Communications: electrical – Condition responsive indicating system – Specific condition
Patent
1994-10-07
1996-06-11
Swann, Glen
Communications: electrical
Condition responsive indicating system
Specific condition
49 31, 292 92, 340531, 340636, G08B 2300
Patent
active
055259634
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to apparatus for actuating a safety device, and more particularly for actuating a door release arrangement on a device for holding open doors such as fire doors in the event of a fire alarm being raised. Such a holding device is referred to herein as a "door holder". The invention also relates to apparatus for releasing or closing a closure (such as a door).
2. Related Art
Door holders are available in several forms. A simple hook and eye is most popular, with other devices using friction between the floor and a rubbing surface. There are magnetic types available which consist of two parts with attracting polarities, one being fixed to the door and the other to an adjacent surface.
Some such magnetic types are electromagnetic with the supply current being connected via an appropriate fire alarm system. The door release arrangement is hard-wired into the system in such a way that it acts to cut the electric supply to the electromagnet on activation of the fire alarm. Hence the door is allowed to close and thus form part of a safety fire break.
Electromagnetic door holders including such a door release arrangement are, however, expensive and complicated to fit, especially retrospectively. Consequently many fire doors are permanently held open with any suitable object that may be to hand. This is often, ironically, a fire extinguisher.
It is known from U.S. Pat. No. 4,520,503 to provide a tone discrimination circuit for use with audible smoke or fire detectors or similar audible devices, which automatically emits an output electronic alarm signal, for notification of persons at remote locations, upon input of a proper audio tone from the smoke detector or other audible device. The circuit contains in series a microphone, a two stage audio amplifier, a frequency detector, and a tone discrimination circuit. The circuit emits an output electronic alarm signal if and only if the audio input signal has sufficient amplitude, the desired frequency, and the desired duration.
SUMMARY OF THE INVENTION
According to the present invention, there is provided apparatus for retaining and releasing a closure, comprising retaining means actuable between a retaining state in which it can retain the closure open and a release state in which it ceases to retain the closure and hence releases it, a sensor for sensing from the ambient medium an alarm signal transmitted into the ambient medium, and means coupled to the sensor for actuating the retaining means to release the closure in response to the alarm signal.
According to a closely related aspect of the present invention, there is provided valve apparatus comprising a valve, a sensor for sensing from the ambient medium an alarm signal transmitted into the ambient medium, and actuating means coupled to the sensor for closing the valve in response to the alarm signal.
According to a preferred aspect of the present invention, there is provided apparatus for actuating a safety device, comprising an acoustic sensor and means coupled to the sensor for actuating the safety device in response to sound of a predetermined character.
Thus, in the case of a fire alarm system, for example, by actuating the safety device in response to sound of a predetermined character (typically the sound of fire alarm), a hard-wired link with the fire alarm system can be avoided. Hence the apparatus can be relatively cheap to instal and relatively easily fitted to react to existing fire alarm systems.
Preferably, the actuating means is adapted to actuate the safety device only in response to sound in one or more predetermined, preferably audible, frequency ranges, of a predetermined continuous duration and above a predetermined intensity threshold. If the above characteristics are carefully chosen, the apparatus can be highly discriminatory against sounds (even loud sounds) which do not emanate from fire alarms, and highly selective of sounds which do emanate from such alarms.
The invention extends to the aforesaid apparatus
REFERENCES:
patent: 3207273 (1965-09-01), Jurin
patent: 3988891 (1976-11-01), Hoyler
patent: 4011716 (1977-03-01), Smith
patent: 4198938 (1980-04-01), Harada
patent: 4344144 (1982-08-01), Damico et al.
patent: 4520503 (1985-05-01), Kirst et al.
patent: 5001466 (1991-03-01), Orlinsky et al.
patent: 5012223 (1991-04-01), Griebell et al.
patent: 5072973 (1991-12-01), Gudgel et al.
Front page of the British Standard on the subject, entitled "Electrically Operated Gas Shut-Offi Valves" dated Aug. 1981.
Page from a product brochure of IMI Webber Limited of City Business Park, Easton Road, Bristol BS5 0SP, UK, May 1979.
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