Patent GB-1399749-A (GB)
Title: Fire extinguishers and fire extinguishing systems
IPC: A62C35/08
Filed: 1972-07-10
Abstract: 1399749 Automatic fire extinguisher systems GRAVINER Ltd 10 July 1972 [12 July 1971] 32152/72 Heading A5A A fire extinguisher includes a container for extinguishant having a normally closed extinguishant discharge opening, first control means on the extinguisher and operative in response to a predetermined incipient fire condition in the neighbourhood of the extinguisher to open the discharge opening if closed, second control means on the extinguisher and operative in response to an input electrical signal fed to the extinguisher to open the discharge opening if closed, and electrical signalling means arranged to produce an electrical output signal when extinguishant is discharged, the signalling means comprising means positioned to detect opening of the discharge opening. The first control means may comprise a rupturable bulb 44 containing thermally expansive fluid, the bulb being mechanically juxtaposed relative to the discharge opening so as to hold valve head 20 closed until the bulb is ruptured by expansion of the fluid. The second control means may be electrically detonatable explosive-actuated means 46 or an electrically energisable heater, adjacent the bulb. The signalling means may be an electrical switch (a) mechanically operated by opening of the discharge opening, (b) having an operating member 61 biased into contact with the bulb so as to operate when the bulb ruptures. The extinguisher may also have signalling means, other than those detecting the opening of the discharge opening, and which (i) include a switch 16 responsive to the change in weight of the extinguisher as a result of loss of extinguishant therefrom; (ii) include mounting means supporting the weight of the extinguishant container and contents, if any, incorporating first and second members one attached to the container for movement therewith relative to the other when the weight of the container is reduced by at least partial loss of extinguishant and electrical switch means responsive to the movement; or (iii) include a pressuresensitive electrical switch 64 responsive to the pressure of extinguishant if any in the extinguisher which operates when the pressure falls below a set level as a result of loss of extinguishant. In (ii) the first and second members 30, 21 may be biased towards a first relative positional setting by spring means 34 having a predetermined rate and arranged such that the weight holds the members in a second relative positional setting, against the spring force, when the 'container: is full, and the electrical switch comprising contact means 26, 28 is actuated when the member 30 moves into the first setting as a result of reduction of the weight. The switches of the signalling means, (a) or (b), and one of (i), (ii) or (iii) may be electrically connected so as to produce an output only when both are operated. In the extinguisher of Fig. 5 (not shown) the discharge opening is held closed by diaphragm 116, Fig. 7, supported by circular support 118 held in position by balls 120, 122 (Fig. 7) and 124 (Fig. 8) which engage the chamfered edge of 118 and are located in the ends of radial bores 126, 128 and 130, respectively, extending through the wall of the member 110. Bore 126 threadably supports explosive actuator 134 which is closed off by removable plug 136 and incorporates piston 138 engaging ball 120. Piston 138 incorporates explosive charge 140 and electrically operated detonator 142, and when in place presses ball 120 into contact with support 118. Bore 128 supports glass bulb 150 which is held in position by hollow cylinder 152 having an open end closed off by removable plug 154. The inner end of 150 presses ball 122 in contact with- 118; bulb 150 incorporates a heat sensitive fluid. Bore 130 supports plunger 160 in hollow cylinder 162, which is closed by removable plug 164, and spring 165 urges plunger 160 to hold ball 124 against 118. Plunger 160 has collar 166 engaged by striker arm 168 of microswitch 170 whose contacts connect with cable 62. The lower end of member 110 is partially closed by apertured disc 180 held in place by apertured dome 182. Actuation of either explosive actuator 134 or ruptura'ble bulb 150 frees diaphragm 116 from the discharge opening, this in turn displacing plunger 160 to actuate switch 170 comprising the electric signalling means. A fire extinguishing system includes at least two extinguishers which may be self contained having a container holding extinguishant under pressure, the electrical signalling means of each extinguisher being electrically connected to the second control means of each other of the extinguishers to operate those extinguishers. The system may include further detecting means in the general neighbourhood of all the extinguishers to produce an electrical signal and means responsive to this signal to actuate the electrical responsive discharge means of each of the extinguishers. A discharge head for an extinguisher comprises at least one heat sensitive element in the form of a frangible liquid filled bulb which ruptures when the ambient temperature rises above a predetermined level to operate the head, and a remotely controlled explosive device selectively operable to break the bulb independently of the ambient temperature. The bulb is surrounded by a supporting structure on which the explosive device is mounted. The explosive device is elect ically ignited and includes a striker for. breaking: the bulb on actuation.