WO2003070487A1

WO2003070487A1 - Retractable writing instrument

Info

Publication number: WO2003070487A1
Application number: PCT/CA2003/000230
Authority: WO
Inventors: Luc Marcel Lafond
Original assignee: Luc Marcel Lafond
Priority date: 2002-02-20
Filing date: 2003-02-20
Publication date: 2003-08-28
Also published as: AU2003206524A1

Abstract

A retractable writing instrument has an elongated body including two opposing hollow cylinders (12;2). One of the two cylinders is fixed to an ink reservoir (6) including a writing tip (8). The ink reservoir is housed within the hollow cylinders. The writing tip is retracted into the body when the cylinders converge along a common axis to a first position. The writing tip is extended from the body when the cylinders diverge along the common axis to a second position. In some instances, one of the cylinders defines a track (3) to direct relative movement of the two cylinders between the first and second positions. The other of the two cylinders defines a guide traveling along the track. A pocket clip is formed on one of the cylinders. A three piece retractable pen is made up of a movable cap mounted on a pen barrel, and a refill secured to either the cap or the barrel. When the cap is moved relative to the barrel, the refill is either extended from or retracted into the pen body. An optional flexible sleeve forming a finger grip may also be provided to act as a spring, under tension or under compression, to urge the cylinders to travel to the first or second positions. The writing instrument may also include a second retractable tip which points in a direction opposite to the first writing tip.

Description

RETRACTABLE WRITING INSTRUMENT

FIELD OF THE INVENTION

The present invention relates to an improved design for a retractable writing instrument, including a pen. More specifically, the invention is directed to an improved mechanism for retracting and extending a writing tip portion of the writing instrument. The writing tip portion may be retracted into the body of the writing instrument or extended outwardly for use.

BACKGROUND OF THE INVENTION Earlier pen designs include two major types of writing instruments: (1 ) stick pens having an exposed, fixed writing tip such as a ball point. A separate cap piece is used to cover the exposed writing tip. The cap is used to protect against accidental application of ink to unintended target surfaces. (2) retractable pen designs of various types. Many of those earlier retractable pen designs require many moving internal parts to provide a workable retraction mechanism. The presence of many parts adds to the cost of manufacture and to the final selling price of the writing instrument. Often, earlier retractable pen designs are also prone to accidental loss of inexpensive component parts which may be difficult or impractical to replace, if lost. An expensive retractable pen may become useless to the purchaser if one of those numerous, inexpensive parts is unavailable for replacement within the writing instrument.

Conventional pen designs are also plagued with other disadvantages. For example, with stick pens, pocket clips are usually featured as a component of the cap portion. If the cap is accidentally misplaced or lost, the exposed writing tip of the stick pen remains exposed and may no longer be safely stored in a person's pocket or elsewhere. Similarly, the loss of the cap will prevent the user from clipping the pen inside of a pocket and other similar storage space.

There is a need for a simplified pen design that provides cost advantages comparable with a simple, stick pen with relatively few parts. In addition, it is desirable to provide a relatively low cost retractable pen mechanism that offers the advantages of both a low cost stick pen design and an expensive pen retraction mechanism. It would be advantageous to provide an improved pen design offering one or more of these advantages, either alone or in combination with other indicated advantages or other advantages that will become apparent from a review of the following description.

SUMMARY OF THE INVENTION

In one aspect, the invention is an improved writing instrument. By way of example, the writing instrument may be a pen containing a reservoir having a writing tip. The reservoir may take the form of a refill, writing cartridge or preformed chamber for storing ink. The writing instrument comprises a hollow pen barrel that defines a longitudinal axis along the length of the hollow barrel. At one end of the barrel, a piston is rotatably and slideably mounted on the pen barrel. The piston rotates about the longitudinal axis, and " the piston is also capable of sliding along the axis. The piston operates between two positions defined along the longitudinal axis of the barrel.

The piston may take the form of either a plunger that extends into a cavity defined at the first end of the barrel, or the piston may comprise a cap piece that defines a cavity for receiving the first end of the pen barrel. The writing tip is housed within the cavity of the pen barrel. The writing tip is moved along the axis when the piston is moved between the first and second position.

One of either the piston or the pen barrel defines a track configured as a line segment having an offset extending in a direction across the axis. The track is formed on or in a curved side wall that is provided by either the piston or the pen barrel. The curved side wall surrounds the hollow core of the barrel. The other of the piston or the barrel defines a follower. The follower advances along the track in a first direction corresponding to extension of the writing tip from the pen barrel and a movement from the second position to the first position, representing retraction of the writing tip into the body of the cavity of the pen barrel. In a preferred case, the follower is a cylindrical pin having a circular cross section.

Movement of the piston between the first and second piston positions advances the follower along the track until the writing tip is exposed and the tip will write. Movement of the piston from the second piston position to the first piston position returns the follower along the track to the retracted, starting position. During the movement of the follower (which is preferably a pin) along the track between the first and second positions, the piston rotates about the longitudinal axis of the pen barrel. When the writing tip is extended, the piston rotates in a first direction about the axis. When the writing tip is retracted, the piston rotates in the opposite direction about the longitudinal axis of the pen barrel.

In another aspect, the track, which is configured as an offset line segment, may also be provided with one or more detents. One detent may be provided to correspond to an extended writing tip position. That is, the detent may urge the writing tip to remain in place to prevent accidental retraction of the writing tip back into the cavity of the pen barrel. A second detent may also be provided to urge the refill to remain in the fully withdrawn position. In a preferred writing instrument design, a single detent is provided to urge the refill to remain in a fully extended position. A second detent may also be provided to retain the refill within the fully retracted position. In a preferred embodiment, a biasing element, such as a spring, is not required to urge the refill back into the retracted position.

In another embodiment, the invention includes a linear track formed on one of two opposing hollow cylinders. A guide is formed on the second cylinder. The guide may take the form of a biased pin formed as part of a single work piece including the second cylinder. One of the two cylinders comprises a pen cap and the other cylinder comprises a pen barrel which is coaxially oriented relative to the pen cap. The guide travels along the linear track between first and second positions so that the two cylinders converge when the writing tip is extended. In traveling between the second and first positions, the two cylinders diverge when the writing tip is withdrawn into the interior of the pen body. The linear track may comprise one or more detents along its length to co-act with the guide, to urge the guide toward one or both of the first and second positions.

In another embodiment, the guide may be urged to remain within a designated position along the track by either providing a friction fitting between the guide and the track walls, or by providing an additional biasing element to urge the guide to remain within one or more selected positions along the track.

In a further embodiment, the additional biasing element may take the form of a spring component formed as part of a single work piece comprising one of the two hollow cylinders. In a preferred embodiment, the biasing element may be a compressible material with memory, forming a compressible sleeve extending between first and second retainers. One of the retainers projects from the first cylinder. The second retainer projects from the second cylinder. When the cylinders converge, the writing tip is extended from the pen body, the guide is moved to a detent, and the sleeve is compressed to load the spring of the sleeve. When the user wishes to retract the writing tip, the guide is urged away from the detent, and the loaded sleeve urges the two cylinders apart, returning the guide to the first position. In a preferred embodiment, the sleeve may comprise a relatively soft, textured and cushioned outer surface to provide a comfortable cushioned grip for the user.

In a further preferred embodiment, a three piece retractable pen design is provided which includes a piston or a cap cast from a suitable material such as a thermoplastic. The second piece is a pen barrel. The third piece is a refill. The refill may be secured to the piston or cap by inserting one end of the refill into a clamp-like recess formed within a centrally positioned cavity in the piston or cap. Either the cap, piston or the pen barrel may be provided with a pocket clip. By way of an example, the clip may be cast together with either the piston to form a single work piece, or the clip may be cast together with the pen barrel to form a single work piece. Of course, other embodiments are also possible. In a preferred embodiment, the pin may be urged to remain within a designated position along the track by either providing a friction fitting between the pin and the track walls, or by providing an additional biasing element to urge the pin to remain within selected positions along the track. In alternate embodiments, a friction fitting may also be provided between the piston body and pen barrel. The friction fitting may be provided in alternative ways to urge the refill to remain in the retracted position.

In another embodiment, it may be desirable to use a design in which the refill is not clamped to the piston. The piston may be used to push the refill from the retracted position to the extended position when the follower advances along the track. In this embodiment, if it is desired to urge the refill to return to the retracted position when the piston is also moved to the corresponding retracted position, the biasing element, such as a spring, may be used to urge the refill to return to the retracted position. In this instance, a simplified four piece pen design is possible. The complete writing instrument would include the rotatable and slidable piston, a pen barrel, a refill housed within the pen barrel and a biasing element to return the refill to the fully retracted position. Other embodiments are also possible and may be desirable in certain instances. IN THE DRAWINGS

FIG. 1 is a sectional view of one embodiment of the present invention showing the mechanism located within a writing instrument.

FIG.2 is a sectional view of one component of an embodiment of the writing instrument shown in FIG. 1. The component is shown in an open position.

FIG. 3 is a sectional view of the component shown in FIG.2, in which the component is now in the closed position.

FIG.4A is a partial sectional view showing one embodiment of the invention namely, one embodiment of the track. FIG. 4B is a partial sectional view showing another embodiment of a component of the retraction mechanism, namely, an embodiment of the track.

FIG. 4C is a partial sectional view showing another embodiment of a component of the retraction mechanism, namely, an embodiment of the track.

FIG. 4D is a partial sectional view showing another embodiment of a component of the retraction mechanism, namely, an embodiment of the track.

FIG. 4E is a perspective view of an end portion of pen barrel component of another embodiment of the invention, to be used in combination with a telescoping end cap of FIG.4F.

FIG.4F is a top view of one embodiment of a telescoping end cap to be combined with the pen barrel component of FIG.4E.

FIG. 4G is a side view, in partial section, of the pen barrel component of FIG.4E.

FIG.4H is a side view, in partial section, of the end cap of FIG.4F.

FIG. 5 is a sectional view of another embodiment of a retractable pen in which the writing tip is fully extended. FIG. 5A is a sectional view of the embodiment of FIG. 5 in which the writing tip is fully retracted.

FIG.6 is a partial sectional view of a further embodiment of a retractable pen in which the writing tip is fully extended. FIG. 6A is a partial sectional view of the embodiment of FIG.6 in which the writing tip is fully retracted.

FIG. 7 is a partial sectional view of another embodiment of a retractable pen in which the writing tip is fully extended. FIG. 7A is a partial sectional view of the embodiment of FIG. 7 in which the writing tip is fully retracted.

FIG. 8 is a side view of another embodiment of the present invention showing the writing instrument with the writing tip extended.

FIG. 9 is a top view of the writing instrument of FIG. 8 with the upper barrel rotated to retract the writing tip.

FIG. 10 is an enlarged side view of the lower barrel part of the writing instrument.

FIG. 10A is a perspective view of the lower barrel and guide pin in the embodiment of FIG. 10.

FIG. 11 is a side view of a flexible finger grip component of the writing instrument shown in FIG. 8.

FIG. 12 is a perspective view of a low friction bushing included in the writing instrument of FIG. 8.

FIG. 13 is a side view in partial section of the upper barrel component of the writing instrument of FIG. 8. FIG. 13A is a simplified representation of the track featured on the writing instrument of FIG. 8.

FIG. 13B is showing an end view, in perspective, of the track of the writing instrument of FIG.8.

FIG. 14 is partial sectional view of another embodiment of the invention, namely a retractable writing instrument having retractable writing tips at opposing ends of the writing instrument. DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

Fig. 1 shows a partial sectional view of an assembled writing instrument, namely, a pen in which the refill is shown in a fully retracted position. A pen body 2 includes a pen barrel 4 which defines a hollow core containing a refill 6. The writing tip 8 of the refill 6 is shown retracted within the pen barrel 4, inward of end 10 of the pen barrel 4.

The refill 6 is positioned along the longitudinal axis of the pen barrel 4. The writing instrument includes a third piece configured as a piston 12. The piston 12 includes a housing portion 13 which defines a cavity 9. End 1 of the barrel extends into the cavity 9 of the piston housing 13. The second end 20 of the refill 6 is secured within clamp 11. Clamp 11 is molded or cast from the same material that forms the piston. Preferably, the piston and pen barrel are cast from thermoplastic materials. The piston includes an integral clip portion 14 that is also cast from the same material as the body of the piston, to form a single work piece. The piston 12 also includes a hinged body 16. When in the closed position, the hinged body snaps into place so that inwardly projecting pin 5 engages with track 3 defined on the circular body of the pen barrel 4. In this embodiment, the track 3 is shown as extending through the wall of the pen barrel 4. (In other embodiments, the track may form a groove that does not extend through a wall.) By engaging pin 5 with the track 3, the piston is locked into position so that it may only travel along the defined tack 3. To remove the piston from the pen barrel 4, it is either necessary to break or deform pin 5 so that it disengages from track 3 or the hinged body 16 must be opened to extract pin 5 from within track 3.

Figs.2 and 3 further illustrate the features of the piston piece provided in the embodiment of Fig. 1. Fig.2 shows the piston 12 in the open position. Hinged body 16 flexes relative to the main body at hinge 18. Hinged body 16 includes a circular pin 5 projecting toward the inner chamber 9 of the piston 12 when hinged body 16 is in the closed position. Hinged body 16 forms a notch 17 to receive lock tab 15 formed on the main body of the piston 12. As shown in Fig. 3, when hinged body 16 is in fully closed position, retainer 15 engages notch 17 to hold the hinged body 16 in the closed position. In the closed position, circular pin 5 projects inwardly toward the chamber 9 defined by the piston 12. Pin 5 projects inwardly a distance sufficient to securely engage track 3 of pen barrel 4 (which is not shown in this figure). With reference to Fig. 2, clamping portion 11 defines a chamber 23 to receive the second end of the refill 6. The inner walls of the clamping portion 11 may be provided with directional teeth or projections 25 to snuggly engage the second end of the refill, to discourage accidental withdrawal or disconnection of the refill from the piston piece. Fig.4A, 4B, 4C and 4D show four embodiments of the track defined on the curved surface of the pen barrel 4. However, in other embodiments, the track may be defined on the inner curved surface of the piston housing 13. In that case, the pen barrel 4 would include an outwardly projecting pin to engage the track defined by the piston 12. In other embodiments not shown, the piston may take the form of a plunger rotatably sliding within the cavity of the pen barrel 4. In that case, the plunger (not shown) may either define the track 4 and outwardly projecting pin to engage the inner surface of the pen barrel 4.

With reference to Fig.4A, the track 3A is shown having a diagonal line segment 30 with detent portions 32 and 31 located at opposite ends of the track. The track is shown as a groove formed in circular pen barrel 4. End 31 of track 3A provides a detent to encourage pin 5 to remain in the fully retracted position. Similarly, the refill is encouraged to remain in the fully extended position also. Detent 32 is provided at the opposite end of track 30 to urge pin 5 and refill 6 to remain within the fully extended position. Fig.4B shows track 3B defined on pen barrel 4. Linear segment 37 of track 3B has an upper end 38, shown without a detent feature. In this embodiment, the pin may be configured and manufactured in an appropriate manner to provide a snug fit within the track 3B. A friction fitting may be used to retain the piston and the refill within the fully retracted position without necessitating the addition of a spring or other biasing element. Opposite end 39 of track 3B is offset from longitudinal straight section 37. Offset portion 39 may also be provided with a detent to urge the pin 5 and refill 6 to remain within the fully retracted position.

Fig.4C shows yet another embodiment of the track, shown as track 3C adjacent end 1 of pen barrel 4. The track 3C includes a linear longitudinal segment 41 having opposing offset end portions 40 and 42. Offset end portion 40 of track 3C is not provided with a detent. However, pin 5 may be manufactured to provide a friction fit with track 3C so that the piston and refill will not accidentally dislodge from the retracted position under normal operating conditions. Opposite offset end 42 may be provided with a detent to urge the piston and refill to remain in the fully extended position. The pin 5 will engage with a detent portion of track segment 42 to inhibit accidental displacement of the piston and refill from the fully extended position.

Fig.4D shows yet another embodiment of the track which may be defined adjacent end 1 of barrel 4. Track 3D includes a linear segment 35. End 34 of the track 3D corresponds to the fully retracted position of the piston and refill. The pin 5 may be configured and constructed in a manner suitable to provide a friction fitting with track 3D sufficient to retain the piston in a fully retracted position under normal operating conditions. Opposite end 36 of track 3D may be offset and angled to provide a detent feature to encourage pin 5 to remain in the extended position.

In the four embodiments illustrated in Figs.4A, 4B, 4C and 4D it will be understood that the pin advances along the track following a path that represents a translational movement parallel to the longitudinal axis and a rotational component representing movement about the axis. When the pin moves from a first position corresponding to a fully retracted pen tip, to a second position corresponding to a fully extended pen tip, the pin advances in the first direction along the track. When it is desired to retract the pen tip, the path of the pin along the track is reversed through each of the track segments of the track until the pen tip is fully retracted within the body of the pen barrel.

Figs.4E, 4F, 4G, and 4H illustrate another embodiment of the invention in which a pen barrel 4' cooperates with a telescoping end cap 12', defining a linear path for retraction and extension of a pen refill 6'. With reference to these figures, telescoping end cap 12', includes an integral clip portion 14', and defines an inner chamber or hollow core 9' having a diameter slightly larger than the outer diameter of pen barrel 4'. The pen barrel may also fit snugly within the end cap to provide a slide-fit. In this embodiment, end 94' of pen barrel 4' fits within inner chamber 9'. A spring mounted pin 55 projects upwardly from the outer surface of the pen barrel 4'. The pin 55 is positioned on a hinged, flexible and resilient arm 50' which urges the pin 55 outwardly away from the surface of the pen barrel 4'. When end 94' of pen barrel 4' is aligned with, and inserted into, the opening of chamber 9' of the end cap 12', the pin 55 first engages with detent 39', corresponding to a position at which the writing tip of the refill 6' is retracted. The end 94' of pen barrel 4' may be urged further into the end cap 12' by telescoping the end cap and barrel together along a common longitudinal axis. Upon applying an appropriate force, the end cap will converge with the pen barrel until the pin engages another detent 38' corresponding to a fully extended position of the writing tip of the refill 6'. In this embodiment, the pen barrel 4' defines a projecting linear track component 93 which engages with a corresponding recessed linear channel (not shown) formed on the inside surface of chamber 9' of the end cap. Pen barrel 4' also has a hollow core 99' to receive the refill 6'. Refill 6' is securely held within a clamp 11' formed within a single work piece of the end cap. The clamp 11' comprises a plurality of inwardly projecting teeth to engage the open end of the refill 6'. The track may also include stops or other features (not shown) to urge the end cap to travel along a desired path, of limited length, defined along the longitudinal axis of the pen barrel. The embodiments illustrated in Figs. 4A, 4B, 4C, 4D, 4E, 4F, 4G, and 4H are merely illustrative. Other embodiments and configurations of the track are possible and are included within the scope of the invention.

It will be appreciated that in the preferred embodiment, the barrel and the piston (and particularly the pin) will be manufactured from relatively resilient materials that exhibit low wear under typical operating conditions. In some embodiments, it may be preferable to select materials of manufacture so that the pin when positioned within the track provides for a relatively snug friction fitting that can resist accidental displacement of the piston (and the refill). However, such a friction fitting would not be necessary in other embodiments comprising a combination of detent features and an optional biasing element such as a spring to urge the refill to move to a preferred position.

In other embodiments of the invention, it will be possible to provide equivalent mechanisms in which the pin is provided on the interior wall of the pen barrel (not shown). In such an embodiment, the track may be defined on the outer surface of the plunger positioned within the internal cavity of the pen barrel. In yet another embodiment, a modified plunger would operate within a channel defined within the cavity of the pen barrel. In this embodiment, the plunger would define an outwardly projecting pin that would engage with a track defined by the pen barrel (similar to the embodiment shown in Fig. 1).

In the embodiment illustrated in Fig. 5, 5A, the writing instrument comprises a first tubular member 101 with outer threads 105 at the top end, and a second tubular member 102 with matched inner threads 103. Threads 105 work in conjunction with inner threads 103. The second tubular member 102 has at its top a cavity 108, smaller in diameter than the diameter of the open end 104 of the ink refill 106. The refill 106 is held firmly at its open end 104 in the cavity 108 and is rotated along with the second tubular member 102. The writing tip 107 extends beyond the finger grip 109 of the first tubular member 101 when the second tubular member 102 is fully rotated in a first direction. The writing tip is retracted into the first tubular member 101 when the second tubular member is fully rotated in the opposite direction. A stopper, not shown, may be used to limit the extent to which the first and second cylinders may be separated by rotation.

With reference to Fig. 6, 6A, the illustrated writing instrument comprises a tubular member 121 and a rotating finger grip 129 with outer threads 125 engaged with inner threads 123 provided on the tubular member 121. The tubular member 121 has a cavity 128 which is press fit or uses gripping means, to firmly hold the open end 124 of the refill 126. The cavity 128 provides a clamping element to secure the refill relative to tubular member 121. When the finger grip 129 is rotated in a first direction, the finger grip 129 moves away from the tubular member 121, along a path defined by the interaction of the matched threads 123, 125, until the writing tip is retracted and covered within finger grip 129. A stopper, not shown, may be used to prevent the finger grip 129 from being accidentally separated away from tubular member 121 during normal use. However, the stopper may be designed to completely release the finger grip 129 from the tubular member to permit change of the refill 126. The finger grip 129 is rotated in the opposite direction, until the grip abuts against the shoulder 120 on tubular member 121 , to expose the writing tip 127.

In other embodiments, the refill 126 may be grasped anywhere along its length. It is not essential that the refill 126 be held at its open end 124. Similarly, a track whether embodied in the form of threading, an offset linear channel, a telescoping arrangement, or otherwise, may be located at various positions along the length of the writing instrument. Cavities 108, 128 and the holding means along the refill may be designed to have gripping jaw features, be tightly press fit, or use patterned or anti-slip materials, or be glued, fastened, or threaded to hold firmly the refills 106 and 126 in the corresponding tubular members 101, 102, 121. Inner threads 103, and outer threads 105 can be reversed from right hand to left hand threads, and from inner threads to outer threads, to achieve a suitable movement between the tubular member and finger grip. In other embodiments, the track forms a telescoping movement. The track may be of various suitable shapes and configurations to co-act with a guide (such as a pin) to direct the relative movement between the tubular member and the finger grip. A detent (which may include a locking mechanism) may be provided to hold the writing tip in the extended or retracted positions.

With reference to the embodiment of Figs.7, 7A, the writing instrument comprises a tubular member 131 and a rotating finger grip 139 with inner threads 133. The tubular ^• member 131 has at the writing end, outer threads 135 that engage with the matching threads 133 of the rotating finger grip 139. When the rotating finger grip 139 is rotated in a first direction, it moves away from the shoulder 140 and covers the writing tip 137 of the refill. The rotating finger grip 139 is rotated in the opposite direction, until it abuts against shoulder 140, to expose the writing tip 137. The conventional refill may also be replaced by a refillable reservoir defined by either the finger grip portion, or by the tubular member. The finger grip portion will be in fluid communication with the reservoir, to supply ink from the reservoir, to the writing tip. In other instances, the refill may take the form of a conventional, self contained reservoir and ink supply with a suitable writing tip.

Fig. 8 shows an assembled pen body and related mechanism for retracting and extending a writing tip from the pen body. In general, the mechanism described herein operates between two positions: a first position in which the writing tip of the refill is fully retracted, and a second position in which the writing tip of the refill is extended from within the pen body to a sufficient extension to allow the user to write with the pen. The details of that operation are described in greater detail below.

The pen body 201 includes a lower barrel or housing 230, and an upper barrel or housing 260, a flexible finger rubber grip sleeve 240, and a low friction ring 250, and a refill 203. In Fig. 8 the pen is in the extended position. In Fig. 9 the upper barrel is rotated in a first direction by a one-quarter turn, positioning the refill in its retracted position.

The dotted lines in Fig. 8 and Fig. 9 show the lower barrel assembled together, in rotational relation to the upper barrel. The barrel portions are held together by the pin 232 which travels along track 262. The pin 232 is shown as being located in detent 268 at the end of the track 262. The features of track 262 are shown in greater detail in Fig. 13. In the Fig.8, the upper barrel 260 is shown in partial section, to show that the refill 203 is securely engaged within cavity 265. The cavity 265 is of a smaller diameter than the outside diameter of the open end of the refill 203, to firmly grasp the refill. The refill 203 and its writing tip 202 are rotated by rotating upper barrel 260 relative to lower barrel 230. The writing tip is extended or retracted when the upper barrel 260 is turned in the clockwise or counterclockwise directions.

Fig. 10 shows a side view of the lower barrel 230 and the guide pin 232. Guide pin 232 engages in slot 262 of the upper barrel 260 to direct the relative movement of the upper and lower barrels during extension and retraction of the writing tip of refill 203. The flexible finger grip 240 is in the shape of a sleeve which fits over the outer diameter of the lower barrel 230 and is slideable to act as a compression spring. The end 241 of grip 240 engages with abutment 236 of the lower barrel tip 231, and the end 242 is engaged with low friction bushing 250. Fig. 10A is a perspective view of the lower barrel 230. The lower barrel has a hollow middle core 233 to permit free movement of the refill 203 within lower barrel 230. In this illustrated embodiment, the pin 232 is an integral molded part of the lower barrel 230, made from the same work piece. In other embodiments, a suitable guide, whether a pin or some other follower, may be connected to one of the barrels by a press fit, glue or mechanically suitable means.

The flexible grip 240 is a sleeve made from any of a number of suitable compressible materials, including but not limited to silicones, polyurethanes or rubbers. To provide the desired spring action, the material should be compressible (or stretchable, where used as a tension spring) and have a good memory. A low friction bushing 250 or washer or disc, is provided between the face 242 of the flexible grip 240, and the face 263 of the upper barrel 260 to minimize frictional resistance to the rotational force exerted by the user when turning the upper barrel 260 to retract or extend the writing tip 202. The low friction bushing 250 has an inside diameter 252 slightly larger than the outside diameter of the lower barrel 230 to permit the bushing to slide freely during the extension and retraction of the writing tip 202. The low friction bushing 250 has a slot 251 to permit the bushing to slide over the pin 232 when assembling the upper barrel 260 with the lower barrel 230.

To replace the refill 203 and to assemble the lower barrel 230 with the upper barrel 260, a track of three segments 266, 267 and 262 is provided for initial access and engagement of the pin with the track, and to thereafter guide the pin 232 during operation of the writing instrument. Track segment 266 provides an access to (or egress from) the primary, operative segment 262 of the track. The track 262 extends beyond the detent 268 and retaining wall 264 to communicate with the track segment 267. The track segment 267 in turn communicates with track 266 to provide a path for a guide to permit operation of the assembled pen, and to allow disassembly and replacement of the refill, when required. Track 266 is shown as being parallel to wall 264 and flared open at the corresponding end of upper barrel, edge 263. The three track segments, 262, 267, 266, can be cut so that they extend completely through the wall of upper barrel 260, or they may be grooved to a sufficient depth on the inside wall of barrel 260, to provide an intact and uncut outer cylindrical wall 261 for aesthetics and strength. To assemble the upper barrel 260 with the lower barrel 230, the entry track 266 is aligned and engaged with the pin 232 .The upper barrel 260 is then forced towards lower barrel 230 , along their common longitudinal axis, compressing the finger grip sleeve 240. The pin 232 travels along track 266 until pin 232 enters slot 267. The upper barrel 260 is then rotated counter-clockwise. The pin 232 is guided along track 267 until the pin reaches the end of the track segment 267, pin 232 has now passed the wall 264. The force on the upper barrel 260 is then released and the flexible grip 240 relaxes and pushes the upper barrel 260 away from the lower barrel 230 until the pin 232 contacts and engages detent 268. The pen at this time is assembled and in the extended position as shown in Fig. 8. in the embodiment shown in Fig. 8 and Fig. 10 the lower barrel 230 includes the pin 232 which projects away from the generally cylindrical outer surface of the lower barrel 230. The inner surface of the upper barrel 260 is provided with a recessed track 262. Track 262 acts as a guide for the travel of the pin 232 during rotation of the upper barrel 260 between the extended and retracted positions for the writing tip 202. The track 262 is a channel cut or grooved into the inside wall of the upper barrel 260. In this embodiment, the track does not cut completely through the wall of the upper barrel. Of course, other such embodiments featuring tracks cut through a barrel portion are possible. With referenced to the illustrated embodiment, the track 262 guides the pin 232 during the rotational movement of the upper barrel 260 from the retracted position 269 to the extended position 268, and from the extended position 268 to the retracted position 269. The cycle may be repeated numerous times over the life of the pen. Of course, the pen may be designed for extended use by allowing users to replace spent ink refills including ink cartridges and other components. With reference to Fig^'. 10A, pin 232 is shown as a generally circular, cylindrical post projecting from the curved outer surface of lower barrel 230. The outer surface of lower barrel 230 is complimentary to the generally curved inner wall of the upper barrel 260 to allow smooth relative rotation of the barrel portions about the longitudinal axis of the assembled pen barrel.

Preferably, the pin 232 is shaped to avoid sharp corners or edges that might otherwise interfere with the smooth operation of the pin 232 within the track 262.

Reference is again made to Fig. 8 and Fig.9. When the upper barrel 260 and the refill 203 are in the retracted position, the pin 232 is located in position 269 of the track 262. The tip 202 of the refill 203 is fully retracted within the tip 231 of the pen barrel 230. The retracted position 269 corresponds to a detent.

The track 262 includes a channel generally spiraled that extends between position 269 and the end of the spiraled track section 268. Section 268 also provides a detent for the extended position. When the upper barrel 260 is rotated clockwise, the pin 232 travels from detent 269 to detent 268 along the track 262.

Force exerted by the user, to compress the sleeve, when the pin 232 is advanced along the track 262 from the fully extended position, to fully retracted position, and the pin 232 is engaged with the detent 268. Preferably, the compression is linear and the washer 250 slides against the edge 263 of the upper barrel 260 and prevents the flexible grip from rotating relative to the lower barrel. Once the pin 232 reaches and engages the detent 268, the lower barrel 230 and upper barrel 260 cannot disengage (without added force from the operator) and the writing tip will remain in the extended position. The barrel portions are held in that position by the pressure exerted by the compressed flexible sleeve 240. The flexible sleeve 240 provides a biasing force between the retainers formed by edges 236 and 263, thereby urging the pin 232 to stay positioned in detent 268.

It will be appreciated that in the preferred embodiment, the barrels 230 and 260, and particularly the pin 232 will be manufactured from relatively resilient, low friction materials that exhibit low wear under typical operating conditions. In other embodiments of the invention, it will be possible to provide equivalent mechanisms in which the pin is provided on the interior wall of the upper barrel (not shown) and the track is defined on the outer surface of the lower barrel. In this example, the pin would rotate with the upper barrel. The track may be configured to reverse the order of the rotational movement. Tracks of various shapes are also possible. The position of the track and pin may be located anywhere along the length of the pen. Furthermore, the sleeve may be connected to the upper and lower barrel segments to act as a spring under tension. For example, the sleeve may be suitably anchored to both barrel segments so as to provide the desired bias to the travel path of the guide within the track.

With reference to Fig. 14, two of the embodiments previously described herein, have been assembled back-to-back to provide a double-ended retractable writing instrument. The upper barrel 260 of Fig. 13 has been duplicated into two mirror image portions connected to form a single pen body. The assembled pen body is essentially symmetrical about a central plane which dissects the longitudinal axis of the pen body. An intermediate, double ended barrel 270 is assembled for rotational movement relative to two opposing outer barrels identified as 271 and 271a. A wall 280 separates the two cavities 265 and 265a and the two refills 203 and 203a. The clip 290 is optional and is attached to the outer barrel at either end of the pen body. The outer barrels are not necessarily the same length. One of the outer barrels may be made shorter at one end of the instrument to hold a different writing tip, refill, or stylus suitable for use with computers, accessories and the like. It will be appreciated that other variations of the retraction mechanism including other variations in configurations of the track will be apparent to a skilled person in the art. The description of the embodiments herein is intended to be illustrative of preferred and other embodiments and is not intended to be limiting. Other variations and modifications to the described invention will become apparent to those skilled in the art. It is intended that those modifications and variations will be included within the scope of any patent granted for this invention.

Claims

I CLAIM:

1. A retractable writing instrument comprising:

A first elongated hollow cylinder aligned with a second elongated hollow cylinder, the first and second cylinders traveling between first and second positions along a common longitudinal axis;

An ink reservoir comprising a writing tip and being housed within the first and second hollow cylinders, the reservoir being secured to one of the first and second cylinders; and

The first and second cylinders converge when in the first position, exposing the writing tip, and the cylinders diverge when in the second position, retracting the writing tip.

2. The retractable writing instrument claimed in claim 1 wherein the first cylinder travels along a track defined relative to the second cylinder.

3. The retractable writing instrument claimed in claim 1 or 2 wherein the first and second positions are defined by a track, the track being defined by the second cylinder, and the first cylinder defines a guide for traveling along the track.

4. The retractable writing instrument claimed in claim 2 or 3 wherein the track comprises a detent corresponding to one of the first and second positions.

5. The retractable writing instrument claimed in claim 4 wherein the track comprises a second detent corresponding to the other of the first and second positions.

6. The retractable writing instrument claimed in claim 3 wherein one of the first and second cylinders defines a clamp for securing the reservoir to the one of the first and second cylinders.

7. The retractable writing instrument claimed in claim 1, 2, 3, 4, 5, or 6 wherein one of the two cylinders comprises a pocket clip.

8. The retractable writing instrument claimed in claim 7 wherein the one of the two cylinders and the pocket clip are made from a single work piece.

9. The retractable writing instrument claimed in claim 3, 4, 5, or 6 wherein the guide and the first cylinder are made from a single work piece.

10. The retractable writing instrument claimed in claim 3, 4, 5, 6 or 9 wherein the first cylinder defines a main first body connected to the guide by an intervening spring section for biasing the guide toward a pre-selected position.

11. The retractable writing instrument claimed in claim 3, 4, 5, 6, 9, or 10 wherein the guide fits snugly within the track.

12. The retractable writing instrument claimed in claim 3, 4, 5, 6, 9, 10, or 11 wherein the guide comprises a pin projecting into the track.

13. The retractable writing instrument claimed in claim 7 or 8 wherein the guide comprises a pin projecting from the pocket clip.

14. The retractable writing instrument claimed in claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or 13 wherein movement between the first and second positions corresponds to rotational movement of one of the two cylinders relative to the other of the two cylinders.

15. The retractable writing instrument claimed in claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, or 14 comprising a flexible sleeve forming a finger grip surrounding an outer wall of at least one of the first and second cylinders.

16. The retractable writing instrument claimed in claim 15 wherein the flexible sleeve defines a spring urging relative movement of the first and second cylinders toward either the first or second position.

17. The retractable writing instrument claimed in claim 15 or 16 wherein the flexible sleeve, when compressed, urges movement of the first and second cylinders toward the first position.

18. The retractable writing instrument claimed in claim 15 or 16 wherein the flexible sleeve, when stretched, urges movement of the first and second cylinders toward the first position.

19. The retractable writing instrument claimed in claim 15, 16, 17, or 18 wherein the flexible sleeve is cushioned.

20. The retractable writing instrument claimed in claim 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 , 12, 13, 14, 15, 16, 17, 18, or 19 wherein the reservoir is an ink refill.

21. The retractable writing instrument claimed in claim 20 comprising a second refill having a retractable second tip pointing in a direction away from the first writing tip.