Abstract:
A screwless quick connection system for connecting a lead connector to a generator of an active implantable medical device is shown and described. The connector head includes a housing receiving a plug of a lead connector. A mechanism for locking the plug into the housing is provided by a U-folded leaf spring. Each branch of the U is provided with a respective hole sized so that the plug passes through the holes on both branches when it is inserted into the housing. The blade is deformable between a free state, in the absence of plug, and a deformed state, with the plug inserted therein. In the free state, both holes are misaligned, while in the deformed state they are aligned. In this way, an edge of both holes exerts by reaction a radial stress force against the smooth outer surface of the plug inserted therein.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 13/100,634, filed May 4, 2011, which claims the benefit of priority to French Application No. 10/53446 entitled “Screwless Quick Connection System Of A Lead Connector To A Generator Of An Implantable Medical Device” and filed May 4, 2010, both of which are hereby incorporated by reference herein in their entireties. 
    
    
     BACKGROUND 
     The present invention relates to an active implantable medical device as defined by the Jun. 20, 1990 directive 90/395/CEE of the European Community Council, including those devices that continuously monitor a patient&#39;s cardiac activity and, if necessary, deliver to the heart electrical pulses for stimulation, cardiac resynchronization, cardioversion and/or defibrillation, in response to a rhythm disorder detected by the device, and those devices such as neurological devices, cochlear implants, drug pumps, and implanted biological sensors. 
     Active implantable medical devices include a housing that is generally designated as “the generator.” The generator is mechanically and electrically connected to one or more “leads” that bear on them one or more electrodes that contact those tissues to which it is desirable to deliver electrical pulses, e.g., to apply stimulation pacing pulses, and/or to collect (detect) an electrical signal. These tissues include, for example, myocardial, nerve, and muscle tissue. 
     The French standard NF EN 50077 and its international counterpart ISO 5841-3, Implants for Surgery—Cardiac Pacemakers—Part 3: Low-Profile Connectors (IS-1) for Implantable Pacemakers, defines a normalized connection system standard in the industry, which is identified as “IS-1”. The IS-1 standard ensures interchangeability and compatibility of the leads and generators produced by different manufacturers. In this regard, it should be understood that the present invention is not limited to the particular case of a connection system according to the IS-1 standard, nor even to connection systems applicable to cardiac pacemakers. 
     Typically, the connection between a lead connector—hereafter more simply referred to as “plug”—and a connector of a generator is made by one or more screws that are tightened by the surgeon using an ad hoc tool (e.g., a screwdriver, possibly equipped with a torque limiter) at the time of implantation of the device and/or the lead. This known screw connection system has several drawbacks. First, in addition to requiring a specific tool for its implementation, this system requires the presence of caps provided with sealed slots through which the tool must pass to prevent the terminals from coming into contact with body fluids after implantation. This requirement for sealing the slots through which the tool passes increases the cost and requires a volume or size of the generator at the connector that is large enough to accommodate the tool. 
     Second, a screw connection system does not prevent from a screwing oversight, whether from an insufficient screwing or from an overtightening of the screw and damaging the device, by the surgeon. 
     Third, a screw connection system also introduces significant risks of damage to the silicone plug by the screwdriver with a consequent loss of insulation, of removal or stripping of the screw thread at the time of its use, of binding thereof, or of damage to the head of the screw in case of incorrect insertion of the screwdriver. 
     From an economic standpoint, the use of a screw system generates certain additional costs (e.g., manufacturing of the screw, threading of inserts) and requires providing with the medical device a special tool (e.g., a screwdriver with torque limiter) for tightening the screw. From an industrial standpoint, the use of a screw connector system requires an operation for inserting and adjusting the position of screws in a predetermined position during the packaging of the device, and of addition of a spot of glue to freeze this position of the screw. From a safety standpoint, the operation of screwing the screw by the physician to secure the plug requires special attention, with an implementation time large enough to make sure that the plug is maintained in the housing, precisely and durably. 
     Despite these acknowledged drawbacks, the screw connection system is still almost universally used. Indeed, the connectivity standards related to implantable medical devices require (i) minimum retention forces sufficient to prevent accidental disconnection at the time of implantation or during the product lifetime, and (ii) a high-quality and enduring electrical contact (i.e., a very low contact resistance) between the connector plug of the lead and the electrical terminal of the implantable device. These two mechanical and electrical requirements are particularly well satisfied by a conventional screw connection system, despite its many disadvantages. 
     Various other systems for securing the plug into the housing of the connector head have been proposed to overcome the many difficulties and drawbacks outlined above. 
     Thus, EP 0890371 A1 and its counterpart U.S. Pat. No. 6,112,120, both assigned to Sorin CRM S.A.S., previously known as ELA Medical, describe separating the electrical contact and mechanical retention functions. The electrical contact is ensured by a spring system exerting a radial pressure against the conductive surface of the plug. The mechanical retention of the plug in the housing is secured by a locking wedge inserted between the body of the plug and the housing wall at the outlet thereof. 
     Another solution is proposed by EP 0900577 A1 (assigned to Sorin CRM S.A.S., previously known as ELA Medical), which implements a locking system with a retractable spring-loaded eccentric, locally applied against the plug and bearing against it response to an attempted extraction. 
     These solutions are functionally effective, but they involve relatively complex, and therefore expensive to produce, mechanical systems (e.g., including elements such as a spring, eccentric, and slide). They also require a specific release mechanism for the removal of the plug, typically requiring the use of a special tool for removing the holding or retraction force provided by the eccentric. Finally, they require special precautions to durably ensure the efficient sealing required at the connector. 
     Other known efforts at alternative connection systems implement deformable elastic elements such as metal blades with one or more orifices through which the plug passes when inserting it into the slot, and exerting a radial point of contact between the edge of the orifice and the surface of the plug. 
     Thus, U.S. Pat. No. 5,252,090 (Giurtino et al.) proposes to block the plug with an elastically deformable metal piece, extending around the plug in a plane substantially radial to the axis of the plug. Deformable tabs formed in the part produce by stemming an anti-kickback effect, preventing any withdrawal or pulling of the plug once it is inserted in the metal part. For disassembly, the part is extended laterally by two symmetrical ears that, by pinching, deforms the piece enough to remove the tabs of the plug and release it. This device is very effective in terms of mechanical retention. However, unlocking the device requires having two entrances on each side of the part, to ensure a symmetrical pinching, and therefore requires providing two release buttons (one on each side of the head connector). 
     FR 2 662 310 A (Darby et al.), refers to an elastic clamp whose ends of the two arms are folded against one another and are provided with holes corresponding to the diameter of the plug. The holes are shifted when the clamp is in the free state, and they can be aligned by moving the two arms of the clamp. The plug can then be introduced through the two holes, and be retained in the clamp after release of the force exerted to bring the two arms together. This connection system is very effective in terms of mechanical retention of the plug, but it is not designed to be integrated with a generator. Rather, it is presented to serve as a dispensing connector between several leads, this connector being placed away from the generator. 
     SUMMARY 
     It is therefore, an objective of the present invention to provide a generator for an active implantable device including a connector head provided with a connecting system for the plug of a lead that is both simple and effective and that would:
         allow connection and disconnection of the plug to the connector terminal without screws and without ad hoc tools;   establish a strong mechanical connection ensuring an effective and permanent retention of the plug, even in the case of plugs with smooth surfaces such as those carried out in accordance with the IS-1 standard mentioned above; and   be integrated into the very small volume of the connector head of an implant, so as to be minimally invasive for the patient.       

     Broadly, the present invention is directed to a leaf spring system which, by its geometric characteristics and the nature of the material used, can provide a tool-free system for securing a plug when it is inserted into the connector housing of the generator of the device with a specific geometry for ensuring the mechanical action of locking/unlocking the plug from one only side of the generator. 
     One embodiment of the invention is a device in which the connector head includes, in a manner in itself known, for example, according to the FR 2 662 310 A cited above, at least one female housing provided with an electrical connection terminal and able to receive a plug, the plug having, for example, a smooth surface of a cylindrical or prismatic lead connector, and locking means for the mechanical immobilisation of the plug in the housing. The locking means preferably has a resilient member adapted to be deformed and placed under elastic tension when inserting the plug into a slot in the housing in which the resilient member is disposed. The resilient member also is adapted to be deformed after insertion of the plug, the elastic deformation then being in an axial direction, such that the resilient member comes to exert a retention force on the plug. This retention force in the radial direction exerts contact pressure against the smooth surface of the plug far exceeds the force of insertion of the plug into the housing, and opposes an extraction force applied to the plug. The device also includes structure for releasing the locking means, able to apply to the resilient member, due to an external force, a mechanical force to neutralize the retention force and thereby permit an extraction of the plug from the housing. 
     In one embodiment, the resilient member is a leaf spring folded to have a generally U-shaped portion including a central region at the base of the U and two legs or branches of the U extending from the central portion. A first branch preferably extends in a plane in a first direction forming a first angle with respect to an axial direction of insertion of the plug into the slot, and a second branch preferably extends in a plane in a second direction forming a second angle with respect to the axial direction of insertion. The two branches are elastically connected in the central region of the U and extend from the central region to a respective end, and each branch is provided with a respective hole sized so that the plug can pass through the holes when the plug is inserted into the slot. 
     The leaf spring is thus deformable between a free state or unstressed position, in the absence of a plug, and a deformed state or stressed position, with the plug inserted. In the free position, the projections of the two holes in the first and second branches in the plane perpendicular to the axial direction of insertion are overlapping but misaligned, while in the stressed position the projections are aligned, so that one edge of each hole crossed by the plug exercises, by a reaction effect of the deformed leaf spring, a radial stress force against the smooth outer surface of the plug, thereby producing said contact pressure and a retention force. 
     The first branch may in particular extend in a direction primarily perpendicular to the axial direction of insertion and the second branch in a direction, primarily oblique to, forming, for example, an angle between 45° and 75° from, the axial direction of insertion. 
     In a first embodiment, the end of one branch of the U-shaped portion is a stationary end relative to the head of the connector, and the end of the other branch is a free end that is extended by a flange which serves as a support element. In an alternate embodiment, an auxiliary elastic body may be interposed between the connector body and the central region of the U at the junction of the two branches. 
     In a second embodiment, the end of one of the branches of the U-shaped portion is a free end extended by a flange serving as a support element, the end of the other branch is a pivoting end moving over the head of the connector, about an axis perpendicular to the axial direction of insertion, and a resilient return member is further inserted between the connector body and the central region of the U at the junction of the two branches. 
     In either embodiment, the flange is advantageously a flat push-button extending in a plane generally or substantially parallel to the axial direction of insertion, which can notably extend into an internal cavity of the connector head, this cavity being isolated in a sealed manner from the outside environment. The flange may also include an element causing a tactile response to the change of state between the free and stressed positions. 
     Preferably, the leaf spring is a metal blade connected to a terminal for making an electrical connection, between the lead and the generator, so as to achieve simultaneous mechanical immobilization of the plug in the housing and electrical connection of this plug to the connection terminal of the generator. 
     Advantageously, the present invention provides a quick screwless connector system that is handled via a single support, located on only one side of the connector head (for the lock as well as for the unlock operation). Further, the present invention locking means is sealed vis-à-vis the outside world, that is to say that no bodily fluid that would promote a loss of electrical insulation or corrosion can leak into the housing through the locking means. It also is simple to manufacture and inexpensive to industrialize. In addition to providing a mechanical connection, it also provides an electrical connection between the terminal of the generator and the plug with, in this case, a sufficiently low contact resistance (in accordance with the industry standards in force for electrical contact resistance, for example, for stimulation/detection below 5 Ohms for static and below 10 Ohms for dynamic resistance, and for defibrillation below 0.5 Ohm for static and 1 Ohm for dynamic resistance), and during the useful life of the product. The present invention also is well suited to manual use by a doctor equipped with gloves, with appropriate forces needed to lock or unlock the plug, and a use that is not affected by the environment in which the device is used (blood medium in particular). Moreover, the invention realizes a reduction of the metal mass used, providing an improved electromagnetic compatibility of the device, and a lever arm effect of reducing the effort needed from the doctor for locking and unlocking the plug and, conversely, producing with an equal force a greater contact force between the connector and the plug, therefore less electrical resistance at the point of contact. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further features, characteristics and advantages of the present invention will become apparent to a person of ordinary skill in the art from the following detailed description of preferred embodiments of the present invention, made with reference to the drawings annexed, in which like reference characters refer to like elements and in which: 
         FIG. 1  is an elevated perspective of a generator partially cutaway to show a lead tip for an implantable cardiac device inserted into a connection system in accordance with the present invention; 
         FIG. 2  is an isolated view of the connector head of the device of  FIG. 1  showing in exploded view the leaf spring before introduction into the slot; 
         FIG. 3  is a detail view in perspective of the underside of the leaf spring of  FIG. 1 ; 
         FIG. 4   a  and  FIG. 4   b  illustrate a first embodiment of the present invention showing the leaf spring in the free state at the beginning of introduction of the plug, and the deformed state once the plug is completely inserted and stressed into place by the leaf spring, respectively; 
         FIG. 5   a  and  FIG. 5   b  are perspective views corresponding to respective configurations of  FIG. 4   a  and  FIG. 4   b;    
         FIG. 6   a  and  FIG. 6   b  are similar to  FIG. 4   a  and  FIG. 4   b , for a second embodiment of the present invention; and 
         FIG. 7   a  and  FIG. 7   b  are counterparts of  FIG. 5   a  and  FIG. 5   b , for the second embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     Preferred embodiments of a device according to the present invention will now be described with reference to  FIGS. 1-7 , 
     In  FIG. 1 , reference  10  generally designates a generator of the device, a cardiac pacemaker given here as an example of any device to implement the teachings of the invention. 
     Generator  10  includes a body  12  enclosing the various electronic circuits and power source (e.g., a battery), coupled with a connector head  14 . In the example shown, connector head  14  is intended to accommodate two different leads and therefore contain the connection terminals (not shown) having conductive elements embedded in the insulating body of the connector head  14 , for example, made of epoxy resin. 
     To allow insertion of lead tips, each of which comprising electrical connection elements, the connector head  14  includes female housings or slots  16 ,  18  (also visible in  FIG. 2 ) in which the proximal end  20  of the lead is introduced, as shown in  FIG. 1 . 
     The lead is, e.g., a bipolar lead including a lead according to the IS-1 standard mentioned above. This lead has at its distal end  20  a first smooth and cylindrical conductive surface  22 , herein simply referred to as “plug”. This plug is protected by a first insulating sheath  24  (also shown in  FIG. 3 ) with peripheral reliefs  26  and  28  to ensure a sealing function vis-à-vis the external environment when the end of the lead is fully inserted into the corresponding slot  16  of connector head  14 . In the case of a bipolar lead, the end  20  carries a second conductive surface, coaxial and shifted from the first (not shown), and protected by a second insulating sheath. 
     The present invention relates to the mechanical retention of the end  20  of the lead once it is fully inserted into the corresponding housing slot  16  or  18 . It should be understood, however, that the present invention is not, prima facie, the electrical connection between conductive surfaces of the plug and the connection terminals of the connector head, because these two functions can be separated. Instead, the present invention focuses on the mechanical locking of the lead end (plug) into the connector head slot. It also should be understood that the plug need not have a smooth and cylindrical conductive surface, although that is a preferred and standard construction. 
     Advantageously, the electrical connection and mechanical locking may be provided by a common element (e.g., a metallic blocking conductive part electrically connected to the circuits of the generator). In other words, the invention is equally applicable in the case wherein the electrical connection is provided by a separate element from the one ensuring the mechanical retention and in the case wherein the same element performs these two functions. 
     In the illustrated example, the mechanical retention of the lead tip  20  in its housing is ensured by the distal end, that is to say by the plug  22 , an area where the diameter of the plug is the smallest. The distal end  22  is generally in the shape of a cylindrical metal surface, but the present invention can be extrapolated by a person of ordinary skill in the art to other materials, conductive or not, and other shapes, including prismatic shapes instead of cylindrical shapes. 
     Retention of the plug is secured by a leaf spring  30  shown in detail in  FIG. 2 , and  FIG. 3 ,  FIG. 4   a ,  FIG. 4   b ,  FIG. 5   a ,  FIG. 5   b  (for a first embodiment) and in  FIG. 6   a ,  FIG. 6   b ,  FIG. 7   a  and  FIG. 7   b  (for a second embodiment). 
     This leaf spring  30  is made of an elastically deformable material, for example, a spring steel. It has a generally U-shaped geometry comprising a first branch  32 , on the plug insertion side, and a second branch  34 , on the opposite side, with the two branches being united by a central region  36 . 
     The first branch  32  extends in a plane substantially normal to the Z direction of insertion of the plug (also referred to as the “Z axis of insertion”), as illustrated in  FIGS. 1 and 4   b . The end  38  of the first branch is provided with structure to immobilize it relative to the connector head, which can be, for example, pins or lugs that engage the housing. The second branch  34  is in a plane that is oblique to the Z axis of insertion, with an inclination angle of about 45° to 750. The second branch  34  is extended at its end by a flattened surface  40 , hereinafter simply designated as a “flange”, extending in a plane substantially parallel to the Z axis of insertion. 
     The leaf spring  30  is provided with two holes whose dimensions are adapted to receive the plug  22 , with a hole  42  in the first branch  32  and a hole  44  in the second branch  34  located approximately vis-à-vis the hole  42 . In a preferred embodiment, the hole  42  (on the branch  32  approximately normal to the axis of insertion) is a circular hole whose dimensions correspond to the diameter of the plug  22 , except for the dimensional tolerances. For example, for an IS-1 distal plug, the dimension is 1.59+/−0.03 mm, and for a DF1 distal plug, the dimension is 1.25+/−0.03 mm. The hole  34  (the second branch  44  which extends obliquely to the Z axis of insertion) is an oblong hole, so that it can also be crossed, except the dimensional tolerances, by the plug inserted along the Z axis of insertion. 
     As can be seen in greater detail in  FIG. 4   a  and  FIG. 4   b , the holes  42  and  44  are slightly shifted with respect to each other when the leaf spring is in the free state, that is to say in the absence of any external forces and before insertion of the plug  22  (see  FIG. 4   a ). However, these holes are aligned when the plug is inserted, the leaf spring  30  then being in a deformed state of elastic stress (see in  FIG. 4   b ). This alignment of the holes geometrically defines a channel through which the cylindrical plug  22  can be inserted, housed and kept in place. 
     The leaf spring  30  may be made by folding of a metal strip or blade of constant or variable thickness, with a sheet thickness typically between 0.4 and 0.6 mm. A variable thickness allows taking advantage of the relative stiffness differences associated with the different thicknesses of leaf spring  30 . The various cuts, including holes  42  and  44 , are preferably made in the metal blade which it is flat and the metal blade is then folded into the desired U-shape and inspected (e.g., for proper stiffness, and position of holes). The bending radius of the central region  36  and of the region connecting the second leg  34  to the flange  40  is preferably about 1.5 times the thickness at this location. It is also possible to stamp some zones to locally stiffen the metal structure. The material used is preferably a medical implantable grade material, e.g., a 316 LVM stainless steel or titanium. 
     The metal blade thus produced is introduced into a cavity  46  formed in the connector head  14 , the latter being preferably made by molding a medical implantable grade polymer material, e.g., Tecothane (trademark) 1075 DM. The molding can directly form the cavity  46  which opens into one of the two housings  16 ,  18  for receiving the plug, providing also a groove  48  receiving the lugs  38  of the end of the first branch  32  of the leaf spring  30 . These grooves can thus secure this end, further providing guidance, direction and positioning of the leaf spring  30  in the connector head  14 . 
     Alternatively, instead of mounting the leaf spring  30  in the polymer block of the connector head, it is possible to mount it in an intermediate part, for example, a shaped cage, which will later be incorporated in and/or bonded to a proper location of the connector head. 
     To ensure sealing after placement of the leaf spring  30 , the housing  46  is sealed by a flexible cover (not shown) of elastomer or plastic, secured to the connector head  14  by known techniques. For example, a seal of silicone adhesive can be deposited at the interface between the connector head  14  and the flexible cover, or the cover can be crimped using a seam framework set in the connector head or ultrasonically welded, to prevent any liquid infiltration. 
     The flexible cover allows the transmission of a force pressing on the flange  40  of the leaf spring  30 , e.g., by a practitioner&#39;s finger. This maneuver, performed through a flexible element, eliminates any sealing problem in connection with locking/unlocking the plug. 
     Preferably, the connector head  14  is provided with as many cavities and leaf springs as there are lead ends to be coupled to the device. In the example shown, on one side of connector head  14  is a cavity  46  for receiving a leaf springblade  30  for blocking the proximal end of the lead (plug) inserted into the cavity  18 . A configuration of the same type is carried on the opposite side (not visible) of the connector head to immobilize the lead tip to be inserted into the cavity  16 . Thus, one of the leaf springs  30  is arranged on one side of the connector head (visible in  FIG. 2 ), the other being disposed on the opposite lateral face (not visible in  FIG. 2 ). The practitioner thus has two support zones with two different buttons, one on each side of the connector head, to lock/unlock either one or the other of the two lead tips, by a maneuver executed with only one finger on either side of the connector head  14 . 
     As shown in the bottom view of  FIG. 3 , the flange  40  preferably comprises on one side a “tactile” device  50  that is like a pushbutton, allowing the practitioner to feel a “click” at end of the support movement when the mechanism is sufficiently engaged, and another “click” when he releases the pressure from the support zone of the pushbutton on flange  40 . 
     The mechanical principle of the invention will now be explained with reference to  FIG. 4   a ,  FIG. 4   b ,  FIG. 5   a  and  FIG. 5   b , as part of a first embodiment (corresponding to  FIGS. 1-3  described above). 
     The principle of tightening results of the deformation of the leaf spring  30 : by exerting pressure (arrow  52 ,  FIG. 4   a ) on the pushbutton of flange  40 , the user flexes (arrow  54 ,  FIG. 4   a ) the second oblique branch  34  at an oblique angle to insertion axis Z whose end is free. This action thus aligns the oblong hole  44  of the second branch  34  and the cylindrical hole  42  of the first branch  32  disposed in a plane essentially normal to insertion axis Z. The plug  22  can then be inserted (arrow  56 ,  FIG. 4   a ). In the final position corresponding to a full insertion, the pressure  52  on the pushbutton of flange  40  is released so that the leaf spring  30  tends to return to its original position, but is completely prevented due to the presence of the plug  22  through the hole  44  (configuration of  FIG. 4   b ). 
     The plug  22  is thereby clamped through a process of “amplified rubbing” to control the retention force and to avoid any undesired disconnection. Specifically, the leaf spring  30  applies a normal force on the plug  22  at contact points  58  and  60  of the first branch  32  and second branch  34 , respectively, thus creating the phenomenon of adhesion between the two mechanical surfaces (that of the leaf spring and that of the plug). From the point of view of statics, this configuration can be described by a friction cone of angle Φ characteristic of the friction coefficient f between the two surfaces, the boundary conditions being given by ƒ=arctan(Φ). The geometry of the leaf spring blade helps maintain the plug in place because any attempt to remove the plug causes at the plug/leaf-spring interface a change of orientation of the normal force at contact points  58  and  60 . Due to friction any withdrawal force in tangential projection is opposed by a greater retention force opposing the withdrawing motion. 
     Preferably, the geometric configuration can even cause a mechanical phenomenon of jamming the plug  22  in leaf spring  30  in case of attempted withdrawal, with such a gripping force that any movement will be effectively prevented, while maintaining the static balance of forces: whatever the intensity of external mechanical actions, the bias generated by the deformation of the leaf-spring  30  causes jamming of the plug  22 . The conditions for this jamming can be calculated according to known methods, taking into account the parameters constituted by the coefficient of friction f (depending on the type of materials used), the guide length L between the two contact points  58  and  60 , the diameter of the plug and the diameter of the holes  42  and  44 . 
     The blocking of the plug by the leaf spring blade  30  is in any case reversible. In this regard, a new pressure (arrow  62 ,  FIG. 4   b ) on the pushbutton of flange  40  allows for a relative movement of branch  34  and provides free passage to pull back the plug (arrow  64 ,  FIG. 4   b ) or to reposition it. 
     In an advantageous embodiment, the elastic properties of tactile feedback device  50  described above with reference to  FIG. 3  can be used to amplify by leveraging the force exerted by the leaf spring blade  30  on the plug  22  after the latter has been introduced. 
     Alternatively or in addition, to further increase the retention force of the leaf spring blade  30 , it is possible to add to the pushbutton of flange  40  a layer of elastomer material which deforms to allow passage of the plug  22 , bringing by reaction extra force at the leaf spring blade to maintain the end of the plug  22  fixed in position. 
     A second embodiment of the present invention is described with reference to  FIG. 6   a ,  FIG. 6   b ,  FIG. 7   a  and  FIG. 7   b , which are counterparts of  FIG. 4   a ,  FIG. 4   b ,  FIG. 5   a  and  FIG. 5   b . In this second embodiment, the end of the second branch  34  is not a free end, but rather one end mounted on pivot  66  in the connector head, for example, by means of two lugs  38  (visible on  FIG. 7   a  and  FIG. 7   b ) mounted without embedding into a corresponding homologous groove of the connector head. 
     The end of the first branch  32 , in turn, is a free end equipped with the flange  40  on which the blocking support (arrow  52 ,  FIG. 6   b ) or release support (arrow  62 ,  FIG. 6   b ) will be exercised. The configuration also includes a fixed elastomer pressure cushion  68  (e.g., placed at the bottom of the cavity receiving the leaf-spring  30 ) and supporting the central region  36  of the U of the leaf-spring  30 . 
     Under the effect of a pressure force (arrow  52 ) exerted on the first branch  32 , the leaf-spring  30  pivots around the connection  66  at the opposite end of the branch, and deforms while releasing the passage of plug  22  through holes  42  and  44  along insertion axis Z. 
     Once the plug  22  is inserted and the force  52  is removed, the plug  22  is blocked under the force of friction at the contact points with the edges of holes  42  and  44 , according to the same principle as that described above in connection with the first embodiment. The deformed elastomer cushion  68  generates a permanent opposing force that helps maintain the plug  22  tight and increases the retention force (arrow  70 ,  FIG. 6   b ). 
     To release the plug  22 , the maneuver is similar: a push (arrow  62 ,  FIG. 6   b ) on the flange  40  causes, against the resisting force of the elastomer cushion  68 , a pivot (arrow  72 ,  FIG. 6   b ) of the leaf spring  30 , which deforms again, releasing the retention force previously held on the plug  22  and allowing plug  22  to move. 
     One skilled in the art will appreciate that the present invention can be practiced by other than the embodiments described herein, which are provided for purposes of illustration and not of limitation.