Abstract:
An electroacoustic transducer unit for a handsfree device in a vehicle includes a loudspeaker, a microphone and a connection to a mobile phone. The microphone can be mounted on a flexible bracket. The unit is constructed for positioning in the upper seatback area of a seat of the vehicle. One way of positioning is an elongated casing with two recesses at both ends and a spring device at one end. The casing can be inserted between the headrest carriers and is elastically fixed to it.

Description:
FIELD OF APPLICATION AND PRIOR ART 
     The invention relates to an electroacoustic transducer unit for a handsfree device in a vehicle, particularly for the connection to a mobile telephone as the transmission device. 
     Handsfree devices are very widely used for telephoning in a vehicle, because the user then does not have to hold the mobile telephone in the hand. This is of major importance, to enable him to devote his entire attention to the road traffic and to the steering of the vehicle. 
     Apart from a type of base station, generally comprising a support for the mobile telephone together with the installed handsfree electronics, known handsfree devices in vehicles have a microphone and a loudspeaker, which are to be connected thereto. Microphones of known handsfree devices are normally fixed to the A-support or panel, partly also to or behind the steering wheel. The loudspeakers are generally constituted by smaller modules, which either have to be fixed in a very complicated manner to the panel or even in the foot space of the passenger. This is due to the fact that for avoiding interference, as well as feedback and echo, there must be no direct, linear acoustic connection between the loudspeaker and microphone of the handsfree device. These extremely disturbing effects more particularly occur in full duplex operation. Besides the fitting of the microphone, the installation of the loudspeaker at an inaccessible location, such as the foot space, is considered to be very disadvantage, inter alia because it is exposed there to dirt and a damage risk. 
     PROBLEM AND SOLUTION 
     The problem of the invention is to provide an electroacoustic transducer unit for a handsfree device, which can be easily fitted, retrofitted and which is operationally reliable. 
     According to the invention this problem is solved by claim  1 . The transducer unit or transducer can be positioned close to the head, mouth or ear of a person sitting in the seat and can be fitted to the seat or vehicle. As opposed to a head mount, e.g. an earphone, the transducer unit does not impede the user and when fitted behind the head it is scarcely optically noticed. In particular, the electroacoustic transducer unit has at least one loudspeaker. As a result of the very short transmission path to the ear, it is possible to keep the sound volume low and to drown the disturbing noises occurring in a vehicle. 
     The transducer unit preferably has a holder or support for fixing to the seat or vehicle, preferably in the vicinity of the headrest of the seat and at least partly between the headrest and seatback. Numerous fixing or fastening possibilities are available. 
     In particularly preferred manner the support is constructed for fixing to at least one headrest carrier of a headrest and the in particular manual fastening can be released. Thus, use is made of the free space present with most vehicle seats between the lateral headrest carriers and the headrest and seatback or one of the indicted components for housing or fixing the transducer unit. The transducer unit for this purpose can be fixed to and in particular at least partly between two headrest carriers. In the case of the normally columnar headrest carriers, they permit a particularly advantageous fixing. It is advantageously possible to fix and/or release without tools the transducer unit with support and with particular preference it is lockable or clampable. A further fitting possibility is to the vehicle roof, e.g. to the sliding roof, or to the B-support. 
     According to an embodiment of the invention, the electroacoustic transducer unit has a housing or casing for receiving at least one loudspeaker. The latter is preferably shock absorbing to the outside for safety reasons, preferably as a result of a fitted or enveloping cushioning. It is also possible to have a casing made from shock absorbing material, particularly hard or rigid foam materials and the like. Particularly the areas which in the fixed state are directed towards the front and rear in the vehicle longitudinal direction, can be resilient and preferably cushioned for safety reasons. 
     In a particularly preferred embodiment of the invention, the casing comprises at least one cavity constructed for receiving at least one transducer or loudspeaker and which is preferably in the form of a resonator chamber for sound amplification for a loudspeaker. In order to improve the sound radiation, the casing or cavity can have at least one sound exit opening, which can in particular be oriented in the forwards direction. As a result of the thus obtained sound radiation in a desired direction, particularly in the direction of the ear or forwards, in the case of limited power or volume of the loudspeaker excellent comprehensibility can be obtained for the operator. 
     The loudspeaker can be a conventional diaphragm loudspeaker, which can be inexpensively mass produced. Alternatively a piezoelectric loudspeaker can be provided, whose advantages include limited size, minimum wear susceptibility, low energy consumption, low susceptibility to electromagnetic fields occurring in a vehicle and a good frequency response corresponding well to the frequency range of human speech. 
     Preferably the transducer unit can be locked, particularly in self-arresting manner by means of the support between two headrest carriers and it is preferably provided with receptacles or recesses for said headrest carriers. As the spacing of the headrest carriers in the case of a vertical adjustment of the headrest remains the same, fixing advantageously takes place thereto. By means of receptacles or recesses it is possible for the transducer unit or its casing to at least partly embrace the headrest carriers and thus ensure an adequately reliable connection. In particularly preferred manner the transducer unit or its casing is length-variable, particularly in a telescopic manner. Alternatively it can have an elastic length variability of an inner area of the casing, preferably along the longitudinal axis of the casing. This permits an adaptation to different spacings of fixing points, e.g. headrest carriers. It is possible to produce a universal retrofitting set, which is usable for numerous vehicle seat variants. The transducer unit or the support can have a longitudinal spring suspension, preferably for the casing, so that it can be locked with prestress to and in particular between the headrest carriers. It can also be fixed or locked between the seatback and headrest or in a standard cutout in the headrest. 
     The longitudinal spring suspension assists the arresting or locking action. It is also possible to house it in the headrest. 
     The casing can have at least two parts, e.g. two shells. One part can be connected in articulated manner to the remaining casing and is in particular slidable or pivotable with respect thereto. One part preferably contains at least one loudspeaker, which permits an advantageous directing of the sound waves towards the ear or head. At least one sound passage opening and/or at least one loudspeaker can be orientable, e.g. in such a way that sound is emitted towards the front of the vehicle, preferably roughly in the direction of an ear of a person sitting in the seat. 
     Alternatively to a microphone as the sole electroacoustic transducer unit, according to a variant of the invention with a loudspeaker as the transducer can additionally be associated a microphone means. At least one microphone can be fixed to the support or casing, preferably by means of a microphone holder constructed for this purpose. Thus, in much the same way as for the loudspeaker, the microphone is advantageously located in the vicinity of the head, without it having to be held or carried by the operator. 
     The microphone means or holder are preferably constructed in such a way that the position and/or orientation of a microphone can be randomly fixed. This is possible by a bracket in the manner of a swanneck or in particular in the form of a flexurally non-rigid, dimensionally stable cable. 
     For the construction of a complete handsfree device directly connected to the electroacoustic transducer, with the latter can be associated handsfree electronics, which can in particular be placed in the casing or on the support. In conjunction with a directly associated microphone, this leads to a compact, but still easily fittable and advantageously usable handsfree device. There is no need for complicated connections to an external handsfree device. In one variant of the invention the transducer unit is connectable in signal-transmitting manner, preferably by means of a connecting cable, to a mobile telephone, car telephone or some other wireless transmission device. It is also possible to have a wireless signal transmission, e.g. through an infrared transmission path between the transducer unit and the telephone or its base or reception station. 
     According to a preferred development of the invention at least one loudspeaker can be fixed behind and one microphone in front of the head or mouth of a person sitting in the seat. Thus, not only are they spatially positioned close to the ear or mouth, but additionally through an interruption of a direct transmission line between loudspeaker and microphone through the head, undesired interference effects of a handsfree device such as feedback or echo are avoided. 
     In order to create a universal transducer unit, with it can be associated its own electric power supply and it or a support or casing can in particular have a receptacle for an insertable battery. Alternatively or additionally a power supply from the mobile telephone is possible. 
     A preferred construction of the invention can have an elongated, at least partly resiliently compressible casing with a loudspeaker at one end, which has two recesses at both ends, a longitudinal spring suspension being positioned in one long recess. When the longitudinal spring suspension is compressed, the transducer unit can be inserted by means of the lateral recesses between two headrest carriers of a vehicle seat and can be automatically arrested there in positively engaging manner in the vehicle longitudinal direction. Such a transducer unit is manually fixable and releasable again in simple manner. To facilitate getting into the vehicle, the part with the loudspeaker is preferably directed towards the centre of the vehicle and advantageously have a microphone means with holder. The casing can be longer than the spacing of the headrest carriers and is inserted in inclined manner. 
     For fitting to vehicle seats, e.g. to headrests without carriers, e.g. integral seats, it is possible to bring about fixing with a textile adhesive connection. It would be possible to loop the upper seatback area or headrest area with such an adhesive tape and the transducer unit can be fixed thereto. Another possibility is the arrangement in or on an envelope, which at least partly engages round the upper seat or headrest area and which is e.g. constructed in the manner of a textile covering or the like, together with the receptacle for the transducer unit. A permanent fixing of an electroacoustic transducer on or in a vehicle seat by screwing or the like is possible. It is possible to invisibly wire a connecting cable to a transmission device, preferably a mobile telephone, or a handsfree device within the vehicle seat or on its back. 
     These and other features can be gathered from the claims, description and drawings and the individual features, either singly or in the form of sub-combinations, can be implemented in an embodiment of the invention and in other fields and can represent advantageous, independently protectable constructions for which protection is claimed here. The subdivision of the application into individual sections and the subtitles in no way restrict the general validity of the statements made thereunder. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Several embodiments of the invention are shown in the drawings, wherein represent: 
     FIG. 1 A view from the front of a loudspeaker with a casing as an inventive electroacoustic transducer unit with a flexible microphone holder, which is fixed between two headrest carriers of a car seat. 
     FIG. 2 The transducer unit with casing from FIG. 1 seen from above, together with the diagrammatically represented head of a person sitting in the seat. 
     FIG. 3 An alternative construction, in which a spring suspension is fitted in a lateral longitudinal slot of the casing. 
     FIG. 4 A minimum construction of a loudspeaker as a transducer unit according to the invention for fitting to a headrest carrier of a vehicle seat. 
    
    
     DESCRIPTION OF EMBODIMENTS 
     FIG. 1 shows an electroacoustic transducer unit  11 , whose support  12 , also referred to as a casing, is fixed to a vehicle seat  13 , namely on or between two headrest carriers  14 , which project out of a seatback  15  and carry a headrest  16 . 
     The casing comprises two parts, namely a loudspeaker part  18  and a casing cover  19 , which passes at least partly over the loudspeaker part. Guidance preferably takes place in such a way that a relative movement of the two casing parts  18  and  19  is only possible in the longitudinal direction thereof. 
     In the left-hand area of the loudspeaker part  18  is provided a not shown loudspeaker in a cavity serving as a resonator chamber and by means of sound exit openings  20  the sound produced by the loudspeaker is removed from the loudspeaker part  18 . Contrary to what is shown, the shape of the sound exit openings  20  is not restricted to a circular shape, all other shapes being possible and the sound exit openings can also be covered by a woven fabric or the like. 
     Laterally a microphone holder  22  is fitted to the loudspeaker part  18  of the casing  12  and has a long, thin, flexible arm  23 , whose free end carries a microphone  24 . It roughly faces the headrest  16 , because the mouth of a person sitting in the vehicle seat  13  is probably directed in this direction. 
     The transducer unit  11  is connected by means of a connecting cable  25 . In the embodiment shown in FIGS. 1 and 2, which contains the loudspeaker, the microphone  24 , the handsfree electronics and a power supply, the connecting cable  25  is merely used for connection to a mobile telephone in the form of the transmission device. As a function of the construction, this can also provide a connection of an external handsfree electronics solely to a loudspeaker and/or a microphone  24  as the electroacoustic transducer in the casing  12 . 
     FIG. 2 shows on a larger scale from above the device of FIG. 1, together with a diagrammatically represented head  27  of a user. This clearly shows the two-part construction of the casing  12  with loudspeaker part  18  and casing cover  19 . The loudspeaker part  18  at least partly engages in the mainly hollow casing cover  19  and is spring-suspended by means of a helical spring  28  engaging on an end face and pressing against the bottom of the casing cover  19 . This makes it possible to vary within a wide range the length of the casing  12  and consequently the spacing of the recesses  29  located on the lateral ends of the casing, which permits an adaptation to different spacings of the headrest carriers  14  for different vehicle seat models. Moreover, in conjunction with the specific shaping of the recesses  29 , at least in the vehicle longitudinal direction (corresponds in FIG. 2 to the longitudinal direction of the sheet from top to bottom), there is a positive connection of the casing  12  to the headrest carriers  14 . As a result of the slightly rearwardly drawn recesses  29 , there is a reinforcement of the arresting action of the carriers  14  with the recesses  29  in a vehicle with respect to a force action occurring from the rear, from above in FIG.  2 . This improves the accident security, because the transducer unit  11  or casing  12  cannot become detached in the case of a rear end collision and cannot injure a person located in the vehicle or seat. 
     In FIG. 2, a diaphragm loudspeaker  31  is shown in broken line form in the thicker portion of the loudspeaker part  18  and its sound produced in the loudspeaker resonator chamber is emitted via the sound passage opening  20  directly towards the head  27  of an operator. In the loudspeaker part  18  are also shown in broken line form handsfree electronics  32  and a battery  33 , so that in conjunction with the microphone  24  a compact handsfree device is provided. It is merely necessary to produce by means of the connecting cable  25  a signal-transmitting connection with a mobile telephone as the transmission device. 
     As can be seen in FIG. 2, for increasing safety the microphone holder  22  is fitted at a point behind the recess  29  in the loudspeaker part  18 , where it prevents a movement of the casing  12  in this area in front of the headrest carrier  14  towards the head  27 . 
     FIG. 3 shows in an inclined view an alternative embodiment, in which in a lateral longitudinal slot  36  is located a long spiral spring  37 , which engages at the left on the casing  12 . Towards the outlet of the slot is inserted a nipple  38 , with which the spiral spring  37  can engage on a headrest carrier. A length adaptor  39  is shown in broken line form and can be inserted in an opening  40  in the nipple  38  when the headrest carriers are particularly far apart. The length adaptor has at its free end a recess  41  similar to the other recesses  29 . 
     The casing contains in broken line form a loudspeaker  31  and two sound exit openings  20 . By means of a screw connection  42  a microphone holder  22  is fixed and connected with a flexible arm  23  carrying the microphone  24 . The connecting cable  25  is connected to a plug  43  on the remote longitudinal side, which in the fitted state is directed towards the vehicle rear. 
     The longitudinal slot  36  is narrower than the diameter of the spiral spring and is hollowed out on its inner walls, so that the spiral spring  37  and nipple  38  are reliably guided in the slot and cannot be pressed out. Not shown stops on the outer end of the slot  36  hold the spring and nipple in the casing  12 . 
     FIG. 4 shows a particularly simple, inexpensive minimum version of an inventive electroacoustic transducer unit  11 . It comprises a casing  12 , which essentially contains a loudspeaker, here a diaphragm loudspeaker  31 , and is only fixed to one headrest carrier  14 , preferably by clipping, clamping or screwing. For this purpose it is possible to provide on one casing side a recess  29 , which has a width smaller than the diameter of the headrest carrier  14  and which is subsequently undercut in widening manner. The cross-section of the undercut roughly corresponds to the cross-section of the headrest carrier  14  or slightly exceeds the same. Screwing is possible with a type of clamping collar. Such a loudspeaker in transducer form is merely connected by means of a connecting cable  25 , which leads to a handsfree device with microphone. 
     FUNCTION 
     As an application of the invention forms a retrofitting set for the owner of a mobile telephone who wishes to install in his car a handsfree device, an electroacoustic transducer unit is preferably constructed in accordance with FIGS. 1 to  3 . The manufacturer installs and connects the loudspeaker  31  and handsfree electronics  32  in the loudspeaker part  18  and connection takes place with a connecting cable  25  and microphone  24 . The microphone  24  is preferably connected to the handsfree electronics  32  by means of a coaxial cable located in the arm  23  of the microphone holder  22 , which in one variant of the invention can essentially form the arm. The casing cover  19  contains no components or subassemblies necessary for the function of the handsfree device. Together with the spring  28 , it merely forms a type of length adaptor for the casing  12  and an arresting possibility for the overall device. 
     In order to put into operation, a user merely places a battery or the like in the casing  12  or loudspeaker part  18 , which can advantageously be locked independently of a casing cover  19 . He then closes the casing and passes the casing cover containing the helical spring over the end of the loudspeaker part and inserts the casing  12  from the rear between the two headrest carriers  14  of the vehicle seat  13 . On fitting he must compress the casing  12  or longitudinal spring suspension to the extent that it can be guided between the headrest carriers  14  until the recesses  29 / 36  at least partly engage round the headrest carriers. This insertion can be facilitated by a bevel  34  of the ends of the casing  12  in the insertion direction or the casing is inserted in tilted manner in a perpendicular plane. Through the release of the casing parts, due to the spring tension of the longitudinal spring suspension, they are forced apart and reliably secure the casing  12  on the headrest carriers  14 . 
     As a function of the head position, the loudspeaker means  11  can be brought along the headrest carriers  14  into an optimum position for the operator. It is subsequently merely necessary to connect the connecting cable  25  to the mobile telephone or its base station in the vehicle. As shown in FIG. 1, the microphone  24  together with most of the support arm  23  can be located somewhat below the headrest  16  and consequently the head  27 . This offers the advantage that in the case of an accident, optionally involving the release of an airbag, the microphone  24  is not located directly in front of the head  27  or face and consequently does not constitute an injury source. The injury risk is reduced even further by a cushioning product. 
     An electroacoustic transducer unit  11  with casing  12  according to FIG. 4 is fixed to a headrest carrier  14  in the described manner, e.g. by snapping on or screwing and can be connected to a handsfree device by the connecting cable  25 . For safety reasons, fixing preferably takes place in such a way that the casing  12  cannot readily rotate with respect to the headrest carrier  14  or become detached therefrom.