Abstract:
An offset pen including a holding portion, a writing portion, and an intermediate portion connected between the holding portion and the writing portion to make the holding portion and the writing portion positioned in different axes is disclosed. The writing portion is separable from the holding portion, for example by dividing the intermediate portion into two engageable parts or by detaching the writing portion from the intermediate portion, in order to facilitate the production of the crooked offset pen and/or the installation of a writing material.

Description:
FIELD OF THE INVENTION 
     The present invention is related to an offset pen, and more particularly to an offset pen having a structure advantageous for easy making and convenient assembling. 
     BACKGROUND OF THE INVENTION 
     So far, conventional writing tools such as fountain pen, pencil, ball point pen, coloring pencil and writing brush on the market are all linear in shape. That is, a writing head and a holding stick of a writing tool are substantially coaxial. Owing to the limit of people&#39;s palm structure, the writing tool generally tilts rearward the wrist while being used so that the vision line of the user will be obstructed by the writing tip of the writing tool. As such, there are several defects in writing or drawing with the conventional writing tool. First of all, a user cannot clearly see the space behind the writing tool along the vision line, so it is difficult for the user to write straight or draw in position. Especially for kids, they are likely to change their sitting posture, e.g. lie their heads upon the desks, while writing in an attempt to bypass the blockage of the vision line by the writing tool, and it is harmful to kids&#39; eyesight and bone. 
     In addition, people are used to holding the writing tool slantwise, so the linear shape of the writing tool results in the slant of the writing portion relative to the working surface, and as such, the user gets no right point to exercise the pressing point and has to exert more stress on the working surface while writing or drawing. The inevitable fatigue would ruin children&#39;s interests in writing. Furthermore, the slant of the writing portion relative to the working surface makes the drawing operations with an assistant tool such as a ruler unable to achieve the best effect, since the writing tip will not be in close contact with the side surface of the ruler. 
     Moreover, under special writing conditions, the writing operation may suffer from the interruption of ink provided that an ink-type pen such as a ball point pen, is used. For example, if a user would like to write on a substantially vertical surface at a position higher than his head, a pen will be held slant so that the writing tip becomes higher than the ink reservoir. It is apparent that such an orientation of the pen is likely to result in the interruption of the ink owing to the adverse flow of the ink from the writing tip due to gravity. Even if the writing operation is performed on a substantially vertical surface at a relatively low position, for example lower than the height of the user&#39;s chest, the wrist of the user&#39;s writing hand has to significantly and uncomfortably bend toward the user&#39;s body in order to assure of good contact between the writing tip and the writing surface for smooth writing. 
     The present inventor found that the above problems can be solved by providing a nonlinear writing tool called an “offset pen” hereinafter. An offset pen includes an intermediate portion between a holding portion, i.e. the pen stick, and a writing portion, i.e. the writing head, to make the holding portion and the writing portion positioned in different axes. For example, FIGS.  1 ˜ 3  schematically show how is an offset pen used to solve the above problems. 
     Please refer to FIG. 1A in which an offset pen including a holding portion A, an intermediate portion B and a writing portion C is shown. Owing to the presence of the crooked intermediate portion B, the axis of the writing portion C and that of the holding portion A will intersect at a certain angle to create a space therebetween. In addition, the angle between the writing portion C and the working surface can be made to be approximately 90 degrees owing to the offset of the writing portion. As such, the vision line of the user will not be obstructed by the writing tool as by the front portion P 1  of a conventional pen. Accordingly, the writing operation of the user will proceed relatively smoothly. Furthermore, the crooked intermediate portion B provides an additional structure suitable for user&#39;s index finger to rest and exert force thereon, as shown in FIG. 1B, so as to lessen the load of user&#39;s fingers. The effect is especially prominent for duplication with carbon paper. 
     Please refer now to FIG. 2 in which an offset pen is used together with a ruler R. By using an offset pen including a holding portion A, an intermediate portion B and a writing portion C as mentioned above, the writing portion C is approximately perpendicular to the working surface K so as to be in close contact with the side surface R 2  of the ruler R. As such, the user will be able to draw a line precisely as desired without being influenced by his palm structure and the thickness of the ruler. 
     FIGS. 3A and 3B schematically show the situations of the offset pen for use to write on a vertical surface at a relatively high and a relatively low positions, respectively. Referring to FIG. 3A, the crooked intermediate portion B allows a section of the ink reservoir B 1  to remain higher than the writing tip C 1  so as to avoid the interruption of the ink. Referring to FIG. 3B, the pen-holding posture can be adjusted to be comfortable by simply turning the offset pen by 180 degrees using the holding portion of the pen as the turning axis. 
     Even though advantageous over conventional linear pens in many aspects, the offset pen encounters problems in manufacturing and assembling. It is complicated to produce a crooked and hollow pen structure. Furthermore, the ink refill or reservoir is difficult to be installed into the crooked pen structure, and also inconvenient to be replaced. 
     SUMMARY OF THE INVENTION 
     Therefore, an objective of the present invention is to provide an offset pen which is mounted therein a writing material to leave marks on a working surface and has a structure advantageous for easy making and convenient assembling. 
     Basically, an offset pen structure according to the present invention includes a holding portion to be supported by a user&#39;s writing hand, a writing portion to be mounted thereon a writing tip of the writing material, and an intermediate portion located between the holding portion and the writing portion to make the writing portion deflect from the axis of the holding portion. Characteristically, the writing portion is separable from the holding portion so as to facilitate the mounting of the writing material. For example, the intermediate portion includes two engageable parts, a first part of which is connected to the holding portion and a second part of which is connected to the writing portion. The first part constitutes an upper part of the intermediate portion, and the second part is partly inserted into the first part to constitute a lower part of the intermediate portion. Alternatively, the second part is integrally formed with the writing portion and completely inserted into the first part to form a lower surface of the intermediate portion. Thereby, the writing portion is allowed to be separated from the holding portion through the disengagement of the first and the second parts of the intermediate portion. 
     Alternatively, the writing portion is detachably mounted to the intermediate portion so that the writing portion is allowed to be separated from the holding portion through the disengagement of the intermediate portion and the writing portion. 
     Preferably, a hollow passage which extends from the writing portion through the intermediate portion to the holding portion is arranged within the offset pen for accommodating a writing material including the writing tip and an ink supply. 
     In a preferred embodiment, the offset pen is a retractable pen which allows the writing tip to selectively protrude from or to be retracted into the writing portion in response to a user&#39;s operation. In order to achieve this purpose, the offset pen includes a button and a spring. The button is mounted on a top end of the holding portion, and has a hollow tube to be engaged with the ink supply. When the button is pushed down to depress the writing material from a relatively high position to a relatively low position, the writing tip can be made to protrude from the writing portion to be used. On the other hand, when the button is pushed down again to release the writing tip from the relatively low position to the relatively high position, the writing tip can be retracted into the writing portion to be received. The spring is installed in the hollow passage around the writing material, and has a first end urging against a sustaining element arranged on the writing material and a second end urging against a wall of the hollow passage. When the button is pushed down, a compressive elastic force of the spring will be generated. When the button is pushed again, the compressive elastic force will be provided for the release of the button so as to retract the writing tip into the writing portion. The second end of the spring mentioned above is a resilient rod sustaining against a facing-up wall of the hollow passage in the intermediate portion. 
     According to the present invention, the holding portion can be detached from the intermediate portion to expose the hollow passage to air so that the ink supply can be installed therefrom. Alternatively, an end portion of the holding portion can be opened to expose the hollow passage to air so that the ink supply can be installed therefrom. On the other hand, the holding portion can be integrally formed with the intermediate portion, and the ink supply can be installed from the intermediate portion. 
     With regard to the ink supply, the holding portion can serve as the ink supply, i.e. ink is directly stored in the hollow passage in the holding portion. If the holding portion is flexible, ink can be transmitted to the writing tip by pressing the holding portion. The ink supply can be an elongated ink refill extending from the writing portion through the intermediate portion to the holding portion. Alternatively, the ink supply can includes an ink reservoir and an ink passage. The ink reservoir is installed in the hollow passage in the holding portion for providing therefrom ink. The ink passage is connected to the ink reservoir and the writing tip for transmitting ink from the ink reservoir to the writing tip, and has a shape and a size complying with a configuration of the hollow passage in the intermediate portion so as to extend through the intermediate portion. 
     Preferably, the ink reservoir is separable from the ink passage so as to allow the ink reservoir to be replaced. 
     The ink reservoir can be a hollow tube for storing therein ink, and the ink passage can be an hollow tube or an ink-soaking strip. Alternatively, the ink reservoir and the ink passage are both ink-soaking strips for adsorbing therein ink. It depends on the type of the writing tip which can be a felt tip, a nib tip or a brush tip. 
     Preferably, the ink supply is wrapped by an ink-proofing material to prevent ink from leakage. The ink-proofing material can be a form of a film or a tube, and may be soft or flexible. 
     According to another aspect of the present invention, the offset pen further includes an illuminating device. The illuminating device is mounted to a lower part of the intermediate portion, e.g. the second part, to lighten an area near the writing tip. Preferably, the writing tip is substantially located in an extension line of the holding portion so that light emitted from the illuminating device can be centered on the writing tip. 
     The illuminating device is preferably a point light source, e.g. a light bulb. A battery for supplying power for the illuminating device can be installed in the holding portion. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The present invention may best be understood through the following description with reference to the accompanying drawings, in which: 
     FIG. 1A is a schematic perspective diagram showing the use of an offset pen compared to the use of a linear pen; 
     FIG. 1B is a schematic perspective diagram showing the use of an offset pen used for duplicate writing; 
     FIG. 2 is a schematic perspective diagram showing the use of an offset pen together with a ruler; 
     FIGS. 3A and 3B are schematic perspective diagrams showing the situations of the offset pen for use to write on a vertical surface at a relatively high and a relatively low positions, respectively; 
     FIG. 4A is a resolving perspective diagram of a first preferred embodiment of an offset pen according to the present invention, which schematically shows the mounting of a writing material into the offset pen; 
     FIG. 4B is a partial cross-sectional view of the offset pen of FIG. 4A, which schematically shows the assembling of the offset pen; 
     FIG. 4C is a perspective diagram of the offset pen of FIG. 4A which schematically shows a partially assembled state of the offset pen; 
     FIG. 5A is a resolving perspective diagram of a second preferred embodiment of an offset pen according to the present invention, which schematically shows the mounting of a writing material into the offset pen; 
     FIG. 5B is a side elevational view of the offset pen of FIG. 5A which schematically shows a partially assembled state of the offset pen; 
     FIGS. 5C and 5D are two side elevational views schematically showing two alternatives of the intermediate portion of the offset pen of FIG. 5A, respectively, in order to illustrate two assembling ways between the holding portion and the intermediate portion of the offset pen; 
     FIG. 5E is a cross-sectional view of the offset pen of FIG. 5A installed therein a writing material having a replaceable ink reservoir; 
     FIG. 6 is a partially side elevational view of a third embodiment of an offset pen according to the present invention, which schematically illustrates various dividing ways of the intermediate portion of the offset pen; 
     FIG. 7A is a partially cross-sectional view of a fourth embodiment of an offset pen according to the present invention, which schematically illustrates an alternative manner to separate the writing portion from the holding portion of an offset pen; 
     FIG. 7B is a partially cross-sectional view of the offset pen of FIG. 7A with a lower surface of the intermediate portion removed; 
     FIG. 8A is a partially cross-sectional view of a fifth embodiment of an offset pen according to the present invention, which schematically shows the inclusion of an illuminating device in the offset pen; 
     FIG. 8B is a front view of the offset pen of FIG. 8A; 
     FIG. 9A is a resolving perspective diagram of a sixth preferred embodiment of an offset pen according to the present invention, which schematically shows the assembling of a retractable offset pen; 
     FIGS. 9B and 9C are two cross-sectional views schematically showing two operation modes of the offset pen of FIG. 9A, for deposit and for use, respectively; 
     FIG. 9D is a cross-sectional view of the offset pen of FIG. 9A, which schematically shows an alternative of the writing material shown in FIG. 9B; 
     FIG. 10A is a partially resolving diagram of a seventh embodiment of an offset pen according to the present invention, which schematically shows the holding portion serving as an ink reservoir; 
     FIGS.  10 B˜ 10 D are cross-sectional views of the offset pen of FIG. 10A with different writing tips; 
     FIG. 11 is a cross-sectional view of an eighth embodiment of an offset pen according to the present invention, which schematically shows a flexible holding portion of the offset pen; 
     FIG. 12A is a resolving perspective diagram of a ninth preferred embodiment of an offset pen according to the present invention, which schematically shows the installation of a writing material consisting of separate parts into the offset pen; 
     FIG. 12B is a cross-sectional view of the assembled offset pen of FIG. 12A; 
     FIGS.  13 A˜ 13 D schematically show four types of writing materials and the assembling manners thereof, respectively; and 
     FIGS. 14A and 14B are cross-sectional views of the offset pen of FIG. 12A with different kinds of writing materials. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention will now be described more specifically with reference to the following embodiments. It is to be noted that the following descriptions of preferred embodiments of this invention are presented herein for purpose of illustration and description only; it is not intended to be exhaustive or to be limited to the precise form disclosed. 
     Embodiment 1 
     Please refer to FIGS.  4 A˜ 4 C. As shown in FIG. 4A, the holding portion  41  of the offset pen is integrally formed with a first part  421  of the intermediate portion  42 , and the writing portion  43  is integrally formed with a second part  422  of the intermediate portion  42 . For assembling the offset pen structure, the second part  422  is partially inserted into the first part  421  to be engaged with each other. The engagement of the two parts  421  and  422  is performed by tooth engagement, as shown in FIG.  4 B. For mounting a writing material  40  which includes a writing tip  403  and an elongated ink refill  402  into the offset pen, the parts  421  and  422  of the intermediate portion  42  are disengaged. The writing material  40  is installed into the pen by inserting the writing tip  403  and the ink supply  402  into an hollow passage  44  inside the pen from the openings  4211  and  4221  of the parts  421  and  422  of the intermediate portion  42 , respectively. A partially assembling state of the offset pen is shown in FIG.  4 C. 
     Embodiment 2 
     Please refer to FIGS. 5A and 5B. The offset pen, as shown in FIG. 5A, is similar to the pen of embodiment 1 except that the holding portion  51  is further separable from the intermediate portion  52 , and the second part  522  is completely inserted into the first part  521  with the lower surface  5221  thereof exposed to air only. 
     The writing material  50  used in this embodiment only for illustration includes an ink reservoir  501 , an ink passage  502  and a writing tip  503 . An assembling state of the offset pen is shown in FIG.  5 B. Principally, the ink reservoir  501  is located in the holding portion  51 , the ink passage  502  in the intermediate portion  52  and the writing tip  503  in the writing portion  53 , respectively. For use, the ink stored in the ink reservoir  501  flows through the ink passage  502  to the writing tip  503  to leave marks on a working surface  55 , as indicated by the arrows. The separation of the holding portion  51  from the intermediate portion  52  allows a relatively thick ink reservoir to be installed into the holding portion  51  in an alternative way, i.e. directly from the interface opening (not shown) between the holding portion  51  and the intermediate portion  52 . As for the coupling of the holding portion and the intermediate portion, it can be achieved for example by sleeve engagement (see numeral reference  523 , FIG. 5C) or screwing (see numeral reference  524 , FIG.  5 D). 
     By the way, although the writing material shown in FIG. 5A is integrated, the ink reservoir and ink passage can alternatively be separate elements so that the ink reservoir is replaceable. For example, referring to FIG. 5E, there is a steel ball  5011  positioned at the bottom end of the ink reservoir  501 , and there is a butting member  5021  at the top of the ink passage  502 . For assembling the writing material, the butting member  5021  forces the steel ball  5011  away to receive ink from the ink reservoir  501 . When the ink reservoir  501  becomes empty, it can be replaced with a new one easily, i.e. the holding portion  51  is disengaged from the intermediate portion  52 , and then the new ink reservoir is inserted from the interface opening (not shown) between the holding portion  51  and the intermediate portion  52 . 
     Embodiment 3 
     Please refer to FIG.  6 . The offset pen is similar to the pen of embodiment 1 except that the division ways of the intermediate portion can be diverse. For example, the intermediate portion  62  can be divided along any one of the lines X—X, Y—Y, Z—Z and W—W, or any other way as long as it facilitates the production of the offset pen and the installation of the writing material. 
     Embodiment 4 
     Please refer to FIG.  7 A. The offset pen is similar to the pen of embodiment 1 except that the intermediate portion  72  is not divided, and in stead, the writing portion  73  is detachably mounted to the intermediate portion  72 . By this way, the writing portion  73  can also be allowed to be separated from the holding portion (not shown) through the disengagement of the intermediate portion  72  and the writing portion  73 . 
     For certain cases, the lower surface  721  of the intermediate portion  72  shown in FIG. 7A can be removed to form an opening  722 , as shown in FIG.  7 B. The opening  722  allows any assistant device to be mounted in the lower part of the intermediate portion  72 . 
     Embodiment 5 
     Please refer to FIGS.  8 A˜ 8 B. The offset pen is similar to the pen of embodiment 2 except that there is an illuminating device  84  mounted to the intermediate portion  82  for lightening an area  85  near the writing portion  83 . 
     The illuminating device  84  includes a light bulb  841  and a battery set  842  which are interconnected via a wire  843 . The light bulb  841  is a point light source having a size suitable for a pen and a light intensity suitable for writing. The light bulb  841  is installed in the lower part of the intermediate portion  82 , and protrudes from the lower surface of the intermediate portion  82  through an opening  821 . The battery set  842  is installed in the holding portion  81  for providing power for the light bulb  841 . Although not shown, a switch for controlling the on/off state of the illuminating device  84  is preferably included. The light emitted from the illuminating device  84  reaches the area  85  near the writing portion  83  so as to let the user clearly see the working surface and avoid damaging the user&#39;s vision. If the writing tip  803  of a writing material  80  is substantially located in an extension line  811  of the holding portion  81 , the light emitted from the illuminating device  84  can be centered on the writing tip  803  so as to enhance the lightening effect. By the way, it is understood that the additional separation of the holding portion  81  from the intermediate portion  82  facilitates the installation of the illuminating device  84 . 
     Embodiment 6 
     Please refer to FIGS.  9 A˜ 9 C. In this embodiment, the holding portion  91  of the offset pen is integrally formed with a part  921  of the intermediate portion  92 , the writing portion  93  is connected to another part  922  of the intermediate portion  92 , and the two parts  921  and  922  are engaged to assemble the pen structure in a way as described in embodiment 2. For mounting a writing material  90  which includes a writing tip  903  and an elongated ink refill  902  into the offset pen, the parts  921  and  922  of the intermediate portion  92  are disengaged with each other. The writing material  90  is installed into the pen by inserting the writing tip  903  and the ink supply  902  into an hollow passage  94  (FIG. 9B) inside the pen from the openings  9211  and  9221  of the parts  921  and  922  of the intermediate portion  92 , respectively. 
     Furthermore, the offset pen in this embodiment is a retractable pen which allows the writing tip  903  to selectively protrude from or to be retracted into the writing portion  93  in response to a user&#39;s operation. In order to achieve this purpose, the offset pen further includes a button  95  and a spring  96 . 
     The button  95  is mounted on a top end of the holding portion  91 , and has a hollow tube  951  (FIG. 9B) to be engaged with the ink supply  902  of the writing material  90 . When the button  95  is pushed down to depress the writing material  90  from a relatively high position (FIG. 9B) to a relatively low position (FIG.  9 C), the writing tip  903  can be made to protrude from the writing portion  93  to be used, as shown in FIG.  9 C. On the other hand, when the button  95  is pushed down again to release the writing tip  903  from the relatively low position (FIG. 9C) to the relatively high position (FIG.  9 B), the writing tip can be retracted into the writing portion  93  to be received, as shown in FIG.  9 B. 
     The spring  96  is installed around the writing material  90  in the hollow passage  94  within the pen. After the pen with the writing material  90  is assembled, the spring  96  has a first end  961  urging against a sustaining element  904  arranged on the writing material  90 , and a resilient rod  962  sustaining against a facing-up wall  941  of the hollow passage  94  in the intermediate portion  92 , as shown in FIGS. 9B and 9C. When the button  95  is pushed down, a compressive elastic force F (FIG. 9C) of the spring will be generated. When the button  95  is pushed again, the compressive elastic force will be provided for the release of the button  95  so as to retract the writing tip  903  into the writing portion  93 . Alternatively, referring to FIG. 9D, the resilient rod  962  can sustain against a side wall  942  of the hollow passage  94  instead of the facing-up wall  941  to achieve the same purpose. 
     Moreover, the offset pen further includes a clip strip  97  (FIG. 9A) for clamping a holding piece such as pocket cloth, a piece of paper, or a plastic pen-holding sleeve of a notebook. It is to be noted that there should be efficient space within the hollow passage  94  in the intermediate portion  92  for the shift of the writing material  90  resulting from the push operation of the button  95 , as compared FIG. 9B with FIG.  9 C. 
     Embodiment 7 
     Please refer to FIGS. 10A and 10B. The offset pen is similar to the pen of embodiment 2 except that the holding portion  101  itself serves as an ink reservoir  1001 . Initially, ink is stored inside the holding portion  101 , and two ends of the holding portion  101  are stopped from ink leakage by a lid  1011  and a stopper  1012 , respectively. For an assembling operation, one end of the ink passage  1002  pierces through the stopper  1012  to introduce therein the ink stored in the ink reservoir  1001 . In other words, ink can flow down to the writing tip  1003  through the ink passage  1002 . If the ink stored in the ink reservoir  1001  is insufficient, it can be supplied from the top end of the holding portion  101  by taking off the lid  1011 . 
     By the way, the writing tip  1003  of the writing material used in this embodiment is a felt tip, and the ink passage  1002  is an ink-soaking strip which adsorbs ink therein. Alternatively, it can be a hollow tube which stores ink therein, depending on the type of the writing tip. The writing tip can also be a fiber tip, a soft rubber tip or a brush tip, and the size and shapes of the writing tip can also be various, depending on the use of the pen. It is to be mentioned that the installation ways of the writing material will also be varied with the shapes of the writing tip. For example, as shown in FIGS. 10C and 10D, the relatively bulky writing tip  1003  should be separable from the ink passage  1002  so that it can be installed from the lower opening  1031  of the writing portion  103  rather than from the interface opening  1023  between the first and the second parts  1021  and  1022  of the intermediate portion  102 . On the other hand, for a writing tip of a fiber, a soft rubber or a brush type having a shape as shown in FIG. 10C or  10 D, the ink passage  1002  is preferably an ink-soaking material in order to provide ink smoothly. 
     Embodiment 8 
     Please refer to FIG.  11 . The offset pen is similar to the pen of embodiment 7 except that the holding portion  111  serving as the ink reservoir  1101  is flexible. By exerting a pressing force (arrows F 1 ) with fingers onto the holding portion  111 , ink can be forced to flow to the writing tip  1103  through the ink passage  1102  (arrow F 2 ). 
     By the way, the writing tip  1103  of a writing material used in this embodiment is a brush tip, and the ink passage  1102  is a hollow tube. 
     Embodiment 9 
     Please refer to FIGS. 12A and 12B. The offset pen is similar to the pen of embodiment 2 except that the holding portion  121  is integrally formed with the first part  1221  of the intermediate portion  122 , and an end portion of the holding portion  121  has a cover  1211  which can be opened to expose the hollow passage  124  to air. Such arrangement of the offset pen is advantageous for mounting a writing material  120  consisting of several separate parts. 
     The writing material  120  used in this embodiment as shown includes an ink reservoir  1201 , ink passages  12021  and  12022 , and a writing tip  1203  having respective shapes shown in FIG. 12A, and made of ink-soaking material. The installation of the writing material  120  is illustrated as follows with reference to FIG. 12A, and the assembled writing material is shown in FIG.  12 B. The ink passages  12021  and  12022  are coupled and placed into the second part  1222  of the intermediate portion  122 . The writing tip  1203  is inserted into the writing portion  123  from the lower opening of the writing portion, and attached to the ink passage  12022 . The ink reservoir  1201  is placed into the hollow passage  124  from the top of the holding portion  121  by temporarily removing the cover  1211 . When the cover  1211  is inserted back into the holding portion  121 , it will press the ink reservoir  1201  to be pieced thereinto the sharp tip of the ink passage  12022 . Accordingly, the writing material has been assembled and installed into the pen, thereby allowing ink to continuously flow through the writing material for writing. 
     By the way, the shapes, sizes and materials of the ink reservoir, the ink passage and the writing tip can be various as long as they are easily combined and installed into the pen. Examples are given as shown in FIGS.  13 A˜ 13 D. 
     FIGS. 14A and 14B show other types of writing materials used with the offset pen structure of this embodiment. As shown, the ink passage  1402  is an ink-soaking strip and wrapped with an ink-proofing material  1404  to prevent from ink leakage. The ink-proofing material can be a film, a plastic tube or any other type of protecting member as long as the same purpose can be achieved. In addition to the difference in writing tips  1403 , another difference between the writing materials of FIGS. 14A and 14B lies in that the ink-proofing tube  1404  enclosing the ink passage  1402  continuously extends to wrap a part of the ink reservoir  1401  in FIG. 14A, but is independent of the ink-proofing tube  1405  wrapping a part of the ink reservoir  1401  in FIG.  14 B. The separation of the ink-proofing tubes has an effect on the installation of the writing material having a relatively large writing tip into the offset pen of this embodiment. 
     Various embodiments of offset pens according to the present invention are described as above, but the embodiments are given only for illustration rather than limitation of the scope of the present invention. For example, the holding portion, intermediate portion and/or the writing portion of an offset pen according to the present invention can be further divided into parts if it is convenient for the manufacturing of the pen and/or the mounting of a writing material into the pen. It should be understood that under the same offset pen structure, a variety of writing materials may be suitable for cooperating therewith to form a specific pen. On the other hand, the selection or design of a writing material should comply with the structure of the offset pen in order to facilitate installation. For example, the ink reservoir, the ink passage and the writing material are optionally separable depending on the sizes and shapes thereof and the design of the offset pen structure. An ink-proofing material is used to wrap the writing material if necessary, especially when the writing material is made of ink-soaking material, in order to prevent ink from leakage. 
     While the invention has been described in terms of what are presently considered to be the most practical and preferred embodiments, it is to be understood that the invention need not be limited to the disclosed embodiment. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.