Abstract:
An expandable pen has a pen barrel with an expanding middle section. The pen barrel holds a retractable ball point pen refill cartridge When the pen is expanded, the writing tip of the refill is extended from a retracted position inside the pen barrel to a writing position, while the barrel becomes full length for comfort when writing. The pen may be collapsed for storage, which simultaneously retracts the writing tip inside the pen barrel.

Description:
FIELD AND BACKGROUND OF THE INVENTION 
     The present invention relates generally to the field of writing instruments and in particular to a new and useful mechanism for expanding the length of a writing instrument barrel while extending a writing tip from a retracted position in the barrel to a writing position. 
     Compact devices of all types are sometimes preferred over full-size versions because they occupy less space. However, some compact devices are not as useful as full-sized versions of the same product for a variety of reasons. 
     In the case of writing instruments, a small or reduced size pen can be difficult to hold and use for many people, including the elderly, children, the infirm, and people with large fingers. At the same time, a pen or pencil which occupies less space is more easily carried in a pocket or purse. 
     Sometimes, pens and pencils are sized to fit with other products they are used with, such as a miniature pen provided with a date planner or a golf pencil stored on the steering wheel of a golf cart. These smaller pens and pencils are non-refillable and must be discarded when the ink or lead is used up. While these writing instruments are a compact, convenient size for storing, they are not as comfortably for writing with and suffer the problem that they can be difficult for some persons to use. 
     Attempts to provide pens having extendable bodies, include a miniaturized ball point pen which is expandable to a more comfortable length for use as disclosed in U.S. Pat. No. 3,174,461. The pen point is always exposed and does not retract within the body of the pen. The body expands by simply sliding two concentric overlapping sections apart. The overlapping sections are frictionally fit to each other. A lower section secures the ball point and ink supply inside the body. The upper section slides inside the lower section and has a tapered end which catches the top of the ink supply to prevent the upper section from being completely separated from the lower section. A cap fits over the upper section and its lower edge stops against the upper edge of the lower section. 
     U.S. Pat. No. 3,709,620 teaches a ball point pen having a body which is expandable for use as a pointer. The pen body is formed by a series of telescoping tubes which support and contain the ball point and ink supply. The ball point may be extended or retracted from the pen body by a spring-loaded operation button at the top end of the body. The button has a horizontal channel with a spring-loaded slider having a tab which is forced into an opening in the side of the upper tube when the button is depressed to hold the button and keep the pen tip extended. Pressing the top end of a clip mounted outside the upper tube over the tab pushes the tab and slider back within the button, releasing the button from the depressed position. The button spring may then force the button back upward, retracting the pen tip. 
     While the pen tip may be retracted in this pen, it requires a relatively complex arrangement of springs and sliders and it requires the presence of a clip. The extension/retraction mechanism for the pen tip is not integrated with the expansion for the device either. The pen tip cannot be extended outside the pen point when the tubes are expanded for use as a pointer. 
     A folding ball point pen is disclosed by U.S. Pat. No. 5,061,104. The pen is hinged near the center of the pen and a recess is provided in the upper section, so that the lower section containing the pen point and ink reservoir may be folded flush into the side of the upper section. The pen point is not retractable. 
     These prior pens suffer from the problem that either the pen tip is always exposed, which either requires the use of a pen cap, or there is the risk of accidental marks. The pen is not replaceable; once the ink is used up, the device must simply be thrown away and replaced in its entirety. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a writing instrument which can be easily expanded from a compact storage size to a longer writing size. 
     It is a further object of the invention to provide a writing instrument which includes a mechanism for extending and retracting a writing tip when the writing instrument is expanded from a compact storage size to a full-size position for use. 
     Accordingly, an expandable pen is provided with a pen barrel having an expanding middle section. The pen barrel holds a retractable ball point pen refill cartridge. When the pen is expanded, the writing tip of the refill is extended from a retracted position inside the pen barrel to a writing position, while the barrel becomes full length for comfort when writing. 
     The pen has a front section secured to a pen body with a cap which slidably fits over the pen body and mates with the front section when the pen is in the compacted state. The refill cartridge fits within a chamber defined by the front section, pen body and cap and is held at a pen point end by a coil spring. A cam at the other end causes the refill cartridge to be extended for use when the cap is slid away from the front section. The cam rotates downwardly on a hinge pin into contact with the top of the refill cartridge, thereby forcing the cartridge downward and the coil spring to compress. The writing tip on the cartridge is thus extended for use, while the length of the pen is expanded for more comfortable writing. 
     The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which a preferred embodiment of the invention is illustrated. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings: 
     FIG. 1 is a front, side, tip end perspective view of a writing instrument according to the invention in a storage position; 
     FIG. 2 is a front, side, tip end perspective view of the writing instrument of FIG. 1 expanded for use; 
     FIG. 3 is a sectional side elevational view of the writing instrument of FIG. 1 in the storage position; and 
     FIG. 4 is a sectional side elevational view of the writing instrument of FIG. 1 expanded for use. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, in which like reference numerals are used to refer to the same or similar elements, FIG. 1 shows a writing instrument according to the invention in the form of an expandable ball point pen  50 . As seen in FIG. 1, the pen  50  is in a collapsed, storage position. The pen  50  may optionally have a key fob  500  which frictionally fits over a pen point  10  connected to the front section  20  of the pen  50 . The key fob  500  may be used to connect the pen  50  to a keychain or lanyard (not shown) for carrying the pen  50 . 
     In the storage position, the front section  20  mates with a cap  30  to form a compact, generally cylindrical pen  50 . A pair of indentations  25 ,  35  are provided in the side of the pen in adjacent portions of the front section  20  and cap  30 , respectively. The indentations  25 ,  35  may be used to grip the pen  50  in order to expand it to the position shown in FIG.  2 . 
     As seen in FIG. 2, when the pen  50  is in the expanded position, the writing tip  60  is extended for use through the pen point  10  at the bottom end of front section  20 . A pen body  40  connected to the front section  20  is exposed by sliding the cap  30  away from the front section  20 . The cap  30  is slidably mounted on the pen body  40  so that the cap  30  can move between the closed and expanded positions without completely separating from the pen body  40 . 
     FIGS. 3 and 4 show the internal connections of the pen  50  components and cam mechanism used to extend and retract refill cartridge  65 . 
     The pen  50  has front section  20  secured to pen body  40  at one end and a pen point  10  at the other end, both by threaded connections  42 ,  12 , respectively. Optionally, a grip covering  22  lines the outside of the front section  20 . The grip covering  22  can be a rubber or other similar material which provides good tactile properties when the pen  50  is used. 
     The cap  30  covers a cap liner  130 , which is slidably mounted on the pen body  40 . The cap  30  and cap liner  130  contact the front section  20  to cover the pen body  40  when the pen  50  is in the storage position. 
     The front section  20 , pen body  40 , pen point  10 , and cap liner  130  and cap  30  define a chamber for holding the refill cartridge  65 . A coil spring  70  supports the bottom end of the refill cartridge  65  against the upper edge of the pen point  10  inside the front section  20 . The spring  70  tends to force the refill cartridge  65  away from the pen point  10  and keep it in a retracted position. 
     A cam  200  is mounted to the pen body  40  on a hinge pin  205  inside the chamber. The cam  200  is positioned at the back end  67  of the refill cartridge  65  inside the cap liner  130 . The cam  200  rotates on the hinge pin  205  to extend the refill cartridge  65  to a writing position when the pen  50  is expanded by sliding the cap  30  and front section  20  apart. 
     The cam  200  is irregularly shaped and has a rounded surface  210  at one end and a tooth  220  at the other end. A ledge  134  on the cap liner  130  contacts the tooth  220  to force the rounded surface  210  of cam  200  to rotate downwardly when the pen  50  is expanded. The rounded surface  210  of the cam  200  in turn contacts the back end  67  of the refill cartridge  65 . The cam  200  forces the cartridge toward the pen point  10  and compresses the coil spring  70  between the front of the refill cartridge  65  and the pen point  10 . When the pen  50  is fully extended, the rounded surface  210  of cam  200  rests in a depression in the back end  67  of the refill cartridge  65 . The cam  200  is thus held in a stable position where it is prevented from rotating back on its own. 
     To retract the refill cartridge  65  and collapse the pen  50 , the front section  20  and cap  30  are forced back together to dislodge the cam  200  from the depression in the back end  67  of the cartridge  65 . A slide stop  140  on the pen body  40  mates with a corresponding stop  132  formed in the cap liner  130  to keep the cap  30  from being forced too far against front section  20  when the pen is closed to the storage position. The slide stop  140  is also shaped to help ensure the cam  200  rotates back to the closed position. 
     The refill cartridge  65  can be replaced by unscrewing threaded connection  42  between the front section  20  and pen body  40 , removing the spent cartridge  65  and replacing it with a new one. The front section  20  and pen body  40  can be rejoined and the pen  50  used as described above. 
     Using the pen  50 , a compact writing instrument can be quickly expanded to a larger writing position while simultaneously extending the pen tip for use. 
     In the event that a disposable version of the pen  50  is desired, the front section  20  and pen body  40  could be fused together as a single piece, rather than connected by a threaded connection. Similarly, the pen point  10  could be formed integral with the front section  20 , and the cap liner  130  and cap  30  could be formed as a single piece instead of as separate components. 
     The use of the term refill cartridge herein is intended to mean any self-contained disposable unit which has both a writing material supply and a marking tip for making a visible mark on paper or other material with the writing material. The refill cartridge may be disposable with the pen, or removable from the pen and replaceable. 
     While a specific embodiment of the invention has been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.