CA1186204A

CA1186204A - Cushioning dunnage apparatus and method

Info

Publication number: CA1186204A
Application number: CA000412942A
Authority: CA
Inventors: Gary W. Ottaviano
Original assignee: Ranpak Corp
Current assignee: Ranpak Corp
Priority date: 1981-11-02
Filing date: 1982-10-06
Publication date: 1985-04-30
Also published as: US4412879A

Abstract

CUSHIONING DUNNAGE APPARATUS AND METHOD
ABSTRACT OF THE DISCLOSURE
A method and apparatus for the production of thermoplastic film air cell cushioning product. The method and apparatus utilize as stock material flexible thermo-plastic film formed of a composite of a stratum of relative-ly high density, high melting point thermoplastic and another stratum of relatively low density, low melting point thermo-plastic bonded to the first mentioned stratum. A sheet of the composite thermoplastic film material is heated well above the melting point of the low melting point stratum but below the melting point of the high density stratum and is applied to a rotating forming drum and vacuum formed, to produce the air cells in the product, and then a sheet of the film material which has been heated, is generally immediately laminated to the heated sheet on the drum, with the temperature of the second mentioned sheet being at its application to the embossed sheet, below the melting point temperature of the low density stratum and at a maximum temperature approximating the mean temperature between the heat softening point and the Vicat softening point of the low density stratum, with the second mentioned sheet being applied with associated pressure to the heated embossed first sheet on the rotating forming drum. The apparatus is relatively compact and the method and apparatus are energy efficient.

Description

CUSHIONING Dl~. ~ ETHOD

SPECIFICATION
_ Thi~s in~ention rel~tes to a novel method and ap~ara~us for the produetion of air cell cushioning material formed of flexible thermoplasti~ sheet or film, and more particularly relate3 to an ~pparatus an~ associated method which is parti~-cularly energy efficient and which is ~ generally compact ~
nature, including an ~pparat~1~ h~ving the capability of provid-ing for the interruption of the production operation ~nd without ~ffectinc~ the work~bility o~ the apparatus and/or method when production oE the ~ir c~11 prodl~ct i~ rein.itiated after terminat~on of the interruptlon, and ~hich re~ults in a quality air cel~ ther-moplasti~ film prod~ct of high strength, poRse~sing the ability to retain it~ originally formed thicknes~ over a relatively lony period of time and under load.
BACXGROUND OF T~E INVENTION
It i~ well known in th~ prior art to produce air c~ll cushioning product on a rotating forming drum utili~ing flex~bl~
thermopl~stic sh~ek material by embossing one of the ~h~ek~ oh the drum and then ~pplying a laminating or cover sheat th~r~to for se~lln~ formation of the air cell~, with such air cell product being u~ilized for in~tance in eushioning appl~c~tion~, See for instance U.S. Pat~nt~ 3,142,5g9 3,285;793 and 3,4~6,g84.
Such prior art methods and apparatu~ uaually compri~e he~tlng' not only the film to be embo~sed to a high temperature either ~ubst~nt~lly at or above the fu~ion t~mperatur~ of th~ film' materi~1, but ~190 h~ating the laminating ~ilm to a ~emperature at abou~ the fu~ion temperature praor to appli~a~ion o~ the laminating ~heet to the heated embo~sed ~heet. ~7 Such prior art arrangements are not only relatively energy inefficien~, resulting in increa~ed production costs, b~t also involve more expenSlve arrangementY for the apparatus and the controls therefor, resultin~ in greater relative overall costs.
In appl.icant~ 5 Canadian Patent Number 1,157,623 issued November 29, 1983 and entitled "Cushioning Dunnage Produc~, ~pparatus and Methsd" there i9 di~closed a method and an apparatus for producing air cell cushioning dun-nage which include~ a cooling step for cooling the product on the rotating forming drum to a particular temperature prior to application of the laminating sheet to the embo~sed sheet on the drum, and which re~ults in an air cell product having some of the same general characteristics as those of the product with the present apparatus and method. In certain other re-spects however, the produced products are different.
Moreovex, there are considerable other prior art patents in the air cell cushioning dunnage field, such as for in~tance U.S. patents 3,018,015: 3,231,4~4; 3,349,990; 3,577,305;
3,586,565; 3, 3as, 53~ 7 3,523,055; 3,575,781; 3,616,155: 3,785,89 3,817,803; 3,~37,~90; 3,837,991, 3,868,056; 4,076,872: 4,096,30 and 2,771,388, and the Au~tralian Patent 160,551. The above are mexely representative, and it i9 not meant to imply that such a list is all inclusive.
These prior art mathods and apparatus are not gen-erally of the type which can be readily and conveniently inter~
rupted in operation and then restarted, without having consider-abl~ undesirable e~fects upon the re~ultant product, or on the film ~tock material utilized to produce the product, and/or on the mechanism or apparatus per ~e. Moreover, such prior art mechanism if they do possess the ability to be interrupted in ~ ,5 ,~, ~,, ~P~

operation, are generally of a rather complex, non-compact nature, and which generally utiliæe considerable energy in the formation of their respective thermoplastic air cell products~
5U~MAR~' OF THE INVENTION
The present inven~ion pro~ides a novel method and a relatively compact apparatus for the production of flex-ible thermoplastic ilm, air cell material which has rela-tively high strength and high resistance to loss of air from the cells, and a method and apparatus which are ener~y effîcient and provide for expeditious pxoduction of the air cell product, and wherein the compact apparatus can be conveniently interrupted in its production operation of the air cell product wi~hout materi~l harmful effects on the thermoplastic film stock utilized in the apparatus, and/or on the method utilized in the production of the air cell product.
Accordingly, an object of the invention is to provide a no~el method for the production o-E flexible thermoplastic film air cell product for use, ~or instance, in protective packaging applications.
Anokher object of the invention is to provide a novel energy efficient apparatus for the production of flexible thermoplastic film air cell material and one wherein the apparatus is of a relatively compact nature and can be seleckively interrupted in its production process without harmful effects on the film stock material utilized to produce the product, or on the associated app~ratus, or on the r~sultant air cell product.

s~ J~
A still further object of the invention is to pxovide a novel method of producing .flexible thermoplastic fllm air cell cushioning material, and which is energy efficient, and wil~ provid~ an air cell product in which the films of thermoplastic forming the product, are efficiently heat bonded together.
A still further object of the invention is to provide a novel apparatus of compact nature for the production of flexible thermoplastic film air cell cushioning material and one which is energy efficient in utilizing lower -temperatures as compared to those previous-ly thought possible for the film material, while still effectively providing for the heat bonding of the films together.
Other objects and advantages of the invention will be apparent: from the ~ollowing description taken in conjunction with the accompanying dxawings wherein:
BRIEF DESCRIPTION OF THE DRAWIMGS
FIGURE 1 is a top plan, fragmentary view of a section of a strip or sheet of the air cell ~ushioniny material product produced by the pres~nt method and apparatus, FI~U~E 2 is a sectional view taken generally along the plane of 2-2 of FIGURE 1, looking in the direction of the arrows f FIGUR~ 3 is an enlarged, vertical sectional view of ona of ~he air cells of the produced product showirlg the stratums of defining layers of the thermo-plastic film or sheet utiliæed to pxoduce the product;

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FIGURE 4 is a further enlarged, vertical sectional view taken through one of the flexible thermo-plastic film sheets utilized in ~he production of the product, illustrating the layers or stratums o~ plastic materials utili~ed in the film of thermoplastic stock material:
FIGURE 5 is a diagrammatic, end elevational view showing a strip of the sheeting product produced on the apparatus and/or utilizing the method o~ the invention, and as rol~ed into generally cylindrical form ~or ready use, or txansportation and/or storage;
FIGURE 6 is a side elevational generally diagrammatic view of an apparatus utiliæable in perform-iny the method of the invention:
FIGURE 7 is a fragmentary illustration of another embodiment of apparatus, including a forming drum, ~or producing flexible thermoplastic film air cell cushioning material.
DESCRIPTION OF PREFERÆ D EMBODIMENTS
Reerring now again to FIGURES 1-4, there is illustrated an air cell cushioning product 10 producible from the method and apparatus o~ the pre~ent invention.
The product is formed of two sheets o~ films 12 and 14 (FIGUR~S 2 and 3~ of flexible thermoplastic makerial, with one of the sheets (i.e. 12) haviny been heat~embossed to define relatively closely spaced cells 16, which are adapted to contain air entrapped therein by the laminating or cover sheet 14. Sheets 12 and 14 are heat sealed to one another at spaced areas 17 (FIGURE ~. Each of the ~; ~5-,:

air cells may be of the general dome shaped config-uration shown, and in view of being filled with air, provide the cushioning effect when the product i~
utilized for i~stance in packaging an item, 30 as to cushion the item from vibration and/or shock damage. It will ba understood, however, that various height~ and diameters and geometric shapes of cel~s may be provided with the cells beiny pre~erably either generally dome shaped as shown or they may be more ~7at on the top, or more rounded on the top than is illustrated in the example of the air cell product~ The con~iguration o~
the recesses in the ~orming drum of the apparatus on which the product is produced wil~ determine, in general, the exterior configuration of the cellsO
Referring now to FIGURE 3 and 4, each of the sheets 12 and 14 used in the formation o~ the air cell product may be and preferably is formed of an inner stratum 22 of flexible nylon and outer stratums 24 of polyethylene. The sheet of thermoplastic film is preferably made by the known cast coextrusion method, with the intermediate nylon stxatum being of a relatively high density relatively high melting point (e.g. 490F) material ~ubstantially impervious to the passage of gases therethrough, while the polyethylene stratums are formed of relatively low density poly-ethylene plastic, having a relatively low melting point (e.g. 230F). The nylon content can be 10%, 20% or 30%
o the overall thicknes~ of the film structure, and the exterior polyethylene layers 24 ganerally equally provide the balance of the thickness of the sheet film material. The cverall thic1cness of the sheet may vary say for instance ~rom 1 or 1.5 mils, to appro~imately 8 mils, but it i~ preferabla that for use as a cushioning dunnage product, the embossed or domed sheet 12 be between approximately 2 to 8 mils in overall thickness, while thP laminating or cover shee~ 14 be approximately 1 or 1.5, to 4 mils in thickness, and preferably being of a lesser thickness as compared to the overall thickness of the embossed sheet 12, but at least being of no ~reater thickness.
The stock sheet of film preferably utilized, has an impact stren~th of from approximately 300 to 310 grams, and a tensile strength in pounds per square inch of from 3400 to approximately 6200, which depends in general on the percentage of nylon in the sheet.
sheet with a higher percentage of nylon, such as for ins~ance 30/O nylon, has the greatex tensile strength.
The exterior polyethylene stratums of the sheet will commence to becorne somewhat "soft" at approximately 160F (known as the softening poi~t) and represents the temperature at which the low melting point low density stratum com~ences to change from a rystalline structure to an amorphous structure. Such low density stratum also has a Vicat softening point of approximately 206~-210~F
which is the temperature at which the stratum becomes too soft to withstand stresses and keep its shape, and more particularly is the temperature at which a flat ended needle of one sq. mm cross section under a load of one kg. will penetrate one mm into the stratum. As aforementioned, stratum ~4 will melt at approximately 230~F.
In ~he sheet stock material illustrated, the nylon layer 22 i~ bonded ts the exterior heat sealable layers 24 by a binder coating 26, the thickness of each of which in the em~odiment shown represen~s about 5% of the overall thickness of the sheet stock. Moreover, each o~ the exterior polyethylene layers 24 preferably comprises an irmer section 24a of a combined low density virgin anc1 recycled polyethylene and a relatively thin (e.g. 5% o the overall sheet thickness) outer section 24b of low density virgin polyethylene bonded together. The thickness of the intermediate stratum 22 is less than one third the overall thickness of the plastic sheet, and prefexably is less than one third the thic]cness of eac]h of the exterior stratums 24.
This multi~layer composite plastic sheet utilized in the production o~ the cushioning dunnage product is available in commercial form from the Crown Zellerbach Corporatiorl of Texas, and two preferahle types are identified by it as "Crown Zellon 305" composite film and "Crown Zellon 355" composite film.
FIGURE 5 illustrates a roll of the embossed cushioning dunnage product as produced on the machine of FIGURE 6, and di~posed or rotated into roll form about a hollow core 27. The cushioning product utilizing the aforedescribed stock film provided gas barrier character-istics rated at no gxeater than approximately 10 to 1~ c.c.

L ~ ` f~
per lO0 square inches per 24 hours at one atmosphere at FIGU~E 6 illustrates diagrammatically, an apparatus for producing the cuqhioning pxoduct of FIGURES
1-3 and 5. In the embodiment illustrated, th~ apparatu~
cornprises a frame 30 on which may be rotatably mounted a supply roll 32 of the polyethylene-nylon-polyethylene flexible plastic sheet or film material F, for rotation about a generally horizontal axis 34. The stock sheet material F is pulled off roll 32 and passes abouk a preferably stationary, generally horizontally oriented shaft 36 which is preferably coated with a layer of some frlction reducing anti-adhe~ion material, such as for instance polytetra~lourethylene, otherwise known as "Te~lon " .
The sheet passes beneath shaft 36 and then pa~ses over a roller 38 which is preferably driven at a peripheral ~cpeed slightly less (e.g. 49.5 feet per minute) than the film F speed (e.g. 51 feet per minute) and about its axis 38a on i.rame 30. Roller 38 should be maintained rotatable and moveable with the film F at a sur~ace ~peed at lea~t not to exceed the speed o~ travel of the film~
Roller 38 is preferably coated with a friction reducing anti-adhesion coating and i9 able to be heated to a temperature of between approximately 130 to 190~F by any suitable means, such as for instance, by thermostatic controlled electric heatlng means of known type, embodied therein. Passage o~ the plastic she~t F around the heated roller 38 causes it to be pre-heated to a temperature approaching that within the heat ran~e of the heated roller of approximately 130 to 190F.

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The web of sheet material F then passes down around roller 40 (which is preferably driven so as to have a surface speed the same as roller 38) and which again i~ heated preferably to a temperature range of between approximately 130-190F. Roller 40 should be maintained rotatable and moveable with the film F at a surface speed the same as that of roller 38, and at least not to exceed the speed of travel of the film.
Heated roller 38, 40 also enhance drying of any applied anti-static material which may be applied by spray head 42 in the conventional manner. Roller 40, is, as illustrated, pre:Eerably of a larger diameter as compared to roller 3~ and is rotatable about axis 40a on framework 30, in a generally similar manner as roller 38. Rol.ler 40 is preferably surface coated with friction reducing anti~adhesion material in a similar manner as roller 38.
From roller 40, the web of plastic sheet moves about preferably non~heated idler roller 44 which again is prefexably surf2lce coated with a layer of anti-sticking material, such as the aforementioned "Teflon". The sheet F may be traveling at a rate of approximately 51 feet per minute as aforementioned.
From idler roller 44, the sheet passes about relatively closely spaced rollers 46, 48, 50, 52, and 54, all of which are heated, and all of which preferably have an exterior surface coating thereon of ~ri~tion reducing anti-adhesion material, such as the aforementioned "Teflon". Roller 46 is preferably at a surface temperature of between approximately 205-300~'. Rollers 48 and 50 are each preferably at a temperature of between approxi-mately 280-330F. Rollers 52 and 54 are each preferably at surface temperature of approximately 330F.
All o~ the rollers 46, 48, 5~, 5~ and 54 are power driven, are of approximately the same size, and are driven at the same speed, and in the embodiment illustxated at a speed to impart a speed of approximately 51 feetr~per mi.nute to the strip or web of film F. As the web of plastio ~heet or film material passes about these rollers, the temperature o~ ~he thermoplastic sheet i9 raised to a temperature o~ approximately 330F, and the polyethylene stratums 24 thereof are melted and turned into substantially liquid form as carr.ied by the nylon intermediate stratum 22 of the sheet.
From roller 54, the heated sheet material is generally immediately applied to the rotatably driven embossing drum 5ÇJ various types of which are known in the art. Embossment o the plastic film ox ~heet on the embossing drum 56 is preferably accomplished by a vacuum means (e.g. producing a vacuum of 3-7 inches of mercury) communicating with each individual depression 58, located on the surface of ths eMbvssing drum~ The depressions 58 are conventionally connected by passages connecting with a vacuum mani~old in the embos~ing drum 56 and coupled to a controlled source of vacuum~ I'he forming drum may be conveniently made of aluminum~ with the surface thereof being preferably coated with a layer o ~dhesion preventing material~ such as the afo.rementioned "~eflonl', so that preheated plastic sheet will not adversely adhere to the ~11-surface of the forming drum 56 during the embossing operation. Although FIGU~E 6 of the drawings shows diagrammatically a gen~rally dome shaped defining surface of the depressions 58, as well as a generally dome shaped exterior surface on the fini~hed air cell cushioning product (as shown in FIGURE 2), i~ will be understood that the size, configuration and distribution of the emboss-ments may be modified as desired so as to provide for diferent purpose~ and/or requirements. However, the generally dome shaped configuratioh illus~rated is preferred for the embos~ed air cell.
The drum is preferably maintained at a rnaximum surface temperature of between approximately 125-130F.
Any suitable mQans can be u~ilized to maintain the temperature of the drum 56~ with an internal electrical heater and fan being one suitable means. The drum 56-cools the formed air cell product thereon, as will be hereinater described.
It will be seen from FIGURE 6 that in the embodiment illustrated, the preheated plastic sheet of film F is preferably applied to the rotating forming drum 56 generally adjacent the latter's lowermost position, and is embossed as the drum rotates. At approximat~ly the same point on the drum as the initial point of application 59 of the first sheet F, to the embossing drum 56 but sub-sequent to the embossment of the sheet F, a laminating or cover sheet L is applied. Accordingly, sin~e the e~b~ssing drum is preferahly at a maxlmum tempera-ture of between appro~imately 125-130F, and the embossed sheet FE is at a much higher temperature (e.g~ 330F) cooling o the embossed sheet FE and the heat bonded laminating sheet L
on the drum occurs as the drum rotates from po~ition point 59 where the sheet F (and then the sheet L) are first applied thereto, to the position 60 where the formed air cell produc~ is stripped from the forming drum. Accord-ingly, the embossed sheet FE o~ the produced air cell product at point 60 preferably is at a maximum tempexature o~ approximately 125~130F, the drum having cooled the formed pla~tic air cell product down to this temperature which is well below the melting temperature of t.he polyethylene exterior layers 24, as well as to a temper~-ture well below the a~orementioned heat softening point (e.g. appxoximately 160F) of the exterior layers or ~tratums of the film.
The supply of laminating sheet L i9 preferably mounted on a rol:L 64 rotatably mounted about an axis 66 on upper frame 67 of the apparatus. Sheet L may be a multi-strakum structure similarly to that aforedeqcribed for embossiny sheet F, and generally similar to that shown in FIGU~E 4 of the application drawings. However, it will be understood that the thicknes~ of laminating sheet ~ is preferably thinner than the thickness of embossing sheet F.
In t:his connaction, i~ ~he embossing sheet F is 2 mils in thickness, the laminating sheet L will be preferably 1 or 1.5 mil thickness.
From roll 64, the laminatlng sheet is pulled off to pa~s around preferably non-rotatable, rod 68 and then downwardly .into interior o~ machine frame 30, to pass onto heat~d pre~erably driven rotatable roller 70 which is pre-ferably heated to a surface temperature within a range of approximately 130 ~o 190F. Roller 70 should be maintained ak a minimum temperature of 130F and i5 moveable with film L, and at a surface speed at least not to exceed the speed of traval of the film L, and prefe.rably at a peripheral speed slightly less than the film L speed (e.g. 49.5 feet per minute), to aid in prevention o~ wrinkling in film L.
From roller 70, the laminating sheet L which is preferably traveling at a speed of between approximately 4g.5 to 52 feet per minute passes around increased diameter roller 72 which is pre~erably heated to a temperature within a range of approximately 160-190F, with roller 72 likewise being pre.~erably driven at a peripheral speed slightly less than the speed of the film L ~e.g. 49.5 ft/min). Roller 72 is maintained a~ least at a minimum ~urface temperature o~ approximately 160F~
The larninating sheet L then pass~s a~out and engages non-heate~d, pxeferably idler rollers 74 and 76, which provide a drying path in the event that anti-sta~ic material has been applied to web ~, as for inqtance by means of spray head 69. Rollers 70, 72, 74 and 76 as well as aforementioned rod 68 are preferably coated with a layer o~
anti-sticking material, such as Teflon, in a similar arrangement and for the same puxpose as the other coated rollers.
From idler roller 76, the laminating sheat passes abouk a heaked non-power dxiven, pressure roller 78 which is at a surface te~lperature within a range of approximately 180-195F, thus irlsurlng that the roll~r 78 not cause or permit any r~pid mi.gration of heat thru or ~rom the laminating film L ill the direction of the rol.ler 78, Thus the temperature of the laminating ~ilm L as the latter passes about a substantial extent o the circumference of roller 78, is at least maintained, and the heat in the embossed ilm F~ migrating to the confronting stratum of the laminating film L is generally concentrated or slowed in its migratiQn movement, at the enga~ed boundry between the two films FE and L, and does not rap:idly escape or mo~e toward or in the direction o:~ the pressure roller 78.
Roller 78 is driven by its engagement with the rotatable driven forming drum 56, and is able to be heated by any suitable means, such as by an internal electrical heating element, to a maximum surPace temperature of approximately 195F, and preferably is maintain~d at a surace tempera-ture of approxirnately 185F. It will be understood there-fore that the web or sheet L at its application to the embossed sheet ]?E on the ~orming drum, will be ataa tempera-20 ture within the range of approximately 180-195F, and preferably i9 at a temperature of approximately 185F for optimum result in ~he production of the air cell cushioning product, together with resultan~ energy conservation. The temperature of the laminating sheet L at its application to the embossed film is thus well below the meltins temperature of the polyethylene exterior layers 24 of the laminating sheet L, and at a temperature approximating the mean temperature between the heat sotening point and the Vicat soEtening point o~ the exterior s~ratum 24.

Rotatable r~ller 78 is uryed toward forming drum 56, and thus the laminating sheet L is applied under pressure to the confronting surface of the hot (e.g. 330F) polyethylene layer on the embossed sheet on the drum, and due to the migration of heat from the embossed film to the cooler laminating film results in an incxease of the temperature of the surface of ~he confronting polyethylene layer 24 on the laminating film and a sufficient softening thereof, and together with the pressure applied by roller 78, providing for a secure bond between the laminating and embossed films or sheets L and ~E, to seal khe air cells, as illustrated in F~GURES 2 and 3.
It will thus be understood that the hot embossed sheet FE raises the overlaid coolex laminating sheet L
from a temperature within a range o~ approximately 180 to 195F, and prefe:rably from a temperature of appro~imately 185F, to a temp~erature which causes su~fici.ent sotening of the surface of layer 24 of sheet ~ con~ronting the hot embossed sheet FE, that togethex with pressure as applied by roller 78, causes a bonding tsgether of externally facing melted layer 24 of the embossed sheet FE and the adjacent confronting heat softening layer 24 of the laminating sheet. It is believed that the underlying non-virgin polyethylene layer 24a of the laminating sheet does not melt, with substantially only the exterior surface of layer 24b o~ the laminating sheet being melted, and due to heat transfer thereto from the hot (e.g. 330F) embossed sheet FE.
The heat and pressure bonded cushioning dunnage product is then moved and cooled by the rotating forming drum from th~ poin~ of pressurized engagement of the laminating shaet with the Gmboss~d sheet to point 60 where the anti~stick coated non-driven roller ~0 which preferably is at a temperature within the range of approximately 35-65F
strips off the form~d air cell pr~duct from ~he forming drum 56~ Since the forming drum 56 is at a maximum temperature of approximately 125-130F the bond between the sheet L and F~ is fully set by time the air cell ~ushioning product is stripped from the forming drum.
The produced air cell product may then be directed about incr~ased diameter preferably driven roller 82 preferably driven roller 84 and pref~rably non~dri~en roller 86 all of which may be cooled to a temperature range of for instance 35 to 65F to further cool the produced air cell product. From rol1er 86 the continuous strip of air cell product can be cdirected to an accumulator ~not shown) where the product can be readily disposed in roller form as shown for instance in FIGU~E 5. Rollers 82 and 84 and the accumulator ar~ driven at the same surface speed as drum 56. Rollers 80 86 axe preferably coated with Teflon or the like. A cutter unit of any ~uitable type may be provided for severing an accumulated roll of air cell product from the producing apparatus.
The driven peripheral speed o~ the forming drum 56 is preferably slightly greater than the peripheral speed of the driven rollar 46-54 controlling the speed of web of sheet material F~ Thus drum 56 preferably has a peripheral speed of for instance approximately 53 feet per minute a~ compared to the speed of approximately 51 feet per minute for rollers 46-54 and the speed of approximately 49.5 ~eet per minute for rollers 70 and 72~ Such a differential in speeds helps to prevent wrinkles on the ~ormed produ~t and aids in controlliny the pos.ition o the webs or sheets on the for~iny drum.
From roller 54, the laminating sheet is directed toward the periphery of the embossing or forming drum 56 where the aforedescribed pressure engagement of the laminating sheet L with the exterior or confronting surface of the embossed sheet FE :is accomplished at line location 88 by means of the aforementioned rotakable pressure roller 78. Roller 78 (which may be reerred to as a nip roller) preferably includes a resilient layer of, for instance, siliccne rubber, which in turn is "Teflon" coated, and with the roller being urged toward engagement with the forming dx~m 56, as by means of a pair of spaced, single acting air cylinders 90, one being disposed adjacent each end of the axle 92 of the nip roller 78, and coacting therewith 30 as to direct the nip roller toward pressurized, generally lineal engagement with the form.ing drum upon actua~ion of motor units 90.
Motor units gO are preferably pivoted as at 90a to a support portion of the apparatus frame thus providing for limited pivotal movement of the motor units 90 with respect to the supporting frame. Motox units 90 prefexably provide a total pressure to the laminating film o approxi~
matel~ 6 pounds force per lineal inch of transverse contact of roller ~8 against the laminating sheet on the forming ,1 ~ b drum. Roller 78 is approximately the same length as drum 56, and in ~he mbodiment illustra~ed i5 about 2 feet long. ~ccordingly, it will be seen that motor units 90 exert a total force of approximat~ly 144 pounds (6 pounds/
in. X 24 inches~. This pressure in conjunction with the aforementioned heat migrating from the embossed sheet or film, produce~ a positive and optimum heat seal between the laminating sheet and the embossed sheet. The generally line contact between pressure roller 78 and the laminating film is preferably disposed in a plane passing throu~h the axis of rotation of the forming drum.
~ ile the aforementioned approximately 6 pounds per lineal inch pressure is preferred for the applied pressure ko the laminating film by roller 78, a pressure within the range of approximately 3 pounds to approximately 8 to 9 pounds per lineal inch will produce useful air cell cushioning dunnage product. A pre~sure of below approxi-mately three pounds per lineal inch, in conjunction with the temperatures specified, would not provide satisfactory air cell cushioning material or most packaging cu~hioning applications. A pressure more than the specified maximum of 8 to 9 pounds per lineal inch would or might cau~e damage to roller 78.
The cushioning dunnage product produced fxom the apparatus and method aforedescribed meets the Federal Specifications entitled Cushioning Material, Flexible Cellular, Plastic Film For Packaging Application.s, of the Federal General Services Administration, and identified ~ PPP-C-795A dated December 2, 1970.

Referring now to FIGURE 7, there is illustra~ed a modified arrangement of the FIGURE 6 apparatus~ In this arxangement, a further pressuxe nip roller 95 is prov.ided, downstream from nip roller 78. Such Eurther nip rollex 95 a~ illustrated, may be reciprocably movable to and from pressuri.zed contact with drum 56, and a~ by means o~ double acting pivotal air unit~ 90 ' disposed at opposite ends of its axle. Roller 9S i9 preferably heated to a temperature o~ about 185GF, but may be heated to a maximum t~mperature of the same extent as roller 78, but such auxiliar~ roller may have a low~r minimum temperatur~
at the other end of its range (e.g. 150F) and may be urged against the laminating film L with the same general pressure as aforedescribed for roller 78 (i.e. six pounds per lineal inch of contact with the drum). Use of such a further nip roller 95 may provide a somewhat stronger pressure bond beltween the embos~ed sheet FE and the laminating ~heet L on the forming drum due to the extended time applicatlon of prsssure via the auxiliary roller 95.
In other respect~, the FIGURE 7 embodiment of app~ us may be generally si~ilar to that of FIGU~ 6.
From the foregoing description and accompanying drawings it will be seen that the invention provides an en~rgy e~ficient method, and a compact, energy efficient apparatus for the production o air cell cushioning product from multi-stratum thermoplastic sheet or film, and wherein ~he reslllkant product has su~stantial str~ngth and the ability to gensrally retain its thickness under load, the laminating ~heet in the production o:~ the resultant product is heated to a temperature approximating the mean temperature be~we~n ~he heat softening point and the Vicat softening point of the low density, low melting point stratum of the laminating sheet, and is applied with associated pressure to the multi-stratum embossed sheet on the forming drum~ in order to obtain effective bonding of the sheets at the areas of engagement therebetween.
~ he terms and expressions which have be~n used ~re used as terms of description and not of limitakion, and there i~ no inten~ion in the use of such terms and ex~ressions of excluding any e~uivalent~ of any of the features shown or described, or portions thereof, and it is r2cognized that various modifications are possible within the ~cope of the invention claimed.

Claims

WHAT IS CLAIMED IS:

1. In an energy efficient method of manufacturing air cell cushioning material from a plurality of flexible thermoplastic films with each film comprising a composite of a stratum of high density high melting point thermoplastic material generally impervious to the passage of gas there-through and at least one other stratum bonded to the first mentioned stratum, with the second mentioned stratum being formed of a low density low melting point thermoplastic, the last mentioned thermoplastic being of a lower density, lower melting point thermoplastic as compared to that of said first mentioned stratum, comprising the steps of heat-ing a first of the composite films to a heated temperature above the melting point temperature of the second mentioned stratum but below the melting point temperature of the first mentioned stratum and to a temperature adequate for permitting thermoforming of said first film, embossing said heated first film by feeding it onto a rotating forming drum maintained at a predetermined temperature range and having a plurality of recesses therein, and forming from the first composite film the air cells in the recesses on said forming drum by vacuum, with said other stratum of said first film facing outwardly of the drum, heating a second composite film of the thermoplastic to a heated temperature below the melting point of said second mentioned stratum of said second film and to a maximum temperature approximating the mean temperature between the heat softening point and the Vicat softening point of said second mentioned stratum, applying said second film with said other stratum thereof facing said first film to said first film with associated pressure, while said first film is at about said heated temperature thereof, whereby the heat in said first film causes a softening of the confronting other stratum of the second film sufficiently in conjunction with said pressure to cause a bonding of said first and second films at the areas of engagement while on the drum so as to seal the air cells in the product, and then cooling the formed air cell product on the rotating drum to a temperature which is below said softening point of said other stratum so as to set the bond between said films.

2. A method in accordance with claim 1 wherein said first mentioned stratum is nylon, and said other stratum is low density polyethylene.

3. A method in accordance with claim 2 wherein said first film is heated to a temperature of approximately 330°F. just prior to its being applied to the forming drum, and the second film is heated to a mean temperature of approximately 185°F. just prior to its being applied to the embossed first film on the forming drum.

4. A method in accordance with claim 3 wherein the forming drum is maintained at a maximum temperature of approximately 125°-130°F. during application of said first and second films thereto in formation of said air cell pro-duct and removal of the latter from the drum.

5. A method in accordance with claim 3 wherein said pressure utilized on said second film to urge it into pressurized contact with the embossed film on the forming drum is via a roller applying a pressure of approximately 6 pounds per lineal inch of contact between the roller and said second film in a direction transversely of the latter.

6. A method in accordance with claim 1 wherein said second film is heated to a mean temperature within the range of 180°F. to 195°F. just prior to its being applied to the embossed first film on the forming drum.

7. A method in accordance with claim 1 wherein said cooling of the formed air cell product is accomplished on said rotating drum by maintaining the latter at a pre-determined temperature substantially below the heated tem-perature of said second film and to a temperature which is below said softening point temperature of said other stratum, and then removing the formed cushioning air cell product from the forming drum.

8. A method in accordance with claim 3 wherein said pressure utilized on said second film to urge it into pressurized contact with the embossed film on the forming drum is via a roller applying a pressure within the range of approximately 3 to 9 pounds per lineal inch of contact between the roller and said second film in a direction transversely of the latter.

9. A method in accordance with claim 3 wherein said first film is progressively heated to a temperature of approximately 330°F. by a plurality of relatively closely spaced heated roller means of substantially the same size engaging the first film prior to application of the latter to the forming drum, and including the step of driving all of said roller means at substantially the same speed.

10. A method in accordance with claim 3 wherein said first and second films are progressively heated to said respective temperatures by a plurality of heated and rotatably powered roller means, and including the step of rotating said forming drum at a peripheral speed slightly greater than the peripheral speed of said roller means.

11. A method in accordance with claim 1 including interrupting the method by stopping rotation of said drum to terminate production of the cushioning product, and then subsequently restarting the method by restarting rotation of said drum and continuing with the production of the product without injurious effect to the method and/or produced product.

12. A method in accordance with claim 1 including the step of applying further pressure by second heated roller means to said films on said drum immediately sub-sequent to said pressurized application of said second film to said first film.

13. A method in accordance with claim 12 wherein said further pressure means is heatable to a maximum tem-perature of 195°F. and is maintained within a temperature range of from approximately 150°F. to said maximum tem-perature of 195°F.

14. A method in accordance with claim 1 including the step of applying anti-static material to at least one of said films prior to its being coacted with the other film on the forming drum.

15. A method in accordance with claim 3 wherein said first film is initially passed about a roller maintained at a temperature of approximately 130° to 190°F.
and of a predetermined diameter, and then is passed around another roller maintained at a temperature in the range of approximately 130° to 190°F. with the second heated roller being of a greater diameter as compared to that of the first roller, and then is passed into engagement with a further roller which is non-heated, and then passing the first film about a group of consecutive relatively closely spaced driven rollers including a driven roller which is maintained at a surface temperature of between approximately 205° to 300°F., and then about a further driven roller which is maintained at a surface temperature between approximately 280° to 330°F. and then about a further driven roller which is maintained at a surface tem-perature of approximately 280°F.-330°F., and then about a further driven roller which is maintained at a surface tem-perature of approximately 330°F., and then about a further driven roller which is maintained at a surface temperature of approximately 330°F., and then is applied to the forming drum which is maintained at a maximum surface temperature of approximately 125°F. to 130°F., all of said driven rollers being of substantially the same diameter, and being driven at substantially the same speed.

16. A method in accordance with claim 3 wherein said first mentioned nylon stratum on both sides thereof is bonded to relatively low density polyethylene stratums having a melting point of approximately 230°F., the melting point of said first mentioned nylon stratum being approximate-ly 490°F., said heat softening point being approximately 160°F.

and said Vicat softening point being in the range of approximately 206°-210°F.

17. A method in accordance with claim 1 wherein the air cell product is stripped from the drum over 180 circumferential degrees from the point of application of said second film to said drum.

18. In an energy efficient apparatus for produc-ing embossed air cell cushioning material from a plurality of flexible thermoplastic film stock, each film of which comprises a composite of a stratum of high density high melting point thermoplastic material generally impervious to the passage of gas therethrough and at least one other stratum bonded to the first mentioned stratum, with the second mentioned stratum being formed of a low density low melting point thermoplastic, the last mentioned thermo-plastic being of a lower density, lower melting point thermoplastic as compared to that of said first mentioned stratum, said apparatus comprising, a rotatably driven forming drum having a plurality of recesses therein for vacuum forming the air cells in a first film of thermo-plastic material fed onto the rotating drum, and a series of rollers at least certain of which are driven, spaced with respect to said forming drum, said series of rollers including means providing for heating a first film prior to its being fed onto said drum to a temperature above the melting point temperature of the second mentioned stratum of the film but below the melting point temperature of the first mentioned stratum and to a temperature adequate for permitting thermoforming of the first film, and a second series of rollers at least certain of which are driven, spaced from said first roller series and having means thereon capable of heating a second film of the thermoplastic stock material to a temperature which is below the melting point of the second mentioned stratum of the second film and to a maximum temperature approximating the mean temperature between the heat softening point and the Vicat softening point of said second mentioned stratum, and movable heated pressure means coacting with said first and said second series of rollers for pressurized application of the second film to the first film on said drum resulting in a bonding of the second film to the first film and sealing of the formed air cells, said pressure means being disposed closely adjacent to the terminal one of said first series of rollers and closely adjacent the point of application for the first film to the drum.

19. An apparatus in accordance with claim 18 wherein each of said rollers is coated with an anti-fric-tion anti-adhesion material.

20. An apparatus in accordance with claim 18 including means thereon for rotatably mounting thereon supply rolls of the thermoplastic stock material.

21. An apparatus in accordance with claim 18 including means coacting with said drum for stripping produced air cell product therefrom.

22. An apparatus in accordance with claim 18 wherein said first series of rollers have heating means coacting therewith for heating the first film to a tem-perature of approximately 330°F. prior to application of the first film to said drum, and said second series of rollers have heating means coacting therewith for heating the second film to a maximum temperature of 190°F. prior to the application of the second film to the first emboss-ed film on the drum, and wherein said pressure means embodies heating means capable of heating said pressure means to a maximum of 195°F. surface temperature.

23. An apparatus in accordance with claim 22 wherein said pressure means comprises a rotatable roller and includes fluid pressure means coacting with the last mentioned roller for urging the latter with predetermined pressure against said forming drum, with the lengthwise axis of said roller extending generally parallel to the lengthwise axis of said forming drum.

24. An apparatus in accordance with claim 18 including means for rotating said forming drum at a peripheral speed slightly greater than the peripheral speed of the rollers of said first and said second series.

25. An apparatus in accordance with claim 18 including means for applying liquid anti-static material to at least one of said films prior to its being applied to said forming drum.

26. An apparatus in accordance with claim 22 including further heated pressure means downstream from the first pressure means for further subsequent applica-tion of pressure to the first and second films on said drum.

27. An apparatus in accordance with claim 26 wherein said further pressure means includes a heated rotatable roller movably mounted so as to be movable toward and away from said forming drum, and fluid pressure actuating means coacting with the last mentioned roller for selectively moving the latter into and out of engaging coaction with said forming drum.

28. An apparatus in accordance with claim 27 wherein said heated rotatable roller is heatable to a maximum surface temperature of approximately 195°F. and conventionally to a surface temperature of approximately 185°F.

29. An apparatus in accordance with claim 23 wherein said fluid pressure means comprises a pair of air cylinders, each one of which at one end thereof is coupled to a respective end of the axle of said pressure roller, and with the other end of each cylinder being pivoted to the apparatus frame, said cylinders being operable to urge said pressure roller in line contact against said drum in a direction and in a common plane extending generally through the rotary axis of said pressure roller and the rotary axis of said drum.

30. An apparatus in accordance with claim 23 wherein said heating means of said first roller series is operable to heat the first film to approximately 330°F.
prior to application of the first film to said forming drum, said second roller series embodying heating means operable to heat said second roller series to a surface temperature having an upper range of approximately 190°F., said rotatable pressure roller embodying heating means operable to heat said pressure roller to a surface tem-perature within the range of approximately 180°-195°F.
maximum, and preferably to a surface temperature of approximately 185°F., said pressure means being operable to apply a pressure in a range of between approximately 3 pounds to 9 pounds per lineal inch, applied along generally line contact of said pressure roller with the second film at its application to the first film on said drum, said fluid pressure means being operable to urge said pressure roller in line contact against said drum in a common plane extending generally through the rotary axis of said pressure roller and the rotary axis of said drum, said apparatus being adapted for use with film wherein the low density, low melting point stratum thereof consists essentially of polyethylene possessing a melting point of approximately 230°F.