US4988884A — High temperature resistant flame detector

Claim 1

Independent Claim 113 words

A flame detector comprising a single-wall housing containing a flame sensor and circuitry for processing signals produced by said sensor, said housing having a predetermined outer diameter, and a thin, highly thermally reflective coating adhered to an outer surface of said housing for shielding said sensor and said circuitry from high ambient temperatures, whereby said detector is operable at said high ambient temperatures while having an outer diameter that is substantially the same as said predetermined diameter, said detector further comprising a thermally insulating material disposed within said housing and surrounding said circuitry and substantially filling all voids between said housing and circuitry to further protect said circuitry from said high ambient temperatures.

Claim 2

Dependent Claim 113 words

A flame detector comprising a single-wall housing containing a flame sensor and circuitry for processing signals produced by said sensor, said housing having a predetermined outer diameter, and a thin, highly thermally reflective coating adhered to an outer surface of said housing for shielding said sensor and said circuitry from high ambient temperatures, whereby said detector is operable at said high ambient temperatures while having an outer diameter that is substantially the same as said predetermined diameter, said detector further comprising a thermally insulating material disposed within said housing and surrounding said circuitry and substantially filling all voids between said housing and circuitry to further protect said circuitry from said high ambient temperatures.

Claim 3

Dependent Claim 24 words

The detector of claim 1 wherein the thickness of said coating is such as to increase said predetermined diameter by less than 0.3 percent.

Claim 4

Dependent Claim 13 words

The detector of claim 1 wherein said highly reflective coating comprises polished chromium.

Claim 5

Dependent Claim 28 words

The detector of claim 1 wherein a region of said housing supports a window for admitting radiation for detection by said flame sensor, said coating exposing said window.

Claim 6

Dependent Claim 35 words

The detector of claim 4 further comprising an intermediate coating disposed between said outer surface and said highly reflective coating in said region of said window to aid in adhering said window to said housing.

Claim 7

Dependent Claim 16 words

The detector of claim 5 wherein said housing comprises aluminum and said intermediate coating comprises copper.

Claim 8

Dependent Claim 10 words

The detector of claim 5 wherein said window comprises sapphire.

Claim 9

Dependent Claim 13 words

The detector of claim 1 wherein said high ambient temperature is 2000° F.

Claim 10

Dependent Claim 14 words

The detector of claim 1 wherein said circuitry is disposed on a circuit card.

Claim 11

Dependent Claim 22 words

The detector of claim 9 wherein electrical connections between components of said circuitry on said circuit card are made with high-temperature-resistant solder.

Claim 12

Dependent Claim 13 words

The detector of claim 9 wherein said circuit card comprises a high-temperature-resistant material.

Claim 13

Dependent Claim 11 words

The detector of claim 11 wherein said material is G-30 material.

Claim 14

Dependent Claim 220 words

A flame detector comprising a single-wall housing containing a flame sensor and circuitry for processing signals produced by said sensor, said housing having a predetermined outer diameter, and a thin, highly thermally reflective coating adhered to an outer surface of said housing for shielding said sensor and said circuitry from high ambient temperatures. whereby said detector is operable at said high ambient temperatures while having an outer diameter that is substantially the same as said predetermined diameter, wherein said detector detects flames having a predetermined flicker rate range, and said sensor detects radiation within said compartment, said circuitry for processing signals comprising (a) a threshold detector for determining whether said detected radiation has an intensity which exceeds a predetermined threshold intensity, (b) a discriminator for determining whether said radiation that exceeds said threshold has a flicker rate that is within said range, and (c) decision circuitry for determining whether a predetermined number of flickers that occur at a rate within said range have been detected within a variable time interval, and, if so, indicating that a flame is present within said compartment, said interval starting upon detection of an initial flicker and ending after a predetermined delay unless a subsequent flicker is detected during said delay, a detected subsequent flicker extending the variable time interval for a predetermined time period.

Claim 15

Dependent Claim 220 words

A flame detector comprising a single-wall housing containing a flame sensor and circuitry for processing signals produced by said sensor, said housing having a predetermined outer diameter, and a thin, highly thermally reflective coating adhered to an outer surface of said housing for shielding said sensor and said circuitry from high ambient temperatures. whereby said detector is operable at said high ambient temperatures while having an outer diameter that is substantially the same as said predetermined diameter, wherein said detector detects flames having a predetermined flicker rate range, and said sensor detects radiation within said compartment, said circuitry for processing signals comprising (a) a threshold detector for determining whether said detected radiation has an intensity which exceeds a predetermined threshold intensity, (b) a discriminator for determining whether said radiation that exceeds said threshold has a flicker rate that is within said range, and (c) decision circuitry for determining whether a predetermined number of flickers that occur at a rate within said range have been detected within a variable time interval, and, if so, indicating that a flame is present within said compartment, said interval starting upon detection of an initial flicker and ending after a predetermined delay unless a subsequent flicker is detected during said delay, a detected subsequent flicker extending the variable time interval for a predetermined time period.

Claim 16

Dependent Claim 39 words

The detector of claim 13 further comprising a thermally insulating material disposed within said housing and surrounding said circuitry and substantially filling all voids between said housing and circuitry to further protect said circuitry from said high ambient temperatures.

Claim 17

Independent Claim 134 words

A method of fabricating a flame detector having a single-wall housing that contains a flame sensor and circuitry for processing signals produced by said sensor, said housing having a predetermined outer diameter, comprising applying a thin layer of material to an outer surface said housing, and making said layer highly thermally reflective to shield said sensor and said circuitry from high ambient temperatures, whereby said detector is operable at said high ambient temperatures while having an outer diameter that is substantially the same as said predetermined outer diameter, said method further comprising installing said sensor and said circuitry in said housing with a thermally insulating material in said housing to surround said circuitry and substantially fill all voids between said housing and circuitry and to further protect said circuitry from said high ambient temperatures.

Claim 18

Independent Claim 134 words

A method of fabricating a flame detector having a single-wall housing that contains a flame sensor and circuitry for processing signals produced by said sensor, said housing having a predetermined outer diameter, comprising applying a thin layer of material to an outer surface said housing, and making said layer highly thermally reflective to shield said sensor and said circuitry from high ambient temperatures, whereby said detector is operable at said high ambient temperatures while having an outer diameter that is substantially the same as said predetermined outer diameter, said method further comprising installing said sensor and said circuitry in said housing with a thermally insulating material in said housing to surround said circuitry and substantially fill all voids between said housing and circuitry and to further protect said circuitry from said high ambient temperatures.

Claim 19

Dependent Claim 32 words

The method of claim 15 wherein said applying step comprises applying a base layer of material over said outer surface, and then applying a finish layer of material over said base layer.

Claim 20

Dependent Claim 22 words

The method of claim 16 wherein said step of making said layer highly thermally reflective comprises polishing said finish layer of material.

Claim 21

Dependent Claim 13 words

The method of claim 16 wherein said base layer of material comprises nickel.

Claim 22

Dependent Claim 13 words

The method of claim 16 wherein said finish layer of material comprises chromium.

Claim 23

Dependent Claim 61 words

The method of claim 15 wherein said housing is further adapted to support a window in a region of said housing for admitting radiation for said sensor, and said method further comprises, before said applying step, applying an intermediate layer of material over said housing in at least said region, securing said window to said housing using said intermediate material layer.

Claim 24

Dependent Claim 19 words

The method of claim 20 further comprising applying said intermediate layer of material over other regions of said housing.

Claim 25

Dependent Claim 13 words

The method of claim 21 further comprising buffing said intermediate layer of material.

Claim 26

Dependent Claim 12 words

The method of claim 21 wherein said intermediate material layer comprises copper.

Claim 27

Dependent Claim 140 words

Apparatus for detecting a flame in a compartment, the flame having a predetermined flicker rate range, comprising a sensor for detecting radiation within said compartment, a threshold detector for determining whether said detected radiation has an intensity which exceeds a predetermined threshold intensity, a discriminator for determining whether said radiation that exceeds said threshold has a flicker rate that is within said range, and decision circuitry for determining whether a predetermined number of flickers that occur at a rate within said range have been detected within a variable time interval, and, if so, indicating that a flame is present within said compartment, said interval starting upon detection of an initial flicker and ending after a predetermined delay unless a subsequent flicker is detected during said delay, a detected subsequent flicker extending the variable time interval for a predetermined time period.

Claim 28

Dependent Claim 140 words

Apparatus for detecting a flame in a compartment, the flame having a predetermined flicker rate range, comprising a sensor for detecting radiation within said compartment, a threshold detector for determining whether said detected radiation has an intensity which exceeds a predetermined threshold intensity, a discriminator for determining whether said radiation that exceeds said threshold has a flicker rate that is within said range, and decision circuitry for determining whether a predetermined number of flickers that occur at a rate within said range have been detected within a variable time interval, and, if so, indicating that a flame is present within said compartment, said interval starting upon detection of an initial flicker and ending after a predetermined delay unless a subsequent flicker is detected during said delay, a detected subsequent flicker extending the variable time interval for a predetermined time period.

Claim 29

Dependent Claim 48 words

The apparatus of claim 24 wherein said threshold detector comprises a comparator that produces signal events whenever said detected radiation exceeds said threshold intensity, said discriminator responding to said signal events by producing output pulses at a rate no higher than a selected flicker rate in said range.

Claim 30

Dependent Claim 38 words

The apparatus of claim 25 wherein said decision circuitry further comprises a counter for counting said output pulses from said discriminator whenever an enable signal is maintained, said counter being reset in the absence of said enable signal.

Claim 31

Dependent Claim 50 words

The apparatus of claim 26 wherein said decision circuitry responds to said signal events by producing said enable signal in response to an initial signal event and maintaining said enable signal as long as successive ones of said signal events are produced at time intervals not exceeding said predetermined delay.

Claim 32

Dependent Claim 35 words

The apparatus of claim 27 wherein said decision circuitry further comprises circuitry for indicating the presence of a flame in said compartment if said counter has counted a predetermined number of said discriminator output pulses.

Claim 33

Dependent Claim 18 words

The apparatus of claim 25 wherein said predetermined flicker rate range is between 3 Hz and 15 Hz.

Claim 34

Dependent Claim 14 words

The apparatus of claim 29 wherein said selected flicker rate is approximately 4 Hz.

Claim 35

Dependent Claim 16 words

The apparatus of claim 24 wherein said predetermined number of flickers is between 2 and 8.

Claim 36

Dependent Claim 13 words

The apparatus of claim 31 wherein said predetermined number of flickers is 5.

Claim 37

Dependent Claim 16 words

The apparatus of claim 24 wherein said predetermined delay is between one second and ten seconds.

Claim 38

Dependent Claim 12 words

The apparatus of claim 33 wherein said predetermined delay is 2.5 seconds.

Claim 39

Dependent Claim 63 words

The apparatus of claim 24 further comprising circuitry for applying a DC bias level to said sensor to cause said sensor to produce output signals reference to said bias level, circuitry for amplifying said output signals and for removing the DC component of said amplified output signals, and means for applying said amplified output signals without the DC component to said threshold detector

Claim 40

Dependent Claim 31 words

The apparatus of claim 24 wherein said sensor is sensitive to infrared radiation and further comprises a spectral filter for passing only radiation within a predetermined wavelength range of said flame.

Claim 41

Dependent Claim 17 words

The apparatus of claim 36 wherein said predetermined wavelength range is between 4 microns and 5 microns.

Claim 42

Dependent Claim 13 words

The apparatus of claim 36 wherein said predetermined wavelength range is 4.3 microns.

Claim 43

Dependent Claim 11 words

The apparatus of claim 24 wherein said sensor comprises a thermopile.

Claim 44

Dependent Claim 14 words

The apparatus of claim 39 wherein said thermopile includes at least one bismuth-antimony junction.

Claim 45

Dependent Claim 12 words

The apparatus of claim 24 wherein said sensor comprises a pyroelectric device.

Claim 46

Dependent Claim 12 words

The apparatus of claim 24 wherein said sensor comprises a photoresistive device.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1994-01-28	1994-07-30	1995-01-29	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1998-01-28	1998-07-30	1999-01-29	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2002-01-28	2002-07-30	2003-01-29	$7700.00	Window Closed / Lapsed

High temperature resistant flame detector

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