GB2619649A

GB2619649A - Assembly for bag forming apparatus

Info

Publication number: GB2619649A
Application number: GB2314283.9A
Authority: GB
Inventors: Dewar Adrian
Original assignee: Alway Loughborough Ltd
Current assignee: Alway Loughborough Ltd
Priority date: 2023-09-18
Filing date: 2023-09-18
Publication date: 2023-12-13
Also published as: GB202314283D0

Abstract

There is provided an assembly for a bag forming apparatus, comprising: a tubular guide member for receiving a feed of elongate sheet material wrapped widthways therearound; a longitudinal attachment configured to releasably connect to one or more engagement features of an outer wall of the tubular guide member to provide an outwardly facing wear surface against which overlapping longitudinal edges of the wrapped-around sheet material can be sealed by a sealing mechanism of the bag forming apparatus.

Description

ASSEMBLY FOR BAG FORMING APPARATUS

FIELD

The invention relates generally to bag forming apparatus. Such bag forming apparatus may commonly be referred to as, or form part of, a vertical form fill seal apparatus.

BACKGROUND

In a typical bag forming apparatus, or vertical form fill and seal apparatus, a supply of packaging material is drawn along a former and then passes downwards in a tubular formation; the edges are then sealed longitudinally, after which horizontal seals are made at regular intervals to form individual packets, bags, or the like. A measured quantity of product to be packaged is dropped into each packet before a top seal is formed.

A variety of bags and pouches for holding contents such as foodstuff (e.g. crisps, cereal, candy, nuts, etc.) can be formed from a single elongate sheet of packaging material using a bag forming apparatus such as a vertical form fill seal apparatus (VFFS). This equipment essentially takes a reel of packaging material and almost simultaneously forms it into a bag shape, fills it with contents and seals it.

When sealing the edges longitudinally, and typically substantially vertically, it may be preferable to not have the packaging material sealed when in direct contact with the tubular guide member of the apparatus. The heat and/or pressure and/or friction applied when creating the seal may over time cause wear to an opposing surface and therefore it is preferable to limit the wear to more substantial, integral and/or expensive components.

Aspects and embodiments of the present invention have been devised with the foregoing in mind.

SUMMARY

According to a first aspect there is provided an assembly for a bag forming apparatus, comprising: a tubular guide member for receiving a feed of elongate sheet material wrapped widthways therearound; a longitudinal attachment configured to releasably connect to one or more engagement features of an outer wall of the tubular guide member to provide an outwardly facing wear surface against which overlapping longitudinal edges of the wrapped-around sheet material can be sealed by a sealing mechanism of the bag forming apparatus.

The one or more engagement features may be or may comprise mechanical engagement features. In this way, the one or more engagement feature may be configured or adapted to provide releasable mechanical connection between the tubular guide member and the attachment.

The attachment may comprise at least two projections that are longitudinally spaced apart, and the one or more engagement features of the outer wall may comprise one or more openings configured to receive and engage the projections of the attachment to connect the attachment.

The one or more engagement features of the wall may comprise at least two projections that are longitudinally spaced apart along the tubular guide member, and the attachment may comprise at least two openings configured to receive and engage the projections of the outer wall to connect thereto.

The attachment may comprise at least three projections that are longitudinally spaced apart, and the engagement features of the outer wall may comprise a corresponding number of openings configured to receive and engage the projections of the attachment to connect the attachment. The at least three projections may be unequally spaced apart in the longitudinal direction. The at least three projections may or may not all be aligned along a central longitudinal axis of the attachment. The corresponding openings of the outer wall may be unequally spaced apart in the longitudinal direction by displacements corresponding to the unequal spacing between the projections. The at least three engagement features may be described as being arranged asymmetrically about a central axis, the central axis being perpendicular to the longitudinal axis.

In this way, the unequal spacing in the longitudinal direction may allow for the at least three engagement features of the outer wall to receive and engage the projections of the attachment to connect the attachment when the attachment is aligned in a first longitudinal direction, but when the attachment is rotated through I 80° the engagement features and the projections will be misaligned such that the engagement features of the outer wall may not receive and engage the projections of the attachment. In this way, the attachment may only be attached to the outer wall when aligned in a first longitudinal direction.

The engagement features of the wall may comprise at least three projections that are longitudinally spaced apart along the tubular guide member, and the attachment may comprise a corresponding number of openings configured to receive and engage the projections of the outer wall to connect thereto. The at least three projections may be unequally spaced apart in the longitudinal direction. The at least three projections may or may not all be aligned along a single longitudinal axis. The corresponding openings may be unequally spaced apart in the longitudinal direction by displacements corresponding to the unequal spacing between the projections. The at least three engagement features may be described as being arranged asymmetrically about a central axis, the central axis being perpendicular to the longitudinal axis In this way, the unequal spacing in the longitudinal direction may allow for the at least three engagement features of the attachment to receive and engage the projections of the outer wall to connect the attachment when the attachment is aligned in a first longitudinal direction, but when the attachment is rotated through 180° the engagement features and the projections will be misaligned such that the engagement features of the attachment may not receive and engage the projections of the outer wall. In this way, the attachment may only be attached to the outer wall when aligned in a first longitudinal direction.

Advantageously, this configuration may prevent the attachment from being connected to the outer wall in an incorrect direction. Advantageously, this configuration may only allow the attachment to be connected to the outer wall when aligned in a first direction.

The projections may comprise a stem portion and an enlarged head portion, wherein the one or more openings comprise respective slots may be configured to receive and slidably engage the projection heads.

The slots may have a first section for receiving the head portion therethrough upon moving the attachment towards the outer wall in an insertion direction, and a narrower section extending longitudinally from the wider section for receiving the stem portion and engaging the underside of the head portion upon subsequently sliding the attachment along the outer wall in a longitudinal direction.

In examples where the outer wall comprises one or more projections and the attachment comprises one or more openings, the first section for receiving the head portion therethrough and the narrower section of the slots may be orientated such that the first section is disposed below the narrower section, in use. In use, the tubular guide member may be arranged substantially vertically and when attached thereto the attachment may also be arranged substantially vertically. in this way, when the attachment is slidably engaged with the outer wall of the tubular guide member, the attachment would need to be moved vertically upwards in order to disengage from the outer wall. In examples where the corresponding openings may be unequally spaced apart in the longitudinal direction by displacements corresponding to the unequal spacing between the projections, the attachment may only be connected to the outer wall in an orientation such that the first section is disposed below the narrower section, in use, in this way, gravity acting on the attachment may cause the projections to be biased towards the narrower section of the slots thereby maintaining a secure connection.

In examples where the attachment comprises one or more projections and the outer wall comprises one or more openings, the first section for receiving the head portion therethrough and the narrower section of the slots may be orientated such that the first section is disposed above the narrower section, in use. In use, the tubular guide member may be arranged substantially vertically and when attached thereto the attachment may also be arranged substantially vertically. In this way, when the attachment is slidably engaged with the outer wall of the tubular guide member, the attachment would need to be moved vertically upwards in order to disengage from the outer wall. In examples where the corresponding openings may be unequally spaced apart in the longitudinal direction by displacements corresponding to the unequal spacing between the projections, the attachment may only be connected to the outer wall in an orientation such that the first section is disposed above the narrower section, in use. in this way, gravity acting on the attachment may cause the projections to be biased towards the narrower section of the slots thereby maintaining a secure connection.

Advantageously, when used with a bag forming apparatus comprising a scaling means arranged to provide a seal through a downwards vertical direction, the downwards forces of the sealing means on the attachment may bias the projections towards the narrower section of the slots thereby maintaining a secure connection between the attachment and the outer wall.

The outer wall may comprise a longitudinal slot or a pair of longitudinally spaced apart openings, and each end of the attachment is or comprises a projection, wherein at least a portion of each projection extends substantially longitudinally, and wherein the attachment is configured to bend or flex along its length to permit insertion of the at least a portion of each projection into respective ends of the longitudinal slot or into respective ones of the pair of openings.

The attachment may comprise a different configuration at one end relative to the longitudinally opposing end. For example, one end may comprise a different size, shape and/or configuration to the opposing end. A distal region of one end may comprise a wider or narrower shape than a distal region of the opposing end. One end may comprise one or more projections and/or cut outs that provide the different size, shape and/or configuration to the opposing end.

The attachment may further comprise a shoulder at each respective end, wherein the shoulders may be configured to engage opposing edges of the longitudinal slot or a respective edge of the pair of openings when the at least a portion of each projection is inserted so as to maintain the attachment in a flexed state. Advantageously, in a flexed state the attachment may be bendable in the direction of the outer wall upon the application of a force, such as from a sealing means of a bag forming apparatus, and also biased to return to its original configuration upon removal of the force. In this way, the attachment may provide a biasing force away from the outer wall and thereby accommodate any minor changes in the operation of a sealing means from wear and tear over time and/or accommodate any 11110 play or misalignment associated with the sealing means.

The tubular guide member may comprise interior wall portions connected to the interior side of the outer wall, wherein the projections may be configured to engage respective interior wall portions when the projections are inserted so as to maintain the attachment in a flexed state.

The outer wall may comprise a longitudinal slot and the tubular guide member may comprise an interior wall portion set back from and connected across the interior side of the longitudinal slot. The interior wall portion may extend along a length that is greater than the length of the longitudinal slot.

Each end of the attachment may be or may comprise a projection, wherein at least a portion of each projection extends substantially longitudinally. The tubular guide member may comprise a pair of exterior wall portions connected to the exterior side of the outer wall to provide a pair of opposing longitudinally facing openings for receiving and engaging the projections of the attachment. The attachment may be configured to bend or flex along its length to permit insertion of the at least a portion of each projection into respective openings.

When the attachment is connected to the outer wall, at least a portion of the wear surface may be biased away from the tubular guide member and moveable theretowards upon application of a compressive force by the sealing mechanism of the bag forming apparatus. Advantageously, upon the application of a compressive force, such as from a sealing means of a bag forming apparatus, the wear surface may be biased to return to its original configuration upon removal of the compressive force. In this way, the attachment may provide a biasing force away from the outer wall and thereby accommodate any minor changes in the operation of a sealing means from wear and tear over time and/or accommodate any minor play or misalignment associated with the sealing means and/or to accommodate dimension changes resulting from wear and tear to the wear surface.

The attachment may comprise one or more spring portions configured to engage the tubular guide member to bias the at least a portion of the wear surface away the tubular guide member.

The attachment may be connected to the outer wall, the attachment is configured to be held in a flexed or sprung state, such that the wear surface is curved outwards.

The attachment may comprise one or more leaf spring portions to engage a surface of the tubular guide member and bias the at least a portion of the wear surface away the tubular guide member.

The attachment may comprise any two or more means for biasing the at least a portion of the wear surface away the tubular guide member.

The attachment may comprise a base portion configured to releasably connect to the engagement features of the outer wall, and a wear strip detachably mounted onto the base portion, the wear strip providing the outwardly facing wear surface. Advantageously, the wear strip may therefore provide a sacrificial portion of material that may be detached and replaced.

The wear strip may comprise a sloped or angled portion at one end. The sloped or angled surface may be configured such that the thinnest section is disposed near to or at a distal region. The sloped or angled surface may be disposed at the end that is disposed vertically above the opposing end, in tse. Advantageously, when used with a bag forming apparatus comprising a sealing means arranged to provide a seal through a downwards vertical direction, the sealing means may first engage with the sloped or angled surface first thereby providing a less abrupt engagement with the wear strip.

The base portion may comprise one or more integral spring portions formed by one or more respective folded tabs to bias the wear surface away from the tubular guide member.

The wear surface may comprise a sloped or angled portion at one end. The sloped or angled surface may be configured such that the thinnest section is disposed near to or at a distal region. The sloped or angled surface may be disposed at the end that is disposed vertically above the opposing end, in use. Advantageously, when used with a bag forming apparatus comprising a sealing means arranged to provide a seal through a downwards vertical direction, the sealing means may first engage with the sloped or angled surface first thereby providing a less abrupt engagement with the wear surface.

The base portion may include two projections that are longitudinally spaced apart, each comprising a stem portion and an enlarged head portion. The wear strip may comprise respective slots configured to receive and slidably engage the projection heads.

The slots may have a first section for receiving the head portion therethrough upon moving the wear strip towards the base portion in an insertion direction, and a narrower section extending longitudinally from the wider section for receiving the stem portion and engaging the underside of the head portion upon subsequently sliding the wear strip along the base portion in a longitudinal direction.

The base portion may include at least three projections that are longitudinally spaced apart, and the wear strip may comprise a corresponding number of slots. The longitudinal spacing of the projections may be unequal. At least one of the projections may be misaligned from a longitudinal axis of the attachment.

The base portion may comprise at least three projections that are longitudinally spaced apart, and the wear strip may comprise a corresponding number of openings configured to receive and engage the projections of the base portion to connect thereto. The at least three projections may be unequally spaced apart in the longitudinal direction. The at least three projections may or may not all be aligned along a single longitudinal axis.

The corresponding openings may be unequally spaced apart in the longitudinal direction by displacements corresponding to the unequal spacing between the projections. In this way, the unequal spacing in the longitudinal direction may allow for the at least three openings of the wear strip to receive and engage the projections of the base portion to connect the wear strip when the wear strip is aligned in a first longitudinal direction, but when the wear strip is rotated through 180° the openings and the projections will be misaligned such that the openings of the wear strip may not receive and engage the projections of the wear strip. in this way, the wear strip may only be attached to the base portion when aligned in a first longitudinal direction.

Advantageously, this configuration may prevent the wear strip from being connected to the base portion in an incorrect direction. Advantageously, this configuration may only allow the wear strip to be connected to the base portion when aligned in a first direction.

The base portion may be formed from or may comprise a metal material, preferably spring steel. The detachable wear strip may be formed of or may comprise a plastic or polymer material, preferably polytetrafluoroethylene (PTFE).

The attachment, base portion and wear strip may comprise any suitable dimensions. For example, the wear strip may comprise a length of between 100mm and 300mm. The wear strip may comprise a length of approximately 200mm. It will be understood by a person skilled in the art that the dimensions of components of bag forming apparatus may be dependent upon the varying use of the apparatus, and as such the attachment, base portion and wear strip may be sized accordingly.

The bag forming apparatus may be or may comprise a vertical form fill seal apparatus, and the tubular guide member may be or may form part of a vertically arranged product delivery chute.

The tubular guide member may have a generally circular or non-circular cross-section.

The tubular guide member may be formed of a continuous or discontinuous outer wall.

According to a second aspect of the invention there is provided an attachment configured to releasably connect to an outer wall of a tubular guide member of a bag forming apparatus, comprising a base portion configured to releasably connect to an outer wall of the tubular guide member, and a wear strip detachably mounted onto the base portion, the wear strip providing an outwardly facing wear surface.

The base portion may be configured to releasably connect to one or more engagement features of the outer wall The attachment may comprise one or more spring portions configured to engage the tubular guide member, in use, to bias the at least a portion of the wear surface away the tubular guide member.

The attachment may be configured such that when connected to the outer wall, the attachment is configured to be held in a flexed or sprung state, such that the wear surface is curved outwards.

The attachment may comprise one or more leaf spring portions configured to engage a surface of the tubular guide member, in use, and bias the at least a portion of the wear surface away the tubular guide member.

The attachment may comprise any two or more means for biasing at least a portion of the wear surface away the tubular guide member.

According to a third aspect of the invention there is provided a tubular guide member for a bag forming apparatus, the tubular guide member comprising a pair of exterior wall portions connected to an exterior side of an outer wall to provide a pair of opposing longitudinally facing openings, the openings being configured for receiving opposing ends of an attachment, wherein the attachment comprises an outwardly facing wear surface against which overlapping longitudinal edges of a wrapped-around sheet material can be sealed by a scaling mechanism of the bag forming apparatus.

According to a fourth aspect of the invention there is provided a method of manufacturing a tubular guide member for a bag forming apparatus, the method comprising affixing a pair of exterior wall portions to an exterior side of an outer wall of the tubular guide member to provide a pair of opposing longitudinally facing openings, the openings being configured for receiving opposing ends of an attachment, wherein the attachment comprises an outwardly facing wear surface against which overlapping longitudinal edges of a wrapped-around sheet material can be sealed by a sealing mechanism of the bag forming apparatus.

The exterior wall portions may be affixed to the exterior side of the outer wall by any suitable means, such as, welding, adhering, bolting, or riveting, for example.

Features which are described in the context of separate aspects and embodiments of the invention may be used together and/or be interchangeable. Similarly, where features arc, for brevity, described in the context of a single embodiment, these may also be provided separately or in any suitable sub-combination. Features described in connection with the device may have corresponding features definable with respect to the method(s), and vice versa, and these embodiments are specifically envisaged.

BRIEF DESCRIPTION OF DRAWINGS

in order that the invention can be well understood, embodiments will now be discussed by way of example only with reference to the accompanying drawings, in which: FIG. I shows schematically a conventional vertical fill form and seal (VFFS) apparatus; FIG. 2 shows a schematic diagram of an assembly for a bag forming apparatus according to the present invention; FIG. 3a shows a schematic diagram of a cross-sectional view of a longitudinal attachment connected to the outer wall of the tubular guide member according to an embodiment; FIG. 3b shows a schematic diagram of a plan view of a longitudinal attachment connected to the outer wall of the tubular guide member according to an embodiment; FIG. 4a shows a schematic cross-sectional view of a longitudinal attachment connected to the outer wall of the tubular guide member according to another embodiment; FIG. 4b shows a schematic plan view of a longitudinal attachment connected to the outer wall of the tubular guide member according to another embodiment; FIG 5a shows a schematic cross-sectional view of a longitudinal attachment connected to the outer wall of the tubular guide member according to another embodiment; FIG 5b shows a schematic plan view of a longitudinal attachment connected to the outer wall of the tubular guide member according to another embodiment; FIG. 6a shows a schematic cross-sectional view of a longitudinal attachment connected to the outer wall of the tubular guide member according to another 20 embodiment; FIG. 6b shows a schematic plan view of a longitudinal attachment connected to the outer wall of the tubular guide member according to another embodiment; FIG. 7a shows a schematic cross-sectional view of a longitudinal attachment connected to the outer wall of the tubular guide member according to another embodiment: FIG. 7b shows a schematic plan view of a longitudinal attachment connected to the outer wall of the tubular guide member according to another embodiment; FIG. 8 shows a schematic cross-sectional view of a longitudinal attachment connected to the outer wall of the tubular guide member according to another 30 embodiment: FIG. 9a shows a schematic cross-sectional view of a longitudinal attachment connected to the outer wall of the tubular guide member according to an alternative embodiment: FIG. 9b shows a schematic cross-sectional view of a longitudinal attachment connected to the outer wall of the tubular guide member according to an altemative embodiment; FIG. 9c shows a schematic cross-sectional view of a longitudinal attachment connected to the outer wall of the tubular guide member according to an alternative embodiment; FIG. 10a shows an embodiment where the tubular guide member comprises interior wall portions connected to the interior side of the outer wall; FIG. 10b shows an embodiment where the tubular guide member comprises interior wall portions connected to the interior side of the outer wall; FIG. 10c shows an embodiment where the tubular guide member comprises interior wall portions connected to the interior side of the outer wall; FIG. 11 shows an example of an alternative configuration to the embodiments of FIGS 9 and 10; FIG. 12 shows an alternative configuration of the embodiment in FIG 11; FIG. 13 shows a plan view of an attachment with asymmetric projections connected to a longitudinal slot in the outer wall; FIG. 14 shows a schematic cross-section of an attachment according to an embodiment; FIG. 15a shows a schematic cross-section of an attachment according to an embodiment; FIG. 15b shows a schematic view of an example wear strip; FIG. 16a shows a schematic plan view of an example wear strip comprising three slots for receiving and engaging three corresponding projections of the base portion; FIG. 16b shows a schematic perspective view of an example wear strip comprising three slots for receiving and engaging three corresponding projections of the base portion; FIG. 17a shows a perspective cross-sectional view of an embodiment of the attachment connected to the tubular guide member; and FIG. 17b shows a transverse cross-sectional view of an embodiment of the attachment connected to the tubular guide member.

It should be noted that the figures are diagrammatic and may not be drawn to scale. Relative dimensions and proportions of parts of these figures may have been shown exaggerated or reduced in size, for the sake of clarity and convenience in the drawings.

The same reference signs are generally used to refer to corresponding or similar features in modified and/or different embodiments.

DETAILED DESCRIPTION

A variety of bags and pouches for holding contents such as foodstuff (e.g. crisps, cereal, candy. nuts. etc.) can be formed from a single elongate sheet of packaging material using a bag forming apparatus such as a vertical form fill seal apparatus (VFFS). This equipment essentially takes a reel of packaging material and almost simultaneously forms it into a bag shape, fills it with contents and seals it.

Figure 1 show part of a conventional VFFS apparatus 10, as in known in the art. The VFFS apparatus 10 comprises a reel or roll of sheet material 11, a sheet guide collar 12 arranged around a vertically arranged tubular guide member 13, a longitudinal sealing unit 14, a pair of drive belts 15 arranged on opposite sides of the guide member 13, and a finishing module 16. The roll of sheet material 11 is rotatably supported on a rod 1 I a, and typically a plurality of tensioners 1 lb are provided between the roll 11 and the guide collar 12.

In use, the elongate sheet material 11 is wound off from the roll, through the tensioners 1 lb, and passed over the guide collar 12 which guides and directs the initially flat or planar elongate sheet onto the vertically arranged tubular guide member 13 in a wrapped-around tubular configuration. As is known in the art, the guide collar 12 has a surface 12a configured to guide and transform the geometry of the sheet material 11 from a substantially flat/planar form to a tubular form wrapped widthways around the guide member 13 whilst also drawing one longitudinal edge 1 lei of the sheet 11 over the other longitudinal edge 11e2 of the sheet 11 in an overlapping configuration. The vertically arranged tubular guide member 13 thus receives the feed of elongate sheet material 11 wrapped widthways therearound. The drive belts 15 are arranged to engage the sheet 11 on the tubular guide member 13 and pull/move/advance the sheet I I downwards in a feed direction F by traction. The longitudinal sealing unit 14 is arranged to align with and seal the overlapping longitudinal portions of the wrapped-around sheet material II. This is typically achieved by moving the sealing unit 14 into contact with the tubular guide member 13 in a stamping motion to engage the overlapping portions of the sheet 11 therebetween and seal or join them by application of heat. Once sealed, the sealing unit 15 is released away from the tubular guide member 13 and the next section of tube-shaped wrapped around sheet material 11 is moved down by the drive belts 14 for sealing in the same manner.

The finishing module 16 is arranged below a lower end of the tubular guide member 13 and typically comprises at least a transverse scaling unit 16a to seal together front and back portions of the tubular sheet material 11 to form (sequentially) lower and upper enclosed end walls 20a, 20b of a bag 20, and a cutting mechanism to separate the formed and sealed bags 20. as is known in the art. The tubular guide member 13 may be connected to or form part of a product delivery tube 17 of the apparatus 10, having an open end 17a through which a product can be delivered to fill a partially formed bag 20 once a lower end wall 20a is formed.

Figure 2 shows a schematic diagram of an assembly 100 for a bag forming apparatus according to the present invention. The assembly 100 comprises a tubular guide member 113 having a longitudinal axis L and a longitudinal attachment 130 releasably connected thereto to provide an outwardly facing wear surface 130s against which overlapping longitudinal portions or edges llei, 1 1e2 of the wrapped-around sheet material 11 can be scaled by a scaling unit 14 of the bag forming apparatus. The wrapped-around sheet material 11 is not shown for clarity, but it will be appreciated that the longitudinal attachment 130 is arranged to align with the overlapping longitudinal portions of the sheet 11 and the longitudinal sealing unit 14. The attachment no serves to prevent the sealing unit 14 of the apparatus 10 from interacting too closely with the outer wall 113w of the tubular guide member 113 and inadvertently sealing the sheet material 11 onto the outer wall 113w thereby interfering with operation of the apparatus 10. Meanwhile, the releasably connection to the tubular guide member 113 allows the attachment 130 to be disconnected and replaced, repaired or the wear surface 130s renewed in the event of wear and tear over time that may lead to degradation in the effectiveness of the sealing unit 14.

In a preferred embodiment, the assembly 100 forms part of the VFFS apparatus 10 described above, for example the tubular guide member 113 can replace the conventional tubular guide member 13 in the VFFS apparatus 10 of figure I. In this case, the tubular guide member 113 and the longitudinal attachment are arranged substantially vertically.

The tubular guide member 113 is configured or adapted to provide a secure but releasable mechanical connection to the attachment 130 so as prevent the attachment 130 from unintentionally falling off into the bag 20 in use. Specifically, the outer wall 113w of the tubular guide member 113 is provided with one or more engagement features to which the attachment 130 can releasably connect.

Preferably, where the sealing unit 14 is or comprises a heat sealing mechanism, at least the wear surface 130s of the attachment 130 is formed of or comprises a polymer material with low thermal conductivity and a melting point above the temperature applied from the scaling unit 14. The wear surface 130s preferably comprises a low friction material. Suitable materials include polvtetrafluoroethylene (PTFE), and nylon. As described further below with referred to figure 13, in a preferred embodiment, the attachment 130 is formed of two pieces including a base plate for connecting to the engagement features of the outer wall 113w, and a wear strip detachably mounted onto the base portion, wherein the wear strip provides the outwardly facing wear surface 130s It will be appreciated that there are numerous ways to achieve the secure mechanical connection of the attachment 130 to the outer wall 113w which arc encompassed by the present invention, in general, the engagement features can comprise one or more openings for receiving portions of the attachment 130, or projections for engaging respective openings in the attachment 130. As will be described in more detail below, the one or more openings can be transverse openings extending into or through the outer wall 113w, and/or longitudinally facing openings formed by additional wall portions attached to the interior or exterior surface of the outer wall 113w. In this way, the tubular guide member of a conventional bag forming apparatus 10 can be either replaced with a tubular guide member 113 including the engagement features for connecting the attachment 130 of the present invention, or adapted to include the engagement features 132 for connecting the attachment 130 Figures 3(a) and 3(b) show, respectively, schematic cross-sectional and plan views of a longitudinal attachment 130 connected to the outer wall 113w of the tubular guide member 113 according to an embodiment. In this example, the attachment 130 comprises at least two projections 130p on an inner side of the attachment 130 that are longitudinally spaced apart, and the engagement features comprise a pair of openings 132o or cut outs in the outer wall 113w to receive and engage the projections 130p of the attachment 130 Figures 4(a) and 4(b) show, respectively, schematic cross-sectional and plan views of a longitudinal attachment 130 connected to the outer wall 113w of the tubular guide member 113 according to another embodiment. In this example. the engagement features comprise at least two projections on an exterior surface of the outer wall 113w that are longitudinally spaced apart. and the attachment 130 comprises respective openings 130o configured to receive and engage the projections of the outer wall 113w.

Although the openings 130o in the example of figure 4 are shown to extend through the thickness of the attachment 130, this is not essential. in other examples (not shown), the openings 130o may be provided in the inner side of the attachment 130 and extend only partially through the thickness of the attachment 130. Further, in other examples (not shown), both the outer wall 113w and the attachment 130 can include a combination of openings I I3o, 130o and projections 113p, 130p that cooperate to provide the connection. Further, it is not necessary for the openings 113o, 130o and projections 113p, 130p to be aligned to a central longitudinal axis, and where there arc more than two corresponding openings 1130, 130o and projections 113p, 130p, these may be equally or unequally spaced apart in the longitudinal direction.

Figures 5(a) and 5(b) show, respectively, schematic cross-sectional and plan views of a longitudinal attachment 130 connected to the outer wall 113w of the tubular guide member 113 according to another embodiment. This example is similar to the example of figure 3, but in this case the attachment 130 comprises at least three projections 130p that are longitudinally spaced apart, and the engagement features of the outer wall comprise a corresponding number of openings 113o configured to receive and engage the projections 130p of the attachment 130 to releasably connect the attachment 130.

Specifically, in this example, the at least three projections 130p are unequally spaced apart in the longitudinal direction and are also not all aligned along a central longitudinal axis of the attachment 130. The corresponding openings 113o of the outer wall 113w are located as positions corresponding to the relative positions of the projections 130p.

In this way, the unequal spacing in the longitudinal direction and the m salign with respect to the longitudinal axis L provides an asymmetry that restricts the orientation in which the attachment 130 can be connected to the outer wall 113w to a single longitudinal direction. Specifically, the attachment 130 can be connected when oriented in a first longitudinal direction whereby the projections 130p align with the openings 113o, but not when the attachment 130 is rotated through 1800 and the projections 130p are misaligned with the openings 113o. A similar asymmetry can be applied to embodiments where the outer wall 113w comprises projections 113p three or more and the attachment comprises corresponding openings 1 30o (not shown). it will be appreciated that in practice, either or both of unequal longitudinal spacing and misalignment to longitudinal axis L can be used to introduce a suitable asymmetry that restricts the insertion orientation.

In the examples of figures 3 to 5, the projections 113p, 130p are configured to frictionally engage the respective openings 113o, 130o, e.g. via an interference fit, and can be connected (disconnected) by simply moving the attachment 130 towards (away from) the outer wall 113w to insert (remove) the projections 113p, 130p into (from) the openings 113o, 130o, Figures 6(a) and 6(b) show, respectively, schematic cross-sectional and plan views of a longitudinal attachment 130 connected to the outer wall 113w of the tubular guide member 113 according to another embodiment. In this example, the projections 1 13p on the outer wall 113w comprise a stem portion 113p1 and an enlarged head portion 113p2, and the openings 130o comprise respective slots configured to receive and slidably engage the projection heads 130p2. Specifically, the slots have a keyhole shape including first section 130o1 for receiving the head portion 113p2 therethrough upon moving the attachment 130 towards the outer wall 113w in an insertion direction I. and a narrower section 130o2 extending longitudinally from the wider section 130o1 for receiving the stem portion 113p1 and engaging the underside of the head portion 113p2 upon subsequently sliding the attachment 130 along the outer wall I 13w in the feed direction F. The slot 130o is provided in a recessed portion 130o3 of the attachment 130 having a depth D sufficient to provide a clearance d from the head portion 113p2 that prevents the head portion 113p2 from protruding past the wear surface 130s and also to accounts for wear and tear of the wear surface 130s over time (whereby the wear surface 130s may retreat towards the outer wall 113w over time with wear). In one example, clearance distance d of approximately 1 mm is suitable.

Figures 7(a) and 7(b) show, respectively, schematic cross-sectional and plan views of a longitudinal attachment 130 connected to the outer wall 113w of the tubular guide member 113 according to another embodiment. This example is similar to the example of figure 6, but in this case, the attachment 130 comprises the projections 113p (on the inner side) including a stem portion 130p1 and an enlarged head portion 113p2, and the outer wall 113w comprises respective slots 1 1 3o configured to receive and slidably engage the projection heads 130p2 of the attachment 130. Specifically, the slots 113o have a keyhole shape (see figure 6(b)) including first section 113o1 for receiving the head portion 130p2 therethrough upon moving the attachment 130 towards the outer wall 113w in an insertion direction I, and a narrower section 113o2 extending longitudinally from the wider section 130o1 for receiving the stem portion 113p1 and engaging the underside of the head portion 113p2 upon subsequently sliding the attachment 130 along the outer wall 113w in the feed direction F which is generally downwards in a VFFS apparatus 10.

With reference to figures 6(b) and 7(b), the orientation of the keyhole shaped slot 113o, 130o is different depending on whether the slot is provided in the outer wall 113w or the attachment 130. Specifically, where the attachment 130 comprises the slot 130o, the narrower section I30o2 is disposed above the first section 130o1 in use, whereas where the outer wall 113w comprises the slot 1 1 3o the narrower section 113o2 is disposed below the first section 113o1 in use. In either case, a secure locking engagement is caused by sliding the attachment 130 relative to the outer wall 113w in the feed direction F such that the stem portion 113p1. 130p1 moves towards and into the narrower section 113o2, 130o2 of the slot 113o, 130o.

In the embodiments of figures 6 and 7, the connection provides a locking engagement that prevents detachment by merely pulling the attachment 130 away from the outer wall 113. Further, the attachment 130 can only be disconnected by sliding it in a direction opposite to the feed direction F (i.e. a generally upwards direction when the tubular guide member 113 is arranged vertically for a VFFS apparatus 10), preventing detachment from the motion of the sheet material 11 in the feed direction F. Additionally, when the tubular guide member 113 is arranged vertically for use in a VFFS apparatus 10, gravity acting on the attachment 130 may help bias the projections 113p, 130p towards the narrower section 113o2, 130o2 of the slots thereby maintaining a secure connection.

As described above, in examples where there are three or more projections 113p, 130p and corresponding openings 113o, 130o, these may be unequally spaced apart in the longitudinal direction and/or misaligned with respect to the longitudinal axis L to introduce a suitable asymmetry that restricts the insertion orientation to a single longitudinal direction. In this way, a secure locking engagement can only be caused by sliding the attachment 130 relative to the outer wall 113w in the feed direction F. Advantageously, when used with a bag forming apparatus 10 comprising a sealing unit 14 arranged to provide a seal through a downwards vertical direction, the downwards forces of the sealing unit 14 on the attachment 130 may bias the projections towards the narrower section 113o2, 130o2 of the slots thereby maintaining a secure connection between the attachment 130 and the outer wall 113w. As such, restricting the insertion orientation may be particularly advantageous in examples where the attachment 130 comprises the slots 130o and could in principle (if the engagement features were symmetric) also engage with the corresponding projections 113p of the outer wall 113w by sliding in an upward direction opposite to the feed direction (and would be more susceptible to displacement and thus detachment under downward forces from gravity, the sealing unit 14 and/or the motion of the sheet material 11).

In various embodiments, the attachment 130 can be configured such that, when connected to the outer wall 113w, at least a portion of the wear surface 130s is biased away from the tubular guide member 113 and moveable theretowards upon application of a compressive force by the sealing unit 14 of the bag forming apparatus 10 that overcomes the bias force. Providing a biased wear surface 130s may advantageously counteract effects of wear of the wear surface 130s that may cause a reduction in thickness and reduced interaction with the sealing unit 14, and may also accommodate any play or misalignment in the sealing unit 14.

Figure 8 shows a schematic cross-sectional view of a longitudinal attachment 130 connected to the outer wall 113w of the tubular guide member 113 according to another embodiment. This example is similar to the example of figure 7, but the stem portions 130p1 of the projections 130p are longer and the attachment 130 comprises one or more biasing elements 132, such as springs, on the inner side of the attachment 130 to engage the tubular guide member 113 and bias the wear surface 130s away the tubular guide member 113. Although one biasing element 132 shown, multiple biasing elements 132 can be implemented dependent on the requirements Figures 9(a) to 9(c) show a schematic cross-sectional view of a longitudinal attachment 130 connected to the outer wall 113w of the tubular guide member 113 according to an alternative embodiment. In these embodiments, each end 131 of the attachment 130 is or comprises a projection 131p. at least a portion of which extends generally longitudinally, and the engagement features of the outer wall 113w comprises a pair of longitudinally spaced apart openings 113o configured to receive the at least a portion of the respective projections 131p. Unlike the previous embodiments described above, in this case the attachment 130 is configured to bend or flex along its length to permit insertion of the projections 131p into respective ones of the pair of openings 113p and effect the connection. Accordingly, in these examples at least a portion of the attachment 130 is formed or comprises a resiliently flexible material, such as sprung steel of other suitable material. Preferably, the attachment 130 and/or engagement features of the tubular guide member 113 are configured to, when connected, hold or maintain the attachment 130 in a flexed or sprung state such that the wear surface 130s is curved outward, as shown and described in more detail below. In this way, the attachment 130 effectively acts as a leaf spring, biasing at least a portion of the wear surface 130s away from the tubular guide member 113 to provide the same or similar advantages described above reference to figure 8.

The example in figure 9(a) shows the basic arrangement, whereby the projections 13 lp are provided by the ends 131 of the attachment 130 that are received in the openings 113o. In the examples of figures 9(b) and 9(c), the attachment 130 further comprises a shoulder 131s at each respective end 131, adjacent the portion of the projection 131p that is received in the opening 113o. The shoulders 131s are configured to engage opposing edges 113o, of the openings 113o when the projections 13 lp are inserted so as to maintain the attachment 130 in a flexed or sprung state. In the example of figure 9(b), the attachment 130 comprises exterior shoulders 131s and the projections 131p can be provided by the ends 131 of the attachment 130. in the example of figure 9(c). the attachment 130 comprises interior shoulders 131s and the projections 131p are located on the inner side of the attachment 130 in the vicinity of the ends 131. In this configuration, the shoulders 131s can be provided as part of the projections 131, as illustrated In an alternative configuration, instead of the outer wall 113w comprising a pair of longitudinally spaced apart openings 1 I3o as shown in figures 9(b)-(c), the outer wall 113w can comprise a single longitudinal slot 113o. In this case, the at least a portion of the respective projections 131p can be inserted into ends of the longitudinal slot 130o and the shoulders 131s engage opposing edges 1130, of the longitudinal slot 130o (not shown, but the same configuration as in figures 9(b)-(c) without the section of wall between the two openings 131o).

As shown in figures 10(a) to 10(c), in various embodiments the tubular guide member 113 can comprise interior wall portions 1 I 3i connected to the interior side of the outer wall 113w. In case, the projections 131p are configured to engage respective interior wall portions 113i when inserted into the respective openings 113o or the respective ends of the longitudinal slot 1 I 3o so as to maintain the attachment in a flexed state. Preferably, the interior wall portion(s) 1I31 form a longitudinal opening or mouth II3io on the interior side of the outer wall 113w adjacent the opposing edges 113oc of the pair of openings 113o or longitudinal slot 130o for receiving the projection 131p as shown in figures 10(a) to 10(c). In some embodiments, the interior wall portion(s) 113i further provides a shoulder or transverse wall portion 113is within the longitudinal opening 1 I3io against which the end of the projection 13Ip can engage/abut when inserted therein. The attachment 130 can additionally or alternatively include the interior or exterior shoulder 131s for engaging the opposing edges 113o, of the pair of openings II3o or longitudinal slot 130o (see e.g. figure I 0(c).

In examples where the outer wall 113w comprises a longitudinal slot 113o, the interior wall portions 113i preferably comprises a longitudinal wall portion that is set back from and connected across the interior side of the longitudinal slot 113o, as shown in figure I0(b) and 10(c).

Figure 11 shows an example of an alternative configuration to the embodiments of figures 9 and 10. in this example, the outer wall II3w does not comprise the openings or slots, but instead comprises a pair of exterior wall portions 1 13e connected to the exterior side of the outer wall 113w for receiving and engaging the projections 131p of the attachment 130. Preferably, each exterior wall portion 113e forms a longitudinally facing opening or mouth 113eo for receiving the projection 131p as shown in figures 10(a) and 10(b). The exterior wall portions 113e can further provide a shoulder or transverse wall portion I 13 es within the longitudinal opening 1 I 3eo against which the end of the projection 13Ip can engage/abut when inserted therein. Alternatively or additionally, the attachment 130 can include the interior or exterior shoulders 131s for engaging the opposing edges 113 co of the pair of exterior wall portions 113c (see figure 11(a)).

In addition to using shoulders 131s and/or interior/exterior wall portions 113i, 113e to maintain the attachment 130 in a flexed or sprung state, the attachment 130 of figures 9 to 11 can also include one or more biasing elements 132, such as springs, on the inner side of the attachment 130 to engage a surface of the tubular guide member I 13 (i.e. the outer wall 113w where there are a pair of opening 113o, or the set-back longitudinal wall portion 113i where there is a longitudinal slot 113o) to further bias the wear surface I 30s away the tubular guide member 113. in a preferred example, the attachment 130 comprises a pair of leaf spring portions 132, as illustrated in figures 9(a), 10(a)-(c), and 11(a). The leaf spring portions are preferably formed of flexible high tensile strength material such as spring steel. Other suitable materials are known in the art.

Figure 12 shows an alternative configuration of the example in figure I I, whereby the exterior wall portions 1I3e are not configured to hold or maintain the attachment 130 in a flexed or spung state.

in the embodiments of figures 9 to 12, one of the projections 13Ip at the ends of the attachment 130 can additionally comprise a distal portion 13 lpw of increased width that can be aligned with corresponding wider section 113ow of the opening 113o or slot 113o during insertion. Similar to the asymmetric projections and openings in figure 5, this may introduce an asymmetric to the engagement features and attachment 130 to restrict the connection orientation of the attachment 130 to a single longitudinal direction. This is illustrated in figure 13 which shows a plan view of an attachment 130 with asymmetric projections 131p connected to a longitudinal slot 113o in the outer wall 113w.

In any of the embodiments described above the attachment 130 can be formed of multiple parts. In a preferred embodiment, the attachment 130 comprises a base portion 1301 configured to releasably connect to the engagement features of the outer wall 113w, and a wear strip 1302 attached to the base portion 1301 such that the wear strip 1302 provides the outwardly facing wear surface 130s, as shown schematically in figure 13. The base portion 1301 can include the projections 130p, flip or the openings 130o for connecting to the tubular guide member 113. In certain embodiments, the wear strip 1302 is preferably dimensioned to be shorter than the base portion 1301 so as to provide the shoulder I30s for engaging the edges 113o, 113e" of the openings 1130, 1 I 3eo.

Preferably, the base portion 1301 is formed of or comprises a metal material, whereas the wear strip 1302 is formed of or comprises a polymer material with low thermal conductivity and a melting point above the temperature applied from the sealing unit 14 (e.g. suitable materials include polytetrafluoroethylene (PTFE), and nylon). The base portion 1301 can further include the one or more biasing elements 132 attached thereto or integrally formed with. For example, the one or more leaf spring portions 132 can be provided by one or more respective folded tabs attached to the inner side of the base portion 1301 or integrally formed from the base portion 1301 by cut-outs.

In a preferred embodiment, the wear strip 1302 is detachably mounted onto the base portion 1301. In one example, this is achieved using the same slidable locking engagement means as described with reference to figures 6 to 8. Figure I5(a) shows a schematic cross-section of an attachment 130 according to an embodiment. in this example, the base portion 1301 comprises two or more longitudinally spaced-apart projections 1301p on an outward facing side thereof including a stem portion 1301p1 and an enlarged head portion 130Ip2, and the wear strip 1302 comprises respective slots 1302o configured to receive and slidably engage the projection heads 1301p2. Specifically, with reference to figure 15(b) the slots 1302o have a keyhole shape including first section 1301o1 for receiving the head portion 1301p2 therethrough upon moving the wear strip 1302 towards the bac portion 1301 in an insertion direction 1, and a narrower section 1302o2 extending longitudinally from the wider section 1302o1 for receiving the stem portion 1301p1 and engaging the underside of the head portion 1301p2 upon subsequently sliding the wear strip relative to base portion 1301 in a longitudinal direction. The slot 1302o is provided in a recessed portion I302o3 of the wear strip 1302 having a depth D sufficient to provide a clearance d from the head portion 1301p2 that prevents the head portion 1301p2 from protruding past the wear surface 130s and also to accounts for wear and tear of the wear surface 130s over time. In one example, clearance distance d of approximately 1 mm is suitable.

The slidable connection between the base portion 1301 and the wear strip 1302 provides a locking engagement prevents the wear strip 1302 from detaching unintentionally, especially when the attachment 130 is flexed or held in a flexed state.

Figures 16(a) and 16(b) show schematic plan and perspective views of another example wear strip 1302 comprising three slots 1302o for receiving and engaging three corresponding projections 1301p of the base portion 1301. The wear strip 1302 comprises a rounded or chamfered leading end 13021 to reduce the possibility of the wear strip 1302 snagging or damaging the sheet of material 11 as it advances over the leading end 13021 in the feed direction F. Accordingly, this sets a preferred connection orientation of the wear strip 1302 on the base portion 1301 (and the connection orientation of the attachment 130 on the tubular guide member 113). In an example implementation, where there are three or more three slots 1302o and corresponding projections 1301p, these can be unequally spaced apart in the longitudinal direction and/or misaligned with respect to the longitudinal axis L to introduce a suitable asymmetry that restricts the connection orientation to a single longitudinal direction.

Figures I7(a) and 17(b) show, respectively, perspective and transverse cross-sectional views of an embodiment of the attachment 130 connected to the tubular guide member 113. This example corresponds substantially to the configuration of figure 10(c) but attachment 130 comprises the base portion 1301 and detachable wear strip 1302. Figure 17(a) shows the end of the attachment 1130 opposite the leading end (the wear strip 1302 includes a rounded or chamfered leading end 13021 which is not visible). The slot 113o includes a wider section 113ow at one end for aligning with the distal portion 13 lpw of the projection 131p of increased width during insertion. The end of the wear strip 1302 provides the shoulder 131s that engages the edge 113oe at the end of the slot 113o when connected so as to maintain the attachment 130 in a flexed or sprung state.

As can be seen from inspection of figure 17(a), the direction of the slot 1302o in the wear strip 1302 prevents the wear strip 1302 from detaching from the base portion 1302 when connected.

With reference to figure 17(b), in this example the longitudinal portion of the outer wall 113w to which the attachment 130 is connected is substantially flat to improve the stability of the attachment 130 when connected.

To connect the attachment 130 in this example (and all those where the attachment 130 bends to connect), first the distal portion 13 lpw of the projection 131p of increased width is located and aligned with the wider section 113ow of the slot 113o and the projection 131p is inserted into the end of the slot 113o and into the longitudinal opening 113io formed between the interior wall portion 113i and the outer wall 113w until the shoulder 1302s at the end of the wear strip 1302 abuts and engages the edge the edge 113oe at the end of the slot 113o. Next, the attachment 130 is bent or compressed so as to feed the other projection 131p into the longitudinal opening 113io at the opposite end of the slot II3o.

From reading the present disclosure, other variations and modifications will be apparent to the skilled person. Such variations and modifications may involve equivalent and other features which are &ready known in the art, and which may be used instead of, or in addition to, features already described herein.

Although the appended claims are directed to particular combinations of features, it should be understood that the scope of the disclosure of the present invention also includes any novel feature or any novel combination of features disclosed herein either explicitly or implicitly or any generalisation thereof, whether or not it relates to the same invention as presently claimed in any claim and whether or not it mitigates any or all of the same technical problems as does the present invention.

Features which are described in the context of separate embodiments may also be provided in combination in a single embodiment. Conversely, various features which arc, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination.

For the sake of completeness it is also stated that the term "comprising" does not exclude other elements or steps, the term "a" or "an" does not exclude a plurality, and any reference signs in the claims shall not be construed as limiting the scope of the claims.

Claims

CLAIMS1. An assembly for a bag forming apparatus, comprising: a tubular guide member for receiving a feed of elongate sheet material wrapped widthways therearound; a longitudinal attachment configured to releasably connect to one or more engagement features of an outer wall of the tubular guide member to provide an outwardly facing wear surface against which overlapping longitudinal edges of the wrapped-around sheet material can be sealed by a sealing mechanism of the bag forming apparatus.
2. The assembly of claim 1, wherein the attachment comprises at least two projections that are longitudinally spaced apart, and the one or more engagement features of the outer wall comprise one or more openings configured to receive and engage the projections of the attachment to connect the attachment.
3. The assembly of claim I or 2, wherein the one or more engagement features of the wall comprise at least two projections that are longitudinally spaced apart along the tubular guide member, and the attachment comprises at least two openings configured to receive and engage the projections of the outer wall to connect thereto.
4. The assembly of claim 2 or 3, wherein the projections comprise a stem portion and an enlarged head portion, and wherein the one or more openings comprise respective slots configured to receive and slidably engage the projection heads; and optionally or 25 preferably, wherein the slots have a first section for receiving the head portion therethrough upon moving the attachment towards the outer wall in an insertion direction, and a narrower section extending longitudinally from the wider section for receiving the stem portion and engaging the underside of the head portion upon subsequently sliding the attachment along the outer wall in a longitudinal direction.
5. The assembly of any of claim 2 to 4, wherein the engagement features comprise at least three projections or openings that are longitudinally spaced apart along the tubular guide member, and the attachment comprises a corresponding number of openings or projections positioned and configured to engage the respective projections or openings of the outer wall, and wherein the longitudinal spacing of the projections or openings of the outer wall is unequal and/or wherein at least one of the projections or openings of the outer wall is misaligned from a longitudinal axis of the tubular guide member.
6. The assembly of claim 2, wherein the outer wall comprises a longitudinal slot or a pair of longitudinally spaced apart openings. and each end of the attachment is or comprises a projection, wherein at least a portion of each projection extends substantially longitudinally, and wherein the attachment is configured to bend or flex along its length to permit insertion of the at least a portion of each projection into respective ends of the longitudinal slot or into respective ones of the pair of openings.
7. The assembly of claim 6, wherein the attachment further comprises a shoulder at each respective end, wherein the shoulders are configured to engage opposing edges of the longitudinal slot or a respective edge of the pair of openings when the at least a portion of each projection is inserted so as to maintain the attachment in a flexed state.
8. The assembly of claim 6 or 7, wherein the tubular guide member comprises interior wall portions connected to the interior side of the outer wall, wherein the projections are configured to engage respective interior wall portions when the projections are inserted so as to maintain the attachment in a flexed state.
9 The assembly of any of claims 6 or 8, wherein, where the outer wall comprises a longitudinal slot, the tubular guide member comprises an interior wall portion set back from and connected across the interior side of the longitudinal slot.
10. The assembly of claim 2, wherein each end of the attachment is or comprises a projection, wherein at least a portion of each projection extends substantially longitudinally, and wherein the tubular guide member comprises a pair of exterior wall portions connected to the exterior side of the outer wall to provide a pair of opposing longitudinally facing openings for receiving and engaging the projections of the attachment, wherein the attachment is configured to bend or flex along its length to permit in sertion of the at least a portion of each projection into respective openings.
11. The assembly of any preceding claim, wherein, when the attachment is connected to the outer wall, at least a portion of the wear surface is biased away from the tubular guide member and moveable theretowards upon application of a compressive force by the sealing mechanism of the bag forming apparatus.
12 The assembly of claim 11, wherein the attachment comprises one or more spring portions configured to engage the tubular guide member to bias the at least a portion of the wear surface away the tubular guide member.
13. The assembly of claim 11 or 12 when dependent from any of claims 6 to 10, wherein, when the attachment is connected to the outer wall, the attachment is configured to be held in a flexed or sprung state, such that the wear surface is curved outwards.
14. The assembly of claim 12 or 13, wherein the attachment comprises one or more leaf spring portions to engage a surface of the tubular guide member and bias the at least a portion of the wear surface away the tubular guide member.
The assembly of any preceding claim, wherein the attachment comprises a base portion configured to releasably connect to the engagement features of the outer wall, and a wear strip detachably mounted onto the base portion, the wear strip providing the outwardly facing wear surface.
16. The assembly of claim 15 when dependent from any of claims 11 to 14, wherein the base portion comprises one or more integral spring portions formed by one or more respective folded tabs to bias the wear surface away from the tubular guide member.
17. The assembly of claim 15 or 16, wherein the base portion includes two projections that are longitudinally spaced apart, each comprising a stem portion and an enlarged head portion, and wherein the wear strip comprises respective slots configured to receive and slidably engage the projection heads; and optionally or preferably, wherein the slots have a first section for receiving the head portion therethrough upon moving the wear strip towards the base portion in an insertion direction, and a narrower section extending longitudinally from the wider section for receiving the stem portion and engaging the underside of the head portion upon subsequently sliding the wear strip along the base portion in a longitudinal direction.
18. The assembly of claim 17, wherein the base portion includes at least three projections that are longitudinally spaced apart, and the wear strip comprises a corresponding number of slots, and wherein the longitudinal spacing of the projections is unequal and/or wherein at least one of the projections is misaligned from a longitudinal axis of the attachment.
19. The assembly of claim 17 or 18, wherein the base position is formed or comprises a metal material, preferably spring steel, and wherein the detachable wear strip is formed of or comprises a plastic or polymer material, preferably polytetrafluoroethylene (PTFE).
20. A bag forming apparatus, comprising an assembly of any of claims 1 to 19; and optionally or preferably, wherein the bag forming apparatus is or comprises a vertical form fill se& apparatus, and wherein the tubular guide member is or forms part of a vertically arranged product deliver chute.
21. An attachment configured to releasably connect to an outer wall of a tubular guide member of a bag forming apparatus, comprising a base portion configured to releasably connect to an outer wall of the tubular guide member, and a wear strip detachably mounted onto the base portion, the wear strip providing an outwardly facing wear surface.
22. A tubular guide member for a bag forming apparatus, the tubular guide member comprising a pair of exterior wall portions connected to the exterior side of the outer wall to provide a pair of opposing longitudinally facing openings, the openings being configured for receiving opposing ends of an attachment, wherein the attachment comprises an outwardly facing wear surface against which overlapping longitudinal edges of a wrapped-around sheet material can be sealed by a sealing mechanism of the bag forming apparatus.
23. A method of manufacturing a tubular guide member for a bag forming apparatus, the method comprising affixing a pair of exterior wall portions to the exterior side of the outer wall of the tubular guide member to provide a pair of opposing longitudinally facing openings, the openings being configured for receiving opposing ends of an attachment, wherein the attachment comprises an outwardly facing wear surface against which overlapping longitudinal edges of a wrapped-around sheet material can be sealed by a sealing mechanism of the bag forming apparatus.