Classifications

• • G—PHYSICS
  • G08—SIGNALLING
  • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
  • G08B15/00—Identifying, scaring or incapacitating burglars, thieves or intruders, e.g. by explosives
  • G08B15/02—Identifying, scaring or incapacitating burglars, thieves or intruders, e.g. by explosives with smoke, gas, or coloured or odorous powder or liquid

Definitions

• the present invention relates to an intruder deterrent system of the type which generates a screen of smoke or vapour.
• a severe limitation of the audible/visible alarm system is that the triggering of the alarm will not automatically deter a burglar and in most circumstances there will be a delay of as much as 10 to 15 minutes before the alarm is responded to by the owner, the pohce or other concerned citizens.
• an intruder deterrent system of the type which generates a smoke screen and which comprises: smoke screen generating means; activating means to activate the smoke screen generating means when an intruder detection means, operatively linked to the activating means, is triggered; and smoke screen density regulating means having a sensor to sense the density of the smoke screen and control means responsive to the sensed density to adjust the output of the smoke screen generating means to maintain the screen density at a desired level.
• the smoke screen generating means suitably comprises a pump the rate and/or duration of operation of which is controllable by said control means to regulate the density of the smoke screen.
• the smoke screen generating means comprises a storage tank for an aqueous liquid composition and delivery pipes extending from the tank to deliver the liquid composition to an outlet, there being further provided heating means to heat the liquid composition which has left the tank to thereby convert the liquid composition into a dense vapour.
• the duration of operation of the pump is controlled to regulate the density of the smoke screen and the rate of operation of the pump is controllable to regulate the efficiency of use of the liquid composition.
• the liquid comprises a mixture of Glycol and water. Heating of this mixture as it passes through the delivery pipes to the outlet will vaporise the mixture to form a fog.
• the smoke density sensor is housed independently of the smoke screen generating means.
• the activating means is advantageously operatively linked to a fire detection system so as to be inactivated if fire detection system detects a fire. This will prevent hindrances to firemen breaking and entering a blazing building in which the intruder deterrent system is installed and armed.
• a smoke screen generating means which comprises a storage tank for an aqueous liquid composition and one or more delivery pipes extending from the tank to deliver the liquid composition to an outlet, the system further comprising heating means adjacent the delivery pipe (s) to heat the liquid composition in the delivery pipe (s) to thereby convert the liquid composition into a dense vapour, control means being provided to control the rate of operation of the pump in dependence upon the temperature of the heating means.
• a smoke-generating intruder deterrent unit 1 comprising a robust metal or plastics casing housing a liquid storage tank 2 which is adapted to act as a reservoir for a Glycol/water mixture or other suitable heat labile fog-generating mixture.
• a liquid storage tank 2 which is adapted to act as a reservoir for a Glycol/water mixture or other suitable heat labile fog-generating mixture.
• One or more delivery pipes
• a powerful oscillating piston pump 4 which, when activated, operates to draw the liquid mixture from the tank 2 and pump it at a selectable variable rate.
• a powerful oscillating piston pump 4 which, when activated, operates to draw the liquid mixture from the tank 2 and pump it at a selectable variable rate.
• two such pumps 4 are provided in parallel to each other to improve fluid flow.
• the fluid pumped by the or each piston pump 4 is forced through a narrow coiled tube 5 located within an insulated heating block 6, to be heated to a thermostatically controlled temperature and vaporised prior to being expelled from the unit 1 via an outlet 7.
• a switch 8 which receives an input from an intruder detection system A, of any suitable known type which is suitably part of a burglar alarm system.
• Switch 8 which may, for example, comprise a latching relay serves to activate the pump 4 when the intruder detection system is triggered.
• Switch 8 may be over ridden or switched off by a signal resulting from activation of a fire smoke detection system B. Furthermore, inhibit circuits may be provided to switch off or over ride the switch 8 in response to switching off of the burglar alarm system which the intruder detection system complements or forms part of. This will prevent accidental activation of the smoke screen generator during dayhght hours when the building is normally occupied
• the intruder detection system is, in the illustrated embodiment shown as being external to the unit 1, it may, if desired, be formed integrally with the unit 1, making the unit 1 a wholly self-contained system enabling the unit to be positioned in a wide range of locations.
• the sensor is suitably of an infrared or microwave transmitting and receiving nature.
• the unit 1 suitably also incorporates its own internal power supply which is suitably a 12 volt battery. This may serve as a back-up power supply in case of failure of the external mains electricity power supply.
• An indicator panel is suitably provided on the unit 1, or, more preferably on the main burglar alarm system control panel to indicate the operational status of the unit 1 and display outputs from fault detection sensors provided in the unit 1 for detecting power failure or malfunction of the heater block 6.
• the indicator panel suitably also displays an output from a reservoir level senses in the unit 1 which sensors the level of fluid within the tank 2 to warn of depletion.
• the intruder detection system may be configured to activate the smoke- generating unit 1 when the intruder breaks the perimeter of the building prior to entering the room in which the unit 1 is installed. By doing so the room will be effectively smoke-filled, preventing vision, even before the burglar enters that room.
• Attainment and maintenance of a satisfactory level of smoke screen density is achieved through feed-back control of the rate of vapour production by the unit 1.
• One or preferably a pluraity of smoke screen density sensors 10 sense the density of the generated smoke screen. These are similar to the sensors used in conventional fire safety smoke detectors employing infrared transmissions and utilizing the Tyndle effect of light dispersion to sense smoke. Unlike conventional smoke detector sensors, however, because the threshold level of smoke screen density for triggering the system to activate it to produce more smoke is suitably around 450 mg of Glycol vapour per cubic metre of air, the sensitivity setting of the relay switch 1 in each sensor 10 which activates the system is suitably lower than conventional. Additionally, the rate at which the sensors 10 sample is faster than conventional, being of the order of once per second to three times per second.
• a control unit 9 having comparator circuits controls the duration of operation and rate at which the piston pump 4 pumps the liquid mixture from the tank 2 and hence controls the rate of vapour generation.
• Use of a triac in the control unit 9 provides not only an on off control but also continuously variable adjustabhty of the rate of pumping. This variable adjustabihty enables economical use of the stored glycol mixture.
• control unit 9 When the smoke screen generating system is first activated in response to triggering of the intruder detection system A the control unit 9 will provide power to the piston pump 4 such that the piston pump will operate.
• the smoke sensors 10 are suitably independent of the unit 1 and operatively linked thereto by one or more electrical cables. By provision of the sensors 10 independently of the unit 1, substantial flexibility in the arrangement of the system is obtained. Amongst other factors, the independent positionability of the sensors enables adjustment by that means of the sensitivity of the system to the smoke screen density.
• temperature sensors 13 are provided to sense the temperature of the heating block 6 and send control inputs to the triac of the control unit 9 to adjust the rate of operation of the pump 4 to correspond with the temperature of the heating block 6.
• the rate of pumping of the fluid to and through the heating block 6 will initially be maintained at a low level and made to rise as the temperature of the heating block 6 rises.
• a number of smoke-generating units may be inter-linked and connected to one or more sensors at a range of locations to provide optimal coverage of an area to be enshrouded in the smoke screens.
• a suitable configuration of the smoke-generating units 1 and the sensors 10 may be arrived at to ensure that no area of a room is vulnerable to dispersion of the smoke screen by opening of doors or windows or the like.
• a long-lasting dense fog may be produce with little or no residue being deposited on the exposed surfaces of the room, leaving the room practically untouched by smoke once it has been dispersed and the smoke being totally innocuous to occupants of the room.
• a smoke screen of this nature is ideal for the purpose in question.
• Variation of the composition of the mixture by, for example, changing the glycol used or altering the water content, provides further selectability of the duration of persistence of the generated smoke screen.

Landscapes

• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Burglar Alarm Systems (AREA)
• Crystals, And After-Treatments Of Crystals (AREA)
• Devices For Checking Fares Or Tickets At Control Points (AREA)
• Fire-Detection Mechanisms (AREA)

Priority Applications (3)

Applications Claiming Priority (4)

Publications (1)

Family

ID=26301614

Family Applications (1)

Country Status (7)

Cited By (7)

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Citations (2)

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• 1993
  • 1993-09-13 WO PCT/GB1993/001935 patent/WO1994007223A1/en active IP Right Grant
  • 1993-09-13 DE DE69306406T patent/DE69306406T2/de not_active Expired - Lifetime
  • 1993-09-13 GB GB9318924A patent/GB2270396B/en not_active Expired - Lifetime
  • 1993-09-13 DK DK93919531.9T patent/DK0659293T3/da active
  • 1993-09-13 EP EP93919531A patent/EP0659293B1/de not_active Expired - Lifetime
  • 1993-09-13 AT AT93919531T patent/ATE146002T1/de not_active IP Right Cessation
  • 1993-09-13 AU AU49792/93A patent/AU4979293A/en not_active Abandoned

Patent Citations (2)

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