Safety ignition control system

Claim 2

A combustion control system comprising a. a burner; b. supply means for supplying fuel to said burner; c. a resistance member comprising a material having a high positive temperature coefficient of electrical resistance disposed to be heated by the combustion of said fuel in said burner whereby said resistance of said member is substantially changed when heated by the combustion of said fuel for a predetermined time; and d. control means responsive to the magnitude of current flow through said resistance member for shutting off the supply of fuel from said supply means to said burner a predetermined time after said fuel is first supplied to said burner during which there is no combustion in said burner.

Claim 3

A system as specified in claim 1 in which a. there is provided ignition means for supplying ignition energy to the supplied fuel during an ignition period, and b. said control means is responsive to the persistence of the magnitude of said resistance at a value below a predetermined value for a predetermined period of time after the beginning of said ignition period.

Claim 4

A combustion control system comprising: a. a burner; b. supply means for supplying fuel to said burner; c. a resistance member comprising a Material having a high positive temperature coefficient of electrical resistance disposed to be heated by the combustion of said fuel in said burner; and d. time delay control means responsive to the magnitude of the resistance of said resistance member for controlling the supply of fuel through said supply means, comprising ignition means for supplying ignition energy to the supplied fuel during an ignition period, said control means being responsive to the persistence of the magnitude of said resistance at a value below a predetermined period of time after the beginning of said ignition period, a time delay relay having a current responsive device in series with a source of voltage and said resistance member, said current responsive device being operative to open a pair of contacts when a current above a predetermined value has passed through said current responsive device for a predetermined time, and a fuel control valve operable by a current responsive device in series with said contacts and a voltage source.

Claim 5

A combustion control system comprising: a. a burner; b. supply means for supplying fuel to said burner; c. a resistance member comprising a Material having a high positive temperature coefficient of electrical resistance disposed to be heated by the combustion of said fuel in said burner; and d. time delay control means responsive to the magnitude of the resistance of said resistance member for controlling the supply of fuel through said supply means, comprising ignition means for supplying ignition energy to the supplied fuel during an ignition period, said control means being responsive to the persistence of the magnitude of said resistance at a value below a predetermined period of time after the beginning of said ignition period, a time delay relay having a current responsive device in series with a source of voltage and said resistance member, said current responsive device being operative to open a pair of contacts when a current above a predetermined value has passed through said current responsive device for a predetermined time, and a fuel control valve operable by a current responsive device in series with said contacts and a voltage source.

Claim 6

A system as specified in claim 3 in which the current responsive devices of said time delay relay and said fuel control valve, said resistance member and said contacts are all in series with a common voltage source.

Claim 7

A system as specified in claim 1 in which the electrical resistivity of said material at the high temperature end of the operating range is substantially greater by a factor of three relative to the electrical resistivity of said material at the low temperature end of the operating range.

Claim 8

A system as specified in claim 1 in which said resistance material is comprised principally of molybdenum disilicide.

Claim 9

In combination: a combustion type heating apparatus; a source of fuel; and a means for ignition and sensing of combustion within said apparatus comprising: serially connected members disposed in communication with the region of combustion within said apparatus; one of said members being dimensioned to provide a low electrical resistivity at the low temperature end of the operating range of the apparatus and serving as the igniter means; the other of said members serving as the sensing means; an electrical control circuit interconnecting said fuel source and said ignition and sensing means to disconnect said fuel source a predetermined period of time after connection of said fuel source in the event of failure of said sensing means to achieve a predetermined high temperature and high electrical resistivity characteristics during said predetermined period of time with a resultant high current in the circuit in excess of a threshold value.

Claim 10

In combination: a combustion type heating apparatus; a source of fuel; and a means for ignition and sensing of combustion within said apparatus comprising: serially connected members disposed in communication with the region of combustion within said apparatus; one of said members being dimensioned to provide a low electrical resistivity at the low temperature end of the operating range of the apparatus and serving as the igniter means; the other of said members serving as the sensing means; an electrical control circuit interconnecting said fuel source and said ignition and sensing means to disconnect said fuel source a predetermined period of time after connection of said fuel source in the event of failure of said sensing means to achieve a predetermined high temperature and high electrical resistivity characteristics during said predetermined period of time with a resultant high current in the circuit in excess of a threshold value.

Claim 11

The combination according to claim 7 wherein the electrical resistivity of said material at the high temperature end of the operating range is substantially greater by a factor of at least about three relative to the electrical resistivity of said material at the low temperature end of the operating range.

Claim 12

The combination according to claim 7 wherein said resistance material comprises principally molybdenum disilicide.

Claim 13

In combination: a combustion type heating apparatus; a source of fuel; and a means for ignition and sensing of combustion within said apparatus comprising: serially connected members of a resistance material having a high positive temperature coefficient of electrical resistance disposed in communication with the region of combustion within said apparatus; one of said members being dimensioned to provide a low electrical resistivity at the low temperature end of the operating range of the apparatus and serving as the igniter means; the other of said members being dimensioned to provide a high electrical resistivity at the high temperature end of the operating range of the apparatus and serving as the sensing means; an electrical time delay control circuit interconnected with the fuel source and said ignition and sensing means to disconnect said fuel source in the event of failure of said sEnsing means to achieve a predetermined high temperature and high electrical resistivity characteristics after a predetermined period of time with a resultant high current in the circuit in excess of a threshold value; a source of electrical potential; means for interruption of the circuit upon the occurrence of a predetermined threshold current value for a predetermined period of time; means for disconnecting said fuel source in response to a predetermined current condition in the circuit; said circuit having an initial high current value resulting in ignition of combustion and a lower average normal running current value resulting from heating of the sensing means by the said electrical control circuit; said circuit interruption means having a threshold value to break the circuit should such a current value be prevalent after a predetermined period of time.

Claim 14

In combination: a combustion type heating apparatus; a source of fuel; and a means for ignition and sensing of combustion within said apparatus comprising: serially connected members of a resistance material having a high positive temperature coefficient of electrical resistance disposed in communication with the region of combustion within said apparatus; one of said members being dimensioned to provide a low electrical resistivity at the low temperature end of the operating range of the apparatus and serving as the igniter means; the other of said members being dimensioned to provide a high electrical resistivity at the high temperature end of the operating range of the apparatus and serving as the sensing means; an electrical time delay control circuit interconnected with the fuel source and said ignition and sensing means to disconnect said fuel source in the event of failure of said sEnsing means to achieve a predetermined high temperature and high electrical resistivity characteristics after a predetermined period of time with a resultant high current in the circuit in excess of a threshold value; a source of electrical potential; means for interruption of the circuit upon the occurrence of a predetermined threshold current value for a predetermined period of time; means for disconnecting said fuel source in response to a predetermined current condition in the circuit; said circuit having an initial high current value resulting in ignition of combustion and a lower average normal running current value resulting from heating of the sensing means by the said electrical control circuit; said circuit interruption means having a threshold value to break the circuit should such a current value be prevalent after a predetermined period of time.

Claim 15

A safety ignition control system for combustion type heating apparatus having a source of fuel comprising: means defining a combustion chamber in said heating apparatus; serially electrically connected ignition and sensing members of a resistance material having a high positive temperature coefficient of electrical resistance exposed to the interior of said combustion chamber; said ignition member being of a reduced cross-sectional area and length relative to said sensing member to provide for a low resistance to current at the low temperature end of the operating range of the apparatus; an electrical time delay control circuit interconnecting said igniter and sensing members and said fuel source including: a source of electrical potential; circuit interruption means having a predetermined minimum current threshold value; electrically actuated means to disconnect said fuel source; said circuit having an initial high current value passing solely through the igniter member to rapidly elevate the temperature thereof to the ignition point of combustion; said circuit further having a lower average normal running current value determined by the heating of the sensing member by the generated combustion heat; and said circuit interruption means being adapted to break the circuit upon failure of combustion and continuance of the circuit current value above the minimum threshold value for a predetermined period of time.

Claim 16

A safety ignition control system for combustion type heating apparatus having a source of fuel comprising: means defining a combustion chamber in said heating apparatus; serially electrically connected ignition and sensing members of a resistance material having a high positive temperature coefficient of electrical resistance exposed to the interior of said combustion chamber; said ignition member being of a reduced cross-sectional area and length relative to said sensing member to provide for a low resistance to current at the low temperature end of the operating range of the apparatus; an electrical time delay control circuit interconnecting said igniter and sensing members and said fuel source including: a source of electrical potential; circuit interruption means having a predetermined minimum current threshold value; electrically actuated means to disconnect said fuel source; said circuit having an initial high current value passing solely through the igniter member to rapidly elevate the temperature thereof to the ignition point of combustion; said circuit further having a lower average normal running current value determined by the heating of the sensing member by the generated combustion heat; and said circuit interruption means being adapted to break the circuit upon failure of combustion and continuance of the circuit current value above the minimum threshold value for a predetermined period of time.

Claim 17

A safety ignition control system according to claim 10, wherein the cross-sectional area and length of said ignition member are approximately one-half of the sensing member similar dimensions.

Claim 18

A temperature responsive device comprising: a. a resistance member comprising a material having a high positive temperature coefficient of electrical resistance disposed to be subjected to an ambient temperature; b. means for supplying a current through said resistance member; and c. means responsive to the magnitude of the resistance of said resistance member for discontinuing said current through said resistance member a predetermined time after said current is first supplied to said resistance member.

Claim 19

A temperature responsive device comprising: a. a resistance member comprising a material having a high positive temperature coefficient of electrical resistance disposed to be subjected to an ambient temperature; b. means for supplying a current through said resistance member; and c. means responsive to the magnitude of the resistance of said resistance member for discontinuing said current through said resistance member a predetermined time after said current is first supplied to said resistance member.

Claim 20

A device as specified in claim 13 in which said temperature indicating means comprises a current responsive device in series with said resistance member and a source of voltage.

Claim 21

A device as specified in claim 13 in which said resistance material is comprised principally of molybdenum disilicide.