Abstract: An object is to reduce the axial dimension of an injection apparatus (31), facilitate the work of removing and inserting a screw (20), and improve the quality of molded products. The injection apparatus (31) comprises a heating cylinder (17), a screw (20), and a drive apparatus. The screw (20) includes a plasticizing portion which includes a body portion (45a) and a flight (53) projectingly formed on an outer circumferential surface of the body portion (45a). An index ?, which is obtained by dividing a value obtained by adding a screw stroke S and a screw effective length L together by the screw stroke S, satisfies the relation 2.0<?<4.5. Even when the screw (20) is shortened, resin can be melted satisfactorily. Accordingly, the axial dimension of the injection apparatus (31) can be reduced.

Abstract: An object is to reduce the axial dimension of an injection apparatus, melt a molding material uniformly, and improve the quality of molded products. A screw (20) comprises a plasticizing portion which comprises a body portion (45a) and a flight (53) projectingly formed on an outer circumferential surface of the body portion (45a). A groove-depth setting region is defined over a predetermined section of the plasticizing portion, and in the groove-depth setting region, the ratio ?1 of a groove depth ?1 to a diameter ?1 of pellets of a molding material falls within the range of 1??1?1.5 where the groove depth ?1 is a depth of a groove (67) formed along the flight (53). In the groove (67), pellets are arranged laterally and caused to advance while rolling along the groove (67). Since the pellets do not aggregate, no solid bed is formed.

Abstract: An object is to reduce the cost of a screw (20) and improve the quality of molded products. A rear end of the screw (20) is connected to a drive apparatus. The screw includes a screw head, a reverse-flow prevention apparatus, and a plasticizing member disposed rearward of the reverse-flow prevention apparatus. The plasticizing member includes a screw body (52), a flight (53) projectingly formed on an outer circumferential surface of the screw body (52), and a pressure member (54) formed to extend over a predetermined distance from the front end of the screw body (52) and to be located adjacent to the reverse-flow prevention apparatus. The pressure member (54) has a flat outer circumferential surface. Since the pressure member (54) has a flat outer circumferential surface having a diameter equal to or greater than the diameter of the screw body (52), the shape of the screw (20) can be simplified, and the cost of the screw (20) can be lowered.