Abstract: An extrusion die configured to have an interior chamber sealed from the atmosphere is disclosed. The extrusion die includes an extrusion die head disposed at a downstream end of the interior chamber; and a vacuum seal disposed at an upstream end of the interior chamber; wherein the vacuum seal is configured to selectively form a seal between the extrusion die and a product disposed in the interior chamber. The vacuum seal includes an annular sealing surface disposed at an inner diameter of the vacuum seal; a hollow, interior chamber; and a plurality of bellows disposed between the annular sealing surface and the extrusion die; wherein the vacuum seal is configured to selectively form a seal between the extrusion die and a product disposed in the interior chamber. A method of selectively sealing an end of an extrusion die is also disclosed.

Abstract: A coupling for three-wall, corrugated pipe, the pipe including a corrugated wall having a plurality of primary corrugations, is disclosed. The coupling includes a first pipe section having disposed at one end a bell portion, the bell portion having a bell portion of corrugated wall and an outer wall; a second pipe section having disposed at one end a spigot portion, the spigot portion having a spigot portion of corrugated wall between an inner wall and an outer wall; and a gasket disposed in a groove extending around a circumference of the spigot portion and engaged between the bell portion of corrugated wall and the spigot portion of corrugated wall. A three-wall, corrugated pipe section, and method for assembling a plurality of three-wall, corrugated pipe sections, are also disclosed.

Abstract: A coupling for three-wall, corrugated pipe, the pipe including a corrugated wall having a plurality of primary corrugations, is disclosed. The coupling includes a first pipe section having disposed at one end a bell portion, the bell portion having a portion of the corrugated wall and an outer wall; a second pipe section having disposed at one end a spigot portion, the spigot portion having a portion of the corrugated wall between an inner wall and an outer wall; and a gasket engaged between the corrugated wall of the bell portion and the outer wall of the spigot portion. A three-wall, corrugated pipe section, and method for assembling a plurality of three-wall, corrugated pipe sections, are also disclosed.

Abstract: A method and apparatus is provided for distributing material through a multilayer pipe extrusion die. A first flow passageway, having a first cross-sectional area and extending along a first flow direction, may be connected to a second flow passageway, having a second cross-sectional area substantially the same as the first cross-sectional area of the first flow passageway, to provide a second flow direction different from the first flow direction of the first flow passageway. A conical passageway may extend from the second passageway toward a dispensing outlet. Material may be distributed from the first flow passageway into the second flow passageway. The method and apparatus may generally maintain the same flow properties of the material at a point before and after the connection of the first flow passageway and the second flow passageway. The flow properties of the material may be altered proximate to the outlet.

Abstract: A pipe extrusion die may be provided having an inner flow passageway having a first cross-sectional area, and an outer flow passageway having a second cross-sectional area, both being in communication with an inlet flow passageway. A ratio adjusting tube may be movably disposed in blocking engagement between the inlet flow passageway and the inner flow passageway. The ratio adjusting tube and the outer flow passageway both may be substantially concentric with the inner flow passageway. Material may be distributed from the inlet flow passageway to the inner and outer flow passageways. The method and apparatus may allow for the manual and automatic control of the proportion of material distributed between the inner and outer flow passageways by adjusting the position of the ratio adjusting tube in relation to a passageway between the inlet flow passageway and the inner flow passageway, based on various operating parameters.