JPS5731297A - Speaker diaphragm and its production - Google Patents

Abstract

PURPOSE:To obtain a diaphragm in which a cone part and an edge part having different modulus of elasticity are unified, by securing a 3-layer structure in which the both surfaces of a heat foamed sheet is held between the thermoplastic resin containing the reinforced fibers and giving three processes of the heating lamination, the foaming softening and the cold pressing respectively. CONSTITUTION:The both surface of a core sheet 1 (low-density polyethylene containing a foaming agent, etc.) are held between surface sheets 2 and 2' (high-density polyethylene synthetic pulp containing carbon fibers, etc.) and heated at a temperature lower than the foaming to obtain a 3-layer lamination sheet. Further this sheet is heated to foam the core material 1 and subjected to the cold pressing while it is soft. In this case, the size of both the upper and lower molds are made that the cone part is contacted and the edge part have a gap respectively. Thus the cone part 9 is pressed into a thin film having no hole and a high modulus of elasticity; while the edge part 10 is kept under a foamed state to secure a large internal loss. In other words, the edge resonance can be suppressed to realize a fixed type diaphragm having the flat sound pressure frequency characteristics. This process is simple, and a continuous production is possible.