GB2105308A - Interlocking connections for container wall - Google Patents

Abstract

Adjacent walls (2, 3) of an open-topped container made from a unitary blank of double-faced corrugated board with the elongate direction of the flutes (A) running away from the base panel (1) in one wall (2), are locked together by a tab (5) of one wall (1) engaging in an opening (8, 9) in the other wall (2). The tab (5) has a curved upper portion which abuts over a region (x) against a similarly curved portion (9) of the opening. <IMAGE>

Description

SPECIFICATION Improvements in or relating to a packaging container This invention relates to a blank for a packaging container, e.g. a meat container, made of double-faced corrugated board. The invention also relates to a container erected from such a blank.

It is known to provide users of packaging containers with a pre-cut, pre-creased blank from which the container can be erected manually without the use of auxiliary fixing means (e.g. glue or staples). To achieve a secure container after such an erection procedure, it is necessary to provide means to interlock adjacent wall panels of the blank and various proposals have been made for the design of locking tabs and the apertures to receive the tabs, so that a secure packaging container will inevitably result.

A secure lock is more difficult to achieve in the case of blanks made from double-faced corrugated board, because of the presence of the flutes which gives the blank different mechanical properties in the elongate direction of the flutes and normal thereto.

This invention employs an improved form of interlocking means for adjacent wall panels of a blank for a packaging container made of double-faced corrugated board which overcomes the problems posed by the differential strength properties of the board in the said two directions.

According to one aspect of the invention a blank for a container made of double-faced corrugated board comprises a substantially rectangular base panel, a pair of first side wall panels hingedly connected to the base panel along a pair of opposed first edges of the latter which extend at least substantially parallel to the elongate direction of the flutes of the corrugated board, a pair of second side wall panels hingedly connected to the base panel along a pair of opposed second side edges of the latter, a pair of spaced apart openings formed in each second side wall panel, one end of each opening terminating short of the hinged connection of the associated second side wall panel with the base panel, and a locking tab hingedly connected to each end of each first side wall panel, the four locking tabs being arranged, when the container is erected, to pass through, so as to be releasably interlockable with, respective ones of the four openings, wherein a portion of each said opening, adjacent its other end, is smoothly curved to turn from a direction towards the said hinged connection of the respective second side wall panel with the base panel to a direction away from the locking tab destined to interlock therein, the locking tab being provided with an edge portion curved to correspond with said curved portion of the respective opening, whereby on inserting a locking tab in its respective opening on erection of the blank, a region of said curved edge portion of the tab bears against a region of said second side wall panel exposed by said curved portion of the respective opening.

Because the elongate direction of the flutes in any given tab and the respective second side wall in which it is locked, run at right angles to one another when the container is erected, said regions of the edge portion of each tab and the second side wall against which it bears will be inclined to the elongate direction of the flutes (typically each will be inclined at 45 thereto) and a secure lock will result. The provision of curved surfaces to define these interlocking regions permits each tab to "bed" into its locking opening to optimise the locking strength and it is immaterial precisely where the flutes lie relative to the opening or an edge of the tab.

Preferably each of the said openings consists of an elongate slot extending towards the base panel from the end of the said smoothly curved portion which is closest to the base panel, the slot facilitating the insertion of the tab through the opening during erection. Conveniently, the smoothly curved portion of each opening turns through 90" and the curved edge portion of the tab turns through somewhat less than 90"C.

Suitably the blank is coated, on at least its side which is intended to provide the inside of the erected container, with a material, e.g. a plastics material, which prevents , or at least deters, adhesion of frozen wet products to the inside of a container erected from the blank.

Conveniently, each locking tab is provided with a hinge line extending substantially normal to the elongate direction of the flutes, so that a distal end portion of the tab can be folded outwardly back against the remainder of the tab, prior to insertion of each tab in its respective opening, the foided-back portion of the tab then being sandwiched between the remainder of the tab and the side wall panel.

Folding each tab back on itself, in this way, can enhance the security of the lock and reduce the possibility of moisture seeping into the flutes.

According to another aspect of the invention there is provided a container erected from a blank according to said one aspect of the invention.

Conveniently such a container is provided with a lid which is suitably formed from a unitary blank of stiff, yet foldable sheet material e.g. double-faced corrugated board, preferably coated with material to prevent or deter the adhesion of frozen wet products to the lid formed from the unitary blank. The lid can be of the type which has walls that slide over the outside of the side wall panels of the container and has a top panel which serves to close the container.

The invention will now be described, by way of example, with reference to the accom panying drawings, in which: Figure 1 is a plan of one corner of an unfolded blank provided with fold and cut lines for making a rectangular container, and Figure 2 is a perspective view of one corner of the blank shown in Fig. 1 after its erection into a container.

Fig. 1 shows one corner of a blank for a raw meat container made of double-faced cor rugated board with the flutes of the corru gated board running in the direction of the arrows A. In Fig. 1 the dashed lines represent fold lines (all foldable in the same direction i.e. upwardly out of the plane of the drawing) and the solid lines within the area of the blank represent cut lines which pass completely through the blank.

Only one corner of the blank is shown in Fig. 1 but the other three corners are similar.

The full blank comprises a rectangular base panel 1, two side wall panels 2 (delimited from the base panel 1 by fold lines 2' extend ing normal to the elongate direction of the flutes) and two end wall panels 3 (delimited from the base panel 1 by fold lines 3' extend ing parallel to the elongate direction of the flutes). Each end of each wall panel 3 is extended by a flap 4 (delimited from the rest of the end wall panel by a fold 4') which terminates in a locking tab 5. An upper edge 6 of each tab 5 has a smoothly curved shape as shown. The lower edge of the tab 5 includes a substantially straight section and is defined in part by a recess 7.

Adjacent each end of each side wall panel 2 is an opening which comprises a slot 8 and an arcuate slit 9. The slit 9 turns approximately 90 and has a radius of curvature which closely corresponds to that of the proximal portion of upper edge 6 of the tab 5.

When the blank is to be erected into a container, the wall panels 2 are turned up through 90 from the plane of the base panel 1 about the respective fold line 2' and each wall panel 3 is, in turn, turned up about the respective fold line 3' with the two flaps 4 attached to the wall panel disposed at right angles thereto. During this operation each flap 4 is brought outside the respective adjacent wall panel 2 and the lower edge of each tab 5 is made to enter the respective slot 8. Completion of the turning up of the wall panels 3 causes each tab to fully enter its respective opening 8, 9 and to lie wholly inside the wall panel 2.This operation brings the upper edge 6 of each tab 5 into close proximity with the cut edge of the wall panel 2 formed by the curved slit 9 and over a region (marked x in Fig. 2) these edges are free to abut one another and lock the wall panels 2 and 3 together at each corner of the container so formed.

Because of the curved form of the abutting edges over this region x, a firm lock is provided since over this region the edges run transverse to the elongate direction (A) of the flutes. The precise location and length of the region x fill vary from sample to sample, but secure lock will be formed in each case.

Fig. 1 shows a chain line 10 on the tab 5 and this indicates the location of a deeply indented crease (e.g. a hinge fold known in the trade as a "Matrix bend") which readily permits the distal end 5a of the tab beyond the line 10 to be folded back to underlie the rest of the tab.

Providing such a crease has been found to be advantageous in the case where the container is destined to be used with raw meat and that face of the blank defining the inside of the container is provided with a moistureresistant coating.

The distal end 5a of each tab is folded-back about the line 10 prior to the insertion of the tab in its opening 8, 9, and then trapped between the side wall panel 2 and the proximal part of the tab 5. The folded-back end 5a encourages even more secure locking and the now folded end of the tab which is exposed to the contents of the container reduces the risk of seepage of moisture from the container contents into the flutes of the tab thus affording greater long-term strength.

The container described would normally be used with a lid also formed from a unitary blank of stiff, yet foldable sheet material, which lid has walls that slide over the outside of the side wall panels of the container and has a top panel which serves to close the container. The lid can also be made of double-faced corrugated board and can also be coated on its inside with moisture-resistant material.

Claims (8)

1. A blank for a container made of doublefaced corrugated board comprising a substantially rectangular base panel, a pair of first side wall panels hingedly connected to the base panel along a pair of opposed first edges of the latter which extend at least substantially parallel to the elongate direction of the flutes of the corrugated board, a pair of second side wall panels hingedly connected to the base panel along a pair of opposed second side edges of the latter, a pair of spaced apart openings formed in each second side wall panel, one end of each opening terminating short of the hinged connection of the associated second side wall panel with the base panel, and a locking tab hingedly connected to each end of each first side wall panel, the four locking tabs being arranged, when the container is erected, to pass through, so as to be releasably interlockable with, respective ones of the four openings, wherein a portion of each said opening, adjacent its other end, is smoothly curved to turn from a direction towards the said hinged connection of the respective second side wall panel with the base panel to a direction away from the locking tab destined to interlock therein, the locking tab being provided with an edge portion curved to correspond with said curved portion of the respective opening, whereby on inserting a locking tab in its respective opening on erection of the blank, a region of said curved edge portion of the tab bears against a region of said second side wall panel exposed by said curved portion of the respective opening.

2. A blank as claimed in claim 1, in which each of the said openings consists of an elongate slot extending towards the base panel from the end of the said smoothly curved portion which is closest to the base panel, the slot facilitating the insertion of the tab through the opening during erection.

3. A blank as claimed in claim 1 or claim 2, in which the smoothly curved portion of each opening turns through 90".

4. A blank as claimed in any preceding claim, in which the blank is coated, on at least its side which is intended to provide the inside of the erected container, with a material, which at least deters adhesion of frozen wet products to the inside of a container erected from the blank.

5. A blank as claimed in any preceding claim, in which each locking tab is provided with a hinge line extending substantially normal to the elongate direction of the flutes, so that a distal end portion of the tab can be folded outwardly back against the remainder of the tab, prior to insertion of each tab in its respective opening, the folded-back portion of the tab then being sandwiched between the remainder of the tab and the side wall panel.

6. A blank substantially as hereinbefore described with reference to, and as illustrated in part in Fig. 1 of the accompanying drawings.

7. A container erected from a blank as claimed in any preceding claim.

8. A container as claimed in claim 7 provided with a lid also formed from a unitary blank of stiff, yet foldable sheet material, which lid has walls that slide over the outside of the side wall panels of the container and has a top panel which serves to close the container.