Off topic (ish) but in case you want to check on patents then each country has its own agency and most can be accessed online. The UK one is at
Intellectual Property Office - Welcome to the Intellectual Property Office
The "patents tab, online patent services and search patent " will bring you to the option of seraching in 4 different ways, the most useful being the EPO database from which you can perform a world wide patent search from the comfort of your own keyboard.
Selecting the quick search, world wide, by person, and entering "sikorsky" gets 838 hits, and you can refine from there using the advance search option.
Interestingly, Eurocopter have 1,798 patents (more than Sikorsky), 373 of them concerning rotors in some way, nothing on variable diameter rotors but 1 (1997 filing) for variable pitch rotor blades made using a resin moulding.
Amazing what you can do with the internet when bored.
Edited to add:
Frank D Robinson has 2 patents and neither relate to tree surgery