Flip-lid cartons having a latching means to latch the carton lid in a closed position are known but such cartons require special machinery, which is of course expensive, in order to form and fill the carton starting from a carton blank. Because the lid is formed by the machinery after the filling operation it is not possible to make the carton tamper evident and as a consequence it is necessary to overwrap the carton in situations where a tamper evident feature is required. The overwrapping is an additional and obviously undesirable operation.

An alternative form of flip-lid carton is tamper evident in that it has membranes or the like extending between the lid and body of the carton which must be severed in order to open the lid in the first instance. However, such cartons are not provided with a latch between the lid and body because it has not been possible with existing carton constructions to construct, assemble and fill cartons having both a latch and tamper evident membrane, using existing machinery.

Accordingly it is an object of this invention to provide a flip-lid carton with latch and with an inherent tamper evident feature, which carton is readily filled and assembled using existing machinery.

A further object is to provide a method of constructing a flip-lid carton with latch and with an inherent tamper evident feature, using existing machinery.

Thus the invention provides a flip-lid carton having a latching means between a body of the carton and the lid, to latch the lid in a closed condition after each use, characterised in that, said latching means comprises a latching flap, and a protrusion which is engaged by the flap, the latching means being on

said body and the protrusion being on said lid, or vice versa and at least one connecting membrane extending between said lid and said body prior to initial opening of the carton to provide a tamper evident flip-lid, said membrane being broken upon initial opening of the carton.

In another form of the invention there is provided a method of constructing a flip-lid carton having latching means between a body of the carton and the lid, said method including the steps of i) manufacturing a carton blank having an additional flap in the form of a converter flap extending from an edge of a front wall part of the blank, said front wall part including part of said flip-lid, said converter flap having a catch member portion defined in said converter flap by a series of die-cuts whereby, said catch member may be separated from said converter flap, and a latch member portion defined in said converter flap by at least one fold line; ii) folding part of said converter flap back on itself such that said catch member portion and said latch member portion are within the folded part; iii) applying glue to the outwardly directed side of said catch member portion and folding said converter flap back on said front wall part whereby said catch member portion becomes attached to said flip-lid and separated from said converter flap on first opening of an assembled carton, and said latch member portion depends from the body of the carton on the inside of said front wall for engagement with said catch member portion when the carton is closed; (iv) providing one or more thin membranes extending between said body and said lid; and (v) assembling the carton either by hand or using existing assembly machinery.

In order that the invention may be more readily understood a particular embodiment will now be described with reference to the accompanying drawings wherein;

FIGURE 1 is a plan view of a carton blank according to the invention; FIGURE 2 is similar to FIGURE 1 but shows the blank after the first step in the construction procedure has been performed ; FIGURE 3 shows the blank after the next construction step; FIGURE 4 shows the blank after a further construction step which completes construction of a converter flap of the carton; FIGURES 5-7 inclusive show the carton after successive further assembly steps which correspond to the procedure for assembling existing cartons; FIGURE 8 is a front perspective view of the carton of FIGURE 7 assembled and ready for receiving contents to be packaged therein; FIGURE 9 is a perspective front view of the carton in a closed condition before initial opening; and FIGURE 10 shows the carton of FIGURE 9 with the lid partially opened.

In the drawings the thicker lines represent cuts where the material of the blank (cardboard or other suitable material) is cut through and the thinner lines represent crease lines where the material is folded or adapted for folding, in order to assemble the carton. Referring to FIGURE 1 a carton blank 10 in the form of a reverse tuck, straight line glued carton having an additional flap 11 referred to as a converter flap, is shown. The converter flap 11 facilitates construction of a carton according to the invention.

In FIGURE 1 the portion of the blank above the cuts 12 and the fold line 13 comprises the lid of the carton, the panel 14 represents the back of the carton body (inside surface shown) and the panel 15 is the front of the carton body (inside surface shown). The sides of the carton body are represented by the

panels 16 and 17, respectively. With the exception of the converter flap 11 the remaining panels represent the base-of the carton. Specifically panel 18 is the main base panel and has tongue 19 which is folded during assembly on fold line 20 and tucks into the base of the carton in a conventional reverse tuck construction. Side flaps 21 and 22 (referred to in the industry as dust flaps) fold inwardly on fold lines 23 and 24, respectively, to complete the base construction.

The flip-lid of the carton consists of front panel 25 side panels 26 and 27 and rear panel 28 which, when assembled form the vertical parts of the flip-lid.

In use the lid pivots on fold line 13 in order to open and close the lid. The top of the lid is similar to the base of the carton and consists of a conventional reverse tuck construction comprising main top panel 29 having tongue 30 which is folded during assembly on fold line 31 and tucks into the top of the lid. Side flaps 32 and 33 fold inwardly on fold lines 34 and 35 respectively, to complete the lid construction.

It should be noted that cut-line 12 is interrupted to provide membranes 31 which join the sides 16 and 17 to the side panels 26 and 27, respectively.

Finally, wing flaps 36 and 37 (referred to in the industry as glue flaps) are glued, during the carton construction, to the side panel 17 of the body, and side panel 27 of the lid, respectively, in order to form the carton.

Turning now to the converter flap 11 it will be seen to extend from the bottom edge of the front panel 15 and is joined thereto by fold line 38. The converter flap 11 has tapered portion 39 and a fold line 40 which enables the end portion (beyond the fold line 40) to be folded back on to the flap during the carton construction process (as will become apparent hereinbelow). A cut line 41 extends across the flap 11 and is parallel to and spaced a short distance from said fold line 40 to define a latching flap 42 therebetween. A further cut line 43 extends across the flap 11 parallel to the line 41 and a catch member 44 is defined between the two cut lines. Each of the cut lines 41 and 43 is interrupted

to form joining membranes 45 which become fractured during first opening of the carton as will become apparent hereinbelow. The free end of the converter flap 11 is a panel 46 which is used for assembly purposes and serves no significant purpose after assembly of the carton. In an alternative embodiment (not shown) the panel 46 is eliminated entirely and the cut-line 43 defines the edge of flap 11.

Having described the carton blank the steps involved in constructing, assembling and filling a carton using the blank, will now be described.

In the first construction step two glue strips 47 and 48 are applied to the panel 46 as shown in FIGURE 2. The panel 46 is then folded back on the main part of the converter flap 11 by folding along the fold line 40 whereby the panel 46 becomes glued to the main part of the converter flap 11. In the alternative embodiment the first step in constructing the carton is to fold on line 40 and the next step is to apply a glue strip on the back of panel 11, parallel and above the edge 43, and glue strip 50 to the catch member 44. This step creates a seal inside the front of the carton which must be ruptured during first opening of the carton, as will become apparent hereinbelow. This step also creates an internal mechanism for latching and releasing the flip lid.

The next step (FIGURE 3) is to apply two further glue strips 49 and 50 to the catch member 44 and the panel 46, respectively, on the outwardly directed sides thereof after the initial folding operation. The converter panel is then folded on fold line 38 and assumes the position shown in FIGURE 4 whereby the catch member 44 becomes attached to the panel 25 (inside of the front panel 25 of the flip lid) and panel 46 becomes glued to the panel 15 (inside front panel of carton body). This completes the assembly of the converter flap 11, and the carton blank, insofar as its perimeter construction is concerned, resembles a standard reverse tuck straight-line glued carton. In other words, from this point in the assembly and filling process, the carton may be treated as a standard carton for the purposes of completing the assembly and filling processes.

More specifically, the blank 10 is folded on fold line 51 and glue strips 52 and 53 are applied to the wing flaps 36 and 37 as shown in FIGURE 5.

Folding on fold lines 50,54 attaches the wing flaps 36 and 37 to the panels 17 and 27, respectively. The glue strips 52,53 attach to the panels 17,27 as shown by the shaded lines. At this point the body of the carton is formed into a flattened open-ended tube.

The next step is to apply a glue strip 55 to the flap 22 and fold the carton blank along fold lines 23,24 and 59. These last described steps, that is, formation of the base, is performed by the customer prior to filling the carton with contents. In other words, the cartons are delivered to the customer in a flat form as shown in FIGURE 6 without the glue strip 55 and the steps thereafter are performed by the customer. The customer has an option to make the carton a tamper evident carton by gluing the side flaps 21,22 and 32,33 in order to seal the carton ends. Once the glue strip 55 (and a similar glue strip on flap 21) is applied and the carton is folded on fold lines 23,24 and 59 to seal the base of the carton, the contents are placed in the carton through the top of the carton as shown by the arrow 56 in FIGURE 7. Glue strip 58 is then applied to the side flap 33 (and a similar glue strip on flap 32) and the top of the carton is closed in a similar manner to the closure of the bottom. The glue strips ensure that the top of the carton is permanently sealed.

FIGURE 8 shows a front view of the carton during the filling step and prior to sealing of the top.

FIGURE 9 shows the front of the carton after the contents have been placed therein and the top flaps have been closed and sealed. Broken lines 59 define a circle which may, if so desired, be printed on the front of the carton to indicate to the user that a force is required on the front of the carton in order to severe the membranes 31 at the front of the carton. By pressing on the area indicated by the circle 59, the membranes are broken at least across the front of the carton and those at the side will be broken on first opening of the lid. The

catch member 44 becomes separated from the converter flap 11 upon first opening of the lid and remains glued to the inside front portion of the flip lid 25.

The converter flap 11 with latching flap 42 is fixed to the inside front of the body portion of the carton and is folded forward as is shown in FIGURE 10.

FIGURE 10 shows the carton after initial opening which breaks the tamper evident membranes 31 on either side of the carton to allow the lid to be opened. As will be evident, the latching flap 42 engages over the catch member 44 on the inside of the lid 25 when the carton is closed, in order to provide a catch which prevents inadvertent opening of the flip lid. Additional force is thereby required in order to open the flip lid by causing disengagement between the catch member 44 and latching flap 42.

It should be apparent from the above that the present invention provides an improved carton which has a flip lid whilst at the same time having a conventional reverse tuck base and lid construction. It will be evident to those skilled in the art that the reverse tuck construction could be replaced by skillet ends at the top and bottom of the carton. Since the carton is a straight-line glued carton and since it may have either a reverse tuck or skillet end, conventional carton assembly and filling equipment can be used for the purpose of assembly and filling of the carton. Therefore, the customer does not need to replace expensive equipment in order to utilise the cartons according to the present invention.

In a further modification (not shown) a second or auxiliary catch member may be provided between the flip lid and the body of the carton. For this purpose the flip lid has a downwardly extending tongue at the front centre thereof which is accommodated in a corresponding cut-out in the front panel 15 of the carton. Since the converter flap 11 extends on the inside of the front panel 15, a slot is cut through the converter flap to coincide with a catch member on the tongue of the flip lid. This provides a secondary catch which acts in addition to the catch member 44 and latching flap 42.

Whilst the invention described in the above embodiment is directed to straight-line glued cartons it must be appreciated that the invention may be adapted for use with other types of existing cartons besides straight-line glued cartons. Also, some cartons are constructed with a double panel front wall in which case the latching flap and protrusion are formed on the inner panel of the double panel which is effectively the converter flap 11 described in the above embodiment. The inner panel or converter flap may depend from the side of the carton blank rather than from the bottom as described above and it will be readily apparent to those skilled in the art that many variations to the described embodiments may be readily effected without departing from the scope of the invention. The critical factors are that the carton has a flip-lid with latch which is tamper evident and the carton blank is adapted for assembly and filling in existing machines with no modification.

It should be apparent that the carton of the present invention provides an improvement over existing cartons by providing a flip-lid construction with latching arrangement to prevent or reduce the likelihood of spurious opening of the carton after the initial seal is broken. It also provides optional tamper evident sealing of the carton which is particularly desirable in the packaging of foodstuffs, such as breakfast cereals, personal hygiene and powdered soap products, for example. All this is achieved without the need for the end user of the carton, that is, the assembly and packaging company, to replace existing assembly and packaging machinery.