Abstract:
A photoelectric smoke detector is provided which is suitable for being downsized without detection capability deterioration. The present invention relates to a photoelectric smoke detector for detecting presence of smoke by utilizing a light emitting element and a light receiving element whose optical axes intersect with each other. Then the photoelectric smoke detector has: a specialized labyrinth function fulfilling part for playing only a labyrinth function of bringing air flow into an interior space thereof and preventing entry of disturbance light into the interior space; and a smoke detecting part which is provided above the specialized labyrinth function fulfilling part so that an interior space of the smoke detecting part is communicated with the interior space of the specialized labyrinth function fulfilling part, and which has the light emitting element and the light receiving element built therein and has a small hole for extracting air flow that has passed through a detection area near an intersection between the optical axes of the light emitting element and the light receiving element.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application is a National Stage Application filed under 35 U.S.C. 371 and claims the benefit of priority to Patent Cooperation Treaty Application PCT/JP2005/023022, filed Dec. 15, 2005, which claims priority to Japanese Patent Application No. 2005-100590 filed Mar. 31, 2005, both of which full contents are incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   1. Technical Field of the Invention 
   The present invention relates to a photoelectric smoke detector utilizing a light emitting element and a light receiving element. 
   2. Background Arts 
   Photoelectric smoke detectors used to mainly detect smoke associated with fire occurring in indoor space, but in recent years have come to be also used as one means adapted to quickly detect device abnormalities while being installed in a device, such as a semiconductor producing device, a machine tool, a switchboard, an industrial controller, or the like. 
   As described above, although installed in different targets, smoke detectors for use in a device also have the same configuration as that of the smoke detectors for use in indoor space, and many of them have been downsized while keeping this configuration. 
     FIG. 4  show a configuration of a conventional typical photoelectric smoke detector (see Patent Document 1 for example). 
   The conventional photoelectric smoke detector  1  is, for example, as shown in  FIG. 4(A) , installed on the ceiling or the like in such a manner that a chamber part  2  having a plurality of inlet and outlet ports circumferentially provided as smoke introduction and extraction ports are oriented downward so that the smoke travel direction can be disregarded. Inside the chamber part  2 , as shown in  FIG. 4(B) , a light emitting element  3  and a light receiving element  4  are arranged so that optical axes intersect with each other at approximately 120 degrees. Smoke enters into a detection area AR located near the intersection between the optical axes, and light emitted from the light emitting element  3  is scattered by the smoke and reaches the light receiving element  4 , thereby achieving detection of the presence of smoke. To prevent erroneous detection under an absence of smoke, a plurality of labyrinths  5  are arranged circumferentially so as to eliminate disturbance light, also even when light emitted from the light emitting element  3  is reflected, prevent this light from traveling toward the light receiving element  4 , and further avoid preventing the entry of smoke into the detection area. Around the plurality of labyrinths  5 , an insect screen  6  is provided for preventing entry of insects from entering into the interior space. 
   Moreover, there conventionally exists a photoelectric smoke detector, as described in Patent Document 2, which introduces smoke to an optical chamber through only one opening provided at a bottom surface and which detects the presence of smoke through functions of a light emitting element and a light receiving element provided on the left and right side surfaces of the optical chamber. 
   [Patent Document 1] Japanese Patent Laid-Open No. 1996-166347 
   [Patent Document 2] Japanese Patent Laid-Open No. 1992-160698 
   DISCLOSURE OF THE INVENTION 
   Problem to be Solved by the Invention 
   The configuration of the conventional smoke detector shown in  FIG. 4 , due to characteristics of a detection system in which the light emitting element  3 , the light receiving element  4 , and the labyrinth  5  are arranged circumferentially, requires some space including the detection area AR. In other words, it is difficult to achieve downsizing only by simply reducing a diameter of the chamber part  2  while maintaining the conventional configuration. 
   The smoke detector is large in size, which restricts its installation places, thus making it not easy to install the smoke detector at places, such as a place where fire is likely to occur, a place where smoke is likely to pass in the event of fire, and the like. 
   A conventional smoke detector as described in Patent Document 2 has an optical chamber with one opening, which makes it difficult for smoke to flow, thus possibly retarding detection on this surface. 
   In view of the points described above, the present invention has been made, and it is an object of the present invention to provide a photoelectric smoke detector suitable for being downsized without detection capability deterioration. 
   Means for Solving the Problems 
   To solve the problem described above, a first aspect of the invention refers to a photoelectric smoke detector for detecting the presence of smoke by utilizing a light emitting element and a light receiving element whose optical axes intersect with each other. The photoelectric smoke detector includes: (1) a specialized labyrinth function fulfilling part for playing only a labyrinth function of bringing air flow into an interior space thereof and preventing entry of disturbance light into the interior space; and (2) a smoke detecting part which is provided above the specialized labyrinth function fulfilling part so that an interior space of the smoke detecting part is communicated with the interior space of the specialized labyrinth function fulfilling part, and which has the light emitting element and the light receiving element built therein and has a small hole for extracting air flow that has passed through a detection area near an intersection between the optical axes of the light emitting element and the light receiving element. 
   A second aspect of the present invention refers to a photoelectric smoke detector for detecting presence of smoke by utilizing a light emitting element and a light receiving element whose optical axes intersect with each other. The photoelectric smoke detector includes: a casing for storing the light emitting element and the light receiving element; inlet and outlet ports which are respectively provided in one and the other sides of the casing, and which brings air flow into the casing; and rectifying light blocking means which is provided contiguously with each of the inlet and outlet ports, and which prevents entry of disturbance light into an interior space and forms a flow line of smoke extending from one or the other inlet and outlet port to the other or the one inlet and outlet port while being made penetrate through a detection area by the light emitting element and the light receiving element. 
   Consequently, smoke that has flown in through any one of the inlet and outlet ports flows into the casing via the rectifying light blocking means. At this point in time, the rectifying light blocking means prevents entry of disturbance light into the interior space and also guides the smoke to the detection area described above. 
   EFFECTS OF THE INVENTION 
   According to the present invention, a specialized labyrinth function fulfilling part for playing only a labyrinth function and a smoke detector for playing a smoke detection function are separated from each other and arranged in the vertical. Thus, this permits achieving a photoelectric smoke detector suitable for being downsized without detection capability deterioration. 
   Moreover, the light emitting element and the light receiving element are stored in the casing and the inlet and outlet ports are provided, and also the rectifying light blocking means is respectively provided at the inlet and outlet ports, so that smoke is guided to the detection area while preventing entry of disturbance light into the interior space. Thus, further downsizing can be achieved without detection capability deterioration. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view showing a photoelectric smoke detector of a first embodiment of the present invention. 
       FIG. 2  is a longitudinal sectional view of the photoelectric smoke detector of the first embodiment of the present invention. 
       FIG. 3  is a perspective view showing a mountain-like labyrinth of the first embodiment of the present invention. 
       FIG. 4  are explanatory diagrams showing a conventional photoelectric smoke detector. 
       FIG. 5  is a longitudinal sectional view of a photoelectric smoke detector of a third embodiment of the present invention. 
       FIG. 6  is a perspective view of the photoelectric smoke detector of the third embodiment of the present invention. 
       FIG. 7  is a longitudinal sectional view of a photoelectric smoke detector of a first modified example of the present invention. 
       FIG. 8  is a longitudinal sectional view of a photoelectric smoke detector of a second modified example of the present invention. 
       FIG. 9  is a perspective view of a photoelectric smoke detector of a third modified example of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Description of the Reference Numerals 
     10  Photoelectric smoke detector 
     11  Circular cylinder part 
     12  Flat box part 
     14  Side small hole 
     20  Mountain-like labyrinth 
     30  Light emitting element 
     31   a  Upper inclined surface 
     40  Light receiving element 
     41   a  Lower inclined surface 
     41   b  Upper inclined surface 
     51  to  53  Labyrinth 
     100  Photoelectric smoke detector 
     101  Casing 
     102  One side end wall 
     105  Storage chamber 
     106  One side air chamber 
     107  The other side air chamber 
     108  Storage chamber side one side end wall 
     111 ,  112  Inlet and outlet port 
     115 ,  116  Rectification light blocking means 
     117  Inflow and outflow port 
     118  Insect screen 
   BEST MODE FOR CARRYING OUT THE INVENTION 
   Hereinafter, embodiments of the present invention will be described. A photoelectric smoke detector according to the present invention is applicable to a smoke detector installed in a place such as ordinary household, public facilities, or the like where people gather, a factory device such as a semiconductor producing device, a machining tool, a switchboard, an industrial controller, or the like, or any of other places where this photoelectric smoke detector has been hardly installed before. 
   (A) First Embodiment 
   Hereinafter, one embodiment of the photoelectric smoke detector according to the present invention will be described in detail, referring to the drawings.  FIG. 1  is a perspective view showing the photoelectric smoke detector of the embodiment.  FIG. 2  is a longitudinal sectional view of the photoelectric smoke detector of the embodiment (a hatched line indicating the cross section is omitted). 
   The fitting directions of the smoke detectors of the embodiments are not limited to a direction shown in  FIG. 1 . However, in the following description, the top (upper), bottom (lower), left, and right are expressed, referring to a condition of  FIG. 1 . 
   The smoke detector  10  of the embodiment includes visually a circular cylinder part  11 , and a flat box part  12  extending upwardly from the circular cylinder part  11 . 
   The circular cylinder part  11  mainly plays a function of introducing smoke into the smoke detector  10  while preventing entry of disturbance light, insects, and the like into this smoke detector  10 . 
   At the bottom opening of the circular cylinder part  11 , a mountain-like labyrinth  20  is provided which has a mountain-like shape as shown in  FIG. 3 . The mountain-like labyrinth  20 , as shown in  FIG. 3 , has a central part  21  ridged in a mountain-like shape and has, near a circumferential edge thereof, a plurality of (six illustrated in the figure) arc-shaped openings  22  provided circumferentially at equal intervals. The openings  22  of the mountain-like labyrinth  20  function as a smoke introduction port. The mountain-like central part  21  plays a function of upwardly guiding smoke introduced through the openings  22  of the mountain-like labyrinth  20  or side holes  13  of the circular cylinder part  11  to be described later and a function of preventing entry of disturbance light. 
   At the lower position of a side surface (outer circumferential surface) of the circular cylinder part  11 , a plurality of (five illustrated in the figure) small holes  13  are provided circumferentially at equal intervals. The area of the small hole  13  permits smoke introduction from the side and is so selected as to minimize entry of disturbance light through this small hole  13 . 
   The flat box part  12  is substantially rectangular-parallelepiped-shaped, and mainly plays a smoke detection function with its inner configuration. A width of the flat box part  12  is equal to an outer diameter of the circular cylinder part  11 . The flat box part  12  extends upwardly from the circular cylinder part  11  in such a manner that its own central axis and the central axis of the circular cylinder part  11  agree with each other. 
   In a right side surface of the flat box part  12  near the top surface thereof, a side small hole  14  of the flat box part  12  is provided. This side small hole  14  functions as an opening upon smoke extraction from the inside to outside of the smoke detector  10 . Specifically, smoke introduced into the smoke detector  10  through the openings  22  of the mountain-like labyrinth  20  or the side small holes  13  of the circular cylinder part  11  is extracted through the side small hole  14  of the flat box part  12 . The above description refers to a flow of smoke intended by the inventor. However, in practice, smoke may flow in a reversed route. 
   Inside the smoke detector  10  (more precisely, inside the flat box part  12 ) of the embodiment, as shown in  FIG. 2 , a light emitting element  30  and a light receiving element  40  are provided. 
   The light emitting element  30  is provided at the upper left position in the interior space of the flat box part  12  by a light emitting element storage part  31 . The light emitting element storage part  31  stores the light emitting element  30  with almost no gap therebetween in such a manner as to emanate light emitted from the light emitting element  30  only forward. In front of the light emitting element storage part  31 , an optical window  32  is provided. The optical window  32  may be a simple opening playing a narrowing-down function. Further the optical window  32  may be such glass that achieves a dust-proofing function. 
   The light receiving element  40  is provided at the lower left position in the interior space of the flat box part  12  by a light receiving element storage part  41 . The light receiving element storage part  41  has a circular-cylindrical interior space, and stores the light receiving element  40  at the bottom thereof and has an objective lens  42  fitted on the top thereof. 
   An optical axis of the light emitting element  30  and an optical axis of the light receiving element  40  intersect with each other at an angle of approximately 120 degrees, and the vicinity of this intersection serves as a detection area AR for smoke. Specifically, the presence of smoke in this detection area causes light emitted from the light emitting element  30  to be scattered by the smoke, and this scattering light reaches the light receiving element  40 , which permits the detection of the presence of smoke. 
   On the immediate left position of the detection area AR, a direct light preventing labyrinth  50  is provided which prevents light emitted from the light emitting element  30  from reaching the light receiving element  40  without scattering. 
   At the boundary between the circular cylinder part  11  and the flat box part  12  in the interior space of the smoke detector  10 , a lower insect screen  60  is provided. This lower insect screen  60  is circular-shaped when provided on a circular cylinder part  11  side and has a rectangular shape when provided on a flat box part  12  side. The lower insect screen  60  is provided for preventing insects entering through the openings  22  of the mountain-like labyrinth  20  or the side small holes  13  of the circular cylinder part  11  from entering further inside. 
   The distance between the mountain-like labyrinth  20  and the lower insect screen  60 , in other words, the height of the circular cylinder part  11  is selected at a distance so that the function of upwardly guiding smoke by the mountain-like labyrinth  20  can be fully fulfilled. 
   Above near the lower insect screen  60  and also on the right of the light receiving element storage part  41 , two labyrinth pieces  51  and  52  are provided which are arranged in the vertical. A pressing piece for the lower insect screen  60  located on the right also functions as a labyrinth piece  53 . The labyrinth piece  51  is oriented diagonally right up, and rightwardly and upwardly guides air flow from the lower side by the bottom surface thereof. The upper end part of the labyrinth piece  51  is bent leftward and upward, fulfilling a function of directing air flow rising along the top surface thereof toward a detection area. The labyrinth piece  52  is provided at the upper left position of the labyrinth piece  51  in a manner such as to be oriented diagonally left up. The labyrinth piece  52  leftwardly and upwardly guides a direct air flow from the central part of the lower insect screen  60 , air flow traveling along an inclination of a lower inclined surface  41   a  of the light receiving element storage part  41 , and the like. In this direction, an upper inclined surface  41   b  of the light receiving element storage part  41  is provided. An air flow directed to the upper inclined surface  41   b  of the light receiving element storage part  41  is directed toward the detection area AR by this upper inclined surface  41   b.    
   On the inner side of the side small hole  14  of the flat box section  12 , an upper insect screen  61  is provided. The upper insect screen  61  prevents entry of insects through the side small hole  14 . 
   A labyrinth piece  54  is provided which extends substantially leftward from the lower end position of the side small hole  14  of the flat box part  12 . This labyrinth piece  54  is so bent as to be directed leftward and upward from the central position thereof. Air flow passing through the detection area AR and further rising is adapted to be narrowed down by an upper inclined surface  31   a  of the light emitting storage part  31  and the bottom inclined surface of the labyrinth piece  54 , then reaches the top side of the interior space, is directed by subsequent air flow pressure toward the side small hole  14 , and then is extracted through the side small hole  14 . 
   The presence of the mountain-like labyrinth  20  greatly reduces entry of disturbance light from the lower side, the metallic lower insect screen  60  also reduces the entry of disturbance light form the lower side, and the lower inclined surface  41   a  of the light receiving element storage part  41  and the labyrinth pieces  51  to  53  further prevents this entry. Even if disturbance light passes through portions of the lower inclined surface  41   a  of the light receiving element storage part  41  and the labyrinth pieces  51  to  53 , its travel direction is substantially upward, while the light receiving element  40  is provided inside the light receiving element storage part  41 , plus at the bottom thereof, so that such disturbance light does not reach the light receiving element  40 . 
   The side small hole  14  of the flat box part  12  has a small area and thus restricts entry of disturbance light therethrough, and the upper insect screen  60  that covers this side small hole  14  from the inside also restricts the entry of disturbance light. The labyrinth piece  54  has a sufficient length and also is inclined leftward and upward from the center thereof, and thus can direct entering disturbance light upward, thus eliminating those directed to the light receiving element  40  side almost completely. Even if the disturbance light travels further ahead of a tip end of the labyrinth piece  54  as a result of its reflection or the like, its travel direction is directed by the upper inclined surface  31   a  of the light emitting storage part  31  in the direction not toward the light receiving element  40 . 
   With the photoelectric smoke detector of the embodiment described above, the number of labyrinths is small and the flat box part plays a main role in detection, which permits achieving downsizing. An electric processing construction can also be provided on one surface of the flat box part, which does not disturb the downsizing. The circular cylinder part  11  mainly fulfills a labyrinth function, which permits reducing the number of labyrinths provided in the flat box part  12 . 
   That is, one characteristic of the present embodiment is that a portion (circular cylinder part  11 ) specialized for a labyrinth function is provided in which a light emitting element, a light receiving element, and a detection area do not exist. 
   Moreover, an introduction port and an extraction port for air flow are both provided, so that an air flow passes through the inside of the smoke detector, which permits achieving a higher detection accuracy than is achieved in a case where only an opening serving as both the introduction port and the extraction port is provided. Although a stream of air flow inside the flat box part is substantially constant, the presence of the circular cylinder part  11 , and the presence of the mountain-like labyrinth  20  in particular, permits introducing to the inside the air flow around the smoke detector  10  directed in any direction, which in turn permits improving the detection accuracy. 
   Further, a simple configuration with a small number of labyrinths is provided, which not only permits easy manufacture but also holds the promise for low costs. 
   The smoke detector of the present embodiment is applicable as both a smoke detector for use in a device and a smoke detector for use in the interior space, thus not limiting its application. 
   (B) Second Embodiment 
   In the embodiment described above, the one illustrated has an extraction hole (side small hole  14 ) for an air flow (smoke) provided at the upper right side surface thereof. However, the extraction hole for air flow (smoke) may be also given at another surface (top surface, another side surface, front surface, or back surface) in the number not limited to one. 
   The aforementioned configuration of the circular cylinder part  11  illustrated serves as the portion specialized for the labyrinth function, although this configuration may be provided in different configuration. For example, from a configuration as shown in  FIG. 4(B) , a light emitting element and a light receiving element may be removed, and resulting a configuration with a smaller diameter may be applied as a portion specialized for a labyrinth function. Moreover, the portion specialized for a labyrinth function may also be formed in the shape of a flat box, which may be integrated with the flat box part  11  of the embodiment described above. 
   It is needless to say that the number of labyrinths in the flat box part  12  and the positional relationship between the light emitting element  30  and the light receiving element  40  are not limited to those of the embodiment described above. For example, the light emitting element  30  may be provided on a lower side and the light receiving element  40  may be provided on an upper side. 
   The photoelectric smoke detector of the present invention is intended to be used in a manner such that the portion specialized for fulfilling the labyrinth function is provided on the lower side thereof. The scope of claims expresses a vertical based on the premise of such installation, but it is needless to say that the photoelectric smoke detector may be so installed as to be oriented in another direction. 
   (C) Third Embodiment 
   Next, a third embodiment will be described referring to  FIGS. 5 and 6 . The present embodiment provides an even more downsized version of the photoelectric smoke detector  100  with an improved casing portion. 
   The photoelectric smoke detector  100  of the present embodiment is, as shown in the figures, mainly includes: the light emitting element  30 , the light receiving element  40 , and the like; and a casing  101 . The light emitting element  30 , the light receiving element  40 , and the like are the same as those of the photoelectric smoke detector of the first embodiment. 
   The entire casing  101  is formed into a circular-cylindrical shape. This casing  101  is very small in size and set at a dimension that is slightly larger than a dimension including the light emitting element  30 , the light emitting element storage part  31 , the light receiving element  40 , the light receiving element storage part  41 , and a circuit board (not shown). 
   At one side end part of the casing  101  (the upper end part in  FIG. 5 ), a one side end wall  102  is provided. This one side end wall  102  encloses a one side air chamber  106  to be described later and serves as a substrate supporting the entire photoelectric smoke detector  100 . On the outer side surface of this one side end wall  102 , an end wall fixing tool (not shown) for fixing the entire photoelectric smoke detector  100  is provided. This end wall fixing tool is a fixing tool for fixing the photoelectric smoke detector  100  to a ceiling plate, the wall, or the like inside the room. In addition, on the outer circumferential surface of the one side end wall  102  (outer circumferential surface of the circular-cylindrical casing  101 ), a circumferential edge fixing tool (not shown) for fixing the entire photoelectric smoke detector  100  is provided. This circumferential edge fixing tool is fixing means adapted to fix the photoelectric smoke detector  100  along the wall surface. Consequently, the photoelectric smoke detector  100  is fixed along or perpendicularly to the wall surface in accordance with a condition of an installation position. Further, the end wall fixing tool and the circumferential edge fixing tool may be so configured as to fix the photoelectric smoke detector  100  by adjusting it at an arbitrary angle, such as a longitudinal, lateral, or diagonal angle. As these end wall fixing tool and circumferential edge fixing tool, any of fixing tools with structure that can be typically used by those skilled in the art can be used. 
   The inside of the casing  101  includes a storage chamber  105 , a one side air chamber  106 , and other side air chamber  107 . 
   The storage chamber  105  is a space for storing: the light emitting element  30 , the light emitting storage part  31 , the light receiving element  40 , and the light receiving element storage part  41  including a detection area AR; a circuit board therefor; and the like. The storage chamber  105  is set at a dimension substantially equal to the entire dimension of the light emitting element  30  and the like. Further, this storage chamber  105  forms a smoke passage. Smoke flowing in the one side air chamber  106  or the other side air chamber  107  from the outside passes through the storage chamber  105  and then flows in the other side air chamber  107  or the one side air chamber  106 . Then, at this point in time, in the storage chamber  105 , a flow line of the smoke is so configured as to be made penetrate through the detection area AR by rectifying light blocking means  115  and  116  to be described later. 
   The light emitting element  30  and the light receiving element  40  are disposed along the central axis direction of the cylindrical casing  101  (longitudinally) in the storage chamber  105 . Orienting them in this direction prevents the diameter of the cylindrical casing  101  from becoming large. 
   The one side air chamber  106  is a space for temporarily reserving external air taken in through an inlet and outlet port  111  to be described later and then delivering it to the one side rectifying light blocking means  115  to be described later. The one side air chamber  106  is provided between the inlet and outlet port  111  and the one side rectifying light blocking means  115 . More specifically, the one side air chamber  106  is provided at a position adjacent to the one side (upper side in  FIG. 5 ) of the storage chamber  105 . The one side air chamber  106  is formed by being enclosed by a storage chamber side one side end wall  108  enclosing the one side end of the storage chamber  105  and the one side end wall  102  of the casing  101 . These one side air chamber  106  and the storage chamber  105  are communicated with each other via the one side rectifying light blocking means  115  to be described later. 
   The other side air chamber  107  is a space for temporarily reserving external air taken in through an inlet and outlet port  112  to be described later and then delivering it to the other side rectifying light blocking means  116  to be described later. The other side air chamber  107  is located on the other side (lower side in  FIG. 5 ) of the storage chamber  105 , and provided between the inlet and outlet port  112  and the other side rectifying light blocking means  116 . These the other side air chamber  107  and the storage chamber  105  are communicated with each other via the other side rectifying light blocking means  116  to be described later. The outer side surface (lower side surface) of the other side air chamber  107  serves as the mountain-like labyrinth  20 . This mountain-like labyrinth  20  is identical to that of the first embodiment. 
   At one and the other end parts of the circular-cylindrical casing  101 , the inlet and outlet ports  111  and  112  are respectively provided. These inlet and outlet ports  111  and  112  are openings for bringing external air flow into the casing  101 . More specifically, the inlet and outlet ports  111  and  112  are so provided as to face the one side air chamber  106  and the other side air chamber  107 , respectively. The one side inlet and outlet port  111  is formed by a plurality of holes provided over the entire circumference of the outer circumferential edge of the one side air chamber  106 . Through this one side inlet and outlet port  111 , external air flows into the one side air chamber  106  from the surrounding thereof. The other side inlet and outlet port  112  is formed by a plurality of holes provided over the entire circumference of the lower side surface part of the other side air chamber  107 . Through this the other side inlet and outlet port  112 , external air flows into the other side air chamber  107  from the lower side surface thereof. Consequently, the one side inlet and outlet port  111  and the other side inlet and outlet port  112  are so provided as to open in mutually orthogonal directions. This is intended to cause smoke flowing to the photoelectric smoke detector  100  from any direction to flow in either of the inlet and outlet ports  111  and  112 . 
   Between the one side air chamber  106  and the storage chamber  105 , the one side rectifying light blocking means  115  is provided. This one side rectifying light blocking means  115  is means adapted to prevent entry of disturbance light into the interior space (storage chamber  105 ) and also form, in cooperation with the other side rectifying light blocking means  116 , a flow line of smoke which has penetrated through the detection area AR described above. This flow line of smoke is so formed as to flow through the one side inlet and outlet port  111  into the storage chamber  105  via the one side air chamber  106 , penetrate through the detection area AR described above, and extend to the other side inlet and outlet port  112  via the other side air chamber  107 . More specifically, the one side rectifying light blocking means  115  is formed by an inflow and outflow port  117  provided at the central part of the one side air chamber  106  and the upper inclined surface  31   a  of the light emitting storage part  31 . This upper inclined surface  31   a  is adapted to rectify air (smoke) which has been once reserved in the one side air chamber  106  and then has flown into the storage chamber  105  after being narrowed down by the inflow and outflow port  117 , and then guide it to the detection area AR. Further, locating the inflow and outflow port  117  at the central part of the one side air chamber  106  blocks light entering through the one side inlet and outlet port  111  by reflecting it into the one side air chamber  106  so that this light does not enter into the storage chamber  105 . The inflow and outflow port  117  is provided with an insect screen  118 . 
   The other side rectifying light blocking means  116 , similarly to the one side rectifying light blocking means  115 , is means adapted to prevent entry of disturbance light into the interior space (storage chamber  105 ) and also form, in cooperation with the one side rectifying light blocking means  115 , a flow line of smoke which has penetrated through the detection area AR described above. The other side rectifying light blocking means  116  is provided at such a position as to face the one side rectifying light blocking means  115  with the detection area AR therebetween. Further, the other side rectifying light blocking means  116  is so configured as to rectify smoke flowing into the storage chamber  105  while blocking light so that this flow line penetrates through the detection area AR described above. This flow line of smoke, contrary to the case described above, is so formed as to flow through the other side inlet and outlet port  112  into the storage chamber  105  via the other side air chamber  107 , penetrate through the detection area AR described above, and extend to the one side inlet and outlet port  111  via the one side air chamber  106 . More specifically, the other side rectifying light blocking means  116  includes: labyrinths  51  to  53  provided at an inflow and outflow port  109 ; and the lower inclined surface  41   a ; and the upper inclined surface  41   b . Further, the labyrinths  51  to  53  block light entering through the other side inlet and outlet port  112  to prevent entry of the light into the detection area AR. Between the storage chamber  105  and the other side air chamber  107 , an insect screen  60  is provided. 
   The photoelectric smoke detector  100  configured as described above operates in the following manner. 
   First, the photoelectric smoke detector  100  is fitted to the ceiling plate, the room wall, or the like via the end wall fixing tool and circumferential edge fixing tool of the one side end wall  102 . The photoelectric smoke detector  100  is small in size; thus, it is not site-specific in terms of fitting in particular and thus fitted at such a position that does not interfere with passage, operation, and the like. It is desirable that, in the event of fire, the photoelectric smoke detector  100  be fitted at a position serving as a smoke passage. 
   Next, upon flow of generated smoke to the photoelectric smoke detector  100 , the smoke first enters into the photoelectric smoke detector  100  through the one side inlet and outlet port  111  or the other side inlet and outlet port  112 . 
   The smoke entering through the one side inlet and outlet port  111  is reserved in the one side air chamber  106  and flows into the storage chamber  105  after being narrowed down at the inflow and outflow port  117 . The smoke flowing into the storage chamber  105  is guided by the upper inclined surface  31   a  to pass through the detection area AR, flows to the other side air chamber  107  through the other side rectifying light blocking means  116 , and flows out to the outside through the other side inlet and outlet port  112 . 
   Then the smoke passing through the detection area AR is detected by the light emitting element  30  and the light receiving element  40 , activating an alarm or the like. 
   The smoke entering through the other side inlet and outlet port  112  is reserved in the other side air chamber  107 , and guided by the other side rectifying light blocking means  116  to pass through the detection area AR, flows to the one side air chamber  106  through the one side rectifying light blocking means  115 , and flows out to the outside through the one side inlet and outlet port  111 . 
   Then the smoke passing through the detection area AR is detected by the light emitting element  30  and the light receiving element  40 , activating the alarm or the like. 
   This consequently provides the same effect as is provided by the first embodiment described above and also the following effect. 
   The flow line of smoke is so configured as to be made penetrate through the detection area AR by the one side rectifying light blocking means  115  and the other side rectifying light blocking means  116  which are so disposed as to face each other with the detection area AR therebetween. Thus, smoke flowing into the storage chamber  105  can be effectively led to the detection area AR, thereby improving the detection accuracy. 
   The one side rectifying light blocking means  115  and the other side rectifying light blocking means  116  described above are so disposed as to face each other with the detection area AR described above therebetween, which permits configuration such that the flow line of smoke reliably penetrates through the detection area AR. Further, the casing  101  is formed into a cylindrical shape so that air easily enters thereinto. Thus, this permits a configuration such that a flow line of smoke is reliably formed with this cylindrical casing  101  and the one side rectifying light blocking means  115  and the other side rectifying light blocking means  116  respectively provided at the both ends of the cylinder, and also such that the flow line of smoke reliably penetrates through the detection area AR. 
   The casing  101  described above is formed into a cylindrical shape and the light emitting element  30  and the light receiving element  40  described above are disposed along the central axis direction of the cylindrical casing  101 , thus permitting downsizing of the casing  101 . Further, it is configured such that all the components are stored in the cylindrical casing  101 , thus permitting further downsizing of the photoelectric smoke detector  100 . That is, by storing the light emitting element  30  in the circular-cylindrical casing  101  along the central axis direction of the casing  101  and also by providing the one side rectifying light blocking means  115  and the other side rectifying light blocking means  116  at such a position in the casing  101  as to face each other with the detection area AR therebetween, a flow line of smoke passes through the detection area AR described above in a manner penetrating therethrough, the inlet and outlet ports and a flow line for smoke are confirmed, and the labyrinths and the insect screens are reduced in size, thus permitting further downsizing of the photoelectric smoke detector  100 . 
   As a result, the photoelectric smoke detector  100  can be provided at various places. In particular, the photoelectric smoke detector  100  can be easily fitted in a place where it used not to be fitted due to its bulkiness, for example, near a place that is likely to become a cause of fire. This permits early detection of fire. 
   The inlet and outlet ports  111  and  112  described above are formed large, and also the air chambers  106  and  107  for temporarily reserving air taken in through the inlet and outlet ports  111  and  112  and then delivering it to the rectifying light blocking means  115  and  116  are provided between these inlet and outlet ports  111  and  112  and the rectifying light blocking means  115  and  116 . Thus, this permits external air containing smoke to easily flow into the air chambers  106  and  107  through the inlet and outlet ports  111  and  112 , be temporarily reserved in the air chambers  106  and  107 , and then be efficiently delivered to the rectifying light blocking means  115  and  116 . 
   Moreover, the one side inlet and outlet port  111  and the other side inlet and outlet port  112  are so provided as to open in the mutually orthogonal directions. Thus, this permits smoke flowing to the photoelectric smoke detector  100  from any direction to flow into the inside through either of the inlet and outlet ports  111  and  112 , thereby improving the detection accuracy. 
   INDUSTRIAL APPLICABILITY 
   In the embodiments described above, the other side inlet and outlet port  112  is provided at a lower side surface of the casing  101 , but it may be, as shown in  FIG. 7 , provided, in addition to the lower side surface, on an outer circumferential edge part. This permits smoke flowing from any direction to flow into the other side air chamber  107 . As a result, the smoke detection accuracy can be improved. 
   In the embodiments described above, the casing  101  is formed into a circular cylindrical shape, but it may be formed into any of cylindrical shapes, such as polygonal cylindrical shapes including a square cylindrical shape, a hexagonal cylindrical shape, and the like, and a barrel shape. Any of cylindrical shapes can be appropriately used which permits easy formation of a flow line penetrating through the detection area AR. In this case, the same operation and effects as are provided by the embodiments described above can be provided. 
   In the embodiments described above, the one side air chamber  106  and the other side air chamber  107  are formed as spaces for temporarily reserving external air. However, as shown in  FIG. 8 , inflow guides  121  and  122  may be respectively provided in the one side air chamber  106  and the other side air chamber  107 . The inflow guide  121  is formed into a truncated conical shape (trapezoidal shape cross-sectionally), and adapted to guide air flowing in through a surrounding inlet and outlet port  123  to the inflow and outflow port  117  by its conical surface. The inflow guide  122  is formed into a conical shape, and adapted to guide air flowing in through a surrounding inlet and outlet port  124  to the inflow and outflow port  109  by its conical surface. 
   Here, the inflow guide  121  is formed in the one side air chamber  106  so that the cross section of the inflow guide  121  is trapezoidal-shaped. However, the shape of this inflow guide  121  is set in accordance with various conditions, such as the dimension of the one side air chamber  106 , the size of the inflow and outflow port  117 , and the like. The inlet and outlet port  123  is formed larger than the inlet and outlet port  111  of the first embodiment, so that external light easily flows into the one side air chamber  106 . Moreover, the light emitting element  30  and the like, and the labyrinths  51  to  53  are integrally provided, thus achieving downsizing, which in turn achieves downsizing of the entire photoelectric smoke detector  100 . 
   The inflow guide  122  of the other side air chamber  107  is formed into a substantially conical shape with its cross section bent in a triangular shape. This bent portion is intended to make it easy for external air (smoke) flowing into the other side air chamber  107  to flow toward the inflow and outflow port  109 . The shape of this inflow guide  122  is set in accordance with various conditions, such as the dimension of the other side air chamber  107 , the size of the inflow and outflow port  119 , and the like. The inlet and outlet port  124  is formed larger than an outer circumferential surface of the casing  101 , thereby making it easy for external air to flow into the other side air chamber  107 . As a result, the same operation and effect as are provided by the third embodiments described above can be provided. 
   Moreover, in the embodiments described above, the storage chamber  105  is configured to be isolated from external air so that external light does not enter inside. However, as shown in  FIG. 9 , a sensitivity adjustment part  126  may be provided. This sensitivity adjustment part  126  is formed by a hole provided in the casing  101 . The size, position, and the like of this hole are appropriately set to adjust the sensitivity of the light emitting element  30  and the light receiving element  40 .