| 摘要 |
<p>For indicating a pressure decrease in a pneumatic tyre a valve cap which is threadable onto the tyre valve is used. The sleeve thereof, which is threadable onto the valve tube, comprises an actuating member which is capable of opening the valve mounted in the valve tube when the sleeve is in the threaded-on (operative) position. Furthermore, a compressed-air chamber is provided, which communicates with the interior of the tyre through the open valve and is sealed by a movable diaphragm or a piston, said diaphragm or piston actuating an axially displaceable indicator biased by a spring towards the actuating member and moving a marking member into its initial position when pressure is applied to the compressed-air chamber. Upon a pressure decrease in the compressed-air chamber, the indicator follows the resultant displacement of the diaphragm or piston, respectively, while a return movement inhibitor retains the marking member in its initial position. The resultant variation of the relative axial distance of both members is used to indicate a pressure decrease. The end of the sleeve which is remote from the valve may hermetically be sealed by a hat-shaped cover of a transparent material permitting extension of the indicator and the marking member.</p> |
