An accessory transmission conversion mechanism of the type disclosed in the U.S. Pat. No. 4,177,539, to Elting, for causing the lance tube of a long retracting soot blower to oscillate about its longitudinal axis, is provided with a lost motion driving connection between the yoke driving gear and the...http://www.google.de/patents/US4351082?utm_source=gb-gplus-sharePatent US4351082 - Oscillating soot blower mechanism
