GB407253A - Improvements in writing implements - Google Patents

Abstract

407,253. Pencil leads. WAHL CO., 1800, Roscoe Street, Chicago, U.S.A. March 10, 1933, No. 22310. Convention date, Aug. 24, 1932. Divided on 407,824. [Class 146 (iii).] A thin lead for propelling pencils is made of octohedral cross-section and has four equal longer straight sides and four equal shorter curved sides arranged alternately. The four shorter sides 10<b>, Fig. 3, of the lead 10 are preferably curved to an equal radius from the centre of the lead. Owing to its oross-section the lead consistently presents a finer writing surface to the paper than one of circular cross-section ; e.g. one of the sides 10<b> may first be used and when this is worn down a second fine surface may be presented by a rotation of the lead through, say, 45‹. If the lead is slightly over size it is still usable, since the faces 10<b> are easily shaved away and the resultant dust can escape through the passages between the faces 10<a> and the tip, thus preventing clogging. When used with a resilient split socket which may be distorted from the true circular shape, the co-operation of the non-circular part K, Fig. 5, of the socket and the flats of the lead prevents rotation of the lead. The lead is also adapted for convenient use with tips of the rigid type, in which ridges on the tip bite into the lead, and has a greater strength against breakage than a polygonal lead with a smaller number of sides.