Flame detector

Claim 2

A flame detector for detecting whether a flame is emitted from an electrically conductive burner member and comprising: an elongated electrically conductive flame rod positioned so as to be within a flame emitted from said burner member; electronic control means having first, second and third electrodes normally in nonconducting condition; circuit means for connecting said first and second electrodes, said bUrner member and said flame rod in a series circuit across an alternating current voltage source, whereby when flame is emitted from said burner member, flame rectified direct current flows through said series circuit for causing conduction of said control means; and output means controlled by conductive condition of said electronic control means for providing an indication as to whether flame rectified direct current flows through said series circuit.

Claim 3

A flame detector as set forth in claim 1 including filtering means for filtering said flame rectified direct current.

Claim 4

A flame detector as set forth in claim 2 including circuit means coupling said filtering means to said electronic means in such a manner to bias said electronic means into conduction when a said flame is present.

Claim 5

A flame detector as set forth in claim 1 wherein said series circuit is coupled across a voltage stepped down secondary winding portion of a transformer having its primary winding connected across an alternating current line voltage source, whereby the value of the alternating current voltage applied between said burner body and said flame rod is substantially less than that of said line voltage source.

Claim 6

A flame detector as set forth in claim 1, wherein said output means includes energizable load control means for operating a load and gating means for energizing said load control means when a said circuit is conductive, indicative of a ''''flame on'''' condition.

Claim 7

A flame detector as set forth in claim 5, including timing means for timing a safe start period and logic circuit means operative during said period to actuate said gating means and, hence, said energizable load control means upon detection of a ''''flame on'''' condition, and circuit disconnect means operative only during said safe start period in response to energization of said load control means to prevent operation of said load.

Claim 8

A flame detector for detecting whether a flame is emitted from an electrically conductive burner member and comprising: an elongated electrically conductive flame rod positioned so as to be with a flame emitted from said burner member; electronic control means having first, second and third electrodes; circuit mans for connecting said first and second electrodes, said burner member and said flame rod in a series circuit across an alternating current voltage source, whereby when flame is emitted from said burner member, flame rectified direct current flows through said series circuit; output means controlled by said electronic control means for providing an indication as to whether a said flame is present in accordance with whether flame rectified direct current flows through said series circuit; and circuit protective means to prevent alternating current from being applied to said electronic control means when said flame rod is short circuited to said burner.

Claim 9

A flame detector for detecting whether a flame is emitted from an electrically conductive burner member and comprising: an elongated electrically conductive flame rod positioned so as to be with a flame emitted from said burner member; electronic control means having first, second and third electrodes; circuit mans for connecting said first and second electrodes, said burner member and said flame rod in a series circuit across an alternating current voltage source, whereby when flame is emitted from said burner member, flame rectified direct current flows through said series circuit; output means controlled by said electronic control means for providing an indication as to whether a said flame is present in accordance with whether flame rectified direct current flows through said series circuit; and circuit protective means to prevent alternating current from being applied to said electronic control means when said flame rod is short circuited to said burner.

Claim 10

A flame detector as set forth in claim 7 wherein said protective means includes a neon lamp coupled between said flame rod and said burner body.

Claim 11

A multiple burner flame failure detector for detecting flame failure of at least one of a plurality of burners and comprising: a plurality of individual flame detector circuit means, each associated with one of said burners and having a ''''flame on'''' condition and a ''''flame off'''' condition in accordance with the actual condition existing at its associated burner; and common output circuit means coupled to and controlled by all of said flame detector circuit means for providing an output indication only when all of said flame detector circuit means are in a particular one of said conditions.

Claim 12

A multiple burner flame failure detector for detecting flame failure of at least one of a plurality of burners and comprising: a plurality of individual flame detector circuit means, each associated with one of said burners and having a ''''flame on'''' condition and a ''''flame off'''' condition in accordance with the actual condition existing at its associated burner; and common output circuit means coupled to and controlled by all of said flame detector circuit means for providing an output indication only when all of said flame detector circuit means are in a particular one of said conditions.

Claim 13

A multiple burner flame failure detector as set forth in claim 9, wherein said common output circuit means includes energizable load control means for controlling a load and gating means for energizing said load control means when all of said flame detector circuit means are in said particular condition.

Claim 14

A multiple burner flame failure detector as set forth in claim 10 wherein all of said flame detector circuit means are coupled to said common output circuit means by circuit means defining an AND circuit.

Claim 15

A multiple burner flame failure detector as set forth in claim 11 wherein said AND circuit has a plurality of inputs, each coupled to one of said flame detector circuit means, and an output coupled to said gating means in said common output circuit means.

Claim 16

A multiple burner flame failure detector as set forth in claim 10 wherein said load control means includes means for switching an alternating current voltage source across a load.

Claim 17

A multiple burner flame failure detector as set forth in claim 10 wherein said load control means includes a relay coil having contacts for switching a voltage source across a load and said gating means includes a transistor having its emitter-collector circuit connected in series with said relay coil.

Claim 18

A multiple burner flame failure detector as set forth in claim 10 including timing means for timing a safe start period and logic circuit means operative during said period to actuate said gating means when any one of said detector circuit means is in a ''''flame on'''' condition to thereby energize said load control means, and circuit disconnect means operative only during said safe start period in response to energization of said load control means to prevent operation of said load.

Claim 19

A multiple burner flame failure detector as set forth in claim 10 wherein each said flame detector circuit means has an output circuit connected in parallel with the output circuits of said other flame detector circuit means; a common resistance circuit connected in series with each of said output circuits across a voltage source; each said output circuit including an impedance means connected in series with an electronic control means for conducting current from said source only when its flame detector circuit means is in a ''''flame off'''' condition, said impedance means exhibiting the characteristic of presenting a relatively high impedance to current flow therethrough until a voltage of at least a given value is applied thereacross, at which time said impedance means exhibits a relatively low impedance to current flow therethrough; said resistance circuit having sufficient resistance so that when a said electronic control means of a first of said output circuits is conducting the value of the voltage applied across said impedance means is at least said given value to cause said impedance to have a said low resistance and thereafter the voltage applied across each of said parallely connected output circuits is below said given value.

Claim 20

A multiple burner flame failure detector as set forth in claim 16 wherein each said impedance means includes a neon lamp, whereby the neon lamp associated with the flame detector circuit means that first exhibits a ''''flame off'''' condition becomes energized to provide a visual indication and the remaining neon lamps are deenergized.

Claim 21

A multiple burner flame failure detector as set forth in claim 9 wherein each said burner is an electrically conductive member and each said flame detector circuit means includes: an elongated electrically conductive flame rod positioned so as to be within a flame emitted from its associated burner; electronic control means having first, second and third electrodes; and circuit means for connecting said first and second electrodes, said burner and said flame rod in a series circuit across an alternating current voltage source, whereby when flame is emitted from said burner, flame rectified direct current flows through said series circuit.

Claim 22

In a flame detector system for detecting flame conditions In at least one burner and having a flame detector circuit associated therewith, said flame detector circuit having a ''''flame on'''' condition and a ''''flame off'''' condition in accordance with the actual condition existing at said burner, a voltage source, an output circuit for connecting said source with a load for energization thereby; the improvement for preventing energization of said load during a safe start time delay period and comprising: circuit means for timing a safe start time delay period; logic circuit means operative only during said time delay period to provide an output signal when said detector circuit is in a ''''flame on'''' condition; first actuatable switching means having a normal current passing condition connected in series with said source and said load; and control means responsive to said output signal to actuate said switching means to a current blocking condition to prevent energization of said load.

Claim 23

In a flame detector system for detecting flame conditions In at least one burner and having a flame detector circuit associated therewith, said flame detector circuit having a ''''flame on'''' condition and a ''''flame off'''' condition in accordance with the actual condition existing at said burner, a voltage source, an output circuit for connecting said source with a load for energization thereby; the improvement for preventing energization of said load during a safe start time delay period and comprising: circuit means for timing a safe start time delay period; logic circuit means operative only during said time delay period to provide an output signal when said detector circuit is in a ''''flame on'''' condition; first actuatable switching means having a normal current passing condition connected in series with said source and said load; and control means responsive to said output signal to actuate said switching means to a current blocking condition to prevent energization of said load.

Claim 24

In a flame detector system as set froth in claim 19 including a second normally nonconductive actuatable switching means connected in series with said voltage source and said first switching means, and said timing means provides a trigger signal upon completion of said time delay period for actuating said second switching means into conduction.

Claim 25

In a flame detector system as set forth in claim 20 wherein said source is an alternating current voltage source and said second switching means is a triac.

Claim 26

In a flame detector system as set forth in claim 20 including means for electrically shunting said first and second switching means upon completion of said safe start time delay period.

Claim 27

A flame detector for detecting whether a flame is emitted from a burner member and comprising: a flame responsive unit with unidirectional current properties and relatively low resistance when flame is present, positioned so as to be in operative relationship to a flame emitted from said burner member; an electronic control means having first, second and third electrodes, normally in nonconducting condition circuit means including a resistor for connecting said first and second electrodes and said flame responsive unit in a series circuit across an alternating voltage source; a filter capacitor bridging the circuit of said first and second electrodes to serve with said resistor as an integrator, the capacitor and resistor having a long time constant in relation to the frequency of the alternating voltage, whereby when flame is emitted from said burner member, rectified direct current starts to flow through said series circuit for causing delayed conduction of said control means.

Claim 28

A flame detector for detecting whether a flame is emitted from a burner member and comprising: a flame responsive unit with unidirectional current properties and relatively low resistance when flame is present, positioned so as to be in operative relationship to a flame emitted from said burner member; an electronic control means having first, second and third electrodes, normally in nonconducting condition circuit means including a resistor for connecting said first and second electrodes and said flame responsive unit in a series circuit across an alternating voltage source; a filter capacitor bridging the circuit of said first and second electrodes to serve with said resistor as an integrator, the capacitor and resistor having a long time constant in relation to the frequency of the alternating voltage, whereby when flame is emitted from said burner member, rectified direct current starts to flow through said series circuit for causing delayed conduction of said control means.