Abstract:
A radio device comprising a housing  50  having an opening  52  and an internal retaining recess  58;  a resilient antenna support sleeve  60  inserted in the opening, the sleeve including a lug  70  projecting into the retaining recess  58  to oppose withdrawal of the antenna support sleeve; and an antenna  10  mounted in the antenna support sleeve. The walls of the retaining recess  58  and the surfaces of the lug  70  are shaped such that on rotation of the sleeve  60  the lug  70  is urged inwardly and escapes from the retaining recess  58.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to radio devices. 
     In such devices, it is known to equip a housing of the device with an external antenna which projects through an opening in the housing. 
     Damage to the antenna through snapping, bending or fracture can occur. It is, therefore, a requirement for the radio device that the damaged antenna be readily replaceable. 
     SUMMARY OF THE INVENTION 
     With this in mind, in one aspect, the present invention provides a radio device comprising: a housing having an opening and an internal retaining recess; a resilient antenna support sleeve inserted in the opening, the sleeve including a lug projecting into the retaining recess to oppose withdrawal of the antenna support sleeve; an antenna mounted in the antenna support sleeve; the walls of the retaining recess and the surfaces of the lug being shaped such that on rotation of the sleeve the lug is urged inwardly and escapes from the retaining recess. 
     By virtue of these features, on rotation of the sleeve the lug is urged inwardly and escapes from the retaining recess, thereby facilitating withdrawal of the antenna support sleeve from the housing. 
     Preferably, the lug comprises a chamfered surface. The chamfered surface on rotation of the sleeve bears against a side wall defining the retaining recess and assists in the progressive inward deformation of the sleeve which helps the lug to escape from the retaining recess. Preferably, the lug comprises a pair of chamfered surfaces such that the same effect can be achieved in either direction. Also, the lug may include a chamfered surface which facilitates the insertion of the lug into the opening. 
     Preferably, the lug includes a face. The face opposes a top wall defining the recess, whereupon if an attempt is made to withdraw the sleeve from the opening, the face bears against the top wall to oppose this withdrawal. 
     In a further aspect, the present invention provides an antenna support sleeve suitable for removable insertion into an opening of the housing of a radio device, comprising a tubular wall from which upstands a lug, the wall being sufficiently deformable such that when an inward force is applied to the lug during said insertion the wall deforms but the lug does not. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Exemplary embodiments of the invention are hereinafter described with reference to the accompanying drawings, in which: 
     FIG. 1 shows a view of an antenna; 
     FIG. 2 shows the antenna of FIG. 1 inserted into an antenna support sleeve prior to the insertion of the antenna support sleeve into a housing; 
     FIG. 3 shows the antenna support sleeve inserted in the housing and the rod antenna in its fully retracted condition; and 
     FIGS.  4 ( a ) and  4 ( b ) show close-up views of the engagement of the locating lug and retaining recess visible in FIG.  3 . 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring to FIG. 1, an antenna for signal transmission and reception in a radio telephone is generally designated  10 . It comprises an elongate radiating element  12  (shown in dashed lines) surrounded by an insulating sleeve or covering  14 . The antenna  10  further comprises first and second electrically-conductive contact elements  16 ,  18  conductively coupled to respective first and second ends of the elongate radiating element  12 . The second contact element  18  is conductively coupled to a helical radiating element which is housed in an insulating cap  22  of cylindrical shape. The bottom surface of the insulating cap is designated  23 . 
     The first contact element  16  is a sleeve of circular but non-uniform cross-section along its length, which is closed off at one end by an hexagonal stop member  20  and receives in the other open end the first end of the elongate radiating element  12 . 
     The first contact element  16  comprises two generally cylindrical end portions  24 , 28  joined by a cylindrical intermediate portion  26 . The end portions  24 , 28  are of a slightly larger outer diameter than the intermediate portion  26 . The end portion  24  abuts the stop member  20 . The end region of end portion  28  which opens to receive the elongate radiating element  12  is slightly tapered relative to the rest of the end portion  28 . The contact element  18  is also generally in the form of a sleeve. The sleeve comprises a cylindrical main portion  30  and a cylindrical end portion  34  which are joined by an intermediate portion  32 . The main portion  30  is open to receive the elongate radiating element  12 . This open end of the main portion  30  is slightly tapered relative to the rest of the main portion  30 . An end region of the end portion  34  abuts the bottom surface of the insulating cap  23 . The intermediate portion  32  flares from its end region connected to the main portion  30  or tapers from its end region connected to the end portion  34 . As a result, the outer diameter of the main portion  30  is less than that of the end portion  34 . The outer diameter of the main portion  30  of the second contact element  18  is the same as that of the end portions  24 , 28  of the first contact element. 
     The outer profile of the rod antenna  10  determines the mechanical functionality of the antenna, in use, as described later. 
     FIG. 2 shows the antenna  10  inserted in an antenna support sleeve  60  just before the antenna  10  and the antenna support sleeve  60  are fitted to the rear casing  50  or so-called ‘B’-cover of a radiotelephone. 
     The support sleeve  60  comprises a cylindrical wall  62  which at a first end thereof includes a pair of planar opposed semi-circular lips  64 . The lips  64  occupy a plane perpendicular to the longitudinal axis of the cylindrical wall  62  and define an aperture of substantially smaller diameter than the inner diameter of the cylindrical wall at the first end thereof. The diameter of the aperture formed by the lips  64  is approximately the same as the outer diameter of the end portion  34  of the second contact element  18 . The cylindrical wall  62  has a pair of opposing slots  64   a,    64   b  which extend longitudinally along most of the length of the wall  62 . The slots  64   a,    64   b  do not, however, reach either end of the wall  62 . The wall regions separating the slots are designated  66   a,    66   b.  A pair of locating lugs  70   a,    70   b  project from the wall regions  66   a,    66   b  respectively from generally midway therealong. From the FIG. 2 view, only the wall region  66   a,  the slot  64   a  and the locating lug  70   a  are visible. FIGS.  4 ( a ) and  4 ( b ) show the locating lug  70   a  in more detail. Locating lug  70   b  is not shown but is identical. Locating lug  70   a  includes a top face  71  which is relatively flat as can be seen in the FIG.  4 ( b ) vertical cross-sectional view. The locating lug  70   a  also includes chamfered side surfaces  72  and a chamfered leading surface  73  as can be seen in the FIG.  4 ( a ) view from below. At the second end of the support sleeve  60 , a friction clip  74  is fitted. The friction clip  74  is a split collar made from a sheet of metal having a stud formed at one end and a guide groove formed in the other end. The sheet is coiled into a closed collar in which the stud rides in the guide groove. The minimum and maximum radii of the collar are controlled by the longitudinal extent of the guide groove. The collar is formed such that at the minimum radius determined by the guide groove the collar urges itself to a still smaller radius. The elongate radiating element  12  passes through the aperture formed by the lips  64  and through the friction clip  74 . 
     As can be seen in FIG. 2, the rear casing  50  includes a chimney  51 , with an opening  52 , which projects from the top of the casing and into which the support sleeve  60  can be inserted. The chimney  51  is defined by a wall  53  of circular cross-section having an inner surface  54   a  and an outer surface  54   b.  The chimney  51  is open at its bottom end region to the inside of the casing. Most of the chimney wall  53  is an exterior wall of the casing  50 . A portion of the chimney wall  53  is, however, interior to the casing  50  and is designated  53   a.  Immediately below the opening  52 , the internal diameter of the chimney wall  53  abruptly narrows to form a circumferential ledge  55 . Extending along the length of the inner surface  54   a  of the chimney wall, a pair of shallow tracks  56   a,    56   b  are formed. In the FIG. 2 view, only track  56   b  is visible. The track  56   a  leads to a retaining recess  58  (visible in FIG. 3) which is formed at the end of the wall portion  53   a.  The retaining recess  58  takes the form of a through-hole in the wall portion  53   a  and is defined by first and second side walls  58   a,    58   b  and a top wall  58   c.    
     From the position illustrated in FIG. 2, the antenna support sleeve  60  is inserted into the opening  52  of the chimney  51  such that the locating lugs  70   a,    70   b  can enter and slide within the tracks  56   a,    56   b.  The chamfered leading surface  73  or nose of the locating lugs  70   a,    70   b  facilitate sliding. The antenna support sleeve  60  reaches its fully inserted position when the lips  64  of the support sleeve abut the ledge  55  of the chimney  51 . As the support sleeve is being inserted in this way, the inner surface  54   a  of the chimney wall  53  in the region of the tracks  56   a,    56   b  imposes (because of the close clearance fit between the support sleeve  60  and the chimney  51 ) a compressive force on the support sleeve  60  via its locating lugs  70   a,    70   b.  The compressive force causes deformation of the wall  62 , which deformation is accommodated by the slots  64   a,    64   b,  but no deformation of the lugs  70   a,    70   b  takes place. As the fully inserted position is reached, the compressive force is relieved by the locating lug  70   a  popping or springing into the retaining recess  58 . This is shown in FIG.  4 ( a ) from a view immediately below the locating lug  70   a  and in FIG.  4 ( b ) from an axial cross-sectional view of the support sleeve  60 . In the fully inserted position, the locating lug  70   b  remains in the track  56   b.  In the fully inserted position, the top wall  58   c  of the retaining recess bears against the top face  71  of the lug  71   a  to oppose withdrawal of the support sleeve  60 . 
     FIG. 3 shows the antenna  10  in its retracted operational condition. In this condition, the friction clip  74  grips around the end portion  34  of the second contact element  18 . Also, the helical radiating element in the cap  22  is coupled via the friction clip  74  to the transmit/receive circuitry of the radiotelephone. In order to extend the antenna  10 , the cap  22  is pulled in the direction of arrow A in FIG.  3 . Because of the relatively large outer diameter of the end portion  34 , it is tightly gripped by the friction clip  74 . This gripping action provides the user with a feeling that the antenna  10  is positively locked in its retracted condition and also assists in maintaining a reliable electrical connection between the friction clip  74  and the second contact element. Once the initial resistive force applied by the friction clip  74  is overcome, the antenna  10  starts to extend and continues to do so until it reaches its extended condition at which point the stop member  20  abuts the friction clip  74 . At this point the end portion  24  of the first contact element  16  is gripped within the friction clip  74  and the relatively large outer diameter of the end portion  24  provides the user with the feeling that the antenna  10  is positively locked in this extended operational condition and serves to ensure that there is a reliable electrical connection between the friction clip  74  and the first contact element  16 . Between these two extreme operational positions, the friction clip  74  provides varying degrees of frictional resistance depending on the diameter of the antenna part within the friction clip  74  in order to provide the desired mechanical functionality, For example, when the covering  14  is passing through the friction clip  74  the frictional resistance afforded by the friction clip  74  can be negligible because the diameter of the covering  14  is less than the minimum possible radius of the collar of the friction clip  74 . 
     In order to withdraw the support sleeve  60 , for example so as to be able to replace a damaged antenna  10 , it is rotated in either direction such that a chamfered side surface  72  of the bears against the neighbouring side wall  58   a,    58   b  of the retaining recess (see FIG.  4 ). The chamfered surface facilitates inward deformation of the support sleeve  60 , whereby the lug  70   a  is able to spring free of the retaining recess so that the support sleeve  60  and the antenna  10  can together be removed from the chimney  51 . 
     During the operations of withdrawing and inserting the antenna support sleeve, no deformation of the lugs  70   a,    70   b  takes place. This means that the antenna support sleeve can be properly inserted/withdrawn many times. It will, of course, be appreciated that during these operations the lugs  70   a,    70   b  do suffer some wear due to frictional contact with the inner surface  54   a  of the well wall. 
     In other embodiments, the side walls  58   a,    58   b  of the retaining recess can be shaped to facilitate the lug  70   a  escaping from the retaining recess on rotation of the support sleeve  60 . This can be additional to or instead of the shaping of the side walls  72  of the lug  70   a.  In other embodiments, the lug  70   b  can be dispensed such that there is only a single lug  70   a.    
     In other embodiments (not shown), the retaining recess  58  can be dispensed with, the clearance fit with the well wall  53  being sufficient to enable the antenna support sleeve to be held in place, yet the flexibility/deformability of the sleeve wall  62  in combination with the frictional interplay between the lugs  70   a,    70   b  and the well wall  53  allowing for insertion/withdrawal of the antenna support sleeve.