Method for molding plastic shutter for magnetic disk cartridge

Abstract

In a method for injection molding a plastic shutter for a magnetic disk cartridge, the shutter having windows corresponding to an opening formed in a magnetic disk cartridge and being substantially U-shaped in section, the diameter of an injection cylinder for injecting molten resin for forming the shutter is determined according to the following equation: D.sup.2 =A.times.C.times.M / .pi. where D is the diameter (mm) of the injection cylinder, C is the number of the plastic shutters molded simultaneously with one metal mold, M is the volume (cm.sup.3) of the plastic shutter, and A is the cylinder coefficient of the injection cylinder and is limited as follows: 130.ltoreq.A.ltoreq.510. The inventive method is considerably stable, being free from the difficulties that short shot occurs with the metal mold, and the resultant shutter is deformed near the gate of the metal mold, or bent in its entirety.

Dependencies are inferred from the claim text.