US2770406A - Carton construction - Google Patents

Description

CARTON CONSTRUCTION 2 Sheets-Sheet l Filed June 28, 1954 fumi 1 CARTON CONSTRUCTION 2 Sheets-Sheet 2 Filed June 28, 1954 m E mw m 5 m w. M G

United States Patent CARTON CONSTRUCTION Gardiner Lane, Darien, Conn., assigner to St. Regis Paper Company, New York, N. Y., a corporation of New York Application June 28, 1954, Serial No. 439,765 7 claims. (Cl. 22a- 3.5)

This invention relates to cartons or container con structions and more particularly to constructions in which the interior and exterior surfaces comprise paper, between which there is located a layer of foamed plastic material.

The invention is adapted for providing a carton construction such as may be used for many of the purposes for which well-known corrugated paper board cartons have been used and which is also well-adapted for use `as a shipping container for many purposes as to which relatively expensive wo'oden boxes or crates are customarily used to meet conditions under which corrugated paper board cartons would fail. For example, in the shipping of food and produce, particularly under more or less refrigerated conditions, containers therefor will be subject to varying moisture conditions so that if corrugated paper boxes are attempted to be used for the purpose, they will collapse, particularly if stacked. Also, some commodities of course have to be well protected against moist atmospheric conditions which would lead to their injury if corrugated paper boxes are used. Consequently, for such purposes resort has had to be had to either relatively expensive wooden or metal containers.

I have found that a carton construction which will economically meet these various conditions of use may be made of a sandwich-like material, the surfaces of which comprise a paper material, such as kraft paper board, between which there is adhered a layer of a foamed plastic material, preferably polystyrene which has been expanded to contain multitudes of closed cells.

If polystyrene for example is foamed to have a density within certain limits, it can be made into sheets or layers which are rather soft, fairly easily compressible and non-brittle. Thus it may be made somewhat softer and more compressible than a comparable layer of cork for example, but by itself such a foamed layer may quite easily be broken or crumbled into small rm pulp-like pieces which do not crackle upon breaking. Yet, if this material is adhered on both surfaces to sheets of paper or paper board, such as kraft paper board for example, then quite surprisingly the resulting sandwich will be fairly stiff and board-like and will withstand being knocked about in the manner of carton surfaces during shipment without serious injury. Cartons made thereof may, for example, be thrust against corners of other cartons, furniture, or the like, with a force which would cause destruction of corrugated paper board boxes or the contents thereof.

Also, quite surprisingly I have found that the abovedescribed sandwich material may be scored or somewhat indented along desired lines as by a blunt blade and then bent along such lines to form the corners of the carton, without rupture of either the foamed plastic layer or the interior and exterior paper board sheets. In fact, the sandwich material may be bent back upon itself, that is to say, through substantially 360, still without rupture of either the plastic layer or the paper or paper board. Thus unexpectedly and surprisingly to those skilled in the art of carton manufacture, I have found that such sandice wich material may be `slit and folded to form cartons by using the same machinery which is in general use for forming corrugated paper board boxes. The fact that the foamed plastic layer does not crack or crumble at the folded score lines is apparently due to the adhesion thereof to the kraft paper board in a manner such that no cracks in the plastic have a chance to start and the plastic wili merely be compressed instead of cracking. And the fact that the kraft surfaces do not rupture at the corner folds, as `would be expected with such a boardlike material, is due to the tendency of the foamed layer to become compressed where folded, to a thinner dimension and so as to allow the outer kraft sheet to assume a smoothly curved corner shape whereas the inner kraft sheet folds to ua blunt corner pressing into the compressible plastic. Since the foamed plastic is somewhat soft, it presents no such rigid corner areas as might tend to scar or start the tearing of the kraft sheets. Apparently as a result of the compression of the foamed plastic to a greater density at the corner regions, such regions acquire even more toughness and impact resistance than places where the sandwich remains flat.

Further objects, features and advantages of the invention hereof will appear from the detailed description given below, taken in connection with the accompanying drawings which form a part of this specification and illustrate by way of example, a preferred embodiment of the invention.

In the drawings:

Fig. l is a perspective view showing a typical carton embodying the invention;

Fig. 2 is a perspective view of a corner portion of the sandwich material used for making the carton, this view showing the kraft board surfacing material torn away or separated from the foamed plastic layer and indicating the manner in which the plastic layer alone may be easily broken apart;

Fig. 3 is an enlarged sectional view showing the manner in which the portions of the sandwich material are shaped and curved at a top corner of the carton, this View being taken substantially along line 3-3 of Fig. l;

Fig. 4 is a view similar to Fig. 3 but taken along line 4--4 of Fig. 1 and showing a top corner in enlarged section before being folded;

Fig.` 5 is an enlarged view taken substantially along line 5-5 of Fig. l and illustrating the shape and curvatures which occur at and within one of the vertical corners of the carton;

Fig. 6 is a view similar to Fig. 5 but showing the shape and curvatures which occur before the fold is made;

Fig. 7 is a perspective view of the finished carton `in collapsed form;

Fig. 8 is an enlarged sectional view taken substantially along line 3 8 of Fig. 7 and showing the shapes and curvatures which occur at and within one of the corners of the carton when the sides of the carton are collapsed; and

Fig. 9 is a perspective View of an alternative edge formation which may be provided at the edges of the various flaps.

Referring to the drawings in further detail, it will be understood that the carton may be made of one integral piece of the sandwich material above referred to which is cut to the desired shape and size to provide side walls as at 10, 11, etc., and top and bottom flaps of conventional shape as at 12, 13, etc., such flaps being separated from each other by forming suitable slits or slots as at 14, 15 (Fig. 7).

After the carton blank has been folded, the meeting or overlapping edges of the vertical joint may be secured together in any of the various well known ways, as for example by an adhering strip of fabric thereon as indicated at 16.

Referring now to Fig. 4, there is here shown in enlarged cross-section, one of the corner regions before being folded and such as occurs at the junction of one of the closure flaps with one of the vertical walls of the carton. When the carton blank is passed through a conventional type of corrugated paper carton-forming machine, the scoring means will be such that the inner kraft sheet 17 will be compressed in a direction outwardly of the finished carton and along a narrow band as indicated at 18. Simultaneously the outer kraft sheet 19 will be supported or pressed inwardly along lines at 20 and 21 at either side of the compressed band 18. This will cause the foamed plastic layer 22 to be compressed in cross-section, the thickness of the cross-section gradually diminishing aS at 23, 24 at points nearer the corner fold region and so that at points which will be within the finished rounded corner, that is at the region 25, it will be of a thickness of about 1/3 or 1/2 of the thickness of such layer at points within the flat side wall areas of the carton.

When the portion shown in Fig. 4 is bent at right angles as in Fig. 3 to form a top corner of the box, the inner kraft sheet 17 at the corner will protrude outwardly at an angle of about 45 to the other portions of this sheet and form a rounded blunt corner 18a about which, over a wide angle, the compressed plastic portion 25 will extend with a semi-circular cross section, this part being covered by a portion 19a of the outer kraft sheet which here has a generally semi-circular cross-section. The plastic portions of gradually reduced thinness at 23, 24, as will be noted, are such as to afford ample clearance for the outwardly projected portions 18a of the inner sheet 17. Thus no portions on the inside of the corner will project inwardly of the carton beyond the fiat planes of the inner kraft sheet and also none of the outer portions of the corner will project beyond the flat planes of the outer kraft sheet.

Referring now to Fig. 6, there is here shown in enlarged cross-section a portion which is to form one of the vertical corners of the carton. In passing the carton blank through the carton-forming machine, the innermost kraft sheet 17 will be compressed along a band 26 in a direction outwardly of the carton, thereby compressing a portion 27 of the plastic layer 22 down to a thickness, for example, of about one-half or one-third of the normal thickness of the plastic layer. Also the portions at 28 and 29 of the plastic layer approaching the portion 2.7 will be of gradually diminishing thickness. Then when this corner is folded at right angles in the carton-forming Inachine, the parts will assume the positions and curvatures as shown in Fig. 5. That is, the inner sheet 17 at the band 26a will have a cross-sectional shape similar to that of an eyelet, somewhat rounded outwardly and covered by the compressed portions 27 of the plastic layer which is now smoothly rounded and covered in turn by a smoothly rounded portion 30 of the outer kraft sheet 19.

While Fig. shows a cross-section of the vertical corner when the carton is folded in condition for use as in Fig. 1, it will be understood that as the carton leaves the usual carton-forming machine, it will be in collapsed condition such as shown in Fig. 7. In that condition, the corner opposite the joint strip 16 will then be flattened out to have a cross-section as per Fig. 6, but the other two corners as at 31, 32 (Fig. 7) will have cross-sections as per Fig. 8. Here it will be noted that the inner kraft sheet 17 at the corner has a substantially T-shaped crosssection as indicated at 26h, this configuration being surrounded by a portion 27 of the compressed plastic which now will have substantially a semicircular cross-section and will be covered by the outer sheet portion 30 which now will also have a substantially semicircular cross-section. When the carton is opened up for use, the parts as shown in Fig. 8 will, of course, again assume the shapes and positions shown in Fig. 5.

If the laminate or sandwich of material of which the carton is made is cut by a shearing action as with scissors-like blades for example, then an edge is formed of the shape shown at 33 in Fig. 9. That is, the inner and outer sheets 17 and 19 will be gradually deflected so as to come almost into contact with each other at the free edge 34, and the plastic layer 22 at regions approaching the free edge, will be gradually compressed as at 35. This kind of edge may in sorne cases be desired for some or all of the edges of the flaps, particularly for the outermost flaps which are to have exposed edges after the carton is filled and closed. With this type of edge, the edge of the plastic layer may be substantially concealed so that the color and appearance of the edges will be substantially the same as other exposed areas and such an edge will be smooth and substantially free of any appearance of irregularities.

To provide a suitable expanded plastic and kraft sheet sandwich for forming a carton with the above-described types of corners, the following factors should be kept within certain predetermined limits:

(a) The density of the foamed layer;

(b) The number of fine cells per unit of volume there- 1n;

(c) The weight and strength of the paper material used; and

(d) The overall thickness of the sandwich.

Preferred examples and limits for these various factors will now be discussed.

In making the paper and foamed plastic sandwich, one may start with fine spherical beads, granules, or with a thin sheet of polystyrene containing distributed therein a suitable heat-sensitive catalyst or other foaming agent, which may be of various known forms, and which, when the composition is heated and softened, will cause fine gas bubbles to occur therein and consequent expansion of the material into the form of the desired plastic layer. Such polystyrene, before being expanded, will have a density such as to weigh about 65.5 lbs. per cubic foot. lf the polystyrene mixture containing the catalyst or foaming agent is heated and allowed to expand only to about several times its original volume, then the resulting foamed product will ordinarily have too great a density and will be too hard for use in accordance with this invention. On the other hand, if the expansion is carried too far, then the gas bubbles formed therein can easily become far too large, and the Aresulting foamed product when cooled will tend to be too brittle and will crackle when any pressure is applied thereto. In order for the foamed plastic to be in a suitable condition for use according to this invention, the foaming action should be carried only to an intermediate stage and so that the product will have a density preferably of about 3 lbs. per cubic foot. However, this may vary between limits in the neighborhood of from about 2 to about 10 lbs. per cubic foot, depending somewhat upon the desired thickness of the plastic layer within the sandwich and the weight and strength of the kraft sheets used therefore.

` Density as high as 10 lbs. per cubic foot however will to permit the corner to be bent without rupturing either the kraft sheets or the compressed plastic layer.

The number of fine cells in the plastic is, of course, related to the degree to which the material is expanded, in other words, its density. In a typical preferred case there were for example about 150,000 fine closed cells per cubic centimeter of the expanded material, such ma-l terial having a density in the neighborhood of 3 lbs. per

cubic foot. With material expanded to lesser densities, the number of cells may vary down to about "50,000 per cubic centimeter as a minimum, whereas with h'e'avier densities, such as lbs. per cubic foot, the number may 'be as many as 1,000,000 per cubic centimeter.

With preferred examples, the paper material used cornprised natural kraft, i. e. so-called kraft liner board, having a weight of about 126 lbs. per 3,000 square feet and 'having a strength such that a one-inch ribbon thereof in the machine direction" will withstand a tension of about 70 lbs. The weight of the kraft paper material used, however, may vary between a minimum of about 60 lbs. to a maximum of about 200 lbs. per 3000 square feet and having tensile strengths (for one inch wide strips in the machine direction) varying from about 25 to l200 lbs. If the sandwiches are relatively thin, for example having an overall thickness of about 3/16, then the lighter weight grades of kraft sheets may be used without danger that they will tear or crack at the corners, whereas for thicker sandwiches such as those of a thickness of a, heavier sheets should be used. The sandwich material in order to be folded as per the collapsed carton of Fig. 7, should preferably not be thicker than about 3/s. However, if the carton blanks are to be shipped in entirely flat -condition and not folded and secured at the joined corner until ready for use, then none of the corners will need to be bent through more than 90.. ln that case, a sandwich material about as thick as 1/2 might be used, if deeply scored along bands where the corner folds are to occur.

If the styrene containing the foaming agent is initially supplied in sheet form, which is a particularly convenient form for the purpose, such a sheet may simply be placed between two of the kraft sheets or other paperboard sheets and heated while located between two spaced plates, for example, which contain a fluid heating medium and through which thereafter cooling fluid may be passed to chill the assembly to stop the foaming action at the desired point. lf the heating and foaming takes place in the polystyrene under some pressure against heated kraft sheets, the sandwich parts may be made to adhere together without interposing any adhesive material. But in some cases, the use of adhesives has been found desirable, for example water mixtures of latex-type adhesives or various formaldehyde adhesives which are non-solvents for polystyrene.

Another form of polystyrene containing a foaming agent is put out by the Koppers Company, Inc., in the form of line spherical beads which may be adhered in a thin layer by the adhesive between the kraft or other paper material sheets before the heating and foaming action takes place. A suitable sandwich for the purpose was made by heating such an assembly between platens at a temperature of about Z50-275 F. for from 4-6 minutes, followed by water cooling of the platens for a period of about 4 minutes before taking out the finished product. Other polystyrene foama'ole materials are available in granular form, such as put out for example by Monsanto Chemical Company.

The appropriate times and temperatures for causing the desired foaming may be readily determined by trial and will usually depend upon the particular foaming agent incorporated in the polystyrene. Preferably the sandwich is scored and folded to form the cartons reasonably soon after the sandwich material is formed, since usually after some ageing it will become somewhat more stiff.

The polystyrene with its foaming agent may be heated and extruded if desired, and expanded to a limited thickness between two of the moving kraft sheets in a continuous operation, the sandwich as it progresses further being cooled to stop any further foaming action after a plastic layer of the desired density has been formed.

While the use of polystyrene is presently preferred for forming the foamed plastic layer because of its low cost and the ease with which it may be foamed into the desired compressible, somewhat soft product having great numbers of fine cells, yet it will be understood that various `other plastics might be used, for example polyvinyl chloride, among others.

Cartons formed in accordance with this invention are highly resistant to water absorption, as well as water vapor transmission, since the cells are not interconnected. Also the nature of the foamed plastic is such that it is highly resistant to fungus and insects and has good thermal and electrical insulating qualities. But perhaps one of the most important advantageous characteristics of the cartons of this invention is that, as compared with corrugated paperboard boxes, for example, they will withstand certain standardized puncture tests some 50% better; and if apertures are punctured through the side walls, the disruption of the sandwich material will extend only for about onequarter inch from the puncture, whereas in corresponding tests with corrugated cartons, the destruction may extend 5 or 6 inches from the puncture points. Despite the board-like nature and strength of this foamed plastic and kraft sheet sandwich material, shocks are not readily transmitted therethrough. uIt is not soft enough to bend readily and `to thereby transfer the shocks through to the contents as `does corrugated material, but the foamed plastic is sufficiently compressible to cushion shocks and the more the compression within limits, the tougher the area of compression appears to be, particularly at the corners, which will resist quite heavy impacts without collapsing or denting more than superiicially. In the process of scoring and folding the corners, the plastic layer there becomes compressed to one-half or less of its normal thickness at other points and its density there is consequently doubled or more than doubled, thereby enhancing the impact resistance where most needed.

In cases where it is desired that all parts `of the container, including the sheets of paper material, be highly resistant to injury by moisture, such sheets may be formed of so-called high-wet strength kraft liner board or other paperboard or the like which has been treated with melamine resinous material or other moisture resisting compositions.

Although a particular embodiment of the invention is herein disclosed for purposes of explanation, various modifications thereof, after study of this specification, will be apparent to those skilledin the art to which the invention pertains, reference should accordingly be had to the appended claims in determining the scope of the invention.

What is claimed and desired to be secured by Letters Patent is:

l. A collapsible carton formed by folding a carton blank, characterized in that the blank constitutes a sandwich having two spaced-apart sheets of paper or the like and the space therebetween being filled with a layer of foarned compressible plastic material containing many thousands of gas cells per cubic centimeter, the opposite surfaces of which layer respectively are secured throughout to such sheets, the corners for the carton being formed along narrow bands at which the plastic material is permanently compressed to a substantially less thickness and substantially higher density than the other areas, the sandwich along said corners being suciently flexible to permit free bending for the formation of at least corners without rupture of the foamed layer or said sheets as secured thereto, but the foamed layer in the main wall areas of the carton being relatively uncompressed and said areas being relatively non-resilient and rigid against deflection and the foamed layer therein being subject to fracture upon substantial bending.

2. A carton construction having side walls and end closure flaps interconnected by corner folds and formed of a sandwich comprising a layer of somewhat compressible foamed plastic material containing tens of thousands of gas-filled cavities per cubic centimeter, said layer by 7 itself being relatively soft but easily broken, the outer .and inner surfaces of said plastic layer having secured thereon sheets of a paper material, whereby the sandwich has a board-like rigidity but is capable of being folded to form said corner folds without rupture of said sheets or the plastic layer, the inner sheet of said paper material in the corners being folded substantially upon itself to project as Va formation of blunt cross-section into the plastic, the plastic within the corner being compressed to a thickness substantially less but to a density substantially greater than at other areas and embracing such blunt formation, said layer being suciently lacking in resilience to maintain of itself such compressed condition at the corner folds, and the outer sheet of paper material at the corners covering and embracing said compressed plastic portion and providing a smoothly rounded outer corner surface.

3. A collapsible carton formed by folding a carton blank constituting a sandwich of board-like rigidity and having a layer of foamed compressible but relatively nonresilient plastic material, on the inner and outer surfaces of which are secured respectively sheets of paperboard, corners of the carton being formed along lines at which the foamed plastic material is compressed to a substantially higher density than at other areas and remains by itself so compressed, such corners being foldable to a degree permitting adjacent side Wall areas to be brought substantially together when the carton is collapsed, without rupture of either said sheets or said plastic layer at the corner.

4. A collapsible carton formed by folding a carton blank constituting a sandwich of board-like rigidity and having a layer of foamed polystyrene on the inner and outer surfaces of which are secured respectivelyV sheets of kraft paperboard, the Afoamed layer being permanently compressed to a substantially higher density at the corners, and the corners of the carton being foldable to a degree permitting adjacent side wall areas to be brought substantially together when the carton is collapsed, without rupture of either said sheets or said plastic layer at the corner.

5. In a container construction, a foldable corner portion formed of a sandwich comprising a layer of foamed plastic material, the inner and outer surfaces -of which have secured thereon sheets of a paper material, the outer sheet forming a smoothly curved corner surface covering a portion of the plastic layer which is free of ruptures 8 and which is substantially thinner but of substantially greater permanent density at the corner region than at adjacent regions, and the inner .sheet at the corner being folded to an outwardly projecting formation of blunt cross-section embraced by said thinner plastic portion.

6. A collapsible carton formed by folding a carton blank constituting a sandwich of board-like rigidity having a layer of foamed plastic material on the inner and outer surfaces of which are secured respectively sheets of paperboard, corners of the carton being foldable to .a degree permitting adjacent side wall areas to be brought substantially together when the carton is collapsed without rupture of either said sheets or said plastic layer at the corner, the outer sheet of paperboard, when such corners are thus folded, forming a smoothly curved outer surface embracing a portion of the plastic layer `of arcuate crosssection and which is compressed to a thickness about onehalf or less than the thickness of said layer in the side walls, and the inner sheet in such corner when thus folded being so folded as to have a substantially T-shaped cross-section embraced by the compressed plastic material.

7. A collapsible carton formed by folding a carton blank constituting a sandwich of board-like rigidity having a layer of foamed plastic material which is compressible without rupture, and on the inner and outer surfaces of which are secured respectively sheets of paperboard, the sandwich being scored internally of the carton along narrow bands of the paperboard at the carton corners, along which bands the plastic layer is permanently compressed to about one half and less of its thickness at other areas, whereby the corners are foldable to a degree permitting adjacent side Wall areas to be brought substantially together when the canton is collapsed without rupture of either said sheets or said plastic layer at the corner.

References Cited in the tile of this patent UNITED STATES PATENTS 1,334,302 Hicks Mar. 23, 1920 1,565,765 Walter Dec. 15, 1925 1,708,700 Maier Apr. 9, 1929 2,099,936 Kieckhefer Nov. 23, 1937 2,484,608 Cheyney Oct. 11, 1949 2,552,641 Morrison May 15, 1951 2,576,073 Kropa Nov. 20, 195,1 2,592,081 Toulmin Apr. 8, 1952

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