Abstract:
Blanks for forming open sided containers and mating covers from carton stock material include strips of non-stick material secured to the blank by means of a strippable adhesive. The adhesive adheres to the carton stock material with a substantially higher adherence force than the adherence force between the adhesive and the non-stick material, so that the non-stick material can be removed, readily, to expose the tacky surface of the adhesive. The carton blanks are marked with a predetermined pattern of fold or crease lines which allows the blank to be bent and folded into the shape of a container or a container cover. The non-stick material facilitates handling and separation of individual blanks that have been shipped and stored in tightly packed, stacked arrays, while the exposed adhesive surface engages specifically formed tabs and/or flaps of the blank in overlapping, abutting relationships to secure the blank in its final, assembled, container/cover shape.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to blanks formed of cardboard or similar carton stock material that can be assembled readily into packages and containers for various goods, and more particularly relates to improvements that facilitate handling, assembly and use of such blanks. 
     Carton blanks, of the type comprising a unitary flat sheet of cardboard carton stock having various pre-marked lines formed thereon in a predetermined pattern that allows the blank to be bent and/or folded from its planar flat stage into a three-dimensional structure having the shape of a carton or box-like container, are well-known. It is also well known that the same carton shape, having a slightly different shape and/or different dimensions can be provided to serve as a telescopically engageable lid or cover for open-sided carton containers of the type herein described. The terms carton, container and the like, as used in this specification, should be understood as being used interchangeably and collectively to identify both containers and/or covers. In this art, flat carton blanks are commonly identified by the initials or monogram, KDF, derived from the first letters of the words in the identifying phrase, “knocked down flat”. 
     KDF blanks characterized by pre-defined patterns of crease and/or fold lines that permit the blank to be bent and folded readily into a three-dimensional structure having the shape of a container with three or more upright sidewalls surrounding a base portion, have been known and used for many years. Such blanks frequently include various forms of tabs and flaps that can be brought into overlapping relationship and then secured together so as to retain the desired finished shape. In the prior art, the overlapping tabs and flaps of KDF blanks have been fastened together mechanically as by staples, and by applying liquid adhesives to one or both of two appropriate opposed abutting surface portions, and then allowing the adhesive to “set” so as to assure that the surfaces are attached to each other. Proper application of the adhesive, to assure both correct positioning of the adhesive on the respective overlapping portions, and controlled application of the proper quantity of adhesive for proper fastening strength, is a difficult and labor-intensive process that cannot be performed readily or conveniently in the field. 
     As an alternative to field assembly, it is known that KDF blanks can be formed and then assembled in a manufacturing plant under carefully controlled conditions, so that completely formed and assembled containers and mating covers can be shipped to end users in finished form, ready to be used without further handling other than packing and closing. However, this method of selling and distributing containers for goods has the serious disadvantage of adding substantial expense to the final cost of the finished product, because the containers generally cannot be nested or otherwise compressed in volume for shipping. As a direct result of the difference between the volume occupied by a stack containing a given number of container blanks and the volume occupied by an equal number of assembled containers, shipping costs for a given quantity of assembled containers are substantially higher than for the same quantity of blanks. 
     Another problem represented by the prior art technology of KDF containers relates to storage and handling of the flat blanks from which containers are formed. It is common in this art to print information and/or designs on the side of the KDF blank that will form the outer surface of the assembled container. The characteristics of the printing materials, such as inks, that are widely used for this purpose are such that the blanks tend to stick to each other when they are stacked in tiered relationship after they have been printed. Separating stored blanks that have become stuck together often requires additional time and effort in handling, and the separation process may result in the loss of any number of blanks due to damage caused by adhesion, all of which can add significant cost to the final product. 
     Still further, and independently of the adhesion caused by the printing materials, it is known that the accumulated weight of a stack of tiered blanks can cause compression that is sufficient to exclude all or substantially all of the air from between the abutting surfaces of adjacent blanks; exclusion of air in this manner can result in the formation of a vacuum that has the effect of sealing of adjacent, abutting blanks to each other. A vacuum formed in this manner can have the effect of slowing the processing of individual blanks because of the time and significant effort that may be required to “break” the vacuum so that adjoining blanks can be separated from each other. 
     Although clinging together of adjacent blanks caused either by printing materials or by vacuum sealing usually can be overcome by manual handling of the blanks, the required time and labor tend to add significant cost to the final product. Any increase in cost, however slight, can have a serious adverse effect on the success of a product in an industry such as this, where cost is a particularly important element of commercial success. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of this invention to provide an improved container blank that can be shipped as a blank singly or in stacked bundles and can be assembled easily, conveniently and accurately in the field. 
     It is another object of this invention to provide a container blank that can be fastened together easily in final form without requiring the use of mechanical fasteners or handling of liquid adhesives. 
     It is still another object of this invention to provide a KDF container blank that can be separated easily and conveniently when blanks are stored in closely packed stacked relationship. 
     These and other and further objects, features and advantages of this invention will be made apparent to those having skill in this art by reference to the following specification in the context of the accompanying drawings, in which: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a plan view of a first embodiment of a blank in accordance with this invention; 
     FIG. 2 is a partial pictorial representation of a partially assembled container formed from the blank of FIG. 1; 
     FIG. 3 is a partial side elevation detail view illustrating how blanks constructed in accordance with this invention interact in a stacked array; 
     FIG. 4 is a partial plan view of a second embodiment of a blank in accordance with this invention; 
     FIG. 5 is a partial pictorial representation of a partially assembled container formed from the blank of FIG.  4 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now more specifically to the drawings, FIG. 1 may be seen to represent a blank  10  of predetermined shape, having a plurality of fold lines  12  formed on its surface  14  in a predetermined pattern. Fold lines  12  are formed in any known manner so as to allow the parts of blank  10  that are adjacent to the lines to fold or bend in a generally upward direction relative to the central planar portion  16  of blank  10 . As will be made evident by the following description, when blank  10  has been bent and folded into its fully assembled position, surface  14  of the blank will correspond generally to the inner surface of the assembled container, while the opposite side (not shown) of blank  10  will correspond to the outer surface of the container. Central planar portion  16  can be considered to remain generally in or parallel to the plane of the drawing, while the various parts of the blank, to be described below, are folded upwardly relative to portion  16 . 
     At the spaced-apart opposite edges  18  of the blank  10 , the predetermined shape of the blank includes a pair of spaced-apart slits  20  that extend inwardly from each of edges  18  to define a central tab or flap  22  and a pair of spaced apart tabs or flaps  42 ,  42  extending in a generally longitudinal direction on either side of central tab  22 . Each one of central flaps  22 , at each end of blank  10 , includes a transversely extending fold line  26  that divides the flap substantially in half, into sub-portions  22 A and  22 B. In FIG. 1, fold line  26  on one of flaps  22  is shown hidden by a cover element  30  in accordance with this invention. 
     Cover element  30 , in accordance with this invention is a strip of non-stick material such as polypropylene coated paper having an exposed non-stick surface thereon. In this preferred embodiment of the invention, cover element  30  is secured to blank  10  by a strippable adhesive interposed between one surface of cover element  30  and the opposed, abutting surface of blank  10 . The characteristics of the adhesive are such that cover  30  may be stripped away after the adhesive has been adhered to the underlying surface of blank  10 , thereby exposing a tacky surface  32  of the adhesive, while the adhesive remains adhered to the underlying surface of blank  10 . 
     In FIG. 2, the exposed surface  32  of the adhesive, with cover strip  30  removed, is illustrated as a shaded area on the surface of one of central flap member  22 , but it should be understood that both of flap portions  22  will have a similarly disposed adhesive surfaces thereon. A suitable adhesive for the purposes of this invention is a high-tack synthetic rubber-based material having a holding force when adhered to carton stock, of approximately 130 oz/in 2 . The holding force between the surface of the adhesive and the surface of the strippable cover strip  30  is substantially less than the holding force between the adhesive and the carton stock, to assure that the strip  30  will separate readily from the adhesive while the adhesive remains adhered to the carton stock surface of the blank. Such an adhesive is available in strip form together with a suitable coated paper backing from the 3M Company, as adhesive product No. 475. 
     In accordance with this invention, the non-stick strip  30  serves two purposes: (1) when the strip is removed to expose the underlying adhesive  32 , the adhesive is available to fasten together any overlapping portion of the blank which is deliberately brought into contact with it; and (2) before the strip is removed, and while the blank to which it is attached remains in closely abutting relationship with adjoining blanks in a stack, the strip serves as a non-stick interface between the inner surface  14  of one blank and the opposite surface (not shown) of an adjoining blank in a stack. 
     Referring again to FIGS. 1 and 2 of the drawings, it can now be seen that flaps  22  can be folded back upon themselves along fold line  26 , so that the exposed surface  32  of the adhesive will secure the two portions of the flap  22 A and  22 B together in overlapping, abutting relationship. As shown clearly in FIG. 2, blank  10  is assembled into a three-dimensional five-sided container shape, having a base surrounded by four upstanding sidewalls, by bending or folding the spaced apart longitudinal side rail portions  40  upwardly at right angles to central body portion  16  of blank  10 , and bending tabs  42  at each end of rails  40  at right angles to the rails. Flaps  22  similarly are folded upwardly relative to central body portion  16 , so that flaps  42  may be brought into overlapping, abutting relationship with the inner surface of flaps  22 . These parts are dimensioned relative to each other so that fold lines  26  on flaps  22  coincide generally with the outer edge  44  of each of flaps  42  when the flaps are brought together in overlapping relationship; the adhesive surface  32  covering part of innermost flap portion  22 B serves to retain flap  42  conveniently in position relative to flap  22 , while final assembly of the blank is being completed. Final assembly of the blank begins in effect when each one of rails  40  and flaps  22  has been folded into upright relationship relative to central portion  16  of blank  10  and each one of flaps  42  has been brought into overlapping abutting relationship with the inner surface of flaps  22 . Final assembly is completed by folding flap portion  22 B over and against the corresponding flap portion  22 A, thereby capturing flap portions  42  in fixed position sandwiched between flap portions  22 A and  22 B of one or more capturing flaps  22 . The adhesive on the inner surface of flap portion  22 A, positioned along the outermost edge  18  of that flap portion, acts to secure it firmly to the abutting surface of flap portion  22 B, to complete the “sandwich” and to assure that flaps  42  remain captured between the overlapping abutting parts of flap  22 . 
     Accordingly, flaps  22  may be designated the capturing flaps, while flaps  42  may be designated, correspondingly, the captured flaps. Flaps  42  are further secured in position by contact with any adhesive on flap  22 B. Depending upon the desired final shape of the container, any number of captured flaps may be used in combination with any number of capturing flaps to complete the assembly, in accordance with this invention. 
     Although the predetermined shape of blank  10  in this preferred embodiment is shown to include slits  20  which help to define flaps  42 , it will be apparent to those skilled in this art that other forms of blank shapes, such as those having “bellows” form corner flap structures, may be adapted readily to incorporate the features of the invention herein disclosed. 
     FIGS. 4 and 5 illustrate an embodiment of this invention in the form of a carton blank  110  incorporating a bellows corner construction for coupling a pair of longitudinal side rails  140  to a capturing flap  122  having a first portion  122 B and a second portion  122 A that is foldable over the first portion in the same manner as portions  22 B and  22 A, shown in the embodiment of FIGS. 1 and 2. The two side rails  140  and capturing flap  122 , will together, define three upright side walls around base portion  116  of blank  110 , to form part of a container or a container cover in accordance with this invention. The bellows corner construction incorporates a bellows corner flap  142  having first and second captured flap portions  142 A and  142 B that are integrally connected to each other along fold line  143 , and are also integrally connected, one to the end of side rail  140  along fold line  145  in the manner of captured flaps  42  shown in FIGS. 1 and 2, and the other to capturing flap  122  along fold line  147 . That is, in this embodiment, flap  142  includes first and second fold lines  145  and  147  that intersect each other at an angle and a third fold line  143  that extends from the intersection of fold lines  145 ,  147  at an angle that substantially bisects the angle defined by lines  145  and  147 , so that flap portions  142 A and  142 B can be folded back upon each other to bring lines  145  and  147  into substantially parallel adjacent relationship to define an upright corner of the desired container shape. It will be understood readily that each of these first, second and third fold lines comprises part of the overall pattern of fold lines that forms part of blank  110 . 
     A principal difference between the corner construction illustrated in the embodiment of FIGS. 1 and 2 and the bellows corner construction illustrated here, in FIGS. 4 and 5, resides in the existence of integrally connected captured flap element  142 B. Those having skill in this art will recognize that a principal advantage of the bellows corner construction, shown in the process of assembly in FIG. 5, is that the integral coupling of captured flap element  142 B to capturing flap  122 , avoids the exposure of a cut edge of carton stock material at the corner that is formed by capturing flap portion  122 B and the end of side rail  140  when the carton blank is fully assembled in carton shape. Instead of a cut edge, capturing flap portion  122 B exposes the folded-over edge where captured flap element  142 B is integrally joined to capturing flap portion  122 B. The resulting corners formed by sandwiching captured flap elements  142 A and  142 B between the adhered-together first and second capturing flap portions  122 A and  122 B, are substantially the same as the corners described above with reference to FIGS. 1 and 2, except that two layers of carton stock, representing flap elements  142 A and  142 B are captured between capturing flap portions  122 A and  122 B at the end of each side rail  140 , instead of just one layer, representing captured flap  42  alone, as in the embodiment of FIGS. 1 and 2. 
     As illustrated in FIG. 3, the edge  38  of each non-stick strip  30  creates a slight discontinuity on the inner surface of each blank arrayed in a stack, due to the finite thickness of the strip, which may be on the order of 9 mils. The irregularity creates a small void or air passage  50  between any two closely abutted surfaces of adjoining blanks in the vicinity of the edge of the strip, so as to help break any vacuum formed therebetween, and to facilitate separation of the adjoining blanks. Similarly, the non-stick characteristics of strip  30  effectively preclude adhesion of adjoining blanks in the surface area covered by the strip, thereby further facilitating convenient separation of adjoining blanks by the simple expedient of, for example, manually prying the two blanks apart in the immediate vicinity of the non stick strips. Although other areas of the stacked blanks may nevertheless stick together, areas such as these adjacent to two spaced apart edges of the blank, where adhesion is precluded effectively, provide an efficient and effective mechanism for facilitating separation of clinging/adhering blanks. It has been found that the total surface area of the adhesive used in accordance with this invention, which is substantially the same as the total surface area of the non-stick strip covering the adhesive, desirably will be within the range of between 2% and 30% of the total surface area of the blank, and preferably within the range of 2% and 15%. 
     The specification and drawings herein set forth clearly and fully describe preferred embodiments of this invention, but it should be readily apparent to those having skill in this art that other forms, embodiments and variations thereof may be conceived and constructed without departing from the spirit and scope of the following claims.