GB841319A - Improvements in and relating to ball point writing instruments - Google Patents

Abstract

841,319. Reservoir pens. SCRIPTO Inc. Jan. 4, 1956 [Sept. 13, 1955], No. 344/56. Class 146(3). Leakage of ink from the rear end of the reservoir tube of a ball-point pen is prevented by a piston system comprising two separate pistons 17, 18, the piston 17 resting on the ink column 15 and the piston 18 floating in a sealing liquid 19, and the sealing liquid 19 also substantially fills the annular spaces between the pistons and the inner wall of the reservoir. In a modification, the piston system comprises a single body having two end cylindrical head portions separated by a narrow intermediate conical portion, the sealing liquid surrounding the peripheries of the head and conical portions : a central hole in the piston communicates with two transverse holes in the conical intermediate portion to allow the sealing liquid to be introduced. A plug 14 in the open end of the reservoir has an inwardly protruding projection through which is an air-hole 22. Thus the top piston 18 cannot fall into contact with the plug 14 if air enters the reservoir from the ball end and the whole ink falls when the pen is inverted. The sealing liquid 19 may consist of a mineral oil bodied with aluminium stearate and a small amount of water ; or a thixotropic liquid substantially of the type described in Specification 828,295 may be used. The sealing liquid, as it follows the ink column, sweeps the inner wall of the reservoir tube to preserve the transparency of the tube, and serves to lubricate the pistons.