GB190710169A - Improvements in Electric Fire Alarms and Thermo-indicators. - Google Patents

Abstract

10,169. McNeil, A. H. May 1. Alarms, fire. - A thermal contact comprises thermal strips of different sensitiveness fixed at both ends and adapted to actuate electric contacts at different rates, so that, on ordinary changes of temperature, the contacts move one behind the other without contact, but, on a sudden rise or a gradual rise above a predermined limit, the leading contact is overtaken and an alarm circuit is closed. The strips a, a<1>, made of different thickness so as to be of different sensitiveness, are fixed at their ends to a casing c, and actuate plungers d, d' tipped with insulating-material. The plungers actuate spring arms i, i<1> which carry contacts h, h<1> arranged a short distance apart and in line with an adjust. able screw stop j carried by a bracket j<1> on an insulating plate g. The stop j may be either insulated or form an electric contact as shown. An adjustable screw i<2> on the contact arm i bears on the end of the plunger d. Both screws j, i<2> are provided with dials and pointers. The leads are held by screws n, n' screwed into brass plates o, o<1> in an insulating block p. Flexible conductors (not shown) fixed by screws o<3>, o<4> to the plates o, o<1> connect the plates with the contact arms i, i<1>, and bracket j<1> through plates o<5>, o<6>. The casing is provided with an open-work cover f and a lid c<4> fixed by screws, a layer of packing being interposed, and is fixed in position on a wall or the like by a bracket r. On a gradual rise in temperature, the contacts h, h<1> move in a line without contact, but, if the rise exceeds a predetermined limit, the contact h is arrested by the stop j and a circuit closed. Another circuit is also closed when the contact h<1> overtakes the contact h, either on a sudden rise in temperature or when the contact h is arrested by the stop j.