Patent ID: 6964748

Claim:
A method of co-injection molding, the method comprising: mixing a plastic inner material and an endothermic-blowing agent to form a core mixture; injecting a plastic outer material from a first injection unit into a co-injection manifold to create a flow of outer material therethrough; injecting the core mixture from a second injection unit into the co-injection manifold to create a flow of core mixture therethrough; allowing the core mixture to enter the mold cavity only after the outer material enters the mold cavity, and then allowing the core mixture and the outer material to flow into the mold cavity concurrently, thereby co-injection molding the core mixture inside the outer material; stopping the flow of the outer material after the outer material concurrently flows with the core mixture, thereby allowing the core mixture to remain flowing; stopping the flow of the core mixture into the mold cavity, and resuming the flow of the outer material into the mold cavity; and expanding the core mixture by providing heat for the endothermic-blowing agent to absorb.