Claims
- 1. An apparatus for extruding a polymer which is subject to periodic surges of pressure or flow rate, said apparatus comprising:
- a barrel having an upstream portion for receiving said polymer, a downstream portion and a discharge port proximal said downstream portion;
- a shaft mounted for rotational movement about a longitudinal axis within said barrel, said shaft having a screw flight positioned upstream from said discharge port and arranged for urging said polymer downstream through at least a portion of said barrel;
- drive means connected for rotating said shaft;
- a surge suppressor connected to said shaft including a reverse screw flight on said shaft and located downstream of said discharge port for urging said polymer upstream toward said discharge port while permitting a portion of said polymer to flow in a downstream direction into said surge suppressor, said reverse screw flight of said surge suppressor being capable of generating a pressure less than or substantially equal to a maximum pressure generated in said screw flight;
- sealing means located downstream of said surge suppressor;
- a sensor positioned to detect said surges of said polymer; and
- a controller connected to said sensor and to said drive means for adjusting said rotational movement of said shaft in response to said surges of said polymer.
- 2. The apparatus described in claim 1, wherein said sensor monitors polymer pressure to detect said surges.
- 3. The apparatus described in claim 2, wherein said sensor monitors said polymer pressure in said barrel.
- 4. A method for extruding a polymer using an extruder having a barrel, a shall mounted for rotation within said barrel, and a discharge, said method comprising the steps of:
- urging polymer through said barrel and toward said discharge with a screw flight on said shaft;
- generating a polymer pressure and a polymer flow rate;
- suppressing surges in said polymer pressure or said polymer flow rate by generating a suppressing pressure less than or equal to a maximum polymer pressure with a reverse screw flight .positioned on said shaft downstream of said discharge;
- sealing against flow of polymer downstream of said reverse screw flight;
- monitoring said polymer pressure or said polymer flow rate;
- controlling said polymer pressure or said polymer flow rate by adjusting said rotation of said shaft to compensate for said surges in said polymer pressure or said polymer flow rate; and
- directing said polymer from said barrel and through said discharge.
Parent Case Info
This application is a continuation-in-part of application Ser. No. 08/250,909, filed May 31, 1994, now Pat. No. 5,486,328.
US Referenced Citations (23)
Foreign Referenced Citations (1)
Number |
Date |
Country |
2413374 |
Oct 1975 |
DEX |
Non-Patent Literature Citations (2)
Entry |
"The Dynamic Behavior of Extruders," I. Patterson et al, 1978 ANTEC, pp. 483-487. |
"Development of Computer Control Strategies for Plastic Extruders", J. Parnaby et al, Polymer Engineering and Science, Aug. 1975, vol. 15, No. 8, pp. 594-605. |
Continuation in Parts (1)
|
Number |
Date |
Country |
Parent |
250909 |
May 1994 |
|