating an electrical resistance heater 117. The heater may alternatively be in the elongate holder 121, or both the holder 121 and the anvil 116 may include a respective electrical resistance heater 117. When the elongate pressure strips 126, 128 are pushed against the anvil 116, the pressure strips 126, 128 urge the flattened tube 114 against the heated anvil 116 so that transverse hermetic heat seals 132, 134 are formed in the flattened tube 114 on opposite sides of the transverse cut 136 made by the knife 112.

Each pressure strip 126, 128 is pressed against the heated anvil surface thereby simultaneously heat sealing together opposed sides of the flattened tube 114 to form an elongate transverse hermetic seal 132, 134 in the vicinity of each cut end of the flattened tube 114. During the pressing action, each elongate bar 126, 128 slides rearwardly in the respective slot 127, 129 against the bias of the biasing element 133, 135 within the slot 127, 129, but the outer edge 131 remains proud of the mounting surface 138. The pressure strips 126, 128, compressed against the bias of the biasing elements 133, 135 ensure uniform high pressure along the flattened tube 114 which forms highly and uniformly bonded hermetic seals 132, 134 of predetermined narrow width. After release of the sealing pressure, the pressure strips 126, 128 are urged outwardly again by the outward bias of the biasing elements 133, 135 so as return to their original rest position.

The pressure strips 126, 128 locally press the film material of the tube 114 against the heated anvil 116 to form the two spaced hermetic seals 132, 134 of defined width determined by the profile of the outer edge 131 of the elongate bar 126, 128. During the sealing action, the plural layers of the film material of the tube 114 are pushed into the channels 162, 164 by the respective elongate bars 126, 128 to form an arcuate hermetic seal. Alternatively, if the anvil 116 has a planar surface 160 then planar hermetic seals are formed.

The elongate pressure strips 126, 128 are parallel to the knife 112 and so the entire assembly of the knife 112 and the elongate pressure strips 126, 128 on opposite sides thereof is mounted at an inclination to the longitudinal direction of the elongate holder 121.

The provision of elongate pressure strips 126, 128 of rigid material such as metal which are urged against a rigid heated anvil 116, which may have a complementarily profiled channelled surface or a planar surface, provides the advantage of a high strength seal of minimum width. The pressure strips 126, 128 can exert a high pressure over a small surface area, providing an enhanced heat seal as compared to providing a lower pressure seal over a greater width. Therefore a narrower heat seal can provide improved hermetic performance and durability as compared to a wider seal. The elongate pressure strips 126, 128 are biased by concealed elastic resilient material, which is not subject to external contact and so is safely retained within the slots 127, 129, and is not subjected to excessive wear.

Typically, the entire width of the assembly of the knife 112 and the elongate pressure strips 126, 128, all inclined to the longitudinal direction of the elongate holder 121, is 8 mm, whereas in the known device the entire width of the assembly of the knife 12 and the heat seal devices 26, 28, all parallel to the longitudinal direction of the elongate holder 21 is 20 mm.

The result of this change of structure and orientation of the knife is shown in FIG. 5.

FIG. 6 shows two adjacent packages 200, 202 which have been separated by a cut formed by the knife 112. Each package 200, 202 has a cut transverse edge 204, 206 which is inclined at the angle β (exaggerated in the Figure) to the longitudinal direction of the package 200, 202. The angle is sufficiently small that it would not ordinarily be noticed by the consumer. A heat seal, forming a hermetic seal 208, 210, is provided at the end of each package 200, 202. An unsealed endmost portion 212, 214 adjacent to the cut transverse edge 204, 206 has a width corresponding to one half of the knife thickness. Therefore the unsealed endmost portion 212, 214 has a typical thickness of 0.5 to 1.5 mm, most typically 1 mm, which can be compared to a typical thickness of 2.5 mm of the corresponding unsealed endmost portion produced by the known device of FIGS. 1 to 3.

Therefore for each package produced in accordance with this embodiment of the invention there is a typical total film material saving of 3 mm in length without having any impact of the security of the heat seal.

This material saving is achieved by reducing the amount of unsealed material at the ends of the packages that has no functional purpose with respect to forming a hermetic seal.

In addition, the heat seal can be narrower than known heat seals by using the specific pressure strips against the heated anvil, providing even greater packaging material savings. Typically, the heat seal has a width of from 1 to 4 mm, optionally 1 to 2 mm.

Such a film material saving has potentially enormous impact on high volume production of products such as snack foods.

The Applicant and its related companies form part of one of the largest snack food companies in the world, and it is estimated that this packaging material saving cumulatively amounts to a global cost saving in packaging material of many tens of millions of dollars per annum, and, importantly, a saving of approximately 16 thousand tonnes of carbon dioxide production per annum. This invention therefore may yield very significant reductions in the carbon footprint of the packaging of a wide variety of products, particularly snack foods.

It will be clear to a person skilled in the art that the angle and dimensions exemplified above are merely indicative of an angle size and dimensions that may be used in accordance with the present invention, and that these parameters may be varied depending upon a number of factors, including package size, shape and dimensions.

The jaw device and method may be used to produce primary packages of a variety of products, of which snack foods are only a preferred example. The jaw device and method may also be adapted to produce secondary packages, for example multi-pack packaging.

As described above for the known device, in the device of the invention plural knives may be mounted about a common shaft disposed along the rotational axis and mutually angularly separated, so that for each cycle of rotation of the common shaft, plural cuts are made by respective knives, and corresponding plural packages are separated by the cutting action for each rotational cycle of the shaft. Plural anvils would be correspondingly provided.

In an alternative embodiment, the jaw device may have a translational action rather than a rotary action, and either or both of the elongate holders for the knife and the anvil may be translationally reciprocated.

Other modifications to the embodiment of the invention disclosed herein will be apparent to those skilled in the art.

Claims

1. A packaging apparatus including a cutting device, the cutting device comprising an elongate holder, an elongate knife having an elongate cutting edge, and a heat seal device located on the elongate holder on opposed sides of the knife, the heat seal device comprising a pair of elongate pressure strips projecting outwardly from the elongate holder, each pressure strip extending along a respective side of the knife, wherein each pressure strip comprises an elongate bar mounted for sliding movement in a respective slot in the elongate holder, the sliding movement varying the distance an outer edge of the elongate bar projects from the elongate holder, and a biasing element within the respective slot, the biasing element engaging an inner edge of the elongate bar and arranged to bias the elongate bar outwardly of the slot.

2. A packaging apparatus according to claim 1 wherein the elongate bar is rigid.

3. A packaging apparatus according to claim 1 or claim 2 wherein the outer edge of the elongate bar has a convex cross-section.

4. A packaging apparatus according to claim 3 wherein the convex cross-section is arcuate.

5. A packaging apparatus according to claim 4 wherein the arcuate cross-section has a radius from 0.75 to 1.25 mm.

6. A packaging apparatus according to any foregoing claim wherein the elongate bar has a thickness of from 1.5 to 2.5 mm.

7. A packaging apparatus according to any foregoing claim wherein the elongate bar is composed of a metal.

8. A packaging apparatus according to claim 7 wherein the metal is stainless steel.

9. A packaging apparatus according to any foregoing claim wherein the elongate bar is captive in the elongate holder.

10. A packaging apparatus according to claim 9 wherein the elongate bar has a first coupling element located at each longitudinal end of the elongate bar which couples with a second coupling element located at each longitudinal end of the slot, the first and second coupling elements retaining the elongate bar captive in the elongate holder.

11. A packaging apparatus according to claim 10 wherein the first coupling element comprises a male element and the second coupling element comprises a channel extending along the sliding direction of the elongate bar.

12. A packaging apparatus according to any foregoing claim wherein the biasing element comprises an elongate strip of elastic resilient material.

13. A packaging apparatus according to claim 12 wherein the elastic resilient material comprises an elastomeric polymer.

14. A packaging apparatus according to claim 12 or claim 13 wherein the elongate strip of elastic resilient material has an upper surface which mates with the inner edge of the elongate bar.

15. A packaging apparatus according to any one of claims 12 to 14 wherein the elongate strip of elastic resilient material has a circular cross-section.

16. A packaging apparatus according to any foregoing claim wherein the elongate knife is mounted on and projects outwardly from the elongate holder.

17. A packaging apparatus according to any foregoing claim wherein the holder is mounted on a mounting support adapted to rotate about a rotational axis, the knife is planar, the elongate cutting edge is parallel to the plane of the knife and the plane of the knife is inclined to the rotational axis.

18. A packaging apparatus according to claim 17 wherein the cutting edge extends along a centre of the knife.

19. A packaging apparatus according to claim 18 wherein the knife has a thickness of from 1 to 3 mm.

20. A packaging apparatus according to any foregoing claim further comprising an anvil mounted in opposition to the elongate holder, so that the elongate holder and the anvil comprise opposed jaws of a jaw device, the anvil having a reaction surface for the cutting action of the knife and for the pressure strips.

21. A packaging apparatus according to claim 20 wherein the holder is mounted on a mounting support adapted to rotate about a rotational axis, the elongate cutting edge is parallel to the plane of the knife and the plane of the knife is inclined to the rotational axis and the knife and anvil are mutually arranged so that as the knife rotates by rotation of the elongate holder, the cutting edge of the knife progressively contacts the reaction surface with a contact point therebetween moving longitudinally along the cutting edge.

22. A packaging apparatus according to claim 20 or claim 21 wherein the anvil comprises a heater for heating the reaction surface.

23. A packaging apparatus according to any foregoing claim adapted for forming pillow packs of film material.

24. A method of making packages, the method comprising the steps of: a. providing a flattened tube of packaging film;b. providing a cutting device mounted in opposition to an anvil so that the cutting device and the anvil comprise opposed jaws of a jaw device, the cutting device having an elongate knife with an elongate cutting edge, a pair of elongate pressure strips projecting outwardly from an elongate holder, each pressure strip extending along a respective side of the knife, wherein each pressure strip comprises an elongate bar mounted for sliding movement in a respective slot in the elongate holder, the sliding movement varying the distance an outer edge of the elongate bar projects from the elongate holder, and a respective biasing element within the slot, the biasing element engaging an inner edge of the elongate bar and arranged to bias the elongate bar outwardly of the slot, and the anvil having a reaction surface for the cutting action of the knife and for the pressure strips, at least the reaction surface for the pressure strips being heated;c. locating a portion of the flattened tube between the cutting device and the anvil;d. relatively moving the cutting device and the anvil together;e. cutting through the portion of the flattened tube between the cutting device and the reaction surface of the anvil by the cutting action of the knife; andf. pressing the pressure strips against the heated reaction surface thereby simultaneously heat sealing together opposed sides of the flattened tube to form an elongate transverse hermetic seal in the vicinity of each cut end of the flattened tube, during the pressing action each elongate bar sliding rearwardly in the respective slot against the bias of the biasing element within the slot.

25. A method according to claim 24 wherein the biasing element comprises an elongate strip of elastic resilient material.

26. A method according to claim 25 wherein the elastic resilient material comprises an elastomeric polymer.

27. A method according to any one of claims 24 to 26 wherein the elongate bar is rigid.

28. A method according to any one of claims 24 to 27 wherein the outer edge of the elongate bar has a convex cross-section.

29. A method according to claim 28 wherein the convex cross-section is arcuate.

30. A method according to claim 29 wherein the arcuate cross-section has a radius from 0.75 to 1.5 mm.

31. A method any one of claims 24 to 30 wherein the elongate bar has a thickness of from 1.5 to 2.5 mm.

32. A method according to any one of claims 24 to 31 wherein the cut edge of each package is 0.5 to 1.5 mm from the hermetic seal.

33. A method according to claim 32 wherein the cut edge of each package is about 1 mm from the hermetic seal.

34. A method according to any one of claims 24 to 33 wherein the hermetic seal has a width of from 1 to 4 mm.

35. A method according to claim 34 wherein the hermetic seal has a width of from 1 to 2 mm.

36. A method according to any one of claims 24 to 35 wherein the packages are pillow packs of film material.

37. A method according to claim 36 wherein the packages contain snack food.