Abstract:
A housing assembly for a mobile telephone comprises a window panel and a front cover, with a clip arrangement which assists in preventing the common problem of the window panel falling out of the front cover. The clip arrangement comprises a rigid clip on the window panel which engages with a beam integrally moulded in the cover. This allows use of a low profile clip which does not extend into the telephone assembly, so permitting strong connections to be made in small assemblies.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to the field of portable electronic apparatus such as mobile telephones, particularly but not exclusively to a housing assembly including a clip arrangement for securely attaching a display window to a mobile phone cover. 
   2. Description of Related Art 
   The majority of conventional mobile telephones have a liquid crystal display for displaying information relating to mobile phone operation, such as the telephone number being dialled, address lists, phone settings and so on. The display is viewed through a protective plastic window, which forms part of the front housing of the phone.  FIGS. 1   a  and  1   b  illustrate several conventional techniques for assembling parts of a housing. For example, referring to  FIG. 1   a , the front housing  1  of a mobile telephone includes a cover portion  2  and a window panel  3 , comprising a clear window  4  and a frame  5 . The window panel  3  is held in the cover portion  2  by layers of adhesive  6 , but this often fails at the higher operational temperatures which may result from prolonged phone use. Tabs  7  can be used to aid retention but often snap off if the phone is accidentally dropped. Furthermore, tabs can only be used at one end of the window panel  3  to allow assembly, so that the opposite end of the panel  3  will peel away from the cover portion  2  and ultimately drop out if the adhesive  6  fails. 
   Referring to  FIG. 1   b , a further known type of clipping arrangement comprises a deformable clip  8  in one housing part  9  which rides over a lip  10   a  of a retaining member  10  in the mating housing part  11  and clips behind the retaining member  10  to hold the respective housing parts  9 ,  11  together. Such clips are generally required to be long and thin in section to achieve the appropriate degree of deformation, as a result of which they snap off easily. In addition, the length of the clip requires significant clearance in the mating part  11 , which is not practical in small assemblies. 
   Clip arrangements are also known in which additional components such as metal spring arrangements are used to provide clip retaining features in one part of the housing. Such solutions increase manufacturing complexity and therefore the cost per unit manufactured. 
   SUMMARY OF THE INVENTION 
   According to the present invention, there is provided a housing assembly for portable electronic apparatus comprising first and second housing portions, the first portion including a substantially rigid clip and the second portion including a receiving arrangement for the clip, the receiving arrangement comprising a displaceable element integrally moulded with the second portion, and the clip comprising means for displacing the element of the second portion, and means for retaining the element between the first portion and the displacing means. 
   The displaceable element can be an elongate beam, which can be defined by first and second slots in the second portion. To assist with location of the first portion onto the second portion, the first slot can be configured to receive the clip only at a part thereof. Further, the beam can have a chamfered edge to assist with movement of the clip over the beam during assembly. 
   The integrally moulded displaceable element obviates the need for additional components and allows the use of a substantially rigid clip, which is less likely to snap. Since a long clip is therefore not required, a low profile clip can advantageously be used to join two substantially planar housing portions, so that, when assembled, the clip does not protrude substantially beyond the plane of the second portion. This can have particular advantages in the manufacture of small assemblies where space is at a premium. 
   In the case of a mobile telephone, the first portion can be a window panel and the second portion the front cover of the telephone. 
   The clip arrangement can be used together with an adhesive and can have the significant advantage that the clip arrangement is itself capable of holding in the window after the adhesive has failed. The window portion can also include one or more tabs for engaging with the cover. The tabs and the clip are preferably arranged at opposite sides of the clear window in the window panel. Even if the tabs snap off, for example when the apparatus is dropped, the clip will remain to hold the window panel. The clip can be reinforced to ensure that it does not deform, so strengthening it further. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     Embodiments of the invention will now be described by way of example, with reference to the accompanying drawings, in which: 
       FIG. 1  shows a conventional display window assembly in a mobile telephone; 
       FIG. 1   b  shows a conventional deformable clip arrangement; 
       FIG. 2  is an exploded view of a mobile telephone according to the invention; 
       FIG. 3  is a rear view of the window panel of the telephone of  FIG. 2  showing the clip which forms part of the clip arrangement according to the invention; 
       FIG. 4  is an enlarged view of the clip shown in  FIG. 3 ; 
       FIG. 5  is a front view of the cover portion of the telephone of  FIG. 2  showing details of the clip receiving arrangement which forms part of the clip arrangement according to the invention; 
       FIG. 6   a  is an enlarged front view of the clip receiving arrangement shown in  FIG. 5 ; 
       FIG. 6   b  is an enlarged rear view of the clip receiving arrangement shown in  FIG. 5 ; 
       FIG. 7   a  is an enlarged cross-sectional view showing a first step in the assembly of the window panel of  FIG. 3  to the cover portion of  FIG. 5 ; and 
       FIG. 7   b  is an enlarged cross-sectional view showing the completed assembly of the window panel of  FIG. 3  to the cover portion of FIG.  5 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to  FIG. 2 , a mobile telephone which includes a housing assembly according to the invention comprises a rear housing  12  including a battery pack  13 , mobile telephone circuitry  14  including an LCD display panel  15 , microphone  16 , ear-piece  17 , keypad  18  and antenna  19 , a front housing portion referred to in this specification as a front cover  20  and a window panel  21  which is designed to fit into the front cover so that the LCD display panel  15  is visible through it. The telephone circuitry  14  is of the type which is well known in the art, for example in the Nokia range of mobile telephones. 
   Referring to  FIG. 3 , the window panel  21  is a single piece plastic moulding having a clear window  22  and a surround  23 , and is made by conventional moulding techniques using conventional materials. A low profile clip  24  is integrally moulded with the panel  21  so as to extend essentially perpendicular to the plane of the panel. The clip is shown in more detail in FIG.  4 . 
   Referring to  FIG. 4 , the clip  24  comprises a body portion  25  extending from the panel  21  and a barbed head portion  26  having a rounded leading edge  26   a  and a trailing edge  26   b . Reinforcing struts  27  are provided for additional strength. The dimensions of the clip  24  are, for example, approximately 1.8 mm high (a), 3 mm wide (b) and 1.8 mm long (c). The reinforcing struts  27  are, for example, 1.5 mm high (d) and 1 mm long (e). The barbed part of the clip head  26  is approximately 0.8 mm long (f) and 1.5 mm (g) from the surface of the window panel  21 . 
   Referring to  FIG. 5 , the front: cover  20  is a moulded plastic unit having a recessed portion  28  for receiving the window panel  21 . The recess is, for example, approximately 1.5 mm deep. The front cover  20  includes cut-outs  29  to accommodate the LCD display panel  15 , microphone  16 , earpiece  17  and keypad  18 , as well as tab receiving slots  30  to accommodate corresponding tabs  31  on the window panel  21 . The front cover  20  also includes a clip receiving arrangement  32  which is shown in more detail in  FIGS. 6   a  and  6   b.    
   Referring to  FIG. 6   a , the clip receiving arrangement  32  is integrally moulded with the front cover and comprises a generally elongate beam  33  defined by two slots  34 ,  35 , one on either side of the beam. 
   The beam length is, for example, approximately 2 cm to allow the beam to be sufficiently flexible so that it deforms without breaking on contact with the clip  24 . It has, for example, a square cross-section 1 mm×1 mm. The first slot  34  is wide enough to receive the clip only at a central portion  36  thereof, the central portion being, for example, approximately 5 mm long and 2 mm wide, the remainder of the slot being 1 mm wide. The second slot  35  is sufficiently wide, for example, 1 mm, to accommodate the beam when it is deflected from its usual position by the action of the clip  24 . 
   The beam  33  has a chamfered portion  33   a  which cooperates with the rounded edge  26   a  of the clip head  26  to assist the clip head  26  to ride over the beam when the clip first contacts it during assembly. The beam can be formed with a thicker portion  37  in the region of the chamfered portion to strengthen it. In this case, the second slot  35  is formed with an offset portion  38  at the level of the thicker portion, to receive the beam  33  as it flexes. 
   Referring to  FIG. 6   b , the beam has a recess  39  for receiving the clip head  26  to assist in ensuring that the head does not protrude significantly into the assembly. The recess is, for example, 6 mm long and 0.3 mm deep. 
   The operation of the clip arrangement will now be described in detail, with reference to  FIGS. 7   a  and  7   b.    
   To assemble the window panel  21  to the front cover  20 , the tabs  31  are first fitted into the tab slots  30 . These then act as a pivot point allowing the panel  21  to be pivoted into position over the front cover  20 . Referring to  FIG. 7   a , as the clip head  26   a  comes into contact with the chamfered portion  33   a  of the beam  33 , it displaces the beam in the direction indicated in  FIG. 7   a , referred to in this specification as downwards, since this generally corresponds to the normal orientation in which the phone would be held in use. The displaced beam  33 ′, shown in dotted outline, is accommodated in the second (lower) slot  35 ,  38 . Once the trailing edge  26   b  of the clip head  26  clears the side of the beam  33   b  furthest from the window panel, the resilience of the beam material moves the beam upwards so that it locates between the clip head  26  and the surface of the window panel  21  from which the clip  24 : extends, as shown in  FIG. 7   b . The window panel  21  is now firmly secured to the front cover  20 . An adhesive can be used between the window panel and the front cover in conjunction with the tabs and clipping arrangement. 
   In an alternative embodiment of the invention, the tabs  31  on the window panel  21  and the corresponding tab slots  30  in the front cover  20  are omitted, the window panel  21  fitting relatively tightly in the recessed portion  28  of the front cover and being held in place by the clip arrangement  24 ,  32  in conjunction with adhesive. It will be evident to a person skilled in the art that various other modifications to the form, details and dimensions of the clip arrangements may be made within the scope of the invention. 
   It will be appreciated that while the invention has been described in relation to mobile telephones, it can be used with any sort of portable electronic apparatus, for example, hand held computers and portable measuring equipment.