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Plastic Extruder: Steam-Jacketed Screw Stuffer with a Heated Nozzle (Andersen & Strasdin, US 2,384,521, 1945)
A screw extruder for thermoplastics: a turning screw in a steam-jacketed barrel pushes hot, softened plastic forward through a short nozzle heated electrically. The barrel is kept a little below the plastic's flow temperature and the nozzle well above it, so the extruded rod comes out with a smooth, glass-like skin.
Result: an extruder that makes rod, tube or strip at 25 to 30 feet a minute.
Source: B. Andersen and R. F. Strasdin (Celanese), US 2,384,521 (1945). Unknown: sizes and metals. Picture: the patent drawing.
Advanced
Unknown
Instructions
1
1
Make the screw
Make the screw
Turn a screw to fit the barrel. Its thread may be single or double; to press the plastic harder toward the nozzle, make the pitch increase or the groove get shallower toward that end. Example: a double-thread screw. Ours: mild steel. Not given: sizes.
Materials for this step:
Mild Steel Round Bar1 screwTools needed:
Metal Lathe
Milling Machine
Unknown Dimensions2
2
Make the jacketed barrel
Make the jacketed barrel
Make the barrel with a steam jacket round it and a steam port into the jacket, and a feed throat at the back end. The inside wall may be grooved, pitched so that every flight of the screw always meets a groove; this stops the plastic slipping. Not given: the metal, the steam pressure.
Materials for this step:
Unknown Metal1 barrel and jacketTools needed:
Metal LatheUnknown Dimensions3
3
Fit the heated nozzle
Fit the heated nozzle
At the front, fit a streamlined nozzle head so no plastic can pocket and decompose, and a nozzle 1/2 to 18 inches long; about 6 inches in the example. Perforated plates may go between the screw and the nozzle. Heat the nozzle with an electric resistance coil. Ours: nichrome wire.
Materials for this step:
Unknown Metal1 nozzle head and nozzle
Nichrome Wire1 nozzle heating coil
Unknown Insulating Material1 coil insulationTools needed:
Metal Lathe4
4
Drive the screw
Drive the screw
Drive the screw through a gear from a motor, so its speed can be kept steady; 20 revolutions a minute in the example. Not given: the drive.
Materials for this step:
Electric Motor1 drive motorUnknown Metal1 drive gearsTools needed:
Unknown Dimensions5
5
Extrude a rod
Extrude a rod
Keep the barrel 0 to 100 °F below the plastic's flow temperature and the nozzle 50 to 100 °F above it. Example: barrel at about 270 °F by steam, nozzle at about 400 °F, for a cellulose acetate with a flow temperature of 307 °F. Feed the hot, softened plastic into the throat at a steady rate. Carry the rod away on a conveyor and cool it at once with cold water, then cut it to length.
Tools needed:
Steam Boiler
Pyrometer
Cooling WaterMaterials
5- 1 screwPlaceholder
- 1 drive gearsPlaceholder
- 1 nozzle heating coilPlaceholder
- 1 coil insulationPlaceholder
- 1 drive motorPlaceholder
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