The present invention generally relates to smoke alarms. More specifically, the present invention relates to a smoke alarm that includes both an ionization smoke detector and a photoelectric smoke detector and includes a dual power source having both an AC power supply and a DC power supply.
Currently, two types of smoke alarms are available on the market. The first type of smoke alarm incorporates photoelectric smoke-sensing technology in which light from an emitter source, such as an infrared light-emitting diode (LED), is directed away from a light-detecting device. When smoke is present within the photo-detecting chamber, the emitted light contacts the smoke particles and is reflected and detected by the photo detector. When enough light is reflected by smoke particles, the signal generated by the photo detector activates an audible alarm.
A second type of currently available smoke alarm utilizes ionization smoke-sensing technology. A smoke alarm incorporating an ionization detector includes an ionization chamber that encloses a pair of electrodes having a voltage generated thereacross. When a fire is present near the smoke alarm, the combustion products enter the ionization chamber and the voltage across the pair of electrodes is altered. The altered voltage across the electrodes is provided to a control circuit that activates an audible alarm to indicate a smoke or fire condition.
Although photoelectric smoke alarms and ionization smoke alarms are both commercially available, each type of alarm has unique operating characteristics that makes each type of alarm better at detecting a different type of fire or smoke condition. As is commonly known, a photoelectric smoke alarm is generally more effective at detecting a slow, smoldering fire that smolders for hours before bursting into flames. In a smoldering fire, a great deal of smoke is created but very little flame is present. Smoldering fires may be caused by cigarettes burning in couches or bedding. Although a smoldering fire can and often will progress into a flaming fire, it is desirable that the occupants be alerted to the existence of the smoldering fire as soon as possible. Photoelectric smoke alarms are best at detecting this type of fire.
An ionization smoke detector is generally more effective at detecting fast, flaming fires which consume combustible materials rapidly and spread quickly. Sources of these types of fires may include paper burning in a waste container or a grease fire in the kitchen. Again, it is desirable to alert a home occupant to the existence of this type of fire as soon as possible, and an ionization detector is most effective in this regard.
Since the mid-1980s, a dual sensing smoke alarm that includes both an ionization detection system and photoelectric detection system has been known and commercially available In 1997, the Maple Chase Company of Downers Grove, Ill., introduced the Firex Model CCPB with dual ionization and photoelectricsensing technology. In each of the commercial dual-sensing smoke alarms mentioned above, the power supply is a 9-volt battery. Additionally, U.S. Pat. Nos. 4,316,184 and 5,633,501 disclose a smoke alarm that includes both photoelectric and ionization smoke detectors.
Smoke alarms that include either an ionization smoke detector or a photoelectric smoke detector are also available that utilize two power sources; an AC main power source and a DC battery back-up. The dual power sources allow the smoke alarm to operate from AC power during normal conditions. However, if AC power is lost, such as while the residents of the home are sleeping, the DC battery back-up will allow the smoke alarm to remain active and generate an alarm during smoke conditions.
Many current local fire protection codes requires that new home constructions include interconnected smoke alarms within a house so that the sensing of smoke by one alarm is transmitted to all the interconnected alarms. Each of these interconnected smoke alarms are powered by an AC power source and interconnected by wiring within the home.
Although individual battery-powered smoke alarms having both ionization and photoelectric-sensing systems and individual smoke alarms having one type of detection system and dual power sources are both currently available, a need exists for a single smoke alarm that includes both photoelectric and ionization smokesensing technology and a dual AC and DC power supply system. Therefore, it is an object of the present invention to provide a smoke alarm that includes both ionization and photoelectric smoke-sensing technology as well as dual power supply connections to both AC and DC power. Further, it is an object of the present invention to provide a smoke alarm that interconnects the photoelectric and ionization detection systems such that a single button can be depressed to test both the ionization and photoelectric-sensing systems. Further, it is an object of the present invention to provide a smoke alarm that interconnects the ionization and photoelectric smokedetecting systems such that either system generates an alarm condition upon smoke detection.
The present invention is a smoke alarm that includes two different distinct types of smoke detectors and two distinct power supply connections. The smoke alarm of the present invention generates an alarm when either one or both of the two distinct smoke sensing detectors signal a potential fire condition.
The smoke alarm of the present invention includes a photoelectric detector having a detector chamber and a photo control circuit. When the detector chamber of the photoelectric detector senses a potential fire, the photo control circuit of the photoelectric detector generates an alarm signal. The photoelectric detector of the smoke alarm is particularly effective at detecting a slow, smoldering fire.
The smoke alarm of the present invention also includes an ionization detector. The ionization detector includes a detector chamber and an ionization control circuit connected to the detector chamber. When smoke particles are received within the detector chamber, the detector chamber signals the ionization control circuit to generate an alarm signal indicating a detected fire. The ionization detector is particularly effective at quickly detecting fast, flaming fires.
The smoke alarm of the present invention further includes an audible alarm that is activated upon generation of an alarm signal from either the ionization detector or the photoelectric detector. Thus, the single audible alarm can be activated by detection of a fire by either the photoelectric detector or the ionization detector.
In the first embodiment of the invention, the photoelectric detector acts as the xe2x80x9cslavexe2x80x9d in a master-slave relationship with the ionization detector. When the photoelectric detector senses a potential fire, the photoelectric detector provides an alarm signal to the ionization detector signaling the sensed fire. Upon receipt of the alarm signal from the photoelectric detector, the ionization detector activates the audible alarm coupled to the ionization control circuit of the ionization detector. In addition to activating the audible alarm upon receiving the alarm signal from the photoelectric detector, the ionization control circuit activates the audible alarm when the ionization detector senses a potential fire.
In a second embodiment of the invention, the ionization detector acts as the xe2x80x9cslavexe2x80x9d in a master-slave relationship with the photoelectric detector. In the second embodiment of the invention, when the ionization detector senses a potential fire, the ionization detector generates an alarm signal that is received by the control circuit of the photoelectric detector. Upon receiving the alarm signal from the ionization detector, the photoelectric detector activates the audible alarm to signal a potential fire. In addition to activating the audible alarm upon receipt of the alarm signal from the ionization detector, the control circuit of the photoelectric detector activates the audible alarm when the photoelectric detector itself senses a potential fire condition.
In both the first and second embodiments of the invention, a multiple station interconnect is included in the smoke alarm. The multiple station interconnect allows multiple smoke alarms to be connected within a household such that when any of the joined alarms senses a fire condition, the sensed fire condition activates each of the joined alarms.
The smoke alarm of the present invention further includes a power supply circuit that is connected to both the photoelectric detector and the ionization detector. The power supply circuit of the present invention includes both an AC power supply and a DC power supply. Preferably, the DC power supply is a conventional 9 volt battery.
The power supply circuit is configured such that whenever the AC power supply is available and operating properly, the AC power supply provides the electric power to operate both the ionization detector and the photoelectric detector.
The power supply circuit is constructed such that if AC power is interrupted or removed from the power supply circuit, the power supply circuit automatically switches to the DC power supplied by the battery. In this manner, the photoelectric detector and the ionization detector are supplied with power even when the AC power supply is interrupted.
The smoke alarm of the present invention thus includes two distinct types of smoke detectors and a dual power supply in a single, integrated unit. The two types of smoke sensing technologies allow the single smoke alarm of the present invention to more quickly respond to different types of smoke conditions. The dual power supply connections allow the single smoke alarm to operate properly when AC power is present or if the AC power supply is interrupted.
Various other features, objects and advantages of the invention will be made apparent from the following description taken together with the drawings.