Abstract: A plurality of internal couplers (A, B, C. D) are integrally connected end to end in a single tubing construction of indeterminant length. Between each coupler is an annular, frangible region (14, 24) of thin plastic. In the field, the individual couplers are readily broken manually from the tubing construction. Each coupler includes a plurality of cleats (40) which are partially surrounded by a region (50) of relatively thin plastic material. The couplers are manufactured by continuously blow molding a sleeve of softened plastic into the tubing construction of indeterminent length.

Abstract: The coextrusion die assembly receives a first and a second plasticized material flow which it forms into a layered, cylindrically tubular flow. An inlet block (100) receives the first material flow axially and the second material flow radially. A manifold block (200) forms the first material flow into a cylindrical flow and divides the second material flow into eight equal flow portions. A spider structure (300) has a first plurality of apertures (302-308) which pass the first material flow and eight second apertures (330-344) which receive the eight second material flow portions from the manifold. Each of the eight second spider apertures has a relatively small upstream opening and fans peripherally outward into a continuous cylindrical downstream region. A non-linear restriction means (440-454) provides a greater restriction in longitudinal alignment with the center of each of the second apertures and a less restrictive region therebetween.

Abstract: The specification discloses an apparatus and method for concurrently manufacturing at least two semiround tubing structures. An extruder including plasticizing means for a plurality of plastic resins extrudes semiround and linear strips of plastic material in generally two back to back D-shaped sleeves. Between the D-shaped sleeves, a strip of adhesively non-compatible material is extruded so that the D-shaped sleeves may be separated. The rounded portions of the D-shaped sleeves are molded in a continuous blow molding arrangement to form the top wall of the semiround tubing. The tubing is cooled, and the two semiround tubing lengths separated from the adhesively non-compatible strip inbetween. Optionally, the base of the semiround tubing may be perforated. The two lengths of semiround tubing are folded with the base inside the top wall and coiled into large reels.

Abstract: A feedblock fashioned from a plurality of plates is disclosed which distributes two flows of dissimilar synthetic resinous materials into a radially stratified annular form for extrusion by a pipehead die. The feedblock is mounted on a pipehead with the plurality of plates defining material flow channels for three strata. Independently operable valves vary stratum thickness and assure radially matched flow conditions between strata at confluence. Each stratum is independently accelerated through a convergent channel to assure that a uniform circumferential distribution of flow conditions develops. Moreover, two strata are developed through channel systems which do not induce circumferential maldistribution. The third stratum is handled to eliminate circumferential maldistribution. Accordingly, the process and apparatus develop stable annular flow with radial stratification having neither radial nor circumferential maldistributions that may later interact to distort the strata.

Abstract: A feedblock fashioned from a plurality of plates is disclosed which distributes two flows of dissimilar synthetic resinous materials into a radially stratified annular form for extrusion by a pipehead die. The feedblock is mounted on a pipehead with the plurality of plates defining material flow channels for three strata. Independently operable valves vary stratum thickness and assure radially matched flow conditions between strata at confluence. Each stratum is independently accelerated through a convergent channel to assure that a uniform circumferential distribution of flow conditions develops. Moreover, two strata are developed through channel systems which do not induce circumferential maldistribution. The third stratum is handled to eliminate circumferential maldistribution. Accordingly, the process and apparatus develop stable annular flow with radial stratification having neither radial nor circumferential maldistributions that may later interact to distort the strata.

Abstract: A pipehead for an extruder includes a die body and a die pin having a central bore, a plurality of radial ports, and a corresponding plurality of helical grooves with a region of decreasing depth. The helical grooves are located at the blind end of an annular channel having a constricted area and terminating in a die opening. The channel is defined by the die body and the die pin. A breaker plate having a multiplicity of openings may be provided downstream of the grooves to generate a multiplicity of filament-like streams that are subsequently recombined as they pass through the constriction of the annular channel. The diameter of the annular channel generally decreases axially along the head. The pipehead is provided with internal and external heating means for temperature control.