FIELD OF THE INVENTION

The invention relates to commercial baking ovens, and more particularly to commercial baking ovens using an endless conveyor.

BACKGROUND OF THE INVENTION Conveyor ovens are increasingly popular in commercial baking. Food to be baked (such as, unbaked loaves of bread) is loaded on a continuous conveyor which passes through a heated oven chamber to emerge in baked form on the other side. In order to be efficient, such ovens must be carefully sealed and insulated to retain heat.

Due to the closed nature of the oven housing, it may be difficult to manage the distribution of heat in the oven chamber, and "hot spots" can result. In the worst case, if excessive heat builds up in a particular area, spontaneous fires can occur. Left unchecked, a fire can cause tremendous damage to the oven, surrounding areas, and may even cause human injury.

Certain types of conveyor ovens have been provided with reflective heat shields or baffles. Often used with radiant heat, these designs reflect heat down onto the food item, which may be desirable for broiling applications (such as for meat). However, this does not provide effective heat distribution for high temperature baking applications, in which it is undesirable to reflect the heat directly onto the food. Such heat shields or baffles would also tend to increase not decrease the fire risk in a high temperature baking application.

The use of stone or ceramic heat sinks in the baking chamber has also been proposed. These materials absorb heat and return it to the baking chamber in an attenuated way. However, under high heat stresses, such materials can fail, causing cracks or crumbling to occur in the stone. Further, such heat sinks are usually provided as a cladding on the walls of the oven. This limits their effectiveness since the slabs are attached to the walls of the oven, and have only one side exposed to the heated baking chamber. There is an outstanding need for a conveyor oven design that can effectively distribute high heat within the oven chamber

SUMMARY OF THE INVENTION According to a first aspect of the invention, a conveyor oven is provided The oven has an oven housing, which has a substantially rectangular box frame, with a top wall and side walls downwardly depending form the top wall, and a bottom wall connecting the side walls Inside the oven housing is an interior baking chamber An exhaust is connected to the baking chamber The oven is heated by a heat source that is capable of heating the baking chamber to a temperature in excess of 700 ⁰ F The oven has an endless conveyor for transporting food items to be baked through the baking chamber

An intermediate panel ceiling assembly is disposed within the baking chamber A plurality of ceiling panel holders are mounted above the conveyor and spaced below the top wall in the baking chamber of the oven Each ceiling panel holder substantially spans the width of the baking chamber The ceiling panel holders each hold at least one ceiling panel The ceiling panel is exposed on both sides to the baking chamber for absorbing and distributing heat in the baking chamber

Preferably, the ceiling panels are insulated boxes having a heat-safe cladding, such as a low-carbon steel Preferably, the boxes are insulated with rock wool They may also be insulated with sand

Each ceiling panel holder has a frame for holding the at least one ceiling panel This frame may be any convenient shape Preferably, the frame is substantially rectangular, having two longer sides and two shorter sides The longer sides are sized to span the width of the baking chamber In one embodiment, the frame preferably has a bowed profile across the width of the baking chamber

Preferably, each ceiling panel holder carries two ceiling panels The ceiling panels may be disposed parallel to each other in the ceiling panel holder, or more preferably, they may be disposed at an angle to each other Preferably, the ceiling panels in the ceiling panel holders are arranged to be non- parallel with the top wall or the bottom wall of the oven housing The ceiling panels are shaped to fit within the ceiling panel holders and may be any convenient shape. However, preferably, they have a substantially planar top surface, and a substantially planar bottom surface.

The frame of the ceiling panel holder preferably has a bottom flange on which the ceiling panels are held. The frame may have a gap beside the ceiling panel or between the ceiling panels to permit combustion products to pass through the ceiling panel holder.

For mounting in the oven, each ceiling panel holder may have a pair of side lips extending outward from the frame to engage with a pair of corresponding rails in the baking chamber. The ceiling panel holders may be mounted in any arrangement that exposes the ceiling panels to the baking chamber. Preferably, the ceiling panel holders are disposed in a line extending substantially over the length of the baking chamber. The ceiling panel holders may be abutted together, or they may be spaced apart. If spaced apart, the ceiling panel holders are preferably disposed at an even spacing from each other over the length of the baking chamber.

The oven itself is preferably heated by gas burners. The heat is preferably zoned.

According to a second aspect of the invention, an intermediate panel ceiling assembly is provided. In the assembly, at least one ceiling panel holder is provided having a frame with mounting edges for mounting in the oven. At least one ceiling panel is held within each ceiling panel holder on flanges of the frame. The flanges carry the at least one ceiling panel without substantially covering a top surface or a bottom surface thereof, such that the ceiling panel is exposed on both sides for absorbing and distributing heat when mounted away from a top wall within a baking chamber of a conveyor oven.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is an end view of a conveyor oven according to the preferred embodiment, showing the intermediate panel ceiling. Fig. 2 is a perspective view of a ceiling panel holder with ceiling panels, showing air and heat flows. Fig. 3 is a top view of a ceiling panel holder with ceiling panels. Fig. 4 is a perspective end view of a ceiling panel holder. Fig. 5 is an isometric end view of a ceiling panel holder and retaining rails. Fig. 6 is a perspective view of a ceiling panel. Fig. 7 is a sectional view of the ceiling panel in Fig. 6.

DETAILED DESCRIPTION OF THE DRAWINGS

A conveyor oven 10 is provided as shown in Figure 1. A conveyor 20 takes unbaked food items 30 and transports them through a baking chamber. The conveyor oven 10 is a high temperature baking oven capable of baking in excess of 700 ⁰ F (and most preferably, in excess of 1000 ⁰ F). This high temperature bake is particularly suited to certain types of flatbreads, particularly naan bread, lavash, and focaccia, wherein a certain amount of charring is considered desirable. The temperature is well above the normal baking temperature of standard loaf breads, muffins, pizza (typically, in the range of 300 ⁰ F to 600 ⁰ F). This high temperature makes the oven particularly susceptible to sudden and very dangerous fires.

The oven housing is basically an insulated box. The housing has a top wall 60 and side walls 40. A bottom wall (not shown) joins the side walls 40 providing a substantially enclosed baking chamber. One or more exhaust stacks 50 are provided. Heat may be provided by gas burners (not shown). Preferably, heat in the baking chamber is "zoned". That is, separate controls are provided for successive "zones" of burners over the length of the oven. This allows fine level of adjustment of the heat profile to promote a better bake.

Within the baking chamber, an intermediate panel ceiling is provided, as shown in Figure 1. The intermediate panel ceiling is mounted to span the width of the baking chamber. It is mounted on the inside of side walls 40 at a distance spaced below the top wall 60, and spaced above conveyor 20 (approximately 12 to 20 inches from the conveyor). The intermediate panel ceiling has heat-safe ceiling panels 80 that absorb and redistribute heat in the baking chamber. The ceiling panels 80 are held in ceiling panel holders 70, as shown in Figures 3 and 4. Each holder has a frame 120 that preferably carries two ceiling panels. The ceiling panel holders 70 preferably have flanges 110 for retaining the ceiling panels in the frame. As shown in Figure 3, the ceiling panels 80 may be retained more or less centrally in the frame 120, having gap openings 100 on either side. These gaps 100 provide a channel for smoky air to escape through the intermediate panel ceiling. As shown in Figure 5, the frames 120 of the ceiling panel holders 70 preferably have side lip flanges 90 that engage corresponding rails/tracks 130 in the oven housing. The ceiling panel holders 70 are preferably mounted in an aligned arrangement along the length of the baking chamber (in abutted or spaced apart relation to each other), such that they serve as an intermediate ceiling in the oven, as shown in Figure 1. The intermediate ceiling may be slightly "domed" as the frames 120 of the panel holders 70 may have a slight bow shape, as shown in Figures 4 and 5. The ceiling panels 80 when held in the panel holders may be at a slight angle to each other due to the bow shape. The overall domed shape of the intermediate ceiling is believed to provide a very stable structure and has good heat redistributing properties. The heat is directed evenly across the dough surface.

The panels 80 themselves may also be bowed, but as shown in the Figures, are not necessarily bowed. These are preferably flat box-shaped structures. As shown in Figures 6 and 7, the panels 80 have a flat top (or bottom) surface 140 and may be reversible. The box is preferably clad with a heat-safe material, such as low-carbon steel (to safely absorb heat and return it safely to the baking chamber). The insulation 150 is preferably sand.

The frames 120 of the ceiling panel holders 70 are designed to retain the ceiling panels near the edges, so that the broad surfaces of the panels 80 are substantially exposed to the baking chamber. The panels absorb heat and re-distribute it over the surface of the panels to minimize hot spots in the oven. Figure 2 illustrates schematically the heat flows (B) over the ceiling panels and air flows (A) through the ceiling panel holder. Smoky air and soot (combustion products) are allowed to escape through gaps 100 for venting through exhaust stack 50. Smoke build-up is a particular concern in high temperature baking as the temperatures are sufficient that singeing of the food readily occurs and small flare-ups are common (and may be desirable - e.g. for slight charring of certain flatbreads, such as naan) in the course of baking.

The foregoing description illustrates only certain preferred embodiments of the invention. The invention is not limited to the foregoing examples. That is, persons skilled in the art will appreciate and understand that modifications and variations are, or will be, possible to utilize and carry out the teachings of the invention described herein. Accordingly, all suitable modifications, variations and equivalents may be resorted to, and such modifications, variations and equivalents are intended to fall within the scope of the invention as described and within the scope of the claims.