| 摘要 |
<p>An apparatus for producing multi-walled thermoplastic tubing having a corrugated wall and a substantially smooth inner wall secured to the corrugated wall, there is incorporated two sets of endless flexible belts each of which is entrained around rotatable end rolls, the outer runs of the belts of one of the sets thereof alternating with the outer runs of the other of the sets thereof, with these outer runs of the various belts serving to urge the inner wall against the corrugations of the corrugated wall while the thermoplastic material of the walls is soft thereby to secure the walls together, and with an electrically energizeable heating coil being provided for softening the thermoplastic material of the corrugated wall to ensure satisfactory securement between the walls. The apparatus also incorporates a suction chamber, a cooling chamber forwardly of the suction chamber, and a pressure chamber forwardly of the cooling chamber, the suction chamber communicating with passages in the mold blocks which constitute a tubular mold tunnel in which the tubing is formed to urge the appropriate wall against the tubular mold tunnel thereby to form the corrugated wall, cooling air flowing from the cooling chamber through these passages and exhausting through spring-loaded check valves to cool the mold blocks, and pressurized air flowing from the pressure chamber through the passages to eject the finished tubing from the tubular mold tunnel at the forward end thereof, during which the check valves are maintained closed.</p> |
