GB1257505A - - Google Patents

Abstract

1,257,505. Magnetrons. MATSUSHITA ELECTRONICS CORP. 13 June, 1969 [21 June, 1968 (2); 7 Aug., 1968 (2); 13 Sept., 1968; 30 Sept., 1968], No. 29990/69. Heading H1D. A magnetron having an upwardly projecting insulator vessel contiguous to its upper polepiece and enclosing the cathode lead, and a downwardly projecting insulator vessel contiguous to its lower polepiece and enclosing an antenna extending from the magnetron resonant cavity, includes a permanent magnet having an axial hole of a diameter exceeding that of the upper insulator vessel and disposed such that that vessel is at least partly within the hole, with an interstice therebetween, the lower end surface of the permanent magnet being coupled with the upper surface of the upper magnetic polepiece either directly or through a yoke member. As shown in Fig. 3, the metal envelope portion 2 of the magnetron has welded thereto a stack of cooling fins 9 through the passages between which air is forced from the intake port 7 to an output port on the opposite side of the assembly. Insulator vessels 3 and 4 house the cathode lead 16 and output antenna 5, vessel 3 being mounted within the axial hole 11 of the cylindrical or conical ferrite permanent magnet 10, the upper end of which is coupled by the high permeability shield 12 to the magnetron lower polepiece, plate 13 of the shield being provided with holes 15 for mounting on an electronic range. In this embodiment the magnet 10 is slotted at 20 to provide a passage for cooling air to pass from the additional input port 18 into and upwardly along the annular space between the magnet and the vessel 3, whereby they are both cooled and the vessel is protected from mechanical damage. In a modification of this arrangement (Fig. 5, not shown) the magnet 10 is a complete annulus and of cylindrical shape, the slot 20 being formed in a conical magnetic yoke (21) interposed between the magnet and the magnetron upper polepiece. In the arrangement of Fig. 6 which employs a cylindrical magnet 10, magnetic shortcircuiting of the shield 12 to the magnetron upper polepiece is reduced by the use of permanent or electromagnets 30 of opposed polarity. In a further embodiment (Fig. 7, not shown) a cylindrical permanent magnet (100) mounted on the plate 13 constitutes the outer shield of the device, an inner cylindrical yoke (102) coupling an end disc closing the magnet to the magnetron upper polepiece.