Magnetic tape cassette, guide roller, and a method of manufacturing a guide roller

A method of manufacturing a guide roller for the magnetic tape cassette comprising steps of:

• injecting a first resin between a sleeve slidably attached to an insert pin and a cylindrical cavity of a first cavity plate so as to mold a tubular primary molding;
• leaving said tubular primary molding by withdrawing said first cavity plate;
• moving a mold onto the outer periphery of said primary molding, said mold comprising a core plate and a cavity plate which define a barrel shaped cavity having its maximum diameter at its parting line when said core and cavity plates are closed, said core plate having a half of said barrel shaped cavity, and said cavity plate having the remaining half of said barrel shaped cavity, disposing a gate within said primary molding ;
• and
• withdrawing said sleeve;
• injecting a second resin between the inner side of said primary molding and said insert pin through said gate;
• and
• bulging said primary molding into the shape of said barrel shaped cavity by the injecting pressure to integrate said primary molding with said second resin injected within said primary molding.

A method of manufacturing a guide roller of a magnetic tape cassette comprising steps of:

• injecting a first resin between a sleeve slidably attached to an insert pin and a cylindrical cavity of a first cavity plate so as to mold a tubular primary molding;
• molding a tubular primary molding by (i) arranging slidable double sleeves within a barrel shaped cavity of a mold which comprises a core plate and a cavity plate which define said barrel shaped cavity having its maximum diameter at its parting line when said core and cavity plates are closed, said core plate having a half of said barrel shaped cavity, and said cavity plate having the remaining half of said barrel shaped cavity, (ii) providing a pin for opening/closing a gate facing toward said barrel shaped cavity half of said cavity plate, (iii) then opening said gate by the action of said pin under a condition that said double sleeves are projected into said barrel shaped cavity, and (iv) injecting a first resin between said double sleeves to form said tubular primary molding;
• leaving said primary molding body within said barrel shaped cavity by closing said gate and withdrawing said double sleeves;
• and
• opening said gate again and injecting a second resin within said primary molding through said gate;
• and
• bulging said primary molding into the shape of said barrel shaped cavity by the injection pressure to integrate said primary molding with said second resin injected within said primary molding.

A method of manufacturing a guide roller of the magnetic tape cassette wherein a mold comprises a core plate, a cavity plate, and a runner plate being able to be detached from said cavity plate and having a gate at the tip thereof, said method comprising steps of:

• molding a tubular primary molding by injecting a first resin between slidable double sleeves through a gate of the runner plate under a condition that said slidable double sleeves are projected within said cavity when closing said mold;
• leaving said primary molding within said cavity;
• injecting a second resin again within the primary molding through said gate of said runner plate;
• and
• bulging said primary molding into the shape of said barrel shaped cavity by the injection pressure to integrate said primary molding with resin injected within said primary molding;
• and
• cutting the gate by detaching said runner plate.