US2926633A - Lead pointer - Google Patents

Description

March 1, 1960 E. w. WILKINSON 2,926,633

' LEAD POINTER Filed Aug. 4, 1958 eylgx. 5 INVENTOR.

[.fTEL L/ MLk/MsoN BY United States PatentO This invention relates to motor driven pencil Sharpeners of the type particularly adaptedfor pointing'the leads of pencils that have been*rough-sharpened byconvential sharpeners, and has as its general object to provide a sharpener for adjustable fine-pointing of leads at varying angles of point-taper.

particular object of the invention is to provide a lead pointer utilizing a revolving abrasive disc action in grinding down a pencil lead to a fine point. More 2,926,633 Patented Mar. 1, rest).

inserted with the point thereof projecting into position r ce to be ground by the grinding disc assembly C.

Casing A may include a shell 10, open at the bottom, having atop portion 11 which is preferably of arched contour as shown, with an aperture 12 therein through which the pencil guide D extends, and with opposed vertical end walls 13 and 14; and a flat bottom plate 15 and gasket 16, interposed between and sealing the bottom plate 151to the open bottom of the shell 10. The space within casing A is divided by a partition 17,

parallel to end walls 13 and 14, into a compartment F receiving the motor B and a compartment G in which is disposed the grinding disc assembly C and the pencil guide assembly D, said compartment G having an unobstructed bottom area in which is collected the dust that is ground from the sharpened lead points. Bottom plate 15 and gasket 16 are secured to the shell- 10. by a removable fastener pin 18 extending through regis teringapertures in end walls 13 and 14 and in spaced cars 19 integral with bottom plate 15 and extending upwardly through apertures in gasket 16. Bywithdrawing pin 18, bottom plate 15 and gasket 16 can be removed particularly,-the invention aims to provide a device wherein a lead is pointed between a pair of diverging abrasive disc surfaces rotating in unison and actingsimultaneouslyjon opposite sides of the pencil point, whereby a fine conical point can be produced by manually rotating the pencil during the sharpening process, or, alternatively, a chisel-edge point can be produced by holdmg the pencil in a fixed position so that opposite sides of the point will be ground to producethereon opposed flat faces converging to a dihedral angle apex providing atransverse chisel edge. i

An important object of the invention is to provide a lead pointer which can be adjusted substantially instantaneously to vary the taper and length of the lead point thatis ground on a pencil. More particularly," the invention contemplates a device wherein the angle of the grinding discs; A further object is to provide a for periodicallying emptying the collected dust fro mthe casing. Partition 17 may be an integral part of shell 10, fabricated as a. die casting ifmade of metal, or as an injection molded part if made of synthetic resin plastic material (either material may be used). Motor B is a small fractional horsepower electric motor and is mounted to the end wall 14 bycap screws 21 extending through the wall 14 and throughspacer sleeves 2'2 andanchored in the body of motor B to suspend the same from the end wall,14. The motor B has a shaft 23jwhich is extended through an aperture 24 in partition 17; with ample "clearance forfree'rotation, and which embodies a face flange 25 made threaded shank 26 onto which the grinding disc assembly is lead pointer adapted to produce a chisel-edge point hav ing an edgewhich may be selectively varied from a square edge normal to the pencil axis, to one having a skewed chisel edge. i j Another important object of the invention is to provide a lead pointer, driven by an electric motor and having an automatic control device responsive to insertion ofthe pencil into the appartus, for closing an electric circuit to operate the motor, and automatically responsive to withdrawal of the pencil for openingthe circuit and stopping the motor. a K

Other objects and advantages will become apparent in the ensuing specification and appended drawing in which: Fig. 1 is a vertical sectional viewof a lead pointer embodying the invention, with the internal operating part thereof shown in side elevation; t j t Fig. 2 is a vertical sectional view of'the same taken on the line 2-2 of Fig. 1; y g F Fig. 3 is anenlarged detail sectional *view taken on theline 3 3ofFig. 2; i

Fig. 4 is a-detail sectional view taken on theline tion maybe embodied, a pointing apparatus embodying,

in general, a casing A, an electric motor B therein, a

grinding disc assembly C driven by the motor B, and j a pencil guide assembly D into which a pencil E can be clamped by a nut 27 threaded there on.

The grinding disc assembly C comprises a pair of abrasive discs 30 of a suitablefabrasive sheet material such as emery cloth or garnet paper, and a pairofi backing discs 31 of tough, flexible, elastic material, prefen ably spring sheet material such as sheet brass or spring" sheet steel or plastic impregnated fabric or paper such as hard fiber in this sheet form, to which the backs of the adhesive sheets 30 are firmly secured as by cementing. The discs 31 are of larger diameter than discs 30, whereby peripheral portions thereof project beyond the discs 30 to define bearing flanges 32 for, spreading the discs as hereinafter described. a I

Discs 30 and 31 are clamped between the mounting flange 25 and retainer nut 27, with or without a thin washer 33 interposed for slightly spacing the abrasive faces of discs 30. v

The pencil guide assembly D comprises a guide sleeve 35 adapted to receive pencils of a common range of sizes, the outer end of the sleeve 35 being slidably mounted in aperture 12 of the casing dome 11. At its inner end, sleeve 35 has a frusto conical shoulder 36 and a reduced neck 37, the latter being received between the projecting flanges 32 of the disc assembly C a and functioning as a spreader. Neck 37 also provides a throat through which the point of a pencil E may project to an extent determined by seating of the point against an annular seat defined at the intersection of such throat and the shoulder 36. Theneck 37 is received between the flanges 32, to spread them in the area where the pencil lead projects between abrasive discs' 30, and maintains the discs in a flaring condition at the area of engagement with neck 37, therebyproviding for grinding the pencil lead to a finely tapering point .as

indicated in Fig. 3. As the discs rotate, they will cori- V tinually flex to maintain the flaring area fixed at the location of spreading contact with the neck 37.

Adjustment of the angle of taper is provided for by shifting the. pencil guide sleeve 35 from the position shown in full lines in Fig. l, in which its longitudinal gamma 7 tion.

axis is located on a radius of the shaft 23 (in which position a point of maximumv flare and minimum length will be ground) to a position where the axis of the sleeve 35 (and thus the axis of the pencil point) is 3 chordally disposed with reference to the peripheries of abrasive discs 30, as indicated in broken lines in Fig. 1. In projecting between the abrasive discs on an axis oblique to a radius, the point will extend further past the peripheries of the discs 30 in order to reach the radius where the converging discs have a spacing of maximum closeness determining the limit of fineness to which a lead can be ground, i.e., the end of the pencil point. Thus the point will be given a longer taper, of n rrower angle than where it is ground on a radius of. the shaft 23.

'For adjusting the sleeve 35 bet-ween its two limit posi-' tions, I provide a bracket 38. having a bore snugly receiving the sleeve, 35 and a set screw 39 securing the. sleeve, in the bore. Bracket 38 has a squared end which bears flatly against the inner face of end wall member 13 and a threaded bore into which is threaded a clamp screw 40 having a'knurled head 41 adapted to be tightened against the outer face of wall member 13. The screw 40 extends througha slot 42 in wall member 13, slot 42 being of arcuate contour and concentric to the axis of grinder shaft 23, whereby the spreader neck 37 is always positioned between the flanges 32 regardless of the adjustment of the pencil guide assembly. By loosening the clamp screw 40 and using knurled head 41 as a handle, the sleeve 35 can be shifted at its inner end in a path defined and limited by the slot 42,.between the two limit positions of adjustment shown in full'lines and dottedlines in Fig. 1. When a selected position of adjustment has been reached, the. guide sleeve 35 can be secured in that position by tightening the clamp screw 40. Automatic control of the motor B, responsive to. the insertion and removal of a pencil E, is provided for by a microswitch '43 secured to the side of sleeve 35. Switch 43 comprises a pair of spring'arms 44 anchored in a casing 45 of insulating material, having contacts 46 that are normally slightly spaced to provide a normally open condition for the switch 43, and adapted to be closed by a plunger 47 engaged between the bottom of casing 45 and the adjacent spring arm 44 and having a stem 48 extending through an opening 49 in the sleeve 35 so as to be engaged by a pencil E when inserted into the sleeve. The stem 48 projects into the sleeve to a sufficient extent so as to provide switch closing response to engagement by a pencil of maximum slenderness. Suflicient clearance between thespring arms 44 and, the. cover 50 of casing 45 is provided so that for maximum displacement of tained by a circumferential array of spring prongs 53.

The access opening 51 is of adequate diameter to accommodate the insertion of the operators fingers for unscrewing the retainer nut 27, and to permit the assembly of discs 30 and 31 to be lifted out of the casing and replaced by a fresh set of discs.

While loosening the retainer nut 27, the drive shaft 23 maybe held fixed against rotation by' jamming the point of a lead pencil between the abrasive faces. of discs, 30 to,v function as a brake. may be provided in the end of the threaded tip. 26 of the. shaft. as. shown.

Alternatively, screw driver SlQL'J In the operation of the device, a pencil to be pointed is inserted in the guide sleeve until its point engages the seat 56 defined at the intersection of shoulder 36 and the throat of neck 37. This positionsthe pencil properly with the lead extending between the abrasive discs 30. As the pencil reaches this position,.the plunger stem 48, engaged by the side of the pencil, will be depressed, closing switch 43 and starting the operation of motor B. If a:conical point is desired, the pencil is rotated between the fingers of the operator during the grinding process. If a chisel-edge point is desired, the pencil is held stationary so that converging fiat faces will be ground on opposite sides of the lead. These faces will converge to an edge normal to the pencil axis if the guide sleeve 35 is adjusted to the radial position shown in full lines in Fig. 1. When adjusted to the tangential position shown in broken lines, the sleeve 35 will hold the pencil for grinding of a skewed chisel point. p 1

The flanges 32, of relatively hard, flexible, elastic sheet material, provide a pair of opposed, smooth, hard, low

frictionbearing faces adapted to ride against the oppobottom plate 15 and the shell 10 is optional, it being com templated, as an alternative, that the bottom be permanently attached to the. shell 10 by any suitable means (such as soldering, welding or cementing) and that accessto the compartment G, for emptying the lead dust therefrom, be provided'for through the front opening 51.

An important advantage of the invention arises from the flexible characteristic of the disc assembly C which effectively discharges any fragment of lead which may become lodged between the discs as the result of being broken from the pencil point (e.g. in the event of ex: cessivetorque being applied thereto during the operation of loosening the nut 27 while holdingthe disc assembly stationary as described above). The flexing of the discs as they come abreast of the spreader neck 37, combined with centrifugal force, will effectively throw out the lodged fragment of lead, temporarily held by the yieldingrembracing grip of the disc.

Another special advantage of the invention is its adaptability to the sharpening of lead points for drafting compasses. For example, by pointing the lead of a standard drafting pencil having a free lead as mechanically fed from the end of a mechanical pencil holder, sharpening it first witha conical point and then converting this to a chisel edge by reinserting the point in the device and holding. it stationary for a short interval; and then breaking oflrthe sharpened end of the lead and inserting it into a draftsmans' pencil compass, a perfectly sharpened corn, pass lead is provided.

I claim: I

1. In a pencil pointer: an electric motor; a grinder unit driven thereby, said grinder unit comprising a pair of flexible grinder discs having opposed inner abrasive faces and having spreader flanges projecting beyond the peripheries of said abrasive faces, said flanges having opposed smooth hard low-friction bearing faces; a pencil guide means adapted. to embrace and positiona pencil,

said guide means having an open outer end to receive a pencil and having at itsinner end a spreader partthrough said abrasive aiscflanges td-niaintain them spread pm" and fl aring outwardly to the peripheral margins of said circumference thereof disposed at a radius inwardly of the peripheries of said abrasive faces, whereby a lead point of maximum angle will be ground when said sleeve is disposed at said radial position and a point of maximum taper will be ground at said chordal position.

3. A pencil pointer as defined in claim 2, and including a housing having a vertical wall, and wherein said holding means comprises a bracket having a squared end bearing against said vertical wall and a clamp screw extending through a slot in said vertical wall and operable to clamp said bracket to said wall in a fixed position, sa d slot extending circumferentially of the periphery of said grinder unit;

4. In a pencil pointer: a housing for an electric motor and a grinder unit driven thereby, both disposed in said housing, said grinder unit comprising a pair of flexible grinder discs having opposed inner abrasive faces and having spreader flanges projecting beyond the periphery of said abrasive faces, said flanges having opposed smooth hard low-friction bearing faces; and a pencil guide means comprising a sleeve adapted to embrace and position a pencil, said sleeve having an open outer end to receive a pencil, said outer end being loosely extended through an aperture in said housing to provide a pivotal connection therewith, said sleeve having at its inner end a reduced neck defining a throat through which the lead of the pencil may project between said abrasive discs, said neck being engaged between said abrasive disc flanges to maintain them spread apart and flaring outwardly to the peripheral margins of said abrasive faces at the position of said lead, to shape the same to a taper determined taper determined by the angle of flare between compartments and closing off the motor I compartment driven thereby, said grinder unit comprising a pair of flexible grinder discs having opposedinner abrasive faces and having spreader flanges projecting beyond I the peripheries of said abrasivegfaces; said flanges having opposed smooth hard low-friction bearing faces; a housing in which saidmotor and said grinding unit are enclosed; a pencil guide means comprising a sleeve having an openouter end to receive a pencil and having at its inner end a reduced neck defining a throat through which the lead of a pencil may project between said discs, said neck being engaged between said abrasive low friction bearing faces of said flanges to maintain said abrasive faces spread apart and flaring outwardly to their peripheral margins at the position of said lead, to shape the same to a taper determined by the angle of flare between said abrasive faces; and a control switch for said motor, mounted on the side of saidsleeve externally thereof and having an actuator stem projecting through the wall of said sleeve and engageable by a pencil. inserted into the sleeve, for closing said switch to cause said motor to operate, said switch being self opening in response to withdrawal of the pencil from said sleeve, to terminate the operation of the motor.

8. In a pencil pointer: an electric motor; a grinder unit driven thereby, said" grinder unit comprising a pair of flexible grinderdiscs having opposed inner abrasive faces and having spreader flanges projecting beyond the peripheries of said abrasive faces, said flanges having opposed smooth hard low-friction bearing faces; a housing in which said motor and said grinding unit are enclosed; and a pencil guide means comprising a sleeve having an open outer end to receive a pencil and having at its inner end a reduced neck defining a throat through which the lead of a pencil may project between said, abrasive discs, said neck being engaged between said low friction bearing faces of said flanges to maintain said abrasive faces spread apart and flaring outwardly to by the angle of flare between said abrasive faces; a bracket I having one end thereof secured to said inner end portion of the sleeve and its other end bearing against a vertical wall of said housing,-a threaded clamp means including a part projecting through a slot in said wall and a part engageable against the outer surface of said wall to clamp said bracket to said wall in any selected position of adjustment of the bracket along the length of said slot, said slot extending generally circumferentially of said grinding unit and providing for swinging adjustment of said sleeve about said pivotal connection, be tween limit positions in one of which said sleeve has its longitudinal axis disposed on a radius of said grinding unit and another of which said longitudinal axis is disposed chordally of the periphery of said grinding unit,

tangent to a circumference thereof disposed at a radius housing provides a pair of sideby side vertically extending compartments in one of which said motor is mounted and in the other of which said grinding unit is enclosed, the latter compartment having an unobstructed lower area in which dust ground from pencil points will be collected, said housing including a vertical partition separating said their peripheral margins at the positionof said lead, to shape the same to a taperdeterminedby the angle of flare between said abrasive faces.

9 In a pencil pointer: an electric motor; a grinder unit driven thereby, said grinder unit comprising a pair of flexible grinder discs having opposed inner abrasive faces and having spreader flanges projecting beyond the peripheries of said abrasive faces, said flanges having op posed smooth hard low-friction bearing faces; a housing in which said motor and said grinding unit are enclosed; a pencil guide means comprising a-sleeve having an open outer end to receive'a pencil and having at its inner end a reduced neck defining -a throat through which the lead of a pencil may project between said abrasive discs, said neck being engaged between said low friction bearing faces spread apart and flaring outwardly to their peripheral margins at the position of'said lead, to shape the same to a taper determined by the angle of flare between said abrasive faces; and means mounting said pencil guide sleeve for adjustment to shift said neck with respect to said flanges so as to vary said angle of flare between said abrasive faces.

10. In a pencil pointer: a housing for an electric motor and a grinder unit driven thereby, both disposed in said housing, said' grinder unit comprising a pair of flexible grinder discs having opposed inner abrasive faces and having spreader flanges projecting beyond theper-iphery of said abrasive faces, said flanges having opposed smooth hard low-friction bearing faces; and a pencil guide means comprising a sleeve adapted to embrace and position a pencil, said sleeve having an open outer end to receive a pencil, said outer end being loosely pivotal; cennec ienz herewith, s id. s eeveah v ng at: its innerend nedueedinee defining a threat thro h which the lead-of me pencil. m y proje between aidabrasive discs, and-.said-neeig being engaged between said abrasive disc flanges to maintain them spread apart and fla 'ing qut'wargily to theperipheral ma gins of said abrasive fiaees at the pesition of said-lead, to shape thesame to a tape;

determined by :the angle of flare between said abrasive facesandmeans for adjusting-said sleeve by longi ud nal sliding movement in saidi aperture so as to shift the position of saideel; with referenee to said flanges, to

I entended thmugh en nelr ure in said, h ousling te provide. a. 7

thereby y w: i m q-:. 1 m bemm sai-cl b s ve faces! 2,266,269] mm i r-' Dec. 16,.19147 1 L1,- A pe il pa n er: q sgd efi ned n cl aim .10; whe in. said adjusting means is eonneetedftq, theinner end' Qf'

Images