| 摘要 |
The equipment comprises a housing mounted on a wheel rim supporting a tire, and a plunger is mounted in the housing for reciprocation in a direction perpendicular to the radius of the tire, this plunger being movable in accordance with the tire pressure. A shaft is rotatably mounted in the housing, to extend substantially in the radial direction of the tire, the shaft being rotatably supported on ball bearings at each end. The ball bearings serve to restrain the shaft against centrifugal force due to the rotation of the wheel rim and tire. The shaft is normally biased to rotate in one direction by a spring, and has a cut-out notch adjacent one end which is engaged by the plunger so long as the tire pressure is equal to or above a preselected value. A permanent magnet is mounted on the opposite end of the shaft. When the tire pressure drops below the predetermined value, the plunger releases the shaft to rotate through 90 DEG , thus bringing the permanent magnet into a position where it can actively influence magnetically a reed switch or the like mounted on a non-rotatable part of the vehicle such as, for example, a brake mounting plate. As the wheel rotates, the magnetic pulses supplied from the permanent magnet to the receiver mounted on the brake plate or the like are effective, in a control circuit, to light a warning lamp adjacent the driver's seat. A reset device, for rotating the shaft back to its original position, is mounted on the wheel rim and has an externally accessible operating end. |
