Splinedrive. I was basing my statement on the patents filed by Karem. So my statement may be out of date, having been based on earlier configuration.
I have not yet seen in a published application a configuration with generators and cooling in the spinner. I’ll do a search.....
https://patents.justia.com/patent/8235667
CTR, my understanding of the system is more recent than 2009, but I don’t have a source handy. I’ll dig around. The patent you linked didn’t really address where power comes from that I noticed.
Generating in the rotating frame does certainly add a gearbox, but a slip ring capable of the power levels and reliability levels required wouldn’t be simple or light, either. I fully admit that I could be remembering incorrectly.
Karem is doing some good research at full scale. I think it’s another significant stretch to integrate their rotor into a practical large aircraft, but they’re making good steps.
This thread has diverged pretty far afield from the CH-148 crash in the Med.