The object of the present invention is a leakproof and liquid-tight packaging box as defined in the preamble of claim 1 .

Numerous different packagings are known in the packaging sector, which have been developed for differing needs. The construction of packaging is primarily determined by the intended use, but other aspects related to the manufacture and use of a packaging must also be taken into account in the design of the packaging. The corner structures in packagings, particularly those that must be liquid-tight and leakproof, are in most cases a problematic point.

For example, liquid-tight and leakproof packagings that can be stacked one on top of another are needed in the food industry for packing meat and fish. Moreover, the packagings of meat and fish must be made of hygienic materials, i.e. the material must be approved for coming into contact with fatty food. In addition to this, boxes for meat and fish must be very firm, because there can be up to 20 kg of weight in one packaging and boxes are generally stacked one on top of another generally 10 layers high. As a consequence of this, another substantial problem has been the structural rigidity of the packagings and their stacking strength.

According to what is known in the art, leakproof packagings fabricated from expanded polystyrene or plastic pressed into shape, fillable from above and stackable one on top of another have often been used for preserving and transporting meat. Such boxes require a large storage space before they are taken into use, and in consequence this incurs unnecessary costs. Also their disposal after use is problematic. Additionally, the materials used in manufacturing them are not renewable, so from an environmental perspective use of the packagings described above is not ecological.

Also known in the art are liquid-tight packagings fabricated from corrugated board, and one such solution is disclosed in utility model Fl 10658. A solution provided with a corner bellows, which is per se known in the art, is used in the aforementioned publication. The structure has a leakproof corner with integrated lid flaps in such a way that the stacking planes of the end lock into the counterslots of the top edge of the leakproof corners. One shortcoming of the structure is the uncertainty of the locking under stress. There is not sufficient friction in the flap coming between stacking planes nor does the flap have the necessary locking to bind the structure; this is particularly true in corrugated board with a slippery PET coating.

A substantial shortcoming of the solution is the liquid-tight corner structure in the right-angle of the end. The corner tries to loosen when erected, because there are a number of board layers in the end. Owing to the aforementioned structure, they function like a spring in the corner, trying to push the box outwards from the corners. Since the flaps coming between the stacking planes do not have proper locking, this results in the bulging of the corner and even in stress endeavoring to open the structure.

For the reason presented above, a substantial problem of corrugated board boxes with liquid-tight corners and provided with corner bellows has been that with heavy box weights the end of the box bulges outwards. As a consequence of this, when another box is stacked upon it, it tries to press inside the box below it. In some liquid-tight corner solutions the long sides are locked with cardboard slips between the end fold; the solution does not, however, provide sufficiently tight locking for the long sides and consequently the loose structure lessens the load-bearing capability.

Leakproof solutions fabricated from corrugated board that are fillable from above and are also better at keeping their shape have also been used for preserving and transporting foodstuffs with liquid content, but in these the stacking planes of the top parts are mechanically glued. This is a substantial drawback, because it requires a separate and expensive packaging machine. At the point where packagings are manufactured, their cost-efficiency is essential and from the structural viewpoint the functional joining and fastening of the parts of packagings is extremely important.

The aim of the present invention is to achieve a solution by means of which the drawbacks of prior art are avoided. With the solution according to the invention a fully liquid-tight and leakproof packaging box can be realized. That being the case, the structure of the packaging according to the invention remains liquid- tight also when heavily packed. In addition, the packaging retains its shape essentially unchanged, even though a number of layers are stacked one on top of another on top of it.

The invention relates to corrugated board packagings, and blanks thereof, to be formed mechanically or manually without adhesive, that are tight against liquid and leaks from inside and also tight against damp and liquid from outside. The packagings are stackable one on top of another; they do not have lid flaps detrimental to packing but instead have short stacking shoulders.

More precisely, the invention is characterized by what is presented in the claims.

In the following, the invention will be described in more detail by the aid of an embodiment with reference to the attached drawings, wherein

Fig. 1 presents a packaging box blank according to the invention.

Fig. 2 presents an erected packaging box according to the invention.

Fig. 3 presents a blank of a corner part of a packaging box.

Fig. 4 presents a blank of a corner part of a packaging box.

Fig. 5 presents a corner part of a packaging box when erected.

The packaging box according to the invention is a one-piece leakproof and liquid-tight packaging box fabricated from corrugated board to be formed mechanically or manually without adhesive. According to Figs. 1 and 2, the box has a base surface 1 , a folding surface 2 of the long sides, a vertical surface 3 of the short side, a stacking plane 4 of the short side, an underside 5 of the stacking plane of the short side, and also corner bellows 6 and 7 for achieving a liquid-tight corner structure. According to Fig. 1 , with these a packaging according to Fig. 2, formed without adhesive mechanically or manually, is obtained from one die-cut blank, in which packaging the surfaces 2, 3, 4, 5, 6, 7 form a liquid-tight and leakproof structure. The corner bellows 6 and 7 fold against each other onto the inside surface of the vertical surface 3 owing to the inclined fold 18.

The inclined conical fold 21 between the folding surface 2 and the corner bellows 7 is essential to the invention; this fold improves the rigidity of the end of the liquid-tight packaging box. The box becomes liquid-tight and leakproof when the crease 22 between the base surface 1 and the vertical surface 3 is folded together with conical fold 21 between the folding surface 2 and the corner bellows 7 and the bottom crease 20 of the long sides. The angle X between the conical fold 21 and the inclined fold 18 is in the range 45-50°, most preferably 47° Correspondingly, the angle Y between the conical fold 21 and the vertical fold 24 of the vertical surface 3 is in the range 90-100°, most preferably 94°.

The inner end A of the inclined folding line of the conical fold 21 connects with the straight crease 22 between the base surface 1 and the vertical surface 3. The inclination of the folding line of the conical fold 21 at the outer end B is 5-20 mm with respect to the crease 22. In this way the end face is formed in the vertical direction into a cone shape sloping to inside the box, in which case the top part of the box is shorter in terms of the length of the box than the length of the base part.

More precisely, in such a way that the inner end A of the inclined folding line of the conical fold 21 refers to the inner corner nearest the base surface 1 . The aforementioned corner connects at the junction point the straight crease 22 between the base surface 1 and the vertical surface 3 of a short side and the straight base crease 20 between the base surface 2 and the vertical surface 2 of a longer side. The outer end B of the inclined folding line of the conical fold 21 refers to the junction point of the long sides 2 farther from the base surface 1 , the second folding lines 19 and the outer end B of the conical fold 21 . The conical fold 21 between the inner end A and the outer end B is folded into an inclination sloping inwards in the direction of the long sides 2 of the box in such a way that the inclination of the folding line of the conical fold 21 at the outer end B is, according to what is specified above, 5-20 mm more inward with respect to the crease 22 of the end A.

In this way a liquid-tight packaging box is obtained in which the folding line of the conical fold 21 is inclined with respect to the crease 22 between the base surface 1 and the vertical surface 3. It is essential to the invention that, by means of the folding line of the conical fold 21 , the end face is formed into a cone shape sloping in the vertical direction in such a way that the top part of the box is shorter than the bottom part of the box in the direction of the long sides 2. Fig. 2 presents a liquid-tight packaging box when it has been erected. In this way the vertical surface 3 of a short side of the packaging box is formed to be deflecting at a slope into the box, becoming essentially conical, by means of the inclined conical fold 21 between the folding surface 2 of the long sides of the box and the second corner bellows 7. In this way the structure is more durable when stacking boxes one on top of another. The cone structure being connected to the liquid-tight corner structure helps to keep the ends more tightly together after erection compared to the structure in a right-angle, because the conicity tightens structure so that it is taut.

In addition to an inclined conical fold 21 into the packaging box, the hook locks 9 that are on a horizontal plane with regard to the base surface 1 are also essential to the invention. That being the case, the packaging box blank comprises second folding surfaces 19 of the long sides and horizontal hook locks 9 functioning as a locking means formed on the outer edges of said surfaces and a double crease 16 of a short side as well as locking slots 1 1.

A liquid-tight packaging box according to the invention can, if necessary, be implemented without hook locks 9, but by far the best end result is achieved with a combination of a conical fold 21 and hook locks 9. According to Figs. 1 -5, in the invention there are second folding surfaces 19 of the long sides, these folding surfaces having hook locks 9 on the horizontal plane that come between the double crease 16 of the end and lock into the locking slots 1 1 . The locking is ensured when the hook locks come through the locking slots 1 1 to outside the box. They ensure that the structure holds together under stress. Moreover, hook locks 9 in the horizontal direction of the packaging box keep the slope of the vertical surface 3 of the short side locked at the angle set by the conical fold 21 when locking the short side into the locking slots 1 1 .

In addition to what is presented above, friction tongues functioning as brake shoes 12 of the corners ensure that the structure does not open into the inside of the box; they lock the double-folded shoulder 10 between the sides 4 and 5. In this way the liquid-tight packaging box locks finally when the crease 17 between the end sides 3 and 4 is folded and the tongues 13 are pushed into the slot 23 formed by the cuts. The tongues also allow the shaping of them into protrusions e.g. for making the carrying and handling of the box easier. The cut- to-shape sides 8 of the long sides are also essential to the invention, the cut-to- shape sides stiffening the structure of the long side already in the filling stage of the box and nevertheless allowing easy filling of the box. Additionally, a shaped tongue 15 is formed on the double-folded shoulder 10, the tongue allowing e.g. the fastening of a separate layer and the keeping of that layer in position on the packaging box.

According to Figs. 1 -5, when fully erected the vertical surfaces 3 of the short sides together with the conical folds 21 form an inward conical structure. When stacking liquid-tight packaging boxes one on top of another, the conical structure of the vertical surfaces 3 is manifestly more durable than a structure at a right angle representing the state of the art. The conicity according to the invention tightens the structure so that it is taut, then the cone structure being connected to the liquid-tight corner structure keeps the ends more tightly together after erection. The best result is achieved when the locking is ensured by means of hook locks 9 on a horizontal plane with respect to the plane of the base surface 1 locking into the locking slots 1 1 .

It is obvious to the person skilled in the art that the invention is not limited to the embodiments presented above, but that it can be varied within the scope of the claims presented below.