This invention relates generally to microwave ovens and more particularly to a microwave oven having a griddle. 
As is known in the art, some microwave ovens include a griddle, alternatively referred to as a grill or hot bottom.  Such a feature is desirable since it provides browning to the food product otherwise not achieved with microwave cooking.  In one such oven, the griddle is disposed in an aperture in the floor of the cooking cavity. 
In designing such an oven, various factors should be considered.  First, a microwave seal should be provided between the griddle and the adjacent cooking cavity floor to prevent microwave energy from leaking. 
Secondly, provisions should be made for relative movement occurring between the griddle and the cooking cavity floor.  More particularly, such movement may result from the griddle having a different thermal coefficient of expansion than the cavity floor in which it is mounted.  Furthermore, this problem may be aggravated by the relatively high temperatures to which the griddle is heated.  For example, where the griddle is comprised of aluminum and the cooking cavity floor is stainless steel, buckling in the cooking cavity floor could occur if the floor is rigidly attached to the griddle.  This is because aluminum has a higher thermal coefficient of expansion than stainless steel and further because of the relatively high temperature to which the griddle is subjected. 
A third factor to be considered when providing a microwave/griddle oven is that water and/or soap is likely to be used in the oven to clean the griddle and food may spill from the griddle onto the adjacent cooking cavity floor.  Thus, a liquid seal should be provided at the junction between the griddle and the cooking cavity floor. 
Finally, due to the relatively high temperature to which the griddle heats, the adjacent cooking cavity floor and the cooking cavity walls may be excessively heated.  This condition is undesirable since the outer housing of the oven may be concomitantly heated rendering it dangerously hot.  One solution to this problem is to provide insulation between the outer housing and the cooking cavity.  However, this solution may be undesirable due to the additional space required for the insulation and its cost.  Another solution is to increase the air circulation within the oven.  However, this solution may require additional blowers or fans, thereby reducing the power available for cooking.