A COOLING DEVICE [001] This invention relates to a cooling device, which comprises a foldable shelf having a supporting surface preferably of a glass material. [002] One or more shelves are used in cooling devices to store food, beverages or other items. The supporting surface of the shelf is preferably made of glass for hygienic and aesthetic purposes. When tall food and beverage containers are to be stored on the shelves, removal or rearrangement of one or more shelves is required. In the current state of the art, foldable or telescopic shelving systems are utilized to create flexible storage volumes allowing for storage of containers with various sizes. In this type of shelving systems, although there are mechanical processing problems like cutting, drilling etc. due to use of glass material, it still has to be efficient, safe and of a structure not damaging the appearance. [003] In the current state of the art, German Patent document DE19751309 a description is given for a glass shelf positioned on the vegetable bin, which may be opened by rotating. [004] In another state of the art, in European Patent EP577939 a description is given for a glass shelf formed of two parts and which can slide over each other giving the op¬ portunity of being used in smaller dimensions. [005] In yet another state of the art, in the Swiss Patent document CH402907 a two-piece wire shelf interconnected by an additional part is described. [006] In another state of the art, in the United States of America Patent US2317232 a wire shelf composed of a plurality of parts, which are interconnected by an additional part is described. [007] The object of this invention is the realization of a cooling device comprising a shelf, which can be folded in its undetached position and can still be used after being folded and being small. [008] The cooling device designed to fulfill the object of the present invention is il¬ lustrated in the attached figures, wherein [009] Figure 1 - is the perspective view of a cooling device [010] Figure 2 - is the exploded perspective view of a shelving unit [011] Figure 3 - is the perspective view of two shelves before being assembled [012] Figure 4 - is the perspective view of an unfolded shelf [013] Figure 5 - is the rear perspective view of a storage surface and a profile before being assembled [014] Figure 6 - is the perspective view of a folded shelf [015] Figure 7 - is the perspective view of a shelving unit consisting of three shelves [016] Figure 8 - is the perspective view of a shelving unit without a profile including two shelves, attached by means of only two corner brackets and a binding element. [017] Figure 9 - is the perspective view of a shelving unit comprising storage surfaces without corner brackets. [018] Elements shown in figures are numbered as follows: 1. Cooling device 2. Shelving unit 3. Profile 4. Shelf 5. Storage surface 6. Ridge 7. Binding element 8. Corner bracket 9. Pin housing 10. Pin 11. Cabinet 12. Door 13. Profile groove 14. Pin lock 15. Corner bracket groove 16. Corner bracket housing 17. Fixing housing 18. Support element 19. Edge support 20. Shelf support 21. Projection 22. Projection housing [019] The cooling device (1) comprises a cabinet (11) in which food, beverages and items to be cooled are stored, at least one door (12) which may be opened and closed enabling the storing of the items to be cooled in the cabinet (11), one or more shelving units (2) positioned inside the cabinet (11), which can be folded without being detached, to be utilized in various sizes and on which items to be cooled may be stored before or after folding, and one or more shelf supports (20) which provide the shelving unit (2) to be mounted into the cabinet (11). [020] The shelving unit (2) comprises of at least two shelves (4) upon which items can be stored, corner brackets (8) on corresponding corners of the adjacent sides of the shelves (4) which are placed without leaving any gap or giving way to any difference in level in between, when it is desired to attach a shelf (4) to another shelf (4) side by side, and a binding element (7) fixed on the corner brackets (8) binding the corner brackets (8) of different shelves without leaving any gap or giving way to any difference in level in between and providing pivotal movement. [021] The shelf (4) comprises at least one storage surface (5) for items to be stored upon, and at least one profile (3) positioned on the side of the storage surface (5) where there is no corner bracket (8), which avoids the contact of user or the cabinet (11) with the sides. [022] The storage surface (5) comprises corner bracket housings (16) on its corners, cor¬ responding to the numbers of corner brackets (8) into which the corner brackets (8) are seated in such a manner that there is no gap or difference in level between the two shelves (4). [023] The corner bracket (8) comprises one or more corner bracket grooves (15) where corner bracket housings (16) can be fitted in, at least one pin (10) onto which the binding element (7) is fixed, a pin lock (14) on top of the pin (10) which ensures that the binding element (7) fixed on the corner bracket (8) is not disengaged and one or more support elements (18) which reinforce its structure. [024] The binding element (7) comprises an equal number of pin housings (9) cor¬ responding to number of pins (10) inserted in. [025] The profile (3), comprises one or more profile grooves (13) into which the storage surface (5) is positioned, at least two edge supports (19) on the sides, which by disposing to the shelf supports (20) enables it to be seated on the cabinet (11) and by sliding in the shelf support (20) provides for the detachment of shelf (4) out of cabinet (11), and a fixing housing (17) into which a projection under the edge support (19), preferably on the cabinet (11), is inserted, thus enabling the fixing of the edge support (19). [026] In the embodiment of the present invention, the profile (3) comprises one or more ridges (6) which face the back wall of the cabinet (11) and cover the entirety of the rear edge of the profile (3) preventing its contact with the cabinet (11) and avoiding the possibility of the rolling off of items stored on the shelving unit (2) from the back side through the space between the shelving unit (2) and the cabinet (11). [027] In the preferred embodiment of the present invention, the storage surface (5) is produced from glass such that sides are honed (stoned), the profile (3), corner bracket (8) and the binding element (7) from plastic material and the profile (3) and the corner bracket (8) are adhered on the storage surface (5) by adhesives. [028] In another embodiment of the present invention, production of the storage surface (5) is of glass material of which the sides are sanded, corner bracket (8) and binding element (7) of plastic material, profile (3) of aluminum material wherein the profile (3) is fixed to the storage surface (5) by tight fitting and the corner bracket (8) is adhered on the storage surface (5) by adhesives. [029] In another embodiment of the present invention, the profile (3) comprises one or more projections (21) which facilitates the fixing or snap fitting of it onto the storage surface (5), and the storage surface (5) comprises projection housings (22) which receive the projections (21) in shape and numbers corresponding to those of the projections (21). In this embodiment while the storage surface (5) is pushed into the profile groove (13), the projections (21) are seated into the projection housings (22) and fix the storage surface (5) to the profile (3), (Figure 5). [030] In the embodiment of the present invention, while the shelf (4) is being arranged, the storage surface (5) is fixed to the profile (3) by way of inserting it in the profile groove (13) and the corner brackets (8) one on each of two exposed corners of the storage surface (5) are assembled into the corner bracket housings (16). At least two shelves (4) thus arranged, are juxtaposed with exposed side lengths of storage surfaces (5) facing each other. In this position, the binding element (7) is pushed towards the corner bracket (8) in such a manner that the pins (10) are inserted into the pin housings (9). In this way the binding element (7), after being engaged in the pin locks (14), in¬ terconnects the pins (10) and thus the shelves (4) to each other preventing an un¬ controlled detachment. The shelves (4) attached by the binding element (7) form a shelving unit (2) and thereafter are seated in the cabinet (11) by being pushed onto the shelf support (20). When the size of the shelving unit (2) is desired to reduce without removing it out of the cabinet (11), the front shelf (4) is moved towards the back shelf (4) by rotating around the axis formed of conjoining adjacent sides of two shelves (4) by means of the binding element (7), and the front shelf (4) folds onto the back shelf (4). Consequently, the shelving unit (2) is disposed for utilization with single shelf (4) dimensions. When the shelving unit (2) is desired to be utilized with normal dimensions, the upper shelf (4) rotates around the axis of conjoining sides and resumes its initial position. When it is desired to detach the shelving unit (2), it is pulled outwards on the shelf support (20) by means of the front profile (3) and thus is taken out of the cabinet (11). [031] In one of the embodiments of the present invention comprising more than one shelves (4), three shelves (4) are used, with four corner brackets (8) on the corners of the middle shelf (4) and the adjacent sides of side shelves (4) conjoining on sides of the middle shelf (4) are supplied with two corner brackets (8) and a profile (3) on their other sides of side shelves. The corner brackets (8) on the middle shelf (4) are connected by way of binding elements (7) with the corner brackets (8) of the shelves on either side and the shelves (4) can be folded onto each other, (Figure 6). [032] In another embodiment of the present invention, the shelving unit (2) made up of two shelves (4), each comprising only one corner bracket (8) where the corner bracket (8) is attached by one binding element (7) and can be pivoted around one another. In this implementation, since the shelving unit (2) is seated on an step-shaped shelf support (20), the shelves (4) can slide on the shelf support (20) without being removed and turned over to be folded onto one another, (Figure 7). [033] In another embodiment of the present invention, the shelving unit (2) comprises at least two storage surfaces (5) without corner bracket housings (16), and at least four corner brackets (8) in shapes conforming to that of storage surface (5) without corner bracket housings (16), which are positioned near the corners of the sides to be attached and at least two binding elements (7) binding the corner brackets (8), (Figure 8). [034] The embodiment of the present invention presents facility of assembling, and benefits in production time and costs during production phase due to the small number of parts. Furthermore the shelves (4) adjacently attached together by way of corner brackets (8) and binding elements (7) which eliminate gaps or differences in level constitute a planar shelving unit (2) surface avoiding stored items to be affected by adjoined edges and risk of injuries to the user caused by the storage surface (5) by limiting his/her contact to the storage surface (5) thereof. [035] With the embodiment of the present invention, the shelf (4) enables both the storing of tall containers by folding and the storing of containers in the unfolded position.