US Patent 11415324 Electric heater

An electric heater includes a substrate, an inner pattern part, and an outer pattern part positioned outside the inner pattern part and spaced apart from the inner pattern part. The inner pattern part includes a plurality of inner tracks spaced apart from each other and a plurality of inner bridges that connect the plurality of inner tracks to each other in series. The outer pattern part includes a plurality of outer tracks spaced apart from each other and a plurality of outer bridges that connect the plurality of outer tracks to each other in series. A length of one or more of the plurality of inner tracks is longer than a length of each of the plurality of the outer tracks.