A die casting machine of an embodiment includes: a base; a fixed die plate fixed onto the base and holding a fixed die; a movable die plate provided on the base to be movable in a mold opening and closing direction and holding a movable die to face the fixed die; an injection device filling a molten metal into a cavity formed by the fixed die and the movable die and applying a first pressure to the molten metal; a first pressurizing device pressurizing the molten metal filled in the cavity in a region other than a product region of the cavity and applying a second pressure to the molten metal; and a control device controlling the first pressurizing device so that the second pressure becomes higher than the first pressure.

A die casting machine of an embodiment includes: a base; a fixed die plate fixed onto the base and holding a fixed die; a movable die plate provided on the base to be movable in a mold opening and closing direction and holding a movable die to face the fixed die; an injection device filling a molten metal into a cavity formed by the fixed die and the movable die and applying a first pressure to the molten metal; a first pressurizing device pressurizing the molten metal filled in the cavity in a region other than a product region of the cavity and applying a second pressure to the molten metal; and a control device controlling the first pressurizing device so that the second pressure becomes higher than the first pressure.

An injection piston drives a screw. An injection hydraulic cylinder drives the injection piston and is partitioned into first and second chambers. A first oil discharge port is disposed in the injection hydraulic cylinder to be blocked by a piston part when the piston part of the injection piston advances to a pressure-holding switching position, and discharges hydraulic oil from the second chamber. A second oil discharge port is disposed in the injection hydraulic cylinder to be capable of discharging hydraulic oil from the second chamber regardless of the position of the injection piston. The injection piston has first and second members. The joint of the first and second members is disposed at a position separated from an end of the piston part on a side of the second chamber by a predetermined distance.

In an injection apparatus, a movable unit includes a ball screw including a moving block and a screw shaft. The moving block moves in a predetermined direction and is joined to an injection plunger. The screw shaft rotates to move the moving block. The screw shaft and the injection plunger are disposed side by side in a direction orthogonal to the predetermined direction. A fixing unit includes a first portion for holding a rear end part of the screw shaft, a second portion for holding a front end part of the screw shaft, and a third portion for holding the injection cylinder. The moving block is provided between the first portion and the second portion. The third portion is provided to be pressed by the injection cylinder when the injection plunger presses the resin.

In an injection apparatus, a movable unit includes a ball screw including a moving block and a screw shaft. The moving block moves in a predetermined direction and is joined to an injection plunger. The screw shaft rotates to move the moving block. The screw shaft and the injection plunger are disposed side by side in a direction orthogonal to the predetermined direction. A fixing unit includes a first portion for holding a rear end part of the screw shaft, a second portion for holding a front end part of the screw shaft, and a third portion for holding the injection cylinder. The moving block is provided between the first portion and the second portion. The third portion is provided to be pressed by the injection cylinder when the injection plunger presses the resin.

A machine for injecting thermoplastic material into mould includes a frame, a bracket, a melt chamber supported by the bracket, a piston designed to plunge into the melt chamber per an injection axis through an upper opening and push a molten material contained in the chamber to the mould. The machine includes a head along which the piston slides, the head also having a hopper which contains the non-melted thermoplastic material, the head being mobile perpendicularly to the injection axis between an injection position, in which the piston is aligned with the melt chamber, and the hopper is blocked off by the bracket, and a feed position, in which the hopper is aligned with the melt chamber to feed it with thermoplastic material, and the movement of the piston is limited by the bracket.

A machine for injecting thermoplastic material into mould includes a frame, a bracket, a melt chamber supported by the bracket, a piston designed to plunge into the melt chamber per an injection axis through an upper opening and push a molten material contained in the chamber to the mould. The machine includes a head along which the piston slides, the head also having a hopper which contains the non-melted thermoplastic material, the head being mobile perpendicularly to the injection axis between an injection position, in which the piston is aligned with the melt chamber, and the hopper is blocked off by the bracket, and a feed position, in which the hopper is aligned with the melt chamber to feed it with thermoplastic material, and the movement of the piston is limited by the bracket.

A method for increasing the injection speed of a melted plastic injection device for injecting said melted plastic into a molding cavity (51), said injection device comprising a first cylinder (1) provided with a tubular casing (2) defining a first inner diameter d.sub.1, and a first piston (3) slidable inside said tubular casing (2), adapted to be loaded with melted plastic and to inject said melted plastic toward the molding cavity (51); a second cylinder (21) constrained to the first cylinder (1) and provided with a second piston (23) which rod (24) is connected to the first piston (3) and is adapted to actuate said first cylinder (1) during an injection operation; the method comprising the steps of: —releasing second cylinder (21) and first cylinder (1) by extracting the first piston (3) from the tubular casing (2); —coaxially inserting a tubular body (12), defining a second inner diameter d.sub.3 which is smaller than the first inner diameter d.sub.1, into the tubular casing (2); —disconnecting the first piston (3) from the rod (24); —connecting a third piston (13) to the rod (24), said third piston (13) being sized to slide inside said tubular body (12); —constraining second cylinder (21) and first cylinder (1) by inserting the third piston (13) into the tubular casing (2).

A method for increasing the injection speed of a melted plastic injection device for injecting said melted plastic into a molding cavity (51), said injection device comprising a first cylinder (1) provided with a tubular casing (2) defining a first inner diameter d.sub.1, and a first piston (3) slidable inside said tubular casing (2), adapted to be loaded with melted plastic and to inject said melted plastic toward the molding cavity (51); a second cylinder (21) constrained to the first cylinder (1) and provided with a second piston (23) which rod (24) is connected to the first piston (3) and is adapted to actuate said first cylinder (1) during an injection operation; the method comprising the steps of: —releasing second cylinder (21) and first cylinder (1) by extracting the first piston (3) from the tubular casing (2); —coaxially inserting a tubular body (12), defining a second inner diameter d.sub.3 which is smaller than the first inner diameter d.sub.1, into the tubular casing (2); —disconnecting the first piston (3) from the rod (24); —connecting a third piston (13) to the rod (24), said third piston (13) being sized to slide inside said tubular body (12); —constraining second cylinder (21) and first cylinder (1) by inserting the third piston (13) into the tubular casing (2).

An injection unit for a shaping machine includes an injection piston arranged displaceably in an injection cylinder and at least two drive units for displacement of the injection piston. Each of the at least two drive units is lubricated by an oil chamber which is oil-tightly sealed off in relation to the surroundings, and each oil chamber holds an oil volume, above which is arranged an air volume. The air volumes of the oil chambers are connected together in air-conducting relationship by a connecting conduit.