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Extrusion of an article of varying content
| Details |
Inventors: Harris, Holton E.;
Assignee: Harrel, Inc. (Norwalk, CT)
Primary Examiner: Nguyen; Khanh P.
Assistant Examiner:
Attorney, Agent or Firm: Brumbaugh, Graves, Donohue & Raymond
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. |
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DETAILED DESCRIPTION I claim: 1.
A process of extruding an extrudate with different materials, the proportions of which vary along the length of the extrudate, including: providing a first extruder having a first gear pump at an output end thereof, providing at least one further extruder having a second gear pump at an output end thereof, providing a die, directing material of a first kind from the first extruder through the first gear pump to the die, directing material of a second kind from the at least one further extruder through the second gear pump to the die, providing a controller operatively connected to the first and second gear pumps, and with the controller, varying the speed of at least one of the first and second gear pumps relative to the remaining of the first and second gear pumps to vary the relative content of the first and second kinds of materials in the extrudate.
2.
The process according to claim 1 or further including varying with the controller the speed of both of the first and second gear pumps to vary the content of both of the first and second kinds of materials in the extrudate.
3.
The process according to claim 1 further including adjusting with the controller the speed of at least one of the first and second gear pumps to control cross-sectional area in the extrudate.
4.
The process according to claim 3 wherein adjusting the speed to control cross-sectional area includes adjusting with the controller the speed of at least one of the first and second gear pumps to compensate for differing dimension-affecting characteristics of the two kinds of materials which affect a cross-sectional dimension of the extrudate.
5.
The process according to claim 4 wherein adjusting the speed of at least one of the first and second gear pumps to compensate for differing dimension-affecting characteristics includes providing a compensatory incremental speed increase to the gear pump that pumps one of the different kinds of materials having a greater shrinkage as it cools.
6.
The process according to claim 4 wherein adjusting the speed of at least one of the first and second gear pumps to compensate for differing dimension-affecting characteristics includes providing a compensatory incremental speed decrease to the gear pump that pumps one of the different kinds of material having a lower shrinkage as it cools
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Nonmetallic Processes 
