US 6,717,121 · Granted 2004-04-06

The Microwave Susceptor Patent That Makes Frozen Pie Cook Evenly

Frozen pizza and pot pie companies use special metallic patterns on the bottom of their containers to focus microwave heat exactly where it's needed. This patent describes how to arrange those heat-focusing features so the crust browns perfectly without the filling getting scalding hot, and how to keep the container from falling apart in the microwave.

Curated and verified by the IsItPatented Editorial team

The plain-English version

What it protects

The claim covers a microwave-safe container with a patterned susceptor element—a specially designed metallic layer on the bottom that concentrates microwave energy. What's protected here is the specific arrangement of these microwave-interactive features along curved paths, combined with transparent (non-reflective) zones in the fold region where the bottom meets the sidewall, and transmissive areas in the flange. The patent also covers how the sidewall shields the food's outer edge while allowing the crust to brown appropriately.

Why it matters

Microwave susceptors have been used for decades, but uneven heating causes soggy middles or burnt edges—a persistent consumer complaint. This patent solves that by mapping out exactly where heat should concentrate and where it should be blocked or allowed to pass through. For companies like Graphic Packaging, which supplies frozen-food manufacturers, this design means fewer customer complaints about unevenly cooked products and the ability to guarantee more consistent results across millions of meals shipped every year.

Real-world use

Every time you microwave a frozen pepperoni pizza or chicken pot pie with a crispy crust, the shiny metallic pattern on the container bottom is working to brown that crust while keeping the filling from turning into lava.

Original USPTO abstract

A container has a patterned susceptor region in the bottom, a fold region between the bottom and the sidewall of the container, a sidewall region, and a flange region that forms a flange or lip of the container. The patterned susceptor region includes arrangements of microwave-interactive features disposed generally along respective close plane curves, which reduces overheating and increases the filling temperature of the food product. The fold region contains microwave transparent features that minimize de-lamination of the container in the folded region, and also create a generally transmissive area in the vicinity of the heel of the food product to improve the cooking thereof. The sidewall region shields the periphery of the food product so that it is not overcooked while promoting an appropriate degree of pie dough shell browning. The flange area is transmissive to promote an appropriate degree of cooking of the food product crust.

Patent details

Publication number: US 6,717,121
Filing date: 2001-12-21
Grant date: 2004-04-06
Assignee: Graphic Packaging International, Inc.
Inventor(s): ZENG NEILSON, LAI LAURENCE M. C.
CPC class: H05B6/6494

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