US3822949A

US3822949A - Ball point pen back end closure

Info

Publication number: US3822949A
Application number: US00060318A
Authority: US
Inventors: F Dick
Original assignee: Dart Industries Inc
Current assignee: Plastic Specialties and Technologies Inc
Priority date: 1970-08-03
Filing date: 1970-08-03
Publication date: 1974-07-09
Anticipated expiration: 1991-07-09
Also published as: DE2137296A1

Abstract

A pen plug particularly useful in ballpoint pens as a stopper to prevent back leakage of ink from the ink reservoir of such pens and yet function to allow passage of air into the pen interior. Such plugs include a plurality of substantially continuous synthetic filaments such as cellulose acetate, natural fibrous threads and synthetic filaments or mixtures of differing synthetic filaments encased in a plastic sheath.

Description

United States Patent 1191 Dick 1 1451 July 9, 1974 BALL POINT PEN BACK END CLOSURE [75] Inventor: Franklin Dick, New York, NY.

[73] Assignee: Dart Industries Inc., Los Angeles,

Calif.

22 Filed: Aug. 3, 1970 21 Appl. No.: 60,318

3,464,775 9/1969 Beal 401/199 FOREIGN PATENTS OR APPLICATIONS 1,164,745 9/1969 Great Britain 401/217 1,229,524 3/1960 France 401/217 806,331 6/1951 Germany 401/217 Primary ExaminerLawrence Charles Attorney, Agent, or Firm-Leigh B. Taylor; Kenneth J. I-Iovet; Paul R. Wylie ABSTRACT A pen plug particularly useful in ballpoint pens as a stopper to prevent back leakage of ink from the ink reservoir of such pens and yet function to allow passage of air into the pen interior. Such plugs include a plurality of substantially continuous synthetic filaments such as cellulose acetate, natural fibrous threads and synthetic filaments or mixtures of differ ing synthetic filaments encased in a plastic sheath.

8 Claims, 3 Drawing Figures 1 BALL POINT PEN BACK END CLOSURE Conventional ballpoint pens include an ink or fluid reservoir from one end of which'the typicalapplicator or writing tip protrudes. This tip, of course, is in contact with the ink and the opposite end of the reservoir is commonly open to the atmosphere so that air may enter the reservoir and displace the writingfluid as it is expelled from the writing tip. Ordinarily, the meniscus of the ink column'or a follower prevents the ink from flowing back through the open end of the reservoir, however, if the pen is jarred violently or a break occurs in the ink film at the ballpoint, the ink may leak from the open back end'of the reservoir. Leakage'of this type is quite undesirable since it may soil not only the users work product, but also his wearing apparel.

In attempting to alleviate this leakage, air-permeable plugs or stoppers of porous materials, such as sintered metal, urethane foams'and treated felts or the like have been inserted in the reservoir back-end opening. These have usually been separated by an air space from the not attained the degree of reliability that is required for such manufacturing techniques. In some instances, placement of stoppersin the reservoir is made difficult due to the size and unusual construction of the stopper, and this mayresult in an improper insertion and fit, thus creating a leaker. Neither is it uncommon for conventional stoppers to impair the flow of air into the reservoir so that the ink will not flow properly to the writing tip. In other situations of backflow past the stopper, the cause usually lies largely in the fact that the'pores of thestopper are toolarge. On the other hand, in instances of insufficient ingress of air to produceprloper writing action, the pores of the stopper are too small, either in the stopper material itself as initially'formed, or as a result of itscompression during installation in the reservoir.

This invention, among other things, provides a backend pen plug construction that is readily adaptable to high volume productivity because of the insertion and cut-off technique which may be employed in the manufacturing assembly process. As is more fully discussed below, this plug construction includes a plastic sheath within which there is retained a bundle of synthetic filamentous material. Similarly, it may, on occasion, be advantageous to use several different synthetic fibers or cotton and synthetic fibers in these plugs to lend additional strength to the bundle for processing purposes. Further, in each instance that fiber which is being relied upon for strength will be uncrimped and unbulked whereas the sealing synthetic fiber may be crimped and bulked or uncrimped and unbulked. I I

The compression of these fibers one upon the other a and fusion of the outermost fibers with the sheath eliminate any potential direct path. between the plug ends through whichink might flow. Likewise,'the compression fit between the exterior of the plug and the reservoir tends to completely seal this area so that in the event of pen failure, no leakage will be experienced around the plug perimeter.

Accordingly this back-end plug provides a reliable stopper means that may be used inside a separate ink cartridge intended for use in a pen or in the reservoir of a pen that is either directly filled or employs a cartridge.

With the foregoing more important features in mind and withsuch other features as may become apparent as this specification proceeds, the invention will be understood from the following description taken in conjunction with the accompanying drawings, wherein like characters of reference are used to designate like'parts and wherein: I I w FIG. 1 is an exploded partially cross-sectioned plan view of a typical ballpoint pen incorporating the airperrneable plug of this invention;

FIG. 2 is an enlarged cross-section of an extended length of air-permeable plug material prior to incorporation in a ballpoint pen or similar writing instrument;

FIG. 3 is a transverse cross-section taken along line 3-3 of FIG. 1. v

Referring now to the accompanying drawings in detail, and more particularly to FIG. 1, the reference numeral l0 designates a typical ballpoint pen. This pen, of course, further includes a barrel member 11 interior of which is a fluid reservoir 14, a writing tip or applicator 12, and-a stopper or back-end plug 16 which is airpermeable yet forms a positive obstruction to writingfluids. Thus, the stopper 16 will permit the ingress of air to displace theoutgoing ink at the writing tip and yet will prevent theback flow of ink 18 out of'the reservoir 14. Similarly, as is common to such pens, there is provided a cap member 20 to shield the tip 12 when the pen is not in use.

The stopper or back-end plug 16 is a sheathed bundle of fibers and is more fully described hereinbelow. Such stopper, however, is positioned at the rear the fluid reservoir 14in a typical press type fit. It should also be obviousfrom FIG, 1 that this form of stopper may be equally effectively used in the back-end portion of a ballpoint pen or similar writing fluid cartridge. Similarly, two or more stoppers of this type may be'employed in series and when several are so used, they may either abut or be spaced from one another. In any event, an air space 22 should be retained between the stopper or stoppers and the writing fluid or ink 18.

FIG. 2 illustrates in cross-section the intermediate tubular product 16A from which the air-permeable plugs 16 are severed during the pen manufacturing sequence.

Each of these plugs-is preferably comprised of an uncrimped, unbulked bundle of filamentous material 24 low-twist, cellulose acetate material having between about 3,000 and 25,000 total denier and being substantially parallelely arranged in the sheath 26. Altematively, the cellulose acetate fibers may be crimped and bulked prior to their encasement in the sheath 26.

Likewise, in certain instances, it may be desirable to incorporate other synthetic fibers, for example, polyester materials into the bundle in order to strengthen the filamentous mass for processing purposes. Preferably such added fibers would be uncrimped and would be positioned on the periphery of the bundle adjacent the sheath 26. Further, it is considered practical to use up to 40 percent of the total bundle of polyester material in these applications.

It is also conceived that an intennixture of natural (mercerized cotton) and synthetic fibers, for example, cellulose acetate, may also provide an effective stopper. In this instance, the cotton will lend strength to the bundle as it is being processed into plug form and may include as many as 50 such threads.

In each instance, however, the sheath 26 will preferably have an inside diameter of between about 0.025 inch and 0.250 inch and be made of a suitable plastic such as polypropylene or the like. Plug material 16A therefore may be manufactured by extruding the sheath over a suitably arranged filamentous bundle typical of which is six strands of 240 ends each.

It should also be obvious from FIG. 3, in particular, that the press fit of back-end plug 16 in pen barrel 11 is such that it seals any possible fluid passageway between the outer surface of sheath 26 and the bore surface forming the fluid reservoir. This then provides the user with a more reliable obstruction member in that positioning of the stopper in the reservoir backend opening is not critical to produce a good seal. Similarly, the intermediate product 16A is one which lends itself to ease of handling for the pen manufacturere. Thus, it should be obvious from the above that an improved stopper construction is here disclosed which in all respects represents a substantial advance of the prior art products and techniques.

In operation and so long as the ink remains out of contact with the plug air may find its way into the interior of the pen barrel and thereby displace the ink 18. Upon pen failure, however, the ink may flow to the rear of the barrel 11 and, of course, begin to permeate the plug. The dense synthetic fiber bundle and particularly the cellulose acetate will attenuate this flow and thereby begin a plugging action within the bundle. Additionally, contact of the acetate with typical pen inks produces a swelling action which further compresses the bundle and effectively produces a positive blockage to further flow as well as the ingress of air.

While in the foregoing there have been described and shown the preferred embodiments of the invention, various modifications may become apparent to those skilled in the art to which the invention relates. Accordingly, it is not desired to limit the invention to this disclosure and various modifications and equivalents may be resorted to, falling within the spirit and scope of the invention as claimed.

[claim:

1. An air-permeable plug adapted to act as a positive obstruction to writing fluids typically used in writing implements and comprising a substantially continuous sheath having an inside diameter of between about 0.025 and 0.250 inches and a low twist substantially continuous parallelly arranged filamentous material having a total denier of between about 3,000 and 25,000 encased in said sheath and further characterized by its perviousness to air and its imperviousness to writing fluids when exposed to and contacted therewith.

2. A plug according to claim 1 wherein said filamentous material is uncrimped and unbulked cellulose acetate.

3. A plug according to claim 2 wherein said filamentous material further includes a plurality of substantially continuous parallelly arranged polyester fibers positioned around the periphery of said cellulose acetate and adjacent said sheath.

4. A plug according to claim 2 wherein said filamentous material further includes a plurality of substantially continuous parallelely arranged cotton threads intermixed with said cellulose acetate.

5. A plug according to claim 1 wherein said sheath between about 0.025 and 0.250 inches in diameter and is of a polypropylene construction.

6. Awriting implement including in combination a fluid reservoir containing an ink supply, an applicator in contact with said ink supply and a back-end plug means comprised of a substantially parallelly arranged bundle of filamentous material having a total denier of between about 3,000 and 25,000, said means being further adapted to permit passage of atmospheric air while preventing backflow therethrough of the content of the reservoir.

7. A writing implement according to claim 3 wherein said plug means also includes a substantially continuous sheath having an inside diameter of between about 0.025 and 0.250 inches, said sheath encasing and retaining the bundle of filaments and being tightly positioned in an opening to said reservoir.

8. A writing implement according to claim 7 wherein said sheath is of a polypropylene construction.

Claims

2. A plug according to claim 1 wherein said filamentous material is uncrimped and unbulked cellulose acetate.
3. A plug according to claim 2 wherein said filamentous material further includes a plurality of substantially continuous parallelly arranged polyester fibers positioned around the periphery of said cellulose acetate and adjacent said sheath.
4. A plug according to claim 2 wherein said filamentous material furtheR includes a plurality of substantially continuous parallelely arranged cotton threads intermixed with said cellulose acetate.
5. A plug according to claim 1 wherein said sheath between about 0.025 and 0.250 inches in diameter and is of a polypropylene construction.
6. A writing implement including in combination a fluid reservoir containing an ink supply, an applicator in contact with said ink supply and a back-end plug means comprised of a substantially parallelly arranged bundle of filamentous material having a total denier of between about 3,000 and 25,000, said means being further adapted to permit passage of atmospheric air while preventing backflow therethrough of the content of the reservoir.
7. A writing implement according to claim 3 wherein said plug means also includes a substantially continuous sheath having an inside diameter of between about 0.025 and 0.250 inches, said sheath encasing and retaining the bundle of filaments and being tightly positioned in an opening to said reservoir.
8. A writing implement according to claim 7 wherein said sheath is of a polypropylene construction.