GB1444858A - Manufacture of permanent magnets - Google Patents

Abstract

1444858 Permanent magnets; magnetization C I KASEI CO Ltd 20 Nov 1974 [3 Dec 1973] 50395/74 Heading H1P In fabrication of a film permanent magnet a flexible base strip, e.g. paper, cloth, plastics or metal film is fed from a roll 2 over guide rolls 3, 4 and a rubber backing roll 5 associated with doctor knives 10, 11 to a take up roll 8 over guide rolls 6, 7. A mixture 9 of polymeric organic binder, solvent, and a powdered hard magnetic substance, e.g. barium ferrite in proportion of 80-90% W/W is fed to roll 5, and coated on the base by the doctor knives which are uniformly spaced from the base. The film is thereafter passed through the field of magnetizing means 13 to produce permanent magnetization perpendicualr to the base, and is dried at 14. It is then hot calendered between metal roll 15a and rubber roll 15b, and after cooling wound on roll 8. The film thickness is determined by the spacings of the doctor knives from the film (Fig. 2, not shown) which co-operate with accumulated banks of coating material to remove entrained bubbles. Further doctor knives may be provided in series. The rear surface of the film may be directly printed or coloured. In a modification (Fig. 3, the base film is tensioned and translated by rolls 20, 21 between which it is supported by plates 22, 23, and doctor knives 24, 25 normal to the film are positioned between plate 23 and roll 21 and between 22, 23 to bow the base film downwardly during coating, and to remove bubbles between accumulated banks 26, 27 of coated material. In a further modification (Fig. 4) an endless belt 30 supported on transit rollers 31 and supporting rollers 33 carries a base film 1 tensioned over guide roller 34. Three doctor knives 35, 36, 37 bear on the upper face of the film and are spaced therefrom to spread the coating mixture 9 and remove bubbles.