Smoke detector adapted to a smoke sensing apparatus

Abstract

A smoke detector is disclosed which comprises an inner electrode, an intermediate electrode with a hole for passing radioactive rays therethrough, an outer electrode having openings for allowing smoke to flow therethrough, and one radioactive source, the inner and intermediate electrodes forming an inner ionization chamber, the intermediate and outer electrodes forming an outer ionization chamber, the radioactive source being disposed in the inner ionization chamber. A proper quantity of radioactive rays from the radioactive source is applied into the outer ionization chamber through the hole provided in the intermediate electrode.

I claim: 
     
       1. An ionization-type smoke detector .Iadd.having only a single radioactive source, .Iaddend.comprising: an inner electrode provided with .[.a.]. .Iadd.said single .Iaddend.radioactive source; an intermediate electrode having at least one throughhole; and an outer electrode having openings through which smoke can enter; .Iadd.an insulating support member supporting said inner electrode, said intermediate electrode and said outer electrode; and an annular wall means projecting from said support member at a position inwardly of the outer circumference of said support member; .Iaddend.said inner electrode and said intermediate electrode forming an inner ionization chamber in which said radiation source is arranged, said intermediate electrode and said outer electrode forming an outer ionization chamber, said inner ionization chamber being .[.arranged inside.]. .Iadd.located in a topmost portion of .Iaddend.said outer ionization chamber .Iadd.which surrounds the inner ionization chamber, said intermediate electrode being secured to said annular wall means such that the surfaces thereof define said inner ionization chamber.Iaddend., and wherein a necessary quantity of radioactive rays emitted from said radioactive source is introduced directly into said outer ionization chamber through said holes. 
     
     
       2. A smoke detector as defined in claim 1, in which said inner electrode is movable upwardly and downwardly. .[.3. A smoke detector as defined in claim 1, in which said inner electrode is movable upwardly and downwardly..]. .[.4. A smoke detector as defined in claim 1, in which said inner electrode is supported on a supporting member having an annular projecting wall, and wherein said intermediate electrode is secured to 
     
     
        said annular projecting wall..]. 5. An ionization-type smoke detector .Iadd.having only a single radioactive source, .Iaddend.which comprises: an inner ionization chamber; an outer ionization chamber within which said inner chamber is .[.positioned.]. .Iadd.located at a topmost portion thereof.Iaddend.; an intermediate electrode common to both of said chambers and forming a boundary therebetween; an inner electrode positioned within said inner chamber; an outer electrode defining the outer boundary of said outer chamber and having openings therein through which smoke can freely pass; .Iadd.an insulating support member supporting said inner electrode, said intermediate electrode and said outer electrode; and an annular wall means projecting from said support member at a position inwardly of the outer circumference of said support member; .Iaddend.said inner electrode being provided with .[.a.]. .Iadd.single .Iaddend.radioactive source positioned within said inner chamber; .Iadd.said intermediate electrode being secured to said annular wall means such that the surfaces thereof define said inner ionization chamber, .Iaddend.said intermediate electrode including aperture means formed therein .[.for substantially preventing smoke from entering said inner chamber from said outer chamber and.]. .Iadd.for substantially preventing smoke from entering said inner chamber from said outer chamber and .Iaddend.for facilitating the passage of radiation from said inner chamber into said outer chamber in order to improve the ionization efficiency therein, said aperture means comprising an unobstructed hole formed through said intermediate electrode. .[.6. The smoke detector as set forth in claim 5, further comprising: an insulating support member having an annular wall projecting therefrom at a position inwardly of the outer circumference thereof; said intermediate electrode being secured to said annular wall such that the inner surfaces thereof define said inner ionization chamber; the portion of said support member outside said annular wall forming a boundary for said outer ionization chamber; said outer electrode being secured to the outer circumference of said 
     
     
        member..]. .Iadd.7.  A smoke detector as defined in claim 1, in which said annular wall means consists of a projecting annular wall of said support member, the portion of said support member inside said annular wall forming a boundary for the top of said inner ionization chamber; the portion of said support member outside said annular wall forming a boundary for the top of said outer ionization chamber; said outer electrode being secured to the outer circumference of said support member. .Iaddend. .Iadd.8. A smoke detector as defined in claim 1, in which said annular wall means consists of a side wall of said intermediate electrode; the portion of said support member inside said side wall forming a boundary for the top of said inner ionization chamber; the portion of said support member outside said side wall forming a boundary for the top of said outer ionization chamber; said outer electrode being secured to the 
     
     
        outer circumference of said support member. .Iaddend. .Iadd.9.  A smoke detector as defined in claim 5 in which said annular wall means consists of a projecting annular wall of said support member, the portion of said support member inside said annular wall forming a boundary for the top of said inner ionization chamber; the portion of said support member outside said annular wall forming a boundary for the top of said outer ionization chamber; said outer electrode being secured to the outer circumference of said support member. .Iaddend.