Abstract:
The unit ( 1 ) comprises two half-shells ( 11, 12 ) and a membrane ( 2 ) acting as a seal. The membrane comprises various zones of shapes and of properties suitable for providing additional functions such as a lightguide ( 21 ), a contact lug ( 23 ) and battery retainer lug ( 4 ), or else an escape path for static electricity discharges ( 25 ).

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a remote control unit, for example of the type used together with a motor vehicle key to remotely control the opening or the closing of the vehicle doors. 
     At present, it is common practice for motor vehicle keys to be combined with remote control devices, housed in the bow end of the key or in an associated key holder. These devices are subject to environmental attacks, such as, for example, falling into a pool of water, and must therefore be especially protected, both for watertightness and for impact resistance. Such a key is known from the prior art, for example, from document EP-A-0 690 189, the bow end of which key forms a unit in two parts, one of these parts comprising a deformable member acting as a control button for the remote control, this member being secured by a seal providing the peripheral watertightness of the unit. However, the remote control device comprises components such as light-emitting diodes or indicator lights which the seal of the prior art is limited to surrounding, thus achieving only purely relative watertightness. Such a unit is further known from document DE 94 00 748, in which the seal is produced in the form of a flexible membrane covering the internal wall of a half-unit and having a window transparent to emitted waves, while maintaining watertightness. Nevertheless, in the case of shock, the components of the device are likely to shift, thus compromising not only the watertightness, but also the proper operation of the device. In addition, this type of unit, combined with a key, is by nature often handled and subject to static electricity discharges likely to damage the enclosed electronic components. 
     SUMMARY OF THE INVENTION 
     The objective of the present invention is therefore to propose a remote control unit which takes into account the various types of environmental attack and allows the remote-control electronic device that it contains to be effectively and economically protected. 
     This objective of the invention together with others which will appear in the rest of the present description are achieved by means of the remote control unit, of the type formed by two half-shells enclosing a printed circuit and a seal designed to isolate said circuit from the external surroundings. 
     According to the invention, the seal is formed by a flexible membrane separating the unit into two chambers and comprising, at least locally, an electrically conducting zone. 
     According to an advantageous characteristic of the invention, one of the half-shells of the unit is designed to house a power-supply battery for the electronic circuit and the flexible membrane comprises at least one conducting zone, forming a protuberance connecting the electronic circuit to at least one of the battery terminals and simultaneously forming a retaining spring for the power-supply conductor and battery. 
     According to another characteristic of the invention, the unit is designed to engage with a metal key bit in order to form a key for a motor vehicle and has a hole through which a keyring passes and the flexible membrane comprises at least one conducting zone forming, on the one hand, a protuberance bearing against part of the key bit and extending, on the other hand, around the hole in the form of a flange projecting into the hole, constituting an escape path for static electricity discharges from the ring to the key bit. 
    
    
     Other characteristics and advantages of the unit according to the unit will appear on reading the description which will follow and on examination of the appended drawings in which: 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a sectional view of the unit according to the invention; 
     FIG. 2 shows another view along the same section, showing other characteristics of the invention; and 
     FIG. 3 shows a plan view of the membrane locating zones with particular characteristics. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows a section through a unit  1  formed by two half-shells  11  and  12 . The inside of the unit is divided into two chambers by an elastomer membrane  2 , the periphery of which is pinched between the two half-shells. The two half-shells are fixed to each other by fixing means such as clips (not shown). The lower chamber, defined by the member  2  and the half-shell  12 , contains a printed circuit  3  equipped with electronic components  31 ,  32 , at least one of which is a light-emitting component such as a light-emitting diode  32 . These components (of the surface mounting type) are attached to the printed circuit  3  by soldering or adhesive bonding. The printed circuit  3  bears against a projection  15  made in the half-shell  12  over at least part of its periphery. The height of this projection is chosen to be slightly less than the thickness of the printed circuit  3 . Thus, when the two half-shells  11  and  12  are closed again, the printed circuit  3  is held firmly by the elasticity of the membrane  2 . The lower chamber also contains a battery  4 , the terminals of which are connected to the printed circuit  3  via contacts  41  and  42 , which are in the form of flexible metal strips bearing on one side against the battery and on the other side against a conducting pad of the printed circuit. When the unit  1  is designed to form the bow end of a key, a key bit  5  is combined with one of the half-shells, here for example to the lower half-shell  12 . 
     Some characteristics of the membrane  2 , which enable it to fulfil other advantageous functions in addition to its basic function of sealing the lower chamber, will now be detailed. 
     The membrane  2  comprises, at right angles to the light-emitting diode  32 , a zone Z 1  (FIG. 3) in which the material used is transparent of translucent. The diode  32  is attached to the printed circuit  3 , for example on the side opposite to that of the membrane. An aperture  33  in the printed circuit allows light emitted by the diode to pass through. At this point, the membrane comprises a tubular protuberance  21  which engages with an orifice  14  made in the upper half-shell  11 . A light-guide is thus obtained, which allows the light information to be transmitted from the diode  32  to the outside of the unit, without sacrificing the seal of the lower chamber, and to do so in a simple manner independent of the height of the half-shell  11 . Of course, if it is imposed by manufacturing restrictions, the diode  32  may be placed on the upper face of the printed circuit  3 , by making a housing  24  to accommodate the diode, as shown in FIG.  2 . 
     The membrane  2  further comprises a deformable part  22  which engages with a movable member  13  passing through the upper half-shell  11  to produce a control button. This deformable part  22  is formed, on its face facing the printed circuit  3 , in such a way as to maintain and center a dome  35  made of flexible material, capable of giving a tactile clicking sensation when, by pressing on the movable member  13 , a contact  36  made of conducting material, borne by the dome, is pressed against the printed circuit  3 . In this respect, it may be noted that the membrane  2  is pressed onto the printed circuit  3  at least on the periphery of the dome. To prevent it coming unstuck from the printed circuit under the effect of the pressure developed under the dome, at least one via  34  or plated-through connection hole has been advantageously placed between the two faces of the printed circuit in this zone. 
     In order to precisely place the membrane  2  with respect to the printed circuit  3 , use can be made of centering lugs obtained during the molding of the membrane and engaging with holes in the printed circuit. The number  23  indicates one of these lugs, which is advantageously placed at right angles to the battery  4 . The lug  23  is long enough to pass through the printed circuit  3  and to bear against the battery  4 , with enough pressure to firmly hold the battery in a housing (not shown) made in the half-shell  12 . Thus, when the unit is closed, the battery is held in place and it does not suffer from intermittent contact with the contacts  41 ,  42  during shocks or vibrations. In addition, the lug  23  enables the printed circuit  3  to be supported when the movable member  13  is pressed, thus limiting the relative movement of the contacts  41 ,  42  over their conducting pads so as to further improve the reliability of the contact. For this same purpose, the half-shell  12  may comprise, as shown in FIG. 2, one or more support lugs  17 , placed at right angles to the deformable zone  22 , in order to limit the flexing of the printed circuit 
     Reference will now be made to FIG. 2 so as to shed light on certain advantageous characteristics which may be obtained by the fact that it is possible, according to a known technique for producing such membranes, to locally combine materials having different physical characteristics. This is because these membranes are obtained by depositing elastomer blanks into a mold, which blanks will be shaped on closing the mold under predetermined temperature and pressure conditions. By using blanks of predetermined color, transparency and electrical conductivity, a multifunction membrane can thus be obtained economically. 
     For example, the reduced current consumption of the electronic device borne by the printed circuit  3  is put to good use in order to make the lug  23  from a material having a high conductivity (for example an elastomer highly filled with carbon particles), defined locally by the zone Z 2  in FIG. 3, which enables an electrical connection to be made between one terminal of this battery and the printed circuit  3  while still mechanically holding the battery  4  in place, as seen previously. In this case, the lug  23  passes through the printed circuit  3  via a plated-through hole  37  in order to connect the first terminal of the battery  4 , and a metal track  16  on the half-shell  12  connects the second terminal to a supply track  38  on the printed circuit  3 . The contacts  41  and  42  in FIG. 1 can thus be omitted. 
     The movable member  13  of FIG. 1 can also be dispensed with by adapting the shape of the deformable part  22  so that it engages with the aperture of the half-shell  11  in order for the control button of the device to be formed directly. Advantageously, this deformable part  22  comprises in its center a protuberance  28  made of conducting material, engaging with a hole in the dome  35  in order to center it under the control button, and with tracks of the printed circuit  3  in order to operate the control contact of the device. 
     Reference will now be made to FIG. 3 in order to detail an additional characteristic of the membrane  2 , which makes it possible to improve the resistance to electrical discharges of the electronic device contained in the unit. As has been seen previously, the unit  1  may be designed to form the bow end of a key intended to open the doors of a vehicle. It has been noted in this use that static electricity discharges could damage the electronic components carried by the printed circuit  3 . The most frequent path for these discharges connects a keyring (not shown), passing through a passage  26  made in the unit, to the key bit  5 , via paths of least resistance, such as the tracks of the printed circuit  3  and the components  31  which are attached thereto. In order to solve this problem, the membrane  2  comprises a conducting zone Z 3 , which connects the ring passage  26  to the key bit  5 . A flange  27 , formed in the membrane, protrudes into the passage  26  in order to make contact with the ring. A contact lug  25  bears against a part of the key bit  5  inserted into the unit, passing, where appropriate, through the printed circuit  3 . The zone Z 3  therefore provides a path of least resistance suitable for diverting electrostatic discharges directly toward the key bit  5 , thus sparing the components.