An injection molding machine that contributes to improving the quality of a workpiece is provided. An injection molding machine configured to causes torpedo pistons to be slid in one way to thereby plasticize a resin material supplied to a first space of a cylinder, and causes a molten resin to flow into a second space of the cylinder and causes the torpedo pistons to be slid in the other way to thereby inject the molten resin. The injection molding machine includes pressurizing pistons inserted into the torpedo pistons so that the pressurizing pistons can be slid in such a way that an amount of protrusion of the cylinder into the second space of the cylinder with respect to the torpedo pistons is changed, and energizing means for energizing the pressurizing pistons toward the second space of the cylinder.

An injection molding machine that contributes to improving the quality of a workpiece is provided. An injection molding machine configured to causes torpedo pistons to be slid in one way to thereby plasticize a resin material supplied to a first space of a cylinder, and causes a molten resin to flow into a second space of the cylinder and causes the torpedo pistons to be slid in the other way to thereby inject the molten resin. The injection molding machine includes pressurizing pistons inserted into the torpedo pistons so that the pressurizing pistons can be slid in such a way that an amount of protrusion of the cylinder into the second space of the cylinder with respect to the torpedo pistons is changed, and energizing means for energizing the pressurizing pistons toward the second space of the cylinder.

[Problem] To provide an injection apparatus including a flow path switching mechanism that is simple in construction and low in cost. [Solution] An injection apparatus (1) includes a plasticization device (2) for melting resin, a first and second plunger injection devices (4, 5) for measuring an amount of resin and injecting the resin, an injecting portion (8), and a flow path switching block (7) that connects the plasticization device, the first and second plunger injection devices and the injecting portion together. A first to fourth connecting flow paths (23a, 23b) and a flow path switching valve (21) are provided in the flow path switching block (7). The plasticization device (2), the first plunger injection device (4), the injecting portion (8) and the second plunger injection device (5) are connected to the first to fourth connecting flow paths (23a, 23b), respectively. When the flow path switching valve (21) is switched to a first position, the first and second connecting flow paths (23a, 23b) communicate with each other, and the third and fourth connecting flow paths (23c, 23d) communicate with each other, whereas when the flow path switching valve (21) is switched to a second position, the first and fourth connecting flow paths (23a, 23d) communicate with each other and the first and third connecting flow paths (23b, 23c) communicate with each other.

[Problem] To provide an injection apparatus including a flow path switching mechanism that is simple in construction and low in cost.

[Solution] An injection apparatus (1) includes a plasticization device (2) for melting resin, a first and second plunger injection devices (4, 5) for measuring an amount of resin and injecting the resin, an injecting portion (8), and a flow path switching block (7) that connects the plasticization device, the first and second plunger injection devices and the injecting portion together. A first to fourth connecting flow paths (23a, 23b) and a flow path switching valve (21) are provided in the flow path switching block (7). The plasticization device (2), the first plunger injection device (4), the injecting portion (8) and the second plunger injection device (5) are connected to the first to fourth connecting flow paths (23a, 23b), respectively. When the flow path switching valve (21) is switched to a first position, the first and second connecting flow paths (23a, 23b) communicate with each other, and the third and fourth connecting flow paths (23c, 23d) communicate with each other, whereas when the flow path switching valve (21) is switched to a second position, the first and fourth connecting flow paths (23a, 23d) communicate with each other and the first and third connecting flow paths (23b, 23c) communicate with each other.

An injection apparatus (100) for injecting molten plastic, in particular PET, into a mold for molding bottle preforms; the injection apparatus (100) comprisinga first injector (1) and a second injector (2) adapted to receive molten plastic and inject it into the mold alternately to each other; a conduit (8) adapted to carry molten plastic from a plasticization apparatus (102) towards the first injector (1) and towards the second injector (2); a third injector (3) provided with a piston (32), the third injector (3) being connected to the conduit (8) so as to receive molten plastic from the conduit (8) and then inject it into the conduit (8); actuation means (34) adapted to cause the piston (32) of the third injector (3) to move forward to inject the molten plastic into the conduit (8); wherein said actuation means (34) are adapted to control the backward movement of the piston (32) of the third injector (3) while it receives the molten plastic from the conduit (8).