Abstract:
For the production of a one-piece corrugated jacket pipe of thermoplastic, the corrugated jacket pipe is formed to have corrugated partial sections which are deformed such that the direction in which they lie one above the other radially to the axis of the corrugated pipe is reverse to the direction in the locked condition after insertion of electric lines.

Description:
This is a continuation of U.S. application Ser. No. 09/489,616 now abandoned filed Jan. 24, 2000. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a method of producing a one-piece corrugated jacket pipe of thermoplastic comprising the steps of forming a thermoplastic tube; shaping the tube into a corrugated pipe, which is closed over its circumference and has an axis and a corrugated section formed by a first corrugated partial section and a second corrugated section, the partial sections being such that when radially overlapping each other, the first partial section lies radially outwards and engages with the radially inward second partial section; cutting the corrugated pipe parallel to the axis in a cutting plane for the corrugated partial sections to form; thermally deforming the corrugated pipe such that the two corrugated partial sections lie one above the other radially and lap over each other in a peripheral direction. The invention further relates to a method of inserting at least one electric line into such a corrugated jacket pipe. 
     2. Background Art 
     A method of the generic type is known from WO98/32 202. In this case, the corrugated jacket pipe is thermally formed in such a way that the first corrugated partial section rests radially outwards on, and engages with, the second corrugated partial section directly after the forming. Practice has shown that the engagement of the first and the second corrugated partial section does not take place with the required radial prestress. This may result in small gaps forming so that electric lines might get squeezed or damaged. Moreover, the corrugated jacket pipe may open when bent during installation for instance in a vehicle, and the electric lines disposed in it may come out. This too may lead to damages of the electric lines. 
     This also applies to the corrugated jacket pipe known from WO97/32 379. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to develop the method of the generic type so that the corrugated partial sections engage with each other by sufficiently high radial prestress after the installation of the electric lines. 
     In a method according to the invention, this object is attained by the first partial section and the second partial section being deformed thermally such that the first partial section lies radially inwards—related to the second partial section—and that the two partial sections lap over each other in the peripheral direction. The measures according to the invention help ensure that the first corrugated partial section, which lies radially outwards after the installation of at least one electric line and once the corrugated jacket pipe has been closed, is positioned radially inwards in the corrugated pipe prior to the installation of the electric line, this corrugated pipe constituting an intermediate product, so that after the change of the radial position of the two partial sections relative to each other, these sections bear against each other by high radial prestress in the position in which they overlap each other. 
     The method of how to open the corrugated pipe produced according to the invention and how to close it after the insertion of at least one electric line is characterized in that in the vicinity of the cutting plane, an aperture is formed between the corrugated partial sections by spreading them elastically in the peripheral direction; in that at least one electric line is inserted through the aperture into the corrugated pipe; and in that by closing the aperture, the first corrugated partial section is moved to lap radially outwards over the second corrugated partial section in the peripheral direction by elastic restoring forces of the corrugated pipe. 
     Further advantages and features of the invention will become apparent from the ensuing description of an exemplary embodiment of the invention, taken in conjunction with the drawing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a lateral longitudinal view of a corrugated pipe as a first intermediate product; 
     FIG. 2 is a cross section through the corrugated pipe on the section line II—II in FIG. 1; 
     FIG. 3 is a cross section through the corrugated pipe on the section line III—III in FIG. 2; 
     FIG. 4 is a cross section through the corrugated pipe on the section line IV—IV in FIG. 2; 
     FIG. 5 is a lateral longitudinal view of the corrugated pipe in a finished condition of assembly; 
     FIG. 6 is a cross section through the corrugated pipe on the section line VI—VI in FIG. 5; 
     FIG. 7 is a cross section through the corrugated pipe on the section line VII—VII in FIG. 6; 
     FIG. 8 is an illustration of a plant for the manufacture of a corrugated pipe according to FIGS. 1 to  7 ; 
     FIG. 9 is a section through a delivery mechanism on the line IX—IX in FIG. 8; 
     FIG. 10 is a section through a postforming device on the line X—X in FIG. 8; 
     FIG. 11 is a plan view of a mounting tool; 
     FIG. 12 is a plan view of the corrugated pipe with the mounting tool in use; 
     FIG. 13 is a section through the corrugated pipe on the line XIII—XIII in FIG. 12; and 
     FIG. 14 is a section through the corrugated pipe on the line XIV—XIV in FIG.  12 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The corrugated pipe  1  seen in FIGS. 1 to  4 , which is a first intermediate product, consists of a known thermoplastic, for instance polyethylene, polypropylene, polyamide or the like. It has a central longitudinal axis  2 , concentrically of which the corrugated pipe  1  is provided with corrugated sections  3 , which extend approximately over three quarters of the periphery as seen in FIG.  2 . These corrugated sections  3  comprise substantially circular cylindrical inner pipe sections  4 , which extend concentrically of the axis  2 , and substantially circular cylindrical outer pipe portions  5 , which are likewise concentric of the axis  2 . An inner pipe section  4  is connected with the neighboring outer pipe portions  5  by way of flanks  6 ,  7 . The flanks  6 ,  7  joined to an outer pipe portion  5  slightly incline towards each other, seen from the axis  2  radially outwards, so that a cavity  8  forms between an outer pipe portion  5  and the adjoining flanks  6 ,  7 , the cavity  8 —seen from the axis  2 —standing back radially outwards relative to the inner pipe sections  4  and in cross section having approximately the shape of a trapezoid that expands towards the pipe portion  5 , as seen in FIG.  3 . This design of a corrugated pipe  1 , seen in FIG. 2 top, bottom and left, is known and general practice. 
     As becomes apparent from FIGS. 1,  2 , and  4 , the corrugated pipe  1  comprises corrugated sections  3 ′ over part of its periphery, which likewise have inner pipe sections  4 ′ that continue the inner pipe sections  4  and close same over the periphery, outer pipe portions  5 ′ that continue the outer pipe portions  5  and close same over the periphery and flanks  6 ′ and  7 ′ that join the inner pipe sections  4 ′ to the outer pipe portions  5 ′. The cross section of the cavity  8 ′ formed in the corrugated section  3 ′ changes over the pheripheral extension of the corrugated section  3 ′. 
     The corrugated sections  3 ′ have a beginning  9  seen at the lower right in FIG.  1  and in FIG. 2, which corresponds to an end of the corrugated section  3 . The corrugated section  3 ′ further comprises an end  10  seen in FIG. 1 top and at the upper right in FIG. 2, which corresponds to the other end of the corrugated section  3 . At the beginning  9 , the outer pipe portion  5  of a corrugated section  3  passes steadily into the outer pipe portion  5 ′ of the corrugated section  3 ′ as becomes apparent from FIGS. 1 and 2. As opposed to this, the inner pipe section  4 ′ is misaligned relative the inner pipe section  4  outwards radially to the axis  2 . The flanks  6 ′ and  7 ′ of the corrugated section  3 ′ are displaced in the axial direction relative to the flanks  6 ,  7  of the adjoining corrugated section  3 . The inner pipe section  4 ′ passes into the inner pipe section  4  by way of a transition section  11 ; the flanks  6 ′ and  7 ′ pass into the flanks  6  and  7 , respectively, by way of transition sections  12 ,  13 , which extend outwards from the flanks  6  and  7  in the axial direction. 
     At the end  10  of the corrugated sections  3 ′, the inner pipe section  4 ′ thereof passes continuously into the adjoining inner pipe section  4  of the adjoining corrugated section  3 , as seen in FIG.  2 . As opposed to this, the outer pipe portion  5 ′ stands back radially inwards relative to the adjoining pipe portion  5 . At the end  10 , the outer pipe portion  5 ′ passes into the adjoining outer pipe portion  5  by way of a transition section  14  that extends outwards. Further, the flanks  6  and  7 ′ pass into the flanks  6 ,  7  by way of transition sections  15 ,  16 , these transition sections  15 ,  16  extending inwards from the flanks  6 ,  7  in the axial direction. 
     When the corrugated pipe  1  is cut up unilaterally in the middle between the beginning  9  and the end  10  of the corrugated sections  3 ′ in a cutting plane  17  that coincides with the section line IV—IV of FIG.  2  and also runs through the axis  2 , then two corrugated partial sections  3 ″ and  3 ′″ are formed from a corrugated section  3 ′, the corrugated partial section  3 ″ extending from the begin  9  to the cutting plane  17  and the corrugated partial section  3 ′″ extending from the cutting plane  17  to the end  10 . Correspondingly, the corrugated partial section  3 ″ comprises an inner partial pipe section  4 ″, an outer partial pipe portion  5 ″ and partial flanks  6 ″ and  7 ″. The corrugated partial section  3 ′″ correspondingly comprises an inner partial pipe section  4 ′″, an outer partial pipe portion  5 ′″ and partial flanks  6 ′″ and  7 ′″. When the corrugated pipe  1  cut through in the cutting plane  17  is bent together—as seen in FIGS. 5 to  7 —then the corrugated outer partial section  3 ″, by reason of the design specified of the corrugated sections  3 ′, houses the corrugated inner partial section  3 ′ 41   in such a way that the inner partial pipe sections  4 ″ and  4 ′″, the outer partial pipe portions  5 ″ and  5 ′″ and the partial flanks  6 ″ and  6 ′″, and  7 ″ and  7 ′″, respectively, rest on each other as seen in FIG.  7 . Further, the inner partial pipe section  4 ′″ extends so as to pass into the adjoining inner pipe section  4  without any serious irregularity at the transition section  11 . Correspondingly, the outer partial pipe portion  5 ″ does not exhibit any serious radial irregularity towards the partial pipe portion  5  at the transition section  14 . As can further be seen from FIGS. 5 and 7, the partial flanks  6 ″ and  7 ″ pass without irregularity into the flanks  6 ,  7  at the transition sections  15 ,  16 . The same applies to the partial flanks  6 ′″ and  7 ′″ at the transition sections  12 ,  13 . Further details of the corrugated pipe  1 , in particular its dimensions, can be seen from WO98/32 202. 
     Manufacturing the corrugated pipe  1  takes place on a plant as diagrammatically illustrated in FIG.  8 . Such a plant comprises an extruder  18 , from the extrusion die  19  of which is extruded a tube  20  of thermoplastic. 
     In a downstream molding machine  21 , the tube  20  is shaped into a corrugated pipe  1  by so-called vacuum treatment or by so-called blow molding or by a combined vacuum treatment and blow molding method. Molding machines  21  of the generic type are generally known from German patents 12 03 940 and 12 11 789 (corresponding to British patent 971 021). The corrugated pipe  1 , which is already inherently stable, leaves the molding machine  21 . 
     This corrugated pipe  1  is further cooled in a downstream cooling bath  22  by means of an appropriate coolant. This may be air or water. Cooling baths  22  of this type are known and general practice. 
     A belt or Caterpillar delivery mechanism  23  is disposed downstream of the cooling bath  22 , by means of which the corrugated pipe  1  is conveyed in the direction of production  24 . Belt or Caterpillar delivery mechanisms  23  of this type are also known and general practice. This delivery mechanism  23  is also provided with a cutting device, which substantially consists of a knife  25 , by means of which the corrugated pipe  1  is slit lengthwise in the cutting plane  17 . Since the belt and Caterpillar delivery mechanism  23  is otherwise known and general practice, the delivery belts  35  are only diagrammatically outlined. 
     In the direction of production  24 , the delivery mechanism  23  is followed by a postforming device  36 , in which heaters  28  are provided by means of which the corrugated pipe  1  is heated to a temperature appropriate for thermal postforming. Shaping rolls  29 ,  30  are disposed by twos in the postforming device  27 , having axes  31 ,  32  that run at right angles to the central longitudinal axis  2  of the corrugated pipe  1 . Further, they have concave surfaces  33 ,  34  which are arched inwards towards the respective axis  31  and  32  and by means of which the corrugated pipe  1  slit in the cutting plane  17  is deformed, losing its original form seen in FIGS. 1,  2  and  9 . The concave surface  33  of the shaping roll  29  is such that it corresponds substantially to the semi-cylindrical periphery of the corrugated pipe  1 . The concavity of the surface  34  of the shaping roll  30  is such that in vicinity to the partial sections  3 ′″, the corrugated pipe  1  is bent in the direction toward the axis  2  so that the corrugated partial sections  3 ″ are pushed under the corrugated partial sections  3 ′″ as seen in FIG.  10 . Shaping the corrugated pipe  1  to form the corrugated pipe  1   a , which is a second intermediate product, can be seen in FIG.  10 . In the peripheral direction, the corrugated partial sections  3 ″ reach beyond the transition sections  14 ,  15 ,  16  at the end  10 . The corrugated pipe  1   a  is then coiled up on a customary coiling device  35 . 
     The finished corrugated pipe  1   b  as illustrated in FIGS. 5 and 6 serves as a corrugated jacket pipe for electric lines  36  or the like, some of which are illustrated in FIG.  6 . The lines  36 , which are to be inserted into the corrugated pipe  1   a , and the plug-type connectors are pre-positioned. Then the respective corrugated pipe  1   a  is opened approximately radially to the axis  2  in the vicinity of the corrugated partial sections  3 ″ and  3 ′″ by means of a corresponding mounting tool  37  and the strand of lines  36  is inserted. 
     Such a mounting tool is illustrated in FIGS. 11,  13 ,  14 . It has an approximately U-shaped cross section. On the outside, its legs  38 ,  39  are concave crosswise to the axis  2  as seen in FIGS. 13,  14 ; they are concave also in the direction of the axis  2  as seen in FIG.  11 . The legs are joined to each other by means of a web  40 . The mounting tool  37  has an opening section  41 , from where the corrugated pipe  1   a  is pushed on the mounting tool  37  for being opened. The opposite end constitutes a locking section  42 , by means of which the opened corrugated pipe  1   a  is closed, forming the corrugated pipe  1   b  (see FIGS.  5  and  6 ). The direction of mounting in which the corrugated pipe  1   a  is pushed on to the mounting tool  37  is mar  43  in FIGS. 11 and 12. Fixed approximately centrally on the web  40  is a handle  44  by means of which to keep the mounting wool  37  stationary or to shift it—counter to the direction of mounting  43  when the corrugated pipe  1   a  is kept stationary. Within the opening section  41 , the holder  44  is followed by an inlet port  45  for electric lines which is open toward the end. 
     As can be seen from FIG. 11 in combination with FIGS. 13 and 14, the mounting tool  37  is curved in such a way that the corrugated pipe  1   a , when approaching the mounting tool  37 , is expanded in the opening section  41  thereof so that the corrugated partial sections  3 ″ and  3 ′″ are spread outwards from their position seen in FIG. 10 into their position seen in FIG. 14, in which the free ends of the corrugated partial sections  3 ″ and  3 ′″ are spaced from each other in the peripheral direction by a distance which is given by the thickness of the handle  44  and in which the corrugated partial section  3 ″ lies radially further outwards than the corrugated partial section  3 ′″ which lies inwards when the corrugated pipe  1   b  has its definitive shape. While the corrugated pipe  1   a  moves continuously over the mounting tool  37 , the collected electric lines  36  are led through the inlet port  45  into the corrugated pipe, namely through the aperture  46 , seen in FIG. 12, formed between the partial sections  3 ″ and  3 ′″ by widening the corrugated pipe  1   a . 
     In the locking section  42 , the design of the leg  38 , which is allocated to the partial section  3 ′″, is such that this corrugated partial section  3 ′″ relaxes radially and in the peripheral direction more rapidly than the corrugated partial section  3 ″, as a result of which the section  3 ″ moves over the partial section  3 ′″ as seen in particular in FIGS. 5 and 6. To this end, a recess  47  is formed between the leg  40  and the leg  38 , widening in the direction of mounting  43  and allowing the partial section  3 ′″ to relax rapidly in the radial direction while the partial section  3 ″ is still guided on a radially projecting shoulder  48  of the mounting tool  37 . 
     The transition from the corrugated pipe  1   a , which is an intermediate product, to the corrugated pipe  1   b , which has the definitive shape, is effected by the corrugated pipe being opened and closed again. The closing of the corrugated pipe after opening and the insertion of the electric lines  36  results from the elasticity of the corrugated pipe. 
     In the definitive shape of the corrugated pipe  1   b , the two corrugated partial sections  3 ″ and  3 ′″ are pressed against each other radially to the axis  2  by the prestress that has been conferred to them by the deformation performed to create the corrugated pipe  1   a.