Conveyor oven having an energy management system for a modulated gas flow

Abstract

A conveyor oven has a modulating gas valve which raises and lowers the thermal output of a burner that heats the oven. A bypass line passes a minimum amount of gas to prevent the burner from completely shutting down during periods while the oven remains above a threshold demand for more heat. Electrical isolation is provided between temperature controlling devices to prevent an electrical feed back which might otherwise prevent a complete shut down of the oven during hazardous conditions.

Description

This invention relates to conveyor ovens having reduced fuel consumption and with quieter operation, and more particularly to such ovens having an energy management system including a modulated gas flow with a safety feature that isolates electrical controls in order to enhance an integrity of the safety features built into the oven.BACKGROUNDPrior art conveyor ovens are shown in U.S. Pat. Nos. 4,964,392 and 5,277,105 owned by the assignee of this invention and in the references cited on the cover pages of these patents. These and other similar patents may be consulted in order to learn details of how conveyor ovens are constructed and operate. Often—but not always—this type of oven is used to cook or bake pizzas, bread, or the like.Conveyor ovens are devices for automatically baking or cooking food products over timed periods. Normally, they have a conveyor belt which travels through an elongated oven cavity having open ends and at a speed which times the exposure of the food produ...

AI Technical Summary

Benefits of technology

Accordingly, an object of the invention is to cook or bake a better food product by maintaining a closer control over the uniformity of the heat in the oven cavity. Here, an object is to maintain a substantially smooth level of heat after the oven is switched on and continuing throughout the oven operation. In particular, an object is to avoid the peaks and valleys of heat swings as the burner switches on and off as it hunts for the targeted temperature.

Another object is to provide a quieter operation by eliminating a blower-like noise which occurred heretofore as the burner switched on.

Still another object is to provide a universal heat controller which can control either a modulating valve or an on / off valve, thereby eliminating a need for many controllers individually dedicated to specific ovens.

The integrity of the safety features built into the oven is preserved by an isolation in the electrical control circuit between the elements which control the modulating valve and a conditioner which converts signals from sensors into signals which can enable an operation of the modulating valve. This isolation prevents feed back which might otherwise cause the modulating valve to behave in a way which would defeat the shutdown of an on / off safety valve. In order to provide a self-healing of this integrity insuring system, it uses transformers for separating and isolating the modulation valve control and conditioner circuits from an ignition control module.

The advantages of the invention are many. There is an improved reliability and a higher quality bake at a shorter bake time and at a lower average temperature. Since the ovens operate at a lower temperature, the components are in a cooler environment which extends their life. The oven is quieter and the energy management system is more efficient due to a use of the modulating gas valve and to a two-way air return, with less turbulence, creating lower DB noise levels. There is an increased flexibility making it easier to rearrange the fingers for delivering heated air to the food product. There is an ability to add a deck, as volume increases, or to remove a deck if volume falls off. All decks are the same.

Problems solved by technology

Also, the cost of the fuel (natural or propane gas) for the burners is increasing sharply.

Images