Combustion – Process of combustion or burner operation – Controlling or proportioning feed
Reexamination Certificate
1999-08-11
2001-06-12
Yeung, James C. (Department: 3743)
Combustion
Process of combustion or burner operation
Controlling or proportioning feed
C431S089000, C431S189000, C431S265000, C431S351000
Reexamination Certificate
active
06244855
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to burners whose air is supplied by a fan and motor. These include oil burners, gas burners and dual-fuel (gas/oil) burners of any practical size and having air flow adjustment mechanisms.
BACKGROUND OF THE INVENTION
Conventional burners generally include an air tube having a fuel supply conduit (or two for dual fuel) extending axially within the tube. Each fuel supply conduit is connected at one end to a fuel supply pump or gas manifold and terminates at the other end near the end of the air tube where the fuel is dispensed as an oil spray or gas. The fuel is mixed with the air which has been delivered by a motor powered blower. A burner-mounted ignition system is connected to an ignition apparatus that is located adjacent to the fuel nozzle near the exit end of the air tube where it ignites the fuel-air mixture.
Burners of these types employ various mechanisms for adjusting air flow. For example, an oil burner disclosed in U.S. Pat. No. 5,184,949 employs an air gate disposed downstream of the blower for controlling the flow through an air flow passage. This fails to disclose a mechanism to control the total flow while simultaneously controlling the pressure behind the flame retention head, which pressure is important for reliable ignition and flame stability.
SUMMARY OF THE INVENTION
In general, the present invention is directed to a burner comprising a motor driven blower in a housing. An air tube has an inlet end portion and an outlet end portion and may be mounted to the housing. The housing forms an air flow path between the blower and the air tube. In an oil burner, a conduit feeds liquid fuel under pressure to the nozzle at the outlet end portion of the air tube where it sprays the fuel.
One aspect of the invention includes two throttling devices affixed to the fuel conduit coaxial to the air tube, each consisting of a tapered ring and a disk located within the ring and coaxial with it. Throttling together they control the air flow to a value proper for the fuel-input rate. The upstream throttle ring is configured to reduce the upstream pressure to a value determined to provide air to the second plate (the retention plate) to an exit velocity just low enough for reliable ignition and flame stability.
Both throttle rings may have tapers that are converging or diverging. Both minimum and maximum firing rates may be achieved by configuring the cones properly. The adjustment direction for converging and diverging cones should be opposite to one another however.
A mechanism is connected to the fuel conduit (a portion of which is preferably external to the housing) to accurately move it axially, thereby controlling the positions of the rigidly affixed throttle plate and the retention plate simultaneously. Consequently, only a single adjustment setting is needed for any firing rate within the range of the burner.
Referring to more specific features of the invention, the air flow control device adjusts the flow rate and two pressures in the air tube, P1 and P2. P1 is the pressure delivered by the blower. It is high at low flows and diminishes more or less uniformly as the flow increases. P2 is the pressure after the first air flow restrictor, and should be quite low at low rates and gradually higher at higher rates to assure good ignition and stability as the air accelerates through the second air flow restrictor to the flame zone where the pressure is near zero. This means that the throttle ring should close down to the throttle plate at the minimum setting where P1 is high, and should open up rapidly with the flow rate as P1 falls while P2 needs to rise.
A preferred configuration of the first air flow restrictor consists of a round throttle plate surrounded concentrically by a throttle ring, forming a venturi which is carefully configured to maintain P2 as described above. A preferred configuration of the second restrictor consists of a round retention head surrounded by a conical retention ring, forming a venturi, which is tapered to produce the minimum and the maximum flow rates required while P2 varies as specified for stability. In the preferred embodiment, the throttle plate and the retention plate are affixed to the fuel conduit and concentric with the air tube and at a fixed axial distance apart. Also, the throttle ring and retention head are affixed to the air tube at the same fixed axial distance apart. As the adjusting mechanism moves the fuel conduit axially, the throttle plate and retention plate are displaced equally within their respective concentric rings to accurately control the flow and maintain P2 for stable combustion and reliable ignition.
An added advantage of this invention relates to the improved uniformity and higher combustion efficiency of the flame. This results from improved air distribution in the air tube after the throttle where air approaches the flame retention head. To enhance this, several holes are incorporated in the throttle plate.
The present invention advantageously enables air pressure to be simply yet precisely controlled with the air flow control device. A user need not make an adjustment near the blower and a separate adjustment in the air tube. Instead, one air flow control device may be used to meter air pressure and air flow at locations near the nozzle and between the blower and the nozzle. This advantageously achieves a desirable range of pressure near the nozzle and results in uniform air flow. The present invention advantageously may adjust air pressure and flow to a desired level using only the air flow control device, although additional adjustment mechanisms may be used, if desired.
In a preferred embodiment of the present invention, the burner includes an air flow control device comprising a first air flow restrictor disposed between the blower and the nozzle, a second air flow restrictor disposed downstream of the first air flow restrictor relative to the direction of air flow, and a mechanism adapted to adjust the position of both the first and second restrictor plates to control air flow. The mechanism comprises a component connected to the conduit and a member that engages the component so as to move it precisely in either direction. The mechanism and the connected portion of the conduit are preferably external of the housing.
In one aspect of the invention the mechanism comprises an apertured support that extends outwardly from the housing. The mechanism component comprises an arm that is pivotally connected to the housing. A protrusion extends outwardly from the arm. The member comprises a threaded rod carried in the aperture of the support. Stops may be threadingly fixed on the rod so as to flank the protrusion, wherein rotation of the rod causes the stop members to engage the protrusion and pivotally move the arm.
In another aspect of the invention the mechanism comprises an apertured support that extends outwardly from the housing. The component comprises a threaded rod carried in the aperture of the support and fastened to the conduit. The member comprises internal threads that engage the rod, wherein rotation of the member against the support causes movement of the rod.
In another aspect of the invention, the mechanism comprises an arm that is pivotally connected to the housing. The member comprises a rack and pinion, one of the rack and pinion being connected to the housing and the other of the rack and pinion being connected to the arm. Motion that is imparted relative to the rack and pinion pivotally moves the arm.
Yet another aspect of the invention is directed to the component comprising at least one plate connected to the conduit. The member is eccentric such that movement of each plate is effected by rotating the member. The mechanism preferably comprises a plurality of plates each containing a conduit opening for receiving the conduit and an opening for receiving the member. A location of the conduit opening in one of the plurality of plates may be offset from a location of the conduit opening in another of the plurality of plates. Each plate c
Fisher Len
Laisy John M.
Turk Victor J.
R. W. Beckett Corporation
Watts Hoffman Fisher & Heinke
Yeung James C.
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