A METHOD OF MANUFACTURING AN IMPROVED POLE PLATE FORMING THE AIR-GAP IN THE MAGNET SYSTEM OF A LOUDSPEAKER,AN IMPROVED POLE PLATE OBTAINED THEREBY AND A LOUDSPEAKER HAVING THE IMPROVED POLE PLATE

摘要

A method of manufacturing an improved pole plate forming the air gap in the magnet system of a loudspeaker, said method comprising:(i) determining (Having regard to the required magnetic field strength in the air-gap) the minimum material thickness of said pole plate required to avoid magnetic saturation thereof, the diameter of the hole to be provided through said pole plate and the height of said air-gap;(ii) selecting or making a magnetic material plate of the determined minimum material thickness;(iii) piercing an opening through said magnetic material plate, the diameter of said opening being smaller than the determined diameter of said hole, the difference in diameters of said opening and hole depending on the height of the rim hereinafter referred to;(iv) simultaneously forming said hole and a rim around the periphery of said hole by push thro or extrusion such that said minimum material thickness of said plate plus the height of said rim is equal to the height of said air-gap;(v) calibrating said hole;(vi) rotofinishing said hole; and(vii) plating the pole plate obtained.