Abstract:
In a method and an apparatus for producing pipes having a transverse profile from thermoplastic material, mold segment halves are used on a molding path and are circulated in pairs. A main conveying device is provided for returning the mold segment halves, the main conveying device being designed like a gantry crane. A conveying bridge encompassing the molding path is provided with two conveying carriages which are displaceable at right angles to a direction of production and in opposite directions relative to each other and to which is in each case attached a downwards facing conveying arm comprising a holding device for in each case one mold segment half. Downstream of the downstream end of the molding path are provided parking positions for additional mold segment halves. Disposed downstream of the molding path is an auxiliary conveying device which is provided for removing the additional mold segment halves from the molding path in order to subsequently return them to the parking positions.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention relates to a method of producing pipes having a transverse profile from thermoplastic material by means of circulating mold segment halves which are arranged in two opposite rows downstream of an extrusion head and combine in pairs to form a closed hollow mold along a linear molding path, 
         [0000]    wherein each of the unconnected mold segment halves of a row are guided out of the molding path at a downstream end in a direction substantially at right angles to a direction of production by means of a conveying device and are guided back to the upstream end of the molding path where they are re-fed into the molding path, and
 
wherein downstream of the downstream end of the molding path and on both sides thereof, a respective additional mold segment half is stored in a parking position, the additional mold segment half being feedable into the molding path by means of the conveying device.
 
         [0003]    Furthermore, the invention relates to an apparatus for producing pipes having a transverse profile. 
         [0004]    2. Background Art 
         [0005]    A method and an apparatus of this type are for example known from U.S. Pat. No. 5,693,347. By means of the conveying device, the respective mold segment halves used in the production of the corrugated pipe are removed from the molding path at the downstream end thereof and returned to the beginning of the molding path at the upstream end of the apparatus where they are fed back into the molding path. Each time a pipe form, in particular a socket, is to be produced which differs from the regular cross-section of a corrugated pipe, a pair of additional mold segment halves is additionally fed into the molding path from a parking position downstream of the molding path by means of the conveying device. After passing through the molding path, these additional mold segment halves are removed from the molding path by the conveying device and returned to the parking positions. Afterwards, the conveying device moves back to the downstream end of the molding path where it removes the next pair of mold segment halves in order to return them to the beginning of the molding path where they are fed into the molding path. The result of this embodiment was that the production speed of these apparatuses is limited. 
       SUMMARY OF THE INVENTION 
       [0006]    Thus it is the object of the invention to develop a method of the generic type such that the production speed can be increased, and to provide an apparatus for realization of the method. 
         [0007]    In a method of the generic type, this object is attained in that the additional mold segment halves are removed from the molding path at the down-stream end by means of a auxiliary conveying device, which is separate from the conveying device acting as main conveying device, before being moved to the parking positions while a pair of mold segment halves, which is disposed directly upstream of the additional mold segment halves in the molding path when seen in the direction of production, is returned to the upstream end of the molding path where it is fed into the molding path. 
         [0008]    Due to the fact that the removal of the additional mold segment halves from the molding path and their transport to their parking position is dispensed with, the entire production process, more specifically the extrusion rate and the speed of the mold segments on the molding path, can be increased considerably since the mold segment halves are moved opposite to the direction of production on a substantially straight line so that conveyance can take place at a very high speed. 
         [0009]    In an apparatus of the generic type, this object is attained in that down-stream of the molding path, an auxiliary conveying device is provided for removing the additional mold segment halves from the molding path at the downstream end thereof and for moving these additional mold segment halves to their parking positions. The main conveying device and the auxiliary conveying device may be formed like a gantry crane. 
         [0010]    Further features, advantages and details of the invention will become apparent from the description of an embodiment by means of the drawing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  shows a plan view of an apparatus according to the invention for the production of pipes; 
           [0012]      FIG. 2  shows a partially broken open front view of the apparatus according to the arrow II in  FIG. 1 ; 
           [0013]      FIGS. 3 to 7  show a plan view of the apparatus according to the invention in operating positions different from  FIG. 1 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0014]      FIGS. 1 and 2  show an apparatus for producing pipes having a transverse profile from thermoplastic material. This apparatus has a base  1  with a molding path situated on it. On this molding path  2 , mold segments  3  are lined up, each consisting of two mold segment halves  4 ,  5 . As long as in each case two mold segment halves  4 ,  5  rest against each other to form a mold segment  3 , and as long as adjacent mold segments  3  rest against each other to form a mold, they move in a straight line along the base  1  in a direction of production  6 . For the continuous drive of the mold formed by the mold segments  3 , a lower driving pinion  8  is provided right behind an extrusion head  7  of an extruder, the driving pinion  8  projecting out of a recess  9  in the base  1  and engaging with a tooth profile  10  formed on the respective lower side of the mold segment halves  4 ,  5 . The lower driving pinion  8  is non-rotatably mounted on a drive shaft  11  which is located underneath the base  1  and driven by a gear motor not shown. The mold segment halves  4 ,  5  are in each case guided or held together, respectively, on the molding path  2  by guide rails  12 ,  13  which engage with the portion of the mold segment halves  4 ,  5  that is adjacent to the base  1 . 
         [0015]    A counterpart bearing  14  is provided above the base  1  and above the mold. It has a base plate  15  on which is supported an upper driving pinion  16 . This upper driving pinion  16  is likewise non-rotatably mounted on a drive shaft  17 , both ends of which are run in bearings  18 ,  19  which are fastened to the base plate  15 . The drive shaft  17  is driven by a gear motor  20  which is attached to the adjacent bearing  19 . Supporting rollers  21  are located on the lower side of the base plate  15 , having a horizontal axis of rotation  22  and supporting themselves on supporting surfaces  23  formed on the upper side of each mold segment half  4 ,  5 , which defines the position of the counterpart bearing  14  relative to the mold segment halves  4 ,  5 . Guide rollers  24  are positioned on the lower side of the base plate  15 , having a vertical axis of rotation  25  and engaging laterally with guide surfaces  26  that are also formed on the upper side of the mold segment halves  4 ,  5 . By means of these guide rollers  24 , two mold segment halves  4 ,  5  that constitute a mold segment  3  are guided and held together by their upper portion. Between the supporting surfaces  23  and the guide surfaces  26 , respectively, the upper driving pinion  16  engages with an indentation  27 , which is formed on the upper sides of the mold segment halves  4 ,  5 . Only one third to one quarter of the amount of advance exercised on the mold segments  3  by the lower driving pinion  8  is transmitted to the mold segments  3  by the upper driving pinion  16 . The counterpart bearing  14  is supported in torque converter bearings  28 , which are mounted on the base  1  and stand vertically upright thereon and which absorb the torque exercised by the gear motor  20  on the counterpart bearing  14 . 
         [0016]    A main conveying device  29  for the mold segment halves  4 ,  5  is provided above the base plate  1 . This main conveying device  29  is designed in the way of a gantry crane. It has two guide rails  31 ,  32  extending parallel to each other and parallel to the direction of conveyance  6 , to the central longitudinal axis  30  of the mold segments  3  and to the base  1 . These guide rails  31 ,  32  are disposed above the counterpart bearing  14  and supported relative to the base  1  by props  33 . A conveying bridge  34  is supported on the guide rails  31 ,  32  by bogie wagons  35 . Displacement of the conveying bridge  34  on the guide rails  31 ,  32  takes place by means of linear drives  36 , which are spindle drives in the concrete embodiment. Consequently, these linear drives  36  have threaded spindles  37 , which are disposed on the guide rails  31 ,  32  and on which are disposed threaded nuts  38  which are again fixed to the bogie wagons  35 . The threaded spindles  37  are driven each by a gear motor  39 ,  40 , these two gear motors  39 ,  40  being forcibly synchronized by way of a horizontal coupling shaft  41  that extends at right angles to the guide rails  31 ,  32 . These two threaded spindles  37  are driven precisely at the same speed so that the conveying bridge  34  is displaced free from tilting on the guide rails  31 ,  32 . The conveying bridge  34  has two bridge sections  42 ,  43 , which, seen from the guide rails  31 ,  32 , run toward each other, inclining toward the base  1 . Consequently, the lowest distance of the bridge  34  from the base  1  is in the middle of the bridge  34  vertically above the central longitudinal axis  30 . A conveying carriage  44 ,  45  is displaceably disposed on each of the two bridge sections  42 ,  43  and is movable in the respective direction of displacement  46  or  47  by means of a linear drive  48  or  49 . These linear drives  48 ,  49  substantially consist of a threaded spindle  50  that is housed in the respective bridge section  42  or  43  and engages with a threaded nut  51  on the respective conveying carriage  44  or  45 . The two threaded spindles  50  are driven by a common gear motor  52 . The gear motors  39 ,  40  and the gear motor  52  are reversible motors, i.e. they are suitable for forward and reverse motion. 
         [0017]    A conveying arm  53 , which extends vertically downwards, is attached to each conveying carriage  44 ,  45 . Each conveying arm  53  is provided with a holding device  54  for a mold segment half  4  and  5 , respectively. Allocated to the holding device  54 , a holding abutment  55  is formed on each mold segment half  4  and  5 , respectively. Each holding device  54  has an upper stop  56  which a holding abutment  55  is pressed against from below. Further, a clamping device  57 , which substantially consists of a pneumatic or hydraulic piston-cylinder drive  58 , belongs to the holding device  54 . A locking pin  60  is formed on the piston rod  59  of this drive  58 , which, upon corresponding actuation of the drive  58 , engages with a locking recess  61  on the lower side of the holding abutment  55 , simultaneously pressing the abutment  55  against the stop  56 . In the position shown on the left of  FIG. 2 , the holding device  54  and the holding abutment  55  of the adjacent mold segment half  4  or  5  are tightly interlocked; consequently, the latter is tightly united with the conveying arm  53 . 
         [0018]    Proximity switches—only some proximity switches  62 ,  63 ,  64 ,  65  of which are shown—are disposed on the guide rails  31 ,  32  and, upon approach of the conveying bridge  34 , transmit signals reflecting the position thereof to a central control unit (not shown). Proximity switches  66 ,  67  are also provided on the conveying bridge  34 , transmitting signals to the central control unit that reflect an inner or outer position of the respective conveying carriage  44 ,  45 . 
         [0019]    Apart from the main conveying device  29 , an auxiliary conveying device  29 ′ is provided which is designed like the main conveying device  29  with the difference that the guide rails  31 ′,  32 ′ thereof, which are arranged between the guide rails  31 ,  32 , only extend from the downstream end  68  of the molding path to the end  69  of the apparatus which is disposed even further down the line when seen in the direction of production  6 . Since the design otherwise corresponds to that of the main conveying device  29 , all equal or similar parts are denoted by reference numerals which are identical to those of the main conveying device  29  but are marked with an apostrophe. Therefore, reference can be made to the entire preceding description. Also shown in  FIG. 1 , the conveying bridge  34 ′ of the auxiliary conveying device  29 ′ is arranged downstream of the conveying bridge  34  of the main conveying device  29  when seen in the direction of production  6 . 
         [0020]    Two tubes of thermally plastic material are extruded from the extrusion head  7  of the extruder, entering the mold at the upstream end  70  of the molding path  2  where they are molded, by means of overpressure or vacuum and, if necessary, support air, into a compound pipe  71  which has a smooth inside wall and an outer corrugation  72 , as known in detail from EP 0 563 575 A1 (corresponding to U.S. Pat. No. 5,320,797) which reference is made to. By alternative, it is also possible to mold single-piece corrugated pipes or ribbed pipes. 
         [0021]    If a profile differing from the corrugation  72 , for instance a socket  73 , is to be produced on the pipe  71  at in each case longer intervals, a pair of special mold segment halves, for instance a pair of socket mold segment halves  74 ,  75 , needs to be fed into the molding path  2 . These mold segment halves  74 ,  75  are stored in parking positions  76 ,  77  which are formed by pedestals  78 ,  79  on which these mold segment halves  74 ,  75  are placed when they are not involved in the pipe molding process. These parking positions  76 ,  77  are adjacent to the end  69  of the apparatus. The auxiliary conveying device  29 ′ serves to return these mold segment halves  74 ,  75  from the downstream end  68  of the molding path  2  to their parking positions  76 ,  77 . 
         [0022]    The mold consisting of the mold segments  3  advances in the direction of production  6 . The pipe  71  produced therein migrates at the same rate. When a mold segment  3  has reached the downstream end  68  of the molding path  2 , the two mold segment halves  4 ,  5  that constitute this mold segment  3  must be removed from the molding path  2  crosswise of the direction of production  6 . As shown in  FIG. 1 , this is done by the transverse conveying means formed by the conveying carriages  44 ,  45  with conveying arms  53 . The conveying bridge  34  has moved ahead of the last mold segment  3  in the direction of production  6 . As soon as this last mold segment  3  has reached the downstream end  68  of the molding path, the holding devices  54  and the holding abutments  55  of the two mold segment halves  4 ,  5  have been interlocked. In this mutually adjacent position, the conveying carriages  44 ,  45  were brought to a stop by way of the proximity switches  67 . Afterwards, the conveying bridge  34 , together with the mold segments  3  forming the mold, moves in the direction of production  6  at the same rate, wherein the two conveying carriages  44 ,  45 , together with the mold segment halves  4 ,  5  with which they are interlocked, are moved away from one another. This movement is triggered by respective actuation of the gear motor  52  by way of a respective signal of the proximity switch  63 . When this happens, the mold segment halves have already traveled in the down-stream direction, in other words beyond the guide rails  12 ,  13 . Owing to the inclination of the two bridge sections  42 ,  43 , the mold segment halves  4 ,  5  held by the conveying arms  53  are lifted off the base  1  and moved outwards without friction. When the conveying carriages  44 ,  45  reach the outer proximity switches  66 , they are stopped. The gear motors  39 ,  40  are triggered so that the conveying bridge  34  is moved counter to the direction of production  6  as far as to the upstream end  67  of the molding path  2 . Also during their transport counter to the direction of production  6 , the mold segment halves  4 ,  5  do not contact the base  1 , but are frictionless thereabove. They are always moved parallel to themselves. 
         [0023]    When the upstream proximity switches  62  are reached, the gear motors  39 ,  40  are stopped so that the conveying bridge  34  is at a standstill. The gear motor  52  is switched on, moving the conveying carriages  44 ,  45  inwards toward the molding path and leads, at the upstream end, the two mold segment halves  4 ,  5  crosswise of the direction of production  6  into the molding path  2 , as shown by dashed lines in  FIG. 1 . Upon displacement of the conveying carriages  44 ,  45  toward the molding path  2 , owing to the inclination of the bridge sections  42 ,  43 , the mold segment halves  4 ,  5  are again lowered toward the base  1 , on which they rest when the two mold segment halves  4 ,  5  of a mold segment  3  contact, as seen in  FIG. 2 . Then the conveying bridge  34  is moved in the direction of production  6  until the two mold segment halves  4 ,  5  that already form a mold segment  3  bear against the mold segment halves  4 ,  5  that lead in the direction of production  6  and are seized and moved on by the driving pinions  8  and  16 . Then the clamping devices  57  are released and the conveying arms  53  are again moved outwards away from the molding path  2 . The conveying bridge  34  is then again displaced as far as to the downstream end  69 , as described above. 
         [0024]    If it is desired to form a socket  73  in the continuous pipe  71 , the main conveying device  29  is moved into the position shown by a dash-dot line according to  FIG. 3  in which it is able to take up the socket mold segment halves  74 ,  75  from their parking positions  76 ,  77 . As shown by the drawing, these parking positions  76 ,  77  are disposed between the guide rails  31 ′,  32 ′ of the auxiliary conveying device  29 ′. The longitudinal movement of the main conveying device  29  towards the end  69  of the apparatus is stopped by way of the proximity switches  65 . Taking up the socket mold segment halves  74 ,  75  is performed in the same manner as described above with respect to the mold segment halves  4 ,  5 . Afterwards, the socket mold segment halves  74 ,  75  are moved beyond the position shown dashed in  FIG. 3  and the intermediate position shown dashed in  FIG. 4  to the end position at the upstream end  70 . Said end position of the main conveying device  29  is shown by a solid line in  FIG. 4 . The socket mold segment halves  74 ,  75  are fed into the molding path  2  in the manner described above. 
         [0025]    As shown by  FIG. 5 , the socket mold segment  80  formed by the socket mold segment halves  74 ,  75  travels downstream in the direction of production  6  along the molding path  2  to the downstream end  68 . As shown by  FIGS. 4 and 5  as well, there is now an additional mold segment  80  in the molding path  2  since none of the pairs of mold segment halves  4 ,  5  was removed from the production when the additional mold segment halves  74 ,  75  were fed in. While the socket mold segment  80  is still being moved along the molding path  2  in the direction of production  6 , a respective pair of mold segment halves  4 ,  5  is removed at the downstream end  68  and returned to the upstream end  70  where it is fed into the molding path  2 . This continues until the last pair of mold segment halves  4 ,  5  disposed upstream of the socket mold segment halves  74 ,  75  when seen in the direction of production  6  has been removed from the still extended molding path  2  and returned to the upstream end  70  where it is fed into the molding path  2 . As shown by  FIGS. 1 and 3  to  6 , the auxiliary conveying bridge  34 ′ is until this moment located between the parking positions  76 ,  77  and the end  69  of the apparatus and does therefore never collide with the main conveying bridge  34 , not even when taking up the socket mold segment halves  74 ,  75 . 
         [0026]    While the last pair of mold segment halves  4 ,  5 , which—according to FIGS.  6  and  7 —had been disposed upstream of the socket mold segment halves  74 ,  75  in the direction of production  6 , is still being returned to the upstream end  70  of the molding path  2 , the auxiliary conveying device  29 ′ is set in motion so as to move to the downstream end  68  where it is stopped by respective signals of the proximity switches  62 ′. The conveying carriages  44 ′,  45 ′ are moved inwards towards each other until they are stopped by way of proximity switches  67 ′, and the conveying arms  53 ′ and the socket mold segment halves  74 ,  75  are interlocked. The conveying carriages  44 ′,  45 ′ are then moved outwards until they are stopped by the proximity switches  66 ′. Afterwards, the auxiliary conveying device  29 ′ is returned to the parking positions  76 ,  77  in the direction of production  6  where the socket mold segment halves  74 ,  75  are placed on the pedestals  78 ,  79 . The auxiliary conveying device  29 ′ is stopped at the parking positions  76 ,  77  by way of proximity switches  65 ′. The entire process takes place simultaneously with the return of the last mold segment halves  4 ,  5 , which move upstream of the socket mold segment halves  74 ,  75 , to the upstream end  70  and the feeding into the molding path  2 . Thus, no additional time is required for removing and conveying the socket mold segment halves  74 ,  75  away from the molding path  2 .