Combustion – Timer – programmer – retarder or condition responsive control – Control of purger – of scavenger or of combustion start-up...
Reexamination Certificate
2001-12-14
2004-12-28
Cocks, Josiah C. (Department: 3749)
Combustion
Timer, programmer, retarder or condition responsive control
Control of purger, of scavenger or of combustion start-up...
C431S062000, C431S089000, C137S115010
Reexamination Certificate
active
06835062
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to oil burners, and more particularly relates to valve mechanisms for controlling oil flow upon start up and shut down of oil burners.
BACKGROUND OF THE INVENTION
Oil burner units have in the past been provided with regulating valves interposed between the nozzles or nozzle which discharge fuel into the combustion chamber and the fuel pump which supplies fuel oil to the nozzles. Generally, these regulating valves open upon delivery of a predetermined supply pressure from the pump, regulate a substantially constant pressure flow to the burner nozzles, and shut off the supply of fuel oil to the nozzles when the pump is turned off upon shut down. In addition to regulating the pressure of fuel oil delivered to the burner nozzles, these valves often have a bypass function of diverting an excess portion of the fuel oil pressurized and delivered by the pump back to the tank or pump reservoir so that only a portion of the fuel oil supplied by the pump is delivered to the nozzles.
One of the problems that has been dealt with in the past is that transient variations in the fuel oil discharge from the nozzles at startup and/or shutdown cause highly undesirable smoking and soot production in the combustion chamber at these times. One known attempt of remedying this problem has been to arrange a mechanical valve bypass, which typically comprises a diaphragm valve (typically in association with a cone valve) downstream of the fuel pump. For example, mechanical valve bypass mechanisms are shown in U.S. Pat. No. 5,692,680 to Harwath, U.S. Pat. No. 5,145,328 to Harwath, and U.S. Pat. No. 3,566,901 to Swedberg, the entire disclosures of these patents are hereby incorporated by reference. This mechanical valve bypass has an open position that returns fuel oil to the tank or pump reservoir (typically through the diaphragm valve) for moments directly after burner startup and upon loss of pressure upon shut down. When sufficient pressure is present, the mechanical valve bypass closes and fuel is allowed to flow through the regulating valve to the nozzles for combustion.
Although the mechanical valve bypass (e.g. the diaphragm valve) has provided acceptable results with respect to reducing most soot production and smoking in the combustion chamber, there is still some smoking and soot production with this approach. This is due to the fact that the blower of the burner is not fully up to speed when the diaphragm valve closes and fuel oil is ported to the nozzles. A good draft up the chimney is also not established at this point. A less than desirable fuel to air ratio still exists momentarily upon start up using the combination of the cone valve and the diaphragm valve.
Attempts have been made to overcome the drawbacks of mechanical valve bypass mechanisms and to provide for longer fuel oil bypass time periods at burner start up. Specifically, according to some fuel oil supply circuits, the mechanical valve bypasses have been eliminated and replaced with electrical control devices such as solenoid valves, which either block flow or bypass flow through the regulating valves to prevent the regulating valves from opening. This prevents flow to the burner nozzles upon startup. For example, fuel pump units according to this fuel circuit arrangement are commercially available from the present assignee, Suntec Industries, Inc. and sold under SUNTEC MODEL A-7400 FUEL UNIT, SUNTEC MODEL B-8400 FUEL UNIT and SUNTEC MODEL A-2100 FUEL UNIT. With electrical control, it is known to provide the solenoid devices with a thermistor that delays movement of the solenoid valve and thereby prevents the opening of the regulator valve. Longer times periods and hence better control can be achieved with thermistor operated solenoid valves over mechanical valve bypasses.
It is also known to use electronic control over the solenoid instead of thermistors to control opening of the regulating valve. The solenoid valve can be controlled directly by the burner control. This provides more precise or exact control over the opening and closing of the regulating valve and thereby provides better results. One problem that can occur with electrical solenoid valves is that improper installation or incompatible electrical set ups can cause failure of the solenoid to delay fuel oil flow to the nozzles upon burner start up. Improper installation can thus cause the regulating valve to open immediately upon burner start up and thereby result in undesirable smoking and soot production in the combustion chamber.
BRIEF SUMMARY OF THE INVENTION
In view of the foregoing it is a primary objective of the present invention to provide a fuel oil supply circuit for an oil burner that more reliably prevents smoking and/or soot production upon burner start up and/or shutdown.
In accordance with these and other objectives, the present invention is directed toward a fuel oil supply circuit that includes two mechanisms for preventing fuel flows to nozzles at burner startup including an electrical control or solenoid valve in parallel circuit with a mechanical valve bypass. The provision of two mechanisms arranged such that one backs up the other better ensures that smoking and soot production is maintained at acceptable levels in the burner, even if for example, the electrical system fails or is improperly installed.
According to disclosed embodiments of the present invention, the fuel oil supply circuit includes an oil pump that is adapted to pressurize fuel oil and a downstream regulating valve assembly that is adapted to regulate pressurized fuel flow to the nozzles of the burner. The regulating valve assembly has an inlet receiving the pressurized fuel oil and an outlet port connected with the nozzles. A solenoid valve controls flow of pressurized fuel oil through the regulating valve assembly to the nozzles. The solenoid valve has a first state keeping the regulating valve assembly closed, and a second state allowing the regulating valve assembly to open. A diaphragm valve is fluidically connected to the pump in parallel circuit with the regulating piston assembly to provide a backup for the solenoid valve. The diaphragm valve has a first position allowing flow of pressurized oil through a return to the fuel supply and a second position forcing oil to flow to the regulating valve assembly.
According to one embodiment of the present invention the solenoid valve bypasses fuel through a return passage leading back to the fuel supply while in the first state. This causes the fuel pressure to stay sufficiently low in the regulating valve assembly such that the regulating valve is kept closed under the force of a spring.
According to another embodiment of the present invention, the solenoid valve blocks fuel flow and prevents fuel from flowing through an outlet port of the regulating valve assembly. This keeps the regulating valve assembly closed.
Other objectives and advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 3566901 (1971-03-01), Swedberg
patent: 4392810 (1983-07-01), Bears et al.
patent: 4544349 (1985-10-01), Nakamura et al.
patent: 4626194 (1986-12-01), Mills
patent: 5145328 (1992-09-01), Harwath
patent: 5339636 (1994-08-01), Donnelly et al.
patent: 5346174 (1994-09-01), Harwath
patent: 5368068 (1994-11-01), Hunsberger et al.
patent: 5448882 (1995-09-01), Dyer et al.
patent: 5458294 (1995-10-01), Zachary et al.
patent: 5692679 (1997-12-01), Marran et al.
patent: 5692680 (1997-12-01), Harwath et al.
patent: 2 099 130 (1982-12-01), None
patent: 2-13707 (1990-01-01), None
Suntec Industries, Inc. Model A 70 Fuel Unit drawing; prior to Nov. 28, 2001;1 page.
SUNTEC Model A-7400 Fuel Unit Solenoid Dumping Pump drawing; prior to Nov. 28, 2001; 2 pages.
SUNTEC Model A-2100 Fuel Unit Line Blocking Solenoid Pump drawing; prior to Nov. 28, 2001; 1 page.
Hunsberger Dale L.
Mitchell Bill
Zierke David
Cocks Josiah C.
Leydig , Voit & Mayer, Ltd.
Suntec Industries Incorporated
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