The present invention relates to the protection of articles by wrappers.

Among the objects of the present invention is protection against weather and handling, of various types articles, including trees.

Additional objects of the present invention include the provision of novel wrapping material with which to effect the desired protection.

The foregoing as well as still further objects of the present invention will be more fully understood from the following description of several of its exemplifications, reference being made to the accompanying drawings wherein.

Fig. 1 is an elevational view partly in section of an orange tree protected pursuant to the present invention;

Fig. 2 is a _έ sectional view of Fig. 1, taken along line 2-2; ^' Fig. 3 is an elevational view of a grape arbor bush protected pursuant to the present invention;

Fig. 4 is an elevational view, partly in section,of a coil of sheet metal protected pursuant to the present invention;

Fig. 5 is a detailed view of the protective wrapper in Fig. 4;

Fig. 6 is a horizontal section of a packaged glass automobile window;

Fig. 7 is an isometric view of a packaging envelope holding an electrically sensitive object pursuant to the present invention, a portion of the envelope being broken away to show its construction; and

Fig. 8 is a similar view of a modified packaging according to the present invention.

The citrus fruit industry in certain geographic locations is threatened by the occasional subjection to sub-freezing weather which not only damages fruit not yet harvested, but also damages the citrus trees themselves. A tree thus damaged and needing replacement is a total and expensive loss, particularly when the tree is young. On the other hand, freeze damage to the fruit itself can be of relatively minor significance.

According to one aspect of the present invention, a citrus tree having a trunk at least about 17 millimeters thick has its trunk pro¬ tected by an encircling wrap of a yieldable plastic foam sheet, the thickness of the sheet being greater than about 2 centimeters and not over about 3 centimeters, the number of turns of the wrap being from about 6 to about 15, the yieldability of the foam being such that it is compressed by the wrapping to essentially fill in the space at the end of the first turn where the foam sheet extends from the trunk surface to the outer face of the interior edge of the sheet, and the sheet does not permit the passage of significant radiant energy.

The wrapping foam is preferably laminated to a backing layer or has one of its surfaces unfoamedormelted to form an unbroken skin that supports and strengthens the foam against mechanical abrasion and other forces.

A particularly effective backing, layer is a film of polyethylene terephthalate about 1/2 to about 1 mil thick. This can be laminated to the foam sheet using as a laminant amorphous polypropylene or any of the other laminants disclosed in PCT application Serial No. US86/ 01731 filed August 20, 1986. Alternatively, the foam can be formed on the backing layer and adheres to that layer by reason of the normal adhesions of the foam-forming mixture.

A polyethylene terephthalate backing film is very effectively used to block the passage of radiant energy to the wrapped tree trunk, by applying a metallized layer to one or both surfaces of the film. Such metallized layer should have reflectivity of at least about 2/3 for radiant energy, and preferably has a reflectivity of at least about 75%, particularly if the metallized layer is on only one face of the backing film. Aluminum is the metal of choice for such metallizing.

By using at least about six turns of the foam laminate to wrap an orange tree trunk, the action of the metallized layer in blocking radiant energy is geometrically multiplied, so that essentially no such energy penetrates all six layers even when as much as 1/3 of the impinging energy succeeds in penetrating through the outside layer.

The foam layer can be colored to also block the passage of radiant

energy. Only about 1/2 to about 1% content of carbon black or of dark dyes or other pigments is enough to block essentially all energy pene¬ tration through a six-layer wrap of such colored foam, whether or not it is laminated to a backing sheet, and whether or not such backing sheet is metallized.

The foam layer should be sufficiently resilient that it squeezes into all spaces at the tree trunk surface. Figs. 1 and 2 show a typical citrus tree wrap in which the trunk 10 of the tree is wrapped with six to fifteen turns of a plastic foam sheeting 12, held in place by encircling ties 14 of plastic or metal or of plastic-coated metal. The innermost turn 18 of the foam sheeting has a leading edge 20 which must be spanned by the sheeting, and normally a gap 22 is formed as the next turn of the wrap extends from the tree surface to the outer face of leading edge 20. However, the foam sheeting 12 is made highly yieldable, as by having its foam of open-celled flexible structure and a density no greater than about 20% that of the unfoamed plastic. Under these conditions the wrapping and tying of the foam sheet in place is enough to squeeze the foam into space 22, thus leaving no significant residual space through which cold air surrounding the tree can penetrate into the wrapped portion of the trunk.

The yieldable wrap also seals against irregularities in the sur¬ face of the wrapped trunk, and permits that trunk to readily expand as the tree grows.

The plastic used to make foam sheet 12 can be of any kind that provides the desired yieldability. Polyurethane plastics are very effective, as are polypropylene, polyethylene and polystyrene plastics. Most inexpensive yieldable plastics are not sufficiently resistant to mechanical abrasion or the deteriorating effects of the weather, and are thus best protected by a strong weather-resistant backing sheet such as polyethylene terephthalate or polyacrylate or polypropylene film or tensilized polyethylene film, loaded with antioxidants and other weather-resistant ingredients.

It is preferred to wrap a 3 to 4 feet height of the tree trunk.

Fig. 3 illustrates another aspect of the invention in which a

grape arbor or bush 40 is protected by a wrap 50. Grapes are gener¬ ally grown where a warm winter sun can start buds forming on the trunk, where they are not wanted. A single turn of protective wrap 50, or as much as a turn and a half, if sufficiently blocking toward sunlight, accordingly provides important protection.

A wrap which is a laminate of 1/8 to 1/4 inch thick yieldable foam secured to a reflective barrier film such as metallized polyethylene terephthalate does a good job, whether the metallizing is on the outer or inner surface of the film, or on both of those surfaces. Because of the small number of wrapping turns, it is preferred that the reflectivity of the metallized layers be at least about 80%, unless the foam is filled with light-blocking ingredients such as dyes, car¬ bon black and other pigments.

The thickness of the backing layer need only be enough to provide the desired overall strength and abrasion resistance. Only about 1/2 mil thick polyethylene terephthalate film is adequate, although such film can also be up to about 1 mil thick. Other backing sheets such as tensilized polyethylene should be at least about 1 mil thick and up to about 1.5 mil thick. Plastics such as polystyrene that are not as strong should be about 1.5 to about 3 mils thick.

The thickness of the foam layer in wrap 50 should be enough to seal against variations in the surface of the grape bush trunk. In many cases, 1/8 inch is an adequate thickness, but 1/4 inch thickness is generally adequate in all instances. The yieldability of this foam need not be as great as that of the foam in Fig. 1, so that wrapper 50 can have its foam of closed-cell or open-cell construction. That foam can be made of any of the plastics described in connection with Fig. 1.

Also, the backing sheet for sheet 50 can be replaced by a skin of unfoamed plastic on the outer surface of the foam, as described in connection with Fig. 1.

Fig. 4 illustrates yet another aspect of the present invention. Here, a coil 60 of sheet tinplate, for example, is wrapped in a pro¬ tective laminate 70 which covers the sides and is folded over the upper and lower edges of the sheet tinplate. Corrugated cardboard

discs 72 can be cemented over the top and bottom folds to add more cushioning. One turn of the laminate wrapping 70 is enough, but an additional turn or an additional half-turn can also be used. The free outer end of that wrap can be tied or cemented into place.

The composition of wrapper 70 is more fully illustrated in Fig. 5. It is made of a layer of foam 81 laminated to a layer of paper 82 which in turn is laminated to layers 83, 84 of tensilized polyethylene. The foam layer is preferably of closed-cell construction and about 1/32 to about 1/8 inch thick, preferably 1/16 inch thick, to resist and cushion against the relatively strong stresses associated with the handling of metal coils that can each weigh over 500 pounds. The foam need not be as resilient as the foams of Figs. 1 and 3, but should not be rigid. A polypropylene closed-cell foam having a density about 1/3 to 1/5 the density of the unfoamed polypropylene is quite satisfactory, although many other foamed plastics can.be used as shown in connection with Figs. 1 and 3.

The paper sheet can be a 25 to 35-pound Kraft paper, preferably 30-pound Kraft paper, laminated to the foam with any of the pressure- sensitive or other laminants described in PCT application US86/01731.

The polyethylene sheets 83 and 84 are tensilized at right angles to each other and are accordingly extremely resistant to puncture. They are laminated to the paper layer and to each other, preferably with a pressure-sensitive laminant, and can have an overall thickness of about 2 to about 3 mils, preferably 2.5 mils. It is also preferred that both of these polyethylene sheets have about the same thickness plus or minus about 20%.

The paper layer 82 can be omitted from the wrapper 70, but its presence makes it simpler to laminate all the layers together.

The combination of Fig. 4 is also very effective for protecting other metals such as aluminum, blackplate, plain steels, copper and brasses, and even stainless steels or other sheet metal that needs a cushioning wrap. Where the wrapped metal is corrodible, the face of the foam layer 81 can be coated with a volatile corrosion inhibitor ("VCI") as described in U.S. Patent No. 4,321,297, as well as in the

above-cited PCT application.

The metal that is packaged can also be in the form of pre-cut sheets or stampings stacked for shipment in bundles.

To simplify the wrapping, the edge portions of the wrap which are folded over the top and bottom of the package can have their faces pre-coated with cement such as the cohesive-nonadhesive cement of the U.S. Patent No. 4,086,384 or of the PCT application or contact cement, so the folded-over portions seal against each other. The cardboard protector disc, or any other protector disc can be similarly pre- coated or can be placed under the folds of the wrap so the sealing of the folds to each other will also hold the protector disc in place.

Objects as heavy as sheets of glass are effectively protected by a wrap of cushiony foam about 1 to about 3 millimeters thick laminated to an open-face corrugated paperboard about 1 to about 4 millimeters thick.

Preferably a glass sheet is sandwiched between the foam faces of two sheets of the laminate and the ^" two laminate sheets are cemented together around the glass sheet.

Fig. 6 illustrates an automobile side window shown at 100 as sandwiched between two wrapper sheets 120 and 130. Each sheet is composed of a layer 141 of cushiony foam laminated to a layer 142 of open-face corrugated paperboard.

The foam layer is preferably a closed-cell microfoam such as described in U.S. Patent No. 4,086,384. Polypropylene makes a very effective plastic for the microfoam, although polyethylene, polyvinyl chloride, cushiony polystyrene and cushiony polyurethanes are also quite suitable.

The open-face corrugated paperboard is composed of two paper webs 151 and 152. Web 151 is corrugated to a depth of about 2 millimeters from paper weighing about 99 pounds per ream. An E-type corrugation, which has about 4 corrugations per centimeter, is very effective although as little as 2 and as many as 6 corrugations per centimeter can also be used.

The face web 152 of layer 142 is also paper weighing about 126

pounds per ream. Each of the paper webs can independently range from about 70 pounds to about 330 pounds per ream, and the corrugations can be any other type such as types A, B or C.

Open-face corrugated paperboards of the foregoing types are dis¬ closed in U.S. Patent No. 3,288,353.

A feature of the present invention is that the open-face corrugated paperboard is a highly developed relatively inexpensive readily available product that, unlike a fully faced corrugated board, is quite flexible when bent along a line parallel to the corrugation of web 151. The open-faced board can accordingly be rolled up into rolls having internal diameters as small as six centimeters. Such a roll can have as much as thirty or more meters of the board in a form that can be readily shipped and used to feed a continuous laminator such as shown in U.S. Patent No. 4,601,157 and in PCT Application Serial No. US 85/00399, published September 26, 1985 under No. WO 85/04150.

Web 151 and/or web 152 can be made of materials other than paper, plastic film for instance, where such film is desired for its imperviousness or other characteristics.

The foam layer 141 is readily laminated to the corrugated web 151 with any adhesive laminant such as hot melt thermoplastic rubber adhesives, polymeric lauryllactone adhesives, amorphous polypropylene, or pressure-sensitive adhesives as disclosed in PCT Application Serial No. US 86/01731 published February 26, 1987 under No. WO 87/01092, or latex-type adhesives — of natural or SBR rubber, for example. The laminant need only be coated on the outermost peaks of the corrugated web 151, so the expense of the laminating is quite low.

Laminants of relatively low bond strength, such as amorphous poly¬ propylene, are preferably applied to the corrugation peaks while those peaks are compressed against their face web sufficiently to flatten the peaks so that they are about 2 to about 3 millimeters wide. This provides more engagement surface for the laminant, but even so the low bond strength adhesives should not be used for packaging objects weighing more than about 1 kilogram.

Some laminants, such as those of the thermoplastic rubber type, are adversely affected by heat that is applied after the lamination is completed and the laminant has cooled down.

The final laminate 120 and 130 is just about as readily rolled up as the open-face corrugated board alone. These laminates can accordingly be readily fed from such rolls to a sandwich packaging machine as disclosed in PCT Application US 86/01731, where they can be cold- or hot-sealed around a series of individual glass automobile windows 100. For cold sealing, the outer faces of the foam 141 are coated with a cohesive-nonadhesive layer 160 such as described in PCT Application US 86/01731.

Where the cohesive-nonadhesive coating is applied with high-speed equipment and thus is dried by heating to temperatures as high as 100"C, adverse effects on the laminant can be avoided by coating the cohesive-nonadhesive coating on the foam before the foam is laminated to the corrugation peaks.

In some cases it may be desirable to apply to the peaks a foam layer carrying a cohesive-nonadhesive coating on one face, and a very thin flexible supporting web on its opposite face. A 30-pound Kraft paper makes a suitable web, as do resin films about 50 microns thick. The supporting web face is then laminated to the peaks with any of the above-mentioned adhesives. The resulting laminants of open-faced corrugated board to the pre-prepared foam is still quite flexible when woundaround an axis parallel to the corrugations, and can be wound up onto rolls on cores as small as 8 centimeters, provided the winding turns have their foam layers facing inwardly toward the wind¬ ing axis. The thin foam support web then bellies a little between peaks to permit the appropriate degree of laminate flexing.

Paper supporting webs should be about one-fourth the thickness of facing 152, or thinner, and not heavier than about 35 pounds per ream.

Each automobile side window glass member can weigh as much as 5 to 10 kilograms. It is preferred that the wrapper sheets 120 and 130 be stiff enough to support the glass members when the wrapped members are stacked on edge. For the heaviest glass members or the lightest

wrapper sheets, the stacking is preferably with the corrugation 151 oriented vertically to provide the maximum supporting stiffness.

It is not absolutely essential to prevent the crumpling of the wrapper sheet edges under the weight of the vertically oriented glass members. Such crumpling does not significantly increase the risk of damage to the glass members, but may slow down the handling of the packaged members when they are stacked as well as when they are unstacked.

To reduce the edge crumpling, the two packaging wrappers can be fed from perpendicular directions to a sealing station so that after the sealing the corrugations of one web 51 run at right angles to the corresponding corrugations of the mating web. This combination pro¬ vides greater stiffness when the stacking of the wrapper glass members is on an edge perpendicular to the stacking position of the drawing figure.

Readily damaged objects other than glass sheets can also- be protected pursuant to the present invention. Thus, plastic sheets or shapes and even electronic circuit boards can be protected the same way, although lighter weight objects need only the lighter weight wrappers.

As noted, plastic webs can be used instead of the paper webs 151 and 152 for packaging lighter weight objects, but are generally more expensive than paper providing the same stiffness. Webs of metal such as aluminum can be used at 151 and 152, and provide stiffnesses even greater than paper webs of the same thickness. Because of the greater expense of metal, only one of the 151 and 152 webs need be metal — the other paper or plastic.

For wrapping circuit boards or other objects sensitive to electric or magnetic fields, the wrapper laminates have their foam layers treated to prevent the build-up of static electricity, as by arranging for the foam to be filled with particles of finely divided carbon or other antistat material. The wrapper laminates can include at least one metal or metallized web and such webs on opposite sides of a wrapped object can be electrically interconnected as by stapling them

together using metal staples wide, enough to establish good electrical contacts or by providing the opposing laminates as folds from a single large laminate sheet. The webs 151 and/or 152 can be made of carbon- filled paper to make them electrically conductive. The foam surface can be coated with corrosion inhibitor with or without cohesive- nonadhesive and/or antistat agents, as described in WO 87/01092.

The foam layer 141 can alternatively be laminated to the facing web 152 of the open-face corrugated board. This arrangement leaves the corrugated web 152 exposed so the stacking orientation is readily visible.

The foregoing laminates are also very effective for similarly wrapping books especially those weighing over one kilogram, or coils or stacks of sheet metal such as used in the canning industry and illustrated in Fig. 4. Coils of this type can weigh as much as a metric ton .or more. The edges of the outermost metal turns particu¬ larly need cushioning.

Heavy objects such as automobile bumpers are also effectively protected in shipment and handling by wrapping in the laminates of the present invention, as are members that have sharp protrusions such as automobile and truck parts like gears.

The laminates of the present invention are also suitable for use as cushiony spacers, as by interleaving them between automobile or truck wheels which are stacked for storage or shipment. For such use, the cohesive-nonadhesive coating can be omitted.

Tote bins or other containers for food or the like can also have their walls coated with the laminates of the present invention. For this purpose, the cohesive-nonadhesive coating can be replaced by an ordinary pressure-sensitive adhesive such as those described in WO 87/01092.

Where in contact with foods, food-grade materials should be used in the laminate.

The laminates of the present invention are also highly suited for use as padding, as for example, pads that are mounted on the internal surfaces of elevators to protect those surfaces when construction

equipment or materials are to be carried. The laminates can be fitted with eyelets for mounting on hooks, or can be coated with pressure- sensitive adhesive so they adhere directly to the surfaces to be protected. When a pad is used to protect a floor, no adhesive is necessary.

Such padding is also suitable for the interiors of truck bodies. They further make excellent winter covers for mounted air condition¬ ers, as well as padding for air conditioners or other large or heavy objects shipped in cartons or crates-.

A still further use for the laminates of the present invention is to help seal the edges of garage doors such as overhead pull-down doors. For this purpose, the laminates can be mounted with their foam faces against the door frame and overlapping the door, so those faces also rest against the adjacent side edges of the door when the door is closed. The top and bottom edges of the door can carry separate pads' that help seal against the upper door frame and- the floor, respect¬ ively.

Uncorrugated face web 152 can be made of a cross-tensilized poly¬ ethylene sandwich to further improve the protection of the laminates of the present invention. Such cross-tensilized sandwiches can be made from foamed polyethylene sheets as described in British Patent Specification No. 989,521, or from unfoamed polyethylene sheets as described in the "Valeron" literature published by Van Leer Plastics, and are exceptionally resistant to tearing and puncture. The sandwich can have its surface corona-treated where it is cemented to corrugated web 151 or to anything else, but such treatment is not necessary where a pressure-sensitive cement is used. Also, the cross-tensilized sand¬ wich should not be heated to a temperature that causes a relaxation of the tensilizing effects.

In some cases, the presence of antistat on the surface of the foam can accelerate corrosion of sensitive objects contacted by that surface. This difficulty is minimized by also including volatile corrosion inhibitor in such coating and/or by inserting non-porous spacer sheets such as films of polyethylene at the points of contact.

The spacer sheets can carry a coating of pressure-sensitive cement or cohesive-nonadhesive cement so they can be adhered to the appropriate locations on the foam face of the protective laminate.

Polyethylene terephthalate films are also strong and tough and can be laminated to foam layers to make very effective packaging. Such films are also desirable in that they can be metallized on one or both faces to help provide a Faraday cage effect. The outer face of the film is desirably protected by a hard plastic coating such as polymethyl methacrylate, which can be as thin as 10 to 20 microns. Such coating can also be an antistat or can be top-coated with an antistat and can be filled with metal whiskers to make it highly con¬ ductive to electricity. Nickel filaments about 2 to about 10 microns thick and about 1 to about 5 millimeters long are very effective, particularly when constituting about 35% to about 50% of the solids' weight in the ^' coating.

The foam in any of the foregoing laminates can be closed-cell or open-cell. Coatings on open-celled foam can make them behave like closed-cell foams.

A feature of the present invention is a packaging laminate having a layer of cushiony foam about 1 to about 7 millimeters thick, laminated to a metallized polyethylene terephthalate backing sheet not over about 25 microns thick, the backing sheet being metallized on both its faces to shield against external electrical influences, and the unlaminated face of the foam carrying a quantity of anti-stat sufficient to prevent the build-up of a damaging amount of static electricity when an object is slid over that face.

The laminant used to adhere the foam to the polyethylene terephthalate is preferably a pressure-sensitive adhesive, particular¬ ly where the laminate is to be heat sealed to itself or to other objects. As noted above typical pressure-sensitive adhesives are described in WO 87/01092.

Fig. 7 shows a package 210 in which an electrically sensitive object 212 such as a circuit board is held in an envelope 214 made of a layer 216 of cushiony foam laminated to a polyethylene terephthalate

sheet 18 that is metallized on both its faces. The metallizing is preferably about the same on both faces; together they are heavy enough to make the polyethylene terephthalate sheet quite opaque even when that sheet is quite transparent before metallizing.

The thickness of that sheet should be not over about 25 microns, and preferably about 15 to about 20 microns. The two metallizing layers, generally aluminum, provide particularly effective dual shielding of the package contents against external electrical influences.

The cushiony foam layer can be the microcellular closed-cell polypropylene foam described in U.S. Patents Nos. 4,086,384 and 4,263,380, but any other cushiony foam of polyethylene, polystyrene, polyvinyl chloride or polyurethane can be used. The thickness of the foam layer is preferably from about 1 to about 7 millimeters, and only 3 millimeters or less are enough for securely packaging light weight objects such as computer discs of the floppy or rigid types.

The outer face of the foam, which is the face not laminated to the polyethylene terephthalate sheet, preferably carries sufficient anti¬ stat to keep from developing a serious static charge build-up when anything is slid over that surface. Any of the antistat agents dis¬ closed in WO 87/01092 or in U.S. Patents Nos. 4,321,297 and 4,584,225 can be used as long as they provide the short static discharge time allowed in the industry, generally about 0.4 second.

The envelope 214 is preferably made by folding a sheet of the laminate along the line 220-220 and adhering the side edges 222,222 of one fold to the corresponding side edges of the other fold. Such adherence can be effected by heat sealing or cold sealing, along the lines described in WO 87/01092 or by ultrasonic bonding as also disclosed there. Substituting ultrasonic vibrators and anvils, for some or all of the melting shoes and supports in the sealing apparatus of WO 87/01092 is particularly desirable.

The folds of the Fig. 7 envelope can alternatively be secured together with ordinary cements or even by stapling. The continuity of the metallized layers from one fold to the other improves their

Faraday cage effect in electrically protecting the objects packaged.

Envelope 214 also has a closure flap 224 which spans the free ends of its folds and thus adds further to the electrical protection. For best protection that flap can be sealed against the fold it over¬ lies, in any of the various ways described for the side-edge sealing, including heat sealing with heated applications or ultrasonic heating, cold sealing with cohesive-nonadhesive cement or pressure-sensitive cement coatings on the underside of the flap, as well as on the fold against which it lies, or even stapling.

Packaging can also be effected by using separate sheets of laminate 214 sandwiched over the top and bottom of the packaged object 212 as described supra.

Those separate laminate sheets can be heat sealed, cold sealed or stapled together around the packaged object.

The highly specular nature of the outer metallized surface of the polyethylene terephthalate laminations can be subdued by graining that surface preferably before it is metallized. A mild sandblasting with very fine sharp sand is quite effective, as is the casting of the polyethylene terephthalate sheet against a grained mold surface or the rolling of that sheet between rollers, at least one of which is grained. Such graining of the polyethylene terephthalate sheet helps mask the fingerprints which are normally picked up upon handling the laminate.

The packaging 260 of Fig. 8 has an envelope 262 generally similar in shape and construction to the envelope 214 of Fig. 7. Instead of the polyethylene terephthalate backing sheet of Fig. 7, envelope 262 has an iron foil backing sheet 264. That foil is preferably a fairly pure essentially carbon-free annealed iron which has a very high magnetic permeability and a very low remanence. A one-to-three mil thick foil of this type provides good magnetic shielding for the contents of envelope 262, such as a magnetic recording disc 266. A similar foil of iron which contains 1% to 3% silicon is also quite effective.

Metal foil 264 provides sufficient rigidity to stiffen the entire envelope and also enable its flap 268 to remain in place without cementing. Envelope 262 can accordingly be used both for shipping its contents, as well as for storing those contents between times when they are intermittently withdrawn for use in a computer or the like. The flap is readily folded open for such withdrawal and re-insertion.

The iron foil can have its external face treated to inhibit corrosion. It can, for example, be coated with aluminum, silver or copper, which provide highly conductive skins that help protect against external electrical influences, or merely coated with a cor¬ rosion inhibitor such as partially reduced zincdichromate. The foam layer can also carry volatile corrosion inhibitor that helps protect the foil, particularly its foam-contacting face.

Any metal having a magnetic permeability and remanence approxima¬ ting those of pure iron provides effective magnetic shielding for the contents of envelope 262.

Envelope 262 can be formed in other ways, as for example, by having its upper fold 271 wider than its lower fold 272 and projecting beyond both side edges of the lower fold. Those projecting margins can then be folded about the edges of the lower fold, and engaged against the lower surface of the lower fold 272. Where those folded- over margins are sufficiently stiff, they need not be adhered to the lower surface of fold 272. Alternatively, they can be adhered to that lower surface as by staples 274 as in Fig. 8, or by adhesives, or by having the extending margins of upper fold 271 free of foam so that those margins can be soldered to the lower surface of fold 272. Where staples are used as in Fig. 8, they are preferably also of pure iron so they magnetically interconnect the foil of the folds at their edges. Adhesives or heat-sealing can also be used and heat sealing can be arranged to melt most or all of the foam in the heat-sealing zone to thus shorten the air gap at the fold edges.

A flap 268 is not needed on the envelope 262 of Fig. 8, particu¬ larly if it is only proposed to hold a thin magnetic disc.

The magnetic protection of Fig. 8 is further improved by dividing

the foil 264 into two layers that are separated by a non-magnetic gap. Thus, two layers of 0.5-to-l mil thick iron foil coated on one face with about a 10-micron thick layer of polyethylene or polystyrene or the like can be laminated together with one of the thin coatings between the foils and the resulting assembly laminated to the foam layer. The foam can be cemented to the uncoated face of one of the iron foils so that the outer face of the outer foil carries the thin coating as a rust-preventative or the like.

Obviously, many modifications and variations of the present invention are possible in the light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.