Patent Publication Number: US-2004045923-A1

Title: Child-resistant safety closure

Description:
FIELD OF THE INVENTION  
       [0001] The invention relates to a safety screw-closure device for a container the mouth piece of which has an external screw thread, the device being child-proof.  
       [0002] The invention relates more particularly to a safety screw-closure device for a container, such as a bottle, comprising an inner cap to be screwed onto said container and a coaxial outer cap integrally covering the inner cap, the outer cap having the ability to drive the inner cap via a mutual-engagement system when an axial pressure and a turning are performed on the outer cap.  
       PRIOR ART  
       [0003] Child-proof safety devices for the screw-closure of containers provided with a screw thread mouth came into being many years ago.  
       [0004] These devices are made up of two caps/tops nested one inside the other, each formed of a cylindrical side wall and of a upper end wall closing the cylindrical wall.  
       [0005] The inner cap comprises a screw thread on the inner surface of its cylindrical wall, allowing it, by screwing, to seal the container, and means on its cylindrical and/or end outer walls allowing it to be rotated by the outer lid.  
       [0006] The outer top coaxial with the inner top which integrally covers the inner top, comprises on its inner walls, means for turning the inner top in the direction of closing or opening of the container, through an axial pressure/turning applied to the outer cap, this pressure allowing the driving means of the outer cap to be engaged mechanically in the corresponding means of the inner cap, then allowing the transmission of the rotating movement of said inner cap.  
       [0007] One or the other of the two caps also comprises elastic means allowing mechanical disengagement of the drive means of the outer and inner caps, these elastic means being produced from the same material as the caps by injection-molding.  
       [0008] Such child-proof safety closure devices have been described in many patents, some of which are mentioned hereinbelow by way of illustration.  
       [0009] A first device, object of the European patent EP 0631943, relates to the safety closure(child-proof) of a container comprising a screw thread, which is made up of two nested caps, one, an inner cap, intended to the closure of said container, the other, an outer cap, intended to drive the inner cap in order to open or close the container, by a combined action of pressure and/or turning.  
       [0010] In that device:  
       [0011] the inner cap to screw comprises, on the outer surface of its cylindrical wall, a grooving consisting of successive ribs, in the form of lamella, which continues on the outer surface of its upper end wall, in the form of a radial grooving, the lamella of which have a long side, directed in the direction of turning for the opening, and a short side preferably lying in the plane containing the longitudinal mid-axis of the container closure;  
       [0012] the outer cap comprises, on the inner surface of its upper end wall, which is deliberately convex (closing the cylindrical wall), projections which engage in the grooving of the inner cap when an elastic deformation of the upper end wall of said outer cap is performed by axial pressure on said wall.  
       [0013] In consequence, by axial pressure exerted on the inner face of the convex end wall of the outer cap, then turning given to said cap, a torque of turning is transmitted to the radial grooving of the inner cap by the projections of the outer cap, so that the inner cap is unscrewed from the container.  
       [0014] The device also comprises, as already stated, the grooving with lamella oriented on the cylindrical outer wall of the inner cap, the function of which is to facilitate the turning of the inner cap to screw in the outer cap, when the projections of the outer cap are not engaged in the slightly inclined lamella of the radial grooving of the inner cap.  
       [0015] The device also comprises a second system for turning the inner cap using the outer cap in the screwing direction, independent of the first drive system, so that the outer cap turns the inner cap in the closure operation, by a simple turning, without any need to apply an axial pressure on the convex external end wall of the outer cap: this drive system is constituted by means placed on the inner cylindrical wall of the outer cap, as denoted as “front surfaces” and means placed on the outer cylindrical wall of the inner cap, as denoted as projections.  
       [0016] This closure device, called safety closure device for children, has disadvantages which may become apparent during its use.  
       [0017] For example, the outer cap (like the inner cap) is made of a single polymer material with a more or less elastic property and the projections of the inner face of the upper end wall of the outer cap are made of the same material and are obtained by injection-molding in superstructure of said inner face of said cap: since the upper end wall of the outer cap is convex and subjected numerous times to an axial-pressure/turning torque to open the container, the elastic memory of the constitutive material becomes weak and the deformation of this upper end wall can become nearly permanent by the effect of the fatigue of the material, so that the projections can become engaged in a relatively permanent manner and the inner cap can be turned in one or the other of the screwing or unscrewing directions.  
       [0018] Thus, when the effect of fatigue of the material occurs, the upper end wall of the outer cap no longer moves sufficiently apart from the outer surface of the end wall of the inner cap: the device is then no longer of an absolute safety, because the mutual-engagement of the two caps can occur independently of the axial pressure-turning needed.  
       [0019] Another device, object of the European patent EP 0602925, relates to the child-proof closure of a container comprising a screw thread which is also made of two caps nested one inside the other, one an inner cap intended to close said container and the other an outer cap intended to drive the first for opening or closing the container by the action of an axial pressure and/or a turning.  
       [0020] In that device:  
       [0021] the outer cap comprises, on the internal face of its top end wall, oblong mutual-engagement strips directed radially and an elastic means in its central part, to keep the top end wall of the outer cap away from the top end wall of the inner cap;  
       [0022] the inner cap to screw comprises, on the internal surface of its cylindrical wall, a screw thread and, on its top end wall, oblong and radially directed mutual-engagement strips. These strips have inclined faces (in the direction of the screwing of the inner cap) and butt against the mutual-engagement strips of the outer cap, when said outer cap is turned in the screwing direction driving the inner cap. However, when said cap is turned in the unscrewing direction, without an axial force being previously applied on the top end wall of the outer cap, the strips of the internal face of the top end wall of the outer cap slide over the inclined faces and the inner cap is not driven.  
       [0023] Thus, it follows that the unscrewing of the inner cap is achieved by the successive application of an axial pressure to the top end wall, moving said wall closer to the top end wall of the inner cap, and causing the mutual-engagement of the strips of the top end wall of the outer cap with the strips of the top end wall of the inner cap, the inner cap then being turned by the outer cap.  
       [0024] As soon as the pressure applied to the top end wall of the outer cap is released, the mutual-engagement strips of the outer cap disengage from the mutual-engagement strips of the inner cap, by virtue of the elastic system which causes the uncoupling of the two caps.  
       [0025] However, this closure device, known as a child safety closure device comprising two caps, has also disadvantages which become apparent only during use.  
       [0026] Concerning, for example, the outer cap, its means constituted by mutual-engagement strips of the outer cap and its elastic means present on the internal surface of the top end wall of said cap are made (by injection molding) by means of a single polymer material with a certain natural elasticity. More precisely, the elastic means is formed of four vertical tabs interdependent by one of their ends of the internal surface of the top end wall of said cap. These four tabs form a virtual cylindrical wall, coaxial with the outer cap. When a pressure is applied to the top end wall of the outer cap, these four tabs have a tendency to diverge from one another, in their lower end, then to crush against the top end wall of the inner cap, throughout the application of the aforesaid pressure.  
       [0027] With the release of said pressure, the tabs ought to return to a vertical position. However, in practice, the repeated axial loadings (axial pressure-turning) on the outer cap for the unscrewing of the device leads to a fatigue of the constitutive polymer materials, and this is manifested by an almost permanent deformation of the elastic means and possibly in its complete or partial breakage.  
       [0028] Thus, the top end faces of the two caps are no longer held sufficiently far apart at rest and their closer-together relative position tends to cause accidental mutual-engagement of the driving teeth of the outer cap with the driving teeth of the inner cap. The so-called child safety closure device is therefore no longer of an absolute safety.  
       [0029] Another device, object of European patent EP 0725012, proposes a closure considered to be child-proof for a container comprising a screw thread which is made of:  
       [0030] an inner cap equipped with a cylindrical side wall and with an end wall, intended to be driven,  
       [0031] an open outer cylindrical drive casing such that the upper opening of this cylindrical casing has a diameter slightly superior to the diameter of the barrel of the inner cap, thus allowing the inner cap to emerge above said outer cylindrical casing.  
       [0032] Once inserted in the outer cylindrical casing, the inner cap holds said cylindrical casing, at the lower part by a ring against which it abuts, and at the upper part by an outer ring against which its upper peripheral surface butts.  
       [0033] The outer cylindrical drive casing has, on its internal surface, mutual-engagement means which may also be means of guiding of the inner cap.  
       [0034] As for the inner cap, its only mutual-engagement means allowing it to be driven by the cylindrical casing is present on the external side wall of said cap. The mechanical driving of the inner cap by the outer cylindrical casing is therefore achieved via the mutual-engagement means of the cylindrical casing and the engaged means of said inner cap when a mechanical torque of pressure on the casing to cause it to descend and engage, and of turning of the casing to drive the inner cap, is applied.  
       [0035] The elastic disengaging means is formed of blades of the low ring of the inner cap, these blades being of same composition and interdependent of said low ring by one of their ends and being housed in said ring when a pressure is exerted downward on the outer cylindrical casing.  
       [0036] Thus, it can be seen that the means implemented in this device make the driving of the inner cap difficult because they require the application of a vertical force to the outer cylindrical casing, demanding first of all the complete peripheral prehension of said casing according to a rather awkward movement, and then the application of the vertical force to the periphery of the casing to cause the mutual-engagement of said casing and of the cap, and finally the driving of the inner cap by turning of the outer cylindrical casing.  
       [0037] It also appears that the disengaging elastic means is placed on the low ring of the inner cap and is made with the same material (composition) constituent of the cap and of the outer cylindrical casing, material which, when frequently stressed, can lose some of its elastic capacity and can reach a state of fatigue such that it can crack and lose its elasticity or even break.  
       [0038] Finally, another device, object of patent GB 2,209,156, describes a safety closure device for a fire hydrant. This device comprises an inner cap made of technical polyamide and an outer cap made of aluminum alloy.  
       [0039] The inner cap has a screw thread on its internal wall and this thread engages with the screw thread on the tip of the water outlet.  
       [0040] The outer cap is held in a position coaxial to the inner cap by a peripheral ring which constitutes the guiding means, holding coaxially the two caps constituting the elastic means of uncoupling of the two caps.  
       [0041] A spring is located between their facing upper faces, resting in the appropriate coaxial circular grooves.  
       [0042] The means of driving by pressure-turning of the inner cap by the outer cap consists of:  
       [0043] three teeth placed on the internal surface of the top end of the outer cap which engage, when a pressure/turning effort is applied, in three cavities present on the external surface of the top end of the inner cap.  
       [0044] Now, it is obvious that such a device is difficult to use because:  
       [0045] it entails a relatively precise mechanical operation which consists in an axial pressure to make the three teeth to enter exactly and simultaneously in three cavities of a diameter very slightly superior to the diameter of the teeth, this demanding a good manual dexterity and a great deal of efforts in order that the drive in opening or closing can be realized;  
       [0046] the disengaging elastic means, which is a metal spring, is engineered for a very long lifetime, but very few operations because of this highly specific application, requiring significant human strength and particular manual dexterity during its operation;  
       [0047] this safety closure proves to be entirely unsuited to the closure of containers such as bottles.  
       OBJECTIVES OF THE INVENTION  
       [0048] The device according to the invention has therefore been set numerous objectives so that it can best eliminate the aforesaid drawbacks and so that it provides suitable and improved solutions compared to the various means implemented in the known safety closure devices.  
       [0049] A first object of the invention is to produce a safety screw-closure device for a container, that is childproof in terms of unscrewing, this device being made of two thermoplastic polymer caps nested one inside the other, operating by a mutual-engagement means of the outer cap on the inner cap by the application of an axial pressure-turning torque, on the upper end wall of the device.  
       [0050] Another object of the invention is to produce a safety screw-closure device for a container, that is child-proof in terms of unscrewing, this device comprising a means for immediately uncoupling the driving outer cap from the driven inner cap as soon as the pressure exerted on the upper end wall of the device ceases.  
       [0051] Another object of the invention is to produce a safety screw-closure device for a container, that is childproof in terms of unscrewing, in which the means allowing mutual-engagement and disengagement of the driving outer cap with respect to the driven inner cap do not, in full or in part, suffer from fatigue, permanent deformation or breakage by the repeated application of an axial-pressure/turning torque on the upper end wall of said device.  
       [0052] Another object of the invention is to produce a safety screw-closure device for a container, that is childproof in terms of unscrewing, in which the means allowing mutual-engagement and uncoupling of the driving outer cap with respect to the driven inner cap compensate for the fit or wear clearances between the outer and inner caps, and provide them with an excellent cohesion when they are mutually engaged and with independence, without clearance, when they are disengaged.  
       SUMMARY OF THE INVENTION  
       [0053] All the objectives set out hereinabove can be achieved by the closure device, object of the invention.  
       [0054] According to the invention, the safety screw-closure device for a container provided with an outer screw thread opening is made up of two coaxial caps made of thermoplastic polymer materials, nested one inside the other, one being an outer cap and the other an inner cap, each formed of a cylindrical side wall and of an upper end wall closing the cylindrical side wall,  
       [0055] the outer cap comprising, on its inner surface, mutual-engagement means allowing it to turn the inner cap, by the application of an axial-pressure/turning mechanical torque;  
       [0056] the inner cap comprising a screw thread on the inner surface of its cylindrical side wall and mutual-engagement means corresponding to those of the outer cap on its outer surface, allowing it to be turned by the outer cap when the latter is subjected to an axial-pressure/turning mechanical torque;  
       [0057] an elastic means for disengaging the mutual-engagement means of the inner and outer caps when the axial-pressure/turning mechanical torque ceases to be applied to the outer cap;  
       [0058] means of guiding of the inner and outer caps ensuring their coaxiality,  
       [0059] which is characterized in that the elastic disengaging means:  
       [0060] is located between the upper end walls of the inner and outer caps, and  
       [0061] is formed of a shape-memory thermoplastic polymer material of different composition from the compositions of the materials constituting the caps themselves.  
       [0062] More precisely, and according to a first alternative form, the safety screw-closure device for a container provided with an outer screw thread opening which is made up of two coaxial caps made of thermoplastic polymer materials, nested one inside the other, one being an outer cap and the other an inner cap, each formed of a cylindrical side wall and of an upper end wall closing the cylindrical side wall, consists in that:  
       [0063] the outer cap comprises, on the inner surface of its upper end wall, mutual-engagement means allowing it to turn the inner cap, by the application of an axial-pressure/turning mechanical torque;  
       [0064] the inner cap comprises a screw thread on the inner surface of its cylindrical side wall and mutual-engagement means corresponding to those of the outer cap, on the outer surface of its upper end wall, allowing it to be turned by the outer cap, when the latter is subjected to an axial-pressure/turning mechanical torque;  
       [0065] means of guiding of the inner and outer caps ensuring their coaxiality, and  
       [0066] an elastic means of disengaging of the mutual-engagement means of the upper end walls of the inner and outer caps when the axial pressure-turning mechanical torque ceases to be applied to the outer cap, this elastic disengaging means:  
       [0067] being located between the upper end walls of the inner and outer caps,  
       [0068] and being made of a shape-memory thermoplastic polymer material of different composition from the compositions of the materials constituting the caps themselves.  
       [0069] More precisely also, and according to a second alternative, the safety screw-closure device for a container provided with an outer screw thread opening, which is made up of two coaxial caps in thermoplastic polymer materials, nested one inside the other, one being an outer cap and the other an inner cap, each formed of a cylindrical side wall and of a upper end wall closing the cylindrical side wall, consists in that:  
       [0070] the outer cap comprises, on the inner surface of its cylindrical side wall, mutual-engagement means allowing it to turn the inner cap, by the application of an axial pressure-turning mechanical torque;  
       [0071] the inner cap comprises a screw thread on the inner surface of its cylindrical side wall and mutual-engagement means corresponding to those of the outer cap, on the outer surface of its cylindrical side wall, allowing it to be turned by the outer cap, when the latter is subjected to an axial pressure-turning mechanical torque;  
       [0072] means of guiding of the inner and outer caps ensuring their coaxiality, and  
       [0073] an elastic means of disengaging of the mutual-engagement means of the cylindrical side walls of the inner and outer caps when the axial-pressure/turning mechanical torque ceases to be applied to the outer cap, this elastic disengaging means:  
       [0074] being located between the upper end walls of the inner and outer caps,  
       [0075] and being made of a shape-memory thermoplastic polymer material of different composition from the compositions of the materials constituting the caps themselves.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0076] The device according to the invention is made up of two caps, nested one inside the other, each of these caps being equipped in superstructure with means such that the outer cap, when subjected to an axial pressure then to a turning, moves vertically in a downward movement, engages with the inner cap and drives it in an opening or closing movement on demand.  
       [0077] As soon as the axial pressure on the outer cap ceases, the device, in order to be truly safe, has to perform the reverse movement of moving the outer cap upward, causing the uncoupling of the outer and inner caps: as soon as the outer cap is in its disengaged position, and is subjected to a simple turning action, it can no longer drive the inner cap in an unscrewing movement.  
       [0078] Such a device is extremely safe in the hands of small children who have not yet acquired the degree of coordination needed to simultaneously effect the axial pressure-turning torque needed in order to open the device.  
       [0079] The outer and inner caps of the device according to the invention are produced by plastics technology methods suited to their manufacture, by means of materials which are thermoplastic polymers, such as, for example, polyethylenes, polypropylenes, ethylene/propylene copolymers and blends thereof, polyamides, polystyrenes (PS), acrylonitrile-butadiene-styrene copolymers (ABS), styrene-acrylonitrile copolymers (SAN), polyvinyl chlorides (PVC), polycarbonates (PC), polymethyl methacrylates (PMMA), polyethyleneterephthalates (PET).  
       [0080] According to the invention, and very much unlike the prior art, the shape-memory elastic means allowing uncoupling of the outer and inner caps, as soon as axial pressure followed by turning ceases to be applied to the outer cap, is made of a shape-memory elastic thermoplastic polymer material of different composition from the compositions of the materials used to make the outer and inner caps.  
       [0081] The shape-memory elastic means can be made by the implementing of at least one thermoplastic elastomer of natural or synthetic origin. The elastomer or elastomers used can be preferably chosen from the group consisting of elastomers of natural rubbers type, synthetic rubbers, in particular mono-olefin rubbers, such as, for example, isobutylene/isoprene polymers, ethylene-vinyl acetate (EVA), ethylene-propylene rubber (EPR), ethylene-propylene-diene (EPDM), ethylene-acrylic ester elastomers (EMA-EEA), fluoropolymers, diolefin rubbers such as, for example, polybutadienes, styrene-butadiene copolymers (SBR), rubbers based on condensation products such as, for example, polyester and polyurethane thermoplastic rubbers, silicones, styrene-butadiene-styrene (SBS) and styrene-isoprene-styrene (SIS) styrene rubbers and others, used alone or in blend.  
       [0082] The shape-memory elastic means can also be realized by means of a thermoplastic polymer foam.  
       [0083] The shape-memory elastic means according to the invention can have the form of a volume, preferably of the approximately cylindrical, truncated-cone, cylindro-truncated, cylindro-hemispherical, or hemispherical type, of which the diameter is adapted to the one of the device and of which the height is at least equal to the minimum distance necessary so that the mutual-engagement means of the outer and inner caps are not in an engaged position.  
       [0084] As already mentioned, the shape-memory elastic means according to the invention can be of various volume. This volume can be solid and, in this case, be embodied in the form of a disk, a frustum of a cone, a dome, or alternatively can be hollow, and in this case, be embodied by a capsule, a frustum of a cone, a cap, this volume being able to be perforated in order to limit the suction cup effects when the axial pressure is exerted and then released (followed by a turning action) on the outer cap.  
       [0085] The elastic means according to the invention is located between the upper end walls of the two caps: it can be inserted freely between these two walls, or can equally be adherent to the inner surface of the upper end wall of the outer cap or to the outer surface of the upper end wall of the inner cap, by adhesive bonding on the surface of the cap or by overmolding on said cap.  
       [0086] The shape-memory elastic means according to the invention, produced by means of thermoplastic polymer materials, can be obtained by one of the means specific to the plastics technology allowing the manufacture of said means.  
       [0087] The mutual-engagement means are generally known, but need to be adapted in terms of their shape to suit the area in which they are fitted, because of the presence of the elastic uncoupling means for uncoupling said mutual-engagement means according to the invention, which means is located between the upper end walls of the inner and outer caps.  
       [0088] When the mutual-engagement means are fitted on the inner surface of the cylindrical side wall of the outer cap and on the outer surface of the cylindrical side wall of the inner cap, the mutual-engagement means are generally of known type and are not subjected to any change: they are formed, for example, of:  
       [0089] blades of square, rectangular, triangular or others cross section, present on at least one part of the height of said side wall and fitted according to the generatrices,  
       [0090] notched rings present at the periphery of said concerned surfaces.  
       [0091] When the mutual-engagement means are fitted simultaneously on the facing surfaces of the cylindrical side walls and on the upper end surfaces of said caps, the mutual-engagement means are often of known type, such as, for example, blades. Such blades, which are described in European patent EP 0631943, form a grooving constituted of successive ribs in the form of lamella extending to at least one of the appropriate surfaces of the upper end walls, in the form of a radial grooving of which the radial length of each blade must be limited in order to create a reserve area, coaxial with the caps, and needed for the fitting of the elastic means according to the invention.  
       [0092] This radial length is at most equal to the radius of the face of the upper end wall of the outer and inner caps, reduced of the radius of the base area of the geometric volume of the elastic means according to the invention.  
       [0093] When the mutual-engagement means are fitted on the inner surface of the upper end wall of the outer cap and on the outer surface of the upper end wall of the inner cap, these means are formed, for example, of teeth in ring, of blades with square, rectangular, triangular or others cross section, in a radial position, the radial dimension of which is limited in order to create a reserve area coaxial with the caps and needed for fitting the elastic means according to the invention.  
       [0094] This radial dimension is preferably at most equal to the radius of the face of the upper end wall of the outer and inner caps, less the radius of the base area of the geometric volume of the elastic means according to the invention.  
       [0095] When the mutual-engagement means are fitted on the inner surface of the upper end wall of the outer cap and on the outer surface of the upper end wall of the inner cap, these means are formed, for example, of teeth in ring, of blades of square, rectangular, triangular or others cross section, in a radial position, the radial length of which is limited so as to create a reserve area coaxial with the caps and needed for fitting the elastic means according to the invention.  
       [0096] According to the invention, it is possible to fit the mutual-engagement means on the facing surfaces that are intended to be fitted with these, which means have:  
       [0097] the same morphology such as, for example, teeth mounted in ring, or radial blades on each of the surfaces of the upper end walls of the caps, or notched peripheral rings on the facing surfaces of the cylindrical side walls of the caps;  
       [0098] different morphologies, such as, for example, teeth mounted in a ring on the inner surface of the upper end wall of the outer cap and radial blades on the outer surface of the upper end wall of the inner cap.  
       [0099] According to a particular alternative form of the invention, the mutual-engagement means placed facing each other on the inner surface of the upper end wall of the outer cap and on the outer surface of the upper end wall of the inner cap are formed on each of these surfaces of a ring of teeth, of which the apparent diameter, which is inferior to that of the caps, is preferably the same for each of the rings.  
       [0100] The teeth forming each of the rings are spaced apart from one another so that the teeth of the ring of the outer cap can sit easily between the teeth of the ring of the inner cap when the outer cap is subjected to axial pressure followed by the beginning of a turning movement.  
       [0101] The teeth of the rings allowing the mutual engagement of the outer cap with the inner cap are in the shape of:  
       [0102] a parallelepiped, ending at their mechanical-engagement end in two symmetric oblique planes separated from one another by a horizontal plane,  
       [0103] a parallelepiped or cylinder, ending at their mechanical-engagement end in a hemisphere or a cone frustum.  
       [0104] This particular shape of the teeth is designed so that the outer cap, when not subjected to an axial pressure but subjected only to a turning movement, can turn in either direction without driving the inner cap, it being possible for the teeth of the ring of the outer cap to slide over the teeth of the ring of the inner cap, if they are in contact with them, without engaging in one another;  
       [0105] the number of teeth present in each ring depends essentially upon the diameter of these rings: the preferred number of teeth is of at least four teeth per ring. As a preference, the ratio of the number of teeth to the diameter of the ring in mm is comprised between 0.15 (4/24) and 0.5 (12/24).  
       [0106] According to the invention, the means of guiding of the outer cap with respect to the inner cap, in order to ensure an excellent coaxiality, can be present on one and/or the other of the cylindrical side walls of each of the caps, on the outer surface of the inner cap and/or on the inner surface of the outer cap.  
       [0107] The guiding means can consist of blades with square, rectangular, triangular or others section, present over all or part of the height of the cylindrical side wall and fitted according to generatrices of said wall.  
       [0108] When these guiding means have the sole function of providing guidance, they are present on one and/or the other of the cylindrical side walls of the outer and inner caps and their height covers all or part of the height of said side walls.  
       [0109] According to the invention, these guiding means can simultaneously have two functions, the first being that of providing guidance, and the second being that of acting as a means of using the outer cap to drive the inner cap only in the screwing direction.  
       [0110] For these two functions to be able to be performed simultaneously, the blades that constitute the means of guidance and of driving in the screwing direction are preferably present over the entire height of the cylindrical side walls of the two caps. These blades in cross section have more or less the shape of a wave of triangular, rectangular cross section, the origin of which lies on a generatrix of the cylindrical side surfaces, and the end of which is directed according to an oblique plane:  
       [0111] in the direction with centripetal tendency, when the blades are on the inner surface of the cylindrical side wall of the outer cap,  
       [0112] in the direction with centrifugal tendency, when the blades are on the outer surface of the cylindrical side wall of the inner cap.  
       [0113] Thus, when the outer cap is turned in the screwing direction, with no axial pressure exerted, the ends of the guiding blades of the outer cap come into abutment with the ends of the guiding blades of the inner cap and turn the inner cap in the screwing direction.  
       [0114] To the contrary, when the outer cap is turned in the unscrewing direction with no axial pressure being exerted, the oblique planes of the guiding blades of the outer cap slide over the oblique planes of the guiding blades of the inner cap without turning said inner cap in the unscrewing direction.  
       [0115] Apart from the single elastic means which is produced independently of the caps or overmolded onto one of the two caps, using a different material to the one used for the caps, the outer and inner caps, the screw thread, the mutual-engagement means and the guiding means are produced simultaneously by injection molding with a polymer material conventionally used for such products. 
     
    
    
     [0116] The invention will be better understood by virtue of the enumerated description of the figures mentioned hereinafter, these figures merely illustrating a particular embodiment of the invention without implying any limitation.  
     [0117]FIG. 1 is a perspective view of the outer cap.  
     [0118]FIG. 2 is a perspective view of an elastic means according to the invention.  
     [0119]FIG. 3 is a perspective view of the inner cap according to the invention.  
     [0120]FIG. 4 is a perspective view of a closure means of a reservoir containing a moisture adsorbent material.  
     [0121]FIG. 5 is a vertical section of the device according to the invention made up of the outer and inner caps.  
     [0122]FIG. 6 is a horizontal section according to B-B of the device according to the invention.  
     [0123]FIG. 7 is an internal view of the outer cap of the device according to the invention.  
     [0124]FIG. 8 is a vertical section of the outer cap of the device according to the invention.  
     [0125]FIG. 9 is a perspective view of a tooth belonging to the mutual-engagement means according to the invention. 
    
    
     [0126] According to FIGS.  1  to  4 , the safety closure device according to the invention is made up of an outer cap ( 1 ), of a shape-memory elastic means ( 20 ), of an inner cap ( 40 ) and of a means of closure ( 60 ) of a reservoir of an hydrophilic substance, absorbing the internal moisture of the container (not shown).  
     [0127] The outer cap ( 1 ) is made up of a cylindrical side wall ( 2 ) and of an upper end wall ( 3 ) closing the cylindrical side wall. On the inner surface of its upper end wall ( 3 ) there is a mutual-engagement means (FIG. 7) formed of a ring ( 4 ) having a diameter smaller than that of the cap, comprising twelve teeth ( 5 ). On the inner surface of the cylindrical side wall are placed (FIGS. 5, 6,  7 ) centering means consisting of blades ( 6 ) which, in this illustrative case, perform simultaneously two functions:  
     [0128] the first of these functions is that of coaxially guiding the movement of the outer cap ( 1 ) with respect to the inner cap ( 40 ), when is applied, then released the axial pressure to the outer cap ( 1 );  
     [0129] the second of these functions is that of contributing to a means of turning of the inner cap only in the direction of the screwing of the device, in the absence of any axial pressure on the outer cap. As illustrated in FIG. 6, the blades ( 6 ) in section have more or less an elongated rectangular shape, whose inclination according to the line of the plane ( 7 ) gives an orientation (according the arrow) in the direction with a centripetal tendency and makes an angle “α” with the plane of tangency ( 8 ) at the origin of the blade ( 6 ).  
     [0130] The inner cap ( 40 ) is also made up of a cylindrical side wall ( 41 ) and of an upper end wall ( 42 ) closing the cylindrical side wall. On the outer surface of the upper end wall ( 42 ) there is a mutual-engagement means (FIG. 3) formed of a ring ( 43 ), of a diameter inferior to that of the inner cap, but identical to the diameter of the ring ( 4 ) located on the inner surface of the upper end wall of the outer cap ( 1 ). The ring ( 43 ) comprises the same number of teeth as the ring ( 4 ).  
     [0131] Also placed on the outer surface of the cylindrical side wall ( 41 ) are guiding means consisting of blades ( 45 ) which simultaneously perform two functions (in this illustrative case):  
     [0132] the first of these functions is that of coaxially guiding the movement of the outer cap ( 1 ) with respect to the inner cap ( 40 ),  
     [0133] the second of these functions is that of contributing to a means of turning of the inner cap only in the direction of the screwing of the device, in the absence of any axial pressure on the outer cap. As illustrated in FIG. 6, the blades ( 45 ) in cross section have approximately a triangular shape in which the line of the plane of the face ( 46 ) gives an orientation (in the direction of the arrow) in the direction with a centrifugal tendency and makes an angle “β” with the plane of tangency ( 47 ) at the origin of the blade ( 45 ).  
     [0134] The shape of the teeth ( 5 ,  44 ) of the rings ( 4 ,  43 ) is of the parallelepiped-rectangle type (FIG. 9) having side walls ( 90 ,  91 ) extended at their mechanical-engagement end, at the time of mutual engagement by truncated facets (oblique planes) ( 92 ,  93 ), separated from one another by a horizontal plane ( 94 ).  
     [0135] This tooth shape is such that, in the absence of axial pressure on the outer cap, but when a turning movement is applied to said outer cap, the oblique planes ( 92 ,  93 ) of the teeth ( 5 ) of the ring ( 4 ) and of the teeth ( 44 ) of the ring ( 43 ) can slide over one another (in the case they should accidentally come closer, causing their contact), without the teeth of said rings being able to engage and allow the inner cap to be turned by turning the outer cap.  
     [0136] The shape-memory elastic means ( 20 ) according to the invention lies between the upper end walls of the inner and outer caps (FIG. 2). Said elastic means ( 20 ) is of the hollow cylindro-truncated cone type, made up of a circular ring ( 21 ), of a cylindro-truncated cone side wall ( 22 ) and of a perforated upper end wall comprising a cross pin ( 23 ) and openings ( 24 ).  
     [0137] The diameter of the shape-memory elastic means is inferior to the inner diameter of the mutual-engagement rings ( 4 ) and ( 43 ), so that it can be easily inserted therein.  
     [0138] The shape-memory elastic means, produced by injection-molding by means of a blend of thermoplastic elastomers, is placed in an operating position between the two upper end walls ( 3 ) and ( 42 ) of the caps.  
     [0139] The thickness of the shape-memory elastic means ( 20 ) is very slightly superior to the distance between the end walls ( 3 ) and ( 42 ), so that, when no axial pressure is exerted, the outer cap ( 1 ) can be subjected to a turning movement (in the direction of the opening) without driving the inner cap ( 40 ).  
     [0140] When an axial pressure is exerted on the outer cap ( 1 ), the shape-memory elastic means ( 20 ) is compressed, and deforms while remaining at the same time contained within the limits of the rings ( 4 ) and ( 43 ). The compressive deformation of the shape-memory elastic means drives out the air present in the region allowing the two rings ( 4 ) and ( 43 ) to mutually engage.  
     [0141] The outer cap can turn the inner cap, particularly in the unscrewing direction. When the axial pressure ceases, the shape-memory elastic means reverts to its initial volume, in particular in recovering its initial volume of air. The two caps, as they move apart from one another, disengage: the outer cap can no longer drive the inner cap, in particular in the unscrewing direction.  
     [0142] Supplementing the device according to the invention, there is a top ( 60 ) intended to close the reservoir ( 48 ) (forming part of the inner cap ( 40 ) ) into which a substance with specific properties, such as for example the ability to adsorb the moisture internal to the container (not shown) closed by said device, is introduced.  
     [0143] In the aforesaid illustrative case of the device according to the invention, the closure of the device according to the invention is implemented via blades ( 6 ) and ( 45 ) which come into abutment when the outer cap ( 1 ) is subjected solely to a turning movement in the screwing direction: the blades ( 6 ) of the outer cap, driven in the direction of the arrow ( 49 ), come into contact with the blades ( 45 ) of the inner cap ( 40 ) by their abrupt face and drive said inner cap in the closing direction.  
     [0144] In another way, when the outer cap ( 4 ) is subjected to a single turning movement in the unscrewing direction, in the direction of the arrow ( 50 ), the blades ( 6 ) slide via their oblique plane ( 7 ) on the oblique plane ( 46 ) of the blades ( 45 ): the inner cap is not driven in the unscrewing movement.  
     [0145] In order for the device according to the invention to be opened by unscrewing, the outer cap ( 1 ) must be subjected to an axial pressure followed by a turning in the unscrewing direction. In this context, the outer cap ( 1 ) moves closer to the inner cap compressing the shape-memory elastic means ( 20 ).  
     [0146] The teeth of the ring ( 4 ) of the outer cap ( 1 ) engage with the teeth of the ring ( 43 ) in the inner cap ( 40 ): the inner cap is therefore turned by the outer cap ( 1 ) and the closure device is easily unscrewed and removed from the container (not shown).  
     [0147] In another alternative form (not shown), the safety closure device comprises all the means described in the first illustrative case, except for the sole existence of the blades ( 6 ) on the outer cap ( 1 ) or ( 45 ) on the inner cap ( 40 ), blades which interact solely for their guiding function. In this case, the closure and the opening of the device according to the invention are performed by an axial pressure on the outer cap followed by an appropriate turning, causing the mutual-engagement of the rings ( 4 ) and ( 43 ) and the driving of the inner cap ( 40 ) in the direction in which the turning is applied to the outer cap ( 1 ).