Stoves and furnaces – Stoves – Cooking
Reexamination Certificate
2002-01-29
2004-04-13
Basichas, Alfred (Department: 3743)
Stoves and furnaces
Stoves
Cooking
C126S02100R, C432S176000, C432S199000
Reexamination Certificate
active
06718965
ABSTRACT:
BACKGROUND
1. Field of the Invention
The invention relates in general to the field of food preparation ovens, and specifically to a gas “true” convection oven.
2. Description of the Related Art
Convection ovens have long been popular in the cooking industry for both residential and commercial use. Typically, a gas convection oven involves a heat source disposed underneath the oven cavity, and a fan within the cooking cavity to circulate the hot air in the cooking cavity. This arrangement has the disadvantage that the air being blown through the fan is only as hot as the air within the oven cavity. Thus the heating of the food in the oven is uneven and much of the heat from the heat source is lost.
In order to improve the heating efficiency and increase oven temperatures, it was contemplated to provide a heat source in close proximity to the fan such that the air being moved by the fan is hotter than the air within the oven cavity. Thus food products within the oven are heated uniformly by air of a higher temperature, thus increasing heat transfer efficiency between the air and food products and reducing cooking times. This arrangement is typically termed “true convection” in the cooking appliance industry. Essentially, the term “true convection” refers to an oven in which a burner, or heat source is disposed in close proximity to the fan and that the air passing through the fan and into the oven cavity is at a higher temperature than the air within the oven, thus the heat is convectively transferred from the hot, moving air to the food products within the oven.
Such “true” convection environments are typically created with an electric heat source disposed immediately in front of, behind, or surrounding the convection fan. This convection heat source is typically provided in addition to heat sources for standard non-convective baking. This has the result of significantly increasing the cost of the oven due to the fact that the oven must be adapted to operate multiple heat sources of various type and size. When the standard heat source is a gas burner or broiler, the oven must be adapted to operate with both gas and electrical power. Additionally, it is difficult to install a gas burner in close proximity to the fan, as the turbulence caused by the fan will greatly affect flame stability and emission. It has also been difficult to design a gas burner which can function in both fan-on and fan-off conditions.
It is therefore desirable to create a gas “true convection” cooking environment in an oven without the necessity of multiple heat sources, while providing the ability to draw hot air from a heating source with stable combustion conditions.
SUMMARY
Therefore an oven is described herein which is capable of producing a “true convection” environment with a single gas burner disposed underneath the oven bottom in a combustion box, and a flue spout disposed at the rear of the oven and attached to a fan to draw hot air and flue products directly from the burner within the combustion box and blow them into the oven cavity.
Thus, one embodiment of an oven having preferred features and advantages includes an oven comprising an oven cavity defined by a plurality of side walls, a bottom wall, a top wall, a back wall, and a door. A fan compartment is disposed substantially centrally on the back wall, and is defined by a baffle plate spaced forwardly from the back wall, a plurality of rearward-extending flanges, and a portion of the back wall. A centrifugal fan is preferably disposed within the fan compartment, and the baffle plate preferably has a central fan-inlet portion. A combustion box having a front wall, a rear wall, a plurality of side walls and a bottom wall is preferably mounted to an underside of the oven bottom. A tube-type gas burner having a longitudinal axis perpendicular to the oven side walls is preferably disposed in a forward portion of the combustion box. A flue spout is preferably disposed between the baffle plate and the oven cavity, and is preferably adapted to join the fan compartment and the combustion box in fluid communication.
The baffle plate preferably comprises peripheral outlets. In one preferred embodiment, the combustion box bottom comprises a rearward, upward slope, the front side of the combustion box comprises a plurality of primary air inlet holes, and the bottom of the combustion box preferably comprises a plurality of secondary air inlet holes. The oven may include exhaust vents located substantially near the bottom of the back wall. Openings may be formed in the oven bottom to provide direct fluid communication between the oven cavity and the combustion box. In one embodiment, the flue spout comprises an upper portion which covers substantially the entire fan inlet. Alternatively, in another embodiment, the flue spout upper portion covers substantially half of the fan inlet portion of the baffle plate. The fan compartment may also comprise an opening in its top or other flange.
Another embodiment of an oven having preferred features and advantages includes an oven cavity defined by two upright side walls, a bottom, a top, a back wall, and a door, the bottom having openings joining the oven cavity and the combustion box in fluid communication. A baffle plate having a central fan inlet portion and peripheral fan outlet portions preferably forms the front of a fan compartment disposed substantially at the center of the back wall. The fan compartment is preferably defined by the baffle plate, a plurality of rearward-extending flanges, and a portion of the back wall. A centrifugal fan is disposed within the fan compartment. A combustion box having a front wall, a rear wall, a plurality of side walls and a bottom is preferably mounted substantially centrally to an underside of the oven bottom. A flue spout with a solid front wall is preferably disposed between the baffle plate and the oven cavity, and preferably joins the fan compartment and the combustion box in fluid communication. According to this embodiment, the fan inlet is preferably substantially entirely covered by the flue spout. A tube-type gas burner having a longitudinal axis perpendicular to the oven side walls, is disposed in the front of the combustion box.
Additionally, the combustion box bottom may comprise a rearward, upward slope, the front side of the combustion box may comprise a plurality of primary air inlet holes, and/or the bottom of the combustion box may comprise a plurality of primary air inlet holes. The combustion box bottom may additionally comprise a plurality of secondary air inlet holes. The oven may include exhaust vents located substantially near the bottom of the back wall. The oven top preferably does not have a fan compartment attached thereto. The fan compartment may also comprise an opening in its top or other flange.
According to another preferred embodiment, an oven having desired features and advantages may include an oven cavity defined by a plurality of walls, a bottom, a top wall, a back wall, and a door; a combustion box having a plurality of upright walls and a bottom wall, the box being mounted to an underside of the oven bottom; the oven bottom having openings joining the oven cavity and the combustion box in fluid communication; a baffle plate having a central fan inlet and peripheral fan outlets; a fan compartment disposed substantially centrally on the back wall, and defined by the baffle plate, a plurality of rearward-extending flanges, and a portion of the back wall; a centrifugal fan disposed within the fan compartment; a tube-type gas burner disposed substantially near and parallel to the front wall of the combustion box; and a flue spout having a front wall, a top wall, a plurality of rearward-extending sides, and a lower inlet portion, the inlet portion being substantially wider than the top wall, the flue spout being disposed between the baffle plate and the oven cavity such that the inlet portion extends into the combustion box, and the flue spout covers a portion of the fan inlet such that the flue spout is placed in fluid communication wit
Deng Eric H. Y.
Rummel Randy L.
Basichas Alfred
Dynamic Cooking Systems, Inc.
Knobbe Martens Olson & Bear LLP
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