| 摘要 |
A proximity detector has permanent magnets positioned within a chassis so that the axis and poles of the flux field of the permanent magnet are substantially normal to the front of the chassis. A switch is positioned along the front of the chassis proximate the magnet. The switch has contacts operable by the magnetic flux field of the magnet. A shield is positioned between the magnet and the rear of the chassis and between the switch and the rear of the chassis. The shield acts to inhibit extraneous magnetic fields from interferring with the detector operation and as a magnetic conductor to focus the magnetic flux field. The flux field of the permanent magnet is modified by a ferromagnetic object positioned at a predetermined distance from the front of the chassis to cause the contacts of the switch to operate in relation to the positioning thereof and in turn send an operate signal indicative of the positioning of the ferromagnetic object at the front of the switch to an external circuit. The switch may be positioned on a ski lift tower to detect the proximity of the ski lift cable and in turn transmit a derope condition signal should the cable become dislodged from tower support apparatus. A test device may be attached to the cable and circulated to test in-place detectors.
|
