This invention relates to a container of foldable laminar material, such as cardboard, particularly, though not exclusively, for frozen food products. The invention also relates to blanks for such containers.
According to the invention, in a first aspect thereof, in a primary laminar container blank a plurality of mutually parallel first fold lines and a plurality of second fold lines transverse to the said first fold lines are so arranged that, when the blank is folded along a first selection of said fold lines in a first manner, it defines a container having a bulk capacity of a first predetermined volume and, when folded along a second selection of said fold lines in a second manner, it defines an open, tray-like container having a bulk capacity of a second predetermined volume larger than the said first volume.
By "primary blank" is meant a blank in the substantially flat, unfolded form in which it would normally be punched or cut of a strip or sheet of the laminar material.
According to the invention, in a second aspect thereof, in a secondary blank a first part of a primary blank according to the said first aspect of the invention is folded back on to a second part thereof about a said second fold line and a third part of the said primary blank is likewise folded back on to the said second part thereof about a said second fold line, the said first and third parts being secured to the said second part of the primary blank, the arangement being such that the said second fold lines about which the said first and third parts are folded define edges of the container.
By "secondary blank" is meant a blank in which a said primary blank has been folded, or folded and glued or otherwise processed ready for erection of the container.
According to the invention, in a third aspect thereof, in a container a secondary blank according to the said second aspect of the invention is erected by folding it into a three-dimensional configuration about the said fold lines.
When erected by folding a said secondary blank in the said first manner, the container is preferably closed on all sides and may, for example, be sealable or sealed.
The invention also includes within its scope a container constructed in accordance with the said third aspect of the invention and charged with goods, for example, frozen bulk food products such as dough or frozen products in the form of a plurality of articles such as fish.
One form of container embodying the invention, in the form of a carton intended as packaging for a frozen food product which, depending on ambient or other conditions may occupy different bulk volumes, for example frozen dough, will now be described, by way of example, with reference to the accompanying drawings in which:
FIG. 1 shows a primary blank for the container;
FIG. 2 shows a secondary blank made from the primary blank of FIG. 1;
FIG. 3 shows a perspective view of the container erected by folding the secondary blank in the said first manner; and
FIG. 4 shows a perspective view of the container erected by folding the secondary blank in the said second manner.
Referring to FIG. 1, the blank is made of cardboard, glazed and/or printed on one side (viz. the side which is to define the outside of the container or carton) and has a thickness conventional for containers of this kind. Typically the overall length L of the blank is approximately 28 cm and the overall width W 30 cm.
It has a plurality of (in the Example five) mutually parallel and equidistantly spaced first fold lines 1 to 5 and a plurality of second fold lines transverse to the said first fold lines, of which two such second fold lines 6, 7 are perpendicular to the said first fold line, six such second fold lines 8 to 13 are disposed at 45.degree. to the fold lines 1 to 7 and two further fold lines 14, 15 are disposed symmetrically about the longitudinal centre line of the blank at an angle of less than 45.degree. to the first fold line 3.
As can be seen in FIG. 3, when the blank is folded along a selection of said fold lines in a particular manner, it defines a closed container having a rectilinear top and base and rectilinear sides and ends.
As will be seen from FIG. 4, when the blank is folded along a different selection of said fold lines, i.e. in a different manner, it defines an open, ray-like container having a rectilinear base and rectilinear sides and ends and a bulk capacity of a volume larger than (in the Example twice) that of the carton shown in FIG. 3.
By the fold lines the blank is thus divided up into a plurality of rectilinear panels, such as the rectangular panels 20 and the square panel 21 and also a plurality of triangular or substantially triangular panels such as the substantially triangular panels 16 and the triangular panels 17A and 17B.
In use, the carton is sold to the consumer in a minimum-volume folded-up condition in which it is fully occupied by frozen unrisen dough. In this condition the carton, as shown in FIG. 3, is erected in the said first manner in which the point A is brought on to the point B at each and of the carton, by infolding the two triangular panels, each of which is internally subdivided by the fold line 14 or the fold line 15, as appropriate, to form the panel 17A and the panel 17B; as a whole against the adjacent triangular panels 17C. Portions 3' of the fold line 3 adjacent the panels 17B are then adjacent portions 6' 7' of the fold lines 6, 7 respectively. In addition the triangular panels 16 are caused to be infolded against the adjacent rectangular panels 20. The fold lines 1 and 5 are therefore brought together and the two terminal panels referenced respectively 18 and 19 are brought into face-to-face contact.
The consumer buys the carton with the terminal panels 18, 19 secured together by glueing or the like. For use, he tears off the panels 18, 19 (for which purpose at least one of the fold lines 1, 5 is provided with a configuration (e.g. indentations) to cause it to be weakened). Thereby the carton can be opened out in tray-like form to assume the configuration shown in FIG. 4, by flexing along the central fold line 3. In order to permit this opening-out, the triangular panels 17A, 17B are not secured in any way to the adjacent panels, whereas the panels 16 are secured, e.g. by glueing or corner locks, to the panels 20 at the stage when the secondary blank shown in FIG. 2 is formed.
The carton illustrated has, in the configuration shown in FIG. 4 twice the bulk capacity which it has in the configuration shown in FIG. 3, this ratio being approximately that of the volume of the dough between its risen and unrisen conditions. Thus, when the consumer has opened out the carton into its FIG. 4 configuration and left it in a warm room for a few hours, the dough rises and approximately fills the carton, without spilling out over the carton sides. After the dough has risen, the consumer puts the carton in the oven, and cooks the dough in the normal way. During cooking little or no further rising of the dough occurs.
If the carton is used for other frozen products, e.g. fish, it will be sold, charged with the product concerned, in its tray-like configuration (FIG. 4) and with a suitable top closure. When the consumer has removed the top closure and reduced its contents to less than half, he may convert the carton to its FIG. 3 configuration for the purpose of saving space in a freezer or refrigerator.
In a modification of the blank shown in FIGS. 1 and 2, one of the terminal panels 18 or 19 is omitted. In the FIG. 3 configuration of a carton erected from such a modified blank, the remaining terminal panel 18 or 19 is tucked inside the carton and contiguous to the panel 20 which is opposite the said terminal panel 18 or 19, or the carton is made re-closable by means of the said terminal panel in some other way. In the application of the carton to frozen dough as aforesaid, the single terminal panel may be overlapped and glued to the opposing panel 20.
It will be appreciated that the laminar material may be any material suitable for the particular one of the large variety of purposes for which the container embodying the invention may be used. Thus, it need not necessarily be cardboard or it may, for example, be cardboard lined on one and/or the other side (viz. the inside and/or the outside of the container) with a suitable lining material such as polypropylene or metal (e.g. aluminium) foil.
Where a food product intended to be baked in the carton, such as the frozen dough hereinbefore mentioned is intended to be baked in an over whilst in the container at, for example, a temperature of 350.degree. F, it is desirable to provide a said lining of polypropylene or metal (e.g. aluminium) foil for the inside of the continer so as to endow it with "non-stick" properties and, if desired, such a lining may also be provided on the outside of the container, for example in order to render the container more heat resistant and therefore less liable to discolouration or charring when exposed to an excessive oven temperature.
Moreover, if the container is intended to be in the form of a carton charged with a product in the tray-like configuration of the carton for subsequent conversion to its other configuration, as aforesaid, and not intended to be exposed to oven heat, the laminar material may be in the form of cardboard whose surface has not been treated in any way, or its surface may be waxed or otherwise treated or lined with polythene or any other suitable lining material.