| 摘要 |
1,136,197. Thermal flashers. WAGNER ELECTRIC CORP. 25 April, 1967 [29 April, 1966], No. 18996/67. Heading H1N. A snap-action switch comprises a buckling vane 10 with a natural curvature about a longitudinal axis (14, Fig. 1) provided with expansible pull means 16 secured to diagonally opposite corners on the naturally convex side so as to bow the vane when cold so that it is concave on the pull means side about an axis perpendicular to the longitudinal axis. A resistance coil 22 having a positive temperature coefficient of resistance, e.g. Ni alloy, is connected in parallel across said pull means 16 by a permanent junction 28 and contacts 20, 21 which close when means 16 is cold. A heater 30 is connected across said pull means 16 by junction 28 and contacts 19, 18 which close when means 16 is cold. A load 36 is energizable through contacts 31, 32, which close when means 16 is hot. When switch S is closed and a potential applied across terminals 6, 8 heater 30 and coil 22 are energized. As coil 22 is heated by heater 30, its resistance increases, thus causing the current through pull means 16 to increase sufficiently to expand means 16 to snap vane 10. Load 36 is energized and coil 22 and heater 30 are de-energized. The pull means 16 is maintained expanded till the potential is removed by the current therethrough. While load 36 is energized coil 22 and heater 30 cool to allow the switch to reset. In a modification (Fig. 4), the permanent junction 28 is replaced by contacts (42, 44) which close when the means 16 is cold and are connected to an additional load (38). In the hot condition, there is no current through the pull means 16; it is maintained expanded by an additional heater (46) adjacent or wound about it and energized with load 36. The load 36 may be a warning signal light on a motor vehicle. |
