| 摘要 |
The invention provides a vacuum cleaner having an airflow path, dust separating apparatus (16) arranged in the airflow path and a motor (24) arranged in the airflow path downstream of the dust separating apparatus (16), a pre-motor filter (20) located immediately upstream of the motor (24) and downstream and separate from the dust separating apparatus (16), and a bleed valve (18) located upstream of the pre-motor filter (20) to allow air to be bled into the airflow path in the event of a blockage occurring upstream of the bleed valve (18), wherein signalling means (30, 32, 34) responsive to a change in an operating condition of the motor (24) are provided to indicate that a blockage has occurred at or downstream of the pre-motor filter (20).
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