In pneumatic low pressure dust extraction apparatus, filter bags are cleaned by reverse flow of air. Each cleaning operation includes a first shock phase of short duration (not longer than 0.05 sec) but at high flow intensity by which accumulated layers of dust are thrown off the outside of the bag,...http://www.google.fr/patents/US4247310?utm_source=gb-gplus-shareBrevet US4247310 - Pneumatic dust extraction
