Klockner-werke Ag

Hans Birkhofer

Werner Schrammel

Arno Stohr

An injection-molding machine has a drive ram with a pressurizable chamber that can be connected either to the high-pressure side or the low-pressure side of a source of fluid under pressure. A control system operating this machine has a pressure-reducing valve with an inlet port connected to the high-pressure side of the source, an outlet port connected through a cut-off valve and a throttle to the chamber of the ram, and a pilot port pressurizable to control the pressure at this outlet port. A pressure-relief valve has an inlet port connected to the pressurizable ram chamber, an outlet port connected to the low-pressure side of the pressure source, and a pilot port pressurizable to control the pressure differential across this pressure-relief valve. A pressure-control valve has an outlet side connected to the low-pressure side of the source and an inlet side and is operable to maintain a first predetermined pressure differential between its inlet and outlet sides in an injection mode and to maintain a certain predetermined pressure differential between its inlet and outlet sides in a clamping mode. A check valve has one side connected to the pilot port of the pressure-reducing valve and another side connected to the pilot port of the pressure-relief valve for fluid flow only from the former to the latter. A function-control valve has a first connection coupled to the inlet side of the pressure-control valve and a second and third connection each coupled to a respective one of the pilot ports. This function-control valve is operable between a filling position connecting the pilot port of the pressure-relief valve to the pressure-control valve and an injecting/holding position connecting the pilot port of the pressure-reducing valve to the pressure-control valve.

Control system for injection-molding machine

An injection molding machine wherein a screw rotates and reciprocates in a barrel to plasticize granular synthetic material and to expel plasticized material into a mold. The screw is reciprocated by the piston of a hydraulic cylinder one chamber of which is connected with the outlet of a first pressure relief valve which determines the pressures of fluid while the screw moves forwardly to expel plasticized material, and with the inlet of a second pressure relief valve which determines the pressure of fluid while the screw moves rearwardly during plastification of granular material. The pressure relief valves are controlled by a pressure selecting valve which, in turn, is controlled by a programming unit. The inlet of the first pressure relief valve is connected directly with a line for highly pressurized fluid, and the outlet of the second pressure relief valve is connected with the tank. A fluid flow regulating valve controls the flow of hydraulic fluid from the high pressure line to the control ports of the pressure relief valves and to one port of the pressure selecting valve. Another port of the latter valve is connected with the tank.

Growing community of inventors

Munich, Georgia

Hans Birkhofer