GB2291635A - Inflatable protective packaging - Google Patents

Abstract

The packaging comprises a plurality of intercommunicating cells 10 and valve means for inflating the cells. It is designed by selecting an appropriate cell layout (see Figure 3 for a number of different cell layouts) for protecting a specific article and then determining, preferably from empirical data, the size of the aperture 12 between each pair of adjacent cells (or the sizes of said apertures and the inflation pressure of the cells) in order to minimise or substantially minimise the peak deceleration felt by each face of the article on impact. The packaging may be formed from two or three sheets of polyurethane superimposed and welded to define the cells. It may provide total encapsulation, end caps or corner pieces. <IMAGE>

Description

IMPROVEMENTS IN OR RELATING TO PROTECTIVE PACKAGING This invention relates to a method of designing protective packaging for articles and to the protective packaging E se.

Cushion packaging has traditionally taken the form of relatively solid expanded plastics, such as polystyrene, polyethylene and polyurethane. In recent years, however, due to environmental pressures, some countries within the EEC, particularly Germany, have started to control the manufacture, use and disposal of these articles. The majority of this type of packaging has to be disposed of in land fill sites, a major problem for countries such as Germany, who are land locked. The manufacturing processes also can produce toxic and harmful bi-products which are equally difficult to dispose of safely and economically. The packaging articles could be re-used, but the financial cost of transporting large amounts of bulky packaging, back to the supplier, is higher than producing new packaging from scratch.

One way of making packaging environmentally friendly, and economically viable, is to make it capable of being re-used and at the end of it's life, recycled.

Cushion packaging using air inflated cells is not new, with articles such as Bubble Wrap, Airbox, Blister Pack, etc. commonly used around the world. All of these articles, however, are not normally re-used, or even recycled. Their only advantage environmentally is that they take up less space when used in land fill sites.

It has recently been proposed, see for example, GB-A-2258446, to provide inflatable packaging which can be wrapped around at least part of the article to protect the article during transportation and which comprises a plurality of intercommunicating cells. This known packaging is not, however, consciously designed to give maximum protection to the article.

The present invention seeks to improve on this known packaging.

According to a first aspect of the present invention, there is provided a method of designing protective packaging for articles, wherein the packaging comprises a plurality of intercommunicating cells and valve means for inflating the cells and wherein the method comprises selecting an appropriate cell layout for protecting a specific article and then determining the size of the aperture between each pair of adjacent cells (or the sizes of said apertures and the inflation pressure of the cells) in order to minimise or substantially minimise the peak deceleration felt by each face of the article on impact.

Preferably, the sizes of said apertures are determined from empirical data.

In some cases, there may be no aperture between an adjacent pair of cells (the size of the aperture thus being zero) with the result that these cells only communicate with one another indirectly via one or more intermediate cells.

Preferably, the packaging is foldable around at least a part of the article and the cells of the cell layout adapted to protect a given face of the article are of equal dimensions.

Conveniently, the packaging is in the form of end caps although the packaging may be designed to fully encapsulate the article or may be designed as corner pieces or bespoke coverings.

Preferably, each cell is rectangular (rectangular herein including square).

Preferably, the cell thickness required to adequately protect the article against a predetermined impact is first determined.

Preferably, the primary flat side length, that being the length of the shortest side of each cell, when deflated, is selected to give the cell a thickness, when inflated, adequate to protect the article against a predetermined impact.

In a preferred embodiment, starting from a plurality of different cell layouts, the appropriate cell layout is selected by: (a) calculating the thickness of the cells, when inflated, of each of said different cell layouts from at least some dimensions of the article which the packaging is to protect and from empirical data, (b) comparing the results of (a) with a determination of the cell thickness required to provide adequate protection for the article, and then (c) selecting a cell layout which will provide at least the required degree of protection.

In this case preferably, the empirical data referred to in step (a) includes the relationship between the primary flat side length, that being the length of the shortest side of the cell when deflated, and the thickness of the cell when inflated.

Additionally or alternatively, the empirical data includes the relationship between the primary flat side length, that being the length of the shortest side of the cell when deflated, and the primary inflated side length, that being the length of the shortest side of the cell when inflated.

Alternatively, the thickness which each cell should have when inflated is determined subjectively and/or objectively and the primary flat side length, that being the length of the shortest side of a deflated cell, necessary to give the inflated cell said determined thickness is then determined from empirical data. In this case, it is preferable to determine said cell thickness at least in part from empirical data which may, to some extent at least, depend upon the weight and fragility factor of the article to be packaged.

In this latter case, after the primary flat side length of each cell has been determined, the primary inflated side length of each cell is determined and thereafter the number of cells required can be calculated in dependence upon one or more dimensions of the article to be packaged.

According to a second aspect of the invention, there is provided protective packaging designed by a method according to the first aspect of the invention.

According to a third aspect of the invention, there is provided protective packaging comprising a plurality of intercommunicating cells and valve means for inflating the cells, the size of the aperture between each pair of adjacent cells (or the sizes of said apertures and the inflation pressure of the cells) being such as to minimise or substantially minimise the peak deceleration felt by each face of the article on impact.

Typically, the packaging is formed from two sheets of non-permeable material arranged one on top of the other and welded together. However, it may be formed from three sheets of material arranged one on top of the other and welded together so that each cell has two separate compartments. In this case, if one or other of the outer sheets of material is punctured, one compartment of each cell will remain inflated.

Preferably, the sheets of material have been welded together by high frequency welding.

Typically, the packaging is made of polyurethane film material.

The invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a simple network of inflatable cells; Figure 2 shows one example of an article to be packaged; Figure 3 shows several different styles of end cap, in a deflated condition; Figure 4 shows the dimensional layout of an end cap; Figure 5 is a graph showing the relationship between the primary flat side length and inflated cell thickness; Figure 6 shows flat and inflated cells; Figure 7 is a graph showing the relationship between cell side lengths, flat and inflated; Figure 8 shows one example of an article to be packaged; Figure 9 shows a dimensional analysis of the protective end caps; Figure 10 is a layout drawing of one of the end caps; Figure 11 shows the method of numbering the apertures of the end cap; ; Figure 12 is a series of graphs showing the results of drop tests performed on the article when packaged according to the invention; and Figure 13 is a series of graphs showing the results of the drop tests performed on the article when packaged with conventional expanded polyethylene foam.

Figure 1 shows a simple network of intercommunicating cells 10. The cells 10 are formed by welding seams 11 into flat sheets of plastics film material to form a collection of different sized cells, rectangular in nature, connected together by apertures 12 of varying sizes to allow differing air flow around the network. The flat sheets and the layout of the welded seams are designed so that once inflated, the system will wrap around the desired area of an article to be packaged and protect it from shock force and vibration.

The packaging is designed from a number of parameters specified by the article to be packaged. These are: (i) The dimensions of the article.

(ii) The weight of the article.

(iii) The fragility factor of the article.

(iv) The static load of each face of the article.

(v) The centre of gravity of the article The variables that are altered to optimise the protection level are: (i) The article coverage, i.e. total encapsulation, end caps or corner pieces.

(ii) The style of layout. Within each coverage type there are several standard styles of cell layout.

(iii) The cell thickness, and hence the cell size.

(iv) The size of the apertures connecting the cells.

(v) The air pressure within the cell network.

The manner in which these variables are altered to achieve maximum protection will be explained hereinafter.

The material used to manufacture the packaging should be wear, tear and puncture resistant, gas tight, and resistant to climatic conditions such as heat, cold and humidity.

Polyurethane film is a suitable material. It fulfils all the above criteria, as well as having good machinability, and weldability. It can be coloured or printed and can be produced in a wide range of gauges.

The manufacturing process used to make the packaging is very simple.

Two or three sheets of polyurethane film are laid on top of each other. The seams are created in one operation, using a high frequency welding machine, with a purpose made electrode. The electrodes used can be shaped to form the exact contours of weld required. The outline shape can be die cut after welding. As an alternative to welding, the seams can be created by heat sealing or other joining methods.

The packaging may be made from three sheets of material so that each cell has two separate compartments. In this case, if one or other of the outer sheets is punctured, one compartment of each cell will remain inflated. However, the packaging is more economically made of only two sheets of material.

The method by which the packaging is designed will now be described.

The initial stage of the design process is to assess the optimum style of packaging required for the article. This is done through experience and common sense, deciding between total encapsulation, end caps, corner pieces, or a bespoke coverage. The factors determining this choice are the size, shape, weight, centre of gravity and areas of fragility (e.g. TV screen) of the article, the last two of these having a significant effect on where the cushioning should be placed around the article. For the majority of articles, end caps will be the optimum method of protection.

The first variable to be determined is the approximate cell thickness required. This is the thickness at the centre of each cell when inflated.

It is approximated using the following equation of motion, together with the articles fragility factor and drop test height.

Drop Height -h (m) Fragility Factor -f (g) V2 = U2 + 2aS Where V = Final velocity U = Initial velocity a= Acceleration S = Distance Rearranging this equation, in terms of V, and substituting the drop height, h, as the distance, the acceleration due to gravity, g (9.81 m/s), as the acceleration, and assuming the initial velocity to be zero, will allow Vl, the velocity at which the article will impact with ground to be calculated, as shown below.

Using this value for the velocity of the article as it impacts with the ground, as the initial velocity, the required maximum deceleration, i.e. the fragility factor measured in multiples of the acceleration due to gravity, and the fact that the final velocity of the article must be zero, the stopping distance can be calculated, as shown below.

Rearranging the first equation for the distance S gives:

S is the minimum possible distance required to decelerate the article from a specified height for its own fragility level. The Estimated Cushion Thickness (ECT) is taken as being at least twice the value of S. This gives a compression factor of 50%.

ECT = 2 x S x 1000 (m) Alternatively, the required cell thickness could be approximated using a table, or curve, formed from a series of static loading experiments, varying weight and cell size, to give results in the form of a static compression factor. This factor is a measure of the distance a certain weight will compress a certain size of cell, at a particular inflation pressure, usually expressed as a percentage of the loaded cell thickness to the normal cell thickness. From this curve, a cell thickness can be chosen that will hold the article above the surface, in a static position, within a predetermined compression limit (e.g. for a cell of 150mm normal thickness, at 60mB inflation pressure, and a compression limit of 126 to 135mm for a 6Kg weight, the static compression factor would be 84 to 90%).The compression limit will be determined by a combination of empirical data, experience and customer preferences, depending upon the weight and fragility factor (a measure of the fragility of the article, i.e. the level of force required for damage to occur, measured in multiples of the acceleration due to gravity) of the packaged article.

Once the cell thickness has been approximated, the next stage is to calculate the dimensions of the end caps, and determine which style end of cap is best suited to the article.

First the article is measured, and the decision taken as to the optimum location of the end caps, from which the controlling edge is determined. The controlling edge is the longest side of the face of the article where the end cap will be positioned, as shown in Figure 2.

For calculation purposes, the controlling edge is termed the Primary Side (PS), the other side on the face where the end cap will be located is termed the Secondary Side (SS), and the remaining side is termed the Third Side (TS), as labelled in Figure 2.

From these article dimensions, the size of the end caps can be calculated, for numerous different styles.

The end caps are grouped into a number of main styles, a sample of which is shown in Figure 3. With alteration in the cushion cell size, and mix and match combinations of the styles for each face of the article, these styles will cover every possible rectangular article. The individual cells can be square or rectangular.

For the calculation of the dimensions, the styles are defined as 'A' cushion cells along the Primary Side, and 'B' cushion cells along the Secondary Side.

For example, referring to Figure 3, for Style 6 A would equal 3 and B would equal 2.

Referring to Figure 4, the dimensions of the end caps are calculated as follows: For a network based upon an A x B cell layout, by defining relationships between the cell thickness (CT) and the cell side lengths, the cell thickness can be determined.

From the cell thickness, using a dimensional analysis curve showing the relationship between cell dimensions and inflated thickness, as shown in Figure 5, the Primary Flat Side Length (PFSL) is determined. The shape of the cell can be rectangular or square, as long as this Primary Flat Side Length is the shortest side, the thickness will remain as required.

This creates the equation:

Where: Kl = the gradient of the dimensional analysis curve (Figure 5).

From the Primary Flat Side Length, the Primary Inflated Side Length (PISL) can be determined. When a flat cushion cell is inflated, the sides curve inwards due to the surface tension in the two sheets, created by the internal pressure, as shown in Figure 6. This causes the overall dimensions of the inflated cushion cell to differ from those of the flat cell, creating what is termed as a shrinkage factor of the primary flat side length. This shrinkage factor is calculated using another dimensional analysis curve, shown in Figure 7, showing the relationship between cushion cell side lengths, flat and inflated.

This creates the equation: PISL = PFSL x K2 (mm) Where: K2 = the shrinkage factor, measured as the gradient of the dimensional analysis curve (Figure 7) The Secondary Inflated Side Length (SISL) is determined from the secondary side (SS) of the article, and the cell thickness, giving the equation: B x SISL = SS + CT (morn) The Secondary Flat Side Length (SFSL) is determined from the Secondary Inflated Side Length, and the dimensional analysis curve (Figure 3), giving the equation:

The Secondary Cell Thickness (SCT) is determined from the Secondary Flat Side Length, and the dimensional analysis curve (Figure 5), giving the equation: SCT = SFSL x K1 (mm) For the cell network to fit exactly around the article rectangle, the following equation must be true: A x PISL = PS + SCT Substituting for CT in previous equation gives the result::

Rearranging this equation in terms of CT gives the result:

By altering the values of 'A' and 'B', the cell thickness (CT) can be calculated for the different styles. Using these calculated values for the cell thickness, all the other dimensions, PISL, SISL, PFSL, SFSL, and SCT can be calculated.

For the third side dimensions of the end caps, the Third Inflated Side Length (TISL) must be at least equal to the Primary Inflated Side Length or the Secondary Inflated Side Length, depending upon which is larger, i.e.

If PISL > SISL then TISL = PISL (mien) or If PISL < SISL then TISL = SISL (mini) To determine whether the end caps will both fit onto the third side (TS) of the article, without overlapping, the following equation is used:

If this is not the case, then that particular style of end cap will not be suitable for the article, as the two end caps will not fit properly over each end of the article.

The values of CT and SCT for each style, for which the previous equation is true, are compared with the value of ECT, and the most appropriate pairing chosen as the optimum style of end cap for that particle. The dimensions can then be placed onto a drawing of that style, ready for the next stage of the design.

In an alternative embodiment, once the required cell thickness has been approximated, the required flat cell size to give this thickness can be calculated from the dimensional analysis curve showing the relationship between cell dimensions and inflated thickness, as shown in Figure 5. The dimension taken from this curve is the shortest flat cell side length, referred to as the primary flat side length. The shape of the cell can be rectangular or square, and as long as this primary flat side length is the shortest side, the thickness will remain as required.

The next stage is to work out the shrinkage factor of the primary flat side length. This is calculated using the dimensional analysis curve, showing the relationship between cell side lengths, flat and inflated shown in Figure 7.

The dimensions so far obtained are: the cell thickness, the primary flat cell side length, and the primary inflated cell side length.

Combining these figures with the article dimensions, the style and size of the end caps can be calculated to suit the article.

The next stage in the design is to use the primary inflated cell side length, together with the longest side of the part of the article where the end cap will be positioned, termed the controlling side and calculate which style would best suit the article. A fitting factor is used to give a level of interference fit between the article and the internal dimensions of the end caps. This figure is typically lOmm. This factor determines the ideal internal dimensions of the end cap such that it fits tightly over the article with a level of pre-stress.

This exercise enables a style to be chosen for one face of the article, usually the smallest in area, and therefore, the side with the most pressure applied under static loading (static loading being a term defined by dividing the weight by the area of the side). For the other two sides, the area of coverage is applied according to the static load of that particular side of the article, bearing in mind that for these two sides, coverage will be divided between the end caps at each end of the article.

This part of the design, i.e. the amount of coverage for each side relative to the static load, is based on historical data gathered from experimentation with standard end caps, building a comprehensive database of examples, which can be updated continuously.

Using this database, the style and size of the end cap can be finalised.

Adjustments may be required for the initial cell thickness, and primary lengths, in order to make the system fit the article perfectly. These adjustments, however, are generally so small that they make virtually no difference to the protection performance (e.g. an initial cell dimension distance of 120mm may end up as 118.7 or 121.2mm, in order for the system to fit). The adjustments come about through necessary changes to the primary inflated cell side length. This is the dimension that has to fit along the controlling edge of the article, and as such even with the various styles, a perfect theoretically calculated fit will not be possible every time.

With the optimum size and style of the end caps calculated, the second stage of the design is complete. The next stage is to determine the size (which may in some cases be zero) of the apertures between the cells. Two sets of end caps can be exactly the same size and shape, but can have markedly different protection performance qualities. By adjusting the size of the apertures, as well as the inflation pressure (although this has a minimal effect), the system can be made very stiff, for heavy articles, or very soft, for fragile delicate articles.

The apertures are designed with the aid of historical data, held in a database, obtained from experimentation. These experiments were based on varying the dynamic load and cell size, and for each combination varying the size of the apertures until the optimum protection performance was attained in terms of minimum G-value (a measure of the deceleration felt by the article during impact, in terms of multiples of the acceleration due to gravity). As the fragility factor of a article is expressed in terms of G-value, this is an effective guide for the cushion performance, as each end cap can be designed for a particular G-value. Also the end caps can be designed in such a way that each face of the article will see the same level of G-value in a drop, despite the different static load values.Large apertures make the system soft, small apertures make the system stiff, and the positioning of them around the system means each face will have it's own bespoke level of stiffness.

When the size of the apertures has been finalised, within the optimum dimensioned style, the design process for the end caps is complete.

A software tool can be developed which will perform the majority of the calculations and analysis. From an input screen where the details of the article dimensions and specifications are entered, the software will generate an output, initially in text form, of the dimensions, style, inflation pressure and aperture sizes.

The software tool can also produce drawings of the cell layout, fully dimensioned, labelled and with the costs estimated, which will be printed directly from the computer.

In order to demonstrate the principles described hereinbefore a practical example will now be given.

The article to be packaged is an RC Unit (RCU), a component used in the base stations of mobile phone networks. This article is delicate and extremely valuable, and as such transit protection has to be of a high standard. Originally, the RCU was packaged in expanded polyethylene foam, but due to German pressure on environmental grounds, this had to be replaced.

The first stage in the design process was to measure all the critical properties of the RCU, i.e. the dimensions, weight, centre of gravity (CG), and fragility factor. These are given below.

Length: 570 mm Width: 96 mm Depth: 285 mm Weight: 14 Kg Centre of Gravity: Middle Fragility Factor: Not Specified (taken to be 60 G relating the RCU to similar types of article, i.e. reasonably delicate, high value electronic equipment) The next task was to determine what style of packaging would be best suited, and where to position the protection around the RCU.

Due to it's rectangular nature, and the position of the CG, two identical end caps would be used, positioned on the two smallest faces of the RCU (face 1), making the controlling side the depth, i.e. 285 mum, as shown in Figure 8.

The first property of the packaging to be calculated was the minimum cushion thickness allowable for the specified drop height and fragility factor. The drop height for the RCU was 0.8m, and the fragility factor was 60g. This gave a minimum cushion thickness of approximately 27mm. For the RCU, however, due to customer preference, the thickness of the original packaging was used as a guide.

This made the approximate cushion cell thickness 80mm.

For various styles of end caps, the Cushion Thickness was calculated, and compared with the approximate requirement. Style 3 was chosen, i.e. 3 cushion cells on the primary and 1 on the secondary. This gave the following values to the dimensions: CT = 65.91 mm SCT = 86.24 mm PFSL = 134.51 mm PISL = 123.75 mm SFSL = 175.99 mm SISL = 161.91 mm These dimensions are converted into drawings, as shown in Figure 9 and Figure 10.

The extra cells shown in Figure 10, at the ends of face 1, are standard corner protectors which are part of every end cap style. The size of these was determined by the basic size of the end cap, and taken from a range of standard sizes.

The first stage of the design process was now complete, the dimensions of the end cap had been calculated. The next stage was to determine the size and position of the apertures between the cells.

For the RCU, a database of historical data was not available, so the design process took the form of constructing sets of end caps, and, starting with large apertures in between each pair of adjacent cells, drop tests were performed and the performance in terms of G-value felt by the RCU measured. The aperture size was then reduced, and the drop tests performed again. For each aperture size, the inflation pressure was also varied, to optimise the combination of aperture size and inflation pressure. This process was continued until the apertures could not be reduced any further. The results of each drop test on each face of the RCU were compared, and the aperture size, and inflation pressure, that gave the minimum peak G-value determined for each face. These were as follows: Face 1 (Small Side Face) l5mm apertures, 65mB pressure Face 2 (Bottom Face) 20mm apertures, 60mB pressure Face 3 (Large Side Face) 40mm apertures, 60mB pressure The inflation pressure for the RCU end caps was averaged to 60mB, as the pressure in the network has to be the same throughout. The difference the pressure made to the performance of the end caps was minimal, as long as there was enough pressure to hold the RCU in static conditions. The way the packaging system works, allowing air to move around the network, means, that it is impossible to have an exact theoretical solution, as the apertures cannot be one size for one direction of air flow, and a different size for the other.The solution to this problem is to provide apertures such that the air flowing from each face of the end caps has a different amount of freedom to expand around the network.

For the design of the end caps, the apertures are numbered in a particular way to aid the design and avoid confusion. For any style of end cap, the rule is the same. With the end cap aligned as shown in Figure 11, from the top left hand corner, starting with the vertical seams, moving to the right, the apertures are numbered in ascending order, moving down and to the far left at the end of a row.

When all the vertical seams have been numbered, again from the top left, the horizontal seams are numbered, moving as before.

Using the numbering system requires a size value to be given for every aperture. If no aperture is required, then the size is set at zero.

For the RCU, the three faces required different levels of stiffness from the end caps. This was achieved as follows: Apertures 1,2,9 and 10 were set at zero.

Apertures 3 and 8 were set at 20mm.

Apertures 4,7,11,12,13,14,15 and 16 were set at 16mm.

Apertures 5 and 6 were set at 31 mum.

This system allowed the air forced from the cells on face 3 to flow easily through apertures 3, 11,12 and 13, (or 8, 14,15 and 16), and then around the rest of the network, giving a relatively soft cushion performance, as required. The air forced from the cells on face 1 could flow through apertures 4, 7, 11, 12, 13, 14, 15, and 16, but only into individual cushion cells creating a relatively stiff cushion performance as required. For face 2, the air could flow through aperture 3 (or 8), and then into a buffer cushion cell, before flowing through aperture 13 (or 14), and then around the whole network, creating a moderately stiff cushion performance as required.

Samples were constructed and drop tests performed. The results of these tests are shown in Figure 12, with a comparison to the original expanded foam packaging shown in Figure 13. As can be seen, the packaging showed an average improvement in performance over the foam of 14.47%, i.e. a reduction in the G-value felt by the RCU of 14.47%.

Another major advantage over the foam was that the packaging demonstrated a 100% memory, that is, the results were the same on the tenth drop as the first, whereas the foam showed a 4.27% decrease in performance by the tenth drop.

Other advantages gained over the foam were a potential reduction in the outer box size of 23.15% and weight of 14.28%. These advantages would save in transit costs. Also, the packaging requires over 70% less space than expanded foam for storage, due to the fact that the end caps can be stored flat prior to use.

The embodiments described above are given by way of example only and various modifications can be made without departing from the scope of the invention as defined by the appended claims. For example, the cells need not be rectangular. They could be circular or of other polygonal shape.

Claims (16)

1. A method of designing protective packaging for articles, wherein the packaging comprises a plurality of intercommunicating cells and valve means for inflating the cells and wherein the method comprises selecting an appropriate cell layout for protecting a specific article and then determining the size of the aperture between each pair of adjacent cells (or the sizes of said apertures and the inflation pressure of the cells) in order to minimise or substantially minimise the peak deceleration felt by each face of the article on impact.

2. A method as claimed in claim 1, wherein the sizes of said apertures are determined from empirical data.

3. A method as claimed in claim 1 or claim 2, wherein not all pairs of adjacent cells have an aperture communicating one cell of the pair directly with the other cell (the size of the aperture thus being zero) with the result that these cells only communicate with one another indirectly via one or more intermediate cells.

4. A method as claimed in any one of claims 1 to 3, wherein the packaging is foldable around at least a part of the article and the cells of the cell layout adapted to protect a given face of the article are of equal dimensions.

5. A method as claimed in any one of the preceding claims, wherein the packaging is in the form of end caps.

6. A method as claimed in any one of the preceding claims, wherein each cell is rectangular.

7. A method as claimed in any one of the preceding claims, wherein the cell thickness required to adequately protect the article against a predetermined impact is first determined.

8. A method as claimed in any one of the preceding claims, wherein the primary flat side length, that being the length of the shortest side of each cell, when deflated, is selected to give the cell a thickness, when inflated, adequate to protect the article against a predetermined impact.

9. A method as claimed in any one of the preceding claims, wherein, starting from a plurality of different cell layouts, the appropriate cell layout is selected by: (a) calculating the thickness of the cells, when inflated, of each of said different cell layouts from at least some dimensions of the article which the packaging is to protect and from empirical data, (b) comparing the results of (a) with a determination of the cell thickness required to provide adequate protection for the article, and then (c) selecting a cell layout which will provide at least the required degree of protection.

10. A method as claimed in claim 9, wherein the empirical data includes the relationship between the primary flat side length, that being the length of the shortest side of the cell when deflated, and the thickness of the cell when inflated.

11. A method as claimed in claim 9 or claim 10, wherein the empirical data includes the relationship between the primary flat side length, that being the length of the shortest side of the cell when deflated, and the primary inflated side length, that being the length of the shortest side of the cell when inflated.

12. A method as claimed in any one of claims 1 to 8, wherein the thickness which each cell should have when inflated is determined subjectively and/or objectively and the primary flat side length, that being the length of the shortest side of a deflated cell, necessary to give the inflated cell said determined thickness is then determined from empirical data.

13. A method as claimed in claim 12, wherein, after the primary flat side length of each cell has been determined, the primary inflated side length of each cell is determined and thereafter the number of cells required can be calculated in dependence upon one or more dimensions of the article to be packaged.

14. A method of designing protective packaging for articles substantially as hereinbefore described with reference to the accompanying drawings.

15. Protective packaging designed by a method according to any one of the preceding claims.

16. Protective packaging comprising a plurality of intercommunicating cells and valve means for inflating the cells, the size of the aperture between each pair of adjacent cells (or the sizes of said apertures and the inflation pressure of the cells) being such as to minimise or substantially minimise the peak deceleration felt by each face of the article on impact.