US2775956A - Fountain pen of the ball point type - Google Patents

Description

Jan. l, 1957 F. RAY

FOUNTAIN PEN oF THE BALL POINT TYPE Filed Nov. 23. 1951 United States Patent O FOUNTAIN PEN F THE BALL POINT TYPE Frederick Ray, Montecito, Calif.

Application November 23, 1951, Serial No. 257,728

6 Claims. (Cl. 1Z0-42.4)

This invention relates to fountain pens and particularly to fountain pens of the ball point type wherein the ink commonly used is of very high viscosity which to prevent air locks necessitates that the ink be maintained in a continuous column from the ball to the air-ink surface at the other end of the column. As a consequence, the reservoir must be provided with an opening beyond the air-ink surface to admit atmospheric pressure to that end of the ink column, and as a result the ink tends to leak out of the opening when this opening is low enough to permit flow of ink by gravity.

Many attempts have been made to overcome this difficulty and one of the common expedients is to make the reservoir of small diameter and relatively long, as it has been found from experience that the ink commonly used will not leak out of a reservoir which is not over approximately one-tenth of an inch in diameter. Due to this small diameter required to prevent leakage, the quantity of ink that can be held in the reservoir is not sufficient to supply continuous Writing for a long enough time to be entirely satisfactory. In some instances, to increase the capacity of the reservoir without increasing the diameter, a tube longer than the holder is used to form the reservoir by folding it back and forth one or more times so that it can still iit within the pen holder or casing. This construction increases the diiculty and expense of manufacture and is used little, if at all, at the present time. Other expedients have been used, such as an elastic sack, to provide a larger supply of ink but all are open to one or more objections so that most, if not all, ball point pens at the presenttime make use of a reservoir consisting of a single straight length of small diameter tubing.

It is an object of this invention to provide a reservoir of relatively large diameter which will maintain a continuous ink column from the ball point to the air-ink surface at the opposite end of the ink column and at the same time prevent the leakage of ink from this air-ink surface to and out of the open end of the reservoir.

Referring to the drawings: y

Fig. l is an enlarged diagrammatic View showing in cross-section the common type of ink reservoirabove described;

Fig. 2 is an enlarged longitudinal section through an ink reservoir containing a surface iilm supporter, in accordance with this invention; .t t.

Fig. 3 is a cross-section taken on the line 3-3 of Fig. 2;

Fig. 4 is also an enlarged longitudinal section through a pen having a holder and a removable reservoir and integral ball point, all of which is commonly designated as the filler;

Fig. 5 shows one modilied form of film supporter in longitudinal section;

Fig. 6 is a plan view of same;

Fig. 7 shows a second modifiedl form of iilrn supporter in longitudinal section;

Fig. 8 shows a plan view of same;

Fig. 9 shows a third modified form of lm supporter; and

frice Fig. 10 shows a plan view of same.

The common understanding of the properties of the ink that prevent How of the ink out of the open end of the reservoir is that the ow characteristics of the ink prevent this flow out of a small diameter tube when one end is closed. In the case of true liquids, which term includes some inks, viscosity is the only property that could be designated by the term flow characteristics. lf the ink has slight plasticity, then the yield point would also be included. Theoretically an ink could be made with a high yield point so that it would not ow under gravity through a relatively large tube but such an ink would not flow through the small passages to feed the ball point. As a consequence, practical inks have low if any yield point and must be used in a reservoir of small diameter to prevent leakage out of the open end.

I have discovered that the real reason that the ink does not leak `out of the open end of a small ydiameter reservoir closed at the opposite end is due, not to the flow characteristics, but to the surface tension of the ink acting in effect as a film stretched across the reservoir against which atmospheric pressure is exerted, The opposite end is closed also by the surface tension acting as a film extending entirely around the ball across the opening between the ball and its housing, against which the pressure of the atmosphere is also exerted. Thus, when the pen is vertical with the ball uppermost, the pull of the surface tension around the ball in an upward direction balances the pull of the surface tension in the reservoir downward plus the head of ink in the reservoir, the atmospheric pressure being the same on the ink-air surface at the ball as on the ink-air surface in the reservoir.

Since the ink wets the surface of the ordinary materials of which the reservoir would be made, such as iron, copper, brass, glass or plastic, the shape of the surface will always be the same under the same conditions, that is, same liquid, same diameter and same inclination, so that it is impossible to increase the critical diameter materially by selection of material of reservoir. Increasing the surface tension increases the critical diameter as the square root of the tension but the surface tension is largely determined by the composition of the ink required to meet Writing conditions and very little increase in surface tension is possible. Specic gravity can not be decreased materially for the same reason.

The present invention provides a reservoir which has greater freedom from the above limitations due to surface tension and specific gravity of the ink. This has been accomplished by providing means in addition to the reservoir wall for supporting the ink-air surface of the ink at all levels within the reservoir to maintain the stability of said surface and thus prevent leakage along the wall of the reservoir when the open end of the reseivoir is low enough to permit ow of ink by gravity. Several different embodiments of the invention are herein illustrated.

Referring to Figs. 2 and 3, 1 is the ink reservo-ir which may be made of brass -tubing 3/16 to 1A inside diameter. 2 is an extension member carrying the feed channel 3 to the ball 4 (both of usual diameters) which is rotatably mounted in the normal manner in a seat in the end of the extension 2. 6 is the novel surface lm suppor-t which, in this case, consists of a helical coil of fine wire preferably of brass or copper about one half ythe diameter of the inside of the reservoir and having a pitch of about 1/16 or less. 7 indicates a support for the helical coil, which support may be in the form of a ring soldered or otherwise attached to the coil, the outside diameter of the ring fitting snugly on the inside of the reservoir -to prevent longitudinal movement of the coil. The number of these supporting rings to be used will depend on the length of the reservoir, two or three usually being sufiicient to center the coil accurately throughout its length. Cuts 8 (Fig. 3) may be made in the outer circumference of the ring to permit the ink to flow therethrough but are not essential.

c, d, e, f indicate diagrammatically the air-inl surface in the reservoir at any given level, this surface extending from the wall of the reservoir to the wire of the coil and across the opening on the interior of the coil. Thus, due to the adhesion of the ink to the wire of the coil, the inkair surface is supported at a substantially circular zone of about one half the diameter of the outer support at the wall of the reservoir. As a consequence, the variation of the pressure difference across the surface between points of support is greatly reduced, and this variation can be further reduced by a more complicated support such as could easily be provided by means of a second smaller helical coil within an outer coil, but l have found that a single helical coil support is sufiicient for a reservoir of one quarter inch diameter, which is about as large as can be used with the ordinary holder.

Fig. 4 merely shows the usual holder 10 with the reservoir 1 of Fig. 2 inserted therein as a filler and with the ordinary cover 11.

Figs. 5 and 6 show a surface lm support 6a also made of a coil of fine wire but with the wire coils arranged in concentric relation and connected by bent portions 6b which space them apart about 1/16. The dimensions of this modified form of coil may be the same as in Figs. 2 and 3 and it may be held in place within the reservoir in the same or any other suitable way.

In Figs. 7 and 8, the surface film support is made up of a series of circular plates 9 having cut-out portions 9, leaving cross arms 9b radiating from a small perforated center portion 9C. These plates are held in spaced relation on a center rod 9d which supports them all as a unit for insertion into the reservoir. Two of the plates, located near the opposite ends of the unit, are formed with small radial lugs 9e to center the unit within the reservoir. Here, again, the dimensions may be of the same order as those given for the coil unit 6 in Fig. 2. That is to say, the diameter of the stamped out plates 9 may be about one-half of the diameter of the inside of the reservoir and the spacing between plates may be of the order of 1/16. The circular portions of the plates may be quite narrow or of a dimension similar to the wire coils of the unit 6 or 6a.

In Figs. 9 and 10 the surface lm support is in the form of a tubular screen 10 arranged within the reservoir 1. and spaced from the reservoir wall by a pair of concentric rings 10a. The mesh of the screen may preferably be of the order of 1/32. It will be obvious that this screen type of film support will function in the same manner as the other forms above described.

Even other forms of film support will readily suggest themselves to those skilled in the art.

What is claimed is:

l. In combination, a tubular ink reservoir for fountain pens of the ball point type having an air opening at the end opposite the ball point through which the ink could freely flow and having a cross-sectional area greater than that which would permit the ink-air surface lrn to be supported only by the reservoir wall, said reservoir providing an ink column of corresponding cross-sectional area, a film supporting member immersed in the ink column and extending throughout the effective length of the reservoir, means positioning said member substantially coaxial with the reservoir and in spaced relation to the reservoir wall, thus permitting ink flow along the reservoir wall in a direction substantially parallel to the -longitudinal axis of the reservoir, said coaxial member presenting ylateral and longitudinal openings at substantially all levels within the reservoir, said lateral openings permitting the ink-air surface film to extend through said lateral openings across the reservoir and thus to receive support at its outer periphery fromthe reservoir wall and additional support inward of said outer periphery from the coaxial member substantially continuously from full to empty condition of the reservoir.

2. An ink reservoir according to claim 1, wherein the coaxial member is in the form of a wire coil presenting a series of closely spaced parallel thin wire rings located at a multitude of levels within the reservoir.

3. An ink reservoir according to claim l, wherein the coaxial member is in the form of a series of closely spaced circular perforated plates located at a multitude of levels within the reservoir.

4. An ink reservoir according to claim l, wherein the coaxial member is in the form of a tubular screen extending throughout the length of the ink column.

5. In combination, a tubular ink reservoir for fountain pens of the ball point type having an air opening at the end opposite the ball point through which the ink could freely flow and having a cross-sectional area greater than that which would permit the ink-air surface film to be supported only by the reservoir wall, said reservoir providing an ink column of corresponding cross-sectional area, and a fixed concentric member immersed in the ink column and positioned substantially coaxial with the tubular reservoir and uniformly spaced at its outer periphery from the inside wall of said reservoir, thus permitting ink flow along the reservoir wall in a direction substantially parallel to the longitudinal axis of the reservoir, said concentric member being in the form of a helical wire coil to permit the ink-air surface film to extend across the reservoir through the spaces between the convolutions of the helical coil and thus receive support at its outer periphery from the reservoir wall and additional support inward of said outer periphery from the helical wire coil substantially continuously from full to empty condition of the reservoir.

6. In combination, a tubular ink reservoir for fountain pens of the ball point type having an air opening at the end opposite the ball point through which the in'r. could freely flow and having a cross-sectional area greater than that which would permit the ink-air surface film to be supported only by the reservoir wall, and means located within the ink reservoir and cooperating with the inside wall thereof for continuously maintaining the ink-air surface film substantially intact from full to empty condition of the reservoir, said means comprising a concentric in- -sert member uniformly spaced around its outermost periphery from the inside wall of the tubular reservoir and extending substantially throughout the effective length of the reservoir, thus allowing the ink-air surface film at substantially all levels to be supported at and around substantially its entire outer periphery by adhesion to substantially the entire inner periphery of the tubular reservoir wall, and said insert member presenting axiallyspaced circumferentially-extending elements having interior and exterior surfaces to which the ink-air surface film, inward of its outer periphery, adheres and from which it receives additional support at substantially all levels asV the film extends across the reservoir through the spaces between said insert elements.

References Cited in the file of this patent UNITED STATES PATENTS 2,208,588 Laforest July 23, 1940 2,504,649 Chesler Apr. 18, 1950 FOREIGN PATENTS 3,958 Great Britain Mar. 14, 1888 813,499 France Feb. 22, 1937 571,698 Great Britain Sept. 5, 1945 935,473 France Feb. 2, 1948 130,303 Australia Nov. 26, 1948 443,439 Italy Dec. 22, 1948 140,600 Australia Apr. 3, 1951 806,331 Germany June 14, 1951 274,548 Switzerland Aug. 1, 1951 n' "A l'

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