Fred M, The Savage ejector system is housed in the underlug just like an H&R. I believe the Savage ejector would cost less to produce than would the H&R. The main difference is that the H&R ejector catch is pivoted at its rear (breech end) while the Savage catch pivots at the front end (toward the muzzle). The ejector catch has a horizontal leg which bends out to the left to catch a shelf in the receiver casting and a vertical leg which sticks up into the ejector boring. The ejector spring is captive between the extractor and that vertical leg of the catch. Thus the one spring powers both the ejector and its catch. As the gun is broken open, the breech rises to a point where the horizontal leg of the catch engages the shelf of the receiver to unlatch the ejector and at that point it works just like an H&R ejector. However, if the case is stuck or if the factory spring has been replaced with a lighter one, farther opening of the gun will cause that vertical leg of the catch to pivot rearward enough to force extraction, where-after, even a very light spring will carry the extractor on to the limit of its travel.
When modifying the H&R I do a very similar thing. I make a new catch which pivots at the front end with a vertical leg sticking up into the ejector boring. It requires a bit of dremel work to open up the cut for the catch and extend it a bit more forward, that is the only modification required on the lug. That, along with building a new catch. I make the new catch out of spring stock and harden and temper it for strength.
As Trotterlg describes the Rossi ejector it sounds very similar and those guns are even cheaper than H&R. Since Savage has used that design for a hundred years, I doubt that any patents would still be viable.