Burning down the doll house

Dear Rich: I want to create original illustrations for a doll house but using existing doll house designs as the canvas for them. The existing doll house designs I am thinking of using were created (and patented) between the 1890s and the 1940s and haven't been reproduced since then though some of the companies or people who obtained the patents might still exist as far as I know. (Googling them hasn't turned up much information.) Since a doll house is a doll house -- meaning that I can't stray much from the original purpose or structural design, just create new illustrations for it -- would I be infringing on their rights? I did a latent patent search and the patents I want to use aren't on that list but I can't tell if it means they have expired naturally or have been extended. The short answer is that you should be fine copying patents from over fifty years ago. Patents from those days lasted 17 years at the most and only in rare cases, were patents extended (and even so, the extension would only be for a year or two). In addition, the majority of doll house patents are design patents (you can tell them because they have a "D" before the numbers) and those patents are narrowly construed. In other words, a few modifications in appearance may remove most infringement concerns. By the way, lately we've been preferring Google patents for patent searching; it seems easier to navigate than the USPTO.

Some other stuff ... Of course, even though a patent has ended, it's possible (though extremely unlikely) that the same dollhouse -- at least if created in the 1940s --  may still be protected under copyright law. We also suppose that a doll house manufacturer could argue that its work is protected by trade dress. In any case, neither copyrights or trade dress protect functional elements which raises the (primarily) academic issue -- is Barbie's pad functional or decorative?