Communications: electrical – Condition responsive indicating system – Specific condition
Patent
1998-09-29
2000-06-27
Wu, Daniel J.
Communications: electrical
Condition responsive indicating system
Specific condition
340628, 320114, 320145, 320164, 320 48, 320 75, G08B 2100
Patent
active
060811978
DESCRIPTION:
BRIEF SUMMARY
This invention relates to smoke and heat alarms as used in buildings to warn of a fire condition, and to methods of monitoring the energy levels of the batteries of these devices to provide a silenceable low battery pre-alarm warning in addition to the low battery warning emitted by smoke and heat alarms.
As used herein, the expression "low battery warning" or "low battery alarm" is to be taken as meaning the warning, visual and/or audible, emitted by a smoke or heat alarm when the battery of the alarm device has reached or exceeded the level of depletion at which the manufacturer recommends that the battery be replaced.
Similarly, as used herein, the expression "low battery pre-alarm" or "low battery pre-alarm warning" is to be taken as meaning the warning, visual and/or audible, emitted by a smoke or heat alarm when the battery of the alarm device has depleted to a level which is close to that required to generate a low battery warning.
It is also to be understood that during the battery discharge process, the energy level of the battery reaches that required to generate the low battery pre-alarm warning first. If the battery is allowed to discharge further after the low battery pre-alarm energy level has been reached, a lower battery energy level is reached at and beyond which the low battery alarm is emitted.
BACKGROUND
Smoke and heat alarms are extensively used in domestic dwellings, motels, hotels, hospitals, old people's homes, and in general commercial premises. Most of these devices incorporate internal batteries and are generally are of two main types, namely: batteries and by an external primary power supply with internal batteries as the standby power source.
It is a characteristic of the above mentioned two types of smoke and heat alarms that at regular intervals, normally not exceeding 60 seconds, the alarm device enters into a self-test mode when a current which is much higher than the quiescent current is briefly drawn from the smoke or heat alarm battery. The electronic circuitry of the alarm device then detects whether the battery voltage in self-test mode is above a certain threshold value. If the battery voltage is detected to be below the low battery voltage threshold value, normally around seven and a half volts, the alarm device activates an internal circuit to produce an audible warning indicating a low or depleted battery requiring replacement. For safety reasons, currently manufactured smoke or heat alarms do not have provisions for the low battery warning to be silenced.
Although the low battery warning is an important safety feature of the smoke and heat alarms described above, as the warning cannot be silenced, a situation very often arises where the low battery audible warning causes major difficulties/disadvantages as exemplified below: heat alarm starts emitting the low battery warning, occupants of the protected premises have to endure the inconvenience of the audible warning until such time as they procure themselves of a new battery and carry out the battery replacement. The audible warning is particularly inconvenient if the alarm device is installed in a bedroom and starts to emit the low battery audible warning signal in the middle of the night with the result that the occupants of the bedroom, or any other bedroom in the area, cannot go back to sleep. drastic unsafe practices in order to eliminate the inconvenience of the low battery warning until such time as a replacement battery is available. These unsafe practices are: supply smoke and heat alarms, and sources of dual supply smoke and heat alarms.
Both the above practices may result in potentially dangerous situations where the fire detection and warning functions of the alarm devices are lost.
It is the object of the present invention to provide a new facility to smoke and heat alarms which overcomes the above difficulties/disadvantages without affecting the functionality and the operation of these alarm devices, including the operation of the low battery warning function currently available.
According to the
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Garrick Gilbert Alain Lindsay
Garrick Marie Jeanette Corinne
Nguyen Tai T.
Phillips Delbert R.
Sonntag James L.
Wu Daniel J.
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