US1826473A - Mechanical pencil - Google Patents

Description

Oefn 46, w31.

c. R. KEERAN MECHANICAL PENCIL Original Filed Sept. 4, 1928 QM. md AM. .NQ

rsu-.aged oct. e, 1931 UNITED s'rA'rEs- PATENT oFFlcEf .m l m, I wml', ILLINOIS. ASSIGNOB T0 DUB-O-LITE PENCIL wurm, 0l' m; ILLINOIS, A. CORPORATION 0F IILIIOIS mIGAL PENCIL annum nea-amener 4. im, :um n. man. renewed ma 1s, mo.

including the usual screw-threaded plunger,

v ibut so designed that if the lead jammed, or when the screw reaches the end of its-operative movement, the forced rotation of the parts will not 'cause injuryv or breakage. Theinvention consists in certain features and elements of construction in com bination as herein shown and described and as indicated by the claims.

In the drawings Figurelisanenlargedaxialsectionofa l5 mechanical cil embodying this invention. Figure 2 1s a side elevation of a liner tube for the barrel. Y Fi 3 is a indicated at line 3--3 on Figure l. y 2 lil" Atis a transverse section taken as indicatd atline44 on l.

5 is a fragmentary axial section of certain parts ofL the feed mechanism on an enlarged scale.A Y

Gisarview similartoFigure showing a modified structure.

Figure 7 is a transverse section indicated at line 7-,-7 on Figure 6.

In general the' pencil illustrated in Fi e 3 1 is of a familiar type, having a barre 1,

which may be -understood as' being molded of bakelite or similar material, and a ta red vmetallic tip 2, rotatively engaged wit the reduced end portion of the arrel, -1. The lead, 3, is fed thro h the terminal, 4, of the tip, 2, by means o a plunger, 5, having a threaded portion, 6, engaged with the threads in the contracted neck portion, 7, of a cylin- 40 projecting into the bore of the hollow barrel, 1. Said bore is fitted with a metallic tubular lining, 9, which may be secured therein during the process of molding the barrel, 1, and

8, in rotation of the tip, 2.

It will be understood that the bore of the barrel with its lining tube, 9, provides anon- Y circular feature in the nature of a longitudinal channel, while the upper or innermost end ofzthe threaded portion,6, of the plunger is transverse section taken as taken asdrical-extension, 8, carried by the tip 2, and

-' which provides a' bearing for the extension,l

formed with a co-operatmg feature to revent rotation of the plunger within the arrel. This insures that when the tip, 2, is rotated onthebarrel, the threads at 7 will cause y the plun er to be fed longitudinally for propelllng t e lead, 3. Y

The tip, 2, is further provided withA a guide tube, 10 and a split sleeve,11, of resilient metal adapted to frictionally grip the lead, 3, 1n the vicinity of the terminal, 4. The sleeve, 1l, is of such a length that when the plunger, 5, enters the opposite threaded end of said sleeve far enough to begin feedin the lead out of the terminal, 4, the threadedF portion, 6, of the plunger will also enter this threaded end ofthe split sleeve, 11, separating it slightly for this purpose and thus causing it to become frictionally engaged on the threads. This arrangement permits the feed mechanism to repe or in other words retract the lead within the tip by reversed rotation of the latter, because the lit sleeve, 11, acts as a coupling by'virtue oits frictional grip upon the lead at one end and upon the threads at the other, and draws the lead back 'into the tip.

In a pencil of this type when the bore of a barrel is provided'merely with a groove or key-way, and the upper end of the plunger is flattened or formed with a laterally extending key which is positively engaged in such key-way, it will be seen that as the key reaches the threaded neck, 7 it will block further rotation of the tip. If, at such a time, the user does not realize that the last of the lead has been expelled, he may attempt to force further rotation of the tip, 2, and may thus twist oli' the end of the threaded plunger, 6, or otherwisedamage the mechanism. The same thing may happen if the leads should become jammed in the bore o f the terminal, 4, so as to oppose longitudinal movement of the plunger; the key-way in the bore of the barrel being positively engaged with the plunger will simply result in stripping of the threads on the plunger 'r in the neck, 7, if forced rotation is continued at the tip.

The present invention protects the mechanism against such injury by providing tlie 10 upper end of the threaded portion, 6, of the plunger with means which yieldinglyholds the plunger against rotation in the barrel, but will permit it to turn when the longitudinal movement of the plunger is definitely opposed either because it has reached the end 0f its normal travel or because its travel is obstructed as by jamming of the lead in the tip. As shown in Figure 1, the liner tube, 9, is cylindrical at the outer or lower end portion which serves as a bearing for the part, 8, of the tip, but the remainder of the length of the tube is polygonal in cross section,- preferably hexagonal,-so that its fiat sides form longitudinal channels of V-shaped cross section extendingalong the bore of the barrel. .The upper end of the threaded plunger, 6, is rigidly secured in the head of a small metallic shell. 12, of approximately cylindrical form having slits. 13, cut in its cylindrical wall to render it somewhat resilient. In the portions of the wall between said slits the shell has small outwardly projecting convex nodes 01' bumps, 14, which are disposed] at intervals to register in the V-shaped channels formed by the hexagonal tube, 9. These nodes or bumps, 14, thus ordinarily prevent rotation of the shell, 12,-and of the threaded plunger, 6, in the bore of the barrel. while they do not oppose longitudinal movement of the shell, but serve merely as keys in these channels or guideways in the normal feeding action. However, if the longitudinal .advance of the threaded plunger is'opposed. as for example, when the threaded portion, 6, has been fed down until the shell, 12, abuts the cylinder, 8, the forced rotation of the tip. 2. will turn the threaded plunger, 6, with the tip., causing the resilient walls ofthe shell, 12, to yield inwardly` and allowing the nodes or projections, 14, to ride out of the V-shaped channels and over the flat intervening side walls of the tube, 9, with a snapping or click? lng action. This will notify the user that the operation is not the normal feeding'action, while at the same time preventing any real injury to the parts. The tip and barrel may be separated at any time by merely pulling them apart longitudinally, thus allowing inspection of the mechanism and permitting the threadedV plunger, 6, to be-operated by hand while disassembled from the barrel for withdrawing it from the threaded part, 7, and either removing the clogged lead o'r inserting a new lead, as the case may require.

In F igures-6 and 7 I have illustrated a modification of this structure which is entirely suitable and satisfactory in a pencil which is adapted onlyto fecd the lead outwardly from the tip terminal, 4, and not to withdraw or` repel it. In this case the cylindrical'shell, 121l is'fitted snugly in a cylindrical' liner tube, 9, and while the shell may have slits. 13, to render. it slightly resilient. there ispo necessity for the nodes, 14,

meagre:

and there is not even a semi-positive engagement between the shell, 12", and the bore of the barrel. The frictional engagement between these parts which are both cylindrical in this form of the device, is sufficient` to hold the threaded plunger against rotation when the tip, 2, is rotated, but this-friction is not suliicient to interfere with the longitudinal movement ofthe plunger in the barrel. With a right-handed thread the feeding action and the frictional drag of the shell, 12a, in the liner tube, 9a, tend to pull the tip, 2, against the end of the barrel, 1. But if this pencil were also provided with a coupling,r sleeve. 11, for withdrawing the lead, it will be seen that opposite rotation of the tip, 2, would tend to feed the tip away from the barrel, 1,.by reason of the friction between the shell, 12, and thc bore which would oppose upward or inward movement of the plunger in the bore. The parts could be readily pushed together, but the average user would not understand thc situation and the tendency of the tipAand barrel to separate during the repelling operation would appear as a defect. Therefore, this modified form is not recommended in combination with a coupling sleeve or other means for causing the lead to be withdrawn, as well as propelled outwardly in the tip. In the structure shown in Figures 1 to 5 the projections. 14, on the shell, 12, do not frictionally engage the hexagonal guide tube, 9, but permit free sliding movement of the plunger along its axis within this bore.

Where barrels of moulded material, such vas bakelitc. are used, the tube, 9, may be dispensed with and the hexagon form moulded directly in the barrel.l

I claim 1. In a mechanical pencil, a threaded leadpropelling plunger, a barrel in which it is longitudinally movable, a hollow threaded member engaging the thread of the plunger, said hollow member being rotatable with respect to the barrel for moving the plunger, and means by which the plunger is yieldingly held against rotation in the barrel.

2. In a mechanical pencil, a lead-propelling plunger, means having a threaded portion. a barrel in which said pl 0er means is longitudinally'movable, ahollow threaded member engaging the thread of the plunger means, said hollow `1nember being rotatablewith respect to the bari-el for moving the plunger means, and yielding means operatively conneeting the plunger means and barrel to normally prevent relative rotation thereof.

3. In a mechanical pencil, a threaded leadpropelling plunger, a barrel in which it is longitudinally movable, a hollow threaded member engaging the thread of the plunger, said hollow member being rotatable withvrespectto the barrel for moving the plunger,

and a substantiallyV cyllndrical shell carried by the plunger and engaging the bore of the barrel, the wall of said shell being slit to make'v it radially resilient.

4. Ina mechanical pencil, a threaded leadpropelling plunger, a barrel in which it is longitudinally movable, a hollow threaded member engaging the thread of the plunger, said hollow member being rotatable with respect to the barrel for moving the plunger, anda substantially cylindrical element carried by the plunger and in frictional engagement with the bore of the barrel.

5. In a mechanical pencil, a threaded lead-` propelling plunger, a barrel in which it is longitudinally movable, a hollow threaded member engaging the thread of the plunger, said hollow member being rotatable with respect to the barrel for-moving the plunger, and a member on the threaded member frictionally engaging the bore of the barrel and adapted to slip therein in the event of forced rotation of the threaded plunger in the barrel.

6. In a mechanical pencil, a threaded leadpropelling plunger, a barrel in which it is longitudinally movable, a hollow threaded member' engaging the thread of the plunger, said hollow member being rotatable with respect to the barrel for moving the plunger, said barrel being provided internally with a V- shaped channel, means projecting from said plunger normally located in said channel and yieldable to permit it to ride out ofthe channel upon forced rotation of the plunger in its barrel.

7 In a mechanical pencil, a threaded leadpropelling plunger, a barrel in which it is drical element longitudinally movable, a hollow threaded member engaging the threadlof the plunger, said hollow member being rotatable with respect to the barrel for moving the plunger, said barrel being provided with a longitudinal'- V-shaped channel, and .a substantially cylindrical shell on the threaded plunger having its cylindrical wall slit to make it radially resilient, and beingprovided with a convex projection normally located inv said channel, but adapted to yield inwardly by reason of the resilience of the cylinder for disengagement upon forced rotation of the plunger in the barrel.

8. In avmechanical pencil, a threaded leadpropelling plunger, a barrel in which it is longitudinally movable, a hollow threaded member engaging the thread of the plunger, said hollow memberbeing rotatable with respect to the barrel for moving the plunger, said barrel being provided with a polygonal bore forming V-shaped channels, and a cylincarried by said plunger, and

in the bore except upon the application of unusual force.

9. Ina mechanical pencil, a barrel having an axial opening, a tip mounted for rotation on the barrel, a tube carried by the tip extending into the axial opening of the barrel, a plunger assembly having'a vthreaded connection with the tube and comprising a tubular component in contactwith the axial opening and movable over the tube.

10. In a mechanical pencil, a barrel provided with an axial opening having a noncircular portion, a tip mounted for rotation on the barrel, a tube carried by the tip, a plunger assembly having a threaded connection with the tube and com risin a plun er rod extending into the tu an a tubu ar component adapted to operatively engage the non-circular portion of the axial opening and move over the tube.

11. In a mechanical pencil, a lead-propelling plunger means having a threaded portion, a barrel in which said plunger means is longitudinally movable, a hollow tubular threaded member engaging the threaded portion of the lun er means, said tubular threaded mem er ing rotatable relative to the barrel for moving the plunger means, said plunger means and barrel being so formed as 'to resist relative rotation during normal longitudinal feeding movement of the plunger means and to permit relative rotation upon forced rotation of the plunger in the barrel. CHARLES R. KEERAN.

having inwardly yieldable walls normally l

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