GB2412904A - A method of stacking items, a stackable item, a pressure activated glue and a stack - Google Patents

Abstract

A method of stacking a plurality of items (14), comprising: applying pressure activated glue (38) to a surface of at least one of the plurality of items; and forming a stack (56) of the items (14) such that the pressure activated glue (18) on said at least one item (14) is in contact with another item in the stack (14), wherein, the pressure activated glue (38) will be activated when a pressure equal to or greater than a predetermined pressure is applied to the pressure activated glue (38). The pressure activated glue 38 can be encapsulated in microcapsules which are spherical. The glue 38 can be a glue mixture comprising the glue and a carrier, the carrier being e.g. ink, varnish or a liquid. The microcapsules can also contain an indicator, which indicates e.g. humidity, pressure, temperature or water.

Description

24 1 2904 A METHOD OF STACKING ITEMS, A STACKABLE ITEM A

PRESSURE ACTIVATED GLUE AND A STACK

The invention relates a method of stacking items, a stackable item a pressure activated glue and a stack. In particular, the invention relates to the use of pressure activated glue for palletising items, i.e., forming a stack of items on a pallet, but is applicable to any situation where items are placed in a stack.

It is convenient to transport many items in the form of a stack on a pallet, and such a stack and pallet is shown in Figure 1. A problem with palletisation is that the stack 56 may be unstable and during transportation some of the items may slide off the stack 56 or slide into each other on the stack 56 causing damage to the items, or the contents of the items, and present a danger to personnel handling the stacked pallet 20. It is not uncommon for a lorry or other vehicle carrying a load of palletised items to arrive at its destination with many of the items having slid from their original positions, this situation is illustrated in Figure 2. Some of the items may be already damaged and some may be in a precarious position.

The intended recipient of the load, in such cases, often rejects the load since it may be dangerous to unload the lorry and the recipient expects that at least part of the load is damaged or will become damaged during unloading. If the load is returned to the supplier then the supplier is faced with the extra cost and expenditure of time associated with repackaging the load, completing the necessary logistics and paperwork and re- transporting the load. If a customer repeatedly receives loads that have slipped or that are unstable then there is likely to be a loss of the customer's goodwill and possibly a loss of the customer's business.

Even if the movement of items in transit is not as large and dramatic as that shown in Figure 2, it can still be detrimental to the quality of the . . . -a- e . . . e e e - . - - - items if they slide over each other a few millimetres or centimetres, but many times, during transit.

To prevent slippage of the palletised items relative to each other it is common to shrink-wrap the items on the pallet 20. This is expensive and is time consuming both for the packager of the load and for the recipient of the load who has to remove the shrink-wrap when the items have reached their destination.

For boxed items, a known technique to reduce slippage is to roughen the top and/or bottom surfaces of the boxes so that when the boxes are stacked there is increased friction between the boxes. This technique, however, has limited effectiveness since the weight of the stack 56 tends to flatten out the roughened surfaces and some slippage may still occur.

Rubberised mats may be placed between layers of items in the stack 56 to prevent slippage, however this is both costly and time consuming.

Warehouse staff can omit the mats if they are busy, or if they run out of time when loading a lorry (for example).

Several gluing techniques are known to be used to secure stacks of items.

These include hot-melt gluing, cold gluing and 'lock n' pop' gluing. Hot melt gluing uses a glue gun to apply hot glue to an item, for example, for boxed items spots of glue may be placed on each corner on the upward facing side of a box, a further box is then placed on the top of this upward facing side and the process is repeated as the stack 56 is built up.

In cold gluing a glue gun is also used to apply the glue 'Lock n' Pop' is the proprietary name of a glue that has been developed specifically for palletising. The 'Lock n' Pop' glue is normally applied cold and is sprayed on to the top surface of the items. The 'Lock n' Pop' glue has a high shear strength so that the glue acts to prevent slippage of the stacked * . . . e en- - . e . . .. . -.

items but has a low tensile strength so that a simple upward push on the top item in the stack 56 releases the adhesive bond holding that item allowing the stack 56 of items to be dismantled when the pallet 20 reaches its destination.

One problem with conventional gluing techniques is that it is difficult to control the amount of glue that is applied. If too much glue is applied then it is difficult to separate the items in the stack 56 and the items may be damaged on separation. If too little glue is applied then slippage of the items may still occur.

Glue may be applied to the items immediately prior to the items being placed on the pallet 20 or the glue may be applied to each item immediately after it is placed on the top of a stack 56 as the stack 56 is being built up. The items may be stacked on to the pallet 20 either manually or with an automated system. In either case there is little time available to apply the glue to an item before stacking, or once an item is on the stack 56, before the next item is placed on top of that item. Thus there is little time available to control the amount and position of the glue that is applied to each item.

For boxed items contents are placed in an open box r, the box is shut and glue is then applied to the top of the shut box. If the boxes are handled by automated machinery the glue on the boxes will tend to build up on this machinery causing the machinery to malfunction or breakdown, or causing the glue to be accidentally present in undesirable places on the boxes (e.g. it can rub off onto the machinery and be transferred to inappropriate places on the box). Careful control of the adhesive qualities of the glue, and of the amount of glue, is desirable.

e e - . . . . . .. .e Another problem with the use of conventional glue is that dust and dirt will adhere to any glue that is on the items which has not been used for sticking the items together (e.g., glue in the wrong place). Even if glue is applied in the correct place, then dust and dirt can adhere to the glue, before the items have been stacked, or after the items have been separated from the stack. This makes the item unsightly and devalues the item in the eyes of the customer. Some retailers have banned the use of hot-melt glue for pallet stabilization because the glue transfers to equipment and shelves, in particular the glue leaves a tacky residue that gradually builds up on the equipment and shelves.

An aspect of the invention provides a method of stacking a plurality of items, comprising: applying pressure activated glue to a surface of at least one of the plurality of items; and forming a stack of the items such that the pressure activated glue on said at least one item is in contact with another item in the stack, wherein the pressure activated glue will be activated when a pressure equal to or greater than a predetermined pressure is applied to the pressure activated glue.

It will be understood that the term 'pressure activated glue' refers to glue or a glue product that requires the application of pressure or force to the glue or glue product for the glue/glue product to function.

The method may comprise applying the predetermined pressure to the pressure activated glue.

An aspect of the invention provides a method of stabilising a stack of stacked items, applying pressure activated glue to a surface of at least one of a plurality of items to be stacked; and forming a stack of the items such that the pressure activated glue on said at least one item is in contact with another item in the stack, wherein the pressure activated glue is e - * * .. * * . . .. . ... ... . activated when a pressure at least as great as a predetermined pressure is applied to the pressure activated glue.

The use of pressure activated glue means that the glue is only activated when and where it is needed. Preferably, the predetermined pressure is set so that it is greater than the pressure the items will normally experience (plus a margin of error) during the normal processing or handling of the items prior to the items being stacked. This avoids the gumming up of packaging machinery since there will not be any active glue in the machinery. The only activated glue that will be present is that which is between the items in the stack 56, hence then there will not be any activated glue that is exposed to dirt or dust and the appearance of the items will be not be degraded.

One application of the invention is for stabilising a stack 56 consisting of boxes containing bottles or cans of beverage. The beverage may be alcoholic or non-alcoholic, gasified (e.g. carbonated) or non-gasified (non-carbonated). It will be appreciated that the invention is beneficial for the palletising of beverage products since breakages caused by one or more of the boxes slipping will cause the beverage to spill over the rest of the boxes. In particular breakage of glass bottles presents a safety hazard.

The invention is also beneficial when applied to boxes or other containers containing fragile goods or high value goods such as, by way of example, electrical/electronic equipment, glassware, crockery, engine parts, cosmetics and cigarettes. It should be understood, however, that the invention could be applied to any items that are stackable and have a surface suitable for the application of glue.

In an embodiment of the invention the pressure activated glue is applied to box preforms. The glue may be applied to the preforms, for example in a printing process. The glue may be applied to the preforms at the e e e e e e e e e e e ëe e e ee e e e e e e e e . .. - - packaging site but preferably the glue is applied to the preforms before the preforms arrive at the packaging site. The preforms will normally arrive at the packaging site in flat pack form. At the packaging site the preforms are folded/assembled into proper boxes and contents then placed in the boxes.

Preferably, the predetermined pressure is set so that it is greater than the pressure the preforms will normally experience (plus a margin of error) during the normal processing or handling of the preforms prior to the boxed items being stacked. The formation of the boxes from preforms is normally achieved using automated machinery and the predetermined pressure is therefore set so the handling of the preforms by the machinery does not activate the glue. Also the predetermined pressure is set such that the glue is not activated when the preforms are transported as a stack of flat-pack preforms.

The items may also be packaged using "tray and wrap". The tray and wrap technique involves placing articles (bottles, cans, cartons etc.) on to a cardboard tray and then placing shrink film over the articles, the shrink film is the shrunk, for example by applying heat to the shrink film. Glue may be applied to the shrink film in a printing process, this may be done once the shrink film has been applied to the articles but it is more convenient for the printing process to be applied to the shrink film before the shrink film is applied to the articles.

The predetermined pressure can also be set so that the glue is not activated by the manhandling of the items by personnel or the placement on to the items of small objects such as those that are commonly found in warehouses and packaging plants (pens, pencils, clipboards, clothing, ear guards etc.).

. . . . . . . .. .. .- Preferably, the pressure activated glue is applied to a surface (e.g. top or bottom) of the at least one item, the surface preferably being substantially horizontal when the item is in the stack. The pressure activated glue will therefore be present as a substantially horizontal layer between at least two of the items when the items are stacked. This has the advantage that the weight of the items in the stack can provide the predetermined pressure required to activate the glue, if the predetermined pressure is chosen appropriately.

The predetermined pressure required to activate the glue may be provided by the weight of some fixed multiple of the weight of an item, for example the weight of 2.0, 2.2, 2.5, 2.8, 3, 3.5, 4, 5 or above of the weight an item. It will be appreciated that the items in a stack may be substantially identical or several different types of item may be stacked (for example the stack may contain cases of cans where different cases have cans of different volumes or a different number of cans, or the stack may contain both boxes of engine parts and boxes of gaskets - or whatever). By using the weight of the items in the stack 56 to activate the glue the glue is activated exactly when it is needed. Furthermore, as the stack 56 on the pallet is being built up it is also being stabilized so that the chance of slippage or toppling during the palletising process is reduced.

By way of example, the items may be boxes of canned beverage, with the weight of one item commonly in the range 1 kg to 30 kg, or more commonly in the range 5 g to 15 kg.

It will appreciate that although kilograms are units of mass the invention will always be practiced in substantially the same gravitational field and that the weight in units of Newtons can be easily be derived. Kilograms . . * . . A r are used as units of 'weight' since these would be the units used by the skilled person.

The one item may substantially weighs one of 7.9 to 8.5 kg, 10.6 to 11.5 kg, 12.0 to 13.0 kg, or 13.6 to 14.7 kg. These weights match the weights of various packs of canned beverage. The weight of a 24 pack of 330 ml cans of beverage weighs in the region of 7.9 - 8.5 kg for a beverage which has an original gravity in the range 1.000 - 1.080 (excluding the weight of the empty cans and packaging). Similarly, using the same range of original gravities, a 24 pack of 440 ml cans of beverage weighs in the region of 10.6 - 11.5 kg, a 24 pack of 500 ml cans of beverage weighs in the region of 12.0 - 13.0 kg and a 24 pack of 568 ml (1 imperial pint) cans of beverage weighs in the region of 13.6 - 14.7 kg.

In a preferred embodiment, the predetermined pressure is the pressure supplied by four or more items.

Typically the weight of a pack of twenty-four 500 ml cans including packaging is about 13 kg and has a footprint of approximately 400 mm x 200 mm (0.08 ma). The downward force exerted by a single pack will therefore be about 130 Newtons and the pressure exerted by the single pack will be about 1.6(25) KN/m2 (130 N/0.08 m2). Therefore, the pressure exerted by four packs would be about 6.5 KN/m2. Accordingly, in a preferred embodiment the predetermined pressure is 6.5 KN/m2.

Instead of cans, the beverage may be contained in other types of container including bottles, cartons, sachets and boxes.

As has been noted, the invention is not limited to a stackable item of any particular form: and each item may be much heavier or much lighter than c c c e c , a c e ace C. ate c the weight ranges given above, for example the item may be a carton of cigarettes or it may a box of engine parts, or whatever.

The predetermined pressure could also be applied to the stack by the use of a clamp, such as a sideways squeezing, or overhead pressure device, that applies pressure to the completed stack 56. This technique would be necessary, for example, to stabilise the uppermost layer (or layers) of items in the stack if the weight of the items bearing down on the glue on the underside of the items in the uppermost layer(s) is not sufficient to activate the glue.

The glue may be applied to both the top and bottom surfaces of each item, only to the bottom surface of each item, only to the top surface of each item, to the top surface only of some items and to the bottom surface only of other items, or the glue may be only applied to a top (or bottom) surface of alternate items that form the stacks. Any of these arrangement will lead to glue being present between layers of items in the stack 56. It is also possible to apply the glue to the sides of the items in addition or instead of to the top/bottom surface. In this case the glue would be activated by applying pressure to the sides of the stack 56. In the case of glue applied to the sides of items it may be applied to a side surface of substantially all items in the stack, or to more than one side surface (e.g. front, back, left side or right side surface) of some or substantially all items in the stack. Items that have one or more surfaces (side or top or bottom) that form the periphery of the stack 56 may have no glue applied to these surfaces so that no glue is exposed when the stack is finished.

The pressure activated glue may comprise micro-encapsulated glue.

e e e e e e e e e e e e e e ee e e e e he e e e e e e e e e e e e e ë. e see see e The skilled person will understand that the term 'microencapsulated' means contained in a microcapsule that has a diameter in the range 0.1 micrometres to a few millimetres.

The microcapsules may be ruptured by a pressure or force at least as great as the predetermined pressure of force.

Preferably, the microcapsules are substantially spherical but other geometries may be used.

The use of microcapsules provides a convenient way of providing active glue only when a predetermined pressure (i.e. a "burst pressure") is applied to the microcapsules. The microcapsules also provide a means of providing glue that is substantially time-insensitive since the encapsulated glue is protected from the surrounding environment and will not evaporate, oxidise or otherwise degrade over time.

The glue that is encapsulated may be a glue similar or substantially the same as Lock 'n' Pop_ glue. such glue has a low tensile strength but a relatively high shear strength. Additionally, such glue does not leave a tacky residue when the items in the stack are separated.

For the situation when the items include packaging, such as cardboard boxes, the micro-encapsulated glue may be applied to the packaging as part of a printing process (possibly the printing also being used to decorate/mark the package). The micro-encapsulated glue may be mixed with printing ink and then applied to the containers with the ink. The microencapsulated glue may also be applied after printing by mixing the glue with a varnish that is applied over the print on the packaging.

Alternatively, the micro-encapsulated glue may be mixed with a dedicated e . e ee . ..e..

carrier such as a solvent so that the glue/carrier mixture can be applied in a process separate from the printing and varnishing processes.

The printing or varnishing stages normally occur before contents are put into the containers. In the case of the containers being cardboard boxes, the ink or varnish may be applied to the cardboard when the cardboard is in the form of a flat blank, template or preform before the cardboard is converted into boxes. The printing and varnishing stages are wellcontrolled processes, for example the ink or varnish is made to a known composition which can be accurately controlled. The addition of encapsulated glue to the ink or varnish can therefore also be closely controlled so that just the right amount of encapsulated glue is added so that the optimum amount of released glue is present between the stacked items when the microcapsules are ruptured. The optimum amount of glue being the amount required to prevent slippage whilst allowing easy separation of the items.

A first complimentary aspect of the invention provides a stackable item having pressure activated glue on at least one surface such that the pressure activated glue is activated when a pressure equal to or greater than a predetermined pressure is applied to the glue.

A second complimentary aspect of the invention provides a stack comprising a plurality of the stackable items of the first complimentary aspect of the invention.

A third complimentary aspect of the invention provides a pressure activated glue which is activated by the weight of one or more items when the one or more items are placed on top of the glue. e

- ë e . e.

An aspect of the invention provides a method comprising: applying pressure activated glue to a surface of a first item; and stacking a further item on top of the first item such that there is contact between the glued surface of the first item and a surface of the further item.

An aspect of the invention provides a method of palletising comprising microencapsulating glue; applying the microencapsulated glue to box templates; constructing boxes from the box templates so that the applied glue is on an outer surface of the box templates; placing items in the boxes; closing the boxes; and stacking the boxes such that the pressure activated glue is sandwiched between the boxes.

The glue may be applied to the entire surface area of a face (i.e. the top or the bottom or a side) of an item. Preferably, the glue may be applied to 20o or more of the surface area of an item. More preferably, the glue is applied between 20% and 40% of the surface area of an item. The required surface area coverage may achieved, for example, by applying the glue to just one face of a box, to more than one face of the box, or to all the faces of the box. The glue may be applied to the item by computer controlled machinery so that accurate coverage of the desired area of the item is provided.

The desired amount of glue required between two items can be applied by splitting the required amount of glue so that the glue is applied to each of the items individually. For example, if it is required to have glue covering 30% of the surface area of the interface between two items then an equal amount of glue may be applied to each of the two items i.e. 15% of the top surface of a first item is covered and 15o of the bottom surface of a second item, to be stacked on top of the first item, is covered.

. . . . . . . . . . . . Alternatively unequal amounts may be applied to the two items, e.g. glue may be applied to cover 10o of the surface of a face of one item and 20% of the abutting face of the surface of the other item. The glue that is applied to the two surfaces may complement each other, e.g. the two areas of glue do not substantially overlap when the two items are placed on one another.

The glue may be a two-component type of glue where the glue is only active when the two components combine. Both of the two components may be applied together to a surface of an item. Alternatively, one component may be applied to a surface of one item and the other component may be applied to the surface of another item so that when the two surfaces are pressed together the glue is activated. In this case the two areas of glue on the respective items should substantially overlap when the two items are butted together. The two components may be in separate compartments of a single microcapsule or in separate microcapsules. Since the glue is only active when the two components meet it is less of a concern if the microcapsules break during the handling of the items (for example, from the processing of box preforms into boxes) - the individual glue components are not sticky (i.e. not active) and therefore will not gum up machinery or hold dirt.

In another embodiment of the invention the pressure activated glue comprises: a first component glue which is activated when a pressure equal to or greater than a first predetermined pressure is applied to the first component glue; and a second component glue which is activated when a pressure equal to or greater than a second predetermined pressure is applied to the first component glue, the second predetermined pressure being greater than the first predetermined pressure.

e e e e -e e - . . . . ë ..e e e In this embodiment the step of forming a stack comprises: forming a first stack of the plurality of items; applying a first pressure to the first stack, the first pressure being equal to or greater than the first predetermined pressure and less than the second predetermined pressure, so that the first component glue is activated but the second component glue is not activated; unstacking at least some of the plurality of items from the first stack; restacking a least some of the unstacked plurality of items to form a second stack; and applying a second pressure to the first stack, the second pressure being equal to or greater than the second predetermined pressure so that the second component glue is activated.

According to this embodiment the first stack of items may be formed, for example at a packaging plant, and the stack transported to its destination, for example a warehouse. At the warehouse the items in the stack are separated so that the items can be restacked according to the spaces available for stacking at the warehouse, for example the warehouse may have shelving racks and there may not be sufficient space between the shelves in a rack to fit the entirety of the first stack - the shelves may be separated by a gap that is smaller than the first stack or the shelves may already be partially filled. In another situation individual shelves are demarcated for different types of items (e.g. some shelves may be for holding crates of beer whilst others may be for holding boxes or bags of plastic spoons or whatever) and the first stack contains different types of items (e.g. both crates of beer and boxes/bags of plastic spoons). The items separated from the first stack are formed into one or more second stacks, each second stack being formed of items of the same type, which are then placed on the appropriate shelving.

When the items in the first stack are separated the surfaces of the items will, generally, not be sticky since the first component glue has already e .. e . . . . .- . set (i.e., it has "gone off") and the second component glue has not yet been activated.

When unstacking the first stack it is not necessary to separate all the items: several layers of the items may be left undisturbed, for example, the bottom layers of a stack on a pallet (which may be the pallet used to transport the stack) may be left undisturbed. Also the items need not be separated from the first stack individually: items may be removed from the first stack as two or more layers of items which remain stuck together. This would be particularly useful if the items are small and light (e.g. cigarette cartons or boxes/bags of plastic spoons) and it would be unnecessarily time consuming to separate the individual items.

Conveniently, the first component glue is glue encapsulated in a first type of microcapsule and the second component glue is glue encapsulated in a second type of microcapsule that has a burst pressure that is greater than the burst pressure of the first type of microcapsule. Microcapsules of different burst pressures may be achieved, for example, by having microcapsule walls of different thickness.

In hindsight, after considering the use of microcapsules as a means for providing pressure activated glue, a further inventive use of microcapsules can be considered. That is, a method of stacking a plurality of items, comprising: applying microencapsulated indicator to a surface of at least one of the plurality of items; and forming a stack of the plurality of items such that the microencapsulated indicator on said at least one item is in contact with another item in the stack, wherein the indicator is released from the microcapsules when a pressure equal to or greater than a predetermined pressure is applied to the microencapsulated indicator. . .

e e . . . . e e..e . - The method may further include the application of the predetermined pressure, which may be applied by the stacking process itself or by a clamp or press that applies the predetermined pressure to a completed stack.

The released indicator may be used to indicate temperature. Thus, the indicator may record the maximum and/or minimum temperature that the indicator has been exposed to since the predetermined pressure was beenapplied. Therefore, a record is provided of the extremes of temperature that the items in the stack have undergone since the stack was formed.

This is useful when the items in the stack are required to be kept cool and/or prevented from freezing. Such a restriction may be found when the items are food or drink items, but similar restriction may apply to other types of goods, e.g. electrical/electronics goods (in this case the movement of the electrical goods from a warm environment to a cold environment may cause precipitation of moisture inside the electrical/electronics goods which may damage the goods when the are turned on).

The indicator may take the form of a chemical that takes different colours at different temperatures.

In a similar manner the indicator may indicate humidity (either maximum or cumulative) that the items in the stack have been subjected to or that the items have otherwise come into contact with water.

The indicator may also be responsive to a shear force that has been applied to the stack once the indicator has been released. This allows rough handling of the stack, for example during transportation of the stack on a pallet, to be recorded. Alternatively, instead of being released e e e e e e e e e e see e . e e e e e e e e eve e..e e-e e by a predetermined pressure the indicator is released by a predetermined shear force.

The use of an indicator can, therefore, allow a manufacturer or supplier to determine if goods have been treated correctly after they have left the manufacturer's or supplier's care. This will deter fraudulent, speculative or otherwise incorrect claims by the recipient or transporter of the goods that the manufacturer or supplier had supplied faulty goods.

The indicator may be used to indicate the pressure that caused the indicator to be released. For example, the microencapsulated indicator applied to an item may be released when, say, more than four items have been placed on top of this item. For example, if there were standing instructions to personnel handling the items which stated "Do not stack more than four high" the indicator would record that these instructions had been contravened.

As mentioned above the indicator may provide an indication or a record of an event or condition by a colour change. The microencapsulated indicator may be applied to the item in the form of writing and/or graphics that becomes visible, or more highly visible, when the indicator has been activated by a predetermined event or condition. For example the writing may read "Too High", "Hot", "Cold", "Frozen", "Wet", "Squashed", "Knocked" or the like according to the event or condition being monitored. Similarly, graphics such as pictures of a broken bottle, an ice crystal, waves, a sun, or the like may be used to indicate the conditions/events the item has been subjected to. Such indications would prove useful to a retailer of goods (or anyone else in a supply change) or a customer to inform him that the goods may be damaged or otherwise substandard.

* * . * * * * * .. . . . . * * * ..e * - Embodiments of the invention will now be described in more detail by way of example with reference to the accompanying drawings, of which: Figure 1 is a schematic view of a pallet partially loaded with boxes; Figure 2 is a schematic illustration of a pallet in the back a lorry where the palletised load has slipped during transportation of the load; Figure 3 is a schematic illustration of a packaging and palletising system; Figure 3a is a schematic illustration of a cardboard blank with a glue mixture applied to one side; Figure 3b illustrates a cardboard box constructed from the cardboard blank illustrated in Figure 3a; Figure 4 shows schematic cross-section views of various glue micro-capsules; Figure 5 is a schematic side view of a first container with a glue mixture applied to the top surface of the container; Figure 6 is a schematic illustration of the first container and a second container placed on top of the first container; Figure 7 is a schematic side view of a third container with a glue mixture applied to part of the top surface of the container; e e e - ë- e e e e ë . be Figure 8 is a schematic illustration of the third container and fourth container placed on top of the third container; Figure 8a is a schematic illustration of the third container with glue mixture applied to the top surface of the third container and a fourth container, to be placed on top of the third container, with glue mixture applied to the bottom surface of the fourth container; Figure 9 is a schematic side view of the fourth container with a glue mixture applied to part of the bottom surface of a container; Figure 10 is a schematic plan view of various containers with a glue mixture applied to the top or bottom surface of the containers according to various patterns; Figure 11 is a schematic plan view of a container with mixture of glue microcapsules and ink applied to the top or bottom surface of a container to form graphics on the container; Figure 12 is a schematic illustration of a stacked pallet and apparatus for applying pressure to the stack; Figure 13 is a schematic illustration of a clamp for applying lateral pressure to a stack; Figure 14 is a schematic illustration of a piece of tape having microencapsulated glue on one side of the tape; Figure 15 is a schematic illustration of two containers having abutting side surfaces and glue mixture between the abutting surfaces; 1 c ce e c I. e ' e ë^ Figure 16 is a schematic illustration of several containers packaged together using a tray and shrink film; Figure 17 is a schematic illustration of an apparatus for applying shrink film to items that are on a tray; Figure 18 is a schematic illustration of several egg boxes stacked on top of one another, the egg boxes having microencapsulated glue applied to them; and Figure 19 is a schematic plan view of some egg boxes taken from the stack illustrated in Figure 18, each egg box indicating a particular condition or event it has been subjected to since being stacked.

The following specific description is directed to the formation of a stable stack of boxes. It will be appreciated that the invention is also applicable to the stacking of many other items, for example, bags, bales, drums, and cartons. The main requirement for the items is that they are stackable and have a surface suitable for the application of glue.

Figure 3 illustrates a system for packaging and palletising items. In this system cardboard blanks 12, which are to be formed into boxes 14, are transported on a conveyor system 10 through printing machinery 16. The print machinery 16 comprises an ink reservoir 22 with an ink applicator 23. A varnish reservoir 24 with a varnish applicator 25 is also provided and may be part of the print machinery 16 or may be a separate apparatus. A glue mixture reservoir 26 and a glue applicator 27 may also be provided as part of the print machinery or as a separate apparatus.

. : . A a, ë a ë e a a a a a a a tea a a ä.

The printing machinery 16 prints writing and/or graphics on to the cardboard blanks 12. The writing and/or graphics may include product branding and safety or storage information. After printing, as an optional process a thin layer of varnish is applied to the cardboard blanks 12 to protect the printing. Generally, the varnish will be substantially transparent. The cardboard blanks 12 are then formed into boxes 14 (a process known in the industry as 'forming') with one end of the boxes 14 open. The open boxes are sent via the conveyor system 10 to a position where they are filled with products. In the case illustrated in Figure 3 the boxes are filled with twelve 500 ml, 330 ml or 275 ml bottles 18 of beverage but it is also common to have each box filled with twenty-four bottles. The boxes 14 are then sealed and removed from the conveyor system 10 and stacked on a pallet 20. The stacking of the boxes 14 may be done manually or an automated stacking machine may be used.

The print machinery may be part of an automated system that first prints on a box and then transports the box on a conveyor system to be filled.

However, the printing process is much quicker than the filing process and it would be more usual to print on a large batch of box blanks/preforms (may be many thousands of blanks) and that the batch of printed blanks/preforms be transported to the packaging plant.

The bottles of beverage 18 (or other articles e.g. cans, packets, sachets, cartons etc.) may be packaged using so-called "tray and shrink packaging". Referring to Figures 16 and 17 tray and shrink packaging involves placing bottles (or other articles) on a cardboard tray 80 and then placing shrink film 82 around the cardboard tray 80 and bottles 18. The shrink film 82 is then shrunk, for example, by the application of heat to the shrink film 82. For small or light articles it possible to form a packaged item that does not require the cardboard tray 80 since, in this case, the articles wrapped in the shrink film 82 alone provide a package : : - : : : . . that has sufficient stiffness for easy handling. The shrink film 82 may have ink applied to it in a printing process that is usually applied to the shrink film 82 before the shrink film 82 is applied to the articles 18 to be packaged.

Referring to Figure 17, writing (or other graphics) 79 is printed onto the shrink film 83 before the shrink film 83 is applied to the bottles 18. The writing 70 is printed so that it will have the required dimensions when the shrink film 83 is applied to the bottles 18. Normally the printing is applied to a length of shrink film 83 sufficient to cover several trays 80 of bottles 18, the film 83 is then aligned with the trays 80 so that the writing 70 is correctly positioned over the trays 80 and then the film 83 is applied to the trays 80.

To improve load stability, glue microcapsules are mixed with the ink or the varnish to produce an ink/glue or varnish/glue mixture that is applied to the boxes (or the shrink film 82 if used) in the printing and varnishing processes. Alternatively, the glue mixture is made up of microcapsules and a dedicated carrier so that the glue mixture can be applied to the boxes 14 in a process that is separate to the printing and varnishing processes. Glue microcapsules are mixed with the varnish, ink or dedicated carrier so that the required concentration of microcapsules is obtained. It may be convenient for the ink/varnish manufacturer to prepare the glue mixture. The use of microcapsules containing ink is well known in the printing industry, therefore a number of ink manufactures are likely to have the required expertise to produce a glue mixture having an accurate and repeatable concentration of glue microcapsules.

Alternatively, the microcapsules may be mixed with the ink, varnish, or dedicated carrier on the site where the box preforms are made or the site where the packaging and palletising is taking place. The glue mixture may : I. . .:. :: . . . . . be made up in batches or the printing machinery 16 or other apparatus may be arranged so that the glue microcapsules are fed into the ink 22, varnish 24 or dedicated carrier 26 reservoirs (or to the ink 23, varnish 25 or glue 27 applicators) from a glue reservoir 9 as a set proportion of the ink, varnish or dedicated carrier, i.e., the glue microcapsules are added on-line. This has the advantage that if it is found that the boxes 14 are either not adhering to each other sufficiently or are adhering too strongly (for example, due to variability in the boxes used) then the concentration of microcapsules in the glue mixture can be changed on site by simply adjusting the flow rate of the microcapsules into the ink 22, varnish 24 or dedicated carrier 26 reservoirs (or to the ink 23, varnish 25 or glue 27 applicators).

The ink 23, varnish 25 and dedicated carrier 27 applicators may take the form of any conventional printing applicator, for example they may take the form of a spray, a roller or a plate.

Figure 3a illustrates a cardboard blank 12 with a glue mixture 38 applied to one face. The glue mixture may be applied, for example, as a mixture of glue microcapsules and ink during the printing process. Figure 3b illustrates a cardboard box 14 constructed from the cardboard blank 12 illustrated in Figure 3a. The pressure/force required to rupture the microcapsules 30 is chosen such that the. glue is not activated during all the processes leading up to paletisation of the boxes. Such processes include the stacking and transportation of the preforms and the handling of the preforms and the formed boxes 14 by packaging machinery.

Therefore the predetermined pressure/force is set to be higher than the pressure expected in these processes (including a margin of error).In this way, there will be no activated glue present during packaging and the packaging machinery will not become gummed. .

: .. :. :: . . . . ... . A typical glue microcapsule 30 is shown, in cross- section, in Figure 4a.

The microcapsule has an outer sheath 32 that encloses a glue solution 34.

Figure 4a shows a microcapsule 30 with a simple 'core-shell' geometry.

many other geometries are possible and some of these are illustrated in a Figures 4b - 4h. The outer sheath 32 is composed of an inert material such as gelatin or a synthetic polymeric material. Generally single microcapsules 30 will not be visible to the unaided human eye and will typically have a diameter in the range 1 1lm to 1 mm. Microcapsules 30 may be made by any one of a number of well-known physical and chemical techniques. Physical techniques include spray drying, rotating disk, extrusion nozzle, air suspension and pan coating techniques; chemical techniques include simple and complex coacervation, interracial polymerization, phase separation, solvent separation and in-situ polymerization.

The microcapsule 30 will rupture under a predetermined pressure or force. The pressure or force is determined by the structure of the microcapsule 30 and in particular the thickness of the outer sheath 32.

The concentration of glue microcapsules 30 in the ink or varnish can be chosen according to the weight of the items being glued together, heavier items requiring a higher concentration of glue microcapsules 30 in the glue mixture. The optimum concentration for a particular item may easily be derived by an iterative method of trial and error. For example, a first concentration is tried and if this is too weak then a second higher concentration is tried, if this is too strong then a concentration between the first and second concentration is tried and so forth. Similarly, the proportion of a surface area of a box to which the glue mixture is applied can be optimised. Once the optimum concentration of glue microcapsules 30 has been determined, the glue mixture can be made up in batch form or the flow rate of glue microcapsules 30 into the ink 22, varnish 24 or -. ... . : : . . : : : . . . . .. . dedicated carrier 26 reservoirs (or to the ink 23, varnish 25 or glue 27 applicators) can be set.

Figure 5 is a side view of a first box 40 with the mixture 38 of glue microcapsules 30 and varnish/ink/carrier 36 applied to substantially the entire top surface of the box 40. Figure 6 shows a second box 42 on top of the first box 40 so that the glue mixture 38 is sandwiched between the two boxes 40, 42. If the weight of the second box 42 exceeds the pressure required to rupture the microcapsules 30 then the microcapsules 30 will rupture and glue 34 will flow out of the microcapsules 30. The glue will then form an adhesive bond between the two boxes 40, 42. The mixture will then contain ink/varnish/carrier, released glue 34, broken microcapsule sheaths 35 and a number of microcapsule 30 which have not broken under the weight of the second box 42. The predetermined pressure can also be set such that the microcapsules do not rupture under the weight of a single box but require the weight of two or more boxes.

The glue mixture 38 need not be applied to the surface of a box in a continuous layer, for example, the mixture 38 may be applied in the form of discrete spots or patches 46, 48 (as shown in Figures 7 and 9).

Figure 10 illustrates a plan view of a number of boxes 14 with the glue mixture 38 applied in various patterns. Figure lO(a) shows the mixture 38 applied in a 'frame' pattern in which the mixture 38 has been applied substantially around the edges of a side of the box 14; Figure lO(b) shows the mixture 28 applied as strips to the box 14 (two strips have been illustrated but any number may be employed); Figure lO(c) shows the mixture 38 applied in the form of a cross that is centred in the middle of a side of the box 14; Figure lO(d) shows a mixture 38 applied in the form of a square that is centred in the middle of a side of the box 14. It will be . . . . . A-:: .e.:. ::: . . . . ... . appreciated that the glue mixture 38 may be applied to the surface of the box 14 in many other patterns that have not been illustrated.

If the glue microcapsules 30 are mixed with ink it is convenient that the glue/ink mixture 38 be applied to form text, logos other graphics on the surface of the boxes 14 as is shown in Figure 11.

Whatever pattern is used the glue mixture 28 can be applied to a box surface which will form the top or bottom surface of the box when the box is placed in a stack 56. Figure 7 illustrates a third box 41 having first 46 and second 48 discrete patches of glue mixture 38 applied to a surface of the box 41 which will be the top surface of the box 41 when the box 41 is stacked. Figure 9 illustrates a fourth box 43 having first 46 and second 48 discrete patches of glue mixture 38 applied to a surface of a box 43 which will be the bottom surface of the box 43 when the box 43 is stacked. Figure 8 shows the fourth box 43 glued on top of the third box 41 with glue patches 46, 48 sandwiched between the boxes 41, 43. It will be appreciated that the arrangement of Figure 8 can be achieved by having all the glue patches 46, 48 applied to the upper surface of the third box 41, having all the glue patches 46, 48 applied to the bottom surface of the fourth box 43 or by having some of the patches 46 applied to the top surface of the third box 41 and some of the patches 48 applied to the bottom surface of the fourth box 43. For example, as is illustrated in Figure 8a, the first patch 46 is applied to the bottom surface 49 of the fourth box 43 and the second patch 48 is applied to the top surface 50 of the third box 41.

Figure 12 illustrates a pallet 20 on which a complete stack 56 of boxes has been placed. If the glue microcapsules 30 only rupture under a pressure that is greater than the weight of a single box then the glue capsules sandwiched between the top two layers of boxes in the stack 56 : I. -:e :: . . will not be activated. In this case, the top layer of boxes will not be secured. To secure the top layer pressure will need to be applied externally from the stack 56. Pressure can be applied to the stack 56, using a press 58 which can be pressed down on to the top surface of the stack 56. The stack may be pressed down by the forks of a fork-lift truck or by an adapter that is fitted to the forks of the truck. Conveniently, the adapter has a footprint that is substantially the same shape and size as the top surface of the stack 56.

Alternatively, pressure can be applied using a force-applying mechanism, in this example provided in the form of a clamp 60, that applies pressure to both the top surface of the stack 56 and to the bottom surface of the stack 56 via the underside of the pallet platform. The clamp 60 may be adapted to be used with a fork lift truck so that the fork lift truck is able to give the stack 56 on the pallet 20 a controlled squeeze to rupture the glue microcapsules 30. The controlled squeeze may be applied as the truck moves the loaded pallet, for example onto a lorry or other transport vehicle, therefore no additional time is used for the palletising operation.

In another technique, the predetermined pressure is achieved by placing a loaded pallet on top of the stack 56 for a short period of time.

Pressure activated glue can also stabilise the stack 56 if it is applied to the sides of the boxes that will be substantially vertical when the boxes are stacked, as is illustrated in Figure 15. In this case pressure would need to be applied by using the clamp 60 acting on opposing vertical sides of the stack 56 as is illustrated in Figure 13. Of course the glue mixture 38 may be applied to any number or all the vertical sides of the box or to a combination of vertical and horizontal (top and bottom) sides.

The current invention is applicable to boxes or items that are not cuboidal for example the items may have a hexagonal or triangular crosssection or : . . . - . : : e . ... some other shape, either regular or irregular, that allows the surfaces of one item to have sufficient contact with another item in a stack for the pressure activated glue to act. For example the glue mixture 38 may be applied to the sides of a hexagonal box that are at an angle to horizontal plane, in this case the predetermined pressure may be applied by a component of the weight of another item or items in the stack that are on top of the item to which glue has been applied.

It will be appreciated that the weight of the upper layers in the stack 56 will act to clamp the lower layers of the stack onto the pallet, that is, the upper layers of the stack 56 will act to stabilise the lower layers of the stack 56. Therefore, the lower layers of the stack 56 may be sufficiently stable so that it is not necessary to apply the glue mixture 38 between the bottom layers of the stack. The number of layers that do not require the glue mixture 38 will depend on the weight of the boxes and the coefficient of friction of the boxes.

Instead of applying the glue microcapsules 20 as part of a liquid mixture 38 with ink, varnish or other carrier the microcapsules may be applied to the boxes in the form of a tape 70. Figure 14 illustrates a tape 70 which has glue microcapsules on one side 72 and has conventional glue on the other side 74. The tape 70, therefore, would be similar to double sided sticky tape' but with one side of the tape having glue which requires pressure to be activated. The side 74 of the tape 70 with the conventional glue is stuck down on to a face of the box with the side 74 with the microcapsules 20 facing outward from the box such that the microcapsules will be activated when another box presses onto the tape 70. The tape may take the form of patches that are applied to the box. The patches may be coloured and be used to form writing, logos or other graphics.

: ... a:: . . . . ... Microcapsules may also be used to encapsulate various types of indicator.

Once released from the microcapsule the indicator can be used to indicate one of several conditions for example temperature, pressure, the presence of water (e.g. humidity), and shear forces. Such microcapsules may be applied to the surface of an item to be stacked in the same way as has been discussed for the application of glue microcapsules 32, for example as part of a printing process applied to an item. In this way pressure, equal to or greater than a predetermined pressure, applied to the microcapsules, once the item is part of the stack, will release the indicator. The indicator will then indicate conditions that have occurred to that item since the item has been stacked (such as maximum or minimum temperature), or the release of the indicator may itself be an indication of an event e.g. an event that causes sufficient pressure or shear force to rupture the microcapsules.

Generally the indicator will change colour, lighten or darken, or give some other visible indication in accord to the conditions the indicator has been subjected to, for example, the indicator may be thermochromic so that the indicator is a certain colour according to the temperature it has been exposed to.

With reference to Figures 18 and 19, the item may be a box 84 of eggs, with the microencapsulated indicator applied to the egg box 84. The egg box 84 is generally made out of cardboard or expanded polystyrene and has writing and graphics applied to the egg boxes 64. The writinglgraphics is generally provide marketing or other consumer information. The writing/graphics is applied to the boxes in a printing process before the boxes 84 are filed with eggs. The microencapsulated glue may be applied as part of this printing process or as a separate process.

: .:. :: * . . . A- . ...

The egg boxes 84 are then filled with eggs and stacked. The egg boxes 84 may be stacked directly onto a pallet 20 but more commonly will be stacked inside a further box (not illustrated) and these further boxes stacked on the pallet. The further boxes may also have microencapsulated indicator on one or more their surfaces.

Preferably the indicator is applied so that writing or graphics will become visible or more highly visible to indicate a particular condition. For example, referring to Figure 19(a) the words "TOO HOT" together with a graphic of a sun may become visible to indicate that the eggs have been exposed to a temperature above a pre-set limit (for example above 25 C) at some time after the egg boxes 84, containing the eggs, were stacked.

This would indicate that the eggs might not be fit for human consumption.

Similarly the words "TOO COLD", as shown in Figure 19 (b), or "FROZEN" or graphics showing ice crystals, could be used to indicate that the eggs have been subjected to freezing conditions since stacking.

Referring to Figure l9(c), a graphic of a broken egg may be used to indicate that egg boxes 84 have been stacked too high or otherwise subjected to excessive downward pressure. In this case a consumer wishing to purchase a box of eggs will not need to open the egg box 84, to check the eggs contained therein are unbroken, before purchasing the box of eggs. Of course, the eggs may also be broken by a side impact. In this case an indicator may be used that is response to a shear force acting on the indicator. One way of achieving this is for the microencapsulated indicator to be released by a shear force rather than a predetermined pressure.

Another example of a stackable item to which microencapsulated indicator may be applied is an electrical item such as a television set. The television set will normally be stored and transported inside a cardboard box (but not necessarily so), therefore the indicator may be applied to the I: .- ::: . . cardboard box, directly to the television set, or, preferably, to both the cardboard box and directly to the television set. The indicator may be of one of the types described with reference to the egg box 19. The indicator may also indicate that the box holding the television set and/or the television set itself has been exposed to water or excessive humidity since it was stacked.

The skilled person will appreciate that microencapsulated indicator can be used for a wide range of stackable items. The skilled person will also appreciate that several types of indicator may be used on the same stackable item to indicate, respectively, several different conditions or events.

. . . I: .e' ::: e .' ..CLME: CLAIMS

Claims (92)

1. A method of stacking a plurality of items, comprising: applying

pressure activated glue to a surface of at least one of the plurality of items; and forming a stack of the items such that the pressure activated glue on said at least one item is in contact with another item in the stack, wherein, the pressure activated glue will be activated when a pressure equal to or greater than a predetermined pressure is applied to the pressure activated glue.

2. The method of claim 1, comprising applying the predetermined pressure to the pressure activated glue.

3. The method of claim 1 or claim 2, wherein the pressure activated glue comprises micro-encapsulated glue.

4. The method of claim 3, wherein the micro-encapsulated glue comprises glue encapsulated in microcapsules having a diameter in the range 10 micrometres to 750 micrometres.

5. The method of claim 3 or claim 4, wherein the microcapsules are substantially spherical.

6. The method of any one of claims 3 to 5, wherein the pressure activated glue is a glue mixture comprising the micro-encapsulated glue and a carrier.

7. The method of claim 6, wherein the carrier comprises ink. . .

- r , . - .

8. The method of claim 7, wherein the glue mixture is applied to the at least one item during a printing process.

9. The method of claim 6, wherein the carrier comprises varnish.

10. The method of claim 9, wherein the varnish is substantially transparent.

11. The method of claim 6, wherein the carrier comprises a liquid.

12. The method of any one of claims 3 to 7, wherein the microencapsulated glue is impregnated on one side of a tape and the tape has glue on the other side so that the glue may be stuck to a surface of the at least one item.

13. The method of any previous claim, wherein the pressure activated glue is applied as patches to the at least one item.

14. The method of any previous claim, wherein the plurality of items are packages.

15. The method of claim 14, wherein the packages are boxes.

16. The method of claim 15, wherein the pressure activated glue is applied to box preforms before the preforms are converted into boxes.

17. The method of claim 15 or claim 16, wherein the boxes are constructed substantially from cardboard.

i.. A.ë.' 2

18. The method of claim 14, wherein each of the packages comprises a plurality articles that are held together by the application of a shrink film to the articles.

19. The method of claim 18, wherein the articles are placed on a tray before the shrink film is applied to the articles.

20. The method of claim 18 or claim 19, wherein the glue is applied to the shrink film.

21. The method of claim 20, wherein the glue is applied to the shrink film before the shrink film is applied to the plurality of articles.

22. The method of any previous claim, wherein the predetermined pressure is greater than the pressure that the items receive under normal processing of the items prior to the items being stacked.

23. The method of any claim dependent on claim 14, wherein the predetermined pressure is greater than the pressure that the packaging of the packages receives under normal processing of the packaging or packages prior to the packages being stacked.

24. The method of any previous claim, wherein the pressure activated glue is applied to a surface of the at least one item that will be substantially horizontal when the item is in the stack.

25. The method of claim 24, wherein the pressure activated glue is applied to a surface of the at least one item that will be the top surface of the item when the item is in the stack.

26. The method of claim 24 or 25, wherein the predetermined pressure is applied by placing a loaded pallet on top of the stack.

e e e e e e e e e e ë. e he e e e e e e e e e e e..e ee- e

27. The method of any claims 2 to 25, wherein the predetermined pressure is applied by a clamp that applies pressure to the stack.

28. The method of any one of claim 2 to 25, wherein the predetermined pressure is applied by a press that applies pressure to the top of stack.

29. The method of any one of claims 2 to 25, wherein the predetermined pressure is chosen such that the pressure activated glue is activated by the weight of one or more items when the one or more items are placed on top of the glue.

30. The method of claim 29, wherein the predetermined pressure is chosen such that the pressure activated glue is activated by the weight of one item when the one item is placed on top of the glue.

31. The method of claim 30, wherein the predetermined pressure is chosen such that the pressure activated glue is activated by the weight of two items when the two items are placed on top of the glue.

32. The method of claim 31, wherein the predetermined pressure is chosen such that the pressure activated glue is activated by the weight of four items when the four items are placed on top of the glue.

33. The method of any one of claims 29 to 32 wherein the weight of one item is in the range 1 kg to 30 kg.

34. The method of claim 33, wherein the weight of one item is in the range 5 g to 15 kg.

. . . . - e e - ë e e e e

35. The method of claim 34, wherein one item has a weight in a range chosen from 7.9 to 8.5 kg, 10.6 to 11.5 kg, 12 to 13.0 kg, and 13.6 to 14. 7 kg.

36. The method of any one of claims 1 to 35, wherein the predetermined pressure is substantially 6.5 KN/m2.

37. The method of any one of claims 2 to 23, wherein the pressure activated glue is applied to a side of the least one item, the side being substantially vertical when the item is in the stack.

38. The method of claim 37, wherein the predetermined pressure is applied by a clamp that applies pressure to the stack.

39. The method of any previous claim, wherein the glue is applied to the surface of items that will form alternate layers of items when the items are stacked.

40. The method of any previous claim, wherein the glue is applied to 20o or more of the surface area of a surface of the at least one item.

41. The method of claim 40, wherein the glue is applied to between 20o and 40% of the surface area of a surface of the at least one item.

42. A stackable item having pressure activated glue on at least one surface such that the pressure activated glue is activated when a pressure equal to or greater than a predetermined pressure is applied to the glue.

43. The stackable item of claim 42, wherein the pressure activated glue comprises glue encapsulated in microcapsules.

e . . . . . . . . . .

44. The stackable item of claim 43, wherein the microcapsules have a diameter in the range 10 micrometres to 750 micrometres.

45. The stackable item of claim 43 or claim 44, wherein the microcapsules are substantially spherical.

46. The stackable item of any one of claims 43 to 45, wherein the pressure activated glue is a glue mixture comprising the micro encapsulated glue and a carrier.

47. The stackable item of claim 46, wherein the carrier comprises ink.

48. The stackable item of claim 47, wherein the glue mixture is applied to the packages during a printing process.

49. The stackable item of claim 46, wherein the carrier comprises varnish.

50. The stackable item of claim 49, wherein the varnish is substantially transparent.

51. The stackable item of claim 46, wherein the carrier comprises a liquid.

52. The stackable item of any one of claims 43 to 51, wherein the micro encapsulated glue is impregnated on one side of a tape and the tape has glue on the other side of the tape which is stuck to a surface of the item.

53. The stackable item of any one of claims 42 to 52, wherein the pressure activated glue is applied as patches to the item.

. . . . .. . . . . . . ... ...

54. The stackable item of any 42 to 53, wherein the item is a package.

55. The stackable item of claim 54, wherein the package is a box.

56. The stackable item of claim 55, wherein the box is constructed substantially from cardboard.

57. The stackable item of claim 56, wherein the pressure activated glue applied to the cardboard before the cardboard is converted into a box.

58. The stackable item of claim 57, wherein the pressure activated glue is applied to box blanks.

59. The stackable item of any one of claims 42 to 58, wherein the glue is applied to 20o or more of the surface area of the stackable item.

60. The stackable item of claim 59, wherein the glue is applied to between 20o and 40o of the surface area the stackable item.

61. The stackable item of any one of claims 42 to 60, wherein the predetermined pressure is chosen such that the pressure activated glue is activated by the weight of one or more further stackable items when the one or more further items are placed on top of the glue.

62. The stackable item of claim 61, wherein the predetermined pressure is chosen such that the pressure activated glue is activated by the weight of one further stackable item when the one further item is placed on top of the glue.

63. The stackable item of claim 62, wherein the predetermined pressure is chosen such that the pressure activated glue is activated by the weight of . . - e - - ë ëe en- - two further stackable items when the two further items are placed on top of the glue.

64. The stackable item of any one of claims 62 to 63 wherein the weight of one stackable item is in the range 1 kg to 30 kg.

65. The stackable item of claim 64, wherein the weight of one stackable item is in the range 5 g to 15 kg.

66. The stackable item of claim 65, wherein one stackable item has a weights in a range chosen from 7.9 to 8.5 kg, 10.6 to 11.5 kg, 12 to 13.0 kg, and 13.6 to 14.7 kg.

67. A pressure activated glue which is activated by the weight of one or more items when the one or more items are placed on top of the glue.

68. The pressure activated glue of claim 67, wherein the pressure activated glue comprises micro-encapsulated glue.

69. The pressure activated glue of claim 68, wherein the pressure activated comprises glue that is encapsulated in microcapsules having a diameter in the range 10 micrometres to 750 micrometres.

70. The pressure activated glue of claim 68 or claim 69, wherein the microcapsules are substantially spherical.

71. The pressure activated glue of any one of claims 68 to 69, wherein the micro-encapsulated glue is mixed with a carrier to form a glue mixture.

. . . . . . . .. . . . . . . . . . . .

72. The pressure activated glue of claim 71, wherein the carrier comprises ink.

73. The pressure activated glue of claim 71, wherein the carrier comprises varnish.

74. The pressure activated glue of claim 73, wherein the varnish is substantially transparent.

75. The pressure activated glue of claim 71, wherein the carrier is a liquid.

76. The pressure activated glue of any one of claims 67 to 75 wherein the weight of one item is in the range 1 kg to 30 kg.

77. The pressure activated glue of claim 76, wherein the weight of one item in the range 5 g to 15 kg.

78. The pressure activated glue of claim 77, wherein one item has a weight in a range chosen from 7.9 to 8.5 kg, 10.6 to 11.5 kg, 12 to 13.0 kg, and 13.6 to 14.7 kg.

79. A stack comprising a plurality of the stackable items according to any one of claims 42 to 65.

80. The method of any one of claims 1 to 41, wherein the pressure activated glue comprises: a first component glue which is activated when a pressure equal to or greater than a first predetermined pressure is applied to the first component glue; and . . . - - e - . e . . . ... .. - a second component glue which is activated when a pressure equal to or greater than a second predetermined pressure is applied to the first component glue, the second predetermined pressure being greater than the first predetermined pressure

81. The method of claim 800, wherein the step of forming a stack comprises: forming a first stack of the plurality of items; applying a first pressure to the first stack, the first pressure being equal to or greater than the first predetermined pressure and less than the second predetermined pressure, so that the first component glue is activated but the second component glue is not activated; unstacking the plurality of items from the first stack; restacking a least some of the unstacked plurality of items to form a second stack; and applying a second pressure to the first stack, the second pressure being equal to or greater than the second predetermined pressure so that the second component glue is activated.

82. A method of stacking a plurality of items, comprising: applying microencapsulated indicator to a surface of at least one of the plurality of items; and forming a stack of the items such that the microencapsulated indicator on said at least one item is in contact with another item in the stack, wherein, the indicator is released from the microcapsules when a pressure equal to or greater than a predetermined pressure is applied to the microencapsulated indicator.

83. The method of claim 82, comprising applying the predetermined pressure to the microencapsulated indicator.

. . . - . ë . e . .-

84. The method of claim 82 or 83, wherein the indicator indicates temperature once the indicator is released.

85. The method of claim 82 or 83, wherein the indicator indicates the pressure applied to the microcapsules to cause the indicator to be released.

86. The method of claim 82 or 83, wherein the indicator indicates a shear force that has been applied to the one or more items once the indicator is released.

87. The method of claim 82 or 83, wherein the indicator indicates that water has been in contact with the indicator once the indicator is released.

88. The method of claim 87, wherein the indicator indicates humidity once the indicator is released.

89. A method as hereinbefore shown and described with reference to figures 3 to 17.

90. A stackable item as hereinbefore shown and described with reference to figures 3 to 17.

91. A pressure activated glue as hereinbefore shown and described with reference to figures 3 to 17.

92. A stack as hereinbefore shown and described with reference to figures 3 to 17.

. - e ..e e ë ... .-