Abstract:
An extendable/contractible writing instrument with a simple rotating operation. The writing medium is exposed through a rotating motion, while at the same time also exposing an auxiliary tool, such as a silicon gum eraser, at the opposite end.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention is related to a twist-type extendable/contractible writing instrument that exposes a writing tip and another auxiliary tool from opposite ends of the writing instrument.  
       BACKGROUND OF THE INVENTION  
       [0002]     The conventional extendable/contractible type ball point pens and mechanical pencils write through the exposure of the writing medium from the pointed end of a cap. An eraser, or the like, with which the writing is erased, is attached at the end opposite to the cap.  
         [0003]     In such cases, the eraser is exposed through an operation entirely separate from that of the extension and contraction of the writing medium. An example is the removal of an eraser cap to expose an eraser. Removing the eraser cap is cumbersome, and there is a possibility that the eraser cap will be lost.  
         [0004]     Also, when the conventional extendable/contractible ballpoint pens are taken out of use, a sliding aglet is pressed to retract the ends of a shaft so as to push the writing tip of the ballpoint refill into a concealed position. When in use, the sliding aglet is pressed so as to cause the ends of the shaft to expand lengthwise and push the writing tip of the ink refill to the exposed position.  
         [0005]     The conventional extendable/contractible type ballpoint pens require a high degree of machining accuracy, and the cost of assembly is high due to the complexity of the moving parts. Accordingly, there is a need to provide a writing instrument that eliminates the aforementioned drawbacks and provides further advantages.  
       SUMMARY OF THE INVENTION  
       [0006]     The invention provides a twist-type writing instrument with a writing tip that can be extended and retracted through a simple rotating operation. A screw-type mechanism allows for an advantageous machining process and a relatively simple assembly. The writing instrument of the invention also provides for the addition of an auxiliary tool, such as an eraser, or the like, attached to the end opposite to the writing tip, which can be extended in connection with the extension or retraction of the writing tip. The writing instrument can be an ink pen, such as a ball point pen, or a mechanical pencil.  
         [0007]     A twist-type extendable/contractible writing instrument has a body with a cap at the tip that can be attached and removed, a sheath that can slide on a narrow posterior section of the body, and a revolving shaft which is located inside the body. The revolving shaft is fixed to the posterior portion of the sheath at the top of the writing instrument. The writing instrument further includes a lead chamber located in the revolving shaft, which is loaded with the writing medium, and an attached casing that is connected to a narrow posterior portion of the lead chamber. The twisting of the rotating shaft, which is done with the body and the sheath, is converted into the linear motion of the lead chamber and attached casing, thereby causing the writing medium to be extended and exposed from the tip of the writing instrument. The attached casing can also be moved in a linear direction to thereby extend and expose an auxiliary tool, such as a silicon eraser, from the opening in the top end cap. The twist-type extendable/contractible writing instrument according to the invention can stop the rotating shaft when the lead tip protrudes from the cap, and can also provide for adjusting the length of the lead tip of the mechanical pencil by pressing on the top, sheath, and casing attached to the lead chamber in an up and down motion.  
         [0008]     The twist-type writing instrument of the invention has the advantage that the writing tip can be extended and retracted through a simple twisting operation, and the screw-type mechanism allows for an advantageous machining process and a relatively simple assembly. Additionally, the writing instrument of the invention eliminates the need to remove a cap, or the like, in order to use an the auxiliary tool, such as an eraser. Moreover, writing can be carried out efficiently without concern about loss of the eraser cap.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:  
         [0010]      FIG. 1  is a sectional illustration of the twist-type extendable/contractible writing instrument of the invention when contracted;  
         [0011]      FIG. 2  is a sectional illustration of the twist-type extendable/contractible writing instrument when extended without the auxiliary tool protruding from the top end cap;  
         [0012]      FIG. 3  is a sectional illustration of the twist-type extendable/contractible writing instrument when extended with the auxiliary tool protruding from the top end cap;  
         [0013]      FIG. 4  is a front elevational view illustration of the rotating shaft;  
         [0014]      FIG. 5  is a sectional illustration of the rotating shaft;  
         [0015]      FIG. 6  is a perspective illustration of the rotating shaft;  
         [0016]      FIG. 7  is a top view illustration of the lead chamber;  
         [0017]      FIG. 8  is a front elevational illustration of the lead chamber;  
         [0018]      FIG. 9  is a bottom view illustration of the lead chamber;  
         [0019]      FIG. 10  is a perspective view illustration of the lead chamber;  
         [0020]      FIG. 11  is a sectional view illustration of an example of the practical application of the twist-type extendable/contractible writing instrument when contracted;  
         [0021]      FIG. 12  is a sectional view illustration of the twist-type extendable/contractible writing instrument when extended;  
         [0022]      FIG. 13  is an enlarged front elevational view illustration of an example of a practical application related to the rotating shaft;  
         [0023]      FIG. 14  is a top view illustration of the lead chamber;  
         [0024]      FIG. 15  is a front elevational illustration of the lead chamber;  
         [0025]      FIG. 16  is a bottom illustration of the lead chamber; and  
         [0026]      FIG. 17  is a perspective illustration of the lead chamber.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0027]     The writing instrument in accordance with the invention includes a body  3  with a cap  1  at one end thereof that can be attached and detached; a sheath  9  that slides freely on a posterior narrow body section  3 ′ of the body  3 ; a slotted rotating shaft  4  on the inside of the body  3  that is fixed to the posterior portion of sheath  9  through top cap  11 ; a slotted lead chamber  5  inside rotating shaft  4 , which is loaded with a writing medium  2 ; and an attached casing  7  that is connected to a posterior narrow portion  5 ′ of the lead chamber  5 . By rotating or twisting the body  3  and sheath  9  to extend each from one another, a rotational movement is imparted to the rotating shaft  4 , which is converted into the linear movement of the lead chamber  5  and the attached casing  7 , such that a writing medium  2 ′ protrudes from a hole in cap  1 . At the same time and by further rotation and extension of the body  3  and sheath  9 , the attached casing  7  moves in the direction of opening  11 ′ of top end cap  11 , and auxiliary tool  10 , such as a silicon gum eraser, or the like, that is attached to the tip of casing  7 , protrudes from opening  11 ′ in the top end cap  11 .  
         [0028]     The linear motion of rotating shaft  4  is accomplished with a twist of the body  3  and sheath  9 . Drive screw slot  12  is provided in the surface of rotating shaft  4 . An axially oriented knocking slot  14  is connected to allowance slot  13 , which is approximately perpendicular to the longitudinal axis of rotating shaft  4 , and at the terminus of the drive screw slot  12 . A bump  8  that protrudes from the inside of the narrow posterior body portion  3 ′ slides freely within the drive screw slot  12 , and is engaged by rotating body  3  and sheath  9 .  
         [0029]     The linear motion for casing  7 , which is attached to lead chamber  5 , is discussed below. The front half of lead chamber  5  contains allowance slot  15 ′, which is perpendicular to the longitudinal axis of the extension screw slot  15  (having a pitch larger than the drive screw slot  12 ). Allowance slot  15 ′ connects to and travels freely on the bump  6  that is fixed on rotating shaft  4 . Narrow section  5 ′ of the posterior half of lead chamber  5  includes extension screw slot  16  that extends out in the opposite direction. Extension screw slot  15  and extension screw slot  16  can be provided with the same pitch and the same rotational length. In addition, the tip portion of lead chamber  5  includes the thrust regulating groove  17 , and connects to slot  18 , which is located on the inside of the tip of body  3  allowing for only forward and backward movement, which provides for the linear motion of lead chamber  5 . Moreover, the narrow auxiliary extension slot  16 ′ with a pitch that is contiguous with the posterior portion of extension slot  16  is provided in a semicircle.  
         [0030]     A pencil lead is provided as the writing medium in the pointed tip portion of lead chamber  5 . When body  3  and sheath  9  are extended in relation to each other, lead  2 ′ of the mechanical pencil  2  extends out from the pointed end of the cap  1 , and the pencil is in ready-to-write condition. Pressing on sheath  9  at the top and wearing down the lead moves the bump  8  along knocking slot  14 . As a consequence, lead chamber  5  moves forward, and the lead in mechanical pencil  2  extends out. Should the writing instrument be a ballpoint pen, knocking slot  14  would not be necessary.  
         [0031]     In some of the  FIGS. 1 through 10 , sheath  9  and body  3  are extended with about half the rotation (about 180 degrees) of sheath  9 . In this state, the silicon gum eraser, as an auxiliary tool  10 , is not extended, but writing with the writing instrument can be done. With repeated pushing on top cap  11  and sheath  9 , the bump  8  moves along knocking slot  14 , and the lead in mechanical pencil  2  is pushed out. Also, by turning sheath  9  about another half revolution in the same direction, only attached casing  7  moves in the posterior direction, and the auxiliary tool attached to the tip (silicon gum eraser in the FIGURES) is pushed out through the opening in top cap  11 ′.  
         [0032]     In  FIGS. 11 through 17 , sheath  9  and body  3  are extended with a single rotation (about 380 degrees) of sheath  9 . In this state, the silicon gum eraser, as auxiliary tool  10 , has been pushed out from top cap  11 . Writing is done in this state through the repeated pressing of silicon gum  10 , cap  11 , and sheath  9 , so that the bump  8  moves along knocking slot  14 , and the pencil lead is pushed out.  
         [0033]     As above, the pitch and length of drive screw slot  12 , extension screw slot  15 , and posterior section extension slot  16  are to be determined relative to the range of movement of writing medium  2  and attached casing  7 .  
         [0034]     In addition, although writing instrument  2  shows a mechanical pencil mechanism, a ballpoint pen would also be acceptable. Although auxiliary tool  10  shows a silicon gum eraser, the use of correcting fluid, different color writing medium, or other writing media, such as lipstick, chalk, etc., are possible.  
         [0035]     The present invention includes a body  3 , a rotating shaft  4 , a lead chamber  5 , and attached casing  7 , all of which are cylindrical. Also, because these can be manufactured easily with a tapping machining process of the exterior surfaces, the manufacturing process permits an advantageous yield rate and simple assembly.  
         [0036]     Also, because the lead tip writing instrument and silicon gum eraser auxiliary tool at both ends of the shaft can be extended out and used, there can be greater writing efficiency.  
         [0037]     While the preferred embodiment of the invention has been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention.