An electrically-operated shiftable article storage device in which a plurality of shiftable article storage units adapted for movement in a direction normal to the article storage faces thereof to form a plurality of article handling aisles therebetween are normally arranged closely adjacent to each...http://www.google.co.uk/patents/US4033649?utm_source=gb-gplus-sharePatent US4033649 - Electrically-operated shiftable article storage device
