| 摘要 |
In a direct ignition gas burner control system wherein two valves are connected fluidically in series with the burner, a make-before-break thermostatically actuated switch is effective, when a set of "cold" contacts are made, to energize an electrical resistance igniter and to open a first of the two valves which opening enables a pressure actuated switch to close its contacts. When the igniter is above a temperature sufficient to ignite gas, the thermostatically actuated switch makes a set of "hot" contacts while its "cold" contacts are still made. In this intermediate contact position, a second of the two valves is opened, allowing gas to flow to the burner. Continued energizing of the igniter causes the thermostatically actuated switch to break its "cold" contacts, effecting de-energizing of the igniter. When the "cold" contacts are open, the pressure actuated switch provides a hold-in circuit for the valves. The transitory intermediate contact position of the thermostatically actuated switch is of sufficient time duration so that, in the event the pressure switch contacts momentarily open due to a drop in pressure when the second valve opens, the valves will remain open.
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