Abstract:
An electronic device including a housing, a transducer and a retainer for mounting the transducer on the housing ( 11 ) is disclosed. The device includes co-operating means ( 21,28 ) on the housing ( 11 ) and on the retainer ( 26 ) for attaching the retainer ( 26 ) to the housing ( 11 ) over the transducer ( 16 ). The retainer ( 26 ) is preferably attached to the housing ( 11 ) with a bayonet type fastener so that rotation of the retainer ( 26 ) against spring pressure positions lugs ( 28 ) on the retainer ( 26 ) in slots ( 22 ) on the housing ( 11 ).  
     The present invention also discloses a housing ( 11 ) for a mobile telephone having a recess ( 39 ) therein and a cover ( 38 ) mounted on the housing ( 11 ) over the recess ( 39 ). The cover ( 38 ) and the housing ( 11 ) together form an acoustic duct in the region of the recess ( 39 ).

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to the field of electronic devices such as mobile telephones.  
         BACKGROUND OF THE INVENTION  
         [0002]    Transducers that convert electrical signals into sound can be used as loudspeakers in conventional mobile telephones. As they are capable of generating sound of a relatively high acoustic volume, they can be used in “hands free” mobile telephones as the sound is of a volume that makes it unnecessary to place the telephone against the ear.  
           [0003]    A transducer in a mobile telephone may be used to fulfil several functions in addition to the conversion of signals received by the telephone into speech so that the user can hear the person they are communicating with. For example, the transducer can also be used as a buzzer to alert the owner to an incoming telephone call. This type of transducer is referred to as multi-functional.  
           [0004]    A conventional mobile telephone may be provided with two speakers mounted to the back and front covers of the telephone respectively. The speaker mounted to the front cover is capable of relatively low acoustic volume only and is used when the telephone is placed against the ear in a conventional manner. Holes are provided in the cover to allow transfer of sound through the cover. The speaker mounted to the rear cover is a transducer capable of relatively high acoustic volume to enable the telephone to be used “hands free”, in which the user can hear a person speaking to them without placing the telephone against the ear. The telephone is provided with a button which switches the transducer on and activates the “hands free” mode.  
           [0005]    It is desirable to keep the thickness of a mobile telephone to a minimum. This means that there is very limited space between components. For example, the gap between the top of the transducer which is usually mounted on the rear of the mobile telephone housing and the PCB components mounted on the front cover is normally only in the region of 0.5 mm. This presents the problem of securely mounting the transducer to the inside of the cover as the gap is too small to enable the transducer to be located beneath, for example, spring clips moulded as part of the cover itself, unless the overall thickness of the mobile telephone is increased.  
           [0006]    A further disadvantage with conventional mobile telephones is that the acoustic seal between the front of the transducer and the inside face of the cover to which it is mounted is poor, leading to inferior sound transfer through the cover. In addition, some of the sound generated by the transducer is transferred into the telephone cover itself causing it to vibrate leading to the introduction of resonance into the assembly and a reduction in sound quality.  
         SUMMARY OF THE INVENTION  
         [0007]    According to an object of the present invention, there is provided an electronic device comprising a housing, a transducer and a retainer for mounting the transducer on the housing, the retainer including a first portion for co-operation with a second portion on the housing to attach the retainer to the housing over the transducer.  
           [0008]    Preferably, the first and second portions are configured so that, when the retainer is placed on the housing over the transducer with the first and second portions in engagement, rotation of the retainer locks it to the housing and mounts the transducer thereto. This is conveniently achieved by means of a bayonet type fitting arrangement.  
           [0009]    The retainer preferably has a substantially planar portion for contact with the upper surface of the transducer, most preferably, the substantially planar portion is an annular ring. As the part of the retainer in contact with the upper surface of the transducer is planar, the overall thickness of the transducer and retainer can be kept low. This low-profile design means that the overall thickness of the telephone can also be kept to a minimum.  
           [0010]    In a preferred embodiment, the first portion on the retainer comprises a plurality of connecting lugs parallel to and spaced from the annular ring which are received in the second portion on the housing.  
           [0011]    Preferably, the connecting lugs are formed on the ends of spacing walls remote from the annular ring. The spacing walls depending substantially at right angles from the outer periphery of the annular ring.  
           [0012]    Conveniently, the connecting lugs are equally spaced from each other about the annular ring.  
           [0013]    Preferably, each lug has a tapered locking face that engages the housing when the retainer is rotated thereon.  
           [0014]    The retainer advantageously includes a spring to apply pressure to the upper surface of the transducer to bias it against the housing when the retainer is attached thereto.  
           [0015]    The spring preferably comprises at least one region of the substantially planar annular ring which is deformed out of the plane of said ring, said region being deflected back toward the plane of said ring when in contact with the upper surface of the transducer and the retainer is rotated to lock it to the housing, the resilience of the or each region biasing the transducer towards the housing. This means that the retainer must be pushed downwardly against the transducer against the force of the spring pressure before it can be rotated to lock it to the housing. When the retainer is released, the lugs and the transducer are both biased into contact with the housing. This pre-loading of the transducer against the housing provides an excellent acoustic seal between the transducer and the housing, and also ensures that any vibration is transferred into the phone body so that little or no resonance is introduced into the assembly.  
           [0016]    The housing may have a circular seat for a transducer having a cylindrical peripheral wall to surround the transducer, the second portion on the housing preferably comprising a plurality of sockets in the peripheral wall.  
           [0017]    In the preferred embodiment each socket has an axially extending opening in the upper edge of the wall for insertion of a lug on the retainer, and a circumferential undercut in the wall extending from the opening to receive the lug on rotation of the retainer.  
           [0018]    According to another object of the present invention, there is also provided a method of attaching a transducer to an electronic device according to the invention, comprising placing a transducer on the housing, moving the retainer towards the housing and over the transducer such that the first and second portions engage, pressing the retainer against the transducer and rotating the retainer to lock the retainer to the housing and mount the transducer thereto.  
           [0019]    A conventional mobile telephone incorporating two speakers for both conventional and “hands free” use of the telephone is provided with acoustic ducts to allow transmission of sound through the cover. The acoustic duct for the speaker having low acoustic volume is provided in the face of the cover immediately beneath the speaker and can be positioned comfortably against the ear. Even if these ducts are placed against the ear when the “hands free” mode is activated, the maximum volume of the transducer capable of relatively high acoustic volume will not be loud enough to damage the ear if this side of the telephone is held against the head. However, the acoustic ducts or openings to allow for the transmission of sound through the cover from the transducer capable of high acoustic volume are formed in the side surface of the telephone housing as, if they were formed in the face of the cover, a user may inadvertently place this side of the telephone against their head with the speaker ducts from this transducer facing the ear. As the volume of sound generated by the “hands free” loudspeaker may be quite high, this could cause them pain or injury. However, this means that an additional manufacturing step is required to form the ducts in the side of the mobile telephone housing.  
           [0020]    According to yet another object of the invention, there is provided a housing for a mobile telephone having a recess therein and a cover mounted on the housing over the recess, the cover and the housing together forming an acoustic duct in the region of the recess.  
           [0021]    This has the advantage that the acoustic duct is formed in the main face of the housing in the line of draw, rather than in the side surfaces. As the cover conceals the acoustic duct, a user is not tempted to inadvertently place this side of the telephone against the ear when the “hands free” mode is activated.  
           [0022]    Preferably, the recess is configured such that when the cover is mounted to the housing, a sound outlet is formed in the join between the cover and the housing in the region of the recess. The aperture is most preferably a narrow slit and is largely obscured by the join between the cover and the housing to prevent a user from being tempted to place this side of the telephone against the ear.  
           [0023]    In a preferred embodiment, the cover is arcuate in shape. This means that when the telephone is placed with the cover against a flat surface, the sound outlet is not obscured as it is spaced from the surface on which the telephone is disposed.  
           [0024]    In another embodiment, both the cover and the recess in the housing are arcuate in shape, the recess being a concave depression in the rear surface of the housing.  
           [0025]    Preferably, the housing has an aperture therein so that a transducer mounted on one surface of the housing is in communication with the recess on the other side of the housing.  
           [0026]    In a preferred embodiment, the edge of the cover locates within a shoulder formed on the housing.  
           [0027]    Preferably, the cover includes a first part for co-operation with a second part on the housing to releasably mount the cover on the housing.  
           [0028]    The present invention also includes an electronic device according to the invention incorporating the housing of the invention.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0029]    [0029]FIG. 1 is a schematic illustration of a preferred embodiment of the invention in which the electronic device is a mobile telephone;  
         [0030]    [0030]FIG. 2 is a perspective view of the rear housing of the mobile telephone shown in FIG. 1;  
         [0031]    [0031]FIG. 3 is an exploded perspective view of the rear housing as shown in FIG. 2, but with a transducer located on the housing and the retaining ring before it is attached thereto over the transducer;  
         [0032]    [0032]FIG. 4 is a perspective view of the housing as shown in FIGS. 2 and 3, with the retainer connected to the housing over the transducer;  
         [0033]    [0033]FIG. 5 is an exploded perspective view of the other side of the housing shown in FIGS.  2  to  5 , with the cover before it is attached to the housing;  
         [0034]    [0034]FIG. 6 is a partial enlarged view of the side of the housing shown in FIG. 5, with the cover attached thereto;  
         [0035]    [0035]FIG. 7 is a partial longitudinal cross sectional view through the assembled mobile telephone shown in FIG. 1; and  
         [0036]    [0036]FIG. 8 is a cross section view through the housing in the region of the recess of a modified version of the housing shown in FIGS.  5  to  7 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0037]    Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:  
         [0038]    A preferred embodiment of the electronic device of the invention is a mobile telephone  1  as illustrated in FIG. 1. The telephone comprises a user interface having a keypad  2 , a display  3 , an on/off button  4 , ear piece  5  for using the telephone in a conventional manner, and a microphone  6 . The telephone  1  is adapted for communication via a wireless telecommunication network, e.g. a cellular network. However, the phone could also have been designed for a cordless network. The keypad  2  has a first group  7  of keys as alphanumeric keys, by means of which the user can enter a telephone number, write a text message (SMS), write a name associated with a telephone number, etc. Each of the twelve alphanumeric keys  7  is provided with a figure “ 0 - 9 ” or a sign “#” or “*”, respectively. In alpha mode, each key is associated with a number of letters and special signs used in text editing.  
         [0039]    The keypad  2  additionally comprises two soft keys  8 , the functionality of which depends on the state of the telephone and the navigation in the menu by means of a navigation key  10 , and two call handling keys  9 , which can be used for establishing a call or a conference call, terminating a call or rejecting an incoming call. The telephone  1  is also provided with a button (not shown) which enables the “hands free” mode to be activated.  
         [0040]    The parts of the telephone relevant to the present invention will now be described. The rear part of a mobile phone housing  11  having a rear wall  12  and side walls  13  upstanding from the rear wall  12  is illustrated in FIG. 2, and provides a receptacle for the location of the various conventional components of the telephone which will not be described further. The housing  11  has an integrally moulded boss  14  through which the antenna of the telephone may extend.  
         [0041]    The inside face of the rear wall  12  is integrally formed with a seat to receive a transducer  16  having an upper surface  16   a,  illustrated in FIG. 2. The transducer  16  is capable of relatively high acoustic volume and is used when the “hands free” mode is selected. The seat has an annular portion  17  against which the transducer  16  rests when placed on the housing  11  as shown in FIG. 3. The annular portion  17  has an aperture  18  which acts as a duct for the transmission of sound generated by the transducer  16  through the rear wall  12  of the housing  11 . The periphery of the annular portion  17  has an integrally formed upstanding wall  19  extending around its circumference having a top edge  20 . The diameter of the annular portion  17  is slightly greater than the diameter of the transducer  16  which locates within the area enclosed by it on the annular portion  17 .  
         [0042]    The upstanding wall  19  has four identical and equally spaced “L” shaped sockets  21  having an opening in the top edge  20  that extends axially for a short distance and then circumferentially to form an undercut slot  22  beneath an overhanging wall portion  23 . Additional sections  24 ,  25  of the wall are also removed to allow space for electrical connections to be made to the transducer  16 .  
         [0043]    The transducer  16  is mounted on the housing  11  by a retainer  26 , shown in FIGS. 3 and 4. The retainer  26  has a planar annular ring  27  for contact with the upper surface  16   a  of the transducer  16 . The retaining ring  27  is provided with means for securely locking it to the housing  11  via the “L” shaped sockets  21  formed in the upstanding wall  19  comprising connecting lugs  28  extending radially inwardly parallel to but spaced from the annular ring  27  by spacing wall portions  29  that depend at right angles therefrom. The means for connecting the retainer  26  to the housing  11  are spaced equally about the circumference of the annular ring  27  so that when the retainer  26  is placed on the housing  11 , in the direction of X, in FIG. 3, each lug  28  is received in a corresponding socket  21 .  
         [0044]    The upper surface  30  of each connecting lug  28  which engages with the underside of the overhanging wall portion  23  is tapered so that once the retainer  26  has been placed on the housing over  11  a transducer  16 , pushed downwardly against the transducer  16  and rotated so that the lugs  28  engage in the undercut slot  22  beneath the overhanging wall portion  23 , the tapered upper surface  30  of each lug  28  is pressed against the housing  11  to prevent the retainer  26  from working loose.  
         [0045]    To apply constant pressure to the transducer  16  and bias it against the housing  11 , the retainer  26  includes a spring arrangement which is formed integrally with the annular ring  27 , and comprises four regions  31  which are deformed out of the plane of the ring  27 . When the retainer  26  is attached to the housing  11  and the tapered upper surface  30  of each lug  28  is biased against the overhanging wall portion  23 , each region  31  is deflected back toward the plane of the ring  27  and the resilience of each region  31  biases or pre-loads the transducer  16  towards the annular portion  17  of the housing  11 . It will be appreciated that the type of connection in which a member is inserted into a socket against spring pressure and turned so that lugs on the side of the member engage in slots in the socket is commonly known as a bayonet fastener.  
         [0046]    The method for mounting the transducer  16  to the housing  11  will now be described. The transducer  16  is positioned on the inside face of the rear wall  12  on the annular portion  17  so that it is surrounded by the upstanding wall  19 . The retainer  26  is then placed over the transducer  16  in the direction shown by X, in FIG. 3, and in an orientation which ensures that the connecting lugs  28  are inserted into the sockets  21  in the wall. The retainer  26  is then attached to the housing  11  to securely mount the transducer  16  thereto by applying a downward force on the retainer  26  against the transducer  16  and then by rotating the retainer  26  in the direction of Y, in FIG. 3, so that each lug  28  moves into the undercut slot  22  beneath the overhanging wall portion  23 . When the downward pressure is removed, the tapered upper surfaces  30  of each lug  28  engage with the underside of the overhanging wall portion  23  and the regions  31  in contact with the upper surface  16   a  of the transducer  16  urge the transducer  16  against the annular wall  17  of the housing  11 .  
         [0047]    Another embodiment will now be explained with reference to FIGS. 5, 6 and  7 . It will be appreciated that this embodiment need may or may not be combined with the first embodiment described with reference to FIGS.  2  to  4 . However, it is envisaged that both embodiments will be used together.  
         [0048]    [0048]FIG. 5 illustrates the opposite side of the housing  11  shown in FIGS.  2  to  4 . The boss  14  for the antenna can be seen, as can a battery chamber  32 . The battery chamber  32  has a casing (not shown) that fits on the housing  11  and engages with detent  33  thereon.  
         [0049]    On the upper part of the housing  11  the rear face  34  of the annular wall  17  can be seen with the aperture  18  therethrough. The housing  11  has an outwardly projecting bulbous section  35  surrounding the aperture  18  that extends from the top edge of the housing  11  and tapers to just above the detent  33 . The edge  36  of the bulbous section  35  starts from slightly below the rear surface of the housing  11  to form a shoulder  37  (see FIG. 7) to receive an outwardly curved arcuate cover  38  so that it is flush with the rear surface of the housing  11  when fitted thereto, as most clearly seen in FIG. 7. A substantially rectangular depression or recess  39  in the surface of the bulbous section  35  extends transversely across it and terminates on opposite edges  36 . The aperture  18  communicates the transducer  16  with the depression  39 .  
         [0050]    The cover  38  is attached to the housing  11  over the bulbous section  35  by pressing it onto the housing  11  in the direction of Z in FIG. 5 so that it seats within the shoulder  37 . As most clearly shown in FIG. 6, when the cover  38  is fitted to the housing  11 , a narrow opening or slit  40  between the edge of the cover  38  and the housing  11  is created in the region of the depression  39 . This opening  40  allows sound generated by the transducer  16  to pass through the aperture  18 , along the space between the depression  39  and the cover  38  and through the opening  40  to the outside. The depression  39  and the cover  38  together form an acoustic duct, the opening  40  being the outlet for the duct. As the outlets  40  are formed in the joint between the cover  38  and the housing  11 , they are concealed or disguised so the user is not tempted to place this side of the housing  11  against their ear, which they might otherwise have done if the acoustic outlets had been more visible and which could result in pain or injury to the eardrum if the telephone is in “hands free” mode. Furthermore, as the cover  38  is bulbous, it is uncomfortable to hold against the ear.  
         [0051]    [0051]FIG. 7 illustrates a partial view of an assembled mobile telephone in which the transducer  16  is mounted to the housing  11  using the retainer  27 . The recess  39  over which the cover  38  extends to form an acoustic duct can be clearly seen. PCB components  41  are mounted to the front portion  42  of the housing  11  and the distance between the top of the transducer  16  and the PCB components  41 , indicated by A in FIG. 7, is 0.5 mm. The thickness of the annular ring  27  in contact with the upper surface  16   a  of the transducer  16  is 0.2 mm, as shown by B in FIG. 7, leaving a space between the annular ring  27  and the PCB components  41  of 0.3 mm. The use of the retainer  26  to mount the transducer  16  is clearly advantageous as it does not require an increase in the size of the gap between the PCB components  41  and the transducer  16  to accommodate it. Therefore the overall thickness of the mobile telephone can be kept to a minimum.  
         [0052]    A modified arrangement of the embodiment described above with reference to FIGS. 5, 6 and  7 , is illustrated in FIG. 8 which shows a cross section through the housing in the region of the recess  39 . In this modified embodiment, it can be seen that the recess  39  is arcuate in shape to form an inwardly directed or convex depression in the rear surface of the housing  11 . This ensures that the sound passing through the acoustic duct and out through the opening  40  is acoustically “clean”, i.e. there is a minimum number of sharp edges or flat faces to obstruct the sound waves passing through the duct, as shown by the arrows in FIG. 8.