He signed a contract with a local hotel, the Rexford, agreeing to fulfill an order for a special robot that could produced alcohol quickly. The result of his efforts was the Drinkin' Buddy. He was able to create a successful prototype by using a heavily modified protectron. Unfortunately, the bombs had won the race first before Buddy could. As a result, the robot's delivery to the hotel was heavily delayed, over 200 years behind schedule.
The only evidence of his activities being on a terminal in the basement of The Shamrock Taphouse and Buddy stored in a charging station there as well. Patrick showed little regard for copyright law, using unauthorized homemade parts to modify a RobCo protectron and cracking a proprietary holotape from the Gwinnett Ale brewery and hoping their lawyers didn't catch wind before he made his ambitions a reality.
Patrick Merryweather is only mentioned in Fallout 4.