Abstract:
A spacer for use in a mobile device fills the space between a component assembly and a housing. The spacer includes a layer of compressible material for insertion between the component assembly and the housing. A plurality of compressible features are provided on a face of the layer. Upon insertion of the component assembly and assembly of the housing, the compressible features are compressed to fill a gap between the component assembly and the housing without over-compressing the main body of the spacer, allowing the body of the spacer to cushion any subsequent impact to the mobile device.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to a mobile devices and particularly, to a device for cushioning a component assembly in a mobile device.  
       BACKGROUND OF THE INVENTION  
       [0002]     Many mobile electronic devices such as hand-held computers, cellular telephones, personal digital assistants (PDAs), have a multi-component assembly housed within a small case or housing. A small housing means that a small change (numerically) in the size of the internal components or the housing can result in a large change (in terms of percentage) in the space within the housing allocated for the component assembly. A typical component assembly is a component stack that includes a display, such as a liquid crystal display (LCD) and a circuit board.  
         [0003]     Typically, the housing consists of two mating halves to contain the assembly. The mated halves define an interior cavity and, of course, the depth of the component assembly must be slightly less than the depth of the interior cavity. The difference in depth results in an undesirable gap between the component assembly and the housing inside the assembled device.  
         [0004]     The gap can be expected to vary in depth due to manufacturing tolerances, assembly tolerances, substitution of components in the component assembly, redesign of the component assembly or the use of a standard housing for different models or devices.  
         [0005]     The gap is undesirable since it can result in movement or play of the interior components of the device allowing components to become displaced, disconnected, damaged or simply rattle around inside the housing, especially if the device suffers a shock such as from being dropped.  
         [0006]     To eliminate these undesirable results, one solution is to employ a cushion or spacer, for example, a layer of compressible foam. Initially, the uncompressed spacer is deeper than the dimension of the gap so that when the depth of the spacer is added to the depth of the component assembly, the total depth is greater than that of the interior of the housing. However, during assembly of the housing of the device, the interior of the housing comes into contact with the spacer and compresses it against the component stack Accordingly, the gap is occupied by the compressed spacer preventing movement of the component assembly in the direction of the stack-up (normal to the plane of the circuit board or the LCD).  
         [0007]     If the spacer is insufficiently deep, it will not span the gap even in an uncompressed state or it will provide inadequate cushioning for the component assembly. If the spacer is too deep then upon compression it will exert excessive pressure to the component assembly including the display. In the situation where the display is an LCD module, the LCD itself is sensitive to the pressure applied to it. Pushing it unevenly or with too much force will cause a blemish or distortion to appear in the viewing area. Excessive pressure can also prevent the spacer from properly dispersing the energy of an impact because its ability to deflect has already been used in taking up the tolerance of the small available space and in extreme cases excessive pressure or the inability to deflect a shock can result in breaking of the screen. This is very costly, especially if the screen is an expensive colour LCD.  
         [0008]     Any of these scenarios can result in an unacceptable product and increase the cost of manufacturing of mobile devices. Accordingly, it is desirable to provide an improved spacer for use with a component assembly to more controllably fill a gap between the component assembly and the housing.  
       SUMMARY OF THE INVENTION  
       [0009]     According to an embodiment, there is provided a spacer for use in a mobile device to space a component assembly from a housing of the mobile device. The spacer comprises a body of compressible material for insertion between the component assembly and the housing; and a plurality of compressible features provided on the body. The compressible features deform to prevent displacement of the component assembly relative to the housing while leaving the body of the spacer relatively uncompressed so that the body cushions the component assembly. The compressible features can be domed, cylindrical, polygonal prism, conical, frusto-conical, pyramidal or frusto-pyramidal in shape.  
         [0010]     According to a further embodiment, there is provided a spacer for use in a mobile device. The spacer fills a space between a component assembly and a housing. The component assembly includes a display component. The spacer comprises a layer of compressible material for insertion between the component assembly and the housing; and a plurality of compressible features provided on a face of the layer. The compressible features are compressible upon assembly of the mobile device and extend between the component assembly and the housing to space the component assembly inside the housing when the mobile device is assembled. The depth of the layer and uncompressed compressible features exceeds the depth of the space between the component assembly and the housing, and the depth of the compressed layer and the compressed compressible features exceeds a predetermined critical depth.  
         [0011]     In another embodiment, there is provided a method of manufacturing a spacer for use in a mobile device. The spacer includes a body of compressible material for insertion between a component assembly of the mobile device and a housing of the mobile device; and a plurality of compressible features are provided on the body for filling space between the component assembly and the housing during assembly of the mobile device while leaving the body of the spacer relatively uncompressed so that the body can cushion the component assembly. The method comprises steps of depositing partially cured solution of material onto a surface; spreading the partially cured solution of material to form a layer of desired thickness; using a patterned roller to flatten and pattern the spread partially cured solution of material; and allowing the partially cured solution of material to cure. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]     Embodiments of the present invention will now be described, by way of example only, with reference to the attached drawings, wherein:  
         [0013]      FIG. 1  is an exploded view of a mobile device including a spacer according to an embodiment of the present invention;  
         [0014]      FIG. 2  shows an alternative embodiment of the present invention;  
         [0015]      FIG. 3  shows another alternative embodiment of the present invention;  
         [0016]      FIG. 4  shows a section view along the line  4 - 4  of  FIG. 3 ;  
         [0017]      FIG. 5  is an exploded view of a mobile device including two spacers;  
         [0018]      FIG. 6  shows a section view of a further embodiment of the present invention;  
         [0019]      FIG. 7  shows a still further embodiment of the present invention;  
         [0020]      FIG. 8  is a section view of an additional embodiment of the present invention;  
         [0021]      FIG. 9  shows a graph illustrating relationship between force and displacement;  
         [0022]      FIG. 10  shows a graph contrasting the compression properties of a spacer according to embodiments of the present invention with those of conventional technology.  
         [0023]      FIGS. 11   a  and  11   b  show the range of gaps accommodated by a conventional spacer;  
         [0024]      FIGS. 12   a  and  12   b  show the range of gaps accommodated by a spacer according to embodiments of the present invention;  
         [0025]      FIGS. 13   a ,  13   b  and  13   b  show the deformation of a spacer in compression;  
         [0026]      FIGS. 14   a ,  14   b  and  14   c  show the steps in a method of manufacturing a spacer; and  
         [0027]      FIG. 15  shows the master roll  1440  of  FIG. 14 . 
     
    
     DETAILED DESCRIPTION  
       [0028]     Generally, a spacer for use with a mobile device having a component assembly enclosed in a housing is provided. The spacer occupies a gap between the component assembly and the housing.  
         [0029]     Referring to  FIG. 1 , a mobile device  100  has a component assembly or component stack contained within a housing. The mobile device  100  is an electronic device such as a hand-held computer, a cellular telephone with or without data communications functionality, a wireless mobile data communication device, a wireless email communication device, a pager, or a PDA, for example. The housing of  FIG. 1  consists of two mating halves, a front half  110  and a back half  150 . When the front and back halves are assembled, they define the housing and an interior cavity. The component assembly includes electronic circuitry  140 , for example, a circuit board and a display such as an LCD  130 . A seal or spacer  120  according to an embodiment of the present invention is used to eliminate any gap between the housing and the component assembly in the direction of the stack-up (normal to the plane of the circuit board  140 ).  
         [0030]     The spacer  120  is made of a suitable material such as compressible foam. The body  122  of the spacer is a layer dimensioned to extend around the perimeter of the cavity at the front or back half of the housing. A central aperture  126  in the body enables the LCD  130  to be visible through a window  112  in the front of the housing. The central aperture also allows actuators  114  to contact or connect with corresponding elements on the circuit board  140 .  
         [0031]     Compressible features, such as the raised feature  124 , are provided on the front surface of the spacer. These compressible features make the spacer or seal hyperelastic as explained below. The raised features  124  illustrated in  FIG. 1  are domed, although they can be any suitable shape such as cylindrical, polygonal prism, conical, frusto-conical, pyramidal and frusto-pyramidal. Alternatively, a pattern of recesses, valleys or dimples can be cut, stamped or otherwise formed into the surface of the spacer, leaving compressible features (e.g. ridges surrounding the cut out portions) formed on the underlying body layer.  
         [0032]     According to the present embodiment, the raised features  124  form a regular grid or arrayed pattern, however, any suitable pattern can be used. The planar density of compressible features can also be varied, for example by the pattern chosen, as discussed below.  
         [0033]     The raised features  124  can be made of a material different than that of the spacer but, according to a preferred embodiment, they are integrally formed with the spacer. The raised features  124  enable the spacer to accommodate larger gaps than a conventional spacer without over compressing the LCD  130  in smaller gaps.  
         [0034]     As illustrated in  FIG. 9 , at the beginning of compression, the raised features  124  deflect with minimal force since the volume of the raised features  124  of the spacer  120  is small. See region  910  in  FIG. 9 . Without the raised features  124  there could be a gap or inadequate cushioning between the housing and the assembly. The raised features  124  overcome the tolerance or gap without affecting the range of the work area of the spacer  120 . This makes the full compression range of at least the body  122  of the spacer  120  available for cushioning the component assembly. The component assembly will have neither pre-compression set nor play.  
         [0035]      FIG. 11   a  illustrates a conventional spacer  1120  having thickness t. In this example, an acceptable maximum amount of compression c in the range 0&lt;c&lt;=0.10t, i.e. any amount of compression up to 10 percent of the original thickness of the spacer  1120  does not over compress the spacer and the spacer retains sufficient resilience to absorb a predefined shock. Of course, the range will vary depending on many factors, including the properties of the material of the spacer and the geometry of the spacer, component stack and housing. In the example of  FIG. 11   a , the spacer  1120  cannot accommodate gap g 1  where g 1 &gt;t. Also the spacer  1120  cannot accommodate too small a gap g 2  which overcompresses the spacer. Accordingly, the spacer  1120  can only accommodate gaps smaller than its thickness, i.e. g&lt;t, and if the acceptable maximum compression is 10% then the spacer can only accommodate gaps larger than (1−0.1)t, or g&gt;0.9t. Accordingly, for a conventional spacer such as the spacer  1120 , 0.9t&lt;g&lt;t, or more generally (1−c)t&lt;g&lt;t, where g is the size of the gap, t is the thickness of the spacer and c is the maximum acceptable amount of compression and 0&lt;c&lt;1.  
         [0036]     By contrast, referring to  FIGS. 12   a  and  12   b , a spacer  1210  according to the present invention includes a main body  1212  with thickness t and protrusions  1214  with thickness h. Assuming that the volume of material in the protrusions is small compared with the volume of material in the body, then the protrusions will be nearly completely collapsed before any substantial compression of the body  1212  occurs, as shown in  FIGS. 13   a  to  13   c . When the protrusions are partially compressed, a compression force is exerted on the component stack preventing it from moving in the stack direction. If there are fewer protrusions, then deformation of the main body resulting from pressure on the protrusions is negligible and the full range of compression of the main body  1212  is available to absorb any shock to which the component stack is subjected. Referring to  FIGS. 12   a  and  12   b , where the body  1212  of spacer  1210  has the same thickness as body  1120  and the same maximum amount of compression, then any gap which satisfies g&lt;t+h and g&gt;(1−c)t can be accommodated, or (1−c)t&lt;g&lt;t+h. Thus, the spacer  1210  accommodates a greater range of gaps, including gaps up to a size of t+h instead of gaps up to size t, without affecting the compression limit c. The ratio of h to t is important, and selected for a desired gap range. For example, the increase in gap range is very significant if h/t is close to 1.  
         [0037]     As indicated above, the maximum amount of compression, expressed in terms of the total thickness of the spacer, can vary substantially. According to an embodiment of the present invention, the maximum amount of compression, c, is in the range 3% to 10%. According to another embodiment, c is in the range 4% to 6%. According to a further embodiment c is approximately 5%.  
         [0038]     More generally, a spacer according to embodiments of the present invention includes a spacer having a body and layer of compressible features provided on the body. The body and the layer of compressible features have different compression properties. The body is relatively resistant to compression and the layer of compressible features is relatively easy to compress. This arrangement can be effected by using different materials or by using the same materials for differently formed structures or differently dimensioned structures as in the examples above. According to the examples provided above, the body comprises a first layer relatively resistant to compression and the protrusions form a sparse second layer of material that is relatively compressible. Alternatively, the relatively compressible layer is formed of a layer similar to the body layer but having depressions, cut-outs, grooves or other volumes of material removed so that the total volume of material compressed is less than the volume of material compressed in a like volume of space.  
         [0039]     Spacers according to aspects of the present invention have different physical characteristics than a conventional spacer. This is illustrated in  FIG. 10 . A conventional spacer without raised features has the compression curve  1010  whereas a spacer according to an embodiment of the present invention has compression curve  1020 .  
         [0040]     The compression curves of  FIG. 10  illustrate the different amounts of force exerted on the LCD due to the compression of each spacer. It is evident that for a given amount of compression, spacers according to embodiments of the present invention advantageously exert less force on a component stack and, in particular, on an LCD or other sensitive component in the component stack.  
         [0041]      FIG. 2  illustrates another embodiment of the present invention, in which a spacer  200  includes a body  220  having raised features  222  that are differently spaced than in the preceding embodiment shown in  FIG. 1 .  FIGS. 3 and 4  illustrate still another embodiment wherein a spacer  300  has a different pattern of raised features  310  on the body  320 .  
         [0042]     According to  FIG. 5 , an alternative embodiment of the present invention is illustrated in which a front spacer  120  and a back spacer  510  are employed, corresponding to each of the two halves  110  and  150  of the housing. This provides additional protection for the components and enables larger tolerances to be overcome.  
         [0043]     According to  FIG. 6 , the spacer  600  has raised features  610  on both its surfaces. Again, this increases the amount of tolerance which can be accommodated by the spacer.  
         [0044]      FIG. 7  illustrates another pattern of raised features  710  which are less densely spaced on the body  720  of the spacer  700  than the raised features of  FIG. 1 . This decreases the volume of spacer  700  to be compressed and decreases the associated pressure. Alternatively, the pattern of compressible features can be more densely spaced to increase the volume of material initially compressed and increase the pressure.  
         [0045]      FIG. 8  illustrates compressible features  810  of varying heights that modify the compression curve of the spacer  800  over its area.  
         [0046]     An example method of manufacturing the spacer of the present invention is illustrated in  FIGS. 14 and 15 . Initially, a mass  1410  of liquid solution of rubber or other suitable material is deposited on a plate  1420 , as shown in  FIG. 14   a . As the solution cures, an oscillating blade  1430  spreads the rubber solution  1410  over the plate  1420  to achieve a layer of rubber  1412  in a half-liquid state, as in  FIG. 14   b . The layer is approximately twice the thickness of the final spacer, although this can be varied as required. Referring now to  FIG. 14   c , a master roll  1440  is then used to flatten and pattern the rubber  1412  and produce a mass of material  1414  of the desired thickness, for example, 0.787 mm not including the thickness of the raised features  1416 . The material is allowed to cure, and is then trimmed to form one or more rolls which can be cut as desired into individual spacers.  
         [0047]      FIG. 15  illustrates an example embodiment of a master roll  1440  having indentations  1442  which result in the raised features  1416 . Of course, other master rolls are used to produce different shapes or patterns of raised features, or to effect dimples or cut outs in a material roll for spacers.  
         [0048]     The above-described embodiments of the present invention are intended to be examples only. Alterations, modifications and variations may be effected to the particular embodiments by those of skill in the art without departing from the scope of the invention, which is defined solely by the claims appended hereto.