Self-diagnosing smoke detector assembly

• US 5,821,866 A
• Filed: 08/13/1996
• Issued: 10/13/1998
• Est. Priority Date: 08/19/1993
• Status: Expired due to Term

• Current Assignee: GE Security Incorporated (Carrier Global Corporation)
• Original Assignee: SLC Technologies, Inc. (General Electric Company)
• Inventors: Fischette, Robert Gerard, Johnson, Kirk Rodney, Marman, Douglas Henry, Bernal, Brian Andrew
• Primary Examiner(s): Wu, Daniel J.
• Application Number:
  US08/696,304
• Time in Patent Office: 791 Days
• Field of Search: 340/628, 340/629, 340/630, 340/693, 250/573, 250/574
• US Class Current: 340/630
• CPC Class Codes: G08B 17/107 for detecting light-scattering due to smoke
• CPC Class Codes: G08B 17/113 Constructional details
• CPC Class Codes: G08B 29/145 of fire detection circuits
• CPC Class Codes: G08B 29/20 Calibration, including self-calibrating arrangements

Abstract

A self-contained smoke detector system has internal self-diagnostic capabilities and accepts a replacement smoke intake canopy (14) without a need for recalibration. The system includes a microprocessor-based self-diagnostic circuit (200) that periodically checks sensitivity of the optical sensor electronics (24, 28) to smoke obscuration level. By setting tolerance limits on the amount of change in voltage measured in clean air, the system can provide an indication of when it has become either under-sensitive or over-sensitive to the ambient smoke obscuration level. An algorithm implemented in software stored in system memory (204) determines whether and provides an indication that for a time (such as 27 hours) the clean air voltage has strayed outside established sensitivity tolerance limits. The replaceable canopy is specially designed with multiple pegs (80) having multi-faceted surfaces (110, 112, 114). The pegs are angularly spaced about the periphery in the interior of the canopy to function as an optical block for external light infiltrating through the porous side surface (64) of the canopy and to minimize spurious light reflections from the interior of the smoke detector system housing (10) toward a light sensor photodiode (28). The pegs are positioned and designed also to form a labyrinth of passageways (116) that permit smoke to flow freely through the interior of the housing.

Claims

1. A self-diagnostic smoke detector assembly, comprising:

a signal sampler cooperating with a radiation sensor to produce signal samples indicative of periodic measurements of a smoke obscuration level in a spatial region;

a smoke detector chamber including a base and a field replaceable optical block that are removably attachable to each other and when attached define an interior of the chamber into which smoke particles representing the smoke obscuration level enter, the base supporting the radiation sensor and the optical block including multiple elements that form low impedance labyrinthine passageways for smoke passing to the interior and direct spurious internally reflected light away from the radiation sensor;

a processor receiving and processing the signal samples, the processor comparing the signal samples to multiple threshold values, one of the threshold values representing a smoke obscuration alarm level and another of the threshold values representing a tolerance limit for the radiation sensor, and the processor determining from the signal samples corresponding to smoke obscuration levels that exceed the alarm level and from signal samples corresponding to smoke obscuration levels that exceed the tolerance limit whether the signal samples are indicative of an alarm condition or an out-of-calibration condition of the smoke detector assembly; and

circuitry operatively associated with the processor for producing a tolerance limit signal in response to a determination by the processor whether the signal samples exceed the tolerance limit, the tolerance limit signal being a visible blinking light pulse sequence that changes to distinguish between in-calibration and out-of-calibration conditions of the smoke detector assembly.

2. The assembly of claim 1 in which the optical block has a periphery and each of the multiple elements has surfaces positioned near the periphery of the optical block to prevent external light infiltrating into the chamber from propagating along the labyrinthine passageways into the interior of the chamber.

3. The assembly of claim 1 in which the optical block has a periphery and the multiple elements are angularly spaced around the periphery.

4. The assembly of claim 1 in which the optical block has a surface with a boundary that defines a periphery of the optical block, the multiple elements depending in the same direction from the surface and being angularly spaced around the periphery.

5. The assembly of claim 4 in which the multiple elements and the surface of the optical block are a unitary article molded from the same plastic material.

6. A self-diagnostic smoke detector assembly, comprising:

a signal sampler cooperating with a radiation sensor to produce signal samples indicative of periodic measurements of a smoke obscuration level in a spatial region;

a processor receiving and processing the signal samples, the processor comparing the signal samples to multiple threshold values, one of the threshold values representing a smoke obscuration alarm level and another of the threshold values representing a tolerance limit for the radiation sensor, and the processor determining from the signal samples corresponding to smoke obscuration levels that exceed the alarm level and from signal samples corresponding to smoke obscuration levels that exceed the tolerance limit whether the signal samples are indicative of an alarm condition or an out-of-calibration condition of the smoke detector assembly; and

self-test circuitry operatively associated with the processor for producing in response to an inquiry provided to the smoke detector assembly an indicator signal whenever an out-of-calibration condition exists, the self-test circuitry including memory sites storing a self-test procedure that the self-test circuitry carries out in response to the inquiry, and the indicator signal providing quantitative representations for multiple undersensitive out-of-calibration conditions and multiple oversensitive out-of-calibration conditions of the smoke detector assembly.

7. The assembly of claim 6, further comprising a housing and in which the inquiry provided to the smoke detector assembly is accomplished by manual placement of a magnet near the housing to cause the self-test circuitry to carry out a self-test procedure.

8. The assembly of claim 7, further comprising a reed switch that changes an electrical switching condition in response to the manual placement of the magnet near the housing.

9. The assembly of claim 6 in which the indicator signal is operatively coupled to a visible light indicator that provides different sequences of blinking light pulses in response to different ones of the undersensitive and oversensitive out-of-calibration conditions represented by the indicator signal.

10. The assembly of claim 9, further comprising a housing and in which the visible light indicator is a single light-emitting device that emits light from the housing.

11. The assembly of claim 10 in which the single light-emitting device is a light-emitting diode (LED).

12. A self-diagnostic smoke detector assembly, comprising:

a signal sampler cooperating with a radiation sensor to produce signal samples indicative of periodic measurements of a smoke obscuration level in a spatial region, consecutive ones of the signal samples being separated by a maximum sample time interval;

a processor receiving and processing the signal samples, the processor comparing the signal samples to multiple threshold values, one of the threshold values representing a smoke obscuration alarm level and another of the threshold values representing a tolerance limit for the radiation sensor, and the processor determining from the signal samples corresponding to smoke obscuration levels that exceed the alarm level and from signal samples corresponding to smoke obscuration levels that exceed the tolerance limit whether the signal samples are indicative of an alarm condition or an out-of-calibration condition of the smoke detector assembly; and

a delay timer characterized by an out-of-calibration measurement period that is long relative to the maximum sample time interval, the delay timer producing an out-of-calibration indicator signal after the occurrence of a number of signal samples indicative of an out-of-calibration condition for a time equal to the out-of-calibration measurement period.

13. The assembly of claim 12 in which the maximum sample time interval is in the order of seconds and the out-of-calibration measurement period is in the order of hours.

14. The assembly of claim 12 in which the delay timer begins timing in response to a signal sample that falls outside the tolerance limit and ends timing before conclusion of the out-of-calibration measurement period in response to occurrences of successive signal samples that fall within the tolerance limit.

15. The assembly of claim 12 in which the delay timer includes a first counter that accumulates counts representing successive signal samples in the out-of-calibration condition, the first counter resetting the delay timer whenever there is absent a predetermined number of consecutive signal samples in the out-of-calibration condition.

16. The assembly of claim 12 in which the processor produces an indicator signal to enunciate the existence of an out-of-calibration condition.

17. The assembly of claim 12 in which the radiation sensor produces a sensor signal and in which the signal sampler includes a signal integrator that integrates a sample of the sensor signal over an integration time interval to produce a corresponding signal sample for comparison to the threshold values.

18. The assembly of claim 17, further comprising an analog-to-digital converter cooperating with the integrator to provide a digital signal corresponding to the sensor signal produced by the radiation sensor.

19. The assembly of claim 12 in which the delay timer includes a second counter that accumulates counts representing successive signal samples in the out-of-calibration condition during the out-of-calibration measurement period.

20. The assembly of claim 19 in which the counts accumulated by the second counter represent consecutive signal samples in the out-of-calibration condition.

21. A self-diagnostic smoke detector assembly, comprising:

a signal sampler cooperating with a radiation sensor to produce signal samples indicative of periodic measurements of a smoke obscuration level in a spatial region;

a processor receiving and processing the signal samples, the processor comparing the signal samples to multiple threshold values, one of the threshold values representing a smoke obscuration alarm level and another of the threshold values representing a tolerance limit for the radiation sensor, and the processor determining from the signal samples corresponding to smoke obscuration levels that exceed the alarm level and from signal samples corresponding to smoke obscuration levels that exceed the tolerance limit whether the signal samples are indicative of an alarm condition or an out-of-calibration condition of the smoke detector assembly; and

a smoke detector chamber including a base and a field replaceable optical block that are removably attachable to each other and when attached define an interior of the chamber into which smoke particles representing the smoke obscuration level enter, the base supporting the radiation sensor and the optical block including multiple elements that form low impedance labyrinthine passageways for smoke passing to the interior and direct spurious internally reflected light away from the radiation sensor.

22. The assembly of claim 21 in which the optical block has a periphery and each of the multiple elements has surfaces positioned near the periphery of the optical block to prevent external light infiltrating into the chamber from propagating along the labyrinthine passageways into the interior of the chamber.

23. The assembly of claim 21 in which the radiation sensor supported by the base includes a radiation emitter and a radiation detector each of which having a line of sight, the lines of sight intersecting to form an angle between them.

24. The assembly of claim 21 in which the optical block has a periphery and the labyrinthine passageways receive smoke particles passing through openings at the periphery, the openings being sufficiently small to function as an insect screen.

25. The assembly of claim 21 in which the optical block has a periphery and the multiple elements are angularly spaced around the periphery.

26. The assembly of claim 25 in which the optical block is of cylindrical shape.

27. The assembly of claim 21 in which the optical block has a surface with a boundary that defines a periphery of the optical block, the multiple elements depending in the same direction from the surface and being angularly spaced around the periphery.

28. The assembly of claim 27 in which the multiple elements and the surface of the optical block are a unitary article molded from the same plastic material.

29. The assembly of claim 21 in which consecutive ones of the signal samples are separated by a maximum sample time interval and further comprising:

a delay timer characterized by an out-of-calibration measurement period that is long relative to the maximum sample time interval, the delay timer producing an out-of-calibration indicator signal after the occurrence of a number of signal samples indicative of an out-of-calibration condition for a time longer than the out-of-calibration measurement period.

30. The assembly of claim 29 in which the maximum sample time interval is in the order of seconds and the out-of-calibration measurement period is in the order of hours.

31. The assembly of claim 29 in which the delay timer begins timing in response to a signal sample that falls outside the tolerance limit and ends timing before conclusion of the out-of-calibration measurement period in response to occurrences of successive signal samples that fall within the tolerance limit.

32. The assembly of claim 21, further comprising self-test circuitry operatively associated with the processor for producing in response to an inquiry provided to the smoke detector assembly an indicator signal whenever an out-of-calibration condition exists, the indicator signal providing quantitative representations of undersensitive and oversensitive out-of-calibration conditions of the smoke detector assembly.

33. The assembly of claim 32 in which the indicator signal is operatively coupled to a visible light indicator that provides different sequences of blinking light pulses in response to the undersensitive and oversensitive out-of-calibration conditions represented by the indicator signal.

34. The assembly of claim 33, further comprising a housing and in which the visible light indicator is a single light-emitting device that emits light from the housing.