The pair of shielding plates 17 and 18 divides the inside of the outer cylindrical casing 4 in front and rear and is provided with {HEAD ~ one or more air holes} 15 and 16 at the outer circumferential section or at {TAIL ~ the central section} 
The pair of shielding plates 17 and 18 divides the inside of the outer cylindrical casing 4 in front and rear and is provided with { HEAD ~ one or more air holes } 15 and 16 at the outer circumferential section or at { TAIL ~ the central section }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL