Plastic article or earthenware shaping or treating: apparatus – With apparatus assembly or dismantling means or with idle part – For extrusion or injection type shaping means
Patent
1994-09-20
1996-12-10
Warden, Robert J.
Plastic article or earthenware shaping or treating: apparatus
With apparatus assembly or dismantling means or with idle part
For extrusion or injection type shaping means
294265, B29C 4708, B23P 1900
Patent
active
055828485
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
a) Field of the Invention
The invention is directed to a process for the automated ejection of screws using pull-out mechanisms or ejector mechanisms which are known per se set forth in the preamble of claim 1 and to a device for carrying out the process. The invention is directed in particular to the automated ejection of screws used in screw presses or screw-type extruders for producing dough and pasta products, these screw extruders being connectable with swivelable mixing kneaders.
b) Description of the Related Art
It is generally common practice to remove pressing screws and conveying or feed screws from the cylinder of a screw extruder for cleaning purposes or for replacing worn screws. Spindle-operated pull-off or ejecting devices and hydraulically actuated pull-off or pull-out devices with one or two cylinders are known for this purpose. For example, DE-AS-1268367 describes a device for ejecting the screw from the cylinder of a screw-type extruder. A pressure rod is connected with the hydraulic piston of a screw adjusting device by means of a mechanical coupling. The coupling carries the pressure rod along only in the screw ejecting direction. In addition, the pressure rod is provided with drivers whose distance from one another corresponds to the piston stroke. A plurality of strokes are required to eject the screw from the cylinder. This device is mechanically costly and occupies a large amount of space. The free cantilevering or protruding length which increases with the number of strokes is not supported, which can lead to tilting and can result in damage to the screw.
European Patent Application No. 271399 describes a process and apparatus for assembling and disassembling extruder screws. The extruder screws are transported and supported in a fixed or stationary manner. However, handling by use of load suspension means and stop means is very cumbersome.
It is also known to provide screw shafts with axial bore holes for tempering (DD-PS 200079). However, such screw shafts are not suitable when higher pressures are applied.
OBJECT AND SUMMARY OF THE INVENTION
Therefore, the primary object of the present invention is to avoid the disadvantages of known prior art and to achieve an automated and reliably functioning ejection of screws. This is effected by ejecting a screw from or pulling out a screw from a surrounding cylinder of the screw extruder in one movement hydraulically to ensure a good sliding capability. In a particularly advantageous construction, this is done 1) by applying an excess of pressure acting against an ejector rod in a chamber in an axial bore of the screw by hydraulic fluid guided via an inlet bore until the screw is ejected entirely or partially from the cylinder, 2) by using water as the hydraulic fluid, and 3) by grasping the screw at a head piece before ejecting. Further, the invention has the object of developing a device for carrying out the process which is realized by a device wherein a screw of a screw extruder is provided with an axial bore for receiving and guiding an ejector rod. The ejector rod is supported in a drive shaft of the screw extruder. The wall of the bore, an end face of the head piece and an end face of the ejector rod form a chamber in which the required ejecting pressure is built up.
Twin-screw extruders with closely meshing shafts, block extruders and the like, also those in which spline shafts, etc. are used, can also be ejected in an advantageous manner by means of the invention.
For a better understanding of the present invention, reference is made to the following description and accompanying drawings while the scope of the invention will be pointed out in the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 shows a screw extruder with an ejector rod of a screw in a detailed cross-sectional view;
FIG. 2 shows a general plan view of the screw extruder.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The device according to the invention for automated ejection of screws substantially cont
REFERENCES:
patent: 3734667 (1973-05-01), Dray
patent: 3902835 (1975-09-01), Theysohn
patent: 4078454 (1978-03-01), Murakami et al.
patent: 4619599 (1986-10-01), Herbert et al.
Buehler AG
Dawson E. Leigh
Warden Robert J.
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