An ear prop prevents a pet’s ears from contacting or substantially contacting food or water in a bowl or dish. By this configuration, the manufacturing process of the oil supply valve assembly is simplified and mis-assembly of the components is prevented by reducing the number of the components. The hardened zone includes first and second hardened areas extending radially from a crest and bottom, respectively, of the thread, to a boundary curve of the hardened zone. The generated ID is transferred to another device and the ID is incremented in each of the devices in the serial interconnection.