Foam Extrusion
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A foam extrusion apparatus and method in which extrudate is extruded
into a sealed chamber which may be subjected to pressure variation such
as a vacuum with the controlled shaping of the plastic being obtained by
power driven rolls within the chamber downstream of the die. Because of
the harsh environmental conditions within the chamber it is desirable
that the shaping or forming rolls be driven by an externally powered
source which will therefore be not subject to the pressure, vacuum, or
other deliterious conditions found within the chamber. Moreover, because
of the external position of the drive with regard to the chamber, the
entire system need not then be shut down in order to open the chamber
and make the required adjustments or repairs. The chamber is preferably
the upper end of a barometric leg into which the extrudate passes. The
upper end of the chamber is closed by one or more bulkheads which are
movable toward and away from the upper end of the chamber. The present
invention utilizes DC drive motors on the exterior of the bulkheads and
of course the chamber to drive the shaping rolls which are downstream of
the die. With this arrangement, both torque and speed may be closely
controlled and of course the chamber does not require to be opened to
make adjustments, replacements or repairs to the power system. |
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