Abstract: A screw-in-plunger injection apparatus is provided which is advantageously used for molding either a large-size or a small-size product. The injection apparatus is capable of selectively carrying out a plunger-type injection operation and an inline-screw-type injection operation. In the plunger-type injection operation, an injection plunger 12 and a screw 10 are advanced in an injection cylinder 14, so that a melted resin fed to a storage space provided on the side of one axial end of the injection plunger 12 is injected. In the inline-screw-type injection operation, a surface of the axial end of the injection plunger 12 is held in abutment with the injection cylinder 14, so that the storage space is reduced to provide a reduced storage space to and from which the melted resin is fed by the rotation of the screw and is injected by the movement of the screw in an axial direction thereof.

Abstract: An injection molding machine for thermoplastic resin consisting of an accumulator in which a plunger is slidably provided and an injection mold, the sprue of which connects with the nozzle of said accumulator, wherein said plunger consists of a cylinder and a screw rotatably arranged in said cylinder, the tip of said screw protrudes from the front end of said cylinder and the maximum diameter of said tip is larger than the diameter of said screw, and the ratio of the effective volume of said plunger to the effective volume of said accumulator is in the range between 1:4 to 1:10 is provided in the present invention. By using said injection molding machine a large size product can be molded at a low injection pressure.