Abstract: Disclosed herein are a method and apparatus for combining two or more streams of a polymeric material to form a plastic object. The method and apparatus are capable of ending an interior layer of the plastic object at a desired length to avoid the need to clean selected surfaces of components used to form the plastic object. The method and apparatus increase the velocity of the polymeric material used to form the plastic object in certain components used to form the plastic object. The increase in the velocity of the polymeric material facilitates the ending of the interior layer of the plastic object.

Abstract: A method of co-extruding a plurality of plastic material flowing streams into a mold cavity produces a molded product. Inner and outer streams of covering plastic materials are combined with at least one interior stream that is to serve as an interior core of a resulting molded plastic product. The combined streams are forced to flow along annular flow paths, with the annular interior stream encased within the inner and outer annular covering plastic material stream layers. The flows of the interior stream and the inner and outer streams are controlled so that: the interior stream has a flow velocity that is greater than an average velocity of the combined stream, and the interior stream does not flow along or across a zero-velocity-gradient streamline of the combined streams.

Abstract: A nozzle for extruding an article has at least three layers of thermoplastic materials. A housing has a longitudinal axis. At least three extrusion dies are contained in the housing and aligned with the longitudinal axis. Each die has a face with a die channel in the face. Each die channel is a closed geometric figure. Each die channel has at least one inlet for receiving a respective thermoplastic material. Each die channel provides a respective outlet for feeding a respective one of the plurality of layers of thermoplastic materials to a respective flow channel within the housing. The flow channels deliver the plurality of layers so that at least three of the layers combine within the nozzle at substantially the same coordinate measured along the longitudinal axis.

Abstract: A novel technique for molding multi-layer polymer plastic articles having inner, outer and interior or core layers by controlling relative volumetric flow rates of the inner and outer layers to enable relative shifting of the position of the core, and also the relative thickness of the inner and outer layers in the molded articles; and with leading, and, where desired, trailing ends of the interior layer flow into the mold cavity substantially positioned on the zero gradient of the velocity profile of the flowing polymer streams.

Abstract: A novel technique for molding multi-layer polymer plastic articles having inner, outer and interior or core layers by controlling relative volumetric flow rates of the inner and outer layers to enable relative shifting of the position of the core, and also the relative thickness of the inner and outer layers in the molded articles; and with leading, and, where desired, trailing ends of the interior layer flow into the mold cavity substantially positioned on the zero gradient of the velocity profile of the flowing polymer streams.

Abstract: A novel technique for molding multi-layer polymer plastic articles having inner, outer and interior or core layers by controlling relative volumetric flow rates of the inner and outer layers to enable relative shifting of the position of the core, and also the relative thickness of the inner and outer layers in the molded articles; and with leading, and, where desired, trailing ends of the interior layer flow into the mold cavity substantially positioned on the zero gradient of the velocity profile of the flowing polymer streams.

Abstract: A novel technique for molding multi-layer polymer plastic articles having inner, outer and interior or core layers by controlling relative volumetric flow rates of the inner and outer layers to enable relative shifting of the position of the core, and also the relative thickness of the inner and outer layers in the molded articles; and with leading, and, where desired, trailing ends of the interior layer flow into the mold cavity substantially positioned on the zero gradient of the velocity profile of the flowing polymer streams.

Abstract: A multiple-plastic stream co-extruder, as for injection-molding cavities, in which the extruder is internally provided therewithin and therealong with a restrictor or throttle pin, rod or element that forces combined plastic material streams, formed with an interior core stream encased in outer and inner stream layers, into corresponding concentric annular flow stream layers that are ultimately split transversely in opposite directions into a cavity gated to the extruder, and with the core stream at a region of zero gradient in the transverse flow velocity profile within the extruder and cavity.

Abstract: A multiple-plastic stream co-extruder as for injection-molding cavities, in which the extruder is internally provided therewithin and therealong with a restrictor or throttle pin, rod or element that forces combined plastic material streams, formed with an interior core stream encased in outer and inner stream layers, into corresponding concentric annular flow stream layers that are ultimately split transversely in opposite directions into a cavity gated to the extruder, and with the core stream at a region of zero gradient in the transverse flow velocity profile within the extruder and cavity.