An electromagnetic spring clutch has an armature (40) which can be moved to and from in the axial direction thereof and cannot be rotated on the axis, and which is biased by a spring (46), and a coil spring (36) which covers over outer faces of a master driving axle (30) and a slave driving axle (34)...http://www.google.fr/patents/US5090538?utm_source=gb-gplus-shareBrevet US5090538 - Electromagnetic spring clutch
