For example, in the field of office supplies, square containers can be used to hold drinks, in the field of bath products, and in the field of smelting, square containers can be used to hold molten metal. Technically, the first two applications solve the same problem, both of which are used to hold ordinary liquids, so they belong to the same technical field, while the latter application is used to hold special liquids, which has special requirements for the material and strength of containers, so it belongs to different technical fields.
2, the same technical field, the same technical scheme, can only apply for a patent; In different technical fields, because of the different problems solved, although their technical schemes are similar in structure and principle, they are bound to have particularity, so they can apply for different patents. It's like two wings of an airplane used on a submarine. Because the use environment has changed, the problem solved is naturally different, and it will definitely be different from that used on the plane, so you can apply for different patents.