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twin screw extruder
A twin screw extruder comprising a cylinder having twin bores therein to receive the twin screw of the extruder and a circular casing with at least one passage to permit heating or cooling fluid to flow between the cylinder and the casing, in which the cylinder has a generally circular outside contour with a first set of grooves and a second set of grooves forming parts of said at least one passage, extending obliquely to the longitudinal axis of the cylinder and formed in the outer surface of the cylinder, the bottom walls of the grooves extending parallel to a plane which includes the two longitudinal axes of the twin bores with the first set of grooves lying on one side of said plane, and the second set of grooves lying on the other side of said plane, the inclination of said first set of grooves to said axis being opposite to the inclination of said second set of grooves to said axis, and the inside of the casing containing spaced recesses forming further parts of said at least one passage and, except for end ones of said recesses, each connecting one end of a respective one of the grooves of the first set of grooves to one end of a respective one of the grooves of the second set of grooves.
The invention relates to twin screw extruders comprising a cylinder having twin bores therein to receive the twin screw and enclosed by a cylindrical casing, with at least one passage to allow heating or cooling fluid to flow between the cylinder and the casing.
A difficulty encountered in the heating or cooling of cylinders in twin screw extruders where the bores partially overlap, is that the portions of the cylinder which absorb the greatest quantity of heat per unit are inwardly directed wedge-shaped projections at the sides of the region where the twin bores overlap. Such wedge-shaped projections can be cooled adequately only with a large technical outlay.
In previously proposed twin screw extruders, the cylinder enclosing the twin screw is in extended form, i.e. it is constructed with two flat outer faces each extending parallel with the plane in which the axes of the twin bores lie. This cylinder, which is difficult to produce in its basic shape, has a helical groove cut into its periphery, to guide the heating or cooling fluid around the cylinder in a helical path. The cylinder is surrounded by a circular casing and the gaps between the upper and lower surfaces of the cylinder and the inner wall of the casing are filled with separate chordal segments. Such a twin screw extruder is expensive to manufacture and it is difficult to maintain a seal between the cylinder and the segments.
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Where can I find an M4 x 25mm set screw that has a flat point or oval point?
Hard to find something in that length, but I need it.
It may not be readily available.
You have to take little bit extra long 4M screws and may have to machine to your requirement
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Set Screw Pipe Marking Tools
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Screw set $3.5 Screw set |
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summary twin screw extruder
(a) Field of the Invention
The present invention relates to a food processing machine applicable to a slurry raw material, and more particularly to a counter-rotating twin screw extruder structure with two oppositely and alternately disposed screw blades.
(b) Description of the Prior Art
In food industry, paste-like material, such as pet food, feeds or human foods, is utilized the co-rotating twin screw extruder which can effectively heat the starch in the material, appropriately mix, and then extrude the material to form the finished products.
Referring to FIG. 1, the co-rotating twin screw extruder comprise with two symmetrical screws driven by motor either directly or indirectly in the barrel casing. The two screws can rotate synchronously in the same direction, either clockwise or counterclockwise. The screw surface set with alternating screw flight. As shown in the drawing, when the co-rotating twin-screw extruder operates, the two screws 1 are all set in clockwise rotation so that material 2 and the helical blades of the screws 1 can rub each other to generate thermal energy through mechanical friction, which continuously heats the mixed material 2 and thus enhance the material cooking by the setting. This kind of co-rotating twin-screw have been widely used in the food industry and in feed manufacturing.
However, the co-rotating twin screw extruder device has several drawbacks in the operation:
(1) Since in the design of the screws 1 of the co-rotating twin screw extruder, the two forwardly and alternately disposed screw blades convey the raw material 2 to be agitated and extruded and the heating source is the friction between the raw material 2 and the screws 1, the production of the mechanical frictional thermal energy cannot be controlled, and extra thermal energy may be produced by unnecessary mechanical friction, whereby this kind of device may not be suitable for materials that do not need heating or cannot be heated.
(2) Due to the reason set above, the conventional co-rotating twin screw extruder cannot precisely set the mechanical friction induced thermal energy inside a desired working zone and may lead to deficiencies of undesired wearing of the helical blades and increase of load of the motor (increased power consumption).
(3) The conventional co-rotating twin screw extruder employs a gear box to raise the torque induced in the rotation thereof and the gear box requires a large number of gears to ensure shafts to rotate in the same direction, so that the gear assembly is complicated and additional cost of design is needed, and the great number of gears arranged inside the gear box comparatively increases the amount of thermal energy generated, whereby extension of lifespan must be realized through an additional external cooling system, which causes additional consumption of electrical power and also increases the cost of potential maintenance.
Thus, the above discussed drawbacks of the conventional co-rotating twin screw extruder cause certain troubles to the manufacturers so that such drawbacks must be overcome.
About the Author
The present invention relates to a food processing machine applicable to a slurry raw material, and more particularly to a counter-rotating twin screw extruder structure with two oppositely and alternately disposed screw blades.
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