Abstract: A process for producing a DVD from two DVD substrates A and B, wherein the first substrate (A-disc) of the DVD is produced by a first injection unit A and the second substrate (B-disc) of the DVD is produced by a second injection unit B, wherein one or both DVD substrates are coated, in particular metallised, in a coating station, wherein one or both DVD substrates are provided with an adhesive in an adhesive application station and wherein the DVD substrates A and B are supplied to at least one joining station for the purpose of joining the A-disc and B-disc to form a DVD. The invention is characterised in that at least one walking beam (12) is provided for transporting the DVD substrates A and B through the production line, in that the A-disc and the B-disc are alternately located behind one another in a row (A-B-A-B-A-B- . . . ) on the walking beam (12), and in that the walking beam is operated in double step fashion.

Abstract: A method for bonding two DVD halves (23, 24) which are so held at a distance as to form a gap therebetween, includes introducing into the gap an adhesive (36) and spreading the adhesive across both disc halves. The invention is characterized by introducing the adhesive via a central opening of the DVD by means of e.g. L-shaped metering needles (63) which are pivotally guided in a central pin that engages the central opening, or flexible plastic needles which are slidably guided in a guide tube. Through introduction of the adhesive via the central opening enables a flow to the outside, without interference from the metering needles, when the DVD halves (23, 24) rotate. There is no buildup of adhesive in front of the metering needle. The bonding process can be carried out without interruption of the application of adhesive until the spin-off has concluded.

Abstract: A method for bonding two DVD halves (23, 24) which are so held at a distance as to form a gap therebetween, includes introducing into the gap an adhesive (36) and spreading the adhesive across both disc halves. The invention is characterized by introducing the adhesive via a central opening of the DVD by means of e.g. L-shaped metering needles (63) which are pivotally guided in a central pin that engages the central opening, or flexible plastic needles which are slidably guided in a guide tube. Through introduction of the adhesive via the central opening enables a flow to the outside, without interference from the metering needles, when the DVD halves (23, 24) rotate. There is no buildup of adhesive in front of the metering needle. The bonding process can be carried out without interruption of the application of adhesive until the spin-off has concluded.

Abstract: An optical disk having a pair of axially oppositely directed faces and an annular outer periphery is made by first forming a mold cavity corresponding to the shape of the disk between a pair of axially spaced parts and a demolding ring sandwiched between the parts. The cavity is then filled with a hardenable resin such that the parts form the respective faces and an inner periphery of the ring forms the outer periphery of the disk and the resin is at least partially hardened in the cavity. The parts are then axially oppositely separated from each other and from the disk to leave the disk in the ring with both of its faces exposed and the ring is then transversely displaced with the disk engaged in it out from between the mold parts. The disk is then cooled and shrunk such that its outer periphery separates from the inner periphery of the ring and the disk separates from the ring.

Abstract: An optical disk having a pair of axially oppositely directed faces and an annular outer periphery is made by first forming a mold cavity corresponding to the shape of the disk between a pair of axially spaced parts and a demolding ring sandwiched between the parts. The cavity is then filled with a hardenable resin such that the parts form the respective faces and an inner periphery of the ring forms the outer periphery of the disk and the resin is at least partially hardened in the cavity. The parts are then axially oppositely separated from each other and from the disk to leave the disk in the ring with both of its faces exposed and the ring is then transversely displaced with the disk engaged in it out from between the mold parts. The disk is then cooled and shrunk such that its outer periphery separates from the inner periphery of the ring and the disk separates from the ring.

Abstract: A sprue part is cut and removed from the injection mold part during the manufacture of information storage disks by an injection molding process. The highly sensitive molding of an information storage disk is protected from damage by the sprue and the deposition of dust particles during stripping by this process. The sprue is punched into a part serving as the die of the injection molding tool and subsequently removed, in particular by suction, through an orifice leading from inside the part, together with the dust particles generated in the punching process. Preferably, the sprue is punched out and removed with the injection molding tool closed. The injection molding tool must be opened only after the sprue and the dust have already been removed, thus ensuring that the molded product has an especially good quality.

Abstract: A injection molded part of thermoplastic material, in particular an information carrier disk, is produced by cutting and removal of a sprue part from the injection molded part. The sprue removal leaves an opening in the injection molded part. In order to obtain a clean and smooth opening surface with a fit diameter that is as accurate as possible, the sprue part is axially offset relative to the injection molded part so that the integral connection between these two parts extends only over a part of the opening. The diameter of the axially projecting part is equal to or larger than the diameter of the opening and the rest of the opening being produced by injection molding. The dimensions are advantageously chosen so that a parting edge inclined at an angle of 45.degree. to the plane of the opening is formed and that the injection molded part amounts to 70% and the part to be separated to 30% of the length of the open. The injection molded length of the opening may also be variable.

Abstract: A sprue part is cut and removed from the injection mold part during the manufacture of information storage disks by an injection molding process. The highly sensitive molding of an information storage disk is protected from damage by the sprue and the deposition of dust particles during stripping by this process. The sprue is punched into a part serving as the die of the injection molding tool and subsequently removed, in particular by suction, through an orifice leading from inside the part, together with the dust particles generated in the punching process. Preferably, the sprue is punched out and removed with the injection molding tool closed. The injection molding tool must be opened only after the sprue and the dust have already been removed, thus ensuring that the molded product has an especially good quality.

Abstract: A check valve at the end of a plastifying worm for an extrusion or injection molding machine comprises a valve ring whose inner diameter is greater than that of a tip at the end of the head of the worm and which surrounds the neck connecting this tip with the valve seat of the worm. Spacers, preferably balls, are disposed between the ring and the tip and the surfaces of the ring and the tip flanking the balls are oriented to allow radial removal of the balls when the valve projects from the cylinder.

Abstract: A backflow preventer on the end of a plastifying screw for an injection molding apparatus has a housing provided with radial bores which are axially and angularly offset. A pin accessible from the exterior of the housing passes through a radial hole but traversing in a valve member with clearance to permit the stroke of the valve member to be adjusted by selective insertion of the pin in the bores.

Abstract: A backflow preventer at the end of an injection molding worm has a pressure ring which abuts directly upon the worm and serves a shank of the valvehead which also bottoms in a bore upon the worm so that force transmission to the worm is over its entire cross section. The shank is surrounded by a blocking ring which can shift in its axial stroke between a position in which it abuts the head and a position in which it abuts the pressure ring, the axial stroke being adjustable by shims forming the floor against which the shank abuts within the bore of the worm.