material the thermoplastic material of the sheath comprises less than 20 wt of staple fibers application_number US 87509304 A description the core is covered by extrusion or coating with a layer of peripheral polymer material the photographs enlarged about 20 times in fig1 show a comparison between a jacketed yarn 1 according to the prior art on the left represented by document fr 2 617 205 and a jacketed yarn 2 according to the present invention on the right owing to the presence of staple fibers the external surface of the yarn 2 obtained by the method according to the invention has an irregular appearance and resembles string the mean diameter may thus be less than 1 mm and vary between 0 6 mm and 0 9 mm in contrast the external surface of the conventional jacketed yarn 1 is smooth advantageously and in practice the core yarn is a high tenacity multifilament yarn that is to say one having a tenacity of around at least 50 cn tex the many filaments of the core may or may not be twisted may or may not be interlaced may or may not be assembled and may or may not be texturized depending on the final jacketed yarn desired 0020 fig2 shows a cross section through the jacketed yarn 2 taken in an optical microscope with a magnification of about 150 times in this embodiment of the jacketed yarn 2 the many polyester filaments 3 of the core 4 appear at the.