Light scattering type smoke sensor

A light scattering type smoke sensor comprising a holder with openings embedded with light emitting part and light detecting part respectively, which do not protrude into the smoke detection chamber. The optical axis of light emitting part intersects at a predetermined first angle α in the horizontal direction with the optical axis of the light detecting part at a predetermined second angle β in the vertical direction. The optical axis of the light emitting part and optical axis of the light detecting part further comprise a configuration angle δ in the range of 90˜120 degrees used as the supplementary angle for the scattering angle θ. Accordingly, the smoke detection part is further constituted in a thin-shaped light scattering smoke sensor which enables the setup of a scattering angle with no directivity in the smoke influx to the smoke detection chamber.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a light scattering type smoke sensor and more particularly to sensing scattered light caused by smoke particles flowing from the outside into the smoke detection chamber to detect a fire.

2. Description of the Related Art

There is a prior art conventional light scattering type smoke sensor as shown in FIG.4. FIG.4(A) shows the lower part of the sensor main body100of a sensor equipped with a cover102and the smoke detection chamber103where smoke flows into the interior section. The sensor main body100includes a holder104mounted inside the smoke detection chamber103. The light emitting part106and light detecting part108are contained within the holder104and positioned in proximity to opening110and opening112, respectively.

FIG.4(B) shows the light emitting part106radiating light in the direction of optical axis114. The monitoring of scattered light caused by the influx of smoke is carried out in the light detecting part108from the direction of optical axis116.

The light emitting part106and the light detecting part108are disposed so optical axis114intersects with optical axis116on an imaginary horizontal plane. The scattering angle θ of optical axis intersecting point118employs a predetermined setting. At this point the intersecting angle δ of the optical axis supplements the scattering angle θ to determine the configuration angle with the referential of θ=180°−δ.

Furthermore, a light barrier is employed consisting of shielding plate120and shielding plate122. Shielding plate120blocks light from passing directly through to the light detecting part108. Residual direct light reflected from the front side of shielding plate120is further reduced by the back shielding plate122.

Additionally, in this conventional structure as shown in FIG.4(A), the optical axis of the light emitting part106and the light detecting part108are arranged at downward grade of about 3˜5 degrees, and the optical axis intersecting point is adjusted so that it will not be too close to the upper surface of the smoke detection chamber103.

However, in this type of conventional light scattering type smoke sensor, as the light emitting part106, light detecting part108, shielding plate120and shielding plate122protrude into the smoke detection chamber103where the smoke flows in, the possibility of a problem with the directivity in the influx of smoke from the outside is high.

FIG. 5shows a prior art light scattering type smoke sensor which is designed not to have directivity in the smoke inflow to the smoke detection chamber103.

InFIG. 5, the sensor main body200is comprised of a cover202and a smoke detection chamber203into which smoke flows into the main interior cavity. The smoke detection chamber203in the sensor main body200includes a holder204, a light emitting part206and a light detecting part208embedded within opening210and opening212in holder204, and thus the structure does not have directivity in the inflow of smoke.

The light emitting part206gives off scattered light in the direction of optical axis214, and the light detecting part208subjected to light is located in the direction of optical axis216. For this reason, on the imaginary vertical plane inside the sensor, the slanting downward arrangement of optical axis214and optical axis216are positioned so that the light emitting part206and the light detecting part208are not facing each other. The scattering angle θ of optical axis intersecting point218is set at a predetermined angle. In addition, the configuration angle δ has the relation of θ=180 degrees−δ.

On the other hand, as for the type of smoke produced by a fire, the diameter of smoke particles vary from comparatively large to small depending on the burning material. For this reason, let it be one subject there be no difference in the various diameters of smoke particles in respect to sensitivity as much as possible.

It is known that the smoke particle diameter relative to a scattering angle θ of about 60˜90 degrees results in the least sensitivity difference (a configuration angle δ90˜120 degrees) (Japanese Laid-open Kokai Patent Publication (1995) No. Heisei 7-72073).

However, in the conventional structure shown inFIG. 5, if the scattering angle θ is enlarged to about 60 degrees to lessen the sensitivity difference over the diameter of smoke particles, the optical axis intersecting point218drops downward from the installation side holder204. Consequently, as the vertical side of the scattering angle θ cannot be made into a suitable angle range of 60˜90 degrees and to avoid the influence of reflected light from the ceiling side, the height of the sensor (smoke detection part) must be enlarged.

In this case, although a thin-shaped smoke sensor is possible if the interval of the light emitting part206and the light detecting part208are narrowed to form a scattering angle θ of 60˜90 degrees, the problems of electrical induction to the light detecting part or the influence of unacceptable direct light leaking through occurs. Therefore, since it is necessary to separate the light emitting part and the light detecting part as much as possible, along with maintaining a scattering angle θ of 60˜90 degrees without changing the height of the smoke detection chamber, a sensor with a thin-shaped smoke detection part cannot be made.

The purpose of this invention constitutes a thin-shaped smoke detection part, which enables the setup of a scattering angle with no directivity in the smoke influx to the smoke detection chamber.

Furthermore, the light emitting part and light detecting part of the smoke scattering senor are arranged to keep them separated as much as possible to block out direct light.

SUMMARY OF THE INVENTION

The present invention has been made in view of the circumstances mentioned above. To achieve this end and in accordance with the present invention, there is provided a light scattering type smoke sensor comprising a plurality of labyrinth members formed around the periphery of the smoke detection chamber to intercept light entering from the outside and for facilitating the inflow of smoke from the outside, a light emitting part for emitting light toward the smoke detection chamber constituted by the labyrinth members, a light detecting part which receives light scattered by the smoke particles in the smoke detection chamber from the light emitting part, a holder with openings embedded with the light emitting part and the light detecting part which do not protrude into the smoke detection chamber, and the optical axis of the light emitting part intersects at a predetermined first angle α in the horizontal direction with the optical axis of the light detecting part at a predetermined second angle β in the vertical direction.

In other features of the present invention, the optical axes further comprise a configuration angle δ in the range of 90˜120 degrees used as the supplementary angle for the scattering angle θ.

Thus, it is in the sensor structure of this invention, the running out height from the attachment plane side of the optical axis intersecting point to the smoke detection chamber can be made lower and miniaturization of the whole smoke detection part can be further attained.

Moreover, the particle selectivity of smoke can be reduced by setting the scattering angle θ of the optical axis intersecting point for the light emitting part and the light detecting part in the range of 60˜90 degrees.

Furthermore, the running out height of the optical axis intersecting point is low in relation to the attachment plane so as to not approach the light emitting part and the light detecting part. This is necessary to counter well-known problems caused by electrical induction and the influence of direct light leak in the proximity of the light detecting part, which do not occur in the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now toFIG. 1, there is depicted a cross sectional view of the light scattering type smoke sensor constructed in accordance with the first embodiment of the present invention. InFIG. 1, the light scattering type smoke sensor of the first embodiment consists of a sensor main body1and a cover2. In the lower part of the sensor main body1in cover2the smoke detection chamber4is formed, and the smoke generated by a fire flows into the smoke influx entrance3around the periphery of cover2. The holder5is arranged at the upper part of the smoke detection chamber in the sensor main body1. The light emitting part6and light detecting part7are located in holder5.

Openings9and10are separated by light trap11and respectively disposed with the light emitting part6and light detecting part7in the smoke detection chamber4. Encircling holder5in the smoke detection chamber4are labyrinth members12formed around the periphery. The incidence of light from the outside is intercepted while at the same time provides a path for smoke from the outside to flow in easily. The circuit board13is located at the upper part of holder5in the sensor main body1. The circuit board13is attached to and supports holder5, as well as connected to the lead wire of the light emitting part6and light detecting part7to perform emission drive and optical processing.

FIG. 2is a plane view of holder5from the smoke detection chamber4side shown in FIG.1. The holder5encircles the internal smoke detection chamber4with labyrinth members12formed around the periphery to block direct light yet allow smoke to freely flow in from the outside. In the smoke detection chamber4surrounded by labyrinth members12, a light emitting part6and a light detecting part7are embedded in the inner part of openings9and10inward toward the center point of the holder side and arranged facing upwards.

When the optical axis14from the light emitting part6and the optical axis15from light detecting part7are set as illustrated inFIG. 2, they intersect at the configuration angle α (first angle) on a seemingly horizontal plane. The optical axis14of the light emitting part6also has an angle φ (second angle) in the vertical direction, which can be clearly seen from the bottom cross-sectional portion of holder5from the point of intersection O of optical axis14and optical axis15. Similarly optical axis15of the light detecting part7has an angle φ inclination in the vertical direction which can be clearly seen from the upper right cross-sectional portion of holder5embedded with light detecting part7and taken from the O-B section of holder5.

Accordingly, both the light emitting part6optical axis14and light detecting part7optical axis15embedded in holder5have a predetermined angle in the horizontal and vertical directions. Therefore, even if the actual setting of the scattering angle θ is θ=60˜90 degrees, the amount of run out of the optical axis intersecting point0from the holder side5to the smoke detection chamber4is low and a thin-shaped smoke detection part can be realized.

FIG.3(A) is the light emitting part6and the light detecting part7expressed in three-dimensional coordinates showing the optical position relationship corresponding to the installation position in holder5of FIG.2.

In FIG.3(A), a vector shows the light emitting optical axis14of light emitting part6from the light emitting point P, and the vector to light detecting point Q shows the light detecting optical axis15of the light detecting part7in which scattered light makes incidence at the optical axis intersecting point0.

In the smoke sensor structure of the present invention for scattered light type smoke detection, the imaginary optical side forms a triangle which connects light emitting point P, the optical axis intersecting point0, and the light detecting point Q. In this POQ triangle, the horizontal plane is formed by the xy plane and the vertical plane is formed by the zx plane arranged at a certain angle.

For ease of explanation, by projecting up the x-axis of light emitting point P so that it is arranged and becomes projecting point A, the angle of inclination φ in the vertical direction of the light emitting optical axis14serves as the angle for the x-axis in this case.

If the xy plane of light emitting optical axis14and the optical axis15are seen from the horizontal plane, as shown in FIG.3(B), the projecting point A corresponds to the light emitting point P and the projecting point B corresponds to light detecting point Q.

More specifically, the light emitting optical axis14and the light detecting optical axis15are set in the horizontal direction and cross the predetermined angle α. Conversely, the light emitting optical axis14and light detecting optical axis15are projected on plane ABQP, and as shown in FIG.3(C), the light emitting optical axis14and light detecting optical axis15cross the predetermined angle β in the vertical direction.

Then, when the coordinates of the light emitting point P are set to (a1, b1, c1) and the coordinates of light detecting point Q are set to (a2, b2, c2), as shown inFIG. 3, the resulting configuration angle δ, the configuration angle α on a horizontal plane above, the perpendicular angle of orientation φ, and the vertical component configuration angle β of the light emitting optical axis14and light detecting optical axis15projected on plane ABQP are expressed in the following formulas:COS⁢⁢δ=a1⁢a2+b1⁢b2+c1⁢c2a12+b12+c12⁢a22+b22+c22(1)COS⁢⁢α=a1⁢b1+a2⁢b2a12+b12⁢a22+b22(2)tan⁢⁢ϕ=c1a1(3)COS⁢⁢β=c1⁢c2-MM+c12⁢M+c22⁢⁢M=(a1-a2)24+(b1-b2)24(4)

It is evident the configuration angle θ on plane ABQP becomes larger when the perpendicular oriented angle of inclination φ becomes larger as shown in FIG.3. To simplify the explanation below, the configuration angle δ of the light emitting optical axis14and the light detecting optical axis15is described using the perpendicular oriented angle of inclination φ and the configuration angle α on the horizontal plane.

For example, when the perpendicular oriented angle of inclination φ is set to 30 degrees and the light emitting point P coordinates are set to (a1, b1, c1) which are equal to (√3, 0, −1) and the light detecting point Q coordinates are set to (a2, b2, C2) which are equal to (√3/2, 3/2, −1), the resultant configuration angle δ becomes about 97 degrees and the upper horizontal plane configuration angle α becomes 120 degrees based on the above formulas (1) and (2).

Moreover, when the horizontal plane configuration angle α=120 degrees result is maintained and only the perpendicular oriented angle of inclination φ is changed to the light emitting point P coordinates set to (a1, b1, c1) which are equal to (−√3, 0, −0.3) and the light detecting point Q coordinates set to (a2, b2, c2) which are equal to (√3/2, 3/2, −0.3), in this case the resultant angle of inclination φ becomes 9.8 degrees and the actual configuration angle δ becomes about 117 degrees based on the above-mentioned formula (1).

In summary, based on the constant configuration angle α equals 120 degrees, the resultant angle of inclination φ equals 9.8 degrees as opposed to 30 degrees which corresponds to the actual configuration angle δ of 117 degrees as opposed to 97 degrees. Accordingly, when the position of the horizontal direction of the light emitting point P and the light detecting point Q remain unchanged, if the perpendicular oriented angle of inclination φ is enlarged, the relationship which makes the actual configuration angle δ smaller is obtained. If the perpendicular oriented angle of inclination φ is made smaller, of course, the height of the optical axis intersecting point O will be lower and a more thin-shaped smoke sensor.

Furthermore, although the above explanation used the angle of inclination φ, the same can be said of configuration angle β of the vertical component projected on plane ABQP. When the position of the horizontal plane of the light emitting point P and the light detecting point Q remain unchanged, the configuration angle β will be enlarged. As a result, the relevance which makes the actual configuration angle δ smaller is obtained.

As the first embodiment in FIG.2and as shown inFIG. 3expressed in the three-dimensional coordinates, the configuration angle δ of the light emitting optical axis14and light detecting optical axis15is considered as 110 degrees. Thus, using the configuration angle δ equals 110 degrees, the corresponding scattering angle θ equates to θ equals 180 degrees −δ equals 70 degrees.

As described above in the present invention, in the condition in which the optical axis14of light emitting part6and the optical axis15of light detecting part7in holder5are set as configuration angle δ equals 90˜120 degrees (scattering angle θ 60˜90 degrees) and arranged so that the configuration angle α appears in the horizontal plane and the angle of inclination φ in the vertical plane, even at optimum angle arrangement the influence on the sensitivity due to the size of smoke particles is little. The height of the optical axis intersecting point O will be lower and a thin-shaped smoke sensor structure can be realized.

In addition to simplify explanation, although the case whereby the light emitting part and the light detecting part are embedded so that the light emitting optical axis14and light detecting optical axis15can be set up to become equiangular in the vertical angle direction as in the above-mentioned embodiment, on the contrary the light emitting part6and light detecting part7can be embedded so that they may become the angle from which the light emitting optical axis14and a light detecting optical axis15differ in the vertical direction, respectively.

As set forth above in detail, the present invention has the following advantages:

(1) An attachment plane as opposed to smoke for the light emitting part and light detecting part embedded in the holder side and arranged at a predetermined angle in both the horizontal and vertical directions. The scattering angle of the optical axis can be set to a suitable scattering angle which is not influenced by the sensitivity to smoke particles, for example 60˜90 degrees. The running out height from the attachment plane of the optical axis intersecting point to the smoke detection chamber can be made lower and miniaturization of the whole smoke detection part can be further attained.

(2) Moreover, simultaneous with the thin-shape is the ability to set the scattering angle at a suitable range of 60˜90 degrees, thereby mitigating selectivity over smoke particle sensitivity. Furthermore, the light emitting part and the light detecting part can be embedded and installed so that the running out height of the optical axis intersection from the attachment plane to the smoke detection chamber can be made lower, and thereby considered a structure which does not have directivity in the smoke inflow.

While the present invention has been described with reference to the preferred embodiments thereof, the invention is not to be limited to the details given herein.