Patent GB-191025812-A (GB)
Title: Improvements in or relating to Detector or Alarm Apparatus for Safes and the like.
Inventor: BRIDGER THEO EUSTACE
IPC: G08B13/00
Filed: 1911-05-01
Granted: 1912-03-14
Abstract: 25,812. Bridger, T. E. May 1, 1911. Burglar alarms.-In an alarm apparatus for use with safes, gasmeters, coin-freed machines, strong rooms, doors, windows, &c., the body to be protected and the indicating-devices are respectively enclosed in exhausted or pressurecontaining casings connected by a composite conduit which is adapted to operate the alarm if severed or deformed. In the arrangement shown, a double-walled casing a contains the device to be protected, and has a contact arrangement b<3> adapted to be set by code so as to interrupt the electric alarm circuit. The casing and double-walled door are connected by a tube a<4> and are exhausted by means of a hand pump a<5> connected with a gauge a<6> adapted to close an electric circuit when the pressure reaches a predetermined amount. The leads from the gauge pass to a mercury contact b<2>, which is adapted to short-circuit the leads if the casing is moved. The casing a is connected to the alarm-containing casing, Fig. 3, by a composite tube c, d<4>, the inner member d<4> of which is electrically insulated and connected to a pole of the contact device by a wire c' and also communicates by openings with the double walls of the casing a and the interior of the casing b<6>. The space between the tubes is filled with fluid, such as oil, under pressure introduced through a pipe f<1>, and communicates with a Bourdon tube e<3> in the casing. The inner tube is connected to a Bourdon tube d<8> enclosed in a part k partitioned off from the casing and contains a wire f connected to the casing a. A change of pressure in either casing, or in either of the concentric tubes, or contact between the tubes, completes one or other of electrical circuits comprising the Bourdon tubes e<3>, d<8>, a battery e<5>, and bell or explosive-alarm devices e<6>, e<9>. While the casing, Fig. 3, is being exhausted the electric circuits of the indicating devices are interrupted by the action of a spring f<7> carrying a projection g which presses a spring bridgepiece f<8> away from contacts f<9>, f<10>. The bridgepiece f is subsequently moved to one side, as by a pin working in a gland, so that it is out of contact with the projection g and engages the contacts f<9>, f<10>. The alarm is also operated on the opening of the door of the safe unless the contact device d<3> has been set. The contact device is of the character described in Specification 22,602/10, and comprises a fork-shaped part b<4>, Fig. 8, adapted to receive a member c<8> having brushes d<2>, d<3> connected to leads c<1>, c<Î>, Fig. 7. The mount for the member c<8> comprises a number of disks b<6>, Fig. 11, carrying the letters &c. of a code, and having sleeve-like extensions c carrying conducting contact-disks c<3> with insertions c<7> of insulating - material. The member c<8> is mounted adjacent to the disks c<3> and carries a conducting-strip d adapted to make contact with the disks. The brushes d<2>, d<3> engage contact-pieces d, b<7> on the part c<8>. The strip b<7> has an opening b<8> which receives the brush d<2> when the door is closed and breaks circuit. The brush d<3> bears on the strip d, and, if the door is opened, the disks being unset, the members c<3> bridge extensions b<7Î>, d<Î> of the parts b<7>, d and complete the circuit. In order to avoid the operation of the alarm by inadvertent closing of the door, the part c<8> carries a spring lever f<3> having teeth f<4> and a tail-piece f<5>. When the door is closed, the tailpiece engages the wall of the casing a and retains the extension f<4> out of engagement with the disks c<3>, but, if the door is opened, the disks being set, the lever f<3> is released and the teeth f<4> engage depressions f<6> in the disks c<3>. When the disks are subsequently turned to upset the combination, the member c<8>, which is elongated in section, will also be rotated so that it cannot enter the slot in the part b<4> and will prevent closure of the door. The ends of the tube a<4> are protected by hard steel bars g<1>, Fig. 9, secured by fusible pins or tubes g<2>. In a modification, Fig. 13, the exhausted jacket is connected to the outer tube e and contains a sinuous pipework connected to the inner tube d<4>. Means such as a brush contact and an electric bell are provided for testing the circuits each time the door is opened or shut.