Abstract:
A input pen for a portable information processing terminal device with an input tip ( 12 ) biased axially forward by pressure applied thereto by a return spring ( 13 ). The pressure applied to the input tip ( 12 ) is optionally adjustable. A front barrel  10  is detachably attached to a front portion of a barrel ( 1 ). The input tip ( 12 ) is axially slidably inserted in the front barrel  10 . The return spring  13  extended in the front barrel ( 10 ) applies pressure to the input tip ( 12 ) so as to bias the input tip ( 12 ) forward.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an input pen for a portable information processing terminal device, such as a PDA (personal digital assistant). 
     2. Description of the Related Art 
     An input pen employed in operating a conventional portable information processing terminal device is provided with an input tip and a tip return spring biasing the input tip forward so that the input pin is able to move backward when an excessively high pressure is applied to the input tip. 
     The pressure of the tip return spring, however, cannot be adjusted to adjust the force biasing the input tip longitudinally forward according to the purpose of the input pen. 
     Another input pen employed in a conventional portable information processing terminal device is provided with a ballpoint refill in a barrel. The replacement of the ballpoint refill contained in the barrel having a small inside diameter with another one requires very troublesome work. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an input pen capable of solving problems in the conventional input pen. 
     To achieve the object, according to one aspect of the present invention, an input pen for a portable information processing terminal device includes a barrel, a front barrel detachably attached to a front portion of the barrel, an input tip axially slidably fitted in the front barrel, and a return spring placed in the front barrel to apply pressure to the input tip so as to bias the input tip forward, wherein the pressure applied to the input tip by the return spring is optionally adjustable. 
     Since the pressure of the return spring can be optionally adjustable according to the user&#39;s preference, the input pen can be operated for input operations in an optimum condition. 
     According to another aspect of the present invention, an input pen for a portable information processing terminal device includes a barrel, an input tip fitted in a front portion of the barrel, a reset pin detachably attached to a front portion of the barrel, and a ballpoint refill having a writing part and detachably mounted on the reset pin, and a cap detachably put on the barrel so as to cover the writing part of the ballpoint refill. The used ballpoint refill can be replaced with a new one simply by removing the reset pin from the barrel, removing the used ballpoint refill from the reset pin and putting the new ballpoint refill on the reset pin. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a longitudinal sectional view of an input pen in a first embodiment according to the present invention; 
     FIG. 2 is a sectional view taken on line A—A in FIG. 1; 
     FIG. 3 is a plan view of the input pen shown in FIG. 1; 
     FIG. 4 is an end view of the input pen shown in FIG. 1 as viewed from the right side in FIG. 1; 
     FIG. 5 is a plan view of a clip included in the input pen shown in FIG. 1; 
     FIG. 6 is a front elevation of an essential portion of the input pen shown in FIG. 1 in a state where a clip is removed; 
     FIG. 7 is a plan view of a bearing member included in the input pen shown in FIG. 1; and 
     FIG. 8 is a longitudinal sectional view of an essential portion of an input pen in a second embodiment according to the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Input pens in preferred embodiments according to the present invention will be described with reference to the accompanying drawings. In the following description, ‘front’ is ‘left’ in the drawings and ‘back’ is ‘right’ in the drawings. 
     FIGS. 1 to  4  show an input pen in a first embodiment according to the present invention. A front bushing  2  of a metal is pressed in a front portion of a barrel  1  of a metal. A reset pin  3  having a slender portion  3 A is detachably screwed in the front bushing  2 . An O ring  4  is placed in an annular groove  3 B formed in the reset pin  3  to prevent the reset pin  3  screwed in the front bushing  2  from loosening. 
     The reset pin  3  is provided in its back portion with a hole  3 C. A tail portion of a ballpoint refill  5  is detachably fitted in the hole  3 C. 
     A writing head  5 A of the ballpoint refill  5  projects properly from the back end of a back bushing  6 . A cap  7  of a synthetic resin is detachably put on the back bushing  6  so as to cover a portion of the writing head  5 A of the ballpoint refill  5  projecting from the back end of the back bushing  6 . An annular ridge  7 A formed on the cap  7  engages in an annular groove  6 A formed in the back bushing  6  to hold the cap  7  on the back bushing  6 . A soft input member  8  is fitted in a hole  7 B formed in a head portion of the cap  7 . The soft input member  8  has a substantially semispherical head  8 A. The cap  7  is provided with a substantially rectangular hole  7 C. A flat portion  3 D of the reset pin  3  can be inserted in the hole  7 C. The flat portion  3 D is unable to turn in the hole  7 C. 
     A back portion of a clip  9  is detachably inserted in a protruded portion  7 D of the cap  7 . As shown in FIG. 5, a bifurcate portion  9 A of the clip  9  engages a projection  7 F extending forward from the bottom of a groove  7 E formed in the cap  7 . A protrusion  7 G formed on the upper inner surface of the groove  7 E of the cap  7  engages in a hole  9 B formed in the clip  9  to restrain the clip  9  from movement relative to the cap  7 . 
     The input pen can be held in a pocket of a garment for carrying by the clip  9 . When the clip  9  is removed from the cap  7  as shown in FIG. 6, the input pen can be held in a pocket of a garment by holding a portion of the fabric of the garment in the groove  7 E of the cap  7 . The protruding portion  7 D of the cap  7  is formed so as to conform to the shape of a portion a finger that will be applied to the cap  7  to remove the input pen from a portable information processing terminal device to enable the finger to engage the cap  7  properly so that the input pen can be easily removed from the portable information processing terminal device. The clip is provided with a rectangular opening  9 C. The flat portion  3 D of the reset pin  3  can be inserted in the opening  9 C. The flat portion  3 D is unable to turn in the hole  9 C. 
     A receiving member  11  is axially movably screwed in a front barrel  10  of a synthetic resin. An input tip  12  of a synthetic resin if axially slidably fitted in a front portion of the front barrel  10 . A return spring  13  is extended between the receiving member  11  and the input tip  12  so as to bias the input tip  12  forward. As shown in FIG. 7, the receiving member  11  is provided in its back end surface with a slot  11 A. The longitudinal position of the receiving member  11  in the front barrel  10  can be adjusted to adjust the resilience of the return spring  13  by removing the front barrel  10  and the cap  7  from the barrel  1 , inserting a flat end portion  9 D of the clip  9  in the slot  11 A of the receiving member  11  and turning the receiving member  11  by turning the cap  7 . Thus, the force biasing the input tip  12  forward can be adjusted through the adjustment of the resilience of the return spring  13 . A head portion  12 A of the input tip  12  is projected by a proper length from the front end of the front barrel  10 . 
     The input pen is pressed against a touch panel included in the portable information processing terminal device to enter data into the portable information processing terminal device. The input tip  12  held in the front barrel  10  is used for entering data by writing letters with fine strokes. Thus, the input tip  12  enables minute input. Pointing can be easily achieved by using the soft input member  8 . Thus, the input operation can be carried out in two input modes simply by inverting the input pen. The input pen is very handy. 
     If an excessively high force is exerted on the input tip  12 , the input tip  12  retracts to avoid breaking the touch panel. 
     The resilience of the return spring  13  can be adjusted according to the purpose of the input pen or the input tip  12  can be fixed if the user desires. 
     Check marks and letters can be written on paper sheets with the ballpoint refill  5  by removing the cap  7  from the barrel  1 . The cap  7  can be put on the front barrel  10  to avoid losing the same during writing with the ballpoint refill  5 . 
     The cap  7  is provided with projections  7 H at diametrically opposite positions on the outer surface thereof. The projections  7 H engages the portable information processing terminal device to hold the input pen on the portable information processing terminal device. 
     When the portable information processing terminal device malfunctions and needs resetting, the front barrel  10  is separated from the barrel  1  to expose the reset pin  3  and the portable information processing terminal device can be reset with the reset pin  3 , which is very convenient. 
     When replacing the used ballpoint refill  5  with a new one, the front barrel  10  is separated from the barrel  1 , the cap  7  is removed from the barrel  1 , and the flat portion  3 D of the reset pin  3  is inserted in the hole  7 C of the cap  7 , and the cap  7  is turned to remove the reset pin  3  from the barrel  1 . Then, the used ballpoint refill  5  is taken out from the barrel  1 . 
     The reset pin  3  can be removed from the barrel  1  also by removing the clip  9  from the cap  7 , inserting the flat portion  3 D of the reset pin  3  in the hole  9 C of the clip  9  and turning the clip  9 . The ballpoint refill  5  is removed together with the reset pin  3  from the barrel  1 . The used ballpoint refill  5  is pulled out of the hole  3 C of the reset pin  3 . A tail portion of a new ballpoint refill is fitted in the hole  3 C of the reset pin  3 , the new ballpoint refill is inserted in the barrel  1  and the reset pin  3  is screwed in the front bushing  2 . 
     The synthetic resin forming the input tip  12  is polyacetal, polyethylene, nylon or the like. 
     The material forming the soft input member  8  is vulcanized rubber or a thermoplastic elastomer. 
     An input pen in a second embodiment according to the present invention will be described with reference to FIG. 8, in which parts like or corresponding to those shown in FIG. 1 are denoted by the same reference characters and the description thereof will be omitted. An internally threaded bushing  14  is fixedly pressed in a back portion of a front barrel  110  of a synthetic resin, and a reset pin  3  is detachably screwed in the internally threaded bushing  14 . A receiving member  11  is axially movably screwed in the internally threaded bushing  14 . 
     As apparent from the foregoing description, according to the present invention, the resilience of the return spring can be adjusted according to the preference of the user and hence the user is able to operate the input pen in an optimum condition. 
     The used ballpoint refill can be replaced with a new one simply by removing the reset pin from the barrel, separating the used ballpoint refill from the reset pin and putting the new ballpoint refill on the reset pin.