| 摘要 |
A vacuum cleaning appliance includes a vacuum cleaning head having a suction opening, the head having a first state and a second state, a fan unit for drawing an air flow through the suction opening, and a control assembly for controlling the state of the head. The control assembly includes a user-operable valve for increasing temporarily an air pressure within an airflow path extending from the suction opening to the fan unit, a pressure chamber having an interior volume in fluid communication with the airflow path, the pressure chamber being moveable from an expanded configuration to a contracted configuration in response to a pressure difference between the interior volume and ambient air, the pressure chamber being biased towards the expanded configuration, and a control mechanism for allowing the pressure chamber to move to the contracted configuration in response to a first operation of the valve to place the head in one of the first and second states, and for preventing the pressure chamber from returning to the contracted configuration in response to a second operation of the valve to place the head in the other of the first and second states. |
