Improvements in or relating to Portable Warning Devices for use in Mines

1,175,095. Portable warning device for mines. R. HUBNER. 8 March, 1967 [26 May, 1966], No. 10855/67. Heading G5J. A portable warning device for use in mines comprises an accumulator 2, an oscillator 3, an amplifier 4, a diaphragm type sound producer 5 including a diaphragm 7 sealed in a window openi...

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1. Verfasser: ROLF HUEBNER
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Sprache:eng
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Zusammenfassung:1,175,095. Portable warning device for mines. R. HUBNER. 8 March, 1967 [26 May, 1966], No. 10855/67. Heading G5J. A portable warning device for use in mines comprises an accumulator 2, an oscillator 3, an amplifier 4, a diaphragm type sound producer 5 including a diaphragm 7 sealed in a window opening in a wall of casing 1, and a switching unit 6 connected to a key-operated switch 8 or plug-in connector. The various components are operated above their intrinsically safe levels of voltage and current to produce an adequate sound output, but the switch or plug-in connector is electrically protected by limiting devices. A grating 14 protects diaphragm 7 from external damage. In Fig. 2, the oscillator 3 is a Wagner's hammer actuated mechanically by the sound producer 5, and a variable output switching transistor TS2 is included in the oscillator circuit. In Fig. 3 (not shown) the oscillator is a transistorized multivibrator. In either case, oscillator 3 is connected to a second low frequency multivibrator 12. When switch 8 is closed, the parallel switching transistor TS1 conducts and amplifier 4 sends current to the relay coil of sound producer 5, operating diaphragm 7 and opening contacts 13 of the Wagner's hammer so that transistor TS2 is de-energized. Multivibrator 12 acts as an intermittent pulse generator so that an intermittent sound signal is emitted. In Fig. 3 (not shown) the useful load is a loudspeaker (5) and a switching transistor relay (TR) is the final output stage. Multivibrator (3) generates the basic signal frequency and multivibrator (12) generates an intermodulation frequency to produce a warbling tone signal. The accumulators 2 are rechargeable through contact 11 via rectifying diode 10. Parallel leads 9 may be included in the switching unit circuit 6 for operation of the warning device by connection to the shot-firing equipment circuit. The switching unit is protected by limiter resistances 15 and a parallel Zener diode Z. Casing 1 may be provided with a lock and chain to secure it to a mine support.