Method and apparatus for processing potentially explosive and sensitive materials for forming longitudinally perforated extrudate strands

In a die system for receiving plastic material extrudate from a mixer or other source of flow under pressure and discharging the material in a cylindrical configuration, having a plurality of axially extending perforations:

• a. a surrounding cylindrical body sleeve providing an axially extending passage means with an axially concentric entrance channel and discharge channel;
• b. an axially extending core portion having generally radially directed ribs connecting it with the sleeve, said ribs separating said passage means into a group of circumferentially spaced die passages with axially convergent marginal walls extending axially between the sleeve and core between said ribs to pass material to said discharge channel, said convergent walls comprising radial surfaces on circumferentially adjacent ribs connecting the core portion with the sleeve which axially converge, there being also axially convergent, radially opposite, circumferential surfaces on the sleeve and core leading to and, with said radial rib surfaces, defining reduced metering openings for said die passages of generally frusto-conical transverse configuration;
• c. a plurality of axially extending elongate pins extending from said core portion into said discharge channel to form said perforations as said material exits the discharge channel;
• and
• d. said sleeve surfaces and said rib surfaces all extending at relatively shallow acute angles relative to the sleeve axis.

In a system for receiving plastic material extrudate from a mixer or other source of flow under pressure and discharging the material in a plurality of cylindrical configurations, each having a plurality of axially extending perforations:

• a. die channel means including a plurality of separate branch lines;
• b. a plurality of downstream dies, each communicating with one of said branch lines;
• c. each die comprising a surrounding cylindrical body sleeve providing an axially extending passage means with an axially concentric entrance channel and reduced diameter discharge channel;
• d. an axially extending core portion having generally radially directed ribs connecting the core portion with the sleeve, said ribs separating said passage means into a group of circumferentially spaced upstream die passage portions with axially convergent marginal walls extending axially between the sleeve and core between said ribs to pass material to said discharge channel, said convergent walls comprising axially convergent radial surfaces on circumferentially adjacent ribs connecting the core portion with the sleeve which axially converge, there being also convergent, radially opposite, circumferential surfaces on the sleeve and core leading to and, with said radial rib surfaces, defining reduced metering openings for said die passage portions of generally frusto-conical transverse configuration;
• e. said ribs also separating said passage means into a group of circumferentially spaced downstream die passage portions extending downstream from said metering openings toward said discharge channel and having divergent marginal walls extending axially between the sleeve and core between said ribs, said divergent walls comprising axially divergent radial surfaces on circumferentially adjacent ribs connecting the core portion with the body which axially diverge, there also being axially divergent, radially opposite, circumferential surfaces on the sleeve and core;
• f. The core portion in each die further having a conically projecting portion at its axially upstream and downstream ends, upstream and downstream respectively of said ribs;
• g. a plurality of axially extending elongate pins extending from said core portion into said discharge channel to form said perforations as said material exits the discharge channel;
• and
• h. said sleeve surfaces, said rib surfaces and said conically projecting portions all extending at relatively shallow acute angles relative to the sleeve axis.

In a die system for receiving plastic material extrudate from a mixer or other source of flow under pressure and discharging the material in a cylindrical configuration, having a plurality of axially extending perforations:

• a. a surrounding cylindrical body sleeve providing an axially extending passage means with an axially concentric entrance channel and reduced diameter discharge channel;
• b. an axially extending core portion having generally radially directed ribs connecting the core portion with the sleeve, said ribs separating said passage means into a group of circumferentially spaced die passage portions with axially convergent marginal walls extending axially between the sleeve and core between said ribs to pass material to said discharge channel, said convergent walls comprising radial surfaces on circumferentially adjacent ribs connecting the core portion with the sleeve which axially converge, there being also axially convergent, radially opposite, circumferential surfaces on the sleeve and core leading to and, with said radial rib surfaces, defining reduced metering openings for said die passage portions of generally frusto-conical transverse configuration;
• c. said ribs also separating said passage means into a group of circumferentially spaced downstream die passage portions extending downstream from said metering openings toward said discharge channel and having divergent marginal walls extending axially between the sleeve and core between said ribs, said divergent walls comprising axially divergent radial surfaces on circumferentially adjacent ribs connecting the core portion with the body which axially diverge, there also being axially divergent, radially opposite, circumferential surfaces on the sleeve and core;
• d. a plurality of axially extending elongate pins extending from said core portion into said discharge channel to form said perforations as said material exits the discharge channel;
• and
• e. said sleeve surfaces and said rib surfaces all extending at relatively shallow acute angles with respect to the axis of said sleeve.

In a system for receiving plastic material extrudate from a continuous mixer or other source of flow under pressure and releasing it in the form of multiple strands having a plurality of axially parallel perforations:

• a. die channel block means having an axially convergent inlet of circular cross-section for receiving the extrudate merging concentrically to a passage of figure-eight section, having opposed saddle portions which gradually neck in axially, and which diverges curvilinearly at a shallowly acute angle relative to the axis of said passage into a pair of separate curvilinear branch lines of circular cross-section perpendicular to their axis of extent, said branch lines then curving gradually to terminate in portions generally axially parallel to said inlet and passage;
• b. a plurality of downstream dies, each communicating with one of said branch lines;
• c. each die comprising a surrounding body sleeve defining passage means having an entrance opening and a discharge channel, and including an axial core portion;
• d. generally radially directed ribs, having axially inclined radial surfaces on adjacent ribs connecting the core portion with the body, defining a plurality of gradually narrowing, axially extending passages through which material flows from the entrance opening to the discharge channel;
• and
• e. a plurality of axially extending elongate pins extending from said core portion into said discharge channel to form said perforations as said material exits the discharge channel.