Abstract:
A machine for continuous processing of flowable materials has a plurality of axis-parallel shafts in a space in a housing along a circle. Each shaft includes shaft bearing processing elements which tightly intermesh adjacent shafts. Between a material inlet at one end of the housing and a material outlet at the other end thereof, the housing jacket is divided radially into short segments with further passages and long segments, the length of the long segments being smaller than the outside distance thereof.

Description:
FIELD OF THE INVENTION 
     This invention relates to a machine for continuous processing of flowable materials. 
     BACKGROUND OF THE INVENTION 
     A machine for continuous processing of flowable materials is known e.g. from EP 0 788 867 A1. The housing wall consists for example of two about equally long segments, one segment being provided with the material inlet and the other segment with the other passages through which gases are sucked out of the material to be processed subsequent to a kneading and retaining zone. 
     The processing elements must engage the semicircular channels in the inside core and in the housing wall largely tightly. On the other hand, the housing is exposed to high wear. The two segments produced at high expense must thus be replaced quite frequently. 
     The problem of the invention is to substantially reduce the costs of such a machine caused by replacement of the segments. 
     This is attained according to the invention by Applicants&#39; machine. 
     SUMMARY OF THE INVENTION 
     As has been ascertained, the wear of the housing is different in the machine in the axial direction, i.e. compared with the rest of the housing wall, mainly where the passages are located for supplying or removing substances. 
     For example, high wear occurs in the area of passages for supplying solid additives to the material to be processed in the machine, for example reinforcing fibers in the form of rovings. The wear in the area of the passages can also be comparatively low, however, e.g. if the passages are used for sucking off gases or for supplying substances with lubricating properties. 
     By reason of this different wear of the housing wall in the area of the passages, short segments provided with these passages are used according to the invention while the other segments of the housing wall are of longer design but not longer than the outer diameter of the housing or the largest part of the housing and thus the long segments. 
     The wear of the housing wall can in addition be dependent on the processing elements. Thus, such a machine can have one or more kneading zones and/or retaining zones between the material inlet and the material outlet. The positively conveying worm elements as processing elements are then replaced in the kneading zone for example by kneading blocks, as known e.g. from EP 0 422 272 A1, and in the retaining zone for example by baffle plates or negatively conveying worm elements. 
     According to the invention, the segments subject to lower wear thus need to be replaced less often than the segments exposed to high wear. This substantially reduces the operating expenses of the machine. 
     Taking as a basis the diameter of the bores for receiving the shafts with the processing elements, the length of the long segments is preferably three to seven times, in particular about five times, this diameter, and the length of the short segments one to three times, in particular about two times, this diameter. 
     Since their strength can be weakened by the passages, the short segments preferably have a larger wall thickness than the long segments. The wall thickness of the long segments can be for example one to three times, in particular about two times, the diameter of the bores for receiving the shafts with the processing elements. In addition, the long segments can be provided on their outside circumference with at least one ring groove for receiving a heater or heat sink. 
     The passages in the short segments are preferably formed at least partly by larger openings having a diameter which is at least half as large as the diameter of the bores for receiving the shafts with the processing elements. 
     The long segments are either completely closed or provided at most with small openings with less than one half, in particular less than one fourth, of the diameter of the bores for receiving the shafts with the processing elements. The small bores in the long segments can be used for example for temperature measurement, for sampling or for supplying viscous substances. 
     If the material to be processed is a solid material which is plasticized in the machine, for example thermoplastic pellets of plastic, the passages can be used for example for sucking gases out of the plasticized material or for supplying additives to the plasticized material. These additives can be for example reinforcing materials, such as reinforcing fibers, which can be supplied e.g. in the form of rovings. 
     For supplying such solid additives one might require passages which are larger than the passages for discharging gases. Thus, the passages for discharging gases can for example correspond to or be smaller than the diameter of the bores for receiving the shafts with the processing elements while the passages for supplying solid additives can be larger than the diameter of the bores for receiving the shafts with the processing elements. 
     Accordingly, it is also possible according to the invention to divide the short segments into ones having at least one passage with a diameter larger than the diameter of the bores for receiving the shafts with the processing elements, and ones having exclusively passages with a diameter corresponding at most to the diameter of the bores for receiving the shafts with the processing elements. The short segments with at least one such large passage whose diameter is larger than the diameter of the bores for receiving the shafts with the processing elements can be equally long as or longer than the other short segments. 
     Besides the short and long segments the housing has a filling segment provided with the material inlet. The filling segment is preferably provided with an opening for discharging gas from the space with the shafts. After entering this space through the material inlet, the material to be processed is conveyed back and forth between adjacent shafts between the outer side and the inner side of the space. If the material to be processed is a powder, the gas component of the powder is thereby separated from the solid. The gas component can thus be sucked off through the gas outlet. 
     The inventive machine accordingly also permits processing of e.g. very finely powdered substances which can otherwise not be processed with such a machine because the high air component leads to problems in the machine. 
     The gas outlet can be provided in the filling segment or, if the inside core has a hollow design, by an opening leading from the space with the shafts into the hollow inside core. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     An embodiment of the inventive machine will be explained in more detail below with reference to the enclosed drawing, in which: 
     FIG. 1 shows a longitudinal section through the machine; 
     FIGS. 2 and 3 show cross sections along line II—II and III—III in FIG. 1; 
     FIG. 4 shows a cross section along line IV—IV through the filling segment in FIG. 1; and 
     FIG. 5 shows a cross section in accordance with FIG. 4 but of a different embodiment of the filling segment. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     According to FIGS. 1 to  3  the machine has in housing  1  space  2  extending along dividing circle  3  (FIG.  2 ). In space  2  there are a plurality of axis-parallel shafts  4 . Space  2  extends between axial inside core  6  and housing jacket  5  coaxial therewith. 
     Housing  1  is closed on its faces by end plates  7 ,  8 . Shafts  4  extending through plate  7  are driven in the same direction by a drive not shown. Plate  8  can for example have fastened thereto an extruder head (not shown) with the material outlet. 
     Disposed on each shaft  4  are a plurality of positively conveying processing elements  9  formed as worm elements. As indicated by FIGS. 2 to  3 , worm elements  9  of adjacent shafts  4  intermesh with little play, i.e. largely tightly. 
     Housing jacket  5  is provided on the inner side, and core  6  on its outer side, with axis-parallel semicircular depressions or channels  10 ,  11 , so as to form circular bores with diameter d. The centers of these bores are located on dividing circle  3 . Channels  10  and  11  are engaged by processing elements  9  with little play, i.e. largely tightly. 
     Housing jacket  5  is formed from end plate  7  to end plate  8  by radial division by filling segment  13 , first short segment  14 , first long segment  15 , second short segment  16  and second long segment  17 . 
     Filling segment  13  is provided on the upper side with inlet  18  through which the material to be processed (not shown) is supplied to space  2  with shafts  4 . 
     According to FIG. 4, the side surfaces of inlet  18  extend tangentially to circular-arc space  2  so that inlet  18  forms a U-shaped space in cross section with space  2 . 
     Between material inlet  18  and the material outlet (not shown) at the other end of housing  1  there is one kneading zone  19 ,  20  in space  2  at a distance from inlet  18  in filling segment  13  and in first long segment  15  in each case, and retaining zone  21  subsequent to kneading zone  19 . In the area of kneading zone  19 ,  20  worm elements  9  are replaced by kneading blocks, as known for example from EP 0 422 272 A1, and in retaining zone  21  by negatively conveying, and thus retaining, worm elements or optionally baffle plates. 
     Long segments  15 ,  17  have length B and short segments  14 ,  16  lengths C and D, respectively. Length B of long segments  15 ,  17  is smaller than outer diameter A of housing jacket  5  in the area of long segments  15 ,  17  or end plates  7 ,  8 . If long segments  15 ,  17  or end plates  7 ,  8  have an angular out-side circumference, A is the distance between the two closest opposite sides. Distance A is thus the distance between the closest opposite sides of the outside contour of long segments  15 ,  17  or end plates  7 ,  8 . 
     Based on diameter d of the bores in space  2 , length B of long segments  15 ,  17  can be for example three to four times diameter d, and length C or D of short segments  14 ,  16  one to three times diameter d. 
     According to FIGS. 2 and 3, a plurality of passages  23 ,  24  in the form of radial bores opening into space  2  are provided in each of short segments  14 ,  16 . 
     First short segment  14  has a bore or passage  23  with a diameter larger than diameter d, and further a plurality of smaller bores or passages  24  with a diameter corresponding to diameter d. 
     Via large passage  23  worm conveyor  25  supplies solid additives, for example glass fibers in the form of short fibers, which are added via inlet  26 . In one of passages  24  body  27  with small-diameter bore  28  is fastened with screw  29 . The other passages  24  are sealed by filling pieces  31  fastened with screws  29 . Screws  29  can be screwed with their heads against body  27  or flanges on filling pieces  31 . Via bore  28  in body  27  one can supply liquid substances, for example water, plasticizers, reaction substances or wetting agents. 
     Passages  24  sealed by filling pieces  31  can be used for sucking off volatile substances in case of need. The same applies to passages  24  in second short segment  16 , which, like short segment  14 , has a substantially angular outside circumference. In short segment  16  there is a ring channel  33  which connects passages  24  with openings  35  on the edges which can be sealed by filling pieces  31 . 
     First short segment  14  with large passage  23  can have length C which corresponds to or is larger than length D of second short segment  16 . 
     First short segment  14  is of massive design, apart from the area of radial passages  24 , i.e. it has a greater wall thickness than long segments  15 ,  17 . 
     Short segments  14 ,  16  are located outside the area of kneading zones  19 ,  20  and retaining zone  21 . 
     Filling segment  13  and long segments  15 ,  17  are in each case provided on the outside circumference with a ring groove in each of which heater  36  is disposed or optionally a heat sink. 
     Through the ring grooves flanges are formed on long segments  15 ,  17 . In order to interconnect alternating short and long segments  14  to  17 , holes are provided in the flanges of long segments  15 ,  17  through which screws  37  are inserted which are screwed into threaded holes  38  in short segments  14 ,  16 . Similarly, end plate  8  is fastened to the facing flange of adjacent long segment  17  while first short segment  14  is fastened to filling segment  13  likewise by screws  37  inserted through holes in the adjacent flange of filling segment  13 . 
     To permit air or other gases to be sucked out of a powdery material supplied to the machine via material inlet  18 , inside core  6  has, according to FIG. 4, axial bore  39  as well as radial bores  41  from space  2  into axial bore  39  to which gas suction means (not shown) are connected. 
     Instead, according to the variant shown in FIG. 5, filling segment  13  can be provided with gas outlet  42  offset at an angle from material inlet  18  in order to suck gas out of the powdery material.