The present invention concerns a hot air circulating oven range using shape memory alloy springs to drive the damper which changes over the airflow inside the oven.
Shape memory alloys try to return to their original shape when they reach a certain temperature, which enables the use of this material as a spring to drive the opening/closing of a damper depending on temperature.
However, with the normal type of shape memory alloy, the force with which the alloy trys to return to its original shape reduces the effective usage or length of use of the alloy, or in other words the alloy deteriorates, so that when a bias spring is used to keep a damper open, the force with which the shape alloy must pull against this spring to close the damper gradually reduces as it deteriorates, and eventually the force of the shape memory alloy is so small that it cannot overcome the force of the bias spring for closing the damper. This in turn results in a lower thermal efficiency when cooking with the hot air circulation method.