US2813512A

US2813512A - Method of improving the life of ballpoint writing instruments

Info

Publication number: US2813512A
Application number: US355536A
Authority: US
Inventors: Clarence O Schrader
Original assignee: Paper Mate Manufacturing Co
Current assignee: Paper Mate Manufacturing Co
Priority date: 1953-05-18
Filing date: 1953-05-18
Publication date: 1957-11-19
Anticipated expiration: 1974-11-19
Also published as: BE561706A; CH344021A; FR1184220A; GB828276A

Description

Nov. 19, 1957 c. o. SCHRAD 2,

METHOD OF IMPROVING THE LIFE OF BALL-POINT WRITING INSTRUMENTS Filed May 18. 1953 A r roelvE Y.

United States Patent 0 2,813,512 ll/IETHOD OF IMPROVING THE LIFE OF BALL- POINT WRITING INSTRUMENTS Clarence 0. Schrader, Lake Tahoe, Califl, assignor, by mesnc assignments, to Paper Mate Manufacturing Company, Culver City, Calif., a corporation of Delaware Application May 18, 1953, Serial No. 355,536 7 Claims. (Cl. 12042.4)

This invention relates to improvements in the construction of ball-pointed writing instruments and is particularly directed to means and methods whereby the writing characteristics and effective life of ball-point pens are improved and prolonged. Although ball-point writing instruments have been known for many years (see Patents No. 189,304, No. 370,599, No. 853,156, No. 1,046,821, No. 1,179,086, No. 1,426,200, No. 2,192,479, etc.) the commercial manufacture of such pens at the rate of several million per month while maintaining the quality and performance characteristics which the purchasing public requires has presented problems which have not been solved heretofore. The principal criticisms leveled against ball-point pens was that the pens would not write and deposit ink immediately upon contact with a writing surface, that they skipped or failed to write in the event the paper or writing surface was caleudered or perhaps slightly oily, and did not continue to function for a long time, i. e. their effective life was often shorter than the ink supply.

This invention is directed to means and methods whereby readily available metals and materials can be utilized in the construction of the pens and whereby commonly employed and inexpensive mechanical operations can be employed in the solution of the problems, thereby permitting the attainment of the desired objectives without greatly disturbing existing manufacturing procedures and without appreciable increase in cost.

Generally stated, the present invention provides means and methods whereby the traction between the small ball (which transfers ink or writing fluid from a supply carried in a cartridge to a writing surface) and the writing surface is increased and enhanced so that the ball does not slide or skip upon a calendered or slightly oily surface and thereby fail to write, but instead deposits ink as soon as contact and relative motion is established. Furthermore, it has been discovered that some of the dilficulties encountered heretofore have been due to a galvanic or electrolytic action and resulting corrosion between parts of a writing instrument, which impaired or destroyed the carefully predetermined clearances and required tolerances and affected the rate at which ink was supplied to the ball, its ink-carrying power, its free rotatability, etc. This invention provides means and methods whereby such galvanic action may be inhibited and permits the use of inks which could not be employed heretofore.

The objects of the present invention may be attained by the use of the materials, methods and procedures hereafter described, it being understood that various changes and modifications may be made from the specific examples and teachings hereafter given. In order to expedite and facilitate understanding, reference will be made to the appended illustrative drawings and diagrams, in which Fig. 1 is an enlarged sectional view of a socket point for use in a ball-point pen.

Fig. 2 is an enlarged sectional view of a socket point provided with a ball.

Fig. 3 is a diagram of fiow chart illustrating operations which may be carried out pursuant to this invention.

Patented Nov. 19, 1957 Fig. 4 is an end view of the socket or cavity of the point illustrated in Fig. 1.

A typical ball-retaining socket point for use with writing instruments of the character here contemplated is indicated in Fig. l and generally comprises a relatively long, small diameter shank 10 carried by a larger head 11, said head being adapted for attachment to one end or a cartridge tube 12, in which a supply of writing fluid is contained. Extending axially through the head and shank is an ink supply bore 15 leading to an enlarged socket or recess 16, the outer walls of the shank being tapered as indicated at 17 in order to leave a thin lip around the edge of the socket. The diameter of the recess or socket 16 is adequate to receive the writing ball. The bottom 18 of the socket 16 is generally formed with a series of radial grooves 18'.

The socket points are preferably made from a malleable, readily machinable metal or alloy, such as for example, a leaded brass (copper-tin-zinc-lead). lt is necessary to use a readily machinable, free-cutting metal in order to be able to produce the socket points in the very large quantities necessary and still maintain the very close tolerances which must be maintained in view of the minute size of the parts. It is to be remembered that the ball which is seated and rotatably held by the socket point is only 0.039 in. in diameter.

The balls normally employed are generally a high carbon, stainless steel and it has been found that in actual use a galvanic action takes place between the brass of the socket point and the steel ball, resulting in corrosion, pitting, leakage of link, seizure of the ball, etc. at the Writing point. As previously stated, it is not possible to use stainless steel for a socket point, since such steels could not be machined and the necessary tolerances could not be maintained. ln accordance with the present invention, socket points of the character illustrated in Fig. l are lightly plated with a metal from the group consisting of nickel, copper, silver, platinum, gold, rhodium, osmium and chromium. A very light film of any one of such metals is applied to the previously machined socket point, the film generally ranging from 0.0001 to 0.001 inch, but not over 0.01 inch in thickness. Any normal or usual plating procedure is employed.

After the socket point has been machined and plated, a ball 20 is forcibly seated upon the tapered bottom 18 of the recess 16 and the thin edge portion 19 of the wall of the recess is swedged or rolled around the ball, the marginal edge portion of the wall extending slightly beyond a plane passing through the center of the ball 20. A suitable method for swedging and rollably holding the ball 20 within the recess of the socket point in described in U. S. Patent No. 2,498,009. It will be noted that in accordance with the present invention, the malleability of the metal of the socket point is utilized so as to facilitate the seating and swedging operations while the surface plating prevents or inhibits subsequent galvanic, electrolytic, or other corrosion. Essentially, the function of this surface plating is to provide an ink-contacting surface that has substantially the same potential as the writing ball so that any tendency toward electrolysis or undesirable electrolytic effect is virtually eliminated. Moreover, since the plating has been applied to the internal surfaces of the socket, a smoother surface is presented to the ball and the ball rolls and rotates within its socket more readily. In addition, the plating imparts wearing characteristics to the internal surfaces of the recess or socket, thereby preventing departure from tolerances established during the rolling and swedging, even though the pen or writing instrument is used for very prolonged periods of time.

Although the above procedure results in a long wearing ball-point writing instrument, the instrument will still fail to suitably deposit ink upon a highly calendered or slightly greasy writing surface. It is to be remembered that ballpoint writing instruments write by reason of the fact that ink is actually carried by the surface of the ball 20 and as the ball 20 rotates in its socket it picks up ink from the supply channel 15 and deposits or lays it down upon the surface over which the ball is rolled. If, however, the surface is highly calendered, excessively smooth, or slightly oily, the ball may not roll, but instead slide or skip, thcrcby failing to deposit ink in a continuous manner.

The above objectional characteristics may be obviated by enhancing the traction of the ball without imparing its freely rotatable characteristics. The traction and rollability of the ball when used in writing upon a surface can be facilitated and enhanced by imparting a matte finish to the surface of the ball. This can be readily accomplished by subjecting the ball to an etching bath before it is seated and swedged into rollable retention within the socket point. Any suitable etching solution may be employed. Solutions of sulfuric acid, l%25% H2504, mixed acid solutions such as mixtures of hydrochloric and nitric acids or mixtures of hydrochloric and sulfuric acids, hydrochloric solutions such as a 50% HCl or solutions of nitric acid in ethyl or amyl alcohol may be employed. At all events, it has been found that the etching bath should not be pro longed for a sufiicient time to impart a microscopically visible etch, it being sufficient if the etching solution imparts a microscopically visibly etched surface to the steel ball which now produces diffuse light reflection. The time during which balls are subjected to the etching bath will, or course, depend upon the temperatures employed and the activity of the etching solution. When mixed acids or sulfuric acid is used, the etching time may vary from ten minutes to one hour, one hour with lll% sulfuric acid at room temperature being adequate. In some instances, after etching, the balls may be subjected to a light polishing operation of short duration, although in most instances such polishing can be dispensed with. These etched balls can then be seated in a socket point in the same manner as unetched balls.

The etching operation not only increases the traction between the ball and a writing surface (thereby insuring immediate rotation of a ball upon relative movement of a writing instrument in contact with a writing surface) but also appears to facilitate the distribution of ink. It is believed that the etched surfaces have a tendency to retain and carry slightly greater quantities of ink than the highly polished surfaces of normal balls. Any suitable method of etching the ball may be used. ln the normal process of manufacturing balls of metal, such as ball bearings and balls used in writing instruments, the later stages of manufacture include a series of tumbling steps during which the balls are polished; when an etched or matte finish is dcsired some of these last finishing steps may be eliminated or a matte finish obtained by changing the grade, fineness and hardness of the abrasive employed. The end result is a writing ball having a matte finish including polished areas conforming to a spherical surface and a multiplicity of fine ink-receiving craters indenting this surface and extending therebelow. such finish resulting from the light polishing of a pitted steel ball. The balls may be provided with a matte finish by very light plating under suitable conditions, or such matte finish may be imparted to the balls by mechanical means, as by being subjected to a high velocity stream of rouge or other fine abrasive.

It will be evident from the above description that the present invention describes methods of improving the writing characteristics and life of ball-pointed writing instruments without interfering with normal manufacturing operations or the use of relatively soft, readily machinable materials.

All changes coming within the scope of the appended claims are embraced thereby.

till

I claim:

1. In a ball-point writing instrument including a socket point and a tubular ink cartridge: a tubular ball socket element made of readily machinable metal; ink in contact with said socket element; a metallic ball of a dissimilar metal from said socket element rotatably confined within a forward portion of said element and projecting therefrom; and a metallic material coating the inner wall of said socket element which is not reactive with said ink in the presence of said ball, said metallic material having substantially the same potential as said ball.

2. In a ball-point writing instrument including a socket point and a tubular ink cartridge: a ball socket element made of a readily machinable metal; ink in contact with said socket element; a metallic ball of dissimilar metal from said socket element rotatably confined within a forward portion of said element and projecting therefrom, the surface of said ball having a matte finish including polished areas conforming to a spherical surface and a multiplicity of fine ink-receiving craters extending therebelow; and a metallic material coating the inner wall of said socket element which is not reactive with said ink in the presence of said ball, said metallic material having substantially the same potential as said ball and providing a smooth, wearresistant bearing-surface for said matte finished ball.

3. A ball-pointed writing instrument as stated in claim 1 wherein the ball is of steel and the socket element of brass, and the metallic coating material is selected from the group consisting of nickel, copper, silver, platinum, palladium, gold, rhodium, osmium, iridium and chromium.

4. A ball-pointed writing instrument as stated in claim 1, wherein the ball is of steel and is characterized by increased traction and improved ink distribution when used in said instrument upon calendered and oily surfaces, said characteristics resulting from the surface of said ball having a matte finish including polished areas conforming to a spherical surface and a multiplicity of fine ink-receiving craters extending thercbelow, said finish resulting from lightly polishing a pitted steel ball.

5. An improved writing tip for ballpoint writing instruments comprising a metallic socket element rotatably mounting a steel ball and containing a quantity of ink, the surface of said ball having a matte finish including polished areas conforming to a spherical surface and a multiplicity of fine, ink receiving craters extending therebclow, and a metallic material coating the inner wall of the socket element and having a lower potential with respect to said ball than the socket element. said metallic coating being nonreactive with said ink in the presence of said steel ball and providing a relatively smooth, wear-resistant bearing surface for said ball.

6. A writing tip as stated in claim 5, wherein the socket element is of brass and the metallic coating material is selected from the group consisting of nickel, copper, silver, platinum, palladium, gold, rhodium, osmium, iridium and chromium.

7. In a ball point writing instrument including a socket point and a tubular ink cartridge: a tubular ball socket element made of readily machinable metal; ink in contact with said socket element; a metallic hail of a dissimilar metal from said socket clement rotatably confined within a forward portion of said element and projecting therefrom; at least the inner all of said socket element being of a material which is not reactive with said ink in the presence of said ball, said material having substantially the same potential as said ball.

References Cited in the file of this patent UNITED STATES PATENTS 2,646,761 Knobel July 28, 1953 FOREEGN PATENTS 250,923 Switzerland Dec. 1, 1947 829,414 Germany Jan. 24, 1952.

U. S. DEPARTMENT OF COMMERCE PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,813,512 November 19, 1957 Clarence O. Schrader It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Let aere Patent should read as corrected below.

Column 3, line 28, for "microscopically" read --macroscopicall Signed and, sealed this 25th day of February 1958.

(SEAL) Atteet:

KARL H. AXLINE ROBERT C WATSON Atteeting Officer Comissioner of Patents