Abstract: An electricity supply device, connected to an electric contact of a heater on a tray, is disposed on the side wall at the upper part of a support member which supports and guides a tray and which is formed on the side wall of a receiving chamber. The electricity supply device has a) a conductive plate spring placed in pressure contact with an electric contact of a heater and b) a conductive pin connected to a power source and is embedded into a plastic mold. The plastic mold is disposed into a casing which is mounted to the side wall of the receiving chamber to secure an insulating property. The plate spring makes positive contact with a contact of the heater.