Combustion – Timer – programmer – retarder or condition responsive control
Patent
1987-09-10
1989-09-12
Garrett, Robert E.
Combustion
Timer, programmer, retarder or condition responsive control
431 16, 431 24, 307234, 307518, 307520, F23N 100, F23N 524, H03K 300
Patent
active
048655384
ABSTRACT:
A fail safe drive circuit for enabling the relay which in turn opens the valve for supplying gas to a burner is disclosed and includes a pair of field effect transistors both of which must be operating properly to enable the relay. One transistor receives an enabling input from a rectifier circuit and will be enabled only if the alternating input signal is of sufficient magnitude and repetition rate. The other transistor is turned on and off by the alternating input signal and the gas valve will be turned on only when each of the transistors is operating in its intended mode. The circuit thus discriminates against false enabling signals such as a direct current signal, line voltage signal, a non-repetitive alternating current signal, or other spurious signal.
REFERENCES:
patent: 3299404 (1967-01-01), Yamarone et al.
patent: 4034235 (1977-07-01), Wade
patent: 4113419 (1978-09-01), Cade
patent: 4373139 (1983-02-01), Beesley
patent: 4444551 (1984-04-01), Mueller et al.
patent: 4507702 (1985-03-01), Grewe
patent: 4518345 (1985-05-01), Mueller et al.
patent: 4575333 (1986-03-01), Bryant
patent: 4634367 (1987-01-01), Kasada
patent: 4695246 (1987-09-01), Beilfuss et al.
Scheele Victor F.
Youtz Stephen E.
Garrett Robert E.
Hamilton Standard Controls Inc.
Price Carl D.
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