Brevetti relativi a trivelle ed escavatrici

potete trovare tutte le informazioni a questi link:
http://www.google.com/patents?id=zHteAAAAEBAJ&printsec=frontcover&dq=drilling&hl=en&sa=X&ei=kp68T6vmHMSr-QbIhLQn&ved=0CDUQ6AEwAA

http://www.google.com/patents?id=LJBKAAAAEBAJ&printsec=frontcover&dq=drilling&hl=en&sa=X&ei=kp68T6vmHMSr-QbIhLQn&ved=0CDgQ6AEwAQ

http://www.google.com/patents?id=ocdZAAAAEBAJ&pg=PA1&dq=drilling&source=gbs_selected_pages&cad=1#v=onepage&q=drilling&f=false

http://www.google.com/patents?id=CtxKAAAAEBAJ&printsec=frontcover&dq=drilling&hl=en&sa=X&ei=kp68T6vmHMSr-QbIhLQn&ved=0CFAQ6AEwCQ

http://www.google.com/patents?id=yIlPAAAAEBAJ&pg=PA4&dq=drilling&hl=en&ei=hqC8T_XPH4HP-gaZ5cEs&sa=X&oi=book_result&ct=book-thumbnail&resnum=3&ved=0CD0Q6wEwAjgK#v=onepage&q=drilling&f=false

http://www.google.com/patents?id=bQ4iAAAAEBAJ&printsec=frontcover&dq=drilling&hl=en&sa=X&ei=hqC8T_XPH4HP-gaZ5cEs&ved=0CEIQ6AEwBDgK