US3583819A - Mechanical pencil - Google Patents

Abstract

A throwaway repeater-type pencil cartridge employs a molded plastic magazine, a molded plastic lead advancing clutch and a tubular point clutch assemblable by the mere dropping of the parts one by one into the casing.

Description

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References Cited UNITED STATES PATENTS 7 77 6 66 1 ll 0 00 4 44 n m mm "mu" mAmm m m m r N r mGmm f. E6 a w PD GS 9 0 6 65 9 99 1 ll ll 4 78 Primary Examiner-Lawrence Charles Attorney-Fidler, Bradley, Patnaude & Laza ABSTRACT: A throwaway repeater-type pencil cartridge employs a molded plastic magazine, a molded plastic lead advancing clutch and a tubular point clutch assemblable by the mere dropping of the parts one by one into the casing.

\ i tilt iii lilillllli illlllll WWI a J L mmj PW m m Mn ED M N4, mm i mm s MECHANICAL PENCIL The present invention relates to a mechanical pencil having a repeater-type step-by-step lead advancing means wherein a plurality of lead rods contained in the pencil are fed seriatim to the writing point in response to repeated actuation of the reciprocal lead feed mechanism. More particularly, this invention relates to a mechanism of this type employing more simplified components which may be assembled in a more facile manner.

Step-by-step lead advancing mechanisms as known in the prior art and exemplified by U.S. Pat. No. 2,528,328 to Baker et al. and U.S. Pat. No. 2,514,6l to Schweitzer are relatively expensive to manufacture because of the complex nature of their components and the difficulty of assembly. As a consequence, pencils employing this type of mechanism have always been relatively expensive compared to the screw type mechanical pencil. However, the step-by-step lead feed mechanism has several important operating advantages over the screw-type and, therefore, it would be desirable to provide a new and improved step-by-step lead feed mechanism wherein the components would be inexpensive compared to those of the prior art and wherein the mechanism is more compatible with automated assembly processes.

Therefore, an object of the present invention is to provide a new and improved mechanical pencil construction.

Another object of the present invention is to provide a new and improved step-by-step lead advancing mechanism using relatively inexpensive components.

A further object of the present invention is to provide a new and improved lead advancing mechanism wherein the components thereof may be formed of plastic in a molding opera tion.

A still further object of the present invention is to provide a new and improved step-by-step lead advancing mechanism wherein the components can be facilely assembled together.

A still further object of the present invention is to provide a new and improved throwaway-type cartridge which includes a supply of lead rods and a step-by-step advancing mechanism for feeding the lead rods from the supply chamber to the writing tip.

Other objects and advantages and a better understanding of the invention may be had by reference to the following detailed description of a preferred embodiment thereof taken in connection with the accompanying drawing wherein:

FIG. 1 is a fragmentary longitudinally sectioned view of a throwaway mechanical pencil cartridge embodying the present invention and showing the mechanism in an at rest writing position;

FIG. 2 is a longitudinally sectioned view similar to FIG. 1 but showing the advancing mechanism in a forwardmost position;

FIG. 3 is an exploded perspective view of a portion of the lead advancing mechanism of the present invention; and

FIG. 4 is a sectional view taken along the line 4-4 of FIG. 1.

Referring now to the drawings and particularly to FIG. 1 thereof, there is shown a self-contained throwaway-type pencil cartridge which is adapted to be used in a writing instrument housing such as that disclosed in U.S. Pat. No. 3,205,863 to Rhoades, which patent is assigned to the same assignee as is the present invention.

The cartridge 10 includes a shell 12 which may be formed of metal but might also be formed of plastic and which is tubular in construction having a plurality of progressively necked down portions 14, 15, 16 and 17. A generally tubular magazine 18 which is preferably molded of plastic defines a lead supplying chamber 19 and is slidably disposed in the main body section of the casing 12. After the chamber 19 has been filled with a supply of lead sticks or rods, a plug 21 is inserted into the rearward end thereof and secured in place. An annular flange 23 is provided at the rearward end of the magazine 18 and a rearwardly facing annular shoulder 25 is provided on the outer surface of the magazine 18 in spaced relationship from the flange 23 to cooperate with a plurality of reentrant tabs 27 at the rear end of the casing 12. These tabs 27 are bent inwardly after the magazine and the other feed mechanism has been placed within the shell 12 to prevent disassembly of the mechanism from the shell.

The magazine 18 further includes a forwardly extending elongated tubular section 29 having a centrally disposed aperture 31 therein whose diameter slightly exceeds that of the lead rods 33 with which the pencil is used. The lower wall 35 of the chamber 19 converges toward the opening 31 so that as the rear end of the lead rod 33 being fed downwardly through the instrument reaches the rear end of the feed opening 31 another lead rod contained in the chamber 19 will automatically follow it into the advancing mechanism. As best shown in FIGS. 1 and 3, the tubular section 29 is provided with a pair of diametrically opposed slots 36 and the forward ends of the thus formed parts of tubular section 29 are pointed at the distal ends 37.

Slidably disposed over the forward tubular section 29 of the magazine 18 is a lead advancing clutch 40 including a rearwardly disposed annular body portion 42 which loosely fits over the tubular section 29 and holds the clutch in place thereon.

The lead advancing clutch 40 further includes a pair of integrally formed fingers 43 and 44 which respectively include external camming surfaces 45 and 46 and internally disposed lead engaging surfaces 47 and 48 which, as best shown in FIG. 4, are semicylindrical. As more fully described hereinafter, when the magazine 18 is moved downwardly within the casing 12 to actuate the lead feeding mechanism, the clutch fingers 43 and 44 are moved downwardly and the cam surfaces 45 and 46 engage the annular shoulder 50 on the inner wall of the casing between the main body portion and the necked down portion 14 thereby to cam the fingers 43 and 44 radially inwardly so that the inner surfaces 47 and 48 finnly engage and grip the lead rod 33 contained therein to prevent movement of the lead rod relative to the advancing clutch 40.

A lead guide tube and point collet 52 extends through the forward portion of the casing 12 and is removably secured at its rearward end to the forward end of the tubular section 29 of the magazine 18. More particularly, the member 52 has an annular groove 53 near its rearward end, and internal beads 54 on the forwardly extending fingerlike portions of the magazine 18 are snap-fitted therein to removably secure the guide tube and point collet 52 to the magazine 18. The forward end of the member 52 is provided with a plurality of Iongitudinal slits which separate the forward end into a plurality of jaws 56 which cooperate with the internal wall of the forward portion 17 of the casing 12 to tightly grip the lead rod 33 contained therein when the point collet is in its rearmost assembled position as shown in FIG. 1. The bore of the collet member 52 is slightly larger than the lead rod 33. The jaws 56 are resiliently biased in an inward condition slightly smaller in aperture than the diameter of the lead rod 33 providing sufficient friction to retain the lead rod during forward movement of the jaws 56 from the reduced section 17 of the casing as shown in FIG. 2. With no lead in the pencil, thejaws 56 have a minimum external diameter less than the internal diameter of the most reduced section 17 of the casing 12 to permit assembly of the collet into the forward end of the casing from the rearward end thereof.

Mounted over the rearward end of the guide tube and point collet 52 is a guide bushing 58 having a rearward tubular portion loosely fitted over the forward end of the tubular projection 29 in the magazine 18 and having a necked down intermediate section 60 defining a forwardly facing annular shoulder 62 against which the rear end of a return spring 64 abuts. The bushing 58 further includes a forward portion 66 of still greater reduced diameter to define an internal annular shoulder 68 which abuts a forwardly facing annular shoulder 70 on the guide tube and point collet 52. As shown, in FIG. 1, the forward end of the return spring 64 abuts against an internal annular shoulder 72 provided intermediate the casing sections 14 and 15.

The cartridge including the lead advancing mechanism of the present invention is adapted to be easily and quickly assembled either by hand or by automated assembly equipment. In order to assemble this cartridge, the coil spring 64 is simply dropped into the rear end of the casing I2 so that it falls against the shoulder 72. The bushing 53 may then be dropped into the rear end of the casing 12 so that it falls into the rear end of the spring 64 and thereafter the lead guide tube and point collet 52 is dropped into place so that its shoulder 70 abuts against the annular shoulder 68 on the bushing 58. The lead advancing clutch 40 may then be dropped into place in the casing 12 and finally the magazine 18 is inserted. It is, of course, necessary that the slots 36 in the forward end of the magazine be aligned with the fingers 43 and 44 of the lead advancing clutch. This is accomplished automatically by virtue of the fact that the rearward ends 74 and 76, respectively, of the clutch fingers 43 and 44 are longitudinally staggered and the forward ends 37 of the tubular section 29 of the magazine 18 are pointed. As a result, the magazine will rotate relative to the clutch when the pointed surfaces 37 engage the lug surfaces 74 and 76. Accordingly, by merely dropping the parts one by one into the shell 12, the individual components automatically occupy the relative positions shown in FIG. I. Thereafter, the magazine 18 is pressed forwardly so that the shoulder 25 thereon lies below the tabs 27, on the shell 12. The tabs are then pressed into place to maintain the unit in an assembled condition.

OPERATION When the mechanical pencil cartridge has been assembled as described above, one of the lead rods 33 contained in the lead supply chamber 119 will slide down the sloping wall 35 at the bottom of the magazine chamber and its forward end will fall into the hole 31 through the forward tubular section 29 to some extent as determined by the misalignment of the apertures 31 and the bore through the guide tube 52. Actuation of the mechanism by depressing the magazine 18 into the casing 12 will result in the following operation. The lead guide and point collet 52 will, because of the snap fit between the beads 54 and the groove 53, move forwardly so that the jaws 56 relax. The forwardly facing annular shoulder 30 of the magazine 18 thereafter engages the rear end of the advancing clutch 40, and the camming surfaces 45 and 46 on the clutch fingers are moved against the shoulder 50. Continued depression of the magazine causes the fingers 43 and 44 to be cammed inwardly to engage the lead rod 33, and the clutch 40 moves forward until the underside of the annular flange 23 engages the end of the casing 12 as shown in FIG. 2. Since the point collet 52 is already in a forward position with the jaws 56 relaxed, the lead rod is held in place primarily by the fingers 43 and 44 on the clutch 40. Therefore, when the magazine is released and the spring 64 expands, the point collet 52 moves back into the shell 112. However, the clutch 40 is frictionally held in the tubular section I4 of the shell l2 and thus holds the lead rod 33 in a fixed position related to the shell. When, during its return movement, the rear end of the point collet 52 engages the forward ends of the clutch fingers 43 and 44 the clutch is moved out of the section 14 and the fingers 43 and 44 expand away from the lead rod 33. By this time the jaws 56 have retracted into a lead holding position. It may then be seen that the length of lead which is advanced upon e each complete actuation of the advancing mechanism is the distance through which the advancing clutch 40 may move relative to the point collet 52.

While the present invention has been described in connection with a particular embodiment thereof, it will be understood that many changes and modifications may be made by those skilled in the art without departing from the invention. Therefore, by the appended claims, it is intended to cover all such changes and modifications as come within the true spirit and scope of the invention.

Iclaim:

1. In a mechanical pencil of the step-by-step propulsion type, the combination com rising an elongated, integral, tu ular casing having a necked down front end,

a lead magazine element having a hollow, cylindrical main body portion for holding a plurality of lead rods and a forwardly extending, generally tubular section of reduced diameter provided with a plurality of longitudinal slots extending to and opening at the forward end to provide a plurality of forwardly extending resilient fingers,

an advancing clutch including a collar surrounding said fingers and slidable thereon and having a plurality of lead engaging clutch fingers respectively disposed in said slots,

an integral lead guide and point clutch element having an internal diameter larger than but approximating the external diameter of said lead rods to permit said rods to slide therein and therethrough,

said lead guide and point clutch element being mounted in said casing forwardly of said advancing clutch and having an enlarged forward end including a plurality of point engaging resilient jaws located forwardly of the front end of said casing,

the external diameter of said enlarged forward end exceeding the internal diameter of said necked down front end of said casing, thereby preventing the passage of said front end through said front end of said casing,

the rear end of said lead guide and point clutch element being snap-fitted into the forward end of said resilient fingers with the hole through said lead guide and point clutch in alignment with the hole through said tubular section of said magazine to permit assembly of said lead guide and point clutch element to said magazine after such parts are placed in said casing,

spring means disposed in said casing for biasing said lead guide and point clutch element in a rearward direction, and

cooperating means on said casing and said clutch fingers for urging said fingers into engagement with a lead rod positioned therebetween when said advancing clutch is moved forwardly in said casing.

2. The invention according to claim-9 wherein the forward ends of said resilient fingers are pointed, and

said clutch fingers have internal lug portions having rearwardly facing shoulders receivable in said slots for cooperating with the ends of said resilient fingers to guide said clutch fingers into said slots during assembly of said pencil.

3. The invention according to claim 2 wherein the rearward ends of said lug portions are longitudinally staggered,

whereby insertion of said tubular section into said advancing clutch causes relative rotation between said tubular section and said clutch to align said fingers with said slots.

4. The invention according to claim 1 wherein said advancing clutch is an integral, molded plastic part.

5. The invention according to claim 4 wherein the lead engaging surfaces of said fingers are semicylindrical.

Claims (5)

1. In a mechanical pencil of the step-by-step propulsion type, the combination comprising an elongated, integral, tubular casing having a necked down front end, a lead magazine element having a hollow, cylindrical main body portion for holding a plurality of lead rods and a forwardly extending, generally tubular section of reduced diameter provided with a plurality of longitudinal slots extending to and opening at the forward end to provide a plurality of forwardly extending resilient fingers, an advancing clutch including a collar surrounding said fingers and slidable thereon and having a plurality of lead engaging clutch fingers respectively disposed in said slots, an integral lead guide and point clutch element having an internal diameter larger than but approximating the external diameter of said lead rods to permit said rods to slide therein and therethrough, said lead guide and point clutch element being mounted in said casing forwardly of said advancing clutch and having an enlarged forward end including a plurality of point engaging resilient jaws located forwardly of the front end of said casing, the external diameter of said enlarged forward end exceeding the internal diameter of said necked down front end of said casing, thereby preventing the passage of said front end through said front end of said casing, the rear end of said lead guide and point clutch element being snap-fitted into the forward end of said resilient fingers with the hole through said lead guide and point clutch in alignment with the hole through said tubular section of said magazine to permit assembly of said lead guide and point clutch element to said magazine after such parts are placed in said casing, spring means disposed in said casing for biasing said lead guide and point clutch element in a rearward direction, and cooperating means on said casing and said clutch fingers for urging said fingers into engagement with a lead rod positioned therebetween when said advancing clutch is moved forwardly in said casing.

2. The invention according to claim 9 wherein the forward ends of said resilient fingers are pointed, and said clutch fingers have internal lug portions having rearwardly facing shoulders receivable in said slots for cooperating with the ends of said resilient fingers to guide said clutch fingers into said slots during assembly of said pencil.

3. The invention according to claim 2 wherein the rearward ends of said lug portions are longitudinally staggered, whereby insertion of said tubular section into said advancing clutch causes relative rotation between said tubular section and said clutch to align said fingers with said slots.

4. The invention according to claim 1 wherein said advancing clutch is an integral, molded plastic part.

5. The invention according to claim 4 wherein the lead engaging surfaces of said fingers are semicylindrical.

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