US3507600A - Solid plastic nib - Google Patents

Description

April 21, 1970 D. R. CRESS SOLID PLASTIC NIB Filed Jan. 18, 1968 l mJy/jf /lVl/E/VTOR.

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fili/5- UnitedStates Patent O 3,507,600 SOLID PLASTIC NIB David R. Cress, Janesville, Wis., assignor t The Parker Pen Company, Janesville, Wis., a corporation of Wisconsrn y Filed Jan. 1s, 196s, ser. No. 698,825 Int. Cl. B43k 1/00 U.S. Cl. 401-258 2 Claims ABSTRACT OF THE DISCLOSURE A solid rod-like writing nib is formed of nylon or other suitable plastic that is distinguished by its ink wettability and that is provided with a plurality of longitudinal, capillary feed slots for conveying a liquid ink to a small, conical writing surface at the forward end of the nib.

The present invention generally relates to writing instruments of the type employing liquid ink, and it relates more particularly to a new and improved solid nib, formed of plastic and having externally disposed, longitudinal feed slots for controllably feeding ink to the writing surface at the forward end thereof.

In recent years, the so-called wick pen employing a relatively porous, soft plastic nib has become of importance in the writing instrument industry. Such pens have gained wide acceptance by the public despite several disadvantages which they exhibit when compared with ball pens and fountain pens. For example, since the ink is fed through the porous body of the nib, residue and sediment from the ink tends to fill and thus clog the pores thereby gradually diminishing the rate of flow of ink to the paper. Other disadvantages of many of these prior art type wick nibs is their tendency to squeal during writing and to lose their shape after relatively short periods of use. Moreover, such nibs do not write as smoothly or have the feel during writing of a good fountain pen or ball pen.

In the prior art, there are disclosed several solid writing nibs having longitudinally extending feed grooves for conveying the ink to the writing end thereof. Such nibs did not, however, perform satisfactorily. They scratched, did not feed the ink to the paper uniformly during writing, were too rigid, and had an extremely short life due to melting and deforming of the nib during use.

Therefore, the principal object of the invention is to provide a new and improved nib which has long life, which writes smoothly on normal writing surfaces such as paper, and which can be manufactured at a cost which will enable it to be competitively marketed.

Another and more specific object of this invention is to provide a plastic nib for use with various types of ink, which nib has an external, integral, and self-cleaning feed system.

A further object of this invention is to provide a new and improved writing instrument.

Briey, the above and further objects are realized in accordance with the present invention by providing a solid plastic nib molded of a plastic having a low coefficient of friction, a high melting point, good wettability characteristics, and having a plurality of capillary feed slots or grooves extending from a location in proximity to a hemispherical writing surface to a rearward location where they are fed with ink from the reservoir.

Further objects and advantages and a better understanding of the present invention may be had by reference to the following detailed description taken in connection with the accompanying drawings wherein:

FIGURE 1 is a longitudinally sectioned view of the forward portion of a writing instrument embodying the present invention;

3,507,600 Patented Apr. 21, 1970 ice FIGURE 2 is a greatly enlarged and partly broken away plan view of a solid nib embodying the present invention;

FIGURE 3 is a cross-sectional view of the nib of FIG. 2 taken along the line 3--3 thereof;

FIGURE 4 is a cross-sectional view of a writing nib similar to that of FIG. 2 but wherein the number and configuration of the feed grooves is modified; and

FIGURE 5 is an enlarged isometric view of another solid writing nib embodying the present invention.

Referring now to the drawings and particularly to FIG. 1 thereof, there is illustrated the forward end of a writing instrument 10 having a tubular barrel 12 which houses an ink supply and feed control mechanism of the instrument, substantially as described in application Ser. No. 419,463 led by Homer T. Green, now Patent No. 3,402,- 008, patented Sept. 17, 1968. An integral nib holder and feed bar 14 is threadedly secured in the forward end of the barrel 12 and includes a feed bar portion 16 which extends through a longitudinal bore in an overflow collector member 18 and into the forward portion of a cartridge type ink reservoir 20. The cartridge 20 is of a conventional type, comprising a tubular member that is sealed from the atmosphere at its rear to provide a vacuum type ink reservoir. Ink is fed from the reservoir through one or more capillary feed grooves 22 provided along the upper surface of the rear portion of the feed bar portion 16 to an annular Weir chamber 24 which surrounds the feed bar and which conveys ink from the rear feed passageways 22 to one or more forwardly disposed feed grooves 26 that also open into the weir chamber 24 and that are laterally displaced from the rear feed grooves 22. Replacement air is supplied through a non-capillary groove 28 which is provided in the nib holder 14 and which extends from a location forward of the barrel 12 to the Weir chamber 24. An annular collector chamber 30 which surrounds the collector member 18 is supplied with air through a non-capillary groove 32 and is supplied with ink through a capillary slot 34 connecting to the weir chamber 24. A hole such as cylindrical hole 36 is provided in the forward end of the nib holder 14 and extends from the forward end thereof to a location overlapping the forward portion of the forward feed groove or grooves 26.

A solid rod-like plastic writing nib 38 is loosely positioned in the hole 36 with the rearward end 40 of the nib press-fitted into the bottom of the hole 36 rearward of the forward end of the feed grooves 26. For optimum performance the diameter of the hole 36 should be greater than the external diameter of the nib 38 by about .001 inch to .O05 inch. In a preferred embodiment, the hole 3'6 is a cylindrical bore .078 inch in diameter and .590 inch in depth, while the nib 38 has a diameter and length, respectively, of .074 and .690 inch.

Ink is drawn by capillary action into the annular space between the nib 38 and the hole 36 in the nib holder 14 and thereby conveyed from the ink feed groove or grooves 26 to the forward end of the nib holder 14. The press t at the rear of the nib holds it in place during use and is provided by molding a small flat in the rear portion of the hole 36. Hence, the nib may be readily removed from the nib holder and yet a continuous capillary feed channel from the feed grooves 26 to the front of the nib is maintained.

The nib 38 which is formed of a suitable plastic, as hereinafter more fully described, is solid and has a forwardly disposed conical portion 42 terminating in a hemispherical writing surface 44. Ink is transferred from the annular space surrounding the nib within the forward portion of the nib holder 14 to the writing surface 44 by means of a plurality of spaced capillary feed slots 46 which extend rearwardly from the forward end of the writing surface 44.

In a preferred embodiment of the invention as best shown in FIG. 3, six equally spaced feed slots 46 are provided and each such slot has a V-shaped bottom 48 for providing an infinite capillary, thereby maintaining the bottoms of the respective slots 46 wetted with ink at all times. Generally, the greater the number of such slots, the less directional or skip-prone will the nib be, although the greater the number of slots, the greater the nib wear and ink metering rate. It has been found that a nib slot width of between .002 inch to .006 inch produces the best Writing nibs, the wider the slot the greater the metering rate. The slots 46 are closely spaced at the forward end of the writing surface 44, i.e., on the order of .00S inch apart, and taper outwardly in a rearward direction so that the cross-sectional area thereof remains approximately constant throughout the greater part of the conical forward section 42. Although the slots can extend all the way to the rear of the nib, the provision of the tapereddepth slots in the forward end of the nib facilitates iniection molding of the nib since the nibs can be withdrawn from the mold cavity without retracting the slot forming ribs from the mold.

It has been found that the nib 38 may best be molded of a polymeric material, and the use of nylon containing a uniform dispersion of about to 30% by volume of polytetrafluoroethylene resin, such as Teflon brand resin of the E. I. du Pont de Nemours Company, of Wilmington, Del., has performed best. Nylon resins are generally characterized by their very high degree of wettability and water absorbability, and by the high degree of toughness, strength and durability, although they are of relatively high coeflicients of friction, exhibiting a stickslip or non-smooth sliding motion, and are somewhat deformable under heat and abrasion such that line capillary grooves in a nylon surface may be smeared over or closed. Polytetrafluoroethylene is characterized by its very low friction, although it is extremely non-wettable and of relatively high cost.

Preferably, poly (hexamethylene adipamide)--nylon 6/6; such as Zytel 101 brand nylon resin of the du Pont company is used, and about 12% by volume of polytetraiiuoroethylene resin in the form of particles which are between tive and ten microns in diameter on the average. The polytetrafluoroethylene may be thermally modified to reduce its molecular weight and to enhance its waxy surface characteristics. A fiber form of polytetrafluoroethylene material may also 'be used. Nibs made of polycaprolactam-nylon 6, such as Plaskon nylon Type 8200 of Allied Chemical Corporation, of Morristown, NJ., containing about 12% by volume of polytetrafluoroethylene resin also performed satisfactorily. The combination of these two plastics, namely nylon and polytetrafluoroethylene, together with the longitudinal feed slots provides a nib which writes smoothly over a long period of time. While many thermoplastics that may be used will result in the feed channels being burnished or smeared closed after about one hour of heavy pressure handwriting, whereby skipping may occur, the highly wettable nylon in this nib maintains good ink flow along the nib and the polytetrauoroethylene resin provides a smooth or slick feel during writing.

Comparable results may also be achieved by making the nib of a nylon resin Iblended with up to about 50% by volume of a smooth wear-resistant polyacetal resin, such as Celcon brand resin of the Celanese Corporation of America, of New York, N.Y., or Delrin brand resin of the du Pont company. Polyacetal resins are characterized by their Very good strength and wear resistance, and by their quite low friction, although they are deformable under heat and abrasion such that tine capillary surface grooves will be smeared over or closed, and are of such low wettability as to require a wetting treatment or additive for use in a nib according to the present invention. In a nib made up of a blend of nylon and polyacetal resins, the polyacetal resin characteristics of smoothness and wear resistance, and the nylon characteristics of toughness and wettability are found, the wettability of the nylon overcoming the relative nonwettability of the polyacetal resin.

Even further, a tough 'but smooth, solid plastic nib provided with ink feeding slots and a wettable surface according to the present invention may also be made of a polyacetal resin or of a 5% to 30% by volume polytetrafluoroethylene-lled polyacetal resin, such as the Delrin and Delrin AF (polyacetal resin filled with about 15% polytetrauoroethylene resin by volume in 'ber form) brand resins of the du Pont company, but with the normal relative non-wettability of nibs formed of such materials being altered by application of a deep chemical, mechanical or other surface etching or satinizing to the nibs, or by incorporation of a wetting agent or a highly wettable ller in the resin.

The nib, when molded of the polytetrafluoroethylene resin lled nylon in the proportions specified above, is somewhat resilient and is slightly exed and compresed during normal writing. The variations in the pressure applied to the nib during writing thus causes movement of the portion of the nib disposed in the nib holder and provide somewhat of a pumping action which aids in maintaining the annular feed space around the nib clear for ink iiow. It will be understood that the amount of compression is too small to be felt by the person using the pen although he does recognize that the nib has a soft feel. However, the rear portion of the nib which is press-fitted into the non-circular cross section at the rear of the hole 36 does not move relative to the nib holder and does not, therefore, work itself loose.

Referring to FIG. 4, there is illustrated another embodiment of the present invention particularly showing a plastic nib having four longitudinally disposed feed slots 50 which are provided with iiat bottoms. Feed slots of this configuration may be more easily and inexpensively molded than the V-bottomed type, but they do not exert as great a capillary force on the ink to maintain the wick wetted at all times.

FIG. 5 is an isometric view of another embodiment of the present invention wherein a solid plastic nib 52, also molded of a polymeric resin consisting of nylon and 5% to 30% by volume polytetrauoroethylene resin, has a plurality of capillary feed slots 54 which extend from the forward portion of the nib to the rear end thereof. In addition, a circumferential capillary equalizer groove 56 is disposed intermediate the ends of the nib to insure that the ink is equally fed to the portions of all of the slots 54 extending to the -writing surface of the nib. As shown, the forward portion 58 of this nib is conical and terminates in a generally hemispherical writing surface 60.

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

I claim:

1. A solid rod-like synthetic plastic pen nib provided with a plurality of external radially-spaced longitudinally extending ink-feed slots of capillary dimension for conveying ink to the Writing end of the nib, said synthetic plastic comprising a combination of wettable plastic selected from the group consisting of nylon and wettability-enhanced polyacetal resins, in admixture within the range of from about 5% to 50% by volume of a resin having a low coeicient of friction selected from the group consisting of polyacetal resin,.polytetraluoroethylene resin and mixtures thereof.

2. A synthetic pen nib according to claim 1, wherein 5 6 said synthetic plastic comprises nylon containing from 3,287,288 11/ 1966 Reilling. 5% to 30% `by volume of polytetrauoroethylene resin. 3,306,267 2/ 1967 Matsumoto 401-258 References Cited FOREIGN PATENTS UNITED STATES PATENTS 5 1,454,400 8/1966 France.

1,237,926 3/1967 Germany. 1,205,920 11/1916 Miura 401-258 1,824,275 9/ 1931 Kellogg 401--258 LAWRENCE CHARLES, Primary Examiner

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