Patent GB-190421455-A (GB)
Title: Electric Time Alarms.
Inventor: BROMHEAD SAMUEL SIDNEY
Filed: 1904-10-06
Granted: 1905-03-09
Abstract: 21,455. Bromhead, S. S., [American Bank Protection Co.]. Oct. 6. Alarms, burglar.-In a burglar-alarm circuit, two connections have to be made to complete the circuit ; one is made automatically during certain hours of the night by a clock, and the other by the withdrawal of bolts &c. Warning and test bell circuits are also arranged. The gear wheel is fast to a sleeve which carries the hour-hand 82 and a metal disc 83, the gearing being such that the hour-hand makes one revolution in twenty-four hours. Between this disc and a friction washer is a disc 85 of insulating-material, held against accidental movement but adjustable when desired. A curved peripheral slot 86 is cut in its edge, and through this a pin 87 extends connecting the gear wheel with the hour-hand, thus setting a limit to the adjustment of the disc. A peripheral metal band or contact-plate 88 is provided on the disc 83, and the ends of this plate are turned in to make connection with the disc 83. Another contactplate 90 is fast to the gear wheel, and under this plate the plate 88 can slide by rotating the disc 85 ; in this way, the length of the metal contact, and therefore the time during which the clock circuit is closed, can be varied. Two springs or brushes 18, 23 insulated from one another carry points which press upon the disc 85, and, at a prearranged time, these points are put in connection by the passage of a small strip 92 of metal embedded in the edge of the disc. A little later, the plates 88, 90 come in turn beneath the points and put both springs into connection with the body of the clock through the disc 83 ; finally, after the interval arranged, the points rest once more upon the insulating-material. In Fig. 1 is shown a diagram of the connections with the bolts of a safe. When the safe is closed and the bolts shot, the contact-pieces 5, 6 are out of contact with the springs 9, 10, 11, 12. If, now, the bolts be withdrawn during the night when the clock is " on," the contact-piece 6 closes a circuit through the contact-spring 11, wires 26, 24, brush 23, the frame of the clock, wires 37, 39, circuit-closer 41, wire 42, battery B, and the wires 43, 44 to the contactspring 12. The passage of current through the circuit-closer 41 releases the drop 45 and closes a circuit through the spring 46, wire 47, gong 48, wires 49, 43, battery B, and the wire 42 to the drop. By the contact of the piece 5 with the contact-spring 10 or with the spring 9, a similar result occurs with the gong 53. A test circuit is provided which rings the small test bell 54 whenever the contact-plate 6 comes into engagement with the springs 11, 12 during the hours when the circuit through the clock is broken. This circuit may be traced through the wires 26, 27, test bell 54, wire 55, rheostat 56, wire 57, battery B, and the wires 43, 44 to the spring 12. A reminder circuit is also furnished, the object of which is to ring a warning- bell a quarter of an hour before the clock enters on its circuit for the night, if the door is open at the time. The contact-spring 9 possesses a longer offset than the other three springs, so that it is in contact with the piece 5 even when the bolts are fully withdrawn. The passage of the small strip 92 of metal closes a circuit between the two springs 18, 23 through the contact-spring 9, wires 14, 17, brushes 18, 23, wires 24, 27. 28, bell 29, wire 30, rheostat 31, wires 32, 33, battery A, wires 34, 35, 36, and the contact-plate 5. The mechanism is shown in connection with a tumbler lock. The tumbler 58 has a series of notches 59 to receive a drop arm and so close a circuit by contact of spring 61 with the plate 63, the former of which is connected to the piece 5 and the latter to the screw 14. Any attempt to rotate this tumbler wheel will cause the arm to fall and in this way close the alarm circuit.