Abstract:
In one embodiment, the invention provides an enclosure for a mobile computing system. The enclosure comprises a hollow body shaped and dimensioned to house a processing module, and a display module for a tablet personal computer, wherein the hollow body is defined by a top panel, a bottom panel, and a peripheral side panel, wherein the top and bottom panels are fabricated to have zones of increased, and reduced thicknesses which correspond to areas of the processing module have produced, and greater height, respectively.

Description:
FIELD OF THE INVENTION 
     This invention relates to mobile computing systems. In particular, it relates to the fabrication of an enclosure for a mobile computing system. 
     BACKGROUND 
     An important determinant of the utility of mobile computing systems, such as notebook computers and pen-based computing systems is the form factor of such systems. Compact form factors promote utility and are therefore desirable. 
     Another determinant of the utility of such systems is the weight of these systems. For greater utility, a lightweight system is desirable. 
     For the above reasons, an enclosure for a mobile computing system should be as thin and as lightweight as possible. However, if the enclosure is made too thin, strength is compromised resulting in breakage or at least damage to the enclosure and to the electronics components within the enclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A to 1E  show various views of a mobile computing system comprising a tablet unit and a base unit, according to one embodiment of the invention; 
         FIG. 2  shows a side view of the mobile computing system of  FIGS. 1A to 1E , in which the tablet unit and the base unit are positioned for use in a laptop mode configuration; 
         FIGS. 3A and 3B  show views of the mobile computing system of  FIGS. 1A to 1E , in which the tablet unit and the base unit are positioned for use in a tablet mode configuration; 
         FIG. 4  shows a perspective view of an enclosure for the mobile computing system of  FIGS. 1A to 1E , in which a top wall of the tablet unit can be seen; 
         FIG. 5  shows a perspective view of an underside of the top wall of  FIG. 4 ; 
         FIG. 6  shows a partial cross-sectional view through an enclosure for a mobile computing system, in accordance with one embodiment of the invention; and 
         FIG. 7  shows a partial cross-sectional view through an enclosure for a mobile computing system, in accordance with another embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the invention. It will be apparent, however, to one skilled in the art that the invention can be practiced without these specific details. In other instances, structures and devices are shown in block diagram form in order to avoid obscuring the invention. 
     Reference in this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Moreover, various features are described which may be exhibited by some embodiments and not by others. Similarly, various requirements are described which may be requirements for some embodiments but not other embodiments. 
       FIGS. 1A to 1E  of the drawings show various views of a pen-based computing system in accordance with one embodiment of the invention. In one embodiment, the computing system  10  is in a form of a tablet personal computer (PC) and accordingly includes a tablet unit  12  and a base unit  14 . The base unit  14  is generally rectangular and comprises first and second panels  16 ,  18 , respectively. The panels  16 ,  18  are hingedly connected together via a hinge  20  which permits articulation of the panels  16 , 18  relative to each other. The first panel  16  bears a keyboard  22  which permits data entry into the tablet unit  12  during a laptop mode of operation. 
     The tablet unit  12  is generally rectangular and comprises various processing and display modules mounted on a motherboard substrate. For example, the processing modules may include a processor and a memory hierarchy comprising memory devices configured to store code for execution by the processer in response to user input. The display modules may include a mini-screen  24 , which in one embodiment may be a liquid crystal display (LCD) screen, and a large screen  26 . The large screen  26  includes a digitizer associated therewith to convert handwriting input via a pen or stylus into a digital signal which can be converted by handwriting recognition software into appropriate characters. 
     The components of the tablet unit  12  are enclosed within a generally rectangular enclosure comprising top and bottom walls  28 ,  30 , respectively, and peripheral side walls  32  (see  FIG. 2 ). The walls  28 ,  30 ,  32  are generally fabricated of a lightweight material having sufficient strength. In one embodiment, the walls  28 ,  30 ,  32  may be fabricated using steel, or aluminum. 
     As will be seen in  FIGS. 1B and 1C , the side walls  32  have airflow vents  34  to permit airflow into the enclosure to facilitate cooling of the electronic components therein. 
     The system  10  includes a carry mode in which the tablet unit  12  is supported on the first panel  16  of the base unit  14  and the second panel  18  is folded over a top of the tablet unit  12 . In order to secure the tablet unit  12  and the base unit  14  in the carry mode configuration, a locking mechanism is provided. The locking mechanism comprises a pair of pivotally mounted latches  36  supported by the second panel  18  of the base unit  14 . The latches  36  are adapted to mate with complementary locking formations provided in the tablet unit  12 . As can be seen in  FIG. 1D , in the carry mode configuration, the system resembles a portfolio. 
     The system  10  also includes a laptop mode configuration, in which the tablet unit  12  is held at an inclined position relative to the base unit  14  by the second panel  18  which functions essentially as a prop to support the tablet unit  12  in the inclined position. The laptop mode configuration is illustrated in  FIG. 2  of the drawings. In the laptop mode configuration, the system  10  may be operated in a fashion similar to a conventional laptop, in which a primary mode of data entry is via the keyboard  22 . 
     The system  10  also includes a tablet mode configuration, in which the second panel  18  of the base unit  14  is folded to lie against the first panel  16 , and the tablet unit  12  is placed over the folded second and first panels  18 ,  16  of the base unit  14 , in an orientation in which the large display screen  26  is exposed. In the tablet mode configuration, a user may input data into the system  10  using a pen or stylus by writing directly on the screen  26  as described above. 
     For greater utility of the system  10 , it will be appreciated that the enclosure should be as lightweight, and as robust, as possible. Further, a form factor of the enclosure should be as compact as possible. 
     In order to achieve an enclosure of lightweight and robust design, and which has a minimum form factor, in one embodiment each of the top wall  28  and the bottom wall  30  are fabricated to have zones of different thicknesses.  FIGS. 4 and 5  of the drawings show perspective views of the top wall  28  of an enclosure for the tablet unit  12 , in accordance with one embodiment. As will be seen from  FIG. 4 , an outer surface of the top wall  28  is smooth. However, an inner surface of the top wall  28  includes zones  40 ,  42 , and  44  of different thicknesses (see  FIG. 5 ). The thickness of each zone  40 ,  42 , and  44  is determined by a height by which adjacent electronic components of the electronic assembly housed within the enclosure stand proud of a substrate surface on which the components are mounted. This concept is illustrated in  FIG. 6  of the drawings, which shows a portion of a motherboard substrate  50  which includes electronic components  52  to  60 . As will be seen, the electronic components  52  to  60  have different heights by which they stand proud of the substrate  50 . Thus, according to the above described technique for fabricating an enclosure, the top and bottom walls  28 ,  30  of the enclosure have zones of different thicknesses, each zone being matched to a height by which the electronic components stand proud of the substrate surface. For example, regions where the electronic components have a greater height above the substrate surface, coincide with zones of those reduced thickness. Conversely, regions that coincide with components of the electronic assembly that have a lesser height, the zones have an increased thickness. 
     In one embodiment, the thick zones may be between 1.5 and 3.0 mm, and the thin zones would have a thickness of between 0.3 and 0.8 mm. 
     In another embodiment of the invention, strengthening formations in the form of strengthening beams  70  are used to strengthen the top and bottom walls  28 ,  30 . In one embodiment, the strengthening beams  70  have a height of 1 to 3 mm by which they stand proud of the top and bottom walls  28 ,  30  and a width of between 0.5 and 2.5 mm. Each of the beams  70  may be integrally formed with top and bottom walls  28 ,  30 . In order to add greater rigidity, in one embodiment, the beams are interconnected, as can be seen in  FIG. 5  of the drawings. 
     In another embodiment, in order to achieve the enclosure of lightweight and robust design, and which has a minimum form factor, each of the top walls  28  and the bottom walls  30  are fabricated by first constructing a frame comprising a plurality of interconnected structural beams. Thereafter, the frame is covered with a sheet material which in addition to functioning as a cover to prevent the ingress of dust into the enclosure, also functions as a strengthening element to strengthen the frame by providing resistance to torsional deflection of the frame. Thereafter, side walls are fabricated to interconnect the top and bottom walls. 
     It will be appreciated that the electronic components of the tablet unit  12  may generate significant quantities of heat. Thus, in one embodiment, the enclosure is provided with a heat sinking mechanism to draw heat away from heat producing electronic components of the tablet unit  12 .  FIG. 7  of the heat producing electronic components of the tablet unit  12 .  FIG. 7  of the drawings, shows one embodiment of the heat sinking mechanism. Referring to  FIG. 7 , reference manual  70  indicates heat producing component mounted on a substrate  72 . The heat sinking mechanism comprises a heat spreader component  74 , which in one embodiment, is integrally formed with the top or bottom wall of the enclosure. As will be noted, the heat spreader component  74  increases in cross-sectional area towards the heat producing component  70 . A heat absorbing block  76  fast with the heat spreading component is in a physical contact with the heat producing component  70 , and defines a thermal interface between the heat spreading component  74  and the heat producing component  70 . A thermal conductivity of the heat spreading component  74  is less than a thermal conductivity of the heat absorbing block  76 . In one embodiment, the heat absorbing block  76  may be of graphite, or diamond, and the heat spreading component  74  may be fabricated of material such as aluminum, copper, steel, etc. In one embodiment, an angle made by inclined side walls  78  of the heat spreading component  74  with respect to a plane that contains the heat absorbing block  76  is between 30 degrees and 60 degrees. In use, the heat absorbing block  76  rapidly absorbs heat from the heat producing component  70  and the heat spreading component  74  transports the heat absorbed by the heat absorbing block  76  to an area  80  of the top and bottom walls with which it is in contact. Since the area  80  is greater than an area of the heat producing component  70 , heat produced by the heat producing component  74  is distributed over a wider area by the heat sink, thus reducing thermal hot spots. The heat transported by the heat spreading component  74  to the surface, is thereafter radiated into the atmosphere. 
     In one embodiment, the inclined side walls  78  of the heat spreading component  74  are insulated with a thermal jacket (not shown) to prevent heat escaping therethrough. This improves the heat transfer to the area  80 . 
     Although the present invention has been described with reference to specific exemplary embodiments, it will be evident that the various modification and changes can be made to these embodiments without departing from the broader spirit of the invention as set forth in the claims. Accordingly, the specification and drawings are to be regarded in an illustrative sense rather than in a restrictive sense.