GB915294A - Improvements in or relating to warning devices - Google Patents

Abstract

915,294. Fire and theft alarms. SMALLPEICE Ltd. Jan. 11, 1961 [Dec. 29, 1959], No. 44064/59. Class 118. [Also in Group XXI] A warning device, for use as a burglar, fire or like alarm, comprises a reservoir 1 containing a fluid at a pressure different from the outside pressure, there being at least one aperture closed by a sealing member 7 connected (e.g. via a pipe system 5) to a wall of the reservoir, the arrangement being such that if a sealing member breaks, a flow of liquid into or out of the system occurs and a pressure-sensitive element 3 connected to a warning means is operated. The sealing member may be made of an inflammable or a fusible material when the device is used as a fire alarm and the fluid in the reservoir (when excess pressure therein is used) can be of a type which extinguishes fires; or for burglar detection, a very fragile sealing member (e.g. at a door or a window) is used and the fluid which escapes when the member is broken can be such as to stupify or mark the intruder. The pressure-sensitive element may be a flexible wall of the reservoir but in Fig. 2 it is shown as a flexible membrane 9 placed over an aperture in a wall of the reservoir and normally it holds a spring-loaded block 10 away from contactsprings 12. When an alarm is to be given, the block moves to the right (excess pressure system) and closes the contacts so that a circuit to a warning bell, lamp &c., is closed and also the membrane may rupture so that a whistle 13 can be operated as an audible alarm by the escaping fluid. In a further embodiment (Fig. 3, not shown) the reservoir is connected through a pipe and collapsible sealing member to a second reservoir of greater capacity which will operate in a similar manner in response to a drop in pressure in the first reservoir.