Screw Set
Screw Set How to set the set screw in my refrigerator thermostat? It stays on too long, and then It cuts back in too? soon. My food is starting to freeze in the refrigerator! So when the fridge cuts o...
Screw Set
Description Of Single Screw Extruder
Description of single screw extruder
Field of single screw extruder
The present invention relates to a single screw extruder.
background of single screw extruder
Thermoplastics resins are typically formed by extruding the material through a through a die which shapes the material. The raw material is placed in a hopper where it is moved into and through a chamber by a screw. The mechanical action of the feeder screw heats and feeds the material through chamber which is typically in the shape of a barrel. The heated and compressed material is forced through the die at the discharge end of the pelletizing machine . The extruded part assumes the cross-sectional shape of a die.
In a single screw extruder, the screw typically has an external diameter corresponding to outer edges of the helical threads or flights. The flights may be under sized in relation to the barrel in the feed or hopper area so as to reduce feedthroat friction. Typically, a single keyway in the shaft area of the screw matches a keyway in a sleeve portion of a drive shaft so that a key positioned in the matching keyways is utilized to transmit rotational movement from the drive shaft to the screw. The key is a separate piece of rectangular metal which fits into the matching keyways.
As the viscosity of the thermoplastic material increases, it has been observed, that in single screws of the above described type, radial screw movement or wobble may develop. Clearance in the feed area between the outside diameter of the screw and the inside of the pet sheet permits movement of screw. As the screw wears, metal may be removed between the exterior of the screw and the inside of the barrel.
Hence, it is desirable, to reduce radial movement without reducing clearance in the feed screw area which clearance is desirable for extruding higher viscosity materials. Reduction in radial movement beneficially reduces screw wear and contamination of the finished product with residual metal particles from the screw or barrel.
Summary of the single screw extruder
It is an object of the present invention to provide a single screw extruder with enhanced coupling to a drive shaft to reduce radial movement of the feed screw when subjected to high loading.
Other and additional objects will become apparent from the description as set forth in the specification.
In accordance with the present invention, there is provided a single screw extruder of the type having a drive shaft coupled to the screw for rotational movement wherein the improvement comprises coupling the drive shaft to one end of the screw through a plurality of splines on the screw.
According to preferred embodiments, the respective ends of the screw is coaxially aligned with the drive shaft and coupled together with a sleeve having a plurality of serrations matching the respective splines on the screw.
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