Abstract:
A driving device for actuating a latch via a lock, for a motor-vehicle door closure system, includes a coupling element including a longitudinal body having ends capable of being rotatably coupled with a part, mounted movably in axial rotation, of the lock and with a part, mounted movably in axial rotation, of the latch. At least one cylinder made from rigid plastic is fixed on the body such that longitudinal portions of the body left visible are smaller than 20 mm (millimeters).

Description:
FIELD OF THE INVENTION 
     The present invention relates to a driving device for actuating a latch via a lock. 
     The invention applies particularly advantageously, but not exclusively, to the field of motor-vehicle door closures. 
     BACKGROUND OF THE INVENTION 
     In a motor-vehicle door, the lock and the latch associated therewith are generally installed at a distance from one another and, above all, at different levels. In order for the lock to be able to control operation of the latch despite this particular relative positioning, it is known to use a driving device that mechanically connects the movable part of said lock to that of said latch. 
     The driving device generally takes the form of a rotating coupling element whose one end is coupled with an axially rotating movable part of the lock via a universal joint-type link. The other end of the coupling element is also rotatably coupled, still by means of a universal joint link, but this time with an axially rotating movable part of the latch. The rotationally movable parts in question are usually constituted by the lock barrel and by the external control lever of the latch, respectively. 
     This type of arrangement nevertheless has the drawback of being extremely vulnerable to tampering. The coupling element is in fact relatively easy to access from the outside if, first, the rubber seal component between the window and the sheet metal outer panel of the door is removed and if, second, said panel is separated from said window as far as possible using an inflatable balloon, for example. It is then not difficult to make sufficient space to allow the insertion of multi-grip pliers with the aim of gripping the coupling element in order to forcibly rotate it. The universal joint is indeed held by the lock, but if a sufficiently high degree of torque is applied it is possible to break at least one component of the rotation drive train, i.e. to cause a breakage inside the lock and/or of the coupling element and/or at the interface between these two members. If a torque continues to be applied thereto via the pliers, the coupling element will actually be rotated. As the coupling element is, furthermore, still coupled with the control lever of the latch, rotation thereof will thus cause said lock to be unlocked. All that remains is then to pull the handle, and the door will open. 
     In order substantially to reduce the vulnerability of such a device, it is generally proposed to add a fixed cap that covers the coupling element. 
     Another method consists in increasing the coupling element&#39;s resistance to torque. 
     Unfortunately, these various solutions have the drawback of being less compact. 
     Thus, the technical problem to be solved by the subject of the present invention is to propose a driving device for actuating a latch via a lock, in particular for a motor-vehicle door closure system, that includes a coupling element whose ends are capable, respectively, of being rotatably coupled with a part, mounted movably in axial rotation, of the lock on the one hand and with a part, mounted movably in axial rotation, of the latch on the other, a driving device of this type making it possible to avoid the prior-art problems by offering, in particular, enhanced compactness and a substantially improved resistance to tampering. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a driving device for actuating a latch via a lock, in particular for a motor-vehicle door closure system, that includes a coupling element  30  whose longitudinal body  40  has ends  43  and  44  that are capable, respectively, of being rotatably coupled with a part, mounted movably in axial rotation, of the lock  10  on the one hand and with a part, mounted movably in axial rotation, of the latch  20  on the other, characterized in that the body  40  of the coupling element includes at least one cylinder  50  made from rigid plastic and fixed on said body  40  such that the longitudinal portions of the body  40  left visible are smaller than 20 mm (millimeters). 
     “Visible longitudinal portions” of the coupling element body is understood to mean the parts not covered or protected by the plastic cylinder, when they are considered in the longitudinal direction of the coupling element body. 
     Furthermore, the plastic will be called “rigid” because it has a low, or very low, elastic deformation. By way of example of a plastic used, mention may be made of POM (polyoxymethylene), PA (polyamide), PBT (polybutylene terephthalate), ABS (acrylonitrile butadiene styrene), PUs (polyurethanes) or epoxies. 
     The longitudinal portions of the body left visible have been limited to 20 mm (millimeters) in order to make it more difficult for the device to be attacked using a conventional tool that grips a visible zone, i.e. a zone not entirely covered or protected by the cylinders, of the coupling element body, thereby forcing it to rotate. 
     Further advantages of the invention will be apparent from the following optional characteristics:
         the cylinders are overmolded on the coupling element body,   the plastic of the overmolded cylinders has a coefficient of friction on the coupling element body of less than 0.4,   the overmolded cylinders are connected together via at least one overmolded coupling zone,   the cylinders are fixed on the coupling element body by adhesive bonding,   the longitudinal portions of the body  40  left visible are less than 12 mm and preferably less than 5 mm, and in this configuration it is impossible, using a conventional tool to force the driving device, to be able to grip a zone, not entirely covered or protected by the cylinders, of the coupling element body, thus forcing it to rotate,   the torque exerted on a cylinder so that it separates from the element body is strictly lower than the torque required for interrupting the drive train of the rotational movement between the lock and the coupling element,   the coupling element body is made from metal or ceramic,   the ends of the coupling element body are overmolded,   the plastic of the cylinders fixed on the coupling element body is constituted by a matrix and a reinforcement,   the plastic of the cylinders fixed on the coupling element body is POM, PA or PBT, optionally with a reinforcement,   the cylinder fixed on the coupling element body covers practically all thereof,   a plurality of cylinders fixed on the coupling element body covers practically all thereof.       

     As the plastic cylinders are overmolded or fixed by adhesive bonding, exerting, on one or more cylinders, a torque lower than the torque necessary to interrupt the drive train of the rotational movement between the lock and the coupling element will be sufficient for said cylinder(s) to detach from the coupling element body, thereby becoming free to rotate relative to the latter. 
     Furthermore, after detachment, as the cylinders have been overmolded or fixed by adhesive bonding the cylinder interface or cylinder plus adhesive with the coupling element body has zero play. Thus, the device according to the invention offers a lower vibration level. 
     Furthermore, owing to their inherent rigidity, the protective cylinders are capable of individually withstanding the deformation forces likely to be applied to them, particularly during an attempt to crush them using pliers. In this respect, it will be understood that the inherent rigidity of the cylinders may arise, in particular, from the nature of the material of which they are composed and/or their structure and/or their dimensions. 
     Within the context of the invention, the fact that the protective cylinders are rigid therefore means that they are substantially non-deformable vis-à-vis at least such crushing forces as are likely to be generated when a conventional gripping tool is wielded manually. 
     Obviously, it would be ideal for the protective cylinders not to deform at all, in order to retain their freedom to rotate axially relative to the coupling element. There would then be no possibility of axially rotating the coupling element from the outside, which enhances the tamperproof nature of the closure system. 
     However, a similar result may be obtained if the protective cylinders deform slightly. Indeed, if crushing is not too great, gripping between the protective cylinders and the coupling element is insufficient for it to be possible for a high enough torque to break one of the lock components to be transmitted. There will indeed be a torque that can be transmitted by the protective cylinders, but it is much less than the torque required to interrupt the transmission train of the rotation movement between the lock and the coupling element. 
     “Covers practically all the coupling element” will be understood to mean that at least 90% of the surface of the coupling element is covered by the cylinders that are overmolded or fixed by adhesive bonding. 
     “Coefficient of friction μ” will be understood usually to mean the ratio of the friction force to a force, customarily gravity, acting perpendicularly to the two contact surfaces. 
     By virtue of a low inherent coefficient of friction, the protective cylinders, after they have been detached from the coupling element body, will be free to rotate axially. There will then be no possibility of axially rotating the coupling element from the outside, which enhances the tamperproof nature of the closure system. It will be understood that the low inherent coefficient of friction of the cylinders emanates from the nature of the material of which they are composed. 
     The invention as defined thus offers the advantage of protecting that portion of the coupling element that is neither integrated into the lock nor integrated into the latch and is theoretically accessible in prior-art closure systems. During a forcible attack using pliers, the overmolded cylinders will become detached and will be able to turn freely about the coupling element body. The cylinders then form a movable interface that prevents direct grasping of the coupling element, preventing it being possible for a torque to be applied axially to the coupling element with a view to forcing the closure system with which the driving device is associated. It will thus be impossible to transmit sufficient torque to the latch and to unlock the door. 
     The present invention also relates to the characteristics that will become apparent during the following description and which should be considered in isolation or in accordance with all their possible technical combinations. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The description, given by way of non-limiting example, relates to one embodiment concerning the fixing of the cylinders by means of overmolding. Naturally, the same functions could be obtained with the cylinders being fixed by adhesive bonding. This description will afford a better understanding of how the invention may be embodied, with reference to the appended drawings, in which: 
         FIG. 1  is a cross-sectional view of a motor-vehicle door provided with a closure system that includes a lock and a latch coupled by means of a driving device according to the invention; 
         FIG. 2  specifically illustrates the driving device of  FIG. 1 , which is in accordance with a first embodiment of the invention; 
         FIG. 3  specifically illustrates the driving device of  FIG. 1 , which is in accordance with a second embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     For reasons of clarity, the same elements have been denoted by identical reference numerals. Similarly, only those elements that are essential for an understanding of the invention have been shown, irrespective of scale and schematically. 
       FIG. 1  illustrates a motor-vehicle door  100  that is conventionally provided with a closure system  1  composed essentially of a lock  10  and a latch  20 . Specifically, the lock  10  is installed through an outer panel  101  of the door  100  by means of a holding module  102  that furthermore supports an opening handle  103 . The assembly is arranged such that the head  11  of the lock  10  emerges on the outside. The latch  20  is arranged further inside the door  100 , beyond a window  104  that, in this case, extends rearwards. 
     In this first representation, it will be clearly noted that the lock  10  and the latch  20  are arranged at a distance from one another and at different levels. In order for the lock  10 , however, to be able to fulfill its principal function, i.e. locking and/or unlocking the latch  20 , the closure system  1  is further provided with a driving device  30  that mechanically connects a movable part of said lock  10  to a movable part of said latch  20 . 
     In this particular embodiment, which is provided solely by way of example, the driving device  30  is rotatably coupled with the barrel  12  of the lock  10  and a control lever  21  of the latch  20 , respectively. It should be noted that the control lever  21  in question here has a deflecting cone that enables it to interact during entrainment with the driving device  30 , despite the offset of the axis of the lock  10  relative to the axis of the latch  20 . It will also be observed that the latch  20  has been only partially represented here, simply for reasons of clarity. 
     As may be seen more clearly in  FIG. 2 , the driving device  30  is provided with a coupling element  40  whose ends  43 ,  44  are, respectively, capable of being rotatably coupled via universal joint-type links with a part, mounted movably in axial rotation, of the lock  10 , namely the barrel  12 , and with a part, mounted movably in axial rotation, of the latch  20 , in this case the control lever  21 . 
     The coupling element  40  is made from steel, which makes it possible to reduce its cross section, as opposed to Zamak, or plastic, without thereby reducing its resistance to torque. 
     As the assembly of the driving device  30  and, in particular, the two ends  43 ,  44  is difficult to produce from steel, the ends of the body in steel of the coupling elements  40  are first flattened and then the two coupling end pieces  43  and  44  are overmolded thereon. 
     Furthermore, and in accordance with the subject of the present invention, the driving device  30  includes, on the steel body of the coupling elements  40 , one or more cylinders  50  overmolded in rigid plastic that has a low coefficient friction. 
     According to the first embodiment illustrated  FIGS. 1 and 2 , the protective cylinders are distributed over the entire length of the element  40 , with a small space separating one cylinder from another and a small space separating the outer cylinders from the coupling end pieces  43  and  44 . This small space is necessary to prevent a tool, used to force the closure system, from being able to gain access to an uncovered zone of the element  40 . 
     Furthermore, in order to facilitate the injection-molding operation, the cylinders are overmolded during a single operation using a reduced number of injection point. To that end, one or more channels of small dimensions are made in the mold between the zones used for the overmolding of the cylinders. The material to be injected can thus pass from a zone of one cylinder where overmolding is to take place to another. When the mold is removed, the result is a plurality of cylinder with a linking zone  60  between them. Preferably, for cylinders 10 mm in length and 1 mm in thickness the linking zones will be 5/10 to 1 mm wide, 1 mm thick and 5 mm long. 
     The plastic used in accordance with the present invention must offer good mechanical strength and a coefficient of friction μ on steel of less than 0.4. POM (polyoxymethylene), PA (polyamide) or PET (polybutylene terephthalate) are examples of materials offering such characteristics. These various materials may be used in charged or uncharged form. 
     The coupling element is generally sized in order to be able to rotate a torque of at least 5 Nm (Newton meter) before rupture. 
     In accordance with the present invention, when a tool used to force the closure system grips the coupling element it is necessarily in contact with the surface of one or more protective cylinders, which at this stage are secured to the steel body of the coupling element via a plastic/steel link. Owing to the low linking force, a torque of the order of 1 to 2 Nm (Newton meter), which is much less than the torque (&gt;5 Nm) required to rupture the drive chain of the rotational movement between the lock and the coupling element, suffices to cause detachment of the cylinder(s) with which the tool was in contact. Once to detach, the cylinder(s) may rotate freely about the axis of the coupling element. It will be clearly understood that the linking zones between two cylinders, given their small dimensions, will soon break. The cylinder(s) forms/form a kind of movable interface that prevents direct grasping of the coupling element, making it impossible for a torque to be applied axially thereto with a view to forcing the closure system with which the driving device is associated. 
     In the second embodiment, illustrated in  FIG. 3 , a single cylinder  50  substantially covers all the steel body  40  of the coupling element. The body  40  of the coupling element  30  in fact refers to the entire central part extending between the two interfaces  43  and  44 , which are designed to be rotatably coupled with the lock  10  and the latch  20 , respectively, which for this reason are designed to be incorporated inside said lock  10  and said latch  20  and which are consequently practically inaccessible. 
     In a manner similar to that of the first embodiment, when a tool used to force the closure system grips the coupling element  30  it is necessarily in contact with the surface of the protective cylinder  50 , which at this stage is secured to the steel body  40  of the coupling element  30  via a plastic/steel link. Owing to the low linking strength, a torque of the order of 1 to 2 Nm, much less than the torque (&gt;5 Nm) required to interrupt the drive train of the rotational movement between the lock and the coupling element, suffices to cause the detachment of the protective cylinder  50  with which the tool was in contact. Once to detach, the cylinder  50  can rotate freely about the axis of the coupling element  30 . The cylinder  50  then forms a kind of movable interface that prevents direct grasping of the coupling element  30 , making it impossible for a torque to be applied axially thereto with a view to forcing the closure system with which the driving device is associated. 
     Naturally, the invention also relates to any closure system  1  provided with a lock  10  and a latch  20  in which said lock  10  is able to actuate said latch  20  by means of a driving device  30 , as described above. 
     Yet more generally, the invention further relates to any motor vehicle provided with at least one closure system  1  as described above.