Scattered light type smoke detector

Claim 2

A scattered light type smoke detector adapted to prevent incident light from entering a detector which comprises: (a) a housing to provide a dark chamber; (b) a holder member in said housing; (c) a light source and a photo-cell detector mounted in said housing, said light source and said photo-cell being disposed at an angle such that light from the light source does not directly enter in the photo-cell, and a smoke detecting area is formed in the vicinity of the intersection of the optical axis of the light source and the photo-cell; (d) a first light trap means extending along a surface of said holder member from adjacent said photo-cell to adjacent said smoke detecting area in a plane parallel to the optical axis of said photo-cell, said first light trap means including a serrated wall surface to attenuate incident light or to reflect incident light so as not to enter the photo-cell; (e) a second light trap means disposed circumferentially around the interior walls of a cylindrical recess in which said photo-cell is mounted, said second light trap means including a serrated surface to attenuate or reflect incident light; (f) the edges of the serrated surfaces of first and second light trap means being directed towards each other.

Claim 3

A scattered light type smoke detector as claimed in claim 1, wherein said serrated wall surface comprises a plurality of ridges each having a tip portion formed by a triangular shaped cross-section having an acute angle and an inner portion in which at least one of the triangular walls deviates at a less acute angle.

Claim 4

A scattered light type smoke detector as claimed in claim 1, wherein the light source is contained in a cylindrical recess provided on the smoke detecting holder and a light trap means is provided in the cylindrical recess which includes a serrated surface with its edges directed towards the light source to attenuate incident light or to reflect incident light into a direction not towards the smoke detecting area.

Claim 5

A scattered light type smoke detector as claimed in claim 1, and further comprising shading members including two boards disposed adjacent the smoke detecting area with a space of 10 mm or more therebetween.

Claim 6

A scattered light type smoke detector as claimed in claim 2, wherein the light source is contained in a cylindrical recess provided on the smoke detecting holder and a light trap means is provided in the cylindrical recess which has a serrated surface with edges directed toward the light source to attenuate incident light or to reflect incident light into a direction not towards the smoke detecting area.

Claim 7

A scattered light type smoke detector as claimed in claim 2, and further comprising shading members including two boards disposed adjacent the smoke detecting area with a space of 10 mm or more therebetween.

Claim 8

A scattered light type smoke detector as claimed in claim 4, wherein the light source is contained in a cylindrical recess provided on the smoke detecting holder and a light trap means is provided in the cylindrical recess which has a serrated surface with edges directed toward the light source to attenuate incident light or to reflect incident light into a direction not towards the smoke detecting area.

Claim 9

A scattered light type smoke detector as claimed in claim 5, and further comprising shading members including two boards disposed adjacent the smoke detecting area with a space of 10 mm or more therebetween.

Claim 10

A scattered light type smoke detector adapted to prevent incident light from entering a detector which comprises: (a) a housing to provide a dark chamber; (b) a holder member in said housing; (c) a light source and a photo-cell detector mounted in said housing, said light source and said photo-cell being disposed at an angle such that light from the light source does not directly enter the photo-cell and a smoke detecting area is formed in the vicinity of the intersection of the optical axis of the light source and the photo-cell; (d) a first light trap means including a ridged surface disposed on a surface of the smoke detecting holder extending along the optical axis of the photo-cell, the peaks of the ridges being directed toward the photo-cell for reflecting incident light into a direction so as not to enter the photo-cell; (e) a second light trap means disposed circumferentially around the interior walls of a cylindrical recess in which said photocell is mounted, said second light trap means including a ridged surface the peaks of the ridges directed oppositely to those of the first light trap means to attenuate incident light or to reflect incident light in a direction so as not to enter the photo-cell; (f) said light source and photo-cell being disposed such that their optical axes are inclined downwardly and intersect at an angle of 145°.

Claim 11

A scattered light type smoke detector adapted to prevent incident light from entering a detector which comprises: (a) a housing to provide a dark chamber; (b) a holder member in said housing; (c) a light source and a photo-cell detector mounted in said housing, said light source and said photo-cell being disposed at an angle such that light from the light source does not directly enter the photo-cell and a smoke detecting area is formed in the vicinity of the intersection of the optical axis of the light source and the photo-cell; (d) a first light trap means including a ridged surface disposed on a surface of the smoke detecting holder extending along the optical axis of the photo-cell, the peaks of the ridges being directed toward the photo-cell for reflecting incident light into a direction so as not to enter the photo-cell; (e) a second light trap means disposed circumferentially around the interior walls of a cylindrical recess in which said photocell is mounted, said second light trap means including a ridged surface the peaks of the ridges directed oppositely to those of the first light trap means to attenuate incident light or to reflect incident light in a direction so as not to enter the photo-cell; (f) said light source and photo-cell being disposed such that their optical axes are inclined downwardly and intersect at an angle of 145°.