Patent ID: 8525413

Claim:
A magnetron for microwave oven comprising: an anode cylinder extending cylindrically along a central axis; a plurality of vanes extending from an inner surface of the anode cylinder to the central axis and free ends thereof forming a vane inscribing circle; a spiral cathode extending spirally along at the central axis; a pair of end hats fixed to both ends of the cathode; and a pair of funnel-shaped pole pieces located so as to pinch the cathode upon expanding from a through-hole face to face with each end hat to an end of the anode cylinder, wherein H =8.0, H/Da<0.95, DEH 1 /DPP 1 <0.8, DEH 1 /DPP 2 <0.8, DEH 2 /DPP 1 <0.8, DEH 2 /DPP 2 <0.8, 0.92<Da/DPP 1 <0.95, and 0.92<Da/DPP 2 <0.95, where H (mm) is the height of the vane; Da (mm) is the diameter of the vane inscribing circle; DEH 1 (mm) and DEH 2 (mm) are outer diameters of the pair of end hats respectively; and DPP 1 (mm) and DPP 2 (mm) are inner diameters of the through-holes of the pair of pole pieces.