Self-cleaning vacuum cleaner

A vacuum cleaner has a filter 53 which is vibrated by a device such as a motor 51 at a range of frequencies to dislodge accumulated dirt and dust and hence clean the filter. A control unit preferably causes the device 51 to successively sweep between different frequencies in an incremental, decremental or cyclic manner. The frequencies may be successive or stepped. Also disclosed is a vacuum cleaner that comprises a tubular filter 53 mounted on a vibrating projection 48 which extends axially into the hollow core of the filter 53. The dislodged dirt and dust fall into a collection chamber below the filter 53 is mounted. Further disclosed is a vacuum cleaner that is provided with a device 52 for vibrating the filter 53 and a control unit which detects a change of state of usage of the vacuum cleaner and actuates the device when a change of state of usage is detected, such as when the cleaner is turned off or on.