US Patent 9038235 Vacuum cleaner

A vacuum cleaner (1, 21, 41, 51) for dry dust comprises at least a dust chamber (3, 23, 43, 53) and a fan unit(13, 63), which dust chamber (3, 23, 43, 53) is provided with an air inlet opening (7, 27, 57) and an air outlet opening (8, 28) communicating with the fan unit (13, 63). The dust chamber (3, 23, 43, 53) comprises a movable body (9, 29, 59) for restricting air flow through the dust chamber (3, 23, 43, 53). In use the movable body (9, 29, 59) is located on dry dust collected in the dust chamber (3, 23, 43, 53) due to kinematic sorting between the movable body (9, 29, 59) and the dry dust.