Is it infringement to transform existing articles into patented products that have applied for patents?

Theoretically, it counts.

From your simple description, it belongs to a change of mechanical structure, so the patent protects the structure. As for whether you are newly produced or transformed with old goods, as long as the structure is the same and the function is the same, it is theoretically infringing.

However, it is meaningless to discuss whether there is infringement in general, and it is best to judge it in combination with specific circumstances.