Extraction apparatus

Extraction apparatus mounted on a roadway wheeled vehicle and comprising:

• a. a storage chamber at the lower part of a detachably mounted tank;
• b. a plenum chamber at the upper part of said tank;
• c. means, including filter means, inter-connecting said storage chamber and said plenum chamber;
• d. outlet means at one end of said plenum chamber and in communication therewith;
• e. an extractor blower unit mounted in fixed position on said wheeled vehicle;
• f. detachable means connecting said extractor unit to said plenum-chamber outlet means, said connecting means being adapted to be disconnected to allow said outlet means, said plenum chamber and said storage chamber to be moved relative to said fixed extractor unit;
• g. a vent to atmosphere at said one end of said plenum chamber;
• h. inlet means at the opposite end of said storage chamber;
• i. valve means in said storage-chamber inlet means, in said plenum-chamber outlet means and in said plenum-chamber vent, whereby when said valves are placed in certain positions said extractor unit is effective to draw air through said inlet means into said storage chamber and through said filter means into said plenum chamber, and in other positions of said valves, air is sucked through said vent into said plenum chamber and through said filter means in the reverse direction into said storage chamber, thereby to effect self-cleaning of said filter means.