| 摘要 |
<p>729,249. Thermal switches; switches, partly electromagnetic. HOLLINS, J. R. Jan. 9, 1953 [Jan. 9, 1952], No. 723/53. Class 38 (5). A switch for flashing vehicle signal lamps comprises a metal frame 17 carrying an electromagnet relay core 18 and a fixed contact 22, and pivotally supporting an L-shaped armature 32 having contacts 27, 34. A spring arm 23 carrying a contact 25 and mounted on an insulating base 16 is biased towards the contact 22, a high-resistance wire 30, when cold, holding the contacts 22, 25 disengaged. Closure of a selector switch 15 to energize a pair of signal lamps 13, 13<SP>1</SP> or 14, 14<SP>1</SP>, completes a circuit from battery 11, core 18, frame 17, conductor wire 26, resistance wire 30, arm 23, conductor wire 42, relay coil 35, conductor wires 43, 46, to the lamps. The resistance 30 limits the current to a value insufficient to illuminate the lamps or to operate the relay. Expansion of the wire 30 upon heating permits contacts 22, 25 to engage whereupon the wire is short-circuited and the increased current illuminates the lamps, and the armature 32 is operated to close contact 27 upon the upper end of contact 25. Operation of the armature thus completes a further shunt circuit around the wire 30, and contact 34 engages a contact 36 to energize a pilot lamp 12. As wire 30 now cools, contact 25 leaves contact 22 under " no-load conditions and arcing does not take place due to the further shunt circuit; also, the movement of contact 25 along contact 27 cleans these contact surfaces and the contact 25 eventually disengages contact 27 to deenergize the lamps and the relay, a fast break being produced by an armature spring 38. The wire 30 then heats up again and the cycle is repeated. Should one of the signal lamps of the selected pair be faulty the current through the coil 35 is insufficient to operate the armature. Specification 729,250 is referred to.</p> |
