FIRE DETECTOR EQUIPPED WITH SENSOR

Abstract: This invention relates to a fire detector equipped with a sensor which detects physical quantity of heat, light or smoke and which, in particular, stores time when the fire detector has operated and output of the sensor at this time and indicates these stored data whenever necessary.

Description: This invention relates to a fire detector equipped with a sensor according to the introductory part of the claim 1. Such fire detectors are used in automatic alarm systems for detecting fire at an early stage, in order to be able to initiate appropriate defense measures. They comprise usually sensor means for detecting a quantity of heat, light or smoke and producing an electrical signal having a characteristic indicative of a monitored condition, threshold detection means for comparing said electrical signal with a predetermined level and generating an alarm when a predetermined basic value is exceeded, and converter means for transmitting the alarm signal to an external signal center. The conventional fire detectors of this kind continuously supervise changes in the output levels of the sensor means and operate when a predetermined basic level is exceeded. Therefore, even though one can know by operation of the fire detector that the output level has exceeded the basic level it is not possible to know later the actual output level at that time or the operating time of the detector. Therefore, it has been impossible to clear up the cause of the false alarm if produced by the fire detector. From the US-A-3,665,399 to M. Zehr et al. is known a system for sequentially monitoring and displaying the instantaneous value of a plurality of parameters associated with a motor driven device such as a multi-stage compressor. Further, from Siemens-Energietechnik 4 (1982) No. 2 (K. Abrahmsen et al.), is known a system for monitoring and documentazing power plants and distant heatings by means of processor computers and colour television monitors. Finally, from US-A-3,623,087 to H. Gallichotte et al. is known an alarm-monitoring system including a central station having a plurality of fire alarm indicating and control panels. All of the mentioned prior art references have the drawback that the monitoring means are provided in a central station and do not allow to identify the special detector which has indicated an alarm stage or caused a false alarm. Therefore, with the foregoing in mind, it is a primary object of the invention to provide a new and improved construction of a fire detector equipped with a sensor means which detects a quantity of heat, light or smoke and with means to store the time and output level of the sensor when the fire detector operated and to indicate the stored time and output level at any time. A further significant object of the invention is to provide a new and improved construction of a fire detector which comprises means to indicate a present time or a present output level of the sensor means. In order to implement these and other objects of the invention, which will become more readily apparent as the description proceeds, the fire detector of the present invention is characterized by means to store the time when the fire detector has operated and the output level of the sensor at that time and means to indicate the stored time and the output level at any time. The invention is explained in more detail on the basis of the exemplary embodiments shown in the drawings which illustrate the following: Fig. 1 shows a block diagram of the embodiment according to this invention and Fig. 2 is a flow chart to illustrate the operation of the central processing unit CPU. Shown in Figure 1 are as follows: a sensor 1 which detects a quantity of heat, light or smoke. an amplifier 2 which amplifies output of the sensor 1. an A - D converter 3 which converts an analogue signal showing an output level of the sensor 1 to a digital signal. a clock part 4. a first indicating part 5 which indicates a present time or a present output level of the sensor 1 whenever necessary. a second indicating part 6 which indicates the time when the fire detector operated and an output level of the sensor 1 at that time. a memory 7 (hereafter referred to as ROM) which stores a predetermined basic level as a basis to determine whether the output level of the sensor 1 should be taken as fire. a memory 8 (hereafter referred to as RAM) which stores the time when the fire detector operated and an output level of the sensor 1 at that time. These parts 1 through 8 are connected to a central processing unit 9 (hereafter referred to as CPU) for their centralized control. Connected further to the CPU9 are an operating means comprising a power supply E, switches SW₁ ∼ SW₄ and resistors R₁ ∼ R₄, input terminals IN₁ ∼ IN₄ to which external apparatus corresponding to the individual switches SW₁ ∼ SW₄ are connected, and output terminals OUT₁ ∼ OUT₄ to which external apparatus corresponding to the indicating parts 5 and 6 are connected. The switch SW₁, resistor R₁ and input terminal IN₁ are provided to clear the RAM8 by operation of the switch or external apparatus. The switch SW₂, resistor R₂ and input terminal IN₂, the switch SW₃, resistor R₃ and input terminal IN₃, and the switch SW₄, resistor R₄ and input terminal IN₄ are provided to switch the indication of the first indicating part 5 from the time to the output level of the sensor 1 by operation of the respective switch or external apparatus, and to cause the second indicating part 6 to indicate the time when the fire detector operated and the output level of the sensor 1 at that time. The output terminals OUT₁ ∼ OUT₄ are used for transmitting the time and output level signal to the external apparatus corresponding to the first indicating part 5 and second indicating part 6. Operation of the embodiment is described below with reference to the flow chart of the CPU9 shown in Figure 2. The output of the sensor 1 is always amplified by the amplifier 2, and the analogue signal indicating the output level is converted to a digital signal by the A - D converter 3, which is then sent to the CPU9. A signal from the clock part 4 indicating the present time, too, is sent to the CPU9. The ROM7 stores the basic level for comparison with the output level of the sensor 1. As the CPU9 starts operating (step 1), the RAM8 in which past data have been stored is cleared (step 3) if the switch SW₁ for clearing the RAM8 is set in the ON position (step 2). In case the switch SW₁ is set in the OFF position (step 2), it is judged that there is no need of clearing the RAM8, and with the signals from the clock part 4 and A - D converter 3 the present time and output level of the sensor 1 are read in (steps 4 and 5) respectively. Then, a discrimination is made as to whether the switch SW₂ used for indicating the output level of the sensor 1 on the first indicating part 5 is set in the ON position (step 6). Nevertheless, since the switch SW₂ is normally set in the OFF position, the first indicating part 5 indicates the present time (step 7). And the output level of the sensor 1 which has been read in at the above step 5 is compared with the basic level stored in the ROM7 (step 9). However, as the output level of the sensor 1 does not reach the basic level before a fire breaks out, a discrimination is made as to whether the second indicating part 6 is giving the past indication (indication given at the time of the previous operation) (step 10). If yes, the second indicating part 6 is cleared (step 11). In both cases a discrimination is made as to whether the switches SW₃ and SW₄ which cause the second indicating part 6 to indicate the operating time and the output level of the sensor 1 at that time are set in the ON position (step 12). Nevertheless, as the switches SW₃ and SW₄ are normally set in the OFF position, the operation goes back to the above step 2 and repeatedly follows the above steps. Now, if the output level exceeds the basic level (step 9), the fire detector produces a fire alarm (step 13), which is transmitted to a control panel which is not shown in the figure. And the time and the output level of the sensor 1 at this time is written in and stored in the RAM8 (step 14), and the operations after the step 2 are repeated. By switching on the switch SW₂ for output level indication (step 6) it is possible to cause the first indicating part 5 to indicate the present output in place of the indicated time (step 8) so that changes in output level of the sensor 1 may be checked whenever necessary. If it is desirous to know the operating time of the fire detector and the output level of the sensor 1 at that time later, the switches SW₃ and SW₄ should be set in the ON position (step 12). Then, the operating time stored in the RAM8 is read out (step 15) and indicated on the second indicating part 6 (step 16). Furthermore the output level of the sensor 1 at the above operating time is read out (step 17) and indicated on the second indicating part 6 together with the above operating time (step 18). The above has described the operating procedure by means of the switches SW₁ ∼ SW₄. It is also possible to remotely cause the above operation to be performed by operating external apparatus which constitute operating means and are connected to the input terminals IN₁ ∼ IN₄. Furthermore it is possible to connect external apparatus which constitute indicating means to the output terminals OUT₁ ∼ OUT₄ so that the above mentioned various indications may be given on these indicating means together with or in place of the indications given by the first and second indication means. Although the first indicating part 5 is so devised that time alone is indicated at all times and the output level can be indicated whenever necessary by operation of the switch SW₂, other indicating methods may also be adopted, e.g. simultaneous indication of both time and the output level, a choise of which should be made properly. As can be seen from the above description the fire detector according to this invention is equipped with a sensor which detects a quantity of heat, light or smoke, and means to store the time and output level of the sensor when the fire detector operated and to indicate the stored time and output level at any time. Therefore it is possible to confirm the time when the fire detector operated and the above mentioned physical quantity at that time whenever necessity arises later. This feature is particularly advantageous in case the fire detector falsely operated, and makes possible to clear up the cause. As described above, this invention offers a fire detector having such advantages that have never been realized in the conventional detectors.

Claims: A fire detector comprising: sensor means (1) for detecting a quantity of heat, light or smoke and producing an electrical signal having a characteristic indicative of a monitored condition, threshold detection means (7, 9) for comparing said electrical signal with a predetermined level and generating an alarm when a predetermined basic value is exceeded, converter means for transmitting the alarm signal to an external signal center, characterized in that the detector further comprises means (8) to store the time when the fire detector has operated and the output level of the sensor at that time and means (6) to indicate the stored time and the output level at any time. A fire detector according to claim 1, characterized in that it additionally comprises means (5) to indicate a present time or a present output level of the sensor means (1).

Inventors: OKAYAMA, YOSHIAKI C/O NOHMI BOSAI KOGYO CO., LTD.
Applicants: NOHMI BOSAI KOGYO CO., LTD.
Application year: 1984
Main classification: G08B17
IPC codes: G08B17