Single screw extruder with interrupted flights
A single screw extruder with interrupted flights is provided with discontinuities or interruptions 7 in the flighting 8 of the screws 2. Stationary resistor teeth 9 protrude at these interruptions into the flow of material being pressed.
The present twin screw extruder relates to an improvement in a screw press, specifically to the configuration of the screws used in a twin screw press.
Screw presses have been used for centuries. Common applications are extracting juices and dewatering fibrous materials. Basically a screw press is a machine in which a helicoid screw rotates inside a cylindrical perforated screen. Entering material is subjected to gradually increasing pressure as it moves toward the exit end of the press, forcing the liquid phase to expel through the screen.
Compression is generally achieved in a screw press by a combination of three features: (a) the diameter of the shaft of the screw is increased, forcing material against the screen; (b) the pitch of the flights of the screw is reduced, compressing the material; and (c) back-pressure is created within the screen chamber by use of a cone (door, choke, plate, stopper or plug) located at the cake discharge end of the press.
A major sheet production extruder in screw press design was patented in 1900 by Valerius D. Anderson. His U.S. Pat. No. 647,354 describes how interruptions can be made in the flighting of the screw. This results in improved performance on slippery or slimy materials such as spent brewers' grain, orange peel, fish, and rendering offal. The use of screw presses with interrupted flights rapidly came to dominate in these applications.
The object of the subject invention is to gain, in one machine, the respective advantages of interrupted flight screw press and twin screw presses. The invention combines the high capacity and low horsepower, relative to size, of the interrupted screw press, along with the strong, positive throughput and dewatering features of the twin screw press.
While the present twin screw extruder has been described with respect to certain preferred embodiments, it is to be understood that the invention is not limited thereto, but rather is susceptible of numerous changes and modifications which will occur to those skilled in the art. Consequently, the present invention is not to be limited to the details shown and described herein, but is intended to cover all such changes and modifications as are encompassed by the scope of the appended single screw extruder claims.