Abstract:
A material processing plant comprises a first screw-type extruding machine ( 1 ) and a second screw-type extruding machine ( 2 ) which is disposed downstream thereof. Between the two screw-type extruding machines ( 1, 2 ), provision is made for a delivery zone ( 28 ) where a delivery orifice is provided, extending radially of the axes ( 12   a   , 13   a ) of the casing bores ( 12, 13 ) of the first screw-type extruding machine ( 1 ) and being directed towards the second screw-type extruding machine ( 2 ). The at least one casing bore ( 12, 13 ) of the first screw-type extruding machine ( 1 ) is lockable in the direction of its axis ( 12   a   , 13   a ) by means of a sealing element.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a United States National Phase application of International Application PCT/EP2004/004157 filed on Apr. 8, 2004 and claims the benefit of priority under 35 U.S.C. § 119 of European Application Number 03 011 994.5 filed May 28, 2003, the entire contents of which are incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The present invention pertains to a material processing plant. 
     BACKGROUND OF THE INVENTION 
     In particular in the processing of plastics, it is often reasonable to provide two or several successive extruders, each of which performing individual processing steps. For example, when plastic material is used in the form of powder, inlet and melting of the powder can take place in a first extruder. 
     Homogenizing and pressure build-up then takes place in a second, downstream extruder. Successive extruder arrangements of the generic type are known for example from EP 1 005 41 1 B 1, U.S. Pat. No. 3,261,056 and DE 2 304 088 A. In the plants of the generic type known from literature and practice, the connecting parts, which often have a weight of several tons, are hard to remove and re-insert, with removal of the connecting parts being indispensable for the screw shafts of the first extruder to be pulled out. In practice, pulling out the screw shaft through the discharge zone is customary, because the other end is provided with the motor, coupling and transmission and pulling out the screw shaft there poses serious problems. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to develop a plant of the generic type in such a way that pulling the screw shaft or shafts of the first screw-type extruding machine is especially easy and time-saving. 
     According to the invention, this object is attained by the features of a first extruder. The first extruder comprises a casing with at least one first casing bore having an axis and a first screw shaft which is disposed in the at least one first casing bore. A second extruder is disposed downstream of the first extruder. A delivery zone connects the first extruder to the second extruder and which is provided with a delivery orifice that extends radially of the axis and is directed towards the second extruder. The at least one first casing bore, in a direction of the axis, is lockable by means of a sealing element. The sealing element can preferably be a movable body having at least one through bore that is movable for congruence with the corresponding casing bore. This body can be a revolute body or a slide body. The body can be a revolute slide body, which offers numerous additional functions to be implemented. 
     The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming apart of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG. 1  is a vertical sectional view of a first embodiment of a plant according to the invention in a screw-shaft pull-out position; 
         FIG. 2  is a plan view, partially broken open, of the plant according to the first embodiment; 
         FIG. 3  is a view of a detail III of  FIG. 1 ; 
         FIG. 4  is a partial sectional view of the plant on the line IV-IV of  FIG. 1 ; 
         FIG. 5  is a partial plan view, partially broken open, of the plant in a modified position of operation as opposed to  FIG. 2 ; 
         FIG. 6  is a sectional view of  FIG. 5  on the line VI-VI in a non-throttled position of delivery; 
         FIG. 7  is a partial sectional view of  FIG. 5  on the line VI-VI in a throttled position; 
         FIG. 8  is a vertical sectional view of a second embodiment of a plant according to the invention in a sealing position; 
         FIG. 9  is a vertical partial sectional view of the second embodiment in a screw-shaft pull-out position; and 
         FIG. 10  is a sectional view on the line X-X of  FIG. 9 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings, the first embodiment seen in  FIGS. 1 to 8  comprises a first extruder  1  and a second extruder  2 . The first extruder  1  is disposed above the second extruder  2 . The first extruder  1  is actuated by a first motor  3  via a first coupling  4  and a first transmission  5 . The second extruder  2  is driven by a second motor  6  via a second coupling  7  and a second transmission  8 . Control of the motors  3  and  6  takes place by way of a control unit  9 . 
     The first extruder  1  comprises a casing  11  which is provided with a heating system  10  and has two first casing bores  12 ,  13  with axes  12   a ,  13   a  that are parallel to one another, the casing bores  12 ,  13  being disposed parallel to each other in approximately figure-eight-type interengagement. Two first screw shafts  14 ,  15  are disposed in these casing bores  12 ,  13 ; they are coupled with the first transmission  5 . The screw shafts  14 ,  15  are driven in the same or opposite directions. The first extruder  1  comprises a feed hopper  17  which is disposed downstream of the first transmission  5  as seen in a feed direction  16  and which is followed by a single or several processing zones  18 . 
     A discharge zone  19  is provided at the end of the first extruder  1 , discharge in a direction of the axes  12   a ,  13   a  taking place from the discharge zone  19 . Instead of two casing bores and correspondingly two screw shafts, it is just as well possible to have only a single bore or three and more bores and a corresponding number of screw shafts. 
     The second extruder  2  also comprises a casing  20  where two casing bores  21 ,  22  are disposed, having axes  21   a ,  22   a  that are parallel to each other, and interengaging i.e., also defining a figure-eight-type cross-sectional shape. Two screw shafts  23 , 24  are disposed in the second casing bores  21 ,  22 ; they are coupled with the second transmission  8  and drivable to rotate in the same or opposite directions. Subsequently to the second transmission  8 , the second extruder  2  comprises a feeder connection piece  25  which is followed by one or several processing zones  26  in the feed direction  16 . A discharge zone  27  is again provided at the end of the second extruder  2 . 
     In the first embodiment according to  FIGS. 1 to 7 , an intermediate casing  29  is provided in the delivery zone  28 , having an interior  30  which is connected with the first casing bores  12 ,  13 . The intermediate casing  29  is connected with the casing  11  of the first extruder by a sliding connection  31  by way of which to compensate thermal expansions. The interior  30  consists of two bores of figure-eight-type interengagement which are parallel to the axes  12   a ,  13   a . The diameter D 2  of these bores is equal to, or slightly exceeds, the diameter D 1  of the first casing bores  12 ,  13 . They are through bores, the intermediate casing  29  being open at its end turned away from the casing  11 . 
     Radially of the axes  12   a ,  13   a  i.e., crosswise of the horizontal plane spanned by these axes  12   a ,  13   a , the intermediate casing  29  comprises a delivery orifice  32  which opens into the feeder connection piece  25  of the second extruder  2 . The overflow passage  33  which is formed in the feeder connection piece  25  has a diameter D 3 . D 1 ≦D 2 ≦D 3  applies. In this way, dead spots, where plastic material deposits, are prevented from forming along the flow path of the material, in particular molten plastic material, from the first extruder  1  to the second extruder  2 . 
     The intermediate casing  29  rests by an adjoining face  34  on an adjoining face  35 , turned thereto, of the feeder connection piece  25 . The intermediate casing  29  is not fixed by screwing to the feeder connection piece  25 . According to  FIG. 3 , the adjoining face  35  is provided with recesses  36  where packings  37  are disposed, sealing towards the adjoining face  34 . 
     A revolute slide body  38  is disposed in the intermediate casing  29 ; it is rotatable about its central longitudinal axis  39  and displaceable in the direction of its central longitudinal axis between two end positions. The central longitudinal axis  39  is parallel to the plane spanned by the axes  12   a ,  13   a  and perpendicular to each of these axes  12   a ,  13   a  and parallel to the axes  21   a ,  22   a  of the second casing bores of the second extruder  2 . The revolute slide body  38  is of cylindrical external shape and displaceably guided in two adapted guide bores  40 , 41  of the intermediate casing  29 . 
     The revolute slide body  38  comprises two through bores  42 , 43  of figure-eight-type interengagement, the axes  42   a ,  43   a  of which are in alignment with the axes  12   a ,  13   a . These through bores  42 , 43  each have a diameter D 2 .  FIGS. 1 and 2  illustrate these through bores  42 , 43  in their functional position upstream of the first casing bores  12 ,  13  i.e., in a screw-shaft pull-out position, in which the revolute slide body  38  simultaneously closes the delivery orifice  32  that opens out radially. 
     In this position of the revolute slide body  38 , the first screw shafts  14 ,  15  can be pulled out of the first casing bores  12 ,  13 , namely through the revolute slide body  38  of the intermediate casing  29 . Moreover, in this end position of the revolute slide body  38 , plastic material can be transferred outwards upon start-up of the plant. 
     In the direction of the central longitudinal axis  39  of the revolute slide body  38 , a pair of blind bores  44 ,  45  of figure-eight-type interengagement is provided by the side of the pair of through bores  42 , 43 , the axes  44   a ,  45   a  of the blind bores  44 , 45  being in alignment with the axes  12   a ,  13   a  when in a position of congruence therewith. The diameter of these blind bores  44 ,  45  is also D 2 . Crosswise of the axes  44   a ,  45   a  of the blind bores  44 , 45 , a connecting bore  46  is formed in the revolute slide body  38 , the diameter of which is D 3 . The blind bores  44 , 45  and the connecting bore  46  constitute a delivery passage. Upon displacement of the revolute slide body  38  from the described screw-shaft pull-out position into its other end position, the first casing bores  12 ,  13  of the first extruder  1  are connected to the feeder connection piece  25 , and thus to the second extruder  2 , by way of the intermediate casing  29  and the blind bores  44 , 45 . The revolute slide body  38 , when in this position of delivery, is in the operational position of the plant. By the revolute slide body  38  being pivoted about the axis  39  in this second end position i.e., in the position of delivery, the flow of plastic material can be throttled, becaus—as seen in FIGS.  6  and  7 —the free cross section between the connecting bore  46  and the delivery orifice  32  in the intermediate casing  29  is modifiable. Upon a pivoting motion by 90°, the delivery orifice  32  can be closed completely by the revolute slide body  38  in both end positions of the revolute slide body  38 . 
     The sliding and pivoting motions of the revolute slide body  38  are carried out by a rotary slide drive  47  which is mounted on the casing  11  of the first extruder  1  by means of a retaining device  48 . Such a drive can be a commercial, hydraulically operable piston-cylinder drive. 
     Of course, the slide body  38  can be embodied without the revolute function that serves for throttling. In this case, the drive  47  is a pure sliding drive, displacing the slide  38  between two end positions i.e., the screw-shaft pull-out position and the delivery position. 
     No special intermediate casing is provided in the embodiment according to  FIGS. 8 to 10 ; rather, in the delivery zone  28 , the delivery orifice  32 ′ opens directly from the casing  11  into the feeder connection piece  25 . In the casing  11 , provision is made for guide bores  40 ′,  41  in which a revolute body  49  is rotarily guided. The revolute body  49  comprises two through bores  42 , 43  which the above description applies to. The pivoting motion of the revolute body  49  about its central longitudinal axis  39 ′ takes place by a drive (not shown) which corresponds to that of the first embodiment, but which allows only a rotary motion. Otherwise the above description of the first embodiment applies. 
     While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.