US1869198A - Mechanical pencil - Google Patents

Description

July 26, 1932. c. R. KEERAN MECHANICAL PENCIL Filed July 2, 1929 Patented `luly 26, 1932 1,869,198 f '.v n

UNITED STATES PATENT oFFicE CHARLES R. KEERAN, F EVANSTON, ILLINOIS MECHANICAL PENCIL v Application mea July 2, 1929. serial No. 375,430.

This invention relates` to mechanical pencils, and has for a main object to provide a generally improved pencil construction that is capable of being economically manufactured. Another objec't resides in the pro-y vision of certain novel and simplified features in the operating mechanism for pencils of the type embodying propel, repel, expel action. A further obj ect of the invention is to provide an improved construction adapted to obviate the slight reciprocating movement of the lead in the tip during use which sometimes occurs due to play resulting from the clearance between certain elements of the feed mechajnism. It consists lin certain features andl elements of construction, herein shown and described, as indicated by the claims.

In the drawing: I Figure 1 is an enlarged fragmentary axial section through a mechanical pencil embodying the present invention.`

Figure 2 is an enlarged fragmentary axial Y section through the lower portion of t-he pencil showing the lead propelling mechanism in 'position just after expulsion of the remnant portion of the lead through the tip.

FigureY 8 is a transverse sectional view taken substantially as indicated att-line 3 3 .on Figure 2, and serving also to illustrate the contour of the parts at the plane of line 3-3 on Figure 6.

Figure 4 is a fragmentary longitudinal sectional view showing the leadv propelling plunger disengaged from the coiled helix andV showing, somewhat exaggerated, a portion of the plunger bent out of axial alignment for a purpose'hereinafter explained.

Figure 5 is a fragmentary sectional view showing a modified form of telescopic concarrier sleeve and respectively; l n "plunger is a tubular lead carrying sleeve S5 yformed intermediate its endswith a circumtion includes the usual barrel 1() madeof any suitable material` such as wood, metal, bake-V lite or other molded composition, provided with an axial borey 11 having'two longitudinally extending diametrically opposite 5e n guideways or grooves '12 formed therein, one

terminating short of the tapered lower end at a stop shoulder 14, andthe other groove stopping just inside the end at 15. lotatably associated. on' the tapered portion E173 of the 6o barrel isa taperedtipl having its lower end swaged to form an Venlarged terminal bearing 17 for guiding thelead 18 therethrough.

The terminal 17 is formed withan annular shoulder19 on the inside of the tip to act as 65 a stop as will hereinafter be described. Adapted tobe telescoped into the bore of the" barrel for rotation therein is an openly coiled yhelix 22 secured at its lower end in a bush! ing 28`whichis vperi'nanently secured inithe 7o tip 16 sweating, soldering or the like. Disposed inl the bore of the barrel is a plunger 25 having( a plurality of laterally extending driving lugs26 adapted to `engage between j the coils of the helix and project laterally beyond said helix into the guideways 12 insaid barrel permitting longitudinally non-rota-v Y Ative movement of the plung'erwhen the helix is rotated.

The plunger proper is preferablyof cylinl drical formation and is provided with an f intermediate reduced `.portion 27 forming` oppositely facing'stop shoulders 28'and 29 Slidably mounted on said ferential groove pressed in the material so as x to result in an inwardly projecting annular bead 31 surrounding the reducedportion'27l of the plunger and serving to secure the lead carrying sleeve on said plunger while per-v mitting a limited range of telescopic movement of these parts with respect tov each other; the movement of the sleeve in the plungerbeing limited by the bead abutting 9,5

against either of the shoulders 28 or'29 of said plunger. As shown in Figure 1, .when v the sleeve is in extended positionv with the bead abutting against the .front shoulder 28,

the end portion of the sleeve-projects *a sub- Y' i plunger for receiving the rear end .tect a split tube;

slit, so that in either case the lead engaging end of the sleeve will act asa yielding clutch to rictionally secure the lead therein.

t will be apparent that as the lead is propelled through the tip by therotation et the tip on the barrel, theplunger with its sleeve in place is axially moved in the helix and barrel, but is restrained against rotation by engagement o'ljitslugs in the longitudinal guideways ot the-barrel. The exterior dimensions of the sleeve and vthe inside of the helix are suchV as togprovide'a relatively close fit to insure vtrue guidance` of: the lead as it is i `being propelled or retracted.v I As the piece of lead is gradually usedup, and' the mechanism approachesthe lower end of the tip'7 asY shown. in Figure2, the endet the` sleeve will. abut a'gainstthe shoulder 19in. 'the tip .and its movement will: befarrested, while by. continued-A rotation otV thetip relative to the barrel, vthe plunger continues-'to eed the remnant of the leadthrougli the terminal portion lf?, the plunger. is so dimensioned. relative to the sleeve .that at the limitof .lead expelling movement itslead engagingv ,end projects slightly beyond the terininalend, of the tip andv the movement. ofA the yplunger in `this.

direction vif'ithrespect to theleadVV carrying sleeveniay be .limited bythe-Y. shoulder 29 abutting against the bead 31 in said sleeve;

'but preferably thef'movementof the plunger with` respect'to the sleeve in this direction is limited by 'encounterv ofV the lug .26 .with the stop shoulderrlllfor'med at the end offene ot' the guidewaysin theba'rrel.. i

To insert a new lead', thetip is rotated in reverse. direction so :as to thread the helix 'outset engagement. with the lugs .of the plunger, thus permittingseparation of the tipv and barrel and aiording access to the plungerV and the leadcarrying sleeve.; The llead carrying sleeve is .then grasped and pulled forwardly. onthe plunger into the extended positioin. as shown iii-=Figiire 1,'with the: bead 3l abutting against ,theV shoulder 28, The. pencil. may' then befreassembled for use. The;

inpositio-nefor yreceivii'ig a. new lead.,

lead engaging endotthe sleeve is preferably 'lla-red or'conically counter-bored asindicated i at '30a-so. as 'to.,facilitate' the insertion ot a new lead in the clutch end'.

rlhis arrangement of. the parts as above de-y scribed is particularly advantageous Vin that it permits direct access to the plunger and lead carryingsleeve so asv tov-facilitate reto give a-more resilient action.

between thelugs et and; the Yhelix insures positive y ot the tip. VAsshown in= Figure 2,.

placement or repair of the parts if necessary. Having direct access to the lead carrier sleeve for insertion ot a new lead also insures against damage to the sleeve or mutilation or breaking of the lead during insertion of a. new lead, which is apt to result iic these parts are. completely housed in the barrel so that the lead must be insertedthrough the tip of the pencil.

As exaggerated in Figure l, ar portion of the plunger intermediate Y the stop shoulder 29 and the lugs 26 is slightly bent out of axial alignment, as shown at 84, so as to increase the frictional drag between the lugs and the helix when the plungerr is in operative -feeding engagement therewith ;,and the portion ofthe 'plunger'intermediate the stopi 29 and the innermost driving lug 261s preterably reduced in'lcrossvsectional area-,so as This Aincreased 'frictional drag theV plunger uniormmoveinent in either propelling or repellingdirection,.and tends to preventlongitudinal play which would* otherwisel result from the clearanceL between thelugs andy .the coils ,et the heliir.

This feature is con]-v sidered ot importancefin that it obviatesthe objectionable'V chattering caused.' bythe slight reciprocatingfmovement of aleadi at. the write-T ingitip, whichfis usually due toithe clearance; between the cooperating`V parts-2 Figure 5 illustrates a modified arra. mentbyrmeans of which Vthe lead; carrying permitting drical'plunger' isA provided with av slotv or guideway. lO-extendingina spiral; direction -Y partially around it`v andthe sleeve is formed with an inward. depression or node 411er 'tending into'the slotY 40.' Thus when.- the sleeve. is arrestedV in ythe;y tip by abutting' f against the shoulder 1,9,.the continued; moves nien-tV of the` plunger willy bepermittedi.'al-4 though it will cause the slot l0 and projec-f tionf 4'1- to act` camwise5 forcingl the r sleeve 38 Ltorotateslightly; around the plungery asf theremnant of thelead is expelledthroiiglr .'115 the tip.. This particular construction; isiespeef ci ally advantageous-in that it .permits posi: l tive eiectment oftheY remnant of vthe lead.

roin. the sleeve by merely. rotatingithe: sleeve on the'plunger.'as in easeslwhentipand'helix:.120 Y arey separated from the barrel l()`r and' a short remnant otthe lead is found remainingriin the lead carriertube; the vpl-ungeix/in sueh'ay case, projects loosely through the lb oreatA the end ot the barrel but offers noA longitudifnal resistancefasfjainst which :the lead 'carrier tube cantbe pushed back to 'release theremnant of lead; however., since the lugs ot the?.

plunger still engage the ,f {uideways 12;` itis' heldagainst-rotation while the sleeve 3S may 'sleevefSS is retained ontheplungerBQ' while 100 a limited rangeA` ot. telescopic` be twisted and thus forced back by the spiral groove, 40, so as to release the lead remnant. In the construction illustrated in Figures 6 and 7, the barrel 45 is preferably formed of balelite or other molded composition, and has included in its bore which extends a substantial portion of the length of the barrel, a pair of diametrically opposite longitudinally extending rounded or convex ribs 47. The tapered end portion 48 of the barrel is provided with a reduced bore 49 substantially the same as in Figures 2 and 3, and dimensioned for receiving the coiled helix, and this bore 49 is also provided with diametrically opposite longitudinally extending guide slots 50 for engagement by the lugs of the plunger. These slots terminate at shoulders 5l and 52 respectively, so as to prevent withdrawal of the plunger from the lower end of the pencil. Mounted in and extending substantially the length of the bore of the barrel is a guide tube 54 having its sides disposed in spaced relation to the inner wall of the barrel forming two spare lead chambers 55 on opposite sides thereof for storing relatively long leads (about four inches in length) such as indicated at 56.

This guide tube is formed with curved sides merging in opposed longitudinally extending ribs 57 which form on the inside of the tube guideways 58, adapted to be aligned with the vuideways 49 in the tapered portion of the tip so as to provide a complete continuous guideway for the lugs of the plunger. The outer contour of the rib portion 57 is shaped to approximately conform to and telescopically engage the contour of the ribs 47 in the barrel,it being understoodv thatthis guide tube is made of sheet metal with the offset ribs 57 slightly flatter on their outer faces than the ribs 47 of the barrel so as to provide a forced lit in assembly, causing the rib portions 57 to be slightly flexed to insure a relatively tight frictional engagement with the ribs 47 for maintaining the tube in position against rotation and longitudinal separation. In this arrangement the helix will extend practically to the upper end of the barrel to provide suflicient movement of the plunger to accommodate the long leads. rIhe upper end of this barrel may be provided with any suitable ferrule or cap and also with any addition-al means for closing the upper end of the guide tube if desired, so as to prevent removal of theplunger after it is once introduced therein.V However, leaving the upper end of the tube accessible is of particular advantage in the event that the plunger needs to be replaced for some reason or other, so that it may be accomplished very easily and quickly and even by inexpert persons.

I claim:

l. In a mechanical pencil, a barrel having an axial bore with a longitudinal guideway,

.a plunger adapted to be an externally accessible member `rotatably l Vmovably,telescop'ed into the barrel Vfor rotation therein, and a plunger in the bore adapted to be disposed-in said helix, said plunger having a lead engaging 'end and the other end having a laterally projectinglug extending through the space between the coils engaging'in the guideway,fa portion of saidv plunger intermediate the lead engaging end and the lug beingsprung out of axial alignment whereby to increase the frictional drag betweenk the lug and the coiled helix. i

2. In a mechanical pencil, a barrel having an axial bore with a a tip'rotatably associated Vwithfthe barrel, an openly coiled helix carried bythe tip and removably telescoped into the barrel for rotation-therein, and a lplunger in the bore adapted to be disposed in said helix, said longitudinal guideway,

plunger having a lead engaging end and the i otherend having a `later-ally projecting lug extending through the space between the l 90.I`

coils engaging in the guideway, a portion of said plunger intermedlate'the lead engaging end and said lug being reduced in crosssection and provided' with aslight-bend to increase the frictional resistance between the'`` i lug and the coiled helix. Y 3. In a mechanical pencil, abarrel having an axial bore rand a longitudinal guideway opening oft' said bore, ciated with/the carried by the'tip and rotatable yinsaid bore, disposed in the helix atip rotatably asso-f barrel, an openly coiled helix 1, o

and having. 'a laterally extending lug projecting throughjthe space between the'coils in sliding engagement with the means of which the plunger is permitted axial non-rotative movement in the barrel, and a lead carrier sleeve telescopically asso- A ciated with the plunger, said plunger having a reduced portionV forming oppositely facing shoulders and said sleeve being formed with an inwardly projecting annular beadin registration with said reduced portion of the plunger and adapted to abut against said shoulders for limiting the telescopic movement of the parts in oppositek directions, and said plunger having a portion intermediate said rear shoulder and the lug reduced in cross sectional area and sprung slightly out of axial alignment whereby to increasethe frictional drag between said lug and coiled helix.

4. In a mechanical pencil, a barrel having a bore and a plurality of lspaced longitudinally extending ribs therein and a guide tube having laterally offs-et portions adapted for euideway by 80H7rotatably associated with the lower end of tionallysec'uringsaid tube in .position in the ,i

barrel. A

6. ln a mechanical pencil, abarrel having a bore and a pair of diametrically opposite longitudinally extending ribs on the inside oi"- the barrel, and a guide tube disposed in the bore of the barrel having laterally oppositevoffset portions extending throughout a substantial portion of its length formed to irictionally engage said `ribs for iirmly securing the tube in place inl the barrel.

.7. In the combination dened in claim 6, the sides of said guide tube intermediate said longitudinal oifset portions being in spaced relation to the inside of the bere to form sp are lead chambers. n e v 8. ln a mechanicalv pencil, a barrel having a bore formed With a pair of diainetrically 0pp osite longitudinally extending inwardly projlecting ribs, a guide tube disposed in thebarrel and having a pair' of opposite longitudinally extending offset portions formed toengage said ribs for trictionally securing said tube therein, said offset portions forming on Ythe inner side of the tube, a

pair of longitudinal guide slots, the lower endof the barrel having a reduced bore and a pairo''dianietr'ie cally opposite guide slots With'vvhich are registered the guide slots of the tube, a tip the barrel, an openly coiled helix carried by the tip and adapted to be telescoped into the barrel inside the guide tube for Vrotation I therein, and a plunger carried in the'bore o1 the barrel and having laterally projecting lugs extending through .the spaces between the coils for engagement with the slots in the c guide tube and lovver end of the tip, whereby said plunger is restrained against rotation ivhile being permitted longitudinal axial movement in the barrel.

` CHARLES R. KEERAN.

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