US2358091A - Mechanical pencil - Google Patents

Description

SCP*- 12, 1944-- C. K. ovEJoY MECHANICAL PENCIL 3 Sheeis-Shee't l Filed Jan. 22, 1944 4 uit'. 1

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27g Wwf Patented Sept. 12, 1944 UNITED STATES PATENT OFFICE u o 2,358,091 I l MECHANICAL PENCIL charles x. Lovejoy, Needham.' mss., armor to The Moore Pen Company, Boston, Mass., a corporation of Massachusetts Application January 22, 1944. Serial No. 519,259

(ci. izorz) Claims.

This invention relates to mechanical pencils.

More particularly it relates to lead pencils in which a short length of fresh lead is fed for the writing point by a simple pressing and releasing of an exterior part of the pencil.

Heretofore pencils intended for this operative result have had complicated internal structure, comprising various combinations of levers, cams, slides, grippers and other mechanisms of very small dimensions, having the functions successively to grip the lead for holding it stationary, release that lead, feed it out, and then to grip it again. The manufacturing and assembling of such small and numerous parts are expensive. Also the operating results have not always been satisfactory.

Objections are that in some forms the point of the lead is not Well supported against writing pressure; or that breakages of the lead occur rather easily, within the barrel or at the point. In some styles the pencil can be used only with leads which conform quite precisely to specliled diameter. In sme the user has no option as to the length' of lead to be fed, at each step; and in s'ome the lead cannot be fed at all'if the pencil happens to be pointed upright.

The pencil of the present invention avoids all these objections.

It provides a firm support for the writing point of lead, and yet alfords complete selective control of the extent to which this point shall project-either by restricted forward feed or by protective adjustment backward, as may be de-y sired. An outstanding feature is its attaining of these results reliably, by differences of frictional grasp of the lead, and without such complications of internal structure as have characterized previous pressure-feed pencils.

These results are attained by two slip-collets which cooperate to hold, and to feed, the lead within a tube that is reciprocable within the pencil barrel. One of these collets is on the tube; the other is on the barrel. When the tube is still, its collet is -firmly seated by a tapered fit in the forward end of the barrel. This collet grasps the lead with resilient prongs that are inclined at a slight angle from parallelism with the axis. The barrel-collet is close behind the barrels point. It has prongs, inclined at a slight angle from perpendicularity to the axis, which reach the lead through slots in the tube. Each collet opposes regression of the lead relative to itself; but offers mild resistance to advance of the lead relative to itself; and permits advance of the lead relative to itself when that mild resistance is overcome. The tube-collet never lets go of the lead; but its construction is such that when it is projected the lead can be forced back through it. The barrel-collet may be arranged so that it never lets go of the lead; but, for the introduction or moving of short leads, means is provided to spread its jaws momentarily out of the path of the lead.

To advance the lead,v one momentarily depresses the tube in the barrel. and so the tube collet at the lpoint draws out a length of lead corresponding to the extent of the depression. During spring return of the tube, vthe barrel collet prevents regression of the lead, thus leaving the point of lead projected, while the tube collet slips back into its seat where it can support the pressure'of writing. Y

'I'his extraordinarilysimple construction is herein illustrated by embodiments in which the tube has a head that protrudes from the top of the barrel, in convenient reach of the user's thumb; and is openable'forintroduction of leads. The lead may be a single long rod, or a succession of short rods which follow each other automatically from a magazine in the upper part of the tube.

The tube-collet prongs, almost parallel to the lead, are sectors of the tube, separated by narrow slits cut lengthwise in the tube, which, in this region, is composed of resilient metal. The slight spaces made by the slits permit of the sectors being deformed from their natural cylindrical position. so that their forward ends stand closer to the axis than-where the surface of the rod of lead will be, which is to be held by them. When the lead is present they are spread correspondingly and grip it bytheir resilience.

The barrel-collet prongs are made of resilient flexible thin sheet metal and they run almost perpendicular to the lead, from opposite walls of the barrel, inward toward the axis, through slots in opposite sides of the tube, to reach opposite sides of the rod of lead. When at rest and tension free, they stand at an angle tapering preferably about 15 forward from perpendicularity, and they extend far enoughinto the their ends toward the axis, and jams them stiiily between the lead andi their peripheral base; so that they oppose recession of the lead. This opposition sustains the lead while the tube-collet is receding after a forward feeding stroke; and at other times it helps sustain the back thrust of writing pressure. I have found that the providing of a slight degree of looseness in the mounting of the peripheral base of the barrel I collet reduces danger of lead breakage,

When an empty pencil is to receive lead, slight pressure on the top of the lead pushes that lead through both collets. For filling an empty pencil with a single lead which is too short to be pushed conveniently, the invention positions and limits the slots so that when the head of the tube is depressed the upper ends of these slots strike their respective barrel-prongs before reaching the limit of their depression stroke. Then the last bit of the tubes depression stroke will bend these prongs forward, and so spread them enough to leave the entire bore of the tube clear for a lead to fall freely by gravity past the location of these prongs. Preferably the stroke is limited so that this spreading' is too little to let the ends of the prongs spread past the outer surface of the tube walls, but only into the annular zone between the outer and inner surfaces of the rather thick walls of 'the tube, so that these prongs neverleave their respective slots. This provision is also useful when a leading lead has been worn too short to reach the barrel-collet, in which case an extreme depressing of the tube permits the next following lead to f all past the barrel-collet by gravity, without n requiring to be drawn by the tube-collet.

The description which follows, and the accompanying drawings. show embodiments of the invention which are illustrative, but it will be understood that variations may be made.

It is intended that the patent shall cover, by suitable expression in the claims. whatever of patentable invention is found in the constructions disclosed.

In the drawings. v

Figure 1 represents in medial longitudinal section a metal barreled pencil of magazine type, embodying the invention, in which the point of lead has been worn short;

Figure 2 is a similar showing of the lower part of the same, with the tube-collet projected, and lead thus drawn out;

Figure3isthesameasFigure 2butwiththe tube-collet retracted, leaving the fresh point of lead ready for writing;

Figure 4 is a similar view of that pencil when being filled from an empty condition, the showing being at the stage in which the leading lead has fallen past the barrel-collet and is temporarily stopped at the entrance to the tube-collet;

Figures 5 and 6 are sections on the lines 5 5, 6-6, of Figure 1:

Figure 7 is a perspective of the barrel-collet of Figures 8 and 9:

Figure 8 is a medial longitudinal section through a pencil embodying the invention in which the barrel is made of plastic Figure 9 is a detail of Figure 8 greatly enlarged;

Figure 10 is a medial longitudinal section through the greater part of a very simple construction of pencil embodying the invention, in which the barrel-collet is an integral portion of the barrel;

Figure 11 is a section, enlarged, on the line II-IP of Figure 10;v

Figure 12. is a medial section, greatly enlarged, through the tube-collet showing, a lead in the position portrayed in Figure 4;

Figure 13A is a medial longitudinal section through another embodiment of the invention having the characteristic that neither the barrel-collet nor the tube-collet ever releases its hold upon the lead; arid v Figures 14, 15 and 16 are cross sections, enlarged, respectively on the lines I4, I5, and I8 of Figure 13.

A simple embodiment of ,the invention is shown in Figure 13, where a pencil barrel I0 made of resilient metal has a collet Il whose prongs are tongues cut from opposite sides of the shell of the barrel, drawn thinner and bent inward toward the axis so as to point about 15% forward from a radial plane. These i pass through slots 22 in the interior tube 20, so as to engage opposite sides of the rod of lead 9 Within the bore 28 of that tube. 'I'he barrels point lportion tapers to an open end orifice I2, through which the tubes collet 2I projects. The tube 20, made of metal, plastic or any suitable material. is reciprocable endwise through the barrel I0, by sliding through a bearing-block I3 fixed in the lower part of the barrel; and the tubes sliding top block 23 normally projects from the top of the barrel, and may carry an eraser there. By thumb pressure on this top, the tube can be depressed against helical spring 25 until a shoulder 24 on the tube encounters the fixed block I3 of the barrel. This vspring 25 ordinarily holds the tube pressed upward-with the conical back 29 of the tube collet 2| seated in the barrels point orifice I2, when lead is present in that collet; or, if the pencil is empty of lead, with the tubes top sliding block 23 stopped by a bushing I4 xed in the top end of the barrel.

Since the prongs II of the barrel-colletcan function only through the slots 22 of the tube, the tube is made non-rotatable with respect to the barrel by giving it a non-round shape where it passes through the xed barrel block I3, as seen in Figures 14 and 15; and below that it may preferably be round, as seen in Figures 15 and 16.

Lead can be inserted when the eraser andits shell 26 are removed from the top of the axial bore 28. A lead of standard long length, illustrated in Figure 13, can be pushed down through the barrel-collet lI until its top en d is flush with the top block 23 of the tube. The leading end of this leadwill not then have reached the tube collet; but a replacing of the eraser will push it further to the tube collet 2|; and the incidental depressing of the tube will project that collet allowing the lead, pressing on the interior slope 2I (Figure 12) of the back of these prongs, to expandthe prongs enough to let the lead enter and be gripped. Repeated depressing of the tube will feed the leading end of the lead to writing position, as explained below.

The lower part of the tube is of resilient material and may be integral with the main body of the tube, as in Figures 13, 10 and 8; or may be Y stitute prongs. These prongs are set at an lncline at a slight angle from parallelism with they f axis. They tend resiliently to close the bore as the conical back 29 of the tube collet is so large' that it cannot fully enter the orifice of the barrel point l2; but it becomes firmly encircled by the end of the barrel; and so the lead point -becomes firmly supported to resist writing pressure.

However, the nearly parallel prongs of the tube-collet 2i, pressed by spring 25 backward toward the seat l2, have insuiliclent frictional holdl on the lead to resist the spring 25;' and so the tube collet 2| slips backward, leaving the lead projected, where it is being held by the barrelcollet, the successive positions being seen in Figures 1, 2 and 3. vThis^operationof step-feeding can be executed without either the barrel-collet or the tube-collet ever releasing its grip on the rod of lead.

When the pencil is empty of lead both collets in Figure 13 mildly oppose the introduction of a lead, but for an initial lling, the lead can easily be pushed through them. Other figures provide means for a lead entering an empty pencil to pass the barrel-collet by gravity.

Figures 10 and 1l illustrate the invention, as

thus far described, applied in a pencil whose barrel is a hexagonal metal shell, in which the prongsof the barrel-collet 5i are based in an ogee formation 52, affording them more resilient basal support. This also illustrates how an` inward bead 53 in the shell may afford a shoulder for fixing the position of an inserted block 54 as a base for the tube-returning spring 25. In this case the tube 68 is of 'metal, expanding in its upper part to constitute the magazine 85 for short leads, which is non-rotatable with respect to the barrel. both the barrel 50 and the magazine 65 being hexagonal.

Figures 1,-6 show a metallic barreled magazine pencil embodying the invention, in which the barrel-collet 'i I` lis an inserted thimble and washer from which the prongs are bent inward to engage the lead through slots 82 in a tube 80 which holds the succession of standard short leads 8.

80, yet not outside of the walls of that tube. This is limited by positioning the top bead 84 of the tube so that it encounters the top e'nd 14 of an internal ferrule which is fast within the barrel 18. The bottom end oi this at 'I8 constitutes the upward limit by which the bead 85 in the tube is arrested when there is no lead in the collet 2 I.

The tube 10 being empty, and having been depressed to' its limit, as seen in Figure 4, a lead lnserted can fall freely through the barrel-collet 1i until its leading end is arrested by the resiliently closed prongs of the tube-collet 2i as in Figure 4 and Figure 12. The bore ends in a conical taper 2i' which constitutes a cam for the 'end of the lead to spread the collet prongs 2|, when the user releases the tube from its depression so that the spring 25 drives the tube upward (to the left inA Figure 12) The barrel-collet 'lli prevents lead from moving upward with thetube; and the prongs 2i are spread by their opposed inclines 2|' as the tubes end rises past the stationary leading end of the lead. The travel upward goes far enough for the lead to. become grasped between the spread prongs. A repetition of the depressing and releasing of the tube will then feed the lead to a desired step of projection, as illustrated in Figures 1, 2 and 3. 'I'he lead point in Figure 1 is presumed to have been worn so that a step feeding is desired. This is attained by 4simply depressing the tube to the position of Figure the distancethrough which the user moves his thumb in depressing the tube, either tothe full extent permitted by its stop 'i4 or any less extent. .Upon releasing, the tube-collet 2| slides back over the projected lead, to the position of Figure 3, this movement being an vadvancing of the stationary lead relative to the tube-collet, while regression of the lead is prevented by the barrel-collet 1i.

The barrel-collet may take various forms. being an integral part of the barrel in Figures 13 and 10; being an inserted element in Figures 1-4; and being a floating washer in Figures 7, 8 and 9,

this last being preferred, and being shown mounted within a magazine pencil having a barrel made of plastic in Figure 8. The whole construction of pencil at present thought most to be preferred is that of Figures 8 and 9, in which a plastic barrel, either circular or polygonal, has taper to a point orifice holding a metallic bushing 81 This tube is composite, its lowest portion having .magazine for filling it with leads. When the pencil is empty, the first lead to be inserted will fall freely through the bore of the tube until it reaches the prongs Il of the barrel-collet. The slots 82, through which those prongs Vof the barrel-collet reach the lead within the tube, are limited in length, and are positioned so that on its depression stroke the tube does not reach the lower limit of its stroke until the upper ends of these slots 82 have reached and pushed slightly the prongs 'il of the barrel-collet, as seen in Figure 2 and Figure 4, where, it will be noted, these prongs 1i stand at an angle of about 30 from i against which the conical back 29 of the tubecollet 2i becomes seated by the tube spring 25.

The barrel-collet of Figures 8 and 9 is a washer, as seen in Figure 7, stamped from a sheet of resilient metal. Its prongs 9i extend inward from an annular base Sia which is mounted loosely in an interior clearance space between a thimble Sib and a block 8 Ic whose peripheral margins are set solidly together in a fixed position in the barrel. The space which they provide for holding the annular base Sia of the barrel-collet loosely between their respective bodies, may allowplay of :.002 inch, both in axial direction and peripherally, and this permits the barrel-collet to "float enough to adjust itself in relation to variations that may occur in the successive leads. In the pencil of Figures 8 and 9,"the limits of travel'of the tube are between the seated position of the tube-collet, illustrated at the bottom of ,Figure 8, andthe projected position in which the bead |04 at the top of the tube engages the -shoulder on a thimble that is fast within the top part of the plastic barrel 90.

In operation, one lls an empty pencil of the type of Figure 13 by removing the eraser and its metallic shell, thumbing down the top end o! the tube 20, and thrusting a long lead or a succession of short leads, or'otherwise pressing a single short lead, through to the tube collet, and then releasing the depressed tube. Repeated depressings and releasings of the top will feed the lead step by step. 'I'he operation is the same in the other figures, except that forv the' filling of an empty pencil it is not necessary to push the lead.

For. an example, to which however the inventor is not limited, the following dimensions are illustrative of the parts to which they relate. The leads to be used may be any of the standard sizes, viz,` diameter of .036' or .046 and length of 4", or 21/2" or 1135"; diameter of pencil barrel inch; diameter of tube 20, 1/8", thickness of wall of tube, .020 original width of slits in tube collet, .008; length of those slits, 3/4 inch; length of feeding stroke 1?; inch.

'I'he lbarrel collet 4is not necessarily a single pair of prongs, nor are the friction faces of tube prongs necessarily smooth, but these are here illustrated thus as such have been found sumcient.

I claim as my invention:

1. In a mechanical pencil of the class comprising a barrel, a lead-holding tube mounted coaxially in the barrel for reciprocation endwise, and a .spring pressing the tube backward of the barrel, the combination therewith of a resilient collet on the forward end of the tube, outside of the point end of the barrel, having prongs of the wall of the tube at a slight inclination from parallelism, for resiliently squeezing lead that is in the tube and so providing friction that is relatively low but is sufficient to drag the lead for-l ward; and a resilient collet on the barrel having prongs penetrating the tube at a slight inclination pointing forward from perpendicularity to the lead that is within the tube, thus providing friction which with regression of the lead becomes relatively high, sufhcient to arrest regression, but with progression of the lead relaxes to less than the frictional drag of the tube collet, sufficiently to permit forward feed of the lead.

2. A mechanical pencil as in claim 1 in which the tube collet has a tapered rear end, which the spring presses lagainst the end of the barrel, thereby increasing the tube collets squeeze of the lead.

3. A mechanical pencil as in claim 1 in which that portion of the tube which is at the region of the point is of resilient metal, longitudinally slitted with removal of metal to make the said tube prongs; those prongs being set obliquely inward toward the axis, and having their terminal portions constitute an external cam tapered backward, having a diameter which when aggregated with the diameter of the lead exceeds that of the barrel's end-orifice.

4. A mechanical pencil as in claim vl in which that portion of the tube which is at the region of the point is of resilient metal, longitudinally slitted with removal of metal to make `the said tube prongs; those prongs ibeing set obliquely inward toward the axis, and having their terminal portions constitute an internal cam tapered forward and yieldingly obstructing exit of a lead from the tube.

5. A mechanical pencil as in claim 1 in which the barrel is of metal and the barrel collet prongs are integral parts of that metal bentinward.

6. A mechanical pencil as in claim l in which the -barrel collet prongs have a. supporting base at the periphery of the barrel.

7. A mechanical pencil as in claim 1 in which the barrel collet has an annular base close to the periphery of the barrel, from which base its prongs extend to the tube and the lead therein; there` being means whoser longitudinal position is fixed within the barrel, holding said base.

8. A mechanical pencil as in claim 1 in which the barrel collet has an annular base close to the periphery of the barrel, from which base its prongs extend to the tube and the lead therein; there being means whose longitudinal position is xed within the barrel, providing play room whose dimensions are microscopic for said base to move about within xed limits.

' 9. A mechanical pencil asin claim 1 in which

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