At the moment I have only a picture to show you scanned by Google from Laxton's Builder's Price Book. I believe the Convergent was produced in or around 1872 and I hope to bring you the report on it in the future.
https://books.google.co.uk/books?id=YX0FAAAAQAAJ&pg=PA317&dq=r+adams+spring+hinge&hl=en&sa=X&redir_esc=y#v=onepage&q=r%20adams%20spring%20hinge&f=false