Patent GB-1462996-A (GB)
Title: Method of manufacturing rods of thermoplastic material having internal capillary ducts for the preparation of pen nibs
IPC: B43K1/00
Filed: 1974-04-10
Abstract: 1462996 Making pen nibs from extruded material GLOBAL CONTROL CORP 10 April 1974 [11 May 1973 30 Oct 1973] 15810/74 Heading B5A [Also in Division B6] A pen nib having capillary ink passages, is made by extruding a rod of polyacetal resin having ducts 1, Fig. 2, extending radially from a central duct 4 and defined between segments 2, 3, cooling the rod to a temperature below that at which the resin fuses, and then mechanically stretching the rod at below its fusing temperature to reduce its external diameter and to reduce the width of the duets, to increase their capillary attraction forces and to bring the tips of the segments into contact. The ducts 1 are of constant width, and alternate segments 2 extend radially inwardly to a greater extent than intermediate segments 3, and a diametrically opposed pair 2a of the segments 2 extends inwardly to a greater extent than intermediate segments 3, and a diametrically opposed pair 2a of the segments 2 extends inwardly to a greater extent than the remaining segments 2. The stretching produces a decreasing width of the ducts 1 towards the centre at which, Fig. 4, capillary passages are defined between the duets 1, by the movement into contact of the segments 2, 3, with the initial contact being effected by overlapping of the segments 2a. The rod may be extruded, Fig. 6, with external channels 4 which are elongate in the radial direction and disposed symmetrically of the radial axis of each segment 2, 3, and the walls of which close together during the stretching, thereby reducing dimensional irregularities which would otherwise arise from the radial contraction of the segments 2, 3 and from variations in the extruded cross-section. The nib is cut from the stretched rod, and provided at each end with the same taper, preferably effected by grinding during the cutting. The nib is inserted as a force fit into one end of a moulded plastics pen barrel, Fig. 1 (not shown), with an end taper penetrating into an ink-impregnated pad, e.g. of polyester chips or threads, which may be under a pressure transmitted by a spacer from a plug force fitted into the other end of the barrel. Prior to the cooling, the extruded rod is preferably initially stretched down to a diameter which is 60% of its extruded diameter, which stretched diameter is further reduced by 50% by the mechanical stretching of the cooled rod. Preferred dimensions are given of the extruded and stretched rod, and of the capillary ducts, and comparative test results are stated measuring the capillary and other writing properties of the nib. The extruded rod is initially stretched from the extrusion die, e.g. from 10 mm. to 4 mm. diameter, in being drawn by drawing means through a cooling bath. The cooled rod is then annealed, reheated to below its fusing temperature in passage through an electric resistance heater, and is then subjected to a first stage of the mechanical stretching in being drawn, e.g. to a diameter of 2 mm., through the progressively decreasing size circular apertures of a series of six draw plates, which are each provided with individual driving means. After being conducted through a cooling bath, the rod is rolled in passage through a circular nip defined by the grooves of four rollers, and the rod is then subjected to a final gauging in being drawn through the circular apertures of three further draw plates. After cooling, the rod is cut to length and provided with tapered ends, by grinding which may be simultaneous with the cutting.