To add to Jim's item on patentable ideas...........
The idea, if it is way out there, or rather bizarre or revolutionary, and you are making a ton of practical claims in your patent in an effort to avoid having folks patent around you, (common), the examiner may ask to see a model or some physical embodiment to back up your claim. Especially, if he nor any of his fellows can figure out just what you have or how it works to their satisfaction.
Likewise, a working model demonstrated to the PTO will not warrant patent issuance if they feel some subtrifuge or bad data collecting makes your claim from the model still suspect.
For instance, no more cold fusion patents are to be examined regardless of working devices, over unity demos, whatever. Every now and then they issue an eddict based on "sound scientific princicples" and if they smell an eddict violation, your patent won't even be considered.
Things such as magnets chasing magnets in a "pertetium mobile" or something that violates certain thermodynamic laws all risk refusal to consider.
So working models are sometimes asked for, but a working model is no proof, in some cases, that your patent is valid or will be issued.
Richard Hull
Created on Tuesday, February 20, 2001 3:04 PM EDT by Richard Hull