I would recommend not only to search Google patents, but also to try
the European patent office via

http://gb.espacenet.com/search97cgi/s97_cgi.exe?Action=FormGen&Template=gb/EN/home.hts

and also to try the German patent office via

https://dpinfo.dpma.de/index_e.html

There are quite some misspellings in all the databases, mostly in
Google.  I always found additional material this way.

Kind regards from the hometown of Welte.

Gerhard Dangel
Augustinermuseum, Freiburg, Germany
http://www.museen.freiburg.de/
http://www.welte-mignon.de/