GB915112A - A refill of a ball point writing means - Google Patents

Abstract

915,112. Reservoir pens. DOLEO S. A. Jan. 29, 1959 [Feb. 4, 1958], No. 3170/59. Class 146 (3). In a ball-point pen, or a refill writing unit therefor, comprising an ink tube 1 closed at its upper end by a plug 4, and a ball writing-point 3 at its lower end the space 5 above the ink column 2 contains a gas above atmospheric pressure generated by the chemical reaction of a liquid 8 and a plug 7, the arrangement being such that the gas pressure progressively decreases as the ink is used to compensate the increased gap between the ball and its housing due to wear. The plug 7 is formed of a pasty substance, and may rest on the ink, or on an interposed solid piston. The gas may be carbon dioxide, hydrogen, ammonia, or nitrogen, in which cases the plug 7 is of sodium bicarbonate, aluminium, calcium hydroxide, and a diazonium compound respectively, and the liquid 8 is acetic acid, sodium hydroxide, ammonium chloride, and an inorganic or organic acid, respectively. In the case where the liquid 8 is acetic acid and the plug 7 contains sodium bicarbonate, the strength of the acid is such that the pressure of the gas produced is only slightly above atmospheric pressure to supply the ink to the ball. Due to the chemical reaction, a coating barrier layer 6 is formed between the liquid and plug to interrupt the reaction; this layer is broken when the upper end of the ink column is lowered, with the result that a fresh reaction takes place until the layer is reformed. Thus, in view of the formation and breakage of the layer 6, the gradual dilution of the acetic acid, and diminution of the sodium bicarbonate, the pressure of gas in the space 5 decreases as the ink is used and the ball housing wears. The plug 4 is of rubber, and its introduction into the tubo 1 sets up an initial gas pressure.