There is disclosed an improvement in a surface maintenance machine whereby means are provided for automatically maintaining a desired normal force by a maintenance tool against a surface being maintained, although there may be undulations in the surface, variations in the condition of the surface and...http://www.google.fr/patents/US4679271?utm_source=gb-gplus-shareBrevet US4679271 - Automatic tool force compensator for a surface maintenance machine
Automatic tool force compensator for a surface maintenance machine
