Patent GB-157772-A (GB)
Title: Improvements in fire-alarm signalling apparatus
IPC: G08B17/06
Filed: 1921-01-10
Abstract: 157,772. Garrison, W. H., (Assignee of Harsch, C. A.). May 10, 1915, [Convention date]. Fire-alarm systems and apparatus.-In a fire-alarm system of the kind adapted to be actuated from any one of a number of substations, such as the various floors of a building, to give, by means of code-wheel transmitters, signals characteristic of the individual substations, and having a single motor-drive common to all the transmitters, arrangement is made whereby, when one transmitter is in use, the others are out of use whilst the signal first initiated is being given, but a signal due to actuation of a substation in the meanwhile is given immediately the first signal ceases. The alarm may be given manually bv the breaking of a glass-cover to the substation switch case, or automatically by the use of a known temperature-operated device comprising two conductors, normally insulated, and adapted to be connected by a fusible conducting substance when the temperature rises sufficiently. As described, the transmitter (which may be situated, for example, in the basement) comprises a gravity motor m, held against movement by a detent 204 engaging a fly f, until released by de-energizing the holding electromagnet 208. The motor drives two shafts s, t, through gearing shown. Shaft s carries a number of signal transmitting wheels c, d corresponding with the substations, the number and arrangement of peripheral teeth on a wheel being characteristic of its substation. Shaft t carries a corresponding number of cam discs k. The transmitting wheels are adapted to co-operate with corresponding pairs of spring contacts e pivoted at 20 and normally held clear of the wheels by detents 30 under the action of electromagnets q. Each magnet q is in circuit with a battery 50 through contacts 65, 66 and switch arm 60 at the corresponding substation. When any switch arm is operated to break this circuit corresponding contact e is released and falls. This movement opens contacts i in circuit of magnet 208, allowing motor m to start. At the same time an arm g closes parallel circuits from a battery 90 through magnets v which hold the remaining detents 30 against release by a subsequent substation switch and signal until shaft t has made one revolution. A pin associated with released contact e enters a cam-groove in the corresponding disc k, whereby the contact is held in positive engagement with the corresponding transmitting wheel during one revolution of the disc, and is then raised again. Contacts e control the circuit of a recording device 300 in series with audible signalling means such as bells 320, which may be placed on the various floors of the building, giving the same characteristic signal simultaneously. Instead of breaking contacts 65, 66 manually, magnets q may be de-energized by means of heat-detecting conductors x, y at each substation adapted to be placed in conductive connection in known way when the temperature rises, and communicating through conductors 43, 44 with opposite sides of corresponding magnet q, which is first short-circuited, circuit through conductors 44 being then broken by electromagnet 310. In the substation switch arrangement described, a preferably cast-metal casing has a hinged door 101 held by a spring catch which can be released by a three-cornered key. The door supports an arm 60 pivoted at 63 and normally held bridging contacts 65, 66 by a slidable detent 113 held in engagement by a glass panel 110 mounted in a frame hinged to the door 101 and locked thereto by a spring catch which can be released by a key.. When the glass is broken, detent 113 is thrown outwards by a spring, releasing the arm 60, which breaks circuit at 65, 66 and immediately snaps over under action of a spring 64 to engage with a contact 67 which is connected with contact 65. A web 91 on the arm 60 prevents the detent being returned until the arm 60 has been reset.