0001 This invention relates to unitary-sheet articles. 0002 According to the present invention there is provided an article of unitary moulded-plastics sheet construction which is convertible between a three-dimensional erect state and a substantially-flat, folded state, the sheet incorporating a multiplicity of flexible membrane portions located between and integral with spaced parts of the sheet to define hinges for enabling those parts to be deflected angularly with respect to one another in conversion between the two states. 0003 The article of the invention when in the erect state may take the form of a container, for example a box (with or without a unitary lid) or a cup, carton or other vessel. The invention is in this respect of particular advantage in that the unitary, seamless nature of the container makes it very suitable on the one hand for containing liquids and other product, and on the other hand for keeping contained product (such as foodstuff or pharmaceutical product) sealed and free from contamination. However, the erect article may take any other form, fob example, that of an article of furniture, or of packaging. 0004 Each membrane portion of the article according to the invention may be defined by a channel in one of the two faces of the sheet leaving a thin web or membrane contiguous with the two parts of the sheet located either side of the channel, for hinging those two parts to one another. The flanks of the channel may be inclined away from one another outwardly of the channel, with the angle between them determining to a substantial extent the range of angular deflection required or possible of the hinge. If, for example, the angle between the flanks is substantially a right angle when the two parts located either side of the channel are coplanar, the angular range of hinging will in general be of the order of 270 degrees, some 90 degrees in the sense closing the channel from the coplanar condition and virtually 180 degrees in the opposite, opening-up sense, The folding of contiguous parts of the sheet flat onto one another is facilitated where the folding movement at the relevant membrane-channel hinge is in the opening-up sense; it may also be obtained, however, for the closing sense by extending the width of the membrane in the channel so as to form, in effect, a double hinge. 0005 The article in the erect state may form a container having at least four walls, and in which each of the walls is individually hinged to three said walls by respective membrane hinges. A container with just four walls each hinged to three others, is of triangular form with an open top. Five walls are required for a rectangular, open-top structure, a rectangular base and two pairs of opposite side-walls. In this case, the side-walls are hinged by respective membrane hinges to the base, and each of a first pair of the side-walls is similarly hinged to the two side-walls respectively of the second pairs. Each side-wall of the second pair may then incorporate a further respective membrane hinge to enable that side-wall to fold onto itself between the side-walls of the first pair in the folded state. Furthermore, the base may incorporate an elongate flexible-membrane portion that extends substantially parallel to the side-walls of the first pair, together with six membrane hinges extending from said elongate membrane portion, four to the four corners respectively of the base and two substantially-aligned with the flexible membrane portion in opposite directions from it.

0006 A foldable box in accordance with the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: 0007 FIG. 1 is a perspective view from below of the foldable box according to the present invention, in its three-dimensional erect state; 0008 FIG. 2 is a plan view of the box of FIG. 1 in one of two possible folded, flat states; 0009 FIG. 3 is illustrative of a membrane hinge typical of a multiplicity of such hinges of the box of FIG. 1 that enable it to be readily converted between its erect and folded states of FIGS. 1 and 2 respectively; 0010 FIG. 4 is a plan view from below of the box of FIG. 1; 0011 FIGS. 5 to 8 are sectional elevations to reduced scale of the box of FIG. 1 taken on the lines V-V, VI-VI, VII-VII and VIII-VIII respectively of FIG. 4; 0012 FIGS. 9 to 11 are views to enlarged scale showing details of regions of the box of FIG. 1, identified as IX, X and XI respectively in FIG. 8; and 0013 FIG. 12 is a perspective view of the box of FIG. 1 modified to include a lid, shown in its three-dimensional erect state.

0014 Referring to FIG. 1, the first box to be described, which is open-topped, has five substantially-flat walls, namely a pair of opposite side-walls 1, a pair of opposite side-walls 2 and a base 3. Each wall 1 is hinged to each wall 2, and all four walls 1 and 2 are individually hinged to the base 3, with the whole of the box, including the hinging, formed by a unitary, injection-moulded sheet of plastics (for example polypropylene). The box is foldable from the erect state in which the walls 1 and 2 are upstanding from the base 3, to a substantially-flat state illustrated in FIG. 2. In this latter state the base 3 and walls 2 are folded to bring the walls 1 flat onto one another with two halves of the walls 2 folded back to back between them. 0015 The folding of the box is enabled by the hinging of the walls 1 and 2 to the base 3, and also by hinging within the walls 2 and the base 3. The hinges involved are each, as illustrated in FIG. 3, defined on one face 10 (specific either to the inside or outside of the box) of the plastics sheet 11 by a channel 12 moulded in that face 10. A thin web or membrane 13 (for example, of 0.3 mm thickness) of the sheet 11 remains intermediate the inclined flanks 14 of the channel 12 to establish a flexible joint integrally with the two parts 15 of the sheet 11 on either side of the channel 12. When the hinge is fully open, that is to say when the parts 15 are coplanar as illustrated in FIG. 3, the flanks 14 are inclined away from one another outwardly of the channel 12 substantially at a right angle to one another. The two parts 15 can accordingly be folded inwardly towards one another closing up the channel 12 as indicated by the arrows A until the flanks 14 come into abutment with one another to limit the extent of turning to some 90 degrees, on the other hand, they can be folded in the opposite, opening-up sense indicated by the arrows B, through some 180 degrees to bring the parts 15 back to back. 0016 Referring again to FIGS. 1 and 2 and also to FIGS. 4 to 8, the side-walls 1 and 2 are integral with one another through membrane hinges 21, and each is integral with the base 3 through membrane hinges 22 and 23 respectively. The profiling of the hinges 21 to 23 is on the outside of the box in the sense that the channels forming them are on the outside (reference to the profile or profiling of a hinge being on the inside or outside refers to whether the channel corresponding to channel 12 of FIG. 3, is located inside or outside, respectively). Each wall 2 also has a membrane hinge 24 which divides the wall 2 into two half-lengths 2a and 2b, the hinge-profile in this case, in contrast to the profiling of the hinges 21 to 23, being on the inside of the box. A break 25 is provided in the outside-profiled hinge 23 halfway along each wall 2. This enables the two half-lengths 2a and 2b of the wall 2 to fold inwardly about the hinge 24, flat onto one another back to back (outside face to outside face) between the two sides 1 in the folded state of the box (FIG. 2). 0017 The base 3 has four membrane hinges 26 profiled on the outside that extend diagonally from the corners of the base 3 to a central, rectangular recess 27. The recess 27, which defines an elongate, double-width membrane-hinge profiled on the outside of the box, extends substantially parallel to the sides 1. Two membrane hinges 28 profiled inside the box extend substantially in alignment with the recess 27 to the hinges 24 respectively, so that two triangular parts 3a of the base 3 defined between each hinge 28 and its adjacent hinges 26, can fold inwardly onto one another back to back (outside face to outside face), The two parts 3a fold about their hinges 26 as the half-lengths 2a and 2b of the adjacent-wall 2 fold inwardly also. The remaining parts 3b of the base 3, each having the configuration of a regular trapezium (that is to say, a quadrilateral with opposite, unequal sides parallel and the other two sides equal), fold towards one another (inside face towards inside face) about the two membrane hinges 29 effectively defined along the longitudinal margins of the recess 27. 0018 The hinge-configuration of the base 3 allows it to fold in another mode from that described above and illustrated in FIG. 2. In this latter respect, folding of the base 3 may be inverted such that, rather than folding outwardly with the parts 3b outside the sides 1, it folds in a mode in which the hinges 26, 28 and 29 turn in the reverse senses to locate the parts 3b between the sides 1. 0019 The box is manufactured by injection moulding in the three-dimensional state. The injection gates are strategically located to ensure that the fronts of the injected material are hot when they meet so that there is good fusion between them. Once the three-dimensional article has been formed and has at least partially cooled, it is folded substantially flat for economic storage and transportation to an appropriate location for filling or other use. Here it is unfolded for erection into its three-dimensional state ready for use. If desired, it can be again folded flat after use, ready for subsequent erection and re-use. 0020 The box described above is open-topped but it may be modified to include a lid for closure, as illustrated in FIG. 12. In this case, the lid 31 is simply formed integrally with one of the sides 32 of the box, through a membrane hinge 33, and has a hinged-down rim 34.