US2992904A - Method of etching metallic writing balls - Google Patents

Description

July 18, 1961 R. w. F. MOREL ET Al 2,992,904

METHOD OF ETCHING METALLIC WRITING BALLS Filed Aug. 20, 1958 flay Jill 14625:.

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United States Patent O 2,992,904 METHOD OF ETCHING METALLIC WRITING BALLS The present invention relates to writing instruments of the ball-point type wherein writing fluid is conveyed from a reservoir into contact with a writing surface by means of a small rotating ball. More particularly, the present invention relates to improvements in characteristics and methods of manufacturing writing balls whereby writing instruments may be caused to deposit ink and write on almost any type of writing surface, including oily, greasy and highly calendered surfaces upon which ordinary instruments of the ball-point type are incapable of writing.

The deposit of ink or other writing fluid by a ballpointed writing instrument depends on the fact that the ball actually rolls in contact with the writing surface so that ink or writing fluid is carried by the surface of the ball from a reservoir within the writing instrument into engagement with such writing surface. It will be understood that the ball will roll only if the frictional resistance offered by the writing surface is greater than that offered by the bearing surface or ball scat against which the ball rotates Within the writing tip. When the Writing surface is oily or greasy, ball-point pens having highly polished balls often fail to make a continuous deposit of ink because the ball tends to skip on the paper and thus fail to revolve in its seat.

One object of the present invention is to provide a writing instrument that will always deposit a uniform, continuous trace regardless of the type of Writing surface, whether oily, greasy, etc., and which employs a writing ball at all times offering greater resistance to the Writing surface over which it is moved than it does to the bearing surfaces or ball seat. For convenience of terminology, this capacity of the writing instruments of the present invention to write on smooth, slick, highly calendered or greasy surfaces will hereinafter be referred to as grease-writing, and writing instruments possessing this unique property as grease-writers.

Friction between a ball and a writing surface can be increased by providing the ball with treads or indented portions. A ball with crossing indented lines was illustrated in Patent No. 1,514,519, but the manufacturing method was not described and would present enormous problems since a normal ball is only about 0.04 inch in diameter, A roughened writing ball (made by mechanical or chemical treatment of a steel ball) was suggested by Zorn in French Patent No. 894,857 published in 1945. A ball having an etched surface, presents sharp asperities or peaks; during Writing, the writing pressure is concentrated on these peaks and movement between the ball and its seat ploughs and wears the seat with great rapidity thereby rendering the writing instrument useless since the desired clearance between the ball and socket cannot be maintained and the pen delivers excessive amounts of ink and blots. When the seat or socket is plated or hard, these ball peaks are rapidly worn away, thereby causing loss of the desired friction with the writing surface in addition to loss of necessary clearance between ball and its socket.

2,992,994 Patented July 18, 1961 The present invention relates to a method which, for the first time, permits the production of a ball with a controlled and regulatable proportion of its surface in the form of spaced area-portions having smooth surfaces corresponding to a true spherical ball surface, areas between said smooth area-portions being in the form of ink-receiving channels extending below the original spherical surface to a controlled and regulatable depth, and presenting wall portions at angles that insure proper frictional engagement with a writing surface. The resulting writing ball is novel and has characteristics which have not been attained heretofore; it is not only a grease writer when used in a Writing instrument, but it retains its grease writing properties for a long time Without undue wear of the seat or socket, even when such seat or socket is made of brass, although good results are obtained in silver and nickel plated seats and sockets. The materials, conditions, proportions, modes of operation, steps and characteristics of the method, the writing ball and writing instrument embodying such ball form the subject matter of this invention.

Generally stated, the present invention relates to a process of producing an improved writing ball for use in a ball-pointed writing instrument, such ball. being characterized by an enhanced ability to frictionally engage and roll upon oily, greasy or highly calendered writing surfaces while oifering a minimum of frictional wear-producing surface areas in engagement with bearing surfaces of the writing instrument. The writing balls of the invention are of any desired solid metal, are substantially spherical, having highly polished surface areas or areaportions constituting part of an original spherical surface, but are uniquely provided with a multiplicity of fine, fluidreceiving channels extending to a depth of between 10 and 300 micro'inches below the surface of the ball (in the case of balls having a diameter of about 0.04 inch) so as to present relatively steep side Wall portions adjacent the polished surface. Upper edges of these side walls, portions of which are at an angle to the ball surface at least as great as 30, enable the ball to frictionally grab the writing surface and thereby insure continued rotation of the ball as the writing instrument is moved in writing. In contrast, the highly polished spaced surface areas remaining between the channels (which preferably constitute about 20% to 30% and not over 50% of the original surface of the ball) present an optimum bearing area to the ball socket and seat with minimal friction. The result is a writing ball that can develop a maximum of sliding friction in contact with almost any type of writing surface, including even oily or greasy surfaces, While actually decreasing the resistive friction adjacent the ball seat.

The writing balls of the invention are produced in unique manner either from conventional highly polished steel or stainless steel writing balls or from other solid metals, by a simple process of first masking surface portions of the ball in a desired pattern, and then removing exposed surface portions of the ball preferably by the action of a chemical or electrolytic etching solution. In a preferred method, the surface of the smooth ball is covered with spaced particles of a finely divided, acid-resistant, solventsoluble organic material in a controlled, substantially reproducible, random pattern. If desired, the coated or masked ball may then be further subjected to treatment, such as exposure to a moderate temperature, to soften the masking particles and enhance their adhesion to the ball surface, still leaving polished portions of the ball exposed. Thereafter, the masked ball is subjected to the effects of an etchant for a period of time sufficient to remove the ball surface, only at the exposed areas, to the desired depth of between 10 and 300 micro-inches. The etching action is then stopped, the ball rinsed, and the masking particles removed to reveal the spaced original, highly polished surface portions of the ball, such portions presenting a smooth, generally spherical surface adapted to slide upon the ball seat of a writing instrument. The method of this invention is not only applicable to the relatively common metals such as steel, stainless steel, and various alloys, but also to all other hard and durable materials from which a writing ball can be made, such as the various sintered or cemented carbides such as silicon carbide, tungsten carbide and boron carbide, alumina, zirconium oxide, etc., and which are sufficiently dense and solid to develop a smooth surface when subject to normal ball forming and polishing operations.

An object of the present invention is to disclose and provide a controllable, regulatable method of treating solid metallic balls for use in writing instruments to develop and impart improved writing characteristics therein.

Another object is to provide a writing ball for use in writing instruments, the ball having a long life as a grease writer.

A further object is to disclose and provide a novel series of steps, utilizing materials and conditions which controllably produce writing balls of novel characteristics.

Those skilled in the art will readily appreciate numerous other objetcives and advantages of the invention from the detailed description given hereinafter.

FIG. 1 is an enlarged sectional view of a writing tip of a writing instrument embodying the ball of this invention, the ball being in elevation and schematically shown, with the ball in writing and rolling contact with a writing surface;

FIG. 2 is a greatly enlarged view of a part of a polished, solid metal ball, the left hand portion being in elevation and the right hand portion in section;

FIG. 3 illustrates the ball portion shown in FIG. 2, after an organic, etch-resistant masking material has been deposited on the surface;

FIG. 4 illustrates the ball portion after the application of the etchant and before removal of the masking material; and

FIG. 5 illustrates the ball portion after the removal of the masking material.

Generally, a ball point writing instrument comprises a barrel including an ink-containing cartridge which terminates in a writing tip having a socket Whose lips 11 are inturned sufficiently to rotatably retain the writing ball 20 in the socket and against a seat 12. A channel 13 supplies ink from the cartridge to the socket. Radial distribution channels such as 14 are often formed in the seat. The tip may be made of any suitable metal (brass 1s easily machined and often used) and may be plated as in Patent 2,813,512. The clearance between the ball and the seat and socket lip is minute (on the order of 0.001 inch or less) and is carefully adhered to in manufacture.

The ball of this invention (more or less idealistically represented at 20) is of solid metal and presents spaced islands or area- portions 21, 22 of the original, polished spherical surface of the ball, these area-portions being surrounded by ink receiving, normally interconnected channels or depressions 23 shown stippled in the drawing. The depth of these channels (below the original spherical surface) varies but the major proportion of such channels have a depth of between 10 and 300 micro-inches, although some depths reach 500 micro-inches (i.e., between 4 and or of the diameter of the usual 1 millimeter ball) and the incidence of channels of 50 to 300 micro-inches is high. Side wall portions of these channels, adjacent the edges of the area-portions or 4 islands, are preferably at angles of between 30 and to tangents to the spherical surfaces of such area-portions.

The deposit of ink by ball-pointed writing instruments involves contact of the writing ball with the writing surface and exertion of writing pressure in a downward and lateral direction on the writing tip. This writing pressure, exerted by the writer, forces the ball 20 onto the surface of the paper 30 which, in turn, forces the ball back onto the bearing seat 12 within the ball recess or socket. The contact of the ball with the paper creates a frictional force tending to cause rotation of the ball 20 when the pen is moved in writing. Likewise, the contact of the ball with the seat 14 sets up a frictional force within the ball socket. These frictional forces are exerted in opposite directions so that the question of Whether the ball will skid or roll on the writing paper depends on the relative magnitude of these two opposing forces. If the ball is to start rolling to initiate writing, the sliding friction at the point of contact of the ball with the paper must be greater than the sliding friction ofiered by the bearing surfaces within the ball socket.

The ball of the present invention presents edges of the spaced islands and wall portions of the channels to the writing surface or paper thereby positively translating the'lateral movement of the writing tip into rotation of the ball. The ink-containing channels convey ink to the writing surface. At the same time, the area-portions of true spherical contour provide low-friction, sliding bearing surfaces against the seat. The ball is free from asperities or sharp peaks which would normally wear the seat and socket. Some of these islands or area-portions may have an average dimension, in plan, on the order of 50 to micro-inches, but in general, their average dimension is on the order of 100 to 500 or 600 microinches, and excessively large islands, exceeding 800 microinches in average plan dimension are undesirable.

The novel construction of the writing balls of the invention actually tends to reduce sliding friction adjacent the ball seats below values normally obtained, and Without the use of special metals and material or procedures in forming the ball seat. As a result, the writing instruments of the invention are enabled to start immediately, and to write continuously with excellent grease writing characteristics and life, on practically any writing surface.

These desirable results and mode of operation have been obtained in accordance with the present invention by means of a novelprocess of masking a substantial portion of the surface of a writing ball, prior to subsequent treatment or etching of unmasked or exposed portions, such process permitting a pattern of microscopic channels of controlled depth to be formed below the Zone of an original spherical surface of the ball while retaining a multiplicity of small island-like highy polished portions of the original surface.

One of the first requirements of the method is that the solid metal balls be polished, smooth and clean. A portion of a polished clean ball 20 is illustrated in FIG. 2. Cleaning with non-oleag-inous materials such as alkaline trisodium phosphate is preferred to the use of trichlorethylene or other material which may leave trace films of oil; material which may interfere with subsequent adhesion of organic, resinous material to the ball surfaces. Pas'sivation is preferably avoided; a degree of passivity exists in stainless steel balls, but de-passivation by hot citric acid and dilute HCl pickling is normally not required. In all instances the balls should be dried, without promoting loss of hardness or surface oxidation. Relatively low temperature air drying is. satisfactory.

Various organic resinous or gummy materials and lacquer-type products may be app-lied to the clean, dry balls to form spaced, protected areas of desired size, distribution and total or aggregate area. The material so applied must be in a state of very fine particles, passing 325 mesh and preferably smaller than 10 microns and on the order Of 1 Q 2 microns in average dimension.

These materials should be virtually insoluble in and unreactive with [the etchant employed. Natural resinous materials and rosins such as abietic acid, dragons blood, shellac, storax, colophony and synthetic resins of the terpene phenolic and phenol formaldehyde types may be used; materials of the type disclosed in Patent 2,168,756 may be employed. Cellulosic derivatives such as cellulose acetate in volatile solvents and similar lacquer-like materials, may be atomized or fogged upon the balls. A terpene phenolic resin having a melting point of about 90 C. (of the type mentioned in Patent 2,168,756) may be used as a fine powder, as a liquid fog or as a solution fog. When powdered organic and resinous materials are employed, it is often desirable to employ an extender in admixture therewith. Corn starch, colloidal clays, such as bentonite or diatomaceous earth, may be used to the extent of from 1 to 4 parts of such inert diluent or extender to 1 part of the resin or rosin by weight.

Attachment of the particles of masking material to the balls (when the material is in finely divided form) can be accomplished by tumbling a batch of clean, dry balls in a container to which a controlled amount of the masking material has been added. From to 50 milligrams of the rosin, resin or effective masking material per 10,- 000 balls may be used; the extender is not included in this loading. Tumbling for 10 to 40 minutes is adequate. The finely divided organic masking material is nipped between the balls and caused to adhere thereto in a random, discontinuous, spaced pattern.

The amount of masking material per 10,000 balls and the tumbling time will vary with fineness of subdivision of the masking material, the melting or softening point of the material, the heat generated during tumbling and the presence of an extender such as starch. The temperature during tumbling should not be permitted to rise sufliciently to excessively soften or melt the masking material; the tumbling time should be suflicient to impart a similar pattern to all of the balls. In some instances and with some masking materials, it is desirable to lightly heat the masked balls after they are removed from the tumblers, and while theyare in a mono-ball layer, to soften and fluidize the resin and take advantage of its surface tension by permitting [the resin to assume more symmetrical, compact form on the surface of the balls and to more tenaciously adhere thereto upon subsequent cooling.

Solutions of masking material in a volatile solvent may be applied in the form of a very fine spray to balls while rolling upon a sinus compound curved incline. By the use of pressure air added (to the nozzles, partial vaporization of solvent takes place before the tiny droplets contact and adhere to the balls, producing very small masked areas in a scattered pattern.

FIG. 3 illustrates particles of masking material 24, 25 and 26 adhering in spaced relation to the polished surface of ball 20", at the conclusion of a masking operation.

After the writing balls have been suitably masked, exposed portions of the ball are removed to a desired depth of between about 10 to 300 micro-inches by subjecting such exposed portions to the action of an etchant. Excellent results have been achieved, for example, through use'of a 35% to 57% solution of ferric chloride, 45 seconds to 2 or 3 minutes exposure to a nearly saturated solution (49%), at room temperatures, produced splendid results. Other suitable chemical etch solutions include 10% to 25% solutions of sulfuric acid or nitric acid, or mixed acid solutions, such as mixtures of hydrochloric and nitric acids or hydrochloric and sulfuric acids, to name but a few. Almost any etching solution used in the treating of steel or similar metal surfaces may be ernployed. Electrolytic etching may also be satisfactorily carried out at room temperatures and with a number of conventional solutions. For example, the application of a relatively low potential (4 to 8 volts) on solutions of hydrochloric acid mixed with methanol and lactic acid has provided satisfactory results.

The effect of the etching solution is to remove surface metal from the writing balls only at the exposed areas between the island-like protective particles of masking materials. It is evident that if the particles of masking material were not present, the entire surface of the ball would be subject to attack by the etching solution, permitting a maximum depth variation between high and low areas of the etched surface of only about 10 to 20 microinches. In contrast, as is clearly shown in FIG. 4, the novel effect of masking in accordance with the invention is to allow a multiplicity of fine ink receiving channels 23 to be etched to any desired depth below polished, masked surface portions of the ball, and over a surface area of the ball predetermined by the masking. Of importance in obtaining this beneficial result is the fact that the etching action on exposed surfaces can be prolonged considerably beyond periods of etch used heretofore, to achieve etched depressions 4 to 20 or more times as deep as has been possible with prior techniques.

After etching has continued for a period suflicient to provide a desired channel depth, the etching action may be terminated by quenching the ball in a large quantity of water or other non-reactive liquid. Thereafter, the balls may be subjected to the action of a solvent capable of removing the masking material from the surface of the ball to expose the masked, highly polished surfaces, and dried.

FIG. 5 illustrates a portion of the ball after the operations of masking, etching and mask removal. Polished spherical surface area portions 21' and 22 are now exposed, providing desired bearing surfaces and, in conjunction with channels, presenting edges which engage a writing surface, insure rotation of the ball during writing and convert the instrument into a grease writer.

The crystal structure of solid metal balls, such as stainless steel balls, varies and the depth of the channels varies from one section to another of the same ball; the conditions during etching are such as to cause the channels to extend a distance of from to $4 of the original ball diameter below the original surface. In FIG. 5, the side wall 28 is seen to meet the tangent T of the spherical surface of area-portion 22 at an angle of about 70, whereas the wall on the other side of the area-portion meets a similar tangent at about 30. In general, the side walls are at angles of between 30 and 90 to these tangents, with substantially no undercutting. The maximum depth of the channels (with respect to diameter of ball) is approximately that illustrated at side wall 28.

The following specific examples are intended to be representative of the practice of the invention, as just described.

EXAMPLE I A group of 10,000 conventional, highly polished steel writing balls (stainless No. 440C, 0.039 in average diameter, approximate weight 39.8 grams) is cleaned by immersion for 5 minutes at C. in a solution of 60 grams per liter of reagent grade tri-sodium-phosphate. After cleaning, the balls are rinsed in water, methanol and dried.

The clean dry balls are placed in a baflled tumbler with from 25 to 50 milligrams of a terpene phenolic resin (melting point C.), ground to pass 325 mesh, and the balls and powder tumbled together for a period between 15 and 25 minutes, particles of the powdered resin adhering to the surface of the balls as a result of heat generated on contact. Thereafter, the balls partially masked with the particles of resin are dusted with talc and placed in an oven maintained at about l60-180 C. for approximately 5 minutes. The heating causes the powder to tenaciously adhere to the surface of the balls, thus fixing the pattern produced by tumbling.

The masked balls are now subjected to chemical etch- .60 seconds.

"7 ing using a near saturated solution of 'FeCl (having a specific gravity of 20 C. of 1.54) for a period of about During the etching, the balls are gently agitated so that bubbles of air adhering to the balls will rise to the surface of the etching solution. At the end .of the period of etch, the etching reaction is quenched by immersion of the balls and etchant in a large quantity of water orstop bath, the balls being subsequently rinsed by decantation. Following the water rinse, the etching powder is dissolved ofi" the surface of the balls by decantation in a solution of acetone until the solution is clear. The halls are then dried, cleaned in a solution of tri-sodium-phosphate for three minutes and again rinsed in water, acetone, and dried.

Observation of the treated balls at various magnifications revealed approximately 75% of the surface areas of the balls covered with etched channels extending below the polished surface of the ball a distance between about and 300 micro-inches, with some at depths of as much as 500 micro-inches and having a width of about 80 to 200 micro-inches. Remaining portions of the surface areas were composed of small irregular islands of approximately 50 to 500 micro-inches in width having highly polished surfaces.

In other runs performed in the same manner, masking was accomplished with finely divided particles of abietic acid and with particles of natural wood rosin. In each case, the particle size was sufficiently small to permit passage through a No. 325 mesh screen. The characteristics of balls so masked were substantially identical to those masked with the synthetic resin.

EXAMPLE II A group of 10,000 stainless steel balls cleaned and masked as in Example I, is subjected to an electrolytic etch employing the following solution:

Etching is accomplished in a Micarta tumbler having either a graphite or steel bottom, with graphite rods used as cathodes. The tumbler containing the balls is immersed in the etching solution, which is maintained at about 25 C., and a potential of 6 volts applied to the electrodes for about one minute. During etching, it is desirable to tilt the tumbler at a 45 angle and to rotate it at about 50 rpm. The etching reaction is immediately quenched in water, and rinsing accomplished by decantation with acetone and water as in Example I.

Microscopic examination of the electro-etched balls reveal results similar to those obtained with the chemical etch described in Example 1.

EXAMPLE III Groups of 10,000 stainless steel writing balls are subjected to chemical and electrolytic etching in accordance with the procedures of Examples I and II, except that the masking powder is diluted prior to tumbling by the addition of approximately 100 grams of corn starch (or calcium silicate, or similar finely divided inert substance) of particle size capable of passing through a 325 mesh sieve. Following tumbling, the balls are etched as in Examples I and II.

Results equivalent to those achieved in Examples I and II are obtained, except that somewhat finer pattern and a greater uniformity in the lateral dimensions of the chan nels etched into the polished surfaces of the balls is observed.

EXAMPLE IV A group of 10,000 steel writing balls, cleaned as in Example I, are placed in a vibratory tray and lightly masked with a fine mist or spray of a clear cellulose acetate lacquer. The balls are then removed from the "8 agitator and allowed-to air dry-for 20' to 40 minutes prior to etching with FeCl as in Example I.

Subsequent to the etching, the balls are rinsed by decantation in a lacquer solvent (a mixture of ethyl and amyl acetate and methylethylketone) for about 15 to 20 minutes or until the solvent is clear indicating complete lacquer removal. Again, the results are similar to those obtained in Example I.

The effect of this surface structure of the ball, including deep channels with sharply inclined cliff edges, is to enable the ball during writing to frictionally grab the fibrous upper surface of the writing paper and thereby insure the presence of substantial sliding frictional forces at the contact interface even though the ball is actually rolling on the writing surface. In contrast, the presence of the channels between the highly polished island portions of the ball surface actually reduces the ball area in sliding frictional contact with the ball seat. In addition, excess ink in the channels acts to flood the ball seat with ink on both sides of the ink supply passage 13 so that a uniform lubricatingeffect is achieved. Moreover, the depth of the channels 23 is sufiicient to stand up to the normal abrading action of the paper and hail seat, during use of the writing instrument, so that the property of grease-writing will be retained throughout long periods of use. In other words, not only does the novel construction of the ball insure excellent grease-writing performance or quality, but also long grease-writing life, and without any impairment of normal writing usefulness of the writing instrument.

The remarkable results obtainable by use of the writing balls and methods of this invention, as compared with writing instruments employing smooth balls or balls roughened in accordance with prior techniques, are exemplified in Table I. In this table, four different groups of writing instruments, each employing writing balls of different characteristics, are evaluated. Group A, used as a standard of comparison, employs conventional highly polished steel balls. Group B employs balls masked and etched in accordance with the invention, specifically by the procedure of Example I. Group C employs balls subjected to superficial etching of the entire ball surface with ferric chloride, whereas Group D employs balls mechanically roughened by rolling between plates coated with an abrasive. The grease-writing ability and life, as well as general writing characteristics, of all groups of writing instruments were tested under identical approved conditions. Grease writing capacity was determined by the ability of a writing ball to deposit a clear trace on No. 379 Bruning paper; grease-writing life being determined by the period of time a Writing instrument would continue to write on such paper. General writing characteristics evaluated included the quality of the trace during normal writing, and the freedom of instruments from In contrast, conventional instruments were completely incapable of writing on the Bruning paper while the masked etched balls of Group B deposited clear unbroken traces immediately upon contact with the paper, such traces being of substantially better quality than those deposited by the balls of Groups C and D. Particularly significant is the fact that the writing life of the masked, etched balls was six to ten times that of the completely etched balls.

It may be noted that the matt or roughened. surface of the channels between the area-portions is readily wetted by the inks normally used. in some instances (as where the metal of the ball is not readily wetted by the ink), it may be desirable to condition the surfaces of the channels to enhance their abilityto become wetted by and filled with ink, to insure adequate supply of ink to the writing surface. This conditioning is preferably carried out after etching and before removal of the masking material and may be attained by thermal vaporization of a suitable metal (or wetting agent) in a vacuum chamber containing such balls, the vaporized metal (silver is an example) being deposited upon the channels only. The masking is then removed as previously indicated. Ionic surfactants and substances such as tricresyl phosphate may be similarly adsorbed on the channel surfaces to enhance wettability with ink.

We claim:

1. A method of controllably generating a textured, channeled, ink-retaining surface on a metallic writing ball provided with an original, smooth, spherical surface while retaining a desired portion of said smooth surface in the form of dispersed bearing areas whereby increased friction is generated between said writing ball and its writing surface comprising: cleaning solid metal balls having polished spherical surfaces with a non-oleaginous cleanser and drying said balls; attaching to the polished surface of each clean ball, in spaced relation, a multiplicity of fine particles of an organic material resistant to etching solutions by tumbling the balls in the presence of said organic material in the proportion of between about 20 and 50 milligrams of said organic material per 10,000 balls having a diameter of about 0.04 inches to thus cover between 20% and 50% of the surface of each ball, said organic material comprising: a material from the group consisting of natural rosins and synthetic resins; subjecting said balls to the action of an etchant for the metal of said balls for a time and at a temperature sufiicient to produce ink-receiving channels extending below the original surfaces a distance of between and of the original diameter of each ball; separating the etchant and its products from the balls; and removing the attached organic material to expose spaced, polished area-portions of the original spherical surface on each ball.

2. A method of controllably generating a textured, channeled, ink-retaining surface on a metallic writing ball provided with an original, smooth, spherical surface while retaining a desired proportion of said smooth surface in the form of dispersed bearing areas whereby increased friction is generated between said writing ball and its writing surface comprising: cleaning solid metal balls having polished spherical surfaces with a non-oleaginous cleanser and drying said balls; attaching to the polished surface of each clean ball, in spaced relation, a multiplicity of fine particles of an organic material resistant to etching solutions by tumbling the balls in the presence of said organic material to thus cover between 20% and 50% of the surface of each ball, said organic material comprising a material from the group consisting of natural rosins and synthetic resins intermixed with an extender; subjecting said balls to the action of an etchant for the metal of said balls for a time and at a temperature sufiicient to produce ink-receiving channels extending above the original surfaces a distance of between and of the original diameter of each ball; separating the etchant and its products of reaction from the ball; and removing the attached organic material to expose spaced, polished area portions of the original spherical surface on each ball.

3. A method of treating a large group of small spherical metallic writing balls with original, smooth, polished surfaces for use in writing instruments to controllably generate on each ball a random pattern of dispersed bearing areas of the original surface surrounded by interconnecting ink-receiving channels whereby friction is increased between each such treated writing ball and a writing surface when it is in use in a writing instrument comprising: tumbling a large group of small spherical metallic writing balls in the presence of a multiplicity of fine particles of an organic material resistant to an etchant to cover be tween 20% and 50% of the original surface of each ball; subjecting the group of balls so treated to the action of an etchant for the metal of the balls for a time and at a temperature sufficient to produce interconnecting inkreceiving channels extending below the original surfaces of said balls at a distance of between 4 and $4 of the original diameter of each ball; removing the etchant and its reaction products from the balls; and removing the attached organic material to expose a random pattern dispersed bearing areas of the original surface surrounded by interconnecting ink-receiving channels.

4. A method of treating a large group of small spherical metallic writing balls with original, smooth, polished surfaces for use in writing instruments to controllably generate on each ball a random pattern of dispersed bearing areas of the original surface surrounded by interconnecting ink-receiving channels whereby friction is increased between each such treated writing ball and a writing surface when it is in use in a writing instrument comprising: agitating a large group of small spherical metallic writing balls while an organic material resistant to an etchant is applied in the form of an atomized spray to cover between 20% and 50% of the original surface of each ball; subjecting the group of balls so treated to the action of an etchant for the metal of the ball for a time and at a temperature sufficient to produce interconnecting ink-receiving channels extending below the original surfaces of said balls a distance of between A and of the original diameter of each ball; removing the etchant and its reaction products from the balls; and removing the attached organic material to ex pose a random pattern of dispersed bearing areas of the original surfaces surrounded by interconnecting inkreceiving channels.

5. A method of treating a large group of small spherical metallic writing balls with original, smooth, polished surfaces and a diameter on the order of 0.04 inch for use in writing instruments to controllably generate on each ball a random pattern of dispersed bearing areas of the original surface surrounded by interconnecting ink-receiving channels whereby friction is increased between each such treated writing ball and a writing surface when it is in use in a writing instrument comprising: attaching to the original smooth polished surfaces of a large group of small spherical metallic writing balls with a diameter on the order of 0.04 inch in spaced, dispersed, random relation, a multiplicity of fine particles of an organic material resistant to an etchant to cover between 20% and 50% of the original surface of each ball; subjecting the group of balls so treated to the action of an etchant for the metal of the balls for a time and at a temperature suflicient to produce interconnecting ink-receiving channels extending below the original surfaces of said balls a distance of between ,4 and 4 of the original diameter of each ball; removing the etchant and its reaction products from the balls; and removing the attached organic material to expose a random pattern of dispersed bearing areas of the original surface surrounded by interconnecting ink-receiving channels.

6. A method as stated in claim 5 wherein said organic material is present in the proportion of between about 20 and 50 milligrams of said material per 10,000 balls having a diameter of about 0.04 inch.

7. A method as stated in claim 5 including the steps of cleaning said balls with a non-oleaginous cleanser and drying said balls prior to the attaching of said organic material.

8. A method as stated in claim 5 wherein said balls are heated to soften said organic material before being subjected to the actiofr of the etchant.

9. A method as stated in claim 5 wherein said balls are 11 I 12 subjected to treatment to enhance wet-tability of etched 2,266,430 Mathews Dec. 16, 1941 areas by ink before removing the organic materiaL- 2,506,604 Lokker et a1. May 9, 1950 2,517,430 Hensel et a1. Aug. .1, 1950 References Cited in the file of this patent 2,536,124 Bolvin et a1. Jan. 2, 1951 UNITED STATES PATENTS 5 2, 57, 63 R ed n 19, 19 1 2,073,237 Yojima M31. 9, 1937 F R N PA N 2,168,756 Alnumt Aug. 8, 1939 EIG TE TS 250,923 Swflzerland June 7, 1946 2,266,377 Neely et a1. Dec. 16, 1941

Claims (1)

1. 5. A METHOD OF TREATING A LARGE GROUP OF SMALL SPHERICAL METALLIC WRITING BALLS WITH ORIGINAL, SMOOTH, POLISHED SURFACE AND A DIAMETER ON THE ORDER OF 0.04 INCH FOR USE IN WRITING INSTRUMENTS TO CONTROLLABLY GENERATE ON EACH BALL A RANDOM PATTERN OF DISPERSED BEARING AREAS OF THE ORIGINAL SURFACE SURROUNDED BY INTERCONNECTING INK-RECEIVING CHANNELS WHEREBY FRICTION IS INCREASED BETWEEN EACH SUCH TREATED WRITING BALL AND A WRITING SURFACE WHEN IT IS IN USE IN A WRITING INSTRUMENT COMPRISING: ATTACHING TO THE ORIGINAL SMOOTH POLISHED SURFACES OF A LARGE GROUP OF SMALL SHERICAL METALLIC WRITING BALLS WITH A DIAMETER ON THE ORDER OF 0.04 INCH IN SPACED, DISPERSED, RANDOM RELATION, A MULTIPLICITY OF FINE PARTICLES OF AN ORGANIC MATERIAL RESISTANT TO AN ETCHANT TO COVER BETWEEN 20% AND 50% OF THE ORIGINAL SURFACE OF EACH BALL, SUBJECTING THE GROUP OF BALLS SO TREATED TO THE ACTION OF AN ETCHANT FOR THE METAL OF THE BALLS FOR A TIME AND AT A TEMPERATURE SUFFICIENT TO PRODUCE INTERCONNECTIG INK-RECEIVING CHANNELS EXTENDING BELOW THE ORIGINAL SURFACES OF SAID BALLS A DISTANCE OF BETWEEN 1/4000 AND 1/80 OF THE ORIGINAL DIAMETER OF EACH BALL, REMOVING THE ETCHANT AND ITS REACTION PRODUCTS FROM THE BALLS, AND REMOVING THE ATTACHED ORGANIC MATERIAL TO EXPOSE A RANDOM PATTERN OF DISPERSED BEARING AREAS OF THE ORIGINAL SURFACE SURROUNDED BY INTERCONNECTING INK-RECEIVING CHANNELS.

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