Abstract:
A method of making a tube for a PDA pen includes the steps of providing a tube having a hollow interior, coating a metal layer on the internal surface of the hollow interior, covering a portion of the metal layer on the internal surface, and producing an oxide layer on the uncovered portions of the metal layer so that the uncovered portions of the metal layer are electrically non-conductive and the covered portion of the metal layer remains electrically conductive.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a method for making the tube of a PDA pen.  
           [0003]    2. Description of the Prior Art  
           [0004]    PDAs (personal digital assistant) have become increasingly popular in recent years. Its popularity can be attributed to a number of factors, including: (1) the fact that it can often function like a personal computer (PC), (2) the fact that it can be conveniently operated by using a touch control pen to touch and choose items on its screen, and (3) the fact that its small size is convenient for carrying about in a pocket, handbag, briefcase or other small carrying bag.  
           [0005]    An important component of every PDA system is the PDA pen. In general, the upper surface of the PDA has a touch control screen and a push key zone. A groove is cut from an upper side edge of the PDA. The PDA pen may be stored in the internal space of the groove. During usage, the stylus of the PDA pen is used to touch the touch control screen of the PDA to cause the PDA to execute the programs or instructions selected by the user.  
           [0006]    In co-pending application Ser. No. 10/039,696, filed Jan. 4, 2002, entitled “Touch Control Pen for PDA”, the present applicant discloses a PDA pen that incorporates a light source retained in the pen holder for generating light that can be used to illuminate the touch control screen in use, so that the PDA can be used even in dark environments. An LED structure provides the illumination and is powered by a battery.  
           [0007]    However, PDA pens must be provided in a small size since the size of conventional PDAs are necessarily quite small. To meet these size requirements, a special lithium battery (e.g., model of BR435 having 3V) has been provided. This lithium battery uses a front portion thereof as a negative pole and a rear portion is used as a positive pole. As a result, the printed circuit board (PCB) for the PDA pen must be installed in the front portion of the tube or housing of the PDA pen for conductive purposes. This means that the rear portion of the tube must be isolated to avoid electrical shorts. To isolate the rear portion of the tube, it is possible to place a metal layer inside the tube, and then use a plastic tubular member as an isolative structure inside the tube of the PDA pen. Unfortunately, this approach will enlarge the inside diameter of the tube, which is undesirable because this may cause the outer diameter of the tube to be so large that the PDA pen may not fit inside the groove of the PDA housing.  
           [0008]    Thus, there remains a need for a PDA pen that addresses the problems described above.  
         SUMMARY OF THE DISCLOSURE  
         [0009]    It is an object of the present invention to provide a PDA pen that has a tube where a portion of the tube is isolated to avoid electrical shorts.  
           [0010]    It is another object of the present invention to provide a PDA pen that has a tube which has a diameter that is small enough to allow the PDA pen to fit inside the groove of a conventional PDA.  
           [0011]    It is yet another object of the present invention to provide a PDA which can provide illumination of the screen in dark environments.  
           [0012]    To achieve the above objectives, the present invention provides a method of making a tube for a PDA pen where the following steps are accomplished:  
           [0013]    providing a tube having a hollow interior that has an internal surface;  
           [0014]    coating a metal layer on the internal surface;  
           [0015]    covering a portion of the metal layer on the internal surface; and  
           [0016]    producing an oxide layer on the uncovered portions of the metal layer so that the uncovered portions of the metal layer are electrically non-conductive and the covered portion of the metal layer remains electrically conductive.  
           [0017]    The above-described method can be used to produce a PDA pen that has a tube, an illuminating element provided at the forward end of the tube, a control circuit retained inside the hollow interior of the tube, a metal layer provided on the internal surface of the tube at one portion of the tube, and an isolative layer provided on the internal surface of the tube at another portion of the tube, with the metal layer electrically connecting the control circuit to the illuminating element. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]    [0018]FIG. 1 illustrates an apparatus that provides an anodized treatment for a PDA pen tube according to one embodiment of the present invention.  
         [0019]    [0019]FIG. 2 illustrates another step in the anodized treatment of FIG. 1.  
         [0020]    [0020]FIG. 3 illustrates a PDA pen tube after it has received the anodized treatment illustrated in FIGS. 1 and 2.  
         [0021]    [0021]FIG. 4 is a sectional side view of a PDA pen that includes the PDA pen tube of FIG. 3, after the PDA pen has been assembled for use. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0022]    The following detailed description is of the best presently contemplated modes of carrying out the invention. This description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating general principles of embodiments of the invention. The scope of the invention is best defined by the appended claims.  
         [0023]    Referring first to FIG. 4, FIG. 4 illustrates a PDA pen  50  that includes a pen tube processed according to the method illustrated in FIGS. 1 and 2 hereinbelow. The PDA pen  50  has a pen tube  51 , a cap  57  and an LED stylus  59 . The LED stylus  59  can produce light to illuminate the touch control screen of a PDA. The interior wall of the front end of the pen tube  51  has a metal layer  52  that electrically connects a PCB  53  (acting as a control circuit) to control the illumination of the LED  59 . At least one battery  54  (FIG. 4 shows two batteries  54 ) is retained inside the tube  51 , with the batteries  54  having a front end that is electrically coupled to the PCB  53 . The rear end of pen tube  51  retains a spring  55  and a conductive block  56  that are positioned between the batteries  54  and the cap  57 . The cap  57  is fitted at the rear end of the pen tube  51 . The bias of the spring  55  against the block  56  and the batteries  54  function to retain the batteries  54  firmly in place inside the pen tube  51  to maintain the necessary electrical connection. The cap  57  also has an external protruding gripping block  58  which can be used by a user to push the PDA pen  50  out of the groove of a PDA. Although FIG. 4 provides a very simple and general description of an illuminating PDA pen  50 , the PDA pen  50  can have a structure and operation that is very similar to the PDA pens shown and described in co-pending application Ser. No. 10/039,696, filed Jan. 4, 2002, entitled “Touch Control Pen for PDA”, whose disclosure is incorporated by this reference as though set forth fully herein.  
         [0024]    [0024]FIGS. 1 and 2 illustrate a method of producing a pen tube  10  (which is the same as pen tube  51  described above) according to the present invention in which the rear portion of the tube  10  is isolated to avoid electrical shorts, yet which has a sufficiently small diameter so that the tube  10  can be fitted inside the groove of any conventional PDA. The method illustrated in FIGS. 1 and 2 involves anodizing a portion of the tube  10 . First, a base plate  20  is provided for processing pen tubes  10 . Each base plate  20  has a plurality of identical plugs  22 ,  24 ,  26 . Each plug (e.g.,  22 ) itself defines a lower primary plug  224  and an upper secondary plug  222 , with the secondary plug  222  having a smaller diameter than the primary plug  224 . The plug  24  also has a primary plug  244  and a smaller-diameter secondary plug  242 .  
         [0025]    Next, each tube  10  is fitted on to a separate plug  22 ,  24 ,  26  by placing one open end of the tube  10  over the secondary plug  222  and  242  of a corresponding plug  22 ,  24  or  26 . A metal layer (e.g., aluminum) is then coated on to the internal surface of the tube  10 . The area of the internal surface of each tube  10  that is occupied by a corresponding secondary plug  222 ,  242  defines an occupied area  15  on the internal surface at one end of the tube  10 . Thus, the size of the occupied area  15  is determined by the size and shape of the secondary plug  222  or  242 .  
         [0026]    Next, as shown in FIG. 2, the base plate  20  and the tubes  10  that have been fitted over the plugs  22 ,  24 ,  26  are turned sideways (e.g., by tilting or turning the base plate  20  by ninety degrees) and placed into an electrolyte solution  32  of an electrobath  30  for anodized treatment. Since each occupied area  15  is being blocked by a corresponding secondary plug  222 ,  242 , the occupied areas  15  are not exposed to electrolyte  32 , so that an oxide (e.g., aluminum oxide) is not formed on these occupied areas  15 , thereby still leaving a conductive metal layer at the occupied areas  15 . The metal on the other portions of the internal surface that are not occupied or blocked by the secondary plugs  222 ,  242  will react with the electrolyte  32  to produce an oxide (e.g., aluminum oxide) that functions as an isolative layer. As a non-limiting example, aluminum oxide is a ceramic material having features of isolation and hardness. In other words, the metal layer not occupied by a secondary plug  222 ,  242  in tube  10  is transformed into an oxide layer  40  (see FIG. 3) for isolative function, while the portion of the metal layer occupied by a secondary plug  222 ,  242  remains a conductor  45 . FIG. 3 illustrates the pen tube  10  after being processed in the manner described and illustrated in connection with FIGS. 1 and 2.  
         [0027]    Referring back to FIG. 4, the conductive portion  45  of the tube  10  is the location where the PCB  53  is positioned. Thus, the conductive portion  53  can electrically connect the PCB  53  with the LED stylus  59 , while having the rest of the tube  10  be electrically isolated to avoid electrical shorts.  
         [0028]    Thus, by utilizing the original metal layer on the internal surface of a tube  10  and isolating a selected portion of this metal layer prior to an oxidation treatment, the present invention can accomplish the objective of isolating a portion of the tube  10  to avoid electrical shorts, yet still providing the tube  10  with a diameter that is small enough to allow the tube  10  to be fitted inside the groove of any conventional PDA.  
         [0029]    While the description above refers to particular embodiments of the present invention, it will be understood that many modifications may be made without departing from the spirit thereof. The accompanying claims are intended to cover such modifications as would fall within the true scope and spirit of the present invention.