GB2459282A

GB2459282A - A gusseted sack having a means for promoting the formation of a flat bottom during filling

Info

Publication number: GB2459282A
Application number: GB0806930A
Authority: GB
Inventors: James Reading
Original assignee: EAST RIDING SACKS Ltd
Current assignee: EAST RIDING SACKS Ltd
Priority date: 2008-04-16
Filing date: 2008-04-16
Publication date: 2009-10-21
Also published as: GB0806930D0

Abstract

A sack 10 comprises a tube 12 of one or more piles 30 having longitudinal fold lines defining opposing side edges 32, two opposing sides 14 and two gussets 16 extending there between. To promote the formation of a substantially flat stable bottom 15 during filling, a portion of each gusset 16 is attached to its corresponding opposing side 14. The inside surface of each half of gusset 16 is adhered to the inside surface of its opposing side 14 in the vicinity of the bottom edge 22 so as to cause each gusset 16 to fold in such a way as to promote the adoption of a substantially flat stable bottom during filling. An adhesive application means (Figure 6, 50) and method of manufacture of the sack is also provided, wherein the adhesive application means comprises a drum, a drive means for rotating the drum and an applicator mounted on the drum for retrieving an amount of adhesive from an adhesive bath and depositing the adhesive on the inside of a sack.

Description

A Sack The present invention relates to sacks and in particular the manufacture of sacks. The invention relates more specifically to paper sacks used, for example, for packaging powdered or granular materials, such as flour, food ingredients or animal feed.

Known types of paper sack for packaging include rolled-bottom paper sacks. A typical rolled-bottom paper sack is shown in Figure 1. Rolled-bottom paper sacks (1) are manufactured from a flattened tube (2), one end of which is formed into a closed rolled-bottom (4). The tube (2) may comprise one or more paper sheets, known as. plies (6). In a flat state, an open end of the tube may be folded over once or twice and a stepped edge (8) of the outer ply may be adhered over the fold(s) (7) to form either a single or double rolled-bottom, depending on customer requirements.

Adhesive is typically used to secure the fold(s) (7) in position to form a closed end. The other end (5) of the tube may be left open or closed in various ways, for example sewn or sealed and left with a valve controlled opening. The sides of the sack may include gussets (3) of varying depth, again depending on customer requirements. Typical rolled-bottom paper sack characteristics may include using one to four plies and a paper grade from 75gsm to 28Ogsm. Of course, customer requirements will govern the *.S.

specific characteristics of the sack. * ** * I I I.. S

*. 25 After fabrication, the sacks are filled with the required contents. Typically, the sacks move along a process line and are filled at high speed. It is I.....

* known to fill open sacks directly on the process line by inserting the end of SI.

* a filler hose in or over the open end of a sack and depositing the contents at high speed therein. In the case of sacks with valve controlled openings, each sack is filled via the valve, which closes when the sack is full.

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Typically, rolled-bottom paper sacks are filled at a rate of about 850 sacks/hr.

A problem associated with sacks, in particular rolled-bottom paper sacks, is inconsistent and poor formation of the bottom of the sack during high speed filling. As a result, the sacks are prone to falling over during filling and stacking/storage on pallets and/or truck load beds is made difficult and inefficient.

Before filling, the bottom of a rolled-bottom sack, as shown in Fig. 1, is substantially flat in a vertical plane relative to a horizontal surface on which the sack is being filled, e.g. a pallet. As the sack is being filled, the bottom and sides of the sack are pushed out and the bottom is forced to adopt a substantially flat profile with the surface on which it is being filled, by the increasing weight of the contents entering the sack. The existing construction of the rolled-bottom means the adoption of a flat bottom during filling is non-symmetrical relative to the sack axis. As the sack is filled, the level of content rises and, as a result, so does the combined centre of gravity. The poor, inconsistent and non-symmetrical formation of the bottom and sides of the sack results in the centre of gravity of a filled sack being differently located to that of another identical filled sack. If the centre of gravity of a sack being filled is substantially off a vertical axis of the sack, combined with an unstable bottom, the sack may fall over resulting in its content being spilled. A result of this may be downtime of ** 25 the process line as the problem is being rectified. In addition, poor and inconsistent formation of the bottom of each sack may make stacking and S. S*** storage of filled sacks on pallets, for example, difficult and inefficient.

Transportation is also made inefficient due to the irregular shape of the filled sacks.

Improvements in sacks, in particular rolled-bottom paper sacks, are required. Such improvements may include one or more of the following features: -adoption of a well defined, flat bottom during filling; -symmetrical adoption of a flat bottom during filling; -improved stability; -simple and easy to manufacture using existing tube material; -inexpensive; -non-contaminating to contents; -additional rigidity and strength; and -improved storage characteristics.

According to a first aspect of the present invention, a sack is provided comprising: -a tube of one or more plies having opposing sides; -a gusset extending between opposing side edges; -a closed end; and -promotion means to promote the formation of a substantially flat bottom at the closed end during filling of the sack.

* ** It will be understood that the term tube' is a standard term in the art * . I referring to the one or more plies in a joined state before or after being folded, e.g. to comprise a substantially box-like cross section. Suitably, the plies are folded longitudinally to define the opposing side edges and *. 25 the gussets there between.

*.**.* Suitably, the closed end may be a standard rolled-bottom as described **.

above. Alternatively, an end may be closed using other techniques known in the art, e.g. sewing. It will be understood that the term rolled-bottom' refers to a standard type of sack and particularly paper sacks as described above and to the process commonly used to produce such a sack.

Preferably, when filled, the sack is substantially box-like, i.e. having a square or rectangular bottom wherein the opposing sides and gussets extend up from its bottom. The opposing sides and gussets may be substantially equal in width, i.e. forming a substantially square sack, or alternatively the opposing sides may be wider than the gussets, i.e. forming a substantially rectangular sack. A sack having a substantially square or rectangular bottom and sides advantageously allows a plurality of filled sacks to be neatly stacked or stored together in a tight square formation. This allows more sacks to be stacked or stored together in a given space, such as on a pallet and/or the load bed of a truck. Efficient storage and transportation desirably reduces handling and storage costs.

Additionally, a substantially square or rectangular sack bottom allows the bottom of the sack to be filled with more material because the corners of the sack bottom can be conveniently utilised, unlike a sack having an irregular sack bottom. Therefore, the height of material in a filled sack will be reduced and the sack height can be reduced accordingly. A sack having a reduced height also requires less material, thereby desirably reducing material costs. S... * . **..

Preferably, the gussets each comprise a longitudinal gusset fold line which extends up each gusset from the bottom of the sack to the top of the sack.

*. 25 Preferably, each longitudinal gusset fold line defines two gusset halves * allowing the inside of each gusset half to fold towards, and interface with, *..S each other when the sack is substantially flattened when empty. This allows one or more empty sacks to be stored more efficiently, e.g. stacked.

Suitably, the promotion means attaches a portion of each gusset half to an opposing side portion of a corresponding opposing side in such a way as to promote the formation of a substantially flat, well defined bottom when the sack is being filled. Suitably, each gusset portion and opposing side portion are attached in the vicinity of the bottom of the sack.

Suitably, the gusset portions may be adhered to their corresponding opposing side portions. Preferably, the adhesive may comprise at least one adhesive line. Advantageously, adhesive is lightweight and may be applied without compromising the integrity of the sack. However, other joining techniques may be used, e.g. sewing, riveting or stapling. The application of adhesive inside the sack was believed to be bad practice within the field of sack manufacture. This belief stemmed from the adhesive being in close proximity to the contents and the risk of contamination to the contents.

Suitably, the adhesive lines may be disposed on the opposing sides.

Alternatively, adhesive lines may be disposed on either or both of the opposing sides and the gussets. When brought together, the corresponding lines of adhesive will form a secure bond between the opposing sides and gussets of the sack. * * *..

Suitably, at least one adhesive line is disposed in or on each gusset half, near the closed end of the sack.

Suitably, the promotion means comprises a plurality of adhesive lines in *..S.* * two sets, wherein one set is disposed in or on each gusset. *I. *

Suitably, each set comprises two adhesive lines arranged in a triangular pattern, the apexes of each set being disposed on the longitudinal gusset fold lines so each adhesive line in a set is a mirror image of its neighbouring adhesive line about the longitudinal gusset fold line and is disposed on each gusset half.

Suitably, the triangular pattern is orientated with its apex pointing towards the bottom of the sack. Thereby, each set of adhesive lines extend from the apex out to the edges of the gussets.

Advantageously, the sets of adhesive lines are disposed symmetrically in the gussets. The sets of adhesive lines attaching the gusset portions to the corresponding opposing side portions, and the longitudinal gusset fold lines, importantly provide the sack with means to promote the formation of a well defined, substantially flat bottom when being filled, whilst allowing the sack to be substantially flattened when empty.

In addition to the sets of adhesive lines, further adhesive may be disposed within the boundaries defined by the adhesive lines. Further adhesive within the triangular pattern conveniently provides additional strength and stability to the bottom of the sack.

The gusset portions are therefore attached to the inside of their corresponding opposing side portions. Suitably, the gusset portions are attached to the inside of the opposing sides along the sets of adhesive lines. This attachment provides an anchor for the gussets and opposing *. 25 sides to hinge about when forming a substantially flat bottom of the sack during filling. The triangular arrangement defines the corners of the S.....

substantially square, or rectangular, bottom. The attachment also ensures S..

the bottom of the sack will consistently adopt a substantially square, or rectangular, flat bottom when being filled and the bottom of the sack will not lose its substantially flat, well defined bottom as a result of being constantly emptied, flattened and refilled.

Suitably, the adhesive lines may comprise continuous lines of adhesive.

Alternatively, the adhesive lines may be intermittent. This advantageously reduces the amount of adhesive required, thereby reducing material costs.

Suitably, the intermittent adhesive lines may comprise a plurality of individual adhesive spots or lines.

Preferably, the adhesive is standard PVA glue but may be hot melt, pressure cured or similar adhesive employing adequate drying and strength characteristics.

Alternatively, the promotion means may comprise at least one fold line. A fold line may be pre-formed in the tube of a sack during manufacture and may conveniently promote the bottom of the sack to unfold and adopt a well defined, substantially flat bottom when being filled. Suitable fold lines may conveniently ensure the bottom of the sack unfolds to be consistently well defined each time it is filled. Suitable fold lines may be disposed on * ** the gusset portion of each gusset and suitable adhesive lines may attach $ S S the gusset portions to their corresponding opposing side portions.

Suitably, the sack may comprise easy opening means. Conveniently, . 25 adhesive securing the closed end of the sack, e.g. a rolled-bottom, as described above, may be intermittent. This adhesive may comprise a ** S...

plurality of individual adhesive spots or lines. Suitably, the adhesive may S..

provide one or more non-adhered portions to provide access, e.g. for a finger, to break the adhesive. Conveniently, the rolled-bottom, for example, may then be unfolded to allow access to the contents of the sack.

Suitably, the top end of the sack is trimmed straight and open. After filling, the top end may be left open or closed by a technique known in the art, e.g. sewn. Alternatively, the sack may suitably comprise a valve, as described above, for filling the sack. The top of the sack may comprise an easy-open feature similar to that described above.

Preferably, the sack is paper but may be any suitable material, e.g. plastic, depending on customer requirements. Alternatively, the plies may comprise a combination of different materials, e.g. an inner ply of a paper sack may be plastic. Conveniently, this may prevent the contents escaping from the sack and/or protect the contents inside the sack.

Suitably, an outer surface of the sack may comprise text or drawings to convey information, e.g. a Trade Mark, logo or content information, printed on to the sack or via a label adhered to the sack.

A method of manufacturing a sack as described above is also provided.

An application means for applying the adhesive to the inside of the tube is also provided. * ., * * . I.. *

The present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: : -Figure 1 is a representation of an empty, flattened rolled-bottom sack as known in the art;

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-Figure 2 is a representation of a sack according to the present invention wherein the bottom of the sack is substantially flat, e.g. when filled; -Figure 3 is a representation of a portion of unfolded tube showing the adhesive lines prior to fabrication of the sack in Figure 2; -Figure 4 is a plan view of the sack in Figure 2; -Figure 5 is a view of the underside of the sack in Figures 2 and 4; and -Figure 6 is a representation of an applicator for applying adhesive to the tube during fabrication of the sack in Figures 2 to 5.

As shown in Figures 2 to 5, a sack (10) may be stored substantially flat (in a similar way to the sack shown in Figure 1) and will adopt a substantially flat, stable bottom (15) when filled (as shown in Figure 2). This ensures the sack (10) remains upright during the filling process, particularly high speed filling, and prevents the contents spilling from the sack. Storage of one or more filled sacks and stacking and transportation of a plurality of filled sacks is also made more efficient.

With reference to Figure 2, the sack (10) comprises a tube (12) of one or * *, more plies (30) having a top edge (12) and a bottom edge (22), the bottom edge (22) being rolled to form at least one closed end (20), e.g. a rolled- bottom. A sack comprising this type of bottom is known as a rolled-bottom sack, as described above. . 25

The sack (10) has longitudinal fold lines defining the opposing side edges (32) and the two opposing sides (14) and two gussets (16) extending there *..

* between. The bottom (15) of the sack may be substantially square wherein the opposing sides (14) and gussets (16) are of equal width.

Alternatively, the bottom (15) may be substantially rectangular wherein the opposing sides (14) of the sack are wider than the gussets (16).

The gussets (16) each have a longitudinal gusset fold line (18) disposed up their centres so as to divide each gusset (16) longitudinally in half. The rolled-bottom (20) and the longitudinal gusset fold lines (18) conveniently allow the sack (10) to be flattened when empty for storage purposes.

Importantly, the gussets (16) also unfold to allow the sack (10) to fill out when the sack (10) is being filled.

In the flat state, the inside of each half of each gusset (18) interfaces with an inside portion of a corresponding opposing side (14). When unfolded, or forced apart by contents entering the sack, each half of each gusset moves away from its adjacent half allowing the sack to open.

To promote the adoption of a substantially flat, stable bottom (15) during filling, a portion of each gusset (16) is attached to its corresponding opposing side (14) preferably near the bottom edge (22) of the sack (10).

The inside surface of each half of each gusset (16) is adhered to the inside surface of its opposing side (14) in the vicinity of the bottom edge * ** (22) so as to cause each gusset (16) to fold in such a way as to promote the adoption of a substantially flat, well defined, stable bottom during filling. An important aspect of the invention is the means to promote the formation of triangular portions (25) in the bottom (22) of the sack (10) during filling, the triangular portion (25) helping to define a substantially square, or rectangular, bottom.

*, *.** * * Preferably, a line of adhesive (23) is applied between the inside surfaces of each gusset (16) and their corresponding opposing sides (14).

Conveniently, a line of adhesive can be arranged in such a way as to force 11 1 the gussets (16) and/or the opposing sides (14) to hinge about a particular fine, defined by the adhesive, and form the triangular portions (25).

A set of adhesive lines (23) disposed inside each gusset (16), extending from the bottom (22), at or in the vicinity of the longitudinal gusset fold line (18), out to an edge (32), some way up from the bottom (22) of the sack (10), as shown in Figure 3. Each set comprises two adhesive lines (23) arranged in a triangular pattern, the apexes of each set being disposed on the gusset longitudinal fold lines (18) so each adhesive line in a set is a mirror image of its neighbouring adhesive line about the gusset longitudinal fold line (18) and is disposed on each gusset half (16).

Adhesive lines (24) may also be disposed on the inside of the opposing sides (14) to correspond with the adhesive lines (23) when each half of each gusset (16) is folded on to its opposing side (14) when the sack (10) is folded flat. The adhesive lines (23, 24) may be continuous or intermittent portions, e.g. spots. This advantageously reduces the amount of adhesive required, thereby reducing material costs. In addition to the adhesive lines (23), further adhesive may be disposed within the boundaries defined by the adhesive lines (23). Further adhesive within the triangular pattern conveniently provides additional strength and stability to the bottom of the sack (10).

The adhesive is standard PVA glue but may be hot melt, pressure cured or similar adhesive employing adequate drying and strength S...

characteristics. * .* * . S ** .

. When filled or whilst filling, the triangular portions (25) are formed on the bottom (15) of the sack (10) to provide the bottom (15) of the sack with a *S'SSS well-defined, flat profile and additional strength. The triangular portions S..

* 30 (25) are folded during filling along their axes (27) to be substantially 12 1 aligned with a bottom fold line (26), disposed along the bottom (15) of the sack (10), and the longitudinal gusset fold lines (18). This advantageously allows the sack (10) to be folded substantially flat when empty.

Importantly, these features allow the sack (10) to fill out and the triangular portions (25) to be formed when the bottom (15) of the sack (10) adopts a substantially flat, well-defined square, or rectangular, profile when being filled. The inwardly orientated triangular portions (25) help to define the corners of the square, or rectangular, bottom. The corners can be effectively utilised by the contents and, as a result, the height of a sack can be reduced thus minimising material costs.

The adoption of a substantially flat, well-defined bottom during filling advantageously provides the sack (10) with stability to prevent the contents spilling out. A result of this could be costly downtime for the process line. Storage of one or more filled sacks is also made more efficient.

The sack (10) may include easy opening means (not shown).

Conveniently, adhesive securing the closed end of the sack, e.g. a rolled-bottom, may be intermittent, such as a plurality of individual adhesive spots or lines. Conveniently, the intermittent adhesive may provide one or more non-adhered portions to provide access, e.g. for a finger, to break the adhesive. The rolled-bottom, for example, may then be unfolded to allow access to the contents of the sack (10), The top end (12) of the sack (10) is trimmed straight and open. After * filling, the top end (12) may be left open or closed by a technique known in the art, e.g. sewn. The top of the sack (10) may comprise an easy-open feature similar to that described above. The sack (10) may include a valve (not shown), as described above, for filling the sack (10).

Preferably, the sack (10) is paper but may be any suitable material, e.g. plastic, depending on customer requirements. Alternatively, the plies (30) may comprise a combination of different materials, e.g. an inner ply of a sack may be plastic and the outer ply paper. Conveniently, this may prevent the contents escaping from the sack (10) and/or protect the contents inside the sack (10).

An outer surface of the sack (10) may include text or drawings to convey information, e.g. a Trade Mark, logo or content information, printed on to the sack (10) or via a label adhered to the sack (10).

A method of fabricating a sack (10), as described above, will now be described. Firstly, one or more plies (30) are laid over one another. Fold lines (32) are formed in the plies (30) to define the edges (32) of the sack (10) between the opposing sides (14) and gussets (16). A longitudinal fold line (18) is disposed in each gusset (16) which allows the sack (10) to be folded substantially flat when empty for storage purposes. Adhesive is applied inside the opposing sides (14) and/or gussets (16) to define one or both of the sets of adhesive lines (23, 24). The gussets (16) are then adhered to the opposing sides (14) along the adhesive lines (23, 24). The adhesive lines (23, 24) provide an anchor for the gussets to hinge around * ** and ensure the sack (10) will consistently form the triangular portions (25) in its bottom and thereby adopt the same well-defined, substantially flat square, or rectangular, bottom (15) when filled. * ** * a * S.. *

A tube (12) is formed by joining the edges of the one or more plies (30).

A join line (28) in the outer ply is shown in Figure 2. A bottom end (22) of *.**** * the sack (10), proximate to the sets of adhesive lines (23, 24), is closed using a standard rolled-bottom (20) wherein the end of the tube (12) is

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folded, or rolled, and a stepped end (22) of the outer ply securely closes the end of the sack (10).

The other, top end of the sack (10) may be closed in a similar way or may use other techniques known in the art, e.g. sewn.

The adhesive (23, 24) may be manually applied. However, this method of application would not be adequate on a high speed process line. A means for applying the adhesive (23, 24) to the inside of a ply is required which does not require additional machinery or expensive tooling.

As shown in Figure 6, an applicator (50) is adapted to attach to a drum of an existing machine (not shown). The applicator (50) comprises a mounting portion (52) having a first channel (62) disposed along its length.

The first channel (62) cooperates with a key on the drum (not shown) to locate the applicator (50) in position. One or more clamps (not shown) interface with shoulders (64) on the mounting portion (52) to secure the applicator (50) in situ on the drum.

One or more pads (54) attach to the mounting portion (52). The pads (54) have second channels (58) disposed along their lengths which engage with corresponding protrusions extending from the mounting portion (52).

These allow the pads to be slidably mounted on the mounting portion (52) and slidably removed when required, e.g. for cleaning or replacement purposes. Each pad (54) may comprise an outer convex surface (66) including a pattern of raised portions, e.g. lines or individual portions such as spots, corresponding with the desired adhesive pattern to be applied.

0 The drum and applicator (50) rotate at a determined speed and pass the *00 pads (54) through a bath of adhesive. The pads (54) pick up an amount of adhesive which is deposited on the ply as the raised portions come into contact therewith. The speeds of drum rotation and ply movement can be phased accordingly. A suitable control means may control the speed at which the drum rotates and/or the ply moves relative to each other. * ** * * * * ** * * * ** * * * *** .

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*..S.. * I

S *. *

Claims

Claims 1. A sack comprising: -a tube of one or more plies having opposing sides; -a gusset extending between opposing side edges; -a closed end; and -promotion means to promote the formation of a substantially flat bottom at the closed end during filling of the sack.
2. A sack according to claim 2, wherein the gussets each comprise a longitudinal gusset fold line to allow the sack to be flattened when empty.
3. A sack according to claim 1 or 2, wherein the promotion means attaches a gusset portion of each gusset to an opposing side portion of a corresponding opposing side.
4. A sack according to claim 3, wherein each gusset portion and opposing side portion are in the vicinity of the bottom of the sack.
5. A sack according to claim 4, wherein the gusset portions are adhered to their corresponding opposing side portions by adhesive. * S. * S *
6. A sack according to claim 5, wherein the adhesive comprises at least **.one adhesive line. * S. * * . S.. S**
7. A sack according to claim 6, wherein the at least one adhesive line is disposed on either or both of an opposing side and gusset.*..S..S SS*

S
8. A sack according to claim 7, wherein the promotion means comprises a plurality of adhesive lines in two sets, wherein one set is disposed in or on each gusset.
9. A sack according to claim 8, wherein each set comprises two adhesive lines arranged in a triangular pattern, the apexes of each set being disposed on the longitudinal gusset fold lines so each adhesive line in a set is a mirror image of its neighbouring adhesive line about the longitudinal gusset fold line.
10. A sack according to claim 9, wherein further adhesive is disposed inside the triangular pattern defined by each set of adhesive lines.
11. A sack according to claim 9 or 10, wherein the triangular pattern is orientated with its apex pointing towards the bottom of the sack.
12. A sack according to any preceding claim, wherein the promotion means comprises at least one fold line.
13. A sack according to any preceding claim, wherein the sack comprises easy opening means.
14. A sack according to claim 13, wherein the easy opening means comprises access portions to provide a user access to easily open e...the sack. * ** * * * S.. S
15. A sack according to any preceding claim, wherein the sack is paper.S*...S.
16. An adhesive application means for applying adhesive to the inside of *.a sack comprising: -a drum; -drive means for rotating the drum; and -an applicator mounted on the drum for retrieving an amount of adhesive from an adhesive bath and depositing the adhesive on the inside of a sack.
17. An adhesive application means according to claim 16, wherein the applicator comprises a mounting portion having a first channel disposed along its length which is co-operable with a key on the drum.
18. An adhesive application means according to claim 17, wherein one or more clamps engage with shoulders on the mounting portion to secure the applicator to the drum.
19. An adhesive application means according to claim 17 or 18, comprising one or more pads removeably attached to the mounting portion.
20. An adhesive application means according to claim 19, wherein the one or more pads comprise a pattern of raised portions corresponding with a desired adhesive pattern to be applied to the * ** sack. * . . * .* * * *.**
21. An adhesive application means according to any one of claims 16 to comprising control means for rotating the drum at a predetermined speed.

**s*.* *
22. A method of manufacturing a sack comprising the steps of: * 30 -providing a sack according to any one of claims 1 to 15; -providing an adhesive application means according to any one of claims 16to21; -rotating the drum to pass the adhesive applicator attached thereto through a reservoir of adhesive; and -applying the adhesive from the applicator to the inside of the sack.
23. A method of manufacturing a sack according to claim 22 further comprising the step of: -curing the adhesive. * ** * * * * ** * .** * * * ** ** S S.. SS IS.IIS.....SS