PROTECTIVE CUSHIONING

Abstract: Cushioned packaging and protecting with laminate (310) of a thin resilient resin foam layer (316) adhered to a strong supporting sheet (322). Laminate may also have metal foil or metallized layer, and/or volatile corrosion inhibitor and/or a cohesive-nonadhesive surface coating or a low-tack pressure-sensitive adhesive coating. Automatic packaging of a series of articles (20) between long webs of wide cushioning laminates having faces of heat-sealable foam. One web (31) is fed foam-face-up across a table (35), the articles (20) to be packaged placed on it in spaced locations, heat applied to foam edges by heating devices (38) and (39), and, optionally (171), to just about melt the foam there, and a second web (32) applied foam-face-down over the spaced articles and heat-sealed to the lower web at its edges. Transverse heat-sealing, and severings, are effected between successive articles by heat sealing means (65). the heat sealings can be set by cold pressings. Web backings can be made relatively nonporous to minimize bleed-through of melted foam.

Description: -i- PROTECTIVE CUSHIONING The present invention relates to the cushioning of articles with thin protective layers of resilient foam that are laminated to even thinner but much stronger supporting sheets. Among the objects of the present invention is the provision of novel cushioning arrangements and techniques with such laminates. These, as well as additional 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 a diagrammatic illustration of an automatic packaging apparatus suitable for use pursuant to the present invention; FIG. 2 is a similar illustration of a modified packaging apparatus; FIGS. 3 and 4 are plan and transverse- sectional views, re¬ spectively of the apparatus of FIG. 2; FIG. 5 is a view of a cushioning package that can be made with the apparatus of FIGS. 1 or 2; and FIGS. 6 and 7 are sectional views of different cushioning arrangements of the present invention. According to the present invention, a backed sheet of thermo¬ plastic foam is heat-sealed to a desired surface by pre-heating to melting or sealing conditions the face of the foam at the proposed sealing location on the sheet, then pressing that sealing location against the desired surface to bring the pre-heated foam in sealing contact with that surface, and maintaining the pressing while causing the melted foam to cool and solidify. The pressing need not immediately follow the melting, but can be delayed a few seconds and thus permit partial cooling. Also, where the backing for the foam is paper, the pre-heating can be controlled to keep the pre-heated foam and the laminant that secures it to its backing, from bleed¬ ing through that paper. The heat sealing can be against another backed sheet of foam, or another portion of the same backed sheet, as for instance, to form an envel¬ ope or wrapper for packaging articles. Such packaging is shown in U.S. Patent No. 4,253,892. Polypropylene resin is a very suitable composition for the thermo¬ plastic foam of both backed sheets, although polyethylene foam and poly¬ styrene foam, as well as other heat-sealable foams, can be used. Thermo¬ plastic resins, when melted by the above-mentioned pre-heating and then pressed, tend to bleed through a porous backing layer like paper. To inhibit or completely prevent such bleed- hrough, such porous backing layers can be rendered more impervious as by providing a metallized stratum of aluminum, for example, on the foam-engaging surface of the backing layer. A layer of metal foil such as 0.0003 inch (7.62 microns) thick aluminum between the foam layer and a paper backing layer is also very effective in preventing bleed-through. In packaging articles between two long advancing sheets or webs of _ the backed foam, as in the above-cited prior processes, it is preferred that the heat-sealing at the longitudinal edges of the advancing sheets be effect¬ ed with the help of melting shoes directly contacting the foam of those edges, and transverse heat sealing be effected between pressing members each of which engages the backing layers of the backed foam laminate. Preferably each transverse seal is made by two pressings, the first pressing being between heated pressing members that are hot enough for the heat to penetrate through the backing layers and thus bring the foam layers to heat-sealing tempera¬ ture. The second pressing is between pressing members that cool the hot pressed location to set the heat seal. The pressing members for the second pressing can also be combined with a cutting mechanism to sever the packages that are completed by that pressing. ___ - For best results when doing the foregoing type of packaging of a succession of articles, each of substantial height, between two advancing long wrapper webs or sheets, the sheets covering the articles sandwiched .between them are advanced at a pre-determined level between upper and lower resilient meπbers or fingers that urge the carried articles toward that level from above and below. This makes the packaging essentially symmetrical with respect to that level, and is more effective than the prior art use of upper fingers with a lower fixed non-resilient stop that can be adjusted in position. Turning now to the drawings, FIG. 1 diagrammatically illustrates the packaging'of a succession of articles 20, such as small packages of pharmaceuticals or engine parts or electronic components, between a lower wrapper web or sheet 31 and an upper wrapper web or sheet 32. Sheet 32 is a paper-foam laminate, and sheet 31 is a paper-foil-foam laminate, as described, for instance, in U.S. Patent No. 4,321,297. Lower sheet 31 is unwound from a supply reel that is not shown, and fed foam-side up across the top of a loading table 32. As that sheet transverses the table, a spaced succession of the articles 20 are placed on its upper surface either by hand or with automatic article feeders. At the discharge end of table 35, the side edges of sheet 31 pass under melting bars 38 and 39 which are electrically heated and have their lower faces about inch (12.7 millimeters) wide and about 4 to 10 inches (10.16 to 25.4 centimeters) long resting on the foam surface. Guide pins can be mounted in the table top along both edges of sheet 31 to help assure proper alignment of the sheet with the melting bars. The melting bars are heated to temperatures high enough to melt at least some of the foam which they contact. Where the foam is polypropylene, the temperature, as measured at the heating coils inside the melting bars, can be about 450°-500°F (232°- 260°C) to about 550°F (287.8°C). For other plastics that melt at temperatures lower than polypropylene, the heating coils can be at lower temperatures. It should be noted that the temperature of the melting bars' foam-engaging surfaces is much lower than the coil temperature. The physical interaction between the melting bars and sheet 31 may tend to cause the sheet edges to move toward each other with the central portion of the sheet bulging upwardly. The weight of the articles 20 resists such distortion, and the distortion resistance can be further opposed by fitting some rollers or spring fingers over sheet 31 where it approaches the melting bars, to press the sheet against table 35 between articles 20 and the melting bars. WO85/04150 - ** -- PCT/US85/00399 Further travel of sheet 31 brings it and the articles carried by it under the upper sheet 32 which is laid over it with the foam layer of sheet 32 facing downwardly. This sandwich moves between a set of downwardly biased upper spring fingers 41 and a set of upwardly biased lower spring fingers 42. These sets of spring fingers are held in adjustable positions along rods 47 and 48 and can be adjusted so that some of the fingers act as edge guides for the sandwiched sheets, as illustrated at 43 and 44. There is no table or other lower support for the sandwiched assembly at the location of the fingers 41 and 42, so that the fingers, all of which have about the same resilience, cause each sandwiched art¬ icle to be held so that it projects about equally above and below the plane of the sheets. This symmetrical positioning helps keep the edges of the upper sheet 32 aligned with the edges of the lower sheet 31, even though the bulge in the sandwich caused by the sandwiched article draws the edges of each sheet toward each other. Immediately downstream of the fingers 41 and 42, is a set of advancing pinch rollers 51, 52, 53 and 54 that are strongly urged toward each other to engage the side edges of the sandwiched assembly and cool them as well as pinch them together. This cools and sets the melted foam to complete the lateral edge sealing of the sandwiched articles. These pinch rollers are adjustably fixed on elongated shafts 56 and 57 and only one of the shafts need be driven as by electric motor 60, to pinch and pull the sandwiched assembly through the apparatus. The circumferences of the rollers can be accurately dimensioned to pre-determined size so that their rotations can be accurately counted and their drive motor controlled as by an electric clutch-and-brake assembly operated by an adjustable counter, to advance the sandwiched assembly in steps, each step corresponding to the length of each package to be formed about an article 20. The rollers themselves are preferably made of steel or aluminum and made as wide as the melting bars 38 and 39 so that the pinched-together rollers effectively cool and set all the plastic melted by the melting bars. Just downstream of the advancing rollers is a transverse heat- sealing bar mechanism 65. Two electrically heated bars 68 and 69 extend transversely across the sandwiched assembly, one above and the other below that assembly. The bars are held for vertical reciprocation on vertically oriented side rails, and are vertically actuated by air cylin¬ ders 71. When retracted from the sandwiched assembly, the bars should leave sufficient clearance above and below that assembly to permit the passage of the tallest article 20 to be packaged. A similar clearance should be provided by the shafts 56 and 57 that hold the advancing rollers, and for any melting bar holder such as lifting bar 37 that can be lifted as by air cylinder 40 to lift the melting bars up and away from sheet 31, as for example, when the equipment is not being used or its use is halted. The sandwiched assembly is advanced in steps in the downstream direction, and the stationery dwell time is adjusted to provide the time required by the transverse bars 68 and 69 to effect heat sealing. Thus, when these bars are heated to an internal coil temperature of 550°F (287.8°C), 1_ seconds may be required for the bars to cycle into, through and out of pressing engagement against the upper and lower faces of a sandwiched assem¬ bly in which the foam is polypropylene resin and the foam is backed by Kraft paper or a paper-alumlnum-foil laminate about 5 mils (127 microns) thick. The dwell is best controlled by a pre-set adjustable timer. The lateral pressing cycle can start slightly before the downstream movement of the sand¬ wich stops, and the downstream movement can resume slightly before the cycle ends. Another set 75 of advancing rollers can be provided downstream of the transverse sealing bar mechanism 65, if desired. Such an extra set helps assure the proper advancing of the sandwiched assembly, particularly when the advancing is abruptly started after the completion of a stationery transverse heat-seal dwell. The distance between successive transverse heat-seals corresponds to the spacing between locations of the individual articles 20. Accordingly, the setting that fixes the amount of advancement effected by motor 60 in one advancement step, can be keyed to an indicator that designates where articles 20 are placed on sheet 31. As shown in FIG. 1, the edge 78 of table 35 can be,provided with scale markings 80 designating the locations of articles 20 when the succes¬ sive advancement steps range, for example, from 5 inches to 11 inches (12.7 to 27.9 centimeters). The 5-inch (12.7 centimeters) marker would then be measured upstream from the transverse heat-seal bars a whole number-of multiples of 5 inches (12.7 centimeters), plus the 2 _ inches (6.35 centi¬ meters) needed to locate the center of the next 5-inch (12.7 centimeters) space. The 6-inch (15.24 centimeters) marker would- similarly be measured to whole numbers of multiples of six inches (15.24 centimeters)—plus three Inches (7.62 centimeters), etc. These markers would then show where the appropriate articles 20 are to be located while the sandwich assembly is stopped during a transverse heat-sealing pressing. Packages to be made with lengths intermediate between those designated by markers 80 can have their locations interpolated between the appropriate markings. -Se¬ lf desired, a separate set of marked strip scales can be provided, one such scale having a group of markings exactly 5 Inches (12.7 centi¬ meters) apart, another exactly 6 inches (15.24 centimeters) apart, etc. For a specifically dimensioned package, the appropriate strip scale can then be mounted over table edge 35 with one marking of that strip scale aligned with the appropriate marking 80. The strip scale then indicates where a series of articles 20 are to be positioned when the sandwich movement pauses during transverse heat sealing. This enables the accurate positioning of a number of the articles during a single such pause. The final stage in the heat-sealing sequence is effected with a set 90 of pressing-and-severing bars. These bars can be very similar to the heat-sealing bars 68 and 69 but do not require heating, and a serrated cut¬ ting blade is fitted in the sandwich-engaging face of one bar so as to pro¬ trude and cut through the sandwich. .A groove can be formed in the other pressing-and-severing bar to mate with and receive the protruding blade when it penetrates through the sandwich. The pressing-and-severing bar mechanism, including its vertical press-guiding rails, is held between longitudinally directed side rails 95 to which it can be fastened at a location that causes its bars to press and sever the sandwich exactly at the transverse heat seal formed by the mechan¬ ism 65. Preferably the pressing-and-severing is effected one advancing step, but not more than two advancing steps, downstream from the first transverse heat-pressing. The pressing-and-severing bars then do a good job of cooling and setting the transverse heat seal, particularly if the faces of the pressing-and-severing bars contacting the sandwich are made of a metal such as aluminum. Where the transverse heat seal has cooled excessively before being engaged by the pressing-and-severing bars, it is helpful to have the latter bars heated to at least partially restore to the heat-seal some of the heat that enables that seal to be set under pressure. Such pressure setting is the preferred heat-sealing technique. A container 99 can be provided to receive the individual packages as they are severed from the advancing end of the sandwich assembly. They show no bleed-through even though upper sheet 32 contained no bleed-blocking stratum. However, both sheets 32 and 31 can contain such strata if, for example, it is desired that those sheets be of identical construction. The bleed-through difficulty at the longitudinal seals can be minimized or completely avoided by careful control of the edge heating. Thus, the melting bars 38 and 39 can be lifted away from the foam face of sheet 31 during the time interval in which that sheet pauses between advancing steps. The resulting edge heating is more uniform in that the large amount of localized heating during advancement pauses, is eliminated. The extra cooling of the melted foam during such no-heat pauses is quite uniform. With such a modification the resulting uniform melting can be controlled so that the melted resin is not too fluid and the porosity of porous foam backings does not permit significant bleed-through. In place of container 99, a take-off conveyor can be supplied to support and remove cut packages as they leave the base of assembly 90. Such take-off conveyor can be of the belt type with the belt travelling a little faster than the package sandwich, to help assure the clearing of sandwiches from the cutting assembly. If desired, a table can be positioned under the package sandwich as it leaves roller assembly 75 to help guide the sandwich to the cutting bars of assembly 90. All of the sealing structures of FIG. 1 are of adjustable width, except for the pressing structures 65 and 90. The adjustable widths can accordingly be adjusted to effect the desired packaging with sheets 31 and 32 of any width within the adjustment range, for instance, from 5 to 12 or more inches (12.7 to 30.48 centimeters). The pressing structures 65 and 90 extend the full width of the widest a ustme-αt j and accordingly need no separate adjustment. The packaging output of the apparatus of FIG. 1 can be increased by using wide packaging sheets and packaging two transversely aligned rows of articles at once. To this end a third melting bar can be longitudinally positioned half-way between the side edges of the sheets, a third pair of pinching-and-advancing rollers can be correspondingly-fitted " on shafts 56 and 57, and a longitudinally oriented stationeryo.- rotating severing blade can be fitted between the pinching-and-advancing rollers of mechanism 75 to sever the wide dual sandwich assembly into two side-by-side halves as the assembly is pulled through it. The packaging technique of the present invention can be modified as by eliminating one of the melting bars in FIG. 1 or cutting off its heat¬ ing current. The packaging operation will then yield packages having an unsealed edge through which articles such as letters can be subsequently inserted, after which the unsealed edge is sealed, for example, with a simple bag-end heat sealer or by cementing or stapling. In such a modification, the articles 20 need not be pre-packaged in the bags, but can be withheld from the packaging apparatus and later inserted in the open-ended packaging bags thus formed. The finger assembly 41 and 42 can then also be omitted. Instead of using two separate wrapper sheets 31 and 32 in FIG. 1, a single sheet twice as wide as either sheet 31 or 32 can be used. Such a wide sheet can then be automatically folded over along its longitudinal axis to make a sandwich similar to that of FIG. 1, which sandwich can then go through the heat-sealing sequence, but without the melting bar that would otherwise be located where the fold line is. Such a foldover combination is shown in U.S. Patent No. 3,696,580. Both melting bars can be omitted with such a folded sandwich, if it is desired, to make open-ended bags. When making open-ended bags, the opposing walls of the bags need not be of identical shape at the open end. Thus, one bag wall can project out further than the opposite wall, so as to provide a flap that can be sub¬ sequently folded over the shorter wall and sealed envelope-style. If desired, the apparatus of FIG. 1 can be fitted with applicators to apply adhesive or heat-sealing improvers such as described in U.S. Patents Nos. 3,916,076, 3,393,081 and 4,367,112 to the sites on sheet 31 and/or sheet 32 before the sealing is effected at those sites. The melting bars can then have their temperatures reduced or the bars completely eliminated. Similarly, the temperature of transverse heating bars 68 and 69 can be re¬ duced, and one set 65 or 90 of the transverse bars can be eliminated. The packaging sheets of the present invention can be treated or coated with materials, such as anti-stat agents, volatile corrosion inhibit¬ ors and the like, such as those mentioned in.U.S. Patent No. 4,321,297. Some coatings of this type improve or do not interfere with the heat-sealing and so can be coated over the entire foam face of one or both packaging sheets. Where such added materials interfere with the heat-sealing, it is preferred that such materials be coated in locations at which heat-sealing is not effected. WO85/04150 _g_ PCT/US85/00399 Thus, a surface-active agent such as a surface-active anti-stat can cause a heated foam layer to delaminate from an aluminum foil to which it had been adhered, particularly if some of that surface-active agent finds its way between the foam layer and the foil. It is accordingly desirable when laminating metal foil to foam that Is to have anti-stat properties, for the foam to be of the closed-cell type and for the anti-stat to be applied to the outer face of the foam after the foam is laminated to the foil. With a metal foil or metallized backer contained in one or both of the packaging sheets, or even with a metallized coating on the foam, the resulting package will protect the article packaged in it against electric fields. Such protection is particularly desirable when packaging trans- sistors or similar electronic articles that are constructed for operation at very low voltage. For such protection it is preferred to have the packaging in a single packaging sheet that is folded over as described above. By such fold-over, the metal foil or metallized layer covering one side of the packaged article is electrically continuous with the metal foil or metallized layer covering the other side of the packaged article, so that the protection against electric fields is improved. For maximum protection against electric fields, copper or silver foils are better than aluminum foils, and thin copper foil with a very thin, e.g. 1/2-micron thick, flash coating of silver may be most cost-effective. Such a flash coating can be applied to only one face of each foil. The backing layer covering a foil-carrying sheet can be provided with openings, as for example, along its borders so that a grounding con¬ nection can be clipped to those borders and thus ground the foil. Whether or not the metal foil shielding is one fold-over sheet or two opposing sheets, it is a very effective barrier against the penetration of moisture vapor. Accordingly, by doing the packaging in a very low humidity atmosphere, e.g. below 30% ' relative humidity at room temperature, the danger of corrosion for packaged water-sensitive material is sharply reduced or completely eliminated. Plastic films like polyethylene terephthalate are also good moisture barriers, particularly when they have metallized surfaces. The rate at which the packaging sheets advance through the packag¬ ing sequence can be varied. It is preferred that the time interval between the respective heatings at the melting bars and transverse heat-sealing bars, -9- and the respective pressings at the pinch rollers and transverse bars 90, be not so long as to permit excessive cooling between those pressings. Six seconds can be well tolerated, but about fifteen seconds is too long. To keep this time interval small, the number of advancing steps during the interval should be no greater than two. It is generally helpful to com¬ plete an advancing step in about one second or less, even if such a step requires a 12-inch (30.48 centimeter) or as much as a 20-inch (50.8 centi¬ meter) travel. Also, the pressing dwells are preferably no longer than two seconds each. Although heat sealing generally takes more time than the cold pressure sealing that has been used with the cohesive-nonadhesive coatings of the prior art, the automatic heat-sealing of a sequence of articles into suc¬ cessive packages pursuant to the present invention can be effected at a rate very close to, if not faster than, the prior art cold sealing. FIGS. 2, 3 and 4 show a succession of relatively flat printed circuit boards 111, 112 and 113 being packaged between two paper-foam packaging laminates 121 and 122. These laminates can be of the types de¬ scribed in U.S. Patent No. 4,321,297, carrying an anti-static or corrosion- inhibiting layer or a layer that contains both an anti-stat and a corrosion inhibitor, on the face of the foam.* The foam layer itself is preferably one that heat seals at about 100°C (for polyethylene, for example), and is no thicker than about 3/16 inch (4.76 millimeters). The anti-stat and/or corrosion inhibitor can lower the heat sealing temperature to about 95°C. The backing for the foam is preferably not over about 1/16 inch (1.587 millimeters) thick with a tensile strength at least twenty times that of the foam layer. Each laminate 121 and 122 is provided as a long sheet rolled up and held on a dispensing reel, not illustrated. Sheet 121 is fed foam side up onto a spaced pair of adjustable supporting angles 126 adjusted so that the floors 130 of the angles are essentially in a horizontal plane, with flanges 128 extending upwardly and closely fitted about the sheet's side edges 134. Sheet 121 is pulled longitudinally along the guiding angles by two pair of gripping discs 141, 142, 151 and 152. Discs 151 and 152 are fitted to an adjustable shaft 154 that is rotatably held in two brackets 156 mounted under the supporting angles 126. Discs 141 and 142 are similarly fitted to an adjustable shaft 144 above the guides, rotatably held by an arm 146 that is resiliently pressed downwardly as by spring 147 to cause the upper discs 141 and 142 to pinch against the lower discs through slots 148 cut in the angle floors 130. Either or both pairs of discs are rotated in the direction of arrows 158 as by sprockets 159 mounted on the disc shafts and driven by worms connected by flexible shafts 157 to the opposite ends of the armature of a drive motor 155, so that the outer face of each-disc is exposed. The discs pinch the packaging sheet 121 between them and in this way pull that sheet in the direction of arrow 162 along the supporting angles. Notches 164 can be cut out of the upwardly extending flanges 128 to keep them from cover¬ ing the outer faces of discs 141 and 142. The articles 111, 112 and 113 are placed on designated spaced locations on the foam face of sheet 121 as it is pulled along. At the same time the second packaging sheet 122 is pulled from its dispensing reel to engage the edges of discs 141 and 142 and to be thus pulled down into firm foam-to-foam engagement with the lower sheet downstream of where the articles to be packaged are placed on the lower sheet. The outer faces of all the discs are heated by reflector-equipped heat lamps 170 placed so that they focus infra-red radiation on those faces as well as on the adjacent edge portions of the packaging sheets. Additional heat lamps 171 can be aimed directly at the sides of the sheet faces at locations just upstream of the disc edges to further pre-heat all or some of those sheet edges immediately before they are pinched together by the discs. This pre-heating supplements the pre-heating of the upper sheet as it is pulled around the hot edges of upper discs 141 from the disc tops to the disc bottoms. For best results, the pre-heating of lamps 171 is confined essen¬ tially to the narrow sheet locations at which the pinching and sealing take place. A transversely extending frame 177 has an upper cross piece 181 held by springs 183 that extend to an overhead mounting site, to thus hold the frame in its upright position, as illustrated. The side members 185 of the frame have their upper portions in the shape of channels 187 that open -11- towards each other to provide tracks within which is slidably itted a guillotine cutter 189 that extends transversely of the packaging sheets and is as long as the widest packaging sheets to be processed. Cutter 189 is connected for vertical reciprocation by a pair of air cylinders 191 actuated by flexible air hoses that are not illustrated. An anvil 193 is fixed between the frame side members 185 and has a slot 195 to receive the guillo¬ tine blade and embedded in the anvil are electric resistance heaters that heat the anvil to heat-sealing temperature. Similar heaters can be incorpo¬ rated in the guillotine cutter 189 on either side 188 of its cutting blade. The lower faces at 188 are horizontally flat so that when the cutter is propelled downwardly the faces at 188 forcefully engage the packaging sheets and press them against heated anvil 193. This act of propulsion also transversely cuts the packaging sheets and is timed so that it occurs when a portion of the packaging sheets about halfway between successive packaging articles, is over the anvil. The forceful pressing of the cutter against the anvil is maintained for the length of time needed for the heat from the anvil and from heaters at 188 to effect a transverse heat-sealing across the packaging sheets. This may take as long as a second or so, and during that time the packaging sheets * continue to be advanced by the pinching discs to push the cutter-and-anvil assembly in the advancing direction, to pivot the cutter frame 177 around its pivot 179. When the transverse heat-sealing is completed the air cylinders 191 cause the guillotine cutter 189 to be retracted away from the anvil, thus releasing its grip on the packaging sheets. The packaging sheet section downstream of the cutter is accordingly released and slides down the curved guide plate 199 as a completed package indicated at 201. Adjustable side guides 203 may be provided to help direct the completed package. Upon the retraction of the cutter 189, the packaging sheets upstream of the cutter are no longer gripped between cutter and anvil, so that springs 183 pivot the frame 177 back to the vertical position against stop 190. The cutter frame is now ready to make the next transverse cut and heat-seal. Arcuate fingers 196 extend from the anvil and follow it in its downstream movement to help support the downstream end of the packaging sheet assembly while the anvil is later returned by springs 183. One cycle of such heat- sealing transversely seals the packaging sheets on both sides of the cutter blade, so that it closes the downstream end of the package being cut loose as well as the upstream end of the next* package. The cutter 189 preferably has its cutting edge serrated or inclined guillotine-style at about a 5 β to 20° angle with respect to the anvil which can be horizontal. This serration or inclination gives the cutting a scissors-like action that reduces the cutting force. The help the incoming packaging sheets push the transverse sealing assembly 175, the cutter actuation can be connected to independently start rotating that assembly, as by having the side face of cutter 189 engage a cam 192 as the cutter reaches heat-sealing engagement. The guide angles 126 and pinch discs are all arranged to be adjust¬ ed for packaging sheets of different width. The transverse cutter extends to the maximum width of the guide angles and needs no width adjustment. It is also helpful to apply some pre-heat to the transverse sealing " site. Thus, a long thin heat lamp 206 can be mounted in a reflector 208 that directs the lamp output as a narrow band approximately _ inch (12.7 millimeters) wide and as long as the entire width of the transverse sealing assembly. * The lamp-carrying reflector 208 is pivotally mounted as at 210 so that it can pivot and In this way longitudinally scan along the longi¬ tudinally sealed packaging sheet assembly immediately upstream of the transverse sealing site. This scanning is shown as controlled by a control arm 212 project¬ ing downwardly from the reflector and having a sensing tip 214 hanging in the path of the bumps formed where the packaged articles are sandwiched. As such a bump reaches the freely hanging tip during the progress of the packaging, it engages and pushes the tip in the downstream direction thus tilting reflector 208 to cause the pre-heat it directs to scan downstream in synchro¬ nism with the sandwiched articles. Sensing tip 214 is shaped and pivoted with relation to the shapes of the bumps, to cause the reflector tilting to remain accurately focused at the same location on the top surface of the upper packaging sheet 122, moving with that sheet so as to effectively pre-heat that location just before the transverse heat-sealing takes place at that location. To this end the sloping nose of a bump co-acts with the tip 214 to gradually slow the rate of reflector tilt a little, after the tilting starts, to thus compensate for the extra advancing effect that the tilting has- on the heat projection. The transverse heat-sealing is shown as controlled by a limit switch 220 in the tilt path of control arm 212. -13- Tip 214 is made springy and short enough to be tilted completely out of the way as, or shortly after, switch 220 is actuated, so that the bump causing the tilting passes by. When that passage is completed, the tip is pulled back to the illustrated position by return spring 222, and is now ready for the next bump. Instead of, or in addition to, the pre-heating of the upper surface of the upper sheet 122, similar pre-heating can be applied to the lower sur¬ face of packaging sheet 121 in corresponding locations. The same control can be used to direct both such transverse pre-heatings. Infra-red radiation can also be used to pre-heat the foam face of packaging sheet 122 along the heat-sealing region, as that sheet travels around disc 141. Pre-heating can also be applied to the lower face of packaging sheet 121. The heat lamps 170 can be replaced by electric resistance heaters fitted to the outer faces of the discs and electrically insulated from those faces. Such heaters have circular contacts that are carried by the discs and are engaged by fixed brushes connected to a supply of electric current. The output of the FIG. 2 packaging machine can also be increased by widening it so that it operates on packaging sheets.twice as wide and then -fitting each pinching disc shaft with an additional pinching disc mid¬ way between the two illustrated in FIG. 3. The two additional pinching discs can moreover be provided with a cutting edge and mating groove so that they slit the wide packaging sheet longitudinally along its center line, and also heat seal on both sides of the slit. Articles can then be simultaneo sly packaged on each lateral half of the packaging sheet combina¬ tion. For the present invention it is desirable to use polyethylene foams, and particularly foams of low-melting polyethylene which can be heat-sealed at 95°C or even somewhat lower. Foams made of well-plasticized resins are also desirable because they also have low-melting points. The anti-stat and volatile corrosion inhibitors are preferably plasticizing agents for the resins they are coated on, to lower their melting points. However poly¬ propylene, polystyrene and other heat-sealable foams can also be used. -1. - Where high output is not needed, the machine of FIG. 2 can be operated stepwise so that the packaging sheets are given a succession of stepwise advances with the sheets stationary between steps. The stationary dwells are made sufficiently long in time to permit the guillotine cutter to cut and heat-seal transversely. At the same time the longitudinal heat- sealing discs should not be so hot as to char the sheets during the dwell for the transverse heat-sealing. The transverse heat-seal frame 177 need then not be pivotally mounted. The supported foam laminates used in the present invention can have, supporting laminations that need not be paper. While paper is a very desir¬ able supporting member by reason of its low cost as well as its strength and resistance to damage by the heat needed for heat-sealing, the paper can be replaced by sheets of felted fibers other than cellulose or by plastic films or even metal foil. Foils of metal such as aluminum preferably have thick¬ nesses of up to about 10 mils (.254 millimeters), inasmuch as greater thick¬ nesses unduly add to the expense as well as to stiffness of the supported foam. Metal foils 0.5 mil (12.7 microns) thick or 0.35 mil (7.62 microns) thick or thinner are preferably laminated to paper, to provide a strong two- layer support for a layer of cushioning foam. Such a support can be used with the paper or foil layer against the foam. Similarly, a metallized paper support can be used with its paper or metallized coating against the foam. Where a paper-foil laminated support has its paper face on the outside of the foam-support combination, the paper preferably has a number of perforations at least about inch (6.36 millimeters) in diameter punched out near an edge before the foil is laminated to it. This is illustrated in FIG. 5, where a sandwich package 300 has edge perforations 302, and is particularly suited for the application of a grounding clip. Metal supporting layers sandwiched about an electrically-sensitive object can be electrically connected together by the cutting action that separates individual packages, and/or by stapling or the like, to form a better electrical shield around the object packaged. Metal supporting layers are also very highly conductive to heat so that heat-sealing times can, with metal-foam laminates, be reduced to less than 1/2 second. Polyethylene terephthalate films or felted fiber sheets that with¬ stand temperatures of about 160°C that may be applied to effect heat-sealing, are also suitable and can be used in film or sheet thicknesses as small as 0415 PCT/US85/00399 mil (12.7 microns) or 1 mil (25.4 microns). Such small thicknesses are still quite strong and also reduce the time required for the heat-sealing heat to penetrate through to the foam. Microwave dielectric heating is also suitable, particularly since it generates heat inside the sheet, and can be used whether or not foils or metallized layers are present. Supporting layers of woven or unwoven strips of plastic film about 1 to 3 millimeters wide can also be laminated to the heat-sealable foam to make packaging sheets. A foam support can be made of combinations of layers. Thus, a paper layer can be reinforced with glass or other fibers or laminated with metal foil or plastic film. The pre-heating of FIGS. 2, 3 and 4 should be adjusted to cause the subsequent sealing operations to barely bring the foam to heat-sealing temperature, slightly below the melting range of the foam, so that no special provision need be made for cooling the heat-seals under pressure. Such sup¬ plemental cooling can be provided if desired, and this enables greater tolerance in the degree of heating used to make the tightest heat seals most difficult to tear open. Without such cooling the heat-sealing adheres the heat-sealed parts together but they are easier to tear apart. Pressure cooling of the heat seals in the apparatus of FIG. 2 can be effected by leaving the discs 141 unheated so that they help cool the pre¬ heated sheet edges as they are pressed together and sealed. The transverse sealing effected by the apparatus of FIG. 2 can also be similarly after-cooled, by having the transverse pre-heating sufficiently intense and leaving the transverse pressing members unheated. The paper-foam laminates are very suitable for protecting a key surface while work is being done. According to the present invention, an important or key surface is protected by a foam laminate while work is being done on or near it, or where the surface is being used as a temporary walkway. The laminate has a thin layer of smooth-or nonabrasive-faced resilient foam not over about 1/8 inch (3.18 millimeters) thick adhered to a supporting wear-resistant layer less than 1/25 inch (1.016 millimeters), preferably less than 1/50 inch (.508 millimeters) thick, the face of the foam layer that is not adhered to the supporting layer carrying a stratum of friction-increasing material that reduces the tendency of the laminate to slide along a surface on which that face is placed. -16- A low-tack pressure-sensitive adhesive is a particularly desirable friction-increasing material to more securely hold a foam laminate against a surface from which it is to be subsequently removed without leaving a residue. Depositing such adhesive from a solvent onto either face of the laminate causes the adhesive to adhere to that face more strongly than to a surface against which the dried adhesive-carrying face is then merely pressed. Any of the foregoing papers may be reinforced with strands of fiber¬ glass to strengthen them. Reinforcement may also be accomplished by adhering other types of mesh such as polypropylene mesh or polyester scrim to the laminate or between the laminae, or the foam-supporting sheet can be a spun- bonded polyolefin or spun-bonded glass fiber sheet or a sheet woven from oriented flat narrow plastic tapes. Such sheets have tremendous resistance to puncturing and tearing. On the other hand, the foam-supporting sheet can be creped or extensible paper to permit the laminate to better follow contours when applied to concave or convex surfaces. Where the foam or the supporting sheet carries a cohesive-nonadhesiv surface stratum, such a stratum can show a residual level of adhesion enough to cause such stratum to block and greatly resist unwinding of a roll of such coated laminate. This blocking effect is much more pronounced when the cohesive-nonadhesive stratum is applied to a paper face, as compared with a foam face, and also when the surface against which it is wrapped around is a corona-treated or untreated polyethylene, but can be reduced or eliminated by incorporating an inert powder such as clay in the cohesive-nonadhesive layer. Between about 5% and about 15% clay does a very good job without substantially reducing the aggressiveness of the cohesive action. Anti-static compositions such as potassium formate or those referred to in U.S. Patent No. 4,321,297 also have a significant friction-increasing effect when present by themselves on the surface of a resilient micro-cellular closed-cell foam. Other improved packaging sheets of the present invention contain opaquing material. FIG. 6 is a cross-sectional view of a laminated sheet highly suited for protecting polished aluminum surfaces or wooden boat decks. The laminated sheet 10 of FIG. 6 has a supporting layer 312 of a wear-resistant paper such as 42-pound Kraft liner board or Kraft paper, to which is laminated by amorphous polypropylene or similar laminant 314, a layer of pliable, resilient plastic foam 316 about 3/32 inch (2.388 milli- _ ~ meters) thick. The face 318 of the foam has adhered to it by laminant stratum 320 a very thin supporting film 322 that, in turn, carries a stratum 324 of low-tack pressure-sensitive adhesive. Adhesive stratum 324 is cover¬ ed by a sheet 26 of release paper which can be waxed or silicone-coated so that It can be readily peeled away from the remainder of the sheet. Film 322 should not be so stiff as to excessively detract from the resilience of the foam which permits cement stratum 324 to follow minor con¬ vexities or concavities of a surface against which the sheet is to be applied. Thus, film 322 can be a plastic film not over 3 to 4 mils (76.2 to 101.6 microns) thick, or it can be aluminum foil not over about 1 mil (25.4 microns) thick. Where film 322 is a film of very strong plastic such as polyethylene terephthalate, it can also be as thin as 1 mil (25.4 microns) or even less. Film 322 can be entirely omitted, along with adhesive stratum 320, by applying the pressure-sensitive adhesive stratum 324 directly to the face 318 of the foam layer 316. Depositing such low-tack adhesive from solution directly on face 318, causes the low-tack adhesive to adhere very well to face 318, although pressing the subsequently dried low-tack face against the surface to be protected, will cause it to not adhere too strongly to that surface. It should take a force of not more than about _ pound (0.225 kilo¬ grams) to peel the protective laminate from the key surface that it protects after the laminate has been firmly pressed against that surface. When measured by the rolling ball method described in U.S. Patent No. 4,104,327 [J. Dow Proc*. Inst. Rub. Ind. 1,105], the desired low tackiness is only enough to stop the rolling of a stainless steel ball no larger than about inch (6.36 millimeters) in diameter. The foam of layer 316 can be of any resilient material as, for example, a thermoplastic resin foam made from resins such as polyolefins, particularly polypropylene, polyethylene or polyvinyl chloride, or a poly- urethane foam that is not thermoplastic. The laminates of FIG. 6 can have their release coverings 326 peeled away and the resulting face of cement 324 applied against a surface to be protected from scuffing or similar damage. Thus, when constructing or re¬ pairing aircraft, it is frequently desirable to walk or place equipment on the wing or fuselage or tail, and this can seriously damage a soft aluminum surface by scratching, particularly where that surface is highly polished. Where the surface to be protected is vulnerable to. corrosion, the protecting -13- laminate should have its contacting face free of corrosive agents, and/or the laminate can carry volatile corrosion inhibitors as described In U.S. Patent No. 4,321,297. The aircraf surface can be protected by placing the foregoing foam laminate on It, with or without pressing the laminate against that surface. With the low-tack adhesive the laminate will not stick so tenacious¬ ly, whether or not pressed in place, that it cannot be completely removed when the protection is no longer needed. The low-tack adhesive will not leave a residue on the protected surface when the laminate is removed. Suitable low-tack adhesives are described in U.S. Patent Nos. 4,165,266, 4,141,319 and 4,104,327. Similar protection can be applied to a boat deck or house floor when it is being built or repairs are being made, or can be applied over a vehicle hood or fender while working on it. Where protective laminates are applied to surfaces that are sub¬ stantially inclined from the horizontal, friction-increasing layer 324 can have a higher degree of tack to help make sure they do not slide down or fall off. In such use the adhesive face can require as much as a pound (0.45 kilogram) of ulling force to be pulled away from the surface being protected. _ However, where there is no such inclination, -adhesive 324 can merely be a cohesive-nonadhesive stratum such as the latex layers described in the parent applications. These layers have an increased frictional resistance to slid¬ ing on a surface against which the laminates are placed, and in some cases this is enough to hold a protective laminate in place. The cohesive-nonadhesive layer is, for example, an uncured natural or synthetic rubber latex composition having the property, after it is applied to the laminate and dried, of remaining adhered to the surface on which it is dried, and will thereafter stick to another layer of the same cohesive-nonadhesive type, but will not adhere to other materials such as other layers of the laminate. Uncured natural rubber latex is the preferred latex. Protective laminates in which the foam is more than about 1/8 inch (3.18 millimeters) thick are more expensive and too easily damaged by rough walking. Moreover, such laminates in which the paper or other supporting layer is thicker than about 1/25 inch (1.016 millimeters), are too stiff for secure no-slip walking. On the other hand, foam thicknesses less than about 1/16 inch (1.59 millimeters) are not particularly helpful, and a supporting -19- layer less than about 5 mils (127 microns) thick is too easily punctured. Omission of the supporting layer, as in U.S. Patent No. 4,313,987 leaves a product that readily tears when it is walked on, particularly where the foam layer is not over 1/8 inch (3.18 millimeters) thick. The friction-increasing effect of layer 324 can also be obtained with coatings that are not considered adhesives. Anit-static coatings such as potassium formate or the surface-active anti-stats described in U.S. Patent No. 4,321,297, do a good job of increasing friction when applied over closed-cell foam in coating weights as low as 0.1 gram per square meter. In FIG. 7 is shown a laminated cushioning material 350 for pack¬ aging or wrapping sensitive material such as solid state circuit boards. Sheet 350 includes a layer of paper material 352 which has two plies, 354, 354 of Kraft paper reinforced by strands of fiberglass 356. Kraft paper plies 354 are each, for example, 50-pound Kraft paper. Other useful types of Kraft paper are, for example, 30-pound, 60-pound, 90-pound or even 42- pound liner board. Fiberglass strands 356 arranged, for example, in a diamond or square pattern with or without longitudinal strands, are inter¬ spersed between paperplies 354 and adhered in place by adhesive 357 which is, for example, of the hot-melt type, such as amorphous polypropylene or polyethylene, and cements the paper plies together. The paper layers are adhered to a foam layer 358 which is a plia¬ ble sealed-cell micro-cellular polymer foam and may, for example, be from about 1/32 inch (0.796 millimeters) to 1/8 inch (3.18 millimeters) thick. A highly effective sealed-cell micro-cellular polymer foam is made from polypropylene resin with approximately fifty thousand (50,000) closed air cushion cells per cubic inch (3,050 cells per cubic centimeter). Foam polymer layer 358 can be adhered to the paper by the same hot-melt adhesive used to adhere together the Kraft paper plies 354 and 354. The ultimately laminated sheet 350 has remarkable strength-to-weight ratio and is extremely useful for wrapping and packaging where substantial tear strength is required. A layer 360 of a water-repellent polymer, such as polyethylene, may be disposed over the top stratum 354 of two-ply Kraft paper layer 352, but it is not needed where the packaging sheet and the package made with it are not exposed to liquid water. Polymer coating 360 may be colored or printed to distinguish it and to control the passage of light through it. Other water- repellent polymers, such as polyvinyl chloride, polypropylene, polycarbonates WO85/04150 - D- PCT/US85/00399 or polyethylene terephthalate can be used in place of the polyethylene, and layer 360 need only be about 25 microns thick. A suitable anti-static stratum 364 can be disposed upon the outer face of the micro-cellular polymer layer 358, as by evaporation of the solvent from a solution of the anti-stat applied over that layer. Alternatively, the polymer of the foam can incorporate anti-static ingredients that impart anti¬ static properties to the foam. Where anti-stat is combined with the cohesive-nonadhesive layer as described in U.S. Patent No. 4,321,297, it is preferred to use an anti-stat like potassium formate or sodium formate, or the corresponding acetates, or even acetylene black which is not surface-active. The surface-active anti- stats tend to materially reduce the cementing strength of adhesives. A mixture of 97 to 100 parts natural rubber latex having 50% solids, with 3 to 3-1/2 parts potassium formate, produces a very effective coating formulation. Applied as a layer that on evaporation leaves a coating weight of 0.6 gram per square meter on a micro-cellular closed-cell polypropylene foam that had been laminated to a paper sheet, yields a product that has very good cohesive properties and also passes the anti-stat test MIL-B-81705.B. In general, the anti-stat concentration can vary from about 0.1 to about 1 gram per square meter, and the cohesive-nonadhesive concentration from about 1 to about 10 grams per square meter. A little glycerol up to an amount equal to that of the anti-stat can also be present in the anti-stat coating or in the combined anti-stat cohesive-nonadhesive coating. As explained in U.S. Patent No. 4,321,297, water-rsoluble anti-stats are preferably deposited from water solution, and water-insoluble ones from solution in a solvent like methanol. The uncured rubbers for the cohesive- nonadhesive cement can also be applied from solution. Anti-stat coatings, including such coatings that are also cohesive- nonadhesive, generally undergo reduction of anti-stat effectiveness when aged over a long period of time. Although U.S. Patent No. 3,658,744 indicates (bottom of its column 8) that the anti-stat can cause instability in a latex, the combinations of anti-stat with cohesive-nonadhesives in accordance with the present invention show gradual diminution in both anti-stat effective¬ ness, as well as cohesiveness, over several months. Such dimunition is slowed by shielding the coatings against light, particularly actinic light, and also by covering the coatings to keep air from them. The laminated products so coated are accordingly best tightly wrapped with opaque paper or -21- the like when they are stored and shipped. Thus, a roll or stack of the laminated sheeting can be so wrapped. Where an anti.-stat is very dark in color, acetylene black, for example, protection against light is,not so important. Increasing the anti-stat additions to over 1 gram per square meter helps counteract its degradation. The foregoing stability factors are of key significance. It is believed in this connection that there has in the past been some advertis¬ ing offering for sale paper-foam wrapping laminates in which the exposed foam surface is rendered anti-static as well as cohesive-nonadhesive, but so far as can be determined no acceptable product has previously been delivered pursuant to such advertising, and the advertising itself appears to have been discontinued. The water barrier 360 can be omitted from FIG. 7 or replaced by aluminum foil or polyester film, and such foil or film can, if desired, be laminated between the foam and the paper. Aluminum foil is a vapor and/or light barrier to also help protect sensitive materials such as light- sensitive photographic films. An aluminum foil .0008 inch (20.32 microns) thick and even .00035 inch (8.89 microns) thick is very effective for this purpose. The aluminum foil can also enhance the protective effect by pro¬ viding an electrostatic barrier that shields against external static electricity. For example, a paper backing of 30-pound Kraft when laminated with 0.0008 inch (20.32 microns) thick aluminum foil and 1/15 inch (1.59 millimeters) thick micro-cellular closed-cell foam, and tested in accordance with U.S. Federal Standard 101-B, Method 3030, Procedure B, showed an MVTR (Moisture Vapor Transmission Rate) of nil. With this value, the product fully complies with the moisture vapor transmission requirements of U.S. Military Specification MIL-B-131-F. Its puncture resistance is also greater than a corresponding packaging sheet that did not include the foil layer. The packaging sheets of this invention have excellent versatility and performance, particularly for the special problems of packaging material sensitive to corrosivity, static electricity, light, abrasion, etc. The micro-cellular polyolefins in such laminates comply with F.D.A. regulations which permit them to be safely used as an article or a component of an article in contact with food. They are unaffected by exposure to grease, water and most acids, bases and solvents. They stay flexible within a wide -22- temperature range, have neutral pH, are non-toxic, non-corrosive, lint-free, have excellent abrasion resistance and will not support the growth of mildew or fungus. They also have an excellent clean whitish appearance which is highly desirable for the packaging of many materials. Some foamr-supporting sheets such as spun-bonded polypropylene sheets can be adversely affected by molten adhesives, and polyester cements or epoxy cement or the oil-resistant cements of U.S. Patent No. 4,321,297 can be used for securing the foam to such sheets. Where a layer of volatile corrosion inhibitors is applied to a laminate of the present invention, it can be applied* as a surface coating by itself or mixed with the natural rubber latex of a cohesive-nonadhesive formulation and/or with anti-stat. Ordinary kraft paper when used in weights as high as 90-pound or even higher per ream, is not perfectly opaque. For use in packaging light- sensitive material such as unexposed micro-fiche film, a single opaque paper ply laminated to the micro-cellular closed-cell foam can be used, as for example, when the paper is a 22.5 kilogram sheet beater-dyed with Basic Violet No. 3 or Pigment Black No. 7, to a dye content of about 1/2% by weight. When two paper plies are present in the laminated assembly, either - one or both can be dyed and when both are dyed, their dye content can be lower and as little as 1/4% by weight. However, thinner sheets should con¬ tain proportionately more dye. Carbon black can also be incorporated in the papers instead of or together with one or more dyes. Aluminum foil that is extremely thin, e.g. 0.3 to 0.8 mil (7.62 to 20.32 microns), is also opaque and can be laminated in an assembly of Kraft paper and foam, but such thin foil usually contains "pin-holes that admit light even when they are filled with adhesive. It is, accordingly, best not to rely on such thin foils for the most light-sensitive of articles. Carbon black can likewise be incorporated in the foam, as by foaming carbon- loaded resin and will impart anti-static properties in addition to opaque¬ ness, particularly if the carbon black is acetylene black. For wrapping light-sensitive material, the opaque wrapping sheet can carry the cohesive-nonadhesive coating, but does not need the VCI unless the light-sensitive material is packaged with corrodible metal. The cohes¬ ive-non-adhesive coating, or the foam surface under it, can also contain the anti-static agent. The wrapping sheets having the cohesive-nonadhesive coating can be used for any wrapping or interleaving application. The cohesive- nonadhesive layer makes such use particularly desirable inasmuch as such sheets are readily secured to each other without the need for supplementary closure materials such as tape, staples or other fasteners, glue, heat- sealing or twine. Examples of such use are given in U.S. Patent No. 4,321,297. While paper sheets are quite suitable for the foam-supporting plies such as 354, 354, these plies can, as noted, be made of interwoven or knitted textile fibers, or of air-felted textile fibers, or even of plastic film. A strong plastic such as polyethylene, terephthalate or poly¬ propylene is preferred for such film or for the fibers. Instead of the usual types of plastic fibers, narrow widths of plastic film can be inter¬ woven to make one or both of the plies. When a ply is made of strong material such as the polyethylene terephthalate, it makes a very effective reinforcement for a paper ply whether such reinforcement be an outer layer of the packaging sheet or a layer between the foam layer and the adjacent ply. Having a relatively smooth surface onone face of the packaging sheet is desirable because such a surface can be printed with advertising or the like. The use of even two paper plies without any reinforcement is not as desirable as having one ply of paper together with a high-strength reinforce¬ ment. Glass fibers or nylon or qiana fibers are very effective and glass is particularlydesirable by reason of its low cost and its minimal elongation properties. An un-reinforced paper-foam packing sheet is only suitable for very light duty packaging use, whereas a well-reinforced packing sheet is very difficult to tear. This is of major importance when packaging items which are likely to puncture or tear the packaging material, and in the event of a puncture, the sheet will generally not tear beyond the nearest re¬ inforcing fiber. It will be noted that as defined herein, the cohesive-nonadhesive layers have essentially no tack and cannot be considered pressure-sensitive adhesive cements,all of which have substantial tack. The thickness of the adhesive layer is distorted in some of the figures and shown much greater than actual thickness. - Such actual thickness -24- is generally about 1 to 2 mils (25.4 to 12.7 microns), and when the adhesive is applied to paper and/or foam, it tends to sink into the pores of the paper and the irregularities in the surface of the foam so that its measured thickness can be less. The paper and liner board designations such as "50-pound Kraft", are standard United States designations that give the weight per ream, that is the weight of 500 sheets each measuring 24 by 36 inches (61 by 91.5 centimeters). Where the materials to be packaged are magnetic recordings that can be damaged by magnetic fields, the packaging laminates can have a layer of iron foil preferably 3 mils (76.2 microns) thick or similar material of high magnetic permeability, preferably with such layer on both sides of the packaged material and also preferably with both such layers in physical contact with each other. An iron layer will also provide shielding against static electricity and other electrical fields, just as an aluminum layer does. Some metal foils are supplied with one or both surfaces carrying an extremely thin coating of a protective oil, in which case such coating should be removed before the foil is laminated to another substrate. Even such thin coatings of oil will reduce the bonding strength to the adjacent lamina. Where a surface-active anti-stat is used, care should also be taken to keep such anti-stat from working its way to the foam surface that is bonded to its support layer. Upon heat-sealing, the action of the heat combined with the presence of a surface-active agent significantly detracts from the heat-seal bonding. This is particularly serious when the foam is originally bonded to an oil-coated metal foil, and in such an arrangement the heat-sealing can actualy cause the foil to delaminate. It is accordingly advisable where a surface-active coating is used, to apply such coating to the face of a closed-cell foam layer after that layer has been bonded to its backing. Also, where such coating is applied to a long length of backed foam to be used in a melt-type heat- sealing as in FIG. 1, the coating can be kept away from the side edges where the melting takes place. Obviously, many modifications and variations of the present invention are possible in the light of the above teachings. It is, there¬ fore, to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

Claims: WHAT IS CLAIMED: _ 2 5- 1. In the process of heat-sealing a spaced succession of articles between a pair of long laminated heat-sealable paper-foam wrapper sheets supplied in spaced-apart relation for the insertion of the articles between them, then longitudinally heat-sealing the sheets together at their edges and also heat-sealing transversely across the sheet sandwich at the spaces between the successive inserted articles, the transverse heat-sealing being effected by essentially stopping the movement of the supplied sheets, the improvement according to which the longitudinal heat-sealing is effected with the help of a heating step that is controlled to keep the temperature of the stepwise moving foam in the laminate sufficiently high to melt the foam but sufficiently low that the melted foam does not bleed through the paper to which it is laminated. 2. The combination of claim 1 in which the foam at the edges of one sheet is pre-heated to melt it before the longitudinal heat-sealing. 3. The combination of claim 2 in which the pre-heating is essen¬ tially interrupted when the movement of the supplied sheets is interrupted. 4. A package of an electronic device sensitive to"damage by static electricity and by physical shock, the device being encircled by a foam- paper wrapping laminate containing a metal electrical shield layer under the paper, the foam of the laminate facing the device and the paper of the lamin¬ ate having perforations large enough to enable a metal clamp to be clamped to the outside of the package and electrically engage the metal electrical shield layer. 5. The process of heat-sealing to a desired surface a backed sheet of thermoplastic resin foam, which process is characterized by applying to the face of the foam at the proposed sealing location on the sheet a melt¬ ing shoe held at a temperature high enough to melt the foam, then pressing that sealing location against the desired surface to bring the melted foam in contact with that surface, and maintaining the pressing while causing the melted foam to cool and solidify. 6. The process of claim 5 in which the thermoplastic resin is polypropylene. 7. The process of claim 5 in which the desired surface is a portion of another backed sheet of foam. 8. The combination of claim 5 in which the backing of the foam sheet is sufficiently impervious to prevent bleed-through" of the melted foam. 9. In the process of packaging a succession of articles by placing them on an advancing sheet of backed thermoplastic resin foam and then heat- sealing another such sheet against the first sheet to hold the articles in place, the improvement according to which the edges of the first sheet have their resin foam melted before they are engaged by the second sheet, the edges of the second sheet are pressed against the melted foam edges of the first sheet and those matted edges cooled to solidify the melted foam during the pressing. 10. The combination of claim 9 in which the sealed-together sheets are subject to transverse heat-sealings between the successive articles packaged, and the resulting packaging transversely severed along the trans¬ verse heat seals to provide successive severed lengths each containing a successive article. 11. The combination of claim 10 in which each of the transverse heat-sealings is affected in two steps, the first step being the pressing together of the sheets along a transverse line between pressing members at least one of which is hot enough to melt some of the foam, and the second step is the pressing together of the sheets along essentially the same transverse line between pressing members that help cool and solidify the melted foam. 12. In the packaging of a succession of articles by placing them on an advancing packaging sheet and then covering the placed articles by a second packaging sheet which is then sealed adjacent its edges to the ad¬ vancing sheet, the improvement according to which the articles have a sub¬ stantial height and the covered article-carrying sheet is advanced at a pre-determined level between upper and lower resilient members that urge the carried articles toward that level from above and below to make the packaging essentially symmetrical with respect to that level. 13. The combination of claim 8 in which the backing of the foam includes a layer of aluminum impervious to bleed-through.

Inventors: ADELMAN HERBERT B, D ANGELO JAMES J, ADELMAN, HERBERT, B., D'ANGELO, JAMES, J.
Applicants: CROWELL CORP, THE CROWELL CORPORATION
Application year: 1985
Main classification: B65B9
IPC codes: B29C65, B65B51