Abstract:
A material processing plant comprises two screw-type extruding machines ( 1, 2 ) which are interconnected by means of a link ( 29 ). The link ( 29 ) is movable from a position of connection into an open position of release of the casing bores ( 12 ). Provision is further made for a mover ( 38 ) which acts on the link ( 29 ) for implementation of the motion.

Description:
FIELD OF THE INVENTION 
     The invention relates to a material processing plant comprising a first screw-type extruding machine, which has a first casing with at least one first casing bore with an axis and a first screw shaft disposed therein, a second screw-type extruding machine, which has a second casing and which is disposed downstream of the first screw-type extruding machine and which has at least one second casing bore and a second screw shaft disposed therein, and a link, which connects the first screw-type extruding machine and the second screw-type extruding machine in a position of connection and which comprises an elbowed overflow passage, which connects the at least one first casing bore with the at least one second casing bore. 
     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, down-stream extruder. Successive extruder arrangements of the generic type are known for example from EP 1 005 411 B1, 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. The term ‘materials’ is to be understood as fundamentally free flowing materials that are treatable in screw-type extruding machines. 
     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 link being movable in guided motion from the position of connection into an open position of release of the at least one first casing bore such that the at least one first screw shaft is freely drawable out of the first casing. The object is further attained by a mover, which acts on the link, being provided and performing the guided motion. The gist of the invention resides in that the link has been developed into an independent function group which, by means of a mover, can be transferred from its position of connection, in which the two screw-type extruding machines are interconnected, into an open position, in which the at least one screw bore lies bare so that the screw shaft or shafts of the first extruder can be pulled out customarily in the vicinity of the discharge zone. 
     Further features, advantages and details of the invention will become apparent from the ensuing description of several embodiments, taken in conjunction with the drawing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG. 1  is a vertical sectional view of a first embodiment of a plant according to the invention, with the link in a position of connection; 
         FIG. 2  is a plan view, partially broken open, of the plant according the first embodiment; 
         FIG. 3  is an illustration of a detail III of  FIG. 1 ; 
         FIG. 4  is a horizontal partial view seen on the line IV-IV of  FIG. 1 ; 
         FIG. 5  is a vertical sectional view of the first embodiment of the plant according to the invention, with the link in an open position; 
         FIG. 6  is a vertical sectional view of a second embodiment of a plant according to the invention, with the link in a position of connection; 
         FIG. 7  is a partial view of a third embodiment, comprising a modified mover; 
         FIG. 8  is a vertical sectional view of a fourth embodiment of a plant according to the invention, with the link in a position of connection, the link having an additional function portion; 
         FIG. 9  is a vertical sectional view of a fifth embodiment of a plant according to the invention, with the link in a position of connection; 
         FIG. 10  is a plan view, partially broken open, of the plant according to the fifth embodiment, with the link in a position of connection; 
         FIG. 11  is a partial plan view of the plant according to the fifth embodiment, with the link in an open position; 
         FIG. 12  is a sectional view of the fifth embodiment plotted vertically through the second extruder, with the link in a position of connection; 
         FIG. 13  is an illustration according to  FIG. 12 , with the link in an open position; and 
         FIG. 14  is a view of a detail XIV of  FIG. 13 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The first embodiment seen in  FIGS. 1 to 5  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  with a heating system, two casing bores  21 ,  22  being disposed in the casing  20 , 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 . 
     It is true also for the second extruder  2  that only a single or more than two bores and a corresponding number of screw shafts can be provided. Also in the second extruder  2 , the screw shafts can be driven in the same or opposite directions. 
     A delivery zone  28  is provided between the first extruder  1  and the second extruder  2 , comprising a link  29  in the form of a pipe elbow. On the side turned towards the first extruder  1 , the link  29  has a connecting flange  30  which is fixed to the casing flange  31 , turned there-to, of the first casing by means of screws  32 . On the side turned towards the second extruder  2 , the link  29  also comprises a connecting flange  33 , the contact surface  34  of which bearing against a contact surface  35 , turned there-to, of the feeder connection piece  25 . The contact surface  35  is provided with recesses  36  where packings  37  are located which, in the non-loaded condition, project upwards beyond the contact surface  35 . The link  29  is not joined by screwing to the feeder connection piece  25 . The contact surfaces  34  and  35  bear tightly against one another due to thermal expansion during operation. 
     A mover  38  for the link  29  is disposed on the casing  11  of the first extruder  1 . It comprises a bracket-style holding device  39  that is mounted on the casing  11 . The holding device  39  supports a motion drive mechanism  40  for the link  29 . This motion drive mechanism  40  can be a hydraulically operable piston-cylinder drive, the cylinder  41  of which is mounted on the holding device  39 , whereas its piston rod  42  is connected to the link  29 . In the first embodiment according to  FIGS. 1 to 5 , the link  29  is lifted vertically upwards crosswise of the direction of the axes  12   a ,  13   a  and  21   a ,  22   a , respectively, of the first extruder  1  and of the second extruder  2 . Consequently, elevating also takes place transversely to the contact surfaces  34 , between the link  29  and the feeder connection piece  25 . For the connecting flange  30  to be as easy as possible to lift off casing flange  31 , the contact surfaces  43 ,  44  of the two flanges  30 ,  31  incline in relation to the vertical lift-off direction  45  so that they are released from one another directly upon start of the elevation process and, when set counter to the lift-off direction  45 , they take contact only at the very last moment. For reliable linear guidance of the link  29  in the lift-off direction  45  and in the opposite direction, guide rails  46  can be joined to the holding device  39  or the casing flange  31 , encompassing the connecting flange  30  and guiding it at least in the area where the link  29  is at least sectionally in congruence with the casing flange  31 . 
     As seen in  FIG. 5 , the lift-off motion of the link  29  is sufficiently far for the first casing bores  12 ,  13  to be definitely free in the vicinity of the discharge zone  19  so that the first screw shafts  14 ,  15 , in the direction of their axes  12   a ,  13   a , can be withdrawn freely from the first casing  11 . 
     At the respective places of transition, the overflow passages  47   a ,  47 ,  48 ,  49 , which are formed in the discharge zone  19  of the first extruder, the link  29  and the feeder connection piece  25 , do not possess any corners or edges that might project into the flow path. The cross-sectional shape of the over-flow passage  47   a  at the end of the first twin-shaft extruder  2  is figure-eight type. The cross-sectional area of the overflow passage  47   a  at the end of the extruder  1  is equal to, or less than, the cross-sectional area of the overflow passage  47  in the link  29 . A transition of this figure-eight type cross-sectional shape of the overflow passage  47  to the circular cross-sectional shape of the overflow passage  48  in the link  29  of a diameter D 1  is integrated in the link  29 . Moreover, the diameter D 2  of the overflow passage  49  in the feeder connection piece  25  equals or exceeds D 1 . D 1 ≦D 2  applies. The same applies to cross-sections of extruders that have more than two screw shafts. 
     The second embodiment according to  FIG. 6 , which is modified only slightly, differs from the first embodiment only in that the link  29 ′ is of block-type design, still having an elbowed overflow passage  48  without its external shape being tubular. 
     By alternative of the specified motion drive mechanism  40 , a motion drive mechanism  40 ′ in the form of a spindle drive can be used in the mover  38 ′ according to claim  7 , having a spindle  50  that acts on the link  29 ′, the spindle  50  being guided in a spindle nut  51  that is rotarily disposed in the holding device  39 ′. The spindle nut  51  is driven by a spindle-drive motor  52 . 
     The mover  38  or  38 ′, respectively, needs not necessarily act in a vertical lift-off direction  45 ; it can just as well act horizontally in the direction of the axes  21   a ,  22   a  of the second extruder  2  or spatially askew of the direction of the axes  12   a ,  13   a  of the first extruder  1 . However, the lift-off direction is preferred to work vertically, crosswise of the direction of the axes  12   a ,  13   a  of the first extruder. 
     The modified fourth embodiment according to  FIG. 8  differs from the above embodiments in that the link  29 ″, which is again of block-type design, is prolonged downwards towards the second extruder  2  by a function portion  53  where parts built in  54 , such as a strainer plate, a sieve, filter, static mixer or the like, are incorporated or can be incorporated. With these built-in function parts having to be accessible too, two functions, namely withdrawal of screws and exchange and/or maintenance of built-in parts  54 , are advantageously combined by only a singly mover device in this fourth embodiment. 
     The fifth embodiment according to  FIGS. 9 to 14  again differs from the above embodiments by the design of the link  29 ′″. Same as the link  29 ′, it is again of block-style configuration. The link  29 ′″ is mounted on the casing  11  of the first extruder  1  by means of a pivoted connection mechanism  55  so that it can be pivoted from the sealed position of connection seen in  FIG. 12  into an open position seen in  FIG. 13 , as a result opening the first casing bores  12 ,  13  so that the first screw shafts  14 ,  15  can be extracted freely and without being impeded in the direction of the axes  12   a ,  13   a.    
     A mover  38 ′″ comprises a motion drive mechanism  40 ′″ which may again be a hydraulically operable piston-cylinder drive, with the cylinder  41 ′″ being secured stationarily by means of a pivot bearing  56 , whereas the piston rod  42 ′″ is joined to the link  29 ′″ by means of a pivot joint  57 . For the link  29 ′″, upon pivoting motion, to be lifted not only off the casing  11  of the first extruder, but also off the feeder connection piece  25 , the pivoted connection mechanism  55  is a pivoted elevation-connection mechanism. To this end, it comprises a pivot  58  with a steeply pitched multiple thread  59 . The bearing sleeve  60  has a corresponding internal thread  61  so that the link  29 ′″ is displaced i.e., elevated in the present case, right at the beginning of the opening motion in the direction of the pivoting axis  62  of the pivoted connection mechanism  55 , with the link  29 ′″ being lifted off the feeder connection piece  25 . In the sealed position of connection according to  FIGS. 9 ,  10  and  12 , the link  29 ′″ is joined by screwing to the casing  11  of the first extruder  1  or the feeder connection piece  25  of the second extruder  2 . The screwing job can be dropped in certain cases, if for example there is only low pressure, or if the materials to be processed are of low viscosity, provided there are no built-in parts. In this case, the link  29 ′″ can be kept in the sealed position of connection by the motion drive mechanism  40 ′″.