Patent Publication Number: US-2011070013-A1

Title: Stylized writing instrument

Description:
CLAIM OF PRIORITY 
     The present application is a continuation of U.S. patent application Ser. No. 11/868,902, filed Oct. 8, 2007, which is a continuation of U.S. patent application Ser. No. 11/401,006, filed Apr. 10, 2006, now U.S. Pat. No. 7,287,924; which is a continuation of U.S. patent application Ser. No. 10/424,573, filed Apr. 28, 2003, now U.S. Pat. No. 7,044,668; which is a continuation of U.S. patent application Ser. No. 09/569,217, filed May 11, 2000, now U.S. Pat. No. 6,585,441; which is a continuation-in-part of U.S. patent application Ser. No. 09/480,009, filed Jan. 10, 2000, now U.S. Pat. No. 6,561,710; which is a continuation of U.S. patent application Ser. No. 09/434,828, filed Nov. 5, 1999, now U.S. Pat. No. 6,428,231, each of which applications are incorporated herein by reference. 
    
    
     COPYRIGHT NOTICE 
     A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever. 
     1. Background 
     The present invention relates to a writing instrument and in particular to a writing instrument shaped like a familiar and/or proprietary object. 
     2. Description of the Related Art 
     Business entities and organizations have long used pens and other writing instruments to promote their name, products and services. By mass distribution of pens having a name, slogan, symbol or other indicia of ownership printed on the pen casing, the entity or organization is able to keep their corporate image in the minds of consumers as the pens pass through commerce. 
     However, there is nothing distinct about the shape of the pen itself which would serve to engender a particular corporate image, and unless the promotional information printed on a pen is read or studied, the information is useless as a promotional tool. Moreover, even when closely examined, words and images printed on pens are less effective at promoting a product or business than the actual products and symbols of that particular business. 
     SUMMARY 
     It is therefore an advantage of the present invention to provide a writing instrument having greater promotional and advertising value than a conventional writing instrument. 
     It is a further advantage of the present invention to provide a writing instrument shaped like a proprietary object which conjures a corporate image without having to read or study information printed on a side of the instrument. 
     It is another advantage of the present invention to provide a novelty writing instrument shaped like a familiar, easily recognizable object. 
     It is another advantage of the present invention that it remains in the shape of a proprietary and/or familiar object at all times, even during use. 
     It is another advantage of the present invention to provide a writing instrument in the shape of a proprietary and/or familiar object in which a pen tip may be easily extended and retracted. 
     These and other advantages are provided by the present invention which in general relates to a stylized writing instrument shaped like a proprietary and/or familiar object. In general, embodiments of the invention include a housing shaped like the proprietary and/or familiar object, a writing implement, and internal mechanisms provided within the housing for moving the writing implement between its extended and retracted positions. The internal mechanisms may comprise a wide variety of actuation systems for extending and retracting the writing implement, including, for example a cam actuation assembly, an edge slide actuation assembly, a gravity actuation assembly, a pressure actuation assembly and a push button actuation assembly. 
     In embodiments of the present invention including the cam actuation assembly, the outer housing may include first and second covers rotatably affixed to each other. The covers define an interior space in which a pen guide having a pen cartridge attached thereto is seated. One of the covers includes a cam on an inner surface, which mates with a cam follower on a juxtaposed surface of the pen guide. Upon rotation of the covers with respect to each other, the cam on the cover and cam follower on the pen guide cause the pen cartridge to move between its extended and retracted positions. 
     In embodiments of the present invention including the edge slide assembly, the outer housing is formed by a pair of fixedly attached covers which enclose a pen cartridge and an edge slide having a finger-actuated portion extending out beyond the housing. The edge slide includes a sloped surface capable of acting on the pen cartridge so that, by sliding the edge slide between a first and second position, the cartridge may be moved between its extended and retracted positions. 
     In embodiments of the present invention including a gravity activation assembly, the outer housing is again formed by a pair of fixedly attached covers which enclose a pen cartridge seated within a channel. The channel further includes a detent along its length, and a locking ball seated atop the pen cartridge. When the writing instrument is tilted downward, gravity causes the pen cartridge to extend from the housing, at which point the locking ball seats partially within the detent, thereby locking the pen in the extended position. In order to retract the pen cartridge, the instrument is tilted upward, so that the ball falls out of the detent and gravity retracts the cartridge. This embodiment may include a cover along an edge of the writing instrument to prevent the pen tip from extending when the instrument is not in use. 
     In embodiments of the present invention including a pressure activation assembly, the outer housing is formed by a pair of covers having a degree of flexibility and elasticity. The covers enclose a cartridge extension mechanism capable of extending the pen cartridge from the housing upon application of a pressure to the respective covers, and retracting the pen cartridge into the housing upon removal of the pressure from the covers. It is also contemplated in this embodiment that the pen cartridge may be extended as a result of a pressure applied to the edges of the housing. 
     In embodiments of the present invention including a push button activation assembly, the housing is formed by a pair of fixedly attached covers which enclose a pen cartridge. The pen cartridge may be moved between its extended and retracted positions by a conventional push button assembly which is well known in the pen industry for extending and retracting a pen out of an elongated pen casing. 
     A writing instrument including any of the above actuation systems may be formed with the shape, appearance, texture and/or color of a wide variety of familiar and/or proprietary objects. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will now be described with reference to the drawings in which: 
         FIG. 1  is a perspective view of the writing instrument; 
         FIG. 2  is a perspective view of the writing instrument with the pen cartridge in an extended position; 
         FIG. 3  is a top view of the writing instrument; 
         FIG. 4  is an exploded bottom perspective view including a perspective view of the inner surface of the first cover, a perspective view of the bottom of the pen guide, and a perspective view of the outer surface of the second cover; 
         FIG. 5  is an exploded top perspective view including a perspective view of the outer surface of the first cover, a perspective view of the top of the pen guide, and a perspective view of the inner surface of the second cover; 
         FIG. 6  is a top view of the pen in a retracted position with hidden members shown in phantom; 
         FIG. 7  is a cross-sectional side view through line A-A in  FIG. 6 ; 
         FIG. 8  is a cross-sectional top view showing the pen cartridge partially extended; 
         FIG. 9  is a cross-sectional top view showing the pen cartridge fully extended; 
         FIG. 10  is a perspective view of the inner surface of the first cover according to an alternative embodiment; 
         FIG. 11  is a perspective view of the inner surface of the second cover according to an alternative embodiment; 
         FIG. 12  is a perspective view of a pen guide and pen cartridge according to the embodiments of  FIGS. 10 and 11 ; 
         FIG. 13  is a top view according to alternative embodiments shown in  FIGS. 10-12  with the various internal components shown in phantom; 
         FIG. 14  is a perspective view of the inner surface of the first cover according to an alternative embodiment; 
         FIG. 15  is a perspective view of the inner surface of the second cover according to an alternative embodiment; 
         FIG. 16  is a perspective view of a pen guide and pen cartridge according to the embodiments of  FIGS. 14 and 15 ; 
         FIG. 17  is a top view according to alternative embodiments shown in  FIGS. 14-16  with the various internal components shown in phantom; 
         FIG. 18  is a cross-sectional view of the embodiment shown in  FIG. 17  with the pen cartridge partially extended; 
         FIG. 19  is a cross-sectional view of the embodiment shown in  FIG. 17  with the pen cartridge fully extended; 
         FIG. 20  is a top view with the cover removed according to an alternative embodiment of the present invention with the pen cartridge in a retracted position; 
         FIG. 21  is a top view with the cover removed according to the alternative embodiment shown in  FIG. 20  with the pen cartridge in an extended position; 
         FIG. 22  is a top view with the cover removed according to a further alternative embodiment of the present invention with the pen cartridge in a retracted position; 
         FIG. 23  is the square-shaped pen embodiment; 
         FIG. 24  is a top view of a square-shaped pen embodiment of  FIG. 23  with the internal components shown in phantom; 
         FIG. 25  is a top view with the cover removed showing the edge slide embodiment with the pen in the retracted position; 
         FIG. 25A  is a perspective view of the pen shown in  FIG. 25 ; 
         FIG. 26  is a top view with the cover removed showing the edge slide embodiment with the pen in the extended position; 
         FIG. 26A  is a perspective view of the pen shown in  FIG. 26 ; 
         FIG. 27  is a top view with the cover removed of the gravity actuated embodiment showing the pen in a retracted position and the locking ball seated within a detent; 
         FIG. 28  is a top view with the cover removed as in  FIG. 27  but further including a cover for covering a hole through which the pen tip extends on the edge of the pen; 
         FIG. 28A  is a top view with the cover removed of the gravity fed embodiment of  FIG. 28  showing the pen cartridge locked in the extended position; 
         FIG. 29  is a top view with the cover removed of an alternative gravity actuated embodiment showing the pen in a retracted position and the locking ball seated atop a back end of the pen cartridge; 
         FIG. 29A  is a top view with the cover removed of the gravity fed embodiment of  FIG. 29  showing the pen cartridge locked in the extended position; 
         FIG. 30A  is a cross-sectional top view through section line A-A of  FIG. 28  showing the detents into which the locking ball locks; 
         FIG. 30B  is a cross-sectional top view showing a single detent; 
         FIG. 30C  is a cross-sectional top view showing greater than two detents; 
         FIG. 31  is an exploded perspective view of the writing instrument including the ratchet-type push button activation protruding from a side of the pen opposite where the pen tip protrudes; 
         FIG. 32  is a cross-sectional side view of the embodiment of  FIG. 31  with the pen in an extended position; 
         FIG. 33  is a cross-sectional side view of the embodiment of  FIG. 31  with the pen in a partially extended position; 
         FIG. 34  is a cross-sectional side view of the embodiment of  FIG. 31  with the pen in a retracted position; 
         FIG. 35  is a perspective view showing the inner surface of the first cover according to a further alternative embodiment including sliding covers; 
         FIG. 36  is a perspective view showing the pen cartridge according to the alternative embodiment including sliding covers; 
         FIG. 37  is a perspective view showing the inner surface of the second cover according to the alternative embodiment including sliding covers; 
         FIG. 38  is a side view according to the alternative embodiment including sliding covers showing the pen tip in a retracted position; 
         FIG. 39  is a side view according to the alternative embodiment including sliding covers showing the covers sliding with respect to each other to extend the pen tip; 
         FIG. 40  is a side view according to the alternative embodiment including sliding covers showing the pen tip extended; 
         FIG. 41  is a perspective view showing the housing shaped like two bottlecaps joined together; 
         FIG. 41A  is a perspective view of bottle cap; 
         FIG. 42  is a perspective view of the present invention shaped like a cookie; 
         FIG. 43  is a perspective view of the present invention shaped like a hamburger; 
         FIG. 44  is a perspective view of the present invention shaped like a compact disc; 
         FIG. 45  is a perspective view of the present invention shaped like a gambling chip; 
         FIG. 46  is a perspective view of the present invention shaped like a chocolate candy piece; 
         FIGS. 47 and 47A  are perspective views of the present invention shaped like a chocolate covered peanut candy piece; 
         FIG. 48  is a perspective view of the present invention shaped like a candy piece; 
         FIGS. 49 and 49A  are perspective views of the present invention shaped like a computer chip; 
         FIG. 50  is a perspective view of the present invention shaped like a floppy disk; 
         FIG. 51  is a perspective view of the present invention shaped like a watch including minute and second hands; 
         FIG. 52  is a perspective view of the present invention shaped like a watch including a digital readout; 
         FIGS. 53 and 53A  are perspective views of the present invention shaped like an ice cream container cover; 
         FIG. 54  is a perspective view of the present invention shaped like a coaster; 
         FIG. 55  is a perspective view of the present invention shaped like a pill; 
         FIGS. 56 and 56A  are perspective views of the present invention shaped like a capsule; 
         FIG. 57  is a perspective view of the present invention shaped like a plate; 
         FIG. 58  is a perspective view of the present invention shaped like a make-up compact; 
         FIG. 59  is a perspective view of the present invention shaped like a rivet; 
         FIGS. 60 and 60A  are perspective views of the present invention shaped like a coin; 
         FIG. 61  is a perspective view of the present invention shaped like a cracker; 
         FIG. 62  is a perspective view of the present invention shaped like a rotary phone dial; 
         FIG. 63  is a perspective view of the present invention shaped like a tire; 
         FIG. 64  is a perspective view of the present invention shaped like a double-sided chocolate chip cookie; 
         FIG. 65  is a perspective view of the present invention shaped like a pizza; 
         FIG. 66  is a perspective view of the present invention shaped like a bottle; 
         FIG. 67  is a perspective view of the present invention shaped like a hockey puck; 
         FIG. 68  is a perspective view of the present invention shaped like a golf ball; 
         FIGS. 68A and 68B  are cross-sectional views of an alternative embodiment to that shown in  FIG. 68 ; 
         FIG. 69  is a perspective view of the present invention shaped like a basketball; 
         FIGS. 69A and 69B  are cross-sectional views of an alternative embodiment to that shown in  FIG. 69 ; 
         FIG. 70  is a perspective view of the present invention shaped like a soccer ball; 
         FIGS. 70A and 70B  are cross-sectional views of an alternative embodiment to that shown in  FIG. 70 ; 
         FIG. 71  is a perspective view of the present invention shaped like a tennis ball; 
         FIGS. 71A and 71B  are cross-sectional views of an alternative embodiment to that shown in  FIG. 71 ; 
         FIG. 72  is a perspective view of the present invention shaped like a football; 
         FIGS. 72A and 72B  are cross-sectional views of an alternative embodiment to that shown in  FIG. 72 ; 
         FIG. 73  is a perspective view of the present invention shaped like a baseball; 
         FIGS. 73A and 73B  are cross-sectional views of an alternative embodiment to that shown in  FIG. 73 ; 
         FIG. 74  is a perspective view of the present invention shaped like a volleyball; 
         FIGS. 74A and 74B  are cross-sectional views of an alternative embodiment to that shown in  FIG. 74 ; 
         FIG. 75  is a perspective view showing a screwdriver extending from the housing instead of a writing instrument; 
         FIG. 76  is a perspective view of the instrument showing a cutting blade extending from the housing instead of a writing instrument; 
         FIG. 77  is a perspective view of the instrument showing a flashlight extending from the housing instead of a writing instrument; 
         FIGS. 78-82  illustrate perspective and top views of an embodiment of the present invention including a hole in the center of the writing instrument; 
         FIGS. 83-85  illustrate an exploded perspective and top views of the gravity activated embodiment of the present invention; 
         FIGS. 86-88  illustrate an exploded perspective and top views of an alternative embodiment of the gravity activated embodiment of the present invention; 
         FIG. 89  is an exploded perspective view of an alternative embodiment of the gravity actuated writing instrument; 
         FIGS. 90-92  are cross-sectional views of the embodiment of the writing instrument shown in  FIG. 89 ; 
         FIGS. 93-95  are perspective views of an alternative embodiment of the ratchet assembly writing instrument shown in  FIGS. 35-40 ; 
         FIGS. 96-98  are exploded perspective and cross-sectional views of an alternative embodiment of the ratchet assembly writing instrument shown in  FIGS. 93-95 ; 
         FIG. 99  is a perspective view of the present invention shaped like a compact disk case; 
         FIG. 100  is a perspective view of the present invention shaped like a book; 
         FIG. 101  is a perspective view of the present invention shaped like a cereal box; 
         FIG. 102  is a perspective view of the present invention shaped like a cigarette pack; 
         FIGS. 103 and 104  are perspective views of the present invention shaped like a laundry detergent container; 
         FIG. 105  is a perspective view of the present invention shaped like a bar of soap; 
         FIG. 106  is a perspective view of the present invention shaped like a bottle of alcohol; 
         FIG. 107  is a perspective view of the present invention shaped like a box for a bar of soap; and 
         FIG. 108  is a perspective view of the present invention shaped like a matchbox. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention will now be described with reference to  FIGS. 1-108 , which in general relate to a writing instrument which may be shaped as a familiar and/or proprietary object. While the writing instrument according to preferred embodiments is a pen, it is understood that the writing instrument may alternatively be a marker, pencil, chalk, crayon or any of various other known writing instruments. Moreover, as set forth in greater detail below, the instrument according to the present invention may alternatively contain a tool such as a screwdriver, cutting blade or light source. 
     Writing Instrument Including Cam Assembly 
     A first embodiment of the present invention will now be described with reference to  FIGS. 1-24 . As shown therein, a writing instrument  100  includes a housing  102  formed of a first circular cover  104  and a second circular cover  106 . As depicted in  FIGS. 1-9 , the writing instrument  100  is formed to look like a bottle cap which may have a proprietary logo thereon (not shown in  FIGS. 1-9 ) such as that of Coke® or Pepsi®. However, the outward appearance of the writing instrument  100  shown in  FIGS. 1-9  is but one of a wide variety of shapes and appearances of the instrument, and is provided by way of example only. As set forth in greater detail below, the outward size, appearance and texture of the writing instrument may be that of various other proprietary objects or symbols, such as for example an auto manufacturer&#39;s emblem, including that of Cadillac™, Lincoln™ or Mercedes™. The outward size, appearance and texture of the writing instrument may alternatively be that of a familiar object, such as a coin or a food item, for example a cracker. Furthermore, the outward size, appearance and texture of the writing instrument may be formed to have an artistic design or picture. As described in greater detail below, various other outward sizes, appearances and textures for writing instrument  100  are contemplated. 
     Referring now to  FIGS. 1-5 , the first cover  104  includes an outer surface  108  formed in the general size, appearance and/or texture of a familiar and/or proprietary object. The cover  104  further includes an inner, generally planar surface  110  including a generally circular shaped outer wall  112  extending away from the inner surface, at an outer circumference of the cover  104 . The outer wall  112  extends around substantially the entire circumference of cover  104 , but has a hole  114  defining an opening through which a pen cartridge tip can extend and retract as explained hereinafter. The second cover  106  similarly includes an outer surface  116  formed in the size, appearance and/or texture of a familiar and/or proprietary object. Inner surface  118  includes a generally circular shaped wall  120  extending away from the inner surface, near an outer circumference of the cover  106 . The inner wall  120  extends around a substantial portion of the cover  106 , but has a break which defines a gap  122 . 
     The first and second covers may fit concentrically over each other so that the wall  112  lies circumjacent around the inner wall  120 , and in close engagement thereto, with an inner surface of the wall  112  lying in contact with an outer surface of the wall  120 . As is known in the art, a small lip may be formed around a top portion of wall  112 , which mates within a small annular detent at the base of wall  120 . The mating of the lip within the detent holds the first and second covers together when assembled while allowing relative rotation of the covers. As would be understood by those of skill in the art, the first and second covers may be rotationally affixed to each other by other fastening schemes. 
     The walls  112  and  120  also serve to space the first and second covers from each other when attached so as to define an internal space within the housing  102  for the internal components of the writing instrument which are discussed hereinafter. The outer surface of wall  112  which is visible on the outside of the writing instrument  100  is also formed to look and/or feel like corresponding portions of the object emulated by the writing instrument. 
     The size of the writing instrument may vary to generally match that of the object being emulated. The covers  104  and  106  are preferably formed of a rigid and durable polymer having smooth inner surfaces, such as any of various plastics, and may be formed by injection molding. It is understood however that the covers  104  and  106  may be formed of various other materials and by various other processes in alternative embodiments. For example, the covers may alternatively be formed of various metals, such as gold, silver and aluminum, various magnetic materials such as for example cobalt or nickel, various woods, such as pine and oak, or various combinations of the above. Moreover, the covers may alternatively be formed by processes such as stamping or machining. The covers  104  and  106  may also be painted, coated and/or textured to take on the appearance and/or feel of the desired object. 
     Referring now to  FIGS. 4-9 , in a preferred embodiment, the inner surface  118  of second cover  106  includes walls which define an arcuate track  124 . The inner surface  110  of the first cover  104  includes a pair of spaced apart walls which form a pair of linear guides  126 . The track  124  may alternatively be located in the inner surface of cover  104 , and the linear guides  126  may alternatively be located in the inner surface of cover  106  in different embodiments. 
     The writing instrument  100  according to the present embodiment further includes a pen guide  128  seated within the housing  102  in the space between the respective covers  104  and  106  in their assembled position. The pen guide  128  has a first surface  130  including a protruding, circular track following section  132 , and a second surface  134  opposite the first including a spaced apart pair of indented guide following sections  136 . The pen guide further includes a writing implement, such as a pen cartridge  138  with a writing tip, pressed into a hole formed in a circumferential edge of the pen guide  128 . It is understood that the writing tip may include a relatively blunt tip to minimize the risk of injury if the pen tip impacts against the skin or eyes of a user of the pen. As previously indicated, writing implements other than pen cartridges may be used. The cartridge  138  stores and supplies ink to the tip of the pen. In alternative embodiments, an interior portion of the pen guide may be hollow to define an additional ink reservoir for storing and supplying ink to the tip of the pen. 
     The pen guide  128  preferably includes smooth, low friction surfaces, and may be formed of a rigid and durable polymer, such as any of various plastics, by injection molding. It is understood however that the pen guide  128  may be formed of various other materials and by various other processes in alternative embodiments. The footprint shape of the pen guide  128  may vary in alternative embodiments with the provision that the pen guide not be inhibited from pivoting within the housing  102  as explained below. The pen guide may also include an air channel  139  communicated through to the hole in which the pen cartridge is seated. The air channel allows equalization of the pressure within the pen cartridge to that of the surrounding atmosphere. 
     The operation of the writing instrument  100  shown in  FIGS. 4 and 5  to extend and retract the pen cartridge upon rotation of the covers  104  and  106  will now be explained with reference to  FIGS. 4-9 . When the writing instrument  100  is assembled, the pen guide  128  lies between the respective covers  104  and  106  with the track following section  132  of the pen guide lying within the track  124  on the inner surface  118  of the second cover  106 . The guide following sections  136  on the opposite side of the pen guide from the track following section ride over the respective linear guides  126  on the inner surface  110  of the first cover  104 . ( FIG. 6  illustrates the components within the respective covers in phantom lines, and  FIGS. 8 and 9  show the pen in cross section, for clarity.) 
     Rotation of the second cover clockwise from the view of  FIGS. 6 ,  8  and  9  with respect to the first cover, (i.e. within a plane of rotation reflected in this instance by the plane of the page), causes rotation of the track  124  as shown. Rotation of the track  124  in turn causes translation of the track following section  132 , which is constrained to translate vertically from the views of  FIGS. 6 ,  8  and  9 , (i.e. within said plane of rotation), as a result of the guide following sections  136  riding along the linear guides  126 . Thus, rotation of the second cover from the position shown in  FIG. 6 , through the position shown in  FIG. 8 , to the position shown in  FIG. 9  results in the writing end of the cartridge  138  moving, within said plane of rotation, from its retracted position to its extended position. In a preferred embodiment, cover  104  preferably further includes a pair of stops  137  extending up from the inner surface  110 . As seen in  FIG. 9 , when in the fully extended position, the pen guide  128  abuts up against the stops  137  to prevent further respective rotation of the covers  104  and  106  and to define a maximum extension of the pen tip from the housing. 
     In a preferred embodiment, as shown in  FIG. 6 , when in the retracted position, the wall  120  covers the hole  114  through which the pen tip extends. However, upon rotation of the cover  106 , the gap  122  in the wall  120  aligns with the hole  114  to allow the pen tip to extend through the hole  114  and out of the housing. It is understood that in alternative embodiments, the wall  120  need not extend as far around the periphery of the cover  106  as shown, so that the wall does not cover the hole  114  when the pen tip is in the retracted position. 
     In order to retract the pen cartridge  138  from its extended position, the first and/or second covers are rotated in the opposite direction than to extend the pen cartridge. This rotation results in the pen guide  128  and the pen cartridge  138  moving from the position shown in  FIG. 9  to the position shown in  FIG. 6 . The arcuate track  124  is configured so that a 90° rotation of the covers with respect to each other results in an approximate ¼ inch translation of the pen cartridge, which is sufficient to move the pen cartridge between its extended and retracted positions. The configuration of the track  124  may be varied so that various other angles of rotation of the covers result in the same translation of the pen cartridge in alternative embodiments. Such various other angles may range between 30° and 180° in one alternative embodiment. It is further contemplated that the relative positions of the track  124  in cover  106  and the track following section  132  in pen guide  128  may be reversed in alternative embodiments. It is similarly contemplated that the positions of the linear guides in cover  104  and the guide following sections  136  in the pen guide  128  may be reversed in alternative embodiments. 
     It is understood that other cam assemblies and configurations may be utilized according to the first embodiment of the present invention to extend and retract the pen cartridge upon rotation of the covers  104  and  106 . One such alternative embodiment is shown in  FIGS. 10-13 . As shown, the cover  106  may include an arcuate track  124  substantially as described above. The cover  104  may similarly include guides  140  between which the pen guide  128  translates. In the current embodiment, the pen guide  128  is slightly modified in shape as shown in  FIG. 12  relative to that described above so as to fit between the guides  140 . However, as described above, the pen guide  128  still includes the track following section  132  which fits within the track  124  when the respective covers  104 ,  106  are assembled as shown in  FIG. 13 . ( FIG. 13  illustrates the components within the respective covers in phantom lines for clarity.) As described above, rotation of the first cover with respect to the second cover causes rotation of the track  124 , which in turn causes translation of the track following section  132 . The track following section  132  is constrained to translate left and right from the view of  FIG. 13  as a result of the guides  140 . The guides  140  may each include a shoulder  142  which define stops against which portions of the pen guide  128  abut when the pen is in the fully extended position. 
     A further alternative embodiment employing a cam arrangement is shown in  FIGS. 14-19 . According to this embodiment, the inner surface  110  of first cover  104  includes a raised section defining an oblong-shaped cam  144  having one end at the center of the cover  104  and having a second end extending radially outward therefrom toward the outer circumference of the cover. The inner surface  118  of the second cover  106  includes a depression defining a track  145  extending diagonally across the inner surface  118 , through the center of the cover  106 . The cam  144  may alternatively be located in the inner surface of cover  106 , and the track  145  may alternatively be located in the inner surface of cover  104  in different embodiments. 
     The writing instrument  100  according to the embodiment of  FIGS. 14-19  further includes a pen guide  128  seated within the housing  102  in the space between the respective covers  104  and  106  in their assembled position. The pen guide  128  according to this embodiment has a first surface  130  including an indented cam following section  146 . The second surface  134  of the pen guide includes a track following section (not shown) which rides within track  145 . 
     When the writing instrument  100  is assembled, the pen guide  128  lies between the respective covers  104  and  106  with the cam following section  146  of the pen guide residing over the cam  144  on the inner surface  110  of the first cover  104 . ( FIG. 17  illustrates the components within the respective covers in phantom lines, and  FIGS. 18 and 19  show the pen in cross section, for clarity.) Rotation of the first cover with respect to the second cover causes the cam  144  to engage against and ride along a first portion  148  of the cam following section  146 . This engagement causes translation of the pen guide and pen cartridge from their retracted position shown in  FIG. 17 , through their position shown in  FIG. 18 , to their extended position shown in  FIG. 19 . This embodiment may optionally further include a pair of guideposts  149  for further guiding the pen cartridge as it translates between its extended and retracted positions. Although not shown, the track  145  in the second cover  106  rides within the track following section on the pen guide  128  to ensure pure translation of the pen guide and pen cartridge. 
     In order to retract the pen cartridge  138  from its extended position, the first and second covers are rotated in the opposite direction than to extend the pen cartridge. Such rotation causes the cam  144  to engage against and ride along a second portion  150  of the cam following section  146 . This engagement results in the pen guide  128  and the pen cartridge  138  moving from the position shown in  FIG. 9  to the position shown in  FIG. 6 . The cam and cam following sections are configured so that a 90° rotation of the covers with respect to each other results in an approximate ¼ inch translation of the pen cartridge, which is sufficient to move the pen cartridge between its extended and retracted positions. The configuration of the cam and cam following section may be varied so that various other angles of rotation of the covers result in the same translation of the pen cartridge in alternative embodiments. Such various other angles may range between 30° and 180° in one alternative embodiment. It is further contemplated that the positions of the cam in cover  104  and the cam following member in pen guide  128  may be reversed in alternative embodiments. It is similarly contemplated that the positions of the track in cover  106  and the track following section in the pen guide  128  may be reversed in alternative embodiments. 
     A further alternative cam embodiment is shown in  FIGS. 20 and 21 . In this embodiment, a pen guide  152  comprises a span  154 , preferably formed of a durable, elastic polymer such as any of various plastics, and having a modulus of elasticity allowing the span to repeatably flex between the positions shown in  FIGS. 20 and 21 . The first cover  104  according to this embodiment preferably includes a pair of braces  156  mounted to the inner cover  110  for supporting the ends  158  of the pen guide  152 . The second cover  106  according to this embodiment preferably includes an oval-shaped cam  160  mounted to inner surface  118  (not shown in  FIGS. 20 and 21 ). It is understood that the positions of the braces  156  and cam  160  on the respective covers may be switched in alternative embodiments. 
     When the second cover  106  is rotated with respect to the first cover  104 , the cam  160  rotates from the position shown in  FIG. 20  to the position shown in  FIG. 21 . During such movement, the cam  160  bears against a central portion  162  of the pen guide  152  to force the pen guide downward and to extend the pen cartridge from the housing  102 . The elasticity of the pen guide according to this embodiment biases the pen guide to its unflexed position shown in  FIG. 20 , so that upon rotation of the second cover from the position shown in  FIG. 21  to the position shown in  FIG. 20 , the pen cartridge retracts back into the housing. 
     As shown in  FIG. 22 , those of skill in the art would appreciate that the ends of pen guide  152  used to bias the pen cartridge back to its retracted position may be omitted, and replaced by some other biasing force such as a spring  164 . Other cam assemblies and configurations are also contemplated. 
     Up to this point, the covers  104  and  106  have been described as being circular. It is understood that the covers may have different shapes in alternative embodiments. For example, as shown in  FIGS. 23 and 24 , the housing  102  may be square. As shown in  FIG. 24 , the pen cartridge  138  may be moved between its extended and retracted positions with internal components such as those described above with respect to  FIGS. 4-9 . It is understood that the internal components according to other embodiments may be used with the square covers as well. It is further contemplated that one of the covers be square, and that the other cover be circular and rotationally mounted within the square cover. One of skill in the art would appreciate for example how to modify cover  106  as described above with respect to  FIGS. 1-9  to have a square footprint. Furthermore, in all embodiments including a square housing, it is understood that the pen tip may protrude from the housing  102  along one of the four straight sides of the housing or at a corner where two sides of the housing come together. 
     The covers  104  and  106  may alternatively be other shapes, such as pentagonal, hexagonal, heptagonal, octagonal, oval, oblong and irregular. Regardless of the shape, it is preferable that the angle through which the covers rotate to extend and retract the pen cartridge tip is provided so that the edges of the two covers align when the pen cartridge is both in the fully extended and retracted positions. It is however contemplated that the edges of the respective covers  104  and  106  not align with each other when the pen cartridge is in its fully extended and/or retracted positions in alternative embodiments. 
     The internal mechanisms according to the above-described cam embodiments allow the respective covers to be easily rotated with a single hand to move the pen cartridge between its extended and retracted positions. Moreover, the present embodiment does not have any elements protruding from the housing (beside the pen cartridge tip itself). As many of the familiar and/or proprietary objects to which the pen is shaped do not have protruding elements, the present embodiment allows an accurate replication of these objects. 
     Writing Instrument Including Edge Slide Assembly 
     A further embodiment of the present invention will now be described with respect to  FIGS. 25-26A . The embodiments of  FIGS. 25-26A  include covers  104  and  106  having outer surfaces and outer edge surfaces substantially as described above. In this embodiment, the covers are fixedly attached to each other with a conventional adhesive or fastener so as not to rotate with respect to each other. It is understood that the housing may alternatively be formed by attaching component parts other than covers  104  and  106 . For example, two semicircular halves may be attached together to form housing  102 . Regardless of how the covers are affixed to each other, the covers define an interior space in which the internal components of the pen are mounted. 
     In particular, an edge slide  166  is mounted within the interior space defined by the covers, which slide  166  is capable of arcuate translation around a portion of the interior space. The edge slide  166  includes an arcuate, wedge-shaped section  168  having a relatively wide rear section  170  which narrows to substantially a point at a front section  172 . The edge slide  166  further includes an arcuate extension  174  extending from rear section  170 . The edge slide  166  additionally has a finger grip  176  attached at the rear section  170  and extending outside of the footprint of the covers  104  and  106 . A portion of the outer circumferential walls formed in covers  104  and  106  may be omitted to allow translation of the edge slide  166  outside of the housing as described below. A pair of guides  171  are additionally mounted to the surface of either cover  104  or  106  between which the pen cartridge  138  is seated. 
     In its retracted position shown in  FIGS. 25 and 25A , the rear of pen cartridge  138  (i.e., the top as shown in  FIG. 25 ) lies engaged with the front section  172  of edge slide  166 . It is also contemplated that the rear pen cartridge  138  not contact any portion of the edge slide  166  when the cartridge is in its retracted position. To extend the pen cartridge to the position shown in  FIGS. 26 and 26A , the finger grip  176  is manually actuated in the counterclockwise direction from the perspective of  FIGS. 25 and 26 . Upon such actuation, a ramp surface  178  of the wedge-shaped section  168  forces the pen cartridge downward with respect to  FIG. 25 , thus moving the pen cartridge to its extended position shown in  FIGS. 26 and 26A . The arcuate extension  174  serves both to facilitate smooth arcuate translation of the edge slide  166 , and also to cover the hole  114  in the housing when the edge slide  166  is in the position shown in  FIGS. 25 and 25A . 
     In a preferred embodiment, a spring  180  may be provided around cartridge  138 , which spring biases the cartridge upward from the perspective of  FIGS. 25 and 26  to its retracted position. Thus, when the edge slide is moved clockwise, spring  180  biases the pen cartridge  138  back into its retracted position as ramp  178  recedes. It is understood that biasing mechanisms other than springs may be used to bias the pen cartridge back to its retracted position. 
     The edge slide is configured so that a 45° arcuate translation of the edge slide will result in an approximate ¼ inch translation of the pen cartridge which is sufficient to move the pen cartridge between its extended and retracted positions. The configuration of edge slide  166 , and in particular the slope of ramp surface  178 , may be varied in alternative embodiments to vary the translation of pen cartridge  138  for a given arcuate translation of edge slide  166 . In one alternative embodiment, the edge slide may translate over an arc ranging between 30° and 180°. 
     As will be appreciated from this embodiment, the finger grip  176  may be easily manipulated by one hand to move the tip of the writing cartridge between its extended and retracted positions. 
     Writing Instrument Including Gravity-Activated Assembly 
     A further embodiment of the present invention will now be described with reference to  FIGS. 27-30C  and  83 - 92 . The embodiments of  FIGS. 27-30C  and  83 - 92  include covers  104  and  106  having outer surfaces and outer edge surfaces substantially as described above. In this embodiment, the covers  104  and  106  are fixedly attached to each other with a conventional adhesive or fastener so as not to rotate with respect to each other. A pair of guides  182  are formed on the inner surface  110  of cover  104 , or alternatively on the inner surface  118  of cover  106 , between which guides the pen cartridge  138  is seated. One or more detents  186  are formed in the guides  182 . The detents are provided at a position along the length of the guides  182  for receiving a locking member such as locking ball  188  to maintain the pen in its extended position. 
     In particular, in its retracted position shown in  FIGS. 27 and 28 , the locking ball  188  is seated within a detent  186 . The cartridge  138  remains in its retracted position as shown in  FIG. 27  due to the forces of gravity. Alternatively, as shown in  FIG. 28 , a gravity-actuated slide cover  190  may seal the hole  114  to maintain the pen cartridge in its retracted position when not in use. In the embodiment of  FIG. 28 , before the pen cartridge may be extended, the pen must be tilted on its side so that gravity moves the cover  190  away from the hole  114 . One of the guides  182  may include a foot portion  191  which, together with the wall of the cover, restricts the movement of the cover to slide between a first position where the hole  114  is covered and a second position where the hole  114  is uncovered. A stop  193  may further be provided to limit the motion of the cover when in the second position. After the pen has been tilted to move the cover  190  to the second position, the pen may be pointed downward so that gravity moves the pen cartridge to the extended position shown in  FIG. 28A . The tilting of the pen to move the cover away from the hole  114  and pointing of the pen downward to extend the pen cartridge may be accomplished in a single hand motion. 
     As shown in  FIG. 28A , when the cartridge  138  moves to its extended position, the locking ball  188  moves out of the detent and seats on top of the back end of the pen cartridge. The position of the detents  186  are determined by the length of pen cartridge  138  so that locking ball  188  is able to move out of the detent  186  when the tip of the pen cartridge is fully extended. The spacing between the guides  182  is smaller than the diameter of the locking ball so that, seated on top of the pen cartridge, the locking ball wedges against corners  195  and  197  of the guides so to lock the pen cartridge in its extended position. As long as the locking ball  188  remains in position on the back end of the pen cartridge, the pen cartridge will remain in its extended position. In order to retract the pen, the pen is lifted off of the writing surface and tilted, at which point the locking ball  188  falls back into a detent  186 . Thereafter, tilting the pen upward retracts the pen cartridge rearward into the housing  102 . 
     In an alternative embodiment shown in  FIGS. 29 and 29A , when the pen is in the retracted position, the locking ball  188  may be seated between the guides  182  at the back end of the pen cartridge  138 . The cartridge  138  may remain in its retracted position due to the forces of gravity as shown in  FIG. 29 . When the writing instrument  100  is oriented so that the tip of the pen cartridge faces generally downward as shown in  FIG. 29A , the forces of gravity will bias the pen cartridge to its extended position (in embodiments including a slide cover  190 , the slide cover must first be opened for the pen cartridge to move to its extended position). As shown in  FIG. 29A , when the cartridge  138  moves to its extended position, the locking ball  188  will seat partially within detent  186 . Seated partially within the detent, the locking ball locks the pen cartridge in its extended position by preventing the cartridge  138  from retracting. As long as the instrument remains tilted in the writing position, locking ball  188  will remain in detent  186 , and the pen cartridge will remain in its extended position. In order to retract the pen, the pen is tilted upward, at which point the locking ball  188  falls out of detent  186  and the forces of gravity retract the pen cartridge rearward into the space between guides  182 . 
       FIG. 30A  shows a cross-section of the detents  186  shown in  FIG. 29A . Instead of having two detents  186 , the guides  182  may be formed with a single discrete detent  186  as shown in  FIG. 30B , or more than two discrete detents  186  as shown in  FIG. 30C  for receiving locking ball  188 . 
     The gravity activated embodiment of the present invention is further shown in  FIGS. 83-85 . The writing instrument  100  shown therein operates in the same manner as the writing instrument  100  shown in  FIGS. 27-28A . It includes a locking member comprising a locking pin  188 , and first and second detents  186   a  and  186   b.  When the writing instrument is tilted upwards, the locking pin  188  resides in first detent  186   a  as shown in  FIG. 84 . In this position, the pen cartridge  138  is free to retract due to the forces of gravity. When the writing instrument is tilted downwards, the locking pin  188  slides partially out of detent  186   a,  across the channel defined by guides  182 , and seats partially within detent  186   b  as shown in  FIG. 85 . In this position, the pen is prevented from retracting and is held in a position for writing. (While the writing instrument shown in  FIGS. 83-85  has a square shape, it is understood that the writing instrument shown in  FIGS. 27-29A  and  83 - 85  may be circular, square or other shapes as described above.) 
     It is understood that the detents  186   a  and  186   b  may be perpendicularly oriented with respect to the channel defined by guides  182  as shown in  FIGS. 83-85 . Alternatively, the detents  186   a  and  186   b  may be angled with respect to the channel defined by guides  182  as shown in  FIGS. 86-88 . The embodiment of the writing instrument  100  shown in  FIGS. 86-88  operates similarly to the embodiment shown in  FIGS. 83-85  and components which are common to both embodiments have been assigned like reference numerals. However, the embodiment of  FIGS. 86-88  makes use of the fact that the pen is generally tilted when in the writing position so that the detents  186   a  and  186   b  shown in  FIGS. 86-88  will be oriented straight up and down when the instrument  100  is tilted in the writing position to ensure that the locking pin  188  is ensured of sliding to the locking position shown in  FIG. 88 . 
     A further alternative embodiment of the gravity activated writing instrument according to the present invention is shown in  FIGS. 89-92 . This embodiment includes covers  104  and  106  as previously described, and a gravity cartridge assembly  194 . Cartridge assembly  194  includes a cartridge housing  196  fixedly mounted to either cover  104  or  106  and sealed at its back end with a cartridge assembly cap  198 . Cap  198  is preferably cylindrically shaped with a central opening  199  facing the interior of the housing  196  when the cap  198  is inserted into the back end of housing  196 . A pen cartridge  138  as described above is located within the cartridge housing  196 , which pen cartridge  138  includes a cap  200 . A gravity tube  202  is also provided within the cartridge housing  196 , which tube  202  has an outer diameter slightly smaller than an inner diameter of cartridge housing  196  so that tube  202  is free to translate between a front end and back end of the housing  196 . The position of the tube  202  is determined by gravity so that when the front end of the cartridge housing faces downward the tube  202  resides in the front end of the housing and when the back end of the cartridge housing faces downward the tube  202  resides in the back end of the housing. Tube  202  includes a central aperture  204  through which the pen cartridge  138  fits. 
     When the writing instrument  100  according to this embodiment is tilted downward as represented in  FIG. 90 , gravity moves tube  202  to the front of the cartridge housing, and moves the pen cartridge to the extended position where the pen tip protrudes out of the housing  102 . When the pen tip is pressed down on a writing surface, the pen tip and pen cartridge will be biased rearward relative to the cartridge housing  196 . As the pen is tilted when writing, a force will also be exerted on the pen cartridge biasing the back end of the pen cartridge into contact with a portion of the cylindrical side walls of the housing  196 . Therefore, upon application of the writing force, the back end of the pen cartridge will move rearward and wedge against a front portion of cartridge assembly cap  198  as shown in  FIG. 90  to maintain the pen in the extended writing position. 
     When the writing instrument  100  according to this embodiment is tilted upward, the tube  202  moves toward the back end of the cartridge housing  196  as shown in  FIG. 91 , and seats atop the cartridge assembly cap  198  as shown in  FIG. 92 . The inner diameter of the tube  202 , at least at its back end, is equal to or slightly smaller than the inner diameter of the cylindrical cartridge assembly cap  198 . Thus, when seated atop the cap  198 , the tube  202  prevents the back end of the pen cartridge from wedging against the cap  198 , and when tilted upwards away from the writing surface as represented in  FIG. 92 , the back end of the pen cartridge funnels into the central opening  199  under the force of gravity to retract the pen tip into the housing  102 . 
     While the cartridge housing  196 , the cap  198  and the tube  202  are preferably cylindrical, it is understood that these components may have other shapes in cross section in alternative embodiments, such as for example rectangular. Moreover, while the pen tip is shown as retracted into the cartridge housing  196  in  FIG. 92 , it is understood that the pen tip need only retract into the housing  102  of the writing instrument, in which housing  102  the cartridge housing  196  is fixedly mounted. In such an embodiment, the pen tip may be in a retracted position within housing  102  and still protrude from cartridge housing  196 . 
     According to the embodiments of  FIGS. 27-30C ,  83 - 89  and  93 - 95 , the pen cartridge may be easily moved between its extended and retracted positions by a simple flick of the wrist or tilting of the writing instrument  100 . In embodiments including a hand-actuated slide cover, the pen may be maintained in its retracted position when not in use, and easily moved to its extended position with a single hand by sliding the slide cover to an open position and then tilting the pen as described above. 
     Writing Instrument with Push Button-Activation Assembly 
     A further embodiment of the present invention will now be described with reference to  FIGS. 31-34 . The embodiments of  FIGS. 31-34  include covers  104  and  106  having outer surfaces substantially as described above. Each cover according to this embodiment preferably further includes a wall  208  extending around the outer circumference of each cover. The walls  208  of the respective covers are preferably of the same diameter and are fixedly attached to each other at their upper edges as by an adhesive or fastener. The walls  208  preferably include aligned openings  210  through which the pen cartridge  138  may extend and retract. 
     According to this embodiment, the pen cartridge  138  may be moved between its extended and retracted positions by a conventional push button assembly  212  which is well known in the pen industry for extending and retracting a pen out of an elongated pen casing. In general, push button assembly  212  includes a plunger  214  having a push button  216  at its top end extending out of the housing  102 , and a plurality of track followers  218  at its bottom end. Push button assembly  212  further includes formations  221  on the inner surfaces  110  and  118  of the covers  104  and  106  (only the formation  221  on the cover  104  is shown). When the covers are assembled together, the formations  221  together define an enclosure having a plurality of tracks  222  in which track followers  218  move up and down upon hand activation of the push button  216  of plunger  214 . The assembly  212  further includes an actuator  228  fitting substantially within the plunger and against which the pen cartridge  138  abuts. A spring  230  is provided around a lower portion of the pen cartridge to bias the pen cartridge upward against the actuator  228 . The actuator includes a number of teeth  232 , which reside in alternating tracks  222  (e.g., there may be four teeth  232  on the actuator  228  and eight tracks  222  defined by the formations  221 ). 
     As shown in  FIGS. 32-34 , and as is known in the art, upon each manual actuation of the plunger  214 , the actuator will rotate the pitch of one track  222  as a result of teeth  232  within the tracks having slanted edges (not shown). When the teeth of the actuator reside in one set of alternating tracks, the teeth catch on stops (not shown) in the tracks so that the actuator is prevented from fully retracting. In this instance, the pen cartridge abutting against the actuator is held in the extended position as shown in  FIG. 32 . Upon the next depression of plunger  214 , the teeth move to the next adjacent set of tracks, where they do not catch ( FIG. 33 ) so that the spring  230  biases the pen cartridge, actuator and plunger downward ( FIG. 34 ) to a retracted position. 
     As would be appreciated by those of skill in the art, other known push button assemblies may be employed wherein the tip of the pen cartridge  138  is alternately extended and retracted upon finger activation of a mechanism extending from the housing  102 . 
     An alternative embodiment of the present invention is shown in  FIGS. 35-40 . This embodiment includes an assembly which operates similarly to the push-button assembly  212  disclosed above with respect to  FIGS. 31-34 , except that the push button  216  is omitted. According to this embodiment, the two covers  104 ,  106  are slidably mounted to each other to provide a so-called “slide by” actuation to move the pen cartridge between its extended and retracted positions. One of the covers, for example cover  104 , includes posts  234 , each of which includes a lip  236 . The other of the covers, for example cover  106 , includes a corresponding number of slots  238  formed partially through the wall on the interior of the cover. The lip  236  of each post  234  mates within a slot  238 . As the slots are wider than the posts and lips, the lip is capable of sliding in the slot to allow the respective covers to slide back and forth with respect to each other. 
     In accordance with this embodiment, the plunger  214  (without the push button  216 ) abuts against an interior wall  240  of either cover  104  or  106 . In an embodiment where the plunger  214  abuts against wall  240  on cover  106 , when it is desired to move the pen cartridge between its extended and retracted positions, the cover  106  is advanced (downward as shown in  FIG. 39 ) relative to cover  104 . This movement in turn moves the plunger downward and the actuator  228  will rotate between alternating ratchet positions as described above. In a first rachet position (shown in  FIG. 38 ), the teeth  232  of the actuator do not catch on the tracks  222 , and the pen remains in the retracted position. In a second rachet position (shown in  FIG. 40 ), the teeth  232  of the actuator do catch on the tracks  222 , and the pen is held in an extended position. A spring  230  as described above biases the pen into a retracted position and also biases the covers into a coextensive position. 
     A further alternative embodiment of the slide by actuation mechanism of  FIGS. 35-40  is shown in  FIGS. 93-98 . Components which are common to both embodiments have been assigned like reference numerals. In this embodiment, instead of formations  221  being formed on the inner surfaces  110  and  118  of the covers  104  and  106  as described above, the formations  221  are formed around an inner diameter of a cylindrical ratchet housing  260  ( FIG. 94 ) so that the formations form a plurality of tracks  222  as described above within ratchet housing  260 . Ratchet housing  260  is in turn fixedly mounted to either cover  104  or  106 . Additionally, a pair of springs  262  are further provided, which springs compress when the covers are moved with respect to each other as shown in  FIG. 39 . The springs  262 , which are preferably provided in cover  104  as shown in  FIG. 93  or in cover  106  as shown in  FIG. 95 , bias the covers in a “home” position with respect to each other, i.e. to a position where the covers are coextensive with each other. 
     The pen tip may protrude from a side between two corners in the slide by ratchet pen assembly as shown in  FIGS. 35-40  and  93 - 95 . Alternatively, as shown in  FIGS. 96-98 , the covers  104  and  106  may be square, but the pen tip may protrude from a corner where two sides come together. Thus, the covers move with respect to each other along a line between a pair of diametrically opposed corners to extend and retract the pen tip by the ratcheting assembly as described above. 
     Writing Instrument Including Pressure-Activated Assembly 
     Although not shown in the drawings, a further embodiment of the present invention may comprise a writing instrument where the pen cartridge is actuated between its extended and retracted positions as a result of applying inwardly directed pressure on the outer surfaces of covers  104  and  106 . According to this embodiment, covers  104  and  106  are preferably formed of an elastic polymer such as any of various plastics, and having a modulus of elasticity that allow the covers to elastically deform upon a pressure applied to the outer surface of the covers. 
     As would be appreciated by those of skill in the art, various mechanisms may be employed in accordance with this embodiment to extend and retract the pen cartridge. For example, the mechanism could be made up of a series of tiny, interconnected four-bar linkages so that a pressure exerted on the mechanism in one direction (i.e., along the upper and lower edge of the mechanism) results in a change in the length of the mechanism. The mechanism would be located within the housing  102  in a plane perpendicular to the inner surfaces of covers  104  and  106 , and colinear with pen cartridge  138 . Each joint in the mechanism could be affixed together by a small pin holding the respective members together while allowing rotation of the joined members with respect to each other. The back end of the pen cartridge would be affixed to or abutting against the end of the mechanism, so that upon extension of the mechanism as a result of pressure on the covers, the mechanism and the cartridge would extend. A rachet and spring assembly as described above could be used to hold the pen extended upon a first application of pressure to the covers, and to allow the pen to retract upon a second application of pressure. 
     As an alternative to covers formed of a polymer, the covers may be formed of a thin gauge metal with an inherent bias into a position where the covers bow slightly outward. In this embodiment, upon application of a threshold pressure to the respective covers, the covers may invert so that the covers bow inward to actuate the cartridge extension mechanism as described above. Due to the inherent bias of the covers to remain in their natural position, the covers will snap quickly inward upon application of the threshold pressure, and will snap quickly back to their natural position upon removal of the pressure. The covers may also be made to make an audible snapping noise when moving between their natural and inwardly bowed positions. 
     Each component used in making the writing instrument  100  according to the various above-described embodiments can be manufactured and assembled at a low cost, thus allowing the finished writing instrument to be economically manufactured. However, it is further understood that high-end writing instruments according to the above-described embodiments may also be provided. In such writing instruments, the focus is not in providing an economical finished product, but in providing a precision, durable and/or elegant finished product. As will be appreciated by those of skill in the art, other components may be substituted for those described above for providing such a high-end writing instrument. 
     As described above, in addition to the bottle cap shown, the appearance of the outer housing  102  may be that of any of several familiar and/or proprietary objects. A partial listing of such objects is set forth below: 
     a double sided bottle cap as shown in  FIG. 41  and a single sided bottle cap, such as a bleach bottle cap, as shown in  FIG. 41A ; 
     food items, such as a cookie and a hamburger as shown in  FIGS. 42-43 ; 
     a compact disk as shown in  FIG. 44 ; 
     a gambling chip as shown in  FIG. 45 ; 
     candy as shown in  FIGS. 46-48 ; 
     a computer chip as shown in  FIGS. 49 and 49A ; 
     a floppy disk such as shown in  FIG. 50 ; 
     rotary and digital watches such as shown in  FIGS. 51 and 52  (this embodiment may comprise an actual working watch affixed to a cover, or a non-working replica of a watch face); 
     a cover of a container, such as an ice cream container, as shown in  FIGS. 53 and 53A ; 
     a coaster as shown in  FIG. 54 ; 
     a pill and capsule such as shown in  FIGS. 55 ,  56  and  56 A; 
     a plate as shown in  FIG. 57 ; 
     a makeup compact as shown in  FIG. 58 ; 
     a rivet such as shown in  FIG. 59 ; 
     a coin as shown in  FIGS. 60 and 60A ; 
     a cracker such as shown in  FIG. 61 ; 
     a rotary phone dial as shown in  FIG. 62 ; 
     a tire as shown in  FIG. 63 ; 
     a chocolate chip cookie as shown in  FIG. 64  (this embodiment may comprise back-to-back cookies as shown or a single cookie); 
     a pizza as shown in  FIG. 65 ; 
     a bottle as shown in  FIG. 66 ; 
     a hockey puck as shown in  FIG. 67 ; 
     a golf ball as shown in  FIG. 68  (the ball may be spherical as in  FIG. 68 , or it may have a slimmer profile including convex surfaces or flattened convex surfaces as shown in the cross-sectional views of the housing  102  in  FIGS. 68A and 68B , respectively, to be more compact); 
     a basketball as shown in  FIG. 69  (the ball may be spherical as in  FIG. 69 , or it may have a slimmer profile including convex surfaces or flattened convex surfaces as shown in the cross-sectional views of the housing  102  in  FIGS. 69A and 69B , respectively, to be more compact); 
     a soccer ball as shown in  FIG. 70  (the ball may be spherical as in  FIG. 70 , or it may have a slimmer profile including convex surfaces or flattened convex surfaces as shown in the cross-sectional views of the housing  102  in  FIGS. 70A and 70B , respectively, to be more compact); 
     a tennis ball as shown in  FIG. 71  (the ball may be spherical as in  FIG. 71 , or it may have a slimmer profile including convex surfaces or flattened convex surfaces as shown in the cross-sectional views of the housing  102  in  FIGS. 71A and 71B , respectively, to be more compact); 
     a football as shown in  FIG. 72  (the ball may be shaped like an inflated football as in  FIG. 72 , or it may have a slimmer profile including convex surfaces or flattened convex surfaces as shown in the cross-sectional views of the housing  102  in  FIGS. 72A and 72B , respectively, to be more compact); 
     a baseball as shown in  FIG. 73  (the ball may be spherical as in  FIG. 73 , or it may have a slimmer profile including convex surfaces or flattened convex surfaces as shown in the cross-sectional views of the housing  102  in  FIGS. 73A and 73B , respectively, to be more compact); 
     a volleyball as shown in  FIG. 74  (the ball may be spherical as in  FIG. 74 , or it may have a slimmer profile including convex surfaces or flattened convex surfaces as shown in the cross-sectional views of the housing  102  in  FIGS. 74A and 74B , respectively, to be more compact); 
     a compact disk case as shown in  FIG. 99 ; 
     a book as shown in  FIG. 100 ; 
     a cereal box as shown in  FIG. 101 ; 
     a cigarette pack as shown in  FIG. 102 ; 
     laundry detergent containers as shown in  FIGS. 103 and 104 ; 
     a bar of soap as shown in  FIG. 105 ; 
     a bottle containing a beverage or alcohol such as shown in  FIG. 106 ; 
     a box for a bar of soap as shown in  FIG. 107 ; and 
     a match box as shown in  FIG. 108 . 
     It is understood that the above list is exemplary and it is understood that the outward appearance of the writing instrument  100  may have many other additional shapes and appearances in alternative embodiments. For example, the writing instrument may comprise a generic object, or slug, having blank covers and edges. Still further examples include a writing instrument  100  having a transparent cover affixed to the outer surface of cover  104  and/or  106 , into which transparent cover a photo or other picture may be placed. The outer surface of cover  104  and/or  106  may alternatively be coated with a material capable of accepting a fingerprint. In a still further example, the outer surface of cover  104  and/or  106  may include a material that changes color with a change in pressure or temperature. Such materials are known and used for example in so-called “mood rings”. In another embodiment, one or both covers may be coated with a fragrance in accordance with so-called “scratch and sniff” technology. Although the pen is shown in the above described figures as protruding from a side between two corners of the generally square-shaped embodiments, it is understood that the pen tip may alternative protrude from a corner where two sides come together. Moreover, it is understood that a writing instrument shaped or appearing as any of the above-described objects can operate in accordance with each of the above-described embodiments for extending and retracting the pen cartridge. 
     For example, the embodiment of  FIG. 48 , including a hole in the middle of the writing instrument, can operate with the cam assembly of  FIGS. 4-9 . This particular configuration is shown in  FIGS. 78-82  where writing instrument  100  includes a central hole  250 . As described above with respect to  FIGS. 4-9 , when the writing instrument  100  in  FIGS. 78-82  is assembled, the pen guide  128  lies between the respective covers  104  and  106 . Rotation of the second cover clockwise from the view of  FIGS. 80-82  with respect to the first cover causes rotation of the track  124  as shown. Rotation of the track  124  in turn causes translation of the track following section  132 , which is constrained to translate horizontally from the views of  FIGS. 78-82  as a result of the guide following sections  136  (not shown in  FIGS. 78-82 ) riding along the linear guides  126 . Thus, rotation of the second cover from the position shown in  FIG. 80 , through the position shown in  FIG. 81 , to the position shown in  FIG. 82  results in the writing end of the cartridge  138  moving from its retracted position to its extended position. 
     As stated above, each of the embodiments shown in  FIGS. 41-74A  can operate in accordance with any of the above-described embodiments for extending and retracting the pen cartridge. Therefore, the seam shown for example in  FIGS. 41 ,  41 A,  44 ,  45 ,  47 A,  48 ,  49 A,  51 - 56 A,  60 A- 65 , and  67 - 47 B can be between two rotationally engaged sections of the housing, or between two fixedly engaged sections of the housing. 
     It is understood that the outward shape of the writing instrument may take on various three dimensional shapes in alternative embodiments. For example, the instrument  100  may be cylindrically shaped, such as for example in the shape of a can or a bottle, or may be irregularly shaped, such as for example in the shape of a person, character or automobile. For such embodiments, the internal components according to the various embodiments described above for extending and retracting the pen cartridge may be housed within an internal compartment within the outer housing. (It may not be practical to use rotating components to extend and retract the pen cartridge in some of these alternative shape embodiments.) 
     In embodiments where the housing  102  is shaped for example like a bottle, a viscous liquid may be provided in a sealed area within the housing  102 , isolated from the internal compartment in which the extending and retracting components are located. In such embodiments, the liquid may create the impression of the liquid being poured from the bottle as the writing instrument is tilted downward to the writing position. Moreover, in for example the gravity-activated embodiment described above, a conventional damper may be employed to slow the movement of the pen cartridge as the pen cartridge extends from and retracts into the housing, thus creating the impression that the pen tip is being poured out of the housing  102 . 
     As set forth briefly above, while a preferred embodiment of the present invention relates to a writing instrument, it is understood that other tools may be mounted within housing  102 . Such tools can have an outer appearance of a familiar and/or proprietary object as described above, and can be extended and retracted in accordance with the various embodiments described above. For example, as shown in  FIGS. 75 and 76 , respectively, a screwdriver or cutting blade may be provided within housing  102 . Moreover, as shown in  FIG. 77 , a light source may be provided within housing  102 . In such an embodiment, in addition to extending and retracting the light source, the internal mechanisms can activate the light source when it is extended, and can deactivate the light source when it is retracted. It is further understood that the mechanisms for activating and deactivating the light source may be separate from those extending and retracting the light source. Further still, it is contemplated that the internal mechanisms merely activate and deactivate the light source, without extending or retracting it. 
     In further alternative embodiments, it is contemplated that writing instrument  100  include a wide variety of battery or solar powered electronics. In such instances the electronics can be activated upon extension or retraction of the pen cartridge. In addition to the light source describe above, the electronics may include a sound chip for emitting audible sounds, words and/or melodies. 
     It is an advantage of the present invention that it provides a much more effective promotional and marketing vehicle than that presented by conventional printing on the side of a writing instrument. This is so because the pen does not have the word “Oreo”® printed on its side, it is an Oreo®; it does not have a picture of an auto manufacturer&#39;s emblem on its side, it is the emblem; it does not have a picture of a Coca-Cola® bottle on its side, it is a Coca-Cola® bottle, or at least close replicas thereof. The present invention conjures a corporate image without having to read or study information printed on a side of a pen, and thus provides a more effective at-a-glance marketing tool than words or information about the object could ever be. Moreover, a writing instrument according to the present invention will have much greater value as a novelty item than conventional pens. 
     Although the invention has been described in detail herein, it should be understood that the invention is not limited to the embodiments herein disclosed. Various changes, substitutions and modifications may be made thereto by those skilled in the art without departing from the spirit or scope of the invention as described and defined by the appended claims.