BACKGROUND OF THE INVENTION 
     The invention relates to a locking mechanism. 
     Systems used to date for the construction of slots of locks, padlocks, etc., are based essentially on the placing, longitudinally or transversally to the axis of the slot, of a set number of mobile elements, which together consist of little pivots pushed by springs, which move between one fixed part integral with the lock and the other mobile in respect to it; thus in a set position of the said mobile elements, obtained by displacing the same, the assembly of the two parts previously mentioned is unblocked, the latter remaining by contrast blocked with respect to each other in any other position of the former parts. 
     In the above-mentioned conventional systems, the displacement of the mobile elements referred to, in order to achieve unblocking, is obtained as a consequence of the adjustment of the said elements by appropriate projections of the corresponding key, whether by length of attack, height of serrations, or depth of drill holes, but in such a way that the displacement is always equal to that produced by the notches of the key according to the height or depth with which they are formed. 
     SUMMARY OF THE INVENTION 
     In accordance with the subject of the invention a system is proposed which differs from this conventional concept in that with this system some more advantageous characteristics are achieved than those of the above-mentioned conventional systems. 
     According to the invention there is provided a locking mechanism, characterised by one or more blocking elements each consisting of two complementary semi-cylindrical parts snugly located in a correspondingly shaped aperture defined between two relatively movable parts to be locked together, one of the semi-cylindrical parts being adapted to be operatively coupled to a key to permit rotation of the two complementary semi-cylindrical parts, whereby the two semi-cylindrical parts can be rotated between a position in which they prevent movement of the two lock parts and a position in which the two lock parts are relatively movable. Preferably the one semi-cylindrical part is operatively coupled to the key by means of a rotatable member, more preferably a cylindrical rod. 
     The system forming the subject of the invention is based on the rotating mobility of a cylinder by the action of the longitudinal displacement of an operating part, due to the sliding of a projection of the operating part through a helical groove in the cylinder in such a way that with the consequent rotation of some complementary semi-cylindrical parts located in a corresponding aperture defined between respective concentric bodies, blocking and unblocking of the said bodies with respect to each other is achieved, according to the rotational position of the above-mentioned semi-cylindrical parts. 
     In this way, if the blockable and unblockable concentric bodies are arranged in a fixed way with respect to the fixed and mobile parts of the lock, the blocking and unblocking of the latter is realisable by means of the simple introduction of the part operating on the cylinder, which thus serves the function of a key, allowing different combinations simply by varying the longitudinal position of its projections, since it is that which determines whether the rotation of the cylinder is accurate in order for the semi-cylindrical parts to remain in the position of unblocking the concentric bodies. 
     In this way a mechanical system is obtained which allows a large number of possible combinations of operating key and perfect security of blocking of the lock for the purpose for which it is applied, with the advantage that the locating or blocking parts are totally inaccessible from outside, and even though the cylinder may break, because they are not lined up, the slot will not be unblocked. 
     This system does not use springs, although the blocking elements can be positioned by simple guided sliding of the key over the rotating cylinder, the blocking position being regained by the very withdrawal of the key, thus avoiding those functional defects arising from the variability of springs, making the said proposed system also more secure. 
     Moreover, this new system also allows the facility for constructing slots with multiple blocking cylinders and even constructing associated multiple slots, which can be operated simultaneously by means of one single key, which would make it possible for the number of possible combinations to be practically limitless, with security at the same time, including the correct use of the key, given that, thanks to various different ways of introducing the key, of which only one is effective, this means that only the proprietor can use it correctly. 
     For all of the above reasons, the system forming the subject of the invention certainly has some very advantageous characteristics, which give it individuality and preferential character over the conventional systems which are being used for the same purpose of blocking slots of similar locks. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is diagramatically illustrated, by way of example, in the accompanying drawings in which: 
     FIG. 1 is a schematic diagram in perspective of the rotating action of a cylinder by means of the longitudinal displacement of an operating key, in accordance with the system formings the subject of the invention; 
     FIG. 2 is an exploded diagram of the housing of the rotating cylinder and the complementary semi-cylindrical part in respect to the two concentric bodies between which blocking is brought about; 
     FIG. 3 shows details of the above-mentioned assembly of the rotating cylinder which can be operated by key and the concentric bodies which can be connected with the fixed and mobile parts of the lock, in the unblocked position between the above-mentioned concentric bodies; 
     FIG. 4 shows details of the above-mentioned assembly of the rotating cylinder with the concentric bodies in the blocked position; 
     FIG. 5 is an exploded diagram in perspective of a slot assembly with six blocking cylinders, only one of the cylinders having been illustrated; 
     FIG. 6 represents the schematic cross-section of a slot with six cylinders, in the unblocked position of the rotating concentric bodies having the semi-cylindrical parts aligned with each other; 
     FIG. 7 represents the schematic cross-section of the slot with six cylinders, in the unblocked position of the rotating concentric bodies having the semi-cylindrical parts allow relative rotation between the concentric bodies; 
     FIG. 8 represents the schematic cross-section of the slot with six cylinders in a position in which one of the sets of semi-cylindrical parts enclosed between the concentric bodies causes blocking between the same, respectively; 
     FIG. 9 corresponds to the schematic view of a longitudinal section of the above-mentioned slot with six cylinders. 
     FIG. 10 is a perspective of the corresponding key for the said slot with six cylinders; 
     FIG. 11 is a schematic frontal view of a slot fitted with an assembly of eighteen cylinders divided into two groups of six and twelve respectively; 
     FIG. 12 is an exploded diagram in perspective of the said slot with eighteen cylinders; 
     FIG. 13 is the view of a transverse section of the said slot with eighteen cylinders, showing the area of blocking and unblocking of the respective concentric bodies; 
     FIG. 14 is a detail corresponding to a partial frontal schematic diagram of a slot with forty-two cylinders divided into three groups of six, twelve and twenty-four respectively; 
     FIG. 15 is the view of a transverse section of the said slot with forty-two cylinders, showing the area of blocking and unblocking of the respective concentric bodies; 
     FIG. 16 is an exploded diagram in perspective of the concentric bodies of the said slot with forty-two cylinders; 
     FIG. 17 is a perspective of a key for the above-mentioned slot with forty-two cylinders, provided with interchangeable elements; 
     FIG. 18 is a view of the longitudinal section of the said slot with forty-two cylinders, with the corresponding key partially introduced; 
     FIG. 19 shows one variation in practical realisation of the cylinders which can be operated by key according to the system forming the subject of the invention wherein each cylinder is hollow; 
     FIG. 20 shows another variation of the cylinders each being hollow and incorporating guide accessories; and 
     FIG. 21 shows a third variation of the cylinders each consisting of two complementary parts which can be connected together. 
    
    
     EXPLANATORY DETAILS 
     1. - Cylinder 
     2. - Semi-cylindrical blocking part 
     3. - Complementary semi-cylindrical part 
     4. - Aperture 
     5. - External concentric body 
     6. - Internal concentric body 
     7. - Helical groove 
     8. - Operating key 
     9. - Projection 
     10. - Interchangeable parts 
     11. - Guide accessories 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The subject of the invention refers to a novel locking mechanism in which the elements for locking consist of a cylindrical rod (1), which has at its front end a semi-cylindrical structure (2), which is complemented by a corresponding independent semi-cylindrical part (3). 
     The said end of cylinder (1), formed by the assembly of semi-cylindrical parts (2) and (3), is enclosed in a respective corresponding aperture (4), defined between each of concentric bodies (5) and (6), which are respectively connected with the fixed and moving parts of the corresponding lock, in such a way that, according to what can be seen from FIGS. 3 and 4, when the assembly of semi-cylindrical parts (2) and (3) is arranged in such a way that its intermediate groove coincides with the division between bodies (5) and (6), rotation between the said bodies (5) and (6) and consequently operation of the lock becomes possible, whereas when this assembly of semi-cylindrical parts (2) and (3) are in any other rotating position, mobility between bodies (5) and (6) is blocked and operation of the lock is consequently blocked. 
     Cylinder (1) is provided to that effect with a helical groove (7) defined along the same, such that the corresponding key (8) for operation of the lock is provided, in the corresponding correlating area of coincidence with the above-mentioned cylinder (1), with a projection (9) which is capable of being fitted by sliding into the above-mentioned groove (7). 
     In this way, when key (8) is introduced into the slot, its own longitudinal displacement on introduction makes cylinder (1) rotate, with the effect that if the location of projection (9) over key (8) is sufficient for rotation of cylinder (1) to be effected precisely, which makes it locate itself at the assembly of semi-cylindrical parts (2) and (3) with their intermediate groove coinciding with the two bodies (5) and (6), the said introduction of key (8) brings about unblocking for the easy operation of the slot to which it is applied; so when the key itself (8) is withdrawn the positioning for the initial blocking occurs again. 
     With such a realisation and operation, the number of possibilities of variations of the state of cylinder (1) in each case becomes great, since according to the longitudinal position in which projection (9) on key (8) is found, the rotation which is achieved by means of the introduction of the latter is different, and this enables a large number of different combinations to be obtained, varying this positioning of projection (9) on key (8) and the angular location of the assembly of semi-cylindrical parts (2) and (3) with respect to groove (7) of cylinder (1), so that when key (8) is introduced it determines the position of unblocking of concentric bodies (5) and (6) with respect to each other. 
     Based on the said fundamental principal, the practical realisation of the assembly of a slot in accordance with this system can consist of two simple concentric bodies (5) and (6) and the inclusion of a set of multiple cylinders (1) for blocking and unblocking with respect to each other, in conformity with the views in FIGS. 5 to 9, in such a way that the position of unblocking has to be accomplished with all the sets of semi-cylindrical parts (2) and (3) corresponding to the different cylinders (1), as can be seen in FIG. 6, so that rotation between concentric bodies (5) and (6) is achievable, as can be seen in FIG. 7; as long as any of the assemblies of parts (2) and (3) are not in the correct position, as can be seen in FIG. 8, blocking of bodies (5) and (6) with respect to each other will be established. 
     Under the said conditions it is clear that all the assemblies of parts (2) and (3) have to be operated simultaneously to bring about unblocking, and for this a key (8) is provided, as shown in FIG. 10, provided with as many projections (9) as the slot contains cylinders (1) and situated adequately for each one of them to operate on one of the cylinders (1) of the slot, as well as positioned longitudinally in a precise way such that by means of them the respective cylinders (1) are positioned in the correct position for unblocking bodies (5) and (6) when the key is introduced into the slot. 
     This in turn brings about a possibility of practically limitless combinations of key (8), with the additional peculiarity that it is necessary to know the precise position of introduction of the latter for the rotating operation to be carried out, given that only one of the six possible positions of introduction is effective. 
     Underlying this aspect of multiple combinations which confer a greater level of security, the realisation of the slot can be carried out with a larger number of cylinders (1), such as for example with a total set of 18 cylinders (1) distributed in two concentric groups of 6 and 12 respectively, as shown in FIGS. 11 to 13, in which case logically a tubular key (8) would be required with interior and exterior projections (9) to operate on all the cylinders (1). 
     Even more complexity can be included, based on multiple associated slots, such as for example an assembly with a central slot with six cylinders (1), forming an integral part of a larger slot with two concentric groups of twelve and twenty-four cylinders (1) respectively, such as is the case in FIGS. 14 to 16, in which case a total of forty-two blocking cylinders would result, with which clearly so complex a combination would be obtained that the security of inviolability would be practically total. 
     In such a case the realisation of the corresponding key (8) would be as shown in FIG. 17, that is to say with a central nucleus and a tubular rim both provided with projections (9) on their surfaces to operate the different cylinders (1), the said key (8) being able to be realised with interchangeable parts (10) for better process of manufacture and to give the user great security in the case of loss of the same. 
     Moreover, the said key (8) for such a complex combination would consist of two independent parts in such a way that, as can be seen in FIG. 18, the central nucleus of the same would be the operating part for the rotating operation and the external rim would only be to position the corresponding cylinders (1) for unblocking, both parts being able to rotate with respect to each other when the slot is operated; this in turn gives a total guarantee of security, even including using the key, given that its many ways of introduction and withdrawal mean that only the proprietor, knowing the appropriate position, can use it correctly. 
     In effect, in the case of the afore-mentioned slot with forty-two cylinders (1), the key (8) only operates rotation in one single position, but however its introduction can be carried out in seventy-two different positions (6) with respect to the central part and twelve with respect to the external rim); inasmuch as withdrawal can be carried out in six different positions (which correspond to the six positions of the central part), this gives such diverse possibilities that only that person who knows the effective position can use the key with efficacy. 
     In any case, the blocking parts formed by the assemblies of semi-cylindrical parts (2) and (3) are totally inaccessible from outside, and even if the corresponding cylinders (1) were broken, blocking of concentric bodies (5) and (6) with respect to each other would continue, without the lock being able to be operated. 
     The possibilities of realisation of slots with multiple cylinders (1) are however not limited to the examples described, since in the same way other different possibilities exist, as there could be, in addition to those already indicated, a slot with twelve cylinders (1) in one single circular group, a slot with twenty-four cylinders (1) also in one single circular group, a slot with thirty cylinders (1) distributed in two concentric groups of six and twenty-four respectively, a slot with thirty-six cylinders (1) distributed in two concentric groups of twelve and twenty-four respectively, as well as any other possible combination imaginable. 
     In another case, the cylinders (1) to realise this system could be formed by one single part, the corresponding semi-cylindrical structure (2) for blocking being formed at its end, or consist of two complementary parts which can be connected together such as is shown in FIG. 21; the said cylinders (1) can also be hollow, as shown in FIGS. 19 and 20, the corresponding key (8), being able in another case to include the internal and/or external parts for operating on the said cylinders (1), and be included in combination With complementary guide accessories (11). 
     The invention thus provides a simple but effective locking mechanism.
A locking mechanism is provided which is characterized by one or more blocking elements each consisting of two complementary semi-cylindrical parts (2),(3) snugly located in a correspondingly shaped aperture (4) defined between two relatively movable parts (5),(6) to be locked together, one of the semi-cylindrical parts (2),(3) being adapted to be operatively coupled to a key (8) to permit rotation of the two complementary semi-cylindrical parts (2),(3), whereby the two semi-cylindrical parts (2),(3) can be rotated between a position in which they prevent movement of the two lock parts (5),(6) and a position in which the two lock parts (5),(6) are relatively movable.