US2690737A

US2690737A - Mechanical pencil

Info

Publication number: US2690737A
Application number: US214595A
Authority: US
Inventors: John P Lynn
Original assignee: Individual
Current assignee: Individual
Priority date: 1951-03-08
Filing date: 1951-03-08
Publication date: 1954-10-05
Anticipated expiration: 1971-10-05

Description

Oct. 5, 1954 J. P. LYNN MECHANICAL PENCIL Filed March 8, 1951 1 N V EN TOR. [Jn/Q Patented ct. 5, 1954 bil'i@ STATES 'PATENT oFFicE Mpora-ANIoAL peuple John P. Lynn, Chicago, Ill. Applicatien. Marcil. 8, 1951, Serial; N91- 214.595

3 Claims, (Cl. 1Z0-18) This invention relates to a mechanical pencil having a hollow body through which a lead may from time to time be propelled into4 position tor writing, and more particularly to the propelling unit itself and the means whereby its parts may be iixedly interconnected'. and whereby the propelling unit may be permanently secured to one end of the pencil body with capacity for rotation relative thereto.

In a pencil of this general character I have incorporated certain improvements which conduce to simplicity of construction and dependability in operation. For this purpose I associate with the body oi the pencil a rotatable tip which induces travel oi a propeller by which an active lead is expelled through the tip end of the pencil. The construction of the tip, its connection with the pencil body, and the assembly of parts which constitute the pencil unit present certain iinproved features with which my invention is mainly concerned.

'in the accompanying drawing is shown a suggestive embodiment of this invention in the manner following:

Figure l is a vertical central longitudinal section through the lower end of the pencil body and of the propelling unit positioned coaXially thereof preliminary to securement thereto;

Fig. 2 is a similar View showing the propelling unit secured to the lower end of the propeller body;

Fig. 3 is a transverse section taken on line 3--3 of 2; and

Fig. e which is a view similar to Fig. 2 shows the coupling and locking sleeves in longitudinal section and rotated through 90 from the position of Fig. 2.

The pencil herein illustrated comprises a body A having at its lower end a rotatable tip B forming part of a propelling unit whereby to advance an active lead Z through the pencil into writing position. The body A is desirably formed of a suitable plastic, i. e. a composition material which may be molded to shape with the aid of heat and pressure. It is formed in the general shape of an axially chambered barrel having a cylindrical wall 6 which is inwardly tapered at 8 in its Vlower end portion. The inner face of the body chamber a in its lower end portion is cylindrical at b for a limited distance.

To a body A of the general kind under description is fitted the rotatable tip B which, together with the parts carried thereby, constitutes the propelling unit. This tip which is desirably allmetallic comprises a frustro-section having its 2. walls iii, at the point of maximum diameter, arranged to abut the proximate. end of the'tapered walls 8 of theA pencil body and lie flush therewith. The tipA conical section is axially hollow to provide therein a chamber c wherein is fiedly anchored the lower end portion of a guide tube Cfthat is'l slotted at M for substantially its entire length. This tube which extends upwardly beyond the tip walls io is accommodated in large part within the body where it is disposed coaxially of its chamber ci in spaced relation to the surrounding walls 5V to denne therewith an annular magazine for reception of reserve. leads. The tip, chamber c in its lower region is somewhat reduced in diameter and at its bottom en d the walls I ,l define a passageway suiiiciently constricted tov supportingly engage the active lead Z whose lower end. is protruded from the tip so as to be exposed for writing purposes. 'v

A helically coiled ribbon formed into a sleeve D surrounds the guide tube Q and extends from a point near its upper end downwardly in to the upper end portionv of the conical tip where the tip walls i0 are thinned to enlarge the chamber c suciently for reception thereof and also of the lower end pQrtion 2 2 of a driving sleeve E. This driving Sleeve is provided with an upper end portion 2 4, slightly enlarged, which is closely fitted within the cylindrical'lower end b of the body chamber a. A notch 26 formed at the top or" the driving sleeve receives a boss 23. that is outset from the helical sleeve D, thereby to establish a non-rotatable connection therebetween. Over the top of the helical sleeve D is placed a washer (or y washers) (i9 fitted upon the guide tube C and there held against removal as by staking the guide tube or spreading its walls 3g on opposite sides of its slot I4 at points above thel washer (or washers).

The upper end portion 24 of the driving sleeve E is snarled longitudinally see Fia 1. and in the process of its axial movement to final position within the lower end portion of the pencil body .A establishes a drive lit With the cylindrical inner face b of the body chamber a. The driving sleeve E is also drive-fitted to a surrounding coupling in the form of a sleeve E which is exteriorlytapered and longitudinally knurled in its lower end portion to engage with the tapered walls 8 in the lower end region of the body A. In the process of assembly, the pencil body may be molded around the coupling sleeve F or, preferably, the coupling sleeve is advanced axially through the chamber a of the body and pressed to a position of rest against its tapered walls 8; it is then held while the driving sleeve E is axially advanced therewithin (or vice versa), thereby establishing a drive fit between (1) the coupling sleeve F and the tapered walls 8 of the pencil body A and (2) the coupling sleeve F and the driving sleeve E therewithin. Fig. 1 illustrates the position of the coupling sleeve F shortly before it enters the tapered lower end portion of the pencil body to ce drive-ltted thereto. A very secure and permanent locking of the tip B to the pencil body A is achieved by the means just described.

Within the guide tube C is slidably tted a plunger G in the form of a wire having its top end laterally turned to provide a nger 34 which extends out through the slot l2 to track freely in the continuously extending helical gap which intervenes between adjacent coils ci the sleeve D. At its lower end this plunger is joined to a clutch H in the form of a slotted sleeve having opposed spring sections which frictionally engage the active lead i therebetween. In response to rotation of the tip B relative to the body A the guide tube C is turned, thereby to turn with it the plunger G whose ringer is thereupon constrained to move endwise within the helical gap of the sleeve D, thereby axially advancing or retracting the plunger, and with it the clutch. A manually operable feed for the lead is thereby provided, and one which will optionally produce propelling, repelling or expelling movements.

The coupling sleeve F acts in a special manner to connect the tip permanently and securely to the pencil body. When the coupling and driving sleeves are advanced axially, one toward the other and with pressure, the knurls of the coupling sleeve F are sunk into the tapered plastic walls 8 at the lower end of the pencil body to establish therewith a drive t which is non-rotatable, axially immovable, and laterally stable. At the same time the driving sleeve E which is forced endwise within the coupling sleeve F establishes therewith a drive fit which is non-rotatable, axially immovable, and laterally stable. The final position of the tip B relative to the pencil body is reached (1) when the large end of the frustoconical tip B abuts the smaller lower end of the body A and (2) when the coupling sleeve F has advanced to its limit in tight frictional engagement with the tapered walls 8 at the lower end of the pencil body.

When so positioned, the tip B will remain inseparably connected to the pencil body A. It will also receive from the coupling sleeve F, through its engagement with the walls 8 of the cylindrical chamber b at the lower end of the pencil body, a lateral support which extends for the entire length of the driving sleeve E. This is important because one of the most common points of weakness in mechanical pencils, where an operating tip is rotatably connected to the lower end of the pencil body, is the inadequacy of provision to prevent angular movement f the tip relative to the axis of the pencil body, with a possible resulting rupture of the connection therebetween. Any tendency toward looseness or lateral motion at this point of connection also militates against satisfactory use of the writing implement. By the means described, I have provided a simple i and dependable form of connection between the tip and the body, and have also reinforced such connection by a lateral support which extends for a substantial distance where there is the greatest eed for it. As a result, the tip will always remain axially aligned with the pencil body, with assurance that it will not become loose or separated therefrom.

I claim:

1. In a pencil having a hollow plastic body having walls denning an axial chamber having an inwardly tapered lower end, and a metallic tip carrying an associated lead propelling mechanisrn, means for rotatably securing the tip to the body comprising a coupling sleeve exteriorly tapered and knurled longitudinally press tted into said lower end of the chamber walls and "icticnally engaging the tapered walls thereof, and a driving sleeve rotatably connected to the tip and extending axially therefrom, said driving sleeve being formed exteriorly with longitudinal lanurls and being press tted at least partially within the coupling sleeve and rictionally engaging the interior thereof to establish therewith a tight driving fit.

2. In a pencil having a hollow plastic body having walls dening an axial chamber having an inwardly tapered lower end, and a metallic tip carrying an associated lead propelling mechanism including means providing a helical slot, means for rotatably securing the tip to the body comprising a coupling sleeve exteriorly tapered and knurled longitudinally press iitted into said lower end of the chamber walls and frictionally engaging the tapered walls thereof, a driving sleeve 10- tatably connected to the tip and extending axially therefrom, said driving sleeve being formed exteriorly with longitudinal knurls and being press at least partially within the coupling sleeve and fricitonally engaging the interior thereof to establish therewith a tight driving nt, and cooperating means on said driving sleeve and said slot providing means for restraining the latter against rotation with rotation of the tip.

3. In a pencil having a hollow plastic body having walls defining an axial chamber having an inwardly tapered. lower end, and a metallic tip carrying an associated lead propelling mechanism, means for rotatably securing the tip to the body comprising a metallic coupling sleeve exteriorly tapered and knurled longitudinally press tted into said lower end of the chamber walls and frictionally engaging the tapered walls thereor", and a metallic driving sleeve rotatably connected to the tip and extending axially therefrom, said driving sleeve being formed exteriorly with longitudinal knurls and being press fitted at least partially within the coupling sleeve and frictionally engaging the interior thereof to establish therewith a tight driving fit.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 1,556,701 Liddell Oct. 13, 1925 2,075,725 Kahn Mar. 30, '1937 2,272,915 Kelley Feb. 10, 1942 2,293,623 Para Aug. 18, 1942