Patent GB-629226-A (GB)
Title: Improvements in writing instruments
IPC: B43K7/02
Filed: 1945-04-19
Abstract: 629,226. Fountain pens ; inks. MARTIN, H. G. April 19, 1945, No. 10026/44. [Class 146 (iii)] In a reservoir writing or marking instrument in which the writing &c. member consists of a hard ball rotatably mounted in a housing, the reservoir is constituted by a 'tube, the dimensions of which are as specified below, one end of the reservoir being joined to a feed duct which feeds the ink to the ball housing and has a passage or passages of smaller crosssectional area than the ball, an opening being provided at or near the other end of the reservoir the arrangement being such that when the instrument is charged with ink, the ink in the reservoir forms a single continuous vein extending from the first mentioned end towards the opening and the end of the vein of ink nearest the opening is subject to atmospheric pressure. The tube forming the reservoir is either (i) substantially circular in cross-section and has an internal diameter of not more than 2.5 mm., or  (ii) if the tube is not circular in cross-section it is such that either (a) no straight line exceeding 2.5 mm. in length can be contained in any cross-section, or (b) no straight line exceeding 3.5 mm. in length can be contained in any cross-section and a straight line not exceeding 1.5 mm. in length can be so placed that its ends lie on or overlap opposite walls. As shown in Fig. 1, the tube 1 which is formed by folding a single length of copper &c. tubing to form four adjacent lengths has one end length b extending into a passage in a member 2 in which a non-corrosive housing 3 for a ball 6 is located and the other end length, which extends towards the member 2, is open to atmosphere. The gap between the ball 6 and the housing 3 is between .001 and .01 mm. in width, and the ball diameter may vary from 0.75 to 1.5 mm. Many other forms of reservoir tubes are shown and described, and methods of manufacture thereof are disclosed. For example, the tube may be built up from separate lengths joined together to form a zig-zag shaped reservoir by end caps, soldering &c. or it may comprise a plastic member formed of moulded sections and having parallel ducts therein. Several arrangements of ball mountings are shown and described. As shown in Fig. 19, the ball 6 rests on an insert 5b held in position by a screw-threaded plug 5c. Ducts or passages 5e in the insert 5b communicate between the bore 5d and an annular space 3a around the insert 5b to allow ink to reach the ball. In other forms, an insert on which the ball rests is retained in position by shoulders in the bore of the housing 3, or the insert is supported by a spring, or the insert comprises a grooved plug which is a tight fit in the bore of the housing 3. The insert may be excluded, the ball resting on shoulders in the housing or on a spring plate seating supported by the shoulders. In another construction, Fig. 23, the longitudinal axis of the bore 4 and the axis of the bore or passage 5 leading to the ball are not in alignment. A number of grooves 5a around the outer end of the bore 5 enable ink to reach the ball. A finger depression on the outer casing assists in correctly locating the instrument when writing. In cases where the ball rests on a shoulder seating in the end of the housing 3, the seating may be formed first into a three-sided inverted pyramid, and spherical seats then formed on this by pressing a ball thereon. The seating may then be plated. The ball seating in some cases may not be of the same radius as that of the ball.. The reservoir tube 1 and housing 3 may, as shown in Fig. 1, be enclosed in an outer casing 14 provided with vent holes 14a, or may be retractably assembled within an outer casing as described in Specifications 584,974 and 584,975. Specifications 564,172, 571,698, 573,747 and 629,283 also are referred to. Inks. The ink for the writing instrument preferably has a viscosity of not less than 15 poise.under the normal conditions of use, and is preferably not less than 15 poise at 37‹ C. It may consist of an oleaginous solvent such as olein, castor oil, ricinoleic acid, an adhesive such as colophony, and an aniline dye. A metal soap such as sodium oleate may also be added. Examples of suitable inks are described.