Time delayed shut-down circuit for recirculation pump
Patent 3963375 Issued on June 15, 1976. Estimated Expiration Date: 
June 15, 1993. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
June 15, 1993. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent References 2661697 2741986 2741987 2765743 2981195 3030890 InventorApplicationNo. 450300 filed on 03/12/1974US Classes:417/12, Having timer or delay means417/38By liquid pressure sensorExaminersPrimary: Freeh, William L.Assistant: LaPointe, G. P. AbstractA circuit is provided for shutting off the motor of an intermittently activated, electrically powered fluid recirculation pump to prevent the pump motor from burning out its windings or bearings. A power control relay is energized to activate the pump motor for a predetermined period of time, allowing the pump to reach steady state flow condition, after which a time delay relay opens and current flows to the power control relay through a pressure switch. The pressure switch opens to shut-off the recirculation pump motor whenever the pump discharge pressure falls below a predetermined minimum. | |
