Abstract: An injection molding apparatus for the injection molding of data storage discs of thermoplastic synthetic material, includes an embossing plate mounted on a movable die for embossing information pits on one side of the discs. An insert confronting the embossing plate is mounted on the fixed die of the apparatus, the insert having a die opening through which the thermoplastic synthetic material may be injected into the die nest formed between the dies, and the insert being of non-corrosive and essentially non-porous, non-metallic material with its outer surface being highly polished, essentially smooth and unpitted so as to produce discs having a smooth side opposite the embossed side.

Abstract: 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.

Abstract: An injection-molding apparatus for making ceramic moldings has a mold provided with a mold cavity, a structure formed with a passage which communicates with the mold cavity, and an injecting arrangement for injecting the molding material via the passage into the cavity. The injecting arrangement has a cylinder a front end of which is provided with an outlet communicating with the passage, and which also has a material inlet rearwardly spaced from the outlet. A ram is reciprocable in the cylinder between a first end position in which it is located rearwardly of the inlet and another end position in which it is located forwardly of the inlet and close to the outlet. The ram carries a rearwardly extending skirt which extends across the inlet when the ram is in its forward or second end position, so as to prevent material from entering the cylinder behind the ram through the inlet.

Abstract: 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.