Traditional convection ovens use a fan to circulate a heated airflow between a fan chamber and an oven chamber. It is known to introduce steam into the circulating airflow downstream of the fan, as shown, for example, in U.S. Pat. Nos. 4,587,946, 4,771,163 and 6,318,246. U.S. Pat. No. 4,771,163 describes a baking oven that injects steam produced by a steam generator adjacent an ingress port through which the airflow enters the oven chamber. The steam generator is shown as an independent unit that provides the steam. Such steam generators are costly and bulky.
U.S. Pat. No. 4,587,946 eliminates a need for a costly steam generator by providing a plurality of metallic plates upon which water is dripped to produce steam, which is inserted into the circulating airflow downstream of the fan.
U.S. Pat. No. 6,318,246 describes a steam generating mechanism for a convection oven. The mechanism comprises a water tube and fan guard disposed at a suction end of the fan. Water is injected into the suction side of the fan and then converted into steam by contact with an electric heater coil disposed about the periphery of the fan blades.
U.S. Pat. No. 6,339,930 describes a convection oven having a laminar airflow in the oven chamber to more efficiently deliver heated convection air above, below and along the sides of a food product. The circulating airflow enters the oven chamber via ingress ports disposed in the four corners of a divider wall and returns along the center of the oven chamber toward a suction port to the fan.
Fans used in convection ovens typically produce a tangential airflow at the high pressure output thereof. The tangential airflow is fraught with turbulence so that it is difficult to obtain an even air pressure in the fan chamber. The turbulent airflow continues through the ingress port to the oven chamber, thereby leading to uneven heating and uneven cooking.
U.S. Pat. No. 4,771,163 also describes a fan having an air diffusing ring about its periphery. The air diffuser ring has a width about equal to the width of the fan chamber with perforations that are shaped and distributed to allow an essentially even flow through the ingress port to the oven chamber, the ingress port surrounding the divider wall between the fan and oven chambers. The air diffuser ring is difficult to make, requires a large footprint within the fan chamber and is a separate unit, thereby adding cost to the convection oven.
Thus, there is a need to provide an improved convection oven with laminar airflow that has a substantially turbulent free airflow.
There is also a need to provide an improved convection oven with moisture that is converted to steam efficiently and at low cost.
There is also a need for an improved fan that produces a radial airflow.
USPTO Backgrounds
USPTO Backgrounds