Patent GB-190428889-A (GB)
Title: Improvements in or relating to Electric Fire Alarm and like Cicuits.
Inventor: ABRAHAMSON MARTIN ARNOLD
Filed: 1904-12-30
Granted: 1905-09-28
Abstract: 28,889. Abrahamson, M. A. Dec. 30. Alarms, fire and temperature. - Relates to automatic systems in which a comparatively small rise of temperature rings a danger alarm bell, and a larger rise of temperature a firealarm bell, while a sudden accident to one of the circuits rings a different bell. Fig. 1 shows a form in which an open-circuit system is used, with a number of May Oatway fire-indicators a. In the case of a comparatively small rise of temperature, the circuit-closing part e closes a gap f, and a current flows from the battery b through a wire 1, resistance f<1>, wire 4, indicators c, and a relay coil d back to the battery. The relay d is provided with two armatures i, j, the first easily actuated and the latter requiring a larger current to move it. Thus, in the case of a small rise of temperature, when the current in the primary circuit has to pass through the resistance f<1>, the armature i only is attracted and a current passes from the battery b through a wire 2, coil h, contact-stop j<1>, armature j, wire 5, contact-stop i<1>, and a wire 6 back to the battery, an alarm bell being placed in this circuit. At the same time, an armature h<1> is brought into contact with a stop p, while an insulated contact-closing piece m makes contact between the two stops n, o. With a further rise of temperature, the gap g is closed and a stronger current flows through the relay d, causing the armaturej to be attracted, so that contact is broken at j<1> and made at j<2>. A current then flows through the wire 2, coil k, contact j<2>, armature j, wire 5, armature i, contact i<1>, and the wire 6 back to the negative terminal. An armature k<1> makes contact with a wire 8, and thus a current flows through an alarm apparatus q. In the case of a sudden closing of the primary circuit through accident, the contact at j' is broken before contact is made at i<1>, and thus only the electromagnet k becomes operative and no current passes through the alarm q, while a bell in the circuit containing the electromagnet k is sounded. The alarm q can be sounded mechanically, after the ' danger ' signal bas been given, by means of a contact-maker r. The two lower fire-indicators shown in the diagram are arranged to sound only the preliminary or ' danger' alarm. Modifications are described in which a similar principle is applied to " autopyrophone " systems, having closed primary circuits in which the current is reduced, or cut off entirely by the displacement of mercury in closed U-tubes, this displacement being caused by the evaporation of a volatile liquid also contained in the tubes. In the modification shown in Fig. 2, the armatures i are released by a reduction, and the armatures j by a complete interruption, of the primary current. A 'danger' signal is thus rung by means of the electromagnet h, and a signal indicating an accident to the circuit by means of an electromagnet k, while, if they are actuated in succession, contacts s, s<1> are closed, and a current flows through the wires 8, 9, thereby ringing an alarm at a fire-station or other place at a distance.