FIELD OF THE INVENTION

The present invention relates to a multi-wall sack for product, including but by no means limited to, an edible product such as milk powder, flour, grain, sugar and so forth. The product may also be non-edible. The present invention also relates to a process for packaging the product in a multi-wall sack.

BACKGROUND OF THE INVENTION

When a multi-wall sack is used for storing edible product, maintaining the contents of the inner liner is of utmost importance. In the event of failure of the seal of the inner liner, the integrity of the sack as a whole is brought into question, which can result in the contents of the sack being downgraded. For example, powder material intended for human consumption may be downgraded to a material for animal consumption, thereby significantly reducing the market value of the material. In the worst case scenario, the entire contents of the sack may be regarded as being completely compromised which results in the material being downgraded to waste of no value. There is therefore a need to minimise this from occurring .

SUMMARY OF THE INVENTION

An embodiment of the present invention relates to a multi-wall sack including: an inner pouch having an inner side wall defining an opening for loading product into the inner pouch; and an outer bag in which the inner pouch is located, wherein the opening of the inner pouch is define by at least part of the inner side wall protruding from the outer bag, and after the product has been loaded into the inner pouch, the opening of the inner pouch is sealed by forming a seam that is located outside of the outer bag and the outer bag is then closed.

A possible advantage this provides is that the seam can be inspected to determine whether the inner pouch has been properly sealed. Being able to inspect the seam enables sacks having an inferior seam to be removed from a production line.

Another advantage is that imperfections in the seam are less likely because the seam is formed in the inner wall extending from the outer bag.

The outer bag may have an outer wall defining a mouth to the outer bag, and a closure flap may extend from outer wall. The closure flap may be used to close the mouth of the outer bag after the inner pouch has been sealed. Before the closure flap is closed, the closure flap can be oriented to extend away from the mouth of the outer bag, so that the inner pouch protrudes from the closure. However, it will be appreciated that the closure flap may also be located to overlap the mouth of the outer bag and close the outer bag.

Ideally, the seam is located outside of the mouth of the outer bag . After the product has been loaded into the inner pouch, the opening of the inner pouch may be sealed by pressing together adjacent layers the inner side wall along a line that is spaced from the opening of the inner pouch and applying heat along the line to form the seam. Ideally, the seam is formed by heat being applied directly to the inner side wall. On account that the seam is located outside the outer bag, heat applied to the inner side wall to form the seam is not required to be conducted through the outer wall of the outer bag.

The seam may be formed by adjacent layers of the inner side wall being welded together.

The seam may be located at a spacing from 5 to 50mm from an outer edge of the inner wall of the inner pouch. Suitably, the seam may be spaced from 10 to 40mm from an outer edge of the inner wall, more suitably the seam may be spaced from 10 to 20mm from the outer edge of the inner wall, and even more suitably the seam may be spaced 10mm from the outer edge of the inner wall .

The seam may be located at a spacing from 5 to 45 mm from the mouth the outer bag before the closure flap is closed.

Suitably, the seam may be spaced from 10 to 40mm from the mouth of the outer bag, more suitably the seam may be spaced from 10 to 20mm from the mouth of the outer bag, and even more suitably the seam may be spaced 10mm from the mouth of the outer bag.

In one embodiment, the seam may be spaced approximately 10mm from the mouth of the outer bag, and may be spaced approximately 10mm from the outer edge of the inner wall.

The section of the inner wall between the seam and the edge of the inner wall may form a skirt section.

The inner pouch may be a polymeric material, and suitably a polyolefin or plastic material. Possible examples include polyethylene, vinyl, polyesters or polypropylene, or a

coextrusion which includes these materials and others.

In one embodiment, the side wall of the inner pouch may include a heat sensitive constituent that changes colour when heated to a particular temperature. For example, the heat sensitive constituent may be a photochromic constituent that is

incorporated in the polymeric material of the inner pouch. The photochromic constituent may change colour when heated to a particular temperature, such as the temperature required to the weld layers of the inner side wall together. Any differences in the colour of the seam may therefore be used as a basis for showing that the seam is imperfect.

Inspection of the seam can be performed using any suitable means, including visual inspection for example using a digital camera and pixel analysis. Inspecting the seam may include measuring the capacitive properties or electrical potential of the seam.

Inspecting the seam may include exposing the seam to an electromagnetic emission and sensing the seam may include a sensor having a transmitter and receiver for monitoring the seam. The sensor may include transmitters and receivers for an ultrasonic device, an infrared device or an x-ray device.

The inner side wall may be adhered to an inner face of the outer bag. By adhering the inner side wall to an inner face of the outer bag, the inner bag is prevented from inadvertently displacing into the outer bag, particularly prior to filling. By adhering the inner side wall to the outer bag, the opening for loading product into the inner bag may be opened, and held opened, by engaging the outer bag.

Ideally, the inner side wall may be releasably adhered to the outer bag. The inner pouch may also have a marker applied thereto, such as barcode or timestamp that can be used for identifying and tracking the movement the inner pouch and, in turn, the product of the inner pouch. The marker may be applied to the inner pouch adjacent to the seam, i.e. above or below the seam.

Ideally, the marker is located on a part of the inner pouch outside of the outer bag. In one embodiment the top end of the outer bag may be closed by the closure flap being positioned over the mouth of the outer bag and attached to an outside face of the outer bag.

In another embodiment, the outer walls at the top end of the outer bag can be located in a closed configuration. For example, the outer walls may be folded to one side of the outer bag and adhered in position to form a pinched top end of the sack. Alternatively, the top end sections of the outer bag on opposite sides of the seam can be folded and adhered to form a block top end.

In another example, the top end sections can be closed by means of sewing or an adhesive tape.

The outer bag may have a closure that allows the outer bag to be opened to allow the inner pouch to be removed from the outer bag.

The closure may include a tear strip that can be used to tear the outer walls .

Ideally the outer bag has a block (i.e. rectangular) bottom end. The block bottom end provides a flat closed base for the sack and is formed by folding the outer bag, and not the inner pouch, in a particular manner during manufacture. This arrangement is such that when the sack is filled with a product, the inner pouch pushes against the folded closed end and takes up the shape of the block bottom end. Another embodiment of the present invention relates to a multi- wall sack containing a product, the sack including: an inner pouch having an inner side wall, the inner pouch being filled with product and sealed along a seam; and an outer bag in which the inner pouch is located; wherein the sealed seam of the inner pouch is located outside of the outer bag.

Ideally, the seam is located outside of the mouth of the outer bag .

Another embodiment of the present invention relates to a process of forming a multi-wall sack which includes the steps of: a) forming an inner pouch having an inner side wall that defines an opening for loading product into the inner pouch ; b) forming the outer bag and locating the inner pouch

inside the outer bag, so that the opening of the inner pouch is define by at least part of the inner side wall protruding from the outer bag.

Another embodiment of the present invention relates to a process of packaging product in the multi-wall sack described herein, in which the process includes the steps of: a) loading product into the inner pouch;

b) sealing the inner pouch by forming a seam across the opening of the inner pouch, wherein the seam is located outside of the outer bag;

c) closing a top end of the outer bag to enclose the inner pouch and form a complete sack.

Another embodiment of the present invention relates to a process including the steps of: a) forming an inner pouch having an inner side wall that defines an opening for loading product into the inner pouch ;

b) forming the outer bag so that the inner pouch is

located inside the outer bag, and that the opening of the inner pouch is define by at least part of the inner side wall protruding from the outer bag;

c) loading product into the inner pouch;

d) sealing the inner pouch by forming a seam across the opening of the inner pouch, wherein the seam is located outside of the outer bag; and

e) closing a top end of the outer bag to enclose the inner pouch .

The steps of the process may be carried in any appropriate order, including some steps being carried out simultaneously, consecutively or disjunctively. For example, in the case of the process described in the paragraph immediately above, steps a) and b) may be carried out at one site, and steps c) , d) and e) may be carried out at another site. The step of forming the outer bag may include arranging an outer wall to from an outer bag having a mouth, and providing a closure flap extending from the outer wall extending away from the mouth.

The step of sealing the inner pouch may include forming a seam in a line across the inner pouch, in which the seam is located outside of the mouth of the outer bag.

Sealing the inner pouch may include pressing together the inner side wall along a line that is spaced from the opening of the inner pouch and applying heat along the line to form the seam. Sealing the inner pouch may include pressing together the inner side wall and applying heat directly to the inner side wall.

The process may include inspecting the seam before closing a top end of the outer bag.

Inspecting the seam may include measuring the capacative properties of the seam. Inspecting the seam may include exposing the seam to an electromagnetic emission and sensing the seam may include a sensor having a transmitter and receiver for monitoring the seam. The sensor may include transmitters and receivers for an ultrasonic device, an infrared device or an x-ray device. It is possible that a combination of these devices may be used to inspect the seam.

Inspecting the seam may include capturing an image of the seam using an image capturing device, generating data based on an output of the image capturing device for the respective seam, and analysing the data to determine whether the seam has sealed the inner pouch. The data may be representative of the pixels of the image captured, and analysing the data may include comparing the data of the image relative to a reference set of data that is representative of an approved seam.

The image capturing device may be a digital photographic camera.

In one example, the image capturing device may be arranged to capture black and white images. In another example, the image capturing device may be arranged to capture colour images.

When the inner pouch includes a heat sensitive constituent that changes colour after being heated to a predetermined temperature for sealing the seam, such as a photochromic material, the images captured by the image capturing device will include visual information about which regions of the seam have been heated to the predetermined temperature based on the colour of the seam. The data generated by the output of the image capturing device may be based on the information about the colour of the different regions of the seam.

Determining whether the seam has formed an acceptable seal may include determining if the seam has failed, and the process may also include ejecting each sack from a processing line whose seam has been failed, i.e., the failed sack. The failed sack may be opened and the product of the inner pouch may be returned back to a loading mechanism so that the product can be reloaded into a fresh inner pouch.

Inspecting the seam may also include manual inspection by a person at some stage of the inspection step. For example, after the failed sack has been ejected from the processing line the seam may be manually inspected.

Ideally, the inspecting step occurs before the top end of the sack being closed (i.e., step e) . The process may also include applying a marker to the inner pouch. The marker may be applied adjacent to the seam and may be applied using one or a combination of laser etching, inkjet coding, hot foil or other means .

The process may include any one or a combination of the features of the sack described herein. Similarly, the sack may include any one or a combination of the features of the process described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the present invention will now be described with reference to the accompanying drawings, of which:

Figure 1 is perspective view of a sack having an opened top end and a closed bottom end;

Figure 2 is an enlarged top end view of the sack shown in figure 1 in which the inner pouch has been closed with a sealed seam and the outer bag opened so that the seam can be inspected;

Figure 3 is an enlarged top end view of the sack shown in figure 1 in which the inner pouch has been closed with a sealed seam and the outer bag closed; and Figure 4 is a block diagram illustrating process steps for making the sack and packaging a product in the sack.

DETAILED DESCRIPTION

The following text describes a preferred embodiment shown in the figures. The text includes reference numerals to help identify the features in the figures. However, in order to maintain clarity of the figures, not all of the reference numerals have been used in each figure.

With reference to figures 1 to 3, the sack 10 of the preferred embodiment includes an outer bag 11 and an inner bag, which is herein referred to as an inner pouch 12. The inner pouch 12 ideally has an inner side wall 13 in the form of a single layer of plastic film that is initially formed as a tubular section having a sealed bottom end and an opening 14 at a top end. The outer bag 11 has an outer side wall 15 comprising one or more sheets or layers that have a tensile strength that is greater than the tensile strength of the inner side wall 13 of the inner pouch 12. Ideally the outer side wall 15 of the outer bag 11 has two paper sheets or layers placed back-to-back. The bottom end 16 of the outer bag 11 may be closed in any suitable arrangement, and ideally the outer side wall is folded so as to form either: a pinch bottom end, a satchel bottom end, or a bock bottom end. A satchel bottom end and a block bottom end have a rectangular shape. The inner pouch 12 is located in the outer bag 11 and the bottom end 16 of the outer bag 11 is formed without the inner pouch 12 being folded with the outer side wall 15 of the outer bag 11. In other words, the inner pouch 12 is unrestricted at the bottom end 16 of the sack 10 and is free to take up the shape of the inside of the outer bag 11 when filled.

The upper portion of the outer side wall 15 of the outer bag 11 defines a mouth 17 at the top end 22 of the sack 10, and a closure flap 18 for closing the mouth 17 of the sack 10. The inner pouch 12 is sized lengthwise so that inner side wall 13 protrudes from the mouth 17 of the outer bag 11 by a

predetermined amount. For example the inner side wall 13 may extend by an amount in the range of 5 to 50 mm from the mouth, ideally in the range of 15 to 25mm, and even more ideally approximately 20mm.

Figure 2 illustrates the closure flap 18 in two positions, namely an upright position as shown in dashed lines, and a folded position away from the mouth 17 of the outer bag 11, as shown in solid lines. The inner pouch 12 protrudes from the mouth 17 of the outer bag 11, irrespective of the position of the closure flap 18. However, when the closure flap 18 is folded or rolled downward into the position shown by solid lines in figure 2, the seam 22 and the skirt section 25 are exposed from opposite sides, thereby making forming the seam 22 and

inspecting the seam 22 more reliable. In the situation in which the closure flap 18 is oriented upright, as shown by means of dashed lines in figure 2, the seam 22 and the skirt section 25 are exposed from one side, thereby making forming the seam 22 and inspecting the seam 22 more reliable. After the inner pouch 12 has been filled with product, the top end of the inner pouch 12 may be sealed using any suitable means, including an adhesive, but suitably by means of a physical bonding in which the inner side wall 13 are pressed together along a line that is spaced from the opening 14 of the inner pouch 12 and applying heat along the line to form a sealed seam 22, as best seen in figure 2. The seam 22 is spaced from an upper edge of the inner side wall 13 so as to form a skirt section 25 between the seam 22 and the top edge of the inner side wall 13. Advantageously, the seam 22 can be formed in the inner side wall 13 outside of the mouth 17 of the outer bag 11, thereby allowing the seam 22 to be formed by directly contacting the inner side wall 13 of the inner pouch 12 by the sealing device. In the situation in which the closure flap 18 of the outer bag 11 is position in the upright position, the sealing device may contact an outside of the closure flap 18 and the inner side wall 13 of the inner pouch 12. In the situation in which the closure flap 18 is folded downward, the sealing device may opposite sides of the inner pouch 12. In other words, the seam 22 of the inner side wall 13 is achieved by means of pressure and heat being applied directly to the inner side wall 13 of the inner pouch 12 along the line of the seam 22. The outer walls 15 of the outer bag 11 are not subjected to heat and pressure. The sealing device may be any suitable device, such as a device having at least one heated bar assembly that direct contact with the inner side wall.

The plastic film of the inner pouch 12 can be physically bonded to itself, and many be any material such a polyethylene, ABS, polypropylene, vinyl, and so forth. Ideally, the inner pouch 12 also includes a heat sensitive constituent such as a

photochromic agent that changes colour when the inner side walls 13 of the inner pouch 12 are heated to a sufficient temperature to allow the side walls 13 of the inner pouch 12 to be

physically bonded together to form the seam 22.

As the seam 22 of the inner pouch 12 is located outside of the mouth 17 of the outer bag 11, the seam 22 can be inspected for faults without deforming or destruction of the outer bag 11. If no flaws or faults are found in the seam 22, the sack 10 can be closed. Specifically, the closure flap 18 at the top end of the outer bag 11 can be closed to cover the mouth 17 and attached to an opposite panel of the side wall of the outer bag.

An inside face of the closure flap 18 includes a glue line 24 that can be applied to the securing panel 20 to hold the closure flap 18 in a closed position. In order to assist in locating the inner pouch 12 in an operative position in the outer bag 11, the inner pouch 12 may be adhered to an inside surface of the outer bag 11 using a releasable adhesive located adjacent to the mouth 14 of the outer bag 11. For example, the releasable adhesive may be a pressure sensitive adhesive.

A marker 23, best seen in figure 2, may also be applied to the inner pouch 11 adjacent to the seam 22, or a section adjacent to the seam 22. The marker 23 may be, for example, a barcode or a timestamp. The marker 23 may therefore be used for tracking the location of an inner pouch 11 either before closing of the outer bag 11, or after the inner pouch 12 has been removed from the outer bag 11.

The marker 23 may be applied to the inner pouch 12 using any suitable means, including laser etching, inkjet, hot foil or other means .

Figure 4 is a block diagram illustrating the steps of a process for making the sack and packaging a product in the sack. The process includes forming an inner pouch having an inner side wall that defines an opening for loading product into the inner pouch. Forming the inner pouch may include extruding a plastic material in a tubular structure and segmenting the tubular structure by forming a bottom seam across the tubular structure to form a closed bottom end of the inner pouch and severing individual bags that provide the inner pouch.

The inner side wall may be made of any plastic material that can be physically bonded to itself by means of pressure and heat. In addition, ideally the inner side wall includes a heat sensitive constituent, such as a photochromic resin, that changes colour when heated to a predetermined temperature. Ideally the predetermined temperature is the temperature at which the inner side wall can physically bond to itself. The process also includes forming an outer bag in which the inner pouch is disposed. The outer bag is ideally formed from 2 layers of paper sheets that form the outer side wall of the outer bag and have been folded and glued to form a block shaped bottom end. The paper sheets may include kraft paper, recycled fibre, or a combination thereof. Forming the outer bag may also include arranging the outer side wall so as to define a mouth and locating the inner pouch in the outer bag so that an upper section of the side wall of the inner pouch protrudes from the mouth.

Forming the outer bag may also include providing a closure flap extending from the mouth of the side wall of the outer bag. The outer side wall of the outer bag may have a front panel and a rear panel, and the closure flap may extend from the rear panel and have substantially the same width as the rear panel.

The inner pouch may be located in the outer bag and secured in position and the outer bag by means of a releasable adhesive. The process may include applying the releasable adhesive at any desired position within the outer bag, but is ideally located at discrete points adjacent to the mouth of the outer side wall of the outer bag.

Once the sack has been assembled by locating and securing the inner pouch in the outer bag, product can be loaded into the inner pouch and the inner pouch sealed. Sealing the inner pouch is ideally carried out by sealing device such as a hot press iron in which opposite layers or panels of the inner side wall of the pouch are pressed together along the line and heated along the line so as to physically bond the side walls in a seam. Ideally, the iron directly contacts, presses and applies heat to the inner side wall of the inner pouch. As the inner side wall of the pouch protrudes from the mouth of the outer bag, the seam can be formed outside of the outer bag. A marker, for example, in the form of a barcode or a timestamp may also be applied to the inner pouch adjacent to the seam.

To provide some assurance that the seam is providing an adequate seal, the process includes an inspecting step for assessing whether the seam has adequately sealed the inner pouch. The inspecting step may include capturing one or more images of seam and generating data based on the image (s) captured, or an output of the image capturing device. The process can then include determining whether the seam provides an acceptable seal by comparing the data generated to a running set of data, or a standard set of data that has been pre-generated and which represents an acceptable quality of seal. A processor can be used for either one or a combination of, generating the data representing the seam captured in the images, and comparing the data for determining whether the seam provides an acceptable seam.

In the situation in which the inner side wall includes a photochromic resin, the data generated may be based on the colours captured in the images. The data generated may be based on a pixel analysis of digital images captured.

Ideally the process is carried out in a continuous processing line, and the inspection step, including capturing one or more images of each seam of each sack can be carried out whilst the sack is moving, for example along the processing line on a conveyor.

In the event that the process determines that the seal does not meet the acceptable standard, the sack can be rejected, i.e., the rejected sack. A rejected sack can be removed from the processing line and manually inspected. In addition, product of the rejected sack can also be reused.

Similarly, the image capturing device may also read or captured by an image of the marker applied to the inner pouch. In the event that a seam of a particular bag has been assessed as not adequately sealing the inner pouch, the marker applied to the inner pouch can be used to track the inner pouch, or track a sack containing the inner pouch. Moreover, the marker allows the inner pouch to be tracked the inner pouch being from removed from the outer bag, or after the inner pouch has been removed from inner bag.

The process further includes closing the closure flap of the outer bag. Specifically, the glue line on an inner face of the closure flaps can be attached to a closure panel having a tear strip, and the tear strip removed.

Some of the advantages provided by the sack and process described herein are as follows: i) The seam of the inner pouch can be formed without paper of outer bag being located between the inner pouch and the device applying the pressure and heat to the inner pouch. In other words, the seam is formed by directly applying heat and pressure to the side wall. This means that the sealed seam can be formed quickly and more reliably .

ii) Locating the sealed seam outside of the mouth of the outer bag enables the sealed seem to be inspected by directly viewing the seam.

iii) Access for viewing the seam improves the appearance and contrast of the seam relative to the inner walls of the inner pouch and the outer bag. Therefore inspection of the seam should be performed reliably.

iv) The sealed seam can be viewed without destruction of the outer bag.

v) The sealed seam can be viewed from a very close

perspective which a) improves efficiency of the inspection, b) reduces the need to capture the whole seam as one image, multiple images of one seam can be obtained, and c) the size and complexity of the machinery can be reduced,

vi ) The marker can be applied to adjacent to the seam

outside of the mouth. The marker may be a barcode or a timestamp, which can be viewed directly before closing the closure flap of the outer bag, or after the inner pouch has been removed from the outer bag.

It will be understood to persons skilled in the art of the invention that many modifications may be made without departing from the spirit and scope of the invention.