STORAGE DEVICE AND METHOD FOR PRODUCING A STORAGE DEVICE Technical field The present disclosure relates to a storage device comprising a substantially rectangular sheet metal frame and a sheet metal component connected to at least two opposing sides of the frame such that it is suspended therefrom, wherein the sheet metal component is at least partially cut and expanded in an expansion direction such that a mesh material is formed. Such a storage device is described for instance in EP-1424287-A1 where a storage device in the form of a container is made from three mesh pieces, and a rail is fitted to the upper edges of the container to form a rim or frame. As illustrated, the rail may comprise an opening in which an edge of a mesh panel is inserted, and the rail may be compressed to pinch the mesh panel. One problem generally associated with storage devices of this kind is how to produce a storage device in an efficient manner which is still robust and user-friendly. Summary One object of the present disclosure is therefore to provide a storage device which allows for efficient production and is robust and user-friendly. This object is achieved by means of a storage device as defined in claim 1. More specifically, in a storage device of the initially mentioned kind, the frame has a cross section in the form of an inverted U, comprising an upper, substantially horizontal section, as well as inner and outer legs extending downwards from the horizontal section. The inner leg extends further downwards than does the outer leg, and the sheet metal component is connected to the outer side of the inner leg such that the edge of the sheet metal component becomes located above the lower end of the outer leg. Thanks to this frame cross section, which extends in two more or less perpendicular directions, the frame becomes very stiff, ensuring a sturdy storage device. At the same time, a suitable area for attaching the sheet metal component is provided at the outer side of the frame’s inner leg, and the upper edge of the sheet metal component is protected by the frame’s outer leg to avoid the end user’s fingers coming into contact with burrs or the like. This provides a storage device that can be produced in an efficient manner, is robust and user-friendly. The sheet metal component may be connected to the frame by means of a first spot- weld row at the upper edge of the sheet metal component. A second spot-weld row may be provided, to connect the sheet metal component to the frame, below the lower end of the outer leg. The substantially horizontal section may be in the range 10-14 mm wide, the inner leg may extend in the range 10-20 mm, and the outer leg may extend 3-6 mm. In one example, the storage device may be a shoe rack shelf. In another example, the storage device may be a mesh container. In this case the substantially horizontal section may be in the range 10-14 mm, the inner leg in the range 13-22 mm, and the outer leg in the range 3-6 mm. The inner leg may form an angle φ in the range 90-110° with the horizontal section. The outer leg may be bent inwards forming a lower horizontal section which is shorter than the horizontal section connecting the inner and outer legs. Generally, the width of the substantially horizontal section may be 10-14 mm, measured between the outer surfaces of the downward extending legs. The present disclosure also considers a method for producing a storage device com- prising a substantially rectangular sheet metal frame and a sheet metal component, connected to at least two opposing sides of the frame such that it is suspended therefrom, wherein the sheet metal component is at least partially cut and expanded in an expansion direction such that a mesh material is formed. The frame is formed to have a cross section in the form of an inverted U, comprising an upper, substan- tially horizontal section, as well as inner and outer legs extending downwards from the horizontal section, wherein the inner leg extends further downwards than the outer leg. The sheet metal component is connected to the outer side of the inner leg such that the upper edge of the sheet metal component becomes located above the lower end of the outer leg. Brief description of the drawings Fig 1 illustrates a storage device in the form of a shoe rack shelf according to the present disclosure. Fig 2 shows a top view of the storage device in fig 1. Fig 3 shows the cross section A-A of fig 2. Fig 4 illustrates isolated the sheet metal portion of the storage device in fig 1. Fig 5 shows the frame of the storage device in fig 1. Fig 6 illustrates a first example of a cross section through the frame of fig 5. Fig 7 shows enlarged the detail B in the cross section of fig 3. Fig 8 illustrates a storage device according to the present disclosure in the form of a mesh container. Fig 9 illustrates a detail of a mesh material. Fig 10 illustrates an alternative second example of a cross section through the frame of fig 5. Detailed description The present disclosure relates to storage devices comprising a substantially rect- angular frame and a sheet metal component spanning the frame, forming a space such that items can be stored in the container. Such a storage device can be directly inserted in a rack suitable for suspending several such storage devices, or can be placed in a drawer frame providing a sliding function for instance such as described in US-7104411-B2. Fig 1 illustrates a first example of a storage device, in the form of a shoe rack shelf 1. This shoe rack shelf 1 comprises a rectangular frame 3, and a sheet metal portion 5, which is folded into two compartments 7. Each of those compartments offer room for a plurality of pairs of shoes. The present disclosure is primarily concerned with the shape of the rectangular frame 3 and the attachment of the sheet metal portion 5 thereto. Fig 2 shows a top view of the storage device 1 in fig 1, and fig 3 shows the cross section A-A of fig 2. With reference to fig 2 and 3, the sheet metal component 5 is mainly connected to the frame 3 at the two opposing long sides 9 thereof. It should however be noted that alternatively the short sides could be connected to, or the frame 3 could be quadratic. Fig 4 illustrates, isolated, the sheet metal portion 5 of the storage device in fig 1. In this case, the sheet metal portion 5 is at least partly stretched to form a mesh as is briefly illustrated with reference to fig 9. By a mesh material 51, is meant sheet metal web being provided with openings and expanded to widen those openings. Typically, the sheet metal may be pierced with short line-shaped openings and stretched or expanded along an expansion direction 53 to form e.g. diamond-shaped openings 55 in the sheet metal, as illustrated in fig 9. Typically cutting and stretching take place in a single step, where the tool cutting the line shaped opening also widens that open- ing to its final shape. Returning to fig 4, most of the sheet metal portion 5 can be stretched in the expan- sion direction 53. In a section close to the edges 11 in the expansion direction 53 and some intervening portions (not shown) the sheet metal web may be left unstretched, although this is not necessary. The sheet metal portion 5 is then bent into the desired shape as illustrated in fig 4 to form the compartments 7 of fig 1. Fig 5 shows the frame 3 of the storage device in fig 1. As illustrated, the frame 3 is rectangular with rounded corners 13, i.e. each having a radius. Typically, the cross section through the frame is uniform along the periphery thereof. It may be advantageous to make the frame from a single piece of sheet metal, roll-shaped into the desired cross section profile, bent into the rectangular shape, and welded at a single position to form the closed, rectangular loop. However, it would be conceivable to form the frame 3 from two or more pieces as well. Fig 6 illustrates a first example of a cross section through the frame of fig 5. The frame cross section has the form of an inverted U, comprising an upper, substantially horizontal section 21. Inner 23 and outer 25 legs extend downwards from the horizontal section 21 forming the legs of the U, inner/outer being in respect to the mid point of the frame 3 as a whole. The inner leg 23 extends further downwards than does the outer leg 25. In the illustrated case, the inner leg 23 extends vertically downwards a distance x about 10-20 mm as seen from the upper surface of the horizontal section, while the outer leg 25 extends a distance z, about 3-6 mm vertically downwards. Typically, the horizontal section width y is about 10-14 mm wide measured between the outer surfaces of the downward extending legs 23, 25. As illustrated, the transition between the horizontal section 21 and the downwards extending legs 23, 35 may be formed with a radius, typically 2 mm with respect to the outer surface, although a radius range between 1-5 mm is conceivable. The sheet metal thickness may be 0,6-1,2 mm. This cross section configuration, which extend in two substantially perpendicular directions and where the downward extending legs 23, 25 are spaced apart provides a very stiff frame, which may be made in a relatively thin material for a given desired stiffness, compared to a flatter overall frame cross section. The longer extending inner leg 23 provides a suitable base for attaching the sheet metal portion 5 as will now be illustrated with reference to fig 7. Fig 7 shows, en- larged, the detail B in the cross section of fig 3. In the illustrated embodiment, the sheet metal component 5 is connected to the outer side 27 of the inner leg 23. This may typically be done by means of dot welding, al- though other alternatives such as for instance soldering or gluing may be considered. The attachment of the sheet metal component 5 is done in such a way that the edge 29 of the sheet metal component 5 is located above the lower end 31 of the outer leg 25. In this way, the edge 29 is located in a protected position, such that accidentally touching the edge 29 may be avoided to a large extent. Some burrs, etc. may exist on the edge 29 which may be sharp. Although not illustrated, it is possible to let the sheet metal component run all the way up to the radius 26 between the inner leg 23 and the horizontal section 21. Thanks to the relatively large outer surface 24 presented by the inner leg 23 of the frame 3, the sheet metal component 5 may be reliably fastened to the frame 3. Typi- cally, spot-welding may be carried out at regular intervals along the edge 29. This may make the edge 29 even less exposed, as the welding tool pushes the edge into contact with the outer surface 24. Additionally, spot welding may take place also in the lower half of the inner leg 23 which makes the connection more stable. Thus, the sheet metal component 5 may be connected to the frame 3 by means of a first spot-weld row 32 at the upper edge 29 of the sheet metal component 5 and a second spot-weld row 34, provided below the lower end 31 of the outer leg 25. It should be noted, in the case of the shoe rack shelf 1 of fig 1, that the sheet metal component 5 may also be attached to the frame 3 at the mid-point of the latter’s short side, but is in that case attached to the inner side of the frame 3, on its inner cross section leg 23. This too may be accomplished with spot welding 36 as illustrated in fig 3. Fig 8 illustrates a storage device according to the present disclosure in the form of a mesh container 31. The mesh container 31 has a sheet metal portion 33 comprising a bottom panel 35, opposing short side panels 37 and opposing long side panels 39. Each side panel 37, 39 connects the bottom panel to the frame 3 and connect to its neighbouring panels by being in one piece therewith or by welding overlapping parts. Different ways of forming the panels are known, for instance from the initially mentioned document. The sheet metal portion 33 may thus be made from one or a plurality of mesh pieces. The finished product may be powder coated. This alternative configuration of the storage device may utilize a very similar or even identical frame 3 as the one described above. Further, each side panel may be con- nected to the frame in the same way as disclosed above with regard to the shoe rack shelf, even though in this case all sides of the frame 3 receive an edge of a mesh panel 5. Some adaptations of the frame may be useful. In this context, as described in fig 10, an alternative second example 3’ of a cross section through the frame of fig 5 is shown. To start with, the inner leg 23’ may be slightly inclined from the vertical direction, typically forming an obtuse to right angle φ in relation to the horizontal section 21, where φ is in the range from 90-110°, for instance. This is advantageous to attach to many forms of mesh container panels 37, 39 as they are often angled outwards from the bottom panel 35 to become stackable. Secondly, it may be advantageous to extend the inner leg 23’ such that the distance x is for instance in the range 13-22 mm. This allows the formation of a stronger connection between the paned and frame, e.g. with two or three rows of weld spots along the frame 3’. Finally, it is possible to bend the outer leg 25 inwards, forming a second, lower and more or less horizontal portion 28. This may facilitate the storage device sliding in an out of a rack if used in such an application and further adds some additional stiffness to the frame. This second horizontal portion 28 however has a length i, which is shorter than the length y of the aforementioned horizontal section 21, such that the upper portion of the inner leg’s 23 outer surface 24 is still accessible for spot welding, for instance. In the case illustrated in fig 10, x is in the range 13-22 mm , y is in the range 10-14 mm, z is in the range 3-6 mm, and i is in the range 5-7 mm. In this case, z represents the distance between the upper surface of the upper horizontal section 21 and the lower surface of the lower horizontal section 28. The distance i refers to the distance between the inner end 31 of the lower horizontal portion 28 and the outer surface of the outer leg 25. Said inner end 31 also forming the end of the outer leg 25. The goods thickness of the sheet metal making up the frame 3’ of fig 10 may typically be 0,6-1,2 mm. In comparison, the sheet metal forming the sheet metal component 33 may be 0,4-0,7 mm before being perforated/expanded. The present disclosure is not restricted to the above-described examples and may be varied and altered in different ways within the scope of the appended claims. .