WO2003101757A2

WO2003101757A2 - Writing instrument with silent clicker mechanism

Info

Publication number: WO2003101757A2
Application number: PCT/CA2003/000794
Authority: WO
Inventors: Luc Marcel Lafond
Original assignee: Luc Marcel Lafond
Priority date: 2002-05-30
Filing date: 2003-05-29
Publication date: 2003-12-11
Also published as: AU2003232540A8; AU2003232540A1; WO2003101757A3

Abstract

A writing instrument is provided with a retractable writing tip (25) moving between a first retracted position (9) and a second extended writing position (6). The writing instrument may be a retractable pen or a pencil. The writing tip (25) is extended for writing, or retracted when not in use, by moving a track follower (1,46) along a track (4). The track is shaped as a closed loop. The writing instrument preferably includes a hollow barrel (12) and a piston (9) connected to the barrel. The writing tip is provided on a writing cartridge housed within the hollow barrel. The piston is activated to move the follower along the track and to move the writing tip between the retracted and extended positions. The track may be a heart-shaped recess located on a surface of one of the piston or pen barrel. The track follower is located on the other one of the piston and pen barrel. Preferably, the track has four returns to guide the follower in a desired direction along the track.

Description

WRITING INSTRUMENT WITH SILENT CLICKER MECHANISM

The present invention relates to an improved retractable pen design. More specifically, the invention is directed to an improved mechanism for retracting and extending the cartridge or refill portion of the writing instrument into the body of the writing instrument.

BACKGROUND OF THE INVENTION

Many earlier pen designs require a multiplicity of moving internal parts to provide a workable retraction mechanism. The use of many parts necessarily adds to the cost of manufacture and ultimately, the selling price of the manufactured pen product. In addition, some performance characteristics or properties may be compromised if numerous parts are used, particularly if manufacturing tolerances and other specifications allow for considerable play between interacting component parts. Among other things, earlier pen designs often generate significant audible clicking noises when the pens are activated to either extend or retract the writing cartridge or refill. In some instances, it may be desirable to reduce operating noises and offer a writing instrument that operates with a smooth, noise free retraction and extension mechanism.

There is a need for a simplified pen design that provides an improved mechanism with improved cost advantages, improved operating characteristics and simplified design features. Alternative advantages are also desirable and possible. It would be advantageous to provide a pen retraction mechanism offering one or more of these advantages, either alone or in combination with the 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 writing cartridge or refill. The writing instrument comprises a hollow pen barrel that defines a longitudinal axis extending along the length of the hollow barrel. At one end, a piston is rotatably mounted on the pen barrel. The piston rotates about the longitudinal axis. The piston also operates between two positions defined along the axis. The piston may be a plunger that extends into a cavity defined at the first end of the barrel. Alternatively, the piston may comprise a cap that defines a cavity for receiving the first end of the barrel. The refill extends along the axis toward the other end of the pen barrel. One of either the piston or the pen barrel defines a track configured as a closed loop. The track is a closed loop formed on a curved side wall of 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 pen barrel defines a follower that advances along the track in a single direction. Preferably, the follower is a circular cylindrical pin.

In one piston position, the writing tip is retracted into the pen barrel. In the.retracted position, the tip cannot write. In the second piston position, the tip is extended outwardly from the pen barrel. In this position, the tip will write.

Movement of the piston between the first and second piston positions advances the follower along the track. For example, as the follower (preferably a pin) advances from the first to the second positions, the piston rotates in a first direction above the longitudinal axis. At the same time, the writing tip is moved from the retracted position to the extended position. Movement of the piston from the second position to the first position advances the follower along the track. In this step, the piston rotates in the opposite direction about the axis. The follower advances along the track and returns to its starting position, corresponding to the first piston position.

In another aspect, the track may be configured as a generally heart-shaped closed loop. The closed loop may be provided with two detents. A first detent may correspond to a first piston position. The second detent may correspond to the second piston position. In addition, the track may be provided with returns to direct the follower to advance in the desired direction along the track. Preferably, four returns are provided in the closed loop.

In a further aspect, the writing instrument comprises: a retractable writing tip moving between a first retracted position and a second extended writing position; a track defining a closed loop; and a track follower operatively associated with the track for moving the writing tip between the first and second positions.

In yet another aspect, the writing instrument may be a retractable pencil. The writing cartridge may be a replaceable pencil lead refill.

In some embodiments of the invention, it will be desirable to provide two or more corresponding tracks and followers located at offset positions along the axis of the pen barrel. The multiple tracks and followers would be suitably configured so that the multiple followers would simultaneously advance along their corresponding tracks, engage their returns at the appropriate time, and come to rest at their intended positions along their tracks. It will be appreciated by those skilled in the art that it will be preferable to position the multiple tracks and followers so that the piston will be balanced for smooth operation during movement between a first retracted position and a second extended position.

It is also preferable that the writing instrument be provided with a biasing element acting in a direction opposite to the direction represented by movement from the first piston position to the second piston position. The biasing element may take the form of a spring acting on the refill to urge the refill to return to the retracted position. Other embodiments are also possible and may be desirable in certain instances.

IN THE DRAWINGS

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

FIGURE 2 is a sectional view of the upper and lower portions of the preferred writing instrument of FIGURE 1.

FIGURE 3 is an enlarged, partial sectional view of a portion of the retraction and extension mechanism of the embodiment shown in FIGURES 1 and 2. FIGURE 4 is an enlarged perspective view of a component of one embodiment of the invention, namely a plunger element.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

Fig. 1 shows a partial sectional view of a preferred embodiment of the upper portion of a pen body 20. The complete pen body and related mechanism are shown in Fig. 2. In general, the preferred mechanism described herein operates between two positions: a first position in which the writing tip of the cartridge is fully retracted, and a second position in which the writing tip of the cartridge is extended from within the pen body to an extent sufficient to allow the user to write with the pen. The details of that operation are described in greater detail below.

Pen body 20 includes an outer barrel or housing 12. The refill or cartridge 11 is loosely fit within port 10 provided at a position somewhere within the plunger 9. (For reasons that will become apparent based on the description provided below, the refill 11 is loosely fit within port 10 to allow the plunger to rotate freely of the refill 11. If the refill is snugly fit within port 10, there will be a tendency to induce rotation of the refill upon rotation of the plunger. That in turn, may lead to undesirable resistance from the spring 31 described further below.) It will be appreciated that the pin 1 , when captured within the track 4, will restrict upward displacement of the plunger. That is, the upward limit of the track (corresponding in this embodiment to detent S) will limit the upward displacement of the pin (and in turn the plunger) caused by the upward force exerted by the spring 31. An optional ring 18 or other retainer may be provided to resist any excessive forces that might otherwise lead to failure or breakage of the pin. The retainer 18 travels within the upper limit 17 and lower limit 28 of annular recess 15. Of course, alternative retainer configurations may be employed.

In the preferred embodiment, the plunger 9 will be designed to utilize a minimum amount of material to manufacture the plunger. The plunger 9 may be cast or otherwise manufactured to employ an economical amount of material. In the pictured embodiment, the plunger 9 is positioned within the housing 12. In other embodiments, it will be possible to provide a comparable actuating component in the form of a cap mounted on the exterior of the housing (not shown).

In the embodiment shown in Fig. 1 , the plunger 9 includes a pin 1 which projects away from the generally cylindrical outer surface of the plunger 9. The inner surface of the housing 12 is provided with a recessed track 4 that acts as a guide or track for the travel of the pin 1 during activation of the plunger 9. The track 4 is a cavity that is preformed to guide the pin during the corresponding movement of the plunger 9 and refill 11 from the retracted position S to the extended position 6, and from the extended position 6 to the retracted position S. 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 cartridges, including refills. Preferably, the pin will be 'slide-fit' within the track with relatively small clearances between the pin and the track walls to provide for a snug fit, while avoiding significant frictional resistance as the pin advances along the track. For example, the clearances between the pin and the track walls will be about 0.005 inches to 0.010 inches (0.127 mm to 0.254 mm).

With reference to Fig. 3, pin 1 is shown as a generally circular, cylindrical post projecting from the curved outer surface of plunger 9. The pin 1 is shown positioned within a portion of the curved, heart shaped track 4. The outer surface of plunger 9 is complimentary to the generally curved inner wall of the pen barrel 12 to allow smooth rotation of the plunger about the longitudinal axis of the pen barrel. The pin is shaped to avoid the presence of sharp corners or edges that might otherwise detract from the smooth operation of the pin 1 within the track 4. Reference is again made to Fig. 1. When the plunger 9 and the refill 11 are in the retracted position, the pin 1 is located in the position marked S on the track. The tip 25 of the writing refill is fully retracted within the tip 22 of the pen barrel 12. The retracted position S corresponds to a detent.

The illustrated embodiment of the invention provides a generally heart shaped track 4. The track includes a generally straight, downwardly directed channel that extends between position S and the end of the straight track section 8. When the plunger is depressed (activated), the pin 1 travels downwardly from detent S to point 8 along the track 4. As the plunger 9 is further depressed, the plunger rotates relative to the pen barrel 12 in a clockwise direction. The downward force exerted by the user on the plunger 9, and in turn the pin 1, causes the pin (and plunger) to rotate in the described manner along the first return presented by the curved track wall between points 8 and 5. As the pin reaches the first return adjacent point 5, the pin and plunger will remain in the position 5 if excessive force is applied by the user, or if the plunger is released, the spring 31 will urge the pin 1 and plunger 9 to rotate in a clockwise manner, diagonally upwardly to the position 6. As the operator depresses the plunger 9 and the pin 1 reaches point 5 along the track 4, the operator senses that the plunger 9 can not be depressed any more in the downwardly direction. Consequently, the operator will realize that it will be appropriate to release the plunger 9. The spring 31 provides a biasing force to urge the pin 1 and plunger in a generally upwardly direction within the channel 4.

When the plunger 9 is released by the operator, the spring 31 will urge the pin 1 (and in turn the plunger 9) in a generally upwardly and clockwise direction (about the axis of rotation of the plunger). That is, the pin 1 will be urged to rotate in a clockwise direction (about the rotational axis) through the interaction of the first return R^ along the track, between points 8 and 5 and the second return R₂ presented on central island portion 3. Central island portion 3 forms the central boundaries of the track 4. The interaction of return R₂ (along the track 4) on the pin 1 urges the pin to rotate and travel to detent position 6. The upward force presented by the spring 31 acting on the refill 11 at spring stop 19 causes the pin 1 and plunger 9 to come to rest within the position corresponding to detent 6. The detent position 6 corresponds to the extended position in which the pen tip 25 is exposed for writing. When the operator decides to retract the pen tip 25 to the fully retracted position S, the operator depresses the plunger 9 (and in turn pin 1), causing the pin to rotate and travel in a downwardly, diagonally clockwise direction to the third return R₃ on track 4. At point 7 along the third return R₃ on the track, the operator will sense increased resistance to further depression of the plunger and pin, presented by the return at point 7. The operator will release the plunger, thus allowing the spring to urge the pin (and in turn the plunger) to travel in a generally, upwardly diagonal direction back along edge 14 to the fourth return R₄, to detent position S, corresponding to the fully retracted position. When travelling from between about point 7 to the detent position S, the plunger will be rotating in a counterclockwise direction relative to the axis of rotation of the plunger. The axis of rotation corresponds to the longitudinal axis of the pen barrel in this embodiment.

As the pin advances along the closed loop track, the pin also rotates about the longitudinal axis of the pen barrel. Although this embodiment is described with respect to a particular direction of travel of the pin along the track, the loop may be configured so that the pin will advance in the opposite direction along the modified track.

With reference to the preferred embodiment, the configuration of the track, detents and the returns will affect the tendency of the retraction and extension mechanism to generate a clicking noise associated with travel of the pin, within the track, and particularly when it comes to rest at the detents. By way of example, it is preferable that the radius of each of the returns should be greater than the radius of the pin 1. If the radius of the returns or detents is approximately equal to, or less than the radius of the pin, there will be a tendency of the pin to generate an audible click as the pin comes to rest at the detents or passes by the returns. The configuration of the second and third returns R₂ and R₃ will also affect the tendency of the pin to generate an audible clicking noise. For example, the returns may be configured to reduce the tendency of the spring 31 to accelerate the pin as it approaches the terminus of each return. For example, the start point of return R₂ may be located a relatively short distance away from the point 5, so that the pin will not be accelerated over an extended distance upon upward motion induced by the action of the spring. Similarly, the return R₃, adjacent point 7 includes the curved outer edge of the track, between point 7 and detent S.

It will be appreciated that in the preferred embodiment, the barrel and plunger (and particularly the pin) will be manufactured from relatively resilient, low friction materials that exhibit low wear under typical operating conditions. In some embodiments, it may also be desirable to provide a bushing or a roller (not shown) on the pin to reduce friction as the pin travels along the track. The bushing or roller will spin about the axis of the pin when the bushing or roller contacts a wall of the track.

Fig. 4 illustrates one simplified embodiment of a plunger body 40. The plunger 40 is intended to be inserted within a corresponding cavity defined by a pen barrel. The plunger 40 is preferably made from a flexible, yet resilient material. For example, the plunger may be made from a thermoplastic material.

The plunger 40 is generally a hollow circular cylinder (or sleeve) that defines an opening 41 to receive a pen refill at one end. The plunger 40 has a top surface 42 at the other end to receive pressure applied by an operator's thumb or finger. A flexible tongue 44 may be deflected inwardly toward the hollow core of plunger 40 upon insertion of the plunger into the pen barrel. The entry to the pen barrel may be also be bevelled to gently urge or deflect the tongue 44 and pin 46 inwardly, as the pin impacts against the outer edge of the pen barrel during insertion of the plunger into the barrel. The tongue and pin will be deflected inwardly as the plunger proceeds into the cavity of the pen barrel. The tongue is defined by a U-shaped cut 43 about the periphery of the tongue 44. A cylindrical pin 46 projects outwardly from the curved surface of the plunger. It will be understood that the tongue will spring back to its preferred position when the pin 46 nests within the track defined by the pin barrel.

Additional features may be added to improve the performance of the plunger component. For example, the topmost surface of the plunger, which is most likely to be contacted by the operator's thumb or finger, may include a freely rotating top. The rotating top, not shown, would allow the operator to maintain downward pressure on the plunger without sensing the rotational movement of the plunger while in skin contact with the plunger. In another optional variation or modification to the plunger (not shown), the topmost surface of the plunger may be beveled or angled in a manner that will enhance the rotational movement of the plunger relative to the pen body. The surface will be angled in a direction that compliments the movement of the pin within the track, while the plunger rotates about the longitudinal axis of the pen body.

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) and the track is defined on the outer surface of the plunger. In this example, the plunger would operate within a channel defined within the cavity of the pen barrel (similar to the embodiment shown in Fig. 1). In yet two other embodiments which are not shown, it will also be possible to provide a plunger in the form of a cap which is positioned outwardly of the pen barrel, so that the cap defines a cavity, and the upper end of the pen barrel is positioned within the cavity of the cap. In one instance, the cap may define a pin projecting from the inner curved surface of the cap (not shown). A complimentary track would be provided on the outer curved surface of the pen barrel, positioned to be within the cavity of the cap. In the second instance, the inner curved surface of the cap may define the track, and the outer curved surface of the barrel may include the pin. In addition, other variations of the track will be apparent to skilled persons in the art. For example, the embodiments described herein have referred to rotational movement of the plunger, relative to the pen barrel, as being generally clockwise from the retracted position to the extended position. The description has also referred to a generally counter clockwise rotation, when the plunger has returned from the extended position to the retracted position. The track may be configured to reverse the order of such relative rotational movement in other embodiments.

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 writing instrument comprising: a retractable writing tip moving between a first retracted position and a second extended writing position; a track defining a closed loop; and a track follower operatively associated with the track for moving the writing tip between the first and second positions.

2. The writing instrument claimed in claim 1 comprising a hollow barrel defining a longitudinal axis extending along the barrel; and the first and second positions are located along the longitudinal axis.

3. The writing instrument claimed in claim 2, wherein the first position is interior of the hollow barrel and the second position is exterior of the hollow barrel.

4. The writing instrument claimed in claim 1 , 2, or 3, wherein the writing tip is provided on a retractable writing cartridge comprising an ink reservoir.

5. The writing instrument claimed in claim 4 comprising a piston rotating relative to the barrel, and the piston is operatively associated with the cartridge to move the writing tip between the first and second positions.

6. The writing instrument claimed in claim 1 , 2, 3, 4, or 5 wherein the track is provided on a curved surface extending radially about the longitudinal axis.

7. The writing instrument claimed in claim 1 , 2, 3, 4, 5, or 6, wherein the follower advances along a generally circular path when the follower is moving from the first to the second position, and moving from the second position to the first position.

8. The writing instrument claimed in claim 1 , 2, 3, 4, 5, 6, or 7, wherein the track defines a generally heart shaped loop.

9. The writing instrument claimed in claim 1 , 2, 3, 4, 5, 6, 7, or 8, wherein the loop defines a first detent corresponding to the first position.

10. The writing instrument claimed in claim 1 , 2, 3, 4, 5, 6, 7, 8, or 9, wherein the loop defines a second detent corresponding to the second position.

11. The writing instrument claimed in claim 1 , 2, 3, 4, 5, 6, 7, 8, 9 or 10, wherein the track defines four curved returns to direct the follower in a desired direction of movement along the track.

12. The writing instrument claimed in claim 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, or 11 , comprising a biasing element urging the writing tip to the first position.

13. The writing instrument claimed in claim 5, 6, 7, 8, 9, 10 11 , or 12 wherein the track is provided on a surface defined by either the piston or the barrel.

14. The writing instrument claimed in claim 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or

13, wherein the track defines a recess.

15. The writing instrument claimed in claim 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 , 12, 13, or 14, wherein the follower is a pin slidably engaged within the recess.

16. The writing instrument claimed in claim 11, 12, 13, 14, or 15, wherein the follower defines a first radius, the four returns each define a second radius, and the second radius is greater than the first radius.

17. The writing instrument claimed in claim 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 , 12, 13, 14, 15, or 16 wherein the follower rotates freely about the longitudinal axis, without rotating the writing tip.

18. The writing instrument claimed in claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 , 12, 13,

14, 15, 16, or 17 wherein the follower is mounted on a flexibly resilient tongue.

19. The writing instrument claimed in claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 , 12, 13, 14, 15, 16, 17, or 18, wherein the tongue is biased to slidably engage a portion of the follower with the track.

20. The 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 follower and the track are made from one or more low friction materials.