a sleeve having a pair of {HEAD ~ inner teeth gears} engaged with said outer teeth gears for transmitting {TAIL ~ power} between the rotary shafts 
a sleeve having a pair of { HEAD ~ inner teeth gears } engaged with said outer teeth gears for transmitting { TAIL ~ power } between the rotary shafts
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH