| 摘要 |
<p>A device (16) for indicating the amount of collected dust, the device (16) having a pointer tube, at least a part of which consists of a transparent material. The pointer tube is provided with a first end section to which a first pressure is applied and also with a second end section to which a second pressure is applied. A pointer is provided within the pointer tube, and the pointer is displaced by the difference between the first pressure which is applied to the first end section and the second pressure which is applied to the second end section. Also, a pointer spring is provided within the pointer tube, and the pointer spring presses the pointer to either the first pressure or the second pressure which is higher than the other.</p> |
