Fastening mechanism for a carton

1. A locking device for locking first and second panels together, the locking device comprising a first part and a second part, the first part comprising an edge flap hingedly connected to the first panel along a first fold line and an aperture defined at least in the edge flap by a cutline which is tiered in shape, the cutline including a first cutline section and a pair of second cutline sections, the first cutline section defining a recess portion of the aperture, the second cutline sections being disposed on opposite sides of the recess portion and defining engaging portions of the edge flap, the second cutline sections being disposed closer to the first fold line than the first cutline section, the second part comprising a projection extending to a second fold line from a free edge of the second panel and a foldable tab hingedly connected to the projection along the second fold line, the foldable tab having a free end edge opposing the second fold line, the free end edge being stepped in shape and including a first step portion and a pair of second step portions, the first step portion defining a tongue of the foldable tab, the second step portions being disposed on opposite sides of the tongue and defining shoulders of the foldable tab, the second step portions being disposed closer to the second fold line than the first step portion, the foldable tab being folded about the second fold line to take a folded position, the second part being received in the aperture with the foldable tab in the folded position, the second part assumes a locking position when in the aperture in which the tongue of the foldable tab is received at least in part in the recess portion of the aperture to cause the shoulders of the foldable tab to engage with the engaging portions of the edge flap.

2. The locking device according to claim 1 , wherein the first fold line is interrupted by the cutline, the first cutline section of the cutline is offset with respect to the first fold line so as to prevent the foldable tab from unfolding, the first cutline section being provided by the edge flap.

3. The locking device according to claim 1 , wherein the second part, when the foldable tab is in the folded position, is tapered so as to be narrower at the leading edge thereof.

4. The locking device according to claim 1 , wherein the cutline defines, at least in part, a protrusion which overlaps at least partially with the second panel when the second part is in the locked position.

5. The locking device according to claim 4 , wherein the protrusion is struck from the edge flap such that the recess portion is defined in the edge flap.

6. The locking device according to claim 1 , wherein the shoulders comprise engaging edges spaced apart from the second fold line.

7. The locking device according to claim 1 , wherein the projection of the second part is received at least in part in the aperture when the second part is in the locking position.

8. The locking device according to claim 1 , wherein the second cutline section defining the second tier portion is disposed at an angle with respect to the first fold line such that one end of the second cutline section that is spaced apart from the first cutline section is disposed closer to the first fold line than the other end of the second cutline section that is next to the first cutline section.

9. The locking device according to claim 1 , wherein the second fold line defines a leading edge of the second part when the foldable tab is in the folded position, and wherein the second part is received with the leading edge first in the aperture.

10. The locking device according to claim 1 , wherein in the folded position, the foldable tab overlaps with the second panel such that a first distance is defined between the free edge of the second panel and the first step portion of the free end edge of the foldable tab, wherein a second distance is defined between the first fold line and the first cutline section of the cutline, and wherein the first distance is greater than second distance such that foldable tab cannot pass entirely through the aperture when the second part is in the locking position.

11. A carton comprising a first panel, second panel and a locking device for locking the first and second panels together, the locking device comprising a first part and a second part, the first part comprising an edge flap hingedly connected to the first panel along a first fold line and an aperture defined at least in the edge flap by a cutline which is tiered in shape, the cutline including a first cutline section and a pair of second cutline sections, the first cutline section defining a recess portion of the aperture, the second cutline sections being disposed on opposite sides of the recess portion and defining engaging portions of the edge flap, the second cutline sections being disposed closer to the first fold line than the first cutline section, the second part comprising a projection extending to a second fold line from a free edge of the second panel and a foldable tab hingedly connected to the projection along the second fold line, the foldable tab having a free end edge opposing the second fold line, the free end edge being stepped in shape and including a first step portion and a pair of second step portions, the first step portion defining a tongue of the foldable tab, the second step portions being disposed on opposite sides of the tongue and defining shoulders of the foldable tab, the second step portions being disposed closer to the second fold line than the first step portion, the foldable tab being folded about the second fold line to take a folded position, the second part being received in the aperture with the foldable tab in the folded position, the second part assumes a locking position when in the aperture in which the tongue of the foldable tab is received at least in part in the recess portion of the aperture to cause the shoulders of the foldable tab to engage with the engaging portions of the edge flap.

12. The carton according to claim 11 , wherein the shoulders comprise engaging edges spaced apart from the second fold line.

13. The carton according to claim 11 , wherein the projection of the second part is received at least in part in the aperture when the second part is in the locking position.

14. The carton according to claim 11 , wherein in the folded position, the foldable tab overlaps with the second panel such that a first distance is defined between the free edge of the second panel and the first step portion of the free end edge of the foldable tab, wherein a second distance is defined between the first fold line and the first cutline section of the cutline, and wherein the first distance is greater than second distance such that foldable tab cannot pass entirely through the aperture even when the second part is in the locking position.