US 2992117 A
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Description (OCR text may contain errors)
July 11, 1961 s. ROSEN ETAL FOOD PACKAGE 2 Sheets-Sheet 1 Filed Sept. 15, 1957 INVENTORS k2. @a-u/n/ BY Zu wen/A4 $642M ATTORNEYS.
July 11, 1961 s. ROSEN ET Al.
FOOD PACKAGE 2 Sheets-Sheet 2 Filed Sept. 13, 1957 NVENTORS fi. me/n/ ATTORNAYS/ oooooooooommmmmw United States Ptent 2,992,117 F801) PACKAGE Shy Rosen, New York, N.Y., and Walter S. Thompson,
East 'Lansdowne, Pa, assignors to Milprint, Inc., Milwnukee, Wis., a corporation of Delaware Filed Sept. 13, 1957, Ser. No. 683,739 7 Claims. (Cl. 99-171) The present invention relates generally to improvements in the art of packaging diverse commodities, and relates more particularly to improvements in the construction and use of commodity Wrappers fabricated from inherently thermoplastic films.
A primary object of this invention is to provide a new and useful commodity wrapper which is highly efiicient in use, simple and economical in construction, capable of being readily fabricated, and which may be used in an improved manner to protectively confine diverse commodities while providing a final package which may be readily opened by the ultimate consumer.
It has long been an accepted fact in the packaging industry that various commodities, and especially certain food products, are more attractive and salable to the purchasing public when wrapped or packaged in transparent or partially transparent containers through which the enwrapped article or a portion thereof may be readily viewed. In addition, the sheet materials used in packaging commodities must possess other desirable characteristics such as economy, both with respect to the wrapping material itself and the fabrication thereof into wrappers and the final packages. The wrappers should furthermore be of such character as to be capable of adequately protecting the packaged commodity against possible deterioration caused by various atmospheric or surrounding conditions, and they should also be readily scalable either with or without the aid of separate adhesives and should be receptive to printing to facilitate application of printed matter adapted to permanently adhere to the sheets. Additionally, it is of great importance that the final packages be capable of being formed in a rapid manner on or with the aid of automatic packaging equipment, and that the packages be adapted for quick and easy opening by the consumer.
According y, it has become common practice in the packaging field to utilize various more-or-less transparent films such as regenerated cellulose or cellophane, rubber hydrochloride or Pliofilm, glassine, and more recently polyethylene, Saran, and certain vinyl and nylon films; and while at least some of these films can be produced with the desired transparency characteristics, they are either lacking in other desired qualities or they have not heretofore been successfully adapted to rapid and automatic fabrication and ready opening.
For example, commercially available cellophane is clear and highly transparent, may be rendered receptive to printing by modern methods, and automatic pack-aging machinery has been developed for wrapping commodities therein; but this film is relatively expensive, has a hard texture and cold feel or touch qualities, is itself subject to deterioration under certain conditions, and does not in itself possess the best possible protective qualities. As for glassine, it too has a relatively hard texture and cold feel in addition to its lack of desired clarity and transparency. Finally, with respect to inherently thermoplastic films such as Pliofilm, Saran, polyethylene, vinyl and nylon, these films have excellent physical properties for providing protection to products packaged therein, are exceedingly durable and strong under varying conditions, have good heat scalability and transparency, and possess exceptionally soft texture and touch qualities. However, despite these attributes, these Patented July 11, 1961 inherently thermoplastic films are not readily adaptable to the packaging of commodities on all available automatic packaging machines, nor are the wrappers fabricated of these materials easily opened and it is frequently necessary to so mutilate the wrapper during the initial opening thereof as to destroy its further protective usefulness.
In efforts to utilize the desirable characteristics or qualities of different available packaging materials, it has also been heretofore proposed to combine the same in a composite wrapper sheet, or to provide mechanical means, score lines or the like to facilitate opening. An example of such a composite wrapper, fabricated of a strip of coated cellophane forming a transparent window portion and bounded on opposite sides by relatively opaque strips of wax coated paper or the like secured to the edges of the transparent strip, may be found in US Patent No. 2,143,844, granted January 17, 1939, to Adrian O. Daller. As for the method and apparatus by means of which these composite wrappers may be produced, attention is directed to US. Patent No. 2,139,- 633, dated December 6, 1938, to Roy E. Hanson and George 0. Frostad, and Us. Patent No. 2,213,957, granted September 10, 1940, to Gordon H. Friend, Jr. Examples of means which have heretofore been proposed for facilitating opening may be found in Shy Rosen US. Patents No. 2,296,951, dated September 29, 1942, No. 2,475,052, dated July 5, 1949, No. 2,476,564, dated July 19, 1949, and No. 2,494,965, dated January 17, 1950.
However, in no known prior instances was it contemplated that an inherently thermoplastic transparent film be utilized as the main body or protective portion of the wrapper, particularly since these films were heretofore believed incapable of use in the production of final commodity packages on automatic equipment wherein overlapped portions of the material are directly subjected to and caused to slide over heated sealing plates during advancement of the wrapper to form the seals a step which is not practical with uncoated or otherwise untreated inherently thermoplastic film which invariably will stick to the heated plates during any prolonged dwell. Furthermore, the extremely limp nature of these thermoplastic films likewise presents serious problems in the use and handling of such films on automatically operable equipment, and these problems also heretofore remained unsolved. As for the means previously proposed for facilitating opening of the final package and subsequent reclosure thereof, special machinery is required for production of the wrappers, and the devices proposed are limited in use to materials of certain characteristics.
It is therefore a more specific object of the present invention to provide an improved commodity wrapper, package assembly, and packaging method which obviate all of the aforementioned objections and disadvantages.
Another specific object of the invention is to provide an improved commodity wrapper formed essentially of inherently thermoplastic transparent film and which may be readily utilized on automatic packaging equipment to produce an improved final package possessing certain desired end use characteristics.
Another specific object of our invention is to provide an improved commodity package which is effectively sealed to afford a tight substantially moistureproof wrapper which may moreover be readily opened at a predetermined area or areas to permit piecemeal removal of the commodity and subsequent reclosure of the wrapper to protect the unused remaining portion of the product;
Still another specific object of this invention is to provide a new and improved commodity wrapper formed s 2,992,117 v g of inherently thermoplastic transparent film having predetermined areas thereof coated or otherwise provided with a heat-scalable material having a sealing temperature somewhat below that of the base fihn whereby a desired commodity may be readily protectively packaged therein in a rapid and economical manner to provide a final package assembly which may be quickly and easily opened at predetermined areas while remaining firmly sealed at all other areas.
A further specific object of the present invention is to provide an improved commodity package comprising, a flexible sheet having a transparent portion of uncoated inherently thermoplastic material and a marginal portion having a heat-scalable coating adapted to be activated at a lower temperature than the base sheet, and a commodity protectively wrapped in the sheet, the major body portion of the commodity being confined within the transparent uncoated portion of the sheet with overlapping uncoated marginal portions thereof directly fused to each other by heat to provide a strong seal while the marginal coated portion of the sheet is folded and heat sealed by fusion of the coating over the folded areas thereof to provide a relatively superficial seal.
An additional specific object of the present invention is to provide an improved method and apparatus for pro ducing the improved commodity package.
These and other specific objects and advantages will become apparent from the following detailed description.
A clear conception of the several features constituting the present improvements, and of the steps involved in the packaging of commodities in accordance with the invention, as well as typical apparatus for performing the methd steps, may be had by referring to the drawings accompanying and forming a part of this specification wherein like reference characters designate the same or similar parts in the various views.
FIG. 1 is a plan view of a typical wrapper sheet illus trating one embodiment of the invention;
FIG. 2 is an end view of the wrapper sheet of FIG. 1;
FIG. 3 is a perspective view of a commodity such as bread packaged in the wrapper of FIG. 1, a part of the outer end fold of the wrapper being broken away to reveal normally hidden structure;
FIG. 4 is a fragmentary diagrammatic side view of typical apparatus for applying a suitable heat sealable coating to certain portions of the wrapper;
FIG. 5 is another plan view of a typical wrapper sheet illustrating another embodiment of the invention, a portion being broken away to reveal normally hidden structure;
FIG. 6 is an end view of the wrapper sheet of FIG. 5;
FIG. 7 is a side elevation of a typical bread package utilizing the wrapper of FIG. 5 and showing one end partially opened;
FIG. 8 is a fragmentary diagrammatic top view of typical apparatus for producing the composite wrappers of FIG. 5;
FIG. 9 is a side view of a typical automatic bread packaging machine modified in accordance with the invention to utilize the improved wrappers of FIGS. 1 and 5; and
FIG. 10 is a somewhat enlarged fragmentary side view of that portion of the apparatus which forms the bottom and end seals of the improved package, portions of the apparatus being broken away to reveal normally hidden structure.
While the invention has been specifically shown and described herein as being especially advantageously applicable to the packaging of bread and as being embodied in a wrapper sheet having opposed marginal portions either coated with heat-scalable strips of wax or secured to separate strips containing a wax or a similar coating, it is not desired or intended to thereby unnecessarily restrict or limit the improvements by reason of such specific embodiments, since the improved wrappers may be used to advantage in packaging diverse other commodities and the inherently thermoplastic base sheet may have only one marginal edge treated so as to render the same readily openable from a single end or side. It is also contemplated that certain specific descriptive terms used herein shall be given the broadest possible interpretation consistent with the disclosure.
Referring to the drawings in which the invention is illustrated as being specifically embodied in a bread wrapper, it will be noted that, although two separate modifications are shown therein, the wrapper in each case compirses essentially the same elements. For example, with particular reference to FIGS. 1 and 2, the wrapper shown therein comprises, in general, a flexible transparent sheet 15 of inherently thermoplastic material having an intermediate uncoated portion 16 and opposed marginal portions 17 provided with a hea -sealable coating of a material adapted to be activated at a lower temperature than the base sheet 15. As for the wrapper shown in FIGS. 5 and 6, this wrapper likewise comprises generally a flexible sheet 15 of which at least the intermediate portion 16' is an inherently thermoplastic film bounded on opposite sides by marginal portions 1'7 which, in this case, consist of separate strips of sheet material carrying a heat-scalable coating also having a sealing temperature somewhat below that of the intermediate portion 16', the edges of the marginal strips 17 and the edges of the intermediate film 16 being overlapped and secured as by heat sealing. However, if desired, the inherently thermoplastic film may extend for the full width of the com posite wrapper sheet with the strips 17' being laminated thereto for their entire width without departing from the invention.
The wrapper 15 of FIGS. 1 and 2 may be readily formed, as shown schematically in FIG. 4, by advancing a web 19 of inherently thermoplastic film between pairs of laterally spaced coacting rollers Zil, 21, the roller 21 of which operates in a supply pot or reservoir 22 to peripherally carry the heat-scalable coating material to the surface of the advancing web which may be subsequently severed into wrapper sheets 15 of the desired lengths. With respect to the wrapper 15' of FIGS. 5 and 6, this wrapper may be readily formed, as shown schematically in FIG. 8, by simultaneously advancing laterally spaced ribbons or strips 24 of the coated material and an inter mediate strip 25 of the inherently thermoplastic film in edge over-lapping relation between laterally spaced heat sealing wheels or glue rolls 26 properly positioned as the case maybe and adapted to seal the overlapping areas.
To package a commodity such as a loaf of bread in either the wrapper 15 or 15' after the wrapper has been initially frabricated as described, the wrapper is distended to enclose the commodity therein with opposed edges of the uncoated intermediate portion 16, 16' of the wrapper 15, 15 overlapping and in face-to-face relation and with the coated marginal portions 17, 17 folded upon them selves. The enwraped commodity is then advanced, as between opposed stationary heat sealing plates, with the folded coated portions 17, 17 being subjected to sufiicient heat to activate the coating and cause relatively superficial sealing of the folded portion by the coating alone during such advancement, the overlapped edges of the uncoated wrapper portion 16, 16' being momentarily subjected to sufficient heat only at a predetermined interval during the advancement of the enwrapped commodity to fuse and integrally unite or Weld the overlapped areas.
The final commodity package 28 thus formed with the wrapper 15 is shown in FIG. 3 While the package 28' formed with the wrapper 15' is shown in FIG. 7; and in each instance, the package comprises a flexible wrapper sheet 15, 15 having a transparent portion 16, 16' of uncoated inherently thermoplastic material and a marginal portion or portions .17, 17 provided with a heat-scalable coating, and a commodity protectively confined Within the sheet, the major body portion of the commodity being surrounded by the transparent uncoated portion 16, 16' of the sheet 15, 15 with overlapping uncoated marginal portlons thereof directly and intimately fused together, as at 29, 29', to thereby provide an integral side seal, and the marginal coated portions 17, 17' of the sheet being folded upon themselves and heat sealed, as at 30, 30, by fusion of the coating over the folded areas to thereby provide a relatively superficial seal.
Referring particularly to FIGS. 9 and of the drawings, the improved apparatus for performing the packaging method hereinabove described has been shown as embodied in and applied to a typical automatically operable bread wrapping machine. With reference first to FIG. 9, the bread loaves are initially loosely wrapped in a conventional manner and are successively fed over the table or platform 35 by a suitably driven overhead chain and finger conveyor 36 past a conventional end label applying unit 37 and between a pair of stationary laterally spaced heated sealing plates 38 coacting directly with the ends of the successive loaves for sealing the folded coated portions of the wrappers as these portions slide across the plates 38. As each of the successive loaves leaves the opposed heat sealing plates 38, they are advanced onto the stationary table 39 in the side or bottom sealing section of the machine, each of the loaves being momentarily arrested in movement on the table 39 until pushed ahead by the next succeeding loaf being conveyed into position by the conveyor 36. The side or bottom sealing unit comprises, in general, a heated sealing bar 40 extending transversely across the path of the advancing loaves at a point where the advancement thereof is momentarily arrested, the heat sealing bar 40 being carried at one end of a pivotally mounted lever 41 connected by a link 42 to a solenoid 43 adapted to be energized by a micro-switch 44 which in turn is actuated by an arm or lever 45 tripped by the successive loaves as they are advanced by the conveyor 36 to thereby intermittently energize the solenoid and cause the heat sealing bar 40 to be broughtinto direct contact with overlapped edges of the uncoated portion of the wrapper to weld or seal the same. If the coated end portions of the successive wrappers are of a width such as to extend inwardly of the ends of the package when wrapped as shown in FIG. 7,
.a pair of laterally spaced elongated hot plates 46 may be provided over which the successive loaves are passed to seal the overlapping bottom of the coated end portions of each of the successive packages, but the provision of these sealing plates 46 is a matter of choice dependent upon the nature of the wrappers being used in packaging the commodity. From the heat sealing section of the wrapping machine, the successive loaves are adwanced to an endless conveyor 47 through a cooling section 48 to a pick-up conveyor 49 from which they may be disbursed. It is to be noted that the coated portions of each of the wrappers are folded and sealed by means of heat applied directly to the folded areas by stationary plates heated to a sufficient extent to activate the coating and cause sealing thereof, the portions thus sealed being slid directly -over the heated plates with the coating supplying its own lubricant during this action. In contrast, the uncoated portions of the inherently thermoplastic wrappers are sealed by means of the intermittently operable heat sealing bar 40 which is brought directly against the overlapping areas of the successive Wrappers while the respective'package is at rest, and this is extremely important in view of the fact that the inherently thermoplastic film does not supply sufficient lubrication for sliding the same over the heat sealing member.
It is thus believed apparent that the present invention contemplates the provision of a commodity wrapper from an inherently thermoplastic film, the improved wrapper ,being capable of ready utilization on automatic packaging equipment to thereby result in a final package having highly desirable end use characteristics. It is desired that the package should be sealed to aiford a tight moistureshould be readily openable at one or both ends of the package to thereby permit removal of the commodity piece-meal while permitting the same to be reclosed in order to protect the remainder of the packaged product. Normally, with inherently thermoplastic films such as polyethylene, the strength of the seals formed by heat sealing is so great as to render it difficult to open the package without tearing or partially destroying the wrapper to such an extent as to make reclosure difficult or impossible, and this objection has been obviated in the present instance either by providing a thermoplastic wrapper in which the end seal areas are coated with a heat sealing material having a sealing temperature below that of the base film or by providing one or both side marginal portions of the wrapper with a non-thermoplastic base sheet secured to the intermediate thermoplastic portion and carrying a heat seal coating having the desired sealing characteristics. In order for the improved Wrapper to operate satisfactorily on conventional bread wrapping machinery, it is necessary that the end portions of the wrapper should slide past the end sealing plates without sticking thereto when exposed directly to these plates, and for the formation of the bottom seals on overlapped areas of the inherently thermoplastic and uncoarted film, a reciprocating sealing device or other intermittently operable mechanism is provided. The wrappers made from a combination of materials as herein described result in a final package in which a readily openable seal is provided on at least one end of the package and in which a strong weld or integral seal is provided on the side or bottom of the package which has suificient strength to avoid ripping open prematurely while the contents of the package are being dspensed.
The intermediate theromplastic portion of the improved wrapper herein described may be formed of any one of several transparent films which are inherently thermoplastic such as polyethylene, Pliofilm, Saran, vinyl films or nylon films. Such films as Mylar are not entirely satisfactory since they are too high in melting point and have poor sealing characteristics, and polystyrene and cellulose acetate are objectionable because of the fact that the mo sture vapor permeability is too high to give the required moisture protection to the product packaged. Properties which the selected thermoplastic films have in common are, for example, good heat-scalability, soft pliable =feel, good strength and durability, good moistureproofness, good transparency, and physical properties which are essentially independent of moisture conditions as opposed to such films as cellophane or waxed paper which soften in the present of moisture but which are hard and brittle when dried out. The preferred thickness of the thermoplastic film used in the present instance could be varied from one to two mils with excellent results, but a film in the range of from one-third mil to four mils might function satisfactorily.
With respect to the marginal portions of the wrapper of the type shown in FIGS. 1 and 2, it is contemplated that the marginal coated portions of this wrapper could be given suitable tack seal characteristics by coating with a suitable heat sealing composition consisting, for example, of sixty percent paraffin wax having a melting point of between F. to F. mixed or blended with thirty-five percent. micro-crystalline wax having a melting point of between 145 F. and F. and five percent polyethylene having a molecular weight of between 2,000 and 12,000. Such a composition has been found to have the required tack sealing characteristics, resists blocking when in rolled form, and has the required slip or self-lubrication when passed over a stationary heat sealing element. In general, it is considered that any heat sealing coating might be usable which would be relatively free from blocking or sticking at normal ternperatures, which adheres properly to the thermoplastic base film, and which heat seals in a range from about 130 F. to approximately 20 below the softening temperature of the thermoplastic film. It is also essential that the coating utilized should be sufficiently self-lubricating so as to be free of sticking when exposed to heat sealing elements, and the waxed or coated areas 17 (FIG. 1) should be of sufficient thickness as to give the base sheet of inherently thermoplastic film the rigidity necessary for wrapping the otherwise limp sheet on existing automatic wrapping equipment.
As for the wrapper of FIGS. 5 and 6, the marginal portions 17' may consist of a non-thermoplastic sheet or non-thermoplastic ribbons carrying a heat-scalable coating preferably applied to both sides. Materials which have been found suitable for the intended use in composite wrappers of this type include waxed paper, heat sealing cellophane, heat seal coated glassine, and paper coated with heat sealing plastic coatings such as polyvinyl acetate, ethyl cellulose, or various emulsion coatings such as Geon, Saran, and the like. In cases wherein the wrapper is to be used for bread, the preferred material is, of course, waxed paper primarily because it is adapted for use on existing wrapping machinery. The thickness of the heat steal coating required is dependent primarily upon the porosity of the non-thermoplastic base sheet, and the amount of coating on the surface of each side could be as low as one pound per ream for the dense sheets like glassine or cellophane or as high as four pounds per ream for a porous sulphite paper.
A preferred embodiment of the present invention consists of one and one-half mil polyethylene for the intermediate portion of the wrapper adhered along the marginal portions to waxed paper, such as is commonly used for bread wrappers, by means of an emulsion adhesive containing polyvinyl acetate and/or rubber latex with modifying resins and plasticizers. A wrapper of this type is adapted to be printed either in the intermediate or in the marginal portions or in both the intermediate and marginal portions as well as on the labels normally attached to the ends of the package. A wrapper of this type has been found to give a strong package which resists breakage during marketing and consumer use, has a soft pliable feel suggestive of the freshness of the product packaged, provides good moisture protection, and does not develop a shop-worn appearance due to handling by the purchasing consumer. It is notable that this wrapper is also adapted for use under frozen storage conditions wherein it is desired to market or store the product for relatively long periods; and as hereinabove mentioned, this type of a wrapper is unique as compared to other available commodity Wrappers in offering a weld or integral type bottom seam for permanent strength with a tack type or relatively superificial end seal for easy opening. Furthermore, while it is normally not desirable to coat the intermediate transparent portion 16, 16' with material which might interfere with or tend to destroy the desirable characteristics of the thermoplastic film, it is contemplated that the film may be treated, if necessary, for receiving printed matter or the like, and it is contemplated that a local printing of this portion of the wrapper shall not be considered a coating thereof in interpreting the claims.
It is not intended or desired to limit this invention to the exact details of construction, precise steps of the production method, or to the exact construction of the apparatus herein shown and described, since various modifications within the scope of the appended claims may occur to persons skilled in the art to which this invention pertains.
l. A food package comprising, a flexible wrapper sheet having a transparent portion of uncoated inherently thermoplastic material and a marginal portion provided with a heat-sealable coating adapted to be activated at a lower temperature than the base sheet, and a food commodity protectively confined within said sheet, the major body portion of said commodity being surrounded by the transparent uncoated portion of said sheet with overlapping uncoated marginal portions thereof directly fused together by heat to provide a strong seal, and the marginal coated portion of said sheet being folded and heat sealed by fusion of the coating over the folded areas thereof to provide a relatively superficial seal.
2. A food package comprising, a flexible wrapper sheet having a transparent portion of uncoated inherently thermoplastic film and marginal portions provided with a heat-scalable self-lubricating coating adapted to be activated at a lower temperature than said film, and a food commodity protectively confined within said sheet, the major body portion of said commodity being surrounded by the transparent uncoated portion of said sheet with overlapping uncoated marginal portions there'- of intimately joined by heat to provide an integral seal, and the marginal coated portions of said sheet being folded and heat sealed only by fusion of the coating over the folded areas thereof at a sealing temperature below the sealing temperature of said film to provide a relatively superficial seal.
3. A food package comprising, a flexible wrapper sheet having an intermediate transparent portion of limp uncoated and inherently thermoplastic film and opposed relatively rigid marginal portions provided with a heatsealable coating of a material adapted to be activated at a lower temperature than said intermediate portion, and a food commodity protectively confined Within said sheet, the major body portion of said commodity being embraced by the transparent uncoated portion of said sheet with overlapping uncoated marginal portions thereof intimately joined by heat to provide an integral seal, and the opposed marginal coated portions of said sheet being folded and heat sealed only by fusion of the coating over the folded areas thereof to provide relatively superficial seals at opposite ends of the package.
4. A food package comprising, a flexible composite wrapper sheet having a transparent portion of uncoated inherently thermoplastic film and at least one marginal portion of non-thermoplastic sheet material secured to said film in overlapping relation and provided with a heat-scalable coating adapted to be activated at a lower temperature than said film, and a food commodity protectively confined within said sheet, the major body portion of said commodity being surrounded by the transparent uncoated portion of said sheet with overlapping uncoated marginal portions thereof intimately joined by heat to provide an integral seal, and the marginal coated portion of said sheet being folded and heat sealed by fusion of the coating thereof over the folded areas to provide a relatively superficial seal.
5. A food package comprising, a flexible composite Wrapper sheet having an intermediate transparent por-- tion of limp uncoated and inherently thermoplastic film and opposed marginal portions of relatively rigid nonthermoplastic sheet material secured to said film in edge overlapping relation and provided with a self-lubricating heat-scalable coating, and a food commodity protectively confined within said sheet, the major body portion of said commodity being embraced by the transparent uncoated portion of said sheet with overlapping uncoated marginal portions thereof intimately joined by heat to provide an integral seal, and the marginal coated portions of said sheet being folded and heat sealed by fusion of the coating thereof over the folded areas to provide relatively superficial seals at opposite ends of the package.
6. A food wrapper sheet comprising, a flexible transparent sheet of uncoated inherently thermoplastic material having at least one marginal portion provided with a heat-scalable coating of a material adapted to be activated at a lower temperature than the base sheet, the wrapper being foldable to a position wherein, edges of the uncoated portion overlap for integral sealing by 2, 9 92, 1 1 7 9 10 heat and wherein the coated marginal portion is foldable References Cited in the file of this patent upon itself for superficial sealing by heat applied at a somewhat lower temperature. UNITED STATES PATENTS 7. A composite food wrapper sheet comprising, a X- 7 5 Mumphy May 21, 1918 ible transparent sheet of limp unwated and inherently 5 04 34 R l July 7 1936 thermoplastic material, and a flexible but more rigid 2048895 Rosen July 6 sheet of normally non-therm0plastic mat rial s d in 2130680 Fmnci n s t 26 1938 edge-overlapping relation to at least 0 1 g 0f Said 931 h 0 5t 11 1938 inherently thermoplastic tsheet, said n0n-therrn0plastic 7 lg n J 1940 sheet being provided with a heat-sealable coating, the [0 0 ac (ma et u wrapper being foldable to a position wherein edges 0f 212151036 Hammm Sept-17, 1940 h t d tion overlap for integral sealing by heat 2Z29287 Gamma 1941 d wh rein the coated marginal portion is folded upon Vogt 19.41 itself for superficial sealing by heat applied at a somewh t 2,475,0 Rosen July 5, 1949' lower temperature. 15 2,692,723 Elsman Oct. 26, 1954