Just found this, what do you think of it?
http://www.google.com/patents?id=Sxw-AAAAEBAJ&printsec=abstract&zoom=4#v=onepage&q&f=false
http://www.google.com/patents?id=Sxw-AAAAEBAJ&printsec=abstract&zoom=4#v=onepage&q&f=false