2. A part of another person's patented machine is not necessarily the patent of the patentee of the patented machine. In other words, it is possible that the patented machine belongs to the patentee, and some of it is not his patent. There are many such cases, just like a small piece of "diaper", which contains many patents, materials, structures and so on. And usually these patentees are cross-licensed.
3. So according to what you said, you should first understand the claim of the patented machine, and then see if your product is the same as or equivalent to the independent claim of the patent, so as to judge whether it is infringing. For reference only!