WRITING INSTRUMENT

Abstract: A writing instrument having a body portion (10), a rotatable tip (12) and an actuating mechanism (14) for driving a writing source (16) axially in response to relative rotation of the body portion and tip. The body portion includes a removable cap that overlies a support tube (40) forming part of the actuating mechanism. The support tube (40) includes an expanded portion (50) defining a splined surface (50a) engageable with internal splines (52) carried by the cap. The splined engagement between the body and the support tube frictionally resists axial movement thereby allowing the cap be the removed with minimal effort, but substantially resists relative rotative motion between the cap and the support tube so that slippage between the members is inhibited when the cap is rotated to actuate the mechanism. The pen body (10) and tip (12) are configured in a triangular cross-section and define respective apices (76, 78). A detent mechanism indicates aligned positions of the tip and body, and includes an axial flange (63) extending from the body which defines slots (82) aligned with the body apiecs (76); the slots are engageable by a detent pin (80) carried by the tip. When the tip and body are aligned, the engagement of the pin with a slot resists relative rotative movement between the two members.

Description: Description Writing Instrument Technical Field The present invention relates generally to writing instruments and in particular to apparatus for releas- ably securing a writing instrument cap to the remainder of a writing instrument body and an apparatus for provid¬ ing detented positions between two relatively rotatable writing instrument members. Background Art Typically a writing instrument such as a ball point pen or mechanical lead pencil, includes a removable cap that forms at least part of the external body structure of the instrument. In the case of a ball point pen, the removable cap is removed in order to gain access to the ink cartridge for replacement. In the case of a mechanical pencil, the cap often overlies an eraser and a compartment containing a supply of lead refills. In many of these writing instrument constructions, the cap is retained to the rest of the instrument by a frictional engagement between itself and another member of the pen or pencil. If the cap forms part of a rotat¬ able portion of the instrument, the frictional coupling between the cap and the rest of the instrument not only serves as a means for retaining a cap to the instrument but also serves as a means for transmitting rotational torque to the actuating mechanism. In these types of writing instruments, failure of the frictional engage¬ ment between the cap and the body results in the inabil¬ ity to- maintain the cap on the writing instrument and, more importantly, the inability to actuate the mechanism. Writing instruments are generally circular in cross- section. The relative rotation of two different por¬ tions of the writing instrument does not produce any apparent structural misalignment between the portions. However, should the writing instrument have a non-circular cross-section, relative rotation of two body portions of the pen may cause a misalignment between sections of the writing instrument body. As is known in the art, in the case of a mechanical pencil, two relatively rotatable body portions are continu¬ ously rotatable over an adjustment range in order to produce axial movement of a lead. The lead is normally driven by a carrier operatively supported within the body of the pencil. The two body portions are rotated continuously to drive the carrier between fully retracted and fully extended positions at which point further rotation in the body portions is .inhibited. A mechanical pencil with a non-circular cross-section, having this type of lead actuating mechanism, would be awkward to use if the body portions became misaligned during use. For this reason, it is believed that mechanical pencils having other than substantially circular cross-sections, have not been commercially successful. Disclosure of Invention The present invention provides a new and improved writing instrument having an axially movable writing source, such as an ink cartridge or a lead, in which a frictional coupling is not relied upon to transmit rota¬ tional torque from a writing instrument cap to a writing source actuator. The present invention also provides a detent arrangement, particularly adapted for a writing instrument having a non-circular cross-section and sub¬ stantially continuously rotatable body portions for actuating the writing source, such as a mechanical pencil. The disclosed detent provides a sensory indication to the user when the relatively rotatable body portions are aligned and once aligned, inhibits relative motion between the members during use. In the preferred and illustrated embodiment, the invention is disclosed as part of a mechanical pencil having a triangular cross-section. In accordance with the invention, the disclosed mechanical pencil includes two relatively rotatable body portions which are opera¬ tively connected to an actuating mechanism for extending and retracting a pencil lead carried within the body. A removable body section is releasably carried by one of the body portions. Unlike the prior art, the remov¬ able body section resists separation from the body por¬ tion by a frictional engagement between itself and the portion. However, the body section is rotatably coupled to the body portion through a mechanical coupling which transmits rotational torque from the body section to the associated body portion without slippage. With the present invention, a frictional type of coupling as commonly found in prior art pencils, is not relied upon to transmit torque to the actuating mechanism. It is believed that with the present construction, the coupling between the removable body section and the rotatable body portion will resist wear and be more reliable than prior constructions. In the preferred and illustrated construction, a lead actuating mechanism is housed between the rotatable writing instruir€ir: portions and preferably, one portion comprises a tip whereas the other portion defines the major body of the writing instrument. The removable body section is preferably a cap that mounts a retaining clip and overlies a portion of the actuator and is rotat¬ able therewith. The actuator includes a lead carrier which is axially movable within the mechanism in response to relative rotation between the tip and the body. The actuator further includes a longitudinal support tube that en¬ closes the upper part of the actuator. In accordance with this feature of the invention, the support tube includes an expanded annular segment that defines a coupling surface engageable by the removable cap. Pre¬ ferably, the coupling surface is formed by a plurality of external splines that mate with internal splines formed in a receiving bore in the cap. The expanded annular segment is constructed of a material that pro¬ vides some resiliency, such as brass, and is formed with a diameter slightly larger than the internal dia¬ meter of the cap. With this construction, when the cap is placed over the expanded segment, the segment is placed in compression thus providing a frictional engage¬ ment in the longitudinal direction, between the cap and the support tube thereby retaining the cap to the writ¬ ing instrument body. With the disclosed construction, although the cap is frictionally retained on the body, rotational torque is transmitted from the cap to the actuator via the splined coupling thereby eliminating a source of slippage. According to another feature of the invention, a detent arrangement is provided for maintaining alignment between the removable cap and the tip, during use. As indicated above, the disclosed writing instrument is substantially triangular in cross-section. The apices of the triangle are defined by both the removable cap and the rotatable tip. According to the invention, whenever the apices of the cap are aligned with the apices of the tip, a detent is engaged which inhibits relative rotation between the tip and the cap. To achieve this feature, the removable cap includes an axial extending flange at its inner end which defines three slots, each slot being aligned with an associated apex. The tip mounts a slot engaging member such as a resilient pin that is engageable with the flange when the cap is placed on the pen. By forming the detent slots on the cap itself, the cap does not have to be placed on the pen in a predetermined aligned position initially. The detent slots are always aligned with apices of the cap and thus properly aligned detent posi¬ tions will be provided regardless of what position the cap is placed on the pencil. Additional features of the invention will become apparent and a fuller understanding obtained, by reading the following detailed description made in connection with the accompanying drawings. Brief Description of Drawings Figure 1 is an enlarged sectional view of a writing instrument embodying the present invention; Figure 2 is an exploded view of the writing instru¬ ment ? Figure 3 is a sectional view of an actuating mechanism forming part of the writing instrument; Figure 4 is a sectional view as seen from the plane 4-4 in Figure 1; Figure 5 is a side, elevational view of an adaptor constructed in accordance with the preferred embodiment of the invention; and. Figure 6 is an end view of the adaptor shown in Figure 5. Best Mode for Carrying Out the Invention Figure 1 shows the overall construction of a mechani- cal pencil embodying the present invention. The pencil comprises an elongate, upper body portion 10 and a rotat¬ able tip 12. An actuating mechanism indicated generally by the reference character 14 is housed between the body 10 and the tip 12 and is actuated by the relative rotation of these two pencil parts 10, 12. As seen best in Figure 1, rotation of the tip 12 produces axial motion in a lead 16 which in normal usage is driven towards the right (as seen in Figure 1) until a portion of the lead 16 extends beyond the end 13 of the tip 12. It should be understood that reverse rotation of the tip 12 would retract the lead 16. Referring also to Figures 2 and 3, the actuator 14 includes a lead carrier 20 reciprocally movable in a longitudinal guide tube 22 (both shown best in Figures 2 and 3) having a threaded end 23. The lead carrier 20 includes a radially extending tab or key 24 which rides in and extends beyond a slot 22a formed in the guide tube 22. The key 24 extends into coengagement with a helix or spiral 26 that surrounds the tube 22 and which is relatively rotatable therewith. With the spiral 26 positioned as shown, rotation of the spiral 26 relative to the tube 22 will produce axial motion in the lead carrier 20. The spiral is secured in its operative position around the guide tube 22, during assembly, by deforming the end 27 of the tube 22 (opposite the threaded end 23) radially outwardly (as shown best in Figure 1) . The diameter of a leading end opening 20a of the carrier 20 is sized to provide an interference fit with the lead 16 thereby retaining the lead at the end of the carrier. In the illustrated embodiment, the tip 12 comprises two separate parts 12a, 12b. The tip parts 12a, 12b are clamped together and secured to the end of the guide tube 22 by a stepped, annular retainer 30. As seen best in Figure 1, both the retainer 30 and the tip por¬ tion 12b are threadedly received at the end of the guide tube 22. The tip portion 12a is clamped between a shoul¬ der 30a " of the retainer and a shoulder 31 of the tip portion 12b. The retainer 30 also serves as a spring seat for a coil spring 34 positioned between one end of the spiral 26 and the retainer 30. As shown best in Figures 1 and 2, a lead ejector 38 is mounted within the lead carrier 20 and includes an upturned portion 38a which extends from an elongate opening 39 at one end of the carrier 20 and also coen- gages both the slot 22a in the support tube 22 and the spiral 26. The key portion 38a, however, engages the coil adjacent the coil engaged by the carrier tab 24. When the carrier 20 reaches the right most position (as viewed in Figure 1) its tab 24 leaves the spiral 26 and further axial movement is resisted by the spring 34. Further rotation of the tip 12 however, causes the ejec¬ tor 38 to continue its axial motion towards the right, and in effect, causes it to move axially relative to the carrier 20 until its right end extends at least flush with the end 20a of the carrier 20, thus ejecting the lead being held at the end of the carrier 20. The actuator mechanism 14 further includes a long¬ itudinal support tube 40 that surrounds a substantial length of the spiral 26. As indicated above, the spiral 26 is rotatable relative to the guide tube 22 and hence the tip 12. To accomplish this feature, the support tube 40 is fixed to the spiral by a suitable method such as adhesive bonding. As seen in Figure 1, a spacer 44 is also fixed to the spiral, a portion 44a of which overlies the right end of the support tube 40. An annu¬ lar washer 46, preferably constructed of a low friction material such as delrin is disposed between the spacer 44 and the left end of the retainer 30 and serves as a thrust bearing. With the disclosed arrangement, rota- tion of the support tube 40, while preventing rotation of the tip 12, produces concurrent rotation in the spiral 26 thus actuating, that is, driving the lead carrier 20 axially ' in the guide tube 22. According to a feature of the invention, the pencil body 10 forms a cap and is removable to gain access to the support tube 40. For this purpose, the removable body cap 10 includes a stepped bore 48 that extends virtually the entire length of the body, unlike the prior art, however, the removable body 10 is rotatably coupled to the support tube so that relative, rotative movement between the body 10 and the support tube is substantially resisted, whereas slidable axial movement is permitted without.undue effort. To accomplish this feature, the support tube 40 includes an expanded annular segment indicated by the reference character 50 and shown best in Figures 1 and 3. Preferably, the expanded portion 50 defines a coupl¬ ing surface 50a which in the preferred embodiment com¬ prises external splines that mate with internal splines 52 carried by the pencil body 10. In accordance with this feature, the expanded segment 50 is sized so that its diameter is slightly larger than the mating internal diameter of the mating splines 52 so that a slight inter¬ ference fit is provided. The support tube 40 is prefer- ably constructed of a material having some resiliency (such as brass) so that when the pencil body 10 is engaged, the expanded segment 50 is placed in slight radial com¬ pression such that relative axial motion between the pencil body 10 and the support tube 40 is resisted. The pen body 10 is retained to the rest of the pencil by the frictional engagement between these two members. Unlike the prior art, a frictional engagement is not relied upon to both maintain the pencil body to the actuating mechanism and for transmitting rotational torque to the actuator itself. In the disclosed arrange¬ ment, the pencil body 10 is rotatably coupled to the actuator through the splined engagement which substanti¬ ally resists rotational slippage between the two members. In the disclosed embodiment the pencil body 10 is substantially triangular in cross-section and may be constructed of a material such as wood. In order to facilitate the coupling arrangement between the body 10 and the support tube 40, an adaptor 60 is employed. Referring to Figures 2, 5 and 6, the adaptor 60 includes a triangular shaped flange 62 having a peripheral extent coincident with the periphery of the pencil body 10. The adaptor also includes an axial flange 63 on one side of the triangular flange and a body engaging plug-like portion 64. The adaptor defines the internal splines 52 that mate with the splines 50a on the expanded portion 50 of the support tube 40 and also defines a body engaging external surface 64a on the plug-like portion. In the illustrated embodiment, the body engag¬ ing surface 64a comprises serrations which rigidly engage the inside of the bore 48 formed in the center of the body 10. With the disclosed construction, the releas- able mechanical coupling between the pencil body 10 and the support tube 22 is borne by the adaptor 60 and not by the pen body directly. The adaptor is preferably constructed of a wear resistant material such as stain¬ less steel. Thus, the rotational coupling for trans¬ mitting torque between the pencil body 10 and the actua¬ tor 14 is accomplished with a durable, wear resistant material, preferably a metal material. Returning to Figure 1, the support tube 40 defines a storage compartment 71 for spare lead 73. In particu¬ lar, a cup-shaped plug 72 is fixed inside the support tube a predetermined distance from the left end (as viewed in Figure 1) of the guide tube 20. The end of the support tube 40 is closed off by a conventional combination eraser and cap 74. In order to gain access to the lead storage compartment, the pencil body 10 is first removed to expose the eraser which is then also removed to gain access to the lead compartment 71. According to another feature of the invention, a detent mechanism is also provided to indicate aligned positions between the pencil body 10 and the tip 12. As described earlier, in the disclosed embodiment both the pencil body 10 and the tip are substantially triangu¬ lar in cross-section. As a result, apices 76 of the body and apices 78 of the tip 12 are aligned every 120 degrees of rotation. ' To facilitate the use of the pen, it is desirable to provide a sensory indication to the user when the body and tip are aligned. The detent mechanism comprises a detent pin 80 carried by the tip 12 engageable with detent slots 82 formed on the pen body 10 that are associated with the apices. The disclosed arrangement remains properly indexed regardless at which relative position the pencil body 10 is engaged with the support tube 40. To accomp¬ lish this feature, the slots 82 are positioned on an axial flange extending from the inner end of the body 10. Preferably the axial flange 63 is formed on the adaptor 60 as shown in Figures 5 and 6. Once the adap¬ tor 60 is properly positioned in the pencil body, the detent depressions or slots 82 will always be aligned with the corners 76 of the triangle. When the pencil body 10 is reinstalled onto the remainder of the pencil, the axial flange 63 (as best seen in Figure 1) engages the lateral pin 80 carried by the tip 12. The engage¬ ment between the pin 80 and one of the slots 82 provides a detent that resists relative rotation between the pencil body 10 and the tip 12 without urging the members apart. It should be apparent that a new and improved writ¬ ing instrument construction is disclosed by the present invention. When embodied on a mechanical pencil, the present invention provides a durable and wear resistant coupling between a removable pencil body cap 10 and the support tube 40 which is operatively connected to the lead actuating mechanism 40. The engagement allows removal of the cap from the remainder of the pencil with little effort but substantially resists relative rotation between the cap and the writing instrument actuator. In addition, the present invention provides method for detenting rotative positions of a writing instrument in which one of the relatively rotatable members is removable, without disturbing the indexing between the two members. Although the invention has been described with a certain degree of particularity, it should be under¬ stood that those skilled in the art can make various changes to it without departing from the spirit or scope of the invention as hereinafter claimed.

Claims: Claims 1. Writing instrument apparatus, comprising: a) a writing instrument structure including two relatively rotatable portions; b) a writing source carried by said struc¬ ture; c) actuating means operated by relative 0 rotation of said portions for moving said writing source axially to extend an end of said source from an end of one of said portions; d) a removable body section received by the other of said portions; ^c e) coupling means, rotatably coupling said body section to said other portion, said coupling means substantially resisting relative rotative movement bet¬ ween said removable body section and said other portion but providing a frictional engagement therebetween, 20 thereby allowing separation of said body section from said other portion in an axial direction. 2. The writing apparatus of claim 1, wherein said coupling means comprises a member forming part of 2 said body section including an axial bore defining inter¬ nal splines and said other portion including a segment defining an enlarged diameter portion having external splines, the diameters of said coupling means being sized to provide a releasable interference fit between 30 said internal bore of said body section and said enlarged diameter segment of said other instrument portion. 3. The writing apparatus of claim 1 wherein said writing instrument structure defines a substantially 25 triangular cross-section. 4. The writing apparatus of claim 3 further com¬ prising detent means for indicating aligned positions between said body section and said one portion. 5. Writing instrument apparatus, comprising: a) a writing instrument body including two relatively rotatable portions and a cap received by one of said portions; b) a writing source carried by said body and axially movable by an actuating mechanism operated by relatively rotating said portions; c) said body defining external, alignable structure, said structure being aligned at predetermined arcs of rotation of said relatively rotatable portions; d) said cap releasably secured to said one portion by a coupling means including means for substan¬ tially inhibiting relative rotation between said cap and said one body portion but providing a frictional engagement between said cap and said one portion which allows relative axial movement therebetween; e) detent means for indicating when said structure defined by said writing instrument body is aligned. 6. The apparatus of claim 5 wherein said detent means comprises a detent pin mounted in said other body portion, said pin extending into operative engagement with said one writing instrument body portion when said cap is fully received by said one body portion. 7. The apparatus of claim 5 wherein a part of said detent means is carried by said cap and another part of said detent means is carried by said other body portion.

Inventors: LUNTZ S RICHARD, LUNTZ, S., RICHARD
Applicants: LUNTZ S RICHARD, LUNTZ, S., RICHARD
Application year: 1985
Main classification: B43K21
IPC codes: B43K21