US1530419A - Electric alarm apparatus - Google Patents

Description

Patente-d Mar, l?, l925.

LSAE@ PA'IN'I GFFEQE.

GEO'RG SCHMIDT, 0F REINICKENDORF-OST, AND CARL BKER, 0F BERLIN, GERMANY, ASSIGNORS TO BAYERISCHE VEREINSBANK, OF MUNICH, GERMANY.

ELECTRIC ALARM APPARATUS.

Application filed May 6,

To all whom t may concern:

Be it known that we, GEORG SCHMIDT and CARL Bxnn, both citizens of the German Republic, residing at the 1st, Reinickendorf- Ost, the 2nd, Berlin, Germany, have invented certain new and useful Improvements in Electric Alarm Apparatus, of which the following is a specification.

This invention relates to an alarm and signaling apparatus designed to protect against burglary and lire. In an apparatus of this character, as is well known, two selenium cells or two similarly acting electric light cells are employed in connection with a IVheatstone bridge. Devices of this construction have the selenium cell, together with the storage battery and the relay employed in connection therewith usually connected in series and upon the device operating the current resulting for operating the device is of a low intensity. Furthermore, in the selenium apparatus of this character the same will opera-te to give an alarm upon the slightest increase of the surrounding temperature. The relay employed must be very finely adjusted in order to signal a feeble gleam of light. The release of the alarm circuit is effected either by exposure or by shading, or by exposure and shading of one or several selenium cells. According to this invention the arrangement has been made, that a working cell and a compensating cell are compensated by two resistances in a Wheatstone bridge in such a manner that the relay in the bridge is currentless. Thus it is ensured that the relay acts only upon the electric light current and that the signalling device signals even a very feeble gleam of light. The inertia and the inconstancy of the working cells are overcome further by the connection which has been just described. The alarm may be given according to this invention by a feeble gleam of light.

In order that the invention may be clearly understood, we will hereafter describe the same with reference to the form of construction which is diagrammatically shown by way of example in the accompanying drawing, wherein 71 and V2 are two selenium cells. W1 is enclosed in the case or box H which excludes all light; W2 is situated behind an indicator disk drop K which closes a win- 1921. Serial No. 467,277.

dow tightly and is adapted to be swung sidewards and away from the window by the action of magnet M1. VV and W4 are the compensating resistances. In the Wheatstone bridge the relay R is arranged which is designed to close the alarm circuit by means of the hand Z and the adjustable contacts K1, K2. FS is a fuse for feeble currents and will fuse when the leads 2, 4 are bridged over, provoking thus the alarm signal. The multiple point switch Sct serves to cut in the alarm apparatus. Ms is a maximum switch designed to short circuit the contact of the relay when the said relay has been operated, so that the relay is protected against over loading. L is an optical signal and G is an acoustic signal. The battery B supplies the required energy.

The operation is as follows When tlie'wdevice has to be switched on, the room to be protected haswto be darkened, whereupon the switch Sch is turned so that the switch lever P is in contact with II.

The circuit is now as follows From the positive pole of the battery through lead 3, switch lever P, contact II, lead 31, lead 4, screw D, spring F, armature A, wire C, winding of magnet M1, lead 2a and back through leads 2, l to the negat-ive pole of the-battery B. Owing to this circuit the armature A is attracted by the electromagnet M1 and the disk K drops away from the selenium cell W2. The spring F is thus moved away from contact screw D so that the current supply to the winding of magnet M1 is interrupted. The switch Sch is now moved to its operative position that is to say the switch lever P is placed upon the contacts III, IV.

The closed circuit current flows as follows v From the positive pole of the battery B, through lead 3, switch lever P, contact III, lead 3b and is then divided, a part thereof flowing through fuse FS, lead 4, selenium cell W2 to selenium cell W1, lead 2, and the remainder through lead 4, resistances W4, W3 and lead l back to the negative pole of the battery B. In the bridge of these connections the relay R is inserted between the leads 5 and 511.

The open current circuit is as follows From the positive pole of battery B through lead 3, switch lever P, contact IV,

lead 3, through bell G, lamp L,lead 1, through the winding of the maximum switch MS interposed in, lead 1 to the adjustable contacts K1, K2 and further from the negative pole of battery B over lead 1 to the contact pointer Z.

The short-circuiting device X, Y of the maximum switch MS is connected by the leads 1 and 1a with the contacts 731, k2 and by the leads la with lthe pointer Z. The plant is thus switched in ready for work. If *nowfamdlight ray penetrantgsgintomthe protected"roomsiivliwthe case with the selenium vcellsv 71, W2 is situated, either from a lighted match, or from a lighted pocket lanter1`,'tli`e'"ie"si'stance'the'sfclenium cell"lvzdiases almost instantaneously and the electric proportion which was established in the working position is disturbed. Current will consequently flow through the bridge so that the hand of relay R comes in contact with k2 and the alarm device is operated. The current of the working circuitflows as follows From the positive pole of battery B to 3, P, IV, 3c, G-L, 1, Ms, 1, k2, Z, 1 to the negative pole of battery B. Owing to the closing of the circuit the armature Y of the maximum switch is attracted and comes in contact with screw X so that the contacts k2, cl, Z of the relay R are bridged over by means of leads 1, 1a and the relay is released from the current. IVhen the closed current circuit is cut or when the leads 5 4, 5-2 are bridged over, the signal is given in the same manner. When the leads 2--1 are directly short-circuited the alrm is operated by the fusing of the fuse F c When the apparatus is to be cut out the contact lever P is brought in contact with I so that the disk K is placed over the selenium cell 72 by the action of the magnet M2.

The circuit is as follows:-

Positive pole of battery B, lead 3, P, I, 3a through the winding of magnet H2, lead 2, over leads 2, 1 back to the negative pole of B. Owing to the closing of this circuit the armature A is attracted by the magnet M2, the spring F is again brought in contact with screw B and the disk K is placed in front of the selenium cell T2 so that this cell is shut oit light-tightly. The switch Sch is now brought back to its initial O position. By this turning of the switch the apparatus is out out. Fire is signalled in the same manner.

7e claim 1. A device of the class described comprising a lVheatstone bridge, means for giving an alarm when said bridge becomes unbalanced, a pair of selenium cells in differd ent legs of said bridge, whereby said bridge will remain balanced under varying temperature conditions, and a light excluding enclosure for one of the cells.

2. In an apparatus of the character described, a lllheatstone bridge, means for giving an alarm when said bridge becomes unbalanced, light responsive resistances inserted in the legs of the bridge, proportioned to maintain the bridge balanced under varying temperature conditions and also adapted to imbalance the bridge upon light falling upon either of said resistances.

In testimony whereof we afliX our signatures in presence of two witnesses.

GEORG SCHMIDT. CARL BKER. llitnesses OARL O. BKER, ELIZABETH VVALF.

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