US 5,695,789 A · Apparatus for extrusion of an article of varying content

Abstract

A coextrusion system employs two or more extruders, each with a gear pump at its output connected to a coextrusion die. Different materials are extruded by each extruder. Varying the speed of one or both gear pumps varies the content of the extrudate. The gear pumps permit precise variation of the relative content of the materials extruded by the several extruders lengthwise along the extrudate. A display of a cross sectional dimension of the extrudate along a length of the extrudate permits observation of the lag that occurs between alteration of gear pump speed (or air pressure in the case of tubular or blown sheet extrudates) and the resultant change in dimension, so that a speed correction can be made at the appropriate time to compensate for differing shrinkage and stretching characteristics between the several extruded materials.

Claims33

Dependent claims

An extrusion system for extruding an extrudate with different materials, the proportions of which vary along the length of the extrudate, the system including:

a first extruder comprising a first output end,
at least one further extruder comprising a further output end,
a first gear pump connected to the first output end;
a second gear pump connected to the further output end,
a die connected to receive the output of the gear pumps, and
at least one controller operatively connected to the gear pumps, wherein material of a first kind is directed from the first extruder through the first gear pump to the die and material of a second kind is directed from the at least one further extruder through the second gear pump to the die, the at least one controller adapted to vary the speed of at least one of the first and second gear pumps relative to the remaining of first and second gear pumps to vary the relative content of the first and second kinds of materials in the extrudate.

3 more elements

An extrusion system for extruding an extrudate with different materials, the proportions of which vary along the length of the extrudate, including:

a first extruder having a first gear pump at an output end thereof,
at least one further extruder having a second gear pump at an output end thereof,
a die connected to receive the output of the gear pumps, and
at least one controller operatively connected to the gear pumps,
wherein material of a first kind is directed from the first extruder through the first gear pump to the die,
and wherein material of a second kind is directed from the at least one further extruder through the second gear pump to the die,
the at least one controller adapted control the gear pumps to vary the speed of at least one of the gear pumps to vary the relative content of the first and second kinds of materials in the extrudate, by
(i) momentarily changing the speed of one of the gear pumps to cause a measurable change in dimension of the extrudate,
(ii) observing the occurrence of the change in dimension at a location downstream of the die to determine an amount of lag between the gear pump speed change and the observed change in dimension, and
(iii) making gear pump speed adjustments in response to subsequently observed extrudate characteristics at a time determined to affect the extrudate at a desired location along its length as determined by the measured amount of lag.

7 more elements

Dependencies are inferred from the claim text.

Apparatus for extrusion of an article of varying content

Life of this patent

Apparatus for extrusion of an article of varying content

Life of this patent

Abstract

Claims33