Fluid handling – Combustion failure responsive fuel safety cut-off for burners – Thermo-electric
Reexamination Certificate
1999-11-10
2001-05-22
Lee, Kevin (Department: 3753)
Fluid handling
Combustion failure responsive fuel safety cut-off for burners
Thermo-electric
C137S614110, C251S111000
Reexamination Certificate
active
06234189
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a gas valve. More particularly this invention concerns such a valve used on a household or commercial heater or stove and provided with a thermoelectric safety system that shuts off flow through the valve if the burner or the like controlled by it goes out.
BACKGROUND OF THE INVENTION
It is standard to provide a gas-control valve assembly with a safety-shutoff system that comprises a thermoelectric sensor positioned at the flame fed by the valve, a safety cutoff valve, and a solenoid system that holds the cutoff valve open so long as the sensor detects heat. To start, the valve knob is typically pressed in against a spring force to override the safety cutoff so that gas can flow to the burner and be ignited, whereupon the heat detected by the sensor will actuate the solenoid to hold the safety valve open and allow the knob to be released. If the burner does not ignite, releasing the knob will cut off gas flow, and if the burner goes out at a later time, the safety cutoff will close to cut off gas flow.
While such a system is well known and considered fairly intuitive and user-friendly, it has the disadvantage that the valve-control knob must be offset sufficiently from the control panel or the like it is mounted on that it can be depressed to override the safety shutoff. This creates an unattractive appearance with the control knob normally standing out, well offset from the surface it is mounted on.
German 29 43 996 proposes a rotary system where the safety shutoff is operated by a cylindrically tubular cam so that rotary action effects the necessary axial displacement to open the shutoff. While operating this system is somewhat easier, not requiring the so-called biaxial movement of both pressing and turning the knob, the knob still moves axially and thus presents the unattractive standing-off appearance of the prior-art systems.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to provide an improved gas valve with a thermoelectric safety shutoff.
Another object is the provision of such an improved gas valve with a thermoelectric safety shutoff which overcomes the above-given disadvantages, that is which uses only rotary movement of the knob to override the safety shutoff and adjust flow through the main valve.
SUMMARY OF THE INVENTION
A gas-valve assembly has according to the invention a housing having an inlet port, an outlet port, and a passage extending between the ports and defining an axis, a valve plug rotatable about the axis in the housing in the passage between a closed end position blocking flow between the ports and an open end position permitting flow between the ports, and a control knob rotatable on the housing and angularly coupled to the valve plug. Structure engaged between the knob and the housing prevents the knob from moving axially relative to the housing while permitting rotation of the knob about the axis relative to the housing. A safety valve in the housing has a valve body displaceable axially between a closed position blocking flow through the passage and an open position permitting flow through the passage. An actuator including a cam with a spiral cam surface generally centered on the axis and a cam follower riding on the cam surface and coupled to the knob displaces the safety-valve body between its positions on rotation of the knob about the axis.
Thus with this system the knob does not move axially at all so that it can sit flush on the control panel. The result is an extremely neat appearance that also does not trap dirt or expose the knob to damage.
The gas-valve assembly further has according to the invention formations inhibiting rotation of the cam about the axis and rotationally coupling the cam follower with the knob. In addition an axially displaceable stem carrying the cam follower has an end engageable with the safety-valve body. The abutment projects radially outward from the stem and the cam is limitedly axially displaceable in the housing. A spring braced axially between the abutment and the stem allows limited axial movement of the stem relative to the abutment and another spring braced axially between the cam and the housing allows limited axial movement of the cam in the housing. The spring between the cam and the housing urges the cam axially outward toward the knob while the spring between the abutment and the stem urges the abutment axially outward toward the knob and away from the safety valve.
The formations inhibiting rotation of the cam in the housing include an axially extending slot in the cam and a radially projecting part of the housing extending into the slot. Furthermore axially extending and interfitting formations angularly couple the knob to the plug. In the open end position the cam follower is at an end of the cam surface. Furthermore the actuator only displaces the safety-valve body into the respective open position in the open end position of the valve plug.
According to the invention a controller including an electromagnet temporarily holds the safety-valve body in the respective open position for a brief time after displacement of the safety-valve body into the open position by the actuator.
REFERENCES:
patent: 3763875 (1973-10-01), Mobus et al.
patent: 5094259 (1992-03-01), Hsu
patent: 5622200 (1997-04-01), Schulze
patent: 5718256 (1998-02-01), Buezis et al.
patent: 5988215 (1999-11-01), Martin et al.
AGT Gas Technology GmbH
Dubno Herbert
Lee Kevin
Wilford Andrew
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