I'm working on construction of robotic gripper. My idea is very similar to robotiq 3 fingers gripper. Is this mechanism patenteded or open? I'm talking about adaptive grasping mechanic and fingers shift.

Hi,
This is a really interesting project that you have! You are right, the initial 3 Fingers architecture is patented and protected. 
You can find the Patent here:
https://robot.gmc.ulaval.ca/fileadmin/documents/Brevet/us5762390.pdf

Best regards,
Nicolas

This patent is older than 20 years, it means that it is expired?

Hi,
For more information, we will suggest you to confirm with your local patent office to have the official confirmation of the validity and jurisdiction of this Patent.
Best Regards,