US 3639070 A
A writing and marking tip comprising a bundle of synthetic fibers disposed in generally longitudinally aligned relation, such fibers being bonded to each other at zones of contact by an adhesive, the tip being preformed to a predetermined cross section and being provided with longitudinally extending sidewalls and a planar end face lying in a plane inclined to the tip axis at an angle of from approximately 60 DEG and comprising the marking face, such marking face having chamfered or beveled edge portions connecting the sidewalls and face for promoting the uniform ink laydown or trace during writing or marking.
Description (OCR text may contain errors)
United States Patent Davidson 1 Feb. 1., 1972  MARKlNG-PEN-TYPE WRITING INSTRUMENT  lnventor:
 Assignee: The Gillette Company, Santa Monica,
 Filed: Jan. 13, i971  Appl.No.: 106,197
Henry Davidson, Huntington Beach, Calif.
Related US. Application Data [MI (,lontinuation-in-part of Ser. No. 846,375, July 31,
 US. Cl ..401/l99 [51 lnt. Cl ..B43k 8/00  Field of Search ..40l/l96207  References Cited UNITED STATES PATENTS 2,025,286 12/1935 Hutchinson ..40l/l98 2,453,201 11/1948 Cushman ..40l/207 2,481,803 9/l949 Weaver ..40l/207 FORElGN PATENTS OR APPLlCATlONS 1,027,095 2/ l 953 France ..40l/202 1,418,087 ll/l965 France ..40l/l99 Primary ExaminerLawrence Charles Alr0meyl-lenry Davidson  ABSTRACT A writing and marking tip comprising a bundle of s \nthetic fibers disposed in generally longitudinally aligned relation. such fibers being bonded to each other at zones of contact by an adhesive, the tip being preformed to a predetermined cross section and being provided with longitudinally extending sidewalls and a planar end face lying in a plane inclined to the tip axis at an angle of from approximately 60 and comprising the marking face, such marking face having chamfered or beveled edge portions connecting the sidewalls and face for promoting the uniform ink laydown or trace during writing or marking.
4 Claims, 4 Drawing Figures MARKING-PEN-TYPE WRITING INSTRUMENT RELATED APPLICATIONS This application is a continuation-in-part application of application Ser. No, 846,375, now abandoned.
BACKGROUND OF THE INVENTION Writing instruments employing porous tips so as to produce wide, rather brushlike strokes or traces are well known in the prior art. Generally, such prior art devices have employed rather soft, easily deformable applicating ends or marking tips which exhibit permanent deformation and loss of original tip .size prior to complete exhaustion of the marking fluid in the container in which the tip is permanently mounted. Such prior art marking devices often employ felt tips or nibs. It is also well known to use a marking tip or nib having a rectangular cross section and a marking face disposed angularly with respect to the axis of the nib; such prior art constructions being shown in U.S. Pat. Nos. 2,713,176, 3,003,181, 3,080,600, 3,089,182 and 3,133,307.
The difficulties and disadvantages with the marking tips of prior art writing instruments of the marking type is that the fiber bundle comprising the tip or nib was of soft, easily deformable, fibers which had a short wear life and were adapted for use with a particular type of ink composition that was notentirely desirable. To overcome these difficulties, it was suggested that the fiber and binder of the tips should be stiffer, of high strength, and constructed of a less flexible fiber. While this construction overcame the difficulties of prior art devices, other problems arose such as the difficulty in providing a good continuous trace left by contact of the marking tip with the paper. Such trace in the stiffer type of marking nib was discontinuous, varied in width and ink density, and still resulted in an excess amount of ink being left at the end of the race where the movement of the pen was terminated. Moreover, the stiffer type of nib still gave rise to audible dissonances which were irritating since they produced noisy, scratchy and squeaky sounds when the nib was moved relative to the paper during writing. Another difficulty of the trace of such writing tips was that the edge of the trace was oftentimes irregular.
SUMMARY OF THE INVENTION Generally, the present invention provides a writing and marking tip comprising a bundle of synthetic fibers disposed in a generally longitudinally aligned relation, such fibers being bonded to each other at zones of contact by an epoxy resin which may be of a thermoplastic or thermosetting type, the tip being preformed to a predetermined crosssection and being provided with longitudinally extending sidewalls and a planar end face lying in a plane inclined to the tip axis and comprising the marking face, and means for promoting the uniform ink laydown or trace through the marking face comprising a chamfered or beveled edge portion connecting the sidewalls and face, said chamfering resulting in the removal of a dense resin peripheral region from the writing face, the width of the removed portion in the plane of the writing face being principally related to the dimensions of the writing face and the concentration of epoxy resin in the solution used in forming the tip.
One object of the above generally described marking tip is g to provide a tip which is relatively stiff, of high strength, and not easily deformable for use in a marker-type pen.
Another object of the marking tip of the above-described invention is to effect a continuous, regular, constant width, relatively constant ink density trace during marking.
Still another object of the above-described invention is to provide a tip which substantially eliminates irritating audible, scratchy, and squeaky noises during the useful writing life of the marker pen.
Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a front elevation view, partly in section, of a writing instrument of the marking type employing an exemplary writing tip constructed in accordance with the present invention;
FIG. 2 is a side elevation view of an exemplary embodiment of a writing tip of the present invention;
FIG. 3 is an end view of the writing tip of FIG. 2; and
FIG. 4 is a partial view taken along the plane IV-IV of FIG. 2.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing, there is shown a writing instrument of the marking type comprising a cylinder, indicated generally at 10; an absorbent ink-carrying reservoir, indicated generally at 20; and a writing tip or nib, indicated generally at 30. The container 10 generally comprises a cylinder 11 which may be of plastic material, as integral base 12 for supporting the cylinder in the upright position, and a neck portion 13 on which a cap (not shown) may be removably secured so as to prevent the inadvertent marking by the tip and to prevent evaporation of the ink in the writing tip 30.
The reservoir 20 may be constructed of material and in a manner well known in the art, such as a plurality of polyester, polyamide, polyvinylacetate or polyethylene fibers which may be drawn into a cylindrical shape, and inserted within the cylinder in a manner to provide venting of the reservoir body.
The writing tip indicated generally at 30 and comprising the subject matter of the present invention may be fixedly mounted in the neck portion 13 of the container 10. The tip 30 has an inner end 31 contacting the reservoir 20 so as to receive and supply ink by capillary action to the outer end of the writing tip. The outer end 32 of the writing tip extends exteriorly of the neck portion 13 of the container to provide a writing face, indicated generally at 33.
The writing tip is constructed from a rod which comprises a plurality of synthetic fibers, such as polyesters or polyamides, that are formed into the rod through a process including heating, sintering, saturating, evaporating and curing. Of specific interest to the problems solved by the present invention, the rod is saturated or impregnated after preheating and sintering in a saturation tank through which the rod is pulled. The tank contains an epoxy solution containing a cross-linking agent which may comprise epoxy resin in a concentration in the range of 6 percent (i /z percent) to 12 percent (:1 percent) in a solvent such as methylethylketone, when the rod has dimensions as will be described hereinafter. During the saturation process, the impregnating solution fills approximately all of the voids between the synthetic fibers in the sintered rod.
Following saturation, the rod is then passed through an evaporator to remove the methylethylketone. The evaporation may be accomplished by passing air at an elevated temperature in a countercurrent direction through a tube surrounding the rod which may accomplish the evaporation of approximately percent of the methylethylketone. It is during this process of evaporation that the problem with respect to proper writing characteristics is believed to develop. During the evaporation, there is a densification of resin at the peripheral regions of the rod which gives rise to excessive hardness of the peripheral region of the rod, prevents proper capillary ink flow in such peripheral region, and prevents contact of the fibers in the peripheral region with the surface being marked so as to give rise to ink laydown irregularities. As the percentage of resin in the impregnating solution is increased, this densification of resin in the peripheral regions of the rod increases so as to aggravate the above described problems. For example, with a 6 percent resin concentration, the dense resin region or shell is approximately 8 to 12 mils and with a 12 percent concentration is approximately 10 to 15 mils for a rod having dimensions as hereinafter described.
To overcome these problems, the writing tip 30 is provided with an outer end 32 which has beveled or chamfered edges so as to remove the high-resin peripheral region of the rod from the writing face 33. The writing face 33 comprises a central region 34 and a peripheral region indicated generally at 35. The peripheral region 35 includes two longitudinal side edge portions 36, 37 and a far end edge portion 38.
The writing face 33 is generally oblique to the longitudinal axis of the writing tip 30 at an angle A, preferably of 60. This angular relation of the writing face to the horizontal when the writing tip 30 is vertically oriented has been found to be an angle suitable for the general user. It has been experimentally found that the chamfered edge portions 36, 37 should be disposed at an angle, indicated at B, in the range of 40 to 50 and preferably 45. It also has been found that the dimension C of the longitudinal chambered edge portions 36, 37, when a 6 percent concentration of epoxy resin is used in making the rod, may be a minimum of 12 mils, but it is preferred that a larger dimension be used to compensate for any variations in the process of forming the rod which would result in a thicker dense region, such as 35 mils, which has been found satisfactory in commercial production of tips. The dimension of the chamfer portions to obtain good writing characteristics depends on the width or area of planar face 34, the size of the fibers used, the concentration of epoxy resin used in impregnation, the evaporation rate, and other factors which affect the tip body peripheral region hardness and thickness. The principal factor, however, is believed to be the epoxy resin concentration. When the concentration is increased from 6 percent to 12 percent, for example, the minimum chamfer width (in the plane of the writing face) would be 15 mils.
The chamfered far end edge portion 38 is disposed at an an gle, indicated at D, relative to the plane of the marking face central region 36, in the range of 92 to 98, preferably 95. The dimension E of the chamfered end edge portion 38 (in the plane of the face 34) must be at least 12 mils with a 6 percent epoxy resin concentration and 15 mils with a 12 percent concentration but it has been found that a dimension of approximately 44 mils is desirable in production.
The above exemplary dimensions, angles and chamfer limits for the writing point 30 have been given for a writing point having a length of approximately 1.20 inches, a cross-sectional longitudinal dimension of approximately 220 mils and a lateral dimension of approximately 130 mils. The face 34 has a longitudinal dimension of 254 mils before chamfering and a lateral dimension of I30 mils. In chamfering the preferred amounts, approximately 62 percent of the original writing face is removed and face 34 is less than 50 percent of the original area. As seen in the exemplary embodiment, both inner and outer ends 31 and 32 are formed with identical marking faces so that during assembly of the marking pen, either end of the writing tip 30 may be inserted into the neck portion of the container. The ends of the writing tip 30 are formed by cutting the oblique writing face with a rotary saw operating at approximately 1,500 to 5,000 rpm. or a guillotine-type chopper operating at from to 100 strokes per minute. The writing tips are then chamfered using a 40 to 60 grit silicon carbide grinding wheel operating in a range of 1,500 to ,000 rpm.
it will be apparent from the above detailed description of the writing face of the exemplary writing tip 30 that the near end edge portion 39, as viewed in FIG. 3, is not chamfered as are the other three edge portions. The reason for this omission of the chamfering of this edge portion will become apparent when it is considered that in use, the marking pen will be held such that a trace will normally not be commenced by contact of the near edge with the writing surface. Normally, the pen will be held such that the chamfered end edge portion 38 is farthest away from the user. The pen will not be held such that its longitudinal axis is less than the angle between the central region 34 of the writing face 33 with the writing surface. Accordingly, the near end edge portion 39 of the writing face will normally not contact the writing surface and therefore there is no reason for chamfering of such edge.
While a specific exemplary embodiment of a writing tip having a writing face has been shown and described above, it will be appreciated that the particular dimensions, angles, and the like relating the chamfered edge portions with the central region of the writing face will depend upon the particular synthetic fibers chosen for the rod of the writing tip and the manufacturing process by which such rod is formed. This, modifications and variations of the present invention are possible in light of the above teachings. lt is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.
1, A writing and marking tip comprising an elongated bundle of longitudinally extending synthetic fibers bonded with a resin so as to comprise a rod having a peripheral region with a density and hardness greater than the density and hardness of the central region of the rod and through which ink flow is attenuated said rod being preformed to a rectangular cross section and provided with a generally planar writing and marking face lying in a plane inclined to the longitudinal axis of the rod, and
means for facilitating a continuous, uniform and regular ink laydown by said writing and marking face comprising three chamfered edge portions including longitudinal side edge portions and the far end edge portion, said chamfer removing, in the plane of the writing and marking face, at leas 12 mils from the longitudinal side edge portions and the far end edge portion, whereby during normal usage only the writing and marking face comprised of the softer central region of the rod will contact the writing surface.
2. The writing and marking tip of claim I wherein the chamfer removes 35 mils from the longitudinal side edge portions and 44 mils from the far edge portion.
3. The writing and marking tip of claim 1 wherein the writing and marking face has an area of less than 50 percent of the original area prior to chamfering the edge portions of said face.
4. The writing and marking tip of claim 2 wherein said rod is impregnated with a solvent containing a 12 percent concentration of epoxy resin prior to evaporation.