Just saw this note on the STTNG IPDB entry (emphasis added):
Patent #5,350,174 [BELOW THE PLAYFIELD BALL DELIVERY SYSTEM FOR A PINBALL GAME] filed October 28, 1993. Granted September 27, 1994 to Ritchie et al. Assignee is Williams Electronic Games, Inc.
EDIT: Yep, Williams (Rick?) still holds the patent: