Smoke and heat detector incorporating an improved smoke chamber

Claim 2

A smoke detector for detecting the presence of smoke particles within a smoke chamber, said smoke detector comprising: radiation source means including a radiation emitting semiconductor device for transmitting a beam of radiation within said smoke chamber; radiation detector means for receiving radiation scattered from said beam by said smoke particles, said radiation detector means providing a detected signal representative of the concentration of said smoke particles in said smoke chamber; alarm means for generating a warning signal whenever said detected signal indicates that a dangerous concentration of said smoke particles is present within said smoke chamber; and self-test means for electronically simulating a preselected concentration of said smoke particles just sufficient to cause said radiation detector means to enable said alarm means.

Claim 3

A smoke detector for detecting the presence of smoke particles within a smoke chamber, said smoke detector comprising: radiation source means including a radiation emitting semiconductor device for transmitting a beam of radiation within said smoke chamber; radiation detector means for receiving radiation scattered from said beam by said smoke particles, said radiation detector means providing a detected signal representative of the concentration of said smoke particles in said smoke chamber; alarm means for generating a warning signal whenever said detected signal indicates that a dangerous concentration of said smoke particles is present within said smoke chamber; fault detection means for enabling said alarm means responsive to said radiation source being disabled as a result of said light emitting semiconductor device being short-circuited or open circuited; and self-test means for electronically simulating a pre-selected concentration of said smoke particles just sufficient to cause said radiation detector means to enable said alarm means.

Claim 4

A smoke detector for detecting the presence of smoke particles within a smoke chamber, said smoke detector comprising: radiation source means including a radiation emitting semiconductor device for transmitting a beam of radiation within said smoke chamber; radiation detector means for receiving radiation scattered from said beam by said smoke particles, said radiation detector means providing a detected signal representative of the concentration of said smoke particles in said smoke chamber; alarm means for generating a warning signal whenever said detected signal indicates that a dangerous concentration of said smoke particles is present within said smoke chamber; fault detection means for enabling said alarm means responsive to said radiation source being disabled as a result of said light emitting semiconductor device being short-circuited or open circuited; and self-test means for electronically simulating a pre-selected concentration of said smoke particles just sufficient to cause said radiation detector means to enable said alarm means.

Claim 5

A smoke detector for detecting the presence of smoke particles within a smoke chamber, said smoke detector comprising: radiation source means including a radiation emitting device for transmitting a beam of radiation within said smoke chamber; radiation detector means for receiving radiation scattered from said beam by said smoke particles, said radiation detector means providing a detected output signal representative of the concentration of said smoke particles in said smoke chamber; voltage reference means developing a substantially constant reference voltage; comparator means for generating a control signal whenever said detected output signal exceeds said threshold level, said comparator means including a transistor having base, emitter and collector electrodes, said reference voltage being coupled to said emitter electrode for establishing a conduction threshold level for said comparator transistor corresponding to a dangerous concentration of said smoke particles, said detected output signal being coupled from said radiation detection means to said base electrode, said comparator transistor being turned on to generate a control signal at said collector electrode when said base electrode is biased to exceed said conduction threshold responsive to a dangerous concentration of said smoke particles; and alarm means coupled to said collector electrode for generating a warning signal whenever said comparator means generates said control signal.

Claim 6

A smoke detector for detecting the presence of smoke particles within a smoke chamber, said smoke detector comprising: radiation source means including a radiation emitting device for transmitting a beam of radiation within said smoke chamber; radiation detector means for receiving radiation scattered from said beam by said smoke particles, said radiation detector means providing a detected output signal representative of the concentration of said smoke particles in said smoke chamber; voltage reference means developing a substantially constant reference voltage; comparator means for generating a control signal whenever said detected output signal exceeds said threshold level, said comparator means including a transistor having base, emitter and collector electrodes, said reference voltage being coupled to said emitter electrode for establishing a conduction threshold level for said comparator transistor corresponding to a dangerous concentration of said smoke particles, said detected output signal being coupled from said radiation detection means to said base electrode, said comparator transistor being turned on to generate a control signal at said collector electrode when said base electrode is biased to exceed said conduction threshold responsive to a dangerous concentration of said smoke particles; and alarm means coupled to said collector electrode for generating a warning signal whenever said comparator means generates said control signal.

Claim 7

A smoke detector in accordance with claim 3 wherein said radiation detector means includes a photo-conductive field effect transistor (FET) having an output electrode coupled to said comparator base electrode, said voltage reference means being coupled to said FET for biasing said FET to develop a detected output signal voltage at said output electrode proportional to the amouNt of radiation scattered by said smoke particles and impinging on said FET, said FET detected output signal voltage biasing said comparator base electrode to turn on said comparator transistor if said conduction threshold of said comparator transistor is exceeded.

Claim 8

A smoke detector in accordance with claim 4 including fault detection means comprising first and second electronic switch means for enabling said alarm means responsive to said radiation emitting device being short-circuited or open-circuited, said first electronic switch means being coupled between said radiation source means and said voltage reference means to reduce said reference voltage for simultaneously reducing said comparator conduction threshold below the level at which said comparator base electrode is biased and increasing the bias applied to said FET to increase said detected FET output voltage to bias said comparator transistor to conduction responsive to said radiation emitting semiconductor device being short-circuited, said second electronic switch means being coupled between said radiation source means and said comparator base electrode to bias said comparator transistor to conduction responsive to said light emitting semiconductor device being open-circuited, said comparator transistor being turned on responsive to either condition to enable said alarm means despite the absence of a dangerous concentration of said smoke particles.

Claim 9

A smoke detector in accordance with claim 5 wherein said voltage reference means includes a Zener diode and a semiconductor device serially coupled between said conductor emitter electrode and two planes of differing reference potential for establishing said constant voltage threshold level, said FET being coupled to the junction of said Zener diode and said semiconductor device for said bias, said first electronic switch means comprising a diode coupled between said radiation emitting device and the junction of said Zener diode and said semiconductor device, said diode being conductive to reduce said reference voltage applied to said comparator emitter electrode and lower said conduction threshold thereof and to bias said FET to turn-on said comparator transistor if said radiation emitting device is short-circuited.

Claim 10

A smoke detector in accordance with claim 5 wherein said second switch means comprises a diode coupled between said radiation emitting device and said comparator base electrode.

Claim 11

A smoke detector in accordance with claim 4 including test switch means for increasing the bias applied to said FET to electronically simulate a preselected concentration of said smoke particles and cause said FET to develop said detected output voltage signal just sufficient to exceed said comparator threshold level and enable said alarm means, said test switch means being effective to check said radiation detector means, said comparator and said alarm means for proper operation.

Claim 12

A smoke detector in accordance with claim 3 including fault detection means comprising a visible light emitting semiconductor device coupled in parallel with said radiation emitting device, said visible light emitting semiconductor device producing a visual light as long as said radiation emitting device is operative.

Claim 13

A smoke detector in accordance with claim 3 including switch means coupled to said comparator collector electrode for enabling said alarm means responsive to said comparator transistor being turned on.

Claim 14

A smoke detector in accordance with claim 10 including lock-up means for biasing said comparator base electrode to maintain said comparator transistor in a conductive state thereby enabling said alarm means even though the detected signal applied to said base electrode has subsequently dropped below said conduction threshold.

Claim 15

A smoke detector in accordance with claim 11 including a reset switch for overriding said lock-up means and disabling said alarm means after said detected signal has dropped below said conductIon threshold.

Claim 16

A smoke detector in accordance with claim 11 wherein said lock-up means comprises a semiconductor switching device coupled between said comparator collector electrode and said base electrode, said semiconductor switching device being conductive to apply a portion of the output voltage developed at said collector electrode to said base electrode when said comparator transistor is turned on.

Claim 17

A smoke detector in accordance with claim 13 wherein said semiconductor switching device comprises a diode.

Claim 18

A smoke detector in accordance with claim 3 wherein said radiation detector means includes a photoconductive semiconductor device positioned substantially orthogonal to said radiation emitting device for detecting said scattered radiation and developing output signal representative of the concentration of said smoke particles.

Claim 19

A smoke detector in accordance with claim 3 including radiation absorber means positioned on the opposite side of said smoke chamber for absorbing said radiation beam to prevent said beam from being reflected to said radiation detector means, said radiation absorber means insuring that any of said radiation detected by said radiation detector means is a result of scattering said beam by said smoke particles.

Claim 20

A smoke detector in accordance with claim 3 including heat sensor means for detecting dangerous levels of heat and enabling said alarm means, said heat sensor means being independent of said radiation source means and said radiation detector means.