Foldable Footwear and Soles for Foldable Footwear 5 Field of the Invention The invention relates to foldable footwear, soles for foldable footwear and particularly, but not exclusively, to footwear that can be folded for packaging in a format suitable for sale from vending machines. 10 Summary of the Invention The invention provides a sole for foldable footwear, said sole having a plurality of defined fold lines arranged such that the sole can be folded so as to have a folded length that is less than its unfolded length, wherein the fold lines extend in a widthways direction of the sole and are inclined with respect to a notional line that 15 bisects said sole in a lengthways direction thereof and there is a said fold line that is inclined from an instep side of the sole towards a toe end of the sole and a said fold line that is inclined from said instep side towards a heel end of the sole. The invention also includes a method of folding a foldable shoe, the foldable shoe 20 having a sole having a plurality of defined fold lines and the method comprising folding the shoe along the fold lines such that the shoe has a folded length that is less than its unfolded length by applying oppositely directed twisting forces to a toe end region and heel end region of the shoe. 25 Brief Description of the Drawings In order that the invention may be well understood, some embodiments thereof, which are given by way of example only, will now be described with reference to the drawings in which: 30 Figure 1 is a plan view of the underside of a sole for foldable footwear; Figure 2 is a side elevation of the sole of Figure 1; 1 Figure 3 is an exploded perspective view of a foldable shoe comprising the sole of Figure 1; Figure 4 is a perspective view showing the foldable shoe of Figure 3 in a folded 5 condition; Figure 5 is a perspective view showing another foldable shoe; and Figure 6 is a schematic perspective view of a package for the foldable shoes of 10 Figures 3 and 5, with the package shown in an open condition. Detailed Description of the Illustrated Embodiments Referring to Figures 1 and 2, a sole 10 for foldable footwear comprises a generally planar moulding having a toe end 12, a heel end 14, an instep side 16 and an outer 15 side 18 that is opposite the instep side. The sole 10 has an upper surface 20 and an underside 22 that in use faces the ground. The underside 22 is provided with a plurality of ground engaging projections in the form of respective sets of ribs 24-32. The sets of ribs 24-32 are separated by spaces that define respective fold lines 34-40 along which the sole 10 can be folded. 20 As can be seen in Figure 1, the fold lines 34-40 extend in a widthways direction of the sole 10 and are inclined with respect to a notional lengthways extending line 42 that bisects the sole in the lengthways direction. The fold lines 34, 38 are inclined from the instep side 16 of the sole towards the toe end 12 and the fold lines 36, 40 are 25 inclined from the instep side towards the heel end 14. It will be noted that the direction of inclination of the fold lines 34-40 alternates. The first two sets of ribs 24, 26 starting at the toe end 12 and the set of ribs 32 at the heel end 14 extend in the lengthways direction of the sole generally parallel to the line 30 42. The two sets of ribs 28, 30 between the lengthways extending sets are inclined with respect to the line 42 from the instep side 16 towards the toe end 12. The arrangement of the sets of ribs 24-32 and fold lines 34-40 is such that when the sole 10 is folded, the sets of ribs on portions of the sole that face one another can mesh (ie the ribs on one of two facing portions enter the spaces between the ribs on the other of 2 the two facing portions). This meshing arrangement minimises the thickness of the folded sole. Referring to Figure 3, a foldable shoe 50 comprises the foldable sole 10, a set of 5 stiffening members in the form of shims 52-60 that lie on the upper surface 22 of the sole and a cushion (or insole) 62, which lies on top of the shims to complete the foot supporting portion of the shoe. The shims 52-60 are shaped to fit over the ribbed areas of the sole 10 and leave gaps between corresponding to the fold lines 34-40. Thus the configuration of the shims 52-60 is such as to maintain the foldababilty of 10 the shoe 50. The sole 10, shims 52-60 and insole 62 are attached by any suitable means such as by the use of adhesives. The foldable shoe 50 further comprises a two-part upper made up of a front upper 64 and a rear upper 66. A hook 68 is provided in the rear upper 66. The front and rear 15 uppers 64, 66 are made of a fabric so as to be lightweight and flexible and are secured to the assembly of the sole 10, shims 52-60 and insole 62 by any suitable conventional means such as adhesives and/or stitching. In the illustrated arrangement, the lower edges 70 of the front and rear uppers 64, 66 are secured between the sole 10 and insole 62 by means of a suitable adhesive. If the shoe 50 is intended for indoor use, 20 for example as a slipper, and particularly where it is intended for one-off use, the upper may simply be a lightweight fabric. Where the shoe 50 is intended for outdoor use, the material used may be a waterproof, or waterproofed, material intended to make the shoe at least capable of withstanding light rainfall or exposure to similar levels of moisture. 25 The hook 68 comprises a length of suitable cord that runs within seams (not shown) that run along the inside of the upper edge 72 of the rear upper 66 and has respective ends that are trapped between the sole 10 and insole 62. 30 In order to fold the shoe 50 to achieve the folded condition shown in Figure 4, the user first folds the shoe along the fold line 36 in the direction of the heel end 14 to bring the rib set 26 into meshing contact with the rib set 28. The shoe is then folded along the fold line 40 to bring the rib set 32 into mesh with the rib set 30. The shoe is then folded along the fold line 38 to move the rear upper 66 into engagement with the 3 rearward end of the front upper 64. The folding process is completed by folding the shoe along the fold line 34 such as to fold the toe end of the front upper back towards the rearward end of the front upper. Once the folding process is complete, the shoe 50 has a generally triangular configuration as shown in Figure 4. The folded length of 5 the shoe 50 is approximately 40% of its unfolded length. It should be noted that the order of folding described above does not represent the only way in which the foldable shoe 50 can be folded to achieve the folded shape shown in Figure 4. For example, the foldable shoe 50 could be folded first along fold 10 line 40, followed by folding along the fold line 36. Regardless of whether the first fold is made along fold line 36 or fold line 40 first, the second fold could be along fold line 38. The particular order of folding is less important that the folds are made in the correct direction. In the illustrated arrangement, the shoe 50 is alternately folded in opposite directions at successive fold lines 34-40. 15 Referring to Figure 5, another foldable shoe 100 has a foldable sole 110 that has a toe end 112, heel end 114, instep side 116 and an outer side 118 opposite the instep side. In the same way as the foldable sole 10, the foldable sole 110 has five sets of ground engaging ribs 124-132, which are spaced to define four fold lines 134-140. The fold 20 lines 134-140 extend in the widthways direction of the shoe 100 and are inclined in the same way as the fold lines 34-40 of the shoe 10. In the same way as the shoe 50, the shoe 100 has shims and an insole (not show) and a front upper 164 and a rear upper 166. 25 The difference between the shoe 100 and the shoe 10 is that the foldable sole 110 is moulded in a contoured mould so that it has a normally non-planar partially folded shape as shown in Figure 5. The shoe 100 and, in particular the foldable sole 110, can be moved to a use position in which it has substantially no folds. This is most readily achieved by the user inserting his/her feet into the shoe. The shoe 100 and sole 110 30 can also be folded into the triangular shape shown in Figure 4. Essentially, the same folds are made as previously described for the sole 10. However, because the sole 110 is made such that once removed from a wearer's foot it relaxes to a partially folded condition, the user does not have to remember the folding sequence. Instead, he/she simply completes the folding process by twisting the shoe 100 as indicated by 4 the arrows in Figure 5. It is not necessary to make the folds one after the other. The user simply grips the shoe in the region of the toe end 112 and twists clockwise (as viewed in the drawing) while simultaneously gripping the heel end 114 and twisting anticlockwise. It will be noted that as with the sole 10, the sole 110 is alternately 5 folded in opposite directions at successive folds 134-140. When the soles 50, 100 are folded, they have a generally triangular outline with approximately equi-length sides. Referring to Figure 6, a triangular package 150 for a pair of the shoes 50 or shoes 100 comprises two triangular receptacles in the form of 10 pockets 152, 154 connected by a hinge 156, which is optionally made of an elastomer. The package 150 is shown in an open condition in which the respective entrances 158 to the pockets 152, 154 (only one of which is visible in the drawing) can be accessed to allow the shoes to be inserted in or removed from the pockets. 15 The package 150 is closed by bringing the two pockets 152, 154 together by folding the package about a notional axis 160 that runs generally parallel to the base sides of the pockets 152, 154 in which the entrances 158 are defined. The direction of folding is indicated by the arrows 162. The two pockets 152, 154 can be secured together by an elasticated loop (not shown) that is fixed to one of the pockets or by any other 20 suitable fastening arrangement. For example, a hook and eye fastening arrangement could be used. The hook and eye fastening arrangement may comprise Velcro @ pads provided on the faces of the pockets 152, 154 that are brought together when the package 150 is closed. A suitable location for such pads is shown by dashed lines 164. 25 The package 150 may be made of any suitable packaging material and could, for example, be made of cardboard printed with information relating to the shoe size and/or folding instructions. 30 The relatively small size of the packaged shoes 50, 100 makes them particularly suitable for sale from vending machines, which might, for example, be provided in hotels or clubs, or at transport locations such as airports. The small packaged size makes it possible to provide a reasonable range of sizes of shoe in a relatively compact vending machine. 5 The foldable sole is typically a one-piece moulding and can be made of any suitable natural or synthetic polymer. 5 It will be appreciated that it is not essential to have four fold lines as in the embodiments. A smaller number may be provided. This would reduce the extent to which the length of the sole could be reduced by folding, but should result in a thinner folded shoe. Alternatively, a greater number of folds could be provided. This allows the possibility of an increase in the extent to which the length of the sole is reduced by 10 folding, but with an increased complexity in the folding arrangement and a potentially thicker folded shoe. It will be appreciated that the fold lines do not have to be in the form of spaces separating sets of ribs as in the embodiments. A foldable sole could instead comprise 15 a generally smooth or dimpled ground engaging surface with fold lines defined as grooves in the ground engaging surface. It will be understood that while it is preferable that the foldable sole has a substantially constant thickness throughout its length, the portion between the heel 20 end and the fold line closest to the heel end could be of increased thickness to define a raised heel. It will be appreciated that the sole of the foldable shoe does not have to be a one-piece moulding as illustrated in the drawings. Instead, a series of pads corresponding, for 25 example, in shape to the shims could be secured to the underside of a relatively soft material with spaces provided to define fold lines corresponding to the illustrated fold lines or any other suitable arrangement. It will be understood that while the upper of the foldable shoes conveniently 30 comprises two parts as illustrated in the drawings, that is not essential. The upper could be a one-piece construction with, for example, an overall shape similar to that of the illustrated two-part upper. Alternatively, the shoe may have an upper just at the toe end, in which case, the upper may have a shape similar to the illustrated front upper 66. Yet another alternative would be to have a system of strapping providing a 6 sandal type structure. Such strapping might take the form of an elasticated band at the toe end of the shoe or one, or more, releasable straps that are securable, for example, by a hook and eye type fastener such as Velcro @. 5 It will be appreciated that while the foldable shoe is particularly suitable for packaging and sale in a folded condition, this is not essential. It could be sold unfolded. This would still give the purchaser the benefit of a shoe that could be conveniently folded when required. 7