| 摘要 |
PURPOSE:To strikingly reduce the flow channel resistance without impairing the mechanical strength by a structure wherein an annular groove is provided on the injection cylinder side of an injection section in order to house a ring valve therein. CONSTITUTION:A ring valve 3, the axial length of which is longer than the sum of the injection stroke of a screw shaft 1 and the axial length of a sealing section at the tip of the screw shaft 1, is provided in a portion forming the pressurizing chamber 4 of an injection cylinder 2. The axial length of a ring valve groove 5, in which said ring valve 3 is housed, is made longer than the axial length of the ring valve by 10-20% of the diameter of the screw shaft 1 and further the diameter of the ring valve groove is made nearly equal to the outer diameter of said ring valve 5 so as to let the ring valve freely slide in the groove in order to include the front and rear zone beyond the injection stroke. A valve seat provided with a curved surface portion having the same form as that of the rear end of the ring valve so as to be able to seat said rear end by closely contacting with each other is provided at the rear wall of said ring valve groove. When the screw shaft is advanced, the ring valve 3 is brought into close contact with the valve seat 6, resulting in occurring no back flow. |
