Corrugated Box Flap Locking Feature for Produce and the Like

This invention relates to containers made of corrugated paperboard, and more particularly to a container which is easily formed from a blank and has a locking bottom.

Paperboard cartons come in a wide variety of structures to enable them to carry heavy loads. To facilitate shipping, the containers are formed from blanks which are then formed into containers on site. Prior art blanks had a solid bottom These blanks, however, are costly and the industry is switching to blanks having side and end walls and a locking bottom formed from flaps which are hingedly connected to the side and end walls.

Booth U.S. Pat. No. 4,821,949 discloses a container blank for forming a container wherein flap locking slits are formed at the ends of a major flap. U.S. Pat. No. 4,650,112 shows earlier technology. The locking slits of Booth include a first portion and a second portion which together define a flap retaining segment and an angular slit extending angularly from the end of the second portion to provide flexibility to the flap retaining segment. Although the angular slit may provide flexibility to the flap retaining segment, it does not aid in the insertion of the flap into the flap retaining segment such as by opening the flap retaining segment. Also, the patent to Peeples U.S. Pat. No. 4,279,377, shows early related structure.

One object is to provide a paperboard blank for forming a paperboard container, wherein a tab receiving slit or slot is opened upon folding of a flap along its hingeline to facilitate insertion of a tab of a second flap therein.

Another object is to provide such a container having new shapes for tab receiving slits or slots to facilitate the folding of the container.

These and other objects will become apparent to those skilled in the art in light of the foregoing description and drawings.

In accordance with the invention, generally stated, there is provided a blank for forming a carton with a locking bottom closure. The blank includes portions for forming a pair of opposing end walls, portions for forming a pair of opposing side walls, a major closure flap hingedly connected to each side wall portion, and a minor closure flap connected to each end wall portion. The major closure flap has a fixed end hingedly adjacent the side wall portion, a free end remote from the fixed end, and tab means at said free end. The minor closure flap has tab receiving means formed at a variety of unique shapes, for receiving the major closure flap tab means. A hinge line between said end wall portion and the minor closure flap hingedly connects the minor closure flap to the end wall portion. The hinge line includes means for opening the tab receiving means to facilitate insertion of said tab means in said tab receiving means. The opening means preferably includes parallel fold lines which are angularly offset from the hinge line and which intersect or extend to the tab receiving means.

FIG. 1 is a fragmentary plan view of a blank of the present invention;

FIG. 2 is a perspective view of the blank of FIG. 1 being folded into a container;

FIG. 3 is a fragmentary plan view of an alternative construction of a minor flap of the present invention; and

FIGS. 4-15 show various modifications that can be made to a slit or slot which receives a tab of the minor flap to lock the container bottom.

Referring generally to FIGS. 1 and 2, there is shown a paperboard blank 1 used for forming an open topped container. Blank 1 includes portions 3 which form end walls 5 of a container 7 and portions 9 which form side walls 11 of container 7. Portions 3 and 9 are separated by hinge lines 13 which allow the portions 3 and 9 to be folded to form walls 5 and 11.

A minor closure flap 15 having a free end 17 and a fixed end 19 is connected to portion 3 at a hingeline 21. Similarly a major closure flap 23 having a free end 25 and a fixed end 27 is connected to the side portions 9 by a hinge line 29. Hinge lines 21 and 29 allow the major and minor closure flaps to fold upon themselves to form the bottom of container 7.

Minor flap 15 includes tabs 31 and 33 at opposite ends of its free end 17. A tab 35 may be left between tabs 31 and 33 or, a cutout 37 having diagonal sides 39 may be formed intermediate tabs 31 (FIG. 3). Or, the cut out may be of rectangular or other shape. The fixed and free ends, 17 and 19, of minor closure flap 15 are separated by a fold line 41.

Major flaps 23 include a T-shaped slit 43 having a vertical portion 45 which extends vertically or inwardly from hinge line 29 and a horizontal slit 47 which crosses slit 45. T-shaped slit 43 receives tab 31 so that flaps 15 and 23 may be interlocked to form a strong, secure bottom to container 7. When forming the bottom of container 7, hingeline 41 allows minor closure flap 15 to bend, thereby facilitating insertion of tab 31 in slit 43.

Hingeline 29 includes parallel diagonally offset compound fold lines 49 and 51 which intersects slit 45. Fold lines 49 and 51 diverge from hinge 29 so that they are spaced apart when they intersect vertical slit 45. When major portion 23 is folded over to form the bottom of container 7, the fold lines 49 and 51 cause the slit 45 to separate creating a small spaced opening 52 with one segment of the portion raised above the other, into which tab 31 can be inserted with facility. Fold lines 49 and 51 thus accommodate entry of tab 31 into slit 43.

As can be seen in FIGS. 5-15, the shape of the tab receiving means 43 may be varied. The vertical slit 45 may be formed as a diagonal slit 45a (FIGS. 4, 8, and 12); it may be formed as a vertical slot 45c (FIGS. 5, 9 and 13); or it may be formed as a diagonal or other slot 45b (FIGS. 6, 10, 14 and 15). Slit 47 may be formed as an opening 47a (FIGS. 7-10) so that tab receiving means 43 resembles a musical note, or it may be formed as an ovoid opening 47b (FIGS. 11-14) which crosses slit 45 or 45a or slot 45b or 45c, so that the tab receiving means 43 somewhat resembles a child's drawing of a tree.

Numerous variations within the scope of the appended claims will be apparent to those skilled in the art in light of the foregoing description and accompanying drawings. For example, a second set of flaps could be added to the side end walls to form a top such closure for the container. This example is merely illustrative.