Photoelectric smoke detector

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.

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. 4show a configuration of a conventional typical photoelectric smoke detector (see Patent Document 1 for example).

The conventional photoelectric smoke detector1is, for example, as shown inFIG. 4(A), installed on the ceiling or the like in such a manner that a chamber part2having 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 part2, as shown inFIG. 4(B), a light emitting element3and a light receiving element4are 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 element3is scattered by the smoke and reaches the light receiving element4, thereby achieving detection of the presence of smoke. To prevent erroneous detection under an absence of smoke, a plurality of labyrinths5are arranged circumferentially so as to eliminate disturbance light, also even when light emitted from the light emitting element3is reflected, prevent this light from traveling toward the light receiving element4, and further avoid preventing the entry of smoke into the detection area. Around the plurality of labyrinths5, an insect screen6is 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.

DISCLOSURE OF THE INVENTION

Problem to be Solved by the Invention

The configuration of the conventional smoke detector shown inFIG. 4, due to characteristics of a detection system in which the light emitting element3, the light receiving element4, and the labyrinth5are 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 part2while 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.

DETAILED DESCRIPTION OF THE INVENTION

Description of the Reference Numerals

11Circular cylinder part

12Flat box part

14Side small hole

40Light receiving element

102One side end wall

106One side air chamber

107The other side air chamber

108Storage chamber side one side end wall

111,112Inlet and outlet port

115,116Rectification light blocking means

117Inflow and outflow port

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. 1is a perspective view showing the photoelectric smoke detector of the embodiment.FIG. 2is 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 inFIG. 1. However, in the following description, the top (upper), bottom (lower), left, and right are expressed, referring to a condition ofFIG. 1.

The smoke detector10of the embodiment includes visually a circular cylinder part11, and a flat box part12extending upwardly from the circular cylinder part11.

The circular cylinder part11mainly plays a function of introducing smoke into the smoke detector10while preventing entry of disturbance light, insects, and the like into this smoke detector10.

At the bottom opening of the circular cylinder part11, a mountain-like labyrinth20is provided which has a mountain-like shape as shown inFIG. 3. The mountain-like labyrinth20, as shown inFIG. 3, has a central part21ridged in a mountain-like shape and has, near a circumferential edge thereof, a plurality of (six illustrated in the figure) arc-shaped openings22provided circumferentially at equal intervals. The openings22of the mountain-like labyrinth20function as a smoke introduction port. The mountain-like central part21plays a function of upwardly guiding smoke introduced through the openings22of the mountain-like labyrinth20or side holes13of the circular cylinder part11to 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 part11, a plurality of (five illustrated in the figure) small holes13are provided circumferentially at equal intervals. The area of the small hole13permits smoke introduction from the side and is so selected as to minimize entry of disturbance light through this small hole13.

The flat box part12is substantially rectangular-parallelepiped-shaped, and mainly plays a smoke detection function with its inner configuration. A width of the flat box part12is equal to an outer diameter of the circular cylinder part11. The flat box part12extends upwardly from the circular cylinder part11in such a manner that its own central axis and the central axis of the circular cylinder part11agree with each other.

In a right side surface of the flat box part12near the top surface thereof, a side small hole14of the flat box part12is provided. This side small hole14functions as an opening upon smoke extraction from the inside to outside of the smoke detector10. Specifically, smoke introduced into the smoke detector10through the openings22of the mountain-like labyrinth20or the side small holes13of the circular cylinder part11is extracted through the side small hole14of the flat box part12. 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 detector10(more precisely, inside the flat box part12) of the embodiment, as shown inFIG. 2, a light emitting element30and a light receiving element40are provided.

The light emitting element30is provided at the upper left position in the interior space of the flat box part12by a light emitting element storage part31. The light emitting element storage part31stores the light emitting element30with almost no gap therebetween in such a manner as to emanate light emitted from the light emitting element30only forward. In front of the light emitting element storage part31, an optical window32is provided. The optical window32may be a simple opening playing a narrowing-down function. Further the optical window32may be such glass that achieves a dust-proofing function.

The light receiving element40is provided at the lower left position in the interior space of the flat box part12by a light receiving element storage part41. The light receiving element storage part41has a circular-cylindrical interior space, and stores the light receiving element40at the bottom thereof and has an objective lens42fitted on the top thereof.

An optical axis of the light emitting element30and an optical axis of the light receiving element40intersect 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 element30to be scattered by the smoke, and this scattering light reaches the light receiving element40, which permits the detection of the presence of smoke.

On the immediate left position of the detection area AR, a direct light preventing labyrinth50is provided which prevents light emitted from the light emitting element30from reaching the light receiving element40without scattering.

At the boundary between the circular cylinder part11and the flat box part12in the interior space of the smoke detector10, a lower insect screen60is provided. This lower insect screen60is circular-shaped when provided on a circular cylinder part11side and has a rectangular shape when provided on a flat box part12side. The lower insect screen60is provided for preventing insects entering through the openings22of the mountain-like labyrinth20or the side small holes13of the circular cylinder part11from entering further inside.

The distance between the mountain-like labyrinth20and the lower insect screen60, in other words, the height of the circular cylinder part11is selected at a distance so that the function of upwardly guiding smoke by the mountain-like labyrinth20can be fully fulfilled.

Above near the lower insect screen60and also on the right of the light receiving element storage part41, two labyrinth pieces51and52are provided which are arranged in the vertical. A pressing piece for the lower insect screen60located on the right also functions as a labyrinth piece53. The labyrinth piece51is 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 piece51is bent leftward and upward, fulfilling a function of directing air flow rising along the top surface thereof toward a detection area. The labyrinth piece52is provided at the upper left position of the labyrinth piece51in a manner such as to be oriented diagonally left up. The labyrinth piece52leftwardly and upwardly guides a direct air flow from the central part of the lower insect screen60, air flow traveling along an inclination of a lower inclined surface41aof the light receiving element storage part41, and the like. In this direction, an upper inclined surface41bof the light receiving element storage part41is provided. An air flow directed to the upper inclined surface41bof the light receiving element storage part41is directed toward the detection area AR by this upper inclined surface41b.

On the inner side of the side small hole14of the flat box section12, an upper insect screen61is provided. The upper insect screen61prevents entry of insects through the side small hole14.

A labyrinth piece54is provided which extends substantially leftward from the lower end position of the side small hole14of the flat box part12. This labyrinth piece54is 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 surface31aof the light emitting storage part31and the bottom inclined surface of the labyrinth piece54, then reaches the top side of the interior space, is directed by subsequent air flow pressure toward the side small hole14, and then is extracted through the side small hole14.

The presence of the mountain-like labyrinth20greatly reduces entry of disturbance light from the lower side, the metallic lower insect screen60also reduces the entry of disturbance light form the lower side, and the lower inclined surface41aof the light receiving element storage part41and the labyrinth pieces51to53further prevents this entry. Even if disturbance light passes through portions of the lower inclined surface41aof the light receiving element storage part41and the labyrinth pieces51to53, its travel direction is substantially upward, while the light receiving element40is provided inside the light receiving element storage part41, plus at the bottom thereof, so that such disturbance light does not reach the light receiving element40.

The side small hole14of the flat box part12has a small area and thus restricts entry of disturbance light therethrough, and the upper insect screen60that covers this side small hole14from the inside also restricts the entry of disturbance light. The labyrinth piece54has 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 element40side almost completely. Even if the disturbance light travels further ahead of a tip end of the labyrinth piece54as a result of its reflection or the like, its travel direction is directed by the upper inclined surface31aof the light emitting storage part31in the direction not toward the light receiving element40.

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 part11mainly fulfills a labyrinth function, which permits reducing the number of labyrinths provided in the flat box part12.

That is, one characteristic of the present embodiment is that a portion (circular cylinder part11) 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 part11, and the presence of the mountain-like labyrinth20in particular, permits introducing to the inside the air flow around the smoke detector10directed 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 hole14) 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 part11illustrated 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 inFIG. 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 part11of the embodiment described above.

It is needless to say that the number of labyrinths in the flat box part12and the positional relationship between the light emitting element30and the light receiving element40are not limited to those of the embodiment described above. For example, the light emitting element30may be provided on a lower side and the light receiving element40may 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.

Next, a third embodiment will be described referring toFIGS. 5 and 6. The present embodiment provides an even more downsized version of the photoelectric smoke detector100with an improved casing portion.

The photoelectric smoke detector100of the present embodiment is, as shown in the figures, mainly includes: the light emitting element30, the light receiving element40, and the like; and a casing101. The light emitting element30, the light receiving element40, and the like are the same as those of the photoelectric smoke detector of the first embodiment.

The entire casing101is formed into a circular-cylindrical shape. This casing101is very small in size and set at a dimension that is slightly larger than a dimension including the light emitting element30, the light emitting element storage part31, the light receiving element40, the light receiving element storage part41, and a circuit board (not shown).

At one side end part of the casing101(the upper end part inFIG. 5), a one side end wall102is provided. This one side end wall102encloses a one side air chamber106to be described later and serves as a substrate supporting the entire photoelectric smoke detector100. On the outer side surface of this one side end wall102, an end wall fixing tool (not shown) for fixing the entire photoelectric smoke detector100is provided. This end wall fixing tool is a fixing tool for fixing the photoelectric smoke detector100to a ceiling plate, the wall, or the like inside the room. In addition, on the outer circumferential surface of the one side end wall102(outer circumferential surface of the circular-cylindrical casing101), a circumferential edge fixing tool (not shown) for fixing the entire photoelectric smoke detector100is provided. This circumferential edge fixing tool is fixing means adapted to fix the photoelectric smoke detector100along the wall surface. Consequently, the photoelectric smoke detector100is 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 detector100by 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 casing101includes a storage chamber105, a one side air chamber106, and other side air chamber107.

The storage chamber105is a space for storing: the light emitting element30, the light emitting storage part31, the light receiving element40, and the light receiving element storage part41including a detection area AR; a circuit board therefor; and the like. The storage chamber105is set at a dimension substantially equal to the entire dimension of the light emitting element30and the like. Further, this storage chamber105forms a smoke passage. Smoke flowing in the one side air chamber106or the other side air chamber107from the outside passes through the storage chamber105and then flows in the other side air chamber107or the one side air chamber106. Then, at this point in time, in the storage chamber105, a flow line of the smoke is so configured as to be made penetrate through the detection area AR by rectifying light blocking means115and116to be described later.

The light emitting element30and the light receiving element40are disposed along the central axis direction of the cylindrical casing101(longitudinally) in the storage chamber105. Orienting them in this direction prevents the diameter of the cylindrical casing101from becoming large.

The one side air chamber106is a space for temporarily reserving external air taken in through an inlet and outlet port111to be described later and then delivering it to the one side rectifying light blocking means115to be described later. The one side air chamber106is provided between the inlet and outlet port111and the one side rectifying light blocking means115. More specifically, the one side air chamber106is provided at a position adjacent to the one side (upper side inFIG. 5) of the storage chamber105. The one side air chamber106is formed by being enclosed by a storage chamber side one side end wall108enclosing the one side end of the storage chamber105and the one side end wall102of the casing101. These one side air chamber106and the storage chamber105are communicated with each other via the one side rectifying light blocking means115to be described later.

The other side air chamber107is a space for temporarily reserving external air taken in through an inlet and outlet port112to be described later and then delivering it to the other side rectifying light blocking means116to be described later. The other side air chamber107is located on the other side (lower side inFIG. 5) of the storage chamber105, and provided between the inlet and outlet port112and the other side rectifying light blocking means116. These the other side air chamber107and the storage chamber105are communicated with each other via the other side rectifying light blocking means116to be described later. The outer side surface (lower side surface) of the other side air chamber107serves as the mountain-like labyrinth20. This mountain-like labyrinth20is identical to that of the first embodiment.

At one and the other end parts of the circular-cylindrical casing101, the inlet and outlet ports111and112are respectively provided. These inlet and outlet ports111and112are openings for bringing external air flow into the casing101. More specifically, the inlet and outlet ports111and112are so provided as to face the one side air chamber106and the other side air chamber107, respectively. The one side inlet and outlet port111is formed by a plurality of holes provided over the entire circumference of the outer circumferential edge of the one side air chamber106. Through this one side inlet and outlet port111, external air flows into the one side air chamber106from the surrounding thereof. The other side inlet and outlet port112is formed by a plurality of holes provided over the entire circumference of the lower side surface part of the other side air chamber107. Through this the other side inlet and outlet port112, external air flows into the other side air chamber107from the lower side surface thereof. Consequently, the one side inlet and outlet port111and the other side inlet and outlet port112are so provided as to open in mutually orthogonal directions. This is intended to cause smoke flowing to the photoelectric smoke detector100from any direction to flow in either of the inlet and outlet ports111and112.

Between the one side air chamber106and the storage chamber105, the one side rectifying light blocking means115is provided. This one side rectifying light blocking means115is means adapted to prevent entry of disturbance light into the interior space (storage chamber105) and also form, in cooperation with the other side rectifying light blocking means116, 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 port111into the storage chamber105via the one side air chamber106, penetrate through the detection area AR described above, and extend to the other side inlet and outlet port112via the other side air chamber107. More specifically, the one side rectifying light blocking means115is formed by an inflow and outflow port117provided at the central part of the one side air chamber106and the upper inclined surface31aof the light emitting storage part31. This upper inclined surface31ais adapted to rectify air (smoke) which has been once reserved in the one side air chamber106and then has flown into the storage chamber105after being narrowed down by the inflow and outflow port117, and then guide it to the detection area AR. Further, locating the inflow and outflow port117at the central part of the one side air chamber106blocks light entering through the one side inlet and outlet port111by reflecting it into the one side air chamber106so that this light does not enter into the storage chamber105. The inflow and outflow port117is provided with an insect screen118.

The other side rectifying light blocking means116, similarly to the one side rectifying light blocking means115, is means adapted to prevent entry of disturbance light into the interior space (storage chamber105) and also form, in cooperation with the one side rectifying light blocking means115, a flow line of smoke which has penetrated through the detection area AR described above. The other side rectifying light blocking means116is provided at such a position as to face the one side rectifying light blocking means115with the detection area AR therebetween. Further, the other side rectifying light blocking means116is so configured as to rectify smoke flowing into the storage chamber105while 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 port112into the storage chamber105via the other side air chamber107, penetrate through the detection area AR described above, and extend to the one side inlet and outlet port111via the one side air chamber106. More specifically, the other side rectifying light blocking means116includes: labyrinths51to53provided at an inflow and outflow port109; and the lower inclined surface41a; and the upper inclined surface41b. Further, the labyrinths51to53block light entering through the other side inlet and outlet port112to prevent entry of the light into the detection area AR. Between the storage chamber105and the other side air chamber107, an insect screen60is provided.

The photoelectric smoke detector100configured as described above operates in the following manner.

First, the photoelectric smoke detector100is 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 wall102. The photoelectric smoke detector100is 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 detector100be fitted at a position serving as a smoke passage.

Next, upon flow of generated smoke to the photoelectric smoke detector100, the smoke first enters into the photoelectric smoke detector100through the one side inlet and outlet port111or the other side inlet and outlet port112.

The smoke entering through the one side inlet and outlet port111is reserved in the one side air chamber106and flows into the storage chamber105after being narrowed down at the inflow and outflow port117. The smoke flowing into the storage chamber105is guided by the upper inclined surface31ato pass through the detection area AR, flows to the other side air chamber107through the other side rectifying light blocking means116, and flows out to the outside through the other side inlet and outlet port112.

Then the smoke passing through the detection area AR is detected by the light emitting element30and the light receiving element40, activating an alarm or the like.

The smoke entering through the other side inlet and outlet port112is reserved in the other side air chamber107, and guided by the other side rectifying light blocking means116to pass through the detection area AR, flows to the one side air chamber106through the one side rectifying light blocking means115, and flows out to the outside through the one side inlet and outlet port111.

Then the smoke passing through the detection area AR is detected by the light emitting element30and the light receiving element40, 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 means115and the other side rectifying light blocking means116which are so disposed as to face each other with the detection area AR therebetween. Thus, smoke flowing into the storage chamber105can be effectively led to the detection area AR, thereby improving the detection accuracy.

The one side rectifying light blocking means115and the other side rectifying light blocking means116described 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 casing101is 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 casing101and the one side rectifying light blocking means115and the other side rectifying light blocking means116respectively 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 casing101described above is formed into a cylindrical shape and the light emitting element30and the light receiving element40described above are disposed along the central axis direction of the cylindrical casing101, thus permitting downsizing of the casing101. Further, it is configured such that all the components are stored in the cylindrical casing101, thus permitting further downsizing of the photoelectric smoke detector100. That is, by storing the light emitting element30in the circular-cylindrical casing101along the central axis direction of the casing101and also by providing the one side rectifying light blocking means115and the other side rectifying light blocking means116at such a position in the casing101as 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 detector100.

As a result, the photoelectric smoke detector100can be provided at various places. In particular, the photoelectric smoke detector100can 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 ports111and112described above are formed large, and also the air chambers106and107for temporarily reserving air taken in through the inlet and outlet ports111and112and then delivering it to the rectifying light blocking means115and116are provided between these inlet and outlet ports111and112and the rectifying light blocking means115and116. Thus, this permits external air containing smoke to easily flow into the air chambers106and107through the inlet and outlet ports111and112, be temporarily reserved in the air chambers106and107, and then be efficiently delivered to the rectifying light blocking means115and116.

Moreover, the one side inlet and outlet port111and the other side inlet and outlet port112are so provided as to open in the mutually orthogonal directions. Thus, this permits smoke flowing to the photoelectric smoke detector100from any direction to flow into the inside through either of the inlet and outlet ports111and112, thereby improving the detection accuracy.

INDUSTRIAL APPLICABILITY

In the embodiments described above, the other side inlet and outlet port112is provided at a lower side surface of the casing101, but it may be, as shown inFIG. 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 chamber107. As a result, the smoke detection accuracy can be improved.

In the embodiments described above, the casing101is 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 chamber106and the other side air chamber107are formed as spaces for temporarily reserving external air. However, as shown inFIG. 8, inflow guides121and122may be respectively provided in the one side air chamber106and the other side air chamber107. The inflow guide121is formed into a truncated conical shape (trapezoidal shape cross-sectionally), and adapted to guide air flowing in through a surrounding inlet and outlet port123to the inflow and outflow port117by its conical surface. The inflow guide122is formed into a conical shape, and adapted to guide air flowing in through a surrounding inlet and outlet port124to the inflow and outflow port109by its conical surface.

Here, the inflow guide121is formed in the one side air chamber106so that the cross section of the inflow guide121is trapezoidal-shaped. However, the shape of this inflow guide121is set in accordance with various conditions, such as the dimension of the one side air chamber106, the size of the inflow and outflow port117, and the like. The inlet and outlet port123is formed larger than the inlet and outlet port111of the first embodiment, so that external light easily flows into the one side air chamber106. Moreover, the light emitting element30and the like, and the labyrinths51to53are integrally provided, thus achieving downsizing, which in turn achieves downsizing of the entire photoelectric smoke detector100.

The inflow guide122of the other side air chamber107is 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 chamber107to flow toward the inflow and outflow port109. The shape of this inflow guide122is set in accordance with various conditions, such as the dimension of the other side air chamber107, the size of the inflow and outflow port119, and the like. The inlet and outlet port124is formed larger than an outer circumferential surface of the casing101, thereby making it easy for external air to flow into the other side air chamber107. 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 chamber105is configured to be isolated from external air so that external light does not enter inside. However, as shown inFIG. 9, a sensitivity adjustment part126may be provided. This sensitivity adjustment part126is formed by a hole provided in the casing101. The size, position, and the like of this hole are appropriately set to adjust the sensitivity of the light emitting element30and the light receiving element40.