Resin molded articles

Abstract

A disk-shape resin molded article such as a gear comprises a rim, a boss, a web having a disk configuration for connecting the rim and the boss, and gear teeth formed on the rim. The molded article is produced by an injection-compression molding process which comprises injecting a molten resin into a cavity of a metal mold, and pressing a web site and at least one site selected from the group consisting of a boss site and a rim site in a thickness direction. The cavity may have a capacity larger than the solidified products by contraction amount of the injected molten resin.

What is claimed is:  
     
         1 . A disk-shape resin molded article comprising a rim forming a peripheral area, a boss forming a concentric inner area, and a web having a disk configuration for connecting the rim and the boss, 
 wherein said molded article is formed by an injection molding process which comprises injecting a molten resin into a metal mold, and pressing a web site and at least one site selected from the group consisting of a boss site and a rim site in a thickness direction.    
     
     
         2 . A resin molded article according to  claim 1 , wherein at least one site selected from the group consisting of the boss and the rim is pressed at least partially in the pressing step.  
     
     
         3 . A disk-shape resin molded article comprising a rim forming a peripheral area, a boss forming a concentric inner area, and a web having a disk configuration for connecting the rim and the boss, 
 wherein said molded article is formed by an injection molding process which comprises injecting a molten resin into a metal mold, and pressing a web site in a thickness direction, and    wherein said web comprises a middle circular site and a inclined area extending inwardly or outwardly from the middle circular site toward to the rim and/or the boss with increasing the thickness.    
     
     
         4 . A resin molded article according to  claim 3 , wherein said middle circular site has a uniform thickness, and said inclined area is formed circumferentially with extending inwardly and outwardly from the middle circular site toward to the rim and the boss with increasing the thickness.  
     
     
         5 . A disk-shape resin molded article according to  claim 3 , wherein the thickness of said inclined area gradually increases toward to the rim and/or the boss.  
     
     
         6 . A disk-shape resin molded article according to  claim 1 , which comprises a rim forming a peripheral circumference area, a boss forming a concentric inner area, a web having a disk configuration for connecting the rim and the boss, and outer teeth formed on the rim, 
 wherein said molded article is molded unitarily as a monobloc article by an injection molding process which comprises injecting a molten resin into a metal mold, and pressing a web site and at least one site selected from the group consisting of a boss site and a rim site in a thickness direction.    
     
     
         7 . A resin molded article according to  claim 1  or  3 , wherein the molded article is a resin-molded gear.  
     
     
         8 . A resin molded article according to  claim 1  or  3 , wherein the molded article is formed with an engineering plastic.  
     
     
         9 . An injection molding process for producing a disk-shape resin molded article comprising a rim forming peripheral area, a boss forming a concentric inner area, and a web having a disk configuration for connecting the rim and the boss, 
 which comprises the steps of; 
 injecting a molten resin into a cavity of a metal mold, and  
 pressing, in the molding process, a web site and at least one site selected from the group consisting of a boss site and a rim site in a thickness direction.  
   
     
     
         10 . An injection molding process according to  claim 9 , wherein said metal mold comprises a fixed mold member, a movable mold member disposed movably relative to the fixed mold member, a pressing core movably disposed or faced to at least one lateral side of the web, and a center pin disposed movably to insert into the bore of the boss and to contact with the lateral surface of the boss, said metal mold members, said pressing core and said center pin form the closed cavity by forward movement in a thickness direction, and said cavity has a capacity larger than a volume of the final molded article by a contraction volume of the injected resin, 
 wherein the pressing core is advanced to an original position separated from the fixed mold member with a distance corresponding to the volume of the injected molten resin,    the molten resin is injected into said cavity in response to the completion of the advance movement of the pressing core to the original position, and    the pressing core is further advanced to a predetermined position which corresponds to the contraction volume or shrinking amount of the injected molten resin in response to the injection of the molten resin.