US3651327A - Radiation sensitive condition responsive system - Google Patents

Radiation sensitive condition responsive system Download PDF

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Publication number
US3651327A
US3651327A US66841A US3651327DA US3651327A US 3651327 A US3651327 A US 3651327A US 66841 A US66841 A US 66841A US 3651327D A US3651327D A US 3651327DA US 3651327 A US3651327 A US 3651327A
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United States
Prior art keywords
condition
capacitor
output signal
frequency
fluctuating
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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US66841A
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English (en)
Inventor
Elihu Craig Thomson
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Electronics Corp of America
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Electronics Corp of America
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N5/00—Systems for controlling combustion
    • F23N5/24—Preventing development of abnormal or undesired conditions, i.e. safety arrangements
    • F23N5/242—Preventing development of abnormal or undesired conditions, i.e. safety arrangements using electronic means
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N5/00—Systems for controlling combustion
    • F23N5/02—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium
    • F23N5/08—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium using light-sensitive elements
    • F23N5/082—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium using light-sensitive elements using electronic means
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N2229/00—Flame sensors
    • F23N2229/08—Flame sensors detecting flame flicker

Definitions

  • condition responsive system comprises a condition sensor n for reducing a fluctuating output signal having a redeter- P I P [22] Filed: Aug.
  • an output device 25, 1970 mined frequency component in response to sensing of the condition to be detected, an output devicea'rranged to assume a [2]] Appl' 66841 first state indicative of the presence of the condition being sensed when the sensor senses the condition and produces the [52] 11.8.
  • CI. ..250/217 F, 250/214 R, 431/79 fluctuating output signal and a second state indicative of the 34 /2282 absence of the condition when the sensor does not produce [51] InLCl.
  • This invention relates to improved control apparatus and more particularly to condition responsive systems such as those useful in supervising fuel burning systems, and to means for insuring fail safe operation of such systems should a component thereof fail.
  • condition responsive systems of the type employed for the supervision of flame in a combustion chamber the system arrangement must reliably and accurately indicate the presence or absence of flame, the absence of flame being promptly detected so that the fuel valve may be closed quickly thus preventing an excessive amount of unburned fuel from accumulating in the combustion chamber. Malfunction of a component of such a system may cause the flame detecting system to falsely indicate the presence of flame and thus create an unsafe condition in the event of flame failure as the system would continue to react as if flame were present.
  • Another object of the invention is to provide a novel and improved combustion supervision system particularly useful with flame sensors responsive to infrared radiation.
  • a condition responsive system comprising a condition sensor for producing a fluctuating output signal having a predetermined frequency component in response to sensing of the condition to be detected, an output device arranged to assume a first state indicative of the presence of the condition being sensed when the sensor senses the condition and produces the fluctuating output signal and a second state indicative of the absence of the condition when the sensor does not produce the fluctuating output signal and means responsive to the fluctuating output signal and connected in circuit between the sensor and the output device including an inductor for blocking signals of higher frequency than the frequency of the fluctuating output signal, a capacitor connected in series with said inductor for blocking signals of lower frequency than the frequency of the fluctuating output signal and a fail safe rectification circuit connected in circuit between the series combination of the capacitor and the inductor and the output device.
  • the system includes frequency selective means which produces a control signal only when signals applied thereto include the predetermined frequency component, and coupling means for applying output signals produced by the condition sensor to the frequency selective means.
  • the frequency selective means produces a fluctuating control signal which alternately applies positive and negative voltages to the inductor. The resulting alternation is passed as an AC signal by the capacitor and is rectified and energizes the control device which in the preferred embodiment is a relay.
  • the sensed condition is fluctuating, either by nature or by electrical modulation and the system is made fail safe by passing the resulting fluctuating signal through the series inductor capacitor circuit and thereafter rectifying it.
  • an amplifier is forced to preserve the fluctuating character of the signal while it amplifies it sufficiently to actuate the output device.
  • a short nor an open circuit can simulate the condition signal for either one will render the amplifier unable to pass amplify the fluctuating signal so that either type of failure is a safe failure, that is the output device will indicate the absence of the condition to be sensed.
  • a static leakage condition in components cannot of itself generate a dynamic signal that can simulate the condition to be sensed.
  • the rectification circuit will either shunt or block that current flow. If the rectification circuit fails, by either open or short circuit or leakage, rectification will be entirely or substantially reduced so that the output device will either be partially or completely deactuated.
  • first shunt diode and a second diode in series between the capacitor and the output device and a second capacitor in shunt across the output device so that the charge required by the first capacitor is transferred to the second capacitor while the shunt diode is blocking and the second capacitor can then be large enough to produce a steady relay current and in addition a deactuation delay.
  • the series inductor in the series circuit effectively blocks power frequency signals (e.g., 60 Hertz) and signals of frequency below the pass band of the series circuit will be blocked by the capacitor. If there is sufficient signal from the condition sensor which in a particular embodiment is a lead sulfide flame sensor, the relay will be held in from the signal within the pass band despite the presence of interfering signal. If there is insufficient signal, however, the presence of an overriding spurious signal will block the response to the fluctuating condition signal and the relay will drop out in a fail safe manner.
  • the condition sensor which in a particular embodiment is a lead sulfide flame sensor
  • the single FIGURE is a schematic diagram of a system for supervising the establishment and maintenance of flame in a supervised combustion chamber.
  • the circuit shown in the drawing includes a transformer 10 having a primary winding 12 which a 115 volt, 60 Hertz signal is applied at terminals 14. Its secondary winding 16 is connected to a full wave rectifier 18 which applies the rectified signal between positive bus 20 and negative bus 22. Capacitor 24 and resistor 26 are connected between buses 20 and 22. Connected to bus 20 by resistor 28 is a subsidiary bus 30 on which the voltage is maintained at plus 7 volts by Zener diode 32. Connected between buses 30 and 22 is a voltage divider network including resistor 34 and a lead sulfide photoresistive flame sensing cell 36 which is arranged to sense the existence of flame in the supervised combustion chamber. Such flame has a fluctuating characteristic within a 5 to 25 Hertz range which characteristic is sensed by photocell 36.
  • the fluctuating output signal from photocell 36 is applied to a first amplification stage that includes transistor 40 and a bridge T null filter in the feedback connection from the collector 42 of transistor 40 to its base electrode 44.
  • the filter network includes capacitors 46 and 48 and resistors 50 and 52.
  • the output of the first amplifier stage is direct coupled to a second amplification stage that includes transistors 54 and 56 and another bridge T filter that provides degenerative feedback to the emitter 58 of transistor 54.
  • That second filter includes capacitors 60 and 62 and resistors 64 and 66. Each filter has a pass band within the 5 to 25 Hertz range of the output signal from photocell 36.
  • the amplified fluctuating flame signal is then coupled by capacitor 70 to a switching circuit that includes transistors 72, 74 and 76.
  • transistor 72 draws base current through resistor 78 from the positive supply bus 20 so that transistor 74 is cut off and transistor 76 is saturated.
  • transistor 74 draws base current in transistor 72.
  • capacitor 70 couples that signal and transistors 72 and 76 are cut off and transistor 74 draws base current through resistor 80 and is switched into conductive state. The result is that the input end of inductor 82 is alternately switched between the positive bus 20 and the negative bus 22 in response to the fluctuating flame signal.
  • lnductor 82 and capacitor 84 form a series circuit tuned to the frequency of the fluctuating flame signal.
  • Inductor 80 is made so that there is a fixed spacing between input and output leads and fixed turn-to-turn and layer-to-layer spacing, and therefore the inductor is as safe from short circuit failure as any two leads in the circuit wiring.
  • lnductor 80 also has enough resistance so that it will limit the current to the shunt diode 86 in case of a short circuit in capacitor 84.
  • Diode 86 is connected in shunt and diode 88 is connected in series between capacitor 84 and coil 90 of output relay.
  • Capacitor 92 is connected across the coil 90.
  • inductor 82 As the input end of inductor 82 is alternately switched between the positive and nega: tive buses 20 and 22 at the frequency of the sensed flame condition, typically about Hertz, the resulting alternation is passed as an AC signal by capacitor 84 and is rectified and charges capacitor 92 so that relay 90'is pulled in.
  • Capacitor 92 provides a 1% second drop out time delay so that the flame flicker signal must be absent for a number of cycles before the relay will drop out.
  • a condition responsive system comprising a radiation sensitive condition sensor for producing a fluctuating output signal having a predetermined frequency component in response to sensing of the condition to be detected
  • an output device arranged to assume a first state indicative of the presence of the condition being sensed when said sensor senses said condition and produces said fluctuating output signal and a second state indicative of the absence of the condition when said sensor does not produce said fluctuating output signal
  • means responsive to said fluctuating output signal and connected in circuit between said sensor and said output device including an inductor for blocking signals of higher frequency than the frequency of said fluctuating output signal, a capacitor connected in series with said inductor for blocking signals of lower frequency than the frequency of said fluctuating output signal and a rectification circuit connected in fail safe cooperation between the series combination of said capacitor and said inductor and said output device.
  • said rectification circuit includes a rectifier device connected in shunt with said capacitor.
  • said rectification circuit further includes a second rectifier connected in series with said capacitor and a second capacitor connected in shunt across said output device.
  • the system as claimed in claim 1 and-further including frequency selective means for producing a control signal only when signals applied thereto include said predetermined frequency component, said frequency selective means including a band pass amplifier tuned to pass signals in the 5 to 25 Hertz range. and coupling means for applying output signals produced by said condition sensing means to said frequency selective means.
  • said rectification circuit includes a rectifier device connected in shunt with said capacitor.
  • said rectification circuit further includes a second rectifier connected in series with said capacitor and a second capacitor connected in shunt across said output device.
  • frequency selective means for producing a control signal only when signals applied thereto include said predetermined frequency component
  • said frequency selective means including a band pass amplifier tuned to pass signals in the 5 to 25 Hertz range, and coupling means for applying output signals produced by said condition sensing means to said frequency selective means.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Fire-Detection Mechanisms (AREA)
  • Control Of Combustion (AREA)
  • Photometry And Measurement Of Optical Pulse Characteristics (AREA)
US66841A 1970-08-25 1970-08-25 Radiation sensitive condition responsive system Expired - Lifetime US3651327A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US6684170A 1970-08-25 1970-08-25

Publications (1)

Publication Number Publication Date
US3651327A true US3651327A (en) 1972-03-21

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Application Number Title Priority Date Filing Date
US66841A Expired - Lifetime US3651327A (en) 1970-08-25 1970-08-25 Radiation sensitive condition responsive system

Country Status (8)

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US (1) US3651327A (xx)
BE (1) BE771614A (xx)
CA (1) CA996660A (xx)
CH (1) CH528703A (xx)
DE (1) DE2142222B2 (xx)
FR (1) FR2103485B1 (xx)
GB (1) GB1348550A (xx)
NL (1) NL7111148A (xx)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3824391A (en) * 1973-05-21 1974-07-16 Central Electr Generat Board Methods of and apparatus for flame monitoring
US3846061A (en) * 1972-03-25 1974-11-05 Lucas Aerospace Ltd Flame-detection circuits
US3852729A (en) * 1973-03-06 1974-12-03 Electronics Corp America Flame failure controls
US3947218A (en) * 1975-01-23 1976-03-30 Honeywell Inc. Safety circuit for monitoring a flickering flame
US4280184A (en) * 1979-06-26 1981-07-21 Electronic Corporation Of America Burner flame detection
US4509041A (en) * 1982-03-22 1985-04-02 The Babcock & Wilcox Company Correlation type flicker flamon
US5567144A (en) * 1995-10-05 1996-10-22 Desa International Inc. Hot surface ignition controller for fuel oil burner
US5899684A (en) * 1997-07-11 1999-05-04 Desa International, Inc. Power phase regulator circuit improvement, motor start switch, self-adjusting preheat and ignition trial improvement, and series-type voltage regulator improvement to hot surface ignition control for fuel oil burner
EP1033535A2 (en) 1999-03-03 2000-09-06 Desa International, Inc. Hot surface ignition controller for fuel oil burner

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2807008A (en) * 1956-05-08 1957-09-17 Scully Signal Co Fail-safe system and technique
US2911540A (en) * 1955-02-14 1959-11-03 Gen Controls Co Flame detection system
US3154724A (en) * 1961-10-09 1964-10-27 Electronics Corp America Combustion control system
US3568074A (en) * 1968-08-01 1971-03-02 Gen Electric Frequency-sensitive circuit

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1389965A (fr) * 1964-04-09 1965-02-19 Fenwal Détecteur de flamme
FR1413496A (fr) * 1964-11-03 1965-10-08 Electronics Corp America Perfectionnements aux appareils de surveillance

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2911540A (en) * 1955-02-14 1959-11-03 Gen Controls Co Flame detection system
US2807008A (en) * 1956-05-08 1957-09-17 Scully Signal Co Fail-safe system and technique
US3154724A (en) * 1961-10-09 1964-10-27 Electronics Corp America Combustion control system
US3568074A (en) * 1968-08-01 1971-03-02 Gen Electric Frequency-sensitive circuit

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3846061A (en) * 1972-03-25 1974-11-05 Lucas Aerospace Ltd Flame-detection circuits
US3852729A (en) * 1973-03-06 1974-12-03 Electronics Corp America Flame failure controls
US3824391A (en) * 1973-05-21 1974-07-16 Central Electr Generat Board Methods of and apparatus for flame monitoring
US3947218A (en) * 1975-01-23 1976-03-30 Honeywell Inc. Safety circuit for monitoring a flickering flame
US4280184A (en) * 1979-06-26 1981-07-21 Electronic Corporation Of America Burner flame detection
US4509041A (en) * 1982-03-22 1985-04-02 The Babcock & Wilcox Company Correlation type flicker flamon
US5567144A (en) * 1995-10-05 1996-10-22 Desa International Inc. Hot surface ignition controller for fuel oil burner
EP0767344B1 (en) * 1995-10-05 2002-02-27 Desa International, Inc. Hot surface ignition controller for fuel oil burner
US5899684A (en) * 1997-07-11 1999-05-04 Desa International, Inc. Power phase regulator circuit improvement, motor start switch, self-adjusting preheat and ignition trial improvement, and series-type voltage regulator improvement to hot surface ignition control for fuel oil burner
US6099295A (en) * 1997-07-11 2000-08-08 Desa International, Inc. Power phase regulator circuit improvement motor start switch self-adjusting preheat and ignition trial improvement and series-type voltage regulator improvement to hot surface ignition controller for fuel oil burner
EP1033535A2 (en) 1999-03-03 2000-09-06 Desa International, Inc. Hot surface ignition controller for fuel oil burner

Also Published As

Publication number Publication date
BE771614A (fr) 1971-12-31
FR2103485A1 (xx) 1972-04-14
CH528703A (de) 1972-09-30
GB1348550A (en) 1974-03-20
CA996660A (en) 1976-09-07
DE2142222A1 (de) 1972-03-02
FR2103485B1 (xx) 1974-08-19
NL7111148A (xx) 1972-02-29
DE2142222B2 (de) 1973-10-31

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