Fire detector

Abstract: A fire detector (12) installed in a low ceiling (10) of a vehicle such as an aircraft or train is equipped with an anti-tampering countermeasure (24) for preventing tampering by covering the exposed portion (14a) of the fire detector with a paper cup or a vinyl bag or by sticking chewing gum or tissue paper in the smoke inlets (14b) thereof which is usually carried out by passengers trying to sneak a smoke in a non-smoking area. The fire detector (12) comprises a main body (14) having a head portin (14a) for letting in a fire phenomenon such as smoke and a fire detection portion for performing fire detection on the basis of the fire phenomenon let in from the head portion, and a mounting portion (16) containing most of the main body (14) and provided with a central opening (16c) for allowing the head portion (14a) to protrude from the ceiling surface (10). The anti-tampering means may comprise a plurality of fins (24) around said central opening portion (16c) of the mounting portion (16), each fin (24) having a high portion (24a) with a height approximately equal to or higher than that of the protruding head portion (14a), and a spreading portion (24b) that gradually decreases in height with distance away from said main body (14).

Description: Technical Field of the Invention The present invention relates to a fire detector to be installed in a ceiling surface and comprising a main body having a fire detection portion for performing fire detection on the basis of a fire phenomenon, a head portion having inlet means for letting in a fire phenomenon to be detected to said detection portion, and a mounting portion for receiving most of said main body above the ceiling surface and provided with a central opening portion for allowing said head portion to be exposed downward from the ceiling, according to the introductive portion of claim 1. Fire detectors of this kind are known from US-A-4 238 679 and are used for detecting the outbreak of a fire in vehicles such as an aircraft or a train, especially in passenger compartments, toilets or lavatories of such vehicles, the height of the ceiling of which from the floor is rather small. Accordingly, fire detectors in such vehicles are generally installed in the ceiling surface such that most of the mostly cylindrical or rectangular body of the fire detctor is put into a portion above the ceiling surface, and only those portions being essential for receiving a fire phenomenon such as a smoke or combustion aerosol inlet are exposed downward or protude a little towards the inside of the vehicle compartment. Description of the Prior Art The drawbacks and problems of such fire detectors are described hereinafter with reference to Fig. 1 to 4. Fig. 1 and 2 show a conventional fire detector 12 corresponding to smoke detectors currently installed in the ceiling surface of vehicles such as aircrafts. The fire detector 12 includes a main body 14 having an ionization chamber type fire detection portion with a structure disclosed in US-A-4 238 679, 4 740 703 or 4 853 544 for example, or an optical smoke detection portion, or the like, and a mounting portion 16 for mounting this main body 14 in the ceiling surface 10 of a vehicle compartment. The mounting portion 16 comprises a receiving portion 16a receiving most of the main body 14, and a surface portion 16b facing the interior of the compartment, with the main body 14 being fixed to the bottom of the receiving portion 16a by srews 18. The lower part of the main body 14, i.e. a head portion 14a, protudes from a central opening portion 16c of the surface portion 16b downwards to the compartment interior side whereby inlet portions 14b of the main body 14 can draw in smoke or combustion aerosol, etc., generated by a fire, from the compartment in order to perform fire detection. The inlet portions 14b are provided at both side faces of the head portion 14a as shown in Fig. 1, and on the surface thereof as shown in Fig. 2, as example, so that both sets of inlet portions 14b can let in smoke. The head portion 14a is shown in the form of a regular square in a plane view shown in Fig. 2, the length of the sides of the square being 39 mm, e.g., with the length of the diagonal line thereof being about 55 mm. But different shapes may be used, e.g. a circular form of the head portion with inlets directed radially outwardly. The mounting portion 16 itself is fixed to the ceiling surface 10 by screws 20, and the main body 14 has a cable 22 connected thereto including a power supply line for transmitting a fire alarm signal from the main body 14 to a fire control panel, etc., not shown in the drawings. In non-smoking areas or compartments of a vehicle such as an aircraft, smoking is forbidden, e.g. for security reasons. Since a fire detector installed in a vehicle would detect any cigarette smoke, etc., in the same way as a real fire, there have been frequent attempts of tampering the fire detectors installed in the rather low ceilings of the compartments of such vehicles which can be easily reached by the passengers. This can be done, as shown in Fig. 1 and 2, by covering the exposed portion of the detector body inside of the compartment by a cover such as a paper or polyethylene cup, etc., sticking chewing gum or tissue paper on the smoke inlet portions, or covering the portion of the main body exposed to the interior of the compartment with a vinyl bag. If such tampering is performed by users trying to sneak a smoke, the normal smoke detecting faculty of a fire detector, e.g. of the ionization type or of the photoelectric type, e.g. of the light scattering type, will be ruined, which can lead to serious problems when a real fire occurs which can no longer be detected during the flight or movement of the vehicle. Actually, many of the disturbances to a fire detector's faculty arise from being covered with a paper cup. Coincidentally, in some small-mouthed paper cups, for example, the inside diameter of their mouth edge is approximately coincident with the lenghth of the head portion 14a of the main body 14 of the fire detector, as shown by dotted line L1 in Fig. 2. Such small- mouthed paper cups can completely cover the head portion 14a of the fire detector as shown by a dotted line C in Fig. 1. If a smoker has smoked while keeping such a small-mouthed paper cup C on the head portion 14a of a fire detector and has forgotten to remove the paper cup from its position, the fire detector cannot detect a fire phenomenon, which can lead to a disaster when a fire occurs during flying, running, etc. Fig. 3 and 4 show another conventional fire detector 112 such as a smoke detector installed in a ceiling surface 10 of a vehicle. This detector differs from the detector shown in Fig. 1 and 2 in that a stepped portion 116d is provided around a central opening portion 116c of a surface portion 116b of a mounting portion 116 surrounding a head portion 114a of a main body 114 to enhance the inflow of smoke. As the other elements in Fig. 3 and 4 are similar to the ones shown in Fig. 1 and 2, they are indicated by similar numerals, but increased by 100. Also in such a fire detector 112, a problem occurs in that small-mouthed paper cups can be inserted entirely into the step portion 116d as shown by dotted line L13 in Fig. 4 when the mouth edge of the paper cup is deformed to the form of a regular square. Summary of the Invention In light of the above, it is an object of the present invention to eliminate the drawbacks of the prior art described above and to obtain a fire detector which is safe from tampering by covering the fire detector with a paper cup or vinyl bag and to provide countermeasures against disturbances to the fire detection faculty. The countermeasures according to the present invention take into account: a) preventing the coverage of the head portion of the fire detctor with small-mouthed paper cups, b) taking into consideration normal type large-mouthed paper cups, having an inside diameter as shown by dotted line L2 in Fig. 2, when devising a counterplan against small-mouthed type paper cups, c) making it difficult to stick chewing gum or tissue paper, etc., into the smoke inlet portions of the fire detector head portion, and d) preventing small-mouthed paper cups from being inserted into a step portion of the mounting portion. The above problems are eliminated, according to the present invention, by the characteristic portion of claim 1. A fire detector of the above-indicated type is equipped with anti-tampering countermeasures comprising blocking means around said central opening portion of said mounting portion for preventing a cover to be mounted on said head portion, said blocking means having a height approximately equal to or higher than that of the head portion protruding from said central opening portion, the height of the blocking means decreasing with the distance away from the head portion. Especially, in the fire detector according to the present invention, said blocking means includes a plurality of fins or the like provided around said central opening portion of said mounting portion, said fins being directed outward from said central opening, and comprising a high portion near said head portion and a spreading portion gradually decreasing in height in a direction away from said head portion. Brief Description of the Drawings Embodiments of the invention will now be described with reference to the accompanying drawings wherin: Fig. 1 is a vertical sectional view of a prior art fire detector installed in a vehicle, Fig. 2 is a bottom plane view of the detector of Fig.1, Fig. 3 is a vertical sectional view of another prior art fire detector installed in a vehicle, Fig. 4 is a bottom plane view of the detector of Fig.3, Fig. 5 is a vertical sectional view of a fire detector according to a first embodiment of the invention similar to the fire detector shown in Fig. 1 and 2, but equipped with countermeasure means against tampering, Fig. 6 is a bottom plane view of the detector of Fig.5, Fig. 7 is a vertical sectional view of a fire detector according to a second embodiment of the invention similar to the fire detector shown in Fig. 3 and 4, but equipped with countermeasure means against tampering, Fig. 8 is a bottom plane view of the detector of Fig.7, Fig. 9 is a vertical sectional view of a fire detector according to a further embodiment of the invention similar to the embodiment shown in Fig. 5 and 6, but equipped with different countermeasure means, Fig.10 is a bottom plane view of the detector of Fig.9, Fig. 11 is a view showing in more detail the countermeasure means shown in Fig. 9 and 10, Fig. 12 is a view showing another embodiment of countermeasure means, Fig. 13 is a bottom plane view of a fire detector equipped with countermeasure means shown in Fig. 12, Fig. 14 is a vertical sectional view of a fire detector according to a yet further embodiment of the invention similar to the fire detector shown in Fig. 3 and 4, but equipped with further countermeasure means, and Fig. 15 is a bottom plane view of the fire detector shown in Fig. 14. Description of Preferred Embodiments Fig. 5 and 6 show a fire detector according to the present invention which is similar to the fire detector described above with reference to Fig. 1 and 2. Therefore, in Fig. 5 and 6 the same numerals are used for corresponding parts shown in Fig. 1 and 2. But aditionally, the fire detector shown in Fig. 5 and 6 is equipped with countermeasure means against tampering. To this end, the surface portion 16b of the mounting portion 16 of the fire detector 12 is provided with a fin arrangement 24 formed integrally thereto. The fin arrangement 24 has a structure such that a portion of the fin arrangement 24 overlies the head portion 14a of the main body 14 as shown in Fig. 6 when the surface portion 16b of the mounting portion 16 is attached to the mounting portion 16 after the main body 14 is mounted into the containing portion 16a of the mounting potion 16. As seen from Fig. 5, each of the fins forming the fin arrangement 24 includes a portion 24a somewhat higher than and overlying the head portion 14a, and an outwardly spreading portion 24b gradually decreasing in height from the overlying portion 24a. The existance of the overlying portions 24a makes it impossible to put small-mouthed type paper cups having a predetermined size over the head portion 14a, while the spreaded portions 24b extend long enough beyond the mouth edge of large-mouthed paper cups having another predetermined size to make it impossible to put them on the ends of the spreading portions 24b remote from the head portion 14a. Also, the constitution shown in Fig. 5 and 6 makes it very difficult to stick chewing gum, tissue paper, vinyl bags, etc., on the inlet portions 14b because the fin arrangement 24 prevents this. Also, for conventional fire detectors that have already been installed, the present invention can be easily applied by merely replacing the surface portion of the mounting portion 16 by a surface portion 16b to which the fin arrangement 24 is integrally formed. Although, in Fig. 5 and 6, the spreading portions 24b were described as extending far enough beyond the mouth edge of normal type paper cups, conversely, the far ends of the spreading portins 24b may also be inside the mouth edge of such cups so that they cannot be fitted on the spreading portions 24b. But, the far ends of the spreading portions 24b should not coincide with the mouth edge of normal paper cups so that engagement between the far ends of the spreading portions 24b and the mouth edge of such paper cups is prevented. The countermeasures considered for the fire detector 112 shown in Fig. 3 and 4 is shown in Fig. 7 and 8, in which the same numerals are used for the like parts shown in Fig. 3 and 4. The countermeasure means shown in Fig. 7 and 8 is generally similar to the one shown in Fig. 5 and 6. The surface portion 116b of the mounting portion 116 has a fin arrangement 124 formed integrally thereto. The fin arrangement 124 has a structure such that a portion thereof overlies the head portion 114a of the main body 114 as shown in Fig. 8 when the surface portion 116b of the mounting portion 116 is attached to the mounting portion 116 after the main body 114 is mounted to the receiving portion 116a of the mounting portion 116. Similar to the case of Fig. 5, as seen from Fig. 8, the fin arrangement 124 includes a portion 124a higher than the head portion 114a that overlies the head portion 114a, and spreading portions 124b gradually decreasing in height from the overlying portion 124a higher than the head portion 114a. The existence of the overlying portion 124a makes it impossible to mount a small-mouthed type paper cup on the head portion 114a, while the spreading portions extend long enough beyond the mouth edge of normal type large-mouthed paper cups to make it impossible to mount such paper cups on the ends of the spreading portions 124b remote from the head portion 114a. Also, the constitution shown in Figures 7 and 8 makes it very difficult to stick chewing gum, tissue paper, vinyl bags, etc., as well as paper cups, on the inlet portions 114b and step portion 116d because the fin arrangement 124 disturbs such mischief. Although the surface portions 16b and 116b of the mounting portions 16 and 116 have fin arrangements 24 and 124, respectively, formed integrally thereto, as described above, it is also possible to attach the fin arrangements 24 or 124, respectively, to the surface portion 16b or 116b at a later date by adhesives or strongly adhesive double coated tapes, etc. Further, as will be explained later on in connection with further embodiments, it is also possible to fixedly attach the fin arrangement 24 or 124 to the surface portion 16b or 116b by providing protrusions on the bottom surface of each of the fins of the fin arrangement. Then, by providing holes on the surface portion of the mounting portion for inserting the protrusions and by providing holding means in each hole for holding the protrusions, the fin arrangement can be attached and prevented from being easily extracted. Still, even though the fin arrangements 24 and 124 provided with the overlying portions 24a and 124a partially overlying the head portions 14a and 114a of the main bodies 14 and 114 have been shown above, such overlying portions 24a and 124a can be omitted. In case the overlying portion 24a or 124a is omitted, the height of the high portion of the fin arrangement 24 or 124, namely the height of each of the fins of the fin arrangement 24 or 124 adjacent to the head portion 14a or 114a may be approximately equal to that of the head portion 14a or 114a protuding from the surface portion 16b or 116b of the mounting portion 16 or 116. Fig. 9 and 10 show a fire detector according to a further embodiment of the invention, adopting another countermeasure for the fire detector shown in Fig. 1 and 2, that differs from the countermeasure explained in Fig. 5 and 6, the same numerals being used for the like parts shown in Figures 1 and 2. The surface portion 16b of the mounting portion 16 of the fire detector 12 has four mounting holes 30 pierced around the central opening portion 16c. Generally triangular or semicircular plate members 26 are mounted as fins into these four mounting holes. A plate member 26 is shown in detail in Fig. 11, in which A is a front view of the plate member 26, and B is a side view seen from the right side of A. The plate member 26 is provided at the bottom surface thereof with a protrusion 26a inserted into one of the mounting holes 30. When the plate member 26 is placed at the right angle to one side adjacent to one of the mounting holes 30 among four sides of the quadrate main body head portion 14a, and the protrusion 26a of the plate member 26 is inserted into the mounting hole 30 of the surface portion 16b of the mounting portions 16, the protrusion 26a engages with the mounting hole 30, thereby fixing the plate member 26 to the surface portion 16b of the mounting portion 16 so that it cannot be easily removed. The shape and the dimensions of the plate member 26 are such that, as shown in Fig. 10, the leading edge portion 26c, i.e. an end portion adjacent to the head portion 14a, of the base of the triangle or semicircle is closely adjacent to or in contact with the head portion 14a and that the vertex or top point 26b of the triangle or semicircle of the plate member 26 would contact with the mouth edge of a small-mouthed type paper cup, as shown by dotted line L1, if someone mischieveous tries to put such a paper cup on the head portion 14a. Further, if one tries to put a large-mouthed paper cup on the head portion 14a, represented in Fig. 10 by a dotted line L2, the trailing edge portion 26d, i.e. an end portion opposite to the leading edga portion 26c, of the plate member 26 is within the dotted line L2 so that the mouth edge of a large-mouthed type paper cup will not engage with the plate members 26. Fig. 12 shows another embodiment of a plate member in which a plate member 28 used as a fin is in the form of a trapezoid. The shape and the dimensions of the plate member 28 are preferably so that, when the plate member 28 is mounted, the mouth edge of a small-mouthed type paper cup will contact with the corner 28c of the trapezoid, as shown by dotted line L1 in Fig. 13, and the mouth edge of a large-mouthed type paper cup will not extend past the upper side of trapezoid, as shown by dotted line L2. Although it is shown that each plate member 26 or 28 is provided respectively with one protrusion 26a or 28a in Figures 11 and 12, it is also possible to prepare a plate member 26 or 28 that is provided with two protrusions and the surface portion 16b of the mounting portion 16 with two mounting holes provided at two positions corresponding to the protrusions of the plate member. In this way, the plate member 26 or 28 can be fixed to the surface portion 16b of the mounting portion 16 at the two positions. As seen from Fig. 9 and 13, a small-mouthed type paper cup cannot be mounted on the head portion 14a of the main body 14 because of the obstruction of the vertex or the top point 26b of the plate member 26 when using the semicircular or triangular plate member 26, and because of the obstruction of the corner 28c of the upper side of the plate member 28 when using the plate member 28 in the form of a trapezoid. On the other hand, a large-mouthed type paper cup can also not be mounted on the head portion 14a because there is no surface such as an edge for the paper cup to be hooked when using the plate member 26, and because the upper side 28b of the plate member 28 blocks the insertion of the cup when using the plate member 28. Further, according to the construction shown in Fig. 9 and 13, the plate member obstructs the placing of tissue paper or vinyl bags, etc., on the inlet portions 14b, so that it is impossible to completely cover those inlet portions 14b. Also, as the fire detectors shown in Fig. 9 and 13 are so configured that mounting of the plate members is performed by inserting them into the mounting holes of the mounting portion, the plate members can also be removed from the mounting portion when they are not needed. Further, the plate members can be easily mounted on the surface portion 16b of the mounting portion 16 of already installed fire detectors by opening the desired number of mounting holes on the surface portion 16b around the central opening portion 16c. Alternatively, the surface portion 16b of the mounting portion 16 may be formed integrally with the plate members 26 and 28. Another countermeasure considered for the fire detector 112 shown in Fig. 3 and 4 differing from the measure explained in Fig. 7 and 8 is shown in Fig. 14 and 15. As mentioned in the explanation of Fig. 7 and 8, the same numerals are used for the like parts shown in Fig. 3 and 4. In the embodiment shown in Fig. 14 and 15, plate members 126 which partially ride on the head portion 114a and which gradually decrease in height therefrom are adhered to the surface portion 116b of the mounting portion 116 by adhesives, etc. The bases of the plate member 126 are provided with protrusions 126a for engagement. On the other side, holes 130 for inserting the protrusions 126a are opened on the surface portion 116b of the mounting portion 116. The plate members 126 are adhered to the surface portion 116b by adhesives after the protrusions 126a of the plate members 126 are engaged with the holes 130. As shown by a dotted line L11 in Fig. 15, the plate maembers 126 obstruct the mounting of small-mouthed type paper cups on the head portion 114a. Also, as the plate members do not extend beyond a dotted line L12 showing the mouth edge of large-mouthed paper cups, it is impossible to engage the mouth edge of large-mouthed type paper cups with the ends of the plate members remote from the head portion 114a so that any tampering can be prevented. Further, the existence of the plate members 126 makes it very difficult to stick chewing gum, tissue paper, vinyls, etc., as well as paper cups in the inlet portions 114b and the stepped portion 116d. Still, the arrangement and structure for each of the fins, or each of the plate members 24, 26, 124, and 126 are devised so that any smoke that rises upwardly and creeps along the ceiling surface can easily flow laterally into the inlet portions 14b and 114b of the fire detectors, namely so that the smoke gathering efficiency can be enhanced, and they are also further devised so that the direct inflow of upwardly rising smoke into the inlet portin 114b is not obstructed. As described above, in accordance with the present invention, in a fire detector comprising a main body having a head portion for letting in a fire phenomenon and a fire detection portion performing fire detection on the basis of the fire phenomenon let in from said head portion, and a mounting portion receiving most of the main body and provided with a a central opening for allowing the head portion to protrude in order to perform fire monitoring, the fire detector further comprises anti-tampering countermeasure means around the central opening portion of the mounting portion for preventing paper cups, etc., from being mounted on the head portion of the fire detector, thereby giving the effect of making it difficult to reach the head portion of the main body to deter any tampering with the head portion. While the embodiments of the present invention, as herein disclosed, constitute preferred forms, it is to be understood that other forms might also be adopted within the scope of the invention, as defined in the appended claims.

Claims: A fire detector (12, 112) to be installed in a ceiling surface (10) and comprising a main body (14, 114) having a fire detection portion for performing fire detection on the basis of a fire phenomenon, a head portion (14a, 114a) having inlet means (14b, 114b) for letting in a fire phenomenon to be detected to said detection portion, and a mounting portion (16, 116) for receiving most of said main body (14, 114) above the ceiling surface (10) and provided with a central opening portion (16c, 116c) for allowing said head portion (14a, 114a) to be exposed downward from the ceiling, characterized in that the fire detector (12, 112) is equipped with anti-tampering countermeasures comprising blocking means (24, 26, 28, 124, 126) around said central opening portion (16c, 116c) of said mounting portion (16, 116) for preventing a cover to be mounted on said head portion (14a, 114a), said blocking means (24, 26, 28, 124, 126) including a plurality of fins or the like (24, 26, 28, 124, 126) provided around said central opening portion (16c, 116c) of said mounting portion (16, 116) and having a height approximately equal to or higher than that of the head portion (14a, 114a) protruding from said central opening portion (16c, 116c), the height at least of the outwardly spreading portions (24b, 26d, 28d, 124b) of the blocking means (24, 26, 28, 124, 126) decreasing with the distance away from the head portion (14a, 114a). A fire detector according to claim 1, characterized in that the head portion (14a, 114a) of said main body (14, 114) has a surface shape generally in the form of a regular square, either diagonal of said regular square being approximately of the same size as the inside diameter (L1) of the mouth edge of flexible cups (C), which could be used to tamper the fire detector. A fire detector according to claim 1 or 2, characterized in that said mounting portion (16, 116) includes a receiving portion (16a, 116a) for receiving most of said main body (14, 114), and a surface portion (16b, 116b) having said central opening portion (16c, 116c). A fire detector according to claim 3, characterized in that said surface portion (116b) is provided with a stepped portion (116d) in the periphery of said central opening portion (116c) to form a space around said main body (114) for letting in the fire phenomenon. A fire detector according to one of claims 1 to 4, characterized in that said fins (24, 26, 28, 124, 126) are directed outward from said central opening (16c, 116c) and comprise a high portion (24a, 28b, 124a) near said head portion (14a, 114a) having a height approximately equal to or greater than that of said head portion of said main body (14, 114) protuding from said surface portion (10), and a spreading portion (24b, 26d, 28d, 124b) gradually decreasing in height in a direction away from said head portion (14a, 114a). A fire detector according to claim 5, characterized in that said spreading portions (24b, 26d, 28d, 124b) of said fins extend from said high portions (24a, 28b, 124a) to ends remote from said main body (14, 114), and have lenghths such that said ends do not coincide with the inside diameter (L2) of the mouth edge of cups (C) which could be used to tamper the fire detector. A fire detector according to one of claims 5 or 6, characterized in that said high portions (24a, 124a) of said fins (24b, 124b, 126) are formed to be higher than the height of said head portion (14a, 114a) of said main body (14, 114) protruding from said surface portion (10) and to partially overlie the upper surface of said head portion (14a, 114a). A fire detector according to one of claims 4 or 5, characterized in that each of said fins is a plate-like member (26, 28) in a triangular, trapezoidal or semi-circular shape with a central top portion (26b, 28b) and downwardly sloping portions (26c, 26d, 28c, 28d) on both sides of said top portion (26b, 28b). A fire detector according to claim 8, characterized in that said fins of said plate-like members (26, 28) are provided in said mounting portion (16, 116) so that the opening edge of a small-mouthed cup having predetermined dimensions contact with said top portions (26b, 28b) to prevent the mounting of such small-mouthed cups on said main body (14, 114). A fire detector according to one of claims 1 to 9, characterized in that said blocking means (24, 26, 28, 124, 126) are formed integrally with said mounting portion (16, 116). A fire detector according to one of claims 1 to 10, characterized in that said mounting portion (16, 116) is provided with a plurality of mounting holes (30, 130) around said central opening portion (16c, 116c) thereof, and said blocking means (26, 28) are removably mounted into said plurality of mounting holes (30, 130).

Inventors: MASANOBU AGATA, MASANOBU, AGATA, MASANOBU, AGATA C/O NOHMI BOSAI LTD.
Applicants: NOHMI BOSAI LTD, NOHMI BOSAI LTD.
Application year: 1992
Main classification: G08B29
IPC codes: G08B17, G08B29