US 3750023 A
A lamp and a radio transmitter are connected in parallel across a battery in a miner's hat to provide a visual and radio-frequency beacon enabling finding him in an emergency situation. In order to prevent the lamp from depleting the battery which would cut off the radio beacon, an involuntarily opened nonresettable switch is provided that disconnects the battery from everything but the transmitter. A voltage detector connected across the lamp senses when the voltage applied to this lamp drops below a predetermined level and closes a circuit to pass current through an electrically actuatable element for opening the switch. This element can be a minute squib or a fuse-type device forming the switch itself.
Description (OCR text may contain errors)
United I States Patent n 1 Weissenborn et a1. I
1451 July 31,1973
1 1 VISUAL AND RF BEACON FOR MINERS HAT WITH CONTROL CIRCUIT  Inventors: Dieter Weissenborn, Mulheim/Ruhr;
Ortwin Bock, Duisburg; Norbert Werding, Essen-Heisingen, all of Germany 3  Assignee: Friemann & Wolf GmbH, Duisburg,
Germany  ',F ile d: Aug. 5, 1971 21 Appl. No. 169,414
 Foreign Application Priority Data  References Cited UNITED STATES PATENTS 1 3,181,135 4/1965 Zoglio ..340/332X 3,321,754 5/1967 Grimm et al 340/249 Primary Examiner-Benedict V. Safourek Attorney-Karl E. Ross  ABSTRACT I A lamp and a radio transmitter are connected in parallel across a battery in a miners hat to provide a visual and radio-frequency beacon enabling finding him in an emergency situation. In order to prevent the lamp. from depleting the battery which would cut off the radio beacon, an involuntarily opened nonresettable switch is provided that disconnects the battery from everything but the transmitter. A voltage detector connected across the lamp senses when thevoltage applied to this ,lamp drops below a predetermined level and closes a circuit to pass current through an electrically actuatable element for opening the switch. This element can be a minute squib or a fuse-type device forming the switch itself.
8 Claims, 3 Drawing Figures PATENIELJII! 1 W 3.750.023
l N VE N TO R S I Dieter Weissenborn Orfwin Bock Norbert Werding Attorney VISUAL AND RF BEACON FOR MINER'S I-IAT WITH CONTROL CIRCUIT l. FIELD OF TI-IE INVENTION 2. BACKGROUND OF THE INVENTION In order to be able to locate a miner in an emergency his hat may'be equipped with a small beacon light or a headlamp and a radio-frequency transmitter toallow a searcher to'find him even ifthe miner is unconscious. 'Since this device must be entirely mounted in'the miners hardhat, it is important that it be small anddifficult to damage. Asimilar devicecan be used in life vests for boaters, pilots, and the like.
It has been found that the relatively high-drain lam may deplete the batteries, thereby making the lowdrain beacon transmitter ineffective. It is desirable to maintain the useful life of the transmitter even when the lamp is extinquished, since this transmitter is ultimately the most effective means for locating a person in emergency conditions. Circuits have been proposed using relaysand the like whichshut off the lamp after the battery voltage drops below a predetermined threshold while continuingto let the beacon transmitter function. All such circuits have been complicated or have possessed such a substantial current drain by themselves that they shorten the service life of the battery considerably, thus defeating their principal purpose.
3. OBJECTS OF THE INVENTION It is therefore an object of the present invention to provide an improved electrical warning apparatus adapted for use in a miners hat, a life vest, or the like.
Another object is the provision of such an apparatus which overcome the above given disadvantages.
Yet another object is to provide such an electrical warning beacon wherein the circuit used to shut off the light consumes very little current and which after shutting off the light consumes none at all. I
4. SUMMARY OF THE INVENTION The above objects are attained according to the present invention by an apparatus wherein the beacon transmitter and beacon lamp are connectable in paralthe circuit of the lamp. Once the current path is interruped by the fusible or mechanically rupturable elebattery while the lamp, in'parallel therewith, is connected at a location separated from the junction between'the transmitter and the battery by a high conductivity rupturableelement-The sensing circuit includes a voltage detector connected across the battery in series with the rupturable elementas well and can activate the latter while being deenergized upon electrical rupture of the element. e
The switchaccording to this invention can be a socalled electrical microtemperatur'e fuse having a small heating coil which when, activated, quickly melts a small mass of fusible metal so that a spring pulls a pair of-contacts apart and interrupts the current path. Alterment to cut off this lamp there is no more power consumption by anything other than the transmitter. Thus the unit is characterized by low power consumption prior to cutoff and virtually none thereafter. In other words,the transmitter is connected directly across the natively a switch having a minute squib or the like'can be provided such that, when this element is electrically activated, it actually blows outthe connection to form an open circuit. In either case, breakdown of the nonresettable element does not depend, as in an ordinary fuse or circuit breaker, on a flow of current therethrough in series with the lamp.
5. DESCRIPTIONOF THE DRAWING The above and other objects, features, andadvan 6. SPECIFIC DESCRIPTION As seen in FIG. 1 a battery 1 has a negative terminal 2 and a positive terminal 2" across which are connected in parallel a small incandescent lamp 3 and a small beacon transmitter 4. A conductor 5' leads from the pole 2 to one side of the lamp 3 and a conductor 5" from the other pole 2" to the other side of the lamp;
A pair of resistors R, and R, are connected in series across the two conductors 5 and 5" and act as a voltage divider for a high-gain transistor T, whose base is coupled to the junction between these resistors. The emitter of transistor T, is coupled to the junction between these resistors. The ernitter of transistor T, is coupled directly to the negative conductor 5' and the collector is connected through a bias resistor R, to the positive conductor 5", with a capcitor C, bridging the base and collector. This transistor T, and the resistors R, and R, are so chosen that when the voltage output of the battery I measured between the conductors 5' and 5" drops to 1.8 Volts the transistor T, ceases to conduct.
Connected to the collector of transistor T, is the base of a driver transistor T whose emitter is connected to line 5' and whose collector feeds directly into the base of a transistor T the emitter of the latter is connected to the line 5" and its collector is connected through a switch unit 6 to the conductor 5'. Inside the switch device 6 is an igniting element MS, which when electrically stimulated sets off a tiny squib b, which opens a switch SW, connected in the conductor 5'. This switch SW, is disposed between all of the ciruitry described with the exception of the transmitter 4 and the battery 1, so that when it is open this transmitter 4 alone remains connected across thebattery.
Thus when the voltage across the voltage divider R R drops below 1.8 volts the transistor T stops conducting thereby switching on the two transistors T, and 3 which is made of an easily meltable metal and which are pulled apart by a spring when the coil 7 has heated .the fusible contact'sufficiently to soften it. In all other respects this arrangement functions identically to that of FIG. ,1. 7
FIG. 3 shows the apparatus A mounted in the crown of a miners hardhat H.
We claim: 1. An electrical warning apparatus comprising: a battery; transmitter means connected across said battery and in circuit therewith for emitting a radio signal; a lamp connected across said battery and illuminable thereby; I I 5 voltage-detector means connected to said battery for detecting a drop in voltage outputthereof below a predetermined threshold level; and
switch means including a rupturable element in series with said lamp across said battery and external of the circuit between said transmitter means, said voltage-detector means being connected to said switch means for rupturing said element to open the circuit to said lamp and extinguish same upon said voltage output of said battery dropping below said predetermined threshold level, while permitting said transmittermeans to remain connected to said battery.
2. The apparatus defined in claim 1 wherein said voltage-detector and switch means present a resistance of at most 2 milliohms in series with said battery.
3. The apparatus defined in claim 1 wherein the switch means includes an electrically actuatable element connected to said voltage-detector means and operable to permanently break said rupturable element, said voltage-detector means being connected across said battery in series with said rupturable element.
4. The apparatus defined in claim 3 wherein said rupturable element includes a pair of contacts fused together and a springbiasing said contacts apart, said electricallyactuatable element including a heater energized by an electric current and being connected electrically to said voltage-detector means for heating said contacts and enabling said contacts to pull apart.
5. The apparatus defined in claim 3 wherein said electrically actuatable element is a squib disposed adjacent said rupturable element.
6. The apparatus defined in claim 3 wherein said voltage-detector means includes a voltage-divider network connected across said lamp and at least one-transistor connected to said network and to said electrically actuatable element.
7. The apparatus defined in claim 6 wherein said voltage-detector means includes a first transistor connected to said network as a sensor and at least one second transistor connected between said element an said electrically actuatable first transistor.
8. The apparatus defined in claim 7 wherein said voltage-detector means includes two such second transistors directly coupled with one another, one of said second transistors being connected to said firsttransistor and the other of said second transistors to said electrically actuatable element.
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